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Sample records for beam hardening correction

  1. Beam hardening correction algorithm in microtomography images

    International Nuclear Information System (INIS)

    Sales, Erika S.; Lima, Inaya C.B.; Lopes, Ricardo T.; Assis, Joaquim T. de

    2009-01-01

    Quantification of mineral density of bone samples is directly related to the attenuation coefficient of bone. The X-rays used in microtomography images are polychromatic and have a moderately broad spectrum of energy, which makes the low-energy X-rays passing through a sample to be absorbed, causing a decrease in the attenuation coefficient and possibly artifacts. This decrease in the attenuation coefficient is due to a process called beam hardening. In this work the beam hardening of microtomography images of vertebrae of Wistar rats subjected to a study of hyperthyroidism was corrected by the method of linearization of the projections. It was discretized using a spectrum in energy, also called the spectrum of Herman. The results without correction for beam hardening showed significant differences in bone volume, which could lead to a possible diagnosis of osteoporosis. But the data with correction showed a decrease in bone volume, but this decrease was not significant in a confidence interval of 95%. (author)

  2. Beam hardening correction algorithm in microtomography images

    Energy Technology Data Exchange (ETDEWEB)

    Sales, Erika S.; Lima, Inaya C.B.; Lopes, Ricardo T., E-mail: esales@con.ufrj.b, E-mail: ricardo@lin.ufrj.b [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Lab. de Instrumentacao Nuclear; Assis, Joaquim T. de, E-mail: joaquim@iprj.uerj.b [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Inst. Politecnico. Dept. de Engenharia Mecanica

    2009-07-01

    Quantification of mineral density of bone samples is directly related to the attenuation coefficient of bone. The X-rays used in microtomography images are polychromatic and have a moderately broad spectrum of energy, which makes the low-energy X-rays passing through a sample to be absorbed, causing a decrease in the attenuation coefficient and possibly artifacts. This decrease in the attenuation coefficient is due to a process called beam hardening. In this work the beam hardening of microtomography images of vertebrae of Wistar rats subjected to a study of hyperthyroidism was corrected by the method of linearization of the projections. It was discretized using a spectrum in energy, also called the spectrum of Herman. The results without correction for beam hardening showed significant differences in bone volume, which could lead to a possible diagnosis of osteoporosis. But the data with correction showed a decrease in bone volume, but this decrease was not significant in a confidence interval of 95%. (author)

  3. Segmentation-free empirical beam hardening correction for CT

    Energy Technology Data Exchange (ETDEWEB)

    Schüller, Sören; Sawall, Stefan [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich [Sirona Dental Systems GmbH, Fabrikstraße 31, 64625 Bensheim (Germany); Kachelrieß, Marc, E-mail: marc.kachelriess@dkfz.de [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

    2015-02-15

    Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the

  4. Segmentation-free empirical beam hardening correction for CT.

    Science.gov (United States)

    Schüller, Sören; Sawall, Stefan; Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich; Kachelrieß, Marc

    2015-02-01

    The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the proposed

  5. Beam-hardening correction in CT based on basis image and TV model

    International Nuclear Information System (INIS)

    Li Qingliang; Yan Bin; Li Lei; Sun Hongsheng; Zhang Feng

    2012-01-01

    In X-ray computed tomography, the beam hardening leads to artifacts and reduces the image quality. It analyzes how beam hardening influences on original projection. According, it puts forward a kind of new beam-hardening correction method based on the basis images and TV model. Firstly, according to physical characteristics of the beam hardening an preliminary correction model with adjustable parameters is set up. Secondly, using different parameters, original projections are operated by the correction model. Thirdly, the projections are reconstructed to obtain a series of basis images. Finally, the linear combination of basis images is the final reconstruction image. Here, with total variation for the final reconstruction image as the cost function, the linear combination coefficients for the basis images are determined according to iterative method. To verify the effectiveness of the proposed method, the experiments are carried out on real phantom and industrial part. The results show that the algorithm significantly inhibits cup and strip artifacts in CT image. (authors)

  6. A new approach for beam hardening correction based on the local spectrum distributions

    International Nuclear Information System (INIS)

    Rasoulpour, Naser; Kamali-Asl, Alireza; Hemmati, Hamidreza

    2015-01-01

    Energy dependence of material absorption and polychromatic nature of x-ray beams in the Computed Tomography (CT) causes a phenomenon which called “beam hardening”. The purpose of this study is to provide a novel approach for Beam Hardening (BH) correction. This approach is based on the linear attenuation coefficients of Local Spectrum Distributions (LSDs) in the various depths of a phantom. The proposed method includes two steps. Firstly, the hardened spectra in various depths of the phantom (or LSDs) are estimated based on the Expectation Maximization (EM) algorithm for arbitrary thickness interval of known materials in the phantom. The performance of LSD estimation technique is evaluated by applying random Gaussian noise to transmission data. Then, the linear attenuation coefficients with regarding to the mean energy of LSDs are obtained. Secondly, a correction function based on the calculated attenuation coefficients is derived in order to correct polychromatic raw data. Since a correction function has been used for the conversion of the polychromatic data to the monochromatic data, the effect of BH in proposed reconstruction must be reduced in comparison with polychromatic reconstruction. The proposed approach has been assessed in the phantoms which involve less than two materials, but the correction function has been extended for using in the constructed phantoms with more than two materials. The relative mean energy difference in the LSDs estimations based on the noise-free transmission data was less than 1.5%. Also, it shows an acceptable value when a random Gaussian noise is applied to the transmission data. The amount of cupping artifact in the proposed reconstruction method has been effectively reduced and proposed reconstruction profile is uniform more than polychromatic reconstruction profile. - Highlights: • A novel Beam Hardening (BH) correction approach was described. • A new concept named Local Spectrum Distributions (LSDs) was used to BH

  7. A new approach for beam hardening correction based on the local spectrum distributions

    Energy Technology Data Exchange (ETDEWEB)

    Rasoulpour, Naser; Kamali-Asl, Alireza, E-mail: a_kamali@sbu.ac.ir; Hemmati, Hamidreza

    2015-09-11

    Energy dependence of material absorption and polychromatic nature of x-ray beams in the Computed Tomography (CT) causes a phenomenon which called “beam hardening”. The purpose of this study is to provide a novel approach for Beam Hardening (BH) correction. This approach is based on the linear attenuation coefficients of Local Spectrum Distributions (LSDs) in the various depths of a phantom. The proposed method includes two steps. Firstly, the hardened spectra in various depths of the phantom (or LSDs) are estimated based on the Expectation Maximization (EM) algorithm for arbitrary thickness interval of known materials in the phantom. The performance of LSD estimation technique is evaluated by applying random Gaussian noise to transmission data. Then, the linear attenuation coefficients with regarding to the mean energy of LSDs are obtained. Secondly, a correction function based on the calculated attenuation coefficients is derived in order to correct polychromatic raw data. Since a correction function has been used for the conversion of the polychromatic data to the monochromatic data, the effect of BH in proposed reconstruction must be reduced in comparison with polychromatic reconstruction. The proposed approach has been assessed in the phantoms which involve less than two materials, but the correction function has been extended for using in the constructed phantoms with more than two materials. The relative mean energy difference in the LSDs estimations based on the noise-free transmission data was less than 1.5%. Also, it shows an acceptable value when a random Gaussian noise is applied to the transmission data. The amount of cupping artifact in the proposed reconstruction method has been effectively reduced and proposed reconstruction profile is uniform more than polychromatic reconstruction profile. - Highlights: • A novel Beam Hardening (BH) correction approach was described. • A new concept named Local Spectrum Distributions (LSDs) was used to BH

  8. X-ray beam hardening correction for measuring density in linear accelerator industrial computed tomography

    International Nuclear Information System (INIS)

    Zhou Rifeng; Wang Jue; Chen Weimin

    2009-01-01

    Due to X-ray attenuation being approximately proportional to material density, it is possible to measure the inner density through Industrial Computed Tomography (ICT) images accurately. In practice, however, a number of factors including the non-linear effects of beam hardening and diffuse scattered radiation complicate the quantitative measurement of density variations in materials. This paper is based on the linearization method of beam hardening correction, and uses polynomial fitting coefficient which is obtained by the curvature of iron polychromatic beam data to fit other materials. Through theoretical deduction, the paper proves that the density measure error is less than 2% if using pre-filters to make the spectrum of linear accelerator range mainly 0.3 MeV to 3 MeV. Experiment had been set up at an ICT system with a 9 MeV electron linear accelerator. The result is satisfactory. This technique makes the beam hardening correction easy and simple, and it is valuable for measuring the ICT density and making use of the CT images to recognize materials. (authors)

  9. Research of beam hardening correction method for CL system based on SART algorithm

    International Nuclear Information System (INIS)

    Cao Daquan; Wang Yaxiao; Que Jiemin; Sun Cuili; Wei Cunfeng; Wei Long

    2014-01-01

    Computed laminography (CL) is a non-destructive testing technique for large objects, especially for planar objects. Beam hardening artifacts were wildly observed in the CL system and significantly reduce the image quality. This study proposed a novel simultaneous algebraic reconstruction technique (SART) based beam hardening correction (BHC) method for the CL system, namely the SART-BHC algorithm in short. The SART-BHC algorithm took the polychromatic attenuation process in account to formulate the iterative reconstruction update. A novel projection matrix calculation method which was different from the conventional cone-beam or fan-beam geometry was also studied for the CL system. The proposed method was evaluated with simulation data and experimental data, which was generated using the Monte Carlo simulation toolkit Geant4 and a bench-top CL system, respectively. All projection data were reconstructed with SART-BHC algorithm and the standard filtered back projection (FBP) algorithm. The reconstructed images show that beam hardening artifacts are greatly reduced with the SART-BHC algorithm compared to the FBP algorithm. The SART-BHC algorithm doesn't need any prior know-ledge about the object or the X-ray spectrum and it can also mitigate the interlayer aliasing. (authors)

  10. Dynamic iterative beam hardening correction (DIBHC) in myocardial perfusion imaging using contrast-enhanced computed tomography.

    Science.gov (United States)

    Stenner, Philip; Schmidt, Bernhard; Allmendinger, Thomas; Flohr, Thomas; Kachelrie, Marc

    2010-06-01

    In cardiac perfusion examinations with computed tomography (CT) large concentrations of iodine in the ventricle and in the descending aorta cause beam hardening artifacts that can lead to incorrect perfusion parameters. The aim of this study is to reduce these artifacts by performing an iterative correction and by accounting for the 3 materials soft tissue, bone, and iodine. Beam hardening corrections are either implemented as simple precorrections which cannot account for higher order beam hardening effects, or as iterative approaches that are based on segmenting the original image into material distribution images. Conventional segmentation algorithms fail to clearly distinguish between iodine and bone. Our new algorithm, DIBHC, calculates the time-dependent iodine distribution by analyzing the voxel changes of a cardiac perfusion examination (typically N approximately 15 electrocardiogram-correlated scans distributed over a total scan time up to T approximately 30 s). These voxel dynamics are due to changes in contrast agent. This prior information allows to precisely distinguish between bone and iodine and is key to DIBHC where each iteration consists of a multimaterial (soft tissue, bone, iodine) polychromatic forward projection, a raw data comparison and a filtered backprojection. Simulations with a semi-anthropomorphic dynamic phantom and clinical scans using a dual source CT scanner with 2 x 128 slices, a tube voltage of 100 kV, a tube current of 180 mAs, and a rotation time of 0.28 seconds have been carried out. The uncorrected images suffer from beam hardening artifacts that appear as dark bands connecting large concentrations of iodine in the ventricle, aorta, and bony structures. The CT-values of the affected tissue are usually underestimated by roughly 20 HU although deviations of up to 61 HU have been observed. For a quantitative evaluation circular regions of interest have been analyzed. After application of DIBHC the mean values obtained deviate by

  11. 2D beam hardening correction for micro-CT of immersed hard tissue

    Science.gov (United States)

    Davis, Graham; Mills, David

    2016-10-01

    Beam hardening artefacts arise in tomography and microtomography with polychromatic sources. Typically, specimens appear to be less dense in the center of reconstructions because as the path length through the specimen increases, so the X-ray spectrum is shifted towards higher energies due to the preferential absorption of low energy photons. Various approaches have been taken to reduce or correct for these artefacts. Pre-filtering the X-ray beam with a thin metal sheet will reduce soft energy X-rays and thus narrow the spectrum. Correction curves can be applied to the projections prior to reconstruction which transform measured attenuation with polychromatic radiation to predicted attenuation with monochromatic radiation. These correction curves can be manually selected, iteratively derived from reconstructions (this generally works where density is assumed to be constant) or derived from a priori information about the X-ray spectrum and specimen composition. For hard tissue specimens, the latter approach works well if the composition is reasonably homogeneous. In the case of an immersed or embedded specimen (e.g., tooth or bone) the relative proportions of mineral and "organic" (including medium and plastic container) species varies considerably for different ray paths and simple beam hardening correction does not give accurate results. By performing an initial reconstruction, the total path length through the container can be determined. By modelling the X-ray properties of the specimen, a 2D correction transform can then be created such that the predicted monochromatic attenuation can be derived as a function of both the measured polychromatic attenuation and the container path length.

  12. MicroCT Bone Densitometry: Context Sensitivity, Beam Hardening Correction and the Effect of Surrounding Media

    Directory of Open Access Journals (Sweden)

    Philip L. Salmon

    2014-12-01

    Full Text Available The context-sensitivity of microCT bone densitometry due to beam hardening artefacts was assessed. Bones and teeth are scanned with varying thickness of surrounding media (water, alcohol, biological tissue and it is important to understand how this affects reconstructed attenuation (“density” of the mineralized tissue. Aluminium tubes and rods with thickness 0.127mm–5mm were scanned both in air or surrounded by up to 2cm of water. Scans were performed with different energy filters and degrees of software beam hardening correction (BHC. Also tested were the effects of signal-to-noise ratio, magnification and truncation. The thickness of an aluminium tube significantly affected its mean reconstructed attenuation. This effect of thickness could be reduced substantially by BHC for scans in air, but not for scans in water. Varying thickness of surrounding water also changed the mean attenuation of an aluminium tube. This artefact could be almost eliminated by an optimal BHC value. The “cupping” artefact of heterogeneous attenuation (elevated at outer surfaces could be corrected if aluminium was scanned in air, but in water BHC was much less effective. Scan truncation, changes to magnification and signal-to-noise ratio also caused artificial changes to measured attenuation. Measurement of bone mineral density by microCT is highly context sensitive. A surrounding layer of liquid or biological tissue reduces the ability of software BHC to remove bone density artefacts. Sample thickness, truncation, magnification and signal to noise ratio also affect reconstructed attenuation. Thus it is important for densitometry that sample and calibration phantom dimensions and mounting materials are standardised.

  13. Improving the accuracy of CT dimensional metrology by a novel beam hardening correction method

    International Nuclear Information System (INIS)

    Zhang, Xiang; Li, Lei; Zhang, Feng; Xi, Xiaoqi; Deng, Lin; Yan, Bin

    2015-01-01

    Its powerful nondestructive characteristics are attracting more and more research into the study of computed tomography (CT) for dimensional metrology, which offers a practical alternative to the common measurement methods. However, the inaccuracy and uncertainty severely limit the further utilization of CT for dimensional metrology due to many factors, among which the beam hardening (BH) effect plays a vital role. This paper mainly focuses on eliminating the influence of the BH effect in the accuracy of CT dimensional metrology. To correct the BH effect, a novel exponential correction model is proposed. The parameters of the model are determined by minimizing the gray entropy of the reconstructed volume. In order to maintain the consistency and contrast of the corrected volume, a punishment term is added to the cost function, enabling more accurate measurement results to be obtained by the simple global threshold method. The proposed method is efficient, and especially suited to the case where there is a large difference in gray value between material and background. Different spheres with known diameters are used to verify the accuracy of dimensional measurement. Both simulation and real experimental results demonstrate the improvement in measurement precision. Moreover, a more complex workpiece is also tested to show that the proposed method is of general feasibility. (paper)

  14. Precise material identification method based on a photon counting technique with correction of the beam hardening effect in X-ray spectra

    International Nuclear Information System (INIS)

    Kimoto, Natsumi; Hayashi, Hiroaki; Asahara, Takashi; Mihara, Yoshiki; Kanazawa, Yuki; Yamakawa, Tsutomu; Yamamoto, Shuichiro; Yamasaki, Masashi; Okada, Masahiro

    2017-01-01

    The aim of our study is to develop a novel material identification method based on a photon counting technique, in which the incident and penetrating X-ray spectra are analyzed. Dividing a 40 kV X-ray spectra into two energy regions, the corresponding linear attenuation coefficients are derived. We can identify the materials precisely using the relationship between atomic number and linear attenuation coefficient through the correction of the beam hardening effect of the X-ray spectra. - Highlights: • We propose a precise material identification method to be used as a photon counting system. • Beam hardening correction is important, even when the analysis is applied to the short energy regions in the X-ray spectrum. • Experiments using a single probe-type CdTe detector were performed, and Monte Carlo simulation was also carried out. • We described the applicability of our method for clinical diagnostic X-ray imaging in the near future.

  15. Electron beam hardened paint binder

    International Nuclear Information System (INIS)

    Johnson, O.B.; Labana, S.S.

    1976-01-01

    The invention concerns a paint binder hardened by the effect of electron beams (0.1-100 Mrad/sec). It consists of a dispersion of (A) an ethylenic unsaturated material in (B) at least one vinyl monomer. The component (A) in a reaction product of degraded rubber particles (0.1-4 μm) and an ethylenic unsaturated component with a reactive epoxy, hydroxy or carboxy group which is bonded to the rubber particles by ester or urethane compounds. The rubber particles possess a nucleus and a cross-linked elastomeric acryl polymer, an outer shell with reactive groups and an intermediate layer formed by the monomers of the nucleus and the shell. The manner of production is described in great detail and supplemented by 157 examples. The coatings are suitable to coat articles which will be subject to deformation. (UWI) [de

  16. A project of X-ray hardening correction in large ICT

    International Nuclear Information System (INIS)

    Fang Min; Liu Yinong; Ni Jianping

    2005-01-01

    This paper presents a means of polychromatic X-ray beam hardening correction using a standard function to transform the polychromatic projection to monochromatic projection in large Industrial Computed Tomography (ICT). Some parameters were defined to verify the validity of hardening correction in large ICT and optimized. Simulated experiments were used to prove that without prior knowledge of the composition of the scanned object, the correction method using monochromatic reconstruction arithmetic could remove beam hardening artifact greatly. (authors)

  17. Beam-hardening correction by a surface fitting and phase classification by a least square support vector machine approach for tomography images of geological samples

    Science.gov (United States)

    Khan, F.; Enzmann, F.; Kersten, M.

    2015-12-01

    In X-ray computed microtomography (μXCT) image processing is the most important operation prior to image analysis. Such processing mainly involves artefact reduction and image segmentation. We propose a new two-stage post-reconstruction procedure of an image of a geological rock core obtained by polychromatic cone-beam μXCT technology. In the first stage, the beam-hardening (BH) is removed applying a best-fit quadratic surface algorithm to a given image data set (reconstructed slice), which minimizes the BH offsets of the attenuation data points from that surface. The final BH-corrected image is extracted from the residual data, or the difference between the surface elevation values and the original grey-scale values. For the second stage, we propose using a least square support vector machine (a non-linear classifier algorithm) to segment the BH-corrected data as a pixel-based multi-classification task. A combination of the two approaches was used to classify a complex multi-mineral rock sample. The Matlab code for this approach is provided in the Appendix. A minor drawback is that the proposed segmentation algorithm may become computationally demanding in the case of a high dimensional training data set.

  18. Reduction of metal artifacts: beam hardening and photon starvation effects

    Science.gov (United States)

    Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

    2014-03-01

    The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

  19. Simulating the influence of scatter and beam hardening in dimensional computed tomography

    Science.gov (United States)

    Lifton, J. J.; Carmignato, S.

    2017-10-01

    Cone-beam x-ray computed tomography (XCT) is a radiographic scanning technique that allows the non-destructive dimensional measurement of an object’s internal and external features. XCT measurements are influenced by a number of different factors that are poorly understood. This work investigates how non-linear x-ray attenuation caused by beam hardening and scatter influences XCT-based dimensional measurements through the use of simulated data. For the measurement task considered, both scatter and beam hardening are found to influence dimensional measurements when evaluated using the ISO50 surface determination method. On the other hand, only beam hardening is found to influence dimensional measurements when evaluated using an advanced surface determination method. Based on the results presented, recommendations on the use of beam hardening and scatter correction for dimensional XCT are given.

  20. Simulation-aided investigation of beam hardening induced errors in CT dimensional metrology

    DEFF Research Database (Denmark)

    Tan, Ye; Kiekens, Kim; Welkenhuyzen, Frank

    2014-01-01

    are mutually correlated, it remains challenging to interpret measurement results and to identify the distinct error sources. Since simulations allow isolating the different affecting factors, they form a useful complement to experimental investigations. Dewulf et al (2012 CIRP Ann. Manuf. Technol. 61 495......–8) investigated the influence of beam hardening correction parameters on the diameter of a calibrated steel pin in different experimental set-ups. It was clearly shown that an inappropriate beam hardening correction can result in significant dimensional errors. This paper confirms these results using simulations...... of a pin surrounded by a stepped cylinder: a clear discontinuity in the measured diameter of the inner pin is observed where it enters the surrounding material. The results are expanded with an investigation of the beam hardening effect on the measurement results for both inner and outer diameters...

  1. The application and processing of paints hardened by electron beams

    International Nuclear Information System (INIS)

    Anon.

    1984-01-01

    Electron beam hardening is a process for changing liquid surface coatings of different thicknesses by irradiation with electrons of high energy into solid, hard, elastic films. In contrast to the UV process, one can harden pigmented paints with electron beams. An electron accelerator, which remits free electrons is used as the energy source for starting the chemical reaction in the coating material. In order to irradiate flat parts, which were coated with liquid paint by rolling, pouring or spraying, equally with electrons, one must produce an 'electron curtain', similar to that in a paint pouring machine. (orig./PW) [de

  2. Coating compositions hardenable by ionization beams

    International Nuclear Information System (INIS)

    Chaudhari, D.; Haering, E.; Dobbelstein, A.; Hoselmann, W.

    1976-01-01

    Coating compositions hardenable by ionizing radiation are described which contain as binding agents a mixture of at least 1 unsaturated olefin compound containing urethane groups, and at least 1 further unsaturated olefin compound that may be copolymerized. The unsaturated olefin compound containing the urethane groups is a reaction product of a compound containing carboxylic acid groups and a compound containing at least 1 isocyanate group where the mixture of the two olefins may contain conventional additives of the lacquer industry. 6 claims, no drawings

  3. Coating compositions hardenable by ionization beams

    International Nuclear Information System (INIS)

    Chaudhari, D.; Haering, E.; Dobbelstein, A.; Hoselmann, W.

    1976-01-01

    Coating compositions hardenable by ionizing radiation comprise as binding agents a mixture of A. at least 1 unsaturated olefin compound containing urethane groups, and B. at least 1 further unsaturated olefin compound that may be copolymerized. The unsaturated olefin compound A. containing the urethane groups in a reaction product of (a) a compound of the general formula (CHR 1 = CR 2 COOCH 2 CH(OH)CH 2 O CO-)/sub n/R where n is 1 or 2, where R stands for a straight chain or branched alkyl group of valence n, where R 1 is hydrogen, methyl; or the group -COOCH 2 CH(OH)CH 2 OCOR 3 - where R 3 is a monovalent alkyl residue and where R 2 is hydrogen or methyl, and (b) a compound containing at least 1 isocyanate group where the mixture of (A) and (B) may contain conventional additives of the lacquer industry. 6 claims

  4. Partial electron beam hardening of cast iron camshafts

    Energy Technology Data Exchange (ETDEWEB)

    Csizmazia, A.; Reti, T. [Szechenyi Istvan Univ., Gyoer (Hungary); Horvath, M.; Olah, I. [Audi Hungaria Motor Kft., Gyoer (Hungary)

    2005-07-01

    In order to improve the local surface properties (hardness, wear and contact fatigue resistance) of cast iron camshafts, detailed experiments with partial electron beam hardening have been performed. It was found that the required case depth of 0.3-0.5 mm and surface hardness of 600-700 HV can be achieved by using appropriately selected, computer-controlled processing parameters (angular speed, specific energy input, beam deflection). (orig.)

  5. A simulation-based study on the influence of beam hardening in X-ray computed tomography for dimensional metrology.

    Science.gov (United States)

    Lifton, Joseph J; Malcolm, Andrew A; McBride, John W

    2015-01-01

    X-ray computed tomography (CT) is a radiographic scanning technique for visualising cross-sectional images of an object non-destructively. From these cross-sectional images it is possible to evaluate internal dimensional features of a workpiece which may otherwise be inaccessible to tactile and optical instruments. Beam hardening is a physical process that degrades the quality of CT images and has previously been suggested to influence dimensional measurements. Using a validated simulation tool, the influence of spectrum pre-filtration and beam hardening correction are evaluated for internal and external dimensional measurements. Beam hardening is shown to influence internal and external dimensions in opposition, and to have a greater influence on outer dimensions compared to inner dimensions. The results suggest the combination of spectrum pre-filtration and a local gradient-based surface determination method are able to greatly reduce the influence of beam hardening in X-ray CT for dimensional metrology.

  6. An energy-based beam hardening model in tomography

    International Nuclear Information System (INIS)

    Casteele, E van de; Dyck, D van; Sijbers, J; Raman, E

    2002-01-01

    As a consequence of the polychromatic x-ray source, used in micro-computer tomography (μCT) and in medical CT, the attenuation is no longer a linear function of absorber thickness. If this nonlinear beam hardening effect is not compensated, the reconstructed images will be corrupted by cupping artefacts. In this paper, a bimodal energy model for the detected energy spectrum is presented, which can be used for reduction of artefacts caused by beam hardening in well-specified conditions. Based on the combination of the spectrum of the source and the detector efficiency, the assumption is made that there are two dominant energies which can describe the system. The validity of the proposed model is examined by fitting the model to the experimental datapoints obtained on a microtomograph for different materials and source voltages

  7. Electron beam hardening type copper plate printing ink

    International Nuclear Information System (INIS)

    Kawamura, Eiji; Inoue, Mitsuo; Kusaki, Satoichiro

    1989-01-01

    Copper plate printing is the printing method of filling ink in the parts of concave printing elements on a type area, and transferring the ink to a base, and it is the feature that the ink in the printing element parts of a print rises. Copper plate prints show profound feeling, in addition, its effect of preventing forgery is high. This method is generally called engraving printing, and is used frequently for printing various bills and artistic prints. The electron beam irradiation apparatus installed in the laboratory of the Printing Bureau, Ministry of Finance, is an experimental machine of area beam type, and is so constructed as to do batch conveyance and web conveyance. As the ink in printing element parts rises, the offset at the delivery part of a printing machine becomes a problem. Electron beam is superior in its transparency, and can dry instantaneously to the inside of opaque ink. At 200 kV of acceleration voltage, the ink of copper plate prints can be hardened by electron beam irradiation. The dilution monomers as the vehicle for ink were tested for their dilution capability and the effect of electron beam hardening. The problem in the utilization of electron beam is the deterioration of papers, and the counter-measures were tested. (K.I.)

  8. An experimental study on the influence of scatter and beam hardening in x-ray CT for dimensional metrology

    International Nuclear Information System (INIS)

    Lifton, J J; McBride, J W; Malcolm, A A

    2016-01-01

    Scattered radiation and beam hardening introduce artefacts that degrade the quality of data in x-ray computed tomography (CT). It is unclear how these artefacts influence dimensional measurements evaluated from CT data. Understanding and quantifying the influence of these artefacts on dimensional measurements is required to evaluate the uncertainty of CT-based dimensional measurements. In this work the influence of scatter and beam hardening on dimensional measurements is investigated using the beam stop array scatter correction method and spectrum pre-filtration for the measurement of an object with internal and external cylindrical dimensional features. Scatter and beam hardening are found to influence dimensional measurements when evaluated using the ISO50 surface determination method. On the other hand, a gradient-based surface determination method is found to be robust to the influence of artefacts and leads to more accurate dimensional measurements than those evaluated using the ISO50 method. In addition to these observations the GUM method for evaluating standard measurement uncertainties is applied and the standard measurement uncertainty due to scatter and beam hardening is estimated. (paper)

  9. Beam Hardening Artifacts: Comparison between Two Cone Beam Computed Tomography Scanners

    Directory of Open Access Journals (Sweden)

    Farzad Esmaeili

    2012-04-01

    Full Text Available Background and aims. At present, cone beam computed tomography (CBCT has become a substitute for computed tomography (CT in dental procedures. The metallic materials used in dentistry can produce artifacts due to the beam hardening phenomenon. These artifacts decrease the quality of images. In the present study, the number of artifacts as a result of beam hardening in the images of dental implants was compared between two NewTom VG and Planmeca Promax 3D Max CBCT machines. Materials and methods. An implant drilling model was used in the present study. The implants (Dentis were placed in the canine, premolar and molar areas. Scanning procedures were carried out by two CBCT machines. The corresponding sections (coronal and axial of the implants were evaluated by two radiologists. The number of artifacts in each image was determined using the scale provided. Mann-Whitney U test was used for two-by-two comparisons at a significance level of P<0.05. Results. There were statistically significant differences in beam hardening artifacts in axial and coronal sections between the two x-ray machines (P<0.001, with a higher quality in the images produced by the NewTom VG. Conclusion. Given the higher quality of the images produced by the NewTom VG x-ray machine, it is recommended for imaging of patients with extensive restorations, multiple prostheses or previous implant treatments.

  10. Reducing beam hardening effects and metal artefacts using Medipix3RX: With applications from biomaterial science

    CERN Document Server

    Rajendran, K; de Ruiter, N J A; Chernoglazov, A I; Panta, R K; Butler, A P H; Butler, P H; Bell, S T; Anderson, N G; Woodfield, T B F; Tredinnick, S J; Healy, J L; Bateman, C J; Aamir, R; Doesburg, R M N; Renaud, P F; Gieseg, S P; Smithies, D J; Mohr, J L; Mandalika, V B H; Opie, A M T; Cook, N J; Ronaldson, J P; Nik, S J; Atharifard, A; Clyne, M; Bones, P J; Bartneck, C; Grasset, R; Schleich, N; Billinghurst, M

    2014-01-01

    This paper discusses methods for reducing beam hardening effects using spectral data for biomaterial applications. A small-animal spectral scanner operating in the diagnostic energy range was used. We investigate the use of photon-processing features of the Medipix3RX ASIC in reducing beam hardening and associated artefacts. A fully operational charge summing mode was used during the imaging routine. We present spectral data collected for metal alloy samples, its analysis using algebraic 3D reconstruction software and volume visualisation using a custom volume rendering software. Narrow high energy acquisition using the photon-processing detector revealed substantial reduction in beam hardening effects and metal artefacts.

  11. Reducing beam hardening effects and metal artefacts using Medipix3RX: With applications from biomaterial science

    OpenAIRE

    Rajendran, K.; Walsh, M. F.; de Ruiter, N. J. A.; Chernoglazov, A. I.; Panta, R. K.; Butler, A. P. H.; Butler, P. H.; Bell, S. T.; Anderson, N. G.; Woodfield, T. B. F.; Tredinnick, S. J.; Healy, J. L.; Bateman, C. J.; Aamir, R.; Doesburg, R. M. N.

    2013-01-01

    This paper discusses methods for reducing beam hardening effects using spectral data for biomaterial applications. A small-animal spectral scanner operating in the diagnostic energy range was used. We investigate the use of photon-processing features of the Medipix3RX ASIC in reducing beam hardening and associated artefacts. A fully operational charge summing mode was used during the imaging routine. We present spectral data collected for metal alloy samples, its analysis using algebraic 3D r...

  12. Quantitative analysis of CT brain images: a statistical model incorporating partial volume and beam hardening effects

    International Nuclear Information System (INIS)

    McLoughlin, R.F.; Ryan, M.V.; Heuston, P.M.; McCoy, C.T.; Masterson, J.B.

    1992-01-01

    The purpose of this study was to construct and evaluate a statistical model for the quantitative analysis of computed tomographic brain images. Data were derived from standard sections in 34 normal studies. A model representing the intercranial pure tissue and partial volume areas, with allowance for beam hardening, was developed. The average percentage error in estimation of areas, derived from phantom tests using the model, was 28.47%. We conclude that our model is not sufficiently accurate to be of clinical use, even though allowance was made for partial volume and beam hardening effects. (author)

  13. A method for hardening or curing adhesives for flocking thermally sensitive substrata by means of an electron-beam

    International Nuclear Information System (INIS)

    Nablo, S.V.; Fussa, A.D.

    1975-01-01

    The invention relates to a method for hardening or curing adhesives for flocking thermally sensitive substrata by means of an electron-beam. That method consists in accurately adjusting the parameters of irradiation by an electron-beam and the beam velocity so as to obtain, a very rapid hardening of adhesives used for fixing flocking materials, or the like, to thermally sensitive substrate. That can be applied to hardening or curing adhesives for flocking thermally-sensitive substrata which normally restrict the hardening rate [fr

  14. Surface hardening of 30CrMnSiA steel using continuous electron beam

    Science.gov (United States)

    Fu, Yulei; Hu, Jing; Shen, Xianfeng; Wang, Yingying; Zhao, Wansheng

    2017-11-01

    30CrMnSiA high strength low alloy (HSLA) carbon structural steel is typically applied in equipment manufacturing and aerospace industries. In this work, the effects of continuous electron beam treatment on the surface hardening and microstructure modifications of 30CrMnSiA are investigated experimentally via a multi-purpose electron beam machine Pro-beam system. Micro hardness value in the electron beam treated area shows a double to triple increase, from 208 HV0.2 on the base metal to 520 HV0.2 on the irradiated area, while the surface roughness is relatively unchanged. Surface hardening parameters and mechanisms are clarified by investigation of the microstructural modification and the phase transformation both pre and post irradiation. The base metal is composed of ferrite and troostite. After continuous electron beam irradiation, the micro structure of the electron beam hardened area is composed of acicular lower bainite, feathered upper bainite and part of lath martensite. The optimal input energy density for 30CrMnSiA steel in this study is of 2.5 kJ/cm2 to attain the proper hardened depth and peak hardness without the surface quality deterioration. When the input irradiation energy exceeds 2.5 kJ/cm2 the convective mixing of the melted zone will become dominant. In the area with convective mixing, the cooling rate is relatively lower, thus the micro hardness is lower. The surface quality will deteriorate. Chemical composition and surface roughness pre and post electron beam treatment are also compared. The technology discussed give a picture of the potential of electron beam surface treatment for improving service life and reliability of the 30CrMnSiA steel.

  15. Progress report on the neutral beam radiation hardening study

    International Nuclear Information System (INIS)

    Lee, J.D.; Condit, R.H.; Hoenig, C.L.; Wilcox, T.P.; Erickson, J.

    1978-01-01

    A neutral beam injector as presently conceived directly views the plasma it is sustaining. In turn the injector is exposed to the primary fusion neutrons plus secondary neutrons and gammas streaming back up the neutral beam duct. The intent of this work is to examine representative beam lines to see how performance and lifetimes could be affected by this radiation environment and to determine how unacceptable effects could be alleviated. Potential radiation induced problems addressed in this report have been limited to: (1) overheating of cryopanels and insulators, (2) gamma flux induced electrical conductivity increase of insulators, and (3) neutron and gamma fluence induced damage to insulator materials

  16. Quality correction factors of composite IMRT beam deliveries: Theoretical considerations

    International Nuclear Information System (INIS)

    Bouchard, Hugo

    2012-01-01

    Purpose: In the scope of intensity modulated radiation therapy (IMRT) dosimetry using ionization chambers, quality correction factors of plan-class-specific reference (PCSR) fields are theoretically investigated. The symmetry of the problem is studied to provide recommendable criteria for composite beam deliveries where correction factors are minimal and also to establish a theoretical limit for PCSR delivery k Q factors. Methods: The concept of virtual symmetric collapsed (VSC) beam, being associated to a given modulated composite delivery, is defined in the scope of this investigation. Under symmetrical measurement conditions, any composite delivery has the property of having a k Q factor identical to its associated VSC beam. Using this concept of VSC, a fundamental property of IMRT k Q factors is demonstrated in the form of a theorem. The sensitivity to the conditions required by the theorem is thoroughly examined. Results: The theorem states that if a composite modulated beam delivery produces a uniform dose distribution in a volume V cyl which is symmetric with the cylindrical delivery and all beams fulfills two conditions in V cyl : (1) the dose modulation function is unchanged along the beam axis, and (2) the dose gradient in the beam direction is constant for a given lateral position; then its associated VSC beam produces no lateral dose gradient in V cyl , no matter what beam modulation or gantry angles are being used. The examination of the conditions required by the theorem lead to the following results. The effect of the depth-dose gradient not being perfectly constant with depth on the VSC beam lateral dose gradient is found negligible. The effect of the dose modulation function being degraded with depth on the VSC beam lateral dose gradient is found to be only related to scatter and beam hardening, as the theorem holds also for diverging beams. Conclusions: The use of the symmetry of the problem in the present paper leads to a valuable theorem showing

  17. Blind beam-hardening correction from Poisson measurements

    Science.gov (United States)

    Gu, Renliang; Dogandžić, Aleksandar

    2016-02-01

    We develop a sparse image reconstruction method for Poisson-distributed polychromatic X-ray computed tomography (CT) measurements under the blind scenario where the material of the inspected object and the incident energy spectrum are unknown. We employ our mass-attenuation spectrum parameterization of the noiseless measurements and express the mass- attenuation spectrum as a linear combination of B-spline basis functions of order one. A block coordinate-descent algorithm is developed for constrained minimization of a penalized Poisson negative log-likelihood (NLL) cost function, where constraints and penalty terms ensure nonnegativity of the spline coefficients and nonnegativity and sparsity of the density map image; the image sparsity is imposed using a convex total-variation (TV) norm penalty term. This algorithm alternates between a Nesterov's proximal-gradient (NPG) step for estimating the density map image and a limited-memory Broyden-Fletcher-Goldfarb-Shanno with box constraints (L-BFGS-B) step for estimating the incident-spectrum parameters. To accelerate convergence of the density- map NPG steps, we apply function restart and a step-size selection scheme that accounts for varying local Lipschitz constants of the Poisson NLL. Real X-ray CT reconstruction examples demonstrate the performance of the proposed scheme.

  18. Development of a wood-polymer composite by electron beam hardening

    International Nuclear Information System (INIS)

    Gotoda, Masao

    1974-01-01

    An incombustible wood-polymer composite (WPC) was studied. The dimensional stability was also tested. The comparison of conversion ratio was made between gamma-ray and electron beam and between a vinylidene chloride 100% impregnated beech composite and bulk. In the case of gamma-ray of low dose rate, the conversion ratio in the vinylidene chloride beech composite was lower than the bulk. In the case of electron beam, though dose rate was higher than that of gamma-ray, the conversion ratio was low, and was influenced by the moisture content of wood. The conversion ratio markedly decreased with the increase of the dose rate of electron beam. Roughly 50% polymer loading can be obtained when the dose rate of electron beam is low. In the case of gamma-ray, the effect of dimensional stability was approximately none with small polymer loading, whereas in the case of electron beam irradiation of moist wood, marked effect of dimensional stability was shown. Incombustibility effect was tested by burning a 150 mm long piece, in which three small pieces of 5 x 10 x 50 mm were connected with epoxy resin adhesive, with a Bunsen burner for 30 seconds. After the completion of burning, the long piece was separated back into three small pieces, and the char length, weight loss and after glow time were tested. The beech composite was expected to become incombustible at 40% polymer loading. The vinyl monomer solution of chlorinated aryl chloride oligomer can be easily hardened by electron beam irradiation. Addition of crosslinking agent such as trimethylol propane trimethracrylate prevents the dissolution of hardened methyl acrylate and methyl methacrylate by acetone. The electron beam hardening of aryl resin compound is possible, using benzen peroxide as a catalyst. Floor material can be produced by this process from low density, low price wood. (Iwakiri, K.)

  19. Efficient, radiation-hardened, 800-keV neutral beam injection system

    International Nuclear Information System (INIS)

    Anderson, O.A.; Cooper, W.S.; Goldberg, D.A.; Ruby, L.; Soroka, L.; Fink, J.H.

    1982-10-01

    Recent advances and new concepts in negative ion generation, transport, acceleration, and neutrailzation make it appear likely that an efficient, radiation-hardened neutral beam injection system could be developed in time for the proposed FED-A tokamak. These new developments include the operation of steady-state H - ion sources at over 5 A per meter of source length, the concept of using strong-focussing electrostatic structures for low-gradient dc acceleration of high-current sheet beams of negative ions and the transport of these beams around corners, and the development of powerful oxygen-iodine chemical lasers which will make possible the efficient conversion of the negative ions to neutrals using a photodetachment scheme in which the ion beam passes through the laser cavity

  20. Beam hardening: Analytical considerations of the effective attenuation coefficient of x-ray tomography

    International Nuclear Information System (INIS)

    Alles, J.; Mudde, R. F.

    2007-01-01

    Polychromatic x-ray beams traveling though material are prone to beam hardening, i.e., the high energy part of the incident spectrum gets over represented when traveling farther into the material. This study discusses the concept of a mean attenuation coefficient in a formal way. The total energy fluence is one-to-one related to the traveled distance in case of a polychromatic beam moving through a given, inhomogeneous material. On the basis of this one-to-one relation, it is useful to define a mean attenuation coefficient and study its decrease with depth. Our results are based on a novel parametrization of the energy dependence of the attenuation coefficient that allows for closed form evaluation of certain spectral integrals. This approach underpins the ad hoc semianalytical expressions given in the literature. An analytical model for the average attenuation coefficient is proposed that uses a simple fit of the attenuation coefficient as a function of the photon energy as input. It is shown that a simple extension of this model gives a rather good description of beam hardening for x-rays traveling through water

  1. An index of beam hardening artifact for two-dimensional cone-beam CT tomographic images: establishment and preliminary evaluation

    Science.gov (United States)

    Yuan, Fusong; Lv, Peijun; Yang, Huifang; Wang, Yong; Sun, Yuchun

    2015-07-01

    Objectives: Based on the pixel gray value measurements, establish a beam-hardening artifacts index of the cone-beam CT tomographic image, and preliminarily evaluate its applicability. Methods: The 5mm-diameter metal ball and resin ball were fixed on the light-cured resin base plate respectively, while four vitro molars were fixed above and below the ball, on the left and right respectively, which have 10mm distance with the metal ball. Then, cone beam CT was used to scan the fixed base plate twice. The same layer tomographic images were selected from the two data and imported into the Photoshop software. The circle boundary was built through the determination of the center and radius of the circle, according to the artifact-free images section. Grayscale measurement tools were used to measure the internal boundary gray value G0, gray value G1 and G2 of 1mm and 20mm artifacts outside the circular boundary, the length L1 of the arc with artifacts in the circular boundary, the circumference L2. Hardening artifacts index was set A = (G1 / G0) * 0.5 + (G2 / G1) * 0.4 + (L2 / L1) * 0.1. Then, the A values of metal and resin materials were calculated respectively. Results: The A value of cobalt-chromium alloy material is 1, and resin material is 0. Conclusion: The A value reflects comprehensively the three factors of hardening artifacts influencing normal oral tissue image sharpness of cone beam CT. The three factors include relative gray value, the decay rate and range of artifacts.

  2. Application and processing of paints hardened by electron beams. Anwendung und Verarbeitung von EB-haertenden Lacken

    Energy Technology Data Exchange (ETDEWEB)

    1984-01-01

    Electron beam hardening is a process for changing liquid surface coatings of different thicknesses by irradiation with electrons of high energy into solid, hard, elastic films. In contrast to the UV process, one can harden pigmented paints with electron beams. An electron accelerator, which remits free electrons is used as the energy source for starting the chemical reaction in the coating material. In order to irradiate flat parts, which were coated with liquid paint by rolling, pouring or spraying, equally with electrons, one must produce an electron curtain, similar to that in a paint pouring machine.

  3. Process for hardening an alkyd resin composition using ionizing radiation. [electron beams, gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, T; Murata, K; Maruyama, T

    1969-11-27

    In an alkyd resin composition having free hydroxide radicals and containing a conjugated unsaturated fatty acid and/or oil as a component thereof, a process for hardening an alkyd resin composition comprises the steps of dissolving into a vinyl monomer, the product obtained by the semi-esterification reaction of said hydroxide radicals with acid anhydrides having polymerizable radicals and hardening by ionizing radiation to provide a coating with a high degree of cross-linking, with favorable properties such as toughness, hardness, chemical resistance and resistance to weather and with the feasibility of being applied as the ground and finish coat on metals, wood, paper, outdoor construction or the like. Any kind of ionization radiation, particularly accelerated electron beams, ..gamma.. radiation can be used at 50/sup 0/C to -5/sup 0/C for a few seconds or minutes, permitting continuous operation. In one example, 384 parts of phthalic anhydride, 115 parts of pentaerythritol, 233 parts of trimethylol ethane, 288 parts of tung fatty acid and 49 parts of para-tertiary-butyl benzoic acid are mixed and heated with 60 parts of xylene to an acid value of 12. In addition, 271 parts of maleic anhydride and 0.6 parts of hydroquinone are admixed with the content and heated to terminate the reaction. 100 parts of a 50% stylene solution of this alkyd resin are mixed with 1 part of a 60% toluene solution of cobalt naphthenate, and then coated on a glass plate and irradiated with high energy electron beams of 300 kV with a dose of 5 Mrad for 1 sec.

  4. MATLAB based beam orbit correction system of HLS storage ring

    International Nuclear Information System (INIS)

    Ding Shichuan; Liu Gongfa; Xuan Ke; Li Weimin; Wang Lin; Wang Jigang; Li Chuan; Bao Xun; Guo Weiqun

    2006-01-01

    The distortion of closed orbit usually causes much side effect which is harmful to synchrotron radiation source such as HLS, so it is necessary to correct the distortion of closed orbit. In this paper, the correction principle, development procedure and test of MATLAB based on beam orbit correction system of HLS storage ring are described. The correction system is consisted of the beam orbit measure system, corrector magnet system and the control system, and the beam orbit correction code based on MATLAB is working on the operation interface. The data of the beam orbit are analyzed and calculated firstly, and then the orbit is corrected by changing corrector strength via control system. The test shows that the distortion of closed orbit is from max 4.468 mm before correction to max 0.299 mm after correction as well as SDEV is from 2.986 mm to 0.087 mm. So the correction system reaches the design goal. (authors)

  5. Edge effect correction using ion beam figuring.

    Science.gov (United States)

    Yang, Bing; Xie, Xuhui; Li, Furen; Zhou, Lin

    2017-11-10

    The edge effect is regarded as one of the most difficult technical issues for fabricating large primary mirrors, as it can greatly reduce the key performance of the optical system. Ion beam figuring (IBF) has the advantage of no edge effect, so we can use it to remove high points on the edge and improve surface accuracy. The edge local correction method (ELCM) of IBF processes only the surface edge zone, and is very different from the current full caliber figuring method (FCFM). Therefore, it is necessary to study the ELCM of IBF. In this paper, the key factors of ELCM are analyzed, such as dwell time algorithm, edge data extension methods, and the outward dimension of the starting figuring point. At the same time, the distinctions between ELCM and FCFM are compared. Finally, a 142 mm diameter fused silica mirror is fabricated to verify the validity of the theoretical of ELCM. The experimental results indicate that the figuring precision and efficiency can be obviously improved by ELCM.

  6. TU-H-207A-03: CT Hounsfield Unit Accuracy: Effect of Beam Hardening On Phantom and Clinical Whole-Body CT Images

    Energy Technology Data Exchange (ETDEWEB)

    Ai, H; Wendt, R [The University of Texas MD Anderson Cancer Center, Houston, TX (United States)

    2016-06-15

    Purpose: To assess the effect of beam hardening on measured CT HU values. Methods: An anthropomorphic knee phantom was scanned with the CT component of a GE Discovery 690 PET/CT scanner (120kVp, 300mAs, 40?0.625mm collimation, pitch=0.984, FOV=500mm, matrix=512?512) with four different scan setups, each of which induces different degrees of beam hardening by introducing additional attenuation media into the field of view. Homogeneous voxels representing “soft tissue” and “bone” were segmented by HU thresholding followed by a 3D morphological erosion operation which removes the non-homogenous voxels located on the interface of thresholded tissue mask. HU values of segmented “soft tissue” and “bone” were compared.Additionally, whole-body CT data with coverage from the skull apex to the end of toes were retrospectively retrieved from seven PET/CT exams to evaluate the effect of beam hardening in vivo. Homogeneous bone voxels were segmented with the same method previously described. Total In-Slice Attenuation (TISA) for each CT slice, defined as the summation of HU values over all voxels within a CT slice, was calculated for all slices of the seven whole-body CT datasets and evaluated against the mean HU values of homogeneous bone voxels within that slice. Results: HU values measured from the phantom showed that while “soft tissue” HU values were unaffected, added attenuation within the FOV caused noticeable decreases in the measured HU values of “bone” voxels. A linear relationship was observed between bone HU and TISA for slices of the torso and legs, but not of the skull. Conclusion: Beam hardening effect is not an issue of concern for voxels with HU in the soft tissue range, but should not be neglected for bone voxels. A linear relationship exists between bone HU and the associated TISA in non-skull CT slices, which can be exploited to develop a correction strategy.

  7. Optimizing contrast agents with respect to reducing beam hardening in nonmedical X-ray computed tomography experiments.

    Science.gov (United States)

    Nakashima, Yoshito; Nakano, Tsukasa

    2014-01-01

    Iodine is commonly used as a contrast agent in nonmedical science and engineering, for example, to visualize Darcy flow in porous geological media using X-ray computed tomography (CT). Undesirable beam hardening artifacts occur when a polychromatic X-ray source is used, which makes the quantitative analysis of CT images difficult. To optimize the chemistry of a contrast agent in terms of the beam hardening reduction, we performed computer simulations and generated synthetic CT images of a homogeneous cylindrical sand-pack (diameter, 28 or 56 mm; porosity, 39 vol.% saturated with aqueous suspensions of heavy elements assuming the use of a polychromatic medical CT scanner. The degree of cupping derived from the beam hardening was assessed using the reconstructed CT images to find the chemistry of the suspension that induced the least cupping. The results showed that (i) the degree of cupping depended on the position of the K absorption edge of the heavy element relative to peak of the polychromatic incident X-ray spectrum, (ii) (53)I was not an ideal contrast agent because it causes marked cupping, and (iii) a single element much heavier than (53)I ((64)Gd to (79)Au) reduced the cupping artifact significantly, and a four-heavy-element mixture of elements from (64)Gd to (79)Au reduced the artifact most significantly.

  8. High-fidelity artifact correction for cone-beam CT imaging of the brain

    Science.gov (United States)

    Sisniega, A.; Zbijewski, W.; Xu, J.; Dang, H.; Stayman, J. W.; Yorkston, J.; Aygun, N.; Koliatsos, V.; Siewerdsen, J. H.

    2015-02-01

    CT is the frontline imaging modality for diagnosis of acute traumatic brain injury (TBI), involving the detection of fresh blood in the brain (contrast of 30-50 HU, detail size down to 1 mm) in a non-contrast-enhanced exam. A dedicated point-of-care imaging system based on cone-beam CT (CBCT) could benefit early detection of TBI and improve direction to appropriate therapy. However, flat-panel detector (FPD) CBCT is challenged by artifacts that degrade contrast resolution and limit application in soft-tissue imaging. We present and evaluate a fairly comprehensive framework for artifact correction to enable soft-tissue brain imaging with FPD CBCT. The framework includes a fast Monte Carlo (MC)-based scatter estimation method complemented by corrections for detector lag, veiling glare, and beam hardening. The fast MC scatter estimation combines GPU acceleration, variance reduction, and simulation with a low number of photon histories and reduced number of projection angles (sparse MC) augmented by kernel de-noising to yield a runtime of ~4 min per scan. Scatter correction is combined with two-pass beam hardening correction. Detector lag correction is based on temporal deconvolution of the measured lag response function. The effects of detector veiling glare are reduced by deconvolution of the glare response function representing the long range tails of the detector point-spread function. The performance of the correction framework is quantified in experiments using a realistic head phantom on a testbench for FPD CBCT. Uncorrected reconstructions were non-diagnostic for soft-tissue imaging tasks in the brain. After processing with the artifact correction framework, image uniformity was substantially improved, and artifacts were reduced to a level that enabled visualization of ~3 mm simulated bleeds throughout the brain. Non-uniformity (cupping) was reduced by a factor of 5, and contrast of simulated bleeds was improved from ~7 to 49.7 HU, in good agreement

  9. Effect of beam hardening on transmural myocardial perfusion quantification in myocardial CT imaging

    Science.gov (United States)

    Fahmi, Rachid; Eck, Brendan L.; Levi, Jacob; Fares, Anas; Wu, Hao; Vembar, Mani; Dhanantwari, Amar; Bezerra, Hiram G.; Wilson, David L.

    2016-03-01

    The detection of subendocardial ischemia exhibiting an abnormal transmural perfusion gradient (TPG) may help identify ischemic conditions due to micro-vascular dysfunction. We evaluated the effect of beam hardening (BH) artifacts on TPG quantification using myocardial CT perfusion (CTP). We used a prototype spectral detector CT scanner (Philips Healthcare) to acquire dynamic myocardial CTP scans in a porcine ischemia model with partial occlusion of the left anterior descending (LAD) coronary artery guided by pressure wire-derived fractional flow reserve (FFR) measurements. Conventional 120 kVp and 70 keV projection-based mono-energetic images were reconstructed from the same projection data and used to compute myocardial blood flow (MBF) using the Johnson-Wilson model. Under moderate LAD occlusion (FFR~0.7), we used three 5 mm short axis slices and divided the myocardium into three LAD segments and three remote segments. For each slice and each segment, we characterized TPG as the mean "endo-to-epi" transmural flow ratio (TFR). BH-induced hypoenhancement on the ischemic anterior wall at 120 kVp resulted in significantly lower mean TFR value as compared to the 70 keV TFR value (0.29+/-0.01 vs. 0.55+/-0.01 pvalues on segments moderately affected or unaffected by BH. In the entire ischemic LAD territory, 120 kVp mean endocardial flow was significantly reduced as compared to mean epicardial flow (15.80+/-10.98 vs. 40.85+/-23.44 ml/min/100g; p<1e-04). At 70 keV, BH was effectively minimized resulting in mean endocardial MBF of 40.85+/-15.3407 ml/min/100g vs. 74.09+/-5.07 ml/min/100g (p=0.0054) in the epicardium. We also found that BH artifact in the conventional 120 kVp images resulted in falsely reduced MBF measurements even under non-ischemic conditions.

  10. Implementation of Highly-Flowable Strain Hardening Fiber Reinforced Concrete in New RC Beam-Column Joints

    Directory of Open Access Journals (Sweden)

    Liao Wen-Cheng

    2018-01-01

    Full Text Available The purpose of New RC project was aimed to reduce the member sections and increase the available space of high rise buildings by using high strength concrete (f’c > 70 MPa and high strength rebars (fy > 685 MPa. Material consumptions and member section sizes can be further reduced owing to the upgrade of strength. However, the nature of brittleness of high strength may also cause early cover spalling and other ductility issues. Addition of steel fibers is an alternative as transverse reinforcement. Highly flowable strain hardening fiber reinforced concrete (HF-SHFRC has excellent workability in the fresh state and exhibits the strain-hardening and multiple cracking characteristics of high performance fiber reinforced cementitious composites (HPFRCC in their hardened state. The objective of this study is to investigate the feasibility of implementing HF-SHFRC in New RC building systems, particularly for beam-column joints as an alternative of transverse reinforcements. Four full-scale exterior beam-column joints, including two specimens with intensive transverse reinforcements and two specimens made of HF-SHFRC without any stirrup, are tested. Test results show that the HF-SHFRC specimens perform as well as specimens with intensive transverse reinforcements regarding failure mode, ductility, energy dissipation and crack width control. Integration of New RC building systems and HF-SHFRC can assuring construction qualities and further diminish labor work and give infrastructure longer service life, and eventually lower the life-cycle cost.

  11. Geometrical E-beam proximity correction for raster scan systems

    Science.gov (United States)

    Belic, Nikola; Eisenmann, Hans; Hartmann, Hans; Waas, Thomas

    1999-04-01

    High pattern fidelity is a basic requirement for the generation of masks containing sub micro structures and for direct writing. Increasing needs mainly emerging from OPC at mask level and x-ray lithography require a correction of the e-beam proximity effect. The most part of e-beam writers are raster scan system. This paper describes a new method for geometrical pattern correction in order to provide a correction solution for e-beam system that are not able to apply variable doses.

  12. Structure and properties of steel case-hardened by non-vacuum electron-beam cladding of carbon fibers

    Science.gov (United States)

    Losinskaya, A. A.; Lozhkina, E. A.; Bardin, A. I.

    2017-12-01

    At the present time, the actual problem of materials science is the increase in the steels performance characteristics. In the paper some mechanical properties of the case-hardened materials received by non-vacuum electron-beam cladding of carbon fibers are determined. The depth of the hardened layers varies from 1.5 to 3 mm. The impact strength of the samples exceeds 50 J/cm2. The wear resistance of the coatings obtained exceeds the properties of steel 20 after cementation and quenching with low tempering. The results of a study of the microhardness of the resulting layers and the microstructure are also given. The hardness of the surface layers exceeds 5700 MPa.

  13. Beam hardening artifacts by dental implants: Comparison of cone-beam and 64-slice computed tomography scanners

    Directory of Open Access Journals (Sweden)

    Farzad Esmaeili

    2013-01-01

    Full Text Available Background: Cone beam computed tomography (CBCT is an alternative to a computed tomography (CT scan, which is appropriate for a wide range of craniomaxillofacial indications. The long-term use of metallic materials in dentistry means that artifacts caused by metallic restorations in the oral cavity should be taken into account when utilizing CBCT and CT scanners. The aim of this study was to quantitatively compare the beam hardening artifacts produced by dental implants between CBCT and a 64-Slice CT scanner. Materials and Methods: In this descriptive study , an implant drilling model similar to the human mandible was used in the present study. The implants (Dentis were placed in the canine, premolar and molar areas. Three series of scans were provided from the implant areas using Somatom Sensation 64-slice and NewTom VGi (CBCT CT scanners. Identical images were evaluated by three radiologists. The artifacts in each image were determined based on pre-determined criteria. Kruskal-Wallis test was used to compare mean values; Mann-Whitney U test was used for two-by-two comparisons when there was a statistical significance ( P < 0.05. Results: The images of the two scanners had similar resolutions in axial sections ( P = 0.299. In coronal sections, there were significant differences in the resolutions of the images produced by the two scanners ( P < 0.001, with a higher resolution in the images produced by NewTom VGi scanner. On the whole, there were significant differences between the resolutions of the images produced by the two CT scanners ( P < 0.001, with higher resolution in the images produced by NewTom VGi scanner in comparison to those of Somatom Sensation. Conclusion: Given the high quality of the images produced by NewTom VGi and the lower costs in comparison to CT, the use of the images of this scanner in dental procedures is recommended, especially in patients with extensive restorations, multiple prostheses and previous implants.

  14. Beam dynamics in rf guns and emittance correction techniques

    International Nuclear Information System (INIS)

    Serafini, L.

    1994-01-01

    In this paper we present a general review of beam dynamics in a laser-driven rf gun. The peculiarity of such an accelerating structure versus other conventional multi-cell linac structures is underlined on the basis of the Panofsky-Wenzel theorem, which is found to give a theoretical background for the well known Kim's model. A basic explanation for some proposed methods to correct rf induced emittance growth is also derived from the theorem. We also present three emittance correction techniques for the recovery of space-charge induced emittance growth, namely the optimum distributed disk-like bunch technique, the use of rf spatial harmonics to correct spherical aberration induced by space charge forces and the technique of emittance filtering by clipping the electron beam. The expected performances regarding the beam quality achievable with different techniques, as predicted by scaling laws and simulations, are analyzed, and, where available, compared to experimental results. (orig.)

  15. Quantitative analysis of artifacts in 4D DSA: the relative contributions of beam hardening and scatter to vessel dropout behind highly attenuating structures

    Science.gov (United States)

    Hermus, James; Szczykutowicz, Timothy P.; Strother, Charles M.; Mistretta, Charles

    2014-03-01

    When performing Computed Tomographic (CT) image reconstruction on digital subtraction angiography (DSA) projections, loss of vessel contrast has been observed behind highly attenuating anatomy, such as dental implants and large contrast filled aneurysms. Because this typically occurs only in a limited range of projection angles, the observed contrast time course can potentially be altered. In this work, we have developed a model for acquiring DSA projections that models both the polychromatic nature of the x-ray spectrum and the x-ray scattering interactions to investigate this problem. In our simulation framework, scatter and beam hardening contributions to vessel dropout can be analyzed separately. We constructed digital phantoms with large clearly defined regions containing iodine contrast, bone, soft issue, titanium (dental implants) or combinations of these materials. As the regions containing the materials were large and rectangular, when the phantoms were forward projected, the projections contained uniform regions of interest (ROI) and enabled accurate vessel dropout analysis. Two phantom models were used, one to model the case of a vessel behind a large contrast filled aneurysm and the other to model a vessel behind a dental implant. Cases in which both beam hardening and scatter were turned off, only scatter was turned on, only beam hardening was turned on, and both scatter and beam hardening were turned on, were simulated for both phantom models. The analysis of this data showed that the contrast degradation is primarily due to scatter. When analyzing the aneurysm case, 90.25% of the vessel contrast was lost in the polychromatic scatter image, however only 50.5% of the vessel contrast was lost in the beam hardening only image. When analyzing the teeth case, 44.2% of the vessel contrast was lost in the polychromatic scatter image and only 26.2% of the vessel contrast was lost in the beam hardening only image.

  16. Correction of beam-beam effects in luminosity measurement in the forward region at CLIC

    CERN Document Server

    Lukic, Strahinja

    2013-01-01

    Procedures for correcting the beam-beam effects in luminosity measurement at CLIC at 3 TeV CM energy are described and tested using Monte Carlo simulations: - Correction of the angular counting loss due to the combined Beamstrahlung and initial-state radiation (ISR) effects, based on the reconstructed velocity of the collision frame of the Bhabha scattering. - Deconvolution of the luminosity spectrum distortion due to the ISR emission. - Correction of the counting bias due to the finite calorimeter energy resolution. All procedures were tested by simulation. Bhabha events were generated using BHLUMI, and used in Guinea-PIG to simulate the outgoing momenta of Bhabha particles in the bunch collisions at CLIC. Residual uncertainties after correction are listed in a table in the conclusions. The beam-beam related systematic counting uncertainty in the luminosity peak can be reduced to the order of permille.

  17. Correction of beam-beam effects in luminosity measurement in the forward region at CLIC

    CERN Document Server

    Lukic, Strahinja

    2013-01-01

    Procedures for correcting the beam-beam effects in luminosity measurement at CLIC at 3 TeV CM energy are described and tested using Monte Carlo simulations: -> Correction of the angular counting loss due to the combined Beamstrahlung and initial-state radiation (ISR) effects, based on the reconstructed velocity of the collision frame of the Bhabha scattering. -> Deconvolution of the luminosity spectrum distortion due to the ISR emission. -> Correction of the counting bias due to the finite calorimeter energy resolution. All procedures were tested by simulation. Bhabha events were generated using BHLUMI, and used in Guinea-PIG to simulate the outgoing momenta of Bhabha particles in the bunch collisions at CLIC. Residual uncertainties after correction are listed in a table in the conclusions. The beam-beam related systematic counting uncertainty in the luminosity peak can be reduced to the order of permille.

  18. Efficient, radiation-hardened, 400- and 800-keV neutral-beam injection systems

    International Nuclear Information System (INIS)

    Anderson, O.A.; Cooper, W.S.; Fink, J.A.; Goldberg, D.A.; Ruby, L.; Soroka, L.; Tanabe, J.

    1983-04-01

    We present designs for two negative-ion based neutral beam lines with reactor-level power output. Both beam lines make use of such technologically advanced features as high-current-density surface-conversion ion sources, transverse-field-focussing (TFF) acceleration and transport, and laser photodetachment. For the second of these designs, we also presented detailed beam and vacuum calculations, as well as a brief description of a proof-of-principle test system currently under development

  19. The Saturne beam measurement system for orbit corrections and high and low intensity beam acceleration

    International Nuclear Information System (INIS)

    Degueurce, L.; Nakach, A.; Sole, J.

    1980-07-01

    This paper summarizes the dipolar and multipolar correction system and the main beam diagnostics of Saturne II: wide-band RF electrostatic pick-up electrode for observation of bunches, beam position and tune measurement systems, special electrodes for observation of emittance blow-up when particles cross a resonance line. For low intensity beams, special electrodes and electronics have been developed. All this instrumentation is computer controlled

  20. Atmospheric Error Correction of the Laser Beam Ranging

    Directory of Open Access Journals (Sweden)

    J. Saydi

    2014-01-01

    Full Text Available Atmospheric models based on surface measurements of pressure, temperature, and relative humidity have been used to increase the laser ranging accuracy by ray tracing. Atmospheric refraction can cause significant errors in laser ranging systems. Through the present research, the atmospheric effects on the laser beam were investigated by using the principles of laser ranging. Atmospheric correction was calculated for 0.532, 1.3, and 10.6 micron wavelengths through the weather conditions of Tehran, Isfahan, and Bushehr in Iran since March 2012 to March 2013. Through the present research the atmospheric correction was computed for meteorological data in base of monthly mean. Of course, the meteorological data were received from meteorological stations in Tehran, Isfahan, and Bushehr. Atmospheric correction was calculated for 11, 100, and 200 kilometers laser beam propagations under 30°, 60°, and 90° rising angles for each propagation. The results of the study showed that in the same months and beam emission angles, the atmospheric correction was most accurate for 10.6 micron wavelength. The laser ranging error was decreased by increasing the laser emission angle. The atmospheric correction with two Marini-Murray and Mendes-Pavlis models for 0.532 nm was compared.

  1. Characterization of weak, fair and strong neutron absorbing materials by means of neutron transmission: Beam hardening effect

    Science.gov (United States)

    Kharfi, F.; Bastuerk, M.; Boucenna, A.

    2006-09-01

    The characterization of neutron absorbing materials as well as quantification of neutron attenuation through matter is very essential in various fields, namely in shielding calculation. The objective of this work is to describe an experimental procedure to be used for the determination of neutron transmission through different materials. The proposed method is based on the relation between the gray value measured on neutron radiography image and the corresponding inducing neutron beam. For such a purpose, three kinds of materials (in shape of plate) were investigated using thermal neutrons: (1) boron-alloyed stainless steel as strong absorber; (2) copper and steel as fair absorbers and (3) aluminum as weak absorber. This work is not limited to the determination of neutron transmission through matters; it is also spread out to the measure of the surface density of the neutron absorbing elements (ρs) as a function of thickness of neutron absorbing material such as boron-alloyed stainless steel. The beam hardening effect depending on material thickness was also studied using the neutron transmission measurements. A theoretical approach was used to interpret the experimental results. The neutron transmission measurements were performed at the Neutron Radiography and Tomography facility of the Atomic Institute of the Austrian Universities in Vienna. Finally, a Maxwellian neutron distribution of incident neutron beam was used in the theoretical calculations of neutron energy shift in order to compare with experiments results. The obtained experimental results are in a good agreement with the developed theoretical approach.

  2. Effects of accelerated electron beam irradiation on surface hardening and fatigue properties in an AISI 4140 steel used for automotive crankshaft

    Energy Technology Data Exchange (ETDEWEB)

    Choo, S.-H.; Lee, S. [Pohang Univ. of Sci. and Technol. (Korea). Center for Adv. Aerospace Mater.; Golkovski, M.G. [Rossijskaya Akademiya Nauk, Novosibirsk (Russian Federation). Inst. Yadernoj Fiziki

    2000-11-30

    This study is concerned with the effects of high-energy accelerated electron beam irradiation on surface hardening and improvement of fatigue properties in an AISI 4140 steel currently used for automotive crankshaft. The 4140 steel specimens were irradiated in air by using a high-energy electron beam accelerator, and then microstructure, hardness, and fatigue properties were examined. Beam power was varied in the range of 5.2{proportional_to}7.7 kW by changing beam current. Upon irradiation, the unirradiated microstructure containing band structure was changed to martensite and bainite in the carbon-rich zone or ferrite, bainite, and martensite in the carbon-depleted zone. This microstructural modification improved greatly surface hardness and fatigue properties due to transformation of martensite whose amount and type were determined by heat input during irradiation. Thus, high-energy electron beam irradiation can be effectively applied to the surface hardening process of automotive parts. In order to investigate the thermal cycle during electron beam irradiation of quickly rotating specimens, the thermal analysis was also carried out using an analytical computer simulation. Analytical solutions gave information about the peak temperature, heating and cooling rate, and hardened depth to correlate with the overall microstructural modification. (orig.)

  3. Calculation of beam quality correction factor using Monte Carlo simulation

    International Nuclear Information System (INIS)

    Kawachi, T.; Saitoh, H.; Myojoyama, A.; Katayose, T.; Kojima, T.; Fukuda, K.; Inoue, M.

    2005-01-01

    In recent years, a number of the CyberKnife systems (Accuray C., U.S.) have been increasing significantly. However, the CyberKnife has unique treatment head structure and beam collimating system. Therefore, the global standard protocols can not be adopted for absolute absorbed dose dosimetry in CyberKnife beam. In this work, the energy spectrum of photon and electron from CyberKnife treatment head at 80 cm SSD and several depths in water are simulated with conscientious geometry using by the EGS Monte Carlo method. Furthermore, for calculation of the beam quality correction factor k Q , the mean restricted mass stopping power and the mass energy absorption coefficient of air, water and several chamber wall and waterproofing sleeve materials are calculated. As a result, the factors k Q CyberKnife beam for several ionization chambers are determined. And the relationship between the beam quality index PDD(10) x in CyberKnife beam and k Q is described in this report. (author)

  4. Prospects for electron beam aberration correction using sculpted phase masks

    Energy Technology Data Exchange (ETDEWEB)

    Shiloh, Roy, E-mail: royshilo@post.tau.ac.il; Remez, Roei; Arie, Ady

    2016-04-15

    Technological advances in fabrication methods allowed the microscopy community to take incremental steps towards perfecting the electron microscope, and magnetic lens design in particular. Still, state of the art aberration-corrected microscopes are yet 20–30 times shy of the theoretical electron diffraction limit. Moreover, these microscopes consume significant physical space and are very expensive. Here, we show how a thin, sculpted membrane is used as a phase-mask to induce specific aberrations into an electron beam probe in a standard high resolution TEM. In particular, we experimentally demonstrate beam splitting, two-fold astigmatism, three-fold astigmatism, and spherical aberration. - Highlights: • Thin membranes can be used as aberration correctors in electron columns. • We demonstrate tilt, twofold-, threefold-astigmatism, and spherical aberrations. • Experimental and physical-optics simulation results are in good agreement. • Advantages in cost, size, nonmagnetism, and nearly-arbitrary correction.

  5. Beam-centric algorithm for pretreatment patient position correction in external beam radiation therapy

    International Nuclear Information System (INIS)

    Bose, Supratik; Shukla, Himanshu; Maltz, Jonathan

    2010-01-01

    Purpose: In current image guided pretreatment patient position adjustment methods, image registration is used to determine alignment parameters. Since most positioning hardware lacks the full six degrees of freedom (DOF), accuracy is compromised. The authors show that such compromises are often unnecessary when one models the planned treatment beams as part of the adjustment calculation process. The authors present a flexible algorithm for determining optimal realizable adjustments for both step-and-shoot and arc delivery methods. Methods: The beam shape model is based on the polygonal intersection of each beam segment with the plane in pretreatment image volume that passes through machine isocenter perpendicular to the central axis of the beam. Under a virtual six-DOF correction, ideal positions of these polygon vertices are computed. The proposed method determines the couch, gantry, and collimator adjustments that minimize the total mismatch of all vertices over all segments with respect to their ideal positions. Using this geometric error metric as a function of the number of available DOF, the user may select the most desirable correction regime. Results: For a simulated treatment plan consisting of three equally weighted coplanar fixed beams, the authors achieve a 7% residual geometric error (with respect to the ideal correction, considered 0% error) by applying gantry rotation as well as translation and isocentric rotation of the couch. For a clinical head-and-neck intensity modulated radiotherapy plan with seven beams and five segments per beam, the corresponding error is 6%. Correction involving only couch translation (typical clinical practice) leads to a much larger 18% mismatch. Clinically significant consequences of more accurate adjustment are apparent in the dose volume histograms of target and critical structures. Conclusions: The algorithm achieves improvements in delivery accuracy using standard delivery hardware without significantly increasing

  6. Surface hardening alloy VT6 of electric explosion and by electron beam

    International Nuclear Information System (INIS)

    Ivanov, Yu. F.; Kobzareva, T. Yu.; Gromov, V. E.; Soskova, N. A.; Budovskikh, E. A.; Raikov, S. V.

    2014-01-01

    The aim is to study the phase composition, structure and properties of the surface layer of the VT6 titanium alloy, subjected to combined treatment, consisting of alloying by the plasma of an electric explosion of a graphite fiber with a charge of the SiC powder and subsequent exposure by a high-intense electron beam. As a result of such treatment, a multiphase surface layer with a submicron and nanosize structure forms with the microhardness manifold exceeding its value in the sample volume are presented

  7. TH-CD-202-02: A Preliminary Study Evaluating Beam-Hardening Artifact Reduction On CT Direct Electron-Density Images

    Energy Technology Data Exchange (ETDEWEB)

    Li, H; Dolly, S; Zhao, T; Anastasio, M; Mutic, S [Washington University School of Medicine, Saint Louis, MO (United States); Ritter, A; Colombo, V; Raupach, R; Huenemohr, N [Siemens Healthcare GmbH, Deutschland (Germany); Mistry, N [Siemens Medical Solutions USA, Malvern, PA (United States); Yu, L [Mayo Clinic, Rochester, MN (United States)

    2016-06-15

    Purpose: A prototype reconstruction algorithm that can provide direct electron density (ED) images from single energy CT scans is being currently developed by Siemens Healthcare GmbH. This feature can eliminate the need for kV specific calibration curve for radiation treatemnt planning. An added benefit is that beam-hardening artifacts are also reduced on direct-ED images due to the underlying material decomposition. This study is to quantitatively analyze the reduction of beam-hardening artifacts on direct-ED images and suggest additional clinical usages. Methods: HU and direct-ED images were reconstructed on a head phantom scanned on a Siemens Definition AS CT scanner at five tube potentials of 70kV, 80kV, 100kV, 120kV and 140kV respectively. From these images, mean, standard deviation (SD), and local NPS were calculated for regions of interest (ROI) of same locations and sizes. A complete analysis of beam-hardening artifact reduction and image quality improvement was conducted. Results: Along with the increase of tube potentials, ROI means and SDs decrease on both HU and direct-ED images. The mean value differences between HU and direct-ED images are up to 8% with absolute value of 2.9. Compared to that on HU images, the SDs are lower on direct-ED images, and the differences are up to 26%. Interestingly, the local NPS calculated from direct-ED images shows consistent values in the low spatial frequency domain for images acquired from all tube potential settings, while varied dramatically on HU images. This also confirms the beam -hardening artifact reduction on ED images. Conclusions: The low SDs on direct-ED images and relative consistent NPS values in the low spatial frequency domain indicate a reduction of beam-hardening artifacts. The direct-ED image has the potential to assist in more accurate organ contouring, and is a better fit for the desired purpose of CT simulations for radiotherapy.

  8. SU-F-J-74: High Z Geometric Integrity and Beam Hardening Artifact Assessment Using a Retrospective Metal Artifact Reduction (MAR) Reconstruction Algorithm

    International Nuclear Information System (INIS)

    Woods, K; DiCostanzo, D; Gupta, N

    2016-01-01

    Purpose: To test the efficacy of a retrospective metal artifact reduction (MAR) reconstruction algorithm for a commercial computed tomography (CT) scanner for radiation therapy purposes. Methods: High Z geometric integrity and artifact reduction analysis was performed with three phantoms using General Electric’s (GE) Discovery CT. The three phantoms included: a Computerized Imaging Reference Systems (CIRS) electron density phantom (Model 062) with a 6.5 mm diameter titanium rod insert, a custom spine phantom using Synthes Spine hardware submerged in water, and a dental phantom with various high Z fillings submerged in water. Each phantom was reconstructed using MAR and compared against the original scan. Furthermore, each scenario was tested using standard and extended Hounsfield Unit (HU) ranges. High Z geometric integrity was performed using the CIRS phantom, while the artifact reduction was performed using all three phantoms. Results: Geometric integrity of the 6.5 mm diameter rod was slightly overestimated for non-MAR scans for both standard and extended HU. With MAR reconstruction, the rod was underestimated for both standard and extended HU. For artifact reduction, the mean and standard deviation was compared in a volume of interest (VOI) in the surrounding material (water and water equivalent material, ∼0HU). Overall, the mean value of the VOI was closer to 0 HU for the MAR reconstruction compared to the non-MAR scan for most phantoms. Additionally, the standard deviations for all phantoms were greatly reduced using MAR reconstruction. Conclusion: GE’s MAR reconstruction algorithm improves image quality with the presence of high Z material with minimal degradation of its geometric integrity. High Z delineation can be carried out with proper contouring techniques. The effects of beam hardening artifacts are greatly reduced with MAR reconstruction. Tissue corrections due to these artifacts can be eliminated for simple high Z geometries and greatly

  9. SU-F-J-74: High Z Geometric Integrity and Beam Hardening Artifact Assessment Using a Retrospective Metal Artifact Reduction (MAR) Reconstruction Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Woods, K; DiCostanzo, D; Gupta, N [Ohio State University Columbus, OH (United States)

    2016-06-15

    Purpose: To test the efficacy of a retrospective metal artifact reduction (MAR) reconstruction algorithm for a commercial computed tomography (CT) scanner for radiation therapy purposes. Methods: High Z geometric integrity and artifact reduction analysis was performed with three phantoms using General Electric’s (GE) Discovery CT. The three phantoms included: a Computerized Imaging Reference Systems (CIRS) electron density phantom (Model 062) with a 6.5 mm diameter titanium rod insert, a custom spine phantom using Synthes Spine hardware submerged in water, and a dental phantom with various high Z fillings submerged in water. Each phantom was reconstructed using MAR and compared against the original scan. Furthermore, each scenario was tested using standard and extended Hounsfield Unit (HU) ranges. High Z geometric integrity was performed using the CIRS phantom, while the artifact reduction was performed using all three phantoms. Results: Geometric integrity of the 6.5 mm diameter rod was slightly overestimated for non-MAR scans for both standard and extended HU. With MAR reconstruction, the rod was underestimated for both standard and extended HU. For artifact reduction, the mean and standard deviation was compared in a volume of interest (VOI) in the surrounding material (water and water equivalent material, ∼0HU). Overall, the mean value of the VOI was closer to 0 HU for the MAR reconstruction compared to the non-MAR scan for most phantoms. Additionally, the standard deviations for all phantoms were greatly reduced using MAR reconstruction. Conclusion: GE’s MAR reconstruction algorithm improves image quality with the presence of high Z material with minimal degradation of its geometric integrity. High Z delineation can be carried out with proper contouring techniques. The effects of beam hardening artifacts are greatly reduced with MAR reconstruction. Tissue corrections due to these artifacts can be eliminated for simple high Z geometries and greatly

  10. Method and system for automatically correcting aberrations of a beam of charged particles

    International Nuclear Information System (INIS)

    1975-01-01

    The location of a beam of charged particles within a deflection field is determined by its orthogonal deflection voltages. With the location of the beam in the field, correction currents are supplied to a focus coil and to each of a pair of stigmator coils to correct for change of focal length and astigmatism due to the beam being deflected away from the center of its deflection field

  11. Radiative corrections to chargino production in electron-positron collisions with polarized beams

    International Nuclear Information System (INIS)

    Diaz, Marco A.; King, Stephen F.; Ross, Douglas A.

    2001-01-01

    We study radiative corrections to chargino production at linear colliders with polarized electron beams. We calculate the one-loop corrected cross sections for polarized electon beams due to three families of quarks and squarks, working in the {ovr MS} scheme, extending our previous calculation of the unpolarized cross section with one-loop corrections due to the third family of quarks and squarks. In some cases we find rather large corrections to the tree-level cross sections. For example, for the case of right-handed polarized electrons and large tanβ the corrections can be of order 30%, allowing sensitivity to the squark mass parameters

  12. The determination of beam quality correction factors: Monte Carlo simulations and measurements.

    Science.gov (United States)

    González-Castaño, D M; Hartmann, G H; Sánchez-Doblado, F; Gómez, F; Kapsch, R-P; Pena, J; Capote, R

    2009-08-07

    Modern dosimetry protocols are based on the use of ionization chambers provided with a calibration factor in terms of absorbed dose to water. The basic formula to determine the absorbed dose at a user's beam contains the well-known beam quality correction factor that is required whenever the quality of radiation used at calibration differs from that of the user's radiation. The dosimetry protocols describe the whole ionization chamber calibration procedure and include tabulated beam quality correction factors which refer to 60Co gamma radiation used as calibration quality. They have been calculated for a series of ionization chambers and radiation qualities based on formulae, which are also described in the protocols. In the case of high-energy photon beams, the relative standard uncertainty of the beam quality correction factor is estimated to amount to 1%. In the present work, two alternative methods to determine beam quality correction factors are prescribed-Monte Carlo simulation using the EGSnrc system and an experimental method based on a comparison with a reference chamber. Both Monte Carlo calculations and ratio measurements were carried out for nine chambers at several radiation beams. Four chamber types are not included in the current dosimetry protocols. Beam quality corrections for the reference chamber at two beam qualities were also measured using a calorimeter at a PTB Primary Standards Dosimetry Laboratory. Good agreement between the Monte Carlo calculated (1% uncertainty) and measured (0.5% uncertainty) beam quality correction factors was obtained. Based on these results we propose that beam quality correction factors can be generated both by measurements and by the Monte Carlo simulations with an uncertainty at least comparable to that given in current dosimetry protocols.

  13. Radiation hardening coating material

    International Nuclear Information System (INIS)

    McDonald, W.H.; Prucnal, P.J.; DeMajistre, Robert.

    1977-01-01

    This invention concerns a radiation hardening coating material. First a resin is prepared by reaction of bisphenol diglycidylic ether with acrylic or methacrylic acids. Then the reactive solvent is prepared by reaction of acrylic or methacrylic acids with epichlorhydrine or epibromhydrine. Then a solution consisting of the resin dissolved in the reactive solvent is prepared. A substrate (wood, paper, polyesters, polyamines etc.) is coated with this composition and exposed to ionizing radiations (electron beams) or ultraviolet radiations [fr

  14. Beam-Based Nonlinear Optics Corrections in Colliders

    CERN Document Server

    Pilat, Fulvia Caterina; Malitsky, Nikolay; Ptitsyn, Vadim

    2005-01-01

    A method has been developed to measure and correct operationally the non-linear effects of the final focusing magnets in colliders, which gives access to the effects of multi-pole errors by applying closed orbit bumps, and analyzing the resulting tune and orbit shifts. This technique has been tested and used during 3 years of RHIC (the Relativistic Heavy Ion Collider at BNL) operations. I will discuss here the theoretical basis of the method, the experimental set-up, the correction results, the present understanding of the machine model, the potential and limitations of the method itself as compared with other non linear correction techniques.

  15. Optics measurement and correction during beam acceleration in the Relativistic Heavy Ion Collider

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Marusic, A. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.

    2014-09-09

    To minimize operational complexities, setup of collisions in high energy circular colliders typically involves acceleration with near constant β-functions followed by application of strong focusing quadrupoles at the interaction points (IPs) for the final beta-squeeze. At the Relativistic Heavy Ion Collider (RHIC) beam acceleration and optics squeeze are performed simultaneously. In the past, beam optics correction at RHIC has taken place at injection and at final energy with some interpolation of corrections into the acceleration cycle. Recent measurements of the beam optics during acceleration and squeeze have evidenced significant beta-beats which if corrected could minimize undesirable emittance dilutions and maximize the spin polarization of polarized proton beams by avoidance of higher-order multipole fields sampled by particles within the bunch. In this report the methodology now operational at RHIC for beam optics corrections during acceleration with simultaneous beta-squeeze will be presented together with measurements which conclusively demonstrate the superior beam control. As a valuable by-product, the corrections have minimized the beta-beat at the profile monitors so reducing the dominant error in and providing more precise measurements of the evolution of the beam emittances during acceleration.

  16. Saturne II: characteristics of the proton beam, field qualities and corrections, acceleration of the polarized protons

    International Nuclear Information System (INIS)

    Laclare, J.-L.

    1978-01-01

    Indicated specifications of Saturne II are summed up: performance of the injection system, quality of the guidance field (magnetic measurements and multipolar corrections), transverse and longitudinal instabilities, characteristics of the beam stored in the machine and of the extracted beam. The problem of depolarization along the acceleration cycle is briefly discussed (1 or 2% between injection and 3 GeV) [fr

  17. Space Charge Correction on Emittance Measurement of Low Energy Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Treado, Colleen J.; /Massachusetts U., Amherst

    2012-09-07

    The goal of any particle accelerator is to optimize the transport of a charged particle beam along a set path by confining the beam to a small region close to the design trajectory and directing it accurately along the beamline. To do so in the simplest fashion, accelerators use a system of magnets that exert approximately linear electromagnetic forces on the charged beam. These electromagnets bend the beam along the desired path, in the case of bending magnets, and constrain the beam to the desired area through alternating focusing and defocusing effects, in the case of quadrupole magnets. We can model the transport of such a beam through transfer matrices representing the actions of the various beamline elements. However, space charge effects, produced from self electric fields within the beam, defocus the beam and must be accounted for in the calculation of beam emittance. We present below the preliminary results of a MATLAB code built to model the transport of a charged particle beam through an accelerator and measure the emittance under the influence of space charge effects. We demonstrate the method of correctly calculating the emittance of a beam under space charge effects using a least square fit to determine the initial properties of the beam given the beam size measured at a specific point after transport.

  18. Corrections in the gold foil activation method for determination of neutron beam density

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage

    1967-01-01

    A finite foil thickness and deviation in the cross section from the 1ν law imply corrections in the determination of neutron beam densities by means of foil activation. These corrections, which depend on the neutron velocity distribution, have been examined in general and are given in a specific...

  19. Analytical fan-beam and cone-beam reconstruction algorithms with uniform attenuation correction for SPECT

    International Nuclear Information System (INIS)

    Tang Qiulin; Zeng, Gengsheng L; Gullberg, Grant T

    2005-01-01

    In this paper, we developed an analytical fan-beam reconstruction algorithm that compensates for uniform attenuation in SPECT. The new fan-beam algorithm is in the form of backprojection first, then filtering, and is mathematically exact. The algorithm is based on three components. The first one is the established generalized central-slice theorem, which relates the 1D Fourier transform of a set of arbitrary data and the 2D Fourier transform of the backprojected image. The second one is the fact that the backprojection of the fan-beam measurements is identical to the backprojection of the parallel measurements of the same object with the same attenuator. The third one is the stable analytical reconstruction algorithm for uniformly attenuated Radon data, developed by Metz and Pan. The fan-beam algorithm is then extended into a cone-beam reconstruction algorithm, where the orbit of the focal point of the cone-beam imaging geometry is a circle. This orbit geometry does not satisfy Tuy's condition and the obtained cone-beam algorithm is an approximation. In the cone-beam algorithm, the cone-beam data are first backprojected into the 3D image volume; then a slice-by-slice filtering is performed. This slice-by-slice filtering procedure is identical to that of the fan-beam algorithm. Both the fan-beam and cone-beam algorithms are efficient, and computer simulations are presented. The new cone-beam algorithm is compared with Bronnikov's cone-beam algorithm, and it is shown to have better performance with noisy projections

  20. Evaluation of a method for correction of scatter radiation in thorax cone beam CT

    International Nuclear Information System (INIS)

    Rinkel, J.; Dinten, J.M.; Esteve, F.

    2004-01-01

    Purpose: Cone beam CT (CBCT) enables three-dimensional imaging with isotropic resolution. X-ray scatter estimation is a big challenge for quantitative CBCT imaging of thorax: scatter level is significantly higher on cone beam systems compared to collimated fan beam systems. The effects of this scattered radiation are cupping artefacts, streaks, and quantification inaccuracies. The beam stops conventional scatter estimation approach can be used for CBCT but leads to a significant increase in terms of dose and acquisition time. At CEA-LETI has been developed an original scatter management process without supplementary acquisition. Methods and Materials: This Analytical Plus Indexing-based method (API) of scatter correction in CBCT is based on scatter calibration through offline acquisitions with beam stops on lucite plates, combined to an analytical transformation issued from physical equations. This approach has been applied with success in bone densitometry and mammography. To evaluate this method in CBCT, acquisitions from a thorax phantom with and without beam stops have been performed. To compare different scatter correction approaches, Feldkamp algorithm has been applied on rough data corrected from scatter by API and by beam stops approaches. Results: The API method provides results in good agreement with the beam stops array approach, suppressing cupping artefact. Otherwise influence of the scatter correction method on the noise in the reconstructed images has been evaluated. Conclusion: The results indicate that the API method is effective for quantitative CBCT imaging of thorax. Compared to a beam stops array method it needs a lower x-ray dose and shortens acquisition time. (authors)

  1. Sextupole correction of the longitudinal transport of relativistic beams in dispersionless translating sections

    Directory of Open Access Journals (Sweden)

    R. J. England

    2005-01-01

    Full Text Available We examine the use of sextupole magnets to correct nonlinearities in the longitudinal phase space transformation of a relativistic beam of charged particles in a dispersionless translating section, or dogleg. Through heuristic analytical arguments and examples derived from recent experimental efforts, augmented by simulations using the particle tracking codes PARMELA and ELEGANT, sextupole corrections are found to be effective in optimizing the use of such structures for beam compression or for shaping the current profile of the beam, by manipulation of the second-order longitudinal dispersion. Recent experimental evidence of the use of sextupoles to manipulate second-order horizontal and longitudinal dispersion of the beam is presented. The theoretical and experimental results indicate that these manipulations can be used to create an electron bunch with a current profile having a long ramp followed by a sharp cutoff, which is optimal for driving large-amplitude wake fields in a plasma wake field accelerator.

  2. Correction of Magnetic Optics and Beam Trajectory Using LOCO Based Algorithm with Expanded Experimental Data Sets

    Energy Technology Data Exchange (ETDEWEB)

    Romanov, A.; Edstrom, D.; Emanov, F. A.; Koop, I. A.; Perevedentsev, E. A.; Rogovsky, Yu. A.; Shwartz, D. B.; Valishev, A.

    2017-03-28

    Precise beam based measurement and correction of magnetic optics is essential for the successful operation of accelerators. The LOCO algorithm is a proven and reliable tool, which in some situations can be improved by using a broader class of experimental data. The standard data sets for LOCO include the closed orbit responses to dipole corrector variation, dispersion, and betatron tunes. This paper discusses the benefits from augmenting the data with four additional classes of experimental data: the beam shape measured with beam profile monitors; responses of closed orbit bumps to focusing field variations; betatron tune responses to focusing field variations; BPM-to-BPM betatron phase advances and beta functions in BPMs from turn-by-turn coordinates of kicked beam. All of the described features were implemented in the Sixdsimulation software that was used to correct the optics of the VEPP-2000 collider, the VEPP-5 injector booster ring, and the FAST linac.

  3. Method and system for correcting an aberration of a beam of charged particles

    International Nuclear Information System (INIS)

    1975-01-01

    A beam of charged particles is deflected in a closed path such as a square over a cross wire grid, for example, at a constant velocity by an X Y deflection system. A small high frequency jitter is added at both axes of deflection to cause oscillation of the beam at 45deg to the X and Y axes. From the time that the leading edge of the oscillating beam passes over the wire until the trailing edge of the beam passes over the wire, an envelope of the oscillations produced by the jitter is obtained. A second envelope is obtained when the leading edge of the beam exits from being over the wire until the trailing edge of the beam ceases to be over the wire. Thus, a pair of envelopes is produced as the beam passes over each wire of the grid. The number of pulses exceeding ten percent of the peak voltage in the eight envelopes produced by the beam completing a cycle in its closed path around the grid are counted and compared with those counted during the previous cycle of the beam moving in its closed path over the grid. As the number of pulses decreases, the quality of the focus of the beam increases so that correction signals are applied to the focus coil in accordance with whether the number of pulses is increasing or decreasing

  4. Method and system for correcting an aberration of a beam of charged particles

    Energy Technology Data Exchange (ETDEWEB)

    1975-06-20

    A beam of charged particles is deflected in a closed path such as a square over a cross wire grid, for example, at a constant velocity by an X Y deflection system. A small high frequency jitter is added at both axes of deflection to cause oscillation of the beam at 45deg to the X and Y axes. From the time that the leading edge of the oscillating beam passes over the wire until the trailing edge of the beam passes over the wire, an envelope of the oscillations produced by the jitter is obtained. A second envelope is obtained when the leading edge of the beam exits from being over the wire until the trailing edge of the beam ceases to be over the wire. Thus, a pair of envelopes is produced as the beam passes over each wire of the grid. The number of pulses exceeding ten percent of the peak voltage in the eight envelopes produced by the beam completing a cycle in its closed path around the grid are counted and compared with those counted during the previous cycle of the beam moving in its closed path over the grid. As the number of pulses decreases, the quality of the focus of the beam increases so that correction signals are applied to the focus coil in accordance with whether the number of pulses is increasing or decreasing.

  5. First turn beam correction for the Advanced Photon Source storage ring

    International Nuclear Information System (INIS)

    Qian, Y.; Crosbie, E.; Teng, L.

    1991-01-01

    A procedure was developed for precise realignment of the quadrupoles in a synchrotron radiation storage ring which can substantially ease the required precision of the initial survey. The procedure consists of first using the injected beam to obtain a closed orbit which is centered on the beam position monitors by the correction dipoles. The strengths of the correction dipoles then give the required fine-adjustment of the quadrupole positions. In this paper the authors discuss only the algorithm for obtaining the closed orbit

  6. A beam-based alignment technique for correction of accelerator structure misalignments

    International Nuclear Information System (INIS)

    Kubo, K.; Raubenheimer, T.O.

    1994-08-01

    This paper describes a method of reducing the transverse emittance dilution in linear colliders due to transverse wakefields arising-from misaligned accelerator structures. The technique is a generalization of the Wake-Free correction algorithm. The structure alignment errors are measured locally by varying the bunch charge and/or bunch length and measuring the change in the beam trajectory. The misalignments can then be corrected by varying the beam trajectory or moving structures. The results of simulations are presented demonstrating the viability of the technique

  7. Prior image constrained scatter correction in cone-beam computed tomography image-guided radiation therapy.

    Science.gov (United States)

    Brunner, Stephen; Nett, Brian E; Tolakanahalli, Ranjini; Chen, Guang-Hong

    2011-02-21

    X-ray scatter is a significant problem in cone-beam computed tomography when thicker objects and larger cone angles are used, as scattered radiation can lead to reduced contrast and CT number inaccuracy. Advances have been made in x-ray computed tomography (CT) by incorporating a high quality prior image into the image reconstruction process. In this paper, we extend this idea to correct scatter-induced shading artifacts in cone-beam CT image-guided radiation therapy. Specifically, this paper presents a new scatter correction algorithm which uses a prior image with low scatter artifacts to reduce shading artifacts in cone-beam CT images acquired under conditions of high scatter. The proposed correction algorithm begins with an empirical hypothesis that the target image can be written as a weighted summation of a series of basis images that are generated by raising the raw cone-beam projection data to different powers, and then, reconstructing using the standard filtered backprojection algorithm. The weight for each basis image is calculated by minimizing the difference between the target image and the prior image. The performance of the scatter correction algorithm is qualitatively and quantitatively evaluated through phantom studies using a Varian 2100 EX System with an on-board imager. Results show that the proposed scatter correction algorithm using a prior image with low scatter artifacts can substantially mitigate scatter-induced shading artifacts in both full-fan and half-fan modes.

  8. Beam-Based Error Identification and Correction Methods for Particle Accelerators

    CERN Document Server

    AUTHOR|(SzGeCERN)692826; Tomas, Rogelio; Nilsson, Thomas

    2014-06-10

    Modern particle accelerators have tight tolerances on the acceptable deviation from their desired machine parameters. The control of the parameters is of crucial importance for safe machine operation and performance. This thesis focuses on beam-based methods and algorithms to identify and correct errors in particle accelerators. The optics measurements and corrections of the Large Hadron Collider (LHC), which resulted in an unprecedented low β-beat for a hadron collider is described. The transverse coupling is another parameter which is of importance to control. Improvement in the reconstruction of the coupling from turn-by-turn data has resulted in a significant decrease of the measurement uncertainty. An automatic coupling correction method, which is based on the injected beam oscillations, has been successfully used in normal operation of the LHC. Furthermore, a new method to measure and correct chromatic coupling that was applied to the LHC, is described. It resulted in a decrease of the chromatic coupli...

  9. Reduction of CT beam hardening artefacts of ethylene vinyl alcohol copolymer by variation of the tantalum content: evaluation in a standardized aortic endoleak phantom

    International Nuclear Information System (INIS)

    Treitl, Karla M.; Scherr, Michael; Foerth, Monika; Braun, Franziska; Maxien, Daniel; Treitl, Marcus

    2015-01-01

    Our aim was to develop an aortic stent graft phantom to simulate endoleak treatment and to find a tantalum content (TC) of ethylene-vinyl-alcohol-copolymer that causes fewer computed tomography (CT) beam hardening artefacts, but still allows for fluoroscopic visualization. Ethylene-vinyl-alcohol-copolymer specimens of different TC (10-50 %, and 100 %) were injected in an aortic phantom bearing a stent graft and endoleak cavities with simulated re-perfusion. Fluoroscopic visibility of the ethylene-vinyl-alcohol-copolymer specimens was analyzed. In addition, six radiologists analyzed endoleak visibility, and artefact intensity of ethylene-vinyl-alcohol-copolymer in CT. Reduction of TC significantly decreased CT artefact intensity of ethylene-vinyl-alcohol-copolymer and increased visibility of endoleak re-perfusion (p < 0.000). It also significantly decreased fluoroscopic visibility of ethylene-vinyl-alcohol-copolymer (R = 0.883, p ≤ 0.01), and increased the active embolic volumes prior to visualization (Δ ≥ 40 μl). Ethylene-vinyl-alcohol-copolymer specimens with a TC of 45-50 % exhibited reasonable visibility, a low active embolic volume and a tolerable CT artefact intensity. The developed aortic stent graft phantom allows for a reproducible simulation of embolization of endoleaks. The data suggest a reduction of the TC of ethylene-vinyl-alcohol-copolymer to 45 -50 % of the original, to interfere less with diagnostic imaging in follow-up CT examinations, while still allowing for fluoroscopic visualization. (orig.)

  10. Correction of the calculation of beam loading based in the RF power diffusion equation

    International Nuclear Information System (INIS)

    Silva, R. da.

    1980-01-01

    It is described an empirical correction based upon experimental datas of others authors in ORELA, GELINA and SLAC accelerators, to the calculation of the energy loss due to the beam loading effect as stated by the RF power diffusion equation theory an accelerating structure. It is obtained a dependence of this correction with the electron pulse full width half maximum, but independent of the electron energy. (author) [pt

  11. Research on automatic correction of electronic beam path for distributed control

    International Nuclear Information System (INIS)

    Guo Xin; Su Haijun; Li Deming; Wang Shengli; Guo Honglei

    2014-01-01

    Background: Dynamitron, an electron irradiation accelerator of high-voltage, is used as a radiation source for industrial and agricultural production. The control system is an important component of dynamitron. Purpose: The aim is to improve the control system to meet the performance requirements of dynamitron for the stability. Methods: A distributed control system for the 1.5-MeV dynamitron is proposed to gain better performance. On this basis, an electron beam trajectory automatic correction method based on Cerebellar Model Articulation Controller and Proportional-Integral Derivative (CMAC-PID) controller is designed to improve the function of electron beam extraction system. Results: The distributed control system can meet the control requirements of the accelerator. The stability of the CMAC PID controller is better than that of conventional PID controller for the electron beam trajectory automatic correction system, and hence the CMAC-PID controller can provide better protection of dynamitron when electron beam deflection occurs. Conclusion: The distributed control system and the electron beam trajectory automatic correction method system can effectively improve the performance and reduce the failure probability of the accelerator, thereby enhancing the efficiency of the accelerator. (authors)

  12. Central X-ray beam correction of radiographic acetabular cup measurement after THA: an experimental study.

    Science.gov (United States)

    Schwarz, T; Weber, M; Wörner, M; Renkawitz, T; Grifka, J; Craiovan, B

    2017-05-01

    Accurate assessment of cup orientation on postoperative radiographs is essential for evaluating outcome after THA. However, accuracy is impeded by the deviation of the central X-ray beam in relation to the cup and the impossibility of measuring retroversion on standard pelvic radiographs. In an experimental trial, we built an artificial cup holder enabling the setting of different angles of anatomical anteversion and inclination. Twelve different cup orientations were investigated by three examiners. After comparing the two methods for radiographic measurement of the cup position developed by Lewinnek and Widmer, we showed how to differentiate between anteversion and retroversion in each cup position by using a second plane. To show the effect of the central beam offset on the cup, we X-rayed a defined cup position using a multidirectional central beam offset. According to Murray's definition of anteversion and inclination, we created a novel corrective procedure to balance measurement errors caused by deviation of the central beam. Measurement of the 12 different cup positions with the Lewinnek's method yielded a mean deviation of [Formula: see text] (95 % CI 1.3-2.3) from the original cup anteversion. The respective deviation with the Widmer/Liaw's method was [Formula: see text] (95 % CI 2.4-4.0). In each case, retroversion could be differentiated from anteversion with a second radiograph. Because of the multidirectional central beam offset ([Formula: see text] cm) from the acetabular cup in the cup holder ([Formula: see text] anteversion and [Formula: see text] inclination), the mean absolute difference for anteversion was [Formula: see text] (range [Formula: see text] to [Formula: see text] and [Formula: see text] (range [Formula: see text] to [Formula: see text] for inclination. The application of our novel mathematical correction of the central beam offset reduced deviation to a mean difference of [Formula: see text] for anteversion and [Formula: see text

  13. Analytical calculations of intense Gaussian laser beam propagating in plasmas with relativistic collision correction

    International Nuclear Information System (INIS)

    Wang Ying; Yuan Chengxun; Gao Ruilin; Zhou Zhongxiang

    2012-01-01

    Theoretical investigations of a Gaussian laser beam propagating in relativistic plasmas have been performed with the WKB method and complex eikonal function. We consider the relativistic nonlinearity induced by intense laser beam, and present the relativistically generalized forms of the plasma frequency and electron collision frequency in plasmas. The coupled differential equations describing the propagation variations of laser beam are derived and numerically solved. The obtained simulation results present the similar variation tendency with experiments. By changing the plasma density, we theoretically analyze the feasibility of using a plasmas slab of a fixed thickness to compress the laser beam-width and acquire the focused laser intensity. The present work complements the relativistic correction of the electron collision frequency with reasonable derivations, promotes the theoretical approaching to experiments and provides effective instructions to the practical laser-plasma interactions.

  14. Calibration of megavoltage cone-beam CT for radiotherapy dose calculations: Correction of cupping artifacts and conversion of CT numbers to electron density

    International Nuclear Information System (INIS)

    Petit, Steven F.; Elmpt, Wouter J. C. van; Nijsten, Sebastiaan M. J. J. G.; Lambin, Philippe; Dekker, Andre L. A. J.

    2008-01-01

    Megavoltage cone-beam CT (MV CBCT) is used for three-dimensional imaging of the patient anatomy on the treatment table prior to or just after radiotherapy treatment. To use MV CBCT images for radiotherapy dose calculation purposes, reliable electron density (ED) distributions are needed. Patient scatter, beam hardening and softening effects result in cupping artifacts in MV CBCT images and distort the CT number to ED conversion. A method based on transmission images is presented to correct for these effects without using prior knowledge of the object's geometry. The scatter distribution originating from the patient is calculated with pencil beam scatter kernels that are fitted based on transmission measurements. The radiological thickness is extracted from the scatter subtracted transmission images and is then converted to the primary transmission used in the cone-beam reconstruction. These corrections are performed in an iterative manner, without using prior knowledge regarding the geometry and composition of the object. The method was tested using various homogeneous and inhomogeneous phantoms with varying shapes and compositions, including a phantom with different electron density inserts, phantoms with large density variations, and an anthropomorphic head phantom. For all phantoms, the cupping artifact was substantially removed from the images and a linear relation between the CT number and electron density was found. After correction the deviations in reconstructed ED from the true values were reduced from up to 0.30 ED units to 0.03 for the majority of the phantoms; the residual difference is equal to the amount of noise in the images. The ED distributions were evaluated in terms of absolute dose calculation accuracy for homogeneous cylinders of different size; errors decreased from 7% to below 1% in the center of the objects for the uncorrected and corrected images, respectively, and maximum differences were reduced from 17% to 2%, respectively. The

  15. Correction of beam-beam effects in luminosity measurement at ILC

    CERN Document Server

    Lukic, S

    2015-01-01

    Three methods for handling beam-beam effects in luminosity measurement at ILC are tested and evaluated in this work. The first method represents an optimization of the LEPtype asymmetric selection cuts that reduce the counting biases. The second method uses the experimentally reconstructed shape of the √ s ′ spectrum to determine the Beamstrahlung component of the bias. The last, recently proposed, collision-frame method relies on the reconstruction of the collision-frame velocity to define the selection function in the collision frame both in experiment and in theory. Thus the luminosity expression is insensitive to the difference between the CM frame of the collision and the lab frame. The collision-frame method is independent of the knowledge of the beam parameters, and it allows an accurate reconstruction of the luminosity spectrum above 80% of the nominal CM energy. However, it gives no precise infromation about luminosity below 80% of the nominal CM energy. The compatibility of diverse selection cut...

  16. Megavoltage photon beam attenuation by carbon fiber couch tops and its prediction using correction factors

    International Nuclear Information System (INIS)

    Hayashi, Naoki; Shibamoto, Yuta; Obata, Yasunori; Kimura, Takashi; Nakazawa, Hisato; Hagiwara, Masahiro; Hashizume, Chisa I.; Mori, Yoshimasa; Kobayashi, Tatsuya

    2010-01-01

    The purpose of this study was to evaluate the effect of megavoltage photon beam attenuation (PBA) by couch tops and to propose a method for correction of PBA. Four series of phantom measurements were carried out. First, PBA by the exact couch top (ECT, Varian) and Imaging Couch Top (ICT, BrainLAB) was evaluated using a water-equivalent phantom. Second, PBA by Type-S system (Med-Tec), ECT and ICT was compared with a spherical phantom. Third, percentage depth dose (PDD) after passing through ICT was measured to compare with control data of PDD. Forth, the gantry angle dependency of PBA by ICT was evaluated. Then, an equation for PBA correction was elaborated and correction factors for PBA at isocenter were obtained. Finally, this method was applied to a patient with hepatoma. PBA of perpendicular beams by ICT was 4.7% on average. With the increase in field size, the measured values became higher. PBA by ICT was greater than that by Type-S system and ECT. PBA increased significantly as the angle of incidence increased, ranging from 4.3% at 180 deg to 11.2% at 120 deg. Calculated doses obtained by the equation and correction factors agreed quite well with the measured doses between 120 deg and 180 deg of angles of incidence. Also in the patient, PBA by ICT was corrected quite well by the equation and correction factors. In conclusion, PBA and its gantry angle dependency by ICT were observed. This simple method using the equation and correction factors appeared useful to correct the isocenter dose when the PBA effect cannot be corrected by a treatment planning system. (author)

  17. Aperture correction with an asymmetrically trimmed gaussian weight in SPECT with a fan-beam collimator

    International Nuclear Information System (INIS)

    Kamiya, Ryo; Ogawa, Koichi

    2013-01-01

    The aim of the study is to improve the spatial resolution of single photon emission computed tomography (SPECT) images acquired with a fan-beam collimator. The aperture angle of a hole in the fan-beam collimator depends on the position of the collimator. To correct the aperture effect in an iterative image reconstruction, an asymmetrically trimmed Gaussian weight was used for a model. To confirm the validity of our method, point source phantoms and brain phantom were used in the simulation, and we applied the method to the clinical data. The results of the simulation showed that the spatial resolution of point sources improved from about 6 to 2 pixels full width at half maximum, and the corrected point sources were isotropic. The results of the simulation with the brain phantom showed that our proposed method could improve the spatial resolution of the phantom, and our method was effective for different fan-beam collimators with different focal lengths. The results of clinical data showed that the quality of the reconstructed image was improved with our proposed method. Our proposed aperture correction method with the asymmetrically trimmed Gaussian weighting function was effective in improving the spatial resolution of SPECT images acquired with the fan-beam collimator. (author)

  18. Clinical introduction of image lag correction for a cone beam CT system

    International Nuclear Information System (INIS)

    Stankovic, Uros; Ploeger, Lennert S.; Sonke, Jan-Jakob; Herk, Marcel van

    2016-01-01

    Purpose: Image lag in the flat-panel detector used for Linac integrated cone beam computed tomography (CBCT) has a degrading effect on CBCT image quality. The most prominent visible artifact is the presence of bright semicircular structure in the transverse view of the scans, known also as radar artifact. Several correction strategies have been proposed, but until now the clinical introduction of such corrections remains unreported. In November 2013, the authors have clinically implemented a previously proposed image lag correction on all of their machines at their main site in Amsterdam. The purpose of this study was to retrospectively evaluate the effect of the correction on the quality of CBCT images and evaluate the required calibration frequency. Methods: Image lag was measured in five clinical CBCT systems (Elekta Synergy 4.6) using an in-house developed beam interrupting device that stops the x-ray beam midway through the data acquisition of an unattenuated beam for calibration. A triple exponential falling edge response was fitted to the measured data and used to correct image lag from projection images with an infinite response. This filter, including an extrapolation for saturated pixels, was incorporated in the authors’ in-house developed clinical CBCT reconstruction software. To investigate the short-term stability of the lag and associated parameters, a series of five image lag measurement over a period of three months was performed. For quantitative analysis, the authors have retrospectively selected ten patients treated in the pelvic region. The apparent contrast was quantified in polar coordinates for scans reconstructed using the parameters obtained from different dates with and without saturation handling. Results: Visually, the radar artifact was minimal in scans reconstructed using image lag correction especially when saturation handling was used. In patient imaging, there was a significant reduction of the apparent contrast from 43 ± 16.7 to

  19. Clinical introduction of image lag correction for a cone beam CT system.

    Science.gov (United States)

    Stankovic, Uros; Ploeger, Lennert S; Sonke, Jan-Jakob; van Herk, Marcel

    2016-03-01

    Image lag in the flat-panel detector used for Linac integrated cone beam computed tomography (CBCT) has a degrading effect on CBCT image quality. The most prominent visible artifact is the presence of bright semicircular structure in the transverse view of the scans, known also as radar artifact. Several correction strategies have been proposed, but until now the clinical introduction of such corrections remains unreported. In November 2013, the authors have clinically implemented a previously proposed image lag correction on all of their machines at their main site in Amsterdam. The purpose of this study was to retrospectively evaluate the effect of the correction on the quality of CBCT images and evaluate the required calibration frequency. Image lag was measured in five clinical CBCT systems (Elekta Synergy 4.6) using an in-house developed beam interrupting device that stops the x-ray beam midway through the data acquisition of an unattenuated beam for calibration. A triple exponential falling edge response was fitted to the measured data and used to correct image lag from projection images with an infinite response. This filter, including an extrapolation for saturated pixels, was incorporated in the authors' in-house developed clinical cbct reconstruction software. To investigate the short-term stability of the lag and associated parameters, a series of five image lag measurement over a period of three months was performed. For quantitative analysis, the authors have retrospectively selected ten patients treated in the pelvic region. The apparent contrast was quantified in polar coordinates for scans reconstructed using the parameters obtained from different dates with and without saturation handling. Visually, the radar artifact was minimal in scans reconstructed using image lag correction especially when saturation handling was used. In patient imaging, there was a significant reduction of the apparent contrast from 43 ± 16.7 to 15.5 ± 11.9 HU without the

  20. SU-E-T-464: On the Equivalence of the Quality Correction Factor for Pencil Beam Scanning Proton Therapy

    International Nuclear Information System (INIS)

    Sorriaux, J; Paganetti, H; Testa, M; Giantsoudi, D; Schuemann, J; Bertrand, D; Orban de Xivry, J.; Lee, J; Palmans, H; Vynckier, S; Sterpin, E

    2014-01-01

    Purpose: In current practice, most proton therapy centers apply IAEA TRS-398 reference dosimetry protocol. Quality correction factors (kQ) take into account in the dose determination process the differences in beam qualities used for calibration unit and for treatment unit. These quality correction factors are valid for specific reference conditions. TRS-398 reference conditions should be achievable in both scattered proton beams (i.e. DS) and scanned proton beams (i.e. PBS). However, it is not a priori clear if TRS-398 kQ data, which are based on Monte Carlo (MC) calculations in scattered beams, can be used for scanned beams. Using TOPAS-Geant4 MC simulations, the study aims to determine whether broad beam quality correction factors calculated in TRS-398 can be directly applied to PBS delivery modality. Methods: As reference conditions, we consider a 10×10×10 cm 3 homogeneous dose distribution delivered by PBS system in a water phantom (32/10 cm range/modulation) and an air cavity placed at the center of the spread-out-Bragg-peak. In order to isolate beam differences, a hypothetical broad beam is simulated. This hypothetical beam reproduces exactly the same range modulation, and uses the same energy layers than the PBS field. Ion chamber responses are computed for the PBS and hypothetical beams and then compared. Results: For an air cavity of 2×2×0.2 cm 3 , the ratio of ion chamber responses for the PBS and hypothetical beam qualities is 0.9991 ± 0.0016. Conclusion: Quality correction factors are insensitive to the delivery pattern of the beam (broad beam or PBS), as long as similar dose distributions are achieved. This investigation, for an air cavity, suggests that broad beam quality correction factors published in TRS-398 can be applied for scanned beams. J. Sorriaux is financially supported by a public-private partnership involving the company Ion Beam Applications (IBA)

  1. Closed-orbit correction using the new beam position monitor electronic of Elsa Bonn

    CERN Document Server

    Dietrich, J; Keil, J

    2000-01-01

    RF and digital electronics, developed at the Forschungszentrum Jülich/IKP were integrated to form the new beam position monitor (BPM) system at the Electron Stretcher Accelerator (ELSA) of the University of Bonn. With this system the preservation of the polarization level during acceleration was currently improved by a good correction of the closed-orbit. All BPM offsets relative to the magnetic quadrupole centers were determined by the method of beam-based alignment. The optics functions measured by the BPM system are in good agreement with theoretical predictions.

  2. A hardenability test proposal

    Energy Technology Data Exchange (ETDEWEB)

    Murthy, N.V.S.N. [Ingersoll-Rand (I) Ltd., Bangalore (India)

    1996-12-31

    A new approach for hardenability evaluation and its application to heat treatable steels will be discussed. This will include an overview and deficiencies of the current methods and discussion on the necessity for a new approach. Hardenability terminology will be expanded to avoid ambiguity and over-simplification as encountered with the current system. A new hardenability definition is proposed. Hardenability specification methods are simplified and rationalized. The new hardenability evaluation system proposed here utilizes a test specimen with varying diameter as an alternative to the cylindrical Jominy hardenability test specimen and is readily applicable to the evaluation of a wide variety of steels with different cross-section sizes.

  3. Motion correction in neurological fan beam SPECT using motion tracking and fully 3D reconstruction

    International Nuclear Information System (INIS)

    Fulton, R.R.; Hutton, B.; Eberl, S.; Meikle, S.; Braun, M.; Westmead Hospital, Westmead, NSW; University of Technology, Sydney, NSW

    1998-01-01

    Full text: We have previously proposed the use of fully three-dimensional (3D) reconstruction and continuous monitoring of head position to correct for motion artifacts in neurological SPECT and PET. Knowledge of the motion during acquisition provided by a head tracking system can be used to reposition the projection data in space in such a way as to negate motion effects during reconstruction. The reconstruction algorithm must deal with variations in the projection geometry resulting from differences in the timing and nature of motion between patients. Rotational movements about any axis other than the camera's axis of rotation give rise to projection geometries which necessitate the use of a fully 3D reconstruction algorithm. Our previous work with computer simulations assuming parallel hole collimation demonstrated the feasibility of correcting for motion. We have now refined our iterative 3D reconstruction algorithm to support fan beam data and attenuation correction, and developed a practical head tracking system for use on a Trionix Triad SPECT system. The correction technique has been tested in fan beam SPECT studies of the 3D Hoffman brain phantom. Arbitrary movements were applied to the phantom during acquisition and recorded by the head tracker which monitored the position and orientation of the phantom throughout the study. 3D reconstruction was then performed using the motion data provided by the tracker. The accuracy of correction was assessed by comparing the corrected images with a motion free study acquired immediately beforehand, visually and by calculating mean squared error (MSE). Motion correction reduced distortion perceptibly and, depending on the motions applied, improved MSE by up to an order of magnitude. 3D reconstruction of the 128x128x128 data set took 20 minutes on a SUN Ultra 1 workstation. The results of these phantom experiments suggest that the technique can effectively compensate for head motion under clinical SPECT imaging

  4. Electron beam position stabilization with a piezo-electric optical correction system

    CERN Document Server

    Averett, T; McKeown, R D; Pitt, M

    1999-01-01

    A piezo-electrically controlled optical correction system was successfully used to reduce the helicity-correlated pulse-to-pulse position differences of a laser spot to better than +-100 nm at a pulse rate of 600 Hz. Using a simple feedback algorithm, average position differences of DELTA x-bar=-3.5+-4.2 nm and DELTA y-bar=2.6+-6.6 nm were obtained over a 6 h period. This optical correction system was successfully used in the polarized electron source at the Bates Linear Accelerator Center to stabilize the position of the electron beam during the recent SAMPLE experiment. Because this experiment measures a parity violating signal at the 10 sup - sup 6 level, it is sensitive to systematic effects which are correlated with the helicity of the incident electrons. One potentially large systematic effect is the helicity-correlated motion of the incident electron beam. By using this optical correction system, electron beam position differences at the location of the experiment were routinely kept well below +-100 n...

  5. Preventive and corrective maintenance for MINT EPS 3000 electron beam machine

    International Nuclear Information System (INIS)

    Siti Aiasah Hashim; Shaari Jahar

    2005-01-01

    Preventive and corrective maintenance of a high energy electron is to ensure that the machine would not fail during operation. MINT's EPS 3000 electron beam machine has been in operation for almost 12 years. Throughout those years, events relating to scheduled overhauls and unscheduled corrective maintenance had provided invaluable experience in the form of informal maintenance training to the operators. With the implementation of ISO 9001:2000 Quality Management System at the facility, the preventive and corrective maintenance program is becoming more structured and orderly. Collected maintenance data shall be used to initiate continual improvement activities in the facility.This paper describes MINT-ALURTRON's 12 years experience in providing maintenance work for the EPS 3000. (Author)

  6. SU-E-I-62: Assessing Radiation Dose Reduction and CT Image Optimization Through the Measurement and Analysis of the Detector Quantum Efficiency (DQE) of CT Images Using Different Beam Hardening Filters

    International Nuclear Information System (INIS)

    Collier, J; Aldoohan, S; Gill, K

    2014-01-01

    Purpose: Reducing patient dose while maintaining (or even improving) image quality is one of the foremost goals in CT imaging. To this end, we consider the feasibility of optimizing CT scan protocols in conjunction with the application of different beam-hardening filtrations and assess this augmentation through noise-power spectrum (NPS) and detector quantum efficiency (DQE) analysis. Methods: American College of Radiology (ACR) and Catphan phantoms (The Phantom Laboratory) were scanned with a 64 slice CT scanner when additional filtration of thickness and composition (e.g., copper, nickel, tantalum, titanium, and tungsten) had been applied. A MATLAB-based code was employed to calculate the image of noise NPS. The Catphan Image Owl software suite was then used to compute the modulated transfer function (MTF) responses of the scanner. The DQE for each additional filter, including the inherent filtration, was then computed from these values. Finally, CT dose index (CTDIvol) values were obtained for each applied filtration through the use of a 100 mm pencil ionization chamber and CT dose phantom. Results: NPS, MTF, and DQE values were computed for each applied filtration and compared to the reference case of inherent beam-hardening filtration only. Results showed that the NPS values were reduced between 5 and 12% compared to inherent filtration case. Additionally, CTDIvol values were reduced between 15 and 27% depending on the composition of filtration applied. However, no noticeable changes in image contrast-to-noise ratios were noted. Conclusion: The reduction in the quanta noise section of the NPS profile found in this phantom-based study is encouraging. The reduction in both noise and dose through the application of beam-hardening filters is reflected in our phantom image quality. However, further investigation is needed to ascertain the applicability of this approach to reducing patient dose while maintaining diagnostically acceptable image qualities in a

  7. Correction

    DEFF Research Database (Denmark)

    Pinkevych, Mykola; Cromer, Deborah; Tolstrup, Martin

    2016-01-01

    [This corrects the article DOI: 10.1371/journal.ppat.1005000.][This corrects the article DOI: 10.1371/journal.ppat.1005740.][This corrects the article DOI: 10.1371/journal.ppat.1005679.].......[This corrects the article DOI: 10.1371/journal.ppat.1005000.][This corrects the article DOI: 10.1371/journal.ppat.1005740.][This corrects the article DOI: 10.1371/journal.ppat.1005679.]....

  8. Laser Surface Hardening of Groove Edges

    Science.gov (United States)

    Hussain, A.; Hamdani, A. H.; Akhter, R.; Aslam, M.

    2013-06-01

    Surface hardening of groove-edges made of 3Cr13 Stainless Steel has been carried out using 500 W CO2 laser with a rectangular beam of 2.5×3 mm2. The processing speed was varied from 150-500 mm/min. It was seen that the hardened depth increases with increase in laser interaction time. A maximum hardened depth of around 1mm was achieved. The microhardness of the transformed zone was 2.5 times the hardness of base metal. The XRD's and microstructural analysis were also reported.

  9. Geometrical correction of the e-beam proximity effect for raster scan systems

    Science.gov (United States)

    Belic, Nikola; Eisenmann, Hans; Hartmann, Hans; Waas, Thomas

    1999-06-01

    Increasing demands on pattern fidelity and CD accuracy in e- beam lithography require a correction of the e-beam proximity effect. The new needs are mainly coming from OPC at mask level and x-ray lithography. The e-beam proximity limits the achievable resolution and affects neighboring structures causing under- or over-exposion depending on the local pattern densities and process settings. Methods to compensate for this unequilibrated does distribution usually use a dose modulation or multiple passes. In general raster scan systems are not able to apply variable doses in order to compensate for the proximity effect. For system of this kind a geometrical modulation of the original pattern offers a solution for compensation of line edge deviations due to the proximity effect. In this paper a new method for the fast correction of the e-beam proximity effect via geometrical pattern optimization is described. The method consists of two steps. In a first step the pattern dependent dose distribution caused by back scattering is calculated by convolution of the pattern with the long range part of the proximity function. The restriction to the long range part result in a quadratic sped gain in computing time for the transformation. The influence of the short range part coming from forward scattering is not pattern dependent and can therefore be determined separately in a second step. The second calculation yields the dose curve at the border of a written structure. The finite gradient of this curve leads to an edge displacement depending on the amount of underground dosage at the observed position which was previously determined in the pattern dependent step. This unintended edge displacement is corrected by splitting the line into segments and shifting them by multiples of the writers address grid to the opposite direction.

  10. Fast shading correction for cone beam CT in radiation therapy via sparse sampling on planning CT.

    Science.gov (United States)

    Shi, Linxi; Tsui, Tiffany; Wei, Jikun; Zhu, Lei

    2017-05-01

    The image quality of cone beam computed tomography (CBCT) is limited by severe shading artifacts, hindering its quantitative applications in radiation therapy. In this work, we propose an image-domain shading correction method using planning CT (pCT) as prior information which is highly adaptive to clinical environment. We propose to perform shading correction via sparse sampling on pCT. The method starts with a coarse mapping between the first-pass CBCT images obtained from the Varian TrueBeam system and the pCT. The scatter correction method embedded in the Varian commercial software removes some image errors but the CBCT images still contain severe shading artifacts. The difference images between the mapped pCT and the CBCT are considered as shading errors, but only sparse shading samples are selected for correction using empirical constraints to avoid carrying over false information from pCT. A Fourier-Transform-based technique, referred to as local filtration, is proposed to efficiently process the sparse data for effective shading correction. The performance of the proposed method is evaluated on one anthropomorphic pelvis phantom and 17 patients, who were scheduled for radiation therapy. (The codes of the proposed method and sample data can be downloaded from https://sites.google.com/view/linxicbct) RESULTS: The proposed shading correction substantially improves the CBCT image quality on both the phantom and the patients to a level close to that of the pCT images. On the phantom, the spatial nonuniformity (SNU) difference between CBCT and pCT is reduced from 74 to 1 HU. The root of mean square difference of SNU between CBCT and pCT is reduced from 83 to 10 HU on the pelvis patients, and from 101 to 12 HU on the thorax patients. The robustness of the proposed shading correction is fully investigated with simulated registration errors between CBCT and pCT on the phantom and mis-registration on patients. The sparse sampling scheme of our method successfully

  11. Electron fluence correction factors for various materials in clinical electron beams

    International Nuclear Information System (INIS)

    Olivares, M.; Blois, F. de; Podgorsak, E.B.; Seuntjens, J.P.

    2001-01-01

    Relative to solid water, electron fluence correction factors at the depth of dose maximum in bone, lung, aluminum, and copper for nominal electron beam energies of 9 MeV and 15 MeV of the Clinac 18 accelerator have been determined experimentally and by Monte Carlo calculation. Thermoluminescent dosimeters were used to measure depth doses in these materials. The measured relative dose at d max in the various materials versus that of solid water, when irradiated with the same number of monitor units, has been used to calculate the ratio of electron fluence for the various materials to that of solid water. The beams of the Clinac 18 were fully characterized using the EGS4/BEAM system. EGSnrc with the relativistic spin option turned on was used to optimize the primary electron energy at the exit window, and to calculate depth doses in the five phantom materials using the optimized phase-space data. Normalizing all depth doses to the dose maximum in solid water stopping power ratio corrected, measured depth doses and calculated depth doses differ by less than ±1% at the depth of dose maximum and by less than 4% elsewhere. Monte Carlo calculated ratios of doses in each material to dose in LiF were used to convert the TLD measurements at the dose maximum into dose at the center of the TLD in the phantom material. Fluence perturbation correction factors for a LiF TLD at the depth of dose maximum deduced from these calculations amount to less than 1% for 0.15 mm thick TLDs in low Z materials and are between 1% and 3% for TLDs in Al and Cu phantoms. Electron fluence ratios of the studied materials relative to solid water vary between 0.83±0.01 and 1.55±0.02 for materials varying in density from 0.27 g/cm3 (lung) to 8.96 g/cm3 (Cu). The difference in electron fluence ratios derived from measurements and calculations ranges from -1.6% to +0.2% at 9 MeV and from -1.9% to +0.2% at 15 MeV and is not significant at the 1σ level. Excluding the data for Cu, electron fluence

  12. Analytic representation of the backscatter correction factor at the exit of high energy photon beams

    International Nuclear Information System (INIS)

    Kappas, K.; Rosenwald, J.C.

    1991-01-01

    In high-energy X-ray beams, the dose calculated near the exit surface under electronic equilibrium conditions is generally over-estimated since it is derived from measurements performed in water with large thickness of backscattering material. The resulting error depends on a number of parameters such as beam energy, field dimension, thickness of overlying and underlying material. The authors have systematically measured for 4 different energies and for different para- meters and for different combinations of the above parameters, the reduction of dose due to backscatter. This correction is expressed as a multiplicative factor, called 'Backscatter Correction Factor' (BCF). This BCF is larger for lower energies, larger field sizes and larger depths. The BCF has been represented by an analytical expression which involves an exponential function of the backscattering thickness and linear relationships with depth field size and beam quality index. Using this expression, the BCF can be calculated within 0.5% for any conditions in the energy range investigated. (author). 14 refs.; 4 figs.; 3 tabs

  13. Correction of patient motion in cone-beam CT using 3D-2D registration

    Science.gov (United States)

    Ouadah, S.; Jacobson, M.; Stayman, J. W.; Ehtiati, T.; Weiss, C.; Siewerdsen, J. H.

    2017-12-01

    Cone-beam CT (CBCT) is increasingly common in guidance of interventional procedures, but can be subject to artifacts arising from patient motion during fairly long (~5-60 s) scan times. We present a fiducial-free method to mitigate motion artifacts using 3D-2D image registration that simultaneously corrects residual errors in the intrinsic and extrinsic parameters of geometric calibration. The 3D-2D registration process registers each projection to a prior 3D image by maximizing gradient orientation using the covariance matrix adaptation-evolution strategy optimizer. The resulting rigid transforms are applied to the system projection matrices, and a 3D image is reconstructed via model-based iterative reconstruction. Phantom experiments were conducted using a Zeego robotic C-arm to image a head phantom undergoing 5-15 cm translations and 5-15° rotations. To further test the algorithm, clinical images were acquired with a CBCT head scanner in which long scan times were susceptible to significant patient motion. CBCT images were reconstructed using a penalized likelihood objective function. For phantom studies the structural similarity (SSIM) between motion-free and motion-corrected images was  >0.995, with significant improvement (p  values of uncorrected images. Additionally, motion-corrected images exhibited a point-spread function with full-width at half maximum comparable to that of the motion-free reference image. Qualitative comparison of the motion-corrupted and motion-corrected clinical images demonstrated a significant improvement in image quality after motion correction. This indicates that the 3D-2D registration method could provide a useful approach to motion artifact correction under assumptions of local rigidity, as in the head, pelvis, and extremities. The method is highly parallelizable, and the automatic correction of residual geometric calibration errors provides added benefit that could be valuable in routine use.

  14. Diffraction corrections for second harmonic beam fields and effects on the nonlinearity parameter evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Hyun Jo; Cho, Sung Jong; Nam, Ki Woong; Lee, Jang Hyun [Division of Mechanical and Automotive Engineering, Wonkwang University, Iksan (Korea, Republic of)

    2016-04-15

    The nonlinearity parameter is frequently measured as a sensitive indicator in damaged material characterization or tissue harmonic imaging. Several previous studies have employed the plane wave solution, and ignored the effects of beam diffraction when measuring the non-linearity parameter β. This paper presents a multi-Gaussian beam approach to explicitly derive diffraction corrections for fundamental and second harmonics under quasilinear and paraxial approximation. Their effects on the nonlinearity parameter estimation demonstrate complicated dependence of β on the transmitter-receiver geometries, frequency, and propagation distance. The diffraction effects on the non-linearity parameter estimation are important even in the nearfield region. Experiments are performed to show that improved β values can be obtained by considering the diffraction effects.

  15. SU-F-T-67: Correction Factors for Monitor Unit Verification of Clinical Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Haywood, J [Mercy Health Partners, Muskegon, MI (United States)

    2016-06-15

    Purpose: Monitor units calculated by electron Monte Carlo treatment planning systems are often higher than TG-71 hand calculations for a majority of patients. Here I’ve calculated tables of geometry and heterogeneity correction factors for correcting electron hand calculations. Method: A flat water phantom with spherical volumes having radii ranging from 3 to 15 cm was created. The spheres were centered with respect to the flat water phantom, and all shapes shared a surface at 100 cm SSD. D{sub max} dose at 100 cm SSD was calculated for each cone and energy on the flat phantom and for the spherical volumes in the absence of the flat phantom. The ratio of dose in the sphere to dose in the flat phantom defined the geometrical correction factor. The heterogeneity factors were then calculated from the unrestricted collisional stopping power for tissues encountered in electron beam treatments. These factors were then used in patient second check calculations. Patient curvature was estimated by the largest sphere that aligns to the patient contour, and appropriate tissue density was read from the physical properties provided by the CT. The resulting MU were compared to those calculated by the treatment planning system and TG-71 hand calculations. Results: The geometry and heterogeneity correction factors range from ∼(0.8–1.0) and ∼(0.9–1.01) respectively for the energies and cones presented. Percent differences for TG-71 hand calculations drop from ∼(3–14)% to ∼(0–2)%. Conclusion: Monitor units calculated with the correction factors typically decrease the percent difference to under actionable levels, < 5%. While these correction factors work for a majority of patients, there are some patient anatomies that do not fit the assumptions made. Using these factors in hand calculations is a first step in bringing the verification monitor units into agreement with the treatment planning system MU.

  16. Statistical reconstruction for cone-beam CT with a post-artifact-correction noise model: application to high-quality head imaging

    International Nuclear Information System (INIS)

    Dang, H; Stayman, J W; Sisniega, A; Xu, J; Zbijewski, W; Siewerdsen, J H; Wang, X; Foos, D H; Aygun, N; Koliatsos, V E

    2015-01-01

    Non-contrast CT reliably detects fresh blood in the brain and is the current front-line imaging modality for intracranial hemorrhage such as that occurring in acute traumatic brain injury (contrast ∼40–80 HU, size  >  1 mm). We are developing flat-panel detector (FPD) cone-beam CT (CBCT) to facilitate such diagnosis in a low-cost, mobile platform suitable for point-of-care deployment. Such a system may offer benefits in the ICU, urgent care/concussion clinic, ambulance, and sports and military theatres. However, current FPD-CBCT systems face significant challenges that confound low-contrast, soft-tissue imaging. Artifact correction can overcome major sources of bias in FPD-CBCT but imparts noise amplification in filtered backprojection (FBP). Model-based reconstruction improves soft-tissue image quality compared to FBP by leveraging a high-fidelity forward model and image regularization. In this work, we develop a novel penalized weighted least-squares (PWLS) image reconstruction method with a noise model that includes accurate modeling of the noise characteristics associated with the two dominant artifact corrections (scatter and beam-hardening) in CBCT and utilizes modified weights to compensate for noise amplification imparted by each correction. Experiments included real data acquired on a FPD-CBCT test-bench and an anthropomorphic head phantom emulating intra-parenchymal hemorrhage. The proposed PWLS method demonstrated superior noise-resolution tradeoffs in comparison to FBP and PWLS with conventional weights (viz. at matched 0.50 mm spatial resolution, CNR = 11.9 compared to CNR = 5.6 and CNR = 9.9, respectively) and substantially reduced image noise especially in challenging regions such as skull base. The results support the hypothesis that with high-fidelity artifact correction and statistical reconstruction using an accurate post-artifact-correction noise model, FPD-CBCT can achieve image quality allowing reliable detection of

  17. A study on microstructure and strain-hardening rate of friction stir welded Al-Mg-Si alloys using a weak beam technique

    International Nuclear Information System (INIS)

    Sukedai, E; Yokoyama, T

    2012-01-01

    Mechanical properties of a friction stir welded Al-Mg-Si (6061-T6Al) alloy are evaluated by a tensile test. It is found that the strain-hardening rate is higher than that of a base material. In order to investigate the origin, TEM observations have been performed about 4 kinds of materials; base- and friction stir welded-materials, and both materials deformed to 5 % strain by tension. There are not so large differences about dislocation density, size and density of precipitates and crystal defects between the base material and the friction stir welded-materials, but a significant decrease of grain-size in the friction stir welded-materials is recognized. These results suggest a dynamic recovery occurs during FSW process, and it is speculated that the recovery leads to the differences of yield stress and strain-hardening rate between both materials.

  18. Experimental and Monte Carlo studies of fluence corrections for graphite calorimetry in low- and high-energy clinical proton beams

    International Nuclear Information System (INIS)

    Lourenço, Ana; Thomas, Russell; Bouchard, Hugo; Kacperek, Andrzej; Vondracek, Vladimir; Royle, Gary; Palmans, Hugo

    2016-01-01

    Purpose: The aim of this study was to determine fluence corrections necessary to convert absorbed dose to graphite, measured by graphite calorimetry, to absorbed dose to water. Fluence corrections were obtained from experiments and Monte Carlo simulations in low- and high-energy proton beams. Methods: Fluence corrections were calculated to account for the difference in fluence between water and graphite at equivalent depths. Measurements were performed with narrow proton beams. Plane-parallel-plate ionization chambers with a large collecting area compared to the beam diameter were used to intercept the whole beam. High- and low-energy proton beams were provided by a scanning and double scattering delivery system, respectively. A mathematical formalism was established to relate fluence corrections derived from Monte Carlo simulations, using the FLUKA code [A. Ferrari et al., “FLUKA: A multi-particle transport code,” in CERN 2005-10, INFN/TC 05/11, SLAC-R-773 (2005) and T. T. Böhlen et al., “The FLUKA Code: Developments and challenges for high energy and medical applications,” Nucl. Data Sheets 120, 211–214 (2014)], to partial fluence corrections measured experimentally. Results: A good agreement was found between the partial fluence corrections derived by Monte Carlo simulations and those determined experimentally. For a high-energy beam of 180 MeV, the fluence corrections from Monte Carlo simulations were found to increase from 0.99 to 1.04 with depth. In the case of a low-energy beam of 60 MeV, the magnitude of fluence corrections was approximately 0.99 at all depths when calculated in the sensitive area of the chamber used in the experiments. Fluence correction calculations were also performed for a larger area and found to increase from 0.99 at the surface to 1.01 at greater depths. Conclusions: Fluence corrections obtained experimentally are partial fluence corrections because they account for differences in the primary and part of the secondary

  19. Experimental and Monte Carlo studies of fluence corrections for graphite calorimetry in low- and high-energy clinical proton beams

    Energy Technology Data Exchange (ETDEWEB)

    Lourenço, Ana, E-mail: am.lourenco@ucl.ac.uk [Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, United Kingdom and Division of Acoustics and Ionising Radiation, National Physical Laboratory, Teddington TW11 0LW (United Kingdom); Thomas, Russell; Bouchard, Hugo [Division of Acoustics and Ionising Radiation, National Physical Laboratory, Teddington TW11 0LW (United Kingdom); Kacperek, Andrzej [National Eye Proton Therapy Centre, Clatterbridge Cancer Centre, Wirral CH63 4JY (United Kingdom); Vondracek, Vladimir [Proton Therapy Center, Budinova 1a, Prague 8 CZ-180 00 (Czech Republic); Royle, Gary [Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT (United Kingdom); Palmans, Hugo [Division of Acoustics and Ionising Radiation, National Physical Laboratory, Teddington TW11 0LW, United Kingdom and Medical Physics Group, EBG MedAustron GmbH, A-2700 Wiener Neustadt (Austria)

    2016-07-15

    Purpose: The aim of this study was to determine fluence corrections necessary to convert absorbed dose to graphite, measured by graphite calorimetry, to absorbed dose to water. Fluence corrections were obtained from experiments and Monte Carlo simulations in low- and high-energy proton beams. Methods: Fluence corrections were calculated to account for the difference in fluence between water and graphite at equivalent depths. Measurements were performed with narrow proton beams. Plane-parallel-plate ionization chambers with a large collecting area compared to the beam diameter were used to intercept the whole beam. High- and low-energy proton beams were provided by a scanning and double scattering delivery system, respectively. A mathematical formalism was established to relate fluence corrections derived from Monte Carlo simulations, using the FLUKA code [A. Ferrari et al., “FLUKA: A multi-particle transport code,” in CERN 2005-10, INFN/TC 05/11, SLAC-R-773 (2005) and T. T. Böhlen et al., “The FLUKA Code: Developments and challenges for high energy and medical applications,” Nucl. Data Sheets 120, 211–214 (2014)], to partial fluence corrections measured experimentally. Results: A good agreement was found between the partial fluence corrections derived by Monte Carlo simulations and those determined experimentally. For a high-energy beam of 180 MeV, the fluence corrections from Monte Carlo simulations were found to increase from 0.99 to 1.04 with depth. In the case of a low-energy beam of 60 MeV, the magnitude of fluence corrections was approximately 0.99 at all depths when calculated in the sensitive area of the chamber used in the experiments. Fluence correction calculations were also performed for a larger area and found to increase from 0.99 at the surface to 1.01 at greater depths. Conclusions: Fluence corrections obtained experimentally are partial fluence corrections because they account for differences in the primary and part of the secondary

  20. Ultrafast cone-beam CT scatter correction with GPU-based Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    Yuan Xu

    2014-03-01

    Full Text Available Purpose: Scatter artifacts severely degrade image quality of cone-beam CT (CBCT. We present an ultrafast scatter correction framework by using GPU-based Monte Carlo (MC simulation and prior patient CT image, aiming at automatically finish the whole process including both scatter correction and reconstruction within 30 seconds.Methods: The method consists of six steps: 1 FDK reconstruction using raw projection data; 2 Rigid Registration of planning CT to the FDK results; 3 MC scatter calculation at sparse view angles using the planning CT; 4 Interpolation of the calculated scatter signals to other angles; 5 Removal of scatter from the raw projections; 6 FDK reconstruction using the scatter-corrected projections. In addition to using GPU to accelerate MC photon simulations, we also use a small number of photons and a down-sampled CT image in simulation to further reduce computation time. A novel denoising algorithm is used to eliminate MC noise from the simulated scatter images caused by low photon numbers. The method is validated on one simulated head-and-neck case with 364 projection angles.Results: We have examined variation of the scatter signal among projection angles using Fourier analysis. It is found that scatter images at 31 angles are sufficient to restore those at all angles with < 0.1% error. For the simulated patient case with a resolution of 512 × 512 × 100, we simulated 5 × 106 photons per angle. The total computation time is 20.52 seconds on a Nvidia GTX Titan GPU, and the time at each step is 2.53, 0.64, 14.78, 0.13, 0.19, and 2.25 seconds, respectively. The scatter-induced shading/cupping artifacts are substantially reduced, and the average HU error of a region-of-interest is reduced from 75.9 to 19.0 HU.Conclusion: A practical ultrafast MC-based CBCT scatter correction scheme is developed. It accomplished the whole procedure of scatter correction and reconstruction within 30 seconds.----------------------------Cite this

  1. Scatter correction, intermediate view estimation and dose characterization in megavoltage cone-beam CT imaging

    Science.gov (United States)

    Sramek, Benjamin Koerner

    The ability to deliver conformal dose distributions in radiation therapy through intensity modulation and the potential for tumor dose escalation to improve treatment outcome has necessitated an increase in localization accuracy of inter- and intra-fractional patient geometry. Megavoltage cone-beam CT imaging using the treatment beam and onboard electronic portal imaging device is one option currently being studied for implementation in image-guided radiation therapy. However, routine clinical use is predicated upon continued improvements in image quality and patient dose delivered during acquisition. The formal statement of hypothesis for this investigation was that the conformity of planned to delivered dose distributions in image-guided radiation therapy could be further enhanced through the application of kilovoltage scatter correction and intermediate view estimation techniques to megavoltage cone-beam CT imaging, and that normalized dose measurements could be acquired and inter-compared between multiple imaging geometries. The specific aims of this investigation were to: (1) incorporate the Feldkamp, Davis and Kress filtered backprojection algorithm into a program to reconstruct a voxelized linear attenuation coefficient dataset from a set of acquired megavoltage cone-beam CT projections, (2) characterize the effects on megavoltage cone-beam CT image quality resulting from the application of Intermediate View Interpolation and Intermediate View Reprojection techniques to limited-projection datasets, (3) incorporate the Scatter and Primary Estimation from Collimator Shadows (SPECS) algorithm into megavoltage cone-beam CT image reconstruction and determine the set of SPECS parameters which maximize image quality and quantitative accuracy, and (4) evaluate the normalized axial dose distributions received during megavoltage cone-beam CT image acquisition using radiochromic film and thermoluminescent dosimeter measurements in anthropomorphic pelvic and head and

  2. Color correction of projected image on color-screen for mobile beam-projector

    Science.gov (United States)

    Son, Chang-Hwan; Sung, Soo-Jin; Ha, Yeong-Ho

    2008-01-01

    With the current trend of digital convergence in mobile phones, mobile manufacturers are researching how to develop a mobile beam-projector to cope with the limitations of a small screen size and to offer a better feeling of movement while watching movies or satellite broadcasting. However, mobile beam-projectors may project an image on arbitrary surfaces, such as a colored wall and paper, not on a white screen mainly used in an office environment. Thus, color correction method for the projected image is proposed to achieve good image quality irrespective of the surface colors. Initially, luminance values of original image transformed into the YCbCr space are changed to compensate for spatially nonuniform luminance distribution of arbitrary surface, depending on the pixel values of surface image captured by mobile camera. Next, the chromaticity values for each surface and white-screen image are calculated using the ratio of the sum of three RGB values to one another. Then their chromaticity ratios are multiplied by converted original image through an inverse YCbCr matrix to reduce an influence of modulating the appearance of projected image due to spatially different reflectance on the surface. By projecting corrected original image on a texture pattern or single color surface, the image quality of projected image can be improved more, as well as that of projected image on white screen.

  3. Minimal residual cone-beam reconstruction with attenuation correction in SPECT

    International Nuclear Information System (INIS)

    La, Valerie; Grangeat, Pierre

    1998-01-01

    This paper presents an iterative method based on the minimal residual algorithm for tomographic attenuation compensated reconstruction from attenuated cone-beam projections given the attenuation distribution. Unlike conjugate-gradient based reconstruction techniques, the proposed minimal residual based algorithm solves directly a quasisymmetric linear system, which is a preconditioned system. Thus it avoids the use of normal equations, which improves the convergence rate. Two main contributions are introduced. First, a regularization method is derived for quasisymmetric problems, based on a Tikhonov-Phillips regularization applied to the factorization of the symmetric part of the system matrix. This regularization is made spatially adaptive to avoid smoothing the region of interest. Second, our existing reconstruction algorithm for attenuation correction in parallel-beam geometry is extended to cone-beam geometry. A circular orbit is considered. Two preconditioning operators are proposed: the first one is Grangeat's inversion formula and the second one is Feldkamp's inversion formula. Experimental results obtained on simulated data are presented and the shadow zone effect on attenuated data is illustrated. (author)

  4. Exact fan-beam and 4π-acquisition cone-beam SPECT algorithms with uniform attenuation correction

    International Nuclear Information System (INIS)

    Tang Qiulin; Zeng, Gengsheng L.; Wu Jiansheng; Gullberg, Grant T.

    2005-01-01

    This paper presents analytical fan-beam and cone-beam reconstruction algorithms that compensate for uniform attenuation in single photon emission computed tomography. First, a fan-beam algorithm is developed by obtaining a relationship between the two-dimensional (2D) Fourier transform of parallel-beam projections and fan-beam projections. Using this relationship, 2D Fourier transforms of equivalent parallel-beam projection data are obtained from the fan-beam projection data. Then a quasioptimal analytical reconstruction algorithm for uniformly attenuated Radon data, developed by Metz and Pan, is used to reconstruct the image. A cone-beam algorithm is developed by extending the fan-beam algorithm to 4π solid angle geometry. The cone-beam algorithm is also an exact algorithm

  5. A monochromatic, aberration-corrected, dual-beam low energy electron microscope.

    Science.gov (United States)

    Mankos, Marian; Shadman, Khashayar

    2013-07-01

    The monochromatic, aberration-corrected, dual-beam low energy electron microscope (MAD-LEEM) is a novel instrument aimed at imaging of nanostructures and surfaces at sub-nanometer resolution that includes a monochromator, aberration corrector and dual beam illumination. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. The aberration corrector utilizes an electron mirror with negative aberrations that can be used to compensate the aberrations of the LEEM objective lens for a range of electron energies. Dual flood illumination eliminates charging generated when a conventional LEEM is used to image insulating specimens. MAD-LEEM is designed for the purpose of imaging biological and insulating specimens, which are difficult to image with conventional LEEM, Low-Voltage SEM, and TEM instruments. The MAD-LEEM instrument can also be used as a general purpose LEEM with significantly improved resolution. The low impact energy of the electrons is critical for avoiding beam damage, as high energy electrons with keV kinetic energies used in SEMs and TEMs cause irreversible change to many specimens, in particular biological materials. A potential application for MAD-LEEM is in DNA sequencing, which demands imaging techniques that enable DNA sequencing at high resolution and speed, and at low cost. The key advantages of the MAD-LEEM approach for this application are the low electron impact energies, the long read lengths, and the absence of heavy-atom DNA labeling. Image contrast simulations of the detectability of individual nucleotides in a DNA strand have been developed in order to refine the optics blur and DNA base contrast requirements for this application. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Scatter measurement and correction method for cone-beam CT based on single grating scan

    Science.gov (United States)

    Huang, Kuidong; Shi, Wenlong; Wang, Xinyu; Dong, Yin; Chang, Taoqi; Zhang, Hua; Zhang, Dinghua

    2017-06-01

    In cone-beam computed tomography (CBCT) systems based on flat-panel detector imaging, the presence of scatter significantly reduces the quality of slices. Based on the concept of collimation, this paper presents a scatter measurement and correction method based on single grating scan. First, according to the characteristics of CBCT imaging, the scan method using single grating and the design requirements of the grating are analyzed and figured out. Second, by analyzing the composition of object projection images and object-and-grating projection images, the processing method for the scatter image at single projection angle is proposed. In addition, to avoid additional scan, this paper proposes an angle interpolation method of scatter images to reduce scan cost. Finally, the experimental results show that the scatter images obtained by this method are accurate and reliable, and the effect of scatter correction is obvious. When the additional object-and-grating projection images are collected and interpolated at intervals of 30 deg, the scatter correction error of slices can still be controlled within 3%.

  7. Laser transformation hardening effect on hardening zone features and surface hardness of tool steel AISI D2

    Directory of Open Access Journals (Sweden)

    D. Lesyk

    2017-06-01

    Full Text Available The relationship of technological input regimes of the laser transformation hardening on change the hardening depth, hardening width, and hardening angle, as well as surface hardness of the tool steel AISI D2 using multifactor experiment with elements of the analysis of variance and regression equations was determined. The laser transformation hardening process implemented by controlling the heating temperature using Nd:YAG fiber laser with scanner, pyrometer and proportional-integral-differential controller. The linear and quadratic regression models are developed, as well as response surface to determine the effect of the heating temperature and feed rate of the treated surface on the energy density of the laser beam, hardening depths, hardening width, hardening angle, and surface hardness are designed. The main effect on the energy density of the laser beam has a velocity laser treatment, on the other hand, the main effect on the geometrical parameters of the laser hardened zone and surface hardness has temperature heating are shown. The optimum magnitudes of the heating temperature (1270 °C and feed rate of the treated surface (90 mm/min for laser transformation hardening of the tool steel AISI D2 using fiber laser with scanner were defined.

  8. SU-F-BRD-15: Quality Correction Factors in Scanned Or Broad Proton Therapy Beams Are Indistinguishable

    Energy Technology Data Exchange (ETDEWEB)

    Sorriaux, J; Lee, J [Molecular Imaging Radiotherapy & Oncology, Universite Catholique de Louvain, Brussels (Belgium); ICTEAM Institute, Universite catholique de Louvain, Louvain-la-Neuve (Belgium); Testa, M; Paganetti, H [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, Massachusetts (United States); Bertrand, D; Orban de Xivry, J [Ion Beam Applications, Louvain-la-neuve, Brabant Wallon (Belgium); Palmans, H [EBG MedAustron GmbH, Wiener Neustadt (Austria); National Physical Laboratory, Teddington (United Kingdom); Vynckier, S [Cliniques Universitaires Saint-Luc, Brussels (Belgium); Sterpin, E [Molecular Imaging Radiotherapy & Oncology, Universite Catholique de Louvain, Brussels (Belgium)

    2015-06-15

    Purpose: The IAEA TRS-398 code of practice details the reference conditions for reference dosimetry of proton beams using ionization chambers and the required beam quality correction factors (kQ). Pencil beam scanning (PBS) requires multiple spots to reproduce the reference conditions. The objective is to demonstrate, using Monte Carlo (MC) calculations, that kQ factors for broad beams can be used for scanned beams under the same reference conditions with no significant additional uncertainty. We consider hereafter the general Alfonso formalism (Alfonso et al, 2008) for non-standard beam. Methods: To approach the reference conditions and the associated dose distributions, PBS must combine many pencil beams with range modulation and shaping techniques different than those used in passive systems (broad beams). This might lead to a different energy spectrum at the measurement point. In order to evaluate the impact of these differences on kQ factors, ion chamber responses are computed with MC (Geant4 9.6) in a dedicated scanned pencil beam (Q-pcsr) producing a 10×10cm2 composite field with a flat dose distribution from 10 to 16 cm depth. Ion chamber responses are also computed by MC in a broad beam with quality Q-ds (double scattering). The dose distribution of Q -pcsr matches the dose distribution of Q-ds. k-(Q-pcsr,Q-ds) is computed for a 2×2×0.2cm{sup 3} idealized air cavity and a realistic plane-parallel ion chamber (IC). Results: Under reference conditions, quality correction factors for a scanned composite field versus a broad beam are the same for air cavity dose response, k-(Q-pcsr,Q-ds) =1.001±0.001 and for a Roos IC, k-(Q-pcsr,Q-ds) =0.999±0.005. Conclusion: Quality correction factors for ion chamber response in scanned and broad proton therapy beams are identical under reference conditions within the calculation uncertainties. The results indicate that quality correction factors published in IAEA TRS-398 can be used for scanned beams in the SOBP of a

  9. SU-F-BRD-15: Quality Correction Factors in Scanned Or Broad Proton Therapy Beams Are Indistinguishable

    International Nuclear Information System (INIS)

    Sorriaux, J; Lee, J; Testa, M; Paganetti, H; Bertrand, D; Orban de Xivry, J; Palmans, H; Vynckier, S; Sterpin, E

    2015-01-01

    Purpose: The IAEA TRS-398 code of practice details the reference conditions for reference dosimetry of proton beams using ionization chambers and the required beam quality correction factors (kQ). Pencil beam scanning (PBS) requires multiple spots to reproduce the reference conditions. The objective is to demonstrate, using Monte Carlo (MC) calculations, that kQ factors for broad beams can be used for scanned beams under the same reference conditions with no significant additional uncertainty. We consider hereafter the general Alfonso formalism (Alfonso et al, 2008) for non-standard beam. Methods: To approach the reference conditions and the associated dose distributions, PBS must combine many pencil beams with range modulation and shaping techniques different than those used in passive systems (broad beams). This might lead to a different energy spectrum at the measurement point. In order to evaluate the impact of these differences on kQ factors, ion chamber responses are computed with MC (Geant4 9.6) in a dedicated scanned pencil beam (Q-pcsr) producing a 10×10cm2 composite field with a flat dose distribution from 10 to 16 cm depth. Ion chamber responses are also computed by MC in a broad beam with quality Q-ds (double scattering). The dose distribution of Q -pcsr matches the dose distribution of Q-ds. k-(Q-pcsr,Q-ds) is computed for a 2×2×0.2cm 3 idealized air cavity and a realistic plane-parallel ion chamber (IC). Results: Under reference conditions, quality correction factors for a scanned composite field versus a broad beam are the same for air cavity dose response, k-(Q-pcsr,Q-ds) =1.001±0.001 and for a Roos IC, k-(Q-pcsr,Q-ds) =0.999±0.005. Conclusion: Quality correction factors for ion chamber response in scanned and broad proton therapy beams are identical under reference conditions within the calculation uncertainties. The results indicate that quality correction factors published in IAEA TRS-398 can be used for scanned beams in the SOBP of a high

  10. Hydrophone area-averaging correction factors in nonlinearly generated ultrasonic beams

    International Nuclear Information System (INIS)

    Cooling, M P; Humphrey, V F; Wilkens, V

    2011-01-01

    The nonlinear propagation of an ultrasonic wave can be used to produce a wavefield rich in higher frequency components that is ideally suited to the calibration, or inter-calibration, of hydrophones. These techniques usually use a tone-burst signal, limiting the measurements to harmonics of the fundamental calibration frequency. Alternatively, using a short pulse enables calibration at a continuous spectrum of frequencies. Such a technique is used at PTB in conjunction with an optical measurement technique to calibrate devices. Experimental findings indicate that the area-averaging correction factor for a hydrophone in such a field demonstrates a complex behaviour, most notably varying periodically between frequencies that are harmonics of the centre frequency of the original pulse and frequencies that lie midway between these harmonics. The beam characteristics of such nonlinearly generated fields have been investigated using a finite difference solution to the nonlinear Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation for a focused field. The simulation results are used to calculate the hydrophone area-averaging correction factors for 0.2 mm and 0.5 mm devices. The results clearly demonstrate a number of significant features observed in the experimental investigations, including the variation with frequency, drive level and hydrophone element size. An explanation for these effects is also proposed.

  11. Hydrophone area-averaging correction factors in nonlinearly generated ultrasonic beams

    Science.gov (United States)

    Cooling, M. P.; Humphrey, V. F.; Wilkens, V.

    2011-02-01

    The nonlinear propagation of an ultrasonic wave can be used to produce a wavefield rich in higher frequency components that is ideally suited to the calibration, or inter-calibration, of hydrophones. These techniques usually use a tone-burst signal, limiting the measurements to harmonics of the fundamental calibration frequency. Alternatively, using a short pulse enables calibration at a continuous spectrum of frequencies. Such a technique is used at PTB in conjunction with an optical measurement technique to calibrate devices. Experimental findings indicate that the area-averaging correction factor for a hydrophone in such a field demonstrates a complex behaviour, most notably varying periodically between frequencies that are harmonics of the centre frequency of the original pulse and frequencies that lie midway between these harmonics. The beam characteristics of such nonlinearly generated fields have been investigated using a finite difference solution to the nonlinear Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation for a focused field. The simulation results are used to calculate the hydrophone area-averaging correction factors for 0.2 mm and 0.5 mm devices. The results clearly demonstrate a number of significant features observed in the experimental investigations, including the variation with frequency, drive level and hydrophone element size. An explanation for these effects is also proposed.

  12. Correction of experimental photon pencil-beams for the effects of non-uniform and non-parallel measurement conditions

    International Nuclear Information System (INIS)

    Ceberg, Crister P.; Bjaerngard, Bengt E.

    1995-01-01

    An approximate experimental determination of photon pencil-beams can be based on the reciprocity theorem. The scatter part of the pencil-beam is then essentially the derivative with respect to the field radius of measured scatter-to-primary ratios in circular fields. Obtained in this way, however, the pencil-beam implicitly carries the influence from the lateral fluence and beam quality variations of the incident photons, as well as the effects of the divergence of the beam. In this work we show how these effects can be corrected for. The procedure was to calculate scatter-to-primary ratios using an analytical expression for the pencil-beam. By disregarding one by one the effects of the divergence and the fluence and beam quality variations, the influence of these effects were separated and quantified. For instance, for a 6 MV beam of 20x20 cm 2 field size, at 20 cm depth and a source distance of 100 cm, the total effect was 3.9%; 2.0% was due to the non-uniform incident profile, 1.0% due to the non-uniform beam quality, and 0.9% due to the divergence of the beam. At a source distance of 400 cm, all these effects were much lower, adding up to a total of 0.3 %. Using calculated correction factors like these, measured scatter-to-primary ratios were then stripped from the effects of non-uniform and non-parallel measurement conditions, and the scatter part of the pencil-beam was determined using the reciprocity theorem without approximations

  13. Library based x-ray scatter correction for dedicated cone beam breast CT

    International Nuclear Information System (INIS)

    Shi, Linxi; Zhu, Lei; Vedantham, Srinivasan; Karellas, Andrew

    2016-01-01

    Purpose: The image quality of dedicated cone beam breast CT (CBBCT) is limited by substantial scatter contamination, resulting in cupping artifacts and contrast-loss in reconstructed images. Such effects obscure the visibility of soft-tissue lesions and calcifications, which hinders breast cancer detection and diagnosis. In this work, we propose a library-based software approach to suppress scatter on CBBCT images with high efficiency, accuracy, and reliability. Methods: The authors precompute a scatter library on simplified breast models with different sizes using the GEANT4-based Monte Carlo (MC) toolkit. The breast is approximated as a semiellipsoid with homogeneous glandular/adipose tissue mixture. For scatter correction on real clinical data, the authors estimate the breast size from a first-pass breast CT reconstruction and then select the corresponding scatter distribution from the library. The selected scatter distribution from simplified breast models is spatially translated to match the projection data from the clinical scan and is subtracted from the measured projection for effective scatter correction. The method performance was evaluated using 15 sets of patient data, with a wide range of breast sizes representing about 95% of general population. Spatial nonuniformity (SNU) and contrast to signal deviation ratio (CDR) were used as metrics for evaluation. Results: Since the time-consuming MC simulation for library generation is precomputed, the authors’ method efficiently corrects for scatter with minimal processing time. Furthermore, the authors find that a scatter library on a simple breast model with only one input parameter, i.e., the breast diameter, sufficiently guarantees improvements in SNU and CDR. For the 15 clinical datasets, the authors’ method reduces the average SNU from 7.14% to 2.47% in coronal views and from 10.14% to 3.02% in sagittal views. On average, the CDR is improved by a factor of 1.49 in coronal views and 2.12 in sagittal

  14. Library based x-ray scatter correction for dedicated cone beam breast CT

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Linxi; Zhu, Lei, E-mail: leizhu@gatech.edu [Nuclear and Radiological Engineering and Medical Physics Programs, The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Vedantham, Srinivasan; Karellas, Andrew [Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655 (United States)

    2016-08-15

    Purpose: The image quality of dedicated cone beam breast CT (CBBCT) is limited by substantial scatter contamination, resulting in cupping artifacts and contrast-loss in reconstructed images. Such effects obscure the visibility of soft-tissue lesions and calcifications, which hinders breast cancer detection and diagnosis. In this work, we propose a library-based software approach to suppress scatter on CBBCT images with high efficiency, accuracy, and reliability. Methods: The authors precompute a scatter library on simplified breast models with different sizes using the GEANT4-based Monte Carlo (MC) toolkit. The breast is approximated as a semiellipsoid with homogeneous glandular/adipose tissue mixture. For scatter correction on real clinical data, the authors estimate the breast size from a first-pass breast CT reconstruction and then select the corresponding scatter distribution from the library. The selected scatter distribution from simplified breast models is spatially translated to match the projection data from the clinical scan and is subtracted from the measured projection for effective scatter correction. The method performance was evaluated using 15 sets of patient data, with a wide range of breast sizes representing about 95% of general population. Spatial nonuniformity (SNU) and contrast to signal deviation ratio (CDR) were used as metrics for evaluation. Results: Since the time-consuming MC simulation for library generation is precomputed, the authors’ method efficiently corrects for scatter with minimal processing time. Furthermore, the authors find that a scatter library on a simple breast model with only one input parameter, i.e., the breast diameter, sufficiently guarantees improvements in SNU and CDR. For the 15 clinical datasets, the authors’ method reduces the average SNU from 7.14% to 2.47% in coronal views and from 10.14% to 3.02% in sagittal views. On average, the CDR is improved by a factor of 1.49 in coronal views and 2.12 in sagittal

  15. On residual stresses and fatigue of laser hardened steels

    International Nuclear Information System (INIS)

    Lin, Ru.

    1992-01-01

    This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10 7 cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au)

  16. On residual stresses and fatigue of laser hardened steels

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Ru.

    1992-01-01

    This thesis deals with studies on residual stresses and fatigue properties of laser-transformation hardened steels. Two types of specimens, cylinders and fatigue specimens were used in the studies. The cylinders, made of Swedish steels SS 2244 and SS 2258 which correspond to AISI 4140 and AISI 52100 respectively, were locally hardened by a single scan of laser beam in the longitudinal direction, with various laser parameters. Residual stress distributions across the hardened tracks were measured by means of X-ray diffraction. The origins of residual stresses were investigated and discussed. For the fatigue specimens, including smooth and notched types made of Swedish steels SS 2244, SS 2225 and SS 1572 (similar to AISI 4140, AISI 4130 and AISI 1035, respectively), laser hardening was carried out in the gauge section. The residual stress field induced by the hardening process and the fatigue properties by plane bending fatigue test were studied. In order to investigate the stability of the residual stress field, stress measurements were also made on specimens being loaded near the fatigue limits for over 10[sup 7] cycles. Further the concept of local fatigue strength was employed to correlate quantitatively the effect of hardness and residual stress field on the fatigue limits. In addition a group of smooth specimens of SS 2244 was induction hardened and the hardening results were compared with the corresponding laser hardened ones in terms of residual stress and fatigue behaviour. It has been found that compressive stresses exist in the hardened zone of all the specimens studied. The laser hardening condition, the specimen and how the hardening is carried out can significantly affect the residual stress field. Laser hardening can greatly improve the fatigue properties by inducing a hardened and compressed surface layer. (112 refs.)(au).

  17. Correction

    CERN Multimedia

    2002-01-01

    Tile Calorimeter modules stored at CERN. The larger modules belong to the Barrel, whereas the smaller ones are for the two Extended Barrels. (The article was about the completion of the 64 modules for one of the latter.) The photo on the first page of the Bulletin n°26/2002, from 24 July 2002, illustrating the article «The ATLAS Tile Calorimeter gets into shape» was published with a wrong caption. We would like to apologise for this mistake and so publish it again with the correct caption.

  18. A level set method for cupping artifact correction in cone-beam CT

    International Nuclear Information System (INIS)

    Xie, Shipeng; Li, Haibo; Ge, Qi; Li, Chunming

    2015-01-01

    Purpose: To reduce cupping artifacts and improve the contrast-to-noise ratio in cone-beam computed tomography (CBCT). Methods: A level set method is proposed to reduce cupping artifacts in the reconstructed image of CBCT. The authors derive a local intensity clustering property of the CBCT image and define a local clustering criterion function of the image intensities in a neighborhood of each point. This criterion function defines an energy in terms of the level set functions, which represent a segmentation result and the cupping artifacts. The cupping artifacts are estimated as a result of minimizing this energy. Results: The cupping artifacts in CBCT are reduced by an average of 90%. The results indicate that the level set-based algorithm is practical and effective for reducing the cupping artifacts and preserving the quality of the reconstructed image. Conclusions: The proposed method focuses on the reconstructed image without requiring any additional physical equipment, is easily implemented, and provides cupping correction through a single-scan acquisition. The experimental results demonstrate that the proposed method successfully reduces the cupping artifacts

  19. Beam-induced motion correction for sub-megadalton cryo-EM particles.

    Science.gov (United States)

    Scheres, Sjors Hw

    2014-08-13

    In electron cryo-microscopy (cryo-EM), the electron beam that is used for imaging also causes the sample to move. This motion blurs the images and limits the resolution attainable by single-particle analysis. In a previous Research article (Bai et al., 2013) we showed that correcting for this motion by processing movies from fast direct-electron detectors allowed structure determination to near-atomic resolution from 35,000 ribosome particles. In this Research advance article, we show that an improved movie processing algorithm is applicable to a much wider range of specimens. The new algorithm estimates straight movement tracks by considering multiple particles that are close to each other in the field of view, and models the fall-off of high-resolution information content by radiation damage in a dose-dependent manner. Application of the new algorithm to four data sets illustrates its potential for significantly improving cryo-EM structures, even for particles that are smaller than 200 kDa. Copyright © 2014, Scheres.

  20. Ion-recombination correction factor κsat for spherical ion chambers irradiated by continuous photom beams

    International Nuclear Information System (INIS)

    Piermattei, A.; Azario, L.; Arcovito, G.

    1996-01-01

    The large range of reference air kerma rates of brachytherapy sources involves the use of large-volume ionization chambers. When such ionization chambers are used the ion-recombination correction factor k sat has to be determined. In this paper three spherical ion chambers with volume ranging from 30 to 10 4 cm 3 have been irradiated by photons of a 192 Ir source to determine the k sat factors. The ionization currents of the ion chambers as a function of the applied voltage and the air kerma rate have been analysed to determine the contribution of the initial and general ion recombination. The k sat values for large-volume ionization chambers obtained by considering the general ion recombination as predominant (Almond's approach) are in disagreement with the results obtained using methods that consider both initial and general ion-recombination contributions (Niatel's approach). Such disagreement can reach 0.7% when high currents are measured for a high-activity source calibration in terms of reference air kerma rate. In this study a new 'two-voltage' method, independent of the voltage ratio given by a dosimetry system, is proposed for practical dosimetry of continuous x-and gamma-radiation beams. In the case where the Almond approach is utilized, the voltage ratio V 1 /V 2 should be less than 2 instead of Almond's limit of V 1 /V 2 <5. (Author)

  1. Calibration artefacts in radio interferometry - III. Phase-only calibration and primary beam correction

    Science.gov (United States)

    Grobler, T. L.; Stewart, A. J.; Wijnholds, S. J.; Kenyon, J. S.; Smirnov, O. M.

    2016-09-01

    This is the third installment in a series of papers in which we investigate calibration artefacts. Calibration artefacts (also known as ghosts or spurious sources) are created when we calibrate with an incomplete model. In the first two papers of this series, we developed a mathematical framework which enabled us to study the ghosting mechanism itself. An interesting concomitant of the second paper was that ghosts appear in symmetrical pairs. This could possibly account for spurious symmetrization. Spurious symmetrization refers to the appearance of a spurious source (the antighost) symmetrically opposite an unmodelled source around a modelled source. The analysis in the first two papers indicates that the antighost is usually very faint, in particular, when a large number of antennas are used. This suggests that spurious symmetrization will mainly occur at an almost undetectable flux level. In this paper, we show that phase-only calibration produces an antighost that is N-times (where N denotes the number of antennas in the array) as bright as the one produced by phase and amplitude calibration and that this already bright ghost can be further amplified by the primary beam correction.

  2. Registration concepts for the just-in-time artefact correction by means of virtual computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kasperl, St.; Franz, M. [Fraunhofer Development Center for X-ray Technology EZRT, a cooperative dept. of the Fraunhofer Institutes IZFP Saarbrucken and IIS Erlangen, Furth (Germany)

    2007-07-01

    This article deals with the enhancement of accuracy in CT by just-in-time correction of artefacts (beam hardening, scattered radiation) caused by the interaction of X-rays with matter. The so called EAR method needs for simulation a registration of the object. Therefore the article presents two different registration concepts. (authors)

  3. Registration concepts for the just-in-time artefact correction by means of virtual computed tomography

    International Nuclear Information System (INIS)

    Kasperl, St.; Franz, M.

    2007-01-01

    This article deals with the enhancement of accuracy in CT by just-in-time correction of artefacts (beam hardening, scattered radiation) caused by the interaction of X-rays with matter. The so called EAR method needs for simulation a registration of the object. Therefore the article presents two different registration concepts. (authors)

  4. Detector to detector corrections: a comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams

    DEFF Research Database (Denmark)

    Azangwe, Godfrey; Grochowska, Paulina; Georg, Dietmar

    2014-01-01

    -doped aluminium oxide (Al2O3:C), organic plastic scintillators, diamond detectors, liquid filled ion chamber, and a range of small volume air filled ionization chambers (volumes ranging from 0.002 cm3 to 0.3 cm3). All detector measurements were corrected for volume averaging effect and compared with dose ratios...... measurements, the authors recommend the use of detectors that require relatively little correction, such as unshielded diodes, diamond detectors or microchambers, and solid state detectors such as alanine, TLD, Al2O3:C, or scintillators....

  5. Correction

    Directory of Open Access Journals (Sweden)

    2012-01-01

    Full Text Available Regarding Gorelik, G., & Shackelford, T.K. (2011. Human sexual conflict from molecules to culture. Evolutionary Psychology, 9, 564–587: The authors wish to correct an omission in citation to the existing literature. In the final paragraph on p. 570, we neglected to cite Burch and Gallup (2006 [Burch, R. L., & Gallup, G. G., Jr. (2006. The psychobiology of human semen. In S. M. Platek & T. K. Shackelford (Eds., Female infidelity and paternal uncertainty (pp. 141–172. New York: Cambridge University Press.]. Burch and Gallup (2006 reviewed the relevant literature on FSH and LH discussed in this paragraph, and should have been cited accordingly. In addition, Burch and Gallup (2006 should have been cited as the originators of the hypothesis regarding the role of FSH and LH in the semen of rapists. The authors apologize for this oversight.

  6. Correction

    CERN Multimedia

    2002-01-01

    The photo on the second page of the Bulletin n°48/2002, from 25 November 2002, illustrating the article «Spanish Visit to CERN» was published with a wrong caption. We would like to apologise for this mistake and so publish it again with the correct caption.   The Spanish delegation, accompanied by Spanish scientists at CERN, also visited the LHC superconducting magnet test hall (photo). From left to right: Felix Rodriguez Mateos of CERN LHC Division, Josep Piqué i Camps, Spanish Minister of Science and Technology, César Dopazo, Director-General of CIEMAT (Spanish Research Centre for Energy, Environment and Technology), Juan Antonio Rubio, ETT Division Leader at CERN, Manuel Aguilar-Benitez, Spanish Delegate to Council, Manuel Delfino, IT Division Leader at CERN, and Gonzalo León, Secretary-General of Scientific Policy to the Minister.

  7. Correction

    Directory of Open Access Journals (Sweden)

    2014-01-01

    Full Text Available Regarding Tagler, M. J., and Jeffers, H. M. (2013. Sex differences in attitudes toward partner infidelity. Evolutionary Psychology, 11, 821–832: The authors wish to correct values in the originally published manuscript. Specifically, incorrect 95% confidence intervals around the Cohen's d values were reported on page 826 of the manuscript where we reported the within-sex simple effects for the significant Participant Sex × Infidelity Type interaction (first paragraph, and for attitudes toward partner infidelity (second paragraph. Corrected values are presented in bold below. The authors would like to thank Dr. Bernard Beins at Ithaca College for bringing these errors to our attention. Men rated sexual infidelity significantly more distressing (M = 4.69, SD = 0.74 than they rated emotional infidelity (M = 4.32, SD = 0.92, F(1, 322 = 23.96, p < .001, d = 0.44, 95% CI [0.23, 0.65], but there was little difference between women's ratings of sexual (M = 4.80, SD = 0.48 and emotional infidelity (M = 4.76, SD = 0.57, F(1, 322 = 0.48, p = .29, d = 0.08, 95% CI [−0.10, 0.26]. As expected, men rated sexual infidelity (M = 1.44, SD = 0.70 more negatively than they rated emotional infidelity (M = 2.66, SD = 1.37, F(1, 322 = 120.00, p < .001, d = 1.12, 95% CI [0.85, 1.39]. Although women also rated sexual infidelity (M = 1.40, SD = 0.62 more negatively than they rated emotional infidelity (M = 2.09, SD = 1.10, this difference was not as large and thus in the evolutionary theory supportive direction, F(1, 322 = 72.03, p < .001, d = 0.77, 95% CI [0.60, 0.94].

  8. Evaluation of ion chamber dependent correction factors for ionisation chamber dosimetry in proton beams using a Monte Carlo method

    International Nuclear Information System (INIS)

    Palmans, H.; Verhaegen, F.

    1995-01-01

    In the last decade, several clinical proton beam therapy facilities have been developed. To satisfy the demand for uniformity in clinical (routine) proton beam dosimetry two dosimetry protocols (ECHED and AAPM) have been published. Both protocols neglect the influence of ion chamber dependent parameters on dose determination in proton beams because of the scatter properties of these beams, although the problem has not been studied thoroughly yet. A comparison between water calorimetry and ionisation chamber dosimetry showed a discrepancy of 2.6% between the former method and ionometry following the ECHED protocol. Possibly, a small part of this difference can be attributed to chamber dependent correction factors. Indications for this possibility are found in ionometry measurements. To allow the simulation of complex geometries with different media necessary for the study of those corrections, an existing proton Monte Carlo code (PTRAN, Berger) has been modified. The original code, that applies Mollire's multiple scattering theory and Vavilov's energy straggling theory, calculates depth dose profiles, energy distributions and radial distributions for pencil beams in water. Comparisons with measurements and calculations reported in the literature are done to test the program's accuracy. Preliminary results of the influence of chamber design and chamber materials on dose to water determination are presented

  9. Correction factors for photon beam quality for cylindrical ionization chambers: Monte Carlo calculations by using the PENELOPE code

    International Nuclear Information System (INIS)

    Barreras Caballero, A. A.; Hernandez Garcia, J.J.; Alfonso Laguardia, R.

    2009-01-01

    Were directly determined correction factors depending on the type camera beam quality, k, Q, and kQ, Qo, instead of the product (w, air p) Q, for three type cylindrical ionization chambers Pinpoint and divergent monoenergetic beams of photons in a wide range of energies (4-20 MV). The method of calculation used dispenses with the approaches taken in the classic procedure considered independent of braking power ratios and the factors disturbance of the camera. A detailed description of the geometry and materials chambers were supplied by the manufacturer and used as data input for the system 2006 of PENELOPE Monte Carlo calculation using a User code that includes correlated sampling, and forced interactions division of particles. We used a photon beam Co-60 as beam reference for calculating the correction factors for beam quality. No data exist for the cameras PTW 31014, 31015 and 31016 in the TRS-398 at they do not compare the results with data calculated or determined experimentally by other authors. (author)

  10. Evaluation of ion chamber dependent correction factors for ionisation chamber dosimetry in proton beams using a Monte Carlo method

    Energy Technology Data Exchange (ETDEWEB)

    Palmans, H [Ghent Univ. (Belgium). Dept. of Biomedical Physics; Verhaegen, F

    1995-12-01

    In the last decade, several clinical proton beam therapy facilities have been developed. To satisfy the demand for uniformity in clinical (routine) proton beam dosimetry two dosimetry protocols (ECHED and AAPM) have been published. Both protocols neglect the influence of ion chamber dependent parameters on dose determination in proton beams because of the scatter properties of these beams, although the problem has not been studied thoroughly yet. A comparison between water calorimetry and ionisation chamber dosimetry showed a discrepancy of 2.6% between the former method and ionometry following the ECHED protocol. Possibly, a small part of this difference can be attributed to chamber dependent correction factors. Indications for this possibility are found in ionometry measurements. To allow the simulation of complex geometries with different media necessary for the study of those corrections, an existing proton Monte Carlo code (PTRAN, Berger) has been modified. The original code, that applies Mollire`s multiple scattering theory and Vavilov`s energy straggling theory, calculates depth dose profiles, energy distributions and radial distributions for pencil beams in water. Comparisons with measurements and calculations reported in the literature are done to test the program`s accuracy. Preliminary results of the influence of chamber design and chamber materials on dose to water determination are presented.

  11. Semi-empirical procedures for correcting detector size effect on clinical MV x-ray beam profiles

    International Nuclear Information System (INIS)

    Sahoo, Narayan; Kazi, Abdul M.; Hoffman, Mark

    2008-01-01

    The measured radiation beam profiles need to be corrected for the detector size effect to derive the real profiles. This paper describes two new semi-empirical procedures to determine the real profiles of high-energy x-ray beams by removing the detector size effect from the measured profiles. Measured profiles are corrected by shifting the position of each measurement point by a specific amount determined from available theoretical and experimental knowledge in the literature. The authors developed two procedures to determine the amount of shift. In the first procedure, which employs the published analytical deconvolution procedure of other investigators, the shift is determined from the comparison of the analytical fit of the measured profile and the corresponding analytical real profile derived from the deconvolution of the fitted measured profile and the Gaussian detector response function. In the second procedure, the amount of shift at any measurement point is considered to be proportional to the value of an analytical function related to the second derivative of the real profile at that point. The constant of proportionality and a parameter in the function are obtained from the values of the shifts at the 90%, 80%, 20%, and 10% dose levels, which are experimentally known from the published results of other investigators to be approximately equal to half of the radius of the detector. These procedures were tested by correcting the profiles of 6 and 18 MV x-ray beams measured by three different ionization chambers and a stereotactic field diode detector with 2.75, 2, 1, and 0.3 mm radii of their respective active cylindrical volumes. The corrected profiles measured by different detectors are found to be in close agreement. The detector size corrected penumbra widths also agree with the expected values based on the results of an earlier investigation. Thus, the authors concluded that the proposed procedures are accurate and can be used to derive the real

  12. Assessment of four shadow band correction models using beam normal irradiance data from the United Kingdom and Israel

    International Nuclear Information System (INIS)

    Lopez, G.; Muneer, T.; Claywell, R.

    2004-01-01

    Diffuse irradiance is a fundamental factor for all solar resource considerations. Diffuse irradiance is accurately determined by calculation from global and beam normal (direct) measurements. However, beam solar measurements and related support can be very expensive, and therefore, shadow bands are often used, along with pyranometers, to block the solar disk. The errors that result from the use of shadow bands are well known and have been studied by many authors. The thrust of this article is to examine four recognized techniques for correcting shadow band based, diffuse irradiance and statistically evaluate their individual performance using data culled from two contrasting sites within the United Kingdom and Israel

  13. Correction for ‘artificial’ electron disequilibrium due to cone-beam CT density errors: implications for on-line adaptive stereotactic body radiation therapy of lung

    International Nuclear Information System (INIS)

    Disher, Brandon; Hajdok, George; Craig, Jeff; Gaede, Stewart; Battista, Jerry J; Wang, An

    2013-01-01

    Cone-beam computed tomography (CBCT) has rapidly become a clinically useful imaging modality for image-guided radiation therapy. Unfortunately, CBCT images of the thorax are susceptible to artefacts due to scattered photons, beam hardening, lag in data acquisition, and respiratory motion during a slow scan. These limitations cause dose errors when CBCT image data are used directly in dose computations for on-line, dose adaptive radiation therapy (DART). The purpose of this work is to assess the magnitude of errors in CBCT numbers (HU), and determine the resultant effects on derived tissue density and computed dose accuracy for stereotactic body radiation therapy (SBRT) of lung cancer. Planning CT (PCT) images of three lung patients were acquired using a Philips multi-slice helical CT simulator, while CBCT images were obtained with a Varian On-Board Imaging system. To account for erroneous CBCT data, three practical correction techniques were tested: (1) conversion of CBCT numbers to electron density using phantoms, (2) replacement of individual CBCT pixel values with bulk CT numbers, averaged from PCT images for tissue regions, and (3) limited replacement of CBCT lung pixels values (LCT) likely to produce artificial lateral electron disequilibrium. For each corrected CBCT data set, lung SBRT dose distributions were computed for a 6 MV volume modulated arc therapy (VMAT) technique within the Philips Pinnacle treatment planning system. The reference prescription dose was set such that 95% of the planning target volume (PTV) received at least 54 Gy (i.e. D95). Further, we used the relative depth dose factor as an a priori index to predict the effects of incorrect low tissue density on computed lung dose in regions of severe electron disequilibrium. CT number profiles from co-registered CBCT and PCT patient lung images revealed many reduced lung pixel values in CBCT data, with some pixels corresponding to vacuum (−1000 HU). Similarly, CBCT data in a plastic lung

  14. Nuclear microprobe characterization of surface hardening by precipitation of chromium carbides after laser beam treatment of a Ni-Cr substrate

    International Nuclear Information System (INIS)

    Mosbah, M.; Gosset, J.; Trocellier, P.; Puig, T.; Cantarel, M.; Condat, M.

    1989-01-01

    Surface treatment by laser provides interesting solutions to the problem of accelerated wear of materials. The aim of the present study is the characterization of chromium carbides rich surface alloys after laser beam melting of a Ni 70 Cr 30 carbon precoated substrate. The carbon profiling of the lasered surface was performed by nuclear microprobe using the 12 C(d,p 0 ) 13 C reaction, Ni and Cr were evaluated by means of PIXE (Particle Induced X Ray Emission). The specificity of the method and the experimental conditions are explained. Wear results are very satisfactory and close to those obtained by injection of chromium carbide powders into the laser beam in the case of a Nimonic alloy: wear rates are divided by two orders of magnitude

  15. Direct cone-beam cardiac reconstruction algorithm with cardiac banding artifact correction

    International Nuclear Information System (INIS)

    Taguchi, Katsuyuki; Chiang, Beshan S.; Hein, Ilmar A.

    2006-01-01

    Multislice helical computed tomography (CT) is a promising noninvasive technique for coronary artery imaging. Various factors can cause inconsistencies in cardiac CT data, which can result in degraded image quality. These inconsistencies may be the result of the patient physiology (e.g., heart rate variations), the nature of the data (e.g., cone-angle), or the reconstruction algorithm itself. An algorithm which provides the best temporal resolution for each slice, for example, often provides suboptimal image quality for the entire volume since the cardiac temporal resolution (TRc) changes from slice to slice. Such variations in TRc can generate strong banding artifacts in multi-planar reconstruction images or three-dimensional images. Discontinuous heart walls and coronary arteries may compromise the accuracy of the diagnosis. A β-blocker is often used to reduce and stabilize patients' heart rate but cannot eliminate the variation. In order to obtain robust and optimal image quality, a software solution that increases the temporal resolution and decreases the effect of heart rate is highly desirable. This paper proposes an ECG-correlated direct cone-beam reconstruction algorithm (TCOT-EGR) with cardiac banding artifact correction (CBC) and disconnected projections redundancy compensation technique (DIRECT). First the theory and analytical model of the cardiac temporal resolution is outlined. Next, the performance of the proposed algorithms is evaluated by using computer simulations as well as patient data. It will be shown that the proposed algorithms enhance the robustness of the image quality against inconsistencies by guaranteeing smooth transition of heart cycles used in reconstruction

  16. Hardening Azure applications

    CERN Document Server

    Gaurav, Suraj

    2015-01-01

    Learn what it takes to build large scale, mission critical applications -hardened applications- on the Azure cloud platform. This 208 page book covers the techniques and engineering principles that every architect and developer needs to know to harden their Azure/.NET applications to ensure maximum reliability and high availability when deployed at scale. While the techniques are implemented in .NET and optimized for Azure, the principles here will also be valuable for users of other cloud-based development platforms. Applications come in a variety of forms, from simple apps that can be bui

  17. Radiation hardenable coating mixture

    International Nuclear Information System (INIS)

    Howard, D.D.

    1977-01-01

    This invention relates to coatings that harden under radiation and to their compositions. Specifically, this invention concerns unsaturated urethane resins polymerisable by addition and to compositions, hardening under the effect of radiation, containing these resins. These resins feature the presence of at least one unsaturated ethylenic terminal group of structure CH 2 =C and containing the product of the reaction of an organic isocyanate compound with at least two isocyanate groups and one polyester polyol with at least two hydroxyl groups, and one unsaturated monomer compound polymerisable by addition having a single active hydrogen group reacting with the isocyanate [fr

  18. Simulation study of the photon quality correction factors of ionization chambers for FiR 1 epithermal neutron beam

    International Nuclear Information System (INIS)

    Koivunoro, H.; Uusi-Simola, J.; Savolainen, S.; Kotiluoto, P.; Auterinen, I.; Kosunen, A.

    2006-01-01

    At FiR 1 BNCT facility in Finland, neutron-insensitive Mg(Ar) ionization chambers are used for photon dose measurements in an epithermal neutron beam. Previously, photon sensitivity factors for the chamber for the measurements in a water phantom in FiR 1 beam have been determined experimentally from measurements in 60 Co gamma and in a 6 MV clinical accelerator photon beams. However, the response of the ionization chamber in a water phantom depends on energy spectrum and angle of the photons and the secondary electrons created inside the phantom and may differ depending on type of the irradiation source (accelerator vs. an epithermal neutron beam). Also, the experimental sensitivity factor does not take into account the possible perturbations in the photon production in phantom caused by the ionization chamber materials. Therefore, it is necessary to determine the photon quality correction factors (k Qγ ) for the Mg(Ar) chamber at the FiR 1 beam through computer simulations. In this study, the k Qγ factors have been determined for Mg(Ar) chamber from Monte Carlo calculations of absorbed photon dose at two depths in a water phantom using MCNP code. The k qγ factors obtained with this method are compared to the sensitivity factors determined with measurements in an accelerator photon beam and to the k Qγ factors published previously. (author)

  19. Accuracy of radiotherapy dose calculations based on cone-beam CT: comparison of deformable registration and image correction based methods

    Science.gov (United States)

    Marchant, T. E.; Joshi, K. D.; Moore, C. J.

    2018-03-01

    Radiotherapy dose calculations based on cone-beam CT (CBCT) images can be inaccurate due to unreliable Hounsfield units (HU) in the CBCT. Deformable image registration of planning CT images to CBCT, and direct correction of CBCT image values are two methods proposed to allow heterogeneity corrected dose calculations based on CBCT. In this paper we compare the accuracy and robustness of these two approaches. CBCT images for 44 patients were used including pelvis, lung and head & neck sites. CBCT HU were corrected using a ‘shading correction’ algorithm and via deformable registration of planning CT to CBCT using either Elastix or Niftyreg. Radiotherapy dose distributions were re-calculated with heterogeneity correction based on the corrected CBCT and several relevant dose metrics for target and OAR volumes were calculated. Accuracy of CBCT based dose metrics was determined using an ‘override ratio’ method where the ratio of the dose metric to that calculated on a bulk-density assigned version of the same image is assumed to be constant for each patient, allowing comparison to the patient’s planning CT as a gold standard. Similar performance is achieved by shading corrected CBCT and both deformable registration algorithms, with mean and standard deviation of dose metric error less than 1% for all sites studied. For lung images, use of deformed CT leads to slightly larger standard deviation of dose metric error than shading corrected CBCT with more dose metric errors greater than 2% observed (7% versus 1%).

  20. Wavefront Tilt And Beam Walk Correction For A Pulsed Laser System

    Science.gov (United States)

    Bartosewcz, Mike; Tyburski, Joe

    1986-05-01

    The Lockheed Beam Alignment Assembly (BAA) is designed to be a space qualifiable, long life, low bandwidth beam stabilization system. The BAA will stabilize a wandering pulsed laser beam with an input beam tilt of ±750 microradians and translation of ±2.5 mm by two orders of magnitude at the bandwidth of interest. A bandwidth of three hertz was selected to remove laser and optical train thermal drifts and launch induced strain effects. The lambda over twenty RMS wavefront will be maintained in the optics at full power under vacuum test, to demonstrate space qualifiability and optical performance.

  1. Correction of Beam Distortion in Negative Hydrogen Ion Source with Multi-Slot Grounded Grid

    International Nuclear Information System (INIS)

    Tsumori, Katsuyoshi; Kaneko, Osamu; Takeiri, Yasuhiko; Oka, Yoshihide; Osakabe, Masaki; Ikeda, Katsunori; Nagaoka, Kenichi; Kawamoto, Toshikazu; Asano, Eiji; Sato, Mamoru; Kondo, Tomoki; Watanabe, Junko; Asano, Shiro; Suzuki, Yasuo

    2005-01-01

    The new beam accelerator with multi-slot grounded grid (MSGG) has been developed to increase the port-through power into large helical device (LHD). Using the accelerator, the maximum power of 5.7 MW was achieved at the beam energy of 186 keV in the beam injection to LHD plasma last year. Although the port-through power increased compared with conventional accelerators with multi-hole grounded grid (MHGG), the accelerator with the MSGG includes a disadvantage of bi-focal condition in parallel and perpendicular direction to the long side of the slots. When the beam width in one of those directions gets narrower, the width in another direction becomes wider. This disadvantage includes the loss of beam port-through power and induces internal damages in neutral beam line. In order to reduce the disadvantage, an experiment has been done using a small-scaled negative ion source with racetrack-shaped apertures for the steering grid installed at beam upstream of the MSGG. By applying the racetrack apertures to the accelerator, it is observed that the beam widths in the parallel and perpendicular directions to the slot long side have almost the same focal condition to obtain minimal beam widths

  2. Correction of nonlinear distortion in high-transverse-emittance ratio-beam production with linear accelerator

    Directory of Open Access Journals (Sweden)

    Shaoheng Wang

    2008-05-01

    Full Text Available Derbenev proposed producing a high quality flat beam of high-transverse-emittance ratio (HTER with a linear accelerator. Kim also discussed the round-to-flat transformation of angular-momentum-dominated beam. Fermilab/NICADD Photoinjector Laboratory has performed many experiments on HTER beam production. Experiments and simulations, collectively, showed an S-shaped transverse distribution in the flat beam. In this paper, the source of this emittance deterioration in the transformation is identified as the nonlinear rf cavity focusing force; and a solution is proposed.

  3. Self-corrected sensors based on atomic absorption spectroscopy for atom flux measurements in molecular beam epitaxy

    International Nuclear Information System (INIS)

    Du, Y.; Liyu, A. V.; Droubay, T. C.; Chambers, S. A.; Li, G.

    2014-01-01

    A high sensitivity atom flux sensor based on atomic absorption spectroscopy has been designed and implemented to control electron beam evaporators and effusion cells in a molecular beam epitaxy system. Using a high-resolution spectrometer and a two-dimensional charge coupled device detector in a double-beam configuration, we employ either a non-resonant line or a resonant line with low cross section from the same hollow cathode lamp as the reference for nearly perfect background correction and baseline drift removal. This setup also significantly shortens the warm-up time needed compared to other sensor technologies and drastically reduces the noise coming from the surrounding environment. In addition, the high-resolution spectrometer allows the most sensitive resonant line to be isolated and used to provide excellent signal-to-noise ratio

  4. Radiative corrections to the beam spin asymmetry in photon electroproduction e polarized p {yields} ep{gamma}

    Energy Technology Data Exchange (ETDEWEB)

    Fonvieille, H.; Bensafa, I. [LPC-Clermont-Fd, Universite Blaise Pascal, F-63170 Aubiere Cedex (France)

    2006-11-15

    We have measured at MAMI the beam single spin asymmetry (SSA) in exclusive photon electroproduction (e polarized p {yields} ep{gamma}) with a longitudinally polarized beam, in the region of the {delta}(1232) resonance. In this document the value of the radiative correction to this asymmetry is obtained for our kinematics. Although the correction is expected to be very small and negligible, its value is needed as a confirmation and for the purpose of systematic error estimate. The parameter of kinematics are given as follows: four-momentum transfer of the virtual photon, Q{sup 2} = 0.35 GeV{sup 2}; total energy in the ({gamma}p) center of mass, W=1.190 GeV; polarization of the virtual photon, {epsilon}=0.48; azimuthal angle (lepton-hadron planes), {phi} = 220 angle; polar angle of Compton scattering in center of mass, {theta}{sub {gamma}}{sub {gamma}} in [0 angle, 40 angle]; incoming electron beam energy, E{sub e} = 0.88 GeV; scattered electron energy, E{sub 0}' = 0.40 GeV; polar angle of scattered electron {theta}{sub e} = 59.9 angle. The radiative correction is calculated by the radcorr code written by M. Vanderhaeghen, in a version adapted to beam spin asymmetries.In practice, the conclusions are twofold: - the asymmetry that was measured in the VCS channel does not need to be corrected for radiative effects, given the large statistical error bar attached to the experimental values (an asymmetry of 1-10 % with a statistical error bar of 3-4 %); - a systematic error {delta}SSA{sub syst} on the asymmetry will be considered, related to uncertainties in the calculation of the radiative correction (at least two of them have been mentioned here: the cross section model and the soft photon limit). To estimate this error a 100 % variation of the radiative correction was assumed. For the radiative correction itself the maximal value found was taken. Therefore one can take: {delta}SSA{sub syst} = {+-}2.7 x 10{sup -3}.

  5. Radiative corrections to the beam spin asymmetry in photon electroproduction e polarized p → epγ

    International Nuclear Information System (INIS)

    Fonvieille, H.; Bensafa, I.

    2006-11-01

    We have measured at MAMI the beam single spin asymmetry (SSA) in exclusive photon electroproduction (e polarized p → epγ) with a longitudinally polarized beam, in the region of the Δ(1232) resonance. In this document the value of the radiative correction to this asymmetry is obtained for our kinematics. Although the correction is expected to be very small and negligible, its value is needed as a confirmation and for the purpose of systematic error estimate. The parameter of kinematics are given as follows: four-momentum transfer of the virtual photon, Q 2 = 0.35 GeV 2 ; total energy in the (γp) center of mass, W=1.190 GeV; polarization of the virtual photon, ε=0.48; azimuthal angle (lepton-hadron planes), φ = 220 angle; polar angle of Compton scattering in center of mass, θ γγ in [0 angle, 40 angle]; incoming electron beam energy, E e = 0.88 GeV; scattered electron energy, E 0 ' = 0.40 GeV; polar angle of scattered electron θ e = 59.9 angle. The radiative correction is calculated by the radcorr code written by M. Vanderhaeghen, in a version adapted to beam spin asymmetries.In practice, the conclusions are twofold: - the asymmetry that was measured in the VCS channel does not need to be corrected for radiative effects, given the large statistical error bar attached to the experimental values (an asymmetry of 1-10 % with a statistical error bar of 3-4 %); - a systematic error ΔSSA syst on the asymmetry will be considered, related to uncertainties in the calculation of the radiative correction (at least two of them have been mentioned here: the cross section model and the soft photon limit). To estimate this error a 100 % variation of the radiative correction was assumed. For the radiative correction itself the maximal value found was taken. Therefore one can take: ΔSSA syst = ±2.7 x 10 -3

  6. Concrete, hardened: Self desiccation

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard; Persson, Bertil

    1999-01-01

    The test method covers the determination of internal relative humidity (RH) in hardened concrete and cement mortar using RH instruments. The determination of RH is done on crushed samples of concrete or cement motar. This test method is only for measuring equipment which gives off or takes up...

  7. Application of the two-dose-rate method for general recombination correction for liquid ionization chambers in continuous beams

    International Nuclear Information System (INIS)

    Andersson, Jonas; Toelli, Heikki

    2011-01-01

    A method to correct for the general recombination losses for liquid ionization chambers in continuous beams has been developed. The proposed method has been derived from Greening's theory for continuous beams and is based on measuring the signal from a liquid ionization chamber and an air filled monitor ionization chamber at two different dose rates. The method has been tested with two plane parallel liquid ionization chambers in a continuous radiation x-ray beam with a tube voltage of 120 kV and with dose rates between 2 and 13 Gy min -1 . The liquids used as sensitive media in the chambers were isooctane (C 8 H 18 ) and tetramethylsilane (Si(CH 3 ) 4 ). The general recombination effect was studied using chamber polarizing voltages of 100, 300, 500, 700 and 900 V for both liquids. The relative standard deviation of the results for the collection efficiency with respect to general recombination was found to be a maximum of 0.7% for isooctane and 2.4% for tetramethylsilane. The results are in excellent agreement with Greening's theory for collection efficiencies over 90%. The measured and corrected signals from the liquid ionization chambers used in this work are in very good agreement with the air filled monitor chamber with respect to signal to dose linearity.

  8. RHOBOT: Radiation hardened robotics

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, P.C.; Posey, L.D. [Sandia National Labs., Albuquerque, NM (United States)

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

  9. RHOBOT: Radiation hardened robotics

    International Nuclear Information System (INIS)

    Bennett, P.C.; Posey, L.D.

    1997-10-01

    A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program

  10. Grind hardening process

    CERN Document Server

    Salonitis, Konstantinos

    2015-01-01

    This book presents the grind-hardening process and the main studies published since it was introduced in 1990s.  The modelling of the various aspects of the process, such as the process forces, temperature profile developed, hardness profiles, residual stresses etc. are described in detail. The book is of interest to the research community working with mathematical modeling and optimization of manufacturing processes.

  11. An experimental study of the scatter correction by using a beam-stop-array algorithm with digital breast tomosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ye-Seul; Park, Hye-Suk; Kim, Hee-Joung [Yonsei University, Wonju (Korea, Republic of); Choi, Young-Wook; Choi, Jae-Gu [Korea Electrotechnology Research Institute, Ansan (Korea, Republic of)

    2014-12-15

    Digital breast tomosynthesis (DBT) is a technique that was developed to overcome the limitations of conventional digital mammography by reconstructing slices through the breast from projections acquired at different angles. In developing and optimizing DBT, The x-ray scatter reduction technique remains a significant challenge due to projection geometry and radiation dose limitations. The most common approach to scatter reduction is a beam-stop-array (BSA) algorithm; however, this method raises concerns regarding the additional exposure involved in acquiring the scatter distribution. The compressed breast is roughly symmetric, and the scatter profiles from projections acquired at axially opposite angles are similar to mirror images. The purpose of this study was to apply the BSA algorithm with only two scans with a beam stop array, which estimates the scatter distribution with minimum additional exposure. The results of the scatter correction with angular interpolation were comparable to those of the scatter correction with all scatter distributions at each angle. The exposure increase was less than 13%. This study demonstrated the influence of the scatter correction obtained by using the BSA algorithm with minimum exposure, which indicates its potential for practical applications.

  12. An improved cone-beam filtered backprojection reconstruction algorithm based on x-ray angular correction and multiresolution analysis

    International Nuclear Information System (INIS)

    Sun, Y.; Hou, Y.; Yan, Y.

    2004-01-01

    With the extensive application of industrial computed tomography in the field of non-destructive testing, how to improve the quality of the reconstructed image is receiving more and more concern. It is well known that in the existing cone-beam filtered backprojection reconstruction algorithms the cone angle is controlled within a narrow range. The reason of this limitation is the incompleteness of projection data when the cone angle increases. Thus the size of the tested workpiece is limited. Considering the characteristic of X-ray cone angle, an improved cone-beam filtered back-projection reconstruction algorithm taking account of angular correction is proposed in this paper. The aim of our algorithm is to correct the cone-angle effect resulted from the incompleteness of projection data in the conventional algorithm. The basis of the correction is the angular relationship among X-ray source, tested workpiece and the detector. Thus the cone angle is not strictly limited and this algorithm may be used to detect larger workpiece. Further more, adaptive wavelet filter is used to make multiresolution analysis, which can modify the wavelet decomposition series adaptively according to the demand for resolution of local reconstructed area. Therefore the computation and the time of reconstruction can be reduced, and the quality of the reconstructed image can also be improved. (author)

  13. A new method for x-ray scatter correction: first assessment on a cone-beam CT experimental setup

    International Nuclear Information System (INIS)

    Rinkel, J; Gerfault, L; Esteve, F; Dinten, J-M

    2007-01-01

    Cone-beam computed tomography (CBCT) enables three-dimensional imaging with isotropic resolution and a shorter acquisition time compared to a helical CT scanner. Because a larger object volume is exposed for each projection, scatter levels are much higher than in collimated fan-beam systems, resulting in cupping artifacts, streaks and quantification inaccuracies. In this paper, a general method to correct for scatter in CBCT, without supplementary on-line acquisition, is presented. This method is based on scatter calibration through off-line acquisition combined with on-line analytical transformation based on physical equations, to adapt calibration to the object observed. The method was tested on a PMMA phantom and on an anthropomorphic thorax phantom. The results were validated by comparison to simulation for the PMMA phantom and by comparison to scans obtained on a commercial multi-slice CT scanner for the thorax phantom. Finally, the improvements achieved with the new method were compared to those obtained using a standard beam-stop method. The new method provided results that closely agreed with the simulation and with the conventional CT scanner, eliminating cupping artifacts and significantly improving quantification. Compared to the beam-stop method, lower x-ray doses and shorter acquisition times were needed, both divided by a factor of 9 for the same scatter estimation accuracy

  14. An adaptive feedback controller for transverse angle and position jitter correction in linear particle beam accelerators

    International Nuclear Information System (INIS)

    Barr, D.S.

    1993-01-01

    It is desired to design a position and angle jitter control system for pulsed linear accelerators that will increase the accuracy of correction over that achieved by currently used standard feedback jitter control systems. Interpulse or pulse-to-pulse correction is performed using the average value of each macropulse. The configuration of such a system resembles that of a standard feedback correction system with the addition of an adaptive controller that dynamically adjusts the gain-phase contour of the feedback electronics. The adaptive controller makes changes to the analog feedback system between macropulses. A simulation of such a system using real measured jitter data from the Stanford Linear Collider was shown to decrease the average rms jitter by over two and a half times. The system also increased and stabilized the correction at high frequencies; a typical problem with standard feedback systems

  15. An adaptive feedback controller for transverse angle and position jitter correction in linear particle beam accelerators

    International Nuclear Information System (INIS)

    Barr, D.S.

    1992-01-01

    It is desired to design a position and angle jitter control system for pulsed linear accelerators that will increase the accuracy of correction over that achieved by currently used standard feedback jitter control systems. Interpulse or pulse-to-pulse correction is performed using the average value of each macropulse. The configuration of such a system resembles that of a standard feedback correction system with the addition of an adaptive controller that dynamically adjusts the gain-phase contour of the feedback electronics. The adaptive controller makes changes to the analog feedback system between macropulses. A simulation of such a system using real measured jitter data from the Stanford Linear Collider was shown to decrease the average rms jitter by over two and a half times. The system also increased and stabilized the correction at high frequencies; a typical problem with standard feedback systems

  16. Laser-plasma interaction with an adaptive optics wavefront-corrected laser beam

    International Nuclear Information System (INIS)

    Lewis, K.

    2008-12-01

    The propagation of an intense laser beam trough a preformed plasma is of particular interest in order to achieve laser inertial confinement fusion. Experiments carried out with a near-diffraction limited laser beam, producing a single hot spot interacting with the plasma, delivered new results, presented in this Ph.D. dissertation. In particular the first experimental observation of the filament instability confirms the numerous theoretical and numerical studies on the subject. Beam spreading and filament-ion thresholds are studied thanks to near-field and far-field images, with respect to laser intensity, time and space, and plasma transverse velocity. Same diagnostics have been applied to the stimulated Brillouin scattered light, enabling the first observation of the transverse Brillouin activity in the plasma. (author)

  17. Correction of the first order beam transport of the SLC Arcs

    International Nuclear Information System (INIS)

    Walker, N.; Barklow, T.; Emma, P.; Krejcik, P.

    1991-05-01

    Correction of the first order transport of the SLC Arcs has been made possible by a technique which allows the full 4x4 transport matrix across any section of Arc to be experimentally determined. By the introduction of small closed bumps into each achromat, it is possible to substantially correct first order optical errors, and notably the cross plane coupling at the exit of the Arcs. 4 refs., 3 figs

  18. Correction of aberrations in beams filling elliptical phase-space areas

    International Nuclear Information System (INIS)

    Wollnik, H.

    1988-01-01

    For the optimization of an optical system it is advantageous to amend the system by a virtual object lens so that the calculation always starts from an upright phase-space distribution. Furthermore, in case of a beam filling an elliptical phase-space volume, the most extreme rays of a beam, filling a parallelogram-like phase-space volume, do not exist, so that the corresponding sum of aberrations is smaller. For an optimization thus corresponding attenuation factors should be taken into accout

  19. A study of energy correction for the electron beam data in the BGO ECAL of the DAMPE

    CERN Document Server

    Li, Zhiying; Wei, Yifeng; Wang, Chi; Zhang, Yunlong; Wen, Sicheng; Wang, Xiaolian; Xu, Zizong; Huang, Guangshun

    2015-01-01

    The DArk Matter Particle Explorer (DAMPE) is an orbital experiment aiming at searching for dark matter indirectly by measuring the spectra of photons, electrons and positrons originating from deep space. The BGO electromagnetic calorimeter is one of the key sub-detectors of the DAMPE, which is designed for high energy measurement with a large dynamic range from 5 GeV to 10 TeV. In this paper, some methods for energy correction are discussed and tried, in order to reconstruct the primary energy of the incident electrons. Different methods are chosen for the appropriate energy ranges. The results of Geant4 simulation and beam test data (at CERN) are presented.

  20. Clinical introduction of image lag correction for a cone beam CT system

    NARCIS (Netherlands)

    Stankovic, Uros; Ploeger, Lennert S.; Sonke, Jan-Jakob; van Herk, Marcel

    2016-01-01

    Image lag in the flat-panel detector used for Linac integrated cone beam computed tomography (CBCT) has a degrading effect on CBCT image quality. The most prominent visible artifact is the presence of bright semicircular structure in the transverse view of the scans, known also as radar artifact.

  1. Wavefront-sensor-induced beam size error: physical mechanism, sensitivity-analysis and correction method

    NARCIS (Netherlands)

    Koek, W.D.; Zwet, E.J. van

    2015-01-01

    When using a commonly-used quadri-wave lateral shearing interferometer wavefront sensor (QWLSI WFS) for beam size measurements on a high power CO2 laser, artefacts have been observed in the measured irradiance distribution. The grating in the QWLSI WFS not only generates the diffracted first orders

  2. SU-F-J-211: Scatter Correction for Clinical Cone-Beam CT System Using An Optimized Stationary Beam Blocker with a Single Scan

    Energy Technology Data Exchange (ETDEWEB)

    Liang, X; Zhang, Z; Xie, Y [Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, GuangDong (China); Gong, S; Niu, T [Department of Radiation Oncology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang (China); Institute of Translational Medicine, Zhejiang University, Hangzhou, Zhejiang (China); Zhou, Q [Department of Radiation Oncology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang (China)

    2016-06-15

    Purpose: X-ray scatter photons result in significant image quality degradation of cone-beam CT (CBCT). Measurement based algorithms using beam blocker directly acquire the scatter samples and achieve significant improvement on the quality of CBCT image. Within existing algorithms, single-scan and stationary beam blocker proposed previously is promising due to its simplicity and practicability. Although demonstrated effectively on tabletop system, the blocker fails to estimate the scatter distribution on clinical CBCT system mainly due to the gantry wobble. In addition, the uniform distributed blocker strips in our previous design results in primary data loss in the CBCT system and leads to the image artifacts due to data insufficiency. Methods: We investigate the motion behavior of the beam blocker in each projection and design an optimized non-uniform blocker strip distribution which accounts for the data insufficiency issue. An accurate scatter estimation is then achieved from the wobble modeling. Blocker wobble curve is estimated using threshold-based segmentation algorithms in each projection. In the blocker design optimization, the quality of final image is quantified using the number of the primary data loss voxels and the mesh adaptive direct search algorithm is applied to minimize the objective function. Scatter-corrected CT images are obtained using the optimized blocker. Results: The proposed method is evaluated using Catphan@504 phantom and a head patient. On the Catphan©504, our approach reduces the average CT number error from 115 Hounsfield unit (HU) to 11 HU in the selected regions of interest, and improves the image contrast by a factor of 1.45 in the high-contrast regions. On the head patient, the CT number error is reduced from 97 HU to 6 HU in the soft tissue region and image spatial non-uniformity is decreased from 27% to 5% after correction. Conclusion: The proposed optimized blocker design is practical and attractive for CBCT guided radiation

  3. SU-F-J-211: Scatter Correction for Clinical Cone-Beam CT System Using An Optimized Stationary Beam Blocker with a Single Scan

    International Nuclear Information System (INIS)

    Liang, X; Zhang, Z; Xie, Y; Gong, S; Niu, T; Zhou, Q

    2016-01-01

    Purpose: X-ray scatter photons result in significant image quality degradation of cone-beam CT (CBCT). Measurement based algorithms using beam blocker directly acquire the scatter samples and achieve significant improvement on the quality of CBCT image. Within existing algorithms, single-scan and stationary beam blocker proposed previously is promising due to its simplicity and practicability. Although demonstrated effectively on tabletop system, the blocker fails to estimate the scatter distribution on clinical CBCT system mainly due to the gantry wobble. In addition, the uniform distributed blocker strips in our previous design results in primary data loss in the CBCT system and leads to the image artifacts due to data insufficiency. Methods: We investigate the motion behavior of the beam blocker in each projection and design an optimized non-uniform blocker strip distribution which accounts for the data insufficiency issue. An accurate scatter estimation is then achieved from the wobble modeling. Blocker wobble curve is estimated using threshold-based segmentation algorithms in each projection. In the blocker design optimization, the quality of final image is quantified using the number of the primary data loss voxels and the mesh adaptive direct search algorithm is applied to minimize the objective function. Scatter-corrected CT images are obtained using the optimized blocker. Results: The proposed method is evaluated using Catphan@504 phantom and a head patient. On the Catphan©504, our approach reduces the average CT number error from 115 Hounsfield unit (HU) to 11 HU in the selected regions of interest, and improves the image contrast by a factor of 1.45 in the high-contrast regions. On the head patient, the CT number error is reduced from 97 HU to 6 HU in the soft tissue region and image spatial non-uniformity is decreased from 27% to 5% after correction. Conclusion: The proposed optimized blocker design is practical and attractive for CBCT guided radiation

  4. Practical aspects of systems hardening

    International Nuclear Information System (INIS)

    Shepherd, W.J.

    1989-01-01

    Applications of hardening technology in a practical system require a balance between the factors governing affordability, producibility, and survivability of the finished design. Without careful consideration of the top-level system operating constraints, a design engineer may find himself with a survivable but overweight, unproductive, expensive design. This paper explores some lessons learned in applying hardening techniques to several laser communications programs and is intended as an introductory guide to novice designers faced with the task of hardening a space system

  5. Open-loop correction for an eddy current dominated beam-switching magnet.

    Science.gov (United States)

    Koseki, K; Nakayama, H; Tawada, M

    2014-04-01

    A beam-switching magnet and the pulsed power supply it requires have been developed for the Japan Proton Accelerator Research Complex. To switch bunched proton beams, the dipole magnetic field must reach its maximum value within 40 ms. In addition, the field flatness should be less than 5 × 10(-4) to guide each bunched beam to the designed orbit. From a magnetic field measurement by using a long search coil, it was found that an eddy current in the thick endplates and laminated core disturbs the rise of the magnetic field. The eddy current also deteriorates the field flatness over the required flat-top period. The measured field flatness was 5 × 10(-3). By using a double-exponential equation to approximate the measured magnetic field, a compensation pattern for the eddy current was calculated. The integrated magnetic field was measured while using the newly developed open-loop compensation system. A field flatness of less than 5 × 10(-4), which is an acceptable value, was achieved.

  6. Evaluation of a method for correction of scatter radiation in thorax cone beam CT; Evaluation d'une methode de correction du rayonnement diffuse en tomographie du thorax avec faisceau conique

    Energy Technology Data Exchange (ETDEWEB)

    Rinkel, J.; Dinten, J.M. [CEA Grenoble (DTBS/STD), Lab. d' Electronique et de Technologie de l' Informatique, LETI, 38 (France); Esteve, F. [European Synchrotron Radiation Facility (ESRF), 38 - Grenoble (France)

    2004-07-01

    Purpose: Cone beam CT (CBCT) enables three-dimensional imaging with isotropic resolution. X-ray scatter estimation is a big challenge for quantitative CBCT imaging of thorax: scatter level is significantly higher on cone beam systems compared to collimated fan beam systems. The effects of this scattered radiation are cupping artefacts, streaks, and quantification inaccuracies. The beam stops conventional scatter estimation approach can be used for CBCT but leads to a significant increase in terms of dose and acquisition time. At CEA-LETI has been developed an original scatter management process without supplementary acquisition. Methods and Materials: This Analytical Plus Indexing-based method (API) of scatter correction in CBCT is based on scatter calibration through offline acquisitions with beam stops on lucite plates, combined to an analytical transformation issued from physical equations. This approach has been applied with success in bone densitometry and mammography. To evaluate this method in CBCT, acquisitions from a thorax phantom with and without beam stops have been performed. To compare different scatter correction approaches, Feldkamp algorithm has been applied on rough data corrected from scatter by API and by beam stops approaches. Results: The API method provides results in good agreement with the beam stops array approach, suppressing cupping artefact. Otherwise influence of the scatter correction method on the noise in the reconstructed images has been evaluated. Conclusion: The results indicate that the API method is effective for quantitative CBCT imaging of thorax. Compared to a beam stops array method it needs a lower x-ray dose and shortens acquisition time. (authors)

  7. Nuclear effects hardened shelters

    International Nuclear Information System (INIS)

    Lindke, P.

    1990-01-01

    This paper reports on the Houston Fearless 76 Government Projects Group that has been actively engaged for more than twenty-five years as a sub-contractor and currently as a prime contractor in the design, manufacture, repair and logistics support of custom mobile ground stations and their equipment accommodations. Other associated products include environmental control units (ECU's), mobilizers for shelters and a variety of mobile power generation units (MPU's). Since 1984, Houston Fearless 76 has designed and manufactured four 8 foot by 8 foot x 22 foot nuclear hardened mobile shelters. These shelters were designed to contain electronic data processing/reduction equipment. One shelter is currently being operated by the Air Force as a Defense Intelligence Agency (DIA) approved and certified Special Compartmented Information Facility (SCIF). During the development and manufacturing process of the shelters, we received continual technical assistance and design concept evaluations from Science Applications International Corporation (SAIC) Operations Analysis and Logistics Engineering Division and the Nondestructive Inspection Lab at McClellan AFB. SAIC was originally employed by the Air Force to design the nuclear hardening specifications applied to these shelters

  8. A cone beam CT-guided online plan modification technique to correct interfractional anatomic changes for prostate cancer IMRT treatment

    International Nuclear Information System (INIS)

    Fu Weihua; Yang Yong; Yue, Ning J; Heron, Dwight E; Huq, M Saiful

    2009-01-01

    The purpose of this work is to develop an online plan modification technique to compensate for the interfractional anatomic changes for prostate cancer intensity-modulated radiation therapy (IMRT) treatment based on daily cone beam CT (CBCT) images. In this proposed technique, pre-treatment CBCT images are acquired after the patient is set up on the treatment couch using an in-room laser with the guidance of the setup skin marks. Instead of moving the couch to rigidly align the target or re-planning using the CBCT images, we modify the original IMRT plan to account for the interfractional target motion and deformation based on the daily CBCT image feedback. The multileaf collimator (MLC) leaf positions for each subfield are automatically adjusted in the proposed algorithm based on the position and shape changes of target projection in the beam's eye view (BEV). Three typical prostate cases were adopted to evaluate the proposed technique, and the results were compared with those obtained with bony-structure-based rigid translation correction, prostate-based correction and CBCT-based re-planning strategies. The study revealed that the proposed modification technique is superior to the bony-structure-based and prostate-based correction techniques, especially when interfractional target deformation exists. Its dosimetric performance is closer to that of the re-planned strategy, but with much higher efficiency, indicating that the introduced online CBCT-guided plan modification technique may be an efficient and practical method to compensate for the interfractional target position and shape changes for prostate IMRT.

  9. A GPU-based finite-size pencil beam algorithm with 3D-density correction for radiotherapy dose calculation

    International Nuclear Information System (INIS)

    Gu Xuejun; Jia Xun; Jiang, Steve B; Jelen, Urszula; Li Jinsheng

    2011-01-01

    Targeting at the development of an accurate and efficient dose calculation engine for online adaptive radiotherapy, we have implemented a finite-size pencil beam (FSPB) algorithm with a 3D-density correction method on graphics processing unit (GPU). This new GPU-based dose engine is built on our previously published ultrafast FSPB computational framework (Gu et al 2009 Phys. Med. Biol. 54 6287-97). Dosimetric evaluations against Monte Carlo dose calculations are conducted on ten IMRT treatment plans (five head-and-neck cases and five lung cases). For all cases, there is improvement with the 3D-density correction over the conventional FSPB algorithm and for most cases the improvement is significant. Regarding the efficiency, because of the appropriate arrangement of memory access and the usage of GPU intrinsic functions, the dose calculation for an IMRT plan can be accomplished well within 1 s (except for one case) with this new GPU-based FSPB algorithm. Compared to the previous GPU-based FSPB algorithm without 3D-density correction, this new algorithm, though slightly sacrificing the computational efficiency (∼5-15% lower), has significantly improved the dose calculation accuracy, making it more suitable for online IMRT replanning.

  10. Evaluation of tumor localization in respiration motion-corrected cone-beam CT: Prospective study in lung

    Energy Technology Data Exchange (ETDEWEB)

    Dzyubak, Oleksandr; Kincaid, Russell; Hertanto, Agung; Hu, Yu-Chi; Pham, Hai; Yorke, Ellen; Zhang, Qinghui; Mageras, Gig S., E-mail: magerasg@mskcc.org [Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10065 (United States); Rimner, Andreas [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065 (United States)

    2014-10-15

    Purpose: Target localization accuracy of cone-beam CT (CBCT) images used in radiation treatment of respiratory disease sites is affected by motion artifacts (blurring and streaking). The authors have previously reported on a method of respiratory motion correction in thoracic CBCT at end expiration (EE). The previous retrospective study was limited to examination of reducing motion artifacts in a small number of patient cases. They report here on a prospective study in a larger group of lung cancer patients to evaluate respiratory motion-corrected (RMC)-CBCT ability to improve lung tumor localization accuracy and reduce motion artifacts in Linac-mounted CBCT images. A second study goal examines whether the motion correction derived from a respiration-correlated CT (RCCT) at simulation yields similar tumor localization accuracy at treatment. Methods: In an IRB-approved study, 19 lung cancer patients (22 tumors) received a RCCT at simulation, and on one treatment day received a RCCT, a respiratory-gated CBCT at end expiration, and a 1-min CBCT. A respiration monitor of abdominal displacement was used during all scans. In addition to a CBCT reconstruction without motion correction, the motion correction method was applied to the same 1-min scan. Projection images were sorted into ten bins based on abdominal displacement, and each bin was reconstructed to produce ten intermediate CBCT images. Each intermediate CBCT was deformed to the end expiration state using a motion model derived from RCCT. The deformed intermediate CBCT images were then added to produce a final RMC-CBCT. In order to evaluate the second study goal, the CBCT was corrected in two ways, one using a model derived from the RCCT at simulation [RMC-CBCT(sim)], the other from the RCCT at treatment [RMC-CBCT(tx)]. Image evaluation compared uncorrected CBCT, RMC-CBCT(sim), and RMC-CBCT(tx). The gated CBCT at end expiration served as the criterion standard for comparison. Using automatic rigid image

  11. SU-E-T-608: Perturbation Corrections for Alanine Dosimeters in Different Phantom Materials in High-Energy Photon Beams

    International Nuclear Information System (INIS)

    Voigts-Rhetz, P von; Czarnecki, D; Anton, M; Zink, K

    2015-01-01

    Purpose: Alanine dosimeters are often used for in-vivo dosimetry purposes in radiation therapy. In a Monte Carlo study the influence of 20 different surrounding/phantom materials for alanine dosimeters was investigated. The investigations were performed in high-energy photon beams, covering the whole range from 60 Co up to 25 MV-X. The aim of the study is the introduction of a perturbation correction k env for alanine dosimeters accounting for the environmental material. Methods: The influence of different surrounding materials on the response of alanine dosimeters was investigated with Monte Carlo simulations using the EGSnrc code. The photon source was adapted with BEAMnrc to a 60 Co unit and an Elekta (E nom =6, 10, 25 MV-X) linear accelerator. Different tissue-equivalent materials ranging from cortical bone to lung were investigated. In addition to available phantom materials, some material compositions were taken and scaled to different electron densities. The depth of the alanine detectors within the different phantom materials corresponds to 5 cm depth in water, i.e. the depth is scaled according to the electron density (n e /n e,w ) of the corresponding phantom material. The dose was scored within the detector volume once for an alanine/paraffin mixture and once for a liquid water voxel. The relative response, the ratio of the absorbed dose to alanine to the absorbed dose to water, was calculated and compared to the corresponding ratio under reference conditions. Results: For each beam quality the relative response r and the correction factor for the environment kenv was calculated. k env =0.9991+0.0049 *((n e /n e,w )−0.7659) 3 Conclusion: A perturbation correction factor k env accounting for the phantom environment has been introduced. The response of the alanine dosimeter can be considered independent of the surrounding material for relative electron densities (n e /n e,w ) between 1 and 1.4. For denser materials such as bone or much less dense

  12. Patient Position Verification and Corrective Evaluation Using Cone Beam Computed Tomography (CBCT) in Intensity modulated Radiation Therapy

    International Nuclear Information System (INIS)

    Do, Gyeong Min; Jeong, Deok Yang; Kim, Young Bum

    2009-01-01

    Cone beam computed tomography (CBCT) using an on board imager (OBI) can check the movement and setup error in patient position and target volume by comparing with the image of computer simulation treatment in real.time during patient treatment. Thus, this study purposed to check the change and movement of patient position and target volume using CBCT in IMRT and calculate difference from the treatment plan, and then to correct the position using an automated match system and to test the accuracy of position correction using an electronic portal imaging device (EPID) and examine the usefulness of CBCT in IMRT and the accuracy of the automatic match system. The subjects of this study were 3 head and neck patients and 1 pelvis patient sampled from IMRT patients treated in our hospital. In order to investigate the movement of treatment position and resultant displacement of irradiated volume, we took CBCT using OBI mounted on the linear accelerator. Before each IMRT treatment, we took CBCT and checked difference from the treatment plan by coordinate by comparing it with the image of CT simulation. Then, we made correction through the automatic match system of 3D/3D match to match the treatment plan, and verified and evaluated using electronic portal imaging device. When CBCT was compared with the image of CT simulation before treatment, the average difference by coordinate in the head and neck was 0.99 mm vertically, 1.14 mm longitudinally, 4.91 mm laterally, and 1.07 degrees in the rotational direction, showing somewhat insignificant differences by part. In testing after correction, when the image from the electronic portal imaging device was compared with DRR image, it was found that correction had been made accurately with error less than 0.5 mm. By comparing a CBCT image before treatment with a 3D image reconstructed into a volume instead of a 2D image for the patient's setup error and change in the position of the organs and the target, we could measure and

  13. Evaluation of tumor localization in respiration motion-corrected cone-beam CT: prospective study in lung.

    Science.gov (United States)

    Dzyubak, Oleksandr; Kincaid, Russell; Hertanto, Agung; Hu, Yu-Chi; Pham, Hai; Rimner, Andreas; Yorke, Ellen; Zhang, Qinghui; Mageras, Gig S

    2014-10-01

    Target localization accuracy of cone-beam CT (CBCT) images used in radiation treatment of respiratory disease sites is affected by motion artifacts (blurring and streaking). The authors have previously reported on a method of respiratory motion correction in thoracic CBCT at end expiration (EE). The previous retrospective study was limited to examination of reducing motion artifacts in a small number of patient cases. They report here on a prospective study in a larger group of lung cancer patients to evaluate respiratory motion-corrected (RMC)-CBCT ability to improve lung tumor localization accuracy and reduce motion artifacts in Linac-mounted CBCT images. A second study goal examines whether the motion correction derived from a respiration-correlated CT (RCCT) at simulation yields similar tumor localization accuracy at treatment. In an IRB-approved study, 19 lung cancer patients (22 tumors) received a RCCT at simulation, and on one treatment day received a RCCT, a respiratory-gated CBCT at end expiration, and a 1-min CBCT. A respiration monitor of abdominal displacement was used during all scans. In addition to a CBCT reconstruction without motion correction, the motion correction method was applied to the same 1-min scan. Projection images were sorted into ten bins based on abdominal displacement, and each bin was reconstructed to produce ten intermediate CBCT images. Each intermediate CBCT was deformed to the end expiration state using a motion model derived from RCCT. The deformed intermediate CBCT images were then added to produce a final RMC-CBCT. In order to evaluate the second study goal, the CBCT was corrected in two ways, one using a model derived from the RCCT at simulation [RMC-CBCT(sim)], the other from the RCCT at treatment [RMC-CBCT(tx)]. Image evaluation compared uncorrected CBCT, RMC-CBCT(sim), and RMC-CBCT(tx). The gated CBCT at end expiration served as the criterion standard for comparison. Using automatic rigid image registration, each CBCT was

  14. Novel circuits for radiation hardened memories

    International Nuclear Information System (INIS)

    Haraszti, T.P.; Mento, R.P.; Moyer, N.E.; Grant, W.M.

    1992-01-01

    This paper reports on implementation of large storage semiconductor memories which combine radiation hardness with high packing density, operational speed, and low power dissipation and require both hardened circuit and hardened process technologies. Novel circuits, including orthogonal shuffle type of write-read arrays, error correction by weighted bidirectional codes and associative iterative repair circuits, are proposed for significant improvements of SRAMs' immunity against the effects of total dose and cosmic particle impacts. The implementation of the proposed circuit resulted in fault-tolerant 40-Mbit and 10-Mbit monolithic memories featuring a data rate of 120 MHz and power dissipation of 880 mW. These experimental serial-parallel memories were fabricated with a nonhardened standard CMOS processing technology, yet provided a total dose hardness of 1 Mrad and a projected SEU rate of 1 x 10 - 12 error/bit/day. Using radiation hardened processing improvements by factors of 10 to 100 are predicted in both total dose hardness and SEU rate

  15. Controlling the Laser Guide Star power density distribution at Sodium layer by combining Pre-correction and Beam-shaping

    Science.gov (United States)

    Huang, Jian; Wei, Kai; Jin, Kai; Li, Min; Zhang, YuDong

    2018-06-01

    The Sodium laser guide star (LGS) plays a key role in modern astronomical Adaptive Optics Systems (AOSs). The spot size and photon return of the Sodium LGS depend strongly on the laser power density distribution at the Sodium layer and thus affect the performance of the AOS. The power density distribution is degraded by turbulence in the uplink path, launch system aberrations, the beam quality of the laser, and so forth. Even without any aberrations, the TE00 Gaussian type is still not the optimal power density distribution to obtain the best balance between the measurement error and temporal error. To optimize and control the LGS power density distribution at the Sodium layer to an expected distribution type, a method that combines pre-correction and beam-shaping is proposed. A typical result shows that under strong turbulence (Fried parameter (r0) of 5 cm) and for a quasi-continuous wave Sodium laser (power (P) of 15 W), in the best case, our method can effectively optimize the distribution from the Gaussian type to the "top-hat" type and enhance the photon return flux of the Sodium LGS; at the same time, the total error of the AOS is decreased by 36% with our technique for a high power laser and poor seeing.

  16. Electron-beam-induced-current and active secondary-electron voltage-contrast with aberration-corrected electron probes

    Energy Technology Data Exchange (ETDEWEB)

    Han, Myung-Geun, E-mail: mghan@bnl.gov [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Garlow, Joseph A. [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Materials Science and Engineering Department, Stony Brook University, Stony Brook, NY 11794 (United States); Marshall, Matthew S.J.; Tiano, Amanda L. [Department of Chemistry, Stony Brook University, Stony Brook, NY 11974 (United States); Wong, Stanislaus S. [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Department of Chemistry, Stony Brook University, Stony Brook, NY 11974 (United States); Cheong, Sang-Wook [Department of Physics and Astronomy, Rutgers Center for Emergent Materials, Rutgers University, Piscataway, NJ 08854 (United States); Walker, Frederick J.; Ahn, Charles H. [Department of Applied Physics and Center for Research on Interface Structures and Phenomena, Yale University, New Haven, CT 06520 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520 (United States); Zhu, Yimei [Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2017-05-15

    Highlights: • Electron-beam-induced-current (EBIC) and active secondary-electron voltage-contrast (SE-VC) are demonstrated in STEM mode combined with in situ electrical biasing in a TEM. • Electrostatic potential maps in ferroelectric thin films, multiferroic nanowires, and single crystals obtained by off-axis electron holography were compared with EBIC and SE-VC data. • Simultaneous EBIC and active SE-VC performed with atomic resolution STEM are demonstrated. - Abstract: The ability to map out electrostatic potentials in materials is critical for the development and the design of nanoscale electronic and spintronic devices in modern industry. Electron holography has been an important tool for revealing electric and magnetic field distributions in microelectronics and magnetic-based memory devices, however, its utility is hindered by several practical constraints, such as charging artifacts and limitations in sensitivity and in field of view. In this article, we report electron-beam-induced-current (EBIC) and secondary-electron voltage-contrast (SE-VC) with an aberration-corrected electron probe in a transmission electron microscope (TEM), as complementary techniques to electron holography, to measure electric fields and surface potentials, respectively. These two techniques were applied to ferroelectric thin films, multiferroic nanowires, and single crystals. Electrostatic potential maps obtained by off-axis electron holography were compared with EBIC and SE-VC to show that these techniques can be used as a complementary approach to validate quantitative results obtained from electron holography analysis.

  17. Nonlinear dynamics of spring softening and hardening in folded-mems comb drive resonators

    KAUST Repository

    Elshurafa, Amro M.; Khirallah, Kareem; Tawfik, Hani H.; Emira, Ahmed; Abdel Aziz, Ahmed K S; Sedky, Sherif M.

    2011-01-01

    This paper studies analytically and numerically the spring softening and hardening phenomena that occur in electrostatically actuated microelectromechanical systems comb drive resonators utilizing folded suspension beams. An analytical expression

  18. Dose-calculation algorithms in the context of inhomogeneity corrections for high energy photon beams

    International Nuclear Information System (INIS)

    Papanikolaou, Niko; Stathakis, Sotirios

    2009-01-01

    Radiation therapy has witnessed a plethora of innovations and developments in the past 15 years. Since the introduction of computed tomography for treatment planning there has been a steady introduction of new methods to refine treatment delivery. Imaging continues to be an integral part of the planning, but also the delivery, of modern radiotherapy. However, all the efforts of image guided radiotherapy, intensity-modulated planning and delivery, adaptive radiotherapy, and everything else that we pride ourselves in having in the armamentarium can fall short, unless there is an accurate dose-calculation algorithm. The agreement between the calculated and delivered doses is of great significance in radiation therapy since the accuracy of the absorbed dose as prescribed determines the clinical outcome. Dose-calculation algorithms have evolved greatly over the years in an effort to be more inclusive of the effects that govern the true radiation transport through the human body. In this Vision 20/20 paper, we look back to see how it all started and where things are now in terms of dose algorithms for photon beams and the inclusion of tissue heterogeneities. Convolution-superposition algorithms have dominated the treatment planning industry for the past few years. Monte Carlo techniques have an inherent accuracy that is superior to any other algorithm and as such will continue to be the gold standard, along with measurements, and maybe one day will be the algorithm of choice for all particle treatment planning in radiation therapy.

  19. Direct focusing error correction with ring-wide TBT beam position data

    International Nuclear Information System (INIS)

    Yang, M.J.

    2011-01-01

    Turn-By-Turn (TBT) betatron oscillation data is a very powerful tool in studying machine optics. Hundreds and thousands of turns of free oscillations are taken in just few tens of milliseconds. With beam covering all positions and angles at every location TBT data can be used to diagnose focusing errors almost instantly. This paper describes a new approach that observes focusing error collectively over all available TBT data to find the optimized quadrupole strength, one location at a time. Example will be shown and other issues will be discussed. The procedure presented clearly has helped to reduce overall deviations significantly, with relative ease. Sextupoles, being a permanent feature of the ring, will need to be incorporated into the model. While cumulative effect from all sextupoles around the ring may be negligible on turn-to-turn basis it is not so in this transfer line analysis. It should be noted that this procedure is not limited to looking for quadrupole errors. By modifying the target of minimization it could in principle be used to look for skew quadrupole errors and sextupole errors as well.

  20. Improving the beam quality of rf guns by correction of rf and space-charge effects

    International Nuclear Information System (INIS)

    Serafini, L.

    1992-01-01

    In this paper we describe two possible strategies to attain ultra-low emittance electron beam generation by laser-driven RF guns. The first one is based on the exploitation of multi-mode resonant cavities to neutralize the emittance degradation induced by RF effects. Accelerating cigar-like (long and thin) electron bunches in multi-mode operated RF guns the space charge induced emittance is strongly decreased at the same time: high charged bunches, as typically requested by future TeV e - e + colliders, can be delivered by the gun at a quite low transverse emittance and good behaviour in the longitudinal phase space, so that they can be magnetically compressed to reach higher peak currents. The second strategy consists in using disk-like electron bunches, produced by very short laser pulses illuminating the photocathode. By means of an analytical study a new regime has been found, where the normalized transverse emittance scales like the inverse of the peak current, provided that the laser pulse intensity distribution is properly shaped in the transverse direction. Preliminary numerical simulations confirm the analytical predictions and show that the minimum emittance achievable is set up, in this new regime, by the wake-field interaction between the bunch and the cathode metallic wall

  1. TH-A-18C-04: Ultrafast Cone-Beam CT Scatter Correction with GPU-Based Monte Carlo Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y [UT Southwestern Medical Center, Dallas, TX (United States); Southern Medical University, Guangzhou (China); Bai, T [UT Southwestern Medical Center, Dallas, TX (United States); Xi' an Jiaotong University, Xi' an (China); Yan, H; Ouyang, L; Wang, J; Pompos, A; Jiang, S; Jia, X [UT Southwestern Medical Center, Dallas, TX (United States); Zhou, L [Southern Medical University, Guangzhou (China)

    2014-06-15

    Purpose: Scatter artifacts severely degrade image quality of cone-beam CT (CBCT). We present an ultrafast scatter correction framework by using GPU-based Monte Carlo (MC) simulation and prior patient CT image, aiming at automatically finish the whole process including both scatter correction and reconstructions within 30 seconds. Methods: The method consists of six steps: 1) FDK reconstruction using raw projection data; 2) Rigid Registration of planning CT to the FDK results; 3) MC scatter calculation at sparse view angles using the planning CT; 4) Interpolation of the calculated scatter signals to other angles; 5) Removal of scatter from the raw projections; 6) FDK reconstruction using the scatter-corrected projections. In addition to using GPU to accelerate MC photon simulations, we also use a small number of photons and a down-sampled CT image in simulation to further reduce computation time. A novel denoising algorithm is used to eliminate MC scatter noise caused by low photon numbers. The method is validated on head-and-neck cases with simulated and clinical data. Results: We have studied impacts of photo histories, volume down sampling factors on the accuracy of scatter estimation. The Fourier analysis was conducted to show that scatter images calculated at 31 angles are sufficient to restore those at all angles with <0.1% error. For the simulated case with a resolution of 512×512×100, we simulated 10M photons per angle. The total computation time is 23.77 seconds on a Nvidia GTX Titan GPU. The scatter-induced shading/cupping artifacts are substantially reduced, and the average HU error of a region-of-interest is reduced from 75.9 to 19.0 HU. Similar results were found for a real patient case. Conclusion: A practical ultrafast MC-based CBCT scatter correction scheme is developed. The whole process of scatter correction and reconstruction is accomplished within 30 seconds. This study is supported in part by NIH (1R01CA154747-01), The Core Technology Research

  2. 3D Dose Reconstruction to Insure Correct External Beam Treatment of Patients

    International Nuclear Information System (INIS)

    Renner, Wendel Dean

    2007-01-01

    Radiation therapy treatments have become increasingly more complicated. There are multiple opportunities for humans, machines, software, and combinations thereof to result in a treatment error that could be of significance. Current methods for quality assurance are often abstract in nature and may have unclear underlying assumptions as to what is assumed to be working correctly, or may depend upon the diligence of persons to discover errors from a review of the treatment plan. Here, an example will be shown of a direct method to reconstruct and demonstrate the dose and the dose distribution delivered to a particular patient. By measuring the radiation fields that come out of the accelerator, and using the measurement as input to a 3-dimensional (3D) dose algorithm, the delivered patient dose is determined and presented in a manner similar to the treatment plan. The intended treatment plan dose may be directly compared. Using this feedback mechanism, there is less abstraction and dependence upon the diligence of individuals checking multiple steps in a treatment process, and assumptions can be clearly stated. With this system, the dose is determined and presented minimizing assumptions and dependence upon other systems

  3. Perturbation correction for alanine dosimeters in different phantom materials in high-energy photon beams.

    Science.gov (United States)

    von Voigts-Rhetz, P; Anton, M; Vorwerk, H; Zink, K

    2016-02-07

    In modern radiotherapy the verification of complex treatments plans is often performed in inhomogeneous or even anthropomorphic phantoms. For dose verification small detectors are necessary and therefore alanine detectors are most suitable. Though the response of alanine for a wide range of clinical photon energies in water is well know, the knowledge about the influence of the surrounding phantom material on the response of alanine is sparse. Therefore we investigated the influence of twenty different surrounding/phantom materials for alanine dosimeters in clinical photon fields via Monte Carlo simulations. The relative electron density of the used materials was in the range [Formula: see text] up to 1.69, covering almost all materials appearing in inhomogeneous or anthropomorphic phantoms used in radiotherapy. The investigations were performed for three different clinical photon spectra ranging from 6 to 25 MV-X and Co-60 and as a result a perturbation correction [Formula: see text] depending on the environmental material was established. The Monte Carlo simulation show, that there is only a small dependence of [Formula: see text] on the phantom material and the photon energy, which is below  ±0.6%. The results confirm the good suitability of alanine detectors for in-vivo dosimetry.

  4. Parametrisation of the collimator scatter correction factors of square and rectangular photon beams

    International Nuclear Information System (INIS)

    Jager, H.N.; Heukelom, S.; Kleffens, H.J. van; Gasteren, J.J.M. van; Laarse, R. van der; Venselaar, J.L.M.; Westermann, C.F.

    1995-01-01

    Collimator scatter correction factors S c have been measured with a cylindrical mini-phantom for five types of dual photon energy accelerators with energies between 6 and 25 MV. Using these S c -data three methods to parametrize S c of square fields have been compared including a third-order polynomial of the natural logarithm of the fieldsize normalised by the fieldsize of 10 cm 2 . Also six methods to calculate S c of rectangular fields have been compared including a new one which determines the equivalent fieldsize by extending Sterling's method. The deviation between measured and calculated S c for every accelerator, energy and all methods are determined resulting in the maximum and average deviation per method. Applied to square fields the maximum and average deviation were for the method of Chen 0.64% and 0.15%, of Szymzcyk 0.98% and 0.21%, and of this work 0.41% and 0.10%. For the rectangular fields the deviations were for the method of Sterling 1.89% and 0.50%, of Vadash 1.60% and 0.28%, of Szymczyk et al. 1.21% and 0.25%, of Chen 1.84% and 0.31% and of this work 0.79% and 0.20%. Finally, a recommendation is given how to limit the number of fields at which S c should be measured

  5. High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

    Science.gov (United States)

    Abu Anas, Emran Mohammad; Kim, Jae Gon; Lee, Soo Yeol; Kamrul Hasan, Md

    2011-10-01

    The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

  6. High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

    International Nuclear Information System (INIS)

    Anas, Emran Mohammad Abu; Hasan, Md Kamrul; Kim, Jae Gon; Lee, Soo Yeol

    2011-01-01

    The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

  7. Photon beam convolution using polyenergetic energy deposition kernels

    International Nuclear Information System (INIS)

    Hoban, P.W.; Murray, D.C.; Round, W.H.

    1994-01-01

    In photon beam convolution calculations where polyenergetic energy deposition kernels (EDKs) are used, the primary photon energy spectrum should be correctly accounted for in Monte Carlo generation of EDKs. This requires the probability of interaction, determined by the linear attenuation coefficient, μ, to be taken into account when primary photon interactions are forced to occur at the EDK origin. The use of primary and scattered EDKs generated with a fixed photon spectrum can give rise to an error in the dose calculation due to neglecting the effects of beam hardening with depth. The proportion of primary photon energy that is transferred to secondary electrons increases with depth of interaction, due to the increase in the ratio μ ab /μ as the beam hardens. Convolution depth-dose curves calculated using polyenergetic EDKs generated for the primary photon spectra which exist at depths of 0, 20 and 40 cm in water, show a fall-off which is too steep when compared with EGS4 Monte Carlo results. A beam hardening correction factor applied to primary and scattered 0 cm EDKs, based on the ratio of kerma to terma at each depth, gives primary, scattered and total dose in good agreement with Monte Carlo results. (Author)

  8. Simultaneous misalignment correction for approximate circular cone-beam computed tomography

    International Nuclear Information System (INIS)

    Kyriakou, Y; Hillebrand, L; Ertel, D; Kalender, W A; Lapp, R M

    2008-01-01

    Currently, CT scanning is often performed using flat detectors which are mounted on C-arm units or dedicated gantries as in radiation therapy or micro CT. For perspective cone-beam backprojection of the Feldkamp type (FDK) the geometry of an approximately circular scan trajectory has to be available for reconstruction. If the system or the scan geometry is afflicted with geometrical instabilities, referred to as misalignment, a non-perfect approximate circular scan is the case. Reconstructing a misaligned scan without knowledge of the true trajectory results in severe artefacts in the CT images. Unlike current methods which use a pre-scan calibration of the geometry for defined scan protocols and calibration phantoms, we propose a real-time iterative restoration of reconstruction geometry by means of entropy minimization. Entropy minimization is performed combining a simplex algorithm for multi-parameter optimization and iterative graphics card (GPU)-based FDK-reconstructions. Images reconstructed with the misaligned geometry were used as an input for the entropy minimization algorithm. A simplex algorithm changes the geometrical parameters of the source and detector with respect to the reduction of entropy. In order to reduce the size of the high-dimensional space required for minimization, the trajectory was described by only eight fix points. A virtual trajectory is generated for each iteration using a least-mean-squares algorithm to calculate an approximately circular path including these points. Entropy was minimal for the ideal dataset, whereas strong misalignment resulted in a higher entropy value. For the datasets used in this study, the simplex algorithm required 64-200 iterations to achieve an entropy value equivalent to the ideal dataset, depending on the grade of misalignment using random initialization conditions. The use of the GPU reduced the time per iteration as compared to a quad core CPU-based backprojection by a factor of 10 resulting in a total

  9. Patient-specific scatter correction in clinical cone beam computed tomography imaging made possible by the combination of Monte Carlo simulations and a ray tracing algorithm

    DEFF Research Database (Denmark)

    Slot Thing, Rune; Bernchou, Uffe; Mainegra-Hing, Ernesto

    2013-01-01

    Abstract Purpose. Cone beam computed tomography (CBCT) image quality is limited by scattered photons. Monte Carlo (MC) simulations provide the ability of predicting the patient-specific scatter contamination in clinical CBCT imaging. Lengthy simulations prevent MC-based scatter correction from...

  10. A simple, direct method for x-ray scatter estimation and correction in digital radiography and cone-beam CT

    International Nuclear Information System (INIS)

    Siewerdsen, J.H.; Daly, M.J.; Bakhtiar, B.

    2006-01-01

    X-ray scatter poses a significant limitation to image quality in cone-beam CT (CBCT), resulting in contrast reduction, image artifacts, and lack of CT number accuracy. We report the performance of a simple scatter correction method in which scatter fluence is estimated directly in each projection from pixel values near the edge of the detector behind the collimator leaves. The algorithm operates on the simple assumption that signal in the collimator shadow is attributable to x-ray scatter, and the 2D scatter fluence is estimated by interpolating between pixel values measured along the top and bottom edges of the detector behind the collimator leaves. The resulting scatter fluence estimate is subtracted from each projection to yield an estimate of the primary-only images for CBCT reconstruction. Performance was investigated in phantom experiments on an experimental CBCT benchtop, and the effect on image quality was demonstrated in patient images (head, abdomen, and pelvis sites) obtained on a preclinical system for CBCT-guided radiation therapy. The algorithm provides significant reduction in scatter artifacts without compromise in contrast-to-noise ratio (CNR). For example, in a head phantom, cupping artifact was essentially eliminated, CT number accuracy was restored to within 3%, and CNR (breast-to-water) was improved by up to 50%. Similarly in a body phantom, cupping artifact was reduced by at least a factor of 2 without loss in CNR. Patient images demonstrate significantly increased uniformity, accuracy, and contrast, with an overall improvement in image quality in all sites investigated. Qualitative evaluation illustrates that soft-tissue structures that are otherwise undetectable are clearly delineated in scatter-corrected reconstructions. Since scatter is estimated directly in each projection, the algorithm is robust with respect to system geometry, patient size and heterogeneity, patient motion, etc. Operating without prior information, analytical modeling

  11. Radiation hardening of diagnostics

    International Nuclear Information System (INIS)

    Siemon, R.E.

    1991-01-01

    The world fusion program has advanced to the stage where it is appropriate to construct a number of devices for the purpose of burning DT fuel. In these next-generation experiments, the expected flux and fluence of 14 MeV neutrons and associated gamma rays will pose a significant challenge to the operation and diagnostics of the fusion device. Radiation effects include structural damage to materials such as vacuum windows and seals, modifications to electrical properties such as electrical conductivity and dielectric strength and impaired optical properties such as reduced transparency and luminescence of windows and fiber optics during irradiation. In preparation for construction and operation of these new facilities, the fusion diagnostics community needs to work with materials scientists to develop a better understanding of radiation effects, and to undertake a testing program aimed at developing workable solutions for this multi-faceted problem. A unique facility to help in this regard is the Los Alamos Spallation Radiation Effects Facility, a neutron source located at the beam stop of the world's most powerful accelerator, the Los Alamos Meson Physics Facility (LAMPF). The LAMPF proton beam generates 10 16 neutrons per second because of ''spallation'' reactions when the protons collide with the copper nuclei in the beam stop

  12. WE-DE-207B-12: Scatter Correction for Dedicated Cone Beam Breast CT Based On a Forward Projection Model

    Energy Technology Data Exchange (ETDEWEB)

    Shi, L; Zhu, L [Georgia Institute of Technology, Atlanta, GA (Georgia); Vedantham, S; Karellas, A [University of Massachusetts Medical School, Worcester, MA (United States)

    2016-06-15

    Purpose: The image quality of dedicated cone-beam breast CT (CBBCT) is fundamentally limited by substantial x-ray scatter contamination, resulting in cupping artifacts and contrast-loss in reconstructed images. Such effects obscure the visibility of soft-tissue lesions and calcifications, which hinders breast cancer detection and diagnosis. In this work, we propose to suppress x-ray scatter in CBBCT images using a deterministic forward projection model. Method: We first use the 1st-pass FDK-reconstructed CBBCT images to segment fibroglandular and adipose tissue. Attenuation coefficients are assigned to the two tissues based on the x-ray spectrum used for imaging acquisition, and is forward projected to simulate scatter-free primary projections. We estimate the scatter by subtracting the simulated primary projection from the measured projection, and then the resultant scatter map is further refined by a Fourier-domain fitting algorithm after discarding untrusted scatter information. The final scatter estimate is subtracted from the measured projection for effective scatter correction. In our implementation, the proposed scatter correction takes 0.5 seconds for each projection. The method was evaluated using the overall image spatial non-uniformity (SNU) metric and the contrast-to-noise ratio (CNR) with 5 clinical datasets of BI-RADS 4/5 subjects. Results: For the 5 clinical datasets, our method reduced the SNU from 7.79% to 1.68% in coronal view and from 6.71% to 3.20% in sagittal view. The average CNR is improved by a factor of 1.38 in coronal view and 1.26 in sagittal view. Conclusion: The proposed scatter correction approach requires no additional scans or prior images and uses a deterministic model for efficient calculation. Evaluation with clinical datasets demonstrates the feasibility and stability of the method. These features are attractive for clinical CBBCT and make our method distinct from other approaches. Supported partly by NIH R21EB019597, R21CA134128

  13. A general framework and review of scatter correction methods in cone beam CT. Part 2: Scatter estimation approaches

    International Nuclear Information System (INIS)

    Ruehrnschopf and, Ernst-Peter; Klingenbeck, Klaus

    2011-01-01

    The main components of scatter correction procedures are scatter estimation and a scatter compensation algorithm. This paper completes a previous paper where a general framework for scatter compensation was presented under the prerequisite that a scatter estimation method is already available. In the current paper, the authors give a systematic review of the variety of scatter estimation approaches. Scatter estimation methods are based on measurements, mathematical-physical models, or combinations of both. For completeness they present an overview of measurement-based methods, but the main topic is the theoretically more demanding models, as analytical, Monte-Carlo, and hybrid models. Further classifications are 3D image-based and 2D projection-based approaches. The authors present a system-theoretic framework, which allows to proceed top-down from a general 3D formulation, by successive approximations, to efficient 2D approaches. A widely useful method is the beam-scatter-kernel superposition approach. Together with the review of standard methods, the authors discuss their limitations and how to take into account the issues of object dependency, spatial variance, deformation of scatter kernels, external and internal absorbers. Open questions for further investigations are indicated. Finally, the authors refer on some special issues and applications, such as bow-tie filter, offset detector, truncated data, and dual-source CT.

  14. Radiation-hardenable diluents for radiation-hardenable compositions

    International Nuclear Information System (INIS)

    Schuster, K.E.; Rosenkranz, H.J.; Furh, K.; Ruedolph, H.

    1979-01-01

    Radiation-crosslinkable diluents for radiation-hardenable compositions (binders) consisting of a mixture of triacrylates of a reaction product of trimethylol propane and ethylene oxide with an average degree of ethoxylation of from 2.5 to 4 are described. The ethoxylated trimethylol propane is substantially free from trimethylol propane and has the following distribution: 4 to 5% by weight of monoethoxylation product, 14 to 16% by weight of diethoxylation product, 20 to 30% by weight of triethoxylation product, 20 to 30% by weight of tetraethoxylation product, 16 to 18% by weight of pentaethoxylation product, and 6 to 8% by weight of hexaethoxylation product. The diluents effectively reduce the viscosity of radiation-hardenable compositions and do not have any adverse effect upon their reactivity or upon the properties of the resulting hardened products

  15. 4D cone-beam computed tomography (CBCT) using a moving blocker for simultaneous radiation dose reduction and scatter correction

    Science.gov (United States)

    Zhao, Cong; Zhong, Yuncheng; Duan, Xinhui; Zhang, You; Huang, Xiaokun; Wang, Jing; Jin, Mingwu

    2018-06-01

    Four-dimensional (4D) x-ray cone-beam computed tomography (CBCT) is important for a precise radiation therapy for lung cancer. Due to the repeated use and 4D acquisition over a course of radiotherapy, the radiation dose becomes a concern. Meanwhile, the scatter contamination in CBCT deteriorates image quality for treatment tasks. In this work, we propose the use of a moving blocker (MB) during the 4D CBCT acquisition (‘4D MB’) and to combine motion-compensated reconstruction to address these two issues simultaneously. In 4D MB CBCT, the moving blocker reduces the x-ray flux passing through the patient and collects the scatter information in the blocked region at the same time. The scatter signal is estimated from the blocked region for correction. Even though the number of projection views and projection data in each view are not complete for conventional reconstruction, 4D reconstruction with a total-variation (TV) constraint and a motion-compensated temporal constraint can utilize both spatial gradient sparsity and temporal correlations among different phases to overcome the missing data problem. The feasibility simulation studies using the 4D NCAT phantom showed that 4D MB with motion-compensated reconstruction with 1/3 imaging dose reduction could produce satisfactory images and achieve 37% improvement on structural similarity (SSIM) index and 55% improvement on root mean square error (RMSE), compared to 4D reconstruction at the regular imaging dose without scatter correction. For the same 4D MB data, 4D reconstruction outperformed 3D TV reconstruction by 28% on SSIM and 34% on RMSE. A study of synthetic patient data also demonstrated the potential of 4D MB to reduce the radiation dose by 1/3 without compromising the image quality. This work paves the way for more comprehensive studies to investigate the dose reduction limit offered by this novel 4D MB method using physical phantom experiments and real patient data based on clinical relevant metrics.

  16. Characterization of cross-section correction to charge exchange recombination spectroscopy rotation measurements using co- and counter-neutral-beam views.

    Science.gov (United States)

    Solomon, W M; Burrell, K H; Feder, R; Nagy, A; Gohil, P; Groebner, R J

    2008-10-01

    Measurements of rotation using charge exchange recombination spectroscopy can be affected by the energy dependence of the charge exchange cross section. On DIII-D, the associated correction to the rotation can exceed 100 kms at high temperatures. In reactor-relevant low rotation conditions, the correction can be several times larger than the actual plasma rotation and therefore must be carefully validated. New chords have been added to the DIII-D CER diagnostic to view the counter-neutral-beam line. The addition of these views allows determination of the toroidal rotation without depending on detailed atomic physics calculations, while also allowing experimental characterization of the atomic physics. A database of rotation comparisons from the two views shows that the calculated cross-section correction can adequately describe the measurements, although there is a tendency for "overcorrection." In cases where accuracy better than about 15% is desired, relying on calculation of the cross-section correction may be insufficient.

  17. On-line correction of beam portals in the treatment of prostate cancer using an endorectal balloon device

    International Nuclear Information System (INIS)

    Ciernik, Ilja F.; Baumert, Brigitta G.; Egli, Peter; Glanzmann, Christoph; Luetolf, Urs M.

    2002-01-01

    Background: Reproducible target volume assessment is required in order to optimize portal field margins in the treatment of prostate cancer. The benefits of an endorectal balloon on target volume assessment remain unclear. Material and methods: Nine patients were treated with a daily placed air filled rectal balloon. Portal films and computer-associated tomography during the treatment were used to determine the position of the structures of interest. Comparative planning with or without a balloon was performed in order to determine rectal wall exposure to radiation. Results: The range of movements during treatment predicting the position of the prostate in relation to the symphysis was 0.05-0.59 cm in the lateral direction, 0.27-2.2 cm in the antero-posterior direction, and 0.33-1.8 cm in the crano-caudal direction, as compared to the position of the prostate predicted by the balloon ranging from 0.18 to 0.76 cm in the lateral direction, 0.22-1.68 cm in the antero-posterior direction, and 0.58-2.99 cm in the crano-caudal direction. Planning target volumes (PTV) margins as defined by the position of the balloon were 10 mm in the antero-posterior direction, 6 mm in the lateral direction, and 16 mm in the crano-caudal direction. The volume of rectal wall exposed to radiation was reduced from 40 (±12%) to 25% (±19%) with an endorectal balloon (P<0.05). Conclusions: Daily online correction with portal vision for external beam set-up is improved by an endorectal balloon device, leading to improved PTV margins and reduced radiation exposure of the rectal wall

  18. Electron beam-cured coating

    International Nuclear Information System (INIS)

    Kishi, Naoyuki

    1976-01-01

    The method for hardening coatings by the irradiation with electron beams is reviewed. The report is divided into seven parts, namely 1) general description and characteristics of electron beam-cured coating, 2) radiation sources of curing, 3) hardening conditions and reaction behaviour, 4) uses and advantages, 5) latest trends of the industry, 6) practice in the field of construction materials, and 7) economy. The primary characteristics of the electron beam hardening is that graft reaction takes place between base resin and coating to produce strong adhesive coating without any pretreatment. A variety of base resins are developed. High class esters of acrylic acid monomers and methacrylic acid monomers are mainly used as dilutants recently. At present, scanning type accelerators are used, but the practical application of the system producing electron beam of curtain type is expected. The dose rate dependence, the repetitive irradiation and the irradiation atmosphere are briefly described. The filed patent applications on the electron beam hardening were analyzed by the officer of Japan Patent Agency. The production lines for coatings by the electron beam hardening in the world are listed. In the electron beam-cured coating, fifty percent of given energy is consumed effectively for the electron beam hardening, and the solvents discharged from ovens and polluting atmosphere are not used, because the paints of high solid type is used. The running costs of the electron beam process are one sixth of the thermal oven process. (Iwakiri, K.)

  19. A method for simultaneous linear optics and coupling correction for storage rings with turn-by-turn beam position monitor data

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xi [Brookhaven National Laboratory, Upton, Long Island, NY 11973 (United States); Huang, Xiaobiao, E-mail: xiahuang@slac.stanford.edu [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

    2016-08-21

    We propose a method to simultaneously correct linear optics errors and linear coupling for storage rings using turn-by-turn (TbT) beam position monitor (BPM) data. The independent component analysis (ICA) method is used to isolate the betatron normal modes from the measured TbT BPM data. The betatron amplitudes and phase advances of the projections of the normal modes on the horizontal and vertical planes are then extracted, which, combined with dispersion measurement, are used to fit the lattice model. The fitting results are used for lattice correction. The method has been successfully demonstrated on the NSLS-II storage ring.

  20. A method for simultaneous linear optics and coupling correction for storage rings with turn-by-turn beam position monitor data

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xi [Brookhaven National Lab. (BNL), Upton, NY (United States); Huang, Xiaobiao [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2016-08-01

    We propose a method to simultaneously correct linear optics errors and linear coupling for storage rings using turn-by-turn (TbT) beam position monitor (BPM) data. The independent component analysis (ICA) method is used to isolate the betatron normal modes from the measured TbT BPM data. The betatron amplitudes and phase advances of the projections of the normal modes on the horizontal and vertical planes are then extracted, which, combined with dispersion measurement, are used to fit the lattice model. Furthermore, the fitting results are used for lattice correction. Our method has been successfully demonstrated on the NSLS-II storage ring.

  1. Binary moving-blocker-based scatter correction in cone-beam computed tomography with width-truncated projections: proof of concept

    Science.gov (United States)

    Lee, Ho; Fahimian, Benjamin P.; Xing, Lei

    2017-03-01

    This paper proposes a binary moving-blocker (BMB)-based technique for scatter correction in cone-beam computed tomography (CBCT). In concept, a beam blocker consisting of lead strips, mounted in front of the x-ray tube, moves rapidly in and out of the beam during a single gantry rotation. The projections are acquired in alternating phases of blocked and unblocked cone beams, where the blocked phase results in a stripe pattern in the width direction. To derive the scatter map from the blocked projections, 1D B-Spline interpolation/extrapolation is applied by using the detected information in the shaded regions. The scatter map of the unblocked projections is corrected by averaging two scatter maps that correspond to their adjacent blocked projections. The scatter-corrected projections are obtained by subtracting the corresponding scatter maps from the projection data and are utilized to generate the CBCT image by a compressed-sensing (CS)-based iterative reconstruction algorithm. Catphan504 and pelvis phantoms were used to evaluate the method’s performance. The proposed BMB-based technique provided an effective method to enhance the image quality by suppressing scatter-induced artifacts, such as ring artifacts around the bowtie area. Compared to CBCT without a blocker, the spatial nonuniformity was reduced from 9.1% to 3.1%. The root-mean-square error of the CT numbers in the regions of interest (ROIs) was reduced from 30.2 HU to 3.8 HU. In addition to high resolution, comparable to that of the benchmark image, the CS-based reconstruction also led to a better contrast-to-noise ratio in seven ROIs. The proposed technique enables complete scatter-corrected CBCT imaging with width-truncated projections and allows reducing the acquisition time to approximately half. This work may have significant implications for image-guided or adaptive radiation therapy, where CBCT is often used.

  2. Method for surface treatment by electron beams

    International Nuclear Information System (INIS)

    Panzer, S.; Doehler, H.; Bartel, R.; Ardenne, T. von.

    1985-01-01

    The invention has been aimed at simplifying the technology and saving energy in modifying surfaces with the aid of electron beams. The described beam-object geometry allows to abandon additional heat treatments. It can be used for surface hardening

  3. Working hardening modelization in zirconium alloys

    International Nuclear Information System (INIS)

    Sanchez, P.; Pochettino, Alberto A.

    1999-01-01

    Working hardening effects on mechanical properties and crystallographic textures formation in Zr-based alloys are studied. The hardening mechanisms for different grain deformations and topological conditions of simple crystal yield are considered. Results obtained show that the differences in the cold rolling textures (L and T textures) can be related with hardening microstructural parameters. (author)

  4. Kinematic Hardening: Characterization, Modeling and Impact on Springback Prediction

    International Nuclear Information System (INIS)

    Alves, J. L.; Bouvier, S.; Jomaa, M.; Billardon, R.; Oliveira, M. C.; Menezes, L. F.

    2007-01-01

    The constitutive modeling of the materials' mechanical behavior, usually carried out using a phenomenological constitutive model, i.e., a yield criterion associated to the isotropic and kinematic hardening laws, is of paramount importance in the FEM simulation of the sheet metal forming processes, as well as in the springback prediction. Among others, the kinematic behavior of the yield surface plays an essential role, since it is indispensable to describe the Bauschinger effect, i.e., the materials' answer to the multiple tension-compression cycles to which material points are submitted during the forming process. Several laws are usually used to model and describe the kinematic hardening, namely: a) the Prager's law, which describes a linear evolution of the kinematic hardening with the plastic strain rate tensor b) the Frederick-Armstrong non-linear kinematic hardening, basically a non-linear law with saturation; and c) a more advanced physically-based law, similar to the previous one but sensitive to the strain path changes. In the present paper a mixed kinematic hardening law (linear + non-linear behavior) is proposed and its implementation into a static fully-implicit FE code is described. The material parameters identification for sheet metals using different strategies, and the classical Bauschinger loading tests (i.e. in-plane forward and reverse monotonic loading), are addressed, and their impact on springback prediction evaluated. Some numerical results concerning the springback prediction of the Numisheet'05 Benchmark no. 3 are briefly presented to emphasize the importance of a correct modeling and identification of the kinematic hardening behavior

  5. A study of respiration-correlated cone-beam CT scans to correct target positioning errors in radiotherapy of thoracic cancer

    Energy Technology Data Exchange (ETDEWEB)

    Santoro, J. P.; McNamara, J.; Yorke, E.; Pham, H.; Rimner, A.; Rosenzweig, K. E.; Mageras, G. S. [Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York 10065 (United States); Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York 10065 (United States); Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York 10065 (United States)

    2012-10-15

    Purpose: There is increasingly widespread usage of cone-beam CT (CBCT) for guiding radiation treatment in advanced-stage lung tumors, but difficulties associated with daily CBCT in conventionally fractionated treatments include imaging dose to the patient, increased workload and longer treatment times. Respiration-correlated cone-beam CT (RC-CBCT) can improve localization accuracy in mobile lung tumors, but further increases the time and workload for conventionally fractionated treatments. This study investigates whether RC-CBCT-guided correction of systematic tumor deviations in standard fractionated lung tumor radiation treatments is more effective than 2D image-based correction of skeletal deviations alone. A second study goal compares respiration-correlated vs respiration-averaged images for determining tumor deviations. Methods: Eleven stage II-IV nonsmall cell lung cancer patients are enrolled in an IRB-approved prospective off-line protocol using RC-CBCT guidance to correct for systematic errors in GTV position. Patients receive a respiration-correlated planning CT (RCCT) at simulation, daily kilovoltage RC-CBCT scans during the first week of treatment and weekly scans thereafter. Four types of correction methods are compared: (1) systematic error in gross tumor volume (GTV) position, (2) systematic error in skeletal anatomy, (3) daily skeletal corrections, and (4) weekly skeletal corrections. The comparison is in terms of weighted average of the residual GTV deviations measured from the RC-CBCT scans and representing the estimated residual deviation over the treatment course. In the second study goal, GTV deviations computed from matching RCCT and RC-CBCT are compared to deviations computed from matching respiration-averaged images consisting of a CBCT reconstructed using all projections and an average-intensity-projection CT computed from the RCCT. Results: Of the eleven patients in the GTV-based systematic correction protocol, two required no correction

  6. A study of respiration-correlated cone-beam CT scans to correct target positioning errors in radiotherapy of thoracic cancer

    International Nuclear Information System (INIS)

    Santoro, J. P.; McNamara, J.; Yorke, E.; Pham, H.; Rimner, A.; Rosenzweig, K. E.; Mageras, G. S.

    2012-01-01

    Purpose: There is increasingly widespread usage of cone-beam CT (CBCT) for guiding radiation treatment in advanced-stage lung tumors, but difficulties associated with daily CBCT in conventionally fractionated treatments include imaging dose to the patient, increased workload and longer treatment times. Respiration-correlated cone-beam CT (RC-CBCT) can improve localization accuracy in mobile lung tumors, but further increases the time and workload for conventionally fractionated treatments. This study investigates whether RC-CBCT-guided correction of systematic tumor deviations in standard fractionated lung tumor radiation treatments is more effective than 2D image-based correction of skeletal deviations alone. A second study goal compares respiration-correlated vs respiration-averaged images for determining tumor deviations. Methods: Eleven stage II–IV nonsmall cell lung cancer patients are enrolled in an IRB-approved prospective off-line protocol using RC-CBCT guidance to correct for systematic errors in GTV position. Patients receive a respiration-correlated planning CT (RCCT) at simulation, daily kilovoltage RC-CBCT scans during the first week of treatment and weekly scans thereafter. Four types of correction methods are compared: (1) systematic error in gross tumor volume (GTV) position, (2) systematic error in skeletal anatomy, (3) daily skeletal corrections, and (4) weekly skeletal corrections. The comparison is in terms of weighted average of the residual GTV deviations measured from the RC-CBCT scans and representing the estimated residual deviation over the treatment course. In the second study goal, GTV deviations computed from matching RCCT and RC-CBCT are compared to deviations computed from matching respiration-averaged images consisting of a CBCT reconstructed using all projections and an average-intensity-projection CT computed from the RCCT. Results: Of the eleven patients in the GTV-based systematic correction protocol, two required no correction

  7. Solution hardening and strain hardening at elevated temperatures

    International Nuclear Information System (INIS)

    Kocks, U.F.

    1982-10-01

    Solutes can significantly increase the rate of strain hardening; as a consequence, the saturation stress, at which strain hardening tends to cease for a given temperature and strain rate, is increased more than the yield stress: this is the major effect of solutes on strength at elevated temperatures, especially in the regime where dynamic strain-aging occurs. It is shown that local solute mobility can affect both the rate of dynamic recovery and the dislocation/dislocation interaction strength. The latter effect leads to multiplicative solution strengthening. It is explained by a new model based on repeated dislocation unlocking, in a high-temperature limit, which also rationalizes the stress dependence of static and dynamic strain-aging, and may help explain the plateau of the yield stress at elevated temperatures. 15 figures

  8. SU-F-I-03: Correction of Intra-Fractional Set-Up Errors and Target Coverage Based On Cone-Beam Computed Tomography for Cervical Cancer Patients

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, JY [Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China); Hong, DL [The First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong (China)

    2016-06-15

    Purpose: The purpose of this study is to investigate the patient set-up error and interfraction target coverage in cervical cancer using image-guided adaptive radiotherapy (IGART) with cone-beam computed tomography (CBCT). Methods: Twenty cervical cancer patients undergoing intensity modulated radiotherapy (IMRT) were randomly selected. All patients were matched to the isocenter using laser with the skin markers. Three dimensional CBCT projections were acquired by the Varian Truebeam treatment system. Set-up errors were evaluated by radiation oncologists, after CBCT correction. The clinical target volume (CTV) was delineated on each CBCT, and the planning target volume (PTV) coverage of each CBCT-CTVs was analyzed. Results: A total of 152 CBCT scans were acquired from twenty cervical cancer patients, the mean set-up errors in the longitudinal, vertical, and lateral direction were 3.57, 2.74 and 2.5mm respectively, without CBCT corrections. After corrections, these were decreased to 1.83, 1.44 and 0.97mm. For the target coverage, CBCT-CTV coverage without CBCT correction was 94% (143/152), and 98% (149/152) with correction. Conclusion: Use of CBCT verfication to measure patient setup errors could be applied to improve the treatment accuracy. In addition, the set-up error corrections significantly improve the CTV coverage for cervical cancer patients.

  9. Monte Carlo computed machine-specific correction factors for reference dosimetry of TomoTherapy static beam for several ion chambers

    International Nuclear Information System (INIS)

    Sterpin, E.; Mackie, T. R.; Vynckier, S.

    2012-01-01

    Purpose: To determine k Q msr ,Q o f msr ,f o correction factors for machine-specific reference (msr) conditions by Monte Carlo (MC) simulations for reference dosimetry of TomoTherapy static beams for ion chambers Exradin A1SL, A12; PTW 30006, 31010 Semiflex, 31014 PinPoint, 31018 microLion; NE 2571. Methods: For the calibration of TomoTherapy units, reference conditions specified in current codes of practice like IAEA/TRS-398 and AAPM/TG-51 cannot be realized. To cope with this issue, Alfonso et al. [Med. Phys. 35, 5179–5186 (2008)] described a new formalism introducing msr factors k Q msr ,Q o f msr ,f o for reference dosimetry, applicable to static TomoTherapy beams. In this study, those factors were computed directly using MC simulations for Q 0 corresponding to a simplified 60 Co beam in TRS-398 reference conditions (at 10 cm depth). The msr conditions were a 10 × 5 cm 2 TomoTherapy beam, source-surface distance of 85 cm and 10 cm depth. The chambers were modeled according to technical drawings using the egs++ package and the MC simulations were run with the egs c hamber user code. Phase-space files used as the source input were produced using PENELOPE after simulation of a simplified 60 Co beam and the TomoTherapy treatment head modeled according to technical drawings. Correlated sampling, intermediate phase-space storage, and photon cross-section enhancement variance reduction techniques were used. The simulations were stopped when the combined standard uncertainty was below 0.2%. Results: Computed k Q msr ,Q o f msr ,f o values were all close to one, in a range from 0.991 for the PinPoint chamber to 1.000 for the Exradin A12 with a statistical uncertainty below 0.2%. Considering a beam quality Q defined as the TPR 20,10 for a 6 MV Elekta photon beam (0.661), the additional correction k Q msr, Q f msr, f ref to k Q,Q o defined in Alfonso et al. [Med. Phys. 35, 5179–5186 (2008)] formalism was in a range from 0.997 to 1.004.Conclusion: The MC computed

  10. Radiation-hardened bulk CMOS technology

    International Nuclear Information System (INIS)

    Dawes, W.R. Jr.; Habing, D.H.

    1979-01-01

    The evolutionary development of a radiation-hardened bulk CMOS technology is reviewed. The metal gate hardened CMOS status is summarized, including both radiation and reliability data. The development of a radiation-hardened bulk silicon gate process which was successfully implemented to a commercial microprocessor family and applied to a new, radiation-hardened, LSI standard cell family is also discussed. The cell family is reviewed and preliminary characterization data is presented. Finally, a brief comparison of the various radiation-hardened technologies with regard to performance, reliability, and availability is made

  11. Superheat effect on bainite steel hardenability

    International Nuclear Information System (INIS)

    Kubachek, V.V.; Sklyuev, P.V.

    1978-01-01

    The bainite hardenability of 34KhN1M and 35 KhN1M2Ph steels has been investigated by the end-face hardening technique. It is established that, as the temperature of austenitization rises from 900 to 1280 deg C, the temperature of bainite transformation increases and bainite hardenability of the steels falls off. A repeated slow heating to 900 deg C of previously overheated 34KhN1M steel breaks up grain, lowers the temperature of the bainite transformation and raises the hardenability to values obtained with ordinary hardening from 900 deg C. A similar heating of previously overheated 35KhN1M2Ph steel is accompanied by restoration of initial coarse grains and maintenance of both the elevated bainite transformation temperature and to lower hardenability corresponding to hardening from the temperature of previous overheating

  12. A non-linear kinematic hardening function

    International Nuclear Information System (INIS)

    Ottosen, N.S.

    1977-05-01

    Based on the classical theory of plasticity, and accepting the von Mises criterion as the initial yield criterion, a non-linear kinematic hardening function applicable both to Melan-Prager's and to Ziegler's hardening rule is proposed. This non-linear hardening function is determined by means of the uniaxial stress-strain curve, and any such curve is applicable. The proposed hardening function considers the problem of general reversed loading, and a smooth change in the behaviour from one plastic state to another nearlying plastic state is obtained. A review of both the kinematic hardening theory and the corresponding non-linear hardening assumptions is given, and it is shown that material behaviour is identical whether Melan-Prager's or Ziegler's hardening rule is applied, provided that the von Mises yield criterion is adopted. (author)

  13. Radiation hardening of semiconductor parts

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    This chapter is an overview of total-ionizing-dose and single-event hardening techniques and should be used as a guide to a range of research publications. It should be stressed that there is no clear and simple route to a radiation-tolerant silicon integrated circuit. What works for one fabrication process may not work for another, and there are many complex interactions within individual processes and designs. The authors have attempted to highlight the most important factors and those process changes which should bring improved hardness. The main point is that radiation-hardening as a procedure must be approached in a methodical fashion and with a good understanding of the response mechanisms involved

  14. Scintillation-Hardened GPS Receiver

    Science.gov (United States)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  15. Radiation-hardened control system

    International Nuclear Information System (INIS)

    Vandermolen, R.I.; Smith, S.F.; Emery, M.S.

    1993-01-01

    A radiation-hardened bit-slice control system with associated input/output circuits was developed to prove that programmable circuits could be constructed to successfully implement intelligent functions in a highly radioactive environment. The goal for this effort was to design and test a programmable control system that could withstand a minimum total dose of 10 7 rads (gamma). The Radiation Hardened Control System (RHCS) was tested in operation at a dose rate that ranged up to 135 krad/h, with an average total dose of 10.75 Mrads. Further testing beyond the required 10 7 rads was also conducted. RHCS performed properly through the target dose of 10 7 rads, and sporadic intermittent failures in some programmable logic devices were noted after ∼ 13 Mrads

  16. Energetic model of metal hardening

    Directory of Open Access Journals (Sweden)

    Ignatova O.N.

    2011-01-01

    Full Text Available Based on Bailey hypothesis on the link between strain hardening and elastic lattice defect energy this paper suggests a shear strength energetic model that takes into consideration plastic strain intensity and rate as well as softening related to temperature annealing and dislocation annihilation. Metal strain hardening was demonstrated to be determined only by elastic strain energy related to the energy of accumulated defects. It is anticipated that accumulation of the elastic energy of defects is governed by plastic work. The suggested model has a reasonable agreement with the available experimental data for copper up to P = 70 GPa , for aluminum up to P = 10 GPa and for tantalum up to P = 20 GPa.

  17. The assessment of four different correction models applied to the diffuse radiation measured with a shadow ring using global and normal beam radiation measurements for Beer Sheva, Israel

    Energy Technology Data Exchange (ETDEWEB)

    Kudish, Avraham I.; Evseev, Efim G. [Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, E D Bergmann Campus, Beer Sheva 84105 (Israel)

    2008-02-15

    The measurement of the diffuse radiation incident on a horizontal surface, a priori a straightforward task, is fraught with difficulties. It is possible to measure the diffuse radiation by three different techniques: two of which measure it directly and the third indirectly. The most accurate is the indirect one, which is based upon the concurrent measurements of the horizontal global and the normal incidence beam radiation. The disadvantage of this being the relatively expensive tracking system required for measuring the latter. The diffuse radiation can be measured directly with a pyranometer outfitted with either an occulting disk or shadow ring, which prevent the beam radiation from impinging on the pyranometer sensor. The occulting disk can provide accurate measurements of the diffuse radiation but it requires a relatively expensive sun tracking system in the east-west axis. The shadow ring is a stationary device with regard to the east-west axis and blocks the beam radiation component by creating a permanent shadow on the pyranometer sensor. The major disadvantage of the shadow ring is that it also blocks that portion of the diffuse radiation obscured by the shadow ring. This introduces a measurement error that must be corrected to account for that portion of the sky obscured by the shadow band. In addition to this geometric correction factor there is a need to correct for anisotropic sky conditions. Four correction models have been applied to the data for Beer Sheva, Israel and the results have been evaluated both graphically and statistically. An attempt has been made to score the relative performance of the models under different sky conditions. (author)

  18. Correction of CT artifacts and its influence on Monte Carlo dose calculations

    International Nuclear Information System (INIS)

    Bazalova, Magdalena; Beaulieu, Luc; Palefsky, Steven; Verhaegen, Frank

    2007-01-01

    Computed tomography (CT) images of patients having metallic implants or dental fillings exhibit severe streaking artifacts. These artifacts may disallow tumor and organ delineation and compromise dose calculation outcomes in radiotherapy. We used a sinogram interpolation metal streaking artifact correction algorithm on several phantoms of exact-known compositions and on a prostate patient with two hip prostheses. We compared original CT images and artifact-corrected images of both. To evaluate the effect of the artifact correction on dose calculations, we performed Monte Carlo dose calculation in the EGSnrc/DOSXYZnrc code. For the phantoms, we performed calculations in the exact geometry, in the original CT geometry and in the artifact-corrected geometry for photon and electron beams. The maximum errors in 6 MV photon beam dose calculation were found to exceed 25% in original CT images when the standard DOSXYZnrc/CTCREATE calibration is used but less than 2% in artifact-corrected images when an extended calibration is used. The extended calibration includes an extra calibration point for a metal. The patient dose volume histograms of a hypothetical target irradiated by five 18 MV photon beams in a hypothetical treatment differ significantly in the original CT geometry and in the artifact-corrected geometry. This was found to be mostly due to miss-assignment of tissue voxels to air due to metal artifacts. We also developed a simple Monte Carlo model for a CT scanner and we simulated the contribution of scatter and beam hardening to metal streaking artifacts. We found that whereas beam hardening has a minor effect on metal artifacts, scatter is an important cause of these artifacts

  19. A novel method and error analysis for beam optics measurements and corrections at the Large Hadron Collider

    Energy Technology Data Exchange (ETDEWEB)

    Langner, Andy Sven

    2017-02-03

    The Large Hadron Collider (LHC) is currently the world's largest particle accelerator with the highest center of mass energy in particle collision experiments. The control of the particle beam focusing is essential for the performance reach of such an accelerator. For the characterization of the focusing properties at the LHC, turn-by-turn beam position data is simultaneously recorded at numerous measurement devices (BPMs) along the accelerator, while an oscillation is excited on the beam. A novel analysis method for these measurements (N-BPM method) is developed here, which is based on a detailed analysis of systematic and statistical error sources and their correlations. It has been applied during the commissioning of the LHC for operation at an unprecedented energy of 6.5TeV. In this process a stronger focusing than its design specifications has been achieved. This results in smaller transverse beam sizes at the collision points and allows for a higher rate of particle collisions. For the derivation of the focusing parameters at many synchrotron light sources, the change of the beam orbit is observed, which is induced by deliberate changes of magnetic fields (orbit response matrix). In contrast, the analysis of turn-by-turn beam position measurements is for many of these machines less precise due to the distance between two BPMs. The N-BPM method overcomes this limitation by allowing to include the measurement data from more BPMs in the analysis. It has been applied at the ALBA synchrotron light source and compared to the orbit response method. The significantly faster measurement with the N-BPM method is a considerable advantage in this case. Finally, an outlook is given to the challenges which lie ahead for the control of the beam focusing at the HL-LHC, which is a future major upgrade of the LHC.

  20. Adaptation of penelope Monte Carlo code system to the absorbed dose metrology: characterization of high energy photon beams and calculations of reference dosimeter correction factors

    International Nuclear Information System (INIS)

    Mazurier, J.

    1999-01-01

    This thesis has been performed in the framework of national reference setting-up for absorbed dose in water and high energy photon beam provided with the SATURNE-43 medical accelerator of the BNM-LPRI (acronym for National Bureau of Metrology and Primary standard laboratory of ionising radiation). The aim of this work has been to develop and validate different user codes, based on PENELOPE Monte Carlo code system, to determine the photon beam characteristics and calculate the correction factors of reference dosimeters such as Fricke dosimeters and graphite calorimeter. In the first step, the developed user codes have permitted the influence study of different components constituting the irradiation head. Variance reduction techniques have been used to reduce the calculation time. The phase space has been calculated for 6, 12 and 25 MV at the output surface level of the accelerator head, then used for calculating energy spectra and dose distributions in the reference water phantom. Results obtained have been compared with experimental measurements. The second step has been devoted to develop an user code allowing calculation correction factors associated with both BNM-LPRI's graphite and Fricke dosimeters thanks to a correlated sampling method starting with energy spectra obtained in the first step. Then the calculated correction factors have been compared with experimental and calculated results obtained with the Monte Carlo EGS4 code system. The good agreement, between experimental and calculated results, leads to validate simulations performed with the PENELOPE code system. (author)

  1. Combined dose and geometry correction (DMG) for low energy multi electron beam lithography (5kV): application to the 16nm node

    Science.gov (United States)

    Martin, Luc; Manakli, Serdar; Bayle, Sebastien; Belledent, Jérôme; Soulan, Sebastien; Wiedemann, Pablo; Farah, Abdi; Schiavone, Patrick

    2012-03-01

    Lithography faces today many challenges to meet the ITRS road-map. 193nm is still today the only existing industrial option to address high volume production for the 22nm node. Nevertheless to achieve such a resolution, double exposure is mandatory for critical level patterning. EUV lithography is still challenged by the availability of high power source and mask defectivity and suffers from a high cost of ownership perspective. Its introduction is now not foreseen before 2015. Parallel to these mask-based technologies, maskless lithography regularly makes significant progress in terms of potential and maturity. The massively parallel e-beam solution appears as a real candidate for high volume manufacturing. Several industrial projects are under development, one in the US, with the KLA REBL project and two in Europe driven by IMS Nanofabrication (Austria; MAPPER (The Netherlands). Among the developments to be performed to secure the takeoff of the multi-beam technology, the availability of a rapid and robust data treatment solution will be one of the major challenges. Within this data preparation flow, advanced proximity effect corrections must be implemented to address the 16nm node and below. This paper will detail this process and compare correction strategies in terms of robustness and accuracy. It will be based on results obtained using a MAPPER tool within the IMAGINE program driven by CEA-LETI, in Grenoble, France. All proximity effects corrections and the dithering step were performed using the software platform Inscale® from Aselta Nanographics. One important advantage of Inscale® is the ability to combine both model based dose and geometry adjustment to accurately pattern critical features. The paper will focus on the advantage of combining those two corrections at the 16nm node instead of using only geometry corrections. Thanks to the simulation capability of Inscale®, pattern fidelity and correction robustness will be evaluated and compared between

  2. WE-AB-207A-08: BEST IN PHYSICS (IMAGING): Advanced Scatter Correction and Iterative Reconstruction for Improved Cone-Beam CT Imaging On the TrueBeam Radiotherapy Machine

    Energy Technology Data Exchange (ETDEWEB)

    Wang, A; Paysan, P; Brehm, M; Maslowski, A; Lehmann, M; Messmer, P; Munro, P; Yoon, S; Star-Lack, J; Seghers, D [Varian Medical Systems, Palo Alto, CA (United States)

    2016-06-15

    Purpose: To improve CBCT image quality for image-guided radiotherapy by applying advanced reconstruction algorithms to overcome scatter, noise, and artifact limitations Methods: CBCT is used extensively for patient setup in radiotherapy. However, image quality generally falls short of diagnostic CT, limiting soft-tissue based positioning and potential applications such as adaptive radiotherapy. The conventional TrueBeam CBCT reconstructor uses a basic scatter correction and FDK reconstruction, resulting in residual scatter artifacts, suboptimal image noise characteristics, and other artifacts like cone-beam artifacts. We have developed an advanced scatter correction that uses a finite-element solver (AcurosCTS) to model the behavior of photons as they pass (and scatter) through the object. Furthermore, iterative reconstruction is applied to the scatter-corrected projections, enforcing data consistency with statistical weighting and applying an edge-preserving image regularizer to reduce image noise. The combined algorithms have been implemented on a GPU. CBCT projections from clinically operating TrueBeam systems have been used to compare image quality between the conventional and improved reconstruction methods. Planning CT images of the same patients have also been compared. Results: The advanced scatter correction removes shading and inhomogeneity artifacts, reducing the scatter artifact from 99.5 HU to 13.7 HU in a typical pelvis case. Iterative reconstruction provides further benefit by reducing image noise and eliminating streak artifacts, thereby improving soft-tissue visualization. In a clinical head and pelvis CBCT, the noise was reduced by 43% and 48%, respectively, with no change in spatial resolution (assessed visually). Additional benefits include reduction of cone-beam artifacts and reduction of metal artifacts due to intrinsic downweighting of corrupted rays. Conclusion: The combination of an advanced scatter correction with iterative reconstruction

  3. Barkas effect, shell correction, screening and correlation in collisional energy-loss straggling of an ion beam

    CERN Document Server

    Sigmund, P

    2003-01-01

    Collisional electronic energy-loss straggling has been treated theoretically on the basis of the binary theory of electronic stopping. In view of the absence of a Bloch correction in straggling the range of validity of the theory includes both the classical and the Born regime. The theory incorporates Barkas effect and projectile screening. Shell correction and electron bunching are added on. In the absence of shell corrections the Barkas effect has a dominating influence on straggling, but much of this is wiped out when the shell correction is included. Weak projectile screening tends to noticeably reduce collisional straggling. Sizable bunching effects are found in particular for heavy ions. Comparisons are made with selected results of the experimental and theoretical literature. (authors)

  4. Radiography method mprising determination of corrected absorption values for members of sets of mutually inclined beam paths

    International Nuclear Information System (INIS)

    McLeMay, C.A.G.

    1978-01-01

    An x-ray apparatus is described for examining a body including a source of a fan of radiation and detectors of the radiation along beams in the fan are transversed in a plane to provide data for a number of sets of parallel beams in the plane. An orbital motion is provided to give data for further sets at different inclinations in the plane. The data can be processed by arrangements using such parallel sets. The orbital motion is continuous but the extent of angular change in one lateral scan is kept small so that lack of parallelism in the parallel sets does not give excessive errors

  5. A study of the dosimetry of small field photon beams used in intensity modulated radiation therapy in inhomogeneous media: Monte Carlo simulations, and algorithm comparisons and corrections

    International Nuclear Information System (INIS)

    Jones, Andrew Osler

    2004-01-01

    There is an increasing interest in the use of inhomogeneity corrections for lung, air, and bone in radiotherapy treatment planning. Traditionally, corrections based on physical density have been used. Modern algorithms use the electron density derived from CT images. Small fields are used in both conformal radiotherapy and IMRT, however, their beam characteristics in inhomogeneous media have not been extensively studied. This work compares traditional and modern treatment planning algorithms to Monte Carlo simulations in and near low-density inhomogeneities. Field sizes ranging from 0.5 cm to 5 cm in diameter are projected onto a phantom containing inhomogeneities and depth dose curves are compared. Comparisons of the Dose Perturbation Factors (DPF) are presented as functions of density and field size. Dose Correction Factors (DCF), which scale the algorithms to the Monte Carlo data, are compared for each algorithm. Physical scaling algorithms such as Batho and Equivalent Pathlength (EPL) predict an increase in dose for small fields passing through lung tissue, where Monte Carlo simulations show a sharp dose drop. The physical model-based collapsed cone convolution (CCC) algorithm correctly predicts the dose drop, but does not accurately predict the magnitude. Because the model-based algorithms do not correctly account for the change in backscatter, the dose drop predicted by CCC occurs farther downstream compared to that predicted by the Monte Carlo simulations. Beyond the tissue inhomogeneity all of the algorithms studied predict dose distributions in close agreement with Monte Carlo simulations. Dose-volume relationships are important in understanding the effects of radiation to the lung. The dose within the lung is affected by a complex function of beam energy, lung tissue density, and field size. Dose algorithms vary in their abilities to correctly predict the dose to the lung tissue. A thorough analysis of the effects of density, and field size on dose to the

  6. Process controls for radiation hardened aluminum gate bulk silicon CMOS

    International Nuclear Information System (INIS)

    Gregory, B.L.

    1975-01-01

    Optimized dry oxides have recently yielded notable improvements in CMOS radiation-hardness. By following the proper procedures and recipes, it is now possible to produce devices which will function satisfactorily after exposure to a total ionizing dose in excess of 10 6 RADS (Si). This paper is concerned with the controls required on processing parameters once the optimized process is defined. In this process, the pre-irradiation electrical parameters must be closely controlled to insure that devices will function after irradiation. In particular, the specifications on n- and p-channel threshold voltages require tight control of fixed oxide charge, surface-state density, oxide thickness, and substrate and p-well surface concentrations. In order to achieve the above level of radiation hardness, certain processing procedures and parameters must also be closely controlled. Higher levels of cleanliness are required in the hardened process than are commonly required for commercial CMOS since, for hardened dry oxides, no impurity gettering can be employed during or after oxidation. Without such gettering, an unclean oxide is unacceptable due to bias-temperature instability. Correct pre-oxidation cleaning, residual surface damage removal, proper oxidation and annealing temperatures and times, and the correct metal sintering cycle are all important in determining device hardness. In a reproducible, hardened process, each of these processing steps must be closely controlled. (U.S.)

  7. A Novel Method and Error Analysis for Beam Optics Measurements and Corrections at the Large Hadron Collider

    CERN Document Server

    Langner, Andy Sven; Rossbach, Jörg; Tomás, Rogelio

    2017-02-17

    The Large Hadron Collider (LHC) is currently the world's largest particle accelerator with the highest center of mass energy in particle collision experiments. The control of the particle beam focusing is essential for the performance reach of such an accelerator. For the characterization of the focusing properties at the LHC, turn-by-turn beam position data is simultaneously recorded at numerous measurement devices (BPMs) along the accelerator, while an oscillation is excited on the beam. A novel analysis method for these measurements ($N$-BPM method) is developed here, which is based on a detailed analysis of systematic and statistical error sources and their correlations. It has been applied during the commissioning of the LHC for operation at an unprecedented energy of 6.5 TeV. In this process a stronger focusing than its design specifications has been achieved. This results in smaller transverse beam sizes at the collision points and allows for a higher rate of particle collisions. For the derivation of ...

  8. Induction Hardening of External Gear

    Science.gov (United States)

    Bukanin, V. A.; Ivanov, A. N.; Zenkov, A. E.; Vologdin, V. V.; Vologdin, V. V., Jr.

    2018-03-01

    Problems and solution of gear induction hardening are described. Main attention is paid to the parameters of heating and cooling systems. ELTA 7.0 program has been used to obtain the required electrical parameters of inductor, power sources, resonant circuits, as well as to choose the quenching media. Comparison of experimental and calculated results of investigation is provided. In order to compare advantages and disadvantages of single- and dual-frequency heating processes, many variants of these technologies were simulated. The predicted structure and hardness of steel gears are obtained by use of the ELTA data base taken into account the Continuous Cooling Transformation diagrams.

  9. A Novel Radiation Hardened CAM

    CERN Document Server

    Shojaii, Seyed Ruhollah; The ATLAS collaboration

    2018-01-01

    This poster describes an innovative Content Addressable Memory cell with radiation hardened (RH-CAM) architecture. The RH-CAM is designed in a commercial 28 nm CMOS technology. The circuit has been simulated in worst-case conditions, and the effects due to single particles are analyzed injecting a fault current into a circuit node. The proposed architecture can perform on-time pattern recognition tasks in harsh environments, such as very front-end electronics in hadron colliders and in space applications.

  10. Optimization of resistively hardened latches

    International Nuclear Information System (INIS)

    Gagne, G.; Savaria, Y.

    1990-01-01

    The design of digital circuits tolerant to single-event upsets is considered. The results of a study are presented on which an analytical model was used to predict the behavior of a standard resistively hardened latch. It is shown that a worst case analysis for all possible single-event upset situations (on the latch or in the logic) can be derived from studying the effects of a transient disturbed write cycle. The existence of an intrinsic minimum write period to tolerate a transient of a given duration is also demonstrated

  11. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...... of gradient hardening are found to delay the onset of localization under plane strain tension, and significantly reduce strain gradients in the localized zone. For plane strain compression gradient hardening is found to increase the load-carrying capacity significantly....

  12. A moving blocker-based strategy for simultaneous megavoltage and kilovoltage scatter correction in cone-beam computed tomography image acquired during volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Ouyang, Luo; Lee, Huichen Pam; Wang, Jing

    2015-01-01

    Purpose: To evaluate a moving blocker-based approach in estimating and correcting megavoltage (MV) and kilovoltage (kV) scatter contamination in kV cone-beam computed tomography (CBCT) acquired during volumetric modulated arc therapy (VMAT). Methods and materials: During the concurrent CBCT/VMAT acquisition, a physical attenuator (i.e., “blocker”) consisting of equally spaced lead strips was mounted and moved constantly between the CBCT source and patient. Both kV and MV scatter signals were estimated from the blocked region of the imaging panel, and interpolated into the unblocked region. A scatter corrected CBCT was then reconstructed from the unblocked projections after scatter subtraction using an iterative image reconstruction algorithm based on constraint optimization. Experimental studies were performed on a Catphan® phantom and an anthropomorphic pelvis phantom to demonstrate the feasibility of using a moving blocker for kV–MV scatter correction. Results: Scatter induced cupping artifacts were substantially reduced in the moving blocker corrected CBCT images. Quantitatively, the root mean square error of Hounsfield units (HU) in seven density inserts of the Catphan phantom was reduced from 395 to 40. Conclusions: The proposed moving blocker strategy greatly improves the image quality of CBCT acquired with concurrent VMAT by reducing the kV–MV scatter induced HU inaccuracy and cupping artifacts

  13. Influence of Cooling Condition on the Performance of Grinding Hardened Layer in Grind-hardening

    Science.gov (United States)

    Wang, G. C.; Chen, J.; Xu, G. Y.; Li, X.

    2018-02-01

    45# steel was grinded and hardened on a surface grinding machine to study the effect of three different cooling media, including emulsion, dry air and liquid nitrogen, on the microstructure and properties of the hardened layer. The results show that the microstructure of material surface hardened with emulsion is pearlite and no hardened layer. The surface roughness is small and the residual stress is compressive stress. With cooling condition of liquid nitrogen and dry air, the specimen surface are hardened, the organization is martensite, the surface roughness is also not changed, but high hardness of hardened layer and surface compressive stress were obtained when grinding using liquid nitrogen. The deeper hardened layer grinded with dry air was obtained and surface residual stress is tensile stress. This study provides an experimental basis for choosing the appropriate cooling mode to effectively control the performance of grinding hardened layer.

  14. Cone beam CT-based set-up strategies with and without rotational correction for stereotactic body radiation therapy in the liver.

    Science.gov (United States)

    Bertholet, Jenny; Worm, Esben; Høyer, Morten; Poulsen, Per

    2017-06-01

    Accurate patient positioning is crucial in stereotactic body radiation therapy (SBRT) due to a high dose regimen. Cone-beam computed tomography (CBCT) is often used for patient positioning based on radio-opaque markers. We compared six CBCT-based set-up strategies with or without rotational correction. Twenty-nine patients with three implanted markers received 3-6 fraction liver SBRT. The markers were delineated on the mid-ventilation phase of a 4D-planning-CT. One pretreatment CBCT was acquired per fraction. Set-up strategy 1 used only translational correction based on manual marker match between the CBCT and planning CT. Set-up strategy 2 used automatic 6 degrees-of-freedom registration of the vertebrae closest to the target. The 3D marker trajectories were also extracted from the projections and the mean position of each marker was calculated and used for set-up strategies 3-6. Translational correction only was used for strategy 3. Translational and rotational corrections were used for strategies 4-6 with the rotation being either vertebrae based (strategy 4), or marker based and constrained to ±3° (strategy 5) or unconstrained (strategy 6). The resulting set-up error was calculated as the 3D root-mean-square set-up error of the three markers. The set-up error of the spinal cord was calculated for all strategies. The bony anatomy set-up (2) had the largest set-up error (5.8 mm). The marker-based set-up with unconstrained rotations (6) had the smallest set-up error (0.8 mm) but the largest spinal cord set-up error (12.1 mm). The marker-based set-up with translational correction only (3) or with bony anatomy rotational correction (4) had equivalent set-up error (1.3 mm) but rotational correction reduced the spinal cord set-up error from 4.1 mm to 3.5 mm. Marker-based set-up was substantially better than bony-anatomy set-up. Rotational correction may improve the set-up, but further investigations are required to determine the optimal correction

  15. HARDENING OF CRANE RAILS BY PLASMA DISCRETE-TIME SURFACE TREATMENT

    Directory of Open Access Journals (Sweden)

    S. S. Samotugin

    2017-01-01

    Full Text Available Crane wheels and rails are subjected to intensive wear in the process of operation. Therefore, improvement of these components’ performance can be considered a task of high importance. A promising direction in this regard is surface treatment by highly concentrated energy flows such as laser beams or plasma jets. This thesis suggests that the use of gradient plasma surface treatment can improve the performance of crane rails. A research was conducted, according to which hardened zones were deposited on crane rails under different treatment modes. Microhardness was measured both at the surface and in depth using custom-made microsections. The article includes the results of study of plasma surface hardening effects on wear resistance of crane rails. Change of plasma surface treatment parameters (current, plasma torch movement speed, argon gas flow rate allows for desired steel hardness and structure, while the choice of optimal location for hardened zones makes it possible to significantly improve wear resistance and crack resistance. As a result of plasma surface hardening, the fine-grained martensite structure is obtained with mainly lamellar morphology and higher hardness rate compared toinduction hardening or overlaying. Wear test of carbon steels revealed that plasma surfacing reduces abrasive wear rate compared to the irinitial state by 2 to 3 times. Enough sharp boundary between hardened and non-hardened portions has a positive effect on the performance of parts under dynamic loads, contributing to the inhibition of cracks during the transition from solid to a soft metal. For carbon and low alloy rail steels, the properties achieved by plasma surface hardening can effectively replace induction hardening or overlaying.The mode range for plasma surface treatment that allow sobtaining a surface layer with certain operating properties has been determined.

  16. Fluence correction factors for graphite calorimetry in a low-energy clinical proton beam: I. Analytical and Monte Carlo simulations.

    Science.gov (United States)

    Palmans, H; Al-Sulaiti, L; Andreo, P; Shipley, D; Lühr, A; Bassler, N; Martinkovič, J; Dobrovodský, J; Rossomme, S; Thomas, R A S; Kacperek, A

    2013-05-21

    The conversion of absorbed dose-to-graphite in a graphite phantom to absorbed dose-to-water in a water phantom is performed by water to graphite stopping power ratios. If, however, the charged particle fluence is not equal at equivalent depths in graphite and water, a fluence correction factor, kfl, is required as well. This is particularly relevant to the derivation of absorbed dose-to-water, the quantity of interest in radiotherapy, from a measurement of absorbed dose-to-graphite obtained with a graphite calorimeter. In this work, fluence correction factors for the conversion from dose-to-graphite in a graphite phantom to dose-to-water in a water phantom for 60 MeV mono-energetic protons were calculated using an analytical model and five different Monte Carlo codes (Geant4, FLUKA, MCNPX, SHIELD-HIT and McPTRAN.MEDIA). In general the fluence correction factors are found to be close to unity and the analytical and Monte Carlo codes give consistent values when considering the differences in secondary particle transport. When considering only protons the fluence correction factors are unity at the surface and increase with depth by 0.5% to 1.5% depending on the code. When the fluence of all charged particles is considered, the fluence correction factor is about 0.5% lower than unity at shallow depths predominantly due to the contributions from alpha particles and increases to values above unity near the Bragg peak. Fluence correction factors directly derived from the fluence distributions differential in energy at equivalent depths in water and graphite can be described by kfl = 0.9964 + 0.0024·zw-eq with a relative standard uncertainty of 0.2%. Fluence correction factors derived from a ratio of calculated doses at equivalent depths in water and graphite can be described by kfl = 0.9947 + 0.0024·zw-eq with a relative standard uncertainty of 0.3%. These results are of direct relevance to graphite calorimetry in low-energy protons but given that the fluence

  17. Direction-dependent Corrections in Polarimetric Radio Imaging. I. Characterizing the Effects of the Primary Beam on Full-Stokes Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Jagannathan, P.; Bhatnagar, S.; Rau, U. [National Radio Astronomy Observatory, Socorro (United States); Taylor, A. R., E-mail: pjaganna@nrao.edu [Department of Astronomy, University of Cape Town (South Africa)

    2017-08-01

    Next generation radio telescope arrays are being designed and commissioned to accurately measure polarized intensity and rotation measures (RMs) across the entire sky through deep, wide-field radio interferometric surveys. Radio interferometer dish antenna arrays are affected by direction-dependent (DD) gains due to both instrumental and atmospheric effects. In this paper, we demonstrate the effect of DD errors of the parabolic dish antenna array on the measured polarized intensities of radio sources in interferometric images. We characterize the extent of polarimetric image degradation due to the DD gains through wide-band VLA simulations of representative point-source simulations of the radio sky at L band (1–2 GHz). We show that at the 0.5 gain level of the primary beam there is significant flux leakage from Stokes I to Q , U amounting to 10% of the total intensity. We further demonstrate that while the instrumental response averages down for observations over large parallactic angle intervals, full-polarization DD correction is required to remove the effects of DD leakage. We also explore the effect of the DD beam on the RM signals and show that while the instrumental effect is primarily centered around 0 rad-m{sup −2}, the effect is significant over a broad range of RM requiring full polarization DD correction to accurately reconstruct the RM synthesis signal.

  18. Calculation of radiative corrections to virtual compton scattering - absolute measurement of the energy of Jefferson Lab. electron beam (hall A) by a magnetic method: arc project

    International Nuclear Information System (INIS)

    Marchand, D.

    1998-11-01

    This thesis presents the radiative corrections to the virtual compton scattering and the magnetic method adopted in the Hall A at Jefferson Laboratory, to measure the electrons beam energy with an accuracy of 10 4 . The virtual compton scattering experiments allow the access to the generalised polarizabilities of the protons. The extraction of these polarizabilities is obtained by the experimental and theoretical cross sections comparison. That's why the systematic errors and the radiative effects of the experiments have to be controlled very seriously. In this scope, a whole calculation of the internal radiative corrections has been realised in the framework of the quantum electrodynamic. The method of the dimensional regularisation has been used to the treatment of the ultraviolet and infra-red divergences. The absolute measure method of the energy, takes into account the magnetic deviation, made up of eight identical dipoles. The energy is determined from the deviation angle calculation of the beam and the measure of the magnetic field integral along the deviation

  19. Fluence correction factors for graphite calorimetry in a low-energy clinical proton beam: I. Analytical and Monte Carlo simulations

    DEFF Research Database (Denmark)

    Palmans, Hugo; Al-Sulaiti, L; Andreo, P

    2013-01-01

    , is required as well. This is particularly relevant to the derivation of absorbed dose-to-water, the quantity of interest in radiotherapy, from a measurement of absorbed dose-to-graphite obtained with a graphite calorimeter. In this work, fluence correction factors for the conversion from dose...

  20. Studies on functional polymer films utilizing low energy electron beam

    International Nuclear Information System (INIS)

    Ando, Masayuki

    1992-01-01

    Also in adhesives and tackifiers, with the expansion of the fields of application, the required characteristics have become high grade and complex. As one of them, the instantaneous hardening of adhesives can be taken up. In the field of lamination works, the low energy type electron beam accelerators having the linear filament of accelerating voltage below 300 kV were developed in 1970s, and the interest in the development of electron beam-handened adhesives has heightend. The authors have carried out research aiming at heightening the functions of the polymer films obtained by electron beam hardening reaction, and developed the adhesives. In this report, the features of electron beam hardening reaction, the structure and properties of electron beam-hardened polymer films and the molecular design of electron beam-hardened monomer oligomers are described. The feature of electron beam hardening reaction is the cross-linking of high degree as the structure of oligomers is maintained. By controlling the structure at the time of electron beam hardening, the heightening of the functions of electron beam-hardened polymer films is feasible. (K.I.)

  1. Ductility and work hardening in nano-sized metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Chen, D. Z., E-mail: dzchen@caltech.edu [Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125 (United States); Gu, X. W. [Department of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States); An, Q.; Goddard, W. A. [Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125 (United States); Greer, J. R. [Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125 (United States); The Kavli Nanoscience Institute, California Institute of Technology, Pasadena, California 91125 (United States)

    2015-02-09

    In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of free volume within molecular dynamics-simulated samples suggests a free surface-mediated relaxation mechanism in nano-sized metallic glasses.

  2. Reduction of ring artifacts in CBCT: Detection and correction of pixel gain variations in flat panel detectors

    International Nuclear Information System (INIS)

    Altunbas, Cem; Lai, Chao-Jen; Zhong, Yuncheng; Shaw, Chris C.

    2014-01-01

    Purpose: In using flat panel detectors (FPD) for cone beam computed tomography (CBCT), pixel gain variations may lead to structured nonuniformities in projections and ring artifacts in CBCT images. Such gain variations can be caused by change in detector entrance exposure levels or beam hardening, and they are not accounted by conventional flat field correction methods. In this work, the authors presented a method to identify isolated pixel clusters that exhibit gain variations and proposed a pixel gain correction (PGC) method to suppress both beam hardening and exposure level dependent gain variations. Methods: To modulate both beam spectrum and entrance exposure, flood field FPD projections were acquired using beam filters with varying thicknesses. “Ideal” pixel values were estimated by performing polynomial fits in both raw and flat field corrected projections. Residuals were calculated by taking the difference between measured and ideal pixel values to identify clustered image and FPD artifacts in flat field corrected and raw images, respectively. To correct clustered image artifacts, the ratio of ideal to measured pixel values in filtered images were utilized as pixel-specific gain correction factors, referred as PGC method, and they were tabulated as a function of pixel value in a look-up table. Results: 0.035% of detector pixels lead to clustered image artifacts in flat field corrected projections, where 80% of these pixels were traced back and linked to artifacts in the FPD. The performance of PGC method was tested in variety of imaging conditions and phantoms. The PGC method reduced clustered image artifacts and fixed pattern noise in projections, and ring artifacts in CBCT images. Conclusions: Clustered projection image artifacts that lead to ring artifacts in CBCT can be better identified with our artifact detection approach. When compared to the conventional flat field correction method, the proposed PGC method enables characterization of nonlinear

  3. Hardening of niobium alloys at precrystallization annealing

    International Nuclear Information System (INIS)

    Vasil'eva, E.V.; Pustovalov, V.A.

    1989-01-01

    Niobium base alloys were investigated. It is shown that precrystallization annealing of niobium-molybdenum, niobium-vanadium and niobium-zirconium alloys elevates much more sufficiently their resistance to microplastic strains, than to macroplastic strains. Hardening effect differs sufficiently for different alloys. The maximal hardening is observed for niobium-vanadium alloys, the minimal one - for niobium-zirconium alloys

  4. Investigation of a Hardened Cement Paste Grout

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Sørensen, Eigil Verner

    This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....

  5. Monte Carlo correction factors for a Farmer 0.6 cm3 ion chamber dose measurement in the build-up region of the 6 MV clinical beam

    International Nuclear Information System (INIS)

    Pena, J; Sanchez-Doblado, F; Capote, R; Terron, J A; Gomez, F

    2006-01-01

    Reference dosimetry of photon fields is a well-established subject and currently available protocols (such as the IAEA TRS-398 and AAPM TG-51) provide methods for converting the ionization chamber (IC) reading into dose to water, provided reference conditions of charged particle equilibrium (CPE) are fulfilled. But these protocols cannot deal with the build-up region, where the lack of CPE limits the applicability of the cavity theorems and so the chamber correction factors become depth dependent. By explicitly including the IC geometry in the Monte Carlo simulations, depth-dependent dose correction factors are calculated for a PTW 30001 0.6 cm 3 ion chamber in the build-up region of the 6 MV photon beam. The corrected percentage depth dose (PDD) agrees within 2% with that measured using the NACP 02 plane-parallel ion chamber in the build-up region at depths greater than 0.4 cm, where the Farmer chamber wall reaches the phantom surface

  6. Radiation hardening of integrated circuits technologies

    International Nuclear Information System (INIS)

    Auberton-Herve, A.J.; Leray, J.L.

    1991-01-01

    The radiation hardening studies started in the mid decade -1960-1970. To survive the different military or space radiative environment, a new engineering science borned, to understand the degradation of electronics components. The different solutions to improve the electronic behavior in such environment, have been named radiation hardening of the technologies. Improvement of existing technologies, and qualification method have been widely studied. However, at the other hand, specific technologies was developped : The Silicon On Insulator technologies for CMOS or Bipolar. The HSOI3HD technology (supported by DGA-CEA DAM and LETI with THOMSON TMS) offers today the highest hardening level for the integration density of hundreds of thousand transistors on the same silicon. Full complex systems would be realized on a single die with a technological radiation hardening and no more system hardening

  7. Challenges in hardening technologies using shallow-trench isolation

    International Nuclear Information System (INIS)

    Shaneyfelt, M.R.; Dodd, P.E.; Draper, B.L.; Flores, R.S.

    1998-02-01

    Challenges related to radiation hardening CMOS technologies with shallow-trench isolation are explored. Results show that trench hardening can be more difficult than simply replacing the trench isolation oxide with a hardened field oxide

  8. Comparison of Thermal Creep Strain Calculation Results Using Time Hardening and Strain Hardening Rules

    International Nuclear Information System (INIS)

    Kim, Junehyung; Cheon, Jinsik; Lee, Byoungoon; Lee, Chanbock

    2014-01-01

    One of the design criteria for the fuel rod in PGSFR is the thermal creep strain of the cladding, because the cladding is exposed to a high temperature for a long time during reactor operation period. In general, there are two kind of calculation scheme for thermal creep strain: time hardening and strain hardening rules. In this work, thermal creep strain calculation results for HT9 cladding by using time hardening and strain hardening rules are compared by employing KAERI's current metallic fuel performance analysis code, MACSIS. Also, thermal creep strain calculation results by using ANL's metallic fuel performance analysis code, LIFE-METAL which adopts strain hardening rule are compared with those by using MACSIS. Thermal creep strain calculation results for HT9 cladding by using time hardening and strain hardening rules were compared by employing KAERI's current metallic fuel performance analysis code, MACSIS. Also, thermal creep strain calculation results by using ANL's metallic fuel performance analysis code, LIFE-METAL which adopts strain hardening rule were compared with those by using MACSIS. Tertiary creep started earlier in time hardening rule than in strain hardening rule. Also, calculation results by MACSIS with strain hardening and those obtained by using LIFE-METAL were almost identical to each other

  9. Radiation hardening of smart electronics

    International Nuclear Information System (INIS)

    Mayo, C.W.; Cain, V.R.; Marks, K.A.; Millward, D.G.

    1991-02-01

    Microprocessor based ''smart'' pressure, level, and flow transmitters were tested to determine the radiation hardness of this class of electronic instrumentation for use in reactor building applications. Commercial grade Complementary Metal Oxide Semiconductor (CMOS) integrated circuits used in these transmitters were found to fail at total gamma dose levels between 2500 and 10,000 rad. This results in an unacceptably short lifetime in many reactor building radiation environments. Radiation hardened integrated circuits can, in general, provide satisfactory service life for normal reactor operations when not restricted to the extremely low power budget imposed by standard 4--20 mA two-wire instrument loops. The design of these circuits will require attention to vendor radiation hardness specifications, dose rates, process control with respect to radiation hardness factors, and non-volatile programmable memory technology. 3 refs., 2 figs

  10. Dynamic correction of the laser beam coordinate in fabrication of large-sized diffractive elements for testing aspherical mirrors

    Science.gov (United States)

    Shimansky, R. V.; Poleshchuk, A. G.; Korolkov, V. P.; Cherkashin, V. V.

    2017-05-01

    This paper presents a method of improving the accuracy of a circular laser system in fabrication of large-diameter diffractive optical elements by means of a polar coordinate system and the results of their use. An algorithm for correcting positioning errors of a circular laser writing system developed at the Institute of Automation and Electrometry, SB RAS, is proposed and tested. Highprecision synthesized holograms fabricated by this method and the results of using these elements for testing the 6.5 m diameter aspheric mirror of the James Webb space telescope (JWST) are described..

  11. Patient-specific scatter correction in clinical cone beam computed tomography imaging made possible by the combination of Monte Carlo simulations and a ray tracing algorithm

    International Nuclear Information System (INIS)

    Thing, Rune S.; Bernchou, Uffe; Brink, Carsten; Mainegra-Hing, Ernesto

    2013-01-01

    Purpose: Cone beam computed tomography (CBCT) image quality is limited by scattered photons. Monte Carlo (MC) simulations provide the ability of predicting the patient-specific scatter contamination in clinical CBCT imaging. Lengthy simulations prevent MC-based scatter correction from being fully implemented in a clinical setting. This study investigates the combination of using fast MC simulations to predict scatter distributions with a ray tracing algorithm to allow calibration between simulated and clinical CBCT images. Material and methods: An EGSnrc-based user code (egs c bct), was used to perform MC simulations of an Elekta XVI CBCT imaging system. A 60keV x-ray source was used, and air kerma scored at the detector plane. Several variance reduction techniques (VRTs) were used to increase the scatter calculation efficiency. Three patient phantoms based on CT scans were simulated, namely a brain, a thorax and a pelvis scan. A ray tracing algorithm was used to calculate the detector signal due to primary photons. A total of 288 projections were simulated, one for each thread on the computer cluster used for the investigation. Results: Scatter distributions for the brain, thorax and pelvis scan were simulated within 2 % statistical uncertainty in two hours per scan. Within the same time, the ray tracing algorithm provided the primary signal for each of the projections. Thus, all the data needed for MC-based scatter correction in clinical CBCT imaging was obtained within two hours per patient, using a full simulation of the clinical CBCT geometry. Conclusions: This study shows that use of MC-based scatter corrections in CBCT imaging has a great potential to improve CBCT image quality. By use of powerful VRTs to predict scatter distributions and a ray tracing algorithm to calculate the primary signal, it is possible to obtain the necessary data for patient specific MC scatter correction within two hours per patient

  12. SU-F-J-108: TMR Correction Factor Based Online Adaptive Radiotherapy for Stereotactic Radiosurgery (SRS) of L-Spine Tumors Using Cone Beam CT

    Energy Technology Data Exchange (ETDEWEB)

    Ghaffar, I; Balik, S; Zhuang, T; Chao, S; Xia, P [The Cleveland Clinic Foundation, Cleveland, OH (United States)

    2016-06-15

    Purpose: To investigate the feasibility of using TMR ratio correction factors for a fast online adaptive plan to compensate for anatomical changes in stereotactic radiosurgery (SRS) of L-spine tumors. Methods: Three coplanar treatment plans were made for 11 patients: Uniform (9 IMRT beams equally distributed around the patient); Posterior (IMRT with 9 posterior beams every 20 degree) and VMAT (2 360° arcs). For each patient, the external body and bowel gas were contoured on the planning CT and pre-treatment CBCT. After registering CBCT and the planning CT by aligning to the tumor, the CBCT contours were transferred to the planning CT. To estimate the actual delivered dose while considering patient’s anatomy of the treatment day, a hybrid CT was created by overriding densities in planning CT using the differences between CT and CBCT external and bowel gas contours. Correction factors (CF) were calculated using the effective depth information obtained from the planning system using the hybrid CT: CF = TMR (delivery)/TMR (planning). The adaptive plan was generated by multiplying the planned Monitor Units with the CFs. Results: The mean absolute difference (MAD) in V16Gy of the target between planned and estimated delivery with and without TMR correction was 0.8 ± 0.7% vs. 2.4 ± 1.3% for Uniform and 1.0 ± 0.9% vs. 2.6 ± 1.3% for VMAT plans(p<0.05), respectively. For V12Gy of cauda-equina with and without TMR correction, MAD was 0.24 ± 0.19% vs. 1.2 ± 1.02% for Uniform and 0.23 ± 0.20% vs. 0.78 ± 0.79% for VMAT plans(p<0.05), respectively. The differences between adaptive and original plans were not significant for posterior plans. Conclusion: The online adaptive strategy using TMR ratios and pre-treatment CBCT information was feasible strategy to compensate for anatomical changes for the patients treated for L-spine tumors, particularly for equally spaced IMRT and VMAT plans.

  13. The recombination correction and the dependence of the response of plane parallel chambers on the polarizing voltage in pulsed electron and photon beams

    International Nuclear Information System (INIS)

    Roos, M.; Derikum, K.

    2000-01-01

    Based on an experimental investigation of the recombination effect in plane parallel chambers, a relation is deduced that allows the correction to be calculated from the electrode spacing and from the dose per pulse. It is shown that the uncertainties caused by the application of the Boag formula for volume recombination (recommended in the International Code of Practice TRS-381) amount to not more than about 0.1% for conventional beams. Calculated recombinations are compared with experimental results concerning the dependence of the response of various commercial plane parallel chambers on the polarizing voltage. Since it cannot be excluded that particular chambers collect a non-negligible amount of charge from regions outside the designated collecting volume or that the effective polarizing voltage is reduced by poor contacts, it seems advisable to experimentally check the chambers before use and before application of the analytical relations. (author)

  14. Performance on a CT Scanner. Application for the dose correction in the presence of heterogeneities, experimental study using high energy photon beams

    International Nuclear Information System (INIS)

    Hanna, Therese.

    1979-01-01

    The purpose of this work is the physical analysis of a second generation C T scanner: the A C T A Scanner 0200 FS (PFIZER) used at the 'Institut Gustave Roussy, Villejuif' and its application in radiotherapy. The first part of the study specifically concerns the physical performance of the C T Scanner, and, the evaluation of the doses, delivered to patients during tomodensitometric examinations. The second part envisages the possibilities of the application of C T scanning in radiotherapy. A particular study is established for the utilization of the physical characteristics, furnished by the C T Scanner, concerning different organs, in dose calculations, in the presence of heterogeneities. An experimental study using high energy photon beams more particularly 25 MV X ray beams produced by a linear accelerator (type Sagittaire) has been realized with materials, simulating different human tissues. Consequently, the validity of different correction methods proposed in the literature has been tested for the soft tissues and bone as for the lungs. Modifications are suggested to allow the use of these methods for the photons of very high energy [fr

  15. INTOR neutral beam injector concept

    International Nuclear Information System (INIS)

    Metzler, D.H.; Stewart, L.D.

    1981-01-01

    The US INTOR phase 1 effort in the plasma heating area is described. Positive ion based sources extrapolated from present day technology are proposed. These sources operate at 175 keV beam energy for 6 s. Five injectors - plus one spare - inject 75 MW. Beam energy, source size, interface, radiation hardening, and many other studies are summarized

  16. Characterization of the Photon Counting CHASE Jr., Chip Built in a 40-nm CMOS Process With a Charge Sharing Correction Algorithm Using a Collimated X-Ray Beam

    Energy Technology Data Exchange (ETDEWEB)

    Krzyżanowska, A. [AGH-UST, Cracow; Deptuch, G. W. [Fermilab; Maj, P. [AGH-UST, Cracow; Gryboś, P. [AGH-UST, Cracow; Szczygieł, R. [AGH-UST, Cracow

    2017-08-01

    This paper presents the detailed characterization of a single photon counting chip, named CHASE Jr., built in a CMOS 40-nm process, operating with synchrotron radiation. The chip utilizes an on-chip implementation of the C8P1 algorithm. The algorithm eliminates the charge sharing related uncertainties, namely, the dependence of the number of registered photons on the discriminator’s threshold, set for monochromatic irradiation, and errors in the assignment of an event to a certain pixel. The article presents a short description of the algorithm as well as the architecture of the CHASE Jr., chip. The analog and digital functionalities, allowing for proper operation of the C8P1 algorithm are described, namely, an offset correction for two discriminators independently, two-stage gain correction, and different operation modes of the digital blocks. The results of tests of the C8P1 operation are presented for the chip bump bonded to a silicon sensor and exposed to the 3.5- μm -wide pencil beam of 8-keV photons of synchrotron radiation. It was studied how sensitive the algorithm performance is to the chip settings, as well as the uniformity of parameters of the analog front-end blocks. Presented results prove that the C8P1 algorithm enables counting all photons hitting the detector in between readout channels and retrieving the actual photon energy.

  17. The microstructural origin of work hardening stages

    DEFF Research Database (Denmark)

    Hughes, D. A.; Hansen, N.

    2018-01-01

    The strain evolution of the flow stress and work hardening rate in stages III and IV is explored by utilizing a fully described deformation microstructure. Extensive measurements by transmission electron microscopy reveal a hierarchical subdivision of grains by low angle incidental dislocation...... addition of the classical Taylor and Hall-Petch formulations. Model predictions agree closely with experimental values of flow stress and work hardening rate in stages III and IV. Strong connections between the evolutionary stages of the deformation microstructure and work hardening rates create a new...... (modern) basis for the classic problem of work hardening in metals and alloys. These connections lead the way for the future development of ultra high strength ductile metals produced via plastic deformation.(c) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved....

  18. COMPLEX SURFACE HARDENING OF STEEL ARTICLES

    Directory of Open Access Journals (Sweden)

    A. V. Kovalchuk

    2014-01-01

    Full Text Available The method of complex surface hardening of steel detailswas designed. The method is a compound of two processes of hardening: chemical heat treatment and physical vapor deposition (PVD of the coating. The result, achieved in this study is much higher, than in other work on this topic and is cumulative. The method designed can be used in mechanical engineering, medicine, energetics and is perspective for military and space technologies.

  19. Study of the mechanisms involved in the laser superficial hardening process of metallic alloys

    International Nuclear Information System (INIS)

    Silva, Edmara Marques Rodrigues da

    2001-01-01

    The laser superficial hardening process of a ferrous alloy (gray cast iron) and of an aluminum-silicon alloy was investigated in this work. These metallic alloys are used in the automobile industry for manufacturing cylinders and pistons, respectively. By application of individual pulses and single tracks, the involved mechanisms during the processing were studied. Variables such as energy density, power density, temporal width, beam diameter on the sample surface, atmosphere of the processing region, overlapping and scanning velocity. The hardened surface was characterized by optical and scanning electronic microscopy, dispersive energy microanalysis, X-ray mapping, X-ray diffraction, and measurements of roughness and Vickers microhardness. Depending on the processing parameters, it is possible to obtain different microstructures. The affected area of gray cast iron, can be hardened by remelting or transformation hardening (total or partial) if the reached temperature is higher or not that of melting temperature. Laser treatment originated new structures such as retained austenite, martensite and, occasionally, eutectic of cellular dendritic structure. Aluminum-silicon alloy does not have phase transformation in solid state, it can be hardened only by remelting. The increase of hardness is a function of the precipitation hardening process, which makes the silicon particles smaller and more disperse in the matrix. Maximal values of microhardness (700-1000 HV) were reached with the laser treatment in gray cast iron samples. The initial microhardness is of 242 HV. For aluminum-silicon alloy, the laser remelting increases the initial microhardness of 128 HV to the range of 160-320 HV. The found results give a new perspective for using the CLA/IPEN's laser in the heat treatment area. Besides providing a higher absorptivity to the materials, compared with the CO 2 laser, and optical fiber access, the superficial hardening with Nd:YAG laser, depending on the level of

  20. The secondary hardening phenomenon in strain-hardened MP35N alloy

    International Nuclear Information System (INIS)

    Asgari, S.; El-Danaf, E.; Shaji, E.; Kalidindi, S.R.; Doherty, R.D.

    1998-01-01

    Mechanical testing and microscopy techniques were used to investigate the influence of aging on the structure and strengthening of MP35N alloy. It was confirmed that aging the deformed material at 600 C for 4 h provided additional strengthening, here referred to as secondary hardening, in addition to the primary strain hardening. The secondary hardening phenomenon was shown to be distinctly different from typical age hardening processes in that it only occurred in material deformed beyond a certain cold work level. At moderate strains, aging caused a shift in the entire stress-strain curve of the annealed material to higher stresses while at high strains, it produced shear localization and limited work softening. The secondary hardening increment was also found to be grain size dependent. The magnitude of the secondary hardening appeared to be controlled by the flow stress in the strain hardened material. A model is proposed to explain the observations and is supported by direct experimental evidence. The model is based on formation of h.c.p. nuclei through the Suzuki mechanism, that is segregation of solute atoms to stacking faults, on aging the strain hardened material. The h.c.p. precipitates appear to thicken only in the presence of high dislocation density produced by prior cold work

  1. Simultaneous surface engineering and bulk hardening of precipitation hardening stainless steel

    DEFF Research Database (Denmark)

    Frandsen, Rasmus Berg; Christiansen, Thomas; Somers, Marcel A. J.

    2006-01-01

    This article addresses simultaneous bulk precipitation hardening and low temperature surface engineering of two commercial precipitation hardening stainless steels: Sandvik Nanoflex® and Uddeholm Corrax®. Surface engineering comprised gaseous nitriding or gaseous carburising. Microstructural....... The duration and temperature of the nitriding/carburising surface hardening treatment can be chosen in agreement with the thermal treatment for obtaining optimal bulk hardness in the precipitation hardening stainless steel....... characterisation of the cases developed included X-ray diffraction analysis, reflected light microscopy and micro-hardness testing. It was found that the incorporation of nitrogen or carbon resulted in a hardened case consisting of a combination of (tetragonal) martensite and expanded (cubic) austenite...

  2. PET measurements of cerebral metabolism corrected for CSF contributions

    International Nuclear Information System (INIS)

    Chawluk, J.; Alavi, A.; Dann, R.; Kushner, M.J.; Hurtig, H.; Zimmerman, R.A.; Reivich, M.

    1984-01-01

    Thirty-three subjects have been studied with PET and anatomic imaging (proton-NMR and/or CT) in order to determine the effect of cerebral atrophy on calculations of metabolic rates. Subgroups of neurologic disease investigated include stroke, brain tumor, epilepsy, psychosis, and dementia. Anatomic images were digitized through a Vidicon camera and analyzed volumetrically. Relative areas for ventricles, sulci, and brain tissue were calculated. Preliminary analysis suggests that ventricular volumes as determined by NMR and CT are similar, while sulcal volumes are larger on NMR scans. Metabolic rates (18F-FDG) were calculated before and after correction for CSF spaces, with initial focus upon dementia and normal aging. Correction for atrophy led to a greater increase (%) in global metabolic rates in demented individuals (18.2 +- 5.3) compared to elderly controls (8.3 +- 3.0,p < .05). A trend towards significantly lower glucose metabolism in demented subjects before CSF correction was not seen following correction for atrophy. These data suggest that volumetric analysis of NMR images may more accurately reflect the degree of cerebral atrophy, since NMR does not suffer from beam hardening artifact due to bone-parenchyma juxtapositions. Furthermore, appropriate correction for CSF spaces should be employed if current resolution PET scanners are to accurately measure residual brain tissue metabolism in various pathological states

  3. Precipitation and Hardening in Magnesium Alloys

    Science.gov (United States)

    Nie, Jian-Feng

    2012-11-01

    Magnesium alloys have received an increasing interest in the past 12 years for potential applications in the automotive, aircraft, aerospace, and electronic industries. Many of these alloys are strong because of solid-state precipitates that are produced by an age-hardening process. Although some strength improvements of existing magnesium alloys have been made and some novel alloys with improved strength have been developed, the strength level that has been achieved so far is still substantially lower than that obtained in counterpart aluminum alloys. Further improvements in the alloy strength require a better understanding of the structure, morphology, orientation of precipitates, effects of precipitate morphology, and orientation on the strengthening and microstructural factors that are important in controlling the nucleation and growth of these precipitates. In this review, precipitation in most precipitation-hardenable magnesium alloys is reviewed, and its relationship with strengthening is examined. It is demonstrated that the precipitation phenomena in these alloys, especially in the very early stage of the precipitation process, are still far from being well understood, and many fundamental issues remain unsolved even after some extensive and concerted efforts made in the past 12 years. The challenges associated with precipitation hardening and age hardening are identified and discussed, and guidelines are outlined for the rational design and development of higher strength, and ultimately ultrahigh strength, magnesium alloys via precipitation hardening.

  4. Influence on dose calculation by difference of dose calculation algorithms in stereotactic lung irradiation. Comparison of pencil beam convolution (inhomogeneity correction: batho power law) and analytical anisotropic algorithm

    International Nuclear Information System (INIS)

    Tachibana, Masayuki; Noguchi, Yoshitaka; Fukunaga, Jyunichi; Hirano, Naomi; Yoshidome, Satoshi; Hirose, Takaaki

    2009-01-01

    The monitor unit (MU) was calculated by pencil beam convolution (inhomogeneity correction algorithm: batho power law) [PBC (BPL)] which is the dose calculation algorithm based on measurement in the past in the stereotactic lung irradiation study. The recalculation was done by analytical anisotropic algorithm (AAA), which is the dose calculation algorithm based on theory data. The MU calculated by PBC (BPL) and AAA was compared for each field. In the result of the comparison of 1031 fields in 136 cases, the MU calculated by PBC (BPL) was about 2% smaller than that calculated by AAA. This depends on whether one does the calculation concerning the extension of the second electrons. In particular, the difference in the MU is influenced by the X-ray energy. With the same X-ray energy, when the irradiation field size is small, the lung pass length is long, the lung pass length percentage is large, and the CT value of the lung is low, and the difference of MU is increased. (author)

  5. A procedure for the hardening of materials

    International Nuclear Information System (INIS)

    Dearnaley, G.

    1984-01-01

    A method of hardening metals or ceramics which have fcc, bcc or hcp structures in which two species of differing atomic radii are introduced into the material to be hardened. One species is of a size such that it can diffuse through the lattice normally. The other is of a size such that it can diffuse readily only along dislocations. Ion bombardment is the preferred method of introducing the species with different atomic radii. The material to be hardened is subjected to heat and plastic deformation so as to cause a large number of dislocations with jogs. The species meet at the jogs where they interact and are trapped and set up strain fields which prevent further deformation of the material. (author)

  6. An Anisotropic Hardening Model for Springback Prediction

    Science.gov (United States)

    Zeng, Danielle; Xia, Z. Cedric

    2005-08-01

    As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test.

  7. An Anisotropic Hardening Model for Springback Prediction

    International Nuclear Information System (INIS)

    Zeng, Danielle; Xia, Z. Cedric

    2005-01-01

    As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test

  8. Technology of hardening fills for mined spaces

    International Nuclear Information System (INIS)

    Simek, P.; Holas, M.; Chyla, A.; Pech, P.

    1985-01-01

    The technology is described of hardening fills for mined spaces of uranium deposits in North Bohemian chalk. A special equipment was developed for the controlled preparation of a hardening mixture. The composition of the fill is determined by the strength of the filled rock, expecially by the standard strength, i.e., the minimal strength of the filling under uniaxial pressure. The said parameter determines the consumption of binding materials and thereby the total costs of the filling. A description is presented of the filling technology, including rabbit tube transport of the mixture and quality control. (Pu)

  9. Radiation hardening revisited: Role of intracascade clustering

    DEFF Research Database (Denmark)

    Singh, B.N.; Foreman, A.J.E.; Trinkaus, H.

    1997-01-01

    be explained in terms of conventional dispersed-barrier hardening because (a) the grown-in dislocations are not free, and (b) irradiation-induced defect clusters are not rigid indestructible Orowan obstacles. A new model called 'cascade-induced source hardening' is presented where glissile loops produced...... directly in cascades are envisaged to decorate the grown-in dislocations so that they cannot act as dislocation sources. The upper yield stress is related to the breakaway stress which is necessary to pull the dislocation away from the clusters/loops decorating it. The magnitude of the breakaway stress has...

  10. WE-DE-207B-10: Library-Based X-Ray Scatter Correction for Dedicated Cone-Beam Breast CT: Clinical Validation

    Energy Technology Data Exchange (ETDEWEB)

    Shi, L; Zhu, L [Georgia Institute of Technology, Atlanta, GA (Georgia); Vedantham, S; Karellas, A [University of Massachusetts Medical School, Worcester, MA (United States)

    2016-06-15

    Purpose: Scatter contamination is detrimental to image quality in dedicated cone-beam breast CT (CBBCT), resulting in cupping artifacts and loss of contrast in reconstructed images. Such effects impede visualization of breast lesions and the quantitative accuracy. Previously, we proposed a library-based software approach to suppress scatter on CBBCT images. In this work, we quantify the efficacy and stability of this approach using datasets from 15 human subjects. Methods: A pre-computed scatter library is generated using Monte Carlo simulations for semi-ellipsoid breast models and homogeneous fibroglandular/adipose tissue mixture encompassing the range reported in literature. Projection datasets from 15 human subjects that cover 95 percentile of breast dimensions and fibroglandular volume fraction were included in the analysis. Our investigations indicate that it is sufficient to consider the breast dimensions alone and variation in fibroglandular fraction does not significantly affect the scatter-to-primary ratio. The breast diameter is measured from a first-pass reconstruction; the appropriate scatter distribution is selected from the library; and, deformed by considering the discrepancy in total projection intensity between the clinical dataset and the simulated semi-ellipsoidal breast. The deformed scatter-distribution is subtracted from the measured projections for scatter correction. Spatial non-uniformity (SNU) and contrast-to-noise ratio (CNR) were used as quantitative metrics to evaluate the results. Results: On the 15 patient cases, our method reduced the overall image spatial non-uniformity (SNU) from 7.14%±2.94% (mean ± standard deviation) to 2.47%±0.68% in coronal view and from 10.14%±4.1% to 3.02% ±1.26% in sagittal view. The average contrast to noise ratio (CNR) improved by a factor of 1.49±0.40 in coronal view and by 2.12±1.54 in sagittal view. Conclusion: We demonstrate the robustness and effectiveness of a library-based scatter correction

  11. WE-AB-BRA-08: Correction of Patient Motion in C-Arm Cone-Beam CT Using 3D-2D Registration

    Energy Technology Data Exchange (ETDEWEB)

    Ouadah, S; Jacobson, M; Stayman, JW; Siewerdsen, JH [Johns Hopkins University, Baltimore, MD (United States); Ehtiati, T [Siemens Medical Solutions USA, Inc., Hoffman Estates, IL (United States)

    2016-06-15

    Purpose: Intraoperative C-arm cone-beam CT (CBCT) is subject to artifacts arising from patient motion during the fairly long (∼5–20 s) scan times. We present a fiducial free method to mitigate motion artifacts using 3D-2D image registration that simultaneously corrects residual errors in geometric calibration. Methods: A 3D-2D registration process was used to register each projection to DRRs computed from the 3D image by maximizing gradient orientation (GO) using the CMA-ES optimizer. The resulting rigid 6 DOF transforms were applied to the system projection matrices, and a 3D image was reconstructed via model-based image reconstruction (MBIR, which accommodates the resulting noncircular orbit). Experiments were conducted using a Zeego robotic C-arm (20 s, 200°, 496 projections) to image a head phantom undergoing various types of motion: 1) 5° lateral motion; 2) 15° lateral motion; and 3) 5° lateral motion with 10 mm periodic inferior-superior motion. Images were reconstructed using a penalized likelihood (PL) objective function, and structural similarity (SSIM) was measured for axial slices of the reconstructed images. A motion-free image was acquired using the same protocol for comparison. Results: There was significant improvement (p < 0.001) in the SSIM of the motion-corrected (MC) images compared to uncorrected images. The SSIM in MC-PL images was >0.99, indicating near identity to the motion-free reference. The point spread function (PSF) measured from a wire in the phantom was restored to that of the reference in each case. Conclusion: The 3D-2D registration method provides a robust framework for mitigation of motion artifacts and is expected to hold for applications in the head, pelvis, and extremities with reasonably constrained operative setup. Further improvement can be achieved by incorporating multiple rigid components and non-rigid deformation within the framework. The method is highly parallelizable and could in principle be run with every

  12. WE-AB-207A-09: Optimization of the Design of a Moving Blocker for Cone-Beam CT Scatter Correction: Experimental Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, X; Ouyang, L; Jia, X; Zhang, Y; Wang, J [UT Southwestern Medical Center, Dallas, TX (United States); Yan, H [Cyber Medical Corporation, Xi’an (China)

    2016-06-15

    Purpose: A moving blocker based strategy has shown promising results for scatter correction in cone-beam computed tomography (CBCT). Different geometry designs and moving speeds of the blocker affect its performance in image reconstruction accuracy. The goal of this work is to optimize the geometric design and moving speed of the moving blocker system through experimental evaluations. Methods: An Elekta Synergy XVI system and an anthropomorphic pelvis phantom CIRS 801-P were used for our experiment. A blocker consisting of lead strips was inserted between the x-ray source and the phantom moving back and forth along rotation axis to measure the scatter signal. Accoriding to our Monte Carlo simulation results, three blockers were used, which have the same lead strip width 3.2mm and different gap between neighboring lead strips, 3.2, 6.4 and 9.6mm. For each blocker, three moving speeds were evaluated, 10, 20 and 30 pixels per projection (on the detector plane). Scatter signal in the unblocked region was estimated by cubic B-spline based interpolation from the blocked region. CBCT image was reconstructed by a total variation (TV) based algebraic iterative reconstruction (ART) algorithm from the partially blocked projection data. Reconstruction accuracy in each condition is quantified as CT number error of region of interest (ROI) by comparing to a CBCT reconstructed image from analytically simulated unblocked and scatter free projection data. Results: Highest reconstruction accuracy is achieved when the blocker width is 3.2 mm, the gap between neighboring lead strips is 9.6 mm and the moving speed is 20 pixels per projection. RMSE of the CT number of ROIs can be reduced from 436 to 27. Conclusions: Image reconstruction accuracy is greatly affected by the geometry design of the blocker. The moving speed does not have a very strong effect on reconstruction result if it is over 20 pixels per projection.

  13. [Microstructural changes in hardened beans (Phaseolus vulgaris)].

    Science.gov (United States)

    Mujica, Maria Virginia; Granito, Marisela; Soto, Naudy

    2015-06-01

    (Phaseolus vulgaris). The hardening of Phaseolus vulgaris beans stored at high temperature and high relative humidity is one of the main constraints for consumption. The objective of this research was to evaluate by scanning electron microscopy, structural changes in cotyledons and testa of the hardened beans. The freshly harvested grains were stored for twelve months under two conditions: 5 ° C-34% RH and 37 ° C-75% RH, in order to promote hardening. The stored raw and cooked grains were lyophilized and fractured. The sections of testa and cotyledons were observed in an electron microscope JSM-6390. After twelve months, grains stored at 37 ° C-75% RH increased their hardness by 503%, whereas there were no significant changes in grains stored at 5 ° C-34% RH. At the microstructural level, the cotyledons of the raw grains show clear differences in appearance of the cell wall, into the intercellular space size and texture matrix protein. There were also differences in compaction of palisade and sub-epidermal layer in the testa of raw grains. After cooking, cotyledon cells of the soft grains were well separated while these ofhard grains were seldom separated. In conclusion, the found differences in hard and soft grains showed a significant participation of both structures, cotyledons and testa, in the grains hardening.

  14. Radiation dose effects, hardening of electronic components

    International Nuclear Information System (INIS)

    Dupont-Nivet, E.

    1991-01-01

    This course reviews the mechanism of interaction between ionizing radiation and a silicon oxide type dielectric, in particular the effect of electron-hole pairs creation in the material. Then effects of cumulated dose on electronic components and especially in MOS technology are examined. Finally methods hardening of these components are exposed. 93 refs

  15. CASE-HARDENING OF STAINLESS STEEL

    DEFF Research Database (Denmark)

    2004-01-01

    The invention relates to case-hardening of a stainless steel article by means of gas including carbon and/or nitrogen, whereby carbon and/or nitrogen atoms diffuse through the surface into the article. The method includes activating the surface of the article, applying a top layer on the activated...

  16. Thermomechanical properties of radiation hardened oligoesteracrylates

    International Nuclear Information System (INIS)

    Lomonosova, N.V.; Chikin, Yu.A.

    1984-01-01

    Thermomechanical properties of radiation hardened oligoesteracrylates are studied by the methods of isothermal heating and thermal mechanics. Films of dimethacrylate of ethylene glycol, triethylene glycol (TGM-3), tetraethylene glycol, tridecaethylene glycol and TGM-3 mixture with methyl methacrylate hardened by different doses (5-150 kGy) using Co 60 installation with a dose rate of 2x10 -3 kGy/s served as a subject of the research. During oligoesteracrylate hargening a space network is formed, chain sections between lattice points of which are in a stressed state. Maximum of deformation is observed at 210-220 deg C on thermomechanical curves of samples hardened by doses > 5 kGy, which form and intensity is dependent on an absorbed dose. Presence of a high-temperature maximum on diaqrams of isometric heating of spatially cross-linked oligoesteracrylates is discovered. High thermal stability of three-dimensional network of radiation hardened oligoesteracrylates provides satisfactory tensile properties (40% of initial strength) in sample testing an elevated temperatures (200-250 deg C)

  17. Radiation hardened COTS-based 32-bit microprocessor

    International Nuclear Information System (INIS)

    Haddad, N.; Brown, R.; Cronauer, T.; Phan, H.

    1999-01-01

    A high performance radiation hardened 32-bit RISC microprocessor based upon a commercial single chip CPU has been developed. This paper presents the features of radiation hardened microprocessor, the methods used to radiation harden this device, the results of radiation testing, and shows that the RAD6000 is well-suited for the vast majority of space applications. (authors)

  18. Residual stresses in surface induction hardening of steels: Comparison between experiment and simulation

    International Nuclear Information System (INIS)

    Coupard, Dominique; Palin-luc, Thierry; Bristiel, Philippe; Ji, Vincent; Dumas, Christian

    2008-01-01

    Deep induction hardening has been performed on two batches of smooth cylindrical specimens with a hardening depth respectively around 2 mm and 3 mm. The distributions of axial and circumferential residual stresses are analysed for the two specimen batches by X-ray diffraction technique. The radial normal stress field is estimated through the use of the well known Moore and Evans correction. Finally, the experimental residual stresses are compared with those obtained from a multiphysic finite element modelling of the whole induction treatment process, including electromagnetic, thermal, metallurgical and mechanical phenomena. The simulated residual stress field is in good agreement with X-ray analysis especially at depths lower than one-tenth the specimen diameter. At deeper depths, a correction of the experimental X-ray analysis has been done to obtain realistic values

  19. WE-AB-BRA-08: Correction of Patient Motion in C-Arm Cone-Beam CT Using 3D-2D Registration

    International Nuclear Information System (INIS)

    Ouadah, S; Jacobson, M; Stayman, JW; Siewerdsen, JH; Ehtiati, T

    2016-01-01

    Purpose: Intraoperative C-arm cone-beam CT (CBCT) is subject to artifacts arising from patient motion during the fairly long (∼5–20 s) scan times. We present a fiducial free method to mitigate motion artifacts using 3D-2D image registration that simultaneously corrects residual errors in geometric calibration. Methods: A 3D-2D registration process was used to register each projection to DRRs computed from the 3D image by maximizing gradient orientation (GO) using the CMA-ES optimizer. The resulting rigid 6 DOF transforms were applied to the system projection matrices, and a 3D image was reconstructed via model-based image reconstruction (MBIR, which accommodates the resulting noncircular orbit). Experiments were conducted using a Zeego robotic C-arm (20 s, 200°, 496 projections) to image a head phantom undergoing various types of motion: 1) 5° lateral motion; 2) 15° lateral motion; and 3) 5° lateral motion with 10 mm periodic inferior-superior motion. Images were reconstructed using a penalized likelihood (PL) objective function, and structural similarity (SSIM) was measured for axial slices of the reconstructed images. A motion-free image was acquired using the same protocol for comparison. Results: There was significant improvement (p 0.99, indicating near identity to the motion-free reference. The point spread function (PSF) measured from a wire in the phantom was restored to that of the reference in each case. Conclusion: The 3D-2D registration method provides a robust framework for mitigation of motion artifacts and is expected to hold for applications in the head, pelvis, and extremities with reasonably constrained operative setup. Further improvement can be achieved by incorporating multiple rigid components and non-rigid deformation within the framework. The method is highly parallelizable and could in principle be run with every acquisition. Research supported by National Institutes of Health Grant No. R01-EB-017226 and academic

  20. Structural heredity influence upon principles of strain wave hardening

    Science.gov (United States)

    Kiricheck, A. V.; Barinov, S. V.; Yashin, A. V.

    2017-02-01

    It was established experimentally that by penetration of a strain wave through material hardened not only the technological modes of processing, but also a technological heredity - the direction of the fibers of the original macrostructure have an influence upon the diagram of microhardness. By penetration of the strain wave along fibers, the degree of hardening the material is less, however, a product is hardened throughout its entire section mainly along fibers. In the direction of the strain waves across fibers of the original structure of material, the degree of material hardening is much higher, the depth of the hardened layer with the degree of hardening not less than 50% makes at least 3 mm. It was found that under certain conditions the strain wave can completely change the original structure of the material. Thus, a heterogeneously hardened structure characterized by the interchange of harder and more viscous areas is formed, which is beneficial for assurance of high operational properties of material.

  1. Hydrogen embrittlement susceptibility of laser-hardened 4140 steel

    Energy Technology Data Exchange (ETDEWEB)

    Tsay, L.W.; Lin, Z.W. [Nat. Taiwan Ocean Univ., Keelung (Taiwan). Inst. of Mater. Eng.; Shiue, R.K. [Institute of Materials Sciences and Engineering, National Dong Hwa University, Hualien, Taiwan (Taiwan); Chen, C. [Institute of Materials Sciences and Engineering, National Taiwan University, Taipei, Taiwan (Taiwan)

    2000-10-15

    Slow strain rate tensile (SSRT) tests were performed to investigate the susceptibility to hydrogen embrittlement of laser-hardened AISI 4140 specimens in air, gaseous hydrogen and saturated H{sub 2}S solution. Experimental results indicated that round bar specimens with two parallel hardened bands on opposite sides along the loading axis (i.e. the PH specimens), exhibited a huge reduction in tensile ductility for all test environments. While circular-hardened (CH) specimens with 1 mm hardened depth and 6 mm wide within the gauge length were resistant to gaseous hydrogen embrittlement. However, fully hardened CH specimens became susceptible to hydrogen embrittlement for testing in air at a lower strain rate. The strength of CH specimens increased with decreasing the depth of hardened zones in a saturated H{sub 2}S solution. The premature failure of hardened zones in a susceptible environment caused the formation of brittle intergranular fracture and the decrease in tensile ductility. (orig.)

  2. Radiation-hardened optoelectronic components: detectors

    International Nuclear Information System (INIS)

    Wiczer, J.J.

    1986-01-01

    In this talk, we will survey recent research in the area of radiation hardened optical detectors. We have studied conventional silicon photodiode structures, special radiation hardened silicon photodiodes, and special double heterojunction AlGaAs/GaAs photodiodes in neutron, gamma, pulsed x-ray and charged particle environments. We will present results of our work and summarize other research in this area. Our studies have shown that detectors can be made to function acceptably after exposures to neutron fluences of 10 15 n/cm 2 , total dose gamma exposures of 10 8 rad (Si), and flash x-ray environments of 10 8 rad/sec (Si). We will describe detector structures that can operate through these conditions, pre-rad and post-rad operational characteristics, and experimental conditions that produced these results. 23 refs., 10 figs., 1 tab

  3. Hardened Solar Array High Temperature Adhesive.

    Science.gov (United States)

    1981-04-01

    SHERWOOO. D SASIU.IS F3361S-0-C-201S UNCLASSI ED 1AC-SCG-IOOIIR AFVAL-TR-OL-201? NLm,,hinii EhhhEE11I1 AFWAL-TR-81- 2017 i : HARDENED SOLAR ARRAY D HIGH...Tg and as a consequence forms a film on the container and also precipitates as tacky waxlike particles, rather than the desired flocullated

  4. Hardening by means of ionising radiation

    International Nuclear Information System (INIS)

    Spoor, H.; Demmler, K.

    1979-01-01

    The polymerisable ethylic unsaturated mixture can be hardened by means of electron irradiation and used as a corrosion preventive layer. The mixture mainly consists of at least a di-olefinic unsaturated polyester, partial esters of polycarbonic acids, in particular the monoester of dicarbonic acids, with a copolymerizable C-C double bond, and mono-olefine unsaturated hydrocarbons, for example vinyl aromatics. The coatings exhibit good adhesion to the substrate, in particular to metal, and good flexibility. (DG) [de

  5. The influence of limited kinematic hardening in shakedown analysis

    International Nuclear Information System (INIS)

    Nery, Domingos E.S.; Jospin, Reinaldo R.; Zouain, Nestor

    2009-01-01

    The use of the Design by Analysis concept is a trend in modern pressure vessel and piping calculations. DBA flexibility allow us to deal with unexpected configurations detected at in-service inspections. It is also important, in life extension calculations, when deviations of the original standard hypothesis adopted initially in Design by Formula, can happen. To apply the DBA to structures under variable mechanic and thermal loads, it is necessary that, alternate plasticity and incremental collapse (with instantaneous plastic collapse as a particular case), be precluded. These are two basic failure modes considered by ASME or European Standards in DBA. The shakedown theory is the tool available to achieve this goal. In order to apply it, is necessary only the range of the variable loads and the material properties. Precise, robust and efficient algorithms to solve the very large nonlinear optimization problems generated in numerical applications of the shakedown theory is a recent achievement. Zouain and co-workers developed one of these algorithms for elastic ideally-plastic materials. But, it is necessary to consider more realistic material properties in real practical applications. This paper shows an enhancement of this algorithm to dealing with limited kinematic hardening, a typical property of the usual steels. This is done using internal thermodynamic variables. A discrete algorithm is obtained using a plane stress, mixed finite element, with internal variable. An example, a beam encased in an end, under constant axial force and variable moment is presented to show the importance of considering the limited kinematic hardening in a shakedown analysis. (author)

  6. Fatigue of coated and laser hardened steels

    International Nuclear Information System (INIS)

    La Cruz, P. de.

    1990-01-01

    In the present work the effect of ion nitriding, laser hardening and hot dip galvanizing upon the fatigue limit and notch sensitivity of a B-Mn Swedish steel SS 2131 have been investigated. The fatigue tests were performed in plane reverse bending fatigue (R=1). The quenched and tempered condition was taken as the reference condition. The microstructure, microhardness, fracture surface and coating appearance of the fatigue surface treated specimens were studied. Residual stress and retained austenite measurements were also carried out. It was found that ion nitriding improves the fatigue limit by 53 % for smooth specimens and by 115 % for notched specimens. Laser hardening improves the fatigue limit by 18 % and 56 % for smooth and notched specimen respectively. Hot dip galvanizing gives a slight deterioration of the fatigue limit (9 % and 10 % for smooth and notched specimen respectively). Ion nitriding and laser hardening decrease the value of the notch sensitivity factor q by 78 % and 65 % respectively. Hot dip galvanizing does not modify it. A simple schematic model based on a residual stress distribution, has been used to explain the different effects. It seems that the presence of the higher compressive residual stresses and the higher uniformity of the microstructure may be the causes of the better fatigue performance of ion nitrided specimens. (119 refs.) (author)

  7. GRAVITY PIPELINE TRANSPORT FOR HARDENING FILLING MIXTURES

    Directory of Open Access Journals (Sweden)

    Leonid KROUPNIK

    2015-12-01

    Full Text Available In underground mining of solid minerals becoming increasingly common development system with stowing hardening mixtures. In this case the natural ore array after it is replaced by an artificial excavation of solidified filling mixture consisting of binder, aggregates and water. Such a mixture is prepared on the surface on special stowing complexes and transported underground at special stowing pipelines. However, it is transported to the horizons of a few kilometers, which requires a sustainable mode of motion of such a mixture in the pipeline. Hardening stowing mixture changes its rheological characteristics over time, which complicates the calculation of the parameters of pipeline transportation. The article suggests a method of determining the initial parameters of such mixtures: the status coefficient, indicator of transportability, coefficient of hydrodynamic resistance to motion of the mixture. These indicators characterize the mixture in terms of the possibility to transport it through pipes. On the basis of these indicators is proposed methodology for calculating the parameters of pipeline transport hardening filling mixtures in drift mode when traffic on the horizontal part of the mixture under pressure column of the mixture in the vertical part of the backfill of the pipeline. This technique allows stable operation is guaranteed to provide pipeline transportation.

  8. Evaluation of Retro recon for SRS planning correction according to the error of recognize to coordinate

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Hyeon Seok; Jeong, Deok Yang; Do, Gyeong Min; Lee, Yeong Cheol; KIm, Sun Myung; Kim, Young Bun [Dept. of Radiation Oncology, Korea University Guro Hospital, Seoul (Korea, Republic of)

    2016-12-15

    The purpose of this study was to evaluate the Retro recon in SRS planning using BranLAB when stereotactic location error occurs by metal artifact. By CT simulator, image were acquired from head phantom(CIRS, PTW, USA). To observe stereotactic location recognizing and beam hardening, CT image were approved by SRS planning system(BrainLAB, Feldkirchen, Germany). In addition, we compared acquisition image(1.25mm slice thickness) and Retro recon image(using for 2.5 mm, 5mm slice thickness). To evaluate these three images quality, the test were performed by AAPM phantom study. In patient, it was verified stereotactic location error. All the location recognizing error did not occur in scanned image of phantom. AAPM phantom scan images all showed the same trend. Contrast resolution and Spatial resolution are under 6.4 mm, 1.0 mm. In case of noise and uniformity, under 11, 5 of HU were measured. In patient, the stereotactic location error was not occurred at reconstructive image. For BrainLAB planning, using Retro recon were corrected stereotactic error at beam hardening. Retro recon may be the preferred modality for radiation treatment planning and approving image quality.

  9. Fatigue hardening and softening studies on strain hardened 18-8 austenitic stainless steel

    International Nuclear Information System (INIS)

    Ramakrishna Prasad, C.; Vasudevan, R.

    1976-01-01

    Metals when subjected to fatigue harden or soften depending on their previous mechanical history. Annealed or mildly cold worked metals are known to harden while severely cold worked metals soften when subjected to fatigue loading. In the present work samples of austenitic 18-8 steel cold worked to 11% and 22% reduction in area were mounted in a vertical pulsator and fatigued in axial tension-compression. Clear cut effects were produced and it was noticed that these depended on the extent of cold work, the amplitude as well as the number of cycles of fatigue and mean stress if any. (orig.) [de

  10. Beam-Beam Effects

    International Nuclear Information System (INIS)

    Herr, W; Pieloni, T

    2014-01-01

    One of the most severe limitations in high-intensity particle colliders is the beam-beam interaction, i.e. the perturbation of the beams as they cross the opposing beams. This introduction to beam-beam effects concentrates on a description of the phenomena that are present in modern colliding beam facilities

  11. Finite element analysis of FRP-strengthened RC beams

    Directory of Open Access Journals (Sweden)

    Teeraphot Supaviriyakit

    2004-05-01

    Full Text Available This paper presents a non-linear finite element analysis of reinforced concrete beam strengthened with externally bonded FRP plates. The finite element modeling of FRP-strengthened beams is demonstrated. Concrete and reinforcing bars are modeled together as 8-node isoparametric 2D RC element. The FRP plate is modeled as 8-node isoparametric 2D elastic element. The glue is modeled as perfect compatibility by directly connecting the nodes of FRP with those of concrete since there is no failure at the glue layer. The key to the analysis is the correct material models of concrete, steel and FRP. Cracks and steel bars are modeled as smeared over the entire element. Stress-strain properties of cracked concrete consist of tensile stress model normal to crack, compressive stress model parallel to crack and shear stress model tangential to crack. Stressstrain property of reinforcement is assumed to be elastic-hardening to account for the bond between concrete and steel bars. FRP is modeled as elastic-brittle material. From the analysis, it is found that FEM can predict the load-displacement relation, ultimate load and failure mode of the beam correctly. It can also capture the cracking process for both shear-flexural peeling and end peeling modes similar to the experiment.

  12. BUSFET -- A radiation-hardened SOI transistor

    International Nuclear Information System (INIS)

    Schwank, J.R.; Shaneyfelt, M.R.; Draper, B.L.; Dodd, P.E.

    1999-01-01

    The total-dose hardness of SOI technology is limited by radiation-induced charge trapping in gate, field, and SOI buried oxides. Charge trapping in the buried oxide can lead to back-channel leakage and makes hardening SOI transistors more challenging than hardening bulk-silicon transistors. Two avenues for hardening the back-channel are (1) to use specially prepared SOI buried oxides that reduce the net amount of trapped positive charge or (2) to design transistors that are less sensitive to the effects of trapped charge in the buried oxide. In this work, the authors propose a partially-depleted SOI transistor structure for mitigating the effects of trapped charge in the buried oxide on radiation hardness. They call this structure the BUSFET--Body Under Source FET. The BUSFET utilizes a shallow source and a deep drain. As a result, the silicon depletion region at the back channel caused by radiation-induced charge trapping in the buried oxide does not form a conducting path between source and drain. Thus, the BUSFET structure design can significantly reduce radiation-induced back-channel leakage without using specially prepared buried oxides. Total dose hardness is achieved without degrading the intrinsic SEU or dose rate hardness of SOI technology. The effectiveness of the BUSFET structure for reducing total-dose back-channel leakage depends on several variables, including the top silicon film thickness and doping concentration, and the depth of the source. 3-D simulations show that for a body doping concentration of 10 18 cm -3 , a drain bias of 3 V, and a source depth of 90 nm, a silicon film thickness of 180 nm is sufficient to almost completely eliminate radiation-induced back-channel leakage. However, for a doping concentration of 3 x 10 17 cm -3 , a thicker silicon film (300 nm) must be used

  13. Cone-beam CT image contrast and attenuation-map linearity improvement (CALI) for brain stereotactic radiosurgery procedures

    Science.gov (United States)

    Hashemi, Sayed Masoud; Lee, Young; Eriksson, Markus; Nordström, Hâkan; Mainprize, James; Grouza, Vladimir; Huynh, Christopher; Sahgal, Arjun; Song, William Y.; Ruschin, Mark

    2017-03-01

    A Contrast and Attenuation-map (CT-number) Linearity Improvement (CALI) framework is proposed for cone-beam CT (CBCT) images used for brain stereotactic radiosurgery (SRS). The proposed framework is used together with our high spatial resolution iterative reconstruction algorithm and is tailored for the Leksell Gamma Knife ICON (Elekta, Stockholm, Sweden). The incorporated CBCT system in ICON facilitates frameless SRS planning and treatment delivery. The ICON employs a half-cone geometry to accommodate the existing treatment couch. This geometry increases the amount of artifacts and together with other physical imperfections causes image inhomogeneity and contrast reduction. Our proposed framework includes a preprocessing step, involving a shading and beam-hardening artifact correction, and a post-processing step to correct the dome/capping artifact caused by the spatial variations in x-ray energy generated by bowtie-filter. Our shading correction algorithm relies solely on the acquired projection images (i.e. no prior information required) and utilizes filtered-back-projection (FBP) reconstructed images to generate a segmented bone and soft-tissue map. Ideal projections are estimated from the segmented images and a smoothed version of the difference between the ideal and measured projections is used in correction. The proposed beam-hardening and dome artifact corrections are segmentation free. The CALI was tested on CatPhan, as well as patient images acquired on the ICON system. The resulting clinical brain images show substantial improvements in soft contrast visibility, revealing structures such as ventricles and lesions which were otherwise un-detectable in FBP-reconstructed images. The linearity of the reconstructed attenuation-map was also improved, resulting in more accurate CT#.

  14. An Innovative Radiation Hardened CAM Architecture

    CERN Document Server

    Shojaii, Seyed Ruhollah; The ATLAS collaboration

    2018-01-01

    This article describes an innovative Content Addressable Memory (CAM) cell with radiation hardened (RH) architecture. The RH-CAM is designed in a commercial 28 nm CMOS technology. The circuit has been simulated in worst-case conditions, and the effects due to single particles have been analyzed by injecting a current pulse into a circuit node. The proposed architecture is suitable for on-time pattern recognition tasks in harsh environments, such as front-end electronics in hadron colliders and in space applications.

  15. Radiation-hardened nonvolatile MNOS RAM

    International Nuclear Information System (INIS)

    Wrobel, T.F.; Dodson, W.H.; Hash, G.L.; Jones, R.V.; Nasby, R.D.; Olson, R.J.

    1983-01-01

    A radiation hardened nonvolatile MNOS RAM is being developed at Sandia National Laboratories. The memory organization is 128 x 8 bits and utilizes two p-channel MNOS transistors per memory cell. The peripheral circuitry is constructed with CMOS metal gate and is processed with standard Sandia rad-hard processing techniques. The devices have memory retention after a dose-rate exposure of 1E12 rad(Si)/s, are functional after total dose exposure of 1E6 rad(Si), and are dose-rate upset resistant to levels of 7E8 rad(Si)/s

  16. Radiation-hardened CMOS integrated circuits

    International Nuclear Information System (INIS)

    Pikor, A.; Reiss, E.M.

    1980-01-01

    Substantial effort has been directed at radiation-hardening CMOS integrated circuits using various oxide processes. While most of these integrated circuits have been successful in demonstrating megarad hardness, further investigations have shown that the 'wet-oxide process' is most compatible with the RCA CD4000 Series process. This article describes advances in the wet-oxide process that have resulted in multimegarad hardness and yield to MIL-M-38510 screening requirements. The implementation of these advances into volume manufacturing is geared towards supplying devices for aerospace requirements such as the Defense Meterological Satellite program (DMSP) and the Global Positioning Satellite (GPS). (author)

  17. Application of submerged induction hardening; Ekichu koshuha yakiire no jitsuyoka

    Energy Technology Data Exchange (ETDEWEB)

    Nishimori, Y; Nagai, Y; Amii, Y [Mazda Motor Corp., Hiroshima (Japan); Tanaka, Y [Netsuren Co. Ltd., Tokyo (Japan); Mizuma, T [Toyo Advanced Technologies Co. Ltd., Hiroshima (Japan)

    1997-10-01

    As a cost-cutting measure, the linerless diesel engine was adopted by applying submerged induction hardening process which can harden partial inner surface of cylinder block bore. In applying this process, (1) development of induction coil which can form any shape of quenched pattern and (2) the development of machining technology which can hone precisely the distorted bore after quenching, were important. With these improvements, submerged Induction hardening was made practical. 1 ref., 11 figs.

  18. Hardening device, by inserts, of electronic component against radiation

    International Nuclear Information System (INIS)

    Val, C.

    1987-01-01

    The hardening device includes at least two materials, one with high atomic number with respect to the other. One of these materials is set as inserts in a layer of the other material. The hardening device is then made by stacking of such layers, the insert density varying from one layer to the other, making thus vary the atomic number resulting from the hardening device along its thickness, following a predefined law [fr

  19. Investigation of srawberry hardening in low temperatures in vitro

    OpenAIRE

    Lukoševičiūtė, Vanda; Rugienius, Rytis; Kavaliauskaitė, Danguolė

    2007-01-01

    Cold resistance of different strawberry varieties in vitro and ability to retain hardening after defrosting and repeated hardening. Phytohormons – gibberellin and abscisic acid added in the growing medium were investigated in Horticulture plant genetic and biotechnology department of LIH. We tried to model common conditions in temperate zone when freeze-thaw cycles often occur during wintertime. For investigation in vitro strawberries for the first time hardened in light at the temperature of...

  20. Configurable Radiation Hardened High Speed Isolated Interface ASIC, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — NVE Corporation will design and build an innovative, low cost, flexible, configurable, radiation hardened, galvanically isolated, interface ASIC chip set that will...

  1. Numerical model of phase transformation of steel C80U during hardening

    Directory of Open Access Journals (Sweden)

    T. Domański

    2007-12-01

    Full Text Available The article concerns numerical modelling of the phase transformations in solid state hardening of tool steel C80U. The transformations were assumed: initial structure – austenite, austenite – perlite, bainite and austenite – martensite. Model for evaluation of fractions of phases and their kinetics based on continuous heating diagram (CHT and continuous cooling diagram (CCT. The dilatometric tests on the simulator of thermal cycles were performed. The results of dilatometric tests were compared with the results of the test numerical simulations. In this way the derived models for evaluating phase content and kinetics of transformations in heating and cooling processes were verified. The results of numerical simulations confirm correctness of the algorithm that were worked out. In the numerical example the simulated estimation of the phase fraction in the hardened axisimmetrical element was performed.

  2. Iterative CT shading correction with no prior information

    Science.gov (United States)

    Wu, Pengwei; Sun, Xiaonan; Hu, Hongjie; Mao, Tingyu; Zhao, Wei; Sheng, Ke; Cheung, Alice A.; Niu, Tianye

    2015-11-01

    Shading artifacts in CT images are caused by scatter contamination, beam-hardening effect and other non-ideal imaging conditions. The purpose of this study is to propose a novel and general correction framework to eliminate low-frequency shading artifacts in CT images (e.g. cone-beam CT, low-kVp CT) without relying on prior information. The method is based on the general knowledge of the relatively uniform CT number distribution in one tissue component. The CT image is first segmented to construct a template image where each structure is filled with the same CT number of a specific tissue type. Then, by subtracting the ideal template from the CT image, the residual image from various error sources are generated. Since forward projection is an integration process, non-continuous shading artifacts in the image become continuous signals in a line integral. Thus, the residual image is forward projected and its line integral is low-pass filtered in order to estimate the error that causes shading artifacts. A compensation map is reconstructed from the filtered line integral error using a standard FDK algorithm and added back to the original image for shading correction. As the segmented image does not accurately depict a shaded CT image, the proposed scheme is iterated until the variation of the residual image is minimized. The proposed method is evaluated using cone-beam CT images of a Catphan©600 phantom and a pelvis patient, and low-kVp CT angiography images for carotid artery assessment. Compared with the CT image without correction, the proposed method reduces the overall CT number error from over 200 HU to be less than 30 HU and increases the spatial uniformity by a factor of 1.5. Low-contrast object is faithfully retained after the proposed correction. An effective iterative algorithm for shading correction in CT imaging is proposed that is only assisted by general anatomical information without relying on prior knowledge. The proposed method is thus practical

  3. Induction surface hardening of hard coated steels

    Energy Technology Data Exchange (ETDEWEB)

    Pantleon, K.; Kessler, O.; Hoffann, F.; Mayr, P. [Stiftung Inst. fuer Werkstofftechnik, Bremen (Germany)

    1999-11-01

    The properties of hard coatings deposited using CVD processes are usually excellent. However, high deposition temperatures negatively influence the substrate properties, especially in the case of low alloyed steels. Therefore, a subsequent heat treatment is necessary to restore the properties of steel substrates. Here, induction surface hardening is used as a method of heat treatment after the deposition of TiN hard coatings on AISI 4140 (DIN42CrMo4) substrates. The influences of the heat treatment on both the coating and the substrate properties are discussed in relation to the parameters of induction heating. Thereby, the heating time, heating atmosphere and the power input into the coating-substrate compounds are varied. As a result of induction surface hardening, the properties of the substrates are improved without losing good coating properties. High hardness values in the substrate near the interface allow the AISI 4140 substrates to support TiN hard coatings very well. Consequently, higher critical loads are measured in scratch tests after the heat treatment. Also, compressive residual stresses in the substrate are generated. In addition, only a very low distortion appears. (orig.)

  4. Adaptation of penelope Monte Carlo code system to the absorbed dose metrology: characterization of high energy photon beams and calculations of reference dosimeter correction factors; Adaptation du code Monte Carlo penelope pour la metrologie de la dose absorbee: caracterisation des faisceaux de photons X de haute energie et calcul de facteurs de correction de dosimetres de reference

    Energy Technology Data Exchange (ETDEWEB)

    Mazurier, J

    1999-05-28

    This thesis has been performed in the framework of national reference setting-up for absorbed dose in water and high energy photon beam provided with the SATURNE-43 medical accelerator of the BNM-LPRI (acronym for National Bureau of Metrology and Primary standard laboratory of ionising radiation). The aim of this work has been to develop and validate different user codes, based on PENELOPE Monte Carlo code system, to determine the photon beam characteristics and calculate the correction factors of reference dosimeters such as Fricke dosimeters and graphite calorimeter. In the first step, the developed user codes have permitted the influence study of different components constituting the irradiation head. Variance reduction techniques have been used to reduce the calculation time. The phase space has been calculated for 6, 12 and 25 MV at the output surface level of the accelerator head, then used for calculating energy spectra and dose distributions in the reference water phantom. Results obtained have been compared with experimental measurements. The second step has been devoted to develop an user code allowing calculation correction factors associated with both BNM-LPRI's graphite and Fricke dosimeters thanks to a correlated sampling method starting with energy spectra obtained in the first step. Then the calculated correction factors have been compared with experimental and calculated results obtained with the Monte Carlo EGS4 code system. The good agreement, between experimental and calculated results, leads to validate simulations performed with the PENELOPE code system. (author)

  5. Simulation-based artifact correction (SBAC) for metrological computed tomography

    Science.gov (United States)

    Maier, Joscha; Leinweber, Carsten; Sawall, Stefan; Stoschus, Henning; Ballach, Frederic; Müller, Tobias; Hammer, Michael; Christoph, Ralf; Kachelrieß, Marc

    2017-06-01

    Computed tomography (CT) is a valuable tool for the metrolocical assessment of industrial components. However, the application of CT to the investigation of highly attenuating objects or multi-material components is often restricted by the presence of CT artifacts caused by beam hardening, x-ray scatter, off-focal radiation, partial volume effects or the cone-beam reconstruction itself. In order to overcome this limitation, this paper proposes an approach to calculate a correction term that compensates for the contribution of artifacts and thus enables an appropriate assessment of these components using CT. Therefore, we make use of computer simulations of the CT measurement process. Based on an appropriate model of the object, e.g. an initial reconstruction or a CAD model, two simulations are carried out. One simulation considers all physical effects that cause artifacts using dedicated analytic methods as well as Monte Carlo-based models. The other one represents an ideal CT measurement i.e. a measurement in parallel beam geometry with a monochromatic, point-like x-ray source and no x-ray scattering. Thus, the difference between these simulations is an estimate for the present artifacts and can be used to correct the acquired projection data or the corresponding CT reconstruction, respectively. The performance of the proposed approach is evaluated using simulated as well as measured data of single and multi-material components. Our approach yields CT reconstructions that are nearly free of artifacts and thereby clearly outperforms commonly used artifact reduction algorithms in terms of image quality. A comparison against tactile reference measurements demonstrates the ability of the proposed approach to increase the accuracy of the metrological assessment significantly.

  6. Determination of recombination and polarity correction factors, kS and kP, for small cylindrical ionization chambers PTW 31021 and PTW 31022 in pulsed filtered and unfiltered beams.

    Science.gov (United States)

    Bruggmoser, Gregor; Saum, Rainer; Kranzer, Rafael

    2018-01-12

    The aim of this technical communication is to provide correction factors for recombination and polarity effect for two new ionization chambers PTW PinPoint 3D (type 31022) and PTW Semiflex 3D (type 31021). The correction factors provided are for the (based on the) German DIN 6800-2 dosimetry protocol and the AAPM TG51 protocol. The measurements were made in filtered and unfiltered high-energy photon beams in a water equivalent phantom at maximum depth of the PDD and a field size on the surface of 10cm×10cm. The design of the new chamber types leads to an ion collection efficiency and a polarity effect that are well within the specifications requested by pertinent dosimetry protocols including the addendum of TG-51. It was confirmed that the recombination effect of both chambers mainly depends on dose per pulse and is independent of the filtration of the photon beam. Copyright © 2018. Published by Elsevier GmbH.

  7. Hardness depth profiling of case hardened steels using a three-dimensional photothermal technique

    International Nuclear Information System (INIS)

    Qu Hong; Wang Chinhua; Guo Xinxin; Mandelis, Andreas

    2010-01-01

    A method of retrieving thermophysical depth profiles of continuously inhomogeneous materials is presented both theoretically and experimentally using the three-dimensional (3-D) photothermal radiometry. A 3-D theoretical model suitable for characterizing solids with arbitrary continuously varying thermophysical property depth profiles and finite (collimated or focused) laser beam spotsize is developed. A numerical fitting algorithm to retrieve the thermophysical profile was demonstrated with three case hardened steel samples. The reconstructed thermal conductivity depth profiles were found to be well anti-correlated with microhardness profiles obtained with the conventional indenter method.

  8. Bake hardening of nanograin AA7075 aluminum alloy

    International Nuclear Information System (INIS)

    Dehghani, Kamran

    2011-01-01

    Highlights: ► The bake hardening behavior of AA7075 was studied and compared with its coarse-grain counterpart. ► Nanograin AA7075 exhibited 88–100% increase in bake hardenability. ► Nanograin AA7075 exhibited 36–38% increase in final yield strength after baking. ► Maximum bake hardenability and final yield stress were about 185 MPa and 719 MPa. - Abstract: In the present work, the bake hardening of nanostructured AA7075 aluminum alloy was compared with that of its coarse-grain counterpart. Surface severe plastic deformation (SSPD) was used to produce nanograin layers on both surfaces of workpieces. The nanostructured layers were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The thickness of nanostructured layer, having the grains of 50–110 nm, was about 75 μm on each side of workpiece. The bake hardenability of nanograin and coarse-grain AA7075 was then compared by pre-straining to 2, 4 and 6% followed by baking at 100 °C and 200 °C for 20 min. Comparing to coarse-grain case, there was about 88–100% increase in bake hardenability and about 36–38% increase in yield strength after the bake hardening of present nanograin AA7075. Such an increase in bake hardenability and strength was achieved when the thickness of two nanograin layers was about only one-tenth of the whole thickness.

  9. Work hardening correlation for monotonic loading based on state variables

    International Nuclear Information System (INIS)

    Huang, F.H.; Li, C.Y.

    1977-01-01

    An absolute work hardening correlation in terms of the hardness parameter and the internal stress based on the state variable approach was developed. It was found applicable to a variety of metals and alloys. This correlation predicts strain rate insensitive work hardening properties at low homologous temperatures and produces strain rate effects at higher homologous temperatures without involving thermally induced recovery processes

  10. Analysis of the work-hardening process in spheroidized steels

    International Nuclear Information System (INIS)

    Pacheco, J.L.

    1981-07-01

    An elementary model for the work-hardening process in duplex-structures steels (ferrite - spheroidite) is proposed and tested on low, medium and high carbon content, which seems to give good results concerning the influence of the volume fraction and particle size of the second phase on the work-hardening behaviour. (Author) [pt

  11. Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

    Science.gov (United States)

    Shane X. Peng; Robert J. Moon; Jeffrey P. Youngblood

    2014-01-01

    Cellulose nanocrystals (CNCs) are renewable, sustainable, and abundant nanomaterial widely used as reinforcing fillers in the field of polymer nanocomposites. In this study, two-part epoxy systems with CNC-enhanced hardeners were fabricated. Three types of hardeners, Jeffamine D400 (JD400), diethylenetriamine (DETA), and (±)-trans-1,2- diaminocyclohexane (DACH), were...

  12. ANISOTROPIC STRAIN-HARDENING IN POLYCRYSTALLINE COPPER AND ALUMINUM

    NARCIS (Netherlands)

    HESS, F

    1993-01-01

    A new viscoplastic model for the plastic stress-strain behaviour of f.c.c. metals is presented. In this model the strain hardening results from increasing dislocation densities. The observed stagnation of strain hardening after strain reversals is explained by a lowering of the increase in

  13. Finite element implementation of strain-hardening Drucker–Prager plasticity model with application to tunnel excavation

    Directory of Open Access Journals (Sweden)

    K. Liu

    2017-09-01

    Full Text Available This paper presents a finite element implementation of a strain-hardening Drucker–Prager model and its application to tunnel excavation. The computational model was constructed based on the return mapping scheme, in which an elastic trial step was first executed, followed by plastic correction involving the Newton–Raphson method to return the predicted state of stresses to the supposed yield surface. By combining the plastic shear hardening rule and stress correction equations, the loading index for the strain-hardening Drucker–Prager model was solved. It is therefore possible to update the stresses, elastic and plastic strains, and slope of the yield locus at the end of each incremental step. As an illustrative example, an integration algorithm was incorporated into ABAQUS through the user subroutine UMAT to solve the tunnel excavation problem in strain-hardening Drucker–Prager rock formations. The obtained numerical results were found to be in excellent agreement with the available analytical solutions, thus indicating the validity and accuracy of the proposed UMAT code, as well as the finite element model.

  14. High dose-per-pulse electron beam dosimetry - A model to correct for the ion recombination in the Advanced Markus ionization chamber.

    Science.gov (United States)

    Petersson, Kristoffer; Jaccard, Maud; Germond, Jean-François; Buchillier, Thierry; Bochud, François; Bourhis, Jean; Vozenin, Marie-Catherine; Bailat, Claude

    2017-03-01

    The purpose of this work was to establish an empirical model of the ion recombination in the Advanced Markus ionization chamber for measurements in high dose rate/dose-per-pulse electron beams. In addition, we compared the observed ion recombination to calculations using the standard Boag two-voltage-analysis method, the more general theoretical Boag models, and the semiempirical general equation presented by Burns and McEwen. Two independent methods were used to investigate the ion recombination: (a) Varying the grid tension of the linear accelerator (linac) gun (controls the linac output) and measuring the relative effect the grid tension has on the chamber response at different source-to-surface distances (SSD). (b) Performing simultaneous dose measurements and comparing the dose-response, in beams with varying dose rate/dose-per-pulse, with the chamber together with dose rate/dose-per-pulse independent Gafchromic™ EBT3 film. Three individual Advanced Markus chambers were used for the measurements with both methods. All measurements were performed in electron beams with varying mean dose rate, dose rate within pulse, and dose-per-pulse (10 -2  ≤ mean dose rate ≤ 10 3 Gy/s, 10 2  ≤ mean dose rate within pulse ≤ 10 7  Gy/s, 10 -4  ≤ dose-per-pulse ≤ 10 1  Gy), which was achieved by independently varying the linac gun grid tension, and the SSD. The results demonstrate how the ion collection efficiency of the chamber decreased as the dose-per-pulse increased, and that the ion recombination was dependent on the dose-per-pulse rather than the dose rate, a behavior predicted by Boag theory. The general theoretical Boag models agreed well with the data over the entire investigated dose-per-pulse range, but only for a low polarizing chamber voltage (50 V). However, the two-voltage-analysis method and the Burns & McEwen equation only agreed with the data at low dose-per-pulse values (≤ 10 -2 and ≤ 10 -1  Gy, respectively). An empirical

  15. A radiation-hardened SOI-based FPGA

    International Nuclear Information System (INIS)

    Han Xiaowei; Wu Lihua; Zhao Yan; Li Yan; Zhang Qianli; Chen Liang; Zhang Guoquan; Li Jianzhong; Yang Bo; Gao Jiantou; Wang Jian; Li Ming; Liu Guizhai; Zhang Feng; Guo Xufeng; Chen, Stanley L.; Liu Zhongli; Yu Fang; Zhao Kai

    2011-01-01

    A radiation-hardened SRAM-based field programmable gate array VS1000 is designed and fabricated with a 0.5 μm partial-depletion silicon-on-insulator logic process at the CETC 58th Institute. The new logic cell (LC), with a multi-mode based on 3-input look-up-table (LUT), increases logic density about 12% compared to a traditional 4-input LUT The logic block (LB), consisting of 2 LCs, can be used in two functional modes: LUT mode and distributed read access memory mode. The hierarchical routing channel block and switch block can significantly improve the flexibility and routability of the routing resource. The VS1000 uses a CQFP208 package and contains 392 reconfigurable LCs, 112 reconfigurable user I/Os and IEEE 1149.1 compatible with boundary-scan logic for testing and programming. The function test results indicate that the hardware and software cooperate successfully and the VS1000 works correctly. Moreover, the radiation test results indicate that the VS1000 chip has total dose tolerance of 100 krad(Si), a dose rate survivability of 1.5 x 10 11 rad(Si)/s and a neutron fluence immunity of 1 x 10 14 n/cm 2 . (semiconductor integrated circuits)

  16. A review of the stages of work hardening

    Energy Technology Data Exchange (ETDEWEB)

    Rollett, A.D.; Kocks, U.F.

    1993-07-01

    Stages of work hardening are reviewed with emphasis on links between each stage. Simple quantitative descriptions are given for each stage. Similarities between stage I, easy glide, and stage IV, large strain hardening, are pointed out both in terms of magnitude of the hardening rate and of the underlying mechanism of dislocation debris accumulation. Stage II is described as an athermal hardening stage that occurs when statistical variations in the dislocation ``forest`` lead to geometrical storage of dislocations. The steadily decreasing hardening rate observed in stage III is characterized by the increasing rate of loss of dislocation density due to dynamic recovery. Stage III appears to have an asymptote to a saturation stress which is determined by the characteristics of the dislocation tangles, or cell walls. The imperfect nature of the dynamic recovery process, however, leads to the accumulation of dislocation debris and this, by analogy with stage 1, causes the apparent saturation stress to rise, thus causing stage IV.

  17. Keystroke Dynamics-Based Credential Hardening Systems

    Science.gov (United States)

    Bartlow, Nick; Cukic, Bojan

    abstract Keystroke dynamics are becoming a well-known method for strengthening username- and password-based credential sets. The familiarity and ease of use of these traditional authentication schemes combined with the increased trustworthiness associated with biometrics makes them prime candidates for application in many web-based scenarios. Our keystroke dynamics system uses Breiman’s random forests algorithm to classify keystroke input sequences as genuine or imposter. The system is capable of operating at various points on a traditional ROC curve depending on application-specific security needs. As a username/password authentication scheme, our approach decreases the system penetration rate associated with compromised passwords up to 99.15%. Beyond presenting results demonstrating the credential hardening effect of our scheme, we look into the notion that a user’s familiarity to components of a credential set can non-trivially impact error rates.

  18. Radiation hardening of MOS devices by boron

    International Nuclear Information System (INIS)

    Danchenko, V.

    1975-01-01

    A novel technique is disclosed for radiation hardening of MOS devices and specifically for stabilizing the gate threshold potential at room temperature of a radiation subjected MOS field-effect device of the type having a semiconductor substrate, an insulating layer of oxide on the substrate, and a gate electrode disposed on the insulating layer. In the preferred embodiment, the novel inventive technique contemplates the introduction of boron into the insulating oxide, the boron being introduced within a layer of the oxide of about 100A to 300A thickness immediately adjacent the semiconductor-insulator interface. The concentration of boron in the oxide layer is preferably maintained on the order of 10 atoms/ cm 3 . The novel technique serves to reduce and substantially annihilate radiation induced positive gate charge accumulations, which accumulations, if not eliminated, would cause shifting of the gate threshold potential of a radiation subjected MOS device, and thus render the device unstable and/or inoperative. (auth)

  19. Rapid cold hardening: a gut feeling.

    Science.gov (United States)

    Worland, M R; Convey, P; Luke ov , A

    2000-01-01

    This study examined the rate of cold hardening of a field population of Antarctic springtails and the effect of eating food with particular levels of ice nucleating activity on the animal's whole body freezing point. The SCPs of samples of c. 20, freshly collected, Cryptopygus antarcticus were measured hourly over a 32 hour collection period using differential scanning calorimetry and related to habitat temperature. The mean SCP of the springtails increased from -24 to -10 degree C during which time the habitat temperature warmed slowly from -2.5 to +2.5 degree C. In laboratory experiments, previously starved, cold tolerant springtails were fed on selected species of algae with measured SCP's but there was no clear correlation between the SCP of food and that of the animals after feeding. Microscopic examination of faecal pellets and guts from springtails showed that algal cells were completely destroyed during digestion.

  20. Laser quench hardening of steel: Effects of superimposed elastic pre-stress on the hardness and residual stress distribution

    Science.gov (United States)

    Meserve, Justin

    Cold drawn AISI 4140 beams were LASER surface hardened with a 2 kW CO2 LASER. Specimens were treated in the free state and while restrained in a bending fixture inducing surface tensile stresses of 94 and 230 MPa. Knoop hardness indentation was used to evaluate the through thickness hardness distribution, and a layer removal methodology was used to evaluate the residual stress distribution. Results showed the maximum surface hardness attained was not affected by pre-stress during hardening, and ranged from 513 to 676 kg/mm2. The depth of effective hardening varied at different magnitudes of pre-stress, but did not vary proportionately to the pre-stress. The surface residual stress, coinciding with the maximum compressive residual stress, increased as pre-stress was increased, from 1040 MPa for the nominally treated specimens to 1270 MPa for specimens pre-stressed to 230 MPa. The maximum tensile residual stress observed in the specimens decreased from 1060 MPa in the nominally treated specimens to 760 MPa for specimens pre-stressed to 230 MPa. Similarly, thickness of the compressive residual stress region increased and the depth at which maximum tensile residual stress occurred increased as the pre-stress during treatment was increased Overall, application of tensile elastic pre-stress during LASER hardening is beneficial to the development of compressive residual stress in AISI 4140, with minimal impact to the hardness attained from the treatment. The newly developed approach for LASER hardening may support efforts to increase both the wear and fatigue resistance of parts made from hardenable steels.

  1. Implementation of a cone-beam reconstruction algorithm for the single-circle source orbit with embedded misalignment correction using homogeneous coordinates

    International Nuclear Information System (INIS)

    Karolczak, Marek; Schaller, Stefan; Engelke, Klaus; Lutz, Andreas; Taubenreuther, Ulrike; Wiesent, Karl; Kalender, Willi

    2001-01-01

    We present an efficient implementation of an approximate cone-beam image reconstruction algorithm for application in tomography, which accounts for scanner mechanical misalignment. The implementation is based on the algorithm proposed by Feldkamp et al. [J. Opt. Soc. Am. A 6, 612-619 (1984)] and is directed at circular scan paths. The algorithm has been developed for the purpose of reconstructing volume data from projections acquired in an experimental x-ray microtomography (μCT) scanner [Engelke et al., Der Radiologe 39, 203-212 (1999)]. To mathematically model misalignment we use matrix notation with homogeneous coordinates to describe the scanner geometry, its misalignment, and the acquisition process. For convenience analysis is carried out for x-ray CT scanners, but it is applicable to any tomographic modality, where two-dimensional projection acquisition in cone beam geometry takes place, e.g., single photon emission computerized tomography. We derive an algorithm assuming misalignment errors to be small enough to weight and filter original projections and to embed compensation for misalignment in the backprojection. We verify the algorithm on simulations of virtual phantoms and scans of a physical multidisk (Defrise) phantom

  2. Comparison of orthogonal kilovolt X-ray images and cone-beam CT matching results in setup error assessment and correction for EB-PBI during free breathing

    International Nuclear Information System (INIS)

    Wang Wei; Li Jianbin; Hu Hongguang; Ma Zhifang; Xu Min; Fan Tingyong; Shao Qian; Ding Yun

    2014-01-01

    Objective: To compare the differences in setup error (SE) assessment and correction between the orthogonal kilovolt X-ray images and CBCT in EB-PBI patients during free breathing. Methods: Nineteen patients after breast conserving surgery EB-PBI were recruited. Interfraction SE was acquired using orthogonal kilovolt X-ray setup images and CBCT, after on-line setup correction,calculate the residual error and compare the SE, residual error and setup margin (SM) quantified for orthogonal kilovolt X-ray images and CBCT. Wilcoxon sign-rank test was used to evaluate the differences. Results: The CBCT based SE (systematic error, ∑) was smaller than the orthogonal kilovolt X-ray images based ∑ in AP direction (-1.2 mm vs 2.00 mm; P=0.005), and there was no statistically significant differences for three dimensional directions in random error (σ) (P=0.948, 0.376, 0.314). After on-line setup correction,CBCT decreases setup residual error than the orthogonal kilovolt X-ray images in AP direction (Σ: -0.20 mm vs 0.50 mm, P=0.008; σ: 0.45 mm vs 1.34 mm, P=0.002). And also the CBCT based SM was smaller than orthogonal kilovolt X-ray images based SM in AP direction (Σ: -1.39 mm vs 5.57 mm, P=0.003; σ: 0.00 mm vs 3.2 mm, P=0.003). Conclusions: Compared with kilovolt X-ray images, CBCT underestimate the setup error in the AP direction, but decreases setup residual error significantly.An image-guided radiotherapy and setup error assessment using kilovolt X-ray images for EB-PBI plans was feasible. (authors)

  3. Hardening and softening mechanisms of pearlitic steel wire under torsion

    International Nuclear Information System (INIS)

    Zhao, Tian-Zhang; Zhang, Shi-Hong; Zhang, Guang-Liang; Song, Hong-Wu; Cheng, Ming

    2014-01-01

    Highlights: • Mechanical behavior of pearlitic steel wire is studied using torsion. • Work hardening results from refinement lamellar pearlitic structure. • Softening results from recovery, shear bands and lamellar fragmentations. • A microstructure based analytical flow stress model is established. - Abstract: The mechanical behaviors and microstructure evolution of pearlitic steel wires under monotonic shear deformation have been investigated by a torsion test and a number of electron microscopy techniques including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), with an aim to reveal the softening and hardening mechanisms of a randomly oriented pearlitic structure during a monotonic stain path. Significantly different from the remarkable strain hardening in cold wire drawing, the strain hardening rate during torsion drops to zero quickly after a short hardening stage. The microstructure observations indicate that the inter-lamellar spacing (ILS) decreases and the dislocations accumulate with strain, which leads to hardening of the material. Meanwhile, when the strain is larger than 0.154, the enhancement of dynamic recovery, shear bands (SBs) and cementite fragmentations results in the softening and balances the strain hardening. A microstructure based analytical flow stress model with considering the influence of ILS on the mean free path of dislocations and the softening caused by SBs and cementite fragmentations, has been established and the predicted flow shear curve meets well with the measured curve in the torsion test

  4. Numerical and experimental comparison of plastic work-hardening rules

    International Nuclear Information System (INIS)

    Haisler, W.E.

    1977-01-01

    The purpose of this paper is to describe recent numerical and experimental correlation studies of several plastic work-hardening rules. The mechanical sublayer model and the combined kinematic-isotropic hardening rules are examined and the numerical results for several structural geometries are compared to experimental results. Both monotonic and cyclic loads are considered. The governing incremental plasticity relations are developed for both work-hardening models. The combined kinematic-isotropic hardening model is developed in terms of a ratio γ which controls the relative contribution of kinematic hardening (yield surface translation) and isotropic hardening (yield surface expansion). In addition to making use of a uniaxial stress-strain curve as input data, the model allows for the input of a yield surface size vs. uniaxial plastic strain curve obtained from a cyclic uniaxial reverse loading test. The mechanical sublayer model is developed in general form and a new method for determining the sublayer parameters (stress weighting factors and yield stresses) is presented. It is demonstrated that former procedures used to obtain the sublayer parameters are inconsistent for multiaxial loading. Numerical and experimental results are presented for a cylinder, circular plate with punch, and a steel pressure vessel. The numerical results are obtained with the computer program AGGIE I. The comparison study indicates that reasonable agreement is obtained with both hardening models; the choice depending upon whether the loading is monotonic or cyclic

  5. Histogram-driven cupping correction (HDCC) in CT

    Science.gov (United States)

    Kyriakou, Y.; Meyer, M.; Lapp, R.; Kalender, W. A.

    2010-04-01

    Typical cupping correction methods are pre-processing methods which require either pre-calibration measurements or simulations of standard objects to approximate and correct for beam hardening and scatter. Some of them require the knowledge of spectra, detector characteristics, etc. The aim of this work was to develop a practical histogram-driven cupping correction (HDCC) method to post-process the reconstructed images. We use a polynomial representation of the raw-data generated by forward projection of the reconstructed images; forward and backprojection are performed on graphics processing units (GPU). The coefficients of the polynomial are optimized using a simplex minimization of the joint entropy of the CT image and its gradient. The algorithm was evaluated using simulations and measurements of homogeneous and inhomogeneous phantoms. For the measurements a C-arm flat-detector CT (FD-CT) system with a 30×40 cm2 detector, a kilovoltage on board imager (radiation therapy simulator) and a micro-CT system were used. The algorithm reduced cupping artifacts both in simulations and measurements using a fourth-order polynomial and was in good agreement to the reference. The minimization algorithm required less than 70 iterations to adjust the coefficients only performing a linear combination of basis images, thus executing without time consuming operations. HDCC reduced cupping artifacts without the necessity of pre-calibration or other scan information enabling a retrospective improvement of CT image homogeneity. However, the method can work with other cupping correction algorithms or in a calibration manner, as well.

  6. Beam Techniques - Beam Control and Manipulation

    International Nuclear Information System (INIS)

    Minty, Michiko G

    2003-01-01

    We describe commonly used strategies for the control of charged particle beams and the manipulation of their properties. Emphasis is placed on relativistic beams in linear accelerators and storage rings. After a brief review of linear optics, we discuss basic and advanced beam control techniques, such as transverse and longitudinal lattice diagnostics, matching, orbit correction and steering, beam-based alignment, and linac emittance preservation. A variety of methods for the manipulation of particle beam properties are also presented, for instance, bunch length and energy compression, bunch rotation, changes to the damping partition number, and beam collimation. The different procedures are illustrated by examples from various accelerators. Special topics include injection and extraction methods, beam cooling, spin transport and polarization

  7. Beam Techniques - Beam Control and Manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Minty, Michiko G

    2003-04-24

    We describe commonly used strategies for the control of charged particle beams and the manipulation of their properties. Emphasis is placed on relativistic beams in linear accelerators and storage rings. After a brief review of linear optics, we discuss basic and advanced beam control techniques, such as transverse and longitudinal lattice diagnostics, matching, orbit correction and steering, beam-based alignment, and linac emittance preservation. A variety of methods for the manipulation of particle beam properties are also presented, for instance, bunch length and energy compression, bunch rotation, changes to the damping partition number, and beam collimation. The different procedures are illustrated by examples from various accelerators. Special topics include injection and extraction methods, beam cooling, spin transport and polarization.

  8. Facial soft-tissue asymmetry in three-dimensional cone-beam computed tomography images of children with surgically corrected unilateral clefts.

    Science.gov (United States)

    Starbuck, John Marlow; Ghoneima, Ahmed; Kula, Katherine

    2014-03-01

    Cleft lip with or without cleft palate (CL/P) is a relatively common craniofacial malformation involving bony and soft-tissue disruptions of the nasolabial and dentoalveolar regions. The combination of CL/P and subsequent craniofacial surgeries to close the cleft and improve appearance of the cutaneous upper lip and nose can cause scarring and muscle pull, possibly resulting in soft-tissue depth asymmetries across the face. We tested the hypothesis that tissue depths in children with unilateral CL/P exhibit differences in symmetry across the sides of the face. Twenty-eight tissue depths were measured on cone-beam computed tomography images of children with unilateral CL/P (n = 55), aged 7 to 17 years, using Dolphin software (version 11.5). Significant differences in tissue depth symmetry were found around the cutaneous upper lip and nose in patients with unilateral CL/P.

  9. Work hardening behavior study of structural alloys for cryogenic applications

    International Nuclear Information System (INIS)

    Chu, D.; Morris, J.W. Jr.

    1992-01-01

    Previous investigation on aluminum-lithium alloys have indicated different dependencies of the work hardening behavior on temperature. This variation in temperature dependence is attributed to differences in microstructure rather than composition. An understanding of the microstructural effect on the observed thermal dependency is important as it may allow the tailoring of deformation properties through mechanical processing. Work hardening analyses on other aluminum alloys and a number of structural steels have been performed to better elucidate the role played by microstructure in determining the work hardening behavior. In the paper correlations between the differences in mechanical behavior and the various microstructures observed are presented

  10. Effect of strain rate and temperature on strain hardening behavior of a dissimilar joint between Ti–6Al–4V and Ti17 alloys

    International Nuclear Information System (INIS)

    Wang, S.Q.; Liu, J.H.; Chen, D.L.

    2014-01-01

    Highlights: • Only stage III hardening occurs after yielding in Ti–6Al–4V/Ti17 dissimilar joints. • Voce stress and strength of the joints increase with increasing strain rate. • With increasing strain rate, hardening capacity and strain hardening exponent decrease. • With increasing temperature, hardening capacity and strain hardening exponent increase. • Strain rate sensitivity of the joints decreases as the true strain increases. - Abstract: The aim of this study was to evaluate the influence of strain rate and temperature on the tensile properties, strain hardening behavior, strain rate sensitivity, and fracture characteristics of electron beam welded (EBWed) dissimilar joints between Ti–6Al–4V and Ti17 (Ti–5Al–4Mo–4Cr–2Sn–2Zr) titanium alloys. The welding led to significant microstructural changes across the joint, with hexagonal close-packed martensite (α′) and orthorhombic martensite (α″) in the fusion zone (FZ), α′ in the heat-affected zone (HAZ) on the Ti–6Al–4V side, and coarse β in the HAZ on the Ti17 side. A distinctive asymmetrical hardness profile across the dissimilar joint was observed with the highest hardness in the FZ and a lower hardness on the Ti–6Al–4V side than on the Ti17 side, where a soft zone was present. Despite a slight reduction in ductility, the yield strength (YS) and ultimate tensile strength (UTS) of the joints lay in-between the two base metals (BMs) of Ti–6Al–4V and Ti17, with the Ti17 alloy having a higher strength. While the YS, UTS, and Voce stress of the joints increased, both hardening capacity and strain hardening exponent decreased with increasing strain rate or decreasing temperature. Stage III hardening occurred in the joints after yielding. The hardening rate was strongly dependent on the strain rate and temperature. As the strain rate increased or temperature decreased, the strain hardening rate increased at a given true stress. The strain rate sensitivity evaluated via

  11. Application of low energy electron beam to precoated steel plates

    International Nuclear Information System (INIS)

    Koshiishi, Kenji

    1989-01-01

    Recently in the fields of home electric appliances, machinery and equipment and interior building materials, the needs for the precoated steel plates having the design and function of high class increase rapidly. In order to cope with such needs, the authors have advanced the examination on the application of electron beam hardening technology to precoated steel plates, and developed the precoated steel plates of high grade and high design 'Super Tecstar EB Series' by utilizing low energy electron beam. The features of this process are (1) hardening can be done at room temperature in a short time-thermally weak films can be adhered, (2) high energy irradiation-the hardening of thick enamel coating and the adhesion of colored films are feasible, (3) the use of monomers of low molecular weight-by high crosslinking, the performance of high sharpness, high hardness, anti-contamination property and so on can be given. The application to precoated steel plate production process is the coating and curing of electron beam hardening type paints, the coating of films with electron beam hardening type adhesives, and the reforming of surface polymer layers by impregnating monomers and causing graft polymerization with electron beam irradiation. The outline of the Super Tecstar EB Series is described. (K.I.)

  12. Open Source Radiation Hardened by Design Technology

    Science.gov (United States)

    Shuler, Robert

    2016-01-01

    The proposed technology allows use of the latest microcircuit technology with lowest power and fastest speed, with minimal delay and engineering costs, through new Radiation Hardened by Design (RHBD) techniques that do not require extensive process characterization, technique evaluation and re-design at each Moore's Law generation. The separation of critical node groups is explicitly parameterized so it can be increased as microcircuit technologies shrink. The technology will be open access to radiation tolerant circuit vendors. INNOVATION: This technology would enhance computation intensive applications such as autonomy, robotics, advanced sensor and tracking processes, as well as low power applications such as wireless sensor networks. OUTCOME / RESULTS: 1) Simulation analysis indicates feasibility. 2)Compact voting latch 65 nanometer test chip designed and submitted for fabrication -7/2016. INFUSION FOR SPACE / EARTH: This technology may be used in any digital integrated circuit in which a high level of resistance to Single Event Upsets is desired, and has the greatest benefit outside low earth orbit where cosmic rays are numerous.

  13. Radiation-hardened microwave communications system

    International Nuclear Information System (INIS)

    Smith, S.F.; Crutcher, R.I.; Vandermolen, R.I.

    1990-01-01

    The consolidated fuel reprocessing program (CFRP) at the Oak Ridge National Laboratory (ORNL) has been developing signal transmission techniques and equipment to improve the efficiency of remote handling operations for nuclear applications. These efforts have been largely directed toward the goals of (a) remotely controlling bilateral force-reflecting servomanipulators for dexterous manipulation-based operations in remote maintenance tasks and (b) providing television viewing of the work site. In September 1987, developmental microwave transceiving hardware operating with dish antennas was demonstrated in the advanced integrated maintenance system (AIMS) facility at ORNL, successfully implementing both high-quality one-way television transmissions and simultaneous bidirectional digital control data transmissions with very low error rates. Initial test results based on digital transmission at a 1.0-Mbaud data rate indicated that the error rates of the microwave system were comparable to those of a hardwired system. During these test intervals, complex manipulator operations were performed, and the AIMS transporter was moved repeatedly without adverse effects on data integrity. Results of these tests have been factored into subsequent phases of the development program, with an ultimate goal of designing a fully radiation-hardened microwave signal transmission system for use in nuclear facilities

  14. Determination of the Kwall correction factor for a cylindrical ionization chamber to measure air-kerma in 60Co gamma beams

    International Nuclear Information System (INIS)

    Laitano, R.F.; Toni, M.P.; Pimpinella, M.; Bovi, M.

    2002-01-01

    The factor K wall to correct for photon attenuation and scatter in the wall of ionization chambers for 60 Co air-kerma measurement has been traditionally determined by a procedure based on a linear extrapolation of the chamber current to zero wall thickness. Monte Carlo calculations by Rogers and Bielajew (1990 Phys. Med. Biol. 35 1065-78) provided evidence, mostly for chambers of cylindrical and spherical geometry, of appreciable deviations between the calculated values of K wall and those obtained by the traditional extrapolation procedure. In the present work an experimental method other than the traditional extrapolation procedure was used to determine the K wall factor. In this method the dependence of the ionization current in a cylindrical chamber was analysed as a function of an effective wall thickness in place of the physical (radial) wall thickness traditionally considered in this type of measurement. To this end the chamber wall was ideally divided into distinct regions and for each region an effective thickness to which the chamber current correlates was determined. A Monte Carlo calculation of attenuation and scatter effects in the different regions of the chamber wall was also made to compare calculation to measurement results. The K wall values experimentally determined in this work agree within 0.2% with the Monte Carlo calculation. The agreement between these independent methods and the appreciable deviation (up to about 1%) between the results of both these methods and those obtained by the traditional extrapolation procedure support the conclusion that the two independent methods providing comparable results are correct and the traditional extrapolation procedure is likely to be wrong. The numerical results of the present study refer to a cylindrical cavity chamber like that adopted as the Italian national air-kerma standard at INMRI-ENEA (Italy). The method used in this study applies, however, to any other chamber of the same type. (author)

  15. The accident of overexposure at the University hospital center of Toulouse. Expertise report n.1. Checking of experimental protocols of micro-beams calibration before and after dysfunction correction

    International Nuclear Information System (INIS)

    2007-01-01

    The regional center of stereotaxic radiosurgery of the University hospital center of Toulouse is equipped since april 2006 of a Novalis accelerator (Brainlab) devoted to the intra-skull stereotaxic radiosurgery. In april 2007, during an intercomparison of dosimetry computer files coming from different sites, the Brainlab society finds an anomaly in the files. The analysis made by the society concludes to to the use of an inappropriate detector for the measurement of a dosimetry parameter during the initial calibration of the accelerator. following this error, 145 patients (on the 172 treated by the service in question) suffer the consequences of an overdose whom importance is variable according the cases. The I.R.S.N. in charge of an expertise about the protocols of calibration of micro-beams before and after the correction of the dysfunction, took up with the search of the technical causes of the dysfunction. This report presents successively: the documents base on which is founded the expertise; the material of dosimetry and quality control necessary to the initial calibration of the device and to its follow-up; the formula made at the accelerator commissioning; the calibration of micro-beams in the two configurations that allows the device (micro-multi-knives and conic collimator) and the definition of parameters of the software of treatment planning; the maintenance and quality control implemented in the frame of its clinical use. (N.C.)

  16. A Radiation Hardened Housekeeping Slave Node (RH-HKSN) ASIC

    Data.gov (United States)

    National Aeronautics and Space Administration — This projects seeks to continue the development of the Radiation Hardened Housekeeping Slave Node (RH-HKSN) ASIC. The effort has taken parallel paths by implementing...

  17. Stress corrosion cracking evaluation of precipitation-hardening stainless steel

    Science.gov (United States)

    Humphries, T. S.; Nelson, E. E.

    1970-01-01

    Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure.

  18. Radiation-chemical hardening of phenol-formaldehyde oligomers

    International Nuclear Information System (INIS)

    Shlapatskaya, V.V.; Omel'chenko, S.I.

    1978-01-01

    Radiation-chemical hardening of phenol formaldehyde oligomers of the resol type has been studied in the presence of furfural and diallylphthalate diluents. The samples have been hardened on an electron accelerator at an electron energy of 1.0-1.1 MeV and a dose rate of 2-3 Mrad/s. The kinetics of hardening has been studied on the yield of gel fraction within the range of absorbed doses from 7 to 400 Mrad. Radiation-chemical hardening of the studied compositions is activated with sensitizers, namely, amines, metal chlorides, and heterocyclic derivatives of metals. Furfural and diallylphthalate compositions are suitable for forming glass-fibre plastic items by the wet method and coatings under the action of ionizing radiations

  19. Technologies Enabling Custom Radiation-Hardened Component Development, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Two primary paths are available for the creation of a Rad-Hard ASIC. The first approach is to use a radiation hardened process such as existing Rad-Hard foundries....

  20. system hardening architecture for safer access to critical business

    African Journals Online (AJOL)

    eobe

    System hardening is a defence strategy, where several different security measures are applied at various layers, all of which .... commerce have tremendously imparted on corporate services ..... Technology and Exploring Engineering, Vol. 2,.

  1. Space Qualified, Radiation Hardened, Dense Monolithic Flash Memory, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Radiation hardened nonvolatile memories for space is still primarily confined to EEPROM. There is high density effective or cost effective NVM solution available to...

  2. Generation Mechanism of Work Hardened Surface Layer in Metal Cutting

    Science.gov (United States)

    Hikiji, Rikio; Kondo, Eiji; Kawagoishi, Norio; Arai, Minoru

    Finish machining used to be carried out in grinding, but it is being replaced by cutting with very small undeformed chip thickness. In ultra precision process, the effects of the cutting conditions and the complicated factors on the machined surface integrity are the serious problems. In this research, work hardened surface layer was dealt with as an evaluation of the machined surface integrity and the effect of the mechanical factors on work hardening was investigated experimentally in orthogonal cutting. As a result, it was found that work hardened surface layer was affected not only by the shear angle varied under the cutting conditions and the thrust force of cutting resistance, but also by the thrust force acting point, the coefficient of the thrust force and the compressive stress equivalent to the bulk hardness. Furthermore, these mechanical factors acting on the depth of the work hardened surface layer were investigated with the calculation model.

  3. Radiation Hardened Ethernet PHY and Switch Fabric, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Innoflight will develop a new family of radiation hardened (up to 3 Mrad(Si)), fault-tolerant, high data-rate (up to 8 Gbps), low power Gigabit Ethernet PHY and...

  4. Space Qualified, Radiation Hardened, Dense Monolithic Flash Memory, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Space Micro proposes to build a radiation hardened by design (RHBD) flash memory, using a modified version of our RH-eDRAM Memory Controller to solve all the single...

  5. System Hardening Architecture for Safer Access to Critical Business ...

    African Journals Online (AJOL)

    System Hardening Architecture for Safer Access to Critical Business Data. ... and the threat is growing faster than the potential victims can deal with. ... in this architecture are applied to the host, application, operating system, user, and the ...

  6. DMILL circuits. The hardened electronics decuples its performances

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Thanks to the DMILL (mixed logic-linear hardening) technology under development at the CEA, MHS, a French company specialized in the fabrication of integrated circuits now produces hardened electronic circuits ten times more resistant to radiations than its competitors. Outside the initial market (several thousands of circuits for the LHC particle accelerator of Geneva), a broad choice of applications is opened to this technology: national defense, space, civil nuclear and medical engineering, and high temperature applications. Short paper. (J.S.)

  7. Micromilling of hardened tool steel for mould making applications

    DEFF Research Database (Denmark)

    Bissacco, Giuliano; Hansen, Hans Nørgaard; De Chiffre, Leonardo

    2005-01-01

    geometries as those characterizing injection moulding moulds. The realization of the micromilling process in connection with hardened tool steel as workpiece material is particularly challenging. The low strength of the miniaturized end mills implies reduction and accurate control of the chip load which...... wear. This paper presents the micromilling process applied to the manufacturing of micro injection moulding moulds in hardened tool steel, presenting experimental evidence and possible solutions to the above-mentioned issues....

  8. Radiation hardening of metals irradiated by heavy ions

    International Nuclear Information System (INIS)

    Didyk, A.Yu.; Skuratov, V.A.; Mikhajlova, N.Yu.; Regel', V.R.

    1988-01-01

    The damage dose dependence in the 10 -4 -10 -2 dpa region of radiation hardening of Al, V, Ni, Cu irradiated by xenon ions with 124 MeV energy is investigated using the microhardness technique and transmission electron microscope. It is shown that the pure metals radiation hardening is stimulated for defects clusters with the typical size less than 5 nm, as in the case of neutron and the light charge ion irradiation

  9. Radiation-hardened bulk Si-gate CMOS microprocessor family

    International Nuclear Information System (INIS)

    Stricker, R.E.; Dingwall, A.G.F.; Cohen, S.; Adams, J.R.; Slemmer, W.C.

    1979-01-01

    RCA and Sandia Laboratories jointly developed a radiation-hardened bulk Si-gate CMOS technology which is used to fabricate the CDP-1800 series microprocessor family. Total dose hardness of 1 x 10 6 rads (Si) and transient upset hardness of 5 x 10 8 rads (Si)/sec with no latch up at any transient level was achieved. Radiation-hardened parts manufactured to date include the CDP-1802 microprocessor, the CDP-1834 ROM, the CDP-1852 8-bit I/O port, the CDP-1856 N-bit 1 of 8 decoder, and the TCC-244 256 x 4 Static RAM. The paper is divided into three parts. In the first section, the basic fundamentals of the non-hardened C 2 L technology used for the CDP-1800 series microprocessor parts is discussed along with the primary reasons for hardening this technology. The second section discusses the major changes in the fabrication sequence that are required to produce radiation-hardened devices. The final section details the electrical performance characteristics of the hardened devices as well as the effects of radiation on device performance. Also included in this section is a discussion of the TCC-244 256 x 4 Static RAM designed jointly by RCA and Sandia Laboratories for this application

  10. Developing precipitation hardenable high entropy alloys

    Science.gov (United States)

    Gwalani, Bharat

    High entropy alloys (HEAs) is a concept wherein alloys are constructed with five or more elements mixed in equal proportions; these are also known as multi-principle elements (MPEs) or complex concentrated alloys (CCAs). This PhD thesis dissertation presents research conducted to develop precipitation-hardenable high entropy alloys using a much-studied fcc-based equi-atomic quaternary alloy (CoCrFeNi). Minor additions of aluminium make the alloy amenable for precipitating ordered intermetallic phases in an fcc matrix. Aluminum also affects grain growth kinetics and Hall-Petch hardenability. The use of a combinatorial approach for assessing composition-microstructure-property relationships in high entropy alloys, or more broadly in complex concentrated alloys; using laser deposited compositionally graded AlxCrCuFeNi 2 (0 mechanically processed via conventional techniques. The phase stability and mechanical properties of these alloys have been investigated and will be presented. Additionally, the activation energy for grain growth as a function of Al content in these complex alloys has also been investigated. Change in fcc grain growth kinetic was studied as a function of aluminum; the apparent activation energy for grain growth increases by about three times going from Al0.1CoCrFeNi (3% Al (at%)) to Al0.3CoCrFeNi. (7% Al (at%)). Furthermore, Al addition leads to the precipitation of highly refined ordered L12 (gamma') and B2 precipitates in Al0.3CoCrFeNi. A detailed investigation of precipitation of the ordered phases in Al0.3CoCrFeNi and their thermal stability is done using atom probe tomography (APT), transmission electron microscopy (TEM) and Synchrotron X-ray in situ and ex situ analyses. The alloy strengthened via grain boundary strengthening following the Hall-Petch relationship offers a large increment of strength with small variation in grain size. Tensile strength of the Al0.3CoFeNi is increased by 50% on precipitation fine-scale gamma' precipitates

  11. Zinc coated sheet steel for press hardening

    Science.gov (United States)

    Ghanbari, Zahra N.

    Galvanized steels are of interest to enhance corrosion resistance of press-hardened steels, but concerns related to liquid metal embrittlement have been raised. The objective of this study was to assess the soak time and temperature conditions relevant to the hot-stamping process during which Zn penetration did or did not occur in galvanized 22MnB5 press-hardening steel. A GleebleRTM 3500 was used to heat treat samples using hold times and temperatures similar to those used in industrial hot-stamping. Deformation at both elevated temperature and room temperature were conducted to assess the coating and substrate behavior related to forming (at high temperature) and service (at room temperature). The extent of alloying between the coating and substrate was assessed on undeformed samples heat treated under similar conditions to the deformed samples. The coating transitioned from an α + Gamma1 composition to an α (bcc Fe-Zn) phase with increased soak time. This transition likely corresponded to a decrease in availability of Zn-rich liquid in the coating during elevated temperature deformation. Penetration of Zn into the substrate sheet in the undeformed condition was not observed for any of the processing conditions examined. The number and depth of cracks in the coating and substrate steel was also measured in the hot-ductility samples. The number of cracks appeared to increase, while the depth of cracks appeared to decrease, with increasing soak time and increasing soak temperature. The crack depth appeared to be minimized in the sample soaked at the highest soak temperature (900 °C) for intermediate and extended soak times (300 s or 600 s). Zn penetration into the substrate steel was observed in the hot-ductility samples soaked at each hold temperature for the shortest soak time (10 s) before being deformed at elevated temperature. Reduction of area and elongation measurements showed that the coated sample soaked at the highest temperature and longest soak time

  12. Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

    Science.gov (United States)

    Mohan, Nisha

    Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

  13. Study of the mechanisms involved in the laser superficial hardening process of metallic alloys; Estudo dos mecanismos envolvidos no processo de endurecimento superficial a laser de ligas metalicas

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Edmara Marques Rodrigues da

    2001-07-01

    The laser superficial hardening process of a ferrous alloy (gray cast iron) and of an aluminum-silicon alloy was investigated in this work. These metallic alloys are used in the automobile industry for manufacturing cylinders and pistons, respectively. By application of individual pulses and single tracks, the involved mechanisms during the processing were studied. Variables such as energy density, power density, temporal width, beam diameter on the sample surface, atmosphere of the processing region, overlapping and scanning velocity. The hardened surface was characterized by optical and scanning electronic microscopy, dispersive energy microanalysis, X-ray mapping, X-ray diffraction, and measurements of roughness and Vickers microhardness. Depending on the processing parameters, it is possible to obtain different microstructures. The affected area of gray cast iron, can be hardened by remelting or transformation hardening (total or partial) if the reached temperature is higher or not that of melting temperature. Laser treatment originated new structures such as retained austenite, martensite and, occasionally, eutectic of cellular dendritic structure. Aluminum-silicon alloy does not have phase transformation in solid state, it can be hardened only by remelting. The increase of hardness is a function of the precipitation hardening process, which makes the silicon particles smaller and more disperse in the matrix. Maximal values of microhardness (700-1000 HV) were reached with the laser treatment in gray cast iron samples. The initial microhardness is of 242 HV. For aluminum-silicon alloy, the laser remelting increases the initial microhardness of 128 HV to the range of 160-320 HV. The found results give a new perspective for using the CLA/IPEN's laser in the heat treatment area. Besides providing a higher absorptivity to the materials, compared with the CO{sub 2} laser, and optical fiber access, the superficial hardening with Nd:YAG laser, depending on the

  14. Optical cone beam tomography of Cherenkov-mediated signals for fast 3D dosimetry of x-ray photon beams in water.

    Science.gov (United States)

    Glaser, Adam K; Andreozzi, Jacqueline M; Zhang, Rongxiao; Pogue, Brian W; Gladstone, David J

    2015-07-01

    To test the use of a three-dimensional (3D) optical cone beam computed tomography reconstruction algorithm, for estimation of the imparted 3D dose distribution from megavoltage photon beams in a water tank for quality assurance, by imaging the induced Cherenkov-excited fluorescence (CEF). An intensified charge-coupled device coupled to a standard nontelecentric camera lens was used to tomographically acquire two-dimensional (2D) projection images of CEF from a complex multileaf collimator (MLC) shaped 6 MV linear accelerator x-ray photon beam operating at a dose rate of 600 MU/min. The resulting projections were used to reconstruct the 3D CEF light distribution, a potential surrogate of imparted dose, using a Feldkamp-Davis-Kress cone beam back reconstruction algorithm. Finally, the reconstructed light distributions were compared to the expected dose values from one-dimensional diode scans, 2D film measurements, and the 3D distribution generated from the clinical Varian ECLIPSE treatment planning system using a gamma index analysis. A Monte Carlo derived correction was applied to the Cherenkov reconstructions to account for beam hardening artifacts. 3D light volumes were successfully reconstructed over a 400 × 400 × 350 mm(3) volume at a resolution of 1 mm. The Cherenkov reconstructions showed agreement with all comparative methods and were also able to recover both inter- and intra-MLC leaf leakage. Based upon a 3%/3 mm criterion, the experimental Cherenkov light measurements showed an 83%-99% pass fraction depending on the chosen threshold dose. The results from this study demonstrate the use of optical cone beam computed tomography using CEF for the profiling of the imparted dose distribution from large area megavoltage photon beams in water.

  15. Process design of press hardening with gradient material property influence

    International Nuclear Information System (INIS)

    Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

    2011-01-01

    Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

  16. Publisher Correction

    DEFF Research Database (Denmark)

    Turcot, Valérie; Lu, Yingchang; Highland, Heather M

    2018-01-01

    In the published version of this paper, the name of author Emanuele Di Angelantonio was misspelled. This error has now been corrected in the HTML and PDF versions of the article.......In the published version of this paper, the name of author Emanuele Di Angelantonio was misspelled. This error has now been corrected in the HTML and PDF versions of the article....

  17. Author Correction

    DEFF Research Database (Denmark)

    Grundle, D S; Löscher, C R; Krahmann, G

    2018-01-01

    A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.......A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper....

  18. Influence of Hardening Model on Weld Residual Stress Distribution

    Energy Technology Data Exchange (ETDEWEB)

    Mullins, Jonathan; Gunnars, Jens (Inspecta Technology AB, Stockholm (Sweden))

    2009-06-15

    This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

  19. Influence of Hardening Model on Weld Residual Stress Distribution

    International Nuclear Information System (INIS)

    Mullins, Jonathan; Gunnars, Jens

    2009-06-01

    This study is the third stage of a project sponsored by the Swedish Radiation Safety Authority (SSM) to improve the weld residual stress modelling procedures currently used in Sweden. The aim of this study was to determine which material hardening model gave the best agreement with experimentally measured weld residual stress distributions. Two girth weld geometries were considered: 19mm and 65mm thick girth welds with Rin/t ratios of 10.5 and 2.8, respectively. The FE solver ABAQUS Standard v6.5 was used for analysis. As a preliminary step some improvements were made to the welding simulation procedure used in part one of the project. First, monotonic stress strain curves and a mixed isotropic/kinematic hardening model were sourced from the literature for 316 stainless steel. Second, more detailed information was obtained regarding the geometry and welding sequence for the Case 1 weld (compared with phase 1 of this project). Following the preliminary step, welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for future use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under estimate the magnitude of the axial stress. It must be noted that two different sources of data were used for the isotropic and mixed models in this study and this may have contributed to the discrepancy in predictions. When defining a mixed hardening model it is difficult to delineate the relative contributions of isotropic and kinematic hardening and for the model used it may be that a greater isotropic hardening component should have been specified. The kinematic hardening model consistently underestimated the magnitude of both the axial and hoop stress and is not recommended for use. Two sensitivity studies were also conducted. In the first the effect of using a

  20. THE SECONDARY EXTINCTION CORRECTION

    Energy Technology Data Exchange (ETDEWEB)

    Zachariasen, W. H.

    1963-03-15

    It is shown that Darwin's formula for the secondary extinction correction, which has been universally accepted and extensively used, contains an appreciable error in the x-ray diffraction case. The correct formula is derived. As a first order correction for secondary extinction, Darwin showed that one should use an effective absorption coefficient mu + gQ where an unpolarized incident beam is presumed. The new derivation shows that the effective absorption coefficient is mu + 2gQ(1 + cos/sup 4/2 theta )/(1 plus or minus cos/sup 2/2 theta )/s up 2/, which gives mu + gQ at theta =0 deg and theta = 90 deg , but mu + 2gQ at theta = 45 deg . Darwin's theory remains valid when applied to neutron diffraction. (auth)

  1. Computer modelling of age hardening for cast aluminium alloys

    International Nuclear Information System (INIS)

    Wu, Linda; Ferguson, W George

    2009-01-01

    Age hardening, or precipitation hardening, is one of the most widely adopted techniques for strengthening of aluminium alloys. Although various age hardening models have been developed for aluminium alloys, from the large volume of literature reviewed, it appears that the bulk of the research has been concentrated on wrought aluminium alloys, only a few of the established precipitation models have been applied to the casting aluminium alloys. In the present work, there are two modelling methods that have been developed and applied to the casting aluminium alloys A356 and A357. One is based on the Shercliff-Ashby methodology to produce a process model, by which we mean a mathematical relationship between process variables (alloy composition, ageing temperature and time) and material properties (yield strength or hardness) through microstructure evolution (precipitate radius, volume fraction). The other method is based on the Kampmann and Wagner Numerical (KWN) model which deals with concomitant nucleation, growth and coarsening and is thus capable of predicting the full evolution of the particle size distribution and then a strength model is used to evaluate the resulting change in hardness or yield strength at room temperature by taking into account contributions from lattice resistance, solid solution hardening and precipitation hardening.

  2. General analytical shakedown solution for structures with kinematic hardening materials

    Science.gov (United States)

    Guo, Baofeng; Zou, Zongyuan; Jin, Miao

    2016-09-01

    The effect of kinematic hardening behavior on the shakedown behaviors of structure has been investigated by performing shakedown analysis for some specific problems. The results obtained only show that the shakedown limit loads of structures with kinematic hardening model are larger than or equal to those with perfectly plastic model of the same initial yield stress. To further investigate the rules governing the different shakedown behaviors of kinematic hardening structures, the extended shakedown theorem for limited kinematic hardening is applied, the shakedown condition is then proposed, and a general analytical solution for the structural shakedown limit load is thus derived. The analytical shakedown limit loads for fully reversed cyclic loading and non-fully reversed cyclic loading are then given based on the general solution. The resulting analytical solution is applied to some specific problems: a hollow specimen subjected to tension and torsion, a flanged pipe subjected to pressure and axial force and a square plate with small central hole subjected to biaxial tension. The results obtained are compared with those in literatures, they are consistent with each other. Based on the resulting general analytical solution, rules governing the general effects of kinematic hardening behavior on the shakedown behavior of structure are clearly.

  3. Investigation of hardening behavior in Xe ion-irradiated Zr–1Nb

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Chunguang [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); China Institute of Atomic Energy, Beijing 102413 (China); Wang, Rongshan [Life Management Technology Center, Suzhou Nuclear Power Research Institute, Suzhou 215004 (China); Dai, Xianyuan [Fujian Fuqing Nuclear Power Co., Ltd., Fuqing 350318 (China); Wang, Yanli, E-mail: wangyl@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Xitao [Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083 (China); Bai, Guanghai; Zhang, Yanwei [Life Management Technology Center, Suzhou Nuclear Power Research Institute, Suzhou 215004 (China)

    2016-05-15

    Irradiation hardening behavior of Zr–1Nb was examined by nanoindentation, slow positron annihilation technique, transmission electron microscopy and coplanar extremely asymmetric X-ray diffraction technique. Samples were irradiated at a dose rate of 2.78 × 10{sup −4} dpa/s to peak doses of 0.15, 0.5, 1.5 and 2.5 dpa with 6.37 MeV Xe{sup 26+} ion beam at room temperature. The increase in hardness as a function of dose followed a power law expression with the exponent of 0.46. With increasing irradiation dose, more mono-, di- and trivacancies were induced, but their concentration remained constant once formed due to the equilibrium between the formation and recombination of vacancy type clusters during irradiation. Meanwhile, the dislocation loops were also introduced and their linear density increased with dose. The dislocation loops played an important role in the irradiation hardening behavior. But the exact contribution of each microstructural components to the overall hardness still needs further study.

  4. A general shakedown theorem for elastic/plastic bodies with work hardening

    International Nuclear Information System (INIS)

    Ponter, A.R.S.

    1975-01-01

    In recent years the design of metallic structures under variable loading has been assisted by the application of Melan's lower bound theorem for the shakedown of an elastic/perfectly plastic structure. The design codes for both portal frames and pressure vessels have taken account of such calculations. The theory of shakedown suffers from two defects, geometry changes are ignored and the material behavior is described by a perfectly plastic constitutive relationship which includes neither work hardening nor the Bauschinger effect. This paper is concerned with the latter problem. A very general lower bound shakedown theorem for an arbitrary time-independent material in terms of functional properties of the constitutive relationship is derived. The theorem is then applied to perfect, isotropic and kinematic hardening plasticity. It is shown that the result for all three constitutive relationships may be related to each other through certain extremal stress histories. As well as providing a sufficient condition for shakedown, the theory also provides bounds of the deflection of the structure in the process of reaching the shakedown state. The bounds are discussed and derived for two simple beam problems. Both static and dynamic problems are considered. The theory derived in this paper demonstrates that shakedown analysis may be extended to a wide range of material behavior without increasing the complexity of the resulting calculation

  5. Dual-beam CRT

    International Nuclear Information System (INIS)

    1975-01-01

    A dual-beam cathode-ray tube having a pair of electron guns and associated deflection means disposed side-by-side on each side of a central axis is described. The electron guns are parallel and the deflection means includes beam centering plates and angled horizontal deflection plates to direct the electron beams toward the central axis, precluding the need for a large-diameter tube neck in which the entire gun structures are angled. Bowing control plates are disposed adjacent to the beam centering plates to minimize trace bowing, and an intergun shield is disposed between the horizontal deflection plates to control and correct display pattern geometry distortion

  6. Analyzing the Curriculum of the Faculty of Medicine, University of Gezira using Harden's 10 questions framework.

    Science.gov (United States)

    Ahmed, Yasar Albushra; Alneel, Salma

    2017-04-01

    Despite the importance of curriculum analysis for internal refinement of a programme, the approach for such a step in under-described in the literature. This article describes the analysis of the medical curriculum at the Faculty of Medicine, University of Gezira (FMUG). This analysis is crucial in the era of innovative medical education since introducing new curricula and curricular changes has become a common occurrence in medical education worldwide. The curriculum analysis was qualitatively approached using descriptive analysis and adopting Harden's 10 Questions of curriculum development framework approach. Answering Harden's questions reflects the fundamental curricular components and how the different aspects of a curriculum framework fit together. The key features highlighted in the curriculum-related material and literature have been presented. The analysis of the curriculum of FMUG reveals a curriculum with interactive components. Clear structured objectives and goals reflect the faculty's vision. The approach for needs assessment is based on a scientific ground, and the curriculum integrated contents have been set to meet national and international requirements. Adopting SPICES strategies helps FMUG and students achieve the objectives of the curriculum. Multiple motivated instructional methods are adopted, fostering coping with the programme objectives and outcomes. A wide range of assessment methods has been adopted to assess the learning outcomes of the curriculum correctly, reliably, and in alignment with the intended outcomes. The prevailing conducive educational environment of FMUG is favourable for its operation and profoundly influences the outcome of the programme. And there is a well-defined policy for curriculum management, monitoring and evaluation. Harden's 10 questions are satisfactorily addressed by the multi-disciplinary and well-developed FMUG curriculum. The current curriculum supports the well-written faculty missions and educational

  7. Influence of coolant motion on structure of hardened steel element

    Directory of Open Access Journals (Sweden)

    A. Kulawik

    2008-08-01

    Full Text Available Presented paper is focused on volumetric hardening process using liquid low melting point metal as a coolant. Effect of convective motion of the coolant on material structure after hardening is investigated. Comparison with results obtained for model neglecting motion of liquid is executed. Mathematical and numerical model based on Finite Element Metod is described. Characteristic Based Split (CBS method is used to uncouple velocities and pressure and finally to solve Navier-Stokes equation. Petrov-Galerkin formulation is employed to stabilize convective term in heat transport equation. Phase transformations model is created on the basis of Johnson-Mehl and Avrami laws. Continuous cooling diagram (CTPc for C45 steel is exploited in presented model of phase transformations. Temporary temperatures, phases participation, thermal and structural strains in hardening element and coolant velocities are shown and discussed.

  8. Investigation of magnesium oxychloride cement at the initial hardening stage

    Directory of Open Access Journals (Sweden)

    Averina Galina

    2018-01-01

    Full Text Available The paper investigates the process of variation of magnesium oxychloride cement deformations at the initial hardening stage depending on the activity of magnesium oxide powder which is determined by the parameters of the source material burning. Investigation is focused on magnesium cements obtained from pure magnesium hydroxide. Source materials were burnt at various temperatures with the purpose to obtain magnesium oxide powder with different activity. Regular content of hydrated phases was determined in hardened magnesium cement prepared on the basis of binders with different activity. The study reveals the influence of magnesium oxide powder activity on the process of deformation occurrence in hardened magnesium cement and its tendency to crack formation.

  9. Effect of ethephon on hardening of Pachystroma longifolium seedlings

    Directory of Open Access Journals (Sweden)

    João Alexandre Lopes Dranski

    2013-06-01

    Full Text Available Immediately after planting, tree seedlings face adverse environmental and biotic stresses that must be overcome to ensure survival and to yield a desirable growth. Hardening practices in the nursery may help improve seedling stress resistance through reduction of aboveground plant tissues and increased root volume and biomass. We conducted an assay to quantify changes in the morphogenesis following application of ethephon on seedlings of Pachystroma longifolium (Ness I. M. Johnst.during hardening. The results showed no effect of the ethephon treatments on the number of leaves but a reduction of up to 50% in seedling height increment, and an increase in stem diameter increment of up to 44% with the 600 mg L-1 ethephon treatment, which consequently altered seedling Dickson Quality Index. Our results indicate that ethephon may help to promote desired morphological changes that occur during seedling hardening in nurseries.

  10. Branching structure and strain hardening of branched metallocene polyethylenes

    International Nuclear Information System (INIS)

    Torres, Enrique; Li, Si-Wan; Costeux, Stéphane; Dealy, John M.

    2015-01-01

    There have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers

  11. Branching structure and strain hardening of branched metallocene polyethylenes

    Energy Technology Data Exchange (ETDEWEB)

    Torres, Enrique; Li, Si-Wan; Costeux, Stéphane; Dealy, John M., E-mail: john.dealy@mcgill.ca [Department of Chemical Engineering, McGill University, Montreal, Quebec H3A 0C4 (Canada)

    2015-09-15

    There have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers.

  12. Nonlinear kinematic hardening under non-proportional loading

    International Nuclear Information System (INIS)

    Ottosen, N.S.

    1979-07-01

    Within the framework of conventional plasticity theory, it is first determined under which conditions Melan-Prager's and Ziegler's kinematic hardening rules result in identical material behaviour. Next, assuming initial isotropy and adopting the von Mises yield criterion, a nonlinear kinematic hardening function is proposed for prediction of metal behaviour. The model assumes that hardening at a specific stress point depends on the direction of the new incremental loading. Hereby a realistic response is obtained for general reversed loading, and a smooth behaviour is assured, even when loading deviates more and more from proportional loading and ultimately results in reversed loading. The predictions of the proposed model for non-proportional loading under plane stress conditions are compared with those of the classical linear kinematic model, the isotropic model and with published experimental data. Finally, the limitations of the proposaed model are discussed. (author)

  13. Why semiconductors must be hardened when used in space

    International Nuclear Information System (INIS)

    Winokur, P.S.

    2000-01-01

    The natural space radiation environment presents a great challenge to present and future satellite systems with significant assets in space. Defining requirements for such systems demands knowledge about the space radiation environment and its effects on electronics and optoelectronics technologies, as well as suitable risk assessment of the uncertainties involved. For mission of high radiation levels, radiation-hardened integrated circuits will be required to preform critical mission functions. The most successful systems in space will be those that are best able to blend standard commercial electronics with custom radiation-hardened electronics in a mix that is suitable for the system of interest

  14. Influence of anisotropic hardening on longitudinal welding strains and stresses

    International Nuclear Information System (INIS)

    Gatovskij, K.M.; Revutskij, M.N.

    1981-01-01

    The algorithm and program for estimation of longitudinal welding strains and stresses with account of hardening and Bauschinger effect, which expand the possibilities of more complete description of stress change during thermodeformation welding cycles at bead surfacing on plate made of the 06Kh18N9T steel and AMg61 alloy. It is shown that for metals, deformation curves which are characterized by considerable yield moduli (Esub(T)/E>=0.05) hardening effect is considerable and its account leads to the decrease of stress level in the heataffected zone (down to 20%) [ru

  15. Radiation Hardened 10BASE-T Ethernet Physical Layer (PHY)

    Science.gov (United States)

    Lin, Michael R. (Inventor); Petrick, David J. (Inventor); Ballou, Kevin M. (Inventor); Espinosa, Daniel C. (Inventor); James, Edward F. (Inventor); Kliesner, Matthew A. (Inventor)

    2017-01-01

    Embodiments may provide a radiation hardened 10BASE-T Ethernet interface circuit suitable for space flight and in compliance with the IEEE 802.3 standard for Ethernet. The various embodiments may provide a 10BASE-T Ethernet interface circuit, comprising a field programmable gate array (FPGA), a transmitter circuit connected to the FPGA, a receiver circuit connected to the FPGA, and a transformer connected to the transmitter circuit and the receiver circuit. In the various embodiments, the FPGA, transmitter circuit, receiver circuit, and transformer may be radiation hardened.

  16. Aspect-oriented security hardening of UML design models

    CERN Document Server

    Mouheb, Djedjiga; Pourzandi, Makan; Wang, Lingyu; Nouh, Mariam; Ziarati, Raha; Alhadidi, Dima; Talhi, Chamseddine; Lima, Vitor

    2015-01-01

    This book comprehensively presents a novel approach to the systematic security hardening of software design models expressed in the standard UML language. It combines model-driven engineering and the aspect-oriented paradigm to integrate security practices into the early phases of the software development process. To this end, a UML profile has been developed for the specification of security hardening aspects on UML diagrams. In addition, a weaving framework, with the underlying theoretical foundations, has been designed for the systematic injection of security aspects into UML models. The

  17. Work hardening and plastic equation of state of tantalum

    International Nuclear Information System (INIS)

    Gypen, L.A.; Aernoudt, E.; Deruyttere, A.

    1983-01-01

    The influence of cold deformation on the thermal and athermal components of the flow stress of tantalum was investigated. Up to high deformation levels the strain hardening is due only to the development of internal stress fields; the effective stress remains almost constant. The athermal strain hardening of tantalum is parabolic at low deformation levels (epsilon < 0.5) and linear at high deformation levels, as for other bcc metals. Hart's plastic equation of state is shown to be valid for tantalum at room temperature in the whole deformation range investigated (from epsilon = 0.005 to epsilon = 2.8). (author)

  18. Microstructure and properties of cast iron after laser surface hardening

    Directory of Open Access Journals (Sweden)

    Stanislav

    2013-12-01

    Full Text Available Laser surface hardening of cast iron is not trivial due to the material’s heterogeneity and coarse-grained microstructure, particularly in massive castings. Despite that, hardening of heavy moulds for automotive industry is in high demand. The present paper summarises the findings collected over several years of study of materials structure and surface properties. Phase transformations in the vicinity of graphite are described using examples from production of body parts in automotive industry. The description relates to formation of martensite and carbide-based phases, which leads to hardness values above 65 HRC and to excellent abrasion resistance.

  19. Numerical simulations of progressive hardening by using ABAQUS FEA software

    Directory of Open Access Journals (Sweden)

    Domański Tomasz

    2018-01-01

    Full Text Available The paper concerns numerical simulations of progressive hardening include phase transformations in solid state of steel. Abaqus FEA software is used for numerical analysis of temperature field and phase transformations. Numerical subroutines, written in fortran programming language are used in computer simulations where models of the distribution of movable heat source, kinetics of phase transformations in solid state as well as thermal and structural strain are implemented. Model for evaluation of fractions of phases and their kinetics is based on continuous heating diagram and continuous cooling diagram. The numerical analysis of thermal fields, phase fractions and strain associated progressive hardening of elements made of steel were done.

  20. Exploration of a radiation hardening stabilized voltage power supply

    International Nuclear Information System (INIS)

    Xie Zeyuan; Xu Xianguo

    2014-01-01

    This paper mainly introduces the design method of radiation hardening stabilized voltage power supply that makes use of commercial radiation resistant electronic devices and the test results of radiation performance of the power supply and devices are presented in detail. The experiment results show that the hardened power supply can normally work until 1000 Gy (Si) total dose and 1 × 10 14 n/cm 2 neutron radiation, and it doesn't latchup at about 1 × l0 9 Gy (Si)/s gamma transient dose rate. (authors)

  1. Effect of aluminizing on hardenability of steel (S45C)

    Science.gov (United States)

    Prayitno, D.; Sugiarto, R.

    2018-01-01

    The objective of research is to know the effect of aluminizing on hardenability of steel (S45C). The research methodologies were as follows. The Steels (S45C) were machined into the Jominy test samples. Next the samples were preheating at 700 ° C for 30 minutes and then the samples were dipped into the molten of aluminium for 3 minutes as a hot dip aluminizng method. The aluminium molten was 700 ° C. Then the samples were cooled into room temperatures. Finally the samples were into the jominy tested. The results show that the aluminizing (include the preheating process) increases the hardenability of steel (S45C).

  2. Structure of hardened alloys of Sr-Rh system

    International Nuclear Information System (INIS)

    Dobromyslov, A.V.; Taluth, N.I.

    1997-01-01

    Methods of X-ray diffraction analysis, optical metallography, transmission electron microscopy and hardness measurement were applied to study the structure of hardened zirconium-rhodium system alloys with rhodium contents up to 4.5 at.%. It is shown that in hardening alloys with rhodium concentration lower 2.2 at.% the eutectoid decomposition takes place and bainite-like structure is formed. A metastable ω-phase is formed in alloys with rhodium concentration equal to 2.65 at.% and above. The formation of ω-phase suppresses the process of eutectoid decomposition

  3. Changes in hardness of magnesium alloys due to precipitation hardening

    Directory of Open Access Journals (Sweden)

    Tatiana Oršulová

    2018-04-01

    Full Text Available This paper deals with the evaluation of changes in hardness of magnesium alloys during precipitation hardening that are nowadays widely used in different fields of industry. It focuses exactly on AZ31, AZ61 and AZ91 alloys. Observing material hardness changes serves as an effective tool for determining precipitation hardening parameters, such as temperature and time. Brinell hardness measurement was chosen based on experimental needs. There was also necessary to make chemical composition analysis and to observe the microstructures of tested materials. The obtained results are presented and discussed in this paper.

  4. Thermal stress ratcheting analysis of a time-hardening structure

    International Nuclear Information System (INIS)

    Hada, Kazuhiko

    1999-01-01

    Thermal stress ratcheting and shakedown is analyzed for a time-hardening structure: the yield stress increases as time goes on under exposure to neutron irradiation or thermal aging. New three modes of ratcheting and shakedown are identified as transition to other deformation modes. Stress regimes and thermal ratchet strains are formulated as a function of time-increasing yield stress. Moreover, a new model of trouble occurrence frequency as a modification to a bath-tube curve is proposed for calculating a time period of a thermal cycle. Application of the proposed formulation tells us a benefit of taking into account the time hardening due to neutron irradiation. (author)

  5. Experimental studies on beam-plasma interaction

    International Nuclear Information System (INIS)

    Kiwamoto, Y.

    1977-01-01

    Beam-handling technology has reached now at such a level as to enable highly controlled experiments of beam-plasma interaction. Varieties of hypotheses and suppositions about the beam propagation and interaction in space plasma can be proved and often be corrected by examining the specific processes in laboratory plasma. The experiments performed in this way by the author are briefed: ion beam instability in unmagnetized plasma; ion beam instability perpendicular to magnetic field; and electron beam instability. (Mori, K.)

  6. Nonlinear dynamics of spring softening and hardening in folded-mems comb drive resonators

    KAUST Repository

    Elshurafa, Amro M.

    2011-08-01

    This paper studies analytically and numerically the spring softening and hardening phenomena that occur in electrostatically actuated microelectromechanical systems comb drive resonators utilizing folded suspension beams. An analytical expression for the electrostatic force generated between the combs of the rotor and the stator is derived and takes into account both the transverse and longitudinal capacitances present. After formulating the problem, the resulting stiff differential equations are solved analytically using the method of multiple scales, and a closed-form solution is obtained. Furthermore, the nonlinear boundary value problem that describes the dynamics of inextensional spring beams is solved using straightforward perturbation to obtain the linear and nonlinear spring constants of the beam. The analytical solution is verified numerically using a Matlab/Simulink environment, and the results from both analyses exhibit excellent agreement. Stability analysis based on phase plane trajectory is also presented and fully explains previously reported empirical results that lacked sufficient theoretical description. Finally, the proposed solutions are, once again, verified with previously published measurement results. The closed-form solutions provided are easy to apply and enable predicting the actual behavior of resonators and gyroscopes with similar structures. © 2011 IEEE.

  7. Application of electron beam irradiation, (1). Development and application of electron beam processors

    International Nuclear Information System (INIS)

    Katsumura, Yosuke

    1994-01-01

    This paper deals with characteristics, equipment (principle and kinds), present conditions, and future issues in the application of electron beam irradiation. Characteristics of electron beams are described in terms of the following: chemical and biological effects of radiation; energy and penetrating power of electron beams; and principle and kinds of electron beam accelerator. Industrial application of electron beam irradiation has advantages of high speed procedure and producibility, less energy, avoidance of poisonous gas, and extreme reduction of organic solvents to be used. The present application of electron beam irradiation cen be divided into the following: (1) hardening of resin or coated membrane; (2) improvement of macromolecular materials; (3) environmental protection; (4) sterilization; (5) food sterilization. The present equipment for electron beam irradiation is introduced according to low energy, medium energy, and high energy equipment. Finally, future issues focuses on (1) the improvement of traceability system and development of electron dosimetric techniques and (2) food sterilization. (N.K.)

  8. X-ray-based attenuation correction for positron emission tomography/computed tomography scanners.

    Science.gov (United States)

    Kinahan, Paul E; Hasegawa, Bruce H; Beyer, Thomas

    2003-07-01

    A synergy of positron emission tomography (PET)/computed tomography (CT) scanners is the use of the CT data for x-ray-based attenuation correction of the PET emission data. Current methods of measuring transmission use positron sources, gamma-ray sources, or x-ray sources. Each of the types of transmission scans involves different trade-offs of noise versus bias, with positron transmission scans having the highest noise but lowest bias, whereas x-ray scans have negligible noise but the potential for increased quantitative errors. The use of x-ray-based attenuation correction, however, has other advantages, including a lack of bias introduced from post-injection transmission scanning, which is an important practical consideration for clinical scanners, as well as reduced scan times. The sensitivity of x-ray-based attenuation correction to artifacts and quantitative errors depends on the method of translating the CT image from the effective x-ray energy of approximately 70 keV to attenuation coefficients at the PET energy of 511 keV. These translation methods are usually based on segmentation and/or scaling techniques. Errors in the PET emission image arise from positional mismatches caused by patient motion or respiration differences between the PET and CT scans; incorrect calculation of attenuation coefficients for CT contrast agents or metallic implants; or keeping the patient's arms in the field of view, which leads to truncation and/or beam-hardening (or x-ray scatter) artifacts. Proper interpretation of PET emission images corrected for attenuation by using the CT image relies on an understanding of the potential artifacts. In cases where an artifact or bias is suspected, careful inspection of all three available images (CT and PET emission with and without attenuation correction) is recommended. Copyright 2003 Elsevier Inc. All rights reserved.

  9. Disorientations and work-hardening behaviour during severe plastic deformation

    DEFF Research Database (Denmark)

    Pantleon, Wolfgang

    2012-01-01

    Orientation differences develop during plastic deformation even in grains of originally uniform orientation. The evolution of these disorientations is modelled by dislocation dynamics taking into account different storage mechanisms. The predicted average disorientation angles across different ty...... pressure torsion, but also rationalizes the work-hardening behaviour at large plastic strains as well as a saturation of the flow stress....

  10. Preparation of Dispersion-Hardened Copper by Internal Oxidation

    DEFF Research Database (Denmark)

    Brøndsted, Povl; Sørensen, Ole Toft

    1978-01-01

    Internal oxidation experiments in CO2/CO atmospheres on Cu-Al alloys for preparation of dispersion-hardened Cu are described. The oxygen pressures of the atmospheres used in the experiments were controlled with a solid electrolyte oxygen cell based on ZrO2 (CaO). The particle size distributions o...

  11. Influence of alloying and secondary annealing on anneal hardening ...

    Indian Academy of Sciences (India)

    Unknown

    Influence of alloying and secondary annealing on anneal hardening effect at sintered copper alloys. SVETLANA NESTOROVIC. Technical Faculty Bor, University of Belgrade, Bor, Yugoslavia. MS received 11 February 2004; revised 29 October 2004. Abstract. This paper reports results of investigation carried out on sintered ...

  12. Influence of degree of deformation in rolling on anneal hardening ...

    Indian Academy of Sciences (India)

    Unknown

    Influence of degree of deformation in rolling on anneal hardening effect of a cast copper alloy. SVETLANA NESTOROVIC*, DESIMIR MARKOVIC and LJUBICA IVANIC. Technical Faculty Bor, University of Belgrade, Belgrade, Yugoslavia. MS received 15 May 2003. Abstract. This paper reports results of investigations carried ...

  13. Fatigue Hardening and Nucleation of Persistent Slip Bands in Copper

    DEFF Research Database (Denmark)

    Pedersen, Ole Bøcker; Winter, A. T.

    1982-01-01

    A study of fatigue hardening in single crystals of pure copper shows that, before saturation, stress-strain loops can display workhardening rates of about a third of the elastic shear modulus. These rates exceed tensile workhardening rates by roughly two orders of magnitude. This suggests that th...

  14. A unified theoretical and experimental study of anisotropic hardening

    International Nuclear Information System (INIS)

    Boehler, J.P.; Raclin, J.

    1981-01-01

    The purpose of this work is to develop a consistent formulation of the constitutive relations regarding anisotropic hardening materials. Attention is focused on the appearance and the evolution of mechanical anisotropies during irreversible processes, such as plastic forming and inelastic deformation of structures. The representation theorems for anisotropic tensor functions constitute a theoretical basis, allowing to reduce arbitrariness and to obtain a unified formulation of anisotropic hardening. In this approach, a general three-dimensional constitutive law is developed for prestrained initially orthotropic materials. Introduction of the plastic behavior results in the general forms of both the flow-law and the yield criterion. The developed theory is then specialized for the case of plane stress and different modes of anisotropic hardening are analyzed. A new generalization of the Von Mises criterion is proposed, in considering a homogeneous form of order two in stress and employing the simplest combinations of the basic invariants entering the general form of the yield condition. The proposed criterion involves specific terms accounting for the initial anisotropy, the deformation induced anisotropy and correlative terms between initial and induced anisotropy. The effects of prestrainings result in both isotropic and anisotropic hardening. An adequate experimental program, consisting of uniaxial tensile tests on oriented specimens of prestrained sheet-metal, was performed, in order to determine the specific form and the evolution of the anisotropic failure criterion for soft-steel subjected to different irreversible prestrainings. (orig.)

  15. Epoxy modified bitumen : Chemical hardening and its interpretation

    NARCIS (Netherlands)

    Apostolidis, P.; Pipintakos, G.; van de Ven, M.F.C.; Liu, X.; Erkens, Sandra; Scarpas, Athanasios

    2018-01-01

    Epoxy modified bitumen (EMB) is a promising technology for long lasting paving materials ensuring higher resistance to rutting, oxygen- and moisture-induced damage. In this paper, an analysis of the chemical reactions that take place during the chemical hardening process (curing) of epoxy modified

  16. New Stainless Steel Alloys for Low Temperature Surface Hardening?

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Dahl, Kristian Vinter; Somers, Marcel A. J.

    2015-01-01

    The present contribution showcases the possibility for developing new surface hardenable stainless steels containing strong nitride/carbide forming elements (SNCFE). Nitriding of the commercial alloys, austenitic A286, and ferritic AISI 409 illustrates the beneficial effect of having SNCFE presen...

  17. The shrinkage of hardening cement paste and mortar

    NARCIS (Netherlands)

    Haas, de G.D.; Kreijger, P.C.; Niël, E.M.M.G.; Slagter, J.C.; Stein, H.N.; Theissing, E.M.; Wallendael, van M.

    1975-01-01

    This paper is an abstract from the report of the commission B10: "The influence of the shrinkage of cement on the shrink-age of concrete", of the Netherlands Committee for Concrete Research. Measurements of pulse velocity, volume shrinkage and heat of hydration on hardening portland cement support

  18. Hardening digital systems with distributed functionality: robust networks

    Science.gov (United States)

    Vaskova, Anna; Portela-Garcia, Marta; Garcia-Valderas, Mario; López-Ongil, Celia; Portilla, Jorge; Valverde, Juan; de la Torre, Eduardo; Riesgo, Teresa

    2013-05-01

    Collaborative hardening and hardware redundancy are nowadays the most interesting solutions in terms of fault tolerance achieved and low extra cost imposed to the project budget. Thanks to the powerful and cheap digital devices that are available in the market, extra processing capabilities can be used for redundant tasks, not only in early data processing (sensed data) but also in routing and interfacing1

  19. BUSFET - A Novel Radiation-Hardened SOI Transistor

    International Nuclear Information System (INIS)

    Dodd, P.E.; Draper, B.L.; Schwank, J.R.; Shaneyfelt, M.R.

    1999-01-01

    A partially-depleted SOI transistor structure has been designed that does not require the use of specially-processed hardened buried oxides for total-dose hardness and maintains the intrinsic SEU and dose rate hardness advantages of SOI technology

  20. Surface Induction Hardening of Axi-Symmetric Bodies

    Czech Academy of Sciences Publication Activity Database

    Barglik, J.; Doležel, Ivo; Škopek, M.; Ulrych, B.

    2001-01-01

    Roč. 1, č. 1 (2001), s. 11-16 ISSN 1335-8243 R&D Projects: GA ČR GA102/01/0184 Grant - others:-(PL) 7T08603716 Keywords : induction heating * induction hardening * numerical solution Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  1. Coefficient of work-hardening in stage-IV

    CSIR Research Space (South Africa)

    Nabarro, FRN

    1994-04-15

    Full Text Available The theory of work hardening in stage IV depends on the relation between the relative misorientation Psi of neighbouring subgrains and the plastic strain gamma (Psi = B gamma exp). The value of the constant B is suggested to be better related...

  2. Multiaxial ratcheting with advanced kinematic and directional distortional hardening rules

    Czech Academy of Sciences Publication Activity Database

    Feigenbaum, H. P.; Dugdale, J.; Dafalias, Y.F.; Kourousis, K. I.; Plešek, Jiří

    2012-01-01

    Roč. 49, č. 22 (2012), s. 3063-3076 ISSN 0020-7683 R&D Projects: GA MŠk(CZ) ME10024 Institutional research plan: CEZ:AV0Z20760514 Keywords : plasticity * directional distortional hardening * thermodynamics Subject RIV: JJ - Other Materials Impact factor: 1.871, year: 2012 http://www.sciencedirect.com/science/article/pii/S0020768312002612

  3. Surface modification on PMMA : PVDF polyblend: hardening under ...

    Indian Academy of Sciences (India)

    Unknown

    Keywords. Polyblend; surface modification; microhardness; hardening; plasticization; segmental mobility. 1. Introduction. Polymeric materials have a specific feature of stability towards various aggressive chemical environments, which depends on a multiplicity of factors like structure and nature of the polymers and chemical ...

  4. Role of work hardening characteristics of matrix alloys in the ...

    Indian Academy of Sciences (India)

    Unknown

    with increasing prismatic punching of dislocations in the order 7075, 2014, 7010, 2024, 6061 and commercial purity aluminium leading to increased strength increments is noted. Keywords. Metal matrix composites; strengthening; work hardening rate; dislocation density. 1. Introduction. While in continuous fibre composites, ...

  5. Process for hardening synthetic resins by ionizing radiation

    International Nuclear Information System (INIS)

    Hesse, W.; Ritz, J.

    1975-01-01

    Synthetic resins containing hydroxy groups and polymerizable carbon-carbon bonds are reacted with diketenes to yield aceto ester derivatives, which when reacted with metal compounds to form chelates, and mixed with copolymerizable monomers, are capable of being hardened by unusually low radiation doses to form coatings and articles with superior properties. (E.C.B.)

  6. Simulation of Hamming Coding and Decoding for Microcontroller Radiation Hardening

    OpenAIRE

    Rehab I. Abdul Rahman; Mazhar B. Tayel

    2015-01-01

    This paper presents a method of hardening the 8051 micro-controller, able to assure reliable operation in the presence of bit flips caused by radiation. Aiming at avoiding such faults in the 8051 micro-controller, Hamming code protection was used in its SRAM memory and registers. A VHDL code has been used for this hamming code protection.

  7. Effect of hardening methods of moulding sands with water glass on structure of bonding bridges

    Directory of Open Access Journals (Sweden)

    M. Stachowicz

    2010-07-01

    Full Text Available Research on influence of hardening methods on structure of bonding bridges in moulding sands with sodium water glass is presented.Moulding sands with addition of 2.5 % of binder with molar module 2.0 were hardened with CO2 and dried in traditional way or hardenedwith microwaves. It was proved that the hardening method affects structure of bonding bridges, correlating with properties of the hardened moulding sands. It was found that strength of the moulding sands hardened with microwaves for 4 min is very close to that measured after traditional drying at 110 °C for 120 min. So, application of microwave hardening ensures significant shortening of the process time to the value comparable with CO2 hardening but guaranteeing over 10-fold increase of mechanical properties. Analysis of SEM images of hardened moulding sands permitted explaining differences in quality parameters of moulding sands by connecting them with structure of the created bonding bridges.

  8. Beam-beam phenomenology

    International Nuclear Information System (INIS)

    Teng, L.C.

    1980-01-01

    In colliding beam storage rings the beam collision regions are generally so short that the beam-beam interaction can be considered as a series of evenly spaced non-linear kicks superimposed on otherwise stable linear oscillations. Most of the numerical studies on computers were carried out in just this manner. But for some reason this model has not been extensively employed in analytical studies. This is perhaps because all analytical work has so far been done by mathematicians pursuing general transcendental features of non-linear mechanics for whom this specific model of the specific system of colliding beams is too parochial and too repugnantly physical. Be that as it may, this model is of direct interest to accelerator physicists and is amenable to (1) further simplification, (2) physical approximation, and (3) solution by analogy to known phenomena

  9. Characterization of Scattered X-Ray Photons in Dental Cone-Beam Computed Tomography.

    Science.gov (United States)

    Yang, Ching-Ching

    2016-01-01

    Scatter is a very important artifact causing factor in dental cone-beam CT (CBCT), which has a major influence on the detectability of details within images. This work aimed to improve the image quality of dental CBCT through scatter correction. Scatter was estimated in the projection domain from the low frequency component of the difference between the raw CBCT projection and the projection obtained by extrapolating the model fitted to the raw projections acquired with 2 different sizes of axial field-of-view (FOV). The function for curve fitting was optimized by using Monte Carlo simulation. To validate the proposed method, an anthropomorphic phantom and a water-filled cylindrical phantom with rod inserts simulating different tissue materials were scanned using 120 kVp, 5 mA and 9-second scanning time covering an axial FOV of 4 cm and 13 cm. The detectability of the CT image was evaluated by calculating the contrast-to-noise ratio (CNR). Beam hardening and cupping artifacts were observed in CBCT images without scatter correction, especially in those acquired with 13 cm FOV. These artifacts were reduced in CBCT images corrected by the proposed method, demonstrating its efficacy on scatter correction. After scatter correction, the image quality of CBCT was improved in terms of target detectability which was quantified as the CNR for rod inserts in the cylindrical phantom. Hopefully the calculations performed in this work can provide a route to reach a high level of diagnostic image quality for CBCT imaging used in oral and maxillofacial structures whilst ensuring patient dose as low as reasonably achievable, which may ultimately make CBCT scan a reliable and safe tool in clinical practice.

  10. Characterization of Scattered X-Ray Photons in Dental Cone-Beam Computed Tomography.

    Directory of Open Access Journals (Sweden)

    Ching-Ching Yang

    Full Text Available Scatter is a very important artifact causing factor in dental cone-beam CT (CBCT, which has a major influence on the detectability of details within images. This work aimed to improve the image quality of dental CBCT through scatter correction.Scatter was estimated in the projection domain from the low frequency component of the difference between the raw CBCT projection and the projection obtained by extrapolating the model fitted to the raw projections acquired with 2 different sizes of axial field-of-view (FOV. The function for curve fitting was optimized by using Monte Carlo simulation. To validate the proposed method, an anthropomorphic phantom and a water-filled cylindrical phantom with rod inserts simulating different tissue materials were scanned using 120 kVp, 5 mA and 9-second scanning time covering an axial FOV of 4 cm and 13 cm. The detectability of the CT image was evaluated by calculating the contrast-to-noise ratio (CNR.Beam hardening and cupping artifacts were observed in CBCT images without scatter correction, especially in those acquired with 13 cm FOV. These artifacts were reduced in CBCT images corrected by the proposed method, demonstrating its efficacy on scatter correction. After scatter correction, the image quality of CBCT was improved in terms of target detectability which was quantified as the CNR for rod inserts in the cylindrical phantom.Hopefully the calculations performed in this work can provide a route to reach a high level of diagnostic image quality for CBCT imaging used in oral and maxillofacial structures whilst ensuring patient dose as low as reasonably achievable, which may ultimately make CBCT scan a reliable and safe tool in clinical practice.

  11. Electron Beam Welding of Gear Wheels by Splitted Beam

    Directory of Open Access Journals (Sweden)

    Dřímal Daniel

    2014-06-01

    Full Text Available This contribution deals with the issue of electron beam welding of high-accurate gear wheels composed of a spur gearing and fluted shaft joined with a face weld for automotive industry. Both parts made of the high-strength low-alloy steel are welded in the condition after final machining and heat treatment, performed by case hardening, whereas it is required that the run-out in the critical point of weldment after welding, i. e. after the final operation, would be 0.04 mm max..

  12. OCCUPATIONAL ASTHMA CAUSED BY A HARDENER CONTAINING AN ALIPHATIC AND A CYCLOALIPHATIC DIAMINE

    NARCIS (Netherlands)

    ALEVA, RM; AALBERS, R; KOETER, GH; DEMONCHY, JGR

    An otherwise healthy 44-yr-old man experienced a serious attack of bronchial obstruction after working with resins and hardeners, releasing fumes of a mixture of an aliphatic and a cycloaliphatic diamine hardener. Eight hours after deliberate challenge with the hardener a large increase of airway

  13. PS Booster Orbit Correction

    CERN Document Server

    Chanel, M; Rumolo, G; Tomás, R; CERN. Geneva. AB Department

    2008-01-01

    At the end of the 2007 run, orbit measurements were carried out in the 4 rings of the PS Booster (PSB) for different working points and beam energies. The aim of these measurements was to provide the necessary input data for a PSB realignment campaign during the 2007/2008 shutdown. Currently, only very few corrector magnets can be operated reliably in the PSB; therefore the orbit correction has to be achieved by displacing (horizontally and vertically) and/or tilting some of the defocusing quadrupoles (QDs). In this report we first describe the orbit measurements, followed by a detailed explanation of the orbit correction strategy. Results and conclusions are presented in the last section.

  14. Publisher Correction

    DEFF Research Database (Denmark)

    Stokholm, Jakob; Blaser, Martin J.; Thorsen, Jonathan

    2018-01-01

    The originally published version of this Article contained an incorrect version of Figure 3 that was introduced following peer review and inadvertently not corrected during the production process. Both versions contain the same set of abundance data, but the incorrect version has the children...

  15. Publisher Correction

    DEFF Research Database (Denmark)

    Flachsbart, Friederike; Dose, Janina; Gentschew, Liljana

    2018-01-01

    The original version of this Article contained an error in the spelling of the author Robert Häsler, which was incorrectly given as Robert Häesler. This has now been corrected in both the PDF and HTML versions of the Article....

  16. Correction to

    DEFF Research Database (Denmark)

    Roehle, Robert; Wieske, Viktoria; Schuetz, Georg M

    2018-01-01

    The original version of this article, published on 19 March 2018, unfortunately contained a mistake. The following correction has therefore been made in the original: The names of the authors Philipp A. Kaufmann, Ronny Ralf Buechel and Bernhard A. Herzog were presented incorrectly....

  17. Longitudinal wake field corrections in circular machines

    International Nuclear Information System (INIS)

    Symon, K.R.

    1996-01-01

    In computations of longitudinal particle motions in accelerators and storage rings, the fields produced by the interactions of the beam with the cavity in which it circulates are usually calculated by multiplying Fourier components of the beam current by the appropriate impedances. This procedure neglects the slow variation with time of the Fourier coefficients and of the beam revolution frequency. When there are cavity elements with decay times that are comparable with or larger than the time during which changes in the beam parameters occur, these changes can not be neglected. Corrections for this effect have been worked out in terms of the response functions of elements in the ring. The result is expressed as a correction to the impedance which depends on the way in which the beam parameters are changing. A method is presented for correcting a numerical simulation by keeping track of the steady state and transient terms in the response of a cavity

  18. Ballistic deficit correction

    International Nuclear Information System (INIS)

    Duchene, G.; Moszynski, M.; Curien, D.

    1991-01-01

    The EUROGAM data-acquisition has to handle a large number of events/s. Typical in-beam experiments using heavy-ion fusion reactions assume the production of about 50 000 compound nuclei per second deexciting via particle and γ-ray emissions. The very powerful γ-ray detection of EUROGAM is expected to produce high-fold event rates as large as 10 4 events/s. Such high count rates introduce, in a common dead time mode, large dead times for the whole system associated with the processing of the pulse, its digitization and its readout (from the preamplifier pulse up to the readout of the information). In order to minimize the dead time the shaping time constant τ, usually about 3 μs for large volume Ge detectors has to be reduced. Smaller shaping times, however, will adversely affect the energy resolution due to ballistic deficit. One possible solution is to operate the linear amplifier, with a somewhat smaller shaping time constant (in the present case we choose τ = 1.5 μs), in combination with a ballistic deficit compensator. The ballistic deficit can be corrected in different ways using a Gated Integrator, a hardware correction or even a software correction. In this paper we present a comparative study of the software and hardware corrections as well as gated integration

  19. Phenomenological interpretation of the shear behavior of reinforced Engineered Cementitious Composite beams

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2016-01-01

    This paper describes an experimental investigation of the shear behavior of beams consisting of steel Reinforced Engineered Cementitious Composites (R/ECC). This study investigates and quantifies the effect of ECC's strain hardening and multiple cracking behavior on the shear capacity of beams...

  20. Radiation hardening and embrittlement of some refractory metals and alloys

    International Nuclear Information System (INIS)

    Fabritsiev, S.; Pokrovskyb

    2007-01-01

    Tungsten is proposed for application in the ITER divertor and limiter as plasma facing material. The tungsten operation temperature in the ITER divertor is relatively high. Hence, the ductile properties of tungsten will be controlled by the low temperature radiation embrittlement. The mechanism of radiation hardening and embrittlement under neutron irradiation at low temperature is well studied for FCC metals, in particular for copper. At the same time, low-temperature radiation hardening of BCC materials, in particular for refractory metals, is less studied. This study presents the results of investigation into radiation hardening and embrittlement of pure metals: W, Mo and Nb, and W-Re and Ta-4W alloys. The materials were in the annealed conditions. The specimens were irradiated in the SM-2 reactor to doses of 10 -4 -10 -1 dpa at 80 C and then tested for tension at 80 C. The study of the stress-strain curves of unirradiated specimens revealed a yield drop for W, Mo, Nb, Ta-4W, W-Re. After the yield drop some metals (Mo,Nb) retain their capability for strain hardening and demonstrate a high elongation (20-50%). Radiation hardening is maximum in Mo (∝400MPa) and minimum in Nb (∝100 MPa). In this case the dependence slope for Nb is similar to that for pure copper irradiated in SM-2 under the same conditions. Ii and Ta-4W have a higher slope. Measurement of electrical resistivity of irradiated specimens showed that for all materials it is increased monotonously with an increase in the irradiation dose. A minimum gain in electrical resistivity with a dose was observed for Nb (∝3% at 0.1 dpa). As for Mo it was essentially higher, i.e. ∝ 30%. The gain was maximum for W-Re alloy. Comparison of radiation hardening dose dependencies obtained in this study with the data for FCC metals (Cu) showed that in spite of the quantitative difference the qualitative behavior of these two classes of metals is similar. (orig.)

  1. Design Features of Hardening Turners with Outstripping Plastic Deformation

    Directory of Open Access Journals (Sweden)

    V. M. Yaroslavtsev

    2014-01-01

    Full Text Available An efficiency of the cutting method with outstripping plastic deformation (OPD in lathe works is defined in many respects by design features of the add-on devices for mechanical hardening of a cut-off layer material in the course of cutting. Applied on lathes, deforming OPD devices can have differing dimensions, placement on the lathe, drive type (manual, electric, hydraulic, pneumatic, pneumohydraulic, electromagnetic, and autonomy degree towards the metalcutting equipment and industrial equipment.At the same time there are a number of inherent design features of work-hardening devices the modernized lathes with OPD use for machining. Now the OPD standard devices implement two principle construction options: loading device is placed on the machine or on the OPD slide support separate of the tool, or it is structurally aligned with the cutting tool. In the latter case the OPD device for turning is called a tool mandrel, which is mounted in a tool post of the machine or, at large dimensions, such a mandrel is mounted on the machine instead of the tool mandrel.When designing the OPD devices, is important to take into consideration production requirements and recommendations for the technological equipment, developed in the course of creation, working off and introduction of such installations for mechanical hardening of material. In compliance with it, OPD devices, their placement on the machine, and working displacements shouldn't limit technological capabilities of the applied metal-cutting equipment. OPD stresses have to be smoothly regulated, with maximum loads being limited to admissible values for the machine model to be modernized. It is necessary to ensure synchronized longitudinal and cross displacements of the cutting tool and OPD hardener with respect to the axis of billet rotation to enable regulation and readjustment of the hardener and tool placement. It ought to foresee the increased mobile components rigidity and manufacturing

  2. Devising Strain Hardening Models Using Kocks–Mecking Plots—A Comparison of Model Development for Titanium Aluminides and Case Hardening Steel

    Directory of Open Access Journals (Sweden)

    Markus Bambach

    2016-08-01

    Full Text Available The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a sharp peak stress and pronounced softening. The work hardening behavior of a TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B alloy is studied using isothermal hot compression tests conducted on a Gleeble 3500 simulator, and compared to the typical case hardening steel 25MoCrS4. The behavior is analyzed with the help of the Kocks-Mecking plots. In contrast to steel the TNB-V4 alloy shows a non-linear course of θ (i.e., no stage-III hardening initially and exhibits neither a plateau (stage IV hardening nor an inflection point at all deformation conditions. The present paper describes the development and application of a methodology for the design of strain hardening models for the TNB-V4 alloy and the 25CrMoS4 steel by taking the course of the Kocks-Mecking plots into account. Both models use different approaches for the hardening and softening mechanisms and accurately predict the flow stress over a wide range of deformation conditions. The methodology may hence assist in further developments of more sophisticated physically-based strain hardening models for TiAl-alloys.

  3. Study of beam-beam long range compensation with octupoles

    CERN Document Server

    AUTHOR|(CDS)2068329; Pieloni, Tatiana; Buffat, Xavier; Tambasco, Claudia

    2017-01-01

    Long range beam-beam effects are responsible for particle losses and define fundamental operational parameters of colliders (i.e. crossing angles, intensities, emittances, ${\\beta}$${^∗}$). In this study we propose octuple magnets as a possible scheme to efficiently compensate long-range beam-beam interactions with a global correction scheme. The impact and improvements on the dynamic aperture of colliding beams together with estimates of the luminosity potentials are dis- cussed for the HL-LHC upgrade and extrapolations made for the FCC project.

  4. Beam Dynamics Simulation for the CTF3 Drive Beam Accelerator

    CERN Document Server

    Schulte, Daniel

    2000-01-01

    A new CLIC Test Facility (CTF3) at CERN will serve to study the drive beam generation for the Compact Linear Collider (CLIC). CTF3 has to accelerate a 3.5 A electron beam in almost fully-loaded structures. The pulse contains more than 2000 bunches, one in every second RF bucket, and has a length of more than one microsecond. Different options for the lattice of the drive-beam accelerator are presented, based on FODO-cells and triplets as well as solenoids. The transverse stability is simulated, including the effects of beam jitter, alignment and beam-based correction.

  5. Skin hardening effect in patients with polymorphic light eruption: comparison of UVB hardening in hospital with a novel home UV-hardening device.

    Science.gov (United States)

    Franken, S M; Genders, R E; de Gruijl, F R; Rustemeyer, T; Pavel, S

    2013-01-01

    An effective prophylactic treatment of patients with polymorphic light eruption (PLE) consists of repeated low, gradually increasing exposures to UVB radiation. This so-called UV(B) hardening induces better tolerance of the skin to sunlight. SunshowerMedical company (Amsterdam) has developed an UV (B) source that can be used during taking shower. The low UV fluence of this apparatus makes it an interesting device for UV hardening. In a group of PLE patients, we compared the effectiveness of the irradiation with SunshowerMedical at home with that of the UVB treatment in the hospital. The PLE patients were randomized for one of the treatments. The hospital treatment consisted of irradiations with broad-band UVB (Waldmann 85/UV21 lamps) twice a week during 6 weeks. The home UV-device was used each day with the maximal irradiation time of 6 min. The outcome assessment was based on the information obtained from patients' dermatological quality of life (DLQI) questionnaires, the ability of both phototherapies to reduce the provocation reaction and from the patients' evaluation of the long-term benefits of their phototherapies. Sixteen patients completed treatment with SunshowerMedical and thirteen completed treatment in hospital. Both types of phototherapy were effective. There was a highly significant improvement in DLQI with either treatment. In most cases, the hardening reduced or even completely suppressed clinical UV provocation of PLE. The patients using SunshowerMedical at home were, however, much more content with the treatment procedure than the patients visiting the dermatological units. Both treatments were equally effective in the induction of skin tolerance to sunlight in PLE patients. However, the home treatment was much better accepted than the treatment in the hospital. © 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.

  6. Corrective Jaw Surgery

    Medline Plus

    Full Text Available ... out more. Corrective Jaw Surgery Corrective Jaw Surgery Orthognathic surgery is performed to correct the misalignment of jaws ... out more. Corrective Jaw Surgery Corrective Jaw Surgery Orthognathic surgery is performed to correct the misalignment of jaws ...

  7. Electron beams in radiation therapy

    International Nuclear Information System (INIS)

    Bruinvis, I.A.D.

    1987-01-01

    Clinical electron beams in interaction with beam flattening and collimating devices are studied, in order to obtain the means for adequate electron therapy. A treatment planning method for arbitrary field shapes is developed that takes the properties of the collimated electron beams into account. An electron multiple-scattering model is extended to incorporate a model for the loss of electrons with depth, in order to improve electron beam dose planning. A study of ionisation measurements in two different phantom materials yields correction factors for electron beam dosimetry. (Auth.)

  8. Modelling and implementation of the “6D” beam-beam interaction

    CERN Document Server

    Iadarola, Giovanni; Papaphilippou, Yannis

    2018-01-01

    These slides illustrate the numerical modelling of a beam-beam interaction using the “Synchro Beam Mapping” approach. The employed description of the strong beam allows correctly accounting for the hour-glass effect as well as for linear coupling at the interaction point. The implementation of the method within the SixTrack code is reviewed and tested.

  9. 6D beam-beam interaction step-by-step

    CERN Document Server

    Iadarola, Giovanni; Papaphilippou, Yannis; CERN. Geneva. ATS Department

    2017-01-01

    This document describes in detail the numerical method used in different simulation codes for the simulation of beam-beam interactions using the “Synchro Beam Mapping” approach, in order to correctly model the coupling introduced by beam-beam between the longitudinal and the transverse plane. The goal is to provide in a compact, complete and self-consistent manner the set of equations needed for the implementation in a numerical code. The effect of a “crossing angle” in an arbitrary “crossing plane” with respect to the assigned reference frame is taken into account with a suitable coordinate transformation. The employed description of the strong beam allows correctly accounting for the hour-glass effect as well as for linear coupling at the interaction point.

  10. The effects of induction hardening on wear properties of AISI 4140 steel in dry sliding conditions

    International Nuclear Information System (INIS)

    Totik, Y.; Sadeler, R.; Altun, H.; Gavgali, M.

    2002-01-01

    Wear behaviour of induction hardened AISI 4140 steel was evaluated under dry sliding conditions. Specimens were induction hardened at 1000 Hz for 6, 10, 14, 18, 27 s, respectively, in the inductor which was a three-turn coil with a coupling distance of 2.8 mm. Normalised and induction hardened specimens were fully characterised before and after the wear testing using hardness, profilometer, scanning electron microscopy and X-ray diffraction. The wear tests using a pin-on-disc machine showed that the induction hardening treatments improved the wear behaviour of AISI 4140 steel specimens compared to normalised AISI 4140 steel as a result of residual stresses and hardened surfaces. The wear coefficients in normalised specimens are greater than that in the induction hardened samples. The lowest coefficient of the friction was obtained in specimens induction-hardened at 875 deg. C for 27 s

  11. The effects of induction hardening on wear properties of AISI 4140 steel in dry sliding conditions

    Energy Technology Data Exchange (ETDEWEB)

    Totik, Y.; Sadeler, R.; Altun, H.; Gavgali, M

    2002-02-15

    Wear behaviour of induction hardened AISI 4140 steel was evaluated under dry sliding conditions. Specimens were induction hardened at 1000 Hz for 6, 10, 14, 18, 27 s, respectively, in the inductor which was a three-turn coil with a coupling distance of 2.8 mm. Normalised and induction hardened specimens were fully characterised before and after the wear testing using hardness, profilometer, scanning electron microscopy and X-ray diffraction. The wear tests using a pin-on-disc machine showed that the induction hardening treatments improved the wear behaviour of AISI 4140 steel specimens compared to normalised AISI 4140 steel as a result of residual stresses and hardened surfaces. The wear coefficients in normalised specimens are greater than that in the induction hardened samples. The lowest coefficient of the friction was obtained in specimens induction-hardened at 875 deg. C for 27 s.

  12. Surface hardening of titanium alloys with melting depth controlled by heat sink

    Science.gov (United States)

    Oden, Laurance L.; Turner, Paul C.

    1995-01-01

    A process for forming a hard surface coating on titanium alloys includes providing a piece of material containing titanium having at least a portion of one surface to be hardened. The piece having a portion of a surface to be hardened is contacted on the backside by a suitable heat sink such that the melting depth of said surface to be hardened may be controlled. A hardening material is then deposited as a slurry. Alternate methods of deposition include flame, arc, or plasma spraying, electrodeposition, vapor deposition, or any other deposition method known by those skilled in the art. The surface to be hardened is then selectively melted to the desired depth, dependent on the desired coating thickness, such that a molten pool is formed of the piece surface and the deposited hardening material. Upon cooling a hardened surface is formed.

  13. Study of radiation hardening in reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Nogiwa, Kimihiro; Nishimura, Akihiko

    2008-01-01

    In order to investigate the dependence of hardening on copper precipitate diameter and density, in-situ transmission electron microscopy (TEM) observations during tensile tests of dislocation gliding through copper rich-precipitates in thermally aged and neutron irradiated Fe-Cu alloys were performed. The obstacle strength has been estimated from the critical bow-out angle, φ, of dislocations. The obstacle distance on the dislocation line measured from in-situ TEM observations were compared with number density and diameter measured by 3D-AP (three dimensional atom probe) and TEM observation. A comparison is made between hardening estimation based on the critical bowing angles and those obtained from conventional tensile tests. (author)

  14. Radiation effects in semiconductors: technologies for hardened integrated circuits

    International Nuclear Information System (INIS)

    Charlot, J.M.

    1983-09-01

    Various technologies are used to manufacture integrated circuits for electronic systems. But for specific applications, including those with radiation environment, it is necessary to choose an appropriate technologie or to improve a specific one in order to reach a definite hardening level. The aim of this paper is to present the main effects induced by radiation (neutrons and gamma rays) into the basic semiconductor devices, to explain some physical degradation mechanisms and to propose solutions for hardened integrated circuit fabrication. The analysis involves essentially the monolithic structure of the integrated circuits and the isolation technology of active elements. In conclusion, the advantages of EPIC and SOS technologies are described and the potentialities of new technologies (GaAs and SOI) are presented

  15. Radiation effects in semiconductors: technologies for hardened integrated circuits

    International Nuclear Information System (INIS)

    Charlot, J.M.

    1984-01-01

    Various technologies are used to manufacture integrated circuits for electronic systems. But for specific applications, including those with radiation environment, it is necessary to choose an appropriate technology or to improve a specific one in order to reach a definite hardening level. The aim of this paper is to present the main effects induced by radiation (neutrons and gamma rays) into the basic semiconductor devices, to explain some physical degradation mechanisms and to propose solutions for hardened integrated circuit fabrication. The analysis involves essentially the monolithic structure of the integrated circuits and the isolation technology of active elements. In conclusion, the advantages of EPIC and SOS technologies are described and the potentialities of new technologies (GaAs and SOI) are presented. (author)

  16. On use of radial evanescence remain term in kinematic hardening

    International Nuclear Information System (INIS)

    Geyer, P.

    1995-01-01

    This paper presents the interest which lies in non-linear kinematic hardening rule with radial evanescence remain term as proposed for modelling multiaxial ratchetting. From analytical calculations in the case of the tension/torsion test, this ratchetting is compared with that proposed by Armstrong and Frederick. A modification is then proposed for Chaboche's elastoplastic model with two non-linear kinematic variables, by coupling the two types of hardening by means of two scalar parameters. Identification of these two parameters returns to speculate on the directions of strain in order to adjust the ratchetting to experimental observations. Using biaxial ratchetting tests on stainless steel 316 L specimens at ambient temperature, it is shown that satisfactory modelling of multiaxial ratchetting is obtained. (author). 4 refs., 5 figs

  17. work hardening, recovery and recrystallization of alloys containing dispersed precipitates

    International Nuclear Information System (INIS)

    Padilha, A.F.

    1989-01-01

    This paper reviews the work hardening, recovery and recrystallization mechanisms in alloys containing dispersed precipitates. In the section on work hardening, the influence od spacing, particle size and shape on the density and distribution of dislocations have been discussed. They represent a large part of the energy stored in the material following drformation, which in turn is driving force for recrystallization. Next, the role of precipitates on recovery, on the formation and the growth of recrystallized regions has been discussed in detail. The competition between recovery and recrystallization and recrystallization of supersaturated solid solutions have also been mentioned. Finally, the technological relevance of the aspects treated in this paper has been discussed. (author) [pt

  18. Hardening by annealing and softening by deformation in nanostructured metals

    DEFF Research Database (Denmark)

    Huang, X.; Hansen, N.; Tsuji, N.

    2006-01-01

    We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation-dislocation and ......We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation....... As a consequence, the strength decreases and the ductility increases. These observations suggest that for materials such as the nanostructured aluminum studied here, deformation should be used as an optimizing procedure instead of annealing....

  19. Coatings hardenable by ionizing radiation and their applications

    International Nuclear Information System (INIS)

    Aronoff, E.J.; Labana, S.S.

    1976-01-01

    The invention deals with the production of a coating medium which can be hardened by ionizing radiation. The composition includes tetravinyl compounds containing no free hydroxyl groups which were obtained by the conversion of di-epoxides with acryl or methacryl acid via the intermediary step of a divinyl ester condensation product. The intermediary product is converted with acryloyl or methacryloyl halides. The mass still contains non-polymerisable solvent (such as tolual, xylol), pigments and fillers. It is of advantage if the di-epoxide has a molecular weight of 140 to 500. Furthermore, coatings are to be made of this coating medium which are hardened by ionizing radiation at temperatures between 20 0 C and 70 0 C. 19 examples. (HK) [de

  20. Assessment of the effects of atmospheric neutrons on onboard electronic equipment and search for hardening solutions

    International Nuclear Information System (INIS)

    Renard, S.

    2013-01-01

    This work deals with the impact of atmospheric neutrons on complex electronic components such as built-in memories or processors. The first part describes the radiation environment, the neutron-matter interaction and the consequences on electronic devices, and presents the commonly used experimental simulations and the testing methods. The potential of laser beam for testing is highlighted. The second chapter presents the development of a testing platform for various types of memories (MRAM and SDRAM). The equipment and the dedicated software are described. A testing platform for processor is also presented. The third chapter is dedicated to the presentation of a 4 Mbit bulk-type SRAM memory and of its testing involving a laser beam equipment. Several results show the presence of error clusters that may endangered the memory as a whole. These error clusters are due to the architecture of the internal addressing scheme of the memory. The simulation of these error clusters must be improved in order to define an optimized strategy of hardening

  1. Product surface hardening in non-self-sustained glow discharge plasma before synthesis of superhard coatings

    International Nuclear Information System (INIS)

    Krasnov, P S; Metel, A S; Nay, H A

    2017-01-01

    Before the synthesis of superhard coating, the product surface is hardened by means of plasma nitriding, which prevents the surface deformations and the coating brittle rupture. The product heating by ions accelerated from plasma by applied to the product bias voltage leads to overheating and blunting of the product sharp edges. To prevent the blunting, it is proposed to heat the products with a broad beam of fast nitrogen molecules. The beam injection into a working vacuum chamber results in filling of the chamber with quite homogeneous plasma suitable for nitriding. Immersion in the plasma of the electrode and heightening of its potential up to 50–100 V initiate a non-self-sustained glow discharge between the electrode and the chamber. It enhances the plasma density by an order of magnitude and reduces its spatial nonuniformity down to 5–10%. When a cutting tool is isolated from the chamber, it is bombarded by plasma ions with an energy corresponding to its floating potential, which is lower than the sputtering threshold. Hence, the sharp edges are sputtered only by fast nitrogen molecules with the same rate as other parts of the tool surface. This leads to sharpening of the cutting tools instead of blunting. (paper)

  2. Plasma nitriding - an eco friendly surface hardening process

    International Nuclear Information System (INIS)

    Mukherjee, S.

    2015-01-01

    Surface hardening is a process of heating the metal such that the surface gets only hardened. This process is adopted for many components like gears, cams, and crankshafts, which desire high hardness on the outer surface with a softer core to withstand the shocks. So, to attain such properties processes like carburising, nitriding, flame hardening and induction hardening are employed. Amongst these processes nitriding is the most commonly used process by many industries. In nitriding process the steel material is heated to a temperature of around 550 C and then exposed to atomic nitrogen. This atomic nitrogen reacts with iron and other alloying elements and forms nitrides, which are very hard in nature. By this process both wear resistance and hardness of the product can be increased. The atomic nitrogen required for this process can be obtained using ammonia gas (gas nitriding), cyanide based salt bath (liquid nitriding) and plasma medium (plasma nitriding). However, plasma nitriding has recently received considerable industrial interest owing to its characteristic of faster nitrogen penetration, short treatment time, low process temperature, minimal distortion, low energy use and easier control of layer formation compared with conventional techniques such as gas and liquid nitriding. This process can be used for all ferrous materials including stainless steels. Plasma nitriding is carried out using a gas mixture of nitrogen and hydrogen gas at sub atmospheric pressures hence, making it eco-friendly in nature. Plasma nitriding allows modification of the surface layers and hardness profiles by changing the gas mixture and temperature. The wide applicable temperature range enables a multitude of applications, beyond the possibilities of gas or salt bath processes. This has led to numerous applications of this process in industries such as the manufacture of machine parts for plastics and food processing, packaging and tooling as well as pumps and hydraulic, machine

  3. Numerical implementation of a model with directional distortional hardening

    Czech Academy of Sciences Publication Activity Database

    Marek, René; Plešek, Jiří; Hrubý, Zbyněk; Parma, Slavomír; Feigenbaum, H. P.; Dafalias, Y.F.

    2015-01-01

    Roč. 141, č. 12 (2015), 04015048-04015048 ISSN 0733-9399 R&D Projects: GA MŠk LH14018; GA ČR(CZ) GA15-20666S Institutional support: RVO:61388998 Keywords : plasticity * directional distortional hardening * finite-element procedures Subject RIV: JG - Metallurgy Impact factor: 1.346, year: 2015 http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000954

  4. Account of low temperature hardening in calculation of permissible stresses

    International Nuclear Information System (INIS)

    Novikov, N.V.; Ul'yanenko, A.P.; Gorodyskij, N.I.

    1980-01-01

    Suggested is a calculation scheme of permissible stresses with the account of temperature hardening for steels and alloys, the dependences of strength, plasticity and rupture work of which on cooling temperature do not have threshold changes in a wide range of low temperatures (from 300 to 4.2 K). Application of the suggested scheme is considered on the example of 12Kh18N10T austenitic chromium-nickel steel

  5. Radiation-hardened CMOS/SOS LSI circuits

    International Nuclear Information System (INIS)

    Aubuchon, K.G.; Peterson, H.T.; Shumake, D.P.

    1976-01-01

    The recently developed technology for building radiation-hardened CMOS/SOS devices has now been applied to the fabrication of LSI circuits. This paper describes and presents results on three different circuits: an 8-bit adder/subtractor (Al gate), a 256-bit shift register (Si gate), and a polycode generator (Al gate). The 256-bit shift register shows very little degradation after 1 x 10 6 rads (Si), with an increase from 1.9V to 2.9V in minimum operating voltage, a decrease of about 20% in maximum frequency, and little or no change in quiescent current. The p-channel thresholds increase from -0.9V to -1.3V, while the n-channel thresholds decrease from 1.05 to 0.23V, and the n-channel leakage remains below 1nA/mil. Excellent hardening results were also obtained on the polycode generator circuit. Ten circuits were irradiated to 1 x 10 6 rads (Si), and all continued to function well, with an increase in minimum power supply voltage from 2.85V to 5.85V and an increase in quiescent current by a factor of about 2. Similar hardening results were obtained on the 8-bit adder, with the minimum power supply voltage increasing from 2.2V to 4.6V and the add time increasing from 270 to 350 nsec after 1 x 10 6 rads (Si). These results show that large CMOS/SOS circuits can be hardened to above 1 x 10 6 rads (Si) with either the Si gate or Al gate technology. The paper also discusses the relative advantages of the Si gate versus the Al gate technology

  6. Concrete hardened characterization using table scanner and microtomography computed

    International Nuclear Information System (INIS)

    Wilson, R.E.; Pessoa, J.R.; Assis, J.T. de; Dominguez, D.S.; Dias, L.A.; Santana, M. R.

    2016-01-01

    This paper proposes the use of image processing technologies to analyze hardened concrete samples obtained from table scanner and micro tomography. Techniques will be used to obtain numerical data on the distribution and geometry of aggregates and pores of the concrete, as well as their relative position. It is expected that the data obtained can produce information on the research of concrete pathologies such as AAR, and the freeze / thaw process. (author)

  7. Heat Flow In Cylindrical Bodies During Laser Surface Transformation Hardening

    Science.gov (United States)

    Sandven, Ole A.

    1980-01-01

    A mathematical model for the transient heat flow in cylindrical specimens is presented. The model predicts the temperature distribution in the vicinity of a moving ring-shaped laser spot around the periphery of the outer surface of a cylinder, or the inner surface of a hollow cylinder. It can be used to predict the depth of case in laser surface transformation hardening. The validity of the model is tested against experimental results obtained on SAE 4140 steel.

  8. Description of hardening curves of fcc single- and polycrystals

    International Nuclear Information System (INIS)

    Mecking, H.

    1975-01-01

    Stress-strain curves are analyzed over their entire strain region and over a wide range of temperatures to arrive at a general analytic description of work-hardening curves. The data were obtained with fcc single and polycrystals, but there is experimental and theoretical evidence that the principles of the analysis are also applicable for other crystal structures and even for more complex technical materials. 9 figs, 1 table, 46 refs

  9. Sequential circuit design for radiation hardened multiple voltage integrated circuits

    Science.gov (United States)

    Clark, Lawrence T [Phoenix, AZ; McIver, III, John K.

    2009-11-24

    The present invention includes a radiation hardened sequential circuit, such as a bistable circuit, flip-flop or other suitable design that presents substantial immunity to ionizing radiation while simultaneously maintaining a low operating voltage. In one embodiment, the circuit includes a plurality of logic elements that operate on relatively low voltage, and a master and slave latches each having storage elements that operate on a relatively high voltage.

  10. Effects of residual stress on irradiation hardening in stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Okubo, N.; Kondo, K.; Kaji, Y. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Miwa, Y. [Nuclear Energy and Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Ibaraki-ken (Japan)

    2007-07-01

    Full text of publication follows: Structural materials in fusion reactor with water cooling system will undergo corrosion in aqueous environment and heavier irradiation than that in LWR. Irradiation assisted stress corrosion (IASCC) may be induced in stainless steels exposed in these environment for a long term of reactor operation. The IASCC is considered to be caused in a welding zone. It is difficult to predict and estimate the IASCC, because several irradiation effects (irradiation hardening, swelling, irradiation induced stress relaxation, etc) work intricately. Firstly, effects of residual stress on irradiation hardening were investigated in stainless steels. Specimens used in this study were SUS316 and SUS316L. By bending deformation, the specimens with several % plastic strain, which corresponds to weld residual stress, were prepared. Ion irradiations of 12 MeV Ni{sup 3+} were performed at 330, 400 and 550 deg. C to 45 dpa in TIARA facility at JAEA. No bent specimen was simultaneously irradiated with the bent specimen. The residual stress was estimated by X-ray residual stress measurements before and after the irradiation. The micro-hardness was measured by using nano-indenter. The irradiation hardening and the stress relaxation were changed by irradiation under bending deformation. The residual stress did not relax even for the case of the higher temperature aging at 500 deg. C for the same time of irradiation. The residual stress after ion irradiation, however, relaxed at these experimental temperatures in SUS316L. The hardness was obviously suppressed in bent SUS316L irradiated at 300 deg. C to 6 or 12 dpa. It was evident that irradiation induced stress relaxation occasionally suppressed the irradiation hardening in SUS316L. (authors)

  11. Hardening in AlN induced by point defects

    International Nuclear Information System (INIS)

    Suematsu, H.; Mitchell, T.E.; Iseki, T.; Yano, T.

    1991-01-01

    Pressureless-sintered AIN was neutron irradiated and the hardness change was examined by Vickers indentation. The hardness was increased by irradiation. When the samples were annealed at high temperature, the hardness gradually decreased. Length was also found to increase and to change in the same way as the hardness. A considerable density of dislocation loops still remained, even after the hardness completely recovered to the value of the unirradiated sample. Thus, it is concluded that the hardening in AIN is caused by isolated point defects and small clusters of point defects, rather than by dislocation loops. Hardness was found to increase in proportion to the length change. If the length change is assumed to be proportional to the point defect density, then the curve could be fitted qualitatively to that predicted by models of solution hardening in metals. Furthermore, the curves for three samples irradiated at different temperatures and fluences are identical. There should be different kinds of defect clusters in samples irradiated at different conditions, e.g., the fraction of single point defects is the highest in the sample irradiated at the lowest temperature. Thus, hardening is insensitive to the kind of defects remaining in the sample and is influenced only by those which contribute to length change

  12. Recent developments in turning hardened steels - A review

    Science.gov (United States)

    Sivaraman, V.; Prakash, S.

    2017-05-01

    Hard materials ranging from HRC 45 - 68 such as hardened AISI H13, AISI 4340, AISI 52100, D2 STL, D3 STEEL Steel etc., need super hard tool materials to machine. Turning of these hard materials is termed as hard turning. Hard turning makes possible direct machining of the hard materials and also eliminates the lubricant requirement and thus favoring dry machining. Hard turning is a finish turning process and hence conventional grinding is not required. Development of the new advanced super hard tool materials such as ceramic inserts, Cubic Boron Nitride, Polycrystalline Cubic Boron Nitride etc. enabled the turning of these materials. PVD and CVD methods of coating have made easier the production of single and multi layered coated tool inserts. Coatings of TiN, TiAlN, TiC, Al2O3, AlCrN over cemented carbide inserts has lead to the machining of difficult to machine materials. Advancement in the process of hard machining paved way for better surface finish, long tool life, reduced tool wear, cutting force and cutting temperatures. Micro and Nano coated carbide inserts, nanocomposite coated PCBN inserts, micro and nano CBN coated carbide inserts and similar developments have made machining of hardened steels much easier and economical. In this paper, broad literature review on turning of hardened steels including optimizing process parameters, cooling requirements, different tool materials etc., are done.

  13. Influences of Steelmaking Slags on Hydration and Hardening of Concretes

    Science.gov (United States)

    Kirsanova, A. A.; Dildin, A. N.; Maksimov, S. P.

    2017-11-01

    It is shown that the slag of metallurgical production can be used in the construction industry as an active mineral additive for concrete. This approach allows us to solve environmental problems and reduce costs for the production of binder and concrete simultaneously. Most often slag is used in the form of a filler, an active mineral additive or as a part of a binder for artificial conglomerates. The introduction of slag allows one to notice a part of the cement, to obtain concretes that are more resistant to the impact of aggressive sulfate media. The paper shows the possibility of using recycled steel-smelting slags in the construction industry for the production of cement. An assessment was made of their effect on the hydration of the cement stone and hardening of the concrete together with the plasticizer under normal conditions. In the process of work, we used the slag of the Zlatoust Electrometallurgical Factory. Possible limitations of the content of steel-slag slag in concrete because of the possible presence of harmful impurities are shown. It is necessary to enter slag in conjunction with superplasticizers to reduce the flow of water mixing. Slags can be used as a hardening accelerator for cement concrete as they allow one to increase the degree of cement hydration and concrete strength. It is shown that slags can be used to produce fast-hardening concretes and their comparative characteristics with other active mineral additives are given.

  14. Importance of calcium and magnesium in water - water hardening

    Science.gov (United States)

    Barloková, D.; Ilavský, J.; Kapusta, O.; Šimko, V.

    2017-10-01

    Basic information about importance of calcium and magnesium in water, about their properties, effect to human health, problems what can cause under the lower ( 5 mmol/L) concentrations in water supply distribution systems, the most commonly used methods of water hardening are presented. The article contains the water hardening results carried out during the pilot plant experiments in WTP Hriňová and WTP Turček. For water hardening, treated water at the end of the process line, i.e., after coagulation, sedimentation and filtration, saturated with CO2 and filtrated through half-burnt dolomite material (PVD) was used. The results show that the filtration rate is 17.1 m/h in the case of WTP Hriňová and 15.2 m/h in the case of WTP Turček to achieve the recommended concentration of Ca and Mg in the treated water after the addition of CO2 and filtration through PVD. The longer the water contact time with PVD (depending on the CO2 content), the more water is enriched with magnesium, but the calcium concentration has not so much increased.

  15. Residual stress analysis of drive shafts after induction hardening

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Guilherme Vieira Braga; Rocha, Alexandre da Silva; Nunes, Rafael Menezes, E-mail: lemos_gl@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Algre, RS (Brazil); Hirsch, Thomas Karl [Stiftung Institut für Werkstofftechnik (IWT), Bremen (Germany)

    2014-08-15

    Typically, for automotive shafts, shape distortion manifests itself in most cases after the induction hardening by an effect known as bending. The distortion results in a boost of costs, especially due to machining parts in the hardened state to fabricate its final tolerances. In the present study, residual stress measurements were carried out on automotive drive shafts made of DIN 38B3 steel. The samples were selected in consequence of their different distortion properties by an industrial manufacturing line. One tested shaft was straightened, because of the considerable dimensional variation and the other one not. Firstly, the residual stress measurements were carried out by using a portable diffractometer, in order to avoid cutting the shafts and evaluate the original state of the stresses, and afterwards a more detailed analysis was realized by a conventional stationary diffractometer. The obtained results presented an overview of the surface residual stress profiles after induction hardening and displayed the influence of the straightening process on the redistribution of residual stresses. They also indicated that the effects of the straightening in the residual stresses cannot be neglected. (author)

  16. Significance of rate of work hardening in tempered martensite embrittlement

    International Nuclear Information System (INIS)

    Pietikainen, J.

    1995-01-01

    The main explanations for tempered martensite embrittlement are based on the effects of impurities and cementite precipitation on the prior austenite grain boundaries. There are some studies where the rate of work hardening is proposed as a potential reason for the brittleness. One steel was studied by means of a specially developed precision torsional testing device. The test steel had a high Si and Ni content so ε carbide and Fe 3 C appear in quite different tempering temperature ranges. The M S temperature is low enough so that self tempering does not occur. With the testing device it was possible to obtain the true stress - true strain curves to very high deformations. The minimum toughness was always associated with the minimum of rate of work hardening. The change of deformed steel volume before the loss of mechanical stability is proposed as at least one reason for tempered martensite embrittlement. The reasons for the minimum of the rate of work hardening are considered. (orig.)

  17. Temperature dependence of work hardening in sparsely twinning zirconium

    International Nuclear Information System (INIS)

    Singh, Jaiveer; Mahesh, S.; Roy, Shomic; Kumar, Gulshan; Srivastava, D.; Dey, G.K.; Saibaba, N.; Samajdar, I.

    2017-01-01

    Fully recrystallized commercial Zirconium plates were subjected to uniaxial tension. Tests were conducted at different temperatures (123 K - 623 K) and along two plate directions. Both directions were nominally unfavorable for deformation twinning. The effect of the working temperature on crystallographic texture and in-grain misorientation development was insignificant. However, systematic variation in work hardening and in the area fraction and morphology of deformation twins was observed with temperature. At all temperatures, twinning was associated with significant near boundary mesoscopic shear, suggesting a possible linkage with twin nucleation. A binary tree based model of the polycrystal, which explicitly accounts for grain boundary accommodation and implements the phenomenological extended Voce hardening law, was implemented. This model could capture the measured stress-strain response and twin volume fractions accurately. Interestingly, slip and twin system hardness evolution permitted multiplicative decomposition into temperature-dependent, and accumulated strain-dependent parts. Furthermore, under conditions of relatively limited deformation twinning, the work hardening of the slip and twin systems followed two phenomenological laws proposed in the literature for non-twinning single-phase face centered cubic materials.

  18. Helium-induced hardening effect in polycrystalline tungsten

    Science.gov (United States)

    Kong, Fanhang; Qu, Miao; Yan, Sha; Zhang, Ailin; Peng, Shixiang; Xue, Jianming; Wang, Yugang

    2017-09-01

    In this paper, helium induced hardening effect of tungsten was investigated. 50 keV He2+ ions at fluences vary from 5 × 1015 cm-2 to 5 × 1017 cm-2 were implanted into polycrystalline tungsten at RT to create helium bubble-rich layers near the surface. The microstructure and mechanical properties of the irradiated specimens were studied by TEM and nano-indentor. Helium bubble rich layers are formed in near surface region, and the layers become thicker with the rise of fluences. Helium bubbles in the area of helium concentration peak are found to grow up, while the bubble density is almost unchanged. Obvious hardening effect is induced by helium implantation in tungsten. Micro hardness increases rapidly with the fluence firstly, and more slowly when the fluence is above 5 × 1016 cm-2. The hardening effect of tungsten can be attributed to helium bubbles, which is found to be in agreement with the Bacon-Orowan stress formula. The growing diameter is the major factor rather than helium bubbles density (voids distance) in the process of helium implantation at fluences below 5 × 1017 cm-2.

  19. Electroweak corrections

    International Nuclear Information System (INIS)

    Beenakker, W.J.P.

    1989-01-01

    The prospect of high accuracy measurements investigating the weak interactions, which are expected to take place at the electron-positron storage ring LEP at CERN and the linear collider SCL at SLAC, offers the possibility to study also the weak quantum effects. In order to distinguish if the measured weak quantum effects lie within the margins set by the standard model and those bearing traces of new physics one had to go beyond the lowest order and also include electroweak radiative corrections (EWRC) in theoretical calculations. These higher-order corrections also can offer the possibility of getting information about two particles present in the Glashow-Salam-Weinberg model (GSW), but not discovered up till now, the top quark and the Higgs boson. In ch. 2 the GSW standard model of electroweak interactions is described. In ch. 3 some special techniques are described for determination of integrals which are responsible for numerical instabilities caused by large canceling terms encountered in the calculation of EWRC effects, and methods necessary to get hold of the extensive algebra typical for EWRC. In ch. 4 various aspects related to EWRC effects are discussed, in particular the dependence of the unknown model parameters which are the masses of the top quark and the Higgs boson. The processes which are discussed are production of heavy fermions from electron-positron annihilation and those of the fermionic decay of the Z gauge boson. (H.W.). 106 refs.; 30 figs.; 6 tabs.; schemes

  20. Irradiation hardening of Fe–9Cr-based alloys and ODS Eurofer: Effect of helium implantation and iron-ion irradiation at 300 °C including sequence effects

    Energy Technology Data Exchange (ETDEWEB)

    Heintze, C. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden (Germany); Bergner, F., E-mail: f.bergner@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden (Germany); Hernández-Mayoral, M. [CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain); Kögler, R.; Müller, G.; Ulbricht, A. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden (Germany)

    2016-03-15

    Single-beam, dual-beam and sequential iron- and/or helium-ion irradiations are widely accepted to emulate more application-relevant but hardly accessible irradiation conditions of generation-IV fission and fusion candidate materials for certain purposes such as material pre-selection, identification of basic mechanisms or model calibration. However, systematic investigations of sequence effects capable to critically question individual approaches are largely missing. In the present study, sequence effects of iron-ion irradiations at 300 °C up to 5 dpa and helium implantations up to 100 appm He are investigated by means of post-irradiation nanoindentation of an Fe9%Cr model alloy, ferritic/martensitic 9%Cr steels T91 and Eurofer97 and oxide dispersion strengthened (ODS) Eurofer. Different types of sequence effects, both synergistic and antagonistic, are identified and tentative interpretations are suggested. It is found that different accelerated irradiation approaches have a great impact on the mechanical hardening. This stresses the importance of experimental design in attempts to emulate in-reactor conditions. - Highlights: • The single-beam He-ion implantations do not give rise to significant hardening. • The single-beam Fe-ion irradiations give rise to significant hardening, ΔH{sub Fe}. • Hardening due to sequential He-/Fe-ion irradiation is smaller than ΔH{sub Fe}. • Hardening due to simultaneous He-/Fe-ion irradiation is larger than ΔH{sub Fe}. • The He–Fe synergism for ODS-Eurofer is less pronounced than for Eurofer97.

  1. Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic and Precipitation Hardening Stainless Steels by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... case included X-ray diffraction analysis, reflected light microscopy and microhardness. The results demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

  2. Correction magnet power supplies for APS machine

    International Nuclear Information System (INIS)

    Kang, Y.G.

    1991-04-01

    A number of correction magnets are required for the advanced photon source (APS) machine to correct the beam. There are five kinds of correction magnets for the storage ring, two for the injector synchrotron, and two for the positron accumulator ring (PAR). Table I shoes a summary of the correction magnet power supplies for the APS machine. For the storage ring, the displacement of the quadrupole magnets due to the low frequency vibration below 25 Hz has the most significant effect on the stability of the positron closed orbit. The primary external source of the low frequency vibration is the ground motion of approximately 20 μm amplitude, with frequency components concentrated below 10 Hz. These low frequency vibrations can be corrected by using the correction magnets, whose field strengths are controlled individually through the feedback loop comprising the beam position monitoring system. The correction field require could be either positive or negative. Thus for all the correction magnets, bipolar power supplies (BPSs) are required to produce both polarities of correction fields. Three different types of BPS are used for all the correction magnets. Type I BPSs cover all the correction magnets for the storage ring, except for the trim dipoles. The maximum output current of the Type I BPS is 140 Adc. A Type II BPS powers a trim dipole, and its maximum output current is 60 Adc. The injector synchrotron and PAR correction magnets are powered form Type III BPSs, whose maximum output current is 25 Adc

  3. Overview of the APT high-energy beam transport and beam expanders

    International Nuclear Information System (INIS)

    Shafer, R.E.; Blind, B.; Gray, E.R.

    1997-01-01

    The APT high energy beam transport (HEBT) and beam expanders convey the 1700-MeV, 100-mA cw proton beam from the linac to the tritium target/blanket assembly, or a tuning beam stop. The HEBT includes extensive beam diagnostics, collimators, and beam jitter correction, to monitor and control the 170-MW beam prior to expansion. A zero-degree beamline conveys the beam to the beam stop, and an achromatic bend conveys the beam to the tritium production target. Nonlinear beam expanders make use of higher-order multipole magnets and dithering dipoles to expand the beam to a uniform-density, 16-cm wide by 160-cm high rectangular profile on the tritium-production target. The overall optics design will be reviewed, and beam simulations will be presented

  4. Ion Beam Propulsion Study

    Science.gov (United States)

    2008-01-01

    The Ion Beam Propulsion Study was a joint high-level study between the Applied Physics Laboratory operated by NASA and ASRC Aerospace at Kennedy Space Center, Florida, and Berkeley Scientific, Berkeley, California. The results were promising and suggested that work should continue if future funding becomes available. The application of ion thrusters for spacecraft propulsion is limited to quite modest ion sources with similarly modest ion beam parameters because of the mass penalty associated with the ion source and its power supply system. Also, the ion source technology has not been able to provide very high-power ion beams. Small ion beam propulsion systems were used with considerable success. Ion propulsion systems brought into practice use an onboard ion source to form an energetic ion beam, typically Xe+ ions, as the propellant. Such systems were used for steering and correction of telecommunication satellites and as the main thruster for the Deep Space 1 demonstration mission. In recent years, "giant" ion sources were developed for the controlled-fusion research effort worldwide, with beam parameters many orders of magnitude greater than the tiny ones of conventional space thruster application. The advent of such huge ion beam sources and the need for advanced propulsion systems for exploration of the solar system suggest a fresh look at ion beam propulsion, now with the giant fusion sources in mind.

  5. Influence of Microstructure and Process Conditions on Simultaneous Low-Temperature Surface Hardening and Bulk Precipitation Hardening of Nanoflex®

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas L.

    2015-01-01

    Precipitation hardening martensitic stainless steel Nanoflex was low-temperature nitrided or nitrocarburized. In these treatments, simultaneous hardening of the bulk, by precipitation hardening, and the surface by dissolving nitrogen/carbon can be obtained because the treatment temperatures...... and times for these essentially different hardening mechanisms are compatible. The effect of the processing history of the steel on the nitrided/nitrocarburized case was investigated by varying the amounts of austenite and martensite through variation of the degree of plastic deformation by tensile strain...... consisting of martensite results in the deepest nitrided case, while a shallow case develops on a microstructure consisting of austenite. For an initial microstructure consisting of both martensite and austenite a non-uniform case depth is achieved. Simultaneous bulk and surface hardening is only possible...

  6. A new trajectory correction technique for linacs

    International Nuclear Information System (INIS)

    Raubenheimer, T.O.; Ruth, R.D.

    1990-06-01

    In this paper, we describe a new trajectory correction technique for high energy linear accelerators. Current correction techniques force the beam trajectory to follow misalignments of the Beam Position Monitors. Since the particle bunch has a finite energy spread and particles with different energies are deflected differently, this causes ''chromatic'' dilution of the transverse beam emittance. The algorithm, which we describe in this paper, reduces the chromatic error by minimizing the energy dependence of the trajectory. To test the method we compare the effectiveness of our algorithm with a standard correction technique in simulations on a design linac for a Next Linear Collider. The simulations indicate that chromatic dilution would be debilitating in a future linear collider because of the very small beam sizes required to achieve the necessary luminosity. Thus, we feel that this technique will prove essential for future linear colliders. 3 refs., 6 figs., 2 tabs

  7. Microstructural changes and strain hardening effects in abrasive contacts at different relative velocities and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rojacz, H., E-mail: rojacz@ac2t.at [AC2T research GmbH, Viktor-Kaplan-Straße 2C, 2700 Wiener Neustadt (Austria); Mozdzen, G. [Aerospace & Advanced Composites GmbH, Viktor-Kaplan-Straße 2F, 2700 Wiener Neustadt (Austria); Weigel, F.; Varga, M. [AC2T research GmbH, Viktor-Kaplan-Straße 2C, 2700 Wiener Neustadt (Austria)

    2016-08-15

    Strain hardening is commonly used to reach the full potential of materials and can be beneficial in tribological contacts. 2-body abrasive wear was simulated in a scratch test, aimed at strain hardening effects in various steels. Different working conditions were examined at various temperatures and velocities. Strain hardening effects and microstructural changes were analysed with high resolution scanning electron microscopy (HRSEM), electron backscatter diffraction (EBSD), micro hardness measurements and nanoindentation. Statistical analysing was performed quantifying the influence of different parameters on microstructures. Results show a crucial influence of temperature and velocity on the strain hardening in tribological contacts. Increased velocity leads to higher deformed microstructures and higher increased surface hardness at a lower depth of the deformed zones at all materials investigated. An optimised surface hardness can be achieved knowing the influence of velocity (strain rate) and temperature for a “tailor-made” surface hardening in tribological systems aimed at increased wear resistance. - Highlights: •Hardening mechanisms and their intensity in tribological contacts are dependent on relative velocity and temperature. •Beneficial surface hardened zones are formed at certain running-in conditions; the scientific background is presented here. •Ferritic-pearlitic steels strain hardens via grain size reduction and decreasing interlamellar distances in pearlite. •Austenitic steels show excellent surface hardening (120% hardness increase) by twinning and martensitic transformation. •Ferritic steels with hard phases harden in the ferrite phase as per Hall-Petch equation and degree of deformation.

  8. Microstructural changes and strain hardening effects in abrasive contacts at different relative velocities and temperatures

    International Nuclear Information System (INIS)

    Rojacz, H.; Mozdzen, G.; Weigel, F.; Varga, M.

    2016-01-01

    Strain hardening is commonly used to reach the full potential of materials and can be beneficial in tribological contacts. 2-body abrasive wear was simulated in a scratch test, aimed at strain hardening effects in various steels. Different working conditions were examined at various temperatures and velocities. Strain hardening effects and microstructural changes were analysed with high resolution scanning electron microscopy (HRSEM), electron backscatter diffraction (EBSD), micro hardness measurements and nanoindentation. Statistical analysing was performed quantifying the influence of different parameters on microstructures. Results show a crucial influence of temperature and velocity on the strain hardening in tribological contacts. Increased velocity leads to higher deformed microstructures and higher increased surface hardness at a lower depth of the deformed zones at all materials investigated. An optimised surface hardness can be achieved knowing the influence of velocity (strain rate) and temperature for a “tailor-made” surface hardening in tribological systems aimed at increased wear resistance. - Highlights: •Hardening mechanisms and their intensity in tribological contacts are dependent on relative velocity and temperature. •Beneficial surface hardened zones are formed at certain running-in conditions; the scientific background is presented here. •Ferritic-pearlitic steels strain hardens via grain size reduction and decreasing interlamellar distances in pearlite. •Austenitic steels show excellent surface hardening (120% hardness increase) by twinning and martensitic transformation. •Ferritic steels with hard phases harden in the ferrite phase as per Hall-Petch equation and degree of deformation.

  9. Comparative Study of Hardening Mechanisms During Aging of a 304 Stainless Steel Containing α'-Martensite

    Science.gov (United States)

    Jeong, S. W.; Kang, U. G.; Choi, J. Y.; Nam, W. J.

    2012-09-01

    Strain aging and hardening behaviors of a 304 stainless steel containing deformation-induced martensite were investigated by examining mechanical properties and microstructural evolution for different aging temperature and time. Introduced age hardening mechanisms of a cold rolled 304 stainless steel were the additional formation of α'-martensite, hardening of α'-martensite, and hardening of deformed austenite. The increased amount of α'-martensite at an aging temperature of 450 °C confirmed the additional formation of α'-martensite as a hardening mechanism in a cold rolled 304 stainless steel. Additionally, the increased hardness in both α'-martensite and austenite phases with aging temperature proved that hardening of both α'-martensite and austenite phases would be effective as hardening mechanisms in cold rolled and aged 304 stainless steels. The results suggested that among hardening mechanisms, hardening of an α'-martensite phase, including the diffusion of interstitial solute carbon atoms to dislocations and the precipitation of fine carbide particles would become a major hardening mechanism during aging of cold rolled 304 stainless steels.

  10. Monte Carlo simulated corrections for beam commissioning measurements with circular and MLC shaped fields on the CyberKnife M6 System: a study including diode, microchamber, point scintillator, and synthetic microdiamond detectors

    Science.gov (United States)

    Francescon, P.; Kilby, W.; Noll, J. M.; Masi, L.; Satariano, N.; Russo, S.

    2017-02-01

    Monte Carlo simulation was used to calculate correction factors for output factor (OF), percentage depth-dose (PDD), and off-axis ratio (OAR) measurements with the CyberKnife M6 System. These include the first such data for the InCise MLC. Simulated detectors include diodes, air-filled microchambers, a synthetic microdiamond detector, and point scintillator. Individual perturbation factors were also evaluated. OF corrections show similar trends to previous studies. With a 5 mm fixed collimator the diode correction to convert a measured OF to the corresponding point dose ratio varies between  -6.1% and  -3.5% for the diode models evaluated, while in a 7.6 mm  ×  7.7 mm MLC field these are  -4.5% to  -1.8%. The corresponding microchamber corrections are  +9.9% to  +10.7% and  +3.5% to  +4.0%. The microdiamond corrections have a maximum of  -1.4% for the 7.5 mm and 10 mm collimators. The scintillator corrections are  15%, reducing to    d max were  M6 Systems and retrospectively checking estimated corrections used previously. We recommend the PDD and OAR corrections are used to guide detector selection and inform the evaluation of results rather than to explicitly correct measurements.

  11. Radiation Hardening and Verification Procedure for Compact Flip-Flop Design

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Inyong; Sung, Seung Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    For radiation-related applications applying electronic devices in nuclear, space, medicine, and scientific experiment, single event transients (SETs) and single event upsets (SEUs) are become primary concern since they can cause malfunctions in a system by affecting the signal transition and flipping digital bits. The D flip-flop as a register is generally used in digital circuits that require data stability and high speed. For many years, radiation-hardened-by-design (RHBD) circuits have been gradually developed from traditional circuit architectures. One of common methods is to exploit redundancy in an important circuit block to preserve the correct signal. This technique uses a voting process to have a correct output when other duplicated systems fail due to a single event effect (SEE) including SET and SEU. For instance, B. Olson applied the redundancy technique, formally referred the triple modular redundancy (TMR). Other researchers use various error detection and correction (EDAC) algorithms including redundant bits in the storage circuits to detect and correct errors at the system level. practical experiments at radiation exposure facilities. Korea Atomic Energy Research Institute (KAERI) operates a laboratory with high energy radioactive isotope, {sup 60}Co in Jeongeup, Korea. The facility can provide various experiments requiring experimental environment changes by controlling radiation activity and radiated energy. The future direction on RHBD circuits would be integration with the digital DFF presented in this paper and analog front-end units such as OP-amp for charge sensitive or shaping amplifier. Analog-to-digital converters (ADCs) are also major components necessarily imbedded in the most of sensor related electronics. Thus RHBD techniques are inevitably required to protect these circuits from SEE; specifically, SEUs for digital logics and SETs for analog signals. Since most ADCs consist of both analog and digital circuits in their architectures

  12. Coherent beam-beam effects

    International Nuclear Information System (INIS)

    Chao, A.W.

    1992-01-01

    There are two physical pictures that describe the beam-beam interaction in a storage ring collider: The weak-strong and the strong-strong pictures. Both pictures play a role in determining the beam-beam behavior. This review addresses only the strong-strong picture. The corresponding beam dynamical effects are referred to as the coherent beam-beam effects. Some basic knowledge of the weak-strong picture is assumed. To be specific, two beams of opposite charges are considered. (orig.)

  13. Beam dynamics in the SLC final focus system

    International Nuclear Information System (INIS)

    Bambade, P.S.

    1987-06-01

    The SLC luminosity is reached by colliding beams focused to about 2 μm transverse sizes. The Final Focus System (FFS) must enable, beyond its basic optical design, the detection and correction of errors accumulated in the system. In this paper, after summarizing the design, we review the sensitivity to such errors and the ability to correct them. The overall tuning strategy involves three phases: single beam spot minimization, steering the beams in collision and luminosity optimization with beam-beam effects

  14. The renormalized theory of beam-beam interaction

    International Nuclear Information System (INIS)

    Chin, Yong Ho.

    1988-06-01

    A new approach to calculate analytically the particle distribution in the presence of beam-beam interaction and synchrotron radiation effects for an electron-positron colliding beam storage ring is presented. The method is based on correct calculation of the Green's function which includes the full effect of the beam-beam force on the distortion of particle orbits, borrowing the renormalization technique of quantum field therory. By this way, the theory is applicable to any level of beam-beam interaction, no matter whether chaos ensues in phase space or not. This paper is devoted mostly to verificaiton of the theory by comparison with the results of computer simulations. Fairly good agreements are obtained. 5 refs., 3 figs

  15. Beam position monitor sensitivity for low-β beams

    International Nuclear Information System (INIS)

    Shafer, R.E.

    1993-01-01

    At low velocities, the EM field of a particle in a conducting beam tube is no longer a TEM wave, but has a finite longitudinal extent. The net effect of this is to reduce the coupling of the high-frequency Fourier components of the beam current to BPM (beam position monitor) electrodes, which modifies the BPM sensitivity to beam displacement. This effect is especially pronounced for high-frequency, large-aperture pickups used for low-β beams. Non-interceptive beam position monitors used in conjunction with high frequency RFQ (radio-frequency-quadrupole) and DTL (drift-tube-linac) accelerators fall into this category. When testing a BPM with a thin wire excited with either pulses or high-frequency sinusoidal currents, the EM wave represents the principal (TEM) mode in a coaxial transmission line, which is equivalent to a highly relativistic (β = 1) beam. Thus wire measurements are not suitable for simulating slow particle beams in high bandwidth diagnostic devices that couple to the image currents in the beam tube wall. Attempts to load the tin wire either capacitively or inductively to slow the EM wave down have met with limited success. In general, the equations used to represent the 2-D response of cylindrical-geometry BPMs to charged-particle beams make several assumptions: (1) the BPM electrodes are flush with and grounded to the surface of the conducting beam tube; (2) the beam is a line source (pencil beam); (3) the longitudinal extent of the EM field of a beam particle at the beam tube wall is zero, corresponding to a highly relativistic beam. The purpose of this paper is to make some quantitative estimates of the corrections to the conventional approximations when a BPM is used to measure the position of low velocity (low-β) beams

  16. The fast correction coil feedback control system

    International Nuclear Information System (INIS)

    Coffield, F.; Caporaso, G.; Zentler, J.M.

    1989-01-01

    A model-based feedback control system has been developed to correct beam displacement errors in the Advanced Test Accelerator (ATA) electron beam accelerator. The feedback control system drives an X/Y dipole steering system that has a 40-MHz bandwidth and can produce ±300-Gauss-cm dipole fields. A simulator was used to develop the control algorithm and to quantify the expected performance in the presence of beam position measurement noise and accelerator timing jitter. The major problem to date has been protecting the amplifiers from the voltage that is inductively coupled to the steering bars by the beam. 3 refs., 8 figs

  17. Scattered radiation in fan beam imaging systems

    International Nuclear Information System (INIS)

    Johns, P.C.; Yaffe, M.

    1982-01-01

    Scatter-to-primary energy fluence ratios (S/P) have been studied for fan x-ray beams as used in CT scanners and slit projection radiography systems. The dependence of S/P on phantom diameter, distance from phantom to image receptor, and kilovoltage is presented. An empirical equation is given that predicts S/P over a wide range of fan beam imaging configurations. For CT body scans on a 4th-generation machine, S/P is approximately 5%. Scattered radiation can produce a significant cupping artefact in CT images which is similar to that due to beam hardening. When multiple slices are used in scanned slit radiography, they can be arranged such that the increase in S/P is negligible. Calculations of scatter-to-primary ratios for first order scattering showed that for fan beams the contribution of coherent scatter is comparable to or greater than that of incoherent first scatter

  18. HU deviation in lung and bone tissues: Characterization and a corrective strategy.

    Science.gov (United States)

    Ai, Hua A; Meier, Joseph G; Wendt, Richard E

    2018-05-01

    In the era of precision medicine, quantitative applications of x-ray Computed Tomography (CT) are on the rise. These require accurate measurement of the CT number, also known as the Hounsfield Unit. In this study, we evaluated the effect of patient attenuation-induced beam hardening of the x-ray spectrum on the accuracy of the HU values and a strategy to correct for the resulting deviations in the measured HU values. A CIRS electron density phantom was scanned on a Siemens Biograph mCT Flow CT scanner and a GE Discovery 710 CT scanner using standard techniques that are employed in the clinic to assess the HU deviation caused by beam hardening in different tissue types. In addition, an anthropomorphic ATOM adult male upper torso phantom was scanned on the GE Discovery 710 scanner. Various amounts of Superflab bolus material were wrapped around the phantoms to simulate different patient sizes. The mean HU values that were measured in the phantoms were evaluated as a function of the water-equivalent area (A w ), a parameter that is described in the report of AAPM Task Group 220. A strategy by which to correct the HU values was developed and tested. The variation in the HU values in the anthropomorphic ATOM phantom under different simulated body sizes, both before and after correction, were compared, with a focus on the lung and bone tissues. Significant HU deviations that depended on the simulated patient size were observed. A positive correlation between HU and A w was observed for tissue types that have an HU of less than zero, while a negative correlation was observed for tissue types with HU values that are greater than zero. The magnitude of the difference increases as the underlying attenuation property deviates further away from that of water. In the electron density phantom study, the maximum observed HU differences between the measured and reference values in the cortical bone and lung materials were 426 and 94 HU, respectively. In the anthropomorphic phantom

  19. Effect of elemental composition of ion beam on the phase formation and surface strengthening of structural materials

    International Nuclear Information System (INIS)

    Avdienko, K.I.; Avdienko, A.A.; Kovalenko, I.A.

    2001-01-01

    The investigation results are reported on the influence of ion beam element composition on phase formation, wear resistance and microhardness of surface layers of titanium alloys VT-4 and VT-16 as well as stainless steel 12Kh18N10T implanted with nitrogen, oxygen and boron. It is stated that ion implantation into structural materials results in surface hardening and is directly dependent on element composition of implanted ion beam. The presence of oxygen in boron or nitrogen ion beams prevents the formation of boride and nitride phases thus decreasing a hardening effect [ru

  20. Multi-MGy Radiation Hardened Camera for Nuclear Facilities

    International Nuclear Information System (INIS)

    Girard, Sylvain; Boukenter, Aziz; Ouerdane, Youcef; Goiffon, Vincent; Corbiere, Franck; Rolando, Sebastien; Molina, Romain; Estribeau, Magali; Avon, Barbara; Magnan, Pierre; Paillet, Philippe; Duhamel, Olivier; Gaillardin, Marc; Raine, Melanie

    2015-01-01

    There is an increasing interest in developing cameras for surveillance systems to monitor nuclear facilities or nuclear waste storages. Particularly, for today's and the next generation of nuclear facilities increasing safety requirements consecutive to Fukushima Daiichi's disaster have to be considered. For some applications, radiation tolerance needs to overcome doses in the MGy(SiO 2 ) range whereas the most tolerant commercial or prototypes products based on solid state image sensors withstand doses up to few kGy. The objective of this work is to present the radiation hardening strategy developed by our research groups to enhance the tolerance to ionizing radiations of the various subparts of these imaging systems by working simultaneously at the component and system design levels. Developing radiation-hardened camera implies to combine several radiation-hardening strategies. In our case, we decided not to use the simplest one, the shielding approach. This approach is efficient but limits the camera miniaturization and is not compatible with its future integration in remote-handling or robotic systems. Then, the hardening-by-component strategy appears mandatory to avoid the failure of one of the camera subparts at doses lower than the MGy. Concerning the image sensor itself, the used technology is a CMOS Image Sensor (CIS) designed by ISAE team with custom pixel designs used to mitigate the total ionizing dose (TID) effects that occur well below the MGy range in classical image sensors (e.g. Charge Coupled Devices (CCD), Charge Injection Devices (CID) and classical Active Pixel Sensors (APS)), such as the complete loss of functionality, the dark current increase and the gain drop. We'll present at the conference a comparative study between these radiation-hardened pixel radiation responses with respect to conventional ones, demonstrating the efficiency of the choices made. The targeted strategy to develop the complete radiation hard camera