WorldWideScience

Sample records for backscattered pu-be neutrons

  1. Validation of neutron data libraries by backscattered spectra of Pu-Be Neutrons

    CERN Document Server

    El-Agib, I

    1999-01-01

    Elastically backscattered spectra of Pu-Be neutrons have been measured for SiO sub 2 , water, graphite, paraffin oil and Al slabs using a proton recoil spectrometer. The results were compared with the calculated spectra obtained by the three-dimensional Monte-Carlo transport code MCNP-4B and point-wise cross sections from the ENDF/B-V, ENDF/B-VI, JENDL-3.1 and BROND-2 data libraries. The good agreement between the measured and calculated results indicates that this procedure can be used for validation of different data libraries. This simple method renders possible the detection of oxygen, carbon and hydrogen in bulk samples. (author)

  2. Characterization of a neutron source of 239PuBe

    International Nuclear Information System (INIS)

    The spectrum equivalent dose and environmental equivalent dose f a 239PuBe source have been determined. The appropriate handling of a neutron source depends on the knowledge of its characteristics, such as its energy distribution, total rate of flowing and dosimetric magnitudes. In many facilities have not spectrometer that allows to determine the spectrum and then area monitors are used that give a dosimetric magnitude starting from measuring the flowing rate and the use of conversion factors, however this procedure has many limitations and it is preferable to measure the spectra and starting from this information the interest dosimetric magnitudes are calculated. In this work a Bonner sphere spectrometer has been used with a 6LiI(Eu) scintillator obtaining the count rates that produce, to a distance of 100 cm, a 239PuBe source of 1.85E(11) Bq. The spectrum was reconstructed starting from the count rates using BUNKIUT code and response matrix UTA4. With the spectrum information was calculated the source intensity, total flow, energy average, equivalent dose rate, environmental equivalent dose rate, equivalent dose coefficient and environmental equivalent dose coefficient. By means of two area monitors for neutrons, Eberline ASP-1 and LB 6411 of Berthold the equivalent dose and environmental equivalent dose were measured. The determinate values were compared with those reported in literature and it found that are coincident inside 17%. (Author)

  3. Characterization of a neutron source of {sup 239}PuBe; Caracterizacion de una fuente de neutrones de {sup 239}PuBe

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez V, R.; Chacon R, A.; Hernandez D, V. M.; Mercado, G. A.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Ramirez G, J. [Instituto Nacional de Estadistica Geografia e Informatica, Direccion General de Innovacion y Tecnologia de Informacion, Av. Heroes de Nacozari Sur 2301, Fracc. Jardines del Parque, 20276 Aguascalientes (Mexico)], e-mail: ruben_zac@yahoo.com

    2009-10-15

    The spectrum equivalent dose and environmental equivalent dose f a {sup 239}PuBe source have been determined. The appropriate handling of a neutron source depends on the knowledge of its characteristics, such as its energy distribution, total rate of flowing and dosimetric magnitudes. In many facilities have not spectrometer that allows to determine the spectrum and then area monitors are used that give a dosimetric magnitude starting from measuring the flowing rate and the use of conversion factors, however this procedure has many limitations and it is preferable to measure the spectra and starting from this information the interest dosimetric magnitudes are calculated. In this work a Bonner sphere spectrometer has been used with a {sup 6}LiI(Eu) scintillator obtaining the count rates that produce, to a distance of 100 cm, a {sup 239}PuBe source of 1.85E(11) Bq. The spectrum was reconstructed starting from the count rates using BUNKIUT code and response matrix UTA4. With the spectrum information was calculated the source intensity, total flow, energy average, equivalent dose rate, environmental equivalent dose rate, equivalent dose coefficient and environmental equivalent dose coefficient. By means of two area monitors for neutrons, Eberline ASP-1 and LB 6411 of Berthold the equivalent dose and environmental equivalent dose were measured. The determinate values were compared with those reported in literature and it found that are coincident inside 17%. (Author)

  4. THERMAL NEUTRON BACKSCATTER IMAGING.

    Energy Technology Data Exchange (ETDEWEB)

    VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.

    2004-10-16

    Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.

  5. Multi-technique characterization of neutron fields from moderated 252Cf and 238PuBe sources

    International Nuclear Information System (INIS)

    At the Lawrence Livermore Laboratory, 252Cf and 238PuBe neutron sources are used for calibration of personnel neutron dose meters and neutron monitoring instrumentation. The sources with emission rates of approximately 2x109 and 2x107 n.s-1, respectively, have been calibrated by the United States National Bureau of Standards. The sources are transferred into a 815 m3 concrete calibration cell through a remotely operated pneumatic system. Calibrations can be made without source moderation, or with spherical moderators of aluminium, polyethylene, water or deuterium oxide placed over the end of the pneumatic irradiation tube. The source is located in the tube at one metre above a false floor in the centre of the cell. Nine different moderators are available in sizes up to 56 cm in diameter. Several techniques have been used to characterize the neutron fields produced by each source-moderator configuration to improve the quality of our calibrations. Measurements and calculations have been made to determine neutron flux, kerma rate, neutron spectrum, quality factor, dose equivalent rate and linear energy transfer (LET) spectrum. Neutron spectra are determined by: (1) Calibration using the ANISN discrete ordinates transport code, (2) Bonner sphere measurements using the LOUHI unfolding code, and (3) measurement with proton recoil counters and liquid scintillation detectors. The spectra are then folded into published energy dependent conversion factors to yield kerma, quality factor and dose equivalent values. We obtain LET spectra using a tissue-equivalent LET chamber and the GANDALF unfolding code. Chamber data are used to determine kerma and quality factor. Finally, an 80 cm3 tissue-equivalent ion chamber and neutron-insensitive Geiger counter are used to measure the neutron kerma. Results of the various techniques are presented and compared. In addition, comparisons are made with results obtained from conventional health physics instrumentation such as moderated rem

  6. Effect of double false pulses in calibrated neutron coincidence collar during measuring time-correlated neutrons from PuBe neutron sources

    International Nuclear Information System (INIS)

    Effect of double false pulses of preamplifiers in neutron coincidence collar was investigated to explain non-parallel shape of calibrated D/S–MPu curves of two commercial neutron coincidence collars, JCC-31 and JCC-13. Two curves, which were constructed from D/S ratio (doubles and singles count rate), and Pu content MPu, of the same set of secondary standard PuBe neutron sources, should be parallel. Non-parallelism rises doubt about usability of the method based on this curve for determination of Pu content in PuBe neutron sources. We have shown in three steps that the problem originates from double false pulses of preamplifiers in JCC-13. First we used a pulse train diagram for analyzing the non-parallel shape, second we used Rossi-Alpha distribution measured by pulse train recorder developed in our institute and finally, we investigated the effect of inserted noise pulses. This implies a new type of QA test option in traditional multiplicity shift registers for excluding presence of double false pulses

  7. Effect of double false pulses in calibrated neutron coincidence collar during measuring time-correlated neutrons from PuBe neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Tam Cong, E-mail: tam.nguyen.cong@energia.mta.hu; Huszti, Jozsef; Nguyen, Quan Van

    2015-09-01

    Effect of double false pulses of preamplifiers in neutron coincidence collar was investigated to explain non-parallel shape of calibrated D/S–M{sub Pu} curves of two commercial neutron coincidence collars, JCC-31 and JCC-13. Two curves, which were constructed from D/S ratio (doubles and singles count rate), and Pu content M{sub Pu}, of the same set of secondary standard PuBe neutron sources, should be parallel. Non-parallelism rises doubt about usability of the method based on this curve for determination of Pu content in PuBe neutron sources. We have shown in three steps that the problem originates from double false pulses of preamplifiers in JCC-13. First we used a pulse train diagram for analyzing the non-parallel shape, second we used Rossi-Alpha distribution measured by pulse train recorder developed in our institute and finally, we investigated the effect of inserted noise pulses. This implies a new type of QA test option in traditional multiplicity shift registers for excluding presence of double false pulses.

  8. Investigation of primary cooling water chemistry following the partial meltdown of Pu-Be neutron source in Tehran Research Reactor Core (TRR)

    International Nuclear Information System (INIS)

    Research highlights: → Effect of Pu-Be neutron source meltdown in core on reactor water chemistry. → Water chemistry of primary cooling before, during and after of above incident was compared. → Training importance. → Management of nuclear incident and accident. - Abstract: Effect of Pu-Be neutron source meltdown in core on reactor water chemistry was main aim of this study. Leaving the neutron source in the core after reactor power exceeds a few hundred Watts was the main reason for its partial meltdown. Water chemistry of primary cooling before, during and after of above incident was compared. Activity of some radio-nuclides such as Ba-140, La-140, I-131, I-132, Te-132 and Xe-135 increased. Other radio-nuclides such as Nd-147, Xe-133, Sr-91, I-133 and I-135 are also detected which were not existed before this incident.

  9. Measurements and calculations of neutron leakage spectra from slabs irradiated with 9Be(d, n)10B 2H(d, n)3He and Pu-Be neutrons

    International Nuclear Information System (INIS)

    The spectra of neutrons from the 9Be(d, n)10B, 2H(d, n)3He and Pu-Be sources passing through slabs of water, graphite, Al, Fe and Pb up to 20 cm in thickness were measured by a pulse height response spectrometer in the 1.5-15 MeV range. The measured leakage spectra have been compared with calculated results obtained using the three dimensional Monte-Carlo code MCNP-4A and point-wise cross sections from the ENDF/B-IV, ENDF/B-VI and JENDL-3.1 data files. A comparison of the measured and calculated data has shown that the MCNP-4A code with an appropriate library can reasonably approximate the measured leakage spectra

  10. Measurements and calculations of neutron leakage spectra from slabs irradiated with {sup 9}Be(d, n){sup 10}B {sup 2}H(d, n){sup 3}He and Pu-Be neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Olah, L.; Jordanova, J.; El-Megrab, A.M.; Darsono, Perez N.; Yousif, M.Y.A.; Csikai, J. [Institute of Experimental Physics, Kossuth University, Debrecen (Hungary); Fenyvesi, A.; Majdeddin, A.D. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary)

    1999-03-01

    The spectra of neutrons from the {sup 9}Be(d, n){sup 10}B, {sup 2}H(d, n){sup 3}He and Pu-Be sources passing through slabs of water, graphite, Al, Fe and Pb up to 20 cm in thickness were measured by a pulse height response spectrometer in the 1.5-15 MeV range. The measured leakage spectra have been compared with calculated results obtained using the three dimensional Monte-Carlo code MCNP-4A and point-wise cross sections from the ENDF/B-IV, ENDF/B-VI and JENDL-3.1 data files. A comparison of the measured and calculated data has shown that the MCNP-4A code with an appropriate library can reasonably approximate the measured leakage spectra.

  11. Neutron monitor calibration with 241AmBe(α, n), 252Cf , 252Cf+D2O and 238PuBe(α, n) used in dose evaluation near Linac

    International Nuclear Information System (INIS)

    The use of linear accelerators in Radiotherapy is becoming increasingly more common. From the Radiation Protection point of view, these instruments represent an advance relative to cobalt and caesium irradiators, mainly due to the absence of radioactive material. On the other hand, accelerators with energies over 10 MeV contaminate with neutrons the therapeutic beam. These neutrons are generated when high-energy photons interact with high-atomic-number materials such as tungsten and lead present in the accelerator itself. Photo-neutrons can also interact with other materials, present in the treatment room, consequently modifying the initial spectrum and causing other types of interactions which privilege the gamma capture. In this way, the measurement of the photo-neutron spectrum can be necessary in a radiometric survey. The present work carries through measurements in a linear accelerator of 15 MeV using three neutron area monitors calibrated using four radioactive sources: three ISO reference sources, 241AmBe (α, n), 252Cf (f, n) and 252Cf+D2O, and a 238PuBe(α, n) source. As the three first sources, this last one was standardized in the LMNRI/IRD manganese bath system. Comparison and evaluation of the response of these instruments were thereby made, analyzing whether the reading of the detectors using standard sources is adequate. In conclusion, the analysis of the response of neutron area calibrated detectors enable the use of them in an environment containing medical linear accelerator. (author)

  12. Backscattering at a pulsed neutron source, the MUSICAL instrument

    International Nuclear Information System (INIS)

    In the first part the principles of the neutron backscattering method are described and some simple considerations about the energy resolution and the intensity are presented. A prototype of a backscattering instrument, the first Juelich instrument, is explained in some detail and a representative measurement is shown which was performed on the backscattering instrument IN10 at the ILL in Grenoble. In the second part a backscattering instrument designed for a pulsed neutron source is proposed. It is shown that a rather simple modification, which consists in the replacement of the Doppler drive of the conventional backscattering instrument by a multi silicon monochromator crystal (MUSICAL) leads to a very effective instrument, benefitting from the peak flux of the pulsed source. ((orig.))

  13. Using Back-Scattering to Enhance Efficiency in Neutron Detectors

    OpenAIRE

    Kittelmann, Thomas; Klinkby, Esben; Cai, Xiao Xiao; Kanaki, Kalliopi; Cooper-Jensen, Carsten P.; Hall-Wilton, Richard

    2015-01-01

    The principle of using strongly scattering materials to recover efficiency in neutron detectors, via back-scattering of unconverted thermal neutrons, is discussed in general. Feasibility of the method is illustrated through Geant4-based simulations of a specific setup involving a moderator-like material placed behind a single layered boron-10 thin film gaseous detector.

  14. Application of neutron backscatter techniques to level measurement problems

    International Nuclear Information System (INIS)

    We have designed and built portable level detectors and fixed level monitors based on neutron scattering and detection principles. The main components of these devices, which we call neutron backscatter gauges, are a neutron emitting radioisotope, a neutron detector, and a ratemeter. The gauge is a good detector for hydrogen but is much less sensitive to most other materials. This allows level measurements of hydrogen bearing materials, such as hydrocarbons, to be made through the walls of metal vessels. Measurements can be made conveniently through steel walls which are a few inches thick. We have used neutron backscatter gauges in a wide variety of level measurement applications encountered in the petrochemical industry. In a number of cases, the neutron techniques have proven to be superior to conventional level measurement methods, including gamma ray methods

  15. BACKSCATTER GUAGE DESCRIPTION FOR INSPECTION OF NEUTRON ABSORBER AND UNIFORMITY

    Energy Technology Data Exchange (ETDEWEB)

    Dewberry, R.; Gibbs, K.; Couture, A.

    2012-05-23

    This paper describes design, calibration, and testing of a dual He-3 detector neutron backscatter gauge for use in the Savannah River Site Mixed Oxide Fuel project. The gauge is demonstrated to measure boron content and uniformity in concrete slabs used in the facility construction.

  16. Backscatter gauge description for inspection of neutron absorber content

    Science.gov (United States)

    Dewberry, R. A.; Gibbs, K. M.; Couture, A. H.

    2013-05-01

    This paper describes design, calibration, and testing of a dual He-3 detector neutron backscatter gauge for use in the Savannah River Site Mixed Oxide Fuel project. The gauge is demonstrated to measure boron content and uniformity in concrete slabs used in the facility construction.

  17. Monte-Carlo simulations of elastically backscattered neutrons from hidden explosives using three different neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    ElAgib, I. [College of Science, King Saud University, P.O. Box 2455 (Saudi Arabia)], E-mail: elagib@ksu.edu.sa; Elsheikh, N. [College of Applied and Industrial Science, University of Juba, Khartoum, P.O. Box 321 (Sudan); AlSewaidan, H. [College of Science, King Saud University, P.O. Box 2455 (Saudi Arabia); Habbani, F. [Faculty of Science, Physics Department, University of Khartoum, Khartoum, P.O. Box 321 (Sudan)

    2009-01-15

    Calculations of elastically backscattered (EBS) neutrons from hidden explosives buried in soil were performed using Monte-Carlo N-particle transport code MCNP5. Three different neutron sources were used in the study. The study re-examines the performance of the neutron backscattering methods in providing identification of hidden explosives through their chemical composition. The EBS neutron energy spectra of fast and slow neutrons of the major constituent elements in soil and an explosive material in form of TNT have shown definite structures that can be used for the identification of a buried landmine.

  18. Development of landmine detection system by using backscattering neutron method

    International Nuclear Information System (INIS)

    Metal detector could not detect many kinds of Anti-Personal landmines which consist of plastic and explosive materials, for example TNT, RDX, etc, hence nuclear radiation detector, namely the gamma rays and neutron detectors, is prospect to be applied. One nuclear method for determining the landmine is measuring the backscattering neutron. The concept of radiation detection is detecting bulk material landmine which contains hydrogen, nitrogen, oxygen, and/or carbon by irradiating the soil with neutrons and detecting the gamma rays and neutron radiation that appears on the soil surface as a result from neutron-soil/target interaction. The development of landmine detection system has been proposed by using thermal backscattering neutron method. However, some difficulties are caused by the complexity of conditions, for example humidity, soil contents, density of each material of landmines and others. The purpose of this study is to setup a detection system with high efficiency for detecting the landmine by utilizing backscattering neutron method. Previously, the landmine detection experiment has been based on measuring the difference in the total counts of neutron in two cases, which are with and without melamine target. Nevertheless, a detection problem still remains in the case of deeply location target to the surface and humid cases due to the domination of hydrogen effect. In the present work, in order to detect as efficient as possible the existence of landmine inside the soil, two methods are applied simultaneously. First, the total counts measurements are performed, and then the determination of epithermal and fast backscattering neutrons effect is measured by using the 3He detector with Cadmium covered. In order to obtain the dominant effect of hydrogen in all energy ranges, the total neutron count will be conducted firstly. The total neutron counts measurement is suitable when higher content hydrogen exist in the landmines rather than in the soil. The

  19. Monte Carlo simulations of landmine detection using neutron backscattering imaging

    Energy Technology Data Exchange (ETDEWEB)

    Datema, Cor P. E-mail: c.datema@iri.tudelft.nl; Bom, Victor R.; Eijk, Carel W.E. van

    2003-11-01

    Neutron backscattering is a technique that has successfully been applied to the detection of non-metallic landmines. Most of the effort in this field has concentrated on single detectors that are scanned across the soil. Here, two new approaches are presented in which a two-dimensional image of the hydrogen distribution in the soil is made. The first method uses an array of position-sensitive {sup 3}He-tubes that is placed in close proximity of the soil. The second method is based on coded aperture imaging. Here, thermal neutrons from the soil are projected onto a detector which is typically placed one to several meters above the soil. Both methods use a pulsed D/D neutron source. The Monte Carlo simulation package GEANT 4 was used to investigate the performance of both imaging systems.

  20. Investigation of sheared liquids by neutron backscattering and reflectivity

    CERN Document Server

    Wolff, M; Hock, R; Frick, B; Zabel, H

    2002-01-01

    We have investigated by neutron scattering structural and dynamical properties of water solutions of the triblock copolymer P85 under shear. To this end a shear cell that suits the requirements for neutron backscattering and another for reflectivity experiments have been built. In reflectivity measurements we find the polymer concentration (nominal concentration of 33% by weight) to vary right at the surface between 12% and 52% for hydrophilic or hydrophobic coated silicon wavers, for temperatures between 18 C and 73 C and for shear rates up to 2500 s sup - sup 1. Additional structural changes deeper in the bulk are also observed. On the backscattering instrument (IN10 at ILL) we find that the liquid appears to stick to the plates of the shear cell, implying an unusual macroscopic velocity distribution that differs from that found earlier for lubrication oils. We report further on changes of the quasielastic line width in the direction of the shear gradient for different temperatures and shear rates. (orig.)

  1. Neutron monitor calibration with {sup 241}AmBe({alpha}, n), {sup 252}Cf , {sup 252C}f+D{sub 2}O and {sup 238}PuBe({alpha}, n) used in dose evaluation near Linac

    Energy Technology Data Exchange (ETDEWEB)

    Salgado, Ana Paula; Pereira, Walsan Wagner; Patrao, Karla Cristina de Souza; Fonseca, Evaldo Simoes da [Instituto de Radioprotecao e Dosimetria (IRD-CNEN/RJ), Rio de Janeiro, RJ (Brazil). Lab. de Neutrons], e-mail: asalgado@ird.gov.br

    2009-07-01

    The use of linear accelerators in Radiotherapy is becoming increasingly more common. From the Radiation Protection point of view, these instruments represent an advance relative to cobalt and caesium irradiators, mainly due to the absence of radioactive material. On the other hand, accelerators with energies over 10 MeV contaminate with neutrons the therapeutic beam. These neutrons are generated when high-energy photons interact with high-atomic-number materials such as tungsten and lead present in the accelerator itself. Photo-neutrons can also interact with other materials, present in the treatment room, consequently modifying the initial spectrum and causing other types of interactions which privilege the gamma capture. In this way, the measurement of the photo-neutron spectrum can be necessary in a radiometric survey. The present work carries through measurements in a linear accelerator of 15 MeV using three neutron area monitors calibrated using four radioactive sources: three ISO reference sources, {sup 241}AmBe ({alpha}, n), {sup 252}Cf (f, n) and 252{sup C}f+D{sub 2}O, and a 238{sup P}uBe({alpha}, n) source. As the three first sources, this last one was standardized in the LMNRI/IRD manganese bath system. Comparison and evaluation of the response of these instruments were thereby made, analyzing whether the reading of the detectors using standard sources is adequate. In conclusion, the analysis of the response of neutron area calibrated detectors enable the use of them in an environment containing medical linear accelerator. (a0011uth.

  2. Landmine detection method combined with backscattering neutrons and capture {gamma}-rays from hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Yoshiyuki, E-mail: ytaka@rri.kyoto-u.ac.j [Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501 (Japan); Misawa, Tsuyoshi; Pyeon, Cheol Ho; Shiroya, Seiji [Research Reactor Institute, Kyoto University, Asashiro-nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Yoshikawa, Kiyoshi [Institute of Advanced Energy, Kyoto University, Gokashou, Uji-shi, Kyoto 611-0011 (Japan)

    2011-07-15

    The usefulness of the measurements of the backscattering neutron and 2.22 MeV capture {gamma}-ray from hydrogen in the landmine detection method is described in this paper. When the soil moisture content is increased, the reaction rates of both the neutron scattering reaction and capture reaction are increased. However, the backscattering neutrons are more influenced than the capture {gamma}-rays by the soil moisture before the reaction with the detector. The facts that the backscattering neutron method is useful in the dry soil case and that the capture {gamma}-ray method is effective in well-wet soil case are confirmed by the experiments and the calculations. The landmine detection efficiency is improved in various soil moisture conditions by combining the backscattering neutron method together with the capture {gamma}-ray method. The effectiveness of the pulse mode operation was confirmed numerically.

  3. Radio-analysis of hydrogenous material using neutron back-scattering technique

    International Nuclear Information System (INIS)

    In this work, we have explored the possibility of using neutron back-scattering technique in performing radio analysis for samples of hydrogenous materials such as explosives, drugs, crude oil and water, looking for different signals that may be used to discriminate these samples. Monte Carlo simulations were carried out to model the detection system and select the optimal geometry as well. The results were determined in terms of the energy spectra of the back-scattered neutrons.(Author)

  4. The status of the Delft University Neutron Backscatter Landmine Detector (DUNBLAD)

    Energy Technology Data Exchange (ETDEWEB)

    Bom, V.R. E-mail: vb@iri.tudelft.nl; Datema, C.P. E-mail: cor.datema@philips.com; Eijk, C.W.E. van E-mail: vaneijk@iri.tudelft.nl

    2004-07-01

    The neutron backscattering technique may be applied to search for non-metallic landmines in relatively dry soils. A detector system using this technique has been constructed. Tests showed that anti-tank mines can reliably be found, but that, depending on the circumstances, anti-personnel mines may escape detection. A first test with a pulsed neutron generator shows that further improvements can be achieved by applying a window on the neutron transit time.

  5. Artificial neural networks applied in the spectrometry of a 239Pu-Be source

    International Nuclear Information System (INIS)

    To explore the potential use of a neutron source and to define the procedure to handle it under safety conditions, features like neutron spectrum and the ambient dose equivalent of the source must be known. The aim of this work was to determine the spectrum, the total fluence rate and the ambient dose equivalent of a 185 GBq 239Pu-Be neutron source. Using Monte Carlo methods the spectrum, the total fluence rate, and the ambient dose equivalent of a 239Pu-Be were calculated. The spectrum was calculated at 50, 100, 200 and 300 cm from the source in air using MCNP X and MCNP 4C codes. The neutron spectrum was also obtained, at 100 cm, using a Bonner sphere spectrometer whose count rates were used to unfold the neutron spectrum, the unfolding was carried out using an Artificial Neural Network for neutron spectrometry. With the spectrum, the total neutron fluence and the ambient dose equivalent were determined. Calculated results were compared with measured values where Monte Carlo results were smaller than those measured. These differences were attributed to the presence of 241Pu during the source manufacturing. In order to match calculated and measured quantities a 0.102 w/o of 241Pu was estimated. After corrections the differences between calculated and experimental results were 1%. This result shows the advantages of using Artificial Neural Networks technology in the unfolding of neutron spectrum using as a single piece of information the count rates of a Bonner sphere spectrometer. (author)

  6. Experimental results and Monte Carlo simulations of a landmine localization device using the neutron backscattering method

    Energy Technology Data Exchange (ETDEWEB)

    Datema, C.P. E-mail: c.datema@iri.tudelft.nl; Bom, V.R.; Eijk, C.W.E. van

    2002-08-01

    Experiments were carried out to investigate the possible use of neutron backscattering for the detection of landmines buried in the soil. Several landmines, buried in a sand-pit, were positively identified. A series of Monte Carlo simulations were performed to study the complexity of the neutron backscattering process and to optimize the geometry of a future prototype. The results of these simulations indicate that this method shows great potential for the detection of non-metallic landmines (with a plastic casing), for which so far no reliable method has been found.

  7. Anti-Personnel Mine Detection by Neutron Backscattering Technique Using MCNP Simulation

    International Nuclear Information System (INIS)

    The neutron backscattering technique NBS has been applied for land mine detection if the soil is sufficiently dry. The detection of anti - personnel (AP) land mine by neutron backscattering technique has been studied by using Monte Carlo N - Particle (MCNP4B) code. The effect of the burial depth and side position of anti-personnel land mine has been discussed. A two dimensional position sensitive detector is simulated by MCNP4B to obtain an image of the back scattered slow neutrons radiation. Results of simulation using mono- energetic point neutron source (2.45 MeV) are presented. The on-mine to no - mine signal ratio images are presented for different positions and depths

  8. Benchmarking of the SOURCES3A code for PuBe sources

    International Nuclear Information System (INIS)

    The SOURCES3A code calculates neutron production rates and spectra from (α,n) reactions, spontaneous fission decays, and delayed neutron emission in homogeneous media, interface problems, and alpha-particle beams. SOURCES3A promises to be a very useful tool for generating the characteristics of unique sources for use in neutron transport calculations. A number of comparisons of SOURCES3A results with experiments for various source types were presented in Ref. 1. Here, additional spectral benchmarks with both experiments and other calculations for homogeneous PuBe13 sources are provided. Preliminary results for neutron production rates from Bu-Pe metal interfaces are also given. Note that SOURCES3A assumes that alpha-particle ranges are small relative to the dimensions of the materials

  9. Combination of Magnetic Susceptibility, Electromagnetic and Neutron Backscattering Techniques for Land mine Detection

    International Nuclear Information System (INIS)

    Current research focuses on the use of multiple sensors for land mine detection, as opposed to approach which use a single sensor. Magnetic and electromagnetic methods are perhaps the most convenient and popular geophysical survey methods for detecting buried manmade metallic objects; which are due to their non-intrusiveness, high survey speed and quality of information. Meanwhile, the neutron backscattering method can detect the explosive materials in the land mine, which cannot detect by the two mentioned methods. An experimental study has been conducted using the three techniques to determine the minimum lateral resolving distance between two adjacent land mines and to detect the buried situated at deeper depths. The results showed that the magnetic susceptibility and neutron backscattering methods have a minimum lateral resolving distance of about 40 cm while, they have a limited penetration depth. Meanwhile, the horizontal-loop electromagnetic (HLEM) method has a relatively wider lateral resolving distance but it can detect the buried metallic object to several meters depths. Therefore, such combination of the three mentioned methods to detect the land mine yields more information about the type, lateral resolving distance between two adjacent land mines and depth of the buried land mines than is obtain, when each method is used individually. Also, such results will help greatly in evaluating any multi-sensors detection approach of magnetic susceptibility, electromagnetic and neutron backscattering techniques

  10. The soil moisture and its effect on the detection of buried hydrogenous material by neutron backscattering technique

    Energy Technology Data Exchange (ETDEWEB)

    Rezaei Ochbelagh, D. [Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil (Iran, Islamic Republic of)], E-mail: ddrezaey@yahoo.com; Miri Hakimabad, H.; Izadi Najafabadi, R. [Physics Department, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

    2009-05-15

    Among the available nuclear techniques, the neutron backscattering technique, based on the detection of the produced thermal neutrons, is thought to be the most promising for landmine detections. The results obtained from Monte Carlo simulation were used for selection of BF{sub 3} detector and Am-Be neutron source shielding. In addition, soil moisture was discussed as a limitation of the neutron backscattering technique. It was experimentally found that this technique is useful for soil whose water content is lower than 14%.

  11. Neutron Backscattered Technique for Quantification of Oil Palm Fruit Oil Content

    International Nuclear Information System (INIS)

    Non-destructive and real time method becomes a well-liked method to researchers in the oil palm industry since 2000. This method has the ability to detect oil content in order to increase the production of oil palm for better profit. Hence, this research investigates the potential of neutron source to estimate oil content in palm oil fruit since oil palm contains hydrogen with chemical formula C55H96O6. For this paper, oil palm loose fruit was being used and divided into three groups. These three groups are ripe, under-ripe and bruised fruit. A total of 21 loose fruit for each group were collected from a private plantation in Malaysia. Each sample was scanned using neutron backscattered technique. The higher neutron count, the more hydrogen content, and the more oil content in palm oil fruit. The best correlation result came from the ripe fruits with r2=0.98. This research proves that neutron backscattered technique can be used as a non-destructive and real time grading system for palm oil. (author)

  12. Probing Dynamics at Interfaces: Molecular Motions in Lipid Bilayers studied by Neutron Backscattering

    CERN Document Server

    Rheinstädter, M C; Salditt, T; Rheinst\\"adter, Maikel C.; Seydel, Tilo; Salditt, Tim

    2004-01-01

    Lipid membranes in a physiological context cannot be understood without taking into account their mobile environment. Here, we report on a high energy-resolution neutron backscattering study to investigate slow motions on nanosecond time scales in highly oriented solid supported phospholipid bilayers of the model system DMPC -d54 (deuterated 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine). This technique allows discriminating the Q-dependent onset of mobility and provides a benchmark test regarding the feasibility of dynamical neutron scattering investigations on these sample systems. Apart from freezing of the lipid acyl-chains, we could observe a second freezing temperature that we attribute to the hydration water in between the membrane stacks. The freezing is lowered several degrees as compared to (heavy) bulk water.

  13. Nuclear Recoil Calibrations in the LUX Detector Using Direct and Backscattered D-D Neutrons

    Science.gov (United States)

    Rhyne, Casey; LUX Collaboration

    2016-03-01

    The LUX dark matter search experiment is a 350 kg two-phase liquid/gas xenon time projection chamber located at the 4850 ft level of the Sanford Underground Research Facility in Lead, SD. I will discuss the latest calibration of the nuclear recoil (NR) response in liquid xenon (LXe), performed in-situ in the LUX detector using mono-energetic 2.45 MeV neutrons produced via the Adelphi Technologies, Inc. DD108 D-D neutron generator. The calibration measured the NR charge yield in LXe (Qy) to 0.7 keVnr recoil energy with an absolute determination of deposited energy and the NR light yield in LXe (Ly) to recoil energies of 1.1 keVnr, both of which improve upon all previous measurements. I will then focus in depth on the extension of this calibration using a new technique for generating a beam of sub-300 keV quasi-mono-energetic neutrons via the backscatter of 2.45 MeV neutrons off a deuterium-based reflector. Current simulations work optimizing the technique, its advantages, and its impact on future research will be discussed, including the extension of the NR Qy calibration down to 0.14 keVnr, an independent NR Ly calibration, and an a priori estimate of the expected 8B solar neutrino-nucleus coherent scattering signal in the upcoming LUX-ZEPLIN experiment.

  14. Detection of antipersonnel landmines by measuring backscattered neutrons. Part I: Detection of thermal neutrons

    International Nuclear Information System (INIS)

    The high sensitivity of neutrons to low-A nuclei (the main constituents of explosives) together with their good penetration ability of soil makes neutrons the choice of nuclear probes for the detection of buried landmines. One obvious way to utilize neutrons is to analyze their quality after scattering from the area of interest. Two methods using scattering of neutrons for mine detection have evolved so far. Both depend on the rather high hydrogen content of practically all known explosives. The thermalization of neutrons by hydrogen is exploited, e.g., by HYDAD (HYdrogen Density Anomaly Detection) systems that have been developed to detect small (< 300 g) antipersonnel landmines (APM) of plastic construction. The present status of the HYDAD-D system is discussed briefly in this contribution. (author)

  15. Determination of hydrogen content of petroleum products from Tema Oil Refinery using neutron backscatter technique

    International Nuclear Information System (INIS)

    The hydrogen content of hydrocarbon materials is very important in several areas of industrial process such as mining, vegetable oil extraction and crude oil exploration and refining. A fast and more universal technique based on thermal neutron reflection was employed to determine the total hydrogen contents of petroleum samples from Tema Oil Refinery (TOR) and Crude oil samples from Jubilee field and Nigeria. The experimental set-up consisted of a source-holder housing a 1Ci Am-Be neutron source and a He-3 neutron detector. Two geometrical arrangements were considered and their sensitivities were compared. The set-up was used to measure the excess neutron count in both geometrical considerations and their reflection parameters were calculated as a function of hydrogen content of the samples. Calibration lines were deduced using liquid hydrocarbons containing well-known hydrogen and carbon contents as standards. Two linear equations were generated from the calibration lines and were used to further determine the hydrogen content of thirteen (13) petroleum samples obtained from Quality Control Department of TOR. The total hydrogen contents were found to be in the range of 7.211(hw %) - 15.069 (hw %) for vertical geometry and 7.206 (hw %) - 14.948 (hw %) for horizontal geometry respectively. The results obtained agreed constructively with other results obtained using different methodologies by other studies. The percentage error of the hydrogen contents denoted by (% E) for the various petroleum samples were also obtained and noticed to be within an acceptable range. The neutron backscatter technique was observed as an alternative and more generalized method for quality assurance and standardization in the petroleum industries

  16. The soil moisture and its relevance to the landmine detection by neutron backscattering technique

    Energy Technology Data Exchange (ETDEWEB)

    Obhodas, Jasmina; Sudac, Davorin; Nad, Karlo; Valkovic, Vlado E-mail: valkovic@rudjer.irb.hr; Nebbia, Giancarlo; Viesti, Giuseppe

    2004-01-01

    The detection of landmines by using available technologies is a time consuming, expensive and extremely dangerous job, so that there is a need for a technological breakthrough in this field. Atomic and nuclear physics based sensors might offer new possibilities in de-mining. Among the available nuclear techniques, the neutron backscattering technique (NBT), based on the detection of the produced thermal neutrons, is thought to be the most promising for field applications. We discuss here two limitations of NBT, being related to the soil moisture. First, the critical value of the soil moisture, reached when the density of the hydrogen atoms in the landmine is equal to that in the background soil, defines a condition for which the detection is not possible. Critical values are small for some of the landmine types, thus suggesting the application of the method to arid countries, where the soil moisture is lower than 10%. Furthermore, small-scale variations of the soil moisture content, experimentally determined for different soil types, are found to be capable of generating false positive readings. To avoid this problem, the integration of the NBT with a second sensor, as the metal detector, is proposed.

  17. Work hardening mechanism in high nitrogen austenitic steel studied by in situ neutron diffraction and in situ electron backscattering diffraction

    International Nuclear Information System (INIS)

    With a focus on microstructural hierarchy, work hardening behaviour in high nitrogen-bearing austenitic steel (HNS) was investigated mainly by a combined technique of in situ neutron diffraction and in situ electron backscattering diffraction (EBSD). Stress partitioning due to difference in deformability among grains is enhanced in HNS. The larger stress partitioning among [h k l]-oriented family grains seems to realize high work hardening at a small strain. At a larger strain, dislocation density is higher in HNS than in low nitrogen austenitic steel (LNS), which is a possible reason for high work hardening after straining proceeds, resulting in large uniform elongation.

  18. New possibilities with inelastic fixed window scans and linear motor Doppler drives on high resolution neutron backscattering spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Frick, B., E-mail: frick@ill.eu [Institut Laue-Langevin, 6, rue Jules Horowitz, BP156, F-38002 Grenoble (France); Combet, J. [Institut Laue-Langevin, 6, rue Jules Horowitz, BP156, F-38002 Grenoble (France); Eijck, L. van [Institut Laue-Langevin, 6, rue Jules Horowitz, BP156, F-38002 Grenoble (France); Reactor Institute Delft, Delft University of Technology, Mekelweg 15, 2629JB Delft (Netherlands)

    2012-03-21

    We report on the realisation of a new type of inelastic fixed window scans (IFWS) in neutron backscattering spectroscopy using the flexibility of linear motor Doppler drives to choose the velocity profile. We discuss more generally the information content obtained from such scans and point out how scans at a few different energy offsets can lead to a large improvement in statistics compared to full quasielastic spectroscopy. We discuss both the technical and statistical aspects and illustrate the method assuming a simple model for the scattering law and show some first experimental results.

  19. New possibilities with inelastic fixed window scans and linear motor Doppler drives on high resolution neutron backscattering spectrometers

    International Nuclear Information System (INIS)

    We report on the realisation of a new type of inelastic fixed window scans (IFWS) in neutron backscattering spectroscopy using the flexibility of linear motor Doppler drives to choose the velocity profile. We discuss more generally the information content obtained from such scans and point out how scans at a few different energy offsets can lead to a large improvement in statistics compared to full quasielastic spectroscopy. We discuss both the technical and statistical aspects and illustrate the method assuming a simple model for the scattering law and show some first experimental results.

  20. Analysis and Assessment of Neutron Backscattering Technique for Landmine Detection%中子背散射探雷技术的分析与评估

    Institute of Scientific and Technical Information of China (English)

    曹琳; 储诚胜; 滕君锐; 胡广春; 熊宗华; 郝樊华; 雷家荣; 陈涵德

    2012-01-01

    The analysis of physics principles of neutron backscattering technique and Monte Carlo simulation were presented for assessment of landmine detection by neutron backscattering technique. The results are greatly valuable for future research and engineering.%本文分析了中子背散射探雷技术的原理,通过数值模拟对中子背散射探雷技术进行研究,并对该技术进行分析评估,为进一步开展中子背散射探雷技术的工程研究提供理论基础.

  1. The perturbation of backscattered fast neutrons spectrum caused by the resonances of C, N and O for possible use in pyromaterial detection

    Energy Technology Data Exchange (ETDEWEB)

    Abedin, Ahmad Firdaus Zainal, E-mail: firdaus087@gmail.com; Ibrahim, Noorddin; Zabidi, Noriza Ahmad; Abdullah, Abqari Luthfi Albert [Department of Defence Science, Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, Kuala Lumpur 57000 (Malaysia)

    2015-04-29

    Neutron radiation is able to determine the signature of land mine detection based on backscattering energy spectrum of landmine. In this study, the Monte Carlo simulation of backscattered fast neutrons was performed on four basic elements of land mine; hydrogen, nitrogen, oxygen and carbon. The moderation of fast neutrons to thermal neutrons and their resonances cross-section between 0.01 eV until 14 MeV were analysed. The neutrons energies were divided into 29 groups and ten million neutrons particles histories were used. The geometries consist of four main components: neutrons source, detectors, landmine and soil. The neutrons source was placed at the origin coordinate and shielded with carbon and polyethylene. Americium/Beryllium neutron source was placed inside lead casing of 1 cm thick and 2.5 cm height. Polyethylene was used to absorb and disperse radiation and was placed outside the lead shield of width 10 cm and height 7 cm. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of Helium-3 was used for neutron detection as it has high absorption cross section for thermal neutrons. For the anomaly, the physical is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. The results show that the energy spectrum for the four basic elements of landmine with specific pattern which can be used as indication for the presence of landmines.

  2. The perturbation of backscattered fast neutrons spectrum caused by the resonances of C, N and O for possible use in pyromaterial detection

    Science.gov (United States)

    Abedin, Ahmad Firdaus Zainal; Ibrahim, Noorddin; Zabidi, Noriza Ahmad; Abdullah, Abqari Luthfi Albert

    2015-04-01

    Neutron radiation is able to determine the signature of land mine detection based on backscattering energy spectrum of landmine. In this study, the Monte Carlo simulation of backscattered fast neutrons was performed on four basic elements of land mine; hydrogen, nitrogen, oxygen and carbon. The moderation of fast neutrons to thermal neutrons and their resonances cross-section between 0.01 eV until 14 MeV were analysed. The neutrons energies were divided into 29 groups and ten million neutrons particles histories were used. The geometries consist of four main components: neutrons source, detectors, landmine and soil. The neutrons source was placed at the origin coordinate and shielded with carbon and polyethylene. Americium/Beryllium neutron source was placed inside lead casing of 1 cm thick and 2.5 cm height. Polyethylene was used to absorb and disperse radiation and was placed outside the lead shield of width 10 cm and height 7 cm. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of Helium-3 was used for neutron detection as it has high absorption cross section for thermal neutrons. For the anomaly, the physical is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. The results show that the energy spectrum for the four basic elements of landmine with specific pattern which can be used as indication for the presence of landmines.

  3. The feasibility study of in-vivo analysis of bone calcium by activation of hand with 5 Ci 238Pu-Be

    International Nuclear Information System (INIS)

    An in-vivo partial-body neutron activation technique (IVNAA) was used for evaluaton of the human bone. It was decided to use the hand for studies of osteroporosis. The 48Ca(n,γ)49Ca reaction was employed (f=0.185%, I=900mb) and 5 Ci 238Pu-Be isotopic neutron source. A sufficient precision was obtained by four 10 min irradiations of the hand phantom tubes, each followed by a 1000 sec counting period. A 5''x5'' NaI (Tl) well-type detector and a 1024 channel multichannel analyser were used for counting gamma rays. The neutron source, covered with 1 cm paraffin wax, is holding during the irradiation in hand

  4. Irradiation alternative method of manganese sulfate solution by a Pu-Be source for efficiency measurements

    International Nuclear Information System (INIS)

    This study intends to create an alternative irradiation system from a Plutonium-Beryllium source for manganese sulphate solution using the Monte Carlo code. Thus seeking to eliminate the issue of institutes that do not have reactors or particle accelerators in its infrastructure, in order to optimize and provide independence for them to carry out efficiency measurements of MnSO4 solution in their own locality. The Monte Carlo simulations defined the technical features of this new system so that the solution reaches the maximum neutron capture by manganese in solution. (author)

  5. On the use of a ({sup 252}Cf-{sup 3}He) assembly for landmine detection by the neutron back-scattering method

    Energy Technology Data Exchange (ETDEWEB)

    Elsheikh, N., E-mail: nassreldeen.elsheikh@yahoo.com [College of Applied and Industrial Science, Department of Physics, University of Juba, Khartoum, P.O. Box 12327/1 (Sudan); Viesti, G. [Dipartimento di Fisica ed Astronomia dell' Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy); ElAgib, I. [College of Science, King Saud University, P.O. Box 2455 (Saudi Arabia); Habbani, F. [Faculty of Science, Physics Department, University of Khartoum, Khartoum, P.O. Box 321 (Sudan)

    2012-04-15

    Experiments were carried out to optimize the performance of the neutron back-scattering (NBS) technique in landmine detection using an assembly consisting of three different layers placed above a {sup 252}Cf neuron source, producing about 10{sup 4} s{sup -1}, in conjunction with a {sup 3}He detector. The assembly was optimized experimentally. The selected assembly configuration was then examined against different {sup 252}Cf stand-off distances and mine burial depths using dummy landmines. Furthermore, Monte Carlo simulations were performed to study the effect of the shield when a {sup 252}Cf source in the range 10{sup 4}-10{sup 7} s{sup -1} was employed, and to optimize the geometry for future prototypes. - Highlights: Black-Right-Pointing-Pointer A suitable shielded ({sup 252}Cf-{sup 3}He) assembly for landmine detection was developed. Black-Right-Pointing-Pointer Experimental tests and MCNP simulations were performed for a {sup 252}Cf of (10{sup 4}-10{sup 7})s{sup -1}. Black-Right-Pointing-Pointer Experimental and MCNP results for {sup 252}Cf of 10{sup 4}s{sup -1} supports the use of the shield. Black-Right-Pointing-Pointer MCNP Results recommends {sup 252}Cf of 10{sup 6}s{sup -1} for hand-held detection system. Black-Right-Pointing-Pointer MCNP Results recommends {sup 252}Cf of 10{sup 7}s{sup -1} for a robotic detection system.

  6. Elemental composition in sealed plutonium–beryllium neutron sources

    International Nuclear Information System (INIS)

    Five sealed plutonium–beryllium (PuBe) neutron sources from various manufacturers were disassembled. Destructive chemical analyses for recovered PuBe materials were conducted for disposition purposes. A dissolution method for PuBe alloys was developed for quantitative plutonium (Pu) and beryllium (Be) assay. Quantitation of Be and trace elements was performed using plasma based spectroscopic instruments, namely inductively coupled plasma mass spectrometry (ICP-MS) and atomic emission spectrometry (ICP-AES). Pu assay was accomplished by an electrochemical method. Variations in trace elemental contents among the five PuBe sources are discussed. - Highlights: • A destructive chemical analysis of the PuBe neutron sources includes the solubilization and digestion of the PuBe alloy material. • Plutonium was assayed by an electrochemical method. • Beryllium assay and trace elemental contents were determined by ICP instruments. • A large variation in trace elemental composition was observed among the five PuBe source materials

  7. Neutron-based techniques for detection of explosives and drugs

    International Nuclear Information System (INIS)

    Neutron reflection, scattering and transmission methods combined with the detection of characteristic gamma rays have an increasing role in the identification of hidden explosives, illicit drugs and other contraband materials. There are about 100 million land mines buried in some 70 countries. Among the abandoned anti-personnel land mines (APL) certain types have low mass (about 100 g) and contain little or no metal. Therefore, these plastic APL cannot be detected by the usual metal detectors. The IAEA Physics Section has organized a CRP in 1999 for the development of novel methods in order to speed up the removing process of APL. The transportation of illicit drugs has shown an increasing trend during the last decade. Developments of fast, non-destructive interrogation methods are required for the inspection of cargo containers, trucks and airline baggage. The major constituents of plastic APL and drugs are H, C, N and O which can be identified by the different neutron interactions. The atom fractions of these elements, in particular the C/O, C/N and C/H ratios, are quite different for drugs and explosives as compared to other materials used to hide them. Recently, we have carried out systematic measurements and calculations on the neutron fields from the 9Be(d,n), 2H(d,n), 252Cf and Pu-Be sources passing through different bulky samples, on the possible use of elastically backscattered Pu-Be neutrons in elemental analysis and on the advantages and limitations of the thermal neutron reflection method in the identification of land mines and illicit drugs. The measured spectral shapes of neutrons were compared with the calculated results using the MCNP-4A and MCNP-4B codes. (author)

  8. Study of the geometrical configuration of a Set-Up for the purpose of analysing organic matter using neutron backscattering with an AM-BE source and a HE3 detector

    International Nuclear Information System (INIS)

    Neutron backscattering is a powerful technique to analyse organic matter and recently a set-up has been developed by our laboratory to determine bitumen content in asphalt concrete [1].This set-up is mainly composed of an Am-Be neutron source and a He-3 detector, the source being placed under the He-3 detector. In this work, we study two geometrical configurations, the first where the source is placed under the detector and the other one is when the source and the detector are side by side. The calibration curves for the determination of bitumen content in asphalt concrete, hydrogen and the ratio C/H are built for the two geometries and then compared in terms of sensitivity. Finally, some Algerian oil samples are analysed with these setups

  9. Neutron source for Neutron Capture Synovectomy

    International Nuclear Information System (INIS)

    Monte Carlo calculations were performed to obtain a thermal neutron field from a 239PuBe neutron source inside a cylindrical heterogeneous moderators for Neutron Capture Synovectomy. Studied moderators were light water and heavy water, graphite and heavy water, lucite and polyethylene and heavy water. The neutron spectrum of polyethylene and heavy water moderator was used to determine neutron spectra inside a knee model. In this model the elemental composition of synovium and synovial liquid was assumed like blood. Kerma factors for synovium and synovial liquid were calculated to compare with water Kerma factors, in this calculations the synovium was loaded with two different concentrations of Boron

  10. GEANT 4 simulation of neutron transport and scattering in media

    International Nuclear Information System (INIS)

    GEANT 4 simulation toolkit and PhysList QGSP BIC HP for simulate neutron transport and scattering was used. Primary neutron spectrum was modeled similar spectrum of 239Pu - Be(alpha, n) neutron source. Spectra of neutron passing through the material and scattered were obtained. Number of thermal neutrons after passing various materials were calculated. Detector-dosimeter MKS-01R was used for measurements of the experimental thermal neutron flux from 239Pu - Be(alpha, n) neutron source. Satisfactory agreement between calculations and experiment was obtained.

  11. Obtaining of laue patterns of a copper crystal by backscattering method

    International Nuclear Information System (INIS)

    Diffraction patterns of neutrons were obtained by the Laue method of a copper crystal and using the direct and indirect neutrography techniques. Unlike the conventional diffraction method by transmission, neutrons backscattered were registered which also satisfy the Bragg relation

  12. Dynamic coherent backscattering mirror

    Energy Technology Data Exchange (ETDEWEB)

    Zeylikovich, I.; Xu, M., E-mail: mxu@fairfield.edu [Physics Department, Fairfield University, Fairfield, CT 06824 (United States)

    2016-02-15

    The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.

  13. Preparation and characterization of a new set of IAEA reference air filters using instrumental neutron activation analysis, proton-induced X-ray emission and Rutherford backscattering

    Czech Academy of Sciences Publication Activity Database

    Kučera, Jan; Havránek, Vladimír; Krausová, Ivana

    2009-01-01

    Roč. 281, č. 1 (2009), s. 123-129. ISSN 0236-5731. [9th International Conference on Nuclear Analytical Methods in the Life Sciences. Lisbon, 07.09.2008-12.09.2008] Institutional research plan: CEZ:AV0Z10480505 Keywords : Reference air filters * instrumental neutron activation analysis * Proton induced X-ray emission Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.631, year: 2009

  14. Different spectra with the same neutron source

    International Nuclear Information System (INIS)

    Using as source term the spectrum of a 239Pu-Be source several neutron spectra have been calculated using Monte Carlo methods. The source term was located in the centre of spherical moderators made of light water, heavy water and polyethylene of different diameters. Also a 239Pu-Be source was used to measure its neutron spectrum, bare and moderated by water. The neutron spectra were measured at 100 cm with a Bonner spheres spectrometer. Monte Carlo calculations were used to calculate the neutron spectra of bare and water-moderated spectra that were compared with those measured with the spectrometer. Resulting spectra are similar to those found in power plants with PWR, BWR and Candu nuclear reactors. Beside the spectra the dosimetric features were determined. Using moderators and a single neutron source can be produced neutron spectra alike those found in workplaces, this neutron fields can be utilized to calibrate neutron dosimeters and area monitors. (Author)

  15. Design of a neutron source for calibration

    International Nuclear Information System (INIS)

    The neutron spectra produced by an isotopic neutron source located at the center of moderating media were calculated using Monte Carlo method in the aim to design a neutron source for calibration purposes. To improve the evaluation of the dosimetric quantities, is recommended to calibrate the radiation protection devices with calibrated neutron sources whose neutron spectra being similar to those met in practice. Here, a 239Pu-Be neutron source was inserted in H2O, D2O and polyethylene cylindrical moderators in order to produce neutron spectra that resembles spectra found in workplaces

  16. Neutron spectra produced by moderating an isotopic neutron source

    International Nuclear Information System (INIS)

    A Monte Carlo study has been carried out to determine the neutron spectra produced by an isotopic neutron source inserted in moderating media. Most devices used for radiation protection have a response strongly dependent on neutron energy. ISO recommends several neutron sources and monoenergetic neutron radiations, but actual working situations have broad spectral neutron distributions extending from thermal to MeV energies, for instance, near nuclear power plants, medical applications accelerators and cosmic neutrons. To improve the evaluation of the dosimetric quantities, is recommended to calibrate the radiation protection devices in neutron spectra which are nearly like those met in practice. In order to complete the range of neutron calibrating sources, it seems useful to develop several wide spectral distributions representative of typical spectra down to thermal energies. The aim of this investigation was to use an isotopic neutron source in different moderating media to reproduce some of the neutron fields found in practice. MCNP code has been used during calculations, in these a 239PuBe neutron source was inserted in H2O, D2O and polyethylene moderators. Moderators were modeled as spheres and cylinders of different sizes. In the case of cylindrical geometry the anisotropy of resulting neutron spectra was calculated from 0 to 2. From neutron spectra dosimetric features were calculated. MCNP calculations were validated by measuring the neutron spectra of a 239PuBe neutron source inserted in a H2O cylindrical moderator. The measurements were carried out with a multisphere neutron spectrometer with a 6LiI(Eu) scintillator. From the measurements the neutron spectrum was unfolded using the BUNKIUT code and the UTA4 response matrix. Some of the moderators with the source produce a neutron spectrum close to spectra found in actual applications, then can be used during the calibration of radiation protection devices

  17. Passive neutron dosemeter design

    International Nuclear Information System (INIS)

    A passive neutron dosemeter was designed to be used in mixed radiation fields. The design was carried out using Monte Carlo method. The dosemeter model was a 25.4 cm-diameter polyethylene sphere with a thermoluminescent dosemeter, TLD600, located at the sphere center. This model was irradiated with 50 monoenergetic neutron sources with energies from 10-8 to 20 MeV. A 506.71 cm2-area disk was used to model the source term whose center was located at 100 cm from polyethylene sphere's center. The dosemeter response was compared with the responses of SNOOPY, Harwell 95/0075 and PNR-4. With these responses it was calculated the dosemeter responses for 252Cf, 252Cf/D2O and 239PuBe neutron sources. The passive dosemeter relative response has the same shape of SNOOPY, Harwell 95/0075 and PNR-4 dosemeters. Due to the type of thermal neutron detector used in the passive dosemeter the absolute response per unit fluence, is lower than the absolute response of SNOOPY, Harwell 95/0075 and PNR-4 dosemeters. However the passive dosemeter response in function of the average neutron energy of the 252Cf, 252Cf/D2O and 239PuBe neutron energy was more linear

  18. Simple recipes for ground scattering in neutron detector calibration

    International Nuclear Information System (INIS)

    Simple formulae are presented to account for ground scattering of neutrons above an earth or concrete surface without relying on albedo data. These formulae, which should be useful in calibrating neutron fluence or dose responding instruments, have been checked against Monte Carlo calculations and measurements with a PuBe source, with agreement to better than 10%. (author)

  19. Backscatter imagery in Jobos Bay

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a 1x1 meter resolution backscatter mosaic of Jobos Bay, Puerto Rico (in NAD83 UTM 19 North). The backscatter values are in relative 8-bit (0 –...

  20. BATS - Backscattering And Time-of-flight Spectrometer

    International Nuclear Information System (INIS)

    The new backscattering spectrometer IN16b will go into commissioning end 2011, providing in its final state about ten times higher count rate than its predecessor, IN16. Here we propose to increase its dynamic range by a factor of 7 with the TOF mode extension, BATS. This will make IN16b the leading high resolution backscattering spectrometer for incoherent quasi-elastic and inelastic neutron scattering; it will be competitive to the coarser resolution inverted geometry backscattering spectrometers that are being brought online at spallation sources. The increased dynamic range will extend the scope of science addressed on IN16b, generating considerable potential in fields such as the hydrogen economy (proton conduction, fuel cells, hydrogen storage), soft matter, biology and nano-science (nano-scale confinement, functionalized polymers). Such a large impact can be achieved using only a moderate investment. (authors)

  1. Neutron scattering. Experiment manuals

    International Nuclear Information System (INIS)

    The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  2. Neutron scattering. Experiment manuals

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  3. Neutron scattering. Experiment manuals

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2012-07-01

    The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, the neutron polarization analyzer DNS, the neutron spin-echo spectrometer J-NSE, the small-angle neutron diffractometers KWS-1/-2, the very-small-angle neutron diffractometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  4. Neutron scattering. Experiment manuals

    International Nuclear Information System (INIS)

    The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, the neutron polarization analyzer DNS, the neutron spin-echo spectrometer J-NSE, the small-angle neutron diffractometers KWS-1/-2, the very-small-angle neutron diffractometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  5. The Harwell back-scattering spectrometer

    International Nuclear Information System (INIS)

    Neutron diffraction spectra in which both high resolution (Δ Q/Q approximately equal to 0.003) and high intensity are maintained up to scattering vectors as high as 30A-1(sin theta/lambda = 2.5) have been obtained with the back-scattering spectrometer (BSS) recently installed on the Harwell electron linac. The theory behind the spectrometer design is described, and it is shown how the above resolution requirement leads to its basic features of a 12m incident flight path, a 2m scattering flight path and a scattering angle (2theta) acceptance from 1650 to 1750. Examples of the resolution, intensity and background are given. It is shown that the problem of frame overlap may be overcome by using an absorbing filter. (author)

  6. Calibration of a special neutron dosemeter based on solid-state track detectors and fission radiators in various neutron fields

    International Nuclear Information System (INIS)

    The calibration of a personnel neutron dosemeter in different neutron fields is described. The badge-like dosemeter contains 5 detectors: polycarbonate foil (10 μm, Makrofol KG), 232Th, natural uranium, natural uranium with boron, and natural uranium with cadmium. Detector sensitivity and calibration factors have been calculated and measured in radiation fields of 252Cf fission neutrons, WWR-S reactor neutrons with and without Cd and Fe shielding, 3-MeV (d,t) generator neutrons, and 238PuBe neutrons. Measurement range and achievable accuracy are discussed from the point of view of applying the dosemeter in routine and emergency uses

  7. On line ultrasonic integrated backscatter

    International Nuclear Information System (INIS)

    A new equipment for on-line evaluation of index based on two-dimensional integrated backscatter from ultrasonic images is described. The new equipment is fully integrated into a B-mode ultrasonic apparatus which provides a simultaneous display of conventional information together with parameters of tissue characterization. The system has been tested with a backscattering model of microbubbles in polysaccharide solution, characterized by a physiological exponential time decay. An exponential fitting to the experimental data was performed which yielded r=0.95

  8. Photoelectron backscattering in vacuum phototubes

    CERN Document Server

    Lubsandorzhiev, B K; Vyatchin, Y E; Shaibonov, B A J

    2006-01-01

    In this article we describe results of a photoelectron backscattering effect in vacuum phototubes: classical photomultipliers (PMT) and hybrid phototubes (PH). Late pulses occurring in PMTs are attributed to the photoelectron backscattering and distinguished from pulses due to an anode glow effect. The late pulses are measured in a number of PMTs and HPs with various photocathode sizes covering 1-50 cm range and different types of the first dynode materials and construction designs. It is shown that the late pulses are a generic feature of all vacuum photodetectors - PMTs and PHs and they don't deteriorate dramatically amplitude and timing responses of vacuum phototubes.

  9. X-ray backscatter imaging

    Science.gov (United States)

    Dinca, Dan-Cristian; Schubert, Jeffrey R.; Callerame, J.

    2008-04-01

    In contrast to transmission X-ray imaging systems where inspected objects must pass between source and detector, Compton backscatter imaging allows both the illuminating source as well as the X-ray detector to be on the same side of the target object, enabling the inspection to occur rapidly and in a wide variety of space-constrained situations. A Compton backscatter image is similar to a photograph of the contents of a closed container, taken through the container walls, and highlights low atomic number materials such as explosives, drugs, and alcohol, which appear as especially bright objects by virtue of their scattering characteristics. Techniques for producing X-ray images based on Compton scattering will be discussed, along with examples of how these systems are used for both novel security applications and for the detection of contraband materials at ports and borders. Differences between transmission and backscatter images will also be highlighted. In addition, tradeoffs between Compton backscatter image quality and scan speed, effective penetration, and X-ray source specifications will be discussed.

  10. Gravitational Laser Back-Scattering

    OpenAIRE

    Novaes, S. F.; Spehler, D.

    1993-01-01

    A possible way of producing gravitons in the laboratory is investigated. We evaluate the cross section electron + photon $\\rightarrow$ electron + graviton in the framework of linearized gravitation, and analyse this reaction considering the photon coming either from a laser beam or from a Compton back-scattering process.

  11. Analytical purpose electron backscattering system

    International Nuclear Information System (INIS)

    In this work an analytical purposes electron backscattering system improved at the Center of Applied Studies for Nuclear Development is described. This system can be applied for fast, exact and nondestructive testing of binary and AL/Cu, AL/Ni in alloys and for other applications

  12. Neutron scattering. Experiment manuals

    International Nuclear Information System (INIS)

    The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot-single-crystal diffractometer HEiDi, the three-axis spectrometer PANDA, the backscattering spectrometer SPHERES, the DNS neutron-polarization analysis, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering at KWS-1 and KWS-2, a very-small-angle neutron scattering diffractometer with focusing mirror, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  13. Neutron scattering. Experiment manuals

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2014-07-01

    The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot-single-crystal diffractometer HEiDi, the three-axis spectrometer PANDA, the backscattering spectrometer SPHERES, the DNS neutron-polarization analysis, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering at KWS-1 and KWS-2, a very-small-angle neutron scattering diffractometer with focusing mirror, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  14. BackscatterA [8101]--Offshore Pacifica, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pacifica map area, California. Backscatter data are provided as two separate grids...

  15. Backscatter B [8101]--Offshore Bolinas, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Bolinas map area, California. Backscatter data are provided as separate grids...

  16. Backscatter D [Snippets]--Offshore Bolinas, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Bolinas map area, California. Backscatter data are provided as separate grids...

  17. BackscatterB [7125]--Offshore Pacifica, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pacifica map area, California. Backscatter data are provided as two separate grids...

  18. Backscatter A [8101]--Offshore Bolinas, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Bolinas map area, California. Backscatter data are provided as separate grids...

  19. Backscatter A [8101]--Offshore San Gregorio, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3306 presents data for the acoustic-backscatter map (see sheet 3, SIM 3306) of the Offshore of San Gregorio map area, California. Backscatter data...

  20. Backscatter E [Swath]--Offshore Bolinas, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Bolinas map area, California. Backscatter data are provided as separate grids...

  1. Backscatter [SWATH]--Offshore Santa Cruz, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Santa Cruz map area, California. Backscatter data are provided as three separate...

  2. Backscatter B [7125]--Offshore San Gregorio, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3306 presents data for the acoustic-backscatter map (see sheet 3, SIM 3306) of the Offshore of San Gregorio map area, California. Backscatter data...

  3. Nodule bottom backscattering study using multibeam echosounder

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Raju, Y.S.N.; Nair, R.R.

    A study is carried out to observe the angular dependence of backscattering strength at nodule area where grab sample and photographic data is available. Theoretical study along with the experimentally observed data shows that the backscattering...

  4. Backscatter C [7125]--Offshore Bolinas, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Bolinas map area, California. Backscatter data are provided as separate grids...

  5. Improvements in backscatter measurement devices

    International Nuclear Information System (INIS)

    Improvements in measuring the thickness of a coating on a substrate by the technique of backscattered particles are described. These improvements enable the measurements to be carried out continuously as an integral part of the coating production line and also permit measurements where the coated elements are separated from one another by a predetermined distance. The former is achieved by situating the backscatter probe and detector on the rim of the measurement wheel and rotating this wheel at a speed such that the coated element and probe are stationary relative to one another. The latter improvement is achieved by an indexing apparatus which automatically positions the probe beside a coated element. (U.K.)

  6. An automatic evaluation system for NTA film neutron dosimeters

    CERN Document Server

    Müller, R

    1999-01-01

    At CERN, neutron personal monitoring for over 4000 collaborators is performed with Kodak NTA films, which have been shown to be the most suitable neutron dosimeter in the radiation environment around high-energy accelerators. To overcome the lengthy and strenuous manual scanning process with an optical microscope, an automatic analysis system has been developed. We report on the successful automatic scanning of NTA films irradiated with sup 2 sup 3 sup 8 Pu-Be source neutrons, which results in densely ionised recoil tracks, as well as on the extension of the method to higher energy neutrons causing sparse and fragmentary tracks. The application of the method in routine personal monitoring is discussed. $9 overcome the lengthy and strenuous manual scanning process with an optical microscope, an automatic analysis system has been developed. We report on the successful automatic scanning of NTA films irradiated with /sup 238/Pu-Be source $9 discussed. (10 refs).

  7. Hanle effect in coherent backscattering

    International Nuclear Information System (INIS)

    We study the shape of the coherent-backscattering (CBS) cone obtained when resonant light illuminates a thick cloud of laser-cooled rubidium atoms in the presence of a homogenous magnetic field. We observe new magnetic field-dependent anisotropies in the CBS signal. We show that the observed behavior is due to the modification of the atomic-radiation pattern by the magnetic field (Hanle effect in the excited state)

  8. Calibration of the IRD two-component TLD albedo neutron dosemeter in some moderated neutron fields

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Bruno M.; Silva, Ademir X. da, E-mail: bfreitas@nuclear.ufrj.br, E-mail: ademir@nuclear.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Martins, Marcelo M.; Pereira, Walsan W.; Mauricio, Claudia L.P., E-mail: marcelo@ird.gov.br, E-mail: walsan@ird.gov.br, E-mail: claudia@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    In some stray neutron fields, like those found in practices involving the handling of radionuclide sources, the neutron calibration factor for albedo neutron dosemeter can vary widely compared to the factor for bare sources. This is the case for well logging, which is the area with the largest number of workers exposed to neutrons in Brazil. The companies employ routinely {sup 241}Am-Be neutron sources. The albedo response variation is mainly due to the presence of scattered and moderated neutrons. This paper studies the response variation of the two-component TLD albedo neutron dosemeter used in the neutron individual monitoring service of Instituto de Radioprotecao e Dosimetria, in different radionuclide neutron source beams. The neutron spectra were evaluated applying a Bonner sphere spectrometer with a {sup 6}LiI(Eu) detector in the Brazilian National Metrology Neutron Laboratory. Standard neutron sources of {sup 241}Am-Be and {sup 252}Cf were employed, besides {sup 238}Pu-Be. Measurements were also made with scattered and moderated neutron beams, including {sup 252}Cf(D{sub 2}O) reference spectrum, {sup 241}Am-Be moderated with paraffin and silicone and a thermal neutron flux facility. New neutron calibration factors, as a function of the incident to albedo neutron ratio, were proposed for use in the albedo algorithm for occupational fields where the primary neutron beam is one of those studied sources. (author)

  9. Calibration of the IRD two-component TLD albedo neutron dosemeter in some moderated neutron fields

    International Nuclear Information System (INIS)

    In some stray neutron fields, like those found in practices involving the handling of radionuclide sources, the neutron calibration factor for albedo neutron dosemeter can vary widely compared to the factor for bare sources. This is the case for well logging, which is the area with the largest number of workers exposed to neutrons in Brazil. The companies employ routinely 241Am-Be neutron sources. The albedo response variation is mainly due to the presence of scattered and moderated neutrons. This paper studies the response variation of the two-component TLD albedo neutron dosemeter used in the neutron individual monitoring service of Instituto de Radioprotecao e Dosimetria, in different radionuclide neutron source beams. The neutron spectra were evaluated applying a Bonner sphere spectrometer with a 6LiI(Eu) detector in the Brazilian National Metrology Neutron Laboratory. Standard neutron sources of 241Am-Be and 252Cf were employed, besides 238Pu-Be. Measurements were also made with scattered and moderated neutron beams, including 252Cf(D2O) reference spectrum, 241Am-Be moderated with paraffin and silicone and a thermal neutron flux facility. New neutron calibration factors, as a function of the incident to albedo neutron ratio, were proposed for use in the albedo algorithm for occupational fields where the primary neutron beam is one of those studied sources. (author)

  10. Neutron monitoring using moderating sphere detectors

    International Nuclear Information System (INIS)

    Three moderating sphere-detector systems are examined as a neutron area monitoring instruments. The thermal neutron detectors used are the (bare-Cd covered) Li6 (Eu) crystal scintillating detector, the U235-mica track detector and the partially Cd-covered R.M. film. The response of the 12 s sphere-detector systems to Pu-Be neutrons are found to be 0.22 counts/neutrons for the Li6I-system. 8x10-4 tracks per neutron for the track-detector system and 10 mR equivalent γ-ray exposure per 2x10-neutrons per cm- for the Cd-covered R.M. film system

  11. Sensitivity of moderator-containing thermal neutron detectors

    International Nuclear Information System (INIS)

    The dependences of the sensitivities of the LiI(Eu) thermal neutron detector and the DN-A-1 dosimeter on the isotopic source neutron energy are analyzed. It is shown that the results obtained permit to choose the most confident values for sensitivity of the thermal neutron detectors in moderators. The given data are compared with the experimental and calculated data of other authors. A conclusion is made that the DN-A-1 dosimeter in the energy range from several fractions of eV Up to dozens of keV, as calibrated using a Pu+Be-neutron source, is close to an ''ideal'' dosimeter

  12. Neutron generators at Purnima Lab

    International Nuclear Information System (INIS)

    Neutron sources are in a great demand in many area like research, nuclear waste management, industrial process control, medical and also security. Major sources of neutrons are nuclear reactors, radioisotopes and accelerator based neutron generators. For many field applications, reactors cannot be used due to its large size, complicated system, high cost and also safety issues. Radioisotopes like Pu-Be, Am-Be, Cf, are extensively used for many industrial applications. But they are limited in their use due to their low source strength and also handling difficulties due to radioactivity. They are also not suitable for pulsed neutron applications. In contrast, compact size, pulsed operation, on/off operation etc.of accelerator based neutron generators make them very popular for many applications. Particle accelerators based on different types of neutron generators have been developed around the world. Among these deuteron accelerator based D-D and D-T neutron generators are widely used as they produce mono-energetic fast neutrons and in particular high yield of D-T neutron can be obtained with less than 300 KV of accelerating voltage

  13. Conductance and noise signatures of Majorana backscattering

    OpenAIRE

    Chung, Suk Bum; Qi, Xiao-Liang; Maciejko, Joseph; Zhang, Shou-Cheng

    2010-01-01

    We propose a conductance measurement to detect the backscattering of chiral Majorana edge states. Because normal and Andreev processes have equal probability for backscattering of a single chiral Majorana edge state, there is qualitative difference from backscattering of a chiral Dirac edge state, giving rise to half-integer Hall conductivity and decoupling of fluctuation in incoming and outgoing modes. The latter can be detected through thermal noise measurement. These experimental signature...

  14. TLD determination of neutron dose contribution in medical linac

    International Nuclear Information System (INIS)

    The increased use of Linacs with accelerating voltage higher than 10 MV in clinical radiotherapy is producing and increasing demand of accurate dosimetric measurements of the photon induced neutron contamination of the radiotherapy beams, due that the associated Bremsstrahlung X rays may produce neutrons as a result of subsequent photonuclear reactions with the different materials constituting the accelerator head. Thermal neutron fluences can be measured with TLD-600/TLD-700 pairs arranged in both a bare and a cadmium (Cd) foil covered methacry-late box. Neutron response of Tl dosemeters irradiated with two different neutron sources has been investigated. The shape of the glow curve of these TLDs after irradiation in a medical Linac and in a Pu Be neutron source has been studied to verify the contribution of neutrons to an additional dose to staff, patients and the general public, due to photonuclear reactions generating neutrons from medical Linacs. (Author)

  15. Experimental spectra unfolding of fast ion backscattering

    International Nuclear Information System (INIS)

    Problems on processing of experimental spectra of fast light ion backscattering are considered to obtain information about element composition in thin films and surface layers of solids. Application of mathematical processing of the spectra is shown to allow considerably to improve analytical characteristics of the ion backscattering method and to expand the field for its application

  16. Detector for high-energy photon backscatter

    Science.gov (United States)

    Silver, Michael D.; Erker, Joseph W.; Duncan, Michael Z.; Hartford, Thomas J.; Sivers, E. A.; Hopkinson, James F.

    1993-12-01

    High energy photon backscatter uses pair production to probe deep beneath surfaces with single side accessibility or to image thick, radiographically opaque objects. At the higher photon energies needed to penetrate thick and/or highly attenuating objects, Compton backscatter becomes strongly forward peaked with relatively little backscatter flux. Furthermore, the downward energy shift of the backscattered photon makes it more susceptible to attenuation on its outbound path. Above 1.022 MeV, pair production is possible; at about 10 MeV, pari production crosses over Compton scatter as the dominant x-ray interaction mechanism. The backscattered photons can be hard x rays from the bremsstrahlung of the electrons and positrons or 0.511 MeV photons from the annihilation of the positron. Monte Carlo computer simulations of such a backscatter system were done to characterize the output signals and to optimize a high energy detector design. This paper touches on the physics of high energy backscatter imaging and describes at some length the detector design for tomographic and radiographic imaging.

  17. Harvesting backscatter electrons for radiation therapy

    International Nuclear Information System (INIS)

    Purpose: An innovative technique is used to harvest backscatter electrons for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials: Backscatter electrons are harvested out of the primary electron beams from the linear accelerators. The design consists of a short cylindrical cone that fits snugly over a long cylindrical electron cone. The short cylindrical cone has a thick circular plate of high atomic number medium (Pb) attached to the distal end, and a lateral slit of variable length and width. The width of the slit could be closed as desired by rotating the two cones and the length can be increased by lowering the short cylindrical cone. Primary electrons strike the Pb plate perpendicularly and produce backscatter electrons that pass through the lateral slit for treatment. Using film and a parallel plate ion chamber, backscattered electron dose characteristics are studied. Results: The depth dose characteristic of the backscatter electron is very similar to that of the 0.2 mm Al half-value layer x-ray beam that is commonly used for the intracavitary and superficial lesions. The backscatter electron energy is nearly constant and effectively ≤ 1 MeV from the clinical megavoltage beams. The backscatter electron dose rate of 0.32-0.8 Gy/min could be achieved from modern accelerators without any modification. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions: The measured data for backscatter electron energy, fluence, depth dose, flatness, dose rate, and absolute dose indicates that the harvested backscattered electrons are suitable for clinical use

  18. Instrument for underwater measurement of optical backscatter

    Science.gov (United States)

    Maffione, Robert A.; Dana, David R.; Honey, Richard C.

    1991-12-01

    A backscatter sensor has been developed for rapidly measuring, in situ, the volume scattering function (VSF) in the backward direction. The backscatter sensor uses a bistatic optical geometry to measure backscatter from a small volume of seawater over a range of scattering angles from approximately 115 degree(s) to 170 degree(s). The calibration of the sensor yields a weighted, angular averaged value of the VSF with a centroid located at a scattering angle of about 150 degree(s). The backscatter sensor design is based on a sensitive synchronous detector and pulsed, light-emitting diode that has been used at visible and near-infrared wavelengths. The entire sensor package, which includes circuitry for digitizing the signal, is contained in a compact, rugged housing. The sensor has been deployed both in towed arrays and in stationary profiling mode. Scattering profiles from two recent deployments are presented.

  19. Stimulated Raman backscattering at high laser intensities

    Energy Technology Data Exchange (ETDEWEB)

    Skoric, M.M. [Vinca Inst. of Nuclear Sciences, Belgrade (Yugoslavia); Tajima, Toshiki; Sasaki, Akira; Maluckov, A.; Jovanovic, M.

    1998-03-01

    Signatures of Stimulated Raman backscattering of a short-pulse high-intensity laser interacting with an underdense plasma are discussed. We introduce a nonlinear three-wave interaction model that accounts for laser pump depletion and relativistic detuning. A mechanism is revealed based on a generic route to chaos, that predicts a progressive increase of the backscatter complexity with a growing laser intensity. Importance of kinetic effects is outlined and demonstrated in fluid-hybrid and particle simulations. As an application, we show that spectral anomalies of the backscatter, predicted by the above model, are consistent with recent sub-picosecond, high-intensity laser gas-target measurements at Livermore and elsewhere. Finally, a recently proposed scheme for generation of ultra-short, low-prepulse laser pulses by Raman backscattering in a thin foil target, is shown. (author)

  20. Automatic scanning of NTA film neutron dosimeters

    CERN Document Server

    Müller, R

    1999-01-01

    At the European Laboratory for Particle Physics CERN, personal neutron monitoring for over 4000 collaborators is performed with Kodak NTA film, one of the few suitable dosemeters in the stray radiation environment of a high energy accelerator. After development, films are scanned with a projection microscope. To overcome this lengthy and strenuous procedure an automated analysis system for the dosemeters has been developed. General purpose image recognition software, tailored to the specific needs with a macro language, analyses the digitised microscope image. This paper reports on the successful automatic scanning of NTA films irradiated with neutrons from a /sup 238/Pu-Be source (E approximately=4 MeV), as well as on the extension of the method to neutrons of higher energies. The question of detection limits is discussed in the light of an application of the method in routine personal neutron monitoring. (9 refs).

  1. Neutron fluence rate measurement using prompt gamma rays

    International Nuclear Information System (INIS)

    A gamma ray spectrometer, with a 3'' X 3'' NaI(Tl) detector, with a moderator sphere has been utilised to measure the neutron fluence rate, with this value the H*(10) was estimated. When a neutron is captured by the hydrogen-based moderator, a 2.22 MeV prompt gamma ray is produced. In a multichannel analyser the net area under the 2.22 MeV photopeak is proportional to the total neutron fluence rate. The features of this system were determined by a Monte Carlo study that includes 3-, 5- and 10-inches diameter, water and polyethylene moderators and a 239Pu-Be source. The prompt gamma response was extended to monoenergetic neutron sources. To verify the response, a 239Pu-Be source in combination with a 10'' polyethylene sphere having a gamma-ray spectrometer with NaI(Tl) was utilised to estimate the neutron fluence rate and the H*(10). These results were compared with neutron fluence rate and H*(10) obtained using a Bonner sphere spectrometer and with the H*(10) measured using a neutron rem-meter. (authors)

  2. New TL detectors for personal neutron dosimetry

    International Nuclear Information System (INIS)

    One of the main objectives in the application of TL detectors to neutron dosimetry is to obtain a high ratio of neutron to gamma response for a better separation of the neutron component. In the case of 6LiF, one may reduce the effective thickness of the detector in order to exploit the difference between neutron and gamma absorption, either by making the sensitive layer of TL chip thinner or by reducing its transparency to TL light. Two new types of sintered 6LiF:Mg,Ti detectors have been developed: a sandwich detector with a non-thermoluminescent LiF base, and a detector in which the phosphor is mixed with graphite. Three thicknesses of the sensitive layer (45, 60, 80 mg.cm-2) and two carbon concentrations (1%, 4%) were tested. The detectors were irradiated by moderated neutrons from Pu-Be and 252Cf sources and by thermal neutrons from a nuclear research reactor. Results of measurements indicate that for the detector of thickness 45 mg.cm-2 the ratio of neutron to gamma response increases 2-4 times, compared with the Harshaw TLD-600 while the neutron sensitivity is maintained. Other dosimetric characteristics of the detector remain unchanged, making it possible to use standard annealing and readout procedures. The new detectors will be applied in a personal neutron albedo dosemeter with a detection limit better than 100 μSv in a gamma background of the range of several mSv. (author)

  3. Exploratory studies on neutron radiography with a small neutron source using a nuclear scintillation imaging technique

    International Nuclear Information System (INIS)

    Neutron radiography based on mobile neutron sources need optimum utilization of available neutron fluxes which are usually lower compared to those available from reactors. For optimum utilization of such low flux devices, a sensitive neutron imaging technique is required. Such a neutron imaging system based on a Li6F-ZnS scintillator screen has been developed using a pair of image intensifier tubes and a charge coupled device. This detector system has been employed to study the feasibility of neutron radiography using low neutron fluences. The main feature of this imaging system is its ability to detect individual neutron scintillation events with a higher degree of spatial resolution. In order to test the efficiency of this imaging system, a small scale moderator-collimator assembly was designed using a Pu-Be neutron source of strength ∼2.107 n/s. Details of this imaging system and results of some exploratory experiments for low fluence neutron imaging are presented in this paper. (orig.)

  4. Card controlled beta backscatter thickness measuring instrument

    International Nuclear Information System (INIS)

    An improved beta backscatter instrument for the nondestructive measurement of the thickness of thin coatings on a substrate is described. Included therein is the utilization of a bank of memory stored data representative of isotope, substrate, coating material and thickness range characteristics in association with a control card having predetermined indicia thereon selectively representative of a particular isotope, substrate material, coating material and thickness range for conditioning electronic circuit means by memory stored data selected in accord with the predetermined indicia on a control card for converting backscattered beta particle counts into indicia of coating thickness

  5. Calibration and intercomparison of neutron moderation spectrometers

    International Nuclear Information System (INIS)

    Results have been reported of comparative measurements of neutron fields from bare PuBe and Cf sources using multisphere (Bonner) spectrometers. The experiments were carried out by the Institute of Biophysics and Nuclear Medicine at Charles University in Prague and the National Board for Atomic Safety and Radiation Protection in Berlin. Both sides agreed upon uniform measuring conditions and calibration factors thus rendering possible the comparability of the dosimetric parameters which have been determined and verified, respectively, to an accuracy of ± 10%. 20 refs., 10 tabs., 2 figs. (author)

  6. Multibeam Sonar Backscatter Data Acquisition and Processing: Guidelines and Recommendations from the GEOHAB Backscatter Working Group

    Science.gov (United States)

    Heffron, E.; Lurton, X.; Lamarche, G.; Brown, C.; Lucieer, V.; Rice, G.; Schimel, A.; Weber, T.

    2015-12-01

    Backscatter data acquired with multibeam sonars are now commonly used for the remote geological interpretation of the seabed. The systems hardware, software, and processing methods and tools have grown in numbers and improved over the years, yet many issues linger: there are no standard procedures for acquisition, poor or absent calibration, limited understanding and documentation of processing methods, etc. A workshop organized at the GeoHab (a community of geoscientists and biologists around the topic of marine habitat mapping) annual meeting in 2013 was dedicated to seafloor backscatter data from multibeam sonars and concluded that there was an overwhelming need for better coherence and agreement on the topics of acquisition, processing and interpretation of data. The GeoHab Backscatter Working Group (BSWG) was subsequently created with the purpose of documenting and synthetizing the state-of-the-art in sensors and techniques available today and proposing methods for best practice in the acquisition and processing of backscatter data. Two years later, the resulting document "Backscatter measurements by seafloor-mapping sonars: Guidelines and Recommendations" was completed1. The document provides: An introduction to backscatter measurements by seafloor-mapping sonars; A background on the physical principles of sonar backscatter; A discussion on users' needs from a wide spectrum of community end-users; A review on backscatter measurement; An analysis of best practices in data acquisition; A review of data processing principles with details on present software implementation; and finally A synthesis and key recommendations. This presentation reviews the BSWG mandate, structure, and development of this document. It details the various chapter contents, its recommendations to sonar manufacturers, operators, data processing software developers and end-users and its implication for the marine geology community. 1: Downloadable at https://www.niwa.co.nz/coasts-and-oceans/research-projects/backscatter-measurement-guidelines

  7. Design of a system for neutrons dosimetry

    International Nuclear Information System (INIS)

    At the present time diverse systems of detection of neutrons exist, as proportional counters based on BF3, He3 and spectrometers of Bonner spheres. However, the cost and the complexity of the implementation of these systems put them far from the reach for dosimetric purposes. For these reasons a system of neutrons detection composed by a medium paraffin moderator that forms a 4π (spheres) arrangement and of several couples of thermoluminescent dosimeters TLD 600/TLD 700. The response of the system presents a minor repeatability to 5% in several assays when being irradiated with a 239PuBe source and a deviation of 13.8% in the Tl readings of four different spheres. The calibration factor of the system with regard to the neutrons source which was of 56.2 p Sv/nc also was calculated. These detectors will be used as passive monitors of photoneutrons in a radiotherapy room with lineal accelerator of high energy. (Author)

  8. Measuring neutron dose and quality factors with tissue equivalent proportional counters

    International Nuclear Information System (INIS)

    The methods used to obtain absolute neutron dose measurements and quality factor determination from the tissue equivalent proportional counter (TEPC) are reviewed. Exposure to nearly monoenergetic neutrons with energies from 200 keV to 7.5 MeV indicate that the absorbed dose due to fast neutrons measured by the TEPC averaged 3% higher, with a standard deviation (1 sigma) of 9%, than the tissue kerma calculated from neutron fluence measurements. The absorbed dose due to fast neutrons measured by the TEPC agreed within 0.6% of the calculated tissue kerma for a PuBe neutron source, whose neutron yield was determined within 2% by the United States National Bureau of Standards. Data are presented which show the TEPC measures quality factors accurately enough for health physics purposes for neutrons with energies between 200 keV and 5 MeV

  9. Design and Characterization of a Collimated Neutron Beam User Facility at SUNY Geneseo

    Science.gov (United States)

    Krieger, Michael; Padalino, Stephen; Russ, Megan; Polsin, Danae; Bienstock, Mollie; Ellison, Drew; Simone, Angela

    2012-10-01

    The Collimated Neutron Beam (CNB) Facility at SUNY Geneseo provides users an opportunity to perform neutron experiments that require a low neutron background. Neutrons with energies up to 10 MeV are produced by a Plutonium-Beryllium (Pu-Be) source and are collimated to form a well characterized beam. A six foot high, 18 inch thick shielding wall made of water-bricks was built to reduce neutron background in the target area. Neutron and gamma radiation were extensively mapped throughout the facility using a calibrated Bonner sphere, Geiger counter, plastic scintillator and an HPGe detector. Potential uses for the CNB include neutron activation, time-of-flight, attenuation and neutron detector calibration experiments. A detailed description and layout of the facility will be displayed on the poster. Funded in part by a grant from the DOE through the Laboratory for Laser Energetics.

  10. On Uncertainty of Compton Backscattering Process

    CERN Document Server

    Mo, X H

    2013-01-01

    The uncertainty of Compton backscattering process is studied by virtue of analytical formulas, and the special effects of variant energy spread and energy drift on the systematic uncertainty estimation are also studied with Monte Carlo sampling technique. These quantitative conclusions are especially important for the understanding the uncertainty of beam energy measurement system.

  11. The single backscattering of gamma rays

    International Nuclear Information System (INIS)

    The paper presents the results of the single backscattering investigations of gamma rays in various materials. A simplified mathematical model is given for determining the probability that a photon scattered back by a single Compton scattering is incident on the detector. The probability is calculated as a function of the primary photon energy and the atomic number Z of the scatterer. (Auth.)

  12. On the effect of the moderator dimensions and energy spectrum of neutrons from isotope sources on the slow neutron flux density distribution in water

    International Nuclear Information System (INIS)

    Results are given of experimental investigations on the effect of moderator dimensions and neutron energy spectra of 238Pu+Be, 238Pu+B, 238Pu+Li+F, 252Cf isotope sources on the distribution of the slow neutron flux density in water moderator. The analysis of obtained results shows that the neutron flux density approximating the maximum possible one is attained in water at dimensions of the cylindrical moderator of the order of 40x40 cm. By comparing the obtained data with the results of calculations a conclusion has been drawn that calculated estimates are 2.5-3 times lower than experimental ones

  13. Optimization of thermal neutron flux in an irradiator assembly with different isotopic sources

    International Nuclear Information System (INIS)

    Highlights: • The aim of this work, is to evaluate the thermal neutron distribution in an irradiator assembly. • Thermal neutron distribution were determined experimentally and calculated by MCNP. • The calculated and experimental results were in good agreement. - Abstract: This work aimed to determine the distribution of thermal neutron flux in an irradiator assembly to study the possibility of use this irradiator for Neutron Activation Analysis; NAA. To establish the facility specifications, the thermal neutron flux values of 252Cf and Pu-Be isotopic neutron sources along the horizontal irradiator axis were determined experimentally and calculated by Monte Carlo N-Particle; MCNP transport code. The irradiator assembly characterized by supplying a stable neutron flux for a long period, eliminating the need to use standard material i.e. comparative method, so that the process becomes efficient, compact, economical and more reliable. The measurements were carried out at different position inside the irradiator assembly using proportional 3He-detector and gold foil activation method. As well as, these measurements were performed without and with two types of neutron reflector such as water and steel to determine the thermal neutron distribution along the irradiation points. The experimental results were compared to the calculations performed with MCNP Code. The calculated and experimental results were in reasonable agreement for both 252Cf and Pu-Be sources. This indicated that the material and geometrical properties of the irradiator were modeled well

  14. BackscatterC [SWATH]--Offshore Pigeon Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pigeon Point map area, California. Backscatter data are provided as three separate...

  15. BackscatterA [8101]--Offshore Pigeon Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pigeon Point map area, California. Backscatter data are provided as three separate...

  16. BackscatterB [7125]--Offshore Pigeon Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Pigeon Point map area, California. Backscatter data are provided as three separate...

  17. BackscatterB [EM300]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  18. BackscatterC [7125]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  19. Backscatter D [USGS]--Offshore of Tomales Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Tomales Point map area, California. Backscatter data are provided as separate...

  20. BackscatterA [SWATH]--Offshore Aptos, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Aptos map area, California. Backscatter data are provided as two separate grids...

  1. BackscatterB [7125]--Offshore Scott Creek, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Scott Creek map area, California. Backscatter data are provided as three separate...

  2. Backscatter B [7125]--Offshore Half Moon Bay, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Half Moon Bay map area, California. Backscatter data are provided as two...

  3. BackscatterC [SWATH]--Offshore Scott Creek, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Scott Creek map area, California. Backscatter data are provided as three separate...

  4. Backscatter C [8101]--Offshore of San Francisco, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of San Francisco map area, California. Backscatter data are provided as separate...

  5. Backscatter D [7125]--Offshore of San Francisco, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of San Francisco map area, California. Backscatter data are provided as separate...

  6. Backscatter C [Swath]--Offshore of Fort Ross, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Fort Ross map area, California. Backscatter data are provided as separate...

  7. Backscatter B [Swath]--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity map area, California. Backscatter data are provided as separate grids...

  8. BackscatterA [8101]--Offshore Scott Creek, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Scott Creek map area, California. Backscatter data are provided as three separate...

  9. BackscatterB [EM300]--Offshore Aptos, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Offshore of Aptos map area, California. Backscatter data are provided as two separate grids...

  10. Backscatter A [8101]--Offshore of Bodega Head, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Bodega Head map area, California. Backscatter data are provided as separate...

  11. Backscatter A [8101]--Offshore of Tomales Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Tomales Point map area, California. Backscatter data are provided as separate...

  12. Backscatter B [8101]--Offshore of San Francisco, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of San Francisco map area, California. Backscatter data are provided as separate...

  13. Backscatter A [8101]--Offshore Half Moon Bay, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Half Moon Bay map area, California. Backscatter data are provided as two...

  14. Backscatter C [Swath]--Offshore of Tomales Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Tomales Point map area, California. Backscatter data are provided as separate...

  15. Backscatter B [7125]--Offshore of Tomales Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Tomales Point map area, California. Backscatter data are provided as separate...

  16. Study of multibeam techniques for bathymetry and seabottom backscatter applications

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Chakraborty, B.

    Indian ocean is presented using Hydrosweep-multibeam installed onboard ORV Sagarkanya. A seabottom classification model is proposed which can be applied for multibeam backscatter data. Certain aspects of the multibeam backscatter signal data processing...

  17. Backscatter A [8101]--Offshore of Fort Ross, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Fort Ross map area, California. Backscatter data are provided as separate...

  18. Backscatter B [7125]--Offshore of Fort Ross, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Fort Ross map area, California. Backscatter data are provided as separate...

  19. Backscatter C [Swath]--Offshore of Bodega Head, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Bodega Head map area, California. Backscatter data are provided as separate...

  20. Backscatter B [7125]--Offshore of Bodega Head, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Bodega Head map area, California. Backscatter data are provided as separate...

  1. Backscatter A [8101]--Offshore of San Francisco, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of San Francisco map area, California. Backscatter data are provided as separate...

  2. Preliminary backscatter results from the hydrosweep multibeam system

    Digital Repository Service at National Institute of Oceanography (India)

    Hagen, R.A.; Chakraborty, B.; Schenke, H.W.

    of Oceanography to convert the measured electrical energy into acoustic backscatter energy. This conversion includes corrections for the position, slope, and area of the scattering surface. In this paper we present backscatter data from several areas surveyed...

  3. Neutron spectra and dosimetric features of isotopic neutron sources: a review

    International Nuclear Information System (INIS)

    A convenient way to produce neutrons is the isotopic neutron source, where the production is through (α, n), (γ, n), and spontaneous fission reactions. Isotopic neutron sources are small, easy to handle, and have a relative low cost. On the other hand the neutron yield is small and mostly of them produces neutrons with a wide energy distribution. In this work, a review is carried out about the the main features of 24NaBe, 24NaD2O, 116InBe, 140LaBe, 238PuLi, 239PuBe, 241AmB, 241AmBe, 241AmF, 241AmLi, 242CmBe, 210PoBe, 226RaBe, 252Cf and 252Cf/D2O isotopic neutron source. Also, using Monte Carlo methods, the neutron spectra in 31 energy groups, the neutron mean energy; the Ambient dose equivalent, the Personal dose equivalent and the Effective dose were calculated for these isotopic neutron sources. (Author)

  4. Neutron spectra and dosimetric features of isotopic neutron sources: a review

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98060 Zacatecas, Zac. (Mexico); Martinez O, S. A., E-mail: fermineutron@yahoo.com [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Av. Central del Norte 39-115, 150003 Tunja, Boyaca (Colombia)

    2015-10-15

    A convenient way to produce neutrons is the isotopic neutron source, where the production is through (α, n), (γ, n), and spontaneous fission reactions. Isotopic neutron sources are small, easy to handle, and have a relative low cost. On the other hand the neutron yield is small and mostly of them produces neutrons with a wide energy distribution. In this work, a review is carried out about the the main features of {sup 24}NaBe, {sup 24}NaD{sub 2}O, {sup 116}InBe, {sup 140}LaBe, {sup 238}PuLi, {sup 239}PuBe, {sup 241}AmB, {sup 241}AmBe, {sup 241}AmF, {sup 241}AmLi, {sup 242}CmBe, {sup 210}PoBe, {sup 226}RaBe, {sup 252}Cf and {sup 252}Cf/D{sub 2}O isotopic neutron source. Also, using Monte Carlo methods, the neutron spectra in 31 energy groups, the neutron mean energy; the Ambient dose equivalent, the Personal dose equivalent and the Effective dose were calculated for these isotopic neutron sources. (Author)

  5. Basic neutronics. Neutrons migration

    International Nuclear Information System (INIS)

    This article presents the basic neutronics necessary for the understanding of the operation of the different types of nuclear reactors: 1 - introduction to neutronics: principle of fission chain reactions, fast neutron reactors and thermal neutron reactors, capture, neutron status, variations with the reactor lattices; 2 - Boltzmann equation: neutrons population, neutrons migration, characterization of neutrons population and reactions, integral form of the Boltzmann equation, integral-differential form, equivalence between the two forms; 3 - reactor kinetics: fast neutrons and delayed neutrons, kinetic equations in punctual model, Nordheim equation, reactivity jumps, reactivity ramp; 4 - diffusion equation: local neutron status, Fick's law, diffusion equation, initial, boundary and interface conditions, nuclei in infinite and homogenous medium, some examples of solutions, developments in Eigenmodes; 5 - one-group theory: equation of the 'one-group - diffusion' theory, critical condition of the naked and homogenous reactor, critical condition of a reactor with reflectors, generalizations; 6 - neutrons moderation: different moderation mechanisms, elastic shock laws, moderation equation, some examples of solutions; 7 - resonance absorption of neutrons: advantage of the discontinuous moderation character, advantage of an heterogenous disposition, classical formula of the anti-trap factor in homogenous and heterogenous situation; 8 - neutrons thermalization: notions of thermalization mechanisms, thermalization equation, Maxwell spectrum, real spectrum, classical formula of the thermal utilisation factor, classical formula of the reproduction factor, moderation optimum. (J.S.)

  6. Inter-Technology Backscatter: Towards Internet Connectivity for Implanted Devices

    OpenAIRE

    Iyer, Vikram; Talla, Vamsi; Kellogg, Bryce; Gollakota, Shyamnath; Smith, Joshua R.

    2016-01-01

    We introduce inter-technology backscatter, a novel approach that transforms wireless transmissions from one technology to another, on the air. Specifically, we show for the first time that Bluetooth transmissions can be used to create Wi-Fi and ZigBee-compatible signals using backscatter communication. Since Bluetooth, Wi-Fi and ZigBee radios are widely available, this approach enables a backscatter design that works using only commodity devices. We build prototype backscatter hardware using ...

  7. Electromagnetic backscattering from one-dimensional drifting fractal sea surface II: Electromagnetic backscattering model

    Science.gov (United States)

    Tao, Xie; William, Perrie; Shang-Zhuo, Zhao; He, Fang; Wen-Jin, Yu; Yi-Jun, He

    2016-07-01

    Sea surface current has a significant influence on electromagnetic (EM) backscattering signals and may constitute a dominant synthetic aperture radar (SAR) imaging mechanism. An effective EM backscattering model for a one-dimensional drifting fractal sea surface is presented in this paper. This model is used to simulate EM backscattering signals from the drifting sea surface. Numerical results show that ocean currents have a significant influence on EM backscattering signals from the sea surface. The normalized radar cross section (NRCS) discrepancies between the model for a coupled wave-current fractal sea surface and the model for an uncoupled fractal sea surface increase with the increase of incidence angle, as well as with increasing ocean currents. Ocean currents that are parallel to the direction of the wave can weaken the EM backscattering signal intensity, while the EM backscattering signal is intensified by ocean currents propagating oppositely to the wave direction. The model presented in this paper can be used to study the SAR imaging mechanism for a drifting sea surface. Project supported by the National Natural Science Foundation of China (Grant No. 41276187), the Global Change Research Program of China (Grant No. 2015CB953901), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, the Program for the Innovation Research and Entrepreneurship Team in Jiangsu Province, China, the Canadian Program on Energy Research and Development, and the Canadian World Class Tanker Safety Service Program.

  8. Nuclear and dosimetric features of an isotopic neutron source

    International Nuclear Information System (INIS)

    A multisphere neutron spectrometer was used to determine the features of a 239PuBe neutron source that is used to operate the ESFM-IPN Subcritical Reactor. To determine the source main features it was located a 100 cm from the spectrometer which was a 6LiI(Eu) scintillator and 2, 3, 5, 8, 10 and 12 in.-diameter polyethylene spheres. Count rates obtained with the spectrometer were unfolded using the NSDUAZ code and neutron spectrum, total fluence, and ambient dose equivalent were determined. A Monte Carlo calculation was carried out to estimate the spectrum and integral features being less than values obtained experimentally due to the presence of 241Pu in the Pu used to fabricate the source. Actual neutron yield and the mass fraction of 241Pu was estimated. - Highlights: • The neutron spectrum of a 239PuBe was measured. • With the spectrum integral features were determined. • It was estimated 0.23 w/o of 241Pu in the Pu used to make the source

  9. Destructive analysis of neutron sources

    International Nuclear Information System (INIS)

    Fuel-liner reactions in Pu--Be neutron sources were examined. The source is contained in an outer jacket of 304 stainless steel and an inner Ta container incorporating a TIG welded Ta plug. Small cracks were observed in some of the outer stainless steel containers as well as in some of the tantalum inner liners. Major cracking was observed as well as penetration of the reaction product through the tantalum sidewalls in two sources. High temperatures aided and accelerated the degradation and ultimate failure of the tantalum inner liner. Traces of beryllium metal as indicated from x-ray results of the fuel and large concentration gradients between tantalum and plutonium as shown in microprobe analysis were found to exist. The fuel was inhomogeneous in nature and the data suggest the possibility of tantalum-beryllium compounds, free unreacted plutonium, and potentially a ternary phase of tantalum, beryllium, plutonium as being present in the fuel

  10. Measurement of quasi-elastic back-scattering of 64Ni+118Sn and 58Ni+124Sn

    International Nuclear Information System (INIS)

    Two systems of 64Ni+118Sn and 58Ni+124Sn produce the same compound nucleus 182Pt in the fusion reaction and they show the similar fusion cross sections below and near the Coulomb barriers, although only the system of 58Ni+124Sn has positive Q-value multi-neutron transfer channels of 1-11 neutron(s). In order to investigate the possible effect of positive Q-value multi-neutron transfer channels on the capture cross sections, the quasi-elastic back-scattering for the two systems were measured below and near the Coulomb barriers at the backward angles of 162 deg. and 172 deg. The beam energies were altered in the energy range and the quasi-elastic back-scattering excitation functions were obtained. They were compared with the coupled-channel calculations of collective excitations and a two-neutron transfer channel, indicating no evidence of a significant effect of the positive Q-value multi-neutron transfer channels on the capture cross sections for the system of 58Ni+124Sn.

  11. Auroral backscatter observed at HF from Ottawa

    International Nuclear Information System (INIS)

    Bistatic HF radar recordings of auroral scattering sources north of Ottawa are reported. Doppler frequency spreads over + or - 100 Hz were obtained at least 35 percent of the time. The peak of the Doppler frequency distribution was sometimes shifted from zero by as much as 50 Hz, and significant contributions often occurred at Doppler frequencies greater than 150 Hz. Signals received simultaneously on both arms of a two-arm direction-finding array were used to identify the specific elevations and bearings of the backscatter signals. A detailed study of a particular hour-long period is reported, and a large number of 'apparent' auroral backscatter sources are identified. The source regions, probably located in the F layer, were elongated mainly in the north-south direction and extended over at least 3 deg of latitude. North-south corridors were found between such sources in which echo returns were either absent or very weak. 14 references

  12. Implementation of Doppler backscattering for MAST

    CERN Document Server

    Hillesheim, J C; Peebles, W A; Meyer, H; Meakins, A; Field, A R; Dunai, D; Carr, M; Hawkes, N

    2014-01-01

    A sixteen channel millimeter-wave diagnostic system, covering the frequency range 30-75 GHz, has been installed on MAST [B. Lloyd et al., Nucl. Fusion 43, 1665 (2003)] and has been successfully used for both Doppler backscattering (DBS) and conventional (normal-incidence) fluctuation reflectometry. DBS has become a well-established and versatile diagnostic technique for the measurement of intermediate- k ($k_{\\bot} \\rho_i \\sim 1$, and higher) density fluctuations and flows in magnetically confined fusion experiments. The $180^{\\circ}$ backscattering for DBS requires three dimensional wave-vector matching between the launched beam and the plasma fluctuations inducing the scattering, which are expected to be highly elongated along the magnetic field. The large pitch angle in MAST means that DBS implementation depends strongly on the capability to accurately launch the probing beam at a toroidal and poloidal angle that is matched to the magnetic field at the scattering location. We report on the scattering consi...

  13. Demonstration of differential backscatter absorption gas imaging

    International Nuclear Information System (INIS)

    Backscatter absorption gas imaging (BAGI) is a technique that uses infrared active imaging to generate real-time video imagery of gas plumes. We describe a method that employs imaging at two wavelengths (absorbed and not absorbed by the gas to be detected) to allow wavelength-differential BAGI. From the frames collected at each wavelength, an absorbance image is created that displays the differential absorbance of the atmosphere between the imager and the backscatter surface. This is analogous to a two-dimensional topographic differential absorption lidar or differential optical absorption spectroscopy measurement. Gas plumes are displayed, but the topographic scene image is removed. This allows a more effective display of the plume image, thus ensuring detection under a wide variety of conditions. The instrument used to generate differential BAGI is described. Data generated by the instrument are presented and analyzed to estimate sensitivity. (c) 2000 Optical Society of America

  14. Connecting forest ecosystem and microwave backscatter models

    Science.gov (United States)

    Kasischke, Eric S.; Christensen, Norman L., Jr.

    1990-01-01

    A procedure is outlined to connect data obtained from active microwave remote sensing systems with forest ecosystem models. The hierarchy of forest ecosystem models is discussed, and the levels at which microwave remote sensing data can be used as inputs are identified. In addition, techniques to utilize forest ecosystem models to assist in the validation of theoretical microwave backscatter models are identified. Several examples to illustrate these connecting processes are presented.

  15. SuperDARN backscatter during intense geomagnetic storms

    Science.gov (United States)

    Currie, J. L.; Waters, C. L.; Menk, F. W.; Sciffer, M. D.; Bristow, W. A.

    2016-06-01

    It is often stated that high-frequency radars experience a loss of backscatter during geomagnetic storm events. The occurrence of backscatter during 25 intense geomagnetic storms was examined using data from the Bruny Island and Kodiak radars and a superposed epoch analysis. It was found that while a reduction of backscatter occurred in the middle to far ranges, there was an increase in the amount of backscatter from close range following storm onset. Ray tracing showed that an enhanced charge density in the E region can reduce the chance of F region and increase the chance of E region backscatter. It was also shown that reduction in backscatter cannot be explained by D region absorption. Using a normalized SYM-H value, percentage time through recovery phase can be estimated during storm progression which allows a prediction of backscatter return in real time that accounts for varying storm recovery phase duration.

  16. Neutron sources and its dosimetric characteristics

    International Nuclear Information System (INIS)

    By means of Monte Carlo methods the spectra of the produced neutrons 252 Cf, 252 Cf/D2O, 241 Am Be, 239 Pu Be, 140 La Be, 239 Pu18O2 and 226 Ra Be have been calculated. With the information of the spectrum it was calculated the average energy of the neutrons of each source. By means of the fluence coefficients to dose it was determined, for each one of the studied sources, the fluence factors to dose. The calculated doses were H, H*(10), Hp,sIab (10, 00), EAP and EISO. During the phase of the calculations the sources were modeled as punctual and their characteristics were determined to 100 cm in the hole. Also, for the case of the sources of 239 Pu Be and 241 Am Be, were carried out calculations modeling the sources with their respective characteristics and the dosimetric properties were determined in a space full with air. The results of this last phase of the calculations were compared with the experimental results obtained for both sources. (Author)

  17. Neutron spectroscopy with scintillation detectors using wavelets

    Science.gov (United States)

    Hartman, Jessica

    The purpose of this research was to study neutron spectroscopy using the EJ-299-33A plastic scintillator. This scintillator material provided a novel means of detection for fast neutrons, without the disadvantages of traditional liquid scintillation materials. EJ-299-33A provided a more durable option to these materials, making it less likely to be damaged during handling. Unlike liquid scintillators, this plastic scintillator was manufactured from a non-toxic material, making it safer to use, as well as easier to design detectors. The material was also manufactured with inherent pulse shape discrimination abilities, making it suitable for use in neutron detection. The neutron spectral unfolding technique was developed in two stages. Initial detector response function modeling was carried out through the use of the MCNPX Monte Carlo code. The response functions were developed for a monoenergetic neutron flux. Wavelets were then applied to smooth the response function. The spectral unfolding technique was applied through polynomial fitting and optimization techniques in MATLAB. Verification of the unfolding technique was carried out through the use of experimentally determined response functions. These were measured on the neutron source based on the Van de Graff accelerator at the University of Kentucky. This machine provided a range of monoenergetic neutron beams between 0.1 MeV and 24 MeV, making it possible to measure the set of response functions of the EJ-299-33A plastic scintillator detector to neutrons of specific energies. The response of a plutonium-beryllium (PuBe) source was measured using the source available at the University of Nevada, Las Vegas. The neutron spectrum reconstruction was carried out using the experimentally measured response functions. Experimental data was collected in the list mode of the waveform digitizer. Post processing of this data focused on the pulse shape discrimination analysis of the recorded response functions to remove the

  18. Nuclear and dosimetric features of an isotopic neutron source

    Science.gov (United States)

    Vega-Carrillo, H. R.; Hernández-Dávila, V. M.; Rivera, T.; Sánchez, A.

    2014-02-01

    A multisphere neutron spectrometer was used to determine the features of a 239PuBe neutron source that is used to operate the ESFM-IPN Subcritical Reactor. To determine the source main features it was located a 100 cm from the spectrometer which was a 6LiI(Eu) scintillator and 2, 3, 5, 8, 10 and 12 in.-diameter polyethylene spheres. Count rates obtained with the spectrometer were unfolded using the NSDUAZ code and neutron spectrum, total fluence, and ambient dose equivalent were determined. A Monte Carlo calculation was carried out to estimate the spectrum and integral features being less than values obtained experimentally due to the presence of 241Pu in the Pu used to fabricate the source. Actual neutron yield and the mass fraction of 241Pu was estimated.

  19. Brazilian two-component TLD albedo neutron individual monitoring system

    International Nuclear Information System (INIS)

    Since 1983, Instituto de Radioprotecao e Dosimetria, Brazil, uses a TLD one-component albedo neutron monitor, which has a single different calibration factor specifically for each installation type. In order to improve its energy response, a two-component albedo monitor was developed, which measure the thermal neutron component besides the albedo one. The two-component monitor has been calibrated in reference neutron fields: thermal, five accelerator-produced monoenergetic beams (70, 144, 565, 1200 and 5000 keV) and five radionuclide sources (252Cf, 252Cf(D2O), 241Am-Be, 241Am-B and 238Pu-Be) at several distances. Since January 2008, mainly Brazilian workers who handle neutron sources at different distances and moderation, such as in well logging and calibration facilities are using it routinely.

  20. Sensitivity of moderator-containing thermal neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Alejnikov, V.E.; Arkhipov, V.A.; Beskrovnaya, L.G.; Komochkov, M.M.; Mokrov, Yu.V. (Joint Inst. for Nuclear Research, Dubna (USSR))

    The dependences of the sensitivities of the LiI(Eu) thermal neutron detector and the DN-A-1 dosimeter on the isotopic source neutron energy are analyzed. It is shown that the results obtained permit to choose the most confident values for sensitivity of the thermal neutron detectors in moderators. The given data are compared with the experimental and calculated data of other authors. A conclusion is made that the DN-A-1 dosimeter in the energy range from several fractions of eV Up to dozens of keV, as calibrated using a Pu+Be-neutron source, is close to an ''ideal'' dosimeter.

  1. Spectrum of isotopic neutron sources inside concrete wall spherical cavities

    International Nuclear Information System (INIS)

    The neutron spectra of 252Cf/D2O, 140LaBe, 252Cf, 238Pu18O2, 241AmB, 241AmBe, 226RaBe and 239PuBe isotopic neutron sources due to room-return have been determined for various source-to-detector distances in concrete spherical cavities of different radius. Changes in the amount of thermal neutrons (E≤0.414eV) were analyzed to estimate, for each neutron source, the coefficient that relates the neutron source strength and room surface area with the thermal neutron fluence rates. The study was carried out using Monte Carlo methods for 200, 400, 500, 800, 1000, 1200 and 1500-cm-radius spherical cavity in vacuum; cavities are 100-cm-thick concrete. Point sources were located at the center of cavity and neutron spectra were calculated at several source-to-detector distances along the cavity radius. The thermal neutron contribution was thereby evaluated. From these calculations a weighted coefficient value that relates the thermal neutron fluence with the neutron source strength and the total inner area surface of the cavity was estimated to be 3.76±0.03

  2. Concrete enclosure to shield a neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Villagrana M, L. E.; Rivera P, E.; De Leon M, H. A.; Soto B, T. G.; Hernandez D, V. M.; Vega C, H. R., E-mail: emmanuelvillagrana@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico)

    2012-10-15

    In the aim to design a shielding for a {sup 239}PuBe isotopic neutron source several Monte Carlo calculations were carried out using MCNP5 code. First, a point-like source was modeled in vacuum and the neutron spectrum and the ambient dose equivalent were calculated at several distances ranging from 5 up to 150 cm, these calculations were repeated including air, and a 1 x 1 x 1 m{sup 3} enclosure that was shielded with 5, 15, 20, 25, 30, 50 and 80 cm-thick Portland type concrete walls. At all the points located inside the enclosure neutron spectra from 10{sup -8} up 0.5 MeV were the same regardless the distance from the source showing the room-return effect, for energies larger than 0.5 MeV neutron spectra are diminished as the distance increases. Outside the enclosure it was noticed that neutron spectra becomes -softer- as the concrete thickness increases due to reduction of mean neutron energy. With the ambient dose values the attenuation curve in terms of concrete thickness was calculated. (Author)

  3. The investigation of Am-Be neutron source shield effect used on landmine detection

    Energy Technology Data Exchange (ETDEWEB)

    Rezaei Ochbelagh, D. [Department of Physics, Faculty of Sciences, University of Mohagheg Ardebily, P.O. Box 179, Ardebil (Iran, Islamic Republic of)]. E-mail: ddrezaey@yahoo.com; Miri Hakimabad, H. [Physics Department, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Najafabadi, R. Izadi [Physics Department, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

    2007-07-11

    In this work, experiments were carried out to investigate the possible use of neutron backscattering for the detection of sample buried in the soil. A series of Monte Carlo simulations were performed to study the complexity of the neutron backscattering process and to optimize the source shield thickness. The results of these simulations indicate that neutron source shield plays an important role for the detection of nonmetallic landmines. This paper experimentally demonstrates, by using suitable shield around Am-Be neutron source, the increase of signal-to-noise ratio up to 130%.

  4. BONDI-97: A novel neutron energy spectrum unfolding tool using a genetic algorithm

    International Nuclear Information System (INIS)

    The neutron spectrum unfolding procedure using the count rate data obtained from a set of Bonner sphere neutron detectors requires the solution of the Fredholm integral equation of the first kind by using complex mathematical methods. This paper reports a new approach for the unfolding of neutron spectra using the Genetic Algorithm tool BONDI-97 (BOnner sphere Neutron DIfferentiation). The BONDI-97 was used as the input for Genetic Algorithm engine EVOLVER to search for a globally optimised solution vector from a population of randomly generated solutions. This solution vector corresponds to the unfolded neutron energy spectrum. The Genetic Algorithm engine emulates the Darwinian 'Survival of the Fittest' strategy, the key ingredient of the 'Theory of Evolution'. The spectra of 241Am/Be (α,n) and 239Pu/Be (α,n) neutron sources were unfolded using the BONDI-97 tool. (author)

  5. Reducing parametric backscattering by polarization rotation

    CERN Document Server

    Barth, Ido

    2016-01-01

    When a laser passes through underdense plasmas, Raman and Brillouin Backscattering can reflect a substantial portion of the incident laser energy. This is a major loss mechanism, for example, in inertial confinement fusion. However, by slow rotation of the incident linear polarization, the overall reflectivity can be reduced significantly. Particle in cell simulations show that, for parameters similar to those of indirect drive fusion experiments, polarization rotation reduces the reflectivity by a factor of $5$. A general, fluid-model based, analytical estimation for the reflectivity reduction agrees with simulations.

  6. Interactive computer analysis of nuclear backscattering spectra

    International Nuclear Information System (INIS)

    A review will be made of computer-based interactive nuclear backscattering analysis system. Users without computer experience can develop moderate competence with the system after only brief instruction because of the menu-driven organization. Publishable quality figures can be obtained without any computer expertise. Among the quantities which can be displayed over the data are depth scales for any element, element identification, relative concentrations and theoretical spectra. Captions and titling can made from a selection of 30 font styles. Lettering is put on the graphs umder joy-stick control such that placement is exact without needing complicated commands. (orig.)

  7. Understanding the radar backscattering from flooded and nonflooded Amazonian forests: results from canopy backscatter modeling

    International Nuclear Information System (INIS)

    To understand the potential of using multiwavelength imaging radars to detect flooding in Amazonian floodplain forests, we simulated the radar backscatter from a floodplain forest with a flooded or nonflooded ground condition at C-, L-, and P-bands. Field measurements of forest structure in the Anavilhanas archipelago of the Negro River, Brazil, were used as inputs to the model. Given the same wavelength or incidence angle, the ratio of backscatter from the flooded forest to that from the nonflooded forest was higher at HH polarization than at VV polarization. Given the same wavelength or polarization, the ratio was larger at small incidence angles than at large incidence angles. Given the same polarization or incidence angle, the ratio was larger at a long wavelength than at a short wavelength. As the surface soil moisture underneath the nonflooded forest increased from 10% to 50% of volumetric moisture, the flooded/nonflooded backscatter ratio decreased; the decreases were small at C- and L-band but large at P-band. When the leaf size was comparable to or larger than the wavelength of C-band, the leaf area index (LAI) had a large effect on the simulated C-band (not L-band or P-band) backscatter from the flooded and nonflooded forests. (author)

  8. CRED Acoustic Backscatter Guam 2003, Imagery Extracted from Gridded Bathymetry

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Backscatter extracted from gridded bathymetry of the banktops and shelf environments of Guam, of the Mariana Islands Archipelago.

  9. Effect of Pressure on Intracardiac Backscatter from Microbubbles

    Institute of Scientific and Technical Information of China (English)

    DENG; Youbin; LI; Chunlei; CHANG; Qing

    2001-01-01

    The backscatter from sonicated albumin microbubbles (Albunex) was analyzed using acoustic densitometry in an in vitro pulsatile heart model to evaluate the effects of pressure on the backscatter from Albunex, and the cardiac cyclic changes of intracardiac backscatter from sonicated albumin microbubbles in 16 healthy persons were analyzed. It was found that the Albunex microbubbles were compressed in systole and decompressed in diastole, causing corresponding changes of backscatter in cardiac cycle. Although the intensities of backscatter in diastole and systole were related to the concentration of microbubbles, the concentration of microbubbles had no effect on the difference of end-diastolic and end-systolic backscatter. The difference of the backscatter was highly correlated with end-systolic pressure (r = 0. 96, P = 0. 001). In human studies, we also observed same intracardiac cyclic changes of backscatter from sonicated albumin microbubbles. Our study indicates that it is possible to evaluate the intracardiac pressure non-invasively by analyzing the intracardiac backscatter from the microbubbles with acoustic densitometry.

  10. Chiral Receiving Antenna With Low Backscattering Levels

    CERN Document Server

    Karilainen, Antti O

    2011-01-01

    Receiving antennas absorb power from incident waves, but they also re-radiate some power into surrounding space. If a receiving antenna is to be used as a sensor which should not disturb the object under study, it should scatter as little power as possible in the receiving direction. We propose to use a chiral element composed of two orthogonal chiral particles as a low-scattering sensor.The element can transmit and receive circular polarization in all directions with the Huygens' pattern. We derive the vector effective length for the antenna using the small dipole approximation for the chiral particles. We observe that the element does not backscatter, regardless of the polarization, when the incidence direction is normal to the plane of the particles. Scattered fields, scattered axial ratio, and the scattering cross section are presented. We show that the zero-backscattering property holds also for the antenna element when it is capable to receive all the available power with conjugate loading. The approxim...

  11. Conceptual design of the time-of-flight backscattering spectrometer, MIRACLES, at the European Spallation Source.

    Science.gov (United States)

    Tsapatsaris, N; Lechner, R E; Markó, M; Bordallo, H N

    2016-08-01

    In this work, we present the conceptual design of the backscattering time-of-flight spectrometer MIRACLES approved for construction at the long-pulse European Spallation Source (ESS). MIRACLES's unparalleled combination of variable resolution, high flux, extended energy, and momentum transfer (0.2-6 Å(-1)) ranges will open new avenues for neutron backscattering spectroscopy. Its remarkable flexibility can be attributed to 3 key elements: the long-pulse time structure and low repetition rate of the ESS neutron source, the chopper cascade that tailors the moderator pulse in the primary part of the spectrometer, and the bent Si(111) analyzer crystals arranged in a near-backscattering geometry in the secondary part of the spectrometer. Analytical calculations combined with instrument Monte-Carlo simulations show that the instrument will provide a variable elastic energy resolution, δ(ħ ω), between 2 and 32 μeV, when using a wavelength of λ ≈ 6.267 Å (Si(111)-reflection), with an energy transfer range, ħ ω, centered at the elastic line from -600 to +600 μeV. In addition, when selecting λ ≈ 2.08 Å (i.e., the Si(333)-reflection), δ(ħ ω) can be relaxed to 300 μeV and ħ ω from about 10 meV in energy gain to ca -40 meV in energy loss. Finally, the dynamic wavelength range of MIRACLES, approximately 1.8 Å, can be shifted within the interval of 2-20 Å to allow the measurement of low-energy inelastic excitations. PMID:27587171

  12. Artificial neural networks technology for neutron spectrometry and dosimetry

    International Nuclear Information System (INIS)

    Artificial Neural Network Technology has been applied to unfold neutron spectra and to calculate 13 dosimetric quantities using seven count rates from a Bonner Sphere Spectrometer with a 6LiI(Eu). Two different networks, one for spectrometry and another for dosimetry, were designed. To train and test both networks, 177 neutron spectra from the IAEA compilation were utilised. Spectra were re-binned into 31 energy groups, and the dosimetric quantities were calculated using the MCNP code and the fluence-to-dose conversion coefficients from ICRP 74. Neutron spectra and UTA4 response matrix were used to calculate the expected count rates in the Bonner spectrometer. Spectra and H*(10) of 239PuBe and 241AmBe were experimentally obtained and compared with those determined with the artificial neural networks. (authors)

  13. Electron backscatter diffraction in materials characterization

    Directory of Open Access Journals (Sweden)

    Dejan Stojakovic

    2012-03-01

    Full Text Available Electron Back-Scatter Diffraction (EBSD is a powerful technique that captures electron diffraction patterns from crystals, constituents of material. Captured patterns can then be used to determine grain morphology, crystallographic orientation and chemistry of present phases, which provide complete characterization of microstructure and strong correlation to both properties and performance of materials. Key milestones related to technological developments of EBSD technique have been outlined along with possible applications using modern EBSD system. Principles of crystal diffraction with description of crystallographic orientation, orientation determination and phase identification have been described. Image quality, resolution and speed, and system calibration have also been discussed. Sample preparation methods were reviewed and EBSD application in conjunction with other characterization techniques on a variety of materials has been presented for several case studies. In summary, an outlook for EBSD technique was provided.

  14. The dose from Compton backscatter screening.

    Science.gov (United States)

    Rez, Peter; Metzger, Robert L; Mossman, Kenneth L

    2011-04-01

    Systems based on the detection of Compton backscattered X rays have been deployed for screening personnel for weapons and explosives. Similar principles are used for screening vehicles at border-crossing points. Based on well-established scattering cross sections and absorption coefficients in conjunction with reasonable estimates of the image contrast and resolution, the entrance skin dose and the dose at a depth of 1 cm can be calculated. The effective dose can be estimated using the same conversion coefficients as used to convert exposure measurements to the effective dose. It is shown that the effective dose is highly dependent on image resolution (i.e. pixel size).The effective doses for personnel screening systems are unlikely to be in compliance with the American National Standards Institute standard NS 43.17 unless the pixel sizes are >4 mm. Nevertheless, calculated effective doses are well below doses associated with health effects. PMID:21068018

  15. Simulation of ultrasound backscatter images from fish

    DEFF Research Database (Denmark)

    Pham, An Hoai; Stage, Bjarne; Hemmsen, Martin Christian;

    2011-01-01

    The objective of this work is to investigate ultrasound (US) backscatter in the MHz range from fis to develop a realistic and reliable simulation model. The long term objective of the work is to develop the needed signal processing for fis species differentiation using US. In in-vitro experiments......, a cod (Gadus morhua) was scanned with both a BK Medical ProFocus 2202 ultrasound scanner and a Toshiba Aquilion ONE computed tomography (CT) scanner. The US images of the fis were compared with US images created using the ultrasound simulation program Field II. The center frequency of the transducer...... is 10 MHz and the Full Width at Half Maximum (FWHM) at the focus point is 0.54 mm in the lateral direction. The transducer model in Field II was calibrated using a wire phantom to validate the simulated point spread function. The inputs to the simulation were the CT image data of the fis converted to...

  16. Strong Localization in Disordered Media: Analysis of the Backscattering Cone

    KAUST Repository

    Delgado, Edgar

    2012-06-01

    A very interesting effect in light propagation through a disordered system is Anderson localization of light, this phenomenon emerges as the result of multiple scattering of waves by electric inhomogeneities like spatial variations of index of refraction; as the amount of scattering is increased, light propagation is converted from quasi-diffusive to exponentially localized, with photons confined in a limited spatial region characterized by a fundamental quantity known as localization length. Light localization is strongly related to another interference phenomenon emerged from the multiple scattering effect: the coherent backscattering effect. In multiple scattering of waves, in fact, coherence is preserved in the backscattering direction and produces a reinforcement of the field flux originating an observable peak in the backscattered intensity, known as backscattering cone. The study of this peak provide quantitative information about the transport properties of light in the material. In this thesis we report a complete FDTD ab-initio study of light localization and coherent backscattering. In particular, we consider a supercontinuum pulse impinging on a sample composed of randomly positioned scatterers. We study coherent backscattering by averaging over several realizations of the sample properties. We study then the coherent backscattering cone properties as the relative permittivity of the sample is changed, relating the latter with the light localization inside the sample. We demonstrate important relationships between the width of the backscattering cone and the localization length, which shows a linear proportionality in the strong localization regime.

  17. Use of cold neutrons for condensed matter research at the neutron guide laboratory ELLA in Juelich

    Energy Technology Data Exchange (ETDEWEB)

    Schaetzler, R.; Monkenbusch, M. [Research Centre Juelich, D-52425 Juelich (Germany)

    1998-07-01

    Cold neutrons produced in the FRJ-2 DIDO reactor are guided into the external hall ELLA. It hosts 10 instruments that are red by three major neutron guides. Cold neutrons allow for diffraction and small angle scattering experiments resolving mesoscopic structures (1 to 100 nm). Contrast variation by isotopic substitution in chemically identical species yields information uniquely accessible bi neutrons. Inelastic scattering of cold neutrons allows investigating slow molecular motions because the low neutron velocity results in large relative velocity changes even at small energy transfers. The SANS machines and the HADAS reflectometer serve as structure probes and the backscattering BSS1 and spin-echo spectrometers NSE as main dynamics probes. Besides this the diffuse scattering instrument DNS and the lattice parameter determination instrument LAP deal mainly with crystals and their defects. Finally the beta-NMR and the EKN position allow for methods other than scattering employing nuclear reactions for solid state physics, chemistry and biology/medicine. (author)

  18. Rutherford backscattering in an industrial environment

    International Nuclear Information System (INIS)

    Rutherford Backscattering spectrometry (RBS) is a well established analytical technique, particularly in the university and major research oriented industrial laboratories. Historically, the accelerators used for RBS analysis have been renovated low energy nuclear physics rather than a dedicated optimally designed analytical instrument. It is this 'requirement' that each machine be individually rebuilt prior to use as a materials analysis tool that has contributed to the limited industrial use of RBS when compared with other analytical techniques such as Auger spectroscopy or Secondary Ion Mass spectrometry (SIMS). This paper will discuss the design criteria and applications of an RBS system for use in an industrial analytical environment. The design issues which are discussed include the backscattered particle detection, sample positioning, charge integration, vacuum, and automation systems. An RBS system for which the design of these systems has been optimized in light of many current industrial applications will be evaluated. The prototype of this system has been tested for the previous two years with a utilization factor of 4000-5000 individual analyses per year. The applications which have been investigated extend from the familiar electronics related topics to many other diverse fields such as polymeric chemistry, catalysis, and surface modification of synthetic fibers. Some of the electronics applications include high throughput 'production line' analysis of silicides, copper doped aluminium, and similar interconnect materials as well as the more sophisticated trace impurity mapping techniques which involve channeled line scans. Catalysis applications include the study of cage compound zeolite particle and the depth distribution of the active catalyst in these particles. Applications in the field of synthesis fibers include the study of the depth distribution of coloring agents and dyes in the near surface region of the fibers. (orig.)

  19. CHANGES OF BACKSCATTERING PARAMETERS DURING CHILLING INJURY IN BANANAS

    Directory of Open Access Journals (Sweden)

    NORHASHILA HASHIM

    2014-06-01

    Full Text Available The change in backscattering parameters during the appearance of chilling injury in bananas was investigated. Bananas were stored at a chilling temperature for two days and the degrees of the chilling injuries that appeared were measured before, during and after storage using backscattering imaging and visual assessment. Laser lights at 660 nm and 785 nm wavelengths were shot consecutively onto the samples in a dark room and a camera was used to capture the backscattered lights that appeared on the samples. The captured images were analysed and the changes of intensity against pixel count were plotted into graphs. The plotted graph provides useful information of backscattering parameters such as inflection point (IP, slope after inflection point (SA, and full width at half maximum (FWHM and saturation radius (RSAT. Results of statistical analysis indicated that there were significant changes of these backscattering parameters as chilling injury developed.

  20. NRF Based Nondestructive Inspection System for SNM by Using Laser-Compton-Backscattering Gamma-Rays

    Science.gov (United States)

    Ohgaki, H.; Omer, M.; Negm, H.; Daito, I.; Zen, H.; Kii, T.; Masuda, K.; Hori, T.; Hajima, R.; Hayakawa, T.; Shizuma, T.; Kando, M.

    2015-10-01

    A non-destructive inspection system for special nuclear materials (SNMs) hidden in a sea cargo has been developed. The system consists of a fast screening system using neutron generated by inertial electrostatic confinement (IEC) device and an isotope identification system using nuclear resonance fluorescence (NRF) measurements with laser Compton backscattering (LCS) gamma-rays has been developed. The neutron flux of 108 n/sec has been achieved by the IEC in static mode. We have developed a modified neutron reactor noise analysis method to detect fission neutron in a short time. The LCS gamma-rays has been generated by using a small racetrack microtoron accelerator and an intense sub-nano second laser colliding head-on to the electron beam. The gamma-ray flux has been achieved more than 105 photons/s. The NRF gamma-rays will be measured using LaBr3(Ce) scintillation detector array whose performance has been measured by NRF experiment of U-235 in HIGS facility. The whole inspection system has been designed to satisfy a demand from the sea port.

  1. Detection of explosives and illicit drugs using neutrons

    Science.gov (United States)

    Király, B.; Sanami, T.; Dóczi, R.; Csikai, J.

    2004-01-01

    A procedure developed for the determination of the flux perturbation factor required for the thermal neutron activation analysis of bulky samples of unknown composition has been extended for epithermal neutrons using hydrogenous and graphite moderators. Measurements on the diffusion and backscattering of thermal neutrons in soil components were carried out for the development of novel nuclear methods in order to speed up the humanitarian demining process. Results obtained for the diffusion length were checked by MCNP-4C calculations. In addition, the effect of the weight and density of the explosives on the observation of the anomaly in the reflected thermal neutrons was examined by using different dummy landmines.

  2. Characterization of the backscattered radiation from petawatt laser matter interactions

    International Nuclear Information System (INIS)

    The development of high peak power and energy laser systems require the assurance that any backscattered radiation will not lead to damage of the laser system. We present the characterization of the backscattered radiation for different target types and conditions at petawatt power levels and intensities (>1020W/cm2). We observe that radiation is generated between 700 and 900 nm, as well as the expected self emission and laser fundamental. The percentage of the incident light backscattered reduces as a function of the incident energy and is typically <1% for petawatt laser interactions

  3. Neutron Radiography

    OpenAIRE

    Reddy, A. R.; Rao, M. V. N.

    2012-01-01

    The field of neutron radiography with special reference to isotopic neutron radiography has been reviewed. Different components viz., sources, collimators, imaging systems are described. Various designs of neutron radiography facilities, their relative merits and demerits , the appropriateness of each design depending on the object to be radiographed, and economics of each technique are also dealt. The applications of neutron radiography are also briefly presented.

  4. Neutron reflectometry

    International Nuclear Information System (INIS)

    Neutron research where reflection, refraction, and interference play an essential role is generally referred to as 'neutron optics'. The neutron wavelength, the scattering length density and the magnetic properties of the material determine the critical angle for total reflection. The theoretical background of neutron reflection, experimental methods and the interpretation of reflection data are presented. (K.A.)

  5. Statistical simulation of multiple Compton backscattering process

    Science.gov (United States)

    Potylitsyn, A. P.; Kolchuzhkin, A. M.

    2014-09-01

    A number of laboratories are currently developing monochromatic sources of X-rays and gamma quanta based on the Compton backscattering (CBS) of laser photons by relativistic electrons. Modern technologies are capable of providing a concentration of electrons and photons in the interaction point such that each primary electron can emit several hard photons. In contrast to the well-known nonlinear CBS process, in which an initial electron "absorbs" a few laser photons and emits a single hard one, the above-mentioned process can be called a multiple CBS process and is characterized by a mean number of emitted photons. The present paper is devoted to simulating the parameters of a beam of back scattered quanta based on the Monte Carlo technique. It is shown that, even in the case of strong collimation of a resulting photon beam, the radiation monochromaticity may deteriorate because of the contribution coming from the multiple photon emission, which is something that must be considered while designing new CBS sources.

  6. X-Ray Backscatter Machine Support Frame

    Science.gov (United States)

    Cannon, Brooke

    2010-01-01

    This summer at Kennedy Space Center, I spent 10 weeks as an intern working at the Prototype Development Lab. During this time I learned about the design and machining done here at NASA. I became familiar with the process from where a design begins in Pro/Engineer and finishes at the hands of the machinists. As an intern I was given various small jobs to do and then one project of my own. My personal project was a job for the Applied Physics Lab; in their work they use an X-Ray Backscatter machine. Previously it was resting atop a temporary frame that limited the use of the machine. My job was to design a frame for the machine to rest upon that would allow a full range of sample sizes. The frame was required to support the machine and provide a strain relief for the cords attached to the machine as it moved in the x and y directions. Calculations also had to be done to be sure the design would be able to withstand any loads or outside sources of stress. After the calculations proved the design to be ready to withstand the requirements, the parts were ordered or fabricated, as required. This helped me understand the full process of jobs sent to the Prototype Development Lab.

  7. Estimating slash pine biomass using radar backscatter

    Science.gov (United States)

    Hussin, Yousif Ali; Reich, Robin M.; Hoffer, Roger M.

    1991-01-01

    L-band HV multiple-incidence-angle aircraft synthetic aperture radar (SAR) data were analyzed in relation to average stand biomass, basal area, and tree height for 55 slash pine plantations located in northern Florida. This information was used to develop a system of equations to predict average stand biomass as a function of L-band (24.5-cm) radar backscatter. The system of equations developed in this study using three-stage least-squares and combinatorial screening accounted for 97 percent of the variability observed in average stand biomass per hectare. When applied to an independent data set, the biomass equations had an average bias of less than 1 percent with a standard error of approximately 3 percent. These results indicate that future Shuttle Imaging Radar Systems (e.g., SIR-C, which will have cross-polarized radar sensors) should be able to obtain better estimates of forest biomass than were obtained with previous satellite radar missions, which utilized only HH-polarized SAR data.

  8. Spectrometry and dosimetry of a neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Manzanares A, E.; Hernandez D, V.M.; Ramirez G, J.; Hernandez V, R.; Chacon R, A. [Universidad Autonoma de Zacatecas, 98068 Zacatecas (Mexico)]. e-mail: fermineutron@yahoo.com

    2007-07-01

    Using Monte Carlo methods the spectrum, dose equivalent and ambient dose equivalent of a {sup 239}PuBe at several distances has been determined. Spectrum and both doses, at 100 cm, were determined-experimentally using a Bonner sphere spectrometer. These quantities were obtained by unfolding the spectrometer count rates using artificial neural networks. The dose equivalent, based in the ICRP 21 criteria, was measured with the area neutron dosemeter Eberline model NRI), at 100, 200 and 300 cm. All measurements were carried out in an open space to avoid the room return. With these results it was found that this source has a yield of 8.41E(6) n/s. (Author)

  9. Some studies for neutron dose determination and collection of basic data of chromosome aberration of radiation workers at the nuclear research institute

    International Nuclear Information System (INIS)

    Contents of some elements in the Human blood and hair samples were determined by the INAA. Neutron dose assessment methods by measuring Na-24 in the human blood and P-32 in the human hair were established. The manganese tank method was carried out for determination of total emission of neutron Am-Be and Pu-Be sources. A new type of neutron personal dosimeter was presented. A basic data collection of chromosome aberration of radiation workers of the Nuclear Research Institute was performed. (author)

  10. Backscatter B [USGS]--Offshore of Ventura, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3254 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3254) of the Offshore Ventura map area, California. The raster data...

  11. Backscatter A [CSUMB]--Offshore of Ventura, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3254 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3254) of the Offshore of Ventura map area, California. The raster...

  12. Backscatter B [USGS]--Offshore of Carpinteria, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3261 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3261) of the Offshore of Carpinteria map area, California. The raster...

  13. Backscatter A [CSUMB]--Offshore of Carpinteria, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3261 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3261) of the Offshore of Carpinteria map area, California. The raster...

  14. Backscatter A [CSUMB]--Offshore of Santa Barbara, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3281 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3281) of the Offshore of Santa Barbara map area, California. The...

  15. Reson 8101 multibeam backscatter data from Galvez Bank.

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Multibeam backscatter imagery extracted from gridded bathymetry of the Mariana archipelago between the U.S. Territory of Guam and Farallon De Pajaros Island in the...

  16. Bathymetry and Acoustic Backscatter: Northern Santa Barbara Channel, Southern California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This report presents bathymetry and acoustic backscatter data collected in July 2008 in the northern Santa Barbara Channel, California, using a bathymetric sidescan...

  17. An algorithm to determine backscattering ratio and single scattering albedo

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, T.; Desa, E.; Matondkar, S.G.P.; Mascarenhas, A.A.M.Q.; Nayak, S.R.; Naik, P.

    Algorithms to determine the inherent optical properties of water, backscattering probability and single scattering albedo at 490 and 676 nm from the apparent optical property, remote sensing reflectance are presented here. The measured scattering...

  18. LIDAR for atmospheric backscatter and temperature measurements Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objectives of this effort are to measure atmospheric backscatter profiles and temperature using a zenith looking lidar, designed for a small lander.The lidar...

  19. Photoelectron backscattering from silicon anodes of hybrid photodetector tubes

    CERN Document Server

    D'Ambrosio, C

    2000-01-01

    The impact of photoelectron backscattering on spectral distributions measured with hybrid photodetector tubes has been calculated. The calculations are based on the backscattering coefficient mu , the average number of photoelectrons N/sub phel/ emitted from the photocathode, and on the distribution of the fractional photoelectron energy q absorbed in silicon during the backscattering process. We obtained the following results: the average number of absorbed (measured) photoelectrons N/sub meas/ in the silicon anode amounts to ~88% of the incident N/sub phel/. Photoelectron- and gamma-absorption peaks are broadened by a factor 1.043 due to backscattering. As an example, for photomultiplier tubes, this broadening can amount to an average factor of 1.18 due to statistic and gain fluctuations on the dynode chain. (15 refs).

  20. Detection of buried landmine with X-ray backscatter technique

    Science.gov (United States)

    Yuk, Sunwoo; Kim, Kwang Hyun; Yi, Yun

    2006-11-01

    We describe a continuously operating scanning X-ray imaging system developed for landmine detection based on a backscatter X-ray principle, thus detection is done from the same side as the source. The source operates at 120 kV p and 3 mA. To study the physics of Compton X-ray backscattering, the photon transport factor, backscatter factor (BSF) and backscatter probability (BSP) were simulated using Monte-Carlo calculations using the generalized particle transport program MCNP. Based on the Monte-Carlo analyses results, a mine detecting system has been designed. It potentially has a low false alarm rate and a high detection probability, and a direct imaging facility.

  1. Detection of buried landmine with X-ray backscatter technique

    Energy Technology Data Exchange (ETDEWEB)

    Yuk, Sunwoo [Department of Electronics and Information Engineering, Korea University, Seoul (Korea, Republic of)]. E-mail: sunwoo@korea.ac.kr; Kim, Kwang Hyun [Chosun University, 375, Seosuk-Dong, Dong-Gu, Gwangju (Korea, Republic of); Yi, Yun [Department of Electronics and Information Engineering, Korea University, Seoul (Korea, Republic of)

    2006-11-30

    We describe a continuously operating scanning X-ray imaging system developed for landmine detection based on a backscatter X-ray principle, thus detection is done from the same side as the source. The source operates at 120 kV p and 3 mA. To study the physics of Compton X-ray backscattering, the photon transport factor, backscatter factor (BSF) and backscatter probability (BSP) were simulated using Monte-Carlo calculations using the generalized particle transport program MCNP. Based on the Monte-Carlo analyses results, a mine detecting system has been designed. It potentially has a low false alarm rate and a high detection probability, and a direct imaging facility.

  2. Backscatter--Offshore of Refugio Beach Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3319 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3319) of Offshore Refugio Beach map area, California. The raster data...

  3. Reson 8101 Backscatter imagery of Penguin Bank, Molokai, Hawaii, USA

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Backscatter imagery extracted from gridded bathymetry of Penguin Bank, Molokai, Hawaii, USA. These data provide almost complete coverage between 0 and 100 meters....

  4. Backscatter [8101]--Offshore of Monterey Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents 2-m-resolution Reson 8101 data for the acoustic-backscatter map of the Offshore of Monterey map area, California. These metadata...

  5. Backscatter [7125]-- Offshore of Monterey Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents 2-m-resolution Reson 7125 data for the acoustic-backscatter map of Offshore of Monterey map area, California. These metadata describe...

  6. Backscatter [Swath]-- Offshore of Monterey Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents 2-m-resolution SWATHPlus data for the acoustic-backscatter map of Offshore of Monterey map area, California. These metadata describe...

  7. The construction of a high resolution crystal backscattering spectrometer HERMES I

    Energy Technology Data Exchange (ETDEWEB)

    Larese, J.Z.

    1998-11-01

    There is a need in the United States for a state-of-the-art, cold-neutron, crystal backscattering spectrometer (CBS) designed to investigate the structure and dynamics of condensed matter systems by the simultaneous utilization of long wavelength elastic diffraction and high-energy-resolution inelastic scattering. Cold neutron spectroscopy with CBS-type instruments has already made many important contributions to the study of atomic and molecular diffusion in biomaterials, polymers, semiconductors, liquid crystals, superionic conductors and the like. Such instruments have also been invaluable for ultra high resolution investigations of the low-lying quantum tunneling processes that provide direct insight into the dynamical response of solids at the lowest energies. Until relatively recently, however, all such instruments were located at steady-state reactors. This proposal describes HERMES I (High Energy Resolution Machines I) a CBS intended for installation at the LANSCE pulsed neutron facility of Los Alamos National Laboratory. As explained in detail in the main text, the authors propose to construct an updated, high-performance CBS which incorporates neutron techniques developed during the decade since IRIS was built, i.e., improved supermirror technology, a larger area crystal analyzer and high efficiency wire gas detectors. The instrument is designed in such a way as to be readily adaptable to future upgrades. HERMES I, they believe, will substantially expand the range and flexibility of neutron investigations in the United States and open new and potentially fruitful directions for condensed matter exploration. This document describes a implementation plan with a direct cost range between $4.5 to 5.6 M and scheduled duration of 39--45 months for identified alternatives.

  8. The construction of a high resolution crystal backscattering spectrometer HERMES I

    International Nuclear Information System (INIS)

    There is a need in the United States for a state-of-the-art, cold-neutron, crystal backscattering spectrometer (CBS) designed to investigate the structure and dynamics of condensed matter systems by the simultaneous utilization of long wavelength elastic diffraction and high-energy-resolution inelastic scattering. Cold neutron spectroscopy with CBS-type instruments has already made many important contributions to the study of atomic and molecular diffusion in biomaterials, polymers, semiconductors, liquid crystals, superionic conductors and the like. Such instruments have also been invaluable for ultra high resolution investigations of the low-lying quantum tunneling processes that provide direct insight into the dynamical response of solids at the lowest energies. Until relatively recently, however, all such instruments were located at steady-state reactors. This proposal describes HERMES I (High Energy Resolution Machines I) a CBS intended for installation at the LANSCE pulsed neutron facility of Los Alamos National Laboratory. As explained in detail in the main text, the authors propose to construct an updated, high-performance CBS which incorporates neutron techniques developed during the decade since IRIS was built, i.e., improved supermirror technology, a larger area crystal analyzer and high efficiency wire gas detectors. The instrument is designed in such a way as to be readily adaptable to future upgrades. HERMES I, they believe, will substantially expand the range and flexibility of neutron investigations in the United States and open new and potentially fruitful directions for condensed matter exploration. This document describes a implementation plan with a direct cost range between $4.5 to 5.6 M and scheduled duration of 39--45 months for identified alternatives

  9. Computer-controlled neutron spectrometer SV 22

    International Nuclear Information System (INIS)

    The neutron spectrometer SV22 is a combined time of flight and back scattering spectrometer. It is located at the tangential beam tube TAN2 of the research reactor FRJ2 DIDO at Kernforschungsanlage Juelich (West-Germany). Both versions are described in their hardware layout. The neutron optical characteristics of the already functioning time of flight spectrometer are summarized. Selected experiments show some possible fields for further research with this instrument. Experimental data for the backscattering version is not yet available. The features of the operating system RSX11M are explained. Examples show the use of indirect command files in control of the experiment. (orig.)

  10. Interlinking backscatter, grain size and benthic community structure

    Science.gov (United States)

    McGonigle, Chris; Collier, Jenny S.

    2014-06-01

    The relationship between acoustic backscatter, sediment grain size and benthic community structure is examined using three different quantitative methods, covering image- and angular response-based approaches. Multibeam time-series backscatter (300 kHz) data acquired in 2008 off the coast of East Anglia (UK) are compared with grain size properties, macrofaunal abundance and biomass from 130 Hamon and 16 Clamshell grab samples. Three predictive methods are used: 1) image-based (mean backscatter intensity); 2) angular response-based (predicted mean grain size), and 3) image-based (1st principal component and classification) from Quester Tangent Corporation Multiview software. Relationships between grain size and backscatter are explored using linear regression. Differences in grain size and benthic community structure between acoustically defined groups are examined using ANOVA and PERMANOVA+. Results for the Hamon grab stations indicate significant correlations between measured mean grain size and mean backscatter intensity, angular response predicted mean grain size, and 1st principal component of QTC analysis (all p response predicted mean grain size (r2 = 0.692; p response predicted grain size (p < 0.001), and QTC class (p = 0.009). Mean grain size (Clamshell) shows a significant difference between groups for mean backscatter (p = 0.001); other methods were not significant. PERMANOVA for the Hamon abundance shows benthic community structure was significantly different between acoustic groups for all methods (p ≤ 0.001). Overall these results show considerable promise in that more than 60% of the variance in the mean grain size of the Clamshell grab samples can be explained by mean backscatter or acoustically-predicted grain size. These results show that there is significant predictive capacity for sediment characteristics from multibeam backscatter and that these acoustic classifications can have ecological validity.

  11. Analysis of forest backscattering characteristics based on polarization coherence tomography

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    It is difficult to make an inventory of vertical profiles of forest structure parameters in field measurements.However,analysis and understanding of forest backscattering characteristics contribute to estimation and detection of forest vertical structure because of the close relationships between backscattering characteristics and structure parameters.The vertical structure function in the complex interferometric coherence definition,which represents the vertical variation of microwave scattering with the penetration depth at a point in the 2-D radar image and can be used to analyze the forest backscattering characteristics,can be reconstructed from polarization coherence tomography(PCT).Based on PCT,the paper analyzes the forest backscattering characteristics and explores the inherent relationship between the result of PCT and the forest structure parameters from numerical simulation of Random Volume over Ground model(RVoG),Polarimetric SAR interferometry(PolInSAR)simulation of forest scene and PolInSAR data at L-band of the test site Traunstein.Firstly,the effects of the extinction coefficient and surface-to-volume scattering ratio in RVoG model on vertical backscattering characteristics are analyzed by means of numerical simulation.Secondly,by applying PCT to L-band POLInSAR simulations of forest scene,different variations of vertical backscattering due to different extinction coefficients and the ratios of surface-to-volume scattering resulting from different polarizations,forest types and densities are displayed and analyzed.Then a concept of relative average backscattering intensity is presented,and the factors which affect its vertical distribution are also discussed.Preliminary results show that there is high sensitivity of the vertical distribution of forest relative average backscattering intensity to the polarization,forest type and density.Finally,based on repeat pass DLR E-SAR L-band airborne POLInSAR data,the capability of PCT technology for detection

  12. Ultrasonic Backscattering from Suspended Erythrocytes: Dependence on Frequency and Size.

    Science.gov (United States)

    Kuo, Ihyuan

    The ultrasonic scattering properties of blood have been intensively investigated since the echo signal from red blood cells carries abundant diagnostic information for the study of blood flow and blood properties in the vessels. Recently, ultrasound of frequency higher than 20 MHz has been implemented in intravascular imaging to obtain better images of the vessel wall. In this research measurements were extended to 30 MHz to better understand the effect of blood on the operation of these intravascular devices. The experimentally measured backscatter of saline suspended porcine erythrocytes for frequency up to 30 MHz agrees very well with the theoretical analysis which indicate that Rayleigh scattering is still valid below this frequency. The analysis utilize the T-matrix method to calculate the backscattering cross section of an erythrocyte modeled as a fluid sphere, disk, and biconcave disk. Measurements on the backscattering coefficients of porcine, bovine, and lamb erythrocytes reveal that the backscatter has a square dependence on cell volume. The cell size dependent backscatter is also analyzed via a continuum approach. It is found that the echo intensity of high frequency ultrasound suffers greatly from the attenuation. The dilemma may be solved by using a spherically focused transducer. An analysis of the focused beam reflected from a perfect planar reflector leads to the modification of the standard substitution method for the backscatter measurement since the "image source" theory is found to be inappropriate for the focused beam. Reflection of the focused beam near the focal point is described based on Huygens' principle. Experimental and theoretical results indicate that the backscatter is dependent upon the position of the scatterer and the geometry of the transducer if a focused beam is used. Since ultrasound velocity information is needed for scattering measurements, an innovative method for measuring the acoustic speed and the attenuation coefficient

  13. Aerosol Lidar for the Relative Backscatter Amplification Measurements

    Science.gov (United States)

    Razenkov, Igor A.; Banakh, Victor A.; Nadeev, Alexander I.

    2016-06-01

    Backscatter amplification presents only in a turbulent atmosphere, when the laser beam is propagates twice through the same inhomogeneities. We proposed technical solution to detect backscatter amplification. An aerosol micro pulse lidar with a beam expansion via receiving telescope was built to study this effect. Our system allows simultaneous detection of two returns from the same scattering volume: exactly on the axis of the laser beam and off the axis.

  14. Radar backscatter modelling of forests using a macroecological approach

    OpenAIRE

    Brolly, Matthew

    2012-01-01

    This thesis provides a new explanation for the behaviour of radar backscatter of forests using vegetation structure models from the field of macroecology. The forests modelled in this work are produced using allometry-based ecological models with backscatter derived from the parameterisation of a radiative transfer model. This work is produced as a series of papers, each portraying the importance of macroecology in defining the forest radar response. Each contribution does so b...

  15. A relationship between ultrasonic integrated backscatter and myocardial contractile function.

    OpenAIRE

    Wickline, S. A.; Thomas, L J; Miller, J.G.; Sobel, B E; J. E. Perez

    1985-01-01

    We have shown previously that the physiologic, mechanical cardiac cycle is associated with a parallel, cardiac cycle-dependent variation of integrated backscatter (IB). However, the mechanisms responsible are not known. The mathematical and physiological considerations explored in the present study suggest that the relationship between backscatter and myocardial contractile function reflects cyclic alterations in myofibrillar elastic parameters, with the juxtaposition of intracellular and ext...

  16. Neutron Skins and Neutron Stars

    OpenAIRE

    Piekarewicz, J

    2013-01-01

    The neutron-skin thickness of heavy nuclei provides a fundamental link to the equation of state of neutron-rich matter, and hence to the properties of neutron stars. The Lead Radius Experiment ("PREX") at Jefferson Laboratory has recently provided the first model-independence evidence on the existence of a neutron-rich skin in 208Pb. In this contribution we examine how the increased accuracy in the determination of neutron skins expected from the commissioning of intense polarized electron be...

  17. Confined dynamics in poly(ethylene terephthalate): a coherent and incoherent neutron scattering study

    International Nuclear Information System (INIS)

    We show that the combination of dielectric relaxation with neutron spin echo and incoherent neutron backscattering measurements performed in deuterated and protonated poly(ethylene terephthalate) suggests that the intrinsic dynamics of semicrystalline polymers occurs in an homogeneous scenario, similar to that valid to describe the dynamics of totally amorphous polymers. The quasielastic neutron scattering data are satisfactorily described by a theoretical model that considers that the proton mobility follows a random jump-diffusion in a restricted environment

  18. FURNACE calculations for JET neutron diagnostics

    International Nuclear Information System (INIS)

    Neutron transport calculations have been performed for the JET-torus, using the two-dimensional toroidal geometry transport code system FURNACE, to predict the response of the time integrated neutron yield monitors on the variation of the plasma conditions. Calculations have been performed for the full aperture D-shaped and circular plasmas, for DD-operation and for DT-operation. For the neutron source distribution a simple model was used based on plasma-plasma interaction. For the torus rotation symmetry around the main torus axis was assumed. Curves have been produced that give the radial plasma shift as function of the ratio of the foil activations measured. It is shown that these curves are sufficiently accurate for application in the DT-phase. For application in the DD-phase, however, the flux of neutrons backscattered from the massive torus needs to be calculated more accurately. (Auth.)

  19. A new technique for neutron monitoring in stray radiation fields

    International Nuclear Information System (INIS)

    At reactors, accelerators and therapy facilities including linear accelerators there is the need to monitor low level stray radiation fields, Neutron monitoring today is based mainly on the application of rem counters. A new approach to neutron monitoring is described which allows one to measure the dose equivalent of neutrons and gamma rays and to interpret neutron spectra in stray radiation fields in terms of Esub(e)sub(f)sub(f) and the dose fractnon of thermat neutrons. Compared to the muttisphere technique only a single moderator sphere of 30 cm diam and various pairs of TLD600/TLD7O0 detectors as passive neutron/gamma detectors are applied to measure moderated neutrons in the center of the sphere, backscattered albedo neutrons on the surface of the sphere and thermal as well as epithermal neutrons from the stray radiation field directly. The passive dosimeter system is sensitive to neutrons in the dose range 10 mrem - 500 rem and permits long-term exposures of several months. Field exposures performed at different facilities are described showing representative results for a neutron stray radiation field with Esub(e)sub(f)sub(f) between 2 MeV down to 100 keV and dose contributions from thermal neutrons between 1% and 30% depending on the kind of neutron stray source, the distance from the source, and the concrete shieldings in the room. (H.K.)

  20. NDA neutron method for UO2 powder humidity

    International Nuclear Information System (INIS)

    In technology of low enriched uranium (up to 5%) dioxide powder production there is a need to restrict the hydrogen content and to measure the moisture content. The considered nondestructive method of the measurement is based on continuous irradiating of powder by fast neutrons from an external Pu-Be source with yield 106 n/sec and registration moderated neutrons with 3He detector. In spite of the fact that the neutron moderation in hydrogen is overwhelming, elastic scattering on oxygen nuclei and inelastic scattering on uranium nuclei is essential. Therefore generated spectrum on neutrons is less rigid in comparison with a initial spectrum of a source. This effect can be considerably strengthened if a volume under measurement has metal reflector. Due to high albedo such reflector decrease of neutron leakage. Mock-up calculations executed by Monte Carlo method and real experiments have confirmed validity of the choice of such reflector. As a result of investigation, geometry of the device have to be as following ∼ (100/250) mm cylinder with reflector. The external fast neutrons source was placed outside of the reflector, the detector 3He with was placed in reflector at the opposite side. The general accuracy of measurement does not exceed 0.15 wt%. Duration of analysis ∼10 minutes. In the reality absolute error of measurement go up by factor 2.5 at attainment of threshold moisture 2 wt%, at the expense of a systematic error due to the value of bulk density of powder. (author)

  1. Neutron Radiography

    Directory of Open Access Journals (Sweden)

    A. R. Reddy

    1982-07-01

    Full Text Available The field of neutron radiography with special reference to isotopic neutron radiography has been reviewed. Different components viz., sources, collimators, imaging systems are described. Various designs of neutron radiography facilities, their relative merits and demerits , the appropriateness of each design depending on the object to be radiographed, and economics of each technique are also dealt. The applications of neutron radiography are also briefly presented.

  2. Electron backscattering from solid targets: Elastic scattering calculations

    International Nuclear Information System (INIS)

    Highlights: • Backscattering coefficient of low-energy electrons. • Elastic scattering cross sections. • Analytical expression of the numerical coefficient in the Nigam atomic screening factor. - Abstract: Analytical expression of the target atomic number dependence of the numerical coefficient in the Nigam atomic screening factor is proposed here to approximate the Rutherford elastic scattering cross sections for slow electron beams impinging on selected solid targets (from Be to Au) in the primary energy range 1–4 keV. Applications are then proposed in terms of Monte Carlo calculation of backscattering coefficient. In this respect, tabulations of backscattering coefficients are here reported for slow electrons in solid targets of interest pointing out a reasonable agreement with the data available in the literature. Analytical expressions of the target atomic number dependence of the electron backscattering coefficient is also suggested for selected electron primary energies ranging from 1 to 4 keV allowing thus an accurate determination of backscattering coefficients for low-energy electrons in solid targets without any resort in Monte Carlo type calculations

  3. Probabilities and statistics for backscatter estimates obtained by a scatterometer

    Science.gov (United States)

    Pierson, Willard J., Jr.

    1989-01-01

    Methods for the recovery of winds near the surface of the ocean from measurements of the normalized radar backscattering cross section must recognize and make use of the statistics (i.e., the sampling variability) of the backscatter measurements. Radar backscatter values from a scatterometer are random variables with expected values given by a model. A model relates backscatter to properties of the waves on the ocean, which are in turn generated by the winds in the atmospheric marine boundary layer. The effective wind speed and direction at a known height for a neutrally stratified atmosphere are the values to be recovered from the model. The probability density function for the backscatter values is a normal probability distribution with the notable feature that the variance is a known function of the expected value. The sources of signal variability, the effects of this variability on the wind speed estimation, and criteria for the acceptance or rejection of models are discussed. A modified maximum likelihood method for estimating wind vectors is described. Ways to make corrections for the kinds of errors found for the Seasat SASS model function are described, and applications to a new scatterometer are given.

  4. Neutron Capture and Neutron Halos

    OpenAIRE

    A.Mengoni; Otsuka, T; Nakamura, T.(International Center for Elementary Particle Physics and Department of Physics, The University of Tokyo, Tokyo, Japan); Ishihara, M.

    1996-01-01

    The connection between the neutron halo observed in light neutron rich nuclei and the neutron radiative capture process is outlined. We show how nuclear structure information such as spectroscopic factors and external components of the radial wave function of loosely bound states can be derived from the neutron capture cross section. The link between the direct radiative capture and the Coulomb dissociation process is elucidated.

  5. Design characteristics of a three-component AEOI Neutriran Albedo Neutron Personnel Dosimeter

    International Nuclear Information System (INIS)

    In establishing a national personnel neutron dosimetry service in Iran, different parameters of the AEOI Neutriran Albedo Neutron Personnel Dosimeter (NANPD) have been optimized. A NANPD was designed with three dosimetry components to measure (a) direct thermal neutrons, (b) direct fast neutrons and (C) direct neutrons by the detection of the albedo neutrons reflected from the body. The dosimeter consists of one or more Lexan polycarbonate and/or CR-39 foils and two 10B (n,α) 7Li converters in a cadmium cover so arranged as to efficiently measure the three neutron dose components separately. The boron converter thickness, its position relative to the beam direction and its distance from the PC foil were studied and the results were incorporated into the design. The dose response of the dosimeter, its lower detection limit as well as the correction factors related to the field neutrons and albedo neutrons were also determined for a 238Pu-Be, an 241Am-Be and a 252Cf sources. In this paper, the dosimeter design and its dosimetric characteristics are presented and discussed. (author)

  6. Experimental tests of the Bonner Sphere spectrometer using filtered neutron beams

    International Nuclear Information System (INIS)

    The operation of a Bonner Sphere neutron detector system has been tested using several unqiue neutron sources. Filtered neutron beams at beamport F at the University of Missouri Research Reactor (MURR) were used as a source of known quasi-monoenergetic neutrons for precise energy spectra analysis and calibration. A PuBe neutron source was used for absolute flux magnitude and spectral verification. Two computer codes, SWIFT and Least Squares Unfolding Techniques (LSUT), were used to unfold the experimental data. Several operational problems were encountered during these tests. First, many of the measurements involved neutron beam measurements in which the beams had a smaller diameter than the moderating spheres. This caused partial illumination of the spheres for which correction factors had to be developed. A partial illumination correction factor has been proposed and tested to account for this problem. Second, reactor core gamma-ray contamination in the neutron beams was of sufficient magnitude to interfere with some measurements. Gamma-ray background subtraction techniques using a multi-channel analyzer were used to alleviate this problem. After correcting for gamma-ray background and applying partial illumination correction factors, unfolded neutron spectra from the unfolding codes gave good results for most neutron sources. In particular the SWIFT results were quite good, exceeding expectations in terms of energy resolution and spectral accuracy. (orig.)

  7. Ultrasonic Characterization of Tissues via Backscatter Frequency Dependence

    DEFF Research Database (Denmark)

    Stetson, Paul F.; Sommer, F.G.

    1997-01-01

    Phantom and patient studies were performed to assess the potential of backscatter frequency dependence as a useful parameter for tissue characterization. A commercial phased-array ultrasonic scanner was adapted to allow digitization of the intermediate-frequency ultrasonic data, Studies of agar...... phantoms containing polystyrene microspheres with 3.5 and 5 MHz transducers indicated the ability for robust differentiation of phantoms having different scatterer size and frequency dependence, based on calculated differences in mean frequencies of backscattered spectra, Using a 3,5-MHz probe......, significantly lower mean frequency of ultrasound backscattered from cirrhotic, compared to normal, liver tissue was noted, Studies of benign and malignant liver tumors (hemangiomas and metastases, respectively) indicated differences in frequency content of these tumors, compared to the adjacent normal liver...

  8. Cosmic-ray neutron spectrometry and dosimetry

    International Nuclear Information System (INIS)

    When primary cosmic rays consisting of galactic cosmic rays and solar particles come into the earth's atmosphere, secondary neutrons generated through nuclear reactions with atmospheric atoms reach the ground. Over the past 10 years, there has been increasing concern about the exposure of air crews to atmospheric cosmic radiation. At aviation altitudes, the neutron component of the secondary cosmic radiation contributes about half of the dose equivalent. Recently, an accumulation of the semiconductor device greatly increases and the soft-errors of SRAM and DRAM on the ground level caused by high-energy cosmic-ray neutrons become a serious problem in the world. Under these circumstances, cosmic-ray neutron spectrometry and dosimetry are presented here in the terrestrial and space environments where neutrons and protons coexist. The neutron detection methods for use in this mixed field are described; 1) multi-moderator spectrometer (Bonner Ball), 2) organic liquid scintillation spectrometer, 3) dose-equivalent counter (rem counter) and 4) Phoswich-type detector. Using these detectors, neutron energy spectra and dose-equivalent rates have been measured on the ground at sea level and at mountain level, aboard an airplane and in space. The space experiments were done using a balloon, space shuttle and space station. The neutron spectrum on the ground has three major peaks, thermal energy peak, evaporation peak around 1 MeV and cascade peak around 100 MeV. While on the other hand, the neutron spectrum apart from the ground has no thermal neutron peak that comes from the albedo neutron effect backscattered from the terrestrial surface. The time-sequential experimental results in Japan, Europe and U.S.A. are described with the experimental procedures by paying attention to variation with latitude, altitude and solar activity. (author)

  9. Bruce Thompson: Adventures and advances in ultrasonic backscatter

    Science.gov (United States)

    Margetan, Frank J.

    2012-05-01

    Over the course of his professional career Dr. R. Bruce Thompson published several hundred articles on non-destructive evaluation, the majority dealing with topics in ultrasonics. One longtime research interest of Dr. Thompson, with applications both to microstructure characterization and defect detection, was backscattered grain noise in metals. Over a 20 year period he led a revolving team of staff members and graduate students investigating various aspects of ultrasonic backscatter. As a member of that team I had the privilege of working along side Dr. Thompson for many years, serving as a sort of Dr. Watson to Bruce's Sherlock Holmes. This article discusses Dr. Thompson's general approaches to modeling backscatter, the research topics he chose to explore to systematically elucidate a better understanding of the phenomena, and the many contributions to the field achieved under his leadership. The backscatter work began in earnest around 1990, motivated by a need to improve inspections of aircraft engine components. At that time Dr. Thompson launched two research efforts. The first led to the heuristic Independent Scatterer Model which could be used to estimate the average grain noise level that would be seen in any given ultrasonic inspection. There the contribution from the microstructure was contained in a measureable parameter known as the Figure-of-Merit or FOM. The second research effort, spearheaded by Dr. Jim Rose, led to a formal relationship between FOM and details of the metal microstructure. The combination of the Independent Scattering Model and Rose's formalism provided a powerful tool for investigating backscatter in metals. In this article model developments are briefly reviewed and several illustrative applications are discussed. These include: the determination of grain size and shape from ultrasonic backscatter; grain noise variability in engine-titanium billets and forgings; and the design of ultrasonic inspection systems to improve defect

  10. Flux maximization techniques for compton backscatter depth profilometry.

    Science.gov (United States)

    Lawson, L

    1993-01-01

    Resolution in x-ray backscatter imaging has often been hampered by low fluxes. But, for a given set of resolution requirements and geometric constraints, it is possible to define a maximization problem in the geometric parameters for which the solution is the maximum flux possible in those circumstances. In this way, resolution in noncritical directions can be traded for improved resolution in a desired direction. Making this the thickness, or surface normal direction, makes practicable the depth profiling of layered structures. Such techniques were applied to the problem of imaging the layered structure of corroding aircraft sheet metal joints using Compton backscatter. PMID:21307450

  11. Probing Molecular Dynamics by Laser-Induced Backscattering Holography

    Science.gov (United States)

    Haertelt, Marko; Bian, Xue-Bin; Spanner, Michael; Staudte, André; Corkum, Paul B.

    2016-04-01

    We use differential holography to overcome the forward scattering problem in strong-field photoelectron holography. Our differential holograms of H2 and D2 molecules exhibit a fishbonelike structure, which arises from the backscattered part of the recolliding photoelectron wave packet. We demonstrate that the backscattering hologram can resolve the different nuclear dynamics between H2 and D2 with subangstrom spatial and subcycle temporal resolution. In addition, we show that attosecond electron dynamics can be resolved. These results open a new avenue for ultrafast studies of molecular dynamics in small molecules.

  12. Corrosion detection in aircraft by X-ray backscatter methods

    International Nuclear Information System (INIS)

    A limited-scan backscatter technique for detecting hidden corrosion and other flaws in aircraft has been demonstrated. Both simulation and experimental results indicate that as little as 5% material loss at depths up to 0.508 cm (0.200 in.) and 10% material loss at depths up to 0.635 cm (0.250 in.) beneath aircraft skin surfaces can be realiably detected. The technology involves analysis of backscattered photon data to yield a figure-of-merit whose value as a function of position indicates with high probability of detection whether or not flaws - such as corrosion, disbonding, macro-cracks, or voids - exist within scanned samples

  13. Coherent Effects in Microwave Backscattering Models for Forest Canopies

    Science.gov (United States)

    Saatchi, Sasan; McDonald, Kyle

    1995-01-01

    In modeling forest canopies, several scattering mechanisms are taken into account: 1) volume scattering, 2) surface-volume interaction, and 3) surface scattering from forest floor. Depending on the structural and dielectric characteristics of forest canopies, the relative contribution of each mechanism in the total backscatter signal of an imaging radar can vary. In this paper, two commonly used first order discrete scattering models, Distorted Born Approximation (DBA) and Radiative Transfer (RT) are used to simulate the backscattered power received by polarimetric radars at P-, L-, and C-bands over coniferous and deciduous forests. The difference between the two models resides on the coherent effect in the surface-volume interaction terms.

  14. Photoneutron production and backscattering in high density concretes used for radiation therapy shielding

    International Nuclear Information System (INIS)

    Highlights: → Photoneutrons are produced in radiation therapy with high energy photons. → We studied high density concretes for photoneutron production and scattering. → Photoneutron production was higher for high density concretes relative to the ordinary. → Neutron backscattering was lower for high density concretes relative to the ordinary concrete. - Abstract: In the current study, the effect of high density concretes on photoneutron productions in radiation therapy was studied using Monte Carlo simulations. The photon and neutron spectra of an 18 MeV photon beam of the Varian linac head were used for all simulations. Ordinary and five high density concretes made of high density elements were simulated. The studied concretes consisted of Magnetite, Datolite-Galena, Magnetite-Steel, Limonite-Steel, and Serpentine. Our results showed that photoneutron production in these concretes strongly depends on their composition. It appears that the application of high density elements with higher probability for photoneutron production, such as Fe and Pb, increases the photoneutron production in concrete walls of radiation therapy bunkers. Further studies on the effect of concrete composition on photoneutrons in radiation therapy room are recommended.

  15. Study on the sensitivity of neutron activation analysis of some elements, using a subcritical nuclear assembly

    International Nuclear Information System (INIS)

    This work describes the sensitivity levels obtained for standards prepared with some elements which, besides having a large cross section, are considered strategic materials, using a 5 Ci Pu-Be neutron source and a subcritical assembly (metallic natural uranium in light water).The irradiation conditions and the activity measurement techniques used are also reported. Finally, the possibilities of using this technique to determine the presence of the chosen elements in the concentrates and wastes from the minerals traditionally mined in the region will be discussed. (Author)

  16. Neutron sources

    International Nuclear Information System (INIS)

    As neutron scattering experiments have grown more and more demanding with respect to resolution and quality, it became more and more necessary to include the neutron source itself in the design of an experimental setup. In this sense the generic representation of a neutron scattering arrangement includes the primary neutron source and the associated spectrum shifter (or moderator). In fact, the design of a modern neutron source will start from a set of users requirements and will proceed 'inwards' through a selection of the moderators (spectrum shifters) to the primary source best suited to meet these often conflicting needs. This paper aims at explaining the options source designers have to match the neutron source performance to the users' demands. (author)

  17. Neutron detector

    Science.gov (United States)

    Stephan, Andrew C.; Jardret; Vincent D.

    2011-04-05

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  18. Determination of the neutron mass; Determinacion de la masa del neutron

    Energy Technology Data Exchange (ETDEWEB)

    Amador V, P.; Chacon R, A.; Arcos P, A.; Rodriguez N, S.; Pinedo S, A.; Vega C, H.R. [Unidad Academica de Estudios Nucleares, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)]. e-mail: paus2281@yahoo.com.mx

    2005-07-01

    The binding energy of the deuteron was measured and it was determined the neutron mass starting from the nuclear reaction, {sup 1}{sub 0} n + {sup 1}{sub 1} H {yields}{sup 2}{sub 1} D + {gamma}. The produced photon is soon a gamma ray that is emitted when the hydrogen captures a thermal neutron. The photon energy was measured using two spectrometric systems for gamma rays. A system with a detector of NaI(TI) of 3'' x 3'' and the other one with a High-purity Germanium detector. The first detector has a bigger efficiency and a smaller resolution in comparison with the second detector. The energy of the measured photon is the binding energy of the deuteron. With the measurement of the photon energy and the masses of the proton and of the deuterium it was determined the neutron mass. The value of the mass obtained with both systems it was compared with the value reported in the literature. The nuclear reaction was induced in a volume of paraffin that it was bombing with a source {sup 239} PuBe whose activity is of 3.7 x 10{sup 10} Bq. (Author)

  19. Design of a system for neutrons dosimetry; Diseno de un sistema para dosimetria de neutrones

    Energy Technology Data Exchange (ETDEWEB)

    Ceron, P.; Rivera, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Legaria No. 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Paredes G, L. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Azorin, J. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Sanchez, A. [IPN, Escuela Superior de Fisica y Matematicas, Av. Instituto Politecnico Nacional s/n, Col. San Pedro Zacatenco, 07738 Mexico D. F. (Mexico); Vega C, H. R., E-mail: victceronr@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2014-08-15

    At the present time diverse systems of detection of neutrons exist, as proportional counters based on BF{sub 3}, He{sub 3} and spectrometers of Bonner spheres. However, the cost and the complexity of the implementation of these systems put them far from the reach for dosimetric purposes. For these reasons a system of neutrons detection composed by a medium paraffin moderator that forms a 4π (spheres) arrangement and of several couples of thermoluminescent dosimeters TLD 600/TLD 700. The response of the system presents a minor repeatability to 5% in several assays when being irradiated with a {sup 239}PuBe source and a deviation of 13.8% in the Tl readings of four different spheres. The calibration factor of the system with regard to the neutrons source which was of 56.2 p Sv/nc also was calculated. These detectors will be used as passive monitors of photoneutrons in a radiotherapy room with lineal accelerator of high energy. (Author)

  20. Realistic neutron spectra for radiation protection and other applications at AERI, Budapest

    CERN Document Server

    Pálfalvi, J; Sajo-Bohus, L

    2002-01-01

    The reconstruction of the Budapest Research Reactor (BRR) gave a good possibility to develop mixed neutron-gamma radiation fields for different applications like: simulation of operational spectra at power reactors, dosimeter development, neutron radiography, biological experiments. Recently, there are 3 horizontal channels available. In addition, isotopic neutron sources are in use in a separate laboratory. In a rotatable holder 4 different sources can be stored and automatically moved into irradiation position. There are changeable collimators and absorbers to modify the spectrum. In the large hall there are possibilities to study the room scatter, angular dependence of detectors, phantom albedo effect etc. Recently available sources are different Pu-Be (from 10 sup 5 -10 sup 7 n/s yield), Ra-Be and Cf. 76.

  1. Bulk - Samples gamma-rays activation analysis (PGNAA) with Isotopic Neutron Sources

    International Nuclear Information System (INIS)

    An overview is given on research towards the Prompt Gamma-ray Neutron Activation Analysis (PGNAA) of bulk-samples. Some aspects in bulk-sample PGNAA are discussed, where irradiation by isotopic neutron sources is used mostly for in-situ or on-line analysis. The research was carried out in a comparative and/or qualitative way or by using a prior knowledge about the sample material. Sometimes we need to use the assumption that the mass fractions of all determined elements add up to 1. The sensitivity curves are also used for some elements in such complex samples, just to estimate the exact percentage concentration values. The uses of 252Cf, 241Arn/Be and 239Pu/Be isotopic neutron sources for elemental investigation of: hematite, ilmenite, coal, petroleum, edible oils, phosphates and pollutant lake water samples have been mentioned.

  2. Atmospheric neutrons

    International Nuclear Information System (INIS)

    Additional calibrations of the University of California double-scatter neutron and additional analysis corrections lead to the slightly changed neutron fluxes reported here. The theoretical angular distributions of Merker (1975) are in general agreement with our experimental fluxes but do not give the peaks for vertical upward and downward moving neutrons. The theoretical neutron escape current J2/sub pi/ (Merker, 1972; Armstrong et al., 1973) is in agreement with the experimental values from 10 to 100 MeV. Our experimental fluxes agree with those of the Kanbach et al. (1974) in the overlap region from 70 to 100 MeV

  3. Neutron dosimetry

    International Nuclear Information System (INIS)

    A neutron irradiation facility was designed and built in order to establish a procedure for calibrating neutron monitors and dosemeters. A 185 GBq 241 Am Be source of known is used as a reference source. The irradiation facility using this source in the air provides neutron dose rates between 9 nSv s-1 and 0,5 μSv s-1. A calibrated 50 nSv s-1 thermal neutron field is obtained by using a specially designed paraffin block in conjunction with the 241 Am Be source. A Bonner multisphere spectrometer was calibrated, using a procedure based on three methods proposed by international standards. The unfold 241 Am Be neutron spectrum was determined from the Bonner spheres data and resulted in a good agreement with expected values for fluence rate, dose rate and mean energy. A dosimetric system based on the electrochemical etching of CR-39 was developed for personal dosimetry. The dosemeter badge using a (n,α) converter, the etching chamber and high frequency power supply were designed and built specially for this project. The electrochemical etching (ECE) parameters used were: a 6N KOH solution, 59 deg C, 20 kVpp cm-1, 2,0 kHz, 3 hours of ECE for thermal and intermediate neutrons and 6 hours for fast neutrons. The calibration factors for thermal, intermediate and fast neutrons were determined for this personal dosemeter. The sensitivities determined for the developed dosimetric system were (1,46± 0,09) 104 tracks cm-2 mSv-1 for thermal neutrons, (9±3) 102 tracks cm-2 mSV-1 for intermediate neutrons and (26±4) tracks cm-2 mSv-1 for fast neutrons. The lower and upper limits of detection were respectively 0,002 mSv and 0,6 mSv for thermal neutrons, 0,04 mSv and 8 mSv for intermediate neutrons and 1 mSv and 12 mSv for fast neutrons. In view of the 1990's ICRP recommendations, it is possible to conclude that the personal dosemeter described in this work is sufficiently sensitive to thermal and intermediate neutrons but fast neutron monitoring ar radiological protection level

  4. About the origin of high-frequency ultrasonic backscattering signals

    International Nuclear Information System (INIS)

    Ultrasonic backscattering measurements allow to make a quick and nondestructive assessment of materials structures. As a qualitative assessment the homogeneity of structural states is determined, but also quantitative measurements are possible, like e.g. the determination of grain sizes in steels. But plottable measuring curves corresponding to the physically described interrelations will only be obtained as a result of a sufficiently large number (approx.= 1024) of averaging operations applied to equidirectional backscattering signals. The individual high-frequency signal is very strongly amplitude modulated. The signals required for averaging are obtained from different acoustic irradiation positions (position averaging), or by means of different center frequencies (frequency averaging). The present paper shows by means of numerical model calculations how the high-frequency backscattering signal is built up by superposition of the backscattering signals from all scattering objects lying in the acoustic beam. The improved understanding of the superposition of individual scattering processes opens up further opportunities of making a local structural analysis by means of ultrasonics. (orig.)

  5. Coherent backscattering of light by cold atoms: theory meets experiment

    OpenAIRE

    Labeyrie, Guillaume; Delande, Dominique; Mueller, Cord A.; Miniatura, Christian; Kaiser, Robin

    2002-01-01

    Coherent backscattering (CBS) of quasi-resonant light by cold atoms presents some specific features due to the internal structure of the atomic scatterers. We present the first quantitative comparison between the experimentally observed CBS cones and Monte-Carlo calculations which take into account the shape of the atomic cloud as well as the internal atomic structure.

  6. Exploring backscattered imaging in low voltage FE-SEM

    OpenAIRE

    Lewis, P.; Micklethwaite, S.; Harrington, J; Dixon, M.; Brydson, R; Hondow, N

    2015-01-01

    Contrast levels in backscattered SEM images were investigated, utilising stage deceleration for low voltage imaging and also electron energy filtering. Image contrast variations are explained via use of Monte Carlo simulations which can predict the optimum accelerating and filter voltages for imaging complex sample mixtures.

  7. Characterization of a γ-backscattering imaging device

    Science.gov (United States)

    González, N.; Fajardo, E.; Blanco, W.; Cristancho, F.

    2012-02-01

    The Compton Camera is a γ-backscattering imaging device that allows us to obtain images of hidden objects. In order to evaluate the factors that affect the quality of those images, experiments were carried out to determine its response to different materials. Mathematical methods have been developed to quantify the image quality.

  8. Analysis of a proposed Compton backscatter imaging technique

    Science.gov (United States)

    Hall, James M.; Jacoby, Barry A.

    1994-03-01

    One-sided imaging techniques are currently being used in nondestructive evaluation of surfaces and shallow subsurface structures. In this work we present both analytical calculations and detailed Monte Carlo simulations aimed at assessing the capability of a proposed Compton backscattering imaging technique designed to detect and characterize voids located several centimeters below the surface of a solid.

  9. Backscatter C [Fugro]--Offshore of Coal Oil Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3302 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3302) of the Offshore of Coal Oil Point map area, California. The...

  10. Backscatter A [CSUMB]--Offshore Coal Oil Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3302 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3302) of the Offshore of Coal Oil Point map area, California. The...

  11. Backscatter B [USGS]--Offshore of Coal Oil Point, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3302 presents data for part of the acoustic-backscatter map (see sheet 3, SIM 3302) of the Offshore of Coal Oil Point map area, California. The...

  12. Coherent backscattering of light by cold atoms: theory meets experiment

    International Nuclear Information System (INIS)

    Coherent backscattering (CBS) of quasi-resonant light by cold atoms presents some specific features due to the internal structure of the atomic scatterers. We present the first quantitative comparison between the experimentally observed CBS cones and Monte Carlo calculations which take into account the shape of the atomic cloud as well as the internal atomic structure. (authors)

  13. Coherent backscattering of light by resonant atomic dipole transitions

    International Nuclear Information System (INIS)

    We study coherent backscattering (CBS) of resonant light by cold atomic vapors, both experimentally and theoretically. The theory predicts a drastic reduction of the CBS enhancement factor when a degenerate internal structure is present in the ground state. We test this prediction in experiments using different atoms and various transitions

  14. Source point calibration from an arbitrary electron backscattering pattern

    DEFF Research Database (Denmark)

    Lassen, Niels Christian Krieger

    1999-01-01

    Precise knowledge of the position of the source point is a requirement if electron backscattering patterns (EBSPs) are to be used for crystal orientation measurements or other types of measurements which demand a geometrical analysis of the patterns. Today, possibly the most popular method for...

  15. BackscatterB [Swath]--Offshore of Salt Point Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Salt Point map area, California. Backscatter data are provided as separate...

  16. BackscatterC [7125]--Offshore of Point Reyes Map Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Point Reyes map area, California. Backscatter data are provided as separate...

  17. BackscatterA [8101]--Offshore of Point Reyes Map Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Point Reyes map area, California. Backscatter data are provided as separate...

  18. BackscatterC [7125]--Offshore of Salt Point Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Salt Point map area, California. Backscatter data are provided as separate...

  19. BackscatterA [8210]--Offshore of Salt Point Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Salt Point map area, California. Backscatter data are provided as separate...

  20. BackscatterB [Swath]--Offshore of Point Reyes Map Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of the Offshore of Point Reyes map area, California. Backscatter data are provided as separate...

  1. Super-virtual Interferometric Separation and Enhancement of Back-scattered Surface Waves

    KAUST Repository

    Guo, Bowen

    2015-08-19

    Back-scattered surface waves can be migrated to detect near-surface reflectors with steep dips. A robust surface-wave migration requires the prior separation of the back-scattered surface-wave events from the data. This separation is often difficult to implement because the back-scattered surface waves are masked by the incident surface waves. We mitigate this problem by using a super-virtual interferometric method to enhance and separate the back-scattered surface waves. The key idea is to calculate the virtual back-scattered surface waves by stacking the resulting virtual correlated and convolved traces associated with the incident and back-scattered waves. Stacking the virtual back-scattered surface waves improves their signal-to-noise ratio and separates the back-scattered surface-waves from the incident field. Both synthetic and field data results validate the robustness of this method.

  2. BackscatterA [USGS SWATH]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  3. BackscatterD [CSUMB Swath]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  4. Multibeam Backscatter Data for Selected U.S. Locations in the Pacific

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Multibeam backscatter imagery extracted from gridded bathymetry for selected U.S. locations in the Pacific. The backscatter datasets include data collected using...

  5. Synovectomy by neutron capture in boron

    International Nuclear Information System (INIS)

    The rheumatoid arthritis is an illness which affect approximately at 3% of the World population. This illness is characterized by the inflammation of the joints which reduces the quality of life and the productivity of the patients. Since, it is an autoimmune illness, the inflammation is due to the overproduction of synovial liquid by the increase in the quantity of synoviocytes. The rheumatoid arthritis does not have a definitive recovery and the patients have three options of treatment: the use of drugs, the surgery and the radio synovectomy. The synovectomy by neutron capture in Boron is a novel proposal of treatment of the rheumatoid arthritis that consists in using a charged compound with Boron 10 that is preferently incorporated in the synoviocytes and to a less extent in the rest of surrounding tissues of the joint. Then, the joint is exposed to a thermal neutron field that induces the reaction (n, α) in the 10 B. the products of this reaction place their energy inside synoviocytes producing their reduction and therefore the reduction of the joint inflammation. Since it is a novel procedure, the synovectomy by neutron capture in boron has two problems: the source design and the design of the adequate drug. In this work it has been realized a Monte Carlo study with the purpose to design a moderating medium that with a 239 Pu Be source in its center, produces a thermal neutron field. With the produced neutron spectra, the neutrons spectra and neutron doses were calculated in different sites inside a model of knee joint. In Monte Carlo studies it is necessary to know the elemental composition of all the joint components, for the case of synovia and the synovial liquid this information does not exist in such way that it is supposed that its composition is equal than the water. In this work also it has been calculated the kerma factors by neutrons of synovia and the synovial liquid supposing that their elemental composition are similar to the blood tissue

  6. Storage of cold and thermal neutrons with perfect crystals at the pulsed source

    International Nuclear Information System (INIS)

    The possibility of storing cold neutrons by sequential Bragg reflections between two parallel perfect crystal plates in backscattering geometry has been implemented as the parasitic instrument VESTA at the pulsed neutron source ISIS. Filling the neutrons into and releasing them from the storage cavity is accomplished by applying a short-pulsed magnetic field at the crystal plates. The method takes advantage of the conservation of the axial component of the neutron wave vector after Bragg reflection and its Zeeman shift in a magnetic field. The setup at ISIS is presented where a monochromatic neutron beam with wavelength 6.27 A and 2.9 x 104 n/scm2 flux is taken out of the neutron guide leading to the IRIS backscattering spectrometer by a pyrolytic graphite crystal monochromator. The longest storage period obtained with the setup was 2.655 s which corresponds to 1574 consecutive Bragg reflections and a distance traveled of 1675 n. The measurements are analyzed by heuristic methods developed for neutron storage experiments. The apparatus is seen as a passive resonator system and characteristics like stored neutron intensity, the efficiency of the storage process, the probability to remain in the system, the mirror reflectivity, the dispersion of the stored distribution, the penetration depth of a neutron into a crystal mirror and the figure of merit of the resonator system are discussed. Monte Carlo simulations of the extracted beam and of the stored neutron distribution were performed to deepen the understanding of the experimental results. (author)

  7. Micromegas neutron beam monitor neutronics.

    Science.gov (United States)

    Stephan, Andrew C; Miller, Laurence F

    2005-01-01

    The Micromegas is a type of ionising radiation detector that consists of a gas chamber sandwiched between two parallel plate electrodes, with the gas chamber divided by a Frisch grid into drift and amplification gaps. Investigators have applied it to a number of different applications, such as charged particle, X-ray and neutron detection. A Micromegas device has been tested as a neutron beam monitor at CERN and is expected to be used for that purpose at the Spallation Neutron Source (SNS) under construction in Oak Ridge, TN. For the Micromegas to function effectively as neutron beam monitor, it should cause minimal disruption to the neutron beam in question. Specifically, it should scatter as few neutrons as possible and avoid neutron absorption when it does not contribute to generating useful information concerning the neutron beam. Here, we present the results of Monte Carlo calculations of the effect of different types of wall materials and detector gases on neutron beams and suggest methods for minimising disruption to the beam. PMID:16381746

  8. Neutron dosimetry; Dosimetria de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Fratin, Luciano

    1993-12-31

    A neutron irradiation facility was designed and built in order to establish a procedure for calibrating neutron monitors and dosemeters. A 185 GBq {sup 241} Am Be source of known is used as a reference source. The irradiation facility using this source in the air provides neutron dose rates between 9 nSv s{sup -1} and 0,5 {sup {mu}}Sv s{sup -1}. A calibrated 50 nSv s{sup -1} thermal neutron field is obtained by using a specially designed paraffin block in conjunction with the {sup 241} Am Be source. A Bonner multisphere spectrometer was calibrated, using a procedure based on three methods proposed by international standards. The unfold {sup 241} Am Be neutron spectrum was determined from the Bonner spheres data and resulted in a good agreement with expected values for fluence rate, dose rate and mean energy. A dosimetric system based on the electrochemical etching of CR-39 was developed for personal dosimetry. The dosemeter badge using a (n,{alpha}) converter, the etching chamber and high frequency power supply were designed and built specially for this project. The electrochemical etching (ECE) parameters used were: a 6N KOH solution, 59 deg C, 20 kV{sub pp} cm{sup -1}, 2,0 kHz, 3 hours of ECE for thermal and intermediate neutrons and 6 hours for fast neutrons. The calibration factors for thermal, intermediate and fast neutrons were determined for this personal dosemeter. The sensitivities determined for the developed dosimetric system were (1,46{+-} 0,09) 10{sup 4} tracks cm{sup -2} mSv{sup -1} for thermal neutrons, (9{+-}3) 10{sup 2} tracks cm{sup -2} mSV{sup -1} for intermediate neutrons and (26{+-}4) tracks cm{sup -2} mSv{sup -1} for fast neutrons. The lower and upper limits of detection were respectively 0,002 mSv and 0,6 mSv for thermal neutrons, 0,04 mSv and 8 mSv for intermediate neutrons and 1 mSv and 12 mSv for fast neutrons. In view of the 1990`s ICRP recommendations, it is possible to conclude that the personal dosemeter described in this work is

  9. Fiber optic backscatter spectroscopic sensor to monitor enamel demineralization and remineralization in vitro

    OpenAIRE

    Kishen, Anil; Shrestha, Annie; Rafique, Adeela

    2008-01-01

    In this study, a Fiber Optic Backscatter Spectroscopic Sensor (FOBSS) is used to monitor demineralization and remineralization induced changes in the enamel. A bifurcated fiber optic backscatter probe connected to a visible light source and a high resolution spectrophotometer was used to acquire the backscatter light spectrum from the tooth surface. The experiments were conducted in two parts. In Part 1, experiments were carried out using fiber optic backscatter spectroscopy on (1) sound enam...

  10. Neutron gun

    International Nuclear Information System (INIS)

    The neutron gun combines a new core ion source of the cold type based on X-ray ionization and new cold type of neutron source working with core ion generation. The neutrons are formed from the impact of core ions on the negatively charged anode. Based on a new conversion function, the function of the positive anode becomes analogous to the beta-unstable decomposition of a neutron. A core ion and neutron amplifier in the sense of amplifying the number is derived from the beta-unstable neutron decomposition, in order to raise the output of a gun in pulsed operation by using the number amplification in the intervals between the pulses. The method of construction is simple and cheap, the equipment has purely linear acceleration or operation with circular acceleration with linear pre-acceleration as an alternative. Purely linear operation should be sufficient for medical applications, e.g. for neutron photography to replay X-ray photography and particularly for neutron scalpels in the surgical treatment of tumours. (orig./HP)

  11. Neutron transport

    International Nuclear Information System (INIS)

    This bibliographical note presents a reference book which addresses the study of neutron transport in matter, the study of conditions for a chain reaction and the study of modifications of matter composition due to nuclear reactions. This book presents the main nuclear data, their measurement, assessment and processing, and the spallation. It proposes an overview of methods applied for the study of neutron transport: basic equations and their derived forms, deterministic methods and Monte Carlo method of resolution of the Boltzmann equation, methods of resolution of generalized Bateman equations, methods of time resolution of space kinetics coupled equations. It presents the main calculation codes, discusses the qualification and experimental aspects, and gives an overview of neutron transport applications: neutron transport calculation of reactors, neutron transport coupled with other disciplines, physics of fuel cycle, criticality

  12. Neutron tubes

    Science.gov (United States)

    Leung, Ka-Ngo; Lou, Tak Pui; Reijonen, Jani

    2008-03-11

    A neutron tube or generator is based on a RF driven plasma ion source having a quartz or other chamber surrounded by an external RF antenna. A deuterium or mixed deuterium/tritium (or even just a tritium) plasma is generated in the chamber and D or D/T (or T) ions are extracted from the plasma. A neutron generating target is positioned so that the ion beam is incident thereon and loads the target. Incident ions cause D-D or D-T (or T-T) reactions which generate neutrons. Various embodiments differ primarily in size of the chamber and position and shape of the neutron generating target. Some neutron generators are small enough for implantation in the body. The target may be at the end of a catheter-like drift tube. The target may have a tapered or conical surface to increase target surface area.

  13. Neutron radiography

    International Nuclear Information System (INIS)

    This introduction is addressed to an audience active in diverse forms of neutron source applications but not directly familiar with neutron radiography. Neutron radiography is, of course, similar to, and complementary to, radiography using x-rays. However, neutrons, being sensitive to the nuclear properties of materials, provide information fundamentally different from x-rays. For example, neutrons can penetrate many dense metals such as uranium, lead, bismuth or steel, and can reveal details of internal hydrogenous components: explosives, lubricants and gaskets. For nuclear fuel inspection neutron radiography offers the ability to penetrate dense uranium-238 and contrast the isotopes U-235 or Pu-239 and also offers the ability to discriminate against unwanted interference from gamma radiation. In addition to advantages in industrial applications, there are special situations in fields such as medical diagnostics, dentistry, agriculture and forensic science. Comprehensive accounts of applications in the field can be found in the proceedings of the world conferences on neutron radiography: USA (1981), FRANCE (1986). A third conference in this series is scheduled for May 1989 in Japan

  14. Neutron radiography

    International Nuclear Information System (INIS)

    The digital processing of the neutron radiography images gives the possibility for data quantification. In this case an exact relation between the measured neutron attenuation and the real macroscopic attenuation coefficient for every point of the sample is required. The assumption that the attenuation of the neutron beam through the sample is exponential is valid only in an ideal case where a monochromatic beam, non scattering sample and non background contribution are assumed. In the real case these conditions are not fulfilled and in dependence on the sample material we have more or less deviation from the exponential attenuation law. Because of the high scattering cross-sections of hydrogen (σs=80.26 barn) for thermal neutrons, the problem with the scattered neutrons at quantitative radiography investigations of hydrogenous materials (as PE, Oil, H2O, etc) is not trivial. For these strong scattering materials the neutron beam attenuation is no longer exponential and a dependence of the macroscopic attenuation coefficient on the material thickness and on the distance between the sample and the detector appears. When quantitative radiography (2 D) or tomography investigations (3 D) are performed, some image correction procedures for a description of the scattering effect are required. This thesis presents a method that can be used to enhance the neutron radiography image for objects with high scattering materials like hydrogen, carbon and other light materials. This method uses the Monte Carlo code, MCNP5, to simulate the neutron radiography process and get the flux distribution for each pixel of the image and determine the scattered neutrons distribution that causes the image blur and then subtract it from the initial image to improve its quality.

  15. Ground water and snow sensor based on directional detection of cosmogenic neutrons.

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Robert Lee; Marleau, Peter; Griffin, Patrick J.

    2011-06-01

    A fast neutron detector is being developed to measure the cosmic ray neutron flux in order to measure soil moisture. Soil that is saturated with water has an enhanced ability to moderate fast neutrons, removing them from the backscatter spectrum. The detector is a two-element, liquid scintillator detector. The choice of liquid scintillator allows rejection of gamma background contamination from the desired neutron signal. This enhances the ability to reconstruct the energy and direction of a coincident neutron event. The ability to image on an event-by-event basis allows the detector to selectively scan the neutron flux as a function of distance from the detector. Calibrations, simulations, and optimization have been completed to understand the detector response to neutron sources at variable distances and directions. This has been applied to laboratory background measurements in preparation for outdoor field tests.

  16. Detection and imaging in strongly backscattering randomly layered media

    International Nuclear Information System (INIS)

    Echoes from small reflectors buried in the heavy clutter are weak and difficult to distinguish from the medium backscatter. Detection and imaging with sensor arrays in such media require filtering out the unwanted backscatter and enhancing the echoes from the reflectors that we wish to locate. We consider a filtering and detection approach based on the singular value decomposition of the local cosine transform of the array response matrix. The algorithm is general and can be used for detection and imaging in the heavy clutter, but its analysis depends on the model of the cluttered medium. This paper is concerned with the analysis of the algorithm in finely layered random media. We obtain a detailed characterization of the singular values of the transformed array response matrix and justify the systematic approach of the filtering algorithm for detecting and refining the time windows that contain the echoes that are useful in imaging

  17. Model for H- and D- production by hydrogen backscattering

    International Nuclear Information System (INIS)

    The Marlowe Monte-Carlo backscattering code has been used to calculate particle reflection coefficients and energy distributions for H, D incident upon Li, K, Ni, Cu, Mo, Ag, Cs, Hf, W, Pt, and U surfaces. The backscattered energy and angular distributions are combined with a model for formation and survival probabilities for H-, D- leaving the surface. A least-squares fit of experimental measurements of H- yields from the composite surface, Cs/Cu, has been used to obtain two semi-empirical constants, α, β which enter into the formation and survival probabilities. These probabilities are used to calculate the production probability which in turn provides an upper limit to the negative ion yield. The choice of electrode material is discussed as a function of atomic number

  18. Radio-wave backscattering from artificial ionospheric turbulence

    International Nuclear Information System (INIS)

    The authors present the characteristics of shortwave signals, backscattered from artificial ionospheric inhomogeneities. The diagnostic equipment is located at a distance of about 100 km from the perturbing transmitter. The experimental results are interpreted on the basis of trajectory computations. The feasibility of investigating the inhomogeneous structure of the perturbed region obtained with the use of a high-power ionospheric station located at a small distance from the heater station is demonstrated. It is shown that the test wave signals backscattered by the perturbed region in the 5-10 MHz frequency range have appreciable amplitudes. The experiments showed that the region occupied by the artificial inhomogeneities extends to more than 50 km below the level of reflection of the heater wave

  19. RFID tag modification for full depth backscatter modulation

    Science.gov (United States)

    Scott, Jeffrey Wayne [Pasco, WA; Pratt, Richard M [Richland, WA

    2010-07-20

    A modulated backscatter radio frequency identification device includes a diode detector configured to selectively modulate a reply signal onto an incoming continuous wave; communications circuitry configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal; and circuitry configured to increase impedance change at the diode detector which would otherwise not occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby reducing the rectified signal increases modulation depth by removing the reverse bias effects on impedance changes. Methods of improving depth of modulation in a modulated backscatter radio frequency identification device are also provided.

  20. Theoretical Analysis of Rayleigh Backscattering Noise in Fiber Raman Amplifiers

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In this paper, a new theoretical model for Rayleigh backscattering (RB) analysis of fiber Raman amplifiers is proposed. The model includes all the interactions among the pumps, signals, and all orders of RB. The results show that the higher order RB has a negligible influence on the performance of the amplifier. The co-propagating and counterpropagating RB power of the signal grow quadratically with the net-gain of the amplifier. The signal to double Rayleigh backscattering noise ratio (OSNRDRB ) of backward-pumped FRAs is better than that of the forward-pumped ones at high net-gain level (> 13 dB), while at low net-gain level the OSNRDrb of the forward-pumped FRAs is slightly better than that of the backward-pumped ones.

  1. Control of coherent backscattering by breaking optical reciprocity

    CERN Document Server

    Bromberg, Y; Popoff, S M; Cao, H

    2015-01-01

    Reciprocity is a universal principle that has a profound impact on many areas of physics. A fundamental phenomenon in condensed-matter physics, optical physics and acoustics, arising from reciprocity, is the constructive interference of quantum or classical waves which propagate along time-reversed paths in disordered media, leading to, for example, weak localization and metal-insulator transition. Previous studies have shown that such coherent effects are suppressed when reciprocity is broken. Here we show that by breaking reciprocity in a controlled manner, we can tune, rather than simply suppress, these phenomena. In particular, we manipulate coherent backscattering of light, also known as weak localization. By utilizing a non-reciprocal magneto-optical effect, we control the interference between time-reversed paths inside a multimode fiber with strong mode mixing, and realize a continuous transition from the well-known peak to a dip in the backscattered intensity. Our results may open new possibilities fo...

  2. ILC Beam Energy Measurement by means of Laser Compton Backscattering

    CERN Document Server

    Muchnoi, N; Viti, M

    2008-01-01

    A novel, non-invasive method of measuring the beam energy at the International Linear Collider is proposed. Laser light collides head-on with beam particles and either the energy of the Compton scattered electrons near the kinematic end-point is measured or the positions of the Compton backscattered $\\gamma$-rays, the edge electrons and the unscattered beam particles are recorded. A compact layout for the Compton spectrometer is suggested. It consists of a bending magnet and position sensitive detectors operating in a large radiation environment. Several options for high spatial resolution detectors are discussed. Simulation studies support the use of an infrared or green laser and quartz fiber detectors to monitor the backscattered photons and edge electrons. Employing a cavity monitor, the beam particle position downstream of the magnet can be recorded with submicrometer precision. Such a scheme provides a feasible and promising method to access the incident beam energy with precisions of $10^{-4}$ or bette...

  3. Characteristics of final particles in multiple Compton backscattering process

    Science.gov (United States)

    Potylitsyn, A.; Kol‘chuzhkin, A.

    2013-08-01

    An electron passing through a counter propagating intense laser beam can interact with a few laser photons with emission of a hard photon in each collision event. In contrast with the well-known nonlinear Compton backscattering process the above mentioned process may be named as multiple Compton backscattering process (MCBS). In this paper we have investigated the evolution of the electron energy distribution during MCBS process using Monte-Carlo (M-C) simulation. The main characteristics of such a distribution as mean energy and variance obtained by M-C technique were compared with analytical solutions of kinetic equations. We found the kinematic region where the analytical solutions are applicable with a good accuracy. A photon spectrum, even for the case when each electron emits one photon (in average) differs significantly from that described by the Klein-Nishina formula.

  4. Gamma-ray backscatter for body composition measurement.

    Science.gov (United States)

    Morgan, H M; Shakeshaft, J T; Lillicrap, S C

    1998-01-01

    The purpose of this study was to examine the potential of using backscatter information to assess regional body composition at selected sites. Two measurement techniques are examined: the measurement of the ratio of coherent to Compton scatter, and the measurement of the Compton scatter profile. Two possible applications are considered: the measurement of trabecular bone mineral density, and the measurement of the average fat/muscle ratio in a tissue volume. The results presented indicate that the analysis of coherent and Compton backscattered gamma-ray spectra from an 241Am source has the potential for measuring both trabecular bone mineral density and average fat/muscle ratio in a tissue volume, with a low absorbed dose to the subject. PMID:9569541

  5. Backscatter, anisotropy, and polarization of solar hard X-rays

    Science.gov (United States)

    Bai, T.; Ramaty, R.

    1978-01-01

    The problems of anisotropy, polarization, center-to-limb variation of the X-ray spectrum, and Compton backscatter are investigated in a study of solar hard X-rays. Effect of backscatter are found particularly important for anisotropic sources which emit hard X-rays predominantly toward the photosphere; for such anisotropic primary X-ray sources, the observed X-ray flux near 30 keV does not depend significantly on the position of the flare. In addition, the degree of polarization of the sum of the primary and reflected X-rays with energies in the 15 to 30 keV range may be as high as 30%. Determination of the height and anisotropy of the primary X-ray sources from study of the albedo patch is also discussed.

  6. Characteristics of Final Particles in Multiple Compton Backscattering Process

    CERN Document Server

    Potylitsyn, A

    2013-01-01

    An electron passing through a counter propagating intense laser beam can interact with a few laser photons with emission of a hard photon in each collision event. In contrast with the well-known nonlinear Compton backscattering process the above mentioned process may be named as multiple Compton backscattering process (MCBS). In this paper we have investigated the evolution of the electron energy distribution during MCBS process using Monte-Carlo (M-C) simulation. The main characteristics of such a distribution as mean energy and variance obtained by M-C technique were compared with analytical solutions of kinetic equations. We found the kinematic region where the analytical solutions are applicable with a good accuracy. A photon spectrum, even for the case when each electron emits one photon (in average) differs significantly from that described by the Klein-Nishina formula.

  7. Present State of Electron Backscatter Diffraction and Prospective Developments

    Energy Technology Data Exchange (ETDEWEB)

    Schwarzer, R A; Field, D P; Adams, B L; Kumar, M; Schwartz, A J

    2008-10-24

    Electron backscatter diffraction (EBSD), when employed as an additional characterization technique to a scanning electron microscope (SEM), enables individual grain orientations, local texture, point-to-point orientation correlations, and phase identification and distributions to be determined routinely on the surfaces of bulk polycrystals. The application has experienced rapid acceptance in metallurgical, materials, and geophysical laboratories within the past decade (Schwartz et al. 2000) due to the wide availability of SEMs, the ease of sample preparation from the bulk, the high speed of data acquisition, and the access to complementary information about the microstructure on a submicron scale. From the same specimen area, surface structure and morphology of the microstructure are characterized in great detail by the relief and orientation contrast in secondary and backscatter electron images, element distributions are accessed by energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), or cathodoluminescence analysis, and the orientations of single grains and phases can now be determined, as a complement, by EBSD.

  8. Neutron tomography

    International Nuclear Information System (INIS)

    In this paper a survey is given of recent developments in selected areas of neutron tomography, within the context of several applications Argonne is involved in, including high penetration of reactor-fuel bundles in thick containers (involving TREAT and NRAD facilities), dual-energy hydrogen imaging (performed at IPNS), dynamic coarse-resolution emission tomography of rector fuel under test (a proposed modification to the TREAT hodoscope), and an associated-particle system that uses neutron flight-time to electronically collimate transmitted neutrons and to tomographically image nuclides identified by reaction gamma-rays

  9. High-precision thickness measurements using beta backscatter

    International Nuclear Information System (INIS)

    A two-axis, automated fixture for use with a high-intensity Pm-147 source and a photomultiplier-scintillation beta-backscatter probe for making thickness measurements has been designed and built. A custom interface was built to connect the system to a minicomputer, and software was written to position the tables, control the probe, and make the measurements. Measurements can be made in less time with much greater precision than by the method previously used

  10. Inspection of reinforced concrete samples by Compton backscattering technique

    International Nuclear Information System (INIS)

    Reinforced concrete structures require frequent monitoring to ensure the concrete quality during its service life and for evaluation of in situ existing conditions. Compton backscattering of gamma rays is a nondestructive technique used for material characterization and detection of defects and inclusions in materials and can be employed on reinforced concrete. The methodology allows one-sided inspection of large structures, is relatively inexpensive and can be portable. The concept is based on detection of backscattered radiation produced from a collimated beam aimed at the sample. By measuring the spectrum of these scattered gamma rays it is possible to determine local density perturbations. In this work we used the Compton backscattering technique to locate and measure steel, defects and crushed stone inside concrete. The samples were irradiated with gamma rays from a Ø2 mm diameter collimated 241Am (100 mCi) source and the inelastically scattered photons were recorded at an angle of 135° by a high resolution CdTe semiconductor detector. Scanning was achieved by lateral movement of the sample blocks across the source and detector field of view in steps of 1 mm. A previous optimization of the experimental setup was performed with Monte Carlo simulation. The results showed that it was possible to locate inclusions and defects with Ø8 mm positioned at a depth of 20 mm below the surface of the sample. It was observed that aggregates such as crushed stone could mask defects at specific points due to high attenuation of the incident and scattered beam. - Highlights: ► Compton Backscattering was used to inspect reinforced concrete samples. ► The positioning of rebars, defects and crushed stone was achieved. ► High attenuation presented by crushed stone can mask defects at specific points

  11. Conservation of energy in coherent backscattering of light

    OpenAIRE

    Fiebig, Susanne; Aegerter, Christof M.; Bührer, Wolfgang; Störzer, Martin; Akkermans, Eric; Montambaux, Gilles; Maret, Georg

    2008-01-01

    Although conservation of energy is fundamental in physics, its principles seem to be violated in the field of wave propagation in turbid media by the energy enhancement of the coherent backscattering cone. In this letter we present experimental data which show that the energy enhancement of the cone is balanced by an energy cutback at all scattering angles. Moreover, we give a complete theoretical description, which is in good agreement with these data. The additional terms needed to enforce ...

  12. ILC Beam Energy Measurement by means of Laser Compton Backscattering

    OpenAIRE

    Muchnoi, N.; Schreiber, H. J.; Viti, M

    2008-01-01

    A novel, non-invasive method of measuring the beam energy at the International Linear Collider is proposed. Laser light collides head-on with beam particles and either the energy of the Compton scattered electrons near the kinematic end-point is measured or the positions of the Compton backscattered $\\gamma$-rays, the edge electrons and the unscattered beam particles are recorded. A compact layout for the Compton spectrometer is suggested. It consists of a bending magnet and position sensitiv...

  13. Electron backscattering rates of light elements in Moliere approximation

    International Nuclear Information System (INIS)

    Electron backscattering rates of light elements (atomic number Z = 6, 13, 29) are evaluated for electron energies of E = 20 ... 60 keV. The scattering amplitude in Moliere approximation is expanded as a series. The series elements are calculated in closed form with the aid of substitute functions. By comparison with the first Born approximation this yields correction factors of 1 ... 1,25. (orig.) 891 WBU

  14. Combined backscatter and transmission method for nuclear density gauge

    OpenAIRE

    Golgoun Seyed Mohammad; Sardari Dariush; Sadeghi Mahdi; Ebrahimi Mohammad; Aminipour Mojtaba; Davarpanah Mohammad Reza

    2015-01-01

    Nowadays, the use of nuclear density gauges, due to the ability to work in harsh industrial environments, is very common. In this study, to reduce error related to the ρ of continuous measuring density, the combination of backscatter and transmission are used simultaneously. For this reason, a 137Cs source for Compton scattering dominance and two detectors are simulated by MCNP4C code for measuring the density of 3 materials. Important advantages of this combined radiometric gauge are diminis...

  15. Proton - deuteron elastic backscattering in the resonance region

    International Nuclear Information System (INIS)

    In order to explain the proton - deuteron backscattering cross section, which show one peak for the incident proton kinetic energy at 600 MeV, the contribution of the Feynman diagram is calculated for the double pion exchange mechanism. This is due to the fact that the observed peak is exactly in the region where the Δ(1232) resonance can be excited in the πN-πN. (L.C.)

  16. Valley-protected backscattering suppression in silicon photonic graphene

    CERN Document Server

    Chen, Xiao-Dong

    2016-01-01

    In this paper, we study valley degree of freedom in all dielectric silicon photonic graphene. Photonic band gap opening physics under inversion symmetry breaking is revisited by the viewpoint of nonzero valley Chern number. Bulk valley modes with opposite orbital angular momentum are unveiled by inspecting time-varying electric fields. Topological transition is well illustrated through photonic Dirac Hamiltonian. Valley dependent edge states and the associated valley-protected backscattering suppression around Z-shape bend waveguide have been demonstrated.

  17. The effects of changes in loblolly pine biomass and soil moisture on ERS-1 SAR backscatter

    International Nuclear Information System (INIS)

    For young (< 15 years old) loblolly pine stands at Duke Forest (North Carolina, USA), when the ground was wet, the observed ERS-1 SAR backscatter from short-grass fields of 0.05 kg/m 2 biomass was >~ the backscatter from the stands, and there was no significant correlation between the backscatter and biomass (r2 = 0.19). Under dry soil conditions, the backscatter increased about 2-3 dB as the biomass increased from 0.05 kg/m2 to about 0.5- 1.5 kg/m ~, and the backscatter may be saturated near a 0.5-1.5 kg / m ~ biomass level. The correlation coefficient between the backscatter and biomass was r2 = 0.46. When the Santa Barbara microwave canopy backscatter model was applied to simulate the ERS-1 SAR backscatter from the stands over dry ground, modeled and observed backscatter had similar trends with increasing biomass. For these stands, sensitivity analyses using the model showed that as the surface-soil moisture increased, the major contributor to the total backscatter was changed from canopy volume scattering to surface backscatter between 0.4 kg / m2 and about I kg/m2. Signal saturating at low standing biomass and high sensitivity to soil moisture conditions limit the value of a short-wave (C-band) and steep local incidence angle (23 °) microwave sensor such as the ERS-1 SAR for forest monitoring

  18. An adjusted location model for SuperDARN backscatter echoes

    Directory of Open Access Journals (Sweden)

    E. X. Liu

    2012-12-01

    Full Text Available The radars that form the Super Dual Auroral Radar Network (SuperDARN receive scatter from ionospheric irregularities in both the E- and F-regions, as well as the Earth's surface, either ground or sea. For ionospheric scatter, the current SuperDARN standard software considers a straight-line propagation from the radar to the scattering zone with an altitude assigned by a standard height model. The knowledge of the group delay to a scatter volume is not sufficient for an exact determination of the location of the irregularities. In this study, the difference between the locations of the backscatter echoes determined by SuperDARN standard software and by ray tracing has been evaluated, using the ionosonde data collected at Sodankylä, which is in the field-of-view of Hankasalmi SuperDARN radar. By studying elevation angle information of backscattered echoes from the data sets of Hankasalmi radar in 2008, we have proposed an adjusted fitting location model determined by slant range and elevation angle. To test the reliability of the adjusted model, an independent data set is selected in 2009. The result shows that the difference between the adjusted model and the ray tracing is significantly reduced and the adjusted model could provide a more accurate location for backscatter targets.

  19. Inspection of reinforced concrete samples by Compton backscattering technique

    Science.gov (United States)

    Boldo, E. M.; Appoloni, C. R.

    2014-02-01

    Reinforced concrete structures require frequent monitoring to ensure the concrete quality during its service life and for evaluation of in situ existing conditions. Compton backscattering of gamma rays is a nondestructive technique used for material characterization and detection of defects and inclusions in materials and can be employed on reinforced concrete. The methodology allows one-sided inspection of large structures, is relatively inexpensive and can be portable. The concept is based on detection of backscattered radiation produced from a collimated beam aimed at the sample. By measuring the spectrum of these scattered gamma rays it is possible to determine local density perturbations. In this work we used the Compton backscattering technique to locate and measure steel, defects and crushed stone inside concrete. The samples were irradiated with gamma rays from a Ø2 mm diameter collimated 241Am (100 mCi) source and the inelastically scattered photons were recorded at an angle of 135° by a high resolution CdTe semiconductor detector. Scanning was achieved by lateral movement of the sample blocks across the source and detector field of view in steps of 1 mm. A previous optimization of the experimental setup was performed with Monte Carlo simulation. The results showed that it was possible to locate inclusions and defects with Ø8 mm positioned at a depth of 20 mm below the surface of the sample. It was observed that aggregates such as crushed stone could mask defects at specific points due to high attenuation of the incident and scattered beam.

  20. A backscattered x-ray imager for medical applications

    Science.gov (United States)

    Morris, Eric Jude L.; Dibianca, Frank A.; Shukla, Hemant; Gulabani, Daya

    2005-04-01

    Conventional X-ray radiographic systems rely on transmitted photons for the production of images. Backscatter imaging makes use of the more abundant scattered photons for image formation. Specifically, incoherently (Compton) scattered X-ray photons are detected and used for image formation in this modality of medical imaging. However, additional information is obtained when the transmitted X-ray photons are also detected and used. Transmission radiography produces a two-dimensional image of a three dimensional system, therefore image information from a shallower object is often contaminated by image information from underlying objects. Backscattered x-ray imaging largely overcomes this deficiency by imaging depth selectively, which reduces corruption of shallow imaging information by information from deeper objects lying under it. Backscattered x-ray imaging may be particularly useful for examining anatomical structures at shallow depths beneath the skin. Some typical applications for such imaging might be breast imaging, middle ear imaging, imaging of skin melanomas, etc. Previous investigations, by way of theoretical calculations and computational simulations into the feasibility of this kind of imaging have uncovered high-contrast and SNR parameters. Simulations indicate that this method can be used for imaging relatively high-density objects at depths of up to approximately five centimeters below the surface. This paper presents both theoretical and experimental SNR results on this new medical imaging modality.

  1. Simulation Studies of the Backscattering Signal in HSRL Technique

    CERN Document Server

    Georgakopoulou, Angelika

    2012-01-01

    The technique of High Spectral Resolution Lidar (HSRL) for atmospheric monitoring allows the determination of the aerosol to molecular ratio and can be used in UHECR Observatories using air fluorescence telescopes. By this technique a more accurate estimate of the Cherenkov radiation superimposed to the fluorescence signal can be achieved. A laboratory setup was developed to determine the backscattering coefficients using microparticles diluted in water and diffusion interfaces. In this setup we used a CW SLM laser at 532 nm and a 250 mm Newtonian telescope. Simulations of the above experimental configuration have been made using Scatlab\\c{opyright}, FINESSE\\c{opyright} 0.99.8 and MATLAB\\c{opyright} and are presented in this work. We compare the simulated 2-dimensional Fabry-Perot fringe images of the backscattering signal recorded in the CCD sensor with that of experimental ones. Additionally, we simulated the backscattering of the laser beam by the atmosphere at a height of 2000 m and we have studied the in...

  2. Relationships between multipolarized radar backscatter and slash pine stand parameters

    Science.gov (United States)

    Hussin, Yousif Ali; Hoffer, Roger M.

    1989-01-01

    Multipolarized L-band (24.5 cm) aircraft radar data was obtained for a primarily forested area in northern Florida. Based on the results of previous studies by Hoffer and Hussin (1989), a swath of medium incidence angle (35-25 deg) data was defined. Three groups of slash pine stands were located in the data: 4- to 17-year-old plantations, 18- to 48-year-old plantations, and 16- to 53-year-old natural stands. Stand data obtained from the forest-products companies operating in the area include age, tree height, diameter-at-breast height, basal area, volume (cords/acre), and density (trees/acre). Each of these stand parameters were compared to each of the four polarizations (HH, VV, VH, and HV) of the radar data for each group of stands. Statistically significant relationships were found between the radar backscatter and the forest stand parameters only for the 4- to 17-year-old slash pine plantation stands. In general, the cross-polarized radar backscatter was more highly correlated with the various stand parameters than the like-polarized backscatter, and the VV-polarized data were more highly correlated than the HH-polarized data.

  3. C-band backscattering characteristics of lake ice in northern Alaska during spring thaw period

    International Nuclear Information System (INIS)

    C-band backscatter intensities from lake ice in Northern Alaska showed a reversal phenomenon from freezing period to spring thaw period. The backscattering mechanisms of this phenomenon have not been clearly explained yet. In order to understand a mechanism of this backscatter reversal, we conducted field observations from April to May in 1997. This paper describes a summary of field observation data analysis and a derived assumption for the backscattering mechanism for the spring thaw period. The backscattering increase of the grounded ice is caused by a roughness increase of the ice surface, while backscattering decrease of the floating ice is by a presence of water film of the ice surface. By using the IEM surface scattering model, a validity of the assumed backscattering mechanisms is confirmed. (author)

  4. Multiple scattering wavelength dependent backscattering of kaolin dust in the IR: Measurements and theory

    Science.gov (United States)

    Ben-David, Avishai

    1992-01-01

    Knowing the optical properties of aerosol dust is important for designing electro-optical systems and for modeling the effect on propagation of light in the atmosphere. As CO2 lidar technology becomes more advanced and is used for multiwavelength measurements, information on the wavelength dependent backscattering of aerosol dust particles is required. The volume backscattering coefficient of aerosols in the IR is relatively small. Thus, only a few field measurements of backscattering, usually at only a few wavelengths, are reported in the literature. We present spectral field measurements of backscattering of kaolin dust in the 9-11 micron wavelength range. As the quantity of dust increases, multiple scattering contributes more to the measured backscattered signal. The measurements show the effect of the dust quantity of the spectral backscatter measurements. A simple analytical two stream radiative transfer model is applied to confirm the measurements and to give insight to the multiple scattering spectra of backscattering.

  5. Neutron scattering

    International Nuclear Information System (INIS)

    This report contains the text of 16 lectures given at the Summer School and the report on a panel discussion entitled ''the relative merits and complementarities of x-rays, synchrotron radiation, steady- and pulsed neutron sources''. figs., tabs., refs

  6. Piezonuclear Neutrons

    CERN Document Server

    Cardone, Fabio; Petrucci, Andrea

    2008-01-01

    We report the results of neutron measurements carried out during the application of ultrasounds to a solution containing only stable elements like Iron and Chlorine, without any other radioactive source of any kind. These measurements, carried out by CR39 detectors and a Boron TriFouride electronic detector, evidenced the emission of neutron pulses. These pulses stand well above the electronic noise and the background of the laboratory where the measurements were carried out.

  7. Neutron Scattering

    International Nuclear Information System (INIS)

    The neutron probe is a standard tool for measuring soil water content. This article provides an overview of the underlying theory, describes the methodology for its calibration and use, discusses example applications, and identifies the safety issues. Soil water makes land-based life possible by satisfying plant water requirements, serving as a medium for nutrient movement to plant roots and nutrient cycling, and controlling the fate and transport of contaminants in the soil environment. Therefore, a successful understanding of the dynamics of plant growth, nutrient cycling, and contaminant behavior in the soil requires knowledge of the soil water content as well as its spatial and temporal variability. After more than 50 years, neutron probes remain the most reliable tool available for field monitoring of soil water content. Neutron probes provide integrated measurements over relatively large volumes of soil and, with proper access, allow for repeated sampling of the subsurface at the same locations. The limitations of neutron probes include costly and time-consuming manual operation, lack of data automation, and costly regulatory requirements. As more non-radioactive systems for soil water monitoring are developed to provide automated profiling capabilities, neutron-probe usage will likely decrease. Until then, neutron probes will continue to be a standard for reliable measurements of field water contents in soils around the globe

  8. Synovectomy by neutron capture in boron; Sinovectomia por captura de neutrones en boro

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R. [Unidades Academicas de Estudios Nucleares, Ingenieria Electrica y Matematicas, Universidad Autonoma de Zacatecas, A.P. 336, C.P. 98000 Zacatecas (Mexico)

    2002-07-01

    The rheumatoid arthritis is an illness which affect approximately at 3% of the World population. This illness is characterized by the inflammation of the joints which reduces the quality of life and the productivity of the patients. Since, it is an autoimmune illness, the inflammation is due to the overproduction of synovial liquid by the increase in the quantity of synoviocytes. The rheumatoid arthritis does not have a definitive recovery and the patients have three options of treatment: the use of drugs, the surgery and the radio synovectomy. The synovectomy by neutron capture in Boron is a novel proposal of treatment of the rheumatoid arthritis that consists in using a charged compound with Boron 10 that is preferently incorporated in the synoviocytes and to a less extent in the rest of surrounding tissues of the joint. Then, the joint is exposed to a thermal neutron field that induces the reaction (n, {alpha}) in the {sup 10} B. the products of this reaction place their energy inside synoviocytes producing their reduction and therefore the reduction of the joint inflammation. Since it is a novel procedure, the synovectomy by neutron capture in boron has two problems: the source design and the design of the adequate drug. In this work it has been realized a Monte Carlo study with the purpose to design a moderating medium that with a {sup 239} Pu Be source in its center, produces a thermal neutron field. With the produced neutron spectra, the neutrons spectra and neutron doses were calculated in different sites inside a model of knee joint. In Monte Carlo studies it is necessary to know the elemental composition of all the joint components, for the case of synovia and the synovial liquid this information does not exist in such way that it is supposed that its composition is equal than the water. In this work also it has been calculated the kerma factors by neutrons of synovia and the synovial liquid supposing that their elemental composition are similar to the

  9. Retrieving forest stand parameters from SAR backscatter data using a neural network trained by a canopy backscatter model

    International Nuclear Information System (INIS)

    It was possible to retrieve the stand mean dbh (tree trunk diameter at breast height) and stand density from the Jet Propulsion Laboratory (JPL) Airborne Synthetic Aperture Radar (AIRSAR) backscatter data by using threelayered perceptron neural networks (NNs). Two sets of NNs were trained by the Santa Barbara microwave canopy backscatter model. One set of the trained NNs was used to retrieve the stand mean dbh, and the other to retrieve the stand density. Each set of the NNs consisted of seven individual NNs for all possible combinations of one, two, and three radar wavelengths. Ground and multiple wavelength AIRSAR backscatter data from two ponderosa pine forest stands near Mt. Shasta, California (U.S.A.) were used to evaluate the accuracy of the retrievals. The r.m.s. and relative errors of the retrieval for stand mean dbh were 6.1 cm and 15.6 per cent for one stand (St2), and 3.1 cm and 6.7 per cent for the other stand (St11). The r.m.s. and relative errors of the retrieval for stand density were 71.2 treesha-1 and 23.0 per cent for St2, and 49.7 treesha-1 and 21.3 per cent for St11. (author)

  10. FOREWORD: Neutron metrology Neutron metrology

    Science.gov (United States)

    Thomas, David J.; Nolte, Ralf; Gressier, Vincent

    2011-12-01

    The International Committee for Weights and Measures (CIPM) has consultative committees covering various areas of metrology. The Consultative Committee for Ionizing Radiation (CCRI) differs from the others in having three sections: Section (I) deals with radiation dosimetry, Section (II) with radionuclide metrology and Section (III) with neutron metrology. In 2003 a proposal was made to publish special issues of Metrologia covering the work of the three Sections. Section (II) was the first to complete their task, and their special issue was published in 2007, volume 44(4). This was followed in 2009 by the special issue on radiation dosimetry, volume 46(2). The present issue, volume 48(6), completes the trilogy and attempts to explain neutron metrology, the youngest of the three disciplines, the neutron only having been discovered in 1932, to a wider audience and to highlight the relevance and importance of this field. When originally approached with the idea of this special issue, Section (III) immediately saw the value of a publication specifically on neutron metrology. It is a topic area where papers tend to be scattered throughout the literature in journals covering, for example, nuclear instrumentation, radiation protection or radiation measurements in general. Review articles tend to be few. People new to the field often ask for an introduction to the various topics. There are some excellent older textbooks, but these are now becoming obsolete. More experienced workers in specific areas of neutron metrology can find it difficult to know the latest position in related areas. The papers in this issue attempt, without presenting a purely historical outline, to describe the field in a sufficiently logical way to provide the novice with a clear introduction, while being sufficiently up-to-date to provide the more experienced reader with the latest scientific developments in the different topic areas. Neutron radiation fields obviously occur throughout the nuclear

  11. X-rays from synchrotron: new challenge for neutron scattering

    International Nuclear Information System (INIS)

    A brief review is given of current developments in x-ray scattering techniques at synchrotron radiation facilities. Highly collimated, intense white radiations open up new areas of research in condensed matter physics and challenge the traditional domains of neutron scattering. These include energy dispersive scattering, the use of anomalous dispersion, magnetic diffraction and direct energy analysis by backscattering. The relative merits of x-ray and neutron scattering techniques will be discussed. The unique advantage of neutron scattering is the capability of performing polarization analysis. We will discuss in some detail the current developments at Brookhaven in inelastic scattering of polarized neutrons. In addition, we will also discuss special technical problems associated with the search for phasons utilizing a high resolution triple axis spectrometer

  12. TOSCA incoherent inelastic neutron spectrometer. Progress and results

    International Nuclear Information System (INIS)

    The back-scattering part (phase I) of the new incoherent inelastic neutron spectrometer, TOSCA, replacing the old TFXA, has been successfully installed at the ISIS pulsed neutron spallation source. The results, owing to the much larger detector area, show a significant enhancement of the counting rate and a slight improvement of the low energy resolution. In spring 2000 the forward scattering bank (phase II) will be completed and, during the final installation, the whole instrument will be moved from the present 12 m of primary flight path to 17 m. This will result in a large improvement of the overall resolution (from 2-3% to 1-1.5% of the energy transfer). In addition, a chopper will be added in order to avoid neutron frame overlap and to reduce the fast neutron background. (author)

  13. Characterisation and determination of the neutron transmission properties of sodium-calcium and sodium borates from different regions in Turkey

    International Nuclear Information System (INIS)

    In this study, ulexite, probertite found within sodium-calcium borates and borax, and tincalconite found within sodium borates retrieved from different regions in Turkey are evaluated for their neutron irradiation performances. Characterisations were performed using XRD, FT-IR, Raman spectroscopy. B2O3 contents were determined experimentally, structural water contents and surface morphologies were determined using DTA/TG and SEM. Neutron transmission values and total macroscopic cross-sections were determined using 239Pu-Be source moderated in a howitzer. Neutron transmission values from lowest to highest were found to be as follows: secondary ulexite (Kirka), tincalconite (Kirka), ulexite (Kestelek), ulexite (Kirka), borax (Kirka), probertite (Kestelek) and ulexite (Bigadic). (author)

  14. Crystal Driven Neutron Source: A New Paradigm for Miniature Neutron Sources

    International Nuclear Information System (INIS)

    Neutron interrogation techniques have specific advantages for detection of hidden, shielded, or buried threats over other detection modalities in that neutrons readily penetrate most materials providing backscattered gammas indicative of the elemental composition of the potential threat. Such techniques have broad application to military and homeland security needs. Present neutron sources and interrogation systems are expensive and relatively bulky, thereby making widespread use of this technique impractical. Development of a compact, high intensity crystal driven neutron source is described. The crystal driven neutron source approach has been previously demonstrated using pyroelectric crystals that generate extremely high voltages when thermal cycled. Placement of a sharpened needle on the positively polarized surface of the pyroelectric crystal results in sufficient field intensification to field ionize background deuterium molecules in a test chamber, and subsequently accelerate the ions to energies in excess of ∼100 keV, sufficient for either D-D or D-T fusion reactions with appropriate target materials. Further increase in ion beam current can be achieved through optimization of crystal thermal ramping, ion source and crystal accelerator configuration. The advantage of such a system is the compact size along with elimination of large, high voltage power supplies. A novel implementation discussed incorporates an independently controlled ion source in order to provide pulsed neutron operation having microsecond pulse width.

  15. Crystal Driven Neutron Source: A New Paradigm for Miniature Neutron Sources

    Science.gov (United States)

    Tang, V.; Morse, J.; Meyer, G.; Falabella, S.; Guethlein, G.; Kerr, P.; Park, H. G.; Rusnak, B.; Sampayan, S.; Schmid, G.; Spadaccini, C.; Wang, L.

    2009-03-01

    Neutron interrogation techniques have specific advantages for detection of hidden, shielded, or buried threats over other detection modalities in that neutrons readily penetrate most materials providing backscattered gammas indicative of the elemental composition of the potential threat. Such techniques have broad application to military and homeland security needs. Present neutron sources and interrogation systems are expensive and relatively bulky, thereby making widespread use of this technique impractical. Development of a compact, high intensity crystal driven neutron source is described. The crystal driven neutron source approach has been previously demonstrated using pyroelectric crystals that generate extremely high voltages when thermal cycled [1-4]. Placement of a sharpened needle on the positively polarized surface of the pyroelectric crystal results in sufficient field intensification to field ionize background deuterium molecules in a test chamber, and subsequently accelerate the ions to energies in excess of ˜100 keV, sufficient for either D-D or D-T fusion reactions with appropriate target materials. Further increase in ion beam current can be achieved through optimization of crystal thermal ramping, ion source and crystal accelerator configuration. The advantage of such a system is the compact size along with elimination of large, high voltage power supplies. A novel implementation discussed incorporates an independently controlled ion source in order to provide pulsed neutron operation having microsecond pulse width.

  16. Neutron Repulsion

    CERN Document Server

    Manuel, Oliver K

    2011-01-01

    Earth is connected gravitationally, magnetically and electrically to its heat source - a neutron star that is obscured from view by waste products in the photosphere. Neutron repulsion is like the hot filament in an incandescent light bulb. Excited neutrons are emitted from the solar core and decay into hydrogen that glows in the photosphere like a frosted light bulb. Neutron repulsion was recognized in nuclear rest mass data in 2000 as the overlooked source of energy, the keystone of an arch that locked together these puzzling space-age observations: 1.) Excess 136Xe accompanied primordial helium in the stellar debris that formed the solar system (Fig. 1); 2.) The Sun formed on the supernova core (Fig. 2); 3.) Waste products from the core pass through an iron-rich mantle, selectively carrying lighter elements and lighter isotopes of each element into the photosphere (Figs. 3-4); and 4.) Neutron repulsion powers the Sun and sustains life (Figs. 5-7). Together these findings offer a framework for understanding...

  17. The role of phantom parameters on the response of the AEOI Neutriran Albedo Neutron Personnel Dosemeter

    International Nuclear Information System (INIS)

    The response of the AEOI Neutriran Albedo Neutron Personnel Dosemeter (NANPD) which can also be used for other albedo dosemeter types was determined on 18 different phantom configurations. The effects of type, geometry, material, thickness, dosemeter-to-phantom angle in particular with the presence of legs were investigated using a Pu-Be neutron source. It was concluded that the slab phantoms (single or double) and circular and elliptical cylinder phantoms seemed to provide a better response, whereas the ICRU sphere geometry does not seem to be appropriate for the calibration of albedo dosemeters. It is interesting to note that the presence of legs maintains the constancy of the response in a situation when a radiation worker bends down during work. (author)

  18. Activation analysis of pit-coal ash content with the use of isotopic fast neutron source

    International Nuclear Information System (INIS)

    The neutron activation techniques of coal ash determination are briefly reviewed and a new version of activation analysis using fast neutrons from 239Pu-Be source and basing on the reactions 28Si(n,p)28Al and 27Al(n,p)27Mg is proposed. 72 samples of pit-coals with ash content ranging from 3 to 40% were measured. The linear calibration function between ash content and both, 1.78 MeV and 0.84 MeV, γ-ray counts was obtained. The precision (0.94% ash for 17% ash content) and accuracy (1.4%ash for the whole range) were evaluated. Comparison of the results with those of fluorescent-scattering methods is made. (author)

  19. A method for moisture measurement in porous media based on epithermal neutron scattering.

    Science.gov (United States)

    El Abd, A

    2015-11-01

    A method for moisture measurement in porous media was proposed. A wide beam of epithermal neutrons was obtained from a Pu-Be neutron source immersed in a cylinder made of paraffin wax. (3)He detectors (four or six) arranged in the backward direction of the incident beam were used to record scattered neutrons from investigated samples. Experiments of water absorption into clay and silicate bricks, and a sand column were investigated by neutron scattering. While the samples were absorbing water, scattered neutrons were recorded from fixed positions along the water flow direction. It was observed that, at these positions scattered neutrons increase as the water uptake increases. Obtained results are discussed in terms of the theory of macroscopic flow in porous media. It was shown that, the water absorption processes were Fickian and non Fickian in the sand column and brick samples, respectively. The advantages of applying the proposed method to study fast as well as slow flow processes in porous media are discussed. PMID:26298060

  20. Determination of the fast neutrons spectra by the Elastic scattering method (n, p)

    CERN Document Server

    Elizalde, J

    1973-01-01

    This work consists in determining the fast neutron spectra emitted by a Pu-Be isotopic source. The implemented technique is based in the spectrometry (n, p). This consists in making to fall on a fast neutrons beams (polyenergetic) over a thin film of hydrogenated material, detecting the spectra of emitted protons at a fix angle. The polyethylene film and the used solid state detector are inside of a vacuum chamber. The detector is placed at 30 degree with respect to direction of the incident neutrons beam. The protons spectra is stored in a multichannel. the energy is obtained with the prior calibration of the system. The data processing involves the transformation of the protons spectra observed at the falling on neutrons spectra over the film. The energy of the neutrons is related with that of the protons, according to the collision kinematical equations. The cross section of elastic collision of the neutrons with the hydrogen atoms is obtained from literature. Applying these relations to the observed spect...

  1. Design considerations for a neutron generator-based total-body irradiator

    International Nuclear Information System (INIS)

    The prompt- and delayed-gamma neutron activation techniques have been used for the non-invasive measurement of human body composition. In recent years, neutron irradiators have used only transuranic isotopic sources (238PuBe, 241AmBe, 252Cf). However, in today's security-minded environment, the use of alternate neutron sources may provide some advantages. Several designs for an irradiator that would use a high-output, miniature D-T neutron generator (MF Physics) have been examined. The use of this type of neutron source will lessen the storage, security, and transport issues associated with continuous-output isotopic neutron sources. To determine the scientific impact of this decision, Monte Carlo simulations (MCNP-4B2; Los Alamos National Laboratory) has been performed to aid in the design of the irradiator system, evaluating shielding materials, collimation, and source-to-subject distance, for the measurement of total body nitrogen (TBN). Based on internal flux distributions within the simulated body region of a subject, several design options were identified. The final design will be selected based on the optimization of precision, dose, and exposure time. (author)

  2. Concentration measurement of yeast suspensions using high frequency ultrasound backscattering.

    Science.gov (United States)

    Elvira, Luis; Vera, Pedro; Cañadas, Francisco Jesús; Shukla, Shiva Kant; Montero, Francisco

    2016-01-01

    This work proposes the use of an ultrasound based technique to measure the concentration of yeasts in liquid suspension. This measurement was achieved by the detection and quantification of ultrasonic echoes backscattered by the cells. More specifically, the technique was applied to the detection and quantification of Saccharomyces cerevisiae. A theoretical approach was proposed to get the average density and sound speed of the yeasts, which were found to be 1116 kg/m(3) and 1679 m/s, respectively. These parameters were needed to model the waves backscattered by each single cell. A pulse-echo arrangement working around 50 MHz, being able to detect echoes from single yeasts was used to characterize experimentally yeast solutions from 10(2) to 10(7)cells/ml. The Non-negative Matrix Factorization denoising technique was applied for data analysis. This technique required a previous learning of the spectral patterns of the echoes reflected from yeasts in solution and the base noise from the liquid medium. Comparison between pulse correlation (without denoising) and theoretical and experimental pattern learning was made to select the best signal processing. A linear relation between ultrasound output and concentration was obtained with correlation coefficient R(2)=0.996 for the experimental learning. Concentrations from 10(4) to 10(7)cells/ml were detected above the base noise. These results show the viability of using the ultrasound backscattering technique to detect yeasts and measure their concentration in liquid cultures, improving the sensitivity obtained using spectrophotometric methods by one order of magnitude. PMID:26361271

  3. Investigations on landmine detection by neutron-based techniques

    Energy Technology Data Exchange (ETDEWEB)

    Csikai, J. E-mail: csikai@delfin.klte.hu; Doczi, R.; Kiraly, B

    2004-07-01

    Principles and techniques of some neutron-based methods used to identify the antipersonnel landmines (APMs) are discussed. New results have been achieved in the field of neutron reflection, transmission, scattering and reaction techniques. Some conclusions are as follows: The neutron hand-held detector is suitable for the observation of anomaly caused by a DLM2-like sample in different soils with a scanning speed of 1 m{sup 2}/1.5 min; the reflection cross section of thermal neutrons rendered the determination of equivalent thickness of different soil components possible; a simple method was developed for the determination of the thermal neutron flux perturbation factor needed for multi-elemental analysis of bulky samples; unfolded spectra of elastically backscattered neutrons using broad-spectrum sources render the identification of APMs possible; the knowledge of leakage spectra of different source neutrons is indispensable for the determination of the differential and integrated reaction rates and through it the dimension of the interrogated volume; the precise determination of the C/O atom fraction requires the investigations on the angular distribution of the 6.13 MeV gamma-ray emitted in the {sup 16}O(n,n'{gamma}) reaction. These results, in addition to the identification of landmines, render the improvement of the non-intrusive neutron methods possible.

  4. Thermal Neutron Radiography of Deuteriated Water in Soils

    Science.gov (United States)

    Tumlinson, L. G.; Hopmans, J. W.; Wilding, M. C.; Silk, W. K.; Huerta, N. J.; Tabor, M. M.

    2004-12-01

    As for x-rays, neutron radiography is a noninvasive imaging technique based on the attenuation of thermal neutrons by the object in question, described by BeerAƒAøAøâ_sA¬Aøâ_zAøs law. However, neutron imaging is complementary to x-rays, as it is especially well suited for materials containing hydrogen atoms and mostly other low atomic weight attenuating materials. Although neutron attenuation techniques are routinely used in engineering, relatively little is known about its application to soils. We will present results demonstrating the tremendous potential of using neutron attenuation techniques to measure spatial and temporal distribution of water in soils at the 50 micrometer spatial resolution. The neutron source is a Mark II Triga Reactor at McClellan Nuclear Radiation Center (MNRC) in Sacramento, CA. The reactor runs at 1.8 MW and emits a poly-energetic neutron beam, including the thermal range. Unfortunately beam hardening and backscattering are a major source of uncertainty. Recent laboratory experiments conducted at MNRC suggest that beam hardening is considerably reduced when using deuteriated water, because its cross-section for attenuation of thermal neutrons is much lower than for regular water.

  5. neutron radiography

    International Nuclear Information System (INIS)

    Neutron radiography (or radiology) is a diverse filed that uses neutrons of various energies, subthermal, thermal, epithermal or fast in either steady state or pulsed mode to examine objects for industrial, medical, or other purposes, both microscopic and macroscopic. The applications include engineering design, biological studies, nondestructive inspection and materials evaluation. In the past decade, over 100 different centers in some 30 countries have published reports of pioneering activities using reactors, accelerators and isotopic neutron sources. While film transparency and electronic video are most common imaging methods for static or in motion objects respectively, there are other important data gathering techniques, including track etch, digital gauging and computed tomography. A survey of the world-wide progress shows the field to be gaining steadily in its diversity, its sophistication and its importance. (author)

  6. HAB detection based on absorption and backscattering properties of phytoplankton

    Science.gov (United States)

    Lei, Hui; Pan, Delu; Bai, Yan; Chen, Xiaoyan; Zhou, Yan; Zhu, Qiankun

    2011-11-01

    The coastal area of East China Sea (ECS) suffers from the harmful algal blooms (HAB) frequently every year in the warm season. The most common causative phytoplankton algal species of HAB in the ECS in recent years are Prorocentrum donghaiense (dinoflagellates), Karenia mikimotoi (dinoflagellates which could produce hemolytic and ichthyotoxins) and Skeletonema costatum (diatom). The discrimination between the dinoflagellates and diatom HAB through ocean color remote sensing approach can add the knowledge of HAB events in ECS and help to the precaution. A series of in-situ measurement consisted of absorption coefficient, total scattering and particulate backscattering coefficient was conducted in the southern coast of Zhejiang Province in May 2009, and the estuary of Changjiang River in August 2009 and December 2010, which encountered two HAB events and a moderate bloom. The Inherent Optical Properties (IOPs) of the bloom waters have significant difference between phytoplankton species in absorption and backscattering properties. The chlorophyll a specific absorption coefficient (a*phy(λ)) for the bloom patches (chlorophyll a concentration >6mg m-3) differ greatly from the adjacent normal seawater, with the a*phy(λ) of bloom water lower than 0.03 m2 mg-1 while the a*phy(λ) of the adjacent normal seawater is much higher (even up to 0.06 m2 mg-1). Meanwhile, the backscattering coefficients at 6 wavebands (420, 442, 470, 510, 590 and 700nm) are also remarkably lower for bloom waters ( 0.02 m-1). The backscattering coefficient ratio (Rbp(λ)) is much lower for diatom bloom waters than for dinoflagellates types (0.01079 vs. 0.01227). A discrimination model based on IOPs is established, and several typical dinoflagellates and diatom bloom events including Prorocentrum donghaiense, Karenia mikimotoi and Skeletonema costatum in the ECS are picked out for testing with the MODIS-L2 and L3 ocean color remote sensing products from NASA website. The result proves that the

  7. The diurnal pattern of microwave backscattering by wheat

    International Nuclear Information System (INIS)

    A truck-mounted Ku-, C-, and L-band scatterometer system was used to obtain diurnal multiparameter radar backscatter measurements of wheat in August 1987 and June and July 1988. Concurrent field measurements of plant and soil moisture content were made in support of the radar data. Analyses of these data demonstrate the sensitivity of the microwave signals to the daily movement of water in the soil/plant system. The dependence of frequency, incidence angle, and polarization are discussed in relationship to the diurnal and seasonal changes in the soil and plant water content. The results are used to identify potential agronomic applications and future research requirements. (author)

  8. Rutherford backscattering and Auger spectroscopy of mercuric iodide detectors

    Energy Technology Data Exchange (ETDEWEB)

    Felter, T.E.; Stulen, R.H. (Sandia National Labs., Livermore, CA (USA)); Schnepple, W.F.; Ortale, C.; Van den Berg, L. (EG and G Energy Measurements, Inc., Goleta, CA (USA). Santa Barbara Operations)

    1989-11-01

    Palladium contacts on mercuric iodide have been studied using Rutherford backscattering spectroscopy and Auger electron spectroscopy. Results on actual detector contacts show some intermixing of both mercury and iodine with the palladium. To investigate the role of processing variables as a possible cause of this effect we have fabricated model contacts at low temperatures (T {approx equal} 100 K) and analyzed in situ. The results demonstrated that significant interdiffusion occurs at temperatures as low as 225 K. We conclude that excessive heating during contact deposition could prove to be detrimental to device performance and that the use of cooled substrates during processing should be explored. (orig.).

  9. Rutherford backscattering and Auger spectroscopy of mercuric iodide detectors

    Science.gov (United States)

    Felter, T. E.; Stulen, R. H.; Schnepple, W. F.; Ortale, C.; van den Berg, L.

    1989-11-01

    Palladium contacts on mercuric iodide have been studied using Rutherford backscattering spectroscopy and Auger electron spectroscopy. Results on actual detector contacts show some intermixing of both mercury and iodine with the palladium. To investigate the role of processing variables as a possible cause of this effect we have fabricated model contacts at low temperatures (T ≈ 100 K) and analyzed in situ. The results demonstrated that significant interdiffusion occurs at temperatures as low as 225 K. We conclude that excessive heating during contact deposition could prove to be detrimental to device performance and that the use of cooled substrates during processing should be explored.

  10. Rutherford backscattering and Auger spectroscopy of mercuric iodide detectors

    International Nuclear Information System (INIS)

    Palladium contacts on mercuric iodide have been studied using Rutherford backscattering spectroscopy and Auger electron spectroscopy. Results on actual detector contacts show some intermixing of both mercury and iodine with the palladium. To investigate the role of processing variables as a possible cause of this effect we have fabricated model contacts at low temperatures (T ≅ 100 K) and analyzed in situ. The results demonstrated that significant interdiffusion occurs at temperatures as low as 225 K. We conclude that excessive heating during contact deposition could prove to be detrimental to device performance and that the use of cooled substrates during processing should be explored. (orig.)

  11. Backscattering from dental restorations and splint materials during therapeutic radiation

    International Nuclear Information System (INIS)

    Models were constructed to simulate as closely as possible the human oral cavity. Radiation absorbed doses were determined for controls and various test situations involving the presence of dental restorative and splint materials during cobalt-60 irradiation of the models. Adjacent gold full crowns and adjacent solid dental silver amalgam cores both increased the dose to the interproximal gingivae by 20%. Use of orthodontic full bands for splinting the jaws increased the dose to the buccal tissues by an average of 10%. Augmentation of dose through backscatter radiation was determined to be only slight for intracoronal amalgam fillings and stainless steel or plastic bracket splints

  12. Statistical Parameter Estimation in Ultrasound Backscattering from Tissue Mimicking Media.

    Science.gov (United States)

    Chen, Jian-Feng

    Several tissue characterization parameters, including the effective scatterer number density and the backscatter coefficient, were derived from the statistical properties of ultrasonic echo signals. The effective scatterer number density is the actual scatterer number density in a medium multiplied by a frequency-dependent factor that depends on the differential scattering cross-sections of all scatterers. The method described in this thesis for determining the scatterer number density explicitly retains both the temporal nature of the data acquisition and the properties of the ultrasound field in the data reduction. Moreover, it accounts for the possibility that different sets of scatterers may dominate the echo signal at different frequencies. The random processes involved in forming ultrasound echo signals from random media give rise to an uncertainty in the estimated effective scatterer number density. This uncertainty is evaluated using error propagation. The statistical uncertainty depends on the effective number of scatterers contributing to the segmented echo signal, increasing when the effective number of scatterers increases. Tests of the scatterer number density data reduction method and the statistical uncertainty estimator were done using phantoms with known ultrasound scattering properties. Good agreement was found between measured values and those calculated from first-principles. The properties of the non-Gaussian and non-Rayleigh parameters of ultrasound echo signals are also studied. Both parameters depend on the measurement system, including the transducer field and pulse frequency content, as well as on the medium's properties. The latter is expressed in terms of the scatterer number density and the second and fourth moments of the medium's scattering function. A simple relationship between the non-Gaussian and non-Rayleigh parameters is derived and verified experimentally. Finally, a reference phantom method is proposed for measuring the

  13. Combined backscatter and transmission method for nuclear density gauge

    Science.gov (United States)

    Golgoun, Seyed Mohammad; Sardari, Dariush; Sadeghi, Mahdi; Ebrahimi, Mohammad; Aminipour, Mojtaba; Davarpanah, Mohammad Reza

    2015-07-01

    Nowadays, the use of nuclear density gauges, due to the ability to work in harsh industrial environments, is very common. In this study, to reduce error related to the ρ of continuous measuring density, the combination of backscatter and transmission are used simultaneously. For this reason, a 137Cs source for Compton scattering dominance and two detectors are simulated by MCNP4C code for measuring the density of 3 materials. Important advantages of this combined radiometric gauge are diminished influence of μ and therefore improving linear regression.

  14. Combined backscatter and transmission method for nuclear density gauge

    Directory of Open Access Journals (Sweden)

    Golgoun Seyed Mohammad

    2015-01-01

    Full Text Available Nowadays, the use of nuclear density gauges, due to the ability to work in harsh industrial environments, is very common. In this study, to reduce error related to the ρ of continuous measuring density, the combination of backscatter and transmission are used simultaneously. For this reason, a 137Cs source for Compton scattering dominance and two detectors are simulated by MCNP4C code for measuring the density of 3 materials. Important advantages of this combined radiometric gauge are diminished influence of μ and therefore improving linear regression.

  15. Development of a microstrip-based neutron detector

    Indian Academy of Sciences (India)

    S S Desai; A M Shaikh; V Radhakrishna; K Rajanna

    2004-08-01

    A gas-filled microstrip detector for thermal neutrons has been built and successfully tested in our laboratory. The detector has an active area of 20 mm × 15 mm and consists of alternate anodes and cathodes of widths 12 m and 300 m respectively. The anode to cathode gap is 150 m and the pitch is 612 m. A high resistance, meandering type horizontal strip connects the anodes at one end and aids in position sensing by charge division method. The detector is tested with gas mixtures 3He+Kr (1 : 2) and 3He+CF4 (2 : 1) at pressure of 3 atmospheres and using a Pu-Be neutron source. The pulse height spectrum shows energy resolution of ∼ 8% (FWHM) for the 764 keV peak at anode voltage of 525 V for 3He+Kr and ∼ 15% at anode voltage of 800 V for 3He+CF4. Gas gains up to 6.3 × 103 and 3.6 × 103 are obtained respectively with these gas mixtures. The overall efficiency of the detector along the sensitive length is tested by exposing the active area to neutrons and recording the position spectrum. The detector shows fairly uniform efficiency (∼ 45\\%) over the active length.

  16. A mobile prompt-gamma in-vivo neutron activation facility

    International Nuclear Information System (INIS)

    A significant environmental-medical problem is the internal deposition of Cd in industrially exposed populations. With the development of 238Pu, Be neutron sources, it has become possible to design facilities that are significantly reduced in size and hence portable. The paper describes the development and fabrication of a self-contained 'neutron-capture' facility in a mobile trailer which is readily transportable. Although the initial project was designed for the measurement of Cd deposited in the liver and kidney of industrial workers, the sensitivity of the system will allow for measurements in normal populations. The limits of detection of Cd are 2.0 mg for kidney and 1.5 μg/g (wet weight) for liver (associated organ radiation dose is 660 mrem). The portable facility makes it possible to study Cd-exposed populations in any geographic location. With minor modifications of the collimator, detectors and counting geometry, it is also possible to make in-vivo measurements of total body nitrogen. The neutron source used in the mobile facility is 85 Ci 238Pu, Be shielded by epoxy resin doped with LiCO3 and 6LiF. Additional shielding is provided by Pb bricks and polyethylene bricks with 1% boron and 80% Pb. For Cd measurement, the detection system consists of two Ge(Li) detectors (25% efficiency each) shielded by Bi and a 1.5-cm layer of paraffin heavily doped with 6LiF. For body nitrogen, two shielded 15.2cmx15.2cm NaI(Tl) detectors are positioned above the scanning bed. This mobile activation facility could be usefully employed in countries which need to monitor industrial populations but do not have ready access to large neutron research facilities and permanently installed whole-body counters

  17. Neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Heger, G. [Rheinisch-Westfaelische Technische Hochschule Aachen, Inst. fuer Kristallographie, Aachen (Germany)

    1996-12-31

    X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (author) 15 figs., 1 tab., 10 refs.

  18. Test and validation of the iterative code for the neutrons spectrometry and dosimetry: NSDUAZ; Prueba y validacion del codigo iterativo para la espectrometria y dosimetria de neutrones: NSDUAZ

    Energy Technology Data Exchange (ETDEWEB)

    Reyes H, A.; Ortiz R, J. M.; Reyes A, A.; Castaneda M, R.; Solis S, L. O.; Vega C, H. R., E-mail: alfredo_reyesh@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Av. Lopez Velarde 801, Col. Centro, 98000 Zacatecas (Mexico)

    2014-08-15

    In this work was realized the test and validation of an iterative code for neutronic spectrometry known as Neutron Spectrometry and Dosimetry of the Universidad Autonoma de Zacatecas (NSDUAZ). This code was designed in a user graph interface, friendly and intuitive in the environment programming of LabVIEW using the iterative algorithm known as SPUNIT. The main characteristics of the program are: the automatic selection of the initial spectrum starting from the neutrons spectra catalog compiled by the International Atomic Energy Agency, the possibility to generate a report in HTML format that shows in graph and numeric way the neutrons flowing and calculates the ambient dose equivalent with base to this. To prove the designed code, the count rates of a spectrometer system of Bonner spheres were used with a detector of {sup 6}LiI(Eu) with 7 polyethylene spheres with diameter of 0, 2, 3, 5, 8, 10 and 12. The count rates measured with two neutron sources: {sup 252}Cf and {sup 239}PuBe were used to validate the code, the obtained results were compared against those obtained using the BUNKIUT code. We find that the reconstructed spectra present an error that is inside the limit reported in the literature that oscillates around 15%. Therefore, it was concluded that the designed code presents similar results to those techniques used at the present time. (Author)

  19. Preliminary study of neutron absorption by concrete with boron carbide addition

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah, Yusof, E-mail: yusofabd@nuclearmalaysia.gov.my; Yusof, Mohd Reusmaazran; Zali, Nurazila Mat; Ahmad, Megat Harun Al Rashid Megat; Yazid, Hafizal [Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia); Ariffin, Fatin Nabilah Tajul; Ahmad, Sahrim [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor (Malaysia); Hamid, Roszilah [Department of Civil and Structural Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor (Malaysia); Mohamed, Abdul Aziz [College of Engineering, Universiti Tenaga National, Jalan Ikram-Uniten, 43000 Kajang, Selangor (Malaysia)

    2014-02-12

    Concrete has become a conventional material in construction of nuclear reactor due to its properties like safety and low cost. Boron carbide was added as additives in the concrete construction as it has a good neutron absorption property. The sample preparation for concrete was produced with different weight percent of boron carbide powder content. The neutron absorption rate of these samples was determined by using a fast neutron source of Americium-241/Be (Am-Be 241) and detection with a portable backscattering neutron detector. Concrete with 20 wt % of boron carbide shows the lowest count of neutron transmitted and this indicates the most neutrons have been absorbed by the concrete. Higher boron carbide content may affect the concrete strength and other properties.

  20. Investigations of Temperature and Backscatter Correlation in the Dry Snow Zone of the Greenland Ice Sheet

    OpenAIRE

    Moon, Kevin R.; Long, David G.

    2012-01-01

    Due to system degradation, satellite-borne scatterometers require post-launch calibrations to maintain accuracy. The dry snow zone of the Greenland ice sheet has been used for calibration due to its relatively constant backscatter properties. However, we recently discovered that some of the variation in the dry snow zone backscatter is seasonal. This paper uses correlation analysis to investigate the relationship between temperature and backscatter in the dry snow zone. The correlation coeffi...

  1. Comparative modelling of X-ray backscattering in the Novillo tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Flores, A.; Castillo, A.; Barocio, S.R.; Chavez, E.; Melendez, L.; Cruz, G.J.; Olayo, M.G.; Gonzalez, P.; Azorin, J. E-mail: azorin@xanum.uam.mx

    2001-08-01

    Results of X-ray backscattering studies on the Novillo tokamak using thermoluminescent dosimeters (TLDs) are presented. Dose measurements were carried out on the equatorial plane of the tokamak along 12 radial directions. The backscattering can be due to the interaction of the radiation with the surrounding walls. Two kinds of phenomenological mathematical methods describing the X-ray backscattering were obtained from the experimental data and compared. Good agreement was found between the data and the predictions of the models.

  2. Multi-beam backscatter image data processing techniques employed to EM 1002 system

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, W.A.; Chakraborty, B.

    backscatter intensities recorded in the raw (*.all) files are corrected during data acquisition for backscatter employing Lambert’s law (Simrad Model) [4]. However, for lower incidence angles (within the 0-25º) it was determined that the gain settings... of seabed during online data acquisition. Thus there will be image distortion, therefore, above correction is made during processing the raw backscatter strengths. • Lambert’s law removal: As discussed in preceding sections [4], the raw data is treated...

  3. Seabottom characterization using multibeam echosounder angular backscatter: An application of the composite roughness theory

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Schenke, H.W.; Kodagali, V.N.; Hagen, R.

    of the contributions from the surface rough- ness and volume inhomogeneities. For an interface backscattering strength within the composite roughness theory, Jackson et al. [1] had applied power law properties of the seafloor roughness spectrum to a Helmholtz...-Kirchhoff’s theory) is employed. A visual examination to observe the match between the theoretical and measured backscattering strengths is performed. In order to determine accurate, unbiased power law parameters, we have avoided using the backscattering strength...

  4. Effect of the Photon's Brownian Doppler Shift on the Weak-Localization Coherent-Backscattering Cone

    OpenAIRE

    Lesaffre, Max; Atlan, Michael; Gross, Michel

    2006-01-01

    We report the first observation of the dependence of the coherent-backscattering (CBS) enhanced cone with the frequency of the backscattered photon. The experiment is performed on a diffusing liquid suspension and the Doppler broadening of light is induced by the Brownian motion of the scatterers. Heterodyne detection on a CCD camera is used to measure the complex field (i.e., the hologram) of the light that is backscattered at a given frequency. The analysis of the holograms yield the freque...

  5. A neutron time of flight spectrometer appropriate for D-T plasma diagnostics

    International Nuclear Information System (INIS)

    A neutron time-of-flight spectrometer with 2 m flight path for diagnostics of deuterium plasmas in JET is presently under construction. An upgrade of this spectrometer to make it appropriate for 14-MeV neutron spectroscopy is presented here. It is suggested to use backscattering in a deuterium based scintillator. The flight path length is 1-2 m and the efficiency is of the order of 2.10-5 cm-5 . Results from test of principle are presented with estimates for neutron and gamma backgrounds

  6. The measurement of concrete density by back-scattered γ-radiation

    International Nuclear Information System (INIS)

    The use of γ backscattering techniques in the quality control of concrete are considered. The performance of an instrument using this technique, the Ekco N 711B, is reported. It was found that quick and accurate measurements could be obtained which were independent of the material chemical constitution and that good correlation existed between ultrasonic pulse velocity, and the backscatter methods. The disadvantage of measuring backscatter from thin concrete members was overcome by using a steel backing plate that compensated for the back-scatter if the concrete depth was less than the semi-infinite depth. (U.K.)

  7. Verification of terahertz-wave spectrophotometry by Compton backscattering of coherent synchrotron radiation

    Science.gov (United States)

    Sei, Norihiro; Takahashi, Toshiharu

    2014-01-01

    We developed a continuous-spectrum light beam from Compton backscattering by using coherent synchrotron radiation in an L-band linac at the Kyoto University Research Reactor Institute. The ratio of Compton backscattered photons to background photons when coherent synchrotron radiation was used was three times larger than when coherent transition radiation was used. The transmission spectrum of a polystyrene film in the terahertz-wave region was evaluated by measuring the spectrum of the Compton backscattered photons and it roughly agreed with that measured by a Martin-Puplett-type interferometer. The spectrophotometry using Compton backscattering shows promise as a new tool for investigations in terahertz-wave science.

  8. Transport equation theory of electron backscattering and x-ray production

    International Nuclear Information System (INIS)

    A transport equation theory of electron backscattering and x ray production is derived and applied to energy dissipation of 30-KeV electrons for copper as a function of depth and to the energy distribution of backscattered electrons for copper, aluminum, and gold. These results are plotted and compared with experiment. Plots for variations of backscattering with atomic number and with angle of incidence, and polar plots of backscattering for 30-keV electrons at normal incidence are also presented. 10 references, seven figures

  9. Data analysis of backscattering LIDAR system correlated with meteorological data

    International Nuclear Information System (INIS)

    In these last years, we had an increase in the interest in the monitoring of the effect of the human activity being on the atmosphere and the climate in the planet. The remote sensing techniques has been used in many studies, also related the global changes. A backscattering LIDAR system, the first of this kind in Brazil, has been used to provide the vertical profile of the aerosol backscatter coefficient at 532 nm up to an altitude of 4-6 km above sea level. In this study, data has was collected in the year of 2005. These data had been correlated with data of solar photometer CIMEL and also with meteorological data. The main results had indicated to exist a standard in the behavior of these meteorological data and the vertical distribution of the extinction coefficient gotten through LIDAR. In favorable periods of atmospheric dispersion, that is, rise of the temperature of associated air the fall of relative humidity, increase of the atmospheric pressure and low ventilation tax, was possible to determine with good precision the height of the Planetary Boundary Layer, as much through the vertical profile of the extinction coefficient how much through the technique of the vertical profile of the potential temperature. The technique LIDAR showed to be an important tool in the determination of the thermodynamic structure of the atmosphere, assisting to characterize the evolution of the CLP throughout the day, which had its good space and secular resolution. (author)

  10. Observations of HF backscatter decay rates from HAARP generated FAI

    Science.gov (United States)

    Bristow, William; Hysell, David

    2016-07-01

    Suitable experiments at the High-frequency Active Auroral Research Program (HAARP) facilities in Gakona, Alaska, create a region of ionospheric Field-Aligned Irregularities (FAI) that produces strong radar backscatter observed by the SuperDARN radar on Kodiak Island, Alaska. Creation of FAI in HF ionospheric modification experiments has been studied by a number of authors who have developed a rich theoretical background. The decay of the irregularities, however, has not been so widely studied yet it has the potential for providing estimates of the parameters of natural irregularity diffusion, which are difficult measure by other means. Hysell, et al. [1996] demonstrated using the decay of radar scatter above the Sura heating facility to estimate irregularity diffusion. A large database of radar backscatter from HAARP generated FAI has been collected over the years. Experiments often cycled the heater power on and off in a way that allowed estimates of the FAI decay rate. The database has been examined to extract decay time estimates and diffusion rates over a range of ionospheric conditions. This presentation will summarize the database and the estimated diffusion rates, and will discuss the potential for targeted experiments for aeronomy measurements. Hysell, D. L., M. C. Kelley, Y. M. Yampolski, V. S. Beley, A. V. Koloskov, P. V. Ponomarenko, and O. F. Tyrnov, HF radar observations of decaying artificial field aligned irregularities, J. Geophys. Res. , 101, 26,981, 1996.

  11. ILC beam energy measurement by means of laser Compton backscattering

    International Nuclear Information System (INIS)

    A novel, non-invasive method of measuring the beam energy at the International Linear Collider is proposed. Laser light collides head-on with beam particles and either the energy of the Compton scattered electrons near the kinematic end-point is measured or the positions of the Compton backscattered γ-rays, the edge electrons and the unscattered beam particles are recorded. A compact layout for the Compton spectrometer is suggested. It consists of a bending magnet and position sensitive detectors operating in a large radiation environment. Several options for high spatial resolution detectors are discussed. Simulation studies support the use of an infrared or green laser and quartz fiber detectors to monitor the backscattered photons and edge electrons. Employing a cavity monitor, the beam particle position downstream of the magnet can be recorded with submicrometer precision. Such a scheme provides a feasible and promising method to access the incident beam energy with precisions of 10-4 or better on a bunch-to-bunch basis while the electron and positron beams are in collision. (orig.)

  12. Classification of kidney and liver tissue using ultrasound backscatter data

    Science.gov (United States)

    Aalamifar, Fereshteh; Rivaz, Hassan; Cerrolaza, Juan J.; Jago, James; Safdar, Nabile; Boctor, Emad M.; Linguraru, Marius G.

    2015-03-01

    Ultrasound (US) tissue characterization provides valuable information for the initialization of automatic segmentation algorithms, and can further provide complementary information for diagnosis of pathologies. US tissue characterization is challenging due to the presence of various types of image artifacts and dependence on the sonographer's skills. One way of overcoming this challenge is by characterizing images based on the distribution of the backscatter data derived from the interaction between US waves and tissue. The goal of this work is to classify liver versus kidney tissue in 3D volumetric US data using the distribution of backscatter US data recovered from end-user displayed Bmode image available in clinical systems. To this end, we first propose the computation of a large set of features based on the homodyned-K distribution of the speckle as well as the correlation coefficients between small patches in 3D images. We then utilize the random forests framework to select the most important features for classification. Experiments on in-vivo 3D US data from nine pediatric patients with hydronephrosis showed an average accuracy of 94% for the classification of liver and kidney tissues showing a good potential of this work to assist in the classification and segmentation of abdominal soft tissue.

  13. Backscatter Matrix Observations by The GV-HSRL

    Science.gov (United States)

    Hayman, Matthew; Spuler, Scott; Morley, Bruce

    2016-06-01

    The GV-HSRL is a high spectral resolution lidar capable of measuring calibrated backscatter, extinction and circular depolarization from the ground or NSF Gulfstream V platform. In the spring of 2012, the instrument was modified to measure the full backscatter matrix of atmospheric scatterers. This modification enabled us to investigate the polarization properties of oriented particles and further understand where particles orient and how they may impact depolarization lidar data. Observations were performed from the ground at different times with the lidar's tilt angle at 4°, 22° and 32° degrees off zenith. This instrument found oriented ice crystals only produced observable polarization effects at the 32° lidar tilt angle. By contrast, a significant fraction of rain observations have oriented scattering matrices at all three lidar tilt angles. Thus conventional depolarization lidar is generally well suited for characterizing ice crystals but not liquid precipitation. Oriented ice crystals are most commonly investigated by looking for specular scatter from horizontally oriented plates. While this method offers excellent sensitivity to small populations of oriented plats, it has very little capability to determine the fraction of oriented plates if the population is larger than about 1%. We show here that observing f12 scattering matrix element at 32° off zenith may be more effective for estimating the oriented fraction of particles in a volume.

  14. Trace contamination measurements using heavy ion backscattering spectrometry

    International Nuclear Information System (INIS)

    Heavy Ion Backscattering Spectrometry (HIBS) is a tool for measuring surface contamination at levels much lower than previously achievable with ion beam analyses. Many areas of materials research and development require very low levels of impurities, with advanced microelectronics as the best example. HIBS uses low-energy, heavy ions for analysis, taking advantage of the increased backscattering yield which can be obtained from high Z ion beams at low energy. Background due to increased yield from the substrate is eliminated by a thin carbon foil as part of the detector, with a thickness chosen to range out ions scattered from the substrate and allow only ions scattered from impurities heavier than the substrate to reach the detector. The authors research system, using 150-200 keV N+ beams and a single time-of-flight detector optimized for large solid angle, has achieved a sensitivity ranging from ∼5xl010 atoms/cm2 for Fe to ∼1x109 atoms/cm2 for Au on Si, without preconcentration. A stand-alone HIBS prototype which the authors have developed for SEMATECH is expected to reach detection limits of ∼5x109 atoms/cm2 for Fe and ∼1x108 atoms/cm2 for Au on Si. In this paper they discuss in detail the factors which affect sensitivity for HIBS

  15. Study of sporadic-E clouds by backscatter radar

    Directory of Open Access Journals (Sweden)

    Z. Houminer

    Full Text Available It is shown that swept-frequency backscatter ionograms covering a range of azimuths can be used to study the dynamics of sporadic-E clouds. A simple technique based on analytic ray tracing can be used to simulate the observed narrow traces associated with Es patches. This enables the location and extent of the sporadic-E clouds to be determined. The motion of clouds can then be determined from a time sequence of records. In order to demonstrate the method, results are presented from an initial study of 5 days of backscatter ionograms from the Jindalee Stage B data base obtained during March-April 1990. Usually 2–3 clouds were observed each day, mainly during the evening and up to midnight. The clouds lasted from 1–4 h and extended between 30°–80° in azimuth and 150-800 km in range. The clouds were mostly stationary or drifted generally westward with velocities of up to 80 m s–1. Only one cloud was observed moving eastward.

  16. ILC beam energy measurement by means of laser Compton backscattering

    Energy Technology Data Exchange (ETDEWEB)

    Muchnoi, N. [Budker Inst. for Nuclear Physics, Novosibirsk (Russian Federation); Schreiber, H.J.; Viti, M. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

    2008-10-15

    A novel, non-invasive method of measuring the beam energy at the International Linear Collider is proposed. Laser light collides head-on with beam particles and either the energy of the Compton scattered electrons near the kinematic end-point is measured or the positions of the Compton backscattered {gamma}-rays, the edge electrons and the unscattered beam particles are recorded. A compact layout for the Compton spectrometer is suggested. It consists of a bending magnet and position sensitive detectors operating in a large radiation environment. Several options for high spatial resolution detectors are discussed. Simulation studies support the use of an infrared or green laser and quartz fiber detectors to monitor the backscattered photons and edge electrons. Employing a cavity monitor, the beam particle position downstream of the magnet can be recorded with submicrometer precision. Such a scheme provides a feasible and promising method to access the incident beam energy with precisions of 10{sup -4} or better on a bunch-to-bunch basis while the electron and positron beams are in collision. (orig.)

  17. Variation of backscatter as an indicator of boundary layer structure

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, M. [UMIST, Dept. of Chemical Engineering, Manchester (United Kingdom); Hunter, G.C. [National Power, Swindon (United Kingdom)

    1997-10-01

    In this work we have developed software to display cross-sections of the variance of backscatter over a given sampling period in addition to its absolute mean. We have analyzed a series of Lidar cross-sections of elevated plumes dispersing into a convective BL and have then derived profiles both of the mean backscatter, , as a function of height and of its relative, shot-to-shot, variation, {radical} /. The latter is a measure of the homogeneity of the aerosol. There is no cheap device for measuring BL depths so we were interested in comparing depths estimated using our Lidar with those predicted by the current ADMS atmospheric dispersion model. This is based on integrating an energy budget to predict the BL development and as such relies on values for the initial lapse rate and for the surface sensible heat flux. A major shortcoming of the model appears to be that, in the absence of measurements, it must assume a default value for the former; the latter may be estimated from surface measurements but is very sensitive to the assumed availability of surface moisture. (LN)

  18. Observations of 2D Doppler backscattering on MAST

    CERN Document Server

    Thomas, D A; Freethy, S J; Huang, B K; Shevchenko, V F; Vann, R G L

    2015-01-01

    The Synthetic Aperture Microwave Imaging (SAMI) diagnostic has conducted proof-of-principle 2D Doppler backscattering (DBS) experiments on MAST. SAMI actively probes the plasma edge using a wide (+-40 degrees vertical and horizontal) and tuneable (10-35.5 GHz) beam. The Doppler backscattered signal is digitised in vector form using an array of eight Vivaldi PCB antennas. This allows the receiving array to be focused in any direction within the field of view simultaneously to an angular range of 6-24 degrees FWHM at 10-34.5 GHz. This capability is unique to SAMI and is an entirely novel way of conducting DBS experiments. In this paper the feasibility of conducting 2D DBS experiments is explored. Initial measurements of phenomena observed on conventional DBS experiments are presented; such as momentum injection from neutral beams and an abrupt change in power and turbulence velocity coinciding with the onset of H-mode. In addition, being able to carry out 2D DBS imaging allows a measurement of magnetic pitch an...

  19. Neutron reflectometer

    International Nuclear Information System (INIS)

    The neutron reflectometer is the most powerful and nondestructive tool to analyze the surface and buried interfaces in the layered films. Such films often have a close relation to the functional devices. Structural information in the vicinity of the interfaces is a key parameter in the field of the nanoscale science. (author)

  20. Neutron radiography

    International Nuclear Information System (INIS)

    Principles of the method, complementarity with X or gamma rays, neutron energy, detection and applications on irradiated materials and for the industrial quality control are exposed. Examples of applications in pyrotechnics, plastics, fuels, lubricants, metallurgy are given. Techniques developed by the CEA for its own needs or for industry and description of facilities in the nuclear centers are reviewed

  1. Methods for absorbing neutrons

    Science.gov (United States)

    Guillen, Donna P.; Longhurst, Glen R.; Porter, Douglas L.; Parry, James R.

    2012-07-24

    A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

  2. Recent Advances in Neutron Physics

    Science.gov (United States)

    Feshbach, Herman; Sheldon, Eric

    1977-01-01

    Discusses new studies in neutron physics within the last decade, such as ultracold neutrons, neutron bottles, resonance behavior, subthreshold fission, doubly radiative capture, and neutron stars. (MLH)

  3. Neutron rich nuclei and neutron stars

    OpenAIRE

    Horowitz, C. J.

    2013-01-01

    The PREX experiment at Jefferson Laboratory measures the neutron radius of 208Pb with parity violating electron scattering in a way that is free from most strong interaction uncertainties. The 208Pb radius has important implications for neutron rich matter and the structure of neutron stars. We present first PREX results, describe future plans, and discuss a follow on measurement of the neutron radius of 48Ca. We review radio and X-ray observations of neutron star masses and radii. These cons...

  4. Development and characterization of two-component albedo based neutron individual monitoring system using thermoluminescent detectors

    International Nuclear Information System (INIS)

    A TLD-albedo based two-component neutron individual monitoring system was developed and characterized in this work. The monitor consists of a black plastic holder, an incident neutron boron loaded shield, a moderator polyethylene body (to increase its response), two pairs of TLD-600 and TLD-700 (one pair to each component) and an adjustable belt. This monitoring system was calibrated in thermal neutron fields and in 70 keV, 144 keV, 565 keV, 1.2 MeV and 5 MeV monoenergetic neutron fields. In addition, it was calibrated in 252Cf(D2O), 252Cf, 241Am-B, 241Am-Be and 238Pu-Be source fields. For the latter, the lower detection levels are, respectively, 0.009 mSv, 0.06 mSv, 0.12 mSv, 0.09 mSv and 0.08 mSv. The participation in an international intercomparison sponsored by IAEA with simulated workplace fields validated the system. The monitoring system was successfully characterized in the ISO 21909 standard and in an IRD - the Brazilian Institute for Radioprotection and Dosimetry - technical regulation draft. Nowadays, the neutron individual system is in use by IRD for whole body individual monitoring of five institutions, which comprehend several activities. (author)

  5. Test and validation of the iterative code for the neutrons spectrometry and dosimetry: NSDUAZ

    International Nuclear Information System (INIS)

    In this work was realized the test and validation of an iterative code for neutronic spectrometry known as Neutron Spectrometry and Dosimetry of the Universidad Autonoma de Zacatecas (NSDUAZ). This code was designed in a user graph interface, friendly and intuitive in the environment programming of LabVIEW using the iterative algorithm known as SPUNIT. The main characteristics of the program are: the automatic selection of the initial spectrum starting from the neutrons spectra catalog compiled by the International Atomic Energy Agency, the possibility to generate a report in HTML format that shows in graph and numeric way the neutrons flowing and calculates the ambient dose equivalent with base to this. To prove the designed code, the count rates of a spectrometer system of Bonner spheres were used with a detector of 6LiI(Eu) with 7 polyethylene spheres with diameter of 0, 2, 3, 5, 8, 10 and 12. The count rates measured with two neutron sources: 252Cf and 239PuBe were used to validate the code, the obtained results were compared against those obtained using the BUNKIUT code. We find that the reconstructed spectra present an error that is inside the limit reported in the literature that oscillates around 15%. Therefore, it was concluded that the designed code presents similar results to those techniques used at the present time. (Author)

  6. Individual neutron dosimetry by means of fission track detectors and albedo in the nuclear power plants

    International Nuclear Information System (INIS)

    A system based on fission fragment tracks has been developed for individual neutron dosimetry. The dosemeter detects both fast neutrons by means of the 232Th(n,f) reaction, and thermal and albedo neutrons by means of the 235U(n,f) reaction. The fission tracks produced in a plastic foil are chemically etched and counted by spark discharges. On the other hand two albedo dosimetric systems have been made operational. They are based on the detection, by thermoluminescence, of neutrons thermalized and backscattered by the wearer's body. The sensitivity of these individual dosemeters has been investigated in 36 different neutron fields: monoenergetic beams, reference fields near isotopic sources, radiation fields encountered in a variety of situations inside nuclear power plants. The results obtained have been compared to those computed by convolution of the neutron spectra with the energy response functions of the dosemeters. The whole set of data constitutes a consistent basis, prerequisite to the use of the systems for neutron individual dosimetry. In practical situations, it is essential to know the shape of the neutron spectrum, approximately at least, in order to perform an accurate dose evaluation. For that purpose, the neutron fields encountered inside nuclear power plants have been grouped into four categories, for which algorithms for dose evaluation have been developed. Concerning the neutron equivalent dose, the residual error associated to this approach does not exceed a factor of 2, which represents a significant improvement in the field of individual neutron dosimetry. (author) figs., tabs., 91 refs

  7. Substrate-mediated zero backscattering from dielectric metasurfaces

    CERN Document Server

    Petrov, Mihail; Baryshnikova, Kseniia; Belov, Pavel

    2015-01-01

    In this work, we study optical properties of all-dielectric metasurfaces on top of the high-index substrate. We show that matching the magnitudes and setting the {\\pi}-phase difference of the electric and magnetic dipole moments in nanoparticles, one can obtain a suppression of reflection from the substrate coated with metasurface. In contrast to homogeneous environment, where zero backscattering, or Kerker effect, is observed when electric and magnetic moments are in-phase, the blooming of the substrate occurs when the out-of-phase condition is satisfied, i.e. for the wavelength between the resonances of electric and magnetic dipole moments. We perform numerical simulations of spherical and disk nanoparticle arrays for different permittivities of the substrate, and confirm our model by numerically separating the contributions into the total reflection from nanoparticle arrays and bare substrate. The influence of high-index substrate is crucial for designing optical metasurfaces and photovoltaic elements with...

  8. Spectral characteristics of Compton backscattering sources. Linear and nonlinear modes

    International Nuclear Information System (INIS)

    Compton backscattering (CBS) of laser photons by relativistic electrons is widely used to design X-ray and gamma sources with a bandwidth better than 1% using a tight collimation. In order to obtain a reasonable intensity of the resulting beam one has to increase power of a laser pulse simultaneously with narrowing of the waist in the interaction point. It can lead to nonlinearity of CBS process which is affected on spectral characteristics of the collimated gamma beam (so-called “red-shift” of the spectral line, emission of “soft” photons with energy much less than the spectral line energy). In this paper we have analyzed such an influence using Monte-Carlo technique and have shown that even weak nonlinearity should be taken into account if the gamma beam is formed by a narrow aperture

  9. Back-scatter based whispering gallery mode sensing

    CERN Document Server

    Knittel, Joachim; McAuslan, David L; Brawley, George A; Bowen, Warwick P

    2013-01-01

    Whispering gallery mode biosensors allow selective unlabelled detection of single proteins and, combined with quantum limited sensitivity, the possibility for noninvasive realtime observation of motor molecule motion. However, to date technical noise sources, most particularly low frequency laser noise, have constrained such applications. Here we introduce a new technique for whispering gallery mode sensing based on direct detection of back-scattered light. This experimentally straightforward technique is immune to frequency noise in principle, and further, acts to suppress thermorefractive noise. We demonstrate 27 dB of frequency noise suppression, eliminating frequency noise as a source of sensitivity degradation and allowing an absolute frequency shift sensitivity of 76 kHz. Our results open a new pathway towards single molecule biophysics experiments and ultrasensitive biosensors.

  10. Backscatter absorption gas imaging systems and light sources therefore

    Science.gov (United States)

    Kulp, Thomas Jan; Kliner, Dahv A. V.; Sommers, Ricky; Goers, Uta-Barbara; Armstrong, Karla M.

    2006-12-19

    The location of gases that are not visible to the unaided human eye can be determined using tuned light sources that spectroscopically probe the gases and cameras that can provide images corresponding to the absorption of the gases. The present invention is a light source for a backscatter absorption gas imaging (BAGI) system, and a light source incorporating the light source, that can be used to remotely detect and produce images of "invisible" gases. The inventive light source has a light producing element, an optical amplifier, and an optical parametric oscillator to generate wavelength tunable light in the IR. By using a multi-mode light source and an amplifier that operates using 915 nm pump sources, the power consumption of the light source is reduced to a level that can be operated by batteries for long periods of time. In addition, the light source is tunable over the absorption bands of many hydrocarbons, making it useful for detecting hazardous gases.

  11. Automated determination of crystal orientations from electron backscattering patterns

    DEFF Research Database (Denmark)

    Lassen, Niels Christian Krieger

    1994-01-01

    pattern recognition procedure which enables 8 to 12 bands to be localized in typical EBSPs from a modern system. It will be described, how these automatically localized bands can be indexed and used for optimal estimation of the unknown crystal orientations. A necessary prerequisite for precise......The electron backscattering pattern (EBSP) technique is widely accepted as being an extremely powerful tool for measuring the crystallographic orientation of individual crystallites in polycrystalline materials. Procedures which allow crystal orientations to be calculated on the bases of the...... determination of crystallographic orientations from EBSPs is accurate knowledge of three calibration parameters which describe the position of the point from which the patterns are emitted relative to the phosphor screen on which they are recorded. This thesis will describe a novel method by which these...

  12. Electron backscatter diffraction: Strategies for reliable data acquisition and processing

    International Nuclear Information System (INIS)

    In electron backscatter diffraction (EBSD) software packages there are many user choices both in data acquisition and in data processing and display. In order to extract maximum scientific value from an inquiry, it is helpful to have some guidelines for best practice in conducting an EBSD investigation. The purpose of this article therefore is to address selected topics of EBSD practice, in a tutorial manner. The topics covered are a brief summary on the principles of EBSD, specimen preparation, calibration of an EBSD system, experiment design, speed of data acquisition, data clean-up, microstructure characterisation (including grain size) and grain boundary characterisation. This list is not meant to cover exhaustively all areas where EBSD is used, but rather to provide a resource consisting of some useful strategies for novice EBSD users.

  13. Spectral characteristics of Compton backscattering sources. Linear and nonlinear modes

    Science.gov (United States)

    Potylitsyn, A. P.; Kolchuzhkin, A. M.

    2015-07-01

    Compton backscattering (CBS) of laser photons by relativistic electrons is widely used to design X-ray and gamma sources with a bandwidth better than 1% using a tight collimation. In order to obtain a reasonable intensity of the resulting beam one has to increase power of a laser pulse simultaneously with narrowing of the waist in the interaction point. It can lead to nonlinearity of CBS process which is affected on spectral characteristics of the collimated gamma beam (so-called "red-shift" of the spectral line, emission of "soft" photons with energy much less than the spectral line energy). In this paper we have analyzed such an influence using Monte-Carlo technique and have shown that even weak nonlinearity should be taken into account if the gamma beam is formed by a narrow aperture.

  14. Results from the Daresbury Compton backscattering X-ray source

    Science.gov (United States)

    Laundy, D.; Priebe, G.; Jamison, S. P.; Graham, D. M.; Phillips, P. J.; Smith, S. L.; Saveliev, Y.; Vassilev, S.; Seddon, E. A.

    2012-10-01

    The Daresbury Compton Backscattering X-ray Source uses a high power Ti Sapphire laser interacting in head on geometry with electron bunches in the ALICE energy recovery linear accelerator. X-ray photons with peak energy of 21 keV were generated with the accelerator operating at an energy of 29.6 MeV. The spatial profile of the X-rays emitted near the electron beam axis was measured. The characteristics of the X-ray yield measured as a function of relative timing between the laser pulse and the interacting electron bunch was found to be consistent with the modelled intensity behaviour using measured electron and laser beam parameters.

  15. Compton Backscattering for the Calibration of KEDR Tagging System

    CERN Document Server

    Kaminskiy, V V; Zhilich, V N

    2014-01-01

    KEDR detector has the tagging system (TS) to study the gamma-gamma processes. To determine the two-photon invariant mass, the energies of the scattered at small angles electrons and positrons are measured by the magnetic spectrometer embedded into the lattice of the VEPP--4M collider. The energy resolution (scattered electron/positron energy resolution divided by the beam energy) of this spectrometer varies from 0.6% to 0.03% depending on the electron/positron energy. The Compton backscattering of laser radiation on the electron/positron beam is used for the accurate energy scale and resolution calibration of the tagging system. The report covers the design, recent results and current status of the KEDR TS calibration system.

  16. Compton backscattering for the calibration of KEDR tagging system

    Science.gov (United States)

    Kaminskiy, V. V.; Muchnoi, N. Yu; Zhilich, V. N.

    2014-08-01

    KEDR detector has the tagging system (TS) to study the gamma-gamma processes. To determine the two-photon invariant mass, the energies of the scattered at small angles electrons and positrons are measured by the magnetic spectrometer embedded into the lattice of the VEPP-4M collider. The energy resolution (scattered electron/positron energy resolution divided by the beam energy) of this spectrometer varies from 0.6% to 0.03% depending on the electron/positron energy. The Compton backscattering of laser radiation on the electron/positron beam is used for the accurate energy scale and resolution calibration of the tagging system. The report covers the design, recent results and current status of the KEDR TS calibration system.

  17. Results from the Daresbury Compton backscattering X-ray source

    International Nuclear Information System (INIS)

    The Daresbury Compton Backscattering X-ray Source uses a high power Ti Sapphire laser interacting in head on geometry with electron bunches in the ALICE energy recovery linear accelerator. X-ray photons with peak energy of 21 keV were generated with the accelerator operating at an energy of 29.6 MeV. The spatial profile of the X-rays emitted near the electron beam axis was measured. The characteristics of the X-ray yield measured as a function of relative timing between the laser pulse and the interacting electron bunch was found to be consistent with the modelled intensity behaviour using measured electron and laser beam parameters.

  18. Remote identification of a shipwreck site from MBES backscatter.

    Science.gov (United States)

    Masetti, Giuseppe; Calder, Brian

    2012-11-30

    The method described attempts to remotely identify the shape of an anthropogenic object, such as a wreck of a modern vessel, using reflectivity data from Multi-Beam Echosounder (MBES) systems. In the beam domain, the backscatter strength values - geometrically and radiometrically corrected - are used to extract a large number of Gray Level Co-occurrence Matrix (GLCM) features with different input parameters. Principal Component Analysis (PCA) is applied in order to achieve dimensionality reduction whilst a K-means algorithm clusters as "shipwreck site" a large number of beams for each line. After the geo-referencing process, a K-nearest-neighbors (K-NN) technique is applied as a filter for possible misclassifications. Finally, the shape of the shipwreck site is defined from the georeferenced beams using the α-shape method, constructing an output compatible with Geographic Information Systems (GIS). PMID:22820745

  19. Determination of RF source power in WPSN using modulated backscattering

    CERN Document Server

    Sreedhar, K

    2012-01-01

    A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. During RF transmission energy consumed by critically energy-constrained sensor nodes in a WSN is related to the life time system, but the life time of the system is inversely proportional to the energy consumed by sensor nodes. In that regard, modulated backscattering (MB) is a promising design choice, in which sensor nodes send their data just by switching their antenna impedance and reflecting the incident signal coming from an RF source. Hence wireless passive sensor networks (WPSN) designed to operate using MB do not have the lifetime constraints. In this we are going to investigate the system analytically. To obtain interference-free communication connectivity with the WPSN nodes number of RF sources is determined and analyzed i...

  20. Many-beam dynamical simulation of electron backscatter diffraction patterns.

    Science.gov (United States)

    Winkelmann, Aimo; Trager-Cowan, Carol; Sweeney, Francis; Day, Austin P; Parbrook, Peter

    2007-01-01

    We present an approach for the simulation of complete electron backscatter diffraction (EBSD) patterns where the relative intensity distributions in the patterns are accurately reproduced. The Bloch wave theory is applied to describe the electron diffraction process. For the simulation of experimental patterns with a large field of view, a large number of reflecting planes has to be taken into account. This is made possible by the Bethe perturbation of weak reflections. Very good agreement is obtained for simulated and experimental patterns of gallium nitride GaN{0001} at 20kV electron energy. Experimental features like zone-axis fine structure and higher-order Laue zone rings are accurately reproduced. We discuss the influence of the diffraction of the incident beam in our experiment. PMID:17126489

  1. Nondestructive testing of concrete by gamma backscattering method

    International Nuclear Information System (INIS)

    Nondestructive testing (NDT) methods are used to examine objects without destroying it. In many situations like working industrial plants and fluid transportation system, inspection of huge or thick sized objects by destructive methods are not desirable. The Compton backscattering of gamma rays, one of NDT techniques could be used for material characterization and detection of defects in materials easily. Concrete structures require testing after the concrete has hardened, to determine whether the structure is suitable for its designed use. There is a possibility of defects in the constructed buildings and structures, and therefore, defects like voids and cracks, if any, have to be evaluated for the purpose. Further, periodic testing of old buildings and structures to know their integrity has become a necessity. These types of testings can be conducted only by employing nondestructive techniques

  2. Diffuse Backscattering Mueller Matrices Patterns from Turbid Media

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lian-Shun; ZHU Chen; WANG Zhi-Ping; ZHANG Jing

    2006-01-01

    We present experimental measurements and theory of the diffusely backscattered Mueller matrix patterns that arise from illuminating a turbid medium with a polarized laser beam. Our technique employs polarized light from a He-Ne laser (λ= 632.8 nm) focused onto the surface of the scattering medium. A surface area of approximately 2×2 cm2 centred on the light input point is imaged through polarization analysis optics onto a CCD camera. The Mueller matrix is reconstructed by 49 intensity measurements with various orientations of polarizer and analyser. The measured Mueller matrix of polystyrene spheres is compared with the theory result of incoherent scattering of light by spheres. It shows that the azimuthal patterns of the Mueller matrix are determined by the symmetry of the turbid media and the shape of scattering particles. The result is further proved by experiments with polystyrene spheres of different concentrations in de-ionized water.

  3. Neutron dosimetry

    International Nuclear Information System (INIS)

    It is the object of the present invention to provide a method of measuring neutron radiation which eliminates the use of powders as dosimeter target materials and reduces the requirement for repetitive weighing of dosimeters, for expensive radioisotopes as dosimeter target material, and for dosimeter housings (in many cases). The invention described is a method of measuring neutron radiation within a nuclear reactor consisting of placing one or more extruded sintered oxide wires comprising a dosimeter target oxide within the reactor and measuring the radioactivity induced in the wires by neutron radiation. These oxide wires consist of a dilution containing at least 0.1% by weight of the dosimeter target oxide in a diluent oxide. The diluent oxide is selected from a group consisting of Al2O3 and BeO. Almost any metal oxide may be used as a target oxide. The wires may be encapsulated within a co-extruded housing. These mixed oxide wires have been found to be sufficiently uniform for quantitative analyses. (JTA)

  4. Neutron scattering

    International Nuclear Information System (INIS)

    The annual report on hand gives an overview of the research work carried out in the Laboratory for Neutron Scattering (LNS) of the ETH Zuerich in 1990. Using the method of neutron scattering, it is possible to examine in detail the static and dynamic properties of the condensed material. In accordance with the multidisciplined character of the method, the LNS has for years maintained a system of intensive co-operation with numerous institutes in the areas of biology, chemistry, solid-state physics, crystallography and materials research. In 1990 over 100 scientists from more than 40 research groups both at home and abroad took part in the experiments. It was again a pleasure to see the number of graduate students present, who were studying for a doctorate and who could be introduced into the neutron scattering during their stay at the LNS and thus were in the position to touch on central ways of looking at a problem in their dissertation using this modern experimental method of solid-state research. In addition to the numerous and interesting ways of formulating the questions to explain the structure, nowadays the scientific programme increasingly includes particularly topical studies in connection with high temperature-supraconductors and materials research

  5. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    The following topics are dealt with: Neutron scattering in contemporary research, neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  6. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    The following topics are dealt with: Neutron sources, symmetry of crystals, nanostructures investigated by small-angle neutron scattering, structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic neutron scattering, strongly correlated electrons, polymer dynamics, applications of neutron scattering. (HSI)

  7. Compton backscattering of intracavity storage ring free-electron laser radiation

    International Nuclear Information System (INIS)

    We discuss the γ- ray production by Compton backscattering of intracavity S.R. FEL radiation. We use a semi-analytical model which provides the build up of the signal combined with the storage ring damping mechanism and derive simple relations yielding the connection between backscattered photons brightness and the intercavity laser equilibrium intensity

  8. Effect of the cortex on ultrasonic backscatter measurements of cancellous bone

    International Nuclear Information System (INIS)

    Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8-3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term 'apparent' means that the parameters are sensitive to the frequency-dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions.

  9. Stratospheric backscatter, extinction, and lidar ratio profiling after the Mt. Pinatubo eruptions

    International Nuclear Information System (INIS)

    Since August 1991 the stratospheric aerosol layer is continuously monitored with a combination Raman elastic-backscatter lidar, groundbased systems. XeCl excimer laser is used as the radiation source. Signals elastically backscattered from air molecules and particles and inelastically Raman backscattered from nitrogen molecules are detected. The measurements of these two signal profiles up to 35 km height allows the separate and independent determination of aerosol extinction and backscatter properties in the perturbed lower stratosphere. The extinction coefficient is derived from the nitrogen Raman signal profile, while the backscatter coefficient is obtained from the elastic-to-inelastic backscatter signal ratio. In this way, also the extinction-to-backscatter, or lidar, ratio profile is determined. For the first time, lidar ratios are determined in the perturbed stratospheric layer by the use of remote sensing only. The lidar ratio contains information about the size range of the stratospheric particles which are assumed to be sulfuric acid droplets, and it is needed in the calculation of aerosol optical properties from data taken with a typical backscatter lidar

  10. Identification of major backscattering sources in trees and shrubs at 10 GHz

    Science.gov (United States)

    Zoughi, R.; Wu, L. K.; Moore, R. K.

    1986-01-01

    A short-range very-fine-resolution FM-CW radar scatterometer has been used to identify the primary contributors to 10-GHz radar backscatter from pine, pin oak, American sycamore and sugar maple trees, and from creeping juniper shrubs. This system provided a range resolution of 11 cm and gave a 16-cm diameter illumination area at the target range of about 4 m. For a pine tree, the needles caused the strongest backscatter as well as the strongest attenuation in the radar signal. Cones, although insignificant contributors to the total backscatter, were more important for backscattering than for attenuation. For the rest of the trees, leaves were the strongest cause of backscattering and attenuation. However, in the absence of leaves, the petioles, small twigs, and branches gave relatively strong backscatter. For American sycamore and sugar maple trees, the fruits did not affect the total backscatter unless they were packed in clusters. For creeping juniper the backscattered energy and attenuation in the radar signal were mainly due to the top two layers of the evergreen scales. The contribution of the tree trunks was not determined.

  11. The Low Backscattering Targets Classification in Urban Areas

    Science.gov (United States)

    Shi, L.

    2012-07-01

    The Polarimetric and Interferometric Synthetic Aperture Radar (POLINSAR) is widely used in urban area nowadays. Because of the physical and geometric sensitivity, the POLINSAR is suitable for the city classification, power-lines detection, building extraction, etc. As the new X-band POLINSAR radar, the china prototype airborne system, XSAR works with high spatial resolution in azimuth (0.1 m) and slant range (0.4 m). In land applications, SAR image classification is a useful tool to distinguish the interesting area and obtain the target information. The bare soil, the cement road, the water and the building shadow are common scenes in the urban area. As it always exists low backscattering sign objects (LBO) with the similar scattering mechanism (all odd bounce except for shadow) in the XSAR images, classes are usually confused in Wishart-H-Alpha and Freeman-Durden methods. It is very hard to distinguish those targets only using the general information. To overcome the shortage, this paper explores an improved algorithm for LBO refined classification based on the Pre-Classification in urban areas. Firstly, the Pre-Classification is applied in the polarimetric datum and the mixture class is marked which contains LBO. Then, the polarimetric covariance matrix C3 is re-estimated on the Pre-Classification results to get more reliable results. Finally, the occurrence space which combining the entropy and the phase-diff standard deviation between HH and VV channel is used to refine the Pre-Classification results. The XSAR airborne experiments show the improved method is potential to distinguish the mixture classes in the low backscattering objects.

  12. THE LOW BACKSCATTERING TARGETS CLASSIFICATION IN URBAN AREAS

    Directory of Open Access Journals (Sweden)

    L. Shi

    2012-07-01

    Full Text Available The Polarimetric and Interferometric Synthetic Aperture Radar (POLINSAR is widely used in urban area nowadays. Because of the physical and geometric sensitivity, the POLINSAR is suitable for the city classification, power-lines detection, building extraction, etc. As the new X-band POLINSAR radar, the china prototype airborne system, XSAR works with high spatial resolution in azimuth (0.1 m and slant range (0.4 m. In land applications, SAR image classification is a useful tool to distinguish the interesting area and obtain the target information. The bare soil, the cement road, the water and the building shadow are common scenes in the urban area. As it always exists low backscattering sign objects (LBO with the similar scattering mechanism (all odd bounce except for shadow in the XSAR images, classes are usually confused in Wishart-H-Alpha and Freeman-Durden methods. It is very hard to distinguish those targets only using the general information. To overcome the shortage, this paper explores an improved algorithm for LBO refined classification based on the Pre-Classification in urban areas. Firstly, the Pre-Classification is applied in the polarimetric datum and the mixture class is marked which contains LBO. Then, the polarimetric covariance matrix C3 is re-estimated on the Pre-Classification results to get more reliable results. Finally, the occurrence space which combining the entropy and the phase-diff standard deviation between HH and VV channel is used to refine the Pre-Classification results. The XSAR airborne experiments show the improved method is potential to distinguish the mixture classes in the low backscattering objects.

  13. Feasibility of using backscattered muons for archeological imaging

    Science.gov (United States)

    Bonal, N.; Preston, L. A.

    2013-12-01

    Use of nondestructive methods to accurately locate and characterize underground objects such as rooms and tools found at archeological sites is ideal to preserve these historic sites. High-energy cosmic ray muons are very sensitive to density variation and have been used to image volcanoes and archeological sites such as the Egyptian and Mayan pyramids. Muons are subatomic particles produced in the upper atmosphere that penetrate the earth's crust up to few kilometers. Their absorption rate depends on the density of the materials through which they pass. Measurements of muon flux rate at differing directions provide density variations of the materials between the muon source (cosmic rays and neutrino interactions) and the detector, much like a CAT scan. Currently, muon tomography can resolve features to the sub-meter scale making it useful for this type of work. However, the muon detector must be placed below the target of interest. For imaging volcanoes, the upper portion is imaged when the detector is placed on the earth's surface at the volcano's base. For sites of interest beneath the ground surface, the muon detector would need to be placed below the site in a tunnel or borehole. Placing the detector underground can be costly and may disturb the historical site. We will assess the feasibility of imaging the subsurface using upward traveling muons, to eliminate the current constraint of positioning the detector below the target. This work consists of three parts 1) determine the backscattered flux rate from theory, 2) distinguish backscattered from forward scattered muons at the detector, and 3) validate the theoretical results with field experimentation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  14. Statistics of vertical backscatter profile of cirrus clouds

    Directory of Open Access Journals (Sweden)

    P. Veglio

    2011-09-01

    Full Text Available A nearly global statistical analysis of vertical backscatter and extinction profiles of cirrus clouds collected by the CALIOP lidar, on-board of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, is presented.

    Statistics on frequency of occurrence and distributions of bulk properties of cirrus clouds in general and, for the first time, of horizontally homogeneous (on a 5-km field of view cirrus clouds only are provided. Annual and seasonal backscatter profiles (BSP are computed for the horizontally homogeneous cirri. Differences found in the day/night cases and for midlatitudes and tropics are studied in terms of the mean physical parameters of the clouds from which they are derived.

    The relation between cloud physical parameters (optical depth, geometrical thickness and temperature and the shape of the BSP is investigated. It is found that cloud geometrical thickness is the main parameter affecting the shape of the mean CALIOP BSP. Specifically, cirrus clouds with small geometrical thicknesses show a maximum in mean BSP curve placed near cloud top. As the cloud geometrical thickness increases the BSP maximum shifts towards cloud base. Cloud optical depth and temperature have smaller effect on the shape of the CALIOP BSPs. In general a slight increase in the BSP maximum is observed as cloud temperature and optical depth increase.

    In order to fit mean BSPs, as functions of geometrical thickness and position within the cloud layer, polynomial functions are provided. The impact on satellite radiative transfer simulations in the infrared spectrum when using either a constant ice-content (IWC along the cloud vertical dimension or an IWC profile derived from the BSP fitting functions is evaluated. It is, in fact, demonstrated that, under realistic hypotheses, the mean BSP is linearly proportional to the IWC profile.

  15. HF radar observations of ionospheric backscatter during geomagnetically quiet periods

    Science.gov (United States)

    Kane, T. A.; Makarevich, R. A.; Devlin, J. C.

    2012-01-01

    The quiet-time coherent backscatter from the F-region observed by the Tasman International Geospace Environment Radar (TIGER) Bruny Island HF radar is analysed statistically in order to determine typical trends and controlling factors in the ionospheric echo occurrence. A comparison of the F-region peak density values from the IRI-2007 model and ionosonde measurements in the vicinity of the radar's footprint shows a very good agreement, particularly at subauroral and auroral latitudes, and model densities within the radar's footprint are used in the following analyses. The occurrence of F-region backscatter is shown to exhibit distinct diurnal, seasonal and solar cycle variations and these are compared with model trends in the F-region peak electron density and Pedersen conductance of the underlying ionosphere. The solar cycle effects in occurrence are demonstrated to be strong and more complex than a simple proportionality on a year-to-year basis. The diurnal and seasonal effects are strongly coupled to each other, with diurnal trends exhibiting a systematic gradual variation from month to month that can be explained when both electron density and conductance trends are considered. During the night, the echo occurrence is suggested to be controlled directly by the density conditions, with a direct proportionality observed between the occurrence and peak electron density. During the day, the echo occurrence appears to be controlled by both conductance and propagation conditions. It is shown that the range of echo occurrence values is smaller for larger conductances and that the electron density determines what value the echo occurrence takes in that range. These results suggest that the irregularity production rates are significantly reduced by the highly conducting E layer during the day while F-region density effects dominate during the night.

  16. HF radar observations of ionospheric backscatter during geomagnetically quiet periods

    Directory of Open Access Journals (Sweden)

    T. A. Kane

    2012-01-01

    Full Text Available The quiet-time coherent backscatter from the F-region observed by the Tasman International Geospace Environment Radar (TIGER Bruny Island HF radar is analysed statistically in order to determine typical trends and controlling factors in the ionospheric echo occurrence. A comparison of the F-region peak density values from the IRI-2007 model and ionosonde measurements in the vicinity of the radar's footprint shows a very good agreement, particularly at subauroral and auroral latitudes, and model densities within the radar's footprint are used in the following analyses. The occurrence of F-region backscatter is shown to exhibit distinct diurnal, seasonal and solar cycle variations and these are compared with model trends in the F-region peak electron density and Pedersen conductance of the underlying ionosphere. The solar cycle effects in occurrence are demonstrated to be strong and more complex than a simple proportionality on a year-to-year basis. The diurnal and seasonal effects are strongly coupled to each other, with diurnal trends exhibiting a systematic gradual variation from month to month that can be explained when both electron density and conductance trends are considered. During the night, the echo occurrence is suggested to be controlled directly by the density conditions, with a direct proportionality observed between the occurrence and peak electron density. During the day, the echo occurrence appears to be controlled by both conductance and propagation conditions. It is shown that the range of echo occurrence values is smaller for larger conductances and that the electron density determines what value the echo occurrence takes in that range. These results suggest that the irregularity production rates are significantly reduced by the highly conducting E layer during the day while F-region density effects dominate during the night.

  17. The feasibility of in vivo quantification of bone-gadolinium in humans by prompt gamma neutron activation analysis (PGNAA) following gadolinium-based contrast-enhanced MRI

    Science.gov (United States)

    Mostafaei, F.; McNeill, F. E.; Chettle, D. R.; Noseworthy, M. D.; Prestwich, W. V.

    2015-11-01

    The feasibility of using a 238Pu/Be-based in vivo prompt γ-ray neutron activation analysis (IVNAA) system, previously successfully used for measurements of muscle, for the detection of gadolinium (Gd) in bone was presented. Gd is extensively used in contrast agents in MR imaging. We present phantom measurement data for the measurement of Gd in the tibia. Gd has seven naturally occurring isotopes, of which two have extremely large neutron capture cross sections; 155Gd (14.8% natural abundance (NA), σ= 60,900 barns) and 157Gd (15.65% NA, σ= 254,000 barns). Our previous work focused on muscle but this only informs about the short term kinetics of Gd. We studied the possibility of measuring bone, as it may be a long term storage site for Gd. A human simulating bone phantom set was developed. The phantoms were doped with seven concentrations of Gd of concentrations 0.0, 25, 50, 75, 100, 120 and 150 ppm. Additional elements important for neutron activation analysis, Na, Cl and Ca, were also included to create an overall elemental composition consistent with Reference Man. The overall conclusion is that the potential application of this Pu-Be-based prompt in vivo NAA for the monitoring of the storage and retention of Gd in bone is not feasible.

  18. SUAK, a Fast Subcritical Facility for Pulsed Neutron Measurements

    International Nuclear Information System (INIS)

    SUAK is a small unreflected unmoderated assembly fuelled with 20% enriched uranium. The fuel is in the form of thin plates of 2 in x 2 in x 1/B in which are held in square tubes. The tubes are closely packed together, so that assemblies of different size and composition can be realized. The maximum size is a cube of about 35-cm side length. The maximum value of keff is 0.90. To reduce the backscattering of neutrons the assembly is located in the centre of a thin-walled building surrounded at a distance of 25 m by a wall for radiation protection. The control room is embedded in this wall. With a 200-keV pulsed neutron generator, measurements of the prompt neutron decay with different detectors and measurements of spectra by the time-of-flight technique are performed. A description of the assembly is given. First preliminary results are presented and compared with calculations. (author)

  19. Profiling of back-scattered electrons in opposed magnetic field of a Twin Electron Beam Gun

    International Nuclear Information System (INIS)

    Electron gun is extensively used in material processing, physical vapour deposition and atomic vapour based laser processes. In these processes where the electron beam is incident on the substrate, a significant fraction of electron beam gets back-scattered from the target surface. The trajectory of this back scattered electron beam depends on the magnetic field in the vicinity. The fraction of back-scattered depends on the atomic number of the target metal and can be as high as ∼40% of the incident beam current. These back-scattered electrons can cause undesired hot spots and also affect the overall process. Hence, the study of the trajectory of these back-scattered electrons is important. This paper provides the details of experimentally mapped back-scattered electrons of a 2×20kW Twin Electron Beam Gun (TEBG) in opposed magnetic field i.e. with these guns placed at 180° to each other.

  20. Neutron reference spectra measurements with the Bonner multi-spheres spectrometer; Medidas de espectros de referencia de neutrons com o espectrometro de multiesferas de Bonner

    Energy Technology Data Exchange (ETDEWEB)

    Lemos Junior, Roberto Mendonca de

    2004-07-01

    This paper aims to define a procedure to use the Bonner Multisphere Spectrometer with a {sup 6}LiI(Eu) detector in order to determine of neutron spectra. It was measured {sup 238}PuBe spectra and same of reference ({sup 241}AmBe, {sup 252}Cf e {sup 252}Cf+D{sub 2}O) published in ISO 8529-1 (2001) Norm. The data were processed by a computer program (BUNKI), which presents the results in neutrons energy fluency. Each input parameter of the program was studied in order to establish their influence in the adjustment result. The environment dose equivalent rate obtained placing the detector 1 m from the {sup 241}AmBe source was 122 {+-} 4 {mu}Sv/h with 7% of uncertainty and 95% of confidence level. The procedure established in this work was tested with the {sup 238}PuBe spectrum, obtaining an environment dose equivalent rate of 286 {+-} 9 {mu}Sv/h, 8% lower than the value measured experimentally used as reference. Through this procedure will be possible to measure neutron spectra in different work places where neutrons sources are used. Knowing these spectra, it will be possible to evaluate which area monitors, are more suitable, as well as, to study better the response of individual neutron monitors, as for instance, to obtain a conversion coefficient more appropriate to the albedo dosimeter used in different work places. As the measurements need a long time to be accomplished, the work optimization is fundamental to reduce the exposing time of the Bonner spectrometer operator. For this reason, an important parameter examined in this paper was the possibility of reducing the number of spheres used during the measurement without changing the final result. Considering the radiation protection standards, this parameter has a huge importance when the measurements are performed in work places where the neutron fluency and gamma rate offer risks to the operator's health, as for instance, in nuclear centrals. Studying this parameter, it was possible to conclude that

  1. The relationship between VHF radar auroral backscatter amplitude and Doppler velocity: a statistical study

    Directory of Open Access Journals (Sweden)

    B. A. Shand

    Full Text Available A statistical investigation of the relationship between VHF radar auroral backscatter intensity and Doppler velocity has been undertaken with data collected from 8 years operation of the Wick site of the Sweden And Britain Radar-auroral Experiment (SABRE. The results indicate three different regimes within the statistical data set; firstly, for Doppler velocities <200 m s–1, the backscatter intensity (measured in decibels remains relatively constant. Secondly, a linear relationship is observed between the backscatter intensity (in decibels and Doppler velocity for velocities between 200 m s–1 and 700 m s–1. At velocities greater than 700 m s–1 the backscatter intensity saturates at a maximum value as the Doppler velocity increases. There are three possible geophysical mechanisms for the saturation in the backscatter intensity at high phase speeds: a saturation in the irregularity turbulence level, a maximisation of the scattering volume, and a modification of the local ambient electron density. There is also a difference in the dependence of the backscatter intensity on Doppler velocity for the flow towards and away from the radar. The results for flow towards the radar exhibit a consistent relationship between backscatter intensity and measured velocities throughout the solar cycle. For flow away from the radar, however, the relationship between backscatter intensity and Doppler velocity varies during the solar cycle. The geometry of the SABRE system ensures that flow towards the radar is predominantly associated with the eastward electrojet, and flow away is associated with the westward electrojet. The difference in the backscatter intensity variation as a function of Doppler velocity is attributed to asymmetries between the eastward and westward electrojets and the geophysical parameters controlling the backscatter amplitude.

  2. Spallation Neutron Source (SNS)

    Data.gov (United States)

    Federal Laboratory Consortium — The SNS at Oak Ridge National Laboratory is a next-generation spallation neutron source for neutron scattering that is currently the most powerful neutron source in...

  3. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  4. REFRACTIVE NEUTRON LENS

    OpenAIRE

    Petrov, P. V.; Kolchevsky, N.N.

    2013-01-01

    Compound concave refractive lenses are used for focusing neutron beam. Investigations of spectral and focusing properties of a refractive neutron lens are presented. Resolution of the imaging system on the base of refractive neutron lenses depends on material properties and parameters of neutron source. Model of refractive neutron lens are proposed. Results of calculation diffraction resolution and focal depth of refractive neutron lens are discussed.

  5. Neutron Capture Nucleosynthesis

    OpenAIRE

    Kiss, Miklos

    2016-01-01

    Heavy elements (beyond iron) are formed in neutron capture nucleosynthesis processes. We have proposed a simple unified model to investigate the neutron capture nucleosynthesis in arbitrary neutron density environment. We have also investigated what neutron density is required to reproduce the measured abundance of nuclei assuming equilibrium processes. We found both of these that the medium neutron density has a particularly important role at neutron capture nucleosynthesis. About these resu...

  6. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  7. Neutron sources for in-situ planetary science applications

    Energy Technology Data Exchange (ETDEWEB)

    Skidmore, M.S. [Space Research Centre, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom)], E-mail: mss16@star.le.ac.uk; Ambrosi, R.M.; O' Brien, R.C. [Space Research Centre, Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom)

    2009-09-21

    There are a number of future European Space Agency (ESA) and NASA planetary science missions that are in the planning or initial study phases, where the scientific objectives include determining the surface composition, measuring planetary surface heat flow and constraining planetary chronology. University of Leicester is developing instrumentation for geophysical applications that include {gamma}-ray spectroscopy, {gamma}-ray densitometry and radiometric dating. This paper describes the modelling of a geophysical package, with the Monte Carlo code MCNPX, in order to determine the impact that a neutron source would have on in-situ composition measurements, radiometric dating and, in particular, trace element detection. The suitability of o 2.54x2.54 cm LaBr{sub 3}(Ce) detectors in the geophysical package for in-situ missions was examined. {sup 252}Cf, Am-Be and Pu-Be neutron sources were compared in a trade-off study to determine mission suitability, potential for thermal and electric power production, mass and shielding requirements. This study is linked to a parallel examination of the suitability of radioisotope thermal generators for in-situ planetary science applications. The aim of the modelling was to optimise the source type and detector geometry in order to measure the elemental peaks of interest with a precision of 10% or better based on the Poisson statistics of the detected counts above background.

  8. A new approach to neutron spectrum unfolding by differentiation

    International Nuclear Information System (INIS)

    A review of previous results in unfolding continuous neutron spectra measured by the recoil-proton method and registered with organic scintillators is presented. Mathematical and numerical aspects of the approach proposed are then discussed. A central element of the method developed is the use of numerically built orthonormal polynomials which account for the optimum condition of matrices involved. Moreover, specific properties of such polynomials lead to a natural and numerically stable way of differentiating both the spectra processed and the auxiliary functions needed, e.g. the light-output function for protons. To further improve the quality of fit, suitable functional transforms are applied. Special attention is also paid to the representation of the spectrometer transfer function and to its energy calibration. Both model and real spectra unfolded are discussed and a comparison with the output of existing programs is carried out. Spectra dealt with include quasi-monoenergetic neutrons, ramp-up, ramp-down, T(d, n)4He and Pu-Be sources. (orig.)

  9. Inelastic neutron scattering method in hard coal quality monitoring

    International Nuclear Information System (INIS)

    Nuclear methods in mining industry and power generation plants are nowadays very important especially because of the need for optimization of combustion processes and reduction of environmental pollution. On-line analysis of coal quality not only economic benefits but contribute to environmental protection too. Neutron methods especially inelastic scattering and PGNAA are very useful for analysis of coal quality where calorific valve, ash and moisture content are the most important. Using Pu-Be or Am-Be isotopic sources and measuring carbon 4.43 MeV γ-rays from neutron inelastic scattering: 12C(n,n'γ)12C we can evaluate calorific valve in hard coals with precision better than in PGNAA method. This is mainly because of large cross-section for inelastic scattering and the strong correlation between carbon content and calorific value shown in the paper for different coal basins. The influence of moisture on 4.43 MeV carbon γ-rays in considered in the paper in theoretical and experimental aspects and appropriate formula is introduced. Also the possibilities of determine ash, moisture, Cl, Na and Si in coal are shown. (author). 11 refs, 15 figs

  10. Neutron Therapy Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Neutron Therapy Facility provides a moderate intensity, broad energy spectrum neutron beam that can be used for short term irradiations for radiobiology (cells)...

  11. Choice of detectors for in vivo elemental analysis by counting natural and neutron-induced gamma rays for medical applications

    International Nuclear Information System (INIS)

    Body fat is measured by detecting C and O in vivo through fast neutron inelastic scattering. A sealed D-T neutron generator is used for the pulsed (4-10 kHz) production of fast neutrons. Carbon and oxygen are detected by counting the 4.44 and 6.13 MeV gamma rays resulting from the inelastic scattering of the fast neutrons from 12C and 16O. Large Bi4Ge3O12 (BGO) crystal detectors (127x76 mm) are used for the gamma ray detection during the 10 μs neutron burst. BGO detectors improved the signal to background ratio for the carbon detection by a factor of six compared to 152x152 mm NaI (Tl) detectors. Exposure to scattered neutrons did not affect the gain stability of the BGOs. Thermal neutrons from a moderated 238Pu-Be source are used for the measurement of total body nitrogen (and thus protein). The resulting high energy prompt gamma rays from nitrogen (10.83 MeV) are detected simultaneously with the irradiation. BGO detectors have superior stability operating in an environment of variable neutron exposure and high counting rates. However, the presence of neutrons creates a 10.2 MeV gamma ray peak from 73Ge in the BGO detector which interferes with the nitrogen peak. Whole body gamma ray counters, consisting of NaI(Tl) crystal detectors in a shielded room, are used to measure the natural radioactivity of the body due to 40K. They are also used to measure body Ca, P, Na and Cl, following total body exposure to thermal neutrons. ((orig.))

  12. Impact of diurnal variation in vegetation water content on radar backscatter of maize during water stress

    Science.gov (United States)

    van Emmerik, Tim; Steele-Dunne, Susan; Judge, Jasmeet; van de Giesen, Nick

    2014-05-01

    Microwave emission and backscatter of vegetated surfaces are influenced by vegetation water content (VWC), which varies in response to availability of soil moisture in the root zone. Understanding the influence of diurnal VWC dynamics on radar backscatter will improve soil moisture retrievals using microwave remote sensing, and will provide insight into the potential use for radar to directly monitor vegetation water status. The goal of this research is to investigate the effect of diurnal variation in VWC of an agricultural canopy on backscatter for different radar configurations. Water stress was induced in a corn (Zea mays) canopy near Citra, Florida, between September 1 and October 20, 2013. Diurnal destructive samples from the canopy were collected to determine leaf, stalk and total VWC. Water stress was quantified by calculating the evaporation deficit and measuring the soil water tension. The water-cloud model was used to model the influence of VWC and soil moisture variations on backscatter for a range of frequencies, polarizations and incidence angles. Furthermore, radar backscatter time series was simulated to show the effect of water stress on the diurnal variation in backscatter due to VWC. Results of this study show the very significant effects that VWC dynamics have on radar backscatter. We also highlight the potential for vegetation and soil water status monitoring using microwave remote sensing.

  13. Conditions for observation of the enhanced backscattering phenomenon in a turbulent atmosphere

    Science.gov (United States)

    Chrzanowski, Janusz; Kirkiewicz, Jozef; Kravtsov, Yuri A.

    2003-11-01

    Influence of enhanced backscattering effect on laser measurements of dust and aerosols content in a turbulent atmosphere is discussed. It is shown that doubling of the backscattered light intensity, characteristic for enhanced backscattering, leads to overestimating dust content in the air. To avoid undesirable effect of overestimation, it is recommended to displace receiving aperture sidewise relatively to laser source. Other method to eliminate overestimation is to use wider laser beam and extended receiving aperture as compared to coherence radius of the scattered wave field.

  14. Backscatter amplification effect for a reflected partially coherent Gaussian beam in turbulent medium

    Science.gov (United States)

    Xiang, Ning-Jing; Wu, Zhen-Sen; Guo, Qiu-Fen; Wang, Ming-Jun

    2015-09-01

    The extended Huygens-Fresnel principle is used to develop a formulation for the backscattered intensity enhancement of a Gaussian Schell-model source beam through a weak turbulence. The results are shown that backscattered intensity enhancement factor of the reflected GSM beam is concerned with the coherence length of source, the wavelength, the size of target and wave structure function. In addition, the closed-form expressions can interpret backscattered intensity enhancement of plane and spherical wave scattered from a diffuse target. The results are illustrated by examples and compared with the previous work.

  15. The Monte Carlo calculation of gamma-ray backscattering from various materials

    International Nuclear Information System (INIS)

    The question is discussed of gamma backscattering on different materials. For coaxial geometry with a point source placed next to the material surface, using the Monte Carlo method the number of backscattered photons in variation with atomic number Z of the scatterer is calculated. A multiple scattering calculation is performed for 60Co and 137Cs. The obtained results are plotted in graphs showing the minima in each period of the periodic system, this for gases. For other elements the number of backscattered photons is dependent on the atomic number Z, primary gamma radiation energy, density, and the geometry of the experiment. (author)

  16. Suppressing Rayleigh backscatter and code noise from all-fiber digital interferometers.

    Science.gov (United States)

    Ngo, Silvie; Shaddock, Daniel A; McRae, Terry G; Lam, Timothy T-Y; Chow, Jong H; Gray, Malcolm B

    2016-01-01

    We configure an all-fiber digital interferometer to eliminate both code noise and Rayleigh backscatter noise from bidirectional measurements. We utilize a sawtooth phase ramp to upconvert code noise beyond our signal bandwidth, demonstrating an in-band noise reduction of approximately two orders of magnitude. In addition, we demonstrate, for the first time to our knowledge, the use of relative code delays within a digital-interferometer system to eliminate Rayleigh-backscatter noise, resulting in a noise reduction of a factor of 50. Finally, we identify double Rayleigh-backscatter noise as our limiting noise source and suggest two methods to minimize this noise source. PMID:26696164

  17. Generation and Investigation of Backscatter Mosaics using TerraSAR-X Data

    OpenAIRE

    Rizzoli, Paola; Bräutigam, Benjamin; Wollstadt, Steffen; Mittermayer, Josef

    2010-01-01

    Global backscatter data is required for accurate performance estimation and instrument commanding inside the TerraSAR-X and TanDEM-X missions. The goal of this work is the generation of an X-Band backscatter map by assembling images acquired by the TSX satellite. The complete data ground coverage will be achievable with TanDEM-X mission data. An interpolator, that allows the estimation of the on ground backscatter for any required polarization and incidence angle from the available data, has ...

  18. Neutron control by inorganic scintillators for detection systems of fissionable radioactive substances

    International Nuclear Information System (INIS)

    Full text : Comparative measurements and analysis of detection efficiency of fast neutrons from 239 Pu-Be source have been carried out in a broad energy range En ≅ 0.1 * 10 MeV using oxide scintillators Bi4Ge3O12, Gd2SiO5, CdWO4, ZnWO4, ZnSe (Te,O), as well as 6 LiI (Eu). Detection efficiency of fast neutrons by heavy oxide scintillators was found to be very high (≅ 40-50 percent). The neutron inelastic scattering reaction is considered as the most probable interaction mechanism of neutrons with nuclei of heavy oxide scintillators. It is concluded that heavy oxide scintillators, which are at the same time efficient gamma-detectors, allow creation of a highly efficient gamma-neutron detector ensuring high detection efficiency of fissionable radioactive substances. Experimental results obtained in this work confirm the correlation between large gamma-quanta excitation cross-sections in reaction and cross-sections of inelastic scattering of fast neutrons. These results show a possibility of obtaining high efficiency (up to ≅ 50-60 percent) of detection of fast neutrons by heavy oxide scintillators Bi4Ge3O12, Gd2SiO5, CdWO4, ZnWO4, ZnSe (Te,O). Comparative analysis of experimental and theoretical data on fast neutron detection efficiency by such scintillators in a broad energy range En ≅ 1 * 10 MeV on atom nuclei have shown that the most probable mechanism of interaction of neutrons with nuclei of the scintillator material is the reaction of inelastic scattering of neutrons. The use of inelastic neutron scattering reaction on nuclei of heavy oxide scintillators allows creation of a high efficiency detector of mixed gamma-neutron fluxes, in which the energy of fast neutrons is directly, without intermediary media, converted into energy of gamma-quanta. This can lead to substantial (by several times) increase in sensitivity of systems for detection of fissionable radioactive substances, accompanied by a reduction in their cost.

  19. An in situ neutron irradiation facility for non-destructive elemental analysis

    International Nuclear Information System (INIS)

    Design and construction of an irradiation facility for nondestructive neutron activation analysis have been investigated. Two facilities have been constructed, using the available 5 Ci, Pu-Be, neutron sources and paraffin as modderator. The first unit has been designed mainly for neutron flux distribution studies. This unit consists of paraffin bricks of various sizes to facilitate placing the Dy, In and gold foils for flux maping. The second unit consists of a single paraffin block 50 x 50 x 50 cm3, having the same dimensions as the first unit. Two horizontal beam ports and one vertical were constructed in the paraffin moderator for sample irradiation. The maximum total absolute flux measured in the median plane was found to be about 1.32 x 104 n/cm2. Sec. at a distance of about 3.5 cm from the source surface. For test on geological sample of commercial interest gold sample were irradiated and measured. More than 10 elements have been clearly identified. Gold which is known to exist in this sample at about 10 parts per million was also clearly observed. This work is a part of joint programme with the international Atomic Energy Agency Research Contract No. 1697/RB. The title of this project is Elemental Activation Analysis with Decay and Prompt Gamma Ray Techniques, Using Isotopic Neutron Sources and Nuclear Research Reactors

  20. Neutron investigation of the rate of water seepage from irrigation channels and reservoirs in loessial loams

    International Nuclear Information System (INIS)

    The author discusses the results of experimental field studies on moisture conditions in the ground near an irrigation channel and a reservoir and the area of ground affected that were carried out in 1968 with neutron moisture gauges and gamma-gamma densimeters. Observations of the moisture movement and soil density were made in permanent boreholes up to 16.5 m deep lined with 2-in. steel tubes sealed at the bottom. To measure the moisture use was made of an all-purpose probe with a high-efficiency slow-neutron detector of the LDNM type (ZnS(Ag ) + B2O3), which was contained in the probe alongside a Pu + Be neutron source, thereby making it possible to obtain a linear dependence between the thermal neutron count and soil moisture. A portable scaler was used as the measuring instrument. When recording soil density, the LDNM scintillation crystal in the probe was replaced by a NaI(Tl) single crystal and a lengthener with a steel screen was screwed onto the probe casing. The conical end of the lengthener contained a gamma source (137Cs) with an activity of 2 meq of radium. In this case the length of the probe was 35 cm. On the basis of these studies the author determines the rate at which the soil near the reservoir is moistened and establishes the areas of loessial loams moistened by the irrigation channel. (author)

  1. Neutron Investigation of the Rate of Water Seepage from Irrigation Channels and Reservoirs on Loessial Loams

    International Nuclear Information System (INIS)

    The author discusses the results of experimental field studies on moisture conditions in the ground near an irrigation channel and a reservoir and the area of ground affected that were carried out in 1968 with neutron moisture gauges and gamma-gamma densimeters. Observations of the moisture movement and soil density were made in permanent boreholes up to 16.5 m deep lined with 2-in. steel tubes sealed at the bottom. To measure the moisture use was made of an all-purpose probe with a high-efficiency slow-neutron detector of the LDNM type (ZnS(Ag) + B2O3), which was contained in the probe alongside a Pu + Be neutron source, thereby making it possible to obtain a linear dependence between the thermal neutron count and soil moisture. A portable scaler was used as the measuring instrument. When recording soil density, the LDNM scintillation crystal in the probe was replaced by a Nal(Tl) single crystal and a lengthener with a steel screen was screwed onto the probe casing. The conical end of the lengthener contained a gamma source (137Cs) with an activity of 2 meq of radium. In this case the length of the probe was-35 cm. On the basis of these studies the author determines the rate at which the soil near the reservoir is moistened and establishes the areas of loessial loams moistened by the irrigation channel. (author)

  2. Backscattering analysis of thin films on non-flat surfaces

    Science.gov (United States)

    Berning, Paul R.; Niiler, Andrus

    1993-02-01

    In order to allow for the analysis of contaminant layers on powder surfaces, methods of adapting ion beam analysis techniques for use on non-flat surfaces have been developed. In this work, particular attention is given to situations where the dimensions of the surface structures are much larger than the thickness of the film, but much smaller than the ion beam spot size. It is assumed that the surface material is conformal and evenly distributed across the surface. Two methods are discussed; both are designed to analyze backscattered ion energy spectra through the use of available simulation programs. These methods rely on knowledge of the distribution of surface-normal to beam-direction angles present on the surface shape to be studied. Examples of this and other relevant distribution functions corresponding to several types of surface shape will be shown. The methods described here are used to study oxide layers grown thermally on small (≈ 130 μm) spherical titanium powder particles. We also show examples of how to empirically determine the distribution of surface tilt angles present on a surface of unknown shape when the nature of the surface film is known.

  3. Compton Backscattering Concept for the Production of Molybdenum-99

    Energy Technology Data Exchange (ETDEWEB)

    L. Merminga, G.A. Krafft

    2009-05-01

    The medical isotope Molybdenum-99 is presently used for 80-85% of all nuclear medicine procedures and is produced by irradiating highly enriched uranium U-235 targets in NRU reactors. It was recently proposed that an electron linac be used for the production of 99Mo via photo-fission of a natural uranium target coming from the excitation of the giant dipole resonance around 15 MeV. The photons can be produced using the braking radiation (“bremsstrahlung”) spectrum of an electron beam impinged on a high Z material. In this paper we present an alternate concept for the production of 99Mo which is also based on photo-fission of U-238, but where the ~15 MeV gamma-rays are produced by Compton backscattering of laser photons from relativistic electrons. We assume a laser wavelength of 330 nm, resulting in 485 MeV electron beam energy, and 10 mA of average current. Because the induced energy spread on the electron beam is a few percent, one may recover most of the electron beam energy, which substantially increases the efficiency of the system. The accelerator concept, based on a three-pass recirculation system with energy recovery, is described and efficiency estimates are presented.

  4. 63Ni β range and backscattering in confined geometries

    International Nuclear Information System (INIS)

    To know the spatial distribution of ion pairs resulting from 63Ni β radiation in the gas phase is important for the electron capture detector. The 63Ni-induced, initial ion pair distribution was therefore measured in a variety of gases with two techniques: a conventional one based on the electrical saturation current at variable interelectrode distances, and an unconventional one based on luminescence from a plastic scintillator. The data are analyzed in terms of two ranges, d50 and d95, that describe the distances from a planar radioactive foil within which 50% and 95% of the total gas-phase ionization occur. The data from the electrical measurement show unexpected evidence of strong β backscattering and secondary electron emission from the counter-electrode. Under these (non-exponential) conditions, d50 values in the common detector gases nitrogen and argon/methane vary from 0.5 to 1.0 mm, depending on the nature of the counter-electrode. Calculations based on the quasi-exponential range found at longer distances in electrical measurements yield values of about 2.5 mm (which are low because of geometric measurement bias). In contrast, the data from the luminescence measurement are almost completely exponential and d50 values for argon (+5% methane) and nitrogen are 2.8 and 3.8 mm, respectively. The d95 values vary from 12 to 16 mm for the luminescence, to 6 and 9 mm for the (less reliable) electrical measurement; all at ambient conditions

  5. Investigation of radar backscattering from second-year sea ice

    Science.gov (United States)

    Lei, Guang-Tsai; Moore, Richard K.; Gogineni, S. P.

    1988-01-01

    The scattering properties of second-year ice were studied in an experiment at Mould Bay in April 1983. Radar backscattering measurements were made at frequencies of 5.2, 9.6, 13.6, and 16.6 GHz for vertical polarization, horizontal polarization and cross polarizations, with incidence angles ranging from 15 to 70 deg. The results indicate that the second-year ice scattering characteristics were different from first-year ice and also different from multiyear ice. The fading properties of radar signals were studied and compared with experimental data. The influence of snow cover on sea ice can be evaluated by accounting for the increase in the number of independent samples from snow volume with respect to that for bare ice surface. A technique for calculating the snow depth was established by this principle and a reasonable agreement has been observed. It appears that this is a usable way to measure depth in snow or other snow-like media using radar.

  6. Measurement of crystal misorientation distribution by electron backscatter diffraction

    International Nuclear Information System (INIS)

    It is well known stress corrosion cracking in stainless steel and nickel based alloy is enhanced by plastic strain induced in the material, although the reason why has not been fully understood. Since stress corrosion cracking begins from small crack initiation and its growth, it is important to know the inhomogeneous distribution of plastic strain. Electron backscatter diffraction (EBSD) enables us to measure crystal orientations on specimen surface with a spatial resolution of nano-meter order. The magnitude of local plastic strain can be estimated from change in crystal orientation (misorientation) obtained. In this study, distributions of the misorientation were evaluated by using EBSD. A tensile specimen made of pure copper was subjected to tensile test to introduce plastic strain. From changes in surface images of the specimen during the test, distribution of plastic strain was identified by using the image correlation technique and was compared with distribution of misorientation obtained by EBSD measurement. It was revealed that the misorientation correlates well with dislocation density introduced by deformation rather than with local plastic strain. A data processing technique for improving accuracy of measured data of crystal orientation was developed and was successfully applied to obtain distributions of misorientation. The improved misorientation map showed that the misorientation tended to concentrate at grain boundaries. Influence of setting parameters in the new processing technique was investigated. Also, other techniques for improving a quality of distribution map were discussed. Finally, a procedure was shown for getting qualified misorientation distribution. (author)

  7. Estimating the breast surface using UWB microwave monostatic backscatter measurements.

    Science.gov (United States)

    Winters, David W; Shea, Jacob D; Madsen, Ernest L; Frank, Gary R; Van Veen, Barry D; Hagness, Susan C

    2008-01-01

    This paper presents an algorithm for estimating the location of the breast surface from scattered ultrawideband (UWB) microwave signals recorded across an antenna array. Knowing the location of the breast surface can improve imaging performance if incorporated as a priori information into recently proposed microwave imaging algorithms. These techniques transmit low-power microwaves into the breast using an antenna array, which in turn measures the scattered microwave signals for the purpose of detecting anomalies or changes in the dielectric properties of breast tissue. Our proposed surface identification algorithm consists of three procedures, the first of which estimates M points on the breast surface given M channels of measured microwave backscatter data. The second procedure applies interpolation and extrapolation to these M points to generate N > M points that are approximately uniformly distributed over the breast surface, while the third procedure uses these N points to generate a 3-D estimated breast surface. Numerical as well as experimental tests indicate that the maximum absolute error in the estimated surface generated by the algorithm is on the order of several millimeters. An error analysis conducted for a basic microwave radar imaging algorithm (least-squares narrowband beamforming) indicates that this level of error is acceptable. A key advantage of the algorithm is that it uses the same measured signals that are used for UWB microwave imaging, thereby minimizing patient scan time and avoiding the need for additional hardware. PMID:18232368

  8. Ion beam polishing for three-dimensional electron backscattered diffraction

    DEFF Research Database (Denmark)

    Saowadee, Nath; Agersted, Karsten; Ubhi, H.S.;

    2013-01-01

    Serial sectioning by focused ion beam milling for three-dimensional electron backscatter diffraction (3D-EBSD) can create surface damage and amorphization in certain materials and consequently reduce the EBSD signal quality. Poor EBSD signal causes longer data acquisition time due to signal...... averaging and/or poor 3D-EBSD data quality. In this work a low kV focused ion beam was successfully implemented to automatically polish surfaces during 3D-EBSD of La- and Nb-doped strontium titanate of volume 12.6 × 12.6 × 3.0 μm. The key to achieving this technique is the combination of a defocused low k......V high current ion beam and line scan milling. The line scan was used to restrict polishing to the sample surface and the ion beam was defocused to ensure the beam contacted the complete sample surface. In this study 1 min polishing time per slice increases total acquisition time by approximately 3...

  9. Compton-backscattered annihilation radiation from the Galactic Center region

    Science.gov (United States)

    Smith, D. M.; Lin, R. P.; Feffer, P.; Slassi, S.; Hurley, K.; Matteson, J.; Bowman, H. B.; Pelling, R. M.; Briggs, M.; Gruber, D.

    1993-01-01

    On 1989 May 22, the High Energy X-ray and Gamma-ray Observatory for Nuclear Emissions, a balloon-borne high-resolution germanium spectrometer with an 18-deg FOV, observed the Galactic Center (GC) from 25 to 2500 keV. The GC photon spectrum is obtained from the count spectrum by a model-independent method which accounts for the effects of passive material in the instrument and scattering in the atmosphere. Besides a positron annihilation line with a flux of (10.0 +/- 2.4) x 10 exp -4 photons/sq cm s and a full width at half-maximum (FWHM) of (2.9 + 1.0, -1.1) keV, the spectrum shows a peak centered at (163.7 +/- 3.4) keV with a flux of (1.55 +/- 0.47) x 10 exp -3 photons/sq cm s and a FWHM of (24.4 +/- 9.2) keV. The energy range 450-507 keV shows no positronium continuum associated with the annihilation line, with a 2-sigma upper limit of 0.90 on the positronium fraction. The 164 keV feature is interpreted as Compton backscatter of broadened and redshifted annihilation radiation, possibly from the source 1E 1740.7-2942.

  10. Vacuum birefringence by Compton backscattering through a strong field

    Science.gov (United States)

    Wistisen, Tobias N.; Uggerhøj, Ulrik I.

    2013-09-01

    We propose a novel scheme to measure nonlinear effects in electrodynamics arising from QED corrections. Our theoretical starting point is the Heisenberg-Euler-Schwinger effective Lagrangian which predicts that a vacuum with a strong static electromagnetic field turns birefringent. We propose to employ a pulsed laser to create Compton backscattered photons off a high energy electron beam. These photons will pass through a strong static magnetic field, which according to the QED prediction changes the state of polarization of the radiation—an effect proportional to the photon energy. This change will be measured by using an aligned single crystal, since a large difference in the pair production cross sections at high energies can be achieved with proper orientation of the crystal. As an example we will consider the machine, LHeC, under consideration at CERN as the source of these electrons, and an LHC dipole magnet as the source of the strong static magnetic field. In the proposed experimental setup the birefringence effect will be manifested in a difference in the number of pairs created in the polarizer crystal as the initial laser light has a varying state of polarization, achieved with a rotating quarter wave plate. This will be seen as a clear peak in the Fourier transform spectrum of the pair-production rate signal, which can be obtained with 3 hours of measurement. We also comment on the sensitivity of the experiment, to the existence of an axion, a hypothetical spin-0 particle that couples to two photons.

  11. Wide aperture periodic lens system for multiple Compton backscattering

    CERN Document Server

    Miyahara, Y

    2002-01-01

    Polarized gamma-ray generation by Compton backscattering in a periodic focusing system of electron and laser beams is discussed for the production of polarized positron beam in a linear collider. Circularly polarized CO sub 2 laser beams are focused by an optical lens series and collided with a 5.8 GeV electron beam to generate circularly polarized gamma-rays with 60 MeV at a maximum. In the present work, the basic concept of periodic lens system discussed previously is reconsidered to reduce the laser power required for a gamma-ray yield of 7x10 sup 1 sup 5 gamma/s and the peak laser power density at lenses as much as possible for technical practice. The electron beam is focused by a series of permanent quadrupole magnets with a FODO structure. The power is reduced to six sources with 5.6 kW each, and the peak power density is reduced to 1.4 GW/cm sup 2. These values can be reduced further by using a longer laser pulse length and a damping ring for the electron beam.

  12. Towards high accuracy calibration of electron backscatter diffraction systems

    Energy Technology Data Exchange (ETDEWEB)

    Mingard, Ken [National Physical Laboratory, Hampton Road, Teddington, TW11 0LW (United Kingdom); Day, Austin, E-mail: Austin.Day@ADSci.co.uk [Aunt Daisy Scientific Ltd., Claremont House, Lydney, GL15 5DX (United Kingdom); Maurice, Claire [Ecole des Mines, Centre SMS-UMR CNRS 5146, 158 cours Fauriel, 42023 Saint Etienne Cedex 2 (France); Quested, Peter [National Physical Laboratory, Hampton Road, Teddington, TW11 0LW (United Kingdom)

    2011-04-15

    For precise orientation and strain measurements, advanced Electron Backscatter Diffraction (EBSD) techniques require both accurate calibration and reproducible measurement of the system geometry. In many cases the pattern centre (PC) needs to be determined to sub-pixel accuracy. The mechanical insertion/retraction, through the Scanning Electron Microscope (SEM) chamber wall, of the electron sensitive part of modern EBSD detectors also causes alignment and positioning problems and requires frequent monitoring of the PC. Optical alignment and lens distortion issues within the scintillator, lens and charge-coupled device (CCD) camera combination of an EBSD detector need accurate measurement for each individual EBSD system. This paper highlights and quantifies these issues and demonstrates the determination of the pattern centre using a novel shadow-casting technique with a precision of {approx}10 {mu}m or {approx}1/3 CCD pixel. -- Research highlights: {yields} Issues with accurate EBSD calibration are discussed. {yields} Optical distortion data for 17 EBSD detectors are tabulated. {yields} A new shadow-casting system is demonstrated; it gives a pattern centre precision of {approx}10 {mu}m and allows changes to be observed on the live EBSP.

  13. Surface roughness from MOLA backscatter pulse-widths

    Science.gov (United States)

    Poole, W. D.; Muller, J.-P.; Gupta, S.; Grindrod, P. M.

    2013-09-01

    The time-spread of backscatter laser altimeter pulses, known as pulse-widths, are thought to be capable of being used to infer variations in topography within the footprint of the laser pulse. Here, Mars Orbiter Laser Altimeter (MOLA) pulse-widths have been compared to surface roughness and slope, as measured from high-resolution digital terrain models (DTMs), over different terrains in order to understand how this dataset can be used in the selection of landing and roving sites, and in inferring surface formation and evolution. The results are varied, and suggest that pulsewidths do not respond consistently to variations in terrain. The results show that over Mars Science Laboratory (MSL) candidate landing sites, the pulse-widths can be used as a rough estimate of surface roughness at baselines much larger than the footprint of the pulse. Over much rougher terrain, these pulse-widths respond best to footprint scale slope, which suggests that an additional slope correction for 75 m baselines slopes is required to infer finer scale roughness. However, this is shown not to be the case, as correcting the pulse-widths for 75 m slopes at the MSL candidate sites, and detrending the DTM data, produced poorer results.

  14. Neutral beam species measurements using in situ Rutherford backscatter spectrometry

    International Nuclear Information System (INIS)

    This work describes a new in situ method for measuring the neutral particle fractions in high power deuterium neutral beams, used to heat magnetically confined fusion plasmas. Deuterium beams, of variable energies, pulse lengths, and powers up to 47 keV, 100 msec, 1.6 MW, were Rutherford backscattered at 1350 from TiC inner neutral beam armor of the PDX, and detected using an electrostatic analyzer with microchannel plates. Complete energy scans were made every 20 msec and data were obtained simultaneously from five different positions across the beam profile. The neutral particle fractions were measured to be D0(E):D0(E/2):D0(E/3)=53:32:15. The corresponding neutral power fractions were P0(E):P0(E/2):P0(E/3)=72:21:7, and the associated ionic fractions at the output of the ion source were D1+(E):D2+(E):D3+(E)=74:20:6. The measured neutral particle fractions were relatively constant over more than 70% of the beam power distribution. A decrease in the yield of the full energy component in the outer regions of the beam was observed. Other possible experimental configurations and geometries are discussed

  15. Determination of RF Source Power in WPSN Using Modulated Backscattering

    Directory of Open Access Journals (Sweden)

    K.Sreedhar

    2012-03-01

    Full Text Available A wireless sensor network (WSN is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. During RF transmission energy consumed by critically energy-constrained sensor nodes in a WSN is related to the life time system, but the life time of the system is inversely proportional to the energy consumed by sensor nodes. In that regard, modulated backscattering (MB is a promising design choice, in which sensor nodes send their data just by switching their antenna impedance and reflecting the incident signal coming from an RF source. Hence wireless passive sensor networks (WPSN designed to operate using MB do not have the lifetime constraints. In this we are going to investigate the system analytically. To obtain interference-free communication connectivity with the WPSN nodes number of RF sources is determined and analyzed in terms of output power and the transmission frequency of RF sources, network size, RF source and WPSN node characteristics. The results of this paper reveal that communication coverage and RF Source Power can be practically maintained in WPSN through careful selection of design parameters

  16. Neutron dosimetry - A review

    International Nuclear Information System (INIS)

    This review summarizes information on the following subjects: (1) physical processes of importance in neutron dosimetry; (2) biological effects of neutrons; (3) neutron sources; and (4) instruments and methods used in neutron dosimetry. Also, possible improvements in dosimetry instrumentation are outlined and discussed. (author)

  17. Borner Ball Neutron Detector

    Science.gov (United States)

    2002-01-01

    The Bonner Ball Neutron Detector measures neutron radiation. Neutrons are uncharged atomic particles that have the ability to penetrate living tissues, harming human beings in space. The Bonner Ball Neutron Detector is one of three radiation experiments during Expedition Two. The others are the Phantom Torso and Dosimetric Mapping.

  18. Superfluid neutron stars

    OpenAIRE

    Langlois, David

    2001-01-01

    Neutron stars are believed to contain (neutron and proton) superfluids. I will give a summary of a macroscopic description of the interior of neutron stars, in a formulation which is general relativistic. I will also present recent results on the oscillations of neutron stars, with superfluidity explicitly taken into account, which leads in particular to the existence of a new class of modes.

  19. Neutrostriction in Neutron stars

    OpenAIRE

    Ignatovich, V. K.

    2003-01-01

    It is demonstrated that not only gravity, but also neutrostriction forces due to optical potential created by coherent elastic neutron-neutron scattering can hold a neutron star together. The latter forces can be stronger than gravitational ones. The effect of these forces on mass, radius and structure of the neutron star is estimated.

  20. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  1. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  2. Neutron standard data

    International Nuclear Information System (INIS)

    The neutron standards are reviewed with emphasis on the evaluation for ENDFB-VI. Also discussed are the neutron spectrum of 252Cf spontaneous fission, activation cross sections for neutron flux measurement, and standards for neutron energies greater than 20 MeV. Recommendations are made for future work. 21 refs., 6 figs., 3 tabs

  3. Evaluation of the health risk of body backscatter x ray scanners; Evaluation du risque sanitaire des scanners corporels a rayons X backscatter

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2010-07-01

    Following the attempted attack between Amsterdam and Detroit on the 25 december 2009, the council of interior safety decided a quick display of equipment using more efficient imaging techniques than metals detectors usually in place in French airports. Two technologies of devices are susceptible to be implemented on the airports: scanners using non ionizing radiation, (called millimetric waves) or scanners using ionizing radiation (x radiation, measurement by backscattering called backscatter). This report evaluates the dosimetric impact and the sanitary risk of backscatter x ray scanners and formulates recommendations to authorities to allow them to rule on the type of technology to use. Then, this report gives leads to conceive elements of information to communicate to travelers susceptible to be controlled by a such scanner in a foreign airport. (N.C.)

  4. Neutron Capture Nucleosynthesis

    CERN Document Server

    Kiss, Miklos

    2016-01-01

    Heavy elements (beyond iron) are formed in neutron capture nucleosynthesis processes. We have proposed a simple unified model to investigate the neutron capture nucleosynthesis in arbitrary neutron density environment. We have also investigated what neutron density is required to reproduce the measured abundance of nuclei assuming equilibrium processes. We found both of these that the medium neutron density has a particularly important role at neutron capture nucleosynthesis. About these results most of the nuclei can formed at medium neutron capture density environment e.g. in some kind of AGB stars. Besides these observations our model is capable to use educational purpose.

  5. Neutrons in cancer therapy

    Science.gov (United States)

    Allen, Barry J.

    1995-03-01

    The role of neutrons in the management of cancer has a long history. However, it is only in recent years that neutrons are beginning to find an accepted place as an efficacious radiation modality. Fast neutron therapy is already well established for the treatment of certain cancers, and clinical trials are ongoing. Californium neutron sources are being used in brachytherapy. Boron neutron capture therapy has been well tested with thermal neutrons and epithermal neutron dose escalation studies are about to commence in the USA and Europe. Possibilities of neutron induced auger electron therapy are also discussed. With respect to chemotherapy, prompt neutron capture analysis is being used to study the dose optimization of chemotherapy in the management of breast cancer. The rationales behind these applications of neutrons in the management of cancer are examined.

  6. Mean square displacement evaluation by elastic neutron scattering self-distribution function

    Science.gov (United States)

    Magazù, Salvatore; Maisano, Giacomo; Migliardo, Federica; Benedetto, Antonio

    2008-06-01

    In the present work an operational recipe for the mean square displacement (MSD) determination, highlighting the connection between elastic incoherent neutron scattering (EINS) intensity profiles and the associated self-distribution function, is presented. The determination of the thermal behavior of the total MSD and of its partial contributions is tested on EINS data collected by the backscattering spectrometer IN13 (ILL, Grenoble) on a model system such as PolyEthylene Glycol with a mean molecular weight of 400 Dalton (PEG 400).

  7. Influence of lithium coating on the optics of Doppler backscatter system

    International Nuclear Information System (INIS)

    This paper presents the first investigation of the effect of lithium coating on the optics of Doppler backscattering. A liquid lithium limiter has been applied in the Experimental Advanced Superconducting Tokamak (EAST), and a Doppler backscattering has been installed in the EAST. A parabolic mirror and a flat mirror located in the vacuum vessel are polluted by lithium. An identical optical system of the Doppler backscattering is set up in laboratory. The power distributions of the emission beam after the two mirrors with and without lithium coating (cleaned before and after), are measured at three different distances under four incident frequencies. The results demonstrate that the influence of the lithium coating on the power distributions are very slight, and the Doppler backscattering can work normally under the dosage of lithium during the 2014 EAST campaign

  8. Sea Floor Topography and Backscatter Intensity of the Historic Area Remediation Site

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set includes topography and backscatter intensity of the sea floor of the Historic Area Remediation Site (HARS), located offshore of New York and New...

  9. Aerosol backscattering profiles of CO2 wavelengths: the NOAA data base

    International Nuclear Information System (INIS)

    NOAA's data base for aerosol backscattering at lambda = 10.6 μm since May 1981, Boulder, Colorado, is presented together with seasonally averaged profiles and statistical analyses. Studies of the El Chichon event are included

  10. High-frequency over-the-horizon radar and ionospheric backscatter studies in China

    Science.gov (United States)

    Li, Le-Wei

    1998-09-01

    China is one of the countries that employs high-frequency over-the-horizon radars for both military and civil applications. The first Chinese high-frequency over-the horizon backscatter radar was developed in the 1970s. This paper briefly introduces the first Chinese over-the-horizon backscatter radar system and reviews ionospheric backscatter and propagation studies in China. The paper discusses the motivation for establishing over-the-horizon radar systems in China, the experimental system, target recognition and detection,and estimation of over-the-horizon radar availability. Observations of aircraft, large-scale traveling ionospheric disturbances, and the effects of a remote nuclear explosion are also presented. Finally, the real-time Chinese ionosonde network and frequency predictions using backscatter ionograms are discussed.

  11. Fine scale analyses of a coralline bank mapped using multi-beam backscatter data

    Digital Repository Service at National Institute of Oceanography (India)

    Menezes, A.A.A.; Naik, M.; Fernandes, W.A.; Haris, K.; Chakraborty, B.; Estiberio, S.; Lohani, R.B.

    In this work, we have developed a classification technique to characterize the seafloor of the Gaveshani (coralline) bank area using multi-beam backscatter data. Softcomputational techniques like the artificial neural networks (ANNs) based...

  12. NOAA TIFF Graphic- 0.5m Backscatter Mosaic of St. Thomas, US Virgin Islands, 2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a 0.5 meter resolution backscatter mosaic of the south shore of St. Thomas, US Virgin Islands.NOAA's NOS/NCCOS/CCMA Biogeography Team and...

  13. Backscatter 0.5m TIFF Mosaic of St. Croix (Buck Island), US Virgin Islands, 2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a 0.5 meter resolution backscatter mosaic of the north shore of Buck Island, St. Croix, US Virgin Islands. NOAA's NOS/NCCOS/CCMA Biogeography...

  14. Effect of grain size distribution on attenuation and backscattered grain noise

    International Nuclear Information System (INIS)

    The attenuation and backscattered grain noises in pure irons were measured. From the backscattered grain noise FOM (Figure-of-merit) which is a material dependent parameter were obtained by using independent scattering model. Attenuation coefficients and FOM's were compared with the results calculated by LPM theory and the general scattering model, respectively. Although the absolute values were not exactly same between measured and calculated results, the dependencies of them on the average grain size could be confirmed. The effect of grain size distribution on attenuation and backscattered grain noise was analyzed. The different scattering mechanisms according to the ratio of wavelength to grain size were applied to the analysis of the attenuation and backscattering even in a specimen.

  15. The application possibilities of the gamma-ray Compton backscattering technique

    Science.gov (United States)

    Flechas, D.; Sarmiento, L. G.; González, N.; Gómez-Muñoz, J.; Garzón, C.; Fajardo, E.; Cristancho, F.

    2013-05-01

    The location of objects hidden in dense matter and the analysis of metallic surfaces using gamma backscattering are two possible applications strongly suggested here with experiments, highlevel Monte Carlo simulations, and some supporting basic theory.

  16. Assessment of Multiple Delamination in Laminated Composites for Aircrafts using X-ray Backscattering

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Noh Yu [College of Medicine, Hanyang University, Cheonan (Korea, Republic of)

    2010-02-15

    A Compton X-ray backscatter technique has been developed to quantitatively assess impact damage in quasi-isotropic laminated composites made by a drop-weight tester. X-ray backscatter imaging system with a slit-type camera is constructed to obtain a cross-sectional profile of impact-damaged laminated composites from the electron-density variation of the cross section. A nonlinear scattering model based on Boltsman equation is introduced to compute Compton X-ray backscattering field for the defect assessment. An adaptive filter is also used to reduce noises from many sources including quantum noise and irregular distributions of fibers and matrix in composites. Delaminations masked or distorted by the first delamination are detected and characterized effectively by the Compton X-ray backscatter technique, both in width and location, by application of error minimization algorithm

  17. Backscatter 0.5m TIFF Mosaic of St. Thomas, US Virgin Islands, 2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This image represents a 0.5 meter resolution backscatter mosaic of the south shore of St. Thomas, US Virgin Islands. NOAA's NOS/NCCOS/CCMA Biogeography Team and...

  18. Backscattering Light Model of Seawater for Modulated Lidar Based on the Stationarity of Light Field

    Institute of Scientific and Technical Information of China (English)

    JI Hang; MA Yong; LIANG Kun; WANG Hong-yuan

    2007-01-01

    The backscattering signal, which arises from the pulsed laser traveling through water, has limited the lidar system sensitivity and underwater target contrast. The transmitted optical carrier is modulated to be ultrashort pulsed laser and i t is effective to suppress the backscattering to adopt the coherent detection technology by identifying the modulation envelope. A nonstationary light field is formed in seawater by the ultrashort pulsed laser. The inherent relationship between the nonstationary light field formed by modulated lidar and the stationary light field formed by conventional lidar was discussed and the backscattering light model of the stationary light field for the ultrashort pulsed laser was proposed. The backscattering signal in modulated lidar system was processed and analyzed in the frequency domain on the basis of the model.

  19. CRED Reson 8101 multibeam backscatter data from the islands and banks in the Mariana archipelago, 2007.

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Multibeam backscatter imagery extracted from gridded bathymetry of the Mariana archipelago between the U.S. Territory of Guam and Uracas Island in the Commonwealth...

  20. Automatically determining the origin direction and propagation mode of high-frequency radar backscatter

    Science.gov (United States)

    Burrell, Angeline G.; Milan, Stephen E.; Perry, Gareth W.; Yeoman, Timothy K.; Lester, Mark

    2015-12-01

    Elevation angles of returned backscatter are calculated at Super Dual Auroral Radar Network radars using interferometric techniques. These elevation angles allow the altitude of the reflection point to be estimated, an essential piece of information for many ionospheric studies. The elevation angle calculation requires knowledge of the azimuthal return angle. This directional angle is usually assumed to lie along a narrow beam from the front of the radar, even though the signals are known to return from both in front of and behind the radar. If the wrong direction of return is assumed, large uncertainties will be introduced through the azimuthal return angle. This paper introduces a means of automatically determining the correct direction of arrival and the propagation mode of backscatter. The application of this method will improve the accuracy of backscatter elevation angle data and aid in the interpretation of both ionospheric and ground backscatter observations.

  1. Reson 8101 Backscatter imagery of Ni'ihau Island, Hawaii, USA

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Backscatter imagery extracted from gridded bathymetry of Ni'ihau Island, Hawaii, USA. These data provide almost complete coverage between 0 and 100 meters. The...

  2. Extracting integrated and differential cross sections in low energy heavy-ion reactions from backscattering measurements

    Science.gov (United States)

    Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Diaz-Torres, A.; Gomes, P. R. S.; Lenske, H.

    2016-07-01

    We suggest new methods to extract elastic (quasi-elastic) scattering angular distribution and reaction (capture) cross sections from the experimental elastic (quasi-elastic) backscattering excitation function taken at a single angle.

  3. Vertical Aerosol Backscatter Variability from an Airborne Focused Continuous Wave CO2 Lidar

    Science.gov (United States)

    Jarzembski, Maurice A.; Srivastava, Vandana; Rothermel, Jeffry

    1998-01-01

    Atmospheric aerosol backscatter measurements using a continuous wave focused Doppler lidar at 9.1 micron wavelength were obtained over western North America and the Pacific Ocean during 13 - 26 September, 1995 as part of National Aeronautics and Space Administration's (NASA) Multi-center Airborne Coherent Atmospheric Wind Sensor (MACAWS) mission on board the NASA DC8 aircraft. Backscatter variability was measured for approximately 52 flight hours, covering equivalent horizontal distance of approximately 25,000 km in the troposphere. Quasi-vertical backscatter profiles were also obtained during various ascents and descents which ranged between approximately 0.1 to 12.0 km altitude. Aerosol haze layers were encountered at different altitudes. Similarities and differences for aerosol loading over land and over ocean were observed. A mid-tropospheric aerosol backscatter background mode was found with modal value approximately 1O(exp -10)/m/sr, consistent with previous airborne and ground-based datasets.

  4. Influence of lithium coating on the optics of Doppler backscatter system

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X. H.; Liu, A. D., E-mail: lad@ustc.edu.cn; Zhou, C.; Hu, J. Q.; Wang, M. Y.; Yu, C. X.; Liu, W. D.; Li, H.; Lan, T.; Xie, J. L. [Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2015-10-15

    This paper presents the first investigation of the effect of lithium coating on the optics of Doppler backscattering. A liquid lithium limiter has been applied in the Experimental Advanced Superconducting Tokamak (EAST), and a Doppler backscattering has been installed in the EAST. A parabolic mirror and a flat mirror located in the vacuum vessel are polluted by lithium. An identical optical system of the Doppler backscattering is set up in laboratory. The power distributions of the emission beam after the two mirrors with and without lithium coating (cleaned before and after), are measured at three different distances under four incident frequencies. The results demonstrate that the influence of the lithium coating on the power distributions are very slight, and the Doppler backscattering can work normally under the dosage of lithium during the 2014 EAST campaign.

  5. Correction of Doppler-broadened Rayleigh backscattering effects in H2O dial measurements

    Science.gov (United States)

    Ansmann, A.; Bosenberg, J.

    1986-01-01

    A general method of solutions for treating effects of Doppler-broadened Rayleigh backscattering in H2O Differential Absorption Lidar (DIAL) measurements are described and discussed. Errors in vertical DIAL measuremtns caused by this laser line broadening effect can be very large and, therfore, this effect has to be accounted for accurately. To analyze and correct effects of Doppler-broadened Rayleigh backscattering in DIAL experiments, a generalized DIAL approximation was derived starting from a lidar equation, which includes Doppler broadening. To evaluate the accuracy of H2O DIAL measurements, computer simulations were performed. It was concluded that correction of Doppler broadened Rayleigh backscattering is possible with good accuracy in most cases of tropospheric H2O DIAL measurements, but great care has to be taken when layers with steep gradients of Mie backscattering like clouds or inversion layers are present.

  6. A Compact In Situ Sensor for Measurement of Absorption and Backscattering in Natural Waters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop an active sensor for in situ measurement of the inherent optical properties (IOPs) absorption and backscattering at multiple wavelengths....

  7. High energy neutron detector

    Energy Technology Data Exchange (ETDEWEB)

    Wiegand, C.

    1948-04-27

    It is the purpose of this paper to describe a neutron detector suitable for monitoring a flux of neutrons whose energy is greater than about 50 MeV. Detection of the neutrons is accomplished by their ability to induce fission in heavy elements. Kelly and Wiegand studied the neutron fission of Bi, Pb, Ti, Hg, Au, and Pt at various neutron energies and the presently described counter is an application of this work.

  8. Imaging with Scattered Neutrons

    CERN Document Server

    Ballhausen, H; Gähler, R; Trapp, M; Van Overberghe, A

    2006-01-01

    We describe a novel experimental technique for neutron imaging with scattered neutrons. These scattered neutrons are of interest for condensed matter physics, because they permit to reveal the local distribution of incoherent and coherent scattering within a sample. In contrast to standard attenuation based imaging, scattered neutron imaging distinguishes between the scattering cross section and the total attenuation cross section including absorption. First successful low-noise millimeter-resolution images by scattered neutron radiography and tomography are presented.

  9. Development and characterization of two-component albedo based neutron individual monitoring system using thermoluminescent detectors; Desenvolvimento e caracterizacao de um sistema de monitoracao individual de neutrons tipo albedo de duas componentes usando detectores termoluminescentes

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Marcelo Marques

    2008-07-01

    A TLD-albedo based two-component neutron individual monitoring system was developed and characterized in this work. The monitor consists of a black plastic holder, an incident neutron boron loaded shield, a moderator polyethylene body (to increase its response), two pairs of TLD-600 and TLD-700 (one pair to each component) and an adjustable belt. This monitoring system was calibrated in thermal neutron fields and in 70 keV, 144 keV, 565 keV, 1.2 MeV and 5 MeV monoenergetic neutron fields. In addition, it was calibrated in {sup 252C}f(D{sub 2}O), {sup 252}Cf, {sup 241}Am-B, {sup 241}Am-Be and {sup 238}Pu-Be source fields. For the latter, the lower detection levels are, respectively, 0.009 mSv, 0.06 mSv, 0.12 mSv, 0.09 mSv and 0.08 mSv. The participation in an international intercomparison sponsored by IAEA with simulated workplace fields validated the system. The monitoring system was successfully characterized in the ISO 21909 standard and in an IRD - the Brazilian Institute for Radioprotection and Dosimetry - technical regulation draft. Nowadays, the neutron individual system is in use by IRD for whole body individual monitoring of five institutions, which comprehend several activities. (author)

  10. Resolving subwavelength objects with a crossed wire mesh superlens operated in backscattering mode

    Energy Technology Data Exchange (ETDEWEB)

    Silveirinha, Mario G [Department of Electrical Engineering-Instituto de Telecomunicacoes, University of Coimbra (Portugal); Medeiros, Carla R; Fernandes, Carlos A; Costa, Jorge R, E-mail: mario.silveirinha@co.it.pt [Technical University of Lisbon, Instituto Superior Tecnico-Instituto de Telecomunicacoes, 1049-001 Lisbon (Portugal)

    2011-05-15

    In this work, we demonstrate that a crossed-wires superlens operated in backscattering mode can resolve targets separated by a subwavelength distance. It is theoretically shown that the effect of the backscattered field on the return loss of a probe antenna is sufficiently strong to allow us to discriminate the targets over a broad range of frequencies. These properties have been experimentally confirmed at microwave frequencies.

  11. Resolving subwavelength objects with a crossed wire mesh superlens operated in backscattering mode

    International Nuclear Information System (INIS)

    In this work, we demonstrate that a crossed-wires superlens operated in backscattering mode can resolve targets separated by a subwavelength distance. It is theoretically shown that the effect of the backscattered field on the return loss of a probe antenna is sufficiently strong to allow us to discriminate the targets over a broad range of frequencies. These properties have been experimentally confirmed at microwave frequencies.

  12. Theoretical analysis of backscattered polarization patterns of turbid media containing glucose

    Institute of Scientific and Technical Information of China (English)

    Lanqing Xu; Hui Li; Shusen Xie

    2007-01-01

    Single scattering model and Stokes-Mueller formalism are introduced to investigate the influence of glucose on backscattered polarization patterns in turbid media. Glucose molecules rotate the polarization plane and induce changes in backscattered Mueller matrix patterns. Some Mueller matrix elements present higher optical rotation as the concentration of glucose augments. Using image subtraction and integration,linear relationship between low glucose concentration in the physiological range and optical rotation degree can be derived.

  13. A Monte Carlo computer program for analysis of backscattering and sputtering in practical vacuum systems

    International Nuclear Information System (INIS)

    A Monte Carlo computer program originally developed for analysis of molecular gas flow in axi-symmetric vacuum systems has been extended to include modelling of high energy backscattering and sputtering processes. This report describes the input data required by the computer program together with the results produced. A general description is given of the program operation and the backscattering and sputtering modelling used. An example calculation is included to illustrate practical application of the program. (author)

  14. Climatology of the aerosol extinction to backscatter ratio from sun photometric measurements

    OpenAIRE

    Baldasano Recio, José María; Pedrós, Roberto; Estallés, Víctor; Sicard, Michaël; Gómez Amo, Jose Luis; Utrillas, Maria Pilar; Martínez Lozano, José Antonio; Rocadenbosch Burillo, Francisco; Pérez, C.

    2010-01-01

    The elastic lidar equation contains two unknown atmospheric parameters, namely, the particulate optical extinction and backscatter coefficients, which are related through the lidar ratio (i.e., the particulate-extinction-to-backscatter ratio). So far, independent inversion of the lidar signal has been carried out by means of Raman lidars (usually limited to nighttime measurements), high-spectral-resolution lidars, or scanning elastic lidars under the assumption of a homog...

  15. An analytical model for backscattered luminance in fog: comparisons with Monte Carlo computations and experimental results

    OpenAIRE

    Taillade, Frédéric; Belin, Etienne; Dumont, Eric

    2008-01-01

    We propose an analytical model for backscattered luminance in fog and derive an expression for the visibility signal-to-noise ratio as a function of meteorological visibility distance. The model uses single scattering processes. It is based on the Mie theory and the geometry of the optical device (emitter and receiver). In particular, we present an overlap function and take the phase function of fog into account. The results of the backscattered luminance obtained with our analytical model...

  16. Calculation of the backscattered ion energy and angular distributions during the grazing implantation

    International Nuclear Information System (INIS)

    Simulation of ion implantation into deep trenches demands the exact evaluation of ion fluxes backscattered from the sidewalls. In this paper an application of Boltzmann Transport Equation (BTE) to backscattered ion energy and angular distribution calculations is presented. Characteristic examples of grazing implantation of Sb, As and P in Si are considered and good agreement with Monte-Carlo (MC) calculations are found. It was also found that BTE gives a more smooth distribution without statistical fluctuations and essentially saves computational time. (author)

  17. An integral model for thermal backscattering from the exhaust plume of space-based HF laser

    OpenAIRE

    Falcovitz, Joseph; Fuhs, Allen E.

    1986-01-01

    The operation of a space-based HF laser may be hampered due to self contamination by corrosive exhaust products. We estimate one effect contributing to contaminating blackflow: thermal backscattering from the rarefaction fans flanking the exhaust ring-jet. Our computational model is based on a first-iterate approximation to the Boltzmann equation in integral form. Results indicate that thermal backscattering of corrosive speies (HF, DF) is negligible.

  18. Modeling the effects of laser-beam smoothing on filamentation and stimulated Brillouin backscattering

    Energy Technology Data Exchange (ETDEWEB)

    Berger, R.L.; Kaiser, T.B.; Lasinski, B.F. [and others

    1996-06-01

    Using the three-dimensional code (F3D), the authors compute the filamentation and backscattering of laser light. The results show that filamentation can be controlled and stimulated Brillouin backscattering (SBBS) can be reduced by using random phase plates (RPP) and small f-numbers or smoothing by spectral dispersion (SSD) with large bandwidth. An interesting result is that, for uniform plasmas, the SBBS amplification takes place over several laser axial coherence lengths (coherence length = speckle length).

  19. The backscatter cloud probe – a compact low-profile autonomous optical spectrometer

    OpenAIRE

    K. Beswick; Baumgardner, D; Gallagher, M; Volz-Thomas, A.; Nedelec, P.; K.-Y. Wang; LANCE, S.

    2014-01-01

    A compact (500 cm3), lightweight (500 g), near-field, single particle backscattering optical spectrometer is described that mounts flush with the skin of an aircraft and measures the concentration and optical equivalent diameter of particles from 5 to 75 μm. The backscatter cloud probe (BCP) was designed as a real-time qualitative cloud detector primarily for data quality control of trace gas instruments developed for the climate monitoring instrument packages that are being...

  20. Enhanced Doppler Effect in the Upper Hybrid Resonance Microwave Backscattering Experiment

    OpenAIRE

    Altukhov, A.B.; Gurchenko, A.D.; Gusakov, E. Z.; Esipov, L. A.; Lashkul, S. I.; Stepanov, A. Yu.

    2004-01-01

    Observations of enhanced Doppler frequency shift effect of the highly localized microwave backscattering in the upper hybrid resonance are reported. The experiment is performed at FT-2 tokamak, where a steerable focusing antenna set, allowing off equatorial plane plasma extraordinary wave probing from high magnetic field side, was installed. A separate line less than 1.5 MHz wide and shifted by up to 2 MHz is routinely observed in the backscattering spectrum under condition of accessible uppe...

  1. Diffusion of Sr in fluorphlogopite determined by Rutherford backscattering spectrometry

    Science.gov (United States)

    Hammouda, T.; Cherniak, D. J.

    2000-05-01

    We have measured the diffusivity of Sr in fluorphlogopite in a direction perpendicular to the basal planes (in the c direction). Annealing experiments were performed on single crystals, and most of them at ambient pressure. The penetration profiles of the diffusant were determined by Rutherford backscattering spectrometry. Sr diffusion parallel to c obeys an Arrhenius law, whose equation is: D Sr=2.7·10 -14 exp - 13 5900±3100/RTwhere DSr is given in m 2 s -1 and activation energy in J mol -1. The values measured in fluorphlogopite overlap the range previously determined in other silicates, but the activation energy for fluorphlogopite is approximately half that of the other minerals for which diffusion data exist. A summary of the available data on diffusion in micas of all compositions shows that activation energies for species such as Sr, O, Rb and K fall in the same range, i.e. 100-175 kJ per mol. When plotted together, these data define two groups of parallel Arrhenian lines. One group consists of the measurements performed in the c direction, the other of those performed normal to the c direction. The distinction between the two groups is clear, and diffusion parallel to the c direction is slower by several orders of magnitude. The corresponding closure temperature for fluorphlogopite, when diffusion occurs in the c direction, is of the order of 700°C, relatively close to that of feldspars. On the basis of some simple assumptions about diffusion anisotropy in micas, we also estimated the closure temperature when diffusion takes place in a direction parallel to the basal planes. In that case, the value is noticeably lower, of the order of 400°C. However, this value, if applicable to other micas, is higher than what is currently accepted, which could have some implications for models of thermal histories or uplift rates of rocks.

  2. Cavitation inception by the backscattering of pressure waves from a bubble interface

    Science.gov (United States)

    Takahira, Hiroyuki; Ogasawara, Toshiyuki; Mori, Naoto; Tanaka, Moe

    2015-10-01

    The secondary cavitation that occurs by the backscattering of focused ultrasound from a primary cavitation bubble caused by the negative pressure part of the ultrasound (Maxwell, et al., 2011) might be useful for the energy exchange due to bubble oscillations in High Intensity Focused Ultrasound (HIFU). The present study is concerned with the cavitation inception by the backscattering of ultrasound from a bubble. In the present experiment, a laser-induced bubble which is generated by a pulsed focused laser beam with high intensity is utilized as a primary cavitation bubble. After generating the bubble, focused ultrasound is emitted to the bubble. The acoustic field and the bubble motion are observed with a high-speed video camera. It is confirmed that the secondary cavitation bubble clouds are generated by the backscattering from the laser-induced bubble. The growth of cavitation bubble clouds is analyzed with the image processing method. The experimental results show that the height and width of the bubble clouds grow in stepwise during their evolution. The direct numerical simulations are also conducted for the backscattering of incident pressure waves from a bubble in order to evaluate a pressure field near the bubble. It is shown that the ratio of a bubble collapse time t0 to a characteristic time of wave propagation tS, η = t0/ts, is an important determinant for generating negative pressure region by backscattering. The minimum pressure location by the backscattering in simulations is in good agreement with the experiment.

  3. Enhanced ion backscattering near 1800 scattering angles in the two-atom scattering model

    International Nuclear Information System (INIS)

    An analytical two-atom scattering model has been developed to treat the recent discovery of the enhancement near 1800 of Rutherford backscattering yields from disordered solids. In contrast to conventional calculations of Rutherford backscattering that treat scattering from a single atom only (the backscattering atom), the present model includes the interaction of a second atom lying between the target surface and the backscattering atom. The projectile ion makes a glancing collision with this second atom both before and after it is backscattered. A weighted average is made over all possible positions of this second atom. The model predicts an enhancement effect whose physical origin arises from the tolerance of path for those ions whose ingoing and outgoing trajectories lie in the vicinity of the critical impact parameter. Results using Moliere scattering show how the yield enhancement depends on ion energy, backscattering depth, exit angle, scattering potential, atomic numbers of the projectile and target, and target density. In the model the critical impact parameter and critical angle play important roles. It is shown that these quantities depend on a single dimensionless parameter and formulas accurate to better than 1% are given for them

  4. Improvement of a 3D radar backscattering model using matrix-doubling method

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Radiative transfer models have been widely used to simulate the radar backscattering from forested areas. A three-dimensional radar backscatter model of forest canopy developed in previous studies takes full account of spatial position of trees in a forest stand, and the interactions among crown, trunk and ground surface. The model predicted well for the co-polarized backscatter measurements, but underestimated the backscattering for cross-polarization, primarily because only the first-order scattering within tree crowns was considered in the model. The backscattering at cross-polarization depends strongly on multiple scatter- ing within tree crowns. To produce good estimations for cross-polarized component, the matrix-doubling method is employed here to compute multiple-scattering within the crown. The modified model is compared with the original model, and the field forest measurements and AIRSAR data are used for validation of the modified model. The cross-polarization backscattering is improved in different degrees for different crown structures and at different bands.

  5. Modeling and analysis of ultrasound backscattering by spherical aggregates and rouleaux of red blood cells.

    Science.gov (United States)

    Teh, B G; Cloutier, G

    2000-01-01

    The present study concerns the modeling and analysis of ultrasound backscattering by red blood cell (RBC) aggregates, which under pathological conditions play a significant role in the rheology of blood within human vessels. A theoretical model based on the convolution between a tissue matrix and a point spread function, representing, respectively, the RBC aggregates and the characteristics of the ultrasound system, was used to examine the influence of the scatterer shape and size on the backscattered power. Both scatterers in the form of clumps of RBC aggregates and rouleaux were modeled. For all simulations, the hematocrit was kept constant at 10%, the ultrasound frequency was 10 MHz, the insonification angle was varied from 0 to 90 degrees , and the scatterer size (diameter for clumps and length for rouleaux) ranged from 4 mum to 120 mum. Under Rayleigh scattering by assuming a Poisson distribution of scatterers in space, the ultrasound backscattered power increased linearly with the particle volume. For non-Rayleigh scatterers, the intensity of the echoes diminished as the scatterer volume increased, with the exception of rouleaux at an angle of 90 degrees . As expected, the backscattered power was angularly dependent for anisotropic particles (rouleaux). The ultrasound backscattered power did not always increase with the size of the aggregates, especially when they were no longer Rayleigh scatterers. In the case of rouleaux, the anisotropy of the backscattered power is emphasized in the non-Rayleigh region. PMID:18238637

  6. Pulsed neutron sources for epithermal neutrons

    International Nuclear Information System (INIS)

    It is shown how accelerator based neutron sources, giving a fast neutron pulse of short duration compared to the neutron moderation time, promise to open up a new field of epithermal neutron scattering. The three principal methods of fast neutron production: electrons, protons and fission boosters will be compared. Pulsed reactors are less suitable for epithermal neutrons and will only be briefly mentioned. The design principle of the target producing fast neutrons, the moderator and reflector to slow them down to epithermal energies, and the cell with its beam tubes and shielding will all be described with examples taken from the new Harwell electron linac to be commissioned in 1978. A general comparison of pulsed neutron performance with reactors is fraught with difficulties but has been attempted. Calculation of the new pulsed source fluxes and pulse widths is now being performed but we have taken the practical course of basing all comparisons on extrapolations from measurements on the old 1958 Harwell electron linac. Comparisons for time-of-flight and crystal monochromator experiments show reactors to be at their best at long wavelengths, at coarse resolution, and for experiments needing a specific incident wavelength. Even existing pulsed sources are shown to compete with the high flux reactors in experiments where the hot neutron flux and the time-of-flight methods can be best exploited. The sources under construction can open a new field of inelastic neutron scattering based on energy transfer up to an electron volt and beyond

  7. Neutron Scintillators for Downscattered Neutron Imaging

    International Nuclear Information System (INIS)

    Images of neutron emission from Inertial Confinement Fusion (ICF) (D,T) targets reveal the internal structure of the target during the fusion burn. 14-MeV neutrons provide images which show the size and shape of the region where (D,T) fusion is most intense. Images based on ''downscattered'' neutrons with energies from 5 to 10 MeV emphasize the distribution of deuterium and tritium fuel within the compressed target. The downscattered images are difficult to record because the lower energy neutrons are detected with less efficiency than the much more intense pulse of 14-MeV neutrons which precedes them at the detector. The success of downscattered neutron imaging will depend on the scintillation decay times and the sensitivities to lower-energy neutrons of the scintillator materials that are used in the detectors. A time-correlated photon counting system measured the decay of neutron-induced scintillation for times as long as several hundred ns. Accelerators at the University of California, Berkeley, and the Lawrence Livermore National Laboratory provided stable 14-MeV neutron sources for the measurements. Measurements of scintillator decay characteristics indicate that some commercially available scintillators should be suitable for recording both 14-MeV and downscattered neutron images of compressed ICF targets

  8. Weapons Neutron Research Facility (WNR)

    Data.gov (United States)

    Federal Laboratory Consortium — The Weapons Neutron Research Facility (WNR) provides neutron and proton beams for basic, applied, and defense-related research. Neutron beams with energies ranging...

  9. A Novel Scanning Land Mine Detector Based on the Technique of Neutron Back Scattering Imaging

    OpenAIRE

    Bom, V.; A.M. Osman; Monem, A.M.A.

    2008-01-01

    The neutron back-scattering (NBS) technique is a well established method to find hydrogen in objects. It can be applied in land mine detection taking advantage of the fact that land mines are abundant in hydrogen. The NBS technique is suitable for land mine scanning e.g., seeking for land mines with a moving detector system, because of the high speed of operation. Scan speeds up to 800 mm/s are reported here depending on the intensity of the neutron source, the mine size and the depth at whic...

  10. Simulation of neutron fluxes around the W7-X Stellarator

    International Nuclear Information System (INIS)

    A new fusion experiment, the WENDELSTEIN 7-X Stellarator (W7-X), will be undertaken in Greifswald in Germany. Measurements of the neutron flux will provide information on fusion reaction rates and possibly also on ion temperatures as function of time. For this purpose moderating neutron counters will be designed, tested, calibrated and eventually used at W7-X. Extensive Monte-Carlo simulations have been performed in order to select the most suitable detector and moderator combination with a flat response function and highest achievable efficiency. Different detector configurations with different moderating materials have been tried out, showing that a 32 cm thick graphite moderating BF3 -counter gives the desired flat response and sufficient efficiency. Neutron spectra calculations have been made for different torus models and the influence of floor, walls and ceiling (i.e. reactor hall) have been investigated. Presented results suggest that a more detailed torus model significantly reduces the number of neutron counts at the detector. Calculations including the reactor hall indicate a tendency of shifting the neutron spectra towards the thermal region. The main part of the scattered neutrons are back-scattered from the floor. Finally, calculations on the graphite moderating BF3 -counter in the detailed torus environment were performed in order to assess the absolute response function under the influence of the reactor hall. The results show that the detector count rate will increase by only 5-7 % when the reactor hall is taken into account. With a stellarator generating 1012 to 1016 neutrons per second the detector count rate will be 2x105 to 2x109 neutrons per second

  11. Predicting seabed properties from acoustic backscatter on the UK continental shelf (Invited)

    Science.gov (United States)

    McGonigle, C.; Collier, J.

    2010-12-01

    The relationship between backscatter imagery, sediment grain size and measures of biological community diversity are investigated using a quantitative approach at an aggregate extraction site in the Southern North Sea, UK. Previous work conducted at Oban in Scotland (Collier and Brown, 2005) showed the potential for estimating sediment grain size from first order backscatter statistics. In particular this study reported r2 correlation values of 0.531 between mean backscatter and mean sediment grain size, with r2=0.351 between standard deviation backscatter and sediment grain size sorting (n=19). Here we test these simple linear relationships in a different environment where the sediments are coarser and the degree of sorting is lower. We present the analysis of a dataset collected in 2008 off the coast of East Anglia, UK. Beam-time series backscatter imagery was acquired from a 300 kHz source MBES (Kongsberg Simard EM3000D), and ground-truth data obtained from a series of 100 Hamon and 16 Clamshell grabs processed for particle size analysis. Pixels were extracted from 32-bit backscatter imagery at 50 m2 window based on the ground-truth data locations. So far 19 of the 100 Hamon samples have been processed. These show a significant correlation between mean backscatter intensity and mean sediment grain size (r2=0.427). The level of agreement between standard deviation backscatter and grain size distribution however, was lower at r2=0.078. Correlation of univariate measures of biological diversity and mean backscatter were low for the 19 samples; the maximum observed value was r2=0.074 (Fisher’s diversity index). Relative to the standard deviation backscatter, the strongest correlation was r2=0.192 (Brillion’s). The analysis of the Clamshell samples is completed. In this case, the MBES backscatter imagery established a stronger positive correlation (r2=0.628) between the means. The level of agreement observed between the standard deviation of the backscatter and

  12. LUPIN, a new instrument for pulsed neutron fields

    Science.gov (United States)

    Caresana, M.; Ferrarini, M.; Manessi, G. P.; Silari, M.; Varoli, V.

    2013-06-01

    A number of studies focused in the last decades on the development of survey meters to be used in pulsed radiation fields. This is a topic attracting widespread interest for applications such as radiation protection and beam diagnostics in accelerators. This paper describes a new instrument specifically conceived for applications in pulsed neutron fields (PNF). The detector, called LUPIN, is a rem counter type instrument consisting of a 3He proportional counter placed inside a spherical moderator. It works in current mode with a front-end electronics consisting of a current-voltage logarithmic amplifier, whose output signal is acquired with an ADC and processed on a PC. This alternative signal processing allows the instrument to be used in PNF without being affected by saturation effects. Moreover, it has a measurement capability ranging over many orders of burst intensity. Despite the fact that it works in current mode, it can measure a single neutron interaction. The LUPIN was first calibrated in CERN's calibration laboratory with a PuBe source. Measurements were carried out under various experimental conditions at the Helmholtz-Zentrum in Berlin, in the stray field at various locations of the CERN Proton Synchrotron complex and around a radiotherapy linear accelerator at the S. Raffaele hospital in Milan. The detector can withstand single bursts with values of H*(10) up to 16 nSv/burst without showing any saturation effect. It efficiently works in pulsed stray fields, where a conventional rem-counter underestimates by a factor of 2. It is also able to reject the very intense and pulsed photon contribution that often accompanies the neutron field with good reliability.

  13. The technique of neutron profile for level determination in a jet oil storage vessel

    International Nuclear Information System (INIS)

    In the present paper, preliminary results related to level determination at a Jet oil storage vessel, located in the International Airport Jose Marti, by the neutron profile technique are brought to discussion. Using an Am-Be (1Ci) neutron source and a thermal He-3 neutron detector, values between 10.8-10.85m in height were encountered during the one wall-side scanning of the vessel. This technique, based on the neutron backscatter principle, was also employed for thickness inspection of wall vessel and as it was expected, lower reinforced steel sheets achieved a slight higher thickness than the upper one. Useful dose rate data are presented in order to show, that this new in our country nondestructive technique can be use in safety conditions for industrial diagnostic assay. (Author)

  14. Analysis of stimulated Raman backscatter and stimulated Brillouin backscatter in experiments performed on SG-III prototype facility with a spectral analysis code

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Liang; Zhao, Yiqing; Hu, Xiaoyan; Zou, Shiyang [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Yang, Dong; Wang, Feng; Peng, Xiaoshi; Li, Zhichao; Li, Sanwei; Xu, Tao; Wei, Huiyue [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Liu, Zhanjun; Zheng, Chunyang, E-mail: zheng-chunyang@iapcm.ac.cn [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing 100871 (China)

    2014-07-15

    Experiments about the observations of stimulated Raman backscatter (SRS) and stimulated Brillouin backscatter (SBS) in Hohlraum were performed on Shenguang-III (SG-III) prototype facility for the first time in 2011. In this paper, relevant experimental results are analyzed for the first time with a one-dimension spectral analysis code, which is developed to study the coexistent process of SRS and SBS in Hohlraum plasma condition. Spectral features of the backscattered light are discussed with different plasma parameters. In the case of empty Hohlraum experiments, simulation results indicate that SBS, which grows fast at the energy deposition region near the Hohlraum wall, is the dominant instability process. The time resolved spectra of SRS and SBS are numerically obtained, which agree with the experimental observations. For the gas-filled Hohlraum experiments, simulation results show that SBS grows fastest in Au plasma and amplifies convectively in C{sub 5}H{sub 12} gas, whereas SRS mainly grows in the high density region of the C{sub 5}H{sub 12} gas. Gain spectra and the spectra of backscattered light are simulated along the ray path, which clearly show the location where the intensity of scattered light with a certain wavelength increases. This work is helpful to comprehend the observed spectral features of SRS and SBS. The experiments and relevant analysis provide references for the ignition target design in future.

  15. Neutron in biology

    Energy Technology Data Exchange (ETDEWEB)

    Niimura, Nobuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-11-01

    Neutron in biology can provide an experimental method of directly locating relationship of proteins and DNA. However, there are relatively few experimental study of such objects since it takes a lot of time to collect a sufficient number of Bragg reflections and inelastic spectra due to the low flux of neutron illuminating the sample. Since a next generation neutron source of JAERI will be 5MW spallation neutron source and its effective neutron flux will be 10{sup 2} to 10{sup 3} times higher than the one of JRR-3M, neutron in biology will open a completely new world for structural biology. (author)

  16. Layered semiconductor neutron detectors

    Science.gov (United States)

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  17. Reactor neutron dosimetry

    International Nuclear Information System (INIS)

    An analysis of requirements and possibilities for experimental neutron spectrum determination during the reactor pressure vessel surveil lance programme is given. Fast neutron spectrum and neutron dose rate were measured in the Fast neutron irradiation facility of our TRIGA reactor. It was shown that the facility can be used for calibration of neutron dosimeters and for irradiation of samples sensitive to neutron radiation. The investigation of the unfolding algorithm ITER was continued. Based on this investigations are two specialized unfolding program packages ITERAD and ITERGS written this year. They are able to unfold data from activation detectors and NaI(T1) gamma spectrometer respectively

  18. Pulsed neutron porosity logging

    International Nuclear Information System (INIS)

    A borehole logging tool employing a pulsed neutron source and a pair of spaced-apart epithermal neutron detectors is lowered into a borehole traversing a subsurface formation. The formation is irradiated with bursts of fast neutrons and the epithermal neutrons returning to the borehole as a result of such irradiation are detected by the pair of epithermal neutrons detectors. These detected epithermal neutrons are both time resolved and time integrated during their epithermal dieaway spectrum to provide indications of lithology independent porosity and lithology dependent porosity respectively. 6 refs

  19. Broadband Neutron Interferometer

    CERN Document Server

    Pushin, Dmitry A; Hussey, Dan; Miao, Houxun; Arif, Muhammad; Cory, David G; Huber, Michael G; Jacobson, David; LaManna, Jacob; Parker, Joseph D; Shinohara, Taken; Ueno, Wakana; Wen, Han

    2016-01-01

    We demonstrate a two phase-grating, multi-beam neutron interferometer by using a modified Ronchi setup in a far-field regime. The functionality of the interferometer is based on the universal \\moire effect that was recently implemented for X-ray phase-contrast imaging in the far-field regime. Interference fringes were achieved with monochromatic, bichromatic, and polychromatic neutron beams; for both continuous and pulsed beams. This far-field neutron interferometry allows for the utilization of the full neutron flux for precise measurements of potential gradients, and expands neutron phase-contrast imaging techniques to more intense polycromatic neutron beams.

  20. Neutron scattering and spallation neutron sources

    International Nuclear Information System (INIS)

    Neutron scattering as a probe of microscopic structure and dynamics is a powerful tool for research in a wide variety of fields, and an accelerator-based spallation neutron source can supply high flux pulses for neutron scattering. The characteristics of neutron scattering, the principle and development of spallation neutron sources, and their advantages in multidisciplinary applications are summarized. In the proposed project of the Chinese Spallation Neutron Source the target station will consist of a piece-stacked tungsten target, a Be/Fe reflector and an Fe/heavy concrete bio-protected shelter. The pulsed neutron flux will be up to 2.4 x 1016 n/cm2/s under a nuclear power of 100 kW. Five neutron scattering instruments--a high flux powder diffractometer, a high resolution powder diffractometer, small angle diffractometer, multi-functional reflectometer and direct geometry inelastic spectrometer, will be constructed as the first step to cover most neutron scattering applications. (authors)