WorldWideScience

Sample records for area position-sensitive ionization

  1. A large area position-sensitive ionization chamber for heavy-ion-induced reaction studies

    CERN Document Server

    Pant, L M; Dinesh, B V; Thomas, R G; Saxena, A; Sawant, Y S; Choudhury, R K

    2002-01-01

    A large area position-sensitive ionization chamber with a wide dynamic range has been developed to measure the mass, charge and energy of the heavy ions and the fission fragments produced in heavy-ion-induced reactions. The split anode geometry of the detector makes it suitable for both particle identification and energy measurements for heavy ions and fission fragments. The detector has been tested with alpha particles from sup 2 sup 4 sup 1 Am- sup 2 sup 3 sup 9 Pu source, fission fragments from sup 2 sup 5 sup 2 Cf and the heavy-ion beams from the 14UD Mumbai Pelletron accelerator facility. Using this detector, measurements on mass and total kinetic energy distributions in heavy-ion-induced fusion-fission reactions have been carried out for a wide range of excitation energies. Results on deep inelastic collisions and mass-energy correlations on different systems using this detector setup are discussed.

  2. Construction and commissioning of a position-sensitive ionization chamber

    Science.gov (United States)

    Kwag, M. S.; Chae, K. Y.; Cha, S. M.; Kim, A.; Kim, M. J.; Lee, E. J.; Lee, J. H.

    2016-05-01

    A position-sensitive ionization chamber has been constructed and commissioned at the Physics Department of Sungkyunkwan University to extract position information on incident charged particles for future nuclear reaction measurements. By utilizing the newly-designed position-sensitive anodes and the previously-commissioned portable gas-filled ionization chamber by Chae et al., position information on incident particles could be obtained. The device was tested with an 241Am α-emitting source, and the standard deviation of the fitted Gaussian distribution was measured to be 1.76 mm when a collimator with a 2 mm hole was used.

  3. Two-dimensional position sensitive ionization chamber with GEM

    Science.gov (United States)

    Kitamura, Noritaka; Noro, Tetsuo; Sakaguchi, Satoshi; Takao, Hideaki; Nishio, Yasutaka

    2014-09-01

    We have been developing a multi-anode ionization chamber for Accelerator Mass Spectrometry (AMS) at Kyushu University. Furthermore, we are planning to construct a neutron detector with high position resolution by combining the chamber with Gas Electron Multiplier (GEM) and a neutron converter. One of purposes is the measurement of p-> , pn knockout reaction from unstable nuclei. The multi-anode ionization chamber is composed of subdivided multiple anodes, a cathode to produce an uniform electric field, and a Frisch grid. The chamber must have position sensitivity because obtaining a beam profile is required for AMS measurements, where counting loss should be avoided. Also in the case of the neutron detector, it is necessary to measure the position to deduce the scattering angles. We have recently established a two-dimensional position readout system by the following methods: the measurement of horizontal position is enabled by trimming some anodes into wedge-like shape, and vertical position can be determined by the ratio of induced charge on the grid to the total charge on anodes. In addition, improvement of S/N ratio is important for isotope separation and position resolution. We installed a rectangular-shaped GEM and tried improving S/N ratio by electron amplification.

  4. A position-sensitive twin ionization chamber for fission fragment and prompt neutron correlation experiments

    Science.gov (United States)

    Göök, A.; Geerts, W.; Hambsch, F.-J.; Oberstedt, S.; Vidali, M.; Zeynalov, Sh.

    2016-09-01

    A twin position-sensitive Frisch grid ionization chamber, intended as a fission fragment detector in experiments to study prompt fission neutron correlations with fission fragment properties, is presented. Fission fragment mass and energies are determined by means of the double kinetic energy technique, based on conservation of mass and linear momentum. The position sensitivity is achieved by replacing each anode plate in the standard twin ionization chamber by a wire plane and a strip anode, both readout by means of resistive charge division. This provides information about the fission axis orientation, which is necessary to reconstruct the neutron emission process in the fully accelerated fragment rest-frame. The energy resolution compared to the standard twin ionization chamber is found not to be affected by the modification. The angular resolution of the detector relative to an arbitrarily oriented axis is better than 7° FWHM. Results on prompt fission neutron angular distributions in 235U(n,f) obtained with the detector in combination with an array of neutron scintillation detectors is presented as a proof of principle.

  5. A fast large-area position-sensitive time-of-flight neutron detection system

    International Nuclear Information System (INIS)

    A new position-sensitive time-of-flight neutron detection and histograming system has been developed for use at the Intense Pulsed Neutron Source. Spatial resolution of roughly 1 cm x 1 cm and time-of-flight resolution of ∼1 μsec are combined in a detection system which can ultimately be expanded to cover several square meters of active detector area. This system is based on the use of arrays of cylindrical one-dimensional position-sensitive proportional counters, and is capable of collecting the x-y-t data and sorting them into histograms at time-averaged data rates up to ∼300,000 events/sec over the full detector area and with instantaneous data rates up to more than fifty times that. Numerous hardware features have been incorporated to facilitate initial tuning of the position encoding, absolute calibration of the encoded positions, and automatic testing for drifts. 7 refs., 11 figs., 1 tabs

  6. Development of large area and of position-sensitive timing RPCs

    CERN Document Server

    Blanco, A; Finck, C; Fonte, Paulo J R; Gobbi, A; Mendiratta, S K; Monteiro, J; Policarpo, Armando; Rozas, M

    2002-01-01

    Resistive Plate Chambers (RPC) made with glass and metal electrodes forming accurately spaced gas gaps of a few hundred micrometers have reached timing accuracies below 50 ps sigma with efficiencies above 99% for MIPs. This type of detector, operating at atmospheric pressure with non-flammable gases, seems well suited for large TOF systems, providing performances comparable to the scintillator-based TOF technology with significantly lower price per channel and being compatible with magnetic fields. In this work, we report recent developments of the timing RPC technology, including a large area counter (0.16 m sup 2) and smaller, position-sensitive, single-gap counters. The latter devices are aimed to be applied in small and accurate TOF systems using a multilayer structure. The large counter has shown a timing resolution between 50 and 75 ps sigma over the whole active area, with 96% efficiency and very small timing tails, along with a longitudinal position-resolution of 1.2 cm sigma. The single-gap counters ...

  7. A Two-dimension Position Sensitive PPAC

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A two-dimensional position sensitive parauel-plate avalanche counter(PPAC)with a 100 mm×100 mm active area is developed for the Radioactive Ion-Beam Line in Lanzhou(RIBLL).The detector consists of one anode plane and two cathodes wire planes which are strip planes for the PPACs used in RIKEN~[1].The anode is a Mylar foil coated with a thin layer of gold on each side.The cathode planes X and Y are made of gold-

  8. Two-dimensional position sensitive neutron detector

    Indian Academy of Sciences (India)

    A M Shaikh; S S Desai; A K Patra

    2004-08-01

    A two-dimensional position sensitive neutron detector has been developed. The detector is a 3He + Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm × 345 mm, pixel size 5 mm × 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 Å neutrons. The detector is tested with 0.5 bar 3He + 1.5 bar krypton gas mixture in active chamber and 2 bar 4He in compensating chamber. The pulse height spectrum recorded at an anode potential of 2000 V shows energy resolution of ∼ 25% for the 764 keV peak. A spatial resolution of 8 mm × 6 mm is achieved. The detector is suitable for SANS studies in the range of 0.02–0.25 Å-1.

  9. Two-dimensional position sensitive Si(Li) detector

    International Nuclear Information System (INIS)

    Circular, large-area two-dimensional Si(Li) position sensitive detectors have been fabricated. The detectors employ a thin lithium-diffused n+ resisitive layer for one contact and a boron implanted p+ resistive layer for the second contact. A position resolution of the order of 100 μm is indicated

  10. Features of position sensitive neutron detectors

    International Nuclear Information System (INIS)

    The phase space of neutron beams - the neutron flux distribution with respect to position, flight direction and energy/wavelength - can be investigated by means of position sensitive detectors in time-of-flight regime, using the pinhole imaging method. These results can serve for experimental verification of numerical simulations, quality assessment of neutron optical components, giving information for quality assurance and corrective actions as well as input data for downstream instrument design and optimization. On-site investigation of highly radiating areas like moderators, cold neutron sources and beam extraction systems, hardly accessible by other means is possible by this procedure. Examples of such experiments performed at the spallation source at Los Alamos Neutron Scattering Center and the reactor at Budapest Neutron Centre are presented. The accuracy and reliability of the obtained detector images can be improved by the development of detector parameters: resolution, limit count rate, detection efficiency and their crossovers. For this purpose, a method is worked out to evaluate the detection depth profile and efficiency of the multiwire proportional detectors with delay-line encoding or parallel readout. A polychromatic, collimated, pulsed beam, tilted with respect to the normal to the detector plane by a known angle is measured. The trace thus recorded is the projection of the beam track through the detector gas chamber. The neutron counts detected in various pixels of this trace is proportional to the number of neutrons absorbed and detected at various gas depths. Measurement of the time of flight allows the determination of the intensity distribution energy dependence. This technique is suitable to adjust the drift voltage to ensure appropriate spectral accuracy of new detectors. The depth detection profile can be determined (number of neutrons detected versus depth and wavelength), as well as the resolution vs. wavelength in one step. (author)

  11. Signal processors for position-sensitive detectors

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, Ken-ichi [Hosei Univ., Koganei, Tokyo (Japan). Coll. of Engineering

    1996-07-01

    Position-sensitive detectors (PSD) are widely used in following various fields: condensed matter studies, material engineering, medical radiology particle physics, astrophysics and industrial applications. X-ray diffraction analysis is one of the field where PSDs are the most important instruments. In this field, many types of PSAs are employed: position-sensitive proportional counters (PSPC), multi-wire proportional chambers (MWPC), imaging plates, image intensifiers combined CCD cameras and semiconductor array devices. Two readout systems used for PSDs, where one is a charge-division type with high stability and the other is an encoder with multiple delay, line readout circuits useful for fast counting, were reported in this paper. The multiple delay line encoding system can be applicable to high counting rate 1D and 2D gas proportional detectors. (G.K.)

  12. Position-sensitive counter telescope for light and heavy ions

    International Nuclear Information System (INIS)

    A position-sensitive counter telescope of 600 mm length has been developed for use in an Enge split-pole spectrograph. The device has an intrinsic position resolution of less than 0.25 mm for light and heavy ions at 450 incidence. Particle identification is provided by a gridded, 22 mm high and 140 mm deep ionization chamber which yields a total energy (E) readout from the cathode plate. Also provided are ΔE signals and a veto signal from a segmented anode. The total energy resolution for 60 MeV 16O ions is 1%, the ΔE resolution 4.4%. The ionization chamber is backed by a fast scintillator which stops penetrating ions. Electrons from short sections of the ion trajectories are selected for position sensing by a drift field, which is perpendicular to the trajectory and to the cathode of the ionization chamber, and by two 0 referred to the reaction angle was obtained. The detector has operated without loss in resolution at up 20000 counts per second. (orig.)

  13. Position sensitive x-ray detector

    International Nuclear Information System (INIS)

    A multi ware position sensitive gas counter for X-ray detection was developed in our laboratory, making use of commercial delay-lines for position sensing. Six delay-line chips (50 ns delay each, 40 Mhz cut-off frequency) cover a total sensitive length of 150 mm leading to a delay-risetime ratio that allows for a high-resolution position detection. Tests using the 5,9 keV X-ray line from a 55 Fe source and integral linearity better than 0,1% and a maximal differential linearity of ±4,0% were obtained operating the detector with an Ar-C H4 (90%-10%) gas mixture at 700 torr. Similar tests were performed, using the 8,04 keV line from a Cu x-ray tube. A total resolution of 330 μm, and the same integral and differential linearities were obtained. (author)

  14. Position sensitive SiPM detector for Cherenkov applications

    CERN Document Server

    Gruber, L; Brunner, S E; Bühler, P; Marton, J; Suzuki, K

    2011-01-01

    A prototype of a position sensitive photo-detector with 5.6 x 5.6 cm2 detection area readout with 64 Hamamatsu MPPCs (S10931-100P) with 3 x 3 mm2 active area each has been built and tested. The photo-sensors are arranged in a 8 x 8 array with a quadratic mirror light guide on top. The module is currently readout by in-house developed preamplifier boards but employing existing ASIC chips optimized for SiPM readout is also planned. Such a device is one of the candidates to be used for photon detection in the PANDA DIRC detectors.

  15. An array of virtual Frisch-grid CdZnTe detectors and a front-end application-specific integrated circuit for large-area position-sensitive gamma-ray cameras

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov, A. E., E-mail: bolotnik@bnl.gov; Ackley, K.; Camarda, G. S.; Cherches, C.; Cui, Y.; De Geronimo, G.; Fried, J.; Hossain, A.; Mahler, G.; Maritato, M.; Roy, U.; Salwen, C.; Vernon, E.; Yang, G.; James, R. B. [Brookhaven National Laboratory, Upton, New York 11793 (United States); Hodges, D. [University of Texas at El Paso, El Paso, Texas 79968 (United States); Lee, W. [Korea University, Seoul 136-855 (Korea, Republic of); Petryk, M. [SUNY Binghamton, Vestal, New York 13902 (United States)

    2015-07-15

    We developed a robust and low-cost array of virtual Frisch-grid CdZnTe detectors coupled to a front-end readout application-specific integrated circuit (ASIC) for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6 × 6 × 15 mm{sup 3} detectors grouped into 3 × 3 sub-arrays of 2 × 2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readout electronics. The further enhancement of the arrays’ performance and reduction of their cost are possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects.

  16. An array of virtual Frisch-grid CdZnTe detectors and a front-end application-specific integrated circuit for large-area position-sensitive gamma-ray cameras.

    Science.gov (United States)

    Bolotnikov, A E; Ackley, K; Camarda, G S; Cherches, C; Cui, Y; De Geronimo, G; Fried, J; Hodges, D; Hossain, A; Lee, W; Mahler, G; Maritato, M; Petryk, M; Roy, U; Salwen, C; Vernon, E; Yang, G; James, R B

    2015-07-01

    We developed a robust and low-cost array of virtual Frisch-grid CdZnTe detectors coupled to a front-end readout application-specific integrated circuit (ASIC) for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6 × 6 × 15 mm(3) detectors grouped into 3 × 3 sub-arrays of 2 × 2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readout electronics. The further enhancement of the arrays' performance and reduction of their cost are possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects.

  17. An array of virtual Frisch-grid CdZnTe detectors and a front-end application-specific integrated circuit for large-area position-sensitive gamma-ray cameras

    International Nuclear Information System (INIS)

    We developed a robust and low-cost array of virtual Frisch-grid CdZnTe detectors coupled to a front-end readout application-specific integrated circuit (ASIC) for spectroscopy and imaging of gamma rays. The array operates as a self-reliant detector module. It is comprised of 36 close-packed 6 × 6 × 15 mm3 detectors grouped into 3 × 3 sub-arrays of 2 × 2 detectors with the common cathodes. The front-end analog ASIC accommodates up to 36 anode and 9 cathode inputs. Several detector modules can be integrated into a single- or multi-layer unit operating as a Compton or a coded-aperture camera. We present the results from testing two fully assembled modules and readout electronics. The further enhancement of the arrays’ performance and reduction of their cost are possible by using position-sensitive virtual Frisch-grid detectors, which allow for accurate corrections of the response of material non-uniformities caused by crystal defects

  18. Position-sensitive gaseous photomultipliers research and applications

    CERN Document Server

    Francke, Tom; Peskov, Vladimir

    2016-01-01

    Gaseous photomultipliers are defined as gas-filled devices capable of recording single ultraviolet (UV) and visible photons with high position resolution. Used in a variety of research areas, these detectors can be paired with computers to treat and store imaging information of UV-light. Position-Sensitive Gaseous Photomultipliers: Research and Applications explores the advancement of gaseous detectors as applied for single photon detection. Emphasizing emerging perspectives and new ways to apply gaseous detectors across research fields, this research-based publication is an essential reference source for engineers, physicists, graduate-level students, and researchers.

  19. Position sensitivity of graphene field effect transistors to X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Cazalas, Edward, E-mail: ejc149@psu.edu; Moore, Michael E.; Jovanovic, Igor [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Sarker, Biddut K.; Childres, Isaac [Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Chen, Yong P. [Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2015-06-01

    Device architectures that incorporate graphene to realize detection of electromagnetic radiation typically utilize the direct absorbance of radiation by graphene. This limits their effective area to the size of the graphene and their applicability to lower-energy, less penetrating forms of radiation. In contrast, graphene-based transistor architectures that utilize the field effect as the detection mechanism can be sensitive to interactions of radiation not only with graphene but also with the surrounding substrate. Here, we report the study of the position sensitivity and response of a graphene-based field effect transistor (GFET) to penetrating, well-collimated radiation (micro-beam X-rays), producing ionization in the substrate primarily away from graphene. It is found that responsivity and response speed are strongly dependent on the X-ray beam distance from graphene and the gate voltage applied to the GFET. To develop an understanding of the spatially dependent response, a model is developed that incorporates the volumetric charge generation, transport, and recombination. The model is in good agreement with the observed spatial response characteristics of the GFET and predicts a greater response potential of the GFET to radiation interacting near its surface. The study undertaken provides the necessary insight into the volumetric nature of the GFET response, essential for development of GFET-based detectors for more penetrating forms of ionizing radiation.

  20. A position sensitive gas detector for tomography with thermal neutrons

    International Nuclear Information System (INIS)

    A position sensitive gas detector originally designed for X-ray has been modified to detect thermal neutrons addressing its utilization in tomography. This work describes the modifications done for this purpose, including the incorporation of neutron-to-charged particle converter materials, and the measurements carried out to evaluate the detector performance for each of them. The first converter studied was a natural gadolinium foil placed close to the detector window, producing an internal conversion electron from the neutron gadolinium interaction, which causes an ionization in the argon-methane filling gas. Another converter studied was high-enriched 3He, replacing both the gadolinium foil and the argon-methane gas. 3 He fulfills the main requirements for thermal neutron detection such as high absorption cross section - 5330 barns - low efficiency for gamma-ray conversion and a good charge amplification factor. The 3He(n,p)3H reaction produces a 573 keV-proton and a 191 keV-tritium which are emitted practically into opposite directions, since the neutron itself, due to its very low energy (0.025 eV) does not contribute significantly to the momentum balance. Tomographic systems for thermal neutrons incorporating the developed detector, present some advantages with regard to the earlier 1st generation equipment, such as a better resolution and a reduction in the image acquiring time. (author)

  1. Emulation workbench for position sensitive gaseous scintillation detectors

    Science.gov (United States)

    Pereira, L.; Margato, L. M. S.; Morozov, A.; Solovov, V.; Fraga, F. A. F.

    2015-12-01

    Position sensitive detectors based on gaseous scintillation proportional counters with Anger-type readout are being used in several research areas such as neutron detection, search for dark matter and neutrinoless double beta decay. Design and optimization of such detectors are complex and time consuming tasks. Simulations, while being a powerful tool, strongly depend on the light transfer models and demand accurate knowledge of many parameters, which are often not available. Here we describe an alternative approach based on the experimental evaluation of a detector using an isotropic point-like light source with precisely controllable light emission properties, installed on a 3D positioning system. The results obtained with the developed setup at validation conditions, when the scattered light is strongly suppressed show good agreement with simulations.

  2. Emulation workbench for position sensitive gaseous scintillation detectors

    CERN Document Server

    Pereira, L; Morozov, A; Solovov, V; Fraga, F A F

    2015-01-01

    Position sensitive detectors based on gaseous scintillation proportional counters with Anger-type readout are being used in several research areas such as neutron detection, search for dark matter and neutrinoless double beta decay. Design and optimization of such detectors are complex and time consuming tasks. Simulations, while being a powerful tool, strongly depend on the light transport models and demand accurate knowledge of many parameters, which are often not available. Here we describe an alternative approach based on the experimental evaluation of a detector using an isotropic point-like light source with precisely controllable light emission properties, installed on a 3D positioning system. The results obtained with the developed setup at validation conditions, when the scattered light is strongly suppressed, show good agreement with simulations.

  3. POSSuMUS: a position sensitive scintillating muon SiPM detector

    CERN Document Server

    Ruschke, Alexander

    The development of a modular designed large scale scintillation detector with a two-dimensional position sensitivity is presented in this thesis. This novel POsition Sensitive Scintillating MUon SiPM Detector is named POSSuMUS. The POSSuMUS detector is capable to determine the particle’s position in two space dimensions with a fast trigger capability. Each module is constructed from two trapezoidal shaped plastic scintillators to form one rectangular shaped detector module. Both trapezoids are optically insulated against each other. In both trapezoids the scintillation light is collected by plastic fibers and guided towards silicon photomultipliers (SiPMs). SiPMs are light sensors which are capable to detect even smallest amounts of light. By combining several detector modules, position sensitive areas from 100 cm2 to few m2 are achievable with few readout channels. Therefore, POSSuMUS provides a cost effective detector concept. The position sensitivity along the trapezoidal geometry of one detector module ...

  4. Measurement and Analysis on Neutron Position Sensitive Detector at CARR

    Institute of Scientific and Technical Information of China (English)

    GAO; Jian-bo; HAO; Li-jie; LIU; Xin-zhi; MA; Xiao-bai; LI; Yu-qing

    2013-01-01

    Neutron position sensitive detector is one of the key components for neutron scattering spectrometer.As the eyes of the spectrometer,the detector is mainly used for recording the position and intensity of the neutrons.The 16 linear position sensitive detectors from GE Reuter-Stokes Company have been measured

  5. Technique of Position Sensitive Detector with Alternating Light Source①

    Institute of Scientific and Technical Information of China (English)

    SUMeijun

    1997-01-01

    The signal processing circuits of position sensitive detector(PSD)with alternating light source are presented.The measuring device of PSD with alternating light source can effectively eliminate the interference made by light noise signal.

  6. Self-Balancing Position-Sensitive Detector (SBPSD)

    OpenAIRE

    Ryan Porrazzo; Leigh Lydecker; Suhasini Gattu; Hassaram Bakhru; Natalya Tokranova; James Castracane

    2015-01-01

    Optical position-sensitive detectors (PSDs) are a non-contact method of tracking the location of a light spot. Silicon-based versions of such sensors are fabricated with standard CMOS technology, are inexpensive and provide a real-time, analog signal output corresponding to the position of the light spot. An innovative type of optical position sensor was developed using two back-to-back connected photodiodes. These so called self-balancing position-sensitive detectors (SBPSDs) eliminate the n...

  7. Pulsed neutron imaging using 2-dimensional position sensitive detectors

    International Nuclear Information System (INIS)

    2-dimensional position sensitive detectors are used for pulsed neutron imaging and at each pixel of the detector a time of flight spectrum is recorded. Therefore, a transmission spectrum through the object has wavelength dependent structure reflecting the neutron total cross section. For such measurements, the detectors are required to have ability to store neutron events as a function of the flight time as well as to have good spatial resolution. Furthermore, high counting rate is also required at the high intensity neutron sources like J-PARC neutron source in Japan. We have developed several types of detectors with different characteristics; two counting type detectors for high counting rate with coarse spatial resolution and one camera type detector for high spatial resolution. One of counting type detectors is a pixel type. The highest counting rate is about 28 MHz. Better spatial resolution is obtained by a GEM detector. Effective area is 10 × 10 cm2, pixel size is 0.8 mm. The maximum counting rate is 3.65 MHz. To get higher spatial resolution we are now developing the camera type detector system using a neutron image intensifier, which have image integration function as a function of time of flight. We have succeeded to obtain time dependent images in this camera system. By using these detectors we performed transmission measurements for obtaining the crystallographic information and elemental distribution images

  8. Pulsed neutron imaging using 2-dimensional position sensitive detectors

    Science.gov (United States)

    Kiyanagi, Y.; Kamiyama, T.; Kino, K.; Sato, H.; Sato, S.; Uno, S.

    2014-07-01

    2-dimensional position sensitive detectors are used for pulsed neutron imaging and at each pixel of the detector a time of flight spectrum is recorded. Therefore, a transmission spectrum through the object has wavelength dependent structure reflecting the neutron total cross section. For such measurements, the detectors are required to have ability to store neutron events as a function of the flight time as well as to have good spatial resolution. Furthermore, high counting rate is also required at the high intensity neutron sources like J-PARC neutron source in Japan. We have developed several types of detectors with different characteristics; two counting type detectors for high counting rate with coarse spatial resolution and one camera type detector for high spatial resolution. One of counting type detectors is a pixel type. The highest counting rate is about 28 MHz. Better spatial resolution is obtained by a GEM detector. Effective area is 10 × 10 cm2, pixel size is 0.8 mm. The maximum counting rate is 3.65 MHz. To get higher spatial resolution we are now developing the camera type detector system using a neutron image intensifier, which have image integration function as a function of time of flight. We have succeeded to obtain time dependent images in this camera system. By using these detectors we performed transmission measurements for obtaining the crystallographic information and elemental distribution images.

  9. Position sensitivity of MAMA detectors. [Multi-Anode Microchannel Array

    Science.gov (United States)

    Morgan, J. S.; Slater, D. S.; Timothy, J. G.; Jenkins, E. B.

    1988-01-01

    The results of laboratory and telescopic measurements of the position sensitivity of a visible MAMA detector utilizing a 'coarse-fine' array are presented. The photometric accuracy of this detector was determined under point source illumination. It was found that computed centroid positions are accurate across the entire array to within 0.04 pixels.

  10. POSSuMUS. A position sensitive scintillating muon SiPM detector

    International Nuclear Information System (INIS)

    The development of a modular designed large scale scintillation detector with a two-dimensional position sensitivity is presented in this thesis. This novel POsition Sensitive Scintillating MUon SiPM Detector is named POSSuMUS. The POSSuMUS detector is capable to determine the particle's position in two space dimensions with a fast trigger capability. Each module is constructed from two trapezoidal shaped plastic scintillators to form one rectangular shaped detector module. Both trapezoids are optically insulated against each other. In both trapezoids the scintillation light is collected by plastic fibers and guided towards silicon photomultipliers (SiPMs). SiPMs are light sensors which are capable to detect even smallest amounts of light. By combining several detector modules, position sensitive areas from 100 cm2 to few m2 are achievable with few readout channels. Therefore, POSSuMUS provides a cost effective detector concept. The position sensitivity along the trapezoidal geometry of one detector module is achieved by the path length dependent amount of detected light for crossing particles. The ratio of the light yields in both trapezoids is calculated. This value corresponds to the position of the particle traversing the detector. A spatial resolution in the order of several mm is foreseen. The position sensitivity along the scintillator module is determined by the propagation time of light to the SiPMs located on opposite sides of the detector. A spatial resolution of few cm is expected for this direction. The POSSuMUS detector is applicable as large area trigger detector with a two dimensional position information of crossing particles. This is suitable in detector tests of large area precesion detectors or for measuring the small angle scattering of cosmic muons. At the beginning of this thesis, the determination of important SiPM characteristics like the breakdown voltage is presented. In the course of this work the detector principle is proven by the

  11. Self-Balancing Position-Sensitive Detector (SBPSD

    Directory of Open Access Journals (Sweden)

    Ryan Porrazzo

    2015-07-01

    Full Text Available Optical position-sensitive detectors (PSDs are a non-contact method of tracking the location of a light spot. Silicon-based versions of such sensors are fabricated with standard CMOS technology, are inexpensive and provide a real-time, analog signal output corresponding to the position of the light spot. An innovative type of optical position sensor was developed using two back-to-back connected photodiodes. These so called self-balancing position-sensitive detectors (SBPSDs eliminate the need for external readout circuitry entirely. Fabricated prototype devices demonstrate linear, symmetric coordinate characteristics and a spatial resolution of 200 μm for a 74 mm device. PSDs are commercially available only up to a length of 37 mm. Prototype devices were fabricated with various lengths up to 100 mm and can be scaled down to any size below that.

  12. Self-Balancing Position-Sensitive Detector (SBPSD).

    Science.gov (United States)

    Porrazzo, Ryan; Lydecker, Leigh; Gattu, Suhasini; Bakhru, Hassaram; Tokranova, Natalya; Castracane, James

    2015-01-01

    Optical position-sensitive detectors (PSDs) are a non-contact method of tracking the location of a light spot. Silicon-based versions of such sensors are fabricated with standard CMOS technology, are inexpensive and provide a real-time, analog signal output corresponding to the position of the light spot. An innovative type of optical position sensor was developed using two back-to-back connected photodiodes. These so called self-balancing position-sensitive detectors (SBPSDs) eliminate the need for external readout circuitry entirely. Fabricated prototype devices demonstrate linear, symmetric coordinate characteristics and a spatial resolution of 200 μm for a 74 mm device. PSDs are commercially available only up to a length of 37 mm. Prototype devices were fabricated with various lengths up to 100 mm and can be scaled down to any size below that. PMID:26205266

  13. Dual Position Sensitive MWPC for tracking reaction products at VAMOS++

    CERN Document Server

    Vandebrouck, Marine; Rejmund, Maurycy; Fremont, Georges; Pancin, Julien; Navin, Alahari; Michelagnoli, Caterina; Goupil, Johan; Spitaels, Charles; Jacquot, Bertrand

    2015-01-01

    The characteristics and performance of a Dual Position Sensitive Multi-Wire Proportional Counter (DPS-MWPC) used to measure the scattering angle, interaction position on the target and the velocity of reaction products, detected in the VAMOS++ magnetic spectrometer, are reported. The detector consists of a pair of position sensitive low pressure MWPCs and provides both fast timing signals, along with the two-dimensional position coordinates required to define the trajectory of the reaction products. A time-of-flight resolution of 305(11) ps (FWHM) was measured. The measured resolutions (FWHM) were 2.5(3) mrad and 560(70) {\\mu}m for the scattering angle and the interaction point at the target respectively. The subsequent improvement of the Doppler correction of the energy of the gamma-rays, detected in the gamma-ray tracking array AGATA in coincidence with isotopically identified ions in VAMOS++, is also discussed.

  14. Signal and Noise Properties of Position-Sensitive Avalanche Photodiodes

    OpenAIRE

    Yang, Yongfeng; Wu, Yibao; Farrell, Richard; Dokhale, Purushottam A.; Shah, Kanai S.; Cherry, Simon R.

    2011-01-01

    After many years of development, position-sensitive avalanche photodiodes (PSAPDs) are now being incorporated into a range of scintillation detector systems, including those used in high-resolution small-animal PET and PET/MR scanners. In this work, the signal, noise, signal-to-noise ratio (SNR), flood histogram and timing resolution were measured for lutetium oxyorthosilicate (LSO) scintillator arrays coupled to PSAPDs ranging in size from 10–20 mm, and the optimum bias voltage and working t...

  15. A New Positioning Algorithm for Position-Sensitive Avalanche Photodiodes

    OpenAIRE

    Zhang, Jin; Olcott, Peter D.; Levin, Craig S

    2007-01-01

    We are using a novel position sensitive avalanche photodiode (PSAPD) for the construction of a high resolution positron emission tomography (PET) camera. Up to now most researchers working with PSAPDs have been using an Anger-like positioning algorithm involving the four corner readout signals of the PSAPD. This algorithm yields a significant non-linear spatial “pin-cushion” distortion in raw crystal positioning histograms. In this paper, we report an improved positioning algorithm, which com...

  16. Diffraction Profile Pole Figures Measured with a Position Sensitive Detector

    OpenAIRE

    Wcislak, L.; Bunge, H.J.

    1996-01-01

    Pole figures in the classical sense are defined by the integral intensities of Bragg reflections. The conventional technique of pole figure measurement uses a single detector (usually a scintillation counter) with a wide receiving slit where the integral intensity of a given Bragg reflection is obtained directly. The usage of a position sensitive detector instead of a single detector allows to measure whole diffraction profiles simultaneously. Integral intensities of the diffraction peaks can...

  17. Position Sensitive Detector Used to Detect Beam Profile

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Non-destructive diagnostic methods are very important for beam adjustments and monitors,especially when the beam intensity is less than 10~8 pps during the heavy-ion treatment of cancer.Now the diagnostic devices of HIFRL can’t satisfy the requests,so we decide to construct a detecting system of the residual-gas beam profile~([1,2]).The system uses the Position Sensitive Detector(PSD)~([3,4])based on microchannel plate(MCP)to

  18. A position sensitive microchannel photomultiplier for ultraviolet space astronomy

    Science.gov (United States)

    Lampton, M.; Siegmund, O. H. W.; Bixler, J.; Bowyer, S.

    1986-01-01

    The 25-mm microchannel-plate, position-sensitive UV astronomy photomultiplier tube presented is intended for the EOM-1 Spacelab Mission's FAUST payload and conducts wide-field imaging surveys in the VUV over the 1400-1800-A range. The sealed detector encompasses a CsI photocathode deposited on the inner surface of a MgF2 window, a stack of microchannel plates, and a wedge-and-strip two-dimensional position-sensing anode. Since the wedge-and-strip principle requires only three anode signals, flight electronics can be reduced to three charge amplifiers and three analog-to-digital converters.

  19. Development of a novel position-sensitive microchannel plate detector

    Science.gov (United States)

    Wiggins, Blake; Siwal, Davinder; Desouza, Romualdo

    2015-10-01

    Position sensitive microchannel plate (MCP) detectors which measure the position of an incident electron, ion, or photon, are useful in imaging applications. Recently, a novel detector, which utilizes an induced approach to provide position sensitivity, has been developed. In the prototype detector, using only the zero-crossing point of the inherently bipolar signals, a position resolution of 466 μm (FWHM) has been achieved. Implementing a differential readout may improve on this resolution. To realize this differential approach, a better understanding of the dependence of the induced signal shape on the position of the electron cloud is required. To characterize the dependence of the induced signal shape on position a resistive anode (RA) has been incorporated into the detector. The RA will allow determination of the centroid of the electron cloud. Factors impacting the position resolution obtained with the RA will be discussed and the achieved position resolution of 157 μm (FWHM) will be presented. Supported by the US DOE NNSA under Award No. DE-NA0002012.

  20. Rapid measurement of 210Po in seafood with large area grid ionization chamber α spectrometry

    Institute of Scientific and Technical Information of China (English)

    Li Yucheng; Yin Liangliang; Chen Fei; Shao Xianzhang; Shen Baoming; Kong Xiangyin; Ji Yanqin

    2015-01-01

    Objective To develop a rapid and reliable method for determination of 210Po using large-area grid ionization chamber α spectrometry.Methods Samples were digested using a microwave digestion system.After preparation of sample source,the concentration of 210Po in clam was detected by large-area grid ionization chamber (φ 25 cm).209Po tracer was used to obtain the recovery.Results Large-area grid ionization chamber could achieve better counting and α spectrum resolution when the optimized thickness was 250 μg/cm2.By spiking 209Po tracer in clam,the minimum detectable activity was 9.870 × 10 4 Bq and the recovery of 210Po was 98%.Conclusions Compared with the traditional method,the developed method can avoid separation process,using less quantity of sample (0.2-0.5 g dry) and simplify the measurement process.This method may be has broad application prospects.

  1. CFD SIMULATION OF AIR ION REGIME IN WORK AREAS AT CONDITION OF ARTIFICIAL AIR IONIZATION

    Directory of Open Access Journals (Sweden)

    M. M. Biliaiev

    2016-04-01

    Full Text Available Purpose. The paper supposes creation of a CFD model for calculating the air ion regime in the premises and in work areas at artificial ionization of the air by the ionizer installation indoors with considering the most important physical factors that influence the formation of ions concentration field. Methodology. The proposed CFD model for calculation of the air ion regime in work areas at artificial ionization of the air by installing ionizer indoors is based on the application of aerodynamics, electrostatics and mass transfer equations. The mass transfer equation takes into account the interaction of different polarities of ions with each other and with the dust particles. The calculation of air flow rate in the room is realized on the basis of the potential flow model by using the Laplace equation for the stream function. Poisson equation for the electric potential is used for calculation of the charged particles drift in an electric field. At the simulation to take into account: 1 influence of the working area geometric characteristics; 2 location of the ventilation holes; 3 placement of furniture and equipment; 4 ventilation regime in the room; 5 presence of obstacles on the ions dispersion process; 6 specific location of dust particles emission and ions of different polarity, and their interaction in the room and in the working zones. Findings. The developed CFD model allows determining the concentration of negative ions in the room and in the area of the human respiratory organs. The distribution of the negative ions concentration is presented in the form of concentration field isolines. Originality. The 2D CFD model for calculating the air ion regime in working areas, providing the ability to determine the ions concentration in a given place in the room was created. The proposed model is developed taking into account: placement of furniture and equipment in the room; geometric characteristics of the room; location of dust emissions

  2. A New Positioning Algorithm for Position-Sensitive Avalanche Photodiodes.

    Science.gov (United States)

    Zhang, Jin; Olcott, Peter D; Levin, Craig S

    2007-06-01

    We are using a novel position sensitive avalanche photodiode (PSAPD) for the construction of a high resolution positron emission tomography (PET) camera. Up to now most researchers working with PSAPDs have been using an Anger-like positioning algorithm involving the four corner readout signals of the PSAPD. This algorithm yields a significant non-linear spatial "pin-cushion" distortion in raw crystal positioning histograms. In this paper, we report an improved positioning algorithm, which combines two diagonal corner signals of the PSAPD followed by a 45° rotation to determine the X or Y position of the interaction. We present flood positioning histogram data generated with the old and new positioning algorithms using a 3 × 4 array of 2 × 2 × 3 mm(3) and a 3 × 8 array of 1 × 1 × 3 mm(3) of LSO crystals coupled to 8 × 8 mm(2) PSAPDs. This new algorithm significantly reduces the pin-cushion distortion in raw flood histogram image. PMID:24307743

  3. Linear position sensitive neutron detector using fiber optic encoded scintillators

    International Nuclear Information System (INIS)

    A linear position sensitive slow neutron detector with 3 mm resolution is described. It uses the fiber optic coding principle in which the resolution elements are separate pieces of lithium loaded glass scintillator each coupled by means of flexible polymer optical fibers to a unique combination of 3 photo multipliers (PM's) out of a bank of 12. A decoder circuit repsponds to a triple coincidence between PM outputs and generates a 12 bit work which identifies the scintillator element which stopped the incident neutron. Some details of the construction and decoding electronics are given together with test results obtained using a laboratory isotope neutron source and a monochomated, collimated neutron beam from a reactor. The count rate in the absence of neutron sources is 2 to 3 c min-1 per element; the element to element variation in response to a uniform flux is a few percent for 95% of the elements; the resolution as measured by a 1 mm wide prode neutron beam is 3 mm; the relative long term stability is about 0.1% over 3 days and the detection efficiency measured by comparison with an end windowed, high pressure gas counter is about 65% at a neutron wavelength of 0.9A0

  4. Developments of a 2D Position Sensitive Neutron Detector

    CERN Document Server

    Tian, Li-Chao; Wang, Xiao-Hu; Liu, Rong-Guang; Zhang, Jian; Chen, Yuan-Bo; Sun, Zhi-Jia; Xu, Hong; Yang, Gui-An; Zhang, Qiang

    2011-01-01

    Chinese Spallation Neutron Source (CSNS), one project of the 12th five-year-plan scheme of China, is under construction in Guangdong province. Three neutron spectrometers will be installed at the first phase of the project, where two-dimensional position sensitive thermal neutron detectors are required. Before the construction of the neutron detector, a prototype of two-dimensional 200 mmx200 mm Multi-wire Proportional Chamber (MWPC) with the flowing gas of Ar/CO2 (90/10) has been constructed and tested with the 55Fe X-Ray using part of the electronics in 2009, which showed a good performance. Following the test in 2009, the neutron detector has been constructed with the complete electronics and filled with the 6atm.3He + 2.5atm.C3H8 gas mixture in 2010. The neutron detector has been primarily tested with an Am/Be source. In this paper, some new developments of the neutron detector including the design of the high pressure chamber, the optimization of the gas purifying system and the gas filling process will ...

  5. Development of arrays of position-sensitive microcalorimeters for Constellation-X

    Science.gov (United States)

    Smith, S. J.; Bandler, S. R.; Brekosky, R. P.; Brown, A.-D.; Chervenak, J. A.; Eckart, M. E.; Finkbeiner, F. M.; Iyomoto, N.; Kelley, R. L.; Kolbourne, C. A.; Porter, F. S.; Figueroa-Feliciano, E.

    2008-01-01

    We are developing arrays of position-sensitive transition-edge sensor (POST) X-ray detectors for future astronomy missions such as NASA's Constellation-X. The POST consists of multiple absorbers thermally coupled to one or more transition-edge sensor (TES). Each absorber element has a different thermal coupling to the TES. This results in a distribution of different pulse shapes and enables position discrimination between the absorber elements. POST'S are motivated by the desire to achieve the largest possible focal plane area with the fewest number of readout channels and are ideally suited to increasing the Constellation-X focal plane area, without comprising on spatial sampling. Optimizing the performance of POST'S requires careful design of key parameters such as the thermal conductances between the absorbers, TES and the heat sink. as well as the absorber heat capacities. Using recently developed signal processing algorithms we have investigated the trade-off between position-sensitivity, energy resolution and pulse decay time. based on different device design parameters for PoST's. Our new generation of PoST's utilize technology successfully developed on high resolution (approximately 2.5eV) single pixels arrays of Mo/Au TESs. also under development for Constellation-X. This includes noise mitigation features on the TES and low resistivity electroplated absorbers. We report on the first experimental results from these new one and two-channel PoST"s, consisting of all Au and composite Au/Bi absorbers, which are designed to achieve an energy resolution of < 10 eV. coupled with count-rates of 100's per pixel per second and position sensitivity over the energy range 0.3-10 keV.

  6. Development of Position-sensitive Transition-edge Sensor X-ray Detectors

    Science.gov (United States)

    Smith, S. J.; Bandler, S. R.; Brekosky, R. P.; Brown, A.-D.; Chervenak, J. A.; Eckard, M. E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. s.; Sad (eor. K/ E/); Figueroa-Feliciano, E.

    2008-01-01

    We report on the development of position-sensitive transition-edge sensors (PoST's) for future x-ray astronomy missions such as the International X-ray Observatory (IXO), currently under study by NASA and ESA. PoST's consist of multiple absorbers each with a different thermal coupling to one or more transition-edge sensor (TES). This differential thermal coupling between absorbers and TES's results in different characteristic pulse shapes and allows position discrimination between the different pixels. The development of PoST's is motivated by a desire to achieve maximum focal-plane area with the least number of readout channels and as such. PoST's are ideally suited to provide a focal-plane extension to the Constellation-X microcalorimeter array. We report the first experimental results of our latest one and two channel PoST's, which utilize fast thermalizing electroplated Au/Bi absorbers coupled to low noise Mo/Au TES's - a technology already successfully implemented in our arrays of single pixel TES's. We demonstrate 6 eV energy resolution coupled with spatial sensitivity in the keV energy range. We also report on the development of signal processing algorithms to optimize energy and position sensitivity of our detectors.

  7. Development of position-sensitive time-of-flight spectrometer for fission fragment research

    CERN Document Server

    Arnold, C W; Meierbachtol, K; Bredeweg, T; Jandel, M; Jorgenson, H J; Laptev, A; Rusev, G; Shields, D W; White, M; Blakeley, R E; Mader, D M; Hecht, A A

    2014-01-01

    A position-sensitive, high-resolution time-of-flight detector for fission fragments has been developed. The SPectrometer for Ion DEterminiation in fission Research (SPIDER) is a $2E-2v$ spectrometer designed to measure the mass of light fission fragments to a single mass unit. The time pick-off detector pairs to be used in SPIDER have been tested with $\\alpha$-particles from $^{229}$Th and its decay chain and $\\alpha$-particles and spontaneous fission fragments from $^{252}$Cf. Each detector module is comprised of a thin electron conversion foil, electrostatic mirror, microchannel plates, and delay-line anodes. Particle trajectories on the order of 700 mm are determined accurately to within 0.7 mm. Flight times on the order of 70 ns were measured with 200 ps resolution FWHM. Computed particle velocities are accurate to within 0.06 mm/ns corresponding to precision of 0.5%. An ionization chamber capable of 400 keV energy resolution coupled with the velocity measurements described here will pave the way for mode...

  8. Performance of a Large Area Avalanche Photodiode in a Liquid Xenon Ionization and Scintillation Chamber

    CERN Document Server

    Ni, K; Day, D; Giboni, K L; Lopes, J A M; Majewski, P; Yamashita, M

    2005-01-01

    Scintillation light produced in liquid xenon (LXe) by alpha particles, electrons and gamma-rays was detected with a large area avalanche photodiode (LAAPD) immersed in the liquid. The alpha scintillation yield was measured as a function of applied electric field. We estimate the quantum efficiency of the LAAPD to be 45%. The best energy resolution from the light measurement at zero electric field is 7.5%(sigma) for 976 keV internal conversion electrons from Bi-207 and 2.6%(sigma) for 5.5 MeV alpha particles from Am-241. The detector used for these measurements was also operated as a gridded ionization chamber to measure the charge yield. We confirm that using a LAAPD in LXe does not introduce impurities which inhibit the drifting of free electrons.

  9. Position-sensitive CdTe detector using improved crystal growth method

    Science.gov (United States)

    1988-09-01

    The feasibility of developing a position-sensitive CdTe detector array for astronomical observations in the hard X-ray, soft gamma ray region is demonstrated. In principle, it was possible to improve the resolution capability for imaging measurements in this region by orders of magnitude over what is now possible through the use of CdTe detector arrays. The objective was to show that CdTe crystals of the quality, size and uniformity required for this application can be obtained with a new high pressure growth technique. The approach was to fabricate, characterize and analyze a 100 element square array and several single-element detectors using crystals from the new growth process. Results show that detectors fabricated from transversely sliced, 7 cm diameter wafers of CdTe exhibit efficient counting capability and a high degree of uniformity over their entire areas. A 100 element square array of 1 sq mm detectors was fabricated and operated.

  10. Ultrafast Readout of Scintillating Fibres Using Upgraded Position-Sensitive Photomultipliers

    CERN Multimedia

    2002-01-01

    % RD-17 \\\\ \\\\To design a high rate topological trigger device for the future DIRAC Experiment at CERN an extensive work is in progress on a scintillating-fibre detector using a position-sensitive photomultiplier. Several detector prototypes with different lengths ($<$~50~cm) of sensitive area have been tested at T7S~PS beam. \\\\ \\\\With 0.5~mm diameter fibres a spatial resolution of $\\sim$125~$\\mu$m was obtained with a detection efficiency higher than 95\\%. The time resolution is $\\sim$600~ps, and the track position is properly digitized in real time (about 10~ns) by multi-channel peak sensing circuit. Based on experimental data simulations were also performed a comparison of different types of front-end electronics for multi-channel readout.

  11. A novel position sensitive detector for nuclear radiation. Final Report

    International Nuclear Information System (INIS)

    Current and next generation experiments in nuclear and elementary particle physics require detectors with high spatial resolution, fast response, and accurate energy information. Such detectors are required for spectroscopy, and imaging of optical and high-energy photons, charged particles, and neutrons, and are of interest not only in nuclear and high-energy physics, but also in other areas such as medical imaging, diffraction, astronomy, nuclear treaty verification, non-destructive evaluation, and geological exploration

  12. A position-sensitive scintillation detector for two-dimensional angular correlation of annihilation radiation using metal-package position-sensitive photomultiplier tubes

    CERN Document Server

    Inoue, K; Saito, H; Nagashima, Y; Hyodo, T; Muramatsu, S; Nagai, S

    1999-01-01

    We have constructed and tested a prototype of a new position sensitive gamma-ray detector which consists of an array of 2.6x2.6x18 mm sup 3 BGO scintillator blocks, a light guide, and four metal-package position-sensitive photomultiplier tubes (R5900-00-C8) recently developed by Hamamatsu Photonics Co. Ltd. Scalability of the detector of this type makes it possible to construct a larger detector using many PS-PMTs, which will be useful for the two-dimensional angular correlation of annihilation radiation apparatus.

  13. Ionizing and non Ionizing radiation damage in a large area CMOS active pixel sensor for medical applications

    OpenAIRE

    Esposito, Michela; Anaxagoras, Thalis; Price, Tony; Manolopoulos, Spyros; Evans, Philip; Wells, Kevin; Allinson, Nigel

    2015-01-01

    Currently, large-area medical sensors are based on amorphous flat panel technology. Sensors based on monolithic CMOS APS can offer many advantages in terms of image quality and reduced dose requirements. One constraint on the take-up of APS has been their restricted operating life due to radiation damage. Here we present a new wafer scale CMOS APS, designed for medical applications and hardened-by-design with reference to its performance in typical operating environments. The detector was ...

  14. A zero dead-time multi-particle time and position sensitive detector based on correlation between brightness and amplitude

    Energy Technology Data Exchange (ETDEWEB)

    Urbain, X., E-mail: xavier.urbain@uclouvain.be; Bech, D.; Van Roy, J.-P. [Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, B-1348 Louvain-la-Neuve (Belgium); Géléoc, M.; Weber, S. J. [Laser, Interactions and Dynamics Laboratory (LIDyL), DSM/IRAMIS, CEA-Saclay, 91191 Gif-sur-Yvette (France); Huetz, A.; Picard, Y. J., E-mail: yan.picard@u-psud.fr [Institut des Sciences Moléculaires d’Orsay, UMR 8214, Université Paris-Sud, Bâtiment 350, Orsay Cedex (France)

    2015-02-15

    A new multi-particle time and position sensitive detector using only a set of microchannel plates, a waveform digitizer, a phosphor screen, and a CMOS camera is described. The assignment of the timing information, as taken from the microchannel plates by fast digitizing, to the positions, as recorded by the camera, is based on the COrrelation between the BRightness of the phosphor screen spots, defined as their integrated intensity and the Amplitude of the electrical signals (COBRA). Tests performed by observing the dissociation of HeH, the fragmentation of H{sub 3} into two or three fragments, and the photo-double-ionization of Xenon atoms are presented, which illustrate the performances of the COBRA detection scheme.

  15. Measurement of material uniformity using 3-D position sensitive CdZnTe gamma-ray spectrometers

    CERN Document Server

    He, Z; Knoll, G F; Wehe, D K; Stahle, C M

    2000-01-01

    We present results from two 1 cm sup 3 CdZnTe gamma-ray spectrometers with full 3-D position sensitivity. To our knowledge, these are the first reported semiconductor spectrometers that provide independent spectral data for each of over 2000 volume elements. Energy resolutions of 1.5-1.6% FWHM and position resolutions of 0.7x0.7x0.5 mm were obtained at 662 keV gamma-ray energy from the central region of both detectors for single-pixel events. With the 3-D position sensing capability, variations in spectral response over the detector volume were recorded using a sup 1 sup 3 sup 7 Cs source. These measurements allow a study of full-energy peak efficiency, mean ionization energy and electron trapping as a function of 3-D position. The effects of material non-uniformity on detector spectroscopic performance are discussed.

  16. Position-sensitive radiation monitoring (surface contamination monitor). Innovative technology summary report

    Energy Technology Data Exchange (ETDEWEB)

    1999-06-01

    The Shonka Research Associates, Inc. Position-Sensitive Radiation Monitor both detects surface radiation and prepares electronic survey map/survey report of surveyed area automatically. The electronically recorded map can be downloaded to a personal computer for review and a map/report can be generated for inclusion in work packages. Switching from beta-gamma detection to alpha detection is relatively simple and entails moving a switch position to alpha and adjusting the voltage level to an alpha detection level. No field calibration is required when switching from beta-gamma to alpha detection. The system can be used for free-release surveys because it meets the federal detection level sensitivity limits requires for surface survey instrumentation. This technology is superior to traditionally-used floor contamination monitor (FCM) and hand-held survey instrumentation because it can precisely register locations of radioactivity and accurately correlate contamination levels to specific locations. Additionally, it can collect and store continuous radiological data in database format, which can be used to produce real-time imagery as well as automated graphics of survey data. Its flexible design can accommodate a variety of detectors. The cost of the innovative technology is 13% to 57% lower than traditional methods. This technology is suited for radiological surveys of flat surfaces at US Department of Energy (DOE) nuclear facility decontamination and decommissioning (D and D) sites or similar public or commercial sites.

  17. Design and performance of a 2-D multi-wire position sensitive X-ray detector

    Indian Academy of Sciences (India)

    S S Desai; J N Joshi; A M Shaikh

    2002-10-01

    A 2-D multi-wire position sensitive detector for X-ray diffraction and small angle X-ray scattering studies is described. The detector has an active area of 100 mm × 100 mm and consists of an anode plane with 10 m SS wires at 3 mm spacing and a pair of orthogonal cathode readout planes with 25 m SS wires placed at 1.5 mm spacing. The position information is obtained using charge division method and recorded using a laboratory built data acquisition system. The resolution and gas gain was measured for 5.9 keV X-rays (55Fe-source) as a function of the anode wire voltage and gas pressure. It was observed that the proportional region of the PSD at 100 kPa pressure extended up to a high voltage value of around 1.5 kV and it shifted to high values up to 2 kV for gas pressure of 300 kPa. The energy resolution improved from 18% (FWHM) to 12% with increase in pressure. The spatial resolution of the PSD also showed improvement, with a value of 1.2 mm × 1.4 mm at 300 kPa gas pressure. A maximum gain of 5 × 104 is obtained.

  18. The residual stress instrument with optimized Si(220) monochromator and position-sensitive detector at HANARO

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chang-Hee [Korea Atomic Energy Research Institute, Yusung, Daejon 305-600 (Korea, Republic of); Moon, Myung-Kook [Korea Atomic Energy Research Institute, Yusung, Daejon 305-600 (Korea, Republic of)]. E-mail: moonmk@kaeri.re.kr; Em, Vyacheslav T. [Korea Atomic Energy Research Institute, Yusung, Daejon 305-600 (Korea, Republic of); Choi, Young-Hyun [Korea Atomic Energy Research Institute, Yusung, Daejon 305-600 (Korea, Republic of); Cheon, Jong-Kyu [Korea Atomic Energy Research Institute, Yusung, Daejon 305-600 (Korea, Republic of); Nam, Uk-Won [Korea Astronomy Observatory, Yusung, Daejon 305-348 (Korea, Republic of); Kong, Kyung-Nam [Korea Astronomy Observatory, Yusung, Daejon 305-348 (Korea, Republic of)

    2005-06-11

    An upgraded residual stress instrument at the HANARO reactor of the KAERI is described. A horizontally focusing bent perfect crystal Si(220) monochromator (instead of a mosaic vertical focusing Ge monochromator) is installed in a drum with a tunable (2{theta}{sub M}=0-60{sup o}) take-off angle/wavelength. A specially designed position-sensitive detector (60% efficiency for {lambda}=1.8A) with 200mm (instead of 100mm) high-active area is used. There are no Soller type collimators in the instrument. The minimum possible monochromator to sample distance, L{sub MS}=2m, and sample to detector distance, L{sub SD}=1.2m, were found to be optimal. The new PSD and bent Si(220) monochromator combined with the possibility of selecting an appropriate wavelength resulted in about a ten-fold gain in data collection rate. The optimal reflections of austenitic and ferritic steels, aluminum and nickel for stress measurements with a Si(220) monochromator were chosen experimentally. The ability of the instrument to make strain measurements deep inside the austenitic and ferritic steels has been tested. For the chosen reflections and wavelengths, no shift of peak position (apparent strain) was observed up to 56mm length of path.

  19. Performance evaluation of novel square-bordered position-sensitive silicon detectors with four-corner readout

    OpenAIRE

    Banu, A; Li, Y.; McCleskey, M.; Bullough, M.; Walsh, S; C.A. Gagliardi; Trache, L.; Tribble, R. E.; Wilburn, C.

    2007-01-01

    We report on a recently developed novel type of large area (62 mm x 62 mm) position sensitive silicon detector with four-corner readout. It consists of a square-shaped ion-implanted resistive anode framed by additional low-resistivity strips with resistances smaller than the anode surface resistance by a factor of 2. The detector position linearity, position resolution, and energy resolution were measured with alpha-particles and heavy ions. In-beam experimental results reveal a position reso...

  20. [Development of recommendations in the area of ionizing and nonionizing radiations

    International Nuclear Information System (INIS)

    This document discusses progress made from March 1, 1990 to October 30, 1990 in terms of publication of reports. This subjects discussed are related to the fields of radiation protection and ionizing and nonionizing radiations. Topics discussed published works, reports in press, printer's manuscript preparation, and scientific committee activities

  1. Measurements of X-rays from Ne recoil ions with a position sensitive detector

    International Nuclear Information System (INIS)

    Measurements of soft X-rays with wavelength 35-47 nm from Ne recoil ions, excited by 24 MeV Cl ions, are reported obtained with a 2.2 m grazing incidence spectrometer. A position sensitive channelplate detector with a two-dimensional wedge and strip readout is used instead of a channeltron, scanning along the Rowland circle. The perfomance of this position sensitive detector is optimized, wavelength calibration procedures are worked out and its efficiency is compared with the scanning channeltron. The detection yield and resolution is measured as a function of the angle of the radiation to the detector normal. An increase by a factor of 12 in the detection efficiency over a spectral region is found for the position sensitive detector compared with a scanning channeltron detector. (orig.)

  2. Development of 2D-ACAR apparatus using position-sensitive photomultiplier tubes

    International Nuclear Information System (INIS)

    A new two-dimensional angular correlation of annihilation radiation apparatus is described. Position-sensitive photomultiplier tubes coupled with two-dimensional arrays of small BGO scintillator blocks make simple and compact position-sensitive γ-ray detectors. With a sample-detector distance of 5m, an angular resolution of 1.1 mrad FWHM and a coincidence count rate of ∼2.4 c.p.s. per mCi are obtained. Its performance is demonstrated by the result of a test measurement for KI crystal in which non-localized positronium exists at low temperatures. (author)

  3. Development of 2D-ACAR apparatus using position-sensitive photomultiplier tubes

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, Yasuyoshi; Saito, Haruo; Iwata, Tetsuya; Nagashima, Yasuyuki; Hyodo, Toshio [Tokyo Univ. (Japan). Coll. of Arts and Sciences; Uchida, Hiroshi; Omura, Tomohide

    1997-03-01

    A new two-dimensional angular correlation of annihilation radiation apparatus is described. Position-sensitive photomultiplier tubes coupled with two-dimensional arrays of small BGO scintillator blocks make simple and compact position-sensitive {gamma}-ray detectors. With a sample-detector distance of 5m, an angular resolution of 1.1 mrad FWHM and a coincidence count rate of {approx}2.4 c.p.s. per mCi are obtained. Its performance is demonstrated by the result of a test measurement for KI crystal in which non-localized positronium exists at low temperatures. (author)

  4. Theory and Development of Position-Sensitive Quantum Calorimeters. Degree awarded by Stanford Univ.

    Science.gov (United States)

    Figueroa-Feliciano, Enectali; White, Nicholas E. (Technical Monitor)

    2001-01-01

    Quantum calorimeters are being developed as imaging spectrometers for future X-ray astrophysics observatories. Much of the science to be done by these instruments could benefit greatly from larger focal-plane coverage of the detector (without increasing pixel size). An order of magnitude more area will greatly increase the science throughput of these future instruments. One of the main deterrents to achieving this goal is the complexity of the readout schemes involved. We have devised a way to increase the number of pixels from the current baseline designs by an order of magnitude without increasing the number of channels required for readout. The instrument is a high energy resolution, distributed-readout imaging spectrometer called a Position-Sensitive Transition-Edge Sensor (POST). A POST is a quantum calorimeter consisting of two Transition-Edge Sensors (TESS) on the ends of a long absorber capable of one-dimensional imaging spectroscopy. Comparing rise time and energy information from the two TESS, the position of the event in the POST is determined. The energy of the event is inferred from the sum of the two pulses. We have developed a generalized theoretical formalism for distributed-readout calorimeters and apply it to our devices. We derive the noise theory and calculate the theoretical energy resolution of a POST. Our calculations show that a 7-pixel POST with 6 keV saturation energy can achieve 2.3 eV resolution, making this a competitive design for future quantum calorimeter instruments. For this thesis we fabricated 7- and 15-pixel POSTS using Mo/Au TESs and gold absorbers, and moved from concept drawings on scraps of napkins to a 32 eV energy resolution at 1.5 keV, 7-pixel POST calorimeter.

  5. Facility for low-dose digital scanning of a large-area image of ionizing radiation

    International Nuclear Information System (INIS)

    The facility scans the unreduced X-ray image by means of moving line sensors which work in parallel. The length of the sensors is much smaller than the width of the image. The facility comprises about 20 identical modules, owing to which the output of the serial manufacture can be increased, and CCD-based line sensors can be employed which are very sensitive and inexpensive. The X-ray image can be taken at the virtually lowest exposure possible, and owing to the parallelization of the scanning process, the scanning rate can be increased considerably as compared with the existing facilities. The facility consists of an ionizing radiation source against which are positioned a movable diaphragm fitted with slits and a movable support plate carrying the line sensors. The sensors make up the line detector whose length is equal to that of the image scanned, synchronously movable with the movable slit diaphragm. (M.D.). 3 figs

  6. Development of position sensitive γ-ray detectors for 2D-ACAR apparatus

    International Nuclear Information System (INIS)

    We report a development of two kinds of position-sensitive γ-ray detectors using position-sensitive photomultiplier tubes (PS-PMT) for 2D-ACAR apparatus; (1) a 5 mm thick, 50 mm diameter Gd2SiO5 (GSO) single crystal disc coupled to a PS-PMT (Hamamatsu R2487), (2) an 2D-array of small Bi4Ge3O12 (BGO) crystal blocks off sizes 2.2 mm x 2.2 mm x 15 mm (25 x 21 pieces in 2.4 mm pitch) coupled to a PS-PMT (Hamamatsu R3941). We employed the type (2) for our new 2D-ACAR. The method of the analysis of the data obtained by the new apparatus and the results are reported. (orig.)

  7. Three-dimensional position sensitivity in two-dimensionally segmented HP-Ge detectors

    CERN Document Server

    Vetter, K; Deleplanque, M A; Lee, I Y; Stephens, F S; Schmid, G J; Beckedahl, D; Blair, J J; Clark, R M; Cromaz, M; Diamond, R M; Fallon, P; Lane, G J; Kammeraad, J E; Macchiavelli, A O; Svensson, C E

    2000-01-01

    Measured- and simulated-pulse shapes in electrically segmented coaxial Ge detectors have been investigated. Three-dimensional position sensitivities have been determined experimentally and theoretically in a 36-fold segmented Ge detector. By using the two-dimensional segmentation in conjunction with pulse-shape analysis, a position sensitivity of better than 1 mm can be obtained in three dimensions at an energy of 374 keV. This is achieved by analyzing the shape of net charge signals of segments containing interactions and of transient image charge signals of neighboring segments. The ability to locate interactions in three-dimensions is one of the crucial properties in the proposed gamma-ray energy tracking array (GRETA). The concept of gamma-ray tracking will not only increase the efficiency in detecting gamma radiation but also enables the localization and characterization of unknown gamma-ray sources with much higher accuracy than is possible with current instruments.

  8. Performance of high-resolution position-sensitive detectors developed for storage-ring decay experiments

    Science.gov (United States)

    Yamaguchi, T.; Suzaki, F.; Izumikawa, T.; Miyazawa, S.; Morimoto, K.; Suzuki, T.; Tokanai, F.; Furuki, H.; Ichihashi, N.; Ichikawa, C.; Kitagawa, A.; Kuboki, T.; Momota, S.; Nagae, D.; Nagashima, M.; Nakamura, Y.; Nishikiori, R.; Niwa, T.; Ohtsubo, T.; Ozawa, A.; Sato, K.; Sato, S.; Suzuki, S.

    2013-12-01

    As next generation spectroscopic tools, heavy-ion cooler storage rings will be a unique application of highly charged RI beam experiments. Decay spectroscopy of highly charged rare isotopes provides us important information relevant to the stellar conditions, such as for the s- and r-process nucleosynthesis. In-ring decay products of highly charged RI will be momentum-analyzed and reach a position-sensitive detector set-up located outside of the storage orbit. To realize such in-ring decay experiments, we have developed and tested two types of high-resolution position-sensitive detectors: silicon strips and scintillating fibers. The beam test experiments resulted in excellent position resolutions for both detectors, which will be available for future storage-ring experiments.

  9. Novel computational methods for image analysis and quantification using position sensitive radiation detectors

    OpenAIRE

    Sanchez Crespo, Alejandro

    2005-01-01

    The major advantage of position sensitive radiation detector systems lies in their ability to non invasively map the regional distribution of the emitted radiation in real-time. Three of such detector systems were studied in this thesis, gamma-cameras, positron cameras and CMOS image sensors. A number of physical factors associated to these detectors degrade the qualitative and quantitative properties of the obtained images. These blurring factors could be divided into two groups. The first g...

  10. Angle-resolved ion TOF spectrometer with a position sensitive detector

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Norio [Electrotechnical Lab., Tsukuba, Ibaraki (Japan); Heiser, F.; Wieliczec, K.; Becker, U.

    1996-07-01

    A angle-resolved ion time-of-flight mass spectrometer with a position sensitive anode has been investigated. Performance of this spectrometer has been demonstrated by measuring an angular distribution of a fragment ion pair, C{sup +} + O{sup +}, from CO at the photon energy of 287.4 eV. The obtained angular distribution is very close to the theoretically expected one. (author)

  11. Design and performance of vacuum capable detector electronics for linear position sensitive neutron detectors

    International Nuclear Information System (INIS)

    We describe the design and performance of electronics for linear position sensitive neutron detectors. The eight tube assembly requires 10 W of power and can be controlled via digital communication links. The electronics can be used without modification in vacuum. Using a transimpedance amplifier and gated integration, we achieve a highly linear system with coefficient of determinations of 0.9999 or better. Typical resolution is one percent of tube length.

  12. A hardware readout system for a curved one dimensional position sensitive proportional counter. Pt. 1

    International Nuclear Information System (INIS)

    We developed a hardware readout system for a curved one dimensional position sensitive X-ray proportional counter. Eight analog signals from cathode strips and wedges are processed to give, within a few microseconds, 14-bit information about the position of detection of an X-ray quantum. Elementary parts of our readout system are 9-bit Flash-ADCs, Multiplying-DACs and EPROMs. (orig.)

  13. A hardware readout system for a curved one-dimensional position-sensitive proportional counter

    International Nuclear Information System (INIS)

    We developed a hardware readout system for a curved one-dimensional position-sensitive X-ray proportional counter. Eight analog signals from cathode strips and wedges are processed to give, within a few microseconds, 14-bit information about the position of detection of an X-ray quantum. Elementary parts of our readout system are 9-bit flash-ADCs, multiplying-DACs and EPROMs. (orig.)

  14. Implementation of Complex Signal Processing Algorithms for Position-Sensitive Microcalorimeters

    Science.gov (United States)

    Smith, Stephen J.

    2008-01-01

    We have recently reported on a theoretical digital signal-processing algorithm for improved energy and position resolution in position-sensitive, transition-edge sensor (POST) X-ray detectors [Smith et al., Nucl, lnstr and Meth. A 556 (2006) 2371. PoST's consists of one or more transition-edge sensors (TES's) on a large continuous or pixellated X-ray absorber and are under development as an alternative to arrays of single pixel TES's. PoST's provide a means to increase the field-of-view for the fewest number of read-out channels. In this contribution we extend the theoretical correlated energy position optimal filter (CEPOF) algorithm (originally developed for 2-TES continuous absorber PoST's) to investigate the practical implementation on multi-pixel single TES PoST's or Hydras. We use numerically simulated data for a nine absorber device, which includes realistic detector noise, to demonstrate an iterative scheme that enables convergence on the correct photon absorption position and energy without any a priori assumptions. The position sensitivity of the CEPOF implemented on simulated data agrees very well with the theoretically predicted resolution. We discuss practical issues such as the impact of random arrival phase of the measured data on the performance of the CEPOF. The CEPOF algorithm demonstrates that full-width-at- half-maximum energy resolution of < 8 eV coupled with position-sensitivity down to a few 100 eV should be achievable for a fully optimized device.

  15. 2 Dimensional position sensitive XAFS by using in-house X-ray spectrometer

    Science.gov (United States)

    Shinoda, Kozo; Suzuki, Shigeru; Kuribayashi, Masaru; Taguchi, Takeyoshi

    2009-09-01

    Position sensitive XAFS measurements by using the in-house X-ray spectrometer and the position sensitive X-ray detector were attempted. The in-house spectrometer produces monochromized divergent X-ray beam. Therefore, an extended direct-beam image projected on the detector can be taken, and its extension rate is depending on the arrangement of the sample and the detector. A position sensitive XAFS measurement was demonstrated by using Ni metal foil and NiO powder as a model sample. Ge(220) or Si(400) Johansson-type bent single-crystal was used as monochromator, and Mo and LaB6 were used as the target and filament, respectively. Tube voltage and current were operated at 16 kV and 100 mA (1.6 kW). XAFS spectra were measured by transmission-mode with sample set/reset method and required time of each experiment is about 6 hours in total. It was confirmed that metal and oxide spectra with enough quality for structural analysis were clearly separated by each position in the sample.

  16. Position sensitive detector of soft x-radiation and alpha particles on the charge-coupled device base

    International Nuclear Information System (INIS)

    The position-sensitive detector based on a matrix of charge-coupled devices (CCD) operating on-line with the Pravets personal computer is designed. Application of the yttrium oxysulfide as a converter and give an opportunity to obtain 1300 electrons in CCD matrix per 1 photon absorbed in a phosphore for 8 keV X-ray photons. The detector ensures detection of single 5.5 MeV α particles. Spatial resolution for the detector with Y2O2S-Tb phosphore 40 mm in-diameter is about 350 μm for both X-ray photons and α particles. Detection efficiency nonuniformity over the detector area is ≤1% when the correcting matrix is used

  17. Two-dimensional position-sensitive gaseous detectors for high-resolution neutron and X-ray diffraction

    CERN Document Server

    Marmotti, M; Kampmann, R

    2002-01-01

    Two-dimensional position-sensitive gaseous detectors have been developed at the Geesthacht Neutron Facility (GeNF) for high-resolution neutron and X-ray diffractometry. They are multi-wire proportional counters with delay-line readout and sensitive areas of 300 mm x 300 mm or 500 mm x 500 mm. For detecting X-rays, neutrons and hard X-rays the counters are filled with Ar/CO sub 2 , sup 3 He/CF sub 4 and Xe/CO sub 2 , respectively. One neutron detector is used at the ARES diffractometer at GKSS, which is dedicated to the analysis of residual stresses. Further ones are used for analysing textures and residual stresses at the hard-X-ray beamline PETRA-2 at HASYLAB, and one detector is being developed for the neutron reflectometer REFSANS at the research reactor FRM-II in Munich, Germany. (orig.)

  18. Performance evaluation of novel square-bordered position-sensitive silicon detectors with four-corner readout

    CERN Document Server

    Banu, A; McCleskey, M; Bullough, M; Walsh, S; Gagliardi, C A; Trache, L; Tribble, R E; Wilburn, C

    2007-01-01

    We report on a recently developed novel type of large area (62 mm x 62 mm) position sensitive silicon detector with four-corner readout. It consists of a square-shaped ion-implanted resistive anode framed by additional low-resistivity strips with resistances smaller than the anode surface resistance by a factor of 2. The detector position linearity, position resolution, and energy resolution were measured with alpha-particles and heavy ions. In-beam experimental results reveal a position resolution below 1 mm (FWHM) and a very good non-linearity of less than 1% (rms). The energy resolution determined from 228Th alpha source measurements is around 2% (FWHM).

  19. Application of a One-Dimensional Position Sensitive Chamber on Synchrotron Radiation

    Science.gov (United States)

    Qi, Huirong; Liu, Mei

    2014-02-01

    In the last few years, wire chambers have been frequently used for X-ray detection because of their low cost, large area and reliability. X-ray diffraction is an irreplaceable method for powder crystal lattice measurements. A one-dimensional single-wire chamber has been developed in our lab to provide high position resolution for powder diffraction experiments using synchrotron radiation. There are 200 readout strips of 0.5 mm width with a pitch of 1.0 mm in the X direction, and the working gas is a mixture of Ar and CO2 (90/10). The one-dimensional position of the original ionization point is determined by the adjacent strip's distribution information using the center of gravity method. Recently, a study of the detector's performance and diffraction image was completed at the 1W1B laboratory of the Beijing Synchrotron Radiation Facility (BSRF) using a sample of SiO2. Most of the relative errors between the measured values of diffraction angles and existing data were less than 1%. The best position resolution achieved for the detector in the test was 71 μm (σ value) with a 20 μm slit collimator. Finally, by changing the detector height in incremental distances from the center of the sample, the one-dimensional detector achieved a two-dimensional diffraction imaging function, and the results are in good agreement with standard data.

  20. Design of a neutron liquid diffractometer with a position-sensitive detector

    International Nuclear Information System (INIS)

    The design of a neutron diffractometer for structural investigations of liquids and amorphous materials to be installed at the R2 reactor at Studsvik, Sweden is described. The Berliner-MURR detector system is utilized which features a stationary array of 16 linear position-sensitive 3He counters which simultaneously collect diffracted neutron intensities for scattering angles from 2 to 140 deg. The sample position is variable and can be displaced up to 50 cm upstream in the primary beam from the centre of the detector circle for experiments which require high resolution at small scattering angles. The predicted instrumental resolution for typical operating conditions is discussed. (author)

  1. Position-sensitive detection of ultracold neutrons with an imaging camera and its implications to spectroscopy

    OpenAIRE

    Wei, Wanchun; Broussard, L. J.; Hoffbauer, M. A.; Makela, M.; Morris, C. L.; Tang, Z.(University of Science & Technology of China, Hefei, 230026, China); Adamek, E. R.; Callahan, N. B.; Clayton, S. M.; Cude-Woods, C.; Currie, S; Dees, E. B.; Ding, X; Geltenbort, P.(Institut Laue-Langevin, Grenoble Cedex 9, 38042, France); Hickerson, K. P.

    2016-01-01

    Position-sensitive detection of ultracold neutrons (UCNs) is demonstrated using an imaging charge-coupled device (CCD) camera. A spatial resolution less than 15 $\\mu$m has been achieved, which is equivalent to an UCN energy resolution below 2 pico-electron-volts through the relation $\\delta E = m_0g \\delta x$. Here, the symbols $\\delta E$, $\\delta x$, $m_0$ and $g$ are the energy resolution, the spatial resolution, the neutron rest mass and the gravitational acceleration, respectively. A mult...

  2. The performance of prototype position-sensitive neutron detectors on SXD at ISIS

    International Nuclear Information System (INIS)

    The performance of two position-sensitive neutron detector designed for use on the single crystal diffractometer (SXD) at ISIS is assessed. The two detectors examined were the Anger camera 6Li-glass scintillator PSD and a prototype fibre-optic encoded PSD based on 6Li-doped ZnS plastic scintillator. The latter detector is found to be both simpler to fabricate and to produce better results on the evidence to date. A summary of some of the expected science from SXD and the performance of the detectors with respect to this is also given. (author)

  3. Developments of position-sensitive X-ray detectors at SPring-8

    CERN Document Server

    Toyokawa, H; Hirota, K

    2003-01-01

    In order to efficiently perform diffraction and scattering experiments at the SPring-8 facility, three types of position sensitive detectors have been developed. A silicon pixel detector could detect X-rays above 6-keV in single counting mode, and an image accumulated could be read out within 5 msec. A 128-channel microstrip Germanium detector has made it possible for the users to efficiently investigate high resolution Compton scattering experiments. A high energy X-ray imager with a 128 x 128 matrix of YAP crystal has been developed for high energy X-ray diffraction experiments. (author)

  4. Coplanar-grid CdZnTe detector with three-dimensional position sensitivity

    CERN Document Server

    Luke, P N; Lee Jae Sik; Yaver, H

    2000-01-01

    A three-dimensional position-sensitive coplanar-grid detector design for use with compound semiconductors is described. This detector design maintains the advantage of a coplanar-grid detector in which good energy resolution can be obtained from materials with poor charge transport. Position readout in two dimensions is accomplished using proximity-sensing electrodes adjacent to the electron-collecting grid electrode of the detector. Additionally, depth information is obtained by taking the ratio of the amplitudes of the collecting grid signal and the cathode signal. Experimental results from a prototype CdZnTe detector are presented.

  5. Reconstruction-free sensitive wavefront sensor based on continuous position sensitive detectors.

    Science.gov (United States)

    Godin, Thomas; Fromager, Michael; Cagniot, Emmanuel; Brunel, Marc; Aït-Ameur, Kamel

    2013-12-01

    We propose a new device that is able to perform highly sensitive wavefront measurements based on the use of continuous position sensitive detectors and without resorting to any reconstruction process. We demonstrate experimentally its ability to measure small wavefront distortions through the characterization of pump-induced refractive index changes in laser material. In addition, it is shown using computer-generated holograms that this device can detect phase discontinuities as well as improve the quality of sharp phase variations measurements. Results are compared to reference Shack-Hartmann measurements, and dramatic enhancements are obtained.

  6. Thermal Neutron Imaging Using A New Pad-Based Position Sensitive Neutron Detector

    Energy Technology Data Exchange (ETDEWEB)

    Dioszegi I.; Vanier P.E.; Salwen C.; Chichester D.L.; Watson S.M.

    2016-10-29

    Thermal neutrons (with mean energy of 25 meV) have a scattering mean free path of about 20 m in air. Therefore it is feasible to find localized thermal neutron sources up to ~30 m standoff distance using thermal neutron imaging. Coded aperture thermal neutron imaging was developed in our laboratory in the nineties, using He-3 filled wire chambers. Recently a new generation of coded-aperture neutron imagers has been developed. In the new design the ionization chamber has anode and cathode planes, where the anode is composed of an array of individual pads. The charge is collected on each of the individual 5x5 mm2 anode pads, (48x48 in total, corresponding to 24x24 cm2 sensitive area) and read out by application specific integrated circuits (ASICs). The high sensitivity of the ASICs allows unity gain operation mode. The new design has several advantages for field deployable imaging applications, compared to the previous generation of wire-grid based neutron detectors. Among these are the rugged design, lighter weight and use of non-flammable stopping gas. For standoff localization of thermalized neutron sources a low resolution (11x11 pixel) coded aperture mask has been fabricated. Using the new larger area detector and the coarse resolution mask we performed several standoff experiments using moderated californium and plutonium sources at Idaho National Laboratory. In this paper we will report on the development and performance of the new pad-based neutron camera, and present long range coded-aperture images of various thermalized neutron sources.

  7. Positron annihilation 2D ACAR device using position-sensitive photoelectron multiplier tube

    International Nuclear Information System (INIS)

    For a positron annihilation 2D ACAR device, the γ ray detector with good position resolution and detection efficiency is indispensable. The authors have examined the performance of the new type γ ray detector, in which the scintillator with high detection efficiency and high luminance is attached to a position-sensitive photoelectron multiplier tube (PS-PMT). As the result, it was found that the detector of attaching many fine columnar BGO scintillators being bundled to a PS-PMT is suitable to the detector for the 2D ACAR device. The 2D ACAR device using this detector was made in the Radioisotope Center, University of Tokyo. The position-sensitive γ ray detector and the method of detecting position are explained. The arrangement of the 2D ACAR device including two detectors and the circuit are shown. The two-dimensional angular correlation of KI at 14K measured with this device is shown. The momentum resolution was estimated to be about 1.2 x 10-3 mc from the width of a positronium peak. 70 counts/s on average was obtained under the conditions of 30 mCi Na-22 source and 7.5 k gauss magnetic field. The detector is compact, its efficiency is high, and price is low. (K.I.)

  8. Exploring the spatial resolution of position-sensitive microchannel plate detectors

    Science.gov (United States)

    Wiggins, Blake; Siwal, Davinder; Desouza, Romualdo

    2016-03-01

    High amplification and excellent timing make microchannel plate (MCP) detectors excellent devices for detection of photons, electrons, and ions. In addition to providing sub-nanosecond time resolution MCP detectors can also provide spatial resolution, thus making them useful in imaging applications. Use of a resistive anode (RA) is a routinely used approach to make an MCP position-sensitive. The spatial resolution of the RA associated with detection of a single incident electron was determined. Factors impacting the spatial resolution obtained with the RA will be discussed and the achieved spatial resolution of 64 μm (FWHM) will be presented. Recently, a novel approach has been developed to provide position-sensitivity for an MCP detector. In this approach, namely the induced signal approach, the position of the incident particle is determined by sensing the electron cloud emanating from a MCP stack. By utilizing the zero-crossing point of the inherently bipolar signals, a spatial resolution of 466 μm (FWHM) has been achieved. Work to improve the spatial resolution of the induced signal approach further will be presented. Supported by the US DOE NNSA under Award No. DE-NA0002012.

  9. Imaging plates as position-sensitive detectors of positrons and gamma-rays

    CERN Document Server

    Doyama, M; Yoshiie, T; Hayashi, Y; Kiritani, M; Oikawa, T

    2000-01-01

    Imaging plates have been used as position-sensitive detectors for positrons. Photo-stimulated luminescent material based on BaFX : Eu sup 2 sup + (X=Cl, Br, I) is used. A linear relation between the positron fluence and output signal intensity readout by a 'PIXsysTEM II' ( pixelized to 25 mu mx25 mu m is obtained, using sup 5 sup 8 Co and sup 2 sup 2 Na positron emitters. The linearity extends to six decades from 10 sup 5 to 10 sup 1 sup 1 positrons/cm sup 2. Sensitivities of one gamma-ray photon relative to a positron are 0.011 and 3.4x10 sup - sup 3 for sup 6 sup 5 Zn and sup 2 sup 2 Na, respectively.

  10. A silicon continuous position sensitive diode and associated electronics modelling and simulation

    CERN Document Server

    Solal, M; Charon, Y; Pitre, S; Mastrippolito, R

    2002-01-01

    In contrast to the segmented detectors (micro-strips and pixels) widely used in high energy physics experiments, continuous detectors such as position sensitive diodes (whose localisation principle is based on charge division) remain of interest when count rate and multiplicity are not critical. That is the case with several imaging applications in nuclear medicine and biology. In that context, our group has developed a gamma camera dedicated to the detection of body tumour tissue during operative cancer surgery. This per-operative compact imager consists of an image intensifier tube viewed by a PSD of 25x25 mm sup 2. In order to improve detection performances of this camera we have developed a simulation model of the PSD (schematic form) and associated electronics (behaviour form) using CAO AWB/Cadence. This allows an accurate estimate of both spatial resolution and linearity. These simulations provide an exhaustive study of the performance of various types of PSD and readout electronics configurations. In o...

  11. Design and development of 1 mm resolution PET detectors with position-sensitive PMTs

    CERN Document Server

    Shao, Y; Chatziioannou, A F

    2002-01-01

    We report our investigation of a positron emission tomography (PET) detector with 1 m spatial resolution. The prototype detector consists of a 9x9 array of 1x1x10 mm sup 3 lutetium oxyorthosilicate (LSO) scintillator crystals coupled to Hamamatsu R5900-M64 or R5900-C12 position sensitive PMT by either optical fibers or an optical fiber bundle. With a 511 eV gamma source, the intrinsic spatial resolution of this detector was measured to be 0.92 mm. All crystals were well resolved in the flood source histogram. The measured energy and coincidence timing resolutions were around 26% and 4 ns, respectively, demonstrating that sufficient light can be extracted from these small crystals for PET applications.

  12. Application of 2-D Position Sensitive Detector in Spatial Straightness Measurement of Guide Rails

    Institute of Scientific and Technical Information of China (English)

    GUO Lifeng; ZHANG Guoxiong; GONG Qiang; ZHENG Qi

    2005-01-01

    A laser collimating system based on 2-D position sensitive detector (PSD) is presented in this paper. The working principle of PSD is depicted in detail. A calibration device was developed to check the nonlinearity errors of PSD and a multilayer feedforward neural network based on error back-propagation algorithm was used to compensate errors. With the aid of computer-based data acquisition system, an automatic dynamic measuring process was realized. A series of experiments, including comparison tests with laser interferometer, were done to evaluate the performance of the measuring system. The experimental results show that the spatial straightness errors of guide rails can be measured with high accuracy. The maximum differences between the device and laser interferometer are 0.027 mm in Y direction, and 0.053 mm in X direction in the measuring distance of 6 m.

  13. Simulation and optimisation of a position sensitive scintillation detector with wavelength shifting fibers for thermal neutrons

    International Nuclear Information System (INIS)

    In neutron scattering experiments it is important to have position sensitive large scale detectors for thermal neutrons. A detector based on a neutron scintillator with wave length shifting fibers is a new kind of such a detector. We present the simulation of the detector based on the microscopic structure of the scintillation material of the mentioned detector. It consists of a converter and a scintillation powder bound in a matrix. The converter in our case is lithium fluoride with enriched lithium 6, to convert thermal neutrons into high energetic alpha and triton particles. The scintillation material is silver doped zinc sulfide. We show that pulse height spectra obtained by these scintillators can be be explained by the simple model of randomly distributed spheres of zinc sulfide and lithium fluoride. With this model, it is possible to optimise the mass ratio of zinc sulfide to lithium fluoride with respect to detection efficiency and/or energy deposition in zinc sulfide.

  14. Two-dimensional photon counting imaging detector based on a Vernier position sensitive anode readout

    Institute of Scientific and Technical Information of China (English)

    YAN Qiu-Rong; ZHAO Bao-Sheng; LIU Yong-An; YANG Hao; SHENG Li-Zhi; WEI Yong-Lin

    2011-01-01

    A two-dimensional photon counting imaging detector based on a Vernier position sensitive anode is reported. The decode principle and design of a two-dimensionai Vernier anode axe introduced in detail. A photon counting imaging system was built based on a Vernier anode. The image of very weak optical radiation can be reconstructed by image processing in a period of integration time. The resolution is superior to 100 μm according to the resolution test. The detector may realize the imaging of very weak particle flow of high- energy photons, electrons and ions, so it can be used for high-energy physics, deep space exploration, spectral measurement and bio-luminescence detection.

  15. High-resolution synchrotron X-ray powder diffraction with a linear position-sensitive detector

    International Nuclear Information System (INIS)

    X-ray synchrotron powder data were collected from a capillary sample of a small-molecule organic peptide compound, glycylglycine (NH2CH2CONHCH2-COOH) by step-scanning at 10 intervals with a linear position-sensitive detector covering an angular range of 2.70 in order to test the feasibility of recording a high-resolution pattern and using the data for Rietveld analysis. Appropriate corrections for detector linearity and position were implemented, and comparison with a diagram recorded with a single scintillation detector and a crystal analyser system showed similar quality for the two sets of data. A detailed comparison of the refined atomic coordinates and those of an earlier X-ray single-crystal study showed the estimated standard deviations to be significantly underestimated in both refinements. A linear detector should be particularly useful for small samples and capillary specimens of moderately absorbing materials. (orig.)

  16. A position sensitive silicon detector for AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy)

    CERN Multimedia

    Gligorova, A

    2014-01-01

    The AEḡIS experiment (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is located at the Antiproton Decelerator (AD) at CERN and studies antimatter. The main goal of the AEḡIS experiment is to carry out the first measurement of the gravitational acceleration for antimatter in Earth’s gravitational field to a 1% relative precision. Such a measurement would test the Weak Equivalence Principle (WEP) of Einstein’s General Relativity. The gravitational acceleration for antihydrogen will be determined using a set of gravity measurement gratings (Moiré deflectometer) and a position sensitive detector. The vertical shift due to gravity of the falling antihydrogen atoms will be detected with a silicon strip detector, where the annihilation of antihydrogen will take place. This poster presents part of the development process of this detector.

  17. Simulation and optimisation of a position sensitive scintillation detector with wavelength shifting fibers for thermal neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Herzkamp, Matthias; Engels, Ralf; Kemmerling, Guenter [ZEA-2, Forschungszentrum Juelich (Germany); Brueckel, Thomas [JCNS, Forschungszentrum Juelich (Germany); Stahl, Achim [III. Physikalisches Institut B, RWTH Aachen (Germany); Waasen, Stefan van [ZEA-2, Forschungszentrum Juelich (Germany); Faculty of Engineering, University of Duisburg-Essen (Germany)

    2015-07-01

    In neutron scattering experiments it is important to have position sensitive large scale detectors for thermal neutrons. A detector based on a neutron scintillator with wave length shifting fibers is a new kind of such a detector. We present the simulation of the detector based on the microscopic structure of the scintillation material of the mentioned detector. It consists of a converter and a scintillation powder bound in a matrix. The converter in our case is lithium fluoride with enriched lithium 6, to convert thermal neutrons into high energetic alpha and triton particles. The scintillation material is silver doped zinc sulfide. We show that pulse height spectra obtained by these scintillators can be be explained by the simple model of randomly distributed spheres of zinc sulfide and lithium fluoride. With this model, it is possible to optimise the mass ratio of zinc sulfide to lithium fluoride with respect to detection efficiency and/or energy deposition in zinc sulfide.

  18. Improving linearity of position-sensitive detector using support vector machines

    Institute of Scientific and Technical Information of China (English)

    Meiying Ye

    2005-01-01

    An intelligent method for improving position linearity of position-sensitive detector (PSD), based on support vector machines (SVMs), is developed. The SVM is established based on the structural risk minimization principle rather than minimizing the empirical error commonly implemented in neural networks.SVM can achieve higher generalization performance. Training SVM is equivalent to solving a linearly constrained quadratic programming problem, thus the solution of SVM is always unique and globally optimal.The improving position linearity procedure has been illustrated using a two-dimensional (2D) PSD. It is pointed out that the position linearity of the measuring system with a proper SVM correction is improved by two orders of magnitude in the measurement range.

  19. Position sensitive detection of thermal neutrons with solid state detectors (Gd Si planar detectors)

    CERN Document Server

    Bruckner, G; Rauch, H; Weilhammer, P

    1999-01-01

    Recent advances in the technology of position sensitive silicon detectors and the corresponding electronics allow the construction of fast time response thermal neutron detectors. These detectors also exhibit excellent position resolution by combination of silicon detectors with thin Gd converter foils. We constructed several one- and two-dimensional prototype detectors, using DC and AC coupled silicon strip detectors, pad detectors and different VLSI readout electronics. The position resolution and the detector efficiency for different converters at wavelengths from 1.1 to 3.3 A were determined at the TRIGA reactor in Vienna and at the ILL in Grenoble. Spatial resolutions of less than 100 mu m and efficiencies up to 40% have been achieved. The results of these measurements are compared with a Monte Carlo simulation of the detector operation. These detectors can also be used for phase topography experiments using perfect crystal neutron interferometers. In certain cases an increase of the sensitivity in the o...

  20. Position-sensitive detection of ultracold neutrons with an imaging camera and its implications to spectroscopy

    CERN Document Server

    Wei, Wanchun; Hoffbauer, M A; Makela, M; Morris, C L; Tang, Z; Adamek, E R; Callahan, N B; Clayton, S M; Cude-Woods, C; Currie, S; Dees, E B; Ding, X; Geltenbort, P; Hickerson, K P; Holley, A T; Ito, T M; Leung, K K; Liu, C -Y; Morley, D J; Ramsey, J C; Pattie,, R W; Salvat, D J; Saunders, A; Seestrom, S J; Sharapov, E I; Sjue, S K; Wexler, J; Womack, T L; Young, A R; Zeck, B A; Wang, Zhehui

    2016-01-01

    Position-sensitive detection of ultracold neutrons (UCNs) is demonstrated using an imaging charge-coupled device (CCD) camera. A spatial resolution less than 15 $\\mu$m has been achieved, which through the relation $\\delta E = m_0g \\delta x$, converts to UCN energy resolution below 2 pico-electron volts. The symbols $\\delta E$, $\\delta x$, $m_0$ and $g$ are for energy resolution, spatial resolution, the neutron rest mass and gravitational acceleration respectively. A multilayer surface convertor described previously is used to capture UCNs and emits visible light for CCD imaging. Particle identification and noise rejection are discussed through light intensity profile analysis. This method allows new types of UCN spectroscopy and various applications.

  1. Position-sensitive detection of ultracold neutrons with an imaging camera and its implications to spectroscopy

    Science.gov (United States)

    Wei, Wanchun; Broussard, L. J.; Hoffbauer, M. A.; Makela, M.; Morris, C. L.; Tang, Z.; Adamek, E. R.; Callahan, N. B.; Clayton, S. M.; Cude-Woods, C.; Currie, S.; Dees, E. B.; Ding, X.; Geltenbort, P.; Hickerson, K. P.; Holley, A. T.; Ito, T. M.; Leung, K. K.; Liu, C.-Y.; Morley, D. J.; Ortiz, Jose D.; Pattie, R. W.; Ramsey, J. C.; Saunders, A.; Seestrom, S. J.; Sharapov, E. I.; Sjue, S. K.; Wexler, J.; Womack, T. L.; Young, A. R.; Zeck, B. A.; Wang, Zhehui

    2016-09-01

    Position-sensitive detection of ultracold neutrons (UCNs) is demonstrated using an imaging charge-coupled device (CCD) camera. A spatial resolution less than 15 μm has been achieved, which is equivalent to a UCN energy resolution below 2 pico-electron-volts through the relation δE =m0 gδx. Here, the symbols δE, δx, m0 and g are the energy resolution, the spatial resolution, the neutron rest mass and the gravitational acceleration, respectively. A multilayer surface convertor described previously is used to capture UCNs and then emits visible light for CCD imaging. Particle identification and noise rejection are discussed through the use of light intensity profile analysis. This method allows different types of UCN spectroscopy and other applications.

  2. Imaging, Detection, and Identification Algorithms for Position-Sensitive Gamma-Ray Detectors

    Science.gov (United States)

    Wahl, Christopher G.

    Three-dimensional-position-sensitive semiconductors record both the locations and energies of gamma-ray interactions with high resolution, enabling spectroscopy and imaging of gamma-ray-emitting materials. Imaging enables the detection of point sources of gamma rays in an otherwise extended-source background, even when the background spectrum is unknown and may share the point source's spectrum. The generalized likelihood ratio test (GLRT) and source-intensity test (SIT) are applied to this situation to detect one-or-more unshielded point sources from a library of isotopes in a spectrally unknown or known background when the background intensity varies spatially by a factor of two or less. In addition to estimating the number of sources present, their activities, isotopes, and directions from the detector are estimated. Experimental and some simulated results are presented for a single detector and an 18-detector array of 2 cm by 2 cm by 1.5 cm CdZnTe crystals and compared with the performance of spectral-only detection when the background and source are assumed to be spectrally different. Furthermore, the expected detection performance of the 18-detector array system is investigated statistically using experimental data in the case where the background is distinct spectrally from the point source and the possible source location and isotopic identity are known. Including imaging gave at least 7% higher SNR compared to ignoring the image dimension. Also, imaging methods based on the maximum-likelihood, expectation-maximization method are introduced to determine the spatial distribution of isotopes and to find the activity distributions within targets moving with known motion through a radioactive background. Software has also been developed to support the analysis of the data from 3D-position-sensitive spectroscopic systems, for a range of detector designs and applications. The software design and unique features that allow fast multidimensional data analysis are

  3. The residual stress instrument with optimized Si(2 2 0) monochromator and position-sensitive detector at HANARO

    Science.gov (United States)

    Lee, Chang-Hee; Moon, Myung-Kook; Em, Vyacheslav T.; Choi, Young-Hyun; Cheon, Jong-Kyu; Nam, Uk-Won; Kong, Kyung-Nam

    2005-06-01

    An upgraded residual stress instrument at the HANARO reactor of the KAERI is described. A horizontally focusing bent perfect crystal Si(2 2 0) monochromator (instead of a mosaic vertical focusing Ge monochromator) is installed in a drum with a tunable (2 θM=0-60°) take-off angle/wavelength. A specially designed position-sensitive detector (60% efficiency for λ=1.8 A) with 200 mm (instead of 100 mm) high-active area is used. There are no Soller type collimators in the instrument. The minimum possible monochromator to sample distance, L=2 m, and sample to detector distance, L=1.2 m, were found to be optimal. The new PSD and bent Si(2 2 0) monochromator combined with the possibility of selecting an appropriate wavelength resulted in about a ten-fold gain in data collection rate. The optimal reflections of austenitic and ferritic steels, aluminum and nickel for stress measurements with a Si(2 2 0) monochromator were chosen experimentally. The ability of the instrument to make strain measurements deep inside the austenitic and ferritic steels has been tested. For the chosen reflections and wavelengths, no shift of peak position (apparent strain) was observed up to 56 mm length of path.

  4. High-Efficiency CdZnTe Position-Sensitive VFG Gamma-Ray Detectors for Safeguards Applications

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov, Aleksey E. [Brookhaven National Lab. (BNL), Upton, NY (United States); James, Ralph B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Cui, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); De Geronimo, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Vernon, E. [Brookhaven National Lab. (BNL), Upton, NY (United States); Camarda, G. S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Hossain, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yang, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Indusi, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Boyer, Brian [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-09-30

    The goal of this project is to incorporate a Cadmium-Zinc-Telluride (CdZnTe or CZT) detector (with 1% or better resolution) into a bench-top prototype for isotope identification and related safeguards applications. The bench-top system is based on a 2x2 array of 6x6x20 mm3 position-sensitive virtual Frisch-grid (VFG) CZT detectors. The key features of the array are that it allows for the use of average-grade CZT material with a moderate content of defects, and yet it provides high-energy resolution, 1% FWHM at 662 keV, large effective area, and low-power consumption. The development of this type of 3D detector and new instruments incorporating them is motivated by the high cost and low availability of large, > 1 cm3, CZT crystals suitable for making multi-pixel detectors with acceptable energy resolution and efficiency.

  5. New Developments in the Position Sensitive Detectors Based on Microchannel Plates

    Science.gov (United States)

    Tremsin, A. S.; Siegmund, O. H. W.

    2002-11-01

    We report on the latest developments in position sensitive photon counting detectors based on microchannel plates. Substantial improvement of the spatial resolution was achieved with introduction of new readout technology, namely crossed strip (XS) anode, and corresponding processing electronics. The spatial resolution of XS readout appeared to be as small as ~3-4 μm FWHM. Reduction of the total detector gain (down to 106 and potentially lower) without compromising the spatial accuracy allows detector operation at much higher local and global counting rates since the microchannel recharge time becomes smaller. Recent developments of novel microchannel plate technologies provide basis for substantial increase of the spectral sensitivity and quantum efficiency of MCP detectors. We have tested a number of new Silicon micromachined MCPs The new MCP technologies should allow deposition of completely new photocathode materials directly on the front surface of microchannel plates (opaque photocathodes). Opposite to standard glass MCPs new Silicon MCPs can sustain high temperatures (-800 C°) required for the photocathode deposition and activation processes.

  6. On-line evaluation of position-sensitive detector (PSD) diffraction data

    International Nuclear Information System (INIS)

    The amount of raw data accumulated in a single-crystal diffraction experiment using a two-dimensional Position Sensitive Detector is usually so large that it is impracticable to store it. It is therefore necessary to reduce each local three-dimensional array of counts to a Bragg intensity, in a time not longer than the average time that one reflection is active. The statistically optimum procedure comprises an estimation of the background from a large number of counts, and an integration of peak intensity within a suitable three-dimensional envelope. A typical on-line method is described, using as an example the D19 diffractometer at the Institut Max von Laue - Paul Langevin (ILL) high-flux reactor. Current methods of PSD data reduction are reviewed. These fall into three groups according to the basis of the method used to find the integration envelope: (a) statistical criteria, (b) three-dimensional sigma(I)/I analysis, and (c) pre-calculation of the resolution function. On-line data reduction imposes special requirements on diagnostics to check the precision of the reduced data, especially at the start of an experiment, when any peculiarities must be identified and allowed for in the data-reduction procedure. The diagnostic possibilities resulting from the comparison of local with global characteristics of the background and the integration envelope are discussed. (author)

  7. MiX: a position sensitive dual-phase liquid xenon detector

    International Nuclear Information System (INIS)

    The need for precise characterization of dual-phase xenon detectors has grown as the technology has matured into a state of high efficacy for rare event searches. The Michigan Xenon detector was constructed to study the microphysics of particle interactions in liquid xenon across a large energy range in an effort to probe aspects of radiation detection in liquid xenon. We report the design and performance of a small 3D position sensitive dual-phase liquid xenon time projection chamber with high light yield (Ly122=15.2 pe/keV at zero field), long electron lifetime (τ > 200 μs), and excellent energy resolution (σ/E = 1% for 1,333 keV gamma rays in a drift field of 200 V/cm). Liquid xenon time projection chambers with such high energy resolution may find applications not only in dark matter direct detection searches, but also in neutrinoless double beta decay experiments and other applications

  8. High-energy resolution μ-XRF analysis by position sensitive spectrometer

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    With a high-energy resolution micro-X-ray fluorescence (μ-XRF) analysis setup, which basically consists of an X-ray microbeam formed by an X-ray focusing lens combined with an X-ray apparatus and a wavelength dispersive position sensitive spectrometer with a flat crystal (PSS), preliminary results have been obtained. The counting rate of the analyzed element linearly increased with the power of X-ray apparatus, and the energy resolution, full width of half maximum (FWHM) of Ka lines of Ti and Cr reached 16.6 and 23.6 eV, respectively. The Cr Kb and Mn Ka lines in a sample of stainless steel could clearly be resolved. The above-mentioned results are also compared with those obtained by synchrotron radiation light microbeam combined with the PSS. The facts show that the high-energy resolution element analysis is feasible by using the setup. Moreover, problems for the setup and the ways to resolve them are discussed as well.

  9. High-resolution and high-intensity neutron diffractometer with linear position-sensitive detector

    Science.gov (United States)

    Lee, Chang-Hee; Moon, Myung-Kook; Em, V. T.; Choi, Young-Nam; Oh, Hwa-Suk; Nam, Uk-Won

    2003-08-01

    The characteristics of a neutron diffractometer using a 3He one-dimensional position-sensitive detector (PSD) with delay line readout, a 200 (length) × 100 (height) mm 2 active window and 2.5 mm spatial resolution have been studied and compared with those of the High-Resolution Powder Diffractometer (HRPD) of KAERI with 32 3He conventional tube (∅50 mm) detectors and Soller collimators (10') before detectors. For the sample to PSD distance R=1200 mm, the PSD subtends 8° angle of 2 θ and provides the resolution and the peak-to-background ratio close to that for HRPD. Time for scanning (with the same statistics) of a 0-160° interval is about 1.6 times longer and the multi-PSD system providing efficiency about 10 times higher than HRPD is proposed. Because of the small angle subtended by the PSD, the parasitic peaks from the sample environment are eliminated and operation without an oscillating radial collimator is possible. Additionally, the proposed diffractometer has an advantage for small samples.

  10. Hard x-ray polarimetry with a thick CdTe position sensitive spectrometer

    Science.gov (United States)

    Caroli, Ezio; Bertuccio, Giuseppe; Cola, Adriano; Curado da Silva, R. M.; Donati, Ariano; Dusi, Waldes; Landini, Gianni; Siffert, Paul; Sampietro, Marco; Stephen, John B.

    2000-12-01

    Even though it is recognized that the study of polarization from cosmic high-energy sources can give very important information about the nature of the emission mechanism, to date very few measurements have been attempted. For several years we have proposed the use of a thick CdTe array as a position sensitive spectrometer for hard X- and soft gamma-ray astronomy, a design which is also efficient for use as a polarimeter at energies above approximately 100 keV. Herein we describe the preliminary results of our study of a polarimeter based on 4096 CdTe microcrystals that we would like to develop for a high altitude balloon experiment. We present the telescope concept with a description of each subsystem together with some results on activities devoted to the optimization of the CdTe detector units' response. Furthermore we give an evaluation of the telescope performance in terms of achievable spectroscopic and polarimetric performance. In particular we will show the results of Monte Carlo simulations developed to evaluate the efficiency of our detector as a hard X ray polarimeter.

  11. Gamma ray measurement of earth formation properties using a position sensitive scintillation detector

    International Nuclear Information System (INIS)

    This patent describes a system for measuring properties of earth formations in the vicinity of a well borehole at different radial distances from the borehole, comprising: a fluid tight hollow body member sized and adapted for passage through a well borehole and housing therein; a source of gamma rays and means for directing gamma rays from the source outwardly from the body member into earth formations in the vicinity of the borehole; and a position sensitive scintillation detector for detecting gamma rays scattered back into the body member from the earth formation in the vicinity of the borehole, means for collimating the scattered gamma rays onto the detector. The detector comprises scintillation crystal means having discrete longitudinally spaced active regions or bins and is longitudinally spaced from the gamma ray source. It has a longitudinal length L and two opposite ends and photomultiplier tubes optically coupled to the opposite ends for providing output voltage signals having voltage amplitudes A and B representative of the intensity of scintillation events occurring in the crystal and impinging at the opposite ends thereof. A means separates the bins for selectively attenuating light passing therebetween, and a means combines the output voltage signals A and B according to a predetermined relationship to derive the discrete bin along the length L of each of the scintillation events in the crystal, thereby providing measurements of the gamma ray scattering properties of the earth formations at different radial distances from the borehole

  12. Performance studies on high pressure 1-D position sensitive neutron detectors

    Indian Academy of Sciences (India)

    S S Desai; A M Shaikh

    2008-11-01

    The powder diffractometer and Hi-Q diffractometer at Dhruva reactor make use of five identical 1-D position sensitive detectors (PSDs) to scan scattering angles in the range 3° to 140°. In order to improve the overall throughput of these spectrometers, it is planned to install a bank of 15 high-efficiency and high-resolution PSDs arranged in three layers with five PSDs in each layer. With each high pressure PSD (3He 10 bar + Kr 2 bar) showing the efficiency gain of 1.8 at 1.2 Å, detector bank is expected to show overall gain of 5.5 times the present detection efficiency and reduction in data collection time by equivalent factor. The 1-D PSDs are developed in batches of five, and are characterized so that all PSDs operate at uniform parameters such as position resolution, uniformity of efficiency and linearity of response. Position spectrum indicates the differential position resolution to be ∼ 1 mm and integral position resolution to be 3–4 mm. Broadening of position spectrum at the extreme end of sensitive length of PSD is analysed using fine shift of the beam. Dependence of position resolution and dynamic range of output pulse on the input impedance of pre-amplifier is also presented.

  13. Position-sensitive change in the transition metal L-edge fine structures

    Energy Technology Data Exchange (ETDEWEB)

    Gulec, Ahmet; Phillips, Patrick J.; Klie, Robert F. [Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607 (United States)

    2015-10-05

    Studying the structure and composition of solid-state materials on the atomic scale has become nearly routine in transmission electron microscopy with the development of novel electron optics and electron sources. In particular, with spatial resolutions better than 0.1 nm and energy resolution smaller than 100 meV, the stoichiometry, bonding, and coordination can now be examined on similar scales. Aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy (EELS) have played a crucial role in identifying charge ordering, valence, and as spin state transitions in transition metal perovskite oxides. In this letter, we investigate the effects of ever-decreasing electron-probe sizes on the measured near-edge fine-structure of the transition metal core-loss edge using EELS. We find that for certain transition metal perovskites, the position of the electron probe with respect to the atomic column is crucial in determining the correct valence state. Several reasons for the observed position-sensitive EELS fine-structure are discussed.

  14. Position sensitive detection of thermal neutrons by Gd-Si-planardiodes

    CERN Document Server

    Bruckner, G

    1998-01-01

    Recent advances in the technology of position sensitive silicon detectors and the corresponding electronics allow the construction of fast time response thermal neutron detectors. These detectors also exhibit excellent position resolution and good efficiency by combination of Silicon sensors with Gadolinium converter foils. The neutron detection is based on the (n,y) reaction in Gd which produces a quite complex conversion electron spectra with significant energy lines between 29 keV and about 200 keV, which can be detected in the Si sensors. Due to the high absorption cross section of Gd the converter can be made very thin. Hence the range of the conversion electrons is sufficient to reach the Si-sensor. This thin converter together with the short charge collection time in Si ensures the good time resolution of the device. We constructed several one- and two-dimensional prototype detectors, using DC and AC coupled silicon strip detectors, pad detectors and different VLSI readout electronics. The position res...

  15. High-speed use of CCD area sensors as high energy particle detectors

    International Nuclear Information System (INIS)

    A position sensitive detector for minimum ionizing particles is described. It is based on charge coupled devices (CCDs) area image sensors with single pixel sizes of 22 x 22 μm2. The operating frequency is 6.75 MHz and the total readout time for 2.3 x 105 pixels is about 40 ms. The devices are operated close to room temperature. (orig.)

  16. Fuel cell with ionization membrane

    Science.gov (United States)

    Hartley, Frank T. (Inventor)

    2007-01-01

    A fuel cell is disclosed comprising an ionization membrane having at least one area through which gas is passed, and which ionizes the gas passing therethrough, and a cathode for receiving the ions generated by the ionization membrane. The ionization membrane may include one or more openings in the membrane with electrodes that are located closer than a mean free path of molecules within the gas to be ionized. Methods of manufacture are also provided.

  17. Calibration of two-dimensional position sensitive detector of triple-axis neutron spectrometer

    International Nuclear Information System (INIS)

    Background: A 200 mm×200 mm two-dimensional positional sensitive detector (PSD) has been designed and constructed for the cold-neutron triple axis spectrometer (CTAS). The parameters of the PSD are necessary for evaluation and analysis of neutron scattering pattern obtained on CTAS and other instrument using PSD, mainly for the correction of angle and spectral shape due to the unequal solid angle and inhomogeneous efficiency of the flat PSD. Purpose: In order to obtain the working bias voltage, pixel size, spatial resolution, detection efficiency and its uniformity , a calibration method was proposed and tested for the PSD of CTAS. Methods: The calibration was carried out at the ATHOS three-axis spectrometer installed at the neutron guide No.1 of the 10-MW steady state reactor of the Budapest Neutron Centre. The focusing copper monochrometer provided well collimated (20' divergence) neutron beam of wavelength equal to 0.572 nm with the second order equal to 0.286 nm. A black neutron detector having >99% efficiency at these wavelengths coated with boron shielding was used for efficiency test and a 0.5-mm wide Cd slit was used for the determination of pixel size and spatial resolution of the PSD. Results: The experimental results show that the working bias voltage is 4.2-4.4 kV, pixel size 0.32 mm. (H and V), the detector spatial resolution of 2.15 mm(H)×2.04 mm(V), the detection efficiency of 90.47% and the efficiency uniformity better than 10%. Conclusion: The established method was successfully used in the PSD calibration, which can be extended to PSD R&D and data analysis of neutron spectrometer. (authors)

  18. Effects of dose and of partial body ionizing radiation on taste aversion learning in rats with lesions of the area postrema

    International Nuclear Information System (INIS)

    The effect of area postrema lesions on the acquisition of a conditioned taste aversion following partial body exposure to ionizing radiation was investigated in rats exposed to head-only irradiation at 100, 200 and 300 rad or to body-only irradiation at 100 and 200 rad. Following head-only irradiation area postrema lesions produced a significant attenuation of the radiation-induced taste aversion at all dose levels, although the rats still showed a significant reduction in sucrose preference. Following body-only exposure, area postrema lesions completely disrupted the acquisition of the conditioned taste aversion. The results are interpreted as indicating that: (a) the acquisition of a conditioned taste aversion following body-only exposure is mediated by the area postrema; and (b) taste aversion learning following radiation exposure to the head-only is mediated by both the area postrema and a mechanism which is independent of the area postrema

  19. Radiation hard position-sensitive cryogenic silicon detectors the Lazarus effect

    CERN Document Server

    Palmieri, V G; Bell, W H; Berglund, P; de Boer, Wim; Borchi, E; Borer, K; Bruzzi, Mara; Buontempo, S; Casagrande, L; Chapuy, S; Cindro, V; D'Ambrosio, N; Via, D; Devine, S R H; Dezillie, B; Dimcovski, Zlatomir; Eremin, V V; Esposito, A P; Granata, V; Grigoriev, E; Hauler, F; Heijne, Erik H M; Heising, S; Janos, S; Jungermann, L; Konorov, I; Li, Z; Lourenço, C; Mikuz, M; Niinikoski, T O; O'Shea, V; Pagano, S; Paul, S; Pirollo, S; Pretzl, Klaus P; Rato-Mendes, P; Ruggiero, G; Smith, K; Sonderegger, P; Sousa, P; Verbitskaya, E; Watts, S; Zavrtanik, M

    2000-01-01

    The discovery of the so-called Lazarus effect, namely the recovery of the charge collection efficiency (CCE) of irradiated silicon detectors by means of cryogenic cooling has entailed an increasing interest in the behavior of silicon detectors at cryogenic temperatures. We have measured the CCE of a silicon p-i-n diode detector previously irradiated with an equivalent fluence of 1*10/sup 15/ n/cm/sup 2/ neutrons of 1 MeV energy. The charge collection efficiency has been measured at 77 K, showing that the low- temperature operation considerably decreases the bias current. This is also the case when forward voltage bias is applied, which then becomes a suitable option. In this condition, the sample shows a charge collection efficiency in excess of 65% at 250 V corresponding to a most probable signal for a minimum ionizing particle of 21000e /sup /. (6 refs).

  20. Large area neutron detector based on Li6 ionization chamber with integrated body-moderator of high density polyethylene

    International Nuclear Information System (INIS)

    A detector was developed and funded by DHS to be a lower cost alternative to 3He detectors. A 6Li foil-lined ionization chamber was prepared with fill gas at one atmosphere and pulse mode operation. The high-density polyethylene (HOPE) body serves also as a neutron moderator. All electrodes, including high voltage bias supply, are hermetically sealed within the plastic slabs.

  1. A position-sensitive gamma-ray detector for positron annihilation 2D-ACAR based on metal package photomultiplier tubes

    CERN Document Server

    Inoue, K; Nagashima, Y; Hyodo, T; Nagai, Y; Muramatsu, S; Nagai, S; Masuda, K

    2002-01-01

    A new position-sensitive gamma-ray detector to be used in a two-dimensional angular correlation of positron annihilation radiation (2D-ACAR) apparatus has been developed. It consists of 36 compact position-sensitive photomultiplier tubes (PS-PMT: HAMAMATSU R5900-00-C8), a light guide, and 2676 Bi sub 4 Ge sub 3 O sub 1 sub 2 (BGO) scintillator pieces of size 2.6 mmx2.6 mmx18 mm. A high detection efficiency for 511 keV gamma-ray is achieved with the length of BGO scintillators used. The detection area is about 160 mmx160 mm. The 288 anode outputs of the PS-PMTs are wired and connected to resistor chains from which 16 outputs (8 outputs each along the X and Y directions) are taken to identify the incident position of the gamma-ray. The spatial resolution is about 3 mm (FWHM). The timing signal taken from the last dynodes of the PS-PMTs gives a timing resolution of 7.7 ns (FWHM) for 511 keV positron annihilation gamma-rays.

  2. A position-sensitive γ-ray detector for positron annihilation 2D-ACAR based on metal package photomultiplier tubes

    Science.gov (United States)

    Inoue, Koji; Saito, Haruo; Nagashima, Yasuyuki; Hyodo, Toshio; Nagai, Yasuyoshi; Muramatsu, Shinichi; Nagai, Shota; Masuda, Keisuke

    2002-07-01

    A new position-sensitive γ-ray detector to be used in a two-dimensional angular correlation of positron annihilation radiation (2D-ACAR) apparatus has been developed. It consists of 36 compact position-sensitive photomultiplier tubes (PS-PMT: HAMAMATSU R5900-00-C8), a light guide, and 2676 Bi 4Ge 3O 12 (BGO) scintillator pieces of size 2.6 mm×2.6 mm×18 mm. A high detection efficiency for 511 keV γ-ray is achieved with the length of BGO scintillators used. The detection area is about 160 mm×160 mm. The 288 anode outputs of the PS-PMTs are wired and connected to resistor chains from which 16 outputs (8 outputs each along the X and Y directions) are taken to identify the incident position of the γ-ray. The spatial resolution is about 3 mm (FWHM). The timing signal taken from the last dynodes of the PS-PMTs gives a timing resolution of 7.7 ns (FWHM) for 511 keV positron annihilation γ-rays.

  3. A position-sensitive γ-ray detector for positron annihilation 2D-ACAR based on metal package photomultiplier tubes

    International Nuclear Information System (INIS)

    A new position-sensitive γ-ray detector to be used in a two-dimensional angular correlation of positron annihilation radiation (2D-ACAR) apparatus has been developed. It consists of 36 compact position-sensitive photomultiplier tubes (PS-PMT: HAMAMATSU R5900-00-C8), a light guide, and 2676 Bi4Ge3O12 (BGO) scintillator pieces of size 2.6 mmx2.6 mmx18 mm. A high detection efficiency for 511 keV γ-ray is achieved with the length of BGO scintillators used. The detection area is about 160 mmx160 mm. The 288 anode outputs of the PS-PMTs are wired and connected to resistor chains from which 16 outputs (8 outputs each along the X and Y directions) are taken to identify the incident position of the γ-ray. The spatial resolution is about 3 mm (FWHM). The timing signal taken from the last dynodes of the PS-PMTs gives a timing resolution of 7.7 ns (FWHM) for 511 keV positron annihilation γ-rays

  4. Comparison of various stopping gases for {sup 3}He-based position sensitive neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Doumas, A. [United States Merchant Marine Academy, Steamboat Road, Kings Point, NY 11024 (United States); Smith, G.C., E-mail: gsmith@bnl.gov [Instrumentation Division, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2012-05-21

    A range of solid state, scintillator and gas based detectors are being developed for use at the next generation of high flux neutron facilities. Since gas detectors are expected to continue to play a key role in future specific thermal neutron experiments, a comparison of the performance characteristics of prospective stopping gases is beneficial. Gas detectors typically utilize the reaction {sup 3}He(n,p)t to detect thermal neutrons; the {sup 3}He gas is used in a mixture containing a particular stopping gas in order to maintain relatively short ranges for the proton and triton pair emitted from the n-{sup 3}He reaction. Common stopping gases include hydrocarbons (e.g. propane), carbon tetrafluoride, and noble gases such as argon and xenon. For this study, we utilized the Monte Carlo simulation code 'Stopping and Range of Ions in Matter' to analyze the expected behavior of argon, xenon, carbon dioxide, difluoroethane and octafluoropropane as stopping gases for thermal neutron detectors. We also compare these findings to our previously analyzed performance of propane, butane and carbon tetrafluoride. A discussion of these gases includes their behavior in terms of proton and triton range, ionization distribution and straggle.

  5. A ΔE-E Telescope with Ionization Chamber Used in Excitation Function Measurement

    Institute of Scientific and Technical Information of China (English)

    LiSonglin; WangQi; DongYuchuan; XuHuagen; ChenRuofu

    2003-01-01

    A thorough study of excitation function in dissipative heavy ion collision requires the identification of the nuclear charge number Z of the reaction products. For this purpose, a special designed ΔE-E telescope is employed, which consists of a gas filled ionization chamber to detect the energy loss and a position sensitive semiconductor Si detector (300μm in thickness and 8 mm×45 mm in active area) as the residual energy detector. The ionization chamber with a sensitive length of about 60 mm, is divided into two parts of ΔE1 and ΔE2, each with length of 30 mm. The trajectory of the incident particles is parallel to the direction of the electric field in the ionization chamber. The anodes of ΔE1 and ΔE2 are realized through the rectangular empty metallic frames. In order to collect ionized charge produced by the incident particle inside the ionization chamber effectively, two equipotential frame-shape electrodes were placed on both sides of each anode, to form a strong electric focused field toward the anode. The advantages of this type of the detector arc as follows: (1)lower energy detection threshold; (2) wide dynamical range both for the light particles and the heavy fragments;(3) larger solid angle coverage with a relatively smaller detector size based on the position information from the Si detector.

  6. Proportional counter for X-ray analysis of lunar and planetary surfaces. [a position sensitive scintillating imaging proportional counter

    Science.gov (United States)

    1979-01-01

    A position sensitive proportional scintillation detector was developed and evaluated for use in applications involving X-ray imaging as well as spectroscopy. Topics covered include limitations of the proportional scintillation counter for use in space; purification of the xenon gas in the detector, and the operation of the detector system. Results show that the light signal in a proportional scintillation detector remains well localized. With modest electric fields in xenon, the primary electrons from a photoelectric absorption of an X-ray can be brought a distance of a few millimeters to a higher field region without spreading more than a millimeter or so. Therefore, it is possible to make a proportional scintillation detector with good position sensitivity that could be used to calibrate out the difference in light collection over its sensitive volume.

  7. Two-dimensional position-sensitive detectors for small-angle neutron scattering

    International Nuclear Information System (INIS)

    In this paper, various detectors available for small angle neutron scattering (SANS) are discussed, along with some current developments being actively pursued. A section has been included to outline the various methodologies of position encoding/decoding with discussions on trends and limitations. Computer software/hardware vary greatly from institute and experiment and only a general discussion is given to this area. 85 refs., 33 figs

  8. Current status and requirements for position-sensitive detectors in medicine

    CERN Document Server

    Speller, R

    2002-01-01

    This review considers the current status of detector developments for medical imaging using ionising radiation. This field is divided into two major areas; the use of X-rays for transmission imaging and the use of radioactive tracers in emission imaging (nuclear medicine). Until recently, most detector developments were for applications in nuclear medicine. However, in the past 5 years new developments in large area, X-ray-sensitive detectors have meant that both application domains are equally served. In X-ray imaging, work in CT and mammography are chosen as examples of sensor developments. Photodiode arrays in multi-slice spiral CT acquisitions are described and for mammography the use of amorphous silicon flat panel arrays is considered. The latter is an excellent example where new detector developments have required a re-think of traditional imaging methods. In gamma-ray imaging the recent developments in small area, task-specific cameras are described. Their limitations and current proposals to overcome...

  9. Molecular Characterization of Organosulfates in Organic Aerosols from Shanghai and Los Angeles Urban Areas by Nanospray-Desorption Electrospray Ionization High-Resolution Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Shikang; Lu, Xiaohui; Levac, Nicole; Bateman, Adam P.; Nguyen, Tran B.; Bones, David L.; Nizkorodov, Sergey A.; Laskin, Julia; Laskin, Alexander; Yang, Xin

    2014-09-16

    Aerosol samples collected in the urban areas of Shanghai and Los Angeles were analyzed by nanospray-desorption electrospray ionization mass spectrometry (nano-DESI MS) with high mass resolution (m/Δm=100,000). Solvent mixtures of acetonitrile/water and acetonitrile/toluene were used to extract and ionize polar and non-polar compounds, respectively. A diverse mixture of oxygenated hydrocarbons, organosulfates, organonitrates, and organics with reduced nitrogen were detected in the Los Angeles sample. Majority of the organics in the Shanghai sample were detected as organosulfates. The dominant organosulfates in the two samples have distinctly different molecular characteristics. Specifically, organosulfates in the Los Angeles sample were dominated by isoprene- or monoterpene-derived products, while organosulfates of yet unknown origin in the Shanghai sample had distinctive characteristics of long aliphatic carbon chains and low degree of oxidation and unsaturation. The use of acetonitrile/toluene solvent facilitated identification of this type of organosulfates, suggesting they could be missed in previous studies relying on sample extraction using common polar solvents. The high molecular weight and low degree of unsaturation and oxidization of the organosulfates detected in the Shanghai sample suggest that they may act as surfactants, and plausibly affect the surface tension and hygroscopicity of the atmospheric particulate matter. We propose that direct esterification of carbonyl or hydroxyl compounds by sulfates or sulfuric acid in liquid phase could be the formation pathway of these special organosulfates. Finally, long-chain alkanes from vehicle emissions might be their precursors.

  10. A radial position-sensitive 127.3 degree electrostatic coaxial cylindrical spectrometer for sputtering ion measurements

    CERN Document Server

    Ruan, Fangfang; Zhang, Mingwu; Wang, Wei; Chen, Jing; Shao, Caojie; Lu, Rongchun; Cai, Xiaohong

    2008-01-01

    A 127 degree electrostatic coaxial cylindrical energy spectrometer with a radial position sensitive MCP detector is designed and constructed. Beyond the traditional step-by-step voltage scanning method, this spectrometer is able to measure a segment of energy spectra at a working voltage. Therefore, the experiment efficiency is notably enhanced and it is suitable for measuring the energy spectra of sputtering ions. The first test was done by measuring an energy spectrum of the sputtering ions in 800keV Ar8+ bombarding on beryllium target.

  11. Applications of one-dimensional position-sensitive detectors for neutron diffraction experiments on powders and liquids

    International Nuclear Information System (INIS)

    The applications of one-dimensional position sensitive detectors (PSDs) are reviewed. The detectors used are multiwire detectors based on the principle of gas-filled proportional counters. The uses include the neutron diffraction from powders and liquids in the study of chemical reactions and phase transitions. However, the angular range and wire separation are insufficient for many experiments. In particular the data acquisition and processing are inadequate for real time experiments with tsub(s) values of seconds or less. (tsub(s) - measuring time per spectrum). From the results obtained it should be possible to optimize the construction of a new 1600 PSD. (U.K.)

  12. Extensive simulation studies on the reconstructed image resolution of a position sensitive detector based on pixelated CdTe crystals

    CERN Document Server

    Zachariadou, K; Kaissas, I; Seferlis, S; Lambropoulos, C; Loukas, D; Potiriadis, C

    2011-01-01

    We present results on the reconstructed image resolution of a position sensitive radiation instrument (COCAE) based on extensive simulation studies. The reconstructed image resolution has been investigated in a wide range of incident photon energies emitted by point-like sources located at different source-to-detector distances on and off the detector's symmetry axis. The ability of the detector to distinguish multiple radioactive sources observed simultaneously is investigating by simulating point-like sources of different energies located on and off the detector's symmetry axis and at different positions

  13. Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration

    International Nuclear Information System (INIS)

    Kerma-area product meters (KAP meters) are frequently used in diagnostic radiology to measure the integral of air-collision kerma over an area A(∫A Kc,air dA) perpendicular to the x-ray beam. In this work, a precise method for calibrating a KAP meter to measure ∫A Kc,air dA is described and calibration factors determined for a broad range of tube potentials (40-200kV). The integral is determined using a large number of TL dosimeters spread over and outside the nominal field area defined as the area within 50% of maximum Kc,air. The method is compared to a simplified calibration method which approximates the integral by multiplying the kerma in the centre of the field by the nominal field area Anom. While the calibration factor using the precise method is independent of field area and distance from the source, that using the simplified method depends on both. This can be accounted for by field inhomogeneities caused by the heel effect, extrafocal radiation and scattered radiation from the KAP meter. The deviations between the calibration factors were as large as ±15% for collimator apertures of 5-100cm2 and distances from the source of 50 - 160 cm. The uncertainty in the calibration factor using the precise method was carefully evaluated and the expanded relative uncertainty estimated to be ±3% with a confidence level of 95%. (author)

  14. Polarization analysis for the 2D position-sensitive detector of the HADAS reflectometer in Jülich

    Science.gov (United States)

    Rücker, U.; Bergs, W.; Alefeld, B.; Kentzinger, E.; Brückel, Th.

    2001-03-01

    A neutron reflectometer with polarization analysis is being built on the basis of the HADAS spectrometer in the neutron guide hall at the research reactor FRJ-2 (DIDO) in Jülich. The new instrument is optimized for reflectivity and diffuse scattering measurements under grazing incidence on layered magnetic structures with thicknesses in the nm range. In order to measure diffuse scattering with polarization analysis, the 2D position-sensitive detector has been equipped with a polarization analyser that consists of a stack of supermirrors parallel to the scattering plane. First tests have revealed that the resolution of the instrument is not reduced by the polarization analyser. A flipping ratio of 20 has been achieved already during the first experiment.

  15. Study of performance of small gamma camera consisting of crystal pixel array and position sensitive photomultiplier tube

    Institute of Scientific and Technical Information of China (English)

    ZHU Jie; LIU Shi-Tao; LEI Xiao-Wen; YAN Tian-Xin; XU Zi-Zong; WANG Zhao-Min

    2005-01-01

    The performance of gamma camera with NaI(T1) array coupled with position sensitive photomultiplier tube (PSPMT) R2486 has been studied. The pixel size of NaI(T1) crystal is 2mm×2mm and the overall dimension of the array is 48.2mm×48.2mm×5mm. There are 484 pixels in a 22×22 matrix. Because each pixel can produce a much focused light spot and restrict the spread of photons, position resolution of the gamma camera is mainly determined by pixel size. It is shown that crystal array pixel can reduce shrinkage effect and improve intrinsic position resolution greatly via restricting the spread of photons. Experimental results demonstrate that its position resolution and linearity are much improved comparing with the gamma camera using planar crystals coupled with PSPMT.

  16. Naponski izlazni signali poziciono-osetljivog optičkog prijemnika / The voltage output signals of the optical position-sensitive receiver

    Directory of Open Access Journals (Sweden)

    Željko Vukobrat

    2006-01-01

    Full Text Available Teorijski model za određivanje naponskih izlaznih signala poziciono-osetljivog prijemnika razvijen je i eksperimentalno verifikovan. Upotrebljen je kvadrantni detektor za konvertovanje svetlosne energije u električnu energiju. Kvadrantni detektor ima četiri nezavisne i identične fotodiode na osetljivoj površini. Korektno fokusiran simetrični laserski ili optički snop formiraće kružni spot na aktivnoj površini detektora nakon prolaska kroz sočivo. Foto-diode su spojene preko otpornika sa izvorom za napajanje. Fotoelektrična struja generisana u fotodiodi uzrokuje pad napona na odgovarajućem otporniku i, na taj način, obezbeđuje izlazni signal. Signal detektovan pomoću svake fotodiode kvadrantnog detektora proporcionalan je površini svetlosnog špota koji je pao nafotodiodu. Izvedeni teorijski model omogućava brzu i korektnu analizu eksperimentalnih rezultata, stoje u osnovi provere zadovoljenja tehničkih zahteva postavljenih u pretprojektnoj fazi dizajniranja poziciono-osetljivog optičkog prijemnika određene namene. Eksperimentalni rezultati se potpuno slažu sa teorijom. / A theoretical model for determining the voltage output signals of the position-sensitive receiver is developed and verified experimentally. A quadrant detector is used for converting light energy into electrical energy. The quadrant detector has four independent and equal photodiodes on the sensing surface. A correctly focused symmetrical laser or optical beam will form a circular spot on the detector's active surface after passing through the lens. The photodiodes are connected to a voltage source via resistors. A photoelectric current generated in the photodiode causes a voltage drop across the associated resistor and thus provides an output signal. The signal detected by each photodiode of the quadrant detector is proportional to the area of the light spot image on the photodiode. The derived theoretical model enables a quick and correct analysis of

  17. Investigation on gamma-ray position sensitivity at 662 keV in a spectroscopic 3” x 3” LaBr{sub 3}:Ce scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Giaz, A., E-mail: agnese.giaz@mi.infn.it [INFN Milano, Via Celoria 16, 20133 Milano (Italy); Camera, F.; Birocchi, F. [INFN Milano, Via Celoria 16, 20133 Milano (Italy); Università degli Studi di Milano, Physics Dept., Via Celoria 16, 20133 Milano (Italy); Blasi, N.; Boiano, C.; Brambilla, S.; Coelli, S. [INFN Milano, Via Celoria 16, 20133 Milano (Italy); Fiorini, C. [INFN Milano, Via Celoria 16, 20133 Milano (Italy); Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Via Golgi 40, 20133, Milano (Italy); Marone, A. [Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Via Golgi 40, 20133, Milano (Italy); Million, B. [INFN Milano, Via Celoria 16, 20133 Milano (Italy); Riboldi, S. [INFN Milano, Via Celoria 16, 20133 Milano (Italy); Università degli Studi di Milano, Physics Dept., Via Celoria 16, 20133 Milano (Italy); Wieland, O. [INFN Milano, Via Celoria 16, 20133 Milano (Italy)

    2015-02-01

    The position sensitivity of a thick, cylindrical and continuous 3” x 3” (7.62 cm x 7.62 cm) LaBr{sub 3}:Ce crystal was studied using a 1 mm collimated beam of 662 keV gamma rays from a 400 MBq intense {sup 137}Cs source and a spectroscopic photomultiplier (PMT) (HAMAMATSU R6233-100SEL). The PMT entrance window was covered by black absorber except for a small window 1 cm x 1 cm wide. A complete scan of the detector over a 0.5 cm step grid was performed for three positions of the 1 cm x 1 cm window. For each configuration the energy spectrum was measured and the peak centroid, the FWHM, the area and peak asymmetry of the 662 keV gamma transition were analyzed. The data show that, even in a 3” thick LaBr{sub 3}:Ce crystal with diffusive surfaces the position of the full energy peak centroid depends on the source position. We verified that, on average, the position of the full energy peak centroids measured in the three 1 cm x 1 cm window configurations is sufficient for the correct identification of the collimated gamma source position.

  18. Ionizing radiations

    International Nuclear Information System (INIS)

    The purpose of this article is to simplify some of the relevant points of legislation, biological effects and protection for the benefit of the occupational health nurse not familiar with the nuclear industries. The subject is dealt with under the following headings; Understanding atoms. What is meant by ionizing radiation. Types of ionizing radiation. Effects of radiation: long and short term somatic effects, genetic effects. Control of radiation: occupational exposure, women of reproductive age, medical aspects, principles of control. The occupational health nurse's role. Emergency arrangements: national arrangements for incidents involving radiation, action to be taken by the nurse. Decontamination procedures: external and internal contamination. (U.K.)

  19. III. Penning ionization, associative ionization and chemi-ionization processes

    International Nuclear Information System (INIS)

    Physical mechanisms of three important ionization processes in a cold plasma and the methods of their experimental study are discussed. An apparatus for the investigation of the Penning ionization using ionization processes of long lived metastable rare gas atoms is described. Methods of determining interaction energies and ionization rates from the measured energy spectra of the originating electrons are described and illustrated by several examples. Typical associative ionization processes are listed and the ionization rates are compared with those of the Penning ionization. Interactions with short-lived excited particles and the transfer of excitation without ionization are discussed. (J.U.)

  20. Measurement and analysis of neutron flux distribution of STACY heterogeneous core by position sensitive proportional counter. Contract research

    CERN Document Server

    Murazaki, M; Uno, Y

    2003-01-01

    We have measured neutron flux distribution around the core tank of STACY heterogeneous core by position sensitive proportional counter (PSPC) to develop the method to measure reactivity for subcritical systems. The neutron flux distribution data in the position accuracy of +-13 mm have been obtained in the range of uranium concentration of 50g/L to 210g/L both in critical and in subcritical state. The prompt neutron decay constant, alpha, was evaluated from the measurement data of pulsed neutron source experiments. We also calculated distribution of neutron flux and sup 3 He reaction rates at the location of PSPC by using continuous energy Monte Carlo code MCNP. The measurement data was compared with the calculation results. As results of comparison, calculated values agreed generally with measurement data of PSPC with Cd cover in the region above half of solution height, but the difference between calculated value and measurement data was large in the region below half of solution height. On the other hand, ...

  1. Development and use of various position sensitive proportional counters for the X-ray structure analysis of biological objects

    International Nuclear Information System (INIS)

    The quantum yield of position sensitive detectors for X-rays was increased by over 50% by increasing the pressure of the counter gas. The anode impulse was thereby slowed down and the cathode impulse was made smaller in that the 'noise' of the electronics determined local resolution. With high pressure and relatively thick anodes an alternate form of the gas amplification is stable. This 'self-quenching streamer mode' (SQS-mode) distinguishes itself by large and regular anode impulses and makes the operation of the detectors with good spatial resolution possible. It is also well suited in other aspects for spatial resolving detectors. Detectors were also developed for use in single crystal diffractometry and small angle scattering. The technical part of the construction of a diffractometer with a spatial resolving detector is settled, as is well known. After completion of the crystalographic part test measurements can supposedly begin in the fall of this year. A measurement station for small angle scattering was constructed. The data is stored directly in the computer, measurement and evaluation occur in suited programs. Statistical and time-resolved measurements of small angle scattering of muscle fibers were conducted. Examples are discussed in this work. (orig.)

  2. Measurement and analysis of neutron flux distribution of STACY heterogeneous core by position sensitive proportional counter. Contract research

    Energy Technology Data Exchange (ETDEWEB)

    Murazaki, Minoru; Uno, Yuichi; Miyoshi, Yoshinori [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    We have measured neutron flux distribution around the core tank of STACY heterogeneous core by position sensitive proportional counter (PSPC) to develop the method to measure reactivity for subcritical systems. The neutron flux distribution data in the position accuracy of {+-}13 mm have been obtained in the range of uranium concentration of 50g/L to 210g/L both in critical and in subcritical state. The prompt neutron decay constant, {alpha}, was evaluated from the measurement data of pulsed neutron source experiments. We also calculated distribution of neutron flux and {sup 3}He reaction rates at the location of PSPC by using continuous energy Monte Carlo code MCNP. The measurement data was compared with the calculation results. As results of comparison, calculated values agreed generally with measurement data of PSPC with Cd cover in the region above half of solution height, but the difference between calculated value and measurement data was large in the region below half of solution height. On the other hand, calculated value agreed well with measurement data of PSPC without Cd cover. (author)

  3. A data acquisition system for two-dimensional position sensitive micropattern gas detectors with delay-line readout

    Energy Technology Data Exchange (ETDEWEB)

    Hanu, A.R., E-mail: hanua@mcmaster.ca [Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada L8S 4K1 (Canada); NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Prestwich, W.V.; Byun, S.H. [Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada L8S 4K1 (Canada)

    2015-04-21

    We present a data acquisition (DAQ) system for two-dimensional position sensitive micropattern gas detectors using the delay-line method for readout. The DAQ system consists of a field programmable gate array (FPGA) as the main data processor and our time-to-digital (TDC) mezzanine card for making time measurements. We developed the TDC mezzanine card around the Acam TDC-GPX ASIC and it features four independent stop channels referenced to a common start, a typical timing resolution of ~81 ps, and a 17-bit measurement range, and is compliant with the VITA 57.1 standard. For our DAQ system, we have chosen the Xilinx SP601 development kit which features a single Spartan 6 FPGA, 128 MB of DDR2 memory, and a serial USB interface for communication. Output images consist of 1024×1024 square pixels, where each pixel has a 32-bit depth and corresponds to a time difference of 162 ps relative to its neighbours. When configured for a 250 ns acquisition window, the DAQ can resolve periodic event rates up to 1.8×10{sup 6} Hz without any loses and will report a maximum event rate of 6.11×10{sup 5} Hz for events whose arrival times follow Poisson statistics. The integral and differential non-linearities have also been measured and are better than 0.1% and 1.5%, respectively. Unlike commercial units, our DAQ system implements the delay-line image reconstruction algorithm entirely in hardware and is particularly attractive for its modularity, low cost, ease of integration, excellent linearity, and high throughput rate.

  4. A high count rate one-dimensional position sensitive detector and a data acquisition system for time resolved X-ray scattering studies

    International Nuclear Information System (INIS)

    A curved multiwire proportional drift chamber has been built as a general purpose instrument for X-ray scattering and X-ray diffraction experiments with synchrotron radiation. This parallaxe-free one-dimensional linear position sensitive detector has a parallel readout with a double hit logic. The data acquisition system, installed as a part of the D11 camera at LURE-DCI, is designed to perform time slicing and cyclic experiments; it has been used with either the fast multiwire chamber or a standard position sensitive detector with delay line readout

  5. Ionization detection system for aerosols

    Science.gov (United States)

    Jacobs, Martin E.

    1977-01-01

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system utilizes a measuring ionization chamber which is modified to minimize false alarms and reductions in sensitivity resulting from changes in ambient temperature. In the preferred form of the modification, an annular radiation shield is mounted about the usual radiation source provided to effect ionization in the measuring chamber. The shield is supported by a bimetallic strip which flexes in response to changes in ambient temperature, moving the shield relative to the source so as to vary the radiative area of the source in a manner offsetting temperature-induced variations in the sensitivity of the chamber.

  6. Ionization by nuclear transitions

    International Nuclear Information System (INIS)

    A phenomenological description of ionization events is given that applies to both shaking transitions of the composite nucleus-atom system and the process in which the charged particles emitted in a nuclear decay transfer energy by a relatively slow ''direct collision'' final state interaction with atomic electrons. Specific areas covered include shakeoff in internal conversion, shakeoff in electron capture, shakeoff in beta decay, and inner electron ejection in alpha decay. (5 figs., 1 table)

  7. Effect of refraction index and thickness of the light guide in the position-sensitive gamma-ray detector using compact PS-PMTs

    CERN Document Server

    Inoue, K; Nagashima, Y; Hyodo, T; Nagai, Y; Muramatsu, S; Nagai, S

    2000-01-01

    We constructed a position-sensitive gamma-ray detector consisting of an array of BGO scintillators, a light guide and compact PS-PMTs. The effects of refractive index and thickness of the light guide of a glass plate on the detector performance were investigated. A light guide with higher refractive index and smaller thickness is found better for a good spatial resolution.

  8. 不同发射区周长面积比双极晶体管的电离辐照效应%Ionizing Irradiation Effects for Emitter Perimeter Area Ratios of the Bipolar Transistor

    Institute of Scientific and Technical Information of China (English)

    吕曼; 张小玲; 张彦秀; 谢雪松; 孙江超; 王鹏鹏; 吕长志

    2013-01-01

    The ionizing irradiation of total dose experiments was carried out on npn and pnp two types of bipolar transistors, which have the same fabrication process, but different ratio of perimeter and area in emitter region. Various damage mechanisms of ionizing radiation of total dose and annealing effects of the bipolar transistors were researched, and the key factors of ionizing irradiation of total dose in bipolar transistors were analyzed. Experimental results show that the bipolar transistors with larger ratio of perimeter and area in emitter region are more sensitive to ionizing irradiation than the smaller ones in the same condition. Positive oxide charge is the key factor of the radiation damage for npn, while the interface trap of the charge density is for lateral pnp, A measure of improving the ionizing irradiation hardness of bipolar transistors was proposed. An experimental basis for the anti-ionizing radiation effects of bipolar transistors is provided, as well as the linear integrated circuits which containing bipolar transistors.%对制作工艺相同但发射区周长面积比不同的npn和pnp两种类型双极晶体管进行了辐照实验,研究了双极晶体管的电离总剂量辐射损伤机理和退火效应,分析了影响双极晶体管电离总剂量辐射特性的关键因素.实验结果表明,在相同累积电离辐射总剂量条件下,发射区周长面积比大的双极晶体管辐照敏感性更强,对于npn双极晶体管其电离总剂量辐照损伤的关键因素是辐照感生的氧化层正电荷,而影响横向pnp的关键因素为辐照感生的界面陷阱电荷的密度.提出了一种提高双极晶体管抗电离总剂量辐射性能的措施,为探索双极晶体管以及含有双极晶体管的电子线路的抗电离总剂量辐射加固技术提供了理论和实验依据.

  9. Femtosecond Laser Ionization of Organic Amines with Very Low Ionization Potential.

    Science.gov (United States)

    Yatsuhashi, Tomoyuki; Obayashi, Takashi; Tanaka, Michinori; Murakami, Masanao; Nakashima, Nobuaki

    2006-03-01

    The interaction between high intensity femtosecond laser and molecules is one of the most attractive areas in laser chemistry and ionization is the most fundamental subject. Theoretical consideration successfully reproduced the ionization behavior of rare gases. However, the understanding of ionization mechanisms of large molecules is difficult more than those of rare gases due to their complexity. Generally speaking, molecules are harder to ionize than rare gases even if they have the same ionization potential. The suppressed ionization phenomena are one of the important features of molecular ionization. Hankin et al. examined 23 organic molecules with ionization potentials between 8.25 and 11.52 eV. We have examined ionization and/ or fragmentation of many organic molecules, including aromatic compounds, halogenated compounds, methane derivatives etc. at various wavelengths below 10^16 Wcm-2. In order to investigate the nature of molecular ionization, it is interesting to examine a variety of molecule in a wide range of ionization potential. In this study, we examined several organic amines because we can explore the uninvestigated ionization potential range down to 5.95 eV. In addition to the significant suppression of the ionization rates, stepwise ionization behavior, which was not observed in rare gases, was observed.

  10. Ionization gage

    International Nuclear Information System (INIS)

    An ionization manometer is proposed which contains a transducer consisting of an anode, a directly heated cathode and a collector, a power source, a cathode emission current stabilizer, an ionic current amplifier connected to a recorder, and a cathode emission current modulator. To increase the accuracy of measurements under conditions of vacuum evaporation of materials, the modulator has been designed to comprise a source of controlling electric unipolar pulses of a specified duration and frequency and a blocking device connected to the collector. The output of the source of controlling electric unipolar pulses is connected to the emission current stabilizer and to the second input of the blocking device whose output is connected to the ionic current amplifier. The amount of pressure exerted in the vacuum chamber is estimated from the magnitude of the variable constituent of the collector signal

  11. Assessment of capabilities and research needs in the area of health effects of low-level ionizing radiation. A joint report to the Congress

    International Nuclear Information System (INIS)

    The report summarizes the capabilities, research needs and on-going projects of the Environmental Protection Agency and the Nuclear Regulatory Commission related to the health effects of low-level ionizing radiation. The statutory authorities of both EPA and NRC related to radiation protection and radiation research are also briefly described. An introductory general section describes current efforts to improve Federal radiation research and general methods used by both agencies for radiation dose assessment and the estimation of the potential health effects of low-level ionizing radiation. Separate sections describe the respective authorities, needs, capabilities, and current research programs of the two agencies. The report was prepared to fulfill a requirement by the US Congress which is contained in Section 5(c) of Public Law 95-601

  12. Construction and performance of one- and two-dimensional large position-sensitive liquid and plastic scintillation detectors - an application to a neutron polarimeter

    International Nuclear Information System (INIS)

    Large one- and two-dimensional position-sensitive neutron detectors have been developed. Their shapes are a long block and a square and their sizes are 100 x 10 x 7.5 cm3 and 100 x 100 x 10 cm3 for one- and two-dimensional detectors, respectively. Both liquid and plastic scintillators are employed as detector materials. Position resolutions are examined by using monoenergetic neutron beams with energies of 61.6 MeV. The obtained position resolutions in FWHM are 3-5 cm and 4-14 cm for one- and two-dimensional detectors, respectively. Position resolutions are poor near the corner of the two-dimensional detector irrespective of scintillator materials. Scintillation light responses have been compared with predictions of Monte Carlo calculations. Neutron polarimeters at an intermediate energy have been developed by utilizing the position sensitivity of these detectors. (orig.)

  13. The noise analysis and optimum filtering techniques for a two-dimensional position sensitive orthogonal strip gamma ray detector employing resistive charge division

    International Nuclear Information System (INIS)

    The analysis of an orthogonal strip, two-dimensional position sensitive high purity germanium gamma ray detector is discussed. Position sensitivity is obtained by connecting each electrode strip on the detector to a resistor network. Charge, entering the network, divides in relation to the resistance between its entry point and the virtual earth points of the charge sensitive preamplifiers located at the end of each resistor network. The difference of the voltage pulses at the output of each preamplifier is proportional to the position at which the charge entered the resistor network and the sum of the pulse is proportional to the energy of the detected gamma ray. The analysis and spatial noise resolution is presented for this type of position sensitive detector. The results of the analysis show that the position resolution is proportional to the square root of the filter amplifier's output pulse time constant and that for energy measurement the resolution is maximized at the filter amplifier's noise corner time constant. The design of the electronic noise filtering system for the prototype gamma ray camera was based on the mathematical energy and spatial resolution equations. For the spatial channel a Gaussian trapezoidal filtering system was developed. Gaussian filtering was used for the energy channel. The detector noise model was verified by taking rms noise measurements of the filtered energy and spatial pulses from resistive readout charge dividing detectors. These measurements were within 10% of theory. (Auth.)

  14. Molecular dynamics of dissociative ionization in OCS probed by soft X-ray synchrotron radiation

    CERN Document Server

    Ramadhan, Ali; Gauthier, Isabelle; Karimi, Reza; MacDonald, Michael; Zuin, Lucia; Sanderson, Joe

    2016-01-01

    Soft X-rays (90-173 eV) from the 3rd generation Canadian Light Source have been used in conjunction with a multi coincidence time and position sensitive detection apparatus to observe the dissociative ionization of OCS. By varying the X-ray energy we can compare dynamics from direct and Auger ionization processes, and access ionization channels which result in two or three body breakup, from 2+ to 4+ ionization states. We make several new observations for the 3+ state such as kinetic energy release limited by photon energy, and using Dalitz plots we can see evidence of timescale effects between the direct and Auger ionization process for the first time. Finally, using Dalitz plots for OCS$^{4+}$ we observe for the first time that breakup involving an O$^{2+}$ ion can only proceed from out of equilibrium nuclear arrangement for S(2p) Auger ionization.

  15. Computed tomography with thermal neutrons and gaseous position sensitive detector; Tomografia computadorizada com neutrons termicos e detetor a gas sensivel a posicao

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Maria Ines Silvani

    2001-12-01

    A third generation tomographic system using a parallel thermal neutron beam and gaseous position sensitive detector has been developed along three discrete phases. At the first one, X-ray tomographic images of several objects, using a position sensitive detector designed and constructed for this purpose have been obtained. The second phase involved the conversion of that detector for thermal neutron detection, by using materials capable to convert neutrons into detectable charged particles, testing afterwards its performance in a tomographic system by evaluation the quality of the image arising from several test-objects containing materials applicable in the engineering field. High enriched {sup 3} He, replacing the argon-methane otherwise used as filling gas for the X-ray detection, as well as, a gadolinium foil, have been utilized as converters. Besides the pure enriched {sup 3} He, its mixture with argon-methane and later on with propane, have been also tested, in order to evaluate the detector efficiency and resolution. After each gas change, the overall performance of the tomographic system using the modified detector, has been analyzed through measurements of the related parameters. This was done by analyzing the images produced by test-objects containing several materials having well known attenuation coefficients for both thermal neutrons and X-rays. In order to compare the performance of the position sensitive detector as modified to detect thermal neutrons, with that of a conventional BF{sub 3} detector, additional tomographs have been conducted using the last one. The results have been compared in terms of advantages, handicaps and complementary aspects for different kinds of radiation and materials. (author)

  16. Performance of a compact position-sensitive photon counting detector with image charge coupling to an air-side anode

    Science.gov (United States)

    Jagutzki, O.; Czasch, A.; Schössler, S.

    2013-05-01

    We discuss a novel micro-channel plate (MCP) photomultiplier with resistive screen (RS-PMT) as a detection device for space- and time-correlated single photon counting, illustrated by several applications. The photomultiplier tube resembles a standard image intensifier device. However, the rear phosphor screen is replaced by a ceramic "window" with resistive coating. The MCP output is transferred through the ceramic plate to the read-out electrode (on the air side) via capacity-coupling of the image charge. This design allows for an easy reconfiguration of the read-out electrode (e.g. pixel, charge-sharing, cross-strip, delay-line) without breaking the vacuum for optimizing the detector performance towards a certain task. It also eases the design and manufacturing process of such a multi-purpose photomultiplier tube. Temporal and spatial resolutions well below 100 ps and 100 microns, respectively, have been reported at event rates as high as 1 MHz, for up to 40 mm effective detection diameter. In this paper we will discuss several applications like wide-field fluorescence microscopy and dual γ/fast-neutron radiography for air cargo screening and conclude with an outlook on large-area detectors for thermal neutrons based on MCPs.

  17. Position sensitive gas discharge detector with filmless optical data readout for nn-bar oscillation search experiment at the INR AS USSR meson factory

    International Nuclear Information System (INIS)

    A position-sensitive gas-discharge multilayer cylindrical detector with optical data readout for neutron-antineutron oscillation search experiments at the INR AS USSR mesn factory is considered. The detector consits of 7 sections each 7 long, with the inner diameter of 2 m and the outer diameter of 3.5 m. Gas-discharge gaps are spacings between steel coaxial tubes where anode wires are tensioned. Data readout from optical fiber matrices will be carried out using teleinput system based on charge coupled matrix device with fast optical key on he base of electron-optical converter. 11 refs.; 2 figs

  18. Comparison of two position sensitive gamma-ray detectors based on continuous YAP and pixellated NaI(TI) for nuclear medical imaging applications

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Dedicated position sensitive gamma-ray detectors based on position sensitive photomultiplier tubes (PSPMTs) coupled to scintillation crystals, have been used for the construction of compact gamma-ray imaging systems, suitable for nuclear medical imaging applications such as small animal imaging and single organ imaging and scintimammography. In this work, the performance of two gamma-ray detectors: a continuous YAP scintillation crystal coupled to a Hamamastu R2486 PSPMT and a pixellated NaI(TI) scintillation array crystal coupled to the same PSPMT, is compared. The results show that the gamma-ray detector based on a pixellated NaI(TI) scintillation array crystal is a promising candidate for nuclear medical imaging applications,since their performance in terms of position linearity, spatial resolution and effective field of view (FOV) is superior than that of the gamma-ray detector based on a continuous YAP scintillation crystal. However, a better photodetector (Hamamatau H8500 Flat Panel PMT, for example) coupled to the continuous crystal is also likely a good selection for nuclear medicine imaging applications.

  19. Performance evaluation of three-dimensional position-sensitive CdTe detector blocks for an ultra-high resolution brain PET scanner

    International Nuclear Information System (INIS)

    We have developed an ultra-high resolution human brain positron emission tomography (PET) scanner with the resolution of less than 1 mm FWHM, in which cadmium telluride (CdTe) semiconductor detectors were used. As the detector of the scanner, we have developed a two-dimensional position-sensitive CdTe detector (2D-PSD) which was developed in our previous study. The 2D-PSD can detect gamma rays with a position resolution of approximately 1.2 mm. We developed a three-dimensional position-sensitive CdTe detector block (3D-PSD block) by stacking 80 2D-PSDs which were connected to subsequent circuits (amplifiers, analog to digital converters, and other data processing circuits). We constructed an ultra-high resolution semiconductor brain PET gantry placing the ten 3D-PSD blocks in decagonal arrangement. In this paper, we checked all 2D-PSDs and classified their performance. As the results, we confirmed that our 3D-PSD blocks can be used to the ultra-high resolution human brain PET. We made a circuit to reduce the dead time due to restoration from polarization phenomena in CdTe detector and we could stabilize count rates. (author)

  20. Foodstuffs preservation by ionization

    International Nuclear Information System (INIS)

    This document contains all the papers presented at the meeting on foodstuffs preservation by ionization. These papers deal especially with the food ionization process, its development and the view of the food industry on ionization. Refs and figs (F.M.)

  1. Ionization Energies of Lanthanides

    Science.gov (United States)

    Lang, Peter F.; Smith, Barry C.

    2010-01-01

    This article describes how data are used to analyze the pattern of ionization energies of the lanthanide elements. Different observed pathways of ionization between different ground states are discussed, and the effects of pairing, exchange, and orbital interactions on ionization energies of the lanthanides are evaluated. When all the above…

  2. Position sensitive solid state detectors

    Energy Technology Data Exchange (ETDEWEB)

    Schnatterly, S.E.; Husk, D.

    1986-05-15

    Solid state detectors have been used for years as high quantum efficiency detectors for visible light. In this paper the use of PDA and CCD, solid state detectors, in the X-ray region will be discussed. In particular examples of data in the soft X-ray region are presented. Finally the use of phosphor coatings to enhance the sensitivity of solid state detectors is described.

  3. De-Li-DAQ-2D - a new data acquisition system for position-sensitive neutron detectors with delay-line readout

    Science.gov (United States)

    Levchanovskiy, F. V.; Murashkevich, S. M.

    2016-09-01

    Software for a data acquisition system of modern one- and two-dimensional position-sensitive detectors with delay-line readout, which includes a software interface to a new electronic module De-Li-DAQ-2D with a USB interface, is presented. The new system after successful tests on the stand and on several spectrometers of the IBR-2 reactor has been integrated into the software complex SONIX+ [1]. The De-Li- DAQ-2D module [2] contains an 8-channel time-code converter (TDC-GPX) with a time resolution of 80 ps, field programmable gate array (FPGA), 1 Gbyte histogram memory and high-speed interface with a fiber-optic communication line. A real count rate is no less than 106 events/s. The De-Li-DAQ-2D module is implemented in the NIM standard. The De-Li-DAQ-2D module can operate in two modes: histogram mode and list mode.

  4. MRI compatibility of position-sensitive photomultiplier depth-of-interaction PET detectors modules for in-line multimodality preclinical studies

    Energy Technology Data Exchange (ETDEWEB)

    Vaquero, J.J., E-mail: juanjose.vaquero@uc3m.es [Universidad Carlos III de Madrid, Departamento de Bioingeniería e Ingeniería Aeroespacial, Avda. de la Universidad 30 Leganés, 28911 Madrid (Spain); Instituto de Investigación Sanitaria Gregorio Marañón, Madrid (Spain); Sánchez, J.J. [Instituto de Investigación Sanitaria Gregorio Marañón, Madrid (Spain); Udías, J.M.; Cal-González, J. [Grupo de Física Nuclear, Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, CEI Moncloa, Madrid (Spain); Desco, M. [Universidad Carlos III de Madrid, Departamento de Bioingeniería e Ingeniería Aeroespacial, Avda. de la Universidad 30 Leganés, 28911 Madrid (Spain); Instituto de Investigación Sanitaria Gregorio Marañón, Madrid (Spain)

    2013-02-21

    This work addresses the feasibility of a small-animal, in-line PET/MR system based on Position-Sensitive Photo Multiplier Tubes (PS-PMTs). To this end, we measured the effects of static magnetic fields on the PS-PMTs performance in order to explore the minimal tandem separation between the PET and MR subsystems to preserve their respective performances. We concluded that it is possible to achieve minimal degradation of the PET scanner performance (after a system recalibration) if the magnetic field strength influencing the PET detectors is less than 1 mT and if it is oriented perpendicularly to the longitudinal axis of the tube. Therefore, we predict that it will be possible to maintain the PET image quality if it is placed outside the 1 mT line.

  5. MRI compatibility of position-sensitive photomultiplier depth-of-interaction PET detectors modules for in-line multimodality preclinical studies

    International Nuclear Information System (INIS)

    This work addresses the feasibility of a small-animal, in-line PET/MR system based on Position-Sensitive Photo Multiplier Tubes (PS-PMTs). To this end, we measured the effects of static magnetic fields on the PS-PMTs performance in order to explore the minimal tandem separation between the PET and MR subsystems to preserve their respective performances. We concluded that it is possible to achieve minimal degradation of the PET scanner performance (after a system recalibration) if the magnetic field strength influencing the PET detectors is less than 1 mT and if it is oriented perpendicularly to the longitudinal axis of the tube. Therefore, we predict that it will be possible to maintain the PET image quality if it is placed outside the 1 mT line

  6. Count rate studies of a box-shaped PET breast imaging system comprised of position sensitive avalanche photodiodes utilizing monte carlo simulation.

    Science.gov (United States)

    Foudray, Angela M K; Habte, Frezghi; Chinn, Garry; Zhang, Jin; Levin, Craig S

    2006-01-01

    We are investigating a high-sensitivity, high-resolution positron emission tomography (PET) system for clinical use in the detection, diagnosis and staging of breast cancer. Using conventional figures of merit, design parameters were evaluated for count rate performance, module dead time, and construction complexity. The detector system modeled comprises extremely thin position-sensitive avalanche photodiodes coupled to lutetium oxy-orthosilicate scintillation crystals. Previous investigations of detector geometries with Monte Carlo indicated that one of the largest impacts on sensitivity is local scintillation crystal density when considering systems having the same average scintillation crystal densities (same crystal packing fraction and system solid-angle coverage). Our results show the system has very good scatter and randoms rejection at clinical activity ranges ( approximately 200 muCi). PMID:17645997

  7. Investigation of transfer ionization processes in the collision of partially stripped carbon ions on Argon

    Institute of Scientific and Technical Information of China (English)

    WANG Jun; Du Juan; SUN GuangZhi; CHEN Lin; CHEN XiMeng; DING BaoWei; FU HongBin; CUI Ying; SHAO JianXiong; LU YanXia; GAO ZhiMin; LIU YuWen

    2008-01-01

    The ratios of the cross section of the transfer-ionization to the single-electroncapture of Argon induced by Cq+ (q=1,2,3) ions are measured by means of position sensitive and time-of-flight techniques. Our experimental results are compared with the data of Heq+ (q=1,2)-Ar of DuBois. A qualitative interpretation is presented based on the Classical-Over-Barrier Model of Bohr,

  8. Investigation of transfer ionization processes in the collision of partially stripped carbon ions on Argon

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The ratios of the cross section of the transfer-ionization to the single-electron-capture of Argon induced by Cq+ (q=1,2,3) ions are measured by means of position sensitive and time-of-flight techniques. Our experimental results are compared with the data of Heq+ (q=1,2)-Ar of DuBois. A qualitative interpretation is presented based on the Classical-Over-Barrier Model of Bohr.

  9. Estimation of ionizing radiation impact on natural Vicia cracca populations inhabiting areas contaminated with uranium mill tailings and radium production wastes

    Energy Technology Data Exchange (ETDEWEB)

    Evseeva, T.; Majstrenko, T. [Institute of Biology, Komi Scientific Center, Ural Division RAS, Kommunisticheskaya 28, 167982 Syktyvkar (Russian Federation); Geras' kin, S. [Russian Institute of Agricultural Radiology and Agroecology RAAS, 249020 Obninsk, Kaluga region (Russian Federation); Brown, J.E., E-mail: Justin.brown@nrpa.no [Norwegian Radiation Protection Authority, Grini naeringspark 13, 1332 Osteras (Norway); Belykh, E. [Institute of Biology, Komi Scientific Center, Ural Division RAS, Kommunisticheskaya 28, 167982 Syktyvkar (Russian Federation)

    2009-10-01

    Industrial areas in proximity to the Vodny settlement in the Komi Republic, Russia, have been contaminated by uranium mill tailings and radium production wastes. These areas, exhibiting high activity concentrations of naturally occurring radionuclides in soils, constitute a field laboratory where the effects of combined chronic exposures to {alpha}-, {beta}- and {gamma}-emitting radionuclides on natural plant populations can be studied. The aim of the present work was to determine dose-effect relationships and the range of doses that cause biological effects in natural Vicia cracca L. populations inhabiting the study area. The studied plant species is native to the area and is found ubiquitously. Soil and vegetation samples were taken at a reference location and six contaminated sites characterized by distinct floodplain depositional units with different enhanced levels of naturally occurring radionuclides. A large fraction of the dose at the study sites (including the reference location) was attributable to internal irradiation and {sup 226}Ra was found to be an important contributor to this component of dose. The relationship between the frequency of chromosome aberrations in seedlings' root tip cells and the absorbed dose was found to be quadratic. An exponential model provided the best result in describing the empirical dependence between the absorbed dose and both the germination capacity of seeds and the survival rate of sprouts of V. cracca. For V. cracca plants inhabiting areas contaminated with uranium mill tailings and radium production wastes, a weighted absorbed dose of 0.2 Gy (weighting factor for alpha particles = 5) during the vegetation period could be considered to be a level below which no increase in genetic variability and decrease in reproductive capacity might be observed above background.

  10. Physics of Partially Ionized Plasmas

    Science.gov (United States)

    Krishan, Vinod

    2016-05-01

    Figures; Preface; 1. Partially ionized plasmas here and everywhere; 2. Multifluid description of partially ionized plasmas; 3. Equilibrium of partially ionized plasmas; 4. Waves in partially ionized plasmas; 5. Advanced topics in partially ionized plasmas; 6. Research problems in partially ionized plasmas; Supplementary matter; Index.

  11. Resonance ionization spectroscopy 1986

    International Nuclear Information System (INIS)

    The paper presents the proceedings of the Third International Symposium on Resonance Ionization Spectroscopy and its Applications, held at the University College of Swansea, Wales, 1986. The Symposium is divided into eight main sections entitled: photophysics and spectroscopy, noble gas atom counting, resonance ionization mass spectrometry, materials and surface analysis, small molecules, medical and environmental applications, resonance ionization and materials separation, and elementary particles and nuclear physics. Thirty papers were chosen for INIS and indexed separately. (U.K.)

  12. Ionizing Radiation and Life

    OpenAIRE

    Dartnell, L. R.

    2011-01-01

    Ionizing radiation is a ubiquitous feature of the Cosmos, from exogenous cosmic rays (CR) to the intrinsic mineral radioactivity of a habitable world, and its influences on the emergence and persistence of life are wide-ranging and profound. Much attention has already been focused on the deleterious effects of ionizing radiation on organisms and the complex molecules of life, but ionizing radiation also performs many crucial functions in the generation of habitable planetary environments and ...

  13. Abnormal ionization in sonoluminescence

    Institute of Scientific and Technical Information of China (English)

    张文娟; 安宇

    2015-01-01

    Sonoluminescence is a complex phenomenon, the mechanism of which remains unclear. The present study reveals that an abnormal ionization process is likely to be present in the sonoluminescing bubble. To fit the experimental data of previous studies, we assume that the ionization energies of the molecules and atoms in the bubble decrease as the gas density increases and that the decrease of the ionization energy reaches about 60%–70%as the bubble flashes, which is difficult to explain by using previous models.

  14. Characterization of a sub-assembly of 3D position sensitive cadmium zinc telluride detectors and electronics from a sub-millimeter resolution PET system

    Science.gov (United States)

    Abbaszadeh, Shiva; Gu, Yi; Reynolds, Paul D.; Levin, Craig S.

    2016-09-01

    Cadmium zinc telluride (CZT) offers key advantages for small animal positron emission tomography (PET), including high spatial and energy resolution and simple metal deposition for fabrication of very small pixel arrays. Previous studies have investigated the intrinsic spatial, energy, and timing resolution of an individual sub-millimeter resolution CZT detector. In this work we present the first characterization results of a system of these detectors. The 3D position sensitive dual-CZT detector module and readout electronics developed in our lab was scaled up to complete a significant portion of the final PET system. This sub-system was configured as two opposing detection panels containing a total of twelve 40~\\text{mm}× 40~\\text{mm}× 5 mm monolithic CZT crystals for proof of concept. System-level characterization studies, including optimizing the trigger threshold of each channel’s comparators, were performed. 68Ge and 137Cs radioactive isotopes were used to characterize the energy resolution of all 468 anode channels in the sub-system. The mean measured global 511 keV photopeak energy resolution over all anodes was found to be 7.35+/- 1.75 % FWHM after correction for photon interaction depth-dependent signal variation. The measured global time resolution was 37 ns FWHM, a parameter to be further optimized, and the intrinsic spatial resolution was 0.76 mm FWHM.

  15. Multiphoton ionization of atoms

    International Nuclear Information System (INIS)

    The paper is devoted to the analysis of high intensity effects which result from multiphoton ionization of atoms in a high laser intensity, ranging from 1010 to 1015 W cm-2. Resonant multiphoton ionization of atoms, the production of multiply charged ions, and electron energy spectra, are all discussed. (U.K.)

  16. Application of ionizing radiation

    International Nuclear Information System (INIS)

    Fundamental studies by the Nuclear Research Institute concerning the use of ionizing radiations are reported. The ROZA irradiation plant is used for sterilization in medicine and for historic objects preservation. Ionizing radiation is used in the radiation treatment of cables and drinking water. Radiopharmaceuticals are developed. The Institute is an all-state centre for research and development of semiconductor detectors. (M.S.)

  17. Multiphoton ionization of atoms

    International Nuclear Information System (INIS)

    This article provides an overview of the current understanding of multiphoton ionization of atoms. It begins with an introductory section to explain the background of the subject. Then the article develops the three topics which have been central themes of discussion in multiphoton ionization of atoms these past few years: multiply charged ion production, very high order harmonic generation, and above-threshold ionization, a name given to the absorption of a very large number of photons by an already ionized electron. A large part of the review is devoted to some theoretical aspects of multiphoton ionization of atoms and especially non-perturbative theories. Finally the article considers the very near future prospects of laser-electron interactions and more generally laser-matter interactions at 1018 -1019 W cm-2, an intensity range now within reach due to new short pulse laser technology. (author)

  18. Biological Effects of Ionizing Radiation

    Science.gov (United States)

    Ingram, M.; Mason, W. B.; Whipple, G. H.; Howland, J. W.

    1952-04-07

    This report presents a review of present knowledge and concepts of the biological effects of ionizing radiations. Among the topics discussed are the physical and chemical effects of ionizing radiation on biological systems, morphological and physiological changes observed in biological systems subjected to ionizing radiations, physiological changes in the intact animal, latent changes following exposure of biological systems to ionizing radiations, factors influencing the biological response to ionizing radiation, relative effects of various ionizing radiations, and biological dosimetry.

  19. Abnormal ionization in sonoluminescence

    Science.gov (United States)

    Zhang, Wen-Juan; An, Yu

    2015-04-01

    Sonoluminescence is a complex phenomenon, the mechanism of which remains unclear. The present study reveals that an abnormal ionization process is likely to be present in the sonoluminescing bubble. To fit the experimental data of previous studies, we assume that the ionization energies of the molecules and atoms in the bubble decrease as the gas density increases and that the decrease of the ionization energy reaches about 60%-70% as the bubble flashes, which is difficult to explain by using previous models. Project supported by the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120002110031) and the National Natural Science Foundation of China (Grant No. 11334005).

  20. MULTIPHOTON IONIZATION OF ATOMS

    OpenAIRE

    Mainfray, G.

    1985-01-01

    Multiphoton ionization of one-electron atoms, such as atomic hydrogen and alkaline atoms, is well understood and correctly described by rigorous theoretical models. The present paper will be devoted to collisionless multiphoton ionization of many-electron atoms as rare gases. It induces removal of several electrons and the production of multiply charged ions. Up to Xe5+ ions are produced in Xe atoms. Doubly charged ions can be produced, either by simultaneous excitation of two electrons, or b...

  1. Influence of temperature and bias voltage on the performance of a high resolution PET detector built with position sensitive avalanche photodiodes

    Science.gov (United States)

    Vandenbroucke, A.; McLaughlin, T. J.; Levin, C. S.

    2012-08-01

    We evaluate the performance of an 8 × 8 array of 0.9 × 0.9 × 1 mm3 cerium doped lutetium oxyothosilicate (LSO) crystals coupled to a position sensitive avalanche photodiode (PSAPD) as a function of bias voltage and temperature. We use this detector to develop a general methodology to optimize bias voltage, temperature, and gain for PET detectors using semiconductor photodetectors. This detector module will be used in a novel high resolution positron emission tomography (PET) camera dedicated to breast imaging under construction in our lab. Due to the tight packing of many PSAPDs in the system a thermal gradient is expected across the imaging heads. Data were collected for 11 PSAPD temperatures between 5°C and 40°C using a thermo-electric (Peltier) device. At each temperature the bias voltage was varied in steps of 5 V over a 50 V range. We present three methods to predict the optimal bias voltage at every temperature: one based on optimizing the coincidence time resolution, the others based on the relative change in PSAPD gain and leakage current due to the onset of hole multiplication. Optimal gain could also be predicted based on the quality of the flood histogram. At optimal bias voltage, the energy resolution degrades as (10.5±0.1)+((0.038±0.006)/ °C·T)%. Time resolution stays constant at 2.37±0.02 ns below 15°C. Above this temperature, time resolution deteriorates as (1.67±0.06)+((0.042±0.002)/°C·T)ns. Even at high temperatures, all 64 crystal position peaks in the flood histogram are still clearly visible. The width of the peaks in the flood histogram show a quadratic degradation with temperature: (2.6±0.1)·10-2+(1.6±0.2)·10-5/(°C)2·T2. We conclude that both the quality of the flood histogram as well as the coincidence time resolution are better parameters to estimate the optimal bias voltage, than energy resolution. Optimal bias voltage is found to be dependent on the value of k, the ratio between hole and electron multiplication. We

  2. "Magic" Ionization Mass Spectrometry.

    Science.gov (United States)

    Trimpin, Sarah

    2016-01-01

    The systematic study of the temperature and pressure dependence of matrix-assisted ionization (MAI) led us to the discovery of the seemingly impossible, initially explained by some reviewers as either sleight of hand or the misinterpretation by an overzealous young scientist of results reported many years before and having little utility. The “magic” that we were attempting to report was that with matrix assistance, molecules, at least as large as bovine serum albumin (66 kDa), are lifted into the gas phase as multiply charged ions simply by exposure of the matrix:analyte sample to the vacuum of a mass spectrometer. Applied heat, a laser, or voltages are not necessary to achieve charge states and ion abundances only previously observed with electrospray ionization (ESI). The fundamentals of how solid phase volatile or nonvolatile compounds are converted to gas-phase ions without added energy currently involves speculation providing a great opportunity to rethink mechanistic understanding of ionization processes used in mass spectrometry. Improved understanding of the mechanism(s) of these processes and their connection to ESI and matrix-assisted laser desorption/ionization may provide opportunities to further develop new ionization strategies for traditional and yet unforeseen applications of mass spectrometry. This Critical Insights article covers developments leading to the discovery of a seemingly magic ionization process that is simple to use, fast, sensitive, robust, and can be directly applied to surface characterization using portable or high performance mass spectrometers. PMID:26486514

  3. "Magic" Ionization Mass Spectrometry

    Science.gov (United States)

    Trimpin, Sarah

    2016-01-01

    The systematic study of the temperature and pressure dependence of matrix-assisted ionization (MAI) led us to the discovery of the seemingly impossible, initially explained by some reviewers as either sleight of hand or the misinterpretation by an overzealous young scientist of results reported many years before and having little utility. The "magic" that we were attempting to report was that with matrix assistance, molecules, at least as large as bovine serum albumin (66 kDa), are lifted into the gas phase as multiply charged ions simply by exposure of the matrix:analyte sample to the vacuum of a mass spectrometer. Applied heat, a laser, or voltages are not necessary to achieve charge states and ion abundances only previously observed with electrospray ionization (ESI). The fundamentals of how solid phase volatile or nonvolatile compounds are converted to gas-phase ions without added energy currently involves speculation providing a great opportunity to rethink mechanistic understanding of ionization processes used in mass spectrometry. Improved understanding of the mechanism(s) of these processes and their connection to ESI and matrix-assisted laser desorption/ionization may provide opportunities to further develop new ionization strategies for traditional and yet unforeseen applications of mass spectrometry. This Critical Insights article covers developments leading to the discovery of a seemingly magic ionization process that is simple to use, fast, sensitive, robust, and can be directly applied to surface characterization using portable or high performance mass spectrometers.

  4. The critical ionization velocity

    International Nuclear Information System (INIS)

    The critical ionization velocity effect was first proposed in the context of space plasmas. This effect occurs for a neutral gas moving through a magnetized plasma and leads to rapid ionization and braking of the relative motion when a marginal velocity, 'the critical velocity', is exceeded. Laboratory experiments have clearly established the significance of the critical velocity and have provided evidence for an underlying mechanism which relies on the combined action of electron impact ionization and a collective plasma interaction heating electrons. There is experimental support for such a mechanism based on the heating of electrons by the modified two-stream instability as part of a feedback process. Several applications to space plasmas have been proposed and the possibility of space experiments has been discussed. (author)

  5. The ionizing treatment of food

    International Nuclear Information System (INIS)

    This book of proceedings contains the talks given by the members of the Society of chemical experts of France (SECF) and by various specialists of the ionizing treatment during the scientific days of September 25-26, 1997. The aim of this meeting was to reconsider the effects of ionization from a scientific point of view and apart from the polemics generated by this domain. The following topics were discussed successively: source and characterization of a ionizing treatment, biological effects of ionization on food and the expected consequences, the ionizing treatment and the reduction of the vitamin C content of fruits and vegetables, is it safe to eat irradiated food?, the organoleptic modifications of food after ionization, quality assurance of dosimetry measurements in an industrial installation of food ionization, the French and European regulations in food ionization, the detection of irradiated foodstuffs, processed food and complex lipid matrices, sterilization of dishes for immuno-depressed patients using ionization. (J.S.)

  6. Radiation dependent ionization model

    International Nuclear Information System (INIS)

    For laser created plasma simulation, hydrodynamics codes need a non-LTE atomic physics package for both EOS and optical properties (emissivity and opacity). However in XRL targets as in some ICF targets, high Z material can be found. In these cases radiation trapping can induce a significant departure from the optically thin ionization description. The authors present a method to change an existing LTE code into a non-LTE code with coupling of ionization to radiation. This method has very low CPU cost and can be used in 2D simulations

  7. Ionizing radiation effects in MOS oxides

    CERN Document Server

    Oldham, Timothy R

    1999-01-01

    This volume is intended to serve as an updated critical guide to the extensive literature on the basic physical mechanisms controlling the radiation and reliability responses of MOS oxides. The last such guide was Ionizing Radiation Effects in MOS Devices and Circuits, edited by Ma and Dressendorfer and published in 1989. While that book remains an authoritative reference in many areas, there has been a significant amount of more recent work on the nature of the electrically active defects in MOS oxides which are generated by exposure to ionizing radiation. These same defects are also critical

  8. Ionization chamber smoke detectors

    International Nuclear Information System (INIS)

    One kind of smoke detector, the ionization-type, is regulated by the Atomic Energy Control Board (AECB) because it uses a radioactive substance in its mechanism. Radioactivity and radiation are natural phenomena, but they are not very familiar to the average householder. This has led to a number of questions being asked of the AECB. These questions and AECB responses are outlined

  9. Alkali ionization detector

    Science.gov (United States)

    Hrizo, John; Bauerle, James E.; Witkowski, Robert E.

    1982-01-01

    A calibration filament containing a sodium-bearing compound is included in combination with the sensing filament and ion collector plate of a sodium ionization detector to permit periodic generation of sodium atoms for the in-situ calibration of the detector.

  10. Applications of ionizing radiations

    International Nuclear Information System (INIS)

    The R and D activities of the application of Ionizing Radiations Program is comprised to four subprograms: Food and Agricultural Productions Irradiation; Radiation and Radioisotopes Applications in Industry and Environment; Radioactive Sources and Radiation Applications in Human Health; and Radioactive Facilities and Equipment for Nuclear Techniques Applications

  11. Ionization beam scanner

    CERN Multimedia

    CERN PhotoLab

    1973-01-01

    Inner structure of an ionization beam scanner, a rather intricate piece of apparatus which permits one to measure the density distribution of the proton beam passing through it. On the outside of the tank wall there is the coil for the longitudinal magnetic field, on the inside, one can see the arrangement of electrodes creating a highly homogeneous transverse electric field.

  12. All short pulse multiphoton ionization is resonant ionization

    International Nuclear Information System (INIS)

    Energy resolved photoelectron spectra of multiphoton ionization taken with a 300 fs laser pulse at 616 nm shows that the ionization probability is highly structured as a function of laser intensity. The spectrum is consistent with all of the ionization occurring at intensity resonances

  13. Proceedings of a Workshop on Genetic Effects of Ionizing Radiation

    International Nuclear Information System (INIS)

    Nine papers were presented at this workshop held to mark the retirement of Dr. D.K. Myers. The papers reviewed recent literature on the heritable effects of ionizing radiation and identified areas of uncertainty. (L.L.)

  14. Electrochemical reactions and ionization processes

    OpenAIRE

    Girault, Hubert; Liu, Baohong; Qiao, Liang; Bi, Hongyan; Prudent, Michel; Lion, Niels; Abonnenc, Mélanie

    2010-01-01

    Electrochemical or photo-electrochemical reactions in both electrospray ionization and laser desorption ionization are discussed stressing the role of the electrode reaction in influencing the ionization process. In particular, upon application of a high voltage during electrospray ionization, the emitter includes a working electrode, where redox reactions are observed, such as electro-generation of benzoquinone and metal ions. In contrast, the target plate in laser-induced desorption ionizat...

  15. Multiphoton ionization of polarized atoms

    International Nuclear Information System (INIS)

    A theory is derived for the multiphoton ionization of polarized atoms. The angular distributions of the differential and total ionization probabilities are studied for various polarizations of the electromagnetic radiation. The circular dichroism is also studied. The multiphoton ionization of oriented s-state atoms near a resonance is studied separately. Some relevant experiments which might be carried out are discussed

  16. Multiphoton ionization of polarized atoms

    International Nuclear Information System (INIS)

    A theory of multiphoton ionization of polarized atoms is developed. The angular dependences of the different and total ionization probabilities for various polarizations of the radiation and the circular dichroism effect are investigated. Multiphoton ionization of oriented in the s-states near resonance is considered separately

  17. Sodium ionization detector and sensor

    International Nuclear Information System (INIS)

    Work conducted on a basic technology development effort with the Westinghouse Sodium Ionization Detector (SID) sensor is reported. Included are results obtained for three task areas: (1) On-line operational response testing - in-situ calibration techniques; (2) Performance-reliability characteristics of aged filaments; and (3) Evaluation of chemical interference effects. The results showed that a calibrator filament coated with a sodium compound, when activated, does supply the necessary sodium atoms to provide a valid operational in-situ test. The life time of new Cr203-protected SID sensor filaments can be extended by operating at a reduced temperature. However, there also is a reduction in the sensitivity. Non-sodium species, such as products from a smoldering fire and organic aerosols, produce an interference response from the sensor comparable to a typical sodium response

  18. Physics of ionized gases

    CERN Document Server

    Smirnov, Boris M

    2001-01-01

    A comprehensive textbook and reference for the study of the physics of ionized gasesThe intent of this book is to provide deep physical insight into the behavior of gases containing atoms and molecules from which one or more electrons have been ionized. The study of these so-called plasmas begins with an overview of plasmas as they are found in nature and created in the laboratory. This serves as a prelude to a comprehensive study of plasmas, beginning with low temperature and "ideal" plasmas and extending to radiation and particle transport phenomena, the response of plasmas to external fields, and an insightful treatment of plasma waves, plasma instabilities, nonlinear phenomena in plasmas, and the study of plasma interactions with surfaces

  19. Electrospray Ionization Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Ryan T.; Marginean, Ioan; Tang, Keqi

    2014-06-13

    Electrospray Ionization (ESI) is a process whereby gas phase ions are created from molecules in solution. As a solution exits a narrow tube in the presence of a strong electric field, an aerosol of charged droplets are is formed that produces gas phase ions as they it desolvates. ESI-MS comprises the creation of ions by ESI and the determination of their mass to charge ratio (m/z) by MS.

  20. Application of ionizing radiations

    International Nuclear Information System (INIS)

    The main subject of the application of Ionizing Radiations Program is to disseminate and consolidate techniques leading to the use of the radiation technology and radioisotopes application in Industry, Human Health, Agriculture and Environmental Preservation. This Program is divided into four subprograms: 1) Food and Agricultural Products Irradiation; 2) Radiation and Radioisotopes Applications in Industry and Environment; Radioactive Sources and Radiation Applications in Human Health; Radioactive Facilities and Equipment for Nuclear Techniques Applications

  1. Pregnancy and ionizing radiation

    International Nuclear Information System (INIS)

    Full text: In this report there will be presented the effects of ionizing radiation at the fetus and the necessary radioprotection. The biological results on the fetus, caused by the irradiation, depend on the dose of ionizing radiation that it receives and the phase of its evolution. The imminent effects of the irradiation can cause the fetus death, abnormalities and mental retardation, which are the result of overdose. The effects are carcinogenesis and leukemia, which are relative to the acceptable irradiating dose at the fetus and accounts about 0,015 % per 1 mSv. The effects of ionizing radiation depend on the phase of the fetus evolution: 1st phase (1st - 2nd week): presence of low danger; 2nd phase (3rd - 8th week): for doses >100 mSv there is the possibility of dysplasia; 3rd phase (8th week - birth): this phase concerns the results with a percentage 0,015 % per 1 mSv. We always must follow some rules of radioprotection and especially at Classical radiation use of necessary protocols (low dose), at Nuclear Medicine use of the right radioisotope and the relative field of irradiation for the protection of the adjacent healthy tissues and at Radiotherapy extreme caution is required regarding the dose and the treatment. In any case, it is forbidden to end a pregnancy when the pregnant undergoes medical exams, in which the uterus is in the beam of irradiation. The radiographer must always discuss the possibility of pregnancy. (author)

  2. Transfer ionization of the isocharge sequence ion and Ar collisions

    Institute of Scientific and Technical Information of China (English)

    Cai Xiao-Hong; Yu De-Yang; Cao Zhu-Rong; Lu Rong-Chun; Yang Wei; Shao Cao-Jie; Chen Xi-Meng

    2004-01-01

    The ratios of transfer ionization to single capture for isocharge Cq+, Nq+, Oq+, Neq+ ions on Ar atoms are measured by using position-sensitive and time-of-flight techniques. It is found that the ratio R1 increases with nuclear charge Z in a q=4 sequence, and the ratio R1 sequences have the minimum values at Z=7 and Z=8 in q=5 and q=6 sequences, respectively, and the ratio R1 decreases with the increase in the nuclear charge Z in a q=7 sequence. The results may be explained within the frame of the statistical model. It may be concluded that the transfer ionization depends remarkably upon the electronic structure of the projectile. The projectiles used in this study have the same charge state and velocity, but different electronic structures. The dependence of the ratio R1 on q is studied for Neq+-Ar collisions. The ratio R1 is found to increase as q increases for Neq+-Ar collisions. The measured dependence of the ratio R1 on q is compared with the calculation using the molecular Coulomb over-barrier model.

  3. Chemical protection against ionizing radiation. Final report

    International Nuclear Information System (INIS)

    The scientific literature on radiation-protective drugs is reviewed. Emphasis is placed on the mechanisms involved in determining the sensitivity of biological material to ionizing radiation and mechanisms of chemical radioprotection. In Section I, the types of radiation are described and the effects of ionizing radiation on biological systems are reviewed. The effects of ionizing radiation are briefly contrasted with the effects of non-ionizing radiation. Section II reviews the contributions of various natural factors which influence the inherent radiosensitivity of biological systems. Inlcuded in the list of these factors are water, oxygen, thiols, vitamins and antioxidants. Brief attention is given to the model describing competition between oxygen and natural radioprotective substances (principally, thiols) in determining the net cellular radiosensitivity. Several theories of the mechanism(s) of action of radioprotective drugs are described in Section III. These mechanisms include the production of hypoxia, detoxication of radiochemical reactive species, stabilization of the radiobiological target and the enhancement of damage repair processes. Section IV describes the current strategies for the treatment of radiation injury. Likely areas in which fruitful research might be performed are described in Section V. 495 references

  4. Chemical protection against ionizing radiation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Livesey, J.C.; Reed, D.J.; Adamson, L.F.

    1984-08-01

    The scientific literature on radiation-protective drugs is reviewed. Emphasis is placed on the mechanisms involved in determining the sensitivity of biological material to ionizing radiation and mechanisms of chemical radioprotection. In Section I, the types of radiation are described and the effects of ionizing radiation on biological systems are reviewed. The effects of ionizing radiation are briefly contrasted with the effects of non-ionizing radiation. Section II reviews the contributions of various natural factors which influence the inherent radiosensitivity of biological systems. Inlcuded in the list of these factors are water, oxygen, thiols, vitamins and antioxidants. Brief attention is given to the model describing competition between oxygen and natural radioprotective substances (principally, thiols) in determining the net cellular radiosensitivity. Several theories of the mechanism(s) of action of radioprotective drugs are described in Section III. These mechanisms include the production of hypoxia, detoxication of radiochemical reactive species, stabilization of the radiobiological target and the enhancement of damage repair processes. Section IV describes the current strategies for the treatment of radiation injury. Likely areas in which fruitful research might be performed are described in Section V. 495 references.

  5. Engineered Ionizable Side Chains.

    Science.gov (United States)

    Cymes, Gisela D; Grosman, Claudio

    2015-01-01

    One of the great challenges of mechanistic ion-channel biology is to obtain structural information from well-defined functional states. In the case of neurotransmitter-gated ion channels, the open-channel conformation is particularly elusive owing to its transient nature and brief mean lifetime. In this Chapter, we show how the analysis of single-channel currents recorded from mutants engineered to contain single ionizable side chains in the transmembrane region can provide specific information about the open-channel conformation without any interference from the closed or desensitized conformations. The method takes advantage of the fact that the alternate binding and unbinding of protons to and from an ionizable side chain causes the charge of the protein to fluctuate by 1 unit. We show that, in mutant muscle acetylcholine nicotinic receptors (AChRs), this fluctuating charge affects the rate of ion conduction in such a way that individual proton-transfer events can be identified in a most straightforward manner. From the extent to which the single-channel current amplitude is reduced every time a proton binds, we can learn about the proximity of the engineered side chain to the lumen of the pore. And from the kinetics of proton binding and unbinding, we can calculate the side-chain's affinity for protons (pK a), and hence, we can learn about the electrostatic properties of the microenvironment around the introduced ionizable group. The application of this method to systematically mutated AChRs allowed us to identify unambiguously the stripes of the M1, M2 and M3 transmembrane α-helices that face the pore's lumen in the open-channel conformation in the context of a native membrane. PMID:26381938

  6. Ionized helium afterglow study

    International Nuclear Information System (INIS)

    In order to take into account the characteristics of ionized helium, under relaxation conditions, in the determination of the unknown coefficients of the reaction rates and more particularly those of the recombination of H2+ ions, a method has been developed which consists in recovering, using a system of differential equations with coupled partial derivatives, the set of all the physical quantities which can at the moment be measured as a function of time in a helium after-discharge. The energy balance of the maxwellian electrons and the speed distribution function of the electrons were studied in details and calculated as a function of time and location in space. The non-maxwellian electrons were included in the calculations. Measurements were made over a large range of experimental conditions using 5 different diagnoses: UHF interferometry in the X band, UHF radiometry in the X band, mass spectrometry, optical absorption spectrometry and optical emission spectrometry. All experimental data, obtained at 293 deg K and at seven different pressures ranging from 5 to 100 Torr were perfectly reproduced by the proposed system of differential equations, with the same reaction rate coefficients and the same constants. The method developed here gives a complete solution for the helium after-discharge at room temperature over a wide range of experimental conditions. It underlines the important reactions within the ionized gas, gives the absolute value and the dependences of the electron-He2+ ion recombination coefficient and allows the determination of the elementary mechanisms causing these dependences. It also gives the coefficients and the reaction rates of all the other elementary mechanisms which, besides recombination, determine the relaxation of ionized helium

  7. Resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    The subject of resonance ionization spectroscopy (RIS) from its inception to the present is summarized. The uses of RIS are principally analytical, and these uses are classified in several different ways for this report. The classifications are: (1) basic ways of counting atoms; (2) RIS applications according to the type of particle detector; (3) applications according to source preparation; (4) applications in chemical physics and chemistry; and (5) applications involving daughter atom detection. Each classification is discussed in some detail, and examples of specific applications are mentioned under each classification. Some other potential applications not necessarily related to these classifications are also mentioned

  8. Single- and multiphoton ionization processes in molecules

    International Nuclear Information System (INIS)

    This dissertation is theoretical in nature and can be separated into two main areas: (1) single- and multiphoton ionization studies of a novel photoelectron effect, and (2) single-photon ionization studies of simple clusters as models for adsorbate photoemission. The first area centers on the phenomenon of circular dichroism in photoelectron angular distributions (CDAD). CDAD is shown to exist from oriented linear molecules, adsorbed atoms, and aligned atoms and molecules in the gas phase. The calculations presented here are the first to demonstrate the experimental feasability of CDAD studies. CDAD is shown to be a measureable effect which exists because the photoelectron collection direction can break the symmetry of these otherwise highly symmetric systems. As a direct results of the work presented here, CDAD has now been observed experimentally. Coupled with resonantly enhanced multiphoton ionization (REMPI), CDAD is shown to be a powerful probe of unknown alignment in gas phase atomic and molecular samples. The second area of research focuses on the simple oriented molecules NiCO and NiN2 as models for the corresponding adsorbate systems. These simple models provide insight into features observed in the experimental angle-resolved photoemission spectra

  9. Breakup of loosely bound nuclei at intermediate energies for nuclear astrophysics and the development of a position sensitive microstrip detector system and its readout electronics using ASICs technologies

    Energy Technology Data Exchange (ETDEWEB)

    Bertulani, Carlos A. [Texas A & M Univ., Commerce, TX (United States)

    2016-01-12

    The work performed under this grant has led to the development of a detection system that will be used to measure reaction rates for proton or neutron capture reactions at stellar energies on radioactive ions far from stability. The reaction rates are needed to better understand the physics of nucleosynthesis in explosive stellar processes such as supernovae and x-ray burst events. The radioactive ions will be produced at the Radioactive Ion Beam Facility (RIBF) at RIKEN near Tokyo, Japan. During the course of this work, the group involved in this project has expanded by several institutions in Europe and Japan and now involves collaborators from the U.S., Japan, Hungary, Romania, Germany, Spain, Italy, China, and South Korea. As part of the project, a novel design based on large-area silicon detectors has been built and tested. The work has involved mechanical construction of a special purpose vacuum chamber, with a precision mounting system for the silicon detectors, development of a new ASICs readout system that has applications with a wide variety of silicon detector systems, and the development of a data acquisition system that is integrated into the computer system being used at RIBF. The parts noted above that are needed to carry out the research program are completed and ready for installation. Several approved experiments that will use this system will be carried out in the near future. The experimental work has been delayed due to a large increase in the cost and availability of electrical power for RIBF that occurred following the massive earthquake and tsunami that hit Japan in the spring of 2011. Another component of the research carried out with this grant involved developing the theoretical tools that are required to extract the information from the experiments that is needed to determine the stellar reaction rates. The tools developed through this part of the work will be made freely available for general use.

  10. Breakup of loosely bound nuclei at intermediate energies for nuclear astrophysics and the development of a position sensitive microstrip detector system and its readout electronics using ASICs technologies

    Energy Technology Data Exchange (ETDEWEB)

    Tribble, Robert E. [Texas A & M Univ., College Station, TX (United States); Sobotka, Lee G. [Washington Univ., St. Louis, MO (United States); Blackmon, Jeff C. [Louisiana State Univ., Baton Rouge, LA (United States); Bertulani, Carlos A. [Texas A & M Univ., Commerce, TX (United States)

    2015-12-29

    The work performed under this grant has led to the development of a detection system that will be used to measure reaction rates for proton or neutron capture reactions at stellar energies on radioactive ions far from stability. The reaction rates are needed to better understand the physics of nucleosynthesis in explosive stellar processes such as supernovae and x-ray burst events. The radioactive ions will be produced at the Radioactive Ion Beam Facility (RIBF) at RIKEN near Tokyo, Japan. During the course of this work, the group involved in this project has expanded by several institutions in Europe and Japan and now involves collaborators from the U.S., Japan, Hungary, Romania, Germany, Spain, Italy, China, and South Korea. As part of the project, a novel design based on large-area silicon detectors has been built and tested and the performance characterized in a series of tests using particle beams with a variety of atomic numbers at the Cyclotron Institute of Texas A&M University and the Heavy Ion Medical Accelerator in Chiba facility (HIMAC) in Chiba, Japan. The work has involved mechanical construction of a special purpose vacuum chamber, with a precision mounting system for the silicon detectors, development of a new ASICs readout system that has applications with a wide variety of silicon detector systems, and the development of a data acquisition system that is integrated into the computer system being used at RIBF. The parts noted above that are needed to carry out the research program are completed and ready for installation. Several approved experiments that will use this system will be carried out in the near future. The experimental work has been delayed due to a large increase in the cost and availability of electrical power for RIBF that occurred following the massive earthquake and tsunami that hit Japan in the spring of 2011. Another component of the research carried out with this grant involved developing the theoretical tools that are required

  11. The MICE Demonstration of Ionization Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Pasternak, J.; Blackmore, V.; Hunt, C.; Lagrange, J-B.; Long, K.; Collomb, N.; Snopok, P.

    2015-05-01

    Muon beams of low emittance provide the basis for the intense, well-characterised neutrino beams necessary to elucidate the physics of flavour at the Neutrino Factory and to provide lepton-antilepton collisions at energies of up to several TeV at the Muon Collider. The International Muon Ionization Cooling Experiment (MICE) will demonstrate ionization cooling, the technique by which it is proposed to reduce the phase-space volume occupied by the muon beam at such facilities. In an ionization cooling channel, the muon beam passes through a material (the absorber) in which it loses energy. The energy lost is then replaced using RF cavities. The combined effect of energy loss and re-acceleration is to reduce the transverse emittance of the beam (transverse cooling). A major revision of the scope of the project was carried out over the summer of 2014. The revised project plan, which has received the formal endorsement of the international MICE Project Board and the international MICE Funding Agency Committee, will deliver a demonstration of ionization cooling by September 2017. In the revised configuration a central lithium-hydride absorber provides the cooling effect. The magnetic lattice is provided by the two superconducting focus coils and acceleration is provided by two 201 MHz single-cavity modules. The phase space of the muons entering and leaving the cooling cell will be measured by two solenoidal spectrometers. All the superconducting magnets for the ionization cooling demonstration are available at the Rutherford Appleton Laboratory and the first single-cavity prototype is under test in the MuCool Test Area at Fermilab. The design of the cooling demonstration experiment will be described together with a summary of the performance of each of its components. The cooling performance of the revised configuration will also be presented.

  12. Applications of ionizing radiations

    International Nuclear Information System (INIS)

    Developments in standard applications and brand new nuclear technologies, with high impact on the future of the agriculture, medicine, industry and the environmental preservation. The Radiation Technology Center (CTR) mission is to apply the radiation and radioisotope technologies in Industry, Health, Agriculture, and Environmental Protection, expanding the scientific knowledge, improving human power resources, transferring technology, generating products and offering services for the Brazilian society. The CTR main R and D activities are in consonance with the IPEN Director Plan (2011-2013) and the Applications of Ionizing Radiation Program, with four subprograms: Irradiation of Food and Agricultural Products; Radiation and Radioisotopes Applications in Industry and Environment; Radioactive Sources and Radiation Applications in Human Health; and Radioactive Facilities and Equipment for the Applications of Nuclear Techniques

  13. Multiphoton ionization of Uracil

    Science.gov (United States)

    Prieto, Eladio; Martinez, Denhi; Guerrero, Alfonso; Alvarez, Ignacio; Cisneros, Carmen

    2016-05-01

    Multiphoton ionization and dissociation of Uracil using a Reflectron time of flight spectrometer was performed along with radiation from the second harmonic of a Nd:YAG laser. Uracil is one of the four nitrogen bases that belong to RNA. The last years special interest has been concentrated on the study of the effects under UV radiation in nucleic acids1 and also in the role that this molecule could have played in the origin and development of life on our planet.2 The MPI mass spectra show that the presence and intensity of the resulting ions strongly depend on the density power. The identification of the ions in the mass spectra is presented. The results are compared with those obtained in other laboratories under different experimental conditions and some of them show partial agreement.3 The present work was supported by CONACYT-Mexico Grant 165410 and DGAPA UNAM Grant IN101215 and IN102613.

  14. Applications of ionizing radiations

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2014-07-01

    Developments in standard applications and brand new nuclear technologies, with high impact on the future of the agriculture, medicine, industry and the environmental preservation. The Radiation Technology Center (CTR) mission is to apply the radiation and radioisotope technologies in Industry, Health, Agriculture, and Environmental Protection, expanding the scientific knowledge, improving human power resources, transferring technology, generating products and offering services for the Brazilian society. The CTR main R and D activities are in consonance with the IPEN Director Plan (2011-2013) and the Applications of Ionizing Radiation Program, with four subprograms: Irradiation of Food and Agricultural Products; Radiation and Radioisotopes Applications in Industry and Environment; Radioactive Sources and Radiation Applications in Human Health; and Radioactive Facilities and Equipment for the Applications of Nuclear Techniques.

  15. Area monitoring

    International Nuclear Information System (INIS)

    The exposure of individuals to ionizing radiation is normally subject to legal controls which specify limits, and restriction, of doses that both occupational workers and members of the public are exposed to. The dose limits recommended by the International Commission on Radiological Protection (ICRP), and adopted by many countries are specified in terms of body dose equivalents, sometimes referred to as limiting quantities. However these quantities are not measurable since they are defined as average doses in organs and tissues of the human body. Thus for the same physical radiation field the dose delivered to an individual will not have a fixed value but will depend upon each individual's sex, age and physical construction as well as upon their orientation in the field. Ionizing radiation, also, cannot be detected by a person's physical senses of sight, smell, hearing and touch. Thus to control the levels of radiation to which individuals are exposed, special operational quantities are used and quantitative measurements have to be made using personal dosemeters or area monitoring equipment. This report describes the operational quantities that are being increasingly used worldwide for area monitoring. It provides information on the international standards that are available on the performance requirements for monitoring equipment designed to measure these operational quantities. It also reviews the recent international standards that have been published on the calibration and type testing of area monitors and gives an example of legislative requirements on area monitoring equipment. (author)

  16. Neutron Position Sensitive Detectors for the ESS

    CERN Document Server

    Kirstein, Oliver; Stefanescu, Irina; Etxegarai, Maddi; Anastasopoulos, Michail; Fissum, Kevin; Gulyachkina, Anna; Höglund, Carina; Imam, Mewlude; Kanaki, Kalliopi; Khaplanov, Anton; Kittelmann, Thomas; Kolya, Scott; Nilsson, Björn; Ortega, Luis; Pfeiffer, Dorothea; Piscitelli, Francesco; Ramos, Judith Freita; Robinson, Linda; Scherzinger, Julius

    2014-01-01

    The European Spallation Source (ESS) in Lund, Sweden will become the world's leading neutron source for the study of materials. The instruments are being selected from conceptual proposals submitted by groups from around Europe. These instruments present numerous challenges for detector technology in the absence of the availability of Helium-3, which is the default choice for detectors for instruments built until today and due to the extreme rates expected across the ESS instrument suite. Additionally a new generation of source requires a new generation of detector technologies to fully exploit the opportunities that this source provides. The detectors will be sourced from partners across Europe through numerous in-kind arrangements; a process that is somewhat novel for the neutron scattering community. This contribution presents briefly the current status of detectors for the ESS, and outlines the timeline to completion. For a conjectured instrument suite based upon instruments recommended for construction, ...

  17. Ionization box type radiation detector

    International Nuclear Information System (INIS)

    An ionization box for monitoring radiation rays, a first amplification circuit of a multi-stage amplification circuit employing a MOS type FET as an initial stage amplification device, a second amplification circuit employing a junction type FET as an initial stage amplification device, a first change-over switch for switching ionization current depending on input signals, a second change-over switch for switching output signals, and a signal level discrimination circuit are constituted integrally. When radiation dose rate is low, the ionization current is inputted to the first amplification circuit and outputted as a radiation ray monitor signal and, when the radiation dose rate is increased to higher than a predetermined value, the ionization current is inputted to the second amplification circuit and outputted as a radiation ray monitor signal. That is, monitoring accuracy is high when the ionization current is low since the MOS type FET of high input impedance is used. If the ionization current is higher than a predetermined value, there is no worry that the detection becomes impossible since the junction type FET having less worry of causing characteristic change due to high radiation dose rate is used. Accordingly, ionization box type monitor at a high monitoring reliability can be obtained. (N.H.)

  18. Photoionization effects in ionization fronts

    Energy Technology Data Exchange (ETDEWEB)

    Arrayas, Manuel [Departamento de Electromagnetismo, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain); Fontelos, Marco A [Departamento de Matematicas, Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones CientIficas, C/Serrano 123, 28006 Madrid (Spain); Trueba, Jose L [Departamento de Electromagnetismo, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2006-12-21

    In this paper we study the effects of photoionization processes on the propagation of both negative and positive ionization fronts in streamer discharge. We show that negative fronts accelerate in the presence of photoionization events. The appearance and propagation of positive ionization fronts travelling with constant velocity is explained as the result of the combined effects of photoionization and electron diffusion. The photoionization range plays an important role in the selection of the velocity of the ionization front as we show in this work.

  19. Ionization in liquids

    International Nuclear Information System (INIS)

    During the 1987--1990 reporting period, studies were conducted that entailed the direct measurement of the transport and reaction properties of excess electrons in nonpolar liquids through the use of pulse-conductivity techniques. The results obtained from these studies should be applicable toward the development of a better understanding of the primary ionizing event in liquids as well as to providing physico-chemical information that is pertinent to electron-transfer processes that are ubiquitous in biological systems. Progress was also made in developing a better understanding of electron attachment reactions in liquids through measurements of the electron attachment rate constants, kes, of a variety of electron-attaching solutes. The effects of several functional groups substituted at different positions on benzene were studied in liquid cyclohexane and isooctane. The electron-attaching properties of chemicals having well characterized carcinogenic properties were studied in cyclohexane to determine if the measure of electron-accepting potential that ke provides can elucidate the role that electrons play in the initiation step of carcinogenesis. The kes that were measured indicate that the ke-carcinogenicity correlation that was observed can be used to complement short-term carcinogen-screening bioassays to identify potential carcinogens. 115 refs., 6 tabs

  20. Optical ionization detector

    Science.gov (United States)

    Wuest, Craig R.; Lowry, Mark E.

    1994-01-01

    An optical ionization detector wherein a beam of light is split so that one arm passes through a fiber optics and the other arm passes through a gas-filled region, and uses interferometry to detect density changes in a gas when charged particles pass through it. The gas-filled region of the detector is subjected to a high electric field and as a charged particle traverses this gas region electrons are freed from the cathode and accelerated so as to generate an electron avalanche which is collected on the anode. The gas density is effected by the electron avalanche formation and if the index or refraction is proportional to the gas density the index will change accordingly. The detector uses this index change by modulating the one arm of the split light beam passing through the gas, with respect to the other arm that is passed through the fiber optic. Upon recombining of the beams, interference fringe changes as a function of the index change indicates the passage of charged particles through the gaseous medium.

  1. The Ionization History of The Intergalactic Medium:

    Science.gov (United States)

    Madau, Piero

    2003-01-01

    The funded project seeked a unified description of the ionization, physical structure, and evolution of the intergalactic medium (IGM) and quasar intervening absorption systems. We proposed to conduct theoretical studies of the IGM and QSO absorbers in the context of current theories of galaxy formation, developing and using numerical and analytical techniques aimed at a detailed modeling of cosmological radiative transfer, gas dynamics, and thermal and ionization evolution. The ionization history of the IGM has important implications for the metagalactic UV background, intergalactic helium absorption 21-cm tomography, metal absorption systems, fluctuations in the microwave background, and the cosmic rate of structure and star formation. All the original objectives of our program have been achieved, and the results widely used and quoted by the community. Indeed, they remain relevant as the level and complexity of research in this area has increased substantially since our proposal was submitted, due to new discoveries on galaxy formation and evolution, a flood of high-quality data on the distant universe, new theoretical ideas and direct numerical simulations of structure formation in hierarchical clustering theories.

  2. Making MUSIC: A multiple sampling ionization chamber

    International Nuclear Information System (INIS)

    A multiple sampling ionization chamber (MUSIC) was developed for use in conjunction with the Atlas scattering chamber (ATSCAT). This chamber was developed to study the (α, p) reaction in stable and radioactive beams. The gas filled ionization chamber is used as a target and detector for both particles in the outgoing channel (p + beam particles for elastic scattering or p + residual nucleus for (α, p) reactions). The MUSIC detector is followed by a Si array to provide a trigger for anode events. The anode events are gated by a gating grid so that only (α, p) reactions where the proton reaches the Si detector result in an anode event. The MUSIC detector is a segmented ionization chamber. The active length of the chamber is 11.95 in. and is divided into 16 equal anode segments (3.5 in. x 0.70 in. with 0.3 in. spacing between pads). The dead area of the chamber was reduced by the addition of a Delrin snout that extends 0.875 in. into the chamber from the front face, to which a mylar window is affixed. 0.5 in. above the anode is a Frisch grid that is held at ground potential. 0.5 in. above the Frisch grid is a gating grid. The gating grid functions as a drift electron barrier, effectively halting the gathering of signals. Setting two sets of alternating wires at differing potentials creates a lateral electric field which traps the drift electrons, stopping the collection of anode signals. The chamber also has a reinforced mylar exit window separating the Si array from the target gas. This allows protons from the (α, p) reaction to be detected. The detection of these protons opens the gating grid to allow the drift electrons released from the ionizing gas during the (α, p) reaction to reach the anode segment below the reaction

  3. Making MUSIC: A multiple sampling ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Shumard, B. [Argonne National Laboratory, Building 203 H-113, Argonne, IL 60439 (United States)]. E-mail: shumard@phy.anl.gov; Henderson, D.J. [Argonne National Laboratory, Building 203 H-113, Argonne, IL 60439 (United States); Rehm, K.E. [Argonne National Laboratory, Building 203 H-113, Argonne, IL 60439 (United States); Tang, X.D. [Argonne National Laboratory, Building 203 H-113, Argonne, IL 60439 (United States)

    2007-08-15

    A multiple sampling ionization chamber (MUSIC) was developed for use in conjunction with the Atlas scattering chamber (ATSCAT). This chamber was developed to study the ({alpha}, p) reaction in stable and radioactive beams. The gas filled ionization chamber is used as a target and detector for both particles in the outgoing channel (p + beam particles for elastic scattering or p + residual nucleus for ({alpha}, p) reactions). The MUSIC detector is followed by a Si array to provide a trigger for anode events. The anode events are gated by a gating grid so that only ({alpha}, p) reactions where the proton reaches the Si detector result in an anode event. The MUSIC detector is a segmented ionization chamber. The active length of the chamber is 11.95 in. and is divided into 16 equal anode segments (3.5 in. x 0.70 in. with 0.3 in. spacing between pads). The dead area of the chamber was reduced by the addition of a Delrin snout that extends 0.875 in. into the chamber from the front face, to which a mylar window is affixed. 0.5 in. above the anode is a Frisch grid that is held at ground potential. 0.5 in. above the Frisch grid is a gating grid. The gating grid functions as a drift electron barrier, effectively halting the gathering of signals. Setting two sets of alternating wires at differing potentials creates a lateral electric field which traps the drift electrons, stopping the collection of anode signals. The chamber also has a reinforced mylar exit window separating the Si array from the target gas. This allows protons from the ({alpha}, p) reaction to be detected. The detection of these protons opens the gating grid to allow the drift electrons released from the ionizing gas during the ({alpha}, p) reaction to reach the anode segment below the reaction.

  4. Theory of resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    Resonance Ionization Spectroscopy (RIS) can be defined as a state selective detection process in which pulsed tunable lasers are used to promote transitions from the selected state of the atoms or molecules in question to higher states, one of which will be ionized by the absorption of another photon. At least one resonance step is used in the stepwise ionization process, and it has been shown that the ionization probability of the spectroscopically selected species can nearly always be made close to unity. Since measurements of the number of photoelectrons or ions can be made very precisely and even one electron (or under vacuum conditions, one ion) can be detected, the technique can be used to make quantitative measurements of very small populations of the state-selected species

  5. Ionization of impurities in silicon

    Science.gov (United States)

    Kuźmicz, Wiesław

    1986-12-01

    A model for calculation of the percentage of ionized dopant atoms as a function of the doping concentration and temperature is proposed. The results are compared with experiment. Analytical approximations that facilitate practical applications of the model are given.

  6. Calculation of multiphoton ionization processes

    Science.gov (United States)

    Chang, T. N.; Poe, R. T.

    1976-01-01

    We propose an accurate and efficient procedure in the calculation of multiphoton ionization processes. In addition to the calculational advantage, this procedure also enables us to study the relative contributions of the resonant and nonresonant intermediate states.

  7. Strong Ionization in carbon Nanowires

    CERN Document Server

    Kaymak, Vural; Shlyaptsev, Vyacheslav N; Rocca, Jorge J

    2015-01-01

    Surfaces covered with nanostructures, such as nanowire arrays, have shown to facilitate a significantly higher absorption of laser energy as compared to flat surfaces. Due to the efficient coupling of the laser energy, highly energetic electrons are produced, which in turn can emit intense ultrafast X-ray pulses. In the present work we use full three dimensional PIC simulations to analyze the behavior of arrays of carbon nanowires $400 nm$ in diameter, irradiated by a $\\lambda_0 = 400 nm$ laser pulse of $60 fs$ duration at FWHM and a vector potential of $a_0 = 18$. We analyze the ionization dynamics of the nanowires. We investigate the difference of the ionization strength and structure between linearly and circularly polarized laser beam. The nanowires are found to be fully ionized after about 30 laser cycles. Circularly polarized light reveals a slightly stronger ionization effect.

  8. Multi-chamber ionization detector

    International Nuclear Information System (INIS)

    For the detector a single beta ionization source and a double- or three-chamber set-up is used, the chambers being designed in the shape of a truncated cone and facing each other with their bases. The source can be positioned with respect to the common center or modal electrode, the adjustment of the ionization in each chamber this becoming easier. The center or modal electrode also can be adjusted with respect to the source. (DG)

  9. Multiphoton double ionization of barium

    International Nuclear Information System (INIS)

    The authors report the observation of the wavelength spectrum of the double ionization of Ba from ∼ 280 nm to nearly 700 nm, using laser pulses 5ns long of peak intensity ∼ 1010 W/cm2. All the strong resonances can be assigned to Ba+ transitions, and many of the assignments have been verified by pump-probe techniques. Thus, the Ba++ observed is due to sequential ionization. The shortest wavelengths used are not as effective as λ ∼ 500 nm

  10. Laser ionization mass spectroscopy

    Science.gov (United States)

    Bernardez, Luis J., III; Siekhaus, W. J.

    1989-10-01

    Laser Ionization Mass Spectroscopy (LIMS) is a simple technique with several advantages and disadvantages over standard mass spectroscopy techniques. The LIMS technique uses a laser to vaporize a small portion of a sample. The vapor from the sample consists of a mixture of charged and neutral atoms or fragments. Using electrostatic grids, the ions (positive or negative) are given a known amount of kinetic energy and sent down a time-of-flight tube. The time it takes the ions to travel down the flight tube is recorded. Knowing the ions' energy, the length of the flight tube, and the time it takes the ions to travel that distance, the masses of the ions can be calculated. The instrument used is a LIMA 3 made by Cambridge Mass Spectrometry. It has a Quanta Ray DCR-11 Nd:YAG laser, which was frequency-quadrupled to 266 nm. The laser spot size is typically between 2 and 5 microns in diameter and the pulse width is between 5 and 10 nanoseconds. The energy of the laser is continually variable between 0.1 and 3.0 millijoules. The detector is a 17-stage venetian-blind multiplier made by Thorn EMI. The analysis is carried out under vacuum, usually between 10(exp -8) and 10(exp -9) Torr. The LIMA 3 has several useful features such as: a He-Ne pilot laser used to target the Nd:YAG laser; a microscope (which is used to view the sample through the laser optics); and a precision sample stage for accurate sample alignment.

  11. MULTIPLE IONIZATION OF ATOMS THROUGH MULTIPHOTON ABSORPTION

    OpenAIRE

    L'Huillier, A

    1987-01-01

    We review the main aspects of multiple ionization of rare gases in strong laser fields (above 1012W.cm-2). We discuss the mechanisms responsible for the multi-electron ejection : inner-shell ionization or outer-shell ionization, one-step or multi-step. We show the differences between one-photon and multi-photon multiple ionization.

  12. Identification of Bacillus spp. colonizing the nasal mucosa of healthy adults living in the suburban area using the matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS system

    Directory of Open Access Journals (Sweden)

    Kosikowska Urszula

    2014-09-01

    Full Text Available Bacillus spp. can be regarded as a rare component of the nasal mucosa microflora. The aim of this study was to identify Bacillus spp. from the nasal mucosa of healthy adults living in the suburban area near Lublin using the matrix-assisted laser desorptionionization time-of-flight mass spectrometry (MALDI-TOF MS system.

  13. Isotope separation with improved selective ionization

    International Nuclear Information System (INIS)

    Method and apparatus for isotope separation by selective ionization of a desired isotope in an environment of plural isotopes without corresponding ionization of the other isotopes in the environment. The selective ionization is achieved through a three step excitation of atoms of the desired isotope in response to laser radiations applied to the environment. The transition for each step is selected to be less than one half the ionization potential for the isotopes to avoid two step nonselective ionization

  14. Design on the key measurement circuit for small displacement measurement system with position sensitive detector%基于位置敏感探测器的微位移测量关键电路设计

    Institute of Scientific and Technical Information of China (English)

    江孝国; 李洪; 杨兴林; 文龙; 石金水; 张开志; 王远

    2012-01-01

    位置敏感探测器PSD(Position Sensitive Detector PSD)具有位置分辨精度高(可达1~2μm)、输出实时性好(响应时间约几微秒)、系统简洁的特点,在位置探测及相关领域内获得了广泛的应用;但PSD的输出信号小,易受到电路噪声的影响,若要充分发挥其性能,则需要高精度、高稳定度、低噪声的测量电路。针对PSD这种较高的使用要求,通过对其等效模型的分析,找到了影响位置分辨精度的主要因素,并提出了一种新形式的测量电路,减少了测量电路级数,降低了电路的噪声以及测量电路内部的漂移,同时具有对位置测量非线性的校正功能。采用上述原理以S1880PSD建立的位置测量系统的位置分辨达到2~3μm。%Position sensitive detectors have been widely applied in the field of displacement measurement and relative field for its good characteristics such as high position resolution (1-2 μm),high speed response ( - μs),simplified system. The output current signal from a PSD is very small and contain noise. A low noise measurement circuit with a high precision and stability must be adopted in order to obtain the best performance. The main factor determining position resolution is discovered by analyzing the equivalent noise model of the measurement principle circuit . One kind of measurement circuit with low noise and good stability is developed . It features a few circuit stages and application of microprocessor. The non-linear error and inner offset or shift can be removed easily . The position displacement measurement system with PSD S1880 developed achieves position resolution of 2-3 μm.

  15. Ambient ionization mass spectrometry: A tutorial

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Min-Zong; Cheng, Sy-Chi; Cho, Yi-Tzu [Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Shiea, Jentaie, E-mail: jetea@fac.nsysu.edu.tw [Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Cancer Center, Kaohsiung Medical University, Kaohsiung, Taiwan (China)

    2011-09-19

    Highlights: {yields} Ambient ionization technique allows the direct analysis of sample surfaces with little or no sample pretreatment. {yields} We sort ambient ionization techniques into three main analytical strategies, direct ionization, direct desorption/ionization, and two-step ionization. {yields} The underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques are described and compared. - Abstract: Ambient ionization is a set of mass spectrometric ionization techniques performed under ambient conditions that allows the direct analysis of sample surfaces with little or no sample pretreatment. Using combinations of different types of sample introduction systems and ionization methods, several novel techniques have been developed over the last few years with many applications (e.g., food safety screening; detection of pharmaceuticals and drug abuse; monitoring of environmental pollutants; detection of explosives for antiterrorism and forensics; characterization of biological compounds for proteomics and metabolomics; molecular imaging analysis; and monitoring chemical and biochemical reactions). Electrospray ionization and atmospheric pressure chemical ionization are the two main ionization principles most commonly used in ambient ionization mass spectrometry. This tutorial paper provides a review of the publications related to ambient ionization techniques. We describe and compare the underlying principles of operation, ionization processes, detecting mass ranges, sensitivity, and representative applications of these techniques.

  16. Health effects of ionizing radiation

    International Nuclear Information System (INIS)

    Ionizing radiation is energy that travels through space as electromagnetic waves or a stream of fast moving particles. In the workplace, the sources of ionizing radiation are radioactive substances, nuclear power plants, x-ray machines and nuclear devices used in medicine, research and industry. Commonly encountered types of radiation are alpha particles, beta particles and gamma rays. Alpha particles have very little penetrating power and pose a risk only when the radioactive substance is deposited inside the body. Beta particles are more penetrating than alpha particles and can penetrate the outer body tissues causing damage to the skin and the eyes. Gamma rays are highly penetrating and can cause radiation damage to the whole body. The probability of radiation-induced disease depends on the accumulated amount of radiation dose. The main health effects of ionizing radiation are cancers in exposed persons and genetic disorders in the children, grandchildren and subsequent generations of the exposed parents. The fetus is highly sensitive to radiation-induced abnormalities. At high doses, radiation can cause cataracts in the eyes. There is no firm evidence that ionizing radiation causes premature aging. Radiation-induced sterility is highly unlikely for occupational doses. The data on the combined effect of ionizing radiation and other cancer-causing physical and chemical agents are inconclusive

  17. Models for multiphoton ionization processes

    International Nuclear Information System (INIS)

    Using the Fourier transform method, several analytical models for multiphoton processes have been developed, which emphasize the non-perturbative regime of C-C transitions. It was found that the population trapping of continuum-continuum (C-C) transitions can occurs under general conditions: for two continua with energy-dependent matrix elements, and for an infinite number of structureless continua with coupled bands. A above-threshold ionization model with two-frequency smooth pulses for hydrogenic atom was first proposed. This model give a simple form for analytical solutions if an ionization threshold is negligible. The results predict that (a) there is no trapping or saturation of the bound-continuum transition and that the ionization rate is independent of the redistribution among the continua for the C-C matrix element chosen; (b) There are peak switch in photoelectron energy spectra which depends on not only redistribution laser intensity, but also the pulses shape and their overlap in time, as well as the coupling between the bound state and continua; (c) peaks about the ionization energy in the photoelectron spectra are symmetric and only appear during the ionization process; (d) as the laser intensity is increased, the total angular photoelectrons distribution peak strongly in forward and backward direction of the redistribution laser polarization; and the minima of this distribution are not zero for higher laser intensity. The photon spectrum is also investigated

  18. Calibration of the position sensitive photomultiplier tube in spot dancing measurement%利用位置敏感型光电倍增管测量光斑漂移的定标方法

    Institute of Scientific and Technical Information of China (English)

    马晓珊; 朱文越; 饶瑞中

    2006-01-01

    将位置敏感光电倍增管(Position sensitive photomultiplier tube,简称PSPMT)引入大气湍流引起的漂移效应的实验测量中.基于PSPMT的工作原理,分析了探测器的放置位置对输出信号的影响,通过实验方法对PSPMT进行了位置定标和增益定标,获得了入射光束在探测面上的位置坐标.测量结果显示:在入射光斑尺度达到厘米量级同时具有较高强度的情况下,一次采样无法正确反映入射位置.因此以若干次测量的统计平均值表示入射位置,并综合考虑采集卡的最高采样率、采样点和信号频率等因素,分析了在漂移测量中如何选择进行统计平均的数据点的个数.

  19. Crystal structure determination of lithium diborate hydrate, LiB2O3(OH).H2O, from X-ray powder diffraction data collected with a curved position-sensitive detector

    International Nuclear Information System (INIS)

    The cystal structure of lithium diborate hydrate, LiB2O3(OH).H2O, has been solved ab initio and refined by the Rietveld method from powder diffraction data collected with a curved position-sensitive detector (INEL CPS120) using Debye-Scherrer diffraction geometry with monochromatic X-rays. In the first stage the indexing of the powder pattern was performed by the successive dichotomy method from data collected with a diffracometer using Bragg-Brentano geometry. The lattice parameters are a = 9.7984 (10), b = 8.2759 (7) and c = 9.6138 (8) A and the space group is Pnna. The structural model was obtained from direct methods and two difference Fourier maps. The Rietveld refinement converged to final crystal structure and profile indicators RF = 0.05, RB = 0.05, Rp = 0.03 and Rwp = 0.04. The structure consists of BO4 tetrahedra (T) and BO2(OH) triangles (Δ) sharing corners in order to form infinite chains along [010], with the shorthand notation 3 : ∞1(Δ + 2T). The particular linkage of the B3O3 rings leads to a new diborate anion [[B2O3(OH)]n-n], in which two tetrahedral B atoms have an occupation factor of 0.5. Li atoms, tetrahedrally surrounded by four O atoms, three belonging to separate chains and one to a water molecule maintain the cohesion of the structure. (orig.)

  20. Atomic Ionization by Electron Impact

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The field of atomic ionization by electron impact is several decades old. In that period of time, significant progress has been made in several aspects of the problem and we have learned a lot about ionizing collisions as a result of this work. Over the years, both the experiments and theories have improved dramatically. Experiments are now able to measure absolute triple differential cross sections for both in-plane or out-of-plane geometries. Theories have been getting better and better at including all the 3-body interactions in the wavefunction for the system. However, during the history of the field, experiment has been ahead of theory and it is just very recently that theory has started to catch up. In this paper, we will show that theory is now able to accurately predict the results of electron impact ionization of hydrogen for intermediate and higher energies.

  1. Theory of dissociative tunneling ionization

    CERN Document Server

    Svensmark, Jens; Madsen, Lars Bojer

    2016-01-01

    We present a theoretical study of the dissociative tunneling ionization process. Analytic expressions for the nuclear kinetic energy distribution of the ionization rates are derived. A particularly simple expression for the spectrum is found by using the Born-Oppenheimer (BO) approximation in conjunction with the reflection principle. These spectra are compared to exact non-BO ab initio spectra obtained through model calculations with a quantum mechanical treatment of both the electronic and nuclear degrees freedom. In the regime where the BO approximation is applicable imaging of the BO nuclear wave function is demonstrated to be possible through reverse use of the reflection principle, when accounting appropriately for the electronic ionization rate. A qualitative difference between the exact and BO wave functions in the asymptotic region of large electronic distances is shown. Additionally the behavior of the wave function across the turning line is seen to be reminiscent of light refraction. For weak fiel...

  2. Probing strong field ionization of solids with a Thomson parabola spectrometer

    Indian Academy of Sciences (India)

    Malay Dalui; T Madhu Trivikram; Ram Gopal; M Krishnamurthy

    2014-01-01

    Intense ultrashort laser pulses are known to generate high-density, high-temperature plasma from any substrate. Copious emission of hot electrons, from a solid substrate, results in strong electrostatic field that accelerates the ions with energies ranging from a few eV to MeV. Ion spectrometry from laser–plasma is convolved with multiple atomic systems, several charge states and a broad energy spread. Conventional mass spectrometric techniques have serious limitations to probe this ionization dynamics. We have developed an imaging ion spectrometer that measures charge/mass-resolved ion kinetic energies over the entire range. Microchannel plate (MCP) is used as the position-sensitive detector to perform online and single shot measurements. The wellresolved spectrum even for the low-energy ions, demonstrates that the spectral width is limited by the space-charge repulsion for the ions generated in the hot dense plasma.

  3. Radiative feedback from ionized gas

    CERN Document Server

    Glover, S C O

    2007-01-01

    H2 formation in metal-free gas occurs via the intermediate H- or H2+ ions. Destruction of these ions by photodissociation therefore serves to suppress H2 formation. In this paper, I highlight the fact that several processes that occur in ionized primordial gas produce photons energetic enough to photodissociate H- or H2+ and outline how to compute the photodissociation rates produced by a particular distribution of ionized gas. I also show that there are circumstances of interest, such as during the growth of HII regions around the first stars, in which this previously overlooked form of radiative feedback is of considerable importance.

  4. About AGN ionization echoes, thermal echoes, and ionization deficits in low redshift Lyman-alpha blobs

    CERN Document Server

    Schirmer, Mischa; Levenson, Nancy A; Fu, Hai; Davies, Rebecca L; Keel, William C; Torrey, Paul; Bennert, Vardha N; Pancoast, Anna; Turner, James E H

    2016-01-01

    We report the discovery of 14 Lyman-alpha blobs (LABs) at z~0.3, existing at least 4-7 billion years later in the Universe than all other LABs known. Their optical diameters are 20-70 kpc, and GALEX data imply Ly-alpha luminosities of (0.4-6.3)x10^43 erg/s. Contrary to high-z LABs, they live in low-density areas. They are ionized by AGN, suggesting that cold accretion streams as a power source must deplete between z=2 and z=0.3. We also show that transient AGN naturally explain the ionization deficits observed in many LABs: Their Ly-alpha and X-ray fluxes decorrelate below 10^6 years because of the delayed escape of resonantly scattering Ly-alpha photons. High Ly-alpha luminosities do not require currently powerful AGN, independent of obscuration. Chandra X-ray data reveal intrinsically weak AGN, confirming the luminous optical nebulae as impressive ionization echoes. For the first time, we also report mid-infrared thermal echoes from the dusty tori. We conclude that the AGN have faded by 3-4 orders of magnit...

  5. Radioprotection in the medical applications of the ionizing radiations

    International Nuclear Information System (INIS)

    This publication presents information about of the radiological safety in the medical application of the ionizing radiation compiled in 11 chapter and 1 annex. The first four chapters are principally dedicated to technical uses in radioprotection, the external and internal irradiation and the biological radiation effects. The radioprotection principles, the individual monitoring techniques, and the radioprotection systems are developed afterwards in the followings three chapters. The second half of the document is dedicated entirely to the medical practices using ionizing radiations, specially to the radioprotection aspects in radiodiagnosis, nuclear medicine and radiotherapy. The final chapter is dedicated to radiological accidents happened worldwide in the field of the medical applications of the ionizing radiations. The annex, about of the regulatory area, established a set of standards, laws, decrees and other force regulations in radiological safety, related in radiodiagnosis, nuclear medicine and radiotherapy

  6. Trends in resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    The author reviews the history of resonance ionization spectroscopy and then comments on the delineations of RIS with reference to many related laser processes. The substance of the paper deals with the trends in RIS and especially how the needs for sensitive analytical methods have overshadowed the orginal plan to study excited species. 9 refs., 1 fig

  7. Theory of resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    Resonance Ionization Spectroscopy (RIS) can be defined as a state selective detection process in which pulsed tunable lasers are used to promote transitions from the selected state of the atoms or molecules in question to higher states, one of which will be ionized by the absorption of another photon. The ability to make saturated RIS measurements opens up a wide variety of applications to both basic and applied research. In reviews of RIS the subject was treated generally, including the underlying photophysics applications, the ability to use it to count single atoms, and its applications to measurements in atomic and molecular physics. They view resonance ionization spectroscopy as a specific type of multiphoton ionization in which the goal is to make quantitative measurements of quantum-selected populations in atomic or molecular systems. This goal attained by requiring that the selective excitation steps be resonant in nature and involve only one- or two-photon (only one-photon if at all possible) absorption processes, thereby allowing the entire process to be carried to saturation without loss of spectroscopic selectivity due to laser power induced shifts or broadening

  8. Negative chemical ionization mass spectrometry

    International Nuclear Information System (INIS)

    This thesis describes some aspects of Negative Chemical Ionization (NCI) mass spectrometry. The reasons for the growing interest in NCI are: (i) to extend the basic knowledge of negative ions and their reactions in the gas phase; (ii) to investigate whether or not this knowledge of negative ions can be used successfully to elucidate the structure of molecules by mass spectrometry. (Auth.)

  9. Electronic measurements of ionization currents

    Energy Technology Data Exchange (ETDEWEB)

    Hutyra, F.; Knapp, K.; Gregor, J. (Tesla, Premysleni (Czechoslovakia). Vyzkumny Ustav Pristroju Jaderne Techniky)

    1982-02-01

    Measurements are discussed of very low currents from ionization chambers. The currents range between 10/sup -15/ and 10/sup -9/ A. Two methods are discussed. A description is given of a dynamic and a semiconductor electrometers. Both meters are parts of dosimetric instruments for monitoring the dose rate (NB 9201) and the neutron-gamma mixed radiation dose rate (NDK 601).

  10. Ionization Potentials for Isoelectronic Series.

    Science.gov (United States)

    Agmon, Noam

    1988-01-01

    Presents a quantitative treatment of ionization potentials of isoelectronic atoms. By looking at the single-electron view of calculating the total energy of an atom, trends in the screening and effective quantum number parameters are examined. Approaches the question of determining electron affinities. (CW)

  11. Transfer Ionization of Isocharge Sequence Ion and Ar Collisions

    Institute of Scientific and Technical Information of China (English)

    CaiXiaohong; YuDeyang; CaoZhurong; LuRongchun; YangWei; ShaoCaojie

    2003-01-01

    The study of multi-electron process has been a very active area of atomic physics research. The simultaneous electron emission and electron transfer is one of the most interesting two-electron processes in the study Of ionatom collisions, In last decade much experimental and theoretical attention has been devoted to the process, named transfer ionization (TI). This process is normally considered as the successive process of the single electron capture and the ionization of the second or more target electrons. The studies of transfer ionization are motivated by the understanding of the role of the electron correlation in ion-atom collisions which is of great interest in basic atomic physics and may provide important information for the applications both in astrophysics and fusion plasmas researches. Different authors have investigated the transfer ionization process by measuring the angular distribution of the emitted electrons. Up to now, the systematic study of the transfer ionization and the dependences of these processes on the collision parameters for the low energy ion-atom collisions are still rarely reported in the literatures.

  12. Thermophysics Characterization of Multiply Ionized Air Plasma Absorption of Laser Radiation

    Science.gov (United States)

    Wang, Ten-See; Rhodes, Robert; Turner, Jim (Technical Monitor)

    2002-01-01

    The impact of multiple ionization of air plasma on the inverse Bremsstrahlung absorption of laser radiation is investigated for air breathing laser propulsion. Thermochemical properties of multiply ionized air plasma species are computed for temperatures up to 200,000 deg K, using hydrogenic approximation of the electronic partition function; And those for neutral air molecules are also updated for temperatures up to 50,000 deg K, using available literature data. Three formulas for absorption are calculated and a general formula is recommended for multiple ionization absorption calculation. The plasma composition required for absorption calculation is obtained by increasing the degree of ionization sequentially, up to quadruple ionization, with a series of thermal equilibrium computations. The calculated second ionization absorption coefficient agrees reasonably well with that of available data. The importance of multiple ionization modeling is demonstrated with the finding that area under the quadruple ionization curve of absorption is found to be twice that of single ionization. The effort of this work is beneficial to the computational plasma aerodynamics modeling of laser lightcraft performance.

  13. Five-photon double ionization of helium

    Science.gov (United States)

    Li, Y.; Pindzola, M. S.; Colgan, J.

    2016-03-01

    A time-dependent close-coupling method is used to calculate the five-photon double ionization of He. It is found that the generalized cross section used in the past for two-photon double ionization of He cannot be extended to five-photon double ionization of He. Therefore only five-photon double ionization probabilities that depend on specific radiation field pulses can be calculated.

  14. Effects of ionization on silicate glasses

    International Nuclear Information System (INIS)

    This evaluation of radiation effects in silicate glasses caused by ionization is based on our own investigations, on material collected in our files (reports, articles, and notes), and on a computer literature search through recent issues of Physics Abstracts and Chemical Abstracts (and the apparently pertinent references which appeared). Some of our recent results, available heretofore only in internal correspondence, are presented in some detail. It is concluded that research into the behavior of silicate glasses generally will be required before the specific effects in the radioactive waste storage glasses can be properly understood and evaluated. Two particular neglected areas of investigation are targeted for immediate concern: a kinetic analysis of annealing data and the acquisition of data on effects of irradiation at controlled elevated temperatures

  15. Secondary Ionization Coefficient of Dielectric Electrode

    Science.gov (United States)

    Kashiwagi, Yasuhide; Suzuki, Susumu; Itoh, Haruo

    Experiments for observations and stabilization of discharge paths in several electrode systems are carried out aiming at precise measurement of the secondary ionization coefficient γ of MgO film electrode. The discharge chamber is filled with Ar gas. The waveforms of the applied voltage between the electrodes and the discharge current are measured with visual observation of the discharge light. Two MgO coated electrodes are placed so that they are facing each other. For these MgO electrodes, the discharge paths take a detour, not the shortest distance. Smaller prebreakdown current pulses are observed before the breakdown. After breakdown, discontinuous discharge current is observed. Therefore, it is prepared a glass tube surrounding the discharge area. As the result, the discharge paths take a straight perpendicular for the electrode surface, and the discharge is stabilized.

  16. Ionization potentials some variations, implications and applications

    CERN Document Server

    Ahrens, L H

    1983-01-01

    Ionization Potentials: Some Variations, Implications and Applications covers several aspects of ionization potential that is a highly significant parameter in controlling the properties of electric discharge. Comprised of 17 chapters, the book covers topic relevant to ionization potentials, such as properties, concepts, and applications, in order to understand and fully comprehend all aspects of ionization potential. The opening chapter is a review of ionization potentials and a discussion of trends and features. The succeeding chapters then tackle complex topics such as the s and p electrons;

  17. Biological effects of ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Blaylock, B.G. [SENES Oak Ridge Inc., Oak Ridge, TN (United States); Theodorakis, C.W.; Shugart, L.R. [Oak Ridge National Lab., Oak Ridge, TN (United States). Environmental Sciences Division

    1996-12-31

    Natural populations have always been exposed to background levels of ionizing radiation; however, with the event of the nuclear age, studies about the effects of higher-than-background levels of ionizing radiation on individuals or populations of organisms became important. Originally, concern was focused on survival after large, acute radiation doses, and numerous studies document the somatic and genetic effects of acute ionizing radiation. However, there is a growing realization that chronic long-term exposure to higher-than-background levels of environmental radiation is more likely than is large acute exposure. Less than 10% of the literature on ionizing radiation effects deals with chronic long-term effects, and very few studies involve natural populations. In 1977, mosquito fish, Gambusia affinis, were experimentally introduced into a 0,45 ha, decommissioned, radioactive waste pond where the measured dose at the sediment-water interface was 1,150 rad/year. One year later, the fecundity of the population had not changed significantly. Eighteen years later, studies of the fish showed an inverse correlation between DNA strand breakage and fecundity in the contaminated pond. More recent studies have provided evidence that genetic diversity of the fish has increased in the contaminated site. These fish also have a greater prevalence of certain DNA banding patterns. Individuals displaying these banding patterns have a higher fecundity and lower degree of DNA strand breakage than individuals with less common banding patterns. Gambusia affinis has apparently adapted to the high background radiation, successfully surviving for approximately 50 generations. 31 refs, 5 figs.

  18. The dosimetry of ionizing radiation

    CERN Document Server

    1990-01-01

    A continuation of the treatise The Dosimetry of Ionizing Radiation, Volume III builds upon the foundations of Volumes I and II and the tradition of the preceeding treatise Radiation Dosimetry. Volume III contains three comprehensive chapters on the applications of radiation dosimetry in particular research and medical settings, a chapter on unique and useful detectors, and two chapters on Monte Carlo techniques and their applications.

  19. Risks Associated with Ionizing Radiations

    International Nuclear Information System (INIS)

    Medical use of ionizing radiations implies certain risks which are widely balanced by their diagnostic and therapeutic benefits. Nevertheless, knowledge about these risks and how to diagnose and prevent them minimizes their disadvantages and optimizes the quality and safety of the method. This article describes the aspects related to skin dose (nonstochastic effects), the importance of dose limit, the physiopathology of biological damage and, finally, the prevention measures.

  20. Nuclear worker and ionizing radiation

    International Nuclear Information System (INIS)

    Research on medical X-ray exposure sheds light on the health effects expected for workers exposed to ionizing radiation. Factual information confirming this relationship and also demonstrating the need for reviewing permissible exposure levels for workers is given. Suggestions for more sophisticated health monitoring of workers exposed to hazardous technologies are made, and the question of occupational hazards which threaten the worker's family is raised

  1. Laser resonance ionization mass spectrometer

    International Nuclear Information System (INIS)

    The setup is elaborated for the trace detection of transuranium elements by the three-step laser resonance ionization combined with the time-of-flight mass spectrometry. The setup efficiency for detection of plutonium was measured to be about 0.5 centre dot 10-8 ion/atom, and its selectivity relative to atoms of another elements has the order of 1013 atom/atom

  2. Ionization of H Rydberg atoms

    International Nuclear Information System (INIS)

    Concepts from the theory of transient chaos are applied to study the classical ionization process of one dimensional model of kicked hydrogen Rydberg atoms. The phase-space dynamics is represented by a mapping T which is proved to be hyperbolic. The fraction of atoms not ionized after time t, PB(t), decays asymptotically according to PB(t)∼t-α with α ∼ 1.65. The observed algebraic decay, which seems to contradict the hyperbolicity of T, is explained by (i) the symbolic dynamics of T consists of a countably infinite number of symbols and (ii) the invariant manifold of phase-space points which never ionize is an anomalously scaling fractal. Therefore, the one-dimensional kicked hydrogen atom provides a counterexample to the hypothesis that algebraic decay marks regular dynamics, whereas hyperbolic systems decay exponentially. The algebraic decay is reproduced by an analytically solvable diffusion model which predicts α = 3/2. Replacing zero-width δ-kicks by smooth finite-width pulses, the mapping T is no longer completely hyperbolic, and a subset of phase-space is regular. For this case we observe that PB(t) shows a transition between two power-law decays with α ∼ 1.65 for short times and α ∼ 2.1 for long times where the effect of the regular domain is felt. (author)

  3. Theory of dissociative tunneling ionization

    Science.gov (United States)

    Svensmark, Jens; Tolstikhin, Oleg I.; Madsen, Lars Bojer

    2016-05-01

    We present a theoretical study of the dissociative tunneling ionization process. Analytic expressions for the nuclear kinetic energy distribution of the ionization rates are derived. A particularly simple expression for the spectrum is found by using the Born-Oppenheimer (BO) approximation in conjunction with the reflection principle. These spectra are compared to exact non-BO ab initio spectra obtained through model calculations with a quantum mechanical treatment of both the electronic and nuclear degrees of freedom. In the regime where the BO approximation is applicable, imaging of the BO nuclear wave function is demonstrated to be possible through reverse use of the reflection principle, when accounting appropriately for the electronic ionization rate. A qualitative difference between the exact and BO wave functions in the asymptotic region of large electronic distances is shown. Additionally, the behavior of the wave function across the turning line is seen to be reminiscent of light refraction. For weak fields, where the BO approximation does not apply, the weak-field asymptotic theory describes the spectrum accurately.

  4. Universal imaging: Dissociative ionization of polyatomic molecules, chemical dynamics beamline 9.0.2

    International Nuclear Information System (INIS)

    A third endstation was recently added to the Chemical Dynamics beamline, designed to exploit the high flux broadband undulator light for a range of studies of reactive scattering, photochemistry and photoionization processes using time-of-flight mass spectroscopy coupled with position-sensitive detection. Two molecular beam sources are fixed at right angles, with the undulator light, or laser beams, intersecting the molecular beams at 45 degrees. To date, beamline experiments have included a study of dissociative photoionization of a variety of molecules including N2O and SF6. In this mode, a single molecular beam source is used, with the tunable undulator light inducing, in SF6 for example, the process SF6 → SF6+ + e- → SF5+ + F + e-. The SF5+ ions are accelerated up the flight tube, mass selected and detected as a function of position on a phosphor screen viewed by a CCD camera. The position directly reveals the recoil speed (or translational energy release) and angular distribution for the dissociative ionization process. Furthermore, this measurement is obtained for all recoil speeds and angles simultaneously. Such detailed angular information has not previously been obtained for dissociative ionization processes; typically ion time-of-flight profiles are deconvoluted to yield rough insight into the angular distributions. The recorded image is actually a 2-dimensional projection of the nascent 3-dimensional velocity distribution, but established tomographic techniques enable the authors to reconstruct the 3-D distribution

  5. Energy expenditure for water molecule ionization by electron impact in weakly ionized plasma

    International Nuclear Information System (INIS)

    The energy balance of the water molecule ionization by a monoenergetic electron beam with the energy of primary electrons in the interval of 15-1000 eV has been calculated. The dependences of the ionization cost on the water ionization degree within the interval from 0 to 0.1 are obtained. The ionization cost is shown to increase with the ionization degree. In particular, for a primary electron energy of 1000 eV, it increases from 25.26 to 52.45 eV in the examined ionization degree interval

  6. Multiphoton ionization of uranium hexafluoride

    International Nuclear Information System (INIS)

    Multiphoton ionization (MPI) time-of-flight mass spectroscopy (TOFMS) and photoelectron spectroscopy (PES) studies of UF6 are reported using focused light from the Nd:YAG laser fundamental (λ=1064 nm) and its harmonics (λ=532, 355, or 266 nm), as well as other wavelengths provided by a tunable dye laser. The MPI mass spectra are dominated by the singly and multiply charged uranium ions rather than by the UF+x fragment ions, even at the lowest laser power densities at which signal could be detected. In general, the doubly charged uranium ion (U2+) intensity is much greater than that of the singly charged uranium ion (U+). For the case of the tunable dye laser experiments, the Un+ (n=1--4) wavelength dependence is relatively unstructured and does not show observable resonance enhancement at known atomic uranium excitation wavelengths. The MPI-PES studies reveal only very slow electrons (≤0.5 eV) for all wavelengths investigated. The dominance of the U2+ ion, the absence or very small intensities of UF+x (x=1--3) fragments, the unstructured wavelength dependence, and the preponderance of slow electrons all indicate that mechanisms may exist other than ionization of bare U atoms following the stepwise photodissociation of F atoms from the parent molecule. The data also argue against stepwise photodissociation of UF+x (x=5,6) ions. Neither of the traditional MPI mechanisms (''neutral ladder'' or the ''ionic ladder'') are believed to adequately describe the ionization phenomena observed. We propose that the multiphoton excitation of UF6 under these experimental conditions results in a highly excited molecule, superexcited UF6**

  7. XUV ionization of aligned molecules

    Energy Technology Data Exchange (ETDEWEB)

    Kelkensberg, F.; Siu, W.; Gademann, G. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Rouzee, A.; Vrakking, M. J. J. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Max-Born-Institut, Max-Born Strasse 2A, D-12489 Berlin (Germany); Johnsson, P. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Department of Physics, Lund University, Post Office Box 118, SE-221 00 Lund (Sweden); Lucchini, M. [Department of Physics, Politecnico di Milano, Istituto di Fotonica e Nanotecnologie CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Lucchese, R. R. [Department of Chemistry, Texas A and M University, College Station, Texas 77843-3255 (United States)

    2011-11-15

    New extreme-ultraviolet (XUV) light sources such as high-order-harmonic generation (HHG) and free-electron lasers (FELs), combined with laser-induced alignment techniques, enable novel methods for making molecular movies based on measuring molecular frame photoelectron angular distributions. Experiments are presented where CO{sub 2} molecules were impulsively aligned using a near-infrared laser and ionized using femtosecond XUV pulses obtained by HHG. Measured electron angular distributions reveal contributions from four orbitals and the onset of the influence of the molecular structure.

  8. Tunneling Ionization of Diatomic Molecules

    DEFF Research Database (Denmark)

    Svensmark, Jens Søren Sieg

    2016-01-01

    When a molecule is subject to a strong laser field, there is a probability that an electron can escape, even though the electrons are bound by a large potential barrier. This is possible because electrons are quantum mechanical in nature, and they are therefore able to tunnel through potential...... of tunneling ionizaion of molecules is presented and the results of numerical calculations are shown. One perhaps surprising result is, that the frequently used Born-Oppenheimer approximation breaks down for weak fields when describing tunneling ionization. An analytic theory applicable in the weak-field limit...

  9. Two-color, Doppler-free ionization of molecular hydrogen for isotopic analysis

    International Nuclear Information System (INIS)

    The authors present a three-step ionization scheme which will selectively ionize any isotopic variant. The projected isotopic selectivity is sufficient to detect tritium hydride at ambient concentrations without the need of mass analysis. The efficiency of the ionization process is high enough to allow work on small samples. The technique can be applied to many areas of research. The physical mechanisms which govern the conflicting objectives of both high isotopic selectivity and detection efficiency can be applied to any molecular system. (author)

  10. Multiphoton ionization with femtosecond laser pulses

    International Nuclear Information System (INIS)

    There are a number of reasons to use subpicosecond pulses in multiphoton ionization experiments. Pulses with shorter risetimes make it possible to study processes with higher rates before one runs into the problem of depletion of target atoms. Furthermore, the momentum of the electron does not change between the point of ionization and the detector if the pulse expires before the electron has time to sample the spatial inhomogeneity of the light intensity. This makes it possible to identify the intensity at which an electron was formed from the energy with which it reaches the detector. Yet another advantage is the fact that the primary ionization products are subject to the ionizing radiation for only a short amount of time, thus reducing the probability of sequential ionization as compared to direct processes. In this paper the experimental results on the multiphoton ionization of xenon with pulses of 100 fs, that were obtained during the preceding year at ENSTA, Palaiseau, will be presented

  11. Influence of multiple ionization in laser filamentation

    International Nuclear Information System (INIS)

    Laser filaments in gases result from the nonlinear balance between optical Kerr self-focusing and plasma generation in the single ionization limit, i.e., the pulse intensity is supposed to remain moderate enough (∼1014 W cm−2) to apply photo-ionization theories valid for an averaged ion charge less than unity. However, no theory has attempted so far to consider how an ionization model allowing a priori multiple-charged states could impact the standard filamentation scenario. Here, we discuss a multiple photo-ionization scheme that relies on probabilities assuming successive single-electron ionizations. We numerically show that a multiple ionization scheme can increase the clamping intensity, the peak electron density and supercontinuum generation in gases with high binding energy, e.g., helium. (paper)

  12. Spatially discontinuous ionization phenomenon in inhomogeneous soil

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    By using X-ray film imaging technology,a phenomenon of discontinuous ionization was observed in the inhomogeneous soil around the grounding electrode on which a surge voltage was applied.A simplified two-phase solid-gas model was built to study the electric field distribution in the soil to explain the discontinuous ionization phenomenon.Analysis showed the differences of the dielectric properties,the shapes and sizes of soil particles can cause discontinuous ionization in the soil.

  13. Quantum electrodynamic perspective on multiphoton ionization

    International Nuclear Information System (INIS)

    A fully quantum nonperturbative method is developed to describe multiphoton ionization in intense fields. It is shown that, treating the radiation field with quantum electrodynamic (QED) theory enables the authors to obtain the above-threshold ionization energy distribution spectrum in analytical form firstly. Moreover, in addition to the well-known semiclassical theory, the framework presented here, derived from a QED perspective, provides a new picture of the multiphoton ionization

  14. ATOMS INTERACTING WITH ELECTROMAGNETIC FIELDS, MULTIPHOTON IONIZATION

    OpenAIRE

    Mainfray, G

    1982-01-01

    The non linear interaction between an intense laser radiation and atoms leads to ionization through the absorption of N photons from the laser radiation via laser-induced virtual states. The multiphoton ionization rate varies as a function of the laser intensity I as IN. We discuss the two most important effects which govern multiphoton ionization processes : resonance effects and laser-coherence effects. In a moderate laser intensity range (107 - 109 W cm-2) corresponding to the two, three o...

  15. Time-of-flight ERD with a 200 mm2 Si3N4 window gas ionization chamber energy detector

    Science.gov (United States)

    Julin, Jaakko; Laitinen, Mikko; Sajavaara, Timo

    2014-08-01

    Low energy heavy ion elastic recoil detection work has been carried out in Jyväskylä since 2009 using home made timing detectors, a silicon energy detector and a timestamping data acquisition setup forming a time-of-flight-energy telescope. In order to improve the mass resolution of the setup a new energy detector was designed to replace the silicon solid state detector, which suffered from radiation damage and had poor resolution for heavy recoils. In this paper the construction and operation of an isobutane filled gas ionization chamber with a 14 × 14 mm2 100 nm thick silicon nitride window are described. In addition to greatly improved energy resolution for heavy ions, the detector is also able to detect hydrogen recoils simultaneously in the energy range of 100-1000 keV. Additionally the detector has position sensitivity by means of timing measurement, which can be performed without compromising the performance of the detector in any other way. The achieved position sensitivity improves the depth resolution near the surface.

  16. Ionizing radiation and orthopaedic prostheses

    Science.gov (United States)

    Rimnac, Clare M.; Kurtz, Steven M.

    2005-07-01

    Ultra high molecular weight polyethylene (UHMWPE) materials have been used successfully as one half of the bearing couple (against metallic alloys or ceramics) in total hip and total knee joint replacements for four decades. This review describes the impact of ionizing radiation (used for sterilization and for microstructural modification via crosslinking) on the performance of UHMWPE total joint replacement components. Gamma radiation sterilization in air leads to oxidative degradation of UHMWPE joint components that occurs during shelf-aging and also during in vivo use. Efforts to mitigate oxidative degradation of UHMWPE joint components include gamma radiation sterilization in inert barrier-packaging and processing treatments to reduce free radicals. Ionizing radiation (both gamma and electron-beam) has recently been used to form highly crosslinked UHMWPEs that have better adhesive and abrasive wear resistance than non-crosslinked UHMWPE, thereby potentially improving the long-term performance of total joint replacements. Along with increased wear resistance, however, there are deleterious changes to ductility and fracture resistance of UHMWPE, and an increased risk of fracture of these components remains a clinical concern.

  17. Biological effects of ionizing radiation

    International Nuclear Information System (INIS)

    It has been emphasised the importance of DNA as the main target for ionizing radiation, that can induce damage by its direct action on this molecule or by an indirect effect mediated by free-radicals generated by water radiolysis. Biological effects of ionizing radiation are influenced not only by the dose but also by the dose-rate and the radiation quality. Radiation induced damage, mainly DNA single and double strand breaks, is detected by molecular sensors which in turn trigger signalling cascades leading to cell cycle arrest to allow DNA repair or programmed cell death (apoptosis). Those effects related with cell death, named deterministic, exhibits a dose-threshold below which they are not observed. Acute radiation syndrome and radiological burns are examples of this kind of effects. Other radiation induced effects, called stochastic, are the consequence of cell transformation and do not exhibit a dose-threshold. This is the case of cancer induction and hereditary effects. The aim of this presentation is briefly describe the main aspects of deterministic and stochastic effects from the point of view of radiobiology and radio pathology. (author)

  18. K-shell ionization by antiprotons

    International Nuclear Information System (INIS)

    We present first calculations for the impact parameter dependence of K-shell ionization rates in anti pCu and in anti pAg collisions at various projectile energies. We show that the effect of the attractive Coulomb potential on the Rutherford trajectory and the anti-binding effect caused by the negative charge of the antiproton result in a considerable increase of the ionization probability. Total ionization cross-sections for proton and antiproton projectiles are compared with each other and with experimental ionization cross-sections for protons. (orig.)

  19. K-shell ionization by antiprotons

    Energy Technology Data Exchange (ETDEWEB)

    Mehler, G.; Mueller, B.; Greiner, W.; Soff, G.

    1987-08-01

    We present calculations for the impact-parameter dependence of K-shell ionization rates in p-bar-Cu and in p-bar-Ag collisions at various projectile energies. We show that the effect of the attractive Coulomb potential on the Rutherford trajectory and the antibinding effect caused by the negative charge of the antiproton result in a considerable increase of the ionization probability. Total ionization cross sections for proton and antiproton projectiles are compared with each other and with experimental ionization cross sections for protons.

  20. Development of dielectric-barrier-discharge ionization.

    Science.gov (United States)

    Guo, Cheng'an; Tang, Fei; Chen, Jin; Wang, Xiaohao; Zhang, Sichun; Zhang, Xinrong

    2015-03-01

    Dielectric-barrier-discharge ionization is an ambient-ionization technique. Since its first description in 2007, it has attracted much attention in such fields as biological analysis, food safety, mass-spectrometry imaging, forensic identification, and reaction monitoring for its advantages, e.g., low energy consumption, solvent-free method, and easy miniaturization. In this review a brief introduction to dielectric barrier discharge is provided, and then a detailed introduction to the dielectric-barrier-discharge-ionization technique is given, including instrumentation, applications, and mechanistic studies. Based on the summary of reported work, possible future uses of this type of ionization source are discussed at the end. PMID:25510973

  1. Tunneling Ionization Time Resolved by Backpropagation

    Science.gov (United States)

    Ni, Hongcheng; Saalmann, Ulf; Rost, Jan-Michael

    2016-07-01

    We determine the ionization time in tunneling ionization by an elliptically polarized light pulse relative to its maximum. This is achieved by a full quantum propagation of the electron wave function forward in time, followed by a classical backpropagation to identify tunneling parameters, in particular, the fraction of electrons that has tunneled out. We find that the ionization time is close to zero for single active electrons in helium and in hydrogen if the fraction of tunneled electrons is large. We expect our analysis to be essential to quantify ionization times for correlated electron motion.

  2. Ionization probes of molecular structure and chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, P.M. [State Univ. of New York, Stony Brook (United States)

    1993-12-01

    Various photoionization processes provide very sensitive probes for the detection and understanding of the spectra of molecules relevant to combustion processes. The detection of ionization can be selective by using resonant multiphoton ionization or by exploiting the fact that different molecules have different sets of ionization potentials. Therefore, the structure and dynamics of individual molecules can be studied even in a mixed sample. The authors are continuing to develop methods for the selective spectroscopic detection of molecules by ionization, and to use these methods for the study of some molecules of combustion interest.

  3. Non-sequential double ionization of molecules

    CERN Document Server

    Prauzner-Bechcicki, J S; Eckhardt, B; Zakrzewski, J; Prauzner-Bechcicki, Jakub S.; Sacha, Krzysztof; Eckhardt, Bruno; Zakrzewski, Jakub

    2004-01-01

    Double ionization of diatomic molecules by short linearly polarized laser pulses is analyzed. We consider the final stage of the ionization process, that is the decay of a highly excited two electron molecule, which is formed after re-scattering. The saddles of the effective adiabatic potential energy close to which simultaneous escape of electrons takes place are identified. Numerical simulations of the ionization of molecules show that the process can be dominated by either sequential or non-sequential events. In order to increase the ratio of non-sequential to sequential ionizations very short laser pulses should be applied.

  4. Evaluation of Background Ionization Radiation Level in some selected Dumpsites in Delta State, Nigeria

    OpenAIRE

    Avwiri, O Gregory; Emmanuel, O Esi

    2014-01-01

    This paper reports on the evaluation of background Ionization radiation level (BIR) in some selected Dumpsites in Uvwie, Udu and Ughelli North Local government area of Delta State, Nigeria. Background ionization radiation measurements were carried out in five Dumpsites. An in- situ measurement was done using a well calibrated nuclear radiation meters Radalert-100 and a geographical positioning system (GPS). Readings were taken once in a week for one month in ten different locations within eac...

  5. Influence of renormalization shielding on the electron-impact ionization process in dense partially ionized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Song, Mi-Young; Yoon, Jung-Sik [Plasma Technology Research Center, National Fusion Research Institute, 814-2 Osikdo-Dong, Gunsan-City, Jeollabuk-Do 573-540 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States); Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

    2015-04-15

    The renormalization shielding effects on the electron-impact ionization of hydrogen atom are investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it is found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed.

  6. Renormalization shielding effect on the electron-impact ionization process in dense partially ionized plasmas

    Science.gov (United States)

    Jung, Young-Dae

    2016-05-01

    The influence of renormalization shielding on the electron-impact ionization process is investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it is found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed.

  7. Influence of renormalization shielding on the electron-impact ionization process in dense partially ionized plasmas

    Science.gov (United States)

    Song, Mi-Young; Yoon, Jung-Sik; Jung, Young-Dae

    2015-04-01

    The renormalization shielding effects on the electron-impact ionization of hydrogen atom are investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it is found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed.

  8. Direct Analysis of Micro Area on Tooth Surface by Surface Desorption Atmospheric Pressure Chemical Ionization Mass Spectrometry%表面解吸常压化学电离质谱法直接分析牙齿微区表面

    Institute of Scientific and Technical Information of China (English)

    王姜; 李倩; 顾海巍; 郭晓暾; 杨水平; 王志豪

    2015-01-01

    A novel analytical platform based on a nanoliter needle for sampling and surface desorption atmos-pheric pressure chemistry ionization mass spectrometry ( SDAPCI-MS ) for analysis was developed for the di-rect, fast and micro-area analysis of different parts of a human tooth, including cavity, cavity edge, tooth cusp and tooth sulcus. The results showed that the mass spectra from the four sampling spots on the same tooth were different, and that SDAPCI-MS detected lactic acid, pyruvic acid, phenylacetic acid and propanoic acid were confirmed using tandem mass spectrometry( MS/MS) . Principal component analysis( PCA) of the mass spec-tral data successfully differentiated the different sampling spots, levels of tooth decay and levels of gum disease. Therefore, our nano-SDAPCI-MS approach provides a promising way for micro-area analysis with fast, minimal pretreatment sampling, enabling rapid, simple and reliable surface MS investigation.%采用纳升取样表面解吸常压化学电离质谱法( nano-SDAPCI-MS)结合主成分分析( PCA),建立了一种采用具有微米级针尖的金属取样针直接对龋齿不同部位取样并进行快速质谱分析的方法。数据分析结果表明,同一颗龋齿不同部位的质谱指纹谱图之间存在差异;在不需要样品预处理的前提下通过串联质谱快速测定了龋齿中的乳酸、丙酮酸、苯乙酸和丙酸等成分。采用PCA方法可较好地将龋齿病灶位置与邻近正常组织进行区分,也可对不同牙病及健康牙齿进行区分。本方法可方便地对牙齿进行直接微区分析,为鉴别牙齿疾病及观测治疗效果提供了一种快速、简单的方法,为生物体中微细部位的快速取样及直接质谱分析提供了一种可能的解决方案。

  9. Current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization

    CERN Document Server

    Stoyanov, Dimitar G

    2007-01-01

    The balances of particles and charges in the volume of parallel-plane ionization chamber are considered. Differential equations describing the distribution of current densities in the chamber volume are obtained. As a result of the differential equations solution an analytical form of the current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization in the volume is got.

  10. Current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization

    Energy Technology Data Exchange (ETDEWEB)

    Stoyanov, D G [Faculty of Engineering and Pedagogy in Sliven, Technical University of Sofia, 59, Bourgasko Shaussee Blvd, 8800 Sliven (Bulgaria)

    2007-08-15

    The balances of particles and charges in the volume of parallel-plane ionization chamber are considered. Differential equations describing the distribution of current densities in the chamber volume are obtained. As a result of the differential equations solution an analytical form of the current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization in the volume is obtained.

  11. Multiphoton ionization of uranium hexafluoride

    Science.gov (United States)

    Armstrong, D. P.; Harkins, D. A.; Compton, R. N.; Ding, D.

    1994-01-01

    Multiphoton ionization (MPI) time-of-flight mass spectroscopy (TOFMS) and photoelectron spectroscopy (PES) studies of UF6 are reported using focused light from the Nd:YAG laser fundamental (λ=1064 nm) and its harmonics (λ=532, 355, or 266 nm), as well as other wavelengths provided by a tunable dye laser. The MPI mass spectra are dominated by the singly and multiply charged uranium ions rather than by the UF+x fragment ions, even at the lowest laser power densities at which signal could be detected. In general, the doubly charged uranium ion (U2+) intensity is much greater than that of the singly charged uranium ion (U+). For the case of the tunable dye laser experiments, the Un+ (n=1-4) wavelength dependence is relatively unstructured and does not show observable resonance enhancement at known atomic uranium excitation wavelengths. The MPI-PES studies reveal only very slow electrons (≤0.5 eV) for all wavelengths investigated. The dominance of the U2+ ion, the absence or very small intensities of UF+x (x=1-3) fragments, the unstructured wavelength dependence, and the preponderance of slow electrons all indicate that mechanisms may exist other than ionization of bare U atoms following the stepwise photodissociation of F atoms from the parent molecule. The data also argue against stepwise photodissociation of UF+x (x=5,6) ions. Neither of the traditional MPI mechanisms (``neutral ladder'' or the ``ionic ladder'') are believed to adequately describe the ionization phenomena observed. We propose that the multiphoton excitation of UF6 under these experimental conditions results in a highly excited molecule, superexcited UF6**. The excitation of highly excited UF6** is proposed to be facilitated by the well known ``giant resonance,'' whose energy level lies in the range of 12-14 eV above that of ground state UF6. The highly excited molecule then primarily dissociates, via multiple channels, into Un+, UF+x, fluorine atoms, and ``slow'' electrons, although dissociation

  12. Social trust and ionizing radiation

    International Nuclear Information System (INIS)

    The linkages that exist between the environmental risks associated with nuclear energy production (both perceived and real) and the myriad of social and political issues and processes that influence social trust are a current issue in literature, but are not well explored, particularly for the Canadian context. This paper will examine one particular issue and its relationship with social trust: ionizing radiation and public health. Social trust is defined for this paper as including interpersonal trust, but having a much broader focus, extending to public trust in governments, institutions, corporations, and the power elite, and across whole societies. Of particular interest for the nuclear energy issue is how waning social trust may impact the functioning of democratic decision-making processes, particularly those associated with the siting of waste facilities. Social trust is a central issue in the management of environmental risks, particularly those related to high technology; its absence is seen as a major cause of intractable conflict in decisions related to nuclear power generation and waste disposal. Understanding the dynamics of social trust is important if a resolution is to be found to the nuclear waste management debate in Canada, that is, one that involves broad public, or social, support. For instance, what factors cause distrust to emerge, and when distrust emerges, what authorities do members of affected communities seek out for information and support? This paper begins to examine social trust in relation to human health and ionizing radiation, particularly low dose radiation from radioactive wastes resulting from uranium and radium processing activities in Port Hope, Ontario. These activities date back to the 1930s and are of great concern to community members. This paper looks at some of the roots of public concern, for example, scientific uncertainty around whether or not human health is compromised by exposure to low dose ionizing radiation

  13. Performance evaluation of multi sampling ionization chamber for heavy ion beams by comparison with GEANT4 simulation

    Science.gov (United States)

    Kanke, Yuki; Himac H093 Collaboration

    2014-09-01

    In high-energy heavy-ion accelerator facilities, multi sampling ionization chambers are often used for the identification of the atomic number Z by detecting the energy deposit in it. In the study at GSI, the picture of the escape of secondary electrons, δ rays, from the ionization chamber explains the experimental data of pulse-height resolution. If this picture is correct, the pulse-height resolution should depend on the effective area of the ionization chamber. The experiment have been performed at NIRS-HIMAC. The pulse-height resolutions of two ionization chambers with different effective area were compared by using a 400-MeV/u Ni beam and their fragments. The difference in the pulse-height resolutions was observed. By comparison with the GEANT4 simulation including the δ-rays emission, the performance of the ionization chamber have been evaluated.

  14. Ionization tube simmer current circuit

    Science.gov (United States)

    Steinkraus, Jr., Robert F.

    1994-01-01

    A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current.

  15. Ionization in antiproton-hydrogen collisions

    International Nuclear Information System (INIS)

    Employing the semiclassical approximation we calculate within the coupled-state formalism the ionization probability in antiproton-hydrogen (anti p+H) collisions. In particular we investigate the adiabatic ionization at the distance of closest approach in almost central collisions. Striking differences in the electron excitation probability compared with proton-hydrogen (p+H) collisions are predicted. (orig.)

  16. An ionization chamber with magnetic levitated electrodes

    CERN Document Server

    Kawaguchi, T

    1999-01-01

    A new type of ionization chamber which has magnetically levitated electrodes has been developed. The electrodes are supplied voltages for the repelling of ions by a battery which is also levitated with the electrodes. The characteristics of this ionization chamber are investigated in this paper.

  17. Strong Turbulence in Partially Ionized Plasmas

    DEFF Research Database (Denmark)

    Mikkelsen, Torben; Pécseli, Hans

    1980-01-01

    Experimental investigations of strong turbulence in partially ionized, low-β plasmas are reported. The observed spectra are interpreted by applying Taylor's hypothesis and related to turbulent fluctuations in the ionosphere.......Experimental investigations of strong turbulence in partially ionized, low-β plasmas are reported. The observed spectra are interpreted by applying Taylor's hypothesis and related to turbulent fluctuations in the ionosphere....

  18. Multicomponent transport in weakly ionized mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Giovangigli, V [CMAP, CNRS, Ecole Polytechnique, 91128 Palaiseau (France); Graille, B [Laboratoire de Mathematiques, Universite Paris-Sud, 91405, Orsay (France); Magin, T [Center for Turbulence Research, Stanford University, CA 94305 (United States); Massot, M, E-mail: vincent.giovangigli@polytechnique.f [Laboratoire EM2C, Ecole Centrale de Paris, 92295 Chatenay-Malabry (France)

    2010-06-15

    We discuss transport coefficients in weakly ionized mixtures. We investigate the situations of weak and strong magnetic fields as well as electron temperature nonequilibrium. We present in each regime the Boltzmann equations, examples of transport fluxes, the structure of transport linear systems and discuss their solution by efficient iterative techniques. Numerical simulations are presented for partially ionized high-temperature air.

  19. Study of the response of low pressure ionization chambers

    CERN Document Server

    Nebot Del Busto, E; Effinger, E; Grishin, V; Herranz Alvarez, J

    2012-01-01

    The Beam Loss Monitoring System (BLM) of the Large Hadron Collider (LHC) is based on parallel plate Ionization Chambers (IC) with active volume 1.5l and a nitrogen filling gas at 0.1 bar overpressure. At the largest loss locations, the ICs generate signals large enough to saturate the read-out electronics. A reduction of the active volume and filling pressure in the ICs would decrease the amount of charge collected in the electrodes, and so provide a higher saturation limit using the same electronics. This makes Little Ionization Chambers (LIC) with both reduced pressure and small active volume a good candidate for these high radiation areas. In this contribution we present measurements performed with several LIC monitors with reduced active volume and various filling pressures. These detectors were tested under various conditions with different beam setups, with standard LHC ICs used for calibration purposes

  20. The place of ionizing radiation in the cancer genesis

    International Nuclear Information System (INIS)

    Two different fields are considered: the field of high radiation doses (over 1 Sv), the contribution of ionizing radiation in the carcinogenesis is doubtless and the linear dose-effect relationship is unshakable. but this high doses area is rare ( major accident of civil nuclear, radiotherapy, war with use of nuclear weapon) and escapes to usual standards. The field of low dose irradiation (inferior to 100 MSv) we cannot assure the absence of carcinogen risk of ionizing radiation. We can tell that this risk is very low, very inferior to 5% by sievert accepted by the ICRP in conformance with the precautionary principle. In any case, very inferior to the risk in relation with the big causes of cancer that are addiction to smoking, (30% of cancers), food (30% of cancers), chronic diseases (11% of cancers) and hormonal processes (10% of cancers). (N.C.)

  1. Multiorbital tunneling ionization of the CO molecule

    CERN Document Server

    Wu, J; Kunitski, M; Meckel, M; Voss, S; Sann, H; Kim, H; Jahnke, T; Czasch, A; Dörner, R

    2012-01-01

    We coincidently measure the molecular frame photoelectron angular distribution and the ion sum-momentum distribution of single and double ionization of CO molecules by using circularly and elliptically polarized femtosecond laser pulses, respectively. The orientation dependent ionization rates for various kinetic energy releases allow us to individually identify the ionizations of multiple orbitals, ranging from the highest occupied to the next two lower-lying molecular orbitals for various channels observed in our experiments. Not only the emission of a single electron, but also the sequential tunneling dynamics of two electrons from multiple orbitals are traced step by step. Our results confirm that the shape of the ionizing orbitals determine the strong laser field tunneling ionization in the CO molecule, whereas the linear Stark effect plays a minor role.

  2. Ionization Scheme Development at the ISOLDE RILIS

    Science.gov (United States)

    Fedosseev, V. N.; Marsh, B. A.; Fedorov, D. V.; Köster, U.; Tengborn, E.

    2005-04-01

    The resonance ionization laser ion source (RILIS) of the ISOLDE on-line isotope separation facility is based on the method of laser step-wise resonance ionization of atoms in a hot metal cavity. The atomic selectivity of the RILIS complements the mass selection process of the ISOLDE separator magnets to provide beams of a chosen isotope with greatly reduced isobaric contamination. Using a system of dye lasers pumped by copper vapour lasers, ion beams of 24 elements have been generated at ISOLDE with ionization efficiencies in the range of 0.5-15%. As part of the ongoing RILIS development off-line resonance ionization spectroscopy studies carried out in 2003 and 2004 have determined the optimal three-step ionization schemes for scandium, antimony, dysprosium and yttrium.

  3. Ionization Scheme Development at the ISOLDE RILIS

    International Nuclear Information System (INIS)

    The resonance ionization laser ion source (RILIS) of the ISOLDE on-line isotope separation facility is based on the method of laser step-wise resonance ionization of atoms in a hot metal cavity. The atomic selectivity of the RILIS complements the mass selection process of the ISOLDE separator magnets to provide beams of a chosen isotope with greatly reduced isobaric contamination. Using a system of dye lasers pumped by copper vapour lasers, ion beams of 24 elements have been generated at ISOLDE with ionization efficiencies in the range of 0.5-15%. As part of the ongoing RILIS development off-line resonance ionization spectroscopy studies carried out in 2003 and 2004 have determined the optimal three-step ionization schemes for scandium, antimony, dysprosium and yttrium.

  4. Electron impact ionization and multiphoton ionization of doped superfluid helium droplets: A comparison.

    Science.gov (United States)

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-02-28

    We compare characteristics of electron impact ionization (EI) and multiphoton ionization (MPI) of doped superfluid helium droplets using the same droplet source. Selected dopant ion fragments from the two ionization schemes demonstrate different dependence on the doping pressure, which could be attributed to the different ionization mechanisms. While EI directly ionizes helium atoms in a droplet therefore has higher yields for bigger droplets (within a limited size range), MPI is insensitive to the helium in a droplet and is only dependent on the number of dopant molecules. The optimal timing of the ionization pulse also varies with the doping pressure, implying a velocity slip among different sized droplets. Calculations of the doping statistics and ionization probabilities qualitatively agree with the experimental data. Our results offer a word of caution in interpreting the pressure and timing dependence of superfluid helium droplets, and we also devise a scheme in achieving a high degree of doping while limiting the contribution of dopant clusters. PMID:26931697

  5. Field ionization of helium in a supersonic beam: Kinetic energy of neutral atoms and probability of their field ionization

    International Nuclear Information System (INIS)

    High detection efficiency combined with spatial resolution on a nm-scale makes the field ionization process a promising candidate for spatially resolved neutral particles detection. The effective cross-sectional area σeff can serve as a measure for the effectiveness of such a field ion detector. In the present contribution, we combine quantum-mechanical calculations of the field-modified electron density distribution near the tungsten tip surface and of the resulting local field distributions, performed using the functional integration method, with a classical treatment of the atom trajectories approaching the tip in order to calculate the σeff values for ionization of free He atoms over an apex of a tungsten field emitter tip. The calculated values are compared with experimental data for supersonic He atomic beams at two different temperatures 95 and 298 K.

  6. Ionization Cooling using Parametric Resonances

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rolland P.

    2008-06-07

    Ionization Cooling using Parametric Resonances was an SBIR project begun in July 2004 and ended in January 2008 with Muons, Inc., (Dr. Rolland Johnson, PI), and Thomas Jefferson National Accelerator Facility (JLab) (Dr. Yaroslav Derbenev, Subcontract PI). The project was to develop the theory and simulations of Parametric-resonance Ionization Cooling (PIC) so that it could be used to provide the extra transverse cooling needed for muon colliders in order to relax the requirements on the proton driver, reduce the site boundary radiation, and provide a better environment for experiments. During the course of the project, the theoretical understanding of PIC was developed and a final exposition is ready for publication. Workshops were sponsored by Muons, Inc. in May and September of 2007 that were devoted to the PIC technique. One outcome of the workshops was the interesting and somewhat unexpected realization that the beam emittances using the PIC technique can get small enough that space charge forces can be important. A parallel effort to develop our G4beamline simulation program to include space charge effects was initiated to address this problem. A method of compensating for chromatic aberrations by employing synchrotron motion was developed and simulated. A method of compensating for spherical aberrations using beamline symmetry was also developed and simulated. Different optics designs have been developed using the OptiM program in preparation for applying our G4beamline simulation program, which contains all the power of the Geant4 toolkit. However, no PIC channel design that has been developed has had the desired cooling performance when subjected to the complete G4beamline simulation program. This is believed to be the consequence of the difficulties of correcting the aberrations associated with the naturally large beam angles and beam sizes of the PIC method that are exacerbated by the fringe fields of the rather complicated channel designs that have been

  7. Electrospray ionization and matrix assisted laser desorption/ionization mass spectrometry: powerful analytical tools in recombinant protein chemistry

    DEFF Research Database (Denmark)

    Andersen, Jens S.; Svensson, B; Roepstorff, P

    1996-01-01

    Electrospray ionization and matrix assisted laser desorption/ionization are effective ionization methods for mass spectrometry of biomolecules. Here we describe the capabilities of these methods for peptide and protein characterization in biotechnology. An integrated analytical strategy is presen......Electrospray ionization and matrix assisted laser desorption/ionization are effective ionization methods for mass spectrometry of biomolecules. Here we describe the capabilities of these methods for peptide and protein characterization in biotechnology. An integrated analytical strategy...

  8. Photoelectron angular distributions from two-photon ionization of atoms near ionization threshold

    Institute of Scientific and Technical Information of China (English)

    Lihua Bai; Tingting Cui; Yuheng Liu; Yan Wang; Dongmei Deng; Jihui Tao

    2011-01-01

    @@ Photoelectron angular distributions (PADs) from two-photon ionization of atoms in linearly polarized strong laser fields are obtained in accordance with the nonperturbative quantum scattering theory. We also study the influence of laser wavelength on PADs. For two-photon ionization very close to the ionization threshold, most of the ionized electrons are vertically ejected to the laser polarization. PADs from twophoton ionization of atoms are determined by the second order generalized phased Bessel function at which the ponderomotive parameter plays a key role. In terms of dependence of PADs on laser wavelength,corresponding variations for the ponderomotive parameter are demonstrated.%Photoelectron angular distributions (PADs) from two-photon ionization of atoms in linearly polarized strong laser fields are obtained in accordance with the nonperturbative quantum scattering theory. We also study the influence of laser wavelength on PADs. For two-photon ionization very close to the ionization threshold, most of the ionized electrons are vertically ejected to the laser polarization. PADs from twophoton ionization of atoms are determined by the second order generalized phased Bessel function at which the ponderomotive parameter plays a key role. In terms of dependence of PADs on laser wavelength,corresponding variations for the ponderomotive parameter are demonstrated.

  9. Non-equilibrium ionized blast wave

    Science.gov (United States)

    Wu, S. T.

    1974-01-01

    The structure of a cylindrical blast wave with ionization at non-LTE conditions was calculated using equations previously developed by Wu and Fu (1970). The degree of ionization was predicted by a modified Saha equation. Temperature profiles show that the temperature at non-LTE conditions is lower than at LTE near the shock front. This corresponds to a higher degree of ionization for the non-LTE limit, which indicates that the neutral gas absorption is much more efficient at non-LTE than at the LTE limit. The decaying velocity under non-LTE is approximately 15% less than under LTE.

  10. Ion and electron impact ionization cross sections

    International Nuclear Information System (INIS)

    Several current projects are described in which cross sections of interest to radiation physics are being measured. These include total and multiple ionization cross sections for protons on several gases covering a wide energy range, the measurement of cross sections differential in the angle and energy of ejected electrons for several gases including water vapor, and a review of proton ionization data. The work on water vapor has also been extended to electron and neutral hydrogen impact. A brief discussion is also given of some systematics of ionization cross sections. 13 references

  11. Ionized Gas in the Smith Cloud

    OpenAIRE

    Hill, Alex S.; Haffner, L. Matthew; Reynolds, Ronald J.

    2009-01-01

    We present WHAM observations of Halpha, [N II], and [S II] in the Smith Cloud. A map of Halpha emission from the cloud shows ionized gas coincident with the brightest H I emission, but nearly-as-bright Halpha in some regions with faint H I. The ionized mass of the cloud is at least as large as the neutral mass, > 10^6 M_sun. Ionized gas in the core of the Smith Cloud has an electron temperature 6000 K < T < 16000 K. The observed ratio [N II] / Halpha = 0.39 \\pm 0.09 shows that the cloud has a...

  12. Ionizing photon budget: constraints from galaxies

    Science.gov (United States)

    Östlin, Göran

    2015-08-01

    I will discuss the the production and propagation of ionizing photons in galaxies. Multi wavelength HST imaging and spectroscopy of local starbursts, including candidate Lyman continuum leakers, from the UV to the i-band plus Halpha and Hbeta are used to investigate where ionizing protons are produced and absorbed. We add IFU data, e.g. from MUSE, to further constrain the optical depth to Lyman continuum photons. I will further discuss rest frame UV observations of galaxies at higher redshifts, and their implications for the ionizing photon budget.

  13. Re-ionization and decaying dark matter

    Science.gov (United States)

    Dodelson, Scott; Jubas, Jay M.

    1991-01-01

    Gunn-Peterson tests suggest that the Universe was reionized after the standard recombination epoch. A systematic treatment is presented of the ionization process by deriving the Boltzmann equations appropriate to this regime. A compact solution for the photon spectrum is found in terms of the ionization ratio. These equations are then solved numerically for the Decaying Dark Matter scenario, wherein neutrinos with mass of order 30 eV radiatively decay producing photons which ionize the intergalactic medium. It was found that the neutrino mass and lifetime are severely constrained by Gunn-Peterson tests, observations of the diffuse photon spectrum in the ultraviolet regime, and the Hubble parameter.

  14. Thermochromic behaviors and ionization potentials of organopolysilanes

    Science.gov (United States)

    Yokoyama, Kenji; Yokoyama, Masaaki

    1989-04-01

    Ionization potentials of organopolysilanes with different kinds of substituents were evaluated from the low energy photo-electron emission measurements in air. An aryl-substituted organopolysilane capable of σ - π mixing between Si backbone σ and side-group π electrons gave smaller ionization potential by about 0.1˜0.15 eV compared with alkyl-substituted organopolysilanes. The value of ionization potentials in some alkyl-substituted organopolysilanes which showed thermochromic behaviors was found to vary substantially with thermally induced reversible changes in polymer backbone conformation, indicating that the effective conjugation length of σ electrons decreases above the thermochromic transition temperature.

  15. Intense-field multiphoton ionization of helium

    International Nuclear Information System (INIS)

    The dynamics of multiphoton ionization of helium are investigated through numerical integration of the two-electron time-dependent Schroedinger equation. Using this work as a benchmark, a new single-active-electron model is introduced that gives agreement with He ionization rates to within a few per cent on average, and gives good agreement with He harmonic generation spectra over a laser intensity range of 0.5x1014 to 8.0x1014 W cm-2, and frequencies corresponding to four- and five-photon ionization. (author). Letter-to-the-editor

  16. Electron impact single ionization of copper

    Indian Academy of Sciences (India)

    L K Jha; O P Roy; B N Roy

    2000-09-01

    Electron impact single ionization cross sections of copper have been calculated in the binary encounter approximation using accurate expression for as given by Vriens and Hartree–Fock momentum distribution for the target electron. The BEA calculation based on the usual procedure does not show satisfactory agreement with experiment in this case but a striking modification is found to be successful in explaining the experimental observations. The discrepancy is linked with the ionization of the 310 electrons and probably effective single ionization does not take place from 3 shell of copper leading to smaller values of experimental cross sections.

  17. Biological Effects of Ionizing Radiation

    International Nuclear Information System (INIS)

    The aim of this work is to verify the existence of the adaptive response phenomenon induced by low doses of ionizing radiation in living cells.A wild-type yeast Saccharomyces cerevisiae (Baker's yeast) was chosen as the biological target.As a parameter to quantify the sensibility of the target to radiation, the Lethal Dose 50 (LD50 ) was observed. In our experimental condition a value of (60 ± 1) Gy was measured for LD50 with Dose Rate of (0.44 ± 0.03) Gy/min. The method employed to show up the adaptive response phenomenon consisted in exposing the sample to low ''conditioning'' doses, which would initiate these mechanisms. Later the samples with and without conditioning were exposed to higher ''challenging'' doses (such as LD50), and the surviving fractions were compared. In order to maximize the differences, the doses and the time between irradiations were varied. The best results were obtained with both a conditioning dose of (0.44 ± 0.03) Gy and a waiting time of 2 hs until the application of the challenging dose. Following this procedures the 80% of the conditioned samples has survived, after receiving the application of the LD50. The adaptive response phenomenon was also verified for a wide range of challenging doses

  18. Mobility of Proteins in Porous Substrates under Electrospray Ionization Conditions.

    Science.gov (United States)

    Hu, Bin; Yao, Zhong-Ping

    2016-06-01

    Proteins are important substances in living organisms and characterization of proteins is an indispensible part for protein study. Analysis of proteins using electrospray ionization-mass spectrometry (ESI-MS) with porous substrates was investigated in this study. The results revealed that the ionization process had two stages. At the first stage, mobility and resulting spectra of proteins were similar to those obtained with conventional capillary-based ESI-MS. At the second stage, hydrophobic-hydrophobic interactions between proteins and the tip surfaces played an important role in mobility and detectability of protein ions, which were size and shape dependent, and a linear relationship could be found between the peak area of selected ion chromatogram and the cross section of protein ions. Preparative separation of proteins could be achieved by collecting the proteins remained on the porous substrates. These results led us to propose that electrospray ionization from porous substrates offer a potential approach for analysis of proteins and investigation of protein structures and conformations. PMID:27149434

  19. Nightside Martian Ionosphere Produced by Electron Impact Ionization

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi-Teng; LI Lei

    2009-01-01

    Based on the Martian magnetic field model established by magnetohydrodynamics simulation,we determine the possible precipitation areas of the solar wind electron in the nightside Martian atmosphere,and analyze the electron impact ionization to estimate the height of the nightside Martian ionospheric peak and the electron density profile using the energy flux analysis method.The influences of the single electron energy,electron energy density and ionization efficiency on the altitude of the ionospheric peak and the electron density profile axe also investigated.Our results show that the solar wind electron moves along the V-shaped solar wind magnetic field lines,to precipitate into the Martian atmosphere.Due to the crustal magnetic field,the precipitation regions on the nightside are quite narrow and unstable.The impact ionization happens at the altitude of 130-500km,and the height of the ionospheric peak is around 170kin,with a peak electron density of 3.0×103 cm-3.The simulation results are consistent with the results from Mars 4/5 and Viking occultation measurements.

  20. Towards a Carbon Nanotube Ionization Source for Planetary Atmosphere Exploration

    Science.gov (United States)

    Oza, A. V.; Leblanc, F.; Berthelier, J. J.; Becker, J.; Coulomb, R.; Gilbert, P.; Hong, N. T.; Lee, S.; Vettier, L.

    2015-12-01

    The characterization of planetary exospheres today, relies on the development of a highly efficient ionization source, due to the scant neutral molecules (n atmospheres provide insight on to physical processes known to occur such as: space weathering, magneto-atmosphere interactions, as well as atmospheric escape mechanisms, all of which are being heavily investigated via current 3D Monte Carlo simulations (Turc et al. 2014, Leblanc et al. 2016 in prep) at LATMOS. Validation of these studies will rely on in-situ observations in the coming decades. Neutral detection strongly depends on electron-impact ionization which via conventional cathode-sources, such as thermal filaments (heated up to 2000 K), may only produce the target ionization essential for energy-measurements with large power consumption. Carbon nanotubes (CNTs) however are ideal low-power, cold cathodes, when subject to moderate electric fields (E ~ 1 MV / m). We present our current device, a small CNT chip, of emission area 15 mm2, emitting electrons that pass through an anode grid and subsequent electrostatic analyzer. The device currently extracts hundreds of µAmperes with applied external voltages ~ -150 Volts, approaching minimum power consumption plasma sputtering the icy regolith with heavy ions and electrons (keV < E < MeV), producing predominately molecular oxygen (Johnson et al. 2002).

  1. The critical ionization velocity - a bibliography

    International Nuclear Information System (INIS)

    A list of all relevant contributions, known to the authors, concerning the critical ionization velocity phenomena is presented. The contributions are classified and described in a few sentences. (Authors)

  2. Multiple ionization of atoms by ion impact

    International Nuclear Information System (INIS)

    In order to model the energy deposition of fast ions as they slow down in gaseous media, information about the ionization occurring in collisions between ions and target atoms/molecules is required. Our measurements of doubly differential electron emission cross sections provide detailed information about the ionization process but do not provide any information about the final states of the target. They also do not distinguish between the emission of one or more target electrons in a single collision. It is important to know the relative importance of multiple-, with respect to single-, target ionization in order to accurately model the energy deposition. To date, multiple ionization of He, Ne, Ar, Kr, and Xe targets has been studied. Primarily, H and He ions were used, although some data for heavier ions (C,N and O) have also been obtained

  3. Electron impact ionization of large krypton clusters

    Institute of Scientific and Technical Information of China (English)

    Li Shao-Hui; Li Ru-Xin; Ni Guo-Quan; Xu Zhi-Zhan

    2004-01-01

    We show that the detection of ionization of very large van der Waals clusters in a pulsed jet or a beam can be realized by using a fast ion gauge. Rapid positive feedback electron impact ionization and fragmentation processes,which are initially ignited by electron impact ionization of the krypton clusters with the electron current of the ion gauge, result in the appearance of a progressional oscillation-like ion spectrum, or just of a single fast event under critical conditions. Each line in the spectrum represents a correlated explosion or avalanche ionization of the clusters.The phenomena have been analysed qualitatively along with a Rayleigh scattering experiment of the corresponding cluster jet.

  4. Classification of the LHC BLM Ionization Chamber

    CERN Document Server

    Stockner, M; Fabjan, Christian Wolfgang; Holzer, E B; Kramer, Daniel

    2008-01-01

    The LHC beam loss monitoring (BLM) system must prevent the super conducting magnets from quenching and protect the machine components from damage. The main monitor type is an ionization chamber. About 4000 of them will be installed around the ring. The lost beam particles initiate hadronic showers through the magnets and other machine components. These shower particles are measured by the monitors installed on the outside of the accelerator equipment. For the calibration of the BLM system the signal response of the ionization chamber is simulated in GEANT4 for all relevant particle types and energies (keV to TeV range). For validation, the simulations are compared to measurements using protons, neutrons, photons and mixed radiation fields at various energies and intensities. This paper will focus on the signal response of the ionization chamber to various particle types and energies including space charge effects at high ionization densities.

  5. High-Temperature Ionization in Protoplanetary Disks

    CERN Document Server

    Desch, Steven J

    2015-01-01

    We calculate the abundances of electrons and ions in the hot (> 500 K), dusty parts of protoplanetary disks, treating for the first time the effects of thermionic and ion emission from the dust grains. High-temperature ionization modeling has involved simply assuming that alkali elements such as potassium occur as gas-phase atoms and are collisionally ionized following the Saha equation. We show that the Saha equation often does not hold, because free charges are produced by thermionic and ion emission and destroyed when they stick to grain surfaces. This means the ionization state depends not on the first ionization potential of the alkali atoms, but rather on the grains' work functions. The charged species' abundances typically rise abruptly above about 800 K, with little qualitative dependence on the work function, gas density, or dust-to-gas mass ratio. Applying our results, we find that protoplanetary disks' dead zone, where high diffusivities stifle magnetorotational turbulence, has its inner edge locat...

  6. Ionization applications in food industry - Generalities

    International Nuclear Information System (INIS)

    This paper outlines different applications of the ionization in food treatments and their purposes. Irradiation of food with low doses (below 1 kgy) is used for germination inhibition, insects sterilization, disinfestation and senescence delays. Applications with medium doses (from 1 to 10 kgy) are used for extension of shelf life, elimination of pathogenic microorganisms and improving technological properties. Applications with high doses (superior to 10 Kgy) are used for food sterilization, only in some specific cases. Necessary doses in various applications of food ionization are given as well as minimal doses for food sterilization. In some cases where treatment of food by only ionization do not permit to attain the fixed object, ionizing treatment is combined with an other type of treatment as: refrigeration, heat treatments, packing, dehydration and chemical treatments. 3 tabs., 5 refs. (F.M.)

  7. Ionization energy of acetone by vacuum ultraviolet mass-analyzed threshold ionization spectrometry

    International Nuclear Information System (INIS)

    Mass-analyzed threshold ionization (MATI) time-of-flight mass spectrometer using coherent vacuum ultraviolet (VUV) laser generated by four-wave difference frequency mixing (FWDFM) in Kr has been constructed and utilized to obtain the accurate ionization energy of acetone. From the MATI onsets measured from various applied pulsed fields, the ionization energy to the ionic ground state of acetone has been determined to be 9.7074 ± 0.0019 eV.

  8. A correction to Birks' Law in liquid argon ionization chamber simulations for highly ionizing particles

    International Nuclear Information System (INIS)

    We present a study of the performance of Birks' Law in liquid argon ionization chamber simulations as applied to highly ionizing particles, such as particles with multiple electric charges or with magnetic charge. We used Birks' Law to model recombination effects in a GEANT4 simulation of heavy ions in a liquid argon calorimeter. We then compared the simulation to published heavy-ion data to extract a highly ionizing particle correction to Birks' Law.

  9. Positron impact ionization of atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Jones, G.O.; Charlton, M.; Slevin, J.; Laricchia, G.; Kover, A.; Poulsen, M.R.; Chormaic, S.N. (University Coll., London (United Kingdom). Dept. of Physics and Astronomy)

    1993-08-14

    Ionization cross sections for positrons impacting on atomic hydrogen have been measured for kinetic energies in the range 15-700 eV. This has been done in a crossed-beam geometry where a magnetically guided positron beam intersects a hydrogen gas jet emanating from a radio frequency discharge tube. Electron impact ionization cross sections were also measured with the same apparatus thus facilitating comparison with, and normalization to, published results. (author).

  10. Positron impact ionization of atomic hydrogen

    International Nuclear Information System (INIS)

    Ionization cross sections for positrons impacting on atomic hydrogen have been measured for kinetic energies in the range 15-700 eV. This has been done in a crossed-beam geometry where a magnetically guided positron beam intersects a hydrogen gas jet emanating from a radio frequency discharge tube. Electron impact ionization cross sections were also measured with the same apparatus thus facilitating comparison with, and normalization to, published results. (author)

  11. Inner-shell ionization and stopping power

    International Nuclear Information System (INIS)

    For better understanding of various aspects in stopping phenomena such as Z13-dependence, shell correction, geometrical effect, direction dependence etc., it seems to be helpful to examine theoretically and experimentally the elementary processes which include plasmon excitation, single electron excitation and inner-shell excitation/ionization. In the present, impact-parameter dependent stopping power is discussed in connection with inner-shell ionization

  12. The warm ionized medium in spiral galaxies

    CERN Document Server

    Haffner, L M; Beckman, J E; Wood, K; Slavin, J D; Giammanco, C; Madsen, G J; Zurita, A; Reynolds, R J

    2009-01-01

    This article reviews observations and models of the diffuse ionized gas that permeates the disk and halo of our Galaxy and others. It was inspired by a series of invited talks presented during an afternoon scientific session of the 65th birthday celebration for Professor Carl Heiles held at Arecibo Observatory in August 2004. This review is in recognition of Carl's long standing interest in and advocacy for studies of the ionized as well as the neutral components of the interstellar medium.

  13. Fundamental studies of molecular multiphoton ionization

    International Nuclear Information System (INIS)

    For several years the authors have performed fundamental studies of molecular multiphoton ionization (MPI). We will present a potpourri of techniques and results chosen to illustrate the interesting complexities of molecular MPI. Techniques used include time-of-flight mass spectroscopy, photoelectron spectroscopy, supersonic expansion cooling of molecular beams, harmonic generation, two-color laser MPI, and polarization spectroscopy. Whenever possible the relevance of these results to resonance ionization spectroscopy schemes will be delineated. 23 references, 10 figures

  14. Drift waves in a weakly ionized plasma

    DEFF Research Database (Denmark)

    Popovic, M.; Melchior, H.

    1968-01-01

    A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated.......A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated....

  15. How periodic orbit bifurcations drive multiphoton ionization

    OpenAIRE

    Huang, S.; Chandre, C; Uzer, T.

    2006-01-01

    The multiphoton ionization of hydrogen by a strong bichromatic microwave field is a complex process prototypical for atomic control research. Periodic orbit analysis captures this complexity: Through the stability of periodic orbits we can match qualitatively the variation of experimental ionization rates with a control parameter, the relative phase between the two modes of the field. Moreover, an empirical formula reproduces quantum simulations to a high degree of accuracy. This quantitative...

  16. Cancer risk from low doses of ionizing radiation

    International Nuclear Information System (INIS)

    The aim of the study was to estimate cancer risk from small doses of ionizing radiation from various sources, including both external and internal exposure. The types of radiation included alpha, gamma, and neutron radiation. A nationwide follow-up study covering the years up to 1992 revealed no significant association between fallout from the Chernobyl accident and incidence of childhood leukemia. An excess of eight cases or more per year could be excluded. However, some indication of an increase was evident in the most heavily affected areas. Furthermore, the risk estimates were in accordance with those reported from Hiroshima and Nagasaki, although the confidence intervals were wide. (282 refs.)

  17. Cancer risk from low doses of ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Auvinen, A.

    1997-06-01

    The aim of the study was to estimate cancer risk from small doses of ionizing radiation from various sources, including both external and internal exposure. The types of radiation included alpha, gamma, and neutron radiation. A nationwide follow-up study covering the years up to 1992 revealed no significant association between fallout from the Chernobyl accident and incidence of childhood leukemia. An excess of eight cases or more per year could be excluded. However, some indication of an increase was evident in the most heavily affected areas. Furthermore, the risk estimates were in accordance with those reported from Hiroshima and Nagasaki, although the confidence intervals were wide. (282 refs.).

  18. The oncogenic action of ionizing radiation on rat skin

    Energy Technology Data Exchange (ETDEWEB)

    Burns, F.J.

    1991-01-01

    Progress has occurred in several areas corresponding to the specific aims of the proposal: (1) Progression and multiple events in radiation carcinogenesis of rat skin as a function of LET; (2) cell cycle kinetics of irradiated rat epidermis as determined by double labeling and double emulsion autoradiography; (3) oncogene activation detected by in situ hybridization in radiation-induced rat skin tumors; (4) amplification of the c-myc oncogene in radiation-induced rat skin tumors as a function of LET; and (5) transformation of rat skin keratinocytes by ionizing radiation in combination with c-Ki-ras and c-myc oncogenes. 111 refs., 13 figs., 12 tabs.

  19. Two-photon ionization thresholds of matrix-assisted laser desorption/ionization matrix clusters.

    Science.gov (United States)

    Lin, Q; Knochenmuss, R

    2001-01-01

    Direct two-photon ionization of the matrix has been considered a likely primary ionization mechanism in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. This mechanism requires that the vertical ionization threshold of matrix materials be below twice the laser photon energy. Because dimers and larger aggregates may be numerous in the early stages of the MALDI plume expansion, their ionization thresholds are important as well. We have used two-color two-photon ionization to determine the ionization thresholds of jet cooled clusters of an important matrix, 2,5-dihydroxy benzoic acid (DHB), and mixed clusters with the thermal decomposition product of DHB, hydroquinone. The thresholds of the clusters were reduced by only a few tenths of an eV compared to the monomers, to an apparent limit of 7.82 eV for pure DHB clusters. None of the investigated clusters can be directly ionized by two nitrogen laser photons (7.36 eV), and the ionization efficiency at the thresholds is low. PMID:11507754

  20. Commercial applications of food ionization in France

    International Nuclear Information System (INIS)

    Due to the long history of nuclear energy in France, French public is not frightened by nuclear applications in its everyday life. The first industrial initiative on food ionization dates back to 1956. In 1980, the Joint Expert Committee on Food Ionization concluded that food ionization up to a certain maximum dose presented neither toxicological nor nutritional hazard. This opened the new era for the industrial development. But in 1988, a draft directive to harmonize national legislations was issued by the Commission of European Communities. This stopped many industrial initiatives due to uncertainty. It is estimated that nearly 14,000 tons of various food items have been ionized in France in 1991. About 40% are spices, followed by dry fruit, vegetables, and deboned poultry meat. Most of the present applications are intended to eliminate microorganisms. In 1992, 8 industrial facilities were in operation, mostly using gamma sources. Local research associations were founded to promote food ionization. Food ionization development in the past 30 years has been rapid and important, but the future of this process depends on the European harmonization of legislations. (K.I.)

  1. New standards for ionizing radiation measurements

    International Nuclear Information System (INIS)

    The Ionizing Radiation Division has developed new national standards for mammographic X rays and for brachytherapy sources, such as iodine-125. The Attix chamber, a variable volume free-air ionization chamber, has been established as the primary national standard for mammographic X rays. The Attix chamber resides in the newly developed NIST Mammography Calibration Range and will be used to perform routine calibrations. The wide-angle free-air ionization chamber utilizes a large volume and a novel electric field configuration in order to circumvent the limitations of conventional free-air chambers. Seventeen beam qualities for X rays from molybdenum (Mo) and rhodium (Rh) anodes have been parameterized for the calibration of mammographic ionization chambers. The beam qualities available include anode/filter combinations of Mo/Mo, Mo/Rh and Rh/Rh. The mammography range was developed in collaborations with the U.S. Food and Drug Administration's (FDA) Center for Devices and Radiological Health, the implementors of the Mammography Quality Standards Act (MQSA) of 1992. The wide-angle free-air ionization chamber has been used to measure the output of two types of iodine-125 seeds, those with resin balls and those with silver wire. Both free-air chambers have been intercompared with the Ritz parallel-plate free-air ionization chamber

  2. Multiple ionization of argon by helium ions

    Science.gov (United States)

    Montanari, C. C.; Miraglia, J. E.

    2016-09-01

    We apply the continuum distorted-wave eikonal initial state and the independent electron model to describe the multiple ionization of Ar by He2+ and He+ in the energy range 0.1-10 Mev amu-1. Auger-like post collisional processes are included, which enhance the high energy multiple ionization cross sections via ionization of the inner shells. All Ar electrons (K, L and M-shells) have been included in these calculations. The results agree well with the experimental data at high energies, where the post-collisional ionization is the main contribution. At intermediate impact energies the description is also good though it tends to overestimate the triple and quadruple ionization data at intermediate energies. We analyze this by comparing the present results for He+2 in Ar, with previous ones for He+2 in Ne and Kr. It was found that the theoretical description improves from Ne to Ar and Kr, with the latter being nicely described even at intermediate energies. The present formalism is also tested for Ar inner shell and total ionization cross sections. In all the cases the results above 0.1 MeV amu-1 are quite reasonable, as compared with the experimental data available and with the ECPSSR values.

  3. Statistical approach to multiphoton multielectron ionization of atoms

    International Nuclear Information System (INIS)

    State density and temperature of excited atom were found. Diffusion equation with sink was suggested for describing ionization process. It was shown that possibility of multielectron ionization was dictated by the competition of atom heating by external field and evaporation ionization. Numerical calculation of xenon atom ionization was conducted and correlation with experimental results was given

  4. Universal imaging: Dissociative ionization of polyatomic molecules, chemical dynamics beamline 9.0.2

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, M.; Chen, D.; Suits, A.G. [Ernest Orlando Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    A third endstation was recently added to the Chemical Dynamics beamline, designed to exploit the high flux broadband undulator light for a range of studies of reactive scattering, photochemistry and photoionization processes using time-of-flight mass spectroscopy coupled with position-sensitive detection. Two molecular beam sources are fixed at right angles, with the undulator light, or laser beams, intersecting the molecular beams at 45{degrees}. To date, beamline experiments have included a study of dissociative photoionization of a variety of molecules including N{sub 2}O and SF{sub 6}. In this mode, a single molecular beam source is used, with the tunable undulator light inducing, in SF{sub 6} for example, the process SF{sub 6} {r_arrow} SF{sub 6}{sup +} + e{sup {minus}} {r_arrow} SF{sub 5}{sup +} + F + e{sup {minus}}. The SF{sub 5}{sup +} ions are accelerated up the flight tube, mass selected and detected as a function of position on a phosphor screen viewed by a CCD camera. The position directly reveals the recoil speed (or translational energy release) and angular distribution for the dissociative ionization process. Furthermore, this measurement is obtained for all recoil speeds and angles simultaneously. Such detailed angular information has not previously been obtained for dissociative ionization processes; typically ion time-of-flight profiles are deconvoluted to yield rough insight into the angular distributions. The recorded image is actually a 2-dimensional projection of the nascent 3-dimensional velocity distribution, but established tomographic techniques enable the authors to reconstruct the 3-D distribution.

  5. Adaptive response in frogs chronically exposed to low doses of ionizing radiation in the environment

    International Nuclear Information System (INIS)

    Using the micronucleus assay, decreased levels of DNA damage were found after high dose ionizing radiation exposure of liver cells taken from frogs inhabiting a natural environment with above-background levels of ionizing radiation, compared to cells taken from frogs inhabiting background areas. The data obtained from a small number of animals suggest that stress present in the above-background environment could induce an adaptive response to ionizing radiation. This study did not reveal harmful effects of exposure to low levels of radioactivity. On the contrary, stress present in the above-background area may serve to enhance cellular defense mechanisms. - Highlights: → Frogs were collected from background and higher tritium level habitats. → The micronucleus assay was conducted on liver cells obtained from the frogs. → No detrimental effects were noted in frogs exposed to elevated tritium. → Adaptive responses were observed in frogs exposed to elevated tritium.

  6. Characterization tests of a homemade ionization chamber in mammography standard radiation beams

    International Nuclear Information System (INIS)

    A mammography homemade ionization chamber was developed to be applied for mammography energy range dosimetry. This chamber has a sensitive volume of 6 cm3 and is made of a Lucite body and graphite coated collecting electrode. Characteristics such as saturation, ion collection efficiency, linearity of chamber response versus air kerma rate and energy dependence were determined. The results obtained with the mammography homemade ionization chamber are within the limits stated in international recommendations. This chamber can be used in quality control programs in the diagnostic radiology area. All measurements were carried out at the Calibration Laboratory of IPEN. - Highlights: • We constructed a mammography homemade ionization chamber. It was submitted to standard mammography X-rays beam qualities. • The results obtained showed good agreement with international standards. • This chamber can be used in quality control programs of diagnostic radiology area

  7. Adaptive response in frogs chronically exposed to low doses of ionizing radiation in the environment

    Energy Technology Data Exchange (ETDEWEB)

    Audette-Stuart, M., E-mail: stuartm@aecl.ca [Environmental Technologies Branch, Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario, K0J 1P0 (Canada); Kim, S.B.; McMullin, D.; Festarini, A.; Yankovich, T.L.; Carr, J.; Mulpuru, S. [Environmental Technologies Branch, Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario, K0J 1P0 (Canada)

    2011-06-15

    Using the micronucleus assay, decreased levels of DNA damage were found after high dose ionizing radiation exposure of liver cells taken from frogs inhabiting a natural environment with above-background levels of ionizing radiation, compared to cells taken from frogs inhabiting background areas. The data obtained from a small number of animals suggest that stress present in the above-background environment could induce an adaptive response to ionizing radiation. This study did not reveal harmful effects of exposure to low levels of radioactivity. On the contrary, stress present in the above-background area may serve to enhance cellular defense mechanisms. - Highlights: > Frogs were collected from background and higher tritium level habitats. > The micronucleus assay was conducted on liver cells obtained from the frogs. > No detrimental effects were noted in frogs exposed to elevated tritium. > Adaptive responses were observed in frogs exposed to elevated tritium.

  8. Development of novel semiconductor detectors for the detection of ionizing radiation

    International Nuclear Information System (INIS)

    The present thesis treats the development of novel energy- and position-resolving semiconductor detectors: Fully depletable pn CCD's. In experiments of high-energy physics they are suited as highly resolving position-sensitive detectors for minimally ionizing particles. In nuclear and atomic physics they can be applied as position-resolving energy spectrometers. Increasing interest detectors of this type find also at synchrotron-radiation sources with photon energies from 20 eV to 50 keV. As focal instruments of X-ray telescopes they are in astrophysical measurements in an energy range from 100 eV to 15 keV of use. The required accuracy in the energy measurement amounts to 100 eV (FWHM) at an X-ray energy of 1 keV, at a simultaneous precision of the position determination of 50 μm. The measurement results which are here presented on the first fully depletable CCD's show that the components posses the potential to fulfill these requirements. (orig.)

  9. Ametryne degradation by ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, Debora Cristina de; Mori, Manoel Nunes; Duarte, Celina Lopes [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mails: deboracandrade@globo.com; mnmori@ipen.br; clduarte@ipen.br; Melo, Rita Paiva [Technological and Nuclear Institute (ITN), Sacavem (Portugal)]. E-mail: ritamelo@itn.pt

    2007-07-01

    Ametryne may be released to the environment during its manufacture, transport, storage, formulation and use as selective herbicide for the control of annual broadleaf and grass weeds. It is applied as an aqueous suspension for preemergence or post-directed applications on crops. Depending on the pesticide formulation and type of application, ametryne residues may be detectable in water, soil and on the surfaces for months or years. The herbicide used to this study was Ametryne (commercial name, Gesapax 500), commonly used on field crops and on corn and commercialized since 1975. Ametryne was analyzed by gas chromatography (GC Shimadzu 17A), after extraction with hexane/dichloromethane (1:1 v/v) solution. The calibration curve was obtained with a regression coefficient of 0.9871. In addition, the relative standard deviation was lower than 10%. The radiation-processing yield was evaluated by the destruction G-value (Gd) (Eq. 1), that is defined by the number of destroyed molecules by absorption of 100 eV of energy from ionizing radiation. Different concentrations of the herbicide (11.4 mol L{sup -1}; 22.7 mol L{sup -1}; 34.1 mol L{sup -1} and 45.5 mol L{sup -1}) were irradiated at the AECL 'Gammacell 220' {sup 60}Co source, with 1 kGy, 3 kGy, 6 kGy, 9 kGy, 12 kGy, 15 kGy and 30 kGy absorbed doses. After irradiation processing, the ametryne highest reduction rate occurs at low doses of radiation: at 6 kGy more than 85-90% of all ametryne compounds were removed. Two products of incomplete degradation of ametryne were identified as s-triazyne isomers. However, further work is needed in order to fully understand the ametryne degradation mechanisms the degradation yield of ametryne depends on its initial concentration and the process seems to be more efficient at higher concentrations. (author)

  10. Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets V: Alfv\\'{e}n Ionization

    CERN Document Server

    Stark, Craig R; Diver, Declan A; Rimmer, Paul B

    2013-01-01

    Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest they harbour localized plasmas in their atmospheric environments. For low-mass objects, the degree of thermal ionization is insufficient to qualify the ionized component as a plasma, posing the question: what ionization processes can efficiently produce the required plasma that is the source of the radiation? We propose Alfv\\'{e}n ionization as a mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficient degrees of ionization ($\\geq10^{-7}$) that they constitute plasmas. We outline the criteria required for Alfv\\'{e}n ionization and demonstrate it's applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs and M-dwarfs for both solar and sub-solar metallicities. We find that Alfv\\'{e}n ionization is most efficient at mid to low atmospheric pressures where a seed plasma is easier to magnetize and the pressure gradients needed to drive the required neut...

  11. Mass spectrometry of solid samples in open air using combined laser ionization and ambient metastable ionization

    Science.gov (United States)

    He, X. N.; Xie, Z. Q.; Gao, Y.; Hu, W.; Guo, L. B.; Jiang, L.; Lu, Y. F.

    2012-01-01

    Mass spectrometry of solid samples in open air was carried out using combined laser ionization and metastable ionization time-of-flight mass spectrometry (LI-MI-TOFMS) in ambient environment for qualitative and semiquantitative (relative analyte information, not absolute information) analysis. Ambient metastable ionization using a direct analysis in realtime (DART) ion source was combined with laser ionization time-of-flight mass spectrometry (LI-TOFMS) to study the effects of combining metastable and laser ionization. A series of metallic samples from the National Institute of Standards and Technology (NIST 494, 495, 498, 499, and 500) and a pure carbon target were characterized using LI-TOFMS in open air. LI-MI-TOFMS was found to be superior to laser-induced breakdown spectroscopy (LIBS). Laser pulse energies between 10 and 200 mJ at the second harmonic (532 nm) of an Nd:YAG laser were applied in the experiment to obtain a high degree of ionization in plasmas. Higher laser pulse energy improves signal intensities of trace elements (such as Fe, Cr, Mn, Ni, Ca, Al, and Ag). Data were analyzed by numerically calculating relative sensitivity coefficients (RSCs) and limit of detections (LODs) from mass spectrometry (MS) and LIBS spectra. Different parameters, such as boiling point, ionization potential, RSC, LOD, and atomic weight, were shown to analyze the ionization and MS detection processes in open air.

  12. Highly efficient ionization of phosphopeptides at low pH by desorption electrospray ionization mass spectrometry†

    OpenAIRE

    Pan, Ning; Liu, Pengyuan; Cui, Weidong; Tang, Bo; Shi, Jingmin; Chen, Hao

    2013-01-01

    A fast and novel strategy for efficient ionization of phosphopeptides in mixtures is reported, in which the sample is acidified to low pH to suppress the deprotonation of phosphate groups and then followed by direct analysis using liquid sample desorption electrospray ionization mass spectrometry (DESI-MS).

  13. Pressurized ionization chamber detectors for industrial use

    International Nuclear Information System (INIS)

    The measurement of the thickness of the sheets made of different materials, e.g. metal, plastic, paper, cellulose, rubber, etc., is one of many industrial applications of nuclear techniques. The ionizing radiation detectors of ionization chamber type are based on measuring the variations in either exposure rate (for gamma radiation) or absorbed dose rate (for beta radiation) occurring in materials of different thickness, placed between the radiation source and the detector. The variations in exposure rate and absorbed dose rate can be traced by using radiation detectors of the ionization chamber type, which convert the exposure rate, X point, or the absorbed dose rate, D point, into a proportional electric current. The more stable the ionization current of the chambers (keeping a constant exposure rate or absorbed dose rate), the slighter the variations that can be detected in either exposure rate or absorbed dose rate, hence in the absorbing material placed between the radiation source and the detector. Based on these facts, several variants of such detectors, including the ionization chamber CIS-P5M-100Kr, CIS-P2M-1000Kr and CIS-P8M-70Kr, have been made. (author)

  14. Conceptual basis of resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    Resonance Ionization Spectroscopy (RIS) can b defined as a state-selective detection process in which tunable lasers are used to promote transitions from the selected state of the atoms or molecules in question to higher states, one of which will be ionized by the absorption of another photon. At least one resonance step is used in the stepwise ionization process, and it has been shown that the ionization probability of the spectroscopically selected species can nearly always be made close to unity. Since measurements of the number of photoelectrons or ions can be made very precisely and even one electron (or under vacuum conditions, one ion) can be detected, the technique can be used to make quantitative measurements of very small populations of the state-selected species. Counting of individual atoms has special meaning for detection of rare events. The ability to make saturated RIS measurements opens up a wide variety of applications to both basic and applied research. We view RIS as a specific type of multi-photon ionization in which the goal is to make quantitative measurements of quantum-selected populations in atomic or molecular systems. 16 references

  15. Multiphoton ionization of large water clusters.

    Science.gov (United States)

    Apicella, B; Li, X; Passaro, M; Spinelli, N; Wang, X

    2014-05-28

    Water clusters are multimers of water molecules held together by hydrogen bonds. In the present work, multiphoton ionization in the UV range coupled with time of flight mass spectrometry has been applied to water clusters with up to 160 molecules in order to obtain information on the electronic states of clusters of different sizes up to dimensions that can approximate the bulk phase. The dependence of ion intensities of water clusters and their metastable fragments produced by laser ionization at 355 nm on laser power density indicates a (3+1)-photon resonance-enhanced multiphoton ionization process. It also explains the large increase of ionization efficiency at 355 nm compared to that at 266 nm. Indeed, it was found, by applying both nanosecond and picosecond laser ionization with the two different UV wavelengths, that no water cluster sequences after n = 9 could be observed at 266 nm, whereas water clusters up to m/z 2000 Th in reflectron mode and m/z 3000 Th in linear mode were detected at 355 nm. The agreement between our findings on clusters of water, especially true in the range with n > 10, and reported data for liquid water supports the hypothesis that clusters above a critical dimension can approximate the liquid phase. It should thus be possible to study clusters just above 10 water molecules, for getting information on the bulk phase structure.

  16. LET measurements with a liquid ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Tegami, Sara

    2013-02-08

    Deep-seated tumors can be efficiently treated with heavy charged particles. The characteristic depth dose profile inside the tissue (Bragg peak) allows to deliver a high dose inside the tumor, while sparing the neighboring healthy tissue. As compared to protons, heavy ions like carbon or oxygen produce a higher amount of ionization events along their track (and in particular at the end of the ion beam path), resulting in an irreparable damage to the DNA of the tumor cells. The density of such ionization events is described in terms of Linear Energy Transfer (LET), an important physical quantity, but difficult to be measured directly. The aim of this work is to determine LET of hadrontherapy beams by using Liquid Ionization Chambers (LIC). The ionization signal in LICs is affected by recombination effects that depend on the LET of the incident radiation. Differences in recombination effects in LICs and air-filled ionization chambers can be exploited to obtain the recombination index, which can be related to the LET, calculated by Monte Carlo methods. We thus developed a method to construct a calibration curve, which relates the recombination index with the LET at each depth in water. The result of this work can be used for online monitoring of the ion beam quality.

  17. The primordial abundance of deuterium: ionization correction

    Science.gov (United States)

    Cooke, Ryan; Pettini, Max

    2016-01-01

    We determine the relative ionization of deuterium and hydrogen in low metallicity damped Lyman α (DLA) and sub-DLA systems using a detailed suite of photoionization simulations. We model metal-poor DLAs as clouds of gas in pressure equilibrium with a host dark matter halo, exposed to the Haardt & Madau background radiation of galaxies and quasars at redshift z ≃ 3. Our results indicate that the deuterium ionization correction correlates with the H I column density and the ratio of successive ion stages of the most commonly observed metals. The N(N II)/N(N I) column density ratio provides the most reliable correction factor, being essentially independent of the gas geometry, H I column density, and the radiation field. We provide a series of convenient fitting formulae to calculate the deuterium ionization correction based on observable quantities. The ionization correction typically does not exceed 0.1 per cent for metal-poor DLAs, which is comfortably below the current measurement precision (2 per cent). However, the deuterium ionization correction may need to be applied when a larger sample of D/H measurements becomes available.

  18. Multiphoton ionization of large water clusters

    International Nuclear Information System (INIS)

    Water clusters are multimers of water molecules held together by hydrogen bonds. In the present work, multiphoton ionization in the UV range coupled with time of flight mass spectrometry has been applied to water clusters with up to 160 molecules in order to obtain information on the electronic states of clusters of different sizes up to dimensions that can approximate the bulk phase. The dependence of ion intensities of water clusters and their metastable fragments produced by laser ionization at 355 nm on laser power density indicates a (3+1)-photon resonance-enhanced multiphoton ionization process. It also explains the large increase of ionization efficiency at 355 nm compared to that at 266 nm. Indeed, it was found, by applying both nanosecond and picosecond laser ionization with the two different UV wavelengths, that no water cluster sequences after n = 9 could be observed at 266 nm, whereas water clusters up to m/z 2000 Th in reflectron mode and m/z 3000 Th in linear mode were detected at 355 nm. The agreement between our findings on clusters of water, especially true in the range with n > 10, and reported data for liquid water supports the hypothesis that clusters above a critical dimension can approximate the liquid phase. It should thus be possible to study clusters just above 10 water molecules, for getting information on the bulk phase structure

  19. Time-of-flight ERD with a 200 mm{sup 2} Si{sub 3}N{sub 4} window gas ionization chamber energy detector

    Energy Technology Data Exchange (ETDEWEB)

    Julin, Jaakko, E-mail: jaakko.julin@jyu.fi; Laitinen, Mikko; Sajavaara, Timo

    2014-08-01

    Low energy heavy ion elastic recoil detection work has been carried out in Jyväskylä since 2009 using home made timing detectors, a silicon energy detector and a timestamping data acquisition setup forming a time-of-flight–energy telescope. In order to improve the mass resolution of the setup a new energy detector was designed to replace the silicon solid state detector, which suffered from radiation damage and had poor resolution for heavy recoils. In this paper the construction and operation of an isobutane filled gas ionization chamber with a 14 × 14 mm{sup 2} 100 nm thick silicon nitride window are described. In addition to greatly improved energy resolution for heavy ions, the detector is also able to detect hydrogen recoils simultaneously in the energy range of 100–1000 keV. Additionally the detector has position sensitivity by means of timing measurement, which can be performed without compromising the performance of the detector in any other way. The achieved position sensitivity improves the depth resolution near the surface.

  20. National Laboratory of Ionizing Radiation Metrology - Brazilian CNEN; Laboratorio Nacional de Metrologia das Radiacoes Ionizantes

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1992-12-31

    The activities of the Brazilian National Laboratory of Ionizing Radiations Metrology are described. They include research and development of metrological techniques and procedures, the calibration of area radiation monitors, clinical dosemeters and other instruments and the preparation and standardization of reference radioactive sources. 4 figs., 13 tabs.

  1. The late biological effects of ionizing radiation

    International Nuclear Information System (INIS)

    Full text: The principal objective of the symposium was to review the current status of understanding of the late biological effects of ionizing radiation from external and internal sources. A second objective was to critically evaluate information obtained from epidemiological studies of human population groups as well as from animal experimentation in order to provide a solid scientific basis upon which problems of current concern, such as radiation protection standards and risk-benefit analysis, could be deliberated. Eighty-one papers were presented in 10 sessions which covered epidemiological studies of late effects in human populations exposed to internal and/or external ionizing radiation; quantitative and qualitative data from animal experimentation of late effects; methodological problems and modern approaches; factors influencing susceptibility or expression of late radiation injury; comparative evaluation of late effects induced by radiation and other environmental pollutants, and problems of risk assessment. In addition, there were two evening sessions for free discussion of problems of interpreting animal data, and of the epidemiological studies of occupationally exposed populations. Reports on atomic bomb survivors showed that these epidemiological studies are providing dependable data, such as dose-related excess infant mortality. The reports also revealed the need for consensus in the method employed in the interpretation of data. That was also the case with studies on occupationally exposed populations at Hanford plant, where disparate results were presented on radiation-induced neoplasia among radiation workers. These data are, however, considered not so significant in relative terms when compared to risks involved in other industries. It was recommended that national registry systems for the dosimetry and medical records of radiation workers be established and co-ordinated internationally in order to facilitate reliable epidemiological

  2. Laser induced avalanche ionization in gases or gas mixtures with resonantly enhanced multiphoton ionization or femtosecond laser pulse pre-ionization

    International Nuclear Information System (INIS)

    The paper discusses the requirements for avalanche ionization in gas or gas mixtures initiated by REMPI or femtosecond-laser pre-ionization. Numerical examples of dependencies on partial composition for Ar:Xe gas mixture with REMPI of argon and subsequent classic avalanche ionization of Xe are presented.

  3. Weak interaction studies using resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    Important developments in laser sources for the vacuum ultraviolet (VUV) region of the spectrum are making it possible to carry out resonance ionization of some of the noble gases. It has already been shown that xenon can be ionized in a two-photon allowed excitation from the ground state. Recently a new method of generating radiation by four-wave mixing in mercury vapor enables excitation of xenon in a one-photon resonance process. With these new laser sources we expect to have effective ionization volumes of 10-3 to 10-2 cm3 for the cases of argon, krypton, and xenon. This has important consequences in weak interaction physics and environmental research

  4. Ionization of atoms by slow heavy particles

    CERN Document Server

    Roberts, B M; Gribakin, G F

    2016-01-01

    Atoms and molecules can become ionized during the scattering of a slow, heavy particle off a bound electron. Such an interaction involving leptophilic weakly interacting massive particles (WIMPs) is a promising possible explanation for the anomalous 9 sigma annual modulation in the DAMA dark matter direct detection experiment [R. Bernabei et al., Eur. Phys. J. C 73, 2648 (2013)]. We demonstrate the applicability of the Born approximation for such an interaction by showing its equivalence to the semiclassical adiabatic treatment of atomic ionization by slow-moving WIMPs. Conventional wisdom has it that the ionization probability for such a process should be exponentially small. We show, however, that due to nonanalytic, cusp-like behaviour of Coulomb functions close to the nucleus this suppression is removed, leading to an effective atomic structure enhancement. We also show that electron relativistic effects actually give the dominant contribution to such a process, meaning that nonrelativistic calculations m...

  5. Nucleation in an ultra low ionization environment

    DEFF Research Database (Denmark)

    Pedersen, Jens Olaf Pepke; Enghoff, Martin Andreas Bødker; Paling, Sean;

    Atmospheric ions can enhance the nucleation of aerosols, as has been established by experiments, observation, and theory. In the clean marine atmosphere ionization is mainly caused by cosmic rays which in turn are controlled by the activity of the Sun, thus providing a potential link between solar...... Laboratory, located 1100 meters below ground, thus reducing the flux of ionizing cosmic radiation by six orders of magnitude. Similarly we have reduced the gamma background by shielding the experiment in lead and copper. Finally we have used air stored for several weeks and passed through an active charcoal...... filter in order to reduce the Radon concentration. In this way we have been able to make nucleation experiments with very low ionizing background, meaning that we can rule out ion induced nucleation as a contributing mechanism. Our experimental setup is a 50 L electropolished stainless steel reactor...

  6. Ionization of atoms by chirped attosecond pulses

    Institute of Scientific and Technical Information of China (English)

    Tan Fang; Peng Liang-You; Gong Qi-Huang

    2009-01-01

    We investigate the ionization dynamics of atoms by chirped attosecond pulses using the strong field approximation method. The pulse parameters are carefully chosen in the regime where the strong field approximation method is valid. We analyse the effects of the chirp of attosecond pulses on the energy distributions and the corresponding left-right asymmetry of the ionized electrons. For a single chirped attosecond pulse, the ionized electrons can be redistributed and the left-right asymmetry shows oscillations because of the introduction of the chirp. For time-delayed double attosecond pulses at different intensities with the weaker one chirped, exchanging the order of the two pulses shows a relative shift of the energy spectra, which can be explained by the different effective time delays of different frequency components because of the chirp.

  7. Code of practice for ionizing radiation

    International Nuclear Information System (INIS)

    Prior to 1984, the use of ionizing radiation in Malaysia was governed by the Radioactive Substances Act of 1968. After 1984, its use came under the control of Act 304, called the Atomic Energy Licensing Act 1984. Under powers vested by the Act, the Radiation Protection (Basic Safety Standards) Regulations 1988 were formulated to regulate its use. These Acts do not provide information on proper working procedures. With the publication of the codes of Practice by The Standards and Industrial Research Institute of Malaysia (SIRIM), the users are now able to follow proper guidelines and use ionizing radiation safely and beneficially. This paper discusses the relevant sections in the following codes: 1. Code of Practice for Radiation Protection (Medical X-ray Diagnosis) MS 838:1983. 2. Code of Practice for Safety in Laboratories Part 4: Ionizing radiation MS 1042: Part 4: 1992. (author)

  8. Ionization-chamber smoke detector system

    Science.gov (United States)

    Roe, Robert F.

    1976-10-19

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system is designed to reduce false alarms caused by fluctuations in ambient temperature. Means are provided for periodically firing the gas discharge triode and each time recording the triggering voltage required. A computer compares each triggering voltage with its predecessor. The computer is programmed to energize an alarm if the difference between the two compared voltages is a relatively large value indicative of particulates in the measuring chamber and to disregard smaller differences typically resulting from changes in ambient temperature.

  9. Multiphoton ionization/dissociation of osmium tetroxide

    International Nuclear Information System (INIS)

    The mechanisms leading to laser multiphoton ionization and dissociation (MPI/MPD) of osmium tetroxide (OsO4) have been investigated from measurements of the kinetic energies of product ions (Os+, Os2+, OsO+, O2+, O+) and photoelectrons as a function of the laser wavelength. Neutral channels, intermediate to the dominant Os+ ionization channel, such as OsO4→OsO4-n+nO are examined using resonance-enhanced multiphoton ionization (REMPI) of the fast O atoms. Equipartition of the available photon energy among the fragments is observed. The wavelength dependence of the Os+ ion signal suggests that one or more of the steps leading to Os+ ions involve molecular ions and/or excited neutral atoms. The observed preponderance of very slow (2+ is shown to result primarily from REMPI of Os+

  10. Capillary electrophoresis electrospray ionization mass spectrometry interface

    Science.gov (United States)

    Smith, Richard D.; Severs, Joanne C.

    1999-01-01

    The present invention is an interface between a capillary electrophoresis separation capillary end and an electrospray ionization mass spectrometry emitter capillary end, for transporting an anolyte sample from a capillary electrophoresis separation capillary to a electrospray ionization mass spectrometry emitter capillary. The interface of the present invention has: (a) a charge transfer fitting enclosing both of the capillary electrophoresis capillary end and the electrospray ionization mass spectrometry emitter capillary end; (b) a reservoir containing an electrolyte surrounding the charge transfer fitting; and (c) an electrode immersed into the electrolyte, the electrode closing a capillary electrophoresis circuit and providing charge transfer across the charge transfer fitting while avoiding substantial bulk fluid transfer across the charge transfer fitting. Advantages of the present invention have been demonstrated as effective in providing high sensitivity and efficient analyses.

  11. Ionizing radiation in the food industry

    International Nuclear Information System (INIS)

    The present state of application of ionizing radiation to food irradiation is surveyed. The nature of ionizing radiation, interactions of radiation with matter, dosimetric procedures, and types of radiation sources are outlined. Ionizing radiation is used for sprout inhibition, sterilization, for killing insects, parasites, moulds and fungi, and for enzyme activity inhibition. Sprouting can be stimulated by using low radiation doses. The chemical and biological changes occurring in irradiated foods are discussed. The irradiation of 49 kinds of food is permitted in 36 countries, and is applied on a commercial basis in 20 countries. Examples of large irradiating facilities over the world are given. Attention is also paid to the legislative basis of this approach. (M.D.). 2 tabs., 17 refs

  12. Electron impact double ionization of Mg+ ions

    International Nuclear Information System (INIS)

    Electron impact ionization of atoms/ions is one of the fundamental atomic collision processes. Absolute cross sections for electron impact single and multiple ionization are of considerable importance in many fields like astrophysics and controlled nuclear fusion. Theoretical studies of electron impact double ionisation cross sections of Mg+ ions have been performed in the binary encounter approximation (BEA). Direct double ionisation has been investigated in the modified double binary encounter model. Ionization cross sections of different shells have been also calculated in order to analyse the contributions to double ionisation from ionisation-autoionization. The effect of the Coulombic field of the target ion on the incident electron has been considered in the present work. Accurate expression of σΔE (cross-section for energy transfer ΔE) and Hartree-Fock velocity distributions for the target electrons have been used throughout the calculations. The theoretical results show satisfactory agreement with the experimental observations. (authors)

  13. Ionization Modeling Astrophysical Gaseous Structures. I. The Optically Thin Regime

    CERN Document Server

    Churchill, Christopher W; Medina, Amber; Vliet, Jacob R Vander

    2014-01-01

    We present a code for modelling the ionization conditions of optically thin astrophysical gas structures. Given the gas hydrogen density, equilibrium temperature, elemental abundances, and the ionizing spectrum, the code solves the equilibrium ionization fractions and number densities for all ions from hydrogen to zinc. The included processes are photoionization, Auger ionization, direct collisional ionization, excitation auto-ionization, charge exchange ionization, two-body radiative recombination, dielectronic recombination, and charge exchange recombination. The ionizing spectrum can be generalized to include the ultraviolet background (UVB) and/or Starburst99 stellar populations of various masses, ages, metallicities, and distances. The ultimate goal with the code is to provide fast computation of the ionization conditions of gas in N-body + hydrodynamics cosmological simulations, in particular adaptive mesh refinement codes, in order to facilitate absorption line analysis of the simulated gas for compari...

  14. An instrument combining an electrospray ionization source and a velocity-map imaging spectrometer for studying delayed electron emission of polyanions

    Science.gov (United States)

    Concina, Bruno; Papalazarou, Evangelos; Barbaire, Marc; Clavier, Christian; Maurelli, Jacques; Lépine, Franck; Bordas, Christian

    2016-03-01

    An instrument combining an electrospray ionization source and a velocity-map imaging (VMI) spectrometer has been developed in order to study the delayed electron emission of molecular anions and especially of polyanions. It operates at a high repetition rate (kHz) in order to increase the acquisition speed. The VMI spectrometer has been upgraded for nanosecond time resolution by gating the voltages applied on the position-sensitive detector. Kinetic energy release distribution of thermionic emission (without any contribution from direct detachment) can be recorded for well-defined delays after the nanosecond laser excitation. The capability of the instrument is demonstrated by recording photodetachment spectra of the benchmark C60- anion and C842- dianion.

  15. Guided ionization waves: Theory and experiments

    Energy Technology Data Exchange (ETDEWEB)

    Lu, X., E-mail: luxinpei@hotmail.com [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430030 (China); Naidis, G.V. [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation); Laroussi, M. [Laser and Plasma Engineering Institute, Old Dominion University, Norfolk, VA 23529 (United States); Ostrikov, K. [CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia)

    2014-07-01

    This review focuses on one of the fundamental phenomena that occur upon application of sufficiently strong electric fields to gases, namely the formation and propagation of ionization waves–streamers. The dynamics of streamers is controlled by strongly nonlinear coupling, in localized streamer tip regions, between enhanced (due to charge separation) electric field and ionization and transport of charged species in the enhanced field. Streamers appear in nature (as initial stages of sparks and lightning, as huge structures—sprites above thunderclouds), and are also found in numerous technological applications of electrical discharges. Here we discuss the fundamental physics of the guided streamer-like structures—plasma bullets which are produced in cold atmospheric-pressure plasma jets. Plasma bullets are guided ionization waves moving in a thin column of a jet of plasma forming gases (e.g., He or Ar) expanding into ambient air. In contrast to streamers in a free (unbounded) space that propagate in a stochastic manner and often branch, guided ionization waves are repetitive and highly-reproducible and propagate along the same path—the jet axis. This property of guided streamers, in comparison with streamers in a free space, enables many advanced time-resolved experimental studies of ionization waves with nanosecond precision. In particular, experimental studies on manipulation of streamers by external electric fields and streamer interactions are critically examined. This review also introduces the basic theories and recent advances on the experimental and computational studies of guided streamers, in particular related to the propagation dynamics of ionization waves and the various parameters of relevance to plasma streamers. This knowledge is very useful to optimize the efficacy of applications of plasma streamer discharges in various fields ranging from health care and medicine to materials science and nanotechnology.

  16. Guided ionization waves: Theory and experiments

    International Nuclear Information System (INIS)

    This review focuses on one of the fundamental phenomena that occur upon application of sufficiently strong electric fields to gases, namely the formation and propagation of ionization waves–streamers. The dynamics of streamers is controlled by strongly nonlinear coupling, in localized streamer tip regions, between enhanced (due to charge separation) electric field and ionization and transport of charged species in the enhanced field. Streamers appear in nature (as initial stages of sparks and lightning, as huge structures—sprites above thunderclouds), and are also found in numerous technological applications of electrical discharges. Here we discuss the fundamental physics of the guided streamer-like structures—plasma bullets which are produced in cold atmospheric-pressure plasma jets. Plasma bullets are guided ionization waves moving in a thin column of a jet of plasma forming gases (e.g., He or Ar) expanding into ambient air. In contrast to streamers in a free (unbounded) space that propagate in a stochastic manner and often branch, guided ionization waves are repetitive and highly-reproducible and propagate along the same path—the jet axis. This property of guided streamers, in comparison with streamers in a free space, enables many advanced time-resolved experimental studies of ionization waves with nanosecond precision. In particular, experimental studies on manipulation of streamers by external electric fields and streamer interactions are critically examined. This review also introduces the basic theories and recent advances on the experimental and computational studies of guided streamers, in particular related to the propagation dynamics of ionization waves and the various parameters of relevance to plasma streamers. This knowledge is very useful to optimize the efficacy of applications of plasma streamer discharges in various fields ranging from health care and medicine to materials science and nanotechnology

  17. Electron-Impact Ionization Cross Section Database

    Science.gov (United States)

    SRD 107 Electron-Impact Ionization Cross Section Database (Web, free access)   This is a database primarily of total ionization cross sections of molecules by electron impact. The database also includes cross sections for a small number of atoms and energy distributions of ejected electrons for H, He, and H2. The cross sections were calculated using the Binary-Encounter-Bethe (BEB) model, which combines the Mott cross section with the high-incident energy behavior of the Bethe cross section. Selected experimental data are included.

  18. Multiphoton core ionization dynamics of polyatomic molecules

    International Nuclear Information System (INIS)

    The two-photon core ionization dynamics of gas-phase methane, carbon monoxide and nitrogen have been studied with a recent implementation of the lowest order perturbation theory in the framework of density functional theory and a multicentric basis set expansion of bound and scattering states. Ionization cross sections and angular asymmetry parameters have been calculated for the case of a single radiation beam and for both linear and circular light polarizations in the fixed nuclei approximation. Expected resonances due to core valence excitations enhance the cross section by several orders of magnitude. (paper)

  19. Generalized Bessel functions in tunnelling ionization

    CERN Document Server

    Reiss, H R

    2003-01-01

    We develop two new approximations for the generalized Bessel function that frequently arises in the analytical treatment of strong-field processes, especially in non-perturbative multiphoton ionization theories. Both these new forms are applicable to the tunnelling environment in atomic ionization, and are analytically much simpler than the currently used low-frequency asymptotic approximation for the generalized Bessel function. The second of the new forms is an approximation to the first, and it is the second new form that exhibits the well-known tunnelling exponential.

  20. Resonance ionization mass spectroscopy of uranium

    International Nuclear Information System (INIS)

    Resonance ionization mass spectroscopy (RIMS) has been used for the sensitive detection of uranium. The apparatus consists of a laser system with three dye lasers and two pulsed copper vapour lasers and a time-of-flight (TOF) mass spectrometer. The uranium atoms are ionized in a three step excitation with the third step leading to an autoionizing state. Several excitation schemes were investigated and for two schemes all three transitions could be saturated with the available laser power. The hyperfine structure splitting (HFS) of 235U, the isotopic shift (IS) between 235U and 238U as well as isotopic ratios in uranium samples were determined. (Author)

  1. A prototype ionization profile monitor for RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Connolly, R.; Cameron, P.; Ryan, W. [and others

    1997-07-01

    Transverse beam profiles in the Relativistic Heavy-Ion Collider (RHIC) will be measured with ionization profile monitors (IPM`s). Each IPM collects and measures the distribution of electrons in the beamline resulting from residual gas ionization during bunch passage. The electrons are swept transversely from the beamline and collected on strip anodes oriented parallel to the beam axis. At each bunch passage the charge pulses are amplified, integrated, and digitized for display as a profile histogram. A prototype detector was tested in the injection line during the RHIC Sextant Test. This paper describes the detector and gives results from the beam tests.

  2. [Oncogenic action of ionizing radiation

    International Nuclear Information System (INIS)

    An extensive experiment involving approximately 400 rats exposed to the neon ion beam at the Bevalac in Berkeley, CA and to electrons is nearing completion. The carcinogenicity of energetic electrons was determined for comparison with the neon ion results. As in past reports we will describe progress in three areas corresponding to the specific aims of the proposal: (1) carcinogenesis and DNA strand breaks in rat skin following exposure by the neon ions or electrons; (2) DNA strand breaks in the epidermis as a function of radiation penetration; (3) oncogene activation in radiation-induced rat skin cancers. 72 refs., 6 tabs

  3. (Oncogenic action of ionizing radiation)

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    An extensive experiment involving approximately 400 rats exposed to the neon ion beam at the Bevalac in Berkeley, CA and to electrons is nearing completion. The carcinogenicity of energetic electrons was determined for comparison with the neon ion results. As in past reports we will describe progress in three areas corresponding to the specific aims of the proposal: (1) carcinogenesis and DNA strand breaks in rat skin following exposure by the neon ions or electrons; (2) DNA strand breaks in the epidermis as a function of radiation penetration; (3) oncogene activation in radiation-induced rat skin cancers. 72 refs., 6 tabs.

  4. Deconstructing Desorption Electrospray Ionization: Independent Optimization of Desorption and Ionization by Spray Desorption Collection

    Science.gov (United States)

    Douglass, Kevin A.; Jain, Shashank; Brandt, William R.; Venter, Andre R.

    2012-11-01

    Spray desorption collection (SDC) and reflective electrospray ionization (RESI) were used to independently study the desorption and ionization processes that together comprise desorption electrospray ionization (DESI). Both processes depend on several instrumental parameters, including the nebulizing gas flow rate, applied potential, and source geometries. Each of these parameters was optimized for desorption, as represented by the results obtained by SDC, and ionization, as represented by the results obtained by RESI. The optimized conditions were then compared to the optimization results for DESI. Our results confirm that optimal conditions for desorption and ionization are different and that in some cases the optimized DESI conditions are a compromise between both sets. The respective results for DESI, RESI, and SDC for each parameter were compared across the methods to draw conclusions about the contribution of each parameter to desorption and ionization separately and then combined within DESI. Our results indicate that desorption efficiency is (1) independent of the applied potential and (2) the impact zone to inlet distance, and that (3) gas pressure settings and (4) sprayer to impact zone distances above optimal for DESI are detrimental to desorption but beneficial for ionization. In addition, possible interpretations for the observed trends are presented.

  5. Matrix Assisted Ionization in Vacuum, a Sensitive and Widely Applicable Ionization Method for Mass Spectrometry

    Science.gov (United States)

    Trimpin, Sarah; Inutan, Ellen D.

    2013-05-01

    An astonishingly simple new method to produce gas-phase ions of small molecules as well as proteins from the solid state under cold vacuum conditions is described. This matrix assisted ionization vacuum (MAIV) mass spectrometry (MS) method produces multiply charged ions similar to those that typify electrospray ionization (ESI) and uses sample preparation methods that are nearly identical to matrix-assisted laser desorption/ionization (MALDI). Unlike these established methods, MAIV does not require a laser or voltage for ionization, and unlike the recently introduced matrix assisted ionization inlet method, does not require added heat. MAIV-MS requires only introduction of a crystalline mixture of the analyte incorporated with a suitable small molecule matrix compound such as 3-nitrobenzonitrile directly to the vacuum of the mass spectrometer. Vacuum intermediate pressure MALDI sources and modified ESI sources successfully produce ions for analysis by MS with this method. As in ESI-MS, ion formation is continuous and, without a laser, little chemical background is observed. MAIV, operating from a surface offers the possibility of significantly improved sensitivity relative to atmospheric pressure ionization because ions are produced in the vacuum region of the mass spectrometer eliminating losses associated with ion transfer from atmospheric pressure to vacuum. Mechanistic aspects and potential applications for this new ionization method are discussed.

  6. Secondary ionization process in laser induced breakdown of molecular gases

    International Nuclear Information System (INIS)

    We studied the separate effect of photo-ionization and collisional ionization of the molecular electronic excited states on the ionization growth rate of nitrogen irradiated with 10 ns pulse of Nd-YAG laser radiation at pressures 7.6x102, 1.79x103 and 5.34x103 Torr. It was found that photo-ionization processes play an important role in enhancing the ionization growth rate at pressures of 7.6x102 Torr. At higher pressures, where there is excess of electron density and hence excited molecule density, collisional ionization processes are dominant. (author). 6 refs, 3 figs

  7. Circular dichroism in XUV + IR multiphoton ionization of atoms

    International Nuclear Information System (INIS)

    Circular dichroism (CD) is theoretically considered for two-colour multiphoton ionization of arbitrary atomic subshells. In particular, p-subshell ionization is analysed and compared with s-subshell ionization. Simple analytical expressions for the CD are obtained for both s- and p-subshell ionization. The calculations performed for Ne(2p) ionization by an extreme ultraviolet pulse in the presence of an infrared laser pulse show that the CD in this case is appreciably larger than in previously discussed s-shell ionization. It makes this case favourable for applications as a sensitive tool for measuring the helicity of short-wavelength free-electron laser beams. (paper)

  8. Atmospheric Pressure Chemical Ionization Sources Used in The Detection of Explosives by Ion Mobility Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Waltman, Melanie J. [New Mexico Inst. of Mining and Technology, Socorro, NM (United States)

    2010-05-01

    Explosives detection is a necessary and wide spread field of research. From large shipping containers to airline luggage, numerous items are tested for explosives every day. In the area of trace explosives detection, ion mobility spectrometry (IMS) is the technique employed most often because it is a quick, simple, and accurate way to test many items in a short amount of time. Detection by IMS is based on the difference in drift times of product ions through the drift region of an IMS instrument. The product ions are created when the explosive compounds, introduced to the instrument, are chemically ionized through interactions with the reactant ions. The identity of the reactant ions determines the outcomes of the ionization process. This research investigated the reactant ions created by various ionization sources and looked into ways to manipulate the chemistry occurring in the sources.

  9. Amphibian nitrate stress as an additional terrestrial threat from astrophysical ionizing radiation events?

    CERN Document Server

    Thomas, Brian C

    2008-01-01

    As diversity in amphibian species declines, the search for causes has intensified. Work in this area has shown that amphibians are especially susceptible to the combination of heightened UVB radiation and increased nitrate concentrations. Various astrophysical events have been suggested as sources of ionizing radiation that could pose a threat to life on Earth, through destruction of the ozone layer and subsequent increase in UVB, followed by deposition of nitrate. In this study, we investigate whether the nitrate deposition following an ionizing event is sufficiently large to cause an additional stress beyond that of the heightened UVB previously considered. We have converted predicted nitrate depositions to concentration values, utilizing data from the New York State Department of Environmental Conservation Acid Rain Monitoring Network web site. Our results show that the increase in nitrate concentration in bodies of water following the most intense ionization event likely in the last billion years would no...

  10. PICsIT a position sensitive detector for space applications

    CERN Document Server

    Labanti, C; Ferriani, S; Ferro, G; Malaguti, G; Mauri, A; Rossi, E; Schiavone, F; Stephen, J B; Traci, A; Visparelli, D

    2002-01-01

    Pixellated Imaging CsI Telescope (PICsIT) is the high energy detector plane of Imager on Board INTEGRAL Satellite (IBIS), one of the main instruments on board the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellite that will be launched in the year 2001. It consists of 4096 CsI(Tl) individual detector elements and operates in the energy range from 120 to 10,000 keV. PICsIT is made up of 8 identical modules, each housing 512 scintillating crystals coupled to PIN photodiodes (PD). Each crystal, 30 mm long and with a cross-section of 8.55x8.55 mm sup 2 , is wrapped with a white diffusing coating and then inserted into an aluminium crate. In order to have a compact design, two electronic boards, mounted directly below the crystal/PD assembly, host both the Analogue and Digital Front-End Electronics (FEE). The behaviour of the read-out FEE has a direct impact on the performance of the whole detector in terms of lower energy threshold, energy resolution and event time tagging. Due to the great numb...

  11. A multi-anode photomultiplier with position sensitivity

    International Nuclear Information System (INIS)

    We have measured the properties of a specially developed photomultiplier with proximity dynodes and 10 wire anodes. This design allows us to determine the position of emission of the photoelectrons from the cathode with an accuracy of 1.3 mm fwhm. This tube is also extremely fast due to the short transit time and the geometry of its dynodes. (orig.)

  12. Photon–photon coincidence apparatus with position sensitive detectors

    International Nuclear Information System (INIS)

    An apparatus for the coincident detection of two photons in the visible and VUV spectral range is presented equipped with two position- and time resolving detectors. The equipment enables angular resolution for the detected photons and thus allows an angular correlation between the two detected photons without changing the target cell geometry. Two different configurations of this apparatus are presented and compared in terms of solid angle coverage, imaging properties and suitability for their use in gas phase experiments at synchrotron radiation facilities

  13. Simulated performance of a position sensitive radiation detecting system (COCAE)

    CERN Document Server

    Karafasoulis, K; Seferlis, S; Kaissas, I; Lambropoulos, C; Loukas, D; Poritiriadis, C

    2011-01-01

    Extensive simulations of a portable radiation detecting system have been performed in order to explore important performance parameters. The instrument consists of a stack of ten detecting layers made of pixelated Cadmium Telluride (CdTe) crystals. Its aim is to localize and identify radiation sources, by exploiting the Compton imaging technique. In this paper we present performance parameters based on simulation studies. Specifically the ratio of incompletely absorbed photons, the detector's absolute efficiency as well as its energy and angular resolution are evaluated in a wide range of incident photon energies.

  14. Cellular automaton-based position sensitive detector equalization

    Energy Technology Data Exchange (ETDEWEB)

    Ferrando, Nestor [Grupo de Diseno de Sistemas Digitales, Instituto de Aplicaciones de las Tecnologias de la Informacion y de las Comunicaciones Avanzadas, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain)], E-mail: nesferjo@upvnet.upv.es; Herrero, V.; Cerda, J.; Lerche, C.W.; Colom, R.J.; Gadea, R.; Martinez, J.D.; Monzo, J.M.; Mateo, F.; Sebastia, A.; Benlloch, J.M. [Grupo de Diseno de Sistemas Digitales, Instituto de Aplicaciones de las Tecnologias de la Informacion y de las Comunicaciones Avanzadas, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain)

    2009-06-01

    Indirect position detectors based on scintillator crystals lack of spacial uniformity in their response. This happens due to crystal inhomogeneities and gain differences among the photomultiplier anodes. In order to solve this, PESIC, an integrated front-end for multianode photomultiplier based nuclear imaging devices was created. One of its main features is the digitally programmable gain adjustment for every photomultiplier output. On another front, cellular automata have been proved to be a useful method for dynamic system modeling. In this paper, a cellular automaton which emulates the behavior of the scintillator crystal, the photomultiplier and the front-end is introduced. Thanks to this model, an automatic energy-based calibration of the detector can be done by configuring the cellular automaton with experimental data and making it evolve up to an stable state. This can be useful as a precalibration method of the detector.

  15. Centroid finding method for position-sensitive detectors

    Energy Technology Data Exchange (ETDEWEB)

    Radeka, V.; Boie, R.A.

    1979-10-01

    A new centroid finding method for all detectors where the signal charge is collected or induced on strips of wires, or on subdivided resistive electrodes, is presented. The centroid of charge is determined by convolution of the sequentially switched outputs from these subdivisions or from the strips with a linear centroid finding filter. The position line width is inversely proportional to N/sup 3/2/, where N is the number of subdivisions.

  16. Historical survey of resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    We have recently celebrated the 10th birthday of Resonance Ionization Spectroscopy (RIS), and this seems an appropriate time to review the history of its development. Basically, RIS is a photophysics process in which tunable light sources are used to remove a valence electron from an atom of selected atomic number, Z. If appropriate lasers are used as the light source, one electron can be removed from each atom of the selected Z in the laser pulse. This implies that RIS can be a very efficient, as well as selective, ionization process. In what we normally call RIS, laser schemes are employed which preserve both of these features. In contrast, multiphoton ionization (MPI) is more general, although not necessarily Z selective or very efficient because resonances are often not used. Early research completed in the USSR and described as selective two-step photoionization, employed resonances to ionize the rubidium atom and served to guide work on laser isotope separation. 29 references, 8 figures

  17. Composite scintillators for detection of ionizing radiation

    Science.gov (United States)

    Dai, Sheng [Knoxville, TN; Stephan, Andrew Curtis [Knoxville, TN; Brown, Suree S [Knoxville, TN; Wallace, Steven A [Knoxville, TN; Rondinone, Adam J [Knoxville, TN

    2010-12-28

    Applicant's present invention is a composite scintillator having enhanced transparency for detecting ionizing radiation comprising a material having optical transparency wherein said material comprises nano-sized objects having a size in at least one dimension that is less than the wavelength of light emitted by the composite scintillator wherein the composite scintillator is designed to have selected properties suitable for a particular application.

  18. IKAR, a ionization chamber for WA9

    CERN Document Server

    1976-01-01

    This ionization chamber arrived at CERN from Leningrad for a high precision study of hadron elastic scattering by a CERN-Clermont-Ferrand-Leningrad-Lyon-Uppsala Collaboration in the H3 beam (WA9). G.A. Korolev (third from right) looks at the drawings.

  19. The GODDESS ionization chamber: developing robust windows

    Science.gov (United States)

    Blanchard, Rose; Baugher, Travis; Cizewski, Jolie; Pain, Steven; Ratkiewicz, Andrew; Goddess Collaboration

    2015-10-01

    Reaction studies of nuclei far from stability require high-efficiency arrays of detectors and the ability to identify beam-like particles, especially when the beam is a cocktail beam. The Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies (GODDESS) is made up of the Oak Ridge-Rutgers University Barrel Array (ORRUBA) of silicon detectors for charged particles inside of the gamma-ray detector array Gammasphere. A high-rate ionization chamber is being developed to identify beam-like particles. Consisting of twenty-one alternating anode and cathode grids, the ionization chamber sits downstream of the target chamber and is used to measure the energy loss of recoiling ions. A critical component of the system is a thin and robust mylar window which serves to separate the gas-filled ionization chamber from the vacuum of the target chamber with minimal energy loss. After construction, windows were tested to assure that they would not break below the required pressure, causing harm to the wire grids. This presentation will summarize the status of the ionization chamber and the results of the first tests with beams. This work is supported in part by the U.S. Department of Energy and National Science Foundation.

  20. Ionization Energy: Implications of Preservice Teachers' Conceptions

    Science.gov (United States)

    Tan, Kim Chwee Daniel; Taber, Keith S.

    2009-01-01

    The results from a study to explore pre-service teachers' understanding of ionization energy, a topic that features in A-level (grade 11 and 12) chemistry courses. in Singapore , is described. A previous study using a two-tier multiple choice diagnostic test has shown that Singapore A-level students have considerable difficulty understanding the…

  1. Limits to Sensitivity in Laser Enhanced Ionization.

    Science.gov (United States)

    Travis, J. C.

    1982-01-01

    Laser enhanced ionization (LEI) occurs when a tunable dye laser is used to excite a specific atomic population in a flame. Explores the origin of LEI's high sensitivity and identifies possible avenues to higher sensitivity by describing instrument used and experimental procedures and discussing ion formation/detection. (Author/JN)

  2. The Primordial Abundance of Deuterium: Ionization correction

    CERN Document Server

    Cooke, Ryan

    2015-01-01

    We determine the relative ionization of deuterium and hydrogen in low metallicity damped Lyman-alpha (DLA) and sub-DLA systems using a detailed suite of photoionization simulations. We model metal-poor DLAs as clouds of gas in pressure equilibrium with a host dark matter halo, exposed to the Haardt & Madau (2012) background radiation of galaxies and quasars at redshift z~3. Our results indicate that the deuterium ionization correction correlates with the H I column density and the ratio of successive ion stages of the most commonly observed metals. The N(N II) / N(N I) column density ratio provides the most reliable correction factor, being essentially independent of the gas geometry, H I column density, and the radiation field. We provide a series of convenient fitting formulae to calculate the deuterium ionization correction based on observable quantities. The ionization correction typically does not exceed 0.1 per cent for metal-poor DLAs, which is comfortably below the current measurement precision (2...

  3. Route to Direct Multiphoton Multiple Ionization

    CERN Document Server

    Lambropoulos, P; Papamihail, K G

    2011-01-01

    We address the concept of direct multiphoton multiple ionization in atoms exposed to intense, short wavelength radiation and explore the conditions under which such processes dominate over the sequential. Their contribution is shown to be quite robust, even under intensity fluctuations and interaction volume integration, and reasonable agreement with experimental data is also found.

  4. Route to direct multiphoton multiple ionization

    International Nuclear Information System (INIS)

    We address the concept of direct multiphoton multiple ionization in atoms exposed to intense, short-wavelength radiation and explore the conditions under which such processes dominate over the sequential. Their contribution is shown to be quite robust, even under intensity fluctuations and interaction volume integration, and reasonable agreement with experimental data is also found.

  5. Ionization smoke detector with controlled sensitivity

    International Nuclear Information System (INIS)

    An ionization smoke detector has been developed which has housing and sensing chambers together controlling the flow of detected smoke or aerosols containing particulate matter. This control of the air flow through the sensing chamber maintains the sensitivity to smoke even in the presence of winds or drafts. (DN)

  6. Fluctuation charge effects in ionization fronts

    Energy Technology Data Exchange (ETDEWEB)

    Arrayas, Manuel; Trueba, Jose L [Area de Electromagnetismo, Universidad Rey Juan Carlos, Camino del Molino s/n, 28943 Fuenlabrada, Madrid (Spain); Baltanas, J P [Departamento de Fisica Aplicada II, Universidad de Sevilla, Av. Reina Mercedes 2, 41012 Sevilla (Spain)

    2008-05-21

    In this paper, we study the effects of charge fluctuations on the propagation of both negative and positive ionization fronts in streamer discharges. We show that fronts accelerate when random charge creation events are present. This effect might play a similar role to photoionization in order to make the front move faster.

  7. Properties of Excitons Bound to Ionized Donors

    DEFF Research Database (Denmark)

    Skettrup, Torben; Suffczynski, M.; Gorzkowski, W.

    1971-01-01

    Binding energies, interparticle distances, oscillator strengths, and exchange corrections are calculated for the three-particle complex corresponding to an exciton bound to an ionized donor. The results are given as functions of the mass ratio of the electron and hole. Binding of the complex is o...

  8. Roles of ionizing radiation in cell transformation

    Energy Technology Data Exchange (ETDEWEB)

    Tobias, C.A.; Albright, N.W.; Yang, T.C.

    1983-07-01

    Earlier the authors described a repair misrepair model (RMR-I) which is applicable for radiations of low LET, e.g., x rays and gamma rays. RMR-II was described later. Here is introduced a mathematical modification of the RMR model, RMR-III, which is intended to describe lethal effects caused by heavily ionizing tracks. 31 references, 4 figures.

  9. Historical survey of resonance ionization spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hurst, G.S.

    1984-04-01

    We have recently celebrated the 10th birthday of Resonance Ionization Spectroscopy (RIS), and this seems an appropriate time to review the history of its development. Basically, RIS is a photophysics process in which tunable light sources are used to remove a valence electron from an atom of selected atomic number, Z. If appropriate lasers are used as the light source, one electron can be removed from each atom of the selected Z in the laser pulse. This implies that RIS can be a very efficient, as well as selective, ionization process. In what we normally call RIS, laser schemes are employed which preserve both of these features. In contrast, multiphoton ionization (MPI) is more general, although not necessarily Z selective or very efficient because resonances are often not used. Early research completed in the USSR and described as selective two-step photoionization, employed resonances to ionize the rubidium atom and served to guide work on laser isotope separation. 29 references, 8 figures.

  10. Liquid ionization chambers for LET determination

    DEFF Research Database (Denmark)

    Kaiser, Franz-Joachim; Bassler, Niels; Tölli, Heikki;

    Liquid ionization chambers [1] (LICs) have have been used in the last decades as background dosemeters. Since a few years LICs are also commercially available for dosimetry and are used for measurements of dose distributions where a high spatial distribution is necessary. Also in the last decades...

  11. Antiproton-impact ionization of H2

    International Nuclear Information System (INIS)

    Ionization processes in antiproton collisions with H2 are studied by direct solution of the time-dependent Schroedinger equation. A time-dependent close-coupling method based on an expansion of a one-electron 3D wavefunction in the field of H+2 is used to calculate single-ionization cross sections at incident energies ranging from 50 keV to 1.5 MeV. Averaging over the molecular orientations, the single-ionization cross sections are in reasonable agreement with time-dependent basis set calculations and experiment. A time-dependent close-coupling method based on an expansion of a two-electron 6D wavefunction in the field of H2+2 is used to calculate single- and double-ionization cross sections at an incident energy of 100 keV. Initiatory 6D results for the H+2 production cross section range are somewhat lower than experiment, while the H+ production cross section range brackets experiment.

  12. Long-term effects of ionizing radiation

    International Nuclear Information System (INIS)

    This paper approaches the long-term effects of ionizing radiation considering the common thought that killing of cells is the basis for deterministic effects and that the subtle changes in genetic information are important in the development of radiation-induced cancer, or genetic effects if these changes are induced in germ cells

  13. Positronium impact ionization of Alkali atoms

    CERN Document Server

    Ghosh, D

    2015-01-01

    Target ionization processes of alkali atoms by Positronium impact are investigated. Calculations are performed in the frame work of model potential formalism using the Coulomb distorted eikonal approximation. Interesting qualitative features are noted both in the scattered Ps and the ejected electron distributions in differential as well as double differential levels of the collision cross sections.

  14. Roles of ionizing radiation in cell transformation

    International Nuclear Information System (INIS)

    Earlier the authors described a repair misrepair model (RMR-I) which is applicable for radiations of low LET, e.g., x rays and gamma rays. RMR-II was described later. Here is introduced a mathematical modification of the RMR model, RMR-III, which is intended to describe lethal effects caused by heavily ionizing tracks. 31 references, 4 figures

  15. The MICE Demonstration of Muon Ionization Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Lagrange, Jean-Baptiste [Imperial Coll., London; Hunt, Christopher [Imperial Coll., London; Palladino, Vittorio [INFN, Naples; Pasternak, Jaroslaw [Imperial Coll., London

    2016-06-01

    Muon beams of low emittance provide the basis for the intense, well-characterised neutrino beams necessary to elucidate the physics of flavour at the Neutrino Factory and to provide lepton-antilepton collisions up to several TeV at the Muon Collider. The international Muon Ionization Cooling Experiment (MICE) will demonstrate muon ionization cooling, the technique proposed to reduce the phase-space volume occupied by the muon beam at such facilities. In an ionization-cooling channel, the muon beam traverses a material (the absorber) loosing energy, which is replaced using RF cavities. The combined effect is to reduce the transverse emittance of the beam (transverse cooling). The configuration of MICE required to deliver the demonstration of ionization cooling is being prepared in parallel to the execution of a programme designed to measure the cooling properties of liquid-hydrogen and lithium hydride. The design of the cooling-demonstration experiment will be presented together with a summary of the performance of each of its components and the cooling performance of the experiment.

  16. Optimization of the ionization time of an atom with tailored laser pulses: a theoretical study

    CERN Document Server

    Kammerlander, David; Marques, Miguel A L

    2016-01-01

    How fast can a laser pulse ionize an atom? We address this question by considering pulses that carry a fixed time-integrated energy per-area, and finding those that achieve the double requirement of maximizing the ionization that they induce, while having the shortest duration. We formulate this double-objective quantum optimal control problem by making use of the Pareto approach to multi-objetive optimization, and the differential evolution genetic algorithm. The goal is to find out how much a precise time-profiling of ultra-fast, large-bandwidth pulses may speed up the ionization process with respect to simple-shape pulses. We work on a simple one-dimensional model of hydrogen-like atoms (the P\\"oschl-Teller potential), that allows to tune the number of bound states that play a role in the ionization dynamics. We show how the detailed shape of the pulse accelerates the ionization process, and how the presence or absence of bound states influences the velocity of the process.

  17. Detoxification of snake venom using ionizing radiation

    International Nuclear Information System (INIS)

    It is generally recognized that energy absorbed by ionizing radiation (gamma rays) can inactivate biological material in tow ways. A direct effects occurs when the primary event, i.e., ionization, is produced in the molecule itself. This is the case when a compound is irradiated in dry state. When a compound is irradiated in a solution, the indirect effect joins the direct. Since water is the most abundant constituent of biological material, it is important to consider the species produced by excitation and ionization of water itself, and the reaction of these species with the target molecules of biological importance. This indirect effect results from the reactions among the studied molecules and the products of radiation interaction with water or other solvents. Highly reactive compounds, the so-called free radicals, which are formed many reactions among themselves, with the dissolved gas, and with other molecules in the solution. With water, the excitation is less important than ionization which is followed within picosecond by the formation of free hydroxyl radicals and hydrated electrons. Alexander and Hamilton showed that irradiation of proteins has revealed damage to aminoacid side chains, production of new groups, splitting of peptide bonds and formation of intramolecular and intermolecular cross-links. With these results it would be possible to use ionizing radiation to change those proteins molecules in order to improve some of their properties according to the necessity. On the other hand, it is recognized that venoms in general are poorly immunogenic, yet fairly toxic. This cause problems because serotherapy is the treatment of choice in snakebite envenomations, and horse antivenom availability is dependent upon. (author)

  18. The multiphoton ionization of uranium hexafluoride

    International Nuclear Information System (INIS)

    Multiphoton ionization (MPI) time-of-flight mass spectroscopy and photoelectron spectroscopy studies of UF6 have been conducted using focused light from the Nd:YAG laser fundamental (λ = 1064 nm) and its harmonics (λ = 532, 355, or 266 nm), as well as other wavelengths provided by a tunable dye laser. The MPI mass spectra are dominated by the singly and multiply charged uranium ions rather than by the UFx+ fragment ions. The laser power dependence of Un+ ion signals indicates that saturation can occur for many of the steps required for their ionization. The doubly-charged uranium ion (U2+) intensity is much greater than that of the singly-charged uranium ion (U+). For the case of the tunable dye laser experiments, the Un+ (n=1-4) wavelength dependence is relatively unstructured and does not show observable resonance enhancement at known atomic uranium excitation wavelengths. The dominance of the U2+ ion and the absence or very small intensities of UFx+ fragments, along with the unstructured wavelength dependence, indicate that mechanisms may exist other than ionization of bare U atoms after the stepwise photodissociation of F atoms from the parent molecule. The data argue against step-wise photodissociation of UFx+ (x = 5,6) ions. Neither the neutral ladder nor the ion ladder mechanisms adequately describe the ionization phenomena observed. These results suggest an alternate mechanism which better explains the multiphoton excitation and dissociative ionization of UF6. It is likely that the multiphoton excitation of UF6 under these experimental conditions results in a superexcited molecule, UF6**, which primarily dissociates into Un+ (through multiple channels), fluorine atoms, and slow electrons. The excitation of such superexcited molecules may be facilitated by the existence of a previously reported giant resonance at 12-14 eV

  19. Detoxification of snake venom using ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Rogero, J.R.; Nascimento, N. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil). Supervisao de Radiobiologia

    1995-07-01

    It is generally recognized that energy absorbed by ionizing radiation (gamma rays) can inactivate biological material in tow ways. A direct effects occurs when the primary event, i.e., ionization, is produced in the molecule itself. This is the case when a compound is irradiated in dry state. When a compound is irradiated in a solution, the indirect effect joins the direct. Since water is the most abundant constituent of biological material, it is important to consider the species produced by excitation and ionization of water itself, and the reaction of these species with the target molecules of biological importance. This indirect effect results from the reactions among the studied molecules and the products of radiation interaction with water or other solvents. Highly reactive compounds, the so-called free radicals, which are formed many reactions among themselves, with the dissolved gas, and with other molecules in the solution. With water, the excitation is less important than ionization which is followed within picosecond by the formation of free hydroxyl radicals and hydrated electrons. Alexander and Hamilton showed that irradiation of proteins has revealed damage to aminoacid side chains, production of new groups, splitting of peptide bonds and formation of intramolecular and intermolecular cross-links. With these results it would be possible to use ionizing radiation to change those proteins molecules in order to improve some of their properties according to the necessity. On the other hand, it is recognized that venoms in general are poorly immunogenic, yet fairly toxic. This cause problems because serotherapy is the treatment of choice in snakebite envenomations, and horse antivenom availability is dependent upon. (author)

  20. Amplitude distribution of ionization jerks in ionization-chamber ASK-1 according long-term measurements

    Science.gov (United States)

    Timofeev, Vladislav

    2016-07-01

    As part of the Yakut complex systems by measuring the intensity of cosmic rays has a unique device spherical - ionization chamber ASK-1 with a lead screen thickness of 12 cm. The camera allows you to explore the physical characteristics of the so-called "ionization jerks " - sharp increases ionization current caused by the passage through the device much ionizing particles of cosmic origin. Due to a large increase in current nuclear cascade "showers", formed mainly by particles of cosmic rays in the camera screen. Over the entire period of observation (50 years old) camera ASK-1 was registered 59125 aftershocks. Their nature and properties still does not sufficiently studied, especially in medium and large amplitudes.

  1. Measurement of the first ionization potential of astatine by laser ionization spectroscopy

    CERN Document Server

    Rothe, S; Antalic, S; Borschevsky, A; Capponi, L; Cocolios, T E; De Witte, H; Eliav, E; Fedorov, D V; Fedosseev, V N; Fink, D A; Fritzsche, S; Ghys, L; Huyse, M; Imai, N; Kaldor, U; Kudryavtsev, Yu; Köster, U; Lane, J; Lassen, J; Liberati, V; Lynch, K M; Marsh, B A; Nishio, K; Pauwels, D; Pershina, V; Popescu, L; Procter, T J; Radulov, D; Raeder, S; Rajabali, M M; Rapisarda, E; Rossel, R E; Sandhu, K; Seliverstov, M D; Sjödin, A M; Van den Bergh, P; Van Duppen, P; Venhart, M; Wakabayashi, Y; Wendt K D A

    2013-01-01

    The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of smallest quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.317510(8) eV. New ab initio calculations were performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of super-heavy element 117, the heaviest homologue of astatine.

  2. Rydberg atom ionization by slow collisions with alkali element atoms

    International Nuclear Information System (INIS)

    A new mechanism for ionization of highexcited atoms due to the electron capture into the autoionization state of a negative ion is suggested. Calculations of cross-sections and the ionization rate for sodium and lithium atoms collisions are performed

  3. The Flatness and Sudden Evolution of the Intergalactic Ionizing Background

    CERN Document Server

    Muñoz, Joseph A; Davies, Frederick B; Furlanetto, Steven R

    2014-01-01

    The ionizing background of cosmic hydrogen is an important probe of the sources and absorbers of ionizing radiation, their evolution and relationship, in the post-reionization universe. Previous studies show that the ionization rate should be very sensitive to changes in the source population: as the emissivity rises, absorbers shrink in size, increasing the ionizing mean free path and, hence, the ionizing background. By contrast, observations of the ionizing background find a very flat evolution from z~2-5, before falling precipitously at z~6. We resolve this discrepancy by pointing out that, at z~2-5, neutral absorbers are associated with the same collapsed halos that additionally host ionizing galactic sources. Thus, an increasing abundance of galaxies is compensated for by a corresponding increase in the absorber population, which moderates the instability in the ionizing background. However, by z~5-6, gas outside of halos dominates the absorption, the coupling between sources and absorbers is lost, and t...

  4. Fully differential cross sections for heavy particle impact ionization

    Energy Technology Data Exchange (ETDEWEB)

    McGovern, M; Walters, H R J [Department of Applied Mathematics and Theoretical Physics, Queen' s University, Belfast BT7 1NN (United Kingdom); Assafrao, D; Mohallem, J R [Laboratorio de Atomos e Moleculas Especiais, Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, P.O Box 702, 30123-970 Belo Horizonte, MG (Brazil); Whelan, Colm T, E-mail: mmcgovern06@qub.ac.u [Department of Physics, Old Dominion University, Norfolk, VA 23529-0116 (United States)

    2009-11-15

    We describe a procedure for extracting fully differential ionization cross sections from an impact parameter coupled pseudostate treatment of the collision. Some examples from antiproton impact ionization of atomic Hydrogen are given.

  5. Ground Levels and Ionization Energies for the Neutral Atoms

    Science.gov (United States)

    SRD 111 Ground Levels and Ionization Energies for the Neutral Atoms (Web, free access)   Data for ground state electron configurations and ionization energies for the neutral atoms (Z = 1-104) including references.

  6. Imaging with high Dynamic using an Ionization Chamber

    CERN Document Server

    Menk, Ralf-Hendrik; Arfelli, Fulvia; Bernstorff, Sigrid; Besch, Hans Juergen; Voltolina, Francesco

    2010-01-01

    In this work a combination of an ionization chamber with one-dimensional spatial resolution and a MicroCAT structure will be presented. The combination between gas gain operations and integrating front-end electronics yields a dynamic range as high as eight to nine orders of magnitude. Therefore this device is well suitable for medical imaging or applications such as small angle x-ray scattering, where the requirements on the dynamic of the detector are exceptional high. Basically the described detector is an ionization chamber adapted to fan beam geometry with an active area of 192 cm and a pitch of the anode strips of 150 micrometer. In the vertical direction beams as high as 10 mm can be accepted. Every read-out strip is connected to an analogue integrating electronics channel realized in a custom made VLSI chip. A MicroCAT structure utilized as a shielding grid enables frame rates as high as 10kHz. The high dynamic range observed stems from the fact that the MicroCAT enables active electron amplification ...

  7. Ionization damage in NPN transistors caused by lower energy electrons

    Science.gov (United States)

    Li, Xingji; Xiao, Jingdong; Liu, Chaoming; Zhao, Zhiming; Geng, Hongbin; Lan, Mujie; Yang, Dezhuang; He, Shiyu

    2010-09-01

    Electrical degradation of two type NPN bipolar junction transistors (BJTs) with different emitter sizes was examined under exposures of 70 and 110 keV electrons. Base and collector currents as a function of base-emitter voltage were in-situ measured during exposure. Experimental results show that both the 70 and 110 keV electrons produce an evident ionization damage to the NPN BJTs. With increasing fluence, collector currents of the NPN BJTs hardly change in the whole range of base-emitter voltage from 0 to 1.2 V, while base currents increase in a gradually mitigative trend. Base currents vary more at lower base-emitter voltages than at higher ones for a given fluence. The change in the reciprocal of current gain at a fixed base-emitter voltage of 0.65 V increases non-linearly at lower fluences and tends to be gradually saturated at higher fluences. Sensitivity to ionization damage increases for BJTs with an emitter having a larger perimeter-to-area ratio.

  8. Charge exchange in fluid description of partially ionized plasmas

    CERN Document Server

    Vranjes, J; Luna, M

    2015-01-01

    The effects of charge exchange on waves propagating in weakly ionized plasmas are discussed. It is shown that for low-frequency processes, ions and neutrals should be treated as a single fluid with some effective charge on all of them. We have derived a new momentum equation which should be used in such an environment. As a result, the low-frequency magnetic waves can propagate even if particles are not magnetized, which is entirely due to the charge exchange and the fact that it is not possible to separate particles into two different populations as charged and neutral species. So there can be no friction force between ions and neutrals in the usual sense. The mean force per particle is proportional to the ionization ratio $n_i/(n_i+ n_n)$. Regarding the application of the theory to the Alfven wave propagation in the lower solar atmosphere, the results predict that the plane of displacement of the fluid must change by 90 degrees when an Alfven wave propagates from the area where particles are un-magnetized (...

  9. Effects of ionizing radiation on aquatic organisms and ecosystems

    International Nuclear Information System (INIS)

    A panel of experts in November 1971 specifically considered the effects of ionizing radiation on aquatic organisms and ecosystems and formulated detailed suggestions for research in the area. A further panel meeting took place in April 1974. The results of the work are presented in this report which is divided into 3 chapters in the first chapter the concentrations of natural and artificial radionuclides in aquatic environments and the radiation dose rates received by aquatic organisms are discussed. In particular, simple dosimetry models for phytoplankton, zooplankton, mollusca, crustacea and fish are presented which permit the estimation of the dose rates from incorporated radionuclides and from radionuclides in the external environment. In the second chapter the somatic and genetic effects of ionizing radiation on aquatic organisms are reviewed. Somatic effects are discussed separately as effects due to short-term (acute) exposure to near-lethal doses of radiation. Great attention is paid to the effects due to long-term (chronic) exposure at lower doses rates. Consideration is given to behaviour, repair mechanisms and metabolic stimulation after exposure, and also the influence of environmental factors on radiation effects. In the third chapter the potential effects of low-level irradiation on aquatic populations are considered. First, the possible consequences of somatic effects on egg and larval mortality, stock-recruitment, fecundity and ecosystem stability are discussed. Subsequently, the assessment of genetic effects as they relate to population genetics and increased mutation rates are considered

  10. Multistage Reactive Transmission-Mode Desorption Electrospray Ionization Mass Spectrometry

    Science.gov (United States)

    Peters, Kevin C.; Comi, Troy J.; Perry, Richard H.

    2015-09-01

    Elucidating reaction mechanisms is important for advancing many areas of science such as catalyst development. It is often difficult to probe fast reactions at ambient conditions with high temporal resolution. In addition, systems involving reagents that cross-react require analytical methods that can minimize interaction time and specify their order of introduction into the reacting system. Here, we explore the utility of transmission mode desorption electrospray ionization (TM-DESI) for reaction monitoring by directing a microdroplet spray towards a series of meshes with micrometer-sized openings coated with reagents, an approach we call multistage reactive TM-DESI (TM n -DESI, where n refers to the number of meshes; n = 2 in this report). Various stages of the reaction are initiated at each mesh surface, generating intermediates and products in microdroplet reaction vessels traveling towards the mass spectrometer. Using this method, we investigated the reactivity of iron porphyrin catalytic hydroxylation of propranolol and other substrates. Our experimental results indicate that TM n -DESI provides the ability to spatially separate reagents and control their order of introduction into the reacting system, thereby minimizing unwanted reactions that lead to catalyst deactivation and degradation products. In addition, comparison with DESI-MS analyses (the Zare and Latour laboratories published results suggesting accessible reaction times desorption/ionization per MS scan, increasing the number of analytes and reactions that can be characterized in a single experiment.

  11. Two-photon ionization of atomic hydrogen above the one-photon ionization threshold

    Energy Technology Data Exchange (ETDEWEB)

    Jayadevan, A.P. [Department of Physics, Cochin University of Science and Technology, Kochi (India); Thayyullathil, Ramesh Babu [Department of Physics, Cochin University of Science and Technology, Kochi (India)]. E-mail: rbt@cusat.ac.in

    2001-02-28

    An alternative method is presented for the evaluation of the two-photon ionization transition amplitude and transition rates of atomic hydrogen in the ground state above the one-photon ionization threshold. In this approach it is straightforward to calculate the angular distribution of the emitted electrons. These angular distributions are plotted and calculated transition rates are compared with the previously reported results. (author)

  12. On the Primary Ionization Mechanism(s) in Matrix-Assisted Laser Desorption Ionization

    OpenAIRE

    Laura Molin; Roberta Seraglia; Zbigniew Czarnocki; Maurin, Jan K; Franciszek A. Pluciński; Pietro Traldi

    2012-01-01

    A mechanism is proposed for the first step of ionization occurring in matrix-assisted laser desorption ionization, leading to protonated and deprotonated matrix (Ma) molecules ([Ma + H]+ and [Ma − H]− ions). It is based on observation that in solid state, for carboxyl-containing MALDI matrices, the molecules form strong hydrogen bonds and their carboxylic groups can act as both donors and acceptors. This behavior leads to stable dimeric structures. The laser irradiation leads to the cleavage ...

  13. Matrix Assisted Ionization Vacuum (MAIV), a New Ionization Method for Biological Materials Analysis Using Mass Spectrometry*

    OpenAIRE

    Inutan, Ellen D.; Trimpin, Sarah

    2012-01-01

    The introduction of electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) for the mass spectrometric analysis of peptides and proteins had a dramatic impact on biological science. We now report that a wide variety of compounds, including peptides, proteins, and protein complexes, are transported directly from a solid-state small molecule matrix to gas-phase ions when placed into the vacuum of a mass spectrometer without the use of high voltage, a laser, or adde...

  14. Advanced quantification of plutonium ionization potential to support nuclear forensic evaluations by resonance ionization mass spectrometry

    OpenAIRE

    Lensegrav, Craig T.

    2015-01-01

    Approved for public release; distribution is unlimited Ongoing work seeks to apply the technology of resonance ionization mass spectrometry (RIMS) to problems related to nuclear forensics and, in particular, to the analysis and quantification of the debris from nuclear detonations. As part of this effort, modeling and simulation methods are being applied to analyze and predict the potential for ionization by laser excitation of isotopes of both uranium and plutonium. Early work focused on ...

  15. A Multistep Algorithm for the Radiation Hydrodynamical Transport of Cosmological Ionization Fronts and Ionized Flows

    OpenAIRE

    Daniel J. Whalen; Norman, Michael L.

    2005-01-01

    Radiation hydrodynamical transport of ionization fronts in the next generation of cosmological reionization simulations holds the promise of predicting UV escape fractions from first principles as well as investigating the role of photoionization in feedback processes and structure formation. We present a multistep integration scheme for radiative transfer and hydrodynamics for accurate propagation of I-fronts and ionized flows from a point source in cosmological simulations. The algorithm is...

  16. Smart ionization chamber for gamma-ray monitoring

    OpenAIRE

    Drndarević Vujo R.; Jevtić Nenad J.; Rajović Vladimir M.; Stanković Srboljub J.

    2014-01-01

    A design and implementation of a smart ionization chamber suitable for connection into gamma radiation monitoring networks is presented in this paper. The smart ionization chamber consists of air-equivalent one liter ionization chamber with associated electronics and a built-in memory for storage of electronic data specifications. Generally, operating and measurement characteristics of the used ionization chamber are written into the memory chip attached to...

  17. Single and double ionization of gallium by electron impact

    Indian Academy of Sciences (India)

    L K Jha

    2002-09-01

    Electron impact single and double ionization cross sections of gallium have been calculated in the binary encounter approximation using accurate expression for including exchange and interference as given by Vriens and Hartree–Fock velocity distributions for the target electrons throughout the calculations. It is concluded that the ionization of 3d shell contributes partly to single ionization and partly to double ionization. The results so obtained show reasonably good agreement with the experimental data.

  18. Statistic approach to multiphoton, multielectron ionization of atoms

    International Nuclear Information System (INIS)

    The density of states and the excitation temperature of an atom are found. To describe the ionization process, a diffusion equation with ejection is proposed. It is shown that the possibility of multielectron ionization is determined by the competition of the heating of an atom by an external field and evaporative ionization. A numerical calculation is made of the ionization of xenon atoms and a comparison with experimental results is given

  19. High-Order Harmonic Generation in the Ionization Process

    Institute of Scientific and Technical Information of China (English)

    CHEN Jing; CHEN Shi-Gang; LIU Jie

    2000-01-01

    Based on the nonperturbative quantum electrodynamics scattering theory for multiphoton ionization developed recently, high-order harmonic generated in the ionization process is discussed. The influence of the Coulomb potential is treated as a perturbation in the expansion of the transition matrix. It is deduced that the harmonic photons are emitted in the resonant process during ionization and the width of the harmonic peaks is just the ionization rate of the atom.

  20. Mechanism of delayed double ionization in a strong laser field

    OpenAIRE

    Mauger, Francois; Kamor, Adam; Chandre, Cristel; UZer, Turgay

    2011-01-01

    When intense laser pulses release correlated electrons, the time delay between the ionizations may last more than one laser cycle. We show that this "Recollision-Excitation with Subsequent Ionization" pathway originates from the inner electron being promoted to a sticky region by a recollision where it is trapped for a long time before ionizing. We identify the mechanism which regulates this region, and predict oscillations in the double ionization yield with laser intensity.

  1. EXCITATION AND IONIZATION OF LASER-PUMPED Ba VAPOUR

    OpenAIRE

    Huber, M.; Jahreiss, L.

    1985-01-01

    We describe the excitation and ionization of dense Ba vapour (1019 to 2021 m-3) by resonant (λ = 553.5 nm) laser radiation and discuss the processes responsible for the transfer of energy from the laser-excited atoms into ionization. Ionization was found to be density-dependent and this pointed to collision-dominated ionization mechanisms. It has been established that seed electrons were heated in superelastic collisions with laser-excited atoms, and that subsequent electron-impact excitation...

  2. Ionizing energy in food processing and pest control. 1. Wholesomeness of food treated with ionizing energy

    International Nuclear Information System (INIS)

    Congressional concerns about the use of ionizing energy for food preservation and to control pests in food products for export and domestic use promoted the preparation of this report by a special task force of the Council for Agricultural Science and Technology (CAST). An overview surveys research conducted on the toxicological safety, nutritional quality, and microbiological safety of foods treated with ionizing energy. Background information is provided on various types of electromagnetic radiation, effects of ionizing energy level and dose, sources of natural background radiation and induced radioactivity, and the nature and safety of various radiolytic products. Objectives, methodologies, and problems associated with feeding studies of toxicological safety are outlined; results of scientific studies, U.S. government wholesomeness studies, and international feeding studies are summarized. Studies on the nutritional value of food products processed using ionized energy have examined the effects of ionizing energy on 1) composite diets, 2) carbohydrates, 3) fats, 4) proteins and amino acids, 5) vitamins (potatoes, onions, fruits, meat, seafood, cereals, vegetables, dairy products, oils), 6) antivitamins, and 7) minerals. The report concludes that currently available scientific evidence indicates that foods exposed to ionizing energy under the conditions proposed for commercial application are 1) wholesome (safe to eat) and 2) comparable in nutritional adequacy to fresh or conventionally processed foods

  3. New Constraints on the Escape of Ionizing Photons From Starburst Galaxies Using Ionization-Parameter Mapping

    CERN Document Server

    Zastrow, Jordan; Veilleux, Sylvain; McDonald, Michael

    2013-01-01

    The fate of ionizing radiation in starburst galaxies is key to understanding cosmic reionization. However, the galactic parameters on which the escape fraction of ionizing radiation depend are not well understood. Ionization-parameter mapping provides a simple, yet effective, way to study the radiative transfer in starburst galaxies. We obtain emission-line ratio maps of [SIII]/[SII] for six, nearby, dwarf starbursts: NGC 178, NGC 1482, NGC 1705, NGC 3125, NGC 7126, and He 2-10. The narrow-band images are obtained with the Maryland-Magellan Tunable Filter at Las Campanas Observatory. Using these data, we previously reported the discovery of an optically thin ionization cone in NGC 5253, and here we also discover a similar ionization cone in NGC 3125. This latter cone has an opening angle of 40+/-5 degrees (0.4 ster), indicating that the passageways through which ionizing radiation may travel correspond to a small solid angle. Additionally, there are three sample galaxies that have winds and/or superbubble act...

  4. Determination of collisional ionization rate and ionization yield from excited levels of cesium in a flame

    International Nuclear Information System (INIS)

    A method is proposed for determining the rate constants of collisional ionization and the ionization yield from excited levels of cesium atoms in a flame, using experimental curves of optical saturation and laser-stimulated ionization of excited atoms. It is shown that deviations of the shape of the saturation curves from ideal shape are due to the time dependence of the trailing edge of the exciting laser pulse. The ionization yield of cesium in an acetylene--air flame during its one-step excitation to the 6p2p1/2 level was 0.95%, rising to 50% for two-step excitation to the 8d2D3/2 level. The corresponding values of the rate constants of collisional ionization were 3.2x105 and 3.3x107 sec-1. From the known value of the ionization yield in the two-step excitation scheme, estimates of the atomization coefficient of cesium in the flame were made. The proposed method can be used for other elements in different flames

  5. High order fluid model for ionization fronts in streamer discharges

    NARCIS (Netherlands)

    Markosyan, A.; Dujko, S.; Hundsdorfer, W.; Ebert, U.

    2011-01-01

    When non-ionized or lowly ionized matter is exposed to high electric fields, non-equilibrium ionization processes, streamer discharges, can develop. Streamers occur in nature and as well in many industrial applications such as the treatment of exhaust gasses, polluted water or biogas. A third order

  6. Intensity dependence of strong field double ionization mechanisms: from field-assisted recollision ionization to recollision-assisted field ionization

    CERN Document Server

    Emmanouilidou, A

    2009-01-01

    Using a three-dimensional quasiclassical technique we explore molecular double ionization by a linearly polarized, infrared (800 nm) and ultrashort (6 fs) laser pulse. We first focus on intensities corresponding to the tunneling regime and identify the main ionization mechanisms in this regime. We devise a selection of observables, such as, the correlated momenta and the sum of the momenta parallel to the laser field as a function of the inter-electronic angle of escape where all the main mechanisms have distinct traces. Secondly, we address intensities above but close to the over-the-barrier intensity regime. We find a surprising anti-correlation of electron momenta similar to the experimental observations reported in Phys. Rev. Lett. \\textbf{101}, 053001 (2008). There, however, the anti-correlation was observed in very low intensities corresponding to the multiphoton regime. We discuss the mechanism responsible for the anti-parallel two-electron escape.

  7. Current research in Canada on biological effects of ionizing radiation

    International Nuclear Information System (INIS)

    A survey of current research in Canada on the biological effects of ionizing radiation has been compiled. The list of projects has been classified according to structure (organizational state of the test system) as well as according to the type of effects. Using several assumptions, ballpark estimates of expenditures on these activities have been made. Agencies funding these research activities have been tabulated and the break-down of research in government laboratories and in academic institutions has been designated. Wherever possible, comparisons have been made outlining differences or similarities that exist between the United States and Canada concerning biological radiation research. It has been concluded that relevant research in this area in Canada is inadequate. Wherever possible, strengths and weaknesses in radiation biology programs have been indicated. The most promising course for Canada to follow is to support adequately fundamental studies of the biological effects of radiation. (auth)

  8. Effects of ionization on silicate glasses. [Silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Primak, W.

    1982-02-01

    This evaluation of radiation effects in silicate glasses caused by ionization is based on our own investigations, on material collected in our files (reports, articles, and notes), and on a computer literature search through recent issues of Physics Abstracts and Chemical Abstracts (and the apparently pertinent references which appeared). Some of our recent results, available heretofore only in internal correspondence, are presented in some detail. It is concluded that research into the behavior of silicate glasses generally will be required before the specific effects in the radioactive waste storage glasses can be properly understood and evaluated. Two particular neglected areas of investigation are targeted for immediate concern: a kinetic analysis of annealing data and the acquisition of data on effects of irradiation at controlled elevated temperatures.

  9. Ionizing radiation for sterilization of medical products and biological tissues

    International Nuclear Information System (INIS)

    The article reviews the deliberations of the International Symposium on Ionizing Radiation for Sterilization of Medical Products and Biological Tissues which was held during 9-13 December 1974 under the auspices of the IAEA at the Bhabha Atomic Research Centre, Bombay. 42 papers were presented in the following broad subject areas: (1) Microbiological Control aspects of radiation sterilization, (2) Dosimetry aspects of radiation sterilization practices, (3) Effects of sterilizing radiation dose on the constituents of medical products, (4) Application of radiation sterilization of medical products of biological origin, (5) Technological aspects of radiation sterilization facilities, (6) Radiation sterilization of pharmaceutical substances, (7) Reports on current status of radiation sterilization of medical products in IAEA member states and (8) Working group discussion on the revision of the IAEA recommended code of practice for radiation sterilization of medical products. (S.K.K.)

  10. Ionizing radiation and legislation for personnel - Annex B

    International Nuclear Information System (INIS)

    This annex B presents a chronological approach on the set of laws related to the ionizing radiation personnel. This paper aims to discuss and clarify the main concepts that constitute the current legislation, pointing the scope of each, as well as its ambiguities or inaccuracies. The consequences of those issues discussed are easily noticeable related to difficulties in legal, administrative and human resource management, when seeking their efficient application. We also discuss issues associated with the extent and frequency of the gradient of risk in 5, 10 and 20%, models for assessing potential exposure in a risk area, dose calculation and criteria for defining benefits and framework for irradiation, bonus for activity, special retirement and period of vacations for personnel occupationally exposed within Unified Legal System (Regime Juridico Unico) and the Consolidation of Labor Laws (CLT)

  11. New constraints on the escape of ionizing photons from starburst galaxies using ionization-parameter mapping

    Energy Technology Data Exchange (ETDEWEB)

    Zastrow, Jordan; Oey, M. S. [Department of Astronomy, University of Michigan, 500 Church Street, 830 Dennison, Ann Arbor, MI 48109-1042 (United States); Veilleux, Sylvain [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); McDonald, Michael, E-mail: jazast@umich.edu [Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139 (United States)

    2013-12-10

    The fate of ionizing radiation in starburst galaxies is key to understanding cosmic reionization. However, the galactic parameters on which the escape fraction of ionizing radiation depend are not well understood. Ionization-parameter mapping provides a simple, yet effective, way to study the radiative transfer in starburst galaxies. We obtain emission-line ratio maps of [S III]/[S II] for six, nearby, dwarf starbursts: NGC 178, NGC 1482, NGC 1705, NGC 3125, NGC 7126, and He 2-10. The narrowband images are obtained with the Maryland-Magellan Tunable Filter at Las Campanas Observatory. Using these data, we previously reported the discovery of an optically thin ionization cone in NGC 5253, and here we also discover a similar ionization cone in NGC 3125. This latter cone has an opening angle of 40° ± 5° (0.4 sr), indicating that the passageways through which ionizing radiation may travel correspond to a small solid angle. Additionally, there are three sample galaxies that have winds and/or superbubble activity, which should be conducive to escaping radiation, yet they are optically thick. These results support the scenario that an orientation bias limits our ability to directly detect escaping Lyman continuum in many starburst galaxies. A comparison of the star formation properties and histories of the optically thin and thick galaxies is consistent with the model that high escape fractions are limited to galaxies that are old enough (≳3 Myr) for mechanical feedback to have cleared optically thin passageways in the interstellar medium, but young enough (≲5 Myr) that the ionizing stars are still present.

  12. Theoretical studies of highly ionized species

    Science.gov (United States)

    Dalgarno, A.; Victor, G. A.

    1980-10-01

    The calculations of the charge transfer recombination and ionization rate coefficients for a wide range of ionic systems in collision with hydrogen and helium at thermal energies were completed. For the carbon ions in hydrogen, the calculations were extended to energies of 100 ev. The importance of the processes in ionized plasmas was demonstrated by studies of the solar corona and of shock waves. Preliminary results were obtained on cross sections for the excitation of fine structure transitions by proton impacts. The mechanisms leading to the photodissociation of alkali metal dimers were identified and quantitative predictions were made for Li2. Calculations using the model potential method of properties of the Cu and Zn sequences were brought to a conclusion. Applications of the relativistic random phase approximation were made to the calculation of photoionization cross sections of magnesium-like and zinc-like ions and of oscillator strengths of mercury.

  13. Secondary ionization and heating by fast electrons

    CERN Document Server

    Furlanetto, Steven

    2009-01-01

    We examine the fate of fast electrons (with energies E>10 eV) in a thermal gas of primordial composition. To follow their interactions with the background gas, we construct a Monte Carlo model that includes: (1) electron-electron scattering (which transforms the electron kinetic energy into heat), (2) collisional ionization of hydrogen and helium (which produces secondary electrons that themselves scatter through the medium), and (3) collisional excitation (which produces secondary photons, whose fates we also follow approximately). For the last process, we explicitly include all transitions to upper levels n<=4, together with a well-motivated extrapolation to higher levels. In all cases, we use recent calculated cross-sections at E<1 keV and the Bethe approximation to extrapolate to higher energies. We compute the fractions of energy deposited as heat, ionization (tracking HI and the helium species separately), and excitation (tracking HI Lyman-alpha separately) under a broad range of conditions approp...

  14. Communication: Electron ionization of DNA bases

    Science.gov (United States)

    Rahman, M. A.; Krishnakumar, E.

    2016-04-01

    No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve the existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space.

  15. Shock Wave Dynamics in Weakly Ionized Plasmas

    Science.gov (United States)

    Johnson, Joseph A., III

    1999-01-01

    An investigation of the dynamics of shock waves in weakly ionized argon plasmas has been performed using a pressure ruptured shock tube. The velocity of the shock is observed to increase when the shock traverses the plasma. The observed increases cannot be accounted for by thermal effects alone. Possible mechanisms that could explain the anomalous behavior include a vibrational/translational relaxation in the nonequilibrium plasma, electron diffusion across the shock front resulting from high electron mobility, and the propagation of ion-acoustic waves generated at the shock front. Using a turbulence model based on reduced kinetic theory, analysis of the observed results suggest a role for turbulence in anomalous shock dynamics in weakly ionized media and plasma-induced hypersonic drag reduction.

  16. Upper Hybrid Effects in Artificial Ionization

    Science.gov (United States)

    Papadopoulos, K.; Eliasson, B. E.

    2014-12-01

    A most fascinating result of recent ionospheric experiments has been the discovery of artificial ionization by Pedersen et al. (GRL, 37, L02106, 2010). The Artificial Ionospheric Layers (AIL) were the result of F-region O-mode HF irradiation using the HAARP ionospheric heater operating at 3.6 MW power. As demonstrated by Eliasson et al. (JGR, 117, A10321, 2012) the physics controlling the observed phenomenon and its threshold can be summarized as: " Collisional ionization due to high energy (~ 20 eV) electron tails generated by the interaction of strong Langmuir turbulence with plasma heated at the upper hybrid resonance and transported at the reflection height". The objective of the current presentation is to explore the role of the upper hybrid heating in the formation of AIL and its implications to future experiments involving HF heaters operating in middle and equatorial latitudes.

  17. Ionization and Dust Charging in Protoplanetary Disks

    CERN Document Server

    Ivlev, A V; Caselli, P

    2016-01-01

    Ionization-recombination balance in dense interstellar and circumstellar environments is a key factor for a variety of important physical processes, such as chemical reactions, dust charging and coagulation, coupling of the gas with magnetic field and the development of magnetorotational instability in protoplanetary disks. We present a self-consistent analytical model which allows us to exactly calculate abundances of charged species in dusty gas, in the regime where the dust-phase recombination dominates over the gas-phase recombination. The model is employed to verify applicability of a conventional approximation of low dust charges in protoplanetary disks, and to discuss the implications for the dust coagulation and the development of the "dead zone" in the disk. Furthermore, the importance of mutually consistent models for the ionization and dust evolution is addressed: These processes are coupled via several mechanisms operating in the disk, and therefore their interplay can be crucial for the ultimate ...

  18. Electrostatic-spray ionization mass spectrometry.

    Science.gov (United States)

    Qiao, Liang; Sartor, Romain; Gasilova, Natalia; Lu, Yu; Tobolkina, Elena; Liu, Baohong; Girault, Hubert H

    2012-09-01

    An electrostatic-spray ionization (ESTASI) method has been used for mass spectrometry (MS) analysis of samples deposited in or on an insulating substrate. The ionization is induced by a capacitive coupling between an electrode and the sample. In practice, a metallic electrode is placed close to but not in direct contact with the sample. Upon application of a high voltage pulse to the electrode, an electrostatic charging of the sample occurs leading to a bipolar spray pulse. When the voltage is positive, the bipolar spray pulse consists first of cations and then of anions. This method has been applied to a wide range of geometries to emit ions from samples in a silica capillary, in a disposable pipet tip, in a polymer microchannel, or from samples deposited as droplets on a polymer plate. Fractions from capillary electrophoresis were collected on a polymer plate for ESTASI MS analysis. PMID:22876737

  19. HCO(+) ionization from SGR1806-20

    Science.gov (United States)

    Hannikainen, D.; Durouchoux, P.; Vilhu, O.; Huovelin, J.; Corbel, S.; Wallyn, P.

    1997-01-01

    The region surrounding the soft gamma ray repeater SGR 1806-20 in the HCO(+) (J = 1-0) transition was observed. Previous observations of compact Galactic objects suggest that a link exists between these objects and molecular clouds in which they are possibly embedded. Such a link would help explain some of the phenomena observed from these objects. A measure of the ionization rate as a function of distance from the source implies that the cloud is associated with the source. The abundance of HCO(+), which varies with increasing or decreasing ionization rates, is considered to be an ideal tool for this measurement. The observations acquired in the direction of the nebula surrounding SGR 1806-20 are presented, and the resulting 7 x 12 arcmin map derived from the HCO(+) data is shown.

  20. Communication: Electron ionization of DNA bases.

    Science.gov (United States)

    Rahman, M A; Krishnakumar, E

    2016-04-28

    No reliable experimental data exist for the partial and total electron ionization cross sections for DNA bases, which are very crucial for modeling radiation damage in genetic material of living cell. We have measured a complete set of absolute partial electron ionization cross sections up to 500 eV for DNA bases for the first time by using the relative flow technique. These partial cross sections are summed to obtain total ion cross sections for all the four bases and are compared with the existing theoretical calculations and the only set of measured absolute cross sections. Our measurements clearly resolve the existing discrepancy between the theoretical and experimental results, thereby providing for the first time reliable numbers for partial and total ion cross sections for these molecules. The results on fragmentation analysis of adenine supports the theory of its formation in space. PMID:27131520

  1. Multiphoton dissociative ionization of molecular deuterium

    International Nuclear Information System (INIS)

    The kinetic energy spectra of deuterium ions produced from D2 arising from collision-free subpicosecond irradiation at 248 nm with intensities spanning the 10/sup 13/--10/sup 16/-W/cm2 range have been measured by time-of-flight analysis. The behaviors of the kinetic energy distributions of the fragments and the relative abundances of atomic (D+) and molecular (D2+) ions reveal the presence of two mechanisms of multiphoton dissociative ionization. Calibration of the energy scale for D+ is facilitated by comparison with He/sup 2+/. For intensities in the 10/sup 13/--10/sup 15/-W/cm2 region, intermediate three-photon resonances and the optical Stark shift play important roles. At an intensity /similar to/0/sup 16/ W/cm2, a direct transition from the molecular ground state to the dissociative ionic level appears as a significant channel. No evidence of direct double ionization was observed

  2. Atomic tunneling ionization in a photon picture

    Science.gov (United States)

    Wang, Yujun; Esry, B. D.

    2015-05-01

    Above-threshold ionization (ATI) and high-harmonic generation (HHG) are studied by the photon-phase formalism in the tunneling regime. Different from the commonly used three-step model for understanding such strong-field phenomena, we show that each order of the ATI or HHG peaks is strongly associated with a single ``photon channel'' in the photon-phase picture. This simplicity allows an identification of pathways for each of the orders. This picture not only provides a convenient means to understand the electron dynamics in the strong field, but also gives insights that may help engineer laser pulses to manipulate the output of the ATI or HHG. We apply this method to quantify the strong-field-induced ionization threshold shift and study the carrier-envelope phase dependence of the HHG. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy

  3. Electrospray Ionization Mass Spectra of Dipeptide Derivatives

    Institute of Scientific and Technical Information of China (English)

    LUO, Zaigang; ZENG, Chengchu; YANG, Daoshan; HUANG, Yali; WANG, Fang; DU, Hongguang; HU, Liming

    2009-01-01

    Based on the structure of the HIV integrase core domain, dipeptide derivatives, as a type of HIV integrase in- hibitor, were synthesized, and their fragmentation pathways were investigated by electrospray ionization mass spec- trometry (ESI-MSN) in conjunction with tandem mass spectrometry (MS/MS). In order to better understand the fragmentation pathways, the MS2 and MS3 spectra of the title compound were obtained. The main fragmentation pathways occur by the cleavage of the C-CO bonds between N-(benzothiazol-2-yl)aminocarbonyl and methylene, NH-CO bonds between the NH groups and carbonyl groups. Electrospray ionization was proven to be a good method for the structural characterization and identification of this kind of compound.

  4. The electron-atom ionization problem

    Energy Technology Data Exchange (ETDEWEB)

    McCarthy, I.E.

    1995-02-01

    Methods of calculating electron-atom ionization as a three-body problem with Coulomb boundary conditions are considered. In the absence of a fully-valid computational method for a time-independent experiment the approximation is made that the incident electron experiences a screened potential. Approximations involving a final state that obeys the three-body Coulomb boundary condition are compared with the distorted-wave Born approximation and the convergent close-coupling method. 24 refs., 6 figs.

  5. Sputter-initiated resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    A new technique, sputter-initiated resonance ionization spectroscopy (SIRIS), which provides an ultrasensitive analysis of solid samples for all elements except helium and neon is described in this paper. Sensitivities down to 1 part in 1012 should be available in routine SIRIS analysis, and greater sensitivities should be available for special cases. The basic concepts of this technology and early results in the development of the new SIRIS process and apparatus are presented. (Auth.)

  6. Evolution of envelope solitons of ionization waves

    International Nuclear Information System (INIS)

    The time evolution of a particle-like envelope soliton of ionization waves in plasma was investigated theoretically. The hydrodynamic equations of one spatial dimension were solved and the nonlinear dispersion relation was derived. For the amplitude of the wave the nonlinear Schroedinger equation was derived. Its soliton solution was interpreted as the envelope soliton which was experimentally found. The damping rate of the envelope soliton was estimated. (D.Gy.)

  7. Structure parameters in molecular tunneling ionization theory

    International Nuclear Information System (INIS)

    We extracted the accurate structure parameters in molecular tunneling ionization theory (so called MO-ADK theory) for 22 selected linear molecules including some inner orbitals. The molecular wave functions with the correct asymptotic behavior are obtained by solving the time-independent Schrödinger equation with B-spline functions and molecular potentials numerically constructed using the modified Leeuwen-Baerends (LBα) model.

  8. Calculation of the resonant ionization of helium

    International Nuclear Information System (INIS)

    Autoionizing resonances in the compound system of an electron and a helium ion are observed in kinematically-complete ionization experiments for electrons on helium atoms. The differential cross section is calculated for comparison with these experiments in an equivalent-local form of the distorted-wave impulse approximation. Resonant scattering amplitudes are calculated by a six-state momentum-space coupled-channels method. 10 refs., 1 tab., 2 figs

  9. Ionization fronts in negative corona discharges

    CERN Document Server

    Arrayas, M; Trueba, J L; Arrayas, Manuel; Fontelos, Marco A.; Trueba, Jose L.

    2004-01-01

    In this paper we use a hydrodynamic minimal streamer model to study negative corona discharge. By reformulating the model in terms of a quantity called shielding factor, we deduce laws for the evolution in time of both the radius and the intensity of ionization fronts. We also compute the evolution of the front thickness under the conditions for which it diffuses due to the geometry of the problem and show its self-similar character.

  10. Ionizing radiation and photosynthetic ability of cyanobacteria

    International Nuclear Information System (INIS)

    Unicellular photoautotrophic cyanobacteria, Anacystis nidulans when exposed to lethal dose of 1.5 kGy of 60Co γ- radiation (D10= 257.32 Gy) were as effective photosynthetical as unirradiated controls immediately after irradiation although level of ROS was higher by several magnitudes in these irradiated cells. The results suggested the preservation of the functional integrity of thylakoids even after exposure to lethal dose of ionizing radiation. (author)

  11. Improvement of a New Gas Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to identify heavier elements, we have developed a new longitudinal field gas ionization chamber (IC)with an angle of 30° of plate (as shown in Fig.1). The IC is operated in flowing iso-butane gas at a pressure of 10kPa. After testing by using a 3- component α particle source and comparing with the old longitudinal field

  12. High-temperature Ionization in Protoplanetary Disks

    Science.gov (United States)

    Desch, Steven J.; Turner, Neal J.

    2015-10-01

    We calculate the abundances of electrons and ions in the hot (≳500 K), dusty parts of protoplanetary disks, treating for the first time the effects of thermionic and ion emission from the dust grains. High-temperature ionization modeling has involved simply assuming that alkali elements such as potassium occur as gas-phase atoms and are collisionally ionized following the Saha equation. We show that the Saha equation often does not hold, because free charges are produced by thermionic and ion emission and destroyed when they stick to grain surfaces. This means the ionization state depends not on the first ionization potential of the alkali atoms, but rather on the grains’ work functions. The charged species’ abundances typically rise abruptly above about 800 K, with little qualitative dependence on the work function, gas density, or dust-to-gas mass ratio. Applying our results, we find that protoplanetary disks’ dead zone, where high diffusivities stifle magnetorotational turbulence, has its inner edge located where the temperature exceeds a threshold value ≈1000 K. The threshold is set by ambipolar diffusion except at the highest densities, where it is set by Ohmic resistivity. We find that the disk gas can be diffusively loaded onto the stellar magnetosphere at temperatures below a similar threshold. We investigate whether the “short-circuit” instability of current sheets can operate in disks and find that it cannot, or works only in a narrow range of conditions; it appears not to be the chondrule formation mechanism. We also suggest that thermionic emission is important for determining the rate of Ohmic heating in hot Jupiters.

  13. About particular use of ionizing radiations

    International Nuclear Information System (INIS)

    Different uses of ionizing radiations are reviewed: tracers techniques, nuclear gauges, dating by carbon 14, silica doping, use of gamma irradiation for the density measurement in civil engineering, use of a electron capture detector to study by gas chromatography chlorinated contaminants in environment, neutron activation as environmental gauge, analysis of lead in paint and pollutants in ground and dusts, help for work of art valuation by x spectrometry. (N.C.)

  14. Interlaboratory test program in ionizing radiation metrology

    International Nuclear Information System (INIS)

    In the framework of national coordination, the primary laboratory for ionizing radiation metrology (LMRI) of the BNM organizes every year an interlaboratory test program. The participation to these programs is on a volontary basis and the results are presented in a nameless way. These tests concern radioactivity, neutron and dosimetry measurements. After presenting the >, a typical test is described and the usual conclusions are stated. Finally a survey of the test programs undertaken up to now is presented

  15. Strong field ionization in arbitrary laser polarizations

    OpenAIRE

    Protopapas, M.; Lappas, D. G.; Knight, P. L.

    1997-01-01

    We present a new method for investigating the nonperturbative quantum mechanical interaction of light with atoms in two dimensions, without a basis expansion. This enables us to investigate intense laser-atom interactions with light of arbitrary polarization without approximation, within the model restrictions. Results are presented for the dependence of ionization and high harmonic generation on ellipticity seen in recent experiments. Strong evidence of stabilization in circular polarization...

  16. Design of an ionization diffusion chamber detector

    International Nuclear Information System (INIS)

    Prototype of an Ionization Diffusion Chamber detector has been made. It is a silindrical glass, 20 cm in diameter, 13,5 cm in height, air gas filled, operated at room pressure and room temperature at the top of this instrument while for the box temperature dry ice (CO2 solid) temperature is used. This detector is ready for seeing alpha and beta particle tracks. (author)

  17. Genetic variation in resistance to ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ayala, F.J.

    1989-01-01

    The very reactive superoxide anion O[sub 2] is generated during cell respiration as well as during exposure to ionizing radiation. Organisms have evolved different mechanisms to protect against the deleterious effects of reduced oxygen species. The copper-zinc superoxide dismutase is a eukaryotic cytoplasmic enzyme that protects the cell by scavenging superoxide radicals and dismutating them to hydrogen peroxide and molecular oxygen: 20[sub 2][sup [minus

  18. Screened cluster expansions for partially ionized gases

    OpenAIRE

    Alastuey, A.; Ballenegger, V.; Cornu, F.; Martin, Ph. A.

    2003-01-01

    We consider a partially ionized gas at thermal equilibrium, in the Saha regime. The system is described in terms of a quantum plasma of nuclei and electrons. In this framework, the Coulomb interaction is the source of a large variety of phenomena occuring at different scales: recombination, screening, diffraction, etc. In this paper, we derive a cluster expansion adequate for a coherent treatment of those phenomena. The expansion is obtained by combining the path integral representation of th...

  19. Food ionization: principles, nutritional aspects and detection

    International Nuclear Information System (INIS)

    This document reviews the possible applications of ionizing radiations in the food industry, pointing out the principles of the treatment and its consequences on the nutritionnal value of the product. The last part gives the present status of the researches about the identification of irradiated foodstuffs and of the concerted action sponsored by the Community Bureau of Reference from the Commission of the European Communities

  20. Ionization photophysics and spectroscopy of cyanoacetylene

    Energy Technology Data Exchange (ETDEWEB)

    Leach, Sydney; Champion, Norbert [LERMA UMR CNRS 8112, Observatoire de Paris-Meudon, 5 place Jules-Jansen, 92195 Meudon (France); Garcia, Gustavo A.; Fray, Nicolas; Gaie-Levrel, François [Synchrotron SOLEIL, L’Orme des Merisiers, St. Aubin, B.P. 48, 91192, Gif-sur-Yvette Cedex (France); Mahjoub, Ahmed; Bénilan, Yves; Gazeau, Marie-Claire; Schwell, Martin [LISA UMR CNRS 7583, Université Paris Est Créteil and Université Paris Diderot, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil (France)

    2014-05-07

    Photoionization of cyanoacetylene was studied using synchrotron radiation over the non-dissociative ionization excitation range 11–15.6 eV, with photoelectron-photoion coincidence techniques. The absolute ionization cross-section and spectroscopic aspects of the parent ion were recorded. The adiabatic ionization energy of cyanoacetylene was measured as 11.573 ± 0.010 eV. A detailed analysis of photoelectron spectra of HC{sub 3}N involves new aspects and new assignments of the vibrational components to excitation of the A{sup 2}Σ{sup +} and B{sup 2}Π states of the cation. Some of the structured autoionization features observed in the 11.94 to 15.5 eV region of the total ion yield (TIY) spectrum were assigned to two Rydberg series converging to the B{sup 2}Π state of HC{sub 3}N{sup +}. A number of the measured TIY features are suggested to be vibrational components of Rydberg series converging to the C{sup 2}Σ{sup +} state of HC{sub 3}N{sup +} at ≈17.6 eV and others to valence shell transitions of cyanoacetylene in the 11.6–15 eV region. The results of quantum chemical calculations of the cation electronic state geometries, vibrational frequencies and energies, as well as of the C–H dissociation potential energy profiles of the ground and electronic excited states of the ion, are compared with experimental observations. Ionization quantum yields are evaluated and discussed and the problem of adequate calibration of photoionization cross-sections is raised.

  1. A gas scintillation counter with imaging optics and large area UV-detector

    Energy Technology Data Exchange (ETDEWEB)

    Nickles, J. E-mail: nickles@hsb.uni-frankfurt.de; Braeuning, H.; Braeuning-Demian, A.; Dangendorf, V.; Breskin, A.; Chechik, R.; Rauschnabel, K.; Schmidt-Boecking, H

    2002-01-21

    We report on the improvements in the position sensitive readout of a xenon-filled gas scintillation proportional counter. Using an imaging optic for UV-light in the region of 170 nm, the position resolution could be improved by more than 30%. In addition, we have obtained first encouraging results for the use of the recently developed gas electron multiplier together with a CsI-photocathode as a large area UV-detector system.

  2. A gas scintillation counter with imaging optics and large area UV-detector

    CERN Document Server

    Nickles, J; Bräuning-Demian, A; Breskin, Amos; Chechik, R; Dangendorf, V; Rauschnabel, K; Schmidt-Böcking, H

    2002-01-01

    We report on the improvements in the position sensitive readout of a xenon-filled gas scintillation proportional counter. Using an imaging optic for UV-light in the region of 170 nm, the position resolution could be improved by more than 30%. In addition, we have obtained first encouraging results for the use of the recently developed gas electron multiplier together with a CsI-photocathode as a large area UV-detector system.

  3. Weak interaction studies using resonance ionization spectroscopy

    International Nuclear Information System (INIS)

    Important developments in laser sources for the vacuum ultraviolet (VUV) region of the spectrum are making it possible to carry out resonance ionization of some of the noble gases. It has already been shown that xenon can be ionized in a two-photon allowed excitation from the ground state. Recently a new method of generating radiation by four-wave mixing in mercury vapor enables excitation of xenon in a one-photon resonance process. With these new laser sources they expect to have effective ionization volumes of 10-3-10-2 cm3 for the cases of argon, krypton, and xenon. This has important consequences in weak interaction physics and environmental research. Widespread applications of noble gas detectors are due to the fact that small numbers of the chemically inert atoms can be recovered from very large targets of materials where they may be generated by rare events. In this lecture they show how lasers can be combined with mass spectrometers to detect a few noble gas atoms of one isotope in the presence of very large numbers of atoms of a neighboring isotope. This technique (which they have called Maxwell's demon because of the atom-sorting functions performed in the apparatus) is described and then followed with a brief discussion of two applications in weak interaction physics - double-beta decay and the solar neutrino problem

  4. Basic Data of Ionized Gas Physics

    International Nuclear Information System (INIS)

    An ionized gas can a priori contain the following types of particle: photons, electrons, atoms, diatomic or polyatomic molecules, atomic or molecular positive ions and atomic or molecular negative ions. A study of the properties of ionized gases must therefore be based on the fundamental data on the interactions between these particles, i.e. elastic or inelastic collision cross-sections and the probability of induced or spontaneous transitions. From these basic data it is possible to calculate theoretically certain elementary macroscopic properties such as ion and electron mobility, diffusion coefficients, Townsend's first coefficient, recombination and attachment coefficients. These results (cross-sections and elementary macroscopic properties) constitute as a body the basic data for the physics of ionized gases. The paper is devoted to these basic data, concentrating on cross-sections, mobilities and diffusion coefficients. Beginning with a brief review of the literature, it consists essentially of tables of suggested numerical values, which the author intends to be used as a basis for discussion. Experts in each of the phenomena are invited to indicate values which seem to them better than those selected, and to fill in, where possible, the gaps in this study. In this way it is hoped that by the next Conference a more precise and more complete collection of data will be available. (author)

  5. Kinematics of 3-body in Ionization Collision

    International Nuclear Information System (INIS)

    In this thesis we study three body problems in the frame of the collision theory. First, we deal with the process of autoionization by ion impact where the line profile of the electron emitted is strongly affected by the post-collision interaction with the Coulomb field of the outgoing projectile.Here we analyze how these effects are modified when the projectile velocity is in the close vicinity of the resonant electron velocity.In this energy range, the analysis of the resonance contribution is hindered by the characteristic 'electron capture to the continuum' divergence in the direct term.Here we present a detailed theoretical study of the interplay between both contributions, based on a generalization of the Final-State Interaction model.Finally we propose a modified parameterization of the autoionization line shape in the vicinity of the ECC cusp.Secondly, we study the direct ionization of an atomic target by the impact of a charge projectile, through analysis of the quintuple differential cross section (QDCS) which gives the most complete information about a ionization collision.Its study, without any approximation on the mass ratios can unveil new, not previously observed, structures.In particular, in this work the ionization of Hydrogen molecules by the impact of positrons and muons was studied and a new structure that has not been identified until now was found. Its main characteristics and a possible explanation are presented

  6. Ionizing radiation induces stemness in cancer cells.

    Directory of Open Access Journals (Sweden)

    Laura Ghisolfi

    Full Text Available The cancer stem cell (CSC model posits the presence of a small number of CSCs in the heterogeneous cancer cell population that are ultimately responsible for tumor initiation, as well as cancer recurrence and metastasis. CSCs have been isolated from a variety of human cancers and are able to generate a hierarchical and heterogeneous cancer cell population. CSCs are also resistant to conventional chemo- and radio-therapies. Here we report that ionizing radiation can induce stem cell-like properties in heterogeneous cancer cells. Exposure of non-stem cancer cells to ionizing radiation enhanced spherogenesis, and this was accompanied by upregulation of the pluripotency genes Sox2 and Oct3/4. Knockdown of Sox2 or Oct3/4 inhibited radiation-induced spherogenesis and increased cellular sensitivity to radiation. These data demonstrate that ionizing radiation can activate stemness pathways in heterogeneous cancer cells, resulting in the enrichment of a CSC subpopulation with higher resistance to radiotherapy.

  7. Air density correction in ionization dosimetry

    International Nuclear Information System (INIS)

    Air density must be taken into account when ionization dosimetry is performed with unsealed ionization chambers. The German dosimetry protocol DIN 6800-2 states an air density correction factor for which current barometric pressure and temperature and their reference values must be known. It also states that differences between air density and the attendant reference value, as well as changes in ionization chamber sensitivity, can be determined using a radioactive check source. Both methods have advantages and drawbacks which the paper discusses in detail. Barometric pressure at a given height above sea level can be determined by using a suitable barometer, or data downloaded from airport or weather service internet sites. The main focus of the paper is to show how barometric data from measurement or from the internet are correctly processed. Therefore the paper also provides all the requisite equations and terminological explanations. Computed and measured barometric pressure readings are compared, and long-term experience with air density correction factors obtained using both methods is described

  8. Electron-impact ionization of W27 +

    Science.gov (United States)

    Pindzola, M. S.; Loch, S. D.

    2016-06-01

    Electron-impact ionization cross sections for W27 + are calculated using a semirelativistic configuration-average distorted-wave (CADW) method. Calculations for direct ionization, excitation autoionization, and branching ratios are compared with recent calculations by Jonauskas et al. [Phys. Rev. A 91, 012715 (2015), 10.1103/PhysRevA.91.012715], who used fully relativistic subconfiguration-average distorted-wave (SCADW) and level-to-level distorted-wave (LLDW) methods. Reasonable agreement is found between the CADW and the recent LLDW calculations for direct ionization of the 4 l (l =0 -1 ,3 ) subshells, but not the 4 d subshell, and between the CADW and recent SCADW-LLDW calculations for excitation autoionization of the 4 l (l =0 -2 ) subshells. Reasonable agreement is also found between the CADW and the recent SCADW calculations, including branching ratios, but both differ from the recent LLDW calculations. Additional CADW calculations are made for excitation autoionization, including branching ratios involving the important 3 l (l =1 -2 ) subshells, not examined by Jonauskas et al. [Phys. Rev. A 91, 012715 (2015), 10.1103/PhysRevA.91.012715].

  9. Ionizing radiation, cancer induction and radioactive fallout

    International Nuclear Information System (INIS)

    One hundred years of observations of ionizing radiation have led to a number of major discoveries, including [1] ionizing radiation induces gene mutations in animals at a rate linearly proportional to dose, [2] certain cancers are induced by relatively high doses at a rate that is linearly proportional to the dose, [3] exposure of the fetus to very low doses of x-rays has been associated with an increased risk of cancer developing during childhood, and [4] many cancers result from somatic mutations in genes that control the normal growth and differentiation of cells. Cancers induced by ionizing radiation are likely therefore to result from somatic mutations, as first predicted by H. J. Muller in 1927. Large scale man-made releases of radioactive fallout have occurred and pose a cancer hazard. A special case is the risk of thyroid cancer to infants who ingest the radioiodines in such fallout. Ongoing epidemiological studies of persons exposed to fallout from the Chernobyl accident in 1986 may eventually help to quantify risks associated with very low radiation doses and low dose rates. Governments and societies will need to be better prepared to cope with any future releases of radioactive fallout. (author)

  10. The Phobos neutral and ionized torus

    Science.gov (United States)

    Poppe, A. R.; Curry, S. M.; Fatemi, S.

    2016-05-01

    Charged particle sputtering, micrometeoroid impact vaporization, and photon-stimulated desorption are fundamental processes operating at airless surfaces throughout the solar system. At larger bodies, such as Earth's Moon and several of the outer planet moons, these processes generate tenuous surface-bound exospheres that have been observed by a variety of methods. Phobos and Deimos, in contrast, are too gravitationally weak to keep ejected neutrals bound and, thus, are suspected to generate neutral tori in orbit around Mars. While these tori have not yet been detected, the distribution and density of both the neutral and ionized components are of fundamental interest. We combine a neutral Monte Carlo model and a hybrid plasma model to investigate both the neutral and ionized components of the Phobos torus. We show that the spatial distribution of the neutral torus is highly dependent on each individual species (due to ionization rates that span nearly 4 orders of magnitude) and on the location of Phobos with respect to Mars. Additionally, we present the flux distribution of torus pickup ions throughout the Martian system and estimate typical pickup ion fluxes. We find that the predicted pickup ion fluxes are too low to perturb the ambient plasma, consistent with previous null detections by spacecraft around Mars.

  11. Resonance ionization laser ion sources for on-line isotope separators (invited).

    Science.gov (United States)

    Marsh, B A

    2014-02-01

    A Resonance Ionization Laser Ion Source (RILIS) is today considered an essential component of the majority of Isotope Separator On Line (ISOL) facilities; there are seven laser ion sources currently operational at ISOL facilities worldwide and several more are under development. The ionization mechanism is a highly element selective multi-step resonance photo-absorption process that requires a specifically tailored laser configuration for each chemical element. For some isotopes, isomer selective ionization may even be achieved by exploiting the differences in hyperfine structures of an atomic transition for different nuclear spin states. For many radioactive ion beam experiments, laser resonance ionization is the only means of achieving an acceptable level of beam purity without compromising isotope yield. Furthermore, by performing element selection at the location of the ion source, the propagation of unwanted radioactivity downstream of the target assembly is reduced. Whilst advances in laser technology have improved the performance and reliability of laser ion sources and broadened the range of suitable commercially available laser systems, many recent developments have focused rather on the laser/atom interaction region in the quest for increased selectivity and/or improved spectral resolution. Much of the progress in this area has been achieved by decoupling the laser ionization from competing ionization processes through the use of a laser/atom interaction region that is physically separated from the target chamber. A new application of gas catcher laser ion source technology promises to expand the capabilities of projectile fragmentation facilities through the conversion of otherwise discarded reaction fragments into high-purity low-energy ion beams. A summary of recent RILIS developments and the current status of laser ion sources worldwide is presented.

  12. Resonance ionization laser ion sources for on-line isotope separators (invited)

    International Nuclear Information System (INIS)

    A Resonance Ionization Laser Ion Source (RILIS) is today considered an essential component of the majority of Isotope Separator On Line (ISOL) facilities; there are seven laser ion sources currently operational at ISOL facilities worldwide and several more are under development. The ionization mechanism is a highly element selective multi-step resonance photo-absorption process that requires a specifically tailored laser configuration for each chemical element. For some isotopes, isomer selective ionization may even be achieved by exploiting the differences in hyperfine structures of an atomic transition for different nuclear spin states. For many radioactive ion beam experiments, laser resonance ionization is the only means of achieving an acceptable level of beam purity without compromising isotope yield. Furthermore, by performing element selection at the location of the ion source, the propagation of unwanted radioactivity downstream of the target assembly is reduced. Whilst advances in laser technology have improved the performance and reliability of laser ion sources and broadened the range of suitable commercially available laser systems, many recent developments have focused rather on the laser/atom interaction region in the quest for increased selectivity and/or improved spectral resolution. Much of the progress in this area has been achieved by decoupling the laser ionization from competing ionization processes through the use of a laser/atom interaction region that is physically separated from the target chamber. A new application of gas catcher laser ion source technology promises to expand the capabilities of projectile fragmentation facilities through the conversion of otherwise discarded reaction fragments into high-purity low-energy ion beams. A summary of recent RILIS developments and the current status of laser ion sources worldwide is presented

  13. Electron-impact ionization of Se2+ and Se3+

    Science.gov (United States)

    Pindzola, M. S.; Loch, S. D.

    2016-06-01

    Electron-impact ionization cross sections for Se2+ and Se3+ are calculated using a semi-relativistic configuration-average distorted-wave (CADW) method. Good agreement between the CADW calculations and recent experimental measurements are found for the single ionization of Se2+ from threshold to 500 eV and for the double ionization of Se2+ from threshold to 225 eV. Good agreement between the CADW calculations and recent experimental measurements are also found for the single ionization of Se3+ from threshold to 200 eV and for the double ionization of Se3+ near the peak of the cross section at 350 eV. Disagreements at other incident electron energies may be due to the complexity of the ionization pathways for low charged Se atomic ions, the various theoretical approximations, and the difficulty in measuring relatively small double ionization events.

  14. The effect of recombination radiation on the temperature and ionization state of partially ionized gas

    Science.gov (United States)

    Raičević, Milan; Pawlik, Andreas H.; Schaye, Joop; Rahmati, Alireza

    2014-01-01

    A substantial fraction of all ionizing photons originate from radiative recombinations. However, in radiative transfer calculations this recombination radiation is often assumed to be absorbed `on-the-spot' because for most methods the computational cost associated with the inclusion of gas elements as sources is prohibitive. We present a new, CPU and memory efficient implementation for the transport of ionizing recombination radiation in the TRAPHIC radiative transfer scheme. TRAPHIC solves the radiative transfer equation by tracing photon packets at the speed of light and in a photon-conserving manner in spatially adaptive smoothed particle hydrodynamics simulations. Our new implementation uses existing features of the TRAPHIC scheme to add recombination radiation at no additional cost in the limit in which the fraction of the simulation box filled with radiation approaches 1. We test the implementation by simulating an H II region in photoionization equilibrium and comparing to reference solutions presented in the literature, finding excellent agreement. We apply our implementation to discuss the evolution of the H II region to equilibrium. We show that the widely used case A and B approximations yield accurate ionization profiles only near the source and near the ionization front, respectively. We also discuss the impact of recombination radiation on the geometry of shadows behind optically thick absorbers. We demonstrate that the shadow region may be completely ionized by the diffuse recombination radiation field and discuss the important role of heating by recombination radiation in the shadow region.

  15. Laser-Induced Ionization Efficiency Enhancement On A Filament For Thermal Ionization Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Siegfried, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-10-14

    The evaluation of trace Uranium and Plutonium isotope ratios for nanogram to femtogram material quantities is a vital tool for nuclear counter-proliferation and safeguard activities. Thermal Ionization Mass Spectrometry (TIMS) is generally accepted as the state of the art technology for highly accurate and ultra-trace measurements of these actinide ratios. However, the very low TIMS ionization yield (typically less than 1%) leaves much room for improvement. Enhanced ionization of Nd and Sm from a TIMS filament was demonstrated using wavelength resonance with a nanosecond (pulse width) laser operating at 10 Hz when light was directed toward the filament.1 For this study, femtosecond and picosecond laser capabilities were to be employed to study the dissociation and ionization mechanisms of actinides/lanthanides and measure the enhanced ionization of the metal of interest. Since the underlying chemistry of the actinide/lanthanide carbides produced and dissociated on a TIMS filament is not well understood, the experimental parameters affecting the photodissociation and photoionization with one and two laser beams were to be investigated.

  16. Orientation-dependent ionization yields from strong-field ionization of fixed-in-space linear and asymmetric top molecules

    CERN Document Server

    Hansen, Jonas L; Nielsen, Jens H; Stapelfeldt, Henrik; Dimitrovski, Darko; Madsen, Lars Bojer

    2011-01-01

    The yield of strong-field ionization, by a linearly polarized probe pulse, is studied experimentally and theoretically, as a function of the relative orientation between the laser field and the molecule. Experimentally, carbonyl sulfide, benzonitrile and naphthalene molecules are aligned in one or three dimensions before being singly ionized by a 30 fs laser pulse centered at 800 nm. Theoretically, we address the behaviour of these three molecules. We consider the degree of alignment and orientation and model the angular dependence of the total ionization yield by molecular tunneling theory accounting for the Stark shift of the energy level of the ionizing orbital. For naphthalene and benzonitrile the orientational dependence of the ionization yield agrees well with the calculated results, in particular the observation that ionization is maximized when the probe laser is polarized along the most polarizable axis. For OCS the observation of maximum ionization yield when the probe is perpendicular to the intern...

  17. Geometry- and diffraction-independent ionization probabilities in intense laser fields: probing atomic ionization mechanisms with effective intensity matching

    CERN Document Server

    Bryan, W A; English, E M L; Goodworth, T R J; Newell, W R; McKenna, J A; Suresh, M; Srigengan, B; Williams, I D; Turcu, I C E; Smith, J M; Divall, E J; Hooker, C J; Langley, A J

    2005-01-01

    We report a novel experimental technique for the comparison of ionization processes in ultrafast laser pulses irrespective of pulse ellipticity. Multiple ionization of xenon by 50 fs 790 nm, linearly and circularly polarized laser pulses is observed over the intensity range 10 TW/cm^2 to 10 PW/cm^2 using Effective Intensity Matching (EIM), which is coupled with Intensity Selective Scanning (ISS) to recover the geometry-independent probability of ionization. Such measurements, made possible by quantifying diffraction effects in the laser focus, are compared directly to theoretical predictions of multiphoton, tunnel and field ionization, and a remarkable agreement demonstrated. EIM-ISS allows the straightforward quantification of the probability of recollision ionization in a linearly polarized laser pulse. Furthermore, probability of ionization is discussed in terms of the Keldysh adiabaticity parameter, gamma, and the influence of the precursor ionic states present in recollision ionization is observed for th...

  18. Instantaneous ionization rate of H$_2^+$ in intense laser field; Interpretation of the Enhanced Ionization

    CERN Document Server

    Vafaee, M; Vafaee, Z; Katanforoush, A; Vafaee, Mohsen; Sabzyan, Hassan; Vafaee, Zahra; Katanforoush, Ali

    2005-01-01

    The fixed-nuclei full dimensional time-dependent Schr \\"odinger equation is directly solved for H$_2^+$ in the linearly polarized laser field of $I \\sim 1.0 \\times 10^{14}$W cm$^{-2}$ and $\\lambda \\sim 1064 $nm. Instantaneous ionization rate has been introduced and calculated by evaluating the instantaneous imaginary energy of the system. It is shown that positive (negative) values of instantaneous imaginary energy of the system represent the incoming (outgoing) instantaneous current of electron. This approach allows us to determine not only the instantaneous intensity but also the instantaneous direction of the electronic current. The instantaneous behavior of the electron wavepacket in intense laser field can thus be probed precisely. Details of the enhanced ionization rates are studied based on the instantaneous ionization rates. This approach gives direct evidence for existence of the effect of charge-resonance-enhanced multiphoton resonances of the quasienergy states (QES) with excited electronic states ...

  19. Determination of the first ionization potential of actinides by resonance ionization mass spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Koehler, S. [Institut fuer Kernchemie Universitaet Mainz, Mainz (Germany); Albus, F. [Institu fuer Physik, Universitaet Mainz, Mainz (Germany); Dibenberger, R.; Erdmann, N.; Funk, H. [Institut fuer Kernchemiess Universitaet Mainz, Mainz (Germany); Hasse, H. [Institut fuer Physik, Universitaet Mainz, Mainz (Germany); Herrmann, G. [Institut fuer Kernchemiess Universitaet Mainz, Mainz (Germany); Huber, G.; Kluge, H.; Nunnemann, M.; Passler, G. [Institut fuer Physik, Universitaet Mainz, Mainz (Germany); Rao, P.M. [Bhabha Atomic Research Centre Bombay (India); Riegel, J.; Trautmann, N. [Institut fuer Kernchemie Universitaet Mainz, Mainz (Germany); Urban, F. [Institut fuer Physik, Universitaet Mainz, Mainz (Germany)

    1995-04-01

    Resonance ionization mass spectroscopy (RIMS) is used for the precise determination of the first ionization potential of transuranium elements. The first ionization potentials (IP) of americium and curium have been measured for the first time to IP{sub {ital Am}}=5.9738(2) and IP{sub {ital Cm}}=5.9913(8) eV, respectively, using only 10{sup 12} atoms of {sup 243}Am and {sup 248}Cm. The same technique was applied to thorium, neptunium, and plutonium yielding IP{sub T{sub H}}=6.3067(2), IP{sub N{sub P}}=6.2655(2), and IP{sub {ital Pu}}=6.0257(8) eV. The good agreement of our results with the literature data proves the precision of the method which was additionally confirmed by the analysis of Rydberg seris of americium measured by RIMS. {copyright}American Institute of Physics 1995

  20. Data on ionization, excitation, dissociation and dissociative ionization of targets by helium ion bombardments, (1)

    International Nuclear Information System (INIS)

    This report presents a compilation of the experimental data on cross sections for the ionization, excitation, dissociation and dissociative ionization processes of targets in helium ion impacts on atoms and molecules under a single collision condition. These measurements were carried out in the energy range from several keV to 3.5 MeV. A systematic survey has been made on the literatures from 1975 to the end of 1982. A list of references is also given, including relevant papers published before 1975. (author)