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Sample records for 3he proportional counters

  1. Neutron fluence determination at reactor filters by 3He proportional counters: Comparison of unfolding algorithms

    Multichannel pulse height measurements with a cylindrical 3He proportional counter obtained at a reactor filter of natural iron are taken to investigate the properties of three algorithms for neutron spectrum unfolding. For a systematic application of uncertainty propagation the covariance matrix of previously determined 3He response functions is evaluated. The calculated filter transmission function together with a covariance matrix estimated from cross-section uncertainties of the filter material is used as fluence pre-information. The results obtained from algorithms with and without pre-information differ in shape and uncertainties for single group fluence values, but there is sufficient agreement when evaluating integrals over neutron energy intervals

  2. An array of low-background 3He proportional counters for theSudbury Neutrino Observatory

    Amsbaugh, J.F.; Anaya, J.M.; Banar, J.; Bowles, T.J.; Browne,M.C.; Bullard, T.V.; Burritt, T.H.; Cox-Mobrand, G.A.; Dai, X.; H.Deng,X.; Di Marco, M.; Doe, P.J.; Dragowsky, M.R.; Duba, C.A.; Duncan, F.A.; Earle, E.D.; Elliott, S.R.; Esch, E.-I.; Fergani, H.; Formaggio, J.A.; Fowler, M.M.; Franklin, J.E.; Geissbuehler, P.; Germani, J.V.; Goldschmidt, A.; Guillian, E.; Hallin, A.L.; Harper, G.; Harvey, P.J.; Hazama, R.; Heeger, K.M.; Heise, J.; Hime, A.; Howe, M.A.; Huang, M.; Kormos, L.L.; Kraus, C.; Krauss, C.B.; Law, J.; Lawson, I.T.; Lesko,K.T.; Loach, J.C.; Majerus, S.; Manor, J.; McGee, S.; Miknaitis, K.K.S.; Miller, G.G.; Morissette, B.; Myers, A.; Oblath, N.S.; O' Kee, H.M.; Ollerhead, R.W.; Peeters, S.J.M.; Poon, A.W.P.; Prior, G.; Reitzner,S.D.; Rielage, K.; Robertson, R.G.H.; Skensved, P.; Smith, A.R.; Smith,M.W.E.; Steiger, T.D.; Stonehill,L.C.; Thornewell, P.M.; Tolich, N.; VanDevender, B.A.; VanWechel, T.D.; Wall, B.L.; Tseung, H.W.C.; Wendland,J.; West, N.; Wilhelmy, J.B.; Wilkerson, J.F.; Wouters, J.M.

    2007-02-01

    An array of Neutral-Current Detectors (NCDs) has been builtin order to make a unique measurement of the total active ux of solarneutrinos in the Sudbury Neutrino Observatory (SNO). Data in the thirdphase of the SNO experiment were collected between November 2004 andNovember 2006, after the NCD array was added to improve theneutral-current sensitivity of the SNO detector. This array consisted of36 strings of proportional counters lled with a mixture of 3He and CF4gas capable of detecting the neutrons liberated by the neutrino-deuteronneutral current reaction in the D2O, and four strings lled with a mixtureof 4He and CF4 gas for background measurements. The proportional counterdiameter is 5 cm. The total deployed array length was 398 m. The SNO NCDarray is the lowest-radioactivity large array of proportional countersever produced. This article describes the design, construction,deployment, and characterization of the NCD array, discusses theelectronics and data acquisition system, and considers event signaturesand backgrounds.

  3. Design and performance of A 3He-free coincidence counter based on parallel plate boron-lined proportional technology

    Henzlova, D.; Menlove, H. O.; Marlow, J. B.

    2015-07-01

    Thermal neutron counters utilized and developed for deployment as non-destructive assay (NDA) instruments in the field of nuclear safeguards traditionally rely on 3He-based proportional counting systems. 3He-based proportional counters have provided core NDA detection capabilities for several decades and have proven to be extremely reliable with range of features highly desirable for nuclear facility deployment. Facing the current depletion of 3He gas supply and the continuing uncertainty of options for future resupply, a search for detection technologies that could provide feasible short-term alternative to 3He gas was initiated worldwide. As part of this effort, Los Alamos National Laboratory (LANL) designed and built a 3He-free full scale thermal neutron coincidence counter based on boron-lined proportional technology. The boron-lined technology was selected in a comprehensive inter-comparison exercise based on its favorable performance against safeguards specific parameters. This paper provides an overview of the design and initial performance evaluation of the prototype High Level Neutron counter-Boron (HLNB). The initial results suggest that current HLNB design is capable to provide ~80% performance of a selected reference 3He-based coincidence counter (High Level Neutron Coincidence Counter, HLNCC). Similar samples are expected to be measurable in both systems, however, slightly longer measurement times may be anticipated for large samples in HLNB. The initial evaluation helped to identify potential for further performance improvements via additional tailoring of boron-layer thickness.

  4. Design and performance of A 3He-free coincidence counter based on parallel plate boron-lined proportional technology

    Thermal neutron counters utilized and developed for deployment as non-destructive assay (NDA) instruments in the field of nuclear safeguards traditionally rely on 3He-based proportional counting systems. 3He-based proportional counters have provided core NDA detection capabilities for several decades and have proven to be extremely reliable with range of features highly desirable for nuclear facility deployment. Facing the current depletion of 3He gas supply and the continuing uncertainty of options for future resupply, a search for detection technologies that could provide feasible short-term alternative to 3He gas was initiated worldwide. As part of this effort, Los Alamos National Laboratory (LANL) designed and built a 3He-free full scale thermal neutron coincidence counter based on boron-lined proportional technology. The boron-lined technology was selected in a comprehensive inter-comparison exercise based on its favorable performance against safeguards specific parameters. This paper provides an overview of the design and initial performance evaluation of the prototype High Level Neutron counter—Boron (HLNB). The initial results suggest that current HLNB design is capable to provide ~80% performance of a selected reference 3He-based coincidence counter (High Level Neutron Coincidence Counter, HLNCC). Similar samples are expected to be measurable in both systems, however, slightly longer measurement times may be anticipated for large samples in HLNB. The initial evaluation helped to identify potential for further performance improvements via additional tailoring of boron-layer thickness

  5. Precision measurement of thermal neutron beam densities using a 3He proportional counter

    Als-Nielsen, Jens Aage; Bahnsen, A.; Brown, W.K.

    1967-01-01

    of ±0.4%. Fundamental advantages of the method include the 1ν dependence of the 3He(n, p)T cross section up to 1 keV, and the assurance of homogeneity even for very small macroscopic cross sections, because of the gaseous detector material. Although the method requires a relatively clean neutron beam...

  6. Calculations of the response functions of Bonner spheres with a spherical 3He proportional counter using a realistic detector model

    A realistic geometry model of a Bonner sphere system with a spherical 3He-filled proportional counter and 12 polyethylene moderating spheres with diameters ranging from 7,62 cm (3'') to 45,72 cm (18'') is introduced. The MCNP Monte Carlo computer code is used to calculate the responses of this Bonner sphere system to monoenergetic neutrons in the energy range between 1 meV to 20 MeV. The relative uncertainties of the responses due to the Monte Carlo calculations are less than 1% for spheres up to 30,48 cm (12'') in diameter and less than 2% for the 15'' and 18'' spheres. Resonances in the carbon cross section are seen as significant structures in the response functions. Additional calculations were made to study the influence of the 3He number density and the polyethylene mass density on the response as well as the angular dependence of the Bonner sphere system. The calculated responses can be adjusted to a large set of calibration measurements with only a single fit factor common to all sphere diameters and energies. (orig.)

  7. Novel and efficient 10B lined tubelet detector as a replacement for 3He neutron proportional counters

    Tsorbatzoglou, Kyriakos; McKeag, Robert D.

    2011-10-01

    This paper presents a novel and robust proportional detector which addresses the well publicized shortage of 3He gas by using a 10B lining applied to a tubelet configuration. The advantage of the tubelet structure is that it yields a detector maintaining the form factor of a conventional 3He tube whilst achieving a sensitivity of up to 75% of a 3 atm 3He device. The design and fabrication of the tubelet detector is presented and discussed with test data comparing the new detector to existing 3He and BF 3 tubes. The application of the tubelet design to security and industrial applications including retro-fitting to existing portals and suitability for high integrity oil and gas installations is addressed.

  8. A study of characteristics of Helium-3 (He-3) proportional counters in order to design electronic circuits for neutron detection

    This study aims to research and develop function circuits, electronic blocks, programming software for He-3 proportional counters using commonly in neutron detection. Results are compared with those of a neutron dosimeter available in Institute for Nuclear Science and Technology (INST). Although the method has been known for a long time on the world, it is newly used in Vietnam. If the study is applied in reality, neutron dosimeters will be manufactured with acceptable price, high quality, and easy maintenance which are suitable with domestic demands. It contributes to nuclear safety and economy-society development. (author)

  9. Independent Measurement of the Total Active 8B Solar Neutrino Flux Using an Array of 3He Proportional Counters at the Sudbury Neutrino Observatory

    Peeters, Simon; SNO Collaboration,

    2008-01-01

    The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54(+0.33/-0.31 stat, +0.36/-0.34 syst) x 10^6 cm^-2 s^-1, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino res...

  10. An Independent Measurement of the Total Active 8B Solar Neutrino Flux Using an Array of 3He Proportional Counters at the Sudbury Neutrino Observatory

    Aharmim, B; Amsbaugh, J F; Anthony, A E; Banar, J; Barros, N; Beier, E W; Bellerive, A; Beltran, B; Bergevin, M; Biller, S D; Boudjemline, K; Boulay, M G; Bowles, T J; Browne, M C; Bullard, T V; Burritt, T H; Cai, B; Chan, Y D; Chauhan, D; Chen, M; Cleveland, B T; Cox-Mobrand, G A; Currat, C A; Dai, X; Deng, H; Detwiler, J; Di Marco, M; Doe, P J; Doucas, G; Drouin, P L; Duba, C A; Duncan, F A; Dunford, M; Earle, E D; Elliott, S R; Evans, H C; Ewan, G T; Farine, J; Fergani, H; Fleurot, F; Ford, R J; Formaggio, J A; Fowler, M M; Gagnon, N; Germani, J V; Goldschmidt, A; Goon, J T M; Graham, K; Guillian, E; Habib, S; Hahn, R L; Hallin, A L; Hallman, E D; Hamian, A A; Harper, G C; Harvey, P J; Hazama, R; Heeger, K M; Heintzelman, W J; Heise, J; Helmer, R L; Henning, R; Hime, A; Howard, C; Howe, M A; Huang, M; Jagam, P; Jamieson, B; Jelley, N A; Keeter, K J; Klein, J R; Kormos, L L; Kos, M; Krüger, A; Kraus, C; Krauss, C B; Kutter, T; Kyba, C C M; Lange, R; Law, J; Lawson, I T; Lesko, K T; Leslie, J R; Loach, J C; MacLellan, R; Majerus, S; Mak, H B; Maneira, J; Martin, R; McBryde, K; McCauley, N; McDonald, A B; McGee, S; Miin, C; Miller, G G; Miller, M L; Monreal, B; Monroe, J; Morissette, B; Myers, A; Nickel, B G; Noble, A J; Oblath, N S; O'Keeffe, H M; Ollerhead, R W; Orebi Gann, G D; Oser, S M; Ott, R A; Peeters, S J M; Poon, A W P; Prior, G; Reitzner, S D; Rielage, K; Robertson, B C; Robertson, R G H; Rollin, E; Schwendener, M H; Secrest, J A; Seibert, S R; Simard, O; Simpson, J J; Sinclair, L; Skensved, P; Smith, M W E; Steiger, T D; Stonehill, L C; Tesic, G; Thornewell, P M; Tolich, N; Tsui, T; Tunnell, C D; Van Wechel, T; Van Berg, R; Van Devender, B A; Virtue, C J; Walker, T J; Wall, B L; Waller, D; Wan Chan Tseung, H; Wendland, J; West, N; Wilhelmy, J B; Wilkerson, J F; Wilson, J R; Wouters, J M; Wright, A; Yeh, M; Zhang, F; Zuber, K

    2008-01-01

    The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54(+0.33/-0.31 stat, +0.36/-0.34 syst) x 10^6 cm^-2 s^-1, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Delta m^2 = 7.94(+0.42/-0.26) x 10^-5 eV^2 and theta = 33.8(+1.4/-1.3) degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.

  11. Safeguards Technology Factsheet 3He-free Neutron Coincidence Counter

    A full scale thermal neutron coincidence counter (High Level Neutron Counter - Boron: HLNB) based on 3He alternative detection technology was designed and built at LANL and field tested at Plutonium Conversion Development Facility (PCDF) of Japan Atomic Energy Agency (JAEA) during FY15. HLNB is based on boron-lined proportional plates that replace the traditional 3He proportional tubes and was designed as a direct alternative to 3He-based High Level Neutron Coincidence Counter (HLNC-II). During the JAEA field trial the HLNB demonstrated comparable performance to HLNC-II, which represents a key development in the area of 3He alternative technologies and provides a complete demonstration of the technology for nuclear safeguards applications including high mass MOX samples.

  12. Proportional counter as neutron detector

    Braby, L. A.; Badhwar, G. D.

    2001-01-01

    A technique to separate out the dose, and lineal energy spectra of neutrons and charged particles is described. It is based on using two proportional counters, one with a wall, and the other with similar characteristics but wall made from a non-hydrogen containing material. Results of a calibration in a neutron field are also shown. c2001 Elsevier Science Ltd. All rights reserved.

  13. Full simulation of the Sudbury Neutrino Observatory proportional counters

    The third phase of the Sudbury Neutrino Observatory (SNO) experiment added an array of 3He proportional counters to the detector. The purpose of this neutral-current detection (NCD) array was to observe neutrons resulting from neutral-current solar-neutrino-deuteron interactions. We have developed a detailed simulation of current pulses from NCD array proportional counters, from the primary neutron capture on 3He through NCD array signal-processing electronics. This NCD array MC simulation was used to model the alpha-decay background in SNO's third-phase 8B solar-neutrino measurement.

  14. Full simulation of the Sudbury Neutrino Observatory proportional counters

    Beltran, B; Cai, B.; Cox, G.A.; Deng, H.; Detwiler, J.; Formaggio, J.A.; Habib, S.; Hallin, A.L.; Hime, A.; Huang, M.; Kraus, C.; Leslie, H.R.; Loach, J.C.; Martin, R.; McGee, S.; Miller, M.L.; Monreal, B.; Monroe, J.; Oblath, N.S.; Peeters, S.J.M.; Poon, A.W.P.; Prior, G.; Rielage, K.; Robertson, R.G.H.; Smith, M.W.E.; Stonehill, L.C.; Tolich, N.; Van Wechel, T.; Wan Chan Tseung, H.; Wendland, J.; Wilkerson, J.F.; Wright, A.

    2011-01-01

    The third phase of the Sudbury Neutrino Observatory (SNO) experiment added an array of 3He proportional counters to the detector. The purpose of this Neutral Current Detection (NCD) array was to observe neutrons resulting from neutral-current solar neutrino-deuteron interactions. We have developed a detailed simulation of the current pulses from the NCD array proportional counters, from the primary neutron capture on 3He through the NCD array signal-processing electronics. This NCD array Monte Carlo simulation was used to model the alpha-decay background in SNO's third-phase 8B solar-neutrino measurement.

  15. Tritium measurement with a proportional counter

    The purpose of this study is to investigate a feasibility of real-time measurement of tritium concentration with a proportional counter. For the purpose, we constructed a flow-through type of proportional counter. The characteristics of the counter for seven gases, PR, H2, D2, Ar, CH4, N2, and air, were investigated to research appropriate gases. (author)

  16. Boron-Lined Multitube Neutron Proportional Counter Test

    Woodring, Mitchell L.; Ely, James H.; Kouzes, Richard T.; Stromswold, David C.

    2010-09-07

    Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world, and thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. These technologies are: 1) Boron trifluoride (BF3)-filled proportional counters, 2) Boron-lined proportional counters, 3) Lithium-loaded glass fibers, and 4) Coated non-scintillating plastic fibers. In addition, a few other companies have detector technologies that might be competitive in the near term as an alternative technology. Reported here are the results of tests of a boron-lined, “multitube” proportional counter manufactured by Centronic Ltd. (Surry, U.K. and Houston, TX). This testing measured the required performance for neutron detection efficiency and gamma-ray rejection capabilities of the detector.

  17. A proportional counter with reduced wall effect

    A proportional counter, using gaseous sources, in which the wall effects are considerably reduced, is described. The counter is fitted with a ring of internal shielding counters in anti-coincidence, separated from the main central counter only by a number of cathode wires. The counter can be readily assembled, giving flexibility in research investigations. Applications to a measurement of the L/K capture ratio in A37 and Fe55 are described. (author)

  18. Large area flow gas proportional counters

    The ZJ-LD-800 and ZJ-LD-240 large area flow gas proportional counter tubes are described in detail, and the design of counter tube is expounded. The counter tube there have better than plateau length of 200 V and plateau slope of 2%/100 V and window uniformity of 90% for beta counting. So the counters are ideally suitable for use in Area and Contamination Monitors where both alpha and beta radiation are anticipated

  19. The use of polycarbonate in proportional counters

    Proportional counters are relatively sensitive to contamination through outgassing and the range of electrical insulators suitable for use in their manufacture is quite limited. Although small amounts of plastics such as polychlorotrifluoroethylene have been used as feedthroughs, ceramics are most commonly used when sealed counters with long lives are required. Ceramics have poor and widely scattered mechanical properties and the use of a more robust material is often highly desirable. Of particular interest is the use of polymers and this work examines polycarbonate in particular. To investigate its suitability in terms of outgassing a simple cylindrical, single anode proportional counter containing a large sample of polycarbonate was baked at ∼100 degree C and filled with a CO2/Ar/Xe mixture (5:47.5:47.5 by pressure, respectively). Subsequent measurements of the counter indicated an increase in gain, which, after a second similar filling, was identified to be associated with a preferential loss of CO2 to the polycarbonate. The consequences of this result and the circumstances under which polycarbonate could be used on a large scale in the construction of proportional counters are discussed

  20. Neutron spectroscopy with the Spherical Proportional Counter

    Bougamont, E; Derre, J; Galan, J; Gerbier, G; Giomataris, I; Gros, M; Katsioulas, I; Jourde, D; Magnier, P; Navick, X F; Papaevangelou, T; Savvidis, I; Tsiledakis, G

    2015-01-01

    A novel large volume spherical proportional counter, recently developed, is used for neutron measurements. Gas mixtures of $N_{2}$ with $C_{2}H_{6}$ and pure $N_{2}$ are studied for thermal and fast neutron detection, providing a new way for the neutron spectroscopy. The neutrons are detected via the ${}^{14}N(n, p)C^{14}$ and ${}^{14}N(n, \\alpha)B^{11}$ reactions. Here we provide studies of the optimum gas mixture, the gas pressure and the most appropriate high voltage supply on the sensor of the detector in order to achieve the maximum amplification and better resolution. The detector is tested for thermal and fast neutrons detection with a ${}^{252}Cf$ and a ${}^{241}Am-{}^{9}Be$ neutron source. The atmospheric neutrons are successfully measured from thermal up to several MeV, well separated from the cosmic ray background. A comparison of the spherical proportional counter with the current available neutron counters is also given.

  1. Energy resolution of the proportional counter

    Resolution values 11.6% and 12.2% for 5.9 keV have been obtained experimentally for proportional counters with gas fillings Ne+0.5% Ar or Ar+0.5% C2H2. This is appreciably better than earlier measurements which exceed 14%. Theoretical computation indicates that even better resolutions can be obtained. (Auth.)

  2. A proportional-scintillation counter beta spectrometer

    Using a proportional counter for coincidence gating of events in a plastic scintillator provides selective registration of beta interactions in the scintillator. This technique has been used to construct a field instrument that can selectively collect beta spectra (coincidence gating) or gamma spectra (anticoincidence gating). Associated dose rates are calculated from the spectra

  3. Development of a 3He/Xe gas scintillation counter to measure the 3He(n,p)T cross section in the intermediate energy range

    A 3He/Xe gas scintillation counter has been developed for measuring the neutron energy range from thermal to 3 MeV. Great effort was concentrated on improving the detector design to optimize light production and collection to improve the energy resolution which is primarily controlled by photon statistics. The detectors were tested using a 238Pu alpha-particle source, a thermal neutron beam from the NBS reactor, and the white-neutron spectrum from the NBS linac. The detector measures an energy resolution of 17 % (FWHM) for the 3He(n,p)T reaction at 2.0 MeV which is sufficient for cross section measurement. (author)

  4. Development of a 3He/Xe gas scintillation counter to measure the 3He(n,p)T cross section in the intermediate energy range

    A 3He/Xe gas scintillation counter has been developed for measuring the neutron energy range from thermal to 3 MeV. Great effort was concentrated on improving the detector design to optimize light production and collection to improve the energy resolution which is primarily controlled by photon statistics. The detectors were tested using a 238Pu alpha-particle source, a thermal neutron beam from the NBS reactor, and the white-neutron spectrum from the NBS linac. The detector measures an energy resolution of 17% (FWHM) for the 3He(n,p)T reaction at 2.0 MeV which is sufficient for cross section measurement. 12 refs., 8 figs

  5. Comparison of Thermal Neutron Detection Efficiency of $^{6}$Li Scintillation Glass and $^{3}$He Gas Proportional Tube

    Xu, Ming; Tang, Zhi-Cheng; Chen, Guo-Ming; Tao, Jun-Quan

    2013-01-01

    We report on a comparison study of the $^{3}$He gas proportional tube and the $^{6}$Li incorporated scintillation glasses on thermal neutron detection efficiency. Both $^{3}$He and $^{6}$Li are used commonly for thermal neutron detection because of their high neutron capture absorption coefficient. By using a neutron source $^{252}$Cf and a paraffin moderator in an alignment system, we can get a small beam of thermal neutrons. A flash ADC is used to measure the thermal neutron spectrum of eac...

  6. An ellipsoidal grid gas proportional scintillation counter

    Silva, Rui M. C.; Santos, J. M. F. dos; Conde, C. A. N.

    1999-01-01

    Gas Proportional Scintillation Counters using curved grids for solid angle and reflection compensation have been described in the recent literature. They allow large radiation windows with diameters of 25 mm keeping at the same time the good energy resolutions characteristic of those X-ray detectors. However, the grids used have a spherical curvature, which does not correspond to the optimal curvature. In the present work we have calculated by computer simulation an improved shape for the cur...

  7. Neutron proportional counter with low self-background level

    It is suggested to cover the inner surface of neutron counter with α-absorption substance layer to reduce level of self-background of neutron counter filled with 3He+30Ar mixture. Application of 50-60 mm thickness fluoroplastic cover turned to be the most perspective. Analysis of energy spectra within 1-10 MeV energy range has shown, that neutron counters with fluoroplastic cover have the background level by one order less, than counters without cover

  8. Neutron spectroscopy with the Spherical Proportional Counter

    Bougamont, E .; Dastgheibi, A.; Derre, J.; Galan, J.; Gerbier, G.; Giomataris, I.; Gros, M.; Katsioulas, I.; Jourde, D.; Magnier, P.; Navick, X. F.; Papaevangelou, T.; Savvidis, I.; Tsiledakis, G.

    2015-01-01

    A novel large volume spherical proportional counter, recently developed, is used for neutron measurements. Gas mixtures of $N_{2}$ with $C_{2}H_{6}$ and pure $N_{2}$ are studied for thermal and fast neutron detection, providing a new way for the neutron spectroscopy. The neutrons are detected via the ${}^{14}N(n, p)C^{14}$ and ${}^{14}N(n, \\alpha)B^{11}$ reactions. Here we provide studies of the optimum gas mixture, the gas pressure and the most appropriate high voltage supply on the sensor o...

  9. Pulse Shape Analysis of the Proportional Counter Data from the Third Phase of the Sudbury Neutrino Observatory

    This poster presented a pulse shape-based analysis of the proportional counter data from the third phase of the Sudbury Neutrino Observatory. It was shown that the neutron signal from the 3He-filled proportional counters could be maintained at about 75% for a suppression of 98% for the alpha background signal.

  10. Measurement of γ-ray dose in a thermal neutron field by using a 3He-filtered GM counter

    A new type of 3He-filtered GM counter has been used to measure the dose of γ-rays existing in a thermal neutron field. The detector assembly consists of a commercially available GM counter surrounded by a cylindrical aluminum vessel filled with 3He gas at a pressure up to 6 atmospheres. The contribution of secondary γ-rays produced by thermal neutron capture in the GM counter itself can be excluded by increasing the 3He pressure, because the thermal neutron capture reaction of 3He(n,p)T results in the emission of charged particles of a proton and a triton. In order to determine the response of the GM counter, the energy spectrum deposited in the counter gas to monoenergetic γ-rays was calculated by EGS4 Monte-Carlo code for a γ-ray energy range from 60 keV to 10 MeV and then the response was derived through calibration of the counter at γ-ray energies of 60 keV, 662 keV and 1.17 MeV + 1.33 MeV. The γ-ray energy distribution in the thermal neutron field was obtained by an MCNP Monte-Carlo calculation, assuming a three dimensional experimental assembly of a graphite pile, which also included the concrete floor in the experimental room. The γ-ray fluence and the effective dose equivalent in the thermal neutron field have been determined by using the GM counter response, the γ-ray energy distribution in the field and the conversion factor from fluence to effective dose equivalent

  11. Improved proportional counters for practical applications

    Gas filled proportional counters are useful room-temperature X-ray detectors in various gauges and spectrometers. New gas mixtures have made it possible to improve the properties of these detectors. Penning mixtures offer some special advantages. These mixtures are formed when parent gas is diluted with a small amount of impurity whose ionization energy is lower than the lowest excited state of the parent atoms. The excitations of these atoms can subsequently be turned into ionizations. The result of this additional ionization is that the average ionization energy of the mixture falls below that of the pure gases. This also improves the energy resolution of the detector. Another feature of Penning mixtures is the fact that the first Townsend ionization coefficient is high. This in turn is reflected by an unusually low anode voltage required by the detector. This makes it possible to use high filling pressures and to realize the advantages such pressures offer: the achievement of good energy resolution with a commercial low noise preamplifier; a decrease in the background caused by the wall effect because of the subsequently shorter photoelectron traces; and an increase in the efficiency of the detector. The type of detector used in this paper is a sealed side window counter. Some of its properties, when filled with the mixtures Ar-C4H10, Ar-Xe, and Ne-Ar, are presented

  12. Fluctuation phenomena in the proportional counter

    Fluctuations in the number of electron-ion pairs produced in the primary ionization and in the size of the subsequent electron avalanche, can be reduced by improving the efficiency of the ionization mechanisms by the Penning effect. Energy spent exciting metastable states is used to increase the ionization yield by introducing a second gas whose first ionization potential is slightly lower than the first metastable level of the main gas. A proportional counter filled with a range of Penning mixtures has been investigated experimentally. The Penning mixture argon-xenon gives an increased resolution over argon-methane. For fundamental studies of avalanche fluctuations in Penning mixtures, a uniform field chamber has been constructed. Experimental studies of f (the relative variance of the avalanche size) are compared with values predicted by various avalanche models. The results are reasonably close to predictions based on experimental measurements of ionization probability. (U.K.)

  13. Absolute calibration of TFTR helium proportional counters

    The TFTR helium proportional counters are located in the central five (5) channels of the TFTR multichannel neutron collimator. These detectors were absolutely calibrated using a 14 MeV neutron generator positioned at the horizontal midplane of the TFTR vacuum vessel. The neutron generator position was scanned in centimeter steps to determine the collimator aperture width to 14 MeV neutrons and the absolute sensitivity of each channel. Neutron profiles were measured for TFTR plasmas with time resolution between 5 msec and 50 msec depending upon count rates. The He detectors were used to measure the burnup of 1 MeV tritons in deuterium plasmas, the transport of tritium in trace tritium experiments, and the residual tritium levels in plasmas following 50:50 DT experiments

  14. An ellipsoidal grid gas proportional scintillation counter

    Gas Proportional Scintillation Counters using curved grids for solid angle and reflection compensation have been described in the recent literature. They allow large radiation windows with diameters of 25 mm keeping at the same time the good energy resolutions characteristic of those X-ray detectors. However, the grids used have a spherical curvature, which does not correspond to the optimal curvature. In the present work we have calculated by computer simulation an improved shape for the curved grid. This shape can be well fitted to an ellipsoid of revolution, with a large eccentricity. A detector was designed with such an ellipsoidal grid and a radiation window 40 mm in diameter, filled with pure xenon at 927 Torr coupled to an EMI D676QB VUV photomultiplier tube having a 2'' diameter window. For the experiments envisaged, detection of solar X-rays in the 20-80 keV energy range, a 7 cm thick drift region was used, leading to efficiencies from 80% to 20%, respectively. Such a thick drift region reduces the performance mainly for soft X-rays. For 22 keV X-rays the energy resolution obtained, for a broad X-ray beam entering the full 40 mm diameter detector window, is 6.0%. Results are presented showing the variation of the energy resolution with the window diameter and a performance, for ellipsoidal grids superior to that for spherical grids. A discussion of the results obtained is presented

  15. Comparison of thermal neutron detection efficiency of 6Li scintillation glass and 3He gas proportional tube

    We report on a comparison study of the 3He gas proportional tube and the 6Li incorporated scintillation glasses on thermal neutron detection efficiency. Both 3He and 6Li are used commonly for thermal neutron detection because of their high neutron capture absorption coefficient. By using a neutron source 252Cf and a paraffin moderator in an alignment system, we can get a small beam of thermal neutrons. A flash ADC is used to measure the thermal neutron spectrum of each detector, and the detected number of events is determined from the spectrum, then we can calculate the detection efficiency of different detectors. Meanwhile, the experiment has been modeled with GEANT4 to validate the results against the Monte Carlo simulation. (authors)

  16. Digital signal processing for He3 proportional counter

    Full text : Data acquisition systems for nuclear spectroscopy have traditionally been based on systems with analog shaping amplifiers followed by analog-to-digital converters. Recently, however, new systems based on digital signal processing make possible to replace the analog shaping and timing circuitry the numerical algorithms to derive properties of the pulse such as its amplitude. DSP is a fully numerical analysis of the detector pulse signals and this technique demonstrates significant advantages over analog systems in some circumstances. From a mathematical point of view, one can consider the signal evolution from the detector to the ADC as a sequence of transformations that can be described by precisely defined mathematical expressions. Digital signal processing with ADCs has the possibility to utilize further information on the signal pulses from radiation detectors. In the experiment each step of the signal generation in the 3He filled proportional counter was described using digital signal processing techniques (DSP). The electronic system has consisted of a detector, a preamplifier and a digital oscilloscope. The pulses from the detector were digitized using a digital storage oscilloscope. This oscilloscope allowed signal digitization with accuracy of 8 bit (256 levels) and with frequency of up to 5 * 108 samples/s. As a neutron source was used Cf-252. To obtain detector output current pulse I(t) created by the motions of the ions/electrons pairs was written an algorithm which can easily be programmed using modern computer programming languages.

  17. Neutron dosimetry using proportional counters with tissue equivalent walls

    The author reminds the calculation method of the neutron absorbed dose in a material and deduce of it the conditions what this material have to fill to be equivalent to biological tissues. Various proportional counters are mode with walls in new tissue equivalent material and filled with various gases. The multiplication factor and neutron energy response of these counters are investigated and compared with those obtained with ethylene lined polyethylene counters. The conditions of working of such proportional counters for neutron dosimetry in energy range 10-2 to 15 MeV are specified. (author)

  18. The 3He Supply Problem

    Kouzes, Richard T.

    2009-05-01

    One of the main uses for 3He is in gas proportional counters for neutron detection. Radiation portal monitors deployed for homeland security and non-proliferation use such detectors. Other uses of 3He are for research detectors, commercial instruments, well logging detectors, dilution refrigerators, for targets or cooling in nuclear research, and for basic research in condensed matter physics. The US supply of 3He comes almost entirely from the decay of tritium used in nuclear weapons by the US and Russia. A few other countries contribute a small amount to the world’s 3He supply. Due to the large increase in use of 3He for homeland security, the supply has dwindled, and can no longer meet the demand. This white paper reviews the problems of supply, utilization, and alternatives.

  19. High pressure proportional counters operating in pure hydrogen

    Construction and operation of high pressure proportional counters designed for pressures up to 92 atm which work in pure hydrogen are described. This type of counter offering track reconstruction as well as energy loss determination will be employed as live-target for low-energy recoil measurements in elastic np scattering. (Auth.)

  20. Gain stabilisation of gas-flow proportional counters

    A stabilisation of the gas gain for proportional counters with a continuous gas flow is described. New gas-flow systems for two end-window counters and one pressurised proportional counter were developed. The gas density of the counting-gas flow is stabilised by a two-stage back-pressure regulation system. The pressure in the gas flow is compared with the pressure in a reference vessel. During one month of operation the gain was stable within ±0.3%

  1. Response of 4π Proportional Counters to γ-Rays

    The response of a 4π proportional counter to γ-rays has been measured as a function of γ-ray energy by the 4π β-γ coincidence-absorption method. The results, which are about a factor of three lower than those obtained using thick absorbers, are slightly lower than, but in general agreement with, those of Williams and Campion. Electrons produced by γ-ray interactions in the absorber are responsible for the higher results obtained with thick absorbers. This effect has been demonstrated by determining the γ-ray response of a 4π proportional counter as a function of absorber thickness for the 478-keV γ-rays of 7Be. In addition, the responses to 478-keV γ-rays of five different 4π proportional counters have been compared. For one of these, a pressurized 4π X-ray counter, the response has also been measured as a function of filling pressure. It is concluded that the intrinsic γ-ray response of 4π proportional counters is small and, if γ-ray absorption in the counting gas may be neglected, is not strongly dependent on the size, shape or material of the cathode. (author)

  2. Features of the microstrip proportional counter technology (invited)

    Budtz-Jørgensen, Carl

    1992-01-01

    The microstrip proportional counter (MSPC) is a new approach in gas-filled detector technology. In contrast with the classical multiwire proportional counter (MWPC) detectors, the electrodes of the MSPC are deposited by photolithographic techniques onto a rigid substrate. The technique offers many...... the anode and cathode strips which allows the positive ion cloud created in the avalanche to be collected rapidly with reduced space charge effects and increased counting-rate capability; A rigid electrode structure which is not deformed under the action of an electric field; A relatively simple fabrication...

  3. A method for optimising the gas replacing period of sealed proportional counter

    Proportional counter can be used as low-energy particles detector because of its gas gain. According to charging manner, proportional counter can be divided into sealed and gas-flow proportional counters. Compared with gas-flow counter, although sealed proportional counter can be operated simply but it is short-lived, needs to replace the sealed gas periodically. It introduces the aging phenomenon of sealed proportional counter and a method for optimising the gas replacing period. (authors)

  4. Performance of gas proportional counters at high pressures

    The performances of gas proportional counters intended to some isotopes absolute activity measurements are investigated at a gas pressure ranging from 5 to 100 atm. The counter working agent (filling gas) is pure Ar and the CH4/Ar,Xe/Ar,CH4/Xe/Ar gas mixtures. The counter has cathode diameters 6,10,14 mm and anode diameters are 10,16,20 μm. It is found that an addition of 0.5% Xe to Ar results in a considerable decrease (approximately by a factor of 2) of working voltage applied to counters, compared to pure Ar filling, just as maximum gas amplification factor is increased. The counter energy resolution is 5.5-7% (FWHM) for 241Am γ-quanta with the 59.57 keV energy at Ar+0.5% Xe mixture pressure ranging from 8 to 100 atm. It is shown that it is more efficiently to use argon with addition of xenon, but no methan for stabilization of the gas counters performance at high pressures

  5. Modeling of electron and ion kinetics in cylindrical proportional counters

    Numerical simulations were performed to study the operating mode of cylindrical proportional counters submitted to irradiation. Such counters are used in astrophysics, high energy physics and microdosimetry. The choice of the filling gas was restricted to argon, methane and their mixtures, in order to allow us to compare our numerical values to experimental results from the literature. The charged particle kinetics in the gaseous volume of the counter were studied by two numerical methods: The electron transport parameters were determined by microscopic calculations. These calculations also showed that electrons and the applied electric field were not in equilibrium in such geometries. The values obtained for the ionization coefficient were used to estimate the effects of the non-equilibrium phenomena on the theoretical value of the counter gas gain. A macroscopic modelling of the electron and ion transport was used to study the electron avalanche induced by a particle crossing the counter. In particular, the consequences of the appearance of the space charge effect on the gas gain value and on the current pulses were studied as a function of the operating conditions of the counter

  6. Using tissue equivalent proportional counters to determine dose equivalent

    Tissue equivalent proportional counters (TEPCs) have been used in the laboratory for over 30 years to determine neutron dose in mixed radiation fields, but they are seldom used by operational health physicists. But a number of TEPC-based instruments are being developed in Europe and in the United States. The purpose of this paper is: to introduce operational health physicists to tissue equivalent proportional counters, to examine some of the algorithms used to convert data from TEPCs into dose equivalent, to examine how TEPC measurements meet the requirements of DOE Order 5480.11 (DOE 1988) and 10CFR20, and to examine some of the TEPC-based instruments that are available. Many operational health physicists are not familiar with the concept of microdosimetry and the specialized terms that are used in analyzing the data from TEPCs, so a brief discussion is included. At present, quality factors are defined in terms of linear energy transfer, but TEPCs measure lineal energy

  7. Boron-lined proportional counters with improved neutron sensitivity

    Dighe, P M; Prasad, K R; Kataria, S K; Athavale, S N; Pappachan, A L; Grover, A K

    2003-01-01

    Boron-lined proportional counters with higher neutron sensitivity have been developed by introducing baffle structures within the sensitive volume. the results are compared to devices developed with multiple cathode assemblies in a single enclosure. in either case, the increase in the boron-coated surface area results in higher neutron sensitivity. one of these counters has 51 annular baffles coated with natural boron with 10 mm hole for the anode wire to pass through. filled with p-10 gas at 20 cm hg, it has an overall diameter of 30 and 300 mm length. multiple dip coating method was employed for better uniformity in boron thickness. the neutron sensitivity of this counter is 1.6 cps/nv, which is 2.5 times that of a counter with standard electrode geometry. another counter was developed with three cathode assemblies (30 mm IDx300 mm) coated with 92% sup 1 sup 0 B while the third has seven assemblies coated with natural boron (16 mm IDx750 mm length). the neutron sensitivity is 10 and 5.5 cps/nv, respectively...

  8. Optimization of a single sphere albedo system using 3He counters for the measurement of neutron dose equivalent rates and the field calibration of personnel albedo neutron dosimeters

    The laboratory type of an active single sphere albedo dosemeter system using three 3He proportional counters in a polyethylene sphere for the measurement of neutron dose equivalent rates and the field calibration of personnel neutron dosemeters was optimized with respect to the detector-moderator combination by means of calibration exposures. One detector is located in the centre of the sphere to measure the neutron dose equivalent rate and the other two detectors near the moderator surface, in order to simulate the response of the albedo neutron detector and the thermal neutron detector. The response of the detectors to neutrons in the range between thermal and 14 MeV neutrons was investigated for various moderator-absorber combinations. Comparison was made between the system response and the response of the passive detector system. After completion the active system could be used for comprehensive neutron field measurements in radiation protection. By means of a microprocessor the linear combination of the three detector readings gives energy independent readings of the neutron dose equivalent rate, the absorbed dose rate and the neutron flux density at particle accelerators and nuclear facilities. (orig./HP)

  9. The suppression of destructive sparks in parallel plate proportional counters

    The authors find that high energy background events produce localised sparks in parallel plate counters when operated in the proportional mode. These sparks increase dead-time and lead to degradation ranging from electrode damage to spurious pulsing and continuous breakdown. The problem is particularly serious in low energy photon detectors for X-ray astronomy which are required to have lifetimes of several years in the high radiation environment of space. For the parallel plate imaging detector developed for the European X-ray Observatory Satellite (EXOSAT) they investigate quantitatively the spark thresholds, spark rates and degradation processes. They discuss the spark mechanism, pointing out differences from the situation in spark chambers and counters. They show that the time profile of the sparks allows them to devise a spark suppression system which reduces the degradation rate by a factor of ''200

  10. High speed pulse digitization in driftless gas scintillation proportional counters

    In a driftless gas scintillation proportional counter the observed light burst profile provides a wealth of information both about the incident photon and the transit of the electron cloud through the scintillation region. The different features of such profiles are difficult to separate with conventional analog electronics. In this work the authors apply the technique of high speed pulse digitization to the problem. They show that by this technique not only can the performance of the instrument be improved (e.g. background rejection) but valuable data can be obtained regarding the design of both the gas cell and the analysis electronics

  11. Low energy recoil detection with a spherical proportional counter

    I. Savvidis; Katsioulas, I.; Eleftheriadis, C.; Giomataris, I.; Papaevangellou, T.

    2016-01-01

    We present low energy recoil detection results in the keV energy region, from measurements performed with the Spherical Proportional Counter (SPC). An ${}^{241}Am-{}^{9}{Be}$ fast neutron source is used in order to obtain neutron-nucleus elastic scattering events inside the gaseous volume of the detector. The detector performance in the $keV$ energy region was resolved by observing the $5.9\\ keV$ line of a ${}^{55}Fe$ X-ray source, with energy resolution of $9\\%$ ($\\sigma$). The toolkit GEANT...

  12. Multiwire gas proportional counters. Decrepit antiques or classic performers?

    An overview of the operational characteristics of multiwire gas proportional counters is given with particular reference to their use in X-ray diffraction. Their strengths and weaknesses are analysed and it is demonstrated that these devices are able to offer a combination of features that is unique. Some examples of synchrotron radiation experiments performed with gas detectors are used to illustrate their performance, and finally, the current status of development and prospects for the future development of gas detectors are reviewed. (au) (34 refs.)

  13. Multiplication factors in ethylene-filled proportional counters.

    Loyola, H; Birstein, L; Hevia, A

    2008-01-01

    Gas multiplication factors were measured in a proportional counter filled with high-purity ethylene in the pressure range 10-40 Torr. The multiplication factors were measured as a function of the reduced electric field S(a). The results show that, within the range of the high values of reduced electric field applied in this work (2648 Townsend coefficient alpha/P for ethylene may still be considered a function of S(a) alone. Good agreement was found with a model proposed by Akande. PMID:18682404

  14. Absolute Measurement of 14C Activity by Internal Proportional Counters

    14CO22 was obtained by decomposing carbonate with sulphuric acid heated to boiling point, after which it was mixed with CH4 in a reserve flask. Three brass internal proportional counters, differing only in length, were filled with this mixture. The counters were connected to the electronic equipment in the usual arrangement. The equipment dead time was determined by means of a modified two-source method, and the total volume of the equipment was obtained from the isothermic expansion of methane from a flask whose volume, together with that of the counters, had been determined by weighing a water filling. The wall effect was determined by measuring a 14CO2 + CH4 mixture at different pressures and by extrapolation to reciprocal pressure zero value; it was discovered that the wall-effect correction did not differ significantly from zero. The end effect was compensated for by using counters of different lengths so that the difference in plateau slope also did not differ significantly from zero. By the t-test power function it was estimated that the maximal error on a 0.01 significance level, caused by neglecting the wall-effect correction, amounted to ± 0.85% due to the end-effect correction (± 0.62% for the equipment used) having been neglected. The relation between wall, end and discrimination effects is discussed, and, in conclusion, the maximal errors from other sources are estimated; the total maximal error on a 0.01 significance level of the standard solution activity is computed as equal to ± 1.1%. (author)

  15. Fano factor implications from gas scintillation proportional counter measurements

    The Fano factor for xenon may be determined using a gas scintillation proportional counter in which the measured energy resolution is extrapolated to the condition of infinite light yield. The true Fano factor is expected to be independent of X-ray energy, photomultiplier type and gas pressure. Using both drifted and driftless GSPCs we have measured the Fano factor over a large range of X-ray energies (0.27-44.23 keV), photomultiplier types and gas pressures (351-878 hPa). In all three cases, when making the assumptions usually adopted in these determinations we find that the extrapolated Fano factor is dependent on the conditions. The implication is that other processes are also contributing to the measured resolution and that the determined values of the Fano factor are in fact upper limits. The Fano factor for xenon is found to be <0.12. (orig.)

  16. X-ray and gamma imaging with multiwire proportional counters

    The role of the Multiwire Proportional Counter (MWPC) as an X-ray image transducer in integrated digital imaging systems for use in a wide variety of fields (X-ray diffraction, medicine, non-destructive testing, etc.) is discussed with particular reference to the suitability of the technology for wider application than has been the case up to the present. A survey is given of the mechanical, electrical and electronic aspects of MWPC system design and the integration of this technology with microprocessor systems is examined. After a survey of the newer developments in the field of multiwire gaseous detectors it is concluded that this type of technology offers good potential for routine production of integrated digital X-ray imaging systems, possibly on a commercial basis. (orig.)

  17. Calibration and optimization of proportional counter modules using Garfield

    Chung, Kiwhan [Los Alamos National Laboratory; Brockwell, Michael I [Los Alamos National Laboratory; Borozdin, Konstantin N [Los Alamos National Laboratory; Green, J Andrew [Los Alamos National Laboratory; Hogan, Gary E [Los Alamos National Laboratory; Makela, Mark F [Los Alamos National Laboratory; Mariam, Fesseha G [Los Alamos National Laboratory; Morris, Christopher L [Los Alamos National Laboratory

    2010-01-01

    Prototypes of radiation detector arrays used for charged-particle radiography require iniliol calibration to correlate the distribution of electron arrival time to the particle track locations. This step is crucial to obtaining the spatial resolution necessary to separate particle tracks traversing the individual proportional counters in the arrays. Our past attempts to use cosmic rays alone for the initial calibration have fallen short of obtaining the desired resolution due to the insufficient cosmic ray flux to provide the necessary number of particle tracks. A theoretical relation between electron drift time and radial drift distance is obtained with Garfield, a CERN gas detector simulation program. This relation is then used as an effective starting point for the initial calibration and results in a shorter calibration period and improved spatial resolution of the detectors.

  18. Scintillation counter with detecting efficiency proportional to gamma radiaiton energy

    A new type of detector on the base of CaF2 fluorite crystal intended for measuring (n, γ)-reaction cross sections in a spectrometer on moderation time of neutrons in lead is described. The detector has an additional cylindrical convertor Bi+BiF3, the inner BiF3 part of which plays the role of light reflector of diffusion type. Decrease of light collection as photomultiplies removing from the window is a characteristic peculiarity of such device. It permits to achieve that efficiency of gamma detection turns to be proportional to their energy. Measurement results of cross section of neutron capture for 30Zn (natural isotope mixture) within the 100 eV-100 keV energy range obtained by means of the described detector are presented. It is concluded that total efficiency of the suggested detector is 4-10 times higher than the efficiency of the earlier used gaseous proportional counters. The detector has a high speed of response. The detector does not have background from recoil nuclei in the neutron energy range more than 20 keV

  19. Compact multiwire proportional counters for the detection of fission fragments

    Two large area multistep position sensitive (two dimensional) multiwire proportional counters have been developed for experiments involving study of fission dynamics using general purpose scattering chamber facility at IUAC. Both detectors have an active area of 20x10 cm2 and provide position signals in horizontal (X) and vertical (Y) planes, timing signal for time of flight measurements and energy signal giving the differential energy loss in the active volume. The design features are optimized for the detection of low energy heavy ions at very low gas pressures. Special care was taken in setting up the readout electronics, constant fraction discriminators for position signals in particular, to get optimum position and timing resolutions along with high count rate handling capability of low energy heavy ions. A custom made charge sensitive preamplifier, having lower gain and shorter decay time, has been developed for extracting the differential energy loss signal. The position and time resolutions of the detectors were determined to be 1.1 mm full width at half maximum (FWHM) and 1.7 ns FWHM, respectively. The detector could handle heavy ion count rates exceeding 20 kHz without any breakdown. Time of flight signal in combination with differential energy loss signal gives a clean separation of fission fragments from projectile and target like particles. The timing and position signals of the detectors are used for fission coincidence measurements and subsequent extraction of their mass, angular, and total kinetic energy distributions. This article describes systematic study of these fission counters in terms of efficiency, time resolution, count rate handling capability, position resolution, and the readout electronics. The detector has been operated with both five electrode geometry and four electrode geometry, and a comparison has been made in their performances.

  20. Performance of a cylindrical tissue-equivalent proportional counter for use in neutron monitoring

    Tissue-equivalent proportional counters (TEPC) allow the measurements of the absorbed dose and the ambient dose equivalent for neutron fields. A device based on this approach, called NAUSICAA(1,2), has already been developed by IRSN to be used in high energy neutron fields for space applications. The response of this detector underestimates significantly the dose equivalent at low energies (several hundred keV) which represent the major component of neutron fields at workplaces in the nuclear industry. A counter with a similar geometry (cylindrical detector) and a lower gas pressure was studied in order to simulate a 1 μm biological site. In 2003, the performance of the device was further improved by adding a small amount of 3He to the tissue-equivalent gas (propane based) in order to increase the response for the lower energies of neutrons. Three amplification circuits were used to cover lineal energy range from 10-1 to 104 keV μm-1. Tests were performed in monoenergetic neutron and source fields. This paper presents the experimental results obtained with this change. (authors)

  1. The background of external γ radiation in the proportional counters in SAGE experiment

    The influence of external γ radiation on the process of 71Ge-decay counting in proportional counters in SAGE experiment of solar neutrino flux measurement is examined. One determines the systematic error of SAGE result, connected with radon decays inside the air volume surrounding the counters, and the background counting rate of proportional counters from γ radiation of passive and active shield

  2. Low energy recoil detection with a spherical proportional counter

    Savvidis, I; Eleftheriadis, C; Giomataris, I; Papaevangellou, T

    2016-01-01

    We present low energy recoil detection results in the keV energy region, from measurements performed with the Spherical Proportional Counter (SPC). An ${}^{241}Am-{}^{9}{Be}$ fast neutron source is used in order to obtain neutron-nucleus elastic scattering events inside the gaseous volume of the detector. The detector performance in the $keV$ energy region was resolved by observing the $5.9\\ keV$ line of a ${}^{55}Fe$ X-ray source, with energy resolution of $9\\%$ ($\\sigma$). The toolkit GEANT4 was used to simulate the irradiation of the detector by an ${}^{241}Am-{}^{9}{Be}$ source, while SRIM was used to calculate the Ionization Quenching Factor (IQF). The GEANT4 simulated energy deposition spectrum in addition with the SRIM calculated quenching factor provide valuable insight to the experimental results. The performance of the SPC in low energy recoil detection makes the detector a good candidate for a wide range of applications, including Supernova or reactor neutrino detection and Dark Matter (WIMP) searc...

  3. Position-sensitive proportional counter with resistive anode

    The position-sensitive proportional counter (PSPC) is devised to deliver signals with pulse heights proportional to the distance from one end of the entrance window to the position where the incident radiations arrive on the window. In this paper, the noise analysis for position resolution of the PSPC with the resistive anode is described. The high-resolution measurement for X-rays emitted from radioactive sources is also briefly introduced. The position resolution of the present PSPC was measured with a 6.4-keV Fe Kα X-ray beam collimated with a width of 25 μm. In the measurement, pressurized gas mixtures, for example, Ar + 5%CH4 and Ar + 10%CH4 with a pressure of 1 to 10 atm were examined as filled gas; the resolution was better at higher pressures. The spectra of X-rays from 35S and 109Cd were observed. A main peak of the spectrum from the purified 109Cd source is caused by the 2.984 keV Ag Lα1,2 line, which was used to calibrate the detection efficiency of the PSPC for the ClKβ1,3 X-rays. The intensities of AgLβ3,4,6, AgLβ2,15 and AgLγ1 lines are about one order of magnitude enhanced comparing with those of AgLα1,2 and AgLβ1, because of the steep increase of the detection efficiency of PSPC at the K edge of argon (3.206 keV). The present observation of the composite spectrum for the Kα X-ray group strongly indicates that the mechanism of the K-IIE (K-shell internal ionization and excitation) process during β decay is quite different from that of the same process during other nuclear decay, for example, electron capture and internal conversion, and by the bombardment of light charged particles. (S.Y.)

  4. The gas amplification factor in Kr + iso-pentane filled proportional counters

    Measurements of gas amplification in a proportional counters with Kr/iso-pentane mixture were performed at pressures ranging from 160 to 970 hPa. A new formula for gas amplification in a proportional counters was derived. A good agreement between the formula and experimental data was found over the range of variables studied. 16 refs., 4 figs., 1 tab. (author)

  5. Development of High Pressure Xe Scintillation Proportional Counter for Experiments in "Low-Background" Physics

    Akimov, D. Yu.; Burenkov, A.A.; Churakov, D. L.; Kuzichev, V. F.; Morgunov, V. L.; Smirnov, G. N.; Solovov, V. N.

    1997-01-01

    Characteristics of a scintillation proportional counter with WLS fiber optics readout is described. The possibility of detection of the proportional scintillation signal produced by the single electron of primary ionization is shown. The counter can be applied for the experiments in "low--background" physics which require a low energy threshold.

  6. Performance of microstrip proportional counters for x-ray astronomy on spectrum-roentgen-gamma

    Budtz-Jørgensen, Carl; BAHNSEN, A; Christensen, Finn Erland;

    1991-01-01

    DSRI will provide a set of four imaging proportional counters for the Danish-Soviet X-ray telescopes XSPECT/SODART. The sensor principle is based on the novel micro-strip proportional counter (MSPC), where the strip electrodes are deposited by photolithography onto a rigid substrate. The MSPC off...

  7. Cryogenic resonance-electron Moessbauer spectroscopy with a helium-filled proportional counter

    As studied in our previous works,a proportional counter filled with pure helium gas works well at low temperatures near 4.2 K. The helium-filled proportional counter (HFPC) provides us with method to detect nuclear radiations at low temperatures. A typical application of this counter is resonance-electron Moessbauer spectroscopy (REMS) at low temperatures (<∼30 K). In this article some examples of REMS measurements with HFPC are given. (author)

  8. Background of external γ radiation in the proportional counters of the SAGE experiment

    The effect of external γ radiation on the process of counting 71Ge decays in the proportional counters of the SAGE experiment measuring the solar-neutrino flux is considered. The systematic uncertainty in the SAGE result due to radon decays inside the air volume surrounding the counters is estimated. The background counting rate in the proportional counters that is caused by γ radiation from the enclosing shield is also determined

  9. Shielding concepts for low-background proportional counter arrays in surface laboratories

    Aalseth, Craig E; Mace, Emily K; Orrell, John L; Seifert, Allen; Williams, Richard M

    2015-01-01

    Development of ultra low background gas proportional counters has made the contribution from naturally occurring radioactive isotopes -- primarily $\\alpha$ and $\\beta$ activity in the uranium and thorium decay chains -- inconsequential to instrumental sensitivity levels when measurements are performed in above ground surface laboratories. Simple lead shielding is enough to mitigate against gamma rays as gas proportional counters are already relatively insensitive to naturally occurring gamma radiation. The dominant background in these surface laboratory measurements using ultra low background gas proportional counters is due to cosmic ray generated muons, neutrons, and protons. Studies of measurements with ultra low background gas proportional counters in surface and underground laboratories as well as radiation transport Monte Carlo simulations suggest a preferred conceptual design to achieve the highest possible sensitivity from an array of low background gas proportional counters when operated in a surface...

  10. 3He and BF3 Neutron Detector Pressure Effect and Model Comparison

    Paper for SORMA conference Radiation detection systems for homeland security applications must possess the capability of detecting both gamma rays and neutrons. The radiation portal monitor (RPM) systems that are currently deployed use a plastic scintillator for detecting gamma rays and 3He gas-filled proportional counters for detecting neutrons. Proportional counters filled with 3He are the preferred neutron detectors for use in RPMs because 3He has a large neutron cross section, is relatively insensitive to gamma-rays, is neither toxic nor corrosive, can withstand extreme environments, and can be operated at a lower voltage than some of the alternative proportional counters. The amount of 3He required for homeland security and science applications has depleted the world supply and there is no longer enough available to fill the demand. Thus, alternative neutron detectors are being explored. Two possible temporary solutions that could be utilized while a more permanent solution is being identified are reducing the 3He pressure in the proportional counters and using boron trifluoride (BF3) gas-filled proportional counters. Reducing the amount of 3He required in each of the proportional counters would decrease the rate at which 3He is being used, not enough to solve the shortage but perhaps enough to increase the amount of time available to find a working replacement. BF3 is not appropriate for all situations as these detectors are less sensitive than 3He, BF3 gas is corrosive, and a much higher voltage is required than what is used with 3He detectors. Measurements of the neutron detection efficiency of 3He and BF3 as a function of tube pressure were made. The experimental results were also used to validate models of the RPMs.

  11. 3He and BF3 neutron detector pressure effect and model comparison

    Radiation detection systems for homeland security applications must possess the capability of detecting both gamma rays and neutrons. The radiation portal monitor systems that are currently deployed use a plastic scintillator for detecting gamma rays and 3He gas-filled proportional counters for detecting neutrons. Proportional counters filled with 3He are the preferred neutron detectors for use in radiation portal monitor systems because 3He has a large neutron cross-section, is relatively insensitive to gamma-rays, is neither toxic nor corrosive, can withstand extreme environments, and can be operated at a lower voltage than some of the alternative proportional counters. The amount of 3He required for homeland security and science applications has depleted the world supply and there is no longer enough available to fill the demand. Thus, alternative neutron detectors are being explored. Two possible temporary solutions that could be utilized while a more permanent solution is being identified are reducing the 3He pressure in the proportional counters and using boron trifluoride gas-filled proportional counters. Reducing the amount of 3He required in each of the proportional counters would decrease the rate at which 3He is being used; not enough to solve the shortage, but perhaps enough to increase the amount of time available to find a working replacement. Boron trifluoride is not appropriate for all situations as these detectors are less sensitive than 3He, boron trifluoride gas is corrosive, and a much higher voltage is required than what is used with 3He detectors. Measurements of the neutron detection efficiency of 3He and boron trifluoride as a function of tube pressure were made. The experimental results were also used to validate models of the radiation portal monitor systems.

  12. A multiwire proportional counter for the detection of plutonium-239 in vivo

    Work is in progress on developing counters to detect plutonium in the human lungs. The need for a low background counter for such work is discussed and the design and construction of a multiwire gas proportional counter described. The performance of the counter with different gas fillings is considered and results obtained on background, resolution, field of view and efficiency are given. Future work will consist of using the counter in conjunction with a realistic chest phantom. An estimate of the limit of detection is derived. (author)

  13. Position sensitive multiwire proportional counter for the crystal X-spectrometer of Tore Supra tokamak

    A position sensitive proportional counter, for use in the Tore Supra X-spectrometer, is developed. The physics of X-photons detection, in those counters, are reviewed. The detector's design and construction are presented. Its surface of detection is five times larger than that of the previous counter (40 cm2 times 8 cm2). The counter's spatial resolution is measured, in order to verify whether or not the spectrometer performance is modified. The dead time influence is studied and correction procedures are obtained. An optical transmission line, between the counter and the electronics of the data acquisition system, is considered for use in gamma radiation or fusion neutron environments

  14. Wall effect study by P ADC detector for an improved proportional counter neutron spectrometer

    Sajo B, L.; Greaves, E. D.; Palacios, D.; Barros, H.; Nemeth, P. [Universidad Simon Bolivar, Laboratorio de Fisica Nuclear, Apdo. Postal 89000, Caracas (Venezuela, Bolivarian Republic of); Palfalvi, J. [Atomic Energy Research Centre AEKI-KFKI, Budapest (Hungary)

    2010-02-15

    Gas filled proportional counter employed for neutron spectrometry may introduce distortion on the resulting spectrum due to the so called wall effect. This can be studied with passive detectors such as P ADC and to estimate the spectrum uncertainty. Results giving information on the charge particle rate entering the proportional counter active detection zone provide the extent of the perturbing effect due to different cathode wall material. In this study we point out some case material (Pt, Al, Ni) response to a radioisotope produced neutron field employing passive detectors. Comments on the resulting data and suggestions on possible materials to build a low wall effect proportional counter for neutron spectrometry are given. (Author)

  15. Monte Carlo studies of electron avalanches in microdosimetric proportional counters

    We present preliminary results from a study of electron avalanches in a low pressure cylindrical microdosimetric counter. The technique is based on the Monte Carlo simulation of the motion of electrons in electric field and their interactions with the molecules of gas. All the electrons are traced simultaneously in time and their coordinates and velocities are recorded. It lets us study all temporal and space aspects of the electron avalanche development. In this work we have concentrated on a study of the dependence of gain, radial extent and time extent of the avalanche on the gas pressure. We explain our results by the existence of seeding region in the avalanche where a relatively small number of secondary electrons are created. Each of these electrons gives subsequently rise to a partial avalanche in the proper avalanche region. (orig.)

  16. Proceedings of the symposium on measurements of neutron energy spectra using recoil proton proportional counters

    This is a report of the symposium on measurements of neutron energy spectra using recoil proton proportional counters held at the Research Reactor Institute of Kyoto University on January 27 in 1986. An energy resolution, wall effects of response functions, n · γ discrimination methods and other fundamental properties of recoil proton counters are discussed for a new development of an application of this counter. (author)

  17. Multiwire proportional counter (lecture by an electromagnetic delay line)

    For track localisation of ionizing particles with multiwire proportional chamber, an electronic chain including amplifying, shaping and memorizing circuits is required for each wire. In order to lower the cost of this type of detector, an electromagnetic delay line is proposed among various possibilities. In this paper, different coupling modes between chamber and delay line are studied with their respective advantages. The realization of one meter long delay line with a unit delay time of 15 ns per cm is also presented

  18. New proportional counter for in vivo detection of traces of plutonium in the lungs

    Development of a multi-wire proportional counter having a uniform response over 250 cm2 thanks to corrections made for boundary effects, and having a low background per sq. cm. due to the use of two identical counters set in anti-coincidence in the same enclosure is described. (author)

  19. Results of measurements of an environment neutron background at BNO INR RAS objects with the helium proportional counter

    Barabanov, I R; Gavrilyuk, Yu M; Gangapshev, A M; Gezhaev, A M; Kazalov, V V; Khokonov, A Kh; Kuzminov, V V; Panasenko, S I; Ratkevich, S S

    2015-01-01

    A method of measurements of the environmental neutron background at the Baksan Neutrino Observatory of the INR RAS are described. Measurements were done by using of a proportional counter filled with mixture of Ar(2 at)+$^3$He(4 at). The results obtained at the surface and the underground laboratory of the BNO INR RAS are presented. It is shown that a neutron background in the underground laboratory at the 4900 m w.e. depth is decreased by $\\sim 260$ times without any special shield in a comparison with the Earth surface. A neutron flux density in the 5-1323.5~cm air height region is constant within the determination error and equal to $(7.1\\pm0.1_{\\rm{stat}}\\pm0.3_{\\rm{syst}})\\times10^{-3}$ s$^{-1}\\cdot$cm$^{-2}$.

  20. Shielding concepts for low-background proportional counter arrays in surface laboratories

    Aalseth, Craig E.; Humble, Paul H.; Mace, Emily K.; Orrell, John L.; Seifert, Allen; Williams, Richard M.

    2016-02-01

    Development of ultra low background gas proportional counters has made the contribution from naturally occurring radioactive isotopes – primarily and activity in the uranium and thorium decay chains – inconsequential to instrumental sensitivity levels when measurements are performed in above ground surface laboratories. Simple lead shielding is enough to mitigate against gamma rays as gas proportional counters are already relatively insensitive to naturally occurring gamma radiation. The dominant background in these surface laboratory measurements using ultra low background gas proportional counters is due to cosmic ray generated muons, neutrons, and protons. Studies of measurements with ultra low background gas proportional counters in surface and underground laboratories as well as radiation transport Monte Carlo simulations suggest a preferred conceptual design to achieve the highest possible sensitivity from an array of low background gas proportional counters when operated in a surface laboratory. The basis for a low background gas proportional counter array and the preferred shielding configuration is reported, especially in relation to measurements of radioactive gases having low energy decays such as 37Ar.

  1. Shielding concepts for low-background proportional counter arrays in surface laboratories.

    Aalseth, C E; Humble, P H; Mace, E K; Orrell, J L; Seifert, A; Williams, R M

    2016-02-01

    Development of ultra low background gas proportional counters has made the contribution from naturally occurring radioactive isotopes - primarily α and β activity in the uranium and thorium decay chains - inconsequential to instrumental sensitivity levels when measurements are performed in above ground surface laboratories. Simple lead shielding is enough to mitigate against gamma rays as gas proportional counters are already relatively insensitive to naturally occurring gamma radiation. The dominant background in these surface laboratory measurements using ultra low background gas proportional counters is due to cosmic ray generated muons, neutrons, and protons. Studies of measurements with ultra low background gas proportional counters in surface and underground laboratories as well as radiation transport Monte Carlo simulations suggest a preferred conceptual design to achieve the highest possible sensitivity from an array of low background gas proportional counters when operated in a surface laboratory. The basis for a low background gas proportional counter array and the preferred shielding configuration is reported, especially in relation to measurements of radioactive gases having low energy decays such as (37)Ar. PMID:26720259

  2. Design of nuclear pulse shaped circuit based on proportional counter

    Use the self-developed proportional to sample gas tritium in environment and make the measurement. For this detector, a kind of pulse shape circuit based on second order active low pass filtering circuit realized filtering and shaping nuclear pulse by high-speed operational amplifier, with less stages that has been approved for filter Gaussian wave. Use Multisim 10.0 to simulate the different parameters of the filter circuit. The simulation result was consistent with the theoretical results. The experiments proved the feasibility of this circuit, and at the same time provided a convenient and reliable method for analysis and optimization of the nuclear pulse waveform in order for discriminating by MCA. (authors)

  3. Characteristics of a high pressure gas proportional counter filled with xenon

    Sakurai, H.; Ramsey, B. D.

    1991-01-01

    The characteristics of a conventional cylindrical geometry proportional counter filled with high pressure xenon gas up to 10 atm. were fundamentally investigated for use as a detector in hard X-ray astronomy. With a 2 percent methane gas mixture the energy resolutions at 10 atm. were 9.8 percent and 7.3 percent for 22 keV and 60 keV X-rays, respectively. From calculations of the Townsend ionization coefficient, it is shown that proportional counters at high pressure operate at weaker reduced electric field than low pressure counters. The characteristics of a parallel grid proportional counter at low pressure showed similar pressure dependence. It is suggested that this is the fundamental reason for the degradation of resolution observed with increasing pressure.

  4. Space-charge effects of the proportional counters in a multiple-ionization chamber

    At the ALADIN spectrometer of the GSI in october 1991 for the first time the new multiple ionization chamber was applied, in the two anode planes of which are additional multiwire-proportional counters. The proportional counters are required in order to make the detection of light fragments (Z4 gold projectiles per second by these positive space charges the homogeneous electric field of the MUSIC is disturbed. This effect is especially strong in the beam plane. As consequence of the space charge additionally electrons are focused on the proportional counter so that their amplitudes in dependence on the beam intensity increase up to the 2.5-fold. Furthermore the y coordinate is falsified, because the electrons are diverted to the medium plane. On the measurement of the x coordinate this diversion has with maximally 0.1% only a small influence. These space-charge effects can be qualitatively described by a schematic model, which assumes a stationary positive space charge. Additionally for the proportional counters, which are not in the beam plane, their resolution was determined. In these counters the space-charge effects are small, because essentially fewer particles are registrated than in the medium MWPC's. By this charges of fragments with Z<10 could be separated. The charge resolution amounted at lithium 0.8 charge units. The position resolution of the proportional counters in y direction was determined to less than 8 mm. The detection probability of the fragments amounts for lithium 90% and from boron all fragments are detected

  5. Development of a drift tissue equivalent proportional counter for radiation protection personnel dosimetry

    A new multicellular geometry for proportional counter has been developed. It is made of several drift regions which are some holes drilled in the cathode in front of anodes wires. The present work is made of 3 parts: 1) A theoretical evaluation of the multicellular counter characteristics: the sensitivity increases by a factor 15 vs the Tinelli Merlin-Gerin counter; the chord length distribution study shows the possibility to use a Dirac function for the dosimetry calculations; a tissue equivalent gas mixture based on argon and propane is designed. 2) The production of a monocellular prototype made of a hole and a needle shaped anode. 3) An experimental study of the prototype electrical characteristics and a computation of the electrical field in the counter. The focalization and the electron drift into the hole, the proportional operating mode are shown. Irradiations in front of photon and neutron sources verify these results

  6. Effect of air on energy and rise-time spectra measured by proportional gas counter

    Kawano, T.; Tanaka, M. [National Institute for Fusion Science, Toki, Gifu (Japan); Isozumi, S. [IsoShieldJP, Co. Ltd., Kohata, Ufi-shi, Kyoto (Japan); Isozumi, Y.; Tosaki, M. [Radioisotope Research Centre, Kyoto University, Kyoto (Japan); Sugiyama, T. [School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya (Japan)

    2015-03-15

    Air exerts a negative effect on radiation detection using a gas counter because oxygen contained in air has a high electron attachment coefficient and can trap electrons from electron-ion pairs created by ionization from incident radiation in counting gas. This reduces radiation counts. The present study examined the influence of air on energy and rise-time spectra measurements using a proportional gas counter. In addition, a decompression procedure method was proposed to reduce the influence of air and its effectiveness was investigated. For the decompression procedure, the counting gas inside the gas counter was decompressed below atmospheric pressure before radiation detection. For the spectrum measurement, methane as well as various methane and air mixtures were used as the counting gas to determine the effect of air on energy and rise-time spectra. Results showed that the decompression procedure was effective for reducing or eliminating the influence of air on spectra measurement using a proportional gas counter. (authors)

  7. Differential dosimetry in a neutron-proton mixed field with low-pressure proportional counters

    For a mixed radiation field of neutrons and protons, radiation events were discriminated between photons, neutrons, and protons using a thin plastic scintillator. Distributions of lineal energy were measured with low-pressure proportional counters (LPPCs). To estimate the distribution of lineal energy for ICRU muscle, measurements were carried out using A-150-walled, graphite-walled, ZrO2-walled, and Zr-walled counters. Data were corrected for different atomic compositions between the A-150 plastic and ICRU muscle. (author)

  8. Effect of self-induced space charge in a high pressure position-sensitive proportional counter

    The response of a position-sensitive proportional counter filled with Ar+30%CH4 counting gas under a pressure of 7 atm has been studied in detail for 8-keV incident X-rays. The counter was operated in the region of limited proportionality, where the avalanche growth is greatly affected by self-induced space charge and hence an unfamiliar distorted energy spectrum is often observed. It is confirmed that the avalanches caused by the halo effect of Ar K X-rays, emitted in photoelectric absorption of incident X-rays, have higher gas amplification as compared to other photopeak avalanches due to different origin of primary electrons. The analysis has revealed that the effect of self-induced space charge hinders the avalanche growth of photopeak events to the extent of 50% of the observed avalanche charge. Comprehensive analysis of the complicated counter response in the region of limited proportionality under high pressure is provided. (orig.)

  9. Design of a hybrid gas proportional counter with CdTe guard counters for 14C dating system

    Nowadays uniform, low-cost and large-size compound semiconductor detectors are available up to several square centimeters. We are trying to combine this technology with conventional gas detectors to upgrade an anticoincidence type proportional counter, Oeschger-type thin wall counter of 2.2 l, used for a 14C dating facility at the University of Tokyo. In order to increase the ratio of the signal to the background for smaller quantity of samples less than 1 g, an effective approach is to minimize the detector volume at higher gas pressure. However, the anticoincidence function suffers from such a small volume. Therefore we designed a new active wall gas counter of 0.13 l counting volume using CdTe compound semiconductor detectors as the wall of the gas proportional counter to perform anticoincidence. Simulation study showed that at noise thresholds less than 70 keV, the wall counters can reject above 99.8% of events arising from outer gamma rays. Measured noise levels of CdTe detectors were smaller than 24 keV which is low enough for 99.8% anticoincidence efficiency. The experiment showed an anticoincidence efficiency for outer gamma rays from 70% to 80%, similar to that of the old 14C counter. The lost anticoincidence efficiency results from the area of 21.74% which was not covered with CdTe due to two holes for the path of the center anode wire and slots between every two sides of CdTe detectors

  10. Design of a hybrid gas proportional counter with CdTe guard counters for {sup 14}C dating system

    Zhang, L. E-mail: lan@sophie.q.t.u-tokyo.ac.jp; Takahashi, H.; Hinamoto, N.; Nakazawa, M.; Yoshida, K

    2002-02-01

    Nowadays uniform, low-cost and large-size compound semiconductor detectors are available up to several square centimeters. We are trying to combine this technology with conventional gas detectors to upgrade an anticoincidence type proportional counter, Oeschger-type thin wall counter of 2.2 l, used for a {sup 14}C dating facility at the University of Tokyo. In order to increase the ratio of the signal to the background for smaller quantity of samples less than 1 g, an effective approach is to minimize the detector volume at higher gas pressure. However, the anticoincidence function suffers from such a small volume. Therefore we designed a new active wall gas counter of 0.13 l counting volume using CdTe compound semiconductor detectors as the wall of the gas proportional counter to perform anticoincidence. Simulation study showed that at noise thresholds less than 70 keV, the wall counters can reject above 99.8% of events arising from outer gamma rays. Measured noise levels of CdTe detectors were smaller than 24 keV which is low enough for 99.8% anticoincidence efficiency. The experiment showed an anticoincidence efficiency for outer gamma rays from 70% to 80%, similar to that of the old {sup 14}C counter. The lost anticoincidence efficiency results from the area of 21.74% which was not covered with CdTe due to two holes for the path of the center anode wire and slots between every two sides of CdTe detectors.

  11. Low-energy gamma-ray spectroscopy using an X-ray-escape gated proportional counter

    Gregers Hansen, P.; Nielsen, H.L.; Williams, E.T.; Wilsky, K.

    1965-01-01

    The utility of a gas-filled proportional counter in low-energy γ spectroscopy is greatly increased if it is operated in coincidence with an escaping fluorescent X-ray. An apparatus, having an efficiency greater than 10% of singles, is described and several examples are given. An efficiency curve is...

  12. Proportional counters as monitoring detectors of BAC chambers at the ZEUS experiment

    The aim of the investigations presented is the elaboration of the system monitoring working conditions of BAC chambers. The backing calorimeter (BAC) at the ZEUS detector of the HERA accelerator consisting of 5000 proportional chambers of a total volume of 60 m3 is supplied with a gas mixture of Ar+10% CO2 by an open gas system. Flow proportional counters with a 55Fe source are used as gas system monitoring detectors. These counters and sources were designed and made exclusively for that application. The ageing effect of the Ar+CO2 mixture has also been studied. Monitoring measurements of the pulse height distribution enable us to follow the changes of gas pressure and composition in BAC proportional chambers. The results of these measurements will be used for off-line corrections of BAC data. (orig.)

  13. A multiple sampling proportional counter for particle identification of relativistic heavy ions

    A multiple sampling dE/dx counter using a multiwire proportional chamber equipped with catbode pads was constructed for the multiple detection of dE/dx values along a particle trajectory. For low-energy particles this counter was proved to be useful as a Bragg-curve detector. At relativistic energies around E=14.6 GeV/nucleon good particle identification was obtained by cathode pad signals as well as anode signals for the range of projectile fragments from Z=1 (minimum ionization) up to a beam charge of Z=14. (orig.)

  14. Gas gain limitation in low pressure proportional counters filled with TEG mixtures—part II

    Kowalski, T. Z.

    2016-01-01

    Proportional counters filled with tissue equivalent gas mixtures are extremely useful instruments and are being used extensively as sensitive detectors for all types of radiations to measure the energy transferred to small tissue volumes. The linearity of their response is of primary importance. So the investigation and clarification of the physical phenomena taking place in the counter and of the limits within which useful results may be obtained would contribute to a more efficient use and a wider application of these counters. The measured gas gain curves have been fitted to the Diethorn and Williams & Sara gas gain models. The models parameters and their dependence on gas pressure have been determined. It was shown that reduced ionization coefficient α/p is not univocal function of the reduced electric field strength EFS/p.

  15. Photon and neutron dose discrimination using low pressure proportional counters with graphite and A150 walls

    A graphite-walled proportional counter with low neutron sensitivity was used in combination with a tissue-equivalent proportional counter (TEPC) to separate the photon and neutron components in mixed radiation fields. Monte Carlo (MCNP4C) simulations of the photon and neutron responses of the two detectors were done to obtain correction factors for the sensitivity differences. In an alternative method the radiation components were determined using constant-yD-values for typical photon and neutron energy distributions. The results show no significant difference between the two methods and the measured neutron dose-equivalent agrees within ±50% with Bonner sphere determined values. The experimental data were obtained in measurement campaigns organised within the EVIDOS-project. (authors)

  16. Study and construction of an air proportional counter for superficial alpha contamination

    Some properties of the proportional counters such as the working principle and the process of the gaseous multiplication are presented. Besides that, the project of Multiwire Proportional Counters is shown, which was tested with anodic wires of different diameters and with windows of several thicknesses. Operational characteristics of the detector were determined with the quoted variations. The chamber was normally operated by atmospheric pressure, but there were also made surveys on its behavior with oxygen, nitrogen and mixture of both. The performance of the chamber with a variations of temperature and relative humidity is analysed, because that is one of the biggest problems faced when measure of field are being made with this kind of detector. (author)

  17. Performance verification of the gas scintillation proportional counters on board the Tenma satellite

    Eight gas scintillation proportional counters (GSPC) with a total effective area of 640 cm2 are the major X-ray astronomy satellite Tenma. The energy resolution at 5.9 keV is 9.5 % (FWHM), which is twice as good as conventional proportional counters. Detected X-ray photons are pulse-height analyzed into either 128 or 256 energy channels. The channel energy can be set to an accuracy of less than 50 eV. The in-flight performance of the GSPC was verified by observations of the Crab Nebula. Remaining systematic errors are estimated to be about 1 % for each energy channel. The practical detection limit (0.5 m Crab intensity in the energy range 2-10 keV) is set mainly by uncertainty in determination of the detector background. (author)

  18. Proportional counters aged anode wire recovering using an 80%CF4 + 20%CO2 gas mixture

    Gavrilov, Gennady; Conti, Richard; Fetisov, Andrey; Maysuzenko, Dmitry; Shvecova, Natalia; Vakhtel, Victor

    2011-01-01

    A technique to recover a gas proportional counter having an aged anode wire using a glow discharge in an 80%CF4 + 20%CO2 gas mixture has been developed and tested. Studies of aging effects were carried out under sustained irradiation by an intense 90Sr -source of the straw proportional counters operated with a 60%Ar + 30%CO2 + 10%CF4 gas mixture. Special attention was paid to the aging mechanism of the anode wires. Our experience showed that using a given gas mixture the swelling of the anode wires is a typical mode of aging that leads to degradation of the gas gain. The proposed method of recovery provided a complete restoration of the gas gain and the signal amplitude in the damaged zone of the wire. SEM/XEM analysis confirmed successful cleaning WOx deposits from the wire surface. The application of this method to recover the aged gaseous detectors in real experimental conditions is discussed.

  19. 39Ar/Ar measurements using ultra-low background proportional counters

    Hall, Jeter C.; Aalseth, Craig E.; Bonicalzi, Ricco; Brandenberger, Jill M.; Day, Anthony R.; Humble, Paul H.; Mace, Emily K.; Panisko, Mark E.; Seifert, Allen

    2016-01-08

    Age dating groundwater and seawater using 39Ar/Ar ratios is an important tool to understand water mass flow rates and mean residence time. For modern or contemporary argon, the 39Ar activity is 1.8 mBq per liter of argon. Radiation measurements at these activity levels require ultra low-background detectors. Low-background proportional counters have been developed at Pacific Northwest National Laboratory. These detectors use traditional mixtures of argon and methane as counting gas, and the residual 39Ar from commercial argon has become a predominant source of background activity in these detectors. We demonstrated sensitivity to 39Ar by using geological or ancient argon from gas wells in place of commercial argon. The low level counting performance of these proportional counters is then demonstrated for sensitivities to 39Ar/Ar ratios sufficient to date water masses as old as 1000 years.

  20. Gas proportional scintillation counter pulse-signature analysis using digital techniques

    Simões, P. C. P. S.; Santos, J.M.F. dos; Conde, C. A. N.

    1999-01-01

    The use of short shaping time-constants (50 ns) followed by digital sampling of gas proportional scintillation counter pulses is investigated. Such short shaping time causes each pulse to closely resemble the scintillation light burst, allowing for an effective pulse-signature analysis. Pulse amplitude is obtained by numerical integration of the digital pulse samples. The shorter total pulse durations, lead to pulse-height distributions that are much less dependent on the total interaction ra...

  1. Driftless gas proportional scintillation counter pulse analysis using digital processing techniques

    Simões, P. C. P. S.; Santos, J.M.F. dos; Conde, C. A. N.

    2001-01-01

    A driftless gas proportional scintillation counter (GPSC) of simple design, using digital pulse-signature analysis, is described. The digital pulse acquisition and processing techniques are shown to be a simple and effective method to determine pulse time duration and to perform pulse amplitude correction in driftless GPSCs. This technique allows the application of driftless GPSCs to x-ray spectrometry up to 60 keV. Although the pulse throughput achieved by the digital pulse-height analyser i...

  2. Study of a neutron spectrometer using a Helium-3 proportional counter

    Theory on helium 3 proportional counters is recalled. Pulse rise time discrimination imply irradiation at the end of the detector. Neutron energy range is from 50 keV to 8 MeV. The realization of the spectrometry assembly is described together with the transfer matrix calculation. Differential spectra of neutron emitted by the source Am-B, Am-F, and Am-Li were experimentally found to verify the process method which is proposed

  3. Primary and secondary scintillation measurements in a Xenon Gas Proportional Scintillation Counter

    Fernandes, L. M. P.; Ball, Markus; Gómez Cadenas, Juan José; Yahlali, Nadia; Santos, J. M. F. dos

    2010-01-01

    NEXT is a new experiment to search for neutrinoless double beta decay using a 100 kg radio-pure high-pressure gaseous xenon TPC. The detector requires excellent energy resolution, which can be achieved in a Xe TPC with electroluminescence readout. Hamamatsu R8520-06SEL photomultipliers are good candidates for the scintillation readout. The performance of this photomultiplier, used as VUV photosensor in a gas proportional scintillation counter, was investigated. Initial results for the detecti...

  4. A novel Tissue-Equivalent Proportional Counter based on a Gas Electron Multiplier

    M. Farahmand

    2004-01-01

    Ionising radiation causes a wide variety of effects in biological targets. In experimental microdosimetry these effects are studied by investigating the statistical distribution of energy deposition events at the microscopic level employing a Tissue-Equivalent Proportional Counter (TEPC). A TEPC is usually designed with a cavity of a few centimetres in diameter containing a central anode wire and operated with a tissue-equivalent wall and counting gas at low pressure to simulate tissue volume...

  5. A position sensitive detector system consisting of an array of mini-proportional counters

    A new position sensitive detector system has been developed for the Hard X-ray Imaging Spectrometer launched aboard the NASA Solar Maximum Mission. The instrument operates in the energy range 3.5 - 30 keV. The Xe-gas filled detector system consists of a photon absorption compartment and an array of 900 mini-proportional counters. The detector lay-out and the system performance are described

  6. Spectrometry of the let LET with track etched detectors-correlation with proportional counter measured spectra

    Spurný, František; Bottollier-Depois, J. F.; Vlček, Bohumil

    2001-01-01

    Roč. 32, 1-6 (2001), s. 193-197. ISSN 1350-4487 R&D Projects: GA ČR GA202/01/0710; GA AV ČR KSK1010104 Institutional research plan: CEZ:AV0Z1048901 Keywords : experimental microdosimetry * track etched LET spectrometry * tissue equivalent proportional counter Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.003, year: 2001

  7. The gas proportional scintillation counter/microstrip gas chamber hybrid detector

    Freitas, D. S. A. P.; Veloso, J. F. C. A.; Monteiro, C. M. B.; Santos, J. M. F. dos; Conde, C. A. N.

    2003-01-01

    The gas proportional scintillation counter/microstrip gas chamber (GPSC/MSGC) hybrid detector for X-ray spectrometry is described. The detector uses a CsI-coated microstrip plate placed in direct contact with the gas-filling as the photosensor readout for the GPSC scintillation substituting for the photomultiplier tube (PMT). Usable photosensor maximum gain is limited by optical positive feedback due to the additional scintillation produced in the electron avalanche process at the MSP anodes,...

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

    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.)

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

    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.)

  10. 3He Neutron Detector Pressure Effect and Comparison to Models

    Reported here are the results of measurements performed to determine the efficiency of 3He filled proportional counters as a function of gas pressure in the SAIC system. Motivation for these measurements was largely to validate the current model of the SAIC system. Those predictions indicated that the neutron detection efficiency plotted as a function of pressure has a simple, logarithmic shape. As for absolute performance, the model results indicated the 3He pressure in the current SAIC system could not be reduced appreciably while meeting the current required level of detection sensitivity. Thus, saving 3He by reducing its pressure was predicted not to be a viable option in the current SAIC system.

  11. A 10B-based neutron detector with stacked Multiwire Proportional Counters and macrostructured cathodes

    Stefanescu, I; Birch, J; Defendi, I; Hall-Wilton, R; Hoglund, C; Hultman, L; Zee, M; Zeitelhack, K

    2013-01-01

    We present the results of the measurements of the detection efficiency for a 4.7 \\r{A} neutron beam incident upon a detector incorporating a stack of up to five MultiWire Proportional Counters (MWPC) with Boron-coated cathodes. The cathodes were made of Aluminum and had a surface exhibiting millimeter-deep V-shaped grooves of 45{\\deg}, upon which the thin Boron film was deposited by DC magnetron sputtering. The incident neutrons interacting with the converter layer deposited on the sidewalls of the grooves have a higher capture probability, owing to the larger effective absorption film thickness. This leads to a higher overall detection efficiency for the grooved cathode when compared to a cathode with a flat surface. Both the experimental results and the predictions of the GEANT4 model suggests that a 5-counter detector stack with coated grooved cathodes has the same efficiency as a 7-counter stack with flat cathodes. The reduction in the number of counters in the stack without altering the detection efficie...

  12. Standardization of large area alpha and beta sources with a windowless multi-wire proportional counter

    A measurement system was assembled and tested for the absolute standardization of large area alpha and beta sources. Such sources are employed to calibrate a variety of contaminometers. A window-less multi-wire proportional counter, donation of the Laboratoire National Henri Becquerel (LNHB), Saclay - France, was used, with pure methane as flowing gas. The needed electronics (high voltage, amplifier, discriminator, counter, clock, MCA) was a CANBERRA one. Point and extended sources of 241 Am, 90 Sr + 90 Y and 204 Tl were standardized. The variation of the counting rate with high voltage provided a 'plateau' at (300-500) V, with a slope of (0.1-1.5)% for 100 V. The efficiency of the counter for a point beta source and a central area of (100x150) mm2, varied with less than 0.2%. To avoid spurious pulses, adequate threshold and working high voltage were chosen, and an imposed 10 ms dead-time was inserted in the counting channel. A procedure for the threshold correction was established. A compound uncertainty of maximum 2% was obtained, a quite acceptable value for extended sources. These results, together with the results obtained at LNHB with an identical counter, but using argon/methane mixture, will be presented at the 2001 Symposium of ICRM (International Committee for Radionuclide Metrology) in Germany. (authors)

  13. Standardization of a large area alpha and beta sources with a windowless multiwire proportional counter

    In The Radionuclide Metrology Group of IFIN-HH, a measurement system was assembled and tested for the absolute standardization of large area alpha and beta sources. Such sources are employed to calibrate a variety of contaminometers. A windowless multi-wire proportional counter, a donation of the 'Laboratoire National Henri Becquerel' (LNHB), Saclay-France, was used, with pure methane as flowing gas. The needed electronics (high voltage supply, amplifier, discriminator, counter, clock, MCA) was a CANBERRA one. Point and extended sources of 241 Am, 90 (Sr+Y) and 204 Tl were standardized. The variation of the counting rate with high voltage provided 'plateaus' of (300-500) V, with a slope of (0.1-1.5)% for 100 V. The efficiency of the counter for a point beta source and a central area of (100 x 150) mm2, varied with less than 0.2%. To avoid spurious pulses, adequate threshold and working high voltage were chosen, and an imposed 10 μs dead-time was inserted in the counting channel. A procedure for the threshold correction was established. A combined uncertainty of maximum ± 2% was obtained, a quite acceptable value for extended sources. These results, together with the results obtained by Romanian specialists in LNHB, with an identical counter, but using argon/methane mixture will be published. The experiment was realised in the frame of the IFIN-HH long term collaboration agreement. (authors)

  14. Measurement of the gas amplification coefficient in a TEPC [tissue-equivalent proportional counter

    Of fundamental importance for the design and application of proportional counters is the knowledge of the gas gain characteristic. For this work the behaviour of the gas gain was investigated in a 1/2 inch spherical TEPC with helix. The counter was filled with methane based tissue-equivalent gas. The internal 244Cm alpha source was used for all measurements. The gas gain was determined for six different gas pressures between 56.27 torr and 562.69 torr, which correspond to simulated diameters between 1 μm and 10 μm. The important parameter governing the gas amplification is the number of electrons created per unit length, which is called the Townsend coefficient, αT. Results show that αT rises with the reduced field strength, reaches a maximum and then decreases with increasing field strength. Possible explanations of this behaviour are discussed as well as the implications for the operating pressures and gas gain ranges of this proportional counter. (author)

  15. Position-sensitive proportional counter with low-resistance metal-wire anode

    A position-sensitive proportional counter circuit is provided which uses a conventional (low-resistance, metal-wire anode) proportional counter for spatial resolution of an ionizing event along the anode of the counther. A pair of specially designed activecapacitance preamplifiers terminate the anode ends wherein the anode is treated as an RC line. The preamplifiers act as stabilized active capacitance loads and each is composed of a series-feedback, lownoise amplifier, a unity-gain, shunt-feedback amplifier whose output is connected through a feedback capacitor to the series-feedback amplifier input. The stabilized capacitance loading of the anode allows distributed RC-line position encoding and subsequent time difference decoding by sensing the difference in rise times of pulses at te anode ends where the difference is primarily in response to the distributed capacitance along the anode. This allows the use of lower resistance wire anodes for spatial radiation detection which simplifies the counter construction and handling of the anodes, and stabilizes the anode resistivity at high count rates

  16. High-efficiency microstructured semiconductor neutron detectors for direct 3He replacement

    High-efficiency Microstructured Semiconductor Neutron Detectors (MSNDs) have been tiled and arranged in a cylindrical form factor in order to serve as a direct replacement to aging and increasingly expensive 3He gas-filled proportional neutron detectors. Two 6-in long by 2-in diameter cylinders were constructed and populated with MSNDs which were then directly compared to a 4 atm Reuter Stokes 3He detector of the same dimensions. The Generation 1 MSND-based 3Helium-Replacement (HeRep Mk I) device contained sixty-four 1-cm2 active-area MSNDs, each with an intrinsic neutron detection efficiency of approximately 7%. A Generation 2 device (the HeRep Mk II) was populated with thirty 4-cm2 active-area MSNDs, with an intrinsic thermal neutron detection efficiency of approximately 30%. The MSNDs of each HeRep were integrated to count as a single device. The 3He proportional counter and the HeRep devices were tested while encased in a cylinder of high-density polyethylene measuring a total of 6-in by 9-in. The 3He counter and the HeRep Mk II were each placed 1 m from a 54-ng 252Cf source and tested for efficiency. The 3He proportional counter had a net count rate of 17.13±0.10 cps at 1 m. The HeRep Mk II device had a net count rate of 17.60±0.10 cps, amounting to 102.71±2.65% of the 3He gas counter while inside of the moderator. Outside of moderator, the 3He tube had a count rate of 3.35±0.05 cps and the HeRep Mk II device reported 3.19±05, amounting to 95.15±9.04% of the 3He neutron detector

  17. Application of neutron spectrometry by proton recoil proportional counters to radioprotection

    In current spectrometry, an NE213 liquid scintillator is used to analyse neutrons in 1.5 MeV - 20 MeV range and the proton recoil proportional counters are employed to explore the 20 keV to 1.5 MeV zone. We have studied two types of proton recoil counters having differents geometries. Preliminary studies of these detectors with monoenergetic neutrons are required in order to determine the experimental characteristics (efficiency, energy resolution, isotopic qualitie). In order to determine neutrons spectra from the pulse distributions recorded by the spectrometer, a computer code based on matrix analysis method has been written. A spectrometry measurement unit was also tested with an Am-Li (n,α) source so as to compare our results with those already published in the literature

  18. Application of low pressure tissue equivalent proportional counter for IHEP radiation protection

    Palliation behind shields of high energy charge particles accelerators (for example, the IHEP 70 GeV proton synchrotron (U-70)) is of a mixed composition. The major component of radiation is high energy neutrons with energy above 20 MeV. The dose equivalent measurement of high energy neutrons is a difficult problem for the radiation protection dosimetry, because there are no standard devices for this energy region. Now only a measurement method on the base of low-pressure tissue equivalent proportional counter (TEPC) is used as universal in mixed radiation fields. This dosimetric method has more than 20 year history of application at the THEP accelerator. The method has been improved in measurements, the counter design and application. The linear energy transfer (LET) spectrometer (SLET-03) on the base of TEPC is used for metrological measurements in IHEP radiation protection. (author)

  19. Application of low-pressure tissue-equivalent proportional counter for IHEP radiation protection

    The dosimetry method based on low-pressure tissue-equivalent proportional counters (TEPS) is described, which is used for radiation dosimetry in IHEP. The main technical data of TEPC and experimental results of dose characteristics measurements are presented for the reference fields of IHEP and JINR (Dubna). The results are compared with other dosimetric systems. An application of correction methods for neutron dose equivalent measurement on the base of TEPC microdosimetry spectra and using the detector with different neutron energy response is discussed. 18 refs., 12 figs., 1 tab

  20. The effect of the photomultiplier nonuniformity on the performance of gas proportional scintillation counters

    Dos Santos, J. M. F.; Bento, A. C. S. S. M.; Conde, C. A. N.

    1992-09-01

    Experimental results are presented showing that the energy resolution of xenon filled gas proportional scintillation counters with large radiation windows depends not only on the radial but also on the azimuthal variation of the efficiency of the photomultiplier. The commonly used venetian blind dynode photomultipliers are found to present a strong azimuth dependent efficiency and so are not advisable for high performance detectors. With properly chosen 2 in. diameter photomultipliers energy resolutions of less than 9% can be achieved with 20 mm diameter radiation windows in nonfocused detectors.

  1. Simulations of electron avalanches in an ultra-low-background proportional counter

    Robinson, John W.; Aalseth, Craig; Dion, Michael P.; Overman, Cory; Seifert, Allen; VanDevender, Brent

    2016-02-01

    New classes have been added to the simulation package Garfield++ to import the potential and electric field solutions generated by ANSYS ® MaxwellTM v.16. Using these tools we report results on the simulation of electron avalanches and induced signal waveforms in comparison to experimental data of the ultra-low-background gas proportional counters being developed at Pacific Northwest National Laboratory. Furthermore, an improved mesh search algorithm based on Delaunay triangulation was implemented and provided at least a three order of magnitude time savings when compared to the built-in point-location search class of Garfield++.

  2. Basic performance of a pressurized backgammon-type position-sensitive proportional counter for thermal neutrons

    Horiguchi, T.; Itoh, T.; Ito, S. E-mail: shinito@msa.kindai.ac.jp; Yamamoto, T.; Miyasaka, T.; Sakai, J.; Shibata, K.; Masuda, Y.; Okumura, A.; Niwa, T

    2004-08-21

    A position-sensitive proportional counter with the backgammon position-reading method has been developed for thermal neutron detection. The use of a thin solid layer of {sup 10}B and a high-pressure counting gas of 6-atm Ar+10%CH{sub 4} has enabled us to obtain the position resolution well below 1.0 mm. Moreover, it was clearly revealed that the deterioration and/or the splitting of position-peak structure, observed in some conditions, originated in the strong correlational behavior between position information and avalanche size. It is explained qualitatively that this phenomenon is caused by the effect of self-induced space charge.

  3. Simulations of Electron Avalanches in an Ultra-Low-Background Proportional Counter

    Robinson, John W.; Aalseth, Craig E.; Dion, Michael P.; Overman, Cory T.; Seifert, Allen; VanDevender, Brent A.

    2016-02-21

    New classes have been added to the simulation package Garfield++ to import the potential and electric field solutions generated by ANSYS R MaxwellTM v.16. Using these tools we report results on the simulation of electron avalanches and induced signal waveforms in comparison to experimental data of the ultra-lowbackground gas proportional counters being developed at Pacific Northwest National Laboratory. Furthermore, an improved mesh search algorithm based on Delaunay triangulation was implemented and provided at least a three order of magnitude time savings when compared to the built-in point-location search class of Garfield++.

  4. Use of tissue equivalent proportional counters to characterize radiation quality on the space shuttle

    Tissue equivalent proportional counters (TEPC) are essentially cavity ionization chambers operating at low pressure and with gas gain. A small, battery powered, TEPC spectrometer, which records lineal energy spectra at one minute intervals, has been used on several space shuttle missions. The data it has collected clearly show the South Atlantic anomaly and indicate a mean quality factor somewhat higher than expected. An improved type of instrument has been developed with sufficient memory to record spectra at 10 second intervals, and with increased resolution for low LET events. This type of instrument will be used on most future space shuttle flights and in some international experiments

  5. The Rutherford Appleton Laboratory's Mark I Multiwire Proportional Counter positron camera

    A small model of a proposed large aperture positron camera has been developed at Rutherford Appleton Laboratory. Based on Multiwire Proportional Counter technology it uses lead foil cathodes which function simultaneously as converters for the 511 keV gamma rays and readout electrodes for a delay line readout system. The detectors have been built up into a portable imaging system complete with a dedicated computer for data taking, processing and display. A complete hardware system and sufficient software was provided to permit hospital based colleagues to generate useful images easily. A complete description of the system is given with performance figures and some of the images obtained are presented. (author)

  6. Annular shape silver lined proportional counter for on-line pulsed neutron yield measurement

    Dighe, P.M., E-mail: pmdighe@barc.gov.in; Das, D.

    2015-04-01

    An annular shape silver lined proportional counter is developed to measure pulsed neutron radiation. The detector has 314 mm overall length and 235 mm overall diameter. The central cavity of 150 mm diameter and 200 mm length is used for placing the neutron source. Because of annular shape the detector covers >3π solid angle of the source. The detector has all welded construction. The detector is developed in two halves for easy mounting and demounting. Each half is an independent detector. Both the halves together give single neutron pulse calibration constant of 4.5×10{sup 4} neutrons/shot count. The detector operates in proportional mode which gives enhanced working conditions in terms of dead time and operating range compared to Geiger Muller based neutron detectors.

  7. A gaseous proportional counter built from a conventional aluminium beverage can

    Winkler, Alexander; Hildén, Timo; Garcia, Francisco; Fedi, Giacomo; Devoto, Francesco; Brücken, Erik J

    2015-01-01

    The gaseous proportional counter is a device that can be used to detect ionizing radiation. These devices can be as simple as a cylindrical cathode and a very thin anode wire centered along its axis. By applying a high voltage, a strong electric field is generated close to the anode wire. Ion-pairs, generated by passing ionizing radiation, create avalanches once they drift into the strong electric field region near the anode. The electrical charges created by the avalanche generate an observable signal which is proportional to the energy loss of the incoming radiation. We discuss the construction of such a device. Our detector was built from an ordinary aluminium beverage can and uses a common electric wire strand as the anode. The construction of this detector offers students at universities or technically oriented high schools a detailed understanding of the design and operation of gaseous radiation detectors. The equipment required to complete the project should be available at most institutions.

  8. A gaseous proportional counter built from a conventional aluminum beverage can

    Winkler, Alexander; Karadzhinova, Aneliya; Hildén, Timo; Garcia, Francisco; Fedi, Giacomo; Devoto, Francesco; Brücken, Erik J.

    2015-08-01

    The gaseous proportional counter is a device that can be used to detect ionizing radiation. These devices can be as simple as a cylindrical cathode and a very thin anode wire centered along its axis. By applying a high voltage, a strong electric field is generated close to the anode wire. Ion-pairs, generated by passing ionizing radiation, create avalanches once they drift into the strong electric field region near the anode. The electrical charges created by the avalanche generate an observable signal which is proportional to the energy loss of the incoming radiation. We discuss the construction of such a device. Our detector was built from an ordinary aluminum beverage can and uses a common electric wire strand as the anode. The construction of this detector offers students at universities or technically oriented high schools a detailed understanding of the design and operation of gaseous radiation detectors. The equipment required to complete the project should be available at most institutions.

  9. New Proportional Counter Suited to the In Vivo Detection of Plutonium Traces in the Lungs

    The authors explain the construction of a gas proportional counter with an effective detecting surface of 250 cm2 and a sensitivity approximately equal to that obtainable with a scintillating crystal. In simplified terms, it consists of two superposed multi-wire counters within the same chamber, one serving as detector and the other to reduce background by anti-coincidence. The window is of beryllium 1 mm thick and the instrument is filled with xenon at a pressure of 2 atm. An important feature of this counter is the excellent uniformity of detection over the entire window surface. This uniformity is obtained by means of corrections for the edge effects, these corrections being very easy to apply. The wires are 25 μm diam. and 3 cm apart, so that it is possible to use much lower voltages than are customary in this type of detector and to suppress parasitic pulses due to spurious emissions. The authors discuss the data obtained from a contaminated animal. (author)

  10. Electronic system for recording proportional counter rare pulses with the pulse shape analysis

    The anutomated system for recording proportional counter rare pulses is described. The proportional counters are aimed at identification of 37Ar and H71Gr decays in chemical radiation detectors of solar neutrino. Pulse shape recording by means of a storage oscilloscope and a TV display is performed in the system considered besides two-parametric selection of events (measurement of pulse amplitude in a slow channel and the amplitude of pulse differentiated with time constant of about 10 ns in a parallel fast channel). Pulse discrimination by a front rise rate provides background decrease in the 55Fe range (5.9 keV) by 6 times; the visual analysis of pulse shapes recorded allows to decrease the background additionally by 25-30%. The background counting rate in the 55Fe range being equal to 1 pulse per 1.5 days, is obtained when using the installation described above, as well as the passive Pb shield 5 cm thick, and the active shield based on the anticoincidence NaI(Tl) detector with the cathode 5.6 mm in-diameter made of Fe fabircated by zone melting. The installation described allows to reach the background level of 0.6 pulse/day (the total coefficient of background attenuation is 400). Further background decrease is supposed to be provided by installation allocation in the low-noise underground laboratory of the Baksan Neutrino Observatory

  11. A proton-recoil proportional-counter array for neutron-image construction

    The fuel-motion measurement capability of the fast-neutron hodoscope has been upgraded by the addition of a 360-detector proton-recoil proportional-counter array, which detects highenergy fission neutrons. The current sensitive amplifier/discriminator module for each detector fits into a 12.7- by 12.7by 102-mm package and costs less than $100 per module. It has a 50-ns rise time, a noise level of 100 nA, and a deadtime per event of 200 ns. Provision has been provided for the independent adjustment of the input current versus discriminator voltage for each module. The new proportional-counters cost approximately $400 each. Each detector has been tested to have the same gain versus voltage response. A space-charge model relating count-rate changes to space-charge effects has also been developed. The new detector array has been operational for approximately two years and has become the main detector system in fuel-motion analysis. It has significantly improved the linearity, stability, count-rate capability, and setup ease of the hodoscope

  12. A model for the secondary scintillation pulse shape from a gas proportional scintillation counter

    Kazkaz, K.; Joshi, T. H.

    2016-03-01

    Proportional scintillation counters (PSCs), both single- and dual-phase, can measure the scintillation (S1) and ionization (S2) channels from particle interactions within the detector volume. The signal obtained from these detectors depends first on the physics of the medium (the initial scintillation and ionization), and second how the physics of the detector manipulates the resulting photons and liberated electrons. In this paper we develop a model of the detector physics that incorporates event topology, detector geometry, electric field configuration, purity, optical properties of components, and wavelength shifters. We present an analytic form of the model, which allows for general study of detector design and operation, and a Monte Carlo model which enables a more detailed exploration of S2 events. This model may be used to study systematic effects in current detectors such as energy and position reconstruction, pulse shape discrimination, event topology, dead time calculations, purity, and electric field uniformity. We present a comparison of this model with experimental data collected with an argon gas proportional scintillation counter (GPSC), operated at 20 C and 1 bar, and irradiated with an internal, collimated 55Fe source. Additionally we discuss how the model may be incorporated in Monte Carlo simulations of both GPSCs and dual-phase detectors, increasing the reliability of the simulation results and allowing for tests of the experimental data analysis algorithms.

  13. Performance of Large Area X-ray Proportional Counters in a Balloon Experiment

    Roy, J; Dedhia, D K; Manchanda, R K; Shah, P B; Chitnis, V R; Gujar, V M; Parmar, J V; Pawar, D M; Kurhade, V B

    2016-01-01

    ASTROSAT is India's first satellite fully devoted to astronomical observations covering a wide spectral band from optical to hard X-rays by a complement of 4 co-aligned instruments and a Scanning Sky X-ray Monitor. One of the instruments is Large Area X-ray Proportional Counter with 3 identical detectors. In order to assess the performance of this instrument, a balloon experiment with two prototype Large Area X-ray Proportional Counters (LAXPC) was carried out on 2008 April 14. The design of these LAXPCs was similar to those on the ASTROSAT except that their field of view (FOV) was 3$^{\\circ}$ $\\times$ 3$^{\\circ}$ versus FOV of 1$^{\\circ}$ $\\times$ 1$^{\\circ}$ for the LAXPCs on the ASTROSAT. The LAXPCs are aimed at the timing and spectral studies of X-ray sources in 3-80 keV region. In the balloon experiment, the LAXPC, associated electronics and support systems were mounted on an oriented platform which could be pre-programmed to track any source in the sky. A brief description of the LAXPC design, laborator...

  14. Proton-recoil proportional-counter array for neutron-image construction

    The fuel-motion measurement capability of the fast-neutron hodoscope has been upgraded by the addition of a 360-detector proton-recoil proportional-counter array, which detects high-energy fission neutrons. The current sensitive amplifier/discriminator module for each detector fits into a 12.7 by 12.7 by 102 mm package and cost less than $100 per module. It has a 50 ns rise time, a noise level of 100 nA, and a deadtime per event of 200 ns. Provision has been provided for the independent adjustment of the input current versus discriminator voltage for each module. The new proportional-counters cost approximately $400 each. Each detector has been tested to have the same gain versus voltage response. A space-charge model relating count-rate changes to space-charge effects has also been developed. The new detector array has been operational for approximately two years and has become the main detector system in fuel-motion analysis. It has significantly improved the linearity, stability, count-rate capability, and setup ease of the hodoscope

  15. Study on the effect of moderator of the proportional Boron-lined counter on the neutron detection efficiency

    The proportional boron-lined counter as a common source-range detector is widely used in reactor monitoring, which has high detection efficiency for thermal neutron. The detection efficiency of the proportional boron-lined counter for fast reactor monitoring can be improved by using proper moderator. The relative detection efficiency and absolute detection efficiency of the proportional boron-lined counter in different thickness of the moderator for mono-energy neutrons of different energy were simulated by using MCNP, the tend-line of the relative detection efficiency and absolute detection efficiency were obtained. Also the detection efficiency of selected proportional boron-lined counter to the typical neutron spectrum of the fast reactor was simulated, and then the optimized moderator was designed. It would have some degree of guiding significance to design the nuclear measurement system of the fast reactor. (authors)

  16. Comprehensive applications of the gas flow proportional counters for radiological surveillance

    Gas Flow Proportional Counters (GFPC) have been developed indigenously for various radiation protection applications. These detectors can be fabricated for 2 inches diameter filter paper sample counting applications to large area (∼1500 cm2) detectors for surface contamination applications. Thin entrance windows allow non penetrating type of radiations like alpha and low energy beta particles, Efficiencies (for alpha and beta radiations) are comparable to conventional detectors used to measure these radiations. Poor gamma efficiency (2/γ ratio, a high figure of merit and enables efficient gamma background rejection. These detectors are quite suitable for Indian environmental conditions. Three systems have been developed and successfully incorporated in to the radiation surveillance program at various nuclear facilities. The systems based on GFPC detectors include: a) Multiple sample gross alpha counting system; b) Laundry monitoring system; c) Alpha hand contamination monitoring system. The first of these enables simultaneous gross alpha counting of five air activity filter paper samples. The area of the detector surface is optimized to cover the 2 inches sized filter paper samples routinely used for the purpose. Five numbers of GFPC 's are arranged sequentially coupled to five individual amplifiers - micro controller modules to process the signal from the five counters. The laundry monitor which is micro controller based system consists of four large area multiwire GFPC detectors (700 cm2 sensitive area) used to monitor alpha contamination of decontaminated laundry, Each detector uses a charge sensitive preamplifier coupled to I2C counter. The alpha hand monitoring system consists of four large area multiwire gas flow proportional detectors (330 cm2 sensitive area each). A micro controller-based module is employed to initiate the counting process automatically when the hands are inserted in to the suitably designed window slots and provides audio and visual

  17. Comprehensive applications of the gas flow proportional counters for radiological surveillance

    Gas Flow Proportional Counters (GFPC) have been developed indigenously for various radiation protection applications. These detectors can be fabricated for 2'' diameter filter paper sample counting applications to large area (∼1500 cm2) detectors for surface contamination applications. Thin entrance windows allow non-penetrating type of radiations like alpha and low energy beta particles. Efficiencies (for alpha and beta radiations) are comparable to conventional detectors used to measure these radiations. Poor gamma efficiency (2/γ ratio, a high figure of merit and enables efficient gamma background rejection. These detectors are quite suitable for Indian environmental conditions. Three systems have been developed and successfully incorporated in to the radiation surveillance program at various nuclear facilities. The systems based on GFPC detectors include (a) Multiple sample gross alpha counting system, (b) Laundry monitoring system and (c) Alpha hand contamination monitoring system. The first of these enables simultaneous gross alpha counting of five air activity filter paper samples. The area of the detector surface is optimized to cover the 2'' sized filter paper samples routinely used for the purpose. Five numbers of GFPC's are arranged sequentially coupled to five individual amplifiers - microcontroller modules to process the signal from the five counters. The laundry monitor which is microcontroller based system consists of four large area multiwire GFPC detectors (700 cm2 sensitive area) used to monitor alpha contamination of decontaminated laundry. Each detector uses a charge sensitive preamplifier coupled to I2C counter. The alpha hand monitoring system consists of four large area multiwire gas flow proportional detectors (330 cm2 sensitive area each). A microcontroller-based module is employed to initiate the counting process automatically when the hands are inserted in to the suitably designed window slots and provides audio and visual alarm

  18. A study of aging effects in the gas-monitoring proportional counters of the BAC calorimeter in the ZEUS experiment

    The multi-cell proportional chambers in the backing calorimeter of the ZEUS experiment at the HERA storage ring are supplied with an Ar/CO2 gas mixture by an open gas system. Flow proportional counters with built-in 55Fe sources are used as gas system monitoring detectors. The results of the measurements of the aging effects of the gas-monitoring counters are presented

  19. Use of the small proportional counter for carbon 14 measurement in 10 milligram carbon samples

    Ten years ago, the measurement of C-14/C-12 ratios in 10 milligram carbon samples seemed to be technically out of reach. However, two developments that make this goal possible have recently occurred: the first is an entirely new mass-spectrometric separation of C-14 and C-12 ions and their subsequent estimation by counting, while the second is simply the extension of conventional proportional counter operation (using CO2 as counter gas) to very small size carbon samples. The first method is very fast, precise, and capable of treating samples of even sub-milligram size, but requires an expensive installation. The second method is slow (counting times of two months or more are necessary), can probably be made sufficiently precise to handle most problems, works down to sample sizes of 10 mg carbon, and is relatively inexpensive, especially to install in already existing radiocarbon laboratories. It is this second method and its implications that are discussed in the present paper

  20. Miniature proportional counter for compression measurements of laser-fusion targets

    Direct drive laser fusion targets consisting of DT gas encapsulated in glass microshells produce 14.1 MeV neutrons that can interact with silicon-28 nuclei in the glass to produce a 2.2 minute aluminum-28 activity. From the number of 28Al nuclei created and the neutron yield, the compressed glass areal density can be found. To determine the number of activated atoms created, we collect approximately one-half of the target debris on a thin metal foil which is transferred to our beta-gamma coincidence detector. This detector consists of a 25 cm x 25 cm NaI(Tl) crystal having a 5 cm x 15 cm well. We have recently built a miniature proportional counter that fits into this well and is used to detect beta particles. It is constructed of .025 cm thick copper and has nine separate chambers through which methane flows. The coincidence background is 0.14 cpm and the measured beta efficiency is 45%. We are now building a .0125 cm thick counter made of aluminum having a predicted efficiency of > 90%

  1. Microdosimetry study of THOR BNCT beam using tissue equivalent proportional counter

    Boron neutron capture therapy (BNCT) is a cancer treatment modality using a nuclear reactor and a boron compound drug. In Taiwan, Tsing Hua open-pool reactor (THOR) has been modulated for the basic research of BNCT for years. A new BNCT beam port was built in 2004 and used to prepare the first clinical trial in the near future. This work reports the microdosimetry study of the THOR BNCT beam by means of the tissue equivalent proportional counter (TEPC). Two self-fabricated TEPCs (the boron-doped versus the boron-free counter wall) were introduced. These dual TEPCs were applied to measure the lineal energy distributions in air and water phantom irradiated by the THOR BNCT mixed radiation field. Dose contributions from component radiations of different linear energy transfers (LETs) were analyzed. Applying a lineal energy dependent biological weighting function, r(y), to the total and individual lineal energy distributions, the effective relative biological effectiveness (RBE), neutron RBE, photon RBE, and boron capture RBE (BNC RBE) were all determined at various depths of the water phantom. Minimum and maximum values of the effective RBE were 1.68 and 2.93, respectively. The maximum effective RBE occurred at 2 cm depth in the phantom. The average neutron RBE, photon RBE, and BNC RBE values were 3.160±0.020, 1.018±0.001, and 1.570±0.270, respectively, for the THOR BNCT beam.

  2. Radiation effects on the proportional counter X-ray detectors on board the NEAR spacecraft

    The X-ray proportional counters on board the Near Earth Asteroid Rendezvous (NEAR) spacecraft have exhibited a resolution degradation and recovery phenomenon several times during the long cruise phase of the mission. The resolution is checked periodically by commanding an 55Fe source into the window area. The degradation is seen as a low energy tailing of the 5.9 keV photopeak. Two events have occurred which provided good spectral data for better understanding the degradation phenomenon. In November 1997 a large solar particle event occurred that degraded the resolution and excited copper in the collimator. Eventually the detectors returned to normal. In January 1998 the spacecraft performed an Earth swingby gravity assist maneuver. The near Earth environment excited the magnesium and aluminum in the filter elements. The copper line was also produced. The NEAR spacecraft was launched in February 1996 and will rendezvous and orbit the asteroid 433 Eros in early 1999

  3. High-Sensitivity X-ray Polarimetry with Amorphous Silicon Active-Matrix Pixel Proportional Counters

    Black, J. K.; Deines-Jones, P.; Jahoda, K.; Ready, S. E.; Street, R. A.

    2003-01-01

    Photoelectric X-ray polarimeters based on pixel micropattern gas detectors (MPGDs) offer order-of-magnitude improvement in sensitivity over more traditional techniques based on X-ray scattering. This new technique places some of the most interesting astronomical observations within reach of even a small, dedicated mission. The most sensitive instrument would be a photoelectric polarimeter at the focus of 2 a very large mirror, such as the planned XEUS. Our efforts are focused on a smaller pathfinder mission, which would achieve its greatest sensitivity with large-area, low-background, collimated polarimeters. We have recently demonstrated a MPGD polarimeter using amorphous silicon thin-film transistor (TFT) readout suitable for the focal plane of an X-ray telescope. All the technologies used in the demonstration polarimeter are scalable to the areas required for a high-sensitivity collimated polarimeter. Leywords: X-ray polarimetry, particle tracking, proportional counter, GEM, pixel readout

  4. Use of 4He-filled proportional counters as neutron spectrometers

    Neutron response functions of two commercially available cylindrical 4He-filled proportional counters (filling pressure about 2 MPa) have been measured in the neutron energy range 144-14000 keV. Measurements were carried out using optimal settings for the detector high voltage and amplifier shaping time which were determined within the scope of this study. The experimental results have been analyzed and compared to calculated response functions using empirically determined energy and resolution calibration functions. The theoretically determined response functions show good agreement with the measured response except for energies above 10 MeV. The discrepancies are attributed to unsatisfactory electronics. The Monte-Carlo code gas-filled neutron spectrometer response (GNSR) which has been developed for the calculation of response functions and efficiencies of gas-filled neutron detectors, is briefly described. (orig.)

  5. Gas gain limitation in low pressure proportional counters filled with TEG mixtures

    Proportional counters filled with tissue equivalent gas mixtures (TEPC) can be used to simulate interactions and energy transferred to small tissue volumes. One criteria which allows to use TEPC as the dose meter is that the particle ranges are larger compared to the gas volume. TEPC achieve this by operating at low gas pressures. Single ionization events dominate the distribution of low-LET radiation at low gas pressure and therefore their detection is of primary importance, a high gas gain is necessary. Therefore gas gain factor has been measured for Methane- and Propane-based tissue equivalent gas mixtures. The highest stable gas gains, second ionization Townsend coefficient and electron avalanche dimensions have been determined

  6. Development of a low pressure tissue equivalent proportional counter for use in radiation protection

    The use of low pressure tissue equivalent proportional counters in radiation protection is based on the simultaneous measurement of dose and single energy depositions allowing to determine the radiation quality. A cylindrical large volume detector has been developed and measurements in reference fields were carried out. To improve the detector response to neutrons in the energy range of about 100 keV a decrease of the pressure inside the sensor is required. In order to define the lowest pressure level for operation of the detector and to further the understanding of the discharge processes in the gas the electrical field was calculated and possibilities to simulate the gas amplification using Monte-Carlo methods were developed. (orig.)

  7. Alpha and beta dose-rate determination using a gas proportional counter

    The use of proportional gas detectors for determination of the alpha (α) and beta (β) dose rate (due to U, Th and K) of pottery and sediment samples in luminescence and ESR dating was investigated. Alpha and beta count-rate measurements on standard powders of U, Th and K at two different counter voltages, low voltage in which the system detects α-particles and β-particles using different pulse height regions, allow the determination of conversion coefficients that relate count rates to dose rates in samples. The conversion coefficients were applied to the alpha and beta count rates measured on different types of test samples. Analysis of the results shows a remarkable accuracy in the evaluation of the beta dose rates. However, under both measurement conditions (low and high voltage), the alpha dose rates were found to deviate from the expected values to the extent that this procedure must be considered unusable at present. (Author)

  8. Background simulation for the Spherical Proportional Counter and its use for the detection of optical photons

    The recently developed Spherical Proportional Counter [1] allows to instrument large target masses with good energy resolution and sub-keV energy threshold. The moderate cost of this detector, its simplicity and robustness, makes this technology a promising approach for many domains of physics and applications, like dark matter detection and low energy neutrino searches. Detailed Monte Carlo simulations are essential to evaluate the background level expected at the sub-keV energy regime. The simulated background here, it refers to the contribution of the construction material of the detector and the effect of the environmental gamma radiation. This detector due to its spherical shape could be also served as an optical photon detector provided it is equipped with PMTs, for Double Beta decay and Dark Matter searches. All calculations shown here are obtained using the FLUKA Monte Carlo code

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

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

  10. New concepts for the design of large area gas proportional scintillation counters

    New concepts are presented that allow the design of gas proportional scintillation counters with large areas and medium size photomultipliers. These designs are based on the compensation of the radial decrease of the scintillation light collected in the photomultiplier due to solid angle and reflection effects, with a radial increase of the light production shaped curved grid. An implementation of these concepts based on a 2 inch diameter photomultiplier is presented. It shows a pulse amplitude variation, along the radial position (0 to 10mm) of less than 0.5%, and an energy resolution of 8.0% for a broad 5.9keV X-ray beam entering the detector through the full 25mm diameter window

  11. Alpha-beta monitoring system based on pair of simultaneous Multi-Wire Proportional Counters

    Wengrowicz, U.; Amidan, D.; Orion, I.

    2016-08-01

    A new approach for a simultaneous alpha-beta Multi-wire Proportional Counter (MWPC) is presented. The popular approach for alpha-beta monitoring systems consists of a large area MWPC using noble gas flow such as Argon Methane. This method of measurement is effective but requires large-scale and expensive maintenance due to the needs of gas flow control and periodic replacements. In this work, a pair of simultaneous MWPCs for alpha-beta measuring is presented. The developed detector consists of a sealed gas MWPC sensor for beta particles, behind a free air alpha sensor. This approach allows effective simultaneous detection and discrimination of both alpha and beta radiation without the maintenance cost noble gas flow required for unsealed detectors.

  12. A Model for the Secondary Scintillation Pulse Shape from a Gas Proportional Scintillation Counter

    Kazkaz, Kareem

    2015-01-01

    Proportional scintillation counters (PSCs), both single- and dual-phase, can measure the scintillation (S1) and ionization (S2) channels from particle interactions within the detector volume. The signal obtained from these detectors depends first on the physics of the medium (the initial scintillation and ionization), and second how the physics of the detector manipulates the resulting photons and liberated electrons. In this paper we develop a model of the detector physics that incorporates event topology, detector geometry, electric field configuration, purity, optical properties of components, and wavelength shifters. We present an analytic form of the model, which allows for general study of detector design and operation, and a Monte Carlo model which enables a more detailed exploration of S2 events. This model may be used to study systematic effects in currents detectors such as energy and position reconstruction, pulse shape discrimination, event topology, dead time calculations, purity, and electric fi...

  13. Gas gain limitation in low pressure proportional counters filled with TEG mixtures

    Kowalski, T. Z.

    2014-12-01

    Proportional counters filled with tissue equivalent gas mixtures (TEPC) can be used to simulate interactions and energy transferred to small tissue volumes. One criteria which allows to use TEPC as the dose meter is that the particle ranges are larger compared to the gas volume. TEPC achieve this by operating at low gas pressures. Single ionization events dominate the distribution of low-LET radiation at low gas pressure and therefore their detection is of primary importance, a high gas gain is necessary. Therefore gas gain factor has been measured for Methane- and Propane-based tissue equivalent gas mixtures. The highest stable gas gains, second ionization Townsend coefficient and electron avalanche dimensions have been determined.

  14. Application of the digital pulse processing techniques to gas proportional scintillation counters

    Digital signal processing techniques have been developed to analyze the signals from a gas proportional scintillation counter (GPSC). Compared to analog systems, the digital technique is a very simple and powerful tool for manipulating and improving pulse-height distributions with no additional electronic components. Among the features inherent in digital signal processing are pulse risetime discrimination, pulse pileup correction and rejection, and background rejection. By allowing the rejection of signal pulses from x-ray interactions within the scintillation region and for near insensitive regions of the detector, an improvement in the pulse-height distribution has been effectively achieved Using this technique the energy resolution for the 22.1 keV line of a 109Cd x-ray source improves from 5.6 to 5.1 % and the peak-to-background ratio increases from 30 to 170

  15. Helium-filled proportional counter (-4.2 K) and its new application

    The helium-filled proportional counter (HFPC) is intensively used as electron detector in the cryogenic resonance-electron Moessbauer spectroscopy for solid-studies. In the present study has been experimentally and theoretically examined the ionization mechanism in HFPC at liquid-helium temperature in order to understand the operation of HFPC from the stand point of atomic and molecular processes in helium. A cathode material of a counter is 2.5 cm diameter x 6.0 cm long nickel pipe. An anode is 30-μm diameter gold plated tungsten wire. The incident direction of 5.3-MeV a particles from 210Po is parallel to the anode after passing through 1 mm diameter hole of collimator. With the experimental data of output pulse, the theoretical curves of a main pulse and after-pulses determined by our calculation are given. Each after-pulse by He*, Hen+ and He2*(A1Σu+) is deduced by ignoring the contribution from other active particles. The electric discharge occurs when R, defined as the number of the electrons from cathode per an avalanche, becomes more then unity. The HFPC operation in the proportional region is practically limited by the electric discharge; the pressure of the filled helium is 10.6 Torr at 4.2 K and the anode voltage is a little higher than 1330 V. A simplified model for the operation of HFPC is given, which illustratively shows the roles of active particles. Application for neutron scattering experiment is explained. (S.Y.)

  16. Performance of an Arrangement of Several Large-Area Proportional Counters for the Assessment of Pu239 Lung Burdens

    If plutonium-239 has been deposited in the human lung, some of the emitted soft X-rays can be measured from the outside by proportional counters. Efficiency of such measurements depends on sensitive area and geometrical arrangement of the counters in regard to the body, on absorption of the X-rays inside the counter, on reduction of the radiation in the wall or window of the counter, on the background of the counter and on stability of this background in spite of β- and γ- radiation coming from other nuclides than plutonium-239 in the body. Most of these parameters are optimized by using three large-area, thin-window, argon filled proportional counters mounted inside a large steel-room opposite the chest and both lung lobes of a sitting patient. These counters are anti-coincidence shielded in such a way that only soft X-rays causing the origination of photoelectrons inside the measuring counter proper are detected. The effect is enforced by passing the electrical pulses through a one-channel pulse height analyser. Construction and performance of such an arrangement are described in the paper. (author)

  17. Imaging micro-well proportional counters fabricated with masked UV laser ablation

    The micro-well detector is a gas-proportional counter similar to the CAT (Bartol et al., J. Phys. III 6 (1996) 337) and WELL detectors (Bellazzini et al., Nucl. Instr. and Meth. A 423 (1999) 125). The micro-well is a cylindrical hole formed in the polymer substrate of commercially fabricated copper-clad flexible printed circuit board by UV laser ablation. The micro-wells are drilled at GSFC's UV laser-ablation facility. The cathode is a metal annulus that surrounds the opening of the well. The anode is a metal pad that fills the bottom of the well. Advantages of this topology include intrinsic two-dimensional sensing, thick robust electrodes, and large localized image charge on the cathodes. We have fabricated 5 cmx5 cm micro-well detectors with segmented anodes (1-d) and with both anodes and cathodes segmented (2-d), and have demonstrated: - stable, proportional operation at gas gains in excess of 30,000 in Ar- and Xe-based gases; - FWHM energy resolution of 20% at 6 keV in P-10; - preliminary 1-d spatial resolution of ≤150 μm (rms) in P-10; and; - the capability of MWDs to produce 2-dimensional images. We report on the design, fabrication, and testing of 1-d, 2-d, and pixelized micro-well detectors

  18. [Development of an inexpensive high resolution positron multiwire proportional counter]. Progress report, 1981

    The development of surgical and medical techniques for the treatment of coronary artery disease has dramatized the need for a safe, relatively non-traumatic measure of regional perfusion. This is particularly critical during the early stages of coronary artery disease, well before symptoms become severe enough to warrant characterization. The primary limitation in the implementation of this new technique is the lack of a high resolution, relatively inexpensive positron detecting system to enable myocardial perfusion scintigraphy with rubidium-82 to be performed as a screening test in hospitals without direct access to cyclotron facilities. The positron multiwire proportional counter which will result from the proposed projects will solve this problem. The dispersion of the absorbing material will be achieved by stringing wires of high Z material, such as tungsten, in a cross pattern. By stacking the wires, an efficiency of 30% can be obtained for 0.5 MeV photons. The wire layers will be at graded voltages; the ionization from the photoelectrons is thereby drifted through the stack and picked up by sense wires operating in the proportional mode. Resolutions within the 3 mm range should also be achievable. 15 figs

  19. Alpha Beta Monitoring System Based on a Pair of Simultaneous Multi Wire Proportional Counters

    A new approach for a simultaneous alpha beta contamination monitoring system is presented. In nuclear environments or laboratories working with open radioactive sources there exists a risk of contamination. In order to avoid external contamination hazards, hand & foot alpha beta monitoring systems are needed. Usually, monitoring systems are based on large area Multi Wire Proportional Counters (MWPC).Generally, in the MWPC detectors the filling gas is supplied by a continuous gas supply system. The filling gas should not exhibit appreciable electron attachment coefficient. Typically, a noble gas such as Argon Methane, 90%Ar+10%CH4 is in use. This method of measurement is effective, yet it requires expensive maintenance costs due to gas flow control and periodical replacements. Several hand held commercial detectors such as Rotem Ind. PA-100, are based on free air flow alpha MWPC. Due to the energy released from the alpha particles in the filling gas a large number of ion pairs are formed. Despite the electron attachment coefficient of free air, a measurable pulse is obtained. Contrary to alpha sources, beta emitters deposit only a small part of their energy. In order to obtain a measurable pulse from beta interactions, oxygen free gas is required. Gas sealed detectors which are appropriate for beta measurements, require a relative thick entrance window in order to avoid gas leakage. Thick windows absorb alpha particles so that they are not appropriate for alpha measurement. The presented approach combines a pair of simultaneous MWPC assembled in a ôpancakeö type configuration; the sealed gas beta counter is located behind a free air alpha detector. This approach enables simultaneous alpha-beta measurement without needing continuous gas supply

  20. Technique for 136Xe double beta decay search by means of wall-less high pressure proportional counters

    The methodology of the experiment for search of the double beta-decay of the 136Xe isotope through the multiple thread wall-less proportional high-pressure counters is described. The characteristics of the counters and low-background facility are presented. The methodology for decreasing the counters background in the 0.5-3.5 MeV energies area through discrimination events by a coordinate along the anode thread and by the pulses growth-time is considered. The results of the background components analysis by the events type and source position are presented

  1. Optimization of measurements procedures for determination of beta emitters using a proportional counter

    Optimization of measurements procedures for beta emitters with proportional counter recently installed at the Hot Cells Facility (HCF) of the Jozef Stefan Institute (JSI) is described. Specific detection efficiencies for 40K, 90Sr, 90Y, 210Pb and 210Bi were determined that allows for more accurate determination of the particular radionuclides as a single 40K efficiency most frequently used. In addition, self-absorption curves for different surface densities for the same nuclides were derived. The detection efficiencies obtained ranged from 10 to 52 %, depending on the beta energy emitted and surface density used including the chemical composition of the salts used or precipitates obtained following radiochemical separation in the experiment. Two empirical equations were constructed allowing for accurate determination of detection efficiencies for 90Sr and 210Pb accounting for the surface densities of the sample and the time of measurement after the radiochemical separation of each nuclide concerned. The procedures and formulae developed and applied include calculation of minimal detectable activities for individual nuclides and uncertainty budgets for the determinations concerned. As an example, determination of total beta activities of mineral waters according to the relevant ISO (International Organisation for Standardisation) standard is presented. The procedure applied is based on calibration using the 40K detection efficiency curve. The values obtained ranged from 0,06 to 1,4 Bq/L, with typical uncertainties of 10 % relative. (author)

  2. Comparison of plastics used in proportional counters for proton and heavy ion measurements

    This study investigates alternative plastics for use in the construction of tissue equivalent gas-filled detectors. Four different alternative plastics (acrylic, nylon, polyethylene, and polystyrene) were tested in comparison with A-150 Five proportional counters were constructed possessing spherical ionization cavities each made of one of the five plastics with wall thickness of 3 mm and sensitive diameters of 4.48 cm. The detectors operated at 1400 V. They were exposed to three different energies of proton beams (87, 162, and 222 MeV) and five different heavy ion beams (143 MeV/amu He, 265 MeV/amu C, 440 MeV/amu Si, 430 MeV/amu Ar, and 421 MeV/amu Fe). The detectors were exposed to bare beams in air and no phantom was used. Lineal energy spectra derived from these measurements of energetic protons and heavy ion beams were used for comparison. Frequency averaged lineal energies and dose averaged lineal energies were calculated from each spectrum. Comparison of the experimental data indicates that the responses of the four alternative plastics tested are very similar to the response of A-150 tissue equivalent plastic

  3. Statistical Fluctuation in Gas Amplification Factor of a Low-Pressure Proportional Counter

    Full text: The electron avalanche formation in low-pressure argon-based gas mixtures at strong non-uniform electric fields was studied by a proportional counter. Concentration of admixtures (propane, DME, isobutane) varied between 1% and 80% and total pressures from 2 kPa to 90 kPa. Gas amplification M and energy resolution R were measured by the 55Fe source as a function of admixture concentration and total gas pressure. The relative variance f of the avalanche size distribution was determined by measuring single-electron (SE) spectra. In pure gases and in mixtures with high content of the admixture, the SE spectra have always a peaked distribution, f1. The f value depends on the partial pressure p of the admixture and on M. Over-exponential increase of gas gain with high voltage above a certain gas gain, M0, was determined in all mixtures. The gas gain where the SE spectra change their shape, f∼1, is roughly equal to M0. Both effects in M and f are caused by avalanche chain formation due to insufficient quenching of the admixture. Energy resolution is directly determined by the f-value, therefore, in 'thin' mixtures above M0 it degrades very quickly. Since this limiting value M0 depends on p, we conclude that partial pressure should be above ∼10 kPa to assure good quenching even at the highest gains obtained in the present experiment. (author)

  4. Primary and secondary scintillation measurements in a xenon Gas Proportional Scintillation Counter

    Fernandes, L M P; Ball, M; Gómez-Cadenas, J J; Monteiro, C M B; Yahlali, N; Nygren, D; Santos, J M F dos

    2010-01-01

    NEXT is a new experiment to search for neutrinoless double beta decay using a 100 kg radio-pure high-pressure gaseous xenon TPC. The detector requires excellent energy resolution, which can be achieved in a Xe TPC with electroluminescence readout. Hamamatsu R8520-06SEL photomultipliers are good candidates for the scintillation readout. The performance of this photomultiplier, used as VUV photosensor in a gas proportional scintillation counter, was investigated. Initial results for the detection of primary and secondary scintillation produced as a result of the interaction of 5.9 keV X-rays in gaseous xenon, at room temperature and at pressures up to 3 bar, are presented. An energy resolution of 8.0% was obtained for secondary scintillation produced by 5.9 keV X-rays. No significant variation of the primary scintillation was observed for different pressures (1, 2 and 3 bar) and for electric fields up to 0.8 V cm-1 torr-1 in the drift region, demonstrating negligible recombination luminescence. A primary scinti...

  5. 2D-sensitive hpxe gas proportional scintillation counter concept for nuclear medical imaging purposes

    The operation and first images of a high pressure xenon Gas Proportional Scintillation Counter (GPSC) are presented. In this setup, primary electrons produced by the absorption of X- or γ-rays in the gas medium drift to a region where the electric field is set to a value above the gas scintillation threshold, the scintillation region. The primary ionization signal is amplified through the electroluminescence produced along the electron drift in this region. A Micro-Hole and Strip Plate covered with CsI (CsI-MHSP) is used as the photosensor for the scintillation readout. The 2D capability of the CsI-MHSP photosensor is achieved by means of two orthogonal resistive lines interconnecting the strips patterned on both surfaces of the MHSP. The interaction position of the incident radiation can be obtained by determining the centroid of the photosensor area irradiated by the electroluminescence pulse. This centroid is obtained from the amplitude of the charge pulses collected at both ends of the resistive lines. Preliminary analyses of the first images obtained with electroluminescence signals at xenon pressures up to 3 bar indicate a position resolution capability of about 1.2 mm at 2.9 bar, for 59.6 keV γ-photons.

  6. Operation of low-pressure proportional counter filled with argon-based gas mixtures

    Mixtures of argon with propane, DME (Dimethyl-ether) and isobutane at total pressures P from 2 kPa to 90 kPa were studied in a low-pressure proportional counter. Strong non-uniform electric fields were thus produced at the anode surface (Sa). Deviations from the exponential dependence of gas gain on high voltage above a certain value of gas gain, M0, were observed in all mixtures. The best energy resolution has been obtained at low gas gains, and at gas gains above M0 resolution degrades much faster in ''thin'' mixtures due to avalanche chain formation. The reduced ionization coefficient α/P under non-equilibrium conditions is a function of mixture composition and of gas pressure. Crossings of α/P curves for different mixture compositions at the same total pressure are observed. The statistics of the avalanche size distribution (relative variance f) was determined by measuring the single-electron (SE) spectra. In pure gases and in mixtures with relatively high content of the molecular gas, the value is f 1. The gas gain where f ∝ 1 is roughly equal to the value of M0, showing that both effects are caused by insufficient quenching of the molecular admixture. (orig.)

  7. Characterization of a Spherical Proportional Counter in argon-based mixtures

    Iguaz, F J; Castel, J F; Irastorza, I G

    2014-01-01

    The Spherical Proportional Counter is a novel type of radiation detector, with a low energy threshold (typically below 100 eV) and good energy resolution. This detector is being developed by the network NEWS, which includes several applications. We can name between many others Dark Matter searches, low level radon and neutron counting or low energy neutrino detection from supernovas or nuclear reactors via neutrino-nucleus elastic scattering. In this context, this works will present the characterization of a spherical detector of 1 meter diameter using two argon-based mixtures (with methane and isobutane) and for gas pressures between 50 and 1250 mbar. In each case, the energy resolution shows its best value in a wide range of gains, limited by the ballistic effect at low gains and by ion-backflow at high gains. Moreover, the best energy resolution shows a degradation with pressure. These effects will be discussed in terms of gas avalanche properties. Finally, the effect of an electrical field corrector in th...

  8. Benchmarking computations using the Monte Carlo code ritracks with data from a tissue equivalent proportional counter

    Brogan, John

    Understanding the dosimetry for high-energy, heavy ions (HZE), especially within living systems, is complex and requires the use of both experimental and computational methods. Tissue-equivalent proportional counters (TEPCs) have been used experimentally to measure energy deposition in volumes similar in dimension to a mammalian cell. As these experiments begin to include a wider range of ions and energies, considerations to cost, time, and radiation protection are necessary and may limit the extent of these studies. Multiple Monte Carlo computational codes have been created to remediate this problem and serve as a mode of verification for pervious experimental methods. One such code, Relativistic-Ion Tracks (RITRACKS), is currently being developed at the NASA Johnson Space center. RITRACKS was designed to describe patterns of ionizations responsible for DNA damage on the molecular scale (nanometers). This study extends RITRACKS version 3.07 into the microdosimetric scale (microns), and compares computational results to previous experimental TEPC data. Energy deposition measurements for 1000 MeV nucleon-1 Fe ions in a 1 micron spherical target were compared. Different settings within RITRACKS were tested to verify their effects on dose to a target and the resulting energy deposition frequency distribution. The results were then compared to the TEPC data.

  9. The Rutherford Appleton Laboratory's Mark I multiwire proportional counter positron camera

    A small (30 cmx30 cm) model of a proposed large aperture positron camera has been developed at Rutherford Appleton Laboratory. Based on multiwire proportional counter technology, it uses lead foil cathodes which function simultaneously as converters for the 511 keV gamma rays and readout electrodes for a delay line readout system. The detectors have been built up into a portable imaging system complete with a dedicated computer for data taking, processing and display. This has permitted evaluation of this type of positron imaging system in the clinical environment using both cyclotron generated isotopes (15O, 11C, 18F, 124I) and available isotopic generator systems (82Rb, 68Ga). AT RAL we provided a complete hardware system and sufficient software to permit our hospital based colleagues to generate useful images with the minimum of effort. A complete description of the system is given with performance figures and some of the images obtained in three hospital visits are presented. Some detailed studies of the imaging performance of the positron camera are reported which have bearing on the design of future, improved systems. (orig.)

  10. Helium-filled proportional counter and its operation mechanism at low temperatures

    Isozumi, Y; Kishimoto, S

    2002-01-01

    The operation mechanism of helium-filled proportional counter (HFPC) at about 4.2 K is explained. Unstable behavior of HFPC is caused by releasing secondary-electron from the cathode by four kinds of active particles such as He sub n sup + , non-resonance photon from excited helium atom, non-resonance photon from He sub 2 sup * (A sup 1 Su sup +) and He sub 2 sup m (a sup 3 Su sup +). On experiments of HFPC behavior at low temperature, the following facts were observed; 1) main charge formation process in the electron avalanche is direct ionization by electron without Hornbeck-Molnar process. Accordingly, the gas amplification factor becomes small at low temperature. 2) Stable helium cation is He sub 2 sup + at room temperature, but cluster at low temperature. Large after-pulse is observed in output signal depends on cluster ion. The probability of secondary-electron emission decreased. The gas gain increased with increasing anode voltage. 3) By decreasing reaction rate of atom and molecule collision at low t...

  11. Simulated Response of a Tissue-equivalent Proportional Counter on the Surface of Mars.

    Northum, Jeremy D; Guetersloh, Stephen B; Braby, Leslie A; Ford, John R

    2015-10-01

    Uncertainties persist regarding the assessment of the carcinogenic risk associated with galactic cosmic ray (GCR) exposure during a mission to Mars. The GCR spectrum peaks in the range of 300(-1) MeV n to 700 MeV n(-1) and is comprised of elemental ions from H to Ni. While Fe ions represent only 0.03% of the GCR spectrum in terms of particle abundance, they are responsible for nearly 30% of the dose equivalent in free space. Because of this, radiation biology studies focusing on understanding the biological effects of GCR exposure generally use Fe ions. Acting as a thin shield, the Martian atmosphere alters the GCR spectrum in a manner that significantly reduces the importance of Fe ions. Additionally, albedo particles emanating from the regolith complicate the radiation environment. The present study uses the Monte Carlo code FLUKA to simulate the response of a tissue-equivalent proportional counter on the surface of Mars to produce dosimetry quantities and microdosimetry distributions. The dose equivalent rate on the surface of Mars was found to be 0.18 Sv y(-1) with an average quality factor of 2.9 and a dose mean lineal energy of 18.4 keV μm(-1). Additionally, albedo neutrons were found to account for 25% of the dose equivalent. It is anticipated that these data will provide relevant starting points for use in future risk assessment and mission planning studies. PMID:26313586

  12. Design of a hybrid gas proportional counter with CdTe guard counters for sup 1 sup 4 C dating system

    Zhang, L; Hinamoto, N; Nakazawa, M; Yoshida, K

    2002-01-01

    Nowadays uniform, low-cost and large-size compound semiconductor detectors are available up to several square centimeters. We are trying to combine this technology with conventional gas detectors to upgrade an anticoincidence type proportional counter, Oeschger-type thin wall counter of 2.2 l, used for a sup 1 sup 4 C dating facility at the University of Tokyo. In order to increase the ratio of the signal to the background for smaller quantity of samples less than 1 g, an effective approach is to minimize the detector volume at higher gas pressure. However, the anticoincidence function suffers from such a small volume. Therefore we designed a new active wall gas counter of 0.13 l counting volume using CdTe compound semiconductor detectors as the wall of the gas proportional counter to perform anticoincidence. Simulation study showed that at noise thresholds less than 70 keV, the wall counters can reject above 99.8% of events arising from outer gamma rays. Measured noise levels of CdTe detectors were smaller t...

  13. Radiocarbon dating of milligram-size samples using gas proportional counters: an evaluation of precision and of design parameters

    Radiocarbon dating parameters, such as instrumental techniques used, dating precision achieved, sample size, cost and availability of equipment and, in more detail, the merit of small gas proportional counting systems are considered. It is shown that small counters capable of handling 10-100mg of carbon are a viable proposition in terms of achievable precision and in terms of sample turnover, if some 10 mini-counters are operated simultaneously within the same shield. After consideration of the factors affecting the performance of a small gas proportional system it is concluded that an automatic, labour saving, cost effective and efficient carbon dating system, based on some sixteen 10 ml-size counters operating in parallel, could be built using state-of-art knowledge and components

  14. Electrodisintegration of 3He

    An experimental study of the reaction 3He(e, d) e'p was carried out by measuring differential cross sections of deuterons as a function of deuteron energy and angle for three incident electron energies. The electrodisintegration cross section was also calculated using an Irving-Gunn wave function for the ground state with a plane wave for the final-state. As in the case of photodisintegration calculations the result indicates the need for including complete final-state rescattering effects

  15. Tissue Equivalent Proportional Counter Microdosimetry Measurements Utilized Aboard Aircraft and in Accelerator Based Space Radiation Shielding Studies

    Gersey, Brad B.; Wilkins, Richard T.

    2010-01-01

    This slide presentation reviews the Tissue Equivalent Proportional Counter (TEPC), a description of the spatially restricted LET Model, high energy proton TEPC and the results of modeling, the study of shielding and the results from the flight exposures with the TEPC.

  16. Helium-filled proportional counter (∼4.2 K) and possible application to high-resolution neutron position detector

    Using a technique for the cryogenic helium-filled proportional counter, we are trying to develop a new neutron position-sensitive detector, of which resolution is expected to be below 1 mm. A basic idea for the position detector is described in this report. (author)

  17. Replacement tissue-equivalent proportional counter for the International Space Station.

    Perez-Nunez, D; Braby, L A

    2011-02-01

    The tissue-equivalent proportional counter (TEPC)-based dosemeters used on the International Space Station have exceeded their planned useful lives, and are scheduled to be replaced with the new units taking advantage of improved technology. The original TEPC detectors used cylindrical geometry with field tubes to achieve good energy resolution and minimum sensitivity to noise created by vibration. The inside diameter of these detectors is 5.1 cm. The new detectors developed for this application produce the resolution and vibration resistance of the cylindrical detector with the isotropic response and compact size of a spherical detector. The cathode structure consists of conductive tissue-equivalent plastic A-150 layers separated by thin polyethylene layers perpendicular to the anode. Each conductive layer is held at the electrical potential needed to produce uniform electric field strength along the anode wire, and thus the same gas gain for electrons produced in different portions of the spherical volume. The new design contains the whole preamplifier inside the vacuum chamber to reduce electronic noise. Also the vacuum chamber has a novel design with a 0.020-inch-thick aluminium wall to allow a total wall thickness of 0.5 g cm(-2), which is typical of the shielding provided by a space suit. This feature will allow measuring the dose on the astronauts' skin due to low-energy electrons and protons produced during solar events. The vacuum chamber has a new bayonet clamping system that reduces the total detector weight to less than half that of the old TEPC. PMID:21115447

  18. Replacement tissue-equivalent proportional counter for the international space station

    The tissue-equivalent proportional counter (TEPC)-based dosemeters used on the International Space Station have exceeded their planned useful lives, and are scheduled to be replaced with the new units taking advantage of improved technology. The original TEPC detectors used cylindrical geometry with field tubes to achieve good energy resolution and minimum sensitivity to noise created by vibration. The inside diameter of these detectors is 5.1 cm. The new detectors developed for this application produce the resolution and vibration resistance of the cylindrical detector with the isotropic response and compact size of a spherical detector. The cathode structure consists of conductive tissue-equivalent plastic A-150 layers separated by thin polyethylene layers perpendicular to the anode. Each conductive layer is held at the electrical potential needed to produce uniform electric field strength along the anode wire, and thus the same gas gain for electrons produced in different portions of the spherical volume. The new design contains the whole preamplifier inside the vacuum chamber to reduce electronic noise. Also the vacuum chamber has a novel design with a 0.020-inch-thick aluminium wall to allow a total wall thickness of 0.5 g cm-2, which is typical of the shielding provided by a space suit. This feature will allow measuring the dose on the astronauts' skin due to low-energy electrons and protons produced during solar events. The vacuum chamber has a new bayonet clamping system that reduces the total detector weight to less than half that of the old TEPC. (authors)

  19. Neutron Dosimetry with Tissue Equivalent Proportional Counters: Their Limitations and How to Deal with Them

    Low-pressure tissue equivalent proportional counters (TEPCs) are instruments that measure absorbed dose based on the Bragg-Gray cavity theory. By keeping the filling pressure low, the energy loss of individual charged particles crossing the detector cavity corresponds to the energy loss in tissue over distances of the order of a few micrometres. However, the efficacy of the TEPC as a meter for ambient dose equivalent H*(10) deteriorates rapidly below a few hundred keV, reflecting the differences between the TEPC and the artifact used in the definition of H*(10); the typical TEPC has walls roughly 1 to 2 mm thick, whereas H*(10) is defined at a point 10 mm below the surface of the 30-cm-diam ICRU sphere. Several laboratories have investigated approaches to improving the TEPC ambient dose equivalent response, but all have involved modifying the detectors themselves by increasing the wall thickness, reducing the filling pressure, altering the gas composition, or some combination there of. Each of these approaches has positive and negative aspects, but, generally speaking, improving an instrument's ambient dose equivalent response in one energy region tends to degrade the response in other regions. However, National Physical Laboratory has, for several years, been refining analytical methods for improving the H*(10) response of TEPCs, which essentially use the shape of the TEPC spectrum, and how it varies with neutron energy to determine a correction factor for the measured ambient dose equivalent. This is achieved by comparing the measured spectra to a catalog of theoretical spectra, generated by a Monte Carlo code developed by the author over many years

  20. Compact Tissue-equivalent Proportional Counter for Deep Space Human Missions.

    Straume, T; Braby, L A; Borak, T B; Lusby, T; Warner, D W; Perez-Nunez, D

    2015-10-01

    Effects on human health from the complex radiation environment in deep space have not been measured and can only be simulated here on Earth using experimental systems and beams of radiations produced by accelerators, usually one beam at a time. This makes it particularly important to develop instruments that can be used on deep-space missions to measure quantities that are known to be relatable to the biological effectiveness of space radiation. Tissue-equivalent proportional counters (TEPCs) are such instruments. Unfortunately, present TEPCs are too large and power intensive to be used beyond low Earth orbit (LEO). Here, the authors describe a prototype of a compact TEPC designed for deep space applications with the capability to detect both ambient galactic cosmic rays and intense solar particle event radiation. The device employs an approach that permits real-time determination of yD (and thus quality factor) using a single detector. This was accomplished by assigning sequential sampling intervals as detectors “1” and “2” and requiring the intervals to be brief compared to the change in dose rate. Tests with g rays show that the prototype instrument maintains linear response over the wide dose-rate range expected in space with an accuracy of better than 5% for dose rates above 3 mGy h(-1). Measurements of yD for 200 MeV n(-1) carbon ions were better than 10%. Limited tests with fission spectrum neutrons show absorbed dose-rate accuracy better than 15%. PMID:26313585

  1. Broad energy range neutron spectroscopy using a liquid scintillator and a proportional counter: Application to a neutron spectrum similar to that from an improvised nuclear device

    Xu, Yanping; Randers-Pehrson, Gerhard; Marino, Stephen A.; Garty, Guy; Harken, Andrew; Brenner, David J.

    2015-09-01

    A novel neutron irradiation facility at the Radiological Research Accelerator Facility (RARAF) has been developed to mimic the neutron radiation from an Improvised Nuclear Device (IND) at relevant distances (e.g. 1.5 km) from the epicenter. The neutron spectrum of this IND-like neutron irradiator was designed according to estimations of the Hiroshima neutron spectrum at 1.5 km. It is significantly different from a standard reactor fission spectrum, because the spectrum changes as the neutrons are transported through air, and it is dominated by neutron energies from 100 keV up to 9 MeV. To verify such wide energy range neutron spectrum, detailed here is the development of a combined spectroscopy system. Both a liquid scintillator detector and a gas proportional counter were used for the recoil spectra measurements, with the individual response functions estimated from a series of Monte Carlo simulations. These normalized individual response functions were formed into a single response matrix for the unfolding process. Several accelerator-based quasi-monoenergetic neutron source spectra were measured and unfolded to test this spectroscopy system. These reference neutrons were produced from two reactions: T(p,n)3He and D(d,n)3He, generating neutron energies in the range between 0.2 and 8 MeV. The unfolded quasi-monoenergetic neutron spectra indicated that the detection system can provide good neutron spectroscopy results in this energy range. A broad-energy neutron spectrum from the 9Be(d,n) reaction using a 5 MeV deuteron beam, measured at 60 degrees to the incident beam was measured and unfolded with the evaluated response matrix. The unfolded broad neutron spectrum is comparable with published time-of-flight results. Finally, the pair of detectors were used to measure the neutron spectrum generated at the RARAF IND-like neutron facility and a comparison is made to the neutron spectrum of Hiroshima.

  2. Broad energy range neutron spectroscopy using a liquid scintillator and a proportional counter: Application to a neutron spectrum similar to that from an improvised nuclear device

    Xu, Yanping, E-mail: yx2132@cumc.columbia.edu; Randers-Pehrson, Gerhard; Marino, Stephen A.; Garty, Guy; Harken, Andrew; Brenner, David J.

    2015-09-11

    A novel neutron irradiation facility at the Radiological Research Accelerator Facility (RARAF) has been developed to mimic the neutron radiation from an Improvised Nuclear Device (IND) at relevant distances (e.g. 1.5 km) from the epicenter. The neutron spectrum of this IND-like neutron irradiator was designed according to estimations of the Hiroshima neutron spectrum at 1.5 km. It is significantly different from a standard reactor fission spectrum, because the spectrum changes as the neutrons are transported through air, and it is dominated by neutron energies from 100 keV up to 9 MeV. To verify such wide energy range neutron spectrum, detailed here is the development of a combined spectroscopy system. Both a liquid scintillator detector and a gas proportional counter were used for the recoil spectra measurements, with the individual response functions estimated from a series of Monte Carlo simulations. These normalized individual response functions were formed into a single response matrix for the unfolding process. Several accelerator-based quasi-monoenergetic neutron source spectra were measured and unfolded to test this spectroscopy system. These reference neutrons were produced from two reactions: T(p,n){sup 3}He and D(d,n){sup 3}He, generating neutron energies in the range between 0.2 and 8 MeV. The unfolded quasi-monoenergetic neutron spectra indicated that the detection system can provide good neutron spectroscopy results in this energy range. A broad-energy neutron spectrum from the {sup 9}Be(d,n) reaction using a 5 MeV deuteron beam, measured at 60 degrees to the incident beam was measured and unfolded with the evaluated response matrix. The unfolded broad neutron spectrum is comparable with published time-of-flight results. Finally, the pair of detectors were used to measure the neutron spectrum generated at the RARAF IND-like neutron facility and a comparison is made to the neutron spectrum of Hiroshima.

  3. ^3He Spin Pump

    Yamaguchi, A.; Ishimoto, H.; Kojima, H.

    2009-03-01

    The superfluid component of ^3He A1 phase is spin-polarized. The process of forcing the superfluid component through a spin filtering structure, in a manner of mechano-magnetic effect, can be used to increase the spin polarization beyond the equilibrium under a given applied magnetic field. We have constructed a test cell in which a glass capillary array acts as the spin (and entropy) filter and an electrostatically actuated diaphragm forces the superfluid flow through it. Preliminary results show that a maximum relative increase of polarization by 50 % could be achieved. The maximum increase in polarization appears to be limited by the critical superfluid flow through the channels in the glass capillary array. The dependence of the observed effects on temperature, pressure and magnetic field will be presented.

  4. Development and use of a position-sensitive multiwire proportional counter as area detector for neutron radiography

    A position sensitive multiwire proportional counter has been developed for applications in neutron radiography and small angle neutron scattering experiments. Its sensitivity for thermal neutrons is about 50% and its spatial resolution was measured to be 5,7 mm (anode) resp. 7,9 mm (cathode). The maximal counting rate for the applied electronic system comes up to about 2 . 104 s-1. By means of a simplified physical model the gamma sensitivity as well as the neutron sensitivity has been calculated taking into account the energy level of discrimination. Some applications for neutron radiography demonstrate the feasibility of this position sensitive counter. With 31 figs., 4 tabs

  5. The analysis of the X-ray event analyzer proportional counter data: A comment

    Wilson, R. M.

    1977-01-01

    The findings, based on a comparison of simultaneous observations of a number of flares obtained with the X-REA and SOLRAD 9 instruments, which reveal the degree of deterioration of the counters with time are presented.

  6. Gas proportional counter with a large volume for measurement of small tritium concentrations

    The design of a multisection counter with a large sensitive volume (2l), which ensures operation at a voltage of 2000-4000 V, is described. The cylindrical volume of the counter is divided by earthed filaments into 55 cells; each cell has 0.74 l volume. To reduce the background, each internal section of the counter is switched into an anticoincidence circuit with respect to the others and, besides, all the external sections make up an additional ring of anticoincidence counters. For a methane-filled counter surrounded by 5 cm Pb layer from the sides and from below, the background in the energy range of 1.5-20 keV for a voltage of 2500 V is 0.34+-0.02 imp/s for a methane pressure of 0.5 kgf/cm and O.46+-0.01 imp/s on increase in pressure to 1 kgf/cm2. The counter design suggested makes it possible to detect a specific activity of tritium of the order of 1x10-13 Ci/l and higher; an activity of 1x10-13 Ci/l can be measured in 200 min with an error of 10%

  7. Numerical determination of the amplification of a cylindrical proportional counter operating at low pressure. Application to nano-dosimetry

    This work is devoted to a study of proportional counters used to measure the energy deposition in micrometer biological sites. Tissue equivalent gas filling improve typical operating mode of those counters. Specially, the extension of the multiplication zone becomes important at low pressures. A Monte Carlo simulation has been used to study the behaviour of an electron swarm in the sensitive volume. The calculations show that electrons are not in equilibrium with the applied electric field in this geometry. The influence of the gradient field and the rotation of the electrons around the anode wire has been studied carefully. The importance of non-equilibrium effects on the theoretical amplification calculated through the ionisation coefficient has been confirmed by experimental investigations. The statistical fluctuations of multiplication process has been calculated by the determination of avalanche spectra at the anode. Resolution of an ultra-miniature counter have been calculated to improve technological limitations of experimental nanodosimetry. (author)

  8. Microdosimetric distribution of protons, Ep=19-65 MeV, measured with a low pressure proportional counter

    Microdosimetric measurements of 19, 32, 43, 55, and 65 MeV protons were carried out with the A-150-walled low pressure proportional counter. The spectra are deconvoluted into three components, which are energy loss by directly incident protons, secondary electrons, and scattered protons and heavy charged particles (including protons) produced by proton nuclear reactions with the TE wall. Dose-mean lineal energies of protons are large as usual, because larger lineal energies by proton reaction events are affected. (author)

  9. Neutron spectrum measurements using proton recoil proportional counters: results of measurements of leakage spectra for the Little Boy assembly

    Measurements of degraded fission-neutron spectra using recoil proportional counters are done routinely for studies involving fast reactor mockups. The same techniques are applicable to measurements of neutron spectra required for personnel dosimetry in fast neutron environments. A brief discussion of current applications of these methods together with the results of a measurement made on the LITTLE BOY assembly at Los Alamos are here described

  10. Multi-level modelling of the response of the ultraminiature proportional counter: gas gain phenomena and pulse height spectra

    The ultraminiature proportional counters, UMC, unique radiation detectors for monitoring high intensity therapy fields, designed by Kliauga and operated at Columbia University (USA), have yielded a number of pulse height distributions for photons, neutrons and ions at simulated diameters of 5-50 nm. Monte Carlo calculations of the gas gain in such a counter questioned the possibility of achieving proportionally at such low simulated diameters. The response of the UMC has now been modelled taking into account both fluctuations of energy deposited in the counter volume and its calculated gas gain. Energy deposition was calculated using the MOCA-14, MOCA-8 and TRION codes, whereby distributions of ionisations d(j) after irradiations with 137Cs, 15 MeV neutrons and 7 MeV.amu-1 deuterons were obtained. Monte Carlo calculations of electron avalanches in UMC show that the size of the single-electron avalanche P(n) reaching the anode depends strongly on the location of the primary ionisation within the counter volume. Distributions of the size of electron avalanches for higher numbers of primary ionisations, P*j(n), were obtained by successive convolutions of P(n). Finally, the counter response was obtained by weighting P*j(n) over d(j) distributions. On comparing the measured and calculated spectra it was concluded that the previously proposed single-electron peak calibration method might not be valid for the UMC due to the excessive width and overlap of electron avalanche distributions. Better agreement between the measured and calculated spectra is found if broader electron avalanche distributions than those used in the present calculations, are assumed. (author)

  11. Multichannel proportional counter for the DARK-2,0 X-ray diffractometer

    A 128-channel X-ray detector developed for application in the DARK-20 X-ray diffractometer for investigation of protein monocrystals is described. A design with separation of registration volumes of each counter is chosen to eliminate double counting at the moment of X-ray quanta reaching the spacing between two neighbooring counters. The base of the desinagn is the tyre in which grooves for metal plates separating certain detectors are threaded. The main parameters of the detector are as follows: the number of channels 128, the radius of the inlet window 250 mm, cell dimensions 1.5 mm, registration efficiency of CuKsub(α)-radiation 65%. The three year operation experience of four sections of the detectors in composition of the DARK-2.0 revealed a high level of their reliability: none of 512 channels failed. The individual detectors reliably stand the loading of up to 5x104 pulses/s

  12. Analysis of cylindrical proportional counter pulses transmission through differentiating and integrating circuits

    The numerical estimations of the effect of the length and orientation of the charged particle track on the shape and amplitude of pulses, passed tough the shaping circuits, are presented. The results are calculated for the following parameters of a counter with the argon-methane gaseous mixture: the anode radius is 0.001 cm, the cathode radius is 4.5 cm, the filling gas pressure is 760 mm Hg, the anode filament voltage is 1800 V, the gaseous ion mobility is 1.6 cm2 V-1s-1. The pulse amplitudes, corresponding to point and extended ionization, which have passed through the differentiating and integrating circuits. It is shown that tracks, having equal energy releases but different orientation with respect to the counter anode filament, can lead to formation of such pulses at the shaping circuit output, which considerably differ in amplitudes and have different pulse rise times. These effects can worsen the spectrometer resolution

  13. Operation of proportional counters under high gas gain, high working gas pressure in mixed field of radiation

    It was noted that gas gain depends on type of detected radiation and for beta particle is higher by 6–8 % than for X-ray . Over some value of current flowing through the counter (IC—critical current) the reduction in gas gain due to space charge defined by the time of evacuation of positive ions is observed. The value of IC for different counter geometries and different mixture pressures was measured. It limits the rate capability of the detector for fixed gas gain. Over some value of gas gain (AC—critical value of gas gain) non-proportionality due to self inducted space charge effect is observed. The value of AC was measured as a function of working gas pressure for different counter geometries. Measurements were made for gas compositions Ar+20% CO2 and Ar+6.4% CO2+2.5% N2, for mixture pressures from 0.05 to 0.65 MPa and for different counter geometries

  14. Design and performance of a heavy ion detector using a gridded ionization chamber with helical position-sensitive proportional counter

    A counter specifically designed for heavy ions and low-energy helium ions has been constructed for use in the focal plane of a Q3D spectrometer. The counter utilizes a gridded ionization chamber to measure energy loss and total energy of the particles incident on the detector and a helical proportional chamber to establish the position and hence the momentum along the focal plane. The ionization chamber information is used to establish the mass and charge of the incident particle with high precision and under low background conditions. The helix provides excellent spatial resolution along with high counting rate performance and a resolution independent of the angle at which the particles enter the detector

  15. Studies with encapsulated sources of 125I. III. Microdosimetry using a non-metallic wall-less proportional counter

    A significant problem in measurement of microdosimetric spectra of low energy X rays has been the perturbing influence of the counters used in experiments. The conventional proportional counters used in microdosimetry have employed electrode structures of stainless steel. Since photoelectric cross-sections are highly sensitive to atomic number (approximately proportional to z4), the photoelectrons, emitted from the steel structures, with correspondingly higher energies, may dominate over the softer Compton electrons emitted from the wall and gas. This is more serious for a wall-less type of counter, in which metallic supporting structures may contribute an additional source of photoelectrons entering the sensitive region. In order to perform accurate measurement with 125I photons and other soft X rays having energies less than 100 keV, a special counter was constructed having no metal parts. The construction is of the grid-defined ''wall-less'' type, contained inside a plastic spherical shell. The plastic was chosen to match the energy absorption coefficient of tissue at 25 keV as closely as possible; therefore, conventional tissue-equivalent A-150 was replaced by an ''air-equivalent'' type, C-552, which at 25 keV matches tissue to within a few percent. This material, based on the plastic polyvinylidene fluoride has additional advantages in terms of tensile strength and rigidity, for the purpose of molding delicate structures. The gas used was a propane-based tissue-equivalent type, modified to match the plastic. A human hair, coated with graphite, was used as the central collecting wire. The construction and details of this detector are described, and measurements are reported of 125I and 60 keV photons from 241Am, as well as high energy photons from 137Cs and 60Co

  16. Response of a proportional counter to 37Ar and 71Ge: Measured spectra versus Geant4 simulation

    Abdurashitov, D. N.; Malyshkin, Yu. M.; Matushko, V. L.; Suerfu, B.

    2016-04-01

    The energy deposition spectra of 37Ar and 71Ge in a miniature proportional counter are measured and compared in detail to the model response simulated with Geant4. A certain modification of the Geant4 code, making it possible to trace the deexcitation of atomic shells properly, is suggested. Modified Geant4 is able to reproduce a response of particle detectors in detail in the keV energy range. This feature is very important for the laboratory experiments that search for massive sterile neutrinos as well as for dark matter searches that employ direct detection of recoil nuclei. This work demonstrates the reliability of Geant4 simulation at low energies.

  17. A model for the operation of helium-filled proportional counter at low temperatures near 4.2 K

    In order to understand the operation of helium-filled proportional counter (HFPC) from the standpoint of fundamental atomic and molecular processes, we have surveyed previous works on collision processes in discharged helium gas. By analyzing gas gain curve, after-pulses and discharge current experimentally observed at 4.2 K, the electron avalanche and the secondary electron emission from cathode have been related to the collision processes in helium. A simplified model for the HFPC operation at low temperatures near 4.2 K has been constructed with the related processes

  18. The dependence of the energy resolution of gas proportional scintillation counters on the scintillation region to photomultiplier distance

    In this paper, the energy resolution for broad X-ray beams of Gas Proportional Scintillation Counters with medium to large size windows, parallel grids and no focusing system is discussed. the variation of the pulse amplitude with the radial distance is calculated for several distances, d (taken from the bottom of the scintillation region to the photomultiplier's photocathode), in the 0 to 50mm range and compared with experimental results. It is shown that for a 2 inch photomultiplier d distances from 10 to 20mm, commonly used in the detector designs, represent a worst case situation

  19. Gas-multiplication factor of a proportional counter operated at low temperature described with the Diethorn, Rose-Korff and townsend expressions

    Fukumura, Kazuko; Nakanishi, Akio; Kobayashi, Takayuki [Shiga Univ. of Medical Science, Otsu (Japan)

    1996-07-01

    In the present work, the gas-multiplication factor is expressed with the Rose-Korff and Townsend methods as well as with the Diethorn method. A proportional counter with helium or neon works only at low temperature. This is discussed in terms of the number of electrons emitted when an ion is neutralized at the cathode of the counter. (J.P.N.)

  20. A technique for searching for the 2K capture in {sup 124}Xe with a copper proportional counter

    Gavrilyuk, Yu. M.; Gangapshev, A. M.; Kazalov, V. V.; Kuzminov, V. V. [Russian Academy of Sciences, Institute for Nuclear Research (Russian Federation); Panasenko, S. I.; Ratkevich, S. S. [Karazin Kharkiv National University (Ukraine); Tekueva, D. A., E-mail: t.jami.a@mail.ru; Yakimenko, S. P. [Russian Academy of Sciences, Institute for Nuclear Research (Russian Federation)

    2015-12-15

    An experimental technique for searching for the 2K capture in {sup 124}Xe with a large low-background copper proportional counter is described. Such an experiment is conducted at the Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Sciences. The experimental setup is located in the Low-Background Deep-Level Laboratory at a depth of 4900 m.w.e., where the flux of muons of cosmic rays is suppressed by a factor of 10{sup 7} relative to that at the Earth’s surface. The setup incorporates a proportional counter and low-background shielding (18 cm of copper, 15 cm of lead, and 8 cm of borated polyethylene). The results of processing the data obtained in 5 months of live measurement time are presented. A new limit on the half-life of {sup 124}Xe with respect to the 2K capture is set at the level of 2.5 × 10{sup 21} years.

  1. A technique for searching for the 2K capture in 124Xe with a copper proportional counter

    An experimental technique for searching for the 2K capture in 124Xe with a large low-background copper proportional counter is described. Such an experiment is conducted at the Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Sciences. The experimental setup is located in the Low-Background Deep-Level Laboratory at a depth of 4900 m.w.e., where the flux of muons of cosmic rays is suppressed by a factor of 107 relative to that at the Earth’s surface. The setup incorporates a proportional counter and low-background shielding (18 cm of copper, 15 cm of lead, and 8 cm of borated polyethylene). The results of processing the data obtained in 5 months of live measurement time are presented. A new limit on the half-life of 124Xe with respect to the 2K capture is set at the level of 2.5 × 1021 years

  2. 10B4C Multi-Grid as an alternative to 3He for Large Area Neutron Detectors

    Correa Magdalena, Jonathan

    2012-01-01

    Despite its present shortage, 3He continues to be the most common neutron converter for detectors in neutron scattering science. However, it is obvious that the development of large area neutron detectors based on alternative neutron converters is rapidly becoming a matter of urgency. In the technique presented, grids each comprising 30 10B4C layers (each 1 µm thick) are used to convert neutrons into ionising particles which are subsequently detected in proportional gas counters. Several pro...

  3. 10B4C Multi-Grid as an alternative to 3He for Large Area Neutron Detectors

    Correa Magdalena, Jonathan; Guerard, Bruno; Campo Ruiz, Jesús Javier

    2013-01-01

    Despite its present shortage, 3He continues to be the most common neutron converter for detectors in neutron scattering science. However, it is obvious that the development of large area neutron detectors based on alternative neutron converters is rapidly becoming a matter of urgency. In the technique presented, grids each comprising 30 10B4C layers (each 1 µm thick) are used to convert neutrons into ionising particles which are subsequently detected in proportional gas counters. Several pro...

  4. Design and in-orbit-performance of the position sensitive proportional counter onboard the X-ray astronomy satellite ROSAT

    A Position Sensitive Proportional Counter (PSPC) was the prime focal plane instrument onboard the X-ray astronomy satellite ROSAT, a conventional multiwire counter for X-ray imaging in the energy range from 0.1 to 2.4 keV. The detector gas was a mixture of 65% Ar, 20% Xe and 15% CH4 at a pressure of about 1.5 bar, replenished at a flow rate of 2.5 cm3 min-1. At 1 keV the detector had an energy resolution of 41% FWHM, a position resolution of 230 μm FWHM, and a quantum efficiency of 65%. The background rejection capability in the space environment was 99.85%. The gain degradation in orbit was 1% per month for the nominal PSPC A and 1% per year for the redundant PSPC B. Within the first 4 years of the mission, the PSPC was used for 80% of the observing time. Thereafter, the gas supply was nearly exhausted and the PSPC was used only for special observations. After eight years a final observation was carried out with the PSPC using extremely reduced gas flow at the border of the radiation belts with a very high particle background. During this observation the detector probably suffered a discharge and within several days an increasing area with 50% gain loss developed. We report on the detector design, the in-orbit-performance of the PSPC and some results of the ROSAT mission

  5. The n,γ discrimination in recoil-proton proportional counters. Application to the measurement of fast neutron spectra

    A description is given of a spectrometry chain working in the energy range of a few keV to 1 MeV, and designed for measurement of fast neutron spectra. It consists of detectors, recoil proton proportional counters built especially for this work by R. COMTE (DEG/SER) and which make it possible to cover the energy range and also associated electronic equipment. A brief description is first given of the physical processes involved: (n,p) collisions in the gas, influence of γ radiation; the method of discrimination is then presented. It is based on the difference in the rise-times of the pulses. In the experiments described here the use of a bi-parametric system made it possible to employ the most simple discrimination device, based on the fact that the high frequency gamma pulse components are, at a given energy, weaker than those of the neutron pulses. Results are given of measurements carried out on the Van der Graaff (mono-energetic neutrons for testing the linearity of the chain and the resolving power of the counters), and of those made in a sub-critical system Hug at Cadarache. (author)

  6. Exploring background variability of a low-level (quartz) gas proportional counter using pulse shape and distribution analysis

    The NIST low-level beta counting system is designed to capture digitally and timestamp each event for retrospective analysis. As a result, low and stable backgrounds are achieved and lead to extremely low detection and quantification limits for measuring, e.g., 14C of atmospheric gases and aerosol. The objective here is to explore the variability of the background count rate (counts per day) of several small (1 mL) freshly-assembled gas proportional counters (GPCs). The mean is 14.0 day-1 with 95 % confidence limits 11.2-16.8 day-1. The raw count per day data was non-normal and so a Log transformation was applied to achieve normality and to rigorously compute normal tolerance limits. Back in the original space such (95 % confidence, 95 % coverage) tolerance limits were 2.5-47.8 day-1. These limits are taken as acceptance criteria for any GPCs assembled in the future. (author)

  7. A study of argon-isobutane mixtures in a proportional counter: gas amplification, W value, and energy resolution

    The mean gas amplification factor, the single electron spectra, the mean energy required to form an ion pair (W), and the energy resolution were measured in argon-isobutane mixtures at various pressures over a wide range of the reduced electric field strengths in a cylindrical proportional counter. In mixtures with low isobutane partial pressure, gas gain is an over-exponential function of the applied high voltage. The relative variance of single electron spectra, the apparent W value and the energy resolution are functions of both gas gain and isobutane partial pressure in the mixture. A better energy resolution is obtained with mixtures containing less isobutane at low gas gains whereas at the higher gas gains usually applied in X-ray spectroscopy the resolution is degraded. (author)

  8. Measurement of the neutron fluence and dose spectra using an extended Bonner sphere and a tissue-equivalent proportional counter

    A conventional Bonner Sphere (BS) set consisting of six polyethylene spheres was modified to enhance its response to a high-energy neutron by putting a lead shell inside a polyethylene moderator. The response matrix of an extended BS was calculated using the MCNPX code and calibrated using a 252Cf neutron source. In order to survey the unknown photon and neutron mixed field, a spherical tissue equivalent proportional counter (TEPC) was constructed and assembled as a portable measurement system. The extended BS and the self-constructed TEPC were employed to determine the dosimetric quantities of the neutron field produced from the thick lead target bombarded by the 2.5 GeV electron beam of Pohang Accelerator Laboratory (PAL) and the neutron calibration field of Korea Atomic Energy Research Inst. (KAERI). (authors)

  9. Response of a proportional counter to $^{37}$Ar and $^{71}$Ge: real spectra versus GEANT4 simulation

    Abdurashitov, D; Matushko, V; Suerfu, B

    2015-01-01

    The energy deposition spectra of $^{37}$Ar and $^{71}$Ge in a miniature proportional counter are measured and compared in detail to the model response simulated with Geant4. The spectrum of $^{71}$Ge is measured with total statistics of 1.7$\\cdot$10$^8$ events and is presented for the first time. A certain modification of the Geant4 code, making it possible to trace the deexcitation of atomic shells properly, is suggested. After the modification Geant4 is able to reproduce a response of particle detectors in detail in a keV energy range. This feature is very important in the laboratory experiments that search for massive sterile neutrinos as well as for dark matter directly by detection of recoil nuclei. We expect this work to convince physicists to trust Geant4 simulations at low energies.

  10. Application of Penning mixture proportional counters for gas turbine engine X-ray fluorescence spectrometer wear metal monitor

    The X-ray fluorescence spectrometry/analysis detection sensitivities for titanium, iron, copper, and silver in a lubricant oil matrix have been determined by using argon-neon, argon-xenon, and argon-isobutane Penning mixture proportional counters and curium-244, iron-55, americium-241, and cadmium-109 isotope source excitation. Three sigma wear metal detections under static conditions of 3 ppm iron, 1.2 ppm copper, 5.4 ppm titanium, and 9.6 ppm silver were achieved for a measurement time of 1000 s. The detection sensitivities of flowing analysis of used gas turbine engine lubricant were 3 ppm for iron and 1.8 ppm for copper. These values can enable the detection of abnormal wear metals in gas turbine engines. 10 references, 12 figures, 6 tables

  11. After-pulse from helium-filled proportional counter at low temperatures near 4.2 K

    After-pulses, which appear in output signals from the helium-filled proportional counter (HFPC) cooled at low temperature (5-10 K), have been analyzed with a technique of non-linear least-squares fit; the drift time Ti of positive helium ions from anode to cathode, the spread in the drift time ΔTi and the second Townsend ionization coefficient Γi of the positive ions have been determined. It is known that the carrier of positive charge in pure helium gas is the dimer ion He+2 at room temperature. We have found that Ti and ΔTi are larger than the values estimated with the mobility of He+2 and Γi is much smaller than the value for He+2. These results indicate that the carrier at low temperatures near 4.2 K is not He+2, but heavier molecular ions He+n; the size n is more than 10 in the present HFPC. It has been concluded that the cluster ion of large molecular helium plays an essential role in the proportional operation of HFPC, especially to suppress the continuous electric discharge. This self-suppression of discharge by the formation of cluster ions is discussed with some data of atomic and molecular heliums. The same quenching mechanism by cluster ions in other rare gases is also suggested. ((orig.))

  12. Far-ultraviolet signatures of the 3He(n,tp) reaction in noble gas mixtures

    Hughes, Patrick P; Thompson, Alan K; Vest, Robert E; Clark, Charles W

    2010-01-01

    Previous work showed that the 3He(n,tp) reaction in a cell of 3He at atmospheric pressure generated tens of far-ultraviolet photons per reacted neutron. Here we report amplification of that signal by factors of 1000 and more when noble gases are added to the cell. Calibrated filter-detector measurements show that this large signal is due to noble-gas excimer emissions, and that the nuclear reaction energy is converted to far-ultraviolet radiation with efficiencies of up to 30%. The results have been placed on an absolute scale through calibrations at the NIST SURF III synchrotron. They suggest possibilities for high-efficiency neutron detectors as an alternative to existing proportional counters.

  13. On the optimisation of the use of {sup 3}He in radiation portal monitors

    Tomanin, Alice [European Commission, Joint Research Centre, ITU—Ispra (Italy); University of Ghent, Engineering Faculty, B-9052 Gent-Zwijnaarde (Belgium); Peerani, Paolo, E-mail: paolo.peerani@jrc.ec.europa.eu [European Commission, Joint Research Centre, ITU—Ispra (Italy); Janssens-Maenhout, Greet [University of Ghent, Engineering Faculty, B-9052 Gent-Zwijnaarde (Belgium)

    2013-02-01

    Radiation Portal Monitors (RPMs) are used to detect illicit trafficking of nuclear or other radioactive material concealed in vehicles, cargo containers or people at strategic check points, such as borders, seaports and airports. Most of them include neutron detectors for the interception of potential plutonium smuggling. The most common technology used for neutron detection in RPMs is based on {sup 3}He proportional counters. The recent severe shortage of this rare and expensive gas has created a problem of capacity for manufacturers to provide enough detectors to satisfy the market demand. In this paper we analyse the design of typical commercial RPMs and try to optimise the detector parameters in order either to maximise the efficiency using the same amount of {sup 3}He or minimise the amount of gas needed to reach the same detection performance: by reducing the volume or gas pressure in an optimised design.

  14. Fast-Neutron Spectrometry Using a 3He Ionization Chamber and Digital Pulse Shape Analysis

    D. L. Chichester; J. T. Johnson; E. H. Seabury

    2010-05-01

    Digital pulse shape analysis (dPSA) has been used with a Cuttler-Shalev type 3He proportional counter to measure the fast neutron spectra of bare 252Cf and 241AmBe neutron sources. Measurements have also been made to determine the attenuated fast neutron spectra of 252Cf shielded by several materials including water, graphite, liquid nitrogen, magnesium, and tungsten. Rise-time dPSA has been employed using the common rise-time approach for analyzing n +3He ? 1H + 3H ionization events and a new approach has been developed to improve the fidelity of these measurements. Simulations have been performed for the different experimental arrangements and are compared, demonstrating general agreement between the dPSA processed fast neutron spectra and predictions.

  15. Realisation and qualification of a tissue equivalent proportional counter with a multi-cellular geometry for the individual neutron dosimetry

    The present day dosimetry means for radiations with a strong ionization density cannot fulfill the future radioprotection regulations which will require an individual dosimetry with active dosemeters. The aim of this work is the study and development of an individual dosemeter based on a tissue equivalent proportional counter and with a multi-cellular geometry allowing to reach a sensibility equivalent to environmental dosemeters. A pressure regulation bench has been added to the detector in order to reduce the degassing of the detector parts and to reach a sufficient service life for the implementation of the characterization tests. The hole counter system has been adopted for the first prototypes in order to reduce the sensibility of the wires multiplication system with respect to mechanical vibrations. Tests performed with an internal alpha source have shown that a better electrical efficiency can be reached when more severe mechanical limits are adopted during the construction. The dose equivalent response of the prototype for mono-energy neutrons of 144 keV to 2.5 MeV is analyzed experimentally and by simulation. During experiments with normal incidence neutrons, the prototype fulfills the requirements of the CEI N O 1323 standard for energies comprised between 400 keV and 2.5 MeV, while the simulation indicates a satisfactory response up to 200 keV. A preliminary study of the behaviour of the detector with respect to the neutrons incidence indicates that the multi-cellular geometry is efficient for large angles (the sensibility of the prototype is increased by a factor 3). Finally, simulation studies have to be made to optimize the electrical operation and the geometry of the next prototype. (J.S.)

  16. Observation of the n(3He,t)p Reaction by Detection of Far-Ultraviolet Radiation

    Thompson, Alan K; Cooper, John W; Hughes, Patrick; Vest, Robert E; Clark, Charles W

    2008-01-01

    We have detected Lyman alpha radiation as a product of the n(3He,t)p nuclear reaction occurring in a cell of 3He gas. The predominant source of this radiation appears to be decay of the 2p state of tritium produced by charge transfer and excitation collisions with the background 3He gas. Under the experimental conditions reported here we find yields of tens of Lyman alpha photons for every neutron reaction. These results suggest a method of cold neutron detection that is complementary to existing technologies that use proportional counters. In particular, this approach may provide single neutron sensitivity with wide dynamic range capability, and a class of neutron detectors that are compact and operate at relatively low voltages.

  17. A High-Pressure Gas-Scintillation-Proportional Counter for the Focus of a Hard-X-Ray Telescope

    Austin, R. A.; Ramsey, B. D.; Tse, C. L.

    1999-01-01

    We are developing a high-pressure Gas Scintillation Proportional Counter (GSPC) for the focus of a balloon-borne hard-x-ray telescope. The device has a total active diameter of 50 mm, of which the central 20 mm only is used, and is filled with xenon + 4% helium at a total pressure of 10 6 Pa giving a quantum efficiency of greater than 85% up to 60 keV. The detector entrance is sealed with a beryllium window, 3-mm thick, which provides useful transmission down to 6 keV, way below the atmospheric cut-off at balloon float altitudes. Scintillation light exits the detector via a UV transmitting window in its base and is registered by a Hamamatsu position-sensitive crossed-grid-readout photomultiplier tube. Initial testing is underway, quantifying light yield and energy resolution. Following that, the spatial resolution and absolute efficiency will be calibrated. Simulations show that a spatial resolution of better than 0.5 mm FWHM should be achievable up to 60 keV, and this is well matched to the angular resolution and plate scale of the mirror system. The energy resolution will be around 5% at 22 keV. Full details of the instrument design and its performance will be presented. A first flight is scheduled for the Fall of 99, on a stratospheric balloon to be launched from Fort Sumner, New Mexico.

  18. A multipurpose 3He refrigerator

    Pizzo, L.; Dall'Oglio, G.; Martinis, L.; Sabbatini, L.

    2006-10-01

    We introduce a mini 3He refrigerator, operating at ˜300 mK starting from 4.2 K without pumping on the main 4He bath. The innovative idea is that the present one is suitable for a very fast operation; for its use, it is sufficient a storage 4He Dewar. In this way we drastically reduce the time required to cool it down, because there is no need for a classic cryostat. This prototype is particularly aimed for all those operations in which it is necessary to test a large number of samples that do not require long duration measurements at low temperature.

  19. First results of a simultaneous measurement of tritium and 14C in an ultra-low-background proportional counter for environmental sources of methane

    Mace, Emily K.; Aalseth, Craig E.; Day, Anthony R.; Hoppe, Eric W.; Keillor, Martin E.; Moran, James J.; Panisko, Mark E.; Seifert, Allen; Tatishvili, Gocha; Williams, Richard M.

    2016-02-01

    Abstract Simultaneous measurement of tritium and 14C would provide an added tool for tracing organic compounds through environmental systems and is possible via beta energy spectroscopy of sample-derived methane in internal-source gas proportional counters. Since the mid-1960’s atmospheric tritium and 14C have fallen dramatically as the isotopic injections from above-ground nuclear testing have been diluted into the ocean and biosphere. In this work, the feasibility of simultaneous tritium and 14C measurements via proportional counters is revisited in light of significant changes in both the atmospheric and biosphere isotopics and the development of new ultra-low-background gas proportional counting capabilities for small samples (roughly 50 cc methane). A Geant4 Monte Carlo model of a Pacific Northwest National Laboratory (PNNL) proportional counter response to tritium and 14C is used to analyze small samples of two different methane sources to illustrate the range of applicability of contemporary simultaneous measurements and their limitations. Because the two methane sources examined were not sample size limited, we could compare the small-sample measurements performed at PNNL with analysis of larger samples performed at a commercial laboratory. The dual-isotope simultaneous measurement is well matched for methane samples that are atmospheric or have an elevated source of tritium (i.e. landfill gas). For samples with low/modern tritium isotopics (rainwater), commercial separation and counting is a better fit.

  20. First results of a simultaneous measurement of tritium and (14)C in an ultra-low-background proportional counter for environmental sources of methane.

    Mace, E K; Aalseth, C E; Day, A R; Hoppe, E W; Keillor, M E; Moran, J J; Panisko, M E; Seifert, A; Tatishvili, G; Williams, R M

    2016-05-01

    Simultaneous measurement of tritium and (14)C would provide an added tool for tracing organic compounds through environmental systems and is possible via beta energy spectroscopy of sample-derived methane in internal-source gas proportional counters. Since the mid-1960's atmospheric tritium and (14)C have fallen dramatically as the isotopic injections from aboveground nuclear testing have been diluted into the ocean and biosphere. In this work, the feasibility of simultaneous tritium and (14)C measurements via proportional counters is revisited in light of significant changes in both the atmospheric and biosphere isotopics and the development of new ultra-low-background gas proportional counting capabilities for small samples (roughly 50 cc methane). A Geant4 Monte Carlo model of a Pacific Northwest National Laboratory (PNNL) proportional counter response to tritium and (14)C is used to analyze small samples of two different methane sources to illustrate the range of applicability of contemporary simultaneous measurements and their limitations. Because the two methane sources examined were not sample size limited, we could compare the small-sample measurements performed at PNNL with analysis of larger samples performed at a commercial laboratory. These first results show that the dual-isotope simultaneous measurement is well matched for methane samples that are atmospheric or have an elevated source of tritium (i.e. landfill gas). However, for samples with low/modern tritium isotopics (rainwater), commercial separation and counting is a better fit. PMID:26990077

  1. Development of NRESP98 Monte Carlo codes for the calculation of neutron response functions of neutron detectors. Calculation of the response function of spherical BF3 proportional counter

    The method to calculate the response function of spherical BF3 proportional counter, which is commonly used as neutron dose rate meter and neutron spectrometer with multi moderator system, is developed. As the calculation code for evaluating the response function, the existing code series NRESP, the Monte Carlo code for the calculation of response function of neutron detectors, is selected. However, the application scope of the existing NRESP is restricted, the NRESP98 is tuned as generally applicable code, with expansion of the geometrical condition, the applicable element, etc. The NRESP98 is tested with the response function of the spherical BF3 proportional counter. Including the effect of the distribution of amplification factor, the detailed evaluation of the charged particle transportation and the effect of the statistical distribution, the result of NRESP98 calculation fit the experience within ±10%. (author)

  2. Methods of Radioactivity Measurement for Beta Emitter Radionuclides of 14C, 36Cl and 90Sr in Area Geometric Using 2π Proportional Counter

    The radioactivity measurement of beta emitter of 14C, 36Cl and 90Sr in area geometric have been carried out by 2π proportional counter in Center for Technology of Safety and Metrology Radiation-BATAN. The measurement is needed to get standard methods for standardized of beta emitter in area geometric without destructing of the sample. The Measurement is carried out by 2π proportional counter using gas flow system of P10 in order that ionization process to be passed continuously. To prevent damage. the sources covered with very thin foil layer. Detection efficiencies are determined by variation of beta discriminator. The activities of sources are determined by extrapolation methods to 100 % of efficiencies. The results measurements are fairly good by (5954 ± 62) Bq for 14C ; (5175 ± 49) Bq for 36Cl and (1619 ± 23) Bq for 90Sr. (author)

  3. Study of a petal-shape proportional counter foreseen to be used in high-granularity and large solid angle detector for identification of intermediate mass fragments

    Available as short communication only. A proportional counter of special geometry, foreseen to be used as component of high granularity and large solid angle devices for complex fragments identification at intermediate energies has been designed. Two geometries have been tested. One has a truncated-pyramidal shape with squared bases (49 x 49 mm2 and 9 x 9 mm2 respectively) and 380 mm length and the other having the same shape for the entrance window but of a constant thickness. In order to have as small as possible dead layers the side walls have been made of 1.5 mm printed circuit plates while the front and back windows were made of aluminized mylar foil. The counter was operated in flow mode with P-10 gas at atmospheric pressure. The signals were collected at one or at both ends of the counter. Preliminary tests with a β source (Sr) have shown that by far the position dependence of the amplitudes as a function of the position, as expected, due to field variation are smaller for the pyramidal shape module. The effects of the field variation were compensated by using resistive wires and by reading the signal at the larger side of the counter. These counters are expected to be used in conjunction with time of flight measurements to identify up to Z=15 and up to 400 MeV/u incident energies. (Author) 1 Fig., 2 Refs

  4. Results of a search for 2\\beta-decay of Xe-136 with high pressure copper proportional counters in Baksan Neutrino Observatory INR RAS

    Gavriljuk, Ju M; Kazalov, V V; Kuzminov, V V; Panasenko, S I; Ratkevich, S S; Zhantudueva, D A; Yakimenko, S P

    2011-01-01

    Search for \\beta \\beta -decay of Xe-136 with two high pressure proportional counters is carried out in Baksan Neutrino Observatory. The experiment is based on comparision of spectra measured with natural and enriched xenon. The measured halfe life is equal to T_{1/2}=5.5^{+4.6}_{-1.7} \\cdot 10^{21} yrs (67% C.L.) for \\beta \\beta 2\

  5. Thin-window high-efficiency position sensitive proportional counter for the vacuum flat crystal spectrometers on the Lawrence Livermore National Laboratory electron beam ion trap (abstract)

    We have mounted 1 μm thick aluminized polyimide windows onto the position sensitive proportional counters employed by the wide-band flat crystal spectrometers at the Lawrence Livermore National Laboratory electron beam ion trap experiment. The aluminized polyimide, supported by thin wires across the short axis of the window, is used to isolate the detection chamber of the proportional counters, which operate at a pressure of 760 Torr, from the vacuum chamber of the spectrometer. The windows are modified versions of those developed for the proportional counters which were used during ground calibration of the Chandra X-ray Observatory. The transmission properties of these windows are, therefore, well known. The increased transmission efficiency of the polyimide windows relative to the 4 μm thick polypropylene window material previously employed by our proportional counters has extended the useful range of the spectrometer from roughly 20 to 30 Aa at energies below the carbon edge, as well as increasing detection efficiency at wavelengths beyond the carbon edge. Using an octadecyl hydrogen maleate crystal with 2d=63.5Aa, we demonstrate the increased wavelength coverage by measuring the resonance, intercombination, and forbidden lines in helium-like NVII in two different density regimes. The thin polyimide windows have also increased the efficiency of the spectrometers entire wavelength range. To demonstrate the increased efficiency we compare the FeXVII spectrum in the 15--17 Aa band measured with the 1 μm aluminized polyimide windows to the 4 μm aluminized polypropylene windows. The comparison shows an average increase in efficiency of ∼40%. The polyimide windows have a significantly lower leak rate than the polypropylene windows making it possible to achieve approximately an order of magnitude lower pressure in the spectrometer vacuum chamber which reduces the gas load on the trap region

  6. Design and Monte Carlo simulation of a multiple cell proportional counter (M.C.P.C.) for continuous airborne 222Rn activity measurements

    A new proportional counter model, baptized Multiple Cell Proportional Counter (M.C.P.C.), intended for continuous airborne radon activity concentration measurements is described and its operation principle presented. This gas-flow proportional counter, consisting in a pile-up of 20 separate proportional counters elements, uses an argon-propane (1%) as a binary gas mixture to which is admixed an appropriate fraction of ambient air, in which radon activity concentration has to be continuously measured through a periodic counting of the a particles emitted by 222Rn and its short-lived decay products within its well defined sensitive volume. A Monte Carlo simulation program, which takes into account the major physical processes involved that determine directly the detector performances, has been written and used for design optimization purposes. According to preliminary design calculations the M.C.P.C. model, now under construction, should achieve an a counting efficiency greater than 100 %. The simulation results also show that the admixture of 10 % of ambient air seems to be sufficient to continuously assess radon concentration levels ranging from about 10 Bq/m3 up to 2.6 105 kBq/m3 for an integral counting period of 10 minutes, when setting the energy discrimination at 250 keV. The expected radon sensitivity is about 1 cpm /10 Bq.m-3, achieving thus a measurement accuracy of ± 10 Bq/m3 at a mean radon concentration level of 100 Bq/m3 for 10 min detector time response. (authors)

  7. Reconstruction algorithm and full area energy resolution of the scientific prototype of the high pressure gas scintillation proportional counter on board the SAX satellite

    In the following paper we describe an event position reconstruction and energy correction technique that is being implemented on the High Pressure Gas Scintillation Proportional Counter (HPGSPC), that will be flown aboard the Italian Satellite for X-ray astronomy, SAX. We discuss how this technique will greatly enhance the spectroscopic performances of the detector and we report some results regarding the full area energy resolution of the scientific model of the HPGSPC. ((orig.))

  8. The Panofsky ratio in 3He

    The branching ratios have been measured for γ-ray channels produced by π- stopping in liquid 3He. The results for the Panofsky ratio are P3 = ω(π-3He → π0t)/ω(π-3He → γt) = 2.83±0.07, and for the ratio of the radiative breakup channels, B3 = ω(π-3He → γnd+γnnp)/ω(π-3He → γt) = 1.35±0.11. (orig.)

  9. Observation of X-ray and Auger electron spectra in a 4π proportional counter for 4π(e, X)–γ coincidence measurements

    For the standardization of electron capture nuclides followed by γ-transitions, the 4π(e, X)–γ coincidence counting method is mainly adopted. To examine how the spectra of the (e, X) channel change with gas nature and pressure, pulse-height spectrum measurements of signals from a 4π pressurized proportional counter were carried out under various conditions for 54Mn and 88Y sources together with 4π(e, X)–γ coincidence counting. The spectra were measured for each half of the counter and for the combined 4π signal. The nature of counting gas (P-10 or methane) and its pressure was reflected in the X-ray peak intensity, and the Auger electron spectra were influenced significantly by the absorption in a thin VYNS film and the source conditions. In the measurements, we employed a pill-box type 4π counter in which the anodes were very thin gold-coated tungsten wires (30 μm ∅). In this system, spectra down to 0.2 keV were clearly seen. The gas pressure can be raised up to 0.6 MPa. Counting electronics used for 4π(e, X)–γ coincidence measurements were conventional modules and a list mode two-parameter data acquisition system. - Highlights: • Spectra of 54Mn and 88Y in a 4π proportional counter measured under various conditions. • Spectra due to X-rays and Auger electrons were clearly seen down to 0.2 keV. • Pulse spectra measured from each half of 4π counter (with P-10 gas or methane). • 4π(e, X)–γ coincidence measurements were also carried out

  10. Experimental microdosimetric distributions of protons, from 19 to 65 MeV, using an A150-walled low pressure proportional counter

    Microdosimetric distributions of protons, from 19 to 65 MeV, were measured using an A150-walled Low Pressure Proportional Counter at the cyclotron facility in the National Inst. of Radiological Sciences. The measured distributions were found to be very different from the spectra assumed by the Continuous Slowing Down Approximation. The measurements consisted of determining the energy deposition by direct incident protons, by secondary electrons produced in the wall of the detector and by scattered protons at the wall. The secondary electron and the scattered proton distributions were studied using analytical functions and the MCNPX Monte Carlo code, respectively. (authors)

  11. A large-area xenon gas scintillation proportional counter (GSPC) with timing information for the detection of low energy muonic X-rays

    A large-area xenon filled gas scintillation proportional counter has been developed and used for the study of the 2 keV K X-ray spectra of muonic hydrogen. An 80 cm long xenon filled light pipe permits operation at a magnetic field of 10 kG. Good time resolution (110 ns at 2 keV) could be obtained by producing secondary scintillation in the first drift space. Preliminary measurements give an energy resolution of 26% at 2 keV. (orig.)

  12. From the High Energy Physics Laboratory to the hospital -some experiences of the application of MWPC [multiwire proportional counter] technology to medicine

    In this talk I wish to briefly review the experience we have obtained at the Rutherford Appleton Laboratory over the past decade in the adaptation of MWPC (multiwire proportional counter) technology to diagnostic imaging applications in medicine. A cursory glance at the history of science and technology quickly shows the often intimate and mutually beneficial relationship between ''pure'' science (and scientists) and practical applications. The following talk traces some of the principal features of the situation which have been brought to my attention in the course of the last decade. (author)

  13. Response Matrix of a Bonner Spheres Spectrometer with 3 He Detector

    Using MCNP code the response matrix of a Bonner spheres spectrometer was calculated. The spectrometer has a 3.2 cm-diameter thermal neutron detector; this is a 3 He-filled proportional counter that is located at the center of a set of polyethylene spheres. The response was calculated for 0, 3, 5, 6, 8, 10, 12 and 16 inches-diameter polyethylene spheres for neutrons whose energy goes from 10-9 to 20 MeV. The response matrix was compared with a set of responses measured with several monoenergetic neutron sources, from this comparison calculated matrix is in agreement with the experimental results. Also this matrix was compared against the response matrix calculated for the PTB C spectrometer, Nevertheless that calculation was carried out using a detailed model to describe the proportional counter both matrices were in agreement, small differences are observed in the bare case because the difference in the model used during calculations. Other differences are in some spheres for 14.8 and 20 MeV neutrons probable due to the differences in the cross sections used during both calculations. (Author)

  14. Monte Carlo calculations and experimental results of Bonner spheres systems with a new cylindrical Helium-3 proportional counter

    Müller, H; Bouassoule, T; Fernández, F; Pochat, J L; Tomas, M; Van Ryckeghem, L

    2002-01-01

    The experimental results on neutron energy spectra, integral fluences and equivalent dose measurements performed by means of a Bonner sphere system placed inside the containment building of the Vandellos II Nuclear Power Plant (Tarragona, Spain) are presented. The equivalent dose results obtained with this system are compared to those measured with different neutron area detectors (Berthold, Dineutron, Harwell). A realistic geometry model of the Bonner sphere system with a new cylindrical counter type 'F' (0,5NH1/1KI--Eurisys Mesures) and with a set of eight polyethylene moderating spheres is described in detail. The response function in fluence of this new device, to mono-energetic neutrons from thermal energy to 20 MeV, is calculated by the MCNP-4B code for each moderator sphere. The system has been calibrated at IPSN Cadarache facility for ISO Am-Be calibrated source and thermal neutron field, then the response functions were confirmed by measurements at PTB (Germany) for ISO recommended energies of mono-e...

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

    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.)

  16. Measurement of polarization of {sup 3}He with mobile polarized {sup 3}He neutron spin filter

    Ino, T. [Neutron Science Laboratory, Institute of Materials Structure Science, KEK, High Energy Accelerator Research Organization, Ibaraki-ken 305-0801 (Japan); Kim, G.N., E-mail: gnkim@knu.ac.kr [Department of Physics, Kyungpook National University, Daehak-ro 80, Buk-gu, Daegu 702-701 (Korea, Republic of); Lee, M.W. [Department of Physics, Kyungpook National University, Daehak-ro 80, Buk-gu, Daegu 702-701 (Korea, Republic of); Lee, S.M. [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Kim, J.Y. [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-353 (Korea, Republic of); Lee, S.W. [School of Mechanical Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Skoy, V.R. [Division of Advanced Nuclear Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2014-03-15

    A mobile polarized {sup 3}He neutron spin filter was developed for both optical pumping and transportation, and the polarization of {sup 3}He was measured with cold neutrons of HANARO in KAERI. The progress of polarization build-up during the optical pumping of the {sup 3}He cell was observed by adiabatic fast-passage NMR system. The {sup 3}He cell was made of an alumino-silicate glass GE-180 with a cylindrical shape of 40 mm in diameter and 60 mm in length from KEK. A cell contained 5.74 bar⋅cm of {sup 3}He gas. The whole installation after 8 h pumping was transported to the general-purpose test station of the HANARO research reactor and the polarization of {sup 3}He was measured with cold neutrons. The measured polarization of {sup 3}He was 0.18 ± 0.01 by measuring the neutron transmission through the {sup 3}He cell.

  17. Spin dynamics of 3He in aerogel

    The authors report continuous-wave NMR measurements on superfluid 3He contained inside high porosity aerogel at 3.24 MPa, in a 28.4 mT magnetic field, and down to 0.9 mK. Three different purities of 3He were used: pure 3He, 3He with enough 4He to replace the first localized layer, and 3He with enough 4He to replace both localized layers. Below 2.26mK, the NMR spectrum does not consist of a single Lorentzian, but a distribution of NR resonant frequencies both above and below the Larmor frequency, ωL. Upon cooling, the component of the spectrum at frequencies below the Larmor frequency moves to higher frequencies over a narrow temperature range and does not return to ω L upon warming. The higher frequency component of the spectrum displays two resolvable peaks which become a complex structure upon removal of the localized 3He spins. The spectrum changes as the magnetic field is rotated about the axis of the aerogel sample, indicating that the 3He is able to detect a preferred direction in the aerogel. The shape of the spectrum shows no rotation or magnetic field hysteresis. The authors find that the average frequency shifts of the NMR spectra do not depend on the presence of the localized 3He spins. These frequency shifts and the presence of a temperature-independent magnetization for the liquid 3He suggest that the aerogel stabilizes a single equal-spin-pairing state in the experiments

  18. 3He(n,p) reaction simulation for formation analyses

    Computer modeling of neutron well logging instrument responses is becoming a necessity for petro-physical research and oil companies. It serves as a low-cost substitute for experimental test pits, as well as a means for obtaining data that are difficult to obtain experimentally. Neutrons in these tools are generally detected through 3He filled detectors. Detection of neutrons in a 3He counter occurs by means of the (n, p) reaction, yielding a proton and a triton. Computational simulation using the Monte Carlo code MCNP has been considered a powerful tool to simulate the response of neutron porosity tools. In the MCNP code the detection of neutrons in a 3He gas has been making by means of energy functions that convert neutron fluxes to reaction rates (n,p). It allows obtaining count values comparable with experimental data. However, it does not allow producing light ions from neutron capture reactions like triton and proton, and nor study the behavior of these particles as a function of the detector design. With the development of the version MCNPX 2.6, the simulation of light ions (protons, triton) from neutron capture reactions was made possible. The purpose of this work is to use the new capabilities included in the MCNPX 2.6 code to simulate the 3He(n,p) reaction for nuclear well logging applications. The results obtained confirm that it is useful to predict the count values, as it allows obtaining results comparable with the literature. Besides, the new capabilities of the MCNPX 2.6 allow producing the triton and proton reaction products and the expected pulse height spectrum from a 3He detector in which the wall effect is significant. (author)

  19. 3He melting pressure temperature scale

    Halperin, W.P.; Archie, C.N.; Richardson, R.C.;

    1976-01-01

    The latent heat for solidification of **3He has been measured along the **3He melting curve between 23 and 1 mK. A temperature scale is established which depends only on measurements of heat, pressure and volume, and on the condition that the entropy of solid **3He approaches R ln 2 at high...... temperatures. The A feature of the melting curve which suggests itself as a thermometric fixed point is found to be T//A equals 2. 75 plus or minus 0. 11 mK. The agreement between this value and independent measurements of T//A, based on nuclear or electronic paramagnetism, Johnson noise thermometry...

  20. Assessment of absorbed dose and stopping power for 109Cd conversion electrons using a pressurized 4π proportional counter

    The evaluation of the absorbed dose in external and internal contamination due to radionuclides is not easy, because of the difficulties in the assessment of the absorbed dose caused by electrons with energy less than 100 keV in skin and in mucous membrane. In this paper we work with a methodology for assessment of absorbed dose and stopping power in VYNS (co-polymer of polylvinyl chloride-acetate) absorbers, for the 32.5 keV and 84-88 keV energy 109 Cd conversion electrons, with a 4 φ proportional pressurized detector. In order to assure the reproducibility of measurement conditions, one of the detector halves was used to obtain a spectrum of a thin 109 Cd source, without absorber. The other half of the detector was used in concomitance to obtain spectra with different thicknesses of absorber. The absorbed energy was obtained subtracting each spectrum absorber from the spectrum without absorber and both were stored in a microcomputer connected to signal processing systems by a ACE type interface. The VYNS weight and thickness were evaluated using common radionuclide metrology procedures. As VYNS has characteristics similar to a tissue equivalent material, the results obtained are consistent with dosimetric concepts and have a good agreement with those of the literature. (author)

  1. 一种改善闭气式正比计数器换气周期的方法%A Method for Optimising the Gas Replacing Period of Sealed Proportional Counter

    张勇; 杨勇

    2011-01-01

    Proportional counter can be used as low - energy particles detector because of its gas gain. According to charging manner, proportional counter can be divided into sealed and gas -flow proportional counters. Compared with gas - flow counter, although sealed proportional counter can be operated simply but it is short -lived, needs to replace the sealed gas periodically. It introduces the aging phenomenon of sealed proportional counter and a method for optimising the gas replacing period.%正比计数器具有气体放大作用,很适合用于低能粒子探测.用于低能X射线和α/β污染监测时,正比计数器按充气方式可以划分为两大类:流气式和闭气式.与流气式相比,闭气式正比计数器使用方便;但是其寿命比较短,需要周期性更换工作气体.介绍了闭气式正比计数器性能老化问题,以及一种改善其换气周期的方法.

  2. Large-area xenon gas scintillation proportional counters (GSPC) with timing information for the detection of low energy X-rays

    von Arb, H.P.; Boecklin, J.; Dittus, F.; Ferreira Marques, R.; Hofer, H.; Kottmann, F.; Schaeren, R.; Taqqu, D.; Waelchli, M. (Eidgenoessische Technische Hochschule, Zurich (Switzerland). Lab. fuer Hochenergiephysik)

    1983-04-01

    A large area xenon gas scintillation proportional counter has been developed for the study of low energy X-rays. A time resolution of 40 ns (fwhm) at 5.5 keV was obtained by producing secondary scintillation light in the drift space. A simple model of the processes leading to secondary light production describes the measured time distributions and their energy dependence. The energy resolution at 5.9 keV was 8.8% (fwhm) for collimated X-rays. For a uniform irradiation over the sensitive area of 314 cm/sup 2/, a resolution of 9.5% is obtained after correcting for the pulse height dependence on the position of X-ray absorption. The reduction of pulse height due to small H/sub 2/O and O/sub 2/ contaminations was measured.

  3. A large-area xenon gas scintillation proportional counters (GSPC) with timing information for the detection of low energy X-rays

    A large area xenon gas scintillation proportional counter has been developed for the study of low energy X-rays. A time resolution of 40 ns (fwhm) at 5.5 keV was obtained by producing secondary scintillation light in the drift space. A simple model of the processes leading to secondary light production describes the measured time distributions and their energy dependence. The energy resolution at 5.9 keV was 8.8% (fwhm) for collimated X-rays. For a uniform irradiation over the sensitive area of 314 cm2, a resolution of 9.5% is obtained after correcting for the pulse height dependence on the position of X-ray absorption. The reduction of pulse height due to small H2O and O2 contaminations was measured. (orig.)

  4. Einstein Observatory SSS and MPC observations of the complex X-ray spectra of Seyfert galaxies. [Solid State Spectrometer and Monitor Proportional Counter

    Turner, T. J.; Weaver, K. A.; Mushotzky, R. F.; Holt, S. S.; Madejski, G. M.

    1991-01-01

    The X-ray spectra of 25 Seyfert galaxies measured with the Solid State Spectrometer on the Einstein Observatory have been investigated. This new investigation utilizes simultaneous data from the Monitor Proportional Counter, and automatic correction for systematic effects in the Solid State Spectrometer which were previously handled subjectively. It is found that the best-fit single-power-law indices generally agree with those previously reported, but that soft excesses of some form are inferred for about 48 percent of the sources. One possible explanation of the soft excess emission is a blend of soft X-ray lines, centered around 0.8 keV. The implications of these results for accretion disk models are discussed.

  5. Photodisintegration of 3H and 3He

    The photoneutron cross sections for 3H and 3He have been measured from threshold to approx. 25 MeV with monoenergetic photons from the annihilation in flight of fast positrons at the LLL Electron-Positron Linear Accelerator facility. These reactions include the two-body breakup of 3H and the three-body breakup of both 3H and 3He; these measurements for 3H are the first to span the energy region across the peaks of the cross sections. An efficient BF3-tube-and-paraffin neutron detector and high-pressure gaseous samples of several moles each (the activity of the 3H sample was approx. 200,000 Ci) were employed in these measurements. Measurements on 16O and 2H also were performed to verify the absolute cross-section scale. The results, when compared with each other and with results for the two-body breakup cross section for 3He from the literature, show that the two-body breakup cross sections for 3H and 3He have nearly the same shape, but the one for 3He lies lower in magnitude; the three-body breakup cross section for 3He lies higher in magnitude and is broader in the peak region and also rises less sharply from threshold than that for 3H; and these measured differences between the cross sections for the breakup modes largely compensate in their sum, so that the total photon absorption cross sections for 3H and 3He are nearly the same in both size and shape at energies near and above their peaks. Theoretical results from the literature disagree with the experimental results to a certain extent over the entire photon-energy region for which the photoneutron cross sections were measured. 50 figures, 7 tables

  6. Heat capacity of 3He in aerogel

    The heat capacity of pure 3He in low density aerogel is measured at 22.5 bars. The superfluid response is simultaneously monitored with a torsional oscillator. A slightly rounded heat capacity peak, 65 μK in width, is observed at the 3He-aerogel superfluid transition, Tca. Subtracting the bulk 3He contribution, the heat capacity shows a Fermi-liquid form above Tca. We can fit the heat capacity attributed to superfluid within the aerogel with a rounded BCS form accounting for 0.30 of the nonbulk fluid in the aerogel, or by assuming a substantial reduction in the superfluid order parameter. Both approaches are consistent with earlier superfluid density measurements

  7. Quantum prewetting transitions in liquid 3He

    Multilayer 3He film growth on weak-binding alkali substrates is investigated with a non-local density functional theory. Although 3He wets all substrates, prewetting transitions are predicted to occur on cesium and potassium. Emphasis is put on the role played by the Fermi statistics. Prewetting critical temperatures are estimated. Continuous wetting at zero temperature is recovered with increasing strength of substrate potential. The heat capacity and the magnetization of the films exhibits steps associated with the occupation of two-dimensional (2D) Fermi discs. (authors). 24 refs., 4 figs

  8. Performance of Boron-10 based Neutron Coincidence Counters

    Helium-3 gas-filled detectors have been used in neutron coincidence counting for non-destructive assay for over 30 years. With the current shortage of 3He gas, GE's Reuter-Stokes business developed a 10B lined proportional counter and a 10B hybrid coincidence counter, in which a small amount of 3He is added to a 10B detector to enhance the neutron sensitivity. GE's Reuter-Stokes business modelled, designed, built and tested prototype coincidence counters using the 10B lined detectors and the 10B hybrid detectors. We will present these systems and their applications for non-destructive assay. (author)

  9. 3He-4He II mixtures

    A theoretical study of the thermodynamic and hydrodynamic properties of 3He-4He II mixtures at temperatures below 250 mK is described. A hydrodynamic model is set up which incorporates mutual friction between the two components. Results of an investigation into the quantitative calculation of the mutual friction are reported. 148 refs.; 34 figs.; 4 tabs

  10. NMR experiments on pure 3He and 3He-4He mixtures in silica aerogel

    We have carried out a series of NMR experiments on 4He systems filling the pores of silica aerogel with 95% porosity. The systems studied included 3He-4He mixtures with a wide range of 3He concentrations x3 as well as pure 3He. All experiments were conducted in an 8 T field and for temperatures T ≥ 6 mK. This resulted in strong spin polarization at the lowest temperatures (up to approximately 80%) for the localized layer observed for a pure 3He sample. For pure 3He, the magnetic behavior is dominated by the localized spins, which are found to constitute 6% of the sample. The coupled system of localized plus liquid spins displays rapid transverse magnetization relaxation with an anomalous temperature dependence. For intermediate x3 magnetization measurements provide a preliminary indication of the phase diagram of mixtures filling this porous material. The magnetization is hysteretic over some ranges of x3