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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. 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

  13. 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.)

  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. 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...

  11. 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.)

  12. 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

  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. 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...

  5. 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)

  6. 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.

  7. 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

  8. 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)

  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. 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)

  16. 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.

  17. 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)

  18. 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)

  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. 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

  1. 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

  2. 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,...

  3. 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...

  4. 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...

  5. 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

  6. 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...

  7. 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...

  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. 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

  15. 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)

  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. 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.

  20. 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

  1. 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.

  2. 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++.

  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. 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

  11. 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.

  12. 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...

  13. 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

  14. 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

  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. 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%

  20. 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.

  1. 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

  2. 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)

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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.)

  9. 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

  10. 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.)

  11. 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

  12. 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.

  13. 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...

  14. 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.

  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. 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...

  2. 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.

  3. 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.)

  4. 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)

  5. 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

  6. 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)

  7. 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...

  8. 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.

  9. 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.)

  10. 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

  11. 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...

  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. 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

  18. 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

  19. 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

  20. 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)

  1. ^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.

  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. 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.

  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. 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

  12. 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

  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. 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

  17. 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

  18. 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.

  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. 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.

  9. 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)

  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. 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.

  13. 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.

  14. 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.

  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. 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)

  2. 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)

  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. 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)

  5. 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\

  6. 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

  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. 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.)

  11. 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)

  12. 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)

  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

  11. A comparison between the measurements of Kr-85 in environmental samples by liquid scintillation and proportional counters; Comparacion de resultados de la medida radiactiva del Kr-85 ambiental por centelleo liquido y contadores proporcionales

    Heras, M. C.; Perez, M. M.

    1983-07-01

    The most used methods for the measurement of Kr-81 beta-activity after their concentration and aisolation are the liquid scintillation counting and the proportional counter. In this work the beta activity of concentrated and aisolated Kr-85 samples measured in collaboration with the Max-Planck Institut fur Kernphyslk, Aussenstelle Freiburg. Samples taken both In Madrid and Frelburg are measured by proportional counters in the Max-Planck lnstitut, Freibury and by liquid scintillation counting in JEN, Madrid. The comparison of both measurements do not show appreciable discrepancy between the results obtained to both techniques. (Author)

  12. Needle counter

    Needle counter had been devised by Geiger about 60 years ago before the present GM counter appeared. It is suitable for the detection of weak radiation because it is limited in effective volume, if the background due to mainly cosmic ray is proportional to the effective volume of the counter. Recently the very low β detector having a needle counter as the main detector has been developed. It showed highly excellent performance in the measurements of small area samples, about ten times sensitive as compared with other detectors. The counter is installed in the very low radiation measuring well at Nokogiriyama, Chiba Prefecture, using a NaI scintillator as its guard counter. D. H. Wilkinson first treated a gas amplification counter theoretically and quantitatively. The authors have obtained good results in the comparison with the experiments of the counter using a generalized form of Wilkinson theory. The findings obtained through this study seem to be applicable to the electrode arrangement which is important for the counter design. It was found that the excellent rise time of induced pulses in a gas amplification counter was achieved in larger amplification factor and smaller convolution effect. In the detection of charged particles with small obstructing capability such as γ ray, faster rise time and higher pulses can be obtained with needle counters than wire counters. (Wakatsuki, Y.)

  13. Search for the K-pp bound state via the in-flight 3He(K-, n) reaction

    Sada, Y.; Ajimura, S.; Beer, G.; Bhang, H.; Bragadireanu, M.; Buehler, P.; Busso, L.; Cargnelli, M.; Choi, S.; Curceanu, C.; Enomoto, S.; Faso, D.; Fujioka, H.; Fujiwara, Y.; Fukuda, T.; Guaraldo, C.; Hashimoto, T.; Hayano, R. S.; Hiraiwa, T.; Iio, M.; Iliescu, M.; Inoue, K.; Ishiguro, Y.; Ishikawa, T.; Ishimoto, S.; Ishiwatari, T.; Itahashi, K.; Iwai, M.; Iwasaki, M.; Kato, Y.; Kawasaki, S.; Kienle, P.; Kou, H.; Ma, Y.; Marton, J.; Matsuda, Y.; Mizoi, Y.; Morra, O.; Nagae, T.; Noumi, H.; Ohnishi, H.; Okada, S.; Outa, H.; Piscicchia, K.; Poli Lener, M.; Romero Vidal, A.; Sakaguchi, A.; Sakuma, F.; Sato, M.; Scordo, A.; Sekimoto, M.; Shi, H.; Sirghi, D.; Sirghi, F.; Suzuki, K.; Suzuki, S.; Suzuki, T.; Tanida, K.; Tatsuno, H.; Tokuda, M.; Tomono, D.; Toyoda, A.; Tsukada, K.; Vazquez Doce, O.; Widmann, E.; Weunschek, B. K.; Yamaga, T.; Yamazaki, T.; Yim, H.; Zhang, Q.; Zmeskal, J.

    2014-11-01

    In the J-PARC E15 experiment, a K- pp search was performed via the 3He(K-, n) reaction at 1.0 GeV/c. A forward-going neutron is detected by a neutron counter with 15 m flight length, and decay particles from K- pp are simultaneously measured by a cylindrical detector system that surrounds a liquid 3He target system. In March and May, 2013, we carried out the first physics data-taking with 5×109 incident kaons on the 3He target, and we have obtained a preliminary exclusive analysis result of 3He(K-, Λp)n reaction.

  14. Measurement of the stochastic radial dose distribution for a 30-MeV proton beam using a wall-less tissue-equivalent proportional counter.

    Tsuda, S; Sato, T; Ogawa, T

    2016-02-01

    The frequency distribution of the lineal energy, y, of a 30-MeV proton beam was measured as a function of the radial distance from the beam path, and the dosed mean of [Formula: see text] was obtained to investigate the radial dependence of [Formula: see text] A wall-less tissue-equivalent proportional counter, in a cylindrical volume with simulated diameters of 0.36, 0.72 and 1.44 µm was used for the measurement of y distributions, yf(y). The measured values of yf(y) summed in the radial direction agreed fairly well with the corresponding data taken from the microdosimetric calculations using the PHITS code. The [Formula: see text] value of the 30-MeV proton beam presented its smallest value at r = 0.0 and gradually increased with radial distance, and the [Formula: see text] values of heavy ions such as iron showed rapid decrease with radial distance. This experimental result demonstrated that the stochastic deposited energy distribution of high-energy protons in the microscopic region is rather constant in the core as well as in the penumbra region of the track structure. PMID:25956785

  15. Monte Carlo simulation of a new air-mixed gas-flow proportional counter for on-line airborne radon activity concentration measurements

    A Monte Carlo simulation code, named PROCSIM, has been written and used to optimize the design of a Multiple Cell Proportional Counter (MCPC) prototype intended for airborne radon activity concentration on-line measurements. PROCSIM code takes into account all the electrical and geometrical parameters and models the main physical processes that determine directly the detector performances such as the electric field distribution, the alpha stopping and primary electron-ion pairs production, the wall effect, the gas amplification process, the electron attachment effect and also the Gaussian broadening of the collected alpha pulse height spectra. The MCPC uses an argon-propane (1%) gas mixture to which is admixed up to 10 % of air, whose radon activity concentration has to be measured. Using PROCSIM code, the main design parameters of the MCPC prototype were optimized in order to achieve alpha detection efficiency greater than 95 %. The first run results show that the admixture of 10 % of air is sufficient to assess radon concentration activities as low as 1 Bq/m3 for a counting time period of 10 minutes, resulting thus in an expected radon activity concentration sensitivity of around 0.2 cpm/Bq.m-3, with an energy-equivalent discrimination threshold set to 0.5 MeV. Finally, the possibility to use the present MCPC prototype for on-line measurement of time varying airborne radon activity concentration is discussed. (author)

  16. Evaluation of a low background proportional counter for detection of high energy beta particles with application to {sup 90}Sr surface contamination

    Islam, K.T.S.; Johnson, L.; Brey, R.R.; Gesell, T.F. [Idaho State Univ., Pocatello, ID (United States); McIsaac, C. [Lockheed Idaho Technologies Co., Idaho Falls, ID (United States)

    1996-06-01

    Conventional radiochemical methods used to quantify {sup 90}Sr are complicated and time-consuming. A relatively simple, inexpensive instrument has been developed for analysis of high energy beta surface contamination in the presence of lower energy beta emitters. The instrument detects beta particles from {sup 90}Y, which is in secular equilibrium with {sup 90}Sr. The device consists of three stacked gas-flow proportional detectors. The bottom two are operated in coincidence mode and the top detector is operated in anti-coincidence to the others for reducing cosmic-ray background. Shielding is used to reduce the background from terrestrial sources. The thickness of the bottom two counters eliminates beta particles with energies below 660 keV from the second detector. The end-point energy of the {sup 90}Sr beta is 546 KeV, while that for {sup 90}Y is 2.28 MeV. Greater than 69% of the particles emitted during the decay of {sup 90}Y have energies above the endpoint energy of {sup 90}Sr. Because of these conditions, this instrument, which has an efficiency of about 10%, is practical for measurements near environmental magnitudes. The instrument is expected to have application in decontamination and decommissioning, decisions concerning release of materials, and waste management.

  17. Evaluation of a low background proportional counter for detection of high energy beta particles with application to 90Sr surface contamination

    Conventional radiochemical methods used to quantify 90Sr are complicated and time-consuming. A relatively simple, inexpensive instrument has been developed for analysis of high energy beta surface contamination in the presence of lower energy beta emitters. The instrument detects beta particles from 90Y, which is in secular equilibrium with 90Sr. The device consists of three stacked gas-flow proportional detectors. The bottom two are operated in coincidence mode and the top detector is operated in anti-coincidence to the others for reducing cosmic-ray background. Shielding is used to reduce the background from terrestrial sources. The thickness of the bottom two counters eliminates beta particles with energies below 660 keV from the second detector. The end-point energy of the 90Sr beta is 546 KeV, while that for 90Y is 2.28 MeV. Greater than 69% of the particles emitted during the decay of 90Y have energies above the endpoint energy of 90Sr. Because of these conditions, this instrument, which has an efficiency of about 10%, is practical for measurements near environmental magnitudes. The instrument is expected to have application in decontamination and decommissioning, decisions concerning release of materials, and waste management

  18. FLUKA simulations of the response of tissue-equivalent proportional counters to ion beams for applications in hadron therapy and space

    For both cancer therapy with protons and ions (hadron therapy) and space radiation environments, the spatial energy deposition patterns of the radiation fields are of importance for quantifying the resulting radiation damage in biological structures. Tissue-equivalent proportional counters (TEPC) are the principal instruments for measuring imparted energy on a microscopic scale and for characterizing energy deposition patterns of radiation. Moreover, the distribution of imparted energy can serve as a complementary quantity to particle fluences of the primary beam and secondary fragments for characterizing a radiation field on a physical basis for radiobiological models. In this work, the Monte Carlo particle transport code FLUKA is used for simulating energy depositions in TEPC by ion beams. The capability of FLUKA in predicting imparted energy and derived quantities, such as lineal energy, for microscopic volumes is evaluated by comparing it with a large set of TEPC measurements for different ion beams with atomic numbers ranging from 1 to 26 and energies from 80 up to 1000 MeV/n. The influence of different physics configurations in the simulation is also discussed. It is demonstrated that FLUKA can simulate energy deposition patterns of ions in TEPC cavities accurately and that it provides an adequate description of the main features of the spectra.

  19. 3He Spin Filter for Neutrons

    Batz, M.; Baeßler, S.; Heil, W.; Otten, E. W.; Rudersdorf, D.; Schmiedeskamp, J.; Sobolev, Y.; Wolf, M.

    2005-01-01

    The strongly spin-dependent absorption of neutrons in nuclear spin-polarized 3He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable 3He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A short survey of their use under experimental conditions, e.g. large solid-angle polarization analysis, is given. In neutron particle physics NSFs are used in precision measurements to test fundamental symmetry concepts.

  20. X-rays from pionic 3He

    Pionic X-ray energies, lorentzian widths, and relative intensities have been measured for the transitions in liquid 3He. The pion-nucleus interaction is found to result in an attractive shift of the 1s level of 27 +- 5 eV and in a lorentzian width of 65 +- 12 eV. The measured Ksub(β) to Ksub(α) intensity ratio is 1.05 +- 0.07. (Auth.)

  1. Size effects in superfluid 3He

    The superfluid density and transition temperature of 3He filling the pores of packed alumina powder have been measured by fourth sound. The measurements were performed simultaneously for three separate fourth sound resonators, each packed with a different nominal grain size of 1.0 μm. 0.3 μm and 0.05 μm. The bulk 3He superfluid transition temperature, which was determined independently, was compared to the transition temperature of each resonator. We observed a systematic depression for both the superfluid density and transition temperature as the powder size was decreased. The depressions in the transition temperature were compared with theoretical estimates of size dependent transition temperatures for the ideal geometry of an infinite cylinder. In the analysis the cylinder radius was replaced by defining an average radius of the pore structure which was empirically determined by nitrogen gas sorption and mercury intrusion techniques. The pressure dependence of the transition temperature depression is found to be consistent with theoretical estimates of the superfluid coherence length. The experimentally determined magnitude of the coherence length based on the pore structure analysis is in agreement with theoretical estimates, confirming that the coherence length of superfluid 3He is about two orders of magnitude larger than that of He II

  2. The response functions of a 3He Bonner Spectrometer and their experimental verification in high energy neutron fields

    The neutron response functions for a Bonner Sphere Spectrometer (BSS) with 3He proportional counter were calculated employing the MCNP and LAHET Monte Carlo codes for the neutron energy range from 10 MeV to 1 GeV. The MCNP calculations were extended up to 100 MeV using the neutron cross-sections from the transport data libraries LA-100 of LANL. The effect of the different physics models implemented in the LAHET code on the response of the Bonner spectrometer are documented and the possible reasons are discussed. The MCNP and LAHET results are also compared with calculations using the Monte Carlo high energy transport code HADRON. Verification experiments were conducted at the CERN high energy calibration facility which gave some insight to the question how appropriate the physical models are which are used for the calculation of the BSS responses. (author)

  3. Coupling between Solid 3He on Aerogel and Superfluid 3He in the Low Temperature Limit

    We have cooled liquid 3He contained in a 98% open aerogel sample surrounded by bulk superfluid 3He-B at zero pressure to below 120 μK. The aerogel sample is placed in a quasiparticle blackbody radiator cooled by a Lancaster-style nuclear cooling stage to ∼200 μK. We monitor the temperature of the 3He inside the blackbody radiator using a vibrating wire resonator. We find that reducing the magnetic field on the aerogel sample causes substantial cooling of all the superfluid inside the blackbody radiator. We believe this is due to the demagnetization of the solid 3He layers on the aerogel strands. This system has potential for achieving extremely low temperatures in the confined fluid

  4. Development of cylindrical type proton-recoil proportional counter and its use for absolute measurements of neutron fluences at 144, 250 and 565 keV monoenergetic calibration fields

    A proton-recoil proportional counter has been developed as a standard instrument for measuring neutron fluence at an accelerator-based neutron calibration field. The counter consists of a cylindrical cathode and an external housing in which hydrogen is filled as counting gas. For neutrons in the energy range between 50 keV and 1 MeV, the fluence of the neutron field can be determined by an absolute measurement with the counter. In designing and manufacturing the counter, careful attention has been paid in order to reduce the uncertainty in measured results. For example, the volume of the effective region of the counter was investigated as accurately as possible. The optimum applied voltage for the counter was examined precisely through the electric field analysis. The developed counter was used for determining the reference neutron fluence of the monoenergetic neutron fields at the Facility of Radiation Standards of JAEA. For the 144, 250 and 565 keV neutron fields, it has been able to measure the fluences with the standard uncertainties less than 2%. The measured fluences for 144 and 565 keV have showed good agreement with the values estimated by another measurements with a transfer instrument traceable to primary standards. (author)

  5. Pion absorption in flight on 3He

    Pion absorption in flight on 3He has been measured in a kinematically complete manner. The experiment was done in the πE1-channel at the Swiss Institute for Nuclear Research, SIN, using π+- and π--beams of 120 and 165 MeV kinetic energy. Two of the emitted particles were measured in coincidence and identified by their time-of-flight/pulseheight relation. The obtained two-dimensional energy representation enabled a separation of the different kinematical regions and exhibited a clear enhancement in the region of quasifree absorption, QFA. (orig./WL)

  6. 3He and 4f instable compounds

    The high localization of the 4f electron and the possibility of a weak delocalization through the coupling with the itinerant electrons lead to Fermi liquid properties. With the example of CeAl3, the main role of the coherence between the Ce is emphasized at low temperature. Thermal dilatation data show the transition from a regime of almost independent Kondo centers to a regime of coherent Kondo centers. The occurence of the superconductivity in the heavy fermion CeCu2Si2 is discussed and compared to the superfluidity of liquid 3He

  7. A development of NRESPG Monte Carlo code for the calculation of neutron response function for gas counters

    A Monte Carlo code Neutron RESPonse function for Gas counters (NRESPG) has been developed for the calculation of neutron response functions and efficiencies for neutron energies up to 20 MeV, which can be applied for 3He, H2, or BF3 gas proportional counters with or without moderator. This code can simulate the neutron behavior in a two-dimensional detector configuration and treat the thermal motion of a moderator atom which becomes important as the neutron energy becomes sufficiently low. Further, a more precise measured data was taken to simulate the position-dependent gas multiplication in the sensitive and insensitive gas region of a proportional counter. The NRESPG code has been applied for the calculation of response functions of 3He cylindrical proportional counters to determine neutron energy and neutron fluence in a monoenergetic calibration field. Thus, a remarkable discrepancy in the lower portion of the full-energy peak produced by the 3He(n,p)T reaction can be removed which results in a good agreement between simulations and experiments. The code has been also used for the simulation of the response of a McTaggart-type long counter consisting of a central cylindrical BF3 counter surrounded by a polyethylene moderator. The results of the NRESPG simulations were compared with those obtained from MCNP calculations

  8. A development of NRESPG Monte Carlo code for the calculation of neutron response function for gas counters

    Takeda, N. [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba-shi, Ibaraki 305-8568 (Japan); Kudo, K. [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba-shi, Ibaraki 305-8568 (Japan); Toyokawa, H. [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba-shi, Ibaraki 305-8568 (Japan); Torii, T. [Japan Power Reactor and Nuclear Fuel Development Corporation, Tsuruga Office, Fukui 919-12 (Japan); Hashimoto, M. [Japan Power Reactor and Nuclear Fuel Development Corporation, O-arai Engineering Center, Ibaraki 311-13 (Japan); Sugita, T. [Science System Laboratory, Ibaraki 309-17 (Japan); Dietze, G. [Physikalisch-Technische Bundesanstalt, 38023 Braunschweig (Germany); Yang, X. [China Institute of Atomic Energy (China)

    1999-02-11

    A Monte Carlo code Neutron RESPonse function for Gas counters (NRESPG) has been developed for the calculation of neutron response functions and efficiencies for neutron energies up to 20 MeV, which can be applied for {sup 3}He, H{sub 2}, or BF{sub 3} gas proportional counters with or without moderator. This code can simulate the neutron behavior in a two-dimensional detector configuration and treat the thermal motion of a moderator atom which becomes important as the neutron energy becomes sufficiently low. Further, a more precise measured data was taken to simulate the position-dependent gas multiplication in the sensitive and insensitive gas region of a proportional counter. The NRESPG code has been applied for the calculation of response functions of {sup 3}He cylindrical proportional counters to determine neutron energy and neutron fluence in a monoenergetic calibration field. Thus, a remarkable discrepancy in the lower portion of the full-energy peak produced by the {sup 3}He(n,p)T reaction can be removed which results in a good agreement between simulations and experiments. The code has been also used for the simulation of the response of a McTaggart-type long counter consisting of a central cylindrical BF{sub 3} counter surrounded by a polyethylene moderator. The results of the NRESPG simulations were compared with those obtained from MCNP calculations.

  9. A density functional for liquid 3He

    We present a density functional for the description of liquid 3He properties at zero temperture in a mean field approximation. Its basic ingredients are a zero-range, particle- and spin-density dependent effective interaction of Skyrme type, and a long-range effective interaction of Lennard-Jones type supplemented with a weighted density approximation similar to the one used in the study of classical fluids, to phenomenologically account for short range correlations. After fixing the value of its parameters, the functional yields a good desription of the equation of state and Landau parameters (spin symmetric and spin antisymmetric as well) from saturation to solidification densities. The zero sound propagation at finite momentum transfer is quantitatively reproduced up to the Fermi momentum, and qualitatively above it. The surface tension is in agreement with experiment, which makes the functional well suited for 3He drop calculations. We describe the structure of drops made of up to 516 atoms. As a novel application, we discuss the possible appearance of triplet pairing in a nl-shell of a drop applying the formalism to the 1j-shell holding up to 30 atoms from N=169 to 198. (orig.)

  10. Duoplasmatron source modifications for 3He+ operation

    A duoplasmatron ion source is used to produce 25 mA of 3He+ with a pulse width of ∼80ms at 360 Hz for acceleration to 10.5 MeV. At this energy, 3He striking water or carbon targets can produce short lived isotopes of 11C, 13N, 15O, and 18F for medical positron emission tomography (PET). A duoplasmatron ion source was chosen originally since it is capable of a sufficient singly charged helium beam with an acceptable gas consumption. Stable long-term operation of the source required a change in the filament material to molybdenum, and a careful understanding of the oxide filament conditioning, operation and geometry. Other improvements, particularly in the electronics, were helpful to increasing the reliability. The source has operated for many months at ∼2.5% duty factor without significant problems and with good stability. We report here the effort that was done to make this source understandable and reliable

  11. New proportional counter for in vivo detection of traces of plutonium in the lungs; Nouveau compteur proportionnel destine a la detection in vivo de traces de plutonium dans les poumons

    Morucci, J. [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

    1966-07-01

    Development of a multi-wire proportional counter having a uniform response over 250 cm{sup 2} 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) [French] Etude et mise au point d'un compteur proportionnel multifils de reponse utile homogene sur une surface de 250 cm{sup 2} grace a la correction des effets de bords et de faible mouvement propre par cm{sup 2} grace a deux compteurs identiques montes en anticoincidence dans la meme enceinte. (auteur)

  12. Formation of 3He droplets in dilute 3He-4He solid solutions

    Huan, Chao; Candela, Don; Kim, Sung; Yin, Liang; Xia, Jiang-Sheng; Sullivan, Neil

    2015-03-01

    We review the different stages of the formation of 3He droplets in dilute solid 3He-4He solutions. The studies are interesting because the phase separation in isotopic helium mixtures is a first-order transition with a conserved order parameter. The rate of growth of the droplets as observed in NMR studies is compared with the rates expected for homogeneous nucleation followed by a period of coarsening known as Ostwald ripening. Work suported by the National Science Foundation - DMR-1303599 and DMR- 1157490 (National High Magnetic Field Laboratory).

  13. Proportionality lost - proportionality regained?

    Werlauff, Erik

    often cannot be done without thorough knowledge of the particular legal field in which the case is anchored, and the ECJ is often left to flounder somewhat on this, with the result that we are suddenly faced with the Court’s acceptance of a restriction. The difficulty often lies - not in recognising the...... restriction, but in testing its proportionality. The article illustrates its point by referring to two categories of decision: (A) proportionality-strong decisions, which illustrate a thorough and firm proportionality assessment, and (B) proportionality-weak decisions, which could have led to a different...... result if the proportionality argument had been based on adequate insight. Proportionality-weak decisions are in the article be categorised as: (1) Cases in which the ECJ allows itself to be “talked into” accepting a restriction, and for which the question of proportionality actually has been considered...

  14. First observation of two hyperfine transitions in antiprotonic 3He

    We report on the first experimental results for microwave spectroscopy of the hyperfine structure of p-bar3He+. Due to the helium nuclear spin, p-bar3He+ has a more complex hyperfine structure than p-bar4He+, which has already been studied before. Thus a comparison between theoretical calculations and the experimental results will provide a more stringent test of the three-body quantum electrodynamics (QED) theory. Two out of four super-super-hyperfine (SSHF) transition lines of the (n,L)=(36,34) state were observed. The measured frequencies of the individual transitions are 11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current theoretical values, but still within their estimated errors. Although the experimental uncertainty for the difference of these frequencies is still very large as compared to that of theory, its measured value agrees with theoretical calculations. This difference is crucial to be determined because it is proportional to the magnetic moment of the antiproton.

  15. Study of response of 3He detectors to monoenergetic neutrons

    In the search of a hybrid system (the coupling of the particle accelerator to an under-critical reactor) for radioactive waste transmutation the TARC (Transmutation by Adiabatic Resonance Crossing) program has been developed. Due to experimental limitations, the time-energy relation at higher neutron energies, particularly, around 2 MeV, which is an important domain for TARC, cannot be applied. Consequently the responses of the 3He ionization neutron detector developed for TARC experiment have been studied using a fast monoenergetic neutron source. The neutrons were produced by the interaction of the proton delivered by Van de Graaff accelerator of CENBG. The originality of the detector consists in its structure of three series of electric conductors which are mounted around the anode: a grid ensuring the detector proportionality, a cylindrical suit of alternating positive voltage and grounded wires aiming at eliminating the radial end effects, serving as veto and two cylinders serving as end plugs to eliminate the perpendicular end effects. Examples of anode spectra conditioned (in anticoincidence) by the mentioned vetoes are given. One can see the contribution of the elastic scattering from H and 3He. By collimating the neutron beam through a borated polyethylene system it was possible to obtain a mapping of the detector allowing the study of its response as a function of the irradiated zones (anode and grid)

  16. Neutron pileup algorithms for multiplicity counters

    Robinson, Sean M.; Stave, Sean; Lintereur, Azaree; Siciliano, Edward; Kouzes, Richard; Bliss, Mary

    2015-06-01

    The shortage of helium-3 (3He) has created a need to identify alternative neutron detection options for a variety of nuclear nonproliferation applications. One application that may be affected by 3He replacement technology is that of mass accountancy for safeguards, which utilizes coincidence and multiplicity counters to verify special nuclear material declarations. The use of neutron scintillation materials, such as LiF-ZnS sheets, as an alternative to 3He proportional tubes in multiplicity counters requires novel techniques for Pulse Shape Discrimination to distinguish between neutrons and gamma rays. These techniques must work under high count rates, as the maximum momentary rate for incoming neutrons from multiplicity events can be quite large. We have created a fast and accurate neutron discrimination algorithm based on time window filtering and signature comparison that can operate quickly on data with high degrees of gamma ray and neutron pileup. This algorithm is evaluated for its capability to separate signals as the pileup rate increases, and the possibility for implementation on fast hardware (e.g., FPGA hardware) for real-time operation is explored.

  17. Development of NRESP98 Monte Carlo codes for the calculation of neutron response functions of neutron detectors. Calculation of the response function of spherical BF{sub 3} proportional counter

    Hashimoto, M.; Saito, K.; Ando, H. [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1998-05-01

    The method to calculate the response function of spherical BF{sub 3} 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 BF{sub 3} 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)

  18. Low temperature adsorption of 3He on silica aerogel surface and its influence on 3He spin kinetics

    Significant influence of the aerogel surface heterogeneity on the processes of 3He nuclear magnetic relaxation at temperatures 1.5 − 4.2 K is discovered. This influence appears, for instance, in differences of the 3He T1 relaxation times for small portion of 3He, adsorbed at different temperatures. Binding energy data of 3He and distributions of this energy in two types of aerogel were obtained experimentally. Adsorbed 3He molecules with binding energies 60 – 250 K play supreme role in processes of nuclear magnetic relaxation of gaseous and liquid 3He in aerogel.

  19. Critical opalescent light scattering from 3He

    The experimental work reported in this paper was stimulated by the widespread revival of interest in critical phenomena. In this experiment the authors measured the intensity of light scattered from 3He while very slowly warming the sample at constant pressure through the critical region. About 0.3 mW from a helium-neon laser was incident on the cell; cell temperature was recorded continuously, as was the light scattered at 45 degrees and 135 degrees. A succession of passes was made at different pressures, all less than c, so these results apply only in the one-phase region above the critical point. Sample density at the beginning of a pass began at ρ > c, then decreased as the sample warmed to ρ c. The scattering intensity increased monotonically as the molar density decreased toward the critical density, then decreased monotonically thereafter on that isobaric pass. The scattering maximum on each pass occurred at the temperature max where the isothermal compressibility was a maximum. The asymptotic divergence of T was evaluated along the locus of these maxima

  20. Possibility of optically pumped 3He as an internal target

    A number of techniques can be listed for obtaining polarized 3He nuclei. This paper focuses only on direct optical pumping of 3He(3S1) with collisional transfer to 3He. A comprehensive review is not attempted. The basic aspects of the method are presented followed by a discussion of only the most recent work

  1. sup 3 He- sup 3 He dating: A case for mixing of young and old groundwaters

    Kamensky, I.L.; Tolstikhin, I.N. (Kola Science Center (Russian Federation)); Tokarev, I.V. (Leningrad Mining Inst., St. Petersburg (Russian Federation))

    1991-10-01

    {sup 3}He/{sup 4}He and {sup 20}Ne/{sup 4}He ratios were measured in shallow underground waters (opened by water-supplying wells) of the Large Vud-Javr intramountain artesian basin in the Khibiny alkaline massif, the Kola Peninsula. The ratios vary from 1.321 {times} 10{sup {minus}6} to 2.065 {times} 10{sup {minus}6} and from 1.412 to 2.941, respectively, and a well-defined correlation is observed between them. Both these ratios in aquifers are known to be time-dependent, the former increases with time due to accumulation of {sup 3}He, produced in waters by {sup 3}H {beta}-decay; the latter decreases due to migration of helium from water-bearing rocks into the waters. The correlation is interpreted as a result of the mixing of two different types of waters. The approximation line enables the authors to estimate the isotopic ratios for the endmembers participating in the mixing and the mean residence time ({tau}) of tritigenic helium-3 in the water: (1) {sup 3}He/{sup 4}He = 3.655 {times} 10{sup {minus}6}, {sup 20}Ne/{sup 4}He = 4.03, and taking into consideration {sup 3}H concentrations in the well waters, {sup 3}H = 31.1 TU (practically the same for all samples), {tau} = 15.8 {plus minus} 1.5 years for the young water; (2) {sup 3}He/{sup 4}He = 0.20 {times} 10{sup {minus}6}, {sup 20}Ne/{sup 4}He = 0.18 and T = 0.11 Ma for the old one, the contribution of the old water being less than 10%. In one well a considerable contribution of modern-day meteoric water, about 16%, is observed.

  2. Negative pion absorption at rest in 3He

    The pnn and dn final states after the absorption of stopped pions in 3He have been measured in a kinematically complete experiment covering the whole phase space. Proton-neutron, deuteron-neutron, and neutron-neutron coincidences have been detected with a charged-particle hodoscope and large-area time-of-flight counters. For the first time, triple coincidences between the pionic K x rays and two particles have been measured thus selecting absorption from the atomic 1s state. It has been found that the absorption is dominated by the two-nucleon mechanism (2NA) on isoscalar nucleon pairs as indicted by the measured ratio of 6.3±1.1 for back-to-back correlated nn and pn pairs. A substantial amount of the three-body final state pnn is affected by the final-state interaction (FSI) or leads to the two-particle final state dn. Ratios of 3.1±0.4 for 2NA to FSI and of 4.2±0.6 for the pnn to the dn final state are measured. No evidence has been found for three-nucleon absorption with an upper limit of %/πstop-

  3. Acoustic and optical investigations of superfluid 3He. Doctoral thesis

    Manninen, A.

    1993-06-15

    The thesis is an experimental survey of properties of rotating and stationary superfluid (3)He. Two techniques, acoustics and optics, were used. Ultrasound, together with NMR, has provided most of the present experimental knowledge about the superfluid phases of (3)He. The author applied acoustics for the first time to study rotating (3)He. The main result was the discovery of a new vortex in (3)He-A when the magnetic field is low. New phenomena were observed in stationary (3)He as well. Most importantly, one of the collective modes, the real squashing (rsq) mode, of (3)He-B could be excited by means of two-phonon absorption. Superfluid (3)He was studied optically for the first time. No one has previously seen (3)He in the superfluid state. The principal achievement was developing techniques which facilitate optical experiments at temperatures below 1 mK, required to study superfluid (3)He. Optical fibers were used to transmit light between room temperature and the cold parts of the cryostat. Before these investigations, photography had not been done below 10 mK. The usefulness of optics as a proble of the superfluid phases of (3)He was demonstrated by studying the macroscopic shape of the free surface of rotating (3)He-B. The classical parabolic meniscus was observed, which is indicative of the equilibrium density of vortices.

  4. Use of proportional counter in X-Ray spectrometry between 5 and 100 keV. Application to the detection of fission products and to the determination of absolute X-Ray disintegration rates

    The measurement of electromagnetic radiations is difficult in the energy range 20-100 keV. We made suitable for this purpose a regular proportional counter, modifying both the nature and pressure of the gaseous mixture filling the detector volume. We selected the CPEN-SAIP counter, which is able to withstand such modifications. In the energy range considered, the counter is to be standardized with radioactive sources. Such standards were selected according to their disintegration schemes. We thus defined the conditions of use (resolution, yield) of the CPN counter, filled with an argon-methane mixture under a pressure of about 3 bars, in the energy range 5-100 keV. With such an equipment, we were able to measure the absolute disintegration rate for the X-rays of 133 Ba and 75 Se, then to perform the study of a mixed fission products sample. In the same way, we used xenon-based gaseous mixtures, in order to improve the detector yield; in the later case, we carefully examined the limitations introduced by the presence of many parasite rays emitted by the gas. We thus displayed in addition to the leakage peak, the fluorescence ray of the gas, whose origin is difficult to explain. (author)

  5. 3He charge form factors by nuclear recoil detection

    3He charge form factors were measured by observing the scattering reaction 3He(e,3He)e from square momentum transfers 0.885 to 3.20 fm-2. The results compare favorably with earlier electron scattering experiments. A model-independent determination of the radial charge density gives an rms radius of 1.877 +- 0.019 fm, in excellent agreement with previous radii determinations

  6. An experimental study of the reaction p + d → 3He + π0 in the Δ(1236) resonance region

    The differential cross section of the reaction p + d → 3He + π0 was measured at an incident proton energy of 462 MeV for 3He cm angles between 50 and 1300. Limited angular distributions were also obtained at 377 and 576 MeV. The 3He particle momentum was measured by using wire spark chambers in conjunction with a total energy absorption scintillation counter. A decay photon from the π0 was detected in a lead glass Cherenkov counter. The results are discussed in terms of a two-nucleon model and a OPE model of the reaction. The cross section at 462 MeV is also compared with that of its isospin conjugate reaction, p + d → 3H + π+, and agreement with the principle of isospin invariance is satisfactory, except at small pion angles. (U.S.)

  7. 3He Neutron Spin Filter cell development program at JCNS

    In order to produce high-quality 3He Neutron Spin Filters (NSF) with a high polarisation level, it is necessary to achieve a long 3He relaxation time by the reduction of the wall relaxation. This requires one to minimise the amount of impurities at the surface of the glass cells, and to have as few contaminants as possible in the gas filling system. In this report we describe the detailed procedure we employ to produce 3He cells using our newly built filling station. The obtained life times for a number of cells are practically approaching the fundamental limit imposed by the dipole-dipole interaction between 3He atoms.

  8. 3He functions in tokamak-pumped laser systems

    3He placed in an annular cell around a tokamak fusion generator can convert moderated fusion neutrons to energetic ions by the 3He(n,p)T reaction, and thereby excite gaseous lasants mixed with the 3He while simultaneously breeding tritium. The total 3He inventory is about 4 kg for large tokamak devices. Special configurations of toroidal-field magnets, neutron moderators and beryllium reflectors are required to permit nearly uniform neutron current into the laser cell with minimal attenuation. The annular laser radiation can be combined into a single output beam at the top of the tokamak

  9. Measurements of the 3He fusion product in TFTR

    The 0.8-MeV 3He ion created in the d(d,n)3He fusion reaction is confined in TFTR and can undergo d(3He,p)α fusion reactions. The time evolution, and profile of the 14.7-MeV proton emission indicates that collisional energy transfer with plasma electrons is the dominant process influencing the charged 3He fusion product for TFTR plasmas and that there is no observable anomalous transport. The magnitude of the burnup exceeds classical expectations by a factor-of-two-to-three which is a little beyond experimental uncertainties. 19 refs., 11 figs

  10. Polarization phenomena for low energy d + 3He collisions

    Polarization phenomena are studied for the reaction d + 3He → p + 4He (for Ed ≤ 1 MeV) using a formalism of partial amplitudes. The nuclei are considered as elementary particles with definite values of spin and P-parity. A general parametrization of the matrix element in terms of a limited number of partial amplitudes (for d + 3He-interaction in s - and p- states) is given and the expressions for all polarization observables are derived for the s-interaction. Relations between different polarization observables are derived and the conditions for maximizing the differential cross section of the process d + 3He → p + 4He are indicated. The spin structure of the matrix elements of the processes d + 3He → d +3He, d + 3He → n +p + 3He, d + 3He → p + p + 3H and d + 3He → d + d + p is established in the near-threshold region. (author)

  11. Three-body 3He photodisintegration in the Δ region

    Three-body 3He photodisintegration was measured in the photon energy range (Eγ) of 145--425 MeV. The total cross section for photon absorption on the np pairs in 3He, σ(3He(γ,np)psp), where psp is a spectator proton, is reported here for the first time. The Eγ dependence of the σ is found to scale to that of σ(2H(γ,np)), and the ratio is determined to be σ(3He(γ,np)psp)/σ(2H(γ,np))=1.24±0.,26

  12. Search for the K−pp bound state via the in-flight 3He(K−, n reaction

    Sada Y.

    2014-01-01

    Full Text Available In the J-PARC E15 experiment, a K− pp search was performed via the 3He(K−, n reaction at 1.0 GeV/c. A forward-going neutron is detected by a neutron counter with 15 m flight length, and decay particles from K− pp are simultaneously measured by a cylindrical detector system that surrounds a liquid 3He target system. In March and May, 2013, we carried out the first physics data-taking with 5×109 incident kaons on the 3He target, and we have obtained a preliminary exclusive analysis result of 3He(K−, Λpn reaction.

  13. The cosmic-ray He-3/He-4 ratio from 200 MeV per nucleon(-1) to 3.7 GeV per nucleon(-1)

    Reimer, O.; Menn, W.; Hof, M.; Simon, M.; Davis, A.J.; Labrador, A.W.; Mewaldt, R.A.; Schindler, S.M.; Barbier, L.M.; Christian, E.R.; Krombel, K.E.; Mitchell, J.W.; Ormes, J.F.; Streitmatter, R.E.; Golden, R.L.; Stochaj, S.J.; Webber, W.R.; Rasmussen, Ib Lundgaard

    1998-01-01

    The abundances of cosmic-ray helium isotopes between 0.2 and 3.7 GeV nucleon(-1) were measured by the Isotope Matter Antimatter Experiment (IMAX) during a flight from Lynn Lake, Manitoba, Canada on 1992 July 16-17. The IMAX balloon-borne magnetic spectrometer realized a direct measurement of the...... charge, the velocity, and the rigidity of cosmic rays using plastic scintillators, a high-resolution time-of-flight system, and two silica-aerogel Cerenkov counters in conjunction with a drift chamber/multiwire proportional chamber tracking system. About 75,000 helium isotopes are identified by their...... mass using the velocity versus magnetic rigidity technique. The measured He-3/He-4 ratios are corrected to the top of the atmosphere, and a comparison with previous data is given. The observed isotopic composition is found to be generally consistent with the predictions of a standard leaky box model of...

  14. Model formalism of liquid 3He-B at equilibrium

    The approximate formal treatment of the nuclear spin system of normal liquid 3He given some time ago is extended to the ordered 3He phase. The formalism leads to the prediction of normal thermal behavior of 3He-B at lower pressures and at temperatures approaching its phase-boundary temperatures. In contrast to the disordered normal liquid phase, which is thermally anomalous, the entropy of the 3He-B decreases on isothermal compression, or its isobaric volume expansion coefficient is positive. The equilibrium thermal behavior of ordered 3He-B is thus qualitatively different from that of disordered liquid 3He. Experimental control of these aspects of the liquid 3He phase transformation is lacking at the present time. Both early and new 3He-B paramagnetic susceptibility data, extended recently over a wide reduced-temperature range, disclose a fundamental competition between the spontaneous ordering mechanism responsible for the existence of 3He-B and the specific ordering process imposed upon this phase on application of an external constant and uniform magnetic field. As a consequence, magnetized 3He-B will be shown to increase its entropy on isothermal magnetization and to cool on adiabatic magnetization. The magnetocaloric effect is, however, only moderate. The competition of the ordering process leads to the delay or possibly even to the suppression of the formation of the ordered phase, a state of affairs foreseen in our earlier work. At low or moderate magnetic field strengths, the zero-field phase-boundary temperatures are shown to shift toward lower temperatures while, simultaneously, the order of the phase change decreases, from second order, in the absence of the field, to first order. Although of model-theoretic character, involving limitations of various types, the rich physical content of 3He-B at equilibrium clearly emerges in the present work

  15. magnetic resonance of 3He nuclei in porous media

    The data on 3He spin kinetics in porous media above the Fermi temperature of 3He are summarized. Presented results are obtained in Kazan Federal University in last ten years and are the base of developing method of helium porometry. Guidelines for investigation of samples with unknown pore sizes and superficial their properties are proposed

  16. 3He(3H,γ)6Li

    The authors have calculated the 3He(3H,γ)6Li reaction rate at big bang temperatures based on a microscopic study in the framework of the Generator Coordinate Method. It is discussed whether 6Li could be made by 3He + 3H fusion in the early epoch of our universe

  17. Some new NMR effects in superfluid 3He--A

    Longitudinal and transverse satellite lines have been observed by CW techniques in superfluid 3He-A under a variety of experimental conditions. A new metastable mode has been observed in superfluid 3He-A using pulsed NMR techniques. The frequency shift of this mode is related to the frequency shift of the transverse satellite line

  18. Ions Preheated in 3He-Rich Solar Particle Events

    王德焴

    2003-01-01

    A wave-particle resonance absorption model in the two-ion plasma is suggested in explanation to the coronal ions preheating in 3He-rich solar particle events. It is found that 3He and Fe ions are preferably preheated by the ion-ion hybrid waves at their fundamental and second harmonic ion cyclotron frequencies, respectively.

  19. Pulsed NMR experiments in superfluid 3He confined in aerogel

    Pulsed NMR experiments have been performed in both B and supercooled A phases of superfluid 3He in aerogel. Dependencies of spin precession frequency on tipping angle in B-phase of superfluid 3He in aerogel are found to be different for pure 3He and for the cell preplated with 4He. A sharp increase of the frequency for tipping angles greater than 104 deg. was observed in low temperature superfluid phase of 3He in 4He preplated aerogel as it is expected for the B-phase structure of the order parameter. Dependencies of the frequency on the tipping angle in supercooled A-phase are similar for both pure 3He and 4He preplated aerogel

  20. Feasibility studies of D—3He fusion power in China

    DengBai-Quan; FengKei-Ming; 等

    1997-01-01

    The systematic study on D-3He advanced fuel fusion in China has been performed.Comparisons between D-3He and D-T fuel cycles in physics,engineering,environmental safety and so on have been made.D-3He fusion offers significant adavantages for reducing the neutron yield by a factor of 10-60,The 3He resource and mining possibility are investigated.The energy payback factor of 97 for mining lunar 3He resource is calculated.The operating parameter scope for D-3He fueled Tokamak reactor is analyzed.The prompt energy broadening for fusion products is calculated and results are consistent with those obtained by Lehner using a different method.Centrally peaked current drive with high efficiency is studied utilizing plasma synchrotron radiation.Centrally peaked current drive with gigh efficiency is studied utilizing plasma synchrotron radiation.More than 80% of plasma current required can be driven passively.A D-3He fueled Tokamak commercial reactor-Mooncity was designed.Neutronics calculations show that the radioactivity,afterheat,BHP value for Mooncity are 10-60 times less than those for D-T fusion.

  1. Cosmogenic and nucleogenic ^3He in apatite, titanite, and zircon

    Farley, K. A.; Libarkin, J.; Mukhopadhyay, S; Amidon, W.

    2006-01-01

    Cosmogenic ^3He was measured in apatite, titanite, and zircon and cosmogenic ^(21)Ne in quartz at 13 depth intervals in a 2.7-m long drill core in a Miocene ignimbrite from the Altiplano of Bolivia. All three ^3He depth profiles as well as the ^(21)Ne profile attenuate exponentially with depth, indicating that both of these isotopes are cosmogenic in origin with no significant contribution from other sources. The attenuation lengthscale for ^3He production of Λ = 180 ± 11 g/cm^2 is consistent...

  2. D-3He fuel cycles for neutron lean reactors

    The intrinsic potential of D-3He as a reactor fuel is investigated for a large range of 3He to D density ratios. A steady-state zero-dimensional reactor model is developed in which much care is attributed to a proper treatment of fast fusion products. Useful ranges of reactor parameters as well as temperature-density windows for driven and ignited operation are identified. Various figures of merit are calculated, such as power densities, net power production, neutron production, tritium load and radiative power. These results suggest several optimistic conclusions about the performance of D-3He as a reactor fuel

  3. Dressed Spin of Polarized 3He in a Cell

    Chu, P H; Peng, J C; Beck, D H; Chandler, D E; Clayton, S; Hu, B Z; Ngan, S Y; Sham, C H; So, L H; Williamson, S; Yoder, J

    2010-01-01

    We report a measurement of the modification of the effective precession frequency of polarized 3He atoms in response to a dressing field in a room temperature cell. The 3He atoms were polarized using the metastability spin-exchange method. An oscillating dressing field is then applied perpendicular to the constant magnetic field. Modification of the 3He effective precession frequency was observed over a broad range of the amplitude and frequency of the dressing field. The observed effects are compared with calculations based on quantum optics formalism.

  4. Coincidence measurements with the use of detectors measuring the energy of the radiances (proportional meters and scintillation counter); Mesures de coincidences avec utilisation de detecteurs mesurant l'energie des rayonnements (compteurs proportionnels et compteur a scintillations)

    Sartory, M. [Commissariat a l' Energie Atomique, Saclay(France). Centre d' Etudes Nucleaires

    1953-07-01

    In the setting of the realization of a set of installations permitting of the measures of coincidences between sorted radiances according to their energies, an installation understanding a proportional counter and a scintillation counter has been constructed and optimized. It has been used to do some measures of coincidences between X{sub K} photons and photons {gamma} issued at the time of the radioactive transformation of the selenium 75 (electronic capture). The efficiency of the proportional meter has been determined roughly. Besides, a proportional counter of solid angle neighboring of 4{pi} was able to achieve measures of coincidences while only doing one selection of amplitudes: indeed, the simultaneity of the detection of two radiances appear by an impulse whose amplitude is the sum of the amplitudes of the impulses resulting from each of the studied radiations. This method, applied to the coincidences between X-rays, permitted to bring the information on the diagram of decay of the arsenic 73. Besides, the coefficient of internal conversion of a consecutive transition to this decay has been valued. (author) [French] Dans le cadre de la realisation d'une serie de montages permettant des mesures de coincidences entre rayonnements tries d'apres leurs energies, un montage comprenant un compteur proportionnel et un compteur a scintillations a ete construit et mis au point. Il a ete utilise pour effectuer quelques mesures de coincidences entre photons X{sub K} et photons {gamma} emis lors de la transformation radioactive du selenium 75 (capture electronique). L'efficacite du compteur proportionnel a ete approximativement determinee. De plus, un compteur proportionnel d'angle solide voisin de 4{pi} a pu etre utilise pour realiser des mesures de coincidences en n'effectuant qu'une selection d'amplitudes: en effet, la simultaneite de la detection de deux rayonnements se manifeste par une impulsion dont l'amplitude est la

  5. Magnetization and spin diffusion of liquid 3He in aerogel

    We report theoretical calculations and experimental measurements of the normal-state spin diffusion coefficient of 3He in aerogel, including both elastic and inelastic scattering of 3He quasiparticles, and compare these results with data for 3He in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase in the same aerogel samples provide a test of the theory of pairbreaking and magnetic response of low-energy excitations in the 'dirty' B phase of 3He in aerogel. A consistent interpretation of the data for the spin-diffusion coefficient, magnetization, and superfluid transition temperature is obtained by including correlation effects in the aerogel density

  6. Applications of 3He neutron spin filters at the NCNR

    At the NIST Center for Neutron Research (NCNR), we have applied 3He neutron spin filters (NSFs) to the instruments where 3He NSFs are advantageous, such as thermal triple-axis spectrometry, small-angle neutron scattering, and diffuse reflectometry. We present the status of our development and application of this method, including polarized gas production by spin-exchange optical pumping, magnetostatic cavities for storage of the polarized gas on the beam line, and nuclear magnetic resonance (NMR)-based, on-line monitoring and reversal of the 3He polarization. We present the status of developing user-friendly interfaces incorporated into the instrument software to handle these 3He neutron spin filters while taking data and performing data analysis. Finally we discuss the status of development of a polarization capability on the multi-axis crystal spectrometer, which requires polarization analysis over a 220 deg. angular range.

  7. Electromagnetic physics with a polarized 3He target

    In the trinucleon system, 3He is preferable for polarization measurements because it is stable and a well-understood polarization method exists. Also, to a good approximation, the 3He spin is effectively due to the spin of its neutron and hence acts as a polarized neutron target. This is important because dense targets of polarized free neutrons are not possible. Thus, in a simple-minded picture, one can think of polarization measurements on 3He as a means of tagging the neutron in this nucleus. In a general program of polarization measurements on the proton, deuteron, and 3He, one could investigate the form-factors and small wave-function components of the nucleon and its excited states in the nuclear medium. (orig./WL)

  8. The 3He spectral function in light-front dynamics

    Rinaldi, Matteo; Kaptari, Leonid; Pace, Emanuele; Salmè, Giovanni; Scopetta, Sergio

    2016-01-01

    A distorted spin-dependent spectral function for 3He is considered for the extraction of the transverse-momentum dependent parton distributions in the neutron from semi-inclusive deep inelastic electron scattering off polarized 3He at finite momentum transfers, where final state interactions are taken into account. The generalization of the analysis to a Poincar\\'e covariant framework within the light-front dynamics is outlined.

  9. Neutron orbital structure from generalized parton distributions of 3He

    Rinaldi, M; Scopetta, S.

    2012-01-01

    The generalized parton distribution H and E of the 3He nucleus, which could be measured in hard exclusive processes, such as coherent deeply virtual Compton scattering, are thoroughly analyzed in impulse approximation, within the Av18 interaction. It is found that their sum is dominated to a large extent by the neutron contribution: The peculiar spin structure of 3He makes this target unique for the extraction of the neutron information. This observation could allow to access for the first ti...

  10. Extracting generalized neutron parton distributions from 3He data

    Rinaldi, M; Scopetta, S.

    2012-01-01

    An impulse approximation analysis is described of the generalized parton distributions (GPDs) H and E of the 3He nucleus, quantities which are accessible in hard exclusive processes, such as coherent deeply virtual Compton scattering (DVCS). The calculation is based on the Av18 interaction. The electromagnetic form factors are correctly recovered in the proper limits. The sum of the GPDs H and E of 3He, at low momentum transfer, is largely dominated by the neutron contribution, thanks to the ...

  11. Analytic vortices in rotating superfluid 3He-A

    Recent works on analytic vortices in rotating 3He-A are reviewed. It is shown that the circular-hyperbolic vortex lattice has the lowest free energy in an axial magnetic field. The associated nuclear magnetic resonance satellites account for not only the observed satellite frequencies in a rotating 3He-A experiment but also the observed intensity of the satellite resonances. 15 references, 3 figures

  12. Elastic and charge exchange scattering of pions from 3He

    Elastic and charge exchange scatterings of pions from 3He are studied using on optical potential in the momentum representation, which includes the second order effect as well as the nucleon binding correction. These corrections are found to be appreaciable but still not enough to resolve the discrepancy between theoretical calculations and recent experimental data on the reaction 3He(π-, π0)3H. (author)

  13. Test of 3He-based neutron polarizers at NIST

    Neutron spin filters based on polarized 3He are useful over a wide neutron energy range and have a large angular acceptance among other advantages. Two optical pumping methods, spin-exchange and metastability-exchange, can produce the volume of highly polarized 3He gas required for such neutron spin filters. We report a test of polarizers based on each of these two methods on a new cold, monochromatic neutron beam line at the NIST Center for Neutron Research

  14. The SLAC high-density gaseous polarized 3He target

    A large-scale high-pressure gaseous 3He polarized target has been developed for use with a high-intensity polarized electron beam at the Stanford Linear Accelerator Center. This target was used successfully in an experiment to study the spin structure of the neutron. The target provided an areal density of about 7 x1021 nuclei/cm2 and operated at 3He polarizations between about 30% and 40% for the six-week duration of the experiment

  15. Polar Phase of Superfluid (3)He in Anisotropic Aerogel.

    Dmitriev, V V; Senin, A A; Soldatov, A A; Yudin, A N

    2015-10-16

    We report the first observation of the polar phase of superfluid (3)He. This phase appears in (3)He confined in a new type of aerogel with a nearly parallel arrangement of strands which play the role of ordered impurities. Our experiments qualitatively agree with theoretical predictions and suggest that in other systems with unconventional Cooper pairing (e.g., in unconventional superconductors) similar phenomena may be found in the presence of anisotropic impurities. PMID:26550884

  16. Electroproduction of low energy π+ from 3He

    Differential cross sections were measured for the electro-pion production from H and 3He at an incident energy of 200 MeV and pion energies from 7.3 to 12.1 MeV. Pion-angular distributions are presented and compared with theory. For hydrogen there is good agreement. A simple three-channel calculation performed for the pion production from 3He was found to over estimate the cross section at forward pion angles

  17. The (t,3He) and (3He,t) reactions as probes of Gamow-Teller strength

    Zegers, R G T; Austin, S M; Bazin, D; Berg, G P A; Brown, B A; Cole, A L; Daito, I; Fujita, Y; Fujiwara, M; Galès, Sydney; Harakeh, M N; Hashimoto, H; Hayami, R; Hitt, G W; Howard, M E; Itoh, M; Jänecke, J; Kawabata, T; Kawase, K; Kinoshita, M; Nakamura, T; Nakanishi, K; Nakayama, S; Okamura, S; Richter, W A; Roberts, D A; Sherrill, B M; Shimbara, Y; Steiner, M; Uchida, M; Ueno, H; Van den Berg, A M; Yamagata, T; Yosoi, M; Austin, Sam M.

    2006-01-01

    Charge-exchange reactions are an important tool for determining weak-interaction rates. They provide stringent tests for nuclear structure models necessary for modeling astrophysical environments such as neutron stars and core-collapse supernovae. In this paper we demonstrate via a study of 26Mg(t,3He) that the (t,3He) reaction at 115 MeV/nucleon is an accurate probe for extracting Gamow-Teller strengths. This study is complemented by 26Mg(3He,t) data taken at 140 MeV/nucleon which allows for a comparison of T=2 analog states excited via the mirror reactions. A good correspondence is found between Gamow-Teller distributions measured via the 26Mg(3He,t) and 26Mg(p,n) experiments, indicating probe-independence of the strength extraction. Results from 26Mg(t,3He) and 26Mg(d,2He) also display good correspondence, showing that with the (t,3He) reaction a new tool has become available for studying Gamow-Teller strengths in the beta+ direction. Furthermore, we test shell-model calculations using the new USD-05B inte...

  18. Experimental Search for μd 3He Fusion

    The vast majority of muon catalyzed fusion research has been concerned with muonic molecules of hydrogen isotopes only, since the dynamics of higher-Z muonic atoms in general preclude the formation of molecular systems. In the specific case of hydrogen-helium mixtures, bound muonic molecular states can exist, and thus it is possible to search for the reactionμd 3Heλ-tilde fμ+α(3.66 MeV)+p(14.64 MeV).Until recently, the theoretical predictions for the nuclear fusion rate in the μd 3He molecule, λ-tildef, ranged over one order of magnitude, from 105 to 106 per second. An experimental upper limit has been measured for λ-tildef in HD + 3He giving a value (4 s-1 [1]). We report on the analysis of an experiment in D2 + 3He which has shown a signal coming either from the muon catalyzed reaction, or from the fusion in flight of 3He's formed from dμd fusion.

  19. Light-Front Dynamics and the 3He Spectral Function

    Pace, Emanuele; Kaptari, Leonid; Rinaldi, Matteo; Salme', Giovanni; Scopetta, Sergio

    2016-01-01

    Two topics are presented. The first one is a novel approach for a Poincare' covariant description of nuclear dynamics based on light-front Hamiltonian dynamics. The key quantity is the light-front spectral function, where both normalization and momentum sum rule can be satisfied at the same time. Preliminary results are discussed for an initial analysis of the role of relativity in the EMC effect in 3He. A second issue, very challenging, is considered in a non-relativistic framework, namely a distorted spin-dependent spectral function for 3He in order to take care of the final state interaction between the observed pion and the remnant in semi-inclusive deep inelastic electron scattering off polarized 3He. The generalization of the analysis within the light-front dynamics is outlined.

  20. Asymmetries in electron-induced breakup of polarized 3He

    The Jefferson Lab Experiment E05-102 'Measurement of Ax' and Az' asymmetries in the quasi-elastic 3He(e,e'd) reaction' was performed in Hall A in 2009. The main physics motivation of the experiment was to investigate the effects of small components of the 3He ground-state wave-function by a simultaneous measurement of double-polarization asymmetries in quasi-elastic kinematics for three exclusive channels, (e,e'd), (e,e'p), and (e,e'n), at almost identical momentum transfers, as well as for (e,e'). This experiment will help map the spin structure of the 3He nucleus onto the picture of the ''free'' polarized neutron. As such, it is of great relevance to the polarized-neutron programs at Jefferson Lab and beyond.

  1. Quark-Hadron Duality in Neutron (3He) Spin Structure

    Solvignon, P; Chen, J -P; Choi, Seonho; Aniol, K; Averett, T; Boeglin, W; Camsonne, A; Cates, G D; Chang, G; Chudakov, E; Craver, B; Cusanno, F; Deur, A; Dutta, D; Ent, R; Feuerbach, R; Frullani, S; Gao, H; Garibaldi, F; Gilman, R; Glashausser, C; Gorbenko, V; Hansen, O; Higinbotham, D W; Ibrahim, H; Jiang, X; Jones, M; Kelleher, A; Kelly, J; Keppel, C; Kim, W; Korsch, W; Krämer, K; Kumbartzki, G; LeRose, J J; Lindgren, R; Ma, B; Margaziotis, D J; Markowitz, P; McCormick, K; Meziani, Z -E; Michaels, R; Moffit, B; Monaghan, P; Camacho, C Munoz; Paschke, K; Reitz, B; Saha, A; Sheyor, R; Singh, J; Slifer, K; Sulkosky, V; Tobias, A; Urciuoli, G M; Wang, K; Wijesooriya, K; Wojtsekhowski, B; Woo, S; Yang, J -C; Zheng, X; Zhu, L

    2008-01-01

    We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_1 of the neutron and $^3$He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c)^2. Global duality is observed for the spin-structure function g_1 down to at least Q^2 = 1.8 (GeV/c)^2 in both targets. We have also formed the photon-nucleon asymmetry A_1 in the resonance region for 3He and found no strong Q^2-dependence above 2.2 (GeV/c)^2.

  2. Quark-Hadron Duality in Neutron (3He) Spin Structure

    Solvignon, Patricia; Liyanage, Nilanga; Chen, Jian-Ping; Choi, Seonho; Aniol, Konrad; Averett, Todd; Boeglin, Werner; Camsonne, Alexandre; Cates, Gordon; Chang, C.; Chang, C.C.; Chang, C.; Chang, C.C.; Chudakov, Eugene; Craver, Brandon; Cusanno, Francesco; Deur, Alexandre; Dutta, Dipangkar; Ent, Rolf; Feuerbach, Robert; Frullani, Salvatore; Gao, Haiyan; Garibaldi, Franco; Gilman, Ronald; Glashausser, Charles; Gorbenko, Viktor; Hansen, Jens-Ole; Higinbotham, Douglas; Ibrahim, Hassan; Jiang, Xiaodong; Jones, Mark; Kelleher, Aidan; Kelly, J.; Keppel, Cynthia; Kim, Wooyoung; Korsch, Wolfgang; Kramer, Kevin; Kumbartzki, Gerfried; LeRose, John; Lindgren, Richard; Ma, Bin; Margaziotis, Demetrius; Markowitz, Pete; McCormick, Kathy; Meziani, Zein-Eddine; Michaels, Robert; Moffit, Bryan; Monaghan, Peter; Munoz-Camacho, Carlos; Paschke, Kent; Reitz, Bodo; Saha, Arunava; Sheyor, Ran; Singh, Jaideep; Slifer, Karl; Sulkosky, Vince; Sulkosky, Vincent; Sulkosky, Vince; Sulkosky, Vincent; Tobias, William; Urciuoli, Guido; Wang, Kebin; Wijesooriya, Krishni; Wojtsekhowski, Bogdan; Woo, Seungtae; Yang, Jae-Choon; Zheng, Xiaochao; Zhu, Lingyan

    2008-10-01

    We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_1 of the neutron and $^3$He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c)^2. Global duality is observed for the spin-structure function g_1 down to at least Q^2 = 1.8 (GeV/c)^2 in both targets. We have also formed the photon-nucleon asymmetry A_1 in the resonance region for 3He and found no strong Q^2-dependence above 2.2 (GeV/c)^2.

  3. Quark-Hadron Duality in Neutron (3He) Spin Structure

    We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g1 of the neutron and 3He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c)2. Global duality is observed for the spin-structure function g1 down to at least Q2=1.8 (GeV/c)2 in both targets. We have also formed the photon-nucleon asymmetry A1 in the resonance region for 3He and found no strong Q2 dependence above 2.2 (GeV/c)2

  4. Ultrasensitive 3He magnetometer for measurements of high magnetic fields

    Nikiel, A; Heil, W; Hehn, M; Karpuk, S; Maul, A; Otten, E; Schreiber, L M; Terekhov, M

    2014-01-01

    We describe a 3He magnetometer capable to measure high magnetic fields (B > 0.1 Tesla) with a relative accuracy of better than 10^-12. Our approach is based on the measurement of the free induction decay of gaseous, nuclear spin polarized 3He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T2* being of order minutes which is achieved for spherical sample cells in the regime of motional narrowing where the disturbing influence of field inhomogeneities is strongly suppressed. The 3He gas is spin polarized in-situ using a new, non-standard variant of the metastability exchange optical pumping. We show that miniaturization helps to increase T2* further and that the measurement sensitivity is not significantly affected by temporal field fluctuations of order 10^-4.

  5. Ultrasensitive 3He magnetometer for measurements of high magnetic fields

    Nikiel, Anna; Blümler, Peter; Heil, Werner; Hehn, Manfred; Karpuk, Sergej; Maul, Andreas; Otten, Ernst; Schreiber, Laura M.; Terekhov, Maxim

    2014-11-01

    We describe a 3He magnetometer capable to measure high magnetic fields ( B> 0.1 T) with a relative accuracy of better than 10-12. Our approach is based on the measurement of the free induction decay of gaseous, nuclear spin polarized 3He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T2 ∗ being of order minutes which is achieved for spherical sample cells in the regime of "motional narrowing" where the disturbing influence of field inhomogeneities is strongly suppressed. The 3He gas is spin polarized in situ using a new, non-standard variant of the metastability exchange optical pumping. We show that miniaturization helps to increase T2 ∗ further and that the measurement sensitivity is not significantly affected by temporal field fluctuations of order 10-4.

  6. Probing Bogoliubov Quasiparticles in Superfluid ^3He with a `Vibrating-Wire Like' MEMS Device

    Defoort, M.; Dufresnes, S.; Ahlstrom, S. L.; Bradley, D. I.; Haley, R. P.; Guénault, A. M.; Guise, E. A.; Pickett, G. R.; Poole, M.; Woods, A. J.; Tsepelin, V.; Fisher, S. N.; Godfrin, H.; Collin, E.

    2016-05-01

    We have measured the interaction between superfluid ^3He-B and a micro-machined goalpost-shaped device at temperatures below 0.2 T_c. The measured damping follows well the theory developed for vibrating wires, in which the Andreev reflection of quasiparticles in the flow field around the moving structure leads to a nonlinear frictional force. At low velocities, the damping force is proportional to velocity, while it tends to saturate for larger excitations. Above a velocity of 2.6 mm s^{-1}, the damping abruptly increases, which is interpreted in terms of Cooper-pair breaking. Interestingly, this critical velocity is significantly lower than that reported with other mechanical probes immersed in superfluid ^3He. Furthermore, we report on a nonlinear resonance shape for large motion amplitudes that we interpret as an inertial effect due to quasiparticle friction, but other mechanisms could possibly be invoked as well.

  7. Second sound, osmotic pressure, and Fermi-liquid parameters in 3He-4He solutions

    Second-sound velocities and osmotic pressures are analyzed to obtain the first experimental values for the Landau compressibility parameter F0/sup s/ in 3He-4He solutions. Data are presented as a function of pressure and 3He concentration, and are compared to theoretical predictions. The square of the second-sound velocity at finite temperature is found to be accurately proportional to the internal energy of a perfect Fermi gas. Using inertial effective masses given by the Landau-Pomeranchuk theory, the square of the velocity is found to separate into two parts: a temperature-dependent part characterized completely by ideal Fermi-gas behavior and a temperature-independent part containing all the Fermi-liquid corrections. This is related to a similar separation found in the osmotic pressure

  8. Neutron orbital structure from generalized parton distributions of 3He

    Rinaldi, M

    2012-01-01

    The generalized parton distribution H and E of the 3He nucleus, which could be measured in hard exclusive processes, such as coherent deeply virtual Compton scattering, are thoroughly analyzed in impulse approximation, within the Av18 interaction. It is found that their sum is dominated to a large extent by the neutron contribution: The peculiar spin structure of 3He makes this target unique for the extraction of the neutron information. This observation could allow to access for the first time, in dedicated experiments, the orbital angular momentum of the partons in the neutron.

  9. Neutron orbital structure from generalized parton distributions of 3He

    Rinaldi, M.; Scopetta, S.

    2012-06-01

    The generalized parton distribution H and E of the 3He nucleus, which can be measured in hard exclusive processes such as coherent deeply virtual Compton scattering, are thoroughly analyzed in impulse approximation, within the Av18 interaction. It is found that their sum, at low momentum transfer, is dominated to a large extent by the neutron contribution: the peculiar spin structure of 3He makes this target unique for the extraction of the neutron information. This observation allows access, in dedicated experiments, to the orbital angular momentum of the partons in the neutron.

  10. Removing gaseous contaminants in 3He by cryogenic stripping

    The Tritium Operations Group at LLNL, Tritium Facility has recently developed a 3He recovery system to remove argon, xenon, neon, hydrogen, and all other contaminants from the 3He stream in an Accelerator Production of Tritium (APT) experimental apparatus. In this paper the authors will describe in detail the background information, technical requirements, the design approach, and the results of their experimental tests. The authors believe this gas purification system may have other applications as it provides at a reasonable cost an efficient method for purification of gaseous helium

  11. Rotational quenching of CS in ultracold 3He collisions

    Kaur, Rajwant; Dhilip Kumar, T. J.

    2016-08-01

    Quantum mechanical scattering calculations of rotational quenching of CS (v = 0) collision with 3He are performed at ultracold temperatures and results are compared with isotopic 4He collision. Rotational quenching cross sections and rate coefficients have been calculated in the ultracold region for rotational levels up to j = 10 using the He-CS potential energy surface computed at the CCSD(T)/aug-cc-pVQZ level of theory. The quenching cross sections are found to be two orders of magnitude larger for the 3He than the 4He isotope under ultracold conditions. Wigner threshold law is found to be valid below 10-3 K temperature.

  12. A measurement of the Panofsky ratio in 3He

    The nucleus 3He is one of the simplest nuclear systems; hence it is often used to study the complications introduced by the presence of additional nucleons on basic processes such as pion absorption on a free nucleon. 3He is the only nucleus for which both the pion charge exchange and radiative capture processes can occur at rest with reasonable probability. The ratio of these two processes is the well-known Panofsky ratio, P3 = ω(π-3He→π0T)/ω(π-+3He→γT). (orig./WL)

  13. 3H and 3He electromagnetic form factors

    We report the results of three experiments on elastic electron scattering from 3H and 3He. A detailed description of the experiments and the data obtained is given. We have performed a combined analysis of the world data on 3H and 3He. This analysis gives a complete experimental information on the trinucleon electromagnetic form factors up to q2=30 fm-2, and also provides a separation into the isoscalar and isovector form factors. The results are compared to selected calculations that include nucleonic and mesonic degrees of freedom. ((orig.))

  14. Transport properties of spin polarized 3He-4He mixtures

    We have calculated the viscosity, thermal conductivity, and longitudinal spin diffusion coefficient in 3He-4He mixtures which are spin polarized. The calculation applies to all temperature regimes. We have also calculated the Onsager cross coefficient which arises because of the coupling between heat and longitudinal spin currents. The interaction between 3He quasiparticles is taken to be a constant as a first approximation. We have also investigated the changes brought about by allowing the interaction to vary with the momentum of the quasiparticle

  15. An internal polarized 3He target for electron storage rings

    We describe an internal polarized 3He target currently under construction which will be used in several electron storage ring experiments. The target is based on the technique of metastability exchange laser optical pumping, where the polarized atoms flow into a cryogenically-cooled storage cell. This novel technique allows for high precision measurements where the beam interacts with the pure atomic species. Both the HERMES experiment at DESY and the BLAST detector at the MIT Bates Laboratory will use the polarized 3He target in their measurements. Details of the target system, including the provisions needed to incorporate the target into the electron storage ring, are presented. (orig.)

  16. Surface Waves on the Superfluids ^3He and ^4He

    Manninen, M. S.; Ranni, A.; Rysti, J.; Todoshchenko, I. A.; Tuoriniemi, J. T.

    2016-06-01

    Free surface waves were examined both in superfluids ^3He and ^4He with the premise that these inviscid media would represent ideal realizations for this fluid dynamics problem. The work in ^3He is one of the first of its kind, but in ^4He, it was possible to produce a much more complete set of data for meaningful comparison with theoretical models. Most measurements were performed at the zero temperature limit, meaning Tmonitored as the liquid depth in the cell was varied. Despite of the wealth of data, perfect agreement with the constructed theoretical models could not be achieved.

  17. Ultrasensitive 3He magnetometer for measurements of high magnetic fields

    Nikiel, A.; Blümler, P.; Heil, W.; Hehn, M.; Karpuk, S.; Maul, A.; Otten, E.; Schreiber, L. M.; Terekhov, M.

    2014-01-01

    We describe a 3He magnetometer capable to measure high magnetic fields (B > 0.1 Tesla) with a relative accuracy of better than 10^-12. Our approach is based on the measurement of the free induction decay of gaseous, nuclear spin polarized 3He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T2* being of order minutes which is achieved for spherical sample cells in the regime of motional narrowing whe...

  18. NMR experiments on rotating superfluid 3He-A and 3He-B and their theoretical interpretation

    We have constructed a rotating nuclear demagnetization cryostat and used it for continuous-wave NMR experiments on superfluid 3He-A and 3He-B. The measurements were performed in a long cylindrical geometry of 5 mm diameter, with the cylinder axis parallel to the axis of rotation and with the external magnetic field H/sub O/ = 284 or 142 Oe in the same direction. The angular velocity of rotation Ω was varied between 0.2 and 1.5 rad/sec, and the experiments were done under 29.3 bar pressure at temperatures between T/sub c/ = 2.72 and about 1.4 mK. As a guide to the new and esoteric field of superfluid 3He in rotation, we first review the general theory at some length in relatively simple terms. Pictorial explanations are often given

  19. 3He-MRI of pulmonary ventilation: First clinical applications

    Purpose of the study is the visualisation of normal pulmonary ventilation in healthy volunteers and the evaluation of abnormalities in patients with different lung diseases using 3He magnetic resonance imaging (3He-MRI). Material und methods: Hyperpolarised 3He gas (V=300 ml, p=3x105 Pa, polarised to 35-45% by optical pumping, provided in special glass cells) was inhaled by eight healthy volunteers and ten patients with different lung diseases. A 3 D FLASH sequence (TR=11.8 ms; TE=5 ms; matrix 144x256, FOV 350 mm, section thickness 7-10 mm, coronal orientation) was performed in a single breath-hold (22-42 s). Clinical and radiological examinations were available for correlation. Results: The studies were successfully carried out in 8/8 volunteers and in 8/10 patients. The central airways were constantly visualised with intermediate to high signal instensity. The lung parenchyma of volunteers with normal ventilatory function showed rather homogeneous intermediate to high signal, whereas patients with chronic abstructive lung disease and/or pneumonia presented severe signal inhomogeneitises. Space-occupying lesions and pleural effusion caused large areas with little or no signal. The represented the lesion and adjacent ventilatory disturbances whose extent had not been presumed from chest X-ray or CT. The spatial resolution was higher than in ventilation scintigraphy. Conclusion: 3He MRI is a promising new modality for the assessment of pulmonary ventilation and its anormalies. (orig.)

  20. Minimal mass-size of a stable 3He cluster

    Guardiola Barcena, Rafael; Navarro Faus, Jesús

    2004-01-01

    The minimal number of 3He atoms required to form a bound cluster has been estimated by means of a Diffusion Monte Carlo procedure within the fixed-node approximation. Several importance sampling wave functions have been employed in order to consider different shell-model configurations. The resulting upper bound for the minimal number is 32 atoms.

  1. Conceptual design of D-3He FRC reactor 'ARTEMIS'

    A comprehensive design study of the D-3He fueled field-reversed configuration (FRC) reactor 'ARTEMIS' is carried out for the purpose of proving its attractive characteristics and clarifying the critical issues for a commercial fusion reactor. The FRC burning plasma is stabilized and sustained in a steady equilibrium by means of a preferential trapping of D-3He fusion-produced energetic protons. A novel direct energy converter for 15MeV protons is also presented. On the bases of a consistent scenario of the fusion plasma production and simple engineering, a compact and simple reactor concept is presented. The design of the D-3He FRC power plant definitely offers the most attractive prospect for energy development. It is environmentally acceptable in view of radio-activity and fuel resources; and the estimated cost of electricity is low compared to a light water reactor. Critical issues concerning physics or engineering for the development of the D-3He FRC reactor are clarified. (author)

  2. Theoretical description of deeply virtual Compton scattering off $^3$He

    Rinaldi, Matteo

    2014-01-01

    Recently, coherent deeply virtual Compton scattering (DVCS) off $^3$He nuclei has been proposed to access the neutron generalized parton distributions (GPDs). In Impulse Approximation (IA) studies, it has been shown, in particular, that the sum of the two leading twist, quark helicity conserving GPDs of $^3$He, $H$ and $E$, at low momentum transfer, is dominated by the neutron contribution, so that $^3$He is very promising for the extraction of the neutron information. Nevertheless, such an extraction could be not trivial. A technique, able to take into account the nuclear effects included in the IA analysis in the extraction procedure, has been therefore developed. In this work, the IA calculation of the spin dependent GPD $\\tilde H$ of $^3$He is presented for the first time. This quantity is found to be largely dominated, at low momentum transfer, by the neutron contribution, which could be extracted using arguments similar to the ones previously proposed for the other GPDs. The known forward limit of the I...

  3. Extracting neutron generalized parton distributions from 3He data

    Rinaldi, M

    2012-01-01

    An impulse approximation analysis is described of the generalized parton distributions (GPDs) H and E of the 3He nucleus, quantities which are accessible in hard exclusive processes, such as coherent deeply virtual Compton scattering (DVCS). The calculation is based on the Av18 interaction. The electromagnetic form factors are correctly recovered in the proper limits. The sum of the GPDs H and E of 3He, at low momentum transfer, is largely dominated by the neutron contribution, thanks to the unique spin structure of 3He. This nucleus is therefore very promising for the extraction of the neutron information. By increasing the momentum transfer, however, this conclusion is somehow hindered by the the fast growing proton contribution. Besides, even when the neutron contribution to the GPDs of 3He is largely dominating, the procedure of extracting the neutron GPDs from it could be, in principle, nontrivial. A technique is therefore proposed, independent on both the nuclear potential and the nucleon model used in ...

  4. Extracting generalized neutron parton distributions from 3He data

    Rinaldi, M.; Scopetta, S.

    2013-03-01

    An impulse-approximation (IA) analysis of the generalized parton distributions (GPDs) H and E of the 3He nucleus, quantities which are accessible in hard exclusive processes, such as coherent deeply virtual Compton scattering (DVCS), is described. The calculation is based on the Av18 interaction. The electromagnetic form factors are correctly recovered in the proper limits. The sum of the GPDs H and E of 3He, at low momentum transfer, is largely dominated by the neutron contribution, thanks to the unique spin structure of 3He. This nucleus is therefore very promising for the extraction of the neutron information. By increasing the momentum transfer, however, this conclusion is somehow hindered by the the fast growing proton contribution. Besides, even when the neutron contribution to the GPDs of 3He is largely dominating, the procedure of extracting the neutron GPDs from it could be, in principle, nontrivial. A technique is therefore proposed, independent of both the nuclear potential and the nucleon model used in the calculation, able to take into account the nuclear effects included in the IA analysis and to safely extract the neutron information at values of the momentum transfer large enough to allow the measurements. Thanks to this observation, coherent DVCS should be considered a key experiment to access the neutron GPDs and, in turn, the orbital angular momentum of the partons in the neutron.

  5. Electron elastic scattering and quark structure of 3He nucleus

    It is shown that for the interpretation of the behaviour of the 3He nucleus form factor at transfer momenta q > 6 fmsup(-1) of importance are nine-quark admixtures and their interference with nucleon and six-quark channels

  6. The design of the 3He readout system on CSNS

    Used in the High-Intensity Powder Diffraction in China Spallation Neutron Sources (CSNS) Project, the electronic parts of the 3He readout system is introduced. The design of the Charge Measurement module (MQ) is described in details, including the structure of the circuit, the firmware of the FPGA on the board. The test results are given out in the final. (authors)

  7. The {sup 3}He neutron-spin filter at ILL

    Tasset, F.; Heil, W.; Humblot, H.; Lelievre-Berna, E.; Roberts, T. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Neutron-Spin Filters (NSF) using gaseous polarised {sup 3}He have long been recognised as of enormous potential value in many polarised neutron-scattering applications and, accordingly, ILL started a development programme some years ago. This report gives an account of the present status of the project. (author). 13 refs.

  8. 3He(t,t)3He elastic scattering measurements from 9 to 17 MeV

    Angular distributions of the analyzing power and differential cross section for 3He(t,t)3He elastic scattering are reported for triton bombarding energies of 9.02, 11.00, 13.02, 15.02, 16.00, and 17.02 MeV, over a c.m. angular range from 25degree to 155degree. Excitation functions for the analyzing power are presented for the energy range 14.42--17.22 MeV. Problems in the phase-shift analysis of the data are discussed

  9. The electrodisintegration of 3He studied with the 3He(e,e'p)2H and 3He(e,e'd)1H reactions

    The author presents a survey of experimental and theoretical results for the ground-state properties of 3He. The formalism of the (e,e'p) and (e,e'd) reactions is presented. A short description of the instrumentation, in particular those elements which are typical for the present study, and of the data analysis is given. This includes a description of the elements required in the 'recoil detection' technique. The kinematics of the experiments and the results are presented. The results are discussed and compared with calculations. (Auth.)

  10. Proportional reasoning

    Dole, Shelley; Hilton, Annette; Hilton, Geoff;

    2015-01-01

    Proportional reasoning is widely acknowledged as a key to success in school mathematics, yet students’ continual difficulties with proportion-related tasks are well documented. This paper draws on a large research study that aimed to support 4th to 9th grade teachers to design and implement tasks...... to foster students’ proportional reasoning. Classroom data revealed limited initial teacher knowledge and awareness of the pervasive nature of proportional reasoning required in the mathematics curriculum. Teacher capacity to seize teachable moments for building students’ proportional reasoning...... skills increased throughout the project. From this background, this paper presents an analysis of the proportional reasoning demands and opportunities of topics within the school mathematics curriculum in Australia. Implications for the study of whole number arithmetic (WNA) and other topics to promote...

  11. Functional {sup 3}He-MRI of the lungs; Funktionelle {sup 3}He-MRT der Lunge

    Gast, K.K.; Wolf, U. [Universitaetsmedizin der Johannes-Gutenberg-Universitaet Mainz, Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie, Mainz (Germany)

    2009-08-15

    Pulmonary diseases have a high health-related and economic significance. {sup 3}He-MRI is an alternative imaging method which can detect ventilatory disturbances with a high sensitivity. The application of different pulse sequences allows static and dynamic assessment of ventilation and bronchial gas flow, non-invasive measurement of intrapulmonary oxygen partial pressure and quantification of pulmonary parenchyma destruction and overinflation. Generally, the method is applicable for obstructive and restrictive ventilatory disturbances but initial approaches also exist for vascular pulmonary diseases. Specific clinical applications remain to be determined but {sup 3}He-MRI is an excellent instrument for the assessment of physiologic and pathophysiologic interrelations in the distribution of ventilation. (orig.) [German] Lungenerkrankungen haben einen hohen gesundheitlichen und volkswirtschaftlichen Stellenwert. Die {sup 3}He-MRT ist eine alternative bildgebende Methode, die sensitiv Ventilationsstoerungen nachweisen kann. Ueber unterschiedliche Pulssequenzen koennen Ventilation und Gasfluesse statisch und dynamisch dargestellt, der intrapulmonale Sauerstoffpartialdruck nichtinvasiv gemessen und die Destruktion und Ueberblaehung des Lungenparenchyms quantifiziert werden. Prinzipiell ist die Methode fuer die Untersuchung obstruktiver und restriktiver Ventilationsstoerungen anwendbar, Ansaetze existieren jedoch auch fuer vaskulaere Lungenerkrankungen. Spezifische klinische Anwendungen fuer die {sup 3}He-MRT muessen noch erarbeitet werden, sie ist jedoch ein hervorragendes Instrument zur Untersuchung physiologischer und pathophysiologischer Zusammenhaenge bei der Ventilationsverteilung. (orig.)

  12. Hyperpolarised sup 3 He gas production for magnetic resonance imaging of the human air ways

    Fichele, S

    2002-01-01

    This thesis describes the experimental techniques, and methods employed in hyperpolarised sup 3 He gas production and magnetic resonance imaging of the human air-ways, using spin-echo sequences and MR tagging techniques. An in-house polariser utilising the metastability optical pumping technique was constructed. The main results of this work are concerned with engineering difficulties involved in compressing HP sup 3 He and a large proportion of this PhD thesis details the design, construction, and performance of an in-house built peristaltic compressor. In preliminary imaging experiments using RARE, high signal to noise projection images of the lungs were acquired using less than 0.5 cm sup 3 (STP) of purely polarised HP gas. Later, increased HP gas quantities (typically 10 cm sup 3) were obtained by employing the peristaltic compressor. Consequently we could acquire 10 mm thick slices spanning the entire lung following a single sup 3 He gas bolus administration. Finally, the first results using MR tagging t...

  13. A theory of low energy π-3He elastic scattering

    The main aim of this work is the construction of a first-order optical potential for the scattering of pions by 3He at low energy with as few approximations as possible. In particular the Fermi motion is treated extremely carefully by using microscopic 3He wave functions and by performing the complete Fermi-integral. Differential cross-sections and analyzing powers have been calculated. In a detailed comparison between the first-order optical with one which results from using the semi-factored approximation, it became clear that the latter has the following shortcomings: 1. the dependence of the subenergy on the pion-nucleus scattering angle, and 2. the independence of this energy on the relative motion of the spectator nucleons. (author). 101 refs.; 15 figs.; 3 tabs

  14. Photoassociation spectroscopy of ultracold metastable ^3He dimers

    Cocks, Daniel G; Whittingham, Ian B

    2011-01-01

    The bound states of the fermionic ^3He(2 ^3S_1)+ ^3He(2 ^3P_j)system, where j=0,1,2, are investigated using the recently available ab initio short-range ${}^{1,3,5}\\Sigma^{+}_{g,u}$ and ${}^{1,3,5}\\Pi_{g,u}$ potentials computed by Deguilhem et al. (J. Phys. B: At. Mol. Opt. Phys., 2009, 42, 015102). Single-channel and multichannel calculations have been undertaken in order to investigate the effects of Coriolis and non-adiabatic couplings. The possible experimental observability of the theoretical levels is assessed using criteria based upon the short-range character of each level and their coupling to metastable ground states. Purely long-range levels have been identified and 30 short-range levels near five asymptotes are suggested for experimental investigation.

  15. Josephson flow oscillations in superfluid 3He-B

    Experiments for observing pressure-induced Josephson oscillations in superfluid 4He renewed the interest for analogous experiments in superfluid 3He. The weak coupling of two superfluids is obtained by a small channel with dimensions in the order of the coherence length. The order-parameter functions, the supercurrent Jψ through the orifice, and the Ginzburg-Landau free energy, Fψ is calculated for different cross sections. A new feature of the function Jψ in comparison to the current-phase relationships for superconducting microbridges is the occurrence of two nontrivial zeros of Jψ. It turns out that the frequency, ω, of the Josephson flow oscillations, which follow the sudden application of a force ΔF on a diaphragm, depends on ΔF in a way similar to that in which the frequency of the parallel ringing experiment in 3He-Α depends on the field step ΔΗ. (6 refs., 12 figs.)

  16. Magnetism of liquid 3He up to 200 T

    We report measurements of nuclear magnetism of degenerate liquid 3He below 0.1 K. Nuclear polarization up to 60% was transiently obtained by rapid melting of a 80% polarized 3He solid. From simultaneous measurements of the magnetization and of the heat released during the relaxation towards magnetic equilibrium, we deduce the magnetization dependence of the free energy of the liquid, and hence the magnetization curve up to 200 T. At 26 bar and 80 mK, we find that the susceptibility decreases with increasing magnetization. This rules out any significant metamagnetism of the liquid, in contradiction with former expectations. In order to confirm this behaviour by a static experiment, we have developed a torque magnetometer to carry out precision measurements of the equilibrium magnetization up to 30 T (corresponding to a 12% polarization) and at 50 mK. Preliminary results of this experiment are reported. (orig.)

  17. Nuclear (K) Bound States in 4He and 3He

    LI Yi-He; WU Shi-Shu

    2009-01-01

    @@ We construct a phenomenological K N interaction which reproduces the two resonances: the energy of the first resonance is 1420MeV and the other is 1392MeV. The A(1405) is found by a superposition of the two reso-nances with appropriate weights. Within the framework of the Brueckner-Hartree-Fock theory, we have studied K- - 3He(T=0) and K- - 4He(T=1/2). The binding energy BK-is 93MeV(72MeV) and the width F is 13 MeV(25 MeV) for K- - 3He(T=0) (K- - 4He(T=1/2)).

  18. Project of polarized 3He source at RARF

    At RIKEN Accelerator Research Facility (RARF), a K540 four-sector ring cyclotron (RRC) was completed in November 1986, and has delivered beams to the experiments since May 1987. At present, a heavy-ion linac (RILAC) with a PIG source is used as an injector for RRC. The construction of another injector, a K70AVF cyclotron, has been started and will be completed at the end of 1988 FY. The AVF cyclotron is equipped with a polarized 3He source as well as an ECR source and a duoplasmatron source. The nuclear polarization of 3He will be obtained with the optical pumping of atoms in the metastable state (23 S1) followed by the metastability exchange collision. Polarized atoms will be ionized with an ECR source. The source is expected to be constructed in three years. (author)

  19. Quasifree photoabsorption on neutron-proton pairs in 3He

    Three-body photodisintegration of 3He is calculated in the photon energy range 200-400 MeV assuming quasifree absorption on np pairs both in initial quasideuteron and singlet configurations. The model includes the normal nucleonic current, explicit meson exchange currents and the Δ(1232)-isobar excitation. The total cross section is increased by a factor of about 1.5 compared with free deuteron photodisintegration. Well below and above the Δ-region also some spin observables differ significantly from the ones of free deuteron disintegration due to the more compressed wave function of the correlated np pairs in 3He compared to the deuteron. The initial singlet state causes a significant change in the analysing power Ay. These differences could presumably be seen at the conjugate angles where two-body effects are maximized and where photoreactions could complement similar pion absorption experiments. ((orig.))

  20. Studies of 3He Induced Nuclear Reactions on Cadmium

    Excitation functions of 3He induced nuclear reactions on natural cadmium were measured using the standard stacked foil technique and high resolution gamma ray spectroscopy. The experimental cross sections for the nuclear reactions natCd(3He,xnp )117m,g,116m115m,114m,113m,111,110m,g,109,108,107 In were measured from their threshold energy up to 27 MeV. The integral yields for some medically important products were determined. Theoretical calculations using the nuclear codes ALICE- IPPE, TAL YS, and EMPIRE-3 were used to describe the formation of these products. Theoretical and experimental results were compared with each other. K

  1. A polarized sup 3 He internal target for storage rings

    Poolman, H R; Bulten, H J; Doets, M; Ent, R; Ferro-Luzzi, M; Geurts, D G; Harvey, M; Mul, F A

    2000-01-01

    A polarized sup 3 He internal target was employed at the internal target facility of the Amsterdam electron Pulse Stretcher and Storage ring (AmPS) at the Dutch National Institute for Nuclear and High-Energy Physics (NIKHEF). The unique features of internal targets such as chemical and isotopic purity, high and rapidly reversible polarization, and the ability to manipulate the target spin orientation were successfully demonstrated. A nuclear polarization of 0.50 (0.42) at a sup 3 He gas flow of 1.0 (2.0)x10 sup 1 sup 7 at s sup - sup 1 could be obtained. Operation at a nominal flow of 1x10 sup 1 sup 7 at s sup - sup 1 resulted in a target thickness of 0.7x10 sup 1 sup 5 at cm sup - sup 2 at a target temperature of 17 K.

  2. Transverse sound in liquid-3He-aerogel system

    Transverse sound in normal liquid 3He in aerogel is studied on the basis of the Landau transport equation taking into account the simultaneous oscillation of the aerogel. We show that the nature of transverse sound is strongly modified if aerogel is immersed in the liquid. Scattering of 3He quasiparticles by the aerogel molecules causes friction between the liquid and the aerogel, giving rise to coupled motion of the two systems. There exists a low-attenuation transverse sound mode in this coupled system. The high-temperature behavior of its attenuation α is given by α∝const+T-2, which is in contrast to α∝T in pure liquid H3e in the hydrodynamic regime

  3. Acoustic properties of superfluid 3He in 97% aerogel

    Superfluid 3He in silica aerogel provides a unique system for studying the effect of quenched disorder in the unconventional superfluid. We have performed longitudinal ultrasound (5.7 MHz) attenuation and sound velocity measurements of the superfluid 3He in 97% porosity aerogel. The attenuation and sound velocity were determined by direct propagation of sound pulses through the medium in a wide range of temperatures, down to 400 μK. The superfluid transition, marked by the increase in sound velocity, is substantially suppressed from that in 98% aerogel used in most of studies. The superfluid fraction determined from the sound velocity is less than 0.02 even at the lowest temperature.

  4. 3He melting curve thermometry in a nuclear polarization experiment

    Temperature measurement and control are important in brute force polarization experiments. We discuss the installation and use of 3He melting curve thermometers in a cryostat used to polarize a TiH2 target. Comparison is made between the melting curve thermometers and the 60CoCo nuclear orientation thermometer, which is often used in such experiments. The melting curve thermometers provide increased temperature resolution and sensitivity, and were used in a feedback heating system to control temperature to ±5.5 μK at 16.5 mK. The 3He melting curve and the 60CoCo temperature scales are found to agree within 2% at 15 mK. The present status of the melting curve scale and the effect of a magnetic field on melting curve thermometry are also discussed. (orig.)

  5. Orbital angular momentum in /sup 3/He-A-italic

    Balatskii-breve, A.V.; Mineev, V.P.

    1985-12-01

    The intrinsic angular momentum in the A-italic phase of superfluid /sup 3/He is found in terms of the response to the angular velocity of rotation. It is shown that in the weak-coupling approximation at an arbitrary temperature and with allowance for the Fermi-liquid renormalization the intrinsic angular momentum is small in accordance with the smallness of the asymmetry in the distribution of particles and holes.

  6. Fluctuations above the superfluid transition in liquid 3He

    It is shown that fluctuations above the superfluid transition in liquid 3He depend strongly upon the relative angular momentum l of a Cooper pair but are insensitive to the fourth order term in the Ginsburg-Landau free energy. The effects are shown to be observable in the static magnetization, viscosity and spin diffusion and give a means of determining the value of l. (U.S.)

  7. Phase slippage in superfluid 3He-B

    We review some applications of the hydrodynamic Josephson effects. The relationship between the quantum mechanical phase difference along a micro-orifice and the flow through it is discussed in terms of a simple model which accounts for the observations performed in 3He-B above 0.7 Tc. Possible uses of the superfluid hydromechanical resonator as a sensitive and stable absolute gyrometer are described

  8. A study of 3He films using SQUID NMR

    Confinement of superfluid 3He to a geometry of order the coherence length is predicted to produce interesting size effects and modify the superfluid phase diagram. This thesis describes the development of an experiment to measure these effects using NMR as a probe of the spin dynamics. A pulsed NMR spectrometer was developed with a low Tc SQUID as the first stage amplifier. The sample was located in a receiver coil that formed part of a tuned circuit with the SQUID input coil. The first spectrometer was operated in an open-loop configuration but was later converted to use feedback to stabilize the SQUID gain. This later version used a DC SQUID with APF operating in flux-locked loop using the Direct Offset Integration Technique. The noise was limited by the Johnson noise in the tuned circuit in tests down to 1.5 K and the estimated noise temperature was ∼100 mK. NMR signals were observed at ∼1 MHz from low-density 3He samples adsorbed on a Mylar substrate which were in reasonable agreement with the estimated signal sizes. A cell was constructed with a highly polished silver substrate to study a 100 nm thick 3He film adsorbed on an area of ∼1 cm2. This was mounted on a newly installed demagnetization cryostat. A dipper probe was constructed for the SQUID spectrometer which demonstrated an overall coupled energy sensitivity of 327 h before being mounted on the cryostat. NMR signals were observed from samples equivalent to films of thickness 100, 400, and 800 nm on the substrate surface at temperatures ranging from 60 mK down to 415 μK. No superfluid transition was detected. With each sample a time dependence of the signal was observed which may be attributable to a thermomechanical effect in normal liquid 3He. Based on the measured signals, it is predicted that ∼1016 spins should be detectable in a single-shot. (author)

  9. Hard Two-body Photodisintegration of 3He

    Pomerantz, I; Gilman, R; Higinbotham, D W; Piasetzky, E; Strauch, S; Adhikari, K P; Aghasyan, M; Allada, K; Amaryan, M J; Pereira, S Anefalos; Anghinolfi, M; Baghdasaryan, H; Ball, J; Baltzell, N A; Battaglieri, M; Batourine, V; Beck, A; Beck, S; Bedlinskiy, I; Berman, B L; Biselli, A S; Boeglin, W; Bono, J; Bookwalter, C; Boiarinov, S; Briscoe, W J; Brooks, W K; Bubis, N; Burkert, V; Camsonne, A; Canan, M; Carman, D S; Celentano, A; Chandavar, S; Charles, G; Chirapatpimol, K; Cisbani, E; Cole, P L; Contalbrigo, M; Crede, V; Cusanno, F; D'Angelo, A; Daniel, A; Dashyan, N; de Jager, C W; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dodge, G E; Doughty, D; Dupre, R; Dutta, C; Egiyan, H; Alaoui, A El; Fassi, L El; Eugenio, P; Fedotov, G; Fegan, S; Fleming, J A; Fradi, A; Garibaldi, F; Geagla, O; Gevorgyan, N; Giovanetti, K L; Girod, F X; Glister, J; Goetz, J T; Gohn, W; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Harrison, N; Heddle, D; Hicks, K; Ho, D; Holtrop, M; Hyde, C E; Ireland, D G; Ishkhanov, B S; Isupov, E L; Jiang, X; Jo, H S; Joo, K; Katramatou, A T; Keller, D; Khandaker, M; Khetarpal, P; Khrosinkova, E; Kim, A; Kim, W; Klein, F J; Koirala, S; Kubarovsky, A; Kubarovsky, V; Kuleshov, S V; Kvaltine, N D; Lee, B; LeRose, J J; Lewis, S; Lindgren, R; Livingston, K; Lu, H Y; MacGregor, I J D; Mao, Y; Martinez, D; Mayer, M; McCullough, E; McKinnon, B; Meekins, D; Meyer, C A; Michaels, R; Mineeva, T; Mirazita, M; Moffit, B; Mokeev, V; Montgomery, R A; Moutarde, H; Munevar, E; Camacho, C Munoz; Nadel-Turonski, P; Nasseripour, R; Nepali, C S; Niccolai, S; Niculescu, G; Niculescu, I; Osipenko, M; Ostrovidov, A I; Pappalardo, L L; Paremuzyan, R; Park, K; Park, S; Petratos, G G; Phelps, E; Pisano, S; Pogorelko, O; Pozdniakov, S; Procureur, S; Protopopescu, D; Puckett, A J R; Qian, X; Qiang, Y; Ricco, G; Rimal, D; Ripani, M; Ritchie, B G; Rodriguez, I; Ron, G; Rosner, G; Rossi, P; Sabatie, F; Saha, A; Saini, M S; Sarty, A J; Sawatzky, B; Saylor, N A; Schott, D; Schulte, E; Schumacher, R A; Seder, E; Seraydaryan, H; Shneor, R; Smith, G D; Sokhan, D; Sparveris, N; Stepanyan, S S; Stepanyan, S; Stoler, P; Subedi, R; Sulkosky, V; Taiuti, M; Tang, W; Taylor, C E; Tkachenko, S; Ungaro, M; Vernarsky, B; Vineyard, M F; Voskanyan, H; Voutier, E; Walford, N K; Wang, Y; Watts, D P; Weinstein, L B; Weygand, D P; Wojtsekhowski, B; Wood, M H; Yan, X; Yao, H; Zachariou, N; Zhan, X; Zhang, J; Zhao, Z W; Zheng, X; Zonta, I

    2013-01-01

    We have measured cross sections for the gamma+3He->p+d reaction at photon energies of 0.4 - 1.4 GeV and a center-of-mass angle of 90 deg. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron.

  10. Investigating Neutron Polarizabilities through Compton Scattering on $^3He$

    Choudhury, D.; Nogga, A.; Phillips, D.R.

    2007-01-01

    We examine manifestations of neutron electromagnetic polarizabilities in coherent Compton scattering from the Helium-3 nucleus. We calculate $\\gamma ^3He$ elastic scattering observables using chiral perturbation theory to next-to-leading order (${\\mathcal O}(e^2 Q)$). We find that the unpolarized differential cross section can be used to measure neutron electric and magnetic polarizabilities, while two double-polarization observables are sensitive to different linear combinations of the four ...

  11. High Efficiency Spin Flipper for the n3He Experiment

    Hayes, Christopher; n3He Collaboration

    2015-10-01

    The n3He experiment, constructed on the Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source, is designed to measure the parity violating (PV) proton asymmetry Ap in the capture reaction n +3 He -->3 H + p + 765 keV The asymmetry has an estimated value Ap ~ - 1 ×10-7 and is directly related to the weak isospin conserved couplings hρ0 and ωρ0 which are of fundamental interest in the verification of the meson exchange model of low energy NN intereactions. Data production for the n3He experiment began in February 2015 and is scheduled to continue thru December 2015 - reaching a statistical sensitivity δAp ~10-8 or better. I will discuss the spin flipper which is designed using the theory of double cosine-theta coils, and capable of flipping neutron spins with an efficiency approaching its maximum value ɛsf = 1 . I will also discuss the theory of Spin Magnetic Resonance (SMR) and how it is employed by the spin flipper to flip 60 Hz pulses of cold neutrons over a range of wavelengths.

  12. Hard Photodisintegration of 3He into pd pair

    Maheswari, Dhiraj

    2016-01-01

    The recent measurements of high energy photodisintegration of the $^3He$ nucleus to the $pd$ pair at $90^0$ center of mass demonstrated an energy scaling consistent with the quark counting rule with unprecedentedly large exponent of $s^{-17}$. To understand the underlying mechanism of this process we extended the theoretical formalism of hard rescattering mechanism to calculate the $\\gamma ^3He\\rightarrow pd$ reaction. In HRM the incoming high energy photon strikes a quark from one of the nucleons in the target which subsequently undergoes hard rescattering with the quarks from the other nucleons generating hard two-body system in the final state of the reaction. Within the HRM we derived the parameter free expression for the differential cross section of the reaction, which is expressed through the $^3He\\rightarrow pd$ transition spectral function, cross section of hard $pd\\rightarrow pd$ scattering and the effective charge of the quarks being interchanged during the hard rescattering process. The numerical ...

  13. Superfluid phase stability of 3He in axially anisotropic aerogel

    Measurements of superfluid 3He in 98% aerogel demonstrate the existence of a metastable A-like phase and a stable B-like phase. It has been suggested that the relative stability of these two phases is controlled by anisotropic quasiparticle scattering in the aerogel. Anisotropic scattering produced by axial compression of the aerogel has been predicted to stabilize the axial state of superfluid 3He. To explore this possibility, we used transverse acoustic impedance to map out the phase diagram of superfluid 3He in a ∼ 98% porous silica aerogel subjected to 17% axial compression. We have previously shown that axial anisotropy in aerogel leads to optical birefringence and that optical cross-polarization studies can be used to characterize such anisotropy. Consequently, we have performed optical cross-polarization experiments to verify the presence and uniformity of the axial anisotropy in our aerogel sample. We find that uniform axial anisotropy introduced by 17% compression does not stabilize the A-like phase. We also find an increase in the supercooling of the A-like phase at lower pressure, indicating a modification to B-like phase nucleation in globally anisotropic aerogels.

  14. Saddle point condition for D - 3He tokamak fusion reactor

    In this paper the concept of a generalized ignition contour map, showing bar PhtT2E, NTE, and T, is used to study the ignition criterion for a D-3He fusion reactor with plasma temperature and density profiles. Direct heating scenarios to the D - 3He ignition regime without the help of deuterium-tritium burning are considered. The machine size and enhancement factor for the confinement time required to reach D - 3He ignition can be simple determined by comparing the height of the operation path with Goldston L-mode scaling and the height of the generalized saddle point. A confinement enhancement factor of 2 to 3 is required in the case of a large plasma current (30 to 80 MA) in a small-aspect-ratio tokamak. On the other hand, for a small plasma current (approx-lt 10 MA), large-aspect-ratio tokamak, an enhancement factor of 5 to 6 is necessary to reach ignition. Fuel dilution effects by fusion products and impurities, the confinement degradation effect due to 14-MeV protons, and the operation paths are also considered. To lower the height of the saddle point, and hence the auxiliary heating power, we optimize the fuel composition and examine operation in the hot ion mode

  15. Development of 3He-BOCA power ramping facility, 1

    Development of a He-3 power controlled boiling water capsule, 3He-BOCS, for LWR fuels power ramping test in JMTR has been carried out since 1978 on a five-year program; in the reactor, irradiation tests of various fuels and structual materials have been made since 1969. Using stagnant-pressurized water as a thermal medium, the capsule provides pressure and temperature conditions similar to those in LWRs. Heat generation of a fuel pin can be controlled by a He-3 gas screen surrounding the capsule. The facility is capable of testing numbers of both fresh and irradiated fuel pins under LWR operating conditions for power ramping and cycling. After explaining the operating priciples of 3He-BOCA and the development program, the following are described: the results of preliminary out-of-pile test on heat conductive characteristics of the capsule and a conceptual design of the 3He-BOCA for power ramping of a short fuel pin from 250 W/cm to 500 W/cm under BWR conditions. (author)

  16. Precision study of the eta-3He system using the d+p->3He+eta reaction

    Mersmann, T; Chiladze, D; Dymov, S; Hartmann, M; Hejny, V; Kacharava, A K; Keshelashvili, I; Khoukaz, A; Kulessa, P; Maeda, Y; Mielke, M; Mikirtychiants, S; Ohm, H; Papenbrock, M; Prasuhn, D; Rathmann, F; Rausmann, T; Schleichert, R; Serdyuk, V; Stein, H J; Ströher, H; Täschner, A; Valdau, Y; Wilkin, C; Wro'nska, A; Valdau, Yu.

    2007-01-01

    The differential and total cross sections for the d+p->3He+eta reaction have been measured in a high precision high statistics COSY-ANKE experiment near threshold using a continuous beam energy ramp up to an excess energy Q of 11.3 MeV with essentially 100% acceptance. The kinematics allowed the mean value of Q to be determined to about 9 keV. Evidence is found for the effects of higher partial waves for Q>4 MeV. The very rapid rise of the total cross section to its maximum value within 0.5 MeV of threshold implies a very large eta-3He scattering length and hence the presence of a quasi-bound state extremely close to threshold.

  17. Superfluid phase of 3He-B near the boundary

    Following our analysis of some older and most recent transverse sound experiments in superfluid 3He-B we have been able to solve one of the long-existing problem of superfluid quantum liquids in confined geometry, namely, answer a question what is the boundary state of 3He-B. We have devoted specific attention to the differences between transverse sound experiments data from that obtained in longitudinal sound experiments. In our analysis, we have considered several potentially possible explanations of the above experimental data: existence of a new superfluid phase in the vicinity of the boundary; excitation of different branches of squashing mode by longitudinal and transverse sounds and, finally, deformation of the B-phase near the boundary. The last possibility seems to be the most likely explanation implying that the boundary state of 3He-B is, in fact, the deformed B- phase, as was first suggested by Brusov and Popov about two decades ago for a case of presence of external perturbations such as a magnetic and an electric fields. Our result implies that influence of a wall or, in other words, a confined geometry does not lead to the existence of a new phase near the boundary, as had been suggested many years ago, but, instead, similarly to the case of other external perturbations (such as magnetic, electric fields etc.), the wall deforms the order parameter of the B-phase and this deformation leads to several very important consequences. For example, frequencies of the collective modes in the vicinity of the boundary change by up to about 20 percent.

  18. Hard breakup of two nucleons from the 3He nucleus

    We investigate a large angle photodisintegration of two nucleons from the 3He nucleus within the framework of the hard rescattering model (HRM). In the HRM a quark of one nucleon knocked out by an incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with large relative momentum. Assuming the dominance of the quark-interchange mechanism in a hard nucleon-nucleon scattering, the HRM allows the expression of the amplitude of a two-nucleon breakup reaction through the convolution of photon-quark scattering, NN hard scattering amplitude, and nuclear spectral function, which can be calculated using a nonrelativistic 3He wave function. The photon-quark scattering amplitude can be explicitly calculated in the high energy regime, whereas for NN scattering one uses the fit of the available experimental data. The HRM predicts several specific features for the hard breakup reaction. First, the cross section will approximately scale as s-11. Second, the s11 weighted cross section will have the shape of energy dependence similar to that of s10 weighted NN elastic scattering cross section. Also one predicts an enhancement of the pp breakup relative to the pn breakup cross section as compared to the results from low energy kinematics. Another result is the prediction of different spectator momentum dependencies of pp and pn breakup cross sections. This is due to the fact that the same-helicity pp-component is strongly suppressed in the ground state wave function of 3He. Because of this suppression the HRM predicts significantly different asymmetries for the cross section of polarization transfer NN breakup reactions for circularly polarized photons. For the pp breakup this asymmetry is predicted to be zero while for the pn it is close to (2/3).

  19. Vortex clusters in superfluid 3He-B

    A unique property of 3He-B is vortex-free rotation, due to a high nucleation threshold of the singular vortices. In contrast to other superfluids, rotational states consisting of a vortex cluster surrounded by vortex-free counterflow form spontaneously and can also be prepared with a fixed number of vortices. The clusters can be analyzed by means of NMR measurements with high precision. These techniques have been exploited to study rotational states in the presence of different phase boundaries. (orig.)

  20. Meson Photoproduction off the Deuteron and off 3He

    Photoproduction of mesons off the deuteron and He nuclei has been studied at the tagged photon facilities of the Bonn ELSA accelerator and the Mainz MAMI accelerator with the Crystal/ setup (Mainz). Meson photoproduction off the neutron has been investigated for different final states (πo, πo πo, πo π-, η, η', ηπo). A surprising finding was a narrow structure in the γn→nη excitation function, which is not seen in the proton case. Photoproduction off 3He has provided further evidence for the formation of an h-mesic state.

  1. /sup 3/He and 4f instable compounds

    Flouquet, J.; Jaccard, J. (Centre de Recherches sur les Tres Basses Temperatures, C.N.R.S., 38 - Grenoble (France)); Ribault, M. (Laboratoire de Physique des Solides, Universite de Paris-Sud, 91 - Orsay (France))

    1984-01-01

    The high localization of the 4f electron and the possibility of a weak delocalization through the coupling with the itinerant electrons lead to Fermi liquid properties. With the example of CeAl/sub 3/, the main role of the coherence between the Ce is emphasized at low temperature. Thermal dilatation data show the transition from a regime of almost independent Kondo centers to a regime of coherent Kondo centers. The occurence of the superconductivity in the heavy fermion CeCu/sub 2/Si/sub 2/ is discussed and compared to the superfluidity of liquid /sup 3/He.

  2. High-pressure /sup 3/He gas scintillation neutron spectrometer

    Derzon, M.S.; Slaughter, D.R.; Prussin, S.G.

    1985-10-01

    A high-pressure, /sup 3/He-Xe gas scintillation spectrometer has been developed for neutron spectroscopy on D-D fusion plasmas. The spectrometer exhibits an energy resolution of (121 +- 20 keV) keV (FWHM) at 2.5 MeV and an efficiency of (1.9 +- 0.4) x 10/sup -3/ (n/cm/sup 2/)/sup -1/. The contribution to the resolution (FWHM) from counting statistics is only (22 +- 3 keV) and the remainder is due predominantly to the variation of light collection efficiency with location of neutron events within the active volume of the detector.

  3. Development of multiwire proportional chambers

    Charpak, G

    1969-01-01

    It has happened quite often in the history of science that theoreticians, confronted with some major difficulty, have successfully gone back thirty years to look at ideas that had then been thrown overboard. But it is rare that experimentalists go back thirty years to look again at equipment which had become out-dated. This is what Charpak and his colleagues did to emerge with the 'multiwire proportional chamber' which has several new features making it a very useful addition to the armoury of particle detectors. In the 1930s, ion-chambers, Geiger- Muller counters and proportional counters, were vital pieces of equipment in nuclear physics research. Other types of detectors have since largely replaced them but now the proportional counter, in new array, is making a comeback.

  4. Hard photodisintegration of a proton pair in {sup 3}He

    Stanley Brodsky; Leonid Frankfurt; Ronald Gilman; J. R. Hiller; G. A. Miller; Eliezer Piasetzky; Misak Sargsian; Mark Strikman

    2003-05-01

    Hard photodisintegration of the deuteron has been extensively studied in order to understand the dynamics of the transition from hadronic to quark-gluon descriptions of the strong interaction. In this work, we discuss the extension of this program to hard photodisintegration of a pp pair in the {sup 3}He nucleus. Experimental confirmation of new features predicted here for the suggested reaction would advance our understanding of hard nuclear reactions. A main prediction, in contrast with low-energy observations, is that the pp breakup cross section is not much smaller than the one for pn break up. In some models, the energy-dependent oscillations observed for pp scattering are predicted to appear in the {gamma} {sup 3}He {yields} pp + n reaction. Such an observation would open up a completely new field in studies of color coherence phenomena in hard nuclear reactions. We also demonstrate that, in addition to the energy dependence, the measurement of the light-cone momentum distribution of the recoil neutron provides an independent test of the underlying dynamics of hard disintegration.

  5. The 3H–3He Charge Radii Difference

    Myers L. S.

    2016-01-01

    Full Text Available The upcoming E12-14-009 [1] experiment at Jefferson Lab will determine the ratio of the electric form factors for the A=3 mirror nuclei 3He and 3H. The measurement will use a 1.1 GeV electron beam, a special collimator plate to allow for simultaneous optics measurements, and the low-activity tritium target being prepared for Jefferson Lab. By observing the dependence of the form factor ratio as a function of Q2 over 0.05–0.09 GeV2, the dependence of the radii extraction on the shape of the form factors is minimized. As a result, we anticipate the uncertainty of the extracted charge radii difference to be 0.03 fm, a reduction of 70% from the current measurement. Using precise measurements of the 3He charge radius from isotopic shift or μHe measurements [2–4], we can deduce the absolute 3H charge radius. The results will provide a direct comparison to recent calculations of the charge radii.

  6. Neutron scattering from liquid {sup 3}He at intermediate energies

    Guckelsberger, K. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Azuah, R.T. [Department of Physics, Keele University, Keele Staffordshire, ST5 5BG (United Kingdom)]|[Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0Qx (United Kingdom); Stirling, W.G. [Keele University (United Kingdom); Bennington, S.M.; Yates, M. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0Qx (United Kingdom)

    1997-06-01

    Understanding the dynamics of strongly interacting quantum liquids is at the heart of much of contemporary physics and the archetypal Fermi liquid is {sup 3}He at low temperatures. However, due to the enormous absorption of neutrons by {sup 3}He, experiments are exceedingly difficult. At very high incident neutron energies (>1 eV), the struck atoms behave as if they were free. In a sense, one can ``switch on the interaction`` by using neutrons with ever lower energies until they are-near 1 meV-comparable to that of the interaction. In the present work we use 80-400 meV neutrons to resolve a long standing puzzle: previous measurements suggested strong fluctuations in the width of the recoil peak that could not be understood in terms of a simple theory. Using improved instrumentation (MARI at the spallation source) and novel sample cell design we could improve statistics by more than one order of magnitude. The new data covering an extended energy range are presented and seem to confirm the theory. (orig.).

  7. Longitudinal nuclear magnetic resonance of 3He-B superfluid

    Experiments which contribute to a better understanding of the 3He superfluid in the B phase are reported: a/ The first direct determinations of the gap parameter at zero temperature are given and the longitudinal N.M.R. frequency signal is measured for various pressures. b/ These experiments show a new saturation phenomenon in the ringing signal decay time Tsub(R)(T) at low temperatures. c/ Under conditions of slight non-linearity the excitation of 3He-B longitudinal N.M.R. gives rise to a special system wherein the ringing signal decay is all the faster as the excitation is stronger. A so-called ''memory'' time is measured distinctly longer than the ringing time measured under quasi-linear excitation conditions. It was found that the ringing signal decay, at first exponential for weak excitations γH1 approximately 7 10-3 Ωsub(L), becomes quasi-linear when the excitation is about γH1 approximately 10-2Ωsub(L). This abnormal behaviour cannot be explained by thermal effects related to N.M.R. excitation nor by inhomogeneity effects of the excitation magnetic field. Our interpretation is that excitations γH1 approximately 10-2 Ωsub(L) cause structural defects in the orientation of the vector n which are found to disappear according to an exponential law in times of around 10 ms

  8. The 3H-3He Charge Radii Difference

    Myers, Luke S. [Bluffton University, Bluffton, OH; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Arrington, John R. [Argonne National Lab. (ANL), Argonne, IL (United States); Higinbotham, Douglas W. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-03-01

    The upcoming E12-14-009 [1] experiment at Jefferson Lab will determine the ratio of the electric form factors for the A=3 mirror nuclei 3He and 3H. The measurement will use a 1.1 GeV electron beam, a special collimator plate to allow for simultaneous optics measurements, and the low-activity tritium target being prepared for Jefferson Lab. By observing the dependence of the form factor ratio as a function of Q2 over 0.05–0.09 GeV2, the dependence of the radii extraction on the shape of the form factors is minimized. As a result, we anticipate the uncertainty of the extracted charge radii difference to be 0.03 fm, a reduction of 70% from the current measurement. Using precise measurements of the 3He charge radius from isotopic shift or μHe measurements [2–4], we can deduce the absolute 3H charge radius. The results will provide a direct comparison to recent calculations of the charge radii.

  9. Study of 40Ca(3He,t)40Sc and 9Be(3He,t)9B reactions

    The objective of this research thesis is to perform additional experiments for a better definition of the interaction occurring during the (3He,t) charge exchange reaction, notably in the case of transitions between different layers, and in the case of a target nucleus with a non null spin. In this respect, this thesis addresses the study of 40Ca and 9Be nuclei. After a description of experimental devices and of the obtained performance, the author reports the development of microscopic calculation model within the framework of the DWBA (Distorted Wave Born Approximation). Experimental results are then presented, analysed and discussed

  10. A dynamic model for power deposition in 3He lasers pumped by 3He(n,p) 3H reactions

    Çetin, Füsun

    2004-07-01

    The coupled variation of power density with gas density in a nuclear-pumped laser, which is excited by 3He(n,p) 3H reaction products, is considered. In the literature, volumetric excitation by reaction products of 3He(n,p) 3H is only considered for the case in which gas density is uniform and does not change during the pumping. In this work, a time-dependent model describing the coupled fluid dynamic and particle transport behaviour of the gas has been developed. In modelling charge particle transport behaviour, a previously reported energy deposition model for a constant gas density is extended for a variable gas density by taking into account variations in the particle range, macroscopic cross sections and neutron flux depending on density field of the gas. The coupled equations, which are obtained by using the power deposition density expression obtained for variable gas density in the acoustically filtered equations of motion of the gas, are solved numerically. Spatial and temporal variations of power deposition density and gas density during the pumping pulse are determined for various operating pressures ranging from 0.5 to 10 atm. In the calculations, the characteristics of I.T.U TRIGA Mark-II Reactor are used and it is assumed that laser tube is placed in the centre of the reactor core. Obtained results are presented and examined.

  11. APT 3He target/blanket. Topical report

    The 3He target/blanket (T/B) preconceptual design for the 3/8-Goal facility is based on a 1000-MeV, 200-mA accelerator to produce a high-intensity proton beam that is expanded and then strikes one of two T/B modules. Each module consists of a centralized neutron source made of tungsten and lead, a proton beam backstop region made of zirconium and lead, and a moderator made of D2O. Helium-3 gas is circulated through the neutron source region and the blanket to create tritium through neutron capture. The gas is continually processed to extract the tritium with an online separation process

  12. Realization of administration unit for 3He with gas recycling

    Since many years hyperpolarized (HP) noble gases are used for MR-imaging of the lung. In the beginning the HP gas was filled in Tedlar-bags and directly inhaled by the patients. An administration unit was built respectively to the Medical Devices Law to administer patients HP noble gas boli (3He,129Xe) in defined quantities and at a predefined time during inspiration with high reproducibility and reliability without reducing MR-quality. The patient's airflows are monitored and recorded. It is possible to use gas admixtures, measure the polarization on line and collect the exhaled gas for later recycling. The first images with healthy volunteers were taken with this setup in a clinical study. Current results will be presented.

  13. Nuclear spin dynamics in solid 3He at ultralow temperatures

    In this thesis the experimental study of the spin dynamics of solid 3He is described. By means of magnetization measurements above 3 mK a Curie-Weiss behaviour was found with θW∼2.1 mK and by this an order parameter of J=θWkB/∼-0.5 KkB was observed, while in the range of 1 to 3 mK a pure Curie behaviour was found. By means of NMR measurements the values of τ1(6 mK)=240 ms±12 ms and τ1(1 mK)∼ 40 ms were determined, while spin-echo measurements yielded the spin-spin relaxation time τ2(6 mK)=4540 μs±140 μs. Furthermore neutron scattering studies were performed. (HSI)

  14. Vortex structure in rotational state superfluid 3He

    The structure of vortices in rotational superfluid 3He is considered. It is marked that in the A-phase quantum vortices are possible, in which the A-phase superfluid state is never disturbed. As a consequence of a discrete combined invariance (calibration transformation plus rotation of a spin subsystem) one more exotic type of vortices is possible in the A-phase. This is a hybrid of disclination in a magnetic anisotropy vector field d (with a half-integer Frank index) and vortex that possesses a half-integer number of circulation quanta. Such vortices can be observed at rotation of the A-phase confined between parallel plates. The vortex properties in the B-phase are determined by a continuous combined symmetry. The calculations show the vortex in the β-phase at low pressures to be in the ν-state. The vortices considered are observed in the NMR experiments

  15. Preparations for HFS spectroscopy of antiprotonic 3He

    Full text: Antiprotonic helium (pHe) is a neutral exotic atom, consisting of a helium nucleus, an electron and an antiproton. The interactions of the angular momenta and spins of its constituents cause splitting within the principle states. The measured transition frequencies between hyperfine levels can be compared with three-body QED calculations as a test of the theory. Previous measurements have been performed on p4He. The next two years will be dedicated to measuring a similar transition within p3He. Due to the additional coupling to the helion spin, it consists of an octuplet of states instead of a quadruplet. A new microwave cavity has been designed and is being constructed for the transition frequency of 11.14 GHz. This cavity has been simulated using the high frequency structure simulator HFSS to obtain the correct cavity dimensions. A new cryostat to cool the target is under construction. Numerical simulations are also in progress. (author)

  16. Muon capture on the deuteron and 3He

    Elmeshneb A. E.

    2014-01-01

    Full Text Available We plan to investigate the role of meson exchange currents in the description of the µ− + d → νµ + n + n and µ− + 3He → νµ + 3H reactions. They both are treated as the decay of the corresponding muonic atoms, with the muon initially on the lowest K shell. The muon binding energy in these atoms can be safely neglected and in the initial state we deal essentially with the deuteron (or 3He and muon at rest. These two reactions are interesting for several reasons. First of all, they offer a testing ground for the nuclear wave functions, which for any nucleon-nucleon (NN and three-nucleon (3N forces can be constructed for such light systems with great accuracy. In these reactions few-nucleon weak current operators are an important dynamical ingredient. In the current operators apart from the relatively well known single nucleon contributions, two-nucleon parts (generated by various meson exchanges play an important role. Their details are not well known and several models should be considered. We present our formalism for dealing with these reactions and a simple method for partial wave decomposition of the two-nucleon operators. The crucial nuclear matrix elements of the corresponding weak current operators will be calculated in the momentum space and using partial wave decomposition. The effect of meson exchanges will be investigated in the energy spectrum of the emitted neutrinos (in the deuteron case and in the total decay rates for the two reactions. We will employ various models of NN and 3N forces, such as the Bonn B or chiral NNLO potentials. Our results with the single nucleon currents look already very promising and we hope for the improvement in the description of the experimental data, when dominant two-nucleon current operators are included in our framework.

  17. Nutrition Counter

    ... Counter: A Reference For The Kidney Patient AAKP Nutrition Counter: A Reference For The Kidney Patient Buy ... Harum RD, CSR, LD Certified Specialist in Renal Nutrition, Miami, Florida Reviewed by: 2005 – Maria Karalis, MBA, ...

  18. Nuclear spin dynamics in solid {sup 3}He at ultralow temperatures; Kernspindynamik in festem {sup 3}He bei ultratiefen Temperaturen

    Kath, Matthias

    2009-11-06

    In this thesis the experimental study of the spin dynamics of solid {sup 3}He is described. By means of magnetization measurements above 3 mK a Curie-Weiss behaviour was found with {theta}{sub W}{approx}2.1 mK and by this an order parameter of J={theta}{sub W}k{sub B}/{approx}-0.5 Kk{sub B} was observed, while in the range of 1 to 3 mK a pure Curie behaviour was found. By means of NMR measurements the values of {tau}{sub 1}(6 mK)=240 ms{+-}12 ms and {tau}{sub 1}(1 mK){approx} 40 ms were determined, while spin-echo measurements yielded the spin-spin relaxation time {tau}{sub 2}(6 mK)=4540 {mu}s{+-}140 {mu}s. Furthermore neutron scattering studies were performed. (HSI)

  19. The interfacial thermal resistance between bulk superfluid 3He and liquid 3He in aerogel at ultralow temperatures

    We present the first measurements of the thermal boundary resistance of the interface between the two different liquid phases: bulk superfluid and liquid confined in aerogel. We set up a heat flow along a liquid-filled tube containing a plug of 98% aerogel, and measure the temperature at the two ends. At the lowest temperatures, the resistance is dominated by the boundary resistance at the aerogel surfaces and is unaffected by the superfluid transition of the 3He in the aerogel. Whereas in conventional Kapitza resistance the boundary conductance is limited by acoustic mismatch, here the conductance is limited by an energy mismatch, since quasiparticles with energies above the bulk B-phase gap may freely cross the interface, while those with lower energies are confined to the aerogel

  20. Executive summary: advanced-fuel fusion systems, the D-3He satellite approach

    An evaluation was made of the potential advantages and feasibility of fusion power plants designed to employ near-term non-D--T fuels such as deuterium and D-3He. The following topics are discussed here: (1) cost studies and net-energy analysis, (2) D-3He Bumpy Torus satellite, (3) exploratory studies of a D-3He field-reversed mirror satellite, (4) preliminary advanced fuel pellet studies, and (5) 3He neutral beam injector

  1. Andreev reflection in rotating superfluid 3He-B

    Andreev reflection of quasiparticle excitations from quantized line vortices is reviewed in the isotropic B phase of superfluid 3He in the temperature regime of ballistic quasiparticle transport at T ≤ 0.20Tc. The reflection from an array of rectilinear vortices in solid-body rotation is measured with a quasiparticle beam illuminating the array mainly in the orientation along the rotation axis. The result is in agreement with the calculated Andreev reflection. The Andreev signal is also used to analyze the spin-down of the superfluid component after a sudden impulsive stop of rotation from an equilibrium vortex state. In a measuring setup where the rotating cylinder has a rough bottom surface, annihilation of the vortices proceeds via a leading rapid turbulent burst followed by a trailing slow laminar decay, from which the mutual friction dissipation can be determined. In contrast to the currently accepted theory, it is found to have a finite value in the zero-temperature limit: α(T→0) = (5 ± 0.5) × 10−4

  2. NMR studies on vortices in rotating 3He-A

    NMR measurements are reported on rotating 3He-A in a long cylindrical geometry of 5 mm diameter at a liquid pressure of 29.3 bar and in axial magnetic fields of 14.2, 28.4, and 56.9 mT. At 28.4 mT, NMR studies are also reported in fields inclined by 250 and 900 from the axis of rotation. The frequency shift, the width, and the intensity of the spin wavemodes localized on the soft vortex cores, as well as the additional broadening of the main NMR line during rotation, were measured as a function of temperature, angular velocity Ω, magnetic field intensity, and its inclination angle. Also observed were a critical angular velocity of vortex formation, hysteretic behavior in the number of vortices when comparing accelerating rotation to decelerating, and metastable vortex densities, presumably a vortex tangle after rapid oscillatory acceleration. The results can be understood in terms of the continuous 4π vortices first proposed by Seppaelae and Volovik

  3. Vortex sheet in superfluid 3He-A

    A new state of rotating superfluid 3He-A has been found recently. Usually superfluids respond to rotation by creating an array of vortex lines, which are parallel to the rotation axis, and the circulation around them is quantized. In the new state the vorticity is located on a 2 dimensional sheet instead of 1 D lines. The sheet is parallel to the rotation axis z but in the x - y plane it folds to equidistant layers. The distance between the layers is larger but on the same order of magnitude as the distance between vortex lines. In contrast to other superfluids, the sheet is stable in the A phase because, of its internal structure. The sheet has as a backbone a topologically stable domain wall called soliton, to which non-singular vorticity is bound. Thus it can exist in spite of its presumably higher energy. The vortex sheet is distinguished by its NMR response, in particular because of its higher absorption at a characteristic frequency. Experiment and theory on the vortex sheet are in good agreement

  4. Measurement of the Coherent Neutron Scattering Length of 3He

    Ketter, W.; Heil, W.; Badurek, G.; Baron, M.; Loidl, R.; Rauch, H.

    2005-01-01

    By means of neutron interferometry the s-wave neutron scattering length of the 3He nucleus was re-measured at the Institut Laue-Langevin (ILL). Using a skew symmetrical perfect crystal Si-interferometer and a linear twin chamber cell, false phase shifts due to sample misalignment were reduced to a negligible level. Simulation calculations suggest an asymmetrically alternating measuring sequence in order to compensate for systematic errors caused by thermal phase drifts. There is evidence in the experiment’s data that this procedure is indeed effective. The neutron refractive index in terms of Sears’ exact expression for the scattering amplitude has been analyzed in order to evaluate the measured phase shifts. The result of our measurement, b′c = (6.000 ± 0.009) fm, shows a deviation towards a greater value compared to the presently accepted value of b′c = (5.74 ± 0.07) fm, confirming the observation of the partner experiment at NIST. On the other hand, the results of both precision measurements at NIST and ILL exhibit a serious 12σ (12 standard uncertainties) deviation, the reason for which is not clear yet.

  5. A Neutron Rem Counter

    A neutron detector is described which measures the neutron dose rate in rem/h independently of the energy of the neutrons from thermal to 15 MeV. The detector consists of a BF3 proportional counter surrounded by a shield made of polyethylene and boron plastic that gives the appropriate amount of moderation and absorption to the impinging neutrons to obtain rem response. Two different versions have been developed. One model can utilize standard BF3 counters and is suitable for use in installed monitors around reactors and accelerators and the other model is specially designed for use in a portable survey instrument. The neutron rem counter for portable instruments has a sensitivity of 2.4 cps/mrem/h and is essentially nondirectional in response. With correct bias setting the counter is insensitive to gamma exposure up to 200 r/h from Co-60

  6. The scattering of polarized deuterons on 3He between 10 and 17 MeV

    Using the LASL polarized beam facility, the cross section and vector and tensor analysing powers for the 3He(d vector,d)3He and 3He(d vector,p)4He reactions have been measured in a large angular range at energies between 10 and 17 MeV. (orig./WL)

  7. Economic evaluation of D-T, D-3He, and catalyzed D-D fusion reactors

    Because the D-3He reaction generates no neutrons and the D-D reaction can use abundant fuel resources, these reactions are expected to be used in advanced fuel fusion reactors. Economic considerations and engineering problems are important for realizing such reactors as commercial plants. Therefore, we estimate and compare the cost of electricity (COE) from D-T, D-3He, and catalyzed D-D (cat D-D) fusion reactors. D-3He and cat D-D reactors have a low neutron wall load. Therefore, the D-3He reactor has no wall replacement cost. In addition, no tritium breeding system is needed for the D-3He reactor, but 3He gas is rare. Because the reaction rates of the D-3He and D-D reactions are less, D-3He and D-D reactors require highly efficient confinement properties and operation at high ion temperatures. Furthermore, the power densities of D-3He and D-D reactors are smaller than that of the D-T reactor; thus, D-3He and D-D reactors require a large plasma volume. Assuming a high ion temperature (= 60 keV) and high normalized beta (= 7-8), the COE of a D-3He reactor is expected to be similar to that of a D-T reactor. In terms of cost, cat D-D is disadvantageous in comparison with D-3He and D-T reactors. (author)

  8. Investigation of adsorption and wetting of 3He on cesium and cesiated glass

    Experiments have been carried out to investigate the binding of 3He on cesium substrates, using optical pumping to spin-polarize the atoms. The behavior of 3He on the walls at low temperature can be analyzed through the evolution of the nuclear magnetization of the sample. Preliminary results are presented, including: (1) adsorption studies of gaseous 3He on cesiated glass; (2) magnetic relaxation time of polarized liquid 3He on cesium and cesiated glass; (3) evidence for wetting of liquid 3He on cesium. 8 refs., 2 figs

  9. Technic and economic viability study on exploitation of lunar 3He resource

    From the energetics point of view, the technic and economic viability study on exploitation of lunar 3He for fuelling the fusion reactor burning D-3He has been carried out. This study is divided into the following sections: analysis of solar wind parameters and estimation of potential quantity 3He in the lunar regolith, the cost evaluation of mining He of lunar soil; the energy cost calculation of He extraction by vacuum heating degassing during lunar day, the cost calculation of cryogenic isotopic separation 3He/4He during the lunar night, the energy cost for earth/moon transportation of liquid 3He, the energy payback calculation of fusion power burning 3He based lunar source, and finally the comparison of the energy multiplication with that for 235U production of nuclear fuel and for coal mining. The comparisons of cost of electricity between D-3He and D-T fuel cycle for different reactor types have been discussed

  10. Nuclear relaxation of 3He at the surface of solid H2

    We present a detailed experimental study of the wall-relaxation on solid H2 surfaces of a dilute 3He gas, oriented by optical pumping. In these experiments, we measure the nuclear relaxation time of the whole sample of 3He which is directly related to the relaxation time Tsub(a) of the 3He atoms adsorbed on the solid H2 coating the sample walls. Measurement of T1 as a function of the temperature leads to an experimental determination of the adsorption energy of a 3He atom on solid H2: ΔW (3He/H2) = 12+-3 K. In addition, experiments have been done on D2 and Ne solid coatings leading to ΔW (3He/D2) = 20+-3 K and ΔW (3He/Ne) = 38+-5 K; all these experimental values are in good agreement with theoretical predictions

  11. An improved long counter for neutron fluence measurement with a flat response over a wide energy range from 1 keV to 15 MeV

    A new long counter has been developed with a flat energy response over a wide range from 1 keV to 15 MeV. It consists of five 3He proportional counter tubes and a number of carefully designed polyethylene moderators. The structure of this detector was determined by careful Monte Carlo simulations. The calculated results show that the efficiency of this counter is uniform from 1 keV neutron energy to 15 MeV. Calibration was performed on an Am–Be source and the accelerator-produced monoenergetic D–D and D–T neutron sources. Fluctuation of the response curve is less than 10% over this energy range

  12. A possible in situ 3H and 3He source in Earth's interior: an alternative explanation of origin of 3He in deep Earth.

    Jiang, Songsheng; Liu, Jing; He, Ming

    2010-07-01

    Origin of (3)He in the Earth is a mystery. Lacking a production mechanism, scientists assume (3)He was trapped in the Earth, when the Earth was formed. In contrast to this assumption, we have found (3)He and (3)H concentrations in excess of the atmospheric values in the deep waters of the volcanic Lakes Pavin (France), Laacher (Germany) and Nemrut (Turkey). This paper reports the result of finding (3)H in these three volcanic lakes that appear to originate from the mantle. Because (3)H has a half-life of 12.3 years, this (3)H and the resulting (3)He must have formed recently in the mantle and not be part of a primordial reservoir. The nuclear reactions that generate tritium might be a source of "missing" energy in the interior of the Earth. PMID:20502855

  13. Interferometric and acoustic measurements in superfluid (3)He-B and wetting studies in (3)He/(4)He mixtures. Doctoral thesis

    Alles, H.

    1995-06-22

    In this thesis work superfluid (3)He was investigated by two methods. First, ultrasonic experiments on (3)He-B were carried out using two coincident zero sound pulses. The second technique is optics, a novel method for ultra low temperatures. The developed method, two-beam interferometry, was employed successfully for studies of wetting phenomena in liquid (3)He/(4)He mixtures as well. This publication contains the results of a acoustic spectroscopy on (3)He-B. Most importantly, the real squashing collective mode (rsq) was excited by two simultaneous sound pulses yielding two phonon absorption (TPA). This nonlinear phenomenon was applied to study the dispersion relation of the rsq-mode. Zeeman splitting of the nonlinearly excited rsq-mode was investigated in a magnetic field. By means of TPA, an anomalous behavior was found also near the pair-breaking edge.

  14. Experimental study of fusion neutron and proton yields produced by petawatt-laser-irradiated D2-3He or CD4-3He clustering gases

    Bang, W; Bonasera, A; Quevedo, H J; Dyer, G; Bernstein, A C; Hagel, K; Schmidt, K; Gaul, E; Donovan, M E; Consoli, F; De Angelis, R; Andreoli, P; Barbarino, M; Kimura, S; Mazzocco, M; Natowitz, J B; Ditmire, T

    2013-01-01

    We report on experiments in which the Texas Petawatt laser irradiated a mixture of deuterium or deuterated methane clusters and helium-3 gas, generating three types of nuclear fusion reactions: D(d, 3He)n, D(d, t)p and 3He(d, p)4He. We measured the yields of fusion neutrons and protons from these reactions and found them to agree with yields based on a simple cylindrical plasma model using known cross sections and measured plasma parameters. Within our measurement errors, the fusion products were isotropically distributed. Plasma temperatures, important for the cross sections, were determined by two independent methods: (1) deuterium ion time-of-flight, and (2) utilizing the ratio of neutron yield to proton yield from D(d, 3He)n and 3He(d, p)4He reactions, respectively. This experiment produced the highest ion temperature ever achieved with laser-irradiated deuterium clusters.

  15. Energy dependence of the 6Li(π+,3He)3He reaction at 60, 75 and 90 MeV

    Differential cross sections for the pionic fission reaction 6Li(π+,3He)3He at T sub(π) = 60, 75 and 90 MeV have been measured for theta sub(c.m.) = 4l degrees. The energy dependence of the differential cross section is found to follow an exponential decrease with increasing incident pion energy and is compared with existing theoretical predictions

  16. A 3He Cryostat for Scientific Measurements in Pulsed High Magnetic Fields

    Wang, Shaoliang; Li, Liang; Liu, Mengyu; Zuo, Huakun; Peng, Tao

    A top loading 3He cryostat has been developed for scientific experiments with a 60 T pulsed magnetic field facility at Wuhan National High Magnetic Field Center. The cryostat consists of a 4He bath cryostat, a 3He insert and a closed circulation system for 3He gas handling. To eliminate the eddy current heating during the pulse, the tail of the 3He insert with a vacuum space at the bottom is made from fiberglass tubing coated with epoxy. The 3He bath is separated from the 4He bath with the vacuum space. The 4He bath cryostat provides cooling power to condense 3He gas by a neck tube on top of the tail. Experimental results have shown that the sample can be cooled down to 385 mK and kept cold for more than 150 second by one-shot cooling, which is sufficiently long for an experiment in a pulsed high magnetic field.

  17. Density dependence of the single particle kinetic energy in {sup 3}He-{sup 4}He

    Azuah, R.T. [Keele Univ. (United Kingdom). Dept. of Physics]|[Rutherford Appleton Lab., Chilton, Didcot (United Kingdom); Stirling, W.G. [Keele Univ. (United Kingdom). Dept. of Physics; Gibbs, M.R. [Keele Univ. (United Kingdom). Dept. of Physics; Sokol, P.E. [Dept. of Physics, Pennsylvania State Univ., University Park, PA (United States); Mayers, J. [Rutherford Appleton Lab., Chilton, Didcot (United Kingdom)

    1995-08-01

    We present inelastic neutron scattering measurements of liquid {sup 3}He-{sup 4}He mixtures at 1.5 K and at {sup 3}He concentrations of 0,15,40,70 and 100%. There is little apparent concentration dependence of the {sup 3}He kinetic energy, in disagreement with recent variational calculations for mixtures. The kinetic energy of the {sup 4}He component for the lower concentration mixtures is consistent with theoretical predictions. (orig.).

  18. Magnetization and Spin-Diffusion of Liquid 3He in Aerogel

    Sauls, J. A.; Bunkov, Yu. M.; Collin, E.; Godfrin, H.; P.Sharma

    2004-01-01

    We report theoretical calculations of the normal-state spin diffusion coefficient of 3He in aerogel, including both elastic and inelastic scattering of 3He quasiparticles, and compare these results with experimental data for 3He in 98% porous silica aerogel. This analysis provides a determination of the elastic mean free path within the aerogel. Measurements of the magnetization of the superfluid phase provide a test of the theory of pairbreaking and magnetic response of low-energy excitation...

  19. Study of the /sup 50/V nucleus with the (/sup 3/He,d), (/sup 3/He,. cap alpha. ), (/sup 3/He,p), and (/sup 3/He,p. gamma. ) reactions. [Angular distribution, 13 and 22 MeV, analog states, DWBA, J,. pi. , spectroscopic factors, angular momentum, transitions

    Smith, J W

    1971-06-01

    The nucleus /sup 50/V with a ground-state configuration (..pi..f/sub 7/2/)/sup 3/(..nu..f/sub 7/2/)/sup -1/ was studied with the /sup 49/Ti(/sup 3/He,d)/sup 50/V, /sup 51/V)/sup 3/He,..cap alpha..)/sup 50/V, and /sup 48/Ti(/sup 3/He,p)/sup 50/V, and /sup 48/Ti(/sup 3/He,p..gamma..)/sup 50/V reactions induced by the /sup 3/He/sup + +/ beam from the tandem Van de Graaff at the Argonne National Laboratory. The angular distributions from (/sup 3/He,d), (/sup 3/He,..cap alpha..), and (/sup 3/He,p) reactions induced by 22-MeV /sup 3/He were studied with overall energy resolution widths of 20, 30, and 42 keV, respectively. The reactions (/sup 3/He,p) and (/sup 3/He,p..gamma..) were also studied at an incident energy of 13 MeV to obtain the ..gamma.. decay of /sup 50/V levels (including two 0/sup +/ isobaric analog states) in which the neutron-proton pair is transferred with zero angular momentum. The angular distributions of the charged-particle reactions were analyzed with the distorted-wave Born approximation (DWBA), and spectroscopic factors have been extracted for the one-nucleon transfer reactions. The two-nucleon transfer reaction (/sup 3/He,p) was analyzed with the DWBA on the assumption that the neutron-proton pair is transferred as a deuteron. The angular momentum L/sub np/ of the transferred deuteron is established for most of the levels, and the possibility that several levels might have spin and parity 1/sup +/ is discussed.

  20. Observation of Majorana Quasiparticles Surface States in Superfluid ${^3}$He-B by Heat Capacity Measurements

    Bunkov, Yury M.; Gazizulin, Rasul R.

    2016-01-01

    We report about direct measurements of heat capacity of Majorana quasiparticles in superfluid ${^3}$He-B which appear near the surface of the experimental bolometer on the coherence length ${\\xi}$. Two bolometers with different surface-to-volume ratios were used which allows us to have different calibrated contributions from Majorana quasiparticles to the ${^3}$He heat capacity. Estimations of possible impact of ${^3}$He layers adsorbed on the walls of the bolometer have been done.

  1. Development of polarized {sup 3}He filter for polarized neutron experiment

    Sakai, K.; Sato, H.; Yoshimi, A.; Asahi, K. [Tokyo Inst. of Tech. (Japan). Faculty of Science; Masuda, Y.; Muto, S.; Ishimoto, S.; Morimoto, K.

    1996-08-01

    A high-pressure polarized {sup 3}He gas cell, pumped with two diode lasers, has been developed at KEK for use as a polarizer and a spin analyzer for low energy neutrons. The polarization attained of {sup 3}He was determined through the measurement of the transmission of the unpolarized neutrons through the {sup 3}He cell. So far we obtained P{sub He}=18% at 10 atm and P{sub He}=12% at 20 atm. (author)

  2. The influence of restricted geometry of the diamagnetic nanoporous media on the 3He relaxation

    The spin kinetics of 3He in contact with diamagnetic samples of inverse SiO2 opals and LaF3 nanopowders is investigated experimentally. The experimental results testify that the nuclear magnetic relaxation of adsorbed 3He occurs through the modulation of dipole-dipole interactions by quantum movements in a 2D layer while the relaxation of liquid 3He occurs through a spin-diffusion to the adsorbed layer. It is shown that the restricted geometry of diamagnetic nanoporous media influences the 3He relaxation process.

  3. Extraterrestrial 3He in marine polymetallic nodules: a potential method for measuring growth rate of nodules

    李延河; 宋鹤彬; 李金城

    2002-01-01

    The comparative measurements of helium isotope compositions between marine polymetallic nodules and their surrounding sediments, their magnetic fractions and bulk from C-C Zone of the East Pacific Basin are reported. The 4He content and 3He/4He ratio of polymetallic nodules and their surrounding sediments are extremely high; the 3He, 4He concentrations and most 3He/4He ratios of magnetic fractions in nodules and sediments are apparently higher than those in bulk. The helium isotope data points of nodules and sediments are all distributed along or closely to the mixing curve of the interplanetary dust particles (IDPs) and the terrigenous sediments in the chart of 3He-3He/4He. In the same sampling site, the 3He/4He ratios of nodules and their surrounding sediments are very similar, and the changes of both ratios are synchronous. It shows that the high 3He/4He ratios in nodules and sediments may all result from IDPs. So, if the flux of extraterrestrial 3He into the nodules and sediments is constant, the growth rate of polymetallic nodules and the sedimentation rate of sediments can be independently calculated according to the concentration of extraterrestrial 3He in nodules and sediments.

  4. Study of the nuclear fusion in dμ3He complex

    Experimental study of the nuclear fusion reaction in charge-asymmetrical dμ3He complex (dμ3He → α (3.5 MeV) + p (14.64 MeV) is presented. The 14.64-MeV protons were detected by three pairs of Si(dE - E) telescopes placed around the cryogenic target filled with the D2 + 3He gas at 34 K. The 6.85 keV γ rays emitted during the de-excitation of the dμ3He complex were detected by a germanium detector. The measurements were performed at two D2 + 3He target densities, ψ = 0.0585 and ψ 0.169 (relative to liquid hydrogen density) with an atomic concentration of 3He c3He = 0.0469. The values of the effective rate of nuclear fusion in dμ3He was obtained for the first time: λf(tilde) (4.5-2.0+2.6) · 105s-1(ψ = 0.0585); λf(tilde) = (6.9-3.03.6) · 105s-1(ψ 0.168). The J =0 nuclear fusion rate in dμ3He was derived: λfJ=0 (9.7-2.6+5.7) · 105s-1 (ψ 0.0585); λfJ=0 = (12.4-5.4+6.5) · 105s-1 (ψ 0.168)

  5. In globally isotropic aerogel, A-B phase separation of superfluid 3He in radial direction

    It is observed that the A-like phase and the B-like phase, which are superfluid phases of 3He in high porosity silica aerogel as an impurity, coexist stably. In this coexisting state, we showed by NMR experiments with radial gradient magnetic field that the A-like phase is in the edge part of a cylindrical aerogel and the B-like phase is in the central part of that. It is proposed that the A-like phase might be more stabilized in globally anisotropic aerogel. According to this proportion, the aerogel might be globally anisotropic in edge part. In order to study whether the aerogel is globally anisotropic, we have performed optical birefringence experiment on aerogel samples in the same batch. This optical method is a useful tool to characterize a global anisotropy of aerogel. Then, we found that aerogel samples are not globally anisotropic. Therefore, there are another mechanism for the A-B phase separation in radial direction.

  6. A moving domain wall and order parameter orientation in 3He-B

    It is shown that movement of domain wall in the earlier considered two-domain structure in superfluid 3He β-phase eliminates the structure double degeneracy. It is suggested to use this fact for one-valued order parameter orientation in 3He-B

  7. DC discharge characteristics and fluorine atom yield in NF3/He

    Liping Duo; Shukai Tang; Haijun Yu; Jian Wang; Xiangde Min; Liucheng Li; Yuqi Jin; Bailing Yang; Fengting Sang

    2006-01-01

    @@ DC discharge characteristics of NF3/He have been investigated experimentally under different experimental conditions, for example, different electrode materials, separations, flow rates of the gas NF3 or He, and series resistances. The optimum discharge parameters and the fluorine atom yield from the DC discharge of NF3/He as function of load power are studied experimentally.

  8. Possible Dimensional Crossover to 1D of ^3He Fluid in Nanochannels Observed in Susceptibilities

    Matsushita, Taku; Kurebayashi, Katsuya; Shibatsuji, Ryosuke; Hieda, Mitsunori; Wada, Nobuo

    2016-05-01

    Dimensional crossover to the one-dimensional (1D) state from higher dimensions has been studied for dilute ^3He fluid adsorbed in 2.4 nm ^4He-preplated nanochannels, by susceptibility measurements down to 70 mK using 4.29 MHz nuclear magnetic resonance. In nanochannels, since energy states of ^3He motion perpendicular to the channel axis are discrete, a genuine 1D ^3He fluid is expected when the Fermi energy is less than the first excitation Δ _{01} for azimuthal motion. The susceptibilities χ above 0.3 K show the Curie-law susceptibilities independent of the ^3He density, which are characteristic of nondegenerate fluid in higher dimensions. With decreasing the temperature, a significant reduction of χ T was observed from about 0.3 K for all ^3He densities. It is considered to be due to the dimensional crossover below Δ _{01}˜ 0.5 K to the 1D ^3He state in the semi-degenerate regime above the Fermi temperature. In the 1D state at lower temperatures, T-independent χ were observed for ^3He of 0.019 layers below 0.1 K. It suggests that the 1D ^3He fluid enters the quantum degenerate regime.

  9. Towards the observation of the magnetic structure of solid 3He

    Experiments involving neutron scattering by 3He for which thermalization problems have been solved, along with the development of novel measurement techniques (density, magnetization, temperature) by polarized neutron transmission, crystallization experiments with 3He and 4He: a single crystal of helium have been obtained within a sintered metal in which the pore size is less than a micron are presented

  10. First detection of 3He+ in the planetary nebula IC 418

    Guzman-Ramirez, L.; Rizzo, J. R.; Zijlstra, A. A.; García-Miró, C.; Morisset, C.; Gray, M. D.

    2016-07-01

    The 3He isotope is important to many fields of astrophysics, including stellar evolution, chemical evolution, and cosmology. The isotope is produced in low-mass stars which evolve through the planetary nebula (PN) phase. 3He abundances in PNe can help test models of the chemical evolution of the Galaxy. We present the detection of the 3He+ emission line using the single dish Deep Space Station 63, towards the PN IC 418. We derived a 3He/H abundance in the range 1.74 ± 0.8 × 10-3 to 5.8 ± 1.7 × 10-3, depending on whether part of the line arises in an outer ionized halo. The lower value for 3He/H ratio approaches values predicted by stellar models which include thermohaline mixing, but requires that large amounts of 3He are produced inside low-mass stars which enrich the interstellar medium (ISM). However, this overpredicts the 3He abundance in H II regions, the ISM, and protosolar grains, which is known to be of the order of 10-5. This discrepancy questions our understanding of the evolution of the 3He, from circumstellar environments to the ISM.

  11. Hyperpolarized 3He MRI and 81mKr SPECT in chronic obstructive pulmonary disease

    Stavngaard, Trine; Søgaard, Lise; Mortensen, J;

    2005-01-01

    compare ventilation imaging methods in 26 patients with chronic obstructive pulmonary disease (COPD) and nine lung healthy volunteers. METHODS: HP 3He MRI, 81mKr single-photon emission computed tomography (SPECT), high-resolution computed tomography (HRCT) and pulmonary function tests were performed. The...... visual defect score (r=0.80, p<0.0001) and objective estimate of ventilation (r=0.45, p=0.0157). In addition, both scanswere well correlated with reference methods for the diagnosis of emphysema (pulmonary function test and HRCT). The defect scores were largest on 81mKr SPECT (the score on HP 3He MRI was...... defect scores are comparable on HP 3He MRI and 81mKr SPECT. Additionally, new insights into the regional pulmonary microstructure via the apparent diffusion coefficient measurements are provided by HP 3He MRI. HP 3He MRI is a promising new diagnostic tool for the assessment of ventilation distribution...

  12. First measurement of the helicity dependence of 3He photoreactions in the Δ(1232 resonance region

    Costanza Susanna

    2014-03-01

    Full Text Available The first measurement of the helicity dependence for several photo-reaction channels on 3He was carried out in the photon energy range between 150 and 500 MeV at the MAMI accelerator (Mainz. The experiment used the large acceptance Crystal Ball spectrometer, complemented by charged particle and vertex detectors, a circularly polarised tagged photon beam and a longitudinally polarised high-pressure 3He gas target. Results of the helicity dependent total inclusive photoabsorption cross section on 3He and of both the unpolarised and polarised partial cross sections for the pion photoproduction channels γ 3He → πX and for the γ 3He → ppn channel, measured for the first time at MAMI, will be shown. They can also be found in [1].

  13. The ground state energy of 3He droplet in the LOCV framework

    The (extended) lowest order constrained variational method was used to calculate the ground state energy of liquid helium 3 (3He) droplets at zero temperature. Different types of density distribution profiles, such as the Gaussian, the Quasi-Gaussian and the Woods-Saxon were used. It was shown that at least, on average, near 20 3He atoms are needed to get the bound state for 3He liquid droplet. Depending on the choice of the density profiles and the atomic radius of 3He, the above estimate can increase to 300. Our calculated ground state energy and the number of atoms in liquid 3He droplet were compared with those of Variational Monte Carlo method, Diffusion Monte Carlo method and Density Functional Theory, for which a reasonable agreement was found.

  14. Burnup of fusion produced tritons and 3He ions in PLT and PDX

    The d(d,p)t and d(d,n)3He fusion reactions produce 1 MeV tritons and 0.8 MeV 3He ions which can subsequently undergo d(t,n)α and d(3He,p)α fusion reactions. The magnitude of this triton and 3He ion burnup was measured on the PLT and PDX tokamaks by detection of the 14 MeV neutron and 15 MeV proton emission. In discharges with B/sub phi/ greater than or equal to 2 T, the measured 3He burnup agrees well with predictions based on classical theories of ion confinement and slowing down, while the triton burnup was about four times lower than theoretically predicted. In discharges with weaker toroidal fields, the burnup of both ions fell by more than a factor of ten

  15. Electron bubbles and Weyl fermions in chiral superfluid 3He-A

    Shevtsov, Oleksii; Sauls, J. A.

    2016-08-01

    Electrons embedded in liquid 3He form mesoscopic bubbles with large radii compared to the interatomic distance between 3He atoms, voids of Nbubble≈200 3He atoms, generating a negative ion with a large effective mass that scatters thermal excitations. Electron bubbles in chiral superfluid 3He-A also provide a local probe of the ground state. We develop a scattering theory of Bogoliubov quasiparticles by negative ions embedded in 3He-A that incorporates the broken symmetries of 3He-A , particularly broken symmetries under time reversal and mirror symmetry in a plane containing the chiral axis l ̂. Multiple scattering by the ion potential, combined with branch conversion scattering by the chiral order parameter, leads to a spectrum of Weyl fermions bound to the ion that support a mass current circulating the electron bubble—a mesoscopic realization of chiral edge currents in superfluid 3He-A films. A consequence is that electron bubbles embedded in 3He-A acquire angular momentum, L ≈-(Nbubble/2 ) ℏ l ̂ , inherited from the chiral ground state. We extend the scattering theory to calculate the forces on a moving electron bubble, both the Stokes drag and a transverse force, FW=e/c v ×BW , defined by an effective magnetic field, BW∝l ̂ , generated by the scattering of thermal quasiparticles off the spectrum of Weyl fermions bound to the moving ion. The transverse force is responsible for the anomalous Hall effect for electron bubbles driven by an electric field reported by the RIKEN group. Our results for the scattering cross section, drag, and transverse forces on moving ions are compared with experiments and shown to provide a quantitative understanding of the temperature dependence of the mobility and anomalous Hall angle for electron bubbles in normal and superfluid 3He-A . We also discuss our results in relation to earlier work on the theory of negative ions in superfluid 3He.

  16. Hyperpolarised 3He MRI and 81mKr SPECT in chronic obstructive pulmonary disease

    During recent years, magnetic resonance imaging (MRI) using hyperpolarised (HP) 3He gas has emerged as a promising new method for the imaging of lung ventilation. However, systematic comparisons with nuclear medicine techniques have not yet been performed. The aim of this study was to compare ventilation imaging methods in 26 patients with chronic obstructive pulmonary disease (COPD) and nine lung healthy volunteers. HP 3He MRI, 81mKr single-photon emission computed tomography (SPECT), high-resolution computed tomography (HRCT) and pulmonary function tests were performed. The three scans were scored visually as percentage of non-ventilated/diseased lung, and a computer-based objective measure of the ventilated volume in HP 3He MRI and 81mKr SPECT and an emphysema index in HRCT were calculated. We found a good correlation between HP 3He MRI and 81mKr SPECT for both visual defect score (r=0.80, p81mKr SPECT (the score on HP 3He MRI was one-third less than that on 81mKr SPECT), but the difference was reduced after normalisation for different breathing depths (HP 3He MRI at total lung capacity; 81mKr SPECT at tidal breathing at functional residual capacity). HP 3He MRI provides detailed ventilation distribution images and defect scores are comparable on HP 3He MRI and 81mKr SPECT. Additionally, new insights into the regional pulmonary microstructure via the apparent diffusion coefficient measurements are provided by HP 3He MRI. HP 3He MRI is a promising new diagnostic tool for the assessment of ventilation distribution. (orig.)

  17. Second sound experiments in superfluid 3He-A1 phase in high magnetic fields

    Bastea, Marina

    The Asb1 phase of sp3He is the first observed magnetic superfluid, stable only in the presence of an external magnetic field. Due to the broken relative gauge and spin rotational symmetry, the two associated collective modes, the second sound and the longitudinal spin waves are expected to appear as a single mode which we call the spin-entropy wave. Our work is focused on consistently mapping the behavior of the spin-entropy wave in the superfluid Asb{1} phase of sp3He, under a wide range of experimental conditions. Our results address fundamental questions such as the identification of the order parameter symmetry in the superfluid states, the nature of the pairing state in the Asb1 phase and the superfluid density anisotropy. We extensively investigated the propagation of the spin-entropy wave as a function of temperature, magnetic field between 1 and 8 Tesla and liquid pressure up to 30 bar. Our results show that the superfluid density is directly proportional to the magnitude of the external field in the specified range, as predicted by theory. We discovered that in the vicinity of the transition to the Asb2 phase, over a fairly large temperature range, the spin-entropy wave suffers a divergent attenuation. The observed effects were suggested as evidence for the presence of a minority condensate population, "down spin" pairs, specific for the Asb2 phase, as predicted by Monien and Tewordt. We measured the superfluid density dependence on the pressure between 10 and 30 bar and directly related it to the fourth order coefficients of the Ginzburg-Landau free energy expansion. The pressure dependence of three of these coefficients and their strong coupling corrections was found to be consistent with the theoretical predictions of Sauls and Serene. Our results support the identification of the A phase as the Anderson-Brinkman-Morel axial state and provide an important consistency check for the phase diagram carried out by groups at USC and Cornell. We performed

  18. T(T,2n)4He and 3He(3He,2p)4He: The Reaction Mechanism from Solar Energies to 10 MeV

    Bacher, A. D.; Brune, C. R.; Sayre, D. B.; Hale, G. M.; Frenje, J. A.; Gatu Johnson, M.

    2016-03-01

    We have studied the energy dependence of the reaction mechanism of the T(t,2n)4He reaction at stellar energies and of its charge symmetric analog reaction 3He(3He,2p)4He at energies up 10 MeV. We find that the reaction mechanism changes dramatically over this energy range in part due to the interference of the two identical fermions in the three-body final state. This contribution is dedicated to the memory of Tom Tombrello, my Ph.D. advisor at Cal Tech, who died in 2014.

  19. Gas cells for 3He hyperpolarized via spin-exchange optical pumping

    Kim, W.; Stepanyan, S. S.; Kim, A.; Tan, J. A.; Woo, S.

    2016-01-01

    We present a device for the production of hyperpolarized 3He, which is widely used in spinrelated nuclear physics research. Spin-exchange optical pumping (SEOP) is employed to polarize 3He enclosed in a circular borosilicate glass cell suitable not only for the production of polarized gas but also for its storage. The portable glass cell can, thus, be transported to any other research facility. The glass cell can be refilled several times. Special attention is given to the preparation and the filling of the cell to minimize the impurities on its walls and in the gas. We employ glass tubes with shorter lengths and larger diameters in the gas-filling system to achieve the improvement in the air flow necessary to obtain purer polarized 3He samples. The cell is prepared, and after it has been filled with rubidium (Rb) and 3He-N2 mixture, it is sealed under high vacuum conditions. The cell containing the mixture is exposed to circularly-polarized laser light with a wavelength of 795 nm at temperatures of 180 - 220 °C for SEOP. The polarization of 3He is measured via nuclear magnetic resonance (NMR). We obtained 40% polarized 3He in less than 15 hours and 50% in about 25 hours. The longitudinal relaxation time T 1 of the polarized 3He we measured was about 58 hours.

  20. Evidence of Cluster Structure of $^9$Be from $^3$He+$^9$Be Reaction

    Lukyanov, S M; Naumenko, M A; Xu, Yi; Trzaska, W H; Burjan, V; Kroha, V; Mrazek, J; Glagolev, V; Piskoř, Š; Voskoboynik, E I; Khlebnikov, S V; Penionzhkevich, Yu E; Skobelev, N K; Sobolev, Yu G; Tyurin, G P; Kuterbekov, K; Tuleushev, Yu

    2015-01-01

    The study of inelastic scattering and multi-nucleon transfer reactions was performed by bombarding a $^{9}$Be target with a $^3$He beam at an incident energy of 30 MeV. Angular distributions for $^9$Be($^3$He,$^3$He)$^{9}$Be, $^9$Be($^3$He,$^4$He)$^{8}$Be, $^9$Be($^3$He,$^5$He)$^{7}$Be, $^9$Be($^3$He,$^6$Li)$^6$Li and $^9$Be($^3$He,$^5$Li)$^7$Li reaction channels were measured. Experimental angular distributions for the corresponding ground states (g.s.) were analysed within the framework of the optical model, the coupled-channel approach and the distorted-wave Born approximation. Cross sections for channels leading to unbound $^5$He$_{g.s.}$, $^5$Li$_{g.s.}$ and $^8$Be systems were obtained from singles measurements where the relationship between the energy and the scattering angle of the observed stable ejectile is constrained by two-body kinematics. Information on the cluster structure of $^{9}$Be was obtained from the transfer channels. It was concluded that cluster transfer is an important mechanism in t...

  1. First Detection of $^3$He$^+$ in the Planetary Nebula IC$\\,$418

    Guzman-Ramirez, L; Zijlstra, A A; García-Miró, C; Morisset, C; Gray, M D

    2016-01-01

    The $^3$He isotope is important to many fields of astrophysics, including stellar evolution, chemical evolution, and cosmology. The isotope is produced in low-mass stars which evolve through the planetary nebula (PN) phase. $^3$He abundances in PNe can help test models of the chemical evolution of the Galaxy. We present the detection of the $^3$He$^+$ emission line using the single dish Deep Space Station 63, towards the PN IC$\\,$418. We derived a $^3$He/H abundance in the range 1.74$\\pm$0.8$\\times$10$^{-3}$ to 5.8$\\pm$1.7$\\times$10$^{-3}$, depending on whether part of the line arises in an outer ionized halo. The lower value for $^3$He/H ratio approaches values predicted by stellar models which include thermohaline mixing, but requires that large amounts of $^3$He are produced inside low-mass stars which enrich the interstellar medium (ISM). However, this over-predicts the $^3$He abundance in HII regions, the ISM, and proto-solar grains, which is known to be of the order of 10$^{-5}$. This discrepancy questi...

  2. Multi-spacecraft observations of recurrent {sup 3}He-rich solar energetic particles

    Bučík, R.; Innes, D. E.; Mall, U.; Korth, A. [Max-Planck-Institut für Sonnensystemforschung, D-37077 Göttingen (Germany); Mason, G. M. [Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723 (United States); Gómez-Herrero, R., E-mail: bucik@mps.mpg.de [Space Research Group, University of Alcalá, E-28871 Alcalá de Henares (Spain)

    2014-05-01

    We study the origin of {sup 3}He-rich solar energetic particles (<1 MeV nucleon{sup –1}) that are observed consecutively on STEREO-B, Advanced Composition Explorer (ACE), and STEREO-A spacecraft when they are separated in heliolongitude by more than 90°. The {sup 3}He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE {sup 3}He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 {sup 3}He-rich events with the same sizeable active region (AR) producing X-ray flares accompanied by prompt electron events, when it was near the west solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous {sup 3}He enrichment, lacking solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged AR near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of (1) solar regions with long-lasting conditions for {sup 3}He acceleration and (2) solar energetic {sup 3}He that is temporarily confined/re-accelerated in interplanetary space.

  3. 3He(d,p)4He reaction calculation with three-body Faddeev equations

    In order to investigate the 3He-n-p system as a three-body problem, we have formulated 3He-n and 3H-p effective potentials using both a microscopic treatment and a phenomenological approach. In the microscopic treatment, potentials are generated by means of the resonating group method (RGM) based on the Minnesota nucleon-nucleon potential. These potentials are converted into separable form by means of the microscopic Pauli correct (MPC) method. The MPC potentials are properly formulated to avoid Pauli forbidden states. The phenomenological potentials are obtained by modifying parameters of the EST approximation to the Paris nucleon-nucleon potential, such that they fit the low-energy 3He-n, 3H-p, and 3He-p phase shifts. Therefore, they describe the 3He-n differential cross section, the polarization observables, and the energy levels of 4He. The 3He-n-p Faddeev equations are solved numerically. We reproduce correctly the ground state and the first excited state of 5Li. Furthermore, the Paris-type potential is used to investigate the 3He(d,p)4He reaction at a deuteron bombarding energy of 270 MeV, where the system is treated as a three-body problem. Results for the polarized and unpolarized differential cross sections demonstrate convergence of the Born series. (orig.)

  4. Study on (n3, He) fusion reactions cross sections using optical model

    Non-elastic cross-sections have been calculated by using optical model for (n3, He) reactions at 22.5 MeV energy. The empirical formula including optical model non-elastic effects by fitting two parameters for the (n3, He) reaction cross-sections have been suggested. Reaction Q-values depending on the asymmetry term effect for the (n3, He) reaction have been investigated. The obtained cross-section formula with new coefficients has been compared with the experimental data and discussed. It has seen that the fit of formula in this paper is in good agreement with the experimental data

  5. Exchange of np-pair in elastic p3He-backscattering at intermidiate energies

    The contribution of loop Feynmann diagrams, describing the np-pair transfer in backward elastic p3He scattering, has been investigated in the framework of the three-dimensional diagram approach at incident energies of 0.2-1.7 GeV. It is shown that the sum of discussed diagrams is equivalent to the Born approximation in NN-interaction potentials. The numerical calculations performed using the five-channel Faddeev wave function of3He show that the sequentional n-p transfer dominates and its amplitude is rather weakly sensitive to the D-components of the 3He wave function and relativistic corrections. 26 resf., 3 figs

  6. What can superconductivity learn from quantized vorticity in 3He superfluids?

    In 3He superfluids quantized vorticity can take many different forms: It can appear as distributed periodic textures, as sheets, or as lines. In the anisotropic 3He-A phase in most cases the amplitude of the order parameter remains constant throughout the vortex structure and only its orientation changes in space. In the quasi-isotropic 3He-B phase vortex lines have a hard core where the order parameter has a reduced, but finite amplitude. The different structures have been firmly identified, based on both measurement and calculation. What parallels can be drawn from this information to the new unconventional superconductors or Bose-Einstein condensates? (orig.)

  7. Static aspects of the fission and fusion of liquid 3He drops

    Using an effective 3He-3He interaction, the fission and fusion of 3He drops have been investigated from a static point of view. The calculations show that a fission barrier develops for these neutral systems, and that their saddle configurations are rather elongate. The transition from oblate to prolate shapes as a function of the angular momentum L, as well as critical values for fission and fusion are discussed for some selected cases. A kind of proximity potential can be extracted from the drop-drop interaction potentials. (author) 33 refs.; 9 figs

  8. Kaonic 3He and 4He X-ray measurements in SIDDHARTA

    Ishiwatari, T; Beer, G; Berucci, C; Bombelli, L; Bragadireanu, A M; Cargnelli, M; Clozza, A; Corradi, G; Curceanu, C; d'Uffizi, A; Fiorini, C; Ghio, F; Girolami, B; Guaraldo, C; Hayano, R S; Iliescu, M; Iwasaki, M; Kienle, P; Sandri, P Levi; Lucherini, V; Marton, J; Okada, S; Pietreanu, D; Piscicchia, K; Lener, M Poli; Ponta, T; Quaglia, R; Rizzo, A; Vidal, A Romero; Scordo, A; Shi, H; Sirghi, D L; Sirghi, F; Tatsuno, H; Tudorache, A; Tudorache, V; Doce, O Vazquez; Widmann, E; Wuenschek, B; Zmeskal, J

    2011-01-01

    The strong-interaction shift of kaonic 3He and 4He 2p states was measured using gaseous targets for the first time in the SIDDHARTA experiment. The determined shift of kaonic 4He is much smaller than the values obtained in the experiments performed in 70's and 80's. Thus, the problems in kaonic helium (the "kaonic helium puzzle") was definitely solved by our measurements. The first observation of the kaonic 3He X-rays was also achieved. The shift both of kaonic 3He and 4He was found to be as small as a few eV.

  9. Study of neutron spin structure functions at low Q2 with polarized 3He

    The recently completed experiment E94-010 at Jefferson Lab studies the neutron spin structure functions at low momentum transfer (Q2) values. Using a polarized 3 He target and polarized electron beam, we have measured the asymmetries and cross sections for 3He(e,e') from the elastic to the deep inelastic region. The covered Q2 ranges from 0.03 to 1.1 GeV2. From the data, the Q2 evolution of the spin structure functions for 3He and neutron, and of the Gerasimov-Drell-Hearn (GDH) sum rule has been studied, and the preliminary results are presented

  10. Specific-heat measurements on dilute 3He-4He mixtures

    The author measured the specific heat of dilute 3He-4He mixtures in the concentration range from X = 1 x 10-3 to X = 3 x 10-3 and in the temperature range from 100 mK to 600 mK. This has been done by means of a thermal relaxation method. This method provides some interesting features and is applied, to our knowledge, for the first time to dilute 3He-4He mixtures. To reach the required temperature range for our experiments a 4He circulating 3He-4He dilution refrigerator has been constructed. The results confirm the deviation of the 3He contribution to the specific heat from the ideal Fermi gas behaviour. (Auth.)

  11. Preconceptual engineering design for the APT 3He Target/Blanket concept

    A preconceptual engineering design has been developed for the 3He Target/Blanket (T/B) System for the Accelerator Production of Tritium Project. This concept uses an array of pressure tubes containing tungsten rods for the neutron spallation source and 3He gas contained in a metal tank and blanket tubes as the tritium production material. The engineering design is based on a physics model optimized for efficient tritium production. Principle engineering consideration were: provisions for cooling all materials including the 3He gas; containment of the gas and radionuclides; remote handling; material compatibility; minimization of 3He, D2O, and activated waste; modularity; and manufacturability. The design provides a basis for estimating the cost to implement the system

  12. The ion optics of a miniature 3He/4He mass spectrometer of high resolution

    To measure the isotopic abundance ratio of 3He and 4He in samples by mass spectrometers is an important detection mean for helium isotope geochemistry research. A symmetrically arranged tandem 3He/4He mass spectrometer is described in the paper. The front stage, used to analyse 3He (including HD and H3) and 4He, is a homogeneous analysing magnet with a bending angle of 90 deg and a bending radius of 6 cm. The end stage, used to analyse 3He, HD and H3, is a non-homogeneous analysing magnet with a bending angle of 180 deg, a bending radius of 15 cm and a magnetic field gradient of 0.75. Because of the use of the non-zero second order coefficient β and curved entrance face of the later magnet for eliminating second order aberrations, the resolving power of the system is notably improved, and theoretically reaches about 3800

  13. Discovery of superfluid 3He phases wins 1996 nobel prize in physics

    The 1996 Nobel prize in physics was awarded to David M. Lee, Douglas D. Osheroff and Robert C. Richardson for their discovery of superfluidity in 3He in 1971. A short account of the discovery and its importance is given

  14. Cryopol: a superconducting magnetostatic cavity for a sup 3 He neutron spin filter

    Dreyer, J; Bourgeat-Lami, E; Lelievre-Berna, E; Pujol, S; Thomas, F; Thomas, M; Tasset, F

    2000-01-01

    We present a device called 'Cryopol' that provides a clean magnetic environment for a sup 3 He spin filter cell, even in the presence of strong magnetic stray fields like those of a superconducting magnet.

  15. Measurements of the structure and nucleation of vorticity in the (3)He superfluids. Doctoral thesis

    Parts, U.

    1995-10-01

    This thesis reports experiments on rotating superfluid 3He, which were performed in the Low Temperature Laboratory during the period 1991-94, and which are published in a series of original publications. Rotation is particularly useful for creating various types of topological objecs, e.g. quantized vortex lines, in large quantities for systematic investigation. The author`s method to study them is the nuclear magnetic resonance (NMR) technique, which has been an important experimental tool in various fields of physics for about fifty years. In the case of superfluid 3He, NMR provides direct information on the spatial distribution of the order parameter field. Both superfluid phases of 3He, the A- and the B-phase, have been under investigation in this thesis work. In 3He-B the main concern has been the nucleation of singular vortices. This process involves an energy barrier, similar to a first order phase transition.

  16. Isospin effects in the exclusive dp -> 3He{\\pi}+{\\pi}- reaction

    Mielke, M; Chiladze, D; Dymov, S; Fritzsch, C; Gebel, R; Goslawski, P; Hartmann, M; Kacharava, A; Khoukaz, A; Kulessa, P; Lorentz, B; Mersmann, T; Mikirtychiants, S; Ohm, H; Papenbrock, M; Rausmann, T; Serdyuk, V; Ströher, H; Täschner, A; Valdau, Y; Wilkin, C

    2014-01-01

    The differential cross section for the exclusive dp -> 3He{\\pi}+{\\pi}- reaction has been measured with high resolution and large statistics over a large fraction of the backward 3He hemisphere at the excess energy 265 MeV using the COSY-ANKE magnetic spectrometer. Though the well-known ABC enhancement is observed in the {\\pi}+{\\pi}- spectrum, the differences detected between the {\\pi}+3He and {\\pi}-3He invariant-mass distributions show that there must be some isospin-one {\\pi}{\\pi} production even at relatively low excess energies. The invariant-mass differences are modeled in terms of the sequential decay N*(1440) -> Delta(1232){\\pi} -> N{\\pi}{\\pi}.

  17. Regional Ventilation Changes in Severe Asthma after Bronchial Thermoplasty with 3He MR Imaging and CT

    Thomen, Robert P.; Sheshadri, Ajay; Quirk, James D.; Kozlowski, Jim; Ellison, Henry D.; Szczesniak, Rhonda D.; Castro, Mario; Woods, Jason C.

    2014-01-01

    We quantified regional lung ventilation in healthy volunteers and patients with severe asthma (both before and after thermoplasty) at the level of individual bronchopulmonary segments by using a combination of 3He MR imaging and CT.

  18. New data and evaluation of sup 3 He-induced nuclear reactions on Cu

    Tarkanyi, F; Takács, S; Al-Abyad, M; Mustafa, M G; Shubin, Y; Zhuang, Y

    2002-01-01

    Excitation functions of sup n sup a sup t Cu( sup 3 He, x) sup 6 sup 6 Ga, sup n sup a sup t Cu( sup 3 He, x) sup 6 sup 7 Ga, sup n sup a sup t Cu( sup 3 He, x) sup 6 sup 3 Zn and sup n sup a sup t Cu( sup 3 He, x) sup 6 sup 5 Zn nuclear reactions were measured up to 36 MeV using stacked foil irradiation arrangement and activation technique. The results were compared with compiled literature data. The status of the experimental database was investigated with the goal to produce recommended values for different applications. The application of the deduced data in the field of beam monitoring and thin layer activation is discussed.

  19. Ignition analysis for D plasma with non-Maxwellian 3He minority in fusion reactors

    Possible fusion reactivity enhancement due to 3He minority ICRF heating in D-3He toroidal plasma is demonstrated in present numerical simulations. On this purpose the particle code based on test-particle approach is developed. This code solves guiding center equations for 3He ions in toroidal magnetic field including Coulomb collisions of these ions with the background deuterons and electrons. A simple Monte Carlo model for ICRF heating is implemented in this code as well. The transformation of 3He distribution function from Maxwellian to non-Maxwellian due to heating plays the key role for reactivity enhancement. The formation of significant energetic tail gives rise to the reactivity enhancement. This is an important issue for the performance of fusion reactors with minority heating of ICRF. (author)

  20. Improved Technique for Measurement of Regional Fractional Ventilation by Hyperpolarized 3He MRI

    Emami, Kiarash; Kadlecek, Stephen J.; Woodburn, John M.; Zhu, Jianliang; Yu, Jiangsheng; Vahdat, Vahid; Pickup, Stephen; Ishii, Masaru; Rizi, Rahim R.

    2010-01-01

    Quantitative measurement of regional lung ventilation is of great significance in assessment of lung function in many obstructive and restrictive pulmonary diseases. A new technique for regional measurement of fractional ventilation using hyperpolarized 3He MRI is proposed, addressing the shortcomings of an earlier approach that limited its use to small animals. The new approach allows for the acquisition of similar quantitative maps over a shortened period and requires substantially less 3He...

  1. Generalized parton distributions of 3He and the neutron orbital structure

    Rinaldi, Matteo; Scopetta, Sergio

    2013-01-01

    The two leading twist, quark helicity conserving generalized parton distributions (GPDs) of 3He, accessible, for example, in coherent deeply virtual Compton scattering (DVCS), are calculated in impulse approximation (IA). Their sum, at low momentum transfer, is found to be largely dominated by the neutron contribution, so that 3He is very promising for the extraction of the neutron information. Anyway, such an extraction could be not trivial. A technique, able to take into account the nuclear...

  2. Ionization of polarized 3He+ ions in EBIS trap with slanted electrostatic mirror.

    Pikin,A.; Zelenski, A.; Kponou, A.; Alessi, J.; Beebe, E.; Prelee, K.; Raparia, D.

    2007-09-10

    Methods of producing the nuclear polarized {sup 3}He{sup +} ions and their ionization to {sup 3}H{sup ++} in ion trap of the electron Beam Ion Source (EBIS) are discussed. Computer simulations show that injection and accumulation of {sup 3}He{sup +} ions in the EBIS trap with slanted electrostatic mirror can be very effective for injection times longer than the ion traversal time through the trap.

  3. Contribution to the study of a helium dilution refrigerator with a 3He - 4He mixture

    New concepts to improve the conditions of operation of a helium dilution refrigerator with 3He additions in 4He are presented. The sealing of several circuits including heat exchangers is studied. A cryostat operating without a 3He condensation system is developed. The cryostat allows temperatures as low as 40 mK to be reached and is small enough to be transportable. The whole system was designed for neutron diffraction studies. The utilization of sintered silver powder heat exchangers is considered

  4. A compact SEOP 3He neutron spin filter with AFP NMR

    Ino, Takashi; Arimoto, Yasushi; Shimizu, Hirohiko M.; Sakaguchi, Yoshifumi; Sakai, Kenji; Kira, Hiroshi; Shinohara, Takenao; Oku, Takayuki; Suzuki, Jun-ichi; Kakurai, Kazuhisa; Chang, Lieh-Jeng

    2012-02-01

    We developed AFP NMR in an aluminum container for polarized noble gas nuclei. The radio frequency magnetic field inside the aluminum container was designed from computer simulations. The polarization loss by the AFP spin flip of 3He was measured to be as low as 3.8×10-4. With this technique, a compact in-situ polarizing 3He neutron spin filter with AFP NMR is demonstrated.

  5. Validity of the evidence for a central depression in the charge density of 3He

    The derivation of proton and neutron charge densities from experimentally obtained form factors is considered. The meson exchange current contribution to the 3He charge form factor for three models of neutron and proton charge form factors is calculated and it is shown that it is not valid to use the short range behavior of nucleon charge density to deduce information on the structure of 3He

  6. Hyperpolarized 3He magnetic resonance imaging: Preliminary evaluation of phenotyping potential in chronic obstructive pulmonary disease

    Rationale and objectives: Emphysema and small airway obstruction are the pathological hallmarks of chronic obstructive pulmonary disease (COPD). The aim of this pilot study in a small group of chronic obstructive pulmonary disease (COPD) patients was to quantify hyperpolarized helium-3 (3He) magnetic resonance imaging (MRI) functional and structural measurements and to explore the potential role for 3He MRI in detecting the lung structural and functional COPD phenotypes. Materials and methods: We evaluated 20 ex-smokers with stage I (n = 1), stage II (n = 9) and stage III COPD (n = 10). All subjects underwent same-day plethysmography, spirometry, 1H MRI and hyperpolarized 3He MRI at 3.0 T. 3He ventilation defect percent (VDP) was generated from 3He static ventilation images and 1H thoracic images and the 3He apparent diffusion coefficient (ADC) was derived from diffusion-weighted MRI. Results: Based on the relative contribution of normalized ADC and VDP, there was evidence of a predominant 3He MRI measurement in seven patients (n = 3 mainly ventilation defects or VDP dominant (VD), n = 4 mainly increased ADC or ADC dominant (AD)). Analysis of variance (ANOVA) showed significantly lower ADC for subjects with predominantly elevated VDP (p = 0.02 compared to subjects with predominantly elevated ADC; p = 0.008 compared to mixed group) and significantly decreased VDP for subjects with predominantly elevated ADC (p = 0.003, compared to mixed group). Conclusion: In this small pilot study, a preliminary analysis shows the potential for 3He MRI to categorize or phenotype COPD ex-smokers, providing good evidence of feasibility for larger prospective studies.

  7. Electropion production in 3He determined by measuring the triton recoil cross section

    The 3He(e,T) π+,e' cross section has been measured as a function of incident electron energy, triton recoil energy and angle. The experiment corresponds to excitation energies near 20 MeV above pion threshold. Comparison is made with a theory including all partial waves using Gaussian and Irving-Gunn ground states for 3He. The forward peaking approximation is also discussed

  8. 3He(e,d)e'p isochromats and angular distribution measurements

    An angular distribution and isochromats for the reaction 3He(e,d)e'p were measured to determine the importance of E2 strength near the peak of the 3He(#betta#,d)p cross section. The angular distribution was analyzed using both a complete and approximate virtual photon spectrum. The isochromats were compared to a plane wave model prediction and least squares fitted to determine the relative amounts of E1 and E2 strength

  9. Study of field assessment methods and worker risks for processing alternatives to support principles for FUSRAP waste materials. Part 2: Preliminary development of a wall-less gas-flow proportional counter for in-situ field analysis of nuclear contamination in soil

    Bush, S.P.; Hamby, D.M.; Martin, J.E.

    1997-03-01

    This study resulted in the design, construction and testing of a gas flow proportional counter for in-situ determination of soil contamination. The uniqueness of this detector is the screened material used for the cathode. A Pu-239 source of 0.006 {micro}Ci was mounted to the outside of the cathode to simulate radioactive soil. The detector probe was placed into a laboratory mock-up and tested to determine operating voltage, efficiency and energy resolution. Two gas flow proportional counters were built and tested. The detectors are cylindrical, each with a radius of 1.905 cm, having an anode wire with a radius of 0.0038 cm. The length of the smaller detector`s anode was 2.54 cm, and the length of the larger detector`s anode was 7.64 cm. Therefore, the active volumes were 28.96 cm{sup 3} and 87.10 cm{sup 3}, respectively, for the small and large detector. An operating voltage of 1975 volts was determined to be sufficient for both detectors. The average efficiency was 2.59 {+-} 0.12% and 76.71 {+-} 10.81% for the small volume and large volume detectors, respectively. The average energy resolution for the low-energy peak of the small detector was 4.24 {+-} 1.28% and for the large-energy peak was 1.37 {+-} 0.66%. The large detectors` energy resolution was 17.75 {+-} 3.74%. The smaller detector, with better energy resolution, exhibited a bi-modal spectrum, whereas the larger detector`s spectrum centered around a single broad peak.

  10. Possibilities for breakeven and ignition of D-3He fusion fuel in a near term tokamak

    The recent realization that the moon contains a large amount of the isotope 3He has rekindled interest in the D-3He fuel cycle. In this study we consider the feasibility of investigating D-3He reactor plasma conditions in a tokamak of the NET/INTOR class. We have found that, depending on the energy confinement scaling law, energy breakeven may be achieved without significant modification to the NET design. The best results are for the more optimistic ASDEX H-mode scaling law. Kaye-Goldston scaling with a modest improvement due to the H-mode is more pessimistic and makes achieving breakeven more difficult. Significant improvement in Q (ratio of the fusion power to the injected power), or the ignition margin, can be achieved by taking advantage of the much reduced neutron production of the D-3He fuel cycle. Removal of the tritium producing blanket and replacing the inboard neutron shield by a thinner shield optimized for the neutron spectrum in D-3He allows the plasma to be increased without changing the magnetic field at the toroidal field magnet. This allows the plasma to achieve higher beta and Q values up to about 3. The implications of D-3He operation for fast ion loss, neutron shielding, heat loads on the first wall and divertor, plasma refuelling, changes to the poloidal field coil system, and pumping of the helium from the vacuum chamber are considered in the report. (orig.)

  11. First doubly polarised photoproduction on 3He at the photon beam of MAMI

    A first experiment with a polarised 3He target was carried out in July 2009 at the MAMI accelerator in Mainz in a photon energy range between 200 MeV and 800 MeV. The aim of this measurement was to investigate the Gerasimov-Drell-Hearn sum rule on the neutron. The use of the data obtained with the polarised 3He target, compared to existing data on the deuteron, gives a complementary and more direct access to the neutron, due to the spin structure of the 3He. The measurement of the helicity dependence of the inclusive total photoabsorption cross section required a beam of tagged circularly polarised photons incident on the longitudinally polarised 3He target. The data were taken using the 4π Crystal Ball photon spectrometer in combination with TAPS as a forward wall and complemented by a threshold Cherenkov detector used to on-line suppress the background from electromagnetic events. The development and preparation of the different components of the 3He experimental setup was an important part of this work and are described in detail in this thesis. The detector system and the analysis method were tested by the measurement of the unpolarised total inclusive photoabsorption cross section on liquid hydrogen. The results obtained are in good agreement with previous published data. Preliminary results of the unpolarised total photoabsorption cross section, as well as the helicity dependent photoabsorption cross section difference on 3He compared with several theoretical models will also be presented. (orig.)

  12. Novel Components for Neutron Counters

    Neutron counters for safeguards proposes have been developed during the last thirty years at the Joint Research Centre. The paper describes some of the latest developments and implementations in modern neutron counter. The design of a neutron counter is nowadays largely done by MCNP calculations. We have studied the behaviour of some components for a specific counter with respect to optimising the performance of the counter. This includes the moderator materials, thermal neutron absorbers, and 3-He detectors. Also the electronics for neutron counter has evolved over the years. Modern neutron counters require a large number of detectors and signal amplifiers to provide optimised parameters for the data interpretation. For this purpose we have developed a new pre-amplifier/amplifier/discriminator circuit which is both compact and inexpensive. The new circuit will be used in existing and future neutron counters. Concerning the treatment of the digital signal pulse train we intend to makes use of the latest advances in computer technology. A novel electronic system has been developed with a maximum of 128 input channels, which can cope with the high count rate of more than 1 million counts per second with zero dead-time. The Multi Input-Pulse Train Analysis (MI-PTA) system can be used with standard instruments, like Shift Register Analysers. However, it has been designed to perform a variety of pulse train analysis techniques itself, or in combination with a Personal Computer to which the system is connected via a High Speed USB2.0 connection. Pulse data can exchanged between the MI-PTA and PC at the rate of 480 Mb/s, allowing real time analysis on a PC and providing the basis for a Virtual Instrument approach: by modifying the software new instruments can be configured. The system consists of a number of base units, each with 8 TTL compatible inputs. Only one unit, configured as a Master, is connected to a PC. Up-to 15 Slave units can be connected to the Master via a

  13. Terrestrial cosmogenic 3He: where are we 30 years after its discovery?

    Blard, Pierre-Henri; Pik, Raphaël; Farley, Kenneth A.; Lavé, Jérôme; Marrocchi, Yves

    2016-04-01

    It is now 30 years since cosmogenic 3He has been detected for the first time in a terrestrial sample (Kurz, 1986). 3He is now a widely used geochemical tool in many fields of Earth sciences: volcanology, tectonics, paleoclimatology. 3He has the advantage to have a high "production rate" to "detection limit" ratio, allowing surfaces as young as hundred of years to be dated. Although its nuclear stability implies several limitations, it moreover represents a useful alternative to 10Be in mafic environments. This contribution is a review of the progresses that have been accomplished since this discovery, and discuss strategies to improve both the accuracy and the precision of this geochronometer. 1) Measurement of cosmogenic 3He Correction of magmatic 3He. To estimate the non-cosmogenic magmatic 3He, Kurz (1986) invented a two steps method involving crushing of phenocrysts (to analyze the isotopic ratio of the magmatic component), followed by a subsequent melting of the sample, to extract the remaining components, including the cosmogenic 3He: 3Hec = 3Hemelt ‑4Hemelt x (3He/4He)magmatic (1) Several studies suggested that the preliminary crushing may induce a loss of cosmogenic 3He (Hilton et al., 1993; Yokochi et al., 2005; Blard et al., 2006), implying an underestimate of the cosmogenic 3He measurement. However, subsequent work did not replicate these observations (Blard et al., 2008; Goerhing et al., 2010), suggesting an influence of the used apparatus. An isochron method (by directly melting several phenocrysts aliquots) is an alternative to avoid the preliminary crushing step (Blard and Pik, 2008). Atmospheric contamination. Protin et al. (in press) provides robust evidences for a large and irreversible contamination of atmospheric helium on silicate surfaces. This unexpected behavior may reconcile the contrasted observations about the amplitude of crushing loss. This undesirable atmospheric contamination is negligible if grain fractions smaller than 150 mm are

  14. The $^{150}$Nd($^3$He,$t$) and $^{150}$Sm($t$,$^3$He) reactions with applications to $\\beta\\beta$ decay of $^{150}$Nd

    Guess, C J; Akimune, H; Algora, A; Austin, Sam M; Bazin, D; Brown, B A; Caesar, C; Deaven, J M; Ejiri, H; Estevez, E; Fang, D; Faessler, A; Frekers, D; Fujita, H; Fujita, Y; Fujiwara, M; Grinyer, G F; Harakeh, M N; Hatanaka, K; Herlitzius, C; Hirota, K; Hitt, G W; Ishikawa, D; Matsubara, H; Meharchand, R; Molina, F; Okamura, H; Ong, H J; Perdikakis, G; Rodin, V; Rubio, B; Shimbara, Y; Süsoy, G; Suzuki, T; Tamii, A; Thies, J H; Tur, C; Verhanovitz, N; Yosoi, M; Yurkon, J; Zegers, R G T; Zenihiro, J

    2011-01-01

    The $^{150}$Nd($^3$He,$t$) reaction at 140 MeV/u and $^{150}$Sm($t$,$^3$He) reaction at 115 MeV/u were measured, populating excited states in $^{150}$Pm. The transitions studied populate intermediate states of importance for the (neutrinoless) $\\beta\\beta$ decay of $^{150}$Nd to $^{150}$Sm. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of Quasiparticle Random-Phase Approximation (QRPA), which is one of the main methods employed for estimating the half-life of the neutrinoless $\\beta\\beta$ decay ($0\

  15. Forward-angle 3He(e,e'π+-) coincident electroproduction and the search for Δ's in the ground state of 3He

    Forward-angle coincident electroproduction cross sections of charged pions from 3He have been measured at the cw electron accelerator MAMI. The overall features of the data are reproduced in terms of a microscopic model, including pole terms, final state rescattering and produced and preformed Δ resonances. Separation of the cross section into its longitudinal and transverse parts was performed for the first time. (K.A.)

  16. Photodisintegration of /sup 3/H and /sup 3/He. [Threshold to 25 MeV

    Faul, D.D.

    1980-09-01

    The photoneutron cross sections for /sup 3/H and /sup 3/He 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 /sup 3/H and the three-body breakup of both /sup 3/H and /sup 3/He; these measurements for /sup 3/H are the first to span the energy region across the peaks of the cross sections. An efficient BF/sub 3/-tube-and-paraffin neutron detector and high-pressure gaseous samples of several moles each (the activity of the /sup 3/H sample was approx. 200,000 Ci) were employed in these measurements. Measurements on /sup 16/O and /sup 2/H 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 /sup 3/He from the literature, show that the two-body breakup cross sections for /sup 3/H and /sup 3/He have nearly the same shape, but the one for /sup 3/He lies lower in magnitude; the three-body breakup cross section for /sup 3/He lies higher in magnitude and is broader in the peak region and also rises less sharply from threshold than that for /sup 3/H; 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 /sup 3/H and /sup 3/He 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.

  17. Performance review of the high efficiency neutron counter

    A performance review of several High Efficiency Neutron Counters (HENCs) has been conducted for the purposes of quantifying the ranges of the inherent operating parameters, and for the qualitative assessment of the application of these parameters for the measurement of various waste types. The HENC is a passive neutron counter intended for use with multiplicity counting techniques for the assay of 200 liter (55 gallon) drums containing plutonium contaminated waste. The counter utilizes 113 3He proportional tubes which are organized into multiple counting channels and are arranged in a 4p geometry about the assay cavity. An Add- A-Source (AAS) Matrix Correction assembly is incorporated into the counter as the basis for compensating the assay values for the perturbation of the drum contents. Prior to use in the field, several fundamental operating parameters for the HENC must be determined during characterization of the counter. These parameters are determined by the neutron response characteristics of the assay cavity and signal processing electronics, and are differentiated from more typical calibration parameters as they are determined without the need for actual or representative plutonium or mixed-oxide samples. Examples of operating parameters include HV plateau, die-away profile, pre-delay setting, dead time parameters, central empty drum efficiency, gate utilization factors and spatial response profiles. The performance review is based on five HENCs manufactured in the span of approximately ten years, all of which are currently operating in the field at various nuclear facilities. The review serves to identify the range of values used for each of the operating parameters, and the impact on performance, if any, as a function of that range. The resulting database can then serve both as a standard by which future systems can be type tested, and as a source of initial settings for the operating parameters with the evident benefit of time-savings in the

  18. Simultaneous measurement of pulmonary partial pressure of oxygen and apparent diffusion coefficient by hyperpolarized 3He MRI

    Yu, Jiangsheng; Law, Michelle; Kadlecek, Stephen; Emami, Kiarash; Ishii, Masaru; Stephen, Michael; Woodburn, John M.; Vahdat, Vahid; Rizi, Rahim R.

    2009-01-01

    Hyperpolarized 3He (HP 3He) MRI shows promise to assess structural and functional pulmonary parameters in a sensitive, regional and non-invasive way. Structural HP 3He MRI has applied the apparent diffusion coefficient (ADC) for the detection of disease-induced lung microstructure changes at the alveolar level, and HP 3He pulmonary partial pressure of oxygen (pO2) imaging measures the oxygen transfer efficiency between the lung and blood stream. Although both parameters are affected in chroni...

  19. Body counter

    The paper gives a survey on some applications of the whole body counter in clinical practice and a critical study of its application as a routine testing method. Remarks on the necessary precautions are followed by a more detailed discussion of the determination of the natural potassium content, the iron metabolism, the vitamin B12 test, investigations of the metabolism of the bone using 47Ca and 85Sr, investigations with iodine and iodine-labelled substances, clearance investigations (in particular the 51Cr EDTA clearance test), as well as the possibilities of neutron activation in vivo. (ORU/AK)

  20. Coherent deeply virtual Compton scattering off 3He and neutron generalized parton distributions

    Rinaldi, Matteo

    2014-01-01

    It has been recently proposed to study coherent deeply virtual Compton scattering (DVCS) off 3He nuclei to access neutron generalized parton distributions (GPDs). In particular, it has been shown that, in Impulse Approximation (IA) and at low momentum transfer, the sum of the quark helicity conserving GPDs of 3He, H and E, is dominated by the neutron contribution. This peculiar result makes the 3He target very promising to access the neutron information. We present here the IA calculation of the spin dependent GPD tilde-H of 3He. Also for this quantity the neutron contribution is found to be the dominant one, at low momentum transfer. The known forward limit of the IA calculation of tilde-H, yielding the polarized parton distributions of 3He, is correctly recovered. The extraction of the neutron information could be anyway non trivial, so that a procedure, able to take into account the nuclear effects encoded in the IA analysis, is proposed. These calculations, essential for the evaluation of the coherent DVC...

  1. Orbital angular momentum and orbital dynamics: /sup 3/He-A and the Bose liquid

    Volovik, G.E.; Mineev, V.P.

    1981-09-01

    General expressions for the superfluid current and the orbital angular momentum in a superfluid liquid with the structure of the A phase of /sup 3/He at T = 0 are derived which go over in the limit ..delta..>>epsilon-c/sub F/ into the corresponding expressions for a Bose liquid consisting of molecules with spin h1. It is shown that the local intrinsic angular momentum in /sup 3/He-A, unlike the corresponding quantity in a Bose liquid, is defined only in variations, and its spontaneous part is small on account of the smallness of (..delta../epsilon-c/sub F/)/sup 2/. The Lagrangian formalism is used to construct the nonlinear orbital dynamics of /sup 3/He-A at T = 0. It is shown that in the presence of textures in the l-vector field the dynamical equations are not Galilean invariant, which is another manifestation of the difference between /sup 3/He-A and a Bose liquid. The noninvariance stems from the fact that, because of the absence of a gap in the excitation spectrum, the nonsingular textures in /sup 3/He-A possess normal momenta, as a result of which the normal-component density is nonzero even at T = 0, and the velocity of the normal component does not drop out of the dynamical equations.

  2. /sup 3/He-A versus bose liquid: orbital angular momentum and orbital dynamics

    Volovik, G.S.; Mineev, V.P. (AN SSSR, Moscow. Inst. Teoreticheskoj Fiziki)

    1981-09-01

    At T=0 are obtained general expressions for the superfluid current and orbital angular momentum in a superfluid liquid with the structure of the /sup 3/He A-phase which in the limit ..delta..<3/He-A is not a total differential and its spontaneous part is small since (..delta../epsilonsub(F))sup(2)<<1. Nonlinear orbital dynamics of He/sup 3/He-A at T=0 is obtained on the basis of the Lagrangian formalism. It is shown that in the presence of textures in the field of the vector I the equations of dynamics do not meet the requirements of Galilean invariance which also displays the difference of /sup 3/He-A from the Bose liquid. The noninvariance is associated with the fact that due to the absence of the gap in the excitation spectrum nonsingular textures in /sup 3/He-A have a normal momentum as a result of which even at T=0 the density of the normal component does not become equal to zero and the velocity of the normal component is retained in the equations of dynamics.

  3. 3He in extreme conditions: from fundamental physics to applications in astrophysics

    This work is composed of three different parts: in the first part, a long term project on a dark matter detector prototype based on superfluid 3He (ULTIMA) is continued, and several precious observations for the operation of a future large detector are presented. The importance of covering the bolometer cell surfaces with 4He, as solid layers of 3He drastically reduce the sensitivity, is demonstrated. The systematic measurement of the influence of the magnetic field on the energy calibration is presented. Most importantly, a difference of the pulse shape for different incident particles has been observed and studied. This is likely to provide a powerful discrimination criterion for a future dark matter detector. In a second part, the existing setup is used to do measurements on fundamental 3He physics. First, the heat capacity of adsorbed layers of 3He is measured at ultra low temperatures and in the presence of magnetic fields. Secondly, the fast transition from the normal to the superfluid phase after a local heating by a neutron capture reaction is studied. The results are interpreted in terms of the Kibble-Zurek vortex creation scenario. In the third part, the influence on the superfluid states of the confinement of 3He in anisotropic aerogel is studied. Using NMR techniques, predictions of the appearance of a new phase labeled polar phase are tested, and evidence for the observation of a new precessing mode is presented. (author)

  4. Oxygen-sensitive {sup 3}He-MRI in bronchiolitis obliterans after lung transplantation

    Gast, Klaus K. [Klinikum der Johannes Gutenberg-Universitaet, Klinik und Poliklinik fuer diagnostische und interventionelle Radiologie, Mainz (Germany); Biedermann, Alexander [Klinikum der Johannes Gutenberg-Universitaet, 3. Medizinische Klinik, Pulmonologie, Mainz (Germany); Herweling, Annette [Klinikum der Johannes Gutenberg-Universitaet, Klinik fuer Anaesthesiologie, Mainz (Germany); Schreiber, Wolfgang G. [Klinikum der Johannes Gutenberg-Universitaet, Klinik und Poliklinik fuer diagnostische und interventionelle Radiologie, MR-Physik, Mainz (Germany); Schmiedeskamp, Joerg [Max-Planck-Institut fuer Polymerforschung, Mainz (Germany); Mayer, Eckhard [Klinikum der Johannes Gutenberg-Universitaet, Klinik fuer Herz-, Thorax- und Gefaesschirurgie, Mainz (Germany); Heussel, Claus P. [Abteilung fuer Radiologie, Thoraxklinik Heidelberg, Heidelberg (Germany); Markstaller, Klaus; Eberle, Balthasar [Inselspital/Universitaetsspital, Klinik fuer Anaesthesiologie, Bern (Switzerland); Kauczor, Hans-Ulrich [Radiologie, Deutsches Krebsforschungszentrum (DKFZ), Heidelberg (Germany)

    2008-03-15

    Oxygen-sensitive {sup 3}He-MRI was studied for the detection of differences in intrapulmonary oxygen partial pressure (pO{sub 2}) between patients with normal lung transplants and those with bronchiolitis obliterans syndrome (BOS). Using software developed in-house, oxygen-sensitive {sup 3}He-MRI datasets from patients with normal lung grafts (n = 8) and with BOS (n = 6) were evaluated quantitatively. Datasets were acquired on a 1.5-T system using a spoiled gradient echo pulse sequence. Underlying diseases were pulmonary emphysema (n = 10 datasets) and fibrosis (n = 4). BOS status was verified by pulmonary function tests. Additionally, {sup 3}He-MRI was assessed blindedly for ventilation defects. Median intrapulmonary pO{sub 2} in patients with normal lung grafts was 146 mbar compared with 108 mbar in patients with BOS. Homogeneity of pO2 distribution was greater in normal grafts (standard deviation pO2 34 versus 43 mbar). Median oxygen decrease rate during breath hold was higher in unaffected patients (-1.75 mbar/s versus -0.38 mbar/s). Normal grafts showed fewer ventilation defects (5% versus 28%, medians). Oxygen-sensitive {sup 3}He-MRI appears capable of demonstrating differences of intrapulmonary pO2 between normal lung grafts and grafts affected by BOS. Oxygen-sensitive {sup 3}He-MRI may add helpful regional information to other diagnostic techniques for the assessment and follow-up of lung transplant recipients. (orig.)

  5. Coherent deeply virtual Compton scattering off 3He and neutron generalized parton distributions

    Rinaldi Matteo

    2014-06-01

    Full Text Available It has been recently proposed to study coherent deeply virtual Compton scattering (DVCS off 3He nuclei to access neutron generalized parton distributions (GPDs. In particular, it has been shown that, in Impulse Approximation (IA and at low momentum transfer, the sum of the quark helicity conserving GPDs of 3He, H and E, is dominated by the neutron contribution. This peculiar result makes the 3He target very promising to access the neutron information. We present here the IA calculation of the spin dependent GPD H See Formula in PDF of 3He. Also for this quantity the neutron contribution is found to be the dominant one, at low momentum transfer. The known forward limit of the IA calculation of H See Formula in PDF , yielding the polarized parton distributions of 3He, is correctly recovered. The extraction of the neutron information could be anyway non trivial, so that a procedure, able to take into account the nuclear effects encoded in the IA analysis, is proposed. These calculations, essential for the evaluation of the coherent DVCS cross section asymmetries, which depend on the GPDs H,E and H See Formula in PDF , represent a crucial step for planning possible experiments at Jefferson Lab.

  6. The development of 3He neutron detectors for applications in high level gamma-ray backgrounds

    To measure high-level-activity scrap and waste, it is necessary to use neutron detectors that are insensitive to the high gamma-ray background. We have developed a combination of 3He tubes and custom preamplifiers to provide the high efficiency associated with 3He detectors with good gamma-ray rejection. We have preamplifiers with short time constants in the signal processing to help separate the neutron signals from the slower risetime gamma signals. We have compared AMPTEK (A-111) preamplifiers with Precision Data Technology (PDT 110A) preamplifiers with experimental tests for gamma rejection and radiation damage. Hot cell radiation tests using a 4.5 Ci radium source were performed using 10B and 3He detectors to evaluate relative efficiency and the ability to separate neutrons and gamma rays. The AMPTEK A-111 and PDT-110A amplifiers were exposed to gamma doses between ∼0.1 R/h and 1500 R/h to observe where the gamma pileup would interfere with the neutron counting. The conclusion is that both amplifiers can operate in gamma fields up to ∼500 R/h with modest loss of neutron efficiency. This is valid for the case of only one 3He tube (30-cm active length) connected to a single amplifier. If an amplifier services multiple tubes or longer tubes, the gamma rejection will get worse. Studies are in progress to determine the lifetime of the amplifiers and 3He tubes in the high-radiation fields

  7. Multi-Spacecraft Observations of Recurrent 3He-Rich Solar Energetic Particles

    Bucik, R; Mall, U; Korth, A; Mason, G M; Gomez-Herrero, R

    2014-01-01

    We study the origin of 3He-rich solar energetic particles (<1 MeV/nucleon) that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when they are separated in heliolongitude by more than 90{\\deg}. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region producing X-ray flares accompanied by prompt electron events, when it was near the west solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged active region near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III r...

  8. Results on Double-polarization Asymmetries in Quasielastic Scattering from Polarized 3He

    Sulkosky Vincent A.

    2016-01-01

    Full Text Available The 3He nucleus has become extremely important in the investigation of the neutron’s spin structure. When polarized, 3He acts as an effective polarized neutron target and hence facilitates our understanding of the neutron’s internal structure. However, to be used in this manner, our understanding of the internal structure of 3He is of extreme importance. As the precision of experiments has improved, the extraction of polarized neutron information from 3He leads to an ever larger share of the systematic uncertainty for these experiments. In these proceedings, I present a precise measurement of beam-target asymmetries in the He→3(e→ ,e′d${}^3\\overrightarrow {He} (\\vec e,e'd$ and He→3(e→,e′p${}^3\\overrightarrow {He} (\\vec e,e'p$ reactions. The former process is a uniquely sensitive probe of hadron dynamics in 3He and the structure of the underlying electromagnetic currents. The measurements have been performed around the quasi-elastic peak at Q2 = 0.25 (GeV/c2 and 0.35 (GeV/c2 for recoil momenta up to 270 MeV/c. The experimental apparatus, analysis and results were presented together with a comparison to state-of-the art Faddeev calculations.

  9. Complementary aspects of the (d,3He) and (e,e'p) reactions

    Proton-hole states have been investigated by both the (d,3He) pick-up and quasi-free (e,e'p) knockout reactions. Both reactions have their advantages and disadvantages. In the (d,3He) reaction employing ploarized deutrons, both the orbital and total angular momenta, l and j, of the transferred proton can be determined, whereas the (e, e'p) reaction presently allows only the determination of the transferred l-value. The (d,3He) reaction samples only the asymptotic tail of the picked-up proton wavefunction due to strong absorption effects on the projectile and ejectile. This incomplete sampling leads to large uncertainties in the extracted spectroscopic factors. The (e,e'p) reaction, on the other hand, probes the entire proton wavefunction in momentum space, thus yielding much more reliable spectroscopic factors. It is argued that some uncertainties in the (d,3He) reaction description can be reduced if information from the (e,e'p) reaction is employed. Two-step processes are sufficiently small in the (e, e'p) reaction, although not negligible, thus enabling a more reliable study of small wavefunction components than with the (d, 3He) reaction. (author). 16 refs., 4 figs

  10. Results on Double-polarization Asymmetries in Quasielastic Scattering from Polarized 3He

    Sulkosky, Vincent A. [Univ. of Virginia, Charlottesville, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-03-01

    The 3He nucleus has become extremely important in the investigation of the neutron’s spin structure. When polarized, 3He acts as an effective polarized neutron target and hence facilitates our understanding of the neutron’s internal structure. However, to be used in this manner, our understanding of the internal structure of 3He is of extreme importance. As the precision of experiments has improved, the extraction of polarized neutron information from 3He leads to an ever larger share of the systematic uncertainty for these experiments. In these proceedings, I present a precise measurement of beam-target asymmetries in the and reactions. The former process is a uniquely sensitive probe of hadron dynamics in 3He and the structure of the underlying electromagnetic currents. The measurements have been performed around the quasi-elastic peak at Q2 = 0.25 (GeV/c)2 and 0.35 (GeV/c)2 for recoil momenta up to 270 MeV/c. The experimental apparatus, analysis and results were presented together with a comparison to state-of-the art Faddeev calculations.

  11. Longitudinal assessment of treatment effects on pulmonary ventilation using 1H/3He MRI multivariate templates

    Tustison, Nicholas J.; Contrella, Benjamin; Altes, Talissa A.; Avants, Brian B.; de Lange, Eduard E.; Mugler, John P.

    2013-03-01

    The utitlity of pulmonary functional imaging techniques, such as hyperpolarized 3He MRI, has encouraged their inclusion in research studies for longitudinal assessment of disease progression and the study of treatment effects. We present methodology for performing voxelwise statistical analysis of ventilation maps derived from hyper­ polarized 3He MRI which incorporates multivariate template construction using simultaneous acquisition of IH and 3He images. Additional processing steps include intensity normalization, bias correction, 4-D longitudinal segmentation, and generation of expected ventilation maps prior to voxelwise regression analysis. Analysis is demonstrated on a cohort of eight individuals with diagnosed cystic fibrosis (CF) undergoing treatment imaged five times every two weeks with a prescribed treatment schedule.

  12. A Short History of the Theory and Experimental Discovery of Superfluidity in 3He

    Brinkman, W. F.

    I discuss the development of the theory and experiments on superfluid 3He. After the discovery of superfluidity in 3He by Osheroff, Richardson and Lee, Phil Anderson quickly recruited Doug Osheroff to come to Bell Labs and set up a dilution fridge to continue his experiments. One of the mysteries at that time was how the high-temperature A-phase, which has a gapless excitation spectrum, could be stabilized relative to the fully gapped, lower temperature B-phase. I explain how Phil Anderson and I developed the spin fluctuation theory of the A-phase of superfluid 3He which accounted for its stability, leading to the Anderson-Brinkman-Morel (ABM) theory of the superfluid A-phase...

  13. Tritium production, management and its impact on safety for a D3He fusion reactor

    This paper reports that about three percent of the fusion energy produced by the D-3He reactor is in the form of neutrons. Those neutrons are generated by D-D and D-T reactions, with the tritium produced by the D-D fusion. The neutrons will react with structural steel, deuterium, 3He and shielding material to produce tritium. about half of the tritium generated by the D-D reaction will not burn in the plasma and will exit as a part of the plasma exhaust. Thus, there is enough tritium produced in a D-3He reactor and careful management will be required. The tritium produced in the shield and plasma can be managed with an acceptable effect on cost and safety

  14. Experimental study of the 56Ni(3He,d)57Cu reaction in inverse kinematics

    Measurements of (3He,d) reactions can provide information on the proton widths of states that play a role in astrophysically important (p,γ) reactions. We report on the first study of the (3He,d) reaction in inverse kinematics with a 56Ni (T1/2=6.1 d) ion beam. The Q-value resolution of ∼ keV achieved in this experiment was sufficient to separate the transitions populating the ground state and the 1/2--5/2- doublet at Ex∼1.1 MeV in 57Cu. Prospects for similar (3He,d) experiments with improved energy resolution are also discussed.

  15. Double-Cell Geometry for 129Xe/3He Co-Magnetometry

    Ohtomo, Yuichi; Ichikawa, Yuichi; Sato, Tomoya; Sakamoto, Yu; Kojima, Shuichiro; Suzuki, Takahiro; Shirai, Hazuki; Chikamori, Masatoshi; Hikota, Eri; Miyatake, Hirokazu; Nanao, Tsubasa; Suzuki, Kunifumi; Tsuchiya, Masato; Inoue, Takeshi; Furukawa, Takeshi; Yoshimi, Akihiro; Bidinosti, Christopher P.; Ino, Takashi; Ueno, Hideki; Matsuo, Yukari; Fukuyama, Takeshi; Asahi, Koichiro

    Comagnetometers play a key role in EDM experiments. They allow one to quantify, and subsequently correct for, any long-term drifts of the external magnetic field. In order to improve the performance of the 3He comagnetometer for our 129Xe EDM measurements, we have decided to incorporate a double-cell geometry which enables us to suppress a frequency shift due to contact interaction with polarized Rb atoms. In this study, the production and relaxation of 3He spin polarization in the double cell were studied. As a result, the followings were achieved: a polarization of 1.04(8)%, a longitudinal spin relaxation time of 10.1(5) h, and a transverse relaxation time of 2,340 s. With these improvements, concurrent operation of the 129Xe and 3He masers has been realized, and EDM measurement will be started in near future using a cell designed based on the results of this study.

  16. Feasibility study of a sup 3 He-magnetometer for neutron electric dipole moment experiments

    Borisov, Y; Leduc, M; Lobashev, V; Otten, E W; Sobolev, Y

    2000-01-01

    We report on a sup 3 He-magnetometer capable of detecting tiny magnetic field fluctuations of less than 10 sup - sup 1 sup 4 T in experiments for measuring the electric dipole moment (EDM) of the neutron. It is based on the Ramsey technique of separated oscillating fields and uses nuclear spin-polarized sup 3 He gas which is stored in two vessels of V approx =10 l in a sandwich-type arrangement around the storage bottle for ultra-cold neutrons (UCN). The gas is polarized by means of optical pumping in a separate, small discharge cell at pressures around 0.5 mbar and is then expanded into the actual magnetometer volume. To detect the polarization of sup 3 He gas at the end of the storage cycle the gas is pumped out by means of an oil-diffusion pump and compressed again into the discharge cell where optical detection of nuclear polarization is used.

  17. The Effect Of Neutron Attenuation On Power Deposition In Nuclear Pumped 3He-Lasers

    Çetin, Füsun

    2007-04-01

    Nuclear-pumped lasers (NPLs) are driven by the products of nuclear reactions and directly convert the nuclear energy to directed optical energy. Pumping gas lasers by nuclear reaction products has the advantage of depositing large energies per reaction. The need for high laser power output implies high operating pressure. In the case of volumetric excitation by 3He(n, p)3H reactions, however, operation at high pressure (more than a few atm) causes excessive neutron attenuation in the 3He gas. This fact adversely effects on energy deposition and, hence, laser output power and beam quality. Here, spatial and temporal variations of neutron flux inside a closed 3He -filled cylindrical laser tube have been numerically calculated for various tube radii and operating pressures by using a previously reported dynamic model for energy deposition. Calculations are made by using ITU TRIGA Mark II Reactor as the neutron source. The effects of neutron attenuation on power deposition are examined.

  18. Study of 68Zn, 70Zn and 74Ge using the (d,3He) reaction

    The 69Ga, 71Ga(d,3He)68Zn, 70Zn and 75As(d,3He)74Ge reactions have been studied at 26MeV with an overall resolution of 18-20keV using a split pole magnetic spectrometer. Spectroscopic factors have been extracted for 16 levels in 68Zn, 14 levels in 70Zn and 24 levels in 74Ge. The ratio R=sigma(02+)/sigma(0+g.s.) shows a singularity at N=40. The small value of R for 74Ge is consistent with a previously proposed description of the structure of the states involved which is based on a simple mixing of psub(3/2) and fsub(5/2) proton configurations. The results for the Ga(d,3He)Zn reactions are compared to a recent shell model calculation

  19. Antisymmetry and channel coupling contributions to the absorption for $p + \\alpha /d + ^{3}He$

    Cooper, S G

    1997-01-01

    To understand recently established empirical p + alpha potentials, RGM calculations followed by inversion are made to study contributions of the d + 3He reaction channels and deuteron distortion effects to the p + alpha potential. An equivalent study of the d + 3He potential is also presented. The contributions of exchange non-locality to the absorption are simulated by including an phenomenological imaginary potential in the RGM. These effects alone strongly influence the shape of the imaginary potentials for both p + alpha and d + 3He. The potentials local-equivalent to the fully antisymmetrised-coupled channels calculations have a significant parity-dependence in both real and imaginary components, which for p + alpha is qualitatively similar to that found empirically. The effects on the potentials of the further inclusion of deuteron distortion are also presented. The inclusion of a spin-orbit term in the RGM, adds additional terms to the phase-equivalent potential, most notably the comparatively large im...

  20. Spin diffusion in normal fluid 3He in 97% porous silica-aerogel

    Spin-relaxation and spin-diffusion were investigated in a liquid 3He sample in contact with solid 3He which was adsorbed on the SiO2 strands of an aerogel. NMR experiments at 950 kHz were performed at pressures and temperatures ranging from 0 to 20 bar and from 0.2 to 100 mK, respectively. The results for the diffusion coefficient D0 are not only affected by the effective mean free path in the aerogel but also by the solid-layer magnetization. For T0∼T has been observed which is caused by scattering processes associated with the spin-polarization of adsorbed solid 3He-layers