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Sample records for pulsed mev positron

  1. Relativistic Positron Creation Using Ultra-Intense Short Pulse Lasers

    SciTech Connect

    Chen, H; Wilks, S; Bonlie, J; Liang, E; Myatt, J; Price, D; Meyerhofer, D; Beiersdorfer, P

    2008-08-25

    We measure up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets when illuminated with short ({approx} 1 ps) ultra-intense ({approx} 1 x 10{sup 20} W/cm{sup 2}) laser pulses. Positrons produced predominately by the Bethe-Heitler process and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. The measurements indicate the laser produced, relativistic positron densities ({approx} 10{sup 16} positrons/cm{sup 3}) are the highest ever created in the laboratory.

  2. Making relativistic positrons using ultraintense short pulse lasers

    SciTech Connect

    Chen Hui; Wilks, S. C.; Bonlie, J. D.; Chen, S. N.; Cone, K. V.; Elberson, L. N.; Price, D. F.; Schneider, M. B.; Shepherd, R.; Stafford, D. C.; Tommasini, R.; Van Maren, R.; Beiersdorfer, P.; Gregori, G.; Meyerhofer, D. D.; Myatt, J.

    2009-12-15

    This paper describes a new positron source using ultraintense short pulse lasers. Although it has been theoretically studied since the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at the Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2x10{sup 10} positrons/s ejected at the back of approximately millimeter thick gold targets were detected. The targets were illuminated with short (approx1 ps) ultraintense (approx1x10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser-based positron source with its unique characteristics may complement the existing sources based on radioactive isotopes and accelerators.

  3. Making Relativistic Positrons Using Ultra-Intense Short Pulse Lasers

    SciTech Connect

    Chen, H; Wilks, S; Bonlie, J; Chen, C; Chen, S; Cone, K; Elberson, L; Gregori, G; Liang, E; Price, D; Van Maren, R; Meyerhofer, D D; Mithen, J; Murphy, C V; Myatt, J; Schneider, M; Shepherd, R; Stafford, D; Tommasini, R; Beiersdorfer, P

    2009-08-24

    This paper describes a new positron source produced using ultra-intense short pulse lasers. Although it has been studied in theory since as early as the 1970s, the use of lasers as a valuable new positron source was not demonstrated experimentally until recent years, when the petawatt-class short pulse lasers were developed. In 2008 and 2009, in a series of experiments performed at Lawrence Livermore National Laboratory, a large number of positrons were observed after shooting a millimeter thick solid gold target. Up to 2 x 10{sup 10} positrons per steradian ejected out the back of {approx}mm thick gold targets were detected. The targets were illuminated with short ({approx}1 ps) ultra-intense ({approx}1 x 10{sup 20} W/cm{sup 2}) laser pulses. These positrons are produced predominantly by the Bethe-Heitler process, and have an effective temperature of 2-4 MeV, with the distribution peaking at 4-7 MeV. The angular distribution of the positrons is anisotropic. For a wide range of applications, this new laser based positron source with its unique characteristics may complements the existing sources using radioactive isotopes and accelerators.

  4. Positron Creation Using the TITAN Short Pulse Laser

    NASA Astrophysics Data System (ADS)

    Chen, Hui; Wilks, S. C.; Liang, E.; Myatt, J.; Cone, K.; Elberson, L.; Meyerhofer, D. D.; Schneider, M.; Shepherd, R.; Stafford, D.; Tommasini, R.; Beiersdorfer, P.

    2008-11-01

    Using ultra-intense lasers to generate positrons was theorized some time ago[1] and demonstrated in principle in two previous experiments[2] where small numbers of positrons were measured. Recently, new experiments were performed on the LLNL Titan laser to study positron creation, where the laser pulse length, pre-plasma condition, target material and thickness were varied. Using newly built positron spectrometers, copious positron production was observed with good signal-to-background ratio. Hot electron spectra (out to 100 MeV) and bremsstrahlung photons were measured simultaneously to further constrain models for the experiment. This talk will present detailed experimental results and their comparison with theory and previous experimental data. [1] Shearer et al, PRA,(1973);Liang, AIP Conf. Proc.(1994); Shkolnikov et al, APL,(1997), Liang, Wilks and Tabak, PRL(1998); Nakashima and Takabe, PoP,(2002); Myatt et al,PRE (2008).[2] Cowan et al, LPB(1999); Gahn et al, APL(1998)

  5. Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies

    NASA Astrophysics Data System (ADS)

    Abbott, D.; Adderley, P.; Adeyemi, A.; Aguilera, P.; Ali, M.; Areti, H.; Baylac, M.; Benesch, J.; Bosson, G.; Cade, B.; Camsonne, A.; Cardman, L. S.; Clark, J.; Cole, P.; Covert, S.; Cuevas, C.; Dadoun, O.; Dale, D.; Dong, H.; Dumas, J.; Fanchini, E.; Forest, T.; Forman, E.; Freyberger, A.; Froidefond, E.; Golge, S.; Grames, J.; Guèye, P.; Hansknecht, J.; Harrell, P.; Hoskins, J.; Hyde, C.; Josey, B.; Kazimi, R.; Kim, Y.; Machie, D.; Mahoney, K.; Mammei, R.; Marton, M.; McCarter, J.; McCaughan, M.; McHugh, M.; McNulty, D.; Mesick, K. E.; Michaelides, T.; Michaels, R.; Moffit, B.; Moser, D.; Muñoz Camacho, C.; Muraz, J.-F.; Opper, A.; Poelker, M.; Réal, J.-S.; Richardson, L.; Setiniyaz, S.; Stutzman, M.; Suleiman, R.; Tennant, C.; Tsai, C.; Turner, D.; Ungaro, M.; Variola, A.; Voutier, E.; Wang, Y.; Zhang, Y.; PEPPo Collaboration

    2016-05-01

    The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19 MeV /c , limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.

  6. Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies.

    PubMed

    Abbott, D; Adderley, P; Adeyemi, A; Aguilera, P; Ali, M; Areti, H; Baylac, M; Benesch, J; Bosson, G; Cade, B; Camsonne, A; Cardman, L S; Clark, J; Cole, P; Covert, S; Cuevas, C; Dadoun, O; Dale, D; Dong, H; Dumas, J; Fanchini, E; Forest, T; Forman, E; Freyberger, A; Froidefond, E; Golge, S; Grames, J; Guèye, P; Hansknecht, J; Harrell, P; Hoskins, J; Hyde, C; Josey, B; Kazimi, R; Kim, Y; Machie, D; Mahoney, K; Mammei, R; Marton, M; McCarter, J; McCaughan, M; McHugh, M; McNulty, D; Mesick, K E; Michaelides, T; Michaels, R; Moffit, B; Moser, D; Muñoz Camacho, C; Muraz, J-F; Opper, A; Poelker, M; Réal, J-S; Richardson, L; Setiniyaz, S; Stutzman, M; Suleiman, R; Tennant, C; Tsai, C; Turner, D; Ungaro, M; Variola, A; Voutier, E; Wang, Y; Zhang, Y

    2016-05-27

    The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19  MeV/c, limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community. PMID:27284661

  7. Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies

    DOE PAGESBeta

    Abbott, D.; Adderley, P.; Adeyemi, A.; Aguilera, P.; Ali, M.; Areti, H.; Baylac, M.; Benesch, J.; Bosson, G.; Cade, B.; et al

    2016-05-27

    The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19~MeV/c, limited only by the electron beam polarization. We report that this technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.

  8. A novel source of MeV positron bunches driven by energetic protons for PAS application

    NASA Astrophysics Data System (ADS)

    Tan, Zongquan; Xu, Wenzhen; Liu, Yanfen; Xiao, Ran; Kong, Wei; Ye, Bangjiao

    2014-11-01

    This paper proposes a novel methodology of MeV positrons generation for PAS application. Feasibility of this proposal analyzed by G4Beamline and Transport have shown reasonable success. Using 2 Hz, 1.6 GeV, 100 ns and 1.5 μC/bunch proton bunches for bombarding a graphite target, about 100 ns e+ bunches are generated. Quasi-monochromatic positrons in the range of 1-10 MeV included in these bunches have a flux of >107/s, peak brightness of 1014/s. A magnetic-confinement beamline is utilized to transport the positrons and a "Fast Beam Chopper" is unprecedentedly extended to chop those relativistic bunches. The positron beam can be finally characterized by the energy range of 1-10 MeV and bunch width from one hundred ps up to 1 ns. Such ultrashort bunches can be useful in tomography-type positron annihilation spectroscopy (PAS) as well as other applications.

  9. A 0. 5 to 3. 0 MeV monoenergetic positron beam

    SciTech Connect

    Huomo, H.; AsokaKumar, P.; Henderson, S.D.; Phlips, B.F.; Mayer, R.; McDonough, J.; Hacker, H.; McCorkle, S.; Schnitzenbaumer, P.; Greenberg, J.S.

    1988-01-01

    An adjustable, 0.5--3 MeV monoenergetic positron beam has been constructed at Brookhaven. Currently a /sup 22/Na source with a W(100) foil transmission moderator produces a 1.1 mm FWHN beam with an intensity of 3/times/10/sup 5/ e/sup +//sec at a target located downstream from the accelerator. The divergence of the beam is less than 0.1/degree/ at 2.2 MeV energy. A SOA gun with 2 lens transport system brings the beam to a focus at the entrance of an electrostatic 3 MeV Dynamitron accelerator. The post acceleration beam transport system comprises 3 focusing solenolds, 4 sets of steering magnets and a 90/degree/ double focusing bending magnet. The beam energy spread at the target is <1 keV FWHN deduced from the beam size. Below we describe the positron extraction optics and acceleration, the construction of the beamline and the beam diagnostic devices. The salient beam parameters are listed at the end of this paper. 2 refs., 3 figs., 1 tab.

  10. Possibilities with pulsed polarized high density slow positrons

    NASA Astrophysics Data System (ADS)

    Mills, A. P., Jr.

    2014-04-01

    A particularly bright and intense polarized slow positron beam could be formed from isotopically enriched 79Kr produced at a reactor. After moderation with solid Ne, accumulation, compression, and bunching, this type of positron beam would enable a number of experiments including: (1) Long term storage of a neutral polarized electron-positron plasma in a cold box; (2) Pulsed e+ ACAR with a pulsed magnet to measure Fermi surfaces of paramagnetic metals; (3) Single shot measurements of positron annihilation in laser-imploding plasmas; (4) Study of a spin-polarized positronium gas at a density around that of ordinary air to produce a Ps Bose-Einstein condensate at room temperature; (5) High energy polarized positron channelling experiments to study polarized electron spatial wave functions in ferromagnets; and (6) Study of supersonic free expansion spin polarized BEC Ps jets formed from, for example, 1011 m=1 triplet Ps atoms created within an open ended 1 μm diameter cylindrical cavity 100 μm in length.

  11. Design of a pulsed positron system at Trombay

    NASA Astrophysics Data System (ADS)

    Mukherjee, S.; Sharma, S. K.; Maheshwari, Priya; Gupta, S. K.; Pujari, P. K.

    2015-06-01

    We present here the design of a pulsed beam setup to deliver narrow time width positron pulses. The major constituents of the setup include- 22Na radioactive source and moderator assembly, ExB deflector for filtering out high energy positron and gamma rays, chopper-prebuncher-buncher assembly for time bunching of the slow positrons. In the ExB section, crossed electric and magnetic fields guide the slow positrons through an off-centered hole in a tungsten block. The initial beam will then be time bunched by using a reflection type chopper and a double gap prebuncher. The main buncheris designed as a quarter wave resonator with base frequency of 150 MHz.To prevent the sagging of the cantilevered inner tube of the resonator, we will support the inner conductor using an alumina post. There will be provision of tuning the frequency by using a tuner made of conducting material. The incident beam energy will be varied by biasing the sample.

  12. Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses.

    PubMed

    Taira, Y; Toyokawa, H; Kuroda, R; Yamamoto, N; Adachi, M; Tanaka, S; Katoh, M

    2013-05-01

    High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90° collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF2 scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF2 scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured. PMID:23742543

  13. Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses

    SciTech Connect

    Taira, Y.; Toyokawa, H.; Kuroda, R.; Yamamoto, N.; Adachi, M.; Tanaka, S.; Katoh, M.

    2013-05-15

    High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90 Degree-Sign collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF{sub 2} scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF{sub 2} scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured.

  14. Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses

    NASA Astrophysics Data System (ADS)

    Taira, Y.; Toyokawa, H.; Kuroda, R.; Yamamoto, N.; Adachi, M.; Tanaka, S.; Katoh, M.

    2013-05-01

    High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90° collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF2 scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF2 scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured.

  15. Interpretation of recent positron-electron measurements between 20 and 800 MeV. [interplanetary cosmic ray solar modulation

    NASA Technical Reports Server (NTRS)

    Pellerin, C. J.; Hartman, R. C.

    1975-01-01

    Recently measured positron and negatron spectra are discussed with regard to the problem of solar modulation. At energies above 180 MeV, the spherically symmetric Fokker-Planck equation with a diffusion coefficient proportional to particle rigidity provides reasonable fits to both the positron and total electron data. At energies below 180 MeV, the data are consistent with a continuation of the same diffusion coefficient and a local source of negatrons or with a change in the diffusion coefficient to a constant value.

  16. Optimization of drift bias in an UHV based pulsed positron beam system

    SciTech Connect

    Anto, C. Varghese; Rajaraman, R.; Rao, G. Venugopal; Abhaya, S.; Parimala, J.; Amarendra, G.

    2012-06-05

    We report here the design of ultra high vacuum (UHV) compatible pulsed positron beam lifetime system, which combines the principles of a conventional slow positron beam and RF based pulsing scheme. The mechanical design and construction of the UHV system to house the beam has been completed and it has been tested for a vacuum of {approx} 10{sup -10} mbar. The voltages applied to the drift tube as a function of positron energies have been optimized using SIMION.

  17. Measurement of cosmic ray positron and negatron spectra between 50 and 800 MeV. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Daugherty, J. K.

    1974-01-01

    A balloon-borne magnetic spectrometer was used to measure the spectra of cosmic ray positrons and negatrons at energies between 50 and 800 MeV. Comparisons of the separate positron and negatron spectra observed near the earth with their expected intensities in interstellar space can be used to investigate the complex (and variable) interaction of galactic cosmic rays with the expanding solar wind. The present measurements, which have established finite values or upper limits for the positron and negatron spectral between 50 and 800 MeV, have confirmed earlier evidence for the existence of a dominant component of negatrons from primary sources in the galaxy. The present results are shown to be consistent with the hypothesis that the positron component is in fact mainly attributable to collisions between cosmic ray nuclei and the interstellar gas. The estimate of the absolute intensities confirm the indications from neutron monitors that in 1972 the interplanetary cosmic ray intensities were already recovering toward their high levels observed in 1965.

  18. Laser Created Relativistic Positron Jets

    SciTech Connect

    Chen, H; Wilks, S C; Meyerhofer, D D; Bonlie, J; Chen, C D; Chen, S N; Courtois, C; Elberson, L; Gregori, G; Kruer, W; Landoas, O; Mithen, J; Murphy, C; Nilson, P; Price, D; Scheider, M; Shepherd, R; Stoeckl, C; Tabak, M; Tommasini, R; Beiersdorder, P

    2009-10-08

    Electron-positron jets with MeV temperature are thought to be present in a wide variety of astrophysical phenomena such as active galaxies, quasars, gamma ray bursts and black holes. They have now been created in the laboratory in a controlled fashion by irradiating a gold target with an intense picosecond duration laser pulse. About 10{sup 11} MeV positrons are emitted from the rear surface of the target in a 15 to 22-degree cone for a duration comparable to the laser pulse. These positron jets are quasi-monoenergetic (E/{delta}E {approx} 5) with peak energies controllable from 3-19 MeV. They have temperatures from 1-4 MeV in the beam frame in both the longitudinal and transverse directions. Positron production has been studied extensively in recent decades at low energies (sub-MeV) in areas related to surface science, positron emission tomography, basic antimatter science such as antihydrogen experiments, Bose-Einstein condensed positronium, and basic plasma physics. However, the experimental tools to produce very high temperature positrons and high-flux positron jets needed to simulate astrophysical positron conditions have so far been absent. The MeV temperature jets of positrons and electrons produced in our experiments offer a first step to evaluate the physics models used to explain some of the most energetic phenomena in the universe.

  19. A new scheme to accumulate positrons in a Penning-Malmberg trap with a linac-based positron pulsed source

    SciTech Connect

    Dupre, P.

    2013-03-19

    The Gravitational Behaviour of Antimatter at Rest experiment (GBAR) is designed to perform a direct measurement of the weak equivalence principle on antimatter by measuring the acceleration of anti-hydrogen atoms in the gravitational field of the Earth. The experimental scheme requires a high density positronium (Ps) cloud as a target for antiprotons, provided by the Antiproton Decelerator (AD) - Extra Low Energy Antiproton Ring (ELENA) facility at CERN. The Ps target will be produced by a pulse of few 10{sup 10} positrons injected onto a positron-positronium converter. For this purpose, a slow positron source using an electron Linac has been constructed at Saclay. The present flux is comparable with that of {sup 22}Na-based sources using solid neon moderator. A new positron accumulation scheme with a Penning-Malmberg trap has been proposed taking advantage of the pulsed time structure of the beam. In the trap, the positrons are cooled by interaction with a dense electron plasma. The overall trapping efficiency has been estimated to be {approx}70% by numerical simulations.

  20. Design of a Pulsed Flux Concentrator for the ILC Positron Source

    SciTech Connect

    Gronberg, J; Abbott, R; Brown, C; Javedani, J; Piggott, W T; Clarke, J

    2010-05-17

    The Positron Source for the International Linear Collider requires an optical matching device after the target to increase the capture efficiency for positrons. Pulsed flux concentrators have been used by previous machines to improve the capture efficiency but the ILC has a 1 ms long pulse train which is too long for a standard flux concentrator. A pulsed flux concentrator with a 40 ms flat top was created for a hyperon experiment in 1965 which used liquid nitrogen cooling to reduce the resistance of the concentrating plates and extend the lifetime of the pulse. We report on a design for a 1 ms device based on this concept.

  1. ION SOLITARY PULSES IN WARM PLASMAS WITH ULTRARELATIVISTIC DEGENERATE ELECTRONS AND POSITRONS

    SciTech Connect

    Zeba, I.; Moslem, W. M.; Shukla, P. K. E-mail: zeba.israr@rub.de E-mail: wmm@tp4.rub.de

    2012-05-01

    The nonlinear propagation of ion solitary pulses in a warm collisionless electron-positron-ion plasma with ultrarelativistic degenerate electrons and positrons has been investigated. Arbitrary and small- (but finite-) amplitude ion solitary pulses are investigated by deriving the Korteweg-de Vries equation and an energy-balance-like expression involving a Sagdeev-like pseudopotential. The existence regions for ion solitary pulses have been precisely defined and numerically investigated. The ion solitary pulse profiles are also displayed. Applications to the interior of white dwarf stars and the corona of magnetars are discussed.

  2. Production of slow-positron beams with an electron linac

    SciTech Connect

    Howell, R.H.; Alvarez, R.A.; Stanek, M.

    1982-03-26

    Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production efficiency for low-energy positrons has been determined for electrons with 60 to 120 MeV energy, low-energy positron beams from a linac can be of much higher intensity than those beams currently derived from radioactive sources.

  3. Novel pulsed particle accelerator for energy dependent positron re-emission experiments.

    PubMed

    Grill, Niklas; Piochacz, Christian; Zimnik, Samantha; Hugenschmidt, Christoph

    2016-05-01

    We report on a novel device for particle acceleration based on elevation of the potential energy of beam pulses. This so-called energy elevator is particularly beneficial if both the particle source and the sample have to be near ground potential due to experimental constraints. We applied this new technique to enable depth dependent measurements of re-emitted positrons using the surface spectrometer at the NEPOMUC positron beam facility. First, a two-stage bunching system is used to generate positron pulses with a repetition rate of 5 MHz and a duration of 1.663(5) ns before their energy is raised to several keV. The whole system was shown to work with an exceptional efficiency of 88%. We demonstrated the usability of our setup by investigating the positron re-emission spectra of Ni and Pd as function of positron implantation energy. For Ni the positron work function could be determined to be ΦNi (+)=-1.4(2)eV. In addition, as predicted by theory, our experimental findings imply a positive positron work function for Pd. PMID:27250411

  4. Electromagnetic cascade in high-energy electron, positron, and photon interactions with intense laser pulses

    NASA Astrophysics Data System (ADS)

    Bulanov, S. S.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2013-06-01

    The interaction of high-energy electrons, positrons, and photons with intense laser pulses is studied in head-on collision geometry. It is shown that electrons and/or positrons undergo a cascade-type process involving multiple emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged particles quickly lose their energy developing an exponentially decaying energy distribution, which suppresses the emission of high-energy photons, thus reducing the number of electron-positron pairs being generated. Therefore, this type of interaction suppresses the development of the electromagnetic avalanche-type discharge, i.e., the exponential growth of the number of electrons, positrons, and photons does not occur in the course of interaction. The suppression will occur when three-dimensional effects can be neglected in the transverse particle orbits, i.e., for sufficiently broad laser pulses with intensities that are not too extreme. The final distributions of electrons, positrons, and photons are calculated for the case of a high-energy e-beam interacting with a counterstreaming, short intense laser pulse. The energy loss of the e-beam, which requires a self-consistent quantum description, plays an important role in this process, as well as provides a clear experimental observable for the transition from the classical to quantum regime of interaction.

  5. Radio frequency elevator for a pulsed positron beam

    NASA Astrophysics Data System (ADS)

    Dickmann, Marcel; Mitteneder, Johannes; Kögel, Gottfried; Egger, Werner; Sperr, Peter; Ackermann, Ulrich; Piochacz, Christian; Dollinger, Günther

    2016-06-01

    An elevator increases the potential energy of a particle beam with respect to ground potential without any alteration of kinetic energy and other beam parameters. This elevator is necessary for the implementation of the Munich Scanning Positron Microscope (SPM) at the intense positron source NEPOMUC at the research reactor FRM II in Munich. The principles of the rf elevator for pure electrostatically guided positrons are described. Measurements of beam quality behind the elevator are reported, which confirm that after the implementation of elevator and SPM at NEPOMUC the SPM can be operated at a considerably improved resolution (~ 0.3 μm) and event rate (~3.7 kHz) compared to the laboratory based β+-source.

  6. A trap-based pulsed positron beam optimised for positronium laser spectroscopy.

    PubMed

    Cooper, B S; Alonso, A M; Deller, A; Wall, T E; Cassidy, D B

    2015-10-01

    We describe a pulsed positron beam that is optimised for positronium (Ps) laser-spectroscopy experiments. The system is based on a two-stage Surko-type buffer gas trap that produces 4 ns wide pulses containing up to 5 × 10(5) positrons at a rate of 0.5-10 Hz. By implanting positrons from the trap into a suitable target material, a dilute positronium gas with an initial density of the order of 10(7) cm(-3) is created in vacuum. This is then probed with pulsed (ns) laser systems, where various Ps-laser interactions have been observed via changes in Ps annihilation rates using a fast gamma ray detector. We demonstrate the capabilities of the apparatus and detection methodology via the observation of Rydberg positronium atoms with principal quantum numbers ranging from 11 to 22 and the Stark broadening of the n = 2 → 11 transition in electric fields. PMID:26520934

  7. A trap-based pulsed positron beam optimised for positronium laser spectroscopy

    SciTech Connect

    Cooper, B. S. Alonso, A. M.; Deller, A.; Wall, T. E.; Cassidy, D. B.

    2015-10-15

    We describe a pulsed positron beam that is optimised for positronium (Ps) laser-spectroscopy experiments. The system is based on a two-stage Surko-type buffer gas trap that produces 4 ns wide pulses containing up to 5 × 10{sup 5} positrons at a rate of 0.5-10 Hz. By implanting positrons from the trap into a suitable target material, a dilute positronium gas with an initial density of the order of 10{sup 7} cm{sup −3} is created in vacuum. This is then probed with pulsed (ns) laser systems, where various Ps-laser interactions have been observed via changes in Ps annihilation rates using a fast gamma ray detector. We demonstrate the capabilities of the apparatus and detection methodology via the observation of Rydberg positronium atoms with principal quantum numbers ranging from 11 to 22 and the Stark broadening of the n = 2 → 11 transition in electric fields.

  8. Positron annihilation lifetime measurement and X-ray analysis on 120 MeV Au+7 irradiated polycrystalline tungsten

    NASA Astrophysics Data System (ADS)

    Dube, Charu Lata; Kulriya, Pawan Kumar; Dutta, Dhanadeep; Pujari, Pradeep K.; Patil, Yashashri; Mehta, Mayur; Patel, Priyanka; Khirwadkar, Samir S.

    2015-12-01

    In order to simulate radiation damages in tungsten, potential plasma facing materials in future fusion reactors, surrogate approach of heavy ion irradiation on polycrystalline tungsten is employed. Tungsten specimen is irradiated with gold heavy ions of energy 120 MeV at different fluences. Positron annihilation lifetime measurements are carried out on pristine and ion beam irradiated tungsten specimens. The variation in positron annihilation lifetime in ion irradiated specimens confirms evolution of vacancy clusters under heavy ion irradiation. The pristine and irradiated tungsten specimens have also been characterized for their microstructural, structural, electrical, thermal, and mechanical properties. X-ray diffractograms of irradiated tungsten specimens show structural integrity of polycrystalline tungsten even after irradiation. Nevertheless, the increase in microstrain, electrical resistivity and microhardness on irradiation indicates creation of lattice damages inside polycrystalline tungsten specimen. On the other hand, the thermal diffusivity has not change much on heavy ion irradiation. The induction of damages in metallic tungsten is mainly attributed to high electronic energy loss, which is 40 keV/nm in present case as obtained from SRIM program. Although, concomitant effect of nuclear losses on damage creation cannot be ignored. It is believed that the energy received by the electronic system is being transferred to the atomic system by electron-phonon coupling. Eventually, elastic nuclear collisions and the transfer of energy from electronic to atomic system via inelastic collision is leading to significant defect generation in tungsten lattice.

  9. Long pulse H- ion beam acceleration in MeV accelerator.

    PubMed

    Taniguchi, M; Mizuno, T; Umeda, N; Kashiwagi, M; Watanabe, K; Tobari, H; Kojima, A; Tanaka, Y; Dairaku, M; Hanada, M; Sakamoto, K; Inoue, T

    2010-02-01

    A multiaperture multigrid accelerator called "MeV accelerator" has been developed for neutral beam injection system of international thermonuclear experimental reactor. In the present work, long pulse H(-) ion beam acceleration was performed by the MeV accelerator equipped with new water-cooled grids. At present, the pulse length was extended to 5 s for the beams of 750 keV, 221 mA, and 10 s for the beams of 600 keV, 158 mA. Energy density, defined as products of beam energy (keV), current (mA), and pulse (s) divided by aperture area (m(2)), increased more than one order of magnitude higher compared with original MeV accelerator without water cooling in its grids. At higher energy and current, the grid was melted by beam deflection. Due to this grid melting, breakdowns occurred between the grids, and hence, the pulse length was limited. Beam deflection will be compensated by aperture displacement in next experiment. PMID:20192408

  10. Cascade phonon-assisted trapping of positrons by divacancies in n-FZ-Si(P) single crystals irradiated with 15 MeV protons

    NASA Astrophysics Data System (ADS)

    Arutyunov, N. Yu.; Emtsev, V. V.; Krause-Rehberg, R.; Kessler, C.; Elsayed, M.; Oganesyan, G. A.; Kozlovski, V. V.

    2014-02-01

    The trapping of positrons by the radiation defects in moderately doped oxygen-lean n-FZ-Si(P) single crystal irradiated with 15 MeV protons has been investigated in a comparative way using the positron lifetime spectroscopy and Hall effect measurements. The experiments were carried out within a wide temperature interval ranging from 25 K - 29 K to 300 K. The positron trapping rate for divacancies was reconstructed in the course of many-stage isochronal annealing. The concentration and the charged states of divacancies (V2- and V2--) were estimated. The temperature dependency of the trapping cross section of positrons by the negatively charged divacancies is in a good agreement with the data of calculations based on the assumptions of the cascade phonon-assisted mechanism of exchange of the energy between the positron and acoustic long-wave phonons. Obeying ˜ T-3 law, the cross-section of the trapping of positrons by divacancies changes considerably ranging from ˜1.7×10-12 cm2 (66 - 100 K) to ˜2×10-14 cm2 (≈ 250 K). The characteristic length of trapping of the positron by V2-- divacancy was estimated to be l0(V2--)≈(3.4±0.2)×10-8 cm.

  11. Pulse compression system for the ANL 20 MeV linac

    SciTech Connect

    Mavrogenes, G.; Norem, J.; Simpson, J.

    1986-01-01

    This paper describes the pulse compression system being built on the Argonne 20 MeV electron linac. The system is designed to rotate the bunch from the present measured pulse length of 38 psec FWHM, to pulse lengths of 5 to 6 ps with the large instantaneous currents (1 to 4 kA) possible instantaneous current. This system was necessary to extend the study of reactive fragments of molecules to the time scale of a few picoseconds, in particular to examine the chemistry of electrons and ions before and during relaxation of the surrounding media. These experiments are not sensitive to the beam energy spread, High Energy Physics experiments studying wake fields have also been proposed using the short bunches and the facility was designed so that the wake field experiment could share the beam bunching system. The 20 MeV electron linac uses a double gap, 12th subharmonic prebuncher together with a one wavelength 1.3 Ghz prebuncher to produce a single pulse of 38 ps from one occupied rf bucket. Beam emittances of 15.7 mmmr have been measured for 40 nC of accelerated charge and 8 mmmr at 10 nC. The energy spread of dE/E = 1% (FWHM) has been measured at 40 nC. Thus the accelerated beam has excellent time structure, high current, and good emittance.

  12. Radiation pressure acceleration of protons to 93 MeV with circularly polarized petawatt laser pulses

    NASA Astrophysics Data System (ADS)

    Kim, I. Jong; Pae, Ki Hong; Choi, Il Woo; Lee, Chang-Lyoul; Kim, Hyung Taek; Singhal, Himanshu; Sung, Jae Hee; Lee, Seong Ku; Lee, Hwang Woon; Nickles, Peter V.; Jeong, Tae Moon; Kim, Chul Min; Nam, Chang Hee

    2016-07-01

    The radiation pressure acceleration (RPA) of charged particles has been a challenging task in laser-driven proton/ion acceleration due to its stringent requirements in laser and target conditions. The realization of radiation-pressure-driven proton acceleration requires irradiating ultrathin targets with an ultrahigh contrast and ultraintense laser pulses. We report the generation of 93-MeV proton beams achieved by applying 800-nm 30-fs circularly polarized laser pulses with an intensity of 6.1 × 10 20 W / cm 2 to 15-nm-thick polymer targets. The radiation pressure acceleration was confirmed from the obtained optimal target thickness, quadratic energy scaling, polarization dependence, and three-dimensional particle-in-cell simulations. We expect this clear demonstration of RPA to facilitate the realization of laser-driven proton/ion sources delivering energetic and short-pulse particle beams for novel applications.

  13. Generation of high-energy (>15 MeV) neutrons using short pulse high intensity lasers

    SciTech Connect

    Petrov, G. M.; Davis, J.; Petrova, Tz. B.; Higginson, D. P.; McNaney, J. M.; McGuffey, C.; Qiao, B.; Beg, F. N.

    2012-09-15

    A roadmap is suggested and demonstrated experimentally for the production of high-energy (>15 MeV) neutrons using short pulse lasers. Investigation with a 3D Monte Carlo model has been employed to quantify the production of energetic neutrons. Numerical simulations have been performed for three nuclear reactions, d(d,n){sup 3}He, {sup 7}Li(d,n){sup 8}Be, and {sup 7}Li(p,n){sup 7}Be, driven by monoenergetic ion beams. Quantitative estimates for the driver ion beam energy and number have been made and the neutron spectra and yield in the ion propagation direction have been evaluated for various incident ion energies. In order to generate neutron fluence above a detection limit of 10{sup 6} neutrons/sr, either {approx}10{sup 10} protons with energy 20-30 MeV or comparable amount of deuterons with energy 5-10 MeV are required. Experimental verification of the concept with deuterons driven by the Titan laser (peak intensity 2 Multiplication-Sign 10{sup 19} W/cm{sup 2}, pulse duration of 9 ps, wavelength 1.05 {mu}m, and energy of 360 J) is provided with the generation of neutrons with energy of up to 18 MeV from {sup 7}Li(d,n){sup 8}Be reactions. Future research will focus on optimized schemes for ion acceleration for production of high-energy neutrons, which will involve efficient target design, laser parameter optimization, and converter material.

  14. MeV electron acceleration by sub-terawatt laser pulses in near critical density plasmas

    NASA Astrophysics Data System (ADS)

    Goers, Andy; Hine, George; Feder, Linus; Miao, Bo; Salehi, Fatholah; Milchberg, Howard

    2015-11-01

    We demonstrate laser-plasma acceleration of high charge electron beams to the 10 MeV scale using ultrashort laser pulses with as little energy as 10 mJ. This result is made possible by an extremely dense and thin hydrogen gas jet where even sub-terawatt laser pulses are well above the critical power for relativistic self-focusing, and the 10 mJ pulses can drive a self-modulated wakefield accelerator. Total charge up to 0.5 nC is measured for energies >1 MeV. Acceleration is correlated to the presence of an intense, coherent, broadband light flash, associated with wavebreaking, which can radiate more than 3% of the laser energy in a sub-femtosecond bandwidth consistent with half-cycle optical emission. Our results enable truly portable applications of laser-driven acceleration, such as low dose radiography, ultrafast probing of matter, and isotope production. This work supported by DTRA and the US Department of Energy.

  15. Repetitive production of positron emitters using deuterons accelerated by multiterawatt laser pulses

    NASA Astrophysics Data System (ADS)

    Fujimoto, Masatoshi; Matsukado, Koji; Takahashi, Hironori; Kawada, Yoichi; Ohsuka, Shinji; Aoshima, Shin-Ichiro

    2009-11-01

    Positron emitters C11, N13, and O15, which can be used in positron emission tomography, were produced using deuterons accelerated by irradiation of laser pulses ˜70 TW in peak power and ˜30 fs in duration with a repetition of 10 Hz during a period of as long as 200 s. Every laser pulse irradiates the fresh surface of a long strip of a solid-state thin film. Deuterons contained in the film are accelerated in the relativistic plasma induced by the pulse. The deuterons are repetitively incident on solid plates, which are placed near the film, to produce positron emitters by nuclear reactions. The radioactivities of the activated plates are measured after the termination of laser irradiation. In activation of graphite, boron-nitride, and melamine plates, the products had total activities of 64, 46, and 153 Bq, respectively. Contamination in the setup was negligible even after several thousands of laser shots. Our apparatus is expected to greatly contribute to the construction of a compact PET diagnostic system in the future.

  16. Positron microprobe at LLNL

    SciTech Connect

    Asoka, P; Howell, R; Stoeffl, W

    1998-11-01

    The electron linac based positron source at Lawrence Livermore National Laboratory (LLNL) provides the world's highest current beam of keV positrons. We are building a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with sub-micron resolution. The widely spaced and intense positron packets from the tungsten moderator at the end of the 100 MeV LLNL linac are captured and trapped in a magnetic bottle. The positrons are then released in 1 ns bunches at a 20 MHz repetition rate. With a three-stage re-moderation we will compress the cm-sized original beam to a 1 micro-meter diameter final spot on the target. The buncher will compress the arrival time of positrons on the target to less than 100 ps. A detector array with up to 60 BaF2 crystals in paired coincidence will measure the annihilation radiation with high efficiency and low background. The energy of the positrons can be varied from less than 1 keV up to 50 keV.

  17. Cascade phonon-assisted trapping of positrons by divacancies in n-FZ-Si(P) single crystals irradiated with 15 MeV protons

    SciTech Connect

    Arutyunov, N. Yu.; Emtsev, V. V.; Oganesyan, G. A.; Krause-Rehberg, R.; Kessler, C.; Elsayed, M.; Kozlovski, V. V.

    2014-02-21

    The trapping of positrons by the radiation defects in moderately doped oxygen-lean n-FZ-Si(P) single crystal irradiated with 15 MeV protons has been investigated in a comparative way using the positron lifetime spectroscopy and Hall effect measurements. The experiments were carried out within a wide temperature interval ranging from 25 K – 29 K to 300 K. The positron trapping rate for divacancies was reconstructed in the course of many-stage isochronal annealing. The concentration and the charged states of divacancies (V{sub 2}{sup −} and V{sub 2}{sup −−}) were estimated. The temperature dependency of the trapping cross section of positrons by the negatively charged divacancies is in a good agreement with the data of calculations based on the assumptions of the cascade phonon-assisted mechanism of exchange of the energy between the positron and acoustic long-wave phonons. Obeying ∼ T{sup −3} law, the cross-section of the trapping of positrons by divacancies changes considerably ranging from ∼1.7×10{sup −12} cm{sup 2} (66 – 100 K) to ∼2×10{sup −14} cm{sup 2} (≈ 250 K). The characteristic length of trapping of the positron by V{sub 2}{sup −−} divacancy was estimated to be l{sub 0}(V{sub 2}{sup −−})≈(3.4±0.2)×10{sup −8} cm.

  18. Characterization of MeV proton acceleration from double pulse irradiation of foil targets

    NASA Astrophysics Data System (ADS)

    Kerr, S.; Mo, M. Z.; Masud, R.; Tiedje, H. F.; Tsui, Y.; Fedosejevs, R.; Link, A.; Patel, P.; McLean, H. S.; Hazi, A.; Chen, H.; Ceurvorst, L.; Norreys, P.

    2014-10-01

    We report on the experimental characterization of proton acceleration from double-pulse irradiation of um-scale foil targets. Temporally separated sub-picosecond pulses have been shown to increase the conversion efficiency of laser energy to MeV protons. Here, two 700 fs, 1 ω pulses were separated by 1 to 5 ps; total beam energy was 100 J, with 5-20% of the total energy contained within the first pulse. In contrast to the ultraclean beams used in previous experiments, prepulse energies on the order of 10 mJ were present in the current experiments which appear to have a moderating effect on the enhancement. Proton beam measurements were made with radiochromic film stacks, as well as magnetic spectrometers. The effect on electron generation was measured using Kα emission from buried Cu tracer layers, while specular light diagnostics (FROG, reflection spectralon) indicated the laser coupling efficiency into the target. The results obtained will be presented and compared to PIC simulations. Work by LLNL was performed under the auspices of U.S. DOE under contract DE-AC52-07NA27344.

  19. Ultrashort megaelectronvolt positron beam generation based on laser-accelerated electrons

    NASA Astrophysics Data System (ADS)

    Xu, Tongjun; Shen, Baifei; Xu, Jiancai; Li, Shun; Yu, Yong; Li, Jinfeng; Lu, Xiaoming; Wang, Cheng; Wang, Xinliang; Liang, Xiaoyan; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

    2016-03-01

    Experimental generation of ultrashort MeV positron beams with high intensity and high density using a compact laser-driven setup is reported. A high-density gas jet is employed experimentally to generate MeV electrons with high charge; thus, a charge-neutralized MeV positron beam with high density is obtained during laser-accelerated electrons irradiating high-Z solid targets. It is a novel electron-positron source for the study of laboratory astrophysics. Meanwhile, the MeV positron beam is pulsed with an ultrashort duration of tens of femtoseconds and has a high peak intensity of 7.8 × 1021 s-1, thus allows specific studies of fast kinetics in millimeter-thick materials with a high time resolution and exhibits potential for applications in positron annihilation spectroscopy.

  20. Optimization of the profile of a pulsed slow positron beam extracted from a buffer-gas positron trap for the production of a variable energy positronium beam

    NASA Astrophysics Data System (ADS)

    Gladen, R.; Michishio, K.; Chiari, L.; Oshima, N.; Nagashima, Y.

    In this poster we will present some details of steps taken to optimize the beam profile of a pulsed slow positron beam extracted from a buffer-gas positron trap. The beam will be employed for the production of a novel positronium beam by the acceleration and photodetachment of positronium negative ions. The TUS group is planning on using this beam to study positronium diffraction from solid surfaces, providing a unique neutral-particle spectroscopic method with several advantages over conventional neutral-particle spectroscopy, such as a reduced particle mass and, hence, the reduction of damage to the sample surface This work was performed at the Tokyo University of Science. The visit of R. G. to the laboratory was sponsored in part by the NSF EAPSI fellowship and the JSPS Summer Program.

  1. A time-pulsed positronium beam and a study of oxides on silicon using positrons

    SciTech Connect

    Khatri, R.K.

    1993-01-01

    The studies on rare gas solid moderators were carried out with a 350 [mu]Ci [sup 22]Na radioactive source. The corrected efficiency for neon moderator in conical geometrical configuration was as high as (1.4 [+-] 0.2)%. The conical configuration moderator performed better by a factor of (2.2 [+-] 0.2) than the cylindrical configuration. A time pulsed positron beam was built to carry out investigations on the positronium formation processes and positronium beam. This beam has the capability to store low energy e[sup +] in a magnetic bottle, with a magnetic bottle at one end and an electrostatic mirror at the other. These stored e[sup +] are then bunched to form a pulse with a buncher. The bunched beam had a FWHM of 17 nsec and contained 1 to 2 e[sup +]/pulse. A thin carbon foil of 50 [angstrom] thickness was used for positronium formation by process of charge exchange. Positronium Annihilation Spectroscopy (PAS) was utilized to carry out studies on the activation energy of hydrogen at the interface of oxide and silicon substrate and the effect of irradiation on the oxides in SiO[sub 2]/Si(100) sample. The activation energy of hydrogen at the interface of SiO[sub 2]/Si(100) samples with n- and p-type substrate was measured to be 2.60(6) eV and 2.47(6) eV respectively. The investigations of the samples irradiated with x-ray and [gamma]-ray led to the first time identification of creation of E[prime] centers with PAS.

  2. Threshold for Trapping Positrons in the Wake Driven by a Ultra-relativistic Electron Bunch

    SciTech Connect

    Wang, X.; Muggli, P.; Katsouleas, T.; Ischebeck, R.; Hogan, M. J.; Joshi, C.; Mori, W. B.

    2009-01-22

    We have recently proposed a new concept for generating, injecting and accelerating positrons in a plasma using a double-pulse electron bunch. Monte Carlo simulations show that the number of the positrons produced in a foil target has an exponentially decay energy spectrum. The energy threshold for the trapping of these positrons in a ultra-relativistic electron wake is investigated numerically. For a typical 28.5 GeV electron drive bunch, the trapping threshold for the positrons is a few MeV, and therefore a majority of positrons generated in the foil target are focused and accelerated by the plasma wake.

  3. Applications and advances of positron beam spectroscopy

    SciTech Connect

    Howell, R., LLNL

    1998-03-18

    Over 50 scientists from DOE-DP, DOE-ER, the national laboratories, academia and industry attended a workshop held on November 5-7, 1997 at Lawrence Livermore National Laboratory. Workshop participants were charged to address two questions: Is there a need for a national center for materials analysis using positron techniques and can the capabilities at Lawrence Livermore National Laboratory serve this need. To demonstrate the need for a national center, the workshop participants discussed the technical advantages enabled by high positron currents and advanced measurement techniques, the role that these techniques would play in materials analysis and the demand for the data. Livermore now leads the world in materials analysis capabilities by positrons due to developments in response to demands of stockpile stewardship. The Livermore facilities now include the world`s highest current beam of keV positrons, a scanning pulsed positron microprobe under development capable of three dimensional maps of defect size and concentration, an MeV positron beam for defect analysis of large samples, and electron momentum spectroscopy by positrons. It was concluded that the positron microprobe under development at LLNL and other new instruments that would be relocated at LLNL at the high current keV source are an exciting step forward in providing results for the positron technique. These new data will impact a wide variety of applications.

  4. Long pulse acceleration of MeV class high power density negative H- ion beam for ITER

    NASA Astrophysics Data System (ADS)

    Umeda, N.; Kojima, A.; Kashiwagi, M.; Tobari, H.; Hiratsuka, J.; Watanabe, K.; Dairaku, M.; Yamanaka, H.; Hanada, M.

    2015-04-01

    R&D of high power density negative ion beam acceleration has been carried out at MeV test facility in JAEA to realize ITER neutral beam accelerator. The main target is H- ion beam acceleration up to 1 MeV with 200 A/m2 for 60 s whose pulse length is the present facility limit. For long pulse acceleration at high power density, new extraction grid (EXG) has been developed with high cooling capability, which electron suppression magnet is placed under cooling channel similar to ITER. In addition, aperture size of electron suppression grid (ESG) is enlarged from 14 mm to 16 mm to reduce direct interception on the ESG and emission of secondary electron which leads to high heat load on the upstream acceleration grid. By enlarging ESG aperture, beam current increased 10 % at high current beam and total acceleration grid heat load reduced from 13 % to 10 % of input power at long pulse beam. In addition, heat load by back stream positive ion into the EXG is measured for the first time and is estimated as 0.3 % of beam power, while heat load by back stream ion into the source chamber is estimated as 3.5 ~ 4.0 % of beam power. Beam acceleration up to 60 s which is the facility limit, has achieved at 683 keV, 100 A/m2 of negative ion beam, whose energy density increases two orders of magnitude since 2011.

  5. Nuclear physics in the 10--300 MeV energy range using a pulsed white neutron source

    SciTech Connect

    Bowman, C.D.; Wender, S.A.; Auchampaugh, G.F.

    1985-01-20

    A new pulsed white neutron source is under construction at the Los Alamos WNR facility. The neutrons are produced by LAMPF proton micropulses striking thick targets of various materials. Beam parameters include energy of 800 MeV, pulse rate of approximately 50,000 Hz, 0.4 nsec pulse width, average current as high as 6..mu..a, and a useful neutron energy range from 3 to 300 MeV. The facility will receive beam approximately 80% of the time LAMPF is operational; it increases by a factor of 1000 the experimental capability over the present system at the WNR when beam intensity, angular distribution, and availability are taken into account. In addition to established white source techniques, the facility is also highly competitive with monoenergetic sources for a wide class of experiments such as neutron capture ..gamma.. ray spectroscopy and neutron-induced charged particle reactions. The facility should be operational in about nine months. Arrangements are underway to make the facility readily accessible to visiting experiments.

  6. Nuclear physics in the 10 to 300 MeV energy range using a pulsed white neutron source

    SciTech Connect

    Bowman, C.D.; Wender, S.A.; Auchampaugh, G.F.

    1984-01-01

    A new pulsed white neutron source is under construction at the Los Alamos WNR facility. The neutrons are produced by LAMPF proton micropulses striking thick targets of various materials. Beam parameters include energy of 800 MeV, pulse rate of approximately 50,000 Hz, 0.4 nsec pulse width, average current as high as 6..mu..a, and a useful neutron energy range from 3 to 300 MeV. The facility will receive beam approximately 80% of the time LAMPF is operational; it increased by a factor of 1000 the experimental capability over the present system at the WNR when beam intensity, angular distribution, and availability are taken into account. In addition to established white source techniques, the facility is also highly competitive with monoenergetic sources for a wide class of experiments such as neutron capture ..gamma.. ray spectroscopy and neutron-induced charged particle reactions. The facility should be operational in about nine months. Arrangements are underway to make the facility readily accessible to visiting experimenters.

  7. Nuclear physics in the 10-300 MeV energy range using a pulsed white neutron source

    NASA Astrophysics Data System (ADS)

    Bowman, C. D.; Wender, S. A.; Auchampaugh, G. F.

    1985-01-01

    A new pulsed white neutron source is under construction at the Los Alamos WNR facility. The neutrons are produced by LAMPF proton micropulses striking thick targets of various materials. Beam parameters include energy of 800 MeV, pulse rate of approximately 50,000 Hz, 0.4 nsec pulse width, average current as high as 6μa, and a useful neutron energy range from 3 to 300 MeV. The facility will receive beam approximately 80% of the time LAMPF is operational; it increases by a factor of 1000 the experimental capability over the present system at the WNR when beam intensity, angular distribution, and availability are taken into account. In addition to established white source techniques, the facility is also highly competitive with monoenergetic sources for a wide class of experiments such as neutron capture γ ray spectroscopy and neutron-induced charged particle reactions. The facility should be operational in about nine months. Arrangements are underway to make the facility readily accessible to visiting experiments.

  8. Nuclear physics in the 10 to 300 MeV energy range using a pulsed white neutron source

    NASA Astrophysics Data System (ADS)

    Bowman, C. D.; Wender, S. A.; Auchampaugh, G. F.

    A new pulsed white neutron source is under construction at the Los Alamos WNR facility. The neutrons are produced by LAMPF proton micropulses striking thick targets of various materials. Beam parameters include energy of 800 MeV, pulse rate of approximately 50,000 Hz, 0.4 nsec pulse width, average current as high as 6(MU)a, and a useful neutron energy range from 3 to 300 MeV. The facility will receive beam approximately 80% of the time LAMPF is operational; it increased by a factor of 1000 the experimental capability over the present system at the WNR when beam intensity, angular distribution, and availability are taken into account. In addition to established white source techniques, the facility is also highly competitive with monoenergetic sources for a wide class of experiments such as neutron capture (GAMMA) ray spectroscopy and neutron-induced charged particle reactions. The facility should be operational in about nine months. Arrangements are underway to make the facility readily accessible to visiting experimenters.

  9. Long pulse acceleration of MeV class high power density negative H{sup −} ion beam for ITER

    SciTech Connect

    Umeda, N. Kojima, A.; Kashiwagi, M.; Tobari, H.; Hiratsuka, J.; Watanabe, K.; Dairaku, M.; Yamanaka, H.; Hanada, M.

    2015-04-08

    R and D of high power density negative ion beam acceleration has been carried out at MeV test facility in JAEA to realize ITER neutral beam accelerator. The main target is H{sup −} ion beam acceleration up to 1 MeV with 200 A/m{sup 2} for 60 s whose pulse length is the present facility limit. For long pulse acceleration at high power density, new extraction grid (EXG) has been developed with high cooling capability, which electron suppression magnet is placed under cooling channel similar to ITER. In addition, aperture size of electron suppression grid (ESG) is enlarged from 14 mm to 16 mm to reduce direct interception on the ESG and emission of secondary electron which leads to high heat load on the upstream acceleration grid. By enlarging ESG aperture, beam current increased 10 % at high current beam and total acceleration grid heat load reduced from 13 % to 10 % of input power at long pulse beam. In addition, heat load by back stream positive ion into the EXG is measured for the first time and is estimated as 0.3 % of beam power, while heat load by back stream ion into the source chamber is estimated as 3.5 ~ 4.0 % of beam power. Beam acceleration up to 60 s which is the facility limit, has achieved at 683 keV, 100 A/m{sup 2} of negative ion beam, whose energy density increases two orders of magnitude since 2011.

  10. Production of neutrons up to 18 MeV in high-intensity, short-pulse laser matter interactions

    SciTech Connect

    Higginson, D. P.; McNaney, J. M.; Swift, D. C.; Mackinnon, A. J.; Patel, P. K.; Petrov, G. M.; Davis, J.; Frenje, J. A.; Jarrott, L. C.; Tynan, G.; Beg, F. N.; Kodama, R.; Nakamura, H.; Lancaster, K. L.

    2011-10-15

    The generation of high-energy neutrons using laser-accelerated ions is demonstrated experimentally using the Titan laser with 360 J of laser energy in a 9 ps pulse. In this technique, a short-pulse, high-energy laser accelerates deuterons from a CD{sub 2} foil. These are incident on a LiF foil and subsequently create high energy neutrons through the {sup 7}Li(d,xn) nuclear reaction (Q = 15 MeV). Radiochromic film and a Thomson parabola ion-spectrometer were used to diagnose the laser accelerated deuterons and protons. Conversion efficiency into protons was 0.5%, an order of magnitude greater than into deuterons. Maximum neutron energy was shown to be angularly dependent with up to 18 MeV neutrons observed in the forward direction using neutron time-of-flight spectrometry. Absolutely calibrated CR-39 detected spectrally integrated neutron fluence of up to 8 x 10{sup 8} n sr{sup -1} in the forward direction.

  11. Generation of relativistic ions, electrons and positrons in high-intensity short-pulse laser-solid interactions

    NASA Astrophysics Data System (ADS)

    Hill, Matthew; Allan, Peter; Brown, Colin; Hobbs, Lauren; James, Steven; Oades, Kevin; Hoarty, David; Chen, Hui

    2012-10-01

    The newly-commissioned Orion laser facility at AWE Aldermaston can deliver intense (10^21 W/cm^2), short (0.6 ps) laser pulses at 1φ (1 μ m) and 3x10^20 W/cm^2 at 2φ with pulse contrasts of 10^7 and 10^13, respectively, in addition to ten 3φ, 500 J long-pulse (˜ns) beams. All can be delivered to target synchronized to ˜20 ps. We report on the production and characterization of multi-MeV protons, ions, positrons and electrons at the Orion facility using 500 J, 0.6 ps, 1φ pulses and 100 J, 0.6 ps, 2φ pulses onto both thin (20 μ m) and thick (1 mm) gold targets. Laser intensities were scanned from 10^19 to 10^21 W/cm^2 by altering pulse energy and length while maintaining a consistent focal spot size of 10 μ. Particle energies were recorded by use of a magnetic and a Thomson spectrometer, with X-ray emissions imaged using a time-integrating pinhole camera in addition to time-integrating crystal spectrometers. The implications for future experiments such as investigations into electron transport mechanisms and proton heating are briefly discussed.

  12. Numerical simulation study of positron production by intense laser-accelerated electrons

    SciTech Connect

    Yan, Yonghong; Science and Technology on Plasma Physics Laboratory, Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 ; Dong, Kegong; Wu, Yuchi; Zhang, Bo; Gu, Yuqiu; Yao, Zeen

    2013-10-15

    Positron production by ultra-intense laser-accelerated electrons has been studied with two-dimensional particle-in-cell and Monte Carlo simulations. The dependence of the positron yield on plasma density, plasma length, and converter thickness was investigated in detail with fixed parameters of a typical 100 TW laser system. The results show that with the optimal plasma and converter parameters a positron beam containing up to 1.9 × 10{sup 10} positrons can be generated, which has a small divergence angle (10°), a high temperature (67.2 MeV), and a short pulse duration (1.7 ps)

  13. A ROLE OF MAGNETOSONIC PULSES ON VARIATIONS OF VOYAGER-1 MeV ELECTRON INTENSITY IN THE HELIOSHEATH

    SciTech Connect

    Washimi, H.; Zank, G. P.; Hu, Q.; Florinski, V.; Webber, W.; Adams, J.; Kubo, Y.

    2012-09-20

    Voyager 1 (V1) spacecraft observed electrons of 6-14 MeV in the heliosheath which showed several enhancements of significant flux variation. We compare these temporal electron flux variations, from the time when V1 crossed the termination shock (TS) up to mid-2008, with dynamical phenomena in the heliosheath that are obtained from our MHD simulations which are based on Voyager 2 (V2) observed solar-wind data. Our simulations indicate that all electron flux enhancements, except for one, correspond fairly well to the times when a magnetosonic (MS) pulse was driven downstream of the TS due to collision of interplanetary shock (IPS) or shock-driven MS pulse and its reflection in the heliosheath that either passed V1, or collided with the TS or with the plasma sheet near the heliopause (HP). This result suggests that these enhancements in the electron flux should correspond to either direct or indirect effects of MS pulses in the heliosheath driven by IPSs. The scale of the heliosphere is estimated by comparing V1-observed magnetic field intensity with the simulated intensity which suggests that V1 is possibly located near the HP within 4-8 AU at the present time.

  14. A Role of Magnetosonic Pulses on Variations of Voyager-1 MeV Electron Intensity in the Heliosheath

    NASA Astrophysics Data System (ADS)

    Washimi, H.; Webber, W.; Zank, G. P.; Hu, Q.; Florinski, V.; Adams, J.; Kubo, Y.

    2012-09-01

    Voyager 1 (V1) spacecraft observed electrons of 6-14 MeV in the heliosheath which showed several enhancements of significant flux variation. We compare these temporal electron flux variations, from the time when V1 crossed the termination shock (TS) up to mid-2008, with dynamical phenomena in the heliosheath that are obtained from our MHD simulations which are based on Voyager 2 (V2) observed solar-wind data. Our simulations indicate that all electron flux enhancements, except for one, correspond fairly well to the times when a magnetosonic (MS) pulse was driven downstream of the TS due to collision of interplanetary shock (IPS) or shock-driven MS pulse and its reflection in the heliosheath that either passed V1, or collided with the TS or with the plasma sheet near the heliopause (HP). This result suggests that these enhancements in the electron flux should correspond to either direct or indirect effects of MS pulses in the heliosheath driven by IPSs. The scale of the heliosphere is estimated by comparing V1-observed magnetic field intensity with the simulated intensity which suggests that V1 is possibly located near the HP within 4-8 AU at the present time.

  15. MeV femtosecond electron pulses from direct-field acceleration in low density atomic gases

    NASA Astrophysics Data System (ADS)

    Varin, Charles; Marceau, Vincent; Hogan-Lamarre, Pascal; Fennel, Thomas; Piché, Michel; Brabec, Thomas

    2016-01-01

    Using three-dimensional particle-in-cell (3DPIC) simulations, we show that few-MeV electrons can be produced by tightly focusing few-cycle radially-polarized laser pulses in a low-density atomic gas. In particular, it is observed that for the few-TW laser power needed to reach relativistic electron energies, longitudinal attosecond microbunching occurs naturally, resulting in femtosecond structures with high-contrast attosecond density modulations. The 3DPIC simulations show that in the relativistic regime the leading pulse of these attosecond substructures survives to propagation over extended distances, suggesting that it could be delivered to a distant target, with the help of a properly designed transport beamline.

  16. Characterization of MeV Electron Generation using 527 nm Laser Pulses for Fast Ignition

    NASA Astrophysics Data System (ADS)

    Fedosejevs, Robert; Higginson, D. P.; Friesen, H.; Sorokovikova, A.; Jarrott, C. C.; Link, A.; Kemp, G. E.; Hey, D.; Ping, Y.; Bush, I.; Tiedje, H. F.; Mo, M. Z.; Tsui, Y. Y.; Westover, B.; Beg, F. N.; Akli, K. U.; Freeman, R. R.; van Woerkom, L. D.; Schumacher, D.; Chen, C.; McLean, H. S.; Patel, P.; Doeppner, T.; Stephens, R. B.; Pasley, J.

    2011-10-01

    J WESTWOOD, J TAIT, A BEAUDRY, S SINGH, U of Alberta, and MH Key, LLNL. We investigate electron generation at intensities of relevance to Fast Ignition using second harmonic laser pulses, motivated by the need to understand the wavelength scaling of the processes and also the ability to obtain clean, prepulse free, target interaction conditions. 700fs duration pulses with peak intensities up to 5 x 1019 W cm-2 were employed at the TITAN laser facility at LLNL. Both planar and cone target geometries were studied using copper k-alpha imaging of tracer layers, Bremsstrahlung x-ray emission measurements of conversion efficiency and beam divergence and magnetic spectrometer measurements of escaping electrons to characterize the electron generation and propagation. Results of electron temperature and angular divergence will be presented.

  17. Towards laboratory produced relativistic electron–positron pair plasmas

    SciTech Connect

    Chen, Hui; Meyerhofer, D. D.; Wilks, S. C.; Cauble, R.; Dollar, F.; Falk, K.; Gregori, G.; Hazi, A.; Moses, E. I.; Murphy, C. D.; Myatt, J.; Park, J.; Seely, J.; Shepherd, R.; Spitkovsky, A.; Stoeckl, C.; Szabo, C. I.; Tommasini, R.; Zulick, C.; Beiersdorfer, P.

    2011-12-01

    We review recent experimental results on the path to producing electron–positron pair plasmas using lasers. Relativistic pair-plasmas and jets are believed to exist in many astrophysical objects and are often invoked to explain energetic phenomena related to Gamma Ray Bursts and Black Holes. On earth, positrons from radioactive isotopes or accelerators are used extensively at low energies (sub-MeV) in areas related to surface science positron emission tomography and basic antimatter science. Experimental platforms capable of producing the high-temperature pair-plasma and high-flux jets required to simulate astrophysical positron conditions have so far been absent. In the past few years, we performed extensive experiments generating positrons with intense lasers where we found that relativistic electron and positron jets are produced by irradiating a solid gold target with an intense picosecond laser pulse. The positron temperatures in directions parallel and transverse to the beam both exceeded 0.5 MeV, and the density of electrons and positrons in these jets are of order 1016 cm-3 and 1013 cm-3, respectively. With the increasing performance of high-energy ultra-short laser pulses, we expect that a high-density, up to 1018 cm-3, relativistic pair-plasma is achievable, a novel regime of laboratory-produced hot dense matter.

  18. Inter-pulse high-resolution gamma-ray spectra using a 14 MeV pulsed neutron generator

    USGS Publications Warehouse

    Evans, L.G.; Trombka, J.I.; Jensen, D.H.; Stephenson, W.A.; Hoover, R.A.; Mikesell, J.L.; Tanner, A.B.; Senftle, F.E.

    1984-01-01

    A neutron generator pulsed at 100 s-1 was suspended in an artificial borehole containing a 7.7 metric ton mixture of sand, aragonite, magnetite, sulfur, and salt. Two Ge(HP) gamma-ray detectors were used: one in a borehole sonde, and one at the outside wall of the sample tank opposite the neutron generator target. Gamma-ray spectra were collected by the outside detector during each of 10 discrete time windows during the 10 ms period following the onset of gamma-ray build-up after each neutron burst. The sample was measured first when dry and then when saturated with water. In the dry sample, gamma rays due to inelastic neutron scattering, neutron capture, and decay were counted during the first (150 ??s) time window. Subsequently only capture and decay gamma rays were observed. In the wet sample, only neutron capture and decay gamma rays were observed. Neutron capture gamma rays dominated the spectrum during the period from 150 to 400 ??s after the neutron burst in both samples, but decreased with time much more rapidly in the wet sample. A signal-to-noise-ratio (S/N) analysis indicates that optimum conditions for neutron capture analysis occurred in the 350-800 ??s window. A poor S/N in the first 100-150 ??s is due to a large background continuum during the first time interval. Time gating can be used to enhance gamma-ray spectra, depending on the nuclides in the target material and the reactions needed to produce them, and should improve the sensitivity of in situ well logging. ?? 1984.

  19. A positron trap and beam apparatus for atomic and molecular scattering experiments.

    PubMed

    Sullivan, J P; Jones, A; Caradonna, P; Makochekanwa, C; Buckman, S J

    2008-11-01

    An instrument has been designed and constructed to provide new insights into fundamental, low energy positron scattering processes. The design is based on the Surko trap system and produces a pulsed positron beam with an energy resolution of as good as 54 meV. The design and operation of the apparatus is explained, while the first experimental results from this apparatus have been demonstrated in recent publications. PMID:19045887

  20. Temporally controlled modulation of antihydrogen production and the temperature scaling of antiproton-positron recombination.

    PubMed

    Fujiwara, M C; Amoretti, M; Amsler, C; Bonomi, G; Bouchta, A; Bowe, P D; Canali, C; Carraro, C; Cesar, C L; Charlton, M; Doser, M; Fontana, A; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Kellerbauer, A; Lagomarsino, V; Landua, R; Lodi-Rizzini, E; Macri, M; Madsen, N; Manuzio, G; Mitchard, D; Montagna, P; Pruys, H; Regenfus, C; Rotondi, A; Testera, G; Variola, A; Venturelli, L; van der Werf, D P; Yamazaki, Y; Zurlo, N

    2008-08-01

    We demonstrate temporally controlled modulation of cold antihydrogen production by periodic RF heating of a positron plasma during antiproton-positron mixing in a Penning trap. Our observations have established a pulsed source of atomic antimatter, with a rise time of about 1 s, and a pulse length ranging from 3 to 100 s. Time-sensitive antihydrogen detection and positron plasma diagnostics, both capabilities of the ATHENA apparatus, allowed detailed studies of the pulsing behavior, which in turn gave information on the dependence of the antihydrogen production process on the positron temperature T. Our data are consistent with power law scaling T (-1.1+/-0.5) for the production rate in the high temperature regime from approximately 100 meV up to 1.5 eV. This is not in accord with the behavior accepted for conventional three-body recombination. PMID:18764390

  1. Generation of energetic (>15 MeV) neutron beams from proton- and deuteron-driven nuclear reactions using short pulse lasers

    NASA Astrophysics Data System (ADS)

    Petrov, G. M.; Higginson, D. P.; Davis, J.; Petrova, Tz B.; McGuffey, C.; Qiao, B.; Beg, F. N.

    2013-10-01

    A roadmap is proposed for the production of high-energy (>15 MeV) neutrons using short pulse lasers. Different approaches are suggested for the two limiting cases of small (E1 ≪ Q) and large (E1 ≫ Q) projectile energies E1 depending on the Q-value of the nuclear reaction. The neutron fluence from many converter materials is evaluated for two projectiles: protons and deuterons. We found profound differences between proton- and deuteron-driven reactions with regard to both converter material and generated neutron fluence. The optimum converter material for deuteron-driven reactions is low-Z elements such as Li and Be, while for proton-driven reactions the converter material is not critical. For a projectile energy of 50 MeV the deuteron-driven reactions are two orders of magnitude more efficient compared to the proton-driven reactions. Two-dimensional particle-in-cell simulations have been performed for laser pulses with peak intensity 3 × 1020 W cm-2, pulse duration 40 fs, spot size 5 µm and energy 3 J interacting with ultrathin (0.1 µm) CD foil. The calculated deuteron beam is highly directional along the laser propagation direction with maximum energy of 45 MeV. The interaction of the deuteron beam with a lithium converter and the production of neutrons is modeled using a Monte Carlo code. The computed neutron spectra show that a forward directed neutron beam is generated with an opening angle of ˜1 sr, maximum energy of 60 MeV and a fluence in the forward direction 1.8 × 108 n sr-1, ˜20% of which are with energy above 15 MeV.

  2. Oxygen-Atom Defects In 6H Silicon Carbide Implanted Using 24- MeV O3+ Ions Measured Using Three-Dimensional Positron Annihilation Spectroscopy System (3DPASS)

    NASA Astrophysics Data System (ADS)

    Williams, Christopher S.; Duan, Xiaofeng F.; Petrosky, James C.; Burggraf, Larry W.

    2011-06-01

    Three dimensional electron-positron (e--e+) momentum distributions were measured for single crystal 6H silicon carbide (SiC); both virgin and having implanted oxygen-atom defects. 6H SiC samples were irradiated by 24- MeV O3+ ions at 20 particle-nanoamps at the Sandia National Laboratory's Ion Beam Facility. O3+ ions were implanted 10.8 μm deep normal to the (0001) face of one side of the SiC samples. During positron annihilation measurements, the opposite face of the 254.0-μm thick SiC samples was exposed to positrons from a 22Na source. This technique reduced the influence on the momentum measurements of vacancy-type defects resulting from knock-on damage by the O3+ ions. A three-dimensional positron annihilation spectroscopy system (3DPASS) was used to measure e--e+ momentum distributions for virgin and irradiated 6H SiC crystal both before and following annealing. 3DPASS simultaneously measures coincident Doppler-broadening (DBAR) and angular correlation of annihilation radiation (ACAR) spectra. DBAR ratio plots and 2D ACAR spectra are presented. Changes in the momentum anisotropies relative to crystal orientation observed in 2D ACAR spectra for annealed O-implanted SiC agree with the local structure of defect distortion predicted using Surface Integrated Molecular Orbital/Molecular Mechanics (SIMOMM). Oxygen atoms insert between Si and C atoms increasing their separation by 0.9 Å forming a Si-O-C bond angle of ˜150°.

  3. Oxygen-Atom Defects In 6H Silicon Carbide Implanted Using 24- MeV O{sup 3+} Ions Measured Using Three-Dimensional Positron Annihilation Spectroscopy System (3DPASS)

    SciTech Connect

    Williams, Christopher S.; Petrosky, James C.; Burggraf, Larry W.

    2011-06-01

    Three dimensional electron-positron (e{sup -}-e{sup +}) momentum distributions were measured for single crystal 6H silicon carbide (SiC); both virgin and having implanted oxygen-atom defects. 6H SiC samples were irradiated by 24- MeV O{sup 3+} ions at 20 particle-nanoamps at the Sandia National Laboratory's Ion Beam Facility. O{sup 3+} ions were implanted 10.8 {mu}m deep normal to the (0001) face of one side of the SiC samples. During positron annihilation measurements, the opposite face of the 254.0-{mu}m thick SiC samples was exposed to positrons from a {sup 22}Na source. This technique reduced the influence on the momentum measurements of vacancy-type defects resulting from knock-on damage by the O{sup 3+} ions. A three-dimensional positron annihilation spectroscopy system (3DPASS) was used to measure e{sup -}-e{sup +} momentum distributions for virgin and irradiated 6H SiC crystal both before and following annealing. 3DPASS simultaneously measures coincident Doppler-broadening (DBAR) and angular correlation of annihilation radiation (ACAR) spectra. DBAR ratio plots and 2D ACAR spectra are presented. Changes in the momentum anisotropies relative to crystal orientation observed in 2D ACAR spectra for annealed O-implanted SiC agree with the local structure of defect distortion predicted using Surface Integrated Molecular Orbital/Molecular Mechanics (SIMOMM). Oxygen atoms insert between Si and C atoms increasing their separation by 0.9 A forming a Si-O-C bond angle of {approx}150 deg.

  4. ON THE SPECTRUM OF THE PULSED GAMMA-RAY EMISSION OF THE CRAB PULSAR FROM 10 MeV TO 400 GeV

    SciTech Connect

    Chkheidze, N.; Machabeli, G.; Osmanov, Z.

    2013-08-20

    In the present paper, a self-consistent theory, interpreting VERITAS and the MAGIC observations of the very high-energy pulsed emission from the Crab pulsar, is considered. The photon spectrum between 10 MeV and 400 GeV can be described by two power-law functions with spectral indices of 2.0 and 3.8. The source of the pulsed emission above 10 MeV is assumed to be synchrotron radiation, which is generated near the light cylinder during the quasi-linear stage of the cyclotron instability. The emitting particles are the primary beam electrons with Lorentz factors up to 10{sup 9}. Such high energies of beam particles can be reached due to Landau damping of the Langmuir waves in the light cylinder region.

  5. Ultra-Intense Short-Pulse Pair Creation Using the Texas Petawatt Laser

    NASA Astrophysics Data System (ADS)

    Liang, Edison; Henderson, Alexander; Clarke, Taylor; Taylor, Devin; Chaguine, Petr; Serratto, Kristina; Riley, Nathan; Dyer, Gilliss; Donovan, Michael; Ditmire, Todd

    2013-10-01

    We report results from the 2012 pair creation experiment using the Texas Petawatt Laser. Up to 1011 positrons per steradian were detected using 100 Joule pulses from the Texas Petawatt Laser to irradiate gold targets, with peak laser intensities up to 1.9 × 1021W/cm2 and pulse durations as short as 130 fs. Positron-to-electron ratios exceeding 20% were measured on some shots. The positron energy, positron yield per unit laser energy, and inferred positron density are significantly higher than those reported in previous experiments. This confirms that, for a given laser energy, higher intensity and shorter pulses irradiating thicker targets are more favorable for pair creation. Narrow-band high-energy positrons up to 23 MeV were observed from thin targets. Supported by DOE Grant DE-SC-0001481 and Rice FIF.

  6. The Fermi LAT/GBM detection of pulsed gamma-ray emission from PSR J1846-0258 up to 100 MeV

    NASA Astrophysics Data System (ADS)

    Kuiper, Lucien; Dekker, Ariane

    2016-05-01

    Applying phase coherent timing models, created using RXTE PCA and Swift XRT monitoring data of PSR J1846-0258 covering the period August 4, 2008 - March 11, 2016 (MJD 54682 - 57458), in timing analyses of Fermi LAT (PASS8) and Fermi GBM (TTE) data yielded for the first time the detection of pulsed gamma-ray emission from PSR J1846-0258 up to 100 MeV. Phase folding the barycentered Fermi LAT events (period MJD 56185-56338, i.e. Sept.

  7. Ultrafast electron diffraction with megahertz MeV electron pulses from a superconducting radio-frequency photoinjector

    SciTech Connect

    Feng, L. W.; Lin, L.; Huang, S. L.; Quan, S. W.; Hao, J. K.; Zhu, F.; Wang, F.; Liu, K. X.; Jiang, T.; Zhu, P. F.; Fu, F.; Wang, R.; Zhao, L.; Xiang, D.

    2015-11-30

    We report ultrafast relativistic electron diffraction operating at the megahertz repetition rate where the electron beam is produced in a superconducting radio-frequency (rf) photoinjector. We show that the beam quality is sufficiently high to provide clear diffraction patterns from gold and aluminium samples. With the number of electrons, several orders of magnitude higher than that from a normal conducting photocathode rf gun, such high repetition rate ultrafast MeV electron diffraction may open up many new opportunities in ultrafast science.

  8. Formation mechanisms and optimization of trap-based positron beams

    NASA Astrophysics Data System (ADS)

    Natisin, M. R.; Danielson, J. R.; Surko, C. M.

    2016-02-01

    Described here are simulations of pulsed, magnetically guided positron beams formed by ejection from Penning-Malmberg-style traps. In a previous paper [M. R. Natisin et al., Phys. Plasmas 22, 033501 (2015)], simulations were developed and used to describe the operation of an existing trap-based beam system and provided good agreement with experimental measurements. These techniques are used here to study the processes underlying beam formation in more detail and under more general conditions, therefore further optimizing system design. The focus is on low-energy beams (˜eV) with the lowest possible spread in energies (<10 meV), while maintaining microsecond pulse durations. The simulations begin with positrons trapped within a potential well and subsequently ejected by raising the bottom of the trapping well, forcing the particles over an end-gate potential barrier. Under typical conditions, the beam formation process is intrinsically dynamical, with the positron dynamics near the well lip, just before ejection, particularly crucial to setting beam quality. In addition to an investigation of the effects of beam formation on beam quality under typical conditions, two other regimes are discussed; one occurring at low positron temperatures in which significantly lower energy and temporal spreads may be obtained, and a second in cases where the positrons are ejected on time scales significantly faster than the axial bounce time, which results in the ejection process being essentially non-dynamical.

  9. Applications and advances of positron beam spectroscopy: appendix a

    SciTech Connect

    Howell, R. H., LLNL

    1997-11-05

    Over 50 scientists from DOE-DP, DOE-ER, the national laboratories, academia and industry attended a workshop held on November 5-7, 1997 at Lawrence Livermore National Laboratory jointly sponsored by the DOE-Division of Materials Science, The Materials Research Institute at LLNL and the University of California Presidents Office. Workshop participants were charged to address two questions: Is there a need for a national center for materials analysis using positron techniques and can the capabilities at Lawrence Livermore National Laboratory serve this need. To demonstrate the need for a national center the workshop participants discussed the technical advantages enabled by high positron currents and advanced measurement techniques, the role that these techniques will play in materials analysis and the demand for the data. There were general discussions lead by review talks on positron analysis techniques, and their applications to problems in semiconductors, polymers and composites, metals and engineering materials, surface analysis and advanced techniques. These were followed by focus sessions on positron analysis opportunities in these same areas. Livermore now leads the world in materials analysis capabilities by positrons due to developments in response to demands of science based stockpile stewardship. There was a detailed discussion of the LLNL capabilities and a tour of the facilities. The Livermore facilities now include the worlds highest current beam of keV positrons, a scanning pulsed positron microprobe under development capable of three dimensional maps of defect size and concentration, an MeV positron beam for defect analysis of large samples, and electron momentum spectroscopy by positrons. This document is a supplement to the written summary report. It contains a complete schedule, list of attendees and the vuegraphs for the presentations in the review and focus sessions.

  10. Positron Injector Accelerator and RF System for the ILC

    SciTech Connect

    Wang, J.W.; Adolphsen, C.; Bharadwaj, V.; Bowden, G.; Jongewaard, E.; Li, Z.; Miller, R.; Sheppard, J.C.; /SLAC

    2007-03-28

    Due to the extremely high energy deposition from positrons, electrons, photons and neutrons behind the positron target, and because a solenoid is required to focus the large emittance positron beam, the 1.3 GHz preaccelerator has to use normal conducting structures up to energy of 400 MeV. There are many challenges in the design of the normal-conducting portion of the ILC positron injector system such as obtaining high positron yield with required emittance, achieving adequate cooling with the high RF and particle loss heating, and sustaining high accelerator gradients during millisecond-long pulses in a strong magnetic field. Considering issues of feasibility, reliability and cost savings for the ILC, the proposed design for the positron injector contains both standing-wave (SW) and traveling-wave (TW) L-band accelerator structures. A short version of the new type of the SW section is under fabrication and testing. An updated status report is given. This paper also covers acceleration vs. deceleration for pre-accelerator sections, SW vs. TW structures, as well as longitudinal matching from target to linac and linac to damping ring.

  11. Positron binding to molecules

    NASA Astrophysics Data System (ADS)

    Danielson, J. R.

    2011-05-01

    While there is theoretical evidence that positrons can bind to atoms, calculations for molecules are much less precise. Unfortunately, there have been no measurements of positron-atom binding, due primarily to the difficulty in forming positron-atom bound states in two-body collisions. In contrast, positrons attach to molecules via Feshbach resonances (VFR) in which a vibrational mode absorbs the excess energy. Using a high-resolution positron beam, this VFR process has been studied to measure binding energies for more than 40 molecules. New measurements will be described in two areas: positron binding to relatively simple molecules, for which theoretical calculations appear to be possible; and positron binding to molecules with large permanent dipole moments, which can be compared to analogous, weakly bound electron-molecule (negative-ion) states. Binding energies range from 75 meV for CS2 (no dipole moment) to 180 meV for acetonitrile (CH3CN). Other species studied include aldehydes and ketones, which have permanent dipole moments in the range 2.5 - 3.0 debye. The measured binding energies are surprisingly large (by a factor of 10 to 100) compared to those for the analogous negative ions, and these differences will be discussed. New theoretical calculations for positron-molecule binding are in progress, and a recent result for acetonitrile will be discussed. This ability to compare theory and experiment represents a significant step in attempts to understand positron binding to matter. In collaboration with A. C. L. Jones, J. J. Gosselin, and C. M. Surko, and supported by NSF grant PHY 07-55809.

  12. Towards laboratory-produced relativistic electron-positron pair-plasmas

    SciTech Connect

    Chen, H; Wilks, S C; Meyerhofer, D D; Beiersdorfer, P; Cauble, R; Dollar, F; Falk, K; Hazi, A; Murphy, C D; Park, J; Seely, J; Szabo, C I; Shepherd, R; Tommasini, R; Zulick, K

    2010-08-31

    Relativistic pair-plasmas and jets are believed to exist in many astrophysical objects and are often invoked to explain energetic phenomena related to Gamma Ray Bursts and Black Holes. On earth, positrons from radioactive isotopes or accelerators are used extensively at low energies (sub-MeV) in areas related to surface science positron emission tomography and basic antimatter science. Experimental platforms capable of producing the high-temperature pair-plasma and high-flux jets required to simulate astrophysical positron conditions have so far been absent. In the last few years, we performed extensive experiments generating positrons with intense lasers where we found that relativistic electron and positron jets are produced by irradiating a solid gold target with an intense picosecond laser pulse. The positron temperatures in directions parallel and transverse to the beam both exceeded 0.5 MeV, and the density of electrons and positrons in these jets are of order 10{sup 16} cm{sup -3} and 10{sup 13} cm{sup -3}, respectively. With the advent of high-energy ultra-short laser pulses, we expect that a charge-neutral, relativistic pair-plasma is achievable, a novel regime of laboratory-produced hot dense matter. This talk will present some details of the laser-produced pair-plasma experiments.

  13. Modification of a pulsed 14-MeV fast neutron generator to a medium-energy ion accelerator for TOF-RBS application

    NASA Astrophysics Data System (ADS)

    Junphong, P.; Suwannakachorn, D.; Yu, L. D.; Singkarat, S.

    2011-12-01

    The first drift-tube neutron generator in Thailand, developed during 1980s under the support by the International Atomic Energy Agency (IAEA), was a 150 kV deuteron accelerator-based 14 MeV fast neutron generator. The accelerator was featured by a nanosecond pulsing system consisting of a beam chopper in combination with a beam buncher. Following the rapid development of ion beam technology and increasing needs for materials applications in the laboratory, the accelerator has been upgraded and modified to a large extent into a medium-energy ion-accelerator for time-of-flight Rutherford backscattering spectrometry (TOF-RBS) applications. The modification of the accelerator included the changing of the ion source, the accelerating tube and the mass-analyzing magnet, the upgrading of the pulsing system, and the installation of a TOF-RBS detecting system. The new accelerator is capable of supplying a 400-keV He-ion beam with ns-pulses for nano-layered materials analysis. This paper provides technical details of the modification.

  14. MeV proton beams generated by 3 mJ ultrafast laser pulses at 0.5 kHz

    SciTech Connect

    Hou Bixue; Nees, John; Easter, James; Thomas, Alexander; Krushelnick, Karl; Davis, Jack; Petrov, George

    2009-09-07

    Well-collimated proton beams are generated from bulk glass along the target normal direction by tightly focused 55 fs, 3 mJ pulses from a laser operating at 0.5 kHz repetition rate. Proton beams with energies of >265 keV have an emission angle of about 16 deg. full width at half maximum. Spectral measurements indicate proton energies exceeding 0.5 MeV with a flux of 3.2x10{sup 9} s{sup -1} sr{sup -1} and the flux of measured protons with energies of greater than 90 keV is 8.5x10{sup 11} s{sup -1} sr{sup -1} on center.

  15. Use of radial self-field geometry for intense pulsed ion beam generation above 6 MeV on Hermes III.

    SciTech Connect

    Renk, Timothy Jerome; Harper-Slaboszewicz, Victor Jozef; Ginn, William Craig; Mikkelson, Kenneth A.; Schall, Michael; Cooper, Gary Wayne

    2012-12-01

    We investigate the generation and propagation of intense pulsed ion beams at the 6 MeV level and above using the Hermes III facility at Sandia National Laboratories. While high-power ion beams have previously been produced using Hermes III, we have conducted systematic studies of several ion diode geometries for the purpose of maximizing focused ion energy for a number of applications. A self-field axial-gap diode of the pinch reflex type and operated in positive polarity yielded beam power below predicted levels. This is ascribed both to power flow losses of unknown origin upstream of the diode load in Hermes positive polarity operation, and to anomalies in beam focusing in this configuration. A change to a radial self-field geometry and negative polarity operation resulted in greatly increased beam voltage (> 6 MeV) and estimated ion current. A comprehensive diagnostic set was developed to characterize beam performance, including both time-dependent and time-integrated measurements of local and total beam power. A substantial high-energy ion population was identified propagating in reverse direction, i.e. from the back side of the anode in the electron beam dump. While significant progress was made in increasing beam power, further improvements in assessing the beam focusing envelope will be required before ultimate ion generation efficiency with this geometry can be completely determined.

  16. Comparison of direct and indirect positron-generation by an ultra-intense femtosecond laser

    SciTech Connect

    Yan, Yonghong; Zhang, Bo; Wu, Yuchi; Dong, Kegong; Gu, Yuqiu; Yao, Zeen

    2013-10-15

    An extensive comparison of the properties of positron beams produced by an ultra-intense femtosecond laser in direct and indirect schemes has been performed with two-dimensional particle-in-cell and Monte Carlo simulations. It is shown that the positron beam generated in the indirect scheme has a higher yield (10{sup 10}), a higher temperature (28.8 MeV), a shorter pulse duration (5 ps), and a smaller divergence (8°) than in the direct case (10{sup 9} yield, 4.4 MeV temperature, 40 ps pulse duration, and 60° divergence). In addition, it was found that the positron/gamma ratio in the indirect scheme is one order of magnitude higher than that in the direct one, which represents a higher signal/noise ratio in positron detection. Nevertheless, the direct generation method still has its own unique advantage, the so-called target normal sheath acceleration, which can result in quasi-monoenergetic positron beams that may serve in some specialized applications.

  17. Comparison of direct and indirect positron-generation by an ultra-intense femtosecond laser

    NASA Astrophysics Data System (ADS)

    Yan, Yonghong; Zhang, Bo; Wu, Yuchi; Dong, Kegong; Yao, Zeen; Gu, Yuqiu

    2013-10-01

    An extensive comparison of the properties of positron beams produced by an ultra-intense femtosecond laser in direct and indirect schemes has been performed with two-dimensional particle-in-cell and Monte Carlo simulations. It is shown that the positron beam generated in the indirect scheme has a higher yield (1010), a higher temperature (28.8 MeV), a shorter pulse duration (5 ps), and a smaller divergence (8°) than in the direct case (109 yield, 4.4 MeV temperature, 40 ps pulse duration, and 60° divergence). In addition, it was found that the positron/gamma ratio in the indirect scheme is one order of magnitude higher than that in the direct one, which represents a higher signal/noise ratio in positron detection. Nevertheless, the direct generation method still has its own unique advantage, the so-called target normal sheath acceleration, which can result in quasi-monoenergetic positron beams that may serve in some specialized applications.

  18. Implementation of water calorimetry in a 180 MeV scanned pulsed proton beam including an experimental determination of kQ for a Farmer chamber

    NASA Astrophysics Data System (ADS)

    Medin, Joakim

    2010-06-01

    Water calorimetric measurements have been performed in a 180 MeV scanned pulsed proton beam and the absorbed dose determined has been compared with the results obtained using two NE2571 Farmer chambers and the IAEA TRS-398 code of practice. The depth of measurement in water corresponded to a residual range of Rres = 16.5 cm, corresponding to a mean energy of about 150 MeV. Ionization chambers were calibrated in terms of the absorbed dose to water in 60Co at the Swedish Secondary Standard Dosimetry Laboratory, directly traceable to Bureau International des Poids et Mesures. The present experimental investigation has shown that water calorimetry is feasible in a high-energy scanned pulsed proton beam. When comparing the results obtained with water calorimetry and ionometry, the beam quality correction factor, kQ, could be determined for the two NE2571 ionization chambers used. The kQ-factor was found to be 1.032 ± 0.013, which is in good agreement with the factor tabulated in IAEA TRS-398 for this chamber type (1.039 ± 0.018). The present result has also been compared with a previously obtained result in a passively scattered proton beam having similar energy. This comparison yielded a 1.1% deviation, which is not significant considering the combined uncertainties of the two experimental determinations of kQ. The dominating contribution to the combined uncertainty stems from the correction factor for ion recombination in the scanned proton beam (1%), and further studies are required in order to reduce this uncertainty and reveal any possible differences in the kQ-factor between these two proton beam delivery techniques.

  19. Primary cosmic ray positrons and galactic annihilation radiation

    NASA Technical Reports Server (NTRS)

    Lingenfelter, R. E.; Ramaty, R.

    1980-01-01

    The observation (Leventhal et al, 1978) of positron annihilation radiation at 0.511 MeV from the direction of the Galactic Center is reexamined, suggesting the possibility of a primary positron component of the cosmic rays. The observed 0.511 MeV emission requires a positron production rate nearly two orders of magnitude greater than the production rate of secondary cosmic ray positrons from pion decay produced in cosmic ray interactions. Possible sources of positrons are reviewed with both supernovae and pulsars appearing to be the more likely candidates. If only about 1% of these positrons were accelerated along with the cosmic ray nucleons and electrons to energies not less than 100 MeV, it is believed that these primary positrons would be comparable in intensity to those secondary positrons resulting from pion decay. Some observational evidence for the existence of primary positrons in the cosmic rays is also discussed.

  20. Intense positron beam at KEK

    NASA Astrophysics Data System (ADS)

    Kurihara, Toshikazu; Yagishita, Akira; Enomoto, Atsushi; Kobayashi, Hitoshi; Shidara, Tetsuo; Shirakawa, Akihiro; Nakahara, Kazuo; Saitou, Haruo; Inoue, Kouji; Nagashima, Yasuyuki; Hyodo, Toshio; Nagai, Yasuyoshi; Hasegawa, Masayuki; Inoue, Yoshi; Kogure, Yoshiaki; Doyama, Masao

    2000-08-01

    A positron beam is a useful probe for investigating the electronic states in solids, especially concerning the surface states. The advantage of utilizing positron beams is in their simpler interactions with matter, owing to the absence of any exchange forces, in contrast to the case of low-energy electrons. However, such studies as low-energy positron diffraction, positron microscopy and positronium (Ps) spectroscopy, which require high intensity slow-positron beams, are very limited due to the poor intensity obtained from a conventional radioactive-isotope-based positron source. In conventional laboratories, the slow-positron intensity is restricted to 10 6 e +/s due to the strength of the available radioactive source. An accelerator based slow-positron source is a good candidate for increasing the slow-positron intensity. One of the results using a high intensity pulsed positron beam is presented as a study of the origins of a Ps emitted from SiO 2. We also describe the two-dimensional angular correlation of annihilation radiation (2D-ACAR) measurement system with slow-positron beams and a positron microscope.

  1. a Search for Peak Structures in the Positron-Electron Sum-Energy Spectra for the URANIUM-238 + TANTALUM-181 System at 6.3, 6.1, and 5.95 Mev/u.

    NASA Astrophysics Data System (ADS)

    Perera, P. A. Aloy

    1995-01-01

    The discovery of unexpected sharp peak structures in the positron energy spectra, and also in the positron -electron sum energy spectra, in the heavy-ion collision experiments carried out at GSI, Germany has initiated a great amount of experimental and theoretical interest. There is no fully consistent explanation for the origin of these peaks. APEX--the ATLAS Positron experiment--has been designed to gain insight into this puzzling positron-line phenomenon. With the data from the APEX spectrometer a search for peak structures in the positron-electron sum energy spectra was carried out for the ^{238}U+ ^{181}Ta system at 6.3, 6.1 and 5.95 MeV/u. The possibility of revealing the previously reported peak structures in positron-electron sum-energy spectra by applying cuts on the distance of closest approach, the difference-energy between positron and electron, the positron-electron opening angle, and the positron emission angle relative to the beam direction was investigated. No statistically significant peaks were observed in the APEX data.

  2. Use of a radial self-field diode geometry for intense pulsed ion beam generation at 6 MeV on Hermes III

    NASA Astrophysics Data System (ADS)

    Renk, T. J.; Harper-Slaboszewicz, V.; Mikkelson, K. A.; Ginn, W. C.; Ottinger, P. F.; Schumer, J. W.

    2014-12-01

    We investigate the generation of intense pulsed focused ion beams at the 6 MeV level using an inductive voltage adder (IVA) pulsed-power generator, which employs a magnetically insulated transmission line (MITL). Such IVA machines typical run at an impedance of few tens of Ohms. Previous successful intense ion beam generation experiments have often featured an "axial" pinch-reflex ion diode (i.e., with an axial anode-cathode gap) and operated on a conventional Marx generator/water line driver with an impedance of a few Ohms and no need for an MITL. The goals of these experiments are to develop a pinch-reflex ion diode geometry that has an impedance to efficiently match to an IVA, produces a reasonably high ion current fraction, captures the vacuum electron current flowing forward in the MITL, and focuses the resulting ion beam to small spot size. A new "radial" pinch-reflex ion diode (i.e., with a radial anode-cathode gap) is found to best demonstrate these properties. Operation in both positive and negative polarities was undertaken, although the negative polarity experiments are emphasized. Particle-in-cell (PIC) simulations are consistent with experimental results indicating that, for diode impedances less than the self-limited impedance of the MITL, almost all of the forward-going IVA vacuum electron flow current is incorporated into the diode current. PIC results also provide understanding of the diode-impedance and ion-focusing properties of the diode. In addition, a substantial high-energy ion population is also identified propagating in the "reverse" direction, i.e., from the back side of the anode foil in the electron beam dump.

  3. Use of a radial self-field diode geometry for intense pulsed ion beam generation at 6 MeV on Hermes III

    SciTech Connect

    Renk, Timothy Jerome; Harper-Slaboszewicz, Victor Jozef; Mikkelson, Kenneth A.; Ginn, W. C.; Ottinger, P. F.; Schumer, J. W.

    2014-12-15

    We investigate the generation of intense pulsed focused ion beams at the 6 MeV level using an inductive voltage adder (IVA) pulsed-power generator, which employs a magnetically insulated transmission line (MITL). Such IVA machines typical run at an impedance of few tens of Ohms. Previous successful intense ion beam generation experiments have often featured an “axial” pinch-reflex ion diode (i.e., with an axial anode-cathode gap) and operated on a conventional Marx generator/water line driver with an impedance of a few Ohms and no need for an MITL. The goals of these experiments are to develop a pinch-reflex ion diode geometry that has an impedance to efficiently match to an IVA, produces a reasonably high ion current fraction, captures the vacuum electron current flowing forward in the MITL, and focuses the resulting ion beam to small spot size. Furthermore, a new “radial” pinch-reflex ion diode (i.e., with a radial anode-cathode gap) is found to best demonstrate these properties. Operation in both positive and negative polarities was undertaken, although the negative polarity experiments are emphasized. Particle-in-cell (PIC) simulations are consistent with experimental results indicating that, for diode impedances less than the self-limited impedance of the MITL, almost all of the forward-going IVA vacuum electron flow current is incorporated into the diode current. PIC results also provide understanding of the diode-impedance and ion-focusing properties of the diode. Additionally, a substantial high-energy ion population is also identified propagating in the “reverse” direction, i.e., from the back side of the anode foil in the electron beam dump.

  4. Use of a radial self-field diode geometry for intense pulsed ion beam generation at 6 MeV on Hermes III

    DOE PAGESBeta

    Renk, Timothy Jerome; Harper-Slaboszewicz, Victor Jozef; Mikkelson, Kenneth A.; Ginn, W. C.; Ottinger, P. F.; Schumer, J. W.

    2014-12-15

    We investigate the generation of intense pulsed focused ion beams at the 6 MeV level using an inductive voltage adder (IVA) pulsed-power generator, which employs a magnetically insulated transmission line (MITL). Such IVA machines typical run at an impedance of few tens of Ohms. Previous successful intense ion beam generation experiments have often featured an “axial” pinch-reflex ion diode (i.e., with an axial anode-cathode gap) and operated on a conventional Marx generator/water line driver with an impedance of a few Ohms and no need for an MITL. The goals of these experiments are to develop a pinch-reflex ion diode geometrymore » that has an impedance to efficiently match to an IVA, produces a reasonably high ion current fraction, captures the vacuum electron current flowing forward in the MITL, and focuses the resulting ion beam to small spot size. Furthermore, a new “radial” pinch-reflex ion diode (i.e., with a radial anode-cathode gap) is found to best demonstrate these properties. Operation in both positive and negative polarities was undertaken, although the negative polarity experiments are emphasized. Particle-in-cell (PIC) simulations are consistent with experimental results indicating that, for diode impedances less than the self-limited impedance of the MITL, almost all of the forward-going IVA vacuum electron flow current is incorporated into the diode current. PIC results also provide understanding of the diode-impedance and ion-focusing properties of the diode. Additionally, a substantial high-energy ion population is also identified propagating in the “reverse” direction, i.e., from the back side of the anode foil in the electron beam dump.« less

  5. Adventures in Gaseous Positronics - An Ultra-High-Energy-Resolution Cryogenic Beam

    NASA Astrophysics Data System (ADS)

    Natisin, Mike

    2016-05-01

    While positron interactions with matter are important in a variety of contexts, many important experiments have been inhibited due to the difficulties encountered in creating beams with narrow energy spreads. This talk focuses on the development of a pulsed positron beam with a total energy spread of 7 meV FWHM; this represents a factor of five improvement over the previous state-of-the-art. Current positron atomic physics experiments rely on high quality beams from buffer gas traps. Although widely used, the physical phenomena operative in beam formation had not previously been fully investigated, and understanding these processes proved crucial to improving beam quality. Experimental measurements and simulation results of positron cooling and beam formation are discussed, with an emphasis on beam energy resolution. Using these results, a new cryogenic, trap-based beam system was built. Positrons are cooled to 50 K using a CO buffer gas, resulting in beams with total energy spreads as low as 6.9 meV FWHM, sub-microsecond temporal spreads and beam diameters as small as 1 mm. Details of this beam system, as well as new experiments that will be enabled by it, will be discussed. Work supported by NSF Grant PHY-1401794.

  6. Positron microscopy

    SciTech Connect

    Hulett, L.D. Jr.; Xu, J.

    1995-02-01

    The negative work function property that some materials have for positrons make possible the development of positron reemission microscopy (PRM). Because of the low energies with which the positrons are emitted, some unique applications, such as the imaging of defects, can be made. The history of the concept of PRM, and its present state of development will be reviewed. The potential of positron microprobe techniques will be discussed also.

  7. Intense source of slow positrons

    NASA Astrophysics Data System (ADS)

    Perez, P.; Rosowsky, A.

    2004-10-01

    We describe a novel design for an intense source of slow positrons based on pair production with a beam of electrons from a 10 MeV accelerator hitting a thin target at a low incidence angle. The positrons are collected with a set of coils adapted to the large production angle. The collection system is designed to inject the positrons into a Greaves-Surko trap (Phys. Rev. A 46 (1992) 5696). Such a source could be the basis for a series of experiments in fundamental and applied research and would also be a prototype source for industrial applications, which concern the field of defect characterization in the nanometer scale.

  8. High-flux low-divergence positron beam generation from ultra-intense laser irradiated a tapered hollow target

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Xun; Ma, Yan-Yun; Zhao, Jun; Yu, Tong-Pu; Yang, Xiao-Hu; Gan, Long-Fei; Zhang, Guo-Bo; Yan, Jian-Feng; Zhuo, Hong-Bin; Liu, Jin-Jin; Zhao, Yuan; Kawata, Shigeo

    2015-10-01

    By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 × 1023 W/cm2, it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >1015 is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ˜15° with an effective temperature of ˜674 MeV. When the laser intensity is doubled, both the positron flux (>1016) and temperature (963 MeV) increase, while the divergence angle gets smaller (˜13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering.

  9. Positrons from accelerated particle interactions

    NASA Technical Reports Server (NTRS)

    Kozlovsky, B.; Lingenfelter, R. E.; Ramaty, R.

    1987-01-01

    Positron production from the decay of radioactive nuclei produced in nuclear interactions of accelerated particles is treated in detail. Laboratory data as well as theoretical considerations are used to construct energy-dependent cross sections for the production of a large number of radioactive positron emitters resulting from proton and alpha-particle interactions with ambient cosmic matter. Using these cross sections, positron production rates are calculated for a variety of energetic particle spectra, assuming solar abundances for both the energetic particles and the ambient medium. These results can be used for the study of astrophysical sites which emit annihilation radiation. In particular, the results have been applied to solar flares, where the observed 0.511 MeV line is shown to be due to positrons resulting from accelerated particle reactions.

  10. The Japanese Positron Factory

    NASA Astrophysics Data System (ADS)

    Okada, S.; Sunaga, H.; Kaneko, H.; Takizawa, H.; Kawasuso, A.; Yotsumoto, K.; Tanaka, R.

    1999-06-01

    The Positron Factory has been planned at Japan Atomic Energy Research Institute (JAERI). The factory is expected to produce linac-based monoenergetic positron beams having world-highest intensities of more than 1010e+/sec, which will be applied for R&D of materials science, biotechnology and basic physics & chemistry. In this article, results of the design studies are demonstrated for the following essential components of the facilities: 1) Conceptual design of a high-power electron linac with 100 MeV in beam energy and 100 kW in averaged beam power, 2) Performance tests of the RF window in the high-power klystron and of the electron beam window, 3) Development of a self-driven rotating electron-to-positron converter and the performance tests, 4) Proposal of multi-channel beam generation system for monoenergetic positrons, with a series of moderator assemblies based on a newly developed Monte Carlo simulation and the demonstrative experiment, 5) Proposal of highly efficient moderator structures, 6) Conceptual design of a local shield to suppress the surrounding radiation and activation levels.

  11. Conceptual design of a slow positron source based on a magnetic trap

    NASA Astrophysics Data System (ADS)

    Volosov, V. I.; Meshkov, O. I.; Mezentsev, N. A.

    2001-09-01

    A unique 10.3 T superconducting wiggler was designed and manufactured at BINP SB RAS. The installation of this wiggler in the SPring-8 storage ring provides a possibility to generate a high-intensity beam of photons (SR) with energy above 1 MeV (Ando et al., J. Synchrotron Radiat. 5 (1998) 360). Conversion of photons to positrons on high- Z material (tungsten) targets creates an integrated positron flux more than 10 13 particles per second. The energy spectrum of the positrons has a maximum at 0.5 MeV and the half-width about 1 MeV (Plokhoi et al., Jpn. J. Appl. Phys. 38 (1999) 604). The traditional methods of positron moderation have the efficiency ɛ= Ns/ Nf of 10 -4 (metallic moderators) to 10 -2 (solid rare gas moderators) (Mills and Gullikson, Appl. Phys. Lett. 49 (1986) 1121). The high flux of primary positrons restricts the choice to a tungsten moderator that has ɛ≈10 -4only (Schultz, Nuc. Instr. and Meth. B 30 (1988) 94). The aim of our project is to obtain the moderation efficiency ɛ⩾10 -1. We propose to moderate the positrons inside a multi-stage magnetic trap based on several (3-6) electromagnetic traps that are connected in series. Magnetic field of the traps grows consecutively from stage to stage. We propose to release the positrons from the converter with the use of an additional relativistic electron beam passing in synchronism with the SR pulse in the vicinity of the converter. The average electron beam energy and current are 1-2 MeV and 100 mA, respectively. The electrical field of the beam is high enough to distort the positron paths by an amount comparable with the Larmor radius. The further drift of the positrons to the trap axis will occur due to the strengthening of the magnetic field. The magnetic field amplitude of adjacent traps varies in time in the antiphase and increases from 0.9 T in the first stage to 6 T in the last one. The positron transition from stage to stage takes place at the moment of the field equalization. The removal

  12. Pulse

    MedlinePlus

    Heart rate; Heart beat ... The pulse can be measured at areas where an artery passes close to the skin. These areas include the: ... side of the foot Wrist To measure the pulse at the wrist, place the index and middle ...

  13. Prototyping of the ILC Baseline Positron Target

    SciTech Connect

    Gronberg, J; Brooksby, C; Piggott, T; Abbott, R; Javedani, J; Cook, E

    2012-02-29

    The ILC positron system uses novel helical undulators to create a powerful photon beam from the main electron beam. This beam is passed through a titanium target to convert it into electron-positron pairs. The target is constructed as a 1 m diameter wheel spinning at 2000 RPM to smear the 1 ms ILC pulse train over 10 cm. A pulsed flux concentrating magnet is used to increase the positron capture efficiency. It is cooled to liquid nitrogen temperatures to maximize the flatness of the magnetic field over the 1 ms ILC pulse train. We report on prototyping effort on this system.

  14. E166: Polarized Positrons & Polarimetry

    SciTech Connect

    Schuler, K.Peter; /DESY

    2011-12-06

    A proof-of-principle experiment has been carried out in the Final Focus Test Beam (FFTB) at Stanford Linear Accelerator Center (SLAC) to demonstrate production of polarized positrons in a manner suitable for implementation at the International Linear Collider (ILC). A helical undulator of 2.54 mm period and 1 -m length produced circularly polarized photons with a first harmonic endpoint energy of 8 MeV when traversed by a 46.6 GeV electron beam. The polarized photons were converted to polarized positrons in a 0.2-radiation-length tungsten target. The polarization of these positrons was measured using a Compton transmission polarimeter to have peak value in excess of 80%.

  15. Positron Physics

    NASA Technical Reports Server (NTRS)

    Drachman, Richard J.

    2003-01-01

    I will give a review of the history of low-energy positron physics, experimental and theoretical, concentrating on the type of work pioneered by John Humberston and the positronics group at University College. This subject became a legitimate subfield of atomic physics under the enthusiastic direction of the late Sir Harrie Massey, and it attracted a diverse following throughout the world. At first purely theoretical, the subject has now expanded to include high brightness beams of low-energy positrons, positronium beams, and, lately, experiments involving anti-hydrogen atoms. The theory requires a certain type of persistence in its practitioners, as well as an eagerness to try new mathematical and numerical techniques. I will conclude with a short summary of some of the most interesting recent advances.

  16. The Buffer-Gas Positron Accumulator and Resonances in Positron-Molecule Interactions

    NASA Technical Reports Server (NTRS)

    Surko, C.M.

    2007-01-01

    This is a personal account of the development of our buffer-gas positron trap and the new generation of cold beams that these traps enabled. Dick Drachman provided much appreciated advice to us from the time we started the project. The physics underlying trap operation is related to resonances (or apparent resonances) in positron-molecule interactions. Amusingly, experiments enabled by the trap allowed us to understand these processes. The positron-resonance "box score" to date is one resounding "yes," namely vibrational Feshbach resonances in positron annihilation on hydrocarbons; a "probably" for positron-impact electronic excitation of CO and NZ;an d a "maybe" for vibrational excitation of selected molecules. Two of these processes enabled the efficient operation of the trap, and one almost killed it in infancy. We conclude with a brief overview of further applications of the trapping technology discussed here, such as "massive" positron storage and beams with meV energy resolution.

  17. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

    2016-06-01

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m-1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.

  18. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    DOE PAGESBeta

    Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; et al

    2016-06-02

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. In this study, we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel ismore » created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m-1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.« less

  19. Update on the Argonne positron accumulator ring

    SciTech Connect

    Borland, M.

    1993-07-01

    The injector for the Advanced Photon Source incorporates a 450-MeV positron accumulator ring (PAR) to decrease the filling time with the 2-Hz synchrotron. In addition to accumulating positrons from the linac, the PAR damps the beam and reduces the bunch length. The PAR lattice has been redesigned to use zero-gradient dipoles, while retaining essentially the same damping partition. Extensive simulations have been performed to set tolerances that will give high capture efficiency, in spite of the large momentum spread of the incoming positron beam.

  20. Conceptual design of an intense positron source based on an LIA

    NASA Astrophysics Data System (ADS)

    Long, Ji-Dong; Yang, Zhen; Dong, Pan; Shi, Jin-Shui

    2012-04-01

    Accelerator based positron sources are widely used due to their high intensity. Most of these accelerators are RF accelerators. An LIA (linear induction accelerator) is a kind of high current pulsed accelerator used for radiography. A conceptual design of an intense pulsed positron source based on an LIA is presented in the paper. One advantage of an LIA is its pulsed power being higher than conventional accelerators, which means a higher amount of primary electrons for positron generations per pulse. Another advantage of an LIA is that it is very suitable to decelerate the positron bunch generated by bremsstrahlung pair process due to its ability to adjustably shape the voltage pulse. By implementing LIA cavities to decelerate the positron bunch before it is moderated, the positron yield could be greatly increased. These features may make the LIA based positron source become a high intensity pulsed positron source.

  1. KEK-IMSS Slow Positron Facility

    NASA Astrophysics Data System (ADS)

    Hyodo, T.; Wada, K.; Yagishita, A.; Kosuge, T.; Saito, Y.; Kurihara, T.; Kikuchi, T.; Shirakawa, A.; Sanami, T.; Ikeda, M.; Ohsawa, S.; Kakihara, K.; Shidara, T.

    2011-12-01

    The Slow Positron Facility at the Institute of Material Structure Science (IMSS) of High Energy Accelerator Research Organization (KEK) is a user dedicated facility with an energy tunable (0.1 - 35 keV) slow positron beam produced by a dedicated 55MeV linac. The present beam line branches have been used for the positronium time-of-flight (Ps-TOF) measurements, the transmission positron microscope (TPM) and the photo-detachment of Ps negative ions (Ps-). During the year 2010, a reflection high-energy positron diffraction (RHEPD) measurement station is going to be installed. The slow positron generator (converter/ moderator) system will be modified to get a higher slow positron intensity, and a new user-friendly beam line power-supply control and vacuum monitoring system is being developed. Another plan for this year is the transfer of a 22Na-based slow positron beam from RIKEN. This machine will be used for the continuous slow positron beam applications and for the orientation training of those who are interested in beginning researches with a slow positron beam.

  2. Pulse

    MedlinePlus

    ... resting for at least 10 minutes. Take the exercise heart rate while you are exercising. ... pulse rate can help determine if the patient's heart is pumping. ... rate gives information about your fitness level and health.

  3. Undulator-Based Production of Polarized Positrons, A Proposal for the 50-GeV Beam in the FFTB

    SciTech Connect

    G. Alexander; P. Anthony; V. Bharadwaj; Yu.K. Batygin; T. Behnke; S. Berridge; G.R. Bower; W. Bugg; R. Carr; E. Chudakov; J.E. Clendenin; F.J. Decker; Yu. Efremenko; T. Fieguth; K. Flottmann; M. Fukuda; V. Gharibyan; T. Handler; T. Hirose; R.H. Iverson; Yu. Kamyshkov; H. Kolanoski; T. Lohse; Chang-guo Lu; K.T. McDonald; N. Meyners; R. Michaels; A.A. Mikhailichenko; K. Monig; G. Moortgat-Pick; M. Olson; T. Omori; D. Onoprienko; N. Pavel; R. Pitthan; M. Purohit; L. Rinolfi; K.P. Schuler; J.C. Sheppard; S. Spanier; A. Stahl; Z.M. Szalata; J. Turner; D. Walz; A. Weidemann; J. Weisend

    2003-06-01

    The full exploitation of the physics potential of future linear colliders such as the JLC, NLC, and TESLA will require the development of polarized positron beams. In the proposed scheme of Balakin and Mikhailichenko [1] a helical undulator is employed to generate photons of several MeV with circular polarization which are then converted in a relatively thin target to generate longitudinally polarized positrons. This experiment, E-166, proposes to test this scheme to determine whether such a technique can produce polarized positron beams of sufficient quality for use in future linear colliders. The experiment will install a meter-long, short-period, pulsed helical undulator in the Final Focus Test Beam (FFTB) at SLAC. A low-emittance 50-GeV electron beam passing through this undulator will generate circularly polarized photons with energies up to 10 MeV. These polarized photons are then converted to polarized positrons via pair production in thin targets. Titanium and tungsten targets, which are both candidates for use in linear colliders, will be tested. The experiment will measure the flux and polarization of the undulator photons, and the spectrum and polarization of the positrons produced in the conversion target, and compare the measurement results to simulations. Thus the proposed experiment directly tests for the first time the validity of the simulation programs used for the physics of polarized pair production in finite matter, in particular the effects of multiple scattering on polarization. Successful comparison of the experimental results to the simulations will lead to greater confidence in the proposed designs of polarized positrons sources for the next generation of linear colliders. This experiment requests six-weeks of time in the FFTB beam line: three weeks for installation and setup and three weeks of beam for data taking. A 50-GeV beam with about twice the SLC emittance at a repetition rate of 30 Hz is required.

  4. A search for solar flare positrons

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Stone, E. C.; Vogt, R. E.

    1975-01-01

    The detection of solar gamma-ray line emission and observations of the isotopes H2, H-3, and He-3 in solar cosmic rays provide direct evidence for the occurrence of high energy nuclear reactions in solar flare events. Appreciable numbers of other reaction products, including positrons with energies near about 1 MeV, should also be produced in such events. We have searched for positrons in the 0.16-1.6 MeV energy interval during 5 H-3 rich solar particle events. Based on calculations of positron and He-3 production at the sun, and using a simplified model of interplanetary propagation, we might expect comparable fluences of positrons and He-3 to be observed. Summing over these 5 events, we find the 0.16 to 1.6 MeV positron fluence to be a maximum of about 10% of the He-3 fluence with more tnan 1 MeV/nuc. This suggests that other processes, such as preferential trapping by the solar magnetic field, may be important.

  5. Trap-Based Beam Formation Mechanisms and the Development of an Ultra-High-Energy-Resolution Cryogenic Positron Beam

    NASA Astrophysics Data System (ADS)

    Natisin, Michael Ryan

    The focus of this dissertation is the development of a positron beam with significantly improved energy resolution over any beam resolution previously available. While positron interactions with matter are important in a variety of contexts, the range of experimental data available regarding fundamental positron-matter interactions is severely limited as compared to analogous electron-matter processes. This difference is due largely to the difficulties encountered in creating positron beams with narrow energy spreads. Described here is a detailed investigation into the physical processes operative during positron cooling and beam formation in state-of-the-art, trap-based beam systems. These beams rely on buffer gas traps (BGTs), in which positrons are trapped and cooled to the ambient temperature (300 K) through interactions with a molecular gas, and subsequently ejected as a high resolution pulsed beam. Experimental measurements, analytic models, and simulation results are used to understand the creation and characterization of these beams, with a focus on the mechanisms responsible for setting beam energy resolution. The information gained from these experimental and theoretical studies was then used to design, construct, and operate a next-generation high-energy-resolution beam system. In this new system, the pulsed beam from the BGT is magnetically guided into a new apparatus which re-traps the positrons, cools them to 50 K, and re-emits them as a pulsed beam with superior beam characteristics. Using these techniques, positron beams with total energy spreads as low as 6.9 meV FWHM are produced. This represents a factor of ˜ 5 improvement over the previous state-of-the-art, making it the largest increase in positron beam energy resolution since the development of advanced moderator techniques in the early 1980's. These beams also have temporal spreads of 0.9 mus FWHM and radial spreads of 1 mm FWHM. This represents improvements by factors of ˜2 and 10

  6. Emittance of positron beams produced in intense laser plasma interaction

    SciTech Connect

    Chen Hui; Hazi, A.; Link, A.; Anderson, S.; Gronberg, J.; Izumi, N.; Tommasini, R.; Wilks, S.; Sheppard, J. C.; Meyerhofer, D. D.; Baldis, H. A.; Marley, E.; Park, J.; Williams, G. J.; Fedosejev, R.; Kerr, S.

    2013-01-15

    The first measurement of the emittance of intense laser-produced positron beams has been made. The emittance values were derived through measurements of positron beam divergence and source size for different peak positron energies under various laser conditions. For one of these laser conditions, we used a one dimensional pepper-pot technique to refine the emittance value. The laser-produced positrons have a geometric emittance between 100 and 500 mm{center_dot}mrad, comparable to the positron sources used at existing accelerators. With 10{sup 10}-10{sup 12} positrons per bunch, this low emittance beam, which is quasi-monoenergetic in the energy range of 5-20 MeV, may be useful as an alternative positron source for future accelerators.

  7. Positron annihilation radiation from solar flares

    NASA Technical Reports Server (NTRS)

    Share, G. H.; Chupp, E. L.; Forrest, D. J.; Rieger, E.

    1983-01-01

    Positron-annihilation radiation has been observed from the June 21, 1980 and June 3, 1982 flares by the gamma-ray spectrometer on the Solar Maximum Mission satellite. The observed 0.511-MeV line fluences from the flares were 14.6 + or - 3.3 gamma/sq cm and 103 + or - 8 gamma/sq cm, respectively. Measurement of the line width establishes an upper limit to the temperature in the annihilation region of 3 x 10 to the 6th K. The time dependence of the 0.511-MeV line during the 1980 flare is consistent with the calculations of Ramaty et al. (1983) for positrons created in the decay of radioactive nuclei. The time dependence of the 0.511-MeV line for the 1982 flare is more complex and requires more detailed study.

  8. Backward-propagating MeV electrons in ultra-intense laser interactions: Standing wave acceleration and coupling to the reflected laser pulse

    SciTech Connect

    Orban, Chris Feister, Scott; Morrison, John T.; Chowdhury, Enam A.; Nees, John A.; Frische, Kyle; Roquemore, W. M.

    2015-02-15

    Laser-accelerated electron beams have been created at a kHz repetition rate from the reflection of intense (∼10{sup 18 }W/cm{sup 2}), ∼40 fs laser pulses focused on a continuous water-jet in an experiment at the Air Force Research Laboratory. This paper investigates Particle-in-Cell simulations of the laser-target interaction to identify the physical mechanisms of electron acceleration in this experiment. We find that the standing-wave pattern created by the overlap of the incident and reflected laser is particularly important because this standing wave can “inject” electrons into the reflected laser pulse where the electrons are further accelerated. We identify two regimes of standing wave acceleration: a highly relativistic case (a{sub 0} ≥ 1), and a moderately relativistic case (a{sub 0} ∼ 0.5) which operates over a larger fraction of the laser period. In previous studies, other groups have investigated the highly relativistic case for its usefulness in launching electrons in the forward direction. We extend this by investigating electron acceleration in the specular (back reflection) direction and over a wide range of intensities (10{sup 17}–10{sup 19 }W cm{sup −2})

  9. Time-dependent 2.2 MeV and 0.5 MeV lines from solar flares

    NASA Technical Reports Server (NTRS)

    Wang, H. T.; Ramaty, R.

    1975-01-01

    The time dependences of the 2.2 MeV and 0.51 MeV gamma ray lines from solar flares are calculated and the results are compared with observations of the 1972, August 4 and 7 flares. Time lag between the nuclear reactions and the formation of these two lines are caused, respectively, by capture of the neutrons, and by deceleration of the positrons and decay of the radioactive nuclei. Results show that the calculation is consistent with the observed rise of the 2.2 MeV line on August 4, and it does not require different time dependences for the accelerated protons and electrons in the flare region. The above lags can explain the delayed gamma ray emission observed on August 7. Positrons of energies greater than about 10 MeV could be detected in interplanetary space following large solar flares.

  10. Positron acceleration in plasma bubble wakefield driven by an ultraintense laser

    NASA Astrophysics Data System (ADS)

    Hou, Ya-Juan; Wan, Feng; Sang, Hai-Bo; Xie, Bai-Song

    2016-01-01

    The dynamics of positrons accelerating in electron-positron-ion plasma bubble fields driven by an ultraintense laser is investigated. The bubble wakefield is obtained theoretically when laser pulses are propagating in the electron-positron-ion plasma. To restrict the positrons transversely, an electron beam is injected. Acceleration regions and non-acceleration ones of positrons are obtained by the numerical simulation. It is found that the ponderomotive force causes the fluctuation of the positrons momenta, which results in the trapping of them at a lower ion density. The energy gaining of the accelerated positrons is demonstrated, which is helpful for practical applications.

  11. Positron Production at JLab Simulated Using Geant4

    SciTech Connect

    Kossler, W. J.; Long, S. S.

    2009-09-02

    The results of a Geant4 Monte-Carlo study of the production of slow positrons using a 140 MeV electron beam which might be available at Jefferson Lab are presented. Positrons are produced by pair production for the gamma-rays produced by bremsstrahlung on the target which is also the stopping medium for the positrons. Positrons which diffuse to the surface of the stopping medium are assumed to be ejected due to a negative work function. Here the target and moderator are combined into one piece. For an osmium target/moderator 3 cm long with transverse dimensions of 1 cm by 1 mm, we obtain a slow positron yield of about 8.5centre dot10{sup 10}/(scentre dotmA) If these positrons were remoderated and re-emitted with a 23% probability we would obtain 2centre dot10{sup 10}/(scentre dotmA) in a micro-beam.

  12. Bremsstrahlung pair-production of positrons with low neutron background.

    SciTech Connect

    Lessner, E.

    1998-09-16

    Minimization of component activation is highly desirable at accelerator-based positron sources. Electrons in the 8- to 14-MeV energy range impinging on a target produce photons energetic enough to create electron-positron pairs; however, few of the photons are energetic enough to produce photoneutrons. Slow positron production by low-energy electrons impinging on a multilayer tungsten target with and without electromagnetic extraction between the layers was studied by simulation. The neutron background from 14-MeV electrons is expected to be significantly lower than that encountered with higher-energy electron beams. Numerical results are presented and some ideas for a low-activation slow-positron source are discussed.

  13. An Undulator Based Polarized Positron Source for CLIC

    SciTech Connect

    Liu, Wanming; Gai, Wei; Rinolfi, Louis; Sheppard, John; /SLAC

    2012-07-02

    A viable positron source scheme is proposed that uses circularly polarized gamma rays generated from the main 250 GeV electron beam. The beam passes through a helical superconducting undulator with a magnetic field of {approx} 1 Tesla and a period of 1.15 cm. The gamma-rays produced in the undulator in the energy range between {approx} 3 MeV - 100 MeV will be directed to a titanium target and produce polarized positrons. The positrons are then captured, accelerated and transported to a Pre-Damping Ring (PDR). Detailed parameter studies of this scheme including positron yield, and undulator parameter dependence are presented. Effects on the 250 GeV CLIC main beam, including emittance growth and energy loss from the beam passing through the undulator are also discussed.

  14. Resonances in low-energy positron-alkali scattering

    NASA Technical Reports Server (NTRS)

    Horbatsch, M.; Ward, S. J.; Mceachran, R. P.; Stauffer, A. D.

    1990-01-01

    Close-coupling calculations were performed with up to five target states at energies in the excitation threshold region for positron scattering from Li, Na and K. Resonances were discovered in the L = 0, 1 and 2 channels in the vicinity of the atomic excitation thresholds. The widths of these resonances vary between 0.2 and 130 MeV. Evidence was found for the existence of positron-alkali bound states in all cases.

  15. Pulsed power supply for three APS septum magnets

    SciTech Connect

    McGhee, D.G.

    1991-03-24

    Three septum magnets will be operated at a repetition-rate of 2 Hz. Two of the septum magnets are identical and operate at the same values; these are the synchrotron extraction and the storage ring injection magnets. They are transformer septum magnets, with a primary inductance of 23 {mu}H and resistance of 6.3 m{Omega}, and must be pulsed at a 2 Hz rate to extract beam from the synchrotron and inject beam into the storage ring at 7.7 GeV. The third septum magnet is used to inject electrons into the synchrotron at 650 MeV or positrons at 450 MeV. It is also a transformer septum magnet, with a primary inductance of 21 {mu}H and resistance of 6.7 m{Omega}, and must be pulsed at a 2 Hz rate. A design study was performed of the power supply proposed in the APS Title I design. This supply produces a pulse that is approximately a half-sine-wave with a base width of approximately 1/3 ms; its peakcurrent is adjustable from 470 A to 4.7 kA and is repeatable within {plus_minus}0.05%. The septum steel is reset by a half-sine pulse of reverse polarity a few milliseconds after the forward current pulse. No beam is present during reset. The use of the transformer design minimizes the cost of the capacitors used for energy storage.

  16. Trapped positrons observed by PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Mikhailov, V. V.; Adriani, O.; Barbarino, G.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F. S.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; Consiglio, L.; De Santis, C.; De Simone, N.; Di Felice, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobsky, S.; Krutkov, S. Yu; Kvashnin, A. N.; Leonov, A. A.; Malakhov, V. V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Merge, M.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Papini, P.; Palma, F.; Panico, B.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Yu I.; Vacchi, A.; Vannuccini, E.; Vasiliev, G. I.; Voronov, S. A.; Yurkin, Yu T.; Zampa, G.; Zampa, N.

    2016-02-01

    Measurements of electron and positron spatial distributions in energy range from 80 MeV to several GeV below the geomagnetic cutoff rigidity were carried out using the PAMELA magnetic spectrometer. The instrument is installed on board the Resurs-DK satellite which was launched June 15th 2006 on an elliptical orbit with the inclination 70 degrees and the altitude 350-600 km. The procedure of trajectories calculations in the geomagnetic filed gives a way to separate stably trapped and short lived albedo components produced in interactions of cosmic ray protons with the residual atmosphere. The work presents spatial distributions of trapped, quasitrapped and short-lived albedo electrons and positrons in the near Earth space. Electron to positron ratio points out on different production mechanism of trapped and quasitrapped particles.

  17. Time-dependent 2.2-MeV and 0.5-MeV lines from solar flares

    NASA Technical Reports Server (NTRS)

    Wang, H. T.; Ramaty, R.

    1975-01-01

    The time dependences of the 2.2- and 0.51-MeV gamma-ray lines from solar flares are calculated, and the results are compared with observations of the 1972 August 4 and 7 flares. The time lag between the nuclear reactions and the formation of these two lines is caused by capture of the neutrons and subsequent deceleration of the positrons and decay of the radioactive nuclei. Our main results are that the calculation is consistent with the observed rise of the 2.2-MeV line on August 4, and it does not require different time dependences for the accelerated protons and high-energy electrons in the flare region. The above lags can explain the delayed gamma-ray emission observed on August 7. Positrons of energies greater than about 10 MeV could be detected in interplanetary space following large solar flares.

  18. Position-resolved Positron Annihilation Lifetime Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wagner, A.; Butterling, M.; Fiedler, F.; Fritz, F.; Kempe, M.; Cowan, T. E.

    2013-06-01

    A new method which allows for position-resolved positron lifetime spectroscopy studies in extended volume samples is presented. In addition to the existing technique of in-situ production of positrons inside large (cm3) bulk samples using high-energy photons up to 16 MeV from bremsstrahlung production, granular position-sensitive photon detectors have been employed. A beam of intense bremsstrahlung is provided by the superconducting electron linear accelerator ELBE (Electron Linear Accelerator with high Brilliance and low Emittance) which delivers electron bunches of less than 10 ps temporal width and an adjustable bunch separation of multiples of 38 ns, average beam currents of 1 mA, and energies up to 40 MeV. Since the generation of bremsstrahlung and the transport to the sample preserves the sharp timing of the electron beam, positrons generated inside the entire sample volume by pair production feature a sharp start time stamp for positron annihilation lifetime studies with high timing resolutions and high signal to background ratios due to the coincident detection of two annihilation photons. Two commercially available detectors from a high-resolution medial positron-emission tomography system are being employed with 169 individual Lu2SiO5:Ce scintillation crystals, each. In first experiments, a positron-lifetime gated image of a planar Si/SiO2 (pieces of 12.5 mm × 25 mm size) sample and a 3-D structured metal in Teflon target could be obtained proving the feasibility of a three dimensional lifetime-gated tomographic system.

  19. On the nature of the cosmic ray positron spectrum

    NASA Technical Reports Server (NTRS)

    Protheroe, R. J.

    1981-01-01

    A calculation was made of the flux of secondary positrons above 100 MeV expected for various propagation models. The models investigated were the leaky box or homogeneous model, a disk halo diffusion model, a dynamical halo model, and the closed galaxy model. In each case the parameters of these models were adjusted for agreement with the observed secondary or primary ratios and Be 10 abundance. The positron flux predicted for these models was compared with the available data. The possibility of a primary positron component was considered.

  20. High intensity positron beam and angular correlation experiments at Livermore

    SciTech Connect

    Howell, R.H.; Rosenberg, I.J.; Meyer, P.; Fluss, M.J.

    1985-03-01

    A positron beam apparatus that produces a variable energy positron beam with sufficient intensity to perform new positron experiments in an ultrahigh vacuum environment has been installed at the Lawrence Livermore 100 MeV electron linac. We have installed two large area position sensitive gamma-ray detectors to measure angular correlations in two dimensions and a separate highly collimated detector to measure positronium energy distributions by time-of-flight velocity determination. Data from measurements on single crystals of Cu will be described.

  1. Positron bunching and electrostatic transport system for the production and emission of dense positronium clouds into vacuum

    NASA Astrophysics Data System (ADS)

    Aghion, S.; Amsler, C.; Ariga, A.; Ariga, T.; Belov, A. S.; Bonomi, G.; Bräunig, P.; Bremer, J.; Brusa, R. S.; Cabaret, L.; Caccia, M.; Caravita, R.; Castelli, F.; Cerchiari, G.; Chlouba, K.; Cialdi, S.; Comparat, D.; Consolati, G.; Demetrio, A.; Di Noto, L.; Doser, M.; Dudarev, A.; Ereditato, A.; Evans, C.; Fesel, J.; Fontana, A.; Forslund, O. K.; Gerber, S.; Giammarchi, M.; Gligorova, A.; Gninenko, S.; Guatieri, F.; Haider, S.; Holmestad, H.; Huse, T.; Jernelv, I. L.; Jordan, E.; Kaltenbacher, T.; Kellerbauer, A.; Kimura, M.; Koetting, T.; Krasnicky, D.; Lagomarsino, V.; Lebrun, P.; Lansonneur, P.; Lehner, S.; Liberadzka, J.; Malbrunot, C.; Mariazzi, S.; Marx, L.; Matveev, V.; Mazzotta, Z.; Nebbia, G.; Nedelec, P.; Oberthaler, M.; Pacifico, N.; Pagano, D.; Penasa, L.; Petracek, V.; Pistillo, C.; Prelz, F.; Prevedelli, M.; Ravelli, L.; Rienäcker, B.; Røhne, O. M.; Rosenberger, S.; Rotondi, A.; Sacerdoti, M.; Sandaker, H.; Santoro, R.; Scampoli, P.; Sorrentino, F.; Spacek, M.; Storey, J.; Strojek, I. M.; Testera, G.; Tietje, I.; Vamosi, S.; Widmann, E.; Yzombard, P.; Zavatarelli, S.; Zmeskal, J.

    2015-11-01

    We describe a system designed to re-bunch positron pulses delivered by an accumulator supplied by a positron source and a Surko-trap. Positron pulses from the accumulator are magnetically guided in a 0.085 T field and are injected into a region free of magnetic fields through a μ -metal field terminator. Here positrons are temporally compressed, electrostatically guided and accelerated towards a porous silicon target for the production and emission of positronium into vacuum. Positrons are focused in a spot of less than 4 mm FWTM in bunches of ∼8 ns FWHM. Emission of positronium into the vacuum is shown by single shot positron annihilation lifetime spectroscopy.

  2. Positron annihilation Doppler broadening measurement for bulk amorphous alloy by using high energy positron generated from LCS gamma-ray at NEW SUBARU

    NASA Astrophysics Data System (ADS)

    Hori, F.; Ueno, Y.; Ishii, K.; Ishiyama, T.; Iwase, A.; Miyamoto, S.; Terasawa, T.

    2016-01-01

    A simple positron annihilation measurement apparatus via pair creation has been developed using high energetic gamma beam generated by laser Compton scattering (LCS) of 1 GeV electrons circulated in a storage ring and laser light with the power more than 1 W at the New SUBARU synchrotron radiation facility, University of Hyogo. This MeV ordered energy changeable positron apparatus is useful to study defects in bulk materials. In this study, the average energy of 8MeV positron was selected by the wavelength of laser light and circulated electron energy in photon factory. As a demonstrate of non-destruction positron measurement by this apparatus, positron annihilation Doppler broadening measurement has performed for bulk size of amorphous and crystal structured Zr based alloys. The larger Doppler broadening S parameter for amorphous alloy than that for crystallized one has been successfully measured.

  3. Formation of a high intensity low energy positron string

    NASA Astrophysics Data System (ADS)

    Donets, E. D.; Donets, E. E.; Syresin, E. M.; Itahashi, T.; Dubinov, A. E.

    2004-05-01

    The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5×109 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production.

  4. Positron emission tomography.

    PubMed

    Hoffman, E J; Phelps, M E

    1979-01-01

    Conventional nuclear imaging techniques utilizing lead collimation rely on radioactive tracers with little role in human physiology. The principles of imaging based on coincidence detection of the annihilation radiation produced in positron decay indicate that this mode of detection is uniquely suited for use in emission computed tomography. The only gamma-ray-emitting isotopes of carbon, nitrogen, and oxygen are positron emitters, which yield energies too high for conventional imaging techniques. Thus development of positron emitters in nuclear medicine imaging would make possible the use of a new class of physiologically active, positron-emitting radiopharmaceuticals. The application of these principles is described in the use of a physiologically active compound labeled with a positron emitter and positron-emission computed tomography to measure the local cerebral metabolic rate in humans. PMID:440173

  5. Positron-rubidium scattering

    NASA Technical Reports Server (NTRS)

    Mceachran, R. P.; Horbatsch, M.; Stauffer, A. D.

    1990-01-01

    A 5-state close-coupling calculation (5s-5p-4d-6s-6p) was carried out for positron-Rb scattering in the energy range 3.7 to 28.0 eV. In contrast to the results of similar close-coupling calculations for positron-Na and positron-K scattering the (effective) total integrated cross section has an energy dependence which is contrary to recent experimental measurements.

  6. Possible detection of flare-generated positrons by Helios 1 on 3 Jun 1982

    NASA Technical Reports Server (NTRS)

    Kirsch, E.; Keppler, E.; Richter, K.

    1985-01-01

    The production of neutrons and gamma-ray lines by solar particles in the photosphere has been studied. The principal positron emiters which lead to the 0.51 MeV gamma-line are C-11 0-14, 0-15, N-13, Ne-19. The energies of the positrons form radioactive nuclei are of the order of few hundred keV. Positrons resulting from the pi(+) decay have energies of approx 10-100 MeV and cannot be measured by the MPAe-detector. Most of the positrons annihilate in the photosphere. A fraction however should be able to escape into the interplanetary space. Proton, electron and , for the first time, positron measurements (E = 152-546 keV) obtained by the MPAe-particle detector on board of Helios 1 are presented.

  7. Comparison of the quantum and classical calculations of flux density of (220) channeled positrons in Si crystal

    NASA Astrophysics Data System (ADS)

    Korotchenko, K. B.; Tukhfatullin, TA; Pivovarov, Yu L.; Eikhorn, Yu L.

    2016-07-01

    Simulation of flux-peaking effect of the 255 MeV positrons channeled in (220) Si crystals is performed in the frame of classical and quantum mechanics. Comparison of the results obtained using both approaches shows relatively good agreement.

  8. Positrons for linear colliders

    SciTech Connect

    Ecklund, S.

    1987-11-01

    The requirements of a positron source for a linear collider are briefly reviewed, followed by methods of positron production and production of photons by electromagnetic cascade showers. Cross sections for the electromagnetic cascade shower processes of positron-electron pair production and Compton scattering are compared. A program used for Monte Carlo analysis of electromagnetic cascades is briefly discussed, and positron distributions obtained from several runs of the program are discussed. Photons from synchrotron radiation and from channeling are also mentioned briefly, as well as positron collection, transverse focusing techniques, and longitudinal capture. Computer ray tracing is then briefly discussed, followed by space-charge effects and thermal heating and stress due to showers. (LEW)

  9. Positron production during relativistic runaway processes associated with thunderstorms

    NASA Astrophysics Data System (ADS)

    Dwyer, J. R.; Smith, D. M.; Rassoul, H.; Cramer, E. S.; Schaal, M.; Saleh, Z. H.; Grefenstette, B.; Hazelton, B. J.; Splitt, M. E.; Lazarus, S. M.; Fishman, G. J.; Briggs, M. S.; Connaughton, V.

    2009-12-01

    Recent spacecraft observations of terrestrial gamma-ray flashes (TGFs) by Fermi/GBM and aircraft observations of the gamma-ray emissions from thunderclouds by ADELE have shown prominent 511 keV positron annihilation lines, demonstrating large enhancements in the positron populations. These observations show that significant pair-production must be taking place, most likely in association with the production of relativistic runaway electron avalanches. Using detailed Monte Carlo simulations, we investigate the production and subsequent transport of positrons by strong electric fields associated with thunderstorms. It will be shown that intense high-energy beams of positrons can be produced with energies reaching 100 MeV, well exceeding the average energy of the runaway electron population. These positrons, which may travel many kilometers before annihilating, generate a substantial amount of bremsstrahlung x-rays and annihilation gamma-rays. In this presentation, we shall discuss the theory of positron production by runaway electron avalanches and the feedback effects produced by these positrons. In addition, we shall use the Monte Carlo simulations to model the recent Fermi/GBM TGF and ADELE gamma-ray data.

  10. The Calibration of the PEPPo Polarimeter for Electrons and Positrons

    SciTech Connect

    Adeyemi, Adeleke Hakeem; Voutier, Eric J-.M.

    2013-06-01

    The PEPPo (Polarized Electrons for Polarized Positrons) experiment at Jefferson Laboratory investigated the polarization transfer from longitudinally polarized electrons to longitudinally polarized positrons, with the aim of developing this technology for a low energy (~MeV) polarized positron source. Polarization of the positrons was measured by means of a Compton transmission polarimeter where incoming positrons transfer their polarization into circularly polarized photons that were subsequently analyzed by a thick polarized iron target. The measurement of the transmitted photon flux with respect to the orientation of the target polarization (+-) or the helicity (+-) of the incoming leptons provided the measurement of their polarization. Similar measurements with a known electron beam were also performed for calibration purposes. This presentation will describe the apparatus and calibrations performed at the injector at the Jefferson Laboratory to measure positron polarization in the momentum range 3.2-6.2 MeV/c, specifically to quantify the positron analyzing power from electron experimental data measured over a comparable momentum range.

  11. Nonlinear Laser Driven Donut Wakefields for Positron and Electron Acceleration

    NASA Astrophysics Data System (ADS)

    Vieira, J.; Mendonça, J. T.

    2014-05-01

    We show analytically and through three-dimensional particle-in-cell simulations that nonlinear wakefields driven by Laguerre-Gaussian laser pulses can lead to hollow electron self-injection and positron acceleration. We find that higher order lasers can drive donut shaped blowout wakefields with strong positron accelerating gradients comparable to those of a spherical bubble. Corresponding positron focusing forces can be more than an order of magnitude stronger than electron focusing forces in a spherical bubble. Required laser intensities and energies to reach the nonlinear donut shaped blowout are within state-of-the-art experimental conditions.

  12. Characterization of 2 MeV, 4 MeV, 6 MeV and 18 MeV buildup caps for use with a 0.6 cubic centimeter thimble ionization chamber

    SciTech Connect

    Salyer, R.L.; VanDenburg, J.W.; Prinja, A.K.; Kirby, T.; Busch, R.; Hong-Nian Jow

    1996-07-01

    The purpose of this research is to characterize existing 2 MeV, 4 MeV and 6 MeV buildup caps, and to determine if a buildup cap can be made for the 0.6 cm{sup 3} thimble ionization chamber that will accurately measure exposures in a high-energy photon radiation field. Two different radiation transport codes were used to computationally characterize existing 2 MeV, 4 MeV, and 6 MeV buildup caps for a 0.6 cm{sup 3} active volume thimble ionization chamber: ITS, The Integrated TIGER Series of Coupled Electron-Photon Monte Carlo Transport Codes; and CEPXS/ONEDANT, A One-Dimensional Coupled Electron-Photon Discrete Ordinates Code Package. These codes were also used to determine the design characteristics of a buildup cap for use in the 18 MeV photon beam produced by the 14 TW pulsed power HERMES-III electron accelerator. The maximum range of the secondary electron, the depth at which maximum dose occurs, and the point where dose and collision kerma are equal have been determined to establish the validity of electronic equilibrium. The ionization chamber with the appropriate buildup cap was then subjected to a 4 MeV and a 6 MeV bremmstrahlung radiation spectrum to determine the detector response.

  13. Positron production at extreme light infrastructure – nuclear physics (ELI-NP)

    SciTech Connect

    Oprisa, A. Balascuta, S. Ur, C. A.

    2015-02-24

    Applied and material physics studies with positron beams of Fermi–surfaces, defects, interfaces etc. offer excellent diagnostics tools. At ELI-NP, an intense γ beam of about 10{sup 11} photons/s with energies up to 3.5 MeV will be used to generate a positron beam via pair production in a tungsten converter target. To obtain a high intensity beam of moderated positrons the design of the positron source is of high importance. The design of a dedicated positron source at ELI–NP is being investigated based on extensive GEANT4 simulations. The goal of the simulations is to optimize the geometry of the target and the gamma beam collimation. We present here the characteristics of the positron beam obtained for different geometries of the converter target.

  14. Observation of Polarized Positrons from an Undulator-Based Source

    SciTech Connect

    Alexander, G; Barley, J.; Batygin, Y.; Berridge, S.; Bharadwaj, V.; Bower, G.; Bugg, W.; Decker, F.-J.; Dollan, R.; Efremenko, Y.; Gharibyan, V.; Hast, C.; Iverson, R.; Kolanoski, H.; Kovermann, J.; Laihem, K.; Lohse, T.; McDonald, K.T.; Mikhailichenko, A.A.; Moortgat-Pick, G.A.; Pahl, P.; /Tel Aviv U. /Cornell U., Phys. Dept. /SLAC /Tennessee U. /Humboldt U., Berlin /DESY /Yerevan Phys. Inst. /Aachen, Tech. Hochsch. /DESY, Zeuthen /Princeton U. /Durham U. /Daresbury

    2008-03-06

    An experiment (E166) at the Stanford Linear Accelerator Center (SLAC) has demonstrated a scheme in which a multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with Geant4 simulations that include the dominant polarization-dependent interactions of electrons, positrons and photons in matter.

  15. Advanced positron sources

    NASA Astrophysics Data System (ADS)

    Variola, A.

    2014-03-01

    Positron sources are a critical system for the future lepton colliders projects. Due to the large beam emittance at the production and the limitation given by the target heating and mechanical stress, the main collider parameters fixing the luminosity are constrained by the e+ sources. In this context also the damping ring design boundary conditions and the final performance are given by the injected positron beam. At present different schemes are being taken into account in order to increase the production and the capture yield of the positron sources, to reduce the impact of the deposited energy in the converter target and to increase the injection efficiency in the damping ring. The final results have a strong impact not only on the collider performance but also on its cost optimization. After a short introduction illustrating their fundamental role, the basic positron source scheme and the performance of the existing sources will be illustrated. The main innovative designs for the future colliders advanced sources will be reviewed and the different developed technologies presented. Finally the positrons-plasma R&D experiments and the futuristic proposals for positron sources will reviewed.

  16. Positrons from supernovae

    NASA Technical Reports Server (NTRS)

    Chan, Kai-Wing; Lingenfelter, Richard E.

    1993-01-01

    Positrons are produced in the ejecta of supernovae by the decay of nucleosynthetic Co-56, Ti-44, and Al-26. We calculate the probability that these positrons can survive without annihilating in the supernova ejecta, and we show that enough of these positrons should escape into the interstellar medium to account for the observed diffuse Galactic annihilation radiation. The surviving positrons are carried by the expanding ejecta into the interstellar medium where their annihilation lifetime of 10 exp 5 - 10 exp 6 yr is much longer than the average supernovae occurrence time of about 100 yr. Thus, annihilating positrons from thousands of supernovae throughout the Galaxy produce a steady diffuse flux of annihilation radiation. We further show that combining the calculated positron survival fractions and nucleosynthetic yields for current supernova models with the estimated supernova rates and the observed flux of diffuse Galactic annihilation radiation suggests that the present Galactic rate of Fe-56 nucleosynthesis is about 0.8 +/- 0.6 solar mass per 100 yr.

  17. FLUKA and PENELOPE simulations of 10 keV to 10 MeV photons in LYSO and soft tissue

    NASA Astrophysics Data System (ADS)

    Chin, M. P. W.; Böhlen, T. T.; Fassò, A.; Ferrari, A.; Ortega, P. G.; Sala, P. R.

    2014-02-01

    Monte Carlo simulations of electromagnetic particle interactions and transport by FLUKA and PENELOPE were compared. 10 keV to 10 MeV incident photon beams impinged a LYSO crystal and a soft-tissue phantom. Central-axis as well as off-axis depth doses agreed within 1 s.d.; no systematic under- or over-estimate of the pulse height spectra was observed from 100 keV to 10 MeV for both materials, agreement was within 5%. Simulation of photon and electron transport and interactions at this level of precision and reliability is of significant impact, for instance, on treatment monitoring of hadrontherapy where a code like FLUKA is needed to simulate the full suite of particles and interactions (not just electromagnetic). At the interaction-by-interaction level, apart from known differences in condensed history techniques, two-quanta positron annihilation at rest was found to differ between the two codes. PENELOPE produced a 511 keV sharp line, whereas FLUKA produced visible acolinearity, a feature recently implemented to account for the momentum of shell electrons.

  18. PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons

    SciTech Connect

    Adeyemi, Adeleke H.

    2015-09-01

    Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high-Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high-energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved.

  19. Hybrid scheme of positron source at SPARC_LAB LNF facility

    NASA Astrophysics Data System (ADS)

    Abdrashitov, S. V.; Bogdanov, O. V.; Dabagov, S. B.; Pivovarov, Yu. L.; Tukhfatullin, T. A.

    2015-07-01

    The hybrid scheme of the positron source for SPARC_LAB LNF facility (Frascati, Italy) is proposed. The comparison of the positron yield in a thin amorphous W converter of 0.1 mm thickness produced by bremsstrahlung, by axial <1 0 0> and planar (1 1 0) channeling radiations in a W crystal is performed for the positron energy range of 1 ÷ 3 MeV. It is shown that the radiation from 200 MeV electrons (parameters of SPARC_LAB LNF Frascati) in a 10 μm W crystal can produce positrons in the radiator of 0.1 mm thickness with the rate of 10-102 s-1 at planar channeling, of 102-103 s-1 at bremsstrahlung and of 103-104 s-1 at axial channeling.

  20. Positron Production by X Rays Emitted By Betatron Motion in a Plasma Wiggler

    SciTech Connect

    Johnson, D.K.; Auerbach, D.; Blumenfeld, I.; Barnes, C.D.; Clayton, C.E.; Decker, F.J.; Deng, S.; Emma, P.; Hogan, M.J.; Huang, C.; Ischebeck, R.; Iverson, R.; Joshi, C.; Katsouleas, T.C.; Kirby, N.; Krejcik, P.; Lu, W.; Marsh, K.A.; Mori, W.B.; Muggli, P.; O'Connell, C.L.; /UCLA /SLAC /Southern California U.

    2007-01-25

    Positrons in the energy range of 3-30 MeV, produced by x rays emitted by betatron motion in a plasma wiggler of 28.5 GeV electrons from the SLAC accelerator, have been measured. The extremely high-strength plasma wiggler is an ion column induced by the electron beam as it propagates through and ionizes dense lithium vapor. X rays in the range of 1-50 MeV in a forward cone angle of 0.1 mrad collide with a 1.7 mm thick tungsten target to produce electron-positron pairs. The positron spectra are found to be strongly influenced by the plasma density and length as well as the electron bunch length. By characterizing the beam propagation in the ion column these influences are quantified and result in excellent agreement between the measured and calculated positron spectra.

  1. Laser Ponderomotive Electron-Positron Collider

    SciTech Connect

    Nakajima, Kazuhisa

    2004-12-07

    Relativistic ultrahigh laser fields can produce plasmas through quantum mechanical tunneling ionization mechanism, and accelerate produced electrons and ions to generate a relativistic electron beam and energetic ions in plasmas. This process will be followed by creation of electron-positron pairs through interaction of relativistic electrons with a Coulomb field of a nucleus in plasma ions or a strong laser field. In a relativistic strong laser field, the longitudinal accelerating force exerted on an electron is proportional to the square of the electric field, whereas the transverse quivering force is just linearly proportional to it. This is essence of the relativistic ponderomotive acceleration that dominantly produces energetic particles in interaction of ultraintese laser fields with particle beams and plasma. Therefore a tightly focused laser field can accelerate an electron-positron bunch longitudinally up to a remarkable energy and at the same time confines it transversely in the superposed ponderomotive potential of an intense ultrashort laser pulse. Here we propose acceleration and focusing of the electron-positron pair beam by the ponderomotive acceleration scheme to compose a high energy electron-positron collider with very high luminosity.

  2. Elastic positron-cadmium scattering at low energies

    SciTech Connect

    Bromley, M. W. J.; Mitroy, J.

    2010-05-15

    The elastic and annihilation cross sections for positron-cadmium scattering are reported up to the positronium-formation threshold (at 2.2 eV). The low-energy phase shifts for the elastic scattering of positrons from cadmium were derived from the bound and pseudostate energies of a very large basis configuration-interaction calculation of the e{sup +}-Cd system. The s-wave binding energy is estimated to be 126{+-}42 meV, with a scattering length of A{sub scat}=(14.2{+-}2.1)a{sub 0}, while the threshold annihilation parameter, Z{sub eff}, was 93.9{+-}26.5. The p-wave phase shift exhibits a weak shape resonance that results in a peak Z{sub eff} of 91{+-}17 at a collision energy of about 490{+-}50 meV.

  3. Construction and commissioning of the positron accumulator ring for the APS

    SciTech Connect

    Borland, M.

    1994-12-31

    The injector for the Advanced Photon Source (APS) incorporates a 450-MeV positron accumulator ring (PAR) to accumulate and damp positrons from the 60Hz linac during each cycle of the 2-Hz synchrotron. An overview of PAR hardware is presented. Commissioning of the PAR is well underway using electrons. Studies have produced a modified lattice model using three free parameters that agrees well with measurements. Principle problems are high leakage fields from the septum and ion trapping.

  4. Angular momenta creation in relativistic electron-positron plasma.

    PubMed

    Tatsuno, T; Berezhiani, V I; Pekker, M; Mahajan, S M

    2003-07-01

    Creation of angular momentum in a relativistic electron-positron plasma is explored. It is shown that a chain of angular momentum carrying vortices is a robust asymptotic state sustained by the generalized nonlinear Schrödinger equation characteristic to the system. The results may suggest a possible electromagnetic origin of angular momenta when it is applied to the MeV epoch of the early Universe. PMID:12935260

  5. Magnetoacoustic solitons in dense astrophysical electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Hussain, S.; Mahmood, S.; Mushtaq, A.

    2013-08-01

    Nonlinear magnetoacoustic waves in dense electron-positron-ion plasmas are investigated by using three fluid quantum magnetohydrodynamic model. The quantum mechanical effects of electrons and positrons are taken into account due to their Fermionic nature (to obey Fermi statistics) and quantum diffraction effects (Bohm diffusion term) in the model. The reductive perturbation method is employed to derive the Korteweg-de Vries (KdV) equation for low amplitude magnetoacoustic soliton in dense electron-positron-ion plasmas. It is found that positron concentration has significant impact on the phase velocity of magnetoacoustic wave and on the formation of single pulse nonlinear structure. The numerical results are also illustrated by taking into account the plasma parameters of the outside layers of white dwarfs and neutron stars/pulsars.

  6. Dispersive effects from a comparison of electron and positron scattering from

    SciTech Connect

    Paul Gueye; M. Bernheim; J. F. Danel; Jean-Eric Ducret; L. Lakehal-Ayat; J. M. Le Goff; A. Magnon; C. March; J. Morgenstern; Jacques Marroncle; Pascal Vernin; A. Zghiche-Lakehal-Ayat; Vincent Breton; Salvatore Frullani; Franco Garibaldi; F. Ghio; Mauro Iodice; D. B. Isabelle; Zein-Eddine Meziani; E. Offermann; M. Traini

    1998-05-01

    Dispersive effects have been investigated by comparing elastic scattering of electrons and positrons from {sup 12}C at the Saclay Linear Accelerator. The results demonstrate that dispersive effects at energies of 262 MeV and 450 MeV are less than 2% below the first diffraction minimum [0.95 < q{sub eff} (fm{sup -1}) < 1.66] in agreement with the prediction of Friar and Rosen. At the position of this minimum (q{sub eff} = 1.84 fm{sup -1}), the deviation between the positron scattering cross section and the cross section derived from the electron results is -44% {+-} 30%.

  7. Positron emission tomography

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y. Lucas; Thompson, Christopher J.; Diksic, Mirko; Meyer, Ernest; Feindel, William H.

    One of the most exciting new technologies introduced in the last 10 yr is positron emission tomography (PET). PET provides quantitative, three-dimensional images for the study of specific biochemical and physiological processes in the human body. This approach is analogous to quantitative in-vivo autoradiography but has the added advantage of permitting non-invasive in vivo studies. PET scanning requires a small cyclotron to produce short-lived positron emitting isotopes such as oxygen-15, carbon-11, nitrogen-13 and fluorine-18. Proper radiochemical facilities and advanced computer equipment are also needed. Most important, PET requires a multidisciplinary scientific team of physicists, radiochemists, mathematicians, biochemists and physicians. This review analyzes the most recent trends in the imaging technology, radiochemistry, methodology and clinical applications of positron emission tomography.

  8. Alternative positron-target design for electron-positron colliders

    SciTech Connect

    Donahue, R.J. ); Nelson, W.R. )

    1991-04-01

    Current electron-positron linear colliders are limited in luminosity by the number of positrons which can be generated from targets presently used. This paper examines the possibility of using an alternate wire-target geometry for the production of positrons via an electron-induced electromagnetic cascade shower. 39 refs., 38 figs., 5 tabs.

  9. Studies of iron exposed to heavy ion implantation using positron annihilation spectroscopy

    NASA Astrophysics Data System (ADS)

    Horodek, P.; Dryzek, J.; Skuratov, V. A.

    2016-05-01

    Variable energy positron beam and positron lifetime spectroscopy were used to study pure iron exposed to irradiation with 167 MeV Xe26+ heavy ions with different doses of 1012, 1013, 5×1013, 1014 ions/cm2. The positron lifetime spectroscopy revealed the presence of large cluster of about 15-27 vacancies and dislocations. The dislocations are distributed at the depth of about 18 μm i.e. almost twice deeper than the ion implantation range from the surface exposed to the heavy ions implantation. Possible explanation is the long-range effect attributed to the ion implantation into materials.

  10. Positron lifetimes in TTF-TCNQ and κ-(BEDT-TTF) 2Cu(NCS) 2 single crystals

    NASA Astrophysics Data System (ADS)

    Ishibashi, Shoji; Tokumoto, Madoka; Kinoshita, Nobumori; Terada, Norio; Ihara, Hideo; Suzuki, Ryoichi; Ohdaira, Toshiyuki; Mikado, Tomohisa; Anzai, Hiroyuki

    1997-05-01

    Positron lifetimes in TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane) and κ-(BEDT-TTF) 2Cu(SCN) 2 (BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene) single crystals have been measured utilizing a pulsed variable-energy positron beam. The bulk positron lifetimes are 338 and 357 ps, respectively. The incident positron energy dependence of the lifetime is rather weak for both materials. Theoretical simulations have been also performed with several descriptions of the electronic wave functions and the electron-positron correlation. Results are compared with each other and the experiments.

  11. History of the ZGS 500 MeV booster.

    SciTech Connect

    Simpson, J.; Martin; R.; Kustom, R.

    2006-05-09

    The history of the design and construction of the Argonne 500 MeV booster proton synchrotron from 1969 to 1982 is described. This accelerator has since been in steady use for the past 25 years to power the Argonne Intense Pulsed Neutron Source (IPNS).

  12. Computer simulation of electron-positron pair production by channeling radiation in amorphous converter

    NASA Astrophysics Data System (ADS)

    Abdrashitov, S. V.; Bogdanov, O. V.; Dabagov, S. B.; Pivovarov, Yu L.; Tukhfatullin, T. A.

    2016-07-01

    We consider the radiator-converter approach at 200 MeV channeled electrons (the SPARC_LAB LNF facility energies) for the case of using W crystalline radiator and W amorphous converter. A comparison of the positron production by the axial channeling radiation and the bremsstrahlung is performed. The positron stopping in the convertor is studied by means of computer simulations. It is shown that for the maximum yield of positrons the thickness of the W amorphous converter should be taken 0.35 cm in the case of using the axial channeling radiation resulting to total yield of positrons 5 10-3 e+/e- and 0.71 cm in the case of using the bremsstrahlung resulting to total yield of positrons 3.3 10-3 e+/e-.

  13. Positron excitation of neon

    NASA Technical Reports Server (NTRS)

    Parcell, L. A.; Mceachran, R. P.; Stauffer, A. D.

    1990-01-01

    The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions.

  14. Positron clouds within thunderstorms

    NASA Astrophysics Data System (ADS)

    Dwyer, Joseph R.; Smith, David M.; Hazelton, Bryna J.; Grefenstette, Brian W.; Kelley, Nicole A.; Lowell, Alexander W.; Schaal, Meagan M.; Rassoul, Hamid K.

    2015-08-01

    We report the observation of two isolated clouds of positrons inside an active thunderstorm. These observations were made by the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray detectors, which flew on a Gulfstream V jet aircraft through the top of an active thunderstorm in August 2009. ADELE recorded two 511 keV gamma-ray count rate enhancements, 35 s apart, each lasting approximately 0.2 s. The enhancements, which were approximately a factor of 12 above background, were both accompanied by electrical activity as measured by a flat-plate antenna on the underside of the aircraft. The energy spectra were consistent with a source mostly composed of positron annihilation gamma rays, with a prominent 511 keV line clearly visible in the data. Model fits to the data suggest that the aircraft was briefly immersed in clouds of positrons, more than a kilometre across. It is not clear how the positron clouds were created within the thunderstorm, but it is possible they were caused by the presence of the aircraft in the electrified environment.

  15. Positron implantation in solids

    SciTech Connect

    Ghosh, V.J.; Lynn, K.G.; Welch, D.O.

    1993-12-31

    The Monte Carlo technique for modeling positron prior to annihilation and electron implantation in semi-infinite metals is described. Particle implantation is modelled as a multistep process, a series of collisions with the atoms of the host material. In elastic collisions with neutral atoms there is no transfer of energy. The particle loses energy by several different channels, excitation of the electron gas, ionization of the ion cores, or, at low energies, by phonon excitation. These competing scattering mechanisms have been incorporated into the Monte Carlo framework and several different models are being used. Brief descriptions of these Monte Carlo schemes, as well as an analytic model for positron implantation are included. Results of the Monte Carlo simulations are presented and compared with expermental data. Problems associated with modeling positron implantation are discuss and the need for more expermental data on energy-loss in different materials is stressed. Positron implantation in multilayers of different metals is briefly described and extensions of this work to include a study of multilayers and heterostructures is suggested.

  16. Energy spectrum and flux of 3- to 20-Mev neutrons and 1- to 10-Mev gamma rays in the atmosphere

    NASA Technical Reports Server (NTRS)

    Klumpar, D. M.; Lockwood, J. A.; Saint Onge, R. N.; Friling, L. A.

    1973-01-01

    An experiment is described which was designed to measure the neutron and gamma ray energy spectrums and fluxes in the energy intervals 3 to 20 MeV and 1 to 10 MeV, respectively. In addition, from the 3 to 20-MeV proton recoil spectrums it is possible to infer the shape of the neutron energy spectrum from 20 to 50 MeV. The detecting system utilized a separate charged particle rejection scheme and a two-parameter display system for the output from the pulse shape discrimination which separated gamma rays from neutrons (n). Two long-duration flights were made with this detector in 1970 at Palestine, Tex. (P sub c = 4.6 Gv) and at Ft. Churchill, Canada (P sub c = 0.3 Gv).

  17. Experiments Enabled by a New High-Resolution Positron Beam

    NASA Astrophysics Data System (ADS)

    Natisin, Mike; Danielson, James; Surko, Cliff

    2016-05-01

    The ability to make state-resolved measurements of positron interactions with atoms and molecules is limited by difficulties encountered in creating beams with narrow energy spreads. Recent experiments and simulations of buffer gas positron cooling and trap-based beam formation have enabled the design and construction of a cryogenic buffer-gas trap with total beam energy spreads as low as 7 meV FWHM and temporal spreads of sub-microsecond duration. The potential effect of this narrow energy spread on the ability to probe new physics in positron scattering and annihilation experiments will be discussed. For example, beams with such energy spreads are expected to enable the first measurements of state-resolved excitation of molecular rotations by positron impact (i.e., H2). Further, these narrow spreads and resulting enhanced resolving power are expected to permit the study of new features in annihilation energy spectra, such as possible overtone, combination, and IR-inactive vibrational modes in Feshbach-resonant positron annihilation. Work supported by NSF Grant PHY-1401794.

  18. Development of mini linac-based positron source and an efficient positronium convertor for positively charged antihydrogen production

    NASA Astrophysics Data System (ADS)

    Muranaka, T.; Debu, P.; Dupré, P.; Liszkay, L.; Mansoulie, B.; Pérez, P.; Rey, J. M.; Ruiz, N.; Sacquin, Y.; Crivelli, P.; Gendotti, U.; Rubbia, A.

    2010-04-01

    We have installed in Saclay a facility for an intense positron source in November 2008. It is based on a compact 5.5 MeV electron linac connected to a reaction chamber with a tungsten target inside to produce positrons via pair production. The expected production rate for fast positrons is 5·1011 per second. The study of moderation of fast positrons and the construction of a slow positron trap are underway. In parallel, we have investigated an efficient positron-positronium convertor using porous silica materials. These studies are parts of a project to produce positively charged antihydrogen ions aiming to demonstrate the feasibility of a free fall antigravity measurement of neutral antihydrogen.

  19. Positron Scanner for Locating Brain Tumors

    DOE R&D Accomplishments Database

    Rankowitz, S.; Robertson, J. S.; Higinbotham, W. A.; Rosenblum, M. J.

    1962-03-01

    A system is described that makes use of positron emitting isotopes for locating brain tumors. This system inherently provides more information about the distribution of radioactivity in the head in less time than existing scanners which use one or two detectors. A stationary circular array of 32 scintillation detectors scans a horizontal layer of the head from many directions simultaneously. The data, consisting of the number of counts in all possible coincidence pairs, are coded and stored in the memory of a Two-Dimensional Pulse-Height Analyzer. A unique method of displaying and interpreting the data is described that enables rapid approximate analysis of complex source distribution patterns. (auth)

  20. Development and Testing of the Positron Identification By Coincident Annihilation Photons (PICAP) System

    NASA Astrophysics Data System (ADS)

    Tran, D.; Connell, J. J.; Lopate, C.; Bickford, B.

    2014-12-01

    Moderate energy positrons (~few to 10 MeV) have seldom been observed in the Heliosphere, due primarily to there not having been dedicated instruments for such measurements. Their detection would have implications in the study of Solar energetic particle events and the transport and modulation of the Solar wind and Galactic cosmic rays. The Positron Identification by Coincident Annihilation Photons (PICAP) system is designed specifically to measure these moderate energy positrons by simultaneously detecting the two 511-keV γ-ray photons that result from a positron stopping in the instrument and the subsequent electron-positron annihilation. This method is also expected to effectively discriminate positrons from protons by measuring the amount of energy deposited in the detectors (dE/dx versus residual energy). PICAP offers a low-mass, low-power option for measuring positrons, electrons, and ions in space. Following Monte Carlo modeling, a PICAP laboratory prototype, adaptable to a space-flight design, was designed, built, and tested. This instrument is comprised of (Si) solid-state detectors, plastic scintillation detectors, and high-Z BGO crystal scintillator suitable for detecting the 511-keV γ rays. The prototype underwent preliminary laboratory testing and calibration using radioactive sources for the purpose of establishing functionality. It has since been exposed to beams of energetic protons (up to ~200 MeV) at Massachusetts General Hospital's Francis H. Burr Proton Beam Therapy Center and positrons and electrons (up to ~10 MeV) at Idaho State University's Idaho Accelerator Center. The goal is to validate modeling and determine the performance of the instrument concept. We will present a summary of modeling calculations and analysis of data taken at the accelerator tests. This work is 95% supported by NASA Grant NNX10AC10G.

  1. Positron acceleration in doughnut wakefields in the blowout regime

    NASA Astrophysics Data System (ADS)

    Vieira, Jorge; Mendonca, Jose; Fonseca, Ricardo; Silva, Luis

    2014-10-01

    Most important plasma acceleration results were reached in the so called bubble or blowout regime. Although ideally suited for electron acceleration, it has been recognized that non-linear regimes are not adequate to accelerate positrons. New configurations enabling positron acceleration in non-linear regimes would therefore open new research paths for future plasma based collider configurations. In this work, we explore, analytically and through 3D OSIRIS simulations, a novel configuration for positron acceleration in strongly non-linear laser wakefield excitation regimes using Laguerre-Gaussian laser drivers to drive doughnut shaped wakefields with positron focusing and accelerating fields. We demonstrate that positron focusing-fields can be up to an order of magnitude larger than electron focusing in the spherical blowout regime. The amplitude of the accelerating fields is similar to the spherical blowout. Simulations demonstrate laser self-guiding and stable positron acceleration until the laser energy has been exhausted to the plasma. Other realisations of the scheme, using two Gaussian laser pulses, will also be explored. FCT Grant No EXPL/FIS-PLA/0834/2012 and European Research Council ERC-2010-AdG Grant No. 267841.

  2. Crab Nebula observations - 0.2-10 MeV

    NASA Technical Reports Server (NTRS)

    Gruber, D. E.

    1975-01-01

    Observations of the total emission from the Crab Nebula and also of the pulsed component were made over the 0.2 to 10-MeV range during three balloon flights in 1971 with an actively-collimated NaI scintillator. The total emission flux was positively observed over the entire interval. The observed spectrum to 1 MeV agrees with an extrapolation of the E to the -2.2 power law, which fits lower-energy data. The observations above 1 MeV are factors of 3 and 20 above this law and are better fit with a spectral index of 0.8. Confidence levels are 3 sigma or better for each half-decade band. The three observations are consistent with a constant flux level. The NP 0532 flux, detected during one flight only (August 8) between 0.2 and 0.38 MeV, agrees with the exponential power law spectrum already determined from other observations. The possibility of a rapidly rising pulsed emission fraction over the 0.1- to 1-MeV interval is excluded by this observation.

  3. Low-energy positron interactions with krypton

    SciTech Connect

    Makochekanwa, C.; Machacek, J. R.; Jones, A. C. L.; Caradonna, P.; Slaughter, D. S.; McEachran, R. P.; Sullivan, J. P.; Buckman, S. J.; Bellm, S.; Lohmann, B.; Fursa, D. V.; Bray, I.; Mueller, D.W.; Stauffer, A. D.; Hoshino, M.

    2011-03-15

    Cross sections for positron scattering from krypton have been measured with an energy resolution of {approx}60 meV over the energy range 0.5-60 eV. Absolute values of the grand total ({sigma}{sub GT}), positronium formation ({sigma}{sub Ps}), and grand total minus positronium formation ({sigma}{sub GT}-{sigma}{sub Ps},) cross sections are presented. Theoretical estimations of {sigma}{sub GT} and {sigma}{sub GT}-{sigma}{sub Ps} are also performed for this target using the convergent close-coupling method and the relativistic optical potential approach. We also provide experimental and theoretical results for elastic differential cross sections, for selected energies both below and above the Ps threshold. Where available, the present results are compared to both experimental and theoretical values from the literature.

  4. Cardiac positron emission tomography

    SciTech Connect

    Geltman, E.M.

    1985-12-01

    Positron emission tomography (PET) is a new technique for noninvasively assessing myocardial metabolism and perfusion. It has provided new insight into the dynamics of myocardial fatty acid and glucose metabolism in normal subjects, patients with ischemic heart disease and those with cardiomyopathies, documenting regionally depressed fatty acid metabolism during myocardial ischemia and infarction and spatial heterogeneity of fatty acid metabolism in patients with cardiomyopathy. Regional myocardial perfusion has been studied with PET using water, ammonia and rubidium labeled with positron emitters, permitting the noninvasive detection of hypoperfused zones at rest and during vasodilator stress. With these techniques the relationship between perfusion and the metabolism of a variety of substrates has been studied. The great strides that have been made in developing faster high-resolution instruments and producing new labeled intermediates indicate the promise of this technique for facilitating an increase in the understanding of regional metabolism and blood flow under normal and pathophysiologic conditions. 16 references, 9 figures, 2 tables.

  5. Positrons at Jefferson Laboratory

    SciTech Connect

    Thomas, A W

    2009-09-01

    We review the compelling case for establishing a capability to accelerate positrons at Jefferson Lab. The potential appplications range from the study of two-photon exchange and deeply-virtual Compton scattering to exploiting the charge current weak interaction to probe the flavor structure of hadrons and nuclei. There are also fascinating ideas for using such a capability to discover new physics beyond the Standard Model of nuclear and particle physics.

  6. Positron fraction, electron and positron spectra measured by AMS-02

    NASA Astrophysics Data System (ADS)

    Pizzolotto, Cecilia

    2016-07-01

    A precise measurement by AMS-02 of the electron spectrum up to 700 GeV and of the positron spectrum and positron fraction in primary cosmic rays up 500 GeV are presented. The combined measurement of the cosmic-ray electron and positron energy spectra and fraction provide a unique tool to improve our understanding of the production, acceleration and propagation mechanism of cosmic rays.

  7. Positron lifetime spectrometer using a DC positron beam

    DOEpatents

    Xu, Jun; Moxom, Jeremy

    2003-10-21

    An entrance grid is positioned in the incident beam path of a DC beam positron lifetime spectrometer. The electrical potential difference between the sample and the entrance grid provides simultaneous acceleration of both the primary positrons and the secondary electrons. The result is a reduction in the time spread induced by the energy distribution of the secondary electrons. In addition, the sample, sample holder, entrance grid, and entrance face of the multichannel plate electron detector assembly are made parallel to each other, and are arranged at a tilt angle to the axis of the positron beam to effectively separate the path of the secondary electrons from the path of the incident positrons.

  8. Low-energy positron interactions with xenon

    NASA Astrophysics Data System (ADS)

    Machacek, J. R.; Makochekanwa, C.; Jones, A. C. L.; Caradonna, P.; Slaughter, D. S.; McEachran, R. P.; Sullivan, J. P.; Buckman, S. J.; Bellm, S.; Lohmann, B.; Fursa, D. V.; Bray, I.; Mueller, D. W.; Stauffer, A. D.

    2011-12-01

    Low-energy interactions of positrons with xenon have been studied both experimentally and theoretically. The experimental measurements were carried out using a trap-based positron beam with an energy resolution of ˜80 meV, while the theoretical calculations were carried out using the convergent close-coupling method and the relativistic optical potential approach. Absolute values of the grand total, positronium formation and grand total minus positronium formation cross sections are presented over the energy range of 1-60 eV. Elastic differential cross sections (DCS), for selected energies, are also presented both below and above the positronium formation threshold. Fine energy-step measurements of the positronium formation cross section over the energy range of 4.4-8.4 eV, and measurements of the elastic DCS at the energies of 5.33 and 6.64 eV, have been carried out to investigate the ionization threshold regions corresponding to the 2P3/2 and 2P1/2 states of the Xe+ ion. The present results are compared with both experimental and theoretical values from the literature where available.

  9. Positron Implantation Profile in Kapton

    NASA Astrophysics Data System (ADS)

    Dryzek, J.; Dryzek, E.

    2006-11-01

    The discussion presented in the paper focuses on processes accompanying positron implantation in condensed matter. They finally constitute the positron implantation profile which generally does not exhibit the exponential behavior as it is concluded from the Monte Carlo simulation made using the EGSnrc 4.0 code. The simulation was performed for the kapton and two commonly used positron sources 22Na and 68Ge\\68Ga. New formula for the implantation profile was proposed.

  10. Nonlinear positron acoustic solitary waves

    SciTech Connect

    Tribeche, Mouloud; Aoutou, Kamel; Younsi, Smain; Amour, Rabia

    2009-07-15

    The problem of nonlinear positron acoustic solitary waves involving the dynamics of mobile cold positrons is addressed. A theoretical work is presented to show their existence and possible realization in a simple four-component plasma model. The results should be useful for the understanding of the localized structures that may occur in space and laboratory plasmas as new sources of cold positrons are now well developed.

  11. The ATLAS Positron Experiment -- APEX

    SciTech Connect

    Ahmad, I.; Back, B.B.; Betts, R.R.; Dunford, R.; Kutschera, W.; Rhein, M.D.; Schiffer, J.P.; Wilt, P.; Wuosmaa, A.; Austin, S.M.; Kashy, E.; Winfield, J.S.; Yurkon, J.E.; Bazin, D.; Calaprice, F.P.; Young, A.; Chan, K.C.; Chisti, A.; Chowhury, P.; Greenberg, J.S.; Kaloskamis, N.; Lister, C.J.; Fox, J.D.; Roa, E.; Freedman, S.; Maier, M.R.; Freer, M.; Gazes, S.; Hallin, A.L.; Liu, M.; Happ, T.; Perera, A.; Wolfs, F.L.H.; Trainor, T.; Wolanski, M. |

    1994-03-01

    APEX -- the ATLAS Positron Experiment -- is designed to measure electrons and positrons emitted in heavy-ion collisions. Its scientific goal is to gain insight into the puzzling positron-line phenomena observed at the GSI Darmstadt. It is in operation at the ATLAS accelerator at Argonne National Lab. The assembly of the apparatus is finished and beginning 1993 the first positrons produced in heavy-ion collisions were observed. The first full scale experiment was carried out in December 1993, and the data are currently being analyzed. In this paper, the principles of operation are explained and a status report on the experiment is given.

  12. Positron-Annihilation Lifetime Spectroscopy using Electron Bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Wagner, A.; Anwand, W.; Butterling, M.; Cowan, T. E.; Fiedler, F.; Fritz, F.; Kempe, M.; Krause-Rehberg, R.

    2015-06-01

    A new type of an intense source of positrons for materials research has been set up at the superconducting electron linear. The source employs hard X-rays from electron- bremsstrahlung production generating energetic electron-positron pairs inside the sample under investigation. CW-operation allows performing experiments with significantly reduced pile-up artefacts in the detectors compared to pulsed mode operation in conventional accelerators. The high-resolution timing of the accelerator with bunch lengths below 10 ps full width at half maximum (FWHM) allows positron annihilation lifetime spectroscopy (PALS) measurements with high time resolution. A single-component annihilation lifetime of Kaptonhas been measured as (381.3 ± 0.3) ps. Employing segmented detectors for the detection of both annihilation photons allows for the first time to perform a 4D tomographic reconstruction of the annihilation sites including the annihilation lifetime.

  13. Coincidence Doppler Broadening of Positron Annihilation Radiation in Fe

    NASA Astrophysics Data System (ADS)

    do Nascimento, E.; Vanin, V. R.; Maidana, N. L.; Helene, O.

    2013-06-01

    We measured the Doppler broadening annihilation radiation spectrum in Fe, using 22NaCl as a positron source, and two Ge detectors in coincidence arrangement. The two-dimensional coincidence energy spectrum was fitted using a model function that included positron annihilation with the conduction band and 3d electrons, 3s and 3p electrons, and in-flight positron annihilation. Detectors response functions included backscattering and a combination of Compton and pulse pileup, ballistic deficit and shaping effects. The core electrons annihilation intensity was measured as 16.4(3) %, with almost all the remainder assigned to the less bound electrons. The obtained results are in agreement with published theoretical values.

  14. Recent progress in tailoring trap-based positron beams

    SciTech Connect

    Natisin, M. R.; Hurst, N. C.; Danielson, J. R.; Surko, C. M.

    2013-03-19

    Recent progress is described to implement two approaches to specially tailor trap-based positron beams. Experiments and simulations are presented to understand the limits on the energy spread and pulse duration of positron beams extracted from a Penning-Malmberg (PM) trap after the particles have been buffer-gas cooled (or heated) in the range of temperatures 1000 {>=} T {>=} 300 K. These simulations are also used to predict beam performance for cryogenically cooled positrons. Experiments and simulations are also presented to understand the properties of beams formed when plasmas are tailored in a PM trap in a 5 tesla magnetic field, then non-adiabatically extracted from the field using a specially designed high-permeability grid to create a new class of electrostatically guided beams.

  15. Gamma ray lines from solar flares. [with 2.2 MeV line being strongest

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Lingenfelter, R. E.

    1974-01-01

    The strongest line, both predicted theoretically and detected observationally at 2.2 MeV, is due to neutron capture by protons in the photosphere. The neutrons are produced in nuclear reactions of flare accelerated particles which also positrons and prompt nuclear gamma rays. From the comparison of the observed and calculated intensities of the lines at 4.4 or 6.1 MeV to that of the 2.2 MeV line, it is possible to deduce the spectrum of accelerated nuclei in the flare region; and from the absolute intensities of these lines, it is possible to obtain the total number of accelerated nuclei at the sun. The study of the 2.2 MeV line also gives information on the amount of He-3 in the photosphere. The study of the line at 0.51 MeV resulting from positron annihilation complements the data obtained from the other lines; in addition it gives information on the temperature and density in the annihilation region.

  16. 10MeV 25KW industrial electron LINAC

    NASA Astrophysics Data System (ADS)

    Kamino, Y.

    1998-06-01

    A 10MeV 25KW plus class electron LINAC was developed for sterilisation of medical devices. The LINAC composed of a standing wave type single cavity prebuncher and a 2m electro-plated travelling wave guide uses a 5MW 2856MHz pulse klystron as an RF source and provides 25KW beam power at the Ti alloy beam window stably after the energy analysing magnet with 10MeV plus-minus 1 MeV energy slit. The practical maximum beam power reached 29 KW and this demonstrated the LINAC as one of the most powerful S-band electron LINACs in the world. The control of the LINAC is fully automated and the "One-Button Operation" is realised, which is valuable for easy operation as a plant system. 2 systems have been delivered and are being operated stably.

  17. Positron Emission Tomography (PET)

    SciTech Connect

    Welch, M.J.

    1990-01-01

    Positron emission tomography (PET) assesses biochemical processes in the living subject, producing images of function rather than form. Using PET, physicians are able to obtain not the anatomical information provided by other medical imaging techniques, but pictures of physiological activity. In metaphoric terms, traditional imaging methods supply a map of the body's roadways, its, anatomy; PET shows the traffic along those paths, its biochemistry. This document discusses the principles of PET, the radiopharmaceuticals in PET, PET research, clinical applications of PET, the cost of PET, training of individuals for PET, the role of the United States Department of Energy in PET, and the futures of PET. 22 figs.

  18. Positron Emission Tomography (PET)

    DOE R&D Accomplishments Database

    Welch, M. J.

    1990-01-01

    Positron emission tomography (PET) assesses biochemical processes in the living subject, producing images of function rather than form. Using PET, physicians are able to obtain not the anatomical information provided by other medical imaging techniques, but pictures of physiological activity. In metaphoric terms, traditional imaging methods supply a map of the body's roadways, its, anatomy; PET shows the traffic along those paths, its biochemistry. This document discusses the principles of PET, the radiopharmaceuticals in PET, PET research, clinical applications of PET, the cost of PET, training of individuals for PET, the role of the United States Department of Energy in PET, and the futures of PET.

  19. Quantum positron acoustic waves

    SciTech Connect

    Metref, Hassina; Tribeche, Mouloud

    2014-12-15

    Nonlinear quantum positron-acoustic (QPA) waves are investigated for the first time, within the theoretical framework of the quantum hydrodynamic model. In the small but finite amplitude limit, both deformed Korteweg-de Vries and generalized Korteweg-de Vries equations governing, respectively, the dynamics of QPA solitary waves and double-layers are derived. Moreover, a full finite amplitude analysis is undertaken, and a numerical integration of the obtained highly nonlinear equations is carried out. The results complement our previously published results on this problem.

  20. Quantum rainbow channeling of positrons in very short carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Petrović, S.; Ćosić, M.; Nešković, N.

    2013-07-01

    This is a theoretical study of transmission of positrons of kinetic energies of 1 and 10 MeV through very short (11,9) single-wall carbon nanotubes of lengths of 200 and 560 nm, respectively. The needed continuum interaction potential of the positron and nanotube is obtained starting from the Molière's approximation of the Thomas-Fermi interaction potential of a positron and a nanotube atom. We calculate the classical and quantum angular distributions of transmitted positrons. In the classical calculations, the approach is via the equations of motion, and in the quantum calculations, the time-dependent Schrödinger equation is solved. The solutions of these equations are obtained numerically. In the quantum calculations, the initial beam is taken to be an ensemble of noninteracting Gaussian wave packets. The angular distributions are generated using the computer simulation method. Our analysis is concentrated on the rainbow effect, which is clearly seen in the angular distributions. The obtained classical and quantum rainbows are analyzed in detail and compared with each other.

  1. Review of pulsed rf power generation

    SciTech Connect

    Lavine, T.L.

    1992-04-01

    I am going to talk about pulsed high-power rf generation for normal-conducting electron and positron linacs suitable for applications to high-energy physics in the Next Linear Collider, or NLC. The talk will cover some basic rf system design issues, klystrons and other microwave power sources, rf pulse-compression devices, and test facilities for system-integration studies.

  2. Portable Positron Measurement System (PPMS)

    SciTech Connect

    2011-01-01

    Portable Positron Measurement System (PPMS) is an automated, non-destructive inspection system based on positron annihilation, which characterizes a material's in situatomic-level properties during the manufacturing processes of formation, solidification, and heat treatment. Simultaneous manufacturing and quality monitoring now are possible. Learn more about the lab's project on our facebook site http://www.facebook.com/idahonationallaboratory.

  3. Cyclotrons and positron emitting radiopharmaceuticals

    SciTech Connect

    Wolf, A.P.; Fowler, J.S.

    1984-01-01

    The state of the art of Positron Emission Tomography (PET) technology as related to cyclotron use and radiopharmaceutical production is reviewed. The paper discusses available small cyclotrons, the positron emitters which can be produced and the yields possible, target design, and radiopharmaceutical development and application. 97 refs., 12 tabs. (ACR)

  4. Positron production within our atmosphere

    NASA Astrophysics Data System (ADS)

    Dwyer, Joseph

    2016-04-01

    Positrons are commonly produced within our atmosphere by cosmic rays and the decay radioactive isotopes. Energetic positrons are also produced by pair production from the gamma rays generated by relativistic runaway electrons. Indeed, such positrons have been detected in Terrestrial Electron Beams (TEBs) in the inner magnetosphere by Fermi/GBM. In addition, positrons play an important role in relativistic feedback discharges (also known as dark lightning). Relativistic feedback models suggest that these discharges may be responsible for Terrestrial Gamma-ray Flashes (TGFs) and some gamma-ray glows. When producing TGFs, relativistic feedback discharges may generate large, lightning-like currents with current moments reaching hundreds of kA-km. In addition, relativistic feedback discharges also may limit the electric field that is possible in our atmosphere, affecting other mechanisms for generating runaway electrons. It is interesting that positrons, often thought of as exotic particles, may play an important role in thunderstorm processes. In this presentation, the role of positrons in high-energy atmospheric physics will be discussed. The unusual observation of positron clouds inside a thunderstorm by the ADELE instrument on an NCAR/NSF Gulfstream V aircraft will also be described. These observations illustrate that we still have much to learn about positron production within our atmosphere.

  5. Plasma Wakefield Acceleration of Positrons

    NASA Astrophysics Data System (ADS)

    Gessner, Spencer

    2016-03-01

    Recent particle beam and laser-driven plasma wakefield experiments have produced high-quality electron beams accelerated by a GeV or more in less than a meter. Efforts are underway to put these beams to work as sources for free-electron lasers. By contrast, little work has been done to demonstrate the tractability of plasma wakefield acceleration (PWFA) of positrons beams. The reasons for this are threefold: 1) positron beams are only useful for high-energy physics experiments, whereas electron beams are also useful as light sources, 2) there is a dearth of positron sources for PWFA experiments, and 3) the dynamics of accelerating positron beams in plasma is fundamentally different than that of electron beams. This talk will focus on the physics of accelerating positrons in plasma and contrast the dynamics of electron and positron beam-driven nonlinear plasma wakes. We describe recent experiments at the FACET test facility at SLAC National Accelerator Laboratory that for the first time demonstrate high-gradient acceleration of a positron beams in plasma. We also discuss an alternative acceleration technique called hollow channel acceleration that aims to symmetrize the dynamics of electron and positron beam-driven wakes.

  6. Portable Positron Measurement System (PPMS)

    ScienceCinema

    None

    2013-05-28

    Portable Positron Measurement System (PPMS) is an automated, non-destructive inspection system based on positron annihilation, which characterizes a material's in situatomic-level properties during the manufacturing processes of formation, solidification, and heat treatment. Simultaneous manufacturing and quality monitoring now are possible. Learn more about the lab's project on our facebook site http://www.facebook.com/idahonationallaboratory.

  7. Positron driven plasma wakefields

    NASA Astrophysics Data System (ADS)

    Pinkerton, S.; Shi, Y.; Huang, C.; An, W.; Mori, W. B.; Muggli, P.

    2010-11-01

    The LHC is producing high-energy, high-charge proton bunches (1e11 protons at 1-7 TeV each) that could be used to accelerate ``witness'' electron bunches to TeV range eneregies via a plasma wakefield accelerator (PWFA). Simulations [1] suggest that a proton ``drive'' bunch is able to excite large wakefields if the bunch size is on the order of 100 μm; however, the LHC paramters are currently on the 1 cm scale. SLAC'S FACET is able to supply positorn bunchs with the ideal parameters for driving a PWFA. Although at lower energy (2e10 positrons at 23 GeV each), initial simiulations in QuickPIC show that the physics of a positron drive bunch is very similar to that of a proton drive bunch. Differences in the physics arise from the mass difference: slower dephasing but faster transverse bunch evolution. Other considerations include driver head erosion and purity of the wakefield ion column. The physics of positive drivers for PWFA and the viability of this scheme for future high-energy colliders will be investigated at SLAC's FACET.[4pt] [1] Caldwell, et al. Nature Physics 5, 363 (2009).[0pt] [2] C.H. Huang, et al., J. Comp. Phys., 217(2), 658, (2006).

  8. Positron Emission Tomography.

    PubMed

    Lameka, Katherine; Farwell, Michael D; Ichise, Masanori

    2016-01-01

    Positron emission tomography (PET) is a minimally invasive imaging procedure with a wide range of clinical and research applications. PET allows for the three-dimensional mapping of administered positron-emitting radiopharmaceuticals such as (18)F-fluorodeoxyglucose (for imaging glucose metabolism). PET enables the study of biologic function in both health and disease, in contrast to magnetic resonance imaging (MRI) and computed tomography (CT), that are more suited to study a body's morphologic changes, although functional MRI can also be used to study certain brain functions by measuring blood flow changes during task performance. This chapter first provides an overview of the basic physics principles and instrumentation behind PET methodology, with an introduction to the merits of merging functional PET imaging with anatomic CT or MRI imaging. We then focus on clinical neurologic disorders, and reference research on relevant PET radiopharmaceuticals when applicable. We then provide an overview of PET scan interpretation and findings in several specific neurologic disorders such as dementias, epilepsy, movement disorders, infection, cerebrovascular disorders, and brain tumors. PMID:27432667

  9. Dechanneling of Positrons in Disordered Lattices Effect of Anharmonic Potential

    NASA Astrophysics Data System (ADS)

    Abu-Assy, M. K.; El-Ashry, M. Y.; Mohamed, A. A.

    2005-01-01

    Dechanneling of positrons due to lattice disorder has been investigated for two stable configurations of the disordered face-centered cubic(fcc) lattices, Dumb-bell configuration (DBC) and Body-centered interstitial (BCI) for channeled positrons with incident energy (10 200) MeV in Cu single crystal in the planar direction (100). The effects of anharmonic terms in the channeling potential have been considered in the calculations. The calculations covered the transition-channeling probability, dechanneling probability, transmission and dechanneling coefficients. It has been found that the transition-channeling probability from the normal into the disordered region occurs only for the transitions n (normal) → n (disordered). Also the dependence of the transmission and dechanneling coefficients on the incident beam position has been studied by using a planar potential function based on shell structure model and compared with the results of a planar potential based on Lindhard's model.

  10. Secondary positrons and electrons in the cosmic radiation

    NASA Technical Reports Server (NTRS)

    Badhwar, G. D.; Stephens, S. A.

    1978-01-01

    An improved calculation of the secondary production and equilibrium spectrum of positrons and electrons in the Galaxy in the energy range from 1 MeV to 100 GeV has been performed. This has been done by obtaining an analytic representation of the accelerator data which describes accurately the invariant cross-section of pions, kaons, and their antiparticles from threshold energy to about 1500 GeV. This calculation takes into account the correct angular distribution of electrons in the decay of muons and the effect of nuclei-nuclei collisions. The contributions of beta-decay positrons and knock-on electrons have been included. A comparison of the present calculations with earlier calculations and experiment is presented.

  11. RADIOACTIVE POSITRON EMITTER PRODUCTION BY ENERGETIC ALPHA PARTICLES IN SOLAR FLARES

    SciTech Connect

    Murphy, R. J.; Kozlovsky, B.; Share, G. H. E-mail: benz@wise.tau.ac.il

    2015-01-01

    Measurements of the 0.511 MeV positron-annihilation line from solar flares are used to explore the flare process in general and ion acceleration in particular. In flares, positrons are produced primarily by the decay of radioactive positron-emitting isotopes resulting from nuclear interactions of flare-accelerated ions with ambient solar material. Kozlovsky et al. provided ion-energy-dependent production cross sections for 67 positron emitters evaluated from their threshold energies (some <1 MeV nucleon{sup –1}) to a GeV nucleon{sup –1}, incorporating them into a computer code for calculating positron-emitter production. Adequate cross-section measurements were available for proton reactions, but not for α-particle reactions where only crude estimates were possible. Here we re-evaluate the α-particle cross sections using new measurements and nuclear reaction codes. In typical large gamma-ray line flares, proton reactions dominate positron production, but α-particle reactions will dominate for steeper accelerated-ion spectra because of their relatively low threshold energies. With the accelerated-{sup 3}He reactions added previously, the code is now reliable for calculating positron production from any distribution of accelerated-ion energies, not just those of typical flares. We have made the code available in the online version of the Journal. We investigate which reactions, projectiles, and ion energies contribute to positron production. We calculate ratios of the annihilation-line fluence to fluences of other gamma-ray lines. Such ratios can be used in interpreting flare data and in determining which nuclear radiation is most sensitive for revealing acceleration of low-energy ions at the Sun.

  12. Monte Carlo modelling of the propagation and annihilation of nucleosynthesis positrons in the Galaxy

    NASA Astrophysics Data System (ADS)

    Alexis, A.; Jean, P.; Martin, P.; Ferrière, K.

    2014-04-01

    Aims: We want to estimate whether the positrons produced by the β+-decay of 26Al, 44Ti, and 56Ni synthesised in massive stars and supernovae are sufficient to explain the 511 keV annihilation emission observed in our Galaxy. Such a possibility has often been put forward in the past. In a previous study, we showed that nucleosynthesis positrons cannot explain the full annihilation emission. Here, we extend this work using an improved propagation model. Methods: We developed a Monte Carlo Galactic propagation code for ~MeV positrons in which the Galactic interstellar medium, the Galactic magnetic field, and the propagation are finely described. This code allows us to simulate the spatial distribution of the 511 keV annihilation emission. We tested several Galactic magnetic fields models and several positron escape fractions from type-Ia supernova for 56Ni positrons to account for the large uncertainties in these two parameters. We considered the collisional/ballistic transport mode and then compared the simulated 511 keV intensity spatial distributions to the INTEGRAL/SPI data. Results: Regardless of the Galactic magnetic field configuration and the escape fraction chosen for 56Ni positrons, the 511 keV intensity distributions are very similar. The main reason is that ~MeV positrons do not propagate very far away from their birth sites in our model. The direct comparison to the data does not allow us to constrain the Galactic magnetic field configuration and the escape fraction for 56Ni positrons. In any case, nucleosynthesis positrons produced in steady state cannot explain the full annihilation emission. The comparison to the data shows that (a) the annihilation emission from the Galactic disk can be accounted for; (b) the strongly peaked annihilation emission from the inner Galactic bulge can be explained by positrons annihilating in the central molecular zone, but this seems to require more positron sources than the population of massive stars and type Ia

  13. Positron-acoustic solitary waves in a magnetized electron-positron-ion plasma with nonthermal electrons and positrons

    NASA Astrophysics Data System (ADS)

    Rahman, M. M.; Alam, M. S.; Mamun, A. A.

    2015-05-01

    Obliquely propagating positron-acoustic solitary waves (PASWs) in a magnetized electron-positron-ion plasma (containing nonthermal hot positrons and electrons, inertial cold positrons, and immobile positive ions) are precisely investigated by deriving the Zakharov-Kuznetsov equation. It is found that the characteristics of the PASWs are significantly modified by the effects of external magnetic field, obliqueness, nonthermality of hot positrons and electrons, temperature ratio of hot positrons and electrons, and respective number densities of hot positrons and electrons. The findings of our results can be employed in understanding the localized electrostatic structures and the characteristics of PASWs in various space and laboratory plasmas.

  14. Positron emission mammography imaging

    SciTech Connect

    Moses, William W.

    2003-10-02

    This paper examines current trends in Positron Emission Mammography (PEM) instrumentation and the performance tradeoffs inherent in them. The most common geometry is a pair of parallel planes of detector modules. They subtend a larger solid angle around the breast than conventional PET cameras, and so have both higher efficiency and lower cost. Extensions to this geometry include encircling the breast, measuring the depth of interaction (DOI), and dual-modality imaging (PEM and x-ray mammography, as well as PEM and x-ray guided biopsy). The ultimate utility of PEM may not be decided by instrument performance, but by biological and medical factors, such as the patient to patient variation in radiotracer uptake or the as yet undetermined role of PEM in breast cancer diagnosis and treatment.

  15. Cosmic Ray Positrons from Pulsars

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2010-01-01

    Pulsars are potential Galactic sources of positrons through pair cascades in their magnetospheres. There are, however, many uncertainties in establishing their contribution to the local primary positron flux. Among these are the local density of pulsars, the cascade pair multiplicities that determine the injection rate of positrons from the pulsar, the acceleration of the injected particles by the pulsar wind termination shock, their rate of escape from the pulsar wind nebula, and their propagation through the interstellar medium. I will discuss these issues in the context of what we are learning from the new Fermi pulsar detections and discoveries.

  16. [Fundamentals of positron emission tomography].

    PubMed

    Ostertag, H

    1989-07-01

    Positron emission tomography is a modern radionuclide method of measuring physiological quantities or metabolic parameters in vivo. The method is based on: (1) radioactive labelling with positron emitters; (2) the coincidence technique for the measurement of the annihilation radiation following positron decay; (3) analysis of the data measured using biological models. The basic aspects and problems of the method are discussed. The main fields of future research are the synthesis of new labelled compounds and the development of mathematical models of the biological processes to be investigated. PMID:2667029

  17. Proton-Proton Scattering at 105 Mev and 75 Mev

    DOE R&D Accomplishments Database

    Birge, R. W.; Kruse, U. E.; Ramsey, N. F.

    1951-01-31

    The scattering of protons by protons provides an important method for studying the nature of nuclear forces. Recent proton-proton scattering experiments at energies as high as thirty Mev{sup 1} have failed to show any appreciable contribution to the cross section from higher angular momentum states, but it is necessary to bring in tensor forces to explain the magnitude of the observed cross section.

  18. Nonlinear propagation of broadband intense electromagnetic waves in an electron-positron plasma

    SciTech Connect

    Marklund, M.; Eliasson, B.; Shukla, P. K.

    2006-08-15

    A kinetic equation describing the nonlinear evolution of intense electromagnetic pulses in electron-positron (e-p) plasmas is presented. The modulational instability is analyzed for a relativistically intense partially coherent pulse, and it is found that the modulational instability is inhibited by the spectral pulse broadening. A numerical study for the one-dimensional kinetic photon equation is presented. Computer simulations reveal a Fermi-Pasta-Ulam-type recurrence phenomenon for localized broadband pulses. The results should be of importance in understanding the nonlinear propagation of broadband intense electromagnetic pulses in e-p plasmas in laser-plasma systems as well as in astrophysical plasma settings.

  19. Positron annihilation lifetime characterization of oxygen ion irradiated rutile TiO2

    NASA Astrophysics Data System (ADS)

    Luitel, Homnath; Sarkar, A.; Chakrabarti, Mahuya; Chattopadhyay, S.; Asokan, K.; Sanyal, D.

    2016-07-01

    Ferromagnetic ordering at room temperature has been induced in rutile phase of TiO2 polycrystalline sample by O ion irradiation. 96 MeV O ion induced defects in rutile TiO2 sample has been characterized by positron annihilation spectroscopic techniques. Positron annihilation results indicate the formation of cation vacancy (VTi, Ti vacancy) in these irradiated TiO2 samples. Ab initio density functional theoretical calculations indicate that in TiO2 magnetic moment can be induced either by creating Ti or O vacancies.

  20. Positron annihilation spectroscopy with magnetically analyzed beams

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Holt, W. H.; Mock, W., Jr.

    1982-01-01

    Lifetime measurements with magnetically analyzed positron beams were made in condensed media with uniform and non-uniform properties. As expected, the lifetime values with magnetically analyzed positron beams in uniform targets are similar to those obtained with conventional positron sources. The lifetime values with magnetically analyzed beams in targets which have non-uniform properties vary with positron energy and are different from the conventional positron source derived lifetime values in these targets.

  1. Resolvability of positron decay channels

    SciTech Connect

    Fluss, M.J.; Howell, R.H.; Rosenberg, I.J.; Meyer, P.

    1985-03-07

    Many data analysis treatments of positron experiments attempt to resolve two or more positron decay or exist channels which may be open simultaneously. Examples of the need to employ such treatments of the experimental results can be found in the resolution of the constituents of a defect ensemble, or in the analysis of the complex spectra which arise from the interaction of slow positrons at or near the surfaces of solids. Experimental one- and two-dimensional angular correlation of annihilation radiation experiments in Al single crystals have shown that two defect species (mono- and divacancies) can be resolved under suitable conditions. Recent experiments at LLNL indicate that there are a variety of complex exit channels open to positrons interacting at surfaces, and ultimely these decay channels must also be suitably resolved from one another. 6 refs., 4 figs.

  2. High Power Polarized Positron Source

    NASA Astrophysics Data System (ADS)

    Mikhailichenko, Alexander

    2009-09-01

    We discuss the basics of polarized positron production by low energy polarized electrons. Efficiency of conversion ˜0.1-1% might be interesting for the Continuous Electron Beam Accelerator Facility (CEBAF) and the International Linear Collider (ILC).

  3. Modelling Positron Interactions with Matter

    NASA Astrophysics Data System (ADS)

    Garcia, G.; Petrovic, Z.; White, R.; Buckman, S.

    2011-05-01

    In this work we link fundamental measurements of positron interactions with biomolecules, with the development of computer codes for positron transport and track structure calculations. We model positron transport in a medium from a knowledge of the fundamental scattering cross section for the atoms and molecules comprising the medium, combined with a transport analysis based on statistical mechanics and Monte-Carlo techniques. The accurate knowledge of the scattering is most important at low energies, a few tens of electron volts or less. The ultimate goal of this work is to do this in soft condensed matter, with a view to ultimately developing a dosimetry model for Positron Emission Tomography (PET). The high-energy positrons first emitted by a radionuclide in PET may well be described by standard formulas for energy loss of charged particles in matter, but it is incorrect to extrapolate these formulas to low energies. Likewise, using electron cross-sections to model positron transport at these low energies has been shown to be in serious error due to the effects of positronium formation. Work was supported by the Australian Research Council, the Serbian Government, and the Ministerio de Ciencia e Innovación, Spain.

  4. Method for photon activation positron annihilation analysis

    DOEpatents

    Akers, Douglas W.

    2006-06-06

    A non-destructive testing method comprises providing a specimen having at least one positron emitter therein; determining a threshold energy for activating the positron emitter; and determining whether a half-life of the positron emitter is less than a selected half-life. If the half-life of the positron emitter is greater than or equal to the selected half-life, then activating the positron emitter by bombarding the specimen with photons having energies greater than the threshold energy and detecting gamma rays produced by annihilation of positrons in the specimen. If the half-life of the positron emitter is less then the selected half-life, then alternately activating the positron emitter by bombarding the specimen with photons having energies greater then the threshold energy and detecting gamma rays produced by positron annihilation within the specimen.

  5. Gamma-ray lines from novae. [relationship to radioactive decay and positron annihilation

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.; Hoyle, F.

    1974-01-01

    An appropriate gamma-ray telescope could detect the gamma-rays associated with radioactive decays. The observable lines would be the annihilation radiation following the positron emission of N-13, O-14, O-15, and Na-22 and the 2.312-MeV line emitted following the O-14 decay and the 1.274-MeV line emitted following the Na-22 decay. The experimental possibility should be borne in mind for the occurrence of novae within a few kiloparsecs.

  6. Detector blur associated with MeV radiographic imaging systems

    NASA Astrophysics Data System (ADS)

    Baker, Stuart A.; Lutz, Stephen S.; Smalley, Duane D.; Brown, Kristina K.; Danielson, Jeremy; Haines, Todd J.; Howe, Russell A.; Mitchell, Stephen E.; Morgan, Dane; Schultz, Larry J.

    2015-08-01

    We are investigating scintillator performance in radiographic imaging systems at x-ray endpoint energies of 0.4 and 2.3 MeV in single-pulse x-ray machines. The effect of scene magnification and geometric setup will be examined along with differences between the detector response of radiation and optical scatter. Previous discussion has reviewed energy absorption and efficiency of various imaging scintillators with a 2.3 MeV x-ray source. The focal point of our study is to characterize scintillator blur to refine system models. Typical detector geometries utilize thin tiled LYSO:Ce (cerium-doped lutetium yttrium orthosilicate) assembled in a composite mosaic. Properties of individual tiles are being studied to understand system resolution effects present in the experimental setup. Comparison of two different experiments with different geometric configurations is examined. Results are then compared to different scene magnifications generated in a Monte-Carlo simulation.

  7. The annihilation of positrons in the cold phase of the interstellar medium revisited

    NASA Technical Reports Server (NTRS)

    Wallyn, P.; Durouchoux, PH.; Chapuis, C.; Leventhal, M.

    1994-01-01

    The positron cross sections in H and H2 media are reevaluated, taking into account new experimental results. Using a Monte Carlo simulation, we find a positronium fraction before thermalization of 0.90 for H2, in good agreement with the previous experimental result given by Brown et al. (1986). For H we obtain an upper limit of 0.98. We study the behavior of the charge exchange annihilation in a cold phase (molecular cloud). We calculate a formula for the slowing-down time t, before annihilation lasting Delta t, via charge exchange, of a positron beam with a given energy for different medium densities and initial energies. An upper limit of 0.7 MeV for the initial energy of the positrons, annihilating in the molecular cloud G0.86 - 0.08 near the gamma ray source positronium and gives new time constraints on their possible observation.

  8. The annihilation of positrons in the cold phase of the interstellar medium revisited

    NASA Astrophysics Data System (ADS)

    Wallyn, P.; Durouchoux, Ph.; Chapuis, C.; Leventhal, M.

    1994-02-01

    The positron cross sections in H and H2 media are reevaluated, taking into account new experimental results. Using a Monte Carlo simulation, we find a positronium fraction before thermalization of 0.90 for H2, in good agreement with the previous experimental result given by Brown et al. (1986). For H we obtain an upper limit of 0.98. We study the behavior of the charge exchange annihilation in a cold phase (molecular cloud). We calculate a formula for the slowing-down time t, before annihilation lasting Delta t, via charge exchange, of a positron beam with a given energy for different medium densities and initial energies. An upper limit of 0.7 MeV for the initial energy of the positrons, annihilating in the molecular cloud G0.86 - 0.08 near the gamma ray source positronium and gives new time constraints on their possible observation.

  9. Positron-electron autocorrelation function study of E-center in silicon

    NASA Astrophysics Data System (ADS)

    Ho, K. F.; Ching, H. M.; Beling, C. D.; Fung, S.; Ng, K. P.; Biasini, M.; Ferro, G.; Gong, M.

    2003-11-01

    Two-dimensional angular correlation of annihilation radiation (2D-ACAR) spectra have been taken for 1019cm-3 phosphorus-doped Si in the as-grown state after having been subjected to 1.8 MeV electron fluences of 1×1018 and 2×1018 cm-2. Positron annihilation lifetime spectroscopy confirms, in accordance with previous works, that positrons are saturation trapping into (VSi:P) pair defect (E-center) monovacancy sites in the electron irradiated samples. In the as-grown case, the positron-electron autocorrelation functions along the [111] and [1-10] directions, obtained through Fourier transformation of the 2D-ACAR data, reveal zero-crossings that deviate only slightly from the lattice points, in a manner consistent with positron-electron correlation effects. Conversely, in the spectra of the irradiated samples, the zero-crossing points are observed to move outward further by between 0.15 and 0.50 Å. This displacement is associated with positron annihilation with electrons in localized orbitals at the defect site. An attempt is made to extract just the component of the defect's positron-electron autocorrelation function that relates to the localized defect orbitals. In doing this features are found that correspond to the expected atomic positions at the vacancy defect site suggesting that this real-space function may provide a convenient means for obtaining a mapping of localized orbitals. The observed approximate separability of positron and electron wave-function autocorrelates leads to an estimate of 0.22 eV for the positron binding energy to the E-center.

  10. Gamma-rays of 3 to 25 MeV from the galactic anti-center and pulsar NP 0532

    NASA Technical Reports Server (NTRS)

    Wilson, R. B.; Moon, S. H.; Ryan, J. M.; Zych, A. D.; White, R. S.; Dayton, B.

    1978-01-01

    Gamma-rays of 3 to 25 MeV are reported from the galactic anticenter region and the Crab Pulsar, NP 0532. The observations were carried out from Palestine, Texas, on May 13, 1975. Gamma-rays from the galactic anticenter were observed as the Crab Nebula passed overhead within 10 deg of the zenith. Pulsed gamma-rays from NP 0532 were observed at a 4.4-sigma significance level. The total flux from 3-25 MeV is 0.0049 + or - 0.002 photon/sq cm-sec. The pulsed flux from NP 0532 from 3 to 25 MeV is 0.00043 + or - 0.00026 photon/sq cm-sec. The ratio of the total to the pulsed flux from 3 to 25 MeV is 11 + or - 8.

  11. Energy matching of 1. 2 GeV positron beam to the SLC (Stanford Linear Collider) damping ring

    SciTech Connect

    Clendenin, J.E.; Helm, R.H.; Jobe, R.K.; Kulikov, A.; Sheppard, J.C.

    1989-08-01

    Positrons collected at the SLC positron source are transported over a 2-km path at 220 MeV to be reinjected into the linac for acceleration to 1.2 GeV, the energy of the emittance damping ring. Since the positron bunch length is a significant fraction of a cycle of the linac-accelerating RF, the energy spread at 1.2 GeV is considerably larger than the acceptance of the linac-to-ring (LTR) transport system. Making use of the large pathlength difference at the beginning of the LTR due to this energy spread, a standard SLAC 3-m accelerating section has been installed in the LTR to match the longitudinal phase space of the positron beam to the acceptance of the damping ring. The design of the matching system is described, and a comparison of operating results within simulations is presented. 5 refs., 4 figs., 1 tab.

  12. Fluence to local skin absorbed dose and dose equivalent conversion coefficients for monoenergetic positrons using Monte-Carlo code MCNP6.

    PubMed

    Bourgois, L; Antoni, R

    2016-01-01

    Conversion coefficients fluence to local skin equivalent dose, as introduced in ICRP Publication 116, 2010, are calculated for positrons of energies ranging from 10 keV to 10 MeV using the code MCNP6. Fluence to dose equivalent conversion coefficients H'(0.07,0°)/Φ are calculated for positrons of energy ranging between 20 keV and 10 MeV. A comparison between operational dose quantity H'(0.07,0°) and the Local-Skin equivalent Dose shows an overall good agreement between these two quantities, except between 60 keV and 100 keV. PMID:26623930

  13. Level Density of COBALT-57 in the Energy Region 1 Mev to 14 Mev

    NASA Astrophysics Data System (ADS)

    Mishra, Vivek

    The level density of ^{57 }Co is studied in the energy region of 1-14 MeV using three experimental techniques. Levels are counted in the resolved region, evaporation spectra are measured in the resolved to continuum region, and the coherence width is measured in the region of level overlap. Use of Hauser-Feshbach fits to the evaporation cross sections requires level densities of the residual nucleus. A two -parameter based Fermi gas form is used for the calculation of level density as a function of the nuclear excitation energy. This procedure enables level density calculation beyond the energy region in which the two fixed parameters provide the best fits to the data. A comparison is made between the level density obtained from the above described methods and the predictions of the microscopic model in an energy range of 1-20 MeV. This model utilizes a BCS pairing Hamiltonian and specific sets of single particle states and calculates numerical values of the level density. Comparisons are also made with level density of ^{57 }Co obtained in various other studies. Both the resolved level studies and the fits to the evaporation spectra were conducted using the ^{56}Fe(d,n)^{57 }Co and ^{57}Fe(p,n) ^{57}Co reactions. Standard neutron time-of-flight techniques including pulse shape discrimination for elimination of gamma -rays were employed. An energy resolution as good as 6 keV at 1-1.5 MeV neutron energy was obtained for high resolution measurements. For Ericson fluctuation measurements, the excitation functions corresponding to the ground state and the first two excited states of the residual nucleus in the ^{56}Fe(p,n) ^{56}Co reaction were obtained for lab angles between 0^circ and 150^circ. The ^{56}Fe(d,n) ^{57}Co reaction proves to be very selective in populating resolved states and includes substantial contributions from mechanisms other than the compound nuclear. The ^{57 }Fe(p,n)^{57}Co reaction populated 14 previously unknown levels. The fits to the

  14. Positron spectroscopy for materials characterization

    SciTech Connect

    Schultz, P.J.; Snead, C.L. Jr.

    1988-01-01

    One of the more active areas of research on materials involves the observation and characterization of defects. The discovery of positron localization in vacancy-type defects in solids in the 1960's initiated a vast number of experimental and theoretical investigations which continue to this day. Traditional positron annihilation spectroscopic techniques, including lifetime studies, angular correlation, and Doppler broadening of annihilation radiation, are still being applied to new problems in the bulk properties of simple metals and their alloys. In addition new techniques based on tunable sources of monoenergetic positron beams have, in the last 5 years, expanded the horizons to studies of surfaces, thin films, and interfaces. In the present paper we briefly review these experimental techniques, illustrating with some of the important accomplishments of the field. 40 refs., 19 figs.

  15. Positron emitter labeled enzyme inhibitors

    DOEpatents

    Fowler, J.S.; MacGregor, R.R.; Wolf, A.P.

    1987-05-22

    This invention involved a new strategy for imaging and mapping enzyme activity in the living human and animal body using positron emitter-labeled suicide enzyme inactivators or inhibitors which become covalently bound to the enzyme as a result of enzymatic catalysis. Two such suicide in activators for monoamine oxidase have been labeled with carbon-11 and used to map the enzyme subtypes in the living human and animal body using PET. By using positron emission tomography to image the distribution of radioactivity produced by the body penetrating radiation emitted by carbon-11, a map of functionally active monoamine oxidase activity is obtained. Clorgyline and L-deprenyl are suicide enzyme inhibitors and irreversibly inhibit monoamine oxidase. When these inhibitors are labeled with carbon-11 they provide selective probes for monoamine oxidase localization and reactivity in vivo using positron emission tomography. 2 figs.

  16. Positron emitter labeled enzyme inhibitors

    DOEpatents

    Fowler, Joanna S.; MacGregor, Robert R.; Wolf, Alfred P.; Langstrom, Bengt

    1990-01-01

    This invention involves a new strategy for imaging and mapping enzyme activity in the living human and animal body using positron emitter-labeled suicide enzyme inactivators or inhibitors which become covalently bound to the enzyme as a result of enzymatic catalysis. Two such suicide inactivators for monoamine oxidase have been labeled with carbon-11 and used to map the enzyme subtypes in the living human and animal body using PET. By using positron emission tomography to image the distribution of radioactivity produced by the body penetrating radiation emitted by carbon-11, a map of functionally active monoamine oxidase activity is obtained. Clorgyline and L-deprenyl are suicide enzyme inhibitors and irreversibly inhibit monoamine oxidase. When these inhibitors are labeled with carbon-11 they provide selective probes for monoamine oxidase localization and reactivity in vivo using positron emission tomography.

  17. Instrumentation for positron emission tomography.

    PubMed

    Budinger, T F; Derenzo, S E; Huesman, R H

    1984-01-01

    Positron emission tomography with a spatial resolution of 2 mm full width at half maximum for quantitation in regions of interest 4 mm in diameter will become possible with the development of detectors that achieve ultrahigh resolution. Improved resolution will be possible using solid-state photodetectors for crystal identification or photomultiplier tubes with many small electron multipliers . Temporal resolution of 2 seconds and gating of cyclic events can be accomplished if statistical requirements are met. The major physical considerations in achieving high-resolution positron emission tomography are the degradation in resolution resulting from positron range, emission angle, parallax error, detector sampling density, the sensitivity of various detector materials and packing schemes, and the trade off between temporal resolution and statistical accuracy. The accuracy of data required for physiological models depends primarily on the fidelity of spatial sampling independent of statistical constraints. PMID:6611124

  18. Positron emitter labeled enzyme inhibitors

    SciTech Connect

    Fowler, J.S.; MacGregor, R.R.; Wolf, A.P.; Langstrom, B.

    1990-04-03

    This invention involves a new strategy for imaging and mapping enzyme activity in the living human and animal body using positron emitter-labeled suicide enzyme inactivators or inhibitors which become covalently bound to the enzyme as a result of enzymatic catalysis. Two such suicide inactivators for monoamine oxidase have been labeled with carbon-11 and used to map the enzyme subtypes in the living human and animal body using PET. By using positron emission tomography to image the distribution of radioactivity produced by the body penetrating radiation emitted by carbon-11, a map of functionally active monoamine oxidase activity is obtained. Clorgyline and L-deprenyl are suicide enzyme inhibitors and irreversibly inhibit monoamine oxidase. When these inhibitors are labeled with carbon-11 they provide selective probes for monoamine oxidase localization and reactivity in vivo using positron emission tomography.

  19. Positron-alkali atom scattering

    NASA Technical Reports Server (NTRS)

    Mceachran, R. P.; Horbatsch, M.; Stauffer, A. D.; Ward, S. J.

    1990-01-01

    Positron-alkali atom scattering was recently investigated both theoretically and experimentally in the energy range from a few eV up to 100 eV. On the theoretical side calculations of the integrated elastic and excitation cross sections as well as total cross sections for Li, Na and K were based upon either the close-coupling method or the modified Glauber approximation. These theoretical results are in good agreement with experimental measurements of the total cross section for both Na and K. Resonance structures were also found in the L = 0, 1 and 2 partial waves for positron scattering from the alkalis. The structure of these resonances appears to be quite complex and, as expected, they occur in conjunction with the atomic excitation thresholds. Currently both theoretical and experimental work is in progress on positron-Rb scattering in the same energy range.

  20. Instrumentation in positron emission tomography

    SciTech Connect

    Not Available

    1988-03-11

    Positron emission tomography (PET) is a three-dimensional medical imaging technique that noninvasively measures the concentration of radiopharmaceuticals in the body that are labeled with positron emitters. With the proper compounds, PET can be used to measure metabolism, blood flow, or other physiological values in vivo. The technique is based on the physics of positron annihilation and detection and the mathematical formulations developed for x-ray computed tomography. Modern PET systems can provide three-dimensional images of the brain, the heart, and other internal organs with resolutions on the order of 4 to 6 mm. With the selectivity provided by a choice of injected compounds, PET has the power to provide unique diagnostic information that is not available with any other imaging modality. This is the first five reports on the nature and uses of PET that have been prepared for the American Medical Association's Council on Scientific Affairs by an authoritative panel.

  1. Particle physics. Positrons ride the wave

    SciTech Connect

    Piot, Philippe

    2015-08-26

    Here, experiments reveal that positrons — the antimatter equivalents of electrons — can be rapidly accelerated using a plasma wave. The findings pave the way to high-energy electron–positron particle colliders.

  2. Particle physics. Positrons ride the wave

    SciTech Connect

    Piot, Philippe

    2015-08-26

    Experiments reveal that positrons — the antimatter equivalents of electrons — can be rapidly accelerated using a plasma wave. The findings pave the way to high-energy electron–positron particle colliders.

  3. Single-shot positron annihilation lifetime spectroscopy with LYSO scintillators

    NASA Astrophysics Data System (ADS)

    Alonso, A. M.; Cooper, B. S.; Deller, A.; Cassidy, D. B.

    2016-08-01

    We have evaluated the application of a lutetium yttrium oxyorthosilicate (LYSO) based detector to single-shot positron annihilation lifetime spectroscopy. We compare this detector directly with a similarly configured PbWO4 scintillator, which is the usual choice for such measurements. We find that the signal to noise ratio obtained using LYSO is around three times higher than that obtained using PbWO4 for measurements of Ps excited to longer-lived (Rydberg) levels, or when they are ionized soon after production. This is due to the much higher light output for LYSO (75% and 1% of NaI for LYSO and PbWO4 respectively). We conclude that LYSO is an ideal scintillator for single-shot measurements of positronium production and excitation performed using a low-intensity pulsed positron beam.

  4. Status and prospects of VEPP-2000 electron-positron collider

    NASA Astrophysics Data System (ADS)

    Rogovsky, Yu. A.; Berkaev, D. E.; Zemlyansky, I. M.; Zharinov, Yu. M.; Kasaev, A. S.; Koop, I. A.; Kyrpotin, A. N.; Lysenko, A. P.; Perevedentsev, E. A.; Prosvetov, V. P.; Romanov, A. L.; Senchenko, A. I.; Skrinsky, A. N.; Shatunov, P. Yu.; Shatunov, Yu. M.; Shwartz, D. B.

    2014-09-01

    High energy physics experiments were started at VEPP-2000 at the end of 2010; the third experimental run was finished in July 2013. The last run was devoted to the energy range 160-510 MeV in a beam. Compton backscattering energy measurements were used for the regular energy calibration of the VEPP-2000, together with resonance depolarization and NMR methods. The conception of the round colliding beam lattice along with precise orbit and lattice correction yielded a record high peak luminosity of 1.2 × 1031 cm-2 s-1 at 510 MeV and an average luminosity of 0.9 × 1031 cm-2 s-1 per run. A total betatron tune shift of 0.174 was achieved at 392.5 MeV. This corresponds to the beam-beam parameter ξ = 0.125 in terms of the collision point. The injection system is currently modernized to allow injection of particles at the VEPP-2000 energy maximum and the elimination of the existing lack of positrons.

  5. Electrostatic Nonplanar Positron-Acoustic Shock Waves in Superthermal Electron-Positron-Ion Plasmas

    NASA Astrophysics Data System (ADS)

    M. J., Uddin; M. S., Alam; A. A., Mamun

    2015-06-01

    The basic properties of the nonlinear propagation of the nonplanar (cylindrical and spherical) positron-acoustic (PA) shock waves (SHWs) in an unmagnetized electron-positron-ion (e-p-i) plasma containing immobile positive ions, mobile cold positrons, and superthermal (kappa distributed) hot positrons and electrons are investigated both analytically and numerically. The modified Burgers equation (mBE) is derived by using the reductive perturbation method. The basic features of PA SHWs are significantly modified by the cold positron kinematic viscosity (η), superthermal parameter of electrons (κe), superthermal parameter of hot positrons (κp), the ratio of the electron temperature to hot positron temperature (σ), the ratio of the electron number density to cold positron number density and the ratio of the hot positron number density to cold positron number density (μph). This study could be useful to identify the basic properties of nonlinear electrostatic disturbances in dissipative space and laboratory plasmas.

  6. 21 CFR 892.1110 - Positron camera.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Positron camera. 892.1110 Section 892.1110 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1110 Positron camera. (a) Identification. A positron camera is a device intended to image...

  7. Source of slow polarized positrons using the brilliant gamma beam at ELI-NP. Converter design and simulations

    NASA Astrophysics Data System (ADS)

    Djourelov, Nikolay; Oprisa, Andreea; Leca, Victor

    2016-01-01

    Simulations of slow positron (es+) source based on interaction of a circularly polarized gamma beam with a W converter were performed. The aim of the study was to propose a converter geometry and to determine the expected slow positron beam intensity and its spot size, and the degree of positron spin polarization, as well. The Monte Carlo simulations by means of GEANT4 were used to estimate the fast positron production and the moderation efficiency of the converter working as a self-moderator, as well. Finite element analysis by means of COMSOL Multiphysics was applied to calculate the fraction of extracted moderated positrons from the converter cells and the quality of the beam formation by focusing. Using the low energy (<3.5 MeV) gamma beam at ELI-NP with intensity of 2.4×1010γ/s the production of a slow positron beam with intensity of 1-2×106 es+/s is predicted. For the optimized converter geometry and in case of 100% circular polarization of the gammas the degree of spin polarization of the slow positron beam is expected to be 33%.

  8. Pulsed neutron detector

    DOEpatents

    Robertson, deceased, J. Craig; Rowland, Mark S.

    1989-03-21

    A pulsed neutron detector and system for detecting low intensity fast neutron pulses has a body of beryllium adjacent a body of hydrogenous material the latter of which acts as a beta particle detector, scintillator, and moderator. The fast neutrons (defined as having En>1.5 MeV) react in the beryllium and the hydrogenous material to produce larger numbers of slow neutrons than would be generated in the beryllium itself and which in the beryllium generate hellium-6 which decays and yields beta particles. The beta particles reach the hydrogenous material which scintillates to yield light of intensity related to the number of fast neutrons. A photomultiplier adjacent the hydrogenous material (scintillator) senses the light emission from the scintillator. Utilization means, such as a summing device, sums the pulses from the photo-multiplier for monitoring or other purposes.

  9. Positron-acoustic shock waves associated with cold viscous positron fluid in superthermal electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Uddin, M. J.; Alam, M. S.; Mamun, A. A.

    2015-06-01

    A theoretical investigation is made on the positron-acoustic (PA) shock waves (SHWs) in an unmagnetized electron-positron-ion plasma containing immobile positive ions, cold mobile positrons, and hot positrons and electrons following the kappa (κ) distribution. The cold positron kinematic viscosity is taken into account, and the reductive perturbation method is used to derive the Burgers equation. It is found that the viscous force acting on cold mobile positron fluid is a source of dissipation and is responsible for the formation of the PA SHWs. It is also observed that the fundamental properties of the PA SHWs are significantly modified by the effects of different parameters associated with superthermal (κ distributed) hot positrons and electrons.

  10. Positron-acoustic shock waves associated with cold viscous positron fluid in superthermal electron-positron-ion plasmas

    SciTech Connect

    Uddin, M. J. Alam, M. S.; Mamun, A. A.

    2015-06-15

    A theoretical investigation is made on the positron-acoustic (PA) shock waves (SHWs) in an unmagnetized electron-positron-ion plasma containing immobile positive ions, cold mobile positrons, and hot positrons and electrons following the kappa (κ) distribution. The cold positron kinematic viscosity is taken into account, and the reductive perturbation method is used to derive the Burgers equation. It is found that the viscous force acting on cold mobile positron fluid is a source of dissipation and is responsible for the formation of the PA SHWs. It is also observed that the fundamental properties of the PA SHWs are significantly modified by the effects of different parameters associated with superthermal (κ distributed) hot positrons and electrons.

  11. Initial results from the Donner 600 crystal positron tomograph

    SciTech Connect

    Derenzo, S.E.; Huesman, R.H.; Cahoon, J.L.; Geyer, A.; Uber, D.; Vuletich, T.; Budinger, T.F.

    1987-02-01

    The authors describe a positron tomography using a single ring of 600 close-packed 3 mm wide bismuth germanate (BGO) crystals coupled to 14 mm phototubes. The phototube preamplifier circuit derives a timing pulse from the first photoelectron, and sends it to address and coincidence circuits only if the integrated pulse height is within a pre-set window. The timing delays and pulse height windows for all 600 detectors and the coincidence timing windows are computer adjustable. An orbiting positron source is used for transmission measurements and look-up table is used to reject scattered and random coincidences that do not pass through the source. Data can be acquired using a stationary mode for 1.57 mm lateral sampling or the two-position clam sampling mode for 0.79 mm lateral sampling. High maximum data rates are provided by 45 parallel coincidence circuits and 4 parallel histogram memory units. With two-position sampling and 1.57 mm bins, the reconstructed point spread function (PSF) of a 0.35 mm diam /sup 22/Na wire source at the center of the tomograph is circular with 2.9 mm full-width at half-maximum (fwhm) and the PSF at a distance of 8 cm from the center is elliptical with a radial fwhm of 4.0 mm and tangential fwhm of 3.0 mm.

  12. Initial results from the Donner 600 crystal positron tomograph

    SciTech Connect

    Derenzo, S.E.; Huesman, R.H.; Cahoon, J.L.; Geyer, A.; Uber, D.; Vuletich, T.; Budinger, T.F.

    1986-10-01

    We describe a positron tomograph using a single ring of 600 close-packed 3 mm wide bismuth germanate (BGO) crystals coupled to 14 mm phototubes. The phototube preamplifier circuit derives a timing pulse from the first photoelectron, and sends it to address and coincidence circuits only if the integrated pulse height is within a pre-set window. The timing delays and pulse height windows for all 600 detectors and the coincidence timing windows are computer adjustable. An orbiting positron source is used for transmission measurements and a look-up table is used to reject scattered and random coincidences that do not pass through the source. Data can be acquired using a stationary mode for 1.57 mm lateral sampling or the two-position clam sampling mode for 0.79 mm lateral sampling. High maximum data rates are provided by 45 parallel coincidence circuits and 4 parallel histogram memory units. With two-position sampling and 1.57 mm bins, the reconstructed point spread function (PSF) of a 0.35 mm diam /sup 22/Na wire source at the center of the tomograph is circular with 2.9 mm full-width at half-maximum (fwhm) and the PSF at a distance of 8 cm from the center is elliptical with a radial fwhm of 4.0 mm and tangential fwhm of 3.0 mm. 12 refs., 6 figs., 3 tabs.

  13. The 50 MeV Beam Test Facility at LBL

    SciTech Connect

    Leemans, W.; Behrsing, G.; Kim, K.J.; Krupnick, J.; Matuk, C.; Selph, F.; Chattopadhyay, S.

    1993-05-01

    A new beam line, expected to be built by September 1993, will transport the 50 MeV electron beam from the ALS LINAC into an experimental area to support various R&D activities in the Center for Beam Physics at LBL. A variety of experiments are planned involving the interaction of such a relativistic electron beam with plasmas (plasma focusing), laser beams (generation of femtosecond X-ray pulses) and electromagnetic cavities (Crab cavities etc....). The beam line is designed using the measured emittance and Twiss parameters of the ALS linac. It accommodates the different requirements of the various experiments on the electron beam properties (charge, energy, pulse length) and on the handling of the beam before and after the interaction point. Special attention has also been given to incorporate diagnostics for measuring the beam properties (such as the electron energy, bunch length and charge) needed in the interpretation of the experiments.

  14. Texas Intense Positron Source (TIPS)

    NASA Astrophysics Data System (ADS)

    O'Kelly, D.

    2003-03-01

    The Texas Intense Positron Source (TIPS) is a state of the art variable energy positron beam under construction at the Nuclear Engineering Teaching Laboratory (NETL). Projected intensities on the order of the order of 10^7 e+/second using ^64Cu as the positron source are expected. Owing to is short half-life (t1/2 12.8 hrs), plans are to produce the ^64Cu isotope on-site using beam port 1 of NETL TRIGA Mark II reactor. Following tungsten moderation, the positrons will be electrostatically focused and accelerated from few 10's of eV up to 30 keV. This intensity and energy range should allow routine performance of several analytical techniques of interest to surface scientists (PALS, PADB and perhaps PAES and LEPD.) The TIPS project is being developed in parallel phases. Phase I of the project entails construction of the vacuum system, source chamber, main beam line, electrostatic/magnetic focusing and transport system as well as moderator design. Initial construction, testing and characterization of moderator and beam transport elements are underway and will use a commercially available 10 mCi ^22Na radioisotope as a source of positrons. Phase II of the project is concerned primarily with the Cu source geometry and thermal properties as well as production and physical handling of the radioisotope. Additional instrument optimizing based upon experience gained during Phase I will be incorporated in the final design. Current progress of both phases will be presented along with motivations and future directions.

  15. Development of a Source of Quasi-Monochromatic MeV Energy Photons

    SciTech Connect

    Umstadter, Donald; Banerjee, Sudeep; Ramanathan, Vidya; Powers, Nathan; Cunningham, Nathaniel; Chandler-Smith, Nate

    2009-03-10

    We report current progress on a project to develop an all-optically-driven x-ray photon source. A laser pulse with 40-50 TW of peak power is focused on a supersonic helium nozzle to drive a relativistic plasma wave. Electron beams with energies of 320 MeV (+/-28 MeV) are accelerated by means of laser wakefield acceleration. Remarkably, the acceleration region is only 3 mm in length. This accelerator is currently being employed to demonstrate the generation of MeV-energy x-ray by means of all-optical Thomson scattering. By this mechanism, a lower power, laser pulse (from the same laser system) is focused onto the above laser-driven electron beam, 1-eV energy photons are Doppler-shifted in energy to >1 MeV.

  16. Positron microanalysis with high intensity beams

    SciTech Connect

    Hulett, L.D. Jr.; Donohue, D.L.

    1990-01-01

    One of the more common applications for a high intensity slow positron facility will be microanalysis of solid materials. In the first section of this paper some examples are given of procedures that can be developed. Since most of the attendees of this workshop are experts in positron spectroscopy, comprehensive descriptions will be omitted. With the exception of positron emission microscopy, most of the procedures will be based on those already in common use with broad beams. The utility of the methods have all been demonstrated, but material scientists use very few of them because positron microbeams are not generally available. A high intensity positron facility will make microbeams easier to obtain and partially alleviate this situation. All microanalysis techniques listed below will have a common requirement, which is the ability to locate the microscopic detail or area of interest and to focus the positron beam exclusively on it. The last section of this paper is a suggestion of how a high intensity positron facility might be designed so as to have this capability built in. The method will involve locating the specimen by scanning it with the microbeam of positrons and inducing a secondary electron image that will immediately reveal whether or not the positron beam is striking the proper portion of the specimen. This scanning positron microscope' will be a somewhat prosaic analog of the conventional SEM. It will, however, be an indispensable utility that will enhance the practicality of positron microanalysis techniques. 6 refs., 1 fig.

  17. Femtosecond time-resolved MeV electron diffraction

    SciTech Connect

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; Wu, L.; Cao, J.; Berger, H.; Geck, J.; Kraus, R.; Pjerov, S.; Shen, Y.; Tobey, R. I.; Hill, J. P.; Wang, X. J.

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 × 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.

  18. Femtosecond time-resolved MeV electron diffraction

    DOE PAGESBeta

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; Wu, L.; Cao, J.; Berger, H.; Geck, J.; Kraus, R.; Pjerov, S.; Shen, Y.; et al

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 × 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing themore » evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.« less

  19. Design of the NLC positron source

    SciTech Connect

    Tang, H.; Emma, P.; Gross, G.; Kulikov, A.; Li, Z.; Miller, R.; Rinolfi, L.; Turner, J.; Yeremian, D.

    1996-08-01

    The design of the positron source for the Next Linear Collider (NLC) is presented. The key features of this design include accelerating positrons at an L-band frequency (1428 MHz) and using a rotating positron target with multi-stage differential pumping. Positron yield simulations show that the L-band design yields at the source 2.5 times the beam intensity required at the interaction point and is easily upgrade to higher intensities required for the 1 TeV NLC upgrade. Multi-bunch beam loading compensation schemes in the positron capture and booster accelerators and the optics design of the positron booster accelerator are described. For improved source efficiency, the design boasts two parallel positron vaults adequately shielded from each other such that one serves as an on-line spare.

  20. Upgraded cavities for the positron accumulator ring of the APS

    SciTech Connect

    Kang, Y.W.; Jiang, X.; Mangra, D.

    1997-08-01

    Upgraded versions of cavities for the APS positron accumulator ring (PAR) have been built and are being tested. Two cavities are in the PAR: a fundamental 9.8-MHz cavity and a twelfth harmonic 117.3-MHz cavity. Both cavities have been manufactured for higher voltage operation with improved Q-factors, reliability, and tuning capability. Both cavities employ current-controlled ferrite tuners for control of the resonant frequency. The harmonic cavity can be operated in either a pulsed mode or a CW mode. The rf properties of the cavities are presented.

  1. The scaling of electron and positron generation in intense laser-solid interactions

    SciTech Connect

    Chen, Hui; Link, A.; Fiuza, F.; Hazi, A.; Heeter, R. F.; Kemp, A. J.; Kemp, G. E.; Nagel, S. R.; Park, J.; Tommasini, R.; Williams, G. J.; Sentoku, Y.; Audebert, P.; Hill, M.; Hobbs, L.; Kerr, S.; Meyerhofer, D. D.; Myatt, J.

    2015-05-15

    This paper presents experimental scalings of the electrons and positrons produced by intense laser-target interactions at relativistic laser intensities (10{sup 18}–10{sup 20} W cm{sup −2}). The data were acquired from three short-pulse laser facilities with laser energies ranging from 80 to 1500 J. We found a non-linear (≈E{sub L}{sup 2}) scaling of positron yield [Chen et al., Phys. Rev. Lett. 114, 215001 (2015)] and a linear scaling of electron yield with the laser energy. These scalings are explained by theoretical and numerical analyses. Positron acceleration by the target sheath field is confirmed by the positron energy spectrum, which has a pronounced peak at energies near the sheath potential, as determined by the observed maximum energies of accelerated protons. The parameters of laser-produced electron-positron jets are summarized together with the theoretical energy scaling. The measured energy-squared scaling of relativistic electron-positron jets indicates the possibility to create an astrophysically relevant experimental platform with such jets using multi-kilojoule high intensity lasers currently under construction.

  2. Little Boy neutron spectrum below 1 MeV

    SciTech Connect

    Evans, A.E.

    1984-01-01

    A high-resolution /sup 3/He ionization chamber of the type development by Cuttler and Shalev was used to study the neutron spectrum from the Little Boy mockup. Measurements were made at distances of 0.75 and 2.0 m and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly, which was operated at power levels from 8.6 to 450 mW. Detector efficiency as a function of energy as well as parameters for correction of pulse-height distributions for proton-recoil and wall effects were determined from a set of response functions for monoenergetic neutrons measured at the Los Alamos 3.75-MeV Van de Graaff Accelerator Facility. Pulse-shape discrimination was used to separate /sup 3/He-recoil pulses from the pulse-height distribution. The spectrum was found to be highly structured, with peaks corresponding to minima in the total neutron cross section of iron. In particular, 15% of the neutrons above the epithermal peak in energy were found to be in the 24-keV iron window. Lesser peaks out to 700 keV are also attributable to filtering action of the weapon's heavy iron casing. Data taken using experimental proton-recoil proportional counters are compared with the high-resolution spectra.

  3. Transverse Beam Emittance Measurements of a 16 MeV Linac at the Idaho Accelerator Center

    SciTech Connect

    S. Setiniyaz, T.A. Forest, K. Chouffani, Y. Kim, A. Freyberger

    2012-07-01

    A beam emittance measurement of the 16 MeV S-band High Repetition Rate Linac (HRRL) was performed at Idaho State University's Idaho Accelerator Center (IAC). The HRRL linac structure was upgraded beyond the capabilities of a typical medical linac so it can achieve a repetition rate of 1 kHz. Measurements of the HRRL transverse beam emittance are underway that will be used to optimize the production of positrons using HRRL's intense electron beam on a tungsten converter. In this paper, we describe a beam imaging system using on an OTR screen and a digital CCD camera, a MATLAB tool to extract beamsize and emittance, detailed measurement procedures, and the measured transverse emittances for an arbitrary beam energy of 15 MeV.

  4. Positron annihilation in transparent ceramics

    NASA Astrophysics Data System (ADS)

    Husband, P.; Bartošová, I.; Slugeň, V.; Selim, F. A.

    2016-01-01

    Transparent ceramics are emerging as excellent candidates for many photonic applications including laser, scintillation and illumination. However achieving perfect transparency is essential in these applications and requires high technology processing and complete understanding for the ceramic microstructure and its effect on the optical properties. Positron annihilation spectroscopy (PAS) is the perfect tool to study porosity and defects. It has been applied to investigate many ceramic structures; and transparent ceramics field may be greatly advanced by applying PAS. In this work positron lifetime (PLT) measurements were carried out in parallel with optical studies on yttrium aluminum garnet transparent ceramics in order to gain an understanding for their structure at the atomic level and its effect on the transparency and light scattering. The study confirmed that PAS can provide useful information on their microstructure and guide the technology of manufacturing and advancing transparent ceramics.

  5. Positron scattering from vinyl acetate

    NASA Astrophysics Data System (ADS)

    Chiari, L.; Zecca, A.; Blanco, F.; García, G.; Brunger, M. J.

    2014-09-01

    Using a Beer-Lambert attenuation approach, we report measured total cross sections (TCSs) for positron scattering from vinyl acetate (C4H6O2) in the incident positron energy range 0.15-50 eV. In addition, we also report an independent atom model with screening corrected additivity rule computation results for the TCSs, differential and integral elastic cross sections, the positronium formation cross section and inelastic integral cross sections. The energy range of these calculations is 1-1000 eV. While there is a reasonable qualitative correspondence between measurement and calculation for the TCSs, in terms of the energy dependence of those cross sections, the theory was found to be a factor of ˜2 larger in magnitude at the lower energies, even after the measured data were corrected for the forward angle scattering effect.

  6. Three-dimensional electron-positron momentum distribution of O3+-irradiated 6H SiC using two positron spectroscopy techniques simultaneously

    NASA Astrophysics Data System (ADS)

    Williams, Christopher; Burggraf, Larry; Adamson, Paul; Petrosky, James

    2011-01-01

    A three-dimensional (3D) positron annihilation spectroscopy system (3DPASS) capable of determining 3D electron-positron (e--e+) momentum densities from measurements of deviations from co-linearity and energies of photons from e--e+ annihilation events was employed to examine the effects of O-atom defects in 6H SiC. Three-dimensional momentum datasets were determined for 6H SiC irradiated with 24 MeV O3+ ions. Angular correlation of annihilation radiation (ACAR) and coincidence Doppler-broadening of annihilation radiation (CDBAR) analyses are presented. In addition, a novel technique is illustrated for analyzing 3D momentum datasets in which the parallel momentum component, p|| (obtained from the CDBAR measurement) is selected for annihilation events that possess a particular perpendicular momentum component, p- observed in the 2D ACAR spectrum.

  7. Construction and commissioning of the positron accumulator ring for the APS

    SciTech Connect

    Borland, M.

    1994-12-31

    The injector for the Advanced Photon Source (APS) consists of a 200-MeV electron linac, a 450-MeV position linac, a positron accumulator ring (PAR). and a 7-GeV synchrotron. The purpose of the PAR is to accumulate, and damp positrons from the 60Hz linac during each cycle of the 2Hz synchrotron, thus increasing the fill rate for the main ring. Construction of the PAR was recently completed, and commissioning is well underway. The PAR contains eight conventional 1.5T, flat field, 45{degrees} dipole magnets with an {approximately} 1m bending radius and no gradient: adjustment of the damping partition was achieved with 25.5{degrees} edge angles. Four families of quadrupole magnets provide focusing, with each dipole closely bracketed by two quadrupoles. Ten sextupole magnets provide both steering and chromatic correction. Extensive magnetic measurements have characterized saturation-dependent effective length in the dipoles and interaction among the closely-spaced, large-aperture dipoles, quadrupoles and sextupoles. For injection and extraction, PAR employs three delay-line kickers with {approximately} 120ns rise and fall times, and a single transformer septum magnet with a 2mm septum wall. A first-harmonic rf system is used to capture positrons and a twelfth-harmonic system provides an additional three-fold bunch compression. Diagnostics include 16 stripline beam position monitors, six fluorescent screens, dual fast/integrating current transformers, a tune measurement system, and two synchrotron light ports. Commissioning of the PAR with electrons has proceeded rapidly, starting at 150MeV and progressing to 450MeV as higher energy electrons became available. Alignment and dipole uniformity are sufficiently good that beam can be stored without the use of steering magnets. Experiments to date show excellent agreement with the machine model. Accumulation at 6Hz and extraction at 2Hz has been performed with essentially 100% efficiency.

  8. Observations of gamma radiation between 0.4 MeV and 7 MeV at balloon altitudes using a Compton telescope

    NASA Astrophysics Data System (ADS)

    Lockwood, J. A.; Webber, W. R.; Friling, L. A.; Macri, J.; Hsieh, L.

    1981-09-01

    Balloon-borne measurements of the atmospheric and diffuse gamma-ray flux in the energy range 0.4-7.0 MeV with a Compton telescope, which included pulse-shape discrimination of the first scattering detector and a time-of-flight system between the first and second detector elements, are reported. Comparison of the diffuse cosmic gamma-ray flux to the atmospheric gamma rays indicates that 0.2-5.0 MeV is the optimum energy range for measurements made at the top of the earth's atmosphere. The measured total atmospheric gamma-ray flux between zero and 40 deg has an energy spectrum that agrees with the calculations of Ling (1975). Observations indicate that the ratio of the diffuse to atmospheric gamma ray fluxes at 3.5 g/sq cm is a maximum, about 1.0, between 0.7 and 3.0 MeV.

  9. Data acquisition with a positron emission tomograph

    SciTech Connect

    Freifelder, R.; Karp, J.S.

    1997-12-31

    Positron Emission Tomography (PET) is a clinical imaging modality used in Nuclear Medicine. PET measures functionality rather than anatomical features and is therefore invaluable in the treatment of diseases which are characterized by functional changes in organs rather than anatomical changes. Typical diseases for which PET is used are cancer, epilepsy, and heart disease. While the scanners are not very complex, the performance demands on the devices are high. Excellent spatial resolution, 4-5 mm, and high sensitivity are key to maintaining high image quality. Compensation or suppression of scattered radiation is also necessary for good image quality. The ability to acquire data under high counting rates is also necessary in order to minimize the injected dose to the patient, minimize the patient`s time in the scanner, and finally to minimize blurring due to patient motion. We have adapted various techniques in our data acquisition system which will be reported on in this talk. These include pulse clipping using lumped delay lines, flash ADCs with short sampling time, the use of a local positioning algorithm to limit the number of data words being used in subsequent second level software triggers and calculations, and finally the use of high speed dedicated calculator boards for on-line rebinning and reduction of the data. Modifications to the system to allow for transmission scanning will also be discussed.

  10. Resonance method to produce a polarisation asymmetry in electron-positron storage rings

    SciTech Connect

    Toner, W.T.

    1988-01-01

    Pulsed solenoids of a few tens of ampere turns, operated in synchronism with the ..gamma..(g-2/2) 'th harmonic of the orbit period, can be used to prevent a stored electron beam from becoming polarised through the emission of synchrotron radiation. With such low fields it is easy to arrange that only some of the stored bunches are affected. This makes it possible to produce collisions between counter-rotating electrons and positrons stored in a single ring in which the electron and positron polarisations are not equal and opposite. 8 refs.