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1

The Compton Effect--Compton Scattering and Gamma Ray Spectroscopy  

E-print Network

The Compton Effect-- Compton Scattering and Gamma Ray Spectroscopy by Dr. James E. Parks Department and procedures for measuring gamma-ray energy distributions, (7) to learn about photomultipliers the interactions of high energy, electromagnetic photon radiation with materials in general. Gamma rays are high

Dai, Pengcheng

2

Resonant Compton scattering and gamma-ray burst continuum spectra  

NASA Technical Reports Server (NTRS)

The Thomson limit of resonant inverse Compton scattering in the strong magnetic fields of neutron stars is considered as a mechanism for producing gamma-ray burst continuum spectra. Photon production spectra and electron cooling rates are presented using the full magnetic Thomson cross-section. Model emission spectra are obtained as self-consistent solutions of a set of photon and electron kinetic equations, displaying spectral breaks and other structure at gamma-ray energies.

Baring, M. G.

1995-01-01

3

COMPACT, TUNABLE COMPTON SCATTERING GAMMA-RAY SOURCES  

SciTech Connect

Recent progress in accelerator physics and laser technology have enabled the development of a new class of gamma-ray light sources based on Compton scattering between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development at LLNL. High-brightness, relativistic electron bunches produced by the linac interact with a Joule-class, 10 ps laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. The source will be used to excite nuclear resonance fluorescence lines in various isotopes; applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. The source design, key parameters, and current status are presented.

Hartemann, F V; Albert, F; Anderson, G G; Anderson, S G; Bayramian, A J; Betts, S M; Chu, T S; Cross, R R; Ebbers, C A; Fisher, S E; Gibson, D J; Ladran, A S; Marsh, R A; Messerly, M J; O'Neill, K L; Semenov, V A; Shverdin, M Y; Siders, C W; McNabb, D P; Barty, C J; Vlieks, A E; Jongewaard, E N; Tantawi, S G; Raubenheimer, T O

2009-08-20

4

Gamma-ray burst spectra from photon-deficient Compton scattering by nonthermal electrons  

NASA Technical Reports Server (NTRS)

Consideration is given to a model of gamma-ray burst sources based on repeated Compton scatterings of soft photons by relativistic nonthermal electrons. Relativistic electrons which are continuously produced in the source radiate the total power L supplied to them. Higher order Compton scatterings, which occur when L(soft) is much less than L make the model distinct. The spectrum having an X-ray energy index of about one results from the superposition of the spectral components from several orders of Compton scattering; the change of the slope at several hundred keV arises from the Klein-Nishina decline of the scattering cross section.

Zdziarski, Andrzej A.; Lamb, Don Q.

1986-01-01

5

A method for determination mass absorption coefficient of gamma rays by Compton scattering.  

PubMed

A method was proposed for determination mass absorption coefficient of gamma rays for compounds, alloys and mixtures. It is based on simulating interaction processes of gamma rays with target elements having atomic numbers from Z=1 to Z=92 using the MCSHAPE software. Intensities of Compton scattered gamma rays at saturation thicknesses and at a scattering angle of 90° were calculated for incident gamma rays of different energies. The obtained results showed that the intensity of Compton scattered gamma rays at saturations and mass absorption coefficients can be described by mathematical formulas. These were used to determine mass absorption coefficients for compound, alloys and mixtures with the knowledge of their Compton scattered intensities. The method was tested by calculating mass absorption coefficients for some compounds, alloys and mixtures. There is a good agreement between obtained results and calculated ones using WinXom software. The advantages and limitations of the method were discussed. PMID:25241360

El Abd, A

2014-12-01

6

Laser Compton back-scattering gamma-ray beamline on NewSUBARU  

Microsoft Academic Search

A laser-Compton scattering system is a unique and useful gamma-ray-beam source. The laser-Compton scattering gamma ray generation was tested on a synchrotron radiation facility, “NewSUBARU” at Lasti\\/UH. Cw Nd:YVO laser (wavelength: 1.064?m, maximum power: 5W) was used in the experiments. Maximum energies of scattered gamma ray are 17.6 and 39.1MeV at the operating electron energy of 1 and 1.5GeV, respectively.

Shuji Miyamoto; Yoshihiro Asano; Sho Amano; Dazhi Li; Kazuo Imasaki; Hiroaki Kinugasa; Yoshihiko Shoji; Tetsuya Takagi; Takayasu Mochizuki

2006-01-01

7

High-Power Laser Pulse Recirculation for Inverse Compton Scattering-Produced Gamma-Rays  

SciTech Connect

Inverse Compton scattering of high-power laser pulses on relativistic electron bunches represents an attractive method for high-brightness, quasi-monoenergetic {gamma}-ray production. The efficiency of {gamma}-ray generation via inverse Compton scattering is severely constrained by the small Thomson scattering cross section. Furthermore, repetition rates of high-energy short-pulse lasers are poorly matched with those available from electron accelerators, resulting in low repetition rates for generated {gamma}-rays. Laser recirculation has been proposed as a method to address those limitations, but has been limited to only small pulse energies and peak powers. Here we propose and experimentally demonstrate an alternative method for laser pulse recirculation that is uniquely capable of recirculating short pulses with energies exceeding 1 J. Inverse Compton scattering of recirculated Joule-level laser pulses has a potential to produce unprecedented peak and average {gamma}-ray brightness in the next generation of sources.

Jovanovic, I; Shverdin, M; Gibson, D; Brown, C

2007-04-17

8

The limitations of resonant Compton scattering as a gamma-ray burst model  

NASA Technical Reports Server (NTRS)

Resonant Compton upscattering is commended as a mechanism that produces a hard gamma-ray spectrum while suppressing X-rays. This model, however, has severe physical and observational limitations. Effective X-ray suppression places a lower limit on the electron density; above this limit X-rays scatter multiple times, so the single-scattering approximation of this mechanism is invalid. Multiple scattering produces a spectrum that is much harder than the single-scattering spectrum. As the Thomson optical depth of a power-law electron beam approaches unity, photon spawning commences at a high rate and physically invalidates the underlying electron distribution. The Compton upscattering model is therefore only valid over a narrow range of electron densities. An observational consequence of this model is the absence of the third cyclotron resonance. Resonant scattering produces gamma-rays that propagate nearly along the magnetic field. The resonant cross section of the third harmonic, which is strongly angle dependent, falls below the Compton continuum for these gamma rays. The observation of a third cyclotron resonance in a gamma-ray burst spectrum would eliminate resonant Compton scattering as a gamma-ray burst process.

Brainerd, J. J.

1992-01-01

9

Energy distribution of Compton-scattered gamma rays  

E-print Network

by Podolsky and Pauling by means of a Dirac transformation from the position eigenfunctions. In 1962 Varma and *numbers refer to references at the end of the thesis. Eswaran, by scattering 662-keV gamma rays from the K electrons in lead, succeeded in showi.... Physik 21, 89 (1934). 9. B. Podolsky and L. Pauling, Phys. Rev. 34, 109 (1929). 10. J. Varma and M. A. Eswaran, Phya Rev. 127, 1197 (1962). 11. J. C. Slater, Phys. Rev. 36, 57 (1930). 12. G. K. Tandon, "A Study Of Nuclear Resonance Fluorescence...

Moreland, Richard Wayne

1966-01-01

10

Multiple resonant scattering in the Compton upscatter model of gamma-ray bursts  

NASA Technical Reports Server (NTRS)

Resonant Compton scattering, an increasingly popular mechanism for suppressing X-rays and producing gamma rays, must be treated as a multiple-scattering process for conditions thought characteristic of gamma-ray bursts. Photons that multiply scatter with a beamed power-law electron distribution in a uniform magnetic field produce a flat spectrum between the cyclotron frequency and an optical-depth-dependent critical energy; this critical energy ranges between several hundred keV and several MeV. Above this critical energy, the gamma-ray spectrum has a shape determined by the electron distribution and described by a single-scattering model. Only electron distributions that are nearly proportional to the electron momentum are able to simultaneously suppress X-rays and produce a single-scattering spectrum. As the Thomson optical depth approaches unity, photons that experience multiple scatterings often spawn additional photons at a rate that makes the model unphysical.

Brainerd, J. J.

1992-01-01

11

An investigation of the electronic wave functions in solids by the Compton scattering of gamma rays  

E-print Network

AN INVESTIGATION OF THE LLECIRONIC NAVE FUNCTIONS IN SOI. IDS BY THE COMPTON SCATTEP, ING OF GAMMA RAYS A Thesis by SANG KYUN NHA Submitted to the Graduate College of the Texas ASM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1968 Major Subject Physics AN INVFSTIGATION OF THE ELECTRONIC l!!AVE FUNCTIONS IN SOLIDS BY THE COMPTON SCATTERING OF' GAB!IA RAYS A Thesis by SANG KYUN NHA AFFroyed as tn style aod coot& at bv J QG g...

Nha, Sang Kyun

1968-01-01

12

Effects of Compton scattering on the Gamma Ray Spectra of Solar flares  

E-print Network

Using fully relativistic GEANT4 simulation tool kit, the transport of energetic electrons generated in solar flares was Monte-Carlo simulated, and resultant bremsstrahlung gamma-ray spectra were calculated. The solar atmosphere was approximated by 10 vertically-stacked zones. The simulation took into account two important physical processes,that the bremsstrahlung photons emitted by precipitating relativistic electrons are strongly forward beamed toward the photosphere, and that the majority of these gamma-rays must be Compton back-scattered by the solar atmosphere in order to reach the observer. Then, the Compton degradation was found to make the observable gamma-ray spectra much softer than is predicted by simple analytic calculations. The gamma-ray signals were found to be enhanced by several conditions, including a broad pitch-angle distribution of the electrons, a near-limb flare longitude, and a significant tilt in the magnetic field lines if the flare longitude is rather small. These results successfully explain several important flare properties observed in the hard X-ray to gamma-ray range, including in particular those obtained with Yohkoh. A comparison of the Yohkoh spectrum from a GOES X3.7 class limb flare on 1998 November 22, with a simulation assuming a broad electron pitch-angle distribution, suggests that gamma-rays from this particular solar flare were a mixture of direct bremsstrahlung photons and their Comptonization.

Jun'ichi Kotoku; Kazuo Makishima; Yukari Matsumoto; Mitsuhiro Kohama; Yukikatsu Terada; Toru Tamagawa

2007-08-01

13

Nondestructive detection of hidden chemical compounds with laser Compton-scattering gamma rays.  

PubMed

A nondestructive assay method for measuring a shielded chemical compound has been proposed. The chemical compound is measured by using a nuclear resonance fluorescence (NRF) measurement technique with an energy tunable laser Compton-scattering (LCS) gamma-ray source. This method has an advantage that hidden materials can be detected through heavy shields such as iron plates of a thickness of several centimeters. A detection of a chemical compound of melamine, C(3)H(6)N(6), shielded by 15-mm-thick iron and 4-mm-thick lead plates is demonstrated. The NRF gamma-rays of (12)C and (14)N of the melamine are measured by using the LCS gamma-rays of the energies of up to 5.0 MeV. The observed ratio ((12)C/(14)N)(exp)=0.39+/-0.12 is consistent with (C/N)(melamine)=0.5. PMID:19405694

Hayakawa, Takehito; Ohgaki, Hideaki; Shizuma, Toshiyuki; Hajima, Ryoichi; Kikuzawa, Nobuhiro; Minehara, Eisuke; Kii, Toshiteru; Toyokawa, Hiroyuki

2009-04-01

14

Feasibility study of ultra-short gamma ray pulse generation by laser Compton scattering in an electron storage ring  

Microsoft Academic Search

We are developing an ultra-short gamma ray pulse source based on laser Compton scattering technology. Ultra-short gamma ray pulses can be generated by injecting femtosecond laser pulses into the electron beam circulating in an electron storage ring from the direction perpendicular to the orbital plane. The energy, intensity, and pulse width of the gamma rays are estimated to be 6.6MeV,

Y. Taira; M. Adachi; H. Zen; T. Tanikawa; M. Hosaka; Y. Takashima; N. Yamamoto; K. Soda; M. Katoh

2011-01-01

15

Application of Laser Compton Scattered gamma-ray beams to nondestructive detection and assay of nuclear material  

NASA Astrophysics Data System (ADS)

Generation of energy-tunable gamma-rays via Laser Compton Scattering is of great interest for scientific studies and applications of "MeV" photons which interact with nuclei. One of the promising applications of such energy-tunable gamma-rays is the nondestructive detection and assay of nuclides which are necessary for nuclear security and safeguards. We are developing technologies relevant to gamma-ray nondestructive detection and assay, which include a high-brightness gamma-ray source based on modern laser and accelerator technologies, and gamma-ray measurement methods optimized for highly radioactive samples.

Hajima, R.; Hayakawa, T.; Shizuma, T.; Angell, C. T.; Nagai, R.; Nishimori, N.; Sawamura, M.; Matsuba, S.; Kosuge, A.; Mori, M.; Seya, M.

2014-05-01

16

Compton scattering and the gamma-ray power-law spectrum in Markarian 421  

NASA Technical Reports Server (NTRS)

The nearest BL Lac object, Mrk 421, has a gamma-ray spectrum which is approximately flat in EF-sub E from E less than about 50 MeV to E greater than about 1 TeV. Inverse Compton scattering can explain this smooth spectrum, despite the structure in the Klein-Nishina cross section, if the injected electron distribution function is proportional to gamma exp -2, where gamma is the electron Lorentz factor. When this is the case, the structure imprinted on the steady state electron distribution function by the structure in the Klein-Nishina cross section is almost exactly compensated in the radiated spectrum. Because particle acceleration in strong shocks injects particles with this distribution function, this shape injection function is in fact quite plausible. Other blazars may be explained by the same model if the cutoff below TeV energies observed in other objects is due to pair production on the cosmological IR background, as suggested by Stecker et al. (1992).

Zdziarski, Andrzej A.; Krolik, Julian H.

1993-01-01

17

Compton scattering overview  

SciTech Connect

An overview of linear and nonlinear Compton scattering is presented, along with a comparison with Thomson scattering. Two distinct processes play important roles in the nonlinear regime: multi-photon interactions, leading to the generation of harmonics, and radiation pressure, yielding a downshift of the radiated spectral features. These mechanisms, their influence on the source brightness, and different modeling strategies are also briefly discussed.

Hartemann, F V

2008-12-01

18

Design and Operation of a tunable MeV-level Compton-scattering-based (gamma-ray) source  

SciTech Connect

A mono-energetic gamma-ray (MEGa-ray) source based on Compton-scattering, targeting nuclear physics applications such as nuclear resonance fluorescence, has been constructed and commissioned at Lawrence Livermore National Laboratory. In this paper, the overall architecture of the system, as well as some of the critical design decisions made in the development of the source, are discussed. The performances of the two laser systems (one for electron production, one for scattering), the electron photoinjector, and the linear accelerator are also detailed, and initial {gamma}-ray results are presented.

Gibson, D J; Albert, F; Anderson, S G; Betts, S M; Messerly, M J; Phan, H H; Semenov, V A; Shverdin, M Y; Tremaine, A M; Hartemann, F V; Siders, C W; McNabb, D P; Barty, C P

2009-07-07

19

Compton scattering effects in the spectra of soft gamma-ray repeaters  

E-print Network

The association of all three soft gamma-ray repeaters (SGRs) with supernova remnants has made possible estimates of the distance to and luminosity of the sources of SGRs, which have provided a starting point for detailed modeling. One of the most popular classes of models involves strongly magnetized neutron stars, with surface dipole fields $B\\sim 10^{14}-10^{15}$ G. In these ``magnetar" models, many otherwise negligible processes can play an important role. Here we consider the spectral effects of strong-field modifications to Compton scattering, in particular those related to the contribution of vacuum polarization to the dielectric tensor. Vacuum polarization introduces a density-dependent photon frequency, called the second vacuum frequency, at which the normal modes of polarization become nonorthogonal and the mean free path of photons decreases sharply. Monte Carlo simulations of photon propagation through a magnetized plasma show that this effect leads, under a wide range of physical conditions, to a broad absorption-like feature in the energy range $\\sim$5 keV---40 keV.

M. Coleman Miller; Tomasz Bulik

1995-12-18

20

The pi- p --> gamma gamma n Reaction and Pion Compton Scattering  

E-print Network

We propose to measure the two--photon capture mode of pionic hydrogen using the RMC pair spectrometer at the TRIUMF cyclotron. Currently, only an experimental upper limit of B.R. gamma gamma annihilation graph. More speculatively, since crossing symmetry relates pi pi --> gamma gamma to gamma pi --> gamma pi, this threshold reaction may be a novel probe of the pion's electric polarizability. We show results of our 1997 engineering run and Monte Carlo studies for the two photon capture mode of pionic hydrogen and carbon. We also present our preliminary upper limit for the pi- p --> gamma gamma n B.R. <= 2.8E-4.

Piotr A. Zolnierczuk

1998-06-19

21

Apodized aperture imaging optics for Compton-scattered x-ray and gamma-ray imaging systems  

NASA Astrophysics Data System (ADS)

To improve the resolution and field of view of high-energy Compton-scattered x-ray and gamma-ray imaging systems, we have developed and tested apodized imaging optics based on apertures with depth-dependent cross sections fabricated in an x-ray-absorbing material. Through ray-tracing modeling, we determined the optimum aperture shapes (apodizations) that maximize the field of view and/or resolution of the system. Such apodized apertures can be used either in single-aperture optics, or in coded-aperture arrays. Potential applications of this technology include nondestructive evaluation (NDE) of materials and structures, in particular Compton imaging tomography (CIT), x-ray and gamma-ray astronomy, and medical imaging.

Romanov, Volodymyr; Grubsky, Victor; Patton, Ned; Jannson, Tomasz

2011-09-01

22

Some implications of inverse-Compton scattering of hot cocoon radiation by relativistic jets in gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Long gamma-ray bursts (GRBs) relativistic jets are surrounded by hot cocoons which confine jets during their punch out from the progenitor star. These cocoons are copious sources of X-ray photons that can be and are inverse-Compton (IC) scattered to MeV-GeV energies by electrons in the relativistic jet. We provide detailed estimates for IC flux resulting from various interactions between X-ray photons and the relativistic jet, and describe what we can learn about GRBs jets and progenitor stars from the detection (or an upper limit) of these IC scattered photons.

Kumar, Pawan; Smoot, George F.

2014-11-01

23

The Compton Gamma Ray Observatory  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments,

N. Gehrels; E. Chipman; D. Kniffen

1994-01-01

24

Compton Gamma Ray Observatory Guest Investigator Program  

NASA Technical Reports Server (NTRS)

This paper presents a final report for the Compton Gamma Ray Observatory Guest Investigator Program from 06/01/91-07/31/97. The topics include: 1) Solar Flare Neutron Spectra and Accelerated Ions; 2) Gamma Ray Lines From The Orion Complex; 3) Implications of Nuclear Line Emission From The Orion Complex; 4) Possible Sites of Nuclear Line Emission From Massive OB Associations; 5) Gamma-Ray Burst Repitition and BATSE Position Uncertainties; 6) Effects of Compton Scattering on BATSE Gamma-Ray Burst Spectra; and 7) Selection Biases on the Spectral and Temporal Distribution of Gamma Ray Bursts.

Lingenfelter, Richard E.

1997-01-01

25

Effective atomic numbers of blue topaz at different gamma-rays energies obtained from Compton scattering technique  

SciTech Connect

Topaz occurs in a wide range of colors, including yellow, orange, brown, pink-to-violet and blue. All of these color differences are due to color centers. In order to improve the color of natural colorless topaz, the most commonly used is irradiated with x- or gamma-rays, indicated that attenuation parameters is important to enhancements by irradiation. In this work, the mass attenuation coefficients of blue topaz were measured at the different energy of ?-rays using the Compton scattering technique. The results show that, the experimental values of mass attenuation coefficient are in good agreement with the theoretical values. The mass attenuation coefficients increase with the decrease in gamma rays energies. This may be attributed to the higher photon interaction probability of blue topaz at lower energy. This result is a first report of mass attenuation coefficient of blue topaz at different gamma rays energies.

Tuschareon, S., E-mail: tuscharoen@hotmail.com; Limkitjaroenporn, P., E-mail: tuscharoen@hotmail.com; Kaewkhao, J., E-mail: tuscharoen@hotmail.com [Center of Excellence in Glass Technology and Materials Science (CEGM), Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000, Thailand and Science Program, Faculty of Science and Technology, Nakhon Pathom Rajabhat University, Nakhon Pathom, 73000 (Thailand)

2014-03-24

26

Effective atomic numbers of blue topaz at different gamma-rays energies obtained from Compton scattering technique  

NASA Astrophysics Data System (ADS)

Topaz occurs in a wide range of colors, including yellow, orange, brown, pink-to-violet and blue. All of these color differences are due to color centers. In order to improve the color of natural colorless topaz, the most commonly used is irradiated with x- or gamma-rays, indicated that attenuation parameters is important to enhancements by irradiation. In this work, the mass attenuation coefficients of blue topaz were measured at the different energy of ?-rays using the Compton scattering technique. The results show that, the experimental values of mass attenuation coefficient are in good agreement with the theoretical values. The mass attenuation coefficients increase with the decrease in gamma rays energies. This may be attributed to the higher photon interaction probability of blue topaz at lower energy. This result is a first report of mass attenuation coefficient of blue topaz at different gamma rays energies.

Tuschareon, S.; Limkitjaroenporn, P.; Kaewkhao, J.

2014-03-01

27

Portable compton gamma-ray detection system  

DOEpatents

A Compton scattered gamma-ray detector system. The system comprises a gamma-ray spectrometer and an annular array of individual scintillators. The scintillators are positioned so that they are arrayed around the gamma-ray spectrometer. The annular array of individual scintillators includes a first scintillator. A radiation shield is positioned around the first scintillator. A multi-channel analyzer is operatively connected to the gamma-ray spectrometer and the annular array of individual scintillators.

Rowland, Mark S. (Alamo, CA); Oldaker, Mark E. (Pleasanton, CA)

2008-03-04

28

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

SciTech Connect

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.

Taira, Y.; Toyokawa, H.; Kuroda, R. [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Yamamoto, N. [Nagoya University Synchrotron Radiation Research Center, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Adachi, M.; Tanaka, S.; Katoh, M. [UVSOR, Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji-cho, Okazaki, Aichi 444-8585 (Japan)

2013-05-15

29

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

30

Electron Linac design to drive bright Compton back-scattering gamma-ray sources  

SciTech Connect

The technological development in the field of high brightness linear accelerators and high energy/high quality lasers enables today designing high brilliance Compton-X and Gamma-photon beams suitable for a wide range of applications in the innovative field of nuclear photonics. The challenging requirements of this kind of source comprise: tunable energy (1-20 MeV), very narrow bandwidth (0.3%), and high spectral density (10{sup 4} photons/s/eV). We present here a study focused on the design and the optimization of an electron Linac aimed to meet the source specifications of the European Extreme Light Infrastructure-Nuclear Physics project, currently funded and seeking for an innovative machine design in order to outperform state-of-the-art facilities. We show that the phase space density of the electron beam, at the collision point against the laser pulse, is the main quality factor characterizing the Linac.

Bacci, A.; Rossi, A. R.; Serafini, L. [INFN-MI, Milano (Italy)] [INFN-MI, Milano (Italy); Alesini, D.; Bellaveglia, M.; Boni, R.; Chiadroni, E.; Di Pirro, G.; Esposito, A.; Ferrario, M.; Gallo, A.; Gatti, G.; Ghigo, A.; Spataro, B.; Vaccarezza, C. [INFN-LNF, Frascati, Roma (Italy)] [INFN-LNF, Frascati, Roma (Italy); Antici, P.; Migliorati, M.; Mostacci, A.; Palumbo, L. [University La Sapienza, Roma (Italy)] [University La Sapienza, Roma (Italy); Cianchi, A. [University of Tor Vergata, Roma (Italy)] [University of Tor Vergata, Roma (Italy); and others

2013-05-21

31

X-ray suppression in gamma-ray bursts through resonant Compton scattering  

NASA Technical Reports Server (NTRS)

An X-ray that scatters with an electron in the first Landau level of a strong magnetic field is converted into a gamma ray. This process has a resonant cross section at X-ray energies and is therefore highly likely to occur even when the first Landau level is sparsely populated. Converted X-rays are cyclotron absorbed, maintaining the equilibrium between the cyclotron photon density and the population of the first Landau level. By suppressing a neutron star's black body emission, this mechanism can produce a gamma-ray burst with a low X-ray flux.

Brainerd, J. J.

1992-01-01

32

Weak Deeply Virtual Compton Scattering  

SciTech Connect

We extend the analysis of the deeply virtual Compton scattering process to the weak interaction sector in the generalized Bjorken limit. The virtual Compton scattering amplitudes for the weak neutral and charged currents are calculated at the leading twist within the framework of the nonlocal light-cone expansion via coordinate space QCD string operators. Using a simple model, we estimate cross sections for neutrino scattering off the nucleon, relevant for future high intensity neutrino beam facilities.

Ales Psaker; Wolodymyr Melnitchouk; Anatoly Radyushkin

2007-03-01

33

The Compton Gamma Ray Observatory  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 30 keV to 30 GeV, with sensitivity over the entire range an order of magnitude better than

N. Gehrels; E. Chipman; D. A. Kniffen

1993-01-01

34

The Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

Gehrels, N.; Chipman, E.; Kniffen, D.

1994-01-01

35

The Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

Gehrels, N.; Chipman, E.; Kniffen, D.

1994-06-01

36

Compton Gamma Ray Observatory/BATSE observations of energetic electrons scattered by cyclotron resonance with waves from powerful VLF transmitters  

NASA Technical Reports Server (NTRS)

To obtain a better understanding of the wave-particle mechanisms responsible for the loss of electrons from the radiation belts, energetic electron data from the Burst and Transient Source Experiment (BATSE) on the NASA's Compton Gamma Ray Observatory (GRO) was studied. Powerful ground-based VLF transmitters resonantly scatter electrons from the inner radiation belt onto trajectories from which they precipitate into the atmosphere as they drift eastward. 563 instances in which the satellite traversed a cloud of energetic electrons which had been scattered into quasi-trapped trajectories were identified. From the longitude distribution, it was concluded that waves from the VLF transmitter NWC at 114 deg E are the origin of 257 of the events, and waves from UMSat 44 deg E related to 45 more. In another 177 cases the electrons had drifted from the longitude of these transmitters to a location in the western hemisphere. The previously reported seasonal variation in the frequency of occurrence of cyclotron resonance interaction is confirmed with the continuous coverage provided by GRO. The frequency of occurrence of the cyclotron resonance interactions is largest before sunrise, which we attribute to the diurnal variations in the transmission VLF waves through the ionosphere. For the first time, unique very narrow sheets of electrons occurring in the aftermath of a large geomagnetic storm are reported.

Datlowe, Dayton W.; Imhof, William L.

1994-01-01

37

THE ROLE OF INVERSE COMPTON SCATTERING IN SOLAR CORONAL HARD X-RAY AND {gamma}-RAY SOURCES  

SciTech Connect

Coronal hard X-ray (HXR) and continuum {gamma}-ray sources associated with the impulsive phase of solar flares have been the subject of renewed interest in recent years. They have been interpreted in terms of thin-target, non-thermal bremsstrahlung emission. This interpretation has led to rather extreme physical requirements in some cases. For example, in one case, essentially all of the electrons in the source must be accelerated to non-thermal energies to account for the coronal HXR source. In other cases, the extremely hard photon spectra of the coronal continuum {gamma}-ray emission suggest that the low-energy cutoff of the electron energy distribution lies in the MeV energy range. Here, we consider the role of inverse Compton scattering (ICS) as an alternate emission mechanism in both the ultra- and mildly relativistic regimes. It is known that relativistic electrons are produced during powerful flares; these are capable of upscattering soft photospheric photons to HXR and {gamma}-ray energies. Previously overlooked is the fact that mildly relativistic electrons, generally produced in much greater numbers in flares of all sizes, can upscatter extreme-ultraviolet/soft X-ray photons to HXR energies. We also explore ICS on anisotropic electron distributions and show that the resulting emission can be significantly enhanced over an isotropic electron distribution for favorable viewing geometries. We briefly review results from bremsstrahlung emission and reconsider circumstances under which non-thermal bremsstrahlung or ICS would be favored. Finally, we consider a selection of coronal HXR and {gamma}-ray events and find that in some cases the ICS is a viable alternative emission mechanism.

Chen Bin [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Bastian, T. S. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States)

2012-05-01

38

Compton scattering on blackbody photons  

Microsoft Academic Search

We examine Compton scattering of electrons on blackbody photons in the case where the electrons are highly relativistic, but the center of mass energy is small in comparison with the electron mass. We derive the partial lifetime of electrons in the large electron positron (LEP) accelerator due to this form of scattering in the vacuum beam pipe and compare it

Lowell S. Brown; Ronald S. Steinke

1997-01-01

39

The Penrose photoproduction scenario for NGC 4151: A black hole gamma-ray emission mechanism for active galactic nuclei and Seyfert galaxies. [Compton scattering and pair production  

NASA Technical Reports Server (NTRS)

A consistent theoretical interpretation is given for the suggestion that a steepening of the spectrum between X-ray and gamma ray energies may be a general, gamma-ray characteristic of Seyfert galaxies, if the diffuse gamma ray spectrum is considered to be a superposition of unresolved contributions, from one or more classes of extragalactic objects. In the case of NGC 4151, the dominant process is shown to be Penrose Compton scattering in the ergosphere of a Kerr black hole, assumed to exist in the Seyfert's active galactic nucleus.

Leiter, D.

1979-01-01

40

High Energy Astrophysics: Compton Scattering II 1/95 Compton Scattering II  

E-print Network

High Energy Astrophysics: Compton Scattering II 1/95 Compton Scattering II 1 Introduction the lobes of radio galaxies can #12;High Energy Astrophysics: Compton Scattering II 2/95 be used, along in mind two possible scenarios: #12;High Energy Astrophysics: Compton Scattering II 3/95 1.The "soft

Bicknell, Geoff

41

Compton scattering on blackbody photons  

Microsoft Academic Search

We examine Compton scattering of electrons on black body photons in the case\\u000awhere the electrons are highly relativistic, but the center of mass energy is\\u000asmall in comparison with the electron mass. We derive the partial lifetime of\\u000aelectrons in the LEP accelerator due to this form of scattering in the vacuum\\u000abeam pipe and compare it with previous

Lowell S. Brown; Ronald S. Steinke

1997-01-01

42

The Compton Gamma Ray Observatory: mission status  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray Observatory (Compton) is the second in NASA's series of Great Observatories. Compton has now been operating for over two and a half years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made and

N. Gehrels; E. Chipman; D. A. Kniffen

1994-01-01

43

Design of a 2 MeV Compton scattering gamma-ray source for DNDO missions  

SciTech Connect

Nuclear resonance fluorescence-based isotope-specific detection and imaging is a powerful new technology that can enable access to new mission spaces for DNDO. Within this context, the development of advanced mono-energetic gamma ray sources plays an important role in the DNDO R&D portfolio, as it offers a faster, more precise, and safer alternative to conventional Bremsstrahlung sources. In this report, a specific design strategy is presented, along with a series of theoretical and computational tools, with the goal of optimizing source parameters for DNDO applications. In parallel, key technologies are outlined, along with discussions justifying specific choices and contrasting those with other alternatives. Finally, a complete conceptual design is described, and machine parameters are presented in detail.

Hartemann, F V; Albert, F

2009-08-24

44

The Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 30 keV to 30 GeV, with sensitivity over the entire range an order of magnitude better than that of previous observations. The 16,000 kilogram observatory contains four instruments on a stabilized platform. The mission began normal operations on 16 May 1991 and is now over half-way through a full-sky survey. The mission duration is expected to be from six to ten years. A Science Support Center has been established at Goddard Space Flight Center for the purpose of supporting a vigorous Guest Investigator Program. New scientific results to date include: (1) the establishment of the isotropy, combined with spatial inhomogeneity, of the distribution of gamma-ray bursts in the sky; (2) the discovery of intense high energy (100 MeV) gamma-ray emission from 3C 279 and other quasars and BL Lac objects, making these the most distant and luminous gamma-ray sources ever detected; (3) one of the first images of a gamma-ray burst; (4) the observation of intense nuclear and position-annihilation gamma-ray lines and neutrons from several large solar flares; and (5) the detection of a third gamma-ray pulsar, plus several other transient and pulsing hard X-ray sources.

Gehrels, N.; Chipman, E.; Kniffen, D. A.

1993-01-01

45

Compton Gamma-Ray Observatory  

NASA Technical Reports Server (NTRS)

This photograph shows the Compton Gamma-Ray Observatory (GRO) being deployed by the Remote Manipulator System (RMS) arm aboard the Space Shuttle Atlantis during the STS-37 mission in April 1991. The GRO reentered Earth atmosphere and ended its successful mission in June 2000. For nearly 9 years, the GRO Burst and Transient Source Experiment (BATSE), designed and built by the Marshall Space Flight Center (MSFC), kept an unblinking watch on the universe to alert scientists to the invisible, mysterious gamma-ray bursts that had puzzled them for decades. By studying gamma-rays from objects like black holes, pulsars, quasars, neutron stars, and other exotic objects, scientists could discover clues to the birth, evolution, and death of stars, galaxies, and the universe. The gamma-ray instrument was one of four major science instruments aboard the Compton. It consisted of eight detectors, or modules, located at each corner of the rectangular satellite to simultaneously scan the entire universe for bursts of gamma-rays ranging in duration from fractions of a second to minutes. In January 1999, the instrument, via the Internet, cued a computer-controlled telescope at Las Alamos National Laboratory in Los Alamos, New Mexico, within 20 seconds of registering a burst. With this capability, the gamma-ray experiment came to serve as a gamma-ray burst alert for the Hubble Space Telescope, the Chandra X-Ray Observatory, and major gound-based observatories around the world. Thirty-seven universities, observatories, and NASA centers in 19 states, and 11 more institutions in Europe and Russia, participated in the BATSE science program.

1991-01-01

46

Compton Gamma-Ray Observatory  

NASA Technical Reports Server (NTRS)

This photograph shows the Compton Gamma-Ray Observatory being released from the Remote Manipulator System (RMS) arm aboard the Space Shuttle Atlantis during the STS-35 mission in April 1991. The GRO reentered the Earth's atmosphere and ended its successful mission in June 2000. For nearly 9 years, GRO's Burst and Transient Source Experiment (BATSE), designed and built by the Marshall Space Flight Center, kept an unblinking watch on the universe to alert scientist to the invisible, mysterious gamma-ray bursts that had puzzled them for decades. By studying gamma-rays from objects like black holes, pulsars, quasars, neutron stars, and other exotic objects, scientists could discover clues to the birth, evolution, and death of star, galaxies, and the universe. The gamma-ray instrument was one of four major science instruments aboard the Compton. It consisted of eight detectors, or modules, located at each corner of the rectangular satellite to simultaneously scan the entire universe for bursts of gamma-rays ranging in duration from fractions of a second to minutes. In January 1999, the instrument, via the Internet, cued a computer-controlled telescope at Las Alamos National Laboratory in Los Alamos, New Mexico, within 20 seconds of registering a burst. With this capability, the gamma-ray experiment came to serve as a gamma-ray burst alert for the Hubble Space Telescope, the Chandra X-Ray Observatory, and major gound-based observatories around the world. Thirty-seven universities, observatories, and NASA centers in 19 states, and 11 more institutions in Europe and Russia, participated in BATSE's science program.

1991-01-01

47

DESIGN OF A 250 MeV, X-BAND PHOTOINJECTOR LINAC FOR A PRECISION COMPTON-SCATTERING BASED GAMMA-RAY SOURCE  

SciTech Connect

We present a compact, X-band, high-brightness accelerator design suitable for driving a precision gamma-ray source. Future applications of gamma-rays generated by Compton-scattering of laser and relativistic electron beams place stringent demands on the brightness and stability of the incident electron beam. This design identifies the beam parameters required for gamma-ray production, including position, and pointing stability. The design uses an emittance compensated, 11.4 GHz photo-gun and linac to generate 400 pC, 1-2 mm-mrad electron bunches at up to 250 MeV and 120 Hz repetition rate. The effects of jitter in the RF power system are analyzed as well as structure and optic misalignments. Finally, strategies for the mitigation of on-axis Bremsstrahlung noise are discussed.

Anderson, S G; Albert, F; Gibson, D J; McNabb, D; Messerly, M; Rusnak, B; Shverdin, M; Hartemann, F V; Siders, C W; Barty, C J; Tantawi, S; Vlieks, A

2009-05-07

48

Deeply Virtual Compton Scattering off the neutron  

SciTech Connect

The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D$({\\vec e},e'\\gamma)X$ cross section measured at $Q^2$=1.9 GeV$^2$ and $x_B$=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to $E_q$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

M. Mazouz; A. Camsonne; C. Munoz Camacho; C. Ferdi; G. Gavalian; E. Kuchina; M. Amarian; K. A. Aniol; M. Beaumel; H. Benaoum; P. Bertin; M. Brossard; J.-P. Chen; E. Chudakov; B. Craver; F. Cusanno; C.W. de Jager; A. Deur; R. Feuerbach; J.-M. Fieschi; S. Frullani; M. Garcon; F. Garibaldi; O. Gayou; R. Gilman; J. Gomez; P. Gueye; P.A.M. Guichon; B. Guillon; O. Hansen; D. Hayes; D. Higinbotham; T. Holmstrom; C.E. Hyde; H. Ibrahim; R. Igarashi; X. Jiang; H.S. Jo; L.J. Kaufman; A. Kelleher; A. Kolarkar; G. Kumbartzki; G. Laveissiere; J.J. LeRose; R. Lindgren; N. Liyanage; H.-J. Lu; D.J. Margaziotis; Z.-E. Meziani; K. McCormick; R. Michaels; B. Michel; B. Moffit; P. Monaghan; S. Nanda; V. Nelyubin; M. Potokar; Y. Qiang; R.D. Ransome; J.-S. Real; B. Reitz; Y. Roblin; J. Roche; F. Sabatie; A. Saha; S. Sirca; K. Slifer; P. Solvignon; R. Subedi; V. Sulkosky; P.E. Ulmer; E. Voutier; K. Wang; L.B. Weinstein; B. Wojtsekhowski; X. Zheng; L. Zhu

2007-12-01

49

Deeply Virtual Compton Scattering off the Neutron  

SciTech Connect

The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e-vector,e{sup '}{gamma})X cross section measured at Q{sup 2}=1.9 GeV{sup 2} and x{sub B}=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E{sub q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

Mazouz, M.; Guillon, B.; Real, J.-S.; Voutier, E. [LPSC, Universite Joseph Fourier, CNRS/IN2P3, INPG, F-38026 Grenoble (France); Camsonne, A.; Ferdi, C.; Brossard, M.; Fieschi, J.-M.; Laveissiere, G.; Michel, B. [LPC Clermont-Ferrand, Universite Blaise Pascal, CNRS/IN2P3, F-63177 Aubiere (France); Camacho, C. Munoz; Beaumel, M.; Garcon, M.; Guichon, P. A. M.; Sabatie, F. [CEA Saclay, DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Gavalian, G.; Amarian, M.; Hayes, D.; Ibrahim, H.; Ulmer, P. E. [Old Dominion University, Norfolk, Virginia 23508 (United States)] (and others)

2007-12-14

50

INVERSE COMPTON SCATTERING MODEL FOR X-RAY EMISSION OF THE GAMMA-RAY BINARY LS 5039  

SciTech Connect

We propose a model for the gamma-ray binary LS 5039 in which the X-ray emission is due to the inverse Compton (IC) process instead of the synchrotron radiation. Although the synchrotron model has been discussed in previous studies, it requires a strong magnetic field which leads to a severe suppression of the TeV gamma-ray flux in conflict with H.E.S.S. observations. In this paper, we calculate the IC emission by low energy electrons ({gamma}{sub e} {approx}< 10{sup 3}) in the Thomson regime. We find that IC emission of the low energy electrons can explain the X-ray flux and spectrum observed with Suzaku if the minimum Lorentz factor of injected electrons {gamma}{sub min} is around 10{sup 3}. In addition, we show that the Suzaku light curve is well reproduced if {gamma}{sub min} varies in proportion to the Fermi flux when the distribution function of injected electrons at higher energies is fixed. We conclude that the emission from LS 5039 is well explained by the model with the IC emission from electrons whose injection properties are dependent on the orbital phase. Since the X-ray flux is primarily determined by the total number of cooling electrons, this conclusion is rather robust, although some mismatches between the model and observations at the GeV band remain in the present formulation.

Yamaguchi, M. S.; Takahara, F. [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

2012-12-20

51

GPDs, form factors and Compton scattering  

E-print Network

The basic theoretical ideas of the handbag factorization and its application to wide-angle scattering reactions are reviewed. With regard to the present experimental program carried out at JLab, wide-angle Compton scattering is discussed in some detail.

P. Kroll

2002-07-09

52

Determination of Rest Mass Energy of the Electron by a Compton Scattering Experiment  

ERIC Educational Resources Information Center

We report here a simple Compton scattering experiment which may be carried out in graduate and undergraduate laboratories to determine the rest mass energy of the electron. In the present experiment, we have measured the energies of the Compton scattered gamma rays with a NaI(Tl) gamma ray spectrometer coupled to a 1 K multichannel analyzer at…

Prasannakumar, S.; Krishnaveni, S.; Umesh, T. K.

2012-01-01

53

High Energy Astrophysics Geoffrey V. Bicknell Compton Scattering I  

E-print Network

High Energy Astrophysics © Geoffrey V. Bicknell Compton Scattering I 1 Introduction Compton. #12;High Energy Astrophysics: Compton Scattering I 2/59 2 Scattering from electrons at rest 2 photons Scattered photons Oscillating electron #12;High Energy Astrophysics: Compton Scattering I 3/59 We

Bicknell, Geoff

54

Gamma-ray sources as Comptonized X-ray sources  

NASA Technical Reports Server (NTRS)

The possible contribution of Compton scattering to the formation of gamma-ray burst spectra is analyzed. Monte Carlo calculations are used to study the spectral distribution emerging from a plasma at temperatures typical of gamma-ray burst spectra (above 100 keV) with an underlying source of photons reprocessed by inverse Compton scattering surrounding a point source of blackbody radiation. Comparison of the computations with the observed spectrum of the burst GB781104 results in a best fit with a blackbody X-ray source at 2.4 keV, plasma temperature of about 150 eV and plasma column density of 4 x 10 to the 24th electrons/sq cm. The Comptonization model is also shown to be capable of accounting for the two-component spectra observed for bursts GB790329 and GB790524, and the moving low-energy spectral cut-off in the burst of November 18, 1978.

Fenimore, E. E.; Klebesadel, R. W.; Laros, J. G.; Stockdale, R. E.; Kane, S. R.

1982-01-01

55

On multiple Compton scattering in plasma clouds  

Microsoft Academic Search

Inverse Compton scattering of low energy photons in a nonrelativistic electron gas is considered. The angle dependence in the Thomson cross section is neglected and spatial and energy transport are separated in a multiple scattering development of the emerging spectrum. The energy transport is determined by a Green function G which may be obtained from the single scattering spectrum for

M. H. Soffel

1982-01-01

56

The electromagnetic calorimeter in JLab Real Compton Scattering Experiment  

SciTech Connect

A hodoscope calorimeter comprising of 704 lead-glass blocks is described. The calorimeter was constructed for use in the JLab Real Compton Scattering experiment. The detector provides a measurement of the coordinates and the energy of scattered photons in the GeV energy range with resolutions of 5 mm and 6\\%/$\\sqrt{E_\\gamma \\, [GeV]}$, respectively. Design features and performance parameters during the experiment are presented.

Albert Shahinyan; Eugene Chudakov; A. Danagoulian; P. Degtyarenko; K. Egiyan; V. Gorbenko; J. Hines; E. Hovhannisyan; Ch. Hyde; C.W. de Jager; A. Ketikyan; V. Mamyan; R. Michaels; A.M. Nathan; V. Nelyubin; I. Rachek; M. Roedelbrom; A. Petrosyan; R. Pomatsalyuk; V. Popov; J. Segal; Yu. Shestakov; J. Templon; H. Voskanyan; B. Wojtsekhowski

2007-04-16

57

An Electromagnetic Calorimeter for the JLab Real Compton Scattering Experiment  

Microsoft Academic Search

A lead-glass hodoscope calorimeter that was constructed for use in the Jefferson Lab Real Compton Scattering experiment is described. The detector provides a measurement of the coordinates and the energy of scattered photons in the GeV energy range with resolutions of 5 mm and 6%\\/\\\\sqrt(E{\\\\gamma} [GeV]). Features of both the detector design and its performance in the high luminosity environment

D. J. Hamilton; A. Shahinyan; B. Wojtsekhowski; J. R. M. Annand; T.-H. Chang; E. Chudakov; A. Danagoulian; P. Degtyarenko; K. Egiyan; R. Gilman; V. Gorbenko; J. Hines; E. Hovhannisyan; C. E. Hyde-Wright; C. W. de Jager; A. Ketikyan; V. H. Mamyan; R. Michaels; A. M. Nathan; V. Nelyubin; I. Rachek; M. Roedelbrom; A. Petrosyan; R. Pomatsalyuk; V. Popov; J. Segal; Y. Shestakov; J. Templon; H. Voskanyan

2007-01-01

58

Advanced Compton scattering light source R&D at LLNL  

SciTech Connect

We report the design and current status of a monoenergetic laser-based Compton scattering 0.5-2.5 MeV {gamma}-ray source. Previous nuclear resonance fluorescence results and future linac and laser developments for the source are presented. At MeV photon energies relevant for nuclear processes, Compton scattering light sources are attractive because of their relative compactness and improved brightness above 100 keV, compared to typical 4th generation synchrotrons. Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable Mono-Energetic Gamma-Ray (MEGa-Ray) light sources based on Compton scattering between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A new precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development and construction at LLNL. High-brightness, relativistic electron bunches produced by an X-band linac designed in collaboration with SLAC will interact with a Joule-class, 10 ps, diode-pumped CPA laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. Based on the success of the previous Thomson-Radiated Extreme X-rays (T-REX) Compton scattering source at LLNL, the source will be used to excite nuclear resonance fluorescence lines in various isotopes; applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. After a brief presentation of successful nuclear resonance fluorescence (NRF) experiments done with T-REX, the new source design, key parameters, and current status are presented.

Albert, F; Anderson, S G; Anderson, G; Betts, S M; Chu, T S; Gibson, D J; Marsh, R A; Messerly, M; Shverdin, M Y; Wu, S; Hartemann, F V; Siders, C W; Barty, C P

2010-02-16

59

Gamma-Ray Polarimetry with Compton Telescope  

SciTech Connect

Compton telescope is a promising technology to achieve very high sensitivity in the soft gamma-ray band (0.1-10 MeV) by utilizing Compton kinematics. Compton kinematics also enables polarization measurement which will open new windows to study gamma-ray production mechanism in the universe. CdTe and Si semiconductor technologies are key technologies to realize the Compton telescope in which their high energy resolution is crucial for high angular resolution and background rejection capability. We have assembled a prototype module using a double-sided silicon strip detector and CdTe pixel detectors. In this paper, we present expected polarization performance of a proposed mission (NeXT/SGD). We also report results from polarization measurements using polarized synchrotron light and validation of EGS4 MC simulation.

Tajima, H

2004-07-06

60

The nonlinear effect in relativistic Compton scattering for an intense circularly polarized laser  

NASA Astrophysics Data System (ADS)

Compton scattering between an intense laser pulse and a relativistic electron beam offers a promising development path toward high-energy, high-brightness x- and gamma-ray sources. Increasing laser peak power to obtain intense x- and gamma rays causes nonlinear Compton scattering to occur. To predict high-order harmonic radiation properties, we upgrade a Monte Carlo laser-Compton scattering simulation code (MCLCSS) by taking into account the nonlinear effect for the relativistic Compton scattering process. The energy spectra and angular and harmonic intensity distributions of the scattered photons are investigated using nonlinear Compton scattering of an intense circularly polarized laser. It is found that the laser parameter {{a}_{0}}\\equiv e{\\rm{A}}\\;{{m}_{e}}{{c}^{-2}} plays an important role in the generation of high-order harmonic radiation. Our study also suggests that the high-energy tails of the second and higher harmonics will stray from the backscattering region.

Luo, W.; Zhuo, H. B.; Ma, Y. Y.; Zhu, Z. C.; Fan, G. T.; Xu, W.; Song, Y. M.

2014-07-01

61

Parton distributions, form factors and Compton scattering  

E-print Network

The soft physics approach to form factors and Compton scattering at moderately large momentum transfer is reviewed. It will be argued that in that approach the Compton cross section is given by the Klein-Nishina cross section multiplied by a factor describing the structure of the proton in terms of two new form factors. These form factors as well as the ordinary electromagnetic form factors represent moments of skewed parton distributions.

Peter Kroll

1999-10-11

62

Deeply Virtual Compton Scattering at HERA II (H1 results)  

E-print Network

New results on the Deeply Virtual Compton Scattering process $\\gamma^* p \\to \\gamma p$ (DVCS) from H1 experiment at the $e p$ collider HERA are presented, using data collected during the year 2004 and corresponding to an integrated luminosity of 39.7 pb$^{-1}$. The DVCS cross section is measured as a function of the photon virtuality, $Q^2$, the $\\gamma^* p $ c.m.s. energy $W$ and differentially in the momentum transfer squared at the proton vertex, $t$, in the kinematic range $6.5 Color Dipole Model.

Benoit Roland

2006-05-22

63

The Compton Gamma Ray Observatory: mission status.  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory (Compton) is the second in NASA's series of Great Observatories. Compton has now been operating for over two and a half years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made and continue to be made. The authors describe the capabilities of the four scientific instruments and the observing programs for the first three years of the mission. During Phases 2 and 3 of the mission a Guest Investigator program has been in progress with the Guest Observers' time share increasing from 30% to over 50% for the later mission phases.

Gehrels, N.; Chipman, E.; Kniffen, D. A.

64

Relativistic induced Compton scattering in synchrotron self-absorbed sources  

NASA Technical Reports Server (NTRS)

We present a model of the radio emission from synchrotron self-absorbed sources, including the effects of induced Compton scattering by the relativistic electrons in the source. Order of magnitude estimates show that stimulated scattering becomes the dominant absorption process when (kT(sub B)/m(sub e) c(exp 2))Tau(sub T) greater than or approximately 1.0. Numerical simulations demonstrate that relativistic induced Compton scattering limits the brightness temperature of a self-absorbed synchroton sources to T(sub B) less than or approximately 2 x 10(exp 11) nu(exp -1/p + 3) (sub zero, 9) gamma(exp p + 2/p + 5) (sub min) K, where gamma(sub min) is the low-energy cutoff to the relativistic electron distribution with a power-law index of p. It can also significantly flatten the radio spectrum. The radio spectrum of the core of 3C 279 is well matched by a model in which stimulated scattering is important, and the additional constraint T(sub B) less than 2 x 10(exp 11)K may be important to the interpretation of the broadband spectra in variable extragalactic compact radio sources. Stimulated scattering reduces the amplitude of the radio frequency variability relative to the X-ray variability, an effect which can be detected by multiwavelength variability studies. Data for a sample of resolved compact radio cores indicate that it is inconsistent to neglect induced Compton scattering when inferring the physical parameters of the sources. The necessary generalizations to the standard synchrotron self-Compton theory are p resented.

Sincell, Mark W.; Krolik, Julian H.

1994-01-01

65

On the Synchrotron Self-Compton Emission from Relativistic Shocks and Its Implications for Gamma-Ray Burst Afterglows  

Microsoft Academic Search

We consider the effects of inverse Compton scattering of synchrotron photons from relativistic electrons in gamma-ray burst (GRB) afterglows. We compute the spectrum of the inverse Compton emission and find that it can dominate the total cooling rate of the afterglow for several months or even years after the initial explosion. We demonstrate that the presence of strong inverse Compton

Re'em Sari; Ann A. Esin

2001-01-01

66

Development of Compton gamma-ray sources at LLNL  

SciTech Connect

Compact Compton scattering gamma-ray sources offer the potential of studying nuclear photonics with new tools. The optimization of such sources depends on the final application, but generally requires maximizing the spectral density (photons/eV) of the gamma-ray beam while simultaneously reducing the overall bandwidth on target to minimize noise. We have developed an advanced design for one such system, comprising the RF drive, photoinjector, accelerator, and electron-generating and electron-scattering laser systems. This system uses a 120 Hz, 250 pC, 2 ps, 0.35 mm mrad electron beam with 250 MeV maximum energy in an X-band accelerator scattering off a 150 mJ, 10 ps, 532 nm laser to generate 5 Multiplication-Sign 10{sup 10} photons/eV/s/Sr at 0.5 MeV with an overall bandwidth of less than 1%. The source will be able to produce photons up to energies of 2.5 MeV. We also discuss Compton scattering gamma-ray source predictions given by numerical codes.

Albert, F.; Anderson, S. G.; Ebbers, C. A.; Gibson, D. J.; Hartemann, F. V.; Marsh, R. A.; Messerly, M. J.; Prantil, M. A.; Wu, S.; Barty, C. P. J. [Lawrence Livermore National Laboratory, NIF and Photon Science, 7000 East avenue, Livermore, CA 94550 (United States)

2012-12-21

67

Compton scatter profiles for warm dense matter.  

PubMed

In this paper, we discuss the possibility of using x-ray Compton scattering as a probe of the outer electronic structure of ions immersed in warm dense matter. It is proposed that the x-ray free-electron lasers currently under construction will provide an ideal tool for this, with the main pulse being used to create a uniform well-defined sample and the third harmonic providing a clean monochromatic probe. We model the plasma photon scatter spectrum by combining self-consistent finite-temperature electronic structure calculations with molecular dynamics simulations of the ion-ion structure factor. In particular, we present bound-free Compton profiles that are more accurate that those obtained using form factor or impulse approximations. PMID:18517740

Sahoo, S; Gribakin, G F; Shabbir Naz, G; Kohanoff, J; Riley, D

2008-04-01

68

Nonlinear X-ray Compton Scattering  

E-print Network

X-ray scattering is a weak linear probe of matter. It is primarily sensitive to the position of electrons and their momentum distribution. Elastic X-ray scattering forms the basis of atomic structural determination while inelastic Compton scattering is often used as a spectroscopic probe of both single-particle excitations and collective modes. X-ray free-electron lasers (XFELs) are unique tools for studying matter on its natural time and length scales due to their bright and coherent ultrashort pulses. However, in the focus of an XFEL the assumption of a weak linear probe breaks down, and nonlinear light-matter interactions can become ubiquitous. The field can be sufficiently high that even non-resonant multiphoton interactions at hard X-rays wavelengths become relevant. Here we report the observation of one of the most fundamental nonlinear X-ray-matter interactions, the simultaneous Compton scattering of two identical photons producing a single photon at nearly twice the photon energy. We measure scattered...

Fuchs, Matthias; Chen, Jian; Ghimire, Shambhu; Shwartz, Sharon; Kozina, Michael; Jiang, Mason; Henighan, Thomas; Bray, Crystal; Ndabashimiye, Georges; Bucksbaum, P H; Feng, Yiping; Herrmann, Sven; Carini, Gabriella; Pines, Jack; Hart, Philip; Kenney, Christopher; Guillet, Serge; Boutet, Sebastien; Williams, Garth; Messerschmidt, Marc; Seibert, Marvin; Moeller, Stefan; Hastings, Jerome B; Reis, David A

2015-01-01

69

Precision 0.5 GW X-band rf system for advanced Compton scattering source  

Microsoft Academic Search

A Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering light source is being developed at LLNL. The electron beam for the Compton scattering interaction will be generated by a X-band RF gun and a X-band LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the electrons to energy of 250 MeV or greater

T. S. Chu; G. Anderson; D. Gibson; F. V. Hartemann; C. P. J. Barty; A. Vlieks; S. Tantawi; E. Jongewaard; S. G. Anderson

2009-01-01

70

Unitary constraints on Deeply Virtual Compton Scattering  

SciTech Connect

At moderately low momentum transfer ($-t$ up to 1 GeV$^2$) the coupling to the vector meson production channels gives the dominant contribution to real Compton and deeply virtual Compton scattering (DVCS). Starting from a Regge Pole approach that successfully describes vector meson production, the singular part of the corresponding box diagrams (where the intermediate vector meson-baryon pair propagates on-shell) is evaluated without any further assumptions (unitarity). Such a treatment explains not only the unexpectedly large DVCS unpolarized cross section that has been recently measured at Jefferson Laboratory (JLab), but also all the beam spin and charge asymmetries that has been measured at JLab and Hermes, without explicit need of Generalized Parton Distributions (GPD). The issue of the relationship between the two approaches is addressed.

J.M. Laget

2007-11-01

71

Deeply Virtual Compton Scattering at JLab Hall A  

SciTech Connect

The deeply virtual Compton scattering reaction has been investigated in the Hall A of the Jefferson Laboratory by measuring longitudinally polarized (e,e'gamma) cross sections, in the valence quark region, for protons and neutrons. In the proton channel, experimental results strongly support the factorization of the cross section at Q2 as low as 2 GeV2, opening the path to systematic measurements of generalized parton distributions (GPDs). In the neutron case, preliminary data show sensitivity to the angular momentum of quarks.

Eric Voutier

2007-04-16

72

Compton scattering measurements from dense plasmas  

SciTech Connect

Compton scattering has been developed for accurate measurements of densities and temperatures in dense plasmas. One future challenge is the application of this technique to characterize compressed matter on the National Ignition Facility where hydrogen and beryllium will approach extremely dense states of matter of up to 1000 g/cc. In this regime, the density, compressibility, and capsule fuel adiabat may be directly measured from the Compton scattered spectrum of a high-energy x-ray line source. Specifically, the scattered spectra directly reflect the electron velocity distribution. In non-degenerate plasmas, the width provides an accurate measure of the electron temperatures, while in partially Fermi degenerate systems that occur in laser-compressed matter it provides the Fermi energy and hence the electron density. Both of these regimes have been accessed in experiments at the Omega laser by employing isochorically heated solid-density beryllium and moderately compressed beryllium foil targets. In the latter experiment, compressions by a factor of 3 at pressures of 40 Mbar have been measured in excellent agreement with radiation hydrodynamic modeling.

Glenzer, S H; Neumayer, P; Doeppner, T; Landen, L; Lee, R W; Wallace, R; Weber, S; Lee, H J; Kritcher, A L; Falcone, R; Regan, S P; Sawada, H; Meyerhofer, D D; Gregori, G; Fortmann, C; Schwarz, V; Redmer, R

2007-10-02

73

Deeply Virtual Compton Scattering at HERA II  

E-print Network

A new measurement is presented of elastic deeply virtual Compton scattering (DVCS) based on data taken by the H1 detector during the complete HERA II period. The data are well described by QCD based calculations. For the first time, a beam charge asymmetry is obtained in a colliding mode, using data recorded in $e^-p$ and $e^+p$. A significant non zero value is measured, related to the interference of QCD and QED processes, namely the DVCS and Bethe-Heitler reactions.

Laurent Schoeffel

2007-05-22

74

Deeply virtual Compton scattering and nucleon structure  

SciTech Connect

Deeply Virtual Compton Scattering (DVCS) is the tool of choice to study Generalized Parton Distributions (GPD) in the nucleon. After a general introduction to the subject, a review of experimental results from various facilities is given. Following the first encouraging results, new generation dedicated experiments now allow unprecedented precision and kinematical coverage. Several new results were presented during the conference, showing significant progress in this relatively new field. Prospects for future experiments are presented. The path for the experimental determination of GPDs appears now open.

M. Garcon

2006-11-01

75

Interference effect in nonlinear Compton scattering  

NASA Astrophysics Data System (ADS)

In this paper we make a theoretical investigation of a new type of high-energy nonlinear Compton scattering phenomenon. In particular we show how, under certain conditions, interference effects arise when two laser pulses of different photon energy are shone upon a high-energy electron beam. The semiclassical operator method of Baier et al. is revisited as the method of investigation of this phenomenon. We show how their result can be cast into a form very similar to the classical result of radiation emission. Experimental verification of the described interference phenomenon is possible with current technology.

Wistisen, Tobias N.

2014-12-01

76

Virtual Compton Scattering Off Protons at Moderately Large Momentum Transfer  

E-print Network

The amplitudes for virtual Compton scattering off protons are calculated within the framework of the diquark model in which protons are viewed as being built up by quarks and diquarks. The latter objects are treated as quasi-elementary constituents of the proton. Virtual Compton scattering, electroproduction of photons and the Bethe-Heitler contamination are discussed for various kinematical situations. We particularly emphasize the r\\^ole of the electron asymmetry for measuring the relative phases between the virtual Compton and the Bethe-Heitler amplitudes. It is also shown that the model is able to describe very well the experimental data for real Compton scattering off protons.

P. Kroll; M. Schürmann; P. A. M. Guichon

1995-07-13

77

Advanced Gamma-Ray Detection Concepts Combined with Real-Time Compton Suppression for Nondestructive, Gamma-Ray Characterization of Remote Handled Waste  

SciTech Connect

Nondestructive gamma ray characterization of remote-handled waste is significantly complicated by the presence of Compton scattering in the detector and waste matrix produced by intense cesium gamma rays. This research seeks to understand the photophysics of a new type of inorganic scintillation gamma ray detector, optimize the combination of this gamma ray detector with a Compton guard detector, develop new Monte Carlo solution algorithms for modeling Compton scattering in the waste, and to model the real time intensity of cesium produced Compton scattering. A successful research program will provide the fundamental information needed to design and develop advanced Compton spectrometers for assay of remote handled waste and new higher sensitivity spectrometers for environmental measurements.

Mcllwain, Michael E.; Haghighat, Alireza; Dorenbos, Pieter; Hartwell, John K.

2005-06-01

78

Studying Deeply Virtual Compton Scattering with Neural Networks  

E-print Network

Neural networks are utilized to fit Compton form factor H to HERMES data on deeply virtual Compton scattering off unpolarized protons. We used this result to predict the beam charge-spin assymetry for muon scattering off proton at the kinematics of the COMPASS II experiment.

Kresimir Kumericki; Dieter Mueller; Andreas Schafer

2011-10-17

79

Skewed Parton Distributions in Real and Virtual Compton Scattering  

E-print Network

The handbag contribution to Compton scattering at moderately large momentum transfer factorises into parton-photon subprocess amplitudes and new form factors representing 1/x-moments of skewed parton distributions. A detailed phenomenological study for polarised and unpolarised real and virtual Compton scattering is presented

M. Diehl; T. Feldmann; R. Jakob; P. Kroll

1999-06-24

80

Small-angle Compton Scattering to Determine the Depth of a Radioactive Source in Matter  

SciTech Connect

A gamma-ray peak in a spectrum is often accompanied by a discontinuity in the Compton continuum at the peak. The Compton continuum results from Compton scattering in the detector. The discontinuity at a peak results from small-angle Compton scattering by the gamma rays in matter situated directly between the gamma-ray source and the detector. The magnitude of this discontinuity with respect to the gamma-ray peak is therefore an indicator of the amount of material or shielding between the gamma-ray source and the detector. This small-angle scattering was used to determine the depth of highly-enriched uranium (HEU) solution standards in a concrete floor mockup. The empirical results of the use of this small-angle scattering discontinuity in a concrete floor experiment will be described. A Monte Carlo calculation of the experiment will also be described. In addition, the depth determined from small-angle scattering was used in conjunction with differential attenuation to more accurately measure the uranium content of the mockup. Following these empirical results, the theory of small-angle scattering will be discussed. The magnitude of the discontinuity compared to the peak count rate is directly related to the depth of the gamma-ray source in matter. This relation can be described by relatively simple mathematical expressions. This is the first instance that we are aware of in which the small-angle Compton scattering has been used to determine the depth of a radioactive source. Furthermore this is the first development of the theoretical expressions for the magnitude of the small-angle scattering discontinuity.

Oberer, R. B.; Gunn, C. A.; Chiang, L. G.; Valiga, R. E.; Cantrell, J. A.

2011-04-01

81

Energy measurement of electron beams by Compton scattering  

NASA Technical Reports Server (NTRS)

A method has been proposed to utilize the well-known Compton scattering process as a tool to measure the centroid energy of a high energy electron beam at the 0.01% level. It is suggested to use the Compton scattering of an infrared laser off the electron beam, and then to measure the energy of the scattered gamma-rays very precisely using solid-state detectors. The technique proposed is applicable for electron beams with energies from 200 MeV to 16 GeV using presently available lasers. This technique was judged to be the most viable of all those proposed for beam energy measurements at the nearby Continuous Electron Beam Accelerator Facility (CEBAF). Plans for a prototype test of the technique are underway, where the main issues are the possible photon backgrounds associated with an electron accelerator and the electron and laser beam stabilities and diagnostics. The bulk of my ASEE summer research has been spent utilizing the expertise of the staff at the Aerospace Electronics Systems Division at LaRC to assist in the design of the test. Investigations were made regarding window and mirror transmission and radiation damage issues, remote movement of elements in ultra-high vacuum conditions, etc. The prototype test of the proposed laser backscattering method is planned for this December.

Keppel, Cynthia

1995-01-01

82

Electron distributions in nonlinear Compton scattering  

E-print Network

Based on quantum theory, we investigate the distribution of the electrons scattered in nonlinear Compton effect by an electromagnetic plane wave. Deviations of the final electron momentum from its initial value are solely due to quantum effects. The monochromatic case, examined in detail, reveals features of the electron distribution, useful in the understanding of the pulsed plane wave case for particular intensity and electron energy regimes. The graphs displayed focus on the case of head-on or near head-on collision of an energetic electron with an electromagnetic circularly polarized pulsed plane wave and show that the deviation in direction is extremely small, while the distribution in energy can be visibly different from that of the initial electron. Two pulse shapes, several laser intensities and high incident electron energies are considered.

Madalina Boca; Victor Dinu; Viorica Florescu

2012-06-29

83

Compton scattering vertex for massive scalar QED  

SciTech Connect

We investigate the Compton scattering vertex of charged scalars and photons in scalar quantum electrodynamics (SQED). We carry out its nonperturbative construction consistent with Ward-Fradkin-Green-Takahashi identity which relates 3-point vertices to the 4-point ones. There is an undetermined part which is transverse to one or both the external photons, and needs to be evaluated through perturbation theory. We present in detail how the transverse part at the 1-loop order can be evaluated for completely general kinematics of momenta involved in covariant gauges and dimensions. This involves the calculation of genuine 4-point functions with three massive propagators, the most nontrivial integrals reported in this paper. We also discuss possible applications of our results.

Bashir, A.; Concha-Sanchez, Y. [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Apartado Postal 2-82, Morelia, Michoacan 58040 (Mexico); Delbourgo, R. [School of Mathematics and Physics, University of Tasmania, Private Bag 37 GPO, Hobart 7001 (Australia); Tejeda-Yeomans, M. E. [Departamento de Fisica, Universidad de Sonora, Apartado Postal 1626, Hermosillo, Sonora 83000 (Mexico)

2009-08-15

84

Neutron and proton interaction backgrounds in compton-telescopes used for gamma-ray astronomy  

Microsoft Academic Search

Gamma-ray background counting rates encountered in astronomy observations are calculated for a double Compton scatter telescope. Backgrounds not eliminated by the usual growth curve could be produced by albedo neutrons and\\/or cosmic ray protons interacting with the carbon and\\/or hydrogen of the detector. They are the albedo neutron-carbon interaction gamma-rays, cosmic ray proton interaction delayed gamma rays and the moderated

R. Stephen White; Volker Schönfelder

1975-01-01

85

Comptonization of gamma rays by cold electrons  

NASA Technical Reports Server (NTRS)

An analytic method is developed for calculating the emergent spectrum of gamma-rays and X-rays scattered in a homogeneous medium with low-temperature electrons. The Klein-Nishina corrections of the scattering cross section and absorption processes are taken in account. The wavelength relaxation and the spatial diffusion problems are solved separately, and the emergent spectrum is calculated by convolving the evolution function of the spectrum in an infinite medium with the photon luminosity resulting from the spatial diffusion in a finite sphere. The analytic results are compared with that of Monte Carlo calculations and it is concluded that the analytic result is quite accurate.

Xu, Yueming; Ross, Randy R.; Mccray, Richard

1991-01-01

86

A novel Compton camera design featuring a rear-panel shield for substantial noise reduction in gamma-ray images  

NASA Astrophysics Data System (ADS)

After the Japanese nuclear disaster in 2011, large amounts of radioactive isotopes were released and still remain a serious problem in Japan. Consequently, various gamma cameras are being developed to help identify radiation hotspots and ensure effective decontamination operation. The Compton camera utilizes the kinematics of Compton scattering to contract images without using a mechanical collimator, and features a wide field of view. For instance, we have developed a novel Compton camera that features a small size (13 × 14 × 15 cm3) and light weight (1.9 kg), but which also achieves high sensitivity thanks to Ce:GAGG scintillators optically coupled wiith MPPC arrays. By definition, in such a Compton camera, gamma rays are expected to scatter in the ``scatterer'' and then be fully absorbed in the ``absorber'' (in what is called a forward-scattered event). However, high energy gamma rays often interact with the detector in the opposite direction - initially scattered in the absorber and then absorbed in the scatterer - in what is called a ``back-scattered'' event. Any contamination of such back-scattered events is known to substantially degrade the quality of gamma-ray images, but determining the order of gamma-ray interaction based solely on energy deposits in the scatterer and absorber is quite difficult. For this reason, we propose a novel yet simple Compton camera design that includes a rear-panel shield (a few mm thick) consisting of W or Pb located just behind the scatterer. Since the energy of scattered gamma rays in back-scattered events is much lower than that in forward-scattered events, we can effectively discriminate and reduce back-scattered events to improve the signal-to-noise ratio in the images. This paper presents our detailed optimization of the rear-panel shield using Geant4 simulation, and describes a demonstration test using our Compton camera.

Nishiyama, T.; Kataoka, J.; Kishimoto, A.; Fujita, T.; Iwamoto, Y.; Taya, T.; Ohsuka, S.; Nakamura, S.; Hirayanagi, M.; Sakurai, N.; Adachi, S.; Uchiyama, T.

2014-12-01

87

Skewed parton distributions and real and virtual Compton scattering  

E-print Network

The soft physics approach to Compton scattering at moderately large momentum transfer is reviewed. It will be argued that in that approach the Compton cross section as well as other exclusive observables exhibit approximate scaling in a limited range of momentum transfer. Invited talk held at the workshop on exclusive and semi-exclusive processes at high momentum transfer, Jefferson Lab, May (1999).

Peter Kroll

1999-08-04

88

Electron-Positron Radiative Annihilation : Timelike Virtual Compton Scattering  

E-print Network

We report on a recent work proposing measurements of the deeply virtual Compton amplitude (DVCS) $\\gamma^* \\to h \\bar h \\gamma$ in the timelike kinematic domain which is accessible at electron-positron colliders via the radiative annihilation process $e^+ e^- \\to h \\bar h \\gamma$.

Asmita Mukherjee

2010-10-01

89

Polarizability relations across real and virtual Compton scattering processes  

E-print Network

We derive two relations involving spin polarizabilities of a spin-1/2 particle and consider their empirical implications for the proton. Using the empirical values of the proton anomalous magnetic moment, electric and magnetic charge radii, moments of the spin structure functions $g_1$, $g_2$, and of two spin polarizabilities, the present relations constrain the low-momentum behavior of generalized polarizabilities appearing in virtual Compton scattering. In the case of the proton, the dispersive model evaluations of the spin and generalized polarizabilities appear to be consistent with these relations. The ongoing measurements of different electromagnetic observables at the MAMI, Jefferson Lab, and HI$\\gamma$S facilities may be able to put these relations to a test, or use them to unravel the low-energy spin structure of the nucleon.

Vladimir Pascalutsa; Marc Vanderhaeghen

2014-11-26

90

Compton scattering of blackbody photons by relativistic electrons  

NASA Astrophysics Data System (ADS)

We present simple and accurate analytical formulas for the rates of Compton scattering by relativistic electrons integrated over the energy distribution of blackbody seed photons. Both anisotropic scattering, in which blackbody photons arriving from one direction are scattered by an anisotropic electron distribution into another direction, and scattering of isotropic seed photons are considered. Compton scattering by relativistic electrons off blackbody photons from either stars or cosmic microwave background takes place, in particular, in microquasars, colliding-wind binaries, supernova remnants, interstellar medium and the vicinity of the Sun.

Zdziarski, Andrzej A.; Pjanka, Patryk

2013-12-01

91

Inverse Compton Scattering in Mildly Relativistic Plasma  

NASA Technical Reports Server (NTRS)

We investigated the effect of inverse Compton scattering in mildly relativistic static and moving plasmas with low optical depth using Monte Carlo simulations, and calculated the Sunyaev-Zel'dovich effect in the cosmic background radiation. Our semi-analytic method is based on a separation of photon diffusion in frequency and real space. We use Monte Carlo simulation to derive the intensity and frequency of the scattered photons for a monochromatic incoming radiation. The outgoing spectrum is determined by integrating over the spectrum of the incoming radiation using the intensity to determine the correct weight. This method makes it possible to study the emerging radiation as a function of frequency and direction. As a first application we have studied the effects of finite optical depth and gas infall on the Sunyaev-Zel'dovich effect (not possible with the extended Kompaneets equation) and discuss the parameter range in which the Boltzmann equation and its expansions can be used. For high temperature clusters (k(sub B)T(sub e) greater than or approximately equal to 15 keV) relativistic corrections based on a fifth order expansion of the extended Kompaneets equation seriously underestimate the Sunyaev-Zel'dovich effect at high frequencies. The contribution from plasma infall is less important for reasonable velocities. We give a convenient analytical expression for the dependence of the cross-over frequency on temperature, optical depth, and gas infall speed. Optical depth effects are often more important than relativistic corrections, and should be taken into account for high-precision work, but are smaller than the typical kinematic effect from cluster radial velocities.

Molnar, S. M.; Birkinshaw, M.

1998-01-01

92

Application of artificial neural network in non-destructive Compton scattering densitometry  

NASA Astrophysics Data System (ADS)

This study investigates the use of artificial neural networks (ANN) in Compton scattering densitometry. Samples with different densities were irradiated by gamma rays and the spectra of photons, scattered at 90°, were recorded by a NaI scintillator. These data were used to train the network and to validate its performance. After various training functions with different structures of layers were examined, by comparing the ANN predicted results with the experimental ones, the best algorithm was adopted for the ANN.

Ashrafi, S.; Jahanbakhsh, O.; Alizadeh, D.

2014-10-01

93

Computations of Model Atmospheres with Account of Compton Scattering  

Microsoft Academic Search

In this paper we formulate new method designed for calculation of hot LTE model stellar atmospheres in hydrostatic and radiative equilibrium, which takes into account Compton scattering on free electrons according to the diffusion approximation. The equation of transfer at each frequency includes both temperature corrections and noncoherent scattering terms. Full set of transfer equations and the closing equation of

Jerzy Madej

1994-01-01

94

Origin of the intensity deficit in neutron Compton scattering  

SciTech Connect

Neutron Compton scattering measurements in a variety of materials have shown a relative deficit in the total signal from hydrogen compared to deuterium and heavier ions. We show here that a breakdown in the Born-Oppenheimer approximation in the final states of the scattering process leads to such a deficit and may be responsible for the effect.

Reiter, G.F.; Platzman, P.M. [Physics Department, University of Houston, Houston, Texas 77204-5506 (United States); Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974-0636 (United States)

2005-02-01

95

Monte Carlo study of multiple scatter effects in Compton scatter densitometry  

SciTech Connect

The contribution of multiple scatter to the measured signal in x- and gamma-ray Compton scatter densitometry has been investigated theoretically by the use of Monte Carlo techniques to follow individual photon life histories. A three component phantom was employed in the computer model to simulate the patient at three examination sites; the radius/ulna, the femoral neck, and the lumbar spine. Monoenergetic radiation beams of 60- and 100-keV photons and polyenergetic x-ray spectra of 100 and 140 kVp were used. Scattered events were detected over 360 degrees and classified according to their origin and frequency of scatter. The single scatter in bone to multiple scatter ratio was studied as an indication of the signal-to-noise ratio and this was found to vary with phantom size but was independent of photon energy. Correction factors to be used in a clinical densitometer to account for the inclusion of multiple scatter events were computed. These were found to be 0.65-0.58 at the optimum scattering angles for the phantoms considered.

Speller, R.D.; Horrocks, J.A.

1988-09-01

96

A Compton reflection model for the cosmic X-ray and gamma-ray backgrounds  

NASA Technical Reports Server (NTRS)

The gamma-ray spectrum of an AGN in the Compton reflection model is calculated and the contribution of such sources to the cosmic gamma-ray background is considered. The spectrum is composed of three parts: an X-ray power law, a broad hump from roughly 10 to 120 keV due to reprocessing of the power-law X-ray spectrum by cold gas, and gamma rays which are due to the inverse-Compton scattering of X-rays. The contribution of such sources to the cosmic gamma-ray background is computed and it is found that they provide an excellent fit to the entire background spectrum from 3 keV to 10 MeV. Constraints on the physical conditions in these sources are derived based on these results and the possibility of observing such sources with GRO is considered.

Rogers, R. D.; Field, G. B.

1991-01-01

97

Coded-aperture Compton camera for gamma-ray imaging  

NASA Astrophysics Data System (ADS)

This dissertation describes the development of a novel gamma-ray imaging system concept and presents results from Monte Carlo simulations of the new design. Current designs for large field-of-view gamma cameras suitable for homeland security applications implement either a coded aperture or a Compton scattering geometry to image a gamma-ray source. Both of these systems require large, expensive position-sensitive detectors in order to work effectively. By combining characteristics of both of these systems, a new design can be implemented that does not require such expensive detectors and that can be scaled down to a portable size. This new system has significant promise in homeland security, astronomy, botany and other fields, while future iterations may prove useful in medical imaging, other biological sciences and other areas, such as non-destructive testing. A proof-of-principle study of the new gamma-ray imaging system has been performed by Monte Carlo simulation. Various reconstruction methods have been explored and compared. General-Purpose Graphics-Processor-Unit (GPGPU) computation has also been incorporated. The resulting code is a primary design tool for exploring variables such as detector spacing, material selection and thickness and pixel geometry. The advancement of the system from a simple 1-dimensional simulation to a full 3-dimensional model is described. Methods of image reconstruction are discussed and results of simulations consisting of both a 4 x 4 and a 16 x 16 object space mesh have been presented. A discussion of the limitations and potential areas of further study is also presented.

Farber, Aaron M.

98

GammaCore: The Compton Observatory research environment  

NASA Technical Reports Server (NTRS)

The Compton Observatory Science Support Center (COSSC) is developing a coherent analysis environment for the analysis of Compton and other gamma-ray astronomy data. This environment, GammaCore, allows the astronomer to access the data analysis systems developed at the Principal Investigator (PI) sites for the four Compton Observatory instruments. In addition users have access to standard astronomical tools such as IRAF, IDL, and XANADU. The user interface of GammaCore is the AGCL (AnswerGarden Command Language), developed at the AXAF Science Center. The parameter interface supported by the AGCL allows GammaCore to access all PI software systems in a uniform fashion. These systems are quite different, having been developed independently on heterogeneous systems without much concern for general portability. The data kibitzer concept, where a window running in a specific PI environment is controlled by the AGCL, has been used extensively. Users can choose to view what is going on in the native environment, to use the window to control PI software directly, or to ignore the PI systems entirely and to work only through the homogeneous AGCL interface. Software developed at the COSSC is also integrated within GammaCore. Extensive facilities for conversions of PI data formats to and from FITS have been developed. Access to the Compton data archive and catalogs will also be completely integrated with the GammaCore. Users can retrieve any publicly available Compton data. This paper examines the issues that have arisen in attempting to meld these widely diverse systems. The advantages and limitations of the parameter interface and the kibitzer are discussed along with issues of data portability, documentation, and the feasibility of multi-instrument analysis. Limited capabilities are now available within GammaCore with significant enhancements planned over the coming year. An implementation including all PI systems will be available within that time. Instructions on how to access GammaCore and how to get more information are given.

Mcglynn, T. A.; Jennings, D. G.; Jordan, J. M.; Ruggiero, N.; Serlemitsos, T. A.

1992-01-01

99

Electron Trajectory Reconstruction for Advanced Compton Imaging of Gamma Rays  

NASA Astrophysics Data System (ADS)

Gamma-ray imaging is useful for detecting, characterizing, and localizing sources in a variety of fields, including nuclear physics, security, nuclear accident response, nuclear medicine, and astronomy. Compton imaging in particular provides sensitivity to weak sources and good angular resolution in a large field of view. However, the photon origin in a single event sequence is normally only limited to the surface of a cone. If the initial direction of the Compton-scattered electron can be measured, the cone can be reduced to a cone segment with width depending on the uncertainty in the direction measurement, providing a corresponding increase in imaging sensitivity. Measurement of the electron's initial direction in an efficient detection material requires very fine position resolution due to the electron's short range and tortuous path. A thick (650 mum), fully-depleted charge-coupled device (CCD) developed for infrared astronomy has 10.5-mum position resolution in two dimensions, enabling the initial trajectory measurement of electrons of energy as low as 100 keV. This is the first time the initial trajectories of electrons of such low energies have been measured in a solid material. In this work, the CCD's efficacy as a gamma-ray detector is demonstrated experimentally, using a reconstruction algorithm to measure the initial electron direction from the CCD track image. In addition, models of fast electron interaction physics, charge transport and readout were used to generate modeled tracks with known initial direction. These modeled tracks allowed the development and refinement of the reconstruction algorithm. The angular sensitivity of the reconstruction algorithm is evaluated extensively with models for tracks below 480 keV, showing a FWHM as low as 20° in the pixel plane, and 30° RMS sensitivity to the magnitude of the out-of-plane angle. The measurement of the trajectories of electrons with energies as low as 100 keV have the potential to make electron track Compton imaging an effective means of reducing image background for photons of energy as low as 500 keV, or even less. The angular sensitivity of the reconstruction algorithm was also evaluated experimentally, by measuring electron tracks in the CCD in coincidence with the scattered photon in a germanium double-sided strip detector. By this method, electron tracks could be measured with the true initial direction known to within 3° FWHM, and the angular response of the algorithm compared to the known direction. The challenge of this experiment lay in the low geometric efficiency for photons scattering into the germanium, the poor time resolution in the current CCD implementation, and the resulting signal-to-background ratio of about 10--4 for photons scattered from the CCD into the germanium detector. Nonetheless, 87 events were measured in the FWHM of the total energy deposited and the angular resolution measure, with electron tracks between 160 keV and 360 keV in energy. The electron tracks from true coincident event sequences showed a FWHM in the pixel plane of 23°, and excellent agreement with the distribution calculated with models, with likelihood p-values of 0.44 and 0.73. Thus, the models used for the more thorough evaluation of angular sensitivities are shown to be consistent with the measured tracks from true coincident event sequences.

Plimley, Brian Christopher

100

Proton polarizabilities from polarized Compton scattering: low-energy expansion  

E-print Network

We reexamine the low-energy expansion of polarized Compton scattering off the proton and show that the leading non-Born contribution to the beam asymmetry of low-energy Compton scattering is given by the magnetic polarizability alone, the electric polarizability cancels out. Based on this fact we propose to determine the magnetic dipole polarizability of the proton from the beam asymmetry. We also present the low-energy expansion of doubly-polarized observables, from which the spin polarizabilities can be extracted.

Nadiia Krupina

2014-05-06

101

The effects of Compton scattering in X-ray spectra  

NASA Technical Reports Server (NTRS)

The ways in which Compton scattering on free electrons influences the continuous spectrum and temperature structure of a hot stellar atmosphere, where most of its radiation is emitted in the 1-10 keV energy range, are discussed. The numerical results pertain to the continuum spectra of X-ray bursters. The formulation and development of the numerical code, which reproduces angle-averaged relativistic Compton scattering of thermal (unpolarized) X-rays in a plane-parallel atmosphere in hydrostatic and radiative equilibrium, are described.

Madej, Jerzy

1989-01-01

102

Compton scattered imaging based on the V-line radon transform and its medical imaging applications  

Microsoft Academic Search

The Radon transform (RT) on straight lines deals as mathematical foundation for many tomographic modalities (e.g. Xray scanner, Positron Emission Tomography), using only primary radiation. In this paper, we consider a new RT defined on a pair of half-lines forming a letter V, arising from the modeling a two-dimensional emission imaging process by Compton scattered gamma rays. We establish its

M. K. Nguyeny; R. Re?gnier; T. T. Truong; H. Zaidi

2010-01-01

103

Gamma-Ray Compton Profiles of Diamond, Silicon, and Germanium  

Microsoft Academic Search

160-keV gamma rays were used to measure the Compton profiles of diamond, silicon, and germanium single crystals in five crystallographic directions (, , , , and ). The data are analyzed so as to obtain the differences in the profiles in the various directions for each material. A direct comparison of the data is made with band calculations for Si

W. A. Reed; P. Eisenberger

1972-01-01

104

Thick silicon strip detector Compton imager  

Microsoft Academic Search

We present initial results obtained with double-sided, thick (2 mm) silicon strip detectors used as a Compton imager. A reconstructed image of a gamma ray source and a spectrum of the gamma ray energy are produced at room temperature using the multiple Compton technique. Multiple Compton interactions allow the energy and Compton scattering angle to be reconstructed without having to

Eric A. Wulf; B. F. Phlips; W. N. Johnson; J. D. Kurfess; E. I. Novikova

2003-01-01

105

Comptonization of diffuse ambient radiation by a relativistic jet: The source of gamma rays from blazars?  

NASA Technical Reports Server (NTRS)

Recent Energy Gamma Ray Experiment Telescope (EGRET) observations of blazars have revealed strong, variable gamma-ray fluxes with no signatures of gamma-ray absorption by pair production. This radiation probably originates from the inner parts of relativistic jets which are aimed nearly toward us. On sub-parsec scales, the jet will be pervaded by radiation from the broad-line region, as well as by photons from the central continuum source (some of which will be scattered by thermal plasma). In a frame moving with the relativistic outflow, the energy of this ambient radiation would be enhanced. This radiation would be Comptonized by both cold and relativistic electrons in the jet, yielding (in the observer's frame) a collimated beam of X-rays and gamma rays. On the assumption that this process dominates self-Comptonization of synchrotron radiation, we develop a self-consistent model for variable gamma-ray emission, involving a single population of relativistic electrons accelerated by a disturbance in the jet. The spectral break between the X-ray and gamma-ray band, observed in 3C 279 and deduced for other blazars, results from inefficient radiative cooling of lower energy electrons. The existence of such a break strongly favors a model involving Comptonization of an external radiation field over a synchrotron self-Compton model. We derive constraints on such model parameters as the location and speed of the source, its dimensions and internal physical parameters, the maximum photon energies produced in the source, and the density and distribution of ambient radiation. Finally, we discuss how observations might discriminate between our model and alternative ones invoking Comptonization of ambient radiation.

Sikora, Marek; Begelman, Mitchell C.; Rees, Martin J.

1994-01-01

106

Directional gamma sensing from covariance processing of inter-detector Compton crosstalk energy asymmetries  

SciTech Connect

Energy asymmetry of inter-detector crosstalk from Compton scattering can be exploited to infer the direction to a gamma source. A covariance approach extracts the correlated crosstalk from data streams to estimate matched signals from Compton gammas split over two detectors. On a covariance map the signal appears as an asymmetric cross diagonal band with axes intercepts at the full photo-peak energy of the original gamma. The asymmetry of the crosstalk band can be processed to determine the direction to the radiation source. The technique does not require detector shadowing, masking, or coded apertures, thus sensitivity is not sacrificed to obtain the directional information. An angular precision of better than 1° of arc is possible, and processing of data streams can be done in real time with very modest computing hardware.

Trainham, R., E-mail: trainhcp@nv.doe.gov; Tinsley, J. [Special Technologies Laboratory of National Security Technologies, LLC, 5520 Ekwill Street, Santa Barbara, California 93111 (United States)

2014-06-15

107

Directional gamma sensing from covariance processing of inter-detector Compton crosstalk energy asymmetries  

NASA Astrophysics Data System (ADS)

Energy asymmetry of inter-detector crosstalk from Compton scattering can be exploited to infer the direction to a gamma source. A covariance approach extracts the correlated crosstalk from data streams to estimate matched signals from Compton gammas split over two detectors. On a covariance map the signal appears as an asymmetric cross diagonal band with axes intercepts at the full photo-peak energy of the original gamma. The asymmetry of the crosstalk band can be processed to determine the direction to the radiation source. The technique does not require detector shadowing, masking, or coded apertures, thus sensitivity is not sacrificed to obtain the directional information. An angular precision of better than 1° of arc is possible, and processing of data streams can be done in real time with very modest computing hardware.

Trainham, R.; Tinsley, J.

2014-06-01

108

Directional gamma sensing from covariance processing of inter-detector Compton crosstalk energy asymmetries.  

PubMed

Energy asymmetry of inter-detector crosstalk from Compton scattering can be exploited to infer the direction to a gamma source. A covariance approach extracts the correlated crosstalk from data streams to estimate matched signals from Compton gammas split over two detectors. On a covariance map the signal appears as an asymmetric cross diagonal band with axes intercepts at the full photo-peak energy of the original gamma. The asymmetry of the crosstalk band can be processed to determine the direction to the radiation source. The technique does not require detector shadowing, masking, or coded apertures, thus sensitivity is not sacrificed to obtain the directional information. An angular precision of better than 1° of arc is possible, and processing of data streams can be done in real time with very modest computing hardware. PMID:24985816

Trainham, R; Tinsley, J

2014-06-01

109

Gamma-ray momentum reconstruction from Compton electron trajectories by filtered back-projection  

SciTech Connect

Gamma-ray imaging utilizing Compton scattering has traditionally relied on measuring coincident gamma-ray interactions to map directional information of the source distribution. This coincidence requirement makes it an inherently inefficient process. We present an approach to gamma-ray reconstruction from Compton scattering that requires only a single electron tracking detector, thus removing the coincidence requirement. From the Compton scattered electron momentum distribution, our algorithm analytically computes the incident photon's correlated direction and energy distributions. Because this method maps the source energy and location, it is useful in applications, where prior information about the source distribution is unknown. We demonstrate this method with electron tracks measured in a scientific Si charge coupled device. While this method was demonstrated with electron tracks in a Si-based detector, it is applicable to any detector that can measure electron direction and energy, or equivalently the electron momentum. For example, it can increase the sensitivity to obtain energy and direction in gas-based systems that suffer from limited efficiency.

Haefner, A., E-mail: ahaefner@berkeley.edu; Plimley, B.; Pavlovsky, R. [Department of Nuclear Engineering, University of California Berkeley, 4155 Etcheverry Hall, MC 1730, Berkeley, California 94720-1730 (United States); Gunter, D. [Applied Nuclear Physics, Lawrence Berkeley National Laboratory, 1 Cyclotron Road Berkeley, California 94720 (United States); Vetter, K. [Department of Nuclear Engineering, University of California Berkeley, 4155 Etcheverry Hall, MC 1730, Berkeley, California 94720-1730 (United States); Applied Nuclear Physics, Lawrence Berkeley National Laboratory, 1 Cyclotron Road Berkeley, California 94720 (United States)

2014-11-03

110

New JLab/Hall A Deeply Virtual Compton Scattering results  

E-print Network

New data points for unpolarized Deeply Virtual Compton Scattering cross sections have been extracted from the E00-110 experiment at Q$^2$=1.9 GeV$^2$ effectively doubling the statistics available in the valence region. A careful study of systematic uncertainties has been performed.

Maxime Defurne

2015-02-11

111

Proof of Factorization for Deeply Virtual Compton Scattering in QCD  

E-print Network

We show that factorization holds for the deeply virtual Compton scattering amplitude in QCD, up to power suppressed terms, to all orders in perturbation theory. Furthermore, we show that the virtuality of the produced photon does not influence the general theorem.

John C. Collins; Andreas Freund

1998-07-02

112

Compton scattering: From deeply virtual to quasi-real  

NASA Astrophysics Data System (ADS)

We address the question of interpolation of the virtual Compton scattering process off a polarized nucleon target between the deeply virtual regime for the initial-state photon and its near on-shell kinematics making use of the photon helicity-dependent Compton Form Factors (CFFs) as a main ingredient of the formalism. The five-fold differential cross section for the reaction with all possible polarization options for the lepton and nucleon spins is evaluated in terms of CFFs in the rest reference frame of the initial-state nucleon. We suggest a rather simple parametrization of the Compton hadronic tensor in terms of CFFs which are free from kinematical singularities and are directly related, at large photon virtualities, to generalized parton distributions. We also provide a relation of our basis spanned by a minimal number of Dirac bilinears to the one introduced by Tarrach for the parametrization of the virtual Compton tensor and utilize the former to establish a set of equalities among our CFFs and generalized polarizabilities. As a complementary result, we express Compton scattering in the Born approximation in terms of CFFs as well.

Belitsky, A. V.; Müller, D.; Ji, Y.

2014-01-01

113

An electromagnetic calorimeter for the JLab real compton scattering experiment  

Microsoft Academic Search

A lead–glass hodoscope calorimeter that was constructed for use in the Jefferson Lab Real Compton Scattering experiment is described. The detector provides a measurement of the coordinates and the energy of scattered photons in the GeV energy range with resolutions of 5mm and 6%\\/E?GeV. Features of both the detector design and its performance in the high luminosity environment during the

D. J. Hamilton; A. Shahinyan; B. Wojtsekhowski; J. R. M. Annand; T.-H. Chang; E. Chudakov; A. Danagoulian; P. Degtyarenko; K. Egiyan; R. Gilman; V. Gorbenko; J. Hines; E. Hovhannisyan; C. E. Hyde-Wright; C. W. de Jager; A. Ketikyan; V. H. Mamyan; R. Michaels; A. M. Nathan; V. Nelyubin; I. Rachek; M. Roedelbrom; A. Petrosyan; R. Pomatsalyuk; V. Popov; J. Segal; Y. Shestakov; J. Templon; H. Voskanyan

2011-01-01

114

Beam-shape effects in nonlinear Compton and Thomson scattering  

Microsoft Academic Search

We discuss intensity effects in collisions between beams of optical photons from a high-power laser and relativistic electrons. Our main focus is on the modifications of the emission spectra due to realistic finite-beam geometries. By carefully analyzing the classical limit we precisely quantify the distinction between strong-field QED Compton scattering and classical Thomson scattering. A purely classical, but fully covariant,

T. Heinzl; D. Seipt; B. Kämpfer

2010-01-01

115

Resonant Compton cooling and annihilation line production in gamma-ray bursts  

NASA Technical Reports Server (NTRS)

Attention is given to a synchrotron self-Compton emission model for gamma-ray bursts which produces narrow annihilation features for a variety of field strengths, primary electron injection energies, and injection rates. In this model, primary electrons are injected and cooled by synchrotron emission in a strong, homogeneous magnetic field, resulting in a pair cascade. Multiple resonant scattering with cyclotron photons efficiently traps and cools pairs in the ground state to an average energy where the Compton energy loss rate is zero, which is in agreement with previous estimates of a Compton temperature. The particle distributions in the ground state are determined by numerically solving the Fokker-Planck equation in the steady state. In the case of isotropic injection of primary electrons, a significant narrow-line feature appears in the overall emission. In the case of beamed injection, the annihilation line is broadened to the extent that it would not be observable.

Preece, R. D.; Harding, A. K.

1992-01-01

116

A low energy bound atomic electron Compton scattering model for Geant4  

NASA Astrophysics Data System (ADS)

A two-body fully relativistic three-dimensional scattering framework has been utilised to develop an alternative Compton scattering computational model to those adapted from Ribberfors' work for Monte Carlo modelling of Compton scattering. Using a theoretical foundation that ensures the conservation of energy and momentum in the relativistic impulse approximation, this new model, the Monash University Compton scattering model, develops energy and directional algorithms for both the scattered photon and ejected Compton electron from first principles. The Monash University Compton scattering model was developed to address the limitation of the Compton electron directionality algorithms of other computational models adapted from Ribberfors' work. Here the development of the Monash University Compton scattering model, including its implementation in a Geant4 low energy electromagnetic physics class, G4LowEPComptonModel, is outlined. Assessment of the performance of G4LowEPComptonModel was undertaken in two steps: (1) comparison with respect to the two standard Compton scattering classes of Geant4 version 9.5, G4LivermoreComptonModel and G4PenelopeComptonModel, and (2) experimental comparison with respect to Compton electron kinetic energy spectra obtained from the Compton scattering of 662 keV photons off the K-shell of gold. Both studies illustrate that the Monash University Compton scattering model, and in turn G4LowEPComptonModel, is a viable replacement for the majority of computational models that have been adapted from Ribberfors' work. It was also shown that the Monash University Compton scattering model is able to reproduce the Compton scattering triply differential cross-section Compton electron kinetic energy spectra of 662 keV photons K-shell scattering off of gold to within experimental uncertainty.

Brown, J. M. C.; Dimmock, M. R.; Gillam, J. E.; Paganin, D. M.

2014-11-01

117

Anomalous neutron Compton scattering cross sections in ammonium hexachlorometallates.  

PubMed

The authors have performed neutron Compton scattering measurements on ammonium hexachloropalladate (NH(4))(2)PdCl(6) and ammonium hexachlorotellurate (NH(4))(2)TeCl(6). Both substances belong to the family of ammonium metallates. The aim of the experiment was to investigate the possible role of electronic environment of a proton on the anomaly of the neutron scattering intensity. The quantity of interest that was subject to experimental test was the reduction factor of the neutron scattering intensities. In both samples, the reduction factor was found to be smaller than unity, thus indicating the anomalous neutron Compton scattering from protons. Interestingly, the anomaly decreases with decreasing scattering angle and disappears at the lowest scattering angle (longest scattering time). The dependence of the amount of the anomaly on the scattering angle (scattering time) is the same in both substances (within experimental error). Also, the measured widths of proton momentum distributions are equal in both metallates. This is consistent with the fact that the attosecond proton dynamics of ammonium cations is fairly well decoupled from the dynamics of the sublattice of the octahedral anions PdCl(6) (2-) and TeCl(6) (2-), respectively. The hypothesis is put forward that proton-electron decoherence processes are responsible for the considered effect. Decoherence processes may have to do rather with the direct electronic environment of ammonium protons and not with the electronic structure of the metal-chlorine bond. PMID:17411138

Krzystyniak, M; Chatzidimitriou-Dreismann, C A; Lerch, M; Lalowicz, Z T; Szymocha, A

2007-03-28

118

Measurements of Double-Polarized Compton Scattering Asymmetries and Extraction of the Proton Spin Polarizabilities  

E-print Network

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to measure the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the $\\Delta(1232)$ region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields $\\gamma_{E1E1} = -3.5 \\pm 1.2$, $\\gamma_{M1M1}= 3.16 \\pm 0.85$, $\\gamma_{E1M2} = -0.7 \\pm 1.2$, and $\\gamma_{M1E2} = 1.99 \\pm 0.29$, in units of $10^{-4}$ fm$^4$.

P. P. Martel; R. Miskimen; P. Aguar-Bartolome; J. Ahrens; C. S. Akondi; J. R. M. Annand; H. J. Arends; W. Barnes; R. Beck; A. Bernstein; N. Borisov; A. Braghieri; W. J. Briscoe; S. Cherepnya; C. Collicott; S. Costanza; A. Denig; M. Dieterle; E. J. Downie; L. V. Fil'kov; S. Garni; D. I. Glazier; W. Gradl; G. Gurevich; P. Hall Barrientos; D. Hamilton; D. Hornidge; D. Howdle; G. M. Huber; T. C. Jude; A. Kaeser; V. L. Kashevarov; I. Keshelashvili; R. Kondratiev; M. Korolija; B. Krusche; A. Lazarev; V. Lisin; K. Livingston; I. J. D. MacGregor; J. Mancell; D. M. Manley; W. Meyer; D. G. Middleton; A. Mushkarenkov; B. M. K. Nefkens; A. Neganov; A. Nikolaev; M. Oberle; H. Ortega Spina; M. Ostrick; P. Ott; P. B. Otte; B. Oussena; P. Pedroni; A. Polonski; V. Polyansky; S. Prakhov; A. Rajabi; G. Reicherz; T. Rostomyan; A. Sarty; S. Schrauf; S. Schumann; M. H. Sikora; A. Starostin; O. Steffen; I. I. Strakovsky; T. Strub; I. Supek; M. Thiel; L. Tiator; A. Thomas; M. Unverzagt; Y. Usov; D. P. Watts; L. Witthauer; D. Werthmüller; M. Wolfes

2015-03-20

119

Astrophysical applications of Delbrück scattering: Dust scattered gamma radiation from gamma ray bursts  

NASA Astrophysics Data System (ADS)

A preliminary, and perhaps the first, study of astrophysical applications of Delbrück scattering in a gamma-ray emitting celestial object like a gamma-ray burst (GRB) has been made. At energies?100 MeV the elastic scattering of gamma-ray photons off the molecular dust surrounding the GRB site is dominated by Delbrück scattering. Expressions for Delbrück-scattered gamma-ray flux as a function of time has been obtained for a few selected energies by assuming a simple model of GRB. These are compared with Compton-scattered flux. At certain situations, interestingly, the former is found to exceed the latter for the first few milliseconds of the burst. The issue of detectability of Delbrück-scattered gamma-ray echo from the cloud of a GRB is discussed. Although it is observed that the detection of such an echo is not within the capability of the presently operating gamma-ray missions such as Fermi LAT, a rough estimate shows that one can be optimistic that future generation gamma-ray telescopes might be able to see such photons' contribution to the total flux.

Kunwar, B.; Bhadra, A.; Gupta, S. K. Sen

2014-02-01

120

The cross section for double Compton scattering  

NASA Technical Reports Server (NTRS)

Employing elementary methods in nonrelativistic quantum electrodynamics, the cross section for gamma sub 0 + e yields e + gamma + gamma is computed for arbitrary energy in the spectrum of the outgoing photons. The final result is given, differential in the energy of one of these photons, for the case where the incident photon is unpolarized and has energy E sub 0 much less than mc-squared, a polarization sum and angular integration being performed for the final-state photons. The cross section has a simple algebraic form resulting from contributions from the sum of squared direct and exchange amplitudes; interference terms from these amplitudes do not contribute to the angular-integrated cross section.

Gould, R. J.

1984-01-01

121

Advanced Laser-Compton Gamma-Ray Sources for Nuclear Materials Detection, Assay and Imaging  

NASA Astrophysics Data System (ADS)

Highly-collimated, polarized, mono-energetic beams of tunable gamma-rays may be created via the optimized Compton scattering of pulsed lasers off of ultra-bright, relativistic electron beams. Above 2 MeV, the peak brilliance of such sources can exceed that of the world's largest synchrotrons by more than 15 orders of magnitude and can enable for the first time the efficient pursuit of nuclear science and applications with photon beams, i.e. Nuclear Photonics. Potential applications are numerous and include isotope-specific nuclear materials management, element-specific medical radiography and radiology, non-destructive, isotope-specific, material assay and imaging, precision spectroscopy of nuclear resonances and photon-induced fission. This review covers activities at the Lawrence Livermore National Laboratory related to the design and optimization of mono-energetic, laser-Compton gamma-ray systems and introduces isotope-specific nuclear materials detection and assay applications enabled by them.

Barty, C. P. J.

2015-10-01

122

MULTIPLE INVERSE COMPTON SCATTERINGS AND THE BLAZAR SEQUENCE  

SciTech Connect

The high frequency component in blazars is thought to be due to inverse Compton scattered radiation. Recent observations by Fermi-LAT are used to evaluate the details of the scattering process. A comparison is made between the usually assumed single scattering scenario and one in which multiple scatterings are energetically important. In the latter case, most of the radiation is emitted in the Klein-Nishina limit. It is argued that several of the observed correlations defining the blazar sequence are most easily understood in a multiple scattering scenario. Observations indicate also that, in such a scenario, the blazar sequence is primarily governed by the energy density of relativistic electrons rather than that of the seed photons. The pronounced X-ray minimum in the spectral energy distribution often observed in the most luminous blazars is discussed. It is shown how this feature can be accounted for in a multiple scattering scenario by an extension of standard one-zone models.

Bjoernsson, C.-I., E-mail: bjornsson@astro.su.s [Department of Astronomy, AlbaNova University Center, Stockholm University, SE-106 91 Stockholm (Sweden)

2010-11-01

123

Expected level of self-Compton scattering in radio loud quasars  

NASA Technical Reports Server (NTRS)

Radio-loud quasars usually contain parsec-scale nonthermal jets. The most compact emission region ('the core'), and perhaps some of the moving 'knots', are expected to be efficient producers of inverse Compton scattered X-rays and gamma-rays since many of the synchrotron photons will upscatter before escaping. Through multifrequency flux density observations and Very Long Baseline Interferometry (VLBI) measurements of angular sizes, one can predict the flux density of this self-Compton high-energy emission. It is not always the case that the brightest synchrotron sources are also the brightest X-ray and gamma-ray sources. Perhaps a better predictor of high-energy brightness is the ratio of hard X-ray to high-frequency radio emission. Using the synchrotron self-Compton relations, we predict the gamma-ray fluxes of several sources we expect to be detected by the Energetic Gamma Ray Experiment Telescope (EGRET). More accurate predictions will be made when we complete a program of contemporaneous radio-submillimeter and X-ray observations during the course of the EGRET all-sky survey.

Bloom, Steven D.; Marscher, Alan P.

1992-01-01

124

Noncommutative QED and $\\\\gamma\\\\gamma$ scattering  

Microsoft Academic Search

We study $\\\\gamma\\\\gamma$ scattering in noncommutative QED (NCQED) where the gauge field has Yang-Mills type coupling, giving new contributions to the scattering process and making it possible for it to occur at tree level. The process takes place at one loop level in the Standard Model (SM) and could be an important signal for physics beyond SM. But it is

Namit Mahajan

2001-01-01

125

On Timelike Compton Scattering at Medium and High Energies  

NASA Astrophysics Data System (ADS)

We emphasize the complementarity of timelike and spacelike studies of deep exclusive processes, taking as an example the case of timelike Compton scattering (TCS) i.e. the exclusive photoproduction of a lepton pair with large invariant mass, versus deeply virtual Compton scattering i.e. the exclusive leptoproduction of a real photon. Both amplitudes factorize with the same generalized parton distributions (GPDs) as their soft parts and coefficient functions which differ significantly at next to leading order in ? s . We also stress that data on TCS at very high energy should be available soon thanks to the study of ultraperipheral collisions at the LHC, opening a window on quark and gluon GPDs at very small skewness.

Pire, B.; Szymanowski, L.; Wagner, J.

2012-07-01

126

Measurement of Deeply Virtual Compton Scattering Beam-Spin Asymmetries  

Microsoft Academic Search

The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton (e-->p-->epgamma) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range (xB from 0.11 to 0.58, Q2 from 1 to 4.8GeV2, -t from 0.09

F. X. Girod; R. A. Niyazov; H. Avakian; J. Ball; I. Bedlinskiy; V. D. Burkert; R. de Masi; L. Elouadrhiri; M. Garçon; M. Guidal; H. S. Jo; K. Joo; V. Kubarovsky; S. V. Kuleshov; M. MacCormick; S. Niccolai; O. Pogorelko; F. Sabatié; S. Stepanyan; P. Stoler; M. Ungaro; B. Zhao; M. J. Amaryan; P. Ambrozewicz; M. Anghinolfi; G. Asryan; H. Bagdasaryan; N. Baillie; N. A. Baltzell; V. Batourine; M. Battaglieri; M. Bellis; N. Benmouna; B. L. Berman; A. S. Biselli; L. Blaszczyk; S. Bouchigny; S. Boiarinov; R. Bradford; D. Branford; W. K. Brooks; S. Bültmann; C. Butuceanu; J. R. Calarco; S. L. Careccia; D. S. Carman; L. Casey; S. Chen; L. Cheng; P. L. Cole; P. Collins; P. Coltharp; D. Crabb; V. Crede; N. Dashyan; E. de Sanctis; R. de Vita; P. V. Degtyarenko; A. Deur; K. V. Dharmawardane; R. Dickson; C. Djalali; G. E. Dodge; J. Donnelly; D. Doughty; M. Dugger; O. P. Dzyubak; H. Egiyan; K. S. Egiyan; L. El Fassi; P. Eugenio; G. Fedotov; G. Feldman; H. Funsten; G. Gavalian; G. P. Gilfoyle; K. L. Giovanetti; J. T. Goetz; A. Gonenc; R. W. Gothe; K. A. Griffioen; N. Guler; L. Guo; V. Gyurjyan; K. Hafidi; H. Hakobyan; C. Hanretty; F. W. Hersman; K. Hicks; I. Hleiqawi; M. Holtrop; C. E. Hyde; Y. Ilieva; D. G. Ireland; B. S. Ishkhanov; E. L. Isupov; M. M. Ito; D. Jenkins; J. R. Johnstone; H. G. Juengst; N. Kalantarians; J. D. Kellie; M. Khandaker; W. Kim; A. Klein; F. J. Klein; A. V. Klimenko; M. Kossov; Z. Krahn; L. H. Kramer; J. Kuhn; S. E. Kuhn; J. Lachniet; J. M. Laget; J. Langheinrich; D. Lawrence; T. Lee; K. Livingston; H. Y. Lu; N. Markov; P. Mattione; M. Mazouz; B. McKinnon; B. A. Mecking; M. D. Mestayer; C. A. Meyer; T. Mibe; B. Michel; K. Mikhailov; M. Mirazita; R. Miskimen; V. Mokeev; K. Moriya; S. A. Morrow; M. Moteabbed; E. Munevar; G. S. Mutchler; P. Nadel-Turonski; R. Nasseripour; G. Niculescu; I. Niculescu; B. B. Niczyporuk; M. R. Niroula; M. Nozar; M. Osipenko; A. I. Ostrovidov; E. Pasyuk; C. Paterson; S. Anefalos Pereira; J. Pierce; N. Pivnyuk; D. Pocanic; S. Pozdniakov; J. W. Price; S. Procureur; Y. Prok; D. Protopopescu; B. A. Raue; G. Ricco; M. Ripani; B. G. Ritchie; G. Rosner; P. Rossi; J. Salamanca; C. Salgado; J. P. Santoro; V. Sapunenko; R. A. Schumacher; V. S. Serov; Y. G. Sharabian; D. Sharov; N. V. Shvedunov; E. S. Smith; L. C. Smith; D. I. Sober; D. Sokhan; A. Stavinsky; B. E. Stokes; I. I. Strakovsky; S. Strauch; M. Taiuti; D. J. Tedeschi; A. Tkabladze; S. Tkachenko; C. Tur; M. F. Vineyard; A. V. Vlassov; E. Voutier; D. P. Watts; L. B. Weinstein; D. P. Weygand; M. Williams; E. Wolin; M. H. Wood; A. Yegneswaran; L. Zana; J. Zhang; Z. W. Zhao

2008-01-01

127

Deeply Virtual Compton Scattering at HERA - A Probe of Asymptotia  

E-print Network

We demonstrate that the measurement of an azimuthal angle asymmetry in deeply virtual Compton scattering (DVCS) at HERA energies, is experimentally feasible and allows one to determine for the first time the ratio $\\eta$, of the real to imaginary part of the DIS amplitude. We further show that such a measurement would discriminate between different scenarios of the energy dependence of $F_2(x,Q^2)$ at energies beyond those reachable at HERA.

L. Frankfurt; A. Freund; M. Strikman

1999-03-05

128

GAMMA-RAY POLARIZATION INDUCED BY COLD ELECTRONS VIA COMPTON PROCESSES  

SciTech Connect

The polarization measurement is an important tool to probe the prompt emission mechanism in gamma-ray bursts (GRBs). The synchrotron photons can be scattered by cold electrons in the outflow via Compton scattering (CS) processes. The observed polarization depends on both the photon energy and the viewing angle. With the typical bulk Lorentz factor {Gamma} {approx} 200, photons with energy E > 10 MeV tend to have smaller polarization than photons with energy E < 1 MeV. At the right viewing angle, i.e., {theta} {approx} {Gamma}{sup -1}, the polarization achieves its maximal value, and the polarization angle changes 90 Degree-Sign relative to the initial polarization direction. Thus, the synchrotron radiation plus CS model can naturally explain the 90 Degree-Sign change of the polarization angle in GRB 100826A.

Chang Zhe; Jiang Yunguo; Lin Hainan, E-mail: changz@ihep.ac.cn, E-mail: jiangyg@ihep.ac.cn, E-mail: linhn@ihep.ac.cn [Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China)

2013-05-20

129

High-Energy Scaling of Compton Scattering Sources  

NASA Astrophysics Data System (ADS)

No monochromatic, high-brightness, tunable light sources currently exist above 100 keV. Important applications that would benefit from such new hard x-ray sources include: nuclear resonance fluorescence spectroscopy, time-resolved positron annihilation spectroscopy, and MeV flash radiography. The peak brightness of Compton scattering light sources is derived for head-on collisions and found to scale with the electron beam brightness and the drive laser pulse energy. This ?^2-scaling shows that for low emittance electron beams (1 nC, 1 mm.mrad, < 1 ps, > 100 MeV), and tabletop laser systems (1-10 J, 5 ps) the x-ray peak brightness can exceed 10^23 photons / mm^2 x mrad^2 x s x 0.1% bandwidth near 1 MeV; this is confirmed by 3D codes that have been benchmarked against Compton scattering experiments performed at LLNL. Important nonlinear effects, including spectral broadening, are also taken into account in our analysis; they show that there is an optimum laser pulse duration in this geometry, of the order of a few picoseconds, in sharp contrast with the initial approach to laser-driven Compton scattering sources where femtosecond laser systems were thought to be mandatory. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Hartemann, Frederic

2005-10-01

130

Compton suppression gamma-counting: The effect of count rate  

USGS Publications Warehouse

Past research has shown that anti-coincidence shielded Ge(Li) spectrometers enhanced the signal-to-background ratios for gamma-photopeaks, which are situated on high Compton backgrounds. Ordinarily, an anti- or non-coincidence spectrum (A) and a coincidence spectrum (C) are collected simultaneously with these systems. To be useful in neutron activation analysis (NAA), the fractions of the photopeak counts routed to the two spectra must be constant from sample to sample to variations must be corrected quantitatively. Most Compton suppression counting has been done at low count rate, but in NAA applications, count rates may be much higher. To operate over the wider dynamic range, the effect of count rate on the ratio of the photopeak counts in the two spectra (A/C) was studied. It was found that as the count rate increases, A/C decreases for gammas not coincident with other gammas from the same decay. For gammas coincident with other gammas, A/C increases to a maximum and then decreases. These results suggest that calibration curves are required to correct photopeak areas so quantitative data can be obtained at higher count rates. ?? 1984.

Millard, H.T., Jr.

1984-01-01

131

COOLING RATES FOR RELATIVISTIC ELECTRONS UNDERGOING COMPTON SCATTERING IN STRONG MAGNETIC FIELDS  

SciTech Connect

For inner magnetospheric models of hard X-ray and gamma-ray emission in high-field pulsars and magnetars, resonant Compton upscattering is anticipated to be the most efficient process for generating continuum radiation. This is in part due to the proximity of a hot soft photon bath from the stellar surface to putative radiation dissipation regions in the inner magnetosphere. Moreover, because the scattering process becomes resonant at the cyclotron frequency, the effective cross section exceeds the classical Thomson value by over two orders of magnitude, thereby enhancing the efficiency of continuum production and the cooling of relativistic electrons. This paper presents computations of the electron cooling rates for this process, which are needed for resonant Compton models of non-thermal radiation from such highly magnetized pulsars. The computed rates extend previous calculations of magnetic Thomson cooling to the domain of relativistic quantum effects, sampled near and above the quantum critical magnetic field of 44.13 TG. This is the first exposition of fully relativistic, quantum magnetic Compton cooling rates for electrons, and it employs both the traditional Johnson and Lippmann cross section and a newer Sokolov and Ternov (ST) formulation of Compton scattering in strong magnetic fields. Such ST formalism is formally correct for treating spin-dependent effects that are important in the cyclotron resonance and has not been addressed before in the context of cooling by Compton scattering. The QED effects are observed to profoundly lower the rates below extrapolations of the familiar magnetic Thomson results, as expected, when recoil and Klein-Nishina reductions become important.

Baring, Matthew G.; Wadiasingh, Zorawar [Department of Physics and Astronomy, MS 108, Rice University, Houston, TX 77251 (United States); Gonthier, Peter L., E-mail: baring@rice.edu, E-mail: zw1@rice.edu, E-mail: gonthier@hope.edu [Department of Physics, Hope College, 27 Graves Place, Holland, MI 49423 (United States)

2011-05-20

132

Beam-charge azimuthal asymmetry and deeply virtual Compton scattering  

NASA Astrophysics Data System (ADS)

The first observation of an azimuthal cross section asymmetry with respect to the charge of the incoming lepton beam is reported from a study of hard exclusive electroproduction of real photons. The data have been accumulated by the HERMES experiment at DESY, in which the HERA 27.6 GeV electron or positron beam scattered off an unpolarized hydrogen gas target. The observed asymmetry is attributed to the interference between the Bethe-Heitler process and the deeply virtual Compton scattering (DVCS) process. The interference term is sensitive to DVCS amplitudes, which provide the most direct access to generalized parton distributions.

Airapetian, A.; Akopov, N.; Akopov, Z.; Amarian, M.; Andrus, A.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetissian, E.; Bailey, P.; Balin, D.; Beckmann, M.; Belostotski, S.; Bianchi, N.; Blok, H. P.; Böttcher, H.; Borissov, A.; Borysenko, A.; Bouwhuis, M.; Brüll, A.; Bryzgalov, V.; Capiluppi, M.; Capitani, G. P.; Chen, T.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; de Leo, R.; Demey, M.; de Nardo, L.; de Sanctis, E.; Devitsin, E.; di Nezza, P.; Dreschler, J.; Düren, M.; Ehrenfried, M.; Elalaoui-Moulay, A.; Elbakian, G.; Ellinghaus, F.; Elschenbroich, U.; Fabbri, R.; Fantoni, A.; Felawka, L.; Frullani, S.; Funel, A.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Garrow, K.; Gaskell, D.; Gavrilov, G.; Gharibyan, V.; Grebeniouk, O.; Gregor, I. M.; Hadjidakis, C.; Hafidi, K.; Hartig, M.; Hasch, D.; Hesselink, W. H. A.; Hillenbrand, A.; Hoek, M.; Holler, Y.; Hommez, B.; Hristova, I.; Iarygin, G.; Ivanilov, A.; Izotov, A.; Jackson, H. E.; Jgoun, A.; Kaiser, R.; Kinney, E.; Kisselev, A.; Kobayashi, T.; Kopytin, M.; Korotkov, V.; Kozlov, V.; Krauss, B.; Krivokhijine, V. G.; Lagamba, L.; Lapikás, L.; Laziev, A.; Lenisa, P.; Liebing, P.; Linden-Levy, L. A.; Lorenzon, W.; Lu, H.; Lu, J.; Lu, S.; Ma, B.-Q.; Maiheu, B.; Makins, N. C. R.; Mao, Y.; Marianski, B.; Marukyan, H.; Masoli, F.; Mexner, V.; Meyners, N.; Michler, T.; Mikloukho, O.; Miller, C. A.; Miyachi, Y.; Muccifora, V.; Murray, M.; Nagaitsev, A.; Nappi, E.; Naryshkin, Y.; Negodaev, M.; Nowak, W.-D.; Oganessyan, K.; Ohsuga, H.; Osborne, A.; Pickert, N.; Potterveld, D. H.; Raithel, M.; Reggiani, D.; Reimer, P. E.; Reischl, A.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Rubacek, L.; Rubin, J.; Ryckbosch, D.; Salomatin, Y.; Sanjiev, I.; Savin, I.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Seele, J.; Seidl, R.; Seitz, B.; Shanidze, R.; Shearer, C.; Shibata, T.-A.; Shutov, V.; Sinram, K.; Sommer, W.; Stancari, M.; Statera, M.; Steffens, E.; Steijger, J. J. M.; Stenzel, H.; Stewart, J.; Stinzing, F.; Tait, P.; Tanaka, H.; Taroian, S.; Tchuiko, B.; Terkulov, A.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; van der Nat, P. B.; van der Steenhoven, G.; van Haarlem, Y.; Vikhrov, V.; Vincter, M. G.; Vogel, C.; Volmer, J.; Wang, S.; Wendland, J.; Ye, Y.; Ye, Z.; Yen, S.; Zihlmann, B.; Zupranski, P.

2007-01-01

133

Testing Photons' Bose-Einstein Statistics With Compton Scattering  

E-print Network

It is an empirical question whether photons always obey Bose-Einstein statistics, but devising and interpreting experimental tests of photon statistics can be a challenge. The nonrelativistic cross section for Compton scattering illustrates how a small admixture nu of wrong-sign statistics leads to a loss of gauge invariance; there is a large anomalous amplitude for scattering timelike photons. Nevertheless, one can interpret the observed transparency of the solar wind plasma at low frequencies as a bound nu < 10^(-25) if Lorentz symmetry is required. If there is instead a universal preferred frame, the bound is nu < 10^(-14), still strong compared with previous results.

Brett Altschul

2010-08-27

134

Compton scattering from nuclei and photo-absorption sum rules  

NASA Astrophysics Data System (ADS)

We revisit the photo-absorption sum rule for real Compton scattering from the proton and from nuclear targets. In analogy with the Thomas-Reiche-Kuhn sum rule appropriate at low energies, we propose a new “constituent quark model” sum rule that relates the integrated strength of hadronic resonances to the scattering amplitude on constituent quarks. We study the constituent quark model sum rule for several nuclear targets. In addition, we extract the ?=0 pole contribution for both proton and nuclei. Using the modern high-energy proton data, we find that the ?=0 pole contribution differs significantly from the Thomson term, in contrast with the original findings by Damashek and Gilman.

Gorchtein, Mikhail; Hobbs, Timothy; Londergan, J. Timothy; Szczepaniak, Adam P.

2011-12-01

135

Polarisation Transfer in Proton Compton Scattering at High Momentum Transfer  

SciTech Connect

The Jefferson Lab Hall A experiment E99-114 comprised a series of measurements to explore proton Compton scattering at high momentum transfer. For the first time, the polarisation transfer observables in the p (~ 0 ~ p) reaction were measured in the GeV energy range, where it is believed that quark-gluon degrees of freedom begin to dominate. The experiment utilised a circularly polarised photon beam incident on a liquid hydrogen target, with the scattered photon and recoil proton detected in a lead-glass calorimeter and a magnetic spectrometer, respectively.

David Hamilton

2004-12-31

136

Nonlinear Compton scattering in ultrashort laser pulses  

SciTech Connect

A detailed analysis of the photon emission spectra of an electron scattered by a laser pulse containing only very few cycles of the carrying electromagnetic field is presented. The analysis is performed in the framework of strong-field quantum electrodynamics, with the laser field taken into account exactly in the calculations. We consider different emission regimes depending on the laser intensity, placing special emphasis on the regime of one-cycle beams and of high laser intensities, where the emission spectra depend nonperturbatively on the laser intensity. In this regime, we, in particular, present an accurate stationary phase analysis of the integrals that are shown to determine the computed emission spectra. The emission spectra show significant differences with respect to those in a long pulsed or monochromatic laser field: The emission lines obtained here are much broader, and more important, no dressing of the electron mass is observed.

Mackenroth, F.; Di Piazza, A. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

2011-03-15

137

500 MW X-BAND RF SYSTEM OF A 0.25 GEV ELECTRON LINAC FOR ADVANCED COMPTON SCATTERING SOURCE APPLICATION  

Microsoft Academic Search

A Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering light source is being developed at LLNL in collaboration with SLAC National Accelerator Laboratory. The electron beam for the Compton scattering interaction will be generated by a X-band RF gun and a X-band LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the electrons

T S Chu; S G Anderson; D J Gibson; F V Hartemann; R A Marsh; C Siders; C P Barty; C Adolphsen; E Jongewaard; S Tantawi; A Vlieks; J W Wang; T Raubenheimer

2010-01-01

138

500 MW X-Band RF System of a 0.25 GeV Electron LINAC for Advanced Compton Scattering Source Application  

Microsoft Academic Search

A Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering light source is being developed at LLNL in collaboration with the SLAC National Accelerator Laboratory. The electron beam for the Compton scattering interaction will be generated by a X-band RF gun and a X-band LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the

2012-01-01

139

Magnetic Compton-induced pair cascade model for gamma-ray pulsars  

NASA Technical Reports Server (NTRS)

Electrons accelerated to relativistic energies in pulsar magnetospheres will Compton scatter surface thermal emission and nonthermal optical, UV, and soft X-ray emission to gamma-ray energies, thereby initiating a pair cascade through synchrotron radiation and magnetic pair production. This process is proposed as the origin of the high-energy radiation that has been detected from six isolated pulsars. We construct an analytic model of magnetic Compton scattering near the polar cap of isolated pulsar magnetospheres and present approximate analytic derivations for scattered spectra, electron energy-loss rates, and photon luminosities. A Monte Carlo simulation is used to model the pair cascade induced by relativistic electrons scattering photons through the cyclotron resonance. For simplicity, the primary electrons are assumed to be monoenergetic and the nonresonant emission is omitted. Assuming that the angle phi(sub B) between the magnetic and spin axes is approximately equal to the polar-cap angle theta(sub pc), this model can produce both double-peaked and broad single-peaked pulse profiles and account for the trend of harder gamma-ray spectra observed from older pulsars.

Sturner, Steven J.; Dermer, Charles D.; Michel, F. Curtis

1995-01-01

140

Energy Calibration of Gamma Spectra in Plastic Scintillators using Compton Kinematics  

SciTech Connect

This paper describes a simple and practicable method for assigning energy values to gamma-ray pulse-height distributions measured with polyvinyl toluene based detectors. It is based upon the characteristic shape of the spectrum in the region of maximum energy deposition resulting from a single Compton scattering. The validity of this method is first demonstrated by applying it to a set of NaI(Tl) spectra, and comparing those results to the standard photo-peak method of calibrating the same spectra. The method is then applied to a set of polyvinyl toluene derived spectra.

Siciliano, Edward R.; Ely, James H.; Kouzes, Richard T.; Schweppe, John E.; Strachan, Denis M.; Yokuda, Satoru T.

2008-09-01

141

From hard exclusive meson electroproduction to deeply virtual Compton scattering  

E-print Network

We systematically evaluate observables for hard exclusive electroproduction of real photons and compare them to experiment using a set of Generalized Parton Distributions (GPDs) whose parameters are constrained by Deeply Virtual Meson Production data, nucleon form factors and parton distributions. The Deeply Virtual Compton Scattering amplitudes are calculated to leading-twist accuracy and leading order in QCD perturbation theory while the leptonic tensor is treated exactly, without any approximation. This study constitutes a check of the universality of the GPDs. We summarize all relevant details on the parametrizations of the GPDs and describe its use in the handbag approach of the aforementioned hard scattering processes. We observe a good agreement between predictions and measurements of deeply virtual Compton scattering on a wide kinematic range, including most data from H1, ZEUS, HERMES, Hall A and CLAS collaborations for unpolarized and polarized targets when available. We also give predictions relevant for future experiments at COMPASS and JLab after the 12 GeV upgrade.

Peter Kroll; Hervé Moutarde; Franck Sabatié

2013-04-23

142

THE VERY HIGH ENERGY EMISSION FROM PULSARS: A CASE FOR INVERSE COMPTON SCATTERING  

SciTech Connect

The observations of gamma-ray emission from pulsars with the Fermi-LAT detector and the detection of the Crab pulsar with the VERITAS array of Cherenkov telescopes at energies above 100 GeV make it unlikely that curvature radiation is the main source of photons above GeV energies in the Crab and many other pulsars. We outline a model in which the broad UV-X-ray component and the very high energy {gamma}-ray emission of pulsars are explained within the synchrotron self-Compton framework. We argue that the bulk of the observed radiation is generated by the secondary plasma, which is produced in cascades in the outer gaps of the magnetosphere. We find that the inverse Compton (IC) scattering occurs in the Klein-Nishina regime, which favors synchrotron photons in the UV band as target field for the scattering process. The primary beam is accelerated in a modest electric field, with a field strength that is of the order of a few percent of the magnetic field near the light cylinder. Overall, for IC scattering occurring in the Klein-Nishina regime, the particle distribution in the gap does not evolve toward a stationary distribution and thus is intrinsically time-dependent. We point out that in a radiation reaction-limited regime of particle acceleration the gamma-ray luminosity L{sub {gamma}} scales linearly with the pulsar spin-down power E-dot , L{sub {gamma}}{proportional_to} E-dot , and not proportional to {radical}( E-dot ) as expected from potential-limited acceleration.

Lyutikov, Maxim [Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907-2036 (United States); Otte, Nepomuk [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95060 (United States); McCann, Andrew [Department of Physics, McGill University, Montreal, QC, H3A 2T8 (Canada)

2012-07-20

143

Studies on Compton scattering of the Fe-C, Fe-Cu and Ni-Cu binary powder mixtures.  

PubMed

Nowadays the Compton scattering is widely applied in various fields. In the present paper, we explore the Compton scattering effects on the binary powder mixture scatterers. By using the Compton scattering theory, we obtain an approximate linear relationship between the scattered photon counts and the contents of the binary powder mixture scatterer. This relationship has been confirmed by conducting the Compton scattering experiments of the binary powder mixture series such as the Fe-C, Fe-Cu and Ni-Cu scatterers. Moreover, we make a discussion on the experimental errors. The Compton scattering method is helpful for measuring the contents of the binary powder mixtures. PMID:23774322

Luo, Guang; Hu, Xianquan

2013-09-01

144

Interpretation of a ?-Compton densitometer response from multi-scattered photons  

NASA Astrophysics Data System (ADS)

A detailed Monte Carlo simulation of the gamma Compton scattering process was performed in order to better understand the global phenomena and to improve the interpretation of a ?-Compton densitometer's response. The experimental set up consists of a mono-energetic gamma ray source (137Cs), a BGO detector (sensitive volume of 3" x 3"), a set of pieces of lead (shielding), a standard electronic signal chain for the energy spectrum acquisition and a material under study (Portland Concrete). The Monte Carlo code, PENELOPE 2008, was modified to obtain additional information, about the "detected" photons, that can be useful to understand the relevance of the number of Compton interactions for each primary photon, and so better interpret the count rate and the shape of the acquired spectrum. It is shown that all this new information added to the total energy spectrum can help not only to determine the bulk density of concrete but also it can help to identify non-homogeneous zones, with very low density in comparison to the concrete density, like cavities, pipes, etc.

Pino, F.; Barros, H.; Sajo-Bohus, L.; Palacios, D.

2012-02-01

145

Transition-radiation-Compton-scattering detector for very relativistic nuclei  

NASA Technical Reports Server (NTRS)

The paper presents the design and predicted performance of a large acceptance (2 sq m sr) transition-radiation-Compton-scattering detector system which can be used to measure energy spectra up to several thousand Gev/nucleon for nuclei with Z between 6 and 28, as well as up to 40,000 GeV/nucleon for He. The following circumstances made such a detector system practicable: (1) transition radiation output is proportional to the square of particle charge; (2) output varies at least as rapidly as the square of Lorentz factor over the range from several hundred to several thousand.

Osborne, W. Z.; Mack, J. E.

1975-01-01

146

Magnetic properties of Ga doped cobalt ferrite: Compton scattering study  

SciTech Connect

We present the spin momentum density of Ga doped CoFe{sub 2}O{sub 4} at 100 K using magnetic Compton scattering. The measurement has been performed using circularly polarized synchrotron radiations of 182.65 keV at SPring8, Japan. The experimental profile is decomposed into its constituent profile to determine the spin moment at individual sites. Co atom has the maximum contribution (about 58%) in the total spin moment of the doped CoFe{sub 2}O{sub 4}.

Sharma, Arvind, E-mail: arvind.phd.swm@gmail.com; Mund, H. S.; Ahuja, B. L. [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur-313001 (India); Sahariya, Jagrati [Department of Physics, Manipal University, Jaipur-303007 (India); Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute, SPring8, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan)

2014-04-24

147

Polarization Transfer in Proton Compton Scattering at High Momentum Transfer  

SciTech Connect

Compton scattering from the proton was investigated at s=6.9 GeV{sup 2} and t=-4.0 GeV{sup 2} via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in disagreement with a prediction of perturbative QCD based on a two-gluon exchange mechanism, but agree well with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton.

Hamilton, D.J.; Annand, J.R.M. [University of Glasgow, Glasgow G12 8QQ (United Kingdom); Mamyan, V.H. [Yerevan Physics Institute, Yerevan 375036 (Armenia); Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Aniol, K.A.; Margaziotis, D.J. [California State University Los Angeles, Los Angeles, California 90032 (United States); Bertin, P.Y.; Camsonne, A.; Laveissiere, G. [Universite Blaise Pascal/IN2P3, F-63177 Aubiere (France); Bimbot, L. [IPN, Orsay B.P. no. 1 F-91406, Orsay (France); Bosted, P.; Paschke, K. [University of Massachusetts, Amherst, Massachusetts 01003 (United States); Calarco, J.R. [University of New Hampshire, Durham, New Hampshire 03824 (United States); Chang, G.C.; Horn, T.; Savvinov, N. [University of Maryland, College Park, Maryland 20742 (United States); Chang, T.-H.; Danagoulian, A.; Nathan, A.M.; Roedelbronn, M. [University of Illinois, Urbana-Champaign, Illinois 61801 (United States); Chen, J.-P. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)] [and others

2005-06-24

148

Quantum Radiation Reaction Effects in Multiphoton Compton Scattering  

SciTech Connect

Radiation reaction effects in the interaction of an electron and a strong laser field are investigated in the realm of quantum electrodynamics. We identify the quantum radiation reaction with the multiple photon recoils experienced by the laser-driven electron due to consecutive incoherent photon emissions. After determining a quantum radiation dominated regime, we demonstrate how in this regime quantum signatures of the radiation reaction strongly affect multiphoton Compton scattering spectra and that they could be measurable in principle with presently available laser technology.

Di Piazza, A.; Hatsagortsyan, K. Z.; Keitel, C. H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

2010-11-26

149

Calibration and performance of the UCR double Compton gamma ray telescope  

SciTech Connect

Results of the field calibration and performance of the UCR double Compton gamma-ray telescope are presented. The telescope is a balloon-borne instrument with an upper array of 16 plastic scintillator bars and a lower one of 16 NaI({ital Tl}) bars. The telescope is sensitive to celestial gamma-rays from 1 to 30 MeV. The data were collected on Feb. 14, 1988 prior to the launch in Alice Springs, Australia to observe SN 1987A. Radioactive sources were used to calibrate the energy deposits in the scintillators. Each bar was analyzed laterally using pulse height or timing to obtain the positions of the gamma-ray interactions. Double scatter events from a {sup 24}Na source simulating a celestial source were studied to obtain the general performance of the telescope and to develop imaging techniques, later used with the flight data.

Ait-Ouamer, F.; Kerrick, A.D.; Sarmouk, A.; O'Neill, T.J.; Sweeney, W.E.; Tumer, O.T.; Zych, A.D.; White, R.S. (California Univ., Riverside, CA (USA). Inst. of Geophysics and Planetary Physics)

1990-04-01

150

Techniques and Applications of Compton Imaging for Position-Sensitive Gamma-Ray Detectors  

E-print Network

Techniques and Applications of Compton Imaging for Position-Sensitive Gamma-Ray Detectors by Weiyi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv CHAPTER I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Gamma-Ray . . . . . . . . . . . . . . . 73 6.3 Directional Isotope Identification . . . . . . . . . . . . . . . . 76 6.4 Image Shielded

He, Zhong

151

Compton Scattering and Photo-absorption Sum Rules on Nuclei  

NASA Astrophysics Data System (ADS)

We revisit the photo-absorption sum rule for real Compton scattering from the proton and from nuclear targets. In analogy with the Thomas-Reiche-Kuhn sum rule appropriate at low energies, we propose a new ``constituent quark model'' sum rule that relates the integrated strength of hadronic resonances to the scattering amplitude on constituent quarks. We study the constituent quark model sum rule for several nuclear targets. In addition we extract the J=0 pole contribution for both proton and nuclei. Using the modern high energy proton data we find that the J=0 pole contribution differs significantly from the Thomson term, in contrast with the original findings by Damashek and Gilman. We discuss phenomenological implications of this new result.

Gorshteyn, Mikhail; Hobbs, Timothy; Londergan, J. Timothy; Szczepaniak, Adam P.

2012-03-01

152

Laser pulse-shape dependence of Compton scattering  

E-print Network

Compton scattering of short and ultra short (sub-cycle) laser pulses off mildly relativistic electrons is considered within a QED framework. The temporal shape of the pulse is essential for the differential cross section as a function of the energy of the scattered photon at fixed observation angle. The partly integrated cross section is sensitive to the non-linear dynamics resulting in a large enhancement of the cross section for short and, in particular, for ultra-short flat-top pulse envelopes which can reach several orders of magnitude, as compared with the case of a long pulse. Such effects can be studied experimentally and must be taken into account in Monte-Carlo/transport simulations of %$e^+e^-$ pair production in the interaction of electrons and photons in a strong laser field.

Alexander I. Titov; Burkhard Kampfer; Takuya Shibata; Atsushi Hosaka; Hideaki Takabe

2014-08-05

153

Laser pulse-shape dependence of Compton scattering  

NASA Astrophysics Data System (ADS)

Compton scattering of short and ultra short (sub-cycle) laser pulses off mildly relativistic electrons is considered within a QED framework. The temporal shape of the pulse is essential for the differential cross section as a function of the energy of the scattered photon at fixed observation angle. The partly integrated cross section is sensitive to the non-linear dynamics resulting in a large enhancement of the cross section for short and, in particular, for ultra-short flat-top pulse envelopes which can reach several orders of magnitude, as compared with the case of a long pulse. Such effects can be studied experimentally and must be taken into account in Monte-Carlo transport simulations of the interaction of electrons and photons in a strong laser field.

Titov, Alexander I.; Kämpfer, Burkhard; Shibata, Takuya; Hosaka, Atsushi; Takabe, Hideaki

2014-10-01

154

Resonant Cyclotron Scattering and Comptonization in Neutron Star Magnetospheres  

E-print Network

Resonant cyclotron scattering of the surface radiation in the magnetospheres of neutron stars may considerably modify the emergent spectra and impede efforts to constraint neutron star properties. Resonant cyclotron scattering by a non-relativistic warm plasma in an inhomogeneous magnetic field has a number of unusual characteristics: (i) in the limit of high resonant optical depth, the cyclotron resonant layer is half opaque, in sharp contrast to the case of non-resonant scattering. (ii) The transmitted flux is on average Compton up-scattered by ~ $1+ 2 beta_T$, where $\\beta_T$ is the typical thermal velocity in units of the velocity of light; the reflected flux has on average the initial frequency. (iii) For both the transmitted and reflected fluxes the dispersion of intensity decreases with increasing optical depth. (iv) The emergent spectrum is appreciably non-Plankian while narrow spectral features produced at the surface may be erased. We derive semi-analytically modification of the surface Plankian emission due to multiple scattering between the resonant layers and apply the model to anomalous X-ray pulsar 1E 1048.1--5937. Our simple model fits just as well as the ``canonical'' magnetar spectra model of a blackbody plus power-law.

Maxim Lyutikov; Fotis P. Gavriil

2006-02-10

155

Observation of the Higgs Boson of strong interaction via Compton scattering by the nucleon  

E-print Network

It is shown that the Quark-Level Linear $\\sigma$ Model (QLL$\\sigma$M) leads to a prediction for the diamagnetic term of the polarizabilities of the nucleon which is in excellent agreement with the experimental data. The bare mass of the $\\sigma$ meson is predicted to be $m_\\sigma=666$ MeV and the two-photon width $\\Gamma(\\sigma\\to\\gamma\\gamma)=(2.6\\pm 0.3)$ keV. It is argued that the mass predicted by the QLL$\\sigma$M corresponds to the $\\gamma\\gamma\\to\\sigma\\to NN$ reaction, i.e. to a $t$-channel pole of the $\\gamma N\\to N\\gamma$ reaction. Large -angle Compton scattering experiments revealing effects of the $\\sigma$ meson in the differential cross section are discussed. Arguments are presented that these findings may be understood as an observation of the Higgs boson of strong interaction while being part of the constituent quark.

Martin Schumacher

2010-03-15

156

The very-high energy emission from pulsars: a case for inverse Compton scattering  

E-print Network

The observations of gamma-ray emission from pulsars with the Fermi-LAT detector and the detection of the Crab pulsar with the VERITAS array of Cherenkov telescopes at energies above 100 GeV make it unlikely that curvature radiation is the main source of photons above GeV energies in the Crab and many other pulsars. We outline a model in which the broad UV-X-ray component and the very high energy \\gamma-ray emission of pulsars are explained within the Synchrotron-Self-Compton (SSC) framework. We argue that the bulk of the observed radiation is generated by the secondary plasma, which is produced in cascades in the outer gaps of the magnetosphere. We find that the inverse-Compton (IC) scattering occurs in the Klein-Nishina regime, which favors synchrotron photons in the UV band as target field for the scattering process. The primary beam is accelerated in a modest electric field, with a field strength that is of the order of a few percent of the magnetic field near the light cylinder. Overall, in the Klein-Nish...

Lyutikov, Maxim; McCann, Andrew

2011-01-01

157

Graud Laveissire Trento, Italy, April 2003 LPC Clermont-Ferrand Virtual Compton Scattering  

E-print Network

Géraud Laveissière Trento, Italy, April 2003 LPC Clermont-Ferrand Virtual Compton Scattering Relations formalism Compton Scattering from low to high momentum transfer Trento, Italy, April 2003 #12;k k(e,e'p) Géraud Laveissière Trento, Italy, April 2003 LPC Clermont-Ferrand #12; N pp Proton Generalized

Boyer, Edmond

158

Observations of GRB 990123 by the Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

GRB 990123 was the first burst from which simultaneous optical, X-ray, and gamma-ray emission was detected; its afterglow has been followed by an extensive set of radio, optical, and X-ray observations. We have studied the gamma-ray burst itself as observed by the Compton Gamma Ray Observatory detectors. We find that gamma-ray fluxes are not correlated with the simultaneous optical observations and that the gamma-ray spectra cannot be extrapolated simply to the optical fluxes. The burst is well fitted by the standard four-parameter GRB function, with the exception that excess emission compared with this function is observed below approx. 15 keV during some time intervals. The burst is characterized by the typical hard-to-soft and hardness-intensity correlation spectral evolution patterns. The energy of the peak of the vf (sub v), spectrum, E (sub p), reaches an unusually high value during the first intensity spike, 1470 plus or minus 110 keV, and then falls to approx. 300 keV during the tail of the burst. The high-energy spectrum above approx. 1 MeV is consistent with a power law with a photon index of about -3. By fluence, GRB 990123 is brighter than all but 0.4% of the GRBs observed with BATSE (Burst and Transient Source Experiment), clearly placing it on the -3/2 power-law portion of the intensity distribution. However, the redshift measured for the afterglow is inconsistent with the Euclidean interpretation of the -3/2 power law. Using the redshift value of greater than or equal to 1.61 and assuming isotropic emission, the gamma-ray energy exceeds 10 (exp 54) ergs.

Briggs, M. S.; Band, D. L.; Kippen, R. M.; Preece, R. D.; Kouveliotou, C.; vanParadijs, J.; Share, G. H.; Murphy, R. J.; Matz, S. M.; Connors, A.

1999-01-01

159

Virtual Compton scattering and neutral pion electroproduction in the resonance region up to the deep inelastic region at backward angles  

Microsoft Academic Search

We have made the first measurements of the virtual Compton scattering (VCS) process via the H(e, e'p)gamma exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the W-dependence at fixed Q2=1GeV2 and for the Q2 dependence at fixed W near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions.

G. Laveissière; Natalie Degrande; Stephanie Jaminion; Christophe Jutier; Luminita Todor; Rachele Di Salvo; L. Van Hoorebeke; L. C. Alexa; Brian Anderson; Konrad Aniol; Kathleen Arundell; Gerard Audit; Leonard Auerbach; F. T. Baker; Maud Baylac; J. Berthot; Pierre Bertin; William Bertozzi; Louis Bimbot; Werner Boeglin; Edward Brash; Vincent Breton; Herbert Breuer; Etienne Burtin; John Calarco; Lawrence Cardman; Christian Cavata; C.-C. Chang; J.-P. Chen; E. Chudakov; E. Cisbani; D. S. Dale; C. W. de Jager; R. de Leo; A. Deur; N. D'Hose; G. E. Dodge; J. J. Domingo; L. Elouadrhiri; M. B. Epstein; L. A. Ewell; J. M. Finn; K. G. Fissum; H. Fonvieille; G. Fournier; B. Frois; S. Frullani; C. Furget; H. Gao; J. Gao; F. Garibaldi; A. Gasparian; S. Gilad; R. Gilman; A. Glamazdin; C. Glashausser; J. Gomez; V. Gorbenko; P. Grenier; P. A. M. Guichon; J. O. Hansen; R. Holmes; M. Holtrop; C. Howell; G. M. Huber; C. E. Hyde; S. Incerti; M. Iodice; J. Jardillier; M. K. Jones; W. Kahl; S. Kamalov; S. Kato; A. T. Katramatou; J. J. Kelly; S. Kerhoas; A. Ketikyan; M. Khayat; K. Kino; S. Kox; L. H. Kramer; K. S. Kumar; G. Kumbartzki; M. Kuss; A. Leone; J. J. Lerose; M. Liang; R. A. Lindgren; N. Liyanage; G. J. Lolos; R. W. Lourie; R. Madey; K. Maeda; S. Malov; D. M. Manley; C. Marchand; D. Marchand; D. J. Margaziotis; P. Markowitz; J. Marroncle; J. Martino; K. McCormick; J. McIntyre; S. Mehrabyan; F. Merchez; Z. E. Meziani; R. Michaels; G. W. Miller; J. Y. Mougey; S. K. Nanda; D. Neyret; E. A. J. M. Offermann; Z. Papandreou; C. F. Perdrisat; R. Perrino; G. G. Petratos; S. Platchkov; R. Pomatsalyuk; D. L. Prout; V. A. Punjabi; T. Pussieux; G. Quémenér; R. D. Ransome; O. Ravel; J. S. Real; F. Renard; Y. Roblin; D. Rowntree; G. Rutledge; P. M. Rutt; A. Saha; T. Saito; A. J. Sarty; A. Serdarevic; T. Smith; G. Smirnov; K. Soldi; P. Sorokin; P. A. Souder; R. Suleiman; J. A. Templon; T. Terasawa; L. Tiator; R. Tieulent; E. Tomasi-Gustaffson; H. Tsubota; H. Ueno; P. E. Ulmer; G. M. Urciuoli; R. Van de Vyver; P. Vernin; B. Vlahovic; H. Voskanyan; E. Voutier; J. W. Watson; L. B. Weinstein; K. Wijesooriya; R. Wilson; B. B. Wojtsekhowski; D. G. Zainea; W.-M. Zhang; J. Zhao; Z.-L. Zhou; Dan Zainea; Wei-Ming Zhang; Jie Zhao

2009-01-01

160

Compton Gamma Ray Observatory: Lessons Learned in Propulsion  

NASA Technical Reports Server (NTRS)

The Compton Gamma Ray Observatory was the second of NASA's Great Observatories. At 17 1/2 tons. it was the heaviest astrophysical payload ever flown at the time of its launch on April 5, 1991 aboard the Space Shuttle. During initial, on-orbit priming of the spacecraft's monopropellant hydrazine propulsion system, a severe waterhammer transient was experienced. At that time, anomalous telemetry readings were received from on-board propulsion system instrumentation. This led to ground analyses and laboratory investigations as to the root cause of the waterhammer, potential damage to system integrity and functionality, and risks for switching from the primary (A-side) propulsion system to the redundant (B-side) system. The switchover to B-side was ultimately performed successfully and the spacecraft completed its basic and extended missions in this configuration. Nine years later, following a critical control gyroscope failure, Compton was safely deorbited and re-entered the Earth's atmosphere on June 4, 2000. Additional risk assessments concerning viability of A- and B-sides were necessary to provide confidence in attitude and delta-V authority and reliability to manage the precisely controlled reentry. This paper summarizes the design and operation of the propulsion system used on the spacecraft and provides "lessons learned" from the system engineering investigations into the propellant loading procedures, the initial priming anomaly, mission operations, and the commanded re-entry following the gyro failure.

Dressler, G. A.; Joseph, G. W.; Behrens, H. W.; Asato, D. I.; Carlson, R. A.; Bauer, Frank H. (Technical Monitor)

2001-01-01

161

High-energy scaling of Compton scattering light sources  

NASA Astrophysics Data System (ADS)

No monochromatic (??x/?x<1%), high peak brightness [>1020photons/(mm2×mrad2×s×0.1%bandwidth)], tunable light sources currently exist above 100 keV. Important applications that would benefit from such new hard x-ray and ?-ray sources include the following: nuclear resonance fluorescence spectroscopy and isotopic imaging, time-resolved positron annihilation spectroscopy, and MeV flash radiography. In this paper, the peak brightness of Compton scattering light sources is derived for head-on collisions and found to scale quadratically with the normalized energy, ?; inversely with the electron beam duration, ??, and the square of its normalized emittance, ?; and linearly with the bunch charge, eNe, and the number of photons in the laser pulse, N?:B^x??2NeN?/?2??. This ?2 scaling shows that for low normalized emittance electron beams (1 nC, 1mm·mrad, <1ps, >100MeV), and tabletop laser systems (1-10J, 5 ps) the x-ray peak brightness can exceed 1023photons/(mm2×mrad2×s×0.1%bandwidth) near ??x=1MeV; this is confirmed by three-dimensional codes that have been benchmarked against Compton scattering experiments performed at Lawrence Livermore National Laboratory. The interaction geometry under consideration is head-on collisions, where the x-ray flash duration is shown to be equal to that of the electron bunch, and which produce the highest peak brightness for compressed electron beams. Important nonlinear effects, including spectral broadening, are also taken into account in our analysis; they show that there is an optimum laser pulse duration in this geometry, of the order of a few picoseconds, in sharp contrast with the initial approach to laser-driven Compton scattering sources where femtosecond laser systems were thought to be mandatory. The analytical expression for the peak on-axis brightness derived here is a powerful tool to efficiently explore the 12-dimensional parameter space corresponding to the phase spaces of both the electron and incident laser beams and to determine optimum conditions for producing high-brightness x rays.

Hartemann, F. V.; Brown, W. J.; Gibson, D. J.; Anderson, S. G.; Tremaine, A. M.; Springer, P. T.; Wootton, A. J.; Hartouni, E. P.; Barty, C. P. J.

2005-10-01

162

Effective atomic number of composite materials for Compton effect in the gamma ray region 280-1115 keV.  

PubMed

In this paper, we report the effective atomic number, Z(eff), of composite materials for Compton effect in the gamma ray region 280-1115 keV based on the theoretically obtained Klein-Nishina scattering cross sections in the angular range 50-100° as well as experimentally measured differential incoherent (Compton) scattering cross sections of some composite materials at three scattering angles of 60°, 80°, and 100°. The Z(eff) values so obtained were found to be both angle and energy independent in the region of interest so that it could be concluded that it is possible to represent such composite materials by a mean atomic number in this region as suggested in earlier reports recently. PMID:20702099

Kumar, S Prasanna; Umesh, T K

2010-12-01

163

Development of the TIGRE Compton telescope for intermediate-energy gamma-ray astronomy  

Microsoft Academic Search

Gamma-ray observations in the low and medium energy range (0.1-100 MeV) with sufficiently sensitive telescopes will provide unique insights into many outstanding high-energy astrophysics questions. The University of California, Riverside (UCR) Tracking and Imaging Gamma-Ray Telescope (TIGRE) Compton gamma-ray telescope uses multilayers of silicon strip detectors to, for the first time, track the Compton electron and CsI(Tl)-photodiode detectors to measure

T. J. O'Neill; D. Bhattacharya; M. Polsen; A. D. Zych; J. Samimi; A. Akyuz

2003-01-01

164

Deeply virtual Compton scattering from gauge/gravity duality  

SciTech Connect

We use gauge/gravity duality to study deeply virtual Compton scattering (DVCS) in the limit of high center of mass energy at fixed momentum transfer, corresponding to the limit of low Bjorken x, where the process is dominated by the exchange of the pomeron. At strong coupling, the pomeron is described as the graviton Regge trajectory in AdS space, with a hard wall to mimic confinement effects. This model agrees with HERA data in a large kinematical range. The behavior of the DVCS cross section for very high energies, inside saturation, can be explained by a simple AdS black disk model. In a restricted kinematical window, this model agrees with HERA data as well.

Costa, Miguel S.; Djuric, Marko [University of Porto (Portugal)

2013-04-15

165

Longitudinal Target-Spin Asymmetries for Deeply Virtual Compton Scattering  

DOE PAGESBeta

A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6-GeV electron beam, a longitudinally polarized proton target and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for ep-->e'p'y events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q2, xB, t and phi, for 166 four-dimensional bins. In the framework of Generalized Parton Distributions (GPDs), at leading twist the t dependence of these asymmetries provides insight on the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. These results also bring important and necessary constraints for the existing parametrizations of chiral-even GPDs.

Seder, E.; Biselli, A; Pisano, S; Niccolai, S; Smith, G D.; Joo, K; Adhikari, K; Amaryan, M J.; Anderson, M D.; Anefalos Pereira, S; Avakian, H; Battaglieri, M; Bedlinskiy, I; Bono, J; Boiarinov, S; Bosted, P; Briscoe, W; Brock, J; Brooks, W K.; Bueltmann, S; Burkert, V D.; Carman, D S.; Carlin, C; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L.; Contalbrigo, M; Crabb, D; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Doughty, D; Dupre, R; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A.; Fradi, A; Garillon, B; Garcon, M; Gevorgyan, N; Ghandilyan, Y; Giovanetti, K L.; Girod, F X.; Goetz, J T.; Gohn, W; Gothe, R W.; Griffioen, K A.; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Harrison, N; Hattawy, M; Hirlinger Saylor, N; Holtrop, M; Hughes, S M.; Ilieva, Y; Ireland, D G.; Ishkhanov, B S.; Isupov, E L.; Jo, H S.; Joosten, S; Keith, C D.; Keller, D; Khachatryan, G; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J.; Koirala, S; Kubarovsky, V; Kuhn, S E.; Lenisa, P; Livingston, K; Lu, H Y.; MacGregor, I J.D.; Markov, N; Mayer, M; McKinnon, B; Meekins, D G.; Mineeva, T; Mirazita, M; Mokeev, V; Montgomery, R; Moody, C I.; Moutarde, H; Movsisyan, A; Munoz Camacho, C; Nadel-Turonski, P; Niculescu, I; Osipenko, M; Ostrovidov, A I.; Paolone, M; Pappalardo, L L.; Park, K; Park, S; Pasyuk, E; Peng, P; Phelps, W; Pogorelko, O; Price, J W.; Prok, Y; Protopopescu, D; Puckett, A J.R.; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatie, F; Salgado, C; Schott, D; Schumacher, R A.; Senderovich, I; Simonyan, A; Skorodumina, I; Sokhan, D; Sparveris, N; Stepanyan, S; Stoler, P; Strakovsky, I I.; Strauch, S; Sytnik, V; Taiuti, M; Tang, W; Tian, Y; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K.; Watts, D P.; Wei, X; Weinstein, L B.; Wood, M H.; Zachariou, N; Zana, L; Zhang, J; Zonta, I

2015-01-01

166

Longitudinal target-spin asymmetries for deeply virtual compton scattering.  

PubMed

A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6 GeV electron beam, a longitudinally polarized proton target, and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for ep?e^{'}p^{'}? events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q^{2}, x_{B}, t, and ?, for 166 four-dimensional bins. In the framework of generalized parton distributions, at leading twist the t dependence of these asymmetries provides insight into the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. These results also bring important and necessary constraints for the existing parametrizations of chiral-even generalized parton distributions. PMID:25658994

Seder, E; Biselli, A; Pisano, S; Niccolai, S; Smith, G D; Joo, K; Adhikari, K; Amaryan, M J; Anderson, M D; Anefalos Pereira, S; Avakian, H; Battaglieri, M; Bedlinskiy, I; Bono, J; Boiarinov, S; Bosted, P; Briscoe, W; Brock, J; Brooks, W K; Bültmann, S; Burkert, V D; Carman, D S; Carlin, C; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L; Contalbrigo, M; Crabb, D; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Doughty, D; Dupre, R; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A; Fradi, A; Garillon, B; Garçon, M; Gevorgyan, N; Ghandilyan, Y; Giovanetti, K L; Girod, F X; Goetz, J T; Gohn, W; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Harrison, N; Hattawy, M; Hirlinger Saylor, N; Holtrop, M; Hughes, S M; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Isupov, E L; Jo, H S; Joosten, S; Keith, C D; Keller, D; Khachatryan, G; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J; Koirala, S; Kubarovsky, V; Kuhn, S E; Lenisa, P; Livingston, K; Lu, H Y; MacGregor, I J D; Markov, N; Mayer, M; McKinnon, B; Meekins, D G; Mineeva, T; Mirazita, M; Mokeev, V; Montgomery, R; Moody, C I; Moutarde, H; Movsisyan, A; Munoz Camacho, C; Nadel-Turonski, P; Niculescu, I; Osipenko, M; Ostrovidov, A I; Paolone, M; Pappalardo, L L; Park, K; Park, S; Pasyuk, E; Peng, P; Phelps, W; Pogorelko, O; Price, J W; Prok, Y; Protopopescu, D; Puckett, A J R; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatié, F; Salgado, C; Schott, D; Schumacher, R A; Senderovich, I; Simonyan, A; Skorodumina, I; Sokhan, D; Sparveris, N; Stepanyan, S; Stoler, P; Strakovsky, I I; Strauch, S; Sytnik, V; Taiuti, M; Tang, W; Tian, Y; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K; Watts, D P; Wei, X; Weinstein, L B; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zonta, I

2015-01-23

167

Measurement of deeply virtual compton scattering beam-spin asymmetries.  

PubMed

The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton (e p-->epgamma) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range (x(B) from 0.11 to 0.58, Q2 from 1 to 4.8 GeV2, -t from 0.09 to 1.8 GeV2), the azimuthal dependence of the asymmetries is compatible with expectations from leading-twist dominance, A approximately a sinphi/(1+c cosphi). This extensive set of data can thus be used to constrain significantly the generalized parton distributions of the nucleon in the valence quark sector. PMID:18518188

Girod, F X; Niyazov, R A; Avakian, H; Ball, J; Bedlinskiy, I; Burkert, V D; De Masi, R; Elouadrhiri, L; Garçon, M; Guidal, M; Jo, H S; Joo, K; Kubarovsky, V; Kuleshov, S V; MacCormick, M; Niccolai, S; Pogorelko, O; Sabatié, F; Stepanyan, S; Stoler, P; Ungaro, M; Zhao, B; Amaryan, M J; Ambrozewicz, P; Anghinolfi, M; Asryan, G; Bagdasaryan, H; Baillie, N; Ball, J P; Baltzell, N A; Batourine, V; Battaglieri, M; Bellis, M; Benmouna, N; Berman, B L; Biselli, A S; Blaszczyk, L; Bouchigny, S; Boiarinov, S; Bradford, R; Branford, D; Briscoe, W J; Brooks, W K; Bültmann, S; Butuceanu, C; Calarco, J R; Careccia, S L; Carman, D S; Casey, L; Chen, S; Cheng, L; Cole, P L; Collins, P; Coltharp, P; Crabb, D; Crede, V; Dashyan, N; De Sanctis, E; De Vita, R; Degtyarenko, P V; Deur, A; Dharmawardane, K V; Dickson, R; Djalali, C; Dodge, G E; Donnelly, J; Doughty, D; Dugger, M; Dzyubak, O P; Egiyan, H; Egiyan, K S; El Fassi, L; Eugenio, P; Fedotov, G; Feldman, G; Funsten, H; Gavalian, G; Gilfoyle, G P; Giovanetti, K L; Goetz, J T; Gonenc, A; Gothe, R W; Griffioen, K A; Guler, N; Guo, L; Gyurjyan, V; Hafidi, K; Hakobyan, H; Hanretty, C; Hersman, F W; Hicks, K; Hleiqawi, I; Holtrop, M; Hyde, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Isupov, E L; Ito, M M; Jenkins, D; Johnstone, J R; Juengst, H G; Kalantarians, N; Kellie, J D; Khandaker, M; Kim, W; Klein, A; Klein, F J; Klimenko, A V; Kossov, M; Krahn, Z; Kramer, L H; Kuhn, J; Kuhn, S E; Lachniet, J; Laget, J M; Langheinrich, J; Lawrence, D; Lee, T; Livingston, K; Lu, H Y; Markov, N; Mattione, P; Mazouz, M; McKinnon, B; Mecking, B A; Mestayer, M D; Meyer, C A; Mibe, T; Michel, B; Mikhailov, K; Mirazita, M; Miskimen, R; Mokeev, V; Moriya, K; Morrow, S A; Moteabbed, M; Munevar, E; Mutchler, G S; Nadel-Turonski, P; Nasseripour, R; Niculescu, G; Niculescu, I; Niczyporuk, B B; Niroula, M R; Nozar, M; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Paterson, C; Anefalos Pereira, S; Pierce, J; Pivnyuk, N; Pocanic, D; Pozdniakov, S; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Raue, B A; Ricco, G; Ripani, M; Ritchie, B G; Rosner, G; Rossi, P; Salamanca, J; Salgado, C; Santoro, J P; Sapunenko, V; Schumacher, R A; Serov, V S; Sharabian, Y G; Sharov, D; Shvedunov, N V; Smith, E S; Smith, L C; Sober, D I; Sokhan, D; Stavinsky, A; Stepanyan, S S; Stokes, B E; Strakovsky, I I; Strauch, S; Taiuti, M; Tedeschi, D J; Tkabladze, A; Tkachenko, S; Tur, C; Vineyard, M F; Vlassov, A V; Voutier, E; Watts, D P; Weinstein, L B; Weygand, D P; Williams, M; Wolin, E; Wood, M H; Yegneswaran, A; Zana, L; Zhang, J; Zhao, Z W

2008-04-25

168

Longitudinal Target-Spin Asymmetries for Deeply Virtual Compton Scattering  

NASA Astrophysics Data System (ADS)

A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6 GeV electron beam, a longitudinally polarized proton target, and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for e p ?e'p'? events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q2 , xB, t , and ? , for 166 four-dimensional bins. In the framework of generalized parton distributions, at leading twist the t dependence of these asymmetries provides insight into the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. These results also bring important and necessary constraints for the existing parametrizations of chiral-even generalized parton distributions.

Seder, E.; Biselli, A.; Pisano, S.; Niccolai, S.; Smith, G. D.; Joo, K.; Adhikari, K.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Battaglieri, M.; Bedlinskiy, I.; Bono, J.; Boiarinov, S.; Bosted, P.; Briscoe, W.; Brock, J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Carlin, C.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Crabb, D.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Doughty, D.; Dupre, R.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Fradi, A.; Garillon, B.; Garçon, M.; Gevorgyan, N.; Ghandilyan, Y.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Gothe, R. W.; Griffioen, K. A.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hirlinger Saylor, N.; Holtrop, M.; Hughes, S. M.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joosten, S.; Keith, C. D.; Keller, D.; Khachatryan, G.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Lenisa, P.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Meekins, D. G.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R.; Moody, C. I.; Moutarde, H.; Movsisyan, A.; Munoz Camacho, C.; Nadel-Turonski, P.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Paolone, M.; Pappalardo, L. L.; Park, K.; Park, S.; Pasyuk, E.; Peng, P.; Phelps, W.; Pogorelko, O.; Price, J. W.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Senderovich, I.; Simonyan, A.; Skorodumina, I.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tang, W.; Tian, Y.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Wei, X.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zonta, I.; CLAS Collaboration

2015-01-01

169

Polarizability relations across real and virtual Compton scattering processes  

NASA Astrophysics Data System (ADS)

We derive two relations involving spin polarizabilities of a spin-1 /2 particle and consider their empirical implications for the proton. Using the empirical values of the proton anomalous magnetic moment, electric and magnetic charge radii, moments of the spin structure functions g1 , g2, and of two spin polarizabilities, the present relations constrain the low-momentum behavior of generalized polarizabilities appearing in virtual Compton scattering. In the case of the proton, the dispersive model evaluations of the spin and generalized polarizabilities appear to be consistent with these relations. The ongoing measurements of different electromagnetic observables at the MAMI, Jefferson Lab, and HI ? S facilities may be able to put these relations to a test, or use them to unravel the low-energy spin structure of the nucleon.

Pascalutsa, Vladimir; Vanderhaeghen, Marc

2015-03-01

170

Hadron Optics: Diffraction Patterns in Deeply Virtual Compton Scattering  

E-print Network

We show that the Fourier transform of the Deeply Virtual Compton Scattering (DVCS) amplitude with respect to the skewness variable $\\zeta$ at fixed invariant momentum transfer squared $t$ provides a unique way to visualize the structure of the target hadron in the boost-invariant longitudinal coordinate space. The results are analogous to the diffractive scattering of a wave in optics. As a specific example, we utilize the quantum fluctuations of a fermion state at one loop in QED to obtain the behavior of the DVCS amplitude for electron-photon scattering. We then simulate the wavefunctions for a hadron by differentiating the above LFWFs with respect to $M^2$ and study the corresponding DVCS amplitudes in light-front longitudinal space. In both cases we observe that the diffractive patterns in the longitudinal variable conjugate to $\\zeta$ sharpen and the positions of the first minima move in with increasing momentum transfer. For fixed $t$, higher minima appear at positions which are integral multiples of the lowest minimum. Both these observations strongly support the analogy with diffraction in optics.

S. J. Brodsky; D. Chakrabarti; A. Harindranath; A. Mukherjee; J. P. Vary

2006-08-10

171

Compton Scattering from the Deuteron and Extracted Neutron Polarizabilities  

E-print Network

Differential cross sections for Compton scattering from the deuteron were measured at MAX-lab for incident photon energies of 55 MeV and 66 MeV at nominal laboratory angles of $45^\\circ$, $125^\\circ$, and $135^\\circ$. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and difference of the isospin-averaged nucleon polarizabilities, $\\alpha_N + \\beta_N = 17.4 \\pm 3.7$ and $\\alpha_N - \\beta_N = 6.4 \\pm 2.4$ (in units of $10^{-4}$ fm$^3$), have been determined. By combining the latter with the global-averaged value for $\\alpha_p - \\beta_p$ and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of $\\alpha_n= 8.8 \\pm 2.4$(total) $\\pm 3.0$(model) and $\\beta_n = 6.5 \\mp 2.4$(total) $\\mp 3.0$(model), respectively.

M. Lundin; J. -O. Adler; M. Boland; K. Fissum; T. Glebe; K. Hansen; L. Isaksson; O. Kaltschmidt; M. Karlsson; K. Kossert; M. I. Levchuk; P. Lilja; B. Lindner; A. I. L'vov; B. Nilsson; D. E. Oner; C. Poech; S. Proff; A. Sandell; B. Schröder; M. Schumacher; D. A. Sims

2003-06-13

172

Compton scattering imaging of a working battery using synchrotron high-energy X-rays  

PubMed Central

Results of studies on Compton scattering imaging using synchrotron high-energy X-rays are reported. The technique is applied to a discharging coin cell, and the intensity of Compton scattered X-rays from the inside of the cell has been measured as a function of position and time. The position–time intensity map captures the migration of lithium ions in the positive electrode and reveals the structural change due to the volume expansion of the electrode. This experiment is a critical step in developing synchrotron-based Compton scattering imaging for electrochemical cells at a product level. PMID:25537603

Itou, Masayoshi; Orikasa, Yuki; Gogyo, Yuma; Suzuki, Kosuke; Sakurai, Hiroshi; Uchimoto, Yoshiharu; Sakurai, Yoshiharu

2015-01-01

173

Compton scattering imaging of a working battery using synchrotron high-energy X-rays.  

PubMed

Results of studies on Compton scattering imaging using synchrotron high-energy X-rays are reported. The technique is applied to a discharging coin cell, and the intensity of Compton scattered X-rays from the inside of the cell has been measured as a function of position and time. The position-time intensity map captures the migration of lithium ions in the positive electrode and reveals the structural change due to the volume expansion of the electrode. This experiment is a critical step in developing synchrotron-based Compton scattering imaging for electrochemical cells at a product level. PMID:25537603

Itou, Masayoshi; Orikasa, Yuki; Gogyo, Yuma; Suzuki, Kosuke; Sakurai, Hiroshi; Uchimoto, Yoshiharu; Sakurai, Yoshiharu

2015-01-01

174

High repetition-rate inverse Compton scattering x-ray source driven by a free-electron laser  

NASA Astrophysics Data System (ADS)

We describe a hybrid free-electron laser (FEL)/inverse Compton scattering (ICS) system that can be operated at very high repetition rates and with higher average gamma-ray fluxes than possible from ICS systems driven by J/kHz laser systems. Also, since the FEL system can generate 100 mJ class photon pulses at UV wavelengths, the electron beam energy can be lower than for systems driven with ˜micron wavelength lasers for attaining gamma rays of similar energy.

Carlsten, B. E.; Krawczyk, F. L.; Lewellen, J. W.; Marksteiner, Q. R.; Nguyen, D. C.; Yampolsky, N. A.

2014-12-01

175

Development of Gamma-Ray Compton Imager Using Room-Temperature 3-D Position Sensitive Semiconductor Detectors  

SciTech Connect

During the three years of this project, two 3-dimensional position sensitive CdZnTe spectrometers were upgraded in collaboration with Johns Hopkins University Applied Physics Laboratory. A prototype Compton-scattering gamma-ray imager was assembled using the two upgraded CdZnTe detectors. The performance of both gamma-ray spectrometers were individually tested. The angular resolution and detection sensitivity of the imaging system were measured using both a point and a line-shaped 137 Cs radiation source. The measurement results are consistent with that obtained from Monte-Carlo simulations performed during the early phase of the project.

Zhong He; David Whe; Glenn Knoll

2003-05-14

176

Development of Gamma-Ray Compton Imager Using Room-Temperature 3-D Position Sensitive Semiconductor Detectors  

E-print Network

During the three years of this project, two 3-dimensional position sensitive CdZnTe spectrometers were upgraded in collaboration with Johns Hopkins University Applied Physics Laboratory. A prototype Compton-scattering gamma-ray imager was assembled using the two upgraded CdZnTe detectors. The performance of both gamma-ray spectrometers were individually tested. The angular resolution and detection sensitivity of the imaging system were measured using both a point and a line-shaped 137 Cs radiation source. The measurement results are consistent with that obtained from Monte-Carlo simulations performed during the early phase of the project.

Zhong He; Whe, D

2003-01-01

177

Simplified Formulae System for Resonant Inverse Compton Scattering of a Fast Electron in an Intense Magnetic Field  

NASA Technical Reports Server (NTRS)

We present simple analytical formulae for the emission spectrum and total power of a special kind of resonant inverse Compton scattering (RICS) of a relativistic electron in an intense magnetic field. In contrast with the available formulae system, we obtain a markedly simplified one based on the semiclassical quantum theory, which is more understandable for people who are unfamiliar with quantum electrodynamics. We show that the RICS process, under an appropriate 'accommodation condition' derived in this paper, is predominantly much more efficient than the coexistent ordinary inverse Compton scattering, and produces highly beamed high-frequency radiation with moderately good monochromaticity. Our formulae are simple to use - thus offering a lucid physical intuition for the theory - and may find wide applications in hard X-ray and gamma-ray astrophysics.

You, J. H.; Chen, W. P.; Zhang, S. N.; Chen, L.; Liu, D.; Chou, C. K.

2003-01-01

178

Observation of sub-MeV gamma rays with an Electron Tracking Compton Telescope using a gaseous TPC at balloon altitudes  

NASA Astrophysics Data System (ADS)

Observations in the low-energy gamma-ray band from hundreds of keV to tens of MeV provide the information of the nucleosynthesis, ultra-hot plasma around a black hole, the particle acceleration and the interaction of cosmic-ray and interstellar matter. However, observation in this energy band is very difficult because the dominant process in a detector is Compton scattering, and then suffers from large backgrounds of photons are produced in the hadronic process between cosmic rays and a satellite body. Therefore, MeV gamma-ray astronomy has not advanced in comparison with X-ray or other gamma-ray bands. For a MeV gamma-ray telescope in the next generation, we hence developed an electron-tracking Compton camera (ETCC) consisting of a three-dimensional gaseous tracker of Compton-recoil electrons and an absorber of Compton-scattered gamma rays using a new detection method with powerful background rejection. Because the camera obtains the energy and the direction of both the scattered gamma-ray and the recoil electron, the ETCC can restrict the incident direction of a gamma ray to a reduced arc on the Compton circle and determines the energy of the incident gamma ray, photon by photon. Moreover, the angle between the direction of the scattered gamma ray and that of the Compton-recoil electron can be used for powerful background rejection by checking the consistency between the measured and kinematically calculated values. We had already confirmed the detection principle of the ETCC by ground-based experiments, and thus have begun the observation of celestial sub-MeV gamma rays with a balloon-borne camera, the Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment (SMILE), since 2006. As the first flight of SMILE, in oder to study background gamma rays for observing celestial objects and verify the background rejection capability, we observed diffuse cosmic gamma rays and atmospheric gamma rays using a small ETCC of a 10x10x15 cm3 detection area, which are generated by interaction between cosmic-ray particles and nuclei in the atmosphere at an altitude of up to approximately 35 km. In this paper, we report the observation results of the first flight of SMILE and the preparations for the next flight using a larger detector.

Takada, Atsushi; Tanimori, Toru; Kubo, Hidetoshi; Miuchi, Kentaro; Kabuki, Shigeto; Parker, Joseph; Nishimura, Hironobu; Hattori, Kaori; Ueno, Kazuki; Kurosawa, Shunsuke; Iwaki, Satoru; Ida, Chiriro; Takahashi, Michiaki; Sawano, Tatsuya; Taniue, Kojiro; Nakamura, Kiseki; Higashi, Naoki

179

Optimizing a three-stage Compton camera for measuring prompt gamma rays emitted during proton radiotherapy  

PubMed Central

In this work, we investigate the use of a three-stage Compton camera to measure secondary prompt gamma rays emitted from patients treated with proton beam radiotherapy. The purpose of this study was (1) to develop an optimal three-stage Compton camera specifically designed to measure prompt gamma rays emitted from tissue and (2) to determine the feasibility of using this optimized Compton camera design to measure and image prompt gamma rays emitted during proton beam irradiation. The three-stage Compton camera was modeled in Geant4 as three high-purity germanium detector stages arranged in parallel-plane geometry. Initially, an isotropic gamma source ranging from 0 to 15 MeV was used to determine lateral width and thickness of the detector stages that provided the optimal detection efficiency. Then, the gamma source was replaced by a proton beam irradiating a tissue phantom to calculate the overall efficiency of the optimized camera for detecting emitted prompt gammas. The overall calculated efficiencies varied from ~10?6 to 10?3 prompt gammas detected per proton incident on the tissue phantom for several variations of the optimal camera design studied. Based on the overall efficiency results, we believe it feasible that a three-stage Compton camera could detect a sufficient number of prompt gammas to allow measurement and imaging of prompt gamma emission during proton radiotherapy. PMID:21048295

Peterson, S W; Robertson, D; Polf, J

2011-01-01

180

Compton scattering in strong magnetic fields: Spin-dependent influences at the cyclotron resonance  

NASA Astrophysics Data System (ADS)

The quantum electrodynamical (QED) process of Compton scattering in strong magnetic fields is commonly invoked in atmospheric and inner magnetospheric models of x-ray and soft gamma-ray emission in high-field pulsars and magnetars. A major influence of the field is to introduce resonances at the cyclotron frequency and its harmonics, where the incoming photon accesses thresholds for the creation of virtual electrons or positrons in intermediate states with excited Landau levels. At these resonances, the effective cross section typically exceeds the classical Thomson value by over 2 orders of magnitude. Near and above the quantum critical magnetic field of 44.13 TeraGauss, relativistic corrections must be incorporated when computing this cross section. This profound enhancement underpins the anticipation that resonant Compton scattering is a very efficient process in the environs of highly magnetized neutron stars. This paper presents formalism for the QED magnetic Compton differential cross section valid for both subcritical and supercritical fields, yet restricted to scattered photons that are below pair creation threshold. Calculations are developed for the particular case of photons initially propagating along the field, and in the limit of zero vacuum dispersion, mathematically simple specializations that are germane to interactions involving relativistic electrons frequently found in neutron star magnetospheres. This exposition of relativistic, quantum, magnetic Compton cross sections treats electron spin dependence fully, since this is a critical feature for describing the finite decay lifetimes of the intermediate states. Such lifetimes are introduced to truncate the resonant cyclotronic divergences via standard Lorentz profiles. The formalism employs both the traditional Johnson and Lippmann (JL) wave functions and the Sokolov and Ternov (ST) electron eigenfunctions of the magnetic Dirac equation. The ST states are formally correct for self-consistently treating spin-dependent effects that are so important in the resonances. It is found that the values of the polarization-dependent differential cross section depend significantly on the choice of ST or JL eigenstates when in the fundamental resonance but not outside of it, a characteristic that is naturally expected. Relatively compact analytic forms for the cross sections are presented that will prove useful for astrophysical modelers.

Gonthier, Peter L.; Baring, Matthew G.; Eiles, Matthew T.; Wadiasingh, Zorawar; Taylor, Caitlin A.; Fitch, Catherine J.

2014-08-01

181

The Violent Universe: New Results from the Compton Gamma Ray Observatory  

Microsoft Academic Search

Discoveries are being made with each new observation of the Compton Gamma Ray Observatory (GRO) including an isotropic sky distribution of gamma- ray bursts, gamma-ray bright quasars, unusual gamma-ray pulsars, gamma- ray lines from explosive nucleosynthesis, and a uniform spatial distribution of positron-annihilation radiation from the disk of our Galaxy. Many of the results are surprising and are challenging our

Neil Gehrels

1993-01-01

182

Inverse Compton Scattering on Solar Photons, Heliospheric Modulation, and Neutrino Astrophysics  

SciTech Connect

We study the inverse Compton scattering of solar photons by Galactic cosmic-ray electrons. We show that the {gamma}-ray emission from this process is significant with the maximum flux in the direction of the Sun; the angular distribution of the emission is broad. This previously neglected foreground should be taken into account in studies of the diffuse Galactic and extragalactic {gamma}-ray emission. Furthermore, observations by GLAST can be used to monitor the heliosphere and determine the electron spectrum as a function of position from distances as large as Saturn's orbit down to close proximity of the Sun, thus enabling studies of solar modulation in the most extreme case. This paves the way for the determination of other Galactic cosmic-ray species, primarily protons, near the solar surface leading to accurate predictions of {gamma}-rays from pp-interactions in the solar atmosphere. These albedo {gamma}-rays will be observable by GLAST, allowing the study of deep atmospheric layers, magnetic field(s), and cosmic-ray cascade development. The latter is necessary to calculate the neutrino flux from pp-interactions at higher energies (>1 TeV). The corresponding neutrino flux from the Sun can be used as a ''standard candle'' for upcoming km{sup 3} neutrino detectors, such as IceCube. Since the solar core is opaque for very high-energy neutrinos, it may be possible to directly study the mass distribution of the Sun.

Moskalenko, Igor V.; /Stanford U., HEPL; Porter, Troy A.; /UC, Santa Cruz; Digel, Seth W.; /SLAC

2006-08-01

183

Observation of Diffuse Cosmic and Atmospheric Gamma Rays at Balloon Altitudes with an Electron-tracking Compton Camera  

E-print Network

We observed diffuse cosmic and atmospheric gamma rays at balloon altitudes with the Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I (SMILE-I) as the first step toward a future all-sky survey with a high sensitivity. SMILE-I employed an electron-tracking Compton camera comprised of a gaseous electron tracker as a Compton-scattering target and a scintillation camera as an absorber. The balloon carrying the SMILE-I detector was launched from the Sanriku Balloon Center of the Institute of Space and Astronomical Science/Japan Space Exploration Agency on September 1, 2006, and the flight lasted for 6.8 hr, including level flight for 4.1 hr at an altitude of 32-35 km. During the level flight, we successfully detected 420 downward gamma rays between 100 keV and 1 MeV at zenith angles below 60 degrees. To obtain the flux of diffuse cosmic gamma rays, we first simulated their scattering in the atmosphere using Geant4, and for gamma rays detected at an atmospheric depth of 7.0 g cm-2, we found that 50% and 21% ...

Takada, Atsushi; Nishimura, Hironobu; Ueno, Kazuki; Hattori, Kaori; Kabuki, Shigeto; Kurosawa, Shunsuke; Miuchi, Kentaro; Mizuta, Eiichi; Nagayoshi, Tsutomu; Nonaka, Naoki; Okada, Yoko; Orito, Reiko; Sekiya, Hiroyuki; Takeda, Atsushi; Tanimori, Toru

2011-01-01

184

Scaling Tests of the Cross Section for Deeply Virtual Compton Scattering  

SciTech Connect

We present the first measurements of the e(vector sign)p{yields}ep{gamma} cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q{sup 2} dependence (from 1.5 to 2.3 GeV{sup 2}) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q{sup 2}. The helicity-independent cross section is also measured at Q{sup 2}=2.3 GeV{sup 2}. We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation.

Camacho, C. Munoz; Beaumel, M.; Garcon, M.; Guichon, P. A. M.; Sabatie, F. [CEA Saclay, DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Camsonne, A.; Ferdi, C.; Brossard, M.; Fieschi, J.-M.; Laveissiere, G.; Michel, B. [Universite Blaise Pascal/CNRS-IN2P3, F-63177 Aubiere (France); Mazouz, M.; Guillon, B.; Real, J.-S.; Voutier, E. [Laboratoire de Physique Subatomique et de Cosmologie, 38026 Grenoble (France); Gavalian, G.; Amarian, M.; Hayes, D.; Hyde-Wright, C. E.; Ibrahim, H. [Old Dominion University, Norfolk, Virginia 23508 (United States)] (and others)

2006-12-31

185

Measurement of Deeply Virtual Compton Scattering with a Polarized Proton Target  

SciTech Connect

The longitudinal target-spin asymmetry A{sub UL} for the exclusive electroproduction of high energy photons was measured for the first time in p(e,e'p/gamma). The data have been accumulated at Jefferson Lab with the CLAS spectrometer using 5.7 GeV electrons and a longitudinally polarized NH{sub 3} target. A significant azimuthal angular dependence was observed, resulting from the interference of the Deeply Virtual Compton Scattering and Bethe-Heitler processes. The amplitude of the sin(phi) moment is 0.252 +/- 0.042(stat) +/- 0.020(sys). Theoretical calculations are in good agreement with the magnitude and the kinematic dependence of the target-spin asymmetry, which is sensitive to the generalized parton distributions H and H-tilde.

S. Chen; H. Avakian; V. Burkert; P. Eugenio

2006-05-05

186

Analysis of the data from Compton X-ray polarimeters which measure the azimuthal and polar scattering angles  

NASA Astrophysics Data System (ADS)

X-ray polarimetry has the potential to make key-contributions to our understanding of galactic compact objects like binary black hole systems and neutron stars, and extragalactic objects like active galactic nuclei, blazars, and Gamma-Ray Bursts. Furthermore, several particle astrophysics topics can be addressed including uniquely sensitive tests of Lorentz invariance. In the energy range from 10 keV to several MeV, Compton polarimeters achieve the best performance. In this paper we evaluate the benefit that comes from using the azimuthal and polar angles of the Compton scattered photons in the analysis, rather than using the azimuthal scattering angles alone. We study the case of an ideal Compton polarimeter and show that a Maximum Likelihood analysis which uses the two scattering angles lowers the Minimum Detectable Polarization (MDP) by ?20% compared to a standard analysis based on the azimuthal scattering angles alone. The accuracies with which the polarization fraction and the polarization direction can be measured improve by a similar amount. We conclude by discussing potential applications of Maximum Likelihood analysis methods for various polarimeter experiments.

Krawczynski, H.

2011-05-01

187

Low-energy K-shell Compton scattering  

SciTech Connect

We calculate the photon energy distribution and the total cross section for the Compton scattering on the K electrons for the case when the photon wave length is much smaller than the size of the K shell. We show that at the energies of the order of the binding energy I of the K electron most part of the spectrum is governed by the low-energy behavior. The total cross section has a local maximum at the energies (1.5-2)I, reaching the values of the order 1 barn. At higher photon energies the spectrum curves have two maxima, corresponding to low-energy ejected photons or electrons. The cross sections in the whole region are calculated. The actual calculations are carried out employing the nonrelativistic Coulomb functions, thus being valid for the single-electron atoms. However, the main features of the analysis are expected to be true for many-electron ions and neutral atoms. The results of the present analysis may be useful in calculations of the laser-induced and laser-assisted processes.

Drukarev, E. G. [Max-Planck Institute fuer Physik Komplexer Systeme, D-01187 Dresden (Germany); Mikhailov, A. I. [Petersburg Nuclear Physics Institute Gatchina, St. Petersburg, 188300 (Russian Federation); Mikhailov, I. A. [Petersburg Nuclear Physics Institute Gatchina, St. Petersburg, 188300 (Russian Federation); University of Central Florida 4000 Central Florida Boulevard, Orlando, Florida 32816 (United States)

2010-08-15

188

Measuring Proton Spin Polarizabilities with Polarized Compton Scattering  

NASA Astrophysics Data System (ADS)

An important test of low-energy QCD theories is the extraction of the proton spin polarizabilities (SPs), which describe the response of the proton spin to a polarized photon. The SPs arise as third order terms in the energy expansion of the Compton scattering amplitude, with theoretical values provided by dispersion and effective field theories, and in the future by lattice calculations. Extraction of these values is possible by measuring two beam-target asymmetries of a circularly polarized photon beam on a transversely polarized target, ?2x, and on a longitudinally polarized target, ?2z, and a beam asymmetry of a linearly polarized photon beam on an unpolarized target, ?3, at photon energies between ? and 2? threshold. The MAMI A2 Bremsstrahlung beam is used in conjunction with either a frozen-spin butanol or an unpolarized hydrogen target, and the Crystal Ball and TAPS detectors which combined provide 97% coverage of 4?. We will report on ?2x measurements, supplemented by initial ?3 measurements, both just below and above 2? threshold.

Martel, Philippe; Barnes, William; Miskimen, Rory; Mushkarenkov, Alexander

2011-10-01

189

Theoretical Description of Deeply Virtual Compton Scattering off 3He  

NASA Astrophysics Data System (ADS)

Recently, coherent deeply virtual Compton scattering (DVCS) off 3He nuclei has been proposed to access the neutron generalized parton distributions (GPDs). In impulse approximation (IA) studies, it has been shown, in particular, that the sum of the two leading twist, quark helicity conserving GPDs of 3He, H and E, at low momentum transfer, is dominated by the neutron contribution, so that 3He is very promising for the extraction of the neutron information. Nevertheless, such an extraction could be not trivial. A technique, able to take into account the nuclear effects included in the IA analysis in the extraction procedure, has been therefore developed. In this work, the IA calculation of the spin dependent GPD of 3He is presented for the first time. This quantity is found to be largely dominated, at low momentum transfer, by the neutron contribution, which could be extracted using arguments similar to the ones previously proposed for the other GPDs. The known forward limit of the IA calculation of , yielding the polarized parton distributions of 3He, is correctly recovered. The knowledge of the GPDs H, E and of 3He will allow now the evaluation of the cross section asymmetries which are relevant for coherent DVCS off 3He at Jefferson Lab kinematics, an important step towards the planning of possible experiments.

Rinaldi, M.; Scopetta, S.

2014-08-01

190

Gamma-Ray Polarization of the Synchrotron Self-compton Process from a Highly Relativistic Jet  

NASA Astrophysics Data System (ADS)

The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization ? ~ 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most ?-ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching ? ~ 20%. This implies that the Klein-Nishina effect, which is often neglected in the literature, should be carefully considered.

Chang, Zhe; Lin, Hai-Nan

2014-11-01

191

Compton scattering cross section for inner-shell electrons in the relativistic impulse approximation  

NASA Astrophysics Data System (ADS)

Total Compton scattering cross sections and inelastic scattering factors for bound electron states of several elements have been evaluated in the framework of the relativistic impulse approximation (RIA). The accuracy of different approximate expressions for the singly differential cross section within the RIA is discussed. Accurate evaluations of bound state scattering factors require the use of the full RIA expression. Compton scattering from K-shell electrons dominates over the photoelectric absorption at higher energies. Energy values at which the Compton interaction become the main process of creation of K-shell vacancies are assessed. The role of binding effects in Compton processes at lower energies are clearly evidenced by the computed total cross sections. Calculated K-shell ionization total cross sections, defined as the sum of the photoelectric absorption and the Compton scattering cross sections, are in good agreement with available experimental data. The total Compton cross section for the 2s atomic orbital exhibits a shoulder-like structure, which can be traced back to the node structure of the 2s wave function.

Stutz, G. E.

2014-01-01

192

Guest Investigator Studies with the Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The cumulative all-sky survey by the Compton Gamma Ray Observatory (CGRO), composed of data acquired during the first three years of the mission, included a number of regions of very limited exposure. The most glaring deficiency in coverage was toward the region of the South Galactic Pole (SGP), which received significantly less exposure than other directions- by a factor of at least 2 to 3. Furthermore, nearly all of the SGP exposure was accumulated during the first year of the mission. Since blazars are known to be time-variable, and of unknown duty cycle, a pointing of the CCRO in that direction was considered highly desirable, and long overdue. In addition, data gathered from a pointing toward the SGP and its comparison with comprehensive data available for the North Galactic Pole would be extremely valuable to investigators studying the extragalactic diffuse emission. The reasons outlined above prompted our initiation of a Cycle 4 campaign to systematically search with EGRET and COMPTEL for gamma-ray emission from sources near the South Galactic Pole. The Cycle 4 SGP campaign consisted of tnvo 14-day observations separated in in time by approximately 10 months. The temporal separation of the observations was requested to allow a test for possible variations in the detected sources. Our primary targets were 38 FSRQs which lie within 30 degrees of the SGP, and which satisfy the basic criteria for candidate gamma-ray AGNs,flat-spectrum radio sources, many of which exhibit blazar-type properties). These targets were selected from the standard references, and from the available on-line databases (e.g., the NASA Extragalactic Database, NED), as the most promising AGN targets in the vicinity of the SGP. A 30 radius from the SGP was chosen as the boundary of our survey, since the selected targets would then fall within the most sensitive portion of the fields of view of EGRET and COMPTEL (i.e., within a 30 zenith angle), for a CGRO pointing directed exactly at the SGP. Our South Galactic Pole Survey yielded a number of exciting results. The EGRET data were analyzed using the maximum likelihood techniques to estimate the intensity, spectrum, and position of gamma-ray sources in the field of view. Our analysis revealed four sources at energies greater than 100 MeV with likelihood ratios corresponding to greater than 30 detections (Vestrand et al. 1996). One of the sources is associated with the well known gamma-ray blazar PKS 0208-512, but the other three were previously unknown. Among the new detections was PKS 2155-304 which is often considered a prototype of the x-ray selected BL Lacs. PKS 2155-304, which was also detected at hard x-ray energies by CGRO/OSSE, is one of the brightest BL Lac objects in the sky at optical through x-ray energies and has a history of rapid, strong multiwavelength variability. As such, it has been the subject of intensive, contemporaneous, multiwavelength monitoring covering radio frequencies to x-ray energies.

Vestrand, W. T.

1998-01-01

193

Thick silicon strip detector Compton imager  

Microsoft Academic Search

We present results obtained with double-sided, thick (2 mm) silicon strip detectors used as a Compton imager. Reconstructed images and spectra from 137Cs and 60Co gamma-ray sources have been produced at room temperature using the multiple Compton technique. Multiple Compton interactions allow the energy and Compton scattering angle to be reconstructed without having to absorb the energy of the incident

Eric A. Wulf; Bernard F. Phlips; W. Neil Johnson; James D. Kurfess; Elena I. Novikova

2004-01-01

194

The Compton Gamma Ray Observatory: highlights from the first three years of the mission  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray observatory is the second in NASA's series of Great Observatories. It has been in operation for over three years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments continue to function nearly flawlessly, and many significant discoveries have been made. The authors describe the capabilities of

N. Gehrels; C. Shrader; D. A. Kniffen

1995-01-01

195

Observation of diffuse gamma-ray with Electron-Tracking Compton imaging camera loaded on balloon  

Microsoft Academic Search

We have developed an electron tracking Compton camera (ETCC) as an MeV gamma-ray telescope in the next generation. Our detector consists of a gaseous time projection chamber and a position sensitive scintillation camera. In order to evaluate the performance of this detector, we constructed a flight model detector as a balloon experiment for the observation of diffuse cosmic gamma rays

A. Takada; T. Tanimori; H. Kubo; K. Miuchi; K. Tsuchiya; S. Kabuki; H. Nishimura; K. Hattori; K. Ueno; S. Kurosawa; N. Nonaka; E. Mizuta; R. Orito; T. Nagayoshi

2007-01-01

196

Si/CdTe Compton Telescope combined with Active Collimator as the Soft Gamma-ray Detector for the 'NeXT' mission  

NASA Astrophysics Data System (ADS)

The Soft Gamma-ray Detector (SGD) is a new generation compton telescope aiming at an order of magnitude improvement of sensitivity at the energy band of 80-1000 keV. The SGD is proposed to be launched at 2010-11, onboard the Japanese new astronomy satellite ``NeXT." Novel idea of the SGD is to use a Si/CdTe semiconductor multi-layer compton telescope within the low background environment achieved by the deep active shield with a narrow opening angle. Because compton telescope hosts an imaging capability, any residual backgrounds, such as the activation of the main detector itself, can by rejected by requiring the compton scattering angle to be consistent with the opening angle of the shield, which is about 4 degree with current design. The key technologies of the SGD are the deep active shield which is a direct heritage of the Hard X-ray Detector onboard Astro-E2 mission, and the newly developed Si/CdTe compton telescope. Current design of the Si/CdTe compton telescope consists of 24 layers of 0.5 mm thick double-sided-silicon-strip-detector (DSSD) as a scatterer, surrounded by thin and thick CdTe pixel detectors with a total thickness of 5 mm as an absorber. The design is optimized for detecting gamma-rays at about 100-700 keV when operated at compton mode. We present the results from the first prototype of Si/CdTe compton telescope, made of a 300 um thick DSSD and 0.5 mm thick CdTe pixel detectors. We also present the estimated performance of the SGD with current design, and possible improvements in the future.

Kazuhiro, N.; Tadayuki, T.; Shin, W.; Tune, K.; Greg, M.; Hiroyasu, T.; Yasushi, F.; Masaharu, N.; Motohide, K.; Kazuo, M.; Makoto, T.; Yukikatsu, T.; Jun, K.; NeXT SGD Collaboration

2004-08-01

197

Anisotropic induced Compton scattering - Constraints on models of active galactic nuclei  

NASA Technical Reports Server (NTRS)

A model for nonlinear radiative transfer on a lattice is used to explore observational signatures of anisotropic induced Compton scattering. Ways in which an intense beam of radiation may be altered in passing through a slab of plasma that is optically thin to spontaneous Thomson scattering are explained. A numerical approach to induced Compton scattering which involves solving the equations of nonlinear transfer on a lattice is described. Results of calculations for some simple geometrical configurations (spheres, disks, cylindrical 'jets', etc.) are presented. Some possible applications of these results to the interpretation of actual data on compact radio sources are outlined, and the FIR spectra of AGN are considered.

Coppi, P.; Blandford, R. D.; Rees, M. J.

1993-01-01

198

Pomeron dominance in deeply virtual Compton scattering and the femto holographic image of the proton  

E-print Network

The dominance of the soft pomeron in soft high energy scattering and the evolution to the deeply virtual regime, predicted by perturbation theory, allow us to reveal generalized parton distributions from H1 and ZEUS measurements of deeply virtual Compton scattering. These distributions encode a holographic image of the proton, which will be presented.

Dieter Müller

2006-04-30

199

Virtual Compton scattering and neutral pion electroproduction in the resonance region up to the deep inelastic region at backward angles  

SciTech Connect

We have made the first measurements of the virtual Compton scattering (VCS) process via the H(e, e{sup '}p){gamma} exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the W-dependence at fixed Q{sup 2}=1 GeV{sup 2} and for the Q{sup 2} dependence at fixed W near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed Q{sup 2} dependence is smooth. The measured ratio of H(e, e{sup '}p){gamma} to H(e, e{sup '}p){pi}{sup 0} cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to real Compton scattering (RCS) at high energy and large angles, our VCS data at the highest W (1.8-1.9 GeV) show a striking Q{sup 2} independence, which may suggest a transition to a perturbative scattering mechanism at the quark level.

Laveissiere, G.; Jaminion, S.; Salvo, R. Di; Berthot, J.; Bertin, P. Y.; Breton, V.; Fonvieille, H.; Grenier, P.; Ravel, O.; Roblin, Y.; Smirnov, G. [LPC-Clermont, Universite Blaise Pascal, CNRS/IN2P3, F-63177 Aubiere Cedex (France); Degrande, N.; Hoorebeke, L. van; Vyver, R. van de [University of Gent, B-9000 Gent (Belgium); Jutier, C.; Hyde, C. E. [LPC-Clermont, Universite Blaise Pascal, CNRS/IN2P3, F-63177 Aubiere Cedex (France); Old Dominion University, Norfolk, Virginia 23529 (United States); Todor, L.; Dodge, G. E.; McCormick, K.; Ulmer, P. E. [Old Dominion University, Norfolk, Virginia 23529 (United States)] (and others)

2009-01-15

200

Virtual Compton scattering off a spinless target in AdS\\/QCD  

Microsoft Academic Search

We study the doubly virtual Compton scattering off a spinless target ?*P ? ?*P? within the Anti-de Sitter(AdS)\\/QCD formalism. We find that the general structure allowed by the Lorentz invariance and gauge\\u000a invariance of the Compton amplitude is not easily reproduced with the standard recipes of the AdS\\/QCD correspondence. In the\\u000a soft-photon regime, where the semi-classical approximation is supposed to

Cyrille Marquet; Claude Roiesnel; Samuel Wallon

2010-01-01

201

Magnetic Compton Scattering Studies of the INVAR Effect in IRON(2) Platinum  

NASA Astrophysics Data System (ADS)

Magnetic Compton scattering (MCS) was used to study the magnetic state of Fe_3Pt at temperatures above and below its critical temperature. As Fe_3Pt is an Invar alloy, it has found widespread commercial use, and thus, it is interesting to study. While the mechanism behind the temperature independent elastic behavior (the "Invar effect") has never been shown, recent experiments have caused most theories to be put aside in favor of the phenomenological Weiss 2 ^{gamma} model. This model claims that the source of the Invar effect is a change in the magnetic state of the alloy. This change is examined by inelastically scattering circularly polarized photons from Fe_3Pt at temperatures above and below its Curie temperature. The result is the momentum distribution of the unpaired (or magnetic) electrons in the alloy. From this, the mechanism behind the Invar effect is inferred to be a substantial decrease of the magnetic moment of the 3d states on the Fe atoms. MCS experiments require a source of circularly polarized x-rays. Unfortunately, such sources are not readily available. Therefore, to accomodate our source requirements, an x-ray phase plate made of single crystal germanium was constructed. It was designed to operate at discrete energies over the range 20-88 keV and found to produce a degree of circular polarization of 90% at 65 keV.

Yahnke, Clifford James

1995-01-01

202

Photon Plasma-Wave Interaction via Compton Scattering  

E-print Network

The Kompaneets theory of photon kinetic evolution due to the Compton effect is extended to the case of the Vlasov plasma wave oscillations. Taking into account Zel'dovich-Levich's approximation we study interaction of accumulating photons with plasma in the long wavelength limit.

Galina Erochenkova; Cristel Chandre

2012-08-16

203

Compton DIV: Using a Compton-Based Gamma-Ray Imager for Design Information Verification of Uranium Enrichment Plants  

SciTech Connect

A feasibility study has been performed to determine the potential usefulness of Compton imaging as a tool for design information verification (DIV) of uranium enrichment plants. Compton imaging is a method of gamma-ray imaging capable of imaging with a 360-degree field of view over a broad range of energies. These systems can image a room (with a time span on the order of one hour) and return a picture of the distribution and composition of radioactive material in that room. The effectiveness of Compton imaging depends on the sensitivity and resolution of the instrument as well the strength and energy of the radioactive material to be imaged. This study combined measurements and simulations to examine the specific issue of UF{sub 6} gas flow in pipes, at various enrichment levels, as well as hold-up resulting from the accumulation of enriched material in those pipes. It was found that current generation imagers could image pipes carrying UF{sub 6} in less than one hour at moderate to high enrichment. Pipes with low enriched gas would require more time. It was also found that hold-up was more amenable to this technique and could be imaged in gram quantities in a fraction of an hour. another questions arises regarding the ability to separately image two pipes spaced closely together. This depends on the capabilities of the instrument in question. These results are described in detail. In addition, suggestions are given as to how to develop Compton imaging as a tool for DIV.

Burks, M; Verbeke, J; Dougan, A; Wang, T; Decman, D

2009-07-04

204

Intercomparison of gamma ray scattering and transmission techniques for gas volume fraction measurements in two phase pipe flow  

NASA Astrophysics Data System (ADS)

Void fraction simulating stratified air-water flow in cylindrical tubes of different radii was measured using transmission and scattering of gamma rays. A simple experimental set-up using 137Cs ?-ray point source of 10 ?Ci and NaI(Tl) detector was used. The void fractions determined from Compton-Compton scattering and transmission peaks were found in good agreement with the real void fractions. However, deviations were noticed between the results obtained from traditional Compton scattered gamma rays and real void fraction. It was shown that sensitivity of gamma ray scattering is better than the transmission measurements. The set-up used in the present work is simpler than those existing in literature and radiation safety and shielding requirements are minimized.

El Abd, A.

2014-01-01

205

Gamma-spectrometry with Compton suppressed detectors arrays  

SciTech Connect

Recent results of experiments performed with two different Compton-suppressed detectors arrays in Daresbury and Berkeley (/sup 163,164/Yb and /sup 154/Er, respectively), are presented together with a brief description of the national French array presently under construction in Strasbourg. 25 refs., 15 figs.

Schueck, C.; Hannachi, F.; Chapman, R.; Lisle, J.C.; Mo, J.N.; Paul, E.; Love, D.J.G.; Nolan, P.J.; Nelson, A.H.; Walker, P.M.

1985-01-01

206

Observation of Diffuse Cosmic and Atmospheric Gamma Rays at Balloon Altitudes with an Electron-tracking Compton Camera  

NASA Astrophysics Data System (ADS)

We observed diffuse cosmic and atmospheric gamma rays at balloon altitudes with the Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I (SMILE-I) as the first step toward a future all-sky survey with a high sensitivity. SMILE-I employed an electron-tracking Compton camera comprised of a gaseous electron tracker as a Compton-scattering target and a scintillation camera as an absorber. The balloon carrying the SMILE-I detector was launched from the Sanriku Balloon Center of the Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency on 2006 September 1, and the flight lasted for 6.8 hr, including level flight for 4.1 hr at an altitude of 32-35 km. During the level flight, we successfully detected 420 downward gamma rays between 100 keV and 1 MeV at zenith angles below 60°. To obtain the flux of diffuse cosmic gamma rays, we first simulated their scattering in the atmosphere using Geant4, and for gamma rays detected at an atmospheric depth of 7.0 g cm-2 we found that 50% and 21% of the gamma rays at energies of 150 keV and 1 MeV, respectively, were scattered in the atmosphere prior to reaching the detector. Moreover, by using Geant4 simulations and the QinetiQ atmospheric radiation model, we estimated that the detected events consisted of diffuse cosmic and atmospheric gamma rays (79%), secondary photons produced in the instrument through the interaction between cosmic rays and materials surrounding the detector (19%), and other particles (2%). The obtained growth curve was comparable to Ling's model, and the fluxes of diffuse cosmic and atmospheric gamma rays were consistent with the results of previous experiments. The expected detection sensitivity of a future SMILE experiment measuring gamma rays between 150 keV and 20 MeV was estimated from our SMILE-I results and was found to be 10 times better than that of other experiments at around 1 MeV.

Takada, Atsushi; Kubo, Hidetoshi; Nishimura, Hironobu; Ueno, Kazuki; Hattori, Kaori; Kabuki, Shigeto; Kurosawa, Shunsuke; Miuchi, Kentaro; Mizuta, Eiichi; Nagayoshi, Tsutomu; Nonaka, Naoki; Okada, Yoko; Orito, Reiko; Sekiya, Hiroyuki; Takeda, Atsushi; Tanimori, Toru

2011-05-01

207

OBSERVATION OF DIFFUSE COSMIC AND ATMOSPHERIC GAMMA RAYS AT BALLOON ALTITUDES WITH AN ELECTRON-TRACKING COMPTON CAMERA  

SciTech Connect

We observed diffuse cosmic and atmospheric gamma rays at balloon altitudes with the Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I (SMILE-I) as the first step toward a future all-sky survey with a high sensitivity. SMILE-I employed an electron-tracking Compton camera comprised of a gaseous electron tracker as a Compton-scattering target and a scintillation camera as an absorber. The balloon carrying the SMILE-I detector was launched from the Sanriku Balloon Center of the Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency on 2006 September 1, and the flight lasted for 6.8 hr, including level flight for 4.1 hr at an altitude of 32-35 km. During the level flight, we successfully detected 420 downward gamma rays between 100 keV and 1 MeV at zenith angles below 60 deg. To obtain the flux of diffuse cosmic gamma rays, we first simulated their scattering in the atmosphere using Geant4, and for gamma rays detected at an atmospheric depth of 7.0 g cm{sup -2} we found that 50% and 21% of the gamma rays at energies of 150 keV and 1 MeV, respectively, were scattered in the atmosphere prior to reaching the detector. Moreover, by using Geant4 simulations and the QinetiQ atmospheric radiation model, we estimated that the detected events consisted of diffuse cosmic and atmospheric gamma rays (79%), secondary photons produced in the instrument through the interaction between cosmic rays and materials surrounding the detector (19%), and other particles (2%). The obtained growth curve was comparable to Ling's model, and the fluxes of diffuse cosmic and atmospheric gamma rays were consistent with the results of previous experiments. The expected detection sensitivity of a future SMILE experiment measuring gamma rays between 150 keV and 20 MeV was estimated from our SMILE-I results and was found to be 10 times better than that of other experiments at around 1 MeV.

Takada, Atsushi; Nonaka, Naoki [Research and Operation Office for Scientific Ballooning, ISAS, JAXA, Yoshinodai 3-1-1, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Kubo, Hidetoshi; Nishimura, Hironobu; Ueno, Kazuki; Hattori, Kaori; Kabuki, Shigeto; Kurosawa, Shunsuke; Miuchi, Kentaro; Nagayoshi, Tsutomu; Okada, Yoko; Orito, Reiko; Sekiya, Hiroyuki; Takeda, Atsushi; Tanimori, Toru [Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan); Mizuta, Eiichi, E-mail: kubo@cr.scphys.kyoto-u.ac.jp [Electronic Components and Devices Group, ISAS, JAXA, Yoshinodai 3-1-1, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2011-05-20

208

Techniques and use of a tunable, laser-based, MeV-Class Compton scattering light source  

SciTech Connect

A Compton scattering {gamma}-ray source, capable of producing photons with energies ranging from 0.1 MeV to 0.9 MeV has been commissioned and characterized, and then used to perform nuclear resonance fluorescence (NRF) experiments. The key source parameters are the size (0.01 mm{sup 2}), horizontal and vertical divergence (6 x 10 mrad{sup 2}), duration (10 ps), spectrum and intensity (10{sup 5} photons/shot). These parameters are summarized by the peak brightness, 1.5 x 10{sup 15} photons/mm{sup 2}/mrad{sup 2}/s/0.1%bandwidth, measured at 478 keV. Additional measurements of the flux as a function of the timing difference between the drive laser pulse and the relativistic photoelectron bunch, {gamma}-ray beam profile, and background evaluations are presented. These results are systematically compared to theoretical models and computer simulations. NRF measurements performed on {sup 7}Li in LiH demonstrate the potential of Compton scattering photon sources to accurately detect isotopes in situ.

Albert, F; Anderson, S G; Gibson, D J; Hagmann, C A; Johnson, M S; Messerly, M; Semenov, V; Shverdin, M Y; Rusnak, B; Tremaine, A M; Hartemann, F V; Siders, C W; McNabb, D P; Barty, C P

2009-06-30

209

COMPTON DEGRADATION OF GAMMA-RAY LINE EMISSION FROM RADIOACTIVE ISOTOPES IN THE CLASSICAL NOVA V2491 CYGNI  

SciTech Connect

To account for the non-thermal emission from the classical nova V2491 Cygni, we perform a series of numerical calculations of radiative transfer of {gamma}-ray photons from the radioactive isotope {sup 22}Na in the matter ejected from a white dwarf. Using a simple wind model for the dynamical evolution of the ejecta and a Monte Carlo code, we calculate radiative transfer of the {gamma}-ray photons in the ejecta. Repeated scattering of the {gamma}-ray photons by electrons in the ejecta, i.e., Compton degradation, results in an extremely flat spectrum in the hard X-ray range, which successfully reproduces the observed spectrum of the X-ray emission from V2491 Cygni. The amount of the isotope {sup 22}Na synthesized in the ejecta is required to be 3 x 10{sup -5} M {sub sun} to account for the flux of the hard X-ray emission. Our model indicates that the ejecta become transparent to the {gamma}-ray photons within several tens days. Using the results, we briefly discuss the detectability of the {gamma}-ray line emission by the INTEGRAL gamma-ray observatory and the Fermi Gamma-ray Space Telescope.

Suzuki, Akihiro; Shigeyama, Toshikazu [Research Center for the Early Universe, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2010-11-01

210

Evidence for Narrow Resonant Structures at $W ~\\sim 1.68$ and $W \\sim 1.72$ GeV in Real Compton Scattering off the Proton  

E-print Network

First measurement of the beam asymmetry $\\Sigma$ for Compton scattering off the proton in the energy range $E_{\\gamma}=0.85 - 1.25$ GeV is presented. The data reveals two narrow structures at $E_{\\gamma}= 1.036$ and $E_{\\gamma}=1.119$ GeV. They may signal either narrow resonances with the masses near $1.68$ and $1.72$ GeV, or can be generated by the sub-threshold $K\\Lambda$ and $\\omega p$ production. Their decisive identification requires additional theoretical and experimental efforts.

V. Kuznetsov; F. Mammoliti; V. Bellini; G. Gervino; F. Ghio; G. Giardina; W. Kim; G. Mandaglio; M. L. Sperduto; C. Sutera

2015-01-18

211

Assessment of a new method for determining elastic to Compton ratios in scattered beam non-destructive examination  

Microsoft Academic Search

The elastic and Compton signals produced when 60 keV radiation is scattered have been separated with an erbium filter, which has a K absorption edge between the two energies, and recorded by a scintillation counter. The elastic to Compton ratios which characterise the scatterer's composition were measured on a range of target elements. The results agree with the values obtained

D. N. Timms; M. J. Cooper; R. S. Holt

1987-01-01

212

Electronic properties and Compton scattering studies of monoclinic tungsten dioxide  

NASA Astrophysics Data System (ADS)

We present the first ever Compton profile measurement of WO2 using a 20 Ci 137Cs ?-ray source. The experimental data have been used to test different approximations of density functional theory in linear combination of atomic orbitals (LCAO) scheme. It is found that theoretical Compton profile deduced using generalized gradient approximation (GGA) gives a better agreement than local density approximation and second order GGA. The computed energy bands, density of states and Mulliken?s populations (MP) data confirm a metal-like behavior of WO2. The electronic properties calculated using LCAO approach are also compared with those obtained using full potential linearized augmented plane wave method. The nature of bonding in WO2 is also compared with isoelectronic WX2 (X=S, Se) compounds in terms of equal-valence-electron-density profiles and MP data, which suggest an increase in ionic character in the order WSe2?WS2?WO2.

Heda, N. L.; Ahuja, Ushma

2015-01-01

213

Narrowband inverse Compton scattering x-ray sources at high laser intensities  

NASA Astrophysics Data System (ADS)

Narrowband x- and ? -ray sources based on the inverse Compton scattering of laser pulses suffer from a limitation of the allowed laser intensity due to the onset of nonlinear effects that increase their bandwidth. It has been suggested that laser pulses with a suitable frequency modulation could compensate this ponderomotive broadening and reduce the bandwidth of the spectral lines, which would allow one to operate narrowband Compton sources in the high-intensity regime. In this paper we therefore present the theory of nonlinear Compton scattering in a frequency-modulated intense laser pulse. We systematically derive the optimal frequency modulation of the laser pulse from the scattering matrix element of nonlinear Compton scattering, taking into account the electron spin and recoil. We show that, for some particular scattering angle, an optimized frequency modulation completely cancels the ponderomotive broadening for all harmonics of the backscattered light. We also explore how sensitively this compensation depends on the electron-beam energy spread and emittance, as well as the laser focusing.

Seipt, D.; Rykovanov, S. G.; Surzhykov, A.; Fritzsche, S.

2015-03-01

214

The Compton Gamma Ray Observatory: highlights from the first three years of the mission.  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray observatory is the second in NASA's series of Great Observatories. It has been in operation for over three years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments continue to function nearly flawlessly, and many significant discoveries have been made. The authors describe the capabilities of the four scientific instruments, and highlight some of the results from the first three years of the mission.

Gehrels, N.; Shrader, C.; Kniffen, D. A.

215

Gamma ray burst source locations with the Ulysses/Compton/PVO network  

NASA Technical Reports Server (NTRS)

The new interplanetary gamma-ray burst network will determine source fields with unprecedented accuracy. The baseline of the Ulysses mission and the locations of Pioneer-Venus Orbiter and of Mars Observer will ensure precision to a few tens of arc seconds. Combined with the event phenomenologies of the Burst and Transient Source Experiment on Compton Observatory, the source locations to be achieved with this network may provide a basic new understanding of the puzzle of gamma ray bursts.

Cline, T. L.; Hurley, K. C.; Boer, M.; Sommer, M.; Niel, M.; Fishman, G. J.; Kouveliotou, C.; Meegan, C. A.; Paciesas, W. S.; Wilson, R. B.

1992-01-01

216

Sensitivity booster for DOI-PET scanner by utilizing Compton scattering events between detector blocks  

NASA Astrophysics Data System (ADS)

In a conventional PET scanner, coincidence events are measured with a limited energy window for detection of photoelectric events in order to reject Compton scatter events that occur in a patient, but Compton scatter events caused in detector crystals are also rejected. Scatter events within the patient causes scatter coincidences, but inter crystal scattering (ICS) events have useful information for determining an activity distribution. Some researchers have reported the feasibility of PET scanners based on a Compton camera for tracing ICS into the detector. However, these scanners require expensive semiconductor detectors for high-energy resolution. In the Anger-type block detector, single photons interacting with multiple detectors can be obtained for each interacting position and complete information can be gotten just as for photoelectric events in the single detector. ICS events in the single detector have been used to get coincidence, but single photons interacting with multiple detectors have not been used to get coincidence. In this work, we evaluated effect of sensitivity improvement using Compton kinetics in several types of DOI-PET scanners. The proposed method promises to improve the sensitivity using coincidence events of single photons interacting with multiple detectors, which are identified as the first interaction (FI). FI estimation accuracy can be improved to determine FI validity from the correlation between Compton scatter angles calculated on the coincidence line-of-response. We simulated an animal PET scanner consisting of 42 detectors. Each detector block consists of three types of scintillator crystals (LSO, GSO and GAGG). After the simulation, coincidence events are added as information for several depth-of-interaction (DOI) resolutions. From the simulation results, we concluded the proposed method promises to improve the sensitivity considerably when effective atomic number of a scintillator is low. Also, we showed that FI estimate accuracy is improved, as DOI resolution is high.

Yoshida, Eiji; Tashima, Hideaki; Yamaya, Taiga

2014-11-01

217

Design and optimization of MeV class Compton scattering MEGa-ray sources  

NASA Astrophysics Data System (ADS)

The design and optimization of a Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering source are presented. A new precision source with up to 2.5 MeV photon energies, enabled by state of the art laser and x-band linac technologies, is currently being built at LLNL. Various aspects of the theoretical design, including dose and brightness optimization, will be presented. In particular, while it is known that nonlinear effects occur in such light sources when the laser normalized potential is close to unity, we show that these can appear at lower values of the potential. A three dimensional analytical model and numerical benchmarks have been developed to model the source characteristics, including nonlinear spectra. Since MEGa-ray sources are being developed for precision applications such as nuclear resonance fluorescence, assessing spectral broadening mechanisms is essential. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Albert, Felicie; Anderson, S. G.; Betts, S. M.; Cross, R. R.; Ebbers, C. A.; Houck, T. L.; Gibson, D. J.; Marsh, R. A.; Messerly, M.; Shverdin, M. Y.; Wu, S. S.; Hartemann, F. V.; Siders, C. W.; Scarpetti, R. D.; Barty, C. P. J.

2010-11-01

218

Asymptotic Completeness for Compton Scattering J. Frohlich 1# , M. Griesemer 2+ and B. Schlein 3#  

E-print Network

electrodynamics (QED) it became possible to calculate the cross section for Compton scattering perturbatively# in the interaction term. Of course, after having calculated suitable cross sections, one attempts to let the photon to work very well; see [YFS61]. If the total energy of the incoming particles, photons and an electron

219

A new model for tracing first-order Compton scatter in quantitative SPECT imaging  

Microsoft Academic Search

A new model for tracing the first-order Compton scatter was implemented based on the Klein-Nishina formula and Siddon method. This model significantly improved the accuracy with comparable computing effort to our previous work. It further extended our previous work in tracing all attenuation factors within each bin view subtended by collimator holes. Therefore, this model simulates SPECT data accurately up

Zhengrong Liang; Juihsi Cheng; Jinghan Ye

1996-01-01

220

Photoproduction of vector mesons at high energies and Compton scattering by nucleons  

Microsoft Academic Search

We consider photoproduction of vector mesons and Compton scattering at high energies. Coupling of the electromagnetic current to neutral vector mesons as given theoretically in quark models and experimentally in storage-ring experiments is assumed. This gives a reasonable theory for rho, omega, phi, psi, and psi' photoproduction processes in a unified manner with appropriate energy dependence for (dsigmadt)0 for phi,

S. P. Misra; L. Maharana

1978-01-01

221

Fixed-Angle Dispersion Relations for Nucleon Compton Scattering. I  

Microsoft Academic Search

The Mandelstam representation is used to derive fixed-angle dispersion relations for the twelve scalar amplitudes describing the process gamma+N-->gamma+N. The electromagnetic interaction is calculated to order e2. The strong interactions are estimated by including one- and two-pion exchange on the left-hand cut. These depend on the pi0-->2gamma decay lifetime and on the T=0 pipi phase shift and the total cross

A. C. Hearn

1962-01-01

222

Intershell correlations in nonresonant Compton scattering of an X-ray photon by an atom  

SciTech Connect

The role of intershell correlations in nonresonant Compton scattering of an X-ray photon by a free multielectron atom is studied theoretically for the Ar atom. The results of calculation are of a predictive nature. The developed mathematical formalism is general in nature and can be applied to a wide set of elements from the Periodic Table, for which the description of the wavefunctions of scattering states in the nonrelativistic Hartree-Fock approximation remains correct.

Hopersky, A. N., E-mail: hopersky_vm_1@rgups.ru; Nadolinsky, A. M.; Ikoeva, K. Kh.; Khoroshavina, O. A. [Rostov State Railway University (Russian Federation)

2011-11-15

223

GPDs, the structure of the proton and wide-angle Compton scattering  

E-print Network

Results from a recent analysis of the zero-skewness generalized parton distributions (GPDs) for valence quarks are reviewed. The analysis bases on a physically motivated parameterization of the GPDs with a few free parameters adjusted to the nucleon form factor data. Results for the GPDs are presented and a number of applications such as moments, Ji's sum rule or their impact parameter representation are discussed. The 1/x moments, in particular, form the soft physics input to Compton scattering off protons within the handbag approach. The Compton cross section evaluated from this information is found to be in good agreement with experiment.

P. Kroll

2006-12-04

224

Electromagnetic Form Factors of the Nucleon and Compton Scattering  

E-print Network

We review the experimental and theoretical status of elastic electron scattering and elastic low-energy photon scattering (with both real and virtual photons) from the nucleon. As a consequence of new experimental facilities and new theoretical insights, these subjects are advancing with unprecedented precision. These reactions provide many important insights into the spatial distributions and correlations of quarks in the nucleon.

Charles Earl Hyde-Wright; Kees de Jager

2005-07-01

225

INVERSE-COMPTON CONTRIBUTION TO THE STAR-FORMING EXTRAGALACTIC GAMMA-RAY BACKGROUND  

SciTech Connect

Fermi has resolved several star-forming galaxies, but the vast majority of the star-forming universe is unresolved, and thus contributes to the extragalactic gamma-ray background (EGB). Here, we calculate the contribution of star-forming galaxies to the EGB in the Fermi range from 100 MeV to 100 GeV due to inverse-Compton (IC) scattering of the interstellar photon field by cosmic-ray electrons. We first construct one-zone models for individual star-forming galaxies assuming that supernovae power the acceleration of cosmic rays. We develop templates for both normal and starburst galaxies, accounting for differences in the cosmic-ray electron propagation and in the interstellar radiation fields. For both types of star-forming galaxies, the same IC interactions leading to gamma rays also substantially contribute to the energy loss of the high-energy cosmic-ray electrons. Consequently, a galaxy's IC emission is determined by the relative importance of IC losses in the cosmic-ray electron energy budget ({sup p}artial calorimetry{sup )}. We calculate the cosmological contribution of star-forming galaxies to the EGB using our templates and the cosmic star formation rate distribution. For all of our models, we find that the IC EGB contribution is almost an order of magnitude less than the peak of the emission due to cosmic-ray ion interactions (mostly pionic p{sub cr} p{sub ism} {yields} {pi}{sup 0} {yields} {gamma}{gamma}); even at the highest Fermi energies, IC is subdominant. The flatter IC spectrum increases the high-energy signal of the pionic+IC sum, bringing it closer to the EGB spectral index observed by Fermi. Partial calorimetry ensures that the overall IC signal is relatively well constrained, with only uncertainties in the amplitude and spectral shape for plausible model choices. We conclude with a brief discussion on how the pionic spectral feature and other methods can be used to measure the star-forming component of the EGB.

Chakraborty, Nachiketa [Department of Astronomy, University of Illinois, Urbana, IL (United States); Fields, Brian D. [Also, Department of Physics, University of Illinois, Urbana, IL (United States)

2013-08-20

226

The results of the in-flight attitude sensor calibration for the Arthur Holly Compton Gamma Ray Observatory  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray Observatory (GRO) was launched by the shuttle Atlantis in April 1991. This paper presents the results of the attitude sensor calibration that was performed during the early mission. The GSFC Flight Dynamics Facility (FDF) performed an alignment calibration of the two fixed-head star trackers (FHST's) and two fine Sun sensors (FSS's) on board Compton

W. S. Davis; A. H. Eudell; L. S. Kulp; L. A. Lindrose; R. R. Harman

1993-01-01

227

Time-step limits for a Monte Carlo Compton-scattering method  

SciTech Connect

Compton scattering is an important aspect of radiative transfer in high energy density applications. In this process, the frequency and direction of a photon are altered by colliding with a free electron. The change in frequency of a scattered photon results in an energy exchange between the photon and target electron and energy coupling between radiation and matter. Canfield, Howard, and Liang have presented a Monte Carlo method for simulating Compton scattering that models the photon-electron collision kinematics exactly. However, implementing their technique in multiphysics problems that include the effects of radiation-matter energy coupling typically requires evaluating the material temperature at its beginning-of-time-step value. This explicit evaluation can lead to unstable and oscillatory solutions. In this paper, we perform a stability analysis of this Monte Carlo method and present time-step limits that avoid instabilities and nonphysical oscillations by considering a spatially independent, purely scattering radiative-transfer problem. Examining a simplified problem is justified because it isolates the effects of Compton scattering, and existing Monte Carlo techniques can robustly model other physics (such as absorption, emission, sources, and photon streaming). Our analysis begins by simplifying the equations that are solved via Monte Carlo within each time step using the Fokker-Planck approximation. Next, we linearize these approximate equations about an equilibrium solution such that the resulting linearized equations describe perturbations about this equilibrium. We then solve these linearized equations over a time step and determine the corresponding eigenvalues, quantities that can predict the behavior of solutions generated by a Monte Carlo simulation as a function of time-step size and other physical parameters. With these results, we develop our time-step limits. This approach is similar to our recent investigation of time discretizations for the Compton-scattering Fokker-Planck equation.

Densmore, Jeffery D [Los Alamos National Laboratory; Warsa, James S [Los Alamos National Laboratory; Lowrie, Robert B [Los Alamos National Laboratory

2008-01-01

228

The integration of improved Monte Carlo compton scattering algorithms into the Integrated TIGER Series.  

SciTech Connect

The Integrated TIGER Series (ITS) is a software package that solves coupled electron-photon transport problems. ITS performs analog photon tracking for energies between 1 keV and 1 GeV. Unlike its deterministic counterpart, the Monte Carlo calculations of ITS do not require a memory-intensive meshing of phase space; however, its solutions carry statistical variations. Reducing these variations is heavily dependent on runtime. Monte Carlo simulations must therefore be both physically accurate and computationally efficient. Compton scattering is the dominant photon interaction above 100 keV and below 5-10 MeV, with higher cutoffs occurring in lighter atoms. In its current model of Compton scattering, ITS corrects the differential Klein-Nishina cross sections (which assumes a stationary, free electron) with the incoherent scattering function, a function dependent on both the momentum transfer and the atomic number of the scattering medium. While this technique accounts for binding effects on the scattering angle, it excludes the Doppler broadening the Compton line undergoes because of the momentum distribution in each bound state. To correct for these effects, Ribbefor's relativistic impulse approximation (IA) will be employed to create scattering cross section differential in both energy and angle for each element. Using the parameterizations suggested by Brusa et al., scattered photon energies and angle can be accurately sampled at a high efficiency with minimal physical data. Two-body kinematics then dictates the electron's scattered direction and energy. Finally, the atomic ionization is relaxed via Auger emission or fluorescence. Future work will extend these improvements in incoherent scattering to compounds and to adjoint calculations.

Quirk, Thomas, J., IV (University of New Mexico)

2004-08-01

229

A Set of Monte Carlo Subroutines for Treating the Physics of Compton Scattering  

SciTech Connect

A set of portable Monte Carlo subroutines is presented to treat the physics of Compton scattering. Electron binding energies are included by the modification of the Klein-Nishina probability distribution by the incoherent scattering function. In addition the scattered photon's energy is calculated by taking into account the momentum distribution of the electron. These subroutines have been verified and validated by calculating the total cross section over incident photon energies of 10 keV to 100 MeV for elements of Z=l to Z=l 00 and are within 1.08% of published values.

John Lestone; Jonathan Earnhart; Thomas Prettyman

1998-12-01

230

One- and two-photon Compton scattering in strong magnetic fields  

NASA Technical Reports Server (NTRS)

Calculations are made of the Compton scattering cross section in a very strong magnetic field, such as encountered in pulsars, for arbitrary photon and electron energies. The effect of the vacuum polarization in the weak-field limit is included as well as the plasma polarizability. Radiative transitions between any pair of Landau levels are included as well as two-photon scattering. The latter process, due to the presence of the cyclotron resonance, becomes comparable to nonresonant one-photon scattering when excited final states are allowed, and acts as a source of photons which is more important than bremsstrahlung at low plasma densities.

Bussard, R. W.; Alexander, S. B.; Meszaros, P.

1986-01-01

231

Testing the homogeneous synchrotron self-Compton model for gamma-ray production in MRK 421  

Microsoft Academic Search

Based on the detected variability time-scales of X-ray and TeV gamma-ray emission, and the observed multiwavelength photon spectrum, of Mrk 421 we place constraints on the allowed parameter space (magnetic field and Doppler factor of the emission region) for the homogeneous synchrotron self-Compton model. The spectra calculated for the allowed parameters are marginally consistent with the available spectral information above

W. Bednarekand; R. J. Protheroe

1997-01-01

232

Photon polarization in Compton scattering: pulse shape effects  

NASA Astrophysics Data System (ADS)

We study in the framework of quantum electrodynamics the scattering of a plane wave electromagnetic field on free electrons in the low intensity limit. We derive analytic formulas describing the polarization properties of the emitted photons. We discuss and illustrate with a numerical example the effects of the electromagnetic pulse duration on their polarization.

Boca, M.; Stoica, C.; Dumitriu, A.; Florescu, V.

2015-03-01

233

Nonlinear Compton scattering of ultrashort intense laser pulses  

NASA Astrophysics Data System (ADS)

The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time-dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed unambiguously in respect of the pulse length. A broad distribution of scattered photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase-space region is identified where the differential photon distribution is strongly modified by quantum effects.

Seipt, D.; Kämpfer, B.

2011-02-01

234

Nonlinear Compton scattering of ultrashort intense laser pulses  

SciTech Connect

The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time-dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed unambiguously in respect of the pulse length. A broad distribution of scattered photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase-space region is identified where the differential photon distribution is strongly modified by quantum effects.

Seipt, D.; Kaempfer, B. [Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany)

2011-02-15

235

Probing Proton Strangeness with Time-Like Virtual Compton Scattering  

E-print Network

We document that p(gamma,e+e-)p measurements will yield new, important information about the off-shell time-like nucleon form factors, especially in the phi meson region (q^2 = M^2_{phi}) governing the phi N couplings g^{V,T}_{\\phi N N}. Calculations for p(gamma,e+e-)p, utilizing vector meson dominance, predict measurable phi enhancements at high |t| compared to the expected phi background production from pi, eta and Pomeron exchange. The phi form factor contribution generates a novel experimental signature for OZI violation and the proton strangeness content. The phi N couplings are determined independently from a combined analysis of the neutron electric form factor and recent high |t| phi photoproduction. The pi, eta and Pomeron transition form factors are also predicted and the observed pi and eta transition moments are reproduced.

Stephen R. Cotanch; Robert A. Williams

2002-05-22

236

Measurements of double-polarized compton scattering asymmetries and extraction of the proton spin polarizabilities.  

PubMed

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the ?(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields ?_{E1E1}=-3.5±1.2, ?_{M1M1}=3.16±0.85, ?_{E1M2}=-0.7±1.2, and ?_{M1E2}=1.99±0.29, in units of 10^{-4}??fm^{4}. PMID:25839263

Martel, P P; Miskimen, R; Aguar-Bartolome, P; Ahrens, J; Akondi, C S; Annand, J R M; Arends, H J; Barnes, W; Beck, R; Bernstein, A; Borisov, N; Braghieri, A; Briscoe, W J; Cherepnya, S; Collicott, C; Costanza, S; Denig, A; Dieterle, M; Downie, E J; Fil'kov, L V; Garni, S; Glazier, D I; Gradl, W; Gurevich, G; Hall Barrientos, P; Hamilton, D; Hornidge, D; Howdle, D; Huber, G M; Jude, T C; Kaeser, A; Kashevarov, V L; Keshelashvili, I; Kondratiev, R; Korolija, M; Krusche, B; Lazarev, A; Lisin, V; Livingston, K; MacGregor, I J D; Mancell, J; Manley, D M; Meyer, W; Middleton, D G; Mushkarenkov, A; Nefkens, B M K; Neganov, A; Nikolaev, A; Oberle, M; Ortega Spina, H; Ostrick, M; Ott, P; Otte, P B; Oussena, B; Pedroni, P; Polonski, A; Polyansky, V; Prakhov, S; Rajabi, A; Reicherz, G; Rostomyan, T; Sarty, A; Schrauf, S; Schumann, S; Sikora, M H; Starostin, A; Steffen, O; Strakovsky, I I; Strub, T; Supek, I; Thiel, M; Tiator, L; Thomas, A; Unverzagt, M; Usov, Y; Watts, D P; Witthauer, L; Werthmüller, D; Wolfes, M

2015-03-20

237

Investigating the proton structure through polarization transfers in real Compton scattering processes at JLAB  

SciTech Connect

In the present work, preliminary results of the analysis of polarization transfers in real Compton scattering (RCS) performed in Hall-C at JLAB are presented, for data collected at large scattering angle (?{sub cm}=70{degrees}) in the experiment E07-002. A previous experiment, E99-114, has already demonstrated a complete inconsistence of its results with a pQCD mechanism at JLAB energy regime. This kind of experiment, therefore, is of crucial importance for understanding the nature of the reaction mechanism for such a simple process, involving a real photon. Furthermore, RCS experiments allow the extraction of Compton form factors and Generalized Parton Distributions (GPDs), the latter connected to the total angular momentum of the nucleon.

Fanelli, Cristiano V. [INFN/Sanita, Roma, ITALY; Cisbani, Evaristo [INFN/Sanita, Roma, ITALY; Hamilton, David J. [Glasgow University; Salme, Giovanni [Instituto Nazionale de Fisica Nucleare, Italy; Wojtsekhowski, Bogdan B. [JLAB

2014-06-01

238

Observation of pulsed x-ray trains produced by laser-electron Compton scatterings  

SciTech Connect

X-ray generation based on laser-electron Compton scattering is one attractive method to achieve a compact laboratory-sized high-brightness x-ray source. We have designed, built, and tested such a source; it combines a 50 MeV multibunch electron linac with a mode-locked 1064 nm laser stored and amplified in a Fabry-Perot optical cavity. We directly observed trains of pulsed x rays using a microchannel plate detector; the resultant yield was found to be 1.2x10{sup 5} Hz in good agreement with prediction. We believe that the result has demonstrated good feasibility of linac-based compact x-ray sources via laser-electron Compton scatterings.

Sakaue, Kazuyuki; Washio, Masakazu [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Araki, Sakae; Fukuda, Masafumi; Higashi, Yasuo; Honda, Yosuke; Omori, Tsunehiko; Taniguchi, Takashi; Terunuma, Nobuhiro; Urakawa, Junji [KEK (High Energy Accelerator Research Organization), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Sasao, Noboru [Department of Physics, Kyoto University, Sakyo, Kyoto 606-8502 (Japan)

2009-12-15

239

Study of the proton structure by measurements of polarization transfers in real Compton scattering at Jlab  

SciTech Connect

A preliminary analysis of polarization-transfer data at large scattering angle (70°), obtained in an experiment of real Compton scattering on proton, performed in Hall-C of Jefferson Lab, is presented. It is also discussed the relevance of this kind of experiments for shedding light on the non-perturbative structure of the proton, at low energy, and on the transition from the non-perturbative regime to the perturbative one, that occurs at high energy. Moreover, the possibility to extract Compton form factors and the Generalized Parton Distributions, one of the most promising theoretical tool to determine the total angular momentum contribution of quarks and gluons to nucleon spin, is emphasized.

Fanelli, Cristiano Fanelli; Cisbani, Evarostp; Hamilton, David; Salme, G.; Wojtsekhowski, Bogdan B. [JLAB

2014-03-01

240

Measurements of Double-Polarized Compton Scattering Asymmetries and Extraction of the Proton Spin Polarizabilities  

NASA Astrophysics Data System (ADS)

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the ? (1232 ) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields ?E 1 E 1=-3.5 ±1.2 , ?M 1 M 1=3.16 ±0.85 , ?E 1 M 2=-0.7 ±1.2 , and ?M 1 E 2=1.99 ±0.29 , in units of 1 0-4 fm4 .

Martel, P. P.; Miskimen, R.; Aguar-Bartolome, P.; Ahrens, J.; Akondi, C. S.; Annand, J. R. M.; Arends, H. J.; Barnes, W.; Beck, R.; Bernstein, A.; Borisov, N.; Braghieri, A.; Briscoe, W. J.; Cherepnya, S.; Collicott, C.; Costanza, S.; Denig, A.; Dieterle, M.; Downie, E. J.; Fil'kov, L. V.; Garni, S.; Glazier, D. I.; Gradl, W.; Gurevich, G.; Hall Barrientos, P.; Hamilton, D.; Hornidge, D.; Howdle, D.; Huber, G. M.; Jude, T. C.; Kaeser, A.; Kashevarov, V. L.; Keshelashvili, I.; Kondratiev, R.; Korolija, M.; Krusche, B.; Lazarev, A.; Lisin, V.; Livingston, K.; MacGregor, I. J. D.; Mancell, J.; Manley, D. M.; Meyer, W.; Middleton, D. G.; Mushkarenkov, A.; Nefkens, B. M. K.; Neganov, A.; Nikolaev, A.; Oberle, M.; Ortega Spina, H.; Ostrick, M.; Ott, P.; Otte, P. B.; Oussena, B.; Pedroni, P.; Polonski, A.; Polyansky, V.; Prakhov, S.; Rajabi, A.; Reicherz, G.; Rostomyan, T.; Sarty, A.; Schrauf, S.; Schumann, S.; Sikora, M. H.; Starostin, A.; Steffen, O.; Strakovsky, I. I.; Strub, T.; Supek, I.; Thiel, M.; Tiator, L.; Thomas, A.; Unverzagt, M.; Usov, Y.; Watts, D. P.; Witthauer, L.; Werthmüller, D.; Wolfes, M.; A2 Collaboration at MAMI

2015-03-01

241

Simulation Studies of Delta-ray Backgrounds in a Compton-Scatter Transition Radiation Detector  

E-print Network

In order to evaluate the response to cosmic-ray nuclei of a Compton-Scatter Transition Radiation Detector in the proposed ACCESS space-based mission, a hybrid Monte Carlo simulation using GEANT3 and an external transition radiation (TR) generator routine was constructed. This simulation was employed to study the effects of delta-ray production induced by high-energy nuclei and to maximize the ratio of TR to delta-ray background. The results demonstrate the ability of a Compton-Scatter Transition Radiation Detector to measure nuclei from boron to iron up to Lorentz factors ~ 10^5 taking into account the steeply falling power-law cosmic ray spectra.

Krizmanic, J F; Streitmatter, R E; Krizmanic, John F.; Cherry, Michael L.; Streitmatter, Robert E.

2006-01-01

242

Compact x-ray source based on burst-mode inverse Compton scattering at 100 kHz  

E-print Network

A design for a compact x-ray light source (CXLS) with flux and brilliance orders of magnitude beyond existing laboratory scale sources is presented. The source is based on inverse Compton scattering of a high brightness ...

Bessuille, J.

243

Virtual Compton scattering and neutral pion electroproduction in the resonance region up to the deep inelastic region at backward angles  

E-print Network

We have made the first measurements of the virtual Compton scattering (VCS) process via the H(e, e'p)? exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the W-dependence at ...

Zhou, Z. -L.

244

Measurement of Deeply Virtual Compton Scattering with a Polarized-Proton Target  

Microsoft Academic Search

The longitudinal target-spin asymmetry AUL for the exclusive electroproduction of high-energy photons was measured for the first time in ep-->-->e'pgamma. The data have been accumulated at JLab with the CLAS spectrometer using 5.7 GeV electrons and a longitudinally polarized NH3 target. A significant azimuthal angular dependence was observed, resulting from the interference of the deeply virtual Compton scattering and Bethe-Heitler

S. Chen; H. Avakian; V. D. Burkert; P. Eugenio; G. Adams; M. Amarian; P. Ambrozewicz; M. Anghinolfi; G. Asryan; H. Bagdasaryan; N. Baillie; J. P. Ball; N. A. Baltzell; S. Barrow; V. Batourine; M. Battaglieri; K. Beard; I. Bedlinskiy; M. Bektasoglu; M. Bellis; N. Benmouna; B. L. Berman; A. S. Biselli; B. E. Bonner; S. Bouchigny; S. Boiarinov; P. Bosted; R. Bradford; D. Branford; W. J. Briscoe; W. K. Brooks; S. Bültmann; C. Butuceanu; J. R. Calarco; S. L. Careccia; D. S. Carman; B. Carnahan; A. Cazes; P. L. Cole; P. Collins; P. Coltharp; D. Cords; P. Corvisiero; D. Crabb; H. Crannell; V. Crede; J. P. Cummings; R. De Masi; R. Devita; E. De Sanctis; P. V. Degtyarenko; H. Denizli; L. Dennis; A. Deur; K. V. Dharmawardane; K. S. Dhuga; C. Djalali; G. E. Dodge; J. Donnelly; D. Doughty; M. Dugger; S. Dytman; O. P. Dzyubak; H. Egiyan; K. S. Egiyan; L. El Fassi; L. Elouadrhiri; R. Fatemi; G. Fedotov; G. Feldman; R. J. Feuerbach; T. A. Forest; H. Funsten; M. Garçon; G. Gavalian; G. P. Gilfoyle; K. L. Giovanetti; F. X. Girod; J. T. Goetz; E. Golovatch; A. Gonenc; R. W. Gothe; K. A. Griffioen; M. Guidal; M. Guillo; N. Guler; L. Guo; V. Gyurjyan; C. Hadjidakis; K. Hafidi; H. Hakobyan; R. S. Hakobyan; J. Hardie; D. Heddle; F. W. Hersman; K. Hicks; I. Hleiqawi; M. Holtrop; M. Huertas; C. E. Hyde-Wright; Y. Ilieva; D. G. Ireland; B. S. Ishkhanov; E. L. Isupov; M. M. Ito; D. Jenkins; H. S. Jo; K. Joo; H. G. Juengst; C. Keith; J. D. Kellie; M. Khandaker; K. Y. Kim; W. Kim; A. Klein; F. J. Klein; M. Klusman; M. Kossov; L. H. Kramer; V. Kubarovsky; J. Kuhn; S. E. Kuhn; S. V. Kuleshov; J. Lachniet; J. M. Laget; J. Langheinrich; D. Lawrence; Ji Li; A. C. S. Lima; K. Livingston; H. Lu; K. Lukashin; M. MacCormick; N. Markov; S. McAleer; B. McKinnon; J. W. C. McNabb; B. A. Mecking; M. D. Mestayer; C. A. Meyer; T. Mibe; K. Mikhailov; R. Minehart; M. Mirazita; R. Miskimen; V. Mokeev; L. Morand; S. A. Morrow; M. Moteabbed; J. Mueller; G. S. Mutchler; P. Nadel-Turonski; J. Napolitano; R. Nasseripour; N. Natasha; S. Niccolai; G. Niculescu; I. Niculescu; B. B. Niczyporuk; M. R. Niroula; R. A. Niyazov; M. Nozar; G. V. O'Rielly; M. Osipenko; A. I. Ostrovidov; E. Pasyuk; C. Paterson; S. A. Philips; J. Pierce; N. Pivnyuk; D. Pocanic; O. Pogorelko; E. Polli; I. Popa; S. Pozdniakov; B. M. Preedom; J. W. Price; Y. Prok; D. Protopopescu; L. M. Qin; B. A. Raue; G. Riccardi; G. Ricco; M. Ripani; B. G. Ritchie; F. Ronchetti; G. Rosner; P. Rossi; D. Rowntree; P. D. Rubin; F. Sabatié; C. Salgado; J. P. Santoro; V. Sapunenko; R. A. Schumacher; V. S. Serov; Y. G. Sharabian; J. Shaw; N. V. Shvedunov; A. V. Skabelin; E. S. Smith; L. C. Smith; D. I. Sober; A. Stavinsky; S. S. Stepanyan; B. E. Stokes; P. Stoler; I. I. Strakovsky; S. Strauch; R. Suleiman; M. Taiuti; D. J. Tedeschi; U. Thoma; A. Tkabladze; S. Tkachenko; L. Todor; C. Tur; M. Ungaro; M. Vanderhaeghen; M. F. Vineyard; A. V. Vlassov; D. P. Watts; L. B. Weinstein; D. P. Weygand; M. Williams; E. Wolin; M. H. Wood; A. Yegneswaran; J. Yun; L. Zana; J. Zhang; B. Zhao; Z. Zhao

2006-01-01

245

Compton-Scattering Cross Section on the Proton at High Momentum Transfer  

Microsoft Academic Search

Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s=5 11 and -t=2 7GeV2 with a statistical accuracy of a few percent. The scaling power for the s dependence of the cross section at fixed center-of-mass angle was found to be 8.0±0.2, strongly inconsistent with the prediction of perturbative QCD. The observed

A. Danagoulian; V. H. Mamyan; M. Roedelbronn; K. A. Aniol; J. R. M. Annand; P. Y. Bertin; L. Bimbot; P. Bosted; J. R. Calarco; A. Camsonne; C. C. Chang; T.-H. Chang; J.-P. Chen; Seonho Choi; E. Chudakov; P. Degtyarenko; C. W. de Jager; A. Deur; D. Dutta; K. Egiyan; H. Gao; F. Garibaldi; O. Gayou; R. Gilman; A. Glamazdin; C. Glashausser; J. Gomez; D. J. Hamilton; J.-O. Hansen; D. Hayes; D. W. Higinbotham; W. Hinton; T. Horn; C. Howell; T. Hunyady; C. E. Hyde-Wright; X. Jiang; M. K. Jones; M. Khandaker; A. Ketikyan; V. Koubarovski; K. Kramer; G. Kumbartzki; G. Laveissière; J. Lerose; R. A. Lindgren; D. J. Margaziotis; P. Markowitz; K. McCormick; D. G. Meekins; Z.-E. Meziani; R. Michaels; P. Moussiegt; S. Nanda; A. M. Nathan; D. M. Nikolenko; V. Nelyubin; B. E. Norum; K. Paschke; L. Pentchev; C. F. Perdrisat; E. Piasetzky; R. Pomatsalyuk; V. A. Punjabi; I. Rachek; A. Radyushkin; B. Reitz; R. Roche; G. Ron; F. Sabatié; A. Saha; N. Savvinov; A. Shahinyan; Y. Shestakov; S. Sirca; K. Slifer; P. Solvignon; P. Stoler; S. Tajima; V. Sulkosky; L. Todor; B. Vlahovic; L. B. Weinstein; K. Wang; B. Wojtsekhowski; H. Voskanyan; H. Xiang; X. Zheng; L. Zhu

2007-01-01

246

Treatment of Compton scattering of linearly polarized photons in Monte Carlo codes  

NASA Astrophysics Data System (ADS)

The basic formalism of Compton scattering of linearly polarized photons is reviewed, and some simple prescriptions to deal with the transport of polarized photons in Monte Carlo simulation codes are given. Fortran routines, based on the described method, have been included in MCNP, a widely used code for neutrons, photons and electrons transport. As this improved version of the code can be of general use, the implementation and the procedures to employ the new version of the code are discussed.

Matt, Giorgio; Feroci, Marco; Rapisarda, Massimo; Costa, Enrico

1996-10-01

247

Time-step limits for a Monte Carlo Compton-scattering method  

SciTech Connect

We perform a stability analysis of a Monte Carlo method for simulating the Compton scattering of photons by free electron in high energy density applications and develop time-step limits that avoid unstable and oscillatory solutions. Implementing this Monte Carlo technique in multi physics problems typically requires evaluating the material temperature at its beginning-of-time-step value, which can lead to this undesirable behavior. With a set of numerical examples, we demonstrate the efficacy of our time-step limits.

Densmore, Jeffery D [Los Alamos National Laboratory; Warsa, James S [Los Alamos National Laboratory; Lowrie, Robert B [Los Alamos National Laboratory

2009-01-01

248

A next-to-leading order analysis of deeply virtual Compton scattering  

E-print Network

We present a complete, next-to-leading-order (NLO), leading-twist QCD analysis of deeply virtual Compton scattering (DVCS) observables, in the ${\\bar {MS}}$ scheme, and in the kinematic ranges of the H1, ZEUS and HERMES experiments. We use a modified form of Radyushkin's ansatz for the input model for the generalized parton distributions. We present results for leading order (LO) and NLO for representative observables and find that they compare favourably to the available data.

A. Freund; M. F. McDermott

2002-04-03

249

A simple method for computing the relativistic Compton scattering kernel for radiative transfer  

NASA Technical Reports Server (NTRS)

Correct computation of the Compton scattering kernel (CSK), defined to be the Klein-Nishina differential cross section averaged over a relativistic Maxwellian electron distribution, is reported. The CSK is analytically reduced to a single integral, which can then be rapidly evaluated using a power series expansion, asymptotic series, and rational approximation for sigma(s). The CSK calculation has application to production codes that aim at understanding certain astrophysical, laser fusion, and nuclear weapons effects phenomena.

Prasad, M. K.; Kershaw, D. S.; Beason, J. D.

1986-01-01

250

Status of the Polarized Nonlinear Inverse Compton Scattering Experiment at UCLA  

SciTech Connect

An Inverse Compton Scattering (ICS) experiment investigating the polarized harmonic production in the nonlinear regime has begun which will utilize the existing terawatt CO2 laser system and 15 MeV photoinjector in the Neptune Laboratory at UCLA. A major motivation for a source of high brightness polarized x-rays is the production of polarized positrons for use in future linear collider experiments. We report on the experimental set-up and status.

Williams, O.; Doyuran, A.; England, R. J.; Rosenzweig, J. B.; Travish, G. [Department of Physics and Astronomy, University of California, Los Angeles (United States); Joshi, C.; Tochitsky, S. [Department of Electrical Engineering, University of California, Los Angeles, Los Angeles, CA 90095 (United States)

2006-11-27

251

Balloon-borne experiment for observation of sub-MeV/MeV gamma-rays from Crab Nebula using an Electron Tracking Compton Camera  

NASA Astrophysics Data System (ADS)

In astronomy, the observations of gamma-ray in sub-MeV/MeV energy band is expected to provide much information of various high energy phenomena, for example, the nucleosynthesis in supernovae, the particle acceleration in active galactic nuclei, gamma-ray bursts, and the strong gravity potential of black holes. However, sufficient observation has not yet been achieved due to difficulties of Compton gamma-ray imaging and rejection of large radiation backgrounds produced by the interaction of cosmic rays with a satellite body. To advance the MeV gamma-ray astronomy, we have developed an Electron Tracking Compton Camera (ETCC) as a next-generation MeV gamma-ray telescope. In comparison with a classical Compton camera, the ETCC measures a three dimensional track of the Compton recoil electron in the gas detector, which makes it possible to restrict the arrival direction of each incident gamma-ray to arc segment and remove backgrounds strongly using the kinematics test of Compton scattering and the particle identification by energy loss rate of charged particle. We planned the balloon experiments “Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment” (SMILE) to check the performance of ETCC in space for the future satellite observation. We have already carried out the first balloon borne experiment in 2006 using a small size ETCC with a 10 times 10 times 15 cm(3) detection area (SMILE-I), and we observed successfully the fluxes of the diffuse cosmic and atmospheric gamma rays at an altitude of 35 km during a live time of 3 hours and reveal the good background rejection ability of an ETCC. As the next step of SMILE, we plan to observe bright celestial sources like Crab Nebula to verify the gamma-ray imaging ability of an ETCC (SMILE-II) at middle latitude in the northern hemisphere. We have already constructed the SMILE-II flight ETCC system using a large size ETCC with (30 cm)(3) detection area and completely upgraded data acquisition system for reducing the dead time and power consumption. Furthermore, we improved the data acquisition algorithm of electron tracking to improve the effective area of the ETCC. Now we have confirmed the performance of the SMILE-II flight ETCC system by ground-based experiments. With the obtained results, Crab Nebula can be detected by the ETCC with a significance above the 5 sigma level in several hours in a one day balloon flight experiment. In this paper, we will report the details of the SMILE-II project and the the performance of the SMILE-II flight ETCC.

Komura, Shotaro

252

X-ray polarization by Compton scattering in Seyfert galaxies.  

NASA Astrophysics Data System (ADS)

The authors have calculated, by means of Montecarlo simulations, the dependence of the intensity and of the degree of polarization on the inclination angle and on the energy of the radiation reflected by cold, optically thick accreting matter located close to the central X-ray source; they have also calculated the polarization of the radiation scattered by a cloud of free electrons possibly surrounding the X-ray source and the Broad Lines Region.

Matt, G.; Perola, G. C.; Piro, L.

253

Evaluation of Compton scattering and self-attenuation coefficient after ? -ray analysis of naturally occurring radioactive elements in environmental samples  

Microsoft Academic Search

Comparison of Compton scattering and Compton scattering cross section with self-attenuation coefficient were explained based\\u000a on the kinematic equation and Klein-Nishina formula. Naturally occurring elements, 238U (226Ra), 40K, 232Th (228Ra) and 137Cs were determined in sediments and water from Ismailia canal in Egypt which were found in the range of permissible level.\\u000a Self-attenuation coefficients, K, the ratio between photopeak detection

A. A. El-Sayed

2007-01-01

254

In-Flight Calibration of the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory  

NASA Technical Reports Server (NTRS)

The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory has been operating for over seven years since its launch in 1991 April. This span of time far exceeds the design lifetime of two years. As the instrument has aged, several changes have occurred due to spark chamber gas exchanges as well as some hardware degradation and failures, all of which have an influence on the instrument sensitivity. This paper describes post-launch measurements and analysis that are done to calibrate the instrument response functions. The updated instrument characteristics are incorporated into the analysis software.

Esposito, J. A.; Bertsch, D. L.; Chen, A. W.; Dingus, B. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mayer-Hasselwander, H. A.; McDonald, L. M.; Michelson, P. F.; vonMontigny, C.; Mukherjee, R.; Nolan, P. L.; Schneid, E.; Sreekumar, P.; Thompson, D. J.; Tompkins, W. F.

1998-01-01

255

Detection of high-energy gamma rays from quasar PKS 0528 + 134 by EGRET on the Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The first several pointing directions of the Compton Gamma Ray Observatory, launched on 1991 April 5, were toward the Galactic anticenter. In addition to the known gamma-ray sources, Crab and Geminga, high-energy gamma-ray emission was observed from the quasar PKS 0528 + 134 by the Energetic Gamma Ray Experiment Telescope (EGRET). A redshift measurement, reported here, of 2.07 confirms the identification of this object as a quasar. The differential photon spectrum is well represented by a power law with an exponent of 2.56 +/- 0.09 and a photon intensity above 100 MeV of (8.4 +/- 1.0) x 10 exp -7 photons sq cm/s. There is evidence for time variability on a time scale of a few days.

Hunter, S. D.; Bertsch, D. L.; Dingus, B. L.; Fichtel, C. E.; Hartman, R. C.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.

1993-01-01

256

Measurement of azimuthal asymmetries associated with deeply virtual Compton scattering on an unpolarized deuterium target  

NASA Astrophysics Data System (ADS)

Azimuthal asymmetries in exclusive electroproduction of a real photon from an unpolarized deuterium target are measured with respect to beam helicity and charge. They appear in the distribution of these photons in the azimuthal angle ? around the virtual-photon direction, relative to the lepton scattering plane. The extracted asymmetries are attributed to either the deeply virtual Compton scattering process or its interference with the Bethe-Heitler process. They are compared with earlier results on the proton target. In the measured kinematic region, the beam-charge asymmetry amplitudes and the leading amplitudes of the beam-helicity asymmetries on an unpolarized deuteron target are compatible with the results from unpolarized protons.

Airapetian, A.; Akopov, N.; Akopov, Z.; Amarian, M.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetisyan, E.; Ball, B.; Belostotski, S.; Bianchi, N.; Blok, H. P.; Böttcher, H.; Borissov, A.; Bowles, J.; Bryzgalov, V.; Burns, J.; Capiluppi, M.; Capitani, G. P.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; de Leo, R.; de Nardo, L.; de Sanctis, E.; Diefenthaler, M.; di Nezza, P.; Dreschler, J.; Düren, M.; Ehrenfried, M.; Elbakian, G.; Ellinghaus, F.; Fabbri, R.; Fantoni, A.; Felawka, L.; Frullani, S.; Gabbert, D.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Giordano, F.; Gliske, S.; Hadjidakis, C.; Hartig, M.; Hasch, D.; Hasegawa, T.; Hill, G.; Hillenbrand, A.; Hoek, M.; Holler, Y.; Hristova, I.; Imazu, Y.; Ivanilov, A.; Izotov, A.; Jackson, H. E.; Jgoun, A.; Jo, H. S.; Joosten, S.; Kaiser, R.; Karyan, G.; Keri, T.; Kinney, E.; Kisselev, A.; Kobayashi, N.; Korotkov, V.; Kozlov, V.; Krauss, B.; Kravchenko, P.; Krivokhijine, V. G.; Lagamba, L.; Lamb, R.; Lapikás, L.; Lehmann, I.; Lenisa, P.; Linden-Levy, L. A.; López Ruiz, A.; Lorenzon, W.; Lu, X.-G.; Lu, X.-R.; Ma, B.-Q.; Mahon, D.; Makins, N. C. R.; Manaenkov, S. I.; Manfré, L.; Mao, Y.; Marianski, B.; de La Ossa, A. Martinez; Marukyan, H.; Miller, C. A.; Miyachi, Y.; Movsisyan, A.; Muccifora, V.; Müller, D.; Murray, M.; Mussgiller, A.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaev, M.; Nowak, W.-D.; Pappalardo, L. L.; Perez-Benito, R.; Pickert, N.; Raithel, M.; Reimer, P. E.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Rubin, J.; Ryckbosch, D.; Salomatin, Y.; Sanftl, F.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Seitz, B.; Shibata, T.-A.; Shutov, V.; Stancari, M.; Statera, M.; Steffens, E.; Steijger, J. J. M.; Stenzel, H.; Stewart, J.; Stinzing, F.; Taroian, S.; Terkulov, A.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; van der Nat, P. B.; van Haarlem, Y.; van Hulse, C.; Varanda, M.; Veretennikov, D.; Vikhrov, V.; Vilardi, I.; Vogel, C.; Wang, S.; Yaschenko, S.; Ye, H.; Ye, Z.; Yen, S.; Yu, W.; Zeiler, D.; Zihlmann, B.; Zupranski, P.; Hermes Collaboration

2010-04-01

257

Breakdown of the Born-Oppenheimer description explains neutron Compton-scattering anomaly  

SciTech Connect

Several neutron Compton scattering experiments reveal an apparent drop of the proton cross section when the collision time {tau}{sub q} is around 1 fs. Such small {tau}{sub q} corresponds to a large energy spread of the proton wave packet after collision, allowing it to access excited electronic levels. This nonadiabatic excitation of electrons leads to a distortion of the shape of the neutron scattering response function with some redistribution of intensity at energies higher than the nuclear recoil energy and a slight shift of the main neutron intensity peak to lower energies.

Gidopoulos, Nikitas I. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX (United Kingdom)

2005-02-01

258

The effect of repeated Compton scatterings on the diffuse X-ray background  

NASA Technical Reports Server (NTRS)

Recent Monte Carlo computations, based on a speculative extrapolation of the electron spectrum, suggested that repeated scatterings contribute most of the extragalactic X-ray background around 3 MeV in a Compton model. We have redone this calculation analytically with a similar electron spectrum, but with very different results. The double-scatter contribution near 3 MeV does not exceed 1 percent and cannot improve the fit to data. The effect is largest near 1 keV but will probably not be observable.

Felten, J. E.; Gould, R. J.

1974-01-01

259

Development of a High-Average-Power Compton Gamma Source for Lepton Colliders  

NASA Astrophysics Data System (ADS)

Gamma- (??) ray beams of high average power and peak brightness are of demand for a number of applications in high-energy physics, material processing, medicine, etc. One of such examples is gamma conversion into polarized positrons and muons that is under consideration for projected lepton colliders. A ?-source based on the Compton backscattering from the relativistic electron beam is a promising candidate for this application. Our approach to the high-repetition ?-source assumes placing the Compton interaction point inside a CO2 laser cavity. A laser pulse interacts with periodical electron bunches on each round-trip inside the laser cavity producing the corresponding train of ?-pulses. The round-trip optical losses can be compensated by amplification in the active laser medium. The major challenge for this approach is in maintaining stable amplification rate for a picosecond CO2-laser pulse during multiple resonator round-trips without significant deterioration of its temporal and transverse profiles. Addressing this task, we elaborated on a computer code that allows identifying the directions and priorities in the development of such a multi-pass picosecond CO2 laser. Proof-of-principle experiments help to verify the model and show the viability of the concept. In these tests we demonstrated extended trains of picosecond CO2 laser pulses circulating inside the cavity that incorporates the Compton interaction point.

Pogorelsky, Igor; Polyanskiy, Mikhail N.; Yakimenko, Vitaliy; Platonenko, Viktor T.

2009-01-01

260

Advanced Scintillator-Based Compton Telescope for Solar Flare Gamma-Ray Measurements  

NASA Astrophysics Data System (ADS)

A major goal of future Solar and Heliospheric Physics missions is the understanding of the particle acceleration processes taking place on the Sun. Achieving this understanding will require detailed study of the gamma-ray emission lines generated by accelerated ions in solar flares. Specifically, it will be necessary to study gamma-ray line ratios over a wide range of flare intensities, down to small C-class flares. Making such measurements over such a wide dynamic range, however, is a serious challenge to gamma-ray instrumentation, which must deal with large backgrounds for faint flares and huge counting rates for bright flares. A fast scintillator-based Compton telescope is a promising solution to this instrumentation challenge. The sensitivity of Compton telescopes to solar flare gamma rays has already been demonstrated by COMPTEL, which was able to detect nuclear emission from a C4 flare, the faintest such detection to date. Modern fast scintillators, such as LaBr3, and CeBr3, are efficient at stopping MeV gamma rays, have sufficient energy resolution (4% or better above 0.5 MeV) to resolve nuclear lines, and are fast enough (~15 ns decay times) to record at very high rates. When configured as a Compton telescope in combination with a modern organic scintillator, such as p-terphenyl, sub-nanosecond coincidence resolving time allows dramatic suppression of background via time-of-flight (ToF) measurements, allowing both faint and bright gamma-ray line flares to be measured. The use of modern light readout devices, such as silicon photomultipliers (SiPMs), eliminates passive mass and permits a more compact, efficient instrument. We have flown a prototype Compton telescope using modern fast scintillators with SiPM readouts on a balloon test flight, achieving good ToF and spectroscopy performance. A larger balloon-borne instrument is currently in development. We present our test results and estimates of the solar flare sensitivity of a possible full-scale instrument suitable for flight on long-duration balloon flights or on an Explorer satellite platform.

Ryan, James Michael; Bloser, Peter; McConnell, Mark; Legere, Jason; Bancroft, Christopher; Murphy, Ronald; de Nolfo, Georgia

2015-04-01

261

Relativistic electron beam acceleration by Compton scattering of extraordinary waves  

SciTech Connect

Relativistic transport equations, which demonstrate that relativistic and nonrelativistic particle acceleration along and across a magnetic field and the generation of an electric field transverse to the magnetic field, are induced by nonlinear wave-particle scattering (nonlinear Landau and cyclotron damping) of almost perpendicularly propagating electromagnetic waves in a relativistic magnetized plasma were derived from the relativistic Vlasov-Maxwell equations. The relativistic transport equations show that electromagnetic waves can accelerate particles in the k{sup ''} direction (k{sup ''}=k-k{sup '}). Simultaneously, an intense cross-field electric field, E{sub 0}=B{sub 0}xv{sub d}/c, is generated via the dynamo effect owing to perpendicular particle drift to satisfy the generalized Ohm's law, which means that this cross-field particle drift is identical to the ExB drift. On the basis of these equations, acceleration and heating of a relativistic electron beam due to nonlinear wave-particle scattering of electromagnetic waves in a magnetized plasma were investigated theoretically and numerically. Two electromagnetic waves interact nonlinearly with the relativistic electron beam, satisfying the resonance condition of {omega}{sub k}-{omega}{sub k{sup '}}-(k{sub perpendicular}-k{sub perpendicula=} r{sup '})v{sub d}-(k{sub parallel}-k{sub parallel}{sup '})v{sub b}{approx_equal}m{omega}{sub ce}, where v{sub b} and v{sub d} are the parallel and perpendicular velocities of the relativistic electron beam, respectively, and {omega}{sub ce} is the relativistic electron cyclotron frequency. The relativistic transport equations using the relativistic drifted Maxwellian momentum distribution function of the relativistic electron beam were derived and analyzed. It was verified numerically that extraordinary waves can accelerate the highly relativistic electron beam efficiently with {beta}m{sub e}c{sup 2} < or approx. 1 GeV, where {beta}=(1-v{sub b}{sup 2}/c{sup 2}){sup -1/2}.

Sugaya, R. [Department of Physics, Faculty of Science, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)

2006-05-15

262

Compton Scattering from the Deuteron below Pion-Production Threshold  

E-print Network

Differential cross sections for elastic scattering of photons from the deuteron have recently been measured at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. These first new measurements in more than a decade further constrain the isoscalar electromagnetic polarizabilities of the nucleon and provide the first-ever results above 100 MeV, where the sensitivity to the polarizabilities is increased. We add 23 points between 70 and 112 MeV, at angles 60deg, 120deg and 150deg. Analysis of these data using a Chiral Effective Field Theory indicates that the cross sections are both self-consistent and consistent with previous measurements. Extracted values of \\alpha_s = [12.1 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 and \\beta_s = [2.4 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 are obtained from a fit to these 23 new data points. This paper presents in detail the experimental conditions and the data analysis used to extract the cross sections.

Luke Myers; John Annand; Jason Brudvik; Gerald Feldman; Kevin Fissum; Harald Grießhammer; Kurt Hansen; Seth Henshaw; Lennart Isaksson; Ramsey Jebali; Michael Kovash; Magnus Lundin; Duncan Middleton; Alan Nathan; Bent Schröder; Sean Stave

2015-03-27

263

Compton Scattering from the Deuteron below Pion-Production Threshold  

E-print Network

Differential cross sections for elastic scattering of photons from the deuteron have recently been measured at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. These first new measurements in more than a decade further constrain the isoscalar electromagnetic polarizabilities of the nucleon and provide the first-ever results above 100 MeV, where the sensitivity to the polarizabilities is increased. We add 23 points between 70 and 112 MeV, at angles 60deg, 120deg and 150deg. Analysis of these data using a Chiral Effective Field Theory indicates that the cross sections are both self-consistent and consistent with previous measurements. Extracted values of \\alpha_s = [12.1 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 and \\beta_s = [2.4 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 are obtained from a fit to these 23 new data points. This paper presents in detail the experimental conditions and the data analysis used to extract the cross sections.

Myers, Luke; Brudvik, Jason; Feldman, Gerald; Fissum, Kevin; Grießhammer, Harald; Hansen, Kurt; Henshaw, Seth; Isaksson, Lennart; Jebali, Ramsey; Kovash, Michael; Lundin, Magnus; Middleton, Duncan; Nathan, Alan; Schröder, Bent; Stave, Sean

2015-01-01

264

A 3D point-kernel multiple scatter model for parallel-beam SPECT based on a gamma-ray buildup factor  

Microsoft Academic Search

A three-dimensional (3D) point-kernel multiple scatter model for point spread function (PSF) determination in parallel-beam single-photon emission computed tomography (SPECT), based on a dose gamma-ray buildup factor, is proposed. This model embraces nonuniform attenuation in a voxelized object of imaging (patient body) and multiple scattering that is treated as in the point-kernel integration gamma-ray shielding problems. First-order Compton scattering is

Predrag Marinkovic; Radovan Ilic; Rajko Spaic

2007-01-01

265

Compton Scattering of Fe K?Lines from Accreting White Dwarfs  

E-print Network

Compton scattering in the bulk accretion flow of the accretion column in magnetic cataclysmic variables (mCVs) can significantly shift photon energies in the X-ray emission lines resulting from accretion shocks. In particular, Compton recoil can potentially broaden the 6.7 and 6.97 keV Fe K$\\alpha$ emission lines produced in the post-shock region, and contaminate the fluorescent 6.4 keV neutral Fe K$\\alpha$ line reflected off the white dwarf surface. We present nonlinear Monte Carlo simulations demonstrating these effects, and we discuss the interpretation of observed Fe K$\\alpha$ linewidths in mCVs in light of these new results. The implications for other accreting compact objects are also discussed.

Z. Kuncic; K. Wu; J. G. Cullen

2004-11-14

266

Compton Scattering by Static and Moving Media. Part 1; The Transfer Equation and its Moments  

NASA Technical Reports Server (NTRS)

Compton scattering of photons by nonrelativistic particles is thought to play an important role in forming the radiation spectrum of many astrophysical systems. Here we derive the time-dependent photon kinetic equation that describes spontaneous and induced Compton scattering, as well as absorption and emission by static and moving media, the corresponding radiative transfer equation, and their zeroth and first angular moments, both in the system frame and in the frame comoving with the medium. We show that it is necessary to use the correct relativistic differential scattering cross section in order to obtain a photon kinetic equation that is correct to first order in Epsilon/m(sub e), T(sub e)/m(sub e), and V, where Epsilon is the photon energy, T(sub e) and m(sub e) are the electron temperature and rest mass, and V is the electron bulk velocity in units of the speed of light. We also demonstrate that the terms in the radiative transfer equation that are second order in V should usually be retained, because if the radiation energy density is sufficiently large, compared to the radiation flux, the effects of bulk Comptonization described by the terms that are second order in V can be as important as the effects described by the terms that are first order in V, even when V is small. The system- and fluid-frame equations that we derive are correct to first order in Epsilon/m(sub e). Our system-frame equations, which are correct to second order in V, may be used when V is not too large. Our fluid-frame equations, which are exact in V, may be used when V approaches 1. Both sets of equations are valid for systems of arbitrary optical depth and can therefore be used in both the free-streaming and diffusion regimes. We demonstrate that Comptonization by the electron bulk motion occurs whether or not the radiation field is isotropic or the bulk flow converges and that it is more important than thermal Comptonization if V(sup 2) is greater than 3T(sub e)/m(sub e).

Psaltis, Dimitrios; Lamb, Frederick K.

1997-01-01

267

Study of Generalized Parton Distributions and Deeply Virtual Compton Scattering on the nucleon with the CLAS and CLAS12 detectors at the Jefferson Laboratory  

SciTech Connect

The exclusive leptoproduction of a real photon is considered to be the "cleanest" way to access the Generalized Parton Distribution (GPD). This process is called Deeply Virtual Compton Scattering (DVCS) lN {yields} lN{gamma} , and is sensitive to all the four GPDs. Measuring the DVCS cross section is one of the main goals of this thesis. In this thesis, we present the work performed to extract on a wide phase-space the DVCS cross-section from the JLab data at a beam energy of 6 GeV.

Baptiste Guegan

2012-11-01

268

Temporal synchronization of GHz repetition rate electron and laser pulses for the optimization of a compact inverse-Compton scattering x-ray source  

NASA Astrophysics Data System (ADS)

The operation of an inverse-Compton scattering source of x-rays or gamma-rays requires the precision alignment and synchronization of highly focused electron bunches and laser pulses at the collision point. The arrival times of electron and laser pulses must be synchronized with picosecond precision. We have developed an RF synchronization technique that reduces the initial timing uncertainty from 350 ps to less than 2 ps, greatly reducing the parameter space to be optimized while commissioning the x-ray source. We describe the technique and present measurements of its performance.

Hadmack, M. R.; Szarmes, E. B.; Madey, J. M. J.; Kowalczyk, J. M. D.

2015-02-01

269

Electronic properties of PbCl2 and PbBr2 using Compton scattering technique.  

PubMed

We present the electron momentum densities of PbCl(2) and PbBr(2) using 661.65 keV gamma-rays from 20 Ci (137)Cs source. To supplement our experimental investigations, we also report energy bands, density of states, Mulliken's population and Compton profiles of PbCl(2) and PbBr(2) using linear combination of atomic orbitals within Hartree-Fock and density functional theories. The energy bands are also computed employing full potential linearized augmented plane wave (FP-LAPW) method. Compton profiles are also analyzed in terms of equal-valence-electron-density scale. It shows that PbCl(2) is more covalent than PbBr(2), which is in agreement with the Mulliken's population analysis. It is seen that the Hartree-Fock and density functional theory based Compton line shapes show similar type of deviations from the experimental data. The luminescence properties of these halides are explained on the basis of energy band and density of states. PMID:19269187

Ahmed, G; Sharma, Y; Ahuja, B L

2009-06-01

270

Experiments in Special Relativity Using Compton Scattering of Gamma Rays.  

ERIC Educational Resources Information Center

Some simple undergraduate laboratory experiments are described, which verify the energy-momentum relationship of special relativity. These experiments have been designed either to be used as classroom demonstrations or to be carried out by second-year students. (Author/JN)

Egelstaff, P. A.; And Others

1981-01-01

271

Spatially resolved hard X-ray polarization in solar flares: effects of Compton scattering and bremsstrahlung  

NASA Astrophysics Data System (ADS)

Aims: We study the polarization of hard X-ray (HXR) sources in the solar atmosphere, including Compton backscattering of photons in the photosphere (the albedo effect) and the spatial distribution of polarization across the source. Methods: HXR photon polarization and spectra produced via electron-ion bremsstrahlung emission are calculated from various electron distributions typical for solar flares. Compton scattering and photoelectric absorption are then modelled using Monte Carlo simulations of photon transport in the photosphere to study the observed (primary and albedo) sources. Polarization maps across HXR sources (primary and albedo components) for each of the modelled electron distributions are calculated at various source locations from the solar centre to the limb. Results: We show that Compton scattering produces a distinct polarization variation across the albedo patch at peak albedo energies of 20-50 keV for all anisotropies modelled. The results show that there are distinct spatial polarization changes in both the radial and perpendicular to radial directions across the extent of the HXR source at a given disk location. In the radial direction, the polarization magnitude and direction at specific positions along the HXR source will either increase or decrease with increased photon distribution directivity towards the photosphere. We also show how high electron cutoff energies influence the direction of polarization at above ~100 keV. Conclusions: Spatially resolved HXR polarization measurements can provide important information about the directivity and energetics of the electron distribution. Our results indicate the preferred angular resolution of polarization measurements required to distinguish between the scattered and primary components. We also show how spatially resolved polarization measurements could be used to probe the emission pattern of an HXR source, using both the magnitude and the direction of the polarization.

Jeffrey, N. L. S.; Kontar, E. P.

2011-12-01

272

A tensor formalism for transfer and Compton scattering of polarized light  

E-print Network

A novel covariant formalism for the treatment of the transfer and Compton scattering of partially polarized light is presented. This was initially developed to aid in the computation of relativistic corrections to the polarization generated by the Sunyaev-Zeldovich effect (demonstrated in a companion paper), but it is of more general utility. In this approach, the polarization state of a light beam is described by a tensor constructed from the time average of quadratic products of the electric field components in a local observer frame. This leads naturally to a covariant description which is ideal for calculations involving the boosting of polarized light beams between Lorentz frames, and is more flexible than the traditional Stokes parameter approach in which a separate set of polarization basis vectors is required for each photon. The covariant kinetic equation for Compton scattering of partially polarized light by relativistic electrons is obtained in the tensor formalism by a heuristic semi-classical line of reasoning. The kinetic equation is derived first in the electron rest frame in the Thomson limit, and then is generalized to account for electron recoil and allow for scattering from an arbitrary distribution of electrons.

Jamie Portsmouth; Edmund Bertschinger

2004-12-03

273

Measurement of Compton scattering from the deuteron and an improved extraction of the neutron electromagnetic polarizabilities.  

PubMed

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data-and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical ?(1232) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as ?n=[11.55±1.25(stat)±0.2(BSR)±0.8(th)]×10(-4)??fm(3) and ?n=[3.65?1.25(stat)±0.2(BSR)?0.8(th)]×10(-4)??fm(3), with ?(2)=45.2 for 44 degrees of freedom. PMID:25615318

Myers, L S; Annand, J R M; Brudvik, J; Feldman, G; Fissum, K G; Grießhammer, H W; Hansen, K; Henshaw, S S; Isaksson, L; Jebali, R; Kovash, M A; Lundin, M; McGovern, J A; Middleton, D G; Nathan, A M; Phillips, D R; Schröder, B; Stave, S C

2014-12-31

274

Measurement of Compton Scattering from the Deuteron and an Improved Extraction of the Neutron Electromagnetic Polarizabilities  

NASA Astrophysics Data System (ADS)

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data—and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical ? (1232 ) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as ?n=[11.55 ±1.25 (stat)±0.2 (BSR )±0.8 (th )]×10-4 fm3 and ?n=[3.65 ?1.25 (stat)±0.2 (BSR )?0.8 (th )]×10-4 fm3 , with ?2=45.2 for 44 degrees of freedom.

Myers, L. S.; Annand, J. R. M.; Brudvik, J.; Feldman, G.; Fissum, K. G.; Grießhammer, H. W.; Hansen, K.; Henshaw, S. S.; Isaksson, L.; Jebali, R.; Kovash, M. A.; Lundin, M.; McGovern, J. A.; Middleton, D. G.; Nathan, A. M.; Phillips, D. R.; Schröder, B.; Stave, S. C.; Compton@Max-Lab Collaboration

2014-12-01

275

Characterization of a bright, tunable, ultrafast Compton scattering X-ray source  

NASA Astrophysics Data System (ADS)

The Compton scattering of a terawatt-class, femtosecond laser pulse by a high-brightness, relativistic electron beam has been demonstrated as a viable approach toward compact, tunable sources of bright, femtosecond, hard X-ray flashes. The main focus of this article is a detailed description of such a novel X-ray source, namely the PLEIADES (Picosecond Laser Electron Inter-Action for the Dynamical Evaluation of Structures) facility at Lawrence Livermore National Laboratory. PLEIADES has produced first light at 70 keV, thus enabling critical applications, such as advanced backlighting for the National Ignition Facility and in situ time-resolved studies of high-Z materials. To date, the electron beam has been focused down to [sigma]x = [sigma]y = 27 [mu]m rms, at 57 MeV, with 266 pC of charge, a relative energy spread of 0.2%, a normalized horizontal emittance of 3.5 mm·mrad, a normalized vertical emittance of 11 mm·mrad, and a duration of 3 ps rms. The compressed laser pulse energy at focus is 480 mJ, the pulse duration 54 fs Intensity Full Width at Half-Maximum (IFWHM), and the 1/e2 radius 36 [mu]m. Initial X rays produced by head-on collisions between the laser and electron beams at a repetition rate of 10 Hz were captured with a cooled CCD using a CsI scintillator; the peak photon energy was approximately 78 keV, and the observed angular distribution was found to agree very well with three-dimensional codes. The current X-ray dose is 3 × 106 photons per pulse, and the inferred peak brightness exceeds 1015 photons/(mm2 × mrad2 × s × 0.1% bandwidth). Spectral measurements using calibrated foils of variable thickness are consistent with theory. Measurements of the X-ray dose as a function of the delay between the laser and electron beams show a 24-ps full width at half maximum (FWHM) window, as predicted by theory, in contrast with a measured timing jitter of 1.2 ps, which contributes to the stability of the source. In addition, K-edge radiographs of a Ta foil obtained at different electron beam energies clearly demonstrate the [gamma]2-tunability of the source and show very good agreement with the theoretical divergence-angle dependence of the X-ray spectrum. Finally, electron bunch shortening experiments using velocity compression have also been performed and durations as short as 300 fs rms have been observed using coherent transition radiation; the corresponding inferred peak X-ray flux approaches 1019 photons/s.

Hartemann, F. V.; Tremaine, A. M.; Anderson, S. G.; Barty, C. P. J.; Betts, S. M.; Booth, R.; Brown, W. J.; Crane, J. K.; Cross, R. R.; Gibson, D. J.; Fittinghoff, D. N.; Kuba, J.; Le Sage, G. P.; Slaughter, D. R.; Wootton, A. J.; Hartouni, E. P.; Springer, P. T.; Rosenzweig, J. B.; Kerman, A. K.

2004-07-01

276

Non-linear Compton scattering of ultrahigh-intensity laser pulses  

E-print Network

We present results for the photon spectrum emitted in non-linear Compton scattering of pulsed ultra-strong laser fields off relativistic electrons for intensities up to $a_0\\gtrsim 100$ and pulse lengths of a few laser cycles. At ultrahigh laser intensity, it is appropriate to average over the sub- structures of the differential photon spectrum. Supplementing this procedure with a stationary phase approximation one can evaluate the total emission probability. We find the photon yield in pulsed fields to be up to a factor of ten larger than results obtained from a monochromatic wave calculation.

D. Seipt; B. Kampfer

2011-11-01

277

Compton scattering in the light-cone Tamm-Dancoff approximation  

NASA Astrophysics Data System (ADS)

The Tamm-Dancoff approximation is used to study Compton scattering in light-cone-quantized QED (D. Mustaki, S. Pinsky, J. Shigemitsu, and K. G. Wilson) The charge-one sector is considered in a two-particle truncated Fock space. The problem is exactly solvable and it is shown that the internal photon propagator develops a singularity similar to the one reported in the light-cone calculation of positronium (M. Krautgärtner, H. C. Pauli, and F. Wölz). This singularity depends on the external energy and therefore cannot be removed by the conventional counterterms.

Mustaki, D.; Pinsky, S.

1992-05-01

278

Compton scattering in the light-cone Tamm-Dancoff approximation  

SciTech Connect

The Tamm-Dancoff approximation is used to study Compton scattering in light-cone-quantized QED (D. Mustaki, S. Pinsky, J. Shigemitsu, and K. G. Wilson) The charge-one sector is considered in a two-particle truncated Fock space. The problem is exactly solvable and it is shown that the internal photon propagator develops a singularity similar to the one reported in the light-cone calculation of positronium (M. Krautgaertner, H. C. Pauli, and F. Woelz). This singularity depends on the external energy and therefore cannot be removed by the conventional counterterms.

Mustaki, D.; Pinsky, S. (Department of Physics, The Ohio State University, 174 West 18th Avenue, Columbus, Ohio 43210 (United States))

1992-05-15

279

Compton-Scattering Cross Section on the Proton at High Momentum Transfer  

SciTech Connect

Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s=5-11 and -t=2-7 GeV{sup 2} with a statistical accuracy of a few percent. The scaling power for the s dependence of the cross section at fixed center-of-mass angle was found to be 8.0{+-}0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.

Danagoulian, A.; Roedelbronn, M.; Chang, T.-H.; Nathan, A. M. [University of Illinois, Urbana-Champaign, Illinois 61801 (United States); Mamyan, V. H. [Yerevan Physics Institute, Yerevan 375036 (Armenia); Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Aniol, K. A.; Margaziotis, D. J. [California State University Los Angeles, Los Angeles, California 90032 (United States); Annand, J. R. M.; Hamilton, D. J. [University of Glasgow, Glasgow G12 8QQ, Scotland (United Kingdom); Bertin, P. Y.; Camsonne, A.; Laveissiere, G. [Universite Blaise Pascal/IN2P3, F-63177 Aubiere (France); Bimbot, L. [IPN Orsay, Boite Postale n1 F-91406, Orsay (France); Bosted, P.; Paschke, K. [University of Massachusetts, Amherst, Massachusetts 01003 (United States); Calarco, J. R. [University of New Hampshire, Durham, New Hampshire 03824 (United States); Chang, C. C.; Horn, T.; Savvinov, N. [University of Maryland, College Park, Maryland 20742 (United States); Chen, J.-P. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)] (and others)

2007-04-13

280

Time evolution analysis of the electron distribution in Thomson/Compton back-scattering  

SciTech Connect

We present the time evolution of the energy distribution of a relativistic electron beam after the Compton back-scattering with a counter-propagating laser field, performed in the framework of the Quantum Electrodynamics, by means of the code CAIN. As the correct angular distribution of the spontaneous emission is accounted, the main effect is the formation of few stripes, followed by the diffusion of the more energetic particles toward lower values in the longitudinal phase space. The Chapman-Kolmogorov master equation gives results in striking agreement with the numerical ones. An experiment on the Thomson source at SPARC-LAB is proposed.

Petrillo, V.; Bacci, A.; Curatolo, C.; Maroli, C.; Serafini, L.; Rossi, A. R. [INFN-Universitá degli Studi Milano, Via Celoria, 16 20133 Milano (Italy)] [INFN-Universitá degli Studi Milano, Via Celoria, 16 20133 Milano (Italy)

2013-07-28

281

A detailed next-to-leading order QCD analysis of deeply virtual Compton scattering observables  

E-print Network

We present a detailed next-to-leading order (NLO) leading twist QCD analysis of deeply virtual Compton scattering (DVCS) observables, for several different input scenarios, in the MS-bar scheme. We discuss the size of the NLO effects and the behavior of the observables in skewedness $\\zeta$, momentum transfer, $t$, and photon virtuality, $q^2=-Q^2$. We present results on the amplitude level for unpolarized and longitudinally polarized lepton probes, and unpolarized and longitudinally polarized proton targets. We make predictions for various asymmetries and for the DVCS cross section and compare with the available data.

Andreas Freund; Martin McDermott

2002-02-14

282

A next-to-leading order QCD analysis of deeply virtual Compton scattering amplitudes  

E-print Network

We present a next-to-leading order (NLO) QCD analysis of unpolarized and polarized deeply virtual Compton scattering (DVCS) amplitudes, for two different input scenarios, in the $\\bar{MS}$ scheme. We illustrate and discuss the size of the NLO effects and the behavior of the amplitudes in skewedness, $\\zeta$, and photon virtuality, $Q^2$. In the unpolarized case, at fixed $Q^2$, we find a remarkable effective power-law behaviour in $\\zeta$, akin to Regge factorization, over several orders of magnitude in $\\zeta$. We also quantify the ratio of real to imaginary parts of the DVCS amplitudes and their sensitivity to changes of the factorization scale.

A. Freund; M. F. McDermott

2002-01-31

283

Neutron angular distribution in (?, n) reactions with linearly polarized ?-ray beam generated by laser Compton scattering  

NASA Astrophysics Data System (ADS)

In 1957, Agodi predicted that the neutron angular distribution in (?, n) reactions with a 100% linearly polarized ?-ray beam for dipole excitation should be anisotropic and universally described by the simple function of a+b?cos?(2?) at the polar angle ?=90°, where ? is the azimuthal angle. However, this prediction has not been experimentally confirmed in over half a century. We have verified experimentally this angular distribution in the (?, n) reaction for 197Au, 127I, and natural Cu targets using linearly polarized laser Compton scattering ?-rays. The result suggests that the (??, n) reaction is a novel tool to study nuclear physics in the giant dipole resonance region.

Horikawa, K.; Miyamoto, S.; Mochizuki, T.; Amano, S.; Li, D.; Imasaki, K.; Izawa, Y.; Ogata, K.; Chiba, S.; Hayakawa, T.

2014-10-01

284

Gamma holography from multiple scattering  

NASA Astrophysics Data System (ADS)

Since the introduction of heterodyne methods for synchrotron radiation (Cousesement et al. in Phys. Rev. B 54:16003, 1996; Callens et al. in Phys. Rev. 67:104423, 2003) one observes interferences between two scattering amplitudes; the scattering amplitude of resonant nuclei in a reference sample and the scattering amplitude of nuclei in the sample under investigation. Theses interferences can easily been observed as resonances in velocity spectra when one uses a time integrated method. They can also been observed as quantum beats, when one would use the time differential method. For both methods it is important that one uses a reference sample and therefore both methods disserved the name “heterodyne methods.” As theses interferences are a product of two scattering amplitudes, the amplitude of a wave scattered form the investigated sample can be known with its phase. But it is assumed that the reference wave is known in advance by a proper choice of the reference sample. At first sight it is very likely that multiple scattering would add more complexity but in this paper it is claimed that on the contrary it provide a bonus, especially for single crystals. It provokes only a line broadening and a line shift of the resonances in the velocity spectra (or a change in the damping and frequency of the quantum beats when the time spectra are registered). Moreover these changes in the line shapes can easily be measured and they provide all the information needed to reconstruct a 3-D picture of the atomic arrangement of resonant nuclei and moreover they distinguish between different hyperfine sites. The method may be more practical for measurements on synchrotron radiation but it does also apply to velocity spectra obtained from resonant scattering with strong sources. The use of radioactive sources suffer from the disadvantage of poorer statistics or much longer accumulation times but they enjoy the advantage to be table-top and at-home experiments. As strong sources are now commercially available this possibility to measure not only the hyperfine fields but also the corresponding crystal structure could give a renewed impetus to the investigations with Moessbauer spectrometry, with “at home and table top” instrumentation.

Coussement, R.

2007-02-01

285

POST-PERIASTRON GAMMA-RAY FLARE FROM PSR B1259-63/LS 2883 AS A RESULT OF COMPTONIZATION OF THE COLD PULSAR WIND  

SciTech Connect

We argue that the bright flare of the binary pulsar PSR B1259-63/LS2883 detected by the Fermi Large Area Telescope is due to the inverse Compton scattering of the unshocked electron-positron pulsar wind with a Lorentz factor {Gamma}{sub 0} Almost-Equal-To 10{sup 4}. The combination of two effects both linked to the circumstellar disk (CD) is a key element in the proposed model. The first effect is related to the impact of the surrounding medium on the termination of the pulsar wind. Inside the disk, the 'early' termination of the wind results in suppression of its gamma-ray luminosity. When the pulsar escapes the disk, the conditions for termination of the wind undergo significant changes. This would lead to a dramatic increase of the pulsar wind zone, and thus to the proportional increase of the gamma-ray flux. On the other hand, if the parts of the CD disturbed by the pulsar can supply infrared photons of density high enough for efficient Comptonization of the wind, almost the entire kinetic energy of the pulsar wind would be converted to radiation, thus the gamma-ray luminosity of the wind could approach the level of the pulsar's spin-down luminosity as reported by the Fermi Collaboration.

Khangulyan, Dmitry [Institute of Space and Astronautical Science/JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Aharonian, Felix A. [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); Bogovalov, Sergey V. [Department of Molecular Physics, National Research Nuclear University (MEPHI), Kashirskoe shosse 31, Moscow 115409 (Russian Federation); Ribo, Marc, E-mail: khangul@astro.isas.jaxa.jp, E-mail: felix.aharonian@dias.ie, E-mail: svbogovalov@mephi.ru, E-mail: mribo@am.ub.es [Departament d'Astronomia i Meteorologia, Institut de Ciences del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E-08028 Barcelona (Spain)

2012-06-10

286

Measurements of Compton Scattering on the Proton at 2 - 6 GeV  

SciTech Connect

Similar to elastic electron scattering, Compton Scattering on the proton at high momentum transfers(and high p?) can be an effective method to study its short-distance structure. An experiment has been carried out to measure the cross sections for Real Compton Scattering (RCS) on the proton for 2.3-5.7 GeV electron beam energies and a wide distribution of large scattering angles. The 25 kinematic settings sampled a domain of s = 5?11(GeV/c)2,?t = ?7(GeV/c)2 and ?u = 0.5?6.5(GeV/c)2. In addition, a measurement of longitudinal and transverse polarization transfer asymmetries was made at a 3.48 GeV beam energy and a scattering angle of ?cm = 120o. These measurements were performed to test the existing theoretical mechanisms for this process as well as to determine RCS form factors. At the heart of the scientific motivation is the desire to understand the manner in which a nucleon interacts with external excitations at the above listed energies, by comparing and contrasting the two existing models – Leading Twist Mechanism and Soft Overlap “Handbag” Mechanism – and identify the dominant mechanism. Furthermore, the Handbag Mechanism allows one to calculate reaction observables in the framework of Generalized Parton Distributions (GPD), which have the function of bridging the wide gap between the exclusive(form factors) and inclusive(parton distribution functions) description of the proton. The experiment was conducted in Hall A of Thomas Jefferson National Accelerator Facility(Jefferson Lab). It used a polarized and unpolarized electron beam, a 6% copper radiator with the thickness of 6.1% radiation lengths (to produce a bremsstrahlung photon beam), the Hall A liquid hydrogen target, a high resolution spectrometer with a focal plane polarimeter, and a photon hodoscope calorimeter. Results of the differential cross sections are presented, and discussed in the general context of the scientific motivation.

Areg Danagoulian

2006-05-01

287

The Simulation of AN Imaging Gamma-Ray Compton Backscattering Device Using GEANT4  

NASA Astrophysics Data System (ADS)

A gamma-backscattering imaging device dubbed Compton Camera, developed at GSI (Darmstadt, Germany) and modified and studied at the Nuclear Physics Group of the National University of Colombia in Bogotá, uses the back-to-back emission of two gamma rays in the positron annihilation to construct a bidimensional image that represents the distribution of matter in the field-of-view of the camera. This imaging capability can be used in a host of different situations, for example, to identify and study deposition and structural defects, and to help locating concealed objects, to name just two cases. In order to increase the understanding of the response of the Compton Camera and, in particular, its image formation process, and to assist in the data analysis, a simulation of the camera was developed using the GEANT4 simulation toolkit. In this work, the images resulting from different experimental conditions are shown. The simulated images and their comparison with the experimental ones already suggest methods to improve the present experimental device

Flechas, D.; Sarmiento, L. G.; Cristancho, F.; Fajardo, E.

2014-02-01

288

Compton scattering of microwave background radiation by gas in galaxy clusters  

NASA Technical Reports Server (NTRS)

Based on data on the X-ray spectrum of the Coma cluster, interpreted as thermal bremsstrahlung, the expected brightness depletion from Compton scattering of the microwave background in the direction of the cluster is computed. The calculated depletion is about one-third that recently observed by Gull and Northover, and the discrepancy is discussed. In comparing the observed microwave depletion in the direction of other clusters which are X-ray sources it is found that there is no correlation with the cluster X-ray luminosity. Consequently, the microwave depletion observations cannot yet be taken as good evidence for a thermal bremsstrahlung origin for the X-ray emission. The perturbation from Compton scattering of photons on the high-frequency (Wien) tail of the blackbody distribution is computed and found to be much larger than predicted in previous calculations. In the Wien tail the effect is a relative increase in the blackbody intensity that is appreciably greater in magnitude than the depletion in the Rayleigh-Jeans domain.

Gould, R. J.; Rephaeli, Y.

1978-01-01

289

Testing Models of Resonant Compton Scattering in X-Ray Pulsars  

NASA Technical Reports Server (NTRS)

Over the performance period covered by the grant, the principal investigator modified a Monte Carlo Compton scattering code to model the propagation of x-rays through the magnetosphere of accreting neutron stars. These modifications were made to enable the author to compare the observations of x-ray pulsars to theoretical models of the system. The original code was designed to study relativistic plasmas with one of two geometries: a plane parallel plasma with a differential relativistic bulk velocity, and a static spherically symmetric plasma.- This code did not treat gravitational bending or bulk motion in the magnetosphere of a neutron star. Under the grant, the author incorporated code to trace light paths in a Schwarzschild metric. The code was modified to keep track of the photon polarization during propagati on. The investigator also modified the code so that bulk motion in an axisymmetric system is treated properly. An approximate treatment for resonant Compton scattering was added to the code. Finally, code was added that creates model observables that can be compared to observations, such as projected x-ray emission maps and energy-dependent light curves. Comparison to observations is now commencing.

Brainerd, Jerome J.

2000-01-01

290

Measurement of the Beam-Spin Azimuthal Asymmetry Associated with Deeply-Virtual Compton Scattering  

NASA Astrophysics Data System (ADS)

The beam-spin asymmetry in hard electroproduction of photons has been measured. The data have been accumulated by the HERMES experiment at DESY using the HERA 27.6 GeV longitudinally polarized positron beam and an unpolarized hydrogen-gas target. The asymmetry in the azimuthal distribution of the produced photons in the angle ? relative to the lepton scattering plane was determined with respect to the helicity state of the incoming positron beam. The beam-spin analyzing power in the sin? moment was measured to be -0.23+/-0.04(stat)+/-0.03(syst) in the missing-mass range below 1.7 GeV. The observed asymmetry is attributed to the interference of the Bethe-Heitler and deeply virtual Compton scattering processes.

Airapetian, A.; Akopov, N.; Akopov, Z.; Amarian, M.; Aschenauer, E. C.; Avakian, H.; Avakian, R.; Avetissian, A.; Avetissian, E.; Bailey, P.; Bains, B.; Baturin, V.; Baumgarten, C.; Beckmann, M.; Belostotski, S.; Bernreuther, S.; Bianchi, N.; Böttcher, H.; Borissov, A.; Bouhali, O.; Bouwhuis, M.; Brack, J.; Brauksiepe, S.; Brückner, W.; Brüll, A.; Brunn, I.; Bulten, H. J.; Capitani, G. P.; Chumney, P.; Cisbani, E.; Ciullo, G.; Court, G. R.; Dalpiaz, P. F.; de Leo, R.; de Nardo, L.; de Sanctis, E.; de Schepper, D.; Devitsin, E.; de Witt Huberts, P. K.; di Nezza, P.; Düren, M.; Ehrenfried, M.; Elbakian, G.; Ellinghaus, F.; Ely, J.; Fabbri, R.; Fantoni, A.; Fechtchenko, A.; Felawka, L.; Filippone, B. W.; Fischer, H.; Fox, B.; Franz, J.; Frullani, S.; Gärber, Y.; Garibaldi, F.; Garutti, E.; Gavrilov, G.; Gharibyan, V.; Golendukhin, A.; Graw, G.; Grebeniouk, O.; Green, P. W.; Greeniaus, L. G.; Gute, A.; Haeberli, W.; Hafidi, K.; Hartig, M.; Hasch, D.; Heesbeen, D.; Heinsius, F. H.; Henoch, M.; Hertenberger, R.; Hesselink, W. H.; Hofman, G.; Holler, Y.; Holt, R. J.; Hommez, B.; Iarygin, G.; Izotov, A.; Jackson, H. E.; Jgoun, A.; Jung, P.; Kaiser, R.; Kanesaka, J.; Kinney, E.; Kisselev, A.; Kitching, P.; Kobayashi, H.; Koch, N.; Königsmann, K.; Kolster, H.; Korotkov, V.; Kotik, E.; Kozlov, V.; Krauss, B.; Krivokhijine, V. G.; Kyle, G.; Lagamba, L.; Laziev, A.; Lenisa, P.; Liebing, P.; Lindemann, T.; Lorenzon, W.; Maas, A.; Makins, N. C.; Marukyan, H.; Masoli, F.; McAndrew, M.; McIlhany, K.; Meissner, F.; Menden, F.; Meyners, N.; Mikloukho, O.; Miller, C. A.; Milner, R.; Muccifora, V.; Mussa, R.; Nagaitsev, A.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaeva, K.; Nowak, W.-D.; Oganessyan, K.; O'Neill, T. G.; Owen, B. R.; Pate, S. F.; Potashov, S.; Potterveld, D. H.; Raithel, M.; Rakness, G.; Rappoport, V.; Redwine, R.; Reggiani, D.; Reolon, A. R.; Rith, K.; Robinson, D.; Rostomyan, A.; Ruh, M.; Ryckbosch, D.; Sakemi, Y.; Sanjiev, I.; Sato, F.; Savin, I.; Scarlett, C.; Schäfer, A.; Schill, C.; Schmidt, F.; Schnell, G.; Schüler, K. P.; Schwind, A.; Seibert, J.; Seitz, B.; Shibata, T.-A.; Shutov, V.; Simani, M. C.; Simon, A.; Sinram, K.; Steffens, E.; Steijger, J. J.; Stewart, J.; Stösslein, U.; Suetsugu, K.; Taroian, S.; Terkulov, A.; Tessarin, S.; Thomas, E.; Tipton, B.; Tytgat, M.; Urciuoli, G. M.; van den Brand, J. F.; van Steenhoven, G.; van Vyver, R.; van Hunen, J. J.; Vetterli, M. C.; Vikhrov, V.; Vincter, M. G.; Visser, J.; Weiskopf, C.; Wendland, J.; Wilbert, J.; Wise, T.; Yen, S.; Yoneyama, S.; Zohrabian, H.

2001-10-01

291

Beam-helicity asymmetry arising from deeply virtual Compton scattering measured with kinematically complete event reconstruction  

NASA Astrophysics Data System (ADS)

The beam-helicity asymmetry in exclusive electroproduction of real photons by the longitudinally polarized Hera positron beam scattering off an unpolarized hydrogen target is measured at Hermes. The asymmetry arises from deeply virtual Compton scattering and its interference with the Bethe-Heitler process. Azimuthal amplitudes of the beam-helicity asymmetry are extracted from a data sample consisting of ep ? ep? events with detection of all particles in the final state including the recoiling proton. The installation of a recoil detector, while reducing the acceptance of the experiment, allows the elimination of background from ep ? eN ?? events, which was estimated to contribute an average of about 12% to the signal in previous Hermes publications. The removal of this background from the present data sample is shown to increase the magnitude of the leading asymmetry amplitude by 0 .054 ± 0 .016 to -0 .328 ± 0 .027 (stat .) ± 0 .045 (syst .).

Airapetian, A.; Akopov, N.; Akopov, Z.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetisyan, E.; Belostotski, S.; Blok, H. P.; Borissov, A.; Bowles, J.; Brodski, I.; Bryzgalov, V.; Burns, J.; Capiluppi, M.; Capitani, G. P.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; De Leo, R.; De Nardo, L.; De Sanctis, E.; Diefenthaler, M.; Di Nezza, P.; Düren, M.; Ehrenfried, M.; Elbakian, G.; Ellinghaus, F.; Etzelmüller, E.; Fabbri, R.; Fantoni, A.; Felawka, L.; Frullani, S.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Giordano, F.; Gliske, S.; Golembiovskaya, M.; Gregor, I. M.; Guler, H.; Hartig, M.; Hasch, D.; Hillenbrand, A.; Hoek, M.; Holler, Y.; Hristova, I.; Ivanilov, A.; Jackson, H. E.; Jo, H. S.; Joosten, S.; Kaiser, R.; Karyan, G.; Keri, T.; Kinney, E.; Kisselev, A.; Korotkov, V.; Kozlov, V.; Krauss, B.; Kravchenko, P.; Krivokhijine, V. G.; Lagamba, L.; Lapikás, L.; Lehmann, I.; Lenisa, P.; Ruiz, A. López; Lorenzon, W.; Lu, S.; Lu, X.; Ma, B.-Q.; Mahon, D.; Makins, N. C. R.; Manaenkov, S. I.; Manfré, L.; Mao, Y.; Marianski, B.; de la Ossa, A. Martinez; Marukyan, H.; Miller, C. A.; Miyachi, Y.; Movsisyan, A.; Murray, M.; Mussgiller, A.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaev, M.; Nowak, W.-D.; Osborne, A.; Pappalardo, L. L.; Perez-Benito, R.; Petrosyan, A.; Reimer, P. E.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Rubacek, L.; Rubin, J.; Ryckbosch, D.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Seitz, B.; Shearer, C.; Shibata, T.-A.; Shutov, V.; Stancari, M.; Statera, M.; Steijger, J. J. M.; Stewart, J.; Taroian, S.; Terkulov, A.; Truty, R.; Trzcinski, A.; Tytgat, M.; Van Haarlem, Y.; Van Hulse, C.; Veretennikov, D.; Vikhrov, V.; Vilardi, I.; Wang, S.; Yaschenko, S.; Ye, Z.; Yen, S.; Zagrebelnyy, V.; Zeiler, D.; Zihlmann, B.; Zupranski, P.

2012-10-01

292

Directional Stand-off Detection of Fast Neutrons and Gammas Using Angular Scattering Distributions  

SciTech Connect

We have investigated the response of a DoubleScatter Neutron Spectrometer (DSNS) for sources at long distances (gr than 200 meters). We find that an alternative method for analyzing double scatter data avoids some uncertainties introduced by amplitude measurements in plastic scintillators.Time of flight is used to discriminate between gamma and neutron events, and the kinematic distributions of scattering angles are assumed to apply. Non-relativistic neutrons are most likely to scatter at 45°, while gammas with energies greater than 2 MeV are most likely to be forward scattered. The distribution of scattering angles of fission neutrons arriving from a distant point source generates a 45° cone, which can be back-projected to give the source direction. At the same time, the distribution of Compton-scattered gammas has a maximum in the forward direction, and can be made narrower by selecting events that deposit minimal energy in the first scattering event. We have further determined that the shape of spontaneous fission neutron spectra at ranges gr than 110 m is still significantly different from thecosmic ray background.

Vanier P. e.; Dioszegi, I.; Salwen, C.; Forman, L.

2009-10-25

293

Compton scattering for spectroscopic detection of ultra-fast, high flux, broad energy range X-rays  

SciTech Connect

Compton side-scattering has been used to simultaneously downshift the energy of keV to MeV energy range photons while attenuating their flux to enable single-shot, spectrally resolved, measurements of high flux X-ray sources to be undertaken. To demonstrate the technique a 1 mm thick pixelated cadmium telluride detector has been used to measure spectra of Compton side-scattered radiation from a Cobalt-60 laboratory source and a high flux, high peak brilliance X-ray source of betatron radiation from a laser-plasma wakefield accelerator.

Cipiccia, S.; Wiggins, S. M.; Brunetti, E.; Vieux, G.; Yang, X.; Welsh, G. H.; Anania, M.; Islam, M. R.; Ersfeld, B.; Jaroszynski, D. A. [Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG (United Kingdom)] [Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG (United Kingdom); Maneuski, D.; Montgomery, R.; Smith, G.; Hoek, M.; Hamilton, D. J.; Shea, V. O. [Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)] [Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Issac, R. C. [Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG (United Kingdom) [Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG (United Kingdom); Research Department of Physics, Mar Athanasius College, Kothamangalam 686666, Kerala (India); Lemos, N. R. C.; Dias, J. M. [GoLP/Instituto de Plasmas eFusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal)] [GoLP/Instituto de Plasmas eFusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal); Symes, D. R. [Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, OX11 0QX Didcot (United Kingdom)] [Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, OX11 0QX Didcot (United Kingdom); and others

2013-11-15

294

Development of a Compton Camera for Online Range Monitoring of Laser-Accelerated Proton Beams via Prompt-Gamma Detection  

NASA Astrophysics Data System (ADS)

Presently large efforts are conducted in Munich towards the development of proton beams for bio-medical applications, generated via the technique of particle acceleration from high-power, short-pulse lasers. While so far mostly offline diagnostics tools are used in this context, we aim at developing a reliable and accurate online range monitoring technique, based on the position-sensitive detection of prompt ? rays emitted from nuclear reactions between the proton beam and the biological sample. For this purpose, we develop a Compton camera, designed to be able to track not only the Compton scattering of the primary photon, but also to detect the secondary Compton electron, thus reducing the Compton cone to an arc segment and by this increasing the source reconstruction efficiency. Design specifications and the status of the protype system are discussed.

Thirolf, P. G.; Lang, C.; Aldawood, S.; Kolff, H. G. v. d.; Maier, L.; Schaart, D. R.; Parodi, K.

2014-03-01

295

Measurement of azimuthal asymmetries associated with deeply virtual Compton scattering on a longitudinally polarized deuterium target  

NASA Astrophysics Data System (ADS)

Azimuthal asymmetries in exclusive electroproduction of a real photon from a longitudinally polarized deuterium target are measured with respect to target polarization alone and with respect to target polarization combined with beam helicity and/or beam charge. The asymmetries appear in the distribution of the real photons in the azimuthal angle ? around the virtual photon direction, relative to the lepton scattering plane. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe-Heitler process. The results for the beam-charge and beam-helicity asymmetries from a tensor polarized deuterium target with vanishing vector polarization are shown to be compatible with those from an unpolarized deuterium target, which is expected for incoherent scattering dominant at larger momentum transfer. Furthermore, the results for the single target-spin asymmetry and for the double-spin asymmetry are found to be compatible with the corresponding asymmetries previously measured on a hydrogen target. For coherent scattering on the deuteron at small momentum transfer to the target, these findings imply that the tensor contribution to the cross section is small. Furthermore, the tensor asymmetry is found to be compatible with zero.

Airapetian, A.; Akopov, N.; Akopov, Z.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetisyan, E.; Belostotski, S.; Bianchi, N.; Blok, H. P.; Borissov, A.; Bowles, J.; Brodski, I.; Bryzgalov, V.; Burns, J.; Capiluppi, M.; Capitani, G. P.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; de Leo, R.; de Nardo, L.; de Sanctis, E.; Diefenthaler, M.; di Nezza, P.; Düren, M.; Ehrenfried, M.; Elbakian, G.; Ellinghaus, F.; Fantoni, A.; Felawka, L.; Frullani, S.; Gabbert, D.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Giordano, F.; Gliske, S.; Golembiovskaya, M.; Hadjidakis, C.; Hartig, M.; Hasch, D.; Hill, G.; Hillenbrand, A.; Hoek, M.; Holler, Y.; Hristova, I.; Imazu, Y.; Ivanilov, A.; Jackson, H. E.; Jgoun, A.; Jo, H. S.; Joosten, S.; Kaiser, R.; Karyan, G.; Keri, T.; Kinney, E.; Kisselev, A.; Kobayashi, N.; Korotkov, V.; Kozlov, V.; Krauss, B.; Kravchenko, P.; Krivokhijine, V. G.; Lagamba, L.; Lamb, R.; Lapikás, L.; Lehmann, I.; Lenisa, P.; Linden-Levy, L. A.; López Ruiz, A.; Lorenzon, W.; Lu, X.-G.; Lu, X.-R.; Ma, B.-Q.; Mahon, D.; Makins, N. C. R.; Manaenkov, S. I.; Manfré, L.; Mao, Y.; Marianski, B.; de La Ossa, A. Martinez; Marukyan, H.; Miller, C. A.; Movsisyan, A.; Muccifora, V.; Murray, M.; Müller, D.; Mussgiller, A.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaev, M.; Nowak, W.-D.; Pappalardo, L. L.; Perez-Benito, R.; Pickert, N.; Raithel, M.; Reimer, P. E.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Rubin, J.; Ryckbosch, D.; Salomatin, Y.; Sanftl, F.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Seitz, B.; Shibata, T.-A.; Shutov, V.; Stancari, M.; Statera, M.; Steffens, E.; Steijger, J. J. M.; Stenzel, H.; Stewart, J.; Stinzing, F.; Taroian, S.; Terkulov, A.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; van der Nat, P. B.; van Haarlem, Y.; van Hulse, C.; Veretennikov, D.; Vikhrov, V.; Vilardi, I.; Vogel, C.; Wang, S.; Yaschenko, S.; Ye, Z.; Yen, S.; Yu, W.; Zeiler, D.; Zihlmann, B.; Zupranski, P.; Hermes Collaboration

2011-01-01

296

Development of Electron Tracking Compton Camera using micro pixel gas chamber for medical imaging  

Microsoft Academic Search

We have developed the Electron Tracking Compton Camera (ETCC) with reconstructing the 3-D tracks of the scattered electron in Compton process for both sub-MeV and MeV gamma rays. By measuring both the directions and energies of not only the recoil gamma ray but also the scattered electron, the direction of the incident gamma ray is determined for each individual photon.

Shigeto Kabuki; Kaori Hattori; Ryota Kohara; Etsuo Kunieda; Atsushi Kubo; Hidetoshi Kubo; Kentaro Miuchi; Tadaki Nakahara; Tsutomu Nagayoshi; Hironobu Nishimura; Yoko Okada; Reiko Orito; Hiroyuki Sekiya; Takashi Shirahata; Atsushi Takada; Toru Tanimori; Kazuki Ueno

2007-01-01

297

Influence of electron-neutral collisions on the Compton scattering cross section and the Salpeter structure factor in warm collisional plasmas  

NASA Astrophysics Data System (ADS)

The electron-neutral collision effects on the Compton scattering process are investigated in warm collisional plasmas. The Compton scattering cross section in warm collisional plasmas is obtained by the Salpeter structure factor with the fluctuation-dissipation theorem and the plasma dielectric function as a function of the electron-neutral collision frequency, Debye length, and wave number. It is shown that the influence of electron-neutral collision strongly suppresses the Compton scattering cross section in warm collisional plasmas. It is also found that the electron-neutral collision effect on the differential Compton scattering cross section is more significant in forward scattering directions. We show that the differential Compton scattering cross section has a maximum at the scattering angle ? = ? / 2 . In addition, we find that the electron-neutral collision effect on the total Compton scattering cross section increases with increasing Debye length and wave number. The variation of the Compton scattering cross section due to the change of collision frequency and plasma parameters is also discussed.

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

2015-03-01

298

Risk management approach for de-orbiting of the Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

De-orbiting of space debris into Earth is one of the methods to control and minimize the degradation of the space environment. The de-orbiting scenario poses a challenge of providing safety for the Earth population and other space-based assets below the orbit track of the spacecraft being de-orbited. Rigorous risk management is needed to provide the necessary safety margin for de-orbit operations. These challenges were faced during the controlled de-orbit of the Compton Gamma Ray Observatory (CGRO) into the Pacific Ocean on June 4, 2000. This paper presents a risk management approach utilized at various stages of this mission; processes used to identify credible contingencies; and planned responses to contingencies for use during mission execution.

Ahmed, Mansoor; Mangus, David; Burch, Preston

2001-10-01

299

Gamma ray monitoring of a AGN and galactic black hole candidates by the Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The Compton Gamma-Ray Observatory's Burst and Transient Source Experiment (BATSE) has a powerful capability to provide nearly uninterrupted monitoring in the 25 keV-10 MeV range of both active galactic nuclei (AGN) and galactic black hole candidates (GBHC) such as Cygnus X-1, using the occultation of cosmic sources by the Earth. Since the Crab is detected by the BATSE Large Area Detectors with roughly 25(sigma) significance in the 15-125 keV range in a single rise or set, a variation by a factor of two of a source having one-tenth the strength of Cygnus X-1 should be detectable within a day. Methods of modeling the background are discussed which will increase the accuracy, sensitivity, and reliability of the results beyond those obtainable from a linear background fit with a single rise or set discontinuity.

Skelton, R. T.; Ling, James C.; Wheaton, William A.; Harmon, Alan; Fishman, G. J.; Meegan, C. A.; Paciesas, William S.; Gruber, Duane E.; Rubin, Brad; Wilson, R. B.

1992-01-01

300

Nuclear Instruments and Methods in Physics Research A 457 (2001) 203}211 Evaluation of a Compton scattering camera using  

E-print Network

potential as radiation imagers in environmental remediation, as survey devices for nuclear industrial sitesNuclear Instruments and Methods in Physics Research A 457 (2001) 203}211 Evaluation of a Compton scattering camera using 3-D position sensitive CdZnTe detectors Y.F. Du*, Z. He, G.F. Knoll, D.K. Wehe, W. Li

He, Zhong

301

Detection of radioactive isotopes by using laser Compton scattered ?-ray beams  

NASA Astrophysics Data System (ADS)

Non-destructive detection and assay of nuclear materials is one of the most critical issues for both the management of nuclear waste and the non-proliferation of nuclear materials. We use laser Compton scattered (LCS) ?-ray beams and the nuclear resonance fluorescence (NRF) for the non-destructive detection of radioactive materials. Quasi-monochromatic and energy-tunable LCS ?-ray beams help improve the signal-to-noise ratio during NRF measurements. We developed the conceptual design of a high-flux ?-ray source with an energy-recovery linac, which produces a ?-ray beam at the flux of 1013 photons/s. In this paper, we discuss the execution of simulation studies using a Monte Carlo code, results of a proof-of-principle experiment for isotope detection, and the status of the development of LCS X-ray and ?-ray facilities.

Hajima, R.; Kikuzawa, N.; Nishimori, N.; Hayakawa, T.; Shizuma, T.; Kawase, K.; Kando, M.; Minehara, E.; Toyokawa, H.; Ohgaki, H.

2009-09-01

302

Rayleigh to Compton ratio scatter tomography applied to breast cancer diagnosis: A preliminary computational study  

NASA Astrophysics Data System (ADS)

In the present work, a tomographic technique based on Rayleigh to Compton scattering ratio (R/C) was studied using computational simulation in order to assess its application to breast cancer diagnosis. In this preliminary study, some parameters that affect the image quality were evaluated, such as: (i) energy beam, (ii) size and glandularity of the breast, and (iii) statistical count noise. The results showed that the R/C contrast increases with increasing photon energy and decreases with increasing glandularity of the sample. The statistical noise showed to be a significant parameter, although the quality of the obtained images was acceptable for a considerable range of noise level. The preliminary results suggest that the R/C tomographic technique has a potential of being applied as a complementary tool in the breast cancer diagnostic.

Antoniassi, M.; Conceição, A. L. C.; Poletti, M. E.

2014-02-01

303

Exploration of deeply virtual Compton scattering on the neutron in the Hall A of Jefferson Laboratory  

SciTech Connect

Generalized Parton Distributions (GPDs) are universal functions which provide a comprehensive description of hadron properties in terms of quarks and gluons. Deeply Virtual Compton Scattering (DVCS) is the simplest hard exclusive process involving GPDs. In particular, the DVCS on the neutron is mostly sensitive to E, the less constrained GPD, wich allows to access to the quark angular momentum. The first dedicated DVCS experiment on the neutron ran in the Hall A of Jefferson Lab in fall 2004. The high luminosity of the experiment and the resulting background rate recquired specific devices which are decribed in this document. The analysis methods and the experiment results, leading to preliminary constraints on the GPD E, are presented.

Malek Mazouz

2006-12-08

304

Modelling generalized parton distributions to describe deeply virtual Compton scattering data  

E-print Network

We present a new model for generalized parton distributions (GPDs), based on the aligned jet model, which successfully describes the deeply virtual Compton scattering (DVCS) data from H1, ZEUS, HERMES and CLAS. We also present an easily implementable and flexible algorithm for their construction. This new model is necessary since the most widely used models for GPDs, which are based on factorized double distributions, cannot, in their current form, describe the DVCS data when employed in a full QCD analysis. We demonstrate explicitly the reason for the shortcoming in the data description. We also highlight several non-perturbative input parameters which could be used to tune the GPDs, and the $t$-dependence, to the DVCS data using a fitting procedure.

A. Freund; M. McDermott; M. Strikman

2002-12-16

305

Analyticity, unitarity and one-loop graviton corrections to Compton scattering  

NASA Astrophysics Data System (ADS)

We compute the difference between the helicity flip and nonflip cross sections for graviton photoproduction on a spin-1/2 target of finite mass. Using this tree-level result, we find one-loop graviton correction to the spin-flip low-energy forward Compton scattering amplitude by using Gerasimov-Drell-Hearn sum rule. We show that this result agrees with the corresponding perturbative computations, implying the validity of the sum rule at one-loop level, contrary to the previous claims. We discuss possible effects from the black hole production and string Regge trajectory exchange at very high energies. Finally, we relate these observations with the models that involve extra dimensions.

Grigoryan, Hovhannes R.

2012-10-01

306

Compton back scatter imaging for mild steel rebar detection and depth characterization embedded in concrete  

NASA Astrophysics Data System (ADS)

A novel non-destructive Compton scattering technique is described to ensure the feasibility, reliability and applicability of detecting the reinforcing steel bar in concrete. The indigenously developed prototype system presented in this paper is capable of detecting the reinforcement of varied diameters embedded in the concrete and as well as up to 60 mm depth, with the aid of Caesium-137(137Cs) radioactive source and a high resolution HPGe detector. The technique could also detect the inhomogeneities present in the test specimen by interpreting the material density variation caused due to the count rate. The experimental results are correlated using established techniques such as radiography and rebar locators. The results obtained from its application to locate the rebars are quite promising and also been successfully used for reinforcement mapping. This method can be applied, especially when the intrusion is located underneath the cover of the concrete or considerably at larger depths and where two sided access is restricted.

Margret, M.; Menaka, M.; Venkatraman, B.; Chandrasekaran, S.

2015-01-01

307

A General Relativistic External Compton-Scattering Model for TeV Emission from M87  

NASA Astrophysics Data System (ADS)

M87 is the first detected non-blazar extragalactic tera-electron-volt (TeV) source with rapid variation and a very flat spectrum in the TeV band. To explain the two peaks in the spectral energy distribution of the nucleus of M87, which is similar to that of blazars, the most commonly adopted models are the synchrotron self-Compton-scattering models and the external inverse Compton (EIC) scattering models. Considering that there is no correlated variation in the soft band (from radio to X-ray) matching the TeV variation and that the TeV sources should not suffer from ?? absorption due to the flat TeV spectrum, the EIC models are advantageous in modeling the TeV emission from M87. In this paper, we propose a self-consistent EIC model to explain the flat TeV spectrum of M87 within the framework of fully general relativity, where the background soft photons are from the advection-dominated accretion flow around the central black hole, and the high-energy electrons are from the mini-jets that are powered by the magnetic reconnection in the main jet. In our model, both the TeV flares observed in the years 2005 and 2008 could be well explained: the ?? absorption for TeV photons is very low, even inside the region very close to the black hole 20Rg ~ 50Rg ; at the same region, the average EIC cooling time (~102 ~ 103 s) is short, which is consistent with the observed timescale of the TeV variation. Furthermore, we also discuss the possibility that the accompanying X-ray flare in 2008 is due to the direct synchrotron radiation of the mini-jets.

Cui, Yu-Dong; Yuan, Ye-Fei; Li, Yan-Rong; Wang, Jian-Min

2012-02-01

308

New sum rules from low energy Compton scattering on arbitrary spin target  

NASA Astrophysics Data System (ADS)

We derive two sum rules by studying the low energy Compton scattering on a target of arbitrary (nonzero) spin j. In the first sum rule, we consider the possibility that the intermediate state in the scattering can have spin | j±1| and the same mass as the target. The second sum rule applies if the theory at hand possesses intermediate narrow resonances with masses different from the mass of the scatterer. These sum rules are generalizations of the Gerasimov-Drell-Hearn-Weinberg sum rule. Along with the requirement of tree level unitarity, they relate different low energy couplings in the theory. Using these sum rules, we show that in certain cases the gyromagnetic ratio can differ from the "natural" value g = 2, even at tree level, without spoiling perturbative unitarity. These sum rules can be used as constraints applicable to all supergravity and higher-spin theories that contain particles charged under some U(1) gauge field. In particular, applied to four dimensional N = 8 supergravity in a spontaneously broken phase, these sum rules suggest that for the theory to have a good ultraviolet behavior, additional massive states need to be present, such as those coming from the embedding of the N = 8 supergravity in type II superstring theory. We also discuss the possible implications of the sum rules for QCD in the large- N c limit.

Grigoryan, Hovhannes R.; Porrati, Massimo

2012-07-01

309

SCATTERING OF GAMMA RAYS BY A STATIC ELECTRIC FIELD  

Microsoft Academic Search

In an effort to observe Delbruck scattering the absolute differential ; cross sections for the elastic scattering of 1.33-Mev gamma rays by lead, tin, ; and uranium and of 2.62-Mev gamma rays by lead and tin have been measured for ; angles between 15 and 105 degrees. The observed scattering is the coherent sum ; of Delbruck, Rayleigh, and nuclear

A. M. Bernstein; A. K. Mann

1958-01-01

310

The kinetic energy of lithium in LiTiS2 as determined by neutron Compton scattering  

NASA Astrophysics Data System (ADS)

Neutron Compton scattering has been used to study lithium-ion dynamics in the intercalation compounds LiTiS2, LiV2O5 and Li0.45MoO3. Mean atomic kinetic energies were determined for LiTiS2 in the temperature range 13<=T<=298 K by isolating the lithium recoil peak in the neutron Compton profile. Low intensity of the lithium recoil peak led to large errors in observed values for LiV2O5 and, in the case of Li0.45MoO3, failure to fit the peak.

Kosidowski, L.; Powell, A. V.; Mayers, J.

1998-04-01

311

X-ray afterglows of gamma-ray bursts in the synchrotron self-Compton dominated regime  

E-print Network

We consider in this paper the effect of synchrotron self-Compton process on X-ray afterglows of gamma-ray bursts. We find that for a wide range of parameter values, especially for the standard values which imply the energy in the electrons behind the afterglow shock is tens times as that in the magnetic field, the electron cooling is dominated by Compton cooling rather than synchrotron one. This leads to a different evolution of cooling frequency in the synchrotron emission component, and hence a different (flatter) light curve slope in the X-ray range. This effect should be taken into account when estimating the afterglow parameters by X-ray observational data. For somewhat higher ambient density, the synchrotron self-Compton emission may be directly detected in X-ray range, showing varying spectral slopes and a quite steep light curve slope.

Zhuo Li; L. M. Song

2003-12-13

312

Measurement of effective atomic number of gunshot residues using scattering of gamma rays  

NASA Astrophysics Data System (ADS)

Better understanding of gunshot residues and the major elemental composition would be valuable to forensic scientists for their analysis work and interpretation of results. In the present work, the effective atomic numbers of gunshot residues (cartridge case, bullet core, bullet jacket and gunpowder) were analyzed using energy dispersive X-ray analysis (EDX). The scattering of 59.54 keV gamma rays is studied using a high-resolution HPGe detector. The experiment is performed on various elements with atomic number in the 4?Z?82. The intensity ratio of coherent to Compton scattered peaks, corrected for photo-peak efficiency of gamma detector and absorption of photons in the sample and air, is plotted as a function of atomic number and constituted a best-fit-curve. From this fit-curve, the respective effective atomic numbers of gunshot residues are determined.

Y?lmaz, Demet; Tur?ucu, Ahmet; Uzuno?lu, Zeynep; Korucu, Demet

2014-09-01

313

500 MW X-BAND RF SYSTEM OF A 0.25 GEV ELECTRON LINAC FOR ADVANCED COMPTON SCATTERING SOURCE APPLICATION  

SciTech Connect

A Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering light source is being developed at LLNL in collaboration with SLAC National Accelerator Laboratory. The electron beam for the Compton scattering interaction will be generated by a X-band RF gun and a X-band LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the electrons to energy of 250 MeV or greater for the interaction. Two high power klystron amplifiers, each capable of generating 50 MW, 1.5 msec pulses, will be the main high power RF sources for the system. These klystrons will be powered by state of the art solid-state high voltage modulators. A RF pulse compressor, similar to the SLED II pulse compressor, will compress the klystron output pulse with a power gain factor of five. For compactness consideration, we are looking at a folded waveguide setup. This will give us 500 MW at output of the compressor. The compressed pulse will then be distributed to the RF gun and to six traveling wave accelerator sections. Phase and amplitude control are located at the RF gun input and additional control points along the LINAC to allow for parameter control during operation. This high power RF system is being designed and constructed. In this paper, we will present the design, layout, and status of this RF system.

Chu, T S; Anderson, S G; Gibson, D J; Hartemann, F V; Marsh, R A; Siders, C; Barty, C P; Adolphsen, C; Jongewaard, E; Tantawi, S; Vlieks, A; Wang, J W; Raubenheimer, T

2010-05-12

314

500 MW X-Band RF System of a 0.25 GeV Electron LINAC for Advanced Compton Scattering Source Application  

SciTech Connect

A Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering light source is being developed at LLNL in collaboration with the SLAC National Accelerator Laboratory. The electron beam for the Compton scattering interaction will be generated by a X-band RF gun and a X-band LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the electrons to energy of 250 MeV or greater for the interaction. Two high power klystron amplifiers, each capable of generating 50 MW, 1.5 msec pulses, will be the main high power RF sources for the system. These klystrons will be powered by state of the art solid-state high voltage modulators. A RF pulse compressor, similar to the SLED II pulse compressor, will compress the klystron output pulse with a power gain factor of five. For compactness consideration, we are looking at a folded waveguide setup. This will give us 500 MW at output of the compressor. The compressed pulse will then be distributed to the RF gun and to six traveling wave accelerator sections. Phase and amplitude control are located at the RF gun input and additional control points along the LINAC to allow for parameter control during operation. This high power RF system is being designed and constructed. In this paper, we will present the design, layout, and status of this RF system.

Chu, Tak Sum; /LLNL, Livermore; Anderson, Scott; /LLNL, Livermore; Barty, Christopher; /LLNL, Livermore; Gibson, David; /LLNL, Livermore; Hartemann, Fred; /LLNL, Livermore; Marsh, Roark; /LLNL, Livermore; Siders, Craig; /LLNL, Livermore; Adolphsen, Chris; /SLAC; Jongewaard, Erik; /SLAC; Raubenheimer, Tor; /SLAC; Tantawi, Sami; /SLAC; Vlieks, Arnold; /SLAC; Wang, Juwen; /SLAC

2012-07-03

315

Magnetism of CaRu{sub 1-x}Mn{sub x}O{sub 3}: Magnetic Compton scattering study  

SciTech Connect

The magnetism of CaRu{sub 1-x}Mn{sub x}O{sub 3} was studied using magnetic Compton scattering measurements for polycrystalline specimens at 10 K under 2.5 T using a synchrotron-radiation x ray. The spin moment deduced from the magnetic Compton profiles has a maximum at x=0.7 and the value agrees with the result of the magnetization measurement. The magnetic Compton profiles indicate that the Mn spin moment is dominant in magnetization and that Ru moment, which is induced with Mn doping, couples with Mn spin moment antiferromagnetically. The results suggest that a sort of ferrimagnetism is established in the CaRu{sub 1-x}Mn{sub x}O{sub 3} system.

Mizusaki, S.; Taniguchi, T.; Okada, N.; Nagata, Y. [College of Science and Engineering, Aoyama Gakuin University, Fuchinobe, Sagamihara, Kanagawa 157-8572 (Japan); Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute (JASRI/Spring-8), Sayo, Mikazuki, Hyogo 679-5198 (Japan); Ozawa, T. C. [Nanoscale Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Noro, Y. [Kawazoe Frontier Technologies, Co., Ltd., Kuden, Sakae, Yokohama, Kanagawa 931-113 (Japan); Samata, H. [Faculty of Maritime Sciences, Kobe University, Fukaeminami, Higashinada, Kobe, Hyogo 658-0022 (Japan)

2008-04-01

316

Using Effective Field Theory to analyse low-energy Compton scattering data from protons and light nuclei  

NASA Astrophysics Data System (ADS)

Compton scattering from protons and neutrons provides important insight into the structure of the nucleon. For photon energies up to about 300 MeV, the process can be parameterised by six dynamical dipole polarisabilities which characterise the response of the nucleon to a monochromatic photon of fixed frequency and multipolarity. Their zero-energy limit yields the well-known static electric and magnetic dipole polarisabilities ? and ?, and the four dipole spin polarisabilities. The emergence of full lattice QCD results and new experiments at MAMI (Mainz), HI?S at TUNL, and MAX-Lab (Lund) makes this an opportune time to review nucleon Compton scattering. Chiral Effective Field Theory (?EFT) provides an ideal analysis tool, since it encodes the well-established low-energy dynamics of QCD while maintaining an appropriately flexible form for the Compton amplitudes of the nucleon. The same ?EFT also describes deuteron and 3He Compton scattering, using consistent nuclear currents, rescattering and wave functions, and respects the low-energy theorems for photon-nucleus scattering. It can thus also be used to extract useful information on the neutron amplitude from Compton scattering on light nuclei. We summarise past work in ?EFT on all of these reactions and compare with other theoretical approaches. We also discuss all proton experiments up to about 400 MeV, as well as the three modern elastic deuteron data sets, paying particular attention to the precision and accuracy of each set. Constraining the ?(1232) parameters from the resonance region, we then perform new fits to the proton data up to ?=170 MeV, and a new fit to the deuteron data. After checking in each case that a two-parameter fit is compatible with the respective Baldin sum rules, we obtain, using the sum-rule constraints in a one-parameter fit, ?E1(p)=10.7±0.3(stat)±0.2(Baldin)±0.8(theory), ?M1(p)=3.1?0.3(stat)±0.2(Baldin)±0.8(theory), for the proton polarisabilities, and ?E1(s)=10.9±0.9(stat)±0.2(Baldin)±0.8(theory), ?M1(s)=3.6?0.9(stat)±0.2(Baldin)±0.8(theory), for the isoscalar polarisabilities, each in units of 10-4 fm. Finally, we discuss plans for polarised Compton scattering on the proton, deuteron, 3He and heavier targets, their promise as tools to access spin polarisabilities, and other future avenues for theoretical and experimental investigation.

Grießhammer, H. W.; McGovern, J. A.; Phillips, D. R.; Feldman, G.

2012-10-01

317

(Gamma scattering in condensed matter with high intensity Moessbauer radiation)  

SciTech Connect

This report discusses: quasielastic scattering studies on glycerol; gamma-ray scattering from alkali halides; lattice dynamics in metals; Moessbauer neutron scattering, x-ray diffraction, and macroscopic studies of high {Tc} superconductors containing tungsten; NiAl scattering studies; and atomic interference factors and nuclear Casimir effect.

Not Available

1992-01-01

318

On the Relevance of Compton Scattering for the Soft X-ray Spectra of Hot DA White Dwarfs  

E-print Network

We re-examine the effects of Compton scattering on the emergent spectra of hot DA white dwarfs in the soft X-ray range. Earlier studies have implied that sensitive X-ray observations at wavelengths $\\lambda < 50$ \\AA might be capable of probing the flux deficits predicted by the redistribution of electron-scattered X-ray photons toward longer wavelengths. We adopt two independent numerical approaches to the inclusion of Compton scattering in the computation of pure hydrogen atmospheres in hydrostatic equilibrium. One employs the Kompaneets diffusion approximation formalism, while the other uses the cross-sections and redistribution functions of Guilbert. Models and emergent spectra are computed for stellar parameters representative of HZ 43 and Sirius B, and for models with an effective temperature $T_{\\rm eff} = 100 000$ K. The differences between emergent spectra computed for Compton and Thomson scattering cases are completely negligible in the case of both HZ 43 and Sirius B models, and are also negligible for all practical purposes for models with temperatures as high as $T_{\\rm eff} = 100 000$ K. Models of the soft X-ray flux from these stars are instead dominated by uncertainties in their fundamental parameters.

V. Suleimanov; J. Madej; J. J. Drake; T. Rauch; K. Werner

2006-05-12

319

The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)  

NASA Astrophysics Data System (ADS)

The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60-600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm×12 cm×12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and the signals from all 13,312 pixels are processed by 208 ASICs developed for the SGD. Good energy resolution is afforded by semiconductor sensors and low noise ASICs, and the obtained energy resolutions with the prototype Si and CdTe pixel sensors are 1.0-2.0 keV (FWHM) at 60 keV and 1.6-2.5 keV (FWHM) at 122 keV, respectively. This results in good background rejection capability due to better constraints on Compton kinematics. Compton camera energy resolutions achieved with the final prototype are 6.3 keV (FWHM) at 356 keV and 10.5 keV (FWHM) at 662 keV, which satisfy the instrument requirements for the SGD Compton camera (better than 2%). Moreover, a low intrinsic background has been confirmed by the background measurement with the final prototype.

Watanabe, Shin; Tajima, Hiroyasu; Fukazawa, Yasushi; Ichinohe, Yuto; Takeda, Shin`ichiro; Enoto, Teruaki; Fukuyama, Taro; Furui, Shunya; Genba, Kei; Hagino, Kouichi; Harayama, Atsushi; Kuroda, Yoshikatsu; Matsuura, Daisuke; Nakamura, Ryo; Nakazawa, Kazuhiro; Noda, Hirofumi; Odaka, Hirokazu; Ohta, Masayuki; Onishi, Mitsunobu; Saito, Shinya; Sato, Goro; Sato, Tamotsu; Takahashi, Tadayuki; Tanaka, Takaaki; Togo, Atsushi; Tomizuka, Shinji

2014-11-01

320

Hadron Optics in Three-Dimensional Invariant Coordinate Space from Deeply Virtual Compton Scattering  

E-print Network

The Fourier transform of the deeply virtual Compton scattering amplitude (DVCS) with respect to the skewness parameter \\zeta= Q^2/ 2 p.q can be used to provide an image of the target hadron in the boost-invariant variable \\sigma, the coordinate conjugate to light-front time \\tau=t+ z/ c. As an illustration, we construct a consistent covariant model of the DVCS amplitude and its associated generalized parton distributions using the quantum fluctuations of a fermion state at one loop in QED, thus providing a representation of the light-front wavefunctions of a lepton in \\sigma space. A consistent model for hadronic amplitudes can then be obtained by differentiating the light-front wavefunctions with respect to the bound-state mass. The resulting DVCS helicity amplitudes are evaluated as a function of \\sigma and the impact parameter \\vec b_\\perp, thus providing a light-front image of the target hadron in a frame-independent three-dimensional light-front coordinate space. Models for the LFWFs of hadrons in (3+1) dimensions displaying confinement at large distances and conformal symmetry at short distances have been obtained using the AdS/CFT method. We also compute the LFWFs in this model in invariant three dimensional coordinate space. We find that in the models studied, the Fourier transform of the DVCS amplitudes exhibit diffraction patterns. The results are analogous to the diffractive scattering of a wave in optics where the distribution in \\sigma measures the physical size of the scattering center in a one-dimensional system.

S. J. Brodsky; D. Chakrabarti; A. Harindranath; A. Mukherjee; J. P. Vary

2006-11-28

321

Compton scattering and charge transfer in Er substituted DyAl2  

NASA Astrophysics Data System (ADS)

A unique applicability of Compton spectroscopy in probing the electronic states of rare earth aluminides using high energy (662 keV) ?-rays is reported. We have measured first-ever Compton profiles of Dy1-xErxAl2 (x=0, 0.2) using 20Ci 137Cs Compton spectrometer. The charge reorganization in Dy1-xErxAl2 (x=0, 0.2), on the formation of compound, has been discussed using the valence band Compton profile data. The experimental Compton profile data unambiguously establish charge transfer from Al to Dy (Dy and Er) on formation of x=0.0 (0.2) compound, which is in tune with spin polarized relativistic Korringa-Kohn-Rostoker (SPR-KKR) calculations. A reasonable agreement between SPR-KKR based Compton profiles and the experimental data show applicability of the Green function method in predicting the electronic properties of rare earth compounds.

Ahuja, B. L.; Mohammad, F. M.; Mohammed, S. F.; Sahariya, Jagrati; Mund, H. S.; Heda, N. L.

2015-02-01

322

Observations of gamma radiation between 0. 4 MeV and 7 MeV at balloon altitudes using a Compton telescope  

SciTech Connect

Results are presented from a balloon flight at Palestine, Texas, in 1978 to measure the atmospheric and diffuse ..gamma..-ray flux in the energy range 0.4--7.0 MeV. The observations were made 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. The total downward ..gamma..-ray flux at 3.7 g cm/sup -2/ is given by the spectrum 3.1 x 10/sup -2/ x E/sup -1.74/ (photons cm/sup -2/ s/sup -1/ MeV/sup -1/ sr/sup -1/) for 0.5gamma..-ray flux to the atmospheric ..gamma..-rays indicate that 0.2 MeV

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

1981-09-15

323

Virtual Compton Scattering and the Generalized Polarizabilities of the Proton at Q^2=0.92 and 1.76 GeV^2  

SciTech Connect

Virtual Compton Scattering (VCS) on the proton has been studied at Jefferson Lab using the exclusive photon electroproduction reaction (e p --> e p gamma). This paper gives a detailed account of the analysis which has led to the determination of the structure functions P{sub LL}-P{sub TT}/epsilon and P{sub LT}, and the electric and magnetic generalized polarizabilities (GPs) alpha{sub E}(Q{sup 2}) and beta{sub M}(Q{sup 2}) at values of the four-momentum transfer squared Q{sup 2} = 0.92 and 1.76 GeV{sup 2}. These data, together with the results of VCS experiments at lower momenta, help building a coherent picture of the electric and magnetic GPs of the proton over the full measured Q{sup 2}-range, and point to their non-trivial behavior.

Helene Fonvieille, Geraud Laveissiere, Natalie Degrande, Stephanie Jaminion, Christophe Jutier, Luminita Todor, L. Van Hoorebeke, Bryon Anderson, Konrad Aniol, Kathleen Arundell, Gerard Audit, Leonard Auerbach, F. Baker, Maud Baylac, J. Berthot, Pierre Bertin, William Bertozzi, Louis Bimbot, Werner Boeglin, Edward Brash, Vincent Breton, Herbert Breuer, Etienne Burtin, John Calarco, Lawrence Cardman, Christian Cavata, Jian-Ping Chen, Eugene Chudakov, Evaristo Cisbani, Daniel Dale, Cornelis De Jager, Raffaele De Leo, Alexandre Deur, Nicole D'Hose, Gail Dodge, John Domingo, Latifa Elouadrhiri, Martin Epstein, Lars Ewell, John Finn, Kevin Fissum, Guy Fournier, Bernhard Frois, Salvatore Frullani, Christophe Furget, Haiyan Gao, Juncai Gao, Franco Garibaldi, Ashot Gasparian, Shalev Gilad, Ronald Gilman, Oleksandr Glamazdin, Charles Glashausser, Javier Gomez, Viktor Gorbenko, Pierre Guichon, Jens-Ole Hansen, Richard Holmes, Maurik Holtrop, Calvin Howell, Garth Huber, Charles Hyde, Sebastien Incerti, Mauro Iodice, Johann Jardillier, Mark Jones, Seigo Kato, James Kelly, Armen Ketikyan, Mohammad Khayat, Kouichi Kino, Serge Kox, Laird Kramer, Krishna Kumar, Gerfried Kumbartzki, Michael Kuss, Antonio Leone, John LeRose, Richard Lindgren, Nilanga Liyanage, George Lolos, Kazushige Maeda, Sergey Malov, D. Manley, Claude Marchand, Dominique Marchand, Demetrius Margaziotis, Pete Markowitz, Jacques Marroncle, Jacques Martino, Kathy McCormick, James McIntyre, Surik Mehrabyan, Fernand Merchez, Zein-Eddine Meziani, Robert Michaels, Jean Mougey, Sirish Nanda, Amra Offermann, Zisis Papandreou, Charles Perdrisat, R. Perrino, Gerassimos Petratos, Stephane Platchkov, Roman Pomatsalyuk, David Prout, Vina Punjabi, Thierry Pussieux, Gilles Quemener, Ronald Ransome, Oliver Ravel, Jean-Sebastien Real, Yves Roblin, David Rowntree, Gary Rutledge, Paul Rutt, Arunava Saha, Teijiro Saito, Adam Sarty, Tim Smith, Paul Souder, Riad Suleiman, Jeffrey Templon, Tatsuo Terasawa, Raphael Tieulent, Egle Tomasi, Hiroaki Tsubota, Hiroaki Ueno, Paul Ulmer, Guido Urciuoli, Marc Vanderhaeghen, Rob van der Meer, R.Van De Vyver, Pascal Vernin, Branislav Vlahovic, Hakob Voskanyan, Eric Voutier, John Watson, Lawrence Weinstein, Krishni Wijesooriya, Richard Wilson, Bogdan Wojtsekhowski, Dan Zainea, Zilu Zhou, Rachele Di Salvo

2012-07-01

324

Electronic structure of CdMoO{sub 4} using Compton scattering technique  

SciTech Connect

The first ever Compton profile of polycrystalline CdMoO{sub 4} has been measured using {sup 137}Cs spectrometer. The results are compared with theoretical Compton profiles deduced from free atom and linear combination of atomic orbitals (LCAO) methods. We have also computed the energy bands using density functional theory (DFT) within LCAO. The computed bands confirm the semiconducting behaviour of this compound. It is seen that the DFT theoretical profile (with local density approximation) gives a better agreement with the experimental Compton data than free atom Compton profile.

Sharma, Khushboo, E-mail: khushboo.phy@gmail.com; Ahuja, B. L. [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur-313001 (India); Sahariya, Jagrati [Department of Physics, Manipal University, Jaipur-303007 (India)

2014-04-24

325

Trajectory Design and Control for the Compton Gamma Ray Observatory Re-Entry  

NASA Technical Reports Server (NTRS)

The Compton Gamma Ray Observatory (CGRO) controlled re-entry operation was successfully conducted in June of 2000. The surviving parts of the spacecraft landed in the Pacific Ocean within the predicted footprint. The design of the maneuvers to control the trajectory to accomplish this re-entry presented several challenges. These challenges included timing and duration of the maneuvers, fuel management, post maneuver position knowledge, collision avoidance with other spacecraft, accounting for the break-up of the spacecraft into several pieces with a wide range of ballistic coefficients, and ensuring that the impact footprint would remain within the desired landing area in the event of contingencies. This paper presents the initial re-entry trajectory design and the evolution of the design into the maneuver sequence used for the re-entry. The paper discusses the constraints on the trajectory design, the modifications made to the initial design and the reasons behind these modifications. Data from the re-entry operation are presented.

Hoge, Susan; Vaughn, Frank; Bauer, Frank H. (Technical Monitor)

2000-01-01

326

ULTRA-BRIGHT X-RAY GENERATION USING INVERSE COMPTON SCATTERING OF PICOSECOND CO(2) LASER PLUSES.  

SciTech Connect

Laser-Compton scattering with picosecond CO{sub 2} laser pulses is proposed for generation of high-brightness x-rays. The interaction chamber has been developed and the experiment is scheduled for the generation of the x-rays of 4.7 keV, 10{sup 7} photons in 10-ps pulse width using 50-MeV, 0.5-nC relativistic electron bunches and 6 GW CO{sub 2} laser.

TSUNEMI,A.; ENDO,A.; POGORELSKY,I.; BEN-ZVI,I.; KUSCHE,K.; SKARITKA,J.; YAKIMENKO,V.; HIROSE,T.; URAKAWA,J.; OMORI,T.; WASHIO,M.; LIU,Y.; HE,P.; CLINE,D.

1999-03-01

327

Virtual Compton Scattering at JLab : Preliminary results Q2 = 1. and 1.9 GeV2  

E-print Network

of Jefferson Lab. SANTORINI 2001 Electromagnetic Interactions with Nucleons and Nuclei 2-7 october 2001 Santorini2001 jaminion@clermont.in2p3.fr #12;2 Virtual Compton Scattering below 0 threshold hadronic system'(p')p(p) e(k) e'(k') + +* (q) * (q) * (q) Bethe-Heitler VCS Santorini2001 jaminion@clermont.in2p3.fr #12;4 P

Paris-Sud XI, Université de

328

Improvement of gamma-ray S{sub n} transport calculations including coherent and incoherent scatterings and secondary sources of bremsstrahlung and fluorescence: Determination of gamma-ray buildup factors  

Microsoft Academic Search

Improvements of gamma-ray transport calculations in S{sub n} codes aim at taking into account the bound-electron effect of Compton scattering (incoherent), coherent scattering (Rayleigh), and secondary sources of bremsstrahlung and fluorescence. A computation scheme was developed to take into account these phenomena by modifying the angular and energy transfer matrices, and no modification in the transport code has been made.

S. Kitsos; C. M. Diop; A. Assad; J. C. Nimal; P. Ridoux

1996-01-01

329

The detector response matrices of the burst and transient source experiment (BATSE) on the Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The detector response matrices for the Burst And Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO) are described, including their creation and operation in data analysis. These response matrices are a detailed abstract representation of the gamma-ray detectors' operating characteristics that are needed for data analysis. They are constructed from an extensive set of calibration data coupled with a complex geometry electromagnetic cascade Monte Carlo simulation code. The calibration tests and simulation algorithm optimization are described. The characteristics of the BATSE detectors in the spacecraft environment are also described.

Pendleton, Geoffrey N.; Paciesas, William S.; Mallozzi, Robert S.; Koshut, Tom M.; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.; Horack, John M.; Lestrade, John Patrick

1995-01-01

330

X-ray generation by inverse Compton scattering at the superconducting RF test facility  

NASA Astrophysics Data System (ADS)

Quasi-monochromatic X-rays with high brightness have a broad range of applications in fields such as life sciences, bio-, medical applications, and microlithography. One method for generating such X-rays is via inverse Compton scattering (ICS). X-ray generation experiments using ICS were carried out at the superconducting RF test facility (STF) accelerator at KEK. A new beam line, newly developed four-mirror optical cavity system, and new X-ray detector system were prepared for experiments downstream section of the STF electron accelerator. Amplified pulsed photons were accumulated into a four-mirror optical cavity and collided with an incoming 40 MeV electron beam. The generated X-rays were detected using a microchannel plate (MCP) detector for X-ray yield measurements and a new silicon-on-insulator (SOI) detector system for energy measurements. The detected X-ray yield by the MCP detector was 1756.8±272.2 photons/(244 electron bunches). To extrapolate this result to 1 ms train length under 5 Hz operations, 4.60×105 photons/1%-bandwidth were obtained. The peak X-ray energy, which was confirmed by the SOI detector, was 29 keV, and this is consistent with ICS X-rays.

Shimizu, Hirotaka; Akemoto, Mitsuo; Arai, Yasuo; Araki, Sakae; Aryshev, Alexander; Fukuda, Masafumi; Fukuda, Shigeki; Haba, Junji; Hara, Kazufumi; Hayano, Hitoshi; Higashi, Yasuo; Honda, Yosuke; Honma, Teruya; Kako, Eiji; Kojima, Yuji; Kondo, Yoshinari; Lekomtsev, Konstantin; Matsumoto, Toshihiro; Michizono, Shinichiro; Miyoshi, Toshinobu; Nakai, Hirotaka; Nakajima, Hiromitsu; Nakanishi, Kota; Noguchi, Shuichi; Okugi, Toshiyuki; Sato, Masato; Shevelev, Mikhail; Shishido, Toshio; Takenaka, Tateru; Tsuchiya, Kiyosumi; Urakawa, Junji; Watanabe, Ken; Yamaguchi, Seiya; Yamamoto, Akira; Yamamoto, Yasuchika; Sakaue, Kazuyuki; Hosoda, Seiichi; Iijima, Hokuto; Kuriki, Masao; Tanaka, Ryuta; Kuramoto, Ayaka; Omet, Mathieu; Takeda, Ayaki

2015-02-01

331

CONSTRAINT ON THE PARAMETERS OF THE INVERSE COMPTON SCATTERING MODEL FOR RADIO PULSARS  

SciTech Connect

The inverse Compton scattering (ICS) model can explain various pulse profile shapes and the diversity of the pulse profile evolution based on the mechanism where the radio emission is generated through ICS between secondary relativistic particles and radio waves from polar gap avalanches. In this paper, we study the parameter space of the ICS model for 15 pulsars that share the common pulse profile evolution phenomenon, where the pulse profiles are narrower at higher observing frequencies. Two key parameters, the initial Lorentz factor and the energy loss factor of secondary particles, are constrained using the least-squares fitting method, where we fit the theoretical curve of the 'beam-frequency mapping' of the ICS model to the observed pulse widths at multiple frequencies. The uncertainty of the inclination and viewing angles are taken into account in the fitting process. It is found that the initial Lorentz factor is larger than 4000, and the energy loss factor is between 20 and 560. The Lorentz factor is consistent with the prediction of the inner vacuum gap model. Such high-energy loss factors suggest significant energy loss for secondary particles at altitudes of a few tens to hundreds of kilometers.

Lv, M.; Wang, H. G. [Center for Astrophysics, Guangzhou University, Guangzhou 510006 (China); Lee, K. J. [Max-Planck Institute for Radio Astronomy, Bonn 53121 (Germany); Qiao, G. J.; Xu, R. X., E-mail: hgwang@gzhu.edu.cn [Department of Astronomy, Peking University, Beijing 100871 (China)

2011-11-01

332

Compton scattering of the microwave background by quasar-blown bubbles  

NASA Technical Reports Server (NTRS)

At least 10% of quasars drive rapid outflows from the central regions of their host galaxies. The mass and energy flow rates in these winds are difficult to measure, but their kinetic luminosities probably exceed 10(exp 45) ergs/s. This kind of outflow easily sunders the interstellar medium of the host and blows a bubble in the intergalactic medium. After the quasar shuts off, the hot bubble continues to shock intergalactic gas until its leading edge merges with the Hubble flow. The interior hot gas Compton scatters microwave background photons, potentially providing a way to detect these bubbles. Assuming that quasar kinetic luminosities scale with their blue luminosities, we integrate over the quasar luminosity function to find the total distortion (y) of the microwave background produced by the entire population of quasar wind bubbles. This calculation of y distortion is remarkably insensitive to the properties of the intergalactic medium (IGM), quasar lifetimes, and cosmological parameters. Current Cosmic Background Explorer (COBE) limits on y constrain the kinetic luminosities of quasars to be less than several times their bolometric radiative luminosities. Within this constraint, quasars can still expel enough kinetic luminosity to shock the entire IGM by z = 0, but cannot heat and ionize the IGM by z = 4 unless omega(sub IGM) much less than 10(exp -2).

Voit, G. Mark

1994-01-01

333

Fermi-Compton scattering due to magnetopause surface fluctuations in Jupiter's magnetospheric cavity  

NASA Technical Reports Server (NTRS)

The effects of boundary surface fluctuations on a spectrum of electromagnetic radiation trapped in a high Q (quality) cavity are considered. Undulating walls introduce small frequency shifts at reflection to the radiation, and it is argued that the process is entirely analogous to both Fermi (particle) acceleration and inverse Compton scattering. A Fokker-Planck formalism is pursued; it yields a diffusion equation in frequency for which the Green's function and steady-state solutions are found. Applying this analysis to the Jovian continuum radiation discovered by Voyager spacecraft, it is suggested that characteristic diffusion times are greater than 1 year, and that in order to account for the steep frequency spectra observed, an unidentified loss mechanism must operate in the cavity with a decay time constant approximately equal to the characteristic diffusion time divided by 28. A radiator-reactor model of the cavity is investigated to provide an estimate for the intrinsic luminosity of the low frequency (approximately 100 Hz) continuum source whose power is approximately 7 x 10 to the 6th W.

Barbosa, D. D.

1981-01-01

334

Hadron Optics in Three-Dimensional Invariant Coordinate Space from Deeply Virtual Compton Scattering  

E-print Network

The Fourier transform of the deeply virtual Compton scattering amplitude (DVCS) with respect to the skewness parameter \\zeta= Q^2/ 2 p.q can be used to provide an image of the target hadron in the boost-invariant variable \\sigma, the coordinate conjugate to light-front time \\tau=t+ z/ c. As an illustration, we construct a consistent covariant model of the DVCS amplitude and its associated generalized parton distributions using the quantum fluctuations of a fermion state at one loop in QED, thus providing a representation of the light-front wavefunctions of a lepton in \\sigma space. A consistent model for hadronic amplitudes can then be obtained by differentiating the light-front wavefunctions with respect to the bound-state mass. The resulting DVCS helicity amplitudes are evaluated as a function of \\sigma and the impact parameter \\vec b_\\perp, thus providing a light-front image of the target hadron in a frame-independent three-dimensional light-front coordinate space. Models for the LFWFs of hadrons in (3+1) ...

Brodsky, S J; Harindranath, A; Mukherjee, A; Vary, J P

2007-01-01

335

Evaluation of Compton gamma camera prototype based on pixelated CdTe detectors  

PubMed Central

A proposed Compton camera prototype based on pixelated CdTe is simulated and evaluated in order to establish its feasibility and expected performance in real laboratory tests. The system is based on module units containing a 2×4 array of square CdTe detectors of 10×10 mm2 area and 2 mm thickness. The detectors are pixelated and stacked forming a 3D detector with voxel sizes of 2 × 1 × 2 mm3. The camera performance is simulated with Geant4-based Architecture for Medicine-Oriented Simulations(GAMOS) and the Origin Ensemble(OE) algorithm is used for the image reconstruction. The simulation shows that the camera can operate with up to 104 Bq source activities with equal efficiency and is completely saturated at 109 Bq. The efficiency of the system is evaluated using a simulated 18F point source phantom in the center of the Field-of-View (FOV) achieving an intrinsic efficiency of 0.4 counts per second per kilobecquerel. The spatial resolution measured from the point spread function (PSF) shows a FWHM of 1.5 mm along the direction perpendicular to the scatterer, making it possible to distinguish two points at 3 mm separation with a peak-to-valley ratio of 8. PMID:24932209

Calderón, Y.; Chmeissani, M.; Kolstein, M.; De Lorenzo, G.

2014-01-01

336

Material efficiency studies for a Compton camera designed to measure characteristic prompt gamma rays emitted during proton beam radiotherapy  

PubMed Central

Prompt gamma rays emitted from biological tissues during proton irradiation carry dosimetric and spectroscopic information that can assist with treatment verification and provide an indication of the biological response of the irradiated tissues. Compton cameras are capable of determining the origin and energy of gamma rays. However, prompt gamma monitoring during proton therapy requires new Compton camera designs that perform well at the high gamma energies produced when tissues are bombarded with therapeutic protons. In this study we optimize the materials and geometry of a three-stage Compton camera for prompt gamma detection and calculate the theoretical efficiency of such a detector. The materials evaluated in this study include germanium, bismuth germanate (BGO), NaI, xenon, silicon and lanthanum bromide (LaBr3). For each material, the dimensions of each detector stage were optimized to produce the maximum number of relevant interactions. These results were used to predict the efficiency of various multi-material cameras. The theoretical detection efficiencies of the most promising multi-material cameras were then calculated for the photons emitted from a tissue-equivalent phantom irradiated by therapeutic proton beams ranging from 50 to 250 MeV. The optimized detector stages had a lateral extent of 10 × 10 cm2 with the thickness of the initial two stages dependent on the detector material. The thickness of the third stage was fixed at 10 cm regardless of material. The most efficient single-material cameras were composed of germanium (3 cm) and BGO (2.5 cm). These cameras exhibited efficiencies of 1.15 × 10?4 and 9.58 × 10?5 per incident proton, respectively. The most efficient multi-material camera design consisted of two initial stages of germanium (3 cm) and a final stage of BGO, resulting in a theoretical efficiency of 1.26 × 10?4 per incident proton. PMID:21508442

Robertson, Daniel; Polf, Jerimy C; Peterson, Steve W; Gillin, Michael T; Beddar, Sam

2011-01-01

337

Of narrow lines and beaming in the strong-field SSC emission model. [synchrotron self-Compton for gamma ray bursts  

NASA Technical Reports Server (NTRS)

The synchrotron self-Compton (SSC) emission model for gamma-ray bursts is capable of producing narrow line features for a variety of modelled field strengths, primary electron injection distributions and burst luminosities. Multiple resonant scattering with synchrotron continuum photons efficiently traps and cools pairs in the ground state to an average energy where the Compton energy loss rate is zero. Annihilation between pairs in these cooled distributions can be very efficient. For isotropic injection of primary electrons, there is an anti-correlation of the intensity of the angular-binned emission between the portions of the continuum spectrum below the cyclotron peak and above the annihilation line feature. Small-angle emission dominates the continuum above the annihilation line feature and is smooth through the line up to the pair production cut-off, which can be above several MeV for small enough angles. The angle-averaged annihilation line is made of components which can have peak emission centered at energies away from 511 keV, due to Doppler shifting. For beamed injection,the annihilation line breaks up into relatively narrow components in the angular emission, which sum into a broad feature in the angle-averaged emission.

Preece, Robert D.

1992-01-01

338

Measurements of the Electron-Helicity Dependent Cross Sections of Deeply Virtual Compton Scattering with CEBAF at 12 GeV  

SciTech Connect

We propose precision measurements of the helicity-dependent and helicity independent cross sections for the ep {yields} ep{gamma} reaction in Deeply Virtual Compton Scattering (DVCS) kinematics. DVCS scaling is obtained in the limits Q{sup 2} >> {Lambda}{sub QCD}{sup 2}, x{sub Bj} fixed, and -{Delta}{sup 2} = -(q-q{prime}){sup 2} << Q{sup 2}. We consider the specific kinematic range Q{sup 2} > 2 GeV{sup 2}, W > 2 GeV, and -{Delta}{sup 2} {le} 1 GeV{sup 2}. We will use our successful technique from the 5.75 GeV Hall A DVCS experiment (E00-110). With polarized 6.6, 8.8, and 11 GeV beams incident on the liquid hydrogen target, we will detect the scattered electron in the Hall A HRS-L spectrometer (maximum central momentum 4.3 GeV/c) and the emitted photon in a slightly expanded PbF{sub 2} calorimeter. In general, we will not detect the recoil proton. The H(e,e{prime}{gamma})X missing mass resolution is sufficient to isolate the exclusive channel with 3% systematic precision.

J. Roche; C. E. Hyde-Wright; B. Michel; C. Munoz Camacho; et al. (The Jefferson Lab Hall A Collaboration)

2006-09-11

339

SCATTERING OF GAMMA-RAYS. I. SCATTERED GAMMA-RAYS IN THE LABYRINTH OF SHIELDED Co⁶° IRRADIATION FACILITIES. II. RADIOGRAPHY USING THE SCATTERED $gamma$-RAYS  

Microsoft Academic Search

The intensities and energy spectra of scattered gamma rays in the ; labyrinth of a 3000-C Co⁶° irradiation facilities were measured by means of ; chamber-type detectors and a scintillation spectrometer. Problems concerning the ; radiation differences between the 2 labyrinth sections, the contribution of the ; scattered-rays to the special dosage rate, and the estimation of the dosage rate

Kaminishi

1961-01-01

340

Simulations of gamma quanta scattering in a single module of the J-PET detector  

E-print Network

This article describes simulations of scattering of annihilation gamma quanta in a strip of plastic scintillator. Such strips constitute basic detection modules in a newly proposed Positron Emission Tomography which utilizes plastic scintillators instead of inorganic crystals. An algorithm simulating chain of Compton scatterings was elaborated and series of simulations have been conducted for the scintillator strip with the cross section of 5 mm x 19 mm. Obtained results indicate that secondary interactions occur only in the case of about 8% of events and out of them only 25$\\%$ take place in the distance larger than 0.5 cm from the primary interaction. It was also established that light signals produced at primary and secondary interactions overlap with the delay which distribution is characterized by FWHM of about 40 ps.

Szyma?ski, K; Bednarski, T; Bia?as, P; Czerwi?ski, E; Giergiel, K; Kap?on, ?; Kochanowski, A; Korcyl, G; Kowal, J; Kowalski, P; Kozik, T; Krzemie?, W; Molenda, M; Moskal, I; Nied?wiecki, Sz; Pa?ka, M; Pawlik, M; Raczy?ski, L; Rudy, Z; Salabura, P; Sharma, N G; Silarski, M; S?omski, A; Smyrski, J; Strzelecki, A; Witkowski, P; Wi?licki, W; Zieli?ski, M; Zo?, N

2013-01-01

341

Real-Time Compton Imaging for the GammaTracker Handheld CdZnTe Detector  

SciTech Connect

We are currently developing a handheld radioisotope identifier containing 18 position-sensitive CdZnTe crystals. In addition to isotope identification, the device performs basic Compton imaging to determine the location of suspected sources. This paper presents two computationally efficient algorithms for this purpose. The first algorithm traces individual Compton cones onto the unit sphere, whereas the second algorithm computes the intersection of two Compton cones and the unit sphere. Simulations demonstrate that the algorithms are suitable for determining the directionality, even with features such as uncertainty calculations omitted. The one-cone algorithm works more efficiently at high count rates, but the two-cone algorithm generates fewer image artifacts.

Myjak, Mitchell J.; Seifert, Carolyn E.

2008-04-01

342

X-ray Fluorescence (XRF) Assay Using Laser Compton Scattered (LCS) X-rays  

NASA Astrophysics Data System (ADS)

Laser Compton Scattered (LCS) X-rays are produced as a result of the interaction between accelerated electrons and a laser beam. The yield of LCS X-rays is dependent on the laser power, angle of collision between interacting particles, and the electron linear accelerator's (linac) electron beam energy and its current. One of our research goals at the Idaho Accelerator Center (IAC) focuses on applications such as detection and imaging of fissionable isotopes for nuclear non-proliferation, safeguards and homeland security. Quasi monochromatic LCS X-rays offer much better signal-to-noise ratios for such applications. The energy of LCS X-rays is tunable, that enable element-specific analysis. Two sharp 36.5 keV and 98.4 keV LCS peaks were observed in two separate experiments based on electron beams tuned at 32 MeV and 37 MeV, that were brought in collision with the (Power)peak = 4 GW Nd.YAG laser operating at 532 nm and 266 nm wavelengths. The linac was operating at 60 Hz with an electron beam pulse length of about 50 ps and a peak current of about 7 A. We exploited X-ray fluorescence (XRF) techniques to identify elemental K?1, K?2, and K?1 lines in a high-purity germanium (HPGe) detector, with a 0.5 mm thick Beryllium (Be) absorbing layer, emitted from tin (Sn), cadmium (Cd), silver (Ag), gold (Au), and lead (Pb) foils with thicknesses ranging from 25-500 ?m, following absorption of 36.1 keV and 98.4 keV LCS X-rays. These reference foils were used for the proof of principle, and some have atomic numbers near to that of relevant fission products.

Naeem, Syed F.; Chouffani, Khalid; Wells, Douglas P.

2009-03-01

343

Measurement of double-spin asymmetries associated with deeply virtual Compton scattering on a transversely polarized hydrogen target  

NASA Astrophysics Data System (ADS)

Double-spin asymmetries in exclusive electroproduction of real photons from a transversely polarized hydrogen target are measured with respect to the product of target polarization with beam helicity and beam charge, and with respect to the product of target polarization with beam helicity alone. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe-Heitler process. They are related to the real part of the same combination of Compton form factors as that determining the previously published transverse target single-spin asymmetries through the imaginary part. The results for the double-spin asymmetries are found to be compatible with zero within the uncertainties of the measurement, and are not incompatible with the predictions of the only available GPD-based calculation.

Airapetian, A.; Akopov, N.; Akopov, Z.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetisyan, E.; Belostotski, S.; Bianchi, N.; Blok, H. P.; Borissov, A.; Bowles, J.; Brodski, I.; Bryzgalov, V.; Burns, J.; Capiluppi, M.; Capitani, G. P.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; de Leo, R.; de Nardo, L.; de Sanctis, E.; di Nezza, P.; Düren, M.; Ehrenfried, M.; Elbakian, G.; Ellinghaus, F.; Fabbri, R.; Fantoni, A.; Felawka, L.; Frullani, S.; Gabbert, D.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Giordano, F.; Gliske, S.; Golembiovskaya, M.; Hartig, M.; Hasch, D.; Hoek, M.; Holler, Y.; Hristova, I.; Imazu, Y.; Ivanilov, A.; Jackson, H. E.; Jo, H. S.; Joosten, S.; Kaiser, R.; Karyan, G.; Keri, T.; Kinney, E.; Kisselev, A.; Korotkov, V.; Kozlov, V.; Kravchenko, P.; Krivokhijine, V. G.; Lagamba, L.; Lapikás, L.; Lehmann, I.; Lenisa, P.; López Ruiz, A.; Lorenzon, W.; Lu, X.-G.; Lu, X.-R.; Ma, B.-Q.; Mahon, D.; Makins, N. C. R.; Manaenkov, S. I.; Manfré, L.; Mao, Y.; Marianski, B.; Martinez de La Ossa, A.; Marukyan, H.; Miller, C. A.; Miyachi, Y.; Movsisyan, A.; Murray, M.; Mussgiller, A.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaev, M.; Nowak, W.-D.; Pappalardo, L. L.; Perez-Benito, R.; Raithel, M.; Reimer, P. E.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Rubin, J.; Ryckbosch, D.; Salomatin, Y.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Seitz, B.; Shibata, T.-A.; Shutov, V.; Stancari, M.; Statera, M.; Steffens, E.; Steijger, J. J. M.; Stinzing, F.; Taroian, S.; Terkulov, A.; Truty, R.; Trzcinski, A.; Tytgat, M.; van Haarlem, Y.; van Hulse, C.; Veretennikov, D.; Vikhrov, V.; Vilardi, I.; Wang, S.; Yaschenko, S.; Ye, Z.; Yen, S.; Zagrebelnyy, V.; Zeiler, D.; Zihlmann, B.; Zupranski, P.; Hermes Collaboration

2011-10-01

344

Frequency scaling law for nonlinear Compton and Thomson scattering: Relevance of spin and polarization effects  

NASA Astrophysics Data System (ADS)

The distributions of Compton and Thomson radiation for a shaped laser pulse colliding with a free electron are calculated in the framework of quantum and classical electrodynamics, respectively. We introduce a scaling law for the Compton and the Thomson frequency distributions which universally applies to long and short incident pulses. Thus, we extend the validity of frequency scaling postulated in previous studies comparing nonlinear Compton and Thomson processes. The scaling law introduced in this paper relates the Compton no-spin flipping process to the Thomson process over nearly the entire spectrum of emitted radiation, including its high-energy portion. By applying the frequency scaling, we identify that both spin and polarization effects are responsible for differences between classical and quantum results. The same frequency scaling applies to angular distributions and to temporal power distributions of emitted radiation, which we illustrate numerically.

Krajewska, K.; Kami?ski, J. Z.

2014-11-01

345

Compton-scattering measurement of diagnostic x-ray spectrum using high-resolution Schottky CdTe detector  

SciTech Connect

The analysis of x-ray spectra is important for quality assurance (QA) and quality control (QC) of radiographic systems. The aim of this study is to measure the diagnostic x-ray spectra under clinical conditions using a high-resolution Schottky CdTe detector. Under clinical conditions, the direct measurement of a diagnostic spectrum is difficult because of the high photon fluence rates that cause significant detector photon pile-up. An alternative way of measuring the output spectra from a tube is first to measure the 90 deg Compton scattered photons from a given sample. With this set-up detector, pile-up is not a problem. From the scattered spectrum one can then use an energy correction and the Klein-Nishina function to reconstruct the actual spectrum incident upon the scattering sample. The verification of whether our spectra measured by the Compton method are accurate was accomplished by comparing exposure rates calculated from the reconstructed spectra to those measured with an ionization chamber. We used aluminum (Al) filtration ranging in thickness from 0 to 6 mm. The half value layers (HVLs) obtained for a 70 kV beam were 2.78 mm via the ionization chamber measurements and 2.93 mm via the spectral measurements. For a 100 kV beam we obtained 3.98 and 4.32 mm. The small differences in HVLs obtained by both techniques suggest that Compton scatter spectroscopy with a Schottky CdTe detector is suitable for measuring the diagnostic x-ray spectra and useful for QA and QC of clinical x-ray equipment.

Maeda, Koji; Matsumoto, Masao; Taniguchi, Akira [Department of Clinical Radiology, Faculty of Health Sciences, Hiroshima International University, 555-36 Gakuen-dai, Kurose-cho, Kamo-gun, Hiroshima 724-0695 (Japan); Division of Health Sciences, Graduate School of Medicine, Osaka University, 1-7 Yamadaoka, Suita, Osaka 565-0871 (Japan); Environment Technology Division, Toyo Medic Co. Ltd., 1-17-22 Kitahorie, Nishi-ku, Osaka 550-0014 (Japan)

2005-06-15

346

Inverse Compton scattering of ambient radiation by a cold relativistic jet - A source of beamed, polarized continuum in blazars?  

NASA Technical Reports Server (NTRS)

A general formalism is developed for computing the intensity and polarization of unpolarized radiation scattered by a group of electrons with a specified distribution of momenta. The case of isotropic incident radiation with a power-law spectrum is addressed, and the 'head-on' approximation is developed to describe the nearly unidirectional character of the incident radiation in the electron rest frame. The formalism is implemented numerically, verifying the validity of the 'head-on' approximation and illustrating the polarization and intensity properties of radiation scattered by jets with different electron momentum distribution. The results are placed in an astrophysical setting, determining the optical depths and kinetic energies required for the scattered radiation to dominate over the isotropic component in blazars. It is argued that Comptonization of unbeamed AGN radiation by a relativistic jet can account for the polarization and the overall spectral shape of the IR-optical continuum in blazars.

Begelman, Mitchell C.; Sikora, Marek

1987-01-01

347

The results of the in-flight attitude sensor calibration for the Arthur Holly Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The Arthur Holly Compton Gamma Ray Observatory (GRO) was launched by the shuttle Atlantis in April 1991. This paper presents the results of the attitude sensor calibration that was performed during the early mission. The GSFC Flight Dynamics Facility (FDF) performed an alignment calibration of the two fixed-head star trackers (FHST's) and two fine Sun sensors (FSS's) on board Compton GRO. The results show a 27-arcsecond shift between the bore sights of the FHST's with respect to prelaunch measurements. The alignments of the two FSS's shifted by 0.20 and 0.05 degree. During the same time period, the Compton GRO science teams performed an alignment calibration of the science instruments with respect to the attitude reported by the on board computer (OBC). In order to preserve these science alignments, FDF adjusted the overall alignments of the FHST's and FSS's, obtained by the FDF calibration, such that when up linked to the OBC, the shift in the OBC-determined attitude is minimized. FDF also calibrated the inertial reference unit (IRU), which consists of three dual-axis gyroscopes. The observed gyro bias matched the bias that was solved for by the OBC. This bias drifted during the first 6 days after release. The results of the FDF calibration of scale factor and alignment shifts showed changes that were of the same order as their uncertainties.

Davis, W. S.; Eudell, A. H.; Kulp, L. S.; Lindrose, L. A.; Harman, R. R.

1993-01-01

348

The results of the in-flight attitude sensor calibration for the Arthur Holly Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory (GRO) was launched by the shuttle Atlantis in April 1991. This paper presents the results of the attitude sensor calibration that was performed during the early mission. The GSFC Flight Dynamics Facility (FDF) performed an alignment calibration of the two fixed-head star trackers (FHST's) and two fine Sun sensors (FSS's) on board Compton GRO. The results show a 27-arcsecond shift between the bore sights of the FHST's with respect to prelaunch measurements. The alignments of the two FSS's shifted by 0.20 and 0.05 degree. During the same time period, the Compton GRO science teams performed an alignment calibration of the science instruments with respect to the attitude reported by the on board computer (OBC). In order to preserve these science alignments, FDF adjusted the overall alignments of the FHST's and FSS's, obtained by the FDF calibration, such that when up linked to the OBC, the shift in the OBC-determined attitude is minimized. FDF also calibrated the inertial reference unit (IRU), which consists of three dual-axis gyroscopes. The observed gyro bias matched the bias that was solved for by the OBC. This bias drifted during the first 6 days after release. The results of the FDF calibration of scale factor and alignment shifts showed changes that were of the same order as their uncertainties.

Davis, W. S.; Eudell, A. H.; Kulp, L. S.; Lindrose, L. A.; Harman, R. R.

1993-02-01

349

Gamma-ray burst spectra and spectral correlations from sub-photospheric Comptonization  

E-print Network

One of the most important unresolved issues in gamma-ray burst physics is the origin of the prompt gamma-ray spectrum. Its general non-thermal character and the softness in the X-ray band remain unexplained. We tackle these issues by performing Monte Carlo simulations of radiation-matter interactions in a scattering dominated photon-lepton plasma. The plasma -- initially in equilibrium -- is driven to non-equilibrium conditions by a sudden energy injection in the lepton population, mimicking the effect of a shock wave or the dissipation of magnetic energy. Equilibrium restoration occurs due to energy exchange between the photons and leptons. While the initial and final equilibrium spectra are thermal, the transitional photon spectra are characterized by non-thermal features such as power-law tails, high energy bumps, and multiple components. Such non-thermal features are observed at infinity if the dissipation occurs at small to moderate optical depths, and the spectrum is released before thermalization is co...

Chhotray, Atul

2015-01-01

350

Virtual Compton scattering and neutral pion electroproduction in the resonance region up to the deep inelastic region at backward angles  

SciTech Connect

We have made the first measurements of the virtual Compton scattering (VCS) process via the H(e,e'p)? exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the W-dependence at fixed Q2=1 GeV2, and for the Q2-dependence at fixed W near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed Q2-dependence is smooth. The measured ratio of H(e,e'p)? to H(e,e'p)?0 cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to Real Compton Scattering (RCS) at high energy and large angles, our VCS data at the highest W (1.8-1.9 GeV) show a striking Q2-independence, which may suggest a transition to a perturbative scattering mechanism at the quark level.

Laveissiere, Geraud; Degrande, Natalie; Jaminion, Stephanie; Jutier, Christophe; Todor, Luminita; Di Salvo, Rachele; Van Hoorebeke, L.; Alexa, L.C.; Anderson, Brian; Aniol, Konrad; Arundell, Kathleen; Audit, Gerard; Auerbach, Leonard; Baker, F.; Baylac, Maud; Berthot, J.; Bertin, Pierre; Bertozzi, William; Bimbot, Louis; Boeglin, Werner; Brash, Edward; Breton, Vincent; Breuer, Herbert; Burtin, Etienne; Calarco, John; Cardman, Lawrence; Cavata, Christian; Chang, C.; Chang, C.C.; Chang, C.; Chang, C.C.; Chang, C.; Chang, C.C.; Chang, C.; Chang, C.C.; Chen, Jian-Ping; Chudakov, Eugene; Cisbani, Evaristo; Dale, Daniel; De Jager, Cornelis; De Leo, Raffaele; Deur, Alexandre; D'Hose, Nicole; Dodge, Gail; Domingo, John; Elouadrhiri, Latifa; Epstein, Martin; Ewell, Lars; Finn, John; Fissum, Kevin; Fonvieille, Helene; Fournier, Guy; Frois, Bernard; Frullani, Salvatore; Furget, Christophe; Gao, Haiyan; Gao, Juncai; Garibaldi, Franco; Gasparian, Ashot; Gilad, Shalev; Gilman, Ronald; Glamazdin, Oleksandr; Glashausser, Charles; Gomez, Javier; Gorbenko, Viktor; Grenier, Philippe; Guichon, Pierre; Hansen, Jens-Ole; Holmes, Richard; Holtrop, Maurik; Howell, Calvin; Huber, Garth; Hyde, Charles; Incerti, Sebastien; Iodice, Mauro; Jardillier, Johann; Jones, Mark; Kahl, William; Kamalov, Sabit; Kato, Seigo; Katramatou, A.T.; Kelly, James; Kerhoas, Sophie; Ketikyan, Armen; Khayat, Mohammad; Kino, Kouichi; Kox, Serge; Kramer, Laird; Kumar, Krishna; Kumbartzki, Gerfried; Kuss, Michael; Leone, Antonio; LeRose, John; Liang, Meihua; Lindgren, Richard; Liyanage, Nilanga; Lolos, George; Lourie, Robert; Madey, Richard; Maeda, Kazushige; Malov, Sergey; Manley, D.; Marchand, Claude; Marchand, Dominique; Margaziotis, Demetrius; Markowitz, Pete; Marroncle, Jacques; Martino, Jacques; McCormick, Kathy; McIntyre, Justin; Mehrabyan, Surik; Merchez, Fernand; Meziani, Zein-Eddine; Michaels, Robert; Miller, Gerald; Mougey, Jean; Nanda, Sirish; Neyret, Damien; Offermann, Edmond; Papandreou, Zisis; Perdrisat, Charles; Perrino, R.; Petratos, Gerassimos; Platchkov, Stephane; Pomatsalyuk, Roman; Prout, David; Punjabi, Vina; Pussieux, Thierry; Quemener, Gilles; Ransome, Ronald; Ravel, Oliver; Real, Jean-Sebastien; Renard, F.; Roblin, Yves; Rowntree, David; Rutledge, Gary; Rutt, Paul; Saha, Arunava; Saito, Teijiro; Sarty, Adam; Serdarevic, A.; Smith, T.; Smirnov, G.; Soldi, K.; Sorokin, Pavel; Souder, Paul; Suleiman, Riad; Templon, Jeffrey; Terasawa, Tatsuo; Tiator, Lothar; Tieulent, Raphael; Tomasi-Gustaffson, E.; Tsubota, Hiroaki; Ueno, Hiroaki; Ulmer, Paul; Urciuoli, Guido; Van De Vyver, R.; van der Meer, Rob; Vernin, Pascal; Vlahovic, B.; Voskanyan, Hakob; Voutier, Eric; Watson, J.W.; Weinstein, Lawrence; Wijesooriya, Krishni; Wilson, R.; Wojtsekhowski, Bogdan; Zainea, Dan; Zhang, Wei-Ming; Zhao, Jie; Zhou, Z.-L.

2009-01-01

351

New Measurement of Compton Scattering from the Deuteron and an Improved Extraction of the Neutron Electromagnetic Polarizabilities  

E-print Network

The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data --- and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world dataset. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using Chiral Effective Field Theory with dynamical \\Delta(1232) degrees of freedom shows the data are consistent with and within the world dataset. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities and combining them with a recent result for the proton, we obtain the neutron polarizabilities as \\alpha_n = [11.55 +/- 1.25(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 and \\beta_n = [3.65 -/+ 1.25(stat) +/- 0.2(BSR) -/+ 0.8(th)] X 10^{-4} fm3, with \\chi^2 = 45.2 for 44 degrees of freedom.

L. S. Myers; J. R. M. Annand; J. Brudvik; G. Feldman; K. G. Fissum; H. W. Grießhammer; K. Hansen; S. S. Henshaw; L. Isaksson; R. Jebali; M. A. Kovash; M. Lundin; J. A. McGovern; D. G. Middleton; A. M. Nathan; D. R. Phillips; B. Schröder; S. C. Stave

2014-11-13

352

Nuclear-mass dependence of azimuthal beam-helicity and beam-charge asymmetries in deeply virtual Compton scattering  

NASA Astrophysics Data System (ADS)

The nuclear-mass dependence of azimuthal cross-section asymmetries with respect to charge and longitudinal polarization of the lepton beam is studied for hard exclusive electroproduction of real photons. The observed beam-charge and beam-helicity asymmetries are attributed to the interference between the Bethe-Heitler and the deeply virtual Compton scattering processes. For various nuclei, the asymmetries are extracted for both coherent and incoherent-enriched regions, which involve different (combinations of) generalized parton distributions. For both regions, the asymmetries are compared to those for a free proton, and no nuclear-mass dependence is found.

Airapetian, A.; Akopov, N.; Akopov, Z.; Amarian, M.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetisyan, E.; Ball, B.; Belostotski, S.; Bianchi, N.; Blok, H. P.; Böttcher, H.; Borissov, A.; Bowles, J.; Bryzgalov, V.; Burns, J.; Capiluppi, M.; Capitani, G. P.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; Leo, R. De; Nardo, L. De; Sanctis, E. De; Diefenthaler, M.; Nezza, P. Di; Düren, M.; Ehrenfried, M.; Elbakian, G.; Ellinghaus, F.; Fabbri, R.; Fantoni, A.; Felawka, L.; Frullani, S.; Gabbert, D.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Giordano, F.; Gliske, S.; Guler, H.; Guzey, V.; Haan, S.; Hadjidakis, C.; Hartig, M.; Hasch, D.; Hill, G.; Hillenbrand, A.; Hoek, M.; Holler, Y.; Hristova, I.; Imazu, Y.; Ivanilov, A.; Jackson, H. E.; Jo, H. S.; Joosten, S.; Kaiser, R.; Karyan, G.; Keri, T.; Kinney, E.; Kisselev, A.; Korotkov, V.; Kozlov, V.; Kravchenko, P.; Lagamba, L.; Lamb, R.; Lapikás, L.; Lehmann, I.; Lenisa, P.; López Ruiz, A.; Lorenzon, W.; Lu, X.-G.; Lu, X.-R.; Ma, B.-Q.; Mahon, D.; Makins, N. C. R.; Manaenkov, S. I.; Manfré, L.; Mao, Y.; Marianski, B.; de La Ossa, A. Martinez; Marukyan, H.; Miller, C. A.; Miyachi, Y.; Movsisyan, A.; Muccifora, V.; Murray, M.; Mussgiller, A.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaev, M.; Nowak, W.-D.; Pappalardo, L. L.; Perez-Benito, R.; Raithel, M.; Reimer, P. E.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Rubin, J.; Ryckbosch, D.; Salomatin, Y.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Shanidze, R.; Shibata, T.-A.; Shutov, V.; Stancari, M.; Statera, M.; Steffens, E.; Steijger, J. J. M.; Stewart, J.; Stinzing, F.; Taroian, S.; Terkulov, A.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; Haarlem, Y. Van; Hulse, C. Van; Varanda, M.; Veretennikov, D.; Vikhrov, V.; Vilardi, I.; Wang, S.; Yaschenko, S.; Ye, H.; Ye, Z.; Yu, W.; Zeiler, D.; Zihlmann, B.; Zupranski, P.; sHERMES Collaboration

2010-03-01

353

Beam spin asymmetries in deeply virtual Compton scattering (DVCS) with CLAS at 4.8 GeV  

Microsoft Academic Search

We report measurements of the beam spin asymmetry in deeply virtual Compton scattering (DVCS) at an electron beam energy of 4.8 GeV using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The DVCS beam spin asymmetry has been measured in a wide range of kinematics, 1.0p-->e'pX. The number of

G. Gavalian; V. D. Burkert; L. Elouadrhiri; M. Holtrop; S. Stepanyan; D. Abrahamyan; G. Adams; M. J. Amaryan; P. Ambrozewicz; M. Anghinolfi; B. Asavapibhop; G. Asryan; H. Avakian; H. Bagdasaryan; N. Baillie; J. P. Ball; N. A. Baltzell; S. Barrow; V. Batourine; M. Battaglieri; K. Beard; I. Bedlinskiy; M. Bektasoglu; M. Bellis; N. Benmouna; B. L. Berman; A. S. Biselli; B. E. Bonner; S. Bouchigny; S. Boiarinov; R. Bradford; D. Branford; W. J. Briscoe; W. K. Brooks; S. Bültmann; C. Butuceanu; J. R. Calarco; S. L. Careccia; D. S. Carman; B. Carnahan; S. Chen; P. L. Cole; A. Coleman; P. Collins; P. Coltharp; D. Cords; P. Corvisiero; D. Crabb; H. Crannell; V. Crede; J. P. Cummings; N. Dashyan; R. de Masi; R. de Vita; E. de Sanctis; P. V. Degtyarenko; H. Denizli; L. Dennis; A. Deur; K. V. Dharmawardane; K. S. Dhuga; R. Dickson; C. Djalali; G. E. Dodge; J. Donnelly; D. Doughty; P. Dragovitsch; M. Dugger; S. Dytman; O. P. Dzyubak; H. Egiyan; K. S. Egiyan; L. El Fassi; A. Empl; P. Eugenio; R. Fatemi; G. Fedotov; G. Feldman; R. J. Feuerbach; T. A. Forest; H. Funsten; M. Garçon; G. P. Gilfoyle; K. L. Giovanetti; F. X. Girod; J. T. Goetz; E. Golovatch; A. Gonenc; R. W. Gothe; K. A. Griffioen; M. Guidal; M. Guillo; N. Guler; L. Guo; V. Gyurjyan; C. Hadjidakis; K. Hafidi; H. Hakobyan; R. S. Hakobyan; J. Hardie; N. Hassall; D. Heddle; F. W. Hersman; K. Hicks; I. Hleiqawi; J. Hu; M. Huertas; C. E. Hyde; Y. Ilieva; D. G. Ireland; B. S. Ishkhanov; E. L. Isupov; M. M. Ito; D. Jenkins; H. S. Jo; K. Joo; H. G. Juengst; N. Kalantarians; J. D. Kellie; M. Khandaker; K. Y. Kim; W. Kim; A. Klein; F. J. Klein; M. Klusman; M. Kossov; L. H. Kramer; V. Kubarovsky; J. Kuhn; S. E. Kuhn; S. V. Kuleshov; M. Kuznetsov; J. Lachniet; J. M. Laget; J. Langheinrich; D. Lawrence; A. C. S. Lima; K. Livingston; H. Y. Lu; K. Lukashin; M. MacCormick; J. J. Manak; N. Markov; S. McAleer; B. McKinnon; J. W. C. McNabb; B. A. Mecking; M. D. Mestayer; C. A. Meyer; T. Mibe; K. Mikhailov; R. Minehart; M. Mirazita; R. Miskimen; V. Mokeev; K. Moriya; S. A. Morrow; M. Moteabbed; J. Mueller; G. S. Mutchler; P. Nadel-Turonski; J. Napolitano; R. Nasseripour; S. Niccolai; G. Niculescu; I. Niculescu; B. B. Niczyporuk; M. R. Niroula; R. A. Niyazov; M. Nozar; G. V. O'Rielly; M. Osipenko; A. I. Ostrovidov; E. Pasyuk; C. Paterson; S. A. Philips; J. Pierce; N. Pivnyuk; D. Pocanic; O. Pogorelko; E. Polli; I. Popa; S. Pozdniakov; B. M. Preedom; J. W. Price; Y. Prok; D. Protopopescu; L. M. Qin; B. A. Raue; G. Riccardi; G. Ricco; M. Ripani; B. G. Ritchie; F. Ronchetti; G. Rosner; P. Rossi; D. Rowntree; P. D. Rubin; F. Sabatié; J. Salamanca; C. Salgado; J. P. Santoro; V. Sapunenko; R. A. Schumacher; V. S. Serov; Y. G. Sharabian; J. Shaw; N. V. Shvedunov; A. V. Skabelin; E. S. Smith; L. C. Smith; D. I. Sober; D. Sokhan; A. Stavinsky; B. E. Stokes; P. Stoler; I. I. Strakovsky; S. Strauch; R. Suleiman; M. Taiuti; S. Taylor; D. J. Tedeschi; U. Thoma; R. Thompson; A. Tkabladze; S. Tkachenko; C. Tur; M. Ungaro; M. F. Vineyard; A. V. Vlassov; D. P. Watts; L. B. Weinstein; D. P. Weygand; M. Williams; E. Wolin; M. H. Wood; A. Yegneswaran; J. Yun; M. Yurov; L. Zana; J. Zhang; B. Zhao; Z. W. Zhao

2009-01-01

354

Nuclear-mass dependence of azimuthal beam-helicity and beam-charge asymmetries in deeply virtual Compton scattering  

E-print Network

The nuclear-mass dependence of azimuthal cross section asymmetries with respect to charge and longitudinal polarization of the lepton beam is studiedfor hard exclusive electroproduction of real photons. The observed beam-charge and beam-helicity asymmetries are attributed to the interference between the Bethe-Heitler and deeply virtual Compton scattering processes. For various nuclei, the asymmetries are extracted for both coherent and incoherent-enriched regions, which involve different (combinations of) generalized parton distributions. For both regions, the asymmetries are compared to those for a free proton, and no nuclear-mass dependence is found.

The HERMES collaboration; A. Airapetian

2010-01-22

355

Next-to-next-to leading order corrections to deeply virtual Compton scattering: the non-singlet case  

E-print Network

We study perturbative QCD corrections to deeply virtual Compton scattering on an unpolarized nucleon target in the flavor non-singlet sector to next-to-next-to-leading order accuracy, restricting ourselves to the kinematically dominant amplitude. The difference between the standard minimal subtraction and the conformal scheme, in which conformal symmetry is manifest, is studied to next-to-leading order. Beyond this order we employ conformal symmetry for the evaluation of perturbative corrections. Within a certain class of generalized parton distributions we find moderate radiative corrections.

Dieter Müller

2006-01-16

356

Phantom study of fusion image of CT and SPECT with body-contour generated from external Compton scatter sources  

Microsoft Academic Search

Purpose  A phantom study was conducted to evaluate the feasibility of body contour definition with Compton scatter photons from extemal\\u000a sources of technetium-99m pertechnetate (Tc-99m) to create a fusion image of CT and SPECT images.\\u000a \\u000a \\u000a \\u000a Methods  External sources of 1 mCi (37 MBq) Tc-99m were placed on each collimator, and bodycontour SPECT images were obtained with\\u000a an energy window of 100 keV±25%

Kazuyoshi Suga; Naofumi Matsunaga; Yasuhiko Kawakami; Mataichi Furukawa

2000-01-01

357

Gamma ray imaging of the Crab and Vale regions with the UCR double-Compton telescope  

NASA Astrophysics Data System (ADS)

Results are presented for a new imaging technique applied to the reconstruction of celestial gamma-ray source images. This algorithm uses an expectation maximization maximum likelihood method (EMML) and is applied to the UCR double Compton telescope. First, this technique is used with simulated data and preflight calibration data. It is then applied to the Crab pulsar/Nebula, and Vela regions. These data were collected in 1988 from Alice Springs, Australia and in 1989 from Fort Summer, NM. An excess of 1200 counts from the Crab has been detected at 4 sigma in the energy range 1-30 MeV, 920 counts at 3.1 sigma in the energy range1-5 MeV and 202 counts at 7 sigma in the energy range 5-10 MeV. The total measured flux from 1-30 MeV is (2.0 +/- 0.5) x 10-3 photons/(sq cm.s). Pulsar analysis was also performed. The pulsed flux in the energy range 1-30 MeV is equal to (1.4 plus or minus 0.4) x 10-4 photons/(sq cm.s) Only upper limits for the pulsed flux have been placed in the individual energy ranges of 5-10 MeV and 10-30 MeV. Our results are compared with other experiments. The Vela region image shows an excess of 575 counts in the energy range 1.1-30 MeV at 2.7 sigma 340 counts at 2.4 sigma in the energy range 1.1-5 MeV and 130 counts from 5 to 10 MeV at 2.2 sigma. No excess is seen above 10 MeV.The total flux for the energy range 1.1 to 30 MeV is equal to (1.0 plus or minus 0.4) x 10-3 photons/(sq cm.s). The Vela pulsed flux in the energy range 1.1 to 30 MeV is equal to (3.5 +/- 1.4) x 10-4 photons/( sq cm.s). The ratio is pulsed flux to total flux in the energy range 1.3-30 MeV, is found to be equal to 0.35 plus or minus 0.2.

Sarmouk, Abderrezak

358

Compton scattering in jets: A mechanism for approximately 0.4 and less than or approximately 0.2 MeV line production  

NASA Technical Reports Server (NTRS)

We show that gamma-ray line emission at approximately 0.4 and less than or approximately 0.2 MeV can be produced by Compton scattering of beamed radiation in the jets of Galactic black hole candidates. This mechanism has the novel feature of not invoking the presence of e(exp +)-e(exp -) pairs. To produce the two lines, we employ a symmetric double-sided jet with bulk flow velocity of about 0.5c and incident beam radiation with a hard energy spectrum. We show that the two lines can be seen at viewing-angle cosines relative to the jet ranging from 0.2 to 0.6. This comprises 40% of the total solid angle. In addition, the line radiation is approximately 10% polarized. Depending on the bulk flow and viewing angle, the model can produce lines at other energies as well. In particular, a broad feature near 1 MeV can be seen by viewing the jet close to its axis. Our model can also accommodate single-line spectra if the beamed gamma-ray emission or the jets themselves are asymmetric.

Skibo, J. G.; Dermer, C. D.; Ramaty, R.

1994-01-01

359

Compton Recoil Electron Tracking With the TIGRE Gamma-Ray Balloon Experiment  

E-print Network

photons and as a critical low energy gamma-ray shield.anticoincidence shield. An incoming gamma-ray undergoes theshield is important at energies below 1 MeV where directional discrimination of the gamma-rays

Kamiya, Kaoru

2011-01-01

360

THE {gamma}-RAY SPECTRUM OF GEMINGA AND THE INVERSE COMPTON MODEL OF PULSAR HIGH-ENERGY EMISSION  

SciTech Connect

We reanalyze the Fermi spectra of the Geminga and Vela pulsars. We find that the spectrum of Geminga above the break is well approximated by a simple power law without the exponential cutoff, making Geminga's spectrum similar to that of Crab. Vela's broadband {gamma}-ray spectrum is equally well fit with both the exponential cutoff and the double power-law shapes. In the broadband double power-law fits, for a typical Fermi spectrum of a bright {gamma}-ray pulsar, most of the errors accumulate due to the arbitrary parameterization of the spectral roll-off. In addition, a power law with an exponential cutoff gives an acceptable fit for the underlying double power-law spectrum for a very broad range of parameters, making such fitting procedures insensitive to the underlying Fermi photon spectrum. Our results have important implications for the mechanism of pulsar high-energy emission. A number of observed properties of {gamma}-ray pulsars-i.e., the broken power-law spectra without exponential cutoffs and stretching in the case of Crab beyond the maximal curvature limit, spectral breaks close to or exceeding the maximal breaks due to curvature emission, patterns of the relative intensities of the leading and trailing pulses in the Crab repeated in the X-ray and {gamma}-ray regions, presence of profile peaks at lower energies aligned with {gamma}-ray peaks-all point to the inverse Compton origin of the high-energy emission from majority of pulsars.

Lyutikov, Maxim [Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907-2036 (United States)

2012-09-20

361

Gamma-ray Burst Spectra and Spectral Correlations from Sub-photospheric Comptonization  

NASA Astrophysics Data System (ADS)

One of the most important unresolved issues in gamma-ray burst (GRB) physics is the origin of the prompt gamma-ray spectrum. Its general non-thermal character and the softness in the X-ray band remain unexplained. We tackle these issues by performing Monte Carlo simulations of radiation–matter interactions in a scattering dominated photon–lepton plasma. The plasma—initially in equilibrium—is driven to non-equilibrium conditions by a sudden energy injection in the lepton population, mimicking the effect of a shock wave or the dissipation of magnetic energy. Equilibrium restoration occurs due to an energy exchange between the photons and leptons. While the initial and final equilibrium spectra are thermal, the transitional photon spectra are characterized by non-thermal features such as power-law tails, high energy bumps, and multiple components. Such non-thermal features are observed at infinity if the dissipation occurs at small to moderate optical depths, and the spectrum is released before thermalization is complete. We model the synthetic spectra with a Band function and show that the resulting spectral parameters are similar to observations for a frequency range of 2–3 orders of magnitude around the peak. In addition, our model predicts correlations between the low-frequency photon index and the peak frequency as well as between the low- and high-frequency indices. We explore baryon and pair-dominated fireballs and reach the conclusion that baryonic fireballs are a better model for explaining the observed features of GRB spectra.

Chhotray, Atul; Lazzati, Davide

2015-04-01

362

Electron density of Rhizophora spp. wood using Compton scattering technique at 15.77, 17.48 and 22.16 keV XRF energies  

NASA Astrophysics Data System (ADS)

Compton (incoherently) scattered photons which are directly proportional to the electron density of the scatterer, have been employed in characterizing Rhizophora spp. as breast tissue equivalent. X-ray fluorescent scattered incoherently from Rhizophora spp. sample was measured using Si-PIN detector and three XRF energy values 15.77, 17.48 and 22.16 keV. This study is aimed at providing electron density information in support of the introduction of new tissue substitute materials for mammography phantoms.

Shakhreet, B. Z.; Bauk, S.; Shukri, A.

2015-02-01

363

Determination of the mass attenuation coefficients for X-ray fluorescence measurements correction by the Rayleigh to Compton scattering ratio  

NASA Astrophysics Data System (ADS)

X-ray fluorescence technique plays an important role in nondestructive analysis nowadays. The development of equipment, including portable ones, enables a wide assortment of possibilities for analysis of stable elements, even in trace concentrations. Nevertheless, despite of the advantages, one important drawback is radiation self-attenuation in the sample being measured, which needs to be considered in the calculation for the proper determination of elemental concentration. The mass attenuation coefficient can be determined by transmission measurement, but, in this case, the sample must be in slab shape geometry and demands two different setups and measurements. The Rayleigh to Compton scattering ratio, determined from the X-ray fluorescence spectrum, provides a link to the mass attenuation coefficient by means of a polynomial type equation. This work presents a way to construct a Rayleigh to Compton scattering ratio versus mass attenuation coefficient curve by using the MCNP5 Monte Carlo computer code. The comparison between the calculated and literature values of the mass attenuation coefficient for some known samples showed to be within 15%. This calculation procedure is available on-line at www.macx.net.br.

Conti, C. C.; Anjos, M. J.; Salgado, C. M.

2014-09-01

364

High Power Experiment of X-Band Thermionic Cathode RF Gun for Compton Scattering X-ray Source  

SciTech Connect

We are currently developing a compact monochromatic X-ray source based on laser-electron collision. To realize remarkably compact-, high-intensity- and highly-stable-system, we adopt an X-band multi-bunch liner accelerator (linac) and reliable Q-switch laser. The X-ray yields by the multi-bunch electron beam and Q-switch Nd: YAG laser of 1.4 J/10 ns (FWHM) (532 nm, second harmonic) is 107 photons/RF-pulse (108 photons/sec for 10 Hz operation). The injector of the system consists of a 3.5-cell X-band thermionic cathode RF gun and an alpha magnet. So far we have achieved beam generation from the X-band thermionic cathode RF gun. The peak beam energy is 2 MeV. This experimental high energy ({approx}2 MeV) beam generation from the X-band thermionic cathode RF gun is the first in the world. In this paper, we describe the system of the Compton scattering X-ray source based on the X-band linac, experimental results of X-band thermionic cathode RF gun and the details of the experimental setup for Compton scattering X-ray generation that are under construction.

Sakamoto, Fumito; Uesaka, Mitsuru; Dobashi, Katsuhiro; Yamamoto, Tomohiko; Meng, De [Nuclear Professional School, the University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188 (Japan); Urakawa, Junji; Higo, Toshiyasu; Akemoto, Mitsuo [High Energy Accelerator Research Organization, 1-1, Oho, Tsukuba, Ibaraki 305-0801 (Japan); Matsuo, Kenichi; Sakae, Hisaharu [Ishikawajima-harima Heavy Industries Co., Ltd., 1 Shin-Nakahara, Isogo, Yokohama, Kanagawa 235-8501 (Japan); Yamamoto, Masashi [Akita National College of Technology, 1-1 Iijima-Bunkyo, Akita, Akita 011-8511 (Japan)

2006-11-27

365

Optimization of a multiple-scattering Compton camera as a photon-tracking imager for 6-MV photon therapy  

NASA Astrophysics Data System (ADS)

During radiation therapy, the irradiated position and the energy deposited in a patient must be monitored. In general, calculations before photon exposure or 2D measurements of the transmitted photons have been widely used for making dose estimates. In this paper, we propose a real-time 3D dose measurement using Compton imaging technology. On the basis of the Monte-Carlo method, we designed a multiple-scattering Compton camera system (MSCC) with semiconductor and scintillation detectors. The MSCC was constructed with two semiconductor detectors as scattering detectors and a cadmium-tungstate (CWO) scintillator detector as an absorber detector. The two planar semiconductor arrays, and the CWO array consisted of 40 × 40 pixels, each with a size of 1 × 1 × ? mm3, where ? is the variable thickness of the detectors. The design parameters, such as the types of semiconductors, detector thicknesses and distances between detectors, were optimized on the basis of the detection efficiency and angular resolution of reconstructed images for a point source. Under the optimized conditions, uncertainty factors in geometry and energy were estimated for various inter-detector distances. We used a source corresponding to photons scattered from a water phantom exposed to 6-MeV peak X-rays. According to our simulation results, the figure of merit, reached its maximum value when the inter-detector distance was 3 cm. In order to achieve a high FOM, we chose 1 cm as the optimum thickness for the scattering and absorbed detectors. A cadmium-zinc-telluride (CZT) detector showed the best performance among the simulated semiconductors. The position uncertainty caused by the pixelization effect was the major factor in degrading the angular resolution of the reconstructed images, and the degradation caused by energy broadening was less than expected. The angular uncertainties caused by Doppler broadening and incorrect sequencing were minimal compared with that of pixelization. Our simulation showed the feasibility of using the semiconductor-based Compton camera to monitor the exposed dose in 3D radiation therapy.

Lee, Taewoong; Yoon, Changyeon; Lee, Wonho

2014-06-01

366

Measurement of Deeply Virtual Compton Scattering (DVCS) cross sections with CLAS  

SciTech Connect

Extraction of DVCS unpolarized and polarized cross sections in the largest kinematic domain ever explored in the valence region. Results are in good agreement with GPD model (VGG) predictions. Extraction of Compton Form Factors (M. Guidal) by fitting simultaneously these unpolarizedand polarized cross sections gives a large set of results in a very large kinematic domain for Re(H ) and Im(H ). Analysis of the data from the second part of the e1-DVCS experiment underway.

Hyon-Suk Jo

2012-04-01

367

Electronic properties of RDX and HMX: Compton scattering experiment and first-principles calculation.  

PubMed

The first-ever electron momentum density (EMD) measurements of explosive materials, namely, RDX (1,3,5-trinitro-1,3,5-triazacyclohexane, (CH2-N-NO2)3) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane, (CH2-N-NO2)4), have been reported using a 740 GBq (137)Cs Compton spectrometer. Experimental Compton profiles (CPs) are compared with the EMDs derived from linear combination of atomic orbitals with density functional theory. It is found that the CPs deduced from generalized gradient approximation (GGA) with Wu-Cohen exchange energies give a better agreement with the corresponding experimental profiles than those from local density approximation and other schemes of GGA. Further, Mulliken population, energy bands, partial and total density of states, and band gap have also been reported using GGA calculations. Present ground state calculations unambiguously show large band gap semiconductor nature of both RDX and HMX. A similar type of bonding in these materials is uniquely established using Compton data and density of states. It is also outstandingly consistent with the Mulliken population, which predicts almost equal amount of charge transfer (0.84 and 0.83 e(-)) from H1 + H2 + N2 to C1 + N1 + O1 + O2 in both the explosives. PMID:23763382

Ahuja, B L; Jain, Pradeep; Sahariya, Jagrati; Heda, N L; Soni, Pramod

2013-07-11

368

Intercomparison of gamma scattering, gammatography, and radiography techniques for mild steel nonuniform corrosion detection  

Microsoft Academic Search

This paper focuses on the mild steel (MS) corrosion detection and intercomparison of results obtained by gamma scattering, gammatography, and radiography techniques. The gamma scattering non-destructive evaluation (NDE) method utilizes scattered gamma radiation for the detection of corrosion, and the scattering experimental setup is an indigenously designed automated personal computer (PC) controlled scanning system consisting of computerized numerical control (CNC)

P. Priyada; M. Margret; R. Ramar; Shivaramu; M. Menaka; L. Thilagam; B. Venkataraman; Baldev Raj; Tamil Nadu

2011-01-01

369

Single and double spin asymmetries for deeply virtual Compton scattering measured with CLAS and a longitudinally polarized proton target  

E-print Network

Single-beam, single-target, and double-spin asymmetries for hard exclusive photon production on the proton $\\vec{e}\\vec{p} \\to e' p'\\gamma$ are presented. The data were taken at Jefferson Lab using the CLAS detector and a longitudinally polarized ${}^{14}$NH$_3$ target. The three asymmetries were measured in 165 4-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. The kinematic dependences of the obtained asymmetries are discussed and compared to the predictions of models of Generalized Parton Distributions. The measurement of three DVCS spin observables at the same kinematic points allows a quasi-model-independent extraction of the imaginary parts of the $H$ and $\\tilde{H}$ Compton Form Factors, which give insight into the electric and axial charge distributions of valence quarks in the proton.

S. Pisano; A. Biselli; S. Niccolai; E. Seder; M. Guidal; M. Mirazita; the CLAS Collaboration

2015-01-28

370

Single and double spin asymmetries for deeply virtual Compton scattering measured with CLAS and a longitudinally polarized proton target  

E-print Network

Single-beam, single-target, and double-spin asymmetries for hard exclusive photon production on the proton $\\vec{e}\\vec{p} \\to e' p'\\gamma$ are presented. The data were taken at Jefferson Lab using the CLAS detector and a longitudinally polarized ${}^{14}$NH$_3$ target. The three asymmetries were measured in 165 4-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. The kinematic dependences of the obtained asymmetries are discussed and compared to the predictions of models of Generalized Parton Distributions. The measurement of three DVCS spin observables at the same kinematic points allows a quasi-model-independent extraction of the imaginary parts of the $H$ and $\\tilde{H}$ Compton Form Factors, which give insight into the electric and axial charge distributions of valence quarks in the proton.

Pisano, S; Niccolai, S; Seder, E; Guidal, M; Mirazita, M

2015-01-01

371

IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL.47, NO. 1,JUNE 2000 RRC Effects of Mechanical Alignment Errors on Compton Scatter Imaging  

E-print Network

IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL.47, NO. 1,JUNE 2000 RRC Effects of Mechanical Alignment Errors on Compton Scatter Imaging Y.F. Du', Z. He, G.F. Knoll, D. K. Wehe Departmcnt of Nuclear detectors is iindcrway in our laboratory. As a practical problem, the mechanical alignmcnt error may

He, Zhong

372

Advances on Ultrafast Silicon Field Emitter Array Photocathodes for Coherent Radiation Sources Based on Inverse Compton Scattering  

NASA Astrophysics Data System (ADS)

Low-cost, compact, and coherent X-rays sources would enable exciting applications such as biomedical imaging of soft tissue and real-time visualisation of molecules at a widespread scale. A promising approach to implement such an X-ray source is based on inverse Compton scattering of a series of nanostructured electron sheets accelerated to relativistic speeds. Photon-triggered field emission arrays can readily produce planar arrays of electron bunches with pC-level sheet charge at high repetition rates using intense laser pulses. In this article, the performance of single-crystal, ultrafast, photon-actuated silicon field emitter arrays is investigated for varying emitter height. Charge vs. incident photon pulse energy characteristics and quantum efficiency of the devices are reported.

Dong, C.; Swanwick, M.; Keathley, P. D.; Kärtner, F. X.; Velásquez-García, L. F.

2014-11-01

373

Diagnostics for the optimization of an 11 keV inverse Compton scattering x-ray source  

SciTech Connect

In a scope of a collaboration between Thales Communications and Security and CEA DAM DIF, 11 keV Xrays were produced by inverse Compton scattering on the ELSA facility. In this type of experiment, X-ray observation lies in the use of accurate electron and laser beam interaction diagnostics and on fitted X-ray detectors. The low interaction probability between < 100 {mu}m width, 12 ps [rms] length electron and photon pulses requires careful optimization of pulse spatial and temporal covering. Another issue was to observe 11 keV X-rays in the ambient radioactive noise of the linear accelerator. For that, we use a very sensitive detection scheme based on radio luminescent screens.

Chauchat, A.-S.; Brasile, J.-P [Thales Communications and Security, 4 avenue des Louvresses 92230 Gennevilliers (France); Le Flanchec, V.; Negre, J.-P.; Binet, A. [CEA DAM DIF, Bruyeres-le-Chatel 91290 Arpajon (France); Ortega, J.-M. [LCP Universite Paris-Sud, Bat. 201, 91405 Orsay (France)

2013-04-19

374

Extracting the Redox Orbitals in Li Battery Materials with High-Resolution X-Ray Compton Scattering Spectroscopy  

NASA Astrophysics Data System (ADS)

We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel LixMn2O4 , a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen 2 p orbital. Moreover, the manganese 3 d states are shown to experience spatial delocalization involving 0.16 ±0.05 electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery.

Suzuki, K.; Barbiellini, B.; Orikasa, Y.; Go, N.; Sakurai, H.; Kaprzyk, S.; Itou, M.; Yamamoto, K.; Uchimoto, Y.; Wang, Yung Jui; Hafiz, H.; Bansil, A.; Sakurai, Y.

2015-02-01

375

Microscopic magnetic properties of an oxygen-doped Tb-Fe thin film by magnetic Compton scattering  

SciTech Connect

The magnetic Compton scattering of a Tb{sub 32}Fe{sub 55}O{sub 13} film was measured in order to investigate the microscopic magnetization processes (i.e., the spin moment, orbital moment, and element specific moments). The trend of the spin magnetic moment was the same as that of the total magnetic moment but opposite to the orbital magnetic moment. In the low magnetic field region, the magnetic moments were not perfectly aligned perpendicular to the film surface, and the perpendicular components were found to mainly arise from the magnetic moment of Tb. Oxygen atoms hinder long range magnetic interaction and hence also affect the magnetization process of the magnetic moments of Tb and Fe.

Agui, Akane, E-mail: agui@spring8.or.jp [Quantum Beam Science Directorate, Japan Atomic Energy Agency, SPring-8, Sayo, Hyogo 679-5148 (Japan); Unno, Tomoya; Matsumoto, Sayaka; Suzuki, Kousuke; Sakurai, Hiroshi [Department of Production Science and Technology, Gunma University, Ota, Gunma 373-0057 (Japan); Koizumi, Akihisa [Graduate School of Material Science, University of Hyogo, Kamigori, Hyogo 678-1297 (Japan)

2013-11-14

376

Microscopic magnetic properties of an oxygen-doped Tb-Fe thin film by magnetic Compton scattering  

NASA Astrophysics Data System (ADS)

The magnetic Compton scattering of a Tb32Fe55O13 film was measured in order to investigate the microscopic magnetization processes (i.e., the spin moment, orbital moment, and element specific moments). The trend of the spin magnetic moment was the same as that of the total magnetic moment but opposite to the orbital magnetic moment. In the low magnetic field region, the magnetic moments were not perfectly aligned perpendicular to the film surface, and the perpendicular components were found to mainly arise from the magnetic moment of Tb. Oxygen atoms hinder long range magnetic interaction and hence also affect the magnetization process of the magnetic moments of Tb and Fe.

Agui, Akane; Unno, Tomoya; Matsumoto, Sayaka; Suzuki, Kousuke; Koizumi, Akihisa; Sakurai, Hiroshi

2013-11-01

377

Electron-tracking Compton gamma-ray camera for small animal and phantom imaging  

NASA Astrophysics Data System (ADS)

We have developed an electron-tracking Compton camera (ETCC) for medical use. Our ETCC has a wide energy dynamic range (200-1300 keV) and wide field of view (3 sr), and thus has potential for advanced medical use. To evaluate the ETCC, we imaged the head (brain) and bladder of mice that had been administered with F-18-FDG. We also imaged the head and thyroid gland of mice using double tracers of F-18-FDG and I-131 ions.

Kabuki, Shigeto; Kimura, Hiroyuki; Amano, Hiroo; Nakamoto, Yuji; Kubo, Hidetoshi; Miuchi, Kentaro; Kurosawa, Shunsuke; Takahashi, Michiaki; Kawashima, Hidekazu; Ueda, Masashi; Okada, Tomohisa; Kubo, Atsushi; Kunieda, Etuso; Nakahara, Tadaki; Kohara, Ryota; Miyazaki, Osamu; Nakazawa, Tetsuo; Shirahata, Takashi; Yamamoto, Etsuji; Ogawa, Koichi; Togashi, Kaori; Saji, Hideo; Tanimori, Toru

2010-11-01

378

Kernel-Integration Scatter Model for the Characterization of Nuclear Waste Drums by Gamma Emission Tomography  

NASA Astrophysics Data System (ADS)

The objective of this study is the determination of the distribution of the activity of radio-elements contained in radioactive waste packages by means of single photon emission computed tomography (SPECT). A three- dimensional (3D) projector simulator for a parallel hole collimator and NaI(Tl) scintillator, based on the point kernel integration method, is proposed. The model takes into account the attenuation and scatter of gamma rays. Primary scattered photons are treated by the Compton process and Klein-Nishina formula, and the multiple scattering is accounted for by means of the dose buildup factor normally used in shielding problems. An advantage of the proposed model is that it offers the possibility of generating a full two-dimensional point-spread function (PSF) that can be used for 3D reconstruction. The developed model is convenient in those situations where more exact techniques (such as Monte Carlo simulation) are not economical. The model has been evaluated for the package having homogenous density with the Cs-137 point source inside.

Marinkovic, Predrag M.; Ljubenov, Vladan Lj.

2002-09-01

379

Compact x-ray source based on burst-mode inverse Compton scattering at 100 kHz  

NASA Astrophysics Data System (ADS)

A design for a compact x-ray light source (CXLS) with flux and brilliance orders of magnitude beyond existing laboratory scale sources is presented. The source is based on inverse Compton scattering of a high brightness electron bunch on a picosecond laser pulse. The accelerator is a novel high-efficiency standing-wave linac and rf photoinjector powered by a single ultrastable rf transmitter at X-band rf frequency. The high efficiency permits operation at repetition rates up to 1 kHz, which is further boosted to 100 kHz by operating with trains of 100 bunches of 100 pC charge, each separated by 5 ns. The entire accelerator is approximately 1 meter long and produces hard x rays tunable over a wide range of photon energies. The colliding laser is a Yb ?YAG solid-state amplifier producing 1030 nm, 100 mJ pulses at the same 1 kHz repetition rate as the accelerator. The laser pulse is frequency-doubled and stored for many passes in a ringdown cavity to match the linac pulse structure. At a photon energy of 12.4 keV, the predicted x-ray flux is 5 ×1 011 photons /second in a 5% bandwidth and the brilliance is 2 ×1 012 photons /(sec mm2 mrad2 0.1 %) in pulses with rms pulse length of 490 fs. The nominal electron beam parameters are 18 MeV kinetic energy, 10 microamp average current, 0.5 microsecond macropulse length, resulting in average electron beam power of 180 W. Optimization of the x-ray output is presented along with design of the accelerator, laser, and x-ray optic components that are specific to the particular characteristics of the Compton scattered x-ray pulses.

Graves, W. S.; Bessuille, J.; Brown, P.; Carbajo, S.; Dolgashev, V.; Hong, K.-H.; Ihloff, E.; Khaykovich, B.; Lin, H.; Murari, K.; Nanni, E. A.; Resta, G.; Tantawi, S.; Zapata, L. E.; Kärtner, F. X.; Moncton, D. E.

2014-12-01

380

The Quantum Mechanics of Nano-Confined Water: New Cooperative Effects Revealed with Neutron and X-Ray Compton Scattering  

NASA Astrophysics Data System (ADS)

Neutron Compton scattering(NCS) measurements of the momentum distribution of light ions using the Vesuvio instrument at ISIS provide a sensitive local probe of the environment of those ions. NCS measurements of the proton momentum distribution in bulk water show only small deviations from the usual picture of water as a collection of molecules, with the protons covalently bonded to an oxygen and interacting weakly, primarily electrostatically, with nearby molecules. However, a series of measurements of the proton momentum distribution in carbon nanotubes, xerogel, and Nafion show that the proton delocalizes over distances of 0.2-0.3Å when water is confined on the scale of 20Å. This delocalization must be the result of changes in the Born-Oppenheimer surface for the protons, which would imply that there are large deviations in the electron distribution from that of a collection of weakly interacting molecules. This has been observed at Spring-8 using x-ray Compton scattering. The observed deviation in the valence electron momentum distribution from that of bulk water is more than an order of magnitude larger than the change observed in bulk water as the water is heated from just above melting to just below boiling. We conclude that the protons and electrons in nano-confined water are in a qualitatively different ground state from that of bulk water. Since the properties of this state persist at room temperature, and the confinement distance necessary to observe it is comparable to the distance between the elements of biological cells, this state presumably plays a role in the functioning of those cells.

Reiter, G. F.; Deb, Aniruddha

2014-12-01

381

Analysis of Data from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The final report consists of summaries of work proposed, work accomplished, papers and presentations published and continuing work regarding the cooperative agreement. The work under the agreement is based on high energy gamma ray source data analysis collected from the Energetic Gamma-Ray Experiment Telescope (EGRET).

Kniffen, Donald A.; Elliott, William W.

1999-01-01

382

High-energy gamma-ray beams from Compton-backscattered laser light  

SciTech Connect

Collisions of light photons with relativistic electrons have previously been used to produce polarized ..gamma..-ray beams with modest (-10%) resolution but relatively low intensity. In contrast, the LEGS project (Laser + Electron Gamma Source) at Brookhaven will produce a very high flux (>2 x 10/sup 7/ s/sup -1/) of background-free polarized ..gamma.. rays whose energy will be determined to a high accuracy (..delta..E = 2.3 MeV). Initially, 300(420)-MeV ..gamma.. rays will be produced by backscattering uv light from the new 2.5(3.0)-GeV X-ray storage ring of the National Synchrotron Light Source (NSLS). The LEGS facility will operate as one of many passive users of the NSLS. In a later stage of the project, a Free Electron Laser is expectred to extend the ..gamma..-ray energy up to 700 MeV.

Sandorfi, A.M.; LeVine, M.J.; Thorn, C.E.; Giordano, G.; Matone, G.

1983-01-01

383

Compton losses, Compton rockets  

NASA Technical Reports Server (NTRS)

The radiation force on a relativistic plasma is shown to accelerate the plasma to relativistic bulk velocities under certain conditions, thus demonstrating that relativistic bulk motion not only alleviates Compton losses, but can also result from such losses. In order to isolate Compton-rocket effects from hydrodynamical ones, it is assumed that the plasma in its instantaneous rest frame has a temporally constant density and is spatially uniform.

Cheng, A. Y. S.; Odell, S. L.

1981-01-01

384

Limits on Light-Speed Anisotropies from Compton Scattering of High-Energy Electrons  

SciTech Connect

The possibility of anisotropies in the speed of light relative to the limiting speed of electrons is considered. The absence of sidereal variations in the energy of Compton-edge photons at the European Synchrotron Radiation Facility's GRAAL facility constrains such anisotropies representing the first nonthreshold collision-kinematics study of Lorentz violation. When interpreted within the minimal standard-model extension, this result yields the two-sided limit of 1.6x10{sup -14} at 95% confidence level on a combination of the parity-violating photon and electron coefficients ({kappa}-tilde{sub o+}){sup YZ}, ({kappa}-tilde{sub o+}){sup ZX}, c{sub TX}, and c{sub TY}. This new constraint provides an improvement over previous bounds by 1 order of magnitude.

Bocquet, J.-P.; Lleres, A.; Perrin, C.; Rebreyend, D. [LPSC, UJF Grenoble 1, CNRS/IN2P3, INPG, 53 avenue des Martyrs 38026 Grenoble (France); Moricciani, D.; Casano, L.; Di Salvo, R. [INFN Sezione di Roma TV, 00133 Roma (Italy); Bellini, V.; Giusa, A.; Mammoliti, F.; Randieri, C.; Russo, G.; Sperduto, M. L.; Sutera, M. C. [INFN Sezione di Catania and Universita di Catania, 95100 Catania (Italy); Beretta, M.; Levi Sandri, P. [INFN Laboratori Nazionali di Frascati, 00044 Frascati (Italy); D'Angelo, A.; Fantini, A.; Franco, D.; Messi, R. [INFN Sezione di Roma TV and Universita di Roma 'Tor Vergata', 00133 Roma (Italy)

2010-06-18

385

Evaluation of orbital moment in Ni-Zn ferrites: A magnetic Compton scattering study  

SciTech Connect

Temperature dependent magnetic Compton profiles of Ni{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} (x = 0.0, 0.1, 0.2) ferrites have been decomposed into component profiles to determine the site-specific magnetic moments. For a quantitative evaluation of orbital moment, the spin momentum density data have been combined with magnetization data. Interestingly, the orbital magnetic moment decreases from 0.25 {+-} 0.03 {mu}{sub B}/f.u. (for x = 0.0) to 0.09 {+-} 0.03 {mu}{sub B}/f.u. (for x = 0.2) which is in contrast to spin moment. A decrease in ratio of orbital to spin moments in Ni rich ferrites is explained on the basis of spin-orbit coupling and crystal field interaction.

Ahuja, B. L.; Mund, H. S.; Tiwari, Shailja; Sahariya, Jagrati; Dashora, Alpa [Department of Physics, M. L. Sukhadia University, Udaipur 313001 (India); Itou, M.; Sakurai, Y. [Experimental Research Division, Japan Synchrotron Radiation Research Institute, SPring8, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan)

2012-03-26

386

The Highest-Energy Photons Seen by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

During its nine-year lifetime, the Energetic Gamma Ray Experiment Telescope (EGBET) on the Compton Gamma Ray Observatory (CGRO) detected 1506 cosmic photons with measured energy E>10 GeV. Of this number, 187 are found within a 1 deg of sources that are listed in the Third EGRET Catalog and were included in determining the detection likelihood, flux, and spectra of those sources. In particular, five detected EGRET pulsars are found to have events above 10 GeV, and together they account for 37 events. A pulsar not included in the Third EGRET Catalog has 2 events, both with the same phase and in one peak of the lower-energy gamma-ray light-curve. Most of the remaining 1319 events appear to be diffuse Galactic and extragalactic radiation based on the similarity of the their spatial and energy distributions with the diffuse model and in the E>100, MeV emission. No significant time clustering which would suggest a burst was detected.

Thompson, D. J.; Bertsch, D. L.; ONeal, R. H., Jr.

2005-01-01

387

Few arc-minute and keV resolutions with the TIGRE Compton telescope  

NASA Technical Reports Server (NTRS)

The tracking and imaging gamma ray experiment (TIGRE) Compton telescope concept can provide an angular resolution of a few arcmin, an energy resolution of a few keV and high sensitivity, while providing the wide field of view necessary for surveying and monitoring observations. Silicon and CdZnTe strip detectors are used to detect Compton pair events and determine their incident directions and energies. Above 400 keV, Compton recoil electrons are tracked through successive layers of thin silicon strip detectors. Compton scattered photons are detected with CdZnTe strip detectors. Pair electrons and positrons are tracked to provide high sensitivity observations in the 10 to 100 MeV range. Polarization studies are performed with large angle Compton scatter events. The TIGRE concept and development status are described.

Zych, A.; Bhattacharya, D.; Dixon, D.; ONeill, T.; Tuemer, T.; White, R. S.; Ryan, J.; McConnell, M.; Macri, J.; Oegelman, H.; Paulos, R.; Wheaton, W.; Akyuez, A.; Samimi, J.; Oezel, M.

1997-01-01

388

Gamma ray astrophysics. [emphasizing processes and absorption  

NASA Technical Reports Server (NTRS)

Gamma ray production processes are reviewed, including Compton scattering, synchrotron radiation, bremsstrahlung interactions, meson decay, nucleon-antinucleon annihilations, and pion production. Gamma ray absorption mechanisms through interactions with radiation and with matter are discussed, along with redshifts and gamma ray fluxes.

Stecker, F. W.

1974-01-01

389

Quantitative 131I SPECT with triple energy window Compton scatter correction  

Microsoft Academic Search

In this work accuracy of quantitative 131I SPECT with triple energy window (TEW) scatter correction is evaluated by phantom measurements. The application is tumor imaging of B-cell lymphoma patients treated with 131I radioimmunotherapy. The TEW method is a pixel by pixel correction where the scatter fraction in the photopeak window is estimated by linear interpolation between two adjacent narrow sub-windows.

Yuni Dewaraja; Jia Li; Kenneth Koral

1998-01-01

390

Quantitative 131I SPECT with triple energy window Compton scatter correction  

Microsoft Academic Search

In this work accuracy of quantitative 131I SPECT with triple energy window (TEW) scatter correction is evaluated by phantom measurements. The TEW method is a pixel by pixel correction where the scatter fraction in the photopeak window is estimated by linear interpolation between two adjacent narrow sub-windows. Quantification procedure includes marker based X-ray CT-SPECT image fusion to determine object boundaries

Yuni Dewaraja; Jia Li; Kenneth Koral

1997-01-01

391

The development of a Compton lung densitometer  

SciTech Connect

A field instrument is being developed for the non-invasive determination of absolute lung density using unique Compton backscattering techniques. A system consisting of a monoenergetic gamma-ray beam and a shielded high resolution high-purity-germanium (HPGe) detector in a close-coupled geometry is designed to minimize errors due to multiple scattering and uncontrollable attenuation in the chestwall. Results of studies on system performance with phantoms, the optimization of detectors, and the fabrication of a practical gamma-ray source are presented. 3 refs., 6 figs., 2 tabs.

Loo, B.W.; Goulding, F.S.; Madden, N.W.; Simon, D.S.

1988-11-01

392

Design of a 4.8-m ring for inverse Compton scattering x-ray source  

NASA Astrophysics Data System (ADS)

In this paper we present the design of a 50 MeV compact electron storage ring with 4.8-meter circumference for the Tsinghua Thomson scattering x-ray source. The ring consists of four dipole magnets with properly adjusted bending radii and edge angles for both horizontal and vertical focusing, and a pair of quadrupole magnets used to adjust the horizontal damping partition number. We find that the dynamic aperture of compact storage rings depends essentially on the intrinsic nonlinearity of the dipole magnets with small bending radius. Hamiltonian dynamics is found to agree well with results from numerical particle tracking. We develop a self-consistent method to estimate the equilibrium beam parameters in the presence of the intrabeam scattering, synchrotron radiation damping, quantum excitation, and residual gas scattering. We also optimize the rf parameters for achieving a maximum x-ray flux.

Xu, H. S.; Huang, W. H.; Tang, C. X.; Lee, S. Y.

2014-07-01

393

Neutron Compton scattering as a molecular characterization technique: A study on NaHF{sub 2}  

SciTech Connect

Inelastic neutron scattering experiments were performed at intermediate and high momentum transfers, up to 85-90 A ring {sup -1}, to study the proton momentum distribution in polycrystalline sodium hydrogen fluoride (NaHF{sub 2}) at low temperature (below 5 K). The H mean kinetic energy was extracted and compared to the results from hydrogen-projected density of phonon states derived from intermediate momentum transfer inelastic neutron scattering and lattice dynamics simulations. A reasonable agreement between the two figures was found. In addition, relevant aspects of high momentum transfer neutron scattering from NaHF{sub 2} were explored in detail, ranging from an alternative evaluation of final state effects to the role played by the instrumental resolution and to the possibility to reconstruct the potential felt by a proton from its momentum distribution.

Colognesi, D. [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Sezione di Firenze, via Madonna del Piano 10, 50019 Sesto Fiorentino, Florence (Italy); Pietropaolo, A.; Senesi, R. [Dipartimento di Fisica and Centro NAST, Universita degli Studi di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Rome (Italy); Ramirez-Cuesta, A. J. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom)

2007-11-01

394

Compton Profile Study of Intermetallic Ti{sub 3}Al  

SciTech Connect

The Compton scattering measurement on intermetallic alloy Ti{sub 3}Al is reported in this work. The measurement is made using 59.54 keV gamma-rays from Am{sup 241} source. Theoretical calculation of Compton profile is also performed employing CRYSTAL code within the framework of density functional theory to compare with the measurement. The theoretical profile of the alloy is also synthesized following the superposition model taking the published Compton profiles of elemental solids from the APW method. The experimental study of charge transfer in the alloys has also been done by performing the experimental Compton profile measurements on Ti and Al following the superposition model and charge transfer from Al to Ti is clearly seen on the alloy formation.

Vyas, V.; Sharma, G. [Department of Physics, Banasthali University, Banasthali-304022 (India); Mishra, M. C.; Sharma, B. K. [Department of Physics, University of Rajasthan, Jaipur-302004 (India); Joshi, K. B. [Department of Physics, University College of Science, M.L.Sukhadia University, Udaipur-313 002 (India)

2011-10-20

395

1618 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 51, NO. 4, AUGUST 2004 4 Compton Imaging Using a 3-D Position-Sensitive  

E-print Network

iterations. Index Terms--Cadmium zinc telluride, Compton camera, gamma-ray imaging, gamma-ray tracking, image with two detectors or arrays of detectors. Sequences in which the gamma ray scatters in the front plane. Also, the second detector must be physically shielded from direct irradiation, increasing size

He, Zhong

396

A practical method for position-dependent Compton-scatter correction in single photon emission CT  

Microsoft Academic Search

A new method is proposed to subtract the count of scattered photons from that acquired with a photopeak window at each pixel in each planar image of single-photon emission computed tomography (SPECT). The subtraction is carried out using two sets of data: one set is acquired with a main window centered at photopeak energy and the other is acquired with

Koichi Ogawa; Yasuo Harata; Takashi Ichihara; Atsushi Kubo; Shozo Hashimoto

1991-01-01

397

Rutherford and Compton scattering in QCD Substructure dependence of jet cross sections at HERA  

E-print Network

in the scattering of # particles by metal sheets led to the discovery of the atomic nucleus. The model of Rutherford for the atomic nucleus predicted an angular dependence for the cross section of the process which rises with cos . In this context, the experimental results of Geiger and Marsden showed that the nucleus of an atom has an spatial

398

Compton scattering monochromatic X-ray source based on X-band multi-bunch linac at the University of Tokyo  

Microsoft Academic Search

We are currently developing a compact monochromatic X-ray source based on laser–electron Compton scattering for the purpose of medical applications at the University of Tokyo. To realize remarkably compact-, high-intensity- and highly stable system, we adopt an X-band (11.424GHz) multi-bunch linear accelerator (linac) and reliable Q-switch Nd:YAG laser. The injector of the system consists of a 3.5-cell X-band thermionic cathode

F. Sakamoto; M. Uesaka; Y. Taniguchi; T. Natsui; E. Hashimoto; L. K. Woo; T. Yamamoto; J. Urakawa; M. Yoshida; T. Higo; S. Fukuda; N. Kaneko; H. Nose; H. Sakae; N. Nakamura; M. Yamamoto

2009-01-01

399

Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2=0.92 and 1.76 GeV2  

Microsoft Academic Search

We report a virtual Compton scattering study of the proton at low c.m. energies. We have determined the structure functions PLL-PTT\\/? and PLT, and the electric and magnetic generalized polarizabilities (GPs) alphaE(Q2) and betaM(Q2) at momentum transfer Q2=0.92 and 1.76 GeV2. The electric GP shows a strong falloff with Q2, and its global behavior does not follow a simple dipole

G. Laveissière; L. Todor; N. Degrande; S. Jaminion; C. Jutier; Rachele Di Salvo; L. van Hoorebeke; L. C. Alexa; B. D. Anderson; K. A. Aniol; K. Arundell; G. Audit; L. Auerbach; F. T. Baker; M. Baylac; J. Berthot; P. Y. Bertin; W. Bertozzi; L. Bimbot; W. U. Boeglin; E. J. Brash; V. Breton; H. Breuer; E. Burtin; J. R. Calarco; L. S. Cardman; C. Cavata; C.-C. Chang; J.-P. Chen; E. Chudakov; E. Cisbani; D. S. Dale; C. W. de Jager; R. de Leo; A. Deur; N. D'Hose; G. E. Dodge; J. J. Domingo; L. Elouadrhiri; M. B. Epstein; L. A. Ewell; J. M. Finn; K. G. Fissum; H. Fonvieille; G. Fournier; B. Frois; S. Frullani; C. Furget; H. Gao; J. Gao; F. Garibaldi; A. Gasparian; S. Gilad; R. Gilman; A. Glamazdin; C. Glashausser; J. Gomez; V. Gorbenko; P. Grenier; P. A. Guichon; J. O. Hansen; R. Holmes; M. Holtrop; C. Howell; G. M. Huber; C. E. Hyde-Wright; S. Incerti; M. Iodice; J. Jardillier; M. K. Jones; W. Kahl; S. Kato; A. T. Katramatou; J. J. Kelly; S. Kerhoas; A. Ketikyan; M. Khayat; K. Kino; S. Kox; L. H. Kramer; K. S. Kumar; G. Kumbartzki; M. Kuss; A. Leone; J. J. Lerose; M. Liang; R. A. Lindgren; N. Liyanage; G. J. Lolos; R. W. Lourie; R. Madey; K. Maeda; S. Malov; D. M. Manley; C. Marchand; D. Marchand; D. J. Margaziotis; P. Markowitz; J. Marroncle; J. Martino; K. McCormick; J. McIntyre; S. Mehrabyan; F. Merchez; Z. E. Meziani; R. Michaels; G. W. Miller; J. Y. Mougey; S. K. Nanda; D. Neyret; E. A. Offermann; Z. Papandreou; B. Pasquini; C. F. Perdrisat; R. Perrino; G. G. Petratos; S. Platchkov; R. Pomatsalyuk; D. L. Prout; V. A. Punjabi; T. Pussieux; G. Quémenér; R. D. Ransome; O. Ravel; J. S. Real; F. Renard; Y. Roblin; D. Rowntree; G. Rutledge; P. M. Rutt; A. Saha; T. Saito; A. J. Sarty; A. Serdarevic; T. Smith; G. Smirnov; K. Soldi; P. Sorokin; P. A. Souder; R. Suleiman; J. A. Templon; T. Terasawa; R. Tieulent; E. Tomasi-Gustaffson; H. Tsubota; H. Ueno; P. E. Ulmer; G. M. Urciuoli; M. Vanderhaeghen; R. van de Vyver; R. L. van der Meer; P. Vernin; B. Vlahovic; H. Voskanyan; E. Voutier; J. W. Watson; L. B. Weinstein; K. Wijesooriya; R. Wilson; B. B. Wojtsekhowski; D. G. Zainea; W.-M. Zhang; J. Zhao; Z.-L. Zhou

2004-01-01

400

Compton Scattering by Internal Shields Based on Melanin-Containing Mushrooms Provides Protection of Gastrointestinal Tract from Ionizing Radiation  

PubMed Central

Abstract There is a need for radioprotectors that protect normal tissues from ionizing radiation in patients receiving high doses of radiation and during nuclear emergencies. We investigated the possibility of creating an efficient oral radioprotector based on the natural pigment melanin that would act as an internal shield and protect the tissues via Compton scattering followed by free radical scavenging. CD-1 mice were fed melanin-containing black edible mushrooms Auricularia auricila-judae before 9?Gy total body irradiation. The location of the mushrooms in the body before irradiation was determined by in vivo fluorescent imaging. Black mushrooms protected 80% of mice from the lethal dose, while control mice or those given melanin-devoid mushrooms died from gastrointestinal syndrome. The crypts of mice given black mushrooms showed less apoptosis and more cell division than those in control mice, and their white blood cell and platelet counts were restored at 45 days to preradiation levels. The role of melanin in radioprotection was proven by the fact that mice given white mushrooms supplemented with melanin survived at the same rate as mice given black mushrooms. The ability of melanin-containing mushrooms to provide remarkable protection against radiation suggests that they could be developed into oral radioprotectors. PMID:23113595

Revskaya, Ekaterina; Chu, Peter; Howell, Robertha C.; Schweitzer, Andrew D.; Bryan, Ruth A.; Harris, Matthew; Gerfen, Gary; Jiang, Zewei; Jandl, Thomas; Kim, Kami; Ting, Li-Min; Sellers, Rani S.; Casadevall, Arturo

2012-01-01

401

Geant4 simulations on Compton scattering of laser photons on relativistic electrons  

NASA Astrophysics Data System (ADS)

Using Geant4, a complex simulation code of the interaction between laser photons and relativistic electrons was developed. We implemented physically constrained electron beam emittance and spacial distribution parameters and we also considered a Gaussian laser beam. The code was tested against experimental data produced at the ?-ray beam line GACKO (Gamma Collaboration Hutch of Konan University) of the synchrotron radiation facility NewSUBARU. Here we will discuss the implications of transverse missallignments of the collimation system relative to the electron beam axis.

Filipescu, D.; Utsunomiya, H.; Gheorghe, I.; Glodariu, T.; Tesileanu, O.; Shima, T.; Takahisa, K.; Miyamoto, S.

2015-02-01

402

A current generation by Compton scattering in a relativistic plasma with velocity shear and temperature gradient  

NASA Technical Reports Server (NTRS)

Current generation by Thomson scattering in a non-relativistic plasma with the velocity shear and the temperature gradient (Hinata and Daneshvar, 1983) is extended to a relativistic plasma by replacing Thomson cross section by the Klein-Nishina formula. Because of the energy dependence of the cross-section, a numerical rather than analytic result is presented. The present calculation may be applied to a supernova implosion where the temperature may reach several MeV and a strong differential rotation is expected. It may also find applications in the early universe, and laser-pellet interaction.

Hinata, S.

1984-01-01

403

First Determination of Generalized Polarizabilities of the Proton by a Virtual Compton Scattering Experiment  

SciTech Connect

Absolute differential cross sections for the reaction ep{yields}ep{gamma} have been measured at a four-momentum transfer with virtuality Q{sup 2}=0.33 GeV{sup 2} and polarization {epsilon}=0.62 in the range 33.6 to 111.5 MeV/c for the momentum of the outgoing photon in the photon-proton center of mass frame. The experiment has been performed with the high-resolution spectrometers at the Mainz Microtron MAMI. From the photon angular distributions, two structure functions which are a linear combination of the generalized polarizabilities have been determined for the first time. (c) 2000 The American Physical Society.

Roche, J. [CEA Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette Cedex, (France)] [CEA Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette Cedex, (France); Friedrich, J. M. [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany)] [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany); Lhuillier, D. [CEA Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette Cedex, (France)] [CEA Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette Cedex, (France); Bartsch, P. [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany)] [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany); Baumann, D. [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany)] [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany); Berthot, J. [LPC de Clermont-Fd, IN2P3-CNRS, Universite Blaise Pascal, 63177 Aubiere Cedex, (France)] [LPC de Clermont-Fd, IN2P3-CNRS, Universite Blaise Pascal, 63177 Aubiere Cedex, (France); Bertin, P. Y. [LPC de Clermont-Fd, IN2P3-CNRS, Universite Blaise Pascal, 63177 Aubiere Cedex, (France)] [LPC de Clermont-Fd, IN2P3-CNRS, Universite Blaise Pascal, 63177 Aubiere Cedex, (France); Breton, V. [LPC de Clermont-Fd, IN2P3-CNRS, Universite Blaise Pascal, 63177 Aubiere Cedex, (France)] [LPC de Clermont-Fd, IN2P3-CNRS, Universite Blaise Pascal, 63177 Aubiere Cedex, (France); Boeglin, W. U. [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany)] [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany); Boehm, R. [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany)] (and others) [Institut fuer Kernphysik, Universitaet Mainz, 55099 Mainz, (Germany)

2000-07-24

404

Polarized ? source based on Compton backscattering in a laser cavity  

NASA Astrophysics Data System (ADS)

We propose a novel gamma source suitable for generating a polarized positron beam for the next generation of electron-positron colliders, such as the International Linear Collider (ILC), and the Compact Linear Collider (CLIC). This 30-MeV polarized gamma source is based on Compton scattering inside a picosecond CO2 laser cavity generated from electron bunches produced by a 4-GeV linac. We identified and experimentally verified the optimum conditions for obtaining at least one gamma photon per electron. After multiplication at several consecutive interaction points, the circularly polarized gamma rays are stopped on a target, thereby creating copious numbers of polarized positrons. We address the practicality of having an intracavity Compton-polarized positron source as the injector for these new colliders.

Yakimenko, V.; Pogorelsky, I. V.

2006-09-01

405

Tracking and imaging gamma ray experiment (TIGRE) for 1 to 100 MeV gamma ray astronomy  

Microsoft Academic Search

A large international collaboration from the high energy astrophysics community has proposed the Tracking and Imaging Gamma Ray Experiment (TIGRE) for future space observations. TIGRE will image and perform energy spectroscopy measurements on celestial sources of gamma rays in the energy range from 1 to 100 MeV. TIGRE is both a double scatter Compton and gamma-ray pair telescope with direct

A. Alpar; D. Bhattacharya; R. Buccheri; K. Dotson; D. Forrest; W. N. Johnson; G. Kanbach; U. Kiziloglu; R. Kroeger; J. Kurfess; M. McConnell; H. Ögelman; B. O'Neill; T. O'Neill; A. Owens; B. Pi; B. Pierce; J. Ryan; B. Sacco; G. Simnett; T. Tümer; W. Wheaton; R. S. White; A. Zych

1994-01-01

406

The Compton Observatory in perspective  

Microsoft Academic Search

The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 15 keV to 30 GeV, with sensitivity over the entire range and order of magnitude better than

N. Gehrels; E. Chipman; D. A. Kniffen

1993-01-01

407

The inability of the resonant Compton upscattering model of gamma-ray bursts to produce a third cyclotron harmonic  

NASA Technical Reports Server (NTRS)

The inability of the resonant Compton upscattering model to produce a third cyclotron resonance, which provides a strong observational test of this model, is discussed. The relevant features of the Compton upscattering model and the thermal cross sections responsible for the cyclotron lines are examined. The impossibility of producing a third cyclotron feature for all realistic temperatures of the line-forming plasma is addressed.

Brainerd, J. J.

1991-01-01

408

Detection of a long-duration solar gamma-ray flare on Jun. 11, 1991 with EGRET on Compton-GRO  

NASA Technical Reports Server (NTRS)

On 11 Jun. 1991, the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (Comption-GRO) observed high energy gamma radiation above 30 MeV from the Sun following an intense flare around 2:00 Universal Time (UT). After the decay of most of the x ray flare, which caused nearly complete deadtime losses in EGRET, high energy emission was registered during the interval from about 3:30 UT to at least 10:30 UT. Gamma rays were detected up to energies above 1 GeV. The solar origin of the emission is assured by the time profile of the gamma ray count rate and by time resolved sky maps, which show a clear maximum at the position of the sun. The gamma ray lightcurve of the flare can be described with two components: a fast decaying emission with an e-folding time constant of about 25 minutes and a slow decay with about 255 minutes. There are indications for a spectral evolution with time, such that the emission below 100 MeV fades away earlier than the 100 to 300 MeV radiation, roughly in the time scale of the fast component. The spectrum of the flare can be fitted with a composite of a proton generated pion neutral spectrum and an electron bremsstrahlung component. The latter can be identified with the fast decaying component of the lightcurve.

Kanbach, G.; Bertsch, D. L.; Fitchel, C. E.; Hartman, R. C.; Hunter, S. D.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.; Mayer-Hasslewander, H. A.

1992-01-01

409

A 3D point-kernel multiple scatter model for parallel-beam SPECT based on a gamma-ray buildup factor.  

PubMed

A three-dimensional (3D) point-kernel multiple scatter model for point spread function (PSF) determination in parallel-beam single-photon emission computed tomography (SPECT), based on a dose gamma-ray buildup factor, is proposed. This model embraces nonuniform attenuation in a voxelized object of imaging (patient body) and multiple scattering that is treated as in the point-kernel integration gamma-ray shielding problems. First-order Compton scattering is done by means of the Klein-Nishina formula, but the multiple scattering is accounted for by making use of a dose buildup factor. An asset of the present model is the possibility of generating a complete two-dimensional (2D) PSF that can be used for 3D SPECT reconstruction by means of iterative algorithms. The proposed model is convenient in those situations where more exact techniques are not economical. For the proposed model's testing purpose calculations (for the point source in a nonuniform scattering object for parallel beam collimator geometry), the multiple-order scatter PSF generated by means of the proposed model matched well with those using Monte Carlo (MC) simulations. Discrepancies are observed only at the exponential tails mostly due to the high statistic uncertainty of MC simulations in this area, but not because of the inappropriateness of the model. PMID:17881800

Marinkovic, Predrag; Ilic, Radovan; Spaic, Rajko

2007-10-01

410

A 3D point-kernel multiple scatter model for parallel-beam SPECT based on a gamma-ray buildup factor  

NASA Astrophysics Data System (ADS)

A three-dimensional (3D) point-kernel multiple scatter model for point spread function (PSF) determination in parallel-beam single-photon emission computed tomography (SPECT), based on a dose gamma-ray buildup factor, is proposed. This model embraces nonuniform attenuation in a voxelized object of imaging (patient body) and multiple scattering that is treated as in the point-kernel integration gamma-ray shielding problems. First-order Compton scattering is done by means of the Klein-Nishina formula, but the multiple scattering is accounted for by making use of a dose buildup factor. An asset of the present model is the possibility of generating a complete two-dimensional (2D) PSF that can be used for 3D SPECT reconstruction by means of iterative algorithms. The proposed model is convenient in those situations where more exact techniques are not economical. For the proposed model's testing purpose calculations (for the point source in a nonuniform scattering object for parallel beam collimator geometry), the multiple-order scatter PSF generated by means of the proposed model matched well with those using Monte Carlo (MC) simulations. Discrepancies are observed only at the exponential tails mostly due to the high statistic uncertainty of MC simulations in this area, but not because of the inappropriateness of the model.

Marinkovic, Predrag; Ilic, Radovan; Spaic, Rajko

2007-09-01

411

The TIGRE instrument for 0.3-100 MeV gamma-ray astronomy  

Microsoft Academic Search

The Tracking and Imaging Gamma-Ray Experiment (TIGRE) uses multilayers of silicon strip detectors both as a gamma-ray converter and to track Compton recoil electrons and positron-electron pairs. The direction and energy of the Compton scattered gamma ray and pair particles are measured with arrays of small CsI(Tl)-photodiode detectors. With a large ?-steradian field-of-view, the prototype instrument described is sensitive to

O. T. Tumer; A. Akyiizl; D. Bhattacharya; S. C. Blair; G. L. Case; D. D. Dixon; C.-J. Liu; T. J. O'Neill; J. Samimi; R. S. White; A. D. Zych

1995-01-01

412

Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2=0.92 and 1.76 Gev2: II. Dispersion Relation Analysis  

SciTech Connect

Virtual Compton Scattering is studied at the Thomas Jefferson National Accelerator Facility in the energy domain below pion threshold and in the Delta(1232) resonance region. The data analysis is based on the Dispersion Relation (DR) approach. The electric and magnetic Generalized Polarizabilities (GPs) of the proton and the structure functions Pll-Ptt/epsilon and Plt are determined at four-momentum transfer squared Q2=0.92 and 1.76 GeV2. The DR analysis is consistent with the low-energy expansion analysis. The world data set indicates that neither the electric nor magnetic GP follows a simple dipole form.

Geraud Laveissiere; Luminita Todor; Natalie Degrande; Stephanie Jaminion; Christophe Jutier; Rachele Di Salvo; L. Van Hoorebeke; et al

2003-12-01

413

Development of electron tracking Compton camera for both balloon and future satellite experiments for MeV gamma-ray astronomy  

NASA Astrophysics Data System (ADS)

In order to explore MeV gamma-ray astronomy, we have developed the Electron Tracking Compton Camera (ETCC) consisting of a Time projection Chamber based on the micro pixel gas counter and pixel array scintillators. By measuring the track of a recoil electron in the TPC event by event, the ETCC measures the direction of each gamma-ray, and provides both good background rejection and an angular resolution over ~1 degree. A 1m-cubic size ETCC in satellite would be a good candidate for an All sky MeV gamma-ray survey of a wide band energy region of 0.1-100MeV with several ten times better sensitivity than COMPTEL. Already we carried out a balloon experiment with a small ETCC (Sub-MeV gamma ray Imaging Loaded-on-balloon Experiment: SMILE-I) in 2006, and measured diffuse cosmic and atmosphere gamma rays. We are now constructing a 30cm-cube ETCC to catch gamma-rays from the Crab and terrestrial gamma-ray bursts at the North Pole from 2013 (SMILE-II project). Terrestrial gamma-ray bursts are generated by relativistic electron precipitation in the Pole region. Recently performance of tracking a recoil electron has been dramatically improved, which may enable us to reach the ideal efficiency expected for the detector. In addition, we mention about the unique capability to find a high-z Gamma-Ray Bursts beyond z>10 by ETCC, in particular long duration GRBs over 1000 sec, which are expected to be due to POP-III stars.

Tanimori, Toru; Ikeno, Masahiro; Kubo, Hidetoshi; Miuchi, Kentaro; Kabuki, Shigeto; Parker, Joseph D.; Kishimoto, Yuji; Komura, Shotaro; Kurosawa, Shunsuke; Iwaki, Satoru; Sawano, Tatsuya; Nakamura, Kiseki; Matsuoka, Yoshihiro; Mizumoto, Tetsuya; Sato, Yasushi; Tanaka, Manobu; Takada, Atsushi; Uchida, Tomohisa; Ueno, Kazuki

2012-09-01

414

Helium Compton Form Factor Measurements at CLAS  

SciTech Connect

The distribution of the parton content of nuclei, as encoded via the generalized parton distributions (GPDs), can be accessed via the deeply virtual Compton scattering (DVCS) process contributing to the cross section for leptoproduction of real photons. Similarly to the scattering of light by a material, DVCS provides information about the dynamics and the spatial structure of hadrons. The sensitivity of this process to the lepton beam polarization allows to single-out the DVCS amplitude in terms of Compton form factors that contain GPDs information. The beam spin asymmetry of the $^4$He($\\vec {\\mathrm e}$,e$' \\gamma ^4$He) process was measured in the experimental Hall B of the Jefferson Laboratory to extract the real and imaginary parts of the twist-2 Compton form factor of the $^4$He nucleus. The experimental results reported here demonstrate the relevance of this method for such a goal, and suggest the dominance of the Bethe-Heitler amplitude to the unpolarized process in the kinematic range explored by the experiment.

Voutier, Eric J.-M. [Laboratoire de Physique Subatomique et Cosmologie

2013-07-01

415

Optimisation of a dual head semiconductor Compton camera using Geant4  

NASA Astrophysics Data System (ADS)

Conventional medical gamma-ray camera systems utilise mechanical collimation to provide information on the position of an incident gamma-ray photon. Systems that use electronic collimation utilising Compton image reconstruction techniques have the potential to offer huge improvements in sensitivity. Position sensitive high purity germanium (HPGe) detector systems are being evaluated as part of a single photon emission computed tomography (SPECT) Compton camera system. Data have been acquired from the orthogonally segmented planar SmartPET detectors, operated in Compton camera mode. The minimum gamma-ray energy which can be imaged by the current system in Compton camera configuration is 244 keV due to the 20 mm thickness of the first scatter detector which causes large gamma-ray absorption. A simulation package for the optimisation of a new semiconductor Compton camera has been developed using the Geant4 toolkit. This paper will show results of preliminary analysis of the validated Geant4 simulation for gamma-ray energies of SPECT, 141 keV.

Harkness, L. J.; Boston, A. J.; Boston, H. C.; Cooper, R. J.; Cresswell, J. R.; Grint, A. N.; Nolan, P. J.; Oxley, D. C.; Scraggs, D. P.; Beveridge, T.; Gillam, J.; Lazarus, I.

2009-06-01

416

Modeling and simulation results on high sensitivity scattered gamma-ray emission imaging  

E-print Network

-medical imaging, gamma-ray astronomy, non-destructive industrial testing, environmental survey and control, etcModeling and simulation results on high sensitivity scattered gamma-ray emission imaging C. Driol a simulations Numerical image reconstruction a b s t r a c t A new modality in gamma-ray emission imaging, based

Nguyen-Verger, Maï K.

417

Compact gamma ray point sources - Are gamma ray sources optically thick at lower frequencies  

NASA Astrophysics Data System (ADS)

The hypothesis is discussed that some of the unidentified gamma ray point sources are objects which emit only at the highest frequencies but are optically thick against stimulated Compton scattering or nonthermal electron bremsstrahlung reabsorption at lower frequencies. From the calculated absorption coefficients it follows that such a scenario is only possible for inverse Compton scattering under extreme conditions which may hold in the core of powerful sources. This would mean that these gamma ray point sources are very energetic and compact objects. However, relativistic electron bremsstrahlung optically thick objects do not occur in nature.

Schlickeiser, R.

1982-03-01

418

Noise evaluation of Compton camera imaging for proton therapy  

NASA Astrophysics Data System (ADS)

Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming ? energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of detection, from the beam particle entering a phantom to the event classification, is simulated using FLUKA. The range determination is later estimated from the reconstructed image obtained from a two and three-event algorithm based on Maximum Likelihood Expectation Maximization. The neutron background and random coincidences due to a therapeutic-like time structure are analyzed for mono-energetic proton beams. The time structure of the beam is included in the simulations, which will affect the rate of particles entering the detector.

Ortega, P. G.; Torres-Espallardo, I.; Cerutti, F.; Ferrari, A.; Gillam, J. E.; Lacasta, C.; Llosá, G.; Oliver, J. F.; Sala, P. R.; Solevi, P.; Rafecas, M.

2015-02-01

419

Noise evaluation of Compton camera imaging for proton therapy.  

PubMed

Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming ? energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of detection, from the beam particle entering a phantom to the event classification, is simulated using FLUKA. The range determination is later estimated from the reconstructed image obtained from a two and three-event algorithm based on Maximum Likelihood Expectation Maximization. The neutron background and random coincidences due to a therapeutic-like time structure are analyzed for mono-energetic proton beams. The time structure of the beam is included in the simulations, which will affect the rate of particles entering the detector. PMID:25658644

Ortega, P G; Torres-Espallardo, I; Cerutti, F; Ferrari, A; Gillam, J E; Lacasta, C; Llosá, G; Oliver, J F; Sala, P R; Solevi, P; Rafecas, M

2015-02-21

420

Inverse Compton e-p pair cascade model for the gamma-ray production in massive binary LSI +61^o 303  

E-print Network

We apply an inverse Compton $e^\\pm$ pair cascade model for $\\gamma$-ray production in massive binary system LSI +61$^{\\rm o}$ 303 assuming that electrons are accelerated already inside the inner part of the jet launched by the compact object. $\\gamma$-ray spectra, affected by the cascade process, and lower energy spectra, from the synchrotron cooling of the highest energy electrons in the jet, are calculated as a function of the phase of this binary system. $\\gamma$-ray spectra expected in such model have different shape than that ones produced by electrons in the jet directly to observer. Moreover, the model predicts clear anti-correlation between $\\gamma$-ray fluxes in the GeV (1-10 GeV) and TeV ($>200$ GeV) energy ranges with the peak of the TeV emission at the phase $\\sim$0.5 (the peak half width ranges between the phases $\\sim$0.4-0.9 for the inclination of the binary system equal to $60^{\\rm o}$, and $\\sim$0.4-0.1 for $30^{\\rm o}$). The fine features of TeV $\\gamma$-ray emission (fluxes and spectral shapes) as a function of the phase of the binary system are consistent with recent observations reported by the MAGIC collaboration. Future simultaneous observations in the GeV energies (by the GLAST and AGILE telescopes) and in the TeV energies (by the MAGIC and VERITAS telescopes) should test other predictions of the considered model supporting or disproving the hypothersis of acceleration of electrons already in the inner part of the microquasar jets.

W. Bednarek

2006-07-13

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