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1

A Compton scatter attenuation gamma ray spectrometer  

NASA Technical Reports Server (NTRS)

A Compton scatter attenuation gamma ray spectrometer conceptual design is discussed for performing gamma spectral measurements in monodirectional gamma fields from 100 R per hour to 1,000,000 R per hour. Selectable Compton targets are used to scatter gamma photons onto an otherwise heavily shielded detector with changeable scattering efficiencies such that the count rate is maintained between 500 and 10,000 per second. Use of two sum-Compton coincident detectors, one for energies up to 1.5 MeV and the other for 600 keV to 10 MeV, will allow good peak to tail pulse height ratios to be obtained over the entire spectrum and reduces the neutron recoil background rate.

Austin, W. E.

1972-01-01

2

A Compton scatter attenuation gamma ray spectrometer  

NASA Technical Reports Server (NTRS)

Compton attenuation technique, utilizing semiconductor sum-Compton detectors, has been proposed for gamma ray spectrometer capable of gamma spectral measurements in radition fields of 100 R/hr to one million R/hr. Spectrometer consists of two or more separate detectors, with only primary detector exposed to primary incident photon flux.

Austin, W. E.

1972-01-01

3

Energy distribution of Compton-scattered gamma rays  

E-print Network

ENERGY DISTRIBUTION OF COMPTON- SCATTERED GAMMA RAYS A Thesis by RICHARD WAYNE MORELAND Submitted to the Graduate College of the Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 1966... - Curve 2 Fig. 20 71 ENERGY DISTRIBUTIONS OF COMPTON SCATTERED GANNA RAYS CHAPTER I INTRODUCTION A beam of monochromatic gamma rays observed after scattering by electrons at a well defined scattering angle suffers a change of wave- length...

Moreland, Richard Wayne

2012-06-07

4

Saturated Compton Scattering Models for the Soft GammaRay  

E-print Network

Saturated Compton Scattering Models for the Soft Gamma­Ray Repeater Bursts I. A. Smith, E. P. Liang, A. Crider, D. Lin Department of Space Physics and Astronomy, Rice University, MS­108, 6100 South 662, Japan Abstract. The Soft Gamma­Ray Repeaters (SGR) are sources of brief intense outbursts of low

Smith, Ian Andrew

5

COMPACT, TUNABLE COMPTON SCATTERING GAMMA-RAY SOURCES  

Microsoft Academic Search

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,

F V Hartemann; F Albert; G G Anderson; S G Anderson; A J Bayramian; S M Betts; T S Chu; R R Cross; C A Ebbers; S E Fisher; D J Gibson; A S Ladran; R A Marsh; M J Messerly; K L ONeill; V A Semenov; M Y Shverdin; C W Siders; D P McNabb; C J Barty; A E Vlieks; E N Jongewaard; S G Tantawi; T O Raubenheimer

2009-01-01

6

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

7

The Compton Effect--Compton Scattering and Gamma Ray Spectroscopy  

E-print Network

of electromagnetic waves by a charged particle in which a portion of the energy of the electromagnetic wave is given scattering involves the scattering of photons by charged particles where both energy and momentum are transferred to the charged particle while the photon moves off with a reduced energy and a change of momentum

Dai, Pengcheng

8

Gamma ray polarimetry. [compton scattering and pair production  

NASA Technical Reports Server (NTRS)

Spectroscopic instruments currently being proposed may possess polarimetric capabilities which sould be nurtured and enhanced to permit characterization of basic emission mechanisms which are impossible using other techniques. Compton scattering and pair production detected the polarization of high energy (E is greater than 50 keV) protons in laboratory experiments. The polarization properties of a detection system consisting of 19 germanium crystals in a closed packed array are examined and the advantages of such a detector over Thompson scattering are discussed. The possiblity of using pair production to detect polarization of high energy gamma rays, and the associated modulation factors are discussed. The central difficulty involved in using pair production polarimeters in astrophysical applications is that the typical opening of the electron or positron direction with respect to the incident photon aircitron is small, of order E/sq mc. Multiple scattering in the material used to convert the photons to an electron positron pair causes deviations in the direction of the electron and positron.

Long, K. S.; Novick, R.

1978-01-01

9

Gamma-gamma collider based on Compton back-scattering  

SciTech Connect

A {gamma}{gamma} collider would extend and complement the physics capability of a linear collider; e.g. it would be suitable for direct measurement of the partial decay width of a Higgs boson into two gamma quanta. This paper discusses choice of laser parameters, luminosity optimization, electron and laser parameters for a gamma- gamma collider as a second interaction region for the Next Linear Collider, laser path, and the lasers. It is concluded that a gamma- gamma collider is technically feasible; however it will require a significant investment in preparatory R&D.

Kim, Kwang-Je; Gamma-Gamma Working Group

1996-08-01

10

Photo-nuclear Science using laser Compton scattering gamma-rays in JAEA  

NASA Astrophysics Data System (ADS)

The laser Compton scattering gamma-rays are a new generation of gamma-rays which have advantages of tunable energy, high energy resolution, and almost 100% polarization. These gamma-rays have been used for wide fields as nuclear physics, nuclear astrophysics, and atomic energy engineering. One of the most important topics is a management of nuclear waste. We have proposed a novel non-destructive assay method for isotopes using nuclear resonance fluorescence measurement with the Compton scattering gamma-rays. This assay system is useful for the nuclear waste management. We have successfully demonstrated the detection of a target isotope hidden in heavy metals. We used these gamma-rays for the study of the nuclear physics and nuclear astrophysics. We also have developed a new Compton scattering gamma-ray source with an energy region of sub-MeV.

Hayakawa, Takehito; Hajima, Ryoichi

2008-06-01

11

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

12

Compton Scattering  

NSDL National Science Digital Library

The purpose of this experiment is to verify the energy dependence of gamma radiation upon scattering angle and to compare the differential cross section obtained from the data with those calculated using the Klein-Nishina formula and classical theory.

2012-03-25

13

Gamma-Ray Compton Scattering: Experimental Compton Profiles for He, N2, Ar, and Kr  

NASA Astrophysics Data System (ADS)

A technique is described for measuring Compton profiles using a Te123m 160-keV ?-ray source together with a Li-drifted-germanium detector. By studying He and N2, whose Compton profiles have been previously measured using x rays and theoretically calculated, it is found that the ?-ray technique gives results which agree with both the theory and the previous x-ray measurements. Measured Compton profiles for Ar and Kr are also presented. These results would have been almost impossible to obtain by the x-ray technique because of the large photoelectric absorption of the low-energy x rays. The Ar and Kr results are compared with atomic Hartree-Fock calculations and found to agree at q=0 within experimental error which is less than 1%. As a result of these studies, it is concluded that all elements and their compounds can now be studied by Compton scattering.

Eisenberger, P.; Reed, W. A.

1972-05-01

14

Deutron binding energy and energy loss by gamma rays in water from Compton scattering  

Microsoft Academic Search

In attempting to understand the low value for the binding energy of the deuteron obtained by Mohahan, Raboy and Trail using a scintillation spectrometer, an experiment was performed to determine the effect of Compton scattering by water of gamma rays from a distributed source closely simulating the source of capture gamma rays. The correction obtained in this way was identical

Benjamin E. Chi; Berol L. Robinson

1967-01-01

15

Quality Control of Pavements and Tarmacs Using ({sup 137}Cs){gamma} Compton Scattering  

SciTech Connect

The {gamma} Compton scattering over a volume of concrete has been studied in order to design an instrument for density measurements. It will be used for the quality control in road construction, where large surfaces must be monitored. The experimental results and Monte Carlo simulations of the {gamma} Compton scattering over homogeneous and inhomogeneous volumes of concrete are shown. MC simulations have been useful to optimize the values of several parameters to improve the experimental set up and to estimate the extension of the explored volume.

Pino, F.; Barros, H.; Bernal, M.; Sajo-Bohus, L.; Palacios, D.; Greaves, E. D.; Viesti, G. [Nuclear Physics Laboratory, Simon Bolivar University, Caracas (Venezuela, Bolivarian Republic of)

2010-08-04

16

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... understood, phenomena. Thus, if a homogeneous beam of gamma rays of wavelength Q, falls on an atom in which all the electrons are at rest, the Compton-scattered gamma ray should have a single wavelength, (1. 1) where the length h/m c is called...

Nha, Sang Kyun

2012-06-07

17

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

18

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

19

Compton scattering tomography  

NASA Astrophysics Data System (ADS)

When a fan beam of monoenergetic gamma rays is emitted from a point source into a plane and the scattered photons are recorded by a point detector, the locus of points over which singly Compton-scattered photons suffer the same energy loss is a circle passing through the source and detector points. Thus, the number of scattered photons recorded at a particular detector and energy can be expressed as a weighted line integral of the electron density over a circular path uniquely determined by the energy and the detector location. This defines a novel tomographic reconstruction problem in which, by recording the number of scattered photons as a function of energy and detector position, an image of electron density can be reconstructed from measurements of its line integrals over many overlapping circular paths. It is shown here that this image reconstruction problem has an analytical solution which bears some resemblance to the filtered-backprojection algorithm used in conventional (transmission) computed tomography (CT). A tomographic imaging scheme based on this idea would have several potential advantages over conventional CT systems in the field of industrial nondestructive evaluation, e.g., the ability to image from one side of the object, and the absence of moving parts.

Norton, Stephen J.

1994-08-01

20

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

Microsoft Academic Search

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

Volodymyr Romanov; Victor Grubsky; Ned Patton; Tomasz Jannson

2011-01-01

21

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

22

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

23

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

24

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

25

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

PubMed

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

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

2013-05-01

26

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

27

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

NASA Astrophysics Data System (ADS)

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 (104 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 InfrastructureNuclear 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.; Alesini, D.; Antici, P.; Bellaveglia, M.; Boni, R.; Chiadroni, E.; Cianchi, A.; Curatolo, C.; Di Pirro, G.; Esposito, A.; Ferrario, M.; Gallo, A.; Gatti, G.; Ghigo, A.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Petrillo, V.; Pompili, R.; Ronsivalle, C.; Rossi, A. R.; Serafini, L.; Spataro, B.; Tomassini, P.; Vaccarezza, C.

2013-05-01

28

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

29

Weak deeply virtual Compton scattering  

NASA Astrophysics Data System (ADS)

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.

Psaker, A.; Melnitchouk, W.; Radyushkin, A. V.

2007-03-01

30

Timelike Compton Scattering at Jlab  

SciTech Connect

It is demonstrated, that with exclusive final state, data from electron scattering experiments that are recorded with loose trigger requirements can be used to analyze photoproduction reactions. A preliminary results on Timelike Compton Scattering using the electroproduction data from the CLAS detector at Jefferson Lab are presented. In particular, using final state (pe{sup -}e{sup +}) photoproduction of vector mesons and timelike photon is studied. Angular asymmetries in Timelike Compton Scattering region is compared with model predictions in the framework of Generalized Parton Distribution.

Paremuzyan, Rafayel G. [Institut de Physique Nucleaire, Orsay (France)

2014-01-01

31

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

32

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

33

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

34

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

35

Compton scattering in strong magnetic fields  

NASA Technical Reports Server (NTRS)

The relativistic cross section for Compton scattering by electrons in strong magnetic fields is derived. The results confirm and extend earlier work which has treated only transitions to the lowest or first excited Landau levels. For the teragauss field strengths expected in neutron star magnetospheres, the relative rates for excited state transitions are found to be significant, especially for incident photon energies several times the cyclotron frequency. Since these transitions must result in the rapid emission of one or more cyclotron photons as well as the Compton-scattered photon, the scattering process actually becomes a photon 'splitting' mechanism which acts to soften hard photon spectra, and also provides a specific mechanism for populating higher Landau levels in the electron distribution function. The results should be significant for models of gamma-ray bursters and pulsating X-ray sources.

Daugherty, Joseph K.; Harding, Alice K.

1986-01-01

36

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

37

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

38

On Compton Scattering Scenarios for Blazar Flares  

E-print Network

The synchrotron reflection scenario recently proposed to explain $\\gamma$-ray flares observed from blazar jets is studied. Our analysis takes into account the angular distribution of the beamed radiation, the finite extent of the scattering region, and light travel-time effects. We compare energy densities and powers for synchrotron, SSC, reflected synchrotron (RSy), and external Compton (EC) scattering processes. If the width of the scattering layer is much larger than $\\Gamma R^\\prime_B$, where $\\Gamma$ and $ R^\\prime_B$ denote the bulk Lorentz factor and comoving-frame radius of the plasma blob, respectively, then the ratio of the RSy and synchrotron energy densities $\\sim 4 \\Gamma^3 n_{BLR} \\sigma_{T} R^\\prime_B$, where $n_{BLR}$ is the mean particle density in the broad line region (BLR). Our results imply that Thomson-thick scattering regions of narrow extent must be present for the synchrotron reflection mechanism to operate effectively. This process seems unlikely to cause flares in lineless BL Lac so...

Bttcher, M

1998-01-01

39

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

40

Compton scattering in terrestrial gamma-ray flashes detected with the Fermi gamma-ray burst monitor  

NASA Astrophysics Data System (ADS)

Terrestrial gamma-ray flashes (TGFs) are short intense flashes of gamma rays associated with lightning activity in thunderstorms. Using Monte Carlo simulations of the relativistic runaway electron avalanche (RREA) process, theoretical predictions for the temporal and spectral evolution of TGFs are compared to observations made with the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope. Assuming a single source altitude of 15 km, a comparison of simulations to data is performed for a range of empirically chosen source electron variation time scales. The data exhibit a clear softening with increased source distance, in qualitative agreement with theoretical predictions. The simulated spectra follow this trend in the data, but tend to underestimate the observed hardness. Such a discrepancy may imply that the basic RREA model is not sufficient. Alternatively, a TGF beam that is tilted with respect to the zenith could produce an evolution with source distance that is compatible with the data. Based on these results, we propose that the source electron distributions of TGFs observed by GBM vary on time scales of at least tens of microseconds, with an upper limit of 100 ?s.

Fitzpatrick, Gerard; Cramer, Eric; McBreen, Sheila; Briggs, Michael S.; Foley, Suzanne; Tierney, David; Chaplin, Vandiver L.; Connaughton, Valerie; Stanbro, Matthew; Xiong, Shaolin; Dwyer, Joseph; Fishman, Gerald J.; Roberts, Oliver J.; von Kienlin, Andreas

2014-08-01

41

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

42

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

43

Real Compton scattering via color dipoles  

SciTech Connect

We study the photoabsorption reaction and real Compton scattering within the color dipole model. We rely on a photon wave function derived in the instanton-vacuum model and on the energy-dependent phenomenological elastic dipole amplitude. Data for the photoabsorption cross section at high energies agree with our parameter-free calculations. We also provide predictions for the differential real Compton scattering cross section. Although no data for small angle Compton scattering are available so far, this process can be measured in ultraperipheral hadronic and nuclear collisions at the LHC.

Kopeliovich, B. Z. [Departamento de Fisica, Centro de Estudios Subatomicos, y Centro Cientifico-Tecnologico de Valparaiso, Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile); Joint Institute for Nuclear Research, Dubna (Russian Federation); Schmidt, Ivan; Siddikov, M. [Departamento de Fisica, Centro de Estudios Subatomicos, y Centro Cientifico-Tecnologico de Valparaiso, Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile)

2009-09-01

44

Measurements of astrophysical polarization using Compton scattering  

NASA Astrophysics Data System (ADS)

The Polarized Gamma-ray Explorer (PoGOLite) is a balloon-borne instrument designed to measure polarization in the energy range 25-80 keV from many classes of astronomical objects, including pulsars, accretion discs and astrophysical jets. Using coincident detection of Compton scattering and photoelectric absorption in an array of 217 detector cells, the modulation in scattering angles can be determined. By this technique, the instrument will be able to measure as low as 10% polarization from a 200 mCrab source in a 6-h flight at an altitude of 40 km.The maiden flight of a 61-unit pathfinder instrument is scheduled to take place from the Esrange ballooning facility in northern Sweden in mid-2011. This flight will focus on measuring polarization from the Crab nebula and possibly Cygnus X-1, as well as to study the in-flight background caused by cosmic ray particles, X-ray and gamma-ray photons, and albedo neutrons. In order to reject such background, the instrument features a combination of active and passive shielding, as well as both active and passive collimation of the incident photons.Here, the design and status of the PoGOLite pathfinder instrument will be reviewed. Pre-flight calibration and performance tests will also be presented.

Kiss, M.; PoGOLite Collaboration

2011-08-01

45

Compton scattering and the study of electron momentum density distributions  

NASA Astrophysics Data System (ADS)

The Doppler-broadening experienced by photons Compton scattered from bound electrons allows the momentum distribution of the target to be probed. The Compton profile so obtained turns out to be sensitive to the wave-mechanical description of the scatterer and has therefore been exploited, for example, to check band theoretical models of solids, to identify electron correlation effects and most recently to extract Fermi surface topography. The technique has suffered from the low photon energy and lack of monochromaticity of X-ray tube sources and the weakness of gamma emitting isotopes. Both these problems have been circumvented with the use of synchrotron radiation which has the added benefit of allowing spin densities to be studied through the extraction of circularly polarised photons. In this paper the interpretation of Compton line-shapes within the Impulse Approximation will be discussed and illustrated with a selection of recent results.

Cooper, Malcolm J.

1997-07-01

46

Compton scattering study of the electronic structure of magnesium hydride  

NASA Astrophysics Data System (ADS)

Compton scattering measurements have been made on magnesium hydride (MgH2) using the 59.54-keV gamma rays from a 300-mCi 241Am source at a scattering angle of 150. Two different theoretical approaches have been used for comparison with the experimental data. In the first approach, the Compton profile of the valence electrons in MgH2 was calculated by the pseudopotential orthogonalized-plane-wave (OPW) method, including core orthogonalization. In the second approach, the Compton profile of MgH2 was calculated using the tight-binding linear combination of atomic orbitals (LCAO) method, including large overlaps. Both calculations yielded profiles which are in fairly good agreement with the experimental isotropic profile. The results indicate that the ionic picture of MgH2 is not simple since its outer electrons are extended. Possible implications of the production process of the hydride are briefly discussed.

Felsteiner, J.; Heilper, M.; Gertner, I.; Tanner, A. C.; Opher, R.; Berggren, K.-F.

1981-05-01

47

Compton Electrons and Electromagnetic Pulse in Supernovae and Gamma-Ray Bursts  

E-print Network

When gamma-rays emerge from a central source they may undergo Compton scattering in surrounding matter. The resulting Compton-scattered electrons radiate. Coherent radiation by such Compton electrons follows nuclear explosions above the Earth's atmosphere. Particle acceleration in instabilities produced by Compton electron currents may explain the radio emission by SN1998bw. Bounds on coherent radiation are suggested for supernovae and gamma-ray bursts; these bounds are very high, but it is unknown if coherent radiation occurs in these objects.

J. I. Katz

1999-08-19

48

Quark-nucleon dynamics and deep virtual Compton scattering  

SciTech Connect

We consider deeply virtual Compton scattering and deep inelastic scattering in presence of Regge exchanges that are part of the nonperturbative quark-nucleon amplitude. In particular we discuss contribution from the Pomeron exchange and demonstrate how it leads to Regge scaling of the Compton amplitude. A new fit of the deeply virtual Compton scattering total cross section data in HERA kinematics is proposed.

Gorchtein, M. [Center for the Exploration of Energy and Matter, Indiana University, Bloomington, Indiana 47408 (United States); Szczepaniak, A. P. [Center for the Exploration of Energy and Matter, Indiana University, Bloomington, Indiana 47408 (United States); Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States)

2010-07-01

49

Compton scattering measurements from dense plasmas  

Microsoft Academic Search

Compton scattering techniques have 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

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

2008-01-01

50

Resonant Compton scattering associated with pair creation  

NASA Astrophysics Data System (ADS)

Studies of Compton scattering by relativistic electrons in a strong magnetic field have been restricted to either incident photon angles ?' aligned along the magnetic field B or incident photon energies ?' below the first pair creation threshold . When these restrictions are relaxed there is a resonance in Compton scattering associated with pair creation (PC), that is analogous to but independent of known resonances associated with gyromagnetic absorption (GA). As with the GA resonances, that may be labeled by the Landau quantum numbers of the relevant states, there is a sequence of PC resonances where the scattering cross section diverges. In this paper, the lowest divergence is studied for incident photon energies satisfying ?'2sin2 ?'/(2 eB)?1, assuming that the scattering electron is in its ground (Landau) state. This lowest resonance affects only parallel-polarized photons.

Weise, Jeanette I.

2014-06-01

51

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

52

Gamma-ray bursts from synchrotron self-Compton emission  

E-print Network

The emission mechanism of the gamma-ray bursts (GRBs) is still a matter of debates. The standard synchrotron energy spectrum of cooling electrons F_E ~ E^{-1/2} is much too soft to account for the majority of the observed spectral slopes. An alternative in the form of quasi-thermal Comptonization in a high compactness source has difficulties in reproducing the peak of the observed photon distribution below a few hundred keV. We show here that for typical parameters expected in the GRB ejecta the observed spectra in the 20-1000 keV BATSE energy range can be produced by inverse Compton scattering of the synchrotron radiation in a partially self-absorbed regime. If the particles are continuously accelerated/heated over the life-time of a source rather than being instantly injected, a prominent peak develops in their distribution at a Lorentz factor gamma ~ 30-100, where synchrotron and inverse-Compton losses are balanced by acceleration and heating due to synchrotron self-absorption. The synchrotron peak should be observed at 10-100 eV, while the self-absorbed low-energy tail with F_E ~ E^2 can produce the prompt optical emission (like in the case of GRB 990123). The first Compton scattering radiation by nearly monoenergetic electrons can then be as hard as F_E ~ E^1 reproducing the hardness of most of the observed GRB spectra. The second Compton peak should be observed in the high energy gamma-ray band, possibly being responsible for the emission detected by EGRET in GRB 941017. A significant electron-positron pair production reduces the available energy per particle, moving the spectral peaks to lower energies as the burst progresses. The regime is very robust, operates in a broad range of parameter space and can explain most of the observed GRB spectra and their temporal evolution.

Boris E. Stern; Juri Poutanen

2004-05-25

53

Nucleon Compton scattering in perturbative QCD  

NASA Astrophysics Data System (ADS)

We have computed the helicity amplitudes for the reactions ?N-->?N (N=p,n) at large momentum transfer to lowest order in perturbative QCD. Our cross section for proton Compton scattering shows good qualitative agreement with experimental data, when the proton is modeled by the Chernyak-Oglobin-Zhitnitsky, King-Sachrajda, or Gari-Stefanis distribution amplitude. Discrepancies between our results and previous calculations seem to be due to different treatments of numerical integration around singularities.

Kronfeld, A. S.; Nii?, B.

1991-12-01

54

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

55

Unitary constraints on Deeply Virtual Compton Scattering  

E-print Network

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

2007-08-09

56

The Mathematical Foundations of 3D Compton Scatter Emission Imaging  

PubMed Central

The mathematical principles of tomographic imaging using detected (unscattered) X- or gamma-rays are based on the two-dimensional Radon transform and many of its variants. In this paper, we show that two new generalizations, called conical Radon transforms, are related to three-dimensional imaging processes based on detected Compton scattered radiation. The first class of conical Radon transform has been introduced recently to support imaging principles of collimated detector systems. The second class is new and is closely related to the Compton camera imaging principles and invertible under special conditions. As they are poised to play a major role in future designs of biomedical imaging systems, we present an account of their most important properties which may be relevant for active researchers in the field. PMID:18382608

Truong, T. T.; Nguyen, M. K.; Zaidi, H.

2007-01-01

57

Proton spin polarizabilities from polarized Compton scattering  

SciTech Connect

Polarized Compton scattering off the proton is studied within the framework of subtracted dispersion relations for photon energies up to 300 MeV. As a guideline for forthcoming experiments, we focus the attention on the role of the proton's spin polarizabilities and investigate the most favorable conditions to extract them with a minimum of model dependence. We conclude that a complete separation of the four spin polarizabilities is possible, at photon energies between threshold and the $\\Delta(1232)$ region, provided one can achieve polarization measurements with an accuracy of a few percent.

B. Pasquini; D. Drechsel; M. Vanderhaeghen

2007-07-01

58

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

59

Timelike Virtual Compton Scattering from Electron-Positron Radiative Annihilation  

SciTech Connect

We propose measurements of the deeply virtual Compton amplitude (DVCS) {gamma}* {yields} H{bar H}{gamma} in the timelike t = (p{sub H} + p{sub {bar H}}){sup 2} > 0 kinematic domain which is accessible at electron-positron colliders via the radiative annihilation process e{sup +}e{sup -} {yields} H{bar H}{gamma}. These processes allow the measurement of timelike deeply virtual Compton scattering for a variety of H{bar H} hadron pairs such as {pi}{sup +}{pi}{sup -}, K{sup +}K{sup -}, and D{bar D} as well as p{bar p}. As in the conventional spacelike DVCS, there are interfering coherent amplitudes contributing to the timelike processes involving C = - form factors. The interference between the amplitudes measures the phase of the C = + timelike DVCS amplitude relative to the phase of the timelike form factors and can be isolated by considering the forward-backward e{sup +} {leftrightarrow} e{sup -} asymmetry. The J = 0 fixed pole contribution which arises from the local coupling of the two photons to the quark current plays a special role. As an example we present a simple model.

Afanasev, Andrei; /Hampton U. /Jefferson Lab; Brodsky, Stanley J.; /SLAC; Carlson, Carl E.; /William-Mary Coll.; Mukherjee, Asmita; /Indian Inst. Tech., Mumbai

2009-03-31

60

Virtual Nucleon Compton Scattering in Perturbative QCD  

NASA Astrophysics Data System (ADS)

Results of perturbative calculation for nucleon Compton scattering are presented. The calculations consider both the case of the incoming photon being real and the case of the incoming photon being virtual. Hard scattering amplitudes are calculated using a software package developed at NC State University footnote[1]A. Pang and C.-R. Ji, Computers in Physics Vol 9 (No. 6), Nov/Dec 1995 p589-593footnote[2]A. Pang and C.-R. Ji, J. Comp. Phys. 115, 267 (1994). The integrations required to calculate total cross section are made following the approach of Kronfeld and Nizicfootnote[3]A. Kronfeld and B. Nizic, Phys. Rev. D 44, 3445 (1991). Poles are split into a real principal part plus an imaginary delta function. The delta functions are evaluated explicitly by hand; principal part integrations are evaluated numerically, after making a variable transformation to render the integrand finite over the range of integration. For the real photon case, there are five previous calculations to consider, each of which produced a different resultfootnote[3]A. Kronfeld and B. Nizic, Phys. Rev. D 44, 3445 (1991)footnote[4]E. Maina and G. Farrar, Phys. Lett. B 206, 120 (1988)footnote[5]G. Farrar and H. Zhang, Phys. Rev. D 41, 3348 (1990)footnote[6]M. Vanderhaeghen, P. Guichon, and J. Van de Wiele, presented at workshop on virtual Compton scattering, Clermont-Ferrand, France, 1996footnote[7]T. Brooks and L. Dixon, Phys. Rev. D 62, 114021 (2000). There is an agreement with the results of Brooks and Dixonfootnote[7]T. Brooks and L. Dixon, Phys. Rev. D 62, 114021 (2000). For the virtual photon case, the new result is compared with that of Farrar and Zhang footnote[5]G. Farrar and H. Zhang, Phys. Rev. D 41, 3348 (1990). Since there are differences, we discuss which result is more believable and why. For the deeply virtual case (DVCS), comparison is made with other non-pertubative methods using GPDs.

Thomson, Richard; Ji, Chueng-Ryong

2004-10-01

61

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

62

Gamma-Ray Studies of Blazars: Synchro-Compton Analysis of Flat Spectrum Radio Quasars  

E-print Network

We extend a method for modeling synchrotron and synchrotron self-Compton radiations in blazar jets to include external Compton processes. The basic model assumption is that the blazar radio through soft X-ray flux is nonthermal synchrotron radiation emitted by isotropically-distributed electrons in the randomly directed magnetic field of outflowing relativistic blazar jet plasma. Thus the electron distribution is given by the synchrotron spectrum, depending only on the Doppler factor $\\delta_{\\rm D}$ and mean magnetic field $B$, given that the comoving emission region size scale $R_b^\\prime \\lesssim c \\dD t_v/(1+z)$, where $t_v$ is variability time and $z$ is source redshift. Generalizing the approach of Georganopoulos, Kirk, and Mastichiadis (2001) to arbitrary anisotropic target radiation fields, we use the electron spectrum implied by the synchrotron component to derive accurate Compton-scattered $\\gamma$-ray spectra throughout the Thomson and Klein-Nishina regimes for external Compton scattering processes. We derive and calculate accurate $\\gamma$-ray spectra produced by relativistic electrons that Compton-scatter (i) a point source of radiation located radially behind the jet, (ii) photons from a thermal Shakura-Sunyaev accretion disk and (iii) target photons from the central source scattered by a spherically-symmetric shell of broad line region (BLR) gas. Calculations of broadband spectral energy distributions from the radio through $\\gamma$-ray regimes are presented, which include self-consistent $\\gamma\\gamma$ absorption on the same radiation fields that provide target photons for Compton scattering. Application of this baseline flat spectrum radio/$\\gamma$-ray quasar model is considered in view of data from $\\gamma$-ray telescopes and contemporaneous multi-wavelength campaigns.

Charles D. Dermer; Justin D. Finke; Hannah Krug; Markus Boettcher

2008-08-25

63

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

64

Deuteron Compton scattering below pion photoproduction threshold  

E-print Network

Deuteron Compton scattering below pion photoproduction threshold is considered in the framework of the nonrelativistic diagrammatic approach with the Bonn OBE potential. A complete gauge-invariant set of diagrams is taken into account which includes resonance diagrams without and with NN-rescattering and diagrams with one- and two-body seagulls. The seagull operators are analyzed in detail, and their relations with free- and bound-nucleon polarizabilities is discussed. It is found that both dipole and higher-order polarizabilities of the nucleon are needed for a quantitative description of recent experimental data. An estimate of the isospin-averaged dipole electromagnetic polarizabilities of the nucleon and the polarizabilities of the neutron is obtained from the data.

M. I. Levchuk; A. I. L'vov

1999-09-28

65

Deuteron Compton scattering below pion photoproduction threshold  

E-print Network

Deuteron Compton scattering below pion photoproduction threshold is considered in the framework of the nonrelativistic diagrammatic approach with the Bonn OBE potential. A complete gauge-invariant set of diagrams is taken into account which includes resonance diagrams without and with NN-rescattering and diagrams with one- and two-body seagulls. The seagull operators are analyzed in detail, and their relations with free- and bound-nucleon polarizabilities is discussed. It is found that both dipole and higher-order polarizabilities of the nucleon are needed for a quantitative description of recent experimental data. An estimate of the isospin-averaged dipole electromagnetic polarizabilities of the nucleon and the polarizabilities of the neutron is obtained from the data.

Levchuk, M I

2000-01-01

66

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

67

Deeply Virtual Compton Scattering off Helium  

NASA Astrophysics Data System (ADS)

Deeply Virtual Compton Scattering (DVCS) is privileged tool to access the partonic structure of hadrons encoded via the so-called Generalized Parton Distributions (GPDs). Similarly to the scattering of light by a material, DVCS provides information about the dynamics and the spatial structure of hadrons. Whether the target nucleus remains intact or not after the reaction, DVCS off a nuclear target allows to address the partonic structure of the nucleus as well as the partonic structure of nucleons embedded in the nuclear medium. Adding transverse degrees of freedom to conventional deep inelastic scattering, these exclusive channels are expected to bring sensitive information about the origin of the EMC effect. The eg6 experiment at the Jefferson Laboratory did explore nuclear DVCS off ^4He. The experimental asymmetry of the DVCS reaction with respect to the electron beam polarization was measured for the coherent and incoherent channels with the CLAS detector, complemented with a small angle electromagnetic calorimeter and a radial time projection chamber. This talk reviews the experimental methods and techniques of the eg6 run, and discusses the preliminary results of DVXS measurements.

Voutier, Eric

2012-03-01

68

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

69

Spin filter in deeply virtual Compton scattering amplitudes  

SciTech Connect

Whether the kinematics includes the hard transverse photon momenta or not makes a dramatic difference in computing deeply virtual Compton scattering in terms of the widely used reduced operators that define generalized parton distributions. Our tree-level complete deeply virtual Compton scattering amplitude including the lepton current plays the role of spin filter to analyze such kinematic dependence on the contribution of longitudinally polarized virtual photon as well as the conservation of angular momentum.

Bakker, Bernard L. G. [Department of Physics and Astrophysics, Vrije Universiteit, Amsterdam (Netherlands); Ji, Chueng-Ryong [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202 (United States)

2011-05-01

70

Measurement of radiative Bhabha and quasi-real Compton scattering  

Microsoft Academic Search

We report on a study of radiative Bhabha and quasi-real Compton scattering at centre-of-mass energies between 50 GeV and 170 GeV, and 20 GeV and 140 GeV, respectively, using the L3 detector at LEP. The analysis is based on data corresponding to an integrated luminosity of 232.2pb?1. A total of 2856 radiative Bhabha and 4641 Compton scattering events are collected.

M. Acciarri; O. Adriani; M. Aguilar-Benitez; S P Ahlen; J. Alcaraz; G. Alemanni; James V Allaby; A. Aloisio; M. G. Alviggi; H. Anderhub; V. P. Andreev; T. Angelescu; F. Anselmo; A. Arefiev; T. Azemoon; P. Bagnaia; L. Baksay; S. Banerjee; K. Banicz; A. Barczyk; R. Barillre; L. Barone; P. Bartalini; A. Baschirotto; M. Basile; R. Battiston; A. Bay; F. Becattini; U. Becker; F. Behner; J. Berdugo; P. Berges; B. Bertucci; S. Bhattacharya; M. Biasini; A. Biland; G. M. Bilei; J. J. Blaising; S. C. Blyth; Gerjan J Bobbink; R K Bck; A. Bhm; L. Boldizsar; B. Borgia; D. Bourilkov; Maurice Bourquin; S. Braccini; J. G. Branson; V. Brigljevic; I. C. Brock; A. Buffini; J. D. Burger; W. J. Burger; A. Button; X. D. Cai; M. Campanelli; M. Campanelli; G. Cara Romeo; A. M. Cartacci; J. Casaus; G. Castellini; F. Cavallari; N. Cavallo; C. Cecchi; M. Cerrada; F. Cesaroni; M. Chamizo; Y. H. Chang; U. K. Chaturvedi; M. Chemarin; A. Chen; G M Chen; H. F. Chen; H. S. Chen; X. Chereau; G. Chiefari; C. Y. Chien; L. Cifarelli; F. Cindolo; C. Civinini; I. Clare; G. Coignet; A. P. Colijn; N. Colino; S. Costantini; F. Cotorobai; B. de la Cruz; A. Csilling; T. S. Dai; R. D'Alessandro; R. de Asmundis; A. Degr; K. Deiters; D. della Volpe; P. Denes; F. DeNotaristefani; M. Diemoz; D. van Dierendonck; F. Di Lodovico; C. Dionisi; M. Dittmar; A. Dominguez; M. T. Dova; D. Duchesneau; P. Duinker; I. Duran; S. Easo; H. El Mamouni; A. Engler; F. J. Eppling; F. C. Ern; J. P. Ernenwein; M. Fabre; R. Faccini; M. A. Falagan; S. Falciano; A. Favara; J. Fay; O. Fedin; M. Felcini; T. Ferguson; F. Ferroni; H. Fesefeldt; E. Fiandrini; J. H. Field; F. Filthaut; P. H. Fisher; I. Fisk; G. Forconi; L. Fredj; K. Freudenreich; C. Furetta; Yu. Galaktionov; S. N. Ganguli; P. Garcia-Abia; M. Gataullin; S Gentile; N. Gheordanescu; S Goldfarb; J. Goldstein; Z. F. Gong; A. Gougas; G. Gratta; M. W. Gruenewald; R. van Gulik; V. K. Gupta; A. Gurtu; L. J. Gutay; D. Haas; B. Hartmann; A. Hasan; D. Hatzifotiadou; T. Hebbeker; A. Herv; P. Hidas; J. Hirschfelder; W. C. van Hoek; H Hoorani; S. R. Hou; G. Hu; I. Iashvili; B. N. Jin; L. W. Jones; P. de Jong; I. Josa-Mutuberria; R. A. Khan; D. Kamrad; J. S. Kapustinsky; M. Kaur; M. N. Kienzle-Focacci; D. Kim; J. K. Kim; S. C. Kim; W. W. Kinnison; A. Kirkby; D. Kirkby; J. Kirkby; D. Kiss; W. Kittel; A. Klimentov; A C Knig; I. Korolko; V. Koutsenko; R. W. Kraemer; A. Kunin; P. Lacentre; P. Ladron de Guevara; I. Laktineh; G. Landi; C. Lapoint; K. Lassila-Perini; P. Laurikainen; A. Lavorato; M. Lebeau; A. Lebedev; P. Lebrun; P. Lecomte; P. Le Coultre; H. J. Lee; J. M. Le Goff; R. Leiste; E. Leonardi; P. Levtchenko; C. Li; C. H. Lin; W. T. Lin; F. L. Linde; Z. A. Liu; W. Lohmann; E. Longo; W. Lu; Y. S. Lu; K. Lbelsmeyer; C. Luci; D. Luckey; L. Luminari; W. Lustermann; W. G. Ma; M. Maity; G. Majumder; L. Malgeri; A. Malinin; C. Maa; D. Mangeol; P. Marchesini; G. Marian; A. Marin; J. P. Martin; F. Marzano; G. G. G. Massaro; K. Mazumdar; R. R. McNeil; S. Mele; L. Merola; M. Meschini; W. J. Metzger; M. von der Mey; D. Migani; A. Mihul; A. J. W. van Mil; H. Milcent; G. Mirabelli; J. Mnich; P. Molnar; B. Monteleoni; R. Moore; T. Moulik; R. Mount; F. Muheim; A. J. M. Muijs; S. Nahn; M. Napolitano; F. Nessi-Tedaldi; H. Newman; T. Niessen; A. Nippe; A. Nisati; H. Nowak; Y. D. Oh; G. Organtini; R. Ostonen; S. Palit; C. Palomares; D. Pandoulas; S. Paoletti; P. Paolucci; H. K. Park; I. H. Park; G. Pascale; G. Passaleva; S. Patricelli; T. Paul; M. Pauluzzi; C. Paus; F. Pauss; D. Peach; Y. J. Pei; S. Pensotti; D. Perret-Gallix; B. Petersen; S. Petrak; A. Pevsner; D. Piccolo; M. Pieri; P. A. Pirou; E. Pistolesi; V. Plyaskin; M. Pohl; V. Pojidaev; H. Postema; J. Pothier; N. Produit; D. Prokofiev; J. Quartieri; G. Rahal-Callot; N. Raja; P. G. Rancoita; M. Rattaggi; G. Raven; P. Razis; D. Ren; M. Rescigno; S. Reucroft; T. van Rhee; K. Riles; A. Robohm; J. Rodin; B. P. Roe; L. Romero; S. Rosier-Lees; J. A. Rubio; D. Ruschmeier; H. Rykaczewski; J. Salicio; E. Sanchez; M. P. Sanders; M. E. Sarakinos; C. Schfer; V. Schegelsky; S. Schmidt-Kaerst; D. Schmitz; N. Scholz; H. Schopper; D. J. Schotanus; G. Schwering; C. Sciacca; D. Sciarrino; L. Servoli; S. Shevchenko; N. Shivarov; V. Shoutko; J. Shukla; E. Shumilov; A. Shvorob; T. Siedenburg; D. Son; B. Smith; P. Spillantini; M. Steuer; D. P. Stickland; A. Stone; H. Stone; B. Stoyanov; A. Straessner; K. Sudhakar; G. Sultanov; L. Z. Sun; G. F. Susinno; H. Suter; J. D. Swain; X. W. Tang; L. Tauscher; C. Timmermans; Samuel C. C. Ting; S. M. Ting; S. C. Tonwar; J. Tth; C. Tully; K. L. Tung; Y. Uchida; J. Ulbricht; E. Valente; G. Vesztergombi; I. Vetlitsky; G. Viertel; M. Vivargent; S. Vlachos; H. Vogel; H. Vogel; I. Vorobiev; A. A. Vorobyov; M. Wadhwa; W. Wallraff; J. C. Wang; X. L. Wang; Z. M. Wang; A. Weber; S. X. Wu; S. Wynhoff; J. Xu; Z. Z. Xu

1998-01-01

71

Scattering Summary/Review Spring 2009 Compton Lecture Series  

E-print Network

Scattering Summary/Review Spring 2009 Compton Lecture Series: From Quantum Mechanics to the String distributed range of impact parameters. ­ This beam is scattered into a distribution of angles. ­ The number of particles scattered into a given angular range depends on the shape of the potential hill. This is what

72

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

73

Threat Detection of Radioactive Contraband Incorporating Compton Scattering Physics: A Model-Based Processing Approach  

Microsoft Academic Search

The detection of radioactive contraband is a crit- ical problem in maintaining national security for any country. Gamma-ray emissions from threat materials challenge both detec- tion and measurement technologies significantly. The development of a sequential, model-based Bayesian processor that captures both the underlying transport physics of gamma-ray emissions including Compton scattering and the measurement of photon energies offers a physics-based

J. V. Candy; D. H. Chambers; E. F. Breitfeller; B. L. Guidry; J. M. Verbeke; M. A. Axelrod; K. E. Sale; A. M. Meyer

2011-01-01

74

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

75

136 3. Scattering The Compton scattering of an x-ray is incoherent because there are de-  

E-print Network

136 3. Scattering The Compton scattering of an x-ray is incoherent because there are de- grees of freedom in each scattering event associated with the atomic electron. Compton scattering provides of an atom are the ones that can participate in Compton scattering because they can be- come unbound from

76

Nucleon Compton scattering in the Dyson-Schwinger approach  

NASA Astrophysics Data System (ADS)

We analyze the nucleons Compton scattering amplitude in the Dyson-Schwinger/Faddeev approach. We calculate a subset of diagrams that implements the nonperturbative handbag contribution as well as all t-channel resonances. At the quark level, these ingredients are represented by the quark Compton vertex whose analytic properties we study in detail. We derive a general form for a fermion two-photon vertex that is consistent with its Ward-Takahashi identities and free of kinematic singularities, and we relate its transverse part to the on-shell nucleon Compton amplitude. We solve an inhomogeneous Bethe-Salpeter equation for the quark Compton vertex in rainbow-ladder truncation and implement it in the nucleon Compton scattering amplitude. The remaining ingredients are the dressed quark propagator and the nucleons bound-state amplitude which are consistently solved from Dyson-Schwinger and covariant Faddeev equations. We verify numerically that the resulting quark Compton vertex and nucleon Compton amplitude both reproduce the ??? transition form factor when the pion pole in the t channel is approached.

Eichmann, Gernot; Fischer, Christian S.

2013-02-01

77

Compton Gamma Ray Observatory/BATSE observations of energetic electrons scattered by cyclotron resonance with waves from powerful VLF transmitters. Final report, 13 October 1992-12 February 1994  

SciTech Connect

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 the authors 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, D.W.; Imhof, W.L.

1994-02-01

78

Compton X-ray and Gamma-ray Emission from Extended Radio Galaxies  

E-print Network

The extended lobes of radio galaxies are examined as sources of X-ray and gamma-ray emission via inverse Compton scattering of 3K background photons. The Compton spectra of two exemplary examples, Fornax A and Centaurus A, are estimated using available radio measurements in the ~10's MHz - 10's GHz range. For average lobe magnetic fields of >~0.3-1 micro-G, the lobe spectra are predicted to extend into the soft gamma-rays making them likely detectable with the GLAST LAT. If detected, their large angular extents (~1 deg and 8 deg) will make it possible to ``image'' the radio lobes in gamma-rays. Similarly, this process operates in more distant radio galaxies and the possibility that such systems will be detected as unresolved gamma-ray sources with GLAST is briefly considered.

C. C. Cheung

2007-04-06

79

Spin and orbital magnetization loops obtained using magnetic Compton scattering  

SciTech Connect

We present an application of magnetic Compton scattering (MCS) to decompose a total magnetization loop into spin and orbital magnetization contributions. A spin magnetization loop of SmAl{sub 2} was measured by recording the intensity of magnetic Compton scattering as a function of applied magnetic field. Comparing the spin magnetization loop with the total magnetization one measured by a vibrating sample magnetometer, the orbital magnetization loop was obtained. The data display an anti-coupled behavior between the spin and orbital magnetizations and confirm that the orbital part dominates the magnetization.

Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan)] [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Koizumi, A. [Graduate School of Materials Science, University of Hyogo, Hyogo 678-1297 (Japan)] [Graduate School of Materials Science, University of Hyogo, Hyogo 678-1297 (Japan)

2013-02-25

80

Generation of laser Compton gamma-rays in the SAGA light source storage ring  

Microsoft Academic Search

A medium-scale synchrotron light source of GeV-class equipped with an infrared high-power laser can generate stable high-flux gamma-rays at several MeV via laser Compton scattering. We constructed an experimental setup for high-flux gamma-ray generation in the SAGA light source storage ring. A head-on collision between a 1.4GeV electron beam and laser photons with a 10.6?m wavelength produced gamma-rays up to

T. Kaneyasu; Y. Takabayashi; Y. Iwasaki; S. Koda

2011-01-01

81

NLO Corrections to Deeply-Virtual Compton Scattering  

E-print Network

We have calculated the NLO corrections to the twist-2 part of the deeply-virtual Compton scattering amplitude. Our results for the transverse and antisymmetric parts agree with recent calculations by Ji and Osborne and by Belitsky and M\\"uller. In addition we present NLO results for the longitudinal part of the amplitude.

L. Mankiewicz; G. Piller; E. Stein; M. Vnttinen; T. Weigl

1997-12-03

82

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

83

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

84

Nuclear photoabsorption and Compton scattering at intermediate energy  

Microsoft Academic Search

Intermediate energy nuclear photoabsorption and Compton scattering within the ..delta..-hole approach are studied. The same ..delta..-nucleus dynamics used to describe a variety of pion-induced reactions are employed. A dynamical model for the photon-nucleon amplitude is constructed, including both resonant-channel and nonresonant backgrounds in addition to ..delta..-excitation. Medium corrections to the full amplitude are included for nuclear scattering. A doorway state

J. H. Koch; E. J. Moniz; N. Ohtsuka

1984-01-01

85

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

NASA Astrophysics Data System (ADS)

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.; Gunter, D.; Plimley, B.; Pavlovsky, R.; Vetter, K.

2014-11-01

86

Evaluation of Compton scattering sequence reconstruction algorithms for a portable position sensitive radioactivity detector based on pixelated Cd(Zn)Te crystals  

E-print Network

We present extensive simulation studies on the performance of algorithms for the Compton sequence reconstruction used for the development of a portable spectroscopic instrument (COCAE), with the capability to localize and identify radioactive sources, by exploiting the Compton scattering imaging. Various Compton Sequence reconstruction algorithms have been compared using a large number of simulated events. These algorithms are based on Compton kinematics, as well as on statistical test criteria that exploit the redundant information of events having two or more photon interactions in the active detector's volume. The efficiency of the best performing technique is estimated for a wide range of incident gamma-ray photons emitted from point-like gamma sources.

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

2010-11-11

87

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

88

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

89

Generalized Parton Distributions from Deep Virtual Compton Scattering at CLAS  

SciTech Connect

We have analyzed the beam spin asymmetry and the longitudinally polarized target spin asymmetry of the Deep Virtual Compton Scattering process, recently measured by the Jefferson Lab CLAS collaboration. Our aim is to extract information about the Generalized Parton Distributions of the proton. By fitting these data, in a largely model-independent procedure, we are able to extract numerical values for the two Compton Form Factors $H_{Im}$ and $\\tilde{H}_{Im}$ with uncertainties, in average, of the order of 30%.

M. Guidal

2010-05-01

90

The effect of an external electric field on radiation transmission and Compton scattering in plexiglass  

NASA Astrophysics Data System (ADS)

The effect of an external electric field on radiation transmission of a plexiglass sample has been studied by using an extremely narrow-collimated-beam transmission method. Also, the photon scattering properties of the charge centers have been determined by changing the charge density distributions of the plexiglass sample with an external electric field having an intensity in the range 0-1000 V/cm. The plexiglass sample was bombarded by 59.5 keV gamma rays emitted from an Am-241 point source. The transmitted and Compton scattered photons were detected by a Si(Li) detector. Appreciable variations were observed in the transmission factors of the plexiglass sample as a function of applied field. The results show that the electrical properties of the plexiglass sample changes with the applied electric field and the gamma ray irradiations although it is a dielectric material. Furthermore, the negatively charged scattering centers are slightly more effective than the positively charged scattering centers in the Compton scattering of gamma rays from an insulator sample, similar to result found for conductor and semiconductors.

Demir, D.

2008-04-01

91

Measurements of the Proton Spin Polarizabilities with Double-Polarized Compton Scattering  

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. Werthmller; M. Wolfes

2014-08-07

92

GAMMA-RAY COMPTON LIGHT SOURCE DEVELOPMENT AT LLNL  

SciTech Connect

A new class of tunable, monochromatic {gamma}-ray sources capable of operating at high peak and average brightness is currently being developed at LLNL for nuclear photoscience and applications. These novel systems are based on Compton scattering of laser photons by a high brightness relativistic electron beam produced by an rf photoinjector. A prototype, capable of producing > 10{sup 8} 0.7 MeV photons in a single shot, with a fractional bandwidth of 1%, and a repetition rate of 10 Hz, is currently under construction at LLNL; this system will be used to perform nuclear resonance fluorescence experiments. A new symmetrized S-band rf gun, using a Mg photocathode, will produce up to 1 nC of charge in an 8 ps bunch, with a normalized emittance modeled at 0.8 mm.mrad; electrons are subsequently accelerated up to 120 MeV to interact with a 500 mJ, 10 ps, 355 nm laser pulse and generate {gamma}-rays. The laser front end is a fiber-based system, using corrugated-fiber Bragg gratings for stretching, and drives both the frequency-quadrupled photocathode illumination laser and the Nd:YAG interaction laser. Two new technologies are used in the laser: a hyper-Michelson temporal pulse stacker capable of producing 8 ps square UV pulses, and a hyper-dispersion compressor for the interaction laser. Other key technologies, basic scaling laws, and recent experimental results will also be presented, along with an overview of future research and development directions.

Hartemann, F V; Anderson, S G; Gibson, D J; Hagmann, C A; Johnson, M S; Jovanovic, I; Messerly, M J; Pruet, J A; Shverdin, M Y; Tremaine, A M; McNabb, D P; Siders, C W; Barty, C J

2007-08-15

93

Attosecond neutron Compton scattering from protons  

E-print Network

The effect of "anomalous" scattering of neutrons and electrons from protons in the electron-volt energy-transfer range is considered, and related experimental results are mentioned. A recent independent confirmation of this effect with a new data analysis procedure is presented. Due to the very short characteristic scattering time, there is no well defined separation of time scales of electronic and protonic motions. An outline of a proposed theoretical interpretation is presented, which is based on the fact that scattering protons represent \\textit{open} quantum systems, thus being subject to decoherence.

C. Aris Chatzidimitriou-Dreismann

2007-02-01

94

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

E-print Network

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 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 c...

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

2014-01-01

95

Backward Compton Scattering in Strong Uniform Magnetic Field  

E-print Network

In strong uniform magnetic field, the vacuum Non-Commutative Plane (NCP) caused by the lowest Landau level(LLL) effect and the QED with NCP (QED-NCP) are studied. Being similar to the theory of Quantum Hall effect, an effective filling factor $f(B)$ is introduced to character the possibility that the electrons stays on LLL. The backward Compton scattering amplitudes of QED-NCP are derived, and the differential cross sections for the process with polarized initial electrons and photons are calculated. The existing Spring-8's data has been analyzed primitively and some hints for QED-NCP effects are shown. We propose to precisely measure the differential cross sections of the backward Compton scattering in perpendicular magnetic field experimentally, which may lead to reveal the effects of QED-NCP. PACS number: 12.20.Ds; 11.10.Nx; 71.70.Di; 73.43.Fj.

Huang, W; Yan, M L; Huang, Wei; Xu, Wang; Yan, Mu-Lin

2006-01-01

96

Backward Compton Scattering in Strong Uniform Magnetic Field  

E-print Network

In strong uniform magnetic field, the vacuum Non-Commutative Plane (NCP) caused by the lowest Landau level(LLL) effect and the QED with NCP (QED-NCP) are studied. Being similar to the theory of Quantum Hall effect, an effective filling factor $f(B)$ is introduced to character the possibility that the electrons stays on LLL. The backward Compton scattering amplitudes of QED-NCP are derived, and the differential cross sections for the process with polarized initial electrons and photons are calculated. The existing Spring-8's data has been analyzed primitively and some hints for QED-NCP effects are shown. We propose to precisely measure the differential cross sections of the backward Compton scattering in perpendicular magnetic field experimentally, which may lead to reveal the effects of QED-NCP. PACS number: 12.20.Ds; 11.10.Nx; 71.70.Di; 73.43.Fj.

Wei Huang; Wang Xu; Mu-Lin Yan

2006-09-21

97

Timelike Compton Scattering from JLAB to RHIC and LHC energies  

E-print Network

Timelike Compton scattering (TCS) i.e. the exclusive photoproduction of a lepton pair with large invariant mass nicely complements the already successful experimental study of deeply virtual Compton scattering (DVCS). The same Generalized Parton Distributions enter both amplitudes, which offer a promissing way to access the quark and gluon nucleon structure. We review recent progress in this domain, emphasizing the fact that analyticity and factorization properties dictate the relation of the NLO corrections to TCS to those of DVCS. We also stress that data on TCS at high energy should be available soon thanks to the proposed experimental program at JLab at 12 GeV, and that, before the future high energy electron ion colliders become reality, the study of ultraperipheral collisions at the RHIC and LHC may open a window on quark and gluon GPDs at very small skewness. .

Pire, B; Wagner, J

2012-01-01

98

Timelike Compton Scattering from JLAB to RHIC and LHC energies  

E-print Network

Timelike Compton scattering (TCS) i.e. the exclusive photoproduction of a lepton pair with large invariant mass nicely complements the already successful experimental study of deeply virtual Compton scattering (DVCS). The same Generalized Parton Distributions enter both amplitudes, which offer a promissing way to access the quark and gluon nucleon structure. We review recent progress in this domain, emphasizing the fact that analyticity and factorization properties dictate the relation of the NLO corrections to TCS to those of DVCS. We also stress that data on TCS at high energy should be available soon thanks to the proposed experimental program at JLab at 12 GeV, and that, before the future high energy electron ion colliders become reality, the study of ultraperipheral collisions at the RHIC and LHC may open a window on quark and gluon GPDs at very small skewness. .

B. Pire; L. Szymanowski; J. Wagner

2012-07-10

99

Low-Intensity Nonlinear Spectral Effects in Compton Scattering  

SciTech Connect

Nonlinear effects are known to occur in Compton scattering light sources, when the laser normalized 4-potential, A = e{radical}-A{sub {mu}}A{sup {mu}}/m{sub 0}c approaches unity. In this letter, it is shown that nonlinear spectral features can appear at arbitrarily low values of A, if the fractional bandwidth of the laser pulse, {Delta}{phi}{sup -1}, is sufficiently small to satisfy A{sup 2} {Delta}{phi} {approx_equal} 1. A three dimensional analysis, based on a local plane-wave, slow-varying envelope approximation, enables the study of these effects for realistic interactions between an electron beam and a laser pulse, and their influence on high-precision Compton scattering light sources.

Hartemann, F V; Albert, F; Siders, C W; Barty, C P

2010-02-23

100

Gamma-ray polarization of synchrotron-self-Compton process from a highly relativistic jet  

E-print Network

The high polarization observed in the prompt phase of some gamma-ray bursts (GRBs) arouses extensive studies on the emission mechanism. In this paper, we investigate the polarization properties of synchrotron-self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from central engine travels with a large Lorentz factor. Shells with slightly different velocities collides with each other and produce shocks. The shocks accelerate electrons to power-law distribution, and at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. The synchrotron photons suffer from Compton scattering process and then escape from the jet and are detected by an observer locating slightly off-axis. We derive analytical formulae of polarization in the SSC process, based on the cross section of an initially polarized photon scattered by an unpolarized electron with any momentum. We show that photons induced by the SSC process can...

Chang, Zhe

2014-01-01

101

Detection of Defects in Acrylic and Steel Inclusions in Gypsum Using Compton Backscattered Gamma Rays  

NASA Astrophysics Data System (ADS)

Compton scattering of gamma radiation is a nondestructive technique used for the detection of defects and inclusions in materials. The methodology allows one-side inspection of large structures, is relatively inexpensive and can be portable. The number of photons inelastically scattered within a well-defined volume element is linearly proportional to the electron density of the material. Targeting a sample with a collimated beam of gamma rays, the energy spectrum of backscattered photons can be used to determine local density perturbations. In this work we used the Compton backscattering technique to detection of small collinear defects in acrylic blocks and steel rods inclusions in gypsum blocks samples. The samples were irradiated with gamma rays from a O/2 mm collimated 241Am (100 mCi) source and the inelastically scattered photons were collected at an angle of 135 by a CdTe detector with a O/7 mm30 mm collimation. Scanning was achieved by lateral movement of the sample blocks across the source and detector field of view in steps of 1 mm. The results showed that defects in the acrylic samples as small as 3 mm in size were visible in the intensity versus energy spectrum. The tests on gypsum blocks with steel rods inclusions suggest that, for a low energy and activity source, the effects of beam attenuation are more decisive to the scattered intensity than increasing of material density. An analysis of the density contrast is also presented.

Boldo, Emerson M.; Appoloni, Carlos R.

2011-08-01

102

Non-linear Compton Scattering in Short Laser Pulses  

NASA Astrophysics Data System (ADS)

The generation of short X-ray laser pulses attracts a great deal of attention. One of mechanisms to achieve this goal is the non-linear Compton scattering at very high laser powers. The majority of previous works on the non-linear Compton scattering have been devoted to the case when the incident laser field is treated as a monochromatic plane wave. There is, however, recent interest in analyzing the effect of a pulsed laser field on the non-linear Compton scattering [1-4]. We study the process for different durations of the incident laser pulse and compare it with the results for both a plane wave laser field and a laser pulse train. [4pt] [1] M. Boca and V. Florescu, Phys. Rev. A 80, 053403 (2009).[0pt] [2] M. Boca and V. Florescu, Eur. Phys. J. D 61, 446 (2011).[0pt] [3] D. Seipt and B. Kmpfer, Phys. Rev. A 83, 022101 (2011).[0pt] [4] F. Mackenroth and A. Di Piazza, Phys. Rev. A 83, 032106 (2011).

Krajewska, Katarzyna; Kami?ski, Jerzy

2012-06-01

103

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

104

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

105

POSSIBLE EXPERIMENTS ON WAVE FUNCTION LOCALIZATION DUE TO COMPTON SCATTERING  

SciTech Connect

The reduction of a particle s wave function in the process of radiation or light scattering is a longstanding problem. Its solution will give a clue on processes that form, for example, wave functions of electrons constantly emitting synchrotron radiation quanta in storage rings. On a more global scale, it may shed light on wave function collapse due to the process of measurement. In this paper we consider various experimental options using Fermilab electron beams and a possible electron beam from the SNS linac and lasers to detect electron wave function change due to Compton scattering.

Aleksandrov, Alexander V [ORNL] [ORNL; Danilov, Viatcheslav V [ORNL] [ORNL; Gorlov, Timofey V [ORNL] [ORNL; Liu, Yun [ORNL] [ORNL; Shishlo, Andrei P [ORNL] [ORNL; Nagaitsev, [FNAL] [FNAL

2013-01-01

106

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

107

Anisotropic inverse Compton scattering of photons from the circumstellar disc in PSR B1259-63  

NASA Astrophysics Data System (ADS)

The gamma-ray binary system PSR B1259-63/LS 2883 consists of a 48 ms pulsar orbiting a Be star. The system is particularly interesting because it is the only gamma-ray binary system where the nature of the compact object is known. The non-thermal radiation from the system is powered by the spin-down luminosity of the pulsar and the unpulsed radiation originates from the stand-off shock front which forms between the pulsar and stellar wind. The Be star/optical companion in the system produces an excess infrared (IR) flux from the associated circumstellar disc. This IR excess provides an additional photon source for inverse Compton scattering. We discuss the effects of the IR excess near periastron, for anisotropic inverse Compton scattering and associated gamma-ray production. We determine the IR excess from the circumstellar disc using a modified version of a curve of growth method, which takes into account the changing optical depth through the circumstellar disc during the orbit. The model is constrained using archive data and additional mid-IR observations obtained with the Very Large Telescope (VLT) during 2011 January. The inverse Compton scattering rate was calculated for three orientations of the circumstellar disc. The predicted gamma-ray light curves show that the disc contribution is a maximum around periastron and not around the disc crossing epoch. This is a result of the disc being brightest near the stellar surface. Additional spectroscopic and near-IR observations were obtained of the system and these are discussed in relation to the possibility of shock heating during the disc crossing epoch. Based, in part, on observations made with ESO Telescopes at the Paranal Observatory under programme ID 086.D-0136(B), and on observations made with the Southern African Large Telescope (SALT) under programme 2012-1-RSA-003.

van Soelen, B.; Meintjes, P. J.; Odendaal, A.; Townsend, L. J.

2012-11-01

108

Measurement of the Beam Spin Asymmetry and Double Spin Asymmetry in Polarized Virtual Compton Scattering at MAMI (Mainz)  

SciTech Connect

Virtual Compton scattering off the proton has been studied at Q2 = 0.33 (GeV/c)2 at MAMI (Mainz, Germany). This paper reports two different experiments. The goal of the experiments is the measurement of the double polarized e-vectorp {yields} e'p-vector'{gamma} reaction below pion production threshold and the (beam) single spin asymmetry for e-vectorp {yields} e'p'{gamma} above the {pi}0 threshold.

Janssens, P. [Department of Subatomic and Radiation Physics, Ghent University, 9000 Ghent (Belgium)

2007-06-13

109

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

110

High resolution low dose scattered gamma-ray tomography  

Microsoft Academic Search

This paper discusses a technique which uses Compton scattered gamma radiation to obtain high contrast, highly spatially resolved, three-dimensional images in optically opaque objects. A highly desirable property of this technology is that this method allows the acquisition of radiographs without the necessity of placing the object between the source and detector. This paper describes a prototype apparatus which is

R. S. Thoe

1996-01-01

111

Separation of Proton Polarizabilities with the Beam Asymmetry of Compton Scattering  

NASA Astrophysics Data System (ADS)

We propose to determine the magnetic dipole polarizability of the proton from the beam asymmetry of low-energy Compton scattering based on the fact that the leading non-Born contribution to the asymmetry is given by the magnetic polarizability alone; the electric polarizability cancels out. The beam asymmetry thus provides a simple and clean separation of the magnetic polarizability from the electric one. Introducing polarizabilities in a Lorentz-invariant fashion, we compute the higher-order (recoil) effects of polarizabilities on beam asymmetry and show that these effects are suppressed in forward kinematics. With the prospects of precision Compton experiments at the Mainz Microtron and High Intensity Gamma Source facilities in mind, we argue why the beam asymmetry could be the best way to measure the elusive magnetic polarizability of the proton.

Krupina, Nadiia; Pascalutsa, Vladimir

2013-06-01

112

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

NASA Astrophysics Data System (ADS)

160-keV ? rays were used to measure the Compton profiles of diamond, silicon, and germanium single crystals in five crystallographic directions (<100>, <110>, <111>, <112>, and <221>). 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 which suggests that the differences in the profiles can provide a sensitive test of band calculations. Interesting comparisons between the three materials are made by normalizing the data to equal electron density for the outer valence electrons. In addition to providing information on the three materials studied, this work demonstrates that systematic studies of families of solid-state systems by Compton scattering can be a very powerful experimental technique.

Reed, W. A.; Eisenberger, P.

1972-12-01

113

Anisotropic inverse Compton scattering of photons from the circumstellar disc in PSR B1259-63  

E-print Network

The gamma-ray binary system PSR B1259-63 consists of a 48 ms pulsar orbiting a Be star. The system is particularly interesting because it is the only gamma-ray binary system where the nature of the compact object is known. The non-thermal radiation from the system is powered by the spin-down luminosity of the pulsar and the unpulsed radiation originates from the stand-off shock front which forms between the pulsar and stellar wind. The Be star/optical companion in the system produces an excess infrared flux from the associated circumstellar disc. This infrared excess provides an additional photon source for inverse Compton scattering. We discuss the effects of the IR excess near periastron, for anisotropic inverse Compton scattering and associated gamma-ray production. We determine the infrared excess from the circumstellar disc using a modified version of a curve of growth method, which takes into account the changing optical depth through the circumstellar disc during the orbit. The model is constrained usi...

van Soelen, B; Odendaal, A; Townsend, L J

2012-01-01

114

Compton scattering off massive fundamental bosons of pure spin 1  

NASA Astrophysics Data System (ADS)

Relativistic particles with spins J>0 are described by means of multicomponent wave functions which transform covariantly according to Lorentz-group representations that contain at rest the spin of interest. The symmetry group of space-time provides not one but an infinity of such representations which are equivalent for free particles but yield different electromagnetic couplings upon gauging; thus, the challenge is to develop criteria which allow us to select those of them which relate to physically detectable particles. We here take the position that the unitarity of the Compton scattering cross sections in the ultrarelativistic limit, when predicted by a consistent method for a spin-1 description, could provide such a criterion. We analyze the properties of massive fundamental spin-1 bosons transforming as antisymmetric tensors of second rank, (1,0)?(0,1). For this purpose, we employ the Poincar covariant projector method, which provides consistent, gauge invariant, causal, and representation specific Lagrangians. This formalism yields a twofold extension of the Proca Lagrangian for the description of spin-1 bosons, first from an in-built g=1 value of the gyromagnetic ratio to an unspecified general g?1, and then from single-parity to parity-doublet degrees of freedom. We find different results for Compton scattering in these theories and track the differences to the lack of universality of the vector-antisymmetric-tensor equivalence theorem which is specific only to Procas framework, and valid for g=1, while it is violated within the more general Poincar covariant projector formalism. Our main result is that a finite Compton scattering differential cross section in the ultrarelativistic limit requires us to consider the contributions of both parities in (1,0)?(0,1). On that basis, we conclude that massive spin-1 bosons transforming as antisymmetric tensors are physical parity doublets.

Delgado-Acosta, E. G.; Kirchbach, M.; Napsuciale, M.; Rodrguez, S.

2013-05-01

115

Proton Compton scattering in a unified proton-?+ model  

NASA Astrophysics Data System (ADS)

We develop a field-theoretic model for the description of the proton Compton scattering in which the proton and its excited state, the ?+ resonance, are described as parts of one multiplet with a single Rarita-Schwinger wave function. To describe the observed phenomena, it is necessary to incorporate both minimal and nonminimal couplings. The minimal coupling reflects the fact that the ?+ is a charged particle, and in this model the minimal coupling contributes also to the ?N? magnetic transition. The nonminimal couplings consist of five electromagnetic form factors, which are accessed at fixed and vanishing momentum transfer squared with real photons in the Compton scattering experiments, therefore it is possible to extract a somewhat well-determined set of optimal parameters which fit the data in the resonance region 140-450 MeV reasonably well. The crucial parameter which determines the ?N? transition amplitude and therefore the height of the resonance peak is equal to 1.830.03, in units of ?N. We find that this parameter is also the primary determinant of the contributions to the magnetic polarizability in this model. In the low-energy region up to 140 MeV, we separately fit the electric and magnetic polarizabilities while keeping the other parameters fixed, and obtain values in line with previous approaches. In addition to proton Compton scattering, the model is applicable to a broad range of processes in the few hundred MeV energy range, whenever the proton appears in some intermediate off-shell state.

Zhang, Yun; Savvidy, Konstantin

2013-12-01

116

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

NASA Astrophysics Data System (ADS)

Conventional Compton telescopes use a single converter and a calorimeter that results in azimuthal uncertainty in the imaging analysis. The University of California, Riverside's (UCR) Tracking and Imaging Gamma Ray Experiment (TIGRE) was designed to minimize the directional uncertainty of the incident photons by using the silicon converter simultaneously as a photon scatterer and an electron tracker to determine the recoil electron path. TIGRE's initial flight was conducted in June, 2007 from Ft. Sumner in New Mexico. This thesis discusses the instrument's design, calibration, flight, and data analysis for Compton events. The time interval of the flight data selected for this analysis was 18,436 seconds. The expected efficiencies of the TIGRE instrument in a balloon-borne stratospheric environment, obtained from MEGAlib, a version of the GEANT 4 high energy simulator, ranged from 0.09% to 0.87% in the (0.3--50) MeV energy range. However, the New Mexico flight yielded only 6.5% of the predicted number of Compton candidates which was attributed primarily to the lower number of functional detectors available during the flight. A repeat simulation with realistic telescope conditions provided the expected number of Compton events that matched the flight results within errors. To take advantage of the tracking feature, one of the necessary procedures is to determine the Direction of Motion (DOM) of the electron track. The Pearson Correlation was used to determine the DOM. This method was successfully tested and verified by using a 90Sr calibration data-set. Using this method, the flight data had 698 downward electron tracks and 862 upward electron tracks, but this result was not successful in reconstructing the Compton events. The Compton angle, determined with the electron tracks, and the Compton angles, determined by the classic Compton formula, did not correlate. The discrepancy came from the low quality NaI calorimeters, its timing window with the silicon and the anti-coincident detectors, and an accidental inclusion of a module clear code within the flight software. The analysis work undertaken for this thesis allowed us to correct and update the telescope circuitry and software for the Australia balloon flight that was carried out in the spring of 2010 (the Australian flight results are not a part of this thesis).

Kamiya, Kaoru

117

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

118

Deeply Virtual Compton Scattering and Prompt Photon production at HERA  

E-print Network

Recent results on the Deeply Virtual Compton Scattering (DVCS) and prompt photon productions from H1 and ZEUS experiments on the $ep$ collider HERA are presented. A new DVCS cross section measurements of the H1 Collaboration, for photon virtualities $Q^2>4$ GeV$^2$ and photon-proton c.m.s. energy $30scattering and photoproduction are presented both in the inclusive case and in the presence of a jet. The results are compared to NLO QCD predictions.

L. Favart

2005-10-11

119

Compton Scattering in Ultrastrong Magnetic Fields: Numerical and Analytical Behavior in the Relativistic Regime  

NASA Astrophysics Data System (ADS)

This paper explores the effects of strong magnetic fields on the Compton scattering of relativistic electrons. Recent studies of upscattering and energy loss by relativistic electrons that have used the nonrelativistic, magnetic Thomson cross section for resonant scattering or the Klein-Nishina cross section for nonresonant scattering do not account for the relativistic quantum effects of strong fields (>41012 G). We have derived a simplified expression for the exact QED scattering cross section for the broadly applicable case in which relativistic electrons move along the magnetic field. To facilitate applications to astrophysical models, we have also developed compact approximate expressions for both the differential and total polarization-dependent cross sections, with the latter representing well the exact total QED cross section even at the high fields believed to be present in environments near the stellar surfaces of soft gamma repeaters and anomalous X-ray pulsars. We find that strong magnetic fields significantly lower the Compton scattering cross section below and at the resonance when the incident photon energy exceeds mec2 in the electron rest frame. The cross section is strongly dependent on the polarization of the final scattered photon. Below the cyclotron fundamental, mostly photons of perpendicular polarization are produced in scatterings, a situation that also arises above this resonance for subcritical fields. However, an interesting discovery is that for supercritical fields, a preponderance of photons of parallel polarization results from scatterings above the cyclotron fundamental. This characteristic is both a relativistic and a magnetic effect not present in the Thomson or Klein-Nishina limits.

Gonthier, Peter L.; Harding, Alice K.; Baring, Matthew G.; Costello, Rachel M.; Mercer, Cassandra L.

2000-09-01

120

The total virtual photoabsorption cross section, deeply virtual Compton scattering and vector-meson production  

E-print Network

Based on the two-gluon-exchange dynamical mechanism for deeply inelastic scattering at low x ~= Q^2/W^2 photoabsorption cross section, deeply virtual Compton scattering and vector-meson electroproduction. A simple expression for the cross section for deeply virtual Compton scattering is derived. Parameter-free predictions are obtained for deeply-virtual Compton forward scattering and vector-meson forward production, once the parameters in the total virtual photoabsorption cross section are determined in a fit to the experimental data on deeply inelastic scattering. Our predictions are compared with the experimental data from HERA.

Masaaki Kuroda; Dieter Schildknecht

2003-09-13

121

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

122

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

2010-01-04

123

Is the High-Energy Emission from Centaurus A Compton-Scattered Jet Radiation?  

E-print Network

We consider whether the hard X-ray and soft gamma-ray emission from Centaurus A is beamed radiation from the active nucleus which is Compton-scattered into our line-of-sight. We derive the spectrum and degree of polarization of scattered radiation when incident beamed radiation is scattered from a cold ($kT<scatterers are not moving relativistically, then the angle the jet makes with respect to our line-of-sight is $61^\\circ\\pm 5^\\circ$. We predict a high degree of polarization of the scattered radiation below $\\sim300$ keV. Future measurements with X-ray and gamma-ray polarimeters could be used to constrain or rule out such a scenario.

J. G. Skibo; C. D. Dermer; R. L. Kinzer

1994-02-18

124

Proposal for an advanced hybrid Kedge\\/XRF densitometry (HKED) using a monochromatic photon beam from laser Compton scattering  

Microsoft Academic Search

The general purpose Monte Carlo electron-gamma shower computer code (EGS5) was used to obtain the U, Np, and Pu X-ray response from the hybrid K-edge\\/XRF densitometry (HKED). In the present simulation, we adopt a monochromatic, linearly polarized photon beam generated by using inverse Compton scattering of laser light with high-energy electrons from an energy recovery linac. The simulation has been

Toshiyuki Shizuma; Ryoichi Hajima; Takehito Hayakawa; Mamoru Fujiwara; Takashi Sonoda; Michio Seya

2011-01-01

125

High-energy scaling of Compton scattering light sources  

NASA Astrophysics Data System (ADS)

No monochromatic (??x/?x<1%), high peak brightness [>1020photons/(mm2mrad2s0.1%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, 1mmmrad, <1ps, >100MeV), and tabletop laser systems (1-10J, 5 ps) the x-ray peak brightness can exceed 1023photons/(mm2mrad2s0.1%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

126

Neutron Polarizabilities From Compton Scattering on the Deuteron?  

E-print Network

A calculation of deuteron Compton scattering using non-relativistic perturbation theory is presented,with the primary motivation of investigating the feasibility of determining the neutron polarizabilities from this type of experiment. This calculation is expected to be valid for energies below 100 MeV. Pion-exchange, relativistic, and recoil corrections are also included. The low-energy theorem for gauge invariance is shown to be satisfied. The relative effects of the different terms and their effects on the determinations of the polarizabilities are discussed at energies of 49, 69, and 95 MeV. The cross-section is dominated by the seagull, polarizability, and electromagnetic multipole interactions. Relativistic and pion-exchange terms are also important, while recoil corrections and multipoles of $L$=2 and greater are negligible. The calculation provides a reasonable description of the experimental data points at 49 and 69 MeV. The polarizabilities are difficult to determine at these energies. A more accura...

Karakowski, J J; Karakowski, Jonathan J.; Miller, Gerald A.

1999-01-01

127

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

2006-04-28

128

Stokes parameters for Compton scattering in a strong magnetic field  

NASA Astrophysics Data System (ADS)

The effect of a superstrong magnetic field of 10 13 G on Compton scattering for thermal photons with electrons is studied by the method of quantum field theory. The Stokes parameters for the scattered photon are computed explicitly in terms of the state of polarization of the incident wave, the electron-cyclotron frequency, the angle of incidence and the angle of scattering. In the nonrelativistic limit, our results reduce to the well known theory for magnetic Thomson scattering. The total scattering cross section derived from the Stokes parameter S' 0 for the extraordinary X-mode in this case may be cast very roughly in the form ?(B) ? ( ?/? c) 2?(0) where ?( B) and ?(0) respectively denote the Thomson cross section with and without the presence of the magnetic field, ?c represents the classical gyrofrequency for the electrons and ? is the frequency of the incident wave provided that the dependence on the angle of incidence is neglected. The criterion for the magnetic field to substantially affect the Stokes parameters is that the photon frequency be less than the electron-cyclotron frequency. For instance, the Thomson cross section is significantly reduced and the photon mean free path is greatly enhanced for photons with ? ? ?c. In the absence of the strong magnetic field, the differential and total cross sections (derived from the first Stokes parameter S' 0) become the famous Klein-Nishina formula. Specific application to high energy astrophysics such as neutron star cooling and models for compact ?-ray source are currently under investigation and will be briefly discussed.

Chen, Hui-Hwa; Chou, Chih-Kang

1996-12-01

129

Nucleon Polarizabilities from Deuteron Compton Scattering within a Green's-Function Hybrid Approach  

E-print Network

We examine elastic Compton scattering from the deuteron for photon energies ranging from zero to 100 MeV, using state-of-the-art deuteron wave functions and NN-potentials. Nucleon-nucleon rescattering between emission and absorption of the two photons is treated by Green's functions in order to ensure gauge invariance and the correct Thomson limit. With this Green's-function hybrid approach, we fulfill the low-energy theorem of deuteron Compton scattering and there is no significant dependence on the deuteron wave function used. Concerning the nucleon structure, we use Chiral Effective Field Theory with explicit \\Delta(1232) degrees of freedom within the Small Scale Expansion up to leading-one-loop order. Agreement with available data is good at all energies. Our 2-parameter fit to all elastic $\\gamma d$ data leads to values for the static isoscalar dipole polarizabilities which are in excellent agreement with the isoscalar Baldin sum rule. Taking this value as additional input, we find \\alpha_E^s= (11.3+-0.7(stat)+-0.6(Baldin)) x 10^{-4} fm^3 and \\beta_M^s = (3.2-+0.7(stat)+-0.6(Baldin)) x 10^{-4} fm^3 and conclude by comparison to the proton numbers that neutron and proton polarizabilities are essentially the same.

Robert P. Hildebrandt; Harald W. Griesshammer; Thomas R. Hemmert

2005-12-16

130

Importance of Compton scattering to radiation spectra of isolated neutron stars  

E-print Network

Model atmospheres of isolated neutron stars with low magnetic field are calculated with Compton scattering taking into account. Models with effective temperatures 1, 3 and 5 MK, with two values of surface gravity log(g)g = 13.9 and 14.3), and different chemical compositions are calculated. Radiation spectra computed with Compton scattering are softer than the computed with Thomson scattering at high energies (E > 5 keV) for hot (T_eff > 1 MK) atmospheres with hydrogen-helium composition. Compton scattering is more significant to hydrogen models with low surface gravity. The emergent spectra of the hottest (T_eff > 3 MK) model atmospheres can be described by diluted blackbody spectra with hardness factors ~ 1.6 - 1.9. Compton scattering is less important for models with solar abundance of heavy elements.

V. Suleimanov; K. Werner

2006-12-22

131

Deeply virtual Compton scattering with CLAS and CLAS12  

SciTech Connect

Generalised Parton Distributions (GPDs) offer an insight into the three-dimensional structure of the nucleon and its internal dynamics, relating the transverse position of quarks to their longitudinal momentum. Two effective means of accessing GPDs are Deeply Virtual Compton Scattering (DVCS) and Meson Production (DVMP), in which a high energy electron scatters from a single quark in the nucleon and, respectively, a real photon or meson is produced as a result. Jefferson Laboratory (JLab), USA, is ideally suited for measuring these processes and a very active experimental programme has been underway in the recent years, making use of the lab's continuous electron beam up to 6 GeV in energy and its large angle spectrometer CLAS. In the future, a vast, new, as-yet unprobed kinematic region will become experimentally accessible when the current upgrade of the JLab accelerator to operate at a maximum energy of 12 GeV is completed in a few years. It is being complemented by the construction of a new suite of detectors, CLAS12, a number of them optimised specifically for exclusive reconstruction of DVCS and DVMP in the new kinematic region. We present a selection of recent results of DVCS and DVMP measurements using CLAS and introduce the exciting experimental programme planned for the future with CLAS12.

Sokhan, Daria [Institut de Physique Nucleaire, Orsay, France

2012-06-01

132

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

133

ROKK-1M is the Compton source of the high intensity polarized and tagged gamma beam at the VEPP-4M collider  

Microsoft Academic Search

The Backward Scattered Compton Quanta light source (ROKK-1M) developed for the high intensity polarized and tagged gamma beam at the Novosibirsk VEPP-4M Collider is described. Energy calibration of the electron and positron beams, real-time measurement of the beam polarization, and the electron-positron beam emittance at the interaction point are discussed. (AIP)

G. Ya. Kezerashvili; A. M. Milov; N. Yu. Muchnoi; A. N. Dubrovin; V. A. Kiselev; A. I. Naumenkov; A. N. Skrinsky; D. N. Shatilov; E. A. Simonov; V. V. Petrov; I. Ya. Protopopov

1995-01-01

134

Collision Integral Cross Sections in Double Photon Compton Scattering and a Possible Method for Their Measurement  

SciTech Connect

The collision integral cross sections are obtained and computed for several experimentally realizable cases to understand the various features of the higher-order process known as double photon Compton scattering. The computational work carried out using the Mathematica software package generally corresponds to three different incident gamma photon energies of {sup 137}Cs (661.65 keV), {sup 65}Zn (1.12 MeV), and that from the radiative capture of {sup 19}F (6.14 MeV). The characteristic features revealed a need to be investigated experimentally to check for their support to the currently acceptable theory of this quantum electrodynamics process. An experimental technique has been suggested for the measurement of these collision integral cross sections.

Sharma, Aarti; Saddi, M.B.; Singh, B.; Sandhu, B.S. [Punjabi University (India)

2004-11-15

135

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

136

A Compton filter to improve photopeak intensity evaluation in gamma ray spectra  

Microsoft Academic Search

A procedure for filtering the photopeak intensity from the Compton continuum interference is described. A continuum energy region of up to 0.478 and the 0.662 MeV photopeak are well defined in a cesium-137 theoretical spectrum. The filter was applied to a high intensity Compton region in the gamma spectrum obtained by the attenuation measurements in laboratory experiments. A Cs-137 (gamma=0.662

P. C. L. da Costa; C. C. Dantas; C. A. B. O. Lira; V. A. Dos Santos

2004-01-01

137

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

138

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

E-print Network

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

Matteo Rinaldi; Sergio Scopetta

2014-01-07

139

Neutron Polarisabilities from Deuteron Compton Scattering in \\chiEFT  

E-print Network

Chiral Effective Field Theory is for photon energies up to 200 MeV the tool to accurately determine the polarisabilities of the neutron from deuteron Compton scattering. A multipole analysis reveals that dispersive effects from an explicit Delta(1232) prove in particular indispensable to understand the data at 95 MeV measured at SAL. Simple power-counting arguments derived from nuclear phenomenology lead to the correct Thomson limit and gauge invariance. At next-to-leading order, the static scalar dipole polarisabilities are extracted as identical for proton and neutron within the error-bar of available data: \\alpha^n=11.6\\pm1.5_stat\\pm0.6_Baldin, \\beta^n=3.6\\mp1.5_stat\\pm0.6_Baldin for the neutron, in units of 10^-4 fm^3, compared to \\alpha^p=11.0\\pm1.4_stat\\pm0.4_Baldin, \\beta}^p=2.8\\mp1.4_stat\\pm0.4_Baldin for the proton in the same framework. New experiments e.g. at MAXlab (Lund) will improve the statistical error-bar.

Griesshammer, Harald W

2007-01-01

140

Neutron Polarisabilities from Deuteron Compton Scattering in \\chiEFT  

E-print Network

Chiral Effective Field Theory is for photon energies up to 200 MeV the tool to accurately determine the polarisabilities of the neutron from deuteron Compton scattering. A multipole analysis reveals that dispersive effects from an explicit Delta(1232) prove in particular indispensable to understand the data at 95 MeV measured at SAL. Simple power-counting arguments derived from nuclear phenomenology lead to the correct Thomson limit and gauge invariance. At next-to-leading order, the static scalar dipole polarisabilities are extracted as identical for proton and neutron within the error-bar of available data: \\alpha^n=11.6\\pm1.5_stat\\pm0.6_Baldin, \\beta^n=3.6\\mp1.5_stat\\pm0.6_Baldin for the neutron, in units of 10^-4 fm^3, compared to \\alpha^p=11.0\\pm1.4_stat\\pm0.4_Baldin, \\beta}^p=2.8\\mp1.4_stat\\pm0.4_Baldin for the proton in the same framework. New experiments e.g. at MAXlab (Lund) will improve the statistical error-bar.

Harald W. Griesshammer

2007-10-15

141

Neutron Polarizabilities From Compton Scattering on the Deuteron?  

E-print Network

A calculation of deuteron Compton scattering using non-relativistic perturbation theory is presented,with the primary motivation of investigating the feasibility of determining the neutron polarizabilities from this type of experiment. This calculation is expected to be valid for energies below 100 MeV. Pion-exchange, relativistic, and recoil corrections are also included. The low-energy theorem for gauge invariance is shown to be satisfied. The relative effects of the different terms and their effects on the determinations of the polarizabilities are discussed at energies of 49, 69, and 95 MeV. The cross-section is dominated by the seagull, polarizability, and electromagnetic multipole interactions. Relativistic and pion-exchange terms are also important, while recoil corrections and multipoles of $L$=2 and greater are negligible. The calculation provides a reasonable description of the experimental data points at 49 and 69 MeV. The polarizabilities are difficult to determine at these energies. A more accurate determination of the polarizabilities may be possible at 95 MeV.

Jonathan J. Karakowski; Gerald A. Miller

1999-01-08

142

de Broglie Wavelength and Frequency of the Scattered Electrons in Compton Effect  

E-print Network

The undergraduate courses on modern physics generally consider the particle interpretation of Compton effect. Motivated by a student's solution in an undergraduate examination on modern physics here we consider the wave characteristics of recoiled electrons in the Compton effect. The de Broglie wavelength, wave and clock frequency of the scattered electrons are expressed in terms of the wavelength and the frequency of the incident and the scattered photons respectively using the familiar particle interpretation of the Compton effect, where initially the electron is at rest and its spin is ignored. Both non-relativistic and relativistic cases are considered. Numerical values of de Broglie wavelength, wave and clock frequency of the scattered electron are calculated for an incident photon energy that was used in the original experiment of Compton as a function of the scattering angle of the recoiled electron. Considering the relativistic effects which are however insignificant for the de Broglie wavelength of the recoiled electron under these conditions, the minimum value obtained is in the range of X-rays. The non-relativistic de Broglie wave frequency obtained by neglecting the rest mass of the electron leads to an underestimation of its value. The implications of de Broglie wavelength and clock frequency for Compton scattering experiments are briefly discussed and possible extensions of the obtained mathematical formulations are indicated. The results are useful for understanding the wave-particle duality of the recoiled electron in the context of the Compton effect.

Vinay Venugopal; Piyush S Bhagdikar

2012-02-21

143

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

144

Calibration and performance of the UCR double Compton gamma ray telescope  

NASA Astrophysics Data System (ADS)

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(Tl) bars. The telescope is sensitive to celestial gamma rays from 1 to 30 MeV. The data were collected on February 14, 1988 prior to 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 an Na-24 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. An angular resolution of 11 deg FWHM and energy resolutions of 13 and 10 percent FWHM at 1.37 and 2.75 MeV, respectively, were found. The efficiency of the telescope is 0.0035 at 1.37 MeV and zenith angle 31 deg.

Ait-Ouamer, Farid; Kerrick, Alan D.; Sarmouk, Abderrezak; O'Neill, Terrence J.; Sweeney, William E.

1990-04-01

145

Calibration and performance of the UCR double Compton gamma ray telescope  

NASA Technical Reports Server (NTRS)

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(Tl) bars. The telescope is sensitive to celestial gamma rays from 1 to 30 MeV. The data were collected on February 14, 1988 prior to 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 an Na-24 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. An angular resolution of 11 deg FWHM and energy resolutions of 13 and 10 percent FWHM at 1.37 and 2.75 MeV, respectively, were found. The efficiency of the telescope is 0.0035 at 1.37 MeV and zenith angle 31 deg.

Ait-Ouamer, Farid; Kerrick, Alan D.; Sarmouk, Abderrezak; O'Neill, Terrence J.; Sweeney, William E.

1990-01-01

146

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

147

Measurement of an inverse Compton scattering source local spectrum using k-edge filters  

SciTech Connect

X-ray sources based on the inverse Compton scattering process are attracting a growing interest among scientists, due to their extremely fast pulse, quasi-monochromatic spectrum, and relatively high intensity. The energy spectrum of the x-ray beam produced by inverse Compton scattering sources in a fixed observation direction is a quasi-monochromatic approximately Gaussian distribution. The mean value of this distribution varies with the scattering polar angle between the electron beam direction and the x-ray beam observation direction. Previous works reported experimental measurements of the mean energy as a function of the polar angle. This work introduces a method for the measurement of the whole local energy spectrum (i.e., the spectrum in a fixed observation direction) of the x-ray beam yielded by inverse Compton scattering sources, based on a k-edge filtering technique.

Golosio, Bruno; Oliva, Piernicola; Carpinelli, Massimo [Universita di Sassari, via Piandanna 4, 07100 Sassari (Italy); INFN, Sezione di Cagliari, 09042 Cagliari (Italy); Endrizzi, Marco [Dipartimento di Fisica, Universita di Siena, Via Roma 56, 53100 Siena (Italy); INFN, Sezione di Pisa, 56127 Pisa (Italy); Delogu, Pasquale [Dipartimento di Fisica, Universita di Pisa, Largo B. Pontecorvo 3, 56127 Pisa (Italy); INFN, Sezione di Pisa, 56127 Pisa (Italy); Pogorelsky, Igor; Yakimenko, Vitaly [Accelerator Test Facility, Brookhaven National Laboratory, 820, Upton, New York 11973 (United States)

2012-04-16

148

Reevaluation of Compton scattering method in characterization of radiation therapy beams  

Microsoft Academic Search

To explore the possibility of using Compton scattering method to characterize the energy spectra of clinical beams. This method is experimentally tested on a Co60 radiation therapy machine and independently verified using Monte Carlo (MCNP4B) simulation. Measured spectrum and MCNP simulated spectrum including detector response for 90 scattered beam show good agreement

Texin Li; Siyong Kim; Chihray Liu; J. Palta; W. Tome; A. Ferrari; Joon Park; S. Anghaie

2000-01-01

149

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

150

A Compton filter to improve photopeak intensity evaluation in gamma ray spectra  

Microsoft Academic Search

A procedure for filtering the photopeak intensity from the Compton continuum interference is described. A continuum energy region of up to 0.478 and the 0.662 MeV photopeak are well defined in a cesium-137 theoretical spectrum. The filter was applied to a high intensity Compton region in the gamma spectrum obtained by the attenuation measurements in laboratory experiments. A Cs-137 (?=0.662

P. C. L. da Costa; C. C. Dantas; C. A. B. O. Lira; V. A. dos Santos

2004-01-01

151

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

152

Electronic structure of lanthanum sesquioxide: A Compton scattering study  

NASA Astrophysics Data System (ADS)

We present the first-ever experimental and theoretical momentum densities of La2O3. The Compton line shape is measured using a 20 Ci 137Cs Compton spectrometer at an intermediate resolution with full width at half maximum of 0.34 a.u. The experimental Compton profile is compared with the theoretical electron momentum densities computed using linear combination of atomic orbitals (LCAO) method with density functional theory (DFT). It is seen that the generalized gradient approximation (GGA) within DFT reconciles better with the experiment than other DFT based approximations, validating the GGA approximation for rare-earth sesquioxides. The energy bands and density of states computed using LCAO calculations show its wide band gap nature which is in tune with the available reflectivity and photo-absorption data. In addition, Mulliken's population and charge density are also computed and discussed.

Sharma, Sonu; Sahariya, Jagrati; Arora, Gunjan; Ahuja, B. L.

2014-10-01

153

Separation of photoabsorption and Compton scattering contributions to He single and double ionization  

SciTech Connect

We have experimentally separated the contributions of photoabsorption and Compton scattering to He single and double ionization for high-energy photon impact by measuring the full momentum vector of the recoiling He{sup 1+,2+} ions. For recoil ions following photoabsorption large momenta and a distinct dipole emission pattern are observed. The ions produced by Compton scattering show small momenta. For the ratio of double to single ionization we find (1.22{plus_minus}0.06)% at 8.8{sub {minus}1.65}{sup +1.5} keV for Compton scattering and (1.72{plus_minus}0.12)% at 7.0{sub {minus}1.6}{sup +2.1} keV for photoabsorption. We compare our data with recent theories.

Spielberger, L.; Jagutzki, O.; Doerner, R.; Ullrich, J.; Meyer, U.; Mergel, V.; Unverzagt, M.; Damrau, M.; Vogt, T.; Ali, I.; Khayyat, K.; Bahr, D.; Schmidt, H.G.; Frahm, R.; Schmidt-Boecking, H. [Institut fuer Kernphysik, Universitaet Frankfurt, D60486 Frankfurt am Main (Germany)] [Institut fuer Kernphysik, Universitaet Frankfurt, D60486 Frankfurt am Main (Germany); [GSI, D64220 Darmstadt (Germany); [HASYLAB am DESY, D22603 Hamburg (Germany)

1995-06-05

154

Experimental separation of photoabsorption and Compton scattering contributions to He single and double ionization  

SciTech Connect

We have experimentally separated the contributions of photoabsorption and Compton scattering to He single and double ionization for high-energy photon impact by measuring the full momentum vector of the recoiling He{sup 1+,2+} ions. For recoil ions following photoabsorption large momenta and a distinct dipole emission pattern are observed. The ions produced by Compton scattering show small momenta. For the ratio of double to single ionization we find (1.22{+-}.06)% at 8.8{sup +1.5}-1.65 keV for Compton scattering and (1.72{+-}.12)% at 7.0{sup +2.1}-1.6 keV for photoabsorption. We compare our data with recent theories.

Spielberger, L.; Jagutzki, O.; Doerner, R.; Ullrich, J.; Meyer, U.; Mergel, V.; Unverzagt, M.; Damrau, M.; Vogt, T.; Ali, I.; Khayyat, Kh.; Bahr, D.; Schmidt, H. G.; Frahm, R.; Schmidt-Boecking, H. [Institut fuer Kernphysik, Universitaet Frankfurt, D60486 Frankfurt/M., Germany, D60486 Hamburg (Germany)

1996-02-25

155

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

2012-07-26

156

Compton scattering in a uniform, constant magnetic field  

Microsoft Academic Search

A general expression for the Compton cross section for a uniform, constant magnetic field was derived based on the Dirac equation and second order perturbation theory, the electrons were represented by single particle wave functions and the photons by plane waves. The solution was programmed for numerical solution by computer; the results were displayed graphically. The solution possesses the usual

E. S. Kinzel

1981-01-01

157

The effect of Compton scattering on the double to single ionization ratio in helium  

SciTech Connect

The ratio of double to single ionization in Helium produced by photon impact has been measured for photon energies from 2.1 to 5.5 keV. The measurements suggest that a significant contribution to the single ionization cross section is caused by Compton scattering for energies greater than {approximately} 3.8 keV. After accounting for the ionizing Compton scattering the measured ratio is not inconsistent with recent calculations of the asymptotic limit of the ionization ratio caused by photoabsorption which predict a limit near 1.66%.

Bartlett, R.J. [Los Alamos National Lab., NM (United States); Sagurton, M. [SFA, Inc., Landover, MD (United States); Samson, J.A.R.; He, Z.X. [Nebraska Univ., Lincoln, NE (United States)

1993-10-01

158

Compton scattering of energetic photons by light atoms in the presence of a low-frequency electromagnetic field  

Microsoft Academic Search

We consider the influence of a weak low-frequency electromagnetic field on Compton scattering of a high-energy photon by an electron which is initially bound in the ground state of a light atomic target. It is shown that this influence can be very substantial for the Compton scattering with a large (on the target scale) momentum transfer to the target when

A B Voitkiv; N Grn; J Ullrich

2003-01-01

159

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

160

SPECIAL ISSUE DEVOTED TO THE 90TH ANNIVERSARY OF A.M. PROKHOROV: Amplification of ultrashort laser pulses upon stimulated Compton scattering in plasma  

NASA Astrophysics Data System (ADS)

Stimulated Compton scattering of counterpropagating laser beams in a moving plasma is studied theoretically. It is shown that, by using Compton scattering, picosecond or femtosecond laser pulses can be amplified under certain conditions by two-three orders of magnitude.

Krasyuk, Igor K.; Pashinin, Pavel P.; Semenov, Andrei Yu

2006-07-01

161

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

162

Galactic medium energy gamma-ray astronomy: A quantitative study of the inverse Compton contribution  

Microsoft Academic Search

The contribution of the inverse Compton process to the galactic medium energy (10 to 100 MeV) gamma ray emission was analyzed quantitatively. The method and the basic model calculations were those outlined in existing work, including a calculation of the source function at the sun as a starting point. The novelty introduced here is in the use of both new

G. Piccinotti; G. F. Bignami

1977-01-01

163

ROKK-1M is the Compton source of the high intensity polarized and tagged gamma beam at the VEPP-4M collider  

SciTech Connect

The Backward Scattered Compton Quanta light source (ROKK-1M) developed for the high intensity polarized and tagged gamma beam at the Novosibirsk VEPP-4M Collider is described. Energy calibration of the electron and positron beams, real-time measurement of the beam polarization, and the electron-positron beam emittance at the interaction point are discussed. (AIP) {copyright} {ital 1995 American Institute of Physics.}

Kezerashvili, G.Y.; Milov, A.M.; Muchnoi, N.Y.; Dubrovin, A.N.; Kiselev, V.A.; Naumenkov, A.I.; Skrinsky, A.N.; Shatilov, D.N.; Simonov, E.A.; Petrov, V.V.; Protopopov, I.Y. [Budker Institute of Nuclear Physics, 630090, Novosibirsk (Russia)

1995-09-01

164

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

165

Influence of Compton scattering on the broad-band X-ray spectra of intermediate polars  

E-print Network

The majority of cataclysmic variables observed in the hard X-ray energy band are intermediate polars where the magnetic field is strong enough to channel the accreting matter to the magnetic poles of the white dwarf. A shock above the stellar surface heats the gas to fairly high temperatures (10--100 keV). The post-shock region cools mostly via optically thin bremsstrahlung. We investigate the influence of Compton scattering on the structure and the emergent spectrum of the post-shock region. We also study the effect it has on the mass of the white dwarfs obtained from fitting the observed X-ray spectrum of intermediate polars. We construct the model of the post-shock region taking Compton scattering into account. The radiation transfer equation is solved in the plane-parallel approximation. The feedback of Compton scattering on the structure of the post-shock region is also accounted for. A set of the post-shock region model spectra for various white dwarf masses is calculated. We find that Compton scattering does not change the emergent spectra significantly for low accretion rates or low white dwarf masses. However, it becomes important at high accretion rates and high white dwarf masses. The time-averaged, broad-band X-ray spectrum of intermediate polar V709 Cas obtained by the RXTE and INTEGRAL observatories is fitted using the set of computed spectral models. We obtained the white dwarf mass of 0.91 +/- 0.02 M_sun and 0.88 +/- 0.02 M_sun using models with Compton scattering taken into account and without it, respectively.

V. Suleimanov; J. Poutanen; M. Falanga; K. Werner

2008-05-04

166

Nucleon Polarisabilities from Deuteron Compton Scattering, and Its Lessons for Chiral Power Counting  

E-print Network

A brief review of Compton scattering off the deuteron in Chiral Effective Field Theory, including gauge invariance and the correct Thomson limit. We model-independently determine the iso-scalar, spin-independent dipole polarisabilities of the nucleon at zero energy from all Compton data below 100 MeV as \\alpha_{E1}^s=11.3+-0.7_{stat}\\+-0.6_{Baldin}+-1_{theory}, \\beta_{M1}^s=3.2-+0.7_{stat}+-0.6_{Baldin}+-1_{theory}, each in 10^{-4} fm^3. Proton and neutron polarisabilities are therefore identical within (predominantly statistical) errors.

Harald W. Griesshammer

2006-11-20

167

Nucleon Polarisabilities from Deuteron Compton Scattering, and Its Lessons for Chiral Power Counting  

E-print Network

A brief review of Compton scattering off the deuteron in Chiral Effective Field Theory, including gauge invariance and the correct Thomson limit. We model-independently determine the iso-scalar, spin-independent dipole polarisabilities of the nucleon at zero energy from all Compton data below 100 MeV as \\alpha_{E1}^s=11.3+-0.7_{stat}\\+-0.6_{Baldin}+-1_{theory}, \\beta_{M1}^s=3.2-+0.7_{stat}+-0.6_{Baldin}+-1_{theory}, each in 10^{-4} fm^3. Proton and neutron polarisabilities are therefore identical within (predominantly statistical) errors.

Griesshammer, H W

2006-01-01

168

Double Ionization of Lithiumlike Ions by Compton Scattering of High-Energy Photons  

NASA Astrophysics Data System (ADS)

The double ionization of lithiumlike ions by Compton scattering of photons is investigated in the asymptotic high-energy region. To leading order of the nonrelativistic perturbation theory, the total cross section for double Compton effect is calculated, taking into account the channels of simultaneous and sequential emission of two electrons. Relationships between the cross sections for double ionization of He- and Li-like ions with the same nuclear charge Z are established. This can open wide perspectives for experimental investigations of ionization processes involving low-lying excited states. The universal scaling is found for the ratio of double-to-single ionization in the lithium isoelectronic sequence.

Mikhailov, A. I.; Nefiodov, A. V.; Plunien, G.

2006-12-01

169

A study of electronic structure of CdSe by Compton scattering technique  

NASA Astrophysics Data System (ADS)

The electronic structure of CdSe through a Compton profile study is presented in this paper. Theoretical calculations are performed following the empirical pseudopotential method and the linear combination of atomic orbitals method. The measurement on a polycrystalline sample of CdSe is performed using 59.54 keV gamma-rays from 241Am radioisotope. The spherically averaged theoretical Compton profiles are in agreement with the measurement. The best agreement is, however, shown by the linear combination of atomic orbitals method based on the Hartree-Fock theory. The electron momentum density is also discussed in terms of theoretical anisotropies in the directional Compton profiles calculated from the linear combination of atomic orbitals method. On the basis of equal valence electron-density profiles, it is found that CdSe is less covalent compared to ZnSe. The superposition model suggests the transfer of 1.6 electrons from Cd to Se on compound formation.

Dhaka, M. S.; Sharma, G.; Mishra, M. C.; Joshi, K. B.; Kothari, R. K.; Sharma, B. K.

2010-09-01

170

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

171

Supercontinuum and ultra-short pulse generation from nonlinear Thomson and Compton scattering  

E-print Network

Nonlinear Thomson and Compton processes, in which energetic electrons collide with an intense optical pulse, are investigated in the framework of classical and quantum electrodynamics. Spectral modulations of the emitted radiation, appearing as either oscillatory or pulsating structures, are observed and explained. It is shown that both processes generate a bandwidth radiation spanning the range of few MeV, which occurs in a small cone along the propagation direction of the colliding electrons. Most importantly, these broad bandwidth structures are temporarily coherent which proves that Thomson and Compton processes lead to generation of a supercontinuum. It is demonstrated that the radiation from the supercontinuum can be synthesized into zeptosecond (possibly even yoctosecond) pulses. Thus, confirming that Thomson and Compton scattering can be used as novel sources of an ultra-short radiation, opening routes to new physical domains for strong laser physics.

K. Krajewska; M. Twardy; J. Z. Kami?ski

2013-11-19

172

Supercontinuum and ultra-short pulse generation from nonlinear Thomson and Compton scattering  

E-print Network

Nonlinear Thomson and Compton processes, in which energetic electrons collide with an intense optical pulse, are investigated in the framework of classical and quantum electrodynamics. Spectral modulations of the emitted radiation, appearing as either oscillatory or pulsating structures, are observed and explained. It is shown that both processes generate a bandwidth radiation spanning the range of few MeV, which occurs in a small cone along the propagation direction of the colliding electrons. Most importantly, these broad bandwidth structures are temporarily coherent which proves that Thomson and Compton processes lead to generation of a supercontinuum. It is demonstrated that the radiation from the supercontinuum can be synthesized into zeptosecond (possibly even yoctosecond) pulses. Thus, confirming that Thomson and Compton scattering can be used as novel sources of an ultra-short radiation, opening routes to new physical domains for strong laser physics.

Krajewska, K; Kami?ski, J Z

2013-01-01

173

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

174

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

175

Comment on 'Anomalous neutron Compton scattering from molecular hydrogen'  

SciTech Connect

Claims in the paper by Chatizidimitiou-Dreismann et al. [Phys. Rev. B 72, 054123 (2005)] that our analysis of the keV neutron scattering data is incorrect are shown to be wrong. Their analysis neglects the effect of the neutron attenuation in the relatively thick samples, thus creating an artificial anomaly of {approx}21% in the scattering intensity ratio of H{sub 2}O relative to that of D{sub 2}O.

Moreh, R. [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva (Israel); Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Block, R. C.; Danon, Y. [Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2007-02-01

176

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

177

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

E-print Network

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 ...

Prok, Yelena

178

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.

179

First demonstration of a Compton gamma imager based on silicon photomultipliers  

NASA Astrophysics Data System (ADS)

We are developing a rugged and person-transportable Compton gamma imager for use in security investigations of radioactive materials, and for radiological incident remediation. The imager is composed of layers of scintillator with light collection for the forward layers provided by silicon photomultipliers and for the rear layer by photomultiplier tubes. As a first step, we have developed a 1/5th-scale demonstration unit of the final imager. We present the imaging performance of this demonstration unit for 137Cs at angles of up to 30 off-axis. Results are also presented for 113Sn and 22Na. This represents the first demonstration of the use of silicon photomultipliers as an embedded component for light collection in a Compton gamma imager.

Saull, P. R. B.; Sinclair, L. E.; Seywerd, H. C. J.; Hanna, D. S.; Boyle, P. J.; MacLeod, A. M. L.

2012-07-01

180

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

181

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

NASA Astrophysics Data System (ADS)

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 (?cm=70o) 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, C.; Cisbani, E.; Hamilton, D.; Salm, G.; Wojtsekhowski, B.

2014-06-01

182

ON THE SPECTRAL SHAPE OF RADIATION DUE TO INVERSE COMPTON SCATTERING CLOSE TO THE MAXIMUM CUTOFF  

SciTech Connect

The spectral shape of radiation due to inverse Compton scattering is analyzed in the Thomson and the Klein-Nishina regime for electron distributions with exponential cutoff. We derive analytical, asymptotic expressions for the spectrum close to the maximum cutoff region. We consider monoenergetic, Planckian, and synchrotron photons as target photon fields. These approximations provide a direct link between the distribution of parent electrons and the upscattered spectrum at the cutoff region.

Lefa, E.; Kelner, S. R.; Aharonian, F. A., E-mail: eva.lefa@mpi-hd.mpg.de [Max-Planck-Institut fuer Kernphysik, P.O. Box 103980, 69029 Heidelberg (Germany)

2012-07-10

183

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

184

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

185

Compton Scattering by the Proton using a Large-Acceptance Arrangement  

E-print Network

Compton scattering by the proton has been measured using the tagged-photon facility at MAMI (Mainz) and the large-acceptance arrangement LARA. The new data are interpreted in terms of dispersion theory based on the SAID-SM99K parameterization of photo-meson amplitudes. It is found that two-pion exchange in the t-channel is needed for a description of the data in the second resonance region. The data are well represented if this channel is modeled by a single pole with mass parameter m(sigma)=600 MeV. The asymptotic part of the spin dependent amplitude is found to be well represented by pi-0-exchange in the t-channel. A backward spin-polarizability of gamma(pi)=(-37.1+-0.6(stat+syst)+-3.0(model))x10^{-4}fm^4 has been determined from data of the first resonance region below 455 MeV. This value is in a good agreement with predictions of dispersion relations and chiral pertubation theory. From a subset of data between 280 and 360 MeV the resonance pion-photoproduction amplitudes were evaluated leading to a E2/M1 multipole ratio of the p-to-Delta radiative transition of EMR(340 MeV)=(-1.7+-0.4(stat+syst)+-0.2(model))%. It was found that this number is dependent on the parameterization of photo-meson amplitudes. With the MAID2K parameterization an E2/M1 multipole ratio of EMR(340 MeV)=(-2.0+-0.4(stat+syst)+-0.2(model))% is obtained.

S. Wolf; V. Lisin; R. Kondratiev; A. M. Massone; G. Galler; J. Ahrens; H. -J. Arends; R. Beck; M. Camen; G. P. Capitani; P. Grabmayr; F. Hrter; T. Hehl; P. Jennewein; K. Kossert; A. I. L'vov; C. Molinari; P. Ottonello; R. O. Owens; J. Peise; I. Preobrajenskij; S. Proff; A. Robbiano; M. Sanzone; M. Schumacher; M. Schmitz; F. Wissmann

2001-09-19

186

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.

187

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

188

Compton Effect  

NSDL National Science Digital Library

The Compton Effect model simulates the the scattering of light off of an electron, the Compton effect. Compton used the idea that light behaves like a particle to explain light-electron (photon-electron) scattering. He used the relation for the energy and momentum of the photon and the relativistic expression for the energy of the electron, and applied relativistic energy and momentum conservation for the collision. The wavelength shift of the light depend on the angle of the scattered photon (and the electron). By changing the scattering angle in the simulation, the angle of the scattered photon changes according to Compton's equation. The panel on the left shows the experimental set up, while the panel on the right shows the resulting photon wavelength from the scattering. In a typical Compton experiment, light is scattered off of the electrons in an atom, and there is little scattering due to the more tightly held electrons while there is more scattering due to the less tightly held electrons. This is what is responsible for the two peak distribution shown. The Compton Effect model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_compton.jar file will run the program if Java is installed.

Palop, Jose I.

2010-12-12

189

Comment on ``Nonlinear Compton scattering in ultrashort laser pulses''  

NASA Astrophysics Data System (ADS)

In a recent paper [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.83.032106 83, 032106 (2011)], Mackenroth and Di Piazza studied photoemission spectra of an electron driven by intense ultrashort laser pulses. Using kinematic principles, they argued that an electron experiences no mass dressing in an ultrashort pulse. They also proposed a method by which one might experimentally verify their claim. We argue that the scattering kinematics do not imply this conclusion nor do they justify the proposed experiment.

Corson, John P.; Peatross, Justin

2012-04-01

190

On Deeply Virtual Compton Scattering at Next-to-Leading Order  

NASA Astrophysics Data System (ADS)

Deeply virtual Compton scattering in the near forward kinematic region is the golden access to Generalized Parton Distributions. We studied the corrections to the scattering amplitude for both spacelike and timelike kinematics relevant respectively to the leptoproduction of a real photon and to the photoproduction of a lepton pair. It turns out that these corrections are phenomenologically important and that the gluonic contributions are by no means negligible, even in the moderate energy range of JLab12 and of the COMPASS-II experiment at CERN.

Moutarde, H.; Pire, B.; Sabati, F.; Szymanowski, L.; Wagner, J.

2014-06-01

191

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

192

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

193

Neutron Compton scattering from water studied with the double-difference technique  

SciTech Connect

A shortfall of the scattering intensity from protons has been observed in liquids (water, benzene, etc.) and solids (metal hydrogen systems, organic polymers, etc.) using neutron Compton scattering (NCS). The standard analysis of NCS data has been subject to severe criticism, e.g., it was claimed that it is the way the energy resolution function is incorporated in the data reduction scheme that leads to an underestimation of the scattering intensity. Here we present NCS experimental results utilizing a technique--referred to as double difference--which significantly improves the energy resolution function. Specifically, the ratio of the scattering cross-section density of H and D in mixtures of light and heavy water are presented. The experimental data reveal that the results published earlier remain unchanged upon the significant improvement of the energy resolution function.

Abdul-Redah, T. [Physics Laboratory, The University of Kent at Canterbury, Canterbury, Kent CT2 7NR (United Kingdom); Krzystyniak, M.; Chatzidimitriou-Dreismann, C.A. [Institute of Chemistry, Stranski Laboratory, Technical University of Berlin, D-10623 Berlin (Germany)

2005-08-01

194

Comptonization Signatures in the Prompt Emission of Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

We report results of a systematic study of the broadband (2-2000 keV) time-resolved prompt emission spectra of a sample of gamma-ray bursts (GRBs) detected with both Wide Field Cameras (WFCs) on board the BeppoSAX satellite and the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory. The main goal of this paper is to test spectral models of the GRB prompt emission that have recently been proposed. In particular, we test a recent photospheric model proposed, i.e., blackbody plus power law, the addition of a blackbody emission to the Band function in the cases in which this function does not fit the data, and a recent Comptonization model. By considering the few spectra for which the simple Band function does not provide a fully acceptable fit to the data, we find a statistically significant better fit by adding a blackbody to this function only in one case. We confirm earlier results found fitting the BATSE spectra alone with a blackbody plus power law. Instead, when the BATSE GRB spectra are joined to those obtained with WFCs (2-28 keV), this model becomes unacceptable in most time intervals in which we subdivide the GRB light curves. We find instead that the Comptonization model is always acceptable, even in the few cases in which the Band function is inconsistent with the data. We discuss the implications of these results.

Frontera, F.; Amati, L.; Farinelli, R.; Dichiara, S.; Guidorzi, C.; Landi, R.; Titarchuk, L.

2013-12-01

195

High resolution low dose scattered gamma-ray tomography  

NASA Astrophysics Data System (ADS)

This paper discusses a technique which uses Compton scattered gamma radiation to obtain high contrast, highly spatially resolved, three-dimensional images in optically opaque objects. A highly desirable property of this technology is that this method allows the acquisition of radiographs without the necessity of placing the object between the source and detector. This paper describes a prototype apparatus which is capable of obtaining images with a spatial resolution of about 1 mm at a depth of 25 mm in steel of normal density with the source and detector both on the same side of the object. Some modeling calculations, reconstruction algorithms, and data verifying the performance of this technique will be presented as well as details of how the efficiency and throughput of this system could be increased by over two orders of magnitude.

Thoe, R. S.

1996-01-01

196

High resolution low dose scattered gamma-ray tomography  

SciTech Connect

This paper discusses a technique which uses Compton scattered gamma radiation to obtain high contrast, highly spatially resolved, three-dimensional images in optically opaque objects. A highly desirable property of this technology is that this method allows the acquisition of radiographs without the necessity of placing the object between the source and detector. This paper describes a prototype apparatus which is capable of obtaining images with a spatial resolution of about 1 mm at a depth of 25 mm in steel of normal density with the source and detector both on the same side of the object. Some modeling calculations, reconstruction algorithms, and data verifying the performance of this technique will be presented as well as details of how the efficiency and throughput of this system could be increased by over two orders of magnitude. {copyright} {ital 1996 American Institute of Physics.}

Thoe, R.S. [V Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [V Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

1996-01-01

197

A fitter code for Deep Virtual Compton Scattering and Generalized Parton Distributions  

E-print Network

We have developped a fitting code based on the leading-twist handbag Deep Virtual Compton Scattering (DVCS) amplitude in order to extract the Generalized Parton Distributions (GPD) information from DVCS observables in the valence region. In a first stage, with simulations and pseudo-data, we show that the full GPD information can be recovered from experimental data if enough observables are measured. If only part of these observables are measured, valuable information can still be extracted, certain observables being particularly sensitive to certain GPDs. In a second stage, we make a practical application of this code to the recent DVCS Jefferson Lab Hall A data from which we can extract numerical constraints for the two $H$ GPD Compton Form Factors.

M. Guidal

2008-07-15

198

Determination of Copper by Neutron Activation Analysis in Conjunction with Compton Suppression Gamma Spectrometry  

SciTech Connect

Copper is considered to be an essential element. Its accurate determination in tissues, foods, and other biological materials is needed to study the effect of copper on human nutrition and health. Using and Advance Prediction Computer Program, it has been shown that short-lived {sup 66}Cu (half-life = 5.09 min) can be used to determine copper in biological materials by instrumental neutron activation analysis (INAA). However, it is seldom done in practice-in particular, for low copper content in high-salt biological materials-because of the Compton background interference from nuclides such as {sup 28}Al, {sup 38}Cl, and {sup 24}Na. To eliminate the Compton interference, a preconcentration NAA method has recently been developed in our laboratory using reversed-phase extraction chromatography of copper followed by short irradiation and conventional gamma-spectrometric counting of {sup 66}Cu; the detection limit is {approx}5 ppb.

W. H. Zhang; A. Chatt

2000-06-04

199

Compton e+ Source Overview (ring + Erl + Linac)  

NASA Astrophysics Data System (ADS)

Short reviews of Compton e+ sources R&D for ILC are given. Especially, the Compton sources using Ring and ERL are discussed according to the scheme of truly 300Hz conventional e+ source with the change of the positron generation scheme from nonpolarized to highly polarized e+. As we have proposed the Ring Compton source since 2005, the improvement of the design is described. The technologies for X-ray and Gamma-ray source based on the inverse-Compton scattering have been improved by recent fiber laser and high finesse optical cavity developments.

Urakawa, Junji

2013-10-01

200

A Compton filter to improve photopeak intensity evaluation in gamma ray spectra  

NASA Astrophysics Data System (ADS)

A procedure for filtering the photopeak intensity from the Compton continuum interference is described. A continuum energy region of up to 0.478 and the 0.662 MeV photopeak are well defined in a cesium-137 theoretical spectrum. The filter was applied to a high intensity Compton region in the gamma spectrum obtained by the attenuation measurements in laboratory experiments. A Cs-137 ( ? = 0.662 MeV) source, of 4 m Ci, steel tubes and a NaI detector was utilized for measuring the catalyst density in a collimated gamma beam. Such an assembly simulates the measuring conditions for gamma tomography in the riser of a FCC-fluid catalyst cracking unit. A Canberra multichannel data acquisition, records the gamma spectrum whose data file is exported to the Matlab software. Following the spectrum reconstruction, the peak area evaluation in both systems, shows a good agreement. Based on the Fourier transform equation, a filtering method for the photopeak, using Matlab functions, was developed. By means of a lowpass filter that lets the low frequencies pass, but not the high frequencies. The filtering results in a significant reduction in the interference from the Compton effect on the photopeak. For little interference and also for a high continuum background under a nonsymmetrical photopeak the filtering works. After the filtering process the peak becomes fairly similar to a Gaussian curve and the liquid counts are enhanced. The associated standard deviation decreases by a factor of 4, while the resolution of the 0.662 MeV photopeak, is kept within detector characteristics.

da Costa, P. C. L.; Dantas, C. C.; Lira, C. A. B. O.; dos Santos, V. A.

2004-11-01

201

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

202

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

203

Curvature and non-resonance Compton gamma-ray emission of a radio pulsar with a non-dipolar magnetic field  

NASA Astrophysics Data System (ADS)

We consider the influence of a non-dipolar magnetic field on the gamma-ray emission from the polar regions of a radio pulsar. The pulsar is treated in a Goldreich-Julian model with a free flow of charge from the surface of the neutron star. When finding the intensity of the gamma-ray radiation of the pulsar tube, both curvature gamma-ray radiation from the primary electrons and non-resonance inverse Compton scattering of thermal photons from the polar cap on primary electrons are taken into account. When finding the height of the upper plate of the pulsar diode, we included only positrons created by the curvature radiation of primary electrons. We assumed that the polar cap is heated by the return positron current. The influence on the gamma-ray emission of variations in both the radius of curvature of the magnetic force lines and in the electric field due to the non-dipolarity of the magnetic field were taken into account. The presence of even weak non-dipolarity of the magnetic field leads to a sharp decrease in the intensity of the gamma-ray emission from the pulsar tube at energies 1 100 MeV, while the intensity of the inverse Compton radiation (at energies 1 100 GeV) varies only relatively weakly.

Barsukov, D. P.; Kantor, E. M.; Tsygan, A. I.

2007-06-01

204

Anisotropic inverse Compton scattering from the trans-relativistic to the ultra-relativistic regime and application to the radio galaxies  

E-print Network

The problem of the anisotropic Inverse Compton scattering between a monochromatic photon beam and relativistic electrons is revisited and formally solved without approximations. Solutions are given for the single scattering with an electron beam and with a population of electrons isotropically distributed, under the assumption that the energy distribution of the relativistic particles follows a simple power law as it is the case in many astrophysical applications. Both the Thomson approximation and the Klein-Nishina regime are considered for the scattering of an unpolarized photon beam. The equations are obtained without the ultra-relativistic approximation and are compared with the ultra-relativistic solutions given in the literature. The main characteristics of the power distribution and spectra of the scattered radiation are discussed for relevant examples. In the Thomson case for an isotropic electron population simple formulae holding down to mildly-relativistic energies are given. As an application the formulae of the anisotropic inverse Compton scattering are used to predict the properties of the X and $\\gamma$-ray spectra from the radio lobes of strong FR II radio galaxies due to the interaction of the relativistic electrons with the incoming photons from the nucleus. The dependence of the emitted power on the relativistic electron energy distribution and on its evolution with time is discussed.

G. Brunetti

1999-08-20

205

Analysis of the Data from Compton X-ray Polarimeters which Measure the Azimuthal and Polar Scattering Angles  

E-print Network

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 neutron stars. Furthermore, several particle astrophysics topics can be addressed including uniquely sensitive tests of Lorentz invariance. In the energy range from 10-20 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 ...

,

2011-01-01

206

Compton Scattering and Photo-Absorption Studies of Charge and Spin Density  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. Directional Compton profiles of zinc and Fe _{0.25}Ni_{0.75} have been measured with 60 keV and 412 keV gamma-rays, and the results compared with the self consistent Korringe -Kohn-Rostoker Coherent-Potential Approximation (KKR-CPA) for the iron nickel alloy. The other investigations reported all involve the use of the synchrotron radiation; the polarisation of synchrotron radiation has been established for the SRS W9.4 line, for energies of the order of 50-65 keV, and good agreements with the theoretical calculations were obtained. The isotropic spin dependent Compton profile of gadolinium and directional spin dependent Compton profile of nickel have been measured for the first time using the inclined view method of extracting circular polarisation of synchrotron radiation. The existence of the spin dependent photoabsorption terms in the absorption coefficient have been established experimentally for iron and nickel, and compared with the first principles spin polarised band calculation.

Brahmia, Abdelbaki

207

Evaluation of a stochastic reconstruction algorithm for use in Compton camera imaging and beam range verification from secondary gamma emission during proton therapy  

PubMed Central

In this paper, we study the feasibility of using the stochastic origin ensemble (SOE) algorithm for reconstructing images of secondary gammas emitted during proton radiotherapy from data measured with a three-stage Compton camera. The purpose of this study was to evaluate the quality of the images of the gamma rays emitted during proton irradiation produced using the SOE algorithm and to measure how well the images reproduce the distal falloff of the beam. For our evaluation, we performed a Monte Carlo simulation of an ideal three-stage Compton camera positioned above and orthogonal to a proton pencil beam irradiating a tissue phantom. Scattering of beam protons with nuclei in the phantom produces secondary gamma rays, which are detected by the Compton camera and used as input to the SOE algorithm. We studied the SOE reconstructed images as a function of the number of iterations, the voxel probability parameter, and the number of detected gammas used by the SOE algorithm. We quantitatively evaluated the capabilities of the SOE algorithm by calculating and comparing the normalized mean square error (NMSE) of SOE reconstructed images. We also studied the ability of the SOE reconstructed images to predict the distal falloff of the secondary gamma production in the irradiated tissue. Our results show that the images produced with the SOE algorithm converge in ~10,000 iterations, with little improvement to the image NMSE for iterations above this number. We found that the statistical noise of the images is inversely proportional to the ratio of the number of gammas detected to the SOE voxel probability parameter value. In our study, the SOE predicted distal falloff of the reconstructed images agrees with the Monte Carlo calculated distal falloff of the gamma emission profile in the phantom to within 0.6 mm for the positions of maximum emission (100%) and 90%, 50%, and 20% distal falloff of the gamma emission profile. We conclude that the SOE algorithm is an effective method for reconstructing images of a proton pencil beam from the data collected by an ideal Compton camera and that these images accurately model the distal falloff of secondary gamma emission during proton irradiation. PMID:22588144

Mackin, Dennis; Peterson, Steve; Beddar, Sam; Polf, Jerimy

2012-01-01

208

Evaluation of a stochastic reconstruction algorithm for use in Compton camera imaging and beam range verification from secondary gamma emission during proton therapy.  

PubMed

In this paper, we study the feasibility of using the stochastic origin ensemble (SOE) algorithm for reconstructing images of secondary gammas emitted during proton radiotherapy from data measured with a three-stage Compton camera. The purpose of this study was to evaluate the quality of the images of the gamma rays emitted during proton irradiation produced using the SOE algorithm and to measure how well the images reproduce the distal falloff of the beam. For our evaluation, we performed a Monte Carlo simulation of an ideal three-stage Compton camera positioned above and orthogonal to a proton pencil beam irradiating a tissue phantom. Scattering of beam protons with nuclei in the phantom produces secondary gamma rays, which are detected by the Compton camera and used as input to the SOE algorithm. We studied the SOE reconstructed images as a function of the number of iterations, the voxel probability parameter, and the number of detected gammas used by the SOE algorithm. We quantitatively evaluated the capabilities of the SOE algorithm by calculating and comparing the normalized mean square error (NMSE) of SOE reconstructed images. We also studied the ability of the SOE reconstructed images to predict the distal falloff of the secondary gamma production in the irradiated tissue. Our results show that the images produced with the SOE algorithm converge in ~10,000 iterations, with little improvement to the image NMSE for iterations above this number. We found that the statistical noise of the images is inversely proportional to the ratio of the number of gammas detected to the SOE voxel probability parameter value. In our study, the SOE predicted distal falloff of the reconstructed images agrees with the Monte Carlo calculated distal falloff of the gamma emission profile in the phantom to within 0.6 mm for the positions of maximum emission (100%) and 90%, 50% and 20% distal falloff of the gamma emission profile. We conclude that the SOE algorithm is an effective method for reconstructing images of a proton pencil beam from the data collected by an ideal Compton camera and that these images accurately model the distal falloff of secondary gamma emission during proton irradiation. PMID:22588144

Mackin, Dennis; Peterson, Steve; Beddar, Sam; Polf, Jerimy

2012-06-01

209

Evaluation of a stochastic reconstruction algorithm for use in Compton camera imaging and beam range verification from secondary gamma emission during proton therapy  

NASA Astrophysics Data System (ADS)

In this paper, we study the feasibility of using the stochastic origin ensemble (SOE) algorithm for reconstructing images of secondary gammas emitted during proton radiotherapy from data measured with a three-stage Compton camera. The purpose of this study was to evaluate the quality of the images of the gamma rays emitted during proton irradiation produced using the SOE algorithm and to measure how well the images reproduce the distal falloff of the beam. For our evaluation, we performed a Monte Carlo simulation of an ideal three-stage Compton camera positioned above and orthogonal to a proton pencil beam irradiating a tissue phantom. Scattering of beam protons with nuclei in the phantom produces secondary gamma rays, which are detected by the Compton camera and used as input to the SOE algorithm. We studied the SOE reconstructed images as a function of the number of iterations, the voxel probability parameter, and the number of detected gammas used by the SOE algorithm. We quantitatively evaluated the capabilities of the SOE algorithm by calculating and comparing the normalized mean square error (NMSE) of SOE reconstructed images. We also studied the ability of the SOE reconstructed images to predict the distal falloff of the secondary gamma production in the irradiated tissue. Our results show that the images produced with the SOE algorithm converge in ?10?000 iterations, with little improvement to the image NMSE for iterations above this number. We found that the statistical noise of the images is inversely proportional to the ratio of the number of gammas detected to the SOE voxel probability parameter value. In our study, the SOE predicted distal falloff of the reconstructed images agrees with the Monte Carlo calculated distal falloff of the gamma emission profile in the phantom to within 0.6 mm for the positions of maximum emission (100%) and 90%, 50% and 20% distal falloff of the gamma emission profile. We conclude that the SOE algorithm is an effective method for reconstructing images of a proton pencil beam from the data collected by an ideal Compton camera and that these images accurately model the distal falloff of secondary gamma emission during proton irradiation.

Mackin, Dennis; Peterson, Steve; Beddar, Sam; Polf, Jerimy

2012-06-01

210

Dissecting deuteron Compton scattering I: The observables with polarised initial states  

NASA Astrophysics Data System (ADS)

A complete set of linearly independent observables in Compton scattering with arbitrarily polarised real photons off an arbitrarily polarised spin-1 target is introduced, for the case that the final-state polarisations are not measured. Adopted from the one widely used, e.g., in deuteron photo-dissociation, it consists of 18 terms: the unpolarised cross section, the beam asymmetry, 4 target asymmetries and 12 asymmetries in which both beam and target are polarised. They are expressed by the helicity amplitudes and where available related to observables discussed by other authors. As application to deuteron Compton scattering, their dependence on the (isoscalar) scalar and spin dipole polarisabilities of the nucleon is explored in Chiral Effective Field Theory with dynamical ?(1232) degrees of freedom at order e 2 ? 3. Some asymmetries are sensitive to only one or two dipole polarisabilities, making them particularly attractive for experimental studies. At a photon energy of 100 MeV, a set of 5 observables is identified from which one may be able to extract the spin polarisabilities of the nucleon. These are experimentally realistic but challenging and mostly involve tensor-polarised deuterons. Relative to Compton scattering from a nucleon, sensitivity to the "mixed" spin polarisabilities ? E1 M2 and ? M1 E2 is increased because of the interference with the D wave component of the deuteron and with its pion-exchange current. An interactive Mathematica 9.0 notebook with results for all observables at photon energies up to 120 MeV is available from hgrie@gwu.edu.

Griehammer, Harald W.

2013-08-01

211

An inverse Compton scattering (ICS) model of pulsar emission: III. polarization  

E-print Network

Qiao and his collaborators recently proposed an inverse Compton Scattering (ICS) model to explain radio emission of pulsars. In this paper, we investigate the polarization properties of pulsar emission in the model. First of all, using the lower frequency approximation, we derived the analytical amplitude of inverse Compton scattered wave of a single electron in strong magnetic field. We found that the out-going radio emission of a single relativistic electron scattering off the ``low frequency waves'' produced by gap-sparking should be linearly polarized and have no circular polarization at all. However, considering the coherency of the emission from a bunch of electrons, we found that the out-going radiation from the inner part of emission beam, i.e., that from the lower emission altitudes, prefers to have circular polarization. Computer simulations show that the polarization properties, such as the sense reversal of circular polarization near the pulse center, S-shape of position angle swing of the linear polarization, strong linear polarization in conal components, can be reproduced in the ICS model.

R. X. Xu; J. F. Liu; J. L. Han; G. J. Qiao

1999-11-15

212

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

213

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

214

Photoabsorption and Compton scattering in ionization of helium at high photon energies  

SciTech Connect

Production of singly and doubly charged helium ions by impact of keV photons is studied. The ratio R{sub ph} = {sigma}{sub ph}{sup ++}/{sigma}{sub ph}{sup +} for photoabsorption is calculated in the photon-energy range 2--18 keV using correlated initial- and final- state wave functions. Extrapolation towards asymptotic photon energies yields R{sub ph}({omega} {yields} {infinity}) = 1.66% in agreement with previous predictions. Ionization due to Compton scattering, which becomes comparable to photoabsorption above {omega} {approximately} 3 keV, is discussed.

Andersson, L.R.; Burgdoerfer, J. [Oak Ridge National Lab., TN (United States)]|[Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy

1993-10-01

215

MeV gamma-ray Compton camera using a gaseous electron tracker for background-suppressed observation  

NASA Astrophysics Data System (ADS)

As a next generation MeV gamma-ray telescope, we develop an electron-tracking Compton camera (ETCC) that consists of a gaseous electron tracker surrounded by pixel scintillator arrays. The tracks of the Compton-recoil electron measured by the tracker restrict the incident gamma-ray direction to an arc region on the sky and reject background by using the energy loss rate dE/dx and a Compton-kinematics test. In 2013, we constructed, for a balloon experiment, a 30-cm-cubic ETCC with an effective area of ~1 cm2 for detecting sub-MeV gamma rays (5 ? detection of the Crab Nebula for 4 h). In future work, we will extend this ETCC to an effective area of ~10 cm2. In the present paper, we report the performance of the current ETCC.

Takada, A.; Tanimori, T.; Kubo, H.; Parker, J. D.; Mizumoto, T.; Mizumura, Y.; Sawano, T.; Nakamura, K.; Matsuoka, Y.; Komura, S.; Nakamura, S.; Oda, M.; Miuchi, K.; Kurosawa, S.

2014-07-01

216

Stability analysis of implicit time discretizations for the Compton-scattering Fokker-Planck equation  

SciTech Connect

The Fokker-Planck equation is a widely used approximation for modeling the Compton scattering of photons in high energy density applications. In this paper, we perform a stability analysis of three implicit time discretizations for the Compton-Scattering Fokker-Planck equation. Specifically, we examine (i) a Semi-Implicit (SI) scheme that employs backward-Euler differencing but evaluates temperature-dependent coefficients at their beginning-of-time-step values, (ii) a Fully Implicit (FI) discretization that instead evaluates temperature-dependent coefficients at their end-of-time-step values, and (iii) a Linearized Implicit (LI) scheme, which is developed by linearizing the temperature dependence of the FI discretization within each time step. Our stability analysis shows that the FI and LI schemes are unconditionally stable and cannot generate oscillatory solutions regardless of time-step size, whereas the SI discretization can suffer from instabilities and nonphysical oscillations for sufficiently large time steps. With the results of this analysis, we present time-step limits for the SI scheme that prevent undesirable behavior. We test the validity of our stability analysis and time-step limits with a set of numerical examples.

Densmore, Jeffery D [Los Alamos National Laboratory; Warsa, James S [Los Alamos National Laboratory; Lowrie, Robert B [Los Alamos National Laboratory; Morel, Jim E [TEXAS A& M UNIV

2008-01-01

217

Nucleon polarizabilities from deuteron Compton scattering within a Green's function hybrid approach  

NASA Astrophysics Data System (ADS)

We examine elastic Compton scattering from the deuteron for photon energies ranging from zero to 100MeV, using state-of-the-art deuteron wave functions and NN potentials. Nucleon-nucleon rescattering between emission and absorption of the two photons is treated by Greens functions in order to ensure gauge invariance and the correct Thomson limit. With this Greens function hybrid approach, we fulfill the low-energy theorem of deuteron Compton scattering and there is no significant dependence on the deuteron wave function used. Concerning the nucleon structure, we use the chiral effective field theory with explicit ?(1232) degrees of freedom within the small-scale expansion up to leading-one-loop order. Agreement with available data is good at all energies. Our 2-parameter fit to all elastic ? d data leads to values for the static isoscalar dipole polarizabilities which are in excellent agreement with the isoscalar Baldin sum rule. Taking this value as additional input, we find ?Es = (11.30.7( stat)0.6( Baldin)1( theory)).10-4 fm^3 and ?Ms = (3.20.7( stat)0.6( Baldin)1( theory)).10-4 fm^3 and conclude by comparison to the proton numbers that neutron and proton polarizabilities are the same within rather small errors.

Hildebrandt, R. P.; Griehammer, H. W.; Hemmert, T. R.

2010-10-01

218

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

219

Stability analysis of implicit time discretizations for the Compton-scattering Fokker-Planck equation  

SciTech Connect

The Fokker-Planck equation is a widely used approximation for modeling the Compton scattering of photons in high energy density applications. In this paper, we perform a stability analysis of three implicit time discretizations for the Compton-Scattering Fokker-Planck equation. Specifically, we examine (i) a Semi-Implicit (SI) scheme that employs backward-Euler differencing but evaluates temperature-dependent coefficients at their beginning-of-time-step values, (ii) a Fully Implicit (FI) discretization that instead evaluates temperature-dependent coefficients at their end-of-time-step values, and (iii) a Linearized Implicit (LI) scheme, which is developed by linearizing the temperature dependence of the FI discretization within each time step. Our stability analysis shows that the FI and LI schemes are unconditionally stable and cannot generate oscillatory solutions regardless of time-step size, whereas the SI discretization can suffer from instabilities and nonphysical oscillations for sufficiently large time steps. With the results of this analysis, we present time-step limits for the SI scheme that prevent undesirable behavior. We test the validity of our stability analysis and time-step limits with a set of numerical examples.

Densmore, Jeffery D. [Computational Physics and Methods Group, Los Alamos National Laboratory, P.O. Box 1663, MS D409, Los Alamos, NM 87545 (United States)], E-mail: jdd@lanl.gov; Warsa, James S. [Computational Physics and Methods Group, Los Alamos National Laboratory, P.O. Box 1663, MS D409, Los Alamos, NM 87545 (United States)], E-mail: warsa@lanl.gov; Lowrie, Robert B. [Computational Physics and Methods Group, Los Alamos National Laboratory, P.O. Box 1663, MS D409, Los Alamos, NM 87545 (United States)], E-mail: lowrie@lanl.gov; Morel, Jim E. [Department of Nuclear Engineering, Texas A and M University, 3133 TAMU, College Station, TX 77843 (United States)], E-mail: morel@tamu.edu

2009-09-01

220

The use of Compton scattering to differentiate between classifications of normal and diseased breast tissue  

NASA Astrophysics Data System (ADS)

This study describes a technique for measuring the electron density of breast tissue utilizing Compton scattered photons. The K?2 line from a tungsten target industrial x-ray tube (57.97 keV) was used and the scattered x-rays collected at an angle of 30. At this angle the Compton and coherent photon peaks can be resolved using an energy dispersive detector and a peak fitting algorithm. The system was calibrated using solutions of known electron density. The results obtained from a pilot study of 22 tissues are presented. The tissue samples investigated comprise four different tissue classifications: adipose, malignancy, fibroadenoma and fibrocystic change (FCC). It is shown that there is a difference between adipose and malignant tissue, to a value of 9.0%, and between adipose and FCC, to a value of 12.7%. These figures are found to be significant by statistical analysis. The differences between adipose and fibroadenoma tissues (2.2%) and between malignancy and FCC (3.4%) are not significant. It is hypothesized that the alteration in glucose uptake within malignant cells may cause these tissues to have an elevated electron density. The fibrotic nature of tissue that has undergone FCC gives the highest measure of all tissue types.

Ryan, Elaine A.; Farquharson, Michael J.; Flinton, David M.

2005-07-01

221

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 Bogot, 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

222

Compton Scattering Cross Sections in Strong Magnetic Fields: Advances for Neutron Star Applications  

NASA Astrophysics Data System (ADS)

Various telescopes including RXTE, INTEGRAL and Suzaku have detected non-thermal X-ray emission in the 10 - 200 keV band from strongly magnetic neutron stars. Inverse Compton scattering, a quantum-electrodynamical process, is believed to be a leading candidate for the production of this intense X-ray radiation. Magnetospheric conditions are such that electrons may well possess ultra-relativistic energies, which lead to attractive simplifications of the cross section. We have recently addressed such a case by developing compact analytic expressions using correct spin-dependent widths and Sokolov & Ternov (ST) basis states, focusing specifically on ground state-to-ground state scattering. However, inverse Compton scattering can cool electrons down to mildly-relativistic energies, necessitating the development of a more general case where the incoming photons acquire nonzero incident angles relative to the field in the rest frame of the electron, and the intermediate state can be excited to arbitrary Landau levels. In this paper, we develop results pertaining to this general case using ST formalism, and treating the plethora of harmonic resonances associated with various cyclotron transitions between Landau states. Four possible scattering modes (parallel-parallel, perpendicular-perpendicular, parallel-perpendicular, and perpendicular-parallel) encapsulate the polarization dependence of the cross section. We present preliminary analytic and numerical investigations of the magnitude of the extra Landau state contributions to obtain the full cross section, and compare these new analytic developments with the spin-averaged cross sections, which we develop in parallel. Results will find application to various neutron star problems, including computation of Eddington luminosities in the magnetospheres of magnetars. We express our gratitude for the generous support of the Michigan Space Grant Consortium, of the National Science Foundation (REU and RUI), and the NASA Astrophysics Theory and Fundamental Program.

Eiles, Matthew; Gonthier, P. L.; Baring, M. G.; Wadiasingh, Z.

2013-04-01

223

Cross section calculations of photoabsorption and Compton scattering contributions to He single and double ionization via recoil momentum observable  

NASA Astrophysics Data System (ADS)

This paper presents a theoretical framework for the calculations of Compton scattering and photoabsorption on bound electrons for single and double ionization, based on recoil-ion observable. For the photoionization of helium (single or double) our calculations of cross sections for photon energy of 7 keV show that the recoil ions from photoabsorption are mainly distributed on a sphere in momentum space of 22 a.u. radius, while recoil ions from Compton scattering show a dominant contribution close to zero radius (?3a.u.). Our calculated cross sections are in agreement with the published experimental values.

Kaliman, Zoran; auhar, Gordana; Jurkovi?, Slaven

2014-02-01

224

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 eFuso Nuclear, Instituto Superior Tcnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal)] [GoLP/Instituto de Plasmas eFuso Nuclear, Instituto Superior Tcnico, 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

225

Compton scattering of an X-ray photon by an open-shell atom  

SciTech Connect

A nonrelativistic quantum theory for the nonresonant Compton scattering of an X-ray photon by a free many-electron atom with an open shell in the ground state has been constructed in the single-configuration Hartree-Fock approximation outside the impulse approximation widely used in the literature. The transition to an atom with closed shells reproduces the results obtained previously in [6, 7]. The results of a test calculation for atoms with open (Ti, Fe) and closed (Zn) 3d core shells are presented. The effects of the radial relaxation of one-electron states in the field of core vacancies have been taken into account. The results of the calculation agree well with the experimental results [15, 16]. It has been established that the results of the impulse approximation in the investigated X-ray photon energy ranges disagree with those of our theory not only quantitatively but also qualitatively. In particular, the impulse approximation near the elastic (Thomson and Rayleigh) scattering line leads to a gross overestimation of the contributions from the deep atomic shells involved in the inelastic photon scattering only virtually to the scattering probability. The presented theory is general in character and its applicability to a particular element of the Mendeleev table with an open core shell or to a many-electron atomic ion is limited only by the requirement that the nonrelativistic Hartree-Fock approximation be properly used in describing the scattering-state wave functions.

Hopersky, A. N., E-mail: hopersky_vm_1@rgups.ru; Nadolinsky, A. M. [Rostov State University of Transport Communication (Russian Federation)

2012-09-15

226

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

227

Compton scattering from the proton in an effective field theory with explicit Delta degrees of freedom  

NASA Astrophysics Data System (ADS)

We analyse the proton Compton-scattering differential cross section for photon energies up to 325 MeV using Chiral Effective Field Theory (?EFT) and extract new values for the electric and magnetic polarisabilities of the proton. Our approach builds in the key physics in two different regimes: photon energies ? ? m ? ("low energy"), and the higher energies where the ?(1232) resonance plays a key role. The Compton amplitude is complete at N4LO, {O}( {e^2 ? ^4 } ), in the low-energy region, and at NLO, {O}( {e^2 ? ^0 } ), in the resonance region. Throughout, the Delta-pole graphs are dressed with ? N loops and ?N ? vertex corrections. A statistically consistent database of proton Compton experiments is used to constrain the free parameters in our amplitude: the M1 ?N ? transition strength b 1 (which is fixed in the resonance region) and the polarisabilities ? E1 and ? M1 (which are fixed from data below 170 MeV). In order to obtain a reasonable fit, we find it necessary to add the spin polarisability ? M1 M1 as a free parameter, even though it is, strictly speaking, predicted in ?EFT at the order to which we work. We show that the fit is consistent with the Baldin sum rule, and then use that sum rule to constrain ? E1 + ? M1. In this way we obtain ? E1 = [10.65 0.35(stat) 0.2(Baldin) 0.3(theory)] 10-4 fm3 and ? M1 = [3.15 ? 0.35(state) 0.2(Baldin) ? 0.3()theory] 10-4 fm3, with ?2 = 113.2 for 135 degrees of freedom. A detailed rationale for the theoretical uncertainties assigned to this result is provided.

McGovern, J. A.; Phillips, D. R.; Griehammer, H. W.

2013-01-01

228

Non Linear Compton Scattering of Strong Laser Radiation on Channeled Particles in a Crystal  

E-print Network

A version for intense $\\gamma $-ray radiation based on the multiphoton scattering of strong laser radiation on relativistic particle beam channeled in a crystal is proposed. The scheme is considered when the incident laser beam and charged paricles beam are counter-propagating and the laser radiation is resonant to the energy levels of transversal motion of channeled particles.

A. K. Avetissian; K. Z. Hatsagortsian; G. F. Mkrtchian; Kh. V. Sedrakian

2001-08-31

229

Proposal for an advanced hybrid K-edge/XRF densitometry (HKED) using a monochromatic photon beam from laser Compton scattering  

NASA Astrophysics Data System (ADS)

The general purpose Monte Carlo electron-gamma shower computer code (EGS5) was used to obtain the U, Np, and Pu X-ray response from the hybrid K-edge/XRF densitometry (HKED). In the present simulation, we adopt a monochromatic, linearly polarized photon beam generated by using inverse Compton scattering of laser light with high-energy electrons from an energy recovery linac. The simulation has been carried out under various conditions of the U, Np, and Pu concentrations to investigate the effect of counting rates as well as counting precision. The results of the simulation show that the assessment time for low concentration Pu input solutions is reduced by improving the signal-to-background ratios. It is also shown that the Np concentration is determined with the counting precision of 0.67-1.8% in standard deviation during 1 h live time measurement for a 3N HNO 3 sample solution (1.1-1.3 g/cm 2) including U (10-200 g/L), Np (0.1 g/L), and Pu (10 g/L).

Shizuma, Toshiyuki; Hajima, Ryoichi; Hayakawa, Takehito; Fujiwara, Mamoru; Sonoda, Takashi; Seya, Michio

2011-10-01

230

A laser-Compton scattering prototype experiment at 100 MeV linac of Shanghai Institute of Applied Physics  

SciTech Connect

As a prototype of the Shanghai Laser Electron Gamma Source in the Shanghai Synchrotron Radiation Facility, an x-ray source based on laser-Compton scattering (LCS) has been installed at the terminal of the 100 MeV linac of the Shanghai Institute of Applied Physics. LCS x-rays are generated by interactions between Q-switched Nd:yttrium aluminum garnet laser pulses [with wavelength of 1064 nm and pulse width of 21 ns (full width at half maximum)] and electron bunches [with energy of 108 MeV and pulse width of 0.95 ns (rms)] at an angle of 42 deg. between laser and electron beam. In order to measure the energy spectrum of LCS x-rays, a Si(Li) detector along the electron beam line axis is positioned at 9.8 m away from a LCS chamber. After background subtraction, the LCS x-ray spectrum with the peak energy of 29.1{+-}4.4|{sub stat}{+-}2.1|{sub syst} keV and the peak width (rms) of 7.8{+-}2.8|{sub stat}{+-}0.4|{sub syst} keV is observed. Normally the 100 MeV linac operates with the electron macropulse charge of 1.0 nC/pulse, and the electron and laser collision repetition rate of 20 Hz. Therefore, the total LCS x-ray flux of (5.2{+-}2.0)x10{sup 2} Hz can be achieved.

Luo, W.; Fan, G. T.; Fan, G. W.; Li, Y. J.; Xu, Y.; Yang, L. F. [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Graduate School, Chinese Academy of Sciences, Beijing 100039 (China); Xu, W. [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Science and Technology of China, Hefei 230026 (China); Pan, Q. Y.; Cai, X. Z.; Chen, J. G.; Chen, Y. Z.; Guo, W.; Liu, W. H.; Lin, G. Q.; Ma, Y. G.; Shen, W. Q.; Xu, B. J.; Xu, J. Q.; Zhang, H. O.; Yan, Z. [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); and others

2010-01-15

231

Scaling tests of the cross section for deeply virtual Compton scattering.  

PubMed

We present the first measurements of the e[over -->]p-->epgamma cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q(2) dependence (from 1.5 to 2.3 GeV(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(2). The helicity-independent cross section is also measured at Q(2)=2.3 GeV(2). We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation. PMID:17280421

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

2006-12-31

232

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

233

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

234

Deeply Virtual Compton Scattering and Meson Production at Jlab/CLAS  

SciTech Connect

This report reviews the recent experimental results from the CLAS collaboration (Hall B of Jefferson Lab, or JLab) on Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) and discusses their interpretation in the framework of Generalized Parton Distributions (GPDs). The impact of the experimental data on the applicability of the GPD mechanism to these exclusive reactions is discussed. Initial results obtained from JLab 6 GeV data indicate that DVCS might already be interpretable in this framework while GPD models fail to describe the exclusive meson production (DVMP) data with the GPD parameterizations presently used. An exception is the {phi} meson production for which the GPD mechanism appears to apply. The recent global analyses aiming to extract GPDs from fitting DVCS CLAS and world data are discussed. The GPD experimental program at CLAS12, planned with the upcoming 12 GeV upgrade of JLab, is briefly presented.

Hyon-Suk Jo

2012-04-01

235

Deeply Virtual Compton Scattering on nucleons and nuclei in generalized vector meson dominance model  

SciTech Connect

We consider Deeply Virtual Compton Scattering (DVCS) on nucleons and nuclei in the framework of generalized vector meson dominance (GVMD) model. We demonstrate that the GVMD model provides a good description of the HERA data on the dependence of the proton DVCS cross section on $Q^2$, $W$ (at $Q^2=4$ GeV$^2$) and $t$. At $Q^2 = 8$ GeV$^2$, the soft $W$-behavior of the GVMD model somewhat underestimates the $W$-dependence of the DVCS cross section due to the hard contribution not present in the GVMD model. We estimate $1/Q^2$ power-suppressed corrections to the DVCS amplitude and the DVCS cross section and find them large. We also make predictions for the nuclear DVCS amplitude and cross section in the kinematics of the future Electron-Ion Collider. We predict significant nuclear shadowing, which matches well predictions of the leading-twist nuclear shadowing in DIS on nuclei.

Vadim Guzey; Klaus Goeke; Marat Siddikov

2008-02-01

236

Spin polarizabilities and polarizabilities of the nucleon studied by free and quasi-free Compton scattering at MAMI (Mainz)  

E-print Network

In addition to the E2/M1 ratio of the N->$\\Delta$ transition, the electromagnetic polarizabilities and spin-polarizabilities are important structure constants of the nucleon which serve as sensitive tests of chiral perturbation theory and of models of the nucleon. Recently, these quantities have been investigated experimentally at MAMI (Mainz) by high-precision Compton scattering using hydrogen and deuterium targets, where for the latter the method of quasi-free scattering has been applied.

Martin Schumacher

2003-09-15

237

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 t...

Myers, L S; Brudvik, J; Feldman, G; Fissum, K G; Griehammer, 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; Schrder, B; Stave, S C

2014-01-01

238

The Role of Inverse Compton Scattering in Solar Coronal Hard X-ray and ?-ray Sources  

NASA Astrophysics Data System (ADS)

We consider the role of inverse Compton scattering (ICS) as a means of producing coronal hard X-ray (HXR) and continuum ?-ray sources during solar flares. Coronal HXR and continuum ?-ray emission observed during solar flares has been interpreted in terms of thin-target bremsstrahlung emission. In one case, this interpretation leads to the conclusion that the number of energetic electrons required to account for the coronal HXR source must be large, implying that essentially all electrons in the source must be accelerated to energies ? 16 keV. In other cases, the spectral index of the photon spectrum of ?-ray sources approaches the theoretical limit for bremsstrahlung emission (? ~ 1.5 - 2). Here we investigate ICS in both the fully relativistic and mildly relativistic regimes as an alternative to non-thermal bremsstrahlung. It is known that relativistic electrons are produced during powerful flares; these are capable of up-scattering soft photospheric photons to HXR energies. Previously overlooked is the fact that mildly relativistic electrons, generally produced in much greater numbers in flares of all sizes, can up-scatter EUV/SXR photons to HXR energies. We also explore ICS on anisotropic electron distributions and show that the resulting emission can be significantly enhanced over the case of scattering on an isotropic electron distribution. We apply our results to a selection of coronal HXR and ?-ray events and find that in some cases the ICS mechanism is a viable alternative to non-thermal bremsstrahlung emission, particularly if the energetic population of electrons responsible for the emission is anisotropic.

Chen, B.; Bastian, T. S.

2011-12-01

239

Reionization and cosmic microwave background distortions: a complete treatment of second order Compton scattering  

E-print Network

The ionization history of the universe provides a major source of ambiguity in constraining cosmological models using small angular scale microwave background anisotropies. To clarify these issues, we consider a complete treatment of Compton scattering to second order, an approach which may be applicable to other astrophysical situations. We find that only the ${\\cal O} (v)$ Doppler effect, and the ${\\cal O} (v\\delta)$ Vishniac effect are important for recent last scattering epochs; the ${\\cal O} (v^2)$ Doppler effect is not significant on any angular scale, and other higher-order effects are completely negligible. However the ${\\cal O}(v^2)$ effect does lead to \\Cy\\ distortions, which although generally below current constraints, set an unavoidable minimum level in reionization models. We consider the small-angle approximation for the Vishniac effect in detail, and show several improvements over previous treatments, particularly for low $\\Omega_0$. For standard cold dark matter models, the effect of reionization is to redistribute the anisotropies to arcminute scales; late reionization leads to partially erased primary fluctuations and a secondary contribution of comparable magnitude. Using recent anisotropy limits from the ATCA experiment, we set new constraints on baryonic dark matter models. Stronger constraints are imposed (in second order) upon models with higher Hubble constant, steeper $n$, and higher density. These limits depend on the specific ionization history assumed, but the factor gained by lowering the ionization fraction is generally small, and may be tested by currently-planned

Wayne Hu; Douglas Scott; Joseph Silk

1993-05-29

240

Compton scattering by the proton through ?cms = 75 and 90 in the ?-resonance region  

NASA Astrophysics Data System (ADS)

Differential cross sections for Compton scattering by the proton have been measured in the energy interval between 200 and 500 MeV at scattering angles of ?cms = 75 and ?cms = 90 using the CATS, the CATS/TRAJAN, and the COPP setups with the Glasgow Tagger at MAMI (Mainz). The data are compared with predictions from dispersion theory using photo-meson amplitudes from the recent VPI solution SM95. The experiment and the theoretical procedure are described in detail. It is found that the experiment and predictions are in agreement as far as the energy dependence of the differential cross sections in the ?-range is concerned. However, there is evidence that a scaling down of the resonance part of the M 1+{3}/{2} photo-meson amplitude by (2.8 0.9)% is required in comparison with the VPI analysis. The deduced value of the M 1+{3}/{2}- photoproduction amplitude at the resonance energy of 320 MeV is: |M 1+{3}/{2}| = (39.6 0.4) 10 -3 m ? +-1.

Hnger, A.; Peise, J.; Robbiano, A.; Ahrens, J.; Anthony, I.; Arends, H.-J.; Beck, R.; Capitani, G. P.; Dolbilkin, B.; Falkenberg, H.; Galler, G.; Hall, S. J.; Kellie, J. D.; Kondratjev, R.; Kordsmeier, R.; Lisin, V.; L'Vov, A. I.; Miller, G. J.; Molinari, C.; Ottonello, P.; Reolon, A. R.; Sanzone, M.; Schmitz, M.; Schneider, M.; Schumacher, M.; Selke, O.; Walcher, Th.; Wissmann, F.; Wolf, S.; Zucchiatti, A.

1997-02-01

241

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

2006-11-12

242

Performance of a low noise front-end ASIC for Si\\/CdTe detectors in Compton gamma-ray telescope  

Microsoft Academic Search

Compton telescopes based on semiconductor technologies are being developed to explore the gamma-ray universe in an energy band 0.1-20 MeV, which is not well covered by the present or near-future gamma-ray telescopes. The key feature of such Compton telescopes is the high energy resolution that is crucial for high angular resolution and high background rejection capability. The energy resolution around

Hiroyasu Tajima; Tatsuya Nakamoto; Takaaki Tanaka; Shingo Uno; Takefumi Mitani; Ed. Ce. Silva; Yasushi Fukazawa; Tuneyoshi Kamae; Grzegorz Madejski; Daniel Marlow; Kazuhiro Nakazawa; Masaharu Nomachi; Y. Okada; Tadayuki Takahashi

2004-01-01

243

Virtual Compton scattering and the generalized polarizabilities of the proton at Q2=0.92 and 1.76 GeV2  

E-print Network

Virtual Compton scattering (VCS) on the proton has been studied at the Jefferson Laboratory using the exclusive photon electroproduction reaction ep?ep?. This paper gives a detailed account of the analysis which has led ...

Bertozzi, William

244

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

245

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

E-print Network

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_LL-P_TT/epsilon and P_LT, and the electric and magnetic generalized polarizabilities (GPs) alpha_E(Q^2) and beta_M(Q^2) at values of the four-momentum transfer squared Q^2= 0.92 and 1.76 GeV^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^2-range, and point to their non-trivial behavior.

H. Fonvieille; G. Laveissiere; N. Degrande; S. Jaminion; C. Jutier; L. Todor; R. 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. deJager; 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; 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. 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; B. Pasquini; C. F. Perdrisat; R. Perrino; G. G. Petratos; S. Platchkov; R. Pomatsalyuk; D. L. Prout; V. A. Punjabi; T. Pussieux; G. Quemener; 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. L. J. Van der Meer; 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

2012-05-15

246

An Improvement of (X, eX) Spectrometer for Coincident Measurement of Compton Scattered Photon and Recoiled Electron  

SciTech Connect

A coincident measurement between the Compton scattered photon and the recoiled electron gives information about three dimensional electron momentum density (3D-EMD). We improve our (X, eX) spectrometer by introducing a two-dimensional area photon detector which consists of an array of BGO scintillators and a position sensitive photoelectron multiplier tube in order to obtain the 3D-EMD over whole momentum space. We present the details of the improved system, performance and some experimental results.

Uchiyama, H.; Adachi, H.; Kishimoto, S.; Itou, M.; Sakurai, H.; Itoh, F.; Kawata, H. [Department of Materials Structure Science, Graduate University for Advanced Studies, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); The Japan Synchrotron Radiation Research Institute (JASRI), Hyogo 679-5198 (Japan); Department of Electronic Engineering, Faculty of Engineering, Gunma University, 1-5-1 Tenjincho, Kiryu, Gunma 376-8515 (Japan)

2004-05-12

247

[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

1992-06-01

248

(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

249

Determination of Vanadium by Instrumental Neutron Activation Analysis in Conjunction with Compton Suppression Gamma-Ray Spectrometry  

SciTech Connect

The toxicity of vanadium has been known for a long time. It is only recently that vanadium has been recognized as an essential trace element. The determination of vanadium with high precision and accuracy in tissues, foods, and other biological materials is needed for the purpose of studying its effect on human nutrition and health. Several techniques such as spectrophotometry, atomic absorption, X-ray fluorescence, and neutron activation analysis (NAA) can be used for its determination. Vanadium can be determined by NAA through its short-lived nuclide {sup 52}V produced via the {sup 51}V(n, {gamma}){sup 52}V reaction; it has a 1434.2-keV gamma ray and a half-life of 3.74 min. It has been reported that {sup 52}V has sufficient sensitivity for its measurement down to nanogram levels. However, it is seldom assayed in practice by instrumental NAA (INAA) in conjunction with conventional gamma-ray spectrometry, in particular for low vanadium content in high-salt biological materials, due to the Compton background interference from nuclides such as {sup 28}Al, {sup 38}Cl, {sup 56}Mn, and {sup 24}Na. Alternatively, radiochemical NAA or preconcentration NAA methods are used to separate vanadium from the major and interfering elements. A Compton suppression counting technique can be beneficially used under such situations. One of the objectives of this work was to fully explore the advantages of Compton suppression counting for the determination of vanadium in biological samples.

W. H. Zhang; A. Chatt

2000-11-12

250

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

E-print Network

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

Matteo Rinaldi; Sergio Scopetta

2014-06-18

251

Second order formalism for spin (1)/(2) fermions and Compton scattering  

NASA Astrophysics Data System (ADS)

We develop a second order formalism for massive spin 1/2 fermions based on the projection over Poincar invariant subspaces in the ((1)/(2),0)?(0,(1)/(2)) representation of the homogeneous Lorentz group. Using the U(1)em gauge principle we obtain a second order description for the electromagnetic interactions of a spin 1/2 fermion with two free parameters, the gyromagnetic factor g and a parameter ? related to odd-parity Lorentz structures. We calculate Compton scattering in this formalism. In the particular case g=2, ?=0, and for states with well-defined parity, we recover Dirac results. In general, we find the correct classical limit and a finite value rc2 for the forward differential cross section, independent of the photon energy and of the value of the parameters g and ?. The differential cross section vanishes at high energies for all g, ? except in the forward direction. The total cross section at high energies vanishes only for g=2, ?=0. We argue that this formalism is more convenient than Dirac theory in the description of low energy electromagnetic properties of baryons and illustrate the point with the proton case.

Delgado-Acosta, E. G.; Napsuciale, Mauro; Rodrguez, Simn

2011-04-01

252

Development of a 4-mirror optical cavity for an inverse Compton scattering experiment in the STF  

NASA Astrophysics Data System (ADS)

To obtain high-brightness quasi-monochromatic X-rays via inverse Compton scattering (ICS), an optical cavity for intensifying laser beams was designed and implemented in a new beam line at the KEK Superconducting RF Test Facility (STF) accelerator. The optical cavity adopts a planar configuration consisting of 4 mirrors. This confocal type resonator provides stable laser storage even with a long mirror distance, enabling head-on collision with the electron beams. To overcome the well-known astigmatism problems of the planar-type optical cavity, two forcibly bendable cylindrical mirrors were introduced instead of flat mirrors. With this new function for laser profile adjustment, an almost round laser profile at the waist point in the accelerator environment was successfully achieved. Estimated waist sizes were 43.7 ?m for the horizontal and 50.8 ?m for the vertical dimensions. The feedback control of this 4-mirror optical cavity worked with a stiff plate supporting all 4 mirrors. 1.7103 finesse and 2.8-kW stored power for a 1-ms duration with 5 Hz were achieved.

Shimizu, Hirotaka; Aryshev, Alexander; Higashi, Yasuo; Honda, Yosuke; Urakawa, Junji

2014-05-01

253

The Operation Modes of Kharkov X-Ray Generator Based on Compton Scattering NESTOR  

SciTech Connect

The results of theoretical and numerical considerations of linear Compton scattering are used to evaluate characteristics of X-rays produced by collision between a low emittance electron beam and intensive laser light in an X-ray generator NESTOR of NSC KIPT. Two main generation modes have been under consideration at preliminary NESTOR design. There are the operation mode for medicine 33.4 keV X-rays production using 43 Mev electron beam and Nd:YAG laser beam and higher energy X-rays production mode providing X-rays with energy up to 900 keV with 225 MeV electron beam and Nd:YAG laser beam. It was supposed to use an optical cavity for laser beam accumulation of about 2.6 m long and an interaction angle of about 3{sup o} in both operation modes. A few more operation modes provide possibility to expand operation range of NESTOR. Using interaction angle 10{sup o} and 150{sup o} along with optical resonator of 42 cm long and the second mode of laser light it is possible to produce X-rays in energy range from a few keV till 1.5 MeV. The intensity and spectral brightness of the X-rays is expected to be {approx} 10{sup 13} phot/s and {approx}10{sup 13} phot/s/mm{sup 2}/mrad{sup 2}/0.1%BW respectively.

Bulyak, E.V.; Gladkikh, P.; Karnaukhov, I.M.; Mytsykov, A.; Shcherbakov, A.A.; Zelinsky, A.Y.; /Kharkov, KIPT; Tatchyn, R.; /SLAC, SSRL

2005-05-09

254

Inverse Compton scattering of coherent synchrotron radiation in an energy recovery linac  

NASA Astrophysics Data System (ADS)

We propose inverse Compton scattering (ICS) of coherent synchrotron radiation (CSR) from a relativistic short electron bunch in energy recovery linacs (ERL) as a high-flux subpicosecond x-ray and ?-ray source. An advantage of the CSR scheme over a conventional ICS source is that no external laser is required, and synchronization between CSR pulses and electron bunches is obtained automatically. Moreover, higher-flux x rays can be generated from the ICS of CSR in an ERL operated at a high repetition rate, 100 MHz to 1.3 GHz. Using parameters of the Compact ERL at KEK, 11013-14phs/s b.w. 10% (the number of photons pulse-1 bandwidth unit-1) x ray with a 100 fs-1 ps pulse duration can be obtained, for an energy range from 0.04 to 4 keV. In the case of a 5-GeV ERL, ? rays with energy around tens of MeV are generated with 1108phs/pulse b.w. 10% at a repetition rate of several hundreds of MHz.

Shimada, M.; Hajima, R.

2010-10-01

255

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

NASA Astrophysics Data System (ADS)

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

Rinaldi, Matteo; Scopetta, Sergio

2014-06-01

256

Nuclear effects and neutron structure in deeply virtual Compton scattering off 3He  

NASA Astrophysics Data System (ADS)

The study of nuclear generalized parton distributions (GPDs) could be a crucial achievement of hadronic physics since they open new ways to obtain new information on the structure of bound nucleons, in particular, to access the neutron GPDs. Here, the results of calculations of 3He GPDs in Impulse Approximation (IA) are presented. The calculation of the sum of GPDs H + E, and , with the correct limits, will be shown. These quantities, at low momentum transfer, are largely dominated by the neutron contribution so that 3He is an ideal target for these kind of studies. Nevertheless the extraction of neutron information from future 3He data could be non trivial. A procedure, which takes into account nuclear effects encoded in IA, is presented. The calculation of H, E and allows also to evaluate the cross section asymmetries for deeply virtual compton scattering (DVCS) at Jefferson Lab kinematics. Thanks to these observations, DVCS off 3He could be an ideal process to access the neutron information in the next future.

Rinaldi, Matteo

2014-07-01

257

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

258

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 24 array of square CdTe detectors of 1010 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

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

2014-01-01

259

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

260

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

261

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

PubMed

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 (LaBr(3)). 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 cm(2) 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

2011-05-21

262

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

NASA Astrophysics Data System (ADS)

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.

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

2011-05-01

263

The Role of Inverse Compton Scattering in Solar Coronal Hard X-Ray and ?-Ray Sources  

NASA Astrophysics Data System (ADS)

Coronal hard X-ray (HXR) and continuum ?-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 ?-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 ?-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 ?-ray events and find that in some cases the ICS is a viable alternative emission mechanism.

Chen, Bin; Bastian, T. S.

2012-05-01

264

Collective Spectra of Resonant Inverse Compton Scattering of Assembly of Relativistic Electrons in Intense Magnetic Fields*  

NASA Astrophysics Data System (ADS)

The resonant inverse Compton scattering (RICS) of relativistic electrons in intense magnetic fields is an efficient mechanism for producing the highenergy ?-rays. In our previous work it is suggested that the early-stage ?-ray radiation of ?-ray bursts (GRBs) may be mainly produced by this mechanism. By using this mechanism, some puzzles in the study of GRBs can be clarified, e.g., the origin of the Amati relation obtained from the statistics of observations, the formation of the observed two-segment (broken) power-law spectra, the relevant "deadline problem", the polarization property, etc. Herein our discussion will be focused on the formation of the broken power-law spectra. Based on the formula of the RICS spectral power of individual fast electrons, we have derived the simplified analytical formula of the collective RICS radiation spectrum (RICS spectral luminosity) produced by the assembly of relativistic electrons in an intense magnetic field when they pass through the ambient low-frequency radiation field, and applied it to several typical low-frequency radiation fields (e.g., the black-body radiation field, power-law radiation field and thermal bremsstrahlung field) around the central neutron star, for the convenience of comparison with the observed spectra. Our calculations indicate that the RICS radiation mechanism has a very high efficiency in the hard X-ray and ?-ray wavebands, if the matching condition (i.e., the condition approximate to resonance) is satisfied, and that independent of the ambient radiation field, the produced spectra are commonly the two-segment power-law spectra. Additionally, it is suggested that the RICS mechanism might be an ideal highly-efficient radiation mechanism for the high-energy emissions (hard X-rays and ?-rays) of the GRBs, soft ?-ray repeated bursts (SGRs) and ?-ray pulsars (GRPs).

Dang-bo, Liu; Yong-feng, Huang; Luo-bu, Danzeng; Tian-lu, Chen

2011-07-01

265

Visualization of microvessels by angiography using inverse-Compton scattering X-rays in animal models.  

PubMed

The fundamental performance of microangiography has been evaluated using the S-band linac-based inverse-Compton scattering X-ray (iCSX) method to determine how many photons would be required to apply iCSX to human microangiography. ICSX is characterized by its quasi-monochromatic nature and small focus size which are fundamental requirements for microangiography. However, the current iCSX source does not have sufficient flux for microangiography in clinical settings. It was determined whether S-band compact linac-based iCSX can visualize small vessels of excised animal organs, and the amount of X-ray photons required for real time microangiography in clinical settings was estimated. The iCSX coupled with a high-gain avalanche rushing amorphous photoconductor camera could visualize a resolution chart with only a single iCSX pulse of ?3?ps duration; the resolution was estimated to be ?500?m. The iCSX coupled with an X-ray cooled charge-coupled device image sensor camera visualized seventh-order vascular branches (80?m in diameter) of a rabbit ear by accumulating the images for 5 and 30?min, corresponding to irradiation of 3000 and 18000 iCSX pulses, respectively. The S-band linac-based iCSX visualized microvessels by accumulating the images. An iCSX source with a photon number of 3.6 10(3)-5.4 10(4) times greater than that used in this study may enable visualizing microvessels of human fingertips even in clinical settings. PMID:25343802

Fujii, Toshiharu; Fukuyama, Naoto; Tanaka, Chiharu; Ikeya, Yoshimori; Shinozaki, Yoshiro; Kawai, Toshiaki; Atsumi, Takuji; Shiraishi, Takashi; Sato, Eiichi; Kuroda, Ryunosuke; Toyokawa, Hiroyuki; Yamada, Kawakatsu; Ikari, Yuji; Mori, Hidezo

2014-11-01

266

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.

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

2013-12-01

267

Blazar Studies with GLAST: Synchro-Compton Analysis of Flat Spectr um Radio Quasars  

E-print Network

We extend a method for modeling synchrotron and synchrotron self-Compton radiations in blazar jets to include external Compton processes. The basic model assumption is that the blazar radio through soft X-ray flux is nonthermal synchrotron radiation emitted by isotropically-distributed electrons in the randomly directed magnetic field of outflowing relativistic blazar jet plasma. Thus the electron distribution is given by the synchrotron spectrum, depending only on the Doppler factor and mean magnetic field, given that the comoving emission region size scale. Generalizing the approach of Georganopoulos, Kirk, and Mastichiadis (2001) to arbitrary anisotropic target radiation fields, we use the electron spectrum implied by the synchrotron component to derive accurate Compton-scattered $\\gamma$-ray spectra throughout the Thomson and Klein-Nishina regimes for external Compton scattering (ECS) processes. We derive and calculate accurate $\\gamma$-ray spectra produced by relativistic electrons that Compton-scatter (...

Dermer, Charles D; Krug, Hannah; Boettcher, Markus

2008-01-01

268

Gamma-Ray Studies of Blazars: Synchro-Compton Analysis of Flat Spectrum Radio Quasars  

Microsoft Academic Search

We extend a method for modeling synchrotron and synchrotron self-Compton\\u000aradiations in blazar jets to include external Compton processes. The basic\\u000amodel assumption is that the blazar radio through soft X-ray flux is nonthermal\\u000asynchrotron radiation emitted by isotropically-distributed electrons in the\\u000arandomly directed magnetic field of outflowing relativistic blazar jet plasma.\\u000aThus the electron distribution is given by the

Charles D. Dermer; Justin D. Finke; Hannah Krug; Markus Boettcher

2008-01-01

269

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

NASA Astrophysics Data System (ADS)

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=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. 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.

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

2009-01-01

270

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

271

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. Griehammer; 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. Schrder; S. C. Stave

2014-09-12

272

The radiative transfer equations for Compton scattering of polarized low frequency radiation on a hot electron gas  

E-print Network

We deduce the equations that describe how polarized radiation is Comptonized by a hot electron gas. Low frequencies are considered, and the equations are expanded to second order in electron velocities. Induced scattering terms are included and a Maxwellian velocity distribution for the electrons is assumed. The special case of an axisymmetric radiation field is also considered, and the corresponding radiative transfer equations are found. Our results correct errors and misprints in previosly published transfer equations. The extension to a moving electron gas is made, and the radiative transfer equations are deduced to second order in gas velocity. We use the equations to study polarization in the Sunyaev-Zeldovich effect.

Frode K. Hansen; Per B. Lilje

1999-01-07

273

A mini transmission gamma-ray Compton polarimeter and measurements of the sign of magnetic moments of radioactive nuclei  

Microsoft Academic Search

A mini transmission gamma-ray Compton polarimeter was developed for the measurement of the sign of magnetic moments of radioactive nuclei with low-temperature nuclear orientation. The signs of the magnetic moments of the following isotopes were determined:193Os [ mu=+0.7297(16) mu N];191 m Ir [ mu=+6.20(9) mu N];192Ir [ mu=+1.924(10) mu N];194Ir [ mu=+0.39(1) mu N];195 m Pt [ mu=-0.605(15) mu N].

E. Scheidemann; R. Eder; E. Hagn; E. Zech

1991-01-01

274

Photon coupling theory for plasmas with strong Compton scattering: Four temperature theory  

NASA Astrophysics Data System (ADS)

When an equimolar mixture of deuterium (D) and tritium (T) at high density undergoes fusion burn, the system becomes extremely nonequilibrium. The ion temperature rises much higher than the electron temperature which, in turn, is much higher than the radiation temperature. Accurately simulating this nonequilibrium burn process has previously required a multigroup representation of the radiation field. Although simulating this D-T burn with a simple three temperature model (3T) also results in significant departures from thermal equilibrium, the ion and electron temperature histories from the 3T simulations are much lower than from the multigroup simulations. In this paper, a theory that overcomes the deficiencies of the 3T model in simulating burn of high density D-T is developed. The primary deficiency of the 3T model for this physical system is with the treatment of the Compton scattering energy exchange. The theory here developed culminates in a four temperature model (4T) which describes the radiation field with two temperatures. These are TR, which is the standard radiation temperature of the 3T model (proportional to the fourth root of the radiation energy density), and Tp, which is the true thermodynamic temperature of the photon distribution. This 4T theory gives excellent agreement with the multigroup model for the nonequilibrium burn of D-T. Further, the 4T model transitions smoothly to the 3T model when this is appropriate. Thus the kinetic theory derivation of the 4T model also provides a solid theoretical foundation for the 3T model. Extensions of the theory to inhomogeneous systems are under development to allow treatment of geometries where the computational efficiency of the 4T approach can convey a sizable advantage. There appear to be at least two important applications where the model can be applied. One is for inertial confinement fusion capsules that are optically thick and utilize volume ignition. The second application involves astrophysical accretion disks in the high temperature regime that also exhibit matter heating radiation, albeit without a fusion energy source. A reduced complexity radiation model with the associated reduced computer resource requirements has the potential to facilitate high resolution two dimensional and three dimensional simulations of these astrophysical objects.

Molvig, Kim; Alme, Marv; Webster, Robert; Galloway, Conner

2009-02-01

275

Electronic structure of Ni2TiAl: Theoretical aspects and Compton scattering measurement  

NASA Astrophysics Data System (ADS)

In this paper, we report electron momentum density of Ni2TiAl alloy using an in-house 20 Ci 137Cs (661.65 keV) Compton spectrometer. The experimental data have been analyzed in terms of energy bands and density of states computed using linear combination of atomic orbitals (LCAO) method. In the LCAO computations, we have considered local density approximation, generalized gradient approximation and recently developed second order generalized gradient approximation within the frame work of density functional theory. Anisotropies in theoretical Compton profiles along [1 0 0], [1 1 0] and [1 1 1] directions are also explained in terms of energy bands.

Sahariya, Jagrati; Ahuja, B. L.

2012-11-01

276

Theory of Compton scattering by interfering electromagnetic fields produced by two independent sources  

Microsoft Academic Search

The interference effect produced by two independent sources can be understood in terms of the detection process, owing to the inability of the detector to know from which of the two sources the photons come. Detection based on the Compton effect seems to be a powerful method for recording the interference between high-frequency coherent fields. It is shown that by

M. Bertolotti; C. Sibilia

1980-01-01

277

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

278

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

279

Blazar Compton Efficiencies  

NASA Astrophysics Data System (ADS)

The Fermi gamma-ray space telescope has dramatically increased the number of gamma-ray blazars known and means that for the first time, a large sample of blazars selected by the strength of their inverse Compton emission exists. We have cross-identified the blazars listed in the first Fermi-LAT catalog (1FGL) with the CRATES radio catalogue. Using the 8.4 GHz flux density as a proxy for the jet power, we have computed their Compton efficiencies, a measure of the ability of the jet to convert the power in the ultrarelativistic jet electrons into gamma-rays through the inverse Compton process. We have compared the Compton efficiencies of the two blazar subsets, BL Lacs and FSRQs, and find no evidence that they are different. We also do not find an anti-correlation between Compton efficiency and synchrotron peak frequency.

Gupta, J. A.; Browne, I. W. A.; Peel, M. W.

2012-03-01

280

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

281

Observations of the Crab pulsar and nebula by the EGRET telescope on the Compton Gamma-Ray Observatory  

NASA Technical Reports Server (NTRS)

The Crab pulsar and nebula were observed three times in 1991 April to June by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO): April 23 to May 7, May 16 to 30, and June 8 to 15. The results of analysis of the gamma-ray emission in the energy range from 50 MeV to more than 10 GeV are reported. The observed gamma-ray light curve exhibits two peaks separated in phase by 0.40 +/- 0.02, consistent with previous observations. The total pulsed emission from the Crab pulsar is found to be well represented by a power-law spectrum, softer than the spectrum measured by COS B (Clear et al., 1987). The interpulse emission has a harder spectrum than either of the pulses. The evidence for pulsed emission above 5 GeV in the EGRET data is not conclusive. Unpulsed emission in the energy range 50 MeV to 5 GeV was detected, with an indication of a hardening of the unpulsed spectrum above about 1 GeV. There was a significant change in the light curve over the 2 months of these observations, although the shape of the spectrum remained constant.

Nolan, P. L.; Arzoumanian, Z.; Bertsch, D. L.; Chiang, J.; Fichtel, C. E.; Fierro, J. M.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.

1993-01-01

282

Quasielastic. gamma. -ray scattering from pentadecane  

SciTech Connect

A recently developed Moessbauer instrument has been used to study the liquid dynamics of pentadecane at various temperatures and scattering angles. Widths of the quasielastic signal extracted from the data ranged between 16 GHz (at 12 {degree}C) and 48 GHz (at 74 {degree}C) at a scattering vector of 1.15 A{sup {minus}1}. Similar measurements at five different scattering angles (at 12 {degree}C) were also taken to investigate the {ital Q} dependence between 0.82 and 1.56 A{sup {minus}1}. The results obtained are in good agreement with classical theory for coherent scattering from liquids.

Schupp, G.; Hammouda, B.; Hsueh, C.M. (Department of Physics and Research Reactor, University of Missouri-Columbia, Columbia, Missouri 65211 (USA))

1990-05-15

283

Measurement of collision integral cross-sections of double-photon Compton effect using a single gamma ray detector: A response matrix approach  

Microsoft Academic Search

The collision integral cross-sections of double-photon Compton process are measured experimentally for 662keV incident gamma photons. The measurements are successfully carried out using a single gamma ray detector, and do not require the complicated slow-fast coincidence technique used till now for observing this higher order quantum electrodynamics (QED) process. The energy spectra of one of the two final photons, originating

M. B. Saddi; Bhajan Singh; B. S. Sandhu

2008-01-01

284

The X-ray and radio emission from SN 2002ap: The importance of Compton scattering  

E-print Network

The radio and X-ray observations of the Type Ic supernova SN 2002ap are modeled. We find that inverse Compton cooling by photospheric photons explains the observed steep radio spectrum, and also the X-ray flux observed by XMM. Thermal emission from the shock is insufficient to explain the X-ray flux. The radio emitting region expands with a velocity of, roughly, 70,000 km/s. From the ratio of X-ray to radio emission we find that the energy densities of magnetic fields and relativistic electrons are close to equipartion.

C. -I. Bjornsson; C. Fransson

2004-01-12

285

Diagnostics for the optimization of an 11 keV inverse Compton scattering x-ray source  

NASA Astrophysics Data System (ADS)

In a scope of a collaboration between Thales Communications & 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 ?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.; Le Flanchec, V.; Ngre, J.-P.; Binet, A.; Ortega, J.-M.

2013-04-01

286

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

287

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

288

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

289

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

290

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

291

Demonstration of single-sided Compton scatter tomography in fan beams with an HPGe array  

Microsoft Academic Search

An instrument is demonstrated whereby radiographic images of a sample's electron density are compiled from the information encoded in the energy spectra of gamma rays backscattered from one side of the sample. Nondestructive inspection of aluminum airframes is the application of interest, so it is assumed that access is restricted to only one surface of the object under inspection. Use

Brian L. Evans; Jeffrey B. Martin; Larry W. Burggraf; T. N. Hangartner; M. C. Roggemann

2001-01-01

292

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

293

Measurement of the Diffuse Atmospheric and Cosmic gamma Radiation in the Energy Range 1-10 Mev with a Balloon-Borne Compton Telescope Messung der Diffusen Atmosphaerischen und Kosmischen gamma-Strahlung im Energiebereich 1-10 Mev MIT Einem Ballongetragenen Compton-Teleskop.  

National Technical Information Service (NTIS)

The operation and the construction of a Compton telescope for the low energy gamma range are reported. The energy resolution of the telescope is 30% for about 1 MeV, its angular resolution plus or minus 20 deg. Notwithstanding its low detection probabilit...

G. Lichti

1975-01-01

294

Photon scatter in intensity modulating filters evaluated by first Compton scatter and Monte Carlo calculations and experiments in broad beams.  

PubMed

High-atomic-number materials may be used as intensity modulating filters for inverse radiation treatment planning with photon beams. Such filters, when placed in a bremsstrahlung beam, attenuate the primary fluence, but also produce scattered photons that will reach the patient. To account for such effects in the optimization of photon beam intensities a semiempirical method based on narrow and broad beam transmission measurements was used to quantify the number of scattered photons produced in these filters. The method was verified by performing analytical calculations based on first scatter and a Monte Carlo simulation in 6 and 18 MV photon beams. The resultant experimental transmission ratios agree with calculations by these methods within 2 per cent under the experimental conditions investigated. The semiempirical method can thus be used as a basis for preliminary decision-making to select the proper material for intensity modulating filters and can provide a fast method to perform independent quality checks of the calculation accuracy of dose planning systems. Change in beam penetration is of less concern when treatments of target volumes at smaller depths are of interest. A 10 g cm(-2) thick filter made of low-melting-point alloy produces a change in percentage depth dose of less than 2 per cent for depths larger than 10 cm independent of field size. Similarly the scatter correction modifies the dose distribution by less than 5-10 per cent in most cases. PMID:11049169

Mejaddem, Y; Hydynmaa, S; Brahme, A

2000-10-01

295

Testing the DC-Electric Field Model in a Solar Flare Observed by YOHKOH and the Compton Gamma-Ray Observatory  

Microsoft Academic Search

We apply a DC-electric field model to the analysis of soft and hard X-ray observations of a solar flare observed by Yohkoh and the Compton Gamma-Ray Observatory CGRO on 1992 September 6. The flare was observed simultaneously in the soft X-ray Ca XIX line by the Yokhoh Bragg Crystal Spectrometer (BCS) and in hard X-rays (>50 keV) by the CGRO

D. M. Zarro; J. T. Mariska; B. R. Dennis

1995-01-01

296

Leading twist nuclear shadowing, nuclear generalized parton distributions, and nuclear deeply virtual Compton scattering at small x  

NASA Astrophysics Data System (ADS)

We generalize the leading twist theory of nuclear shadowing and calculate quark and gluon generalized parton distributions (GPDs) of spinless nuclei. We predict very large nuclear shadowing for nuclear GPDs. In the limit of the purely transverse momentum transfer, our nuclear GPDs become impact-parameter-dependent nuclear parton distribution functions (PDFs). Nuclear shadowing induces nontrivial correlations between the impact parameter b and the light-cone fraction x. We make predictions for the deeply virtual Compton scattering (DVCS) amplitude and the DVCS cross section on Pb208 at high energies. We calculate the cross section of the Bethe-Heitler (BH) process and address the issue of the extraction of the DVCS signal from the eA?e?A cross section. We find that the eA?e?A differential cross section is dominated by DVCS at the momentum transfer t near the minima of the nuclear form factor. We also find that nuclear shadowing leads to dramatic oscillations of the DVCS beam-spin asymmetry, ALU, as a function of t. The position of the points where ALU changes sign is directly related to the magnitude of nuclear shadowing.

Goeke, K.; Guzey, V.; Siddikov, M.

2009-03-01

297

Deep Virtual Compton Scattering (DVCS) with the CLAS detector at Jefferson Lab, first results and future plans  

NASA Astrophysics Data System (ADS)

The first results on Deeply Virtual Compton Scattering (DVCS) using CLAS electroproduction data on hydrogen with a 4.2 GeV polarized beam will be presented. The main focus of these studies is the measurement of the Beam Spin Asymmetry (BSA) in the reaction ep arrow ep?. The asymmetry arises from the interference of the DVCS and Bethe-Heitler processes. The BSA is directly proportional to the imaginary part of the DVCS amplitude, and gives access to the Generalized Parton Distributions (GPDs) H and E. Theoretical evaluation at the twist-3 level shows that the CLAS data is consistent with a significant anti-quark-gluon-quark correlation effect[1]. The Q^2 and xB dependence of magnitude of BSA will be a sensitive test for the Bjorken regime. We will also present preliminary data on the DVCS process from 6 GeV longitudinally polarized beam from the data taken this fall. A dedicated experiment to study DVCS with an optimized CLAS configuration to detect all particles in the final state using a 6 GeV polarized beam is planned for the year 2003. The goals and the detector upgrade for this experiment will be briefly discussed. 1. A. Belitsky, D. Mueller and A. Kirchner hep-ph/0112108

Elouadrhiri, L.

2002-04-01

298

Quasielastic gamma-ray scattering from polydimethylsiloxane in benzene solutions  

SciTech Connect

Quasielastic gamma-ray scattering of 46.5-keV Moessbauer photons by polydimethylsiloxane has been studied at room temperature as a function of dilution in benzene. The high energy resolution of this novel technique allowed the separation of the scattering signal into a narrow component associated with stiff motions along the polymer chain backbone and a quasielastic component associated with softer side group motions. The narrow component disappears upon dilution in benzene while the intensity of the quasielastic component grows proportionately. This result is interpreted as a softening of the backbone normal modes upon dilution.

Hammouda, B.; Schupp, G.; Maglic, S. (Research Reactor, University of Missouri-Columbia, Columbia, MO (USA) Department of Physics, University of Missouri-Columbia, Columbia, MO (USA))

1990-10-15

299

Proton Compton scattering cross section in different variants of chiral effective field theory  

NASA Astrophysics Data System (ADS)

We compare the predictions of different variants of chiral effective field theory for the ?p elastic scattering differential cross section. We pay particular attention to the role of pion loops, and the impact that a heavy-baryon expansion has on the behavior of those loops. We also correct erroneous results for these loops that were published by Pascalutsa and Phillips [Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.67.055202 67, 055202 (2003)].

Lensky, Vadim; McGovern, Judith A.; Phillips, Daniel R.; Pascalutsa, Vladimir

2012-10-01

300

Target mass corrections for virtual Compton scattering at twist-2 and generalized, nonforward Wandzura-Wilczek and Callan-Gross relations  

NASA Astrophysics Data System (ADS)

The off-cone Compton operator of twist-2 is Fourier transformed using a general procedure which is applicable, in principle, to any QCD tensor operator of definite (geometric) twist. That method allows, after taking the nonforward matrix elements, to separate quite effectively their imaginary part and to reveal some hidden structure in terms of appropriately defined variables, including generalized Nachtmann variables. In this way, without using the equations of motion, generalizations of the Wandzura-Wilczek relation and of the mass-corrected Callan-Gross relation to the nonforward scattering, having the same shape as in the forward case, are obtained. In addition, new relations for those structure functions which vanish in the forward case are derived. All the structure functions are expressed in terms of iterated generalized parton distributions of nth order. In addition, we showed that the absorptive part of twist-2 virtual Compton amplitude is determined by the nonforward extensions of g,W and W only.

Geyer, Bodo; Robaschik, Dieter; Eilers, Jrg

2005-01-01

301

Testing quantum electrodynamics in the Compton scattering process of quasi-real photons on electrons and positrons in the VEPP-2M storage ring  

SciTech Connect

Results of neutral detector experiments in Compton scattering of quasi-real photons on electrons and positrons are given over the range of total energy of the beams of 2E = 1000 to 1048 MeV. The total cross section of the process and the angular distributions are in full agreement with predictions made on the basis of quantum electrodynamics (QED). The ratio of the observed total cross section of quasi-real photons on electrons to that on positrons is equal to 0.99 +- 0.02. The quantitative limits of the cross section for production of a heavy electron (HE) are established.

Golubev, V.B.; Druzhinin, V.P.; Ivanov, P.M.; Ivanchenko, V.N.; Koop, I.A.; Kezerashvili, G.Y.; Peryshkin, A.N.; Serednyakov, S.I.; Sidorov, V.A.; Shatunov, Y.M.

1985-05-01

302

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; S. Jaminion; Christophe Jutier; Rachele Di Salvo; L. Van Hoorebeke; et. Al.

2003-12-01

303

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

304

Laser-Compton Scattered x-rays for non-destructive assay of surrogate fuel-cycle samples and imaging  

NASA Astrophysics Data System (ADS)

One of our research goals at the Idaho Accelerator Center focuses on Laser-Compton Scattering (LCS) based nuclear science applications such as non-destructively quantifying concentrations of transuranic (TRIJ) elements in a surrogate of spent nuclear fuel and imaging. Non-destructive techniques include x-ray transmission and x-ray fluorescence. Both of these can be very sensitive techniques with tunable monochromatic x-rays. We investigated quasi-monochromatic x-rays from LCS for this purpose. Four sharp 20 keV, 36.7 keV, 99 keV, and 122 keV LCS peaks were produced in four separate experiments using electron beams tuned to 33 MeV, -32 MeV, 37 MeV, and 41 MeV that were brought in collision with the Nd:YAG laser (the peak laser power was 4 GW) operating at 1064 nm, 532 nm and 266 nm wavelengths respectively. 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. X-ray fluorescence (XRF) experiments were first carried out to identify elemental XRF emission from Ag, Cd, and Sn foils with thicknesses ranging from 25--500 mum, following the absorption of 36.7 keV LCS x-rays. The intensities of the measured Kalpha1 emission lines were then compared to the predicted Kalpha1 intensities; based on the comparison, there was an estimated deviation of up to ?10.4% between the predicted and measured Kalpha1 intensities. Next, the transmission experiments were carried out by transmitting a 99 keV LCS x-ray beam through Bi foils of thicknesses ranging from 50--250 mum to measure the transmission of the interrogating LCS x-ray beam. There was a relative deviation of up to ?9.4 % between the predicted and measured transmission respectively. We then focused on exploiting the Hybrid K-Edge Densitometry (HKED) technique for the purpose of quantifying the concentrations of Uranium in the surrogate of spent nuclear fuel using a 122 keV LCS x-ray beam. The measured concentrations deviated by about 2.87% and 11.86% between the HKED measurement procedure and the point source transmission measurement procedure respectively. Finally, experiments were carried out to demonstrate phase-contrast imaging by transmitting 20 keV LCS x-ray beam through fish samples. The vital organs were distinguishable in the processed radiographic image.

Naeem, Syed F.

305

Compton scattering effects on the duration of terrestrial gamma-ray flashes  

E-print Network

correlated TGFs with initial development stages of normal polarity intracloud lightning that transports-scale electric fields ((Ek, where Ek is the conventional breakdown threshold electric field at a given altitude that the number of energetic electrons produced by very high potential negative lightning leaders is consistent

Pasko, Victor

306

Study on ion-irradiation-induced ferromagnetism in FeRh intermetallic compound by means of magnetic Compton scattering  

SciTech Connect

The magnetic Compton profiles of Fe-50 at. % Rh intermetallic compound were measured to study the ferromagnetism induced by 200 MeV Xe ion irradiation. The magnetic effect at 50 K increases with increasing the ion-fluence. The analysis of the experimental result revealed that the values of spin moment induced by the irradiation were close to the values of magnetization obtained by a superconducting quantum interference device magnetometer, suggesting that the ion irradiation mainly induces the spin magnetic moment. The difference in magnetic Compton profiles between the irradiation-induced ferromagnetism and the intrinsic ferromagnetism in pure Fe is also discussed.

Kosugi, S.; Matsui, T.; Aikoh, K.; Shimizu, K.; Tahara, Y.; Hori, F.; Iwase, A. [Department of Materials Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan); Ishikawa, N. [Japan Atomic Energy Agency(JAEA-Tokai), Tokai, Ibaraki, 319-1195 (Japan); Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute(JASRI), Spring-8, Sayo, Hyogo 679-5198 (Japan)

2011-04-01

307

ILC Positron Source Based on Laser Compton  

SciTech Connect

Positron generation is one of the most difficult technical challenges among the ILC (International Linear Collider) subsystems. A positron source based on Laser Compton back scattering is an attractive and advanced option for the ILC positron source. Here, the positrons are generated, via the pair creation process, from high energy gamma rays which themselves are produced by Compton scattering of laser photons off a high-energy electron beam. Polarized positrons can be generated by employing a circularly polarized laser. The positron polarization is easily controlled and switched by changing the laser polarity. The electron beam can be unpolarized. The required electron energy is only a few GeV (in contrast, the ''undulator scheme'', another advanced option, requires at least 100 GeV or more) and the system can be prototyped and tested prior to the real construction. The laser Compton technology has many other applications like advanced X-ray sources and a good synergy is expected. In addition, this technology can be a powerful driving force for the ILC project attracting many researchers from outside the ILC community. The ILC positron source is a technical challenge and it will be realized only if the latest technologies are integrated seamlessly with the necessary R and D efforts for system specific issues. The latest technologies include high power lasers, high brightness electron beams, high finesse optical cavities for as laser-beam interaction point, etc. We present the design status and the related experimental efforts for the ILC positron source based on Laser Compton scattering. The respective advantages of various options for the electron beam (based on Linac, storage ring, and ERL) are also compared.

Kuriki, M. [KEK, Ibaraki (Japan); Hiroshima U., Hiroshima, (Japan); Araki, S.; Higashi, Y.; Honda, Y.; Kurihara, Y.; Okugi, T.; Omori, T.; Taniguchi, T.; Terunuma, N.; Urakawa, J. [KEK, Ibaraki (Japan); Fukuda, M.; Hirano, K.; Takano, M. [NIRS, Chiba (Japan); Hirose, T.; Sakaue, K.; Washio, M. [Waseda U., Tokyo (Japan); Takahashi, T.; Shimizu, H. [Hiroshima U., Hiroshima (Japan); Tsunemi, A. [Sumitomo Heavy Industries Ltd., Tokyo (Japan); Zimmermann, F. [CERN, Geneva (Switzerland)] (and others)

2008-02-06

308

A Simple Comptonization Model  

NASA Astrophysics Data System (ADS)

We present an empirical model of Comptonization for fitting the spectra of X-ray binaries. This model, named simpl, has been developed as a package implemented in XSPEC. With only two free parameters, simpl is competitive as the simplest model of Compton scattering. Unlike the pervasive standard power-law model, simpl incorporates the basic features of Compton scattering of soft photons by energetic coronal electrons. Using a simulated spectrum, we demonstrate that simpl closely matches the behavior of physical Comptonization models that consider the effects of optical depth, coronal electron temperature, and geometry. We present fits to RXTE spectra of the black hole transient H1743-322 and a BeppoSAX spectrum of LMC X-3 using both simpl and the standard power-law model. A comparison of the results shows that simpl gives equally good fits, while eliminating the troublesome divergence of the standard power-law model at low energies. simpl is completely flexible and can be used self-consistently with any seed spectrum of photons. We show an example of how simpl-unlike the standard power law-teamed up with diskbb (the standard model of disk accretion) provides a uniform disk normalization that is unaffected by moderate Comptonization.

Steiner, James F.; Narayan, Ramesh; McClintock, Jeffrey E.; Ebisawa, Ken

2009-11-01

309

The Diffuse Galactic gamma Radiation: The Compton Contribution and Component Separation by Energy Interval and Galactic Coordinates.  

National Technical Information Service (NTIS)

The radiation to be expected from cosmic ray interactions with matter and photons was examined. Particular emphasis is placed on the Compton emission. Both the photon density in and near the visible region and that in the region are deduced from the estim...

D. A. Kniffen, C. E. Fichtel

1981-01-01

310

Giant Compton Shifts in Hyperbolic Metamaterial  

E-print Network

We study the Compton scattering of light by free electrons inside a hyperbolic medium. We demonstrate that the unconventional dispersion and local density of states of the electromagnetic modes in such media can lead to a giant Compton shift and dramatic enhancement of the scattering cross section. We develop an universal approach for the study of coupled multi-photon processes in nanostructured media and derive the spectral intensity function of the scattered radiation for realistic metamaterial structures. We predict the Compton shift of the order of a few meVs for the infrared spectrum that is at least one order of magnitude larger than the Compton shift in any other system.

Iorsh, Ivan; Ginzburg, Pavel; Belov, Pavel; Kivshar, Yuri

2014-01-01

311

Excitation of high-lying levels of nuclei in resonance scattering of. gamma. rays from (n,. gamma. ) reactions  

SciTech Connect

The method of resonance scattering of neutron-capture ..gamma.. rays has been used to observe excitation of the nuclear levels 6104 +- 3 keV in Mn and Ni, 5603 +- 2 keV in /sup 113/Cd, and also 5087 +- 5 and 6190 +- 3 keV in /sup 208/Pb. The cross section for resonance scattering of the ..gamma.. rays is determined, and also the values GAMMA/sub ..gamma..//sub 0/ = (180 +- 30)x10/sup -3/ eV, delta = 7.5 +- 2.0 eV and GAMMA/sub ..gamma..//sub 0/ = (175 +- 25)x10/sup -3/ eV, delta = 6.5 +- 2.0 eV respectively for 5603 and 6190 keV levels.

Begzhanov, R.B.; Kobilov, O.S.; Kulabdullaev, G.A.

1988-07-01

312

Spectral measurements of direct and scattered gamma radiation at a boiling-water reactor site  

Microsoft Academic Search

Quantitative surveys of direct and scattered gamma radiation emitted from the steam-power conversion systems of a boiling-water reactor and other on-site radiation sources were made using a directionally shielded HPGe gamma spectrometry system. The purpose of this study was to obtain data on the relative contributions and energy distributions of direct and scattered gamma radiation in the site environs. The

R. C. Block; I. L. Preiss; R. M. Ryan; G. J. Vargo

1990-01-01

313

Gamma Spectroscopy  

NSDL National Science Digital Library

Students use NaI/PMT gamma detectors to gather spectra of several radioactive sources. The full-enrgy peak, Compton edge, Compton shelf and backscatter peaks are identified. The physics of the detection process is emphasized.

Bistrow, Van

2009-01-05

314

Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2=0.92 and 1.76 GeV2  

NASA Astrophysics Data System (ADS)

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) ?E(Q2) and ?M(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 form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from ?N intermediate states.

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

2004-09-01

315

Measurement of the generalized polarizabilities of the proton in virtual Compton scattering at Q2=0.92 and 1.76 GeV2.  

PubMed

We report a virtual Compton scattering study of the proton at low c.m. energies. We have determined the structure functions P(LL)-P(TT)/epsilon and P(LT), and the electric and magnetic generalized polarizabilities (GPs) alpha(E)(Q2) and beta(M)(Q2) at momentum transfer Q(2)=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 form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from piN intermediate states. PMID:15447252

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

2004-09-17

316

In-line phase-contrast imaging of a biological specimen using a compact laser-Compton scattering-based x-ray source  

SciTech Connect

Laser-Compton scattering (LCS) x-ray sources have recently attracted much attention for their potential use at local medical facilities because they can produce ultrashort pulsed, high-brilliance, and quasimonochromatic hard x rays with a small source size. The feasibility of in-line phase-contrast imaging for a 'thick' biological specimens of rat lumbar vertebrae using the developed compact LCS-X in AIST was investigated for the promotion of clinical imaging. In the higher-quality images, anatomical details of the spinous processes of the vertebrae are more clearly observable than with conventional absorption radiography. The results demonstrate that phase-contrast radiography can be performed using LCS-X.

Ikeura-Sekiguchi, H.; Kuroda, R.; Yasumoto, M.; Toyokawa, H.; Koike, M.; Yamada, K. [National Institute of Advanced Industrial Science and Technology (AIST), Central 2-5, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Sakai, F. [Sumitomo Heavy Industries, Ltd. (SHI), 2-1-1, Yatocho, Nishitokyo, Tokyo 188-8585 (Japan); Mori, K.; Maruyama, K. [Ibaraki Prefectural University of Health Sciences, 4669-2, Ami, Inashiki, Ibaraki 300-0394 (Japan); Oka, H.; Kimata, T. [St. Marianna University School of Medicine, 2-16-1, Sugao, Miyamae-ku, Kawasaki City 216-8512 (Japan)

2008-03-31

317

Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2= 0.92 and 1.76 GeV2  

SciTech Connect

We report a Virtual Compton Scattering study of the proton at low CM energies. We have determined 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 momentum transfer Q{sup 2} = 0.92 and 1.76 GeV{sup 2}. The electric GP shows a strong fall-off with Q{sup 2}, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a fall-off; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q{sup 2}, compensated at higher Q{sup 2} by a paramagnetic contribution from {pi}N intermediate states.

Geraud Laveissiere; Natalie Degrande; Stephanie Jaminion; Christophe Jutier; Luminita Todor; Rachele Di Salvo; L. Van Hoorebeke; Et. Al.

2004-09-01

318

Virtual Compton scattering and the generalized polarizabilities of the proton at Q2=0.92 and 1.76 GeV2  

NASA Astrophysics Data System (ADS)

Virtual Compton scattering (VCS) on the proton has been studied at the Jefferson Laboratory using the exclusive photon electroproduction reaction ep?ep?. This paper gives a detailed account of the analysis which has led to the determination of the structure functions PLL-PTT/? and PLT and the electric and magnetic generalized polarizabilities (GPs) ?E(Q2) and ?M(Q2) at values of the four-momentum transfer squared Q2=0.92 and 1.76 GeV2. 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 Q2 range and point to their nontrivial behavior.

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

2012-07-01

319

Experimental and simulated validation of the energy dependence of saturation thickness of multiple scattered gamma rays  

NASA Astrophysics Data System (ADS)

Saturation thickness for multiple scattering gamma rays from multiple sources has been measured experimentally and simulated using the Monte Carlo N-Particle (MCNP) Code. Experimental measurements were performed using a collimated beam of gamma-rays from 57Co, 203Hg, 133Ba, 22Na, 137Cs, 65Zn and 60Co sources. The gamma rays were directed at rectangular aluminium targets of varying thickness. A NaI (Tl) scintillation detector placed at a backscattering angle of 180 was used to detect the scattered photons. The measured and calculated saturation thickness increases with increasing energy of incident gamma-rays. Experimental and simulated values are compared and are in good agreement.

Eshwarappa, Kunabevu Mallikarjunappa; Kiran, Kiggal Udayashankar; Ravindraswami, Kalladka; Somashekarappa, Hiriyur Mallaiah

2014-11-01

320

Use of nuclear resonant scattering of gamma rays for in vivo measurement of iron  

SciTech Connect

A technique for determination of elements in human body in-vivo, utilizing nuclear resonant scattering of gamma rays has been developed. 847 keV photons emitted from a gaseous /sup 56/MnCl/sub 2/ source are resonantly scattered from /sup 56/Fe present in the body. The detection of these gamma rays is used to estimate the iron content of the liver or heart of patients. Details of the calibration procedure and potential molecular effects are described.

Vartsky, D.; Wielopolski, L.; Ellis, K.J.; Cohn, S.H.

1981-01-01

321

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

E-print Network

We propose precision measurements of the helicity-dependent and helicity independent cross sections for the ep->epg reaction in Deeply Virtual Compton Scattering (DVCS) kinematics. DVCS scaling is obtained in the limits Q^2>>Lambda_{QCD}^2, x_Bj fixed, and -\\Delta^2=-(q-q')^22 GeV^2, W>2 GeV, and -\\Delta^21 GeV^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_2 calorimeter. In general, we will not detect the recoil proton. The H(e,e'g)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

2006-09-11

322

Study of scattered photons from the collimator system of Leksell Gamma Knife using the EGS4 Monte Carlo Code  

Microsoft Academic Search

In the algorithm of Leksell GAMMAPLAN (the treatment planning software of Leksell Gamma Knife), scattered photons from the collimator system are presumed to have negligible effects on the Gamma Knife dosimetry. In this study, we used the EGS4 Monte Carlo (MC) technique to study the scattered photons coming out of the single beam channel of Leksell Gamma Knife. The PRESTA

K. N. Yu; Joel Y. C. Cheung

2006-01-01

323

Industrial scattering densitometry using a mCi gamma-ray source  

NASA Astrophysics Data System (ADS)

The aim of the present work is to investigate the feasibility of using weak sources in Compton scattering tomography to minimize radiological hazards. We designed a portable scanning system using a 5 mCi137Cs source and a scintillation NaI detector. To compensate the source weakness a rectangular shaped collimator was placed in front of the detector which increased the solid angle subtended by the detector. Due to the lightweight and small size, the system can be easily used for in situ tomography.

Jahanbakhsh, O.; Ashrafi, S.; Salehpour, B.; Bodaghi Hossein Abadi, R.; Khaiiatali, N.

2013-10-01

324

Simultaneous X-Ray and Gamma-Ray Observations of TeV Blazars: Testing Synchro-Compton Emission Models and Probing the Infrared Extragalactic Background  

E-print Network

The last years have seen a revolution in ground-based gamma-ray detectors. We can now detect the spectra of nearby TeV blazars like Mrk 421 and 501 out to approximately 20 TeV, and during the strongest flares, we can now follow fluctuations in these spectra on timescales close to the shortest ones likely in these objects. We point out that this represents a unique opportunity. Using these and future detectors in combination with broadband X-ray satellites like SAX and RXTE, we will be able to simultaneously follow all significant X-ray/gamma-ray variations in a blazar's emission. This will provide the most stringent test yet of the synchrotron-Compton emission model for these objects. In preparation for the data to come, we present sample SSC model calculations using a fully self-consistent, accurate code to illustrate the variability behavior one might see (the range of behavior is wider than many expect) and to show how good timing information can probe physical conditions in the source. If the model works, i.e., if X-ray/TeV variations are consistent with being produced by a common electron distribution, then we show it is possible to robustly estimate the blazar's intrinsic TeV spectrum from its X-ray spectrum. Knowing this spectrum, we can then determine the level of absorption in the observed spectrum. Constraining this absorption, due to gamma-ray pair production on diffuse radiation, provides an important constraint on the infrared extragalactic background intensity. Without the intrinsic spectrum, we show that detecting absorption is very difficult and argue that Mrk 421 and 501, as close as they are, may already be absorbed by a factor 2 at approximately 3 TeV. This should not be ignored when fitting emission models to the spectra of these objects.

Paolo S. Coppi; Felix A. Aharonian

1999-03-10

325

Improvements to a Compton Polarimeter  

NASA Astrophysics Data System (ADS)

The Jefferson Lab in Newport News, Virginia, uses a polarized beam of electrons to perform research on the substructure of nuclei and nucleons. Jefferson Lab uses a relatively new Compton polarimeter to continuously measure the polarization of the electron beam delivered by the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator. The Compton polarimeter determines beam polarization by colliding a high-power laser with the electron beam and measuring the scattered photons and electrons. The Compton polarimeter utilizes this asymmetry of Compton scattering rates to measure polarization to (+/-)1% every few hours. For an accurate measurement, the laser polarization and the position of the scattered photon cone must be well known. The focus of this project was to expand the instrumentation to monitor and control the Compton polarimeter with the intent of improving the electron beam polarization measurement. The individual components of the system are all working as intended, but the system as a whole will not be tested until beam operations resume. An improved measurement of the electron beam polarization will reduce the uncertainty of future experiments.

Cavness, Brandon; Gaskell, Dave; Dalton, Mark

2011-10-01

326

The source function for the inverse Compton process in the solar vicinity  

Microsoft Academic Search

For the assessment of the relative importance of the inverse Compton scattering process in galactic medium-energy gamma-ray production, a precise evaluation of the local source function is provided. The improved precision with respect to existing estimates relies on the local photon field description, taken from recent data including the few available far-IR ones, and on an exact integration over a

G. Piccinotti; G. F. Bignami

1976-01-01

327

Compton backscattering for the calibration of KEDR tagging system  

NASA Astrophysics Data System (ADS)

KEDR detector has the tagging system (TS) to study the gamma-gamma processes. To determine the two-photon invariant mass, the energies of the scattered at small angles electrons and positrons are measured by the magnetic spectrometer embedded into the lattice of the VEPP-4M collider. The energy resolution (scattered electron/positron energy resolution divided by the beam energy) of this spectrometer varies from 0.6% to 0.03% depending on the electron/positron energy. The Compton backscattering of laser radiation on the electron/positron beam is used for the accurate energy scale and resolution calibration of the tagging system. The report covers the design, recent results and current status of the KEDR TS calibration system.

Kaminskiy, V. V.; Muchnoi, N. Yu; Zhilich, V. N.

2014-08-01

328

Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO) V. Andersson  

E-print Network

Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO) V. Andersson , P. Chen, T. Kamae, G, Japan We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma of balloon experiments lasting 6-8 hours each. Compton scattering has highest potential for measuring low

Haviland, David

329

N-SAP and G-SAP neutron and gamma ray albedo model scatter shield analysis program  

NASA Technical Reports Server (NTRS)

Computer program calculates neutron or gamma ray first order scattering from a plane or cylindrical surface to a detector point. The SAP Codes, G-SAP and N-SAP, constitute a multiple scatter albedo model shield analysis.

Sapovchak, B. J.; Stephenson, L. D.

1967-01-01

330

Compton scattering from C12 using tagged photons in the energy range 65-115 MeV  

NASA Astrophysics Data System (ADS)

Elastic scattering of photons from C12 has been investigated using quasimonoenergetic tagged photons with energies in the range 65-115 MeV at laboratory angles of 60?, 120?, and 150? at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the 12C(? ,?)12C cross section to the bound-nucleon polarizabilities.

Myers, L. S.; Shoniyozov, K.; Preston, M. F.; Anderson, M. D.; Annand, J. R. M.; Boselli, M.; Briscoe, W. J.; Brudvik, J.; Capone, J. I.; Feldman, G.; Fissum, K. G.; Hansen, K.; Henshaw, S. S.; Isaksson, L.; Jebali, R.; Kovash, M. A.; Lewis, K.; Lundin, M.; MacGregor, I. J. D.; Middleton, D. G.; Mittelberger, D. E.; Murray, M.; Nathan, A. M.; Nutbeam, S.; O'Rielly, G. V.; Schrder, B.; Seitz, B.; Stave, S. C.; Weller, H. R.; Compton@Max-Lab Collaboration

2014-03-01

331

Compton scattering from 12C using tagged photons in the energy range 65 - 115 MeV  

E-print Network

Elastic scattering of photons from 12C has been investigated using quasi-monoenergetic tagged photons with energies in the range 65 - 115 MeV at laboratory angles of 60 deg, 120 deg, and 150 deg at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the 12C(g,g)12C cross section to the bound-nucleon polarizabilities.

L. S. Myers; K. Shoniyozov; M. F. Preston; M. D. Anderson; J. R. M. Annand; M. Boselli; W. J. Briscoe; J. Brudvik; J. I. Capone; G. Feldman; K. G. Fissum; K. Hansen; S. S. Henshaw; L. Isaksson; R. Jebali; M. A. Kovash; K. Lewis; M. Lundin; I. J. D. MacGregor; D. G. Middleton; D. E. Mittelberger; M. Murray; A. M. Nathan; S. Nutbeam; G. V. O'Rielly; B. Schrder; B. Seitz; S. C. Stave; H. R. Weller

2014-01-16

332

Cyclotron resonant scattering in the spectra of gamma-ray bursts  

NASA Technical Reports Server (NTRS)

Data on the GB880205 gamma-ray bursts are presented that have implications for the nature of gamma-ray burst sources. It is shown that cyclotron resonant scattering and Raman scattering account well for the positions, strengths, and shapes of the relative strengths of the first and second harmonics and their narrow widths. These results imply the existence of a superstrong (B of about 2 x 10 to the 12th G) magnetic field in the vicinity of the X-ray emission region of GB880205. Such a superstrong magnetic field points to a strongly magnetic neutron star as the origin of gamma-ray bursts, and to the fact that the gamma-ray sources belong to the Galaxy.

Lamb, D. Q.; Wang, J. C. L.; Loredo, T. J.; Wasserman, I.; Fenimore, E. E.

1989-01-01

333

The Compton Observatory Science Workshop  

NASA Technical Reports Server (NTRS)

The Compton Observatory Science Workshop was held in Annapolis, Maryland on September 23-25, 1991. The primary purpose of the workshop was to provide a forum for the exchange of ideas and information among scientists with interests in various areas of high energy astrophysics, with emphasis on the scientific capabilities of the Compton Observatory. Early scientific results, as well as reports on in-flight instrument performance and calibrations are presented. Guest investigator data products, analysis techniques, and associated software were discussed. Scientific topics covered included active galaxies, cosmic gamma ray bursts, solar physics, pulsars, novae, supernovae, galactic binary sources, and diffuse galactic and extragalactic emission.

Shrader, Chris R. (editor); Gehrels, Neil (editor); Dennis, Brian (editor)

1992-01-01

334

Study of gamma rays from neutron inelastic scattering  

E-print Network

The energy and intensity of the inelastic gamma rays of twenty low atomic number elements: Li, C, N, 0, Mg, Al, Na, Si, S, Cl, K, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Pb, are measured with a 30 cc Ge(Li) detector using an ...

Hui, Bertram Ho Wai

1970-01-01

335

Diamond Detectors for Compton Polarimetry  

NASA Astrophysics Data System (ADS)

Parity-violating electron scattering experiments aim to test the standard model of particle physics through precise low-energy determinations of the weak mixing angle. These experiments require determination of the polarization of the incident electron beam to the 1% level or better. An example of this type of experiment is the Q-weak experiment, which will be conducted in Hall C at Jefferson Lab in 2010 and beyond. We are constructing a Compton polarimeter in Hall C to provide continuous monitoring of the polarization with the goal of 1% absolute polarization determination. In our Compton polarimeter, circularly polarized laser light will impinge upon the electron beam. Electrons scattered by the Compton process will be momentum-analyzed in a dipole magnet downstream of the interaction point. A diamond strip tracker will be placed further downstream of the dipole to sense the Compton-scattered electrons and determine their momenta. The design of the polarimeter, focusing on electron detection, and our progress in prototyping and constructing the diamond strip tracker, are discussed.

Martin, J. W.; Dutta, D.; Narayan, A.; Wang, P.

2009-12-01

336

Diamond Detectors for Compton Polarimetry  

SciTech Connect

Parity-violating electron scattering experiments aim to test the standard model of particle physics through precise low-energy determinations of the weak mixing angle. These experiments require determination of the polarization of the incident electron beam to the 1% level or better. An example of this type of experiment is the Q-weak experiment, which will be conducted in Hall C at Jefferson Lab in 2010 and beyond. We are constructing a Compton polarimeter in Hall C to provide continuous monitoring of the polarization with the goal of 1% absolute polarization determination. In our Compton polarimeter, circularly polarized laser light will impinge upon the electron beam. Electrons scattered by the Compton process will be momentum-analyzed in a dipole magnet downstream of the interaction point. A diamond strip tracker will be placed further downstream of the dipole to sense the Compton-scattered electrons and determine their momenta. The design of the polarimeter, focusing on electron detection, and our progress in prototyping and constructing the diamond strip tracker, are discussed.

Martin, J. W. [Physics Department, University of Winnipeg, Winnipeg, MB, R3B 2E9 (Canada); Dutta, D.; Narayan, A. [Dept. of Physics and Astronomy, Mississippi State University, Mississippi State, MS 39762-5167 (United States); Wang, P. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB, R3T 2N2 (Canada)

2009-12-17

337

Development of polarization-controlled multi-pass Thomson scattering system in the GAMMA 10 tandem mirror  

SciTech Connect

In the GAMMA 10 tandem mirror, the typical electron density is comparable to that of the peripheral plasma of torus-type fusion devices. Therefore, an effective method to increase Thomson scattering (TS) signals is required in order to improve signal quality. In GAMMA 10, the yttrium-aluminum-garnet (YAG)-TS system comprises a laser, incident optics, light collection optics, signal detection electronics, and a data recording system. We have been developing a multi-pass TS method for a polarization-based system based on the GAMMA 10 YAG TS. To evaluate the effectiveness of the polarization-based configuration, the multi-pass system was installed in the GAMMA 10 YAG-TS system, which is capable of double-pass scattering. We carried out a Rayleigh scattering experiment and applied this double-pass scattering system to the GAMMA 10 plasma. The integrated scattering signal was made about twice as large by the double-pass system.

Yoshikawa, M.; Morimoto, M.; Shima, Y.; Kohagura, J.; Sakamoto, M.; Nakashima, Y.; Imai, T. [Plasma Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); Yasuhara, R.; Yamada, I.; Kawahata, K.; Funaba, H. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan); Minami, T. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

2012-10-15

338

Neutron-neutron scattering length from the reaction gamma d --> pi^+ nn employing chiral perturbation theory  

E-print Network

We discuss the possibility to extract the neutron-neutron scattering length a_{nn} from experimental spectra on the reaction gamma d --> pi^+ nn. The transition operator is calculated to high accuracy from chiral perturbation theory. We argue that for properly chosen kinematics, the theoretical uncertainty of the method can be as low as 0.1 fm.

V. Lensky; V. Baru; E. Epelbaum; C. Hanhart; J. Haidenbauer; A. Kudryavtsev; Ulf-G. Meiner

2007-04-03

339

Quantitative measurement of scattered photons during gamma ray transmission CT by means of Monte Carlo simulations  

Microsoft Academic Search

Quantitative image reconstruction in single photon emission CT requires an accurate attenuation map of a cross section of an object. Several data acquisition geometries have been proposed to obtain the true attenuation map by means of gamma-ray transmission CT (TCT). In the transmission data scattered photons are sometimes measured and they reduce the accuracy of reconstructed TCT images. To investigate

K. Ogawa; Y. Kawamura; A. Kubo; T. Ichihara

1996-01-01

340

Estimation of scattered photons in gamma ray transmission CT using Monte Carlo simulations  

Microsoft Academic Search

Quantitative image reconstruction in single photon emission CT requires an accurate attenuation map of a cross section of an object. Several data acquisition geometries have been proposed to obtain the true attenuation map by means of gamma-ray transmission CT (TCT). In the transmission data scattered photons are sometimes measured and they reduce the accuracy of reconstructed TCT images. To investigate

K. Ogawa; Y. Kawamura; A. Kubo; T. Ichihara

1997-01-01

341

Cyclotron resonant scattering in gamma-ray bursts - Line strengths and signature of neutron star rotation  

NASA Technical Reports Server (NTRS)

We explain the relative line strengths in gamma-ray bursts in terms of cyclotron resonant scattering. We describe the line signature of neutron star rotation and discuss the possibility that variations seen in the strengths and widths of the lines in GB780325 and GB870303 are due to rotation.

Lamb, D. Q.; Wang, J. C. L.; Wasserman, I.

1992-01-01

342

A Germanium Detector with Optimized Compton Veto for High Sensitivity at Low Energy  

SciTech Connect

We have built a prototype germanium detector with a Compton veto that is optimized for high sensitivity in the low-energy range around {approx}100 keV. It is specifically designed to address the problem to directly detect plutonium gamma emissions in spent nuclear fuel by non-destructive assay. This is not possible with current detectors due to the large low-energy background of Compton-scattered high-energy radiation from the fission products, whose gamma flux is at least 6 to 7 orders of magnitude higher than the Pu signal. Our instrument is designed to assess the feasibility to selectively suppress the background in the low-energy region around {approx}100 keV with the strongest Pu X-ray and gamma emissions lines. It employs a thin Ge detector with a large Compton veto directly behind it to suppress the background from forward-scattered radiation by anti-coincidence vetoing. This report summarizes the design considerations and the performance of the instrument.

Friedrich, S

2011-11-30

343

Constrained gamma-Z interference corrections to parity-violating electron scattering  

SciTech Connect

We present a comprehensive analysis of gamma-Z interference corrections to the weak charge of the proton measured in parity-violating electron scattering, including a survey of existing models and a critical analysis of their uncertainties. Constraints from parton distributions in the deep-inelastic region, together with new data on parity-violating electron scattering in the resonance region, result in significantly smaller uncertainties on the corrections compared to previous estimates. At the kinematics of the Qweak experiment, we determine the gamma-Z box correction to be Re\\box_{gamma-Z}^V = (5.61 +- 0.36) x 10^{-3}. The new constraints also allow precise predictions to be made for parity-violating deep-inelastic asymmetries on the deuteron.

Hall, Nathan Luke [Adelaide U.; Blunden, Peter Gwithian [Manitoba U.; Melnitchouk, Wally [JLAB; Thomas, Anthony W. [Adelaide U.; Young, Ross D. [Adelaide U.

2013-07-01

344

Characteristics of the Duke\\/OK4 storage ring FEL and gamma-ray source  

Microsoft Academic Search

The Duke\\/OK-4 storage ring is a dedicated device for driving a short wavelength Free Electron Laser (FEL). In addition, Compton scattering of the laser light from the circulating electron beam products a semi-monochromatic gamma-ray source. The dynamics of such a system including accelerator physics, FEL physics, and Compton backscattering is complex and requires special study, This dissertation is a detailed

Seong Hee Park

2000-01-01

345

Crab crossing in a gamma-gamma collider  

SciTech Connect

The crabbing of an incident photon beam from a laser, and the electron beam with which it interacts at the conversion point, is shown to have the same efficiency as in head-on Compton scattering, but with the advantages of a crossing geometry. The resulting {gamma}-ray beam is also crabbed, which allows for a crossing collision point, while maintaining the luminosity at the same value it would have in a head-on collision.

Xie, M.; Kim, K.J.; Sessler, A.

1994-08-01

346

Gamma-Z box contributions to parity violating elastic e-p scattering  

E-print Network

Parity-violating (PV) elastic electron-proton scattering measures Q-weak for the proton, $Q_W^p$. To extract $Q_W^p$ from data, all radiative corrections must be well-known. Recently, disagreement on the gamma-Z box contribution to $Q_W^p$ has prompted the need for further analysis of this term. Here, we support one choice of a debated factor, go beyond the previously assumed equality of electromagnetic and gamma-Z structure functions, and find an analytic result for one of the gamma-Z box integrals. Our numerical evaluation of the gamma-Z box is in agreement within errors with previous reports, albeit somewhat larger in central value, and is within the uncertainty requirements of current experiments.

Benjamin C. Rislow; Carl E. Carlson

2010-11-10

347

Influence of humidity on the scattering of {gamma}-rays in soil  

SciTech Connect

Transmission and backscattering of {gamma}-rays have been used to study soil properties such as its porosity, hydraulic conductivity and also for the detection of organic material buried in soil. These applications require a deeper understanding of the interaction of {gamma}-rays with soil. In the present work a study of the interaction of 511 keV {gamma}-rays with layers of sand varying both its humidity and thickness is presented. The experimental set-up uses the positron decay of a {sup 22}Na source, and two gamma detectors connected in fast time-coincidence. Both transmitted and backscattered spectra are obtained. For transmission, the photopeak and the low angle scattered photons are studied, and for backscattering we analyze the number of single and multiple backscattered photons as a function of thickness. Finally, a theoretical model for the derivative of the number of backscattered photons as a function of depth is presented.

Cortes, M. L.; Melo, L. M.; Cristancho, F. [Departamento de Fisica, Universidad Nacional de Colombia (Colombia); Centro Internacional de Fisica, Bogota (Colombia)

2010-08-04

348

Inelastic neutron scatter iron concentrations of the moon from orbital gamma ray data  

NASA Technical Reports Server (NTRS)

The considered investigation is concerned with the relation between KREEP and thermal neutron flux depression. The Fe(n, n-prime gamma) concentrations of selected lunar regions were calculated by energy-band analysis of the 0.803-0.872 MeV band. The result of the investigation will be used to evaluate the reliability of the previously determined Fe(n, gamma) values. A 0.803-0.872 MeV band was isolated from the Apollo 15 and 16 orbital gamma ray spectra. Preliminary regression analysis of regional ground truth count rates and Fe concentrations showed this energy interval to be optimum for the 0.8467 MeV inelastic scatter (n, n-prime gamma)Fe peak.

Davis, P. A., Jr.; Bielefeld, M. J.

1981-01-01

349

A double photomultiplier Compton camera and its readout system for mice imaging  

SciTech Connect

We have designed a Compton Camera (CC) to image the bio-distribution of gamma-emitting radiopharmaceuticals in mice. A CC employs the 'electronic collimation', i.e. a technique that traces the gamma-rays instead of selecting them with physical lead or tungsten collimators. To perform such a task, a CC measures the parameters of the Compton interaction that occurs in the device itself. At least two detectors are required: one (tracker), where the primary gamma undergoes a Compton interaction and a second one (calorimeter), in which the scattered gamma is completely absorbed. Eventually the polar angle and hence a 'cone' of possible incident directions are obtained (event with 'incomplete geometry'). Different solutions for the two detectors are proposed in the literature: our design foresees two similar Position Sensitive Photomultipliers (PMT, Hamamatsu H8500). Each PMT has 64 output channels that are reduced to 4 using a charge multiplexed readout system, i.e. a Series Charge Multiplexing net of resistors. Triggering of the system is provided by the coincidence of fast signals extracted at the last dynode of the PMTs. Assets are the low cost and the simplicity of design and operation, having just one type of device; among drawbacks there is a lower resolution with respect to more sophisticated trackers and full 64 channels Readout. This paper does compare our design of our two-Hamamatsu CC to other solutions and shows how the spatial and energy accuracy is suitable for the inspection of radioactivity in mice.

Fontana, Cristiano Lino [Physics Department Galileo Galilei, University of Padua, Via Marzolo 8, Padova 35131 (Italy) and INFN Padova, Via Marzolo 8, Padova 35131 (Italy); Atroshchenko, Kostiantyn [Physics Department Galileo Galilei, University of Padua, Via Marzolo 8, Padova 35131 (Italy) and INFN Legnaro, Viale dell'Universita 2, Legnaro PD 35020 (Italy); Baldazzi, Giuseppe [Physics Department, University of Bologna, Viale Berti Pichat 6/2, Bologna 40127, Italy and INFN Bologna, Viale Berti Pichat 6/2, Bologna 40127 (Italy); Bello, Michele [INFN Legnaro, Viale dell'Universita 2, Legnaro PD 35020 (Italy); Uzunov, Nikolay [Department of Natural Sciences, Shumen University, 115 Universitetska str., Shumen 9712, Bulgaria and INFN Legnaro, Viale dell'Universita 2, Legnaro PD 35020 (Italy); Di Domenico, Giovanni [Physics Department, University of Ferrara, Via Saragat 1, Ferrara 44122 (Italy) and INFN Ferrara, Via Saragat 1, Ferrara 44122 (Italy)

2013-04-19

350

Development of a Compton imager based on bars of scintillator  

NASA Astrophysics Data System (ADS)

We have developed a compact Compton gamma-ray imager with a large field of view and a low channel-count that is capable of quickly localizing gamma-ray sources in the few hundred keV - several MeV range. The two detector planes (scatter and absorber) employ bars of NaI(Tl) read out by photomultiplier tubes (PMTs) located at each end. The long-range imaging performance has been tested from 392 keV to 1274 keV. An angular resolution measure of 2.720.06 and an efficiency of (1.790.04)10-3 at 662 keV is obtained. A 137Cs (662 keV) source equivalent to a 10 mCi source 40 m away can be located in 60 s with an uncertainty of about a degree. No significant degradation in imaging performance is observed for source angles up to 40 off axis.

MacLeod, A. M. L.; Boyle, P. J.; Hanna, D. S.; Saull, P. R. B.; Sinclair, L. E.; Seywerd, H. C. J.

2014-12-01

351

Feasibility study on Compton imaging for visualization of flow patterns using radiotracers  

NASA Astrophysics Data System (ADS)

The radiotracer technique could be used in studies on multiphase flow systems by three-dimensional visualization of flow patterns, and, relatedly, there have been attempts to develop an industrial-purpose single photon emission computed tomography (SPECT) system. Compton cameras also have a great potential for industrial applications, due specifically to their inherent three-dimensional imaging capability, multi-tracing capability, and higher imaging sensitivity than imaging devices based on mechanical collimation. In the present study, the feasibility of Compton imaging for visualization of detailed flow patterns was determined using a Geant4 Monte Carlo simulation toolkit. The Compton camera considered is a double-scattering type consisting of three gamma-ray detectors: two double-sided silicon strip detectors (DSSDs) as scatterer detectors and one NaI(Tl) scintillation detector as an absorber detector. The results showed that the three-dimensional source distributions can be determined with the Compton camera under various source conditions, including a point source at the center, and two cylinderial volume sources of different dimensions or energies.

Seo, H.; Park, J. H.; Park, J. G.; Ushakov, A.; Kim, C. H.; Lee, J. H.; Lee, C. S.; Lee, J. S.

2011-01-01

352

Intercomparison of gamma scattering, gammatography and radiography techniques for mild steel nonuniform corrosion detection  

SciTech Connect

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) controlled six-axis source detector system and four-axis job positioning system. The system has been successfully used to quantify the magnitude of corrosion and the thickness profile of a MS plate with nonuniform corrosion, and the results are correlated with those obtained from the conventional gammatography and radiography imaging measurements. A simple and straightforward reconstruction algorithm to reconstruct the densities of the objects under investigation and an unambiguous interpretation of the signal as a function of material density at any point of the thick object being inspected is described. In this simple and straightforward method the density of the target need not be known and only the knowledge of the target material's mass attenuation coefficients (composition) for the incident and scattered energies is enough to reconstruct the density of the each voxel of the specimen being studied. The Monte Carlo (MC) numerical simulation of the phenomena is done using the Monte Carlo N-Particle Transport Code (MCNP) and the quantitative estimates of the values of signal-to-noise ratio for different percentages of MS corrosion derived from these simulations are presented and the spectra are compared with the experimental data. The gammatography experiments are carried out using the same PC controlled scanning system in a narrow beam, good geometry setup, and the thickness loss is estimated from the measured transmitted intensity. Radiography of the MS plates is carried out using 160 kV x-ray machine. The digitized radiographs with a resolution of 50 {mu}m are processed for the detection of corrosion damage in five different locations. The thickness losses due to the corrosion of the MS plate obtained by gamma scattering method are compared with those values obtained by gammatography and radiography techniques. The percentage thickness loss estimated at different positions of the corroded MS plate varies from 17.78 to 27.0, from 18.9 to 24.28, and from 18.9 to 24.28 by gamma scattering, gammatography, and radiography techniques, respectively. Overall, these results are consistent and in line with each other.

Priyada, P.; Margret, M.; Ramar, R. (Shivaramu Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, Tamil Nadu (India)); Menaka, M. (Quality Assurance Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, Tamil Nadu (India)); Thilagam, L. (Atomic Energy Regulatory Board Safety Research Institute, Kalpakkam-603 102, Tamil Nadu (India)); Venkataraman, B. (Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, Tamil Nadu (India); Quality Assurance Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, Tamil Nadu (India)); Baldev Raj (Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, Tamil Nadu (India))

2011-03-01

353

Investigating the Compton Effect with a Spreadsheet.  

ERIC Educational Resources Information Center

Describes a computer simulation of the Compton effect designed to lead students to discover (1) the relationship of the electron's final kinetic energy to its angle of scattering and (2) the relationship between the scattering angles of the outgoing electron and photon. (MDH)

Kinderman, Jesusa Valdez

1992-01-01

354

Compton Polarization with Nustar  

NASA Astrophysics Data System (ADS)

In this study we assess the NuSTAR capabilities to detect polarized signals in the Compton regime, through the use of Monte Carlo simulations and comparison with observational data. Both NuSTAR focal plane detectors are equipped with high resolution pixilated CZT arrays, sensitive in the energy range 2.5-80 keV. These units have intrinsic polarization capabilities due to their high quality factor, very low background and scattering angles of ~90, which is ideal for incident photon energies below 100 keV. However the sensitivity is limited by the very low efficiency of the CZT for Compton interactions and by intrinsic readout systematics, such as charge sharing between pixels. An additional source of degradation is the incompleteness of double events information in the science telemetry. We estimated the Minimum Detectable Polarization of cosmic sources as a function of intensity, and the results obtained were validated through the comparison with the first actual data from the Crab Nebula and Cygnus X-1. We also evaluated the count rate and the background expected for polarization measurements, comparing our estimates with the data measured in flight. Our simulations reproduce well the actual NuSTAR data, showing that the focal plane detectors should be able to detect polarization from highly polarized sources like the Crab and other potential bright sources, dominated by synchrotron and/or SSC emission. The background for polarization measurements was found to be negligible.

Lotti, Simone; Natalucci, Lorenzo; Harrison, Fiona A.; Madsen, Kristin; Perri, Matteo; Puccetti, Simonetta

355

Testing the DC-electric field model in a solar flare observed by Yohkoh and the Compton Gamma-Ray Observatory  

NASA Technical Reports Server (NTRS)

We apply a DC-electric field model to the analysis of soft and hard X-ray observations of a solar flare observed by Yohkoh and the Compton Gamma Ray Observatory (CGRO) on 6 September 1992. The flare was observed simultaneously in the soft X-ray Ca XIX line by the Yohkoh Bragg Crystal Spectrometer (BCS) and in hard X-rays (greater than 50 keV) by the CGRO Burst and Transient Spectrometer Experiment (BATSE). A strong stationary component of Ca XIX emission was present at the start of impulsive hard X-ray emission indicating an extended phase of heating prior to the production of energetic nonthermal electrons. We interpret the preflare Ca XIX emission as a signature of Joule heating by field-aligned currents. We relate the temporal variation of impulsive hard X-ray emission to the rate of runaway electron acceleration by the DC-electric field associated with the current. We find that the initial rise in hard X-ray emission is consistent with electron acceleration by a DC-electric field that increased from a preflare value of less than approximately 10(exp -5) V/cm to approximately (9 +/- 1) x 10(exp -5) V/cm at the time of the first hard X-ray peak and then remained constant during the rest of the impulsive phase. We attribute the increase in electric field strength to the formation of a current sheet at the reconnection point of two loop structures. The decrease in hard X-ray emission after flare maximum is consistent with a reduction in the number of runaway electrons due to an increase in coronal density produced by chromospheric evaporation. The increased density quenches the runaway process by enhancing collisional thermalization of electrons. To avoid the generation of an unrealistically large magnetic field, the flaring region must be highly filamented into greater than approximately 10(exp 6) oppositely directed current channels of approximately 30 cm width with an initial preflare current of approximately 3 x 10(exp 10) A per channel.

Zarro, D. M.; Mariska, J. T.; Dennis, B. R.

1995-01-01

356

The Compton polarimeter for SLC  

SciTech Connect

We report on the use of a Compton scattering based polarimeter to measure beam polarization near the e{sup +}e{sub -} interaction point at the SLAC Linear Collider (SLC). Measurement of the beam polarization to a statistical precision of {delta}P/P={plus_minus}3% requires approximately three minutes under normal conditions. An average beam polarization of 22.4{plus_minus}0.7%(syst.) was measured over the course of the 1992 polarized beam run.

Fero, M.J. [Massachusetts Inst. of Tech., Cambridge, MA (United States); The SLD Collaboration

1992-12-01

357

The Compton polarimeter for SLC  

SciTech Connect

We report on the use of a Compton scattering based polarimeter to measure beam polarization near the e[sup +]e[sub -] interaction point at the SLAC Linear Collider (SLC). Measurement of the beam polarization to a statistical precision of [delta]P/P=[plus minus]3% requires approximately three minutes under normal conditions. An average beam polarization of 22.4[plus minus]0.7%(syst.) was measured over the course of the 1992 polarized beam run.

Fero, M.J. (Massachusetts Inst. of Tech., Cambridge, MA (United States))

1992-12-01

358

First results of electron temperature measurements by the use of multi-pass Thomson scattering system in GAMMA 10a)  

NASA Astrophysics Data System (ADS)

A multi-pass Thomson scattering (TS) has the advantage of enhancing scattered signals. We constructed a multi-pass TS system for a polarisation-based system and an image relaying system modelled on the GAMMA 10 TS system. We undertook Raman scattering experiments both for the multi-pass setting and for checking the optical components. Moreover, we applied the system to the electron temperature measurements in the GAMMA 10 plasma for the first time. The integrated scattering signal was magnified by approximately three times by using the multi-pass TS system with four passes. The electron temperature measurement accuracy is improved by using this multi-pass system.

Yoshikawa, M.; Yasuhara, R.; Nagasu, K.; Shimamura, Y.; Shima, Y.; Kohagura, J.; Sakamoto, M.; Nakashima, Y.; Imai, T.; Ichimura, M.; Yamada, I.; Funaba, H.; Kawahata, K.; Minami, T.

2014-11-01

359

Compton Sources of Electromagnetic Radiation  

SciTech Connect

When a relativistic electron beam interacts with a high-field laser beam, intense and highly collimated electromagnetic radiation will be generated through Compton scattering. Through relativistic upshifting and the relativistic Doppler effect, highly energetic polarized photons are radiated along the electron beam motion when the electrons interact with the laser light. For example, X-ray radiation can be obtained when optical lasers are scattered from electrons of tens-of-MeV beam energy. Because of the desirable properties of the radiation produced, many groups around the world have been designing, building, and utilizing Compton sources for a wide variety of purposes. In this review article, we discuss the generation and properties of the scattered radiation, the types of Compton source devices that have been constructed to date, and the prospects of radiation sources of this general type. Due to the possibilities of producing hard electromagnetic radiation in a device that is small compared to the alternative storage ring sources, it is foreseen that large numbers of such sources may be constructed in the future.

Geoffrey Krafft,Gerd Priebe

2011-01-01

360

OVERVIEW OF MONO-ENERGETIC GAMMA-RAY SOURCES & APPLICATIONS  

Microsoft Academic Search

Recent progress in accelerator physics and laser technology have enabled the development of a new class of tunable 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 Mono-Energetic Gamma-ray (MEGa-ray) source driven by a compact, high-gradient X-band linac is currently under development

F V Hartemann; F Albert; G G Anderson; S G Anderson; A J Bayramian; S M Betts; T S Chu; R R Cross; C A Ebbers; S E Fisher; D J Gibson; A S Ladran; R A Marsh; M J Messerly; K L ONeill; V A Semenov; M Y Shverdin; C W Siders; D P McNabb; C P Barty; A E Vlieks; E N Jongewaard; S G Tantawi; T O Raubenheimer

2010-01-01

361

Shock geometry and inverse Compton emission from the wind of a binary pulsar  

E-print Network

PSR B1259-63 is a 47ms radio pulsar with a high spin-down luminosity which is in a close, highly eccentric 3.5-year orbit about a bright stellar companion. The binary system may be a detectable source of hard gamma-rays produced by inverse Compton scattering of photons from the B2e star SS2883 by electrons and positrons in the pulsar wind. The star provides an enormous density of optical photons in the vicinity of the pulsar, particularly at epochs near periastron. We calculate the emission from the unshocked region of the pulsar wind, assuming that it terminates at a shock where it attains pressure balance with the companion's wind. The spectra and light curves for the inverse Compton emission from the shock-terminated wind are compared with those for an unterminated wind. If the pulsar's wind is weaker than that from the companion star, the termination of the wind decreases the inverse Compton flux, particularly near periastron. The termination shock geometry has the effect of decreasing the asymmetry of the gamma-ray light curve around periastron, which arises because of the asymmetrical variation of the scattering angle.

Lewis Ball; Jennifer Dodd

2000-11-16

362

Measurement of the polarization resulting from the scattering of 1250-keV gamma rays from bound electrons in lead  

E-print Network

MEASUREMENT OF THE POLARIZATION RESULTING FROM THE SCATTERING OF 1250 KEY GAMMA RAYS FROM BOUND ELECTRONS IN LEAD A Thesis By Michael Clinton Hamilton Submitted to the Graduate College of the Texas AIM University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE May 1966 Major Subject: Physics MEASUREMENT OF THE POLARIZATION RESULTING FROM THE SCATTERING OF 1250"KEY GAMMA RAYS FROM BOUND ELECTRONS IN LEAD A Thesis By Michael Clinton Hamilton Approved...

Hamilton, Michael Clinton

2012-06-07

363

Spin momentum density of Nd using Compton spectroscopy  

SciTech Connect

Spin momentum density of Nd has been measured at 6K temperature using magnetic Compton scattering. The individual contribution of different electronic states, in the formation of total spin moment, is deduced from the analysis of magnetic Compton profile. The electron-specific spin moments deduced from the experimental Compton data are compared with the theoretical results obtained from full potential linearized augmented plane wave method and are found to be in good agreement.

Sahariya, Jagrati; Dashora, Alpa; Mund, H. S.; Ahuja, B. L. [Department of Physics, ML Sukhadia University, Udaipur-313001, Rajasthan (India); Tiwari, Shailja [Department of Physics, Govt. Women Engineering College, Ajmer-305001, Rajasthan (India); Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute, SPring8, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan)

2013-02-05

364

\\Gamma\\Gamma \\Gamma\\Gamma  

E-print Network

\\Gamma\\Gamma @@@ @@@ ### ### ### ### \\Gamma\\Gamma\\Gamma \\Gamma\\Gamma\\Gamma @@@ @@@ ### ### ### ### \\Gamma\\Gamma\\Gamma \\Gamma\\Gamma\\Gamma yyy yyy \\Gamma\\Gamma@@####\\Gamma\\Gamma@@####\\Gamma\\Gamma@@####\\Gamma\\Gamma@@####\\Gamma\\Gamma@@####\\Gamma\\Gamma\\Gamma @@@ @@@ ### ### ### ### \\Gamma\\Gamma\\Gamma \\Gamma\\Gamma\\Gamma @@@ @@@ ### ### ### ### \\Gamma\\Gamma\\Gamma \\Gamma\\Gamma\\Gamma yyy

Laske, Gabi

365

Discrimination of gamma rays due to inelastic neutron scattering in AGATA  

E-print Network

Possibilities of discriminating neutrons and gamma rays in the AGATA gamma-ray tracking spectrometer have been investigated with the aim of reducing the background due to inelastic scattering of neutrons in the high-purity germanium crystals. This background may become a serious problem especially in experiments with neutron-rich radioactive ion beams. Simulations using the Geant4 toolkit and a tracking program based on the forward tracking algorithm were carried out by emitting neutrons and gamma rays from the center of AGATA. Three different methods were developed and tested in order to find 'fingerprints' of the neutron interaction points in the detectors. In a simulation with simultaneous emission of six neutrons with energies in the range 1-5 MeV and ten gamma rays with energies between 150 and 1450 keV, the peak-to-background ratio at a gamma-ray energy of 1.0 MeV was improved by a factor of 2.4 after neutron rejection with a reduction of the photopeak efficiency at 1.0 MeV of only a factor of 1.25.

A. Ata; A. Ka?ka?; S. Akkoyun; M. ?enyi?it; T. Hyk; S. O. Kara; J. Nyberg

2009-06-06

366

Modeling And Correcting Scattering In Industrial Applications Of Computerized Tomography  

NASA Astrophysics Data System (ADS)

The Compton effect is an elastic collision between gamma and Xrays and electrons, and in tomographic imaging systems can produce spectral artifacts and distort the signals received through one or more scattering steps. In most tomography systems, energy sensitive detectors or collimation can be used to diminish the effects of Compton scattering. However, in fourth generation tomography systems, it is difficult to utilize collimators due to the fact that detectors receive signals from more than one direction. As a result, in those cases where collimation and energy sensitive detectors are not employed, there is a need to find other methods that reduce the distortion due to scatter. We developed a model for the distribution of Compton scattered photons for industrial applications by implementing a Monte Carlo simulation routine based on a single beam scanner geometry, and compared the results to expermental data collected from a single beam system at Bethlehem Steel Corporation. Significant differences appeared between the experimental and simulated data. In addition, existing scatter correction techniques were applied to data obtained from Bethlehem Steel's fourth generation tomographic system. The existing scatter correction techniques involve both point-wise and convolution models which are subtracted from the measured data to correct for scatter. Improved results were obtained in both image quality and dimensional measures. Finally, using the model of scattering obtained from the simulation data, we proposed further modification to the existing point-wise scatter correction technique, which further correct for scatter in computerized tomographic systems.

Straining, R. Joseph; Abdou, Ikram

1988-01-01

367

Performance of the IBIS Compton mode  

NASA Astrophysics Data System (ADS)

The IBIS instrument launched on board the ESA INTEGRAL observatory on October 2002 is a coded mask telescope composed by two position sensitive detection planes, one with 16384 Cadmium Telluride pixels (ISGRI) and the other with 4096 Caesium Iodide pixels (PICsIT). Events detected in coincidence in the two detector layers are flagged as generated by Compton scattered photons and can be then processed and filtered using the Compton kinematic equations. The analysis of these data is, however, quite complex, mainly due to the presence of a great number of fake events generated by random coincidences between uncorrelated ISGRI and PICsIT events; if this component is not subtracted with great accuracy, false source detections can be produced. In this work, we present the performance (spectral and imaging) obtainable from the IBIS Compton data, by analyzing ground calibration acquisitions. We also analyze the IBIS Compton flight data relative to the Crab observation, to determine its scientific capabilities.

Segreto, Alberto

2004-10-01

368

The time evolution of GRB spectra by a precessing lighthouse gamma jet  

Microsoft Academic Search

Inverse Compton Scattering (ICS) by a relativistic electron beam jet at GeV energies (emitted by a compact object as a NS, BH,...), a NSJ, onto thermal BBR photons (from a nearby stellar companion) may originate a collinear gamma jet (GJ). Due to the binary system interaction the GJ precession would blaze suddenly toward the observer leading to a GRB event.

Daniele Fargion; Andrea Salis

1996-01-01

369

Pair Production and Radiation Effects in Clouds Illuminated by Gamma Ray Sources  

E-print Network

Many classes of gamma-ray sources, such as gamma-ray bursts, blazars, Seyfert galaxies, and galactic black hole sources are surrounded by large amounts of gas and dust. X-rays and gamma-rays that traverse this material will be attenuated by Compton scattering and photoelectric absorption. One signature of an intervening scattering cloud is radiation-hardening by electrons that have been scattered and heated by the incident radiation, as illustrated by a Monte Carlo calculation. Compton scattering provides backscattered photons that will attenuate subsequent gamma rays through \\gamma\\gamma pair-production processes. We calculate the pair efficiency for a cloud illuminated by gamma-ray burst radiation. An analytic calculation of the flux of X-rays and gamma rays Thomson scattered by an intervening cloud is presented. Illuminated clouds near GRBs will form relativistic plasmas containing large numbers of electron-positron pairs that can be detected within ~1-2 days of the explosion before expanding and dissipating. Localized regions of pair annihilation radiation in the Galaxy could reveal gamma-ray sources embedded in dense clouds, or sites of past GRB explosions.

C. D. Dermer; M. Boettcher; E. P. Liang

2001-07-12

370

Radio and gamma-ray emission from pulsars  

E-print Network

The radiation of pulsars have been observed for many years. A few pulsars are discovered to have both radio and gamma-ray emission. Many models on pulsar radiation have been developed, but so far we are still lacking an elaborate model which can explain the emission from radio to gamma-rays in detail. In this paper we present a joint model for radio and gamma-ray emission, in which both the dominate emission mechanisms are inverse Compton scattering. The pulse profiles at radio and gamma-ray bands are reproduced for the Crab-like, Vela-like and Geminga-like pulsars, in good agreement with observations.

G. J. Qiao; K. J. Lee; H. G. Wang; R. X. Xu

2003-03-11

371

Exact Solutions of the Kompaneets Equation for Photon "Comptonization" Kinetics  

NASA Astrophysics Data System (ADS)

The nonlinear Kompaneets equation for the evolution of the spectrum of a photon gas with Compton scattering in a rarefied nonrelativistic electron plasma (i.e., the "comptonization" of the radiation) is examined. Exact solutions of this equation are obtained by separation of variables. The solutions are expressed in terms of transcendental Heun and Bessel functions.

Dubinov, A. E.; Kitayev, I. N.

2014-09-01

372

Time-Dependent Synchrotron and Compton Spectra from Jets of Microquasars  

E-print Network

Jet models for the high-energy emission of Galactic X-ray binary sources have regained significant interest with detailed spectral and timing studies of the X-ray emission from microquasars, the recent detection by the HESS collaboration of very-high-energy gamma-rays from the microquasar LS~5039, and the earlier suggestion of jet models for ultraluminous X-ray sources observed in many nearby galaxies. Here we study the synchrotron and Compton signatures of time-dependent electron injection and acceleration, adiabatic and radiative cooling, and different jet geometries in the jets of Galactic microquasars. Synchrotron, synchrotron-self-Compton, and external-Compton radiation processes with soft photons provided by the companion star and the accretion disk are treated. An analytical solution is presented to the electron kinetic equation for general power-law geometries of the jets for Compton scattering in the Thomson regime. We pay particular attention to predictions concerning the rapid flux and spectral var...

Gupta, S; Dermer, C D; Boettcher, Markus; Dermer, Charles D.; Gupta, Swati

2006-01-01

373

Time-Dependent Synchrotron and Compton Spectra from Jets of Microquasars  

E-print Network

Jet models for the high-energy emission of Galactic X-ray binary sources have regained significant interest with detailed spectral and timing studies of the X-ray emission from microquasars, the recent detection by the HESS collaboration of very-high-energy gamma-rays from the microquasar LS~5039, and the earlier suggestion of jet models for ultraluminous X-ray sources observed in many nearby galaxies. Here we study the synchrotron and Compton signatures of time-dependent electron injection and acceleration, adiabatic and radiative cooling, and different jet geometries in the jets of Galactic microquasars. Synchrotron, synchrotron-self-Compton, and external-Compton radiation processes with soft photons provided by the companion star and the accretion disk are treated. An analytical solution is presented to the electron kinetic equation for general power-law geometries of the jets for Compton scattering in the Thomson regime. We pay particular attention to predictions concerning the rapid flux and spectral variability signatures expected in a variety of scenarios, making specific predictions concerning possible spectral hysteresis, similar to what has been observed in several TeV blazars. Such predictions should be testable with dedicated monitoring observations of Galactic microquasars and ultraluminous X-ray sources using Chandra and/or XMM-Newton.

Swati Gupta; Markus Boettcher; Charles D. Dermer

2006-02-20

374

The X-Ray Jet of PKS 0637-752: Inverse Compton Radiation from the Cosmic Microwave Background ?  

E-print Network

We propose that the X-ray emission detected by Chandra from the 100-kiloparsec-scale jet of PKS 0637-752 is produced through inverse Compton scattering of the Cosmic Microwave Background (CMB). We analyze the physical state of the jet and show that inverse Compton scattering from the CMB is consistent with equipartition for a moderate beaming of the emission, with Doppler factor delta~10. The power transported by the jet is then similar to that of other powerful blazars, Lj~10^{48} erg/s and the jet has low radiative efficiency. The radiative cooling times of the electrons are a few thousand years, compatible with the size of the knot. The low-energy cutoff of the electron distribution is constrained to be gamma_min~10, the first such constraint from spectral considerations. A parallel analysis for the SSC model yields far less reasonable physical conditions.

F. Tavecchio; L. Maraschi R. M. Sambruna; C. M. Urry

2000-07-28

375

Spectral measurements of direct and scattered gamma radiation at a boiling-water reactor site  

NASA Astrophysics Data System (ADS)

Quantitative surveys of direct and scattered gamma radiation emitted from the steam-power conversion systems of a boiling-water reactor and other on-site radiation sources were made using a directionally shielded HPGe gamma spectrometry system. The purpose of this study was to obtain data on the relative contributions and energy distributions of direct and scattered gamma radiation in the site environs. The principal radionuclide of concern in this study is 16N produced by the 16O(n,p) 16N reaction in the reactor coolant. Due to changes in facility operation resulting from the implementation of hydrogen water chemistry (HWC), the amount of 16N transported from the reactor to the main steam system under full power operation is excepted to increase by a factor of 1.2 to 5.0. This increase in the 16N source term in the nuclear steam must be considered in the design of new facilities to be constructed on site as well as the evaluation of existing facilities with repect to ALARA (As Low As Reasonably Achievable) dose limits in unrestricted areas. This study consisted of base-line measurements taken under normal BWR chemistry conditions in October, 1987 and a corresponding set taken under HWC conditions in July, 1988. Ground-level and elevated measurements, corresponding to second-story building height, were obtained. The primary conclusion of this study is that direct radiation from the steam-power conversion system is the predominant source of radiation in the site environs of this reactor and that air scattering (i.e. skyshine) does not appear to be significant.

Block, R. C.; Preiss, I. L.; Ryan, R. M.; Vargo, G. J.

1990-12-01

376

Comptonization signatures in the rapid aperiodic variability of Galactic BlackHole Candidates  

E-print Network

Comptonization signatures in the rapid aperiodic variability of Galactic Black­Hole Candidates M. B¨ottcher, E. P. Liang 1 ABSTRACT We investigate the effect of Compton scattering of flares of soft radiation of a comparison with existing data we find arguments against Comptonization of external soft radiation as well

Boettcher, Markus

377

Incoherent scattering of gamma photons for non-destructive tomographic inspection of pipeline.  

PubMed

A scanner system, operating in a non-destructive and non-invasive way, is presented for pipeline to determine its location in land soil, wall thickness, type of liquid flowing and crack/blockage position. The present experiment simulates a real case where pipe corrosion (wall thinning) under insulation can be known from the study of incoherent scattering of 662 keV gamma photons. The incoherent scattered intensity, obtained by unfolding (deconvolution) the experimental pulse-height distribution of NaI(Tl) scintillation detector with the help of inverse response matrix, provides the desired information. The method is quite sensitive for small change (approximately 1 mm) in the thickness of pipe wall, locating a defect of 1mm width under insulation and a small change (approximately 0.1 gm cm(-3)) in the density of liquid flowing through pipe. PMID:20542441

Sharma, Amandeep; Sandhu, B S; Singh, Bhajan

2010-12-01

378

Optimal Design of a Tunable Thomson-Scattering Based Gamma-Ray Source  

SciTech Connect

Thomson-Scattering based systems offer a path to high-brightness high-energy (> 1 MeV) x-ray and {gamma}-ray sources due to their favorable scaling with electron energy. LLNL is currently engaged in an effort to optimize such a device, dubbed the ''Thomson-Radiated Extreme X-Ray'' (T-REX) source, targeting up to 680 keV photon energy. Such a system requires precise design of the interaction between a high-intensity laser pulse and a high-brightness electron beam. Presented here are the optimal design parameters for such an interaction, including factors such as the collision angle, focal spot size, optimal bunch charge, and laser energy. These parameters were chosen based on extensive modeling using PARMELA and in-house, well-benchmarked scattering simulation codes.

Gibson, D J; Anderson, S G; Betts, S M; Hartemann, F V; Jovanovic, I; McNabb, D P; Messerly, M J; Pruet, J A; Shverdin, M Y; Siders, C W; Tremaine, A M; Barty, C J

2007-06-07

379

All-sky Compton imager  

NASA Astrophysics Data System (ADS)

The All-Sky Compton Imager (ASCI) is a mission concept for MeV Gamma-Ray astronomy. It consists of a compact array of cross-strip germanium detectors, shielded only by a plastic anticoicidence, and weighting less than 100 kg. Situated on a deployable structure at a distance of 10 m from the spacecraft orbiting at L2 or in a HEO, the ASCI not only avoids albedo- and spacecraft-induced background, but it benefits from a continuous all-sky exposure. The modest effective area is more than compensated by the 4 ? field-of-view. Despite its small size, ASCI's ?-ray line sensitivity after its nominal lifetime of 3 years is ~ 10-6 ph cm-2 s-1 at 1 MeV for every ?-ray source in the sky. With its high spectral and 3-D spatial resolution, the ASCI will perform sensitive ?ray spectroscopy and polarimetry in the energy band 100 keV-10 MeV. The All-Sky Compton Imager is particularly well suited to the task of measuring the Cosmic Gamma-Ray Background - and simultaneously covering the wide range of science topics in gamma-ray astronomy.

von Ballmoos, Peter; Boggs, Steven E.; Jean, Pierre; Zoglauer, Andreas

2014-07-01

380

Study of scattered photons from the collimator system of Leksell Gamma Knife using the EGS4 Monte Carlo Code  

SciTech Connect

In the algorithm of Leksell GAMMAPLAN (the treatment planning software of Leksell Gamma Knife), scattered photons from the collimator system are presumed to have negligible effects on the Gamma Knife dosimetry. In this study, we used the EGS4 Monte Carlo (MC) technique to study the scattered photons coming out of the single beam channel of Leksell Gamma Knife. The PRESTA (Parameter Reduced Electron-Step Transport Algorithm) version of the EGS4 (Electron Gamma Shower version 4) MC computer code was employed. We simulated the single beam channel of Leksell Gamma Knife with the full geometry. Primary photons were sampled from within the {sup 60}Co source and radiated isotropically in a solid angle of 4{pi}. The percentages of scattered photons within all photons reaching the phantom space using different collimators were calculated with an average value of 15%. However, this significant amount of scattered photons contributes negligible effects to single beam dose profiles for different collimators. Output spectra were calculated for the four different collimators. To increase the efficiency of simulation by decreasing the semiaperture angle of the beam channel or the solid angle of the initial directions of primary photons will underestimate the scattered component of the photon fluence. The generated backscattered photons from within the {sup 60}Co source and the beam channel also contribute to the output spectra.

Cheung, Joel Y.C.; Yu, K.N. [Gamma Knife Centre, Canossa Hospital, 1 Old Peak Road, Hong Kong (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China)

2006-01-15

381

Study of scattered photons from the collimator system of Leksell Gamma Knife using the EGS4 Monte Carlo code.  

PubMed

In the algorithm of Leksell GAMMAPLAN (the treatment planning software of Leksell Gamma Knife), scattered photons from the collimator system are presumed to have negligible effects on the Gamma Knife dosimetry. In this study, we used the EGS4 Monte Carlo (MC) technique to study the scattered photons coming out of the single beam channel of Leksell Gamma Knife. The PRESTA (Parameter Reduced Electron-Step Transport Algorithm) version of the EGS4 (Electron Gamma Shower version 4) MC computer code was employed. We simulated the single beam channel of Leksell Gamma Knife with the full geometry. Primary photons were sampled from within the 60Co source and radiated isotropically in a solid angle of 4pi. The percentages of scattered photons within all photons reaching the phantom space using different collimators were calculated with an average value of 15%. However, this significant amount of scattered photons contributes negligible effects to single beam dose profiles for different collimators. Output spectra were calculated for the four different collimators. To increase the efficiency of simulation by decreasing the semiaperture angle of the beam channel or the solid angle of the initial directions of primary photons will underestimate the scattered component of the photon fluence. The generated backscattered photons from within the 60Co source and the beam channel also contribute to the output spectra. PMID:16485407

Cheung, Joel Y C; Yu, K N

2006-01-01

382

A high-energy Compton polarimeter for the POET SMEX mission  

NASA Astrophysics Data System (ADS)

The primary science goal of the Polarimeters for Energetic Transients (POET) mission is to measure the polarization of gamma-ray bursts over a wide energy range, from X rays to soft gamma rays. The higher-energy portion of this band (50 - 500 keV) will be covered by the High Energy Polarimeter (HEP) instrument, a non-imaging, wide field of view Compton polarimeter. Incident high-energy photons will Compton scatter in low-Z, plastic scintillator detector elements and be subsequently absorbed in high-Z, CsI(Tl) scintillator elements; polarization is detected by measuring an asymmetry in the azimuthal scatter angle distribution. The HEP design is based on our considerable experience with the development and flight of the Gamma-Ray Polarimeter Experiment (GRAPE) balloon payload. We present the design of the POET HEP instrument, which incorporates lessons learned from the GRAPE balloon design and previous work on Explorer proposal efforts, and its expected performance on a two-year SMEX mission.

Bloser, Peter F.; McConnell, Mark L.; Legere, Jason S.; Ertley, Camden D.; Hill, Joanne E.; Kippen, Marc; Ryan, James M.

2014-07-01

383

The Advanced Compton Telescope Mission  

E-print Network

The Advanced Compton Telescope (ACT), the next major step in gamma-ray astronomy, will probe the fires where chemical elements are formed by enabling high-resolution spectroscopy of nuclear emission from supernova explosions. During the past two years, our collaboration has been undertaking a NASA mission concept study for ACT. This study was designed to (1) transform the key scientific objectives into specific instrument requirements, (2) to identify the most promising technologies to meet those requirements, and (3) to design a viable mission concept for this instrument. We present the results of this study, including scientific goals and expected performance, mission design, and technology recommendations.

Steven E. Boggs; James Kurfess; James Ryan; Elena Aprile; Neil Gehrels; Marc Kippen; Mark Leising; Uwe Oberlack; Cornelia Wunderer; Allen Zych; Peter Bloser; Michael Harris; Andrew Hoover; Alexei Klimenk; Dan Kocevski; Mark McConnell; Peter Milne; Elena I. Novikova; Bernard Phlips; Mark Polsen; Steven Sturner; Derek Tournear; Georg Weidenspointner; Eric Wulf; Andreas Zoglauer; Matthew Baring; John Beacom; Lars Bildsten; Charles Dermer; Dieter Hartmann; Margarita Hernanz; David Smith; Sumner Starrfield; for the larger ACT collaboration

2006-08-24

384

Pair Production and Radiation Effects in Clouds Illuminated by Gamma Ray Sources  

E-print Network

Many classes of gamma-ray sources, such as gamma-ray bursts, blazars, Seyfert galaxies, and galactic black hole sources are surrounded by large amounts of gas and dust. X-rays and gamma-rays that traverse this material will be attenuated by Compton scattering and photoelectric absorption. One signature of an intervening scattering cloud is radiation-hardening by electrons that have been scattered and heated by the incident radiation, as illustrated by a Monte Carlo calculation. Compton scattering provides backscattered photons that will attenuate subsequent gamma rays through \\gamma\\gamma pair-production processes. We calculate the pair efficiency for a cloud illuminated by gamma-ray burst radiation. An analytic calculation of the flux of X-rays and gamma rays Thomson scattered by an intervening cloud is presented. Illuminated clouds near GRBs will form relativistic plasmas containing large numbers of electron-positron pairs that can be detected within ~1-2 days of the explosion before expanding and dissipati...

Dermer, C D; Liang, E P

2000-01-01

385

Statistical simulation of multiple Compton backscattering process  

NASA Astrophysics Data System (ADS)

A number of laboratories are currently developing monochromatic sources of X-rays and gamma quanta based on the Compton backscattering (CBS) of laser photons by relativistic electrons. Modern technologies are capable of providing a concentration of electrons and photons in the interaction point such that each primary electron can emit several hard photons. In contrast to the well-known nonlinear CBS process, in which an initial electron "absorbs" a few laser photons and emits a single hard one, the above-mentioned process can be called a multiple CBS process and is characterized by a mean number of emitted photons. The present paper is devoted to simulating the parameters of a beam of back scattered quanta based on the Monte Carlo technique. It is shown that, even in the case of strong collimation of a resulting photon beam, the radiation monochromaticity may deteriorate because of the contribution coming from the multiple photon emission, which is something that must be considered while designing new CBS sources.

Potylitsyn, A. P.; Kolchuzhkin, A. M.

2014-09-01

386

A Compton-Vetoed Germanium Detector with Increased Sensitivity at Low Energies  

SciTech Connect

The difficulty to directly detect plutonium in spent nuclear fuel due to the high Compton background of the fission products motivates the design of a Gamma detector with improved sensitivity at low energies. We have built such a detector by operating a thin high-purity Ge detector with a large scintillator Compton veto directly behind it. The Ge detector is thin to absorb just the low-energy Pu radiation of interest while minimizing Compton scattering of high energy radiation from the fission products. The subsequent scintillator is large so that forward scattered photons from the Ge detector interact in it at least once to provide an anti-coincidence veto for the Ge detector. For highest sensitivity, additional material in the line-of-sight is minimized, the radioactive sample is kept thin, and its radiation is collimated. We will discuss the instrument design, and demonstrate the feasibility of the approach with a prototype that employs two large CsI scintillator vetoes. Initial spectra of a thin Cs-137 calibration source show a background suppression of a factor of {approx}2.5 at {approx}100 keV, limited by an unexpectedly thick 4 mm dead layer in the Ge detector.

Friedrich, S; Bates, C; Drury, O B; Burks, M; DiPrete, D

2012-03-29

387

Range verification of passively scattered proton beams based on prompt gamma time patterns  

NASA Astrophysics Data System (ADS)

We propose a proton range verification technique for passive scattering proton therapy systems where spread out Bragg peak (SOBP) fields are produced with rotating range modulator wheels. The technique is based on the correlation of time patterns of the prompt gamma ray emission with the range of protons delivering the SOBP. The main feature of the technique is the ability to verify the proton range with a single point of measurement and a simple detector configuration. We performed four-dimensional (time-dependent) Monte Carlo simulations using TOPAS to show the validity and accuracy of the technique. First, we validated the hadronic models used in TOPAS by comparing simulations and prompt gamma spectrometry measurements published in the literature. Second, prompt gamma simulations for proton range verification were performed for the case of a water phantom and a prostate cancer patient. In the water phantom, the proton range was determined with 2?mm accuracy with a full ring detector configuration for a dose of ~2.5?cGy. For the prostate cancer patient, 4?mm accuracy on range determination was achieved for a dose of ~15?cGy. The results presented in this paper are encouraging in view of a potential clinical application of the technique.

Testa, Mauro; Min, Chul Hee; Verburg, Joost M.; Schmann, Jan; Lu, Hsiao-Ming; Paganetti, Harald

2014-07-01

388

The contribution of unresolved radio-loud AGN to the extragalactic diffuse gamma-ray background  

Microsoft Academic Search

We present a calculation of the blazar contribution to the extragalactic diffuse gamma-ray background (EGRB) in the EGRET energy range. Our model is based on inverse-Compton scattering as the dominant gamma-ray production process in the jets of flat spectrum radio quasars (FSRQs) and BL Lac objects, and on the unification scheme of radio-loud AGN. According to this picture, blazars represent

A. Mcke; M. Pohl

2000-01-01

389

A Monte Carlo evaluation of three Compton camera absorbers.  

PubMed

We present a quantitative study on the performance of cadmium zinc telluride (CZT), thallium-doped sodium iodide (NaI(Tl)) and germanium (Ge) detectors as potential Compton camera absorbers. The GEANT4 toolkit was used to model the performance of these materials over the nuclear medicine energy range. CZT and Ge demonstrate the highest and lowest efficiencies respectively. Although the best spatial resolution was attained for Ge, its lowest ratio of single photoelectric to multiple interactions suggests that it is most prone to inter-pixel cross-talk. In contrast, CZT, which demonstrates the least positioning error due to multiple interactions, has a comparable spatial resolution with Ge. Therefore, we modelled a Compton camera system based on silicon (Si) and CZT as the scatterer and absorber respectively. The effects of the detector parameters of our proposed system on image resolution were evaluated and our results show good agreement with previous studies. Interestingly, spatial resolution which accounted for the least image degradation at 140.5 keV became the dominant degrading factor at 511 keV, indicating that the absorber parameters play some key roles at higher energies. The results of this study have validated the predictions by An et al. which state that the use of a higher energy gamma source together with reduction of the absorber segmentation to sub-millimetre could achieve the image resolution of 5 mm required in medical imaging. PMID:21710232

Uche, C Z; Round, W H; Cree, M J

2011-09-01

390

Temperature-dependent spin magnetization density in Mn-rich Ni-Mn-Sn shape memory alloy by magnetic Compton scattering  

NASA Astrophysics Data System (ADS)

Temperature-dependent spin momentum densities in Ni2Mn1.4Sn0.6 shape memory alloy have been measured using 182 keV circularly polarized synchrotron radiations. Near the martensitic phase transition (T_{{M}}=200\\ \\text{K}) , experimental magnetic Compton profiles (MCPs) unravel a dominating spin moment contribution from Mn sites. First-principles calculations are found to produce higher magnetic moment for orthorhombic structure than that for the L21 (cubic) structure, which is in tune with the present MCP data. It is also concluded that the spin moments of excess Mn atoms lying at Sn sites are antiferromagnetically coupled with Mn local spin moment in both the phases.

Ahuja, B. L.; Dashora, Alpa; Mund, H. S.; Priolkar, K. R.; Yusuf, S. M.; Itou, M.; Sakurai, Y.

2014-07-01

391

Absorption of X-rays and gamma rays at cosmological distances  

Microsoft Academic Search

The absorption of X-rays and gamma-rays in interactions with the cosmic thermal background and baryonic matter at cosmological redshifts is studied. Analytical formulae for the optical depths to photoionization, Compton scattering, photon-matter pair production, photon-photon scattering, and photon-photon single- and double-pair production are derived as functions of redshift and photon energy. The redshift-energy plane is divided into regions of dominance

Andrzej A. Zdziarski; Roland Svensson

1989-01-01

392

Large area double scattering telescope for balloon-borne studies of neutrons and gamma rays  

NASA Technical Reports Server (NTRS)

A large area double scattering telescope for balloon-borne research is described. It measures the flux, energy and direction of 2-100 MeV neutrons and 0.5-30 MeV gamma rays. These measurements are made using time-of-flight and pulse height analysis techniques with two large tanks of mineral oil liquid scintillator. Results from Monte Carlo calculations of the efficiency, energy resolution and angular resolution are presented and the electronics implementation for the processing of 80 photomultiplier tubes signals will be discussed. The detector weighs 800 kg with a large part of this weight being the liquid scintillator (320 kg). It will be flown at 3 mbars for flight durations up to 40 hours. The first flight is planned for Spring, 1975.

Zych, A. D.; Herzo, D.; Koga, R.; Millard, W. A.; Moon, S.; Ryan, J.; Wilson, R.; White, R. S.; Dayton, B.

1975-01-01

393

On the performance of the scattering and crystal polarimeters for the Spectrum-X-Gamma mission  

NASA Technical Reports Server (NTRS)

X-ray scattering from a lithium disk and Bragg reflection from a mosaic graphite crystal can be exploited to measure the linear polarization of radiation emitted from cosmic X-ray sources. The sensitivity is enhanced if the polarimeters are placed at the focus of an X-ray telescope. Such devices form two of the components of the Stellar X-ray Polarimeter experiment scheduled to fly on the Spectrum-X-Gamma mission. The expected on-axis performance of the two components is described based on detailed Monte Carlo simulations. The polarimetry experiment is expected to provide sensitive measurements of linear polarization for many cosmic X-ray sources. The nature and utility of such observations is described for pulsing X-ray sources such as the Crab pulsar and Her X-1.

Elsner, R. F.; Weisskopf, M. C.; Novick, R.; Kaaret, P.; Silver, E.

1990-01-01

394

Synchrotron vs Compton Interpretations for Extended X-ray Jets  

E-print Network

A widely discussed explanation for the origin of the X-ray emission observed from knots in extended quasar jets with the Chandra X-ray Obseratory is Compton-scattered CMBR by electrons with Lorentz factors $\\gamma^\\prime \\sim 10^2$. This model faces difficulties in terms of total energy requirements, and in explaining the spatial profiles of the radio, optical, and X-ray knots in sources such as PKS 0637-752, 3C 273, or PKS 1127-145. These difficulties can be resolved in the framework of one- and two-component synchrotron models. We propose a model where the broad band radio to X-ray synchrotron emission in quasar jets is powered by collimated beams of ultra-high energy neutrons and gamma-rays formed in the sub-parsec scale jets. The decay of the neutral beam in the intergalactic medium drives relativistic shocks to accelerate nonthermal electrons out of the ambient medium. A second synchrotron component arises from the injection of leptons with Lorentz factors $\\gg 10^7$ that appear in the extended jet in the process of decay of ultra-high energy gamma rays. This approach could account for qualitative differences in the extended X-ray jets of FR1 and FR2 galaxies. Detection of high-energy neutrinos from blazars and core-dominated quasars will provide strong evidence for this model.

A. Atoyan; C. D. Dermer

2004-02-26

395

A nonlinear plasma retroreflector for single pulse Compton backscattering  

E-print Network

Compton scattered x-rays can be generated using a configuration consisting of a single, ultra-intense laser pulse, and a shaped gas target. The gas target incorporates a hydrodynamically formed density spike, which nonlinearly scatters the incident pump radiation, to produce a counter-propagating electromagnetic wiggler. This self-generated wiggler field Compton scatters from electrons accelerated in the laser wakefield of the pump radiation. The nonlinear scattering mechanism in the density spike is examined theoretically and numerically in order to optimize the Compton scattered radiation. It is found that narrow-band x-rays are produced by moderate intensity pump radiation incident on the quarter-critical surface of the density spike, while high fluence, broadband x-rays are produced by high intensity pump radiation reflected near the critical surface.

Palastro, J P; Gordon, D; Hafizi, B; Helle, M; Penano, J; Ting, A

2014-01-01

396

High sensitivity high resolution double scatter 1-30 MeV gamma ray telescope  

NASA Astrophysics Data System (ADS)

The design and performance of the double-scatter 1-30-MeV gamma-ray telescope developed at the University of California for balloon-borne observations are reported and illustrated with drawings, diagrams, and graphs. The telescope comprises an upper array of 16 6.03 x 6.03 x 100-cm plastic scintillator bars viewed by photomultiplier tubes (PMTs) at both ends, a lower array (at 100-cm distance) of 16 4.83 x 4.83 x 100-cm NaI(Tl) bars viewed at both ends by PMTs, and four 122 x 122 x 0.64-cm plastic sheets viewed by four PMTs each as charged-particle anticoincidence shielding. The operating principle of the telescope, the tests conducted on the NaI(Tl) bars, the on-board data-processing electronics, and the overall performance are characterized. Performance parameters include area 1 sq m, field of view pi sr, 4-sigma sensitivity above 1 MeV 0.00004 gamma/sq cm sec over 25 h, angular resolution about 3.5 deg FWHM, and energy resolution 10 percent at 1 MeV and 6 percent at 6 MeV.

Zych, A. D.; Tumer, O. T.; White, R. S.; Dayton, B.

1983-08-01

397

High sensitivity high resolution double scatter 1-30 MeV gamma ray telescope  

NASA Technical Reports Server (NTRS)

The design and performance of the double-scatter 1-30-MeV gamma-ray telescope developed at the University of California for balloon-borne observations are reported and illustrated with drawings, diagrams, and graphs. The telescope comprises an upper array of 16 6.03 x 6.03 x 100-cm plastic scintillator bars viewed by photomultiplier tubes (PMTs) at both ends, a lower array (at 100-cm distance) of 16 4.83 x 4.83 x 100-cm NaI(Tl) bars viewed at both ends by PMTs, and four 122 x 122 x 0.64-cm plastic sheets viewed by four PMTs each as charged-particle anticoincidence shielding. The operating principle of the telescope, the tests conducted on the NaI(Tl) bars, the on-board data-processing electronics, and the overall performance are characterized. Performance parameters include area 1 sq m, field of view pi sr, 4-sigma sensitivity above 1 MeV 0.00004 gamma/sq cm sec over 25 h, angular resolution about 3.5 deg FWHM, and energy resolution 10 percent at 1 MeV and 6 percent at 6 MeV.

Zych, A. D.; Tumer, O. T.; White, R. S.; Dayton, B.

1983-01-01

398

Cyclotron resonant scattering in the spectra of gamma-ray bursts  

NASA Technical Reports Server (NTRS)

Fits of theoretical spectra from Monte Carlo radiation-transfer calculations to dips at approximately 20 and 40 keV in a spectrum of the gamma-ray burst source GB 880 205 give best-fit values and 68 percent-confidence intervals for the magnetic field of (1.71 + or - 0.07) x 10 to the 12th G, the electron density of (1.2 + or - 0.6) x 10 to the 21st electrons/cm-squared, and the cosine of the viewing angle relative to the field of 0.31 + or - 0.05. The dips observed at approximately 20 keV in the spectra are interpreted as cyclotron resonant scattering, in which electrons undergo radiative 0 to 1 to 0 Landau transitions initiated by photons near the first harmonic. Physical self-consistency fixes the temperature, and the equilibrium temperature equals 5.3 + 0.3 or - 0.2 keV. These results suggest that this gamma-ray burst and many others which exhibit a low-energy dip originate from strongly magnetic neutron stars and are galactic in origin.

Wang, J. C. L.; Lamb, D. Q.; Loredo, T. J.; Wasserman, I. M.; Salpeter, E. E.

1989-01-01

399

Monte Carlo simulations of global Compton cooling in inner regions of hot accretion flows  

Microsoft Academic Search

Hot accretion flows such as advection-dominated accretion flows are generally optically thin in the radial direction. Thus, photons generated at some radii can cool or heat electrons at other radii via Compton scattering. Such global Compton scattering has previously been shown to be important for the dynamics of accretion flows. Here, we extend previous treatments of this problem by using

Fu-Guo Xie; Andrzej Niedzwiecki; Andrzej A. Zdziarski; Feng Yuan

2010-01-01

400

Upcoming Flight of the Nuclear Compton Telescope  

NASA Astrophysics Data System (ADS)

Our collaboration is developing a 2-detector prototype high resolution Compton telescope utilizing 3D imaging germanium detectors (GeDs) for a test balloon flight in 2003. This instrument is a prototype for a full 12-GeD instrument, the Nuclear Compton Telescope. NCT is a balloon-borne soft gamma-ray (0.2-15 MeV) telescope designed to study astrophysical sources of nuclear line emission and polarization. The NCT program is designed to develop and test the technologies and analysis techniques crucial for the Advanced Compton Telescope, while studying gamma-ray radiation with very high spectral resolution, moderate angular resolution, and high sensitivity. NCT has a novel, ultra-compact design optimized for studying nuclear line emission in the critical 0.5-2 MeV range, and polarization in the 0.2-0.5 MeV range. This prototype flight will critically test the novel instrument technologies, analysis techniques, and background rejection procedures we have developed for high resolution Compton telescopes. We will present the design, status, and expected performance of this prototype NCT instrument. This project is funded under the NASA SR&T program.

Boggs, S. E.; Coburn, W.; Lin, R. P.; Smith, D. M.; Amman, M.; Luke, P. N.; Jean, P.; von Ballmoos, P.; Burks, M. T.; Craig, W.; Madden, N. W.; Ziock, K.

2003-03-01

401

Evidence for TeV Gamma-Ray Emission from a Region of the Galactic Plane R. Atkins,1,* W. Benbow,2,  

E-print Network

-ray production by energetic cos- mic rays. Mechanisms include interactions with gas cloud nuclei that produce gamma rays via 0 decay, cosmic-ray electron bremsstrahlung, and inverse Compton scattering to models with 0 production as the sole mechanism [3] using the local cosmic-ray spectrum. Models predicting

California at Santa Cruz, University of

402

Fermi gamma-ray "bubbles" from stochastic acceleration of electrons.  

PubMed

Gamma-ray data from Fermi Large Area Telescope reveal a bilobular structure extending up to ?50 above and below the Galactic Center. It has been argued that the gamma rays arise from hadronic interactions of high-energy cosmic rays which are advected out by a strong wind, or from inverse-Compton scattering of relativistic electrons accelerated at plasma shocks present in the bubbles. We explore the alternative possibility that the relativistic electrons are undergoing stochastic 2nd-order Fermi acceleration by plasma wave turbulence through the entire volume of the bubbles. The observed gamma-ray spectral shape is then explained naturally by the resulting hard electron spectrum modulated by inverse-Compton energy losses. Rather than a constant volume emissivity as in other models, we predict a nearly constant surface brightness, and reproduce the observed sharp edges of the bubbles. PMID:21929220

Mertsch, Philipp; Sarkar, Subir

2011-08-26

403

Prototype of hand-held Compton spectrometer for the spectrometric and dosimetric control of X-ray generators  

NASA Astrophysics Data System (ADS)

The Compton spectrometer is a device in which radiation coming from an X-ray generator is scattered at a known angle in order to reduce the flux and to allow spectrometric measurements without saturating the detector. A small-size prototype Compton spectrometer usable in the range 20-150 keV was developed, using a pen-type NaI detector. The source spectrum is reconstructed by unfolding the measured spectrum, using the response matrix calculated by the Monte-Carlo method. The Monte-Carlo geometrical model was validated with gamma-ray point sources. Unfolding is performed using a modified version of the GRAVEL algorithm. Results are presented for the unfolded spectrum obtained with a test measurement on a medical X-ray device.

Marwaha, Lara; Tondeur, Franois; Bar, Jonathan; Gerardy, Isabelle

2014-11-01

404

Improvement of Noise Equivalent Count Rate Using Compton Kinematics in a Compton PET  

Microsoft Academic Search

The timing performance of a Compton PET device for very high resolution small animal imaging was investigated using Monte Carlo simulation data and timing simulations. The PET instrument was designed with an inner cylindrical silicon detector for scattering, surrounded by an outer cylindrical BGO scintillation detector for absorption. The time intervals between adjacent decay events of the annihilation photon source

Sang-June Park; W. L. Rogers; Neal H. Clinthorne

2007-01-01

405

Spectral properties of Compton inverse radiation: Application of Compton beams  

NASA Astrophysics Data System (ADS)

Compton inverse radiation emitted due to backscattering of laser pulses off the relativistic electrons possesses high spectral density and high energy of photons - in hard x-ray up to gamma-ray energies - because of short wavelength of laser radiation as compared with the classical electromagnetic devices such as undulators. In this report, the possibility of such radiation to monochromatization by means of collimation is studied. Two approaches have been considered for the description of the spectral-angular density of Compton radiation based on the classical field theory and on the quantum electrodynamics. As is shown, both descriptions produce similar total spectra. On the contrary, angular distribution of the radiation is different: the classical approach predicted a more narrow radiation cone. Also proposed and estimated is a method of the 'electronic' monochromatization based on the electronic subtraction of the two images produced by the electron beams with slightly different energies. A 'proof-of-principle' experiment of this method is proposed for the LUXC facility of KEK (Japan).

Bulyak, Eugene; Urakawa, Junji

2014-05-01

406

Analysis of a proposed Compton backscatter imaging technique  

SciTech Connect

Imaging techniques which require access to only one side of the object being viewed are potentially useful in situations where conventional projection radiography and tomography cannot be applied, such as looking for voids in a large container where access to the back of the object is inconvenient or even impossible. One-sided imaging techniques are currently being used in nondestructive evaluation of surfaces and shallow subsurface structures. In this work we present both analytical calculations and detailed Monte Carlo simulations aimed at assessing the capability of a proposed Compton backscatter imaging technique designed to detect and characterize voids located several centimeters below the surface of a solid. The proposed technique, based on a scheme suggested by Farmer and Collins, encodes the spatial position and structure of voids in a solid in the energy spectrum of the Compton-scattered photons as recorded by a high resolution detector. Our calculations model a {sup 137}Cs source projecting a 1 mm{sup 2} pencil beam of 662 keV gammas into a target slab at an incident angle of 45{degrees} and a collimated detector (also oriented at 45{degrees} with respect to the surface) which views the beam path at a central angle of 90{degrees}. The detector collimator is modeled here as a triangular slit viewing a 2.54 cm (1.000``) segment of the beam path at a depth of 2 cm below the surface of the slab. Our results suggest that the proposed technique should be capable of an absolute position resolution of {approx} 0.25 mm ({approx} 0.010``) for isolated voids and an overall object resolution of {approx} 1.00 Ip/mm ({approx} 0.04``). The predicted signal contrast for voids packed with various contraband materials will be discussed as well as multiple scattering contributions to the predicted yields.

Hall, J.; Jacoby, B.

1992-12-01

407

High-Resolution Compton-Suppressed CZT Detector for Fission Products Identification  

SciTech Connect

Room temperature semiconductor CdZnTe (CZT) detectors are currently limited to total detector volumes of 1-2 cm3, which is dictated by the poor charge transport characteristics. Because of this size limitation one of the problems in accurately determining isotope identification is the enormous background from the Compton scattering events. Eliminating this background will not only increase the sensitivity and accuracy of measurements but also help us to resolve peaks buried under the background and peaks in close vicinity of others. We are currently developing a fission products detection system based on the Compton-suppressed CZT detector. In this application, the detection system is required to operate in high radiation fields. Therefore, a small 10x10x5 mm3 CZT detector is placed inside the center of a well-shielded 3" in diameter by 3" long Nal detector. So far we have been able to successfully reduce the Compton background by a factor of 5.4 for a 137Cs spectrum. This reduction of background will definitely enhance the quality of the gamma-ray spectrum in the information-rich energy range below 1 MeV, which consequently increases the detection sensitivity. In this work, we will discuss the performance of this detection system as well as its applications.

R. Aryaeinejd; J. K. Hartwell; Wade W. Scates

2004-10-01

408

Geant4 Model Validation of Compton Suppressed System for Process monitoring of Spent Fuel  

SciTech Connect

Nuclear material accountancy is of continuous concern for the regulatory, safeguards, and verification communities. In particular, spent nuclear fuel reprocessing facilities pose one of the most difficult accountancy challenges: monitoring highly radioactive, fluid sample streams in near real-time. The Multi-Isotope Process monitor will allow for near-real-time indication of process alterations using passive gamma-ray detection coupled with multivariate analysis techniques to guard against potential material diversion or to enhance domestic process monitoring. The Compton continuum from the dominant 661.7 keV 137Cs fission product peak obscures lower energy lines which could be used for spectral and multivariate analysis. Compton suppression may be able to mitigate the challenges posed by the high continuum caused by scattering. A Monte Carlo simulation using the Geant4 toolkit is being developed to predict the expected suppressed spectrum from spent fuel samples to estimate the reduction in the Compton continuum. Despite the lack of timing information between decay events in the particle management of Geant4, encouraging results were recorded utilizing only the information within individual decays without accounting for accidental coincidences. The model has been validated with single and cascade decay emitters in two steps: as an unsuppressed system and with suppression activated. Results of the Geant4 model validation will be presented.

Bender, Sarah; Unlu, Kenan; Orton, Christopher R.; Schwantes, Jon M.

2013-05-01

409

Status of the inverse Compton backscattering source at Daresbury Laboratory  

Microsoft Academic Search

Inverse Compton scattering is a promising method to implement a high-brightness, ultra-short, energy tuneable X-ray source at accelerator facilities and at laser facilities using laser wake-field acceleration. We have developed an inverse Compton X-ray source driven by the multi-10-TW laser installed at Daresbury Laboratory. Polarized X-ray pulses will be generated through the interaction of laser pulses with electron bunches delivered

G. Priebe; D. Filippetto; O. Williams; Y. M. Saveliev; L. B. Jones; D. Laundy; M. A. MacDonald; G. P. Diakun; P. J. Phillips; S. P. Jamison; K. M. Spohr; S. Ter-Avetisyan; G. J. Hirst; J. Collier; E. A. Seddon; S. L. Smith

2009-01-01

410

Bin mode estimation methods for Compton camera imaging  

NASA Astrophysics Data System (ADS)

We study the image reconstruction problem of a Compton camera which consists of semiconductor detectors. The image reconstruction is formulated as a statistical estimation problem. We employ a bin-mode estimation (BME) and extend an existing framework to a Compton camera with multiple scatterers and absorbers. Two estimation algorithms are proposed: an accelerated EM algorithm for the maximum likelihood estimation (MLE) and a modified EM algorithm for the maximum a posteriori (MAP) estimation. Numerical simulations demonstrate the potential of the proposed methods.

Ikeda, S.; Odaka, H.; Uemura, M.; Takahashi, T.; Watanabe, S.; Takeda, S.

2014-10-01

411

Simultaneous X-Ray and Gamma-Ray Observations of TeV Blazars: Testing Synchro-Compton Emission Models and Probing the Infrared Extragalactic Background  

Microsoft Academic Search

The last years have seen a revolution in ground-based gamma-ray detectors. We\\u000acan now detect the spectra of nearby TeV blazars like Mrk 421 and 501 out to\\u000aapproximately 20 TeV, and during the strongest flares, we can now follow\\u000afluctuations in these spectra on timescales close to the shortest ones likely\\u000ain these objects. We point out that this

Paolo S. Coppi; Felix A. Aharonian

1999-01-01

412

Studies on solar hard X-Rays and gamma-rays: Compton backscatter, anisotropy, polarization and evidence for two phases of acceleration. Ph.D. Thesis - Maryland Univ.  

NASA Technical Reports Server (NTRS)

Observations of solar X-rays and gamma-rays from large flares show that the hard X-ray spectrum extends into the gamma ray region, where a flattening in the spectrum of the continuum emission is observed above about 1 MeV. This emission is believed to be due to bremsstrahlung. In addition to electron-proton collisions, at energies greater than approximately 500 keV, bremsstrahlung due to electron-electron collisions becomes significant. Bremsstrahlung production was calculated for a variety of electron spectra extending from the nonrelativistic region to relativistic energies and electron-electron bremsstrahlung is taken into account. By comparing these calculations with data, it is shown that the flattening in the spectrum of the continuum emission can be best explained by an electron spectrum consisting of two distinctive components. This evidence, together with information on the X-ray and gamma ray time profiles, implied the existence of two phases of acceleration. The first phase accelerates electrons mainly up to about several hundred keV; the second phase accelerates a small fraction of the electrons accelerated in the first phase to relativistic energies and accelerates protons to tens and hundreds of MeV.

Bai, T.

1977-01-01

413

Recent progress in single sided gamma-ray tomography  

SciTech Connect

The use of scattered radiation for radiography has many potential advantages over conventional projection techniques: For high energy photons the scattering process strongly dominates all other processes. The intensity of scattered radiation is due directly to the electron density and highly insensitive to chemical composition. Finally, the use of scattered radiation allows the investigator to position the radiation source-on-the same side of the object as the detector. In this paper I will present some recent results of a set of measurements made with our uncollimated Compton backscattering tomography apparatus. This technique uses the Compton energy shift of scattered gamma rays to determine the scattering site. By measuring the spectrum of these scattered gamma rays it is then possible to determine the electron density of the object being investigated. I will give a brief description of the apparatus and present the results of numerous measurements made on a brass phantom with voids placed at various depths. These results imply that for this crude apparatus occlusions as small as one cubic millimeter may be located to an accuracy of about one millimeter at depths of about 15 millimeters in solid brass.

Thoe, R.S.

1994-04-01

414

Recent progress in single-sided gamma-ray tomography  

NASA Astrophysics Data System (ADS)

The use of scattered radiation for radiography has many potential advantages over conventional projection techniques: for high energy photons the scattering process strongly dominates all other processes. The intensity of scattered radiation is due directly to the electron density and highly insensitive to chemical composition. Finally, the use of scattered radiation allows the investigator to position the radiation source on the same side of the object as the detector. In this paper I will present some recent results of a set of measurements made with our uncollimated Compton backscattering tomography apparatus. This technique uses the Compton energy shift of scattered gamma rays to determine the scattering site. By measuring the spectrum of these scattered gamma rays it is then possible to determine the electron density of the object being investigated. I will give a brief description of the apparatus and present the results of numerous measurements made on a brass phantom with voids placed at various depths. These results imply that for this crude apparatus occlusions as small as one cubic millimeter may be located to an accuracy of about one millimeter at depths of about 15 millimeters in solid brass.

Thoe, Robert S.

1994-07-01

415

Gamma Ray Bursts Sudden, intense flashes of gamma rays  

E-print Network

Gamma Ray Bursts #12;The Case Sudden, intense flashes of gamma rays come from nowhere and disappear with out a trace. Incredibly powerful: A single gamma ray burst is hundreds of times brighter a supernova #12;Who Vela (1960's) Looking for arms testing, found gamma ray bursts Compton Gamma Ray Observatory

Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group

416

Novel design of a parallax free Compton enhanced PET scanner  

NASA Astrophysics Data System (ADS)

Molecular imaging by PET is a powerful tool in modern clinical practice for cancer diagnosis. Nevertheless, improvements are needed with respect to the spatial resolution and sensitivity of the technique for its application to specific human organs (breast, prostate, brain, etc.), and to small animals. Presently, commercial PET scanners do not detect the depth of interaction of photons in scintillators, which results in a not negligible