707 research outputs found
Integrated Simulation of Fragmentation, Evaporation, and Gamma-decay Processes in the Interaction of Cosmic-ray Heavy Ions with the Atmosphere using PHITS
General-purpose Monte-Carlo radiation tranport calculation code PHITS is applied to calculate prompt gamma-ray emission from cosmic-ray heavy ions fragmented in the atmosphere. Event-by-event simulation of spallation reactions by cosmic-ray heavy ions was performed by combination of three reaction models, responsible for different reaction phases
Semi-Topological Analysis of Linear Networks
Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Programs / DA 28 043 AMC 00073(E)Air Force Office of Scientific Research / AF AFOSR 913.6
Studying the High-Energy Gamma-Ray Sky with Glast
Building on the success of the Energetic Gamma Ray Experiment Telescope
(EGRET) on the Compton Gamma Ray Observatory, the Gamma-ray Large Area Space
Telescope (GLAST) will make a major step in the study of such subjects as
blazars, gamma-ray bursts, the search for dark matter, supernova remnants,
pulsars, diffuse radiation, and unidentified high-energy sources. The
instrument will be built on new and mature detector technologies such as
silicon strip detectors, low-power low-noise LSI, and a multilevel data
acquisition system. GLAST is in the research and development phase, and one
full tower (of 25 total) is now being built in collaborating institutes. The
prototype tower will be tested thoroughly at SLAC in the fall of 1999.Comment: 6 pages with 2 figures, to appear in the proceedings of the COSPAR 98
Symposium E 1.1, postscript file also available at
http://glast.gsfc.nasa.gov/COSPAR
Graph-Theoretical Properties of Major Submatrices
Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / DA 28 043 AMC 00073(E)Air Force Office of Scientific Research (U.S. Air Force) / AF AFOSR-931-6
Performance of a Low Noise Front-end ASIC for Si/CdTe Detectors in Compton Gamma-ray Telescope
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 1 keV is required to approach physical limit of the angular
resolution due to Doppler broadening. We have developed a low noise front-end
ASIC (Application-Specific Integrated Circuit), VA32TA, to realize this goal
for the readout of Double-sided Silicon Strip Detector (DSSD) and Cadmium
Telluride (CdTe) pixel detector which are essential elements of the
semiconductor Compton telescope. We report on the design and test results of
the VA32TA. We have reached an energy resolution of 1.3 keV (FWHM) for 60 keV
and 122 keV at 0 degree C with a DSSD and 1.7 keV (FWHM) with a CdTe detector.Comment: 6 pages, 7 figures, IEEE style file, to appear in IEEE Trans. Nucl.
Sc
Measuring energy dependent polarization in soft gamma-rays using Compton scattering in PoGOLite
Linear polarization in X- and gamma-rays is an important diagnostic of many
astrophysical sources, foremost giving information about their geometry,
magnetic fields, and radiation mechanisms. However, very few X-ray polarization
measurements have been made, and then only mono-energetic detections, whilst
several objects are assumed to have energy dependent polarization signatures.
In this paper we investigate whether detection of energy dependent polarization
from cosmic sources is possible using the Compton technique, in particular with
the proposed PoGOLite balloon-experiment, in the 25-100 keV range. We use
Geant4 simulations of a PoGOLite model and input photon spectra based on Cygnus
X-1 and accreting magnetic pulsars (100 mCrab). Effective observing times of 6
and 35 hours were simulated, corresponding to a standard and a long duration
flight respectively. Both smooth and sharp energy variations of the
polarization are investigated and compared to constant polarization signals
using chi-square statistics. We can reject constant polarization, with energy,
for the Cygnus X-1 spectrum (in the hard state), if the reflected component is
assumed to be completely polarized, whereas the distinction cannot be made for
weaker polarization. For the accreting pulsar, constant polarization can be
rejected in the case of polarization in a narrow energy band with at least 50%
polarization, and similarly for a negative step distribution from 30% to 0%
polarization.Comment: 11 pages, 12 figures; updated to match version accepted for
publication in Astroparticle Physics (only minor changes
3-D Model of Broadband Emission from Supernova Remnants Undergoing Non-linear Diffusive Shock Acceleration
We present a 3-dimensional model of supernova remnants (SNRs) where the
hydrodynamical evolution of the remnant is modeled consistently with nonlinear
diffusive shock acceleration occuring at the outer blast wave. The model
includes particle escape and diffusion outside of the forward shock, and
particle interactions with arbitrary distributions of external ambient
material, such as molecular clouds. We include synchrotron emission and
cooling, bremsstrahlung radiation, neutral pion production, inverse-Compton
(IC), and Coulomb energy-loss. Boardband spectra have been calculated for
typical parameters including dense regions of gas external to a 1000 year old
SNR. In this paper, we describe the details of our model but do not attempt a
detailed fit to any specific remnant. We also do not include magnetic field
amplification (MFA), even though this effect may be important in some young
remnants. In this first presentation of the model we don't attempt a detailed
fit to any specific remnant. Our aim is to develop a flexible platform, which
can be generalized to include effects such as MFA, and which can be easily
adapted to various SNR environments, including Type Ia SNRs, which explode in a
constant density medium, and Type II SNRs, which explode in a pre-supernova
wind. When applied to a specific SNR, our model will predict cosmic-ray spectra
and multi-wavelength morphology in projected images for instruments with
varying spatial and spectral resolutions. We show examples of these spectra and
images and emphasize the importance of measurements in the hard X-ray, GeV, and
TeV gamma-ray bands for investigating key ingredients in the acceleration
mechanism, and for deducing whether or not TeV emission is produced by IC from
electrons or neutral pions from protons.Comment: 12 pages, 9 figures, accepted by Apj, 24 June 200
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