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

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

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

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

GLAST and Suzaku: Study on Cosmic-Ray Acceleration And Interaction in the Cosmos

The Gamma-Ray Large Area Space Telescope (GLAST) is an international and multiagency mission scheduled for launch in the fall 2007. The Large Area Telescope (LAT), the primary instrument of the mission, will survey the high energy sky found to be very dynamic and surprisingly diverse by its predecessor the Energetic Gamma Ray Experiment Telescope (EGRET). GLAST-LAT will have a much improved sensitivity when compared with EGRET and extend the higher energy coverage to {approx} 300 GeV. The instrument is now mounted on the spacecraft and undergoing a suite of pre-flight tests. Data analysis software has been tried out by collaborators in two rounds of 'Data Challenges' using simulated observations including backgrounds. The instrument performance and observational data on selected sources presented here have been obtained through the Data Challenges in the collaborative efforts. There are features in the GLAST-LAT observation possibly unfamiliar to X-ray astronomers: (1) GLAST will operate mostly in the survey mode; (2) the foreground objects (gas, dust, and star-light) become gamma-ray sources; (3) multiple sources will be 'confused' because of the wide point-spread-function. The last two features will pose a challenge for analysis on extended Galactic sources such as supernova remnants and pulsar wind nebulae: multi-wavelength study with X-ray instruments like Suzaku and atmospheric Chrenkov telescopes will become essential to dig out the underlying physics