Tracking and imaging gamma-ray experiment (TIGRE) for 300-keV to 100-MeV gamma-ray astronomy

摘要

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 silicon strip detectors also measure the energy losses of these particles. For Compton events, the direction and energy of the Compton scattered gamma ray are measured with arrays of small CsI(TI)-photodiode detectors so that an unique direction and energy can be found for each incident gamma ray. The incident photon direction for pair events is found from the initial pair particle directions. TIGRE is the first Compton telescope with a direct imaging capability. With a large $pi@-steradian field-of-view, it is sensitive to gamma rays from 0.3 to 100 MeV with a typical energy resolution of 3% (FWHM) and a 1-$sigma angular resolution of 40 arc-minutes at 2 MeV. A small balloon prototype instrument is being constructed that has a high absolute detection efficiency of 8% over the full energy range and a sensitivity of 10 milliCrabs for an exposure of 500,000 s. TIGRE's innovative design also uses the polarization dependence of the Klein-Nishina formula for gamma-ray source polarization measurements. The telescope will be described in detail and new results from measurements at 0.5 MeV and Monte Carlo calculations from 1 to 100 MeV will be presented.