Simulations of a Si-based Advanced Compton Telescope

Extensive simulations of a silicon-based concept for Advanced Compton Telescope (ACT) are performed using MGGPOD and GEANT4 Monte Carlo packages, and MEGAlib event reconstruction and imaging package (using multiple Compton technique). Special attention is given to the sensitivity of the telescope at the broadened 847 keV 56Co line, which is important for the understanding of the nature of Type Ia supernovae, the objects used as standard candles for measurement of cosmological distances, and thus playing an important role in answering some fundamental questions about the Universe. Backgrounds for the low Earth orbit of 550 km and 8deg inclination, and the high Earth orbit of about 40,000 km are modeled, and sensitivity estimates, as well as some other characteristics, are obtained for three Si-based mass models. The silicon Compton imager concept is proven as a high sensitivity gamma-ray instrument providing excellent spectral and imaging capabilities, and a good candidate for NASA's next generation gamma-ray telescope