IMAGE RECONSTRUCTION FOR THE MEGA TELESCOPE

摘要

The Compton scattering and pair creation telescope MEGA detects gamma-rays in the energy range from 400 keV up to at least 50 MeV. Its multidimensional response presents a challenge for image reconstruction: The large amount of measured parameters and the geometry result in a response, which depends on incidence angle, energy, Compton scatter angle, direction and energy of scattered electrons, etc. Moreover the image reconstruction algorithm has to incorporate different event types into one image (tracked und untracked Compton events as well as pair events) and has to cope with high background conditions. An algorithm, which meets this challenges, is the iterative List-Mode Maximum-Likelihood Expectation-Maximization algorithm. The adoptions of this algorithm to the needs of the MEGA telescope are shown along with selected results.