An advanced Compton telescope based on thick, position-sensitive solid-state detectors

The development of high-resolution, position-sensitive solid-state detectors enables γ-ray instruments with improved sensitivity and imaging capabilities. For γ-ray astronomy, an improvement in sensitivity of 20–50 over previous missions is anticipated with the Advanced Compton Telescope (ACT) mission. The γ-ray astrophysics group at NRL has been developing germanium strip detectors for several years. We have shown that 3D locations for γ-ray interactions can be determined with mm accuracy, and have also demonstrated imaging capability within a single germanium strip detector and in detector arrays. Based on the realization that three Compton interactions would enable the energy and direction cone of the incident γ-ray to be determined, even when the total incident γ-ray energy is not deposited in the detector, we have also initiated work on thick silicon strip detectors. We are investigating the use of both thick Si(Li) and thick intrinsic silicon detectors. Progress on this work, including initial tests of the multiple-Compton imaging technique, is presented.