Gamma-ray astronomy in the MeV range suffers from weak fluxes from sources and high background in the nuclear energy range. The background comes primarily from neutron-induced gamma rays with the neutrons being produced by cosmic-ray interactions in the Earth's atmosphere, the spacecraft and the instrument. Compton telescope designs often suppress this background by requiring coincidences in multiple detectors and a narrow time-of-flight (ToF) acceptance window. The COMPTEL experience on the Compton Gamma Ray Observatory shows that a 1.5-ns ToF window is insufficiently narrow to achieve the required low background count rate. Furthermore, neutron interactions in the detectors themselves generate an irreducible background. Judicious choices of instrument materials and new spacecraft designs improve the situation. However, large gains come from new scintillator technology that combines intrinsic neutron insensitivity with exceptional speed to reduce the instrument background rate by upwards of 90%, thereby greatly improving the sensitivity of searches and measurements, while simultaneously improving energy and angle resolution.

Date Published: 4 August 2009
PDF: 12 pages
Proc. SPIE 7385, International Symposium on Photoelectronic Detection and Imaging 2009: Terahertz and High Energy Radiation Detection Technologies and Applications, 738502 (4 August 2009); doi: 10.1117/12.836015

Published in SPIE Proceedings Vol. 7385:
International Symposium on Photoelectronic Detection and Imaging 2009: Terahertz and High Energy Radiation Detection Technologies and Applications
X.-C. Zhang; James M. Ryan; Cun-lin Zhang; Chuan-xiang Tang, Editor(s)