Development of a Compton telescope calorimeter module for MeV-range gamma-ray astronomy

Abstract

Gamma-ray astronomy in the MeV energy range shows a lack of sensitivity compared to other gamma-ray energy bands. Several space observatory projects are proposed to space agencies to fill this gap. The COMCUBE CubeSat project will focus on the measurement of the polarization of the prompt emission of gamma-ray bursts (GRBs) which can provide an understanding of the physics of ultra-relativistic jets. Furthermore, the linear polarization of distant gamma-ray sources could be a probe to study the fundamental physics related to the Lorentz invariance violation. A Compton telescope is particularly well-suited for that purpose. We develop an instrument including double-sided silicon strip detectors and scintillation crystals coupled to a pixelated photodetector. The incoming photon undergoes an inelastic scattering in one or several layers of a position-sensitive silicon strip detector before being absorbed in a position-sensitive calorimeter based on inorganic scintillators. The measurement of both positions and energy deposits enables the determination of the photon’s source direction. It also enables measurement of the linear polarization of the incident gamma-rays. In this contribution, we present the results of the extensive work we have carried out to develop the calorimeter and its integration into a Compton telescope prototype. We conclude by showing the first image and polarization measurements.