Characterization of avalanche photodiodes (APDs) for the CUbesat Solar Polarimeter (CUSP) mission

TL;DR

This paper characterizes avalanche photodiodes (APDs) for use in the CUSP CubeSat mission's solar flare polarimeter, focusing on their gain, energy resolution, and performance when coupled with scintillators, to support space-based solar observations.

Contribution

It provides detailed characterization data of APDs for space applications, specifically for the CUSP mission's polarimeter, including temperature dependence and scintillator coupling performance.

Findings

APDs' gain varies with temperature

Energy resolution assessed with 3Fe source

APDs effectively coupled with GAGG scintillator

Abstract

The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow the study of the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed at developing new CubeSat missions. It is approved for a Phase B study. In this work, we report on the characterization of the Avalanche Photodiodes (APDs) that will be used as readout sensors of the absorption stage of the Compton polarimeter. We assessed the APDs gain and energy resolution as a function of temperature by irradiating the sensor with a \textsuperscript{55}Fe radioactive source. Moreover, the APDs were also characterized as being coupled to a GAGG scintillator.