Development and calibration of a measurement system for the characterization of avalanche photodiodes prospectively used as sensors in X-ray Compton polarimeters for space

Abstract

Solar flares, dynamic eruptions of electromagnetic radiation from the Sun's surface, represent a potential risk for various human technological infrastructures. The CUbesat Solar Polarimeter (CUSP) project, part of the Alcor Program of the Italian Space Agency, aims to measure solar flare polarization in the hard X-ray band. This paper focuses on the design and setup of a measurement system to characterize the response of the avalanche photodiodes (APD) used in the CUSP polarimeter. The system is tested at room temperature conditions by varying both incident photon energy between 20 keV and 135 keV, using X-ray sources as references, and APD bias voltage from 260 V to 410 V. Using the calibrated system, the dependence of APD gain on bias voltage, and its energy resolution, are measured, matching the metrological standards of the polarimeter