Proton Irradiation of SiPM arrays for POLAR-2

Abstract

POLAR-2 is a space-borne polarimeter, built to investigate the polarization of Gamma-Ray Bursts and help elucidate their mechanisms. The instrument is targeted for launch in 2024 or 2025 aboard the China Space Station and is being developed by a collaboration between institutes from Switzerland, Germany, Poland and China. The instrument will orbit at an altitude of approximately 300 km with an inclination of 42o and will be subjected to background radiation from cosmic rays and solar events. It is therefore pertinent to better understand the performance of sensitive devices under space-like conditions. Proton Irradiation of SiPM arrays for POLAR-2 In this paper we focus on the radiation damage of the silicon photo-multiplier arrays S13361-6075NE-04 and S14161-6050HS-04 from Hama-matsu. The S13361 are irradiated with 58 MeV protons at several doses up to 4.96 Gy, whereas the newer series S14161 are irradiated at doses of 0.254 Gy and 2.31 Gy. Their respective performance degradation due to radiation damage are discussed. The equivalent exposure time in space for silicon photomultipliers inside POLAR-2 with a dose of 4.96 Gy is 78.1 years (or 5.04 years when disregarding the shielding from the instrument). Primary characteristics of the I-V curves are an increase in the dark current and dark counts, mostly through cross-talk events. Annealing processes at 25C were observed but not studied in further detail. Biasing channels while being irradiated have not resulted in any significant impact. Activation analyses showed a dominant contribution of β + particles around 511 keV. These resulted primarily from copper and carbon, mostly with decay times shorter than the orbital period.

Measuring the Cosmic X-ray Background accurately

“…The radiation damage is more problematic and unavoidable, it will result in an increase of the threshold energy of the detector. The SiPM degradation was studied 1 and constrained with an irradiation campaign [77] showing that the CeBr 3 crystal is efficiently protecting the SiPM and that an order of magnitude of increase of the dark current can be expected after one year in space which would result in a threshold increase of a few keV per year at around −20 • C [78,79].…”