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 altitudes between 340km and 450km with an inclination of $${42}{^{\circ }}$$ 42 ∘ 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. In this paper we focus on the radiation damage of the silicon photomultiplier arrays S13361-6075NE-04 and S14161-6050HS-04 from Hamamatsu. The S13361 are irradiated with 58MeV protons at several doses up to 4.96Gy, whereas the newer series S14161 are irradiated at doses of 0.254Gy and 2.31Gy. 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 4.96Gy is 62.9years (or 1.78years 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 $${25}{^{\circ }C}$$ 25 ∘ C 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 $$\beta ^{+}$$ β + particles around 511 keV. These resulted primarily from copper and carbon, mostly with decay times shorter than the orbital period.

Proton irradiation of plastic scintillator bars for POLAR-2

“…The total dose, activation and optical performances of the plastic bars are of interest. This analysis completes our previous studies, that were focused on silicon photomultipliers properties in radiation environments [ 1 ]. Those photodetectors were chosen to read the light from the plastic scintillator bars, that are the subject of this paper.…”

“…A schematic of this facility, a photo of the exit of the beam line and proton beam parameters were presented and more detailed described in [ 1 , 7 ]. The dose rate at which the scintillators are exposed in space, averaged over the entire polarimeter, were computed using LEOBackground [ 8 ] and SPENVIS [ 9 ] for modelling the radiation environment and Geant4 [ 10 ] for simulating the radiation deposition in the bars.…”

“…The dose rate at which the scintillators are exposed in space, averaged over the entire polarimeter, were computed using LEOBackground [ 8 ] and SPENVIS [ 9 ] for modelling the radiation environment and Geant4 [ 10 ] for simulating the radiation deposition in the bars. A detailed description of the simulation setup is given in [ 1 ]. Figure 3 shows the dose distribution among the POLAR-2 modules, the outside channels being more exposed to cosmic radiations.…”

“…The activation analysis performed in this section is similar to that performed for silicon photomultiplier arrays (SiPMs) in our previous publication [ 1 ]. In analog way, two High Purity Germanium detectors (HPGe) with very good energy resolution were used to measure proton activation products for EJ-200 and EJ-248M.…”

“…The CSS (and hence POLAR-2) is orbiting at a typical altitude of 383 km with an inclination of 42°. As a result, it is exposed to radiation from cosmic rays of galactic, solar and trapped origin [ 1 ].…”