Radiation Damage Studies of Silicon Photomultipliers

TL;DR

This study evaluates the radiation hardness of various silicon photomultipliers (SiPMs) from different manufacturers by exposing them to proton irradiation and monitoring their performance degradation and recovery over time.

Contribution

It provides detailed measurements of SiPMs' radiation tolerance, including leakage current and dark count behavior, and demonstrates their annealing properties at room temperature.

Findings

Leakage current increases with proton fluence.

Dark counts are due to increased pixel activation.

SiPMs remain functional after irradiation and anneal over time.

Abstract

We report on the measurement of the radiation hardness of silicon photomultipliers (SiPMs) manufactured by Fondazione Bruno Kessler in Italy (1 mm$^2$ and 6.2 mm$^2$), Center of Perspective Technology and Apparatus in Russia (1 mm$^2$ and 4.4 mm$^2$), and Hamamatsu Corporation in Japan (1 mm$^2$). The SiPMs were irradiated using a beam of 212 MeV protons at Massachusetts General Hospital, receiving fluences of up to $3 \times 10^{10}$ protons per cm$^2$ with the SiPMs at operating voltage. Leakage currents were read continuously during the irradiation. The delivery of the protons was paused periodically to record scope traces in response to calibrated light pulses to monitor the gains, photon detection efficiencies, and dark counts of the SiPMs. The leakage current and dark noise are found to increase with fluence. Te leakage current is found to be proportional to the mean square deviation of the noise distribution, indicating the dark counts are due to increased random individual pixel activation, while SiPMs remain fully functional as photon detectors. The SiPMs are found to anneal at room temperature with a reduction in the leakage current by a factor of 2 in about 100 days.