# Radiation Tests of Hamamatsu Multi-Pixel Photon Counters

## TL;DR

This study evaluates the radiation tolerance of Hamamatsu MPPCs by exposing them to neutron and proton irradiation, finding stable electrical performance but increased noise, relevant for high-energy physics detectors.

## Contribution

First comprehensive radiation testing of Hamamatsu MPPCs with neutron and proton doses, assessing their suitability for use in particle physics experiments.

## Key findings

- Breakdown voltage and gain remain stable after irradiation.
- Noise rates increase significantly with radiation exposure.
- Performance metrics are acceptable for detector applications.

## Abstract

Results of radiation tests of Hamamatsu 2.0 x 2.0~mm2 through-silicon-via (S13360-2050VE) multi-pixel photon counters, or MPPCs [1], are presented. Distinct sets of eight MPPCs were exposed to four different 1~MeV neutron equivalent doses of 200 MeV protons. Measurements of the breakdown voltage, gain and noise rates at different bias overvoltages, photoelectron thresholds, and LED illumination levels were taken before and after irradiation. No significant deterioration in performance was observed for breakdown voltage, gain, and response. Noise rates increased significantly with irradiation. These studies were undertaken in the context of MPPC requirements for the Cosmic Ray Veto detector of the Mu2e experiment at the Fermi National Accelerator Laboratory.