Pre-Production and Quality Assurance of the Mu2e Calorimeter Silicon Photomultipliers

TL;DR

This paper details the development, quality assurance, and testing of custom Silicon Photomultipliers for the Mu2e calorimeter, including performance metrics and durability assessments through neutron exposure and aging tests.

Contribution

It introduces a novel modular SiPM layout for the Mu2e calorimeter and provides comprehensive quality assurance and durability testing results for the first batch of prototypes.

Findings

Breakdown voltage, gain, quenching time, dark current, and PDE measured for each SiPM cell.

Neutron irradiation causes a linear increase in dark current, reaching tens of mA.

Accelerated aging tests suggest a mean time to failure exceeding 10^6 hours.

Abstract

The Mu2e electromagnetic calorimeter has to provide precise information on energy, time and position for $\sim$100 MeV electrons. It is composed of 1348 un-doped CsI crystals, each coupled to two large area Silicon Photomultipliers (SiPMs). A modular and custom SiPM layout consisting of a 3$\times$2 array of 6$\times$6 mm$^2$ UV-extended monolithic SiPMs has been developed to fulfill the Mu2e calorimeter requirements and a pre-production of 150 prototypes has been procured by three international firms (Hamamatsu, SensL and Advansid). A detailed quality assurance process has been carried out on this first batch of photosensors: the breakdown voltage, the gain, the quenching time, the dark current and the Photon Detection Efficiency (PDE) have been determined for each monolithic cell of each SiPMs array. One sample for each vendor has been exposed to a neutron fluency up to $\sim$8.5~$\times$~10$^{11}$ 1 MeV (Si) eq. n/cm$^{2}$ and a linear increase of the dark current up to tens of mA has been observed. Others 5 samples for each vendor have undergone an accelerated aging in order to verify a Mean Time To Failure (MTTF) higher than $\sim$10$^{6}$ hours.