Development, production, and testing of the Mu2e Calorimeter Silicon Photomultipliers

Abstract The development and production of the custom Silicon Photomultipliers (SiPMs) for the Mu2e Calorimeter (Mu2e SiPMs) was a complex endeavor, involving meticulous design, procurement, testing, and integration processes. After a thorough analysis of the calorimeter requirements, which translated into detailed technical specifications for the photosensors, a design and pre-production phase was conducted, to evaluate their construction parameters, via an international bidding process with the fabrication contract eventually awarded to Hamamatsu. The production phase, which started in 2018, consisted of manufacturing 3950 Mu2e SiPMs at a rate of 300 units per month, each engineered and quality-controlled to meet the stringent technical requirements. Assembly into the calorimeter disks was completed by December 2023, representing a significant milestone of the Mu2e project. This article offers a comprehensive account of the entire process, from design and procurement to testing and integration.