Production and Quality Assurance of the Mu2e Calorimeter Silicon Photomultipliers

D Caiulo,G Corradi,S Miscetti,R Donghia,F Cervelli,E Pedreschi,F Happacher,E Diociaiuti,Gianantonio Pezzullo ,M Cordelli,M Ricci,A Saputi,M Martini,L Morescalchi,S Giovannella,D Pasciuto,S Donati,S Di Falco,A Ferrari,Leonardo Lucchesi ,S Müller ,F Raffaelli,I Sarra,F Spinella

doi:10.1088/1742-6596/1162/1/012024

Abstract

The Mu2e calorimeter consists of 1348 undoped CsI crystals coupled to two large area UV-extended Silicon Photomultipliers (SiPMs). A modular and custom SiPM layout, a 3×2 matrix of 6×6 mm2 monolithic SiPMs, has been developed to satisfy the Mu2e requirements. As well as ensuring the performances needed for the muon-to-electron conversion search, these photosensors have to guarantee a good reliability while operating maintenance-free in the Mu2e hostile environment: any failure can only be replaced during a long technical shut-down scheduled once a year. After testing prototypes from different vendors, we selected Hamamatsu and the final production of about 4000 pieces is now ongoing. A detailed Quality Assurance (QA) program is then mandatory to minimize the risk of an unexpected further degradation in the performances. The QA process for each photosensor includes a first visual inspection and the subsequent characterization of each of its monolithic cells by means of an automatized test station, able to measure the breakdown voltage, the gain and the dark current. For each production batch (∼300 pieces), 5 devices are exposed to a neutron fluency up to ∼1.4×1011 1 MeV (Si) eq. n/cm2; others 15 devices are undergone an accelerated aging in order to verify the Mean Time To Failure (MTTF) of the batch. A summary of the QA and the results for the firsts 4 production batches are presented in the paper.

Highlights

The Mu2e calorimeter consists of 1348 undoped CsI crystals coupled to two large area UV-extended Silicon Photomultipliers (SiPMs)
For each production batch (∼300 pieces), 5 devices are exposed to a neutron fluency up to ∼1.4×1011 1 MeV (Si) eq n/cm2; others 15 devices are undergone an accelerated aging in order to verify the Mean Time To Failure (MTTF) of the batch
The Mu2e Experiment [1] will search for the Charged Lepton Flavour Violation (CLFV) coherent conversion of muon into electron in the field of an aluminum nucleus with an unprecedented accuracy, allowing to indirectly probe energy scales up to thousands TeV

Summary

Introduction

The Mu2e Experiment [1] will search for the Charged Lepton Flavour Violation (CLFV) coherent conversion of muon into electron in the field of an aluminum nucleus with an unprecedented accuracy, allowing to indirectly probe energy scales up to thousands TeV. Measurement of SiPMs parameters In view of the large number of measurements to perform (∼ 24k single cell characterizations), a fully automatized station has been developed It is controlled with dedicated Labview software, allowing to test at a controlled temperature 25 sensors per time without any external intervention of an operator. Going down with temperature the dark current decreases of a factor ∼2 every 10◦C, reaching at -10◦C the nA level around Vbr. The I-V curve is performed while illuminating the sensor with a low level light, so to increase the current and to obtain a more fast and precise measurement. To obtain an MTTF experimental estimation for each batch of the Mu2e custom SiPMs, 15 sensors per batch are subjected to accelerated aging These sensors are stressed by operating them at Vop inside a dedicated station kept at a temperature of 65◦ C for 18 days.

Tstress

Findings

Conclusions