Characterization of Silicon Photomultipliers for nEXO

TL;DR

This paper evaluates silicon photomultipliers (SiPMs) for use in nEXO, focusing on their photon detection efficiency at xenon scintillation wavelengths and radioactivity levels, to determine their suitability for next-generation liquid xenon detectors.

Contribution

The study characterizes SiPMs from multiple vendors, demonstrating their photon detection efficiency meets nEXO requirements and providing radioassay data for material purity.

Findings

Photon detection efficiency approaches nEXO requirements at 175-178 nm.

Radioassay shows low levels of radioactive contaminants in tested SiPMs.

FBK and Hamamatsu devices are promising for nEXO applications.

Abstract

Silicon Photomultipliers (SiPMs) are attractive candidates for light detectors for next generation liquid xenon double-beta decay experiments, like nEXO. In this paper we discuss the requirements that the SiPMs must satisfy in order to be suitable for nEXO and similar experiments, describe the two test setups operated by the nEXO collaboration, and present the results of characterization of SiPMs from several vendors. In particular, we find that the photon detection efficiency at the peak of xenon scintillation light emission (175-178 nm) approaches the nEXO requirements for tested FBK and Hamamatsu devices. Additionally, the nEXO collaboration performed radioassay of several grams of bare FBK devices using neutron activation analysis, indicating levels of 40K, 232Th, and 238U of the order of <0.15, (6.9e10-4 - 1.3e10-2), and <0.11 mBq/kg, respectively.