Qualification Tests of the R11410-21 Photomultiplier Tubes for the XENON1T Detector

TL;DR

This paper details the comprehensive testing procedures and performance evaluation of the Hamamatsu R11410-21 photomultiplier tubes used in the XENON1T dark matter detector, emphasizing their suitability and reliability in cryogenic conditions.

Contribution

It introduces standardized testing protocols and performance metrics for large-scale PMT selection in cryogenic dark matter experiments, ensuring optimal detector performance.

Findings

248 tubes selected out of 321 tested for XENON1T

Performance metrics meet the criteria for dark matter detection

Testing in cryogenic environments confirms operational reliability

Abstract

The Hamamatsu R11410-21 photomultiplier tube is the photodetector of choice for the XENON1T dual-phase time projection chamber. The device has been optimized for a very low intrinsic radioactivity, a high quantum efficiency and a high sensitivity to single photon detection. A total of 248 tubes are currently operated in XENON1T, selected out of 321 tested units. In this article the procedures implemented to evaluate the large number of tubes prior to their installation in XENON1T are described. The parameter distributions for all tested tubes are shown, with an emphasis on those selected for XENON1T, of which the impact on the detector performance is discussed. All photomultipliers have been tested in a nitrogen atmosphere at cryogenic temperatures, with a subset of the tubes being tested in gaseous and liquid xenon, simulating their operating conditions in the dark matter detector. The performance and evaluation of the tubes in the different environments is reported and the criteria for rejection of PMTs are outlined and quantified.