Measurement of the Quantum Efficiency of Hamamatsu R8520 Photomultipliers at Liquid Xenon Temperature

TL;DR

This paper measures the quantum efficiency of Hamamatsu R8520 photomultiplier tubes at liquid xenon temperatures, revealing an increase in efficiency at cryogenic conditions relevant for dark matter detectors.

Contribution

It provides the first detailed measurement of the quantum efficiency of these photomultipliers at cryogenic temperatures, crucial for liquid xenon detector performance.

Findings

Quantum efficiency increases by 5-11% at 160-170K.

Room temperature measurements agree with manufacturer data.

Cryogenic efficiency enhancement improves detector sensitivity.

Abstract

Vacuum ultraviolet light sensitive photomultiplier tubes directly coupled to liquid xenon are being used to efficiently detect the 178 nm scintillation light in a variety of liquid xenon based particle detectors. Good knowledge of the performance of these photomultipliers under cryogenic conditions is needed to properly characterize these detectors. Here, we report on measurements of the quantum efficiency of Hamamatsu R8520 photomultipliers, used in the XENON Dark Matter Experiments. The quantum efficiency measurements at room temperature agree with the values provided by Hamamatsu. At low temperatures, between 160K and 170K, the quantum efficiency increases by $\sim5-11$% relative to the room temperature values.