Demonstration and Comparison of Operation of Photomultiplier Tubes at Liquid Argon Temperature

TL;DR

This paper evaluates the performance of photomultiplier tubes operating at liquid argon temperatures, demonstrating their suitability for dark matter detection by achieving high quantum efficiency and effective light yield in cryogenic conditions.

Contribution

It presents a comprehensive comparison and demonstration of photomultiplier tubes at cryogenic temperatures, highlighting their enhanced performance for liquid argon dark matter detectors.

Findings

PMTs with high quantum efficiency operate effectively at 87 K.

Achieved a light yield of around 7 phel/keVee in a liquid argon detector.

Demonstrated suitability of new PMTs for low-energy dark matter detection.

Abstract

Liquified noble gases are widely used as a target in direct Dark Matter searches. Signals from scintillation in the liquid, following energy deposition from the recoil nuclei scattered by Dark Matter particles (e.g. WIMPs), should be recorded down to very low energies by photosensors suitably designed to operate at cryogenic temperatures. Liquid Argon based detectors for Dark Matter searches currently implement photo multiplier tubes for signal read-out. In the last few years PMTs with photocathodes operating down to liquid Argon temperatures (87 K) have been specially developed with increasing Quantum Efficiency characteristics. The most recent of these, Hamamatsu Photonics Mod. R11065 with peak QE up to about 35%, has been extensively tested within the R&D program of the WArP Collaboration. During these testes the Hamamatsu PMTs showed superb performance and allowed obtaining a light yield around 7 phel/keVee in a Liquid Argon detector with a photocathodic coverage in the 12% range, sufficient for detection of events down to few keVee of energy deposition. This shows that this new type of PMT is suited for experimental applications, in particular for new direct Dark Matter searches with LAr-based experiments.