Characterization of new photo-detectors for the future dark matter experiments with liquid xenon

Abstract

In the last three decades, numerous terrestrial experiments were built to search for a faint interaction between Weakly Interacting Massive Particles (WIMP) and ordinary matter. Among them, experiments using dual-phase xenon time projection chambers (TPCs) are leading the search especially for high mass WIMPs. In these experiments, photomultipliers (PMTs) are used to detect the prompt primary scintillation and secondary electro-luminescence of ionized electrons generated following an interaction between WIMP and a Xe nucleus. However, PMTs have several important shortcomings: their residual radioactivity levels, cost, bulkiness, and stability at cryogenic temperatures. Therefore, several alternative technologies are under consideration toward future dark matter experiments using ~50 tons of liquid xenon (LXe). One such technology is silicon photomultipliers (SiPM). SiPM have very low radioactivity, compact geometry, low operation voltages and reasonable photo-detection efficiency for vacuum ultra violet (VUV) light. However, current SiPM still have ~two order of magnitude higher dark count rate compared to PMTs. In order to solve this problem, we are currently developing a new SiPM with the help of Hamamatsu. In this paper, we report the current status of the performance measurements of the new SiPM developed with Hamamatsu to improve the dark count rate (DCR).