Development of low radioactivity photomultiplier tubes for the XMASS-I detector

Abstract

XMASS-I is a single-phase liquid xenon detector whose purpose is direct detection of dark matter. To achieve the low background requirements necessary in the detector, a new model of photomultiplier tubes (PMTs), R10789, with a hexagonal window was developed based on the R8778 PMT used in the XMASS prototype detector. We screened the numerous component materials for their radioactivity. During development, the largest contributions to the reduction of radioactivity came from the stem and the dynode support. The glass stem was exchanged to the Kovar alloy one and the ceramic support were changed to the quartz one. R10789 is the first model of Hamamatsu Photonics K. K. that adopted these materials for low background purposes and provided a groundbreaking step for further reductions of radioactivity in PMTs. Measurements with germanium detectors showed 1.2$\pm$0.3 mBq/PMT of ${}^{226}$Ra, less than 0.78 mBq/PMT of ${}^{228}$Ra, 9.1$\pm$2.2 mBq/PMT of ${}^{40}$K, and 2.8$\pm$0.2 mBq/PMT of ${}^{60}$Co. In this paper, the radioactive details of the developed R10789 are described together with our screening methods and the components of the PMT.

arXiv comment7 pages, 3 figures

References in corpus (10)

• XMASS detector
• Material screening and selection for XENON100
• Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment
• Search for solar axions in XMASS, a large liquid-xenon detector
• A direct dark matter search in XMASS-I
• Light WIMP search in XMASS
• An Ultra-Low Background PMT for Liquid Xenon Detectors
• Search for bosonic superweakly interacting massive dark matter particles with the XMASS-I detector
• Direct dark matter search by annual modulation with 2.7 years of XMASS-I data
• Self-shielding effect of a single phase liquid xenon detector for direct dark matter search

Cited by in corpus (7)

• Performance of novel VUV-sensitive Silicon Photo-Multipliers for nEXO
• Development of a low-$\alpha$-emitting $\mu$-PIC as a readout device for direction-sensitive dark matter detectors
• Direct dark matter searches with the full data set of XMASS-I
• Measurement of the relative Quantum Efficiency of Hamamatsu model R5912-20MOD photomultiplier tubes at liquid argon temperature
• Development of low-background photomultiplier tubes for liquid xenon detectors
• Development of a low-background HPGe detector at Kamioka Observatory
• Search for neutrinoless quadruple beta decay of ${}^{136}$Xe in XMASS-I