Future XMASS project

Abe, K.

doi:10.22323/1.282.1175

Cited by 1 publication

(1 citation statement)

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“…purposes. This knowledge and these materials were adopted in the development of R11410 [14][15][16][17] and R13111 [18] with improved background. This clearly indicates the development of R10789 is a groundbreaking step for further improvement of radioactivity in PMTs.…”

Section: Components Which Have Largest Contributionsmentioning

confidence: 99%

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

Abe

Hiraide

Ichimura

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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XMASS-I is a single-phase liquid xenon detector whose purpose is direct de- tection 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±0.3 mBq/PMT of 226 Ra, less than 0.78 mBq/PMT of 228 Ra, 9.1±2.2 mBq/PMT of 40 K, and 2.8±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.

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