An Ultra-Low Background PMT for Liquid Xenon Detectors

Abstract

Results are presented from radioactivity screening of two models of photomultiplier tubes designed for use in current and future liquid xenon experiments. The Hamamatsu 5.6 cm diameter R8778 PMT, used in the LUX dark matter experiment, has yielded a positive detection of four common radioactive isotopes: 238U, 232Th, 40K, and 60Co. Screening of LUX materials has rendered backgrounds from other detector materials subdominant to the R8778 contribution. A prototype Hamamatsu 7.6 cm diameter R11410 MOD PMT has also been screened, with benchmark isotope counts measured at <0.4 238U / <0.3 232Th / <8.3 40K / 2.0+-0.2 60Co mBq/PMT. This represents a large reduction, equal to a change of \times 1/24 238U / \times 1/9 232Th / \times 1/8 40K per PMT, between R8778 and R11410 MOD, concurrent with a doubling of the photocathode surface area (4.5 cm to 6.4 cm diameter). 60Co measurements are comparable between the PMTs, but can be significantly reduced in future R11410 MOD units through further material selection. Assuming PMT activity equal to the measured 90% upper limits, Monte Carlo estimates indicate that replacement of R8778 PMTs with R11410 MOD PMTs will change LUX PMT electron recoil background contributions by a factor of \times1/25 after further material selection for 60Co reduction, and nuclear recoil backgrounds by a factor of \times 1/36. The strong reduction in backgrounds below the measured R8778 levels makes the R11410 MOD a very competitive technology for use in large-scale liquid xenon detectors.

v2 updated to include content after reviewer comments (Sep 2012)

References in corpus (5)

• The XENON100 Dark Matter Experiment
• Observation of Two-Neutrino Double-Beta Decay in Xe-136 with EXO-200
• Material screening and selection for XENON100
• Evaluation of (alpha,n) Induced Neutrons as a Background for Dark Matter Experiments
• LUXSim: A Component-Centric Approach to Low-Background Simulations

Cited by in corpus (36)

• First results from the LUX dark matter experiment at the Sanford Underground Research Facility
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• Projected WIMP sensitivity of the LUX-ZEPLIN (LZ) dark matter experiment
• A Next-Generation Liquid Xenon Observatory for Dark Matter and Neutrino Physics
• Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment
• Radiogenic and Muon-Induced Backgrounds in the LUX Dark Matter Detector
• Performance of the Hamamatsu R11410 Photomultiplier Tube in cryogenic Xenon Environments
• A Review of Basic Energy Reconstruction Techniques in Liquid Xenon and Argon Detectors for Dark Matter and Neutrino Physics Using NEST
• Radiopurity control in the NEXT-100 double beta decay experiment: procedures and initial measurements
• Calibration, event reconstruction, data analysis and limits calculation for the LUX dark matter experiment
• Projected sensitivity of the LUX-ZEPLIN experiment to the $0\nu \beta \beta$ decay of ${}^{136}$Xe
• Chromatographic separation of radioactive noble gases from xenon
• Radiopurity assessment of the tracking readout for the NEXT double beta decay experiment
• Measurement of the absolute Quantum Efficiency of Hamamatsu model R11410-10 photomultiplier tubes at low temperatures down to liquid xenon boiling point
• Direct Detection of Dark Matter -- APPEC Committee Report
• Position Reconstruction in LUX
• Radiopurity assessment of the energy readout for the NEXT double beta decay experiment
• Development of low radioactivity photomultiplier tubes for the XMASS-I detector
• Development of a low background liquid scintillation counter for a shallow underground laboratory
• First results of a large-area cryogenic gaseous photomultiplier coupled to a dual-phase liquid xenon TPC
• Study on the large area MCP-PMT glass radioactivity reduction
• A Liquid Scintillation Detector for Radioassay of Gadolinium-Loaded Liquid Scintillator for the LZ Outer Detector
• Radon and material radiopurity assessment for the NEXT double beta decay experiment
• Reflectance dependence of polytetrafluoroethylene on thickness for xenon scintillation light
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• Study of cryogenic photomultiplier tubes for the future two-phase cryogenic avalanche detector
• Fast and Flexible Analysis of Direct Dark Matter Search Data with Machine Learning
• Development of low-background photomultiplier tubes for liquid xenon detectors
• The LUX Dark Matter Search -- Status Update
• Measurements of the position-dependent photo-detection sensitivity of the Hamamatsu R11410 and R8520 photomultiplier tubes
• LUX Trigger Efficiency
• The Impact of Photon Flight Path on S1 Pulse Shape Analysis in Liquid Xenon Two-phase Detectors
• The low temperature performance of CsI(Na) crystals for WIPMs direct searches
• Cryogenic Gaseous Photomultiplier for Position Reconstruction of Liquid Argon Scintillation Light
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• Study of light detection and sensitivity for a ton-scale liquid xenon dark matter detector