An Ultra-Low Background PMT for Liquid Xenon Detectors-猫眼课题宝

DOI：

10.1016/j.nima.2012.11.020

发表时间：

2012-05

期刊：

Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment

影响因子：

1.4

通讯作者：

中科院分区：

物理与天体物理3区

文献类型：

作者：

D. Akerib;X. Bai;E. Bernard;A. Bernstein;A. Bradley;D. Byram;S. Cahn;M. Carmona-Benitez;D. Carr;J. Chapman;Y. Chan;K. Clark;T. Coffey;L. deViveiros;M. Dragowsky;E. Druszkiewicz;B. Edwards;C. Faham;S. Fiorucci;R. Gaitskell;K. Gibson;C. Hall;M. Hanhardt;B. Holbrook;M. Ihm;R. Jacobsen;L. Kastens;K. Kazkaz;N. Larsen;C. Lee;K. Lesko;A. Lindote;M. Lopes;A. Lyashenko;D. Malling;R. Mannino;D. Mckinsey;D. Mei;J. Mock;M. Morii;H. Nelson;F. Neves;J. Nikkel;M. Pangilinan;K. Pech;P. Phelps;T. Shutt;C. Silva;W. Skulski;V. Solovov;P. Sorensen;J. Spaans;T. Stiegler;M. Sweany;M. Szydagis;D. Taylor;J. Thomson;M. Tripathi;S. Uvarov;J. Verbus;N. Walsh;R. Webb;J. White;M. Własenko;F. Wolfs;M. Woods;C. Zhang

给出了两种型号的光电倍增管的放射性筛选结果，这些光电倍增管设计用于当前和未来的液体氙气实验。用于LUX暗物质实验的滨松5.6厘米直径R8778 PMT对四种常见的放射性同位素238U、232Th、40K和60Co产生了阳性检测。对LUX材料的筛选使其他探测器材料的背景低于R8778的贡献。还筛选了一个直径7.6 cm的滨松R11410 MOD PMT原型，基准同位素计数在&lt；0.4238U/&lt；0.3232Th/&lt；8.340K/2.0±0.260Co MBQ/PMT上测量。这意味着在R8778和R11410 MOD之间有很大的减少，相当于每个PMT×124238U/×19232Th/×1840K的变化，同时光电阴极表面积(4.5-6.4 cm直径)翻了一番。60Co测量结果在两个PMT之间是相似的，但通过进一步的材料选择，在未来的R11410 MOD单元中可以显著减少。假设PMT活度等于测量的90%上限，蒙特卡罗估计表明，在进一步选择用于60Co还原的材料后，用R11410 MOD PMT替换R8778 PMT将使LUX PMT电子反冲本底贡献改变×125倍，使核反冲本底贡献改变×136倍。R11410MOD的本底大大低于测量的R8778水平，使其成为用于大型液体氙气探测器的一项非常有竞争力的技术。

Results are presented from radioactivity screening of two models of photomultiplier tubes designed for use in current and future liquid xenon experiments. The Hamamatsu 5.6cm diameter R8778 PMT, used in the LUX dark matter experiment, has yielded a positive detection of four common radioactive isotopes:238U,232Th,40K, and60Co. Screening of LUX materials has rendered backgrounds from other detector materials subdominant to the R8778 contribution. A prototype Hamamatsu 7.6cm diameter R11410 MOD PMT has also been screened, with benchmark isotope counts measured at <0.4238U/<0.3232Th/<8.340K/2.0±0.260Co mBq/PMT. This represents a large reduction, equal to a change of ×124238U/×19232Th/×1840K per PMT, between R8778 and R11410 MOD, concurrent with a doubling of the photocathode surface area (4.5–6.4cm 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 ×125 after further material selection for60Co reduction, and nuclear recoil backgrounds by a factor of ×136. 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.

An Ultra-Low Background PMT for Liquid Xenon Detectors

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