Multi-PMT development for the Hyper-Kamiokande project

在这项RTI资助申请中，我们建议为E61（NuPRISM）和Hyper-Kamiokande水切伦科夫探测器项目建造第一个工作原型并建立多PMT（mPMT）模块的生产过程。大型水切伦科夫探测器最初是为了寻找质子衰变而建造的，导致了超新星1987 A中微子、太阳中微子振荡、大气中微子振荡和长基线中微子振荡的发现。这项建议是为了开发一个光电传感器模块，这将导致加拿大对下一代大型水切伦科夫探测器Hyper-Kamiokande（HK）做出重大贡献。加拿大研究小组为香港的水切伦科夫近探测器E61（NuPRISM）开发了一个新概念。该探测器可以在很宽的离轴角度范围内对来自同一个源的不同光谱的中微子通量进行采样。通过对不同离轴位置的事件进行线性组合，可以精确地研究中微子截面。HyperK的基准质量比目前的Super-Kamiokande（SK）探测器和Water Cherenkov附近的E61（NuPRISM）大一个数量级，可以在很宽的CP破坏相位δcp范围内观察到优于5σ显著性的CP破坏，并进一步探索大气中微子混合（θ23）是否最大。长基线中微子研究由香港的大气中微子样本补充，其基线范围更广，可达地球大小。HK还扩大了质子衰变和中微子天体物理学的灵敏度，如太阳和超新星中微子，以及寻找暗物质。为E61（NuPRISM）提出的光电传感器阵列被称为多PMT（mPMT）。它是一个集成模块，由26个3英寸光电倍增管组成，位于20英寸直径的容器内，19个光电倍增管观察探测器体积，7个光电倍增管面向否决区。由于切伦科夫环的像较小，所以对于较小的水切伦科夫探测器来说，精细的粒度和较好的时间分辨率是必不可少的。mPMT可以显著改善HK的事件重建，并且也被认为是其光电探测器系统的一部分。2017年夏天，香港项目被选为日本资助机构（MEXT）的路线图，东京大学为香港建设开设了一个新的香港研究所。全部资金预计将在一两年内获得批准。在2017年9月的合作会议上，E61（NuPRISM）采用了分阶段探测器构造策略。一个直径3- 4米的带电束测试原型，使用150 mPMT，将在2019-2021年建造。 光束测试之后是全E61（NuPRISM），在香港使用500 mPMT的水切伦科夫近探测器。E61（NuPRISM）mPMT建造之后，将直接为香港生产数千mPMT，以便在2025年安装在香港罐中。该提案中的mPMT发展将为中微子物理学开辟令人兴奋的未来提供关键发展。

In this RTI grant request, we propose to build the first working prototype and establish the production process of multi-PMT (mPMT) modules for E61(NuPRISM) and Hyper-Kamiokande water Cherenkov detector projects. Large water Cherenkov detectors, which were first built to search for proton decay, led to the discovery of neutrinos from supernova 1987A, solar neutrino oscillations, atmospheric neutrino oscillations, and long baseline neutrino oscillations. This proposal is for the development of a photosensor module which will lead to a major Canadian contribution to the next generation large water Cherenkov detector, Hyper-Kamiokande (HK).******The Canadian group has developed a new concept for a water Cherenkov near detector, E61 (NuPRISM) for HK. The detector spans a wide range of off-axis angles to sample neutrino fluxes with different spectra from the same source. By linear combination of the events at different off-axis positions the neutrino cross section can be studied precisely. With an order of magnitude larger fiducial mass than the current Super-Kamiokande (SK) detector and E61(NuPRISM) near Water Cherenkov, HyperK can observe CP violation at better than 5σ significance for a wide range of the CP violating phase δcp and further explore if the atmospheric neutrino mixing (θ23) is maximal. The long baseline neutrino study is complemented by the atmospheric neutrino samples of HK with a much wider range of baseline up to the size of the earth. HK also expands the sensitivities for proton decays and neutrino astrophysics such as solar and supernova neutrinos, and the search for dark matter.******The photosensor array proposed for E61 (NuPRISM) is called a multi-PMT (mPMT). It is an integrated module consisting of 26 3-inch PMTs inside a 20-inch diameter vessel, 19 looking into the detector volume and 7 facing the veto region. The fine granularity and the better timing resolution are essential for a smaller water Cherenkov detector due to the smaller image of the Cherenkov ring. The mPMT can significantly improve the event reconstruction of HK and is considered as part of its photodetector system as well.******In summer 2017, HK project was selected to be on the road map of the Japanese funding agency (MEXT), and a new HK institute is started at University of Tokyo for the HK construction. The full funding approval is expected in a year or two. At its September 2017 collaboration meeting, E61 (NuPRISM) adapted a staged detector con- struction strategy. A 3-4m diameter charged beam test prototype, which uses 150 mPMTs, will be constructed in 2019-2021. The beam test is followed by the full E61(NuPRISM), the water Cherenkov near detector at HK using 500 mPMTs. The E61(NuPRISM) mPMT construction will be directly followed by a production of a few thousand mPMTs for HK in time of the installation in HK tank in 2025. The mPMT development in this proposal will provide key development to open up the exciting future in neutrino physics.