Multi-PMT development for the Hyper-Kamiokande project

在这项RTI拨款申请中，我们建议为E61（NuPRISM）和Hyper-Kamiokande水切伦科夫探测器项目建立第一个工作原型和多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，它导致了超新星1987A的中微子、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。该提案是为了开发一种光敏传感器模块，这将导致加拿大对下一代大型水切伦科夫探测器Hyper-Kamiokande （HK）的重大贡献。******加拿大小组为香港开发了一种新的水切伦科夫近距离探测器E61 （NuPRISM）。该探测器跨越了大范围的离轴角度来采样来自同一源的不同光谱的中微子通量。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的横截面。HyperK的基准质量比现有的Super-Kamiokande （SK）探测器和Water Cherenkov附近的E61（NuPRISM）探测器大一个数量级，可以在较宽的CP违背相位δcp范围内以优于5σ的显著性观测到CP违背，并进一步探索大气中微子混合（θ23）是否最大。香港的大气中微子样本补充了长基线中微子研究，其基线范围更广，甚至达到地球的大小。HK还扩大了质子衰变和中微子天体物理学（如太阳和超新星中微子）的灵敏度，以及对暗物质的搜索。******为E61 （NuPRISM）提出的光敏传感器阵列称为多pmt （mPMT）。它是一个集成模块，由26个3英寸的pmt组成，安装在直径20英寸的容器中，19个面向检测器体积，7个面向否决权区域。由于切伦科夫环的图像较小，因此对于更小的水切伦科夫探测器来说，更细的粒度和更好的定时分辨率是必不可少的。mPMT可以显著改善HK的事件重建，也被认为是其光电探测器系统的一部分。****** 2017年夏季，香港项目被选为日本资助机构（MEXT）的路线图，并在东京大学启动了一个新的香港研究所，用于香港的建设。预计全部资金将在一两年内获得批准。在2017年9月的合作会议上，E61 （NuPRISM）采用了分阶段构建探测器的策略。一个直径3-4m的充电束测试原型，使用150个mpmt，将在2019-2021年建造。光束测试之后是完整的E61(NuPRISM)，在香港使用500 mpmt的水切伦科夫近探测器。E61(NuPRISM) mPMT的建造将在2025年安装在香港储罐时直接为香港生产几千个mPMT。本提案中mPMT的发展将为打开中微子物理学令人兴奋的未来提供关键的发展。

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.