RII Track-4: Liquid Xenon Time Projection Chamber R&D on the Large Xenon Test Stand at LLNL

唯一已知的中性基本粒子，也有质量，是中微子。这使它们成为唯一的候选者，成为自己的反粒子。如果中微子是它自己的反粒子，我们就可以解决一些突出的好奇心，其中最重要的是：“为什么宇宙是由物质组成的，而不是由数量大致相等的物质和反物质组成的？“该奖学金将启动南达科他州大学（USD）和劳伦斯利弗莫尔国家实验室（LLNL）之间的长期合作，该实验室将为下一代稀有衰变搜索进行液体氙探测器技术的研究和开发。该奖学金将为PI和USD研究生提供机会，以实验最先进的探测器技术，这些技术有一天可以部署在南达科他州的下一代多吨级液态氙暗物质或无中微子双β衰变搜索中。对后者的观测是确定中微子实际上是它自己的反粒子的唯一可行的方法。USD和LLNL都是更广泛的nEXO合作的成员，该合作正在努力提出一项建议，即在地下深处建立这样的实验，例如在南达科他州的桑福德地下研究设施。技术说明大型单片液体氙时间投影室已被证明是低背景稀有事件搜索的最强大工具之一。特别是，直接暗物质搜索社区已经接受他们作为开始形成的下一代计划的领导者。EXO-200还展示了这种探测器满足下一代吨级无中微子双β衰变搜索目标的潜力。 该奖学金的目标是启动南达科他州大学（USD）和劳伦斯利弗莫尔国家实验室（LLNL）之间的长期合作。这项合作将利用LLNL的大型氙测试设施，对一个（五）吨级的液体氙时间投影室进行研发，最终通过nEXO实验寻找氘-136的无中微子双β衰变。一旦我们完成建造和调试，LLNL测试设施的主要目标将是使nEXO的全直径电场合格。然而，它可以容纳许多为nEXO原型设计的新型探测器系统，包括新型电荷读出瓦片和定制硅光电倍增管。该测试设施还将用于外部氙气处理系统的原型。将PI融入nEXO的研发关系中将确保PI拥有专业知识，为nEXO实验的持续成功做出贡献。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical DescriptionThe only known neutral fundamental particles, that also have mass, are neutrinos. This makes them the only candidates to be their own antiparticle. If the neutrino is its own antiparticle, we could resolve some outstanding curiosities, not the least of which being: "Why is the Universe made up of matter and not roughly equal amounts of matter and antimatter?" This fellowship will initiate a long-term collaboration between the University of South Dakota (USD) and the Lawrence Livermore National Laboratory (LLNL) that will perform research and development of liquid xenon detector technologies for the next generation of rare decay searches. This fellowship will provide the PI and USD graduate students with the opportunity to experiment with state of the art detector technologies that could one day be deployed in South Dakota in a next-generation multi-tonne-scale liquid xenon dark matter or neutrinoless double-beta decay search. Observation of the latter is the only feasible way to determine that the neutrino is, in fact, its own antiparticle. Both USD and LLNL are members of the much broader nEXO Collaboration that is working towards a proposal to build such an experiment deep underground, such as in the Sanford Underground Research Facility in South Dakota.Technical DescriptionLarge, monolithic liquid xenon time-projection chambers have been demonstrated to be among the most powerful tools for low-background rare-event searches. In particular, the direct dark matter search community has embraced them as the leaders of the next generation program that is beginning to take shape. EXO-200 has also demonstrated the potential for such a detector to meet the next generation target for a tonne-scale neutrinoless double-beta decay search. The goal of this fellowship will be to initiate a long-term collaboration between the University of South Dakota (USD) and the Lawrence Livermore National Laboratory (LLNL). This collaboration will leverage the large xenon test facility at LLNL to perform R&D towards a (five) tonne scale liquid-xenon time-projection chamber to eventually search for the neutrinoless double-beta decay of Xe-136 with the nEXO experiment. The primary objective of the LLNL test facility, once we finish construction and commissioning, will be to qualify the electric field for the full diameter of nEXO. However, it can house many of the novel detector systems being prototyped for nEXO including novel charge readout tiles and custom silicon photomultipliers. The test facility will also be used to prototype external xenon handling systems. Immersing the PI in this R&D nexus for nEXO will ensure that the PI will have the expertise to contribute to the ongoing success of the nEXO experiment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.