RII Track-4: Operating High Purity Germanium Detectors in Liquid Scintillator

中微子是自然界中大量产生的亚原子粒子。研究幽灵中微子的内在特性一直是一项挑战，因为它们可以穿过仪器和材料，几乎没有任何相互作用。由于技术的进步和科学界的长期努力，最近的突破揭示了中微子的关键但意想不到的特性，例如中微子具有非零质量。关于中微子的新知识可以探索自然界的基本对称性，并可能揭示宇宙中物质比反物质过剩的关键奥秘。太阳系外的中微子也是携带宇宙信息的信使之一，这些信息可以让我们对宇宙有一个更完整的了解。这项提议旨在开发技术，以促进实验，加深我们对中微子的理解，包括探索非零中微子质量的起源。它还将推动南达科他州大学（USD）和洛斯阿拉莫斯国家实验室（Los Alamos National Laboratory， LANL）在新方向上的合作。USD集团获得的变革性新专业知识将增强该集团在地下科学与工程方面的研究能力，地下科学与工程是南达科他州目标行业的高价值研究领域和资产之一。USD的PI计划访问LANL，开发使用液态氩（LAr）的主动否决技术，用于拟议的中微子双β衰变大富集锗实验（LEGEND）项目。主机组和主机组都是LEGEND的合作者。LEGEND合作旨在开发一个分阶段的、基于Ge-76的中微子双β衰变（NLDBD）实验项目，其半衰期可能超过10e28年。LEGEND将在大量的LAr中运行高达一吨的高纯度锗探测器。LAr屏蔽作为一种主动否决权，在消除广泛的NLDBD背景方面具有强大的作用。具体而言，PI和学员将与LANL的研究人员合作，将LANL现有的低温恒温器转换为具有净化能力和光收集仪器的LAr试验台。我们将直接将高纯锗探测器浸入液氩中进行操作。通过USD与LANL的合作研究，我们可以评估集成系统的整体性能，提高我们对LAr主动否决的背景拒绝性能的理解。除了推进LEGEND项目的准备工作外，该研究奖学金将为PI提供液体闪烁体技术方面的专业知识，并使PI能够长期维持他在实验中微子物理方面的职业生涯。LANL的硬件基础设施和技术专门知识的结合对于执行拟议的活动至关重要。该奖项反映了美国国家科学基金会的法定使命，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。

Neutrinos are subatomic particles abundantly produced in Nature. It has been challenging to investigate the intrinsic properties of the ghostly neutrinos, because they can pass through instruments and materials with barely any interactions. Thanks to advancements of technology as well as long-term commitment of the science community, recent breakthroughs have revealed critical yet unexpected properties of neutrinos, such as the fact that neutrinos have non-zero masses. New knowledge on neutrinos can probe fundamental symmetries in Nature and could shed light on the key mystery of matter-over-antimatter excess in the universe. Extrasolar neutrinos are also one of the messengers carrying information about the universe that can lead us to a more complete picture of the universe. This proposal aims at developing techniques that could facilitate experiments to deepen our understanding of neutrinos, including probing the origin of non-zero neutrino masses. It will also advance the collaboration between the University of South Dakota (USD) and Los Alamos National Laboratory (LANL) in new directions. The transformative new expertise gained by the USD group will enhance the group's research capability in Underground Science and Engineering, one of the high value research areas and assets aligned with target industry sectors for South Dakota.The PI at USD plans to visit LANL to develop active veto techniques employing liquid argon (LAr), intended for the proposed Large Enriched Germanium Experiment for Neutrinoless double-beta Decay (LEGEND) project. Both the home and host groups are LEGEND collaborators. The LEGEND collaboration aims to develop a phased, Ge-76 based neutrinoless double-beta decay (NLDBD) experimental program with discovery potential at a half-life beyond 10e28 years. LEGEND will operate up to one tonne of high-purity germanium detectors inside a large volume of LAr. The LAr shield serves as an active veto that is powerful in eliminating a wide range of backgrounds for NLDBD. Specifically, the PI and trainees will collaborate with LANL researchers to convert an existing cryostat at LANL into a LAr test stand with purification capability and light collection instrumentation. We will directly immerse and operate high-purity germanium detectors inside liquid argon. Through this collaborative research between USD and LANL, we can evaluate the overall performance of the integrated system and improve our understanding of the background rejection performance of a LAr active veto. In addition to advancing the preparation for the LEGEND project, this Research Fellowship will arm the PI with expertise on liquid scintillator technologies and enable the PI to sustain his career in experimental neutrino physics in the long-term. A combination of hardware infrastructure and technical expertise at LANL is essential to carry out the proposed activities.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.