Development of Germanium Ring-Contact Detectors for LEGEND-1000

如果中微子确实是它们自己的反粒子，这就可以解释宇宙中物质相对于反物质的普遍性。研究这种可能性需要探索无中微子双β衰变（NLDBD），这是一种可能但罕见的核衰变过程。在这种情况下，大的锗（Ge）晶体是优秀的NLDBD探测器，由于其高体积-表面比，这使得有效的信号收集和背景抑制在寻找NLDBD衰减。这个NSF资助的项目支持首席研究员（PI）和研究生和本科生进行研究，为即将到来的LEGEND实验开发创新的Ge探测器。LEGEND的目标是采用超纯Ge探测器和主动抑制背景反应的方法来寻找NLDBD。 PI的作用包括培训研究生和本科生的新技术和装备他们的技能，在高科技领域的竞争性职业生涯。此外，PI还实施了一项吸引人的外展计划，以促进公众对科学的兴趣和理解。LEGEND实验建立在MAJORANA合作在超纯材料和GERDA合作在液体冷冻剂主动屏蔽方面取得的进步的基础上。LEGEND包括分阶段部署一项吨级实验，该实验能够检测半衰期超过10 e28年的NLDBD事件。为了减少背景、复杂性和成本，LEGEND-1000倾向于使用大尺寸探测器（每个探测器3 kg）。为了探索这种方法，PI将使用南达科他州大学（USD）生长的高纯度Ge晶体对大尺寸Ge环接触（GeRC）探测器进行研究和开发。值得注意的是，GeRC探测器的尺寸可能超过6公斤，大大减少了LEGEND-1000实验所需的单个探测器的数量。探测器数量的减少将进一步减轻背景，提高实验的整体灵敏度。与LEGEND的合作将使GERC探测器的制造和测试在USD和其他LEGEND机构。这些大尺寸的锗探测器，结合脉冲形状的歧视能力，将是至关重要的进一步减少背景事件在吨级NLDBD衰变实验，如LEGEND。该项目不仅有助于推进我们对中微子性质的理解，例如它们的马约拉纳性质和极小的质量，而且还为探索目前高能对撞机无法达到的能量的新物理学打开了大门。该项目由核物理计划和激励竞争性研究的既定计划（EPSCoR）共同资助。该奖项反映了NSF的法定使命，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。

If neutrinos are indeed their own antiparticles, this could explain the prevalence of matter over anti-matter in the universe. Investigating this possibility requires exploring neutrinoless double-beta decay (NLDBD), a possible but rare nuclear decay process. In this context, large germanium (Ge) crystals are excellent detectors of NLDBD due to their high volume-to-surface ratio, which enables effective signal collection and background rejection in the search for NLDBD decay. This NSF-funded project supports the Principal Investigator (PI) and graduate and undergraduate students in conducting research on the development of innovative Ge detectors for the upcoming LEGEND experiment. LEGEND aims to employ ultra-pure Ge detectors and active ways to reject background reactions to search for NLDBD. The PI's role includes training graduate and undergraduate students in novel techniques and equipping them with skills for competitive careers in high-technology fields. Additionally, the PI has implemented an engaging outreach program to foster public interest and understanding in science. The LEGEND Experiment builds upon the advancements made by the MAJORANA Collaboration in ultra-pure materials and the GERDA Collaboration in liquid cryogen active shielding. LEGEND includes a phased deployment of a ton-scale experiment capable of detecting NLDBD events with half-lives exceeding 10e28 years. To reduce backgrounds, complexity, and cost, LEGEND-1000 favors large-size detectors (3 kg per detector). To explore this approach, the PI will conduct research and development on large-size Ge ring-contact (GeRC) detectors using high-purity Ge crystals grown by the University of South Dakota (USD). Notably, the GeRC detectors can potentially reach sizes exceeding 6 kg, significantly reducing the number of individual detectors required for the LEGEND-1000 experiment. This reduction in detector count will further mitigate backgrounds, elevating the overall sensitivity of the experiment. Collaboration with LEGEND will enable the fabrication and testing of GeRC detectors at USD and other LEGEND institutions. These large-size Ge detectors, incorporating pulse shape discrimination capabilities, will be crucial for further minimizing background events in a ton-scale NLDBD decay experiment like LEGEND. The project not only contributes to advancing our understanding of neutrino properties, such as their Majorana nature and extremely small masses, but also opens doors for exploring new physics at energies beyond the reach of current high energy colliders. Moreover, it has a broader impact by training students in cutting-edge techniques and engaging the public through outreach initiatives.This project is jointly funded by the Nuclear Physics Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.