CAREER: Investigation of Spin Evolution in Magnetic Ultracold Neutron Bottles Used to Measure the Free Neutron Lifetime

职业：研究用于测量自由中子寿命的磁性超冷中子瓶中的自旋演化

• 批准号: 1553861
• 负责人: Adam Holley
• 金额: $ 52万
• 依托单位: Tennessee Technological University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1553861&HistoricalAwards=false
• 关键词: CAREER; Investigation; Spin; Evolution; Magnetic

An isolated neutron lives for about fifteen minutes before disintegrating into three lighter particles. This fundamental process plays a significant role in cosmology, and its study complements current efforts to discover new physics. Two laboratory techniques exist to determine the lifetime of a neutron with high precision, but they disagree significantly in their reported values. This discrepancy must be addressed in order to realize the potential of these techniques to help probe new physics. The research conducted with this award directly supports that effort by examining the behavior of very low energy (or "ultracold") neutrons which are magnetically confined in order to determine the neutron lifetime. The research involves a broad set of ideas and skills appropriate for undergraduate involvement and will be used to form the kernel for an interdisciplinary undergraduate research training, mentoring, and outreach program at Tennessee Technological University. Research activities will be carried out in conjunction with the UCNtau collaboration, which has constructed a magneto-gravitational ultracold neutron trap with a long intrinsic neutron storage time and demonstrated a detection strategy capable of making multiple high-precision measurements in a single accelerator cycle at the Los Alamos National Laboratory ultracold neutron source. Losses due to spin evolution in this trap will be empirically characterized by developing a high-fidelity spin-tracking Monte Carlo simulation of the experiment which, when combined with measurements of the mean trap lifetime as a function of the polarization-preserving ambient magnetic field magnitude, will be used to characterize indirectly the loss rate associated with spin evolution in the trap, sufficient for completing measurement of the neutron lifetime to an accuracy of one second. Measurements in a dedicated test cell will provide information necessary to assess directly the effect of spin evolution in a very high-precision (well below 0.1%) magnetic trap measurement of the free neutron lifetime.

孤立的中子存活约15分钟，然后分解成三个较轻的粒子。这一基本过程在宇宙学中扮演着重要的角色，它的研究是对目前发现新物理学的努力的补充。有两种实验室技术可以高精度地确定中子的寿命，但它们在报告值上存在显著差异。必须解决这种差异，以实现这些技术帮助探索新物理的潜力。获得该奖项的研究直接支持了这一努力，它通过检查被磁限制的极低能量(或“超冷”)中子的行为来确定中子寿命。这项研究涉及一系列适合本科生参与的广泛想法和技能，并将被用于形成田纳西理工大学跨学科本科生研究培训、指导和推广计划的核心。将与UCNtau合作开展研究活动，UCNtau合作建造了一个具有较长本征中子存储时间的磁引力超冷中子陷阱，并展示了一种能够在洛斯阿拉莫斯国家实验室超冷中子源的一个加速器周期内进行多次高精度测量的探测战略。将通过开发实验的高保真自旋跟踪蒙特卡罗模拟来经验地表征该陷阱中自旋演化造成的损失，当与作为保偏环境磁场大小的函数的平均陷阱寿命的测量相结合时，将被用于间接表征与陷阱中自旋演化相关的损失率，这足以完成对中子寿命的测量，精度达到一秒。在专用测试单元中的测量将提供在非常高精度(远低于0.1%)的磁陷阱测量自由中子寿命中直接评估自旋演化的影响所需的信息。