Polarized Ultra-Cold Neutron Transport for Neutron Beta Decay Asymmetry Measurements

用于中子 Beta 衰变不对称测量的极化超冷中子传输

• 批准号: 0099448
• 负责人: ROBERT VOGELAAR
• 金额: $ 27.77万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-01 至 2005-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0099448&HistoricalAwards=false
• 关键词: Polarized; Ultra; Cold; Neutron; Transport

Nuclear beta decay was important in motivating the Standard Model, andit continues to be of importance in searches for physics beyond the Standard Model.The simplest system for studying beta decay is the neutron. By measuring theneutron's lifetime (from the Ft value) and the neutron's beta asymmetry A, onehas enough information to independently determine the weak vector and axial-vectorcouplings, GV and GA. An approved experiment (located at Los Alamos) will again measure the A coefficient,utilizing Ultra-Cold Neutrons (UCN), dramatically reducing systematic errors otherwisepresent due to beam-induced backgrounds and incomplete polarization. The keyfeatures are 1) the ability to port the neutrons to a significant distance awayfrom their production site, 2) vetoing events when the beam pulse is on target,and 3) obtain 100% polarization using an axial magnetic field. This proposal covers efforts to develop an optimum coating fortransporting polarized neutrons, and implementing a suitable DAQ system for the experiment.It appears pulsed-laser-deposition (PLD) diamond films may be suitable.A successful campaign to make suitably coated guides would havean significant impact, not just for this experiment, but planned futureexperiments as well.5

核贝塔衰变是激发标准模型的重要因素，它在探索超越标准模型的物理方面也继续发挥着重要作用。研究贝塔衰变最简单的系统是中子。通过测量中子的寿命(从Ft值)和中子的β不对称性A，人们就有了足够的信息来独立地确定弱矢量和轴矢量耦合，GV和GA。一项获得批准的实验(位于洛斯阿拉莫斯)将利用超冷中子(UCN)再次测量A系数，大大减少由于束流诱导背景和不完全极化而存在的系统误差。其主要特点是：1)能够将中子转移到离其产生地点很远的地方，2)当束流脉冲对准目标时阻止事件发生，3)使用轴向磁场获得100%的极化。这项建议包括努力开发一种传输极化中子的最佳涂层，并为实验实施合适的DAQ系统。似乎脉冲激光沉积(PLD)金刚石薄膜可能是合适的。成功地制造适当涂层的导轨将产生重大影响，不仅对本实验，而且对计划中的未来实验也是如此