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

核衰变在推动标准模型方面是很重要的，并且在探索标准模型之外的物理方面仍然很重要。研究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A，人们有足够的信息来独立确定弱矢量和轴向矢量耦合，GV和GA。一项被批准的实验（位于洛斯阿拉莫斯）将再次测量A系数，利用超冷中子（UCN），极大地减少由于光束诱导背景和不完全极化而存在的系统误差。关键特点是1)能够将中子移植到远离其生产地点的显著距离，2)当光束脉冲到达目标时否决事件，以及3)使用轴向磁场获得100%极化。本提案涵盖了开发极化中子传输的最佳涂层，以及实现适合实验的DAQ系统的努力。看来脉冲激光沉积（PLD）金刚石薄膜可能是合适的。一个成功的运动，使适当的涂层引导将产生重大的影响，不仅是对这个实验，但计划未来的实验

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