Polarized Ultra Cold Neutrons for Fundamental Symmetry Study

用于基本对称性研究的极化超冷中子

• 批准号: 1002814
• 负责人: ROBERT VOGELAAR
• 金额: $ 38.1万
• 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: 2010
• 资助国家: 美国
• 起止时间: 2010-07-15 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1002814&HistoricalAwards=false
• 关键词: Polarized; Ultra; Cold; Neutrons; Fundamental

The universe displays several very fundamental symmetries with major consequences. Three of these are very familiar: that the origin in space of an experiment doesn't matter gives rise to momentum conservation; that the orientation in space doesn't matter gives rise to angular momentum conservation; that the time you start an experiment doesn't matter gives rise to energy conservation. These are known as 'continuous' symmetries.Less familiar are the 'discrete' symmetries. The most familiar ones are: (P) looking at the universe through a mirror; (C) changing all matter to anti-matter (and vice-versa); and (T) running the clock backwards. These are known to not be 'exact', but the combination of all three 'CPT' is at the foundation of all our theories. That the combination of 'CP' is violated is necessary to explain the origin of the small asymmetry which gives rise to our matter dominated universe.The cleanest way to study such fundamental symmetries is with simple well-understood systems. The neutron is a prime example. By measuring correlations in its beta decay properties we can probe fine details of its symmetry violation as well as several other important physics questions.Using ultra-cold neutrons makes these measurements very clean, and this grant supports one of the technologies required to make such experiments possible: the transport of ultra-cold neutrons from their production area to the experimental area and subsequent storage. Specialized coatings are required for this, and both evaporation (such as Ni-58) and laser deposition (of diamond films) have been developed with excellent results.The program is to improve the capabilities (such as with multi-layer films) and to integrate the technology into fundamental physics studies. These coatings are already being used in the UCN-A experiment at the Los Alamos National Laboratory, and several other groups are interested in using them as well.The techniques necessary to produce high-quality coatings include precision surface preparation, careful environment control, and comprehensive diagnostics. This provides an excellent training venue for students and new researchers, and couples them directly into critical roles for physics research both from a technology viewpoint, and as part of larger collaborative efforts to probe for new physics.In addition, these techniques find application in a variety of industrial processes, where successful coatings require very specialized skills and hand-on experience. For example, diamond coatings can significantly prolong the life of quartz process systems, can improve environment resistance of micro strain gauges, and provide harder surfaces for knife-edges. In accelerator systems, coatings play a significant role in ion source efficiencies and the holding time of polarized target cells.

宇宙表现出几个非常基本的对称性，并产生了重大后果。其中有三个是非常熟悉的：实验在太空中的起源并不重要，会引起动量守恒；空间中的方位不重要，会引起角动量守恒；开始实验的时间不重要，会引起能量守恒。这些对称被称为“连续的”对称。不太熟悉的是“离散的”对称。最常见的是：(P)通过镜子观察宇宙；(C)将所有物质变成反物质(反之亦然)；以及(T)让时钟倒转。众所周知，这些并不“准确”，但这三个“CPT”的组合是我们所有理论的基础。“CP”的组合被破坏是解释小的不对称的起源所必需的，这种小的不对称导致了我们的物质支配的宇宙。研究这种基本对称性的最干净的方法是用简单的、众所周知的系统。中子就是一个很好的例子。通过测量其β衰变特性的相关性，我们可以探索其对称性破坏的细节以及其他几个重要的物理问题。使用超冷中子使这些测量变得非常干净，这项拨款支持使此类实验成为可能所需的技术之一：将超冷中子从其生产区传输到实验区并随后进行存储。为此需要专门的涂层，蒸发(如Ni-58)和激光沉积(金刚石薄膜)都已开发出出色的结果。该计划旨在提高性能(如多层膜)，并将该技术整合到基础物理研究中。这些涂层已经在洛斯阿拉莫斯国家实验室的UCN-A实验中使用，其他几个组织也对使用它们感兴趣。生产高质量涂层所需的技术包括精密表面处理、仔细的环境控制和全面的诊断。这为学生和新的研究人员提供了一个极好的培训场所，并将他们直接结合到物理研究的关键角色中，从技术的角度来看，以及作为探索新物理的更大合作努力的一部分。此外，这些技术在各种工业过程中得到应用，在这些过程中，成功的涂层需要非常专业的技能和实践经验。例如，金刚石涂层可以显著延长石英工艺系统的寿命，可以提高微型应变仪的环境耐受性，并为刀刃提供更坚硬的表面。在加速器系统中，涂层对离子源效率和极化靶细胞的保持时间起着重要作用。