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.

宇宙表现出几种非常基本的对称性，并产生重大后果。 其中三个是非常熟悉的：实验的空间起源并不重要，会引起动量守恒；空间方向并不重要，导致角动量守恒；开始实验的时间并不重要，这会产生能量守恒。 这些被称为“连续”对称性。不太熟悉的是“离散”对称性。 最熟悉的有：（P）透过镜子看宇宙； (C) 将所有物质转变为反物质（反之亦然）； (T) 倒转时钟。 众所周知，这些并不“准确”，但所有三个“CPT”的结合是我们所有理论的基础。 “CP”组合被破坏对于解释产生我们的物质主导宇宙的微小不对称性的起源是必要的。研究这种基本对称性的最干净的方法是使用简单的、易于理解的系统。 中子就是一个典型的例子。通过测量其β衰变特性的相关性，我们可以探测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，这笔赠款支持进行此类实验所需的技术之一可能：将超冷中子从生产区运输到实验区并随后储存。 为此需要专门的涂层，蒸发（例如 Ni-58）和激光沉积（金刚石薄膜）都已开发出来，并取得了优异的效果。该计划旨在提高能力（例如多层薄膜）并将技术融入基础物理研究中。 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，其他几个小组也有兴趣使用它们。生产高质量涂层所需的技术包括精密的表面处理、仔细的环境控制和全面的诊断。 这为学生和新研究人员提供了一个极好的培训场所，并从技术角度和作为探索新物理学的更大协作努力的一部分，将他们直接耦合到物理研究的关键角色。此外，这些技术还应用于各种工业流程，其中成功的涂层需要非常专业的技能和实践经验。 例如，金刚石涂层可以显着延长石英加工系统的寿命，可以提高微应变计的耐环境性，并为刀刃提供更硬的表面。 在加速器系统中，涂层在离子源效率和极化靶细胞的保持时间方面发挥着重要作用。