MRI Consortium: Development of a Room-Temperature Apparatus to Measure the Electric Dipole Moment of the Neutron, for a Fast-track Ten-fold Improvement in Sensitivity

MRI 联盟：开发测量中子电偶极矩的室温装置，快速将灵敏度提高十倍

• 批准号: 1828568
• 负责人: Bradley Plaster
• 金额: $ 17.94万
• 依托单位: University of Kentucky Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1828568&HistoricalAwards=false
• 关键词: MRI; Consortium; Development; Room; Temperature

This award supports the building of a new experiment at the Los Alamos National Laboratory (LANL) that will be sensitive to a neutron electric dipole moment at a very small scale. Neutrons are subatomic particles and, along with the proton, are the basic constituents of atomic nuclei. They are electrically neutral, but nothing in principle prevents the neutron from having positive and negative poles, a so-called "electric dipole moment"(EDM). Big-bang theories of the origin of the universe predict that matter and antimatter are created in equal parts, which should have annihilated long ago. The current observable universe has much more matter than antimatter, thus there should be processes which caused this imbalance in the evolution of the cosmos. These mechanisms require the behavior of matter and antimatter to be slightly different from each other's mirror image. The same underlying mechanism also predicts that the neutron should have an EDM large enough to be observable. Thus, neutron EDM experiments attempt to shed light on the question as to why there is any matter in the universe at all. This award supports the construction of instrumentation needed to improve the sensitivity to the nEDM by a factor of ten beyond current limits, taking advantage of the increased ultracold neutron (UCN) yield from the upgraded UCN source at LANL. In developing the knowledge and technical basis needed for the nEDM search, students and postdoctoral researchers will become the next generation of scientists.Experimental searches for the neutron electric dipole moment (nEDM) have been conducted since 1951. To date, no evidence for an nEDM has been found. In many theoretical scenarios, successful matter creation leads to strict lower bounds on the nEDM on the order of 10^-27 e-cm. If no nEDM is discovered, this experiment, in combination with ongoing EDM searches in atomic and nuclear systems, will push the limits on the mass scale for new symmetry violating physics above 100 TeV. This exceeds the current and future energy reach of the Large Hadron Collider. On the other hand, discovery of a nonzero nEDM at this level would reveal a completely new source of symmetry violations, contributing to the development of a unified theory of the fundamental forces of nature that is consistent with cosmology. Achieving the target nEDM sensitivity requires high densities of polarized ultra-cold neutrons (UCN) and an apparatus capable of controlling systematic effects. The experiment design is based on Ramsey's method of separated oscillatory fields using a two-cell measurement chamber, state-of-the-art magnetic shielding, novel magnetic field configurations, and sensitive magnetometry (both external and co-habitating) to control systematics. This room-temperature design (unlike many cryogenic designs under development) will allow the instrument to be assembled, tested, and commissioned on a three-year timescale. The development is leveraged by the existing technical strengths of Indiana University, the University of Kentucky, LANL, the University of Michigan, and Yale University. This project will partner with the private sector to build a magnetically shielded space for the experiment, atomic magnetometers, and improve magnetic resonance measurements which may have an impact on medical imaging technology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该奖项支持在洛斯阿拉莫斯国家实验室(LANL)建立一项新的实验，该实验将在非常小的范围内对中子电偶极矩敏感。中子是亚原子粒子，与质子一起是原子核的基本成分。它们是电中性的，但原则上没有什么能阻止中子有正极和负极，即所谓的“电偶极矩”(EDM)。宇宙起源的大爆炸理论预测，物质和反物质是等量产生的，这应该在很久以前就已经消失了。当前可观测的宇宙中的物质比反物质多得多，因此应该有一些过程导致了宇宙演化的这种不平衡。这些机制要求物质和反物质的行为与彼此的镜像略有不同。同样的潜在机制还预测，中子应该有一个足够大的EDM，以便观察到。因此，中子电火花实验试图阐明宇宙中为什么会有物质这个问题。该奖项支持建造所需的仪器，利用LANL升级的UCN源增加的超冷中子(UCN)产额，将nEDM的灵敏度提高10倍，超出当前限制。在发展nEDM研究所需的知识和技术基础方面，学生和博士后研究人员将成为下一代科学家。自1951年以来，一直在进行中子电偶极矩(NEDM)的实验研究。到目前为止，还没有发现nEDM的证据。在许多理论场景中，成功的物质创造导致nEDM的严格下限在10^-27e-cm数量级。如果没有发现nEDM，这项实验与正在进行的原子和核系统中的EDM搜索相结合，将把违反对称性的新物理的质量标度限制推到100TeV以上。这超过了大型强子对撞机目前和未来的能量覆盖范围。另一方面，在这个水平上发现非零的nEDM将揭示一个全新的对称性破坏的来源，有助于发展与宇宙学一致的自然基本力的统一理论。要达到目标的nEDM灵敏度，需要高密度的极化超冷中子(UCN)和能够控制系统效应的装置。实验设计基于Ramsey的分离振荡场的方法，使用两个单元的测量室、最先进的磁屏蔽、新的磁场配置和灵敏的磁测量(外部和共居)来控制系统。这种室温设计(与许多正在开发的低温设计不同)将允许该仪器在三年的时间尺度上进行组装、测试和调试。印第安纳大学、肯塔基大学、LANL、密歇根大学和耶鲁大学的现有技术优势充分利用了这一发展。该项目将与私营部门合作，为实验建造一个磁屏蔽空间，原子磁强计，并改进可能对医学成像技术产生影响的磁共振测量。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。