Collaborative Research: Experimental and Theoretical Study of the Plasma Physics of Antihydrogen Generation and Trapping

去年，欧洲核子研究中心的阿尔法合作首次捕获了反氢。到目前为止，数以百计的反原子已经被捕获的时间相当于S的1000倍。虽然这是一个了不起的成就，但阿尔法仪器的配置不适合大多数反氢性质的测量，必须进行重建，以允许激光和更好的微波接入。此外，尽管捕获率足以开始研究反物质的性质，但仍低于最佳水平。要提高捕获率有两大挑战：(1)了解合成反氢的正电子和反质子等离子体的行为；(2)了解正电子和反质子重组的原子过程。反氢合成位于原子物理和等离子体物理之间，如果不使用这两个领域的工具，就不可能进行适当的研究。反氢研究的长期目标是寻找氢和反氢性质之间的差异。这种差异可能发生在两个物种的光谱之间。光谱的不同只能由CPT破坏造成。另一个可能出现差异的地方是氢和反氢的引力相互作用。这样的差异可能会解决重子产生的问题。电势差的第三个区域是反氢的分数电荷。反氢的净电荷仅为单位电荷的约10^-7。任何这些测量的积极结果都将彻底改变我们对基本粒子和场的理解。物理问题将通过欧洲核子研究中心的实验、经典轨迹蒙特卡罗、分子动力学和3DPIC代码以及解析理论来研究。将解决的一些问题包括：实现更好的(更低的)轻子和反质子温度；研究轻子如何与背景辐射场相互作用；研究轻子如何与共振腔相互作用；改进等离子体诊断；改进正电子和反质子的混合，以便产生的更多反氢可以被保存在非常浅的中性陷阱中。虽然寻求这些问题答案的动机来自反氢研究，但其中许多问题在等离子体和原子物理中提出了新的和深刻的问题。这项研究的长期目标是为我们理解我们周围的世界奠定基础。潜在地，它对粒子相互作用的性质、物质-反物质对称性问题和宇宙学都有深刻的影响。同时，这项研究具有独特的可见性，因为反物质的研究对公众来说是容易理解和吸引人的。去年的反氢捕获事件在非专业媒体和科学媒体上引起了极大的关注。反氢实验足够简单，研究生可以完整地理解它们。因此，它们为学生提供了广泛的教育。实验者学习束流和等离子体物理、实验规划和设计、仪器仪表、特高压实践、电子学、低温、磁学和软件开发。随着理论的发展，理论家可以对实验的设计、操作和分析做出重要贡献。材料的相对可访问性使本科生很容易融入实验和理论课程。拟议的研究包括代表人数不足的群体成员的大量参与。

Last year, antihydrogen was trapped for the first time by the ALPHA collaboration at CERN. By this point hundreds of antiatoms have been trapped for times as long as 1000 s. While this was a remarkable achievement, the ALPHA apparatus is not well configured for most measurements of the properties of antihydrogen, and must be rebuilt to allow laser and better microwave access. Furthermore, the trapping rates, while sufficient to begin studies of the properties of antimatter, are lower than optimal. There are two broad challenges to improving the trapping rate: (1) Understanding the behavior of the positron and antiproton plasmas from which the antihydrogen is synthesized; and (2) Understanding the atomic processes by which positrons and antiprotons recombine. Antihydrogen synthesis lies on the boundary between atomic and plasma physics, and cannot be studied properly without employing tools from both fields. The long term goal of antihydrogen research is to search for differences between the properties of hydrogen and antihydrogen. Such differences might occur between the spectra of the two species. Differences in the spectra could only result from CPT violation. Another place differences might occur is in the gravitational interactions of hydrogen and antihydrogen. Such differences could solve the baryogenesis problem. A third area of potential difference is in the fractional charge of antihydrogen. The net charge of antihydrogen is only known to about 10^-7 relative to the unit charge. Positive results from any of these measurements would completely change our understanding of fundamental particles and fields. The physics issues will be studied with experiments at CERN, with classical trajectory Monte Carlo, molecular dynamics, and 3D PIC codes, and with analytic theory. Some of the questions that will be addressed include: achieving improved (lower) lepton and antiproton temperatures; studying how leptons interact with the background radiation field; studying how leptons interact with resonant cavities; improved plasma diagnostics; and improved mixing of positrons and antiprotons, so that more of the resultant antihydrogen can be held in a very shallow neutral trap. While the motivation for seeking answers to these questions comes from antihydrogen research, many of these questions raise novel and deep issues in plasma and atomic physics. The long-¬term goals of this research address the very basis of our understanding of the world around us. Potentially, it has deep implications on the nature of particle interactions, on the question of matter-¬antimatter symmetry, and on cosmology. At the same time, this research is uniquely visible because the study of antimatter is accessible and fascinating to the public. The trapping of antihydrogen last year was extraordinarily widely noted in the lay and scientific press. Antihydrogen experiments are sufficiently simple that they can be comprehended in their entirety by graduate students. Consequently, they offer students a broad education. Experimentalists learn beam and plasma physics, experimental planning and design, instrumentation, UHV practice, electronics, cryogenics, magnetics and software development. Along with theory development, theorists can make critical contributions to the design, operation, and analysis of the experiments. The relative accessibility of the material makes it easy to integrate undergraduate students into both the experimental and theoretical program. The proposed research includes significant participation by members of underrepresented groups.