RUI: Rydberg Atoms and their Effect on Ultra-Cold Plasma Dynamics

RUI：里德伯原子及其对超冷等离子体动力学的影响

• 批准号: 1068191
• 负责人: Duncan Tate
• 金额: $ 10万
• 依托单位: Colby College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1068191&HistoricalAwards=false
• 关键词: RUI; Rydberg; Atoms; their; Effect

Research in the PI's laboratory at Colby College is directed towards characterizing and controlling ultra-cold neutral plasmas (UNPs). In particular, we are investigating non-optical measurements of the electron temperature in UNPs, and techniques that offer the ability to control the electron temperature during the plasma evolution process. Our UNPs are made by pulsed-laser photoionization of laser-cooled, magnetically trapped rubidium atoms. Such a plasma is initially 95% neutral, and the initial electron temperature and ion density are easily controllable functions of the pulsed laser intensity and frequency. Atomic processes, principally involving Rydberg states, are critical to the plasma evolution process, and generally heat the plasma in its initial stage. Nevertheless, the UNP may exist for longer than 100 microseconds. As it expands, the electron temperature decreases, and electrons evaporate from the plasma. In UNPs made from alkaline-earth atoms, optically accessible ionic transitions are used to extract precise values for the electron temperature from the plasma ion expansion velocity. However, this is not feasible in alkali atoms such as rubidium. We are pursuing several electron temperature measurement techniques in alkali plasmas that potentially offer precision equal to the optical technique in alkaline earth UNPs. In addition, preliminary experiments in the PI's lab, in which Rydberg atoms are embedded in a UNP, indicate that it may be possible to control electron-atom collisions to counteract heating of the UNP caused by three-body recombination, and push the UNP into the strongly-coupled regime.Plasmas are ubiquitous: they illuminate our lives in the form of fluorescent lights,; a long-existing goal of physicists is to use plasmas to perform controlled thermonuclear fusion; and they occur in many other manifestations in the Universe and our everyday lives. UNPs are of fundamental interest because they can be made with uniquely low electron (0-1000 K) and ion (1 K) temperatures, and because they approach the strongly-coupled regime in which the potential energy of interaction between particles becomes comparable to their kinetic energies. They therefore bridge the gap between atomic systems and the correlations found in the solid or liquid state. In addition, UNPs are an exceptionally useful environment for testing theoretical modeling techniques used in plasma physics. Experiments can be carried out in a very reproducible manner, and one has the ability to set the initial conditions with a high degree of precision compared with other kinds of plasma experiment. At a more practical level, the PI's research on UNPs is carried out at an undergraduate-only institution, and undergraduates have been critically involved at all levels of the research, from equipment construction and data-acquisition programming, through to performing the experiments.

PI在科尔比学院的实验室的研究是针对表征和控制超冷中性等离子体（UNPs）。特别是，我们正在研究非光学测量的电子温度在UNPs，和技术，提供的能力，以控制电子温度在等离子体演化过程中。我们的UNPs是由激光冷却的脉冲激光光电离，磁捕获铷原子。这样的等离子体最初是95%中性的，并且初始电子温度和离子密度是容易控制的脉冲激光强度和频率的函数。原子过程，主要涉及里德伯态，对等离子体演化过程至关重要，并且通常在其初始阶段加热等离子体。然而，UNP可以存在超过100微秒。当它膨胀时，电子温度降低，电子从等离子体中蒸发。在由碱土金属原子制成的UNPs中，光学上可接近的离子跃迁用于从等离子体离子膨胀速度中提取电子温度的精确值。然而，这在诸如铷的碱金属原子中是不可行的。我们正在寻求在碱性等离子体中的几种电子温度测量技术，这些技术可能提供与碱土UNPs中的光学技术相等的精度。此外，PI实验室的初步实验表明，通过控制电子-原子碰撞来抵消三体复合对UNP的加热，并将UNP推向强耦合状态是可能的。物理学家的一个长期目标是利用等离子体进行受控的热核聚变;它们在宇宙和我们的日常生活中有许多其他表现形式。UNPs具有根本的意义，因为它们可以用独特的低电子（0-1000 K）和离子（1 K）温度制成，并且因为它们接近强耦合状态，其中粒子之间相互作用的势能变得与它们的动能相当。因此，它们弥合了原子系统与固态或液态中发现的相关性之间的差距。此外，UNPs是测试等离子体物理学中使用的理论建模技术的一个非常有用的环境。实验可以以非常可重复的方式进行，并且与其他种类的等离子体实验相比，能够以高精度设置初始条件。在更实际的层面上，PI对UNPs的研究是在一个只招收本科生的机构进行的，本科生一直积极参与各级研究，从设备建造和数据采集编程，到进行实验。