Collaborative Research: Understanding Ion Losses to Plasma Boundaries Sheaths and Presheaths

该奖项是为了响应提交给NSF/DOE基础等离子体科学与工程合作伙伴关系NSF 09-596的提案。该奖项提供资金，以支持本科生参与整体研究工作，这是由能源部根据合同单独资助的威斯康星州-麦迪逊大学（授权号DE-FG 02 - 97 ER 54437）。“理解鞘层是理解所有有界等离子体的基础。该项目的实验旨在确定各种情况下鞘和相关预鞘的基本特性，这些情况下的理论预测和假设尚未得到验证。协调研究将在威斯康星州大学和圣地亚哥大学进行。实验将确定预鞘和鞘等离子体电位分布和由此产生的离子速度分布函数（IVDFs）与离子加速。大部分实验将在麦迪逊进行，由私人侦探领导，Noah Hershkowitz教授LIF诊断开发将在两个校区进行，并由其他P.I.领导。格雷格教授塞文。等离子体参数将用两种或更多种技术来确定，例如，发射探针、Ar、Ar和Kr亚稳离子LIF、朗缪尔探针、离子声波的相速度和光学发射光谱的组合。这项工作的智力价值是，经过80多年的时间，许多与鞘相关的重要问题将首次得到解决。事实上，它是在目前的资助期间，我们以前发现的异常鞘边缘速度在多个离子物种等离子体会见了一个新的理论元素：离子流不稳定性的引入与理论的理由。新的理论，这是最新鲜的思想介质样的行为与鞘形成80年来，直接应用到我们的实验结果与极好的协议。因此，必须根据新理论重新评估鞘层形成的许多不同方面。我们的研究活动也将产生更广泛的影响。研究结果将通过参考出版物和P.I.的演讲广泛传播给科学界。他们和他们的学生在科学会议上，以及在大学和国家实验室的研讨会上，并通过专利。例如，以前关于电子鞘的工作导致了一项专利申请和美国航天局的STTR支持，以开发一种电子源，取代空心阴极电子源，作为远程空间探索任务中离子推进器的中和器。此外，我们在这个项目中追求的调查中使用的相对便宜的桌面实验适合学生实验室课程，允许学生进行最先进的实验。Hershkowitz教授已经开发了三个新的基于等离子体的课程，多次提供给跨学科的观众。采用了几项学生实验室实验来培训波特兰社区学院的半导体加工技术人员。塞文教授在美国圣地亚哥大学的现代物理实验课程中介绍了新的离子声波实验。在过去，与赫什科维茨教授一起工作的几名本科生都是已发表论文的第一作者，后来又获得了等离子体物理学和其他领域的博士学位，并在各个领域工作，其中一名现在是《纽约》的记者。此外，学生还在社区学院和中学担任导师，以提高对科学职业的认识。与塞文教授一起进行本科研究工作的一名学生是2009年在佐治亚州亚特兰大举行的第51届美国物理学会等离子体物理部会议上因等离子体物理学杰出本科研究而获奖的六名学生之一。这个学生是第一代大学生。我们的活动将继续对美国STEM领域的多样性产生积极影响。

This award is made in response to a proposal submitted to and reviewed under the NSF/DOE Partnership in Basic Plasma Science and Engineering joint solicitation NSF 09-596. The award provides funds to support undergraduate participation in the overall research effort, which is being funded separately by the DOE under contract to the University of Wisconsin - Madison (Grant Number DE-FG02-97ER54437)." Understanding sheaths is fundamental to the understanding of all bounded plasmas. Experiments for this project are aimed at establishing the basic properties of sheaths and associated presheaths for a variety of situations for which theoretical predictions and assumptions have not yet been verified. Coordinated studies will be carried out at the University of Wisconsin and the University of San Diego. Experiments will determine the presheath and sheath plasma potential profiles and the resulting ion velocity distribution functions (IVDFs) associated with ion acceleration. Most of the experiments will be carried out in Madison and led by the P.I., Prof. Noah Hershkowitz. LIF diagnostic development will be carried out on both campuses and led by the other P.I. Prof. Greg Severn. Plasma parameters will be determined with two or more techniques, e.g. combinations of emissive probes, Ar, Xe, and Kr metastable ion LIF, Langmuir probes, the phase velocities of ion acoustic waves, and optical emission spectroscopy. The intellectual merit of this work is that after more than 80 years, many important questions associated with sheaths will be addressed for the first time. Indeed it was during the current funded period that our previous discovery of anomalous sheath edge velocities in multiple ion species plasmas met with theoretical justification by the introduction of a new theoretical element: ion streaming instabilities. The new theory, which is the freshest thinking about medium like behavior in connection with sheath formation in 80 years, was applied directly to our experimental results with excellent agreement. It follows then that many different aspects of sheath formation must be reevaluated in light of the new theory. Our research activities will also have a broader impact. Results will be disseminated widely to the scientific community through refereed publications and talks by the P.I.'s and their students at scientific meetings, as well as in seminars at universities and national Labs, and through patents. For example, previous work on electron sheaths resulted in a patent application and STTR support from NASA to develop an electron source to replace hollow cathode electron sources as neutralizers of ion-thrusters on long-range space exploration missions. Further, the relatively inexpensive tabletop experiments used in the investigations we are pursuing in this project are suited to student laboratory courses, permitting students to perform state-of-the-art experiments. Prof. Hershkowitz has developed three new plasma-based courses offered several times to a very inter-disciplinary audience. Several student lab experiments were adopted to train semiconductor-processing technicians at Portland Community College. New ion acoustic wave experiments have been introduced by Prof. Severn in the upper division experimental modern physics course at the University of San Diego. In the past, several undergraduates who worked with Prof. Hershkowitz have been first authors on published papers, have gone on to receive Ph.D.s in plasma physics and other areas, and to work in a variety of fields, including one who is now a reporter for the New York Times. Further, students have served as tutors in community colleges and secondary schools to increase awareness in careers in science. A student who performed undergraduate research work with Prof. Severn was one of six students honored for outstanding undergraduate research in plasma physics at the 51st American Physical Society, Division of Plasma Physics meeting in Atlanta, GA, in 2009. This student was a first generation college attendee. Our activities will continue to have a positive impact on diversity in STEM fields in the US.