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

合作研究：等离子体边界鞘和预鞘的离子损失

• 批准号: 1206421
• 负责人: Greg Severn
• 金额: $ 16.5万
• 依托单位: University of San Diego
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206421&HistoricalAwards=false
• 关键词: Collaborative; Research; Ion; Losses; Plasma

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.

该奖项是对提交给NSF/美国能源部基础等离子体科学与工程伙伴关系联合征集NSF 09-596的提案的回应。该奖项为本科生参与整个研究工作提供资金，该研究工作由美国能源部根据与威斯康星大学麦迪逊分校的合同(补助金编号DE-FG02-97ER54437)单独提供资金。理解鞘是理解所有束缚等离子体的基础。该项目的实验目的是在理论预测和假设尚未得到证实的各种情况下，确定护套和相关预置管道的基本性质。威斯康星大学和圣地亚哥大学将进行协调研究。实验将确定健康前和鞘内等离子体的电势分布，以及与离子加速相关的离子速度分布函数(IVDF)。大多数实验将在麦迪逊进行，由私人侦探诺亚·赫什科维茨教授领导。LIF诊断开发将在两个校区进行，并由另一位P.I.格雷格·塞文教授领导。等离子体参数将使用两种或两种以上技术来确定，例如，发射探头、Ar、Xe和Kr亚稳态离子激光诱导荧光、朗缪尔探头、离子声波相速度和光学发射光谱的组合。这项工作的学术价值在于，在80多年后，许多与鞘相关的重要问题将首次得到解决。事实上，正是在当前的资助期间，我们之前发现的多离子物种等离子体中的异常鞘边缘速度通过引入一个新的理论元素--离子流动不稳定性--而得到了理论上的证明。这一新理论是80年来对与鞘形成有关的类介质行为的最新思考，它被直接应用于我们的实验结果，并获得了极好的一致性。因此，必须根据新的理论重新评估鞘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S及其学生在科学会议上的演讲，以及大学和国家实验室的研讨会，以及通过专利向科学界广泛传播。例如，之前关于电子鞘的工作导致了一项专利申请和美国国家航空航天局的STTR支持，即开发一种电子源，以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，我们在这个项目中进行的调查中使用的相对便宜的桌面实验适用于学生实验室课程，允许学生进行最先进的实验。赫什科维茨教授开发了三门基于等离子体的新课程，多次面向跨学科的受众。波特兰社区学院采用了几个学生实验室实验来培训半导体加工技术人员。Severn教授在圣地亚哥大学现代物理高级实验课程中介绍了新的离子声波实验。过去，曾与赫什科维茨共事过的几名本科生是已发表论文的第一作者，后来获得了等离子体物理和其他领域的博士学位，并在多个领域工作，其中一人现在是《纽约时报》的记者。此外，学生还在社区大学和中学担任导师，以提高对科学职业的认识。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分部会议上，一名与塞文教授一起进行本科研究工作的学生是获得等离子体物理杰出本科研究荣誉的六名学生之一。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。