Collaborative Research (RUI): Understanding Potential Structures and Ion Dynamics Near Sheaths in Electronegative and Electropositive Multiple Ion Species Bounded Plasma

协作研究 (RUI)：了解负电和正电多离子物质束缚等离子体中鞘层附近的潜在结构和离子动力学

• 批准号: 1804654
• 负责人: Oliver Schmitz
• 金额: $ 34.5万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1804654&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Understanding; Potential

The common states of matter on Earth are solids, liquids and gases. Putting energy into gases can result in the 4th state of matter known as plasma, which consists of electrically charged particles (electrons and ions, both positive and negative) and neutral atoms and molecules. While uncommon on the Earth, plasma makes up more than 99% of the visible matter in the universe. Where plasma comes in contact with material boundaries, a thin region near the plasma boundary usually forms to isolate the plasma from the boundary. This thin region is called the plasma sheath. Experiments to be performed under this award will improve our understanding of plasma sheaths and associated phenomena as fundamental to understanding all bounded plasmas. Plasmas studied in this work are similar to those used in plasma applications such as the etching of semiconducting materials to make computer chips, in plasma space propulsion satellite engines, and in experimental plasma fusion devices. The majority of experimental studies will be carried out at the University of San Diego (USD), which is primarily an undergraduate institution. The award will also support outreach activities to promote engagement of students with diverse backgrounds in science, technology, engineering and mathematics (STEM) disciplines.Experiments to be carried out at USD, in collaboration with University of Wisconsin - Madison, will address important questions associated with sheaths and the Bohm Criterion in multiple ion species plasma, both electropositive and electronegative, many for the first time. In previous work, this collaborative group discovered anomalous sheath edge velocities while testing the Bohm Criterion in two ion species plasma. This effect has now been theoretically explained via the introduction of ion-ion streaming instabilities. As a result, many different aspects of sheath formation must be reevaluated in light of the new theory. Moreover, there are as yet no such corresponding measurements for electronegative plasma with multiple ion species. This project will pursue experiments to perform such measurements, measurements that determine the presheath and sheath plasma potential profiles with emissive probes. Ion velocity distribution functions (IVDFs) associated with ion acceleration will be determined with tunable diode lasers using the laser-induced fluorescence (LIF) technique. The award will also support transfer of cutting edge research techniques to the classrooms and teaching laboratories for undergraduate and graduate students at the University of San Diego, and at the University of Wisconsin-Madison.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.

地球上物质的常见状态是固体、液体和气体。将能量注入气体可以产生物质的第四种状态，称为等离子体，它由带电粒子（电子和离子，正负）和中性原子和分子组成。 虽然在地球上不常见，但等离子体构成了宇宙中99%以上的可见物质。在等离子体与材料边界接触的地方，通常在等离子体边界附近形成薄区域以将等离子体与边界隔离。这个薄的区域被称为等离子体鞘。根据该奖项进行的实验将提高我们对等离子体鞘层和相关现象的理解，这些现象是理解所有束缚等离子体的基础。 在这项工作中研究的等离子体类似于那些在等离子体应用中使用的，如蚀刻半导体材料，使计算机芯片，在等离子体空间推进卫星发动机，并在实验等离子体聚变装置。 大多数实验研究将在圣地亚哥大学（USD）进行，该大学主要是一所本科院校。 该奖项还将支持外展活动，以促进学生在科学，技术，工程和数学（STEM）学科的不同背景的参与。实验将在USD进行，与威斯康星州-麦迪逊大学合作，将解决与鞘层和玻姆判据相关的重要问题，在多离子物种等离子体中，正电和负电，许多是第一次。 在以前的工作中，这个合作小组发现了异常鞘边缘速度，同时测试玻姆标准在两个离子物种等离子体。这种效应现在已经通过引入离子-离子流不稳定性在理论上得到了解释。因此，必须根据新理论重新评估鞘形成的许多不同方面。此外，对于具有多个离子种类的负电性等离子体，还没有这样的相应测量。这个项目将进行实验，以执行这样的测量，测量，确定鞘前和鞘等离子体电位分布与发射探头。与离子加速相关的离子速度分布函数（IVDFs）将使用激光诱导荧光（LIF）技术用可调谐二极管激光器确定。 该奖项还将支持前沿研究技术转移到圣地亚哥大学和威斯康星大学麦迪逊分校的本科生和研究生的教室和教学实验室。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Experimental studies of the difference between plasma potentials measured by Langmuir probes and emissive probes in presheaths

• DOI: 10.1088/1361-6595/ab69e5
• 发表时间: 2020-02-01
• 期刊: PLASMA SOURCES SCIENCE & TECHNOLOGY
• 影响因子: 3.8
• 作者: Li, Peixuan;Hershkowitz, Noah;Severn, Greg
• 通讯作者: Severn, Greg