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

地球上物质的常见状态有固体、液体和气体。将能量注入气体可以产生被称为等离子体的物质的第四种状态，它由带电粒子(电子和离子，包括正负离子)和中性原子和分子组成。虽然等离子体在地球上并不常见，但它占宇宙中可见物质的99%以上。当等离子体与材料边界接触时，通常在等离子体边界附近形成一个薄区域，以将等离子体与边界隔离。这个薄薄的区域被称为等离子体鞘。根据该奖项将进行的实验将提高我们对等离子体鞘和相关现象的理解，以此作为理解所有束缚等离子体的基础。这项工作中研究的等离子体类似于用于等离子体应用的等离子体，例如用于蚀刻半导体材料以制造计算机芯片的等离子体，用于等离子体空间推进卫星发动机的等离子体，以及用于实验等离子体聚变设备的等离子体。大部分实验研究将在圣地亚哥大学进行，该大学主要是一所本科院校。该奖项还将支持外展活动，以促进具有不同科学、技术、工程和数学(STEM)学科背景的学生的参与。将在美国大学与威斯康星大学麦迪逊分校合作进行的实验，将解决与多离子物种等离子体中的鞘和玻姆标准相关的重要问题，包括正电和电负离子，其中许多是第一次。在之前的工作中，这个合作小组在测试两个离子物种的等离子体中的玻姆标准时，发现了鞘边缘的异常速度。这种效应现在已经通过离子-离子流动不稳定性的引入在理论上得到了解释。因此，必须根据新的理论重新评估鞘形成的许多不同方面。此外，对于多离子物种的电负性等离子体，目前还没有相应的测量方法。该项目将继续进行实验，以执行此类测量，即使用发射探头确定鞘前和鞘内等离子体电势分布的测量。与离子加速有关的离子速度分布函数(IVDF)将利用激光诱导荧光(LIF)技术在可调谐二极管激光器中确定。该奖项还将支持将尖端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课堂和教学实验室。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.