Collaborative Research (RUI): Understanding Sheath Formation in Electronegative and Electropositive Multiple Ion Species Plasma

地球上物质的常见状态是固体、液体和气体。向气体中注入能量可以产生被称为等离子体的物质的第四种状态，等离子体可以由带电粒子和中性原子和分子组成，它们共同作用。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。当等离子体与其他物质边界接触时，通常在等离子体边界附近形成一个称为等离子体鞘层的薄区域，以平衡从等离子体到边界的电荷粒子流。在这个合作奖项下进行的实验将提高我们对等离子鞘层和相关现象的理解，这是理解所有有界等离子体的基础。在这项工作中研究的等离子体类似于用于制造计算机芯片的半导体材料蚀刻、等离子体空间推进卫星发动机和实验等离子体聚变装置的等离子体。大多数实验研究将在圣地亚哥大学进行，这是一个主要的本科院校；摩根州立大学将支持本科生与圣地亚哥大学合作，并将开始建立一个内部等离子相关的研究实验室。该奖项还将支持推广活动，以促进具有不同科学、技术、工程和数学学科背景的学生的参与。主要在圣地亚哥大学进行的实验将解决与多离子等离子体中的鞘层和玻姆准则相关的重要问题，包括正电和负电，其中许多是第一次。在以前的工作中，在测试两种离子等离子体的玻姆准则时发现了异常鞘层边缘速度。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层形成的许多不同方面。此外，对于多离子的电负性等离子体，还没有相应的测量方法。该项目将继续进行实验以进行此类测量，并使用发射探针确定鞘前和鞘内等离子体电位分布。与离子加速度相关的离子速度分布函数将用激光诱导荧光技术确定可调谐二极管激光器。该奖项还将支持尖端研究技术的转移，以加强摩根州立大学对大气压微等离子体对纳米颗粒制造的影响的研究，改善等离子体诊断，供更广泛的等离子体科学研究界使用，并刺激参与机构的本科生和研究生在教室和教学实验室的教学和学习。该奖项反映了美国国家科学基金会的法定使命，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。

The common states of matter on Earth are solids, liquids and gases. Putting energy into gases can produce the fourth state of matter known as plasma, which can consist of electrically charged particles and neutral atoms and molecules, all acting collectively. While uncommon on the Earth, plasma makes up more than 99% of the visible matter in the universe. Where plasma comes in contact with other material boundaries, a thin region called the plasma sheath usually forms near the plasma boundary to balance charge particle flow from the plasma to the boundary. Experiments to be performed under this collaborative award will improve our understanding of plasma sheaths and associated phenomena that is fundamental to understanding all bounded plasmas. Plasmas to be studied in this work are similar to those used in 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, a primarily undergraduate institution; Morgan State University will support undergraduate students to collaborate with the University of San Diego and will begin developing an in-house plasma related research laboratory. The award will also support outreach activities to promote engagement of students with diverse backgrounds in science, technology, engineering and mathematics disciplines.Experiments to be carried out principally at the University of San Diego 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, anomalous sheath edge velocities were discovered 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, and measurements that determine the presheath and sheath plasma potential profiles with emissive probes. Ion velocity distribution functions associated with ion acceleration will be determined with tunable diode lasers using the laser-induced fluorescence technique. The award will also support transfer of cutting edge research techniques to enhance investigation of atmospheric pressure micro-plasma effects on nanoparticle fabrication at Morgan State University, to improve plasma diagnostics for use by the wider plasma science research community, and to stimulate teaching and learning in classrooms and teaching laboratories for undergraduate and graduate students at the participating institutions.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.