Effect of ion flows on heating and instabilities in weakly coupled dusty plasmas

尘埃（复杂）等离子体是由离子、电子、中性粒子和第四种带电微观粒子或“尘埃”组成的四组分等离子体系统。带电尘埃通常由微米或纳米大小的粒子组成，它们完全相互作用，并自我一致地改变周围等离子体的特性。曾经主要集中在天体物理现象，如行星环或星际尘埃，带电微粒在等离子体中的作用的实验室研究的增长提供了一个独特的机会，在动力学水平上观察等离子体物理现象。因此，在过去的二十年里，这个领域已经成为等离子体科学这个更大领域中的一个强大的科学事业。在实验室研究中，微粒通过从背景等离子体中收集离子和电子而带电。这一过程改变了等离子体中的离子和电子分布。此外，在等离子体中存在流动，特别是离子流的情况下，不仅微粒的充电条件被改变，而且流动改变了力平衡，使微粒保持悬浮在等离子体中，并为加热微粒和驱动不稳定性提供了自由能源。因此，对尘埃等离子体理解的持续挑战仍然是带电微粒和离子之间的相互作用。然而，这种离子阻力的完整模型仍然存在，并且在许多实验中往往难以获得解决模型之间差异的重要信息“离子漂移速度”。大多数离子-尘埃相互作用的研究要么从探测器上收集的电流推断出离子流，要么通过尘埃粒子对施加扰动的响应推断出离子流。在这项研究中，PI建议直接和独立地测量离子流和粉尘响应，以确定这两个参数之间的相关性。要做到这一点，PI？该团队将利用其独特的能力，利用二维和立体粒子成像测速技术（PIV）对微粒速度进行光学测量。PIV有助于测量微粒输运和等离子体微粒成分的速度空间分布函数。此外，通过与西弗吉尼亚大学Earl Scime教授小组的合作，并使用奥本聚变实验室的染料激光系统，PI提议使用激光诱导荧光（LIF）直接测量等离子体中的离子流动速度。此外，利用爱荷华大学Robert Merlino教授的Dusty等离子体装置进行的补充研究将允许对在奥本大学PI实验室进行的测量进行验证。因此，这项提议的工作提供了一个独特的机会来解决一些对尘埃等离子体群落重要的悬而未决的问题。具体而言，该项目将研究离子-尘埃相互作用的两个具体方面：(a)测试通过离子-尘埃两流不稳定性发生的尘埃等离子体加热的拟议模型；(b)描述了离子流如何触发粉尘声波的产生。这个拟议的研究项目有几个机会产生更广泛的影响。PI将继续积极开展本科生、研究生和博士后的实践研究培训。PI在学生培训方面有着成功的记录，并将继续鼓励学生参与出版物、国内和国际会议以及实验室外展活动。此外，这项工作将支持尘埃等离子体社区内不同研究人员之间的合作活动（例如，在奥本和爱荷华州），并建立新的伙伴关系（与WVU），从而加强参与基础等离子体科学的研究人员社区。此外，该项目将继续支持PI实验室开展的许多公众宣传活动，以阐明等离子体和尘埃等离子体的物理学。该奖项的资金由美国国家科学基金会数学和物理科学理事会的物理部和多学科活动办公室，美国国家科学基金会工程理事会的燃烧、火灾和等离子体系统，以及美国能源部的聚变能科学办公室提供，该办公室在美国国家科学基金会/美国能源部基础等离子体科学与工程伙伴关系的背景下。

Dusty (complex) plasmas are four-component plasma systems that consist of ions, electrons, neutral particles, and the addition of a fourth species, charged microscopic particles or "dust". The charged dust, which is typically composed of micron- or nanometer-sized particles, fully interacts and self-consistently modifies the properties of the surrounding plasma. Once primarily focused on astrophysical phenomena such as planetary rings or interstellar dust, the growth of laboratory studies of the role of charged microparticles in plasmas has offered a unique opportunity to observe plasma physics phenomena at the kinetic level. As a result, this field has become, over the last two decades, a robust scientific enterprise within the larger field of plasma science.In laboratory studies, the microparticles become charged through the collection of ions and electrons from the background plasma. This process alters the ion and electron distributions in the plasma. Furthermore, in the presence of flows in the plasma, particularly ion flows, not only are the charging conditions of the microparticles modified, but the flows alter the force balance that allows the microparticles to remain suspended in the plasma and provide a free energy source for heating the microparticles and driving instabilities. Thus, a continuing challenge to the understanding of dusty plasmas remains the interaction between the charged microparticles and the ions. However, a complete model of this ion drag force remainselusive and an essential piece of information for resolving the differences among the models "the ion drift velocity" is often difficult to obtain in many experiments.Most studies of ion-dust interactions infer the ion flow either from collected currents on probes or by the response of the dust particles to an applied perturbation. In this investigation, the PI proposes to directly and independently measure both the ion flow and the dust response to determine the correlation between these two parameters. To accomplish this, the PI?s group will utilize its unique capabilities for optical measurements of microparticle velocities using two-dimensional and stereoscopic particle imaging velocimetry (PIV). PIV facilitates measurements of microparticle transport and the velocityspace distribution function of the microparticle component of the plasma. Furthermore, through a collaboration with Prof. Earl Scime's group at West Virginia University and access to the Auburn Fusion Laboratory's dye laser system, the PI proposes to use laser induced fluorescence (LIF) to directlymeasure ion flow velocities in the plasma. Additionally, complementary studies using Prof. Robert Merlino's Dusty Plasma Device at the University of Iowa will allow a verification of the measurements performed at the PI's laboratory at Auburn University.Consequently, this proposed work offers a unique opportunity to address a number of outstanding questions of importance to the dusty plasma community. Specifically, this project will investigate two specific aspects of ion-dust interactions: (a) testing a proposed model of dusty plasma heating thatoccurs via an ion-dust two-stream instability; and (b) characterizing how ion flow acts as a trigger for the generation of dust acoustic waves.This proposed research project has several opportunities to have a broader impact. The PI will continue to actively engage undergraduate and graduate students and post-doctoral scholars in hands-on research training. The PI has a successful track-record of student training and will continue encourageand include student participation in publications, national and international conferences, and laboratory outreach activities. Additionally, this work will support collaborative activities among different researchers within the dusty plasma community (e.g., at Auburn and Iowa) and establish a newpartnership (with WVU), thereby strengthening the community of researchers involved in basic plasma science. Furthermore, this project will provide continuing support for many of the public outreach activities that have been undertaken by the PI's laboratory to illuminate the physics of plasmas and dusty plasmas.Funds for this award are provided by the Physics Division and the Office of Multi-disciplinary Activities within the NSF's Mathematics and Physical Sciences Directorate, Combustion, Fire, and Plasma Systems within NSF's Engineering Directorate, and the Office of Fusion Energy Sciences of the DoE within the context of the NSF/DOE Partnership in Basic Plasma Science and Engineering.