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、中性粒子和第四种物质（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尺寸的颗粒组成，它们完全相互作用并自洽地改变周围等离子体的性质。一旦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，观察等离子体物理现象的动力学水平。因此，在过去的二十年里，这一领域已经成为等离子体科学领域中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。这个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，特别是离子流的情况下，不仅微粒的充电条件被改变，而且流改变力平衡，这允许微粒保持悬浮在等离子体中并提供用于加热微粒和驱动不稳定性的自由能量源。因此，对尘埃等离子体的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，在许多实验中，很难得到一个完整的离子拖曳力模型，而这一模型又是解决各种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都是通过探测器上收集的电流或尘埃粒子对外加扰动的响应来推断离子流。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。为了实现这一目标，PI？该小组将利用其独特的能力，使用二维和立体粒子成像测速（PIV）的微粒速度的光学测量。PIV有助于测量微粒的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的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提出使用激光诱导荧光（LIF）直接测量等离子体中的离子流速。此外，在爱荷华州大学使用Robert梅尔利诺教授的尘埃等离子体设备进行的补充研究将允许在奥本大学PI实验室进行的测量进行验证。因此，这项拟议的工作提供了一个独特的机会，以解决一些悬而未决的问题的重要性尘埃等离子体社区。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-尘埃双流不稳定性发生的尘埃等离子体加热的拟议模型;（B）表征离子流如何作为产生尘埃声波的触发器。PI将继续积极吸引本科生和研究生以及博士后学者参与实践研究培训。PI在学生培训方面有着成功的记录，并将继续努力，包括学生参与出版物，国家和国际会议以及实验室推广活动。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），并建立一个新的伙伴关系（与西弗吉尼亚大学），从而加强社区的研究人员参与基础等离子体科学。此外，该项目将为PI实验室开展的许多公共宣传活动提供持续的支持，以阐明等离子体和尘埃等离子体的物理学。该奖项的资金由物理部和NSF数学和物理科学理事会内的多学科活动办公室，NSF工程理事会内的燃烧，火灾和等离子体系统，和能源部聚变能源科学办公室在基础等离子体科学和工程的NSF/DOE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.