CAREER: Charging and Coagulation of Dust Grains I Astrophysical and Laboratory Environments

复杂等离子体领域为空间和实验室物理领域的研究提供了丰富的领域。 沉浸在等离子体环境中的尘埃颗粒能够将自己组织成复杂的结构，这为系统的物理学提供了深入的见解，从原行星盘中行星的形成到晶体固体的结构和相变。最近的天文学证据表明，我们的行星系统在银河系中并不独特。 相反，一颗星星伴随着行星运行似乎更像是一种规律，而不是例外。 行星必然是由母星星形成时遗留下来的气体和尘埃盘形成的。 因此，行星的形成最初取决于浸没在等离子体和辐射环境中的微米级颗粒如何能够碰撞，粘附并组织成更大，更坚固的结构，然后在引力相互作用下聚集。 本研究的目的是发展一个详细的模型，带电分形聚集在原行星盘凝聚。 这将通过数值模拟和实验研究的结合来实现，旨在进一步理解分形聚集体的充电和凝聚所涉及的微观物理。分形聚集体的充电和增长是必然联系在一起的，必须包括自洽正确建模带电聚集体的相互作用。 聚集体上的电荷分布影响它们在碰撞和粘附时的取向，这反过来又决定了分形结构的开放或紧凑程度，这是对混凝速率的主要影响。 数值模型将用于确定不规则灰尘聚集体上的电荷和电荷排列。 充电模型的结果，然后可以被纳入现有的凝结模型。 新算法将被添加到凝固模型中，以考虑带电颗粒之间的偶极-偶极相互作用、分形颗粒与气体环境的耦合，并包括各种碰撞结果（无重组的粘附、破碎、破裂等）。以确定分形晶粒生长的极限。 与数值模拟同时进行的实验室实验将对理论模型进行检验，并为改进模型提供额外的数据。该项目的结果将提供有关带电尘埃颗粒自组装和生长的新的和基本的原始信息。该项目不仅将对理解尘埃增长作为行星形成的第一步产生影响，而且还将有助于理解受控实验室等离子体环境中尘埃的自我排序和增长，例如在等离子体半导体制造和磁约束等离子体聚变实验中发现的情况。 颗粒聚集也是理解地球和太阳系其他天体大气过程的一个重要过程。带电颗粒的凝聚也可能与理解催化和污染控制等过程有关。研究生，本科生，技术和高中学生在这个项目上工作将接受培训和经验，这将为他们在学术界，工业界或政府实验室的职业生涯做好准备。他们将不仅学习物理原理和实验协议，而且还将发展关键技能，如计算和建模，真空系统，仪器和诊断的实践经验，以及技术写作和演示技能。

The field of complex plasmas provides a rich field for inquiry into the areas of space and laboratory physics. The ability of dust grains immersed in a plasma environment to organize themselves into complex structures provides insights into the physics of systems as diverse as the formation of planets in protoplanetary disks to the structure and phase transitions of crystalline solids. Recent astronomical evidence has shown that our planetary system is not unique in the galaxy. Rather, it seems more the rule than the exception for a star to be accompanied by orbiting planets. The planets must necessarily form from the disk of gas and dust left over from the formation of the parent star. Thus the formation of planets initially depends on how micron-sized grains, immersed in a plasma and radiative environment, are able to collide, stick and organize themselves into larger, more robust structures which may then agglomerate under gravitational interactions. The objective of this research is to develop a detailed model for the coagulation of charged fractal aggregates in a protoplanetary disk. This will be achieved by a combination of numerical modeling and experimental research directed at furthering the understanding of the microphysics involved in the charging and coagulation of fractal aggregates. The charging and growth of fractal aggregates are necessarily linked and must be included self-consistently to correctly model the interaction of charged aggregates. The charge distribution on aggregates influences their orientation as they collide and stick, which in turn determines how open or compact the fractal structure is, a major influence on the coagulation rate. Numerical models will be used to determine the charge and charge arrangement on irregular dust aggregates. The results of the charging models can then be incorporated into existing coagulation models. New algorithms will be added to the coagulation models to allow for the dipole-dipole interactions between charged grains, the coupling of the fractal grains to the gas environment, and include various collision outcomes (sticking without restructuring, crushing, disruption, etc.) to determine limits on fractal grain growth. Laboratory experiments run concurrently with the numerical simulations will provide a check on theoretical models and provide additional data to improve the models.The results of this project will provide new and fundamentally original information about the self-assembly and growth of charged dust grains. This project will have implications not only for understanding dust growth as an initial step towards planet formation, but will also contribute to the understanding of the self-ordering and growth of dust in controlled laboratory plasma environments, such as those found in plasma semi-conductor manufacturing and magnetically confined plasma fusion experiments. Grain aggregation is also an important process in understanding atmospheric processes both here on earth and on other bodies in the solar system. The coagulation of charged grains may also prove relevant to understanding processes such as catalysis and pollution control. Graduate, undergraduate, technical, and high school students working on this project will receive training and experience that will prepare them for careers in academia, industry, or government laboratories. They will learn not only physical principles and experimental protocols, but will also develop critical skills such as computation and modeling, practical experience with vacuum systems, instrumentation and diagnostics, and technical writing and presentation skills.