Theory and simulation of electron sheaths and anode spots in low pressure laboratory plasmas

Abstract

ACKNOWLEDGEMENTSThis work benefited from the input, help, and feedback of several people. This research was done in collaboration with Scott Baalrud, Matt Hopkins, Ed Barnat, and Ben Yee. Scott has been a great advisor. He took the time to check the details of nearly all of my work, pointing out countless mistakes and making several suggestions along the way. This not only included research results, but also seminar and conference talks, papers, and abstracts. I'm grateful for the encouragement and feedback when exploring new ideas and the pressure to stay focused and not stray too far from the current task at hand. Matt Hopkins was my mentor during the year I spent at Sandia National Lab under the O ce of Science Graduate Student Research program. Matt sponsored my application to the SCGSR program. Without his e↵ort, simulation of plasmas would not have played as great of a role as it has. I consider my experience simulating plasma experiments at Sandia to have been the most transformative of my graduate career. This will be invaluable as I move on to study new problems. At Sandia, I benefited from weekly discussions with Ed, Matt, and Ben on di↵erent issues relating to their various research topics in low temperature plasmas. Being in an environmentsurrounded by other plasma physicists working on related problems helped me distinguish which problems were interesting and useful to other people working in the field. The discussion of experimental results with Ben and Ed helped me to develop an understanding of these topics and to understand what things are and are not di cult to measure in the lab. Eventually I learned to stop asking for the impossible, although Ed may disagree. I enjoyed the hours spent talking plasma physics (or other less useful topics) around Andy Fierro's giant candy bowl with Ben, Ricky Tang, and Jim Franek. Also, the near daily breakfast burrito trips that Andy and I took made the food further east seem bland and nearly unbearable.At Iowa, there were several people who made day to day life more interesting. The two most notable are Ryan Hood and Nathaniel Sha↵er. Ryan always stopped by to talk about the latest thing that happened in the lab, or the latest Regular Car Review, and was always kind enough to show me his experiment and latest measurements. I've known Nathaniel since 2009 and am glad to have had a friend with whom I could bounce ideas o↵ of for so many years. I have no doubt that our various 'idiot checks' have vastly reduced the number of mistakes that could have been in these chapters. I have no doubt that both Nathaniel and Ryan will be great plasma physicists.Finally, I want to thank my family and friends for their support, especially my fiancè Mary ii for understanding the many late nights and stress filled days. I could not have done this without her support and love. ABSTRACTElectrodes in low pressure laboratory plasmas have a multitude of possible sheath structures when biased at a large positive potential. When the size of the electrode is small enough the electrode bia...