Preface
Plasma science and applications have been seeing great progress over the last few decades. This progress is the consequence of development of modern plasma sources based on plasma generation in electrical discharges in vacuum, in low- and high-pressure gases, RF-discharges, magnetrons, etc. On the other hand, it is the result of novel plasma applications in plasma processing of materials, in space propulsion and, especially, in plasma-based nano- and biomedical technology. An important characteristic of the plasma research realm is the strong overlap between plasma science, technology, and application. This interplay of the plasma science, technology, and application is referred as the plasma engineering.
This book is an attempt to present aspects of plasma engineering by describing the physics of plasmas, plasma generation in different conditions, and technique of plasma applications from a unified point of view through the theoretical and experimental prism. The book consists of seven chapters considering plasma fundamentals, plasma diagnostics and methodology of the plasma engineering and various plasma applications. While describing the state of the art of plasma applications, authors often included their own research results. The material in the book is self-contained and it was our intention to make the presentation as simple and easily understandable as possible.
In the introductory part of the book (Chapter 1), basic plasma concepts and foundation of plasma engineering are introduced. Fundamental plasma phenomena including the different types of plasma particle collisions, waves, and instabilities are described. The boundary effects such as plasma-wall transition, electron emission mechanisms, and ablation of the walls contacted with relatively hot plasmas are detailed and explained. This is followed by the introduction of various diagnostic tools used to characterize plasmas in engineering systems. Fundamental principles and experimental methodology of plasma diagnostics are reviewed. The probe diagnostic description includes the planar, spherical, and emissive probes as well as probes operating in a collision-dominated plasma and in a magnetic field. Furthermore, electrostatic analyzer, interferometric technique, plasma spectroscopy, optical measurements, fast imaging, and others were explained giving appreciation of their advantages as well as limitations.
Physics of different types of electrical discharges is considered. The description begins with the classical Townsend mechanism of gas electrical breakdown and the Townsend discharge followed by the streamer mechanism and glow discharges. The nature of gas breakdown according to Paschen law is detailed. A broad range of high-current discharges including atmospheric and vacuum arcs are described taking into account recent developments. New results of simulation of very complicated cathode phenomena in a vacuum arc are presented.
Basic approaches and theoretical methodologies for plasma modeling and, in particular, approaches that are based on numerical simulations are described. The analysis begins with analysis of the behavior of a single particle in electric and magnetic fields. It is followed by the description of two basic approaches. The first one is based on the fluid description of plasma solving numerically magnetohydrodynamic (MHD) equations. The second one is the kinetic model particle techniques that take into account kinetic interactions among particles and electromagnetic fields. This simulation is computationally extensive as it is able to resolve local parameters of the rarified plasmas.
A significant part of this book is devoted to plasma engineering application in space propulsion. Space propulsion is required for satellite motion in outer space. Plasma physics and engineering of thrusters based mainly on the electromagnetic plasma acceleration are described. Hall thruster, pulsed plasma thrusters, and microthruster are some examples of plasma thrusters considered. In the case of a Hall thruster, the basic mechanisms of electron transport are considered. In the framework of the pulsed plasma thruster, this book covers the ablation phenomena in the presence of dense plasma.
The important part of the book covers the plasma effects in nanoscience and nanotechnology. Nanoscience and Nanotechnology study nanoscopic objects used across many scientific fields, such as chemistry, biology, physics, materials science, and engineering. Application of low-temperature plasmas in nanoscience and nanotechnology is a relatively new and quickly emerging area at the frontier of plasma physics, gas discharge, nanoscience, and bioengineering. The description involves recent original experimental and theoretical results in the field of plasma-based techniques of nanomaterial synthesis. Particular emphasis is given on the carbon-based nanoparticle synthesis such as single-walled carbon nanotubes and graphene which are fundamental building blocks. A magnetically based novel approaches to control length and electric properties of nanoparticles in plasma-based synthesis are described.
Plasma medicine is an emerging field combining plasma physics and engineering, medicine, and bioengineering to use plasmas for therapeutic applications. This field is emerging due to advance in the cold atmospheric plasma (CAP) technology. The latest original results on CAP applications in medicine are presented in the last part of the book. Physics of cold plasmas and diagnostics employed such as fast imaging, microwave scattering, and so on are covered. The effects associated with CAP interaction with cells such as cell migration, apoptosis, and integrins activation are explained. The therapeutic potential of CAP with a focus on selective tumor cell eradication capabilities and signaling pathway deregulation is shown.
We should note that the aforementioned topics cover an extensive research field and we certainly understand that the present book does not exhaustively answer all questions. While we tried to address plasma engineering issues in both width and depth, we could not avoid just “scratching the surface” by considering some aspects. However, we hope that the wide range of research areas described will be very useful for understanding the physics and the plasma engineering applications and ultimately will stimulate future research.
This book can be used as a text for courses on Plasma Engineering or Plasma Physics in Departments of Aerospace Engineering, Electrical Engineering, and Physics. It can also be useful as a reference for early career researchers and practicing engineers.
The authors would like to acknowledge colleagues and friends, their encouragement, fruitful discussions, and support.
Firstly, we would like to thank our colleagues Raymond Boxman and Samuel Goldsmith with whom the original models of the plasma jet expansion in vacuum arc were developed. We are particularly thankful to Ian Brown who guided one of us (MK) during his tenure as a postdoctoral scientist at Berkeley and with whom we collaborated on some important aspects of multiple-charged ion transport. We thank Andre Anders with whom we worked on problems related to plasma transport in curved magnetic field and ion implantation. Very special thanks goes to Iain Boyd with whom we worked for a number of years and who introduced one of us (MK) to the world of particle simulation of rarefied gases and plasmas. Results of our collaborative work served as the foundation of a significant part of Chapter 5 dealing with modeling of plasma propulsion devices. The work on Hall thruster modeling and simulation would not be possible without the experimental insight and experience of Yevgeny Raitses with whom we have long-term collaboration of various aspects of plasma propulsion physics and most recently plasma-based nanotechnology. Our long-term collaboration with Nathaniel Fisch produced many important results used in this book. One of us (MK) would like to thank Michael Schulman with whom we collaborated on fundamental aspects of high-current vacuum arc interrupters. Michael Schulman, Paul Slade, and Eric Taylor contributed greatly in developing models of the high-current vacuum arcs and the interruption process. The work on carbon arcs for synthesis of carbon nanotubes performed with Anthony Waas triggered our consequent work on the plasma-based nanotechnology. We are particularly very thankful to Igor Levchenko and Kostya (Ken) Ostrikov with whom we have long-term research collaboration on various topics related to plasma nanoscience and nanotechnology. Our joint work with Mary Ann Stepp on cold plasma–controlled cell migration planted seeds for development of the cold plasma application in medicine. Most recent work on cold plasma cancer therapy would be impossible without contributions from Barry Trink, Anthony Sandler, Jonathan Sherman, Alan Siu, and Jerome Canady. We are very grateful to Mikhail Shneider who contributed a lot to understanding on the cold plasma physics. Our great appreciation and thanks to our colleague Alexey Shashurin for his contribution to a number of original works described in this book. We are also grateful to our coauthors (in alphabetic order) Robert Aharonov, Erik Antonsen, Rodney Burton, Jean Luc Cambier, Yongjun Choi, Uros Cvelbar, Jeffrey Fagan, Alec Gallimore, Brian Gilchrist, Rafael Guerrero-Preston, Terese Hawley, Michael Kong, Mahadevan Krishnan, Richard Miles, Othon Monteiro, Anthony Murphy, Leonid Pekker, Frederick Phelan, Claude Phipps, Jochen Schein, Vladimir Sotnikov, Gregory Spanjers, and John Yim who made very significant contributions to the original publications used in this book. We are particularly grateful to our former and current graduate students Andrew Porwitzky, Minkwan Kim, Madhu Kundrapu, Jarrod Fenstermacher, Therese Suaris, Lubos Brieda, Jian Li, Taisen Zhuang, and Olga Volotskova who contributed to some original work used in the book.
Last but not least, we owe very special gratitude to our families for their support and encouragement.
November 2012