GASEOUS IONIZATION AND ION TRANSPORT: An …

1 GASEOUS IONIZATION AND IONTRANSPORT: An Introduction to Gas DischargesProf. David B. GoDepartment of Aerospace and Mechanical EngineeringUniversity of Notre DameNotre Dame, IN 46556 March 19, 2012 Chapter 1 PrefaceGas-phase ions are ubiquitous in the universe, and are often cited as making up more than 99 % ofknown matter [REF-Burnett] in the universe - all stars, for example are in a plasma state consisting ofgaseous ions and electrons. However, in every day life on Earth, GASEOUS ions are not as common andcertainly not understood by the general public.

2 If you were to take a poll of the general populationabout engineering and science topics, nearly everyone would understand what robotics is and mostwould likely be able to surmise, on some level, what an aerospace engineer does. In fact, most peoplecan probably identify that a car is more aerodynamically sound than a truck. However, if you askthe general population what the plasma in plasma television stands for, they would not be able totell you. Further, most scientists and engineers do not really understand either as plasma science andtechnology is not a common subject covered by undergraduate students most core disciplines suchas mechanical engineering, biochemistry, or materials science.

3 But plasma science is an incrediblyimportant field. Besides entertainment (the aforementioned plasma television), plasmas and theirclosely related cousin, gas discharges, have been instrumental in modern life, affecting everythingfrom the computer revolution to everyday lighting and transportation. Plasma processing, suchas reactive ion etching and sputter metal deposition, has been essential to the development of themodern day computer chip. Automobiles are started by spark plugs, which are, at their heart,gas discharges.

4 Fluorescent lighting and the more recent, energy-efficient compact fluorescent lightbulbs found in most homes are gas-discharge lamps. The list could really go on and on, fromprinters to air filters, from analytical chemistry to manufacturing, plasmas and gas discharges havea profound impact on modern life. Even today, there are promising developments in plasma sciencesuch as atmospheric plasma jets for killing tumors and healing wound, microplasma arrays for highefficiency lighting, and plasma thrusters for more efficient space travel.

5 Regardless of how wellappreciated plasma science is, it continues to be relevant in a wide-variety of technologies as well asa field of active research and fundamental purpose of this text is to introduce graduate-level engineering and science students to thefundamentals of GASEOUS IONIZATION and ion transport in order to (a) expand their understanding ofthe physics behind many key technologies today and (b) prepare them to conduct research both intheir graduate career and beyond. At the conclusion of this book, the reader should understandwhat an ion is, common methods of generating ions , methods of manipulating their motion, and thebasic properties of some of the more common discharges used today.

6 Additionally, this book willintroduce some choice applications that are of high interest to author as well as emerging topics thatwill be shaping research in the near and long-term future. That, in sum, is essentially what this bookis. It would be prudent, however, to also address what this book isn t. This book is not a plasmaiiiphysics book, and it is not meant to cover all aspects of plasma physics. In fact, if such a bookexisted that covered all aspects of plasma physics, it would be both extremely dense and extremelylarge.

7 Rather, this book is focused on specific concepts that are important tonon-equilibrium, lowtemperaturedischarges. These discharges find wide applicability today and are of significant interestin the scientific know of no single book that covered all the topics I am interested in, in the depth I aminterested in. Therefore, I pulled information from many sources - both textbooks and journalarticles. However, because this is essentially a formal collection of class notes, I do not cite thesereferences especially well.

8 Therefore, I d like to acknowledge these five books that I found especiallyuseful in putting together this manuscript:1. Fundamentals of GASEOUS IONIZATION and Plasma Electronics, E. Nasser, Wiley-Interscience/NewYork, Gas Discharge Physics, Y. P. Raizer, Springer-Verlag/Brelin, Principles of Plasma Discharges and Materials Processing, 2nd ed., M. A. Lieberman and Lichtenberg, Wiley-Interscience/New York, Non Equilibrium Air Plasmas at Atmospheric Pressure, edited by: K. H. Becker, U. Kogelschatz,K.

9 H. Schoenbach, and R. J. Barker, Institute of Physics Publishing/Philadelphia, Low Temperature Plasmas: Fundamentals, Technologies, and Techniques, 2nd ed., edited by:R. Hippler, H. Kersten, M. Schmidt, and K. H. Schoenbach, Wiley-VCH/Weinheim, book is a living document, meaning that it will be updated, modified, and corrected aslong as I continue to study and teach in this field. Those readers who stumble across this documentand find errors, please do send them to me as they are unavoidable. Those who wish to use thistext to support their research, appropriate citation would be appreciated.

10 Suggestions on ways toimprove it are most regards,David B. Go Prefacei2 Classification of Gas Discharges .. 2I Ionization43 Overview54 GASEOUS GASEOUS Reactions .. Elastic Collisions .. Excitation Collisions .. IONIZATION Collisions .. Collisions Summary .. Electron Impact IONIZATION - The Process .. IONIZATION Frequency .. Temporal Electron Avalanche .. Spatial Electron Avalanche .. Townsend s First IONIZATION Coefficient .. Ion Impact IONIZATION - The Process.