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`ISB N 3-540-19462-2
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`9 783540 194620
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`TSMC-1215
`TSMC v. Zond, Inc.
`Page 1 of 25
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`Yuri P. Raizer
`»
`Gas Discharge Physics
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`TSMC-1215 / Page 2 of 25
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`
`
`Yuri P. Raizer
`
`
`
`Gas Discharge Physics
`
`With 209 Figures
`
`
`
`Springer
`
`Springer
`
`Heidelberg
`New York
`Barcelona
`
`Budapest
`Hong Kong
`London ~
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`Santa Clara
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`TSMC-1215 / Page 3 of 25
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`
`
`Professor Dr. Yuri P. Raizer
`The Institute for Problems in Mechanics, Russian Academy of Sciences,
`Vernadsky Street 101, 117526 Moscow, Russia
`
`.
`Dr. Iohn E. Allen
`Department of Engineering Science, University of Oxford, Parks Road,
`Oxford OX1 3P], United Kingdom
`'
`'
`
`Translator:
`
`Dr. Vitaly I. Kisin
`24 Varga Street, Apt. 9, 117133 Moscow, Russia
`
`
`
`This edition is based on the original second Russian edition: Fizika gazovogo razryada
`© Nauka, Moscow 1987, 1992
`
`1st Edition 1991
`Corrected 2nd Printing 1997
`
`ISBN 3-540-19462-2 Springer-Verlag Berlin Heidelberg New York
`
`Library of Congress Cataloging—in-Publication Data.
`Raizer, II}. P. (lllrii Petrovich) [Fizika gazovogo razriada. English] Gas discharge physics / Yuri P.
`Raizer. p. cm. “Corr. printing i997” — t.p. verso. Includes bibliographical references and index.
`ISBN 3-540-19462-2 (hardcover: alk. paper)
`1. Electric discharges through gases. 1. Title.
`QC711-R22713
`1997
`537.5’3-dc21 96-53988
`
`This work is subject to copyright. All rights are reserved, whether the whole or part of the material is
`concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broad-
`casting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of
`this publication or parts thereof is permitted only under the provisions of the German Copyright
`Law of September 9, 1965, in its current version, and permission for use must always be obtained
`from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law.
`© Springer-Verlag Berlin Heidelberg 1991
`Printed in Germany
`The use of general descriptive names, registered names, trademarks, etc. in this publication does not
`imply, even in the absence of a specific statement, that such names are exempt from the relevant pro-
`tective laws and regulations and therefore free for general use.
`
`as
`
`K.» 7 l
`A (‘$2 29 2”
`
`l
`
`l ‘3 C? ~22
`
`Preface
`
`Gas discharges are of interest to physicists and engineers in a number of fields.
`Several decades ago excellent textbooks were written by von Engel and Steen-
`beckv L°"b= Brow“: KaPtS0V and several other authors. These books faithfully
`served many generations of students, and specialists still refer to them. Never-
`theless, their usefulness does suffer from the time elapsed since publication: It
`is not that the material they present has become’ §'ib;'s'oll=,j:§eai1d irrelevant — this
`has happened to a very minor extent,
`atlall. Rathlélr, 'tli‘e"“s-iiibj,ect has greatly
`advanced both in scope and in depth, and its erriphases
`e somewhat shifted,
`Of course, new books have been written, mostly niond
`phs devdted to nanow
`branches of gas discharge physics. But these_booksgai"e’typically.intended for the
`specialist and not so much for the novice infithe fie~'ld.~.._.«+~'”""
`I The need for a new textbook that is understandable to a beginner in gas
`discharge physics, and that conveys the right amount of information (even more
`important: information of the right kind) making it also useful to the specialist is
`apparent. \V1th this in mind, our intention has been to produce a book that serves
`both as a textbook and a handbook.
`From an immense amount of material we -have selected, as best we could,
`
`the parts that are required for an understanding of the physics and those points
`that are most frequently needed in research. As a convenient and comprehensive
`volume, the book contains a maximum of useful data: experimental results, results
`of calculations, and reference data; formulas required for estimates have been
`reduced to a form suitable for computations.
`This work was published in Russian in 1987 as a substanfially larger volume
`The English edition has been abridged at the expense of ancillary material con-
`cerning collisions, elementary processes, plasma radiation, plasma diagnostics
`and other topics, though the chapters dealing with the central themes of discharge
`physics are retained in full, and even expanded by the addition of new data
`We have decided not to cover actual circuits, techniques, or methods (we will
`;(::roth<;.hideas, though) of experimentsand measurements; instead we concen-
`_n
`6 physics of the processes of interest. Purely technical applications of
`gas discharges are not discussed for the same reason.
`sucllta:0ilI11l1C1lnlé:1s1:l1p0‘:Si:;)l6 to givefa comprehensive bibliography when ‘covering
`when r
`ly
`e scope 0 topics, hence, original papers are cited only
`ecent resu ts are discussed. In all other cases we refer to a book or review
`
`TSMC-1215 / Page 4 of 25
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`
`
`The author is deeply grateful to Professors A. V. Eletsky and L. D. Tsendin,
`who read the Russian version of the manuscript, and Professor J. E. Allen, who
`read the English for a number of useful comments. In addition, theauthor would
`like to thank the translator, Dr. V. I. Kisin, for a fruitful collaboration.
`
`Moscow April 1991
`
`Yu'P' Rail”
`
`
`
`Contents
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`1.
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`Introduction
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`1.1 What Is the Subject of Gas Discharge Physics
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`1.2
`Typical Discharges in a Constant Electric Field
`1.3
`Classification of Discharges
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`1.4
`Brief History of Electric Discharge Research
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`1.5 Organization of the Book. Bibliography .
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`2. Drift, Energy and Diffusion of Charged Particles
`in Constant Fields
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`2.1 Drift of Electrons in a Weakly Ionized Gas
`2.2
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`Electron Energy .
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`2.4 Diffusion of Electrons
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`2.6 Ambipolar Diffusion
`2.7
`Electric Current in Plasma in the Presence
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`of Longitudinal Gradients of Charge Density
`2.8 Hydrodynamic Description of Electrons .
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`Interaction of Electrons in an Ionized Gas
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`3.1
`The Motion of Electrons in Oscillating Fields
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`Electron Energy .
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`3.3
`Basic Equations of Electrodynamics of Continuous Media .
`3.4
`High—Frequency Conductivity
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`and Dielectric Permittivity of Plasma .
`Propagation of Electromagnetic Waves in Plasmas
`Total Reflection of Electromagnetic Waves
`from Plasma and Plasma Oscillations .
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`4. Production and Decay of Charged Particles
`4.1
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`4.2 Other Ionization Mechanisms
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`TSMC-1215 / Page 5 of 25
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`
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`Glow Discharge Instabilities and Their Consequences
`9.1
`Causes and Consequences of Instabilities .
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`9.2 QuasisteadyParameters
`9.3
`Field and Electron Temperature Perturbations
`in the Case of Quasisteady—State Te
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`Some Other Frequently Encountered Destabilizing Mechanisms
`9.7
`Striations
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`Arc Discharge
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`10.3 Arclnitiation
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`Positive Column of High—Pressure Arc (Experimental Data)
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`Plasma Temperature and V — 2' Characteristic
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`10.
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`. Electric Probes
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`Theoretical Foundations of Electronic Current Diagnostics
`of Rarefied Plasmas
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`Essential Characteristics of the Phenomenon . .
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`Breakdown and Triggering of Self-Sustained Discharge
`in a Constant Homogeneous Field at Moderately Large Product
`of Pressure and Discharge Gap Vlfidth
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`Placed in an Electric Field
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`oftheDistributionFunction
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`Validity Criteria for the Specuum Equation .
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`Stationary Spectrum of Electrons
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`7.5 Optical Breakdown
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`8.1
`General Structure and Observable Features
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`Between Electrodes
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`8.3 Dark Discharge and the Role Played by Space Charge
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`8.7 Heating of the Gas and Its Effect
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`ll. Sustainment and Production of Equilibrium Plasma
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`by Fields in Various Frequency Ranges
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`Introduction. Energy Balance in Plasma . . . .
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`11.2 Arc Column in a Constant Field . . . .
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`11.3 Inductively Coupled Radio-Frequency Discharge
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`11.4 Discharge in Microwave Fields . .
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`11.5 Continuous Optical Discharges
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`11.6 Plasmatronsz Generators of Dense Low—Temperature Plasma .
`12. Spark and Corona Discharges
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`12.1 General Concepts
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`12.2 Indjvidu31 Electron Avalanche
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`12.3 Concept of Streamers .
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`12.4 Breakdown and Streamers in Electronegative Gases (Air)
`in Moderately Vlfide Gaps with a Uniform Field .
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`12.5 Spark Channel
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`12.6 Corona Discharge .
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`12.7 Models of Streamer Propagation . .
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`12.8 Breakdown in Long Air Gaps
`with Strongly Nonunifoim Fields (Experimental Data)
`12.9 Leader Mechanism of Breakdown of Long Gaps
`. .
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`12.10 Return Wave (Return Stroke)
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`12.11 Lightning
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`12.12 Negative Stepped Leader
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`1
`1
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`1
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`14. Discharges in High.p¢we,- Cw C02 Lasers
`14.1 Principles of Operation of Electric—Discharge C02 Lasers
`14.2 Two Methods of Heat Removal from Lasers
`.
`14.3 Methods of Suppressing Instabilities
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`14.4 Organization of Large-Volume Discharges
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`Invoking Gas pumping _
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`t
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`Appendix . . .
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`References . .
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`Subject Index . .
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`. . . ..
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`415
`415
`417
`421
`425
`433
`439
`447
`
`288
`288
`290
`291
`299
`306
`315
`324
`324
`328
`334
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`338
`343
`345
`352
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`359
`363
`368
`370
`375
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`78
`378
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`385
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`387
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`396
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`400
`403
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`408
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`41.3
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`13. Capacitively Coupled Radio-Frequency Discharge
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`13.1 Drift Oscillations of Electron Gas . . .
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`. .
`13.2 Idealized Model of the Passage of High-Frequency Current
`.
`Through a Long Plane Gap at Elevated Pressures
`.
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`. . .
`13.3 V — i Characteristic of Homogeneous Positive Columns
`. .
`13.4 Two Forms of CCRF Discharge Realization
`.
`and Constant Positive Potential of Space: Experiment
`13.5 Electrical Processes in a Nonconducting Electrode Layer
`and the Mechanism of Closing the Circuit Current
`. .
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`13.6 Constant Positive Potential
`.
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`of the Weak-Current Discharge Plasma
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`13.7 High—Current Mode
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`.6 .
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`13.8 The Structure of a Medium—Pressure Discharge:
`Results of Numerical Modeling
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`13.9 Normal Current Density in Weak—Current Mode
`and Limits on the Existence of this Mode . .
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`
`TSMC-1215 / Page 7 of 25
`
`
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`
`
`1. Introduction
`
`1.1 What Is the Subject of Gas Discharge Physics
`
`The term “gas discharge’; originates with the process of discharge of a capacitor
`into a circuit incorporating a gap between electrodes. If the voltage is sufficiently
`high, electric break down occurs in the gas and an ionized state is formed. The
`circuit is closed and the capacitor discharges. Later the term “discharge” was
`applied to any flow of electric current through ionized gas, and to any process of
`ionization of the gas by the applied electric field. As gases ionized to a sufficient
`degree emit light, it has become customary to say that a discharge “lights up,”
`or is “buming.”
`As a rule, the flow of electric current is associated with the notion of a circuit
`composed of conductors. Actually, a closed circuit or electrodes are not needed
`for a directed motion of charges (electric current) in rapidly oscillating elec-
`tric fields, and even less so in the field of electromagentic radiation. However,
`quite a few effects observed in gases subjected to oscillating electric fields and
`electromagnetic waves (breakdown, maintaining the state of ionization, dissipa-
`tion of energy of the field) are not different, in principle, from dc phenomena.
`Nowadays all such processes are" referred to as discharges and included within
`gas discharge physics. The fact that electric current flow in open circuits in the
`field of electromagnetic waves is of no general significance. In such cases, the
`dissipation of the energy of the field is described not as the release of the Joule
`heat by electric current, but as the absorption of radiation.
`The modem field of gas discharge physics is thus occupied with processes
`connected with electric currents in gases and with generating and maintaining
`the ability of a gas to conduct electricity and absorb electromagnetic radiation.
`Gas discharge physics covers a great variety of complex, multi-faceted phe-
`nomena; it is full of an enormous amount of experimental facts and theoretical
`models. Before we begin their analysis, it is expedient to single out the main
`types of discharge processes and clarify them.
`
`1.2 Typical Discharges in a Constant Electric Field
`
`A relatively simple experiment introduces us to several fundamental types of
`
`TSMC-1215 / Page 8 of 25
`
`
`
` plasma is very weakly ionized, to :5 -_- 10-8 __10—5 ( h
`
`d
`,
`of ionized atoms), and is nonequilibrium in two X-,s;I;; gllgzsogletfl11’action
`energy directly from the field have a mean energy E z lell and a rein attset
`1; m 104K. The temperature T of the gas, including the ions is ntilerguéfi
`higher than the ambient temperature of 300K This state with widel
`se
`ed
`616011011 and gas temperatures, is sustained by a low rate of Joule hy
`parat
`under conditions of relatively high specific heat of the gas and h‘ heat release
`natural Cooling. Also as a result of the high rate of char e ne
`tale of us
`cold gas, its degree of ionization is many orders of ma gimdeul
`ization in a
`thermodynamic equflibfium Value °°m‘—SP0nding to the efielbuon te(r)riVp:r afltiiar: the
`If the
`re
`‘
`ch
`'
`-
`.
`r
`'
`sistance of)th:Sl::tel:1na1 e-gas.1s.h1gh (ab°ut.thc atmospheric level) and ‘he F6-
`. Clfclllt IS low (the circuit allows the passa e
`h‘
`f
`current), an arc discharge usually develops soon after breakdow Afi 0 a‘
`lgh
`burn at a high current (i > lA) at a low VOl[3gg of several
`11.
`fps typically
`form a bright column. The are releases large thermal
`oweiertllf (t) volts; they
`the glass tube: Arcs are often started in open air‘ Atr:0spheficapf;:ur:st;oY
`usually form th
`od
`‘
`-
`-
`-
`'
`'
`cs
`1
`)
`_th °1'm~ Ynamlc C4q111l1bI'1um plasmas (the so—called low-temperature
`p asma , wi
`Te ~ T w 10 K and the ionization of :e = 10—3 . 10-1
`rcspondlng to such temperatures. The are discharge differs essentiaTl
`fro cor-
`glow discharge in the mechanism of electron emission from the c thgd m the
`is vital for the flow of dc current of the are In the glow disch;
`cl whlch
`are knockcd fl.
`th
`‘
`_
`gf. e ectrons
`the arc dischar(g:n theelisilglifaffrrztfttfllie cold metal by Impacts of Po-smve ionS' In
`devclolm
`eats “P ‘h3 °3th0d6.and thermionic emission
`’
`If 12 ~ latrn the interelectrode gap L > 10 cm and
`‘
`.
`,
`th
`1
`'
`.
`’
`high, sparking occurs. The breakdown in the gap develops?/b‘yor2tta ls csiiftfihclcfnttlliy
`Plasma channel from one electrode to another. Then the electrodgs a: as if ghorte
`circuited b
`th
`1
`'
`'
`.
`.
`‘
`are a charged Elcirtirdmagricl $21263 sléafl-C chapel‘ Llghmmg’ whose “°1°°”°d°3”
`Finally’ a corona discharge ms: 1:11;v,e1l(S) a'grant variety of the spark discharge.
`i
`-
`y
`_P 1“ 5301181)’ nonumforrn fields that are
`-
`21 appears at s aip
`nsufficient for the breakdown of the entire gap‘ A radiant coron
`h
`ends of wires at sufficientl
`'
`y high Volta
`d
`-
`-
`_
`line conductors.
`gc an also around power mmsmlsslon
`
`1.3 Classification of Discharges
`
`~
`.
`.
`Dischar
`'
`dc
`.ClCClI'1C field can be classified into (a) non—self—sustaining
`and b ges in a .
`( ) Self-Sustaining types. The latter are more wides read
`dj
`'
`and richer in physical effects; and they are the Subbct OE; th. ’ SHOE’ Vcrslfifid.
`quasi-steady se1f—sustaining discharges contain (1) Jglow and1s(2)o:I Slteagy and
`we hav ah. d
`.
`.
`sc arges.
`e
`ea y mentioned in Sect. 1.2 that the cathode processes of two types
`differ '
`'
`'
`1
`-
`.
`
`_.
`
`
`
`Fig. 1.1. Typical gas discharge tube
`gases at different pressures. The quantities measured in the experiment are the
`voltage between the electrodes and the current in the circuit. This classical device
`served the study of discharge processes for nearly 150 years, and still remains
`
`If a low voltage is applied to the electrodes, say several tens of volts, no
`a supersensitive instrument would record
`visible effects are produced, although
`order of 10"” A. Charges are generated in the
`an extremely low current, on the
`'oactivity. The field pulls them to the opposite-
`gas by cosmic rays and natural ra
`current. If the gas is intentionally irradiated by a
`sign electrodes, producing a
`a current of up to 1()“6 A can be produced. The
`ra 'oactive or X—ray source,
`all to make the gas emit light. A dis-
`resultant ionization is nevertheless too sm
`y while an external ionizing agent
`charge and an electric current that survive onl
`or the emission of electrons or ions from electrodes is deliberately maintained
`—self-sustaining. As the voltage is
`(e.g. by heating the cathode) are said to be non
`because most of the charges
`raised, the non-self-sustaining current first increases
`produced by ionization are pulled away to electrodes before recombination oc-
`all new charges, the current ceases
`curs. However, if the field manages to remove
`to grow and reaches saturation, being limited by the rate of ionization.
`As the voltage is raised further, the current sharply increases at a certain value
`of V and light emission is observed These are the manifestations of breakdown,
`one of the most important discharge processes. At pressure p ~ lTorr and in-
`terelectrode gap L ~ lcm, the breakdown voltage is several hundred volts.
`Breakdown starts with a small number of spurious electrons or electrons injected
`intentionally to stimulate the process: The discharge immediately becomes self-
`sustaining. The energy of electrons increases while they move in the field. Hav-
`ing reached the atomic ionization potential, the electron spends this energy on
`knocking out another electron. Two slow electrons are thus produced, which go
`on to repeat the cycle described above. The result is an electron avalanche, and
`electrons proliferate. The gas is appreciably ionized in 10‘7 to l0‘3 s, which is
`sufficient for the current to grow by several orders of magnitude.
`Several conditions determine how the process develops at higher voltage.
`At low pressure, say 1 to 10Torr, and high resistance of the external circuit (it
`prevents the current from reaching a large value), ‘a glow discharge develops.
`This is one of the most frequently used and important types of discharge. It is
`characterized by low current, i ~ 10"‘ — 10*‘ A in tubes of radius R ~ 1 cm, and
`fairly high voltage: hundreds to thousands of volts. A beautiful radiant column,
`uniform along its length, is formed in sufficiently long tubes of, say, L ~ 30 cm at
`
`TSMC-1215 / Page 9 of 25
`
`
`
`worked in the Saint Petersburg Medical Surgery Academy in Russia, reported
`the discovery in 1803. The are was obtained by bringing two carbon electrodes
`connected to battery terminals into contact and then separating them. Several
`years later Humphrey Davy in Britain produced and studied the arc in air. This
`type of discharge became known as “arc” because its bright horizontal column
`between two electrodes bends up and arches the middle owing to the Archimedes’
`force. In 1831-1835, Faraday discovered and studied the glow discharge. Faraday
`worked with tubes evacuated to a pressure p ~ 1Torr and applied voltages up
`to 1000 V.
`The history of physics of gas discharges in the late 19th and early 20th
`centuries is inseparable from that of atomic physics. After Wflfiarn Crookes’s
`cathode ray experiments and J.J. Thomson’s measurements of the e/m ratio, it
`became clear that the current in gases is mostly carried by electrons. A great
`deal of information on elementary processes involving electrons, ions, atoms,
`and light fields was obtained by studying phenomena in discharge tubes.
`Beginning in 1900, J.S.E. Townsend, a student of J.J. Thomson and the cre-
`ator of a school in the physics of gas discharges discovered the laws governing
`ionization and the gaseous discharge (known as the Townsend discharge) in a uni-
`form electric field. Numerous experimental results were gradually accumulated
`on cross sections of various electron-atom collisions, drift velocities of electrons
`and ions, their recombination coefficients, etc. This work built the foundations
`of the current reference sources, without which no research in discharge physics
`would be possible. The concept of a plasma was introduced by I. Langmuir and
`L. Tonks in 1928. Langmuir made many important contributions to the physics
`of gas discharge, including probe techniques of plasma diagnostics.
`As regards difierent frequency ranges, the development of field generators
`and the research into the discharges they produce followed the order of increasing
`frequencies. Radio frequency (rf) discharges were observed by N. Tesla in 1891.
`This kind of discharge is easily produced if an evacuated vessel is placed inside
`a solenoid coil_ to which high-frequency voltage is applied. The electric field
`induced by the oscillating magnetic field produces breakdown in the residual
`gas, and discharge is initiated. The understanding of the mechanism of discharge
`initiation came much latter, in fact, after the work of J.J. Thomson in 1926-1927.
`Inductively coupled rf discharges up to tens of kW in power were obtained by
`G.I. Babat in Leningrad around 1940.
`The progress in radar technology drew attention to phenomena in microwave
`fields. S.S. Brown in the USA began systematic studies of microwave discharges
`in the late 1940s. Discharges in the optical frequency range were realized after
`the advent of the laser: A spark flashed in air when the beam of a ruby laser
`producing so—cal1ed giant pulses (of more than IOMW in power) was focused
`by a lens, this success being achieved in 1963.
`Continuously burning optical discharges, in which dense steady-state plasma
`
`Corona has common features with glow and dark discharges. Among transient
`discharges, the (5) spark discharge stands out sharply, among others.
`Many features of purely plasma processes, characterizing breakdown in a dc
`electric field, as well as the glow and are discharges, are typical for discharges in
`rapidly oscillating fields, where electrodes are not necessary at all. It is therefore
`expedient to construct a classification avoiding the attributes related to electrode
`effects, and the following two properties will be basic for the classification: the
`state of the ionized gas and the frequency range of the field. The former serves
`to distinguish between (1) breakdown in the gas, (2) sustaining nonequilibrium
`plasma by the field, and (3) sustaining equilibrium plasma. Frequency serves
`to classify fields into (1) dc, low-frequency, and pulsed fields (excluding very
`short pulses), (2) radio—frequency fields (f ~ 105 —- 103 Hz), (3) microwave
`fields (f ~ 109 -— 10“ Hz, /\ ~ 102 — l0‘1cm), and (4) optical fields (far from
`infrared to ultraviolet light). The field of any subrange can interact with each
`type of discharge plasma. In total, we have 12 combinations. All of them are
`experimentally realizable, and quite a few are widely employed in physics and
`technology. Typical conditions under which each of the combinations can be
`observed are summarized in Table 1.1.
`'
`
`Table 1.1. Classification of discharge processes
`Breakdown
`Noncquilibrium plasma
`Equilibrium plasma
`
`
`
`Constant electric
`
`Initiation of glow
`discharge in tubes
`
`Positive column of glow
`discharge
`
`Positive column of high-
`pressure are
`
`Radio frequencies
`
`Initiation of If discharge
`in vessels filled with
`rarefied gases
`
`Capacitivcly coupled rf
`discharges in rarefied
`gases
`
`Inductively coupled
`plasma torch
`’
`4,,
`
`Microwave range
`
`Breakdown in waveguides Microwave discharges irt Microwave plasrnatron
`and resonators
`rarefied gases
`
`
`
`Gas breakdown by laser
`radiation
`
`Final stages of optical
`breakdown
`
`Continuous optical
`discharge
`
`1.4 Brief History of Electric Discharge Research
`
`Leaving lightning aside, man’s first acquaintance with electric discharges was
`the observation, dating back to 1600, that friction-charged insulated conductors
`lose their charge. Coulomb proved experimentally in“ 1785 that charge leaks
`through air, not through imperfect insulation. We understand now that the cause
`of leakage is the non—self-sustaining discharge.
`Occasional experiments were conducted in the 18th century with sparks pro-
`duced by charging a body by an electrostatic generator, and with atmospheric
`
`TSMC-1215 / Page 10 of 25
`
`
`
`microwave and optical discharges have by now been studied with at least the
`same thoroughness that the discharges in constant electric fields has been during
`nearly 100 years of research.
`The physics of the glow discharge, one of the oldest and, presumably, best-
`studied fields, has lived through an unparallel revival in the past 15-20 years,
`and numerous new aspects of this phenomenon have been revealed. This surge
`of attention was stimulated by the use of glow discharges in electric-discharge
`CO2 lasers developed for the needs of laser technologies. Likewise, the applica-
`tion of plasmatrons (generators of dense low—temperature plasma) to metallurgy,
`plasma chemistry, plasma welding and cutting, etc. provided a stimulus for new
`extensive, detailed studies of arc plasma at p ~ latm, T ~ 104 K, and of similar
`discharges in all frequency ranges. These, and many other practical applications
`of gas discharge physics place it within the range of sciences that lie at the
`foundation of modem engineering.
`
`1.5 Organization of the Book. Bibliography
`
`A long-standing tradition demands that a general-type book on gas discharges
`begin with a discussion of elementary processes: possible types of collisions of
`electrons and ions with atoms and molecules, the fundamentals of kinetic theory
`of gases, statistical physics, theory of radiation, and so forth. In this book, we
`mostly ignore these topics, wishing to use to maximum effect the severely limited
`space; besides, these topics “are well represented in the literature, including some
`general textbooks. The reader is expected to have mastered a university general
`physics course, although some required information is cited in direct relation to
`processes to be studied.
`The book starts by describing the behaviour of char