Plasma diagnostics Cambridge International Science Publishing Ltd. 7 Meadow Walk, Great Abington Cambridge CB1 6AZ United Kingdom Edited by A. A. Ovsyannikov and M. F. Zhukov www.cisp-publishing.com ISBN 1898326231 Cambridge International Science Publishing Plasma diagnostics Ovsyannikov and Zhukov PLASMA DIAGNOSTICS i ii PLASMA DIAGNOSTICS Editors A.A. Ovsyannikov Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow M.F. Zhukov Institute of Thermophysics, Suberian Division of Russian Academy of Sciences, Novosibirsk CAMBRIDGE INTERNATIONAL SCIENCE PUBLISHING iii Published by Cambridge International Science Publishing 7 Meadow Walk, Great Abington, Cambridge CB1 6AZ, UK http://www.cis-publishing.com First published March 2000 Reprinted 2005 © Cambridge International Science Publishing Conditions of sale All rights reserved. No part of this publication may be reproduced or trans- mitted in any form or by any means, electronic or mechanical, including pho- tocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 1 898326231 Translated by Victor Riecansky Production Irina Stupak Printed and bound by Lightning Source UK Ltd iv Part I SPECTRAL AND OPTICAL METHODS Chapter 1 ....................................................................................................... 1 SPECTRAL DIAGNOSTICS METHODS ................................................ 1 1.1 Integral relationships. Optical measurement circuits .................................... 4 1.2 Spectral emission line ...................................................................................... 16 1.3 Width and shift of spectral lines ..................................................................... 22 1.4 Continuous spectrum........................................................................................ 25 1.5 Kirchhoff law .................................................................................................... 27 1.6 Spectral absorption lines ................................................................................. 28 Chapter 2 ..................................................................................................... 32 KINETIC ENERGY, TRANSLATIONAL RELAXATION AND DOPPLER BROADENING OF LINES IN NON-EQUILIBRIUM PLASMA SPECTRA ............................................................................ 32 2.1 Introduction ...................................................................................................... 32 2.2 Determination of the type of velocity distribution of excited particles from spectral measurements ..................................................................................... 34 2.3 Velocity distribution of atoms and molecules in excited electronic states .. 35 2.4 Measurement of gas temperature from Doppler broadening of spectral lines ............................................................................................................................ 37 2.5 A simple model of relaxation of the mean kinetic energy. Effect of gas density ................................................................................................................ 41 2.6 Identification of excitation mechanisms ......................................................... 45 Chapter 3 ..................................................................................................... 50 OPTICAL ACTINOMETRY OF PLASMA............................................ 50 Chapter 4 ..................................................................................................... 59 LASER METHODS OF PLASMA DIAGNOSTICS ............................. 59 4.1 Introduction ...................................................................................................... 59 4.2 Interference examination of plasma using lasers .......................................... 59 4.3 Holographic plasma diagnostic methods ....................................................... 74 4.4 Plasma diagnostics on the basis of scattering of laser radiation ................. 95 Chapter 5 ................................................................................................... 127 SPECTROSCOPY OF GROUND ELECTRONIC STATES OF MOLECULES IN PLASMA USING TUNABLE LASERS......... 127 5.1 Diode spectroscopy ......................................................................................... 127 5.2 CALS spectroscopy ........................................................................................ 136 i Chapter 6 ................................................................................................... 147 DETERMINATION OF THE CONCENTRATION AND TEMPERA- TURE OF HEAVY PARTICLES FROM THE SPECTRA OF RAYLEIGH-SCATTERED LIGHT.................................................. 147 6.1 Introduction .................................................................................................... 147 6.2 Principles of the method ................................................................................ 147 6.3 Concentration and temperature of gas in flames and electric arc ............ 151 6.4 Plasma jet diagnostics .................................................................................... 155 6.5 Gas temperature in glow discharge .............................................................. 158 Chapter 7 ................................................................................................... 160 REFRACTOMETRIC PLASMA DIAGNOSTICS METHODS......... 160 7.1 Refractive index of plasma ............................................................................ 160 7.2 Plasma interferometry ................................................................................... 165 7.3 Shadow method ............................................................................................... 173 7.4 Diffraction interferometer based on IAB-451 shadow equipment for plasma investigations ................................................................................................... 177 7.5 Examination of the nature of the plasma flow ............................................. 181 7.6 Temperature measurements by the interferometric method ..................... 189 Chapter 8 ................................................................................................... 196 DIAGNOSTICS OF PLASMA FLOWS WITH A DISPERSED PHASE ...... 196 8.1 Introduction .................................................................................................... 196 8.2 Methods of measuring particle size .............................................................. 199 8.3 Measuring the flow and particle velocities .................................................. 203 8.4 Particle temperature ...................................................................................... 206 Chapter 9 ................................................................................................... 207 MEASURING THE PLASMA FLOW VELOCITY BY THE TRACER PARTICLE METHOD ....................................................................... 207 Part II PROBE METHODS Chapter 10 ................................................................................................. 219 ELECTRIC PROBES IN NON-EQUILIBRIUM PLASMA ............... 219 10.1 Introduction .................................................................................................. 219 10.2 Probe measurements of the energy distribution of electrons ................... 221 10.3 Determination of plasma parameters from probe measurements ........... 245 10.4 Selected problems of probe diagnostics ...................................................... 250 Chapter 11 ................................................................................................. 258 ELECTRIC PROBES IN CONTINUUM REGIME ............................ 258 11.1 Introduction ................................................................................................... 258 11.2 A system of equations and boundary conditions of the hydrodynamic theory of electric probes ................................................................................. 259 ii 11.3 Volt–ampere characteristics of probes under hydrodynamic regimes .... 266 11.4 Diagnostic methods ....................................................................................... 275 11.5 Special features of experimental procedure ............................................... 292 11.6 Comparison of theoretical and experimental results ................................ 294 11.7 Conclusion ..................................................................................................... 297 Chapter 12 ................................................................................................. 299 PROBE METHODS OF DIAGNOSTICS OF CHEMICALLY REACT- ING DENSE PLASMA ....................................................................... 299 12.1 Formulation of the problem and solution method ..................................... 300 12.2 Numerical solution results ........................................................................... 304 12.3 Experiments .................................................................................................. 305 12.4 Discussion of the results ............................................................................... 306 12.5 Electric probes in special conditions .......................................................... 312 12.6 Diagnostics of dense chemically reacting still plasma with electric probes with a modulated potential ............................................................................ 326 Chapter 13 ................................................................................................. 338 ELECTRIC AND THERMAL PROBES IN THE PRESENCE OF CHEMICAL REACTIONS IN NON-EQUILIBRIUM PLASMA. 338 13.1 Electric probe ............................................................................................... 338 13.2 Thermal probe .............................................................................................. 350 Chapter 14 ................................................................................................. 356 MEASUREMENTS OF THE ENTHALPY OF HIGH-TEMPERA- TURE GAS FLOWS ........................................................................... 356 14.1 Introduction .................................................................................................. 356 14.2 Main methods of measuring the enthalpy of ............................................. 357 high-temperature gas ........................................................................................... 357 14.3 Enthalpy sensors and probes ....................................................................... 363 14.4 Sensitivity of the enthalpy sensor and measurement error ...................... 381 14.4 Conclusions ................................................................................................... 385 Chapter 15 ................................................................................................. 386 PROBE MEASUREMENTS OF HEAT FLOWS IN PLASMA JETS386 15.1 Measurement procedure .............................................................................. 386 15.2 Determination of plasma temperature ....................................................... 390 Part III MACROSCOPIC DIAGNOSTICS Chapter 16 ................................................................................................. 394 METHODS OF EXAMINING THE SPATIAL STRUCTURE OF RADIO-FREQUENCY CAPACITANCE DISCHARGES ............. 394 16.1 Introduction .................................................................................................. 394 16.2 Specific features of producing, examining and using radio-frequency iii capacitance discharge plasma. Forms of existence of RFCD ..................... 395 16.3 Interpretation of volt–ampere characteristics of RFCD and their relationship with the spatial structure of the discharge .............................. 402 16.4 Constant electric fields in RFCD ................................................................ 415 16.5 Using the battery effect in examining RFCD ............................................ 427 16.6 Effect of the frequency of RF field on the structure of the discharge and plasma characteristics .................................................................................... 429 16.7 Active probing of RFCD using a constant electric current ...................... 434 16.8 The radial structure of the RF capacitance discharge ............................. 440 16.9 Optical methods of examining the spatial structure of the RF capacitance discharge .......................................................................................................... 445 16.10 Conclusions ................................................................................................. 448 Chapter 17 ................................................................................................. 449 WAVE BREAKDOWN IN DISTRIBUTED SYSTEMS ...................... 449 17.1 Introduction .................................................................................................. 449 17.2 History ........................................................................................................... 450 17.3 Transition processes ..................................................................................... 454 17.4 Generalised block diagram of experiment ................................................ 457 17.5 Spatial–time structure of breakdown waves. Effect of preliminary ionisation .......................................................................................................... 469 17.6 Electrodynamic processes in wave breakdown ......................................... 471 17.7 X-radiation during a wave breakdown ...................................................... 490 17.8 Initiation of laser radiation by the breakdown wave ............................... 494 17.9 Effect of the type of gas ............................................................................... 496 17.10 Current state of the theory of wave breakdown...................................... 497 17.11 Wave breakdown - a method of examining processes in plasma ........... 501 17.12 Conclusion ................................................................................................... 505 Chapter 18 ................................................................................................. 506 PROBE MEASUREMENTS OF POTENTIAL DISTRIBUTION IN DENSE PLASMA ................................................................................ 506 18.1 Special features of the method .................................................................... 506 18.2 Electric field of the high-current arc ......................................................... 510 18.3 Electric field in the laminar plasma jet of the electric arc plasma torch 515 18.4 The electric field of the plasma flow of a two-jet plasma torch...... 518 Part IV METHODS OF PROCESSING RESULTS AND AUTOMATION OF DIAGNOSTICS Chapter 19 ................................................................................................. 522 REDUCTION TO A UNIFORM LAYER IN AXISYMMETRIC OBJECTS ............................................................................................ 522 19.1 Smoothing experimental data ..................................................................... 522 iv 19.2 Numerical solution of Abel’s integral equation ......................................... 524 19.3 Numerical solution of the Volterra integral equation ............................... 527 19.4 Simplified reduction algorithms ................................................................. 532 Chapter 20 ................................................................................................. 538 RECONSTRUCTION OF VELOCITY DISTRIBUTION FUNCTIONS OF EMITTING PARTICLES FROM THE SHAPE OF THE CON- TOUR OF SPECTRAL LINES ......................................................... 538 Chapter 21 ................................................................................................. 545 AUTOMATION OF MEASUREMENTS IN PLASMA DIAGNOS- TICS...................................................................................................... 545 REFERENCES ......................................................................................... 549 INDEX ....................................................................................................... 577 v