Physics of Plasma-Wall Interactions in Controlled Fusion

Transcription

1 Physics of Plasma-Wall Interactions in Controlled Fusion

2 NATO ASI Series Advanced Science Institutes Series A series presenting the results of activities sponsored by the NA TO Science Committee, which aims at the dissemination of advanced scientific and technological knowledge, with a view to strengthening links between scientific communities. The series is published by an international board of publishers in conjunction with the NATO Scientific Affairs Division A Life Sciences B Physics C Mathematical and Physical Sciences o Behavioral and Social Sciences E Engineering and Materials Sciences F Computer and Systems Sciences G Ecological Sciences Plenum Publishing Corporation New York and London D. Reidel Publishing Company Dordrecht, Boston, and Lancaster Martinus Nijhoff Publishers The Hague, Boston, and Lancaster Springer -Verlag Berlin, Heidelberg, New York, and Tokyo Recent Volumes in this Series Volume 126-Perspectives in Particles and Fields: Cargese 1983 edited by Maurice Levy, Jean-Louis Basdevant, David Speiser, Jacques Weyers, Maurice Jacob, and Raymond Gastmans Volume 127-Phenomena Induced by Intermolecular Interactions edited by G. Birnbaum Volume 128-Techniques and Concepts of High-Energy Physics III edited by Thomas Ferbel Volume 129-Transport in Nonstoichiometric Compounds edited by George Simkovich and Vladimir S. Stubican Volume 130-Heavy Ion Collisions: Cargese 1984 edited by Paul Bonche, Maurice Levy, Philippe Quentin, and Dominique Vautherin Volume 131-Physics of Plasma-Wall Interactions in Controlled Fusion edited by D. E. Post and R. Behrisch Volume 132-Physics of New Laser Sources edited by Neal B. Abraham, F. T. Arecchi, Aram Mooradian, and Alberto Sona Series B: Physics

3 Physics of Plasma-Wall Interactions in Controlled Fusion Edited by D. E. Post Princeton University Plasma Physics Laboratory Princeton, New Jersey, USA and R. Behrisch Max-Planck-Institut for Plasmaphysik Garching/Munich, Federal Republic of Germany Plenum Press New York and London Published in cooperation with NATO Scientific Affairs Division

4 Proceedings of a NATO Advanced Study Institute entitled Physics of Plasma-Wall Interactions in Controlled Fusion, held July 30-August 10, 1984, in Val-Morin, Quebec, Canada Library of Congress Cataloging in Publication Data NATO Advanced Study Institute (1984: Val-Morin, Quebec) Physics of plasma-wall interactions in controlled fusion. (NATO ASI series. Series B, Physics; v. 131) "Published in cooperation with NATO Scientific Affairs Division." "Proceedings of a NATO Advanced Study Institute entitled Physics of Plasma-wall Interactions in Controlled Fusion, held July 30-August 10, 1984, Val-Morin, Quebec, Canada"-Verso t.p. Includes bibliographical references and index. 1. Plasma-wall interactions-congresses. 2. Controlled fusion-congresses. I. Post, D. E. (Douglas Edmund), II. Behrisch, Rainer. III. North Atlantic Treaty Organization. Scientific Affairs Division. IV. Title. V. Series. QC P5N ' ISBN / ISBN (ebook) 1986 Plenum Press, New York Softcover reprint of the hardcover 1 st edition 1986 A Division of Plenum Publishing Corporation 233 Spring Street, New York, N.Y All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher

5 PREFACE Controlled thermonuclear fusion is one of the possible candidates for long term energy sources which will be indispensable for our highly technological society. However, the physics and technology of controlled fusion are extremely complex and still require a great deal of research and development before fusion can be a practical energy source. For producing energy via controlled fusion a deuterium-tritium gas has to be heated to temperatures of a few 100 Million c corresponding to about 10 kev. For net energy gain, this hot plasma has to be confined at a certain density for a certain time One promising scheme to confine such a plasma is the use of i~tense magnetic fields. However, the plasma diffuses out of the confining magnetic surfaces and impinges on the surrounding vessel walls which isolate the plasma from the surrounding air. Because of this plasma wall interaction, particles from the plasma are lost to the walls by implantation and are partially reemitted into the plasma. In addition, wall atoms are released and can enter the plasma. These wall atoms or impurities can deteriorate the plasma performance due to enhanced energy losses through radiation and an increase of the required magnetic pressure or a dilution of the fuel in the plasma. Finally, the impact of the plasma and energy on the wall can modify and deteriorate the thermal and mechanical properties of the vessel walls. The subject of this NATO advanced Study Institute is the physics and technology important for control of the plasma-wall interaction. Research in this field has been important since the beginning of fusion research. Wall released impurities have always been a major concern in each experiment and considerable effort has been devoted to this problem. In the 1950's and 1960's the fusion community was one of the driving forces in the advance of ultra high vacuum technology. Metallic vacuum vessel walls have replaced glass and wall cleaning techniques have been developed. For reducing and controling the plasma wall interaction, limiters and divertors have been introduced. v

6 Further, fusion research has stimulated a high level of fundamental research in the interaction of energetic particles with solid surfaces. Significant progress has been made in understanding and characterizing the basic processes such as sputtering, ion reflection, trapping and desorption. Complementary theoretical models and computer codes have been d~veloped to understand and predict the properties of the boundary plasma. Only a detailed understanding of all these processes will allow practical systems for particle and impurity control to be designed, tested and built for the forthcoming machines. Over the last 5 years, the field has matured considerably. There have been substantial developments in the basic science, in theory and modelling of plasma wall interaction processes, and in the experimental application of impurity control techniques. Particularly noteworthy has been the development of the "high recycling" divertor and the pumped limiter, which offers promising solutions to the particle and impurity control problem. The aim of this NATO Advanced Study Institute was to present a comprehensive set of lectures on all the major aspects of the plasma-wall interaction problem. The Institute begins with lectures covering the basic processes and science, then covers theory and modelling, applications in current experiments, and summarizes with the design aspects for future experiments. In addition to the lectures printed in this volume, approximately 35 participants presented their work in two poster sessions. The Institute was held in the Auberge Far Hills Inn in Val Morin, Quebec, Canada, near Montreal, from July 30 to August 10, We would like to express our gratitude to the NATO Scientific Affairs Division for its support, which allowed the meeting to take place, and to Dr. Craig Sinclair of NATO for his advice and encouragement. The Institute was further supported by the Canadian Material Research Council (NCR), the Natural Sciences and Engineering Research Council of Canada (NSERC), the U.S. Department of Energy, INRS Energy, University of Quebec, and the Princeton University Plasma Physics Laboratory. In particular, Dr. Charles Daughney of the Canadian NRC and Dr. Erol Oktay of the US Department of Energy were very helpful. The members of the Scientific Organizing Committee, Dr. R. Conn, Dr. F. Engelmann, Dr. E. Hintz, Dr. G.M. McCracken, and Dr. B. Stansfield assisted in preparing and organizing the program of the lectures. We wish to thank all lecturers who not only gave excellent lectures but also prepared the manuscripts which comprise this book. Dr. D. Manos served as treasurer, handling the complicated funding arrangements from five different sources, two different banks and currencies, and widely diverse disbursements. vi

7 The conference secretary, Mrs. E. Carey, handled the applications, prepared much of the conference material, and helped to manage the conference. Mrs. Carol Phillips was the program secretary and organized the announcements, handled the preparation of the lecture notes for the Institute and assisted in running the meeting. She had a major role in editing the materials for this book. All of these contributions are great fully acknowledged. The local arrangements at the conference site and the local activities were very successfully organized by Dr. B. Stansfield, who headed the local committee of Dr. C. Boucher, Dr. K. Dimoff, Dr. B. Gregory, Dr. G. Ross, Dr. B. Terreault, Dr. J. Vitali, Dr. C. Neufield, and Dr. Tarasick, from the INRS-Energy, University of Quebec at Varennes. They contributed immensely to the success of the Advanced Institute. The hospitality and fine service of Mrs. L. Pemberton-Smith and her staff at the Auberge Far Hills Inn made the lectures go smoothly and made the conference a delightful experience for the conference organizers and the conference participants. We are also grateful to Prof. Charles Joachain of the University of Bruxelles, for the example he provided as Director in organizing another Advanced Study Institute on Atomic Processes in Fusion Plasmas for which D. Post served a co-director. D.E. Post R. Behrisch Directors of the Advanced Study Institute

8 CONTENTS Introduction to the Physics of Plasma Wall Interactions in Controlled Fusion... 1 D.E. Post, R. Behrisch, and B. Stansfield Introduction: Approaches to Controlled Fusion and Role of Plasma-Wall Interactions 15 F. Engelmann PLASMA PHYSICS The Plasma Sheath 41 P.C. Stangeby Plasma Flow in the Sheath and Presheath of a Scrape-off Layer. 99 R. Chodura Probes for Plasma Edge Diagnostics in Magnetic Confinement Fusion Devices 135 D.M. Manos and G.M. McCracken Plasma Edge Diagnostics using Optical Methods 211 P. Bogen and E. Hintz ATOMIC PHYSICS Atomic and Molecular Collisions in the Plasma Boundary 281 M.F.A. Harrison SURFACE PHYSICS Physical Sputtering of Solids at Ion Bombardment 351 J. Roth ix

9 Chemical Sputtering and Radiation Enhanced Sublimation of Carbon J. Roth Ion Backscattering from Solid Surfaces 413 R. Behrisch and W. Eckstein Implantation, Retention and Release of Hydrogen Isotopes in Solids 439 W. Moller and J. Roth Surfaqe Erosion by Electrical Arcs 495 R. Behrisch Electron Emission from Solid Surfaces 515 K. Ert1 and R. Behrisch BULK MATERIAL PROPERTIES Properties of Materials 539 M.F. Smith and J.B. Whitley FUSION EXPERIMENTS AND THEORY Plasma Transport near Material Boundaries 607 C.E. Singer Plasma Models for Impurity Control Experiments 627 D.E. Post and K. Lackner Neutral Particle Transport Heifetz Particle Confinement and Control in Existing Tokamaks 773 S.A. Cohen Limiters and Divertor Plates 855 M. U1rickson Advanced Limters 891 P. Mioduszewski Divertor Tokamak Experiments 931 F. Wagner and K. Lackner Plasma Wall Interactions in Heated Plasmas 1005 J. Tachon x

10 Plasma-Wall Interactions i~ Tandem Mirror Machines 1067 S.L. Allen and the TMX-U/MFTF-B Experimental Team Impurity Control Systems for Reactor Experiments 1101 D.E. Post and R.F. Mattas Lecturers Participants and Staff Index 1165