Foundations of vacuum science and technology

1121 Pages·1998·9.036 MB·English

by  J M Lafferty

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title : Foundations of Vacuum Science and Technology
author : Lafferty, J. M.
publisher : John Wiley & Sons, Inc. (US)
isbn10 | asin : 0471175935
print isbn13 : 9780471175933
ebook isbn13 : 9780585339368
language : English
subject Vacuum, Kinetic theory of gases.
publication date : 1998
lcc : QC166.F68 1998eb
ddc : 621.5/5
subject : Vacuum, Kinetic theory of gases.
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Page iii
Foundations of Vacuum Science and Technology
Edited By
James M. Lafferty

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This book is printed on acid-free paper.
Copyright © 1998 by John Wiley & Sons, Inc. All rights reserved.
Published simultaneously in Canada.
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means,
electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108
of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization
through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers,
MA 01923, [phone], fax [phone]. Requests to the Publisher for permission should be addressed to the
Permissions Department, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, [phone], fax
[phone], E-mail: PERMREQ @ WILEY.COM.
Library of Congress Cataloging in Publication Data:
Foundations of vacuum science and technology/edited by J. M. Lafferty.
p. cm.
"A Wiley-Interscience publication."
Includes bibliographical references and index.
ISBN 0-471-17593-5
1. Vacuum. 2. Kinetic theory of gases. I. Lafferty, J. M.
(James Martin), 1916.
QC166.F68 1997
¢
621.55dc21 96-29895
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1

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Preface
The industrial and scientific importance of vacuum technique has continued to grow during the past 30 years, even with
the demise of television and radio receiving tubes and many gas-filled tubes. The replacement of vacuum and low-
pressure gas discharge tubes by semiconductors and integrated circuits has placed an even greater demand and more
stringent conditions on vacuum technique for the processing and manufacture of these devices. This has led to the
development of a number of "dry" vacuum pumps to produce a "clean vacuum" free of hydrocarbons. The space
programs, high-energy accelerators, analytical instruments, freeze-drying of foods and drugs, and the manufacture of
color television picture tubes, incandescent and metal vapor lamps, high-power vacuum, and x-ray tubes all continue to
require the need for vacuum technique.
While the material in this book is totally new, it follows in the tradition set by Scientific Foundations of Vacuum
Technique by Saul Dushman, published in 1949. That book enjoyed unprecedented success and is now a classic in its
field. By 1960 it was badly in need of revision. This editor had the privilege of participating as editor of the revised
edition, which was published in 1962. This second edition was brought up to date by a number of contributors with
specialized knowledge in the disciplines involved. An attempt was made to introduce the new developments made in
vacuum technique but keep the original plan of the book and retain much of the material that was still of current interest.
The editor was encouraged by Leonard Beavis of the American Vacuum Society Education Committee and the
publishers of the previous editions to undertake the publication of the present volume. The advances made in vacuum
science and technology during the past three decades has required a complete reworking of the material in the previous
volume. However, every effort has been made to follow the unique style of the original bookthat is, to present a survey
of fundamental ideas in physics and chemistry that would be useful to both scientists and engineers dealing with
problems associated with the use, production, and measurement of high vacuums. This volume is a critical survey of
important developments in vacuum technique with many references for those who seek a better understanding and more
detailed information in the field. It is not a vacuum handbook, many of which are listed in the Appendix of this book.
Every effort was made to select on a worldwide basis a number of outstanding vacuum specialists who were willing to
take time to contribute to this volume. With

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Page vi
the curtailment of vacuum research in the major industrial laboratories, one now only finds vacuum experts as
independent consultants or in companies manufacturing vaccum systems and components, a few educational
institutions, and government laboratories.
While the basic laws of kinetic theory of gases have not changed over the years, a better understanding of gas flow over
a wide range of pressures has necessitated an expanded chapter on the subject. It now encompasses all flow regimes
from free molecular flow to atmospheric pressure. It treats compressible flow through tubes and orifices under choked
and nonchoked conditions as well as turbulent flow in ducts of any cross section.
Many topics that were only mentioned in the second edition of Scientific Foundations of Vacuum Technique now have
full chapters devoted to them. The progress made in vacuum pumps over the past three decades, for example, is
remarkable. Three chapters are now devoted to this subject. Detailed information is given for the first time on liquid
ring pumps, dry pumps, turbo pumps, getter pumps, and cryopumps.
The subject of leak detection, which had only a few paragraphs devoted to it in the old edition, now has a full chapter
describing leak detectors as a rugged industrial tool for everyday use capable of quantitative measurements.
Information on the design of high-vacuum systems has been expanded to help the reader in selecting pump sets for
various system applications and in predicting their performance.
Pressure measurements continue to be important on every vacuum system. This subject is fully covered in the chapter
on vacuum gauges. While the ionization gauge continues to be the principal pressure sensor for measuring total pressure
in high- and ultrahigh-vacuum systems, modern solid-state electronics has simplified its use. The accuracy of this
device in measuring pressure depends on a knowledge of the composition of the gas being measured. The partial
pressure analyzer has become a far more sophisticated way to measure pressure and give the vacuum system operator an
insight of what is occurring within the system. The invention of the quadrupole mass spectrometer with solid-state
electronics has done much to make partial pressure measurements relatively simple and inexpensive. A full chapter is
devoted to this subject.
In discussing pressure measurements, a word about pressure units seems appropriate. While use of the pascal, the ISO
unit of pressure, has been encouraged in this book, many of the European contributors strongly preferred using the
millibar (mbar). The mbar falls in a class of units that are temporarily accepted for use by the ISO. You will find both
units in this book. The advantage of the mbar is that it is nearly equal in magnitude to the Torr or mmHg found in earlier
publications and is familiar to many readers (1 mbar = 0.75 Torr). When several orders of magnitude of pressure are
plotted on a log scale, the mbar and Torr plots are nearly indistinguishable. Some of the figures in this book that have
been copied from earlier publications may still have the pressure plotted in Torr.
Ultrahigh-vacuum technique had its infancy in midcentury. Today it is a matured procedure used in a great variety of
applications and in commercially available equipment. Researchers do not appear to have reached a limit yet in their
quest to produce and measure a perfect vacuum. This work is described in the chapter devoted to ultrahigh and extreme
high vacuum. Considerable progress has been made in this area by pushing vacuum techniques to their limit and gaining
a better

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understanding of the gassurface interactions and diffusion in solids as described in the chapter on this subject. While
pressures as low as 1011 Pa have been measured in the laboratory, this is still at least three orders of magnitude higher
than that in interstellar space.
The final chapter is devoted to calibration and standards. It describes the physical background and state of the art of
today's primary vacuum standards in the various national laboratories. It should be useful reading not only for those
involved in calibration and quality control but for those interested in the accuracy limitations of various vacuum
instruments.
The editor is indebted to several people for suggestions concerning this volume. Special mention is made of the late
Hermann Adam for helpful discussions and for suggesting a number of German contributors for the book. John Weed, a
member of the American Vacuum Society Education Committee, solicited suggestions for the volume from a number of
A.V.S. members. Nigel Dennis coordinated chapters three and four on vacuum pumps, and Benjamin Dayton and Paul
Redhead have made many helpful suggestions.
J. M. LAFFERTY
SCHENECTADY, NEW YORK

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Contributors
Helmut Bannwarth, LEDERLE GmbH, Gundelfingen, Germany
Benjamin B. Dayton, Consultant, East Flatrock, North Carolina, USA
Nigel T. M. Dennis, Edwards High Vacuum International, Crawley, West Sussex, England
Johan E. de Rijke, Vacuum Technical Services, Morgan Hill, California, USA
Robert E. Ellefson, Leybold Inficon, Inc., East Syracuse, New York, USA
Bruno Ferrario, SAES Getters S.p.A., Lainate (Milano), Italy
Werner Grosse Bley, Leybold Vakuum GmbH, Cologne, Germany
Hinrich Henning, Leybold Vakuum GmbH, Cologne, Germany
Jörgen Henning, intervac Henning, GmbH, Kreuzwertheim, Germany
John B. Hudson, Materials Science and Engineering Department, Rensselaer Polytechnic Institute, Troy, New York,
USA
Karl Jousten, Physikalisch-Technische Bundesanstalt, Berlin, Germany
R. Gordon Livesey, Edwards High Vacuum International, Crawley, West Sussex, England
R. Norman Peacock, MKS Instruments, HPS Division, Boulder, Colorado, USA
Paul A. Redhead, Institute for Microstructural Sciences, National Research Council, Ottawa, Ontario, Canada
Wolfgang Schwarz, Leybold Systems GmbH, Hanau, Germany

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Contents
Preface v
Contributors ix
Acronyms xxiii
1. Kinetic Theory of Gases 1
Benjamin B. Dayton
2
1.1. Ideal Gas Law
6
1.2. Avogadro's Number
8
1.3. Molecular Collisions; Mean Free Path; MaxwellBoltzmann Distribution Laws
16
1.3.1. Relation Between Molecular Velocities and Velocity of Sound
17
1.3.2. Determination of Avogadro's Constant from Distribution of Particles in Brownian Motion
18
1.4. Gas Pressure and Rate at Which Molecules Strike a Surface
22
1.5. Rate of Evaporation and Vapor Pressure
26
1.6. Free Paths of Molecules
29
1.7. Relation Between Coefficient of Viscosity, Mean Free Path, and Molecular Diameter
37
1.7.1. Viscosity at Low Pressures
39
1.7.2. Molecular Diameters
39
1.7.3. Application of the van der Waals Equation
40
1.7.4. From the Density of the Solid or Liquid
41
1.7.5. Cross Section for Collision with Electrons
41
1.8. Heat Conductivity of Gases
44
1.9. Thermal Conductivity at Low Pressures
46
1.9.1. Free-Molecule Conductivity (Knudsen)
50
1.9.2. Temperature Discontinuity (Smoluchowski)

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53
1.10. Thermal Transpiration (Thermomolecular Flow)
57
1.11. Thermal Diffusion
62
1.12. Theory of Diffusion of Gases
65
1.12.1. MaxwellLoschmidt Method for Determination of Diffusion Coefficients
67
1.12.2. Effect of Pressure of Gas on Rates of Evaporation of Metals
69
1.13. Random Motions and Fluctuations
71
1.14. Scattering of Particle Beams at Low Gas Pressures
73
References and Notes
2. Flow of Gases Through Tubes and Orifices 81
R. Gordon Livesey
83
2.1. Flow Conductance, Impedance, and Gas Throughput
85
2.2. Molecular Flow
86
2.2.1. Conductance of an Aperture
87
2.2.2. General Considerations for Long Ducts
87
2.2.3. General Considerations for Short Ducts
88
2.2.4. Uniform Circular Cross Section
90
2.2.5. Duct of Uniform Rectangular Cross Section