RF Linear Accelerators (Wiley Series in Beam Physics and Accelerator Technology)

397 Pages·1998·0.34 MB·English

by  Thomas P. Wangler

WllEY SERIES IN BEAM PHYSICS
AND ACCELERATOR TECHNOLOGY
Principles of RF Linear Accelerators
I'll"%1 Wl lEY SERIES IN BEAM PHYSICS AND
4.
ACCELERATOR TECHNOLOGY
,
Series Editor MEL MONTH
CHAO PHYSICS OF COLLECTIVE BEAM INSTABILITIES
IN HlGH ENERGY ACCELERATORS
EDWARDS AND SYPHERS AN INTRODUCTION TO THE PHYSICS
OF HlGH ENERGY ACCELERATORS
INTERMEDIATE CLASSICAL DYNAMICS
WITH APPLICATIONS TO BEAM PHYSICS
THEORY AND DESIGN OF CHARGED
PARTICLE BEAMS
PADAMSEE, KNOBLOCH, RF SUPERCONDUCTIVITY FOR
AND HAYS ACCELERATORS
WANGLER PRINCIPLES OF RF LINEAR ACCELERATORS
Principles of RF Linear Accelerators
THOMAS P. WANGLER
Los Alamos Notional laboratory
Los Alamos, New Mexico
A wiley-Interscience Publication
JOHN WllEY & SONS, INC.
New York / Chichester / Weinheim / Brisbane / Toronto / Singapore
This book is printed on acid-free paper. @
Copyright 0 1998 by John Wiley & Sons, Inc. All right reserved.
Published simultaneously in Canada.
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Library of Congress Cataloging-in-Publication Data:
Wangler, Thomas, 1937-
Principles of RF linear accelerators / by Thomas P. Wangler.
P. cm. - (Wiley serie's. in. be'pm physics and accelerator
technology)
Includes bibliographical references and index.
ISBN 0-471-16814-9 (cloth : alk. paper)
1. Linear accelerators. I. Title. 11. Series.
QC787.L5W36 1998
539.7' 33--dc21
Printed in the United States of America.
To my wife, Julie, and to the memory of
my fother, Froncis X. Wangler

Preface xiii
1 Introduction 1
Linear Accelerators: Historical Perspective / 2
Linac Structures / 6
Linac Beam Dynamics / 11
Multiparticle Effects / 13
Applications of Modern RF Linacs / 14
Accelerator-Physics Units, Unit Conversions, and Physical
Constants / 18
Useful Relativistic Mechanics Relationships / 19
Maxwell's Equations / 19
Conducting Walls / 22
Group Velocity and Energy Velocity / 23
Coaxial Resonator / 25
Transverse Magnetic Mode of a Circular Cylindrical
Cavity / 28
Cylindrical Resonator Transverse Magnetic Modes / 30
Cylindrical Resonator Transverse Electric Modes / 30
2 RF Acceleration in Linats
2.1 Particle Acceleration in an RF Field / 35
2.2 Energy Gain on Axis in an RF Gap / 36
*2.3 Longitudinal Electric Field as a Fourier Integral / 40
*2.4 Transit-Time-Factor Models / 43
2.5 Power and Acceleration Efficiency Figures of Merit / 46
2.6 Cavity Design Issues / 48
2.7 Frequency Scaling of Cavity Parameters / 50
2.8 Linac Economics / 51
/
Problems 53
vii
viii = CONTENTS
3 Periodic Accelerating Structures 57
Synchronous Acceleration and Periodic Structures / 57
Floquet Theorem and Space Harmonics / 58
General Description of Periodic Structures / 62
Equivalent-Circuit Model for Periodic Structures / 63
Periodic Array of Low-Pass Filters / 65
Periodic Array of Electrically Coupled Circuits / 66
Periodic Array of Magnetically Coupled Circuits / 68
Periodic Array of Cavities with Resonant Coupling
Element / 69
Measurement of Dispersion Curves in Periodic Structures / 71
Traveling-Wave Linac Structures / 73
/
Analysis of Periodic Iris-Loaded Waveguide 74
Constant-Impedance Traveling-Wave Structure / 78
Constant-Gradient Structure / 80
Comparison of Different Normal Modes for
Particle Acceleration / 82
Physics Regimes of Traveling- and Standing-Wave
Structures / 85
Problems / 86
4 Standard Linac Structures
4.1 Independent-Cavity Linacs / 88
4.2 Wideroe Linac / 93
4.3 Alvarez Drift-Tube Linac / 95
4.4 Design of Drift-Tube Linacs / 101
/
4.5 Coupled-Cavity Linacs 102
4.6 Three Coupled Oscillators / 103
4.7 Perturbation Theory and Effects of Resonant Frequency
Errors / 106
4.8 Effects from Ohmic Power Dissipation / 108
4.9 General Problem of N + 1 Coupled Oscillators / 110
4.10 Biperiodic Structures for Linacs / 11 3
4.1 1 Design of Coupled-Cavity Linacs / 1 17
*4.12 Intercell Coupling Constant / 120
"4.13 Decoupling of Cavities Connected by a Beam Pipe / 122
4.14 Resonant Coupling / 123
Problems / 128
5 Microwave Topics for Linacs
5.1 Shunt Resonant-Circuit Model / 130
*5.2 Theory of Resonant Cavities / 132
*5.3 Coupling to Cavities / 134
-.
CONTENTS IZIZII IX
5.4 Equivalent Circuit for a Resonant Cavity System / 135
*5.5 Equivalent Circuit for a Cavity Coupled to Two
Waveguides / 140
*5.6 Transient Behavior of a Resonant-Cavity System / 141
*5.7 Wave Description of a Waveguide to Cavity Coupling / 144
5.8 Microwaye Power Systems for Linacs / 152
5.9 Multipacting / 155
5.10 Electron Field Emission / 159
5.1 I RF Electric Breakdown: Kilpatrick Criterion / 160
5.12 Adiabatic Invariant of an Oscillator / 161
/
5.13 Slater Perturbation Theorem 162
*5.14 Quasistatic Approximation / 165
*5.15 Panofsky-Wenzel Theorem / 166
Problems / 168
6 Longitudinal Particle Dynamics
6.1 Longitudinal Focusing / 173
6.2 Difference Equations of Longitudinal Motion for
Standing-Wave Linacs / 173
6.3 Differential Equations of Longitudinal Motion / 175
6.4 Longitudinal Motion When ~ccelerationR ate Is Small / 175
/
*6.5 Hamiltonian and Liouville's Theorem 179
6.6 Small- Amplitude Oscillations / I84
6.7 Adiabatic Phase Damping / 185
*6.8 Longitudinal Dynamics of Ion Beams in Coupled-Cavity
/
Linacs 187
*6.9 Longitudinal Dynamics in Independent-Cavity Ion Linacs / 188
*6.10 Longitudinal Dynamics of Low-Energy Beams Injected
into a v = c Linac / 190
Problems / 193
7 Transverse Particle Dynamics
Transverse RF Focusing and Defocusing / 195
Radial Impulse from a Synchronous Traveling Wave / 196
/
Radial Impulse near the Axis in an Accelerating Gap 198
Including Electrostatic Focusing in the Gap / 201
Coordinate Transformation Through an Accelerating Gap / 202
Quadrupole Focusing in a Linac / 203
Transfer Matrix Solution of Hill's Equation / 205
Phase-Amplitude Form of Solution to Hill's Equation / 207
/
Transfer Matrix Through One Period 208
Thin-Lens FODO Periodic Lattice / 209
Transverse Stability Plot in a Linac / 21 1