Techniques for Nuclear and Particle Physics Experiments

William R. Leo

Techniques for Nuclear and Particle Physics Experiments A How-to Approach

Second Revised Edition With 256 Figures, 40 Tables and Numerous Worked Examples

Springer-Verlag Berlin Heidelberg GmbH

Dr. William R. Leo

Route de St. Maurice 34. CH-1814 La Tour de Peilz Switzerland

ISBN 978-3-540-57280-0 ISBN 978-3-642-57920-2 (eBook) DOI 10.1007/978-3-642-57920-2

Library of Congress Cataloging-in-Publication Data. Leo. William R .. 1948- . Techniques for nuciear and particle physics experiments: a how-to approach 1 William R. Leo. - 2nd rev. ed. p. cm. Includes bibliographical references and index. ISBN 978-3-540-57280-0 I. Particles (Nuclear physics)- Technique. 2. Particles (Nuclear physics)- Experiments. 3. Nuclear physics-Technique. 4. Nuclear physics-Experiments. 5. Nuclear counters. I. Title. QC793.46.L46 1994 539.7'2'078-dc20 93-38494

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, broadcasting, 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 1987, 1994 Originally published by Springer-Verlag Berlin Heidelberg New York in 1994

The use of general descriptive names, regi stered 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 protective laws and regulations and therefore free for general use.

Typesetting: K+V Fotosatz GmbH, 0-64743 Beerfelden

SPIN: 11018308 56/3111 - 5 - Printed on acid-free paper

To my wife Elisabeth for her love and encouragement

Preface to the Second Edition

Not quite six years have passed since the appearance of the first edition of this book. This is not a long period. Yet the rapid pace of scientific and technological development today is such that any book on experimental technique must be wary of becoming ob­solete in some way or another even in such a short span of time. Thus, when the publisher Springer-Verlag informed me of the need for a new printing of this book, I decided it was an opportune moment to update some of the chapters as well as to include some new material. The result is this second edition.

The most notable changes have been in Chapters 2 and 3. In the latter, which con­cerns radiation protection, most of the sections have been rewritten to take into account the new recommendations from the International Commission on Radiation Protection, the most important of which are the new dose limits for exposure to ionizing radiation. In addition, emphasis has now been put on the use of SI units in dosimetry, i.e., the Gray and Sievert, which have now become standard.

In Chapter 2, new material has been added in addition to updated information. In particular, Cherenkov radiation and electron-photon shower production are now treated more thoroughly. These are not phenomena normally encountered in a student laborato­ry, but they are presented here so as to provide a foundation for understanding detectors based on these effects. Hopefully this will increase the usefulness of this book especially for those entering high-energy physics. The section on multiple scattering in the Gaussian approximation has also been updated with a new and more accurate empirical formula.

Throughout these chapters and indeed the entire book, an updating of the references has also been made. During this period, of course, many new papers and books on various experimental techniques have appeared, most of a very specific nature. I have had to be selective therefore and have included only those which bear directly on the more general aspects of a technique or method, or provide new data. However, I can in no way claim to have included all possible new references and I apologize for those that I have missed.

Finally, I have included a number of new examples in the text which I hope will enhance understanding of the material. Like the rest of the examples, these are all based on real problems which have been encountered either by myself or by students that I have taught.

That I am writing this preface to the second edition at all is a pleasant surprise for me as it attests to the success of the first edition. For this I am infinitely grateful to the people who have helped with its realization, not the least of which are the readers who have written to me with their comments, suggestions and corrections to the first edition. Where possible, I have tried to incorporate these in one way or another in this edition. Hopefully, I have not disappointed them. Last but not least, my deepest gratitude is due to Prof. Catherine Leluc for her invaluable aid and advice once again, and to my wife and children for their infinite patience.

La Tour de Peilz, November 1993 William R. Leo

Preface to the First Edition

This book is an outgrowth of an advanced laboratory course in experimental nuclear and particle physics the author gave to physics majors at the University of Geneva during the years 1978 - 1983. The course was offered to third and fourth year students, the latter of which had, at this point in their studies, chosen to specialize in experi­mental nuclear or particle physics. This implied that they would go on to do a "diplom" thesis with one of the high- or intermediate-energy research groups in the physics department.

The format of the course was such that the students were required to concentrate on only one experiment during the trimester, rather than perform a series of experiments as is more typical of a traditional course of this type. Their tasks thus included planning the experiment, learning the relevant techniques, setting up and troubleshooting the measuring apparatus, calibration, data-taking and analysis, as well as responsibility for maintaining their equipment, i.e., tasks resembling those in a real experiment. This more intensive involvement provided the students with a better understanding of the experimental problems encountered in a professional experiment and helped instill a certain independence and confidence which would prepare them for entry into a research group in the department. Teaching assistants were present to help the students during the trimester and a series of weekly lectures was also given on various topics in experimental nuclear and particle physics. This included general information on detec­tors, nuclear electronics, statistics, the interaction of radiation in matter, etc., and a good deal of practical information for actually doing experiments.

Many of the chapters in this book are essentially based on notes which were prepared for these lectures. The information contained in this book, therefore, will hopefully provide the reader with a practical "guide" to some of the techniques, the equipment, the technical jargon, etc., which make up the world of current experimental nuclear and particle physics but which never seem to appear in the literature. As those in the field already know, the art of experimental physics is learned through a type of "apprenticeship" with a more experienced physicist or physicists, not unlike medieval artisans. It is to these "apprentices" that I address these chapters.

The book is laid out in three parts. The first four chapters treat some of the funda­mental background knowledge required of experimental nuclear or particle physicists, such as the passage of radiation through matter, statistics, and radiation protection. Since detailed descriptions of the theory can be found elsewhere, these chapters only summarize the basic ideas and present only the more useful formulae. However, refer­ences are provided for the reader desiring more information. In this form, then, these chapters may serve as a reference. A basic understanding of quantum mechanics and fundamental nuclear physics is assumed throughout.

Chapters 5 -10 are primarily concerned with the functioning and operation of the principal types of detectors used in nuclear and particle physics experiments. In addi­tion to the basic principles, sections dealing with modern detectors such as the time-

x Preface to the First Edition

projection chamber or silicon microstrip detectors have also been included. It might be argued, of course, that some of these detectors are too specialized or still too novel to be included in a textbook of this level. However, for the student going on to more ad­vanced work or the experienced researcher, it is these types of detectors he will most likely encounter. Moreover, it gives the student an idea of the state of the art and the in­credible advances that have been made. Hopefully, it will provide food for thought on the advances that can still be made!

The final chapters, 11 -18, are concerned with "nuclear electronics" and the logic which is used in setting up electronics systems for experiments. This has always been a difficult point for many students as most approaches have been from a circuit design point of view requiring analysis of analog circuits, which, of course, is a subject unto itself. With the establishment of standardized systems such as NIM and CAMAC and the availability of commercial modules, however, the experimental physicist can func­tion very well with only a knowledge of electronic logic. These chapters thus treat the characteristics of the pulse signals from detectors and the various operations which can be performed on these signals by commercially available modules. Chapter 18 also presents an introduction to the CAMAC system, which, up to a few years ago, was used only in high-energy physics but which now, with the advent of microcomputers, may also be found on smaller experiments undertaken by students.

Although this book is based on a specific laboratory course, the treatment of the topics outlined above is general and was made without specific reference to any par­ticular experiment, except, perhaps, as an example. As such I hope the book will also be of use to researchers and students in other domains who are called upon to work with detectors and radiation.

I would like to thank the many people who have at some point or another helped realize this book. In particular, my very special thanks are due to Dr. Rene Hausam­mann, Dr. Catherine Lechanoine-Leluc, Dr. Jacques Ligou, and Dr. Trivan Pal for having read some of the chapters and for their helpful comments and suggestions. I am also grateful to J .-C. Bostedeche and J. Covillot who helped construct, establish and maintain the experiments in the laboratory, to C. Jacquat for the many hours spent on the drawings for this book and to the many authors who have kindly allowed me to use figures from their articles or books. Finally, I would like to thank Elisabeth, who, although not a physicist, was the first to have the idea for this book.

Lausanne, March 1987 William R. Leo

Contents

1. Basic Nuclear Processes in Radioactive Sources ........................ 1 1.1 Nuclear Level Diagrams ........................................ 2 1.2 Alpha Decay ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Beta Decay ................................................... 4 1.4 Electron Capture (EC) ......................................... 6 1.5 Gamma Emission ............................................. 6

1.5.1 Isomeric States ......................................... 6 1.6 Annihilation Radiation ......................................... 7 1.7 Internal Conversion ........................................... 7 1.8 Auger Electrons ............................................... 8 1.9 Neutron Sources .............................................. 8

1.9.1 Spontaneous Fission ..................................... 8 1.9.2 Nuclear Reactions ....................................... 8

1.10 Source Activity Units .......................................... 9 1.11 The Radioactive Decay Law .................................... 10

1 .11.1 Fluctuations in Radioactive Decay ........................ 11 1.11.2 Radioactive Decay Chains ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.11.3 Radioisotope Production by Irradiation .................... 14

2. Passage of Radiation Through Matter ................................ 17 2.1 Preliminary Notions and Definitions ............................. 17

2.1.1 The Cross Section ....................................... 18 2.1.2 Interaction Probability in a Distance x. Mean Free Path ..... 19 2.1.3 Surface Density Units ................................... 20

2.2 Energy Loss of Heavy Charged Particles by Atomic Collisions ...... 21 2.2.1 Bohr's Calculation - The Classical Case .................. 22 2.2.2 The Bethe-Bloch Formula ................................ 24 2.2.3 Energy Dependence ..................................... 27 2.2.4 Scaling Laws for dE/dx ................................. 28 2.2.5 Mass Stopping Power ................................... 28 2.2.6 dE/dx for Mixtures and Compounds ...................... 29 2.2.7 Limitations of the Bethe-Bloch Formula and Other Effects ... 29 2.2.8 Channeling............................................. 30 2.2.9 Range ................................................. 30

2.3 Cherenkov Radiation .......................................... 35 2.4 Energy Loss of Electrons and Positrons .......................... 37

2.4.1 Collision Loss .......................................... 37 2.4.2 Energy Loss by Radiation: Bremsstrahlung ................. 38 2.4.3 Electron-Electron Bremsstrahlung ......................... 40 2.4.4 Critical Energy ......................................... 40

XII Contents

2.4.5 Radiation Length ........................................ 41 2.4.6 Range of Electrons ....................................... 42 2.4.7 The Absorption of fJ Electrons ............................ 43

2.5 Multiple Coulomb Scattering ................................... 44 2.5.1 Multiple Scattering in the Gaussian Approximation .......... 46 2.5.2 Backscattering of Low-Energy Electrons .................... 48

2.6 Energy Straggling: The Energy Loss Distribution .................. 49 2.6.1 Thick Absorbers: The Gaussian Limit ...................... 49 2.6.2 Very Thick Absorbers .................................... 50 2.6.3 Thin Absorbers: The Landau and Vavilov Theories .......... 50

2.7 The Interaction of Photons ..................................... 53 2.7.1 Photoelectric Effect ...................................... 54 2.7.2 Compton Scattering ...................................... 55 2.7.3 Pair Production ......................................... 57 2.7.4 Electron-Photon Showers ................................. 59 2.7.5 The Total Absorption Coefficient and Photon Attenuation .,. 62

2.8 The Interaction of Neutrons .................................... 63 2.8.1 Slowing Down of Neutrons. Moderation. . . . . . . .. . . . . . . . . . . . 65

3. Radiation Protection. Biological Effects of Radiation .. . . . . . . . . . . . . . . . . . 69 3.1 Dosimetric Units .............................................. 69

3.1.1 The Roentgen ........................................... 69 3.1.2 Absorbed Dose .......................................... 70 3.1.3 Relative Biological Effectiveness (RBE) ..................... 71 3.1.4 Equivalent Dose ......................................... 72 3.1.5 Effective Dose ........................................... 73

3.2 Typical Doses from Sources in the Environment .................. 73 3.3 Biological Effects ............................................. 74

3.3.1 High Doses Received in a Short Time ...................... 75 3.3.2 Low-Level Doses. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

3.4 Dose Limits .................................................. 77 3.5 Shielding ..................................................... 78 3.6 Radiation Safety in the Nuclear Physics Laboratory ............... 79

4. Statistics and the Treatment of Experimental Data ..................... 81 4.1 Characteristics of Probability Distributions ....................... 81

4.1.1 Cumulative Distributions .......... . . . . . . . . . . . . . . . . . . . . . . . . 82 4.1.2 Expectation Values ....................................... 82 4.1.3 Distribution Moments. The Mean and Variance ............. 82 4.1.4 The Covariance .......................................... 83

4.2 Some Common Probability Distributions ......................... 84 4.2.1 The Binomial Distribution ................................ 84 4.2.2 The Poisson Distribution ................................. 85 4.2.3 The Gaussian or Normal Distribution ...................... 86 4.2.4 The Chi-Square Distribution .............................. 88

4.3 Measurement Errors and the Measurement Process ................ 89 4.3.1 Systematic Errors ........................................ 89 4.3.2 Random Errors .......................................... 90

4.4 Sampling and Parameter Estimation. The Maximum Likelihood Method 91

Contents XIII

4.4.1 Sample Moments ......................................... 91 4.4.2 The Maximum Likelihood Method .......................... 92 4.4.3 Estimator for the Poisson Distribution ...................... 93 4.4.4 Estimators for the Gaussian Distribution . . . . . . . . . . . . . . . . . . . . . 94 4.4.5 The Weighted Mean. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

4.5 Examples of Applications ....................................... 97 4.5.1 Mean and Error from a Series of Measurements .............. 97 4.5.2 Combining Data with Different Errors ...................... 97 4.5.3 Determination of Count Rates and Their Errors .............. 98 4.5.4 Null Experiments. Setting Confidence Limits

When No Counts Are Observed ............................ 98 4.5.5 Distribution of Time Intervals Between Counts ............... 100

4.6 Propagation of Errors .......................................... 101 4.6.1 Examples ................................................ 102

4.7 Curve Fitting .................................................. 103 4.7.1 The Least Squares Method ................................. 104 4.7.2 Linear Fits. The Straight Line .............................. 105 4.7.3 Linear Fits When Both Variables Have Errors. . .. . . .. . . .. . . .. 108 4.7.4 Nonlinear Fits ............................................ 108

4.8 Some General Rules for Rounding-off Numbers for Final Presentation .......................................... 112

5. General Characteristics of Detectors .................................. 115 5.1 Sensitivity ..................................................... 115 5.2 Detector Response .............................................. 116 5.3 Energy Resolution. The Fano Factor ............................. 117 5.4 The Response Function ......................................... 119 5.5 Response Time ................................................. 120 5.6 Detector Efficiency ............................................. 121 5.7 Dead Time .................................................... 122

5.7.1 Measuring Dead Time ..................................... 124

6. Ionization Detectors ................................................ 127 6.1 Gaseous Ionization Detectors .................................... 127 6.2 Ionization and Transport Phenomena in Gases ..................... 130

6.2.1 Ionization Mechanisms .................................... 130 6.2.2 Mean Number of Electron-Ion Pairs Created ...... , .. . . ... . .. 131 6.2.3 Recombination and Electron Attachment .................... 132

6.3 Transport of Electrons and Ions in Gases ......................... 133 6.3.1 Diffusion ................................................ 133 6.3.2 Drift and Mobility ........................................ 134

6.4 Avalanche Multiplication. . . . . . ... . . . . . .. . . . . . . . . . . . . . . .. . . . .. . .. 135 6.5 The Cylindrical Proportional Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 137

6.5.1 Pulse Formation and Shape ................................ 137 6.5.2 Choice of Fill Gas ........................................ 140

6.6 The Multiwire Proportional Chamber (MWPC) .................... 141 6.6.1 Basic Operating Principle .................................. 141 6.6.2 Construction ............................................. 143 6.6.3 Chamber Gas .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 144

XIV Contents

6.6.4 Timing Resolution ........................................ 144 6.6.5 Readout Methods ......................................... 145 6.6.6 Track Clu~ers ............................................ 147 6.6.7 MWPC Efficiency ........................................ 147

6.7 The Drift Chamber ............................................. 149 6.7.1 Drift Gases. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . ... 150 6.7.2 Spatial Resolution. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 151 6.7.3 Operation in Magnetic Fields. . . . . . . . . . . . . . . . . . . . . .. . . . . . . .. 151

6.8 The Time Projection Chamber (TPC) ............................. 151 6.9 Liquid Ionization Detectors (LID) ................................ 154

7. Scintillation Detectors .............................................. 157 7.1 General Characteristics .......................................... 157 7.2 Organic Scintillators ............................................ 159

7.2.1 Organic Crystals .......................................... 162 7.2.2 Organic Liquids .......................................... 163 7.2.3 Plastics .................................................. 164

7.3 Inorganic Crystals .............................................. 165 7.4 Gaseous Scintillators ............................................ 166 7.5 Glasses ........................................................ 167 7.6 Light Output Response ......................................... 167

7.6.1 Linearity................................................. 168 7.6.2 Temperature Dependence .................................. 171 7.6.3 Pulse Shape Discrimination (PSD) .......................... 171

7.7 Intrinsic Detection Efficiency for Various Radiations ............... 173 7.7.1 Heavy Ions............................................... 173 7.7.2 Electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 174 7.7.3 Gamma Rays............................................. 174 7.7.4 Neutrons ................................................. 175

8. Photomultipliers ................................................... 177 8.1 Basic Construction and Operation ................................ 177 8.2 The Photocathode .............................................. 178 8.3 The Electron-Optical Input System ............................... 180 8.4 The Electron-Multiplier Section .................................. 181

8.4.1 Dynode Configurations .................................... 182 8.4.2 Multiplier Response: The Single-Electron Spectrum ........... 184

8.5 Operating Parameters ........................................... 185 8.5.1 Gain and Voltage Supply .................................. 185 8.5.2 Voltage Dividers .......................................... 186 8.5.3 Electrode Current. Linearity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 188 8.5.4 Pulse Shape .............................................. 189

8.6 Time Response and Resolution .............. . . . . . . . . . . . . . . . . . . . .. 190 8.7 Noise ......................................................... 192

8.7.1 Dark Current and Afterpulsing ............................. 192 8.7.2 Statistical Noise. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 193

8.8 Environmental Factors .......................................... 194 8.8.1 Exposure to Ambient Light ................................ 194 8.8.2 Magnetic Fields ........................................... 195

Contents XV

8.8.3 Temperature Effects .......................... , .... , . . .. 196 8.9 Gain Stability, Count Rate Shift ............................... 197

9. Scintillation Detector Mounting and Operation ....................... 199 9.1 Light Collection .............................................. 199

9.1.1 Reflection............................................. 200 9.2 Coupling to the PM .......................................... 201 9.3 Multiple Photomultipliers ..................................... 202 9.4 Light Guides .......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 202 9.5 Fluorescent Radiation Converters .............................. 204 9.6 Mounting a Scintillation Detector: An Example .................. 205 9.7 Scintillation Counter Operation ................................ 208

9.7.1 Testing the Counter .................................... 208 9.7.2 Adjusting the PM Voltage .............................. 209 9.7.3 The Scintillation Counter Plateau ........................ 209 9.7.4 Maintaining PM Gain .................................. 213

10. Semiconductor Detectors ........................................... 215 10.1 Basic Semiconductor Properties ................................ 215

10.1.1 Energy Band Structure ................................. 216 10.1.2 Charge Carriers in Semiconductors ....................... 217 10.1.3 Intrinsic Charge Carrier Concentration ................... 217 10.1.4 Mobility .............................................. 218 10.1.5 Recombination and Trapping ............................ 219

10.2 Doped Semiconductors ........................................ 220 10.2.1 Compensation ......................................... 222

10.3 The np Semiconductor Junction. Depletion Depth ................ 223 10.3.1 The Depletion Depth ................................... 224 10.3.2 Junction Capacitance ................................... 226 10.3.3 Reversed Bias Junctions ................................ 226

10.4 Detector Characteristics of Semiconductors ...................... 227 10.4.1 Average Energy per Electron-Hole Pair ................... 228 10.4.2 Linearity .............................................. 229 10.4.3 The Fano Factor and Intrinsic Energy Resolution .......... 229 10.4.4 Leakage Current ....................................... 229 10.4.5 Sensitivity and Intrinsic Efficiency ....................... 230 10.4.6 Pulse Shape. Rise Time ............................... " 231

10.5 Silicon Diode Detectors ....................................... 233 10.5.1 Diffused Junction Diodes ............................... 233 10.5.2 Surface Barrier Detectors (SSB) .......................... 233 10.5.3 Ion-Implanted Diodes .................................. 234 10.5.4 Lithium-Drifted Silicon Diodes - Si(Li) .................. 235

10.6 Position-Sensitive Detectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 235 10.6.1 Continuous and Discrete Detectors ....................... 235 10.6.2 Micro-Strip Detectors ................................... 237 10.6.3 Novel Position-Sensing Detectors ........................ 238

10.7 Germanium Detectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239 10.7.1 Lithium-Drifted Germanium - Ge(Li) ................... 239 10.7.2 Intrinsic Germanium ................................... 240

XVI Contents

10.7.3 Gamma Spectroscopy with Germanium Detectors .......... 241 10.8 Other Semiconductor Materials ................................ 242 10.9 Operation of Semiconductor Detectors .......................... 243

10.9.1 Bias Voltage........................................... 243 10.9.2 Signal Amplification ................................... 243 10.9.3 Temperature Effects.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 245 10.9.4 Radiation Damage ..................................... 245 10.9.5 Plasma Effects ........................................ 246

11. Pulse Signals in Nuclear Electronics ................................. 249 11.1 Pulse Signal Terminology ..................................... 249 11.2 Analog and Digital Signals .................................... 250 11.3 Fast and Slow Signals ...................... . . . . . . . . . . . . . . . . . .. 252 11.4 The Frequency Domain. Bandwidth ............................ 253

12. The NIM Standard ............................................... . 12.1 Modules .................................................... . 12.2 Power Bins ................................................. . 12.3 NIM Logic Signals .......................................... . 12.4 TTL and ECL Logic Signals .................................. . 12.5 Analog Signals .............................................. .

13. Signal Transmission 13.1 Coaxial Cables

13.1.1 Line Constituents ..................................... . 13.2 The General Wave Equation for a Coaxial Line ................. . 13.3 The Ideal Lossless Cable ..................................... .

13.3.1 Characteristic Impedance .............................. . 13.4 Reflections ................................................. . 13.5 Cable Termination. Impedance Matching ....................... . 13.6 Losses in Coaxial Cables. Pulse Distortion ..................... .

13.6.1 Cable Response. Pulse Distortion ....................... .

257 257 258 258 261 261

263 263 265 266 267 268 268 270 272 275

14. Electronics for Pulse Signal Processing .............................. 277 14.1 Preamplifiers ................................................ 277

14.1.1 Resistive vs Optical Feedback. . . . . . . . . . . . . . . . . . . . . . . . . . .. 279 14.2 Main Amplifiers ............................................. 280 14.3 Pulse Shaping Networks in Amplifiers .......................... 280

14.3.1 CR-RC Pulse Shaping.................................. 281 14.3.2 Pole-Zero Cancellation and Baseline Restoration. . . . . . . . . .. 281 14.3.3 Double Differentiation or CR-RC-CR Shaping ............ 282 14.3.4 Semi-Gaussian Shaping ................................. 283 14.3.5 Delay Line Shaping .................................... 283

14.4 Biased Amplifiers ............................................ 284 14.5 Pulse Stretchers .............................................. 284 14.6 Linear Transmission Gate ..................................... 284 14.7 Fan-out and Fan-in ........................................... 285 14.8 Delay Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 286 14.9 Discriminators ............................................... 286

Contents XVII

14.9.1 Shapers............................................. 287 14.10 Single-Channel Analyzer (Differential Discriminator) ............ 287 14.11 Analog-to-Digital Converters (ADC or AID) ................... 289

14.11.1 ADC Linearity ...................................... 291 14.12 Multichannel Analyzers ...................................... 291 14.13 Digital-to-Analog Converters (DAC or DI A) ................... 292 14.14 Time to Amplitude Converters (TAC or TPHC) ................ 294 14.15 Scalers ..................................................... 294 14.16 Ratemeter .................................................. 294 14.17 Coincidence Units ........................................... 295 14.18 Majority Logic Units ........................................ 295 14.19 Flip-Flops .................................................. 296 14.20 Registers (Latches) .......................................... 297 14.21 Gate and Delay Generators ................................... 297 14.22 Some Simple and Handy Circuits for Pulse Manipulation ........ 297

14.22.1 Attenuators ......................................... 298 14.22.2 Pulse Splitting ....................................... 298 14.22.3 Pulse Inversion ...................................... 299

14.23 Filtering and Shaping ........................................ 299 14.23.1 Pulse Clipping ...................................... , 299 14.23.2 High-Pass Filter or CR Differentiating Circuit ........... 300 14.23.3 RC Low-Pass Filter or Integrating Circuit .............. 301

15. Pulse Height Selection and Coincidence Technique .................... 303 15.1 A Simple Counting System ................................... 303 15.2 Pulse Height Selection ....................................... 304

15.2.1 SCA Calibration and Energy Spectrum Measurement .... , 305 15.2.2 A Note on Calibration Sources ........................ 306

15.3 Pulse Height Spectroscopy with Multichannel Analyzers ......... 307 15.4 Basic Coincidence Technique ................................. 310

15.4.1 Adj usting the Delays. The Coincidence Curve ........... 311 15.4.2 Adjusting Delays with the Oscilloscope ................. 312 15.4.3 Accidental Coincidences .............................. 313

15.5 Combining Pulse Height Selection and Coincidence Determination. The Fast-Slow Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 313

15.6 Pulse Shape Discrimination 314

16. Electronic Logic for Experiments ................................... 317 16.1 Basic Logic Gates: Symbols .................................. 317 16.2 Boolean Laws and Identities .................................. 319 16.3 The Inhibit or Busy ......................................... 321 16.4 Triggers .................................................... 321

16.4.1 One-Body Scattering ................................. 322 16.4.2 Two-Body Scattering ................................. 322 16.4.3 Measurement of the Muon Lifetime .................... 323

17. Timing Methods and Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 325 17.1 Walk and Jitter ............................................. 325 17.2 Time-Pickoff Methods ....................................... 326

XVIII Contents

17.2.1 Leading Edge Triggering (LE) ........................... 326 17.2.2 Fast Zero-Crossing Triggering ........................... 327 17.2.3 Constant Fraction Triggering (CFT) ...................... 327 17.2.4 Amplitude and Risetime Compensated Triggering (ARC) ... 327

17.3 Analog Timing Methods ...................................... 328 17.3.1 The START-STOP Time-to-Amplitude Converter .......... 329 17.3.2 Time Overlap TAC's ................................... 330

17.4 Digital Timing Methods ....................................... 330 17.4.1 The Time-to-Digital Converter (TDC) .................... 330 17.4.2 The Vernier TDC ...................................... 332 17.4.3 Calibrating the Timing System........................... 333

18. Computer Controlled Electronics: CAMAC .......................... 335 18.1 CAMAC Systems ............................................ 336 18.2 The CAMAC Standard ....................................... 338

18.2.1 Mechanical Standards .................................. 338 18.2.2 Electrical Standards: Digital Signals ...................... 338

18.3 The CAMAC Dataway .. . . . . .. . .. . . . . . . . . . . . . . . . . .. . . . . . . . .. .. 338 18.3.1 Common Control Signals (Z,C,I) ........................ 341 18.3.2 Status Signals ......................................... 341 18.3.3 Timing Signals. . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 341 18.3.4 Data Signals. . . . . .. . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . . . . .. 341 18.3.5 Address Signals ........................................ 341 18.3.6 Command Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 342 18.3.7 Pin Allocations ........................................ 342

18.4 Dataway Operations .......................................... 343 18.4.1 Dataway Timing ....................................... 344 18.4.2 Block Transfers ........................................ 346

18.5 Multi-Crate Systems - The Branch Highway .................... 348 18.6 CAMAC Software. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 349

Appendix ............................................................ 353 A. A Review of Oscilloscope Functions ................................. 353

A.l Basic Structure ............................................... 353 A.l.1 Bandwidth and Risetime ................................ 353

A.2 Controls and Operating Modes ................. . . . . . . . . . . . . . . .. 354 A.2.1 Input Coupling ........................................ 354 A.2.2 Vertical and Horizontal Sensitivity ....................... 354 A.2.3 Triggering (Synchronization) ............................ 355 A.2.4 Display Modes ........................ . . . . . . . . . . . . . . . .. 355

A.3 Applications and Examples .................................... 356 A.3.1 Signal Viewing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 356 A.3.2 Comparison of Signals ................................. 356

B. Physical and Numerical Constants .................................. 357 C. Resistor Color Code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 358

References ........................................................... 359

Subject Index ........................................................ 371