High Sensitivity Counting Techniques

Foreword

Authors' Preface

Acknowledgments

Chapter 1. Counting Parameters


1.1 The Minimum Observable Counting Rate


1.2 The Factor of Merit

References

Chapter 2. The Attainment of Low Backgrounds in Radiation Detectors — (I) The Cosmic Radiation


2.1 Sources of Background


2.2 The Extensive Air Shower


2.3 Neutron Production


2.4 Gamma Shielding


2.5 Summary of Cosmic-ray Shield Requirements


2.6 Types of Anticoincidence System


2.7 Experimental Tests


1. Proportional Counting


2. Sodium Iodide Scintillation Counting


2.8 Conclusions on Shielding for


1. Gas Proportional and Geiger Counters


2. Sodium Iodide Crystals

References

Chapter 3. The Attainment of Low Backgrounds in Radiation Detectors — (II) Secondary Effects


3.1 Local Radioactivity


3.2 Construction Materials


3.3 Electronics and Electrical System


1. Amplifier Noise


2. Photomultiplier Noise


3. Amplifier Overload


4. Gamma Spectrometer Overload Pulse Inhibit Circuit


5. Cable Reflections


6. Pick-up from the Mains Supply, etc


7. E.H.T. Breakdown

References

Chapter 4. Low-Background Laboratories


4.1 Underground Laboratories


4.2 Steel Rooms


4.3 The Aldermaston Low-background Laboratory

References

Chapter 5. The Measurement of Weak Alpha Activities


5.1 General Considerations on Sensitivity


5.2 Scintillation Counting


1. ZnS(Ag) Phosphors


2. CsI(Tl) Scintillators


3. Thin Plastic Scintillators


4. The Wetted-anthracene Method for Counting Aqueous Sources


5. Loaded Liquid Scintillators


5.3 Gas-filled Detectors


1. Large Area Counter for Total Alpha Counting


2. Alpha Spectroscopy with Gas-filled lonization Chambers


5.4 The Gridded lonization Chamber


1. Electronic Collimation


5.5 The Coaxial-electrode lonization Chamber as an Alpha Spectrometer


1. Design of a Coaxial Chamber for Alpha Spectrometry


2. Description of Counter


5.6 Semiconductor Counters


5.7 Preparation of Sources


1. Electrodeposition


2. Lacquer Technique


3. Tetraethyleneglycol (TEG) Spread Sources


4. Evaporation of Organic Solutions


5. Vacuum Sublimation


6. Large Area Sources by Evaporation in Air


5.8 Self-absorption in Homogeneously Dispersed Sources


5.9 Distortion of Energy Spectrum of Alpha-particles from a Thick Source


5.10 Backscattering of Alpha-particles from the Source Backing

References

Chapter 6. Carbon-14 Beta Counting


6.1 Radiocarbon Dating


1. Introduction


2. Statistics of Carbon Dating


3. Solid Source Counters


4. Gaseous Source Counters


5. Liquid Scintillation Counting of Natural C14


6.2 Detection of Artificial C14 Activities


1. Solid Sources


2. Gaseous Sources


3. Liquid Sources


4. Ionization Chambers

Bibliography and References

Chapter 7. Counting of Soft Radiations Using Internal Sources


7.1 Counting of Tritium


1. Liquid Scintillation Counting


2. Gas Counting


7.2 Errors in Gas Counting Techniques


7.3 Electron Attachment in Counters


7.4 Counting of S35


7.5 High Temperature Gas Counters


7.6 Counting of Other Soft Beta-emitters


7.7 Detection of X-radiations from Low Z Isotopes


1. Solid Sources


2. Gaseous Sources

Bibliography and References

Chapter 8. Beta Counting of Solid and Liquid Sources


8.1 Systems with 4π Geometry


8.2 Systems with 2π Geometry


8.3 Systems with less than 2π Geometry


1. Loop Anode Proportional Counter with Geiger Ring


2. Multiple-anode Annular Counter System


3. Van Duuren Counter


8.4 Organic Scintillator Anticoincidence Shields


8.5 Double Geiger Counter Technique


8.6 The Cancellation Technique


8.7 An "End-window" Beta Spectrometer


8.8 Source Preparation


1. Sources for 4π counters


2. Sources for 2π and End-window Counters


8.9 Source Deposition Methods


1. Evaporation in Air


2. Freeze-dry Techniques


3. Slurry Method


4. Vacuum Evaporation


5. Electro-spraying


8.10 Self-absorption and Self-scattering Corrections for Homogeneously Dispersed Sources


8.11 Backscattering and Self-scattering


8.12 Experimental Methods of Assessing Absorption and Scattering Corrections


1. Extrapolation Method


2. 4π ß-γ Coincidence Method


3. Comparison of Sources of Varying Thickness with a Very Thin Source


8.13 Absorption in the Source-backing Foil


1. Sandwich Method


2. Summation Technique


8.14 Annomalous Background Effects in Thick Sources


1. Shielding Effects


2. Characteristic X-ray Excitation


8.15 Correction for Source Decay during the Counting Period


8.16 Scintillation Counting of Solid Beta Sources


1. Plastic Scintillators


2. Scintillation Counting of Solids in Suspension


3. Background and Efficiency Measurement


8.17 Scintillation Counting of Beta-emitters in Aqueous Solutions


1. Crystal-wetting Method


2. Counting of Solution in Phosphor Vials


3. Counting of Aqueous Solutions in Liquid Scintillators

References

Chapter 9. Gamma-Ray Detection


9.1 General


9.2 Conditions for Counting under the Total Absorption Peak


9.3 Selection of Counting Geometry


1. The Detection Efficiency for a Cylindrical NaI(Tl) Crystal and a Disk Source


2. Minimum Detectable Activity for a Disk Source


3. Source Material Surrounding a Cylindrical Crystal


9.4 Effects caused by Thick Sources


1. Self-absorption in the Source


2. Shielding and Scattering Effects of a Thick Source


3. Excitation of Characteristic X-radiation by Background Bombardment of the Source


9.5 Errors Caused by Gain Drift


9.6 Ability to Detect One Gamma-ray in the Presence of Another Line at Higher Energy


9.7 Counting of Cascade Gamma-rays


1. A Cylindrical Crystal with a Disk Source in 2π Geometry


2. A Cylindrical Well Crystal with Source giving 4π Geometry


9.8 Calculation of the Absolute Disintegration Rate


1. The Half-life of Long-lived Lu


9.9 The Sum-Coincidence Method


1. Principle of Operation


2. Resolution and Efficiency


9.10 Coincidence Counting of Positrons Among More Intense Negatron or Gamma Activity


1. Determination of Zr89 in the Presence of Large Amounts of Zr95 and Zr97


9.11 Detector Calibration


9.12 Scintillation Spectrometers Operated in Anticoincidence with a Guard Detector

References

Chapter 10. Measurement of Gamma Radioactivity from the Body


10.1 Application of Whole Body Counters


10.2 Counting Systems


1. Ionization Chambers


2. Organic Scintillators


3. NaI(Tl) Scintillators


10.3 Calibration

References

Author Index

Subject Index