Paul Lecoq Alexander Annenkov Alexander Gektin Mikhail Korzhik Christian Pedrini Inorganic ScintiUators for Detector Systems Physical Principles and Crystal Engineering With 125 Figures Sprin ger
:-. Contents 1 Scintillation and Inorganic Scintillators 1 1.1 The Phenomenon of Scintillation 1 1.1.1 Scintillation Yield 6 1.1.2 Kinetics of Scintillations 7 1.1.3 Radioluminescence Spectrum 7 1.1.4 Photoluminescence Spectrum 7 1.2 Survey of Scintillation Mechanisms 8 1.3 Scintillation-Radiating Centers 14 1.3.1 Ions of the Iron Group 14 1.3.2 Ions With s 2 Outer Shell (Mercury-Like Ions) 16 1.3.3 Ion of Molybdenum 17 1.3.4 Uranium Anionic Complexes 17 1.3.5 Rare-Earth Ions 17 1.4 Classification of Inorganic Scintillation Materials 21 1.4.1 Classification Based on the User's Requirements 21 1.4.2 Classification Based on Scintillation Mechanisms 21 1.4.3 Classification Based on Structural Types of Crystals.. 22 1.4.4 Classification Based on Specific Features of Materials. 22 1.4.5 Combined Classification 22 References 27 2 How User's Requirements Influence the Development of a Scintillator 35 2.1 User's Requirements for High Energy Physics 38 2.1.1 Introduction 38 2.1.2 Physics Requirements for High Energy Physics Experiments 39 2.1.3 Scintillator Requirements for High-Energy Physics Experiments 42 2.1.4 Cost Considerations 44 2.1.5 Crystal Calorimeters in the World 45 2.2 Spectrometry of Low-Energy 7-Quanta 45 2.2.1 Nonlinearity of Scintillator Response 45 2.2.2 Spectrometric Properties of YAP:Ce Crystals 49 2.3 User's Requirements for Medical Imaging 51
Contents 2.3.1 Introduction and Historical Background 51 2.3.2 The Different Medical Imaging Modalities 53 2.4 Safety Systems 66 2.5 Astrophysics 69 References 76 Scintillation Mechanisms in Inorganic Scintillators 81 3.1 Introduction: How to Answer High Light Yield, Short Decay Time, and Good Energy Resolution 81 3.2 Relaxation of Electronic Excitations 82 3.3 Limiting Factors at Each Step of the Energy Relaxation 86 3.3.1 Creation of Electronic Excitations 86 3.3.2 Transfer to Luminescence Centers 88 3.3.3 Emission of Luminescent Centers 93 3.4 Creation and Quenching of Radiating Centers 95 3.5 Thermal Quenching 103 3.5.1 Nonradiative Relaxation to the Ground State 103 3.5.2 Thermostimulated Photoionization and Trapping Effects 107 3.6 Charge Exchange Processes Photoionization and Charge Transfer 109 3.6.1 Charge Transfer 110 3.6.2 Photoionization 113 3.6.3 Impurity-Trapped Exciton 114 References 117 Influence of the Crystal Structure Defects on Scintillation Properties 123 4.1 Scintillation Media 124 4.2 Defects in a Crystal 126 4.2.1 Internal Point Defects 127 4.2.2 Impurities 127 4.2.3 Linear Defects 128 4.3 Change of the Optical and Luminescence Properties by Crystal Defects 132 4.3.1 Scintillation Light Absorption by Crystal Defects 132 4.3.2 Harmful Luminescence and Afterglow 136 4.3.3 Low Background Problem 137 4.4 Radiation Damage of Scintillators and Radiation Hardness Improvement 138 4.4.1 Radiation Defects in Dielectrics 139 4.4.2 Radiation Stimulated Losses of Scintillator Transparency 141 4.4.3 Radiation-stimulated Losses Scintillation Efficiency.. 149
Contents XI 4.4.4 Approaches to Radiation Hardness Improvement 154 4.5 Recovery of the Radiation-Induced Absorption 161 References 169 Crystal Engineering 175 5.1 Phase Diagrams 175 5.1.1 Phase Diagram of Continuous Solid Solutions 176 5.1.2 Eutectic and Distectic Phase Diagram Without Solid Solutions 177 5.1.3 Eutectic Phase Diagram with Areas of Solid Solutions 178 5.1.4 Impurity Solubility During the Growth 179 5.1.5 Scintillation Crystal Phase Diagrams 179 5.2 Single Crystal Growth 183 5.2.1 General Considerations on the Crystallization Process. 183 5.2.2 Basic Methods for Scintillation Crystal Growth 184 5.2.3 Bridgeman and Stockbarger Methods 185 5.2.4 Czochralski and Kyropolos Growth Techniques 187 5.2.5 Modern Trends in Scintillation Crystal Manufacturing 190 5.2.6 State-of-the-Art for Crystal Growth 199 5.3 Activator Distribution in a Single Crystal 201 5.4 Raw Material Preparation for Scintillator Crystal Growth 204 5.4.1 Raw Material Purity 204 5.4.2 Raw Material Treatment and Preparation for the Crystal Growth 204 5.4.3 Special Atmosphere for the Crystal Growth 205 5.4.4 Additional Melt Purification 206 5.4.5 Nonstoichiometry 206 5.5 Light Collection 206 5.5.1 Simulations 207 5.5.2 Detector Shaping 210 5.5.3 Optical Guide 212 5.5.4 Wavelength Shifters 213 References 215 Two Examples of Recent Crystal Development 219 6.1 Example of Lead Tungstate Development for High Energy Physics Experiments 219 6.1.1 Introduction 219 6.1.2 The Conditions of Scintillator Development for High Energy Physics (HEP) 222 6.1.3 Strategy for the CMS Calorimeter 223 6.1.4 Progress on Lead Tungstate 225 6.1.5 Other Experiments Using Lead Tungstate 230
XII Contents 6.2 Development of Ce 3+ -Doped Lutetium-Yttrium Aluminum Perovskite Crystals for Medical Imaging Applications 231 6.2.1 Introduction 231 6.2.2 (Lui_ x -Y 2: )A103:Ce Production Technology 233 6.2.3 (h\ii- x -Y x )A10 3 :Ce Scintillation Properties 235 References 242 Conclusion 245 Glossary 247 Tndfix 249