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Scintillator Crystals, Radiation Detectors & Instruments on Their B.Grynyov V.Ryzhikov Jong Kyung Kim Moosung Jae Scintillator Crystals, Radiation Detectors & Instruments on Their Base Editor V.Ryzhikov Ukraine – Kharkiv – 2004 This monograph deals with modern problems of scintillator materials sci- ence and advanced technologies for creation of small-sized scintillator detection systems for radiation instruments of different purpose. Principal scientific and technical aspects are considered of raw material synthesis and growth of scintil- lator crystals, and studies of their physico-technical, luminescent and radiation parameters are described. Data are presented on characteristics of ultra-low background spectrometric detection blocks of new generation of “scintillator- PMT” type on the basis of heavy oxide scintillators. Properties are described of a new type of integrated detectors of “scintillator-photodiode” type on the basis of ZnSe(Te) crystals. Examples are presented of practical applications of scintil- lators and scintielectronic detectors in medical, inspection and industrial intro- scopes, small-sized household and professional multi-functional and emergency dosimeters, as well as radiometric and spectrometric systems. Editor V.Ryzhikov Executive Editor E.V.Sherbina B.Grynyov V.Ryzhikov Jong Kyung Kim Moosung Jae Scintillator Crystals, Radiation Detectors & Instruments on Their Base Ukraine – Kharkiv – 2004 ISBN 966-02-3314-0 © B.Grynyov, V.Ryzhikov, Jong Kyung Kim Moosung Jae Contents Introduction 7 Chapter 1. Alkali Halide Crystals 10 1.1. Crystal and zone structure of alkali halide crystals 10 1.2. Preparation technology of alkali halide crystals 11 1.3. Main physico-chemical properties and scintillation characteristics of alkali halide scintillators 16 1.4. The activator state and scintillation process in AHC 27 1.5. Basic concepts of the radioluminescence mechanism in AHC 31 1.6. Structure of luminescence centers and luminescence activation in AHC 33 1.7. Application fields of AHC-based scintillators: present-day state and further prospects 37 References 41 Chapter 2. Single Crystals of Complex Oxides 47 2.1. Bismuth germanate Bi4Ge3O12 (BGO) and silicate Bi4Si3O12 (BSO) single crystals 49 2.1.1. Crystal and electron structure of Bi4Ge3O12 and Bi4Si3O12 49 2.1.2. Theoretical description of thermal conditions for growth of oxide crystals of constant radius by the Czochralski method 53 2.1.3. Technological features of single crystal growthof bismuth germanate and silicate 58 2.1.4. Thermal treatment of BGO single crystals 65 2.1.5. Main physico-chemical properties and scintillation characteristics of bismuth germanate and silicate crystals 68 2.1.6. Applications of BGO and BSO single crystals. 78 2.2. Compounds of yttrium, scandium and rare-earth element silicates 80 2.2.1. Crystal structure of compounds Ln2SiO5 80 2.2.2. Technological features of Ln2SiO5 single crystal growth 83 2.2.3. Main physico-chemical properties and scintillation characteristics of yttrium, scandium and rare-earth element silicates 85 2.3. Tungstates 99 4 Contents 2.3.1. Crystal structure of tungstates 100 2.3.2. Technological preparation features of tungstate single crystals 103 2.3.3. Main physico-chemical properties and scintillation characteristics of tungstates 108 2.3.4. The nature of luminescence centers in tungstates and their energy diagrams 124 References 132 Chapter 3. Scintillators on the Basis of Semiconductor Compounds 143 3.1. Peculiar features of defect formation 143 3.2. Kinetics of formation processes of semiconductor scintillator crystals with isovalent dopants accounting for effects of gas media 158 3.3. Optical and electron properties of trapping centers and luminescence mechanisms in SCS 169 3.3.1. Experimental studies of spectral-kinetic characteristics 169 3.3.2. Theoretical analysis of radiative recombination center formation upon IVD introduction. 183 3.3.3. Photoluminescence decay kinetics of ZnSe(Te)-based scintillators 186 3.3.4. Parameters of emission centers in ZnSe(Te) crystals as studied by spectroscopic and thermoluminescent methods 190 3.3.5. Methods of two-photon spectroscopy for determination of parameters of deep centers in ZnSe(Te) 193 3.4. The nature of radiative recombination in AIIBVI compounds with isovalent dopants (IVD) 200 References 203 Chapter 4. Application Prospects of Oxide and Chalcogenide Crystals for Detection of Neutrons 209 4.1. Neutron flux measurements using «scintillator-photodiode- preamplifier» system and new typesof scintillators 209 4.1.1. Experimental set-up: scintillators and components of the receiving electronic circuit 210 4.1.2. Experimental results 214 4.1.3. Possibilities for neutron detection: discussion and conclusions 217 4.2. Oxide and semiconductor scintillatorsin scintielectronic detectors for detectionof neutrons 222 References 227 Contents 5 Chapter 5. Optimization of the Detector Size 229 References 236 Chapter 6 . Detectors «Scintillator-PMT» 237 References 248 Chapter 7. Detectors of «Scintillator-photodiode» Type 249 7.1. Criteria for the optimum choice of scintillators. Efficiency and light collection in scintielectronic detectors 251 7.2. Photodiodes for scintielectronic detectors 254 7.3. General development principles and main properties of scintielectronic detectors 258 7.3.1. Energy characteristics 258 7.3.2. Noises in scintielectronic detectors 266 7.3.3. Scintielectronic detectors in the current mode:RDT noises 271 7.3.4. Pre-amplifiers for detectors operating in the current mode 273 7.3.5. Peculiar features of design and construction of charge-sensitive preamplifiers 276 References 281 Chapter 8. Instruments for Radiation Monitoring 284 8.1. Introduction 284 8.2. Development of radiation monitoring devices using “scintillator-photodiode” detectors 286 8.2.1. Measurements up from the background level 286 8.2.2. Application of scintillator-photodiode detectors for dosimetric monitoring in the current mode 290 8.2.3. Gamma-spectrometer on the base of a “Notebook” computer and detector “scintillator-photodiode” 295 8.3. New ideology of detection of 241Am and accompanying radionuclides 304 8.3.1. Introduction 304 8.3.2. Composition of radioactive contaminants from NPP 305 8.3.3. A new approach to americium detection 307 8.3.4. Application fields of RK-AG-02M radiometer 311 8.2.5. Operation algorithm of RK-AG-02M radiometer 312 8.3.6. Original features of RK-AG-02 radiometer 315 8.3.7. Design features of the radiometer 316 8.3.8. Parameters and characteristics of RK-AG-02 radiometer units 318 8.4. Dosimeters for detection of solar radiation 319 8.4.1. Detector 321 8.4.2. Household UV radiation dose meter 324 8.4.3. Professional UV radiation meter 326 References 330 6 Contents Chapter 9 . Instrumentsand Detectors on the Base of Scintillator Crystals for Security and Customs Inspection Systems 335 9.1. Introduction 335 9.2. Experimental procedures 336 9.3. Discussion 339 9.4. Conclusion 344 References 345 Chapter 10. A Simple Method for the Calculation of Photon Dose Conversion Factors in Non-tissue Phantom as Like the PMMA Slab 346 10.1. Introduction 346 10.2. Computational model 347 10.3. Indirect method 348 10.4. Direct method 350 10.5. Results 352 10.6. Conclusions 353 References 355 Chapter 11. Dose Equivalent Per Unit Fluence Near the Surface of the Icru Phantom by Including the Secondary Electron Transport For Photons 356 11.1. Introduction 356 11.2. Computational method 358 11.3. Results and discussions 359 11.4. Conclusions 367 References 373 INTRODUCTION For an average person, the beginning of each day is marked by a natural wish to know the weather forecast, comparing it with the per- sonal observation of the surrounding world through the window. Such information about the quantity of heat, moisture and solar radiation in the environment seems to be sufficient for taking adequate measures and precautions that should protect our rather fragile organism from unfavorable external conditions. Until recently, not much attention has been paid to the fact that, alongside the visible light and perceptible heat, the surround ing world is permeated with myriads of particles and flows of radiation that are not accessible for our sensual perception. It was assumed that this sphere of scientists’ interests and activities does not come into a close touch with our personal existence. The Chernobyl catastrophe has destroyed these illusions, as death and illness of tens and hundreds of thousands of human beings were largely caused by the absence of information on the extraordinary high level of invisible penetrating radiation or the presence of local sources with high concentration of radioactive particles, found sometimes tens and hundreds of miles away from the site of the catastrophe. This was a powerful incentive to start off the works on modern - iza tion of instruments for radiation monitoring of the envi ron ment, led to realization of the importance of these means for large masses of population. Systematic studies of radiation levels in many regions of the former Soviet Union have unexpectedly revealed a number of important factors that had no relationship to consequences of the Cher- nobyl catastrophe. First of all, one should note broad uncon trolled use of potassium fertilizers, which often contained high concen tra tion of the radionuclide 40K, as well as the use of building materials contain- ing fission products of transuranic elements. One should also add fuel transportation to nuclear power plants and disposal of the radioactive 8 B.Grynyov, V.Ryzhikov, Jong Kyung Kim, Moosung Jae wastes, un con trolled
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