5.7
Ionization Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
5.8
Proportional Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5.8.1 Design of a Gas Flow Proportional Counter . . . . . . . . 66
5.8.2 Process of Ion-Pair Formation . . . . . . . . . . . . . . . . . . 67
5.8.3 Operating Condition . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.8.4 Type of Radioactivity Measurable by the Counter . . . 69
5.8.5 Background Counting . . . . . . . . . . . . . . . . . . . . . . . . 70
5.8.6 Pulse Height Analyzer in Proportional Counter . . . . . 70
5.8.7 Advantages of Gas Flow Proportional Counter . . . . . . 72
5.9
Geiger–Müller Counter (G.M. Counter) . . . . . . . . . . . . . . . . . 75
5.9.1 Design of the End-Window G.M. Counter . . . . . . . . . 75
5.9.2 Principle of a G.M. Counter . . . . . . . . . . . . . . . . . . . 76
5.10 Liquid Geiger–Müller Counter . . . . . . . . . . . . . . . . . . . . . . . . 77
5.10.1 The Assembly of the Liquid G.M. Counter . . . . . . . . 78
5.10.2 Thickness of the Window and Density Correction . . . 78
5.10.3 Necessary Precautions While Using Liquid G.M.
Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.11 Current–Voltage Characteristics of the G.M. Counter . . . . . . . 82
5.12 Dead Time of Geiger–Müller Counter . . . . . . . . . . . . . . . . . . 84
5.12.1 What is a Dead Time? . . . . . . . . . . . . . . . . . . . . . . . 84
5.12.2 Impact of Dead Time on the Anode . . . . . . . . . . . . . . 85
5.12.3 Correction of Lost Counts . . . . . . . . . . . . . . . . . . . . . 87
5.12.4 Determination of Dead Time of the Counter . . . . . . . . 87
5.13 Chemically Quenched G.M. Counter . . . . . . . . . . . . . . . . . . . 90
5.13.1 Organic Gas Quenched G.M. Counter . . . . . . . . . . . . 90
5.13.2 Halogen Quenched G.M. Counter . . . . . . . . . . . . . . . 91
5.14 Window Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.15 Limitations of Ionization Counters . . . . . . . . . . . . . . . . . . . . . 92
6 Scintillation Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
6.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
6.2
Scintillation Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
6.3
Principle of Scintillation Counter . . . . . . . . . . . . . . . . . . . . . . 96
6.4
Components of a Scintillation Counter . . . . . . . . . . . . . . . . . . 97
6.5
Design of Photomultiplier Tube . . . . . . . . . . . . . . . . . . . . . . . 98
6.6
Scintillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
6.6.1 Inorganic Scintillator . . . . . . . . . . . . . . . . . . . . . . . . . 100
6.6.2 Organic Scintillator . . . . . . . . . . . . . . . . . . . . . . . . . . 101
6.6.3 Composition of Scintillator . . . . . . . . . . . . . . . . . . . . 101
6.7
Precautions Liquid Scintillation . . . . . . . . . . . . . . . . . . . . . . . 102
6.7.1 Size of the Sample Holder . . . . . . . . . . . . . . . . . . . . 102
6.7.2 Composition of Sample for Counting . . . . . . . . . . . . . 103
6.8
Gel Scintillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
6.9
Filter Paper Soaked with Scintillator . . . . . . . . . . . . . . . . . . . 104
Contents
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