Ahmed S.N. Physics and Engineering of Radiation Detection
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Physics and Engineering
of Radiation Detection
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Physics and Engineering
of Radiation Detection
Syed Naeem Ahmed
Queen’s University, Kingston, Ontario
AMSTERDAM •BOSTON •HEIDELBERG •LONDON
NEW YORK •OXFORD •PARIS •SAN DIEGO
SAN FRANCISCO •SINGAPORE •SYDNEY •TOKYO
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First edition 2007
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Printed and bound in Great Britain
07 08 09 10 10 9 8 7 6 5 4 3 2 1
ISBN–13:
978-0-12-045581-2
ISBN–10: 0-12-045581-1
Dedicated to:
my parents whose loving memories still guide me through difficult times; my
wife, Rahat, without whose utmost love, support, and encouragements it
would not have been possible to write this book; and to my children Hiba,
Shozab, and Shanib, who have taught me things about life I could never have
learned myself.
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Contents
Preface xxiii
1 Properties and Sources of Radiation 1
1.1 TypesofRadiation............................ 1
1.2 WavesorParticles?............................ 2
1.3 RadioactivityandRadioactiveDecay ................. 4
1.3.A Decay Energy or Q-Value .................... 9
1.3.B TheDecayEquation....................... 11
1.3.C CompositeRadionuclides .................... 15
1.3.D RadioactiveChain ........................ 18
1.3.E Decay Equilibrium . . . . . . . . . ............... 22
E.1 Secular Equilibrium ...................... 22
E.2 Transient Equilibrium . . . . . . ............... 24
E.3 No Equilibrium . . . . . . . . . . ............... 24
1.3.F BranchingRatio ......................... 24
1.3.G UnitsofRadioactivity ...................... 25
1.4 Activation................................. 26
1.5 SourcesofRadiation ........................... 27
1.5.A NaturalSources.......................... 27
A.1 CosmicRadiationSources................... 27
A.2 TerrestrialRadiationSources ................. 28
A.3 InternalRadiationSources .................. 28
1.5.B Man-MadeSources........................ 29
1.6 General Properties and Sources of Particles and Waves . . . . . . . . 30
1.6.A Photons.............................. 31
A.1 SourcesofPhotons....................... 32
1.6.B Electrons ............................. 41
B.1 SourcesofElectrons ...................... 42
1.6.C Positrons ............................. 45
C.1 SourcesofPositrons ...................... 45
1.6.D Protons .............................. 46
D.1 SourcesofProtons ....................... 47
1.6.E Neutrons ............................. 48
E.1 SourcesofNeutrons ...................... 49
1.6.F AlphaParticles.......................... 53
F.1 Sources of α-Particles ..................... 54
1.6.G FissionFragments ........................ 54
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1.6.H Muons,NeutrinosandotherParticles ............. 56
H.1 Muons.............................. 56
H.2 Neutrinos ............................ 56
H.3 SomeOtherParticles ..................... 57
2 Interaction of Radiation with Matter 65
2.1 SomeBasicConceptsandTerminologies ................ 65
2.1.A InverseSquareLaw........................ 66
2.1.B CrossSection .......................... 67
2.1.C MeanFreePath ......................... 68
2.1.D RadiationLength......................... 70
2.1.E ConservationLaws........................ 74
E.1 ConservationofEnergy .................... 75
E.2 ConservationofMomentum.................. 75
E.3 ConservationofElectricalCharge............... 76
2.2 TypesofParticleInteractions...................... 76
2.2.A ElasticScattering......................... 77
2.2.B InelasticScattering........................ 77
2.2.C Annihilation ........................... 77
2.2.D Bremsstrahlung.......................... 79
2.2.E CherenkovRadiation....................... 80
2.3 InteractionofPhotonswithMatter................... 82
2.3.A InteractionMechanisms ..................... 82
A.1 PhotoelectricEffect ...................... 83
A.2 ComptonScattering ...................... 87
A.3 ThompsonScattering ..................... 94
A.4 RayleighScattering ...................... 94
A.5 PairProduction ........................ 95
2.3.B PassageofPhotonsthroughMatter .............. 97
B.1 MeasuringAttenuationCoefficient .............. 101
B.2 Mixtures and Compounds ................... 102
B.3 StackedMaterials ....................... 103
2.4 Interaction of Heavy Charged Particles with Matter . . . . . . . . . 105
2.4.A RutherfordScattering ...................... 105
2.4.B Passage of Charged Particles through Matter . . . . . . . . . 110
2.4.C BraggCurve ........................... 116
2.4.D EnergyStraggling ........................ 117
2.4.E RangeandRangeStraggling .................. 118
E.1 Range of α-Particles ...................... 119
E.2 RangeofProtons........................ 121
2.5 InteractionofElectronswithMatter .................. 122
2.5.A InteractionModes ........................ 122
A.1 Ionization............................ 122
A.2 MoellerScattering ....................... 123
A.3 BhabhaScattering ....................... 123
A.4 Electron-PositronAnnihilation ................ 124
A.5 Bremsstrahlung......................... 124
A.6 CherenkovRadiation...................... 125
viii
2.5.B PassageofElectronsthroughMatter.............. 127
2.5.C EnergyStraggling ........................ 130
2.5.D RangeofElectrons........................ 132
2.6 InteractionofNeutralParticleswithMatter.............. 137
2.6.A Neutrons ............................. 137
A.1 ElasticScattering........................ 138
A.2 InelasticScattering....................... 138
A.3 Transmutation ......................... 139
A.4 RadiativeCapture ....................... 139
A.5 Spallation............................ 139
A.6 Fission.............................. 139
A.7 TotalCrossSection ...................... 140
A.8 PassageofNeutronsthroughMatter ............. 140
2.7 Problems ................................. 143
3 Gas Filled Detectors 149
3.1 ProductionofElectron-IonPairs .................... 149
3.2 DiffusionandDriftofChargesinGases ................ 152
3.2.A DiffusionintheAbsenceofElectricField ........... 152
A.1 DiffusioninthePresenceofElectricField .......... 153
3.2.B DriftofChargesinElectricField................ 153
B.1 DriftofIons........................... 153
B.2 DriftofElectrons........................ 155
3.2.C EffectsofImpuritiesonChargeTransport........... 157
3.3 Regions of Operation of Gas Filled Detectors . . . . . . . . ..... 161
3.3.A RecombinationRegion...................... 161
3.3.B IonChamberRegion....................... 161
3.3.C ProportionalRegion ....................... 162
C.1 AvalancheMultiplication ................... 163
3.3.D RegionofLimitedProportionality ............... 166
3.3.E Geiger-MuellerRegion...................... 166
E.1 Breakdown ........................... 166
3.3.F ContinuousDischarge ...................... 169
3.4 IonizationChambers........................... 169
3.4.A CurrentVoltageCharacteristics................. 170
3.4.B MechanicalDesign ........................ 170
B.1 ParallelPlateGeometry.................... 170
B.2 CylindricalGeometry ..................... 174
3.4.C ChoiceofGas........................... 177
3.4.D SpecialTypesofIonChambers................. 178
D.1 ParallelPlateFrischGridChamber ............. 178
D.2 Boron-linedIonChamber ................... 179
D.3 CompensatedIonChamber .................. 180
3.4.E ApplicationsofIonChambers.................. 181
3.4.F AdvantagesandDisadvantagesofIonChambers ....... 181
3.5 ProportionalCounters .......................... 182
3.5.A MultiplicationFactor....................... 184
3.5.B ChoiceofGas........................... 188
ix