Dr. Ahmed has several years of extensive practical experience in the field of radiation detection and measurement. He holds degrees of Masters in Physics, Masters in Nuclear Engineering, and PhD in Physics. He has heavily contributed to research and development in some of the world renowned Physics laboratories, such as Max-Planck-Institute for Physics in Germany, Fermi National Accelerator Laboratory in USA, and Sudbury Neutrino Observatory in Canada. Particle/radiation detection and measurement are his primary areas of expertise. Currently he is working at Laurentian University/Penguin ASI Inc. as a Senior Research Scientist. Apart from research and development, Dr. Ahmed also teaches in the Physics department of Laurentian University. Dr. Ahmed is a Chartered Scientist and a Chartered Physicist of the Institute of Physics, UK. He holds memberships of the Institute of Physics, UK, the Canadian Association of Physicists, and the Institute of Particle Physics, Canada.
Physics and Engineering of Radiation Detection presents an overview of the physics of radiation detection and its applications. It covers the origins and properties of different kinds of ionizing radiation, their detection and measurement, and the procedures used to protect people and the environment from their potentially harmful effects. The second edition is fully revised and provides the latest developments in detector technology and analyses software. Also, more material related to measurements in particle physics and a complete solutions manual have been added. - Discusses the experimental techniques and instrumentation used in different detection systems in a very practical way without sacrificing the physics content- Provides useful formulae and explains methodologies to solve problems related to radiation measurements- Contains many worked-out examples and end-of-chapter problems- Detailed discussions on different detection media, such as gases, liquids, liquefied gases, semiconductors, and scintillators- Chapters on statistics, data analysis techniques, software for data analysis, and data acquisition systems
Front Cover 1
Physics and Engineering of Radiation Detection 4
Copyright Page 5
Dedication 6
Contents 8
Preface to the second edition 16
Preface to the first edition 18
1 Properties and sources of radiation 22
1.1 Types of radiation 22
1.2 Waves or particles? 23
1.3 Radioactivity and radioactive decay 25
1.3.A Decay energy or Q-value 30
1.3.B The decay equation 33
1.3.C Composite radionuclides 38
1.3.D Radioactive chain 41
1.3.E Decay equilibrium 45
E.1 Secular equilibrium 46
E.2 Transient equilibrium 48
E.3 No equilibrium 48
1.3.F Branching ratio 49
1.3.G Units of radioactivity 50
1.4 Activation 50
1.5 Sources of radiation 51
1.5.A Natural sources 52
A.1 Cosmic radiation sources 52
A.2 Terrestrial radiation sources 53
A.3 Internal radiation sources 53
1.5.B Man-made sources 53
1.6 General properties and sources of particles and waves 55
1.6.A Photons 55
A.1 Sources of photons 57
X-ray machine 57
Synchrotron radiation 60
Laser 60
Gas lasers 61
Liquid lasers 62
Solid-state lasers 62
New developments 62
Radioactive sources of photons 63
1.6.B Electrons 65
B.1 Sources of electrons 66
Electron gun 66
Radioactive sources of electrons 68
1.6.C Positrons 69
C.1 Sources of positrons 69
Particle accelerators 69
Radioactive sources of positrons 70
1.6.D Protons 70
D.1 Sources of protons 71
Particle accelerators 71
Laser ion accelerators 71
Radioactive sources of protons 72
1.6.E Neutrons 72
E.1 Sources of neutrons 73
Spallation sources 73
Composite sources 74
Fusion sources 75
Nuclear reactors 75
Radioactive sources of neutrons 75
1.6.F Alpha particles 76
F.1 Sources of a-particles 77
Accelerator-based sources 77
Radioactive sources of a-particles 78
1.6.G Fission fragments 78
1.6.H Muons, neutrinos, and other particles 79
H.1 Muons 79
H.2 Neutrinos 80
H.3 Some other particles 81
Problems 81
Bibliography 82
2 Interaction of radiation with matter 86
2.1 Some basic concepts and terminologies 86
2.1.A Inverse square law 87
2.1.B Cross section 88
2.1.C Mean free path 90
2.1.D Radiation length 92
2.1.E Conservation laws 97
E.1 Conservation of energy 97
E.2 Conservation of momentum 98
E.3 Conservation of electrical charge 98
2.2 Types of particle interactions 99
2.2.A Elastic scattering 99
2.2.B Inelastic scattering 100
2.2.C Annihilation 100
2.2.D Bremsstrahlung 102
2.2.E Cherenkov radiation 104
2.3 Interaction of photons with matter 106
2.3.A Interaction mechanisms 106
A.1 Photoelectric effect 106
A.2 Compton scattering 111
A.3 Thompson scattering 119
A.4 Rayleigh scattering 119
A.5 Pair production 119
2.3.B Passage of photons through matter 123
B.1 Measuring attenuation coefficient 127
B.2 Mixtures and compounds 128
B.3 Stacked materials 130
2.4 Interaction of heavy charged particles with matter 132
2.4.A Rutherford scattering 132
2.4.B Passage of charged particles through matter 137
2.4.C Bragg curve 144
2.4.D Energy straggling 145
2.4.E Range and range straggling 147
E.1 Range of a-particles 147
E.2 Range of protons 149
2.5 Interaction of electrons with matter 150
2.5.A Interaction modes 151
A.1 Ionization 151
A.2 Møller scattering 152
A.3 Bhabha scattering 152
A.4 Electron–positron annihilation 152
A.5 Bremsstrahlung 153
A.6 Cherenkov radiation 154
2.5.B Passage of electrons through matter 156
2.5.C Energy straggling 160
2.5.D Range of electrons 162
2.6 Interaction of neutral particles with matter 167
2.6.A Neutrons 167
A.1 Elastic scattering 167
A.2 Inelastic scattering 167
A.3 Transmutation 168
A.4 Radiative capture 168
A.5 Spallation 169
A.6 Fission 169
A.7 Total cross section 169
A.8 Passage of neutrons through matter 170
Problems 172
Bibliography 174
3 Gas-filled detectors 178
3.1 Production of electron–ion pairs 178
3.2 Diffusion and drift of charges in gases 181
3.2.A Diffusion in the absence of electric field 181
A.1 Diffusion in the presence of electric field 182
3.2.B Drift of charges in electric field 183
B.1 Drift of ions 183
B.2 Drift of electrons 184
3.2.C Effects of impurities on charge transport 187
3.3 Regions of operation of gas-filled detectors 190
3.3.A Recombination region 190
3.3.B Ion chamber region 191
3.3.C Proportional region 192
C.1 Avalanche multiplication 192
3.3.D Region of limited proportionality 195
3.3.E Geiger–Mueller region 195
E.1 Breakdown 196
3.3.F Continuous discharge 199
3.4 Ionization chambers 200
3.4.A Current–voltage characteristics 200
3.4.B Mechanical design 200
B.1 Parallel plate geometry 201
B.2 Cylindrical geometry 204
3.4.C Choice of gas 208
3.4.D Special types of ion chambers 208
D.1 Parallel plate Frisch grid chamber 208
D.2 Boron-lined ion chamber 210
D.3 Compensated ion chamber 211
3.4.E Applications of ion chambers 211
3.4.F Advantages and disadvantages of ion chambers 212
3.5 Proportional counters 213
3.5.A Multiplication factor 215
3.5.B Choice of gas 219
B.1 Threshold for avalanche multiplication 219
B.2 Quenching 220
B.3 Gas gain 222
3.5.C Special types of proportional counters 222
C.1 BF3 proportional counter 222
C.2 Helium proportional counters 223
C.3 Multi-wire proportional counters 224
3.6 Geiger–Mueller counters 224
3.6.A Current–voltage characteristics 225
3.6.B Dead time 225
3.6.C Choice of gas 228
3.6.D Quenching 229
D.1 Internal quenching 229
D.2 External quenching 230
3.6.E Advantages and disadvantages of GM counters 230
3.7 Sources of error in gaseous detectors 230
3.7.A Recombination losses 230
3.7.B Effects of contaminants 232
B.1 Radiative capture 234
B.2 Dissociative capture 234
B.3 Capture without dissociation 235
3.7.C Effects of space charge buildup 235
3.8 Detector efficiency 240
3.8.A Signal-to-noise ratio 246
Problems 249
Bibliography 250
4 Liquid-filled detectors 254
4.1 Properties of liquids 254
4.1.A Charge pair generation and recombination 254
4.1.B Drift of charges 259
B.1 Drift of electrons 259
B.2 Drift of ions 261
4.2 Liquid ionization chamber 261
4.2.A Applications of liquid-filled ion chambers 263
4.3 Liquid proportional counters 263
4.3.A Charge multiplication 263
4.4 Commonly used liquid detection media 266
4.5 Sources of error in liquid-filled ionizing detectors 267
4.5.A Recombination 267
4.5.B Parasitic electron capture and trapping 269
4.6 Cherenkov detectors 274
4.7 Bubble chamber 276
4.8 Liquid scintillator detectors 277
Problems 277
Bibliography 278
5 Solid-state detectors 280
5.1 Semiconductor detectors 280
5.1.A Structure of semiconductors 280
5.1.B Charge carrier distribution 282
5.1.C Intrinsic, compensated, and extrinsic semiconductors 283
5.1.D Doping 283
D.1 Doping with acceptor impurity 285
D.2 Doping with donor impurity 286
5.1.E Mechanism and statistics of electron–hole pair production 287
E.1 Intrinsic energy resolution 291
E.2 Recombination 293
5.1.F Charge conductivity 296
F.1 Drift of electrons and holes 296
5.1.G Materials suitable for radiation detection 298
G.1 Silicon 299
G.2 Germanium 306
G.3 Gallium arsenide 311
G.4 Cadmium–zinc–tellurium 314
5.1.H The pn-Junction 315
H.1 Characteristics of a reverse-biased pn-Diode 317
H.2 Signal generation 323
H.3 Frequency response 327
5.1.I Modes of operation of a pn-Diode 327
I.1 Photovoltaic mode 328
I.2 Photoconductive mode 328
5.1.J Desirable properties 329
J.1 High radiation fields 331
J.2 Low radiation fields 331
5.1.K Specific semiconductor detectors 331
K.1 PIN diode 331
K.2 Schottky diode 333
K.3 Heterojunction diode 334
K.4 Avalanche photodiode 334
K.5 Surface barrier detector 334
K.6 Position-sensitive detectors 334
Microstrip detectors 334
Pixel detectors 335
Other position-sensitive detectors 335
5.1.L Radiation damage in semiconductors 335
L.1 Damage mechanism and NIEL scaling 336
L.2 Leakage current 336
L.3 Type inversion 338
L.4 Depletion voltage 338
L.5 Charge trapping and carrier lifetime 339
L.6 Annealing 339
5.2 Diamond detectors 339
5.2.A Charge pair production 340
5.2.B Recombination 341
5.2.C Drift of charge pairs 341
5.2.D Leakage current 344
5.2.E Detector design 344
5.2.F Radiation hardness 345
5.2.G Applications 346
5.3 Thermoluminescent detectors 346
5.3.A Principle of thermoluminescence 347
Problems 348
Bibliography 349
6 Scintillation detectors and photodetectors 352
6.1 Scintillation mechanism and scintillator properties 353
6.1.A Basic scintillation mechanism 353
6.1.B Light yield 354
6.1.C Rise and decay times 358
6.1.D Quenching 360
D.1 Self-quenching 360
D.2 Impurity quenching 360
D.3 Thermal quenching 361
D.4 Energy quenching 361
6.1.E Density and atomic weight 361
6.1.F Mechanical properties and stability 361
6.1.G Optical properties 362
6.1.H Phosphorescence or afterglow 362
6.1.I Temperature dependence 363
6.1.J Radiation damage 365
6.1.K Scintillation efficiency 366
6.2 Organic scintillators 370
6.2.A Scintillation mechanism 370
6.2.B Plastic scintillators 373
6.2.C Liquid scintillators 378
6.2.D Crystalline scintillators 382
D.1 Anthracene (C14H10) 382
D.2 p-Terphenyl (C18C14) 383
D.3 Stilbene (C14H12) 384
6.3 Inorganic scintillators 384
6.3.A Scintillation mechanism 385
A.1 Exciton luminescence 385
A.2 Dopant luminescence 386
A.3 Core valence band luminescence 386
6.3.B Radiation damage 388
6.3.C Some common inorganic scintillators 388
C.1 Thallium-doped sodium iodide (NaI:Tl) 390
C.2 Sodium-doped cesium iodide (CsI:Na) 390
C.3 Thallium-doped cesium iodide (CsI:Tl) 390
C.4 Bismuth germanate (BGO) 391
C.5 Cadmium tungstate (CWO) 391
C.6 Lead tungstate (PWO) 391
C.7 Cerium-doped gadolinium silicate (GSO) 391
C.8 Cerium-doped lutetium aluminum garnet (LuAG:Ce) 392
C.9 Cerium-doped yttrium aluminum perovskite (YAP:Ce) 392
C.10 Liquid xenon 392
6.4 Transfer of scintillation photons 394
6.4.A Types of light guides 394
A.1 Simple reflection type 395
A.2 Total internal reflection type 395
A.3 Hybrid light guides 398
6.5 Photodetectors 400
6.5.A Photomultiplier tubes 400
A.1 Photocathode 401
A.2 Electron focusing structure 406
A.3 Electron multiplication structure 406
A.4 Voltage divider circuit 411
A.5 Electron collection 411
A.6 Signal readout 412
A.7 Enclosure 414
A.8 Efficiency 415
Quantum efficiency 416
Electron collection efficiency 416
Overall detection efficiency 416
A.9 Sensitivity 417
Radiant sensitivity 417
Cathode luminous sensitivity 419
Anode luminous sensitivity 419
Blue sensitivity 419
A.10 Gain 420
A.11 Spatial uniformity 423
A.12 Time response 424
A.13 Frequency response 425
A.14 Energy resolution 426
A.15 Modes of operation 427
A.16 Noise considerations 430
A.17 Noise in analog mode 430
A.18 Noise in digital mode 435
A.19 Effect of magnetic field 437
6.5.B Photodiode detectors 438
6.5.C Avalanche photodiode detectors 440
C.1 Basic desirable characteristics 441
C.2 Multiplication process and gain fluctuations 441
C.3 Quantum efficiency and responsivity 445
C.4 Modes of operation 447
C.5 Noise considerations 448
C.6 Radiation damage 451
Problems 451
Bibliography 452
7 Position-sensitive detection and imaging 456
7.1 Some important terms and quantities 456
7.1.A Spatial resolution 457
A.1 Crosstalk 457
A.2 Aliasing and antialiasing 458
Aliasing due to sampling frequency 458
Aliasing due to reconstruction 464
A.3 Point spread function 465
A.4 Line spread function 467
A.5 Edge spread function 468
A.6 Modulation transfer function 469
7.1.B Efficiency 471
B.1 Quantum efficiency 472
B.2 Spatial detective quantum efficiency (DQE(f)) 473
7.1.C Sensitivity 474
7.1.D Dynamic range 474
7.1.E Uniformity 474
7.1.F Temporal linearity 474
7.1.G Noise and signal-to-noise ratio (S/N) 475
7.2 Position-sensitive detection 475
7.2.A Types of position-sensitive detectors 475
A.1 Array devices 475
A.2 Scanning devices 476
A.3 Timing devices 476
7.2.B Multiwire proportional chamber 476
7.2.C Multiwire drift chamber (MWPC) 479
7.2.D Microstrip gas chamber 481
7.2.E Semiconductor microstrip detector 481
7.3 Imaging devices 485
7.3.A Conventional imaging 485
A.1 X-Ray photographic film 485
A.2 Thermoluminescent detector arrays 486
7.3.B Electronic imaging 486
7.3.C Charge-coupled devices 487
7.3.D Direct imaging 487
D.1 Properties of a direct imaging CCD 488
D.2 Disadvantages of direct imaging 491
7.3.E Indirect imaging 491
7.3.F Microstrip and multiwire detectors 492
7.3.G Scintillating fiber detectors 492
Problems 494
Bibliography 494
8 Signal processing 498
8.1 Preamplification 499
8.1.A Voltage-sensitive preamplifiers 500
8.1.B Current-sensitive preamplifiers 502
8.1.C Charge-sensitive preamplifiers 504
C.1 Resistive feedback mechanism 507
C.2 Pulsed reset mechanism 509
8.2 Signal transport 511
8.2.A Type of cable 512
A.1 Coaxial cable 513
A.2 Twisted pair cable 515
A.3 Flat ribbon cable 516
8.3 Pulse shaping 516
8.3.A Delay line pulse shaping 517
8.3.B CR–RC pulse shaping 517
B.1 Pole–zero cancelation 522
B.2 Baseline shift minimization 525
8.3.C Semi-Gaussian pulse shaping 525
8.3.D Semi-triangular pulse shaping 526
8.4 Filtering 527
8.4.A Low pass filter 527
8.4.B High pass filter 530
8.4.C Band pass filter 531
8.5 Amplification 531
8.6 Discrimination 531
8.6.A Pulse counting 533
A.1 Single-channel analyzer 533
A.2 Multichannel analyzer 534
8.7 Analog-to-digital conversion 535
8.7.A A/D conversion-related parameters 535
A.1 Conversion time 535
A.2 Dead time 535
A.3 Resolution 536
A.4 Nonlinearity 537
A.5 Stability 537
8.7.B A/D conversion methods 537
B.1 Digital ramp ADC 537
B.2 Successive approximation ADC 538
B.3 Tracking ADC 540
B.4 Wilkinson ADC 540
B.5 Flash ADC 542
8.7.C Hybrid ADCs 544
8.8 Digital signal processing 544
8.8.A Digital filters 546
8.9 Electronic noise 547
8.9.A Types of electronic noise 549
A.1 Johnson noise 549
A.2 Shot noise 551
A.3 1/f noise 552
A.4 Quantization noise 553
8.9.B Noise in specific components 554
B.1 Noise in amplifiers 554
B.2 Noise in ADCs 556
8.9.C Measuring system noise 557
8.9.D Noise-reduction techniques 558
D.1 Detector signal 558
D.2 Frequency filters 558
Problems 559
Bibliography 560
9 Essential statistics for data analysis 562
9.1 Measures of centrality 563
9.2 Measure of dispersion 565
9.3 Probability 565
9.3.A Frequentist approach 566
9.3.B Bayesian approach 566
9.3.C Probability density function 567
C.1 Quantities derivable from a p.d.f. 568
C.2 Maximum likelihood method 571
9.3.D Some common distribution functions 574
D.1 Binomial distribution 574
D.2 Poisson distribution 575
D.3 Normal or Gaussian distribution 577
D.4 Chi-square (.2) distribution 581
D.5 Student’s t distribution 582
D.6 Gamma distribution 583
Using the maximum likelihood method 584
9.4 Confidence intervals 585
9.5 Measurement uncertainty 588
9.5.A Systematic errors 588
9.5.B Random errors 588
9.5.C Error propagation 589
C.1 Addition of parameters 589
C.2 Multiplication of parameters 590
9.5.D Presentation of results 590
9.6 Confidence tests 591
9.6.A Chi-square (.2) test 592
9.6.B Student’s t test 593
9.7 Regression 595
9.7.A Simple linear regression 595
9.7.B Nonlinear regression 597
9.8 Correlation 598
9.8.A Pearson r or simple linear correlation 599
9.9 Time series analysis 601
9.9.A Smoothing 602
9.10 Frequency domain analysis 603
9.11 Counting statistics 604
9.11.A Measurement precision and detection limits 606
Problems 612
Bibliography 613
10 Software for data analysis 616
10.1 Standard analysis packages 616
10.1.A ROOT 616
A.1 Availability 617
A.2 Data handling, organization, and storage 617
A.3 Data analysis capabilities 620
A.4 Graphics capabilities 620
A.5 Using ROOT 621
A.6 Examples 622
10.1.B Origin® 626
B.1 Data import capabilities 628
B.2 Graphics capabilities 628
B.3 Data analysis capabilities 628
B.4 Programming environment 629
B.5 Examples 629
10.1.C MATLAB 632
C.1 Toolboxes 632
Math, statistics, and optimization 632
Control system design and analysis 633
Signal processing and communications 633
Image processing and computer vision 634
Test and measurement 634
C.2 Data acquisition and import capabilities 634
C.3 Data analysis capabilities 634
C.4 Visualization capabilities 635
C.5 Programming environment 635
C.6 Examples 635
10.2 Custom-made data analysis packages 638
10.2.A Data import/export routines 638
10.2.B Data analysis routines 639
10.2.C Code generation 640
10.2.D Result display 640
Bibliography 640
11 Dosimetry and radiation protection 642
11.1 Importance of dosimetry 642
11.1.A Dose and dose rate 643
11.2 Quantities related to dosimetry 643
11.2.A Radiation exposure and dose 643
A.1 Roentgen (R) 644
A.2 Absorbed dose 644
A.3 Equivalent dose 644
A.4 Effective dose 647
11.2.B Flux or fluence rate 648
11.2.C Integrated flux or fluence 649
11.2.D Exposure and absorbed dose: mathematical definitions 651
11.2.E Kerma, cema, and terma 655
E.1 Kerma 655
E.2 Cema 659
E.3 Terma 659
11.2.F Measuring kerma and exposure 659
11.2.G Cavity theories 660
G.1 Bragg–Gray cavity theory 660
G.2 Spencer–Attix cavity theory 662
11.2.H LET and RBE 663
11.2.I Beam size 664
11.2.J Internal dose 665
J.1 Internal dose from charged particles 666
J.2 Internal dose from thermal neutrons 666
11.3 Passive dosimetry 668
11.3.A Thermoluminescent dosimetry 668
A.1 Working principle and glow curve 669
A.2 Common TL materials 670
A.3 Advantages and disadvantages of TL dosimeters 672
11.3.B Optically stimulated luminescence dosimetry 672
B.1 Working principle and OSL curve 673
B.2 Common OSL materials 673
11.3.C Film dosimetry 674
C.1 Advantages and disadvantages of film dosimeters 674
C.2 Common radiochromatic materials 675
11.3.D Track etch dosimetry 675
D.1 Advantages and disadvantages of track etch dosimeters 676
11.4 Active dosimetry 677
11.4.A Ion chamber dosimetry 677
A.1 Free in air ion chamber dosimetry 677
A.2 Cavity ion chamber dosimetry 680
11.4.B Solid-state dosimetry 684
B.1 MOSFET dosimeter 684
B.2 Diamond dosimeter 686
11.4.C Plastic scintillator dosimeter 687
11.4.D Quartz fiber electroscope 687
D.1 Advantages and disadvantages of quartz fiber electroscope 689
11.5 Microdosimetry 689
11.5.A Microdosimetric quantities 690
A.1 Linear energy transfer and dose 690
A.2 Specific energy 691
A.3 Lineal energy 691
11.5.B Experimental techniques 692
B.1 Tissue equivalent proportional counter 692
B.2 Solid-state nuclear track detector 695
B.3 Silicon microdosimeter 696
11.6 Biological effects of radiation 697
11.6.A Acute and chronic radiation exposure 699
A.1 Acute exposure 699
A.2 Chronic exposure 700
11.6.B Effects and symptoms of exposure 700
B.1 Somatic effects of radiation 700
B.2 Genetic effects of radiation 700
11.6.C Exposure limits 701
11.7 Radiation protection 702
11.7.A Exposure reduction 703
A.1 Time 703
A.2 Distance 703
A.3 Shielding 704
Problems 707
Bibliography 708
12 Radiation spectroscopy 710
12.1 Spectroscopy of photons 710
12.1.A .-ray spectroscopy 710
12.1.B Calibration 714
12.1.C X-ray spectroscopy 715
C.1 X-ray absorption spectroscopy 715
C.2 X-ray photoelectron spectroscopy (XPS) 723
C.3 X-ray diffraction spectroscopy (XDS) 725
12.2 Spectroscopy of charged particles 729
12.2.A a-particle spectroscopy 729
A.1 Energy of an unknown a source 733
A.2 Range and stopping power of a-particles in a gas 733
A.3 Activity of an a source 733
12.2.B Electron spectroscopy 734
12.3 Neutron spectroscopy 735
12.3.A Neutrons as matter probes 735
12.3.B Neutron spectrometry techniques 738
Triple-axis spectrometry 741
B.1 High flux backscattering spectrometer 742
B.2 Filter analyzer spectrometer 743
B.3 Disk chopper spectrometer 743
B.4 Fermi chopper spectrometer 744
B.5 Spin echo spectrometer 745
12.4 Mass spectroscopy 747
12.5 Time spectroscopy 748
Problems 750
Bibliography 750
13 Data acquisition systems 752
13.1 Data acquisition chain 752
13.1.A Pulse counting 752
A.1 Slow pulse counting 753
A.2 Fast pulse counting 753
13.1.B Energy spectroscopy 754
13.1.C Time spectroscopy 754
13.1.D Coincidence spectroscopy 755
13.2 Modular instruments 756
13.2.A NIM standard 756
A.1 NIM layout 756
A.2 NIM modules 757
A.3 NIM logic 757
A.4 Signal transport 758
13.2.B CAMAC standard 759
B.1 CAMAC layout 760
B.2 CAMAC controllers 761
B.3 CAMAC logic 761
13.2.C VME standard 761
C.1 VME layout 762
C.2 VME backplane 762
C.3 VME modules 762
C.4 VME logic 763
13.2.D FASTBUS standard 763
D.1 FASTBUS layout 763
D.2 FASTBUS backplane 763
13.3 PC-based systems 764
13.3.A PCI boards 764
13.3.B PC serial port modules 764
13.3.C PC parallel port modules 766
13.3.D USB-based modules 767
13.3.E TCP/IP-based systems 767
Bibliography 768
Appendix A: Essential electronic measuring devices 770
A.1 Multimeters 770
A.1.A Measuring voltage and current 770
A.1.B Analog multimeter 771
A.1.C Digital multimeter 771
A.1.D Measuring voltage 772
A.1.E Measuring current 772
A.2 Oscilloscopes 772
A.2.A Analog oscilloscope 772
A.1 Attenuator 773
A.2 Electron gun 773
A.3 Electron beam deflection systems 774
A.4 Trigger system 775
A.2.B Digital oscilloscopes 776
A.2.C Signal probes 777
C.1 Passive probes 777
C.2 Active probes 778
Appendix B: Constants and conversion factors 780
B.1 Constants 780
B.2 Masses and electrical charges of particles 780
B.3 Conversion prefixes 781
Appendix C: VME connector pin assignments 782
Properties and sources of radiation
This chapter gives an overview of the properties and sources of radiation. All the particles that are important with respect to radiation detection and measurements have been described and their properties have been discussed. The emission of particles from radioactive sources and their passage through different materials have been qualitatively and quantitatively elaborated.
Keywords
Radioactivity; Particles and Waves; Sources of Radiation; Particle Interactions; Alpha Particles; Beta Particles; Elementary Particles; Radiation Sources
Mass and energy are the two entities that make up our universe. At the most basic level, these two entities represent a single reality that sometimes shows itself as mass and sometimes as energy. They are intricately related to each other through Einstein’s famous mass–energy relation, E=mc2. Just like matter, energy is also capable of moving from one point in space to another through particles or waves. These carriers of energy always originate from some source and continue their travel in space until they get absorbed by or annihilated in some material. The term “radiation” is used to describe this transportation of mass and energy through space.
Since the realization of its potential, radiation has played a central role in technological developments in a variety of fields. For example, we all enjoy the benefits of radiation in medical diagnostics and treatment. On the other hand, the world has also witnessed the hazards of radiation in the form of atomic explosions and radiation exposure.
Whether we think of radiation as a hazard or a blessing, its study is of paramount importance for our survival and development. If we look carefully at the benefits and harms brought about by the use or misuse of radiation, we would reach the conclusion that its advantages clearly outweigh its disadvantages. Radiation has unlimited potential, and its proper use can be highly beneficial for mankind.
This chapter will introduce the reader to different types of radiation, their properties, and their sources. The mechanisms through which the particles interact with matter will be discussed in detail in the next chapter.
1.1 Types of radiation
Radiation can be categorized in different ways, such as ionizing and non-ionizing, particles and waves, hazardous and non-hazardous, etc. However, none of these categorizations draw solid boundaries between properties of the individual particles comprising the radiation; rather, they show the bulk behavior of particle beams. For example, it would not be correct to assert that an electron always ionizes atoms with which it interacts by arguing that it belongs to the category of ionizing particles. All we can say is that if a large number of electrons interact with a large number of atoms, the predominant mode of interaction will lead to the ionization of atoms.
Sometimes radiation is characterized on the basis of its wave and particle properties. However, as we will explore in the next section, this characterization is somewhat vague and can be a cause of confusion. The reason is that, according to modern physics, one can associate a wavelength with every particle whether it carries a mass or not. This implies that a particle having mass can act as a wave and take part in the formation of interference and diffraction patterns. On the other hand, light, which is comprised of photons, is generally described by its wave character.
Let us have a look at the third category mentioned above: hazardous and non-hazardous. There are particles that pass through our bodies in large numbers every second (such as neutrinos from the Sun) but do not cause any observable damage. Still, there is a possibility that some of these particles could cause mutations in our body cells, which could ultimately lead to cancer.1 On the other hand, there are particles, such as neutrons, that are known to be extremely hazardous to biological organisms, but no one can ever be absolutely certain that a particular neutron would definitely cause harm.
The above arguments point toward the idea that the characterization of particles should be based on statistical nature of their interactions. What this really means is that if we have a very large number of a certain kind of particle, there is a high probability that most of them would behave in the manner characteristic of their categorization. For example, long exposure to a highly intense beam of neutrons would most definitely cause skin burns and most probably cancer, but it would be wrong to assume that a single neutron would definitely cause the same effects.
The words probability and chance were mentioned in the preceding paragraphs. What does particle interaction have to do with chance? Well, the theoretical foundation of particle interaction is quantum mechanics, which quantifies the variables related to particle motion, such as momentum, energy, and position, in probabilistic terms. For example, in quantum mechanics we talk about the probability of a particle being present at a specific place at a certain time, but we do not claim that the particle will definitely be there at that time. Nothing is absolute in quantum mechanics. We will learn more about this when we study the concept of cross section in the next chapter.
1.2 Waves or particles?
If we think about light without any prior knowledge, we would assume it to be composed of waves that are continuously emitted from a source (such as a light bulb). In fact, this was the dominant perception among scientists until the start of the twentieth century. In those days a major problem of theoretical physics had started boggling the minds of physicists. They had found it impossible to explain the dependence of energy radiated by a black body (a heated cavity) on the wavelength of emitted radiation if they considered light to have continuous wave characteristics. This mystery was solved by Max Planck, who developed a theory in which light waves were not continuous but quantized and propagated in small wave packets. This wave packet was later called a photon. This theory and the corresponding mathematical model were extremely successful in explaining the black body spectrum. The concept was further confirmed by Einstein when he explained the photoelectric effect, an effect in which a photon having the right amount of energy knocks off a bound electron from an atom.
Max Planck proposed that electromagnetic energy is emitted and absorbed in the form of discrete bundles. The energy carried by such a bundle (i.e., a photon) is proportional to the frequency of the radiation.
=hν (1.2.1)
Here h=6.626×10−34 J s is Planck’s constant, which was initially determined by Max Planck to solve the black body spectrum anomaly. It is now considered to be a universal constant. The frequency v and wavelength λ of electromagnetic radiation are related to its velocity of propagation in a vacuum by c=vλ. If the radiation is traveling through another medium, its velocity should be calculated by
=nνλ, (1.2.2)
where n is the refractive index of the medium. It has been found that the refractive index of a material has a nonlinear dependence on the frequency of radiation.
Experiments confirmed that radiation sometimes behaves as particles and not as continuous waves. On the other hand, there were effects like interference, which could only be explained if light was considered to have continuous wave characteristics.
To add to the confusion, de Broglie in 1920 introduced the idea that sometimes particles, such as electrons, behave like waves. He proposed that one could associate a wavelength to any particle having momentum through the relation
=hp. (1.2.3)
For a particle moving close to the speed of light (the so-called relativistic particle) and rest mass m0 (mass of the particle when it is not moving), the above equation can be written as
=hm0v1−v2c2. (1.2.4)
For slow-moving particles with vc, the de Broglie relation reduces to
=hmv. (1.2.5)
De Broglie’s theory was experimentally confirmed at Bell Labs, where electron diffraction patterns consistent with the wave picture were observed. Based on these experiments and their theoretical explanations, it is now believed that all the entities in the universe simultaneously possess localized (particle-like) and distributed (wave-like) properties. In simple terms, particles can behave as waves and waves can behave as particles.2 This principle, known as the wave–particle duality, has played a central role in the development of quantum physics.
Example:
Compare the de Broglie wavelengths of a proton and an alpha particle moving at the same speed. Assume the velocity to be much smaller than the velocity of light. The mass of an α-particle is about four times the mass of a proton.
Solution:
Since the velocity is much less than the speed of light, we can use the approximation 1.2.5, which for a proton and an α-particle becomes
λp=hmpvandλα=hmαv.
Dividing the first equation with the second gives
pλα=mαmp.
An α-particle consists of two...
| Erscheint lt. Verlag | 20.11.2014 |
|---|---|
| Sprache | englisch |
| Themenwelt | Naturwissenschaften ► Physik / Astronomie ► Atom- / Kern- / Molekularphysik |
| Naturwissenschaften ► Physik / Astronomie ► Elektrodynamik | |
| Technik ► Elektrotechnik / Energietechnik | |
| ISBN-10 | 0-12-801644-2 / 0128016442 |
| ISBN-13 | 978-0-12-801644-2 / 9780128016442 |
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