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25 //
26 /// \file medical/fanoCavity/src/MyKleinNishinaCompton.cc
27 /// \brief Implementation of the MyKleinNishinaCompton class
28 //
29 //
30 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
31 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
32
33 #include "MyKleinNishinaCompton.hh"
34
35 #include "DetectorConstruction.hh"
36 #include "MyKleinNishinaMessenger.hh"
37
38 #include "G4DataVector.hh"
39 #include "G4Electron.hh"
40 #include "G4Gamma.hh"
41 #include "G4ParticleChangeForGamma.hh"
42 #include "G4PhysicalConstants.hh"
43 #include "Randomize.hh"
44
45 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
46
47 using namespace std;
48
49 MyKleinNishinaCompton::MyKleinNishinaCompton(DetectorConstruction* det, const G4ParticleDefinition*,
50 const G4String& nam)
51 : G4KleinNishinaCompton(0, nam), fDetector(det), fMessenger(0)
52 {
53 fCrossSectionFactor = 1.;
54 fMessenger = new MyKleinNishinaMessenger(this);
55 }
56
57 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
58
59 MyKleinNishinaCompton::~MyKleinNishinaCompton()
60 {
61 delete fMessenger;
62 }
63
64 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
65
66 G4double MyKleinNishinaCompton::CrossSectionPerVolume(const G4Material* mat,
67 const G4ParticleDefinition* part,
68 G4double GammaEnergy, G4double, G4double)
69 {
70 G4double xsection = G4VEmModel::CrossSectionPerVolume(mat, part, GammaEnergy);
71
72 return xsection * fCrossSectionFactor;
73 }
74 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
75
76 void MyKleinNishinaCompton::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
77 const G4MaterialCutsCouple*,
78 const G4DynamicParticle* aDynamicGamma, G4double,
79 G4double)
80 {
81 // The scattered gamma energy is sampled according to Klein - Nishina formula.
82 // The random number techniques of Butcher & Messel are used
83 // (Nuc Phys 20(1960),15).
84 // Note : Effects due to binding of atomic electrons are negliged.
85
86 G4double gamEnergy0 = aDynamicGamma->GetKineticEnergy();
87 G4double E0_m = gamEnergy0 / electron_mass_c2;
88
89 G4ThreeVector gamDirection0 = aDynamicGamma->GetMomentumDirection();
90
91 //
92 // sample the energy rate of the scattered gamma
93 //
94
95 G4double epsilon, epsilonsq, onecost, sint2, greject;
96
97 G4double eps0 = 1. / (1. + 2. * E0_m);
98 G4double eps0sq = eps0 * eps0;
99 G4double alpha1 = -log(eps0);
100 G4double alpha2 = 0.5 * (1. - eps0sq);
101
102 do {
103 if (alpha1 / (alpha1 + alpha2) > G4UniformRand()) {
104 epsilon = exp(-alpha1 * G4UniformRand()); // eps0**r
105 epsilonsq = epsilon * epsilon;
106 }
107 else {
108 epsilonsq = eps0sq + (1. - eps0sq) * G4UniformRand();
109 epsilon = sqrt(epsilonsq);
110 };
111
112 onecost = (1. - epsilon) / (epsilon * E0_m);
113 sint2 = onecost * (2. - onecost);
114 greject = 1. - epsilon * sint2 / (1. + epsilonsq);
115
116 } while (greject < G4UniformRand());
117
118 //
119 // scattered gamma angles. ( Z - axis along the parent gamma)
120 //
121
122 G4double cosTeta = 1. - onecost;
123 G4double sinTeta = sqrt(sint2);
124 G4double Phi = twopi * G4UniformRand();
125 G4double dirx = sinTeta * cos(Phi), diry = sinTeta * sin(Phi), dirz = cosTeta;
126
127 //
128 // update G4VParticleChange for the scattered gamma
129 //
130 // beam regeneration trick : restore incident beam
131
132 G4ThreeVector gamDirection1(dirx, diry, dirz);
133 gamDirection1.rotateUz(gamDirection0);
134 G4double gamEnergy1 = epsilon * gamEnergy0;
135 fParticleChange->SetProposedKineticEnergy(gamEnergy0);
136 fParticleChange->ProposeMomentumDirection(gamDirection0);
137
138 //
139 // kinematic of the scattered electron
140 //
141
142 G4double eKinEnergy = gamEnergy0 - gamEnergy1;
143
144 if (eKinEnergy > DBL_MIN) {
145 G4ThreeVector eDirection = gamEnergy0 * gamDirection0 - gamEnergy1 * gamDirection1;
146 eDirection = eDirection.unit();
147
148 // create G4DynamicParticle object for the electron.
149 G4DynamicParticle* dp = new G4DynamicParticle(theElectron, eDirection, eKinEnergy);
150 fvect->push_back(dp);
151 }
152 }
153
154 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
155