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25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4RDGenerator2BS
33 //
34 // Author: Andreia Trindade (andreia@lip.pt)
35 // Pedro Rodrigues (psilva@lip.pt)
36 // Luis Peralta (luis@lip.pt)
37 //
38 // Creation date: 2 June 2003
39 //
40 // Modifications:
41 // 02 Jun 2003 First implementation acording with new design
42 // 05 Nov 2003 MGP Fixed std namespace
43 // 17 Nov 2003 MGP Fixed compilation problem on Windows
44 //
45 // Class Description:
46 //
47 // Concrete base class for Bremsstrahlung Angular Distribution Generation - 2BS Distribution
48 //
49 // Class Description: End
50 //
51 // -------------------------------------------------------------------
52 //
53 //
54
55 #include "G4RDGenerator2BS.hh"
56 #include "Randomize.hh"
57 #include "G4PhysicalConstants.hh"
58 //
59
60 G4RDGenerator2BS::G4RDGenerator2BS(const G4String& name):G4RDVBremAngularDistribution(name)
61 {;}
62
63 //
64
65 G4RDGenerator2BS::~G4RDGenerator2BS()
66 {;}
67
68 //
69
70 G4double G4RDGenerator2BS::PolarAngle(const G4double initial_energy,
71 const G4double final_energy,
72 const G4int Z)
73 {
74
75 // Adapted from "Improved bremsstrahlung photon angular sampling in the EGS4 code system"
76 // by Alex F. Bielajew, Rahde Mohan anc Chen-Shou Chui, PIRS-0203
77 // Ionizing Radiation Standards
78 // Institute for National Measurement Standards
79 // National Research Council of Canada
80 // Departement of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York
81
82
83 G4double theta = 0;
84
85 G4double initialTotalEnergy = (initial_energy+electron_mass_c2)/electron_mass_c2;
86 G4double finalTotalEnergy = (final_energy+electron_mass_c2)/electron_mass_c2;
87 EnergyRatio = finalTotalEnergy/initialTotalEnergy;
88 G4double gMaxEnergy = (pi*initialTotalEnergy)*(pi*initialTotalEnergy);
89
90 G4double Zeff = std::sqrt(static_cast<G4double>(Z) * (static_cast<G4double>(Z) + 1.0));
91 z = (0.00008116224*(std::pow(Zeff,0.3333333)));
92
93 // Rejection arguments
94 rejection_argument1 = (1.0+EnergyRatio*EnergyRatio);
95 rejection_argument2 = - 2.0*EnergyRatio + 3.0*rejection_argument1;
96 rejection_argument3 = ((1-EnergyRatio)/(2.0*initialTotalEnergy*EnergyRatio))*
97 ((1-EnergyRatio)/(2.0*initialTotalEnergy*EnergyRatio));
98
99 // Calculate rejection function at 0, 1 and Emax
100 G4double gfunction0 = RejectionFunction(0);
101 G4double gfunction1 = RejectionFunction(1);
102 G4double gfunctionEmax = RejectionFunction(gMaxEnergy);
103
104
105 // Calculate Maximum value
106 G4double gMaximum = std::max(gfunction0,gfunction1);
107 gMaximum = std::max(gMaximum,gfunctionEmax);
108
109 G4double rand, gfunctionTest, randTest;
110
111 do{
112 rand = G4UniformRand();
113 rand = rand/(1-rand+1.0/gMaxEnergy);
114 gfunctionTest = RejectionFunction(rand);
115 randTest = G4UniformRand();
116
117 }while(randTest > (gfunctionTest/gMaximum));
118
119 theta = std::sqrt(rand)/initialTotalEnergy;
120
121
122 return theta;
123 }
124 //
125
126 G4double G4RDGenerator2BS::RejectionFunction(G4double value) const
127 {
128
129 G4double argument = (1+value)*(1+value);
130
131 G4double gfunction = (4+std::log(rejection_argument3+(z/argument)))*
132 ((4*EnergyRatio*value/argument)-rejection_argument1)+rejection_argument2;
133
134 return gfunction;
135
136 }
137
138 void G4RDGenerator2BS::PrintGeneratorInformation() const
139 {
140 G4cout << "\n" << G4endl;
141 G4cout << "Bremsstrahlung Angular Generator is 2BS Generator from 2BS Koch & Motz distribution (Rev Mod Phys 31(4), 920 (1959))" << G4endl;
142 G4cout << "Sampling algorithm adapted from PIRS-0203" << G4endl;
143 G4cout << "\n" << G4endl;
144 }
145
146