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G4RDGenerator2BS.cc
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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 
61 {;}
62 
63 //
64 
66 {;}
67 
68 //
69 
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 
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 
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