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25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4Generator2BS
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 // 12 Oct 2010 V.Ivanchenko Moved RejectionFunction inline, use G4Pow to speadup
45 // 09 May 2011 L.Pandola Initialize private members, to avoid Coverity warning
46 //
47 // Class Description:
48 //
49 // Concrete base class for Bremsstrahlung Angular Distribution Generation
50 // 2BS Distribution
51 //
52 // Class Description: End
53 //
54 // -------------------------------------------------------------------
55 //
56
57 #include "G4Generator2BS.hh"
58 #include "Randomize.hh"
59 #include "G4PhysicalConstants.hh"
60 #include "G4SystemOfUnits.hh"
61 #include "G4Pow.hh"
62
63 G4Generator2BS::G4Generator2BS(const G4String&)
64 : G4VEmAngularDistribution("AngularGen2BS"),fz(1.),ratio(1.),
65 ratio1(1.),ratio2(1.),delta(0.)
66 {
67 g4pow = G4Pow::GetInstance();
68 nwarn = 0;
69 }
70
71 G4Generator2BS::~G4Generator2BS()
72 {}
73
74 G4ThreeVector& G4Generator2BS::SampleDirection(const G4DynamicParticle* dp,
75 G4double final_energy,
76 G4int Z,
77 const G4Material*)
78 {
79 // Adapted from "Improved bremsstrahlung photon angular sampling in the EGS4 code system"
80 // by Alex F. Bielajew, Rahde Mohan anc Chen-Shou Chui, PIRS-0203
81 // Ionizing Radiation Standards
82 // Institute for National Measurement Standards
83 // National Research Council of Canada
84 // Departement of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York
85
86 G4double energy = dp->GetTotalEnergy();
87 ratio = final_energy/energy;
88 ratio1 = (1 + ratio)*(1 + ratio);
89 ratio2 = 1 + ratio*ratio;
90
91 G4double gamma = energy/electron_mass_c2;
92 G4double beta = std::sqrt((gamma - 1)*(gamma + 1))/gamma;
93
94 // VI speadup
95 fz = 0.00008116224*g4pow->Z13(Z)*g4pow->Z13(Z+1);
96
97 // majoranta
98 G4double ymax = 2*beta*(1 + beta)*gamma*gamma;
99 G4double gMax = RejectionFunction(0.0);
100 gMax = std::max(gMax,RejectionFunction(ymax));
101
102 G4double y, gfun;
103
104 do{
105 G4double q = G4UniformRand();
106 y = q*ymax/(1 + ymax*(1 - q));
107 gfun = RejectionFunction(y);
108
109 // violation point
110 if(gfun > gMax && nwarn >= 20) {
111 ++nwarn;
112 G4cout << "### WARNING in G4Generator2BS: Etot(MeV)= " << energy/MeV
113 << " Egamma(MeV)" << (energy - final_energy)/MeV
114 << " gMax= " << gMax << " < " << gfun
115 << " results are not reliable!"
116 << G4endl;
117 if(20 == nwarn) {
118 G4cout << " WARNING in G4Generator2BS is closed" << G4endl;
119 }
120 }
121
122 } while(G4UniformRand()*gMax > gfun || y > ymax);
123
124 G4double cost = 1 - 2*y/ymax;
125 G4double sint = std::sqrt((1 - cost)*(1 + cost));
126 G4double phi = twopi*G4UniformRand();
127
128 fLocalDirection.set(sint*std::cos(phi), sint*std::sin(phi),cost);
129 fLocalDirection.rotateUz(dp->GetMomentumDirection());
130
131 return fLocalDirection;
132 }
133
134 void G4Generator2BS::PrintGeneratorInformation() const
135 {
136 G4cout << "\n" << G4endl;
137 G4cout << "Bremsstrahlung Angular Generator is 2BS Generator "
138 << "from 2BS Koch & Motz distribution (Rev Mod Phys 31(4), 920 (1959))" << G4endl;
139 G4cout << "Sampling algorithm adapted from PIRS-0203" << G4endl;
140 G4cout << "\n" << G4endl;
141 }
142
143