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G4Generator2BS.cc
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26 // $Id: G4Generator2BS.cc 66241 2012-12-13 18:34:42Z gunter $
27 //
28 // -------------------------------------------------------------------
29 //
30 // GEANT4 Class file
31 //
32 //
33 // File name: G4Generator2BS
34 //
35 // Author: Andreia Trindade (andreia@lip.pt)
36 // Pedro Rodrigues (psilva@lip.pt)
37 // Luis Peralta (luis@lip.pt)
38 //
39 // Creation date: 2 June 2003
40 //
41 // Modifications:
42 // 02 Jun 2003 First implementation acording with new design
43 // 05 Nov 2003 MGP Fixed std namespace
44 // 17 Nov 2003 MGP Fixed compilation problem on Windows
45 // 12 Oct 2010 V.Ivanchenko Moved RejectionFunction inline, use G4Pow to speadup
46 // 09 May 2011 L.Pandola Initialize private members, to avoid Coverity warning
47 //
48 // Class Description:
49 //
50 // Concrete base class for Bremsstrahlung Angular Distribution Generation
51 // 2BS Distribution
52 //
53 // Class Description: End
54 //
55 // -------------------------------------------------------------------
56 //
57 
58 #include "G4Generator2BS.hh"
59 #include "Randomize.hh"
60 #include "G4PhysicalConstants.hh"
61 #include "G4SystemOfUnits.hh"
62 #include "G4Pow.hh"
63 
65  : G4VEmAngularDistribution("AngularGen2BS"),fz(1),ratio(1),
66  ratio1(1),ratio2(1),delta(0)
67 {
68  g4pow = G4Pow::GetInstance();
69  nwarn = 0;
70 }
71 
73 {}
74 
76  G4double final_energy,
77  G4int Z,
78  const G4Material*)
79 {
80 
81  // Adapted from "Improved bremsstrahlung photon angular sampling in the EGS4 code system"
82  // by Alex F. Bielajew, Rahde Mohan anc Chen-Shou Chui, PIRS-0203
83  // Ionizing Radiation Standards
84  // Institute for National Measurement Standards
85  // National Research Council of Canada
86  // Departement of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York
87 
89  ratio = final_energy/energy;
90  ratio1 = (1 + ratio)*(1 + ratio);
91  ratio2 = 1 + ratio*ratio;
92 
93  G4double gamma = energy/electron_mass_c2;
94  G4double beta = std::sqrt((gamma - 1)*(gamma + 1))/gamma;
95 
96  //G4double Zeff = std::sqrt(static_cast<G4double>(Z) * (static_cast<G4double>(Z) + 1.0));
97  //z = (0.00008116224*(std::pow(Zeff,0.3333333)));
98 
99  // VI speadup
100  fz = 0.00008116224*g4pow->Z13(Z)*g4pow->Z13(Z+1);
101 
102  // majoranta
103  G4double ymax = 2*beta*(1 + beta)*gamma*gamma;
104  G4double gMax = RejectionFunction(0.0);
105  gMax = std::max(gMax,RejectionFunction(ymax));
106 
107  G4double y, gfun;
108 
109  do{
110  G4double q = G4UniformRand();
111  y = q*ymax/(1 + ymax*(1 - q));
112  gfun = RejectionFunction(y);
113 
114  // violation point
115  if(gfun > gMax && nwarn >= 20) {
116  ++nwarn;
117  G4cout << "### WARNING in G4Generator2BS: Etot(MeV)= " << energy/MeV
118  << " Egamma(MeV)" << (energy - final_energy)/MeV
119  << " gMax= " << gMax << " < " << gfun
120  << " results are not reliable!"
121  << G4endl;
122  if(20 == nwarn) {
123  G4cout << " WARNING in G4Generator2BS is closed" << G4endl;
124  }
125  }
126 
127  } while(G4UniformRand()*gMax > gfun || y > ymax);
128 
129 
130  G4double cost = 1 - 2*y/ymax;
131  G4double sint = std::sqrt((1 - cost)*(1 + cost));
132  G4double phi = twopi*G4UniformRand();
133 
134  fLocalDirection.set(sint*std::cos(phi), sint*std::sin(phi),cost);
136 
137  return fLocalDirection;
138 }
139 
141 {
142  G4cout << "\n" << G4endl;
143  G4cout << "Bremsstrahlung Angular Generator is 2BS Generator "
144  << "from 2BS Koch & Motz distribution (Rev Mod Phys 31(4), 920 (1959))" << G4endl;
145  G4cout << "Sampling algorithm adapted from PIRS-0203" << G4endl;
146  G4cout << "\n" << G4endl;
147 }
148 
void set(double x, double y, double z)
static G4Pow * GetInstance()
Definition: G4Pow.cc:55
G4double RejectionFunction(G4double value) const
G4double GetTotalEnergy() const
void PrintGeneratorInformation() const
int G4int
Definition: G4Types.hh:78
static constexpr double twopi
Definition: G4SIunits.hh:76
#define G4UniformRand()
Definition: Randomize.hh:97
G4GLOB_DLL std::ostream G4cout
G4double Z13(G4int Z) const
Definition: G4Pow.hh:127
const G4ThreeVector & GetMomentumDirection() const
Hep3Vector & rotateUz(const Hep3Vector &)
Definition: ThreeVector.cc:38
float electron_mass_c2
Definition: hepunit.py:274
T max(const T t1, const T t2)
brief Return the largest of the two arguments
G4double energy(const ThreeVector &p, const G4double m)
#define G4endl
Definition: G4ios.hh:61
static constexpr double MeV
Definition: G4SIunits.hh:214
double G4double
Definition: G4Types.hh:76
G4Generator2BS(const G4String &name="")
virtual G4ThreeVector & SampleDirection(const G4DynamicParticle *dp, G4double out_energy, G4int Z, const G4Material *mat=0)
virtual ~G4Generator2BS()