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25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4PhotoElectricAngularGeneratorSauterGavrila
33 //
34 // Creation date: 10 May 2004
35 //
36 // Modifications:
37 // 10 May 2003 P. Rodrigues First implementation acording with new design
38 //
39 // Class Description:
40 //
41 // Concrete class for PhotoElectric Electron Angular Distribution Generation
42 // This model is a re-implementation of the Photolectric angular distribution
43 // developed my M. Maire for the Standard EM Physics G4PhotoElectricEffect
44 //
45 // Class Description: End
46 //
47 // -------------------------------------------------------------------
48 //
49
50 #include "G4PhotoElectricAngularGeneratorSauterGavrila.hh"
51 #include "G4PhysicalConstants.hh"
52 #include "Randomize.hh"
53
54 // -------------------------------------------------------------------
55 G4PhotoElectricAngularGeneratorSauterGavrila::G4PhotoElectricAngularGeneratorSauterGavrila():
56 G4VEmAngularDistribution("AngularGenSauterGavrilaLowE")
57 {}
58
59 // -------------------------------------------------------------------
60
61 G4PhotoElectricAngularGeneratorSauterGavrila::~G4PhotoElectricAngularGeneratorSauterGavrila()
62 {}
63
64 // -------------------------------------------------------------------
65
66 G4ThreeVector&
67 G4PhotoElectricAngularGeneratorSauterGavrila::SampleDirection(
68 const G4DynamicParticle* dp,
69 G4double, G4int, const G4Material*)
70 {
71
72 // Compute Theta distribution of the emitted electron, with respect to the
73 // incident Gamma.
74 // The Sauter-Gavrila distribution for the K-shell is used.
75 G4double costeta = 1.;
76 G4double Phi = twopi * G4UniformRand();
77 G4double cosphi = std::cos(Phi);
78 G4double sinphi = std::sin(Phi);
79 G4double sinteta = 0;
80 G4double gamma = 1. + dp->GetKineticEnergy()/electron_mass_c2;
81
82 if (gamma > 5.) {
83 fLocalDirection = dp->GetMomentumDirection();
84 return fLocalDirection;
85 // Bugzilla 1120
86 // SI on 05/09/2010 as suggested by JG 04/09/10
87 }
88
89 G4double beta = std::sqrt((gamma - 1)*(gamma + 1))/gamma;
90 G4double b = 0.5*gamma*(gamma - 1)*(gamma - 2);
91
92 G4double rndm,term,greject,grejsup;
93 if (gamma < 2.) grejsup = gamma*gamma*(1.+b-beta*b);
94 else grejsup = gamma*gamma*(1.+b+beta*b);
95
96 do { rndm = 1.-2*G4UniformRand();
97 costeta = (rndm+beta)/(rndm*beta+1.);
98 term = 1.-beta*costeta;
99 greject = (1.-costeta*costeta)*(1.+b*term)/(term*term);
100 } while(greject < G4UniformRand()*grejsup);
101
102 sinteta = std::sqrt((1 - costeta)*(1 + costeta));
103 fLocalDirection.set(sinteta*cosphi, sinteta*sinphi, costeta);
104 fLocalDirection.rotateUz(dp->GetMomentumDirection());
105 return fLocalDirection;
106 }
107
108 // -------------------------------------------------------------------
109
110 void G4PhotoElectricAngularGeneratorSauterGavrila::PrintGeneratorInformation() const
111 {
112 G4cout << "\n" << G4endl;
113 G4cout << "" << G4endl;
114 G4cout << "Re-implementation of the photolectric angular distribution" << G4endl;
115 G4cout << "developed my M. Maire for the Standard EM Physics G4PhotoElectricEffect" << G4endl;
116 G4cout << "It computes the theta distribution of the emitted electron, with respect to the" << G4endl;
117 G4cout << "incident Gamma, using the Sauter-Gavrila distribution for the K-shell\n" << G4endl;
118 }
119