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25 //
26 // G4RToEConvForGamma class implementation
27 //
28 // Author: H.Kurashige, 05 October 2002 - First implementation
29 // --------------------------------------------------------------------
30
31 #include "G4RToEConvForGamma.hh"
32 #include "G4ParticleDefinition.hh"
33 #include "G4ParticleTable.hh"
34 #include "G4SystemOfUnits.hh"
35 #include "G4Log.hh"
36 #include "G4Exp.hh"
37 #include "G4Pow.hh"
38
39 // --------------------------------------------------------------------
40 G4RToEConvForGamma::G4RToEConvForGamma()
41 : G4VRangeToEnergyConverter()
42 {
43 theParticle = G4ParticleTable::GetParticleTable()->FindParticle("gamma");
44 if (theParticle == nullptr)
45 {
46 #ifdef G4VERBOSE
47 if (GetVerboseLevel()>0)
48 {
49 G4cout << " G4RToEConvForGamma::G4RToEConvForGamma() - ";
50 G4cout << "Gamma is not defined !!" << G4endl;
51 }
52 #endif
53 }
54 else
55 {
56 fPDG = theParticle->GetPDGEncoding();
57 }
58 }
59
60 // --------------------------------------------------------------------
61 G4RToEConvForGamma::~G4RToEConvForGamma()
62 {}
63
64 // --------------------------------------------------------------------
65 G4double G4RToEConvForGamma::ComputeValue(const G4int Z,
66 const G4double energy)
67 {
68 // Compute the "absorption" cross-section of the photon "absorption".
69 // Cross-section means here the sum of the cross-sections of the
70 // pair production, Compton scattering and photoelectric processes
71
72 const G4double t1keV = 1.*CLHEP::keV;
73 const G4double t200keV = 200.*CLHEP::keV;
74 const G4double t100MeV = 100.*CLHEP::MeV;
75
76 G4double Zsquare = Z*Z;
77 G4double Zlog = G4Pow::GetInstance()->logZ(Z);
78 G4double Zlogsquare = Zlog*Zlog;
79
80 G4double tmin = (0.552+218.5/Z+557.17/Zsquare)*CLHEP::MeV;
81 G4double tlow = 0.2*G4Exp(-7.355/std::sqrt(Z))*CLHEP::MeV;
82
83 G4double smin = (0.01239+0.005585*Zlog-0.000923*Zlogsquare)*G4Exp(1.5*Zlog);
84 G4double s200keV = (0.2651-0.1501*Zlog+0.02283*Zlogsquare)*Zsquare;
85
86 G4double cminlog = G4Log(tmin/t200keV);
87 G4double cmin = G4Log(s200keV/smin)/(cminlog*cminlog);
88
89 G4double slowlog = G4Log(t200keV/tlow);
90 G4double slow = s200keV * G4Exp(0.042*Z*slowlog*slowlog);
91 G4double logtlow = G4Log(tlow/t1keV);
92 G4double clow = G4Log(300.*Zsquare/slow)/logtlow;
93 G4double chigh = (7.55e-5 - 0.0542e-5*Z)*Zsquare*Z/G4Log(t100MeV/tmin);
94
95 // Calculate the cross-section (using an approximate empirical formula)
96 G4double xs;
97 if ( energy < tlow )
98 {
99 xs = (energy < t1keV) ? slow*G4Exp(clow*logtlow) :
100 slow*G4Exp(clow*G4Log(tlow/energy));
101 }
102 else if ( energy < t200keV )
103 {
104 G4double x = G4Log(t200keV/energy);
105 xs = s200keV * G4Exp(0.042*Z*x*x);
106 }
107 else if( energy<tmin )
108 {
109 const G4double x = G4Log(tmin/energy);
110 xs = smin * G4Exp(cmin*x*x);
111 }
112 else
113 {
114 xs = smin + chigh*G4Log(energy/tmin);
115 }
116 return xs * CLHEP::barn;
117 }
118
119 // --------------------------------------------------------------------
120