| Geant4 Cross Reference |
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26
27 #include "G4StrawTubeXTRadiator.hh"
28
29 #include "G4Gamma.hh"
30 #include "G4PhysicalConstants.hh"
31 #include "G4SystemOfUnits.hh"
32
33 ////////////////////////////////////////////////////////////////////////////
34 // Constructor, destructor
35 G4StrawTubeXTRadiator::G4StrawTubeXTRadiator(G4LogicalVolume* anEnvelope,
36 G4Material* foilMat,
37 G4Material* gasMat, G4double a,
38 G4double b, G4Material* mediumMat,
39 G4bool unishut,
40 const G4String& processName)
41 : G4VXTRenergyLoss(anEnvelope, foilMat, gasMat, a, b, 1, processName)
42 {
43 if(verboseLevel > 0)
44 G4cout << "Straw tube X-ray TR radiator EM process is called" << G4endl;
45
46 if(unishut)
47 {
48 fAlphaPlate = 1. / 3.;
49 fAlphaGas = 12.4;
50 if(verboseLevel > 0)
51 G4cout << "straw uniform shooting: "
52 << "fAlphaPlate = " << fAlphaPlate
53 << " ; fAlphaGas = " << fAlphaGas << G4endl;
54 }
55 else
56 {
57 fAlphaPlate = 0.5;
58 fAlphaGas = 5.;
59 if(verboseLevel > 0)
60 G4cout << "straw isotropical shooting: "
61 << "fAlphaPlate = " << fAlphaPlate
62 << " ; fAlphaGas = " << fAlphaGas << G4endl;
63 }
64
65 // index of medium material
66 fMatIndex3 = (G4int)mediumMat->GetIndex();
67 if(verboseLevel > 0)
68 G4cout << "medium material = " << mediumMat->GetName() << G4endl;
69
70 // plasma energy squared for plate material
71 fSigma3 = fPlasmaCof * mediumMat->GetElectronDensity();
72 if(verboseLevel > 0)
73 G4cout << "medium plasma energy = " << std::sqrt(fSigma3) / eV << " eV"
74 << G4endl;
75
76 // Compute cofs for preparation of linear photo absorption in external medium
77 ComputeMediumPhotoAbsCof();
78 }
79
80 ///////////////////////////////////////////////////////////////////////////
81 G4StrawTubeXTRadiator::~G4StrawTubeXTRadiator() = default;
82
83 void G4StrawTubeXTRadiator::ProcessDescription(std::ostream& out) const
84 {
85 out << "Simulation of forward X-ray transition radiation for the case of\n"
86 "a straw tube radiator.\n";
87 }
88
89 ///////////////////////////////////////////////////////////////////////////
90 // Approximation for radiator interference factor for the case of
91 // straw tube radiator. The plate (window, straw wall) and gas (inside straw)
92 // gap thicknesses are gamma distributed.
93 // The mean values of the plate and gas gap thicknesses
94 // are supposed to be about XTR formation zone.
95 G4double G4StrawTubeXTRadiator::GetStackFactor(G4double energy, G4double gamma,
96 G4double varAngle)
97 {
98 G4double result, L2, L3, M2, M3;
99
100 L2 = GetPlateFormationZone(energy, gamma, varAngle);
101 L3 = GetGasFormationZone(energy, gamma, varAngle);
102
103 M2 = GetPlateLinearPhotoAbs(energy);
104 M3 = GetGasLinearPhotoAbs(energy);
105
106 G4complex C2(1.0 + 0.5 * fPlateThick * M2 / fAlphaPlate,
107 fPlateThick / L2 / fAlphaPlate);
108 G4complex C3(1.0 + 0.5 * fGasThick * M3 / fAlphaGas,
109 fGasThick / L3 / fAlphaGas);
110
111 G4complex H2 = std::pow(C2, -fAlphaPlate);
112 G4complex H3 = std::pow(C3, -fAlphaGas);
113 G4complex H = H2 * H3;
114
115 G4complex Z1 = GetMediumComplexFZ(energy, gamma, varAngle);
116 G4complex Z2 = GetPlateComplexFZ(energy, gamma, varAngle);
117 G4complex Z3 = GetGasComplexFZ(energy, gamma, varAngle);
118
119 G4complex R = (Z1 - Z2) * (Z1 - Z2) * (1. - H2 * H) +
120 (Z2 - Z3) * (Z2 - Z3) * (1. - H3) +
121 2. * (Z1 - Z2) * (Z2 - Z3) * H2 * (1. - H3);
122
123 result = 2.0 * std::real(R) * (varAngle * energy / hbarc / hbarc);
124
125 return result;
126 }
127
128 ////////////////////////////////////////////////////////////////////////
129 // Calculates formation zone for external medium. Omega is energy !!!
130 G4double G4StrawTubeXTRadiator::GetMediumFormationZone(G4double omega,
131 G4double gamma,
132 G4double varAngle)
133 {
134 G4double cof, lambda;
135 lambda = 1.0 / gamma / gamma + varAngle + fSigma3 / omega / omega;
136 cof = 2.0 * hbarc / omega / lambda;
137 return cof;
138 }
139
140 ////////////////////////////////////////////////////////////////////////
141 // Calculates complex formation zone for external medium. Omega is energy !!!
142 G4complex G4StrawTubeXTRadiator::GetMediumComplexFZ(G4double omega,
143 G4double gamma,
144 G4double varAngle)
145 {
146 G4double cof, length, delta, real_v, image_v;
147
148 length = 0.5 * GetMediumFormationZone(omega, gamma, varAngle);
149 delta = length * GetMediumLinearPhotoAbs(omega);
150 cof = 1.0 / (1.0 + delta * delta);
151
152 real_v = length * cof;
153 image_v = real_v * delta;
154
155 G4complex zone(real_v, image_v);
156 return zone;
157 }
158
159 ////////////////////////////////////////////////////////////////////////
160 // Computes matrix of Sandia photo absorption cross section coefficients for
161 // medium material
162 void G4StrawTubeXTRadiator::ComputeMediumPhotoAbsCof()
163 {
164 const G4MaterialTable* theMaterialTable = G4Material::GetMaterialTable();
165 const G4Material* mat = (*theMaterialTable)[fMatIndex3];
166 fMediumPhotoAbsCof = mat->GetSandiaTable();
167 }
168
169 //////////////////////////////////////////////////////////////////////
170 // Returns the value of linear photo absorption coefficient (in reciprocal
171 // length) for medium for given energy of X-ray photon omega
172 G4double G4StrawTubeXTRadiator::GetMediumLinearPhotoAbs(G4double omega)
173 {
174 G4double omega2, omega3, omega4;
175
176 omega2 = omega * omega;
177 omega3 = omega2 * omega;
178 omega4 = omega2 * omega2;
179
180 const G4double* SandiaCof =
181 fMediumPhotoAbsCof->GetSandiaCofForMaterial(omega);
182
183 G4double cross = SandiaCof[0] / omega + SandiaCof[1] / omega2 +
184 SandiaCof[2] / omega3 + SandiaCof[3] / omega4;
185 return cross;
186 }
187