| Geant4 Cross Reference |
1 // 1 //
2 // ******************************************* 2 // ********************************************************************
3 // * License and Disclaimer 3 // * License and Disclaimer *
4 // * 4 // * *
5 // * The Geant4 software is copyright of th 5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided 6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License 7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/ 8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. 9 // * include a list of copyright holders. *
10 // * 10 // * *
11 // * Neither the authors of this software syst 11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing fin 12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warran 13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assum 14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file 15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitatio 16 // * for the full disclaimer and the limitation of liability. *
17 // * 17 // * *
18 // * This code implementation is the result 18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboratio 19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distri 20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you ag 21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publicati 22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Sof 23 // * acceptance of all terms of the Geant4 Software license. *
24 // ******************************************* 24 // ********************************************************************
25 // 25 //
>> 26 // $Id: G4eeToTwoGammaModel.cc,v 1.14 2007/05/23 08:47:35 vnivanch Exp $
>> 27 // GEANT4 tag $Name: geant4-09-00-patch-01 $
26 // 28 //
27 // ------------------------------------------- 29 // -------------------------------------------------------------------
28 // 30 //
29 // GEANT4 Class file 31 // GEANT4 Class file
30 // 32 //
31 // 33 //
32 // File name: G4eeToTwoGammaModel 34 // File name: G4eeToTwoGammaModel
33 // 35 //
34 // Author: Vladimir Ivanchenko on base 36 // Author: Vladimir Ivanchenko on base of Michel Maire code
35 // 37 //
36 // Creation date: 02.08.2004 38 // Creation date: 02.08.2004
37 // 39 //
38 // Modifications: 40 // Modifications:
39 // 08-04-05 Major optimisation of internal int 41 // 08-04-05 Major optimisation of internal interfaces (V.Ivanchenko)
40 // 18-04-05 Compute CrossSectionPerVolume (V.I 42 // 18-04-05 Compute CrossSectionPerVolume (V.Ivanchenko)
41 // 06-02-06 ComputeCrossSectionPerElectron, Co 43 // 06-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
42 // 29-06-06 Fix problem for zero energy incide 44 // 29-06-06 Fix problem for zero energy incident positron (V.Ivanchenko)
43 // 20-10-06 Add theGamma as a member (V.Ivanch 45 // 20-10-06 Add theGamma as a member (V.Ivanchenko)
44 // 18-01-20 Introduce thermal model of annihil <<
45 // 46 //
46 // 47 //
47 // Class Description: 48 // Class Description:
48 // 49 //
49 // Implementation of e+ annihilation into 2 ga 50 // Implementation of e+ annihilation into 2 gamma
50 // 51 //
51 // The secondaries Gamma energies are sampled 52 // The secondaries Gamma energies are sampled using the Heitler cross section.
52 // 53 //
53 // A modified version of the random number tec 54 // A modified version of the random number techniques of Butcher & Messel
54 // is used (Nuc Phys 20(1960),15). 55 // is used (Nuc Phys 20(1960),15).
55 // 56 //
56 // GEANT4 internal units. 57 // GEANT4 internal units.
57 // 58 //
58 // Note 1: The initial electron is assumed fre << 59 // Note 1: The initial electron is assumed free and at rest.
59 // is not defined <<
60 // 60 //
61 // Note 2: The annihilation processes producin 61 // Note 2: The annihilation processes producing one or more than two photons are
62 // ignored, as negligible compared to 62 // ignored, as negligible compared to the two photons process.
63 63
>> 64
>> 65
64 // 66 //
65 // ------------------------------------------- 67 // -------------------------------------------------------------------
66 // 68 //
67 //....oooOO0OOooo........oooOO0OOooo........oo 69 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
68 //....oooOO0OOooo........oooOO0OOooo........oo 70 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
69 71
70 #include "G4eeToTwoGammaModel.hh" 72 #include "G4eeToTwoGammaModel.hh"
71 #include "G4PhysicalConstants.hh" <<
72 #include "G4SystemOfUnits.hh" <<
73 #include "G4TrackStatus.hh" 73 #include "G4TrackStatus.hh"
74 #include "G4Electron.hh" 74 #include "G4Electron.hh"
75 #include "G4Positron.hh" 75 #include "G4Positron.hh"
76 #include "G4Gamma.hh" 76 #include "G4Gamma.hh"
77 #include "Randomize.hh" 77 #include "Randomize.hh"
78 #include "G4RandomDirection.hh" <<
79 #include "G4ParticleChangeForGamma.hh" 78 #include "G4ParticleChangeForGamma.hh"
80 #include "G4EmParameters.hh" <<
81 #include "G4Log.hh" <<
82 #include "G4Exp.hh" <<
83 79
84 //....oooOO0OOooo........oooOO0OOooo........oo 80 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
85 81
>> 82 using namespace std;
>> 83
86 G4eeToTwoGammaModel::G4eeToTwoGammaModel(const 84 G4eeToTwoGammaModel::G4eeToTwoGammaModel(const G4ParticleDefinition*,
87 const 85 const G4String& nam)
88 : G4VEmModel(nam), 86 : G4VEmModel(nam),
89 pi_rcl2(CLHEP::pi*CLHEP::classic_electr_ra << 87 pi_rcl2(pi*classic_electr_radius*classic_electr_radius),
>> 88 isInitialised(false)
90 { 89 {
91 theGamma = G4Gamma::Gamma(); 90 theGamma = G4Gamma::Gamma();
92 fParticleChange = nullptr; <<
93 } 91 }
94 92
95 //....oooOO0OOooo........oooOO0OOooo........oo 93 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
96 94
97 G4eeToTwoGammaModel::~G4eeToTwoGammaModel() = << 95 G4eeToTwoGammaModel::~G4eeToTwoGammaModel()
>> 96 {}
98 97
99 //....oooOO0OOooo........oooOO0OOooo........oo 98 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
100 99
101 void G4eeToTwoGammaModel::Initialise(const G4P 100 void G4eeToTwoGammaModel::Initialise(const G4ParticleDefinition*,
102 const G4D 101 const G4DataVector&)
103 { 102 {
104 if (nullptr != fParticleChange) { return; } << 103 if(isInitialised) return;
105 fParticleChange = GetParticleChangeForGamma( << 104
>> 105 if(pParticleChange)
>> 106 fParticleChange =
>> 107 reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
>> 108 else
>> 109 fParticleChange = new G4ParticleChangeForGamma();
>> 110
>> 111 isInitialised = true;
106 } 112 }
107 113
108 //....oooOO0OOooo........oooOO0OOooo........oo 114 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
109 115
110 G4double << 116 G4double G4eeToTwoGammaModel::ComputeCrossSectionPerElectron(
111 G4eeToTwoGammaModel::ComputeCrossSectionPerEle << 117 const G4ParticleDefinition*,
>> 118 G4double kineticEnergy,
>> 119 G4double, G4double)
112 { 120 {
113 // Calculates the cross section per electron 121 // Calculates the cross section per electron of annihilation into two photons
114 // from the Heilter formula. 122 // from the Heilter formula.
115 << 123
116 G4double ekin = std::max(CLHEP::eV, kinetic << 124 G4double tau = kineticEnergy/electron_mass_c2;
117 <<
118 G4double tau = ekin/CLHEP::electron_mass_c <<
119 G4double gam = tau + 1.0; 125 G4double gam = tau + 1.0;
120 G4double gamma2= gam*gam; 126 G4double gamma2= gam*gam;
121 G4double bg2 = tau * (tau+2.0); 127 G4double bg2 = tau * (tau+2.0);
122 G4double bg = std::sqrt(bg2); << 128 G4double bg = sqrt(bg2);
123 129
124 G4double cross = pi_rcl2*((gamma2+4*gam+1.)* << 130 G4double cross = pi_rcl2*((gamma2+4*gam+1.)*log(gam+bg) - (gam+3.)*bg)
125 / (bg2*(gam+1.)); 131 / (bg2*(gam+1.));
126 return cross; 132 return cross;
127 } 133 }
128 134
129 //....oooOO0OOooo........oooOO0OOooo........oo 135 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
130 136
131 G4double G4eeToTwoGammaModel::ComputeCrossSect 137 G4double G4eeToTwoGammaModel::ComputeCrossSectionPerAtom(
132 const G4Pa << 138 const G4ParticleDefinition* p,
133 G4double k 139 G4double kineticEnergy, G4double Z,
134 G4double, G4double, G4double) 140 G4double, G4double, G4double)
135 { 141 {
136 // Calculates the cross section per atom of 142 // Calculates the cross section per atom of annihilation into two photons
137 return Z*ComputeCrossSectionPerElectron(kine << 143
>> 144 G4double cross = Z*ComputeCrossSectionPerElectron(p,kineticEnergy);
>> 145 return cross;
138 } 146 }
139 147
140 //....oooOO0OOooo........oooOO0OOooo........oo 148 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
141 149
142 G4double G4eeToTwoGammaModel::CrossSectionPerV 150 G4double G4eeToTwoGammaModel::CrossSectionPerVolume(
143 const G4Material* material, 151 const G4Material* material,
144 const G4ParticleDefinition*, << 152 const G4ParticleDefinition* p,
145 G4double kineticEnergy, 153 G4double kineticEnergy,
146 G4double, G4double) 154 G4double, G4double)
147 { 155 {
148 // Calculates the cross section per volume o 156 // Calculates the cross section per volume of annihilation into two photons
149 return material->GetElectronDensity()*Comput << 157
>> 158 G4double eDensity = material->GetElectronDensity();
>> 159 G4double cross = eDensity*ComputeCrossSectionPerElectron(p,kineticEnergy);
>> 160 return cross;
150 } 161 }
151 162
152 //....oooOO0OOooo........oooOO0OOooo........oo 163 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
153 164
154 // Polarisation of gamma according to M.H.L.Pr << 165 void G4eeToTwoGammaModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
155 // Nature 4065 (1947) 435. <<
156 <<
157 void G4eeToTwoGammaModel::SampleSecondaries(st <<
158 const G4MaterialCutsCouple*, 166 const G4MaterialCutsCouple*,
159 const G4DynamicParticle* dp, 167 const G4DynamicParticle* dp,
160 G4double, 168 G4double,
161 G4double) 169 G4double)
162 { 170 {
163 // kill primary positron << 171 G4double PositKinEnergy = dp->GetKineticEnergy();
164 fParticleChange->SetProposedKineticEnergy(0. <<
165 fParticleChange->ProposeTrackStatus(fStopAnd <<
166 172
167 // Case at rest not considered anymore insid << 173 // Case at rest
168 G4LorentzVector lv(dp->GetMomentum(), << 174 if(PositKinEnergy == 0.0) {
169 dp->GetKineticEnergy() + 2*CLHEP::ele << 175 G4double cost = 2.*G4UniformRand()-1.;
170 G4double eGammaCMS = 0.5 * lv.mag(); << 176 G4double sint = sqrt((1. - cost)*(1. + cost));
171 << 177 G4double phi = twopi * G4UniformRand();
172 G4ThreeVector dir1 = G4RandomDirection(); << 178 G4ThreeVector dir (sint*cos(phi), sint*sin(phi), cost);
173 G4double phi = CLHEP::twopi * G4UniformRand( << 179 G4DynamicParticle* aGamma1 = new G4DynamicParticle(theGamma,
174 G4double cosphi = std::cos(phi); << 180 dir, electron_mass_c2);
175 G4double sinphi = std::sin(phi); << 181 G4DynamicParticle* aGamma2 = new G4DynamicParticle(theGamma,
176 G4ThreeVector pol1(cosphi, sinphi, 0.0); << 182 -dir, electron_mass_c2);
177 pol1.rotateUz(dir1); << 183 vdp->push_back(aGamma1);
178 G4LorentzVector lv1(eGammaCMS*dir1, eGammaCM << 184 vdp->push_back(aGamma2);
179 << 185
180 G4ThreeVector pol2(-sinphi, cosphi, 0.0); << 186 } else {
181 pol2.rotateUz(dir1); << 187
182 << 188 G4ThreeVector PositDirection = dp->GetMomentumDirection();
183 // transformation to lab system << 189
184 lv1.boost(lv.boostVector()); << 190 G4double tau = PositKinEnergy/electron_mass_c2;
185 lv -= lv1; << 191 G4double gam = tau + 1.0;
186 << 192 G4double tau2 = tau + 2.0;
187 //!!! boost of polarisation vector is not ye << 193 G4double sqgrate = sqrt(tau/tau2)*0.5;
188 << 194 G4double sqg2m1 = sqrt(tau*tau2);
189 // use constructors optimal for massless par << 195
190 auto aGamma1 = new G4DynamicParticle(G4Gamma << 196 // limits of the energy sampling
191 aGamma1->SetPolarization(pol1); << 197 G4double epsilmin = 0.5 - sqgrate;
192 auto aGamma2 = new G4DynamicParticle(G4Gamma << 198 G4double epsilmax = 0.5 + sqgrate;
193 aGamma2->SetPolarization(pol2); << 199 G4double epsilqot = epsilmax/epsilmin;
194 << 200
195 vdp->push_back(aGamma1); << 201 //
196 vdp->push_back(aGamma2); << 202 // sample the energy rate of the created gammas
>> 203 //
>> 204 G4double epsil, greject;
>> 205
>> 206 do {
>> 207 epsil = epsilmin*pow(epsilqot,G4UniformRand());
>> 208 greject = 1. - epsil + (2.*gam*epsil-1.)/(epsil*tau2*tau2);
>> 209 } while( greject < G4UniformRand() );
>> 210
>> 211 //
>> 212 // scattered Gamma angles. ( Z - axis along the parent positron)
>> 213 //
>> 214
>> 215 G4double cost = (epsil*tau2-1.)/(epsil*sqg2m1);
>> 216 if(std::abs(cost) > 1.0) {
>> 217 G4cout << "### G4eeToTwoGammaModel WARNING cost= " << cost
>> 218 << " positron Ekin(MeV)= " << PositKinEnergy
>> 219 << " gamma epsil= " << epsil
>> 220 << G4endl;
>> 221 if(cost > 1.0) cost = 1.0;
>> 222 else cost = -1.0;
>> 223 }
>> 224 G4double sint = sqrt((1.+cost)*(1.-cost));
>> 225 G4double phi = twopi * G4UniformRand();
>> 226
>> 227 G4double dirx = sint*cos(phi) , diry = sint*sin(phi) , dirz = cost;
>> 228
>> 229 //
>> 230 // kinematic of the created pair
>> 231 //
>> 232
>> 233 G4double TotalAvailableEnergy = PositKinEnergy + 2.0*electron_mass_c2;
>> 234 G4double Phot1Energy = epsil*TotalAvailableEnergy;
>> 235
>> 236 G4ThreeVector Phot1Direction (dirx, diry, dirz);
>> 237 Phot1Direction.rotateUz(PositDirection);
>> 238 G4DynamicParticle* aGamma1 =
>> 239 new G4DynamicParticle (theGamma,Phot1Direction, Phot1Energy);
>> 240 vdp->push_back(aGamma1);
>> 241
>> 242 G4double Phot2Energy =(1.-epsil)*TotalAvailableEnergy;
>> 243 G4double PositP= sqrt(PositKinEnergy*(PositKinEnergy+2.*electron_mass_c2));
>> 244 G4ThreeVector dir = PositDirection*PositP - Phot1Direction*Phot1Energy;
>> 245 G4ThreeVector Phot2Direction = dir.unit();
>> 246
>> 247 // create G4DynamicParticle object for the particle2
>> 248 G4DynamicParticle* aGamma2=
>> 249 new G4DynamicParticle (theGamma,Phot2Direction, Phot2Energy);
>> 250 vdp->push_back(aGamma2);
>> 251 /*
>> 252 G4cout << "Annihilation in fly: e0= " << PositKinEnergy
>> 253 << " m= " << electron_mass_c2
>> 254 << " e1= " << Phot1Energy
>> 255 << " e2= " << Phot2Energy << " dir= " << dir
>> 256 << " -> " << Phot1Direction << " "
>> 257 << Phot2Direction << G4endl;
>> 258 */
>> 259 }
>> 260 fParticleChange->SetProposedKineticEnergy(0.);
>> 261 fParticleChange->ProposeTrackStatus(fStopAndKill);
197 } 262 }
198 263
199 //....oooOO0OOooo........oooOO0OOooo........oo 264 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
200 265