source: trunk/source/processes/electromagnetic/standard/src/G4KleinNishinaModel.cc@ 1357

Last change on this file since 1357 was 1350, checked in by garnier, 15 years ago

update to last version 4.9.4
File size: 9.7 KB
Line 
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// $Id: G4KleinNishinaModel.cc,v 1.1 2010/09/03 14:11:16 vnivanch Exp $
27// GEANT4 tag $Name: emstand-V09-03-24 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4KleinNishinaModel
35//
36// Author: Vladimir Ivanchenko on base of G4KleinNishinaCompton
37//
38// Creation date: 13.06.2010
39//
40// Modifications:
41//
42// Class Description:
43//
44// -------------------------------------------------------------------
45//
46//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
47//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
48
49#include "G4KleinNishinaModel.hh"
50#include "G4Electron.hh"
51#include "G4Gamma.hh"
52#include "Randomize.hh"
53#include "G4RandomDirection.hh"
54#include "G4DataVector.hh"
55#include "G4ParticleChangeForGamma.hh"
56#include "G4VAtomDeexcitation.hh"
57#include "G4LossTableManager.hh"
58
59//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
60
61using namespace std;
62
63G4KleinNishinaModel::G4KleinNishinaModel(const G4String& nam)
64 : G4VEmModel(nam),isInitialized(false)
65{
66 theGamma = G4Gamma::Gamma();
67 theElectron = G4Electron::Electron();
68 lowestGammaEnergy = 1.0*eV;
69 fProbabilities.resize(9,0.0);
70}
71
72//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
73
74G4KleinNishinaModel::~G4KleinNishinaModel()
75{}
76
77//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
78
79void G4KleinNishinaModel::Initialise(const G4ParticleDefinition* p,
80 const G4DataVector& cuts)
81{
82 fAtomDeexcitation = G4LossTableManager::Instance()->AtomDeexcitation();
83 InitialiseElementSelectors(p, cuts);
84
85 if (isInitialized) { return; }
86 fParticleChange = GetParticleChangeForGamma();
87 isInitialized = true;
88}
89
90//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
91
92G4double
93G4KleinNishinaModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*,
94 G4double GammaEnergy,
95 G4double Z, G4double,
96 G4double, G4double)
97{
98 G4double CrossSection = 0.0 ;
99 if ( Z < 0.9999 || GammaEnergy < 0.1*keV) { return CrossSection; }
100
101 static const G4double a = 20.0 , b = 230.0 , c = 440.0;
102
103 static const G4double
104 d1= 2.7965e-1*barn, d2=-1.8300e-1*barn, d3= 6.7527 *barn, d4=-1.9798e+1*barn,
105 e1= 1.9756e-5*barn, e2=-1.0205e-2*barn, e3=-7.3913e-2*barn, e4= 2.7079e-2*barn,
106 f1=-3.9178e-7*barn, f2= 6.8241e-5*barn, f3= 6.0480e-5*barn, f4= 3.0274e-4*barn;
107
108 G4double p1Z = Z*(d1 + e1*Z + f1*Z*Z), p2Z = Z*(d2 + e2*Z + f2*Z*Z),
109 p3Z = Z*(d3 + e3*Z + f3*Z*Z), p4Z = Z*(d4 + e4*Z + f4*Z*Z);
110
111 G4double T0 = 15.0*keV;
112 if (Z < 1.5) { T0 = 40.0*keV; }
113
114 G4double X = max(GammaEnergy, T0) / electron_mass_c2;
115 CrossSection = p1Z*std::log(1.+2.*X)/X
116 + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X);
117
118 // modification for low energy. (special case for Hydrogen)
119 if (GammaEnergy < T0) {
120 G4double dT0 = keV;
121 X = (T0+dT0) / electron_mass_c2 ;
122 G4double sigma = p1Z*log(1.+2*X)/X
123 + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X);
124 G4double c1 = -T0*(sigma-CrossSection)/(CrossSection*dT0);
125 G4double c2 = 0.150;
126 if (Z > 1.5) { c2 = 0.375-0.0556*log(Z); }
127 G4double y = log(GammaEnergy/T0);
128 CrossSection *= exp(-y*(c1+c2*y));
129 }
130 // G4cout << "e= " << GammaEnergy << " Z= " << Z
131 // << " cross= " << CrossSection << G4endl;
132 return CrossSection;
133}
134
135//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
136
137void G4KleinNishinaModel::SampleSecondaries(
138 std::vector<G4DynamicParticle*>* fvect,
139 const G4MaterialCutsCouple* couple,
140 const G4DynamicParticle* aDynamicGamma,
141 G4double,
142 G4double)
143{
144 G4double energy = aDynamicGamma->GetKineticEnergy();
145 G4ThreeVector direction = aDynamicGamma->GetMomentumDirection();
146
147 // select atom
148 const G4Element* elm = SelectRandomAtom(couple, theGamma, energy);
149
150 // select shell first
151 G4int Z = (G4int)elm->GetZ();
152 G4int nShells = elm->GetNbOfAtomicShells();
153 if(nShells > (G4int)fProbabilities.size()) { fProbabilities.resize(nShells); }
154 G4double totprob = 0.0;
155 G4int i = 0;
156 for(; i<nShells; ++i) {
157 G4double prob = 0.0;
158 if(energy > elm->GetAtomicShell(i)) {
159 prob = (G4double)elm->GetNbOfShellElectrons(i);
160 }
161 totprob += prob;
162 fProbabilities[i] = totprob;
163 }
164 if(totprob == 0.0) { return; }
165
166 G4LorentzVector lv1, lv2, lv3;
167 G4LorentzVector lv0(energy*direction.x(),energy*direction.y(),
168 energy*direction.z(),energy);
169 G4double eKinEnergy = 0.0;
170 G4double gamEnergy1 = 0.0;
171
172 // Loop on sampling
173 do {
174 G4double xprob = totprob*G4UniformRand();
175
176 for(i=0; i<nShells; ++i) { if(xprob <= fProbabilities[i]) {break;} }
177 if( i == nShells ) { return; }
178
179 G4double bindingEnergy = elm->GetAtomicShell(i);
180 G4double tkin = bindingEnergy*0.5;
181 G4double eEnergy = tkin + electron_mass_c2;
182 G4double eTotMomentum = sqrt(tkin*(tkin + electron_mass_c2*2));
183 G4ThreeVector eDir = G4RandomDirection();
184 lv1 = lv0;
185 lv2.set(eTotMomentum*eDir.x(),eTotMomentum*eDir.y(),
186 eTotMomentum*eDir.z(),eEnergy);
187 G4ThreeVector bst = lv2.boostVector();
188 lv1.boost(-bst);
189
190 // In the rest frame of an electron
191 // The scattered gamma energy is sampled according to Klein - Nishina formula.
192 // The random number techniques of Butcher & Messel are used
193 // (Nuc Phys 20(1960),15).
194
195 G4double gamEnergy0 = lv1.e();
196 G4double E0_m = gamEnergy0 / electron_mass_c2 ;
197
198 G4ThreeVector gamDirection0 = (lv1.vect()).unit();
199
200 //
201 // sample the energy rate of the scattered gamma
202 //
203
204 G4double epsilon, epsilonsq, onecost, sint2, greject ;
205
206 G4double epsilon0 = 1./(1. + 2.*E0_m);
207 G4double epsilon0sq = epsilon0*epsilon0;
208 G4double alpha1 = - log(epsilon0);
209 G4double alpha2 = 0.5*(1.- epsilon0sq);
210
211 do {
212 if ( alpha1/(alpha1+alpha2) > G4UniformRand() ) {
213 epsilon = exp(-alpha1*G4UniformRand()); // epsilon0**r
214 epsilonsq = epsilon*epsilon;
215
216 } else {
217 epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand();
218 epsilon = sqrt(epsilonsq);
219 };
220
221 onecost = (1.- epsilon)/(epsilon*E0_m);
222 sint2 = onecost*(2.-onecost);
223 greject = 1. - epsilon*sint2/(1.+ epsilonsq);
224
225 } while (greject < G4UniformRand());
226
227 //
228 // scattered gamma angles. ( Z - axis along the parent gamma)
229 //
230
231 G4double cosTeta = 1. - onecost;
232 G4double sinTeta = sqrt (sint2);
233 G4double Phi = twopi * G4UniformRand();
234 G4double dirx = sinTeta*cos(Phi), diry = sinTeta*sin(Phi), dirz = cosTeta;
235
236 //
237 // update G4VParticleChange for the scattered gamma
238 //
239
240 G4ThreeVector gamDirection1 ( dirx,diry,dirz );
241 gamDirection1.rotateUz(gamDirection0);
242 gamEnergy1 = epsilon*gamEnergy0;
243
244 // before scattering
245 lv2.set(0.0,0.0,0.0,electron_mass_c2);
246 lv2 += lv1;
247
248 // after scattering
249 lv1.set(gamEnergy1*gamDirection1.x(),gamEnergy1*gamDirection1.y(),
250 gamEnergy1*gamDirection1.z(),gamEnergy1);
251 lv2 -= lv1;
252 lv2.boost(bst);
253 lv1.boost(bst);
254 eKinEnergy = lv2.e() - electron_mass_c2 - bindingEnergy;
255 } while ( eKinEnergy < 0.0 );
256
257 // gamma kinematics
258 gamEnergy1 = lv1.e();
259 if(gamEnergy1 > lowestGammaEnergy) {
260 fParticleChange->SetProposedKineticEnergy(gamEnergy1);
261 fParticleChange->ProposeMomentumDirection((lv1.vect()).unit());
262 } else {
263 fParticleChange->ProposeTrackStatus(fStopAndKill);
264 fParticleChange->ProposeLocalEnergyDeposit(gamEnergy1);
265 }
266
267 //
268 // kinematic of the scattered electron
269 //
270 if(eKinEnergy > DBL_MIN) {
271 G4ThreeVector eDirection = (lv2.vect()).unit();
272 G4DynamicParticle* dp = new G4DynamicParticle(theElectron,eDirection,eKinEnergy);
273 fvect->push_back(dp);
274 }
275 // sample deexcitation
276 //
277 if(fAtomDeexcitation) {
278 G4AtomicShellEnumerator as = G4AtomicShellEnumerator(i);
279 const G4AtomicShell* shell = fAtomDeexcitation->GetAtomicShell(Z, as);
280 fAtomDeexcitation->GenerateParticles(fvect, shell, Z, couple->GetIndex());
281 }
282}
283
284//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
285
Note: See TracBrowser for help on using the repository browser.