source: trunk/source/processes/electromagnetic/standard/src/G4HeatedKleinNishinaCompton.cc@ 1201

Last change on this file since 1201 was 1196, checked in by garnier, 16 years ago

update CVS release candidate geant4.9.3.01
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25//
26// $Id: G4HeatedKleinNishinaCompton.cc,v 1.5 2009/04/12 17:09:57 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03-cand-01 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4HeatedKleinNishinaCompton
35//
36// Author: Vladimir Grichine on base of M. Maire and V. Ivanchenko code
37//
38// Creation date: 15.03.2009
39//
40// Modifications:
41//
42//
43// Class Description:
44//
45// -------------------------------------------------------------------
46//
47//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
48//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
49
50#include <CLHEP/Random/RandGamma.h>
51#include "globals.hh"
52#include "G4RandomDirection.hh"
53#include "Randomize.hh"
54
55#include "G4HeatedKleinNishinaCompton.hh"
56#include "G4Electron.hh"
57#include "G4Gamma.hh"
58#include "Randomize.hh"
59#include "G4DataVector.hh"
60#include "G4ParticleChangeForGamma.hh"
61
62//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
63
64using namespace std;
65
66G4HeatedKleinNishinaCompton::G4HeatedKleinNishinaCompton(const G4ParticleDefinition*,
67 const G4String& nam)
68 : G4VEmModel(nam)
69{
70 theGamma = G4Gamma::Gamma();
71 theElectron = G4Electron::Electron();
72 lowestGammaEnergy = 1.0*eV;
73 fTemperature = 1.0*keV;
74 fParticleChange = 0;
75}
76
77//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
78
79G4HeatedKleinNishinaCompton::~G4HeatedKleinNishinaCompton()
80{}
81
82//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
83
84void G4HeatedKleinNishinaCompton::Initialise(const G4ParticleDefinition*,
85 const G4DataVector&)
86{
87 if(!fParticleChange) fParticleChange = GetParticleChangeForGamma();
88}
89
90////////////////////////////////////////////////////////////////////////////
91//
92//
93
94G4double G4HeatedKleinNishinaCompton::ComputeCrossSectionPerAtom(
95 const G4ParticleDefinition*,
96 G4double GammaEnergy,
97 G4double Z, G4double,
98 G4double, G4double)
99{
100 G4double CrossSection = 0.0 ;
101 if ( Z < 0.9999 ) return CrossSection;
102 if ( GammaEnergy < 0.01*keV ) return CrossSection;
103 // if ( GammaEnergy > (100.*GeV/Z) ) return CrossSection;
104
105 static const G4double a = 20.0 , b = 230.0 , c = 440.0;
106
107 static const G4double
108 d1= 2.7965e-1*barn, d2=-1.8300e-1*barn, d3= 6.7527 *barn, d4=-1.9798e+1*barn,
109 e1= 1.9756e-5*barn, e2=-1.0205e-2*barn, e3=-7.3913e-2*barn, e4= 2.7079e-2*barn,
110 f1=-3.9178e-7*barn, f2= 6.8241e-5*barn, f3= 6.0480e-5*barn, f4= 3.0274e-4*barn;
111
112 G4double p1Z = Z*(d1 + e1*Z + f1*Z*Z), p2Z = Z*(d2 + e2*Z + f2*Z*Z),
113 p3Z = Z*(d3 + e3*Z + f3*Z*Z), p4Z = Z*(d4 + e4*Z + f4*Z*Z);
114
115 G4double T0 = 15.0*keV;
116 if (Z < 1.5) T0 = 40.0*keV;
117
118 G4double X = max(GammaEnergy, T0) / electron_mass_c2;
119 CrossSection = p1Z*std::log(1.+2.*X)/X
120 + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X);
121
122 // modification for low energy. (special case for Hydrogen)
123 if (GammaEnergy < T0) {
124 G4double dT0 = 1.*keV;
125 X = (T0+dT0) / electron_mass_c2 ;
126 G4double sigma = p1Z*log(1.+2*X)/X
127 + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X);
128 G4double c1 = -T0*(sigma-CrossSection)/(CrossSection*dT0);
129 G4double c2 = 0.150;
130 if (Z > 1.5) c2 = 0.375-0.0556*log(Z);
131 G4double y = log(GammaEnergy/T0);
132 CrossSection *= exp(-y*(c1+c2*y));
133 }
134 // G4cout << "e= " << GammaEnergy << " Z= " << Z << " cross= " << CrossSection << G4endl;
135 return CrossSection;
136}
137
138//////////////////////////////////////////////////////////////////////////
139//
140//
141
142void G4HeatedKleinNishinaCompton::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
143 const G4MaterialCutsCouple*,
144 const G4DynamicParticle* aDynamicGamma,
145 G4double,
146 G4double)
147{
148 // The scattered gamma energy is sampled according to Klein - Nishina formula.
149 // The random number techniques of Butcher & Messel are used
150 // (Nuc Phys 20(1960),15).
151 // Note : Effects due to binding of atomic electrons are negliged.
152
153 // We start to prepare a heated electron from Maxwell distribution.
154 // Then we try to boost to the electron rest frame and make scattering.
155 // The final step is to recover new gamma 4momentum in the lab frame
156
157 G4double eMomentumC2 = CLHEP::RandGamma::shoot(1.5,1.);
158 eMomentumC2 *= 2*electron_mass_c2*fTemperature; // electron (pc)^2
159 G4ThreeVector eMomDir = G4RandomDirection();
160 eMomDir *= std::sqrt(eMomentumC2);
161 G4double eEnergy = std::sqrt(eMomentumC2+electron_mass_c2*electron_mass_c2);
162 G4LorentzVector electron4v = G4LorentzVector(eMomDir,eEnergy);
163 G4ThreeVector bst = electron4v.boostVector();
164
165 G4LorentzVector gamma4v = aDynamicGamma->Get4Momentum();
166 gamma4v.boost(-bst);
167
168 G4ThreeVector gammaMomV = gamma4v.vect();
169 G4double gamEnergy0 = gammaMomV.mag();
170
171
172 // G4double gamEnergy0 = aDynamicGamma->GetKineticEnergy();
173 G4double E0_m = gamEnergy0 / electron_mass_c2 ;
174
175 // G4ThreeVector gamDirection0 = /aDynamicGamma->GetMomentumDirection();
176
177 G4ThreeVector gamDirection0 = gammaMomV/gamEnergy0;
178
179 // sample the energy rate of the scattered gamma in the electron rest frame
180 //
181
182 G4double epsilon, epsilonsq, onecost, sint2, greject ;
183
184 G4double epsilon0 = 1./(1. + 2.*E0_m);
185 G4double epsilon0sq = epsilon0*epsilon0;
186 G4double alpha1 = - log(epsilon0);
187 G4double alpha2 = 0.5*(1.- epsilon0sq);
188
189 do
190 {
191 if ( alpha1/(alpha1+alpha2) > G4UniformRand() )
192 {
193 epsilon = exp(-alpha1*G4UniformRand()); // epsilon0**r
194 epsilonsq = epsilon*epsilon;
195
196 }
197 else
198 {
199 epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand();
200 epsilon = sqrt(epsilonsq);
201 };
202
203 onecost = (1.- epsilon)/(epsilon*E0_m);
204 sint2 = onecost*(2.-onecost);
205 greject = 1. - epsilon*sint2/(1.+ epsilonsq);
206
207 } while (greject < G4UniformRand());
208
209 //
210 // scattered gamma angles. ( Z - axis along the parent gamma)
211 //
212
213 G4double cosTeta = 1. - onecost;
214 G4double sinTeta = sqrt (sint2);
215 G4double Phi = twopi * G4UniformRand();
216 G4double dirx = sinTeta*cos(Phi), diry = sinTeta*sin(Phi), dirz = cosTeta;
217
218 //
219 // update G4VParticleChange for the scattered gamma
220 //
221
222 G4ThreeVector gamDirection1 ( dirx,diry,dirz );
223 gamDirection1.rotateUz(gamDirection0);
224 G4double gamEnergy1 = epsilon*gamEnergy0;
225 gamDirection1 *= gamEnergy1;
226
227 G4LorentzVector gamma4vfinal = G4LorentzVector(gamDirection1,gamEnergy1);
228
229
230 // kinematic of the scattered electron
231 //
232
233 G4double eKinEnergy = gamEnergy0 - gamEnergy1;
234 G4ThreeVector eDirection = gamEnergy0*gamDirection0 - gamEnergy1*gamDirection1;
235 eDirection = eDirection.unit();
236 G4double eFinalMom = std::sqrt(eKinEnergy*(eKinEnergy+2*electron_mass_c2));
237 eDirection *= eFinalMom;
238 G4LorentzVector e4vfinal = G4LorentzVector(eDirection,gamEnergy1+electron_mass_c2);
239
240 gamma4vfinal.boost(bst);
241 e4vfinal.boost(bst);
242
243 gamDirection1 = gamma4vfinal.vect();
244 gamEnergy1 = gamDirection1.mag();
245 gamDirection1 /= gamEnergy1;
246
247
248
249
250 fParticleChange->SetProposedKineticEnergy(gamEnergy1);
251
252 if( gamEnergy1 > lowestGammaEnergy )
253 {
254 gamDirection1 /= gamEnergy1;
255 fParticleChange->ProposeMomentumDirection(gamDirection1);
256 }
257 else
258 {
259 fParticleChange->ProposeTrackStatus(fStopAndKill);
260 gamEnergy1 += fParticleChange->GetLocalEnergyDeposit();
261 fParticleChange->ProposeLocalEnergyDeposit(gamEnergy1);
262 }
263
264 eKinEnergy = e4vfinal.t()-electron_mass_c2;
265
266 if( eKinEnergy > DBL_MIN )
267 {
268 // create G4DynamicParticle object for the electron.
269 eDirection = e4vfinal.vect();
270 G4double eFinMomMag = eDirection.mag();
271 eDirection /= eFinMomMag;
272 G4DynamicParticle* dp = new G4DynamicParticle(theElectron,eDirection,eKinEnergy);
273 fvect->push_back(dp);
274 }
275}
276
277//////////////////////////////////////////////////////////////////////////
278
279
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