source: trunk/source/processes/electromagnetic/lowenergy/src/G4LivermoreGammaConversionModel.cc@ 1005

Last change on this file since 1005 was 1005, checked in by garnier, 17 years ago

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[968]1//
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25//
[1005]26// $Id: G4LivermoreGammaConversionModel.cc,v 1.2 2009/01/21 10:58:13 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
[968]28//
29
30#include "G4LivermoreGammaConversionModel.hh"
31
32//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
33
34using namespace std;
35
36//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
37
38G4LivermoreGammaConversionModel::G4LivermoreGammaConversionModel(const G4ParticleDefinition*,
39 const G4String& nam)
[1005]40:G4VEmModel(nam),smallEnergy(2.*MeV),isInitialised(false),crossSectionHandler(0),meanFreePathTable(0)
[968]41{
42 lowEnergyLimit = 1.022000 * MeV;
43 highEnergyLimit = 100 * GeV;
44
45 G4cout << "Livermore Gamma conversion is constructed " << G4endl
46 << "Energy range: "
47 << lowEnergyLimit / keV << " keV - "
48 << highEnergyLimit / GeV << " GeV"
49 << G4endl;
50
51 verboseLevel= 0;
52 // Verbosity scale:
53 // 0 = nothing
54 // 1 = warning for energy non-conservation
55 // 2 = details of energy budget
56 // 3 = calculation of cross sections, file openings, sampling of atoms
57 // 4 = entering in methods
58
59}
60
61//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
62
63G4LivermoreGammaConversionModel::~G4LivermoreGammaConversionModel()
64{
[1005]65 if (meanFreePathTable) delete meanFreePathTable;
66 if (crossSectionHandler) delete crossSectionHandler;
[968]67}
68
69//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
70
71void G4LivermoreGammaConversionModel::Initialise(const G4ParticleDefinition* particle,
72 const G4DataVector& cuts)
73{
74 if (verboseLevel > 3)
75 G4cout << "Calling G4LivermoreGammaConversionModel::Initialise()" << G4endl;
76
[1005]77 if (crossSectionHandler)
78 {
79 crossSectionHandler->Clear();
80 delete crossSectionHandler;
81 }
[968]82
83 // Energy limits
84
85 if (LowEnergyLimit() < lowEnergyLimit)
86 {
87 G4cout << "G4LivermoreGammaConversionModel: low energy limit increased from " <<
88 LowEnergyLimit()/eV << " eV to " << lowEnergyLimit << " eV" << G4endl;
89 SetLowEnergyLimit(lowEnergyLimit);
90 }
91
92 if (HighEnergyLimit() > highEnergyLimit)
93 {
94 G4cout << "G4LivermoreGammaConversionModel: high energy limit decreased from " <<
95 HighEnergyLimit()/GeV << " GeV to " << highEnergyLimit << " GeV" << G4endl;
96 SetHighEnergyLimit(highEnergyLimit);
97 }
98
99 // Read data tables for all materials
100
101 crossSectionHandler = new G4CrossSectionHandler();
102 crossSectionHandler->Initialise(0,1.0220*MeV,100.*GeV,400);
103 G4String crossSectionFile = "pair/pp-cs-";
104 crossSectionHandler->LoadData(crossSectionFile);
105
106 meanFreePathTable = 0;
107 meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
108
109 //
110
111 if (verboseLevel > 2)
112 G4cout << "Loaded cross section files for PenelopeGammaConversion" << G4endl;
113
[1005]114 InitialiseElementSelectors(particle,cuts);
115
[968]116 G4cout << "Livermore Gamma Conversion model is initialized " << G4endl
117 << "Energy range: "
118 << LowEnergyLimit() / MeV << " MeV - "
119 << HighEnergyLimit() / GeV << " GeV"
120 << G4endl;
121
122 if(isInitialised) return;
123
124 if(pParticleChange)
125 fParticleChange = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
126 else
127 fParticleChange = new G4ParticleChangeForGamma();
128 isInitialised = true;}
129
130//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
131
132G4double G4LivermoreGammaConversionModel::ComputeCrossSectionPerAtom(
133 const G4ParticleDefinition*,
134 G4double GammaEnergy,
135 G4double Z, G4double,
136 G4double, G4double)
137{
138 if (verboseLevel > 3)
139 G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreGammaConversionModel" << G4endl;
140
141 G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
142 return cs;
143}
144
145//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
146
147void G4LivermoreGammaConversionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
148 const G4MaterialCutsCouple* couple,
149 const G4DynamicParticle* aDynamicGamma,
150 G4double,
151 G4double)
152{
153
154// The energies of the e+ e- secondaries are sampled using the Bethe - Heitler
155// cross sections with Coulomb correction. A modified version of the random
156// number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15).
157
158// Note 1 : Effects due to the breakdown of the Born approximation at low
159// energy are ignored.
160// Note 2 : The differential cross section implicitly takes account of
161// pair creation in both nuclear and atomic electron fields. However triplet
162// prodution is not generated.
163
164 if (verboseLevel > 3)
165 G4cout << "Calling SampleSecondaries() of G4LivermoreGammaConversionModel" << G4endl;
166
167 G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
168 G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
169
170 G4double epsilon ;
171 G4double epsilon0 = electron_mass_c2 / photonEnergy ;
172
173 // Do it fast if photon energy < 2. MeV
174 if (photonEnergy < smallEnergy )
175 {
176 epsilon = epsilon0 + (0.5 - epsilon0) * G4UniformRand();
177 }
178 else
179 {
180 // Select randomly one element in the current material
181 const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy);
182
183 if (element == 0)
184 {
185 G4cout << "G4LivermoreGammaConversionModel::SampleSecondaries - element = 0" << G4endl;
186 }
187 G4IonisParamElm* ionisation = element->GetIonisation();
188 if (ionisation == 0)
189 {
190 G4cout << "G4LivermoreGammaConversionModel::SampleSecondaries - ionisation = 0" << G4endl;
191 }
192
193 // Extract Coulomb factor for this Element
194 G4double fZ = 8. * (ionisation->GetlogZ3());
195 if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb());
196
197 // Limits of the screening variable
198 G4double screenFactor = 136. * epsilon0 / (element->GetIonisation()->GetZ3()) ;
199 G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ;
200 G4double screenMin = std::min(4.*screenFactor,screenMax) ;
201
202 // Limits of the energy sampling
203 G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ;
204 G4double epsilonMin = std::max(epsilon0,epsilon1);
205 G4double epsilonRange = 0.5 - epsilonMin ;
206
207 // Sample the energy rate of the created electron (or positron)
208 G4double screen;
209 G4double gReject ;
210
211 G4double f10 = ScreenFunction1(screenMin) - fZ;
212 G4double f20 = ScreenFunction2(screenMin) - fZ;
213 G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.);
214 G4double normF2 = std::max(1.5 * f20,0.);
215
216 do {
217 if (normF1 / (normF1 + normF2) > G4UniformRand() )
218 {
219 epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ;
220 screen = screenFactor / (epsilon * (1. - epsilon));
221 gReject = (ScreenFunction1(screen) - fZ) / f10 ;
222 }
223 else
224 {
225 epsilon = epsilonMin + epsilonRange * G4UniformRand();
226 screen = screenFactor / (epsilon * (1 - epsilon));
227 gReject = (ScreenFunction2(screen) - fZ) / f20 ;
228 }
229 } while ( gReject < G4UniformRand() );
230
231 } // End of epsilon sampling
232
233 // Fix charges randomly
234
235 G4double electronTotEnergy;
236 G4double positronTotEnergy;
237
238 if (CLHEP::RandBit::shootBit())
239 {
240 electronTotEnergy = (1. - epsilon) * photonEnergy;
241 positronTotEnergy = epsilon * photonEnergy;
242 }
243 else
244 {
245 positronTotEnergy = (1. - epsilon) * photonEnergy;
246 electronTotEnergy = epsilon * photonEnergy;
247 }
248
249 // Scattered electron (positron) angles. ( Z - axis along the parent photon)
250 // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211),
251 // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977)
252
253 G4double u;
254 const G4double a1 = 0.625;
255 G4double a2 = 3. * a1;
256 // G4double d = 27. ;
257
258 // if (9. / (9. + d) > G4UniformRand())
259 if (0.25 > G4UniformRand())
260 {
261 u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ;
262 }
263 else
264 {
265 u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ;
266 }
267
268 G4double thetaEle = u*electron_mass_c2/electronTotEnergy;
269 G4double thetaPos = u*electron_mass_c2/positronTotEnergy;
270 G4double phi = twopi * G4UniformRand();
271
272 G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle);
273 G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos);
274
275
276 // Kinematics of the created pair:
277 // the electron and positron are assumed to have a symetric angular
278 // distribution with respect to the Z axis along the parent photon
279
280// aParticleChange.SetNumberOfSecondaries(2) ;
281 G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
282
283// SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
284
285 G4ThreeVector electronDirection (dxEle, dyEle, dzEle);
286 electronDirection.rotateUz(photonDirection);
287
288 G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(),
289 electronDirection,
290 electronKineEnergy);
291
292 // The e+ is always created (even with kinetic energy = 0) for further annihilation
293 G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
294
295// SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
296
297 G4ThreeVector positronDirection (dxPos, dyPos, dzPos);
298 positronDirection.rotateUz(photonDirection);
299
300 // Create G4DynamicParticle object for the particle2
301 G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(),
302 positronDirection, positronKineEnergy);
303 // Fill output vector
304 fvect->push_back(particle1);
305 fvect->push_back(particle2);
306
307 // kill incident photon
308 fParticleChange->SetProposedKineticEnergy(0.);
309 fParticleChange->ProposeTrackStatus(fStopAndKill);
310
311}
312
313//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
314
315G4double G4LivermoreGammaConversionModel::ScreenFunction1(G4double screenVariable)
316{
317 // Compute the value of the screening function 3*phi1 - phi2
318
319 G4double value;
320
321 if (screenVariable > 1.)
322 value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
323 else
324 value = 42.392 - screenVariable * (7.796 - 1.961 * screenVariable);
325
326 return value;
327}
328
329//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
330
331G4double G4LivermoreGammaConversionModel::ScreenFunction2(G4double screenVariable)
332{
333 // Compute the value of the screening function 1.5*phi1 - 0.5*phi2
334
335 G4double value;
336
337 if (screenVariable > 1.)
338 value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
339 else
340 value = 41.405 - screenVariable * (5.828 - 0.8945 * screenVariable);
341
342 return value;
343}
344
345//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
346
347G4double G4LivermoreGammaConversionModel::GetMeanFreePath(const G4Track& track,
348 G4double, // previousStepSize
349 G4ForceCondition*)
350{
351 const G4DynamicParticle* photon = track.GetDynamicParticle();
352 G4double energy = photon->GetKineticEnergy();
353 const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
354 size_t materialIndex = couple->GetIndex();
355
356 G4double meanFreePath;
357 if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
358 else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
359 else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
360 return meanFreePath;
361}
362
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