source: trunk/source/processes/electromagnetic/muons/src/G4MuBremsstrahlungModel.cc@ 1199

Last change on this file since 1199 was 1196, checked in by garnier, 16 years ago

update CVS release candidate geant4.9.3.01
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25//
26// $Id: G4MuBremsstrahlungModel.cc,v 1.35 2009/04/12 17:48:45 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03-cand-01 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4MuBremsstrahlungModel
35//
36// Author: Vladimir Ivanchenko on base of Laszlo Urban code
37//
38// Creation date: 24.06.2002
39//
40// Modifications:
41//
42// 04-12-02 Change G4DynamicParticle constructor in PostStepDoIt (V.Ivanchenko)
43// 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
44// 24-01-03 Fix for compounds (V.Ivanchenko)
45// 27-01-03 Make models region aware (V.Ivanchenko)
46// 13-02-03 Add name (V.Ivanchenko)
47// 10-02-04 Add lowestKinEnergy (V.Ivanchenko)
48// 08-04-05 Major optimisation of internal interfaces (V.Ivanchenko)
49// 03-08-05 Angular correlations according to PRM (V.Ivanchenko)
50// 13-02-06 add ComputeCrossSectionPerAtom (mma)
51// 21-03-06 Fix problem of initialisation in case when cuts are not defined (VI)
52// 07-11-07 Improve sampling of final state (A.Bogdanov)
53// 28-02-08 Use precomputed Z^1/3 and Log(A) (V.Ivanchenko)
54//
55
56//
57// Class Description:
58//
59//
60// -------------------------------------------------------------------
61//
62//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
63//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
64
65#include "G4MuBremsstrahlungModel.hh"
66#include "G4Gamma.hh"
67#include "G4MuonMinus.hh"
68#include "G4MuonPlus.hh"
69#include "Randomize.hh"
70#include "G4Material.hh"
71#include "G4Element.hh"
72#include "G4ElementVector.hh"
73#include "G4ProductionCutsTable.hh"
74#include "G4ParticleChangeForLoss.hh"
75
76//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
77//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
78
79using namespace std;
80
81G4MuBremsstrahlungModel::G4MuBremsstrahlungModel(const G4ParticleDefinition* p,
82 const G4String& nam)
83 : G4VEmModel(nam),
84 particle(0),
85 sqrte(sqrt(exp(1.))),
86 bh(202.4),
87 bh1(446.),
88 btf(183.),
89 btf1(1429.),
90 fParticleChange(0),
91 lowestKinEnergy(1.0*GeV),
92 minThreshold(1.0*keV)
93{
94 theGamma = G4Gamma::Gamma();
95 nist = G4NistManager::Instance();
96 if(p) SetParticle(p);
97}
98
99//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
100
101G4MuBremsstrahlungModel::~G4MuBremsstrahlungModel()
102{
103 size_t n = partialSumSigma.size();
104 if(n > 0) {
105 for(size_t i=0; i<n; i++) {
106 delete partialSumSigma[i];
107 }
108 }
109}
110
111//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
112
113G4double G4MuBremsstrahlungModel::MinEnergyCut(const G4ParticleDefinition*,
114 const G4MaterialCutsCouple*)
115{
116 return minThreshold;
117}
118
119//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
120
121void G4MuBremsstrahlungModel::Initialise(const G4ParticleDefinition* p,
122 const G4DataVector& cuts)
123{
124 if(p) SetParticle(p);
125
126 highKinEnergy = HighEnergyLimit();
127
128 // partial cross section is computed for fixed energy
129 G4double fixedEnergy = 0.5*highKinEnergy;
130
131 const G4ProductionCutsTable* theCoupleTable=
132 G4ProductionCutsTable::GetProductionCutsTable();
133 if(theCoupleTable) {
134 G4int numOfCouples = theCoupleTable->GetTableSize();
135
136 // clear old data
137 G4int nn = partialSumSigma.size();
138 G4int nc = cuts.size();
139 if(nn > 0) {
140 for (G4int ii=0; ii<nn; ii++){
141 G4DataVector* a = partialSumSigma[ii];
142 if ( a ) delete a;
143 }
144 partialSumSigma.clear();
145 }
146 // fill new data
147 if (numOfCouples>0) {
148 for (G4int i=0; i<numOfCouples; i++) {
149 G4double cute = DBL_MAX;
150
151 // protection for usage with extrapolator
152 if(i < nc) cute = cuts[i];
153
154 const G4MaterialCutsCouple* couple =
155 theCoupleTable->GetMaterialCutsCouple(i);
156 const G4Material* material = couple->GetMaterial();
157 G4DataVector* dv = ComputePartialSumSigma(material,fixedEnergy,cute);
158 partialSumSigma.push_back(dv);
159 }
160 }
161 }
162
163 // define pointer to G4ParticleChange
164 if(!fParticleChange) fParticleChange = GetParticleChangeForLoss();
165}
166
167//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
168
169G4double G4MuBremsstrahlungModel::ComputeDEDXPerVolume(
170 const G4Material* material,
171 const G4ParticleDefinition*,
172 G4double kineticEnergy,
173 G4double cutEnergy)
174{
175 G4double dedx = 0.0;
176 if (kineticEnergy <= lowestKinEnergy) return dedx;
177
178 G4double tmax = kineticEnergy;
179 G4double cut = std::min(cutEnergy,tmax);
180 if(cut < minThreshold) cut = minThreshold;
181
182 const G4ElementVector* theElementVector = material->GetElementVector();
183 const G4double* theAtomicNumDensityVector =
184 material->GetAtomicNumDensityVector();
185
186 // loop for elements in the material
187 for (size_t i=0; i<material->GetNumberOfElements(); i++) {
188
189 G4double loss =
190 ComputMuBremLoss((*theElementVector)[i]->GetZ(), kineticEnergy, cut);
191
192 dedx += loss*theAtomicNumDensityVector[i];
193 }
194 // G4cout << "BR e= " << kineticEnergy << " dedx= " << dedx << G4endl;
195 if(dedx < 0.) dedx = 0.;
196 return dedx;
197}
198
199//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
200
201G4double G4MuBremsstrahlungModel::ComputMuBremLoss(G4double Z,
202 G4double tkin, G4double cut)
203{
204 G4double totalEnergy = mass + tkin;
205 G4double ak1 = 0.05;
206 G4int k2=5;
207 G4double xgi[]={0.03377,0.16940,0.38069,0.61931,0.83060,0.96623};
208 G4double wgi[]={0.08566,0.18038,0.23396,0.23396,0.18038,0.08566};
209 G4double loss = 0.;
210
211 G4double vcut = cut/totalEnergy;
212 G4double vmax = tkin/totalEnergy;
213
214 G4double aaa = 0.;
215 G4double bbb = vcut;
216 if(vcut>vmax) bbb=vmax ;
217 G4int kkk = (G4int)((bbb-aaa)/ak1)+k2 ;
218 G4double hhh=(bbb-aaa)/float(kkk) ;
219
220 G4double aa = aaa;
221 for(G4int l=0; l<kkk; l++)
222 {
223 for(G4int i=0; i<6; i++)
224 {
225 G4double ep = (aa + xgi[i]*hhh)*totalEnergy;
226 loss += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
227 }
228 aa += hhh;
229 }
230
231 loss *=hhh*totalEnergy ;
232
233 return loss;
234}
235
236//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
237
238G4double G4MuBremsstrahlungModel::ComputeMicroscopicCrossSection(
239 G4double tkin,
240 G4double Z,
241 G4double cut)
242{
243 G4double totalEnergy = tkin + mass;
244 G4double ak1 = 2.3;
245 G4int k2 = 4;
246 G4double xgi[]={0.03377,0.16940,0.38069,0.61931,0.83060,0.96623};
247 G4double wgi[]={0.08566,0.18038,0.23396,0.23396,0.18038,0.08566};
248 G4double cross = 0.;
249
250 if(cut >= tkin) return cross;
251
252 G4double vcut = cut/totalEnergy;
253 G4double vmax = tkin/totalEnergy;
254
255 G4double aaa = log(vcut);
256 G4double bbb = log(vmax);
257 G4int kkk = (G4int)((bbb-aaa)/ak1)+k2 ;
258 G4double hhh = (bbb-aaa)/G4double(kkk);
259
260 G4double aa = aaa;
261
262 for(G4int l=0; l<kkk; l++)
263 {
264 for(G4int i=0; i<6; i++)
265 {
266 G4double ep = exp(aa + xgi[i]*hhh)*totalEnergy;
267 cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
268 }
269 aa += hhh;
270 }
271
272 cross *=hhh;
273
274 //G4cout << "BR e= " << tkin<< " cross= " << cross/barn << G4endl;
275
276 return cross;
277}
278
279//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
280
281G4double G4MuBremsstrahlungModel::ComputeDMicroscopicCrossSection(
282 G4double tkin,
283 G4double Z,
284 G4double gammaEnergy)
285// differential cross section
286{
287 G4double dxsection = 0.;
288
289 if( gammaEnergy > tkin) return dxsection ;
290
291 G4double E = tkin + mass ;
292 G4double v = gammaEnergy/E ;
293 G4double delta = 0.5*mass*mass*v/(E-gammaEnergy) ;
294 G4double rab0=delta*sqrte ;
295
296 G4int iz = G4int(Z);
297 if(iz < 1) iz = 1;
298
299 G4double z13 = 1.0/nist->GetZ13(iz);
300 G4double dn = 1.54*nist->GetA27(iz);
301
302 G4double b,b1,dnstar ;
303
304 if(1 == iz)
305 {
306 b = bh;
307 b1 = bh1;
308 dnstar = dn;
309 }
310 else
311 {
312 b = btf;
313 b1 = btf1;
314 dnstar = dn/std::pow(dn, 1./Z);
315 }
316
317 // nucleus contribution logarithm
318 G4double rab1=b*z13;
319 G4double fn=log(rab1/(dnstar*(electron_mass_c2+rab0*rab1))*
320 (mass+delta*(dnstar*sqrte-2.))) ;
321 if(fn <0.) fn = 0. ;
322 // electron contribution logarithm
323 G4double epmax1=E/(1.+0.5*mass*rmass/E) ;
324 G4double fe=0.;
325 if(gammaEnergy<epmax1)
326 {
327 G4double rab2=b1*z13*z13 ;
328 fe=log(rab2*mass/((1.+delta*rmass/(electron_mass_c2*sqrte))*
329 (electron_mass_c2+rab0*rab2))) ;
330 if(fe<0.) fe=0. ;
331 }
332
333 dxsection = coeff*(1.-v*(1. - 0.75*v))*Z*(fn*Z + fe)/gammaEnergy;
334
335 return dxsection;
336}
337
338//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
339
340G4double G4MuBremsstrahlungModel::ComputeCrossSectionPerAtom(
341 const G4ParticleDefinition*,
342 G4double kineticEnergy,
343 G4double Z, G4double,
344 G4double cutEnergy,
345 G4double maxEnergy)
346{
347 G4double cross = 0.0;
348 if (kineticEnergy <= lowestKinEnergy) return cross;
349 G4double tmax = std::min(maxEnergy, kineticEnergy);
350 G4double cut = std::min(cutEnergy, kineticEnergy);
351 if(cut < minThreshold) cut = minThreshold;
352 if (cut >= tmax) return cross;
353
354 cross = ComputeMicroscopicCrossSection (kineticEnergy, Z, cut);
355 if(tmax < kineticEnergy) {
356 cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
357 }
358 return cross;
359}
360
361//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
362
363G4DataVector* G4MuBremsstrahlungModel::ComputePartialSumSigma(
364 const G4Material* material,
365 G4double kineticEnergy,
366 G4double cut)
367
368// Build the table of cross section per element.
369// The table is built for material
370// This table is used to select randomly an element in the material.
371{
372 G4int nElements = material->GetNumberOfElements();
373 const G4ElementVector* theElementVector = material->GetElementVector();
374 const G4double* theAtomNumDensityVector =
375 material->GetAtomicNumDensityVector();
376
377 G4DataVector* dv = new G4DataVector();
378
379 G4double cross = 0.0;
380
381 for (G4int i=0; i<nElements; i++ ) {
382 cross += theAtomNumDensityVector[i]
383 * ComputeMicroscopicCrossSection(kineticEnergy,
384 (*theElementVector)[i]->GetZ(), cut);
385 dv->push_back(cross);
386 }
387 return dv;
388}
389
390//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
391
392void G4MuBremsstrahlungModel::SampleSecondaries(
393 std::vector<G4DynamicParticle*>* vdp,
394 const G4MaterialCutsCouple* couple,
395 const G4DynamicParticle* dp,
396 G4double minEnergy,
397 G4double maxEnergy)
398{
399 G4double kineticEnergy = dp->GetKineticEnergy();
400 // check against insufficient energy
401 G4double tmax = std::min(kineticEnergy, maxEnergy);
402 G4double tmin = std::min(kineticEnergy, minEnergy);
403 if(tmin < minThreshold) tmin = minThreshold;
404 if(tmin >= tmax) return;
405
406 // ===== sampling of energy transfer ======
407
408 G4ParticleMomentum partDirection = dp->GetMomentumDirection();
409
410 // select randomly one element constituing the material
411 const G4Element* anElement = SelectRandomAtom(couple);
412 G4double Z = anElement->GetZ();
413
414 G4double totalEnergy = kineticEnergy + mass;
415 G4double totalMomentum = sqrt(kineticEnergy*(kineticEnergy + 2.0*mass));
416
417 G4double func1 = tmin*
418 ComputeDMicroscopicCrossSection(kineticEnergy,Z,tmin);
419
420 G4double lnepksi, epksi;
421 G4double func2;
422
423 do {
424 lnepksi = log(tmin) + G4UniformRand()*log(kineticEnergy/tmin);
425 epksi = exp(lnepksi);
426 func2 = epksi*ComputeDMicroscopicCrossSection(kineticEnergy,Z,epksi);
427
428 } while(func2 < func1*G4UniformRand());
429
430 G4double gEnergy = epksi;
431
432 // ===== sample angle =====
433
434 G4double gam = totalEnergy/mass;
435 G4double rmax = gam*std::min(1.0, totalEnergy/gEnergy - 1.0);
436 G4double rmax2= rmax*rmax;
437 G4double x = G4UniformRand()*rmax2/(1.0 + rmax2);
438
439 G4double theta = sqrt(x/(1.0 - x))/gam;
440 G4double sint = sin(theta);
441 G4double phi = twopi * G4UniformRand() ;
442 G4double dirx = sint*cos(phi), diry = sint*sin(phi), dirz = cos(theta) ;
443
444 G4ThreeVector gDirection(dirx, diry, dirz);
445 gDirection.rotateUz(partDirection);
446
447 partDirection *= totalMomentum;
448 partDirection -= gEnergy*gDirection;
449 partDirection = partDirection.unit();
450
451 // primary change
452 kineticEnergy -= gEnergy;
453 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
454 fParticleChange->SetProposedMomentumDirection(partDirection);
455
456 // save secondary
457 G4DynamicParticle* aGamma =
458 new G4DynamicParticle(theGamma,gDirection,gEnergy);
459 vdp->push_back(aGamma);
460}
461
462//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
463
464const G4Element* G4MuBremsstrahlungModel::SelectRandomAtom(
465 const G4MaterialCutsCouple* couple) const
466{
467 // select randomly 1 element within the material
468
469 const G4Material* material = couple->GetMaterial();
470 G4int nElements = material->GetNumberOfElements();
471 const G4ElementVector* theElementVector = material->GetElementVector();
472 if(1 == nElements) return (*theElementVector)[0];
473 else if(1 > nElements) return 0;
474
475 G4DataVector* dv = partialSumSigma[couple->GetIndex()];
476 G4double rval = G4UniformRand()*((*dv)[nElements-1]);
477 for (G4int i=0; i<nElements; i++) {
478 if (rval <= (*dv)[i]) return (*theElementVector)[i];
479 }
480 return (*theElementVector)[nElements-1];
481}
482
483//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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