source: trunk/source/processes/electromagnetic/muons/src/G4MuBremsstrahlungModel.cc @ 1196

Last change on this file since 1196 was 1196, checked in by garnier, 15 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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