source: trunk/source/processes/electromagnetic/muons/src/G4MuBremsstrahlungModel.cc @ 961

Last change on this file since 961 was 961, checked in by garnier, 15 years ago

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26// $Id: G4MuBremsstrahlungModel.cc,v 1.33 2009/02/20 14:48:16 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
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) {
165    if(pParticleChange)
166      fParticleChange = 
167        reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange);
168    else
169      fParticleChange = new G4ParticleChangeForLoss();
170  }
171}
172
173//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
174
175G4double G4MuBremsstrahlungModel::ComputeDEDXPerVolume(
176                                              const G4Material* material,
177                                              const G4ParticleDefinition*,
178                                                    G4double kineticEnergy,
179                                                    G4double cutEnergy)
180{
181  G4double dedx = 0.0;
182  if (kineticEnergy <= lowestKinEnergy) return dedx;
183
184  G4double tmax = kineticEnergy;
185  G4double cut  = std::min(cutEnergy,tmax);
186  if(cut < minThreshold) cut = minThreshold;
187
188  const G4ElementVector* theElementVector = material->GetElementVector();
189  const G4double* theAtomicNumDensityVector =
190    material->GetAtomicNumDensityVector();
191
192  //  loop for elements in the material
193  for (size_t i=0; i<material->GetNumberOfElements(); i++) {
194
195    G4double loss = 
196      ComputMuBremLoss((*theElementVector)[i]->GetZ(), kineticEnergy, cut);
197
198    dedx += loss*theAtomicNumDensityVector[i];
199  }
200  //  G4cout << "BR e= " << kineticEnergy << "  dedx= " << dedx << G4endl;
201  if(dedx < 0.) dedx = 0.;
202  return dedx;
203}
204
205//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
206
207G4double G4MuBremsstrahlungModel::ComputMuBremLoss(G4double Z,
208                                                   G4double tkin, G4double cut)
209{
210  G4double totalEnergy = mass + tkin;
211  G4double ak1 = 0.05;
212  G4int    k2=5;
213  G4double xgi[]={0.03377,0.16940,0.38069,0.61931,0.83060,0.96623};
214  G4double wgi[]={0.08566,0.18038,0.23396,0.23396,0.18038,0.08566};
215  G4double loss = 0.;
216
217  G4double vcut = cut/totalEnergy;
218  G4double vmax = tkin/totalEnergy;
219
220  G4double aaa = 0.;
221  G4double bbb = vcut;
222  if(vcut>vmax) bbb=vmax ;
223  G4int kkk = (G4int)((bbb-aaa)/ak1)+k2 ;
224  G4double hhh=(bbb-aaa)/float(kkk) ;
225
226  G4double aa = aaa;
227  for(G4int l=0; l<kkk; l++)
228  {
229    for(G4int i=0; i<6; i++)
230    {
231      G4double ep = (aa + xgi[i]*hhh)*totalEnergy;
232      loss += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
233    }
234    aa += hhh;
235  }
236
237  loss *=hhh*totalEnergy ;
238
239  return loss;
240}
241
242//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
243
244G4double G4MuBremsstrahlungModel::ComputeMicroscopicCrossSection(
245                                           G4double tkin,
246                                           G4double Z,
247                                           G4double cut)
248{
249  G4double totalEnergy = tkin + mass;
250  G4double ak1 = 2.3;
251  G4int    k2  = 4;
252  G4double xgi[]={0.03377,0.16940,0.38069,0.61931,0.83060,0.96623};
253  G4double wgi[]={0.08566,0.18038,0.23396,0.23396,0.18038,0.08566};
254  G4double cross = 0.;
255
256  if(cut >= tkin) return cross;
257
258  G4double vcut = cut/totalEnergy;
259  G4double vmax = tkin/totalEnergy;
260
261  G4double aaa = log(vcut);
262  G4double bbb = log(vmax);
263  G4int    kkk = (G4int)((bbb-aaa)/ak1)+k2 ;
264  G4double hhh = (bbb-aaa)/G4double(kkk);
265
266  G4double aa = aaa;
267
268  for(G4int l=0; l<kkk; l++)
269  {
270    for(G4int i=0; i<6; i++)
271    {
272      G4double ep = exp(aa + xgi[i]*hhh)*totalEnergy;
273      cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
274    }
275    aa += hhh;
276  }
277
278  cross *=hhh;
279
280  //G4cout << "BR e= " << tkin<< "  cross= " << cross/barn << G4endl;
281
282  return cross;
283}
284
285//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
286
287G4double G4MuBremsstrahlungModel::ComputeDMicroscopicCrossSection(
288                                           G4double tkin,
289                                           G4double Z,
290                                           G4double gammaEnergy)
291//  differential cross section
292{
293  G4double dxsection = 0.;
294
295  if( gammaEnergy > tkin) return dxsection ;
296
297  G4double E = tkin + mass ;
298  G4double v = gammaEnergy/E ;
299  G4double delta = 0.5*mass*mass*v/(E-gammaEnergy) ;
300  G4double rab0=delta*sqrte ;
301
302  G4int iz = G4int(Z);
303  if(iz < 1) iz = 1;
304
305  G4double z13 = 1.0/nist->GetZ13(iz);
306  G4double dn  = 1.54*nist->GetA27(iz);
307
308  G4double b,b1,dnstar ;
309
310  if(1 == iz)
311  {
312    b  = bh;
313    b1 = bh1;
314    dnstar = dn;
315  }
316  else
317  {
318    b  = btf;
319    b1 = btf1;
320    dnstar = dn/std::pow(dn, 1./Z);
321  }
322
323  // nucleus contribution logarithm
324  G4double rab1=b*z13;
325  G4double fn=log(rab1/(dnstar*(electron_mass_c2+rab0*rab1))*
326              (mass+delta*(dnstar*sqrte-2.))) ;
327  if(fn <0.) fn = 0. ;
328  // electron contribution logarithm
329  G4double epmax1=E/(1.+0.5*mass*rmass/E) ;
330  G4double fe=0.;
331  if(gammaEnergy<epmax1)
332  {
333    G4double rab2=b1*z13*z13 ;
334    fe=log(rab2*mass/((1.+delta*rmass/(electron_mass_c2*sqrte))*
335                              (electron_mass_c2+rab0*rab2))) ;
336    if(fe<0.) fe=0. ;
337  }
338
339  dxsection = coeff*(1.-v*(1. - 0.75*v))*Z*(fn*Z + fe)/gammaEnergy;
340
341  return dxsection;
342}
343
344//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
345
346G4double G4MuBremsstrahlungModel::ComputeCrossSectionPerAtom(
347                                           const G4ParticleDefinition*,
348                                                 G4double kineticEnergy,
349                                                 G4double Z, G4double,
350                                                 G4double cutEnergy,
351                                                 G4double maxEnergy)
352{
353  G4double cross = 0.0;
354  if (kineticEnergy <= lowestKinEnergy) return cross;
355  G4double tmax = std::min(maxEnergy, kineticEnergy);
356  G4double cut  = std::min(cutEnergy, kineticEnergy);
357  if(cut < minThreshold) cut = minThreshold;
358  if (cut >= tmax) return cross;
359
360  cross = ComputeMicroscopicCrossSection (kineticEnergy, Z, cut);
361  if(tmax < kineticEnergy) {
362    cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
363  }
364  return cross;
365}
366
367//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
368
369G4DataVector* G4MuBremsstrahlungModel::ComputePartialSumSigma(
370                                       const G4Material* material,
371                                       G4double kineticEnergy,
372                                       G4double cut)
373
374// Build the table of cross section per element.
375// The table is built for material
376// This table is used to select randomly an element in the material.
377{
378  G4int nElements = material->GetNumberOfElements();
379  const G4ElementVector* theElementVector = material->GetElementVector();
380  const G4double* theAtomNumDensityVector = 
381    material->GetAtomicNumDensityVector();
382
383  G4DataVector* dv = new G4DataVector();
384
385  G4double cross = 0.0;
386
387  for (G4int i=0; i<nElements; i++ ) {
388    cross += theAtomNumDensityVector[i] 
389      * ComputeMicroscopicCrossSection(kineticEnergy, 
390                                       (*theElementVector)[i]->GetZ(), cut);
391    dv->push_back(cross);
392  }
393  return dv;
394}
395
396//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
397
398void G4MuBremsstrahlungModel::SampleSecondaries(
399                              std::vector<G4DynamicParticle*>* vdp,
400                              const G4MaterialCutsCouple* couple,
401                              const G4DynamicParticle* dp,
402                              G4double minEnergy,
403                              G4double maxEnergy)
404{
405  G4double kineticEnergy = dp->GetKineticEnergy();
406  // check against insufficient energy
407  G4double tmax = std::min(kineticEnergy, maxEnergy);
408  G4double tmin = std::min(kineticEnergy, minEnergy);
409  if(tmin < minThreshold) tmin = minThreshold;
410  if(tmin >= tmax) return;
411
412  // ===== sampling of energy transfer ======
413
414  G4ParticleMomentum partDirection = dp->GetMomentumDirection();
415
416  // select randomly one element constituing the material
417  const G4Element* anElement = SelectRandomAtom(couple);
418  G4double Z = anElement->GetZ();
419
420  G4double totalEnergy   = kineticEnergy + mass;
421  G4double totalMomentum = sqrt(kineticEnergy*(kineticEnergy + 2.0*mass));
422
423  G4double func1 = tmin*
424    ComputeDMicroscopicCrossSection(kineticEnergy,Z,tmin);
425
426  G4double lnepksi, epksi;
427  G4double func2;
428
429  do {
430    lnepksi = log(tmin) + G4UniformRand()*log(kineticEnergy/tmin);
431    epksi   = exp(lnepksi);
432    func2   = epksi*ComputeDMicroscopicCrossSection(kineticEnergy,Z,epksi);
433
434  } while(func2 < func1*G4UniformRand());
435
436  G4double gEnergy = epksi;
437
438  // ===== sample angle =====
439
440  G4double gam  = totalEnergy/mass;
441  G4double rmax = gam*std::min(1.0, totalEnergy/gEnergy - 1.0);
442  G4double rmax2= rmax*rmax;
443  G4double x = G4UniformRand()*rmax2/(1.0 + rmax2);
444
445  G4double theta = sqrt(x/(1.0 - x))/gam;
446  G4double sint  = sin(theta);
447  G4double phi   = twopi * G4UniformRand() ;
448  G4double dirx  = sint*cos(phi), diry = sint*sin(phi), dirz = cos(theta) ;
449
450  G4ThreeVector gDirection(dirx, diry, dirz);
451  gDirection.rotateUz(partDirection);
452
453  partDirection *= totalMomentum;
454  partDirection -= gEnergy*gDirection;
455  partDirection = partDirection.unit();
456
457  // primary change
458  kineticEnergy -= gEnergy;
459  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
460  fParticleChange->SetProposedMomentumDirection(partDirection);
461
462  // save secondary
463  G4DynamicParticle* aGamma = 
464    new G4DynamicParticle(theGamma,gDirection,gEnergy);
465  vdp->push_back(aGamma);
466}
467
468//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
469
470const G4Element* G4MuBremsstrahlungModel::SelectRandomAtom(
471           const G4MaterialCutsCouple* couple) const
472{
473  // select randomly 1 element within the material
474
475  const G4Material* material = couple->GetMaterial();
476  G4int nElements = material->GetNumberOfElements();
477  const G4ElementVector* theElementVector = material->GetElementVector();
478  if(1 == nElements) return (*theElementVector)[0];
479  else if(1 > nElements) return 0;
480
481  G4DataVector* dv = partialSumSigma[couple->GetIndex()];
482  G4double rval = G4UniformRand()*((*dv)[nElements-1]);
483  for (G4int i=0; i<nElements; i++) {
484    if (rval <= (*dv)[i]) return (*theElementVector)[i];
485  }
486  return (*theElementVector)[nElements-1];
487}
488
489//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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