source: trunk/source/processes/electromagnetic/standard/src/G4eBremsstrahlungRelModel.cc @ 1315

Last change on this file since 1315 was 1315, checked in by garnier, 14 years ago

update geant4-09-04-beta-cand-01 interfaces-V09-03-09 vis-V09-03-08
File size: 17.5 KB
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26// $Id: G4eBremsstrahlungRelModel.cc,v 1.15 2010/04/06 17:02:23 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-04-beta-cand-01 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name:     G4eBremsstrahlungRelModel
35//
36// Author:        Andreas Schaelicke
37//
38// Creation date: 12.08.2008
39//
40// Modifications:
41//
42// 13.11.08    add SetLPMflag and SetLPMconstant methods
43// 13.11.08    change default LPMconstant value
44//
45// Main References:
46//  Y.-S.Tsai, Rev. Mod. Phys. 46 (1974) 815; Rev. Mod. Phys. 49 (1977) 421.
47//  S.Klein,  Rev. Mod. Phys. 71 (1999) 1501.
48//  T.Stanev et.al., Phys. Rev. D25 (1982) 1291.
49//  M.L.Ter-Mikaelian, High-energy Electromagnetic Processes in Condensed Media, Wiley, 1972.
50//
51// -------------------------------------------------------------------
52//
53//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
54//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
55
56#include "G4eBremsstrahlungRelModel.hh"
57#include "G4Electron.hh"
58#include "G4Positron.hh"
59#include "G4Gamma.hh"
60#include "Randomize.hh"
61#include "G4Material.hh"
62#include "G4Element.hh"
63#include "G4ElementVector.hh"
64#include "G4ProductionCutsTable.hh"
65#include "G4ParticleChangeForLoss.hh"
66#include "G4LossTableManager.hh"
67
68
69//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
70
71const G4double G4eBremsstrahlungRelModel::xgi[]={ 0.0199, 0.1017, 0.2372, 0.4083,
72                                                  0.5917, 0.7628, 0.8983, 0.9801 };
73const G4double G4eBremsstrahlungRelModel::wgi[]={ 0.0506, 0.1112, 0.1569, 0.1813,
74                                            0.1813, 0.1569, 0.1112, 0.0506 };
75const G4double G4eBremsstrahlungRelModel::Fel_light[]  = {0., 5.31  , 4.79  , 4.74 ,  4.71} ;
76const G4double G4eBremsstrahlungRelModel::Finel_light[] = {0., 6.144 , 5.621 , 5.805 , 5.924} ;
77
78
79using namespace std;
80
81G4eBremsstrahlungRelModel::G4eBremsstrahlungRelModel(const G4ParticleDefinition* p,
82                                                     const G4String& name)
83  : G4VEmModel(name),
84    particle(0),
85    fXiLPM(0), fPhiLPM(0), fGLPM(0),
86    isElectron(true),
87    fMigdalConstant(classic_electr_radius*electron_Compton_length*electron_Compton_length*4.0*pi),
88    fLPMconstant(fine_structure_const*electron_mass_c2*electron_mass_c2/(4.*pi*hbarc)*0.5),
89    bremFactor(fine_structure_const*classic_electr_radius*classic_electr_radius*16./3.),
90    use_completescreening(true),isInitialised(false)
91{
92  if(p) SetParticle(p);
93  theGamma = G4Gamma::Gamma();
94
95  minThreshold = 0.1*keV;
96  SetLowEnergyLimit(GeV); 
97
98  nist = G4NistManager::Instance(); 
99  InitialiseConstants();
100
101  SetLPMFlag(true);
102}
103
104//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
105
106void G4eBremsstrahlungRelModel::InitialiseConstants()
107{
108  facFel = log(184.15);
109  facFinel = log(1194.);
110
111  preS1 = 1./(184.15*184.15);
112  logTwo = log(2.);
113}
114
115//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
116
117G4eBremsstrahlungRelModel::~G4eBremsstrahlungRelModel()
118{
119}
120
121//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
122
123void G4eBremsstrahlungRelModel::SetParticle(const G4ParticleDefinition* p)
124{
125  particle = p;
126  particleMass = p->GetPDGMass();
127  if(p == G4Electron::Electron()) isElectron = true;
128  else                            isElectron = false;
129}
130
131//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
132
133G4double G4eBremsstrahlungRelModel::MinEnergyCut(const G4ParticleDefinition*,
134                                                 const G4MaterialCutsCouple*)
135{
136  return minThreshold;
137}
138
139//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
140
141void G4eBremsstrahlungRelModel::SetupForMaterial(const G4ParticleDefinition*,
142                                                 const G4Material* mat, G4double kineticEnergy)
143{
144  densityFactor = mat->GetElectronDensity()*fMigdalConstant;
145  lpmEnergy = mat->GetRadlen()*fLPMconstant;
146
147  // Threshold for LPM effect (i.e. below which LPM hidden by density effect)
148  if (LPMFlag()) 
149    energyThresholdLPM=sqrt(densityFactor)*lpmEnergy;
150  else
151     energyThresholdLPM=1.e39;   // i.e. do not use LPM effect
152
153  // calculate threshold for density effect
154  kinEnergy   = kineticEnergy;
155  totalEnergy = kineticEnergy + particleMass;
156  densityCorr = densityFactor*totalEnergy*totalEnergy;
157
158  // define critical gamma energies (important for integration/dicing)
159  klpm=totalEnergy*totalEnergy/lpmEnergy;
160  kp=sqrt(densityCorr);
161   
162}
163
164
165//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
166
167void G4eBremsstrahlungRelModel::Initialise(const G4ParticleDefinition* p,
168                                           const G4DataVector& cuts)
169{
170  if(p) SetParticle(p);
171
172  highKinEnergy = HighEnergyLimit();
173  lowKinEnergy  = LowEnergyLimit();
174
175  currentZ = 0.;
176
177  InitialiseElementSelectors(p, cuts);
178
179  if(isInitialised) return;
180  fParticleChange = GetParticleChangeForLoss();
181  isInitialised = true;
182}
183
184//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
185
186G4double G4eBremsstrahlungRelModel::ComputeDEDXPerVolume(
187                                             const G4Material* material,
188                                             const G4ParticleDefinition* p,
189                                                   G4double kineticEnergy,
190                                                   G4double cutEnergy)
191{
192  if(!particle) SetParticle(p);
193  if(kineticEnergy < lowKinEnergy) return 0.0;
194  G4double cut = std::min(cutEnergy, kineticEnergy);
195  if(cut == 0.0) return 0.0;
196
197  SetupForMaterial(particle, material,kineticEnergy);
198
199  const G4ElementVector* theElementVector = material->GetElementVector();
200  const G4double* theAtomicNumDensityVector = material->GetAtomicNumDensityVector();
201
202  G4double dedx = 0.0;
203
204  //  loop for elements in the material
205  for (size_t i=0; i<material->GetNumberOfElements(); i++) {
206
207    G4VEmModel::SetCurrentElement((*theElementVector)[i]);
208    SetCurrentElement((*theElementVector)[i]->GetZ());
209
210    dedx += theAtomicNumDensityVector[i]*currentZ*currentZ*ComputeBremLoss(cut);
211  }
212  dedx *= bremFactor;
213
214
215  return dedx;
216}
217
218//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
219
220G4double G4eBremsstrahlungRelModel::ComputeBremLoss(G4double cut)
221{
222  G4double loss = 0.0;
223
224  // number of intervals and integration step
225  G4double vcut = cut/totalEnergy;
226  G4int n = (G4int)(20*vcut) + 3;
227  G4double delta = vcut/G4double(n);
228
229  G4double e0 = 0.0;
230  G4double xs; 
231
232  // integration
233  for(G4int l=0; l<n; l++) {
234
235    for(G4int i=0; i<8; i++) {
236
237      G4double eg = (e0 + xgi[i]*delta)*totalEnergy;
238
239      if(totalEnergy > energyThresholdLPM) {
240        xs = ComputeRelDXSectionPerAtom(eg);
241      } else {
242        xs = ComputeDXSectionPerAtom(eg);
243      }
244      loss += wgi[i]*xs/(1.0 + densityCorr/(eg*eg));
245    }
246    e0 += delta;
247  }
248
249  loss *= delta*totalEnergy;
250
251  return loss;
252}
253
254//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
255
256G4double G4eBremsstrahlungRelModel::ComputeCrossSectionPerAtom(
257                                              const G4ParticleDefinition* p,
258                                              G4double kineticEnergy, 
259                                              G4double Z,   G4double,
260                                              G4double cutEnergy, 
261                                              G4double maxEnergy)
262{
263  if(!particle) SetParticle(p);
264  if(kineticEnergy < lowKinEnergy) return 0.0;
265  G4double cut  = std::min(cutEnergy, kineticEnergy);
266  G4double tmax = std::min(maxEnergy, kineticEnergy);
267
268  if(cut >= tmax) return 0.0;
269
270  SetCurrentElement(Z);
271
272  G4double cross = ComputeXSectionPerAtom(cut);
273
274  // allow partial integration
275  if(tmax < kinEnergy) cross -= ComputeXSectionPerAtom(tmax);
276 
277  cross *= Z*Z*bremFactor;
278
279  return cross;
280}
281 
282//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
283
284
285G4double G4eBremsstrahlungRelModel::ComputeXSectionPerAtom(G4double cut)
286{
287  G4double cross = 0.0;
288
289  // number of intervals and integration step
290  G4double vcut = log(cut/totalEnergy);
291  G4double vmax = log(kinEnergy/totalEnergy);
292  G4int n = (G4int)(0.45*(vmax - vcut)) + 4;
293  //  n=1; //  integration test
294  G4double delta = (vmax - vcut)/G4double(n);
295
296  G4double e0 = vcut;
297  G4double xs; 
298
299  // integration
300  for(G4int l=0; l<n; l++) {
301
302    for(G4int i=0; i<8; i++) {
303
304      G4double eg = exp(e0 + xgi[i]*delta)*totalEnergy;
305
306      if(totalEnergy > energyThresholdLPM) {
307        xs = ComputeRelDXSectionPerAtom(eg);
308      } else {
309        xs = ComputeDXSectionPerAtom(eg);
310      }
311      cross += wgi[i]*xs/(1.0 + densityCorr/(eg*eg));
312    }
313    e0 += delta;
314  }
315
316  cross *= delta;
317
318  return cross;
319}
320
321//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
322void  G4eBremsstrahlungRelModel::CalcLPMFunctions(G4double k)
323{
324  // *** calculate lpm variable s & sprime ***
325  // Klein eqs. (78) & (79)
326  G4double sprime = sqrt(0.125*k*lpmEnergy/(totalEnergy*(totalEnergy-k)));
327
328  G4double s1 = preS1*z23;
329  G4double logS1 = 2./3.*lnZ-2.*facFel;
330  G4double logTS1 = logTwo+logS1;
331
332  xiLPM = 2.;
333
334  if (sprime>1) 
335    xiLPM = 1.;
336  else if (sprime>sqrt(2.)*s1) {
337    G4double h  = log(sprime)/logTS1;
338    xiLPM = 1+h-0.08*(1-h)*(1-sqr(1-h))/logTS1;
339  }
340
341  G4double s = sprime/sqrt(xiLPM); 
342
343  // *** merging with density effect***  should be only necessary in region "close to" kp, e.g. k<100*kp
344  // using Ter-Mikaelian eq. (20.9)
345  G4double k2 = k*k;
346  s = s * (1 + (densityCorr/k2) );
347
348  // recalculate Xi using modified s above
349  // Klein eq. (75)
350  xiLPM = 1.;
351  if (s<=s1) xiLPM = 2.;
352  else if ( (s1<s) && (s<=1) ) xiLPM = 1. + log(s)/logS1;
353 
354
355  // *** calculate supression functions phi and G ***
356  // Klein eqs. (77)
357  G4double s2=s*s;
358  G4double s3=s*s2;
359  G4double s4=s2*s2;
360
361  if (s<0.1) {
362    // high suppression limit
363    phiLPM = 6.*s - 18.84955592153876*s2 + 39.47841760435743*s3
364      - 57.69873135166053*s4;
365    gLPM = 37.69911184307752*s2 - 236.8705056261446*s3 + 807.7822389*s4;
366  }
367  else if (s<1.9516) {
368    // intermediate suppression
369    // using eq.77 approxim. valid s<2.     
370    phiLPM = 1.-exp(-6.*s*(1.+(3.-pi)*s)
371                +s3/(0.623+0.795*s+0.658*s2));
372    if (s<0.415827397755) {
373      // using eq.77 approxim. valid 0.07<s<2
374      G4double psiLPM = 1-exp(-4*s-8*s2/(1+3.936*s+4.97*s2-0.05*s3+7.50*s4));
375      gLPM = 3*psiLPM-2*phiLPM;
376    }
377    else {
378      // using alternative parametrisiation
379      G4double pre = -0.16072300849123999 + s*3.7550300067531581 + s2*-1.7981383069010097 
380        + s3*0.67282686077812381 + s4*-0.1207722909879257;
381      gLPM = tanh(pre);
382    }
383  }
384  else {
385    // low suppression limit valid s>2.
386    phiLPM = 1. - 0.0119048/s4;
387    gLPM = 1. - 0.0230655/s4;
388  }
389
390  // *** make sure suppression is smaller than 1 ***
391  // *** caused by Migdal approximation in xi    ***
392  if (xiLPM*phiLPM>1. || s>0.57)  xiLPM=1./phiLPM;
393}
394
395//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
396
397
398G4double G4eBremsstrahlungRelModel::ComputeRelDXSectionPerAtom(G4double gammaEnergy)
399// Ultra relativistic model
400//   only valid for very high energies, but includes LPM suppression
401//    * complete screening
402{
403  if(gammaEnergy < 0.0) return 0.0;
404
405  G4double y = gammaEnergy/totalEnergy;
406  G4double y2 = y*y*.25;
407  G4double yone2 = (1.-y+2.*y2);
408
409  // ** form factors complete screening case **     
410
411  // ** calc LPM functions -- include ter-mikaelian merging with density effect **
412  //  G4double xiLPM, gLPM, phiLPM;  // to be made member variables !!!
413  CalcLPMFunctions(gammaEnergy);
414
415  G4double mainLPM   = xiLPM*(y2 * gLPM + yone2*phiLPM) * ( (Fel-fCoulomb) + Finel/currentZ );
416  G4double secondTerm = (1.-y)/12.*(1.+1./currentZ);
417
418  G4double cross = mainLPM+secondTerm;
419  return cross;
420}
421
422//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
423
424G4double G4eBremsstrahlungRelModel::ComputeDXSectionPerAtom(G4double gammaEnergy)
425// Relativistic model
426//  only valid for high energies (and if LPM suppression does not play a role)
427//  * screening according to thomas-fermi-Model (only valid for Z>5)
428//  * no LPM effect
429{
430
431  if(gammaEnergy < 0.0) return 0.0;
432
433  G4double y = gammaEnergy/totalEnergy;
434
435  G4double main=0.,secondTerm=0.;
436
437  if (use_completescreening|| currentZ<5) {
438    // ** form factors complete screening case **     
439    main   = (3./4.*y*y - y + 1.) * ( (Fel-fCoulomb) + Finel/currentZ );
440    secondTerm = (1.-y)/12.*(1.+1./currentZ);
441  }
442  else {
443    // ** intermediate screening using Thomas-Fermi FF from Tsai only valid for Z>=5**
444    G4double dd=100.*electron_mass_c2*y/(totalEnergy-gammaEnergy);
445    G4double gg=dd*z13;
446    G4double eps=dd*z23;
447    G4double phi1=Phi1(gg,currentZ),  phi1m2=Phi1M2(gg,currentZ);
448    G4double psi1=Psi1(eps,currentZ),  psi1m2=Psi1M2(eps,currentZ);
449   
450    main   = (3./4.*y*y - y + 1.) * ( (0.25*phi1-1./3.*lnZ-fCoulomb) + (0.25*psi1-2./3.*lnZ)/currentZ );
451    secondTerm = (1.-y)/8.*(phi1m2+psi1m2/currentZ);
452  }
453  G4double cross = main+secondTerm;
454  return cross;
455}
456
457//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
458
459void G4eBremsstrahlungRelModel::SampleSecondaries(
460                                      std::vector<G4DynamicParticle*>* vdp, 
461                                      const G4MaterialCutsCouple* couple,
462                                      const G4DynamicParticle* dp,
463                                      G4double cutEnergy,
464                                      G4double maxEnergy)
465{
466  G4double kineticEnergy = dp->GetKineticEnergy();
467  if(kineticEnergy < lowKinEnergy) return;
468  G4double cut  = std::min(cutEnergy, kineticEnergy);
469  G4double emax = std::min(maxEnergy, kineticEnergy);
470  if(cut >= emax) return;
471
472  SetupForMaterial(particle, couple->GetMaterial(),kineticEnergy);
473
474  const G4Element* elm = 
475    SelectRandomAtom(couple,particle,kineticEnergy,cut,emax);
476  SetCurrentElement(elm->GetZ());
477
478  kinEnergy   = kineticEnergy;
479  totalEnergy = kineticEnergy + particleMass;
480  densityCorr = densityFactor*totalEnergy*totalEnergy;
481  G4ThreeVector direction = dp->GetMomentumDirection();
482
483  //  G4double fmax= fMax;
484  G4bool highe = true;
485  if(totalEnergy < energyThresholdLPM) highe = false;
486 
487  G4double xmin = log(cut*cut + densityCorr);
488  G4double xmax = log(emax*emax  + densityCorr);
489  G4double gammaEnergy, f, x; 
490
491  do {
492    x = exp(xmin + G4UniformRand()*(xmax - xmin)) - densityCorr;
493    if(x < 0.0) x = 0.0;
494    gammaEnergy = sqrt(x);
495    if(highe) f = ComputeRelDXSectionPerAtom(gammaEnergy);
496    else      f = ComputeDXSectionPerAtom(gammaEnergy);
497
498    if ( f > fMax ) {
499      G4cout << "### G4eBremsstrahlungRelModel Warning: Majoranta exceeded! "
500             << f << " > " << fMax
501             << " Egamma(MeV)= " << gammaEnergy
502             << " E(mEV)= " << kineticEnergy
503             << G4endl;
504    }
505
506  } while (f < fMax*G4UniformRand());
507
508  //
509  //  angles of the emitted gamma. ( Z - axis along the parent particle)
510  //
511  //  universal distribution suggested by L. Urban
512  // (Geant3 manual (1993) Phys211),
513  //  derived from Tsai distribution (Rev Mod Phys 49,421(1977))
514
515  G4double u;
516  const G4double a1 = 0.625 , a2 = 3.*a1 , d = 27. ;
517
518  if (9./(9.+d) > G4UniformRand()) u = - log(G4UniformRand()*G4UniformRand())/a1;
519     else                          u = - log(G4UniformRand()*G4UniformRand())/a2;
520
521  G4double theta = u*particleMass/totalEnergy;
522  G4double sint = sin(theta);
523  G4double phi = twopi * G4UniformRand();
524  G4ThreeVector gammaDirection(sint*cos(phi),sint*sin(phi), cos(theta));
525  gammaDirection.rotateUz(direction);
526
527  // create G4DynamicParticle object for the Gamma
528  G4DynamicParticle* g = new G4DynamicParticle(theGamma,gammaDirection,
529                                                        gammaEnergy);
530  vdp->push_back(g);
531 
532  G4double totMomentum = sqrt(kineticEnergy*(totalEnergy + electron_mass_c2));
533  G4ThreeVector dir = totMomentum*direction - gammaEnergy*gammaDirection;
534  direction = dir.unit();
535
536  // energy of primary
537  G4double finalE = kineticEnergy - gammaEnergy;
538
539  // stop tracking and create new secondary instead of primary
540  if(gammaEnergy > SecondaryThreshold()) {
541    fParticleChange->ProposeTrackStatus(fStopAndKill);
542    fParticleChange->SetProposedKineticEnergy(0.0);
543    G4DynamicParticle* el = 
544      new G4DynamicParticle(const_cast<G4ParticleDefinition*>(particle),
545                            direction, finalE);
546    vdp->push_back(el);
547
548    // continue tracking
549  } else {
550    fParticleChange->SetProposedMomentumDirection(direction);
551    fParticleChange->SetProposedKineticEnergy(finalE);
552  }
553}
554
555//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
556
557
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