source: trunk/source/processes/electromagnetic/standard/src/G4BetheBlochModel.cc @ 968

Last change on this file since 968 was 961, checked in by garnier, 15 years ago

update processes
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26// $Id: G4BetheBlochModel.cc,v 1.25 2009/02/20 12:06:37 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class header file
32//
33//
34// File name:     G4BetheBlochModel
35//
36// Author:        Vladimir Ivanchenko on base of Laszlo Urban code
37//
38// Creation date: 03.01.2002
39//
40// Modifications:
41//
42// 04-12-02 Fix problem of G4DynamicParticle constructor (V.Ivanchenko)
43// 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
44// 27-01-03 Make models region aware (V.Ivanchenko)
45// 13-02-03 Add name (V.Ivanchenko)
46// 24-03-05 Add G4EmCorrections (V.Ivanchenko)
47// 11-04-05 Major optimisation of internal interfaces (V.Ivanchenko)
48// 11-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
49// 12-02-06 move G4LossTableManager::Instance()->EmCorrections()
50//          in constructor (mma)
51// 12-08-08 Added methods GetParticleCharge, GetChargeSquareRatio,
52//          CorrectionsAlongStep needed for ions(V.Ivanchenko)
53//
54// -------------------------------------------------------------------
55//
56
57
58//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
59//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
60
61#include "G4BetheBlochModel.hh"
62#include "Randomize.hh"
63#include "G4Electron.hh"
64#include "G4LossTableManager.hh"
65#include "G4EmCorrections.hh"
66#include "G4ParticleChangeForLoss.hh"
67#include "G4NistManager.hh"
68
69//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
70
71using namespace std;
72
73G4BetheBlochModel::G4BetheBlochModel(const G4ParticleDefinition* p, 
74                                     const G4String& nam)
75  : G4VEmModel(nam),
76    particle(0),
77    tlimit(DBL_MAX),
78    twoln10(2.0*log(10.0)),
79    bg2lim(0.0169),
80    taulim(8.4146e-3),
81    isIon(false),
82    isInitialised(false)
83{
84  fParticleChange = 0;
85  if(p) SetParticle(p);
86  theElectron = G4Electron::Electron();
87  corr = G4LossTableManager::Instance()->EmCorrections(); 
88  nist = G4NistManager::Instance();
89  SetLowEnergyLimit(2.0*MeV);
90}
91
92//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
93
94G4BetheBlochModel::~G4BetheBlochModel()
95{}
96
97//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
98
99G4double G4BetheBlochModel::MinEnergyCut(const G4ParticleDefinition*,
100                                         const G4MaterialCutsCouple* couple)
101{
102  return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy();
103}
104
105//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
106
107void G4BetheBlochModel::Initialise(const G4ParticleDefinition* p,
108                                   const G4DataVector&)
109{
110  if (!particle) SetParticle(p);
111
112  corrFactor = chargeSquare;
113  // always false before the run
114  SetDeexcitationFlag(false);
115
116  if(!isInitialised) {
117    isInitialised = true;
118
119    if(!fParticleChange) {
120      if (pParticleChange) {
121        fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>
122          (pParticleChange);
123      } else { 
124        fParticleChange = new G4ParticleChangeForLoss();
125      }
126    }
127  }
128}
129
130//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
131
132void G4BetheBlochModel::SetParticle(const G4ParticleDefinition* p)
133{
134  if(particle != p) {
135    particle = p;
136    G4String pname = particle->GetParticleName();
137    if (particle->GetParticleType() == "nucleus" &&
138        pname != "deuteron" && pname != "triton") {
139      isIon = true;
140    }
141   
142    mass = particle->GetPDGMass();
143    spin = particle->GetPDGSpin();
144    G4double q = particle->GetPDGCharge()/eplus;
145    chargeSquare = q*q;
146    ratio = electron_mass_c2/mass;
147    G4double magmom = particle->GetPDGMagneticMoment()
148      *mass/(0.5*eplus*hbar_Planck*c_squared);
149    magMoment2 = magmom*magmom - 1.0;
150    formfact = 0.0;
151    if(particle->GetLeptonNumber() == 0) {
152      G4double x = 0.8426*GeV;
153      if(spin == 0.0 && mass < GeV) {x = 0.736*GeV;}
154      else if(mass > GeV) {
155        x /= nist->GetZ13(mass/proton_mass_c2);
156        //      tlimit = 51.2*GeV*A13[iz]*A13[iz];
157      }
158      formfact = 2.0*electron_mass_c2/(x*x);
159      tlimit   = 2.0/formfact;
160    }
161  }
162}
163
164//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
165
166G4double G4BetheBlochModel::GetChargeSquareRatio(const G4ParticleDefinition* p,
167                                                 const G4Material* mat,
168                                                 G4double kineticEnergy)
169{
170  // this method is called only for ions
171  G4double q2 = corr->EffectiveChargeSquareRatio(p,mat,kineticEnergy);
172  corrFactor = q2*corr->EffectiveChargeCorrection(p,mat,kineticEnergy);
173  return corrFactor;
174}
175
176//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
177
178G4double G4BetheBlochModel::GetParticleCharge(const G4ParticleDefinition* p,
179                                              const G4Material* mat,
180                                              G4double kineticEnergy)
181{
182  // this method is called only for ions
183  return corr->GetParticleCharge(p,mat,kineticEnergy);
184}
185
186//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
187
188G4double
189G4BetheBlochModel::ComputeCrossSectionPerElectron(const G4ParticleDefinition* p,
190                                                  G4double kineticEnergy,
191                                                  G4double cutEnergy,
192                                                  G4double maxKinEnergy)       
193{
194  G4double cross = 0.0;
195  G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
196  G4double maxEnergy = min(tmax,maxKinEnergy);
197  if(cutEnergy < maxEnergy) {
198
199    G4double totEnergy = kineticEnergy + mass;
200    G4double energy2   = totEnergy*totEnergy;
201    G4double beta2     = kineticEnergy*(kineticEnergy + 2.0*mass)/energy2;
202
203    cross = 1.0/cutEnergy - 1.0/maxEnergy
204      - beta2*log(maxEnergy/cutEnergy)/tmax;
205
206    // +term for spin=1/2 particle
207    if( 0.5 == spin ) cross += 0.5*(maxEnergy - cutEnergy)/energy2;
208
209    // High order correction different for hadrons and ions
210    // nevetheless they are applied to reduce high energy transfers
211    //    if(!isIon)
212    //cross += corr->FiniteSizeCorrectionXS(p,currentMaterial,
213    //                                    kineticEnergy,cutEnergy);
214
215    cross *= twopi_mc2_rcl2*chargeSquare/beta2;
216  }
217 
218   // G4cout << "BB: e= " << kineticEnergy << " tmin= " << cutEnergy
219   //        << " tmax= " << tmax << " cross= " << cross << G4endl;
220 
221  return cross;
222}
223
224//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
225
226G4double G4BetheBlochModel::ComputeCrossSectionPerAtom(
227                                           const G4ParticleDefinition* p,
228                                                 G4double kineticEnergy,
229                                                 G4double Z, G4double,
230                                                 G4double cutEnergy,
231                                                 G4double maxEnergy)
232{
233  G4double cross = Z*ComputeCrossSectionPerElectron
234                                         (p,kineticEnergy,cutEnergy,maxEnergy);
235  return cross;
236}
237
238//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
239
240G4double G4BetheBlochModel::CrossSectionPerVolume(
241                                           const G4Material* material,
242                                           const G4ParticleDefinition* p,
243                                                 G4double kineticEnergy,
244                                                 G4double cutEnergy,
245                                                 G4double maxEnergy)
246{
247  currentMaterial   = material;
248  G4double eDensity = material->GetElectronDensity();
249  G4double cross = eDensity*ComputeCrossSectionPerElectron
250                                         (p,kineticEnergy,cutEnergy,maxEnergy);
251  return cross;
252}
253
254//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
255
256G4double G4BetheBlochModel::ComputeDEDXPerVolume(const G4Material* material,
257                                                 const G4ParticleDefinition* p,
258                                                 G4double kineticEnergy,
259                                                 G4double cut)
260{
261  G4double tmax      = MaxSecondaryEnergy(p, kineticEnergy);
262  G4double cutEnergy = min(cut,tmax);
263
264  G4double tau   = kineticEnergy/mass;
265  G4double gam   = tau + 1.0;
266  G4double bg2   = tau * (tau+2.0);
267  G4double beta2 = bg2/(gam*gam);
268
269  G4double eexc  = material->GetIonisation()->GetMeanExcitationEnergy();
270  G4double eexc2 = eexc*eexc;
271  G4double cden  = material->GetIonisation()->GetCdensity();
272  G4double mden  = material->GetIonisation()->GetMdensity();
273  G4double aden  = material->GetIonisation()->GetAdensity();
274  G4double x0den = material->GetIonisation()->GetX0density();
275  G4double x1den = material->GetIonisation()->GetX1density();
276
277  G4double eDensity = material->GetElectronDensity();
278
279  G4double dedx = log(2.0*electron_mass_c2*bg2*cutEnergy/eexc2)
280                - (1.0 + cutEnergy/tmax)*beta2;
281
282  if(0.5 == spin) {
283    G4double del = 0.5*cutEnergy/(kineticEnergy + mass);
284    dedx += del*del;
285  }
286
287  // density correction
288  G4double x = log(bg2)/twoln10;
289  if ( x >= x0den ) {
290    dedx -= twoln10*x - cden ;
291    if ( x < x1den ) dedx -= aden*pow((x1den-x),mden) ;
292  }
293
294  // shell correction
295  dedx -= 2.0*corr->ShellCorrection(p,material,kineticEnergy);
296
297  // now compute the total ionization loss
298
299  if (dedx < 0.0) dedx = 0.0 ;
300
301  dedx *= twopi_mc2_rcl2*chargeSquare*eDensity/beta2;
302
303  //High order correction different for hadrons and ions
304  if(isIon) {
305    dedx += corr->IonBarkasCorrection(p,material,kineticEnergy);
306  } else {     
307    dedx += corr->HighOrderCorrections(p,material,kineticEnergy,cutEnergy);
308  }
309  return dedx;
310}
311
312//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
313
314void G4BetheBlochModel::CorrectionsAlongStep(const G4MaterialCutsCouple* couple,
315                                             const G4DynamicParticle* dp,
316                                             G4double& eloss,
317                                             G4double&,
318                                             G4double length)
319{
320  const G4ParticleDefinition* p = dp->GetDefinition();
321  const G4Material* mat = couple->GetMaterial();
322  G4double preKinEnergy = dp->GetKineticEnergy();
323  G4double e = preKinEnergy - eloss*0.5;
324  if(e < 0.0) e = preKinEnergy*0.5;
325
326  if(isIon) {
327    G4double q2 = corr->EffectiveChargeSquareRatio(p,mat,e);
328    GetModelOfFluctuations()->SetParticleAndCharge(p, q2);
329    eloss *= q2*corr->EffectiveChargeCorrection(p,mat,e)/corrFactor; 
330    eloss += length*corr->IonHighOrderCorrections(p,couple,e);
331  }
332
333  if(nuclearStopping && preKinEnergy*proton_mass_c2/mass < chargeSquare*100.*MeV) {
334
335    G4double nloss = length*corr->NuclearDEDX(p,mat,e,false);
336
337    // too big energy loss
338    if(eloss + nloss > preKinEnergy) {
339      nloss *= (preKinEnergy/(eloss + nloss));
340      eloss = preKinEnergy;
341    } else {
342      eloss += nloss;
343    }
344    /*
345    G4cout << "G4ionIonisation::CorrectionsAlongStep: e= " << preKinEnergy
346           << " de= " << eloss << " NIEL= " << nloss
347           << " dynQ= " << dp->GetCharge()/eplus << G4endl;
348    */
349    fParticleChange->ProposeNonIonizingEnergyDeposit(nloss);
350  }
351
352}
353
354//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
355
356void G4BetheBlochModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
357                                          const G4MaterialCutsCouple*,
358                                          const G4DynamicParticle* dp,
359                                          G4double minKinEnergy,
360                                          G4double maxEnergy)
361{
362  G4double kineticEnergy = dp->GetKineticEnergy();
363  G4double tmax = MaxSecondaryEnergy(dp->GetDefinition(),kineticEnergy);
364
365  G4double maxKinEnergy = std::min(maxEnergy,tmax);
366  if(minKinEnergy >= maxKinEnergy) return;
367
368  G4double totEnergy     = kineticEnergy + mass;
369  G4double etot2         = totEnergy*totEnergy;
370  G4double beta2         = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
371
372  G4double deltaKinEnergy, f; 
373  G4double f1 = 0.0;
374  G4double fmax = 1.0;
375  if( 0.5 == spin ) fmax += 0.5*maxKinEnergy*maxKinEnergy/etot2; 
376
377  // sampling without nuclear size effect
378  do {
379    G4double q = G4UniformRand();
380    deltaKinEnergy = minKinEnergy*maxKinEnergy
381                    /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
382
383    f = 1.0 - beta2*deltaKinEnergy/tmax;
384    if( 0.5 == spin ) {
385      f1 = 0.5*deltaKinEnergy*deltaKinEnergy/etot2;
386      f += f1;
387    }
388
389  } while( fmax*G4UniformRand() > f);
390
391  // projectile formfactor - suppresion of high energy
392  // delta-electron production at high energy
393 
394  G4double x = formfact*deltaKinEnergy;
395  if(x > 1.e-6) {
396
397    G4double x1 = 1.0 + x;
398    G4double g  = 1.0/(x1*x1);
399    if( 0.5 == spin ) {
400      G4double x2 = 0.5*electron_mass_c2*deltaKinEnergy/(mass*mass);
401      g *= (1.0 + magMoment2*(x2 - f1/f)/(1.0 + x2));
402    }
403    if(g > 1.0) {
404      G4cout << "### G4BetheBlochModel WARNING: g= " << g
405             << dp->GetDefinition()->GetParticleName()
406             << " Ekin(MeV)= " <<  kineticEnergy
407             << " delEkin(MeV)= " << deltaKinEnergy
408             << G4endl;
409    }
410    if(G4UniformRand() > g) return;
411  }
412
413  // delta-electron is produced
414  G4double totMomentum = totEnergy*sqrt(beta2);
415  G4double deltaMomentum =
416           sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
417  G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
418                                   (deltaMomentum * totMomentum);
419  if(cost > 1.0) {
420    G4cout << "### G4BetheBlochModel WARNING: cost= " 
421           << cost << " > 1 for "
422           << dp->GetDefinition()->GetParticleName()
423           << " Ekin(MeV)= " <<  kineticEnergy
424           << " p(MeV/c)= " <<  totMomentum
425           << " delEkin(MeV)= " << deltaKinEnergy
426           << " delMom(MeV/c)= " << deltaMomentum
427           << " tmin(MeV)= " << minKinEnergy
428           << " tmax(MeV)= " << maxKinEnergy
429           << " dir= " << dp->GetMomentumDirection()
430           << G4endl;
431    cost = 1.0;
432  }
433  G4double sint = sqrt((1.0 - cost)*(1.0 + cost));
434
435  G4double phi = twopi * G4UniformRand() ;
436
437
438  G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost);
439  G4ThreeVector direction = dp->GetMomentumDirection();
440  deltaDirection.rotateUz(direction);
441
442  // create G4DynamicParticle object for delta ray
443  G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
444                                                 deltaDirection,deltaKinEnergy);
445
446  vdp->push_back(delta);
447
448  // Change kinematics of primary particle
449  kineticEnergy       -= deltaKinEnergy;
450  G4ThreeVector finalP = direction*totMomentum - deltaDirection*deltaMomentum;
451  finalP               = finalP.unit();
452 
453  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
454  fParticleChange->SetProposedMomentumDirection(finalP);
455}
456
457//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
458
459G4double G4BetheBlochModel::MaxSecondaryEnergy(const G4ParticleDefinition* pd,
460                                               G4double kinEnergy) 
461{
462  if(isIon) SetParticle(pd);
463  G4double tau  = kinEnergy/mass;
464  G4double tmax = 2.0*electron_mass_c2*tau*(tau + 2.) /
465                  (1. + 2.0*(tau + 1.)*ratio + ratio*ratio);
466  return std::min(tmax,tlimit);
467}
468
469//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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