source: trunk/source/processes/electromagnetic/standard/src/G4BetheBlochModel.cc @ 1312

Last change on this file since 1312 was 1228, checked in by garnier, 15 years ago

update geant4.9.3 tag
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26// $Id: G4BetheBlochModel.cc,v 1.36 2009/12/03 17:26:40 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03 $
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
68//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
69
70using namespace std;
71
72G4BetheBlochModel::G4BetheBlochModel(const G4ParticleDefinition* p, 
73                                     const G4String& nam)
74  : G4VEmModel(nam),
75    particle(0),
76    tlimit(DBL_MAX),
77    twoln10(2.0*log(10.0)),
78    bg2lim(0.0169),
79    taulim(8.4146e-3),
80    isIon(false),
81    isInitialised(false)
82{
83  fParticleChange = 0;
84  if(p) {
85    SetGenericIon(p);
86    SetParticle(p);
87  }
88  theElectron = G4Electron::Electron();
89  corr = G4LossTableManager::Instance()->EmCorrections(); 
90  nist = G4NistManager::Instance();
91  SetLowEnergyLimit(2.0*MeV);
92}
93
94//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
95
96G4BetheBlochModel::~G4BetheBlochModel()
97{}
98
99//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
100
101G4double G4BetheBlochModel::MinEnergyCut(const G4ParticleDefinition*,
102                                         const G4MaterialCutsCouple* couple)
103{
104  return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy();
105}
106
107//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
108
109void G4BetheBlochModel::Initialise(const G4ParticleDefinition* p,
110                                   const G4DataVector&)
111{
112  SetGenericIon(p);
113  SetParticle(p);
114
115  //G4cout << "G4BetheBlochModel::Initialise for " << p->GetParticleName()
116  //     << "  isIon= " << isIon
117  //     << G4endl;
118
119  corrFactor = chargeSquare;
120  // always false before the run
121  SetDeexcitationFlag(false);
122
123  if(!isInitialised) {
124    isInitialised = true;
125    fParticleChange = GetParticleChangeForLoss();
126  }
127}
128
129//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
130
131G4double G4BetheBlochModel::GetChargeSquareRatio(const G4ParticleDefinition* p,
132                                                 const G4Material* mat,
133                                                 G4double kineticEnergy)
134{
135  // this method is called only for ions
136  G4double q2 = corr->EffectiveChargeSquareRatio(p,mat,kineticEnergy);
137  corrFactor = q2*corr->EffectiveChargeCorrection(p,mat,kineticEnergy);
138  return corrFactor;
139}
140
141//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
142
143G4double G4BetheBlochModel::GetParticleCharge(const G4ParticleDefinition* p,
144                                              const G4Material* mat,
145                                              G4double kineticEnergy)
146{
147  // this method is called only for ions
148  return corr->GetParticleCharge(p,mat,kineticEnergy);
149}
150
151//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
152
153G4double
154G4BetheBlochModel::ComputeCrossSectionPerElectron(const G4ParticleDefinition* p,
155                                                  G4double kineticEnergy,
156                                                  G4double cutEnergy,
157                                                  G4double maxKinEnergy)       
158{
159  G4double cross = 0.0;
160  G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
161  G4double maxEnergy = min(tmax,maxKinEnergy);
162  if(cutEnergy < maxEnergy) {
163
164    G4double totEnergy = kineticEnergy + mass;
165    G4double energy2   = totEnergy*totEnergy;
166    G4double beta2     = kineticEnergy*(kineticEnergy + 2.0*mass)/energy2;
167
168    cross = 1.0/cutEnergy - 1.0/maxEnergy
169      - beta2*log(maxEnergy/cutEnergy)/tmax;
170
171    // +term for spin=1/2 particle
172    if( 0.5 == spin ) cross += 0.5*(maxEnergy - cutEnergy)/energy2;
173
174    // High order correction different for hadrons and ions
175    // nevetheless they are applied to reduce high energy transfers
176    //    if(!isIon)
177    //cross += corr->FiniteSizeCorrectionXS(p,currentMaterial,
178    //                                    kineticEnergy,cutEnergy);
179
180    cross *= twopi_mc2_rcl2*chargeSquare/beta2;
181  }
182 
183   // G4cout << "BB: e= " << kineticEnergy << " tmin= " << cutEnergy
184   //        << " tmax= " << tmax << " cross= " << cross << G4endl;
185 
186  return cross;
187}
188
189//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
190
191G4double G4BetheBlochModel::ComputeCrossSectionPerAtom(
192                                           const G4ParticleDefinition* p,
193                                                 G4double kineticEnergy,
194                                                 G4double Z, G4double,
195                                                 G4double cutEnergy,
196                                                 G4double maxEnergy)
197{
198  G4double cross = Z*ComputeCrossSectionPerElectron
199                                         (p,kineticEnergy,cutEnergy,maxEnergy);
200  return cross;
201}
202
203//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
204
205G4double G4BetheBlochModel::CrossSectionPerVolume(
206                                           const G4Material* material,
207                                           const G4ParticleDefinition* p,
208                                                 G4double kineticEnergy,
209                                                 G4double cutEnergy,
210                                                 G4double maxEnergy)
211{
212  currentMaterial   = material;
213  G4double eDensity = material->GetElectronDensity();
214  G4double cross = eDensity*ComputeCrossSectionPerElectron
215                                         (p,kineticEnergy,cutEnergy,maxEnergy);
216  return cross;
217}
218
219//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
220
221G4double G4BetheBlochModel::ComputeDEDXPerVolume(const G4Material* material,
222                                                 const G4ParticleDefinition* p,
223                                                 G4double kineticEnergy,
224                                                 G4double cut)
225{
226  G4double tmax      = MaxSecondaryEnergy(p, kineticEnergy);
227  G4double cutEnergy = min(cut,tmax);
228
229  G4double tau   = kineticEnergy/mass;
230  G4double gam   = tau + 1.0;
231  G4double bg2   = tau * (tau+2.0);
232  G4double beta2 = bg2/(gam*gam);
233
234  G4double eexc  = material->GetIonisation()->GetMeanExcitationEnergy();
235  G4double eexc2 = eexc*eexc;
236  //G4double cden  = material->GetIonisation()->GetCdensity();
237  //G4double mden  = material->GetIonisation()->GetMdensity();
238  //G4double aden  = material->GetIonisation()->GetAdensity();
239  //G4double x0den = material->GetIonisation()->GetX0density();
240  //G4double x1den = material->GetIonisation()->GetX1density();
241
242  G4double eDensity = material->GetElectronDensity();
243
244  G4double dedx = log(2.0*electron_mass_c2*bg2*cutEnergy/eexc2)
245                - (1.0 + cutEnergy/tmax)*beta2;
246
247  if(0.5 == spin) {
248    G4double del = 0.5*cutEnergy/(kineticEnergy + mass);
249    dedx += del*del;
250  }
251
252  // density correction
253  G4double x = log(bg2)/twoln10;
254  //if ( x >= x0den ) {
255  //  dedx -= twoln10*x - cden ;
256  //  if ( x < x1den ) dedx -= aden*pow((x1den-x),mden) ;
257  //}
258  dedx -= material->GetIonisation()->DensityCorrection(x);
259
260  // shell correction
261  dedx -= 2.0*corr->ShellCorrection(p,material,kineticEnergy);
262
263  // now compute the total ionization loss
264
265  if (dedx < 0.0) dedx = 0.0 ;
266
267  dedx *= twopi_mc2_rcl2*chargeSquare*eDensity/beta2;
268
269  //High order correction different for hadrons and ions
270  if(isIon) {
271    dedx += corr->IonBarkasCorrection(p,material,kineticEnergy);
272  } else {     
273    dedx += corr->HighOrderCorrections(p,material,kineticEnergy,cutEnergy);
274  }
275  return dedx;
276}
277
278//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
279/*
280void G4BetheBlochModel::CorrectionsAlongStep(const G4MaterialCutsCouple*,
281                                             const G4DynamicParticle*,
282                                             G4double&,
283                                             G4double&,
284                                             G4double)
285{}
286*/
287
288void G4BetheBlochModel::CorrectionsAlongStep(const G4MaterialCutsCouple* couple,
289                                             const G4DynamicParticle* dp,
290                                             G4double& eloss,
291                                             G4double&,
292                                             G4double length)
293{
294  if(isIon) {
295    const G4ParticleDefinition* p = dp->GetDefinition();
296    const G4Material* mat = couple->GetMaterial();
297    G4double preKinEnergy = dp->GetKineticEnergy();
298    G4double e = preKinEnergy - eloss*0.5;
299    if(e < 0.0) e = preKinEnergy*0.5;
300
301    G4double q2 = corr->EffectiveChargeSquareRatio(p,mat,e);
302    GetModelOfFluctuations()->SetParticleAndCharge(p, q2);
303    G4double qfactor = q2*corr->EffectiveChargeCorrection(p,mat,e)/corrFactor;
304    G4double highOrder = length*corr->IonHighOrderCorrections(p,couple,e);
305    eloss *= qfactor; 
306    eloss += highOrder;
307    //G4cout << "G4BetheBlochModel::CorrectionsAlongStep: e= " << preKinEnergy
308    //     << " qfactor= " << qfactor
309    //     << " highOrder= " << highOrder << " (" << highOrder/eloss << ")" << G4endl;   
310  }
311}
312
313//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
314
315void G4BetheBlochModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
316                                          const G4MaterialCutsCouple*,
317                                          const G4DynamicParticle* dp,
318                                          G4double minKinEnergy,
319                                          G4double maxEnergy)
320{
321  G4double kineticEnergy = dp->GetKineticEnergy();
322  G4double tmax = MaxSecondaryEnergy(dp->GetDefinition(),kineticEnergy);
323
324  G4double maxKinEnergy = std::min(maxEnergy,tmax);
325  if(minKinEnergy >= maxKinEnergy) return;
326
327  G4double totEnergy     = kineticEnergy + mass;
328  G4double etot2         = totEnergy*totEnergy;
329  G4double beta2         = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
330
331  G4double deltaKinEnergy, f; 
332  G4double f1 = 0.0;
333  G4double fmax = 1.0;
334  if( 0.5 == spin ) fmax += 0.5*maxKinEnergy*maxKinEnergy/etot2; 
335
336  // sampling without nuclear size effect
337  do {
338    G4double q = G4UniformRand();
339    deltaKinEnergy = minKinEnergy*maxKinEnergy
340                    /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
341
342    f = 1.0 - beta2*deltaKinEnergy/tmax;
343    if( 0.5 == spin ) {
344      f1 = 0.5*deltaKinEnergy*deltaKinEnergy/etot2;
345      f += f1;
346    }
347
348  } while( fmax*G4UniformRand() > f);
349
350  // projectile formfactor - suppresion of high energy
351  // delta-electron production at high energy
352 
353  G4double x = formfact*deltaKinEnergy;
354  if(x > 1.e-6) {
355
356    G4double x1 = 1.0 + x;
357    G4double g  = 1.0/(x1*x1);
358    if( 0.5 == spin ) {
359      G4double x2 = 0.5*electron_mass_c2*deltaKinEnergy/(mass*mass);
360      g *= (1.0 + magMoment2*(x2 - f1/f)/(1.0 + x2));
361    }
362    if(g > 1.0) {
363      G4cout << "### G4BetheBlochModel WARNING: g= " << g
364             << dp->GetDefinition()->GetParticleName()
365             << " Ekin(MeV)= " <<  kineticEnergy
366             << " delEkin(MeV)= " << deltaKinEnergy
367             << G4endl;
368    }
369    if(G4UniformRand() > g) return;
370  }
371
372  // delta-electron is produced
373  G4double totMomentum = totEnergy*sqrt(beta2);
374  G4double deltaMomentum =
375           sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
376  G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
377                                   (deltaMomentum * totMomentum);
378  /*
379  if(cost > 1.0) {
380    G4cout << "### G4BetheBlochModel WARNING: cost= "
381           << cost << " > 1 for "
382           << dp->GetDefinition()->GetParticleName()
383           << " Ekin(MeV)= " <<  kineticEnergy
384           << " p(MeV/c)= " <<  totMomentum
385           << " delEkin(MeV)= " << deltaKinEnergy
386           << " delMom(MeV/c)= " << deltaMomentum
387           << " tmin(MeV)= " << minKinEnergy
388           << " tmax(MeV)= " << maxKinEnergy
389           << " dir= " << dp->GetMomentumDirection()
390           << G4endl;
391    cost = 1.0;
392  }
393  */
394  G4double sint = sqrt((1.0 - cost)*(1.0 + cost));
395
396  G4double phi = twopi * G4UniformRand() ;
397
398
399  G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost);
400  G4ThreeVector direction = dp->GetMomentumDirection();
401  deltaDirection.rotateUz(direction);
402
403  // create G4DynamicParticle object for delta ray
404  G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
405                                                   deltaDirection,deltaKinEnergy);
406
407  vdp->push_back(delta);
408
409  // Change kinematics of primary particle
410  kineticEnergy       -= deltaKinEnergy;
411  G4ThreeVector finalP = direction*totMomentum - deltaDirection*deltaMomentum;
412  finalP               = finalP.unit();
413 
414  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
415  fParticleChange->SetProposedMomentumDirection(finalP);
416}
417
418//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
419
420G4double G4BetheBlochModel::MaxSecondaryEnergy(const G4ParticleDefinition* pd,
421                                               G4double kinEnergy) 
422{
423  // here particle type is checked for any method
424  SetParticle(pd);
425  G4double tau  = kinEnergy/mass;
426  G4double tmax = 2.0*electron_mass_c2*tau*(tau + 2.) /
427                  (1. + 2.0*(tau + 1.)*ratio + ratio*ratio);
428  return std::min(tmax,tlimit);
429}
430
431//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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