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G4MuBetheBlochModel.cc
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26 // $Id$
27 //
28 // -------------------------------------------------------------------
29 //
30 // GEANT4 Class header file
31 //
32 //
33 // File name: G4MuBetheBlochModel
34 //
35 // Author: Vladimir Ivanchenko on base of Laszlo Urban code
36 //
37 // Creation date: 09.08.2002
38 //
39 // Modifications:
40 //
41 // 04-12-02 Fix problem of G4DynamicParticle constructor (V.Ivanchenko)
42 // 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
43 // 27-01-03 Make models region aware (V.Ivanchenko)
44 // 13-02-03 Add name (V.Ivanchenko)
45 // 10-02-04 Calculation of radiative corrections using R.Kokoulin model (V.I)
46 // 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
47 // 12-04-05 Add usage of G4EmCorrections (V.Ivanchenko)
48 // 13-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
49 //
50 
51 //
52 // -------------------------------------------------------------------
53 //
54 
55 
56 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
57 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
58 
59 #include "G4MuBetheBlochModel.hh"
60 #include "G4PhysicalConstants.hh"
61 #include "G4SystemOfUnits.hh"
62 #include "Randomize.hh"
63 #include "G4Electron.hh"
64 #include "G4LossTableManager.hh"
65 #include "G4EmCorrections.hh"
66 #include "G4ParticleChangeForLoss.hh"
67 
68 G4double G4MuBetheBlochModel::xgi[]={ 0.0199, 0.1017, 0.2372, 0.4083, 0.5917,
69  0.7628, 0.8983, 0.9801 };
70 
71 G4double G4MuBetheBlochModel::wgi[]={ 0.0506, 0.1112, 0.1569, 0.1813, 0.1813,
72  0.1569, 0.1112, 0.0506 };
73 
74 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
75 
76 using namespace std;
77 
78 G4MuBetheBlochModel::G4MuBetheBlochModel(const G4ParticleDefinition* p,
79  const G4String& nam)
80  : G4VEmModel(nam),
81  particle(0),
82  limitKinEnergy(100.*keV),
83  logLimitKinEnergy(log(limitKinEnergy)),
84  twoln10(2.0*log(10.0)),
85  bg2lim(0.0169),
86  taulim(8.4146e-3),
87  alphaprime(fine_structure_const/twopi)
88 {
89  theElectron = G4Electron::Electron();
90  corr = G4LossTableManager::Instance()->EmCorrections();
91  fParticleChange = 0;
92 
93  // initial initialisation of memeber should be overwritten
94  // by SetParticle
95  mass = massSquare = ratio = 1.0;
96 
97  if(p) { SetParticle(p); }
98 }
99 
100 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
101 
102 G4MuBetheBlochModel::~G4MuBetheBlochModel()
103 {}
104 
105 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
106 
107 G4double G4MuBetheBlochModel::MinEnergyCut(const G4ParticleDefinition*,
108  const G4MaterialCutsCouple* couple)
109 {
110  return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy();
111 }
112 
113 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
114 
115 G4double G4MuBetheBlochModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
116  G4double kinEnergy)
117 {
118  G4double tau = kinEnergy/mass;
119  G4double tmax = 2.0*electron_mass_c2*tau*(tau + 2.) /
120  (1. + 2.0*(tau + 1.)*ratio + ratio*ratio);
121  return tmax;
122 }
123 
124 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
125 
126 void G4MuBetheBlochModel::Initialise(const G4ParticleDefinition* p,
127  const G4DataVector&)
128 {
129  if(p) { SetParticle(p); }
130  if(!fParticleChange) { fParticleChange = GetParticleChangeForLoss(); }
131 }
132 
133 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
134 
135 G4double G4MuBetheBlochModel::ComputeCrossSectionPerElectron(
136  const G4ParticleDefinition* p,
137  G4double kineticEnergy,
138  G4double cutEnergy,
139  G4double maxKinEnergy)
140 {
141  G4double cross = 0.0;
142  G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
143  G4double maxEnergy = min(tmax,maxKinEnergy);
144  if(cutEnergy < maxEnergy) {
145 
146  G4double totEnergy = kineticEnergy + mass;
147  G4double energy2 = totEnergy*totEnergy;
148  G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/energy2;
149 
150  cross = 1.0/cutEnergy - 1.0/maxEnergy - beta2*log(maxEnergy/cutEnergy)/tmax
151  + 0.5*(maxEnergy - cutEnergy)/energy2;
152 
153  // radiative corrections of R. Kokoulin
154  if (maxEnergy > limitKinEnergy) {
155 
156  G4double logtmax = log(maxEnergy);
157  G4double logtmin = log(max(cutEnergy,limitKinEnergy));
158  G4double logstep = logtmax - logtmin;
159  G4double dcross = 0.0;
160 
161  for (G4int ll=0; ll<8; ll++)
162  {
163  G4double ep = exp(logtmin + xgi[ll]*logstep);
164  G4double a1 = log(1.0 + 2.0*ep/electron_mass_c2);
165  G4double a3 = log(4.0*totEnergy*(totEnergy - ep)/massSquare);
166  dcross += wgi[ll]*(1.0/ep - beta2/tmax + 0.5*ep/energy2)*a1*(a3 - a1);
167  }
168 
169  cross += dcross*logstep*alphaprime;
170  }
171 
172  cross *= twopi_mc2_rcl2/beta2;
173 
174  }
175 
176  // G4cout << "tmin= " << cutEnergy << " tmax= " << tmax
177  // << " cross= " << cross << G4endl;
178 
179  return cross;
180 }
181 
182 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
183 
184 G4double G4MuBetheBlochModel::ComputeCrossSectionPerAtom(
185  const G4ParticleDefinition* p,
186  G4double kineticEnergy,
187  G4double Z, G4double,
188  G4double cutEnergy,
189  G4double maxEnergy)
190 {
191  G4double cross = Z*ComputeCrossSectionPerElectron
192  (p,kineticEnergy,cutEnergy,maxEnergy);
193  return cross;
194 }
195 
196 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
197 
198 G4double G4MuBetheBlochModel::CrossSectionPerVolume(
199  const G4Material* material,
200  const G4ParticleDefinition* p,
201  G4double kineticEnergy,
202  G4double cutEnergy,
203  G4double maxEnergy)
204 {
205  G4double eDensity = material->GetElectronDensity();
206  G4double cross = eDensity*ComputeCrossSectionPerElectron
207  (p,kineticEnergy,cutEnergy,maxEnergy);
208  return cross;
209 }
210 
211 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
212 
213 G4double G4MuBetheBlochModel::ComputeDEDXPerVolume(const G4Material* material,
214  const G4ParticleDefinition* p,
215  G4double kineticEnergy,
216  G4double cut)
217 {
218  G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
219  G4double tau = kineticEnergy/mass;
220  G4double cutEnergy = min(cut,tmax);
221  G4double gam = tau + 1.0;
222  G4double bg2 = tau * (tau+2.0);
223  G4double beta2 = bg2/(gam*gam);
224 
225  G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
226  G4double eexc2 = eexc*eexc;
227  //G4double cden = material->GetIonisation()->GetCdensity();
228  //G4double mden = material->GetIonisation()->GetMdensity();
229  //G4double aden = material->GetIonisation()->GetAdensity();
230  //G4double x0den = material->GetIonisation()->GetX0density();
231  //G4double x1den = material->GetIonisation()->GetX1density();
232 
233  G4double eDensity = material->GetElectronDensity();
234 
235  G4double dedx = log(2.0*electron_mass_c2*bg2*cutEnergy/eexc2)
236  -(1.0 + cutEnergy/tmax)*beta2;
237 
238  G4double totEnergy = kineticEnergy + mass;
239  G4double del = 0.5*cutEnergy/totEnergy;
240  dedx += del*del;
241 
242  // density correction
243  G4double x = log(bg2)/twoln10;
244  //if ( x >= x0den ) {
245  // dedx -= twoln10*x - cden ;
246  // if ( x < x1den ) dedx -= aden*pow((x1den-x),mden) ;
247  //}
248  dedx -= material->GetIonisation()->DensityCorrection(x);
249 
250  // shell correction
251  dedx -= 2.0*corr->ShellCorrection(p,material,kineticEnergy);
252 
253  // now compute the total ionization loss
254 
255  if (dedx < 0.0) dedx = 0.0 ;
256 
257  // radiative corrections of R. Kokoulin
258  if (cutEnergy > limitKinEnergy) {
259 
260  G4double logtmax = log(cutEnergy);
261  G4double logstep = logtmax - logLimitKinEnergy;
262  G4double dloss = 0.0;
263  G4double ftot2= 0.5/(totEnergy*totEnergy);
264 
265  for (G4int ll=0; ll<8; ll++)
266  {
267  G4double ep = exp(logLimitKinEnergy + xgi[ll]*logstep);
268  G4double a1 = log(1.0 + 2.0*ep/electron_mass_c2);
269  G4double a3 = log(4.0*totEnergy*(totEnergy - ep)/massSquare);
270  dloss += wgi[ll]*(1.0 - beta2*ep/tmax + ep*ep*ftot2)*a1*(a3 - a1);
271  }
272  dedx += dloss*logstep*alphaprime;
273  }
274 
275  dedx *= twopi_mc2_rcl2*eDensity/beta2;
276 
277  //High order corrections
278  dedx += corr->HighOrderCorrections(p,material,kineticEnergy,cutEnergy);
279 
280  return dedx;
281 }
282 
283 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
284 
285 void G4MuBetheBlochModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
286  const G4MaterialCutsCouple*,
287  const G4DynamicParticle* dp,
288  G4double minKinEnergy,
289  G4double maxEnergy)
290 {
291  G4double tmax = MaxSecondaryKinEnergy(dp);
292  G4double maxKinEnergy = min(maxEnergy,tmax);
293  if(minKinEnergy >= maxKinEnergy) { return; }
294 
295  G4double kineticEnergy = dp->GetKineticEnergy();
296  G4double totEnergy = kineticEnergy + mass;
297  G4double etot2 = totEnergy*totEnergy;
298  G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
299 
300  G4double grej = 1.;
301  if(tmax > limitKinEnergy) {
302  G4double a0 = log(2.*totEnergy/mass);
303  grej += alphaprime*a0*a0;
304  }
305 
306  G4double deltaKinEnergy, f;
307 
308  // sampling follows ...
309  do {
310  G4double q = G4UniformRand();
311  deltaKinEnergy = minKinEnergy*maxKinEnergy
312  /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
313 
314 
315  f = 1.0 - beta2*deltaKinEnergy/tmax
316  + 0.5*deltaKinEnergy*deltaKinEnergy/etot2;
317 
318  if(deltaKinEnergy > limitKinEnergy) {
319  G4double a1 = log(1.0 + 2.0*deltaKinEnergy/electron_mass_c2);
320  G4double a3 = log(4.0*totEnergy*(totEnergy - deltaKinEnergy)/massSquare);
321  f *= (1. + alphaprime*a1*(a3 - a1));
322  }
323 
324  if(f > grej) {
325  G4cout << "G4MuBetheBlochModel::SampleSecondary Warning! "
326  << "Majorant " << grej << " < "
327  << f << " for edelta= " << deltaKinEnergy
328  << " tmin= " << minKinEnergy << " max= " << maxKinEnergy
329  << G4endl;
330  }
331 
332 
333  } while( grej*G4UniformRand() > f );
334 
335  G4double deltaMomentum =
336  sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
337  G4double totalMomentum = totEnergy*sqrt(beta2);
338  G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
339  (deltaMomentum * totalMomentum);
340 
341  G4double sint = sqrt(1.0 - cost*cost);
342 
343  G4double phi = twopi * G4UniformRand() ;
344 
345  G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ;
346  G4ThreeVector direction = dp->GetMomentumDirection();
347  deltaDirection.rotateUz(direction);
348 
349  // primary change
350  kineticEnergy -= deltaKinEnergy;
351  G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
352  direction = dir.unit();
353  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
354  fParticleChange->SetProposedMomentumDirection(direction);
355 
356  // create G4DynamicParticle object for delta ray
357  G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
358  deltaDirection,deltaKinEnergy);
359  vdp->push_back(delta);
360 }
361 
362 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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