source: trunk/source/processes/electromagnetic/muons/src/G4MuBetheBlochModel.cc@ 1317

Last change on this file since 1317 was 1228, checked in by garnier, 16 years ago

update geant4.9.3 tag
File size: 12.8 KB
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25//
26// $Id: G4MuBetheBlochModel.cc,v 1.27 2009/11/09 19:18:01 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class header file
32//
33//
34// File name: G4MuBetheBlochModel
35//
36// Author: Vladimir Ivanchenko on base of Laszlo Urban code
37//
38// Creation date: 09.08.2002
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// 10-02-04 Calculation of radiative corrections using R.Kokoulin model (V.I)
47// 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
48// 12-04-05 Add usage of G4EmCorrections (V.Ivanchenko)
49// 13-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
50//
51
52//
53// -------------------------------------------------------------------
54//
55
56
57//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
58//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
59
60#include "G4MuBetheBlochModel.hh"
61#include "Randomize.hh"
62#include "G4Electron.hh"
63#include "G4LossTableManager.hh"
64#include "G4EmCorrections.hh"
65#include "G4ParticleChangeForLoss.hh"
66
67G4double G4MuBetheBlochModel::xgi[]={ 0.0199, 0.1017, 0.2372, 0.4083, 0.5917,
68 0.7628, 0.8983, 0.9801 };
69
70G4double G4MuBetheBlochModel::wgi[]={ 0.0506, 0.1112, 0.1569, 0.1813, 0.1813,
71 0.1569, 0.1112, 0.0506 };
72
73//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
74
75using namespace std;
76
77G4MuBetheBlochModel::G4MuBetheBlochModel(const G4ParticleDefinition* p,
78 const G4String& nam)
79 : G4VEmModel(nam),
80 particle(0),
81 limitKinEnergy(100.*keV),
82 logLimitKinEnergy(log(limitKinEnergy)),
83 twoln10(2.0*log(10.0)),
84 bg2lim(0.0169),
85 taulim(8.4146e-3),
86 alphaprime(fine_structure_const/twopi)
87{
88 theElectron = G4Electron::Electron();
89 corr = G4LossTableManager::Instance()->EmCorrections();
90 fParticleChange = 0;
91
92 if(p) SetParticle(p);
93}
94
95//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
96
97G4MuBetheBlochModel::~G4MuBetheBlochModel()
98{}
99
100//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
101
102G4double G4MuBetheBlochModel::MinEnergyCut(const G4ParticleDefinition*,
103 const G4MaterialCutsCouple* couple)
104{
105 return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy();
106}
107
108//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
109
110G4double G4MuBetheBlochModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
111 G4double kinEnergy)
112{
113 G4double tau = kinEnergy/mass;
114 G4double tmax = 2.0*electron_mass_c2*tau*(tau + 2.) /
115 (1. + 2.0*(tau + 1.)*ratio + ratio*ratio);
116 return tmax;
117}
118
119//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
120
121void G4MuBetheBlochModel::Initialise(const G4ParticleDefinition* p,
122 const G4DataVector&)
123{
124 if(p) SetParticle(p);
125 if(!fParticleChange) fParticleChange = GetParticleChangeForLoss();
126}
127
128//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
129
130G4double G4MuBetheBlochModel::ComputeCrossSectionPerElectron(
131 const G4ParticleDefinition* p,
132 G4double kineticEnergy,
133 G4double cutEnergy,
134 G4double maxKinEnergy)
135{
136 G4double cross = 0.0;
137 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
138 G4double maxEnergy = min(tmax,maxKinEnergy);
139 if(cutEnergy < maxEnergy) {
140
141 G4double totEnergy = kineticEnergy + mass;
142 G4double energy2 = totEnergy*totEnergy;
143 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/energy2;
144
145 cross = 1.0/cutEnergy - 1.0/maxEnergy - beta2*log(maxEnergy/cutEnergy)/tmax
146 + 0.5*(maxEnergy - cutEnergy)/energy2;
147
148 // radiative corrections of R. Kokoulin
149 if (maxEnergy > limitKinEnergy) {
150
151 G4double logtmax = log(maxEnergy);
152 G4double logtmin = log(max(cutEnergy,limitKinEnergy));
153 G4double logstep = logtmax - logtmin;
154 G4double dcross = 0.0;
155
156 for (G4int ll=0; ll<8; ll++)
157 {
158 G4double ep = exp(logtmin + xgi[ll]*logstep);
159 G4double a1 = log(1.0 + 2.0*ep/electron_mass_c2);
160 G4double a3 = log(4.0*totEnergy*(totEnergy - ep)/massSquare);
161 dcross += wgi[ll]*(1.0/ep - beta2/tmax + 0.5*ep/energy2)*a1*(a3 - a1);
162 }
163
164 cross += dcross*logstep*alphaprime;
165 }
166
167 cross *= twopi_mc2_rcl2/beta2;
168
169 }
170
171 // G4cout << "tmin= " << cutEnergy << " tmax= " << tmax
172 // << " cross= " << cross << G4endl;
173
174 return cross;
175}
176
177//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
178
179G4double G4MuBetheBlochModel::ComputeCrossSectionPerAtom(
180 const G4ParticleDefinition* p,
181 G4double kineticEnergy,
182 G4double Z, G4double,
183 G4double cutEnergy,
184 G4double maxEnergy)
185{
186 G4double cross = Z*ComputeCrossSectionPerElectron
187 (p,kineticEnergy,cutEnergy,maxEnergy);
188 return cross;
189}
190
191//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
192
193G4double G4MuBetheBlochModel::CrossSectionPerVolume(
194 const G4Material* material,
195 const G4ParticleDefinition* p,
196 G4double kineticEnergy,
197 G4double cutEnergy,
198 G4double maxEnergy)
199{
200 G4double eDensity = material->GetElectronDensity();
201 G4double cross = eDensity*ComputeCrossSectionPerElectron
202 (p,kineticEnergy,cutEnergy,maxEnergy);
203 return cross;
204}
205
206//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
207
208G4double G4MuBetheBlochModel::ComputeDEDXPerVolume(const G4Material* material,
209 const G4ParticleDefinition* p,
210 G4double kineticEnergy,
211 G4double cut)
212{
213 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
214 G4double tau = kineticEnergy/mass;
215 G4double cutEnergy = min(cut,tmax);
216 G4double gam = tau + 1.0;
217 G4double bg2 = tau * (tau+2.0);
218 G4double beta2 = bg2/(gam*gam);
219
220 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
221 G4double eexc2 = eexc*eexc;
222 //G4double cden = material->GetIonisation()->GetCdensity();
223 //G4double mden = material->GetIonisation()->GetMdensity();
224 //G4double aden = material->GetIonisation()->GetAdensity();
225 //G4double x0den = material->GetIonisation()->GetX0density();
226 //G4double x1den = material->GetIonisation()->GetX1density();
227
228 G4double eDensity = material->GetElectronDensity();
229
230 G4double dedx = log(2.0*electron_mass_c2*bg2*cutEnergy/eexc2)
231 -(1.0 + cutEnergy/tmax)*beta2;
232
233 G4double totEnergy = kineticEnergy + mass;
234 G4double del = 0.5*cutEnergy/totEnergy;
235 dedx += del*del;
236
237 // density correction
238 G4double x = log(bg2)/twoln10;
239 //if ( x >= x0den ) {
240 // dedx -= twoln10*x - cden ;
241 // if ( x < x1den ) dedx -= aden*pow((x1den-x),mden) ;
242 //}
243 dedx -= material->GetIonisation()->DensityCorrection(x);
244
245 // shell correction
246 dedx -= 2.0*corr->ShellCorrection(p,material,kineticEnergy);
247
248 // now compute the total ionization loss
249
250 if (dedx < 0.0) dedx = 0.0 ;
251
252 // radiative corrections of R. Kokoulin
253 if (cutEnergy > limitKinEnergy) {
254
255 G4double logtmax = log(cutEnergy);
256 G4double logstep = logtmax - logLimitKinEnergy;
257 G4double dloss = 0.0;
258 G4double ftot2= 0.5/(totEnergy*totEnergy);
259
260 for (G4int ll=0; ll<8; ll++)
261 {
262 G4double ep = exp(logLimitKinEnergy + xgi[ll]*logstep);
263 G4double a1 = log(1.0 + 2.0*ep/electron_mass_c2);
264 G4double a3 = log(4.0*totEnergy*(totEnergy - ep)/massSquare);
265 dloss += wgi[ll]*(1.0 - beta2*ep/tmax + ep*ep*ftot2)*a1*(a3 - a1);
266 }
267 dedx += dloss*logstep*alphaprime;
268 }
269
270 dedx *= twopi_mc2_rcl2*eDensity/beta2;
271
272 //High order corrections
273 dedx += corr->HighOrderCorrections(p,material,kineticEnergy,cutEnergy);
274
275 return dedx;
276}
277
278//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
279
280void G4MuBetheBlochModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
281 const G4MaterialCutsCouple*,
282 const G4DynamicParticle* dp,
283 G4double minKinEnergy,
284 G4double maxEnergy)
285{
286 G4double tmax = MaxSecondaryKinEnergy(dp);
287 G4double maxKinEnergy = min(maxEnergy,tmax);
288 if(minKinEnergy >= maxKinEnergy) return;
289
290 G4double kineticEnergy = dp->GetKineticEnergy();
291 G4double totEnergy = kineticEnergy + mass;
292 G4double etot2 = totEnergy*totEnergy;
293 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
294
295 G4double grej = 1.;
296 if(tmax > limitKinEnergy) {
297 G4double a0 = log(2.*totEnergy/mass);
298 grej += alphaprime*a0*a0;
299 }
300
301 G4double deltaKinEnergy, f;
302
303 // sampling follows ...
304 do {
305 G4double q = G4UniformRand();
306 deltaKinEnergy = minKinEnergy*maxKinEnergy
307 /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
308
309
310 f = 1.0 - beta2*deltaKinEnergy/tmax
311 + 0.5*deltaKinEnergy*deltaKinEnergy/etot2;
312
313 if(deltaKinEnergy > limitKinEnergy) {
314 G4double a1 = log(1.0 + 2.0*deltaKinEnergy/electron_mass_c2);
315 G4double a3 = log(4.0*totEnergy*(totEnergy - deltaKinEnergy)/massSquare);
316 f *= (1. + alphaprime*a1*(a3 - a1));
317 }
318
319 if(f > grej) {
320 G4cout << "G4MuBetheBlochModel::SampleSecondary Warning! "
321 << "Majorant " << grej << " < "
322 << f << " for edelta= " << deltaKinEnergy
323 << " tmin= " << minKinEnergy << " max= " << maxKinEnergy
324 << G4endl;
325 }
326
327
328 } while( grej*G4UniformRand() > f );
329
330 G4double deltaMomentum =
331 sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
332 G4double totalMomentum = totEnergy*sqrt(beta2);
333 G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
334 (deltaMomentum * totalMomentum);
335
336 G4double sint = sqrt(1.0 - cost*cost);
337
338 G4double phi = twopi * G4UniformRand() ;
339
340 G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ;
341 G4ThreeVector direction = dp->GetMomentumDirection();
342 deltaDirection.rotateUz(direction);
343
344 // primary change
345 kineticEnergy -= deltaKinEnergy;
346 G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
347 direction = dir.unit();
348 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
349 fParticleChange->SetProposedMomentumDirection(direction);
350
351 // create G4DynamicParticle object for delta ray
352 G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
353 deltaDirection,deltaKinEnergy);
354 vdp->push_back(delta);
355}
356
357//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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