source: trunk/source/processes/electromagnetic/muons/src/G4MuBetheBlochModel.cc@ 1006

Last change on this file since 1006 was 1005, checked in by garnier, 17 years ago

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25//
26// $Id: G4MuBetheBlochModel.cc,v 1.25 2009/02/20 14:48:16 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
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
126 if(!fParticleChange) {
127 if(pParticleChange) {
128 fParticleChange =
129 reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange);
130 } else {
131 fParticleChange = new G4ParticleChangeForLoss();
132 }
133 }
134}
135
136//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
137
138G4double G4MuBetheBlochModel::ComputeCrossSectionPerElectron(
139 const G4ParticleDefinition* p,
140 G4double kineticEnergy,
141 G4double cutEnergy,
142 G4double maxKinEnergy)
143{
144 G4double cross = 0.0;
145 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
146 G4double maxEnergy = min(tmax,maxKinEnergy);
147 if(cutEnergy < maxEnergy) {
148
149 G4double totEnergy = kineticEnergy + mass;
150 G4double energy2 = totEnergy*totEnergy;
151 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/energy2;
152
153 cross = 1.0/cutEnergy - 1.0/maxEnergy - beta2*log(maxEnergy/cutEnergy)/tmax
154 + 0.5*(maxEnergy - cutEnergy)/energy2;
155
156 // radiative corrections of R. Kokoulin
157 if (maxEnergy > limitKinEnergy) {
158
159 G4double logtmax = log(maxEnergy);
160 G4double logtmin = log(max(cutEnergy,limitKinEnergy));
161 G4double logstep = logtmax - logtmin;
162 G4double dcross = 0.0;
163
164 for (G4int ll=0; ll<8; ll++)
165 {
166 G4double ep = exp(logtmin + xgi[ll]*logstep);
167 G4double a1 = log(1.0 + 2.0*ep/electron_mass_c2);
168 G4double a3 = log(4.0*totEnergy*(totEnergy - ep)/massSquare);
169 dcross += wgi[ll]*(1.0/ep - beta2/tmax + 0.5*ep/energy2)*a1*(a3 - a1);
170 }
171
172 cross += dcross*logstep*alphaprime;
173 }
174
175 cross *= twopi_mc2_rcl2/beta2;
176
177 }
178
179 // G4cout << "tmin= " << cutEnergy << " tmax= " << tmax
180 // << " cross= " << cross << G4endl;
181
182 return cross;
183}
184
185//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
186
187G4double G4MuBetheBlochModel::ComputeCrossSectionPerAtom(
188 const G4ParticleDefinition* p,
189 G4double kineticEnergy,
190 G4double Z, G4double,
191 G4double cutEnergy,
192 G4double maxEnergy)
193{
194 G4double cross = Z*ComputeCrossSectionPerElectron
195 (p,kineticEnergy,cutEnergy,maxEnergy);
196 return cross;
197}
198
199//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
200
201G4double G4MuBetheBlochModel::CrossSectionPerVolume(
202 const G4Material* material,
203 const G4ParticleDefinition* p,
204 G4double kineticEnergy,
205 G4double cutEnergy,
206 G4double maxEnergy)
207{
208 G4double eDensity = material->GetElectronDensity();
209 G4double cross = eDensity*ComputeCrossSectionPerElectron
210 (p,kineticEnergy,cutEnergy,maxEnergy);
211 return cross;
212}
213
214//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
215
216G4double G4MuBetheBlochModel::ComputeDEDXPerVolume(const G4Material* material,
217 const G4ParticleDefinition* p,
218 G4double kineticEnergy,
219 G4double cut)
220{
221 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
222 G4double tau = kineticEnergy/mass;
223 G4double cutEnergy = min(cut,tmax);
224 G4double gam = tau + 1.0;
225 G4double bg2 = tau * (tau+2.0);
226 G4double beta2 = bg2/(gam*gam);
227
228 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
229 G4double eexc2 = eexc*eexc;
230 G4double cden = material->GetIonisation()->GetCdensity();
231 G4double mden = material->GetIonisation()->GetMdensity();
232 G4double aden = material->GetIonisation()->GetAdensity();
233 G4double x0den = material->GetIonisation()->GetX0density();
234 G4double x1den = material->GetIonisation()->GetX1density();
235
236 G4double eDensity = material->GetElectronDensity();
237
238 G4double dedx = log(2.0*electron_mass_c2*bg2*cutEnergy/eexc2)
239 -(1.0 + cutEnergy/tmax)*beta2;
240
241 G4double totEnergy = kineticEnergy + mass;
242 G4double del = 0.5*cutEnergy/totEnergy;
243 dedx += del*del;
244
245 // density correction
246 G4double x = log(bg2)/twoln10;
247 if ( x >= x0den ) {
248 dedx -= twoln10*x - cden ;
249 if ( x < x1den ) dedx -= aden*pow((x1den-x),mden) ;
250 }
251
252 // shell correction
253 dedx -= 2.0*corr->ShellCorrection(p,material,kineticEnergy);
254
255 // now compute the total ionization loss
256
257 if (dedx < 0.0) dedx = 0.0 ;
258
259 // radiative corrections of R. Kokoulin
260 if (cutEnergy > limitKinEnergy) {
261
262 G4double logtmax = log(cutEnergy);
263 G4double logstep = logtmax - logLimitKinEnergy;
264 G4double dloss = 0.0;
265 G4double ftot2= 0.5/(totEnergy*totEnergy);
266
267 for (G4int ll=0; ll<8; ll++)
268 {
269 G4double ep = exp(logLimitKinEnergy + xgi[ll]*logstep);
270 G4double a1 = log(1.0 + 2.0*ep/electron_mass_c2);
271 G4double a3 = log(4.0*totEnergy*(totEnergy - ep)/massSquare);
272 dloss += wgi[ll]*(1.0 - beta2*ep/tmax + ep*ep*ftot2)*a1*(a3 - a1);
273 }
274 dedx += dloss*logstep*alphaprime;
275 }
276
277 dedx *= twopi_mc2_rcl2*eDensity/beta2;
278
279 //High order corrections
280 dedx += corr->HighOrderCorrections(p,material,kineticEnergy,cutEnergy);
281
282 return dedx;
283}
284
285//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
286
287void G4MuBetheBlochModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
288 const G4MaterialCutsCouple*,
289 const G4DynamicParticle* dp,
290 G4double minKinEnergy,
291 G4double maxEnergy)
292{
293 G4double tmax = MaxSecondaryKinEnergy(dp);
294 G4double maxKinEnergy = min(maxEnergy,tmax);
295 if(minKinEnergy >= maxKinEnergy) return;
296
297 G4double kineticEnergy = dp->GetKineticEnergy();
298 G4double totEnergy = kineticEnergy + mass;
299 G4double etot2 = totEnergy*totEnergy;
300 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
301
302 G4double grej = 1.;
303 if(tmax > limitKinEnergy) {
304 G4double a0 = log(2.*totEnergy/mass);
305 grej += alphaprime*a0*a0;
306 }
307
308 G4double deltaKinEnergy, f;
309
310 // sampling follows ...
311 do {
312 G4double q = G4UniformRand();
313 deltaKinEnergy = minKinEnergy*maxKinEnergy
314 /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
315
316
317 f = 1.0 - beta2*deltaKinEnergy/tmax
318 + 0.5*deltaKinEnergy*deltaKinEnergy/etot2;
319
320 if(deltaKinEnergy > limitKinEnergy) {
321 G4double a1 = log(1.0 + 2.0*deltaKinEnergy/electron_mass_c2);
322 G4double a3 = log(4.0*totEnergy*(totEnergy - deltaKinEnergy)/massSquare);
323 f *= (1. + alphaprime*a1*(a3 - a1));
324 }
325
326 if(f > grej) {
327 G4cout << "G4MuBetheBlochModel::SampleSecondary Warning! "
328 << "Majorant " << grej << " < "
329 << f << " for edelta= " << deltaKinEnergy
330 << " tmin= " << minKinEnergy << " max= " << maxKinEnergy
331 << G4endl;
332 }
333
334
335 } while( grej*G4UniformRand() > f );
336
337 G4double deltaMomentum =
338 sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
339 G4double totalMomentum = totEnergy*sqrt(beta2);
340 G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
341 (deltaMomentum * totalMomentum);
342
343 G4double sint = sqrt(1.0 - cost*cost);
344
345 G4double phi = twopi * G4UniformRand() ;
346
347 G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ;
348 G4ThreeVector direction = dp->GetMomentumDirection();
349 deltaDirection.rotateUz(direction);
350
351 // primary change
352 kineticEnergy -= deltaKinEnergy;
353 G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
354 direction = dir.unit();
355 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
356 fParticleChange->SetProposedMomentumDirection(direction);
357
358 // create G4DynamicParticle object for delta ray
359 G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
360 deltaDirection,deltaKinEnergy);
361 vdp->push_back(delta);
362}
363
364//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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