source: trunk/source/processes/electromagnetic/standard/src/G4BetheBlochModel.cc@ 1344

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25//
26// $Id: G4BetheBlochModel.cc,v 1.40 2010/11/04 17:30:31 vnivanch Exp $
27// GEANT4 tag $Name: emstand-V09-03-25 $
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 theElectron = G4Electron::Electron();
85 if(p) {
86 SetGenericIon(p);
87 SetParticle(p);
88 } else {
89 SetParticle(theElectron);
90 }
91 corr = G4LossTableManager::Instance()->EmCorrections();
92 nist = G4NistManager::Instance();
93 SetLowEnergyLimit(2.0*MeV);
94}
95
96//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
97
98G4BetheBlochModel::~G4BetheBlochModel()
99{}
100
101//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
102
103G4double G4BetheBlochModel::MinEnergyCut(const G4ParticleDefinition*,
104 const G4MaterialCutsCouple* couple)
105{
106 return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy();
107}
108
109//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
110
111void G4BetheBlochModel::Initialise(const G4ParticleDefinition* p,
112 const G4DataVector&)
113{
114 SetGenericIon(p);
115 SetParticle(p);
116
117 //G4cout << "G4BetheBlochModel::Initialise for " << p->GetParticleName()
118 // << " isIon= " << isIon
119 // << G4endl;
120
121 // always false before the run
122 SetDeexcitationFlag(false);
123
124 if(!isInitialised) {
125 isInitialised = true;
126 fParticleChange = GetParticleChangeForLoss();
127 }
128}
129
130//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
131
132G4double G4BetheBlochModel::GetChargeSquareRatio(const G4ParticleDefinition* p,
133 const G4Material* mat,
134 G4double kineticEnergy)
135{
136 // this method is called only for ions
137 G4double q2 = corr->EffectiveChargeSquareRatio(p,mat,kineticEnergy);
138 corrFactor = q2*corr->EffectiveChargeCorrection(p,mat,kineticEnergy);
139 return corrFactor;
140}
141
142//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
143
144G4double G4BetheBlochModel::GetParticleCharge(const G4ParticleDefinition* p,
145 const G4Material* mat,
146 G4double kineticEnergy)
147{
148 // this method is called only for ions, so no check if it is an ion
149 return corr->GetParticleCharge(p,mat,kineticEnergy);
150}
151
152//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
153
154void G4BetheBlochModel::SetupParameters()
155{
156 mass = particle->GetPDGMass();
157 spin = particle->GetPDGSpin();
158 G4double q = particle->GetPDGCharge()/eplus;
159 chargeSquare = q*q;
160 corrFactor = chargeSquare;
161 ratio = electron_mass_c2/mass;
162 G4double magmom =
163 particle->GetPDGMagneticMoment()*mass/(0.5*eplus*hbar_Planck*c_squared);
164 magMoment2 = magmom*magmom - 1.0;
165 formfact = 0.0;
166 if(particle->GetLeptonNumber() == 0) {
167 G4double x = 0.8426*GeV;
168 if(spin == 0.0 && mass < GeV) {x = 0.736*GeV;}
169 else if(mass > GeV) {
170 x /= nist->GetZ13(mass/proton_mass_c2);
171 // tlimit = 51.2*GeV*A13[iz]*A13[iz];
172 }
173 formfact = 2.0*electron_mass_c2/(x*x);
174 tlimit = 2.0/formfact;
175 }
176}
177
178//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
179
180G4double
181G4BetheBlochModel::ComputeCrossSectionPerElectron(const G4ParticleDefinition* p,
182 G4double kineticEnergy,
183 G4double cutEnergy,
184 G4double maxKinEnergy)
185{
186 G4double cross = 0.0;
187 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
188 G4double maxEnergy = min(tmax,maxKinEnergy);
189 if(cutEnergy < maxEnergy) {
190
191 G4double totEnergy = kineticEnergy + mass;
192 G4double energy2 = totEnergy*totEnergy;
193 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/energy2;
194
195 cross = 1.0/cutEnergy - 1.0/maxEnergy
196 - beta2*log(maxEnergy/cutEnergy)/tmax;
197
198 // +term for spin=1/2 particle
199 if( 0.5 == spin ) { cross += 0.5*(maxEnergy - cutEnergy)/energy2; }
200
201 // High order correction different for hadrons and ions
202 // nevetheless they are applied to reduce high energy transfers
203 // if(!isIon)
204 //cross += corr->FiniteSizeCorrectionXS(p,currentMaterial,
205 // kineticEnergy,cutEnergy);
206
207 cross *= twopi_mc2_rcl2*chargeSquare/beta2;
208 }
209
210 // G4cout << "BB: e= " << kineticEnergy << " tmin= " << cutEnergy
211 // << " tmax= " << tmax << " cross= " << cross << G4endl;
212
213 return cross;
214}
215
216//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
217
218G4double G4BetheBlochModel::ComputeCrossSectionPerAtom(
219 const G4ParticleDefinition* p,
220 G4double kineticEnergy,
221 G4double Z, G4double,
222 G4double cutEnergy,
223 G4double maxEnergy)
224{
225 G4double cross = Z*ComputeCrossSectionPerElectron
226 (p,kineticEnergy,cutEnergy,maxEnergy);
227 return cross;
228}
229
230//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
231
232G4double G4BetheBlochModel::CrossSectionPerVolume(
233 const G4Material* material,
234 const G4ParticleDefinition* p,
235 G4double kineticEnergy,
236 G4double cutEnergy,
237 G4double maxEnergy)
238{
239 currentMaterial = material;
240 G4double eDensity = material->GetElectronDensity();
241 G4double cross = eDensity*ComputeCrossSectionPerElectron
242 (p,kineticEnergy,cutEnergy,maxEnergy);
243 return cross;
244}
245
246//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
247
248G4double G4BetheBlochModel::ComputeDEDXPerVolume(const G4Material* material,
249 const G4ParticleDefinition* p,
250 G4double kineticEnergy,
251 G4double cut)
252{
253 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
254 G4double cutEnergy = std::min(cut,tmax);
255
256 G4double tau = kineticEnergy/mass;
257 G4double gam = tau + 1.0;
258 G4double bg2 = tau * (tau+2.0);
259 G4double beta2 = bg2/(gam*gam);
260
261 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
262 G4double eexc2 = eexc*eexc;
263
264 G4double eDensity = material->GetElectronDensity();
265
266 G4double dedx = log(2.0*electron_mass_c2*bg2*cutEnergy/eexc2)
267 - (1.0 + cutEnergy/tmax)*beta2;
268
269 if(0.5 == spin) {
270 G4double del = 0.5*cutEnergy/(kineticEnergy + mass);
271 dedx += del*del;
272 }
273
274 // density correction
275 G4double x = log(bg2)/twoln10;
276 dedx -= material->GetIonisation()->DensityCorrection(x);
277
278 // shell correction
279 //dedx -= 2.0*corr->ShellCorrection(p,material,kineticEnergy);
280 dedx -= corr->ShellCorrection(p,material,kineticEnergy);
281
282 // now compute the total ionization loss
283 dedx *= twopi_mc2_rcl2*chargeSquare*eDensity/beta2;
284
285 //High order correction different for hadrons and ions
286 if(isIon) {
287 dedx += corr->IonBarkasCorrection(p,material,kineticEnergy);
288 } else {
289 dedx += corr->HighOrderCorrections(p,material,kineticEnergy,cutEnergy);
290 }
291
292 if (dedx < 0.0) { dedx = 0.0; }
293 return dedx;
294}
295
296//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
297
298void G4BetheBlochModel::CorrectionsAlongStep(const G4MaterialCutsCouple* couple,
299 const G4DynamicParticle* dp,
300 G4double& eloss,
301 G4double&,
302 G4double length)
303{
304 if(isIon) {
305 const G4ParticleDefinition* p = dp->GetDefinition();
306 const G4Material* mat = couple->GetMaterial();
307 G4double preKinEnergy = dp->GetKineticEnergy();
308 G4double e = preKinEnergy - eloss*0.5;
309 if(e < 0.0) e = preKinEnergy*0.5;
310
311 G4double q2 = corr->EffectiveChargeSquareRatio(p,mat,e);
312 GetModelOfFluctuations()->SetParticleAndCharge(p, q2);
313 G4double qfactor = q2*corr->EffectiveChargeCorrection(p,mat,e)/corrFactor;
314 G4double highOrder = length*corr->IonHighOrderCorrections(p,couple,e);
315 eloss *= qfactor;
316 eloss += highOrder;
317 //G4cout << "G4BetheBlochModel::CorrectionsAlongStep: e= " << preKinEnergy
318 // << " qfactor= " << qfactor
319 // << " highOrder= " << highOrder << " (" << highOrder/eloss << ")" << G4endl;
320 }
321}
322
323//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
324
325void G4BetheBlochModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
326 const G4MaterialCutsCouple*,
327 const G4DynamicParticle* dp,
328 G4double minKinEnergy,
329 G4double maxEnergy)
330{
331 G4double kineticEnergy = dp->GetKineticEnergy();
332 G4double tmax = MaxSecondaryEnergy(dp->GetDefinition(),kineticEnergy);
333
334 G4double maxKinEnergy = std::min(maxEnergy,tmax);
335 if(minKinEnergy >= maxKinEnergy) return;
336
337 G4double totEnergy = kineticEnergy + mass;
338 G4double etot2 = totEnergy*totEnergy;
339 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
340
341 G4double deltaKinEnergy, f;
342 G4double f1 = 0.0;
343 G4double fmax = 1.0;
344 if( 0.5 == spin ) fmax += 0.5*maxKinEnergy*maxKinEnergy/etot2;
345
346 // sampling without nuclear size effect
347 do {
348 G4double q = G4UniformRand();
349 deltaKinEnergy = minKinEnergy*maxKinEnergy
350 /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
351
352 f = 1.0 - beta2*deltaKinEnergy/tmax;
353 if( 0.5 == spin ) {
354 f1 = 0.5*deltaKinEnergy*deltaKinEnergy/etot2;
355 f += f1;
356 }
357
358 } while( fmax*G4UniformRand() > f);
359
360 // projectile formfactor - suppresion of high energy
361 // delta-electron production at high energy
362
363 G4double x = formfact*deltaKinEnergy;
364 if(x > 1.e-6) {
365
366 G4double x1 = 1.0 + x;
367 G4double g = 1.0/(x1*x1);
368 if( 0.5 == spin ) {
369 G4double x2 = 0.5*electron_mass_c2*deltaKinEnergy/(mass*mass);
370 g *= (1.0 + magMoment2*(x2 - f1/f)/(1.0 + x2));
371 }
372 if(g > 1.0) {
373 G4cout << "### G4BetheBlochModel WARNING: g= " << g
374 << dp->GetDefinition()->GetParticleName()
375 << " Ekin(MeV)= " << kineticEnergy
376 << " delEkin(MeV)= " << deltaKinEnergy
377 << G4endl;
378 }
379 if(G4UniformRand() > g) return;
380 }
381
382 // delta-electron is produced
383 G4double totMomentum = totEnergy*sqrt(beta2);
384 G4double deltaMomentum =
385 sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
386 G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
387 (deltaMomentum * totMomentum);
388 /*
389 if(cost > 1.0) {
390 G4cout << "### G4BetheBlochModel WARNING: cost= "
391 << cost << " > 1 for "
392 << dp->GetDefinition()->GetParticleName()
393 << " Ekin(MeV)= " << kineticEnergy
394 << " p(MeV/c)= " << totMomentum
395 << " delEkin(MeV)= " << deltaKinEnergy
396 << " delMom(MeV/c)= " << deltaMomentum
397 << " tmin(MeV)= " << minKinEnergy
398 << " tmax(MeV)= " << maxKinEnergy
399 << " dir= " << dp->GetMomentumDirection()
400 << G4endl;
401 cost = 1.0;
402 }
403 */
404 G4double sint = sqrt((1.0 - cost)*(1.0 + cost));
405
406 G4double phi = twopi * G4UniformRand() ;
407
408
409 G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost);
410 G4ThreeVector direction = dp->GetMomentumDirection();
411 deltaDirection.rotateUz(direction);
412
413 // create G4DynamicParticle object for delta ray
414 G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
415 deltaDirection,deltaKinEnergy);
416
417 vdp->push_back(delta);
418
419 // Change kinematics of primary particle
420 kineticEnergy -= deltaKinEnergy;
421 G4ThreeVector finalP = direction*totMomentum - deltaDirection*deltaMomentum;
422 finalP = finalP.unit();
423
424 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
425 fParticleChange->SetProposedMomentumDirection(finalP);
426}
427
428//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
429
430G4double G4BetheBlochModel::MaxSecondaryEnergy(const G4ParticleDefinition* pd,
431 G4double kinEnergy)
432{
433 // here particle type is checked for any method
434 SetParticle(pd);
435 G4double tau = kinEnergy/mass;
436 G4double tmax = 2.0*electron_mass_c2*tau*(tau + 2.) /
437 (1. + 2.0*(tau + 1.)*ratio + ratio*ratio);
438 return std::min(tmax,tlimit);
439}
440
441//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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