source: trunk/source/processes/electromagnetic/standard/src/G4eBremsstrahlungRelModel.cc@ 1344

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25//
26// $Id: G4eBremsstrahlungRelModel.cc,v 1.18 2010/11/04 17:30:32 vnivanch Exp $
27// GEANT4 tag $Name: emstand-V09-03-25 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4eBremsstrahlungRelModel
35//
36// Author: Andreas Schaelicke
37//
38// Creation date: 12.08.2008
39//
40// Modifications:
41//
42// 13.11.08 add SetLPMflag and SetLPMconstant methods
43// 13.11.08 change default LPMconstant value
44// 13.10.10 add angular distributon interface (VI)
45//
46// Main References:
47// Y.-S.Tsai, Rev. Mod. Phys. 46 (1974) 815; Rev. Mod. Phys. 49 (1977) 421.
48// S.Klein, Rev. Mod. Phys. 71 (1999) 1501.
49// T.Stanev et.al., Phys. Rev. D25 (1982) 1291.
50// M.L.Ter-Mikaelian, High-energy Electromagnetic Processes in Condensed Media, Wiley, 1972.
51//
52// -------------------------------------------------------------------
53//
54//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
55//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
56
57#include "G4eBremsstrahlungRelModel.hh"
58#include "G4Electron.hh"
59#include "G4Positron.hh"
60#include "G4Gamma.hh"
61#include "Randomize.hh"
62#include "G4Material.hh"
63#include "G4Element.hh"
64#include "G4ElementVector.hh"
65#include "G4ProductionCutsTable.hh"
66#include "G4ParticleChangeForLoss.hh"
67#include "G4LossTableManager.hh"
68#include "G4ModifiedTsai.hh"
69
70//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
71
72const G4double G4eBremsstrahlungRelModel::xgi[]={ 0.0199, 0.1017, 0.2372, 0.4083,
73 0.5917, 0.7628, 0.8983, 0.9801 };
74const G4double G4eBremsstrahlungRelModel::wgi[]={ 0.0506, 0.1112, 0.1569, 0.1813,
75 0.1813, 0.1569, 0.1112, 0.0506 };
76const G4double G4eBremsstrahlungRelModel::Fel_light[] = {0., 5.31 , 4.79 , 4.74 , 4.71} ;
77const G4double G4eBremsstrahlungRelModel::Finel_light[] = {0., 6.144 , 5.621 , 5.805 , 5.924} ;
78
79
80using namespace std;
81
82G4eBremsstrahlungRelModel::G4eBremsstrahlungRelModel(const G4ParticleDefinition* p,
83 const G4String& name)
84 : G4VEmModel(name),
85 particle(0),
86 fXiLPM(0), fPhiLPM(0), fGLPM(0),
87 isElectron(true),
88 fMigdalConstant(classic_electr_radius*electron_Compton_length*electron_Compton_length*4.0*pi),
89 fLPMconstant(fine_structure_const*electron_mass_c2*electron_mass_c2/(4.*pi*hbarc)*0.5),
90 bremFactor(fine_structure_const*classic_electr_radius*classic_electr_radius*16./3.),
91 use_completescreening(true),isInitialised(false)
92{
93 theGamma = G4Gamma::Gamma();
94
95 minThreshold = 0.1*keV;
96 lowKinEnergy = GeV;
97 SetLowEnergyLimit(lowKinEnergy);
98
99 nist = G4NistManager::Instance();
100
101 SetLPMFlag(true);
102 SetAngularDistribution(new G4ModifiedTsai());
103
104 particleMass = kinEnergy = totalEnergy = currentZ = z13 = z23 = lnZ = Fel
105 = Finel = fCoulomb = fMax = densityFactor = densityCorr = lpmEnergy
106 = xiLPM = phiLPM = gLPM = klpm = kp = 0.0;
107
108 energyThresholdLPM = 1.e39;
109
110 InitialiseConstants();
111 if(p) { SetParticle(p); }
112}
113
114//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
115
116void G4eBremsstrahlungRelModel::InitialiseConstants()
117{
118 facFel = log(184.15);
119 facFinel = log(1194.);
120
121 preS1 = 1./(184.15*184.15);
122 logTwo = log(2.);
123}
124
125//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
126
127G4eBremsstrahlungRelModel::~G4eBremsstrahlungRelModel()
128{
129}
130
131//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
132
133void G4eBremsstrahlungRelModel::SetParticle(const G4ParticleDefinition* p)
134{
135 particle = p;
136 particleMass = p->GetPDGMass();
137 if(p == G4Electron::Electron()) { isElectron = true; }
138 else { isElectron = false;}
139}
140
141//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
142
143G4double G4eBremsstrahlungRelModel::MinEnergyCut(const G4ParticleDefinition*,
144 const G4MaterialCutsCouple*)
145{
146 return minThreshold;
147}
148
149//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
150
151void G4eBremsstrahlungRelModel::SetupForMaterial(const G4ParticleDefinition*,
152 const G4Material* mat,
153 G4double kineticEnergy)
154{
155 densityFactor = mat->GetElectronDensity()*fMigdalConstant;
156 lpmEnergy = mat->GetRadlen()*fLPMconstant;
157
158 // Threshold for LPM effect (i.e. below which LPM hidden by density effect)
159 if (LPMFlag()) {
160 energyThresholdLPM=sqrt(densityFactor)*lpmEnergy;
161 } else {
162 energyThresholdLPM=1.e39; // i.e. do not use LPM effect
163 }
164 // calculate threshold for density effect
165 kinEnergy = kineticEnergy;
166 totalEnergy = kineticEnergy + particleMass;
167 densityCorr = densityFactor*totalEnergy*totalEnergy;
168
169 // define critical gamma energies (important for integration/dicing)
170 klpm=totalEnergy*totalEnergy/lpmEnergy;
171 kp=sqrt(densityCorr);
172
173}
174
175
176//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
177
178void G4eBremsstrahlungRelModel::Initialise(const G4ParticleDefinition* p,
179 const G4DataVector& cuts)
180{
181 if(p) { SetParticle(p); }
182
183 lowKinEnergy = LowEnergyLimit();
184
185 currentZ = 0.;
186
187 InitialiseElementSelectors(p, cuts);
188
189 if(isInitialised) { return; }
190 fParticleChange = GetParticleChangeForLoss();
191 isInitialised = true;
192}
193
194//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
195
196G4double G4eBremsstrahlungRelModel::ComputeDEDXPerVolume(
197 const G4Material* material,
198 const G4ParticleDefinition* p,
199 G4double kineticEnergy,
200 G4double cutEnergy)
201{
202 if(!particle) { SetParticle(p); }
203 if(kineticEnergy < lowKinEnergy) { return 0.0; }
204 G4double cut = std::min(cutEnergy, kineticEnergy);
205 if(cut == 0.0) { return 0.0; }
206
207 SetupForMaterial(particle, material,kineticEnergy);
208
209 const G4ElementVector* theElementVector = material->GetElementVector();
210 const G4double* theAtomicNumDensityVector = material->GetAtomicNumDensityVector();
211
212 G4double dedx = 0.0;
213
214 // loop for elements in the material
215 for (size_t i=0; i<material->GetNumberOfElements(); i++) {
216
217 G4VEmModel::SetCurrentElement((*theElementVector)[i]);
218 SetCurrentElement((*theElementVector)[i]->GetZ());
219
220 dedx += theAtomicNumDensityVector[i]*currentZ*currentZ*ComputeBremLoss(cut);
221 }
222 dedx *= bremFactor;
223
224
225 return dedx;
226}
227
228//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
229
230G4double G4eBremsstrahlungRelModel::ComputeBremLoss(G4double cut)
231{
232 G4double loss = 0.0;
233
234 // number of intervals and integration step
235 G4double vcut = cut/totalEnergy;
236 G4int n = (G4int)(20*vcut) + 3;
237 G4double delta = vcut/G4double(n);
238
239 G4double e0 = 0.0;
240 G4double xs;
241
242 // integration
243 for(G4int l=0; l<n; l++) {
244
245 for(G4int i=0; i<8; i++) {
246
247 G4double eg = (e0 + xgi[i]*delta)*totalEnergy;
248
249 if(totalEnergy > energyThresholdLPM) {
250 xs = ComputeRelDXSectionPerAtom(eg);
251 } else {
252 xs = ComputeDXSectionPerAtom(eg);
253 }
254 loss += wgi[i]*xs/(1.0 + densityCorr/(eg*eg));
255 }
256 e0 += delta;
257 }
258
259 loss *= delta*totalEnergy;
260
261 return loss;
262}
263
264//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
265
266G4double G4eBremsstrahlungRelModel::ComputeCrossSectionPerAtom(
267 const G4ParticleDefinition* p,
268 G4double kineticEnergy,
269 G4double Z, G4double,
270 G4double cutEnergy,
271 G4double maxEnergy)
272{
273 if(!particle) { SetParticle(p); }
274 if(kineticEnergy < lowKinEnergy) { return 0.0; }
275 G4double cut = std::min(cutEnergy, kineticEnergy);
276 G4double tmax = std::min(maxEnergy, kineticEnergy);
277
278 if(cut >= tmax) { return 0.0; }
279
280 SetCurrentElement(Z);
281
282 G4double cross = ComputeXSectionPerAtom(cut);
283
284 // allow partial integration
285 if(tmax < kinEnergy) { cross -= ComputeXSectionPerAtom(tmax); }
286
287 cross *= Z*Z*bremFactor;
288
289 return cross;
290}
291
292//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
293
294
295G4double G4eBremsstrahlungRelModel::ComputeXSectionPerAtom(G4double cut)
296{
297 G4double cross = 0.0;
298
299 // number of intervals and integration step
300 G4double vcut = log(cut/totalEnergy);
301 G4double vmax = log(kinEnergy/totalEnergy);
302 G4int n = (G4int)(0.45*(vmax - vcut)) + 4;
303 // n=1; // integration test
304 G4double delta = (vmax - vcut)/G4double(n);
305
306 G4double e0 = vcut;
307 G4double xs;
308
309 // integration
310 for(G4int l=0; l<n; l++) {
311
312 for(G4int i=0; i<8; i++) {
313
314 G4double eg = exp(e0 + xgi[i]*delta)*totalEnergy;
315
316 if(totalEnergy > energyThresholdLPM) {
317 xs = ComputeRelDXSectionPerAtom(eg);
318 } else {
319 xs = ComputeDXSectionPerAtom(eg);
320 }
321 cross += wgi[i]*xs/(1.0 + densityCorr/(eg*eg));
322 }
323 e0 += delta;
324 }
325
326 cross *= delta;
327
328 return cross;
329}
330
331//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
332void G4eBremsstrahlungRelModel::CalcLPMFunctions(G4double k)
333{
334 // *** calculate lpm variable s & sprime ***
335 // Klein eqs. (78) & (79)
336 G4double sprime = sqrt(0.125*k*lpmEnergy/(totalEnergy*(totalEnergy-k)));
337
338 G4double s1 = preS1*z23;
339 G4double logS1 = 2./3.*lnZ-2.*facFel;
340 G4double logTS1 = logTwo+logS1;
341
342 xiLPM = 2.;
343
344 if (sprime>1)
345 xiLPM = 1.;
346 else if (sprime>sqrt(2.)*s1) {
347 G4double h = log(sprime)/logTS1;
348 xiLPM = 1+h-0.08*(1-h)*(1-sqr(1-h))/logTS1;
349 }
350
351 G4double s = sprime/sqrt(xiLPM);
352
353 // *** merging with density effect*** should be only necessary in region "close to" kp, e.g. k<100*kp
354 // using Ter-Mikaelian eq. (20.9)
355 G4double k2 = k*k;
356 s = s * (1 + (densityCorr/k2) );
357
358 // recalculate Xi using modified s above
359 // Klein eq. (75)
360 xiLPM = 1.;
361 if (s<=s1) xiLPM = 2.;
362 else if ( (s1<s) && (s<=1) ) xiLPM = 1. + log(s)/logS1;
363
364
365 // *** calculate supression functions phi and G ***
366 // Klein eqs. (77)
367 G4double s2=s*s;
368 G4double s3=s*s2;
369 G4double s4=s2*s2;
370
371 if (s<0.1) {
372 // high suppression limit
373 phiLPM = 6.*s - 18.84955592153876*s2 + 39.47841760435743*s3
374 - 57.69873135166053*s4;
375 gLPM = 37.69911184307752*s2 - 236.8705056261446*s3 + 807.7822389*s4;
376 }
377 else if (s<1.9516) {
378 // intermediate suppression
379 // using eq.77 approxim. valid s<2.
380 phiLPM = 1.-exp(-6.*s*(1.+(3.-pi)*s)
381 +s3/(0.623+0.795*s+0.658*s2));
382 if (s<0.415827397755) {
383 // using eq.77 approxim. valid 0.07<s<2
384 G4double psiLPM = 1-exp(-4*s-8*s2/(1+3.936*s+4.97*s2-0.05*s3+7.50*s4));
385 gLPM = 3*psiLPM-2*phiLPM;
386 }
387 else {
388 // using alternative parametrisiation
389 G4double pre = -0.16072300849123999 + s*3.7550300067531581 + s2*-1.7981383069010097
390 + s3*0.67282686077812381 + s4*-0.1207722909879257;
391 gLPM = tanh(pre);
392 }
393 }
394 else {
395 // low suppression limit valid s>2.
396 phiLPM = 1. - 0.0119048/s4;
397 gLPM = 1. - 0.0230655/s4;
398 }
399
400 // *** make sure suppression is smaller than 1 ***
401 // *** caused by Migdal approximation in xi ***
402 if (xiLPM*phiLPM>1. || s>0.57) { xiLPM=1./phiLPM; }
403}
404
405//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
406
407
408G4double G4eBremsstrahlungRelModel::ComputeRelDXSectionPerAtom(G4double gammaEnergy)
409// Ultra relativistic model
410// only valid for very high energies, but includes LPM suppression
411// * complete screening
412{
413 if(gammaEnergy < 0.0) { return 0.0; }
414
415 G4double y = gammaEnergy/totalEnergy;
416 G4double y2 = y*y*.25;
417 G4double yone2 = (1.-y+2.*y2);
418
419 // ** form factors complete screening case **
420
421 // ** calc LPM functions -- include ter-mikaelian merging with density effect **
422 // G4double xiLPM, gLPM, phiLPM; // to be made member variables !!!
423 CalcLPMFunctions(gammaEnergy);
424
425 G4double mainLPM = xiLPM*(y2 * gLPM + yone2*phiLPM) * ( (Fel-fCoulomb) + Finel/currentZ );
426 G4double secondTerm = (1.-y)/12.*(1.+1./currentZ);
427
428 G4double cross = mainLPM+secondTerm;
429 return cross;
430}
431
432//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
433
434G4double G4eBremsstrahlungRelModel::ComputeDXSectionPerAtom(G4double gammaEnergy)
435// Relativistic model
436// only valid for high energies (and if LPM suppression does not play a role)
437// * screening according to thomas-fermi-Model (only valid for Z>5)
438// * no LPM effect
439{
440
441 if(gammaEnergy < 0.0) { return 0.0; }
442
443 G4double y = gammaEnergy/totalEnergy;
444
445 G4double main=0.,secondTerm=0.;
446
447 if (use_completescreening|| currentZ<5) {
448 // ** form factors complete screening case **
449 main = (3./4.*y*y - y + 1.) * ( (Fel-fCoulomb) + Finel/currentZ );
450 secondTerm = (1.-y)/12.*(1.+1./currentZ);
451 }
452 else {
453 // ** intermediate screening using Thomas-Fermi FF from Tsai only valid for Z>=5**
454 G4double dd=100.*electron_mass_c2*y/(totalEnergy-gammaEnergy);
455 G4double gg=dd*z13;
456 G4double eps=dd*z23;
457 G4double phi1=Phi1(gg,currentZ), phi1m2=Phi1M2(gg,currentZ);
458 G4double psi1=Psi1(eps,currentZ), psi1m2=Psi1M2(eps,currentZ);
459
460 main = (3./4.*y*y - y + 1.) * ( (0.25*phi1-1./3.*lnZ-fCoulomb) + (0.25*psi1-2./3.*lnZ)/currentZ );
461 secondTerm = (1.-y)/8.*(phi1m2+psi1m2/currentZ);
462 }
463 G4double cross = main+secondTerm;
464 return cross;
465}
466
467//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
468
469void G4eBremsstrahlungRelModel::SampleSecondaries(
470 std::vector<G4DynamicParticle*>* vdp,
471 const G4MaterialCutsCouple* couple,
472 const G4DynamicParticle* dp,
473 G4double cutEnergy,
474 G4double maxEnergy)
475{
476 G4double kineticEnergy = dp->GetKineticEnergy();
477 if(kineticEnergy < lowKinEnergy) { return; }
478 G4double cut = std::min(cutEnergy, kineticEnergy);
479 G4double emax = std::min(maxEnergy, kineticEnergy);
480 if(cut >= emax) { return; }
481
482 SetupForMaterial(particle, couple->GetMaterial(),kineticEnergy);
483
484 const G4Element* elm =
485 SelectRandomAtom(couple,particle,kineticEnergy,cut,emax);
486 SetCurrentElement(elm->GetZ());
487
488 kinEnergy = kineticEnergy;
489 totalEnergy = kineticEnergy + particleMass;
490 densityCorr = densityFactor*totalEnergy*totalEnergy;
491 G4ThreeVector direction = dp->GetMomentumDirection();
492
493 // G4double fmax= fMax;
494 G4bool highe = true;
495 if(totalEnergy < energyThresholdLPM) { highe = false; }
496
497 G4double xmin = log(cut*cut + densityCorr);
498 G4double xmax = log(emax*emax + densityCorr);
499 G4double gammaEnergy, f, x;
500
501 do {
502 x = exp(xmin + G4UniformRand()*(xmax - xmin)) - densityCorr;
503 if(x < 0.0) x = 0.0;
504 gammaEnergy = sqrt(x);
505 if(highe) f = ComputeRelDXSectionPerAtom(gammaEnergy);
506 else f = ComputeDXSectionPerAtom(gammaEnergy);
507
508 if ( f > fMax ) {
509 G4cout << "### G4eBremsstrahlungRelModel Warning: Majoranta exceeded! "
510 << f << " > " << fMax
511 << " Egamma(MeV)= " << gammaEnergy
512 << " E(mEV)= " << kineticEnergy
513 << G4endl;
514 }
515
516 } while (f < fMax*G4UniformRand());
517
518 //
519 // angles of the emitted gamma. ( Z - axis along the parent particle)
520 // use general interface
521 //
522 G4double theta = GetAngularDistribution()->PolarAngle(totalEnergy,
523 totalEnergy-gammaEnergy,
524 (G4int)currentZ);
525
526 G4double sint = sin(theta);
527 G4double phi = twopi * G4UniformRand();
528 G4ThreeVector gammaDirection(sint*cos(phi),sint*sin(phi), cos(theta));
529 gammaDirection.rotateUz(direction);
530
531 // create G4DynamicParticle object for the Gamma
532 G4DynamicParticle* g = new G4DynamicParticle(theGamma,gammaDirection,
533 gammaEnergy);
534 vdp->push_back(g);
535
536 G4double totMomentum = sqrt(kineticEnergy*(totalEnergy + electron_mass_c2));
537 G4ThreeVector dir = totMomentum*direction - gammaEnergy*gammaDirection;
538 direction = dir.unit();
539
540 // energy of primary
541 G4double finalE = kineticEnergy - gammaEnergy;
542
543 // stop tracking and create new secondary instead of primary
544 if(gammaEnergy > SecondaryThreshold()) {
545 fParticleChange->ProposeTrackStatus(fStopAndKill);
546 fParticleChange->SetProposedKineticEnergy(0.0);
547 G4DynamicParticle* el =
548 new G4DynamicParticle(const_cast<G4ParticleDefinition*>(particle),
549 direction, finalE);
550 vdp->push_back(el);
551
552 // continue tracking
553 } else {
554 fParticleChange->SetProposedMomentumDirection(direction);
555 fParticleChange->SetProposedKineticEnergy(finalE);
556 }
557}
558
559//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
560
561
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