source: trunk/source/processes/electromagnetic/standard/src/G4eBremsstrahlungRelModel.cc@ 1005

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25//
26// $Id: G4eBremsstrahlungRelModel.cc,v 1.13 2009/02/20 12:06:37 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
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//
45// Main References:
46// Y.-S.Tsai, Rev. Mod. Phys. 46 (1974) 815; Rev. Mod. Phys. 49 (1977) 421.
47// S.Klein, Rev. Mod. Phys. 71 (1999) 1501.
48// T.Stanev et.al., Phys. Rev. D25 (1982) 1291.
49// M.L.Ter-Mikaelian, High-energy Electromagnetic Processes in Condensed Media, Wiley, 1972.
50//
51// -------------------------------------------------------------------
52//
53//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
54//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
55
56#include "G4eBremsstrahlungRelModel.hh"
57#include "G4Electron.hh"
58#include "G4Positron.hh"
59#include "G4Gamma.hh"
60#include "Randomize.hh"
61#include "G4Material.hh"
62#include "G4Element.hh"
63#include "G4ElementVector.hh"
64#include "G4ProductionCutsTable.hh"
65#include "G4ParticleChangeForLoss.hh"
66#include "G4LossTableManager.hh"
67
68
69//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
70
71const G4double G4eBremsstrahlungRelModel::xgi[]={ 0.0199, 0.1017, 0.2372, 0.4083,
72 0.5917, 0.7628, 0.8983, 0.9801 };
73const G4double G4eBremsstrahlungRelModel::wgi[]={ 0.0506, 0.1112, 0.1569, 0.1813,
74 0.1813, 0.1569, 0.1112, 0.0506 };
75const G4double G4eBremsstrahlungRelModel::Fel_light[] = {0., 5.31 , 4.79 , 4.74 , 4.71} ;
76const G4double G4eBremsstrahlungRelModel::Finel_light[] = {0., 6.144 , 5.621 , 5.805 , 5.924} ;
77
78
79using namespace std;
80
81G4eBremsstrahlungRelModel::G4eBremsstrahlungRelModel(const G4ParticleDefinition* p,
82 const G4String& name)
83 : G4VEmModel(name),
84 particle(0),
85 fXiLPM(0), fPhiLPM(0), fGLPM(0),
86 isElectron(true),
87 fMigdalConstant(classic_electr_radius*electron_Compton_length*electron_Compton_length*4.0*pi),
88 fLPMconstant(fine_structure_const*electron_mass_c2*electron_mass_c2/(4.*pi*hbarc)*0.5),
89 bremFactor(fine_structure_const*classic_electr_radius*classic_electr_radius*16./3.),
90 use_completescreening(true),isInitialised(false)
91{
92 if(p) SetParticle(p);
93 theGamma = G4Gamma::Gamma();
94
95 minThreshold = 1.0*keV;
96 SetLowEnergyLimit(GeV);
97
98 nist = G4NistManager::Instance();
99 InitialiseConstants();
100
101 SetLPMFlag(true);
102}
103
104//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
105
106void G4eBremsstrahlungRelModel::InitialiseConstants()
107{
108 facFel = log(184.15);
109 facFinel = log(1194.);
110
111 preS1 = 1./(184.15*184.15);
112 logTwo = log(2.);
113}
114
115//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
116
117G4eBremsstrahlungRelModel::~G4eBremsstrahlungRelModel()
118{
119}
120
121//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
122
123void G4eBremsstrahlungRelModel::SetParticle(const G4ParticleDefinition* p)
124{
125 particle = p;
126 particleMass = p->GetPDGMass();
127 if(p == G4Electron::Electron()) isElectron = true;
128 else isElectron = false;
129}
130
131//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
132
133G4double G4eBremsstrahlungRelModel::MinEnergyCut(const G4ParticleDefinition*,
134 const G4MaterialCutsCouple*)
135{
136 return minThreshold;
137}
138
139//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
140
141void G4eBremsstrahlungRelModel::SetupForMaterial(const G4ParticleDefinition*,
142 const G4Material* mat, G4double kineticEnergy)
143{
144 densityFactor = mat->GetElectronDensity()*fMigdalConstant;
145 lpmEnergy = mat->GetRadlen()*fLPMconstant;
146
147 // Threshold for LPM effect (i.e. below which LPM hidden by density effect)
148 if (LPMFlag())
149 energyThresholdLPM=sqrt(densityFactor)*lpmEnergy;
150 else
151 energyThresholdLPM=1.e39; // i.e. do not use LPM effect
152
153 // calculate threshold for density effect
154 kinEnergy = kineticEnergy;
155 totalEnergy = kineticEnergy + particleMass;
156 densityCorr = densityFactor*totalEnergy*totalEnergy;
157
158 // define critical gamma energies (important for integration/dicing)
159 klpm=totalEnergy*totalEnergy/lpmEnergy;
160 kp=sqrt(densityCorr);
161
162}
163
164
165//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
166
167void G4eBremsstrahlungRelModel::Initialise(const G4ParticleDefinition* p,
168 const G4DataVector& cuts)
169{
170 if(p) SetParticle(p);
171
172 highKinEnergy = HighEnergyLimit();
173 lowKinEnergy = LowEnergyLimit();
174
175 currentZ = 0.;
176
177 InitialiseElementSelectors(p, cuts);
178
179 if(isInitialised) return;
180
181 if(pParticleChange) {
182 fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange);
183 } else {
184 fParticleChange = new G4ParticleChangeForLoss();
185 }
186 isInitialised = true;
187}
188
189//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
190
191G4double G4eBremsstrahlungRelModel::ComputeDEDXPerVolume(
192 const G4Material* material,
193 const G4ParticleDefinition* p,
194 G4double kineticEnergy,
195 G4double cutEnergy)
196{
197 if(!particle) SetParticle(p);
198 if(kineticEnergy < lowKinEnergy) return 0.0;
199 G4double cut = std::min(cutEnergy, kineticEnergy);
200 if(cut == 0.0) return 0.0;
201
202 SetupForMaterial(particle, material,kineticEnergy);
203
204 const G4ElementVector* theElementVector = material->GetElementVector();
205 const G4double* theAtomicNumDensityVector = material->GetAtomicNumDensityVector();
206
207 G4double dedx = 0.0;
208
209 // loop for elements in the material
210 for (size_t i=0; i<material->GetNumberOfElements(); i++) {
211
212 G4VEmModel::SetCurrentElement((*theElementVector)[i]);
213 SetCurrentElement((*theElementVector)[i]->GetZ());
214
215 dedx += theAtomicNumDensityVector[i]*currentZ*currentZ*ComputeBremLoss(cut);
216 }
217 dedx *= bremFactor;
218
219
220 return dedx;
221}
222
223//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
224
225G4double G4eBremsstrahlungRelModel::ComputeBremLoss(G4double cut)
226{
227 G4double loss = 0.0;
228
229 // number of intervals and integration step
230 G4double vcut = cut/totalEnergy;
231 G4int n = (G4int)(20*vcut) + 3;
232 G4double delta = vcut/G4double(n);
233
234 G4double e0 = 0.0;
235 G4double xs;
236
237 // integration
238 for(G4int l=0; l<n; l++) {
239
240 for(G4int i=0; i<8; i++) {
241
242 G4double eg = (e0 + xgi[i]*delta)*totalEnergy;
243
244 if(totalEnergy > energyThresholdLPM) {
245 xs = ComputeRelDXSectionPerAtom(eg);
246 } else {
247 xs = ComputeDXSectionPerAtom(eg);
248 }
249 loss += wgi[i]*xs/(1.0 + densityCorr/(eg*eg));
250 }
251 e0 += delta;
252 }
253
254 loss *= delta*totalEnergy;
255
256 return loss;
257}
258
259//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
260
261G4double G4eBremsstrahlungRelModel::ComputeCrossSectionPerAtom(
262 const G4ParticleDefinition* p,
263 G4double kineticEnergy,
264 G4double Z, G4double,
265 G4double cutEnergy,
266 G4double maxEnergy)
267{
268 if(!particle) SetParticle(p);
269 if(kineticEnergy < lowKinEnergy) return 0.0;
270 G4double cut = std::min(cutEnergy, kineticEnergy);
271 G4double tmax = std::min(maxEnergy, kineticEnergy);
272
273 if(cut >= tmax) return 0.0;
274
275 SetCurrentElement(Z);
276
277 G4double cross = ComputeXSectionPerAtom(cut);
278
279 // allow partial integration
280 if(tmax < kinEnergy) cross -= ComputeXSectionPerAtom(tmax);
281
282 cross *= Z*Z*bremFactor;
283
284 return cross;
285}
286
287//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
288
289
290G4double G4eBremsstrahlungRelModel::ComputeXSectionPerAtom(G4double cut)
291{
292 G4double cross = 0.0;
293
294 // number of intervals and integration step
295 G4double vcut = log(cut/totalEnergy);
296 G4double vmax = log(kinEnergy/totalEnergy);
297 G4int n = (G4int)(0.45*(vmax - vcut)) + 4;
298 // n=1; // integration test
299 G4double delta = (vmax - vcut)/G4double(n);
300
301 G4double e0 = vcut;
302 G4double xs;
303
304 // integration
305 for(G4int l=0; l<n; l++) {
306
307 for(G4int i=0; i<8; i++) {
308
309 G4double eg = exp(e0 + xgi[i]*delta)*totalEnergy;
310
311 if(totalEnergy > energyThresholdLPM) {
312 xs = ComputeRelDXSectionPerAtom(eg);
313 } else {
314 xs = ComputeDXSectionPerAtom(eg);
315 }
316 cross += wgi[i]*xs/(1.0 + densityCorr/(eg*eg));
317 }
318 e0 += delta;
319 }
320
321 cross *= delta;
322
323 return cross;
324}
325
326//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
327void G4eBremsstrahlungRelModel::CalcLPMFunctions(G4double k)
328{
329 // *** calculate lpm variable s & sprime ***
330 // Klein eqs. (78) & (79)
331 G4double sprime = sqrt(0.125*k*lpmEnergy/(totalEnergy*(totalEnergy-k)));
332
333 G4double s1 = preS1*z23;
334 G4double logS1 = 2./3.*lnZ-2.*facFel;
335 G4double logTS1 = logTwo+logS1;
336
337 xiLPM = 2.;
338
339 if (sprime>1)
340 xiLPM = 1.;
341 else if (sprime>sqrt(2.)*s1) {
342 G4double h = log(sprime)/logTS1;
343 xiLPM = 1+h-0.08*(1-h)*(1-sqr(1-h))/logTS1;
344 }
345
346 G4double s = sprime/sqrt(xiLPM);
347
348 // *** merging with density effect*** should be only necessary in region "close to" kp, e.g. k<100*kp
349 // using Ter-Mikaelian eq. (20.9)
350 G4double k2 = k*k;
351 s = s * (1 + (densityCorr/k2) );
352
353 // recalculate Xi using modified s above
354 // Klein eq. (75)
355 xiLPM = 1.;
356 if (s<=s1) xiLPM = 2.;
357 else if ( (s1<s) && (s<=1) ) xiLPM = 1. + log(s)/logS1;
358
359
360 // *** calculate supression functions phi and G ***
361 // Klein eqs. (77)
362 G4double s2=s*s;
363 G4double s3=s*s2;
364 G4double s4=s2*s2;
365
366 if (s<0.1) {
367 // high suppression limit
368 phiLPM = 6.*s - 18.84955592153876*s2 + 39.47841760435743*s3
369 - 57.69873135166053*s4;
370 gLPM = 37.69911184307752*s2 - 236.8705056261446*s3 + 807.7822389*s4;
371 }
372 else if (s<1.9516) {
373 // intermediate suppression
374 // using eq.77 approxim. valid s<2.
375 phiLPM = 1.-exp(-6.*s*(1.+(3.-pi)*s)
376 +s3/(0.623+0.795*s+0.658*s2));
377 if (s<0.415827397755) {
378 // using eq.77 approxim. valid 0.07<s<2
379 G4double psiLPM = 1-exp(-4*s-8*s2/(1+3.936*s+4.97*s2-0.05*s3+7.50*s4));
380 gLPM = 3*psiLPM-2*phiLPM;
381 }
382 else {
383 // using alternative parametrisiation
384 G4double pre = -0.16072300849123999 + s*3.7550300067531581 + s2*-1.7981383069010097
385 + s3*0.67282686077812381 + s4*-0.1207722909879257;
386 gLPM = tanh(pre);
387 }
388 }
389 else {
390 // low suppression limit valid s>2.
391 phiLPM = 1. - 0.0119048/s4;
392 gLPM = 1. - 0.0230655/s4;
393 }
394
395 // *** make sure suppression is smaller than 1 ***
396 // *** caused by Migdal approximation in xi ***
397 if (xiLPM*phiLPM>1. || s>0.57) xiLPM=1./phiLPM;
398}
399
400//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
401
402
403G4double G4eBremsstrahlungRelModel::ComputeRelDXSectionPerAtom(G4double gammaEnergy)
404// Ultra relativistic model
405// only valid for very high energies, but includes LPM suppression
406// * complete screening
407{
408 if(gammaEnergy < 0.0) return 0.0;
409
410 G4double y = gammaEnergy/totalEnergy;
411 G4double y2 = y*y*.25;
412 G4double yone2 = (1.-y+2.*y2);
413
414 // ** form factors complete screening case **
415
416 // ** calc LPM functions -- include ter-mikaelian merging with density effect **
417 // G4double xiLPM, gLPM, phiLPM; // to be made member variables !!!
418 CalcLPMFunctions(gammaEnergy);
419
420 G4double mainLPM = xiLPM*(y2 * gLPM + yone2*phiLPM) * ( (Fel-fCoulomb) + Finel/currentZ );
421 G4double secondTerm = (1.-y)/12.*(1.+1./currentZ);
422
423 G4double cross = mainLPM+secondTerm;
424 return cross;
425}
426
427//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
428
429G4double G4eBremsstrahlungRelModel::ComputeDXSectionPerAtom(G4double gammaEnergy)
430// Relativistic model
431// only valid for high energies (and if LPM suppression does not play a role)
432// * screening according to thomas-fermi-Model (only valid for Z>5)
433// * no LPM effect
434{
435
436 if(gammaEnergy < 0.0) return 0.0;
437
438 G4double y = gammaEnergy/totalEnergy;
439
440 G4double main=0.,secondTerm=0.;
441
442 if (use_completescreening|| currentZ<5) {
443 // ** form factors complete screening case **
444 main = (3./4.*y*y - y + 1.) * ( (Fel-fCoulomb) + Finel/currentZ );
445 secondTerm = (1.-y)/12.*(1.+1./currentZ);
446 }
447 else {
448 // ** intermediate screening using Thomas-Fermi FF from Tsai only valid for Z>=5**
449 G4double dd=100.*electron_mass_c2*y/(totalEnergy-gammaEnergy);
450 G4double gg=dd*z13;
451 G4double eps=dd*z23;
452 G4double phi1=Phi1(gg,currentZ), phi1m2=Phi1M2(gg,currentZ);
453 G4double psi1=Psi1(eps,currentZ), psi1m2=Psi1M2(eps,currentZ);
454
455 main = (3./4.*y*y - y + 1.) * ( (0.25*phi1-1./3.*lnZ-fCoulomb) + (0.25*psi1-2./3.*lnZ)/currentZ );
456 secondTerm = (1.-y)/8.*(phi1m2+psi1m2/currentZ);
457 }
458 G4double cross = main+secondTerm;
459 return cross;
460}
461
462//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
463
464void G4eBremsstrahlungRelModel::SampleSecondaries(
465 std::vector<G4DynamicParticle*>* vdp,
466 const G4MaterialCutsCouple* couple,
467 const G4DynamicParticle* dp,
468 G4double cutEnergy,
469 G4double maxEnergy)
470{
471 G4double kineticEnergy = dp->GetKineticEnergy();
472 if(kineticEnergy < lowKinEnergy) return;
473 G4double cut = std::min(cutEnergy, kineticEnergy);
474 G4double emax = std::min(maxEnergy, kineticEnergy);
475 if(cut >= emax) return;
476
477 SetupForMaterial(particle, couple->GetMaterial(),kineticEnergy);
478
479 const G4Element* elm =
480 SelectRandomAtom(couple,particle,kineticEnergy,cut,emax);
481 SetCurrentElement(elm->GetZ());
482
483 kinEnergy = kineticEnergy;
484 totalEnergy = kineticEnergy + particleMass;
485 densityCorr = densityFactor*totalEnergy*totalEnergy;
486 G4ThreeVector direction = dp->GetMomentumDirection();
487
488 // G4double fmax= fMax;
489 G4bool highe = true;
490 if(totalEnergy < energyThresholdLPM) highe = false;
491
492 G4double xmin = log(cut*cut + densityCorr);
493 G4double xmax = log(emax*emax + densityCorr);
494 G4double gammaEnergy, f, x;
495
496 do {
497 x = exp(xmin + G4UniformRand()*(xmax - xmin)) - densityCorr;
498 if(x < 0.0) x = 0.0;
499 gammaEnergy = sqrt(x);
500 if(highe) f = ComputeRelDXSectionPerAtom(gammaEnergy);
501 else f = ComputeDXSectionPerAtom(gammaEnergy);
502
503 if ( f > fMax ) {
504 G4cout << "### G4eBremsstrahlungRelModel Warning: Majoranta exceeded! "
505 << f << " > " << fMax
506 << " Egamma(MeV)= " << gammaEnergy
507 << " E(mEV)= " << kineticEnergy
508 << G4endl;
509 }
510
511 } while (f < fMax*G4UniformRand());
512
513 //
514 // angles of the emitted gamma. ( Z - axis along the parent particle)
515 //
516 // universal distribution suggested by L. Urban
517 // (Geant3 manual (1993) Phys211),
518 // derived from Tsai distribution (Rev Mod Phys 49,421(1977))
519
520 G4double u;
521 const G4double a1 = 0.625 , a2 = 3.*a1 , d = 27. ;
522
523 if (9./(9.+d) > G4UniformRand()) u = - log(G4UniformRand()*G4UniformRand())/a1;
524 else u = - log(G4UniformRand()*G4UniformRand())/a2;
525
526 G4double theta = u*particleMass/totalEnergy;
527 G4double sint = sin(theta);
528 G4double phi = twopi * G4UniformRand();
529 G4ThreeVector gammaDirection(sint*cos(phi),sint*sin(phi), cos(theta));
530 gammaDirection.rotateUz(direction);
531
532 // create G4DynamicParticle object for the Gamma
533 G4DynamicParticle* g = new G4DynamicParticle(theGamma,gammaDirection,
534 gammaEnergy);
535 vdp->push_back(g);
536
537 G4double totMomentum = sqrt(kineticEnergy*(totalEnergy + electron_mass_c2));
538 G4ThreeVector dir = totMomentum*direction - gammaEnergy*gammaDirection;
539 direction = dir.unit();
540
541 // energy of primary
542 G4double finalE = kineticEnergy - gammaEnergy;
543
544 // stop tracking and create new secondary instead of primary
545 if(gammaEnergy > SecondaryThreshold()) {
546 fParticleChange->ProposeTrackStatus(fStopAndKill);
547 fParticleChange->SetProposedKineticEnergy(0.0);
548 G4DynamicParticle* el =
549 new G4DynamicParticle(const_cast<G4ParticleDefinition*>(particle),
550 direction, finalE);
551 vdp->push_back(el);
552
553 // continue tracking
554 } else {
555 fParticleChange->SetProposedMomentumDirection(direction);
556 fParticleChange->SetProposedKineticEnergy(finalE);
557 }
558}
559
560//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
561
562
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