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26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4KleinNishinaModel
33 //
34 // Author: Vladimir Ivanchenko on base of G4KleinNishinaCompton
35 //
36 // Creation date: 13.06.2010
37 //
38 // Modifications:
39 //
40 // Class Description:
41 //
42 // -------------------------------------------------------------------
43 //
44 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
45 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
46
47 #include "G4KleinNishinaModel.hh"
48 #include "G4PhysicalConstants.hh"
49 #include "G4SystemOfUnits.hh"
50 #include "G4Electron.hh"
51 #include "G4Gamma.hh"
52 #include "Randomize.hh"
53 #include "G4RandomDirection.hh"
54 #include "G4DataVector.hh"
55 #include "G4ParticleChangeForGamma.hh"
56 #include "G4VAtomDeexcitation.hh"
57 #include "G4AtomicShells.hh"
58 #include "G4LossTableManager.hh"
59 #include "G4Log.hh"
60 #include "G4Exp.hh"
61
62 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
63
64 using namespace std;
65
66 G4KleinNishinaModel::G4KleinNishinaModel(const G4String& nam)
67 : G4VEmModel(nam),
68 lv1(0.,0.,0.,0.),
69 lv2(0.,0.,0.,0.),
70 bst(0.,0.,0.)
71 {
72 theGamma = G4Gamma::Gamma();
73 theElectron = G4Electron::Electron();
74 lowestSecondaryEnergy = 10*eV;
75 limitFactor = 4;
76 fProbabilities.resize(9,0.0);
77 SetDeexcitationFlag(true);
78 fParticleChange = nullptr;
79 fAtomDeexcitation = nullptr;
80 }
81
82 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
83
84 G4KleinNishinaModel::~G4KleinNishinaModel() = default;
85
86 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
87
88 void G4KleinNishinaModel::Initialise(const G4ParticleDefinition* p,
89 const G4DataVector& cuts)
90 {
91 fAtomDeexcitation = G4LossTableManager::Instance()->AtomDeexcitation();
92 if(IsMaster()) { InitialiseElementSelectors(p, cuts); }
93 if(nullptr == fParticleChange) {
94 fParticleChange = GetParticleChangeForGamma();
95 }
96 }
97
98 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
99
100 void G4KleinNishinaModel::InitialiseLocal(const G4ParticleDefinition*,
101 G4VEmModel* masterModel)
102 {
103 SetElementSelectors(masterModel->GetElementSelectors());
104 }
105
106 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
107
108 G4double
109 G4KleinNishinaModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*,
110 G4double gammaEnergy,
111 G4double Z, G4double,
112 G4double, G4double)
113 {
114 G4double xSection = 0.0 ;
115 if (gammaEnergy <= LowEnergyLimit()) { return xSection; }
116
117 static const G4double a = 20.0 , b = 230.0 , c = 440.0;
118
119 static const G4double
120 d1= 2.7965e-1*CLHEP::barn, d2=-1.8300e-1*CLHEP::barn,
121 d3= 6.7527 *CLHEP::barn, d4=-1.9798e+1*CLHEP::barn,
122 e1= 1.9756e-5*CLHEP::barn, e2=-1.0205e-2*CLHEP::barn,
123 e3=-7.3913e-2*CLHEP::barn, e4= 2.7079e-2*CLHEP::barn,
124 f1=-3.9178e-7*CLHEP::barn, f2= 6.8241e-5*CLHEP::barn,
125 f3= 6.0480e-5*CLHEP::barn, f4= 3.0274e-4*CLHEP::barn;
126
127 G4double p1Z = Z*(d1 + e1*Z + f1*Z*Z), p2Z = Z*(d2 + e2*Z + f2*Z*Z),
128 p3Z = Z*(d3 + e3*Z + f3*Z*Z), p4Z = Z*(d4 + e4*Z + f4*Z*Z);
129
130 G4double T0 = 15.0*keV;
131 if (Z < 1.5) { T0 = 40.0*keV; }
132
133 G4double X = max(gammaEnergy, T0) / electron_mass_c2;
134 xSection = p1Z*G4Log(1.+2.*X)/X
135 + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X);
136
137 // modification for low energy. (special case for Hydrogen)
138 static const G4double dT0 = keV;
139 if (gammaEnergy < T0) {
140 X = (T0+dT0) / electron_mass_c2 ;
141 G4double sigma = p1Z*G4Log(1.+2*X)/X
142 + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X);
143 G4double c1 = -T0*(sigma-xSection)/(xSection*dT0);
144 G4double c2 = 0.150;
145 if (Z > 1.5) { c2 = 0.375-0.0556*G4Log(Z); }
146 G4double y = G4Log(gammaEnergy/T0);
147 xSection *= G4Exp(-y*(c1+c2*y));
148 }
149
150 if(xSection < 0.0) { xSection = 0.0; }
151 // G4cout << "e= " << GammaEnergy << " Z= " << Z
152 // << " cross= " << xSection << G4endl;
153 return xSection;
154 }
155
156 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
157
158 void G4KleinNishinaModel::SampleSecondaries(
159 std::vector<G4DynamicParticle*>* fvect,
160 const G4MaterialCutsCouple* couple,
161 const G4DynamicParticle* aDynamicGamma,
162 G4double,
163 G4double)
164 {
165 // primary gamma
166 G4double energy = aDynamicGamma->GetKineticEnergy();
167
168 // do nothing below the threshold
169 if(energy <= LowEnergyLimit()) { return; }
170
171 G4ThreeVector direction = aDynamicGamma->GetMomentumDirection();
172
173 // select atom
174 const G4Element* elm = SelectRandomAtom(couple, theGamma, energy);
175
176 // select shell first
177 G4int nShells = elm->GetNbOfAtomicShells();
178 if(nShells > (G4int)fProbabilities.size()) { fProbabilities.resize(nShells); }
179 G4double totprob = 0.0;
180 G4int i;
181 for(i=0; i<nShells; ++i) {
182 //G4double bindingEnergy = elm->GetAtomicShell(i);
183 totprob += elm->GetNbOfShellElectrons(i);
184 //totprob += elm->GetNbOfShellElectrons(i)/(bindingEnergy*bindingEnergy);
185 fProbabilities[i] = totprob;
186 }
187
188 // Loop on sampling
189 static const G4int nlooplim = 1000;
190 G4int nloop = 0;
191
192 G4double bindingEnergy, ePotEnergy, eKinEnergy;
193 G4double gamEnergy0, gamEnergy1;
194
195 CLHEP::HepRandomEngine* rndmEngineMod = G4Random::getTheEngine();
196 G4double rndm[4];
197
198 do {
199 ++nloop;
200
201 // 4 random numbers to select e-
202 rndmEngineMod->flatArray(4, rndm);
203 G4double xprob = totprob*rndm[0];
204
205 // select shell
206 for(i=0; i<nShells; ++i) { if(xprob <= fProbabilities[i]) { break; } }
207
208 bindingEnergy = elm->GetAtomicShell(i);
209 lv1.set(0.0,0.0,energy,energy);
210 /*
211 G4cout << "nShells= " << nShells << " i= " << i
212 << " Egamma= " << energy << " Ebind= " << bindingEnergy
213 << G4endl;
214 */
215 // for rest frame of the electron
216 G4double x = -G4Log(rndm[1]);
217 eKinEnergy = bindingEnergy*x;
218 ePotEnergy = bindingEnergy*(1.0 + x);
219
220 // for rest frame of the electron
221 G4double eTotMomentum = sqrt(eKinEnergy*(eKinEnergy + 2*electron_mass_c2));
222 G4double phi = rndm[2]*twopi;
223 G4double costet = 2*rndm[3] - 1;
224 G4double sintet = sqrt((1 - costet)*(1 + costet));
225 lv2.set(eTotMomentum*sintet*cos(phi),eTotMomentum*sintet*sin(phi),
226 eTotMomentum*costet,eKinEnergy + electron_mass_c2);
227 bst = lv2.boostVector();
228 lv1.boost(-bst);
229
230 gamEnergy0 = lv1.e();
231
232 // In the rest frame of the electron
233 // The scattered gamma energy is sampled according to Klein-Nishina formula
234 // The random number techniques of Butcher & Messel are used
235 // (Nuc Phys 20(1960),15).
236 G4double E0_m = gamEnergy0/electron_mass_c2;
237
238 //G4cout << "Nloop= "<< nloop << " Ecm(keV)= " << gamEnergy0/keV << G4endl;
239 //
240 // sample the energy rate of the scattered gamma
241 //
242
243 G4double epsilon, epsilonsq, onecost, sint2, greject ;
244
245 G4double eps0 = 1./(1 + 2*E0_m);
246 G4double epsilon0sq = eps0*eps0;
247 G4double alpha1 = - G4Log(eps0);
248 G4double alpha2 = alpha1 + 0.5*(1 - epsilon0sq);
249
250 do {
251 ++nloop;
252 // false interaction if too many iterations
253 if(nloop > nlooplim) { return; }
254
255 // 3 random numbers to sample scattering
256 rndmEngineMod->flatArray(3, rndm);
257
258 if ( alpha1 > alpha2*rndm[0] ) {
259 epsilon = G4Exp(-alpha1*rndm[1]); // epsilon0**r
260 epsilonsq = epsilon*epsilon;
261
262 } else {
263 epsilonsq = epsilon0sq + (1.- epsilon0sq)*rndm[1];
264 epsilon = sqrt(epsilonsq);
265 }
266
267 onecost = (1.- epsilon)/(epsilon*E0_m);
268 sint2 = onecost*(2.-onecost);
269 greject = 1. - epsilon*sint2/(1.+ epsilonsq);
270
271 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
272 } while (greject < rndm[2]);
273 gamEnergy1 = epsilon*gamEnergy0;
274
275 // before scattering total 4-momentum in e- system
276 lv2.set(0.0,0.0,0.0,electron_mass_c2);
277 lv2 += lv1;
278
279 //
280 // scattered gamma angles. ( Z - axis along the parent gamma)
281 //
282 if(sint2 < 0.0) { sint2 = 0.0; }
283 costet = 1. - onecost;
284 sintet = sqrt(sint2);
285 phi = twopi * rndmEngineMod->flat();
286
287 // e- recoil
288 //
289 // in rest frame of the electron
290 G4ThreeVector gamDir = lv1.vect().unit();
291 G4ThreeVector v = G4ThreeVector(sintet*cos(phi),sintet*sin(phi),costet);
292 v.rotateUz(gamDir);
293 lv1.set(gamEnergy1*v.x(),gamEnergy1*v.y(),gamEnergy1*v.z(),gamEnergy1);
294 lv2 -= lv1;
295 //G4cout<<"Egam(keV)= " << lv1.e()/keV
296 // <<" Ee(keV)= " << (lv2.e()-electron_mass_c2)/keV << G4endl;
297 lv2.boost(bst);
298 eKinEnergy = lv2.e() - electron_mass_c2 - ePotEnergy;
299 //G4cout << "Nloop= " << nloop << " eKinEnergy= " << eKinEnergy << G4endl;
300
301 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
302 } while ( eKinEnergy < 0.0 );
303
304 //
305 // update G4VParticleChange for the scattered gamma
306 //
307
308 lv1.boost(bst);
309 gamEnergy1 = lv1.e();
310 if(gamEnergy1 > lowestSecondaryEnergy) {
311 G4ThreeVector gamDirection1 = lv1.vect().unit();
312 gamDirection1.rotateUz(direction);
313 fParticleChange->ProposeMomentumDirection(gamDirection1);
314 } else {
315 fParticleChange->ProposeTrackStatus(fStopAndKill);
316 gamEnergy1 = 0.0;
317 }
318 fParticleChange->SetProposedKineticEnergy(gamEnergy1);
319
320 //
321 // kinematic of the scattered electron
322 //
323
324 if(eKinEnergy > lowestSecondaryEnergy) {
325 G4ThreeVector eDirection = lv2.vect().unit();
326 eDirection.rotateUz(direction);
327 auto dp = new G4DynamicParticle(theElectron,eDirection,eKinEnergy);
328 fvect->push_back(dp);
329 } else { eKinEnergy = 0.0; }
330
331 G4double edep = energy - gamEnergy1 - eKinEnergy;
332 G4double esec = 0.0;
333
334 // sample deexcitation
335 //
336 if(nullptr != fAtomDeexcitation) {
337 G4int index = couple->GetIndex();
338 if(fAtomDeexcitation->CheckDeexcitationActiveRegion(index)) {
339 G4int Z = elm->GetZasInt();
340 auto as = (G4AtomicShellEnumerator)(i);
341 const G4AtomicShell* shell = fAtomDeexcitation->GetAtomicShell(Z, as);
342 G4int nbefore = (G4int)fvect->size();
343 fAtomDeexcitation->GenerateParticles(fvect, shell, Z, index);
344 G4int nafter = (G4int)fvect->size();
345 //G4cout << "N1= " << nbefore << " N2= " << nafter << G4endl;
346 for (G4int j=nbefore; j<nafter; ++j) {
347 G4double e = ((*fvect)[j])->GetKineticEnergy();
348 if(esec + e > edep) {
349 // correct energy in order to have energy balance
350 e = edep - esec;
351 ((*fvect)[j])->SetKineticEnergy(e);
352 esec += e;
353 /*
354 G4cout << "### G4KleinNishinaModel Edep(eV)= " << edep/eV
355 << " Esec(eV)= " << esec/eV
356 << " E["<< j << "](eV)= " << e/eV
357 << " N= " << nafter
358 << " Z= " << Z << " shell= " << i
359 << " Ebind(keV)= " << bindingEnergy/keV
360 << " Eshell(keV)= " << shell->BindingEnergy()/keV
361 << G4endl;
362 */
363 // delete the rest of secondaries (should not happens)
364 for (G4int jj=nafter-1; jj>j; --jj) {
365 delete (*fvect)[jj];
366 fvect->pop_back();
367 }
368 break;
369 }
370 esec += e;
371 }
372 edep -= esec;
373 }
374 }
375 if(std::abs(energy - gamEnergy1 - eKinEnergy - esec - edep) > eV) {
376 G4cout << "### G4KleinNishinaModel dE(eV)= "
377 << (energy - gamEnergy1 - eKinEnergy - esec - edep)/eV
378 << " shell= " << i
379 << " E(keV)= " << energy/keV
380 << " Ebind(keV)= " << bindingEnergy/keV
381 << " Eg(keV)= " << gamEnergy1/keV
382 << " Ee(keV)= " << eKinEnergy/keV
383 << " Esec(keV)= " << esec/keV
384 << " Edep(keV)= " << edep/keV
385 << G4endl;
386 }
387 // energy balance
388 if(edep > 0.0) {
389 fParticleChange->ProposeLocalEnergyDeposit(edep);
390 }
391 }
392
393 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
394
395