source: trunk/source/processes/electromagnetic/standard/src/G4eCoulombScatteringModel.cc@ 1199

Last change on this file since 1199 was 1196, checked in by garnier, 16 years ago

update CVS release candidate geant4.9.3.01
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25//
26// $Id: G4eCoulombScatteringModel.cc,v 1.78 2009/10/28 10:14:13 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03-cand-01 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4eCoulombScatteringModel
35//
36// Author: Vladimir Ivanchenko
37//
38// Creation date: 22.08.2005
39//
40// Modifications:
41//
42// 01.08.06 V.Ivanchenko extend upper limit of table to TeV and review the
43// logic of building - only elements from G4ElementTable
44// 08.08.06 V.Ivanchenko build internal table in ekin scale, introduce faclim
45// 19.08.06 V.Ivanchenko add inline function ScreeningParameter
46// 09.10.07 V.Ivanchenko reorganized methods, add cut dependence in scattering off e-
47// 09.06.08 V.Ivanchenko add SelectIsotope and sampling of the recoil ion
48// 16.06.09 C.Consolandi fixed computation of effective mass
49//
50//
51// Class Description:
52//
53// -------------------------------------------------------------------
54//
55//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
56//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
57
58#include "G4eCoulombScatteringModel.hh"
59#include "Randomize.hh"
60#include "G4DataVector.hh"
61#include "G4ElementTable.hh"
62#include "G4PhysicsLogVector.hh"
63#include "G4ParticleChangeForGamma.hh"
64#include "G4Electron.hh"
65#include "G4Positron.hh"
66#include "G4Proton.hh"
67#include "G4ParticleTable.hh"
68#include "G4ProductionCutsTable.hh"
69#include "G4NucleiProperties.hh"
70
71//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
72
73G4double G4eCoulombScatteringModel::ScreenRSquare[] = {0.0};
74G4double G4eCoulombScatteringModel::FormFactor[] = {0.0};
75
76using namespace std;
77
78G4eCoulombScatteringModel::G4eCoulombScatteringModel(const G4String& nam)
79 : G4VEmModel(nam),
80 cosThetaMin(1.0),
81 cosThetaMax(-1.0),
82 q2Limit(TeV*TeV),
83 alpha2(fine_structure_const*fine_structure_const),
84 faclim(100.0),
85 isInitialised(false)
86{
87 fNistManager = G4NistManager::Instance();
88 theParticleTable = G4ParticleTable::GetParticleTable();
89 theElectron = G4Electron::Electron();
90 thePositron = G4Positron::Positron();
91 theProton = G4Proton::Proton();
92 currentMaterial = 0;
93 currentElement = 0;
94 lowEnergyLimit = 0.1*keV;
95 G4double p0 = electron_mass_c2*classic_electr_radius;
96 coeff = twopi*p0*p0;
97 tkin = targetZ = mom2 = DBL_MIN;
98 elecXSection = nucXSection = 0.0;
99 recoilThreshold = 0.*keV;
100 ecut = DBL_MAX;
101 particle = 0;
102 currentCouple = 0;
103
104 // Thomas-Fermi screening radii
105 // Formfactors from A.V. Butkevich et al., NIM A 488 (2002) 282
106
107 if(0.0 == ScreenRSquare[0]) {
108 G4double a0 = electron_mass_c2/0.88534;
109 G4double constn = 6.937e-6/(MeV*MeV);
110
111 ScreenRSquare[0] = alpha2*a0*a0;
112 for(G4int j=1; j<100; j++) {
113 G4double x = a0*fNistManager->GetZ13(j);
114 ScreenRSquare[j] = alpha2*x*x;
115 x = fNistManager->GetA27(j);
116 FormFactor[j] = constn*x*x;
117 }
118 }
119}
120
121//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
122
123G4eCoulombScatteringModel::~G4eCoulombScatteringModel()
124{}
125
126//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
127
128void G4eCoulombScatteringModel::Initialise(const G4ParticleDefinition* p,
129 const G4DataVector& cuts)
130{
131 SetupParticle(p);
132 currentCouple = 0;
133 elecXSection = nucXSection = 0.0;
134 tkin = targetZ = mom2 = DBL_MIN;
135 ecut = etag = DBL_MAX;
136 cosThetaMin = cos(PolarAngleLimit());
137 pCuts = G4ProductionCutsTable::GetProductionCutsTable()->GetEnergyCutsVector(3);
138 //G4cout << "!!! G4eCoulombScatteringModel::Initialise for "
139 // << p->GetParticleName() << " cos(TetMin)= " << cosThetaMin
140 // << " cos(TetMax)= " << cosThetaMax <<G4endl;
141 // G4cout << "cut0= " << cuts[0] << " cut1= " << cuts[1] << G4endl;
142 if(!isInitialised) {
143 isInitialised = true;
144 fParticleChange = GetParticleChangeForGamma();
145 }
146 if(mass < GeV && particle->GetParticleType() != "nucleus") {
147 InitialiseElementSelectors(p,cuts);
148 }
149}
150
151//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
152
153void G4eCoulombScatteringModel::ComputeMaxElectronScattering(G4double cutEnergy)
154{
155 ecut = cutEnergy;
156 G4double tmax = tkin;
157 cosTetMaxElec = 1.0;
158 if(mass > MeV) {
159 G4double ratio = electron_mass_c2/mass;
160 G4double tau = tkin/mass;
161 tmax = 2.0*electron_mass_c2*tau*(tau + 2.)/
162 (1.0 + 2.0*ratio*(tau + 1.0) + ratio*ratio);
163 cosTetMaxElec = 1.0 - std::min(cutEnergy, tmax)*electron_mass_c2/mom2;
164 } else {
165
166 if(particle == theElectron) tmax *= 0.5;
167 G4double t = std::min(cutEnergy, tmax);
168 G4double mom21 = t*(t + 2.0*electron_mass_c2);
169 G4double t1 = tkin - t;
170 //G4cout << "tkin= " << tkin << " t= " << t << " t1= " << t1 << G4endl;
171 if(t1 > 0.0) {
172 G4double mom22 = t1*(t1 + 2.0*mass);
173 G4double ctm = (mom2 + mom22 - mom21)*0.5/sqrt(mom2*mom22);
174 //G4cout << "ctm= " << ctm << G4endl;
175 if(ctm < 1.0) cosTetMaxElec = ctm;
176 if(ctm < -1.0) cosTetMaxElec = -1.0;
177 }
178 }
179}
180
181//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
182
183G4double G4eCoulombScatteringModel::ComputeCrossSectionPerAtom(
184 const G4ParticleDefinition* p,
185 G4double kinEnergy,
186 G4double Z, G4double,
187 G4double cutEnergy, G4double)
188{
189 //G4cout << "### G4eCoulombScatteringModel::ComputeCrossSectionPerAtom for "
190 // << p->GetParticleName()<<" Z= "<<Z<<" e(MeV)= "<< kinEnergy/MeV << G4endl;
191 G4double xsec = 0.0;
192 SetupParticle(p);
193 if(kinEnergy < lowEnergyLimit) return xsec;
194 SetupKinematic(kinEnergy, cutEnergy);
195 if(cosTetMaxNuc < cosTetMinNuc) {
196 SetupTarget(Z, kinEnergy);
197 xsec = CrossSectionPerAtom();
198 }
199 /*
200 G4cout << "e(MeV)= " << ekin/MeV << "cosTetMinNuc= " << cosTetMinNuc
201 << " cosTetMaxNuc= " << cosTetMaxNuc
202 << " cosTetMaxElec= " << cosTetMaxElec
203 << " screenZ= " << screenZ
204 << " formfactA= " << formfactA << G4endl;
205 */
206 return xsec;
207}
208
209//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
210
211G4double G4eCoulombScatteringModel::CrossSectionPerAtom()
212{
213 // This method needs initialisation before be called
214 //G4double fac = coeff*targetZ*chargeSquare*invbeta2/mom2;
215
216 G4double meff = targetMass/(mass+targetMass);
217 G4double fac = coeff*targetZ*chargeSquare*invbeta2/(mom2*meff*meff);
218
219 elecXSection = 0.0;
220 nucXSection = 0.0;
221
222 G4double x = 1.0 - cosTetMinNuc;
223 G4double x1 = x + screenZ;
224
225 if(cosTetMaxElec2 < cosTetMinNuc) {
226 elecXSection = fac*(cosTetMinNuc - cosTetMaxElec2)/
227 (x1*(1.0 - cosTetMaxElec2 + screenZ));
228 nucXSection = elecXSection;
229 }
230
231 //G4cout << "XS tkin(MeV)= " << tkin<<" xs= " <<nucXSection
232 // << " costmax= " << cosTetMaxNuc2
233 // << " costmin= " << cosTetMinNuc << " Z= " << targetZ <<G4endl;
234 if(cosTetMaxNuc2 < cosTetMinNuc) {
235 G4double s = screenZ*formfactA;
236 G4double z1 = 1.0 - cosTetMaxNuc2 + screenZ;
237 G4double s1 = 1.0 - s;
238 G4double d = s1/formfactA;
239 //G4cout <<"x1= "<<x1<<" z1= " <<z1<<" s= "<<s << " d= " <<d <<G4endl;
240 if(d < 0.2*x1) {
241 G4double x2 = x1*x1;
242 G4double z2 = z1*z1;
243 x = (1.0/(x1*x2) - 1.0/(z1*z2) - d*1.5*(1.0/(x2*x2) - 1.0/(z2*z2)))/
244 (3.0*formfactA*formfactA);
245 } else {
246 G4double x2 = x1 + d;
247 G4double z2 = z1 + d;
248 x = (1.0/x1 - 1.0/z1 + 1.0/x2 - 1.0/z2 - 2.0*log(z1*x2/(z2*x1))/d)/(s1*s1);
249 }
250 nucXSection += fac*targetZ*x;
251 }
252 //G4cout<<" cross(bn)= "<<nucXSection/barn<<" xsElec(bn)= "<<elecXSection/barn
253 // << " Asc= " << screenZ << G4endl;
254
255 return nucXSection;
256}
257
258//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
259
260void G4eCoulombScatteringModel::SampleSecondaries(
261 std::vector<G4DynamicParticle*>* fvect,
262 const G4MaterialCutsCouple* couple,
263 const G4DynamicParticle* dp,
264 G4double cutEnergy,
265 G4double)
266{
267 G4double kinEnergy = dp->GetKineticEnergy();
268 if(kinEnergy < lowEnergyLimit) return;
269 DefineMaterial(couple);
270 SetupParticle(dp->GetDefinition());
271
272 SetupKinematic(kinEnergy, cutEnergy);
273 //G4cout << "G4eCoulombScatteringModel::SampleSecondaries e(MeV)= "
274 // << kinEnergy << " " << particle->GetParticleName()
275 // << " cut= " << cutEnergy<< G4endl;
276
277 // Choose nucleus
278 currentElement = SelectRandomAtom(couple,particle,
279 kinEnergy,cutEnergy,kinEnergy);
280
281 SetupTarget(currentElement->GetZ(),kinEnergy);
282
283 G4int ia = SelectIsotopeNumber(currentElement);
284 targetMass = G4NucleiProperties::GetNuclearMass(ia, iz);
285
286 G4double cost = SampleCosineTheta();
287 G4double z1 = 1.0 - cost;
288 if(z1 < 0.0) return;
289
290 G4double sint = sqrt(z1*(1.0 + cost));
291
292 //G4cout<<"## Sampled sint= " << sint << " Z= " << targetZ << " A= " << ia
293 // << " screenZ= " << screenZ << " cn= " << formfactA << G4endl;
294
295 G4double phi = twopi * G4UniformRand();
296
297 G4ThreeVector direction = dp->GetMomentumDirection();
298 G4ThreeVector newDirection(cos(phi)*sint,sin(phi)*sint,cost);
299 newDirection.rotateUz(direction);
300
301 fParticleChange->ProposeMomentumDirection(newDirection);
302
303 // recoil sampling assuming a small recoil
304 // and first order correction to primary 4-momentum
305 G4double q2 = 2*z1*mom2;
306 G4double trec = q2/(sqrt(targetMass*targetMass + q2) + targetMass);
307 G4double finalT = kinEnergy - trec;
308 //G4cout<<"G4eCoulombScatteringModel: finalT= "<<finalT<<" Trec= "<<trec<<G4endl;
309 if(finalT <= lowEnergyLimit) {
310 trec = kinEnergy;
311 finalT = 0.0;
312 }
313
314 fParticleChange->SetProposedKineticEnergy(finalT);
315 G4double tcut = recoilThreshold;
316 if(pCuts) { tcut= std::max(tcut,(*pCuts)[currentMaterialIndex]); }
317
318 if(trec > tcut) {
319 G4ParticleDefinition* ion = theParticleTable->FindIon(iz, ia, 0, iz);
320 G4ThreeVector dir = (direction*sqrt(mom2) -
321 newDirection*sqrt(finalT*(2*mass + finalT))).unit();
322 G4DynamicParticle* newdp = new G4DynamicParticle(ion, dir, trec);
323 fvect->push_back(newdp);
324 } else {
325 fParticleChange->ProposeLocalEnergyDeposit(trec);
326 fParticleChange->ProposeNonIonizingEnergyDeposit(trec);
327 }
328
329 return;
330}
331
332//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
333
334G4double G4eCoulombScatteringModel::SampleCosineTheta()
335{
336 G4double costm = cosTetMaxNuc2;
337 G4double formf = formfactA;
338 G4double prob = 0.0;
339 G4double xs = CrossSectionPerAtom();
340 if(xs > 0.0) prob = elecXSection/xs;
341
342 // scattering off e or A?
343 if(G4UniformRand() < prob) {
344 costm = cosTetMaxElec2;
345 formf = 0.0;
346 }
347
348 /*
349 G4cout << "SampleCost: e(MeV)= " << tkin
350 << " 1-ctmaxN= " << 1. - cosTetMinNuc
351 << " 1-ctmax= " << 1. - costm
352 << " Z= " << targetZ
353 << G4endl;
354 */
355
356 if(costm >= cosTetMinNuc) return 2.0;
357
358 G4double x1 = 1. - cosTetMinNuc + screenZ;
359 G4double x2 = 1. - costm + screenZ;
360 G4double x3 = cosTetMinNuc - costm;
361 G4double grej, z1;
362 do {
363 z1 = x1*x2/(x1 + G4UniformRand()*x3) - screenZ;
364 grej = 1.0/(1.0 + formf*z1);
365 } while ( G4UniformRand() > grej*grej );
366
367 if(mass > MeV) {
368 if(G4UniformRand() > (1. - z1*0.5)/(1.0 + z1*sqrt(mom2)/targetMass)) {
369 return 2.0;
370 }
371 }
372 //G4cout << "z1= " << z1 << " cross= " << nucXSection/barn
373 // << " crossE= " << elecXSection/barn << G4endl;
374
375 return 1.0 - z1;
376}
377
378//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
379
380
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