source: trunk/source/processes/electromagnetic/standard/src/G4eCoulombScatteringModel.cc@ 1120

Last change on this file since 1120 was 1055, checked in by garnier, 17 years ago

maj sur la beta de geant 4.9.3
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[819]1//
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25//
[1055]26// $Id: G4eCoulombScatteringModel.cc,v 1.69 2009/05/10 16:09:29 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03-beta-cand-01 $
[819]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// 01.08.06 V.Ivanchenko extend upper limit of table to TeV and review the
42// logic of building - only elements from G4ElementTable
43// 08.08.06 V.Ivanchenko build internal table in ekin scale, introduce faclim
44// 19.08.06 V.Ivanchenko add inline function ScreeningParameter
45// 09.10.07 V.Ivanchenko reorganized methods, add cut dependence in scattering off e-
[961]46// 09.06.08 V.Ivanchenko add SelectIsotope and sampling of the recoil ion
[819]47//
48// Class Description:
49//
50// -------------------------------------------------------------------
51//
52//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
53//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
54
55#include "G4eCoulombScatteringModel.hh"
56#include "Randomize.hh"
57#include "G4DataVector.hh"
58#include "G4ElementTable.hh"
59#include "G4PhysicsLogVector.hh"
60#include "G4ParticleChangeForGamma.hh"
61#include "G4Electron.hh"
62#include "G4Positron.hh"
63#include "G4Proton.hh"
[961]64#include "G4ParticleTable.hh"
[819]65
66//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
67
[1055]68G4double G4eCoulombScatteringModel::ScreenRSquare[] = {0.0};
69G4double G4eCoulombScatteringModel::FormFactor[] = {0.0};
70
[819]71using namespace std;
72
[961]73G4eCoulombScatteringModel::G4eCoulombScatteringModel(const G4String& nam)
[819]74 : G4VEmModel(nam),
[961]75 cosThetaMin(1.0),
76 cosThetaMax(-1.0),
77 q2Limit(TeV*TeV),
[819]78 alpha2(fine_structure_const*fine_structure_const),
79 faclim(100.0),
80 isInitialised(false)
81{
82 fNistManager = G4NistManager::Instance();
[961]83 theParticleTable = G4ParticleTable::GetParticleTable();
[819]84 theElectron = G4Electron::Electron();
85 thePositron = G4Positron::Positron();
86 theProton = G4Proton::Proton();
[961]87 currentMaterial = 0;
88 currentElement = 0;
[1055]89 lowEnergyLimit = keV;
[819]90 G4double p0 = electron_mass_c2*classic_electr_radius;
91 coeff = twopi*p0*p0;
[961]92 tkin = targetZ = mom2 = DBL_MIN;
[819]93 elecXSection = nucXSection = 0.0;
[1055]94 recoilThreshold = 100.*keV;
[819]95 ecut = DBL_MAX;
96 particle = 0;
[961]97 currentCouple = 0;
[1055]98
99 // Thomas-Fermi screening radii
100 // Formfactors from A.V. Butkevich et al., NIM A 488 (2002) 282
101
102 if(0.0 == ScreenRSquare[0]) {
103 G4double a0 = electron_mass_c2/0.88534;
104 G4double constn = 6.937e-6/(MeV*MeV);
105
106 ScreenRSquare[0] = alpha2*a0*a0;
107 for(G4int j=1; j<100; j++) {
108 G4double x = a0*fNistManager->GetZ13(j);
109 ScreenRSquare[j] = alpha2*x*x;
110 x = fNistManager->GetA27(j);
111 FormFactor[j] = constn*x*x;
112 }
113 }
[819]114}
115
116//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
117
118G4eCoulombScatteringModel::~G4eCoulombScatteringModel()
[961]119{}
[819]120
121//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
122
123void G4eCoulombScatteringModel::Initialise(const G4ParticleDefinition* p,
[961]124 const G4DataVector& cuts)
[819]125{
[961]126 SetupParticle(p);
127 currentCouple = 0;
128 elecXSection = nucXSection = 0.0;
129 tkin = targetZ = mom2 = DBL_MIN;
130 ecut = etag = DBL_MAX;
131 cosThetaMin = cos(PolarAngleLimit());
132 currentCuts = &cuts;
133 //G4cout << "!!! G4eCoulombScatteringModel::Initialise for "
134 // << p->GetParticleName() << " cos(TetMin)= " << cosThetaMin
135 // << " cos(TetMax)= " << cosThetaMax <<G4endl;
[819]136 if(!isInitialised) {
137 isInitialised = true;
[1055]138 fParticleChange = GetParticleChangeForGamma();
[819]139 }
[961]140 if(mass < GeV && particle->GetParticleType() != "nucleus") {
141 InitialiseElementSelectors(p,cuts);
142 }
143}
[819]144
[961]145//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
[819]146
[961]147void G4eCoulombScatteringModel::ComputeMaxElectronScattering(G4double cutEnergy)
148{
149 ecut = cutEnergy;
150 G4double tmax = tkin;
151 cosTetMaxElec = 1.0;
152 if(mass > MeV) {
153 G4double ratio = electron_mass_c2/mass;
154 G4double tau = tkin/mass;
155 tmax = 2.0*electron_mass_c2*tau*(tau + 2.)/
156 (1.0 + 2.0*ratio*(tau + 1.0) + ratio*ratio);
157 cosTetMaxElec = 1.0 - std::min(cutEnergy, tmax)*electron_mass_c2/mom2;
158 } else {
159
160 if(particle == theElectron) tmax *= 0.5;
161 G4double t = std::min(cutEnergy, tmax);
162 G4double mom21 = t*(t + 2.0*electron_mass_c2);
163 G4double t1 = tkin - t;
164 //G4cout << "tkin= " << tkin << " t= " << t << " t1= " << t1 << G4endl;
165 if(t1 > 0.0) {
166 G4double mom22 = t1*(t1 + 2.0*mass);
167 G4double ctm = (mom2 + mom22 - mom21)*0.5/sqrt(mom2*mom22);
168 //G4cout << "ctm= " << ctm << G4endl;
[1055]169 if(ctm < 1.0) cosTetMaxElec = ctm;
170 if(ctm < -1.0) cosTetMaxElec = -1.0;
[961]171 }
172 }
[819]173}
174
175//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
176
177G4double G4eCoulombScatteringModel::ComputeCrossSectionPerAtom(
178 const G4ParticleDefinition* p,
179 G4double kinEnergy,
[961]180 G4double Z, G4double,
[819]181 G4double cutEnergy, G4double)
182{
183 //G4cout << "### G4eCoulombScatteringModel::ComputeCrossSectionPerAtom for "
[961]184 // << p->GetParticleName()<<" Z= "<<Z<<" e(MeV)= "<< kinEnergy/MeV << G4endl;
185 G4double xsec = 0.0;
186 SetupParticle(p);
187 G4double ekin = std::max(lowEnergyLimit, kinEnergy);
188 SetupKinematic(ekin, cutEnergy);
189 if(cosTetMaxNuc < cosTetMinNuc) {
190 SetupTarget(Z, ekin);
191 xsec = CrossSectionPerAtom();
192 }
193 /*
194 G4cout << "e(MeV)= " << ekin/MeV << "cosTetMinNuc= " << cosTetMinNuc
195 << " cosTetMaxNuc= " << cosTetMaxNuc
196 << " cosTetMaxElec= " << cosTetMaxElec
197 << " screenZ= " << screenZ
198 << " formfactA= " << formfactA
199 << " cosTetMaxHad= " << cosTetMaxHad << G4endl;
200 */
201 return xsec;
[819]202}
203
204//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
205
[961]206G4double G4eCoulombScatteringModel::CrossSectionPerAtom()
[819]207{
[961]208 // This method needs initialisation before be called
[1055]209 G4double fac = coeff*targetZ*chargeSquare*kinFactor;
[819]210 elecXSection = 0.0;
[961]211 nucXSection = 0.0;
[819]212
[961]213 G4double x = 1.0 - cosTetMinNuc;
214 G4double x1 = x + screenZ;
[819]215
[961]216 if(cosTetMaxElec2 < cosTetMinNuc) {
217 elecXSection = fac*(cosTetMinNuc - cosTetMaxElec2)/
218 (x1*(1.0 - cosTetMaxElec2 + screenZ));
219 nucXSection = elecXSection;
[819]220 }
221
[961]222 //G4cout << "XS tkin(MeV)= " << tkin<<" xs= " <<nucXSection
223 // << " costmax= " << cosTetMaxNuc2
224 // << " costmin= " << cosTetMinNuc << " Z= " << targetZ <<G4endl;
225 if(cosTetMaxNuc2 < cosTetMinNuc) {
226 G4double s = screenZ*formfactA;
227 G4double z1 = 1.0 - cosTetMaxNuc2 + screenZ;
[1055]228 G4double s1 = 1.0 - s;
229 G4double d = s1/formfactA;
[961]230 //G4cout <<"x1= "<<x1<<" z1= " <<z1<<" s= "<<s << " d= " <<d <<G4endl;
231 if(d < 0.2*x1) {
232 G4double x2 = x1*x1;
233 G4double z2 = z1*z1;
234 x = (1.0/(x1*x2) - 1.0/(z1*z2) - d*1.5*(1.0/(x2*x2) - 1.0/(z2*z2)))/
235 (3.0*formfactA*formfactA);
236 } else {
237 G4double x2 = x1 + d;
238 G4double z2 = z1 + d;
[1055]239 x = (1.0/x1 - 1.0/z1 + 1.0/x2 - 1.0/z2 - 2.0*log(z1*x2/(z2*x1))/d)/(s1*s1);
[961]240 }
241 nucXSection += fac*targetZ*x;
[819]242 }
[961]243 //G4cout<<" cross(bn)= "<<nucXSection/barn<<" xsElec(bn)= "<<elecXSection/barn
244 // << " Asc= " << screenZ << G4endl;
[819]245
[961]246 return nucXSection;
[819]247}
248
249//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
250
251void G4eCoulombScatteringModel::SampleSecondaries(
[961]252 std::vector<G4DynamicParticle*>* fvect,
[819]253 const G4MaterialCutsCouple* couple,
254 const G4DynamicParticle* dp,
255 G4double cutEnergy,
[961]256 G4double)
[819]257{
258 G4double kinEnergy = dp->GetKineticEnergy();
[961]259 if(kinEnergy <= DBL_MIN) return;
260 DefineMaterial(couple);
261 SetupParticle(dp->GetDefinition());
262 G4double ekin = std::max(lowEnergyLimit, kinEnergy);
263 SetupKinematic(ekin, cutEnergy);
264 //G4cout << "G4eCoulombScatteringModel::SampleSecondaries e(MeV)= "
265 // << kinEnergy << " " << particle->GetParticleName() << G4endl;
266
267 // Choose nucleus
268 currentElement = SelectRandomAtom(couple,particle,ekin,cutEnergy,ekin);
[819]269
[961]270 SetupTarget(currentElement->GetZ(),ekin);
271
272 G4double cost = SampleCosineTheta();
273 G4double z1 = 1.0 - cost;
274 if(z1 < 0.0) return;
[819]275
[961]276 G4double sint = sqrt(z1*(1.0 + cost));
277
278 //G4cout<<"## Sampled sint= " << sint << " Z= " << targetZ
279 // << " screenZ= " << screenZ << " cn= " << formfactA << G4endl;
280
281 G4double phi = twopi * G4UniformRand();
[819]282
[961]283 G4ThreeVector direction = dp->GetMomentumDirection();
284 G4ThreeVector newDirection(cos(phi)*sint,sin(phi)*sint,cost);
285 newDirection.rotateUz(direction);
286
287 fParticleChange->ProposeMomentumDirection(newDirection);
288
289 // recoil sampling assuming a small recoil
290 // and first order correction to primary 4-momentum
291 if(lowEnergyLimit < kinEnergy) {
292 G4int ia = SelectIsotopeNumber(currentElement);
293 G4double Trec = z1*mom2/(amu_c2*G4double(ia));
294
[1055]295 if(Trec > recoilThreshold) {
[961]296 G4ParticleDefinition* ion = theParticleTable->FindIon(iz, ia, 0, iz);
297 Trec = z1*mom2/ion->GetPDGMass();
298 if(Trec < kinEnergy) {
299 G4ThreeVector dir = (direction - newDirection).unit();
300 G4DynamicParticle* newdp = new G4DynamicParticle(ion, dir, Trec);
301 fvect->push_back(newdp);
302 fParticleChange->SetProposedKineticEnergy(kinEnergy - Trec);
303 }
304 }
305 }
306
307 return;
308}
309
310//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
311
312G4double G4eCoulombScatteringModel::SampleCosineTheta()
313{
314 G4double costm = cosTetMaxNuc2;
[819]315 G4double formf = formfactA;
[961]316 G4double prob = 0.0;
317 G4double xs = CrossSectionPerAtom();
318 if(xs > 0.0) prob = elecXSection/xs;
319
320 // scattering off e or A?
321 if(G4UniformRand() < prob) {
322 costm = cosTetMaxElec2;
[819]323 formf = 0.0;
324 }
[961]325
[819]326 /*
[961]327 G4cout << "SampleCost: e(MeV)= " << tkin
[819]328 << " ctmin= " << cosThetaMin
329 << " ctmaxN= " << cosTetMaxNuc
330 << " ctmax= " << costm
[961]331 << " Z= " << targetZ << " A= " << targetA
[819]332 << G4endl;
333 */
[961]334 if(costm >= cosTetMinNuc) return 2.0;
[819]335
[961]336 G4double x1 = 1. - cosTetMinNuc + screenZ;
337 G4double x2 = 1. - costm + screenZ;
338 G4double x3 = cosTetMinNuc - costm;
339 G4double grej, z1;
[819]340 do {
[961]341 z1 = x1*x2/(x1 + G4UniformRand()*x3) - screenZ;
[819]342 grej = 1.0/(1.0 + formf*z1);
343 } while ( G4UniformRand() > grej*grej );
344
[961]345 //G4cout << "z= " << z1 << " cross= " << nucXSection/barn
346 // << " crossE= " << elecXSection/barn << G4endl;
[819]347
[961]348 return 1.0 - z1;
[819]349}
350
351//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
352
353
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