source: trunk/source/processes/electromagnetic/standard/src/G4eCoulombScatteringModel.cc @ 1152

Last change on this file since 1152 was 1055, checked in by garnier, 15 years ago

maj sur la beta de geant 4.9.3
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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 $
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-
46// 09.06.08 V.Ivanchenko add SelectIsotope and sampling of the recoil ion
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"
64#include "G4ParticleTable.hh"
65
66//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
67
68G4double G4eCoulombScatteringModel::ScreenRSquare[] = {0.0};
69G4double G4eCoulombScatteringModel::FormFactor[]    = {0.0};
70
71using namespace std;
72
73G4eCoulombScatteringModel::G4eCoulombScatteringModel(const G4String& nam)
74  : G4VEmModel(nam),
75    cosThetaMin(1.0),
76    cosThetaMax(-1.0),
77    q2Limit(TeV*TeV),
78    alpha2(fine_structure_const*fine_structure_const),
79    faclim(100.0),
80    isInitialised(false)
81{
82  fNistManager = G4NistManager::Instance();
83  theParticleTable = G4ParticleTable::GetParticleTable();
84  theElectron = G4Electron::Electron();
85  thePositron = G4Positron::Positron();
86  theProton   = G4Proton::Proton();
87  currentMaterial = 0; 
88  currentElement  = 0;
89  lowEnergyLimit = keV;
90  G4double p0 = electron_mass_c2*classic_electr_radius;
91  coeff  = twopi*p0*p0;
92  tkin = targetZ = mom2 = DBL_MIN;
93  elecXSection = nucXSection = 0.0;
94  recoilThreshold = 100.*keV;
95  ecut = DBL_MAX;
96  particle = 0;
97  currentCouple = 0;
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  }
114}
115
116//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
117
118G4eCoulombScatteringModel::~G4eCoulombScatteringModel()
119{}
120
121//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
122
123void G4eCoulombScatteringModel::Initialise(const G4ParticleDefinition* p,
124                                           const G4DataVector& cuts)
125{
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;
136  if(!isInitialised) {
137    isInitialised = true;
138    fParticleChange = GetParticleChangeForGamma();
139  }
140  if(mass < GeV && particle->GetParticleType() != "nucleus") {
141    InitialiseElementSelectors(p,cuts);
142  }
143}
144
145//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
146
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;
169      if(ctm <  1.0) cosTetMaxElec = ctm;
170      if(ctm < -1.0) cosTetMaxElec = -1.0;
171    }
172  }
173}
174
175//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
176
177G4double G4eCoulombScatteringModel::ComputeCrossSectionPerAtom(
178                const G4ParticleDefinition* p,
179                G4double kinEnergy,
180                G4double Z, G4double,
181                G4double cutEnergy, G4double)
182{
183  //G4cout << "### G4eCoulombScatteringModel::ComputeCrossSectionPerAtom  for "
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; 
202}
203
204//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
205
206G4double G4eCoulombScatteringModel::CrossSectionPerAtom()
207{
208  // This method needs initialisation before be called
209  G4double fac = coeff*targetZ*chargeSquare*kinFactor;
210  elecXSection = 0.0;
211  nucXSection  = 0.0;
212
213  G4double x  = 1.0 - cosTetMinNuc;
214  G4double x1 = x + screenZ;
215
216  if(cosTetMaxElec2 < cosTetMinNuc) {
217    elecXSection = fac*(cosTetMinNuc - cosTetMaxElec2)/
218      (x1*(1.0 - cosTetMaxElec2 + screenZ));
219    nucXSection  = elecXSection;
220  }
221
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;
228    G4double s1 = 1.0 - s;
229    G4double d  = s1/formfactA;
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;
239      x = (1.0/x1 - 1.0/z1 + 1.0/x2 - 1.0/z2 - 2.0*log(z1*x2/(z2*x1))/d)/(s1*s1);
240    }
241    nucXSection += fac*targetZ*x;
242  }
243  //G4cout<<" cross(bn)= "<<nucXSection/barn<<" xsElec(bn)= "<<elecXSection/barn
244  //    << " Asc= " << screenZ << G4endl;
245 
246  return nucXSection;
247}
248
249//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
250
251void G4eCoulombScatteringModel::SampleSecondaries(
252                std::vector<G4DynamicParticle*>* fvect,
253                const G4MaterialCutsCouple* couple,
254                const G4DynamicParticle* dp,
255                G4double cutEnergy,
256                G4double)
257{
258  G4double kinEnergy = dp->GetKineticEnergy();
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);
269
270  SetupTarget(currentElement->GetZ(),ekin);
271 
272  G4double cost = SampleCosineTheta();
273  G4double z1   = 1.0 - cost;
274  if(z1 < 0.0) return;
275
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();
282
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
295    if(Trec > recoilThreshold) {
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;
315  G4double formf = formfactA;
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;
323    formf = 0.0;
324  }
325
326  /*
327  G4cout << "SampleCost: e(MeV)= " << tkin
328         << " ctmin= " << cosThetaMin
329         << " ctmaxN= " << cosTetMaxNuc
330         << " ctmax= " << costm
331         << " Z= " << targetZ << " A= " << targetA
332         << G4endl;
333  */
334  if(costm >= cosTetMinNuc) return 2.0; 
335
336  G4double x1 = 1. - cosTetMinNuc + screenZ;
337  G4double x2 = 1. - costm + screenZ;
338  G4double x3 = cosTetMinNuc - costm;
339  G4double grej, z1; 
340  do {
341    z1 = x1*x2/(x1 + G4UniformRand()*x3) - screenZ;
342    grej = 1.0/(1.0 + formf*z1);
343  } while ( G4UniformRand() > grej*grej ); 
344
345  //G4cout << "z= " << z1 << " cross= " << nucXSection/barn
346  // << " crossE= " << elecXSection/barn << G4endl;
347
348  return 1.0 - z1;
349}
350
351//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
352
353
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