source: trunk/source/processes/electromagnetic/standard/src/G4eCoulombScatteringModel.cc @ 961

Last change on this file since 961 was 961, checked in by garnier, 15 years ago

update processes
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26// $Id: G4eCoulombScatteringModel.cc,v 1.59 2008/10/22 18:39:29 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
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
68using namespace std;
69
70G4eCoulombScatteringModel::G4eCoulombScatteringModel(const G4String& nam)
71  : G4VEmModel(nam),
72    cosThetaMin(1.0),
73    cosThetaMax(-1.0),
74    q2Limit(TeV*TeV),
75    alpha2(fine_structure_const*fine_structure_const),
76    faclim(100.0),
77    isInitialised(false)
78{
79  fNistManager = G4NistManager::Instance();
80  theParticleTable = G4ParticleTable::GetParticleTable();
81  theElectron = G4Electron::Electron();
82  thePositron = G4Positron::Positron();
83  theProton   = G4Proton::Proton();
84  currentMaterial = 0; 
85  currentElement  = 0;
86  a0 = alpha2*electron_mass_c2*electron_mass_c2/(0.885*0.885);
87  G4double p0 = electron_mass_c2*classic_electr_radius;
88  coeff  = twopi*p0*p0;
89  constn = 6.937e-6/(MeV*MeV);
90  tkin = targetZ = mom2 = DBL_MIN;
91  elecXSection = nucXSection = 0.0;
92  recoilThreshold = DBL_MAX;
93  ecut = DBL_MAX;
94  particle = 0;
95  currentCouple = 0;
96  for(size_t j=0; j<100; j++) {
97    FF[j] = 0.0;
98  } 
99}
100
101//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
102
103G4eCoulombScatteringModel::~G4eCoulombScatteringModel()
104{}
105
106//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
107
108void G4eCoulombScatteringModel::Initialise(const G4ParticleDefinition* p,
109                                           const G4DataVector& cuts)
110{
111  SetupParticle(p);
112  currentCouple = 0;
113  elecXSection = nucXSection = 0.0;
114  tkin = targetZ = mom2 = DBL_MIN;
115  ecut = etag = DBL_MAX;
116  cosThetaMin = cos(PolarAngleLimit());
117  currentCuts = &cuts;
118  //G4cout << "!!! G4eCoulombScatteringModel::Initialise for "
119  //     << p->GetParticleName() << "  cos(TetMin)= " << cosThetaMin
120  //     << "  cos(TetMax)= " << cosThetaMax <<G4endl;
121  if(!isInitialised) {
122    isInitialised = true;
123
124    if(pParticleChange)
125      fParticleChange = 
126        reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
127    else
128      fParticleChange = new G4ParticleChangeForGamma();
129  }
130  if(mass < GeV && particle->GetParticleType() != "nucleus") {
131    InitialiseElementSelectors(p,cuts);
132  }
133}
134
135//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
136
137void G4eCoulombScatteringModel::ComputeMaxElectronScattering(G4double cutEnergy)
138{
139  ecut = cutEnergy;
140  G4double tmax = tkin;
141  cosTetMaxElec = 1.0;
142  if(mass > MeV) {
143    G4double ratio = electron_mass_c2/mass;
144    G4double tau = tkin/mass;
145    tmax = 2.0*electron_mass_c2*tau*(tau + 2.)/
146      (1.0 + 2.0*ratio*(tau + 1.0) + ratio*ratio); 
147    cosTetMaxElec = 1.0 - std::min(cutEnergy, tmax)*electron_mass_c2/mom2;
148  } else {
149
150    if(particle == theElectron) tmax *= 0.5;
151    G4double t = std::min(cutEnergy, tmax);
152    G4double mom21 = t*(t + 2.0*electron_mass_c2);
153    G4double t1 = tkin - t;
154    //G4cout << "tkin= " << tkin << " t= " << t << " t1= " << t1 << G4endl;
155    if(t1 > 0.0) {
156      G4double mom22 = t1*(t1 + 2.0*mass);
157      G4double ctm = (mom2 + mom22 - mom21)*0.5/sqrt(mom2*mom22);
158      //G4cout << "ctm= " << ctm << G4endl;
159      if(ctm < 1.0) cosTetMaxElec = ctm;
160    }
161  }
162}
163
164//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
165
166G4double G4eCoulombScatteringModel::ComputeCrossSectionPerAtom(
167                const G4ParticleDefinition* p,
168                G4double kinEnergy,
169                G4double Z, G4double,
170                G4double cutEnergy, G4double)
171{
172  //G4cout << "### G4eCoulombScatteringModel::ComputeCrossSectionPerAtom  for "
173  //  << p->GetParticleName()<<" Z= "<<Z<<" e(MeV)= "<< kinEnergy/MeV << G4endl;
174  G4double xsec = 0.0;
175  SetupParticle(p);
176  G4double ekin = std::max(lowEnergyLimit, kinEnergy);
177  SetupKinematic(ekin, cutEnergy);
178  if(cosTetMaxNuc < cosTetMinNuc) {
179    SetupTarget(Z, ekin);
180    xsec = CrossSectionPerAtom(); 
181  }
182  /*
183  G4cout << "e(MeV)= " << ekin/MeV << "cosTetMinNuc= " << cosTetMinNuc
184         << " cosTetMaxNuc= " << cosTetMaxNuc
185         << " cosTetMaxElec= " << cosTetMaxElec
186         << " screenZ= " << screenZ
187         << " formfactA= " << formfactA
188         << " cosTetMaxHad= " << cosTetMaxHad << G4endl;
189  */
190  return xsec; 
191}
192
193//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
194
195G4double G4eCoulombScatteringModel::CrossSectionPerAtom()
196{
197  // This method needs initialisation before be called
198
199  G4double fac = coeff*targetZ*chargeSquare*invbeta2/mom2; 
200  elecXSection = 0.0;
201  nucXSection  = 0.0;
202
203  G4double x  = 1.0 - cosTetMinNuc;
204  G4double x1 = x + screenZ;
205
206  if(cosTetMaxElec2 < cosTetMinNuc) {
207    elecXSection = fac*(cosTetMinNuc - cosTetMaxElec2)/
208      (x1*(1.0 - cosTetMaxElec2 + screenZ));
209    nucXSection  = elecXSection;
210  }
211
212  //G4cout << "XS tkin(MeV)= " << tkin<<" xs= " <<nucXSection
213  //     << " costmax= " << cosTetMaxNuc2
214  //     << " costmin= " << cosTetMinNuc << "  Z= " << targetZ <<G4endl;
215  if(cosTetMaxNuc2 < cosTetMinNuc) {
216    G4double s  = screenZ*formfactA;
217    G4double z1 = 1.0 - cosTetMaxNuc2 + screenZ;
218    G4double d  = (1.0 - s)/formfactA;
219    //G4cout <<"x1= "<<x1<<" z1= " <<z1<<" s= "<<s << " d= " <<d <<G4endl;
220    if(d < 0.2*x1) {
221      G4double x2 = x1*x1;
222      G4double z2 = z1*z1;
223      x = (1.0/(x1*x2) - 1.0/(z1*z2) - d*1.5*(1.0/(x2*x2) - 1.0/(z2*z2)))/
224        (3.0*formfactA*formfactA);
225    } else {
226      G4double x2 = x1 + d;
227      G4double z2 = z1 + d;
228      x = (1.0 + 2.0*s)*((cosTetMinNuc - cosTetMaxNuc2)*(1.0/(x1*z1) + 1.0/(x2*z2)) -
229                         2.0*log(z1*x2/(z2*x1))/d);
230    }
231    nucXSection += fac*targetZ*x;
232  }
233
234  //G4cout<<" cross(bn)= "<<nucXSection/barn<<" xsElec(bn)= "<<elecXSection/barn
235  //    << " Asc= " << screenZ << G4endl;
236 
237  return nucXSection;
238}
239
240//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
241
242void G4eCoulombScatteringModel::SampleSecondaries(
243                std::vector<G4DynamicParticle*>* fvect,
244                const G4MaterialCutsCouple* couple,
245                const G4DynamicParticle* dp,
246                G4double cutEnergy,
247                G4double)
248{
249  G4double kinEnergy = dp->GetKineticEnergy();
250  if(kinEnergy <= DBL_MIN) return;
251  DefineMaterial(couple);
252  SetupParticle(dp->GetDefinition());
253  G4double ekin = std::max(lowEnergyLimit, kinEnergy);
254  SetupKinematic(ekin, cutEnergy);
255  //G4cout << "G4eCoulombScatteringModel::SampleSecondaries e(MeV)= "
256  //     << kinEnergy << "  " << particle->GetParticleName() << G4endl;
257 
258  // Choose nucleus
259  currentElement = SelectRandomAtom(couple,particle,ekin,cutEnergy,ekin);
260
261  SetupTarget(currentElement->GetZ(),ekin);
262 
263  G4double cost = SampleCosineTheta();
264  G4double z1   = 1.0 - cost;
265  if(z1 < 0.0) return;
266
267  G4double sint = sqrt(z1*(1.0 + cost));
268 
269  //G4cout<<"## Sampled sint= " << sint << "  Z= " << targetZ
270  //    << "  screenZ= " << screenZ << " cn= " << formfactA << G4endl;
271 
272  G4double phi  = twopi * G4UniformRand();
273
274  G4ThreeVector direction = dp->GetMomentumDirection(); 
275  G4ThreeVector newDirection(cos(phi)*sint,sin(phi)*sint,cost);
276  newDirection.rotateUz(direction);   
277
278  fParticleChange->ProposeMomentumDirection(newDirection);   
279
280  // recoil sampling assuming a small recoil
281  // and first order correction to primary 4-momentum
282  if(lowEnergyLimit < kinEnergy) {
283    G4int ia = SelectIsotopeNumber(currentElement);
284    G4double Trec = z1*mom2/(amu_c2*G4double(ia));
285    G4double th = 
286      std::min(recoilThreshold,
287               targetZ*currentElement->GetIonisation()->GetMeanExcitationEnergy());
288
289    if(Trec > th) {
290      G4int iz = G4int(targetZ);
291      G4ParticleDefinition* ion = theParticleTable->FindIon(iz, ia, 0, iz);
292      Trec = z1*mom2/ion->GetPDGMass();
293      if(Trec < kinEnergy) {
294        G4ThreeVector dir = (direction - newDirection).unit();
295        G4DynamicParticle* newdp = new G4DynamicParticle(ion, dir, Trec);
296        fvect->push_back(newdp);
297        fParticleChange->SetProposedKineticEnergy(kinEnergy - Trec);
298      }
299    }
300  }
301 
302  return;
303}
304
305//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
306
307G4double G4eCoulombScatteringModel::SampleCosineTheta()
308{
309  G4double costm = cosTetMaxNuc2;
310  G4double formf = formfactA;
311  G4double prob  = 0.0; 
312  G4double xs = CrossSectionPerAtom();
313  if(xs > 0.0) prob = elecXSection/xs;
314
315  // scattering off e or A?
316  if(G4UniformRand() < prob) {
317    costm = cosTetMaxElec2;
318    formf = 0.0;
319  }
320
321  /*
322  G4cout << "SampleCost: e(MeV)= " << tkin
323         << " ctmin= " << cosThetaMin
324         << " ctmaxN= " << cosTetMaxNuc
325         << " ctmax= " << costm
326         << " Z= " << targetZ << " A= " << targetA
327         << G4endl;
328  */
329  if(costm >= cosTetMinNuc) return 2.0; 
330
331  G4double x1 = 1. - cosTetMinNuc + screenZ;
332  G4double x2 = 1. - costm + screenZ;
333  G4double x3 = cosTetMinNuc - costm;
334  G4double grej, z1; 
335  do {
336    z1 = x1*x2/(x1 + G4UniformRand()*x3) - screenZ;
337    grej = 1.0/(1.0 + formf*z1);
338  } while ( G4UniformRand() > grej*grej ); 
339
340  //G4cout << "z= " << z1 << " cross= " << nucXSection/barn
341  // << " crossE= " << elecXSection/barn << G4endl;
342
343  return 1.0 - z1;
344}
345
346//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
347
348
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