source: trunk/source/processes/electromagnetic/lowenergy/src/G4LivermoreComptonModel.cc @ 989

Last change on this file since 989 was 968, checked in by garnier, 15 years ago

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26// $Id: G4LivermoreComptonModel.cc,v 1.2 2009/01/21 10:58:13 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
28//
29
30#include "G4LivermoreComptonModel.hh"
31
32//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
33
34using namespace std;
35
36//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
37
38G4LivermoreComptonModel::G4LivermoreComptonModel(const G4ParticleDefinition*,
39                                             const G4String& nam)
40:G4VEmModel(nam),isInitialised(false),meanFreePathTable(0),scatterFunctionData(0),crossSectionHandler(0)
41{
42  lowEnergyLimit = 250 * eV; // SI - Could be 10 eV ?
43  highEnergyLimit = 100 * GeV;
44  SetLowEnergyLimit(lowEnergyLimit);
45  SetHighEnergyLimit(highEnergyLimit);
46
47  verboseLevel=0 ;
48  // Verbosity scale:
49  // 0 = nothing
50  // 1 = warning for energy non-conservation
51  // 2 = details of energy budget
52  // 3 = calculation of cross sections, file openings, sampling of atoms
53  // 4 = entering in methods
54 
55  G4cout << "Livermore Compton model is constructed " << G4endl
56         << "Energy range: "
57         << lowEnergyLimit / keV << " keV - "
58         << highEnergyLimit / GeV << " GeV"
59         << G4endl;
60 
61}
62
63//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
64
65G4LivermoreComptonModel::~G4LivermoreComptonModel()
66{ 
67
68  if (meanFreePathTable)   delete meanFreePathTable;
69  if (crossSectionHandler) delete crossSectionHandler;
70  if (scatterFunctionData) delete scatterFunctionData;
71
72}
73
74//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
75
76void G4LivermoreComptonModel::Initialise(const G4ParticleDefinition* particle,
77                                       const G4DataVector& cuts)
78{
79
80  if (verboseLevel > 3)
81    G4cout << "Calling G4LivermoreComptonModel::Initialise()" << G4endl;
82
83  if (crossSectionHandler)
84  {
85    crossSectionHandler->Clear();
86    delete crossSectionHandler;
87  }
88 
89  // Energy limits
90 
91  if (LowEnergyLimit() < lowEnergyLimit)
92    {
93      G4cout << "G4LivermoreComptonModel: low energy limit increased from " << 
94        LowEnergyLimit()/eV << " eV to " << lowEnergyLimit << " eV" << G4endl;
95      SetLowEnergyLimit(lowEnergyLimit);
96    }
97
98  if (HighEnergyLimit() > highEnergyLimit)
99    {
100      G4cout << "G4LivermoreComptonModel: high energy limit decreased from " << 
101        HighEnergyLimit()/GeV << " GeV to " << highEnergyLimit << " GeV" << G4endl;
102      SetHighEnergyLimit(highEnergyLimit);
103    }
104
105  // Reading of data files - all materials are read
106 
107  crossSectionHandler = new G4CrossSectionHandler;
108  crossSectionHandler->Clear();
109  G4String crossSectionFile = "comp/ce-cs-";
110  crossSectionHandler->LoadData(crossSectionFile);
111
112  G4VDataSetAlgorithm* scatterInterpolation = new G4LogLogInterpolation;
113  G4String scatterFile = "comp/ce-sf-";
114  scatterFunctionData = new G4CompositeEMDataSet(scatterInterpolation, 1., 1.);
115  scatterFunctionData->LoadData(scatterFile);
116
117  // For Doppler broadening
118  shellData.SetOccupancyData();
119  G4String file = "/doppler/shell-doppler";
120  shellData.LoadData(file);
121
122  meanFreePathTable = 0;
123  meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
124 
125  if (verboseLevel > 2) 
126    G4cout << "Loaded cross section files for Livermore Compton model" << G4endl;
127
128  InitialiseElementSelectors(particle,cuts);
129
130  G4cout << "Livermore Compton model is initialized " << G4endl
131         << "Energy range: "
132         << LowEnergyLimit() / keV << " keV - "
133         << HighEnergyLimit() / GeV << " GeV"
134         << G4endl;
135
136  //
137 
138  if(isInitialised) return;
139
140  if(pParticleChange)
141    fParticleChange = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
142  else
143    fParticleChange = new G4ParticleChangeForGamma();
144   
145  isInitialised = true;
146
147}
148
149//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
150
151G4double G4LivermoreComptonModel::ComputeCrossSectionPerAtom(
152                                       const G4ParticleDefinition*,
153                                             G4double GammaEnergy,
154                                             G4double Z, G4double,
155                                             G4double, G4double)
156{
157
158  if (verboseLevel > 3)
159    G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreComptonModel" << G4endl;
160
161  G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
162 
163  return cs;
164
165}
166
167//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
168
169void G4LivermoreComptonModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
170                                              const G4MaterialCutsCouple* couple,
171                                              const G4DynamicParticle* aDynamicGamma,
172                                              G4double,
173                                              G4double)
174{
175
176  // The scattered gamma energy is sampled according to Klein - Nishina formula.
177  // then accepted or rejected depending on the Scattering Function multiplied
178  // by factor from Klein - Nishina formula.
179  // Expression of the angular distribution as Klein Nishina
180  // angular and energy distribution and Scattering fuctions is taken from
181  // D. E. Cullen "A simple model of photon transport" Nucl. Instr. Meth.
182  // Phys. Res. B 101 (1995). Method of sampling with form factors is different
183  // data are interpolated while in the article they are fitted.
184  // Reference to the article is from J. Stepanek New Photon, Positron
185  // and Electron Interaction Data for GEANT in Energy Range from 1 eV to 10
186  // TeV (draft).
187  // The random number techniques of Butcher & Messel are used
188  // (Nucl Phys 20(1960),15).
189
190  if (verboseLevel > 3)
191    G4cout << "Calling SampleSecondaries() of G4LivermoreComptonModel" << G4endl;
192
193  G4double photonEnergy0 = aDynamicGamma->GetKineticEnergy();
194 
195  if (photonEnergy0 <= lowEnergyLimit)
196  {
197      fParticleChange->ProposeTrackStatus(fStopAndKill);
198      fParticleChange->SetProposedKineticEnergy(0.);
199      fParticleChange->ProposeLocalEnergyDeposit(photonEnergy0);
200      return ;
201  }
202
203  G4double e0m = photonEnergy0 / electron_mass_c2 ;
204  G4ParticleMomentum photonDirection0 = aDynamicGamma->GetMomentumDirection();
205
206  // Select randomly one element in the current material
207  G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0);
208
209  G4double epsilon0 = 1. / (1. + 2. * e0m);
210  G4double epsilon0Sq = epsilon0 * epsilon0;
211  G4double alpha1 = -std::log(epsilon0);
212  G4double alpha2 = 0.5 * (1. - epsilon0Sq);
213
214  G4double wlPhoton = h_Planck*c_light/photonEnergy0;
215
216  // Sample the energy of the scattered photon
217  G4double epsilon;
218  G4double epsilonSq;
219  G4double oneCosT;
220  G4double sinT2;
221  G4double gReject;
222 
223  do
224  {
225      if ( alpha1/(alpha1+alpha2) > G4UniformRand())
226      {
227        epsilon = std::exp(-alpha1 * G4UniformRand());  // std::pow(epsilon0,G4UniformRand())
228        epsilonSq = epsilon * epsilon;
229      }
230      else
231      {
232        epsilonSq = epsilon0Sq + (1. - epsilon0Sq) * G4UniformRand();
233        epsilon = std::sqrt(epsilonSq);
234      }
235
236      oneCosT = (1. - epsilon) / ( epsilon * e0m);
237      sinT2 = oneCosT * (2. - oneCosT);
238      G4double x = std::sqrt(oneCosT/2.) / (wlPhoton/cm);
239      G4double scatteringFunction = scatterFunctionData->FindValue(x,Z-1);
240      gReject = (1. - epsilon * sinT2 / (1. + epsilonSq)) * scatteringFunction;
241
242  } while(gReject < G4UniformRand()*Z);
243
244  G4double cosTheta = 1. - oneCosT;
245  G4double sinTheta = std::sqrt (sinT2);
246  G4double phi = twopi * G4UniformRand() ;
247  G4double dirx = sinTheta * std::cos(phi);
248  G4double diry = sinTheta * std::sin(phi);
249  G4double dirz = cosTheta ;
250
251  // Doppler broadening -  Method based on:
252  // Y. Namito, S. Ban and H. Hirayama,
253  // "Implementation of the Doppler Broadening of a Compton-Scattered Photon Into the EGS4 Code"
254  // NIM A 349, pp. 489-494, 1994
255 
256  // Maximum number of sampling iterations
257  G4int maxDopplerIterations = 1000;
258  G4double bindingE = 0.;
259  G4double photonEoriginal = epsilon * photonEnergy0;
260  G4double photonE = -1.;
261  G4int iteration = 0;
262  G4double eMax = photonEnergy0;
263  do
264    {
265      iteration++;
266      // Select shell based on shell occupancy
267      G4int shell = shellData.SelectRandomShell(Z);
268      bindingE = shellData.BindingEnergy(Z,shell);
269     
270      eMax = photonEnergy0 - bindingE;
271     
272      // Randomly sample bound electron momentum (memento: the data set is in Atomic Units)
273      G4double pSample = profileData.RandomSelectMomentum(Z,shell);
274      // Rescale from atomic units
275      G4double pDoppler = pSample * fine_structure_const;
276      G4double pDoppler2 = pDoppler * pDoppler;
277      G4double var2 = 1. + oneCosT * e0m;
278      G4double var3 = var2*var2 - pDoppler2;
279      G4double var4 = var2 - pDoppler2 * cosTheta;
280      G4double var = var4*var4 - var3 + pDoppler2 * var3;
281      if (var > 0.)
282        {
283          G4double varSqrt = std::sqrt(var);       
284          G4double scale = photonEnergy0 / var3; 
285          // Random select either root
286          if (G4UniformRand() < 0.5) photonE = (var4 - varSqrt) * scale;               
287          else photonE = (var4 + varSqrt) * scale;
288        } 
289      else
290        {
291          photonE = -1.;
292        }
293   } while ( iteration <= maxDopplerIterations && 
294             (photonE < 0. || photonE > eMax || photonE < eMax*G4UniformRand()) );
295 
296  // End of recalculation of photon energy with Doppler broadening
297  // Revert to original if maximum number of iterations threshold has been reached
298
299  if (iteration >= maxDopplerIterations)
300    {
301      photonE = photonEoriginal;
302      bindingE = 0.;
303    }
304
305  // Update G4VParticleChange for the scattered photon
306
307  G4ThreeVector photonDirection1(dirx,diry,dirz);
308  photonDirection1.rotateUz(photonDirection0);
309  fParticleChange->ProposeMomentumDirection(photonDirection1) ;
310
311  G4double photonEnergy1 = photonE;
312
313  if (photonEnergy1 > 0.)
314  {
315    fParticleChange->SetProposedKineticEnergy(photonEnergy1) ;
316  }
317  else
318  {
319    fParticleChange->SetProposedKineticEnergy(0.) ;
320    fParticleChange->ProposeTrackStatus(fStopAndKill);
321  }
322
323  // Kinematics of the scattered electron
324  G4double eKineticEnergy = photonEnergy0 - photonEnergy1 - bindingE;
325  G4double eTotalEnergy = eKineticEnergy + electron_mass_c2;
326
327  G4double electronE = photonEnergy0 * (1. - epsilon) + electron_mass_c2; 
328  G4double electronP2 = electronE*electronE - electron_mass_c2*electron_mass_c2;
329  G4double sinThetaE = -1.;
330  G4double cosThetaE = 0.;
331  if (electronP2 > 0.)
332    {
333      cosThetaE = (eTotalEnergy + photonEnergy1 )* (1. - epsilon) / std::sqrt(electronP2);
334      sinThetaE = -1. * sqrt(1. - cosThetaE * cosThetaE); 
335    }
336 
337  G4double eDirX = sinThetaE * std::cos(phi);
338  G4double eDirY = sinThetaE * std::sin(phi);
339  G4double eDirZ = cosThetaE;
340
341  G4ThreeVector eDirection(eDirX,eDirY,eDirZ);
342  eDirection.rotateUz(photonDirection0);
343
344// SI - The range test has been removed wrt original G4LowEnergyCompton class
345
346  fParticleChange->ProposeLocalEnergyDeposit(bindingE);
347 
348  G4DynamicParticle* dp = new G4DynamicParticle (G4Electron::Electron(),eDirection,eKineticEnergy) ;
349  fvect->push_back(dp);
350
351}
352
353//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
354
355G4double G4LivermoreComptonModel::GetMeanFreePath(const G4Track& track,
356                                             G4double, // previousStepSize
357                                             G4ForceCondition*)
358{
359  const G4DynamicParticle* photon = track.GetDynamicParticle();
360  G4double energy = photon->GetKineticEnergy();
361  const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
362  size_t materialIndex = couple->GetIndex();
363
364  G4double meanFreePath;
365  if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
366  else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
367  else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
368  return meanFreePath;
369}
370
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