source: trunk/source/processes/electromagnetic/lowenergy/src/G4LivermoreComptonModel.cc @ 1050

Last change on this file since 1050 was 1007, checked in by garnier, 15 years ago

update to geant4.9.2
File size: 12.8 KB
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26// $Id: G4LivermoreComptonModel.cc,v 1.1 2008/10/30 14:17:46 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-02 $
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)
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  delete meanFreePathTable;
68  delete crossSectionHandler;
69  delete scatterFunctionData;
70}
71
72//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
73
74void G4LivermoreComptonModel::Initialise(const G4ParticleDefinition* particle,
75                                       const G4DataVector& cuts)
76{
77  if (verboseLevel > 3)
78    G4cout << "Calling G4LivermoreComptonModel::Initialise()" << G4endl;
79
80  InitialiseElementSelectors(particle,cuts);
81
82  // Energy limits
83 
84  if (LowEnergyLimit() < lowEnergyLimit)
85    {
86      G4cout << "G4LivermoreComptonModel: low energy limit increased from " << 
87        LowEnergyLimit()/eV << " eV to " << lowEnergyLimit << " eV" << G4endl;
88      SetLowEnergyLimit(lowEnergyLimit);
89    }
90
91  if (HighEnergyLimit() > highEnergyLimit)
92    {
93      G4cout << "G4LivermoreComptonModel: high energy limit decreased from " << 
94        HighEnergyLimit()/GeV << " GeV to " << highEnergyLimit << " GeV" << G4endl;
95      SetHighEnergyLimit(highEnergyLimit);
96    }
97
98  // Reading of data files - all materials are read
99 
100  crossSectionHandler = new G4CrossSectionHandler;
101  crossSectionHandler->Clear();
102  G4String crossSectionFile = "comp/ce-cs-";
103  crossSectionHandler->LoadData(crossSectionFile);
104
105  G4VDataSetAlgorithm* scatterInterpolation = new G4LogLogInterpolation;
106  G4String scatterFile = "comp/ce-sf-";
107  scatterFunctionData = new G4CompositeEMDataSet(scatterInterpolation, 1., 1.);
108  scatterFunctionData->LoadData(scatterFile);
109
110  // For Doppler broadening
111  shellData.SetOccupancyData();
112  G4String file = "/doppler/shell-doppler";
113  shellData.LoadData(file);
114
115  meanFreePathTable = 0;
116  meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
117 
118  if (verboseLevel > 2) 
119    G4cout << "Loaded cross section files for Livermore Compton model" << G4endl;
120
121  G4cout << "Livermore Compton model is initialized " << G4endl
122         << "Energy range: "
123         << LowEnergyLimit() / keV << " keV - "
124         << HighEnergyLimit() / GeV << " GeV"
125         << G4endl;
126
127  //
128 
129  if(isInitialised) return;
130
131  if(pParticleChange)
132    fParticleChange = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
133  else
134    fParticleChange = new G4ParticleChangeForGamma();
135   
136  isInitialised = true;
137}
138
139//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
140
141G4double G4LivermoreComptonModel::ComputeCrossSectionPerAtom(
142                                       const G4ParticleDefinition*,
143                                             G4double GammaEnergy,
144                                             G4double Z, G4double,
145                                             G4double, G4double)
146{
147  if (verboseLevel > 3)
148    G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreComptonModel" << G4endl;
149
150  G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
151  return cs;
152}
153
154//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
155
156void G4LivermoreComptonModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
157                                              const G4MaterialCutsCouple* couple,
158                                              const G4DynamicParticle* aDynamicGamma,
159                                              G4double,
160                                              G4double)
161{
162  // The scattered gamma energy is sampled according to Klein - Nishina formula.
163  // then accepted or rejected depending on the Scattering Function multiplied
164  // by factor from Klein - Nishina formula.
165  // Expression of the angular distribution as Klein Nishina
166  // angular and energy distribution and Scattering fuctions is taken from
167  // D. E. Cullen "A simple model of photon transport" Nucl. Instr. Meth.
168  // Phys. Res. B 101 (1995). Method of sampling with form factors is different
169  // data are interpolated while in the article they are fitted.
170  // Reference to the article is from J. Stepanek New Photon, Positron
171  // and Electron Interaction Data for GEANT in Energy Range from 1 eV to 10
172  // TeV (draft).
173  // The random number techniques of Butcher & Messel are used
174  // (Nucl Phys 20(1960),15).
175
176  if (verboseLevel > 3)
177    G4cout << "Calling SampleSecondaries() of G4LivermoreComptonModel" << G4endl;
178
179  G4double photonEnergy0 = aDynamicGamma->GetKineticEnergy();
180 
181  if (photonEnergy0 <= lowEnergyLimit)
182  {
183      fParticleChange->ProposeTrackStatus(fStopAndKill);
184      fParticleChange->SetProposedKineticEnergy(0.);
185      fParticleChange->ProposeLocalEnergyDeposit(photonEnergy0);
186      // SI - IS THE FOLLOWING RETURN NECESSARY ?
187      return ;
188  }
189
190  G4double e0m = photonEnergy0 / electron_mass_c2 ;
191  G4ParticleMomentum photonDirection0 = aDynamicGamma->GetMomentumDirection();
192
193  // Select randomly one element in the current material
194  G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0);
195
196  G4double epsilon0 = 1. / (1. + 2. * e0m);
197  G4double epsilon0Sq = epsilon0 * epsilon0;
198  G4double alpha1 = -std::log(epsilon0);
199  G4double alpha2 = 0.5 * (1. - epsilon0Sq);
200
201  G4double wlPhoton = h_Planck*c_light/photonEnergy0;
202
203  // Sample the energy of the scattered photon
204  G4double epsilon;
205  G4double epsilonSq;
206  G4double oneCosT;
207  G4double sinT2;
208  G4double gReject;
209 
210  do
211  {
212      if ( alpha1/(alpha1+alpha2) > G4UniformRand())
213      {
214        epsilon = std::exp(-alpha1 * G4UniformRand());  // std::pow(epsilon0,G4UniformRand())
215        epsilonSq = epsilon * epsilon;
216      }
217      else
218      {
219        epsilonSq = epsilon0Sq + (1. - epsilon0Sq) * G4UniformRand();
220        epsilon = std::sqrt(epsilonSq);
221      }
222
223      oneCosT = (1. - epsilon) / ( epsilon * e0m);
224      sinT2 = oneCosT * (2. - oneCosT);
225      G4double x = std::sqrt(oneCosT/2.) / (wlPhoton/cm);
226      G4double scatteringFunction = scatterFunctionData->FindValue(x,Z-1);
227      gReject = (1. - epsilon * sinT2 / (1. + epsilonSq)) * scatteringFunction;
228
229  } while(gReject < G4UniformRand()*Z);
230
231  G4double cosTheta = 1. - oneCosT;
232  G4double sinTheta = std::sqrt (sinT2);
233  G4double phi = twopi * G4UniformRand() ;
234  G4double dirx = sinTheta * std::cos(phi);
235  G4double diry = sinTheta * std::sin(phi);
236  G4double dirz = cosTheta ;
237
238  // Doppler broadening -  Method based on:
239  // Y. Namito, S. Ban and H. Hirayama,
240  // "Implementation of the Doppler Broadening of a Compton-Scattered Photon Into the EGS4 Code"
241  // NIM A 349, pp. 489-494, 1994
242 
243  // Maximum number of sampling iterations
244  G4int maxDopplerIterations = 1000;
245  G4double bindingE = 0.;
246  G4double photonEoriginal = epsilon * photonEnergy0;
247  G4double photonE = -1.;
248  G4int iteration = 0;
249  G4double eMax = photonEnergy0;
250  do
251    {
252      iteration++;
253      // Select shell based on shell occupancy
254      G4int shell = shellData.SelectRandomShell(Z);
255      bindingE = shellData.BindingEnergy(Z,shell);
256     
257      eMax = photonEnergy0 - bindingE;
258     
259      // Randomly sample bound electron momentum (memento: the data set is in Atomic Units)
260      G4double pSample = profileData.RandomSelectMomentum(Z,shell);
261      // Rescale from atomic units
262      G4double pDoppler = pSample * fine_structure_const;
263      G4double pDoppler2 = pDoppler * pDoppler;
264      G4double var2 = 1. + oneCosT * e0m;
265      G4double var3 = var2*var2 - pDoppler2;
266      G4double var4 = var2 - pDoppler2 * cosTheta;
267      G4double var = var4*var4 - var3 + pDoppler2 * var3;
268      if (var > 0.)
269        {
270          G4double varSqrt = std::sqrt(var);       
271          G4double scale = photonEnergy0 / var3; 
272          // Random select either root
273          if (G4UniformRand() < 0.5) photonE = (var4 - varSqrt) * scale;               
274          else photonE = (var4 + varSqrt) * scale;
275        } 
276      else
277        {
278          photonE = -1.;
279        }
280   } while ( iteration <= maxDopplerIterations && 
281             (photonE < 0. || photonE > eMax || photonE < eMax*G4UniformRand()) );
282 
283  // End of recalculation of photon energy with Doppler broadening
284  // Revert to original if maximum number of iterations threshold has been reached
285
286  if (iteration >= maxDopplerIterations)
287    {
288      photonE = photonEoriginal;
289      bindingE = 0.;
290    }
291
292  // Update G4VParticleChange for the scattered photon
293
294  G4ThreeVector photonDirection1(dirx,diry,dirz);
295  photonDirection1.rotateUz(photonDirection0);
296  fParticleChange->ProposeMomentumDirection(photonDirection1) ;
297
298  G4double photonEnergy1 = photonE;
299
300  if (photonEnergy1 > 0.)
301  {
302    fParticleChange->SetProposedKineticEnergy(photonEnergy1) ;
303  }
304  else
305  {
306    fParticleChange->SetProposedKineticEnergy(0.) ;
307    fParticleChange->ProposeTrackStatus(fStopAndKill);
308  }
309
310  // Kinematics of the scattered electron
311  G4double eKineticEnergy = photonEnergy0 - photonEnergy1 - bindingE;
312  G4double eTotalEnergy = eKineticEnergy + electron_mass_c2;
313
314  G4double electronE = photonEnergy0 * (1. - epsilon) + electron_mass_c2; 
315  G4double electronP2 = electronE*electronE - electron_mass_c2*electron_mass_c2;
316  G4double sinThetaE = -1.;
317  G4double cosThetaE = 0.;
318  if (electronP2 > 0.)
319    {
320      cosThetaE = (eTotalEnergy + photonEnergy1 )* (1. - epsilon) / std::sqrt(electronP2);
321      sinThetaE = -1. * sqrt(1. - cosThetaE * cosThetaE); 
322    }
323 
324  G4double eDirX = sinThetaE * std::cos(phi);
325  G4double eDirY = sinThetaE * std::sin(phi);
326  G4double eDirZ = cosThetaE;
327
328  G4ThreeVector eDirection(eDirX,eDirY,eDirZ);
329  eDirection.rotateUz(photonDirection0);
330
331// SI - The range test has been removed wrt original G4LowEnergyCompton class
332
333  fParticleChange->ProposeLocalEnergyDeposit(bindingE);
334 
335  G4DynamicParticle* dp = new G4DynamicParticle (G4Electron::Electron(),eDirection,eKineticEnergy) ;
336  fvect->push_back(dp);
337}
338
339//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
340
341G4double G4LivermoreComptonModel::GetMeanFreePath(const G4Track& track,
342                                             G4double, // previousStepSize
343                                             G4ForceCondition*)
344{
345  const G4DynamicParticle* photon = track.GetDynamicParticle();
346  G4double energy = photon->GetKineticEnergy();
347  const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
348  size_t materialIndex = couple->GetIndex();
349
350  G4double meanFreePath;
351  if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
352  else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
353  else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
354  return meanFreePath;
355}
356
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