source: trunk/source/processes/electromagnetic/lowenergy/src/G4PenelopeGammaConversionModel.cc @ 1350

Last change on this file since 1350 was 1347, checked in by garnier, 14 years ago

geant4 tag 9.4
File size: 17.7 KB
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26// $Id: G4PenelopeGammaConversionModel.cc,v 1.7 2010/11/25 09:45:13 pandola Exp $
27// GEANT4 tag $Name: geant4-09-04-ref-00 $
28//
29// Author: Luciano Pandola
30//
31// History:
32// --------
33// 06 Oct 2008   L Pandola    Migration from process to model
34// 17 Apr 2009   V Ivanchenko Cleanup initialisation and generation of secondaries:
35//                  - apply internal high-energy limit only in constructor
36//                  - do not apply low-energy limit (default is 0)
37//                  - do not apply production threshold on level of the model
38// 19 May 2009   L Pandola    Explicitely set to zero pointers deleted in
39//                            Initialise(), since they might be checked later on
40//
41
42#include "G4PenelopeGammaConversionModel.hh"
43#include "G4ParticleDefinition.hh"
44#include "G4MaterialCutsCouple.hh"
45#include "G4ProductionCutsTable.hh"
46#include "G4DynamicParticle.hh"
47#include "G4Element.hh"
48#include "G4Gamma.hh"
49#include "G4Electron.hh"
50#include "G4Positron.hh"
51#include "G4CrossSectionHandler.hh"
52#include "G4VEMDataSet.hh"
53
54//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
55
56
57G4PenelopeGammaConversionModel::G4PenelopeGammaConversionModel(const G4ParticleDefinition*,
58                                             const G4String& nam)
59  :G4VEmModel(nam),fTheScreeningRadii(0),crossSectionHandler(0),isInitialised(false)
60{
61  fIntrinsicLowEnergyLimit = 2.0*electron_mass_c2;
62  fIntrinsicHighEnergyLimit = 100.0*GeV;
63  fSmallEnergy = 1.1*MeV;
64
65  //  SetLowEnergyLimit(fIntrinsicLowEnergyLimit);
66  SetHighEnergyLimit(fIntrinsicHighEnergyLimit);
67  //
68  verboseLevel= 0;
69  // Verbosity scale:
70  // 0 = nothing
71  // 1 = warning for energy non-conservation
72  // 2 = details of energy budget
73  // 3 = calculation of cross sections, file openings, sampling of atoms
74  // 4 = entering in methods
75}
76
77//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
78
79G4PenelopeGammaConversionModel::~G4PenelopeGammaConversionModel()
80{ 
81  if (crossSectionHandler) delete crossSectionHandler;
82  if (fTheScreeningRadii) delete fTheScreeningRadii;
83}
84
85//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
86
87void G4PenelopeGammaConversionModel::Initialise(const G4ParticleDefinition*,
88                                                const G4DataVector& )
89{
90  if (verboseLevel > 3)
91    G4cout << "Calling  G4PenelopeGammaConversionModel::Initialise()" << G4endl;
92
93  //Delete the old cross section handler, if necessary
94  if (crossSectionHandler)
95    {
96      crossSectionHandler->Clear();
97      delete crossSectionHandler;
98      crossSectionHandler = 0;
99    }
100 
101  //Re-initialize cross section handler
102  crossSectionHandler = new G4CrossSectionHandler();
103  crossSectionHandler->Initialise(0,fIntrinsicLowEnergyLimit,HighEnergyLimit(),400);
104  crossSectionHandler->Clear();
105  G4String crossSectionFile = "penelope/pp-cs-pen-";
106  crossSectionHandler->LoadData(crossSectionFile);
107  //This is used to retrieve cross section values later on
108  G4VEMDataSet* emdata =
109    crossSectionHandler->BuildMeanFreePathForMaterials();
110  //The method BuildMeanFreePathForMaterials() is required here only to force
111  //the building of an internal table: the output pointer can be deleted
112  delete emdata;
113
114  if (verboseLevel > 2) 
115    G4cout << "Loaded cross section files for PenelopeGammaConversion" << G4endl;
116
117  if (verboseLevel > 0) { 
118    G4cout << "Penelope Gamma Conversion model is initialized " << G4endl
119           << "Energy range: "
120           << LowEnergyLimit() / MeV << " MeV - "
121           << HighEnergyLimit() / GeV << " GeV"
122           << G4endl;
123  }
124
125  if(isInitialised) return;
126  fParticleChange = GetParticleChangeForGamma();
127  isInitialised = true;
128}
129
130//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
131
132G4double G4PenelopeGammaConversionModel::ComputeCrossSectionPerAtom(
133                                       const G4ParticleDefinition*,
134                                             G4double energy,
135                                             G4double Z, G4double,
136                                             G4double, G4double)
137{
138  //
139  // Penelope model.
140  // Cross section (including triplet production) read from database and managed
141  // through the G4CrossSectionHandler utility. Cross section data are from
142  // M.J. Berger and J.H. Hubbel (XCOM), Report NBSIR 887-3598
143  //
144 
145  if (verboseLevel > 3)
146    G4cout << "Calling ComputeCrossSectionPerAtom() of G4PenelopePhotoElectricModel" << G4endl;
147
148  G4int iZ = (G4int) Z;
149  //  if (!crossSectionHandler) //VI: should not be checked in run time
150  //  {
151  //    G4cout << "G4PenelopeGammaConversionModel::ComputeCrossSectionPerAtom" << G4endl;
152  //    G4cout << "The cross section handler is not correctly initialized" << G4endl;
153  //    G4Exception();
154  //  }
155  G4double cs = crossSectionHandler->FindValue(iZ,energy);
156
157  if (verboseLevel > 2)
158    G4cout << "Gamma conversion cross section at " << energy/MeV << " MeV for Z=" << Z << 
159      " = " << cs/barn << " barn" << G4endl;
160  return cs;
161}
162
163//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
164
165void 
166G4PenelopeGammaConversionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
167                                                  const G4MaterialCutsCouple* couple,
168                                                  const G4DynamicParticle* aDynamicGamma,
169                                                  G4double,
170                                                  G4double)
171{
172  //
173  // Penelope model.
174  // Final state is sampled according to the Bethe-Heitler model with Coulomb
175  // corrections, according to the semi-empirical model of
176  //  J. Baro' et al., Radiat. Phys. Chem. 44 (1994) 531.
177  //
178  // The model uses the high energy Coulomb correction from
179  //  H. Davies et al., Phys. Rev. 93 (1954) 788
180  // and atomic screening radii tabulated from
181  //  J.H. Hubbel et al., J. Phys. Chem. Ref. Data 9 (1980) 1023
182  // for Z= 1 to 92. This managed in this model by the method
183  // GetScreeningRadius().
184  //
185  if (verboseLevel > 3)
186    G4cout << "Calling SamplingSecondaries() of G4PenelopeGammaConversionModel" << G4endl;
187
188  G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
189
190  // Always kill primary
191  fParticleChange->ProposeTrackStatus(fStopAndKill);
192  fParticleChange->SetProposedKineticEnergy(0.);
193
194  if (photonEnergy <= fIntrinsicLowEnergyLimit)
195    {
196      fParticleChange->ProposeLocalEnergyDeposit(photonEnergy);
197      return ;
198    }
199
200  G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
201
202  G4double eps ;
203  G4double eki = electron_mass_c2 / photonEnergy ;
204
205  // Do it fast if photon energy < 1.1 MeV
206  if (photonEnergy < fSmallEnergy )
207    {
208      eps = eki + (1-2*eki) * G4UniformRand();
209    }
210  else
211    {
212      // Select randomly one element in the current material
213      if (verboseLevel > 2)
214        G4cout << "Going to select element in " << couple->GetMaterial()->GetName() << G4endl;
215      //use crossSectionHandler instead of G4EmElementSelector because in this case
216      //the dimension of the table is equal to the dimension of the database
217      //(less interpolation errors)
218      G4int Z_int = crossSectionHandler->SelectRandomAtom(couple,photonEnergy);
219      if (verboseLevel > 2)
220        G4cout << "Selected Z = " << Z_int << G4endl;
221     
222      //Low energy and Coulomb corrections
223      G4double Z=(G4double) Z_int;
224      G4double ZAlpha = Z*fine_structure_const;
225      G4double ScreenRadius = GetScreeningRadius(Z);
226      G4double funct1=0,g0=0;
227      G4double g1min=0,g2min=0;
228      funct1 = 4.0*std::log(ScreenRadius);
229      g0 = funct1-4*CoulombCorrection(ZAlpha)+LowEnergyCorrection(ZAlpha,eki); 
230      G4double bmin = 2*eki*ScreenRadius;
231      std::vector<G4double> ScreenFunctionValues = ScreenFunction(bmin);
232      if (ScreenFunctionValues.size() != 2)
233        {
234          G4cout << "G4PenelopeGammaConversionModel::SampleSecondaries" << G4endl;
235          G4cout << "ScreenFunction did not return 2 values! Something wrong! " << G4endl;
236          G4Exception();
237        }
238      g1min=g0+ScreenFunctionValues[0];
239      g2min=g0+ScreenFunctionValues[1];
240      G4double xr,a1,p1;
241      xr=0.5-eki;
242      a1=(2.0/3.0)*g1min*xr*xr;
243      p1=a1/(a1+g2min);
244
245      //Random sampling of eps
246      G4double rand1,rand2,rand3,b;
247      G4double g1;
248   
249      do{
250        rand1 = G4UniformRand();
251        if (rand1 < p1) {
252          rand2 = 2.0*G4UniformRand()-1.0;
253          if (rand2 < 0) {
254            eps = 0.5 - xr*std::pow(std::abs(rand2),(1./3.));
255          }
256          else
257            {
258              eps = 0.5 + xr*std::pow(rand2,(1./3.));
259            }
260          b = (eki*ScreenRadius)/(2*eps*(1.0-eps));
261          std::vector<G4double> ScreenFunctionSampling = ScreenFunction(b);
262          g1 = g0+ScreenFunctionSampling[0];
263          if (g1 < 0) g1=0;
264          rand3 = G4UniformRand()*g1min;
265        }
266        else
267          {
268            eps = eki+2.0*xr*G4UniformRand();
269            b = (eki*ScreenRadius)/(2*eps*(1.0-eps));
270            std::vector<G4double> ScreenFunctionSampling = ScreenFunction(b);
271            g1 = g0+ScreenFunctionSampling[1];
272            if (g1 < 0) g1=0; 
273            rand3 = G4UniformRand()*g2min;
274          }       
275      } while (rand3>g1);
276    } //End of eps sampling
277
278  G4double electronTotEnergy = eps*photonEnergy;
279  G4double positronTotEnergy = (1.0-eps)*photonEnergy;
280 
281  // Scattered electron (positron) angles. ( Z - axis along the parent photon)
282
283  //electron kinematics
284  G4double costheta_el,costheta_po;
285  G4double phi_el,phi_po;
286  G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ; 
287  costheta_el = G4UniformRand()*2.0-1.0;
288  G4double kk = std::sqrt(electronKineEnergy*(electronKineEnergy+2.*electron_mass_c2));
289  costheta_el = (costheta_el*electronTotEnergy+kk)/(electronTotEnergy+costheta_el*kk);
290  phi_el  = twopi * G4UniformRand() ;
291  G4double dirX_el = std::sqrt(1.-costheta_el*costheta_el) * std::cos(phi_el);
292  G4double dirY_el = std::sqrt(1.-costheta_el*costheta_el) * std::sin(phi_el);
293  G4double dirZ_el = costheta_el;
294
295  //positron kinematics
296  G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
297  costheta_po = G4UniformRand()*2.0-1.0;
298  kk = std::sqrt(positronKineEnergy*(positronKineEnergy+2.*electron_mass_c2));
299  costheta_po = (costheta_po*positronTotEnergy+kk)/(positronTotEnergy+costheta_po*kk);
300  phi_po  = twopi * G4UniformRand() ;
301  G4double dirX_po = std::sqrt(1.-costheta_po*costheta_po) * std::cos(phi_po);
302  G4double dirY_po = std::sqrt(1.-costheta_po*costheta_po) * std::sin(phi_po);
303  G4double dirZ_po = costheta_po;
304
305  // Kinematics of the created pair:
306  // the electron and positron are assumed to have a symetric angular
307  // distribution with respect to the Z axis along the parent photon
308  G4double localEnergyDeposit = 0. ;
309
310  //Generate explicitely the electron in the pair, only if it is > threshold
311  //VI: applying cut here provides inconsistency
312
313  if (electronKineEnergy > 0.0)
314    {
315      G4ThreeVector electronDirection ( dirX_el, dirY_el, dirZ_el);
316      electronDirection.rotateUz(photonDirection);
317      G4DynamicParticle* electron = new G4DynamicParticle (G4Electron::Electron(),
318                                                           electronDirection,
319                                                           electronKineEnergy);
320      fvect->push_back(electron);
321    }
322  else
323    {
324      localEnergyDeposit += electronKineEnergy;
325      electronKineEnergy = 0;
326    }
327
328  //Generate the positron. Real particle in any case, because it will annihilate. If below
329  //threshold, produce it at rest
330  // VI: here there was a bug - positron and electron cuts are different
331  if (positronKineEnergy < 0.0)
332    {
333      localEnergyDeposit += positronKineEnergy;
334      positronKineEnergy = 0; //produce it at rest
335    }
336  G4ThreeVector positronDirection(dirX_po,dirY_po,dirZ_po);
337  positronDirection.rotateUz(photonDirection);
338  G4DynamicParticle* positron = new G4DynamicParticle(G4Positron::Positron(),
339                                                      positronDirection, positronKineEnergy);
340  fvect->push_back(positron);
341
342  //Add rest of energy to the local energy deposit
343  fParticleChange->ProposeLocalEnergyDeposit(localEnergyDeposit);
344 
345  if (verboseLevel > 1)
346    {
347      G4cout << "-----------------------------------------------------------" << G4endl;
348      G4cout << "Energy balance from G4PenelopeGammaConversion" << G4endl;
349      G4cout << "Incoming photon energy: " << photonEnergy/keV << " keV" << G4endl;
350      G4cout << "-----------------------------------------------------------" << G4endl;
351      if (electronKineEnergy)
352        G4cout << "Electron (explicitely produced) " << electronKineEnergy/keV << " keV" 
353               << G4endl;
354      if (positronKineEnergy)
355        G4cout << "Positron (not at rest) " << positronKineEnergy/keV << " keV" << G4endl;
356      G4cout << "Rest masses of e+/- " << 2.0*electron_mass_c2/keV << " keV" << G4endl;
357      if (localEnergyDeposit)
358        G4cout << "Local energy deposit " << localEnergyDeposit/keV << " keV" << G4endl;
359      G4cout << "Total final state: " << (electronKineEnergy+positronKineEnergy+
360                                          localEnergyDeposit+2.0*electron_mass_c2)/keV <<
361        " keV" << G4endl;
362      G4cout << "-----------------------------------------------------------" << G4endl;
363    }
364 if (verboseLevel > 0)
365    {
366      G4double energyDiff = std::fabs(electronKineEnergy+positronKineEnergy+
367                                      localEnergyDeposit+2.0*electron_mass_c2-photonEnergy);
368      if (energyDiff > 0.05*keV)
369        G4cout << "Warning from G4PenelopeGammaConversion: problem with energy conservation: " 
370               << (electronKineEnergy+positronKineEnergy+
371                   localEnergyDeposit+2.0*electron_mass_c2)/keV
372               << " keV (final) vs. " << photonEnergy/keV << " keV (initial)" << G4endl;
373    } 
374}
375
376//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
377
378std::vector<G4double> G4PenelopeGammaConversionModel::ScreenFunction(G4double b)
379{
380  std::vector<G4double> result;
381  result.clear();
382  G4double bsquare=b*b;
383  G4double a0,f1,f2;
384  f1=2.0-2*std::log(1+bsquare);
385  f2=f1-(2.0/3.0);
386  if (b < 1.0e-10)
387    {
388      f1=f1-twopi*b;
389    }
390  else
391    {
392      a0 = 4*b*std::atan(1.0/b);
393      f1 = f1 - a0;
394      f2 = f2+2*bsquare*(4.0-a0-3*std::log((1+bsquare)/bsquare));
395    }
396  result.push_back(0.5*(3*f1-f2));
397  result.push_back(0.25*(3*f1+f2));
398  return result;
399}
400
401//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
402
403G4double G4PenelopeGammaConversionModel::GetScreeningRadius(G4double Z)
404{
405  G4double result = 0;
406  G4bool foundElement = false;
407  G4int iZ = (G4int) Z;
408  if (!fTheScreeningRadii)
409    fTheScreeningRadii = new std::map<G4int,G4double>;
410 
411  if (fTheScreeningRadii->count(iZ))
412    {
413      //The element is already loaded: just return it
414      result = fTheScreeningRadii->find(iZ)->second;
415      return result;
416    }
417  else //retrieve all from file
418    {
419      char* path = getenv("G4LEDATA");
420      if (!path)
421        {
422          G4String excep = "G4PenelopeGammaConversionModel - G4LEDATA environment variable not set!";
423          G4Exception(excep);
424          return result;
425        }
426      G4String pathString(path);
427      G4String pathFile = pathString + "/penelope/pp-pen.dat";
428      std::ifstream file(pathFile);
429     
430      if (!(file.is_open()))
431        {
432          G4String excep = "G4PenelopeGammaConversionModel - data file " + pathFile + "not found!";
433          G4Exception(excep);
434        }
435      G4int k;
436      G4double a1,a2;
437      while(!file.eof()) {
438        file >> k >> a1 >> a2;
439        fTheScreeningRadii->insert(std::make_pair(k,a1));
440        if ((G4double) k == Z)
441          {
442            result = a1;
443            foundElement = true;
444          }
445      }
446      file.close();
447      if (verboseLevel > 2)
448        G4cout << "Read file pp-pen.dat" << G4endl;
449      if (foundElement)
450        return result;
451      else
452        {
453          G4String excep = "G4PenelopeGammaConversionModel - Screening Radius for not found in the data file";
454          G4Exception(excep);
455          return 0;
456        }
457    }
458}
459
460//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
461
462G4double G4PenelopeGammaConversionModel::CoulombCorrection(G4double a)
463{
464  G4double fc=0;
465  G4double b[7] = {0.202059,-0.03693,0.00835,-0.00201,0.00049,-0.00012,0.00003};
466  G4double aSquared = a*a;
467  G4double aFourth = aSquared*aSquared;
468  G4double aEighth = aFourth*aFourth;
469
470  fc = ((1.0/(1.0+a*a))+b[0]+b[1]*aSquared+b[2]*aFourth+b[3]*(aSquared*aFourth)+
471        b[4]*aEighth+b[5]*(aEighth*aSquared)+b[6]*(aEighth*aFourth));
472  fc=aSquared*fc;
473  return fc;
474}
475
476//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
477
478G4double G4PenelopeGammaConversionModel::LowEnergyCorrection(G4double a,G4double eki)
479{
480  G4double f0=0,t=0;
481  G4double b[12] = {-1.744,-12.10,11.18,8.523,73.26,-41.41,-13.52,-121.1,94.41,8.946,62.05,-63.41};
482  t=std::sqrt(2.0*eki);
483  G4double tSq = t*t;
484  f0=(b[0]+b[1]*a+b[2]*a*a)*t+(b[3]+b[4]*a+b[5]*a*a)*(tSq)+(b[6]+b[7]*a+b[8]*a*a)*(tSq*t)+
485    (b[9]+b[10]*a+b[11]*a*a)*(tSq*tSq);
486  return f0;
487
488}
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