source: trunk/source/processes/electromagnetic/lowenergy/src/G4PenelopeGammaConversionModel.cc @ 991

Last change on this file since 991 was 991, checked in by garnier, 15 years ago

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26// $Id: G4PenelopeGammaConversionModel.cc,v 1.2 2008/12/04 14:09:36 pandola Exp $
27// GEANT4 tag $Name: geant4-09-02 $
28//
29// Author: Luciano Pandola
30//
31// History:
32// --------
33// 06 Oct 2008   L Pandola    Migration from process to model
34//
35
36#include "G4PenelopeGammaConversionModel.hh"
37#include "G4ParticleDefinition.hh"
38#include "G4MaterialCutsCouple.hh"
39#include "G4ProductionCutsTable.hh"
40#include "G4DynamicParticle.hh"
41#include "G4Element.hh"
42#include "G4Gamma.hh"
43#include "G4Electron.hh"
44#include "G4Positron.hh"
45#include "G4CrossSectionHandler.hh"
46
47//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
48
49
50G4PenelopeGammaConversionModel::G4PenelopeGammaConversionModel(const G4ParticleDefinition*,
51                                             const G4String& nam)
52  :G4VEmModel(nam),fTheScreeningRadii(0),crossSectionHandler(0),isInitialised(false)
53{
54  fIntrinsicLowEnergyLimit = 2.0*electron_mass_c2;
55  fIntrinsicHighEnergyLimit = 100.0*GeV;
56  fSmallEnergy = 1.1*MeV;
57
58  SetLowEnergyLimit(fIntrinsicLowEnergyLimit);
59  SetHighEnergyLimit(fIntrinsicHighEnergyLimit);
60  //
61  verboseLevel= 0;
62  // Verbosity scale:
63  // 0 = nothing
64  // 1 = warning for energy non-conservation
65  // 2 = details of energy budget
66  // 3 = calculation of cross sections, file openings, sampling of atoms
67  // 4 = entering in methods
68}
69
70//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
71
72G4PenelopeGammaConversionModel::~G4PenelopeGammaConversionModel()
73{ 
74  if (crossSectionHandler) delete crossSectionHandler;
75  if (fTheScreeningRadii) delete fTheScreeningRadii;
76}
77
78//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
79
80void G4PenelopeGammaConversionModel::Initialise(const G4ParticleDefinition*,
81                                                const G4DataVector& )
82{
83  if (verboseLevel > 3)
84    G4cout << "Calling  G4PenelopeGammaConversionModel::Initialise()" << G4endl;
85
86  //Delete the old cross section handler, if necessary
87  if (crossSectionHandler)
88    {
89      crossSectionHandler->Clear();
90      delete crossSectionHandler;
91    }
92 
93  //Check energy limits
94  if (LowEnergyLimit() < fIntrinsicLowEnergyLimit)
95    {
96      G4cout << "G4PenelopeGammaConversionModel: low energy limit increased from " << 
97        LowEnergyLimit()/eV << " eV to " << fIntrinsicLowEnergyLimit/eV << " eV" << G4endl;
98      SetLowEnergyLimit(fIntrinsicLowEnergyLimit);
99    }
100  if (HighEnergyLimit() > fIntrinsicHighEnergyLimit)
101    {
102      G4cout << "G4PenelopeGammaConversionModel: high energy limit decreased from " << 
103        HighEnergyLimit()/GeV << " GeV to " << fIntrinsicHighEnergyLimit/GeV << " GeV" << G4endl;
104      SetHighEnergyLimit(fIntrinsicHighEnergyLimit);
105    }
106
107  //Re-initialize cross section handler
108  crossSectionHandler = new G4CrossSectionHandler();
109  crossSectionHandler->Initialise(0,LowEnergyLimit(),HighEnergyLimit(),400);
110  crossSectionHandler->Clear();
111  G4String crossSectionFile = "penelope/pp-cs-pen-";
112  crossSectionHandler->LoadData(crossSectionFile);
113  //This is used to retrieve cross section values later on
114  crossSectionHandler->BuildMeanFreePathForMaterials();
115
116  if (verboseLevel > 2) 
117    G4cout << "Loaded cross section files for PenelopeGammaConversion" << G4endl;
118
119  G4cout << "Penelope Gamma Conversion model is initialized " << G4endl
120         << "Energy range: "
121         << LowEnergyLimit() / MeV << " MeV - "
122         << HighEnergyLimit() / GeV << " GeV"
123         << G4endl;
124
125  if(isInitialised) return;
126
127  if(pParticleChange)
128    fParticleChange = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
129  else
130    fParticleChange = new G4ParticleChangeForGamma();
131  isInitialised = true;
132}
133
134//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
135
136G4double G4PenelopeGammaConversionModel::ComputeCrossSectionPerAtom(
137                                       const G4ParticleDefinition*,
138                                             G4double energy,
139                                             G4double Z, G4double,
140                                             G4double, G4double)
141{
142  //
143  // Penelope model.
144  // Cross section (including triplet production) read from database and managed
145  // through the G4CrossSectionHandler utility. Cross section data are from
146  // M.J. Berger and J.H. Hubbel (XCOM), Report NBSIR 887-3598
147  //
148 
149  if (verboseLevel > 3)
150    G4cout << "Calling ComputeCrossSectionPerAtom() of G4PenelopePhotoElectricModel" << G4endl;
151
152  G4int iZ = (G4int) Z;
153  if (!crossSectionHandler)
154    {
155      G4cout << "G4PenelopeGammaConversionModel::ComputeCrossSectionPerAtom" << G4endl;
156      G4cout << "The cross section handler is not correctly initialized" << G4endl;
157      G4Exception();
158    }
159  G4double cs = crossSectionHandler->FindValue(iZ,energy);
160
161  if (verboseLevel > 2)
162    G4cout << "Gamma conversion cross section at " << energy/MeV << " MeV for Z=" << Z << 
163      " = " << cs/barn << " barn" << G4endl;
164  return cs;
165}
166
167//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
168
169void G4PenelopeGammaConversionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
170                                              const G4MaterialCutsCouple* couple,
171                                              const G4DynamicParticle* aDynamicGamma,
172                                              G4double,
173                                              G4double)
174{
175  //
176  // Penelope model.
177  // Final state is sampled according to the Bethe-Heitler model with Coulomb
178  // corrections, according to the semi-empirical model of
179  //  J. Baro' et al., Radiat. Phys. Chem. 44 (1994) 531.
180  //
181  // The model uses the high energy Coulomb correction from
182  //  H. Davies et al., Phys. Rev. 93 (1954) 788
183  // and atomic screening radii tabulated from
184  //  J.H. Hubbel et al., J. Phys. Chem. Ref. Data 9 (1980) 1023
185  // for Z= 1 to 92. This managed in this model by the method
186  // GetScreeningRadius().
187  //
188  if (verboseLevel > 3)
189    G4cout << "Calling SamplingSecondaries() of G4PenelopeGammaConversionModel" << G4endl;
190
191  G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
192
193  if (photonEnergy <= LowEnergyLimit())
194  {
195      fParticleChange->ProposeTrackStatus(fStopAndKill);
196      fParticleChange->SetProposedKineticEnergy(0.);
197      fParticleChange->ProposeLocalEnergyDeposit(photonEnergy);
198      return ;
199  }
200
201  G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
202
203  G4double eps ;
204  G4double eki = electron_mass_c2 / photonEnergy ;
205
206  // Do it fast if photon energy < 1.1 MeV
207  if (photonEnergy < fSmallEnergy )
208    {
209      eps = eki + (1-2*eki) * G4UniformRand();
210    }
211  else
212    {
213      // Select randomly one element in the current material
214      if (verboseLevel > 2)
215        G4cout << "Going to select element in " << couple->GetMaterial()->GetName() << G4endl;
216      //use crossSectionHandler instead of G4EmElementSelector because in this case
217      //the dimension of the table is equal to the dimension of the database
218      //(less interpolation errors)
219      G4int Z_int = crossSectionHandler->SelectRandomAtom(couple,photonEnergy);
220      if (verboseLevel > 2)
221        G4cout << "Selected Z = " << Z_int << G4endl;
222     
223      //Low energy and Coulomb corrections
224      G4double Z=(G4double) Z_int;
225      G4double ZAlpha = Z*fine_structure_const;
226      G4double ScreenRadius = GetScreeningRadius(Z);
227      G4double funct1=0,g0=0;
228      G4double g1min=0,g2min=0;
229      funct1 = 4.0*std::log(ScreenRadius);
230      g0 = funct1-4*CoulombCorrection(ZAlpha)+LowEnergyCorrection(ZAlpha,eki); 
231      G4double bmin = 2*eki*ScreenRadius;
232      std::vector<G4double> ScreenFunctionValues = ScreenFunction(bmin);
233      if (ScreenFunctionValues.size() != 2)
234        {
235          G4cout << "G4PenelopeGammaConversionModel::SampleSecondaries" << G4endl;
236          G4cout << "ScreenFunction did not return 2 values! Something wrong! " << G4endl;
237          G4Exception();
238        }
239      g1min=g0+ScreenFunctionValues[0];
240      g2min=g0+ScreenFunctionValues[1];
241      G4double xr,a1,p1;
242      xr=0.5-eki;
243      a1=(2.0/3.0)*g1min*xr*xr;
244      p1=a1/(a1+g2min);
245
246      //Random sampling of eps
247      G4double rand1,rand2,rand3,b;
248      G4double g1;
249   
250      do{
251        rand1 = G4UniformRand();
252        if (rand1 < p1) {
253          rand2 = 2.0*G4UniformRand()-1.0;
254          if (rand2 < 0) {
255            eps = 0.5 - xr*std::pow(std::abs(rand2),(1./3.));
256          }
257          else
258            {
259              eps = 0.5 + xr*std::pow(rand2,(1./3.));
260            }
261          b = (eki*ScreenRadius)/(2*eps*(1.0-eps));
262          std::vector<G4double> ScreenFunctionSampling = ScreenFunction(b);
263          g1 = g0+ScreenFunctionSampling[0];
264          if (g1 < 0) g1=0;
265          rand3 = G4UniformRand()*g1min;
266        }
267        else
268          {
269            eps = eki+2.0*xr*G4UniformRand();
270            b = (eki*ScreenRadius)/(2*eps*(1.0-eps));
271            std::vector<G4double> ScreenFunctionSampling = ScreenFunction(b);
272            g1 = g0+ScreenFunctionSampling[1];
273            if (g1 < 0) g1=0; 
274            rand3 = G4UniformRand()*g2min;
275          }       
276      } while (rand3>g1);
277    } //End of eps sampling
278
279  G4double electronTotEnergy = eps*photonEnergy;
280  G4double positronTotEnergy = (1.0-eps)*photonEnergy;
281 
282  // Scattered electron (positron) angles. ( Z - axis along the parent photon)
283
284  //electron kinematics
285  G4double costheta_el,costheta_po;
286  G4double phi_el,phi_po;
287  G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ; 
288  costheta_el = G4UniformRand()*2.0-1.0;
289  G4double kk = std::sqrt(electronKineEnergy*(electronKineEnergy+2.*electron_mass_c2));
290  costheta_el = (costheta_el*electronTotEnergy+kk)/(electronTotEnergy+costheta_el*kk);
291  phi_el  = twopi * G4UniformRand() ;
292  G4double dirX_el = std::sqrt(1.-costheta_el*costheta_el) * std::cos(phi_el);
293  G4double dirY_el = std::sqrt(1.-costheta_el*costheta_el) * std::sin(phi_el);
294  G4double dirZ_el = costheta_el;
295
296  //positron kinematics
297  G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
298  costheta_po = G4UniformRand()*2.0-1.0;
299  kk = std::sqrt(positronKineEnergy*(positronKineEnergy+2.*electron_mass_c2));
300  costheta_po = (costheta_po*positronTotEnergy+kk)/(positronTotEnergy+costheta_po*kk);
301  phi_po  = twopi * G4UniformRand() ;
302  G4double dirX_po = std::sqrt(1.-costheta_po*costheta_po) * std::cos(phi_po);
303  G4double dirY_po = std::sqrt(1.-costheta_po*costheta_po) * std::sin(phi_po);
304  G4double dirZ_po = costheta_po;
305
306  // Kinematics of the created pair:
307  // the electron and positron are assumed to have a symetric angular
308  // distribution with respect to the Z axis along the parent photon
309  G4double localEnergyDeposit = 0. ;
310
311  //Generate explicitely the electron in the pair, only if it is > threshold
312  const G4ProductionCutsTable* theCoupleTable=
313    G4ProductionCutsTable::GetProductionCutsTable();
314  size_t indx = couple->GetIndex();
315  G4double cutE = (*(theCoupleTable->GetEnergyCutsVector(1)))[indx];
316  //G4double cutP = (*(theCoupleTable->GetEnergyCutsVector(2)))[indx];
317
318  if (electronKineEnergy > cutE)
319    {
320      G4ThreeVector electronDirection ( dirX_el, dirY_el, dirZ_el);
321      electronDirection.rotateUz(photonDirection);
322      G4DynamicParticle* electron = new G4DynamicParticle (G4Electron::Electron(),
323                                                           electronDirection,
324                                                           electronKineEnergy);
325      fvect->push_back(electron);
326    }
327  else
328    {
329      localEnergyDeposit += electronKineEnergy;
330      electronKineEnergy = 0;
331    }
332
333  //Generate the positron. Real particle in any case, because it will annihilate. If below
334  //threshold, produce it at rest
335  if (positronKineEnergy < cutE)
336    {
337      localEnergyDeposit += positronKineEnergy;
338      positronKineEnergy = 0; //produce it at rest
339    }
340  G4ThreeVector positronDirection(dirX_po,dirY_po,dirZ_po);
341  positronDirection.rotateUz(photonDirection);
342  G4DynamicParticle* positron = new G4DynamicParticle(G4Positron::Positron(),
343                                                      positronDirection, positronKineEnergy);
344  fvect->push_back(positron);
345
346  //Update the status of the primary gamma (kill it)
347  fParticleChange->SetProposedKineticEnergy(0.);
348  fParticleChange->ProposeLocalEnergyDeposit(localEnergyDeposit);
349  fParticleChange->ProposeTrackStatus(fStopAndKill);
350
351 
352 if (verboseLevel > 1)
353    {
354      G4cout << "-----------------------------------------------------------" << G4endl;
355      G4cout << "Energy balance from G4PenelopeGammaConversion" << G4endl;
356      G4cout << "Incoming photon energy: " << photonEnergy/keV << " keV" << G4endl;
357      G4cout << "-----------------------------------------------------------" << G4endl;
358      if (electronKineEnergy)
359        G4cout << "Electron (explicitely produced) " << electronKineEnergy/keV << " keV" << G4endl;
360      if (positronKineEnergy)
361        G4cout << "Positron (not at rest) " << positronKineEnergy/keV << " keV" << G4endl;
362      G4cout << "Rest masses of e+/- " << 2.0*electron_mass_c2/keV << " keV" << G4endl;
363      if (localEnergyDeposit)
364        G4cout << "Local energy deposit " << localEnergyDeposit/keV << " keV" << G4endl;
365      G4cout << "Total final state: " << (electronKineEnergy+positronKineEnergy+
366                                          localEnergyDeposit+2.0*electron_mass_c2)/keV <<
367        " keV" << G4endl;
368      G4cout << "-----------------------------------------------------------" << G4endl;
369    }
370 if (verboseLevel > 0)
371    {
372      G4double energyDiff = std::fabs(electronKineEnergy+positronKineEnergy+
373                                      localEnergyDeposit+2.0*electron_mass_c2-photonEnergy);
374      if (energyDiff > 0.05*keV)
375        G4cout << "Warning from G4PenelopeGammaConversion: problem with energy conservation: " << 
376          (electronKineEnergy+positronKineEnergy+
377           localEnergyDeposit+2.0*electron_mass_c2)/keV << " keV (final) vs. " << 
378          photonEnergy/keV << " keV (initial)" << G4endl;
379    }
380 
381}
382
383//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
384
385std::vector<G4double> G4PenelopeGammaConversionModel::ScreenFunction(G4double b)
386{
387  std::vector<G4double> result;
388  result.clear();
389  G4double bsquare=b*b;
390  G4double a0,f1,f2;
391  f1=2.0-2*std::log(1+bsquare);
392  f2=f1-(2.0/3.0);
393  if (b < 1.0e-10)
394    {
395      f1=f1-twopi*b;
396    }
397  else
398    {
399      a0 = 4*b*std::atan(1.0/b);
400      f1 = f1 - a0;
401      f2 = f2+2*bsquare*(4.0-a0-3*std::log((1+bsquare)/bsquare));
402    }
403  result.push_back(0.5*(3*f1-f2));
404  result.push_back(0.25*(3*f1+f2));
405  return result;
406}
407
408//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
409
410G4double G4PenelopeGammaConversionModel::GetScreeningRadius(G4double Z)
411{
412  G4double result = 0;
413  G4bool foundElement = false;
414  G4int iZ = (G4int) Z;
415  if (!fTheScreeningRadii)
416    fTheScreeningRadii = new std::map<G4int,G4double>;
417 
418  if (fTheScreeningRadii->count(iZ))
419    {
420      //The element is already loaded: just return it
421      result = fTheScreeningRadii->find(iZ)->second;
422      return result;
423    }
424  else //retrieve all from file
425    {
426      char* path = getenv("G4LEDATA");
427      if (!path)
428        {
429          G4String excep = "G4PenelopeGammaConversionModel - G4LEDATA environment variable not set!";
430          G4Exception(excep);
431        }
432      G4String pathString(path);
433      G4String pathFile = pathString + "/penelope/pp-pen.dat";
434      std::ifstream file(pathFile);
435     
436      if (!(file.is_open()))
437        {
438          G4String excep = "G4PenelopeGammaConversionModel - data file " + pathFile + "not found!";
439          G4Exception(excep);
440        }
441      G4int k;
442      G4double a1,a2;
443      while(!file.eof()) {
444        file >> k >> a1 >> a2;
445        fTheScreeningRadii->insert(std::make_pair(k,a1));
446        if ((G4double) k == Z)
447          {
448            result = a1;
449            foundElement = true;
450          }
451      }
452      file.close();
453      if (verboseLevel > 2)
454        G4cout << "Read file pp-pen.dat" << G4endl;
455      if (foundElement)
456        return result;
457      else
458        {
459          G4String excep = "G4PenelopeGammaConversionModel - Screening Radius for not found in the data file";
460          G4Exception(excep);
461          return 0;
462        }
463    }
464}
465
466//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
467
468G4double G4PenelopeGammaConversionModel::CoulombCorrection(G4double a)
469{
470  G4double fc=0;
471  G4double b[7] = {0.202059,-0.03693,0.00835,-0.00201,0.00049,-0.00012,0.00003};
472  G4double aSquared = a*a;
473  G4double aFourth = aSquared*aSquared;
474  G4double aEighth = aFourth*aFourth;
475
476  fc = ((1.0/(1.0+a*a))+b[0]+b[1]*aSquared+b[2]*aFourth+b[3]*(aSquared*aFourth)+
477        b[4]*aEighth+b[5]*(aEighth*aSquared)+b[6]*(aEighth*aFourth));
478  fc=aSquared*fc;
479  return fc;
480}
481
482//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
483
484G4double G4PenelopeGammaConversionModel::LowEnergyCorrection(G4double a,G4double eki)
485{
486  G4double f0=0,t=0;
487  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};
488  t=std::sqrt(2.0*eki);
489  G4double tSq = t*t;
490  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)+
491    (b[9]+b[10]*a+b[11]*a*a)*(tSq*tSq);
492  return f0;
493
494}
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