source: trunk/source/processes/electromagnetic/lowenergy/src/G4PenelopeGammaConversion.cc

Last change on this file was 1055, checked in by garnier, 15 years ago

maj sur la beta de geant 4.9.3
File size: 13.5 KB
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26// --------------------------------------------------------------------
27//
28//
29//
30// --------------------------------------------------------------
31//
32// Author: L.Pandola
33// History:
34// --------
35// 02 Dec 2002 L.Pandola    1st implementation
36// 12 Feb 2003   MG Pia     Migration to "cuts per region"
37// 10 Mar 2003 V.Ivanchenko Remove CutPerMaterial warning
38// 13 Mar 2003 L.Pandola    Code "cleaned"
39// 25 Mar 2003 L.Pandola    Changed the name of the database file to read
40// 24 Apr 2003 V.Ivanchenko Cut per region mfpt
41// 17 Mar 2004 L.Pandola    Removed unnecessary calls to std::pow(a,b)
42// --------------------------------------------------------------
43
44#include "G4PenelopeGammaConversion.hh"
45
46#include "Randomize.hh"
47#include "G4ParticleDefinition.hh"
48#include "G4Track.hh"
49#include "G4Step.hh"
50#include "G4ForceCondition.hh"
51#include "G4Gamma.hh"
52#include "G4Electron.hh"
53#include "G4DynamicParticle.hh"
54#include "G4VParticleChange.hh"
55#include "G4ThreeVector.hh"
56#include "G4Positron.hh"
57#include "G4IonisParamElm.hh"
58#include "G4Material.hh"
59#include "G4VCrossSectionHandler.hh"
60#include "G4CrossSectionHandler.hh"
61#include "G4VEMDataSet.hh"
62#include "G4VDataSetAlgorithm.hh"
63#include "G4LogLogInterpolation.hh"
64#include "G4VRangeTest.hh"
65#include "G4RangeTest.hh"
66#include "G4MaterialCutsCouple.hh"
67
68
69G4PenelopeGammaConversion::G4PenelopeGammaConversion(const G4String& processName)
70  : G4VDiscreteProcess(processName),   
71    lowEnergyLimit(1.022000*MeV),
72    highEnergyLimit(100*GeV),
73    intrinsicLowEnergyLimit(1.022000*MeV),
74    intrinsicHighEnergyLimit(100*GeV),
75    smallEnergy(1.1*MeV)
76
77{
78  if (lowEnergyLimit < intrinsicLowEnergyLimit || 
79      highEnergyLimit > intrinsicHighEnergyLimit)
80    {
81      G4Exception("G4PenelopeGammaConversion::G4PenelopeGammaConversion - energy limit outside intrinsic process validity range");
82    }
83
84  // The following pointer is owned by G4DataHandler 
85  crossSectionHandler = new G4CrossSectionHandler();
86  // Log log interpolation (default)
87  crossSectionHandler->Initialise(0,1.0220*MeV,100.*GeV,400);
88  meanFreePathTable = 0;
89  rangeTest = new G4RangeTest;
90
91   if (verboseLevel > 0) 
92     {
93       G4cout << GetProcessName() << " is created " << G4endl
94              << "Energy range: " 
95              << lowEnergyLimit / MeV << " MeV - "
96              << highEnergyLimit / GeV << " GeV" 
97              << G4endl;
98     }
99
100   G4cout << G4endl;
101   G4cout << "*******************************************************************************" << G4endl;
102   G4cout << "*******************************************************************************" << G4endl;
103   G4cout << "   The class G4PenelopeGammaConversion is NOT SUPPORTED ANYMORE. " << G4endl;
104   G4cout << "   It will be REMOVED with the next major release of Geant4. " << G4endl;
105   G4cout << "   Please consult: https://twiki.cern.ch/twiki/bin/view/Geant4/LoweProcesses" << G4endl;
106   G4cout << "*******************************************************************************" << G4endl;
107   G4cout << "*******************************************************************************" << G4endl;
108   G4cout << G4endl;
109}
110 
111G4PenelopeGammaConversion::~G4PenelopeGammaConversion()
112{
113  delete meanFreePathTable;
114  delete crossSectionHandler;
115  delete rangeTest;
116}
117
118void G4PenelopeGammaConversion::BuildPhysicsTable(const G4ParticleDefinition& )
119{
120
121  crossSectionHandler->Clear();
122  G4String crossSectionFile = "penelope/pp-cs-pen-";
123  crossSectionHandler->LoadData(crossSectionFile);
124  delete meanFreePathTable;
125  meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
126}
127
128G4VParticleChange* G4PenelopeGammaConversion::PostStepDoIt(const G4Track& aTrack,
129                                                            const G4Step& aStep)
130{
131  aParticleChange.Initialize(aTrack);
132
133  const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();
134 
135  const G4DynamicParticle* incidentPhoton = aTrack.GetDynamicParticle();
136  G4double photonEnergy = incidentPhoton->GetKineticEnergy();
137  G4ParticleMomentum photonDirection = incidentPhoton->GetMomentumDirection();
138
139  G4double eps ;
140  G4double eki = electron_mass_c2 / photonEnergy ;
141
142  // Do it fast if photon energy < 1.1 MeV
143  if (photonEnergy < smallEnergy )
144    {
145      eps = eki + (1-2*eki) * G4UniformRand();
146    }
147  else
148    {
149      // Select randomly one element in the current material
150      const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy);
151
152      if (element == 0)
153        {
154          G4cout << "G4PenelopeGammaConversion::PostStepDoIt - element = 0" << G4endl;
155        }
156      G4IonisParamElm* ionisation = element->GetIonisation();
157      if (ionisation == 0) 
158        {
159          G4cout << "G4PenelopeGammaConversion::PostStepDoIt - ionisation = 0" << G4endl;
160        }
161     
162      //Low energy and Coulomb corrections
163      G4double Z=ionisation->GetZ(); 
164      G4double ZAlpha = Z*fine_structure_const;
165      G4double ScreenRadius = GetScreeningRadius(Z);
166      G4double funct1=0,g0=0;
167      G4double g1min=0,g2min=0;
168      funct1 = 4.0*std::log(ScreenRadius);
169      g0 = funct1-4*CoulombCorrection(ZAlpha)+LowEnergyCorrection(ZAlpha,eki); 
170      G4double bmin = 2*eki*ScreenRadius;
171      g1min=g0+ScreenFunction(bmin,1);
172      g2min=g0+ScreenFunction(bmin,2);
173      G4double xr,a1,p1;
174      xr=0.5-eki;
175      a1=(2.0/3.0)*g1min*xr*xr;
176      p1=a1/(a1+g2min);
177
178      //Random sampling of eps
179      G4double rand1,rand2,rand3,b;
180      G4double g1;
181   
182      do{
183        rand1 = G4UniformRand();
184        if (rand1 < p1) {
185          rand2 = 2.0*G4UniformRand()-1.0;
186          if (rand2 < 0) {
187            eps = 0.5 - xr*std::pow(std::abs(rand2),(1./3.));
188          }
189          else
190            {
191              eps = 0.5 + xr*std::pow(rand2,(1./3.));
192            }
193          b = (eki*ScreenRadius)/(2*eps*(1.0-eps));
194          g1 = g0+ScreenFunction(b,1);
195          if (g1 < 0) g1=0;
196          rand3 = G4UniformRand()*g1min;
197        }
198        else
199          {
200            eps = eki+2.0*xr*G4UniformRand();
201            b = (eki*ScreenRadius)/(2*eps*(1.0-eps));
202            g1 = g0+ScreenFunction(b,2); 
203            if (g1 < 0) g1=0; 
204            rand3 = G4UniformRand()*g2min;
205          }       
206      } while (rand3>g1);
207    } //End of eps sampling
208
209  G4double electronTotEnergy;
210  G4double positronTotEnergy;
211
212  electronTotEnergy = eps*photonEnergy;
213  positronTotEnergy = (1.0-eps)*photonEnergy;
214 
215  // Scattered electron (positron) angles. ( Z - axis along the parent photon)
216
217  //electron kinematics
218  G4double costheta_el,costheta_po;
219  G4double phi_el,phi_po;
220  G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ; 
221  costheta_el = G4UniformRand()*2.0-1.0;
222  G4double kk = std::sqrt(electronKineEnergy*(electronKineEnergy+2.*electron_mass_c2));
223  costheta_el = (costheta_el*electronTotEnergy+kk)/(electronTotEnergy+costheta_el*kk);
224  phi_el  = twopi * G4UniformRand() ;
225  G4double dirX_el = std::sqrt(1.-costheta_el*costheta_el) * std::cos(phi_el);
226  G4double dirY_el = std::sqrt(1.-costheta_el*costheta_el) * std::sin(phi_el);
227  G4double dirZ_el = costheta_el;
228
229  //positron kinematics
230  G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
231  costheta_po = G4UniformRand()*2.0-1.0;
232  kk = std::sqrt(positronKineEnergy*(positronKineEnergy+2.*electron_mass_c2));
233  costheta_po = (costheta_po*positronTotEnergy+kk)/(positronTotEnergy+costheta_po*kk);
234  phi_po  = twopi * G4UniformRand() ;
235  G4double dirX_po = std::sqrt(1.-costheta_po*costheta_po) * std::cos(phi_po);
236  G4double dirY_po = std::sqrt(1.-costheta_po*costheta_po) * std::sin(phi_po);
237  G4double dirZ_po = costheta_po;
238
239// Kinematics of the created pair:
240// the electron and positron are assumed to have a symetric angular
241// distribution with respect to the Z axis along the parent photon
242
243  G4double localEnergyDeposit = 0. ;
244
245  aParticleChange.SetNumberOfSecondaries(2) ;
246
247
248  // Generate the electron only if with large enough range w.r.t. cuts and safety
249
250  G4double safety = aStep.GetPostStepPoint()->GetSafety();
251
252  if (rangeTest->Escape(G4Electron::Electron(),couple,electronKineEnergy,safety))
253    {
254      G4ThreeVector electronDirection ( dirX_el, dirY_el, dirZ_el);
255      electronDirection.rotateUz(photonDirection);
256      G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(),
257                                                            electronDirection,
258                                                            electronKineEnergy);
259      aParticleChange.AddSecondary(particle1) ;
260    }
261  else
262    {
263      localEnergyDeposit += electronKineEnergy ;
264    }
265
266
267  if (! (rangeTest->Escape(G4Positron::Positron(),couple,positronKineEnergy,safety)))
268    {
269      localEnergyDeposit += positronKineEnergy ;
270      positronKineEnergy = 0. ;
271    }
272  G4ThreeVector positronDirection(dirX_po,dirY_po,dirZ_po);
273  positronDirection.rotateUz(photonDirection);
274
275  // Create G4DynamicParticle object for the particle2
276  G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(),
277                                                       positronDirection, positronKineEnergy);
278  aParticleChange.AddSecondary(particle2) ;
279
280  aParticleChange.ProposeLocalEnergyDeposit(localEnergyDeposit) ;
281
282  // Kill the incident photon
283  aParticleChange.ProposeMomentumDirection(0.,0.,0.) ;
284  aParticleChange.ProposeEnergy(0.) ;
285  aParticleChange.ProposeTrackStatus(fStopAndKill) ;
286
287  //  Reset NbOfInteractionLengthLeft and return aParticleChange
288  return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
289}
290
291G4bool G4PenelopeGammaConversion::IsApplicable(const G4ParticleDefinition& particle)
292{
293  return ( &particle == G4Gamma::Gamma() );
294}
295
296G4double G4PenelopeGammaConversion::GetMeanFreePath(const G4Track& track,
297                                                    G4double, // previousStepSize
298                                                    G4ForceCondition*)
299{
300  const G4DynamicParticle* photon = track.GetDynamicParticle();
301  G4double energy = photon->GetKineticEnergy();
302  const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
303  size_t materialIndex = couple->GetIndex();
304
305  G4double meanFreePath;
306  if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
307  else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
308  else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
309  return meanFreePath;
310}
311
312G4double G4PenelopeGammaConversion::ScreenFunction(G4double b,G4int icase)
313{
314  G4double bsquare=b*b;
315  G4double a0,f1,f2,g1,g2;
316  f1=2.0-2*std::log(1+bsquare);
317  f2=f1-(2.0/3.0);
318  if (b < 1.0e-10)
319    {
320      f1=f1-twopi*b;
321    }
322  else
323    {
324      a0 = 4*b*std::atan(1.0/b);
325      f1 = f1 - a0;
326      f2 = f2+2*bsquare*(4.0-a0-3*std::log((1+bsquare)/bsquare));
327    }
328  g1=0.5*(3*f1-f2);
329  g2=0.25*(3*f1+f2);
330  if (icase==1) {
331   return g1;
332  }
333  else
334    {
335      return g2;
336    }
337}
338     
339G4double G4PenelopeGammaConversion::CoulombCorrection(G4double a)
340{
341  G4double fc=0;
342  G4double b[7] = {0.202059,-0.03693,0.00835,-0.00201,0.00049,-0.00012,0.00003};
343  G4double aSquared = a*a;
344  G4double aFourth = aSquared*aSquared;
345  G4double aEighth = aFourth*aFourth;
346
347  fc = ((1.0/(1.0+a*a))+b[0]+b[1]*aSquared+b[2]*aFourth+b[3]*(aSquared*aFourth)+
348        b[4]*aEighth+b[5]*(aEighth*aSquared)+b[6]*(aEighth*aFourth));
349  fc=aSquared*fc;
350  return fc;
351}
352
353G4double G4PenelopeGammaConversion::LowEnergyCorrection(G4double a,G4double eki)
354{
355  G4double f0=0,t=0;
356  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};
357  t=std::sqrt(2.0*eki);
358  G4double tSq = t*t;
359  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)+
360    (b[9]+b[10]*a+b[11]*a*a)*(tSq*tSq);
361  return f0;
362}
363
364G4double G4PenelopeGammaConversion::GetScreeningRadius(G4double Z) 
365{
366  char* path = getenv("G4LEDATA");
367  if (!path)
368    {
369      G4String excep = "G4PenelopeGammaConversion - G4LEDATA environment variable not set!";
370      G4Exception(excep);
371    }
372  G4String pathString(path);
373  G4String pathFile = pathString + "/penelope/pp-pen.dat";
374  std::ifstream file(pathFile);
375  std::filebuf* lsdp = file.rdbuf();
376 
377  if (!(lsdp->is_open()))
378    {
379      G4String excep = "G4PenelopeGammaConversion - data file " + pathFile + "not found!";
380      G4Exception(excep);
381    }
382  G4int k;
383  G4double a1,a2;
384  while(!file.eof()) {
385    file >> k >> a1 >> a2;
386    if ((G4double) k == Z)
387      {
388        return a1;
389      }
390  } 
391  G4String excep = "G4PenelopeGammaConversion - Screening Radius for not found in the data file";
392  G4Exception(excep);
393  return 0;
394}
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