source: trunk/source/processes/electromagnetic/lowenergy/src/G4LivermoreGammaConversionModelRC.cc @ 1353

Last change on this file since 1353 was 1350, checked in by garnier, 14 years ago

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26// $Id: G4LivermoreGammaConversionModelRC.cc,v 1.1 2010/11/10 17:12:22 flongo Exp $
27// GEANT4 tag $Name: geant4-09-04-ref-00 $
28//
29//
30// Author: Sebastien Inserti
31//         30 October 2008
32//
33// History:
34// --------
35// 12 Apr 2009   V Ivanchenko Cleanup initialisation and generation of secondaries:
36//                  - apply internal high-energy limit only in constructor
37//                  - do not apply low-energy limit (default is 0)
38//                  - use CLHEP electron mass for low-enegry limit
39//                  - remove MeanFreePath method and table
40
41
42#include "G4LivermoreGammaConversionModelRC.hh"
43
44//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
45
46using namespace std;
47
48//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
49
50G4LivermoreGammaConversionModelRC::G4LivermoreGammaConversionModelRC(const G4ParticleDefinition*,
51                                                                 const G4String& nam)
52  :G4VEmModel(nam),smallEnergy(2.*MeV),isInitialised(false),
53   crossSectionHandler(0),meanFreePathTable(0)
54{
55  lowEnergyLimit = 2.0*electron_mass_c2;
56  highEnergyLimit = 100 * GeV;
57  SetHighEnergyLimit(highEnergyLimit);
58         
59  verboseLevel= 0;
60  // Verbosity scale:
61  // 0 = nothing
62  // 1 = warning for energy non-conservation
63  // 2 = details of energy budget
64  // 3 = calculation of cross sections, file openings, sampling of atoms
65  // 4 = entering in methods
66
67  if(verboseLevel > 0) {
68    G4cout << "Livermore Gamma conversion is constructed " << G4endl
69           << "Energy range: "
70           << lowEnergyLimit / MeV << " MeV - "
71           << highEnergyLimit / GeV << " GeV"
72           << G4endl;
73  }
74}
75
76//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
77
78G4LivermoreGammaConversionModelRC::~G4LivermoreGammaConversionModelRC()
79{ 
80  if (crossSectionHandler) delete crossSectionHandler;
81}
82
83//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
84
85void 
86G4LivermoreGammaConversionModelRC::Initialise(const G4ParticleDefinition*,
87                                            const G4DataVector&)
88{
89  if (verboseLevel > 3)
90    G4cout << "Calling G4LivermoreGammaConversionModelRC::Initialise()" << G4endl;
91
92  if (crossSectionHandler)
93  {
94    crossSectionHandler->Clear();
95    delete crossSectionHandler;
96  }
97
98  // Read data tables for all materials
99 
100  crossSectionHandler = new G4CrossSectionHandler();
101  crossSectionHandler->Initialise(0,lowEnergyLimit,100.*GeV,400);
102  G4String crossSectionFile = "pair/pp-cs-";
103  crossSectionHandler->LoadData(crossSectionFile);
104
105  //
106 
107  if (verboseLevel > 2) 
108    G4cout << "Loaded cross section files for PenelopeGammaConversion" << G4endl;
109
110  if (verboseLevel > 0) { 
111    G4cout << "Livermore Gamma Conversion model is initialized " << G4endl
112           << "Energy range: "
113           << LowEnergyLimit() / MeV << " MeV - "
114           << HighEnergyLimit() / GeV << " GeV"
115           << G4endl;
116  }
117
118  if(isInitialised) return;
119  fParticleChange = GetParticleChangeForGamma();
120  isInitialised = true;
121}
122
123//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
124
125G4double
126G4LivermoreGammaConversionModelRC::ComputeCrossSectionPerAtom(const G4ParticleDefinition*,
127                                                            G4double GammaEnergy,
128                                                            G4double Z, G4double,
129                                                            G4double, G4double)
130{
131  if (verboseLevel > 3) {
132    G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreGammaConversionModelRC" 
133           << G4endl;
134  }
135  if (GammaEnergy < lowEnergyLimit || GammaEnergy > highEnergyLimit) return 0;
136
137  G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
138  return cs;
139}
140
141//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
142
143void G4LivermoreGammaConversionModelRC::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
144                                              const G4MaterialCutsCouple* couple,
145                                              const G4DynamicParticle* aDynamicGamma,
146                                              G4double,
147                                              G4double)
148{
149
150// The energies of the e+ e- secondaries are sampled using the Bethe - Heitler
151// cross sections with Coulomb correction. A modified version of the random
152// number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15).
153
154// Note 1 : Effects due to the breakdown of the Born approximation at low
155// energy are ignored.
156// Note 2 : The differential cross section implicitly takes account of
157// pair creation in both nuclear and atomic electron fields. However triplet
158// prodution is not generated.
159
160  if (verboseLevel > 3)
161    G4cout << "Calling SampleSecondaries() of G4LivermoreGammaConversionModelRC" << G4endl;
162
163  G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
164  G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
165
166  G4double epsilon ;
167  G4double epsilon0 = electron_mass_c2 / photonEnergy ;
168  G4double electronTotEnergy;
169  G4double positronTotEnergy;
170
171
172  // Do it fast if photon energy < 2. MeV
173  if (photonEnergy < smallEnergy )
174    {
175      epsilon = epsilon0 + (0.5 - epsilon0) * G4UniformRand();
176 
177    if (CLHEP::RandBit::shootBit())
178      {
179        electronTotEnergy = (1. - epsilon) * photonEnergy;
180        positronTotEnergy = epsilon * photonEnergy;
181      }
182     else
183      {
184         positronTotEnergy = (1. - epsilon) * photonEnergy;
185         electronTotEnergy = epsilon * photonEnergy;
186       }
187    }
188  else
189    {
190      // Select randomly one element in the current material
191      //const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy);
192      const G4ParticleDefinition* particle =  aDynamicGamma->GetDefinition();
193      const G4Element* element = SelectRandomAtom(couple,particle,photonEnergy);
194      G4cout << "G4LivermoreGammaConversionModelRC::SampleSecondaries" << G4endl;
195
196      if (element == 0)
197        {
198          G4cout << "G4LivermoreGammaConversionModelRC::SampleSecondaries - element = 0" 
199                 << G4endl;
200          return;
201        }
202      G4IonisParamElm* ionisation = element->GetIonisation();
203      if (ionisation == 0)
204        {
205          G4cout << "G4LivermoreGammaConversionModelRC::SampleSecondaries - ionisation = 0" 
206                 << G4endl;
207          return;
208        }
209
210      // Extract Coulomb factor for this Element
211      G4double fZ = 8. * (ionisation->GetlogZ3());
212      if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb());
213
214      // Limits of the screening variable
215      G4double screenFactor = 136. * epsilon0 / (element->GetIonisation()->GetZ3()) ;
216      G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ;
217      G4double screenMin = std::min(4.*screenFactor,screenMax) ;
218
219      // Limits of the energy sampling
220      G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ;
221      G4double epsilonMin = std::max(epsilon0,epsilon1);
222      G4double epsilonRange = 0.5 - epsilonMin ;
223
224      // Sample the energy rate of the created electron (or positron)
225      G4double screen;
226      G4double gReject ;
227
228      G4double f10 = ScreenFunction1(screenMin) - fZ;
229      G4double f20 = ScreenFunction2(screenMin) - fZ;
230      G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.);
231      G4double normF2 = std::max(1.5 * f20,0.);
232      G4double a=393.3750918, b=115.3070201, c=810.6428451, d=19.96497475, e=1016.874592, f=1.936685510,
233               g=751.2140962, h=0.099751048, i=299.9466339, j=0.002057250, k=49.81034926;
234      G4double aa=-18.6371131, bb=-1729.95248, cc=9450.971186, dd=106336.0145, ee=55143.09287, ff=-117602.840,
235               gg=-721455.467, hh=693957.8635, ii=156266.1085, jj=533209.9347;                           
236      G4double Rechazo = 0.;
237      G4double logepsMin = log(epsilonMin);
238      G4double NormaRC = a + b*logepsMin + c/logepsMin + d*pow(logepsMin,2.) + e/pow(logepsMin,2.) + f*pow(logepsMin,3.) +
239                            g/pow(logepsMin,3.) + h*pow(logepsMin,4.) + i/pow(logepsMin,4.) + j*pow(logepsMin,5.) +
240                            k/pow(logepsMin,5.);
241 
242      do {
243         do {
244           if (normF1 / (normF1 + normF2) > G4UniformRand() )
245             {
246               epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ;
247               screen = screenFactor / (epsilon * (1. - epsilon));
248               gReject = (ScreenFunction1(screen) - fZ) / f10 ;
249             }
250           else
251             {
252               epsilon = epsilonMin + epsilonRange * G4UniformRand();
253               screen = screenFactor / (epsilon * (1 - epsilon));
254               gReject = (ScreenFunction2(screen) - fZ) / f20 ;
255             }
256         } while ( gReject < G4UniformRand() );
257                 
258         if (CLHEP::RandBit::shootBit()) epsilon = (1. - epsilon); // Extención de Epsilon hasta 1.
259       
260         G4double logepsilon = log(epsilon);
261         G4double deltaP_R1 = 1. + (a + b*logepsilon + c/logepsilon + d*pow(logepsilon,2.) + e/pow(logepsilon,2.) + 
262                              f*pow(logepsilon,3.) + g/pow(logepsilon,3.) + h*pow(logepsilon,4.) + i/pow(logepsilon,4.) + 
263                              j*pow(logepsilon,5.) + k/pow(logepsilon,5.))/100.;
264         G4double deltaP_R2 = 1.+((aa + cc*logepsilon +  ee*pow(logepsilon,2.) + gg*pow(logepsilon,3.) + ii*pow(logepsilon,4.))
265                             / (1. + bb*logepsilon + dd*pow(logepsilon,2.) + ff*pow(logepsilon,3.) + hh*pow(logepsilon,4.) 
266                             + jj*pow(logepsilon,5.) ))/100.;
267       
268         if (epsilon <= 0.5)
269            {
270            Rechazo = deltaP_R1/NormaRC;
271            }
272          else
273            {
274            Rechazo = deltaP_R2/NormaRC;
275            }       
276            G4cout << Rechazo << " " << NormaRC << " " << epsilon << G4endl;
277      } while (Rechazo < G4UniformRand() );
278     
279      electronTotEnergy = (1. - epsilon) * photonEnergy;
280      positronTotEnergy = epsilon * photonEnergy;
281
282    }   //  End of epsilon sampling
283   
284  // Fix charges randomly
285
286  // Scattered electron (positron) angles. ( Z - axis along the parent photon)
287  // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211),
288  // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977)
289
290  G4double u;
291  const G4double a1 = 0.625;
292  G4double a2 = 3. * a1;
293  //  G4double d = 27. ;
294
295  //  if (9. / (9. + d) > G4UniformRand())
296  if (0.25 > G4UniformRand())
297    {
298      u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ;
299    }
300  else
301    {
302      u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ;
303    }
304
305  G4double thetaEle = u*electron_mass_c2/electronTotEnergy;
306  G4double thetaPos = u*electron_mass_c2/positronTotEnergy;
307  G4double phi  = twopi * G4UniformRand();
308
309  G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle);
310  G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos);
311 
312 
313  // Kinematics of the created pair:
314  // the electron and positron are assumed to have a symetric angular
315  // distribution with respect to the Z axis along the parent photon
316 
317  G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
318 
319  // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
320
321  G4ThreeVector electronDirection (dxEle, dyEle, dzEle);
322  electronDirection.rotateUz(photonDirection);
323     
324  G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(),
325                                                            electronDirection,
326                                                            electronKineEnergy);
327
328  // The e+ is always created (even with kinetic energy = 0) for further annihilation
329  G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
330
331  // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
332
333  G4ThreeVector positronDirection (dxPos, dyPos, dzPos);
334  positronDirection.rotateUz(photonDirection);   
335 
336  // Create G4DynamicParticle object for the particle2
337  G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(),
338                                                       positronDirection, positronKineEnergy);
339  // Fill output vector
340//  G4cout  << "Cree el e+ " <<  epsilon << G4endl;
341  fvect->push_back(particle1);
342  fvect->push_back(particle2);
343
344  // kill incident photon
345  fParticleChange->SetProposedKineticEnergy(0.);
346  fParticleChange->ProposeTrackStatus(fStopAndKill);   
347
348}
349
350//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
351
352G4double G4LivermoreGammaConversionModelRC::ScreenFunction1(G4double screenVariable)
353{
354  // Compute the value of the screening function 3*phi1 - phi2
355
356  G4double value;
357 
358  if (screenVariable > 1.)
359    value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
360  else
361    value = 42.392 - screenVariable * (7.796 - 1.961 * screenVariable);
362 
363  return value;
364} 
365
366//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
367
368G4double G4LivermoreGammaConversionModelRC::ScreenFunction2(G4double screenVariable)
369{
370  // Compute the value of the screening function 1.5*phi1 - 0.5*phi2
371 
372  G4double value;
373 
374  if (screenVariable > 1.)
375    value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
376  else
377    value = 41.405 - screenVariable * (5.828 - 0.8945 * screenVariable);
378 
379  return value;
380} 
381
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