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G4LivermoreNuclearGammaConversionModel.cc
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26 // $Id: G4LivermoreNuclearGammaConversionModel.cc 66241 2012-12-13 18:34:42Z gunter $
27 //
28 // Authors: G.Depaola & F.Longo
29 //
30 
32 #include "G4PhysicalConstants.hh"
33 #include "G4SystemOfUnits.hh"
34 
35 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
36 
37 using namespace std;
38 
39 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
40 
42  const G4String& nam)
43  :G4VEmModel(nam),fParticleChange(0),smallEnergy(2.*MeV),
44  isInitialised(false),
45  crossSectionHandler(0),meanFreePathTable(0)
46 {
47  lowEnergyLimit = 2.0*electron_mass_c2;
48  highEnergyLimit = 100 * GeV;
49  SetHighEnergyLimit(highEnergyLimit);
50 
51  verboseLevel= 0;
52  // Verbosity scale:
53  // 0 = nothing
54  // 1 = warning for energy non-conservation
55  // 2 = details of energy budget
56  // 3 = calculation of cross sections, file openings, sampling of atoms
57  // 4 = entering in methods
58 
59  if(verboseLevel > 0) {
60  G4cout << "Livermore Nuclear Gamma conversion is constructed " << G4endl
61  << "Energy range: "
62  << lowEnergyLimit / MeV << " MeV - "
63  << highEnergyLimit / GeV << " GeV"
64  << G4endl;
65  }
66 }
67 
68 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
69 
71 {
72  if (crossSectionHandler) delete crossSectionHandler;
73 }
74 
75 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
76 
77 void
79  const G4DataVector&)
80 {
81  if (verboseLevel > 3)
82  G4cout << "Calling G4LivermoreNuclearGammaConversionModel::Initialise()" << G4endl;
83 
84  if (crossSectionHandler)
85  {
86  crossSectionHandler->Clear();
87  delete crossSectionHandler;
88  }
89 
90  // Read data tables for all materials
91 
92  crossSectionHandler = new G4CrossSectionHandler();
93  crossSectionHandler->Initialise(0,lowEnergyLimit,100.*GeV,400);
94  G4String crossSectionFile = "pairdata/pp-pair-cs-"; // here only pair in nuclear field cs should be used
95  crossSectionHandler->LoadData(crossSectionFile);
96 
97  //
98 
99  if (verboseLevel > 0) {
100  G4cout << "Loaded cross section files for Livermore GammaConversion" << G4endl;
101  G4cout << "To obtain the total cross section this should be used only " << G4endl
102  << "in connection with G4ElectronGammaConversion " << G4endl;
103  }
104 
105  if (verboseLevel > 0) {
106  G4cout << "Livermore Nuclear Gamma Conversion model is initialized " << G4endl
107  << "Energy range: "
108  << LowEnergyLimit() / MeV << " MeV - "
109  << HighEnergyLimit() / GeV << " GeV"
110  << G4endl;
111  }
112 
113  if(isInitialised) return;
115  isInitialised = true;
116 }
117 
118 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
119 
120 G4double
122  G4double GammaEnergy,
123  G4double Z, G4double,
125 {
126  if (verboseLevel > 3) {
127  G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreNuclearGammaConversionModel"
128  << G4endl;
129  }
130  if (GammaEnergy < lowEnergyLimit || GammaEnergy > highEnergyLimit) return 0;
131 
132  G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
133  return cs;
134 }
135 
136 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
137 
138 void G4LivermoreNuclearGammaConversionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
139  const G4MaterialCutsCouple* couple,
140  const G4DynamicParticle* aDynamicGamma,
141  G4double,
142  G4double)
143 {
144 
145 // The energies of the e+ e- secondaries are sampled using the Bethe - Heitler
146 // cross sections with Coulomb correction. A modified version of the random
147 // number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15).
148 
149 // Note 1 : Effects due to the breakdown of the Born approximation at low
150 // energy are ignored.
151 // Note 2 : The differential cross section implicitly takes account of
152 // pair creation in both nuclear and atomic electron fields. However triplet
153 // prodution is not generated.
154 
155  if (verboseLevel > 3)
156  G4cout << "Calling SampleSecondaries() of G4LivermoreNuclearGammaConversionModel" << G4endl;
157 
158  G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
159  G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
160 
161  G4double epsilon ;
162  G4double epsilon0Local = electron_mass_c2 / photonEnergy ;
163 
164  // Do it fast if photon energy < 2. MeV
165  if (photonEnergy < smallEnergy )
166  {
167  epsilon = epsilon0Local + (0.5 - epsilon0Local) * G4UniformRand();
168  }
169  else
170  {
171  // Select randomly one element in the current material
172  //const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy);
173  const G4ParticleDefinition* particle = aDynamicGamma->GetDefinition();
174  const G4Element* element = SelectRandomAtom(couple,particle,photonEnergy);
175 
176  if (element == 0)
177  {
178  G4cout << "G4LivermoreNuclearGammaConversionModel::SampleSecondaries - element = 0"
179  << G4endl;
180  return;
181  }
182  G4IonisParamElm* ionisation = element->GetIonisation();
183  if (ionisation == 0)
184  {
185  G4cout << "G4LivermoreNuclearGammaConversionModel::SampleSecondaries - ionisation = 0"
186  << G4endl;
187  return;
188  }
189 
190  // Extract Coulomb factor for this Element
191  G4double fZ = 8. * (ionisation->GetlogZ3());
192  if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb());
193 
194  // Limits of the screening variable
195  G4double screenFactor = 136. * epsilon0Local / (element->GetIonisation()->GetZ3()) ;
196  G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ;
197  G4double screenMin = std::min(4.*screenFactor,screenMax) ;
198 
199  // Limits of the energy sampling
200  G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ;
201  G4double epsilonMin = std::max(epsilon0Local,epsilon1);
202  G4double epsilonRange = 0.5 - epsilonMin ;
203 
204  // Sample the energy rate of the created electron (or positron)
205  G4double screen;
206  G4double gReject ;
207 
208  G4double f10 = ScreenFunction1(screenMin) - fZ;
209  G4double f20 = ScreenFunction2(screenMin) - fZ;
210  G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.);
211  G4double normF2 = std::max(1.5 * f20,0.);
212 
213  do {
214  if (normF1 / (normF1 + normF2) > G4UniformRand() )
215  {
216  epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ;
217  screen = screenFactor / (epsilon * (1. - epsilon));
218  gReject = (ScreenFunction1(screen) - fZ) / f10 ;
219  }
220  else
221  {
222  epsilon = epsilonMin + epsilonRange * G4UniformRand();
223  screen = screenFactor / (epsilon * (1 - epsilon));
224  gReject = (ScreenFunction2(screen) - fZ) / f20 ;
225  }
226  } while ( gReject < G4UniformRand() );
227 
228  } // End of epsilon sampling
229 
230  // Fix charges randomly
231 
232  G4double electronTotEnergy;
233  G4double positronTotEnergy;
234 
235  if (G4int(2*G4UniformRand()))
236  {
237  electronTotEnergy = (1. - epsilon) * photonEnergy;
238  positronTotEnergy = epsilon * photonEnergy;
239  }
240  else
241  {
242  positronTotEnergy = (1. - epsilon) * photonEnergy;
243  electronTotEnergy = epsilon * photonEnergy;
244  }
245 
246  // Scattered electron (positron) angles. ( Z - axis along the parent photon)
247  // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211),
248  // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977)
249 
250  G4double u;
251  const G4double a1 = 0.625;
252  G4double a2 = 3. * a1;
253  // G4double d = 27. ;
254 
255  // if (9. / (9. + d) > G4UniformRand())
256  if (0.25 > G4UniformRand())
257  {
258  u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ;
259  }
260  else
261  {
262  u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ;
263  }
264 
265  G4double thetaEle = u*electron_mass_c2/electronTotEnergy;
266  G4double thetaPos = u*electron_mass_c2/positronTotEnergy;
267  G4double phi = twopi * G4UniformRand();
268 
269  G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle);
270  G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos);
271 
272 
273  // Kinematics of the created pair:
274  // the electron and positron are assumed to have a symetric angular
275  // distribution with respect to the Z axis along the parent photon
276 
277  G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
278 
279  // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
280 
281  G4ThreeVector electronDirection (dxEle, dyEle, dzEle);
282  electronDirection.rotateUz(photonDirection);
283 
285  electronDirection,
286  electronKineEnergy);
287 
288  // The e+ is always created (even with kinetic energy = 0) for further annihilation
289  G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
290 
291  // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
292 
293  G4ThreeVector positronDirection (dxPos, dyPos, dzPos);
294  positronDirection.rotateUz(photonDirection);
295 
296  // Create G4DynamicParticle object for the particle2
298  positronDirection, positronKineEnergy);
299  // Fill output vector
300 
301  fvect->push_back(particle1);
302  fvect->push_back(particle2);
303 
304  // kill incident photon
307 
308 }
309 
310 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
311 
312 G4double G4LivermoreNuclearGammaConversionModel::ScreenFunction1(G4double screenVariable)
313 {
314  // Compute the value of the screening function 3*phi1 - phi2
315 
316  G4double value;
317 
318  if (screenVariable > 1.)
319  value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
320  else
321  value = 42.392 - screenVariable * (7.796 - 1.961 * screenVariable);
322 
323  return value;
324 }
325 
326 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
327 
328 G4double G4LivermoreNuclearGammaConversionModel::ScreenFunction2(G4double screenVariable)
329 {
330  // Compute the value of the screening function 1.5*phi1 - 0.5*phi2
331 
332  G4double value;
333 
334  if (screenVariable > 1.)
335  value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
336  else
337  value = 41.405 - screenVariable * (5.828 - 0.8945 * screenVariable);
338 
339  return value;
340 }
341 
G4double LowEnergyLimit() const
Definition: G4VEmModel.hh:599
G4double GetKineticEnergy() const
G4double HighEnergyLimit() const
Definition: G4VEmModel.hh:592
G4double GetfCoulomb() const
Definition: G4Element.hh:190
G4ParticleDefinition * GetDefinition() const
int G4int
Definition: G4Types.hh:78
void SetHighEnergyLimit(G4double)
Definition: G4VEmModel.hh:683
G4double FindValue(G4int Z, G4double e) const
#define G4UniformRand()
Definition: Randomize.hh:87
G4GLOB_DLL std::ostream G4cout
G4LivermoreNuclearGammaConversionModel(const G4ParticleDefinition *p=0, const G4String &nam="LivermoreNuclearGammaConversion")
const G4ThreeVector & GetMomentumDirection() const
Hep3Vector & rotateUz(const Hep3Vector &)
Definition: ThreeVector.cc:72
float electron_mass_c2
Definition: hepunit.py:274
virtual G4double ComputeCrossSectionPerAtom(const G4ParticleDefinition *, G4double kinEnergy, G4double Z, G4double A=0, G4double cut=0, G4double emax=DBL_MAX)
G4double GetlogZ3() const
virtual void SampleSecondaries(std::vector< G4DynamicParticle * > *, const G4MaterialCutsCouple *, const G4DynamicParticle *, G4double tmin, G4double maxEnergy)
void Initialise(G4VDataSetAlgorithm *interpolation=0, G4double minE=250 *CLHEP::eV, G4double maxE=100 *CLHEP::GeV, G4int numberOfBins=200, G4double unitE=CLHEP::MeV, G4double unitData=CLHEP::barn, G4int minZ=1, G4int maxZ=99)
static G4Positron * Positron()
Definition: G4Positron.cc:94
T max(const T t1, const T t2)
brief Return the largest of the two arguments
G4IonisParamElm * GetIonisation() const
Definition: G4Element.hh:198
void LoadData(const G4String &dataFile)
T min(const T t1, const T t2)
brief Return the smallest of the two arguments
virtual void Initialise(const G4ParticleDefinition *, const G4DataVector &)
const XML_Char int const XML_Char * value
static G4Electron * Electron()
Definition: G4Electron.cc:94
void SetProposedKineticEnergy(G4double proposedKinEnergy)
#define G4endl
Definition: G4ios.hh:61
double G4double
Definition: G4Types.hh:76
void ProposeTrackStatus(G4TrackStatus status)
G4double GetZ3() const
const G4Element * SelectRandomAtom(const G4MaterialCutsCouple *, const G4ParticleDefinition *, G4double kineticEnergy, G4double cutEnergy=0.0, G4double maxEnergy=DBL_MAX)
Definition: G4VEmModel.hh:510
G4ParticleChangeForGamma * GetParticleChangeForGamma()
Definition: G4VEmModel.cc:121