source: trunk/source/processes/electromagnetic/lowenergy/src/G4DNAScreenedRutherfordElasticModel.cc @ 991

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26// $Id: G4DNAScreenedRutherfordElasticModel.cc,v 1.4 2009/02/16 11:00:11 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
28//
29
30#include "G4DNAScreenedRutherfordElasticModel.hh"
31
32//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
33
34using namespace std;
35
36//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
37
38G4DNAScreenedRutherfordElasticModel::G4DNAScreenedRutherfordElasticModel
39(const G4ParticleDefinition*, const G4String& nam)
40:G4VEmModel(nam),isInitialised(false)
41{
42
43  killBelowEnergy = 8.23*eV; // Minimum e- energy for energy loss by excitation
44  lowEnergyLimit = 0 * eV; 
45  lowEnergyLimitOfModel = 7 * eV; // The model lower energy is 7 eV
46  intermediateEnergyLimit = 200 * eV; // Switch between two final state models
47  highEnergyLimit = 10 * MeV;
48  SetLowEnergyLimit(lowEnergyLimit);
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  G4cout << "Screened Rutherford Elastic model is constructed " << G4endl
60         << "Energy range: "
61         << lowEnergyLimit / eV << " eV - "
62         << highEnergyLimit / MeV << " MeV"
63         << G4endl;
64 
65}
66
67//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
68
69G4DNAScreenedRutherfordElasticModel::~G4DNAScreenedRutherfordElasticModel()
70{}
71
72//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
73
74void G4DNAScreenedRutherfordElasticModel::Initialise(const G4ParticleDefinition* /*particle*/,
75                                       const G4DataVector& /*cuts*/)
76{
77
78  if (verboseLevel > 3)
79    G4cout << "Calling G4DNAScreenedRutherfordElasticModel::Initialise()" << G4endl;
80
81  // Energy limits
82 
83  if (LowEnergyLimit() < lowEnergyLimit)
84  {
85    G4cout << "G4DNAScreenedRutherfordElasticModel: low energy limit increased from " << 
86        LowEnergyLimit()/eV << " eV to " << lowEnergyLimit/eV << " eV" << G4endl;
87    SetLowEnergyLimit(lowEnergyLimit);
88    }
89
90  if (HighEnergyLimit() > highEnergyLimit)
91  {
92    G4cout << "G4DNAScreenedRutherfordElasticModel: high energy limit decreased from " << 
93        HighEnergyLimit()/MeV << " MeV to " << highEnergyLimit/MeV << " MeV" << G4endl;
94    SetHighEnergyLimit(highEnergyLimit);
95  }
96
97  // Constants for final stae by Brenner & Zaider
98 
99  betaCoeff.push_back(7.51525);
100  betaCoeff.push_back(-0.41912);   
101  betaCoeff.push_back(7.2017E-3);
102  betaCoeff.push_back(-4.646E-5);   
103  betaCoeff.push_back(1.02897E-7);
104
105  deltaCoeff.push_back(2.9612); 
106  deltaCoeff.push_back(-0.26376); 
107  deltaCoeff.push_back(4.307E-3); 
108  deltaCoeff.push_back(-2.6895E-5);
109  deltaCoeff.push_back(5.83505E-8);
110
111  gamma035_10Coeff.push_back(-1.7013); 
112  gamma035_10Coeff.push_back(-1.48284); 
113  gamma035_10Coeff.push_back(0.6331); 
114  gamma035_10Coeff.push_back(-0.10911); 
115  gamma035_10Coeff.push_back(8.358E-3); 
116  gamma035_10Coeff.push_back(-2.388E-4);
117
118  gamma10_100Coeff.push_back(-3.32517); 
119  gamma10_100Coeff.push_back(0.10996); 
120  gamma10_100Coeff.push_back(-4.5255E-3); 
121  gamma10_100Coeff.push_back(5.8372E-5); 
122  gamma10_100Coeff.push_back(-2.4659E-7);
123
124  gamma100_200Coeff.push_back(2.4775E-2);
125  gamma100_200Coeff.push_back(-2.96264E-5);
126  gamma100_200Coeff.push_back(-1.20655E-7);
127
128  //
129
130  G4cout << "Screened Rutherford elastic model is initialized " << G4endl
131         << "Energy range: "
132         << LowEnergyLimit() / eV << " eV - "
133         << HighEnergyLimit() / MeV << " MeV"
134         << G4endl;
135
136  if(!isInitialised) 
137  {
138    isInitialised = true;
139 
140    if(pParticleChange)
141      fParticleChangeForGamma = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
142    else
143      fParticleChangeForGamma = new G4ParticleChangeForGamma();
144  }   
145
146  // InitialiseElementSelectors(particle,cuts);
147
148  // Test if water material
149
150  flagMaterialIsWater= false;
151  densityWater = 0;
152
153  const G4ProductionCutsTable* theCoupleTable = G4ProductionCutsTable::GetProductionCutsTable();
154
155  if(theCoupleTable) 
156  {
157    G4int numOfCouples = theCoupleTable->GetTableSize();
158 
159    if(numOfCouples>0) 
160    {
161          for (G4int i=0; i<numOfCouples; i++) 
162          {
163            const G4MaterialCutsCouple* couple = theCoupleTable->GetMaterialCutsCouple(i);
164            const G4Material* material = couple->GetMaterial();
165
166            size_t j = material->GetNumberOfElements();
167            while (j>0)
168            {
169               j--;
170               const G4Element* element(material->GetElement(j));
171               if (element->GetZ() == 8.)
172               {
173                  G4double density = material->GetAtomicNumDensityVector()[j];
174                  if (density > 0.) 
175                  { 
176                    flagMaterialIsWater = true; 
177                    densityWater = density; 
178                   
179                    if (verboseLevel > 3) 
180                    G4cout << "Water material is found with density(cm^-3)=" << density/(cm*cm*cm) << G4endl;
181                  }
182               }
183            }
184 
185          }
186   } // if(numOfCouples>0)
187
188  } // if (theCoupleTable)
189
190}
191
192//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
193
194G4double G4DNAScreenedRutherfordElasticModel::CrossSectionPerVolume(const G4Material*,
195                                           const G4ParticleDefinition*,
196                                           G4double ekin,
197                                           G4double,
198                                           G4double)
199{
200  if (verboseLevel > 3)
201    G4cout << "Calling CrossSectionPerVolume() of G4DNAScreenedRutherfordElasticModel" << G4endl;
202
203 // Calculate total cross section for model
204
205 G4double sigma=0;
206 
207 if (flagMaterialIsWater)
208 {
209
210  if (ekin >= lowEnergyLimitOfModel && ekin < highEnergyLimit)
211  {
212      G4double z = 10.;
213      G4double n = ScreeningFactor(ekin,z);
214      G4double crossSection = RutherfordCrossSection(ekin, z);
215      sigma = pi *  crossSection / (n * (n + 1.)); 
216  }
217
218  if (verboseLevel > 3)
219  {
220    G4cout << "---> Kinetic energy(eV)=" << ekin/eV << G4endl;
221    G4cout << " - Cross section per water molecule (cm^2)=" << sigma/cm/cm << G4endl;
222    G4cout << " - Cross section per water molecule (cm^-1)=" << sigma*densityWater/(1./cm) << G4endl;
223  } 
224
225 } // if (flagMaterialIsWater)
226
227 return sigma*densityWater;               
228}
229
230//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
231
232G4double G4DNAScreenedRutherfordElasticModel::RutherfordCrossSection(G4double k, G4double z)
233{
234  //   
235  //                               e^4         /      K + m_e c^2      \^2
236  // sigma_Ruth(K) = Z (Z+1) -------------------- | --------------------- |
237  //                          (4 pi epsilon_0)^2  \  K * (K + 2 m_e c^2)  /
238  //
239  // Where K is the electron non-relativistic kinetic energy
240  //
241  // NIM 155, pp. 145-156, 1978
242 
243  G4double length =(e_squared * (k + electron_mass_c2)) / (4 * pi *epsilon0 * k * ( k + 2 * electron_mass_c2));
244  G4double cross = z * ( z + 1) * length * length;
245 
246  return cross;
247}
248
249//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
250
251G4double G4DNAScreenedRutherfordElasticModel::ScreeningFactor(G4double k, G4double z)
252{
253  //
254  //         alpha_1 + beta_1 ln(K/eV)   constK Z^(2/3)
255  // n(T) = -------------------------- -----------------
256  //              K/(m_e c^2)            2 + K/(m_e c^2)
257  //
258  // Where K is the electron non-relativistic kinetic energy
259  //
260  // n(T) > 0 for T < ~ 400 MeV
261  //
262  // NIM 155, pp. 145-156, 1978
263  // Formulae (2) and (5)
264
265  const G4double alpha_1(1.64);
266  const G4double beta_1(-0.0825);
267  const G4double constK(1.7E-5);
268
269  G4double numerator = (alpha_1 + beta_1 * std::log(k/eV)) * constK * std::pow(z, 2./3.);
270
271  k /= electron_mass_c2;
272
273  G4double denominator = k * (2 + k);
274
275  G4double value = 0.;
276  if (denominator > 0.) value = numerator / denominator;
277
278  return value;
279}
280
281//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
282
283void G4DNAScreenedRutherfordElasticModel::SampleSecondaries(std::vector<G4DynamicParticle*>* /*fvect*/,
284                                              const G4MaterialCutsCouple* /*couple*/,
285                                              const G4DynamicParticle* aDynamicElectron,
286                                              G4double,
287                                              G4double)
288{
289
290  if (verboseLevel > 3)
291    G4cout << "Calling SampleSecondaries() of G4DNAScreenedRutherfordElasticModel" << G4endl;
292
293  G4double electronEnergy0 = aDynamicElectron->GetKineticEnergy();
294 
295  if (electronEnergy0 < killBelowEnergy)
296  {
297    fParticleChangeForGamma->ProposeTrackStatus(fStopAndKill);
298    fParticleChangeForGamma->ProposeLocalEnergyDeposit(electronEnergy0);
299    return ;
300  }
301
302  G4double cosTheta = 0.;
303
304  if (electronEnergy0>= killBelowEnergy && electronEnergy0 < highEnergyLimit)
305  { 
306    if (electronEnergy0<intermediateEnergyLimit)
307    {
308    if (verboseLevel > 3) G4cout << "---> Using Brenner & Zaider model" << G4endl;
309    cosTheta = BrennerZaiderRandomizeCosTheta(electronEnergy0);
310    } 
311
312    if (electronEnergy0>=intermediateEnergyLimit)
313    {
314    if (verboseLevel > 3) G4cout << "---> Using Screened Rutherford model" << G4endl;
315    G4double z = 10.;
316    cosTheta = ScreenedRutherfordRandomizeCosTheta(electronEnergy0,z);
317    } 
318
319    G4double phi = 2. * pi * G4UniformRand();
320
321    G4ThreeVector zVers = aDynamicElectron->GetMomentumDirection();
322    G4ThreeVector xVers = zVers.orthogonal();
323    G4ThreeVector yVers = zVers.cross(xVers);
324
325    G4double xDir = std::sqrt(1. - cosTheta*cosTheta);
326    G4double yDir = xDir;
327    xDir *= std::cos(phi);
328    yDir *= std::sin(phi);
329
330    G4ThreeVector zPrimeVers((xDir*xVers + yDir*yVers + cosTheta*zVers));
331
332    fParticleChangeForGamma->ProposeMomentumDirection(zPrimeVers.unit()) ;
333
334    fParticleChangeForGamma->SetProposedKineticEnergy(electronEnergy0);
335  }
336
337}
338
339//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
340
341G4double G4DNAScreenedRutherfordElasticModel::BrennerZaiderRandomizeCosTheta(G4double k)
342{
343  //  d sigma_el                         1                                 beta(K)
344  // ------------ (K) ~ --------------------------------- + ---------------------------------
345  //   d Omega           (1 + 2 gamma(K) - cos(theta))^2     (1 + 2 delta(K) + cos(theta))^2
346  //
347  // Maximum is < 1/(4 gamma(K)^2) + beta(K)/((2+2delta(K))^2)
348  //
349  // Phys. Med. Biol. 29 N.4 (1983) 443-447
350 
351  // gamma(K), beta(K) and delta(K) are polynomials with coefficients for energy measured in eV
352
353  k /= eV;
354 
355  G4double beta = std::exp(CalculatePolynomial(k,betaCoeff)); 
356  G4double delta = std::exp(CalculatePolynomial(k,deltaCoeff)); 
357  G4double gamma;
358 
359  if (k > 100.)
360  {
361      gamma = CalculatePolynomial(k, gamma100_200Coeff); 
362      // Only in this case it is not the exponent of the polynomial
363  } 
364  else 
365  {
366      if (k>10)
367      {
368          gamma = std::exp(CalculatePolynomial(k, gamma10_100Coeff));
369      }
370      else
371      {
372          gamma = std::exp(CalculatePolynomial(k, gamma035_10Coeff));
373      }
374  }
375
376  // ***** Original method
377
378  G4double oneOverMax = 1. / (1./(4.*gamma*gamma) + beta/( (2.+2.*delta)*(2.+2.*delta) ));
379 
380  G4double cosTheta = 0.;
381  G4double leftDenominator = 0.;
382  G4double rightDenominator = 0.;
383  G4double fCosTheta = 0.;
384 
385  do
386  {
387      cosTheta = 2. * G4UniformRand() - 1.;
388     
389      leftDenominator = (1. + 2.*gamma - cosTheta);
390      rightDenominator = (1. + 2.*delta + cosTheta);
391      if ( (leftDenominator * rightDenominator) != 0. )
392      {
393          fCosTheta = oneOverMax * (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator));
394      }
395  }
396  while (fCosTheta < G4UniformRand());
397
398  return cosTheta; 
399
400  // ***** Alternative method using cumulative probability
401/*
402 G4double cosTheta = -1;
403 G4double cumul = 0;
404 G4double value = 0;
405 G4double leftDenominator = 0.;
406 G4double rightDenominator = 0.;
407 
408 // Number of integration steps in the -1,1 range
409 G4int iMax=200;
410 
411 G4double random = G4UniformRand();
412 
413 // Cumulate differential cross section
414 for (G4int i=0; i<iMax; i++)
415 {
416   cosTheta = -1 + i*2./(iMax-1);
417   leftDenominator = (1. + 2.*gamma - cosTheta);
418   rightDenominator = (1. + 2.*delta + cosTheta);
419   if ( (leftDenominator * rightDenominator) != 0. )
420   {
421     cumul = cumul + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator));
422   }
423 }
424 
425 // Select cosTheta
426 for (G4int i=0; i<iMax; i++)
427 {
428   cosTheta = -1 + i*2./(iMax-1);
429   leftDenominator = (1. + 2.*gamma - cosTheta);
430   rightDenominator = (1. + 2.*delta + cosTheta);
431   if (cumul !=0 && (leftDenominator * rightDenominator) != 0.)
432       value = value + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator)) / cumul;
433   if (random < value) break;
434 }
435
436 return cosTheta;
437*/
438
439}
440
441//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
442
443G4double G4DNAScreenedRutherfordElasticModel::CalculatePolynomial(G4double k, std::vector<G4double>& vec)
444{
445  // Sum_{i=0}^{size-1} vector_i k^i
446  //
447  // Phys. Med. Biol. 29 N.4 (1983) 443-447
448
449  G4double result = 0.;
450  size_t size = vec.size();
451
452  while (size>0)
453    {
454      size--; 
455     
456      result *= k;
457      result += vec[size];
458    }
459 
460  return result;
461}
462
463//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
464
465G4double G4DNAScreenedRutherfordElasticModel::ScreenedRutherfordRandomizeCosTheta(G4double k, G4double z)
466{
467
468 //  d sigma_el                sigma_Ruth(K)
469 // ------------ (K) ~ -----------------------------
470 //   d Omega           (1 + 2 n(K) - cos(theta))^2
471 //
472 // We extract cos(theta) distributed as (1 + 2 n(K) - cos(theta))^-2
473 //
474 // Maximum is for theta=0: 1/(4 n(K)^2) (When n(K) is positive, that is always satisfied within the validity of the process)
475 //
476 // Phys. Med. Biol. 45 (2000) 3171-3194
477
478 // ***** Original method
479
480 G4double n = ScreeningFactor(k, z);
481
482 G4double oneOverMax = (4.*n*n);
483
484 G4double cosTheta = 0.;
485 G4double fCosTheta;
486
487 do 
488 { 
489   cosTheta = 2. * G4UniformRand() - 1.;
490//G4cout << "SR cos=" << cosTheta << G4endl;
491   fCosTheta = (1 + 2.*n - cosTheta);
492   if (fCosTheta !=0.) fCosTheta = oneOverMax / (fCosTheta*fCosTheta);
493 }
494 while (fCosTheta < G4UniformRand());
495 
496 return cosTheta;
497 
498 // ***** Alternative method using cumulative probability
499/*
500 G4double cosTheta = -1;
501 G4double cumul = 0;
502 G4double value = 0;
503 G4double n = ScreeningFactor(k, z);
504 G4double fCosTheta;
505 
506 // Number of integration steps in the -1,1 range
507 G4int iMax=200;
508 
509 G4double random = G4UniformRand();
510 
511 // Cumulate differential cross section
512 for (G4int i=0; i<iMax; i++)
513 {
514   cosTheta = -1 + i*2./(iMax-1);
515   fCosTheta = (1 + 2.*n - cosTheta);
516   if (fCosTheta !=0.) cumul = cumul + 1./(fCosTheta*fCosTheta);
517 }
518 
519 // Select cosTheta
520 for (G4int i=0; i<iMax; i++)
521 {
522   cosTheta = -1 + i*2./(iMax-1);
523   fCosTheta = (1 + 2.*n - cosTheta);
524   if (cumul !=0.) value = value + (1./(fCosTheta*fCosTheta)) / cumul;
525   if (random < value) break;
526 }
527 return cosTheta;
528*/
529}
530
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