source: trunk/source/processes/electromagnetic/lowenergy/src/G4DNAScreenedRutherfordElasticModel.cc @ 1196

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26// $Id: G4DNAScreenedRutherfordElasticModel.cc,v 1.9 2009/08/13 11:32:47 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-03-cand-01 $
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  if( verboseLevel>0 ) 
60  { 
61    G4cout << "Screened Rutherford Elastic model is constructed " << G4endl
62           << "Energy range: "
63           << lowEnergyLimit / eV << " eV - "
64           << highEnergyLimit / MeV << " MeV"
65           << G4endl;
66  }
67 
68}
69
70//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
71
72G4DNAScreenedRutherfordElasticModel::~G4DNAScreenedRutherfordElasticModel()
73{}
74
75//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
76
77void G4DNAScreenedRutherfordElasticModel::Initialise(const G4ParticleDefinition* /*particle*/,
78                                       const G4DataVector& /*cuts*/)
79{
80
81  if (verboseLevel > 3)
82    G4cout << "Calling G4DNAScreenedRutherfordElasticModel::Initialise()" << G4endl;
83
84  // Energy limits
85 
86  if (LowEnergyLimit() < lowEnergyLimit)
87  {
88    G4cout << "G4DNAScreenedRutherfordElasticModel: low energy limit increased from " << 
89        LowEnergyLimit()/eV << " eV to " << lowEnergyLimit/eV << " eV" << G4endl;
90    SetLowEnergyLimit(lowEnergyLimit);
91    }
92
93  if (HighEnergyLimit() > highEnergyLimit)
94  {
95    G4cout << "G4DNAScreenedRutherfordElasticModel: high energy limit decreased from " << 
96        HighEnergyLimit()/MeV << " MeV to " << highEnergyLimit/MeV << " MeV" << G4endl;
97    SetHighEnergyLimit(highEnergyLimit);
98  }
99
100  // Constants for final stae by Brenner & Zaider
101 
102  betaCoeff.push_back(7.51525);
103  betaCoeff.push_back(-0.41912);   
104  betaCoeff.push_back(7.2017E-3);
105  betaCoeff.push_back(-4.646E-5);   
106  betaCoeff.push_back(1.02897E-7);
107
108  deltaCoeff.push_back(2.9612); 
109  deltaCoeff.push_back(-0.26376); 
110  deltaCoeff.push_back(4.307E-3); 
111  deltaCoeff.push_back(-2.6895E-5);
112  deltaCoeff.push_back(5.83505E-8);
113
114  gamma035_10Coeff.push_back(-1.7013); 
115  gamma035_10Coeff.push_back(-1.48284); 
116  gamma035_10Coeff.push_back(0.6331); 
117  gamma035_10Coeff.push_back(-0.10911); 
118  gamma035_10Coeff.push_back(8.358E-3); 
119  gamma035_10Coeff.push_back(-2.388E-4);
120
121  gamma10_100Coeff.push_back(-3.32517); 
122  gamma10_100Coeff.push_back(0.10996); 
123  gamma10_100Coeff.push_back(-4.5255E-3); 
124  gamma10_100Coeff.push_back(5.8372E-5); 
125  gamma10_100Coeff.push_back(-2.4659E-7);
126
127  gamma100_200Coeff.push_back(2.4775E-2);
128  gamma100_200Coeff.push_back(-2.96264E-5);
129  gamma100_200Coeff.push_back(-1.20655E-7);
130
131  //
132
133  if( verboseLevel>0 ) 
134  { 
135    G4cout << "Screened Rutherford elastic model is initialized " << G4endl
136           << "Energy range: "
137           << LowEnergyLimit() / eV << " eV - "
138           << HighEnergyLimit() / MeV << " MeV"
139           << G4endl;
140  }
141 
142  if(!isInitialised) 
143  {
144    isInitialised = true;
145 
146    if(pParticleChange)
147      fParticleChangeForGamma = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
148    else
149      fParticleChangeForGamma = new G4ParticleChangeForGamma();
150  }   
151
152  // InitialiseElementSelectors(particle,cuts);
153
154  // Test if water material
155
156  flagMaterialIsWater= false;
157  densityWater = 0;
158
159  const G4ProductionCutsTable* theCoupleTable = G4ProductionCutsTable::GetProductionCutsTable();
160
161  if(theCoupleTable) 
162  {
163    G4int numOfCouples = theCoupleTable->GetTableSize();
164 
165    if(numOfCouples>0) 
166    {
167          for (G4int i=0; i<numOfCouples; i++) 
168          {
169            const G4MaterialCutsCouple* couple = theCoupleTable->GetMaterialCutsCouple(i);
170            const G4Material* material = couple->GetMaterial();
171
172            if (material->GetName() == "G4_WATER") 
173            {
174              G4double density = material->GetAtomicNumDensityVector()[1];
175              flagMaterialIsWater = true; 
176              densityWater = density; 
177             
178              if (verboseLevel > 3) 
179              G4cout << "****** Water material is found with density(cm^-3)=" << density/(cm*cm*cm) << G4endl;
180            }
181 
182          }
183
184    } // if(numOfCouples>0)
185
186  } // if (theCoupleTable)
187
188}
189
190//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
191
192G4double G4DNAScreenedRutherfordElasticModel::CrossSectionPerVolume(const G4Material*,
193                                           const G4ParticleDefinition*,
194                                           G4double ekin,
195                                           G4double,
196                                           G4double)
197{
198  if (verboseLevel > 3)
199    G4cout << "Calling CrossSectionPerVolume() of G4DNAScreenedRutherfordElasticModel" << G4endl;
200
201 // Calculate total cross section for model
202
203 G4double sigma=0;
204 
205 if (flagMaterialIsWater)
206 {
207
208  if (ekin < highEnergyLimit)
209  {
210     
211      //SI : XS must not be zero otherwise sampling of secondaries method ignored
212      if (ekin < lowEnergyLimitOfModel) ekin = lowEnergyLimitOfModel;
213      //
214     
215      G4double z = 10.;
216      G4double n = ScreeningFactor(ekin,z);
217      G4double crossSection = RutherfordCrossSection(ekin, z);
218      sigma = pi *  crossSection / (n * (n + 1.)); 
219  }
220
221  if (verboseLevel > 3)
222  {
223    G4cout << "---> Kinetic energy(eV)=" << ekin/eV << G4endl;
224    G4cout << " - Cross section per water molecule (cm^2)=" << sigma/cm/cm << G4endl;
225    G4cout << " - Cross section per water molecule (cm^-1)=" << sigma*densityWater/(1./cm) << G4endl;
226  } 
227
228 } // if (flagMaterialIsWater)
229
230 return sigma*densityWater;               
231}
232
233//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
234
235G4double G4DNAScreenedRutherfordElasticModel::RutherfordCrossSection(G4double k, G4double z)
236{
237  //   
238  //                               e^4         /      K + m_e c^2      \^2
239  // sigma_Ruth(K) = Z (Z+1) -------------------- | --------------------- |
240  //                          (4 pi epsilon_0)^2  \  K * (K + 2 m_e c^2)  /
241  //
242  // Where K is the electron non-relativistic kinetic energy
243  //
244  // NIM 155, pp. 145-156, 1978
245 
246  G4double length =(e_squared * (k + electron_mass_c2)) / (4 * pi *epsilon0 * k * ( k + 2 * electron_mass_c2));
247  G4double cross = z * ( z + 1) * length * length;
248 
249  return cross;
250}
251
252//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
253
254G4double G4DNAScreenedRutherfordElasticModel::ScreeningFactor(G4double k, G4double z)
255{
256  //
257  //         alpha_1 + beta_1 ln(K/eV)   constK Z^(2/3)
258  // n(T) = -------------------------- -----------------
259  //              K/(m_e c^2)            2 + K/(m_e c^2)
260  //
261  // Where K is the electron non-relativistic kinetic energy
262  //
263  // n(T) > 0 for T < ~ 400 MeV
264  //
265  // NIM 155, pp. 145-156, 1978
266  // Formulae (2) and (5)
267
268  const G4double alpha_1(1.64);
269  const G4double beta_1(-0.0825);
270  const G4double constK(1.7E-5);
271
272  G4double numerator = (alpha_1 + beta_1 * std::log(k/eV)) * constK * std::pow(z, 2./3.);
273
274  k /= electron_mass_c2;
275
276  G4double denominator = k * (2 + k);
277
278  G4double value = 0.;
279  if (denominator > 0.) value = numerator / denominator;
280
281  return value;
282}
283
284//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
285
286void G4DNAScreenedRutherfordElasticModel::SampleSecondaries(std::vector<G4DynamicParticle*>* /*fvect*/,
287                                              const G4MaterialCutsCouple* /*couple*/,
288                                              const G4DynamicParticle* aDynamicElectron,
289                                              G4double,
290                                              G4double)
291{
292
293  if (verboseLevel > 3)
294    G4cout << "Calling SampleSecondaries() of G4DNAScreenedRutherfordElasticModel" << G4endl;
295
296  G4double electronEnergy0 = aDynamicElectron->GetKineticEnergy();
297 
298  if (electronEnergy0 < killBelowEnergy)
299  {
300    fParticleChangeForGamma->ProposeTrackStatus(fStopAndKill);
301    fParticleChangeForGamma->ProposeLocalEnergyDeposit(electronEnergy0);
302    return ;
303  }
304
305  G4double cosTheta = 0.;
306
307  if (electronEnergy0>= killBelowEnergy && electronEnergy0 < highEnergyLimit)
308  { 
309    if (electronEnergy0<intermediateEnergyLimit)
310    {
311    if (verboseLevel > 3) G4cout << "---> Using Brenner & Zaider model" << G4endl;
312    cosTheta = BrennerZaiderRandomizeCosTheta(electronEnergy0);
313    } 
314
315    if (electronEnergy0>=intermediateEnergyLimit)
316    {
317    if (verboseLevel > 3) G4cout << "---> Using Screened Rutherford model" << G4endl;
318    G4double z = 10.;
319    cosTheta = ScreenedRutherfordRandomizeCosTheta(electronEnergy0,z);
320    } 
321
322    G4double phi = 2. * pi * G4UniformRand();
323
324    G4ThreeVector zVers = aDynamicElectron->GetMomentumDirection();
325    G4ThreeVector xVers = zVers.orthogonal();
326    G4ThreeVector yVers = zVers.cross(xVers);
327
328    G4double xDir = std::sqrt(1. - cosTheta*cosTheta);
329    G4double yDir = xDir;
330    xDir *= std::cos(phi);
331    yDir *= std::sin(phi);
332
333    G4ThreeVector zPrimeVers((xDir*xVers + yDir*yVers + cosTheta*zVers));
334
335    fParticleChangeForGamma->ProposeMomentumDirection(zPrimeVers.unit()) ;
336
337    fParticleChangeForGamma->SetProposedKineticEnergy(electronEnergy0);
338  }
339
340}
341
342//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
343
344G4double G4DNAScreenedRutherfordElasticModel::BrennerZaiderRandomizeCosTheta(G4double k)
345{
346  //  d sigma_el                         1                                 beta(K)
347  // ------------ (K) ~ --------------------------------- + ---------------------------------
348  //   d Omega           (1 + 2 gamma(K) - cos(theta))^2     (1 + 2 delta(K) + cos(theta))^2
349  //
350  // Maximum is < 1/(4 gamma(K)^2) + beta(K)/((2+2delta(K))^2)
351  //
352  // Phys. Med. Biol. 29 N.4 (1983) 443-447
353 
354  // gamma(K), beta(K) and delta(K) are polynomials with coefficients for energy measured in eV
355
356  k /= eV;
357 
358  G4double beta = std::exp(CalculatePolynomial(k,betaCoeff)); 
359  G4double delta = std::exp(CalculatePolynomial(k,deltaCoeff)); 
360  G4double gamma;
361 
362  if (k > 100.)
363  {
364      gamma = CalculatePolynomial(k, gamma100_200Coeff); 
365      // Only in this case it is not the exponent of the polynomial
366  } 
367  else 
368  {
369      if (k>10)
370      {
371          gamma = std::exp(CalculatePolynomial(k, gamma10_100Coeff));
372      }
373      else
374      {
375          gamma = std::exp(CalculatePolynomial(k, gamma035_10Coeff));
376      }
377  }
378
379  // ***** Original method
380
381  G4double oneOverMax = 1. / (1./(4.*gamma*gamma) + beta/( (2.+2.*delta)*(2.+2.*delta) ));
382 
383  G4double cosTheta = 0.;
384  G4double leftDenominator = 0.;
385  G4double rightDenominator = 0.;
386  G4double fCosTheta = 0.;
387 
388  do
389  {
390      cosTheta = 2. * G4UniformRand() - 1.;
391     
392      leftDenominator = (1. + 2.*gamma - cosTheta);
393      rightDenominator = (1. + 2.*delta + cosTheta);
394      if ( (leftDenominator * rightDenominator) != 0. )
395      {
396          fCosTheta = oneOverMax * (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator));
397      }
398  }
399  while (fCosTheta < G4UniformRand());
400
401  return cosTheta; 
402
403  // ***** Alternative method using cumulative probability
404/*
405 G4double cosTheta = -1;
406 G4double cumul = 0;
407 G4double value = 0;
408 G4double leftDenominator = 0.;
409 G4double rightDenominator = 0.;
410 
411 // Number of integration steps in the -1,1 range
412 G4int iMax=200;
413 
414 G4double random = G4UniformRand();
415 
416 // Cumulate differential cross section
417 for (G4int i=0; i<iMax; i++)
418 {
419   cosTheta = -1 + i*2./(iMax-1);
420   leftDenominator = (1. + 2.*gamma - cosTheta);
421   rightDenominator = (1. + 2.*delta + cosTheta);
422   if ( (leftDenominator * rightDenominator) != 0. )
423   {
424     cumul = cumul + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator));
425   }
426 }
427 
428 // Select cosTheta
429 for (G4int i=0; i<iMax; i++)
430 {
431   cosTheta = -1 + i*2./(iMax-1);
432   leftDenominator = (1. + 2.*gamma - cosTheta);
433   rightDenominator = (1. + 2.*delta + cosTheta);
434   if (cumul !=0 && (leftDenominator * rightDenominator) != 0.)
435       value = value + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator)) / cumul;
436   if (random < value) break;
437 }
438
439 return cosTheta;
440*/
441
442}
443
444//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
445
446G4double G4DNAScreenedRutherfordElasticModel::CalculatePolynomial(G4double k, std::vector<G4double>& vec)
447{
448  // Sum_{i=0}^{size-1} vector_i k^i
449  //
450  // Phys. Med. Biol. 29 N.4 (1983) 443-447
451
452  G4double result = 0.;
453  size_t size = vec.size();
454
455  while (size>0)
456    {
457      size--; 
458     
459      result *= k;
460      result += vec[size];
461    }
462 
463  return result;
464}
465
466//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
467
468G4double G4DNAScreenedRutherfordElasticModel::ScreenedRutherfordRandomizeCosTheta(G4double k, G4double z)
469{
470
471 //  d sigma_el                sigma_Ruth(K)
472 // ------------ (K) ~ -----------------------------
473 //   d Omega           (1 + 2 n(K) - cos(theta))^2
474 //
475 // We extract cos(theta) distributed as (1 + 2 n(K) - cos(theta))^-2
476 //
477 // 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)
478 //
479 // Phys. Med. Biol. 45 (2000) 3171-3194
480
481 // ***** Original method
482
483 G4double n = ScreeningFactor(k, z);
484
485 G4double oneOverMax = (4.*n*n);
486
487 G4double cosTheta = 0.;
488 G4double fCosTheta;
489
490 do 
491 { 
492   cosTheta = 2. * G4UniformRand() - 1.;
493   fCosTheta = (1 + 2.*n - cosTheta);
494   if (fCosTheta !=0.) fCosTheta = oneOverMax / (fCosTheta*fCosTheta);
495 }
496 while (fCosTheta < G4UniformRand());
497 
498 return cosTheta;
499 
500 // ***** Alternative method using cumulative probability
501/*
502 G4double cosTheta = -1;
503 G4double cumul = 0;
504 G4double value = 0;
505 G4double n = ScreeningFactor(k, z);
506 G4double fCosTheta;
507 
508 // Number of integration steps in the -1,1 range
509 G4int iMax=200;
510 
511 G4double random = G4UniformRand();
512 
513 // Cumulate differential cross section
514 for (G4int i=0; i<iMax; i++)
515 {
516   cosTheta = -1 + i*2./(iMax-1);
517   fCosTheta = (1 + 2.*n - cosTheta);
518   if (fCosTheta !=0.) cumul = cumul + 1./(fCosTheta*fCosTheta);
519 }
520 
521 // Select cosTheta
522 for (G4int i=0; i<iMax; i++)
523 {
524   cosTheta = -1 + i*2./(iMax-1);
525   fCosTheta = (1 + 2.*n - cosTheta);
526   if (cumul !=0.) value = value + (1./(fCosTheta*fCosTheta)) / cumul;
527   if (random < value) break;
528 }
529 return cosTheta;
530*/
531}
532
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