source: trunk/source/processes/electromagnetic/lowenergy/src/G4DNAScreenedRutherfordElasticModel.cc@ 1066

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26// $Id: G4DNAScreenedRutherfordElasticModel.cc,v 1.5 2009/04/29 13:43:00 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-03-beta-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 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 < highEnergyLimit)
211 {
212
213 //SI : XS must not be zero otherwise sampling of secondaries method ignored
214 if (ekin < lowEnergyLimitOfModel) ekin = lowEnergyLimitOfModel;
215 //
216
217 G4double z = 10.;
218 G4double n = ScreeningFactor(ekin,z);
219 G4double crossSection = RutherfordCrossSection(ekin, z);
220 sigma = pi * crossSection / (n * (n + 1.));
221 }
222
223 if (verboseLevel > 3)
224 {
225 G4cout << "---> Kinetic energy(eV)=" << ekin/eV << G4endl;
226 G4cout << " - Cross section per water molecule (cm^2)=" << sigma/cm/cm << G4endl;
227 G4cout << " - Cross section per water molecule (cm^-1)=" << sigma*densityWater/(1./cm) << G4endl;
228 }
229
230 } // if (flagMaterialIsWater)
231
232 return sigma*densityWater;
233}
234
235//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
236
237G4double G4DNAScreenedRutherfordElasticModel::RutherfordCrossSection(G4double k, G4double z)
238{
239 //
240 // e^4 / K + m_e c^2 \^2
241 // sigma_Ruth(K) = Z (Z+1) -------------------- | --------------------- |
242 // (4 pi epsilon_0)^2 \ K * (K + 2 m_e c^2) /
243 //
244 // Where K is the electron non-relativistic kinetic energy
245 //
246 // NIM 155, pp. 145-156, 1978
247
248 G4double length =(e_squared * (k + electron_mass_c2)) / (4 * pi *epsilon0 * k * ( k + 2 * electron_mass_c2));
249 G4double cross = z * ( z + 1) * length * length;
250
251 return cross;
252}
253
254//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
255
256G4double G4DNAScreenedRutherfordElasticModel::ScreeningFactor(G4double k, G4double z)
257{
258 //
259 // alpha_1 + beta_1 ln(K/eV) constK Z^(2/3)
260 // n(T) = -------------------------- -----------------
261 // K/(m_e c^2) 2 + K/(m_e c^2)
262 //
263 // Where K is the electron non-relativistic kinetic energy
264 //
265 // n(T) > 0 for T < ~ 400 MeV
266 //
267 // NIM 155, pp. 145-156, 1978
268 // Formulae (2) and (5)
269
270 const G4double alpha_1(1.64);
271 const G4double beta_1(-0.0825);
272 const G4double constK(1.7E-5);
273
274 G4double numerator = (alpha_1 + beta_1 * std::log(k/eV)) * constK * std::pow(z, 2./3.);
275
276 k /= electron_mass_c2;
277
278 G4double denominator = k * (2 + k);
279
280 G4double value = 0.;
281 if (denominator > 0.) value = numerator / denominator;
282
283 return value;
284}
285
286//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
287
288void G4DNAScreenedRutherfordElasticModel::SampleSecondaries(std::vector<G4DynamicParticle*>* /*fvect*/,
289 const G4MaterialCutsCouple* /*couple*/,
290 const G4DynamicParticle* aDynamicElectron,
291 G4double,
292 G4double)
293{
294
295 if (verboseLevel > 3)
296 G4cout << "Calling SampleSecondaries() of G4DNAScreenedRutherfordElasticModel" << G4endl;
297
298 G4double electronEnergy0 = aDynamicElectron->GetKineticEnergy();
299
300 if (electronEnergy0 < killBelowEnergy)
301 {
302 fParticleChangeForGamma->ProposeTrackStatus(fStopAndKill);
303 fParticleChangeForGamma->ProposeLocalEnergyDeposit(electronEnergy0);
304 return ;
305 }
306
307 G4double cosTheta = 0.;
308
309 if (electronEnergy0>= killBelowEnergy && electronEnergy0 < highEnergyLimit)
310 {
311 if (electronEnergy0<intermediateEnergyLimit)
312 {
313 if (verboseLevel > 3) G4cout << "---> Using Brenner & Zaider model" << G4endl;
314 cosTheta = BrennerZaiderRandomizeCosTheta(electronEnergy0);
315 }
316
317 if (electronEnergy0>=intermediateEnergyLimit)
318 {
319 if (verboseLevel > 3) G4cout << "---> Using Screened Rutherford model" << G4endl;
320 G4double z = 10.;
321 cosTheta = ScreenedRutherfordRandomizeCosTheta(electronEnergy0,z);
322 }
323
324 G4double phi = 2. * pi * G4UniformRand();
325
326 G4ThreeVector zVers = aDynamicElectron->GetMomentumDirection();
327 G4ThreeVector xVers = zVers.orthogonal();
328 G4ThreeVector yVers = zVers.cross(xVers);
329
330 G4double xDir = std::sqrt(1. - cosTheta*cosTheta);
331 G4double yDir = xDir;
332 xDir *= std::cos(phi);
333 yDir *= std::sin(phi);
334
335 G4ThreeVector zPrimeVers((xDir*xVers + yDir*yVers + cosTheta*zVers));
336
337 fParticleChangeForGamma->ProposeMomentumDirection(zPrimeVers.unit()) ;
338
339 fParticleChangeForGamma->SetProposedKineticEnergy(electronEnergy0);
340 }
341
342}
343
344//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
345
346G4double G4DNAScreenedRutherfordElasticModel::BrennerZaiderRandomizeCosTheta(G4double k)
347{
348 // d sigma_el 1 beta(K)
349 // ------------ (K) ~ --------------------------------- + ---------------------------------
350 // d Omega (1 + 2 gamma(K) - cos(theta))^2 (1 + 2 delta(K) + cos(theta))^2
351 //
352 // Maximum is < 1/(4 gamma(K)^2) + beta(K)/((2+2delta(K))^2)
353 //
354 // Phys. Med. Biol. 29 N.4 (1983) 443-447
355
356 // gamma(K), beta(K) and delta(K) are polynomials with coefficients for energy measured in eV
357
358 k /= eV;
359
360 G4double beta = std::exp(CalculatePolynomial(k,betaCoeff));
361 G4double delta = std::exp(CalculatePolynomial(k,deltaCoeff));
362 G4double gamma;
363
364 if (k > 100.)
365 {
366 gamma = CalculatePolynomial(k, gamma100_200Coeff);
367 // Only in this case it is not the exponent of the polynomial
368 }
369 else
370 {
371 if (k>10)
372 {
373 gamma = std::exp(CalculatePolynomial(k, gamma10_100Coeff));
374 }
375 else
376 {
377 gamma = std::exp(CalculatePolynomial(k, gamma035_10Coeff));
378 }
379 }
380
381 // ***** Original method
382
383 G4double oneOverMax = 1. / (1./(4.*gamma*gamma) + beta/( (2.+2.*delta)*(2.+2.*delta) ));
384
385 G4double cosTheta = 0.;
386 G4double leftDenominator = 0.;
387 G4double rightDenominator = 0.;
388 G4double fCosTheta = 0.;
389
390 do
391 {
392 cosTheta = 2. * G4UniformRand() - 1.;
393
394 leftDenominator = (1. + 2.*gamma - cosTheta);
395 rightDenominator = (1. + 2.*delta + cosTheta);
396 if ( (leftDenominator * rightDenominator) != 0. )
397 {
398 fCosTheta = oneOverMax * (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator));
399 }
400 }
401 while (fCosTheta < G4UniformRand());
402
403 return cosTheta;
404
405 // ***** Alternative method using cumulative probability
406/*
407 G4double cosTheta = -1;
408 G4double cumul = 0;
409 G4double value = 0;
410 G4double leftDenominator = 0.;
411 G4double rightDenominator = 0.;
412
413 // Number of integration steps in the -1,1 range
414 G4int iMax=200;
415
416 G4double random = G4UniformRand();
417
418 // Cumulate differential cross section
419 for (G4int i=0; i<iMax; i++)
420 {
421 cosTheta = -1 + i*2./(iMax-1);
422 leftDenominator = (1. + 2.*gamma - cosTheta);
423 rightDenominator = (1. + 2.*delta + cosTheta);
424 if ( (leftDenominator * rightDenominator) != 0. )
425 {
426 cumul = cumul + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator));
427 }
428 }
429
430 // Select cosTheta
431 for (G4int i=0; i<iMax; i++)
432 {
433 cosTheta = -1 + i*2./(iMax-1);
434 leftDenominator = (1. + 2.*gamma - cosTheta);
435 rightDenominator = (1. + 2.*delta + cosTheta);
436 if (cumul !=0 && (leftDenominator * rightDenominator) != 0.)
437 value = value + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator)) / cumul;
438 if (random < value) break;
439 }
440
441 return cosTheta;
442*/
443
444}
445
446//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
447
448G4double G4DNAScreenedRutherfordElasticModel::CalculatePolynomial(G4double k, std::vector<G4double>& vec)
449{
450 // Sum_{i=0}^{size-1} vector_i k^i
451 //
452 // Phys. Med. Biol. 29 N.4 (1983) 443-447
453
454 G4double result = 0.;
455 size_t size = vec.size();
456
457 while (size>0)
458 {
459 size--;
460
461 result *= k;
462 result += vec[size];
463 }
464
465 return result;
466}
467
468//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
469
470G4double G4DNAScreenedRutherfordElasticModel::ScreenedRutherfordRandomizeCosTheta(G4double k, G4double z)
471{
472
473 // d sigma_el sigma_Ruth(K)
474 // ------------ (K) ~ -----------------------------
475 // d Omega (1 + 2 n(K) - cos(theta))^2
476 //
477 // We extract cos(theta) distributed as (1 + 2 n(K) - cos(theta))^-2
478 //
479 // 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)
480 //
481 // Phys. Med. Biol. 45 (2000) 3171-3194
482
483 // ***** Original method
484
485 G4double n = ScreeningFactor(k, z);
486
487 G4double oneOverMax = (4.*n*n);
488
489 G4double cosTheta = 0.;
490 G4double fCosTheta;
491
492 do
493 {
494 cosTheta = 2. * G4UniformRand() - 1.;
495//G4cout << "SR cos=" << cosTheta << G4endl;
496 fCosTheta = (1 + 2.*n - cosTheta);
497 if (fCosTheta !=0.) fCosTheta = oneOverMax / (fCosTheta*fCosTheta);
498 }
499 while (fCosTheta < G4UniformRand());
500
501 return cosTheta;
502
503 // ***** Alternative method using cumulative probability
504/*
505 G4double cosTheta = -1;
506 G4double cumul = 0;
507 G4double value = 0;
508 G4double n = ScreeningFactor(k, z);
509 G4double fCosTheta;
510
511 // Number of integration steps in the -1,1 range
512 G4int iMax=200;
513
514 G4double random = G4UniformRand();
515
516 // Cumulate differential cross section
517 for (G4int i=0; i<iMax; i++)
518 {
519 cosTheta = -1 + i*2./(iMax-1);
520 fCosTheta = (1 + 2.*n - cosTheta);
521 if (fCosTheta !=0.) cumul = cumul + 1./(fCosTheta*fCosTheta);
522 }
523
524 // Select cosTheta
525 for (G4int i=0; i<iMax; i++)
526 {
527 cosTheta = -1 + i*2./(iMax-1);
528 fCosTheta = (1 + 2.*n - cosTheta);
529 if (cumul !=0.) value = value + (1./(fCosTheta*fCosTheta)) / cumul;
530 if (random < value) break;
531 }
532 return cosTheta;
533*/
534}
535
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