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

Last change on this file was 1347, checked in by garnier, 15 years ago

geant4 tag 9.4
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26// $Id: G4DNAScreenedRutherfordElasticModel.cc,v 1.15 2010/11/11 22:32:22 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-04-ref-00 $
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 = 9*eV;
44 lowEnergyLimit = 0 * eV;
45 intermediateEnergyLimit = 200 * eV; // Switch between two final state models
46 highEnergyLimit = 1. * MeV;
47 SetLowEnergyLimit(lowEnergyLimit);
48 SetHighEnergyLimit(highEnergyLimit);
49
50 verboseLevel= 0;
51 // Verbosity scale:
52 // 0 = nothing
53 // 1 = warning for energy non-conservation
54 // 2 = details of energy budget
55 // 3 = calculation of cross sections, file openings, sampling of atoms
56 // 4 = entering in methods
57
58 if( verboseLevel>0 )
59 {
60 G4cout << "Screened Rutherford Elastic model is constructed " << G4endl
61 << "Energy range: "
62 << lowEnergyLimit / eV << " eV - "
63 << highEnergyLimit / MeV << " MeV"
64 << G4endl;
65 }
66
67}
68
69//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
70
71G4DNAScreenedRutherfordElasticModel::~G4DNAScreenedRutherfordElasticModel()
72{}
73
74//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
75
76void G4DNAScreenedRutherfordElasticModel::Initialise(const G4ParticleDefinition* /*particle*/,
77 const G4DataVector& /*cuts*/)
78{
79
80 if (verboseLevel > 3)
81 G4cout << "Calling G4DNAScreenedRutherfordElasticModel::Initialise()" << G4endl;
82
83 // Energy limits
84
85 if (LowEnergyLimit() < lowEnergyLimit)
86 {
87 G4cout << "G4DNAScreenedRutherfordElasticModel: low energy limit increased from " <<
88 LowEnergyLimit()/eV << " eV to " << lowEnergyLimit/eV << " eV" << G4endl;
89 SetLowEnergyLimit(lowEnergyLimit);
90 }
91
92 if (HighEnergyLimit() > highEnergyLimit)
93 {
94 G4cout << "G4DNAScreenedRutherfordElasticModel: high energy limit decreased from " <<
95 HighEnergyLimit()/MeV << " MeV to " << highEnergyLimit/MeV << " MeV" << G4endl;
96 SetHighEnergyLimit(highEnergyLimit);
97 }
98
99 // Constants for final stae by Brenner & Zaider
100
101 betaCoeff.push_back(7.51525);
102 betaCoeff.push_back(-0.41912);
103 betaCoeff.push_back(7.2017E-3);
104 betaCoeff.push_back(-4.646E-5);
105 betaCoeff.push_back(1.02897E-7);
106
107 deltaCoeff.push_back(2.9612);
108 deltaCoeff.push_back(-0.26376);
109 deltaCoeff.push_back(4.307E-3);
110 deltaCoeff.push_back(-2.6895E-5);
111 deltaCoeff.push_back(5.83505E-8);
112
113 gamma035_10Coeff.push_back(-1.7013);
114 gamma035_10Coeff.push_back(-1.48284);
115 gamma035_10Coeff.push_back(0.6331);
116 gamma035_10Coeff.push_back(-0.10911);
117 gamma035_10Coeff.push_back(8.358E-3);
118 gamma035_10Coeff.push_back(-2.388E-4);
119
120 gamma10_100Coeff.push_back(-3.32517);
121 gamma10_100Coeff.push_back(0.10996);
122 gamma10_100Coeff.push_back(-4.5255E-3);
123 gamma10_100Coeff.push_back(5.8372E-5);
124 gamma10_100Coeff.push_back(-2.4659E-7);
125
126 gamma100_200Coeff.push_back(2.4775E-2);
127 gamma100_200Coeff.push_back(-2.96264E-5);
128 gamma100_200Coeff.push_back(-1.20655E-7);
129
130 //
131
132 if( verboseLevel>0 )
133 {
134 G4cout << "Screened Rutherford elastic model is initialized " << G4endl
135 << "Energy range: "
136 << LowEnergyLimit() / eV << " eV - "
137 << HighEnergyLimit() / MeV << " MeV"
138 << G4endl;
139 }
140
141 if(!isInitialised)
142 {
143 isInitialised = true;
144
145 if(pParticleChange)
146 fParticleChangeForGamma = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
147 else
148 fParticleChangeForGamma = new G4ParticleChangeForGamma();
149 }
150
151 // InitialiseElementSelectors(particle,cuts);
152
153}
154
155//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
156
157G4double G4DNAScreenedRutherfordElasticModel::CrossSectionPerVolume(const G4Material* material,
158 const G4ParticleDefinition*,
159 G4double ekin,
160 G4double,
161 G4double)
162{
163 if (verboseLevel > 3)
164 G4cout << "Calling CrossSectionPerVolume() of G4DNAScreenedRutherfordElasticModel" << G4endl;
165
166 // Calculate total cross section for model
167
168 G4double sigma=0;
169
170 if (material->GetName() == "G4_WATER")
171 {
172
173 if (ekin < highEnergyLimit)
174 {
175
176 if (ekin < killBelowEnergy) return DBL_MAX;
177
178 G4double z = 10.;
179 G4double n = ScreeningFactor(ekin,z);
180 G4double crossSection = RutherfordCrossSection(ekin, z);
181 sigma = pi * crossSection / (n * (n + 1.));
182 }
183
184 if (verboseLevel > 3)
185 {
186 G4cout << "---> Kinetic energy(eV)=" << ekin/eV << G4endl;
187 G4cout << " - Cross section per water molecule (cm^2)=" << sigma/cm/cm << G4endl;
188 G4cout << " - Cross section per water molecule (cm^-1)=" << sigma*material->GetAtomicNumDensityVector()[1]/(1./cm) << G4endl;
189 }
190
191 }
192
193 return sigma*material->GetAtomicNumDensityVector()[1];
194}
195
196//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
197
198G4double G4DNAScreenedRutherfordElasticModel::RutherfordCrossSection(G4double k, G4double z)
199{
200 //
201 // e^4 / K + m_e c^2 \^2
202 // sigma_Ruth(K) = Z (Z+1) -------------------- | --------------------- |
203 // (4 pi epsilon_0)^2 \ K * (K + 2 m_e c^2) /
204 //
205 // Where K is the electron non-relativistic kinetic energy
206 //
207 // NIM 155, pp. 145-156, 1978
208
209 G4double length =(e_squared * (k + electron_mass_c2)) / (4 * pi *epsilon0 * k * ( k + 2 * electron_mass_c2));
210 G4double cross = z * ( z + 1) * length * length;
211
212 return cross;
213}
214
215//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
216
217G4double G4DNAScreenedRutherfordElasticModel::ScreeningFactor(G4double k, G4double z)
218{
219 //
220 // alpha_1 + beta_1 ln(K/eV) constK Z^(2/3)
221 // n(T) = -------------------------- -----------------
222 // K/(m_e c^2) 2 + K/(m_e c^2)
223 //
224 // Where K is the electron non-relativistic kinetic energy
225 //
226 // n(T) > 0 for T < ~ 400 MeV
227 //
228 // NIM 155, pp. 145-156, 1978
229 // Formulae (2) and (5)
230
231 const G4double alpha_1(1.64);
232 const G4double beta_1(-0.0825);
233 const G4double constK(1.7E-5);
234
235 G4double numerator = (alpha_1 + beta_1 * std::log(k/eV)) * constK * std::pow(z, 2./3.);
236
237 k /= electron_mass_c2;
238
239 G4double denominator = k * (2 + k);
240
241 G4double value = 0.;
242 if (denominator > 0.) value = numerator / denominator;
243
244 return value;
245}
246
247//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
248
249void G4DNAScreenedRutherfordElasticModel::SampleSecondaries(std::vector<G4DynamicParticle*>* /*fvect*/,
250 const G4MaterialCutsCouple* /*couple*/,
251 const G4DynamicParticle* aDynamicElectron,
252 G4double,
253 G4double)
254{
255
256 if (verboseLevel > 3)
257 G4cout << "Calling SampleSecondaries() of G4DNAScreenedRutherfordElasticModel" << G4endl;
258
259 G4double electronEnergy0 = aDynamicElectron->GetKineticEnergy();
260
261 if (electronEnergy0 < killBelowEnergy)
262 {
263 fParticleChangeForGamma->ProposeTrackStatus(fStopAndKill);
264 fParticleChangeForGamma->ProposeLocalEnergyDeposit(electronEnergy0);
265 return ;
266 }
267
268 G4double cosTheta = 0.;
269
270 if (electronEnergy0>= killBelowEnergy && electronEnergy0 < highEnergyLimit)
271 {
272 if (electronEnergy0<intermediateEnergyLimit)
273 {
274 if (verboseLevel > 3) G4cout << "---> Using Brenner & Zaider model" << G4endl;
275 cosTheta = BrennerZaiderRandomizeCosTheta(electronEnergy0);
276 }
277
278 if (electronEnergy0>=intermediateEnergyLimit)
279 {
280 if (verboseLevel > 3) G4cout << "---> Using Screened Rutherford model" << G4endl;
281 G4double z = 10.;
282 cosTheta = ScreenedRutherfordRandomizeCosTheta(electronEnergy0,z);
283 }
284
285 G4double phi = 2. * pi * G4UniformRand();
286
287 G4ThreeVector zVers = aDynamicElectron->GetMomentumDirection();
288 G4ThreeVector xVers = zVers.orthogonal();
289 G4ThreeVector yVers = zVers.cross(xVers);
290
291 G4double xDir = std::sqrt(1. - cosTheta*cosTheta);
292 G4double yDir = xDir;
293 xDir *= std::cos(phi);
294 yDir *= std::sin(phi);
295
296 G4ThreeVector zPrimeVers((xDir*xVers + yDir*yVers + cosTheta*zVers));
297
298 fParticleChangeForGamma->ProposeMomentumDirection(zPrimeVers.unit()) ;
299
300 fParticleChangeForGamma->SetProposedKineticEnergy(electronEnergy0);
301 }
302
303}
304
305//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
306
307G4double G4DNAScreenedRutherfordElasticModel::BrennerZaiderRandomizeCosTheta(G4double k)
308{
309 // d sigma_el 1 beta(K)
310 // ------------ (K) ~ --------------------------------- + ---------------------------------
311 // d Omega (1 + 2 gamma(K) - cos(theta))^2 (1 + 2 delta(K) + cos(theta))^2
312 //
313 // Maximum is < 1/(4 gamma(K)^2) + beta(K)/((2+2delta(K))^2)
314 //
315 // Phys. Med. Biol. 29 N.4 (1983) 443-447
316
317 // gamma(K), beta(K) and delta(K) are polynomials with coefficients for energy measured in eV
318
319 k /= eV;
320
321 G4double beta = std::exp(CalculatePolynomial(k,betaCoeff));
322 G4double delta = std::exp(CalculatePolynomial(k,deltaCoeff));
323 G4double gamma;
324
325 if (k > 100.)
326 {
327 gamma = CalculatePolynomial(k, gamma100_200Coeff);
328 // Only in this case it is not the exponent of the polynomial
329 }
330 else
331 {
332 if (k>10)
333 {
334 gamma = std::exp(CalculatePolynomial(k, gamma10_100Coeff));
335 }
336 else
337 {
338 gamma = std::exp(CalculatePolynomial(k, gamma035_10Coeff));
339 }
340 }
341
342 // ***** Original method
343
344 G4double oneOverMax = 1. / (1./(4.*gamma*gamma) + beta/( (2.+2.*delta)*(2.+2.*delta) ));
345
346 G4double cosTheta = 0.;
347 G4double leftDenominator = 0.;
348 G4double rightDenominator = 0.;
349 G4double fCosTheta = 0.;
350
351 do
352 {
353 cosTheta = 2. * G4UniformRand() - 1.;
354
355 leftDenominator = (1. + 2.*gamma - cosTheta);
356 rightDenominator = (1. + 2.*delta + cosTheta);
357 if ( (leftDenominator * rightDenominator) != 0. )
358 {
359 fCosTheta = oneOverMax * (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator));
360 }
361 }
362 while (fCosTheta < G4UniformRand());
363
364 return cosTheta;
365
366 // ***** Alternative method using cumulative probability
367/*
368 G4double cosTheta = -1;
369 G4double cumul = 0;
370 G4double value = 0;
371 G4double leftDenominator = 0.;
372 G4double rightDenominator = 0.;
373
374 // Number of integration steps in the -1,1 range
375 G4int iMax=200;
376
377 G4double random = G4UniformRand();
378
379 // Cumulate differential cross section
380 for (G4int i=0; i<iMax; i++)
381 {
382 cosTheta = -1 + i*2./(iMax-1);
383 leftDenominator = (1. + 2.*gamma - cosTheta);
384 rightDenominator = (1. + 2.*delta + cosTheta);
385 if ( (leftDenominator * rightDenominator) != 0. )
386 {
387 cumul = cumul + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator));
388 }
389 }
390
391 // Select cosTheta
392 for (G4int i=0; i<iMax; i++)
393 {
394 cosTheta = -1 + i*2./(iMax-1);
395 leftDenominator = (1. + 2.*gamma - cosTheta);
396 rightDenominator = (1. + 2.*delta + cosTheta);
397 if (cumul !=0 && (leftDenominator * rightDenominator) != 0.)
398 value = value + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator)) / cumul;
399 if (random < value) break;
400 }
401
402 return cosTheta;
403*/
404
405}
406
407//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
408
409G4double G4DNAScreenedRutherfordElasticModel::CalculatePolynomial(G4double k, std::vector<G4double>& vec)
410{
411 // Sum_{i=0}^{size-1} vector_i k^i
412 //
413 // Phys. Med. Biol. 29 N.4 (1983) 443-447
414
415 G4double result = 0.;
416 size_t size = vec.size();
417
418 while (size>0)
419 {
420 size--;
421
422 result *= k;
423 result += vec[size];
424 }
425
426 return result;
427}
428
429//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
430
431G4double G4DNAScreenedRutherfordElasticModel::ScreenedRutherfordRandomizeCosTheta(G4double k, G4double z)
432{
433
434 // d sigma_el sigma_Ruth(K)
435 // ------------ (K) ~ -----------------------------
436 // d Omega (1 + 2 n(K) - cos(theta))^2
437 //
438 // We extract cos(theta) distributed as (1 + 2 n(K) - cos(theta))^-2
439 //
440 // 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)
441 //
442 // Phys. Med. Biol. 45 (2000) 3171-3194
443
444 // ***** Original method
445
446 G4double n = ScreeningFactor(k, z);
447
448 G4double oneOverMax = (4.*n*n);
449
450 G4double cosTheta = 0.;
451 G4double fCosTheta;
452
453 do
454 {
455 cosTheta = 2. * G4UniformRand() - 1.;
456 fCosTheta = (1 + 2.*n - cosTheta);
457 if (fCosTheta !=0.) fCosTheta = oneOverMax / (fCosTheta*fCosTheta);
458 }
459 while (fCosTheta < G4UniformRand());
460
461 return cosTheta;
462
463 // ***** Alternative method using cumulative probability
464/*
465 G4double cosTheta = -1;
466 G4double cumul = 0;
467 G4double value = 0;
468 G4double n = ScreeningFactor(k, z);
469 G4double fCosTheta;
470
471 // Number of integration steps in the -1,1 range
472 G4int iMax=200;
473
474 G4double random = G4UniformRand();
475
476 // Cumulate differential cross section
477 for (G4int i=0; i<iMax; i++)
478 {
479 cosTheta = -1 + i*2./(iMax-1);
480 fCosTheta = (1 + 2.*n - cosTheta);
481 if (fCosTheta !=0.) cumul = cumul + 1./(fCosTheta*fCosTheta);
482 }
483
484 // Select cosTheta
485 for (G4int i=0; i<iMax; i++)
486 {
487 cosTheta = -1 + i*2./(iMax-1);
488 fCosTheta = (1 + 2.*n - cosTheta);
489 if (cumul !=0.) value = value + (1./(fCosTheta*fCosTheta)) / cumul;
490 if (random < value) break;
491 }
492 return cosTheta;
493*/
494}
495
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