source: trunk/source/processes/electromagnetic/lowenergy/src/G4PenelopeGammaConversionModel.cc@ 1199

Last change on this file since 1199 was 1196, checked in by garnier, 16 years ago

update CVS release candidate geant4.9.3.01
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25//
26// $Id: G4PenelopeGammaConversionModel.cc,v 1.6 2009/06/11 15:47:08 mantero Exp $
27// GEANT4 tag $Name: geant4-09-03-cand-01 $
28//
29// Author: Luciano Pandola
30//
31// History:
32// --------
33// 06 Oct 2008 L Pandola Migration from process to model
34// 17 Apr 2009 V Ivanchenko Cleanup initialisation and generation of secondaries:
35// - apply internal high-energy limit only in constructor
36// - do not apply low-energy limit (default is 0)
37// - do not apply production threshold on level of the model
38// 19 May 2009 L Pandola Explicitely set to zero pointers deleted in
39// Initialise(), since they might be checked later on
40//
41
42#include "G4PenelopeGammaConversionModel.hh"
43#include "G4ParticleDefinition.hh"
44#include "G4MaterialCutsCouple.hh"
45#include "G4ProductionCutsTable.hh"
46#include "G4DynamicParticle.hh"
47#include "G4Element.hh"
48#include "G4Gamma.hh"
49#include "G4Electron.hh"
50#include "G4Positron.hh"
51#include "G4CrossSectionHandler.hh"
52
53//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
54
55
56G4PenelopeGammaConversionModel::G4PenelopeGammaConversionModel(const G4ParticleDefinition*,
57 const G4String& nam)
58 :G4VEmModel(nam),fTheScreeningRadii(0),crossSectionHandler(0),isInitialised(false)
59{
60 fIntrinsicLowEnergyLimit = 2.0*electron_mass_c2;
61 fIntrinsicHighEnergyLimit = 100.0*GeV;
62 fSmallEnergy = 1.1*MeV;
63
64 // SetLowEnergyLimit(fIntrinsicLowEnergyLimit);
65 SetHighEnergyLimit(fIntrinsicHighEnergyLimit);
66 //
67 verboseLevel= 0;
68 // Verbosity scale:
69 // 0 = nothing
70 // 1 = warning for energy non-conservation
71 // 2 = details of energy budget
72 // 3 = calculation of cross sections, file openings, sampling of atoms
73 // 4 = entering in methods
74}
75
76//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
77
78G4PenelopeGammaConversionModel::~G4PenelopeGammaConversionModel()
79{
80 if (crossSectionHandler) delete crossSectionHandler;
81 if (fTheScreeningRadii) delete fTheScreeningRadii;
82}
83
84//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
85
86void G4PenelopeGammaConversionModel::Initialise(const G4ParticleDefinition*,
87 const G4DataVector& )
88{
89 if (verboseLevel > 3)
90 G4cout << "Calling G4PenelopeGammaConversionModel::Initialise()" << G4endl;
91
92 //Delete the old cross section handler, if necessary
93 if (crossSectionHandler)
94 {
95 crossSectionHandler->Clear();
96 delete crossSectionHandler;
97 crossSectionHandler = 0;
98 }
99
100 //Re-initialize cross section handler
101 crossSectionHandler = new G4CrossSectionHandler();
102 crossSectionHandler->Initialise(0,fIntrinsicLowEnergyLimit,HighEnergyLimit(),400);
103 crossSectionHandler->Clear();
104 G4String crossSectionFile = "penelope/pp-cs-pen-";
105 crossSectionHandler->LoadData(crossSectionFile);
106 //This is used to retrieve cross section values later on
107 crossSectionHandler->BuildMeanFreePathForMaterials();
108
109 if (verboseLevel > 2)
110 G4cout << "Loaded cross section files for PenelopeGammaConversion" << G4endl;
111
112 if (verboseLevel > 0) {
113 G4cout << "Penelope Gamma Conversion model is initialized " << G4endl
114 << "Energy range: "
115 << LowEnergyLimit() / MeV << " MeV - "
116 << HighEnergyLimit() / GeV << " GeV"
117 << G4endl;
118 }
119
120 if(isInitialised) return;
121 fParticleChange = GetParticleChangeForGamma();
122 isInitialised = true;
123}
124
125//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
126
127G4double G4PenelopeGammaConversionModel::ComputeCrossSectionPerAtom(
128 const G4ParticleDefinition*,
129 G4double energy,
130 G4double Z, G4double,
131 G4double, G4double)
132{
133 //
134 // Penelope model.
135 // Cross section (including triplet production) read from database and managed
136 // through the G4CrossSectionHandler utility. Cross section data are from
137 // M.J. Berger and J.H. Hubbel (XCOM), Report NBSIR 887-3598
138 //
139
140 if (verboseLevel > 3)
141 G4cout << "Calling ComputeCrossSectionPerAtom() of G4PenelopePhotoElectricModel" << G4endl;
142
143 G4int iZ = (G4int) Z;
144 // if (!crossSectionHandler) //VI: should not be checked in run time
145 // {
146 // G4cout << "G4PenelopeGammaConversionModel::ComputeCrossSectionPerAtom" << G4endl;
147 // G4cout << "The cross section handler is not correctly initialized" << G4endl;
148 // G4Exception();
149 // }
150 G4double cs = crossSectionHandler->FindValue(iZ,energy);
151
152 if (verboseLevel > 2)
153 G4cout << "Gamma conversion cross section at " << energy/MeV << " MeV for Z=" << Z <<
154 " = " << cs/barn << " barn" << G4endl;
155 return cs;
156}
157
158//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
159
160void
161G4PenelopeGammaConversionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
162 const G4MaterialCutsCouple* couple,
163 const G4DynamicParticle* aDynamicGamma,
164 G4double,
165 G4double)
166{
167 //
168 // Penelope model.
169 // Final state is sampled according to the Bethe-Heitler model with Coulomb
170 // corrections, according to the semi-empirical model of
171 // J. Baro' et al., Radiat. Phys. Chem. 44 (1994) 531.
172 //
173 // The model uses the high energy Coulomb correction from
174 // H. Davies et al., Phys. Rev. 93 (1954) 788
175 // and atomic screening radii tabulated from
176 // J.H. Hubbel et al., J. Phys. Chem. Ref. Data 9 (1980) 1023
177 // for Z= 1 to 92. This managed in this model by the method
178 // GetScreeningRadius().
179 //
180 if (verboseLevel > 3)
181 G4cout << "Calling SamplingSecondaries() of G4PenelopeGammaConversionModel" << G4endl;
182
183 G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
184
185 // Always kill primary
186 fParticleChange->ProposeTrackStatus(fStopAndKill);
187 fParticleChange->SetProposedKineticEnergy(0.);
188
189 if (photonEnergy <= fIntrinsicLowEnergyLimit)
190 {
191 fParticleChange->ProposeLocalEnergyDeposit(photonEnergy);
192 return ;
193 }
194
195 G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
196
197 G4double eps ;
198 G4double eki = electron_mass_c2 / photonEnergy ;
199
200 // Do it fast if photon energy < 1.1 MeV
201 if (photonEnergy < fSmallEnergy )
202 {
203 eps = eki + (1-2*eki) * G4UniformRand();
204 }
205 else
206 {
207 // Select randomly one element in the current material
208 if (verboseLevel > 2)
209 G4cout << "Going to select element in " << couple->GetMaterial()->GetName() << G4endl;
210 //use crossSectionHandler instead of G4EmElementSelector because in this case
211 //the dimension of the table is equal to the dimension of the database
212 //(less interpolation errors)
213 G4int Z_int = crossSectionHandler->SelectRandomAtom(couple,photonEnergy);
214 if (verboseLevel > 2)
215 G4cout << "Selected Z = " << Z_int << G4endl;
216
217 //Low energy and Coulomb corrections
218 G4double Z=(G4double) Z_int;
219 G4double ZAlpha = Z*fine_structure_const;
220 G4double ScreenRadius = GetScreeningRadius(Z);
221 G4double funct1=0,g0=0;
222 G4double g1min=0,g2min=0;
223 funct1 = 4.0*std::log(ScreenRadius);
224 g0 = funct1-4*CoulombCorrection(ZAlpha)+LowEnergyCorrection(ZAlpha,eki);
225 G4double bmin = 2*eki*ScreenRadius;
226 std::vector<G4double> ScreenFunctionValues = ScreenFunction(bmin);
227 if (ScreenFunctionValues.size() != 2)
228 {
229 G4cout << "G4PenelopeGammaConversionModel::SampleSecondaries" << G4endl;
230 G4cout << "ScreenFunction did not return 2 values! Something wrong! " << G4endl;
231 G4Exception();
232 }
233 g1min=g0+ScreenFunctionValues[0];
234 g2min=g0+ScreenFunctionValues[1];
235 G4double xr,a1,p1;
236 xr=0.5-eki;
237 a1=(2.0/3.0)*g1min*xr*xr;
238 p1=a1/(a1+g2min);
239
240 //Random sampling of eps
241 G4double rand1,rand2,rand3,b;
242 G4double g1;
243
244 do{
245 rand1 = G4UniformRand();
246 if (rand1 < p1) {
247 rand2 = 2.0*G4UniformRand()-1.0;
248 if (rand2 < 0) {
249 eps = 0.5 - xr*std::pow(std::abs(rand2),(1./3.));
250 }
251 else
252 {
253 eps = 0.5 + xr*std::pow(rand2,(1./3.));
254 }
255 b = (eki*ScreenRadius)/(2*eps*(1.0-eps));
256 std::vector<G4double> ScreenFunctionSampling = ScreenFunction(b);
257 g1 = g0+ScreenFunctionSampling[0];
258 if (g1 < 0) g1=0;
259 rand3 = G4UniformRand()*g1min;
260 }
261 else
262 {
263 eps = eki+2.0*xr*G4UniformRand();
264 b = (eki*ScreenRadius)/(2*eps*(1.0-eps));
265 std::vector<G4double> ScreenFunctionSampling = ScreenFunction(b);
266 g1 = g0+ScreenFunctionSampling[1];
267 if (g1 < 0) g1=0;
268 rand3 = G4UniformRand()*g2min;
269 }
270 } while (rand3>g1);
271 } //End of eps sampling
272
273 G4double electronTotEnergy = eps*photonEnergy;
274 G4double positronTotEnergy = (1.0-eps)*photonEnergy;
275
276 // Scattered electron (positron) angles. ( Z - axis along the parent photon)
277
278 //electron kinematics
279 G4double costheta_el,costheta_po;
280 G4double phi_el,phi_po;
281 G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
282 costheta_el = G4UniformRand()*2.0-1.0;
283 G4double kk = std::sqrt(electronKineEnergy*(electronKineEnergy+2.*electron_mass_c2));
284 costheta_el = (costheta_el*electronTotEnergy+kk)/(electronTotEnergy+costheta_el*kk);
285 phi_el = twopi * G4UniformRand() ;
286 G4double dirX_el = std::sqrt(1.-costheta_el*costheta_el) * std::cos(phi_el);
287 G4double dirY_el = std::sqrt(1.-costheta_el*costheta_el) * std::sin(phi_el);
288 G4double dirZ_el = costheta_el;
289
290 //positron kinematics
291 G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
292 costheta_po = G4UniformRand()*2.0-1.0;
293 kk = std::sqrt(positronKineEnergy*(positronKineEnergy+2.*electron_mass_c2));
294 costheta_po = (costheta_po*positronTotEnergy+kk)/(positronTotEnergy+costheta_po*kk);
295 phi_po = twopi * G4UniformRand() ;
296 G4double dirX_po = std::sqrt(1.-costheta_po*costheta_po) * std::cos(phi_po);
297 G4double dirY_po = std::sqrt(1.-costheta_po*costheta_po) * std::sin(phi_po);
298 G4double dirZ_po = costheta_po;
299
300 // Kinematics of the created pair:
301 // the electron and positron are assumed to have a symetric angular
302 // distribution with respect to the Z axis along the parent photon
303 G4double localEnergyDeposit = 0. ;
304
305 //Generate explicitely the electron in the pair, only if it is > threshold
306 //VI: applying cut here provides inconsistency
307
308 if (electronKineEnergy > 0.0)
309 {
310 G4ThreeVector electronDirection ( dirX_el, dirY_el, dirZ_el);
311 electronDirection.rotateUz(photonDirection);
312 G4DynamicParticle* electron = new G4DynamicParticle (G4Electron::Electron(),
313 electronDirection,
314 electronKineEnergy);
315 fvect->push_back(electron);
316 }
317 else
318 {
319 localEnergyDeposit += electronKineEnergy;
320 electronKineEnergy = 0;
321 }
322
323 //Generate the positron. Real particle in any case, because it will annihilate. If below
324 //threshold, produce it at rest
325 // VI: here there was a bug - positron and electron cuts are different
326 if (positronKineEnergy < 0.0)
327 {
328 localEnergyDeposit += positronKineEnergy;
329 positronKineEnergy = 0; //produce it at rest
330 }
331 G4ThreeVector positronDirection(dirX_po,dirY_po,dirZ_po);
332 positronDirection.rotateUz(photonDirection);
333 G4DynamicParticle* positron = new G4DynamicParticle(G4Positron::Positron(),
334 positronDirection, positronKineEnergy);
335 fvect->push_back(positron);
336
337 //Add rest of energy to the local energy deposit
338 fParticleChange->ProposeLocalEnergyDeposit(localEnergyDeposit);
339
340 if (verboseLevel > 1)
341 {
342 G4cout << "-----------------------------------------------------------" << G4endl;
343 G4cout << "Energy balance from G4PenelopeGammaConversion" << G4endl;
344 G4cout << "Incoming photon energy: " << photonEnergy/keV << " keV" << G4endl;
345 G4cout << "-----------------------------------------------------------" << G4endl;
346 if (electronKineEnergy)
347 G4cout << "Electron (explicitely produced) " << electronKineEnergy/keV << " keV"
348 << G4endl;
349 if (positronKineEnergy)
350 G4cout << "Positron (not at rest) " << positronKineEnergy/keV << " keV" << G4endl;
351 G4cout << "Rest masses of e+/- " << 2.0*electron_mass_c2/keV << " keV" << G4endl;
352 if (localEnergyDeposit)
353 G4cout << "Local energy deposit " << localEnergyDeposit/keV << " keV" << G4endl;
354 G4cout << "Total final state: " << (electronKineEnergy+positronKineEnergy+
355 localEnergyDeposit+2.0*electron_mass_c2)/keV <<
356 " keV" << G4endl;
357 G4cout << "-----------------------------------------------------------" << G4endl;
358 }
359 if (verboseLevel > 0)
360 {
361 G4double energyDiff = std::fabs(electronKineEnergy+positronKineEnergy+
362 localEnergyDeposit+2.0*electron_mass_c2-photonEnergy);
363 if (energyDiff > 0.05*keV)
364 G4cout << "Warning from G4PenelopeGammaConversion: problem with energy conservation: "
365 << (electronKineEnergy+positronKineEnergy+
366 localEnergyDeposit+2.0*electron_mass_c2)/keV
367 << " keV (final) vs. " << photonEnergy/keV << " keV (initial)" << G4endl;
368 }
369}
370
371//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
372
373std::vector<G4double> G4PenelopeGammaConversionModel::ScreenFunction(G4double b)
374{
375 std::vector<G4double> result;
376 result.clear();
377 G4double bsquare=b*b;
378 G4double a0,f1,f2;
379 f1=2.0-2*std::log(1+bsquare);
380 f2=f1-(2.0/3.0);
381 if (b < 1.0e-10)
382 {
383 f1=f1-twopi*b;
384 }
385 else
386 {
387 a0 = 4*b*std::atan(1.0/b);
388 f1 = f1 - a0;
389 f2 = f2+2*bsquare*(4.0-a0-3*std::log((1+bsquare)/bsquare));
390 }
391 result.push_back(0.5*(3*f1-f2));
392 result.push_back(0.25*(3*f1+f2));
393 return result;
394}
395
396//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
397
398G4double G4PenelopeGammaConversionModel::GetScreeningRadius(G4double Z)
399{
400 G4double result = 0;
401 G4bool foundElement = false;
402 G4int iZ = (G4int) Z;
403 if (!fTheScreeningRadii)
404 fTheScreeningRadii = new std::map<G4int,G4double>;
405
406 if (fTheScreeningRadii->count(iZ))
407 {
408 //The element is already loaded: just return it
409 result = fTheScreeningRadii->find(iZ)->second;
410 return result;
411 }
412 else //retrieve all from file
413 {
414 char* path = getenv("G4LEDATA");
415 if (!path)
416 {
417 G4String excep = "G4PenelopeGammaConversionModel - G4LEDATA environment variable not set!";
418 G4Exception(excep);
419 }
420 G4String pathString(path);
421 G4String pathFile = pathString + "/penelope/pp-pen.dat";
422 std::ifstream file(pathFile);
423
424 if (!(file.is_open()))
425 {
426 G4String excep = "G4PenelopeGammaConversionModel - data file " + pathFile + "not found!";
427 G4Exception(excep);
428 }
429 G4int k;
430 G4double a1,a2;
431 while(!file.eof()) {
432 file >> k >> a1 >> a2;
433 fTheScreeningRadii->insert(std::make_pair(k,a1));
434 if ((G4double) k == Z)
435 {
436 result = a1;
437 foundElement = true;
438 }
439 }
440 file.close();
441 if (verboseLevel > 2)
442 G4cout << "Read file pp-pen.dat" << G4endl;
443 if (foundElement)
444 return result;
445 else
446 {
447 G4String excep = "G4PenelopeGammaConversionModel - Screening Radius for not found in the data file";
448 G4Exception(excep);
449 return 0;
450 }
451 }
452}
453
454//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
455
456G4double G4PenelopeGammaConversionModel::CoulombCorrection(G4double a)
457{
458 G4double fc=0;
459 G4double b[7] = {0.202059,-0.03693,0.00835,-0.00201,0.00049,-0.00012,0.00003};
460 G4double aSquared = a*a;
461 G4double aFourth = aSquared*aSquared;
462 G4double aEighth = aFourth*aFourth;
463
464 fc = ((1.0/(1.0+a*a))+b[0]+b[1]*aSquared+b[2]*aFourth+b[3]*(aSquared*aFourth)+
465 b[4]*aEighth+b[5]*(aEighth*aSquared)+b[6]*(aEighth*aFourth));
466 fc=aSquared*fc;
467 return fc;
468}
469
470//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
471
472G4double G4PenelopeGammaConversionModel::LowEnergyCorrection(G4double a,G4double eki)
473{
474 G4double f0=0,t=0;
475 G4double b[12] = {-1.744,-12.10,11.18,8.523,73.26,-41.41,-13.52,-121.1,94.41,8.946,62.05,-63.41};
476 t=std::sqrt(2.0*eki);
477 G4double tSq = t*t;
478 f0=(b[0]+b[1]*a+b[2]*a*a)*t+(b[3]+b[4]*a+b[5]*a*a)*(tSq)+(b[6]+b[7]*a+b[8]*a*a)*(tSq*t)+
479 (b[9]+b[10]*a+b[11]*a*a)*(tSq*tSq);
480 return f0;
481
482}
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