source: trunk/source/processes/electromagnetic/lowenergy/src/G4LivermoreComptonModel.cc@ 973

Last change on this file since 973 was 968, checked in by garnier, 17 years ago

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25//
26// $Id: G4LivermoreComptonModel.cc,v 1.2 2009/01/21 10:58:13 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
28//
29
30#include "G4LivermoreComptonModel.hh"
31
32//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
33
34using namespace std;
35
36//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
37
38G4LivermoreComptonModel::G4LivermoreComptonModel(const G4ParticleDefinition*,
39 const G4String& nam)
40:G4VEmModel(nam),isInitialised(false),meanFreePathTable(0),scatterFunctionData(0),crossSectionHandler(0)
41{
42 lowEnergyLimit = 250 * eV; // SI - Could be 10 eV ?
43 highEnergyLimit = 100 * GeV;
44 SetLowEnergyLimit(lowEnergyLimit);
45 SetHighEnergyLimit(highEnergyLimit);
46
47 verboseLevel=0 ;
48 // Verbosity scale:
49 // 0 = nothing
50 // 1 = warning for energy non-conservation
51 // 2 = details of energy budget
52 // 3 = calculation of cross sections, file openings, sampling of atoms
53 // 4 = entering in methods
54
55 G4cout << "Livermore Compton model is constructed " << G4endl
56 << "Energy range: "
57 << lowEnergyLimit / keV << " keV - "
58 << highEnergyLimit / GeV << " GeV"
59 << G4endl;
60
61}
62
63//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
64
65G4LivermoreComptonModel::~G4LivermoreComptonModel()
66{
67
68 if (meanFreePathTable) delete meanFreePathTable;
69 if (crossSectionHandler) delete crossSectionHandler;
70 if (scatterFunctionData) delete scatterFunctionData;
71
72}
73
74//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
75
76void G4LivermoreComptonModel::Initialise(const G4ParticleDefinition* particle,
77 const G4DataVector& cuts)
78{
79
80 if (verboseLevel > 3)
81 G4cout << "Calling G4LivermoreComptonModel::Initialise()" << G4endl;
82
83 if (crossSectionHandler)
84 {
85 crossSectionHandler->Clear();
86 delete crossSectionHandler;
87 }
88
89 // Energy limits
90
91 if (LowEnergyLimit() < lowEnergyLimit)
92 {
93 G4cout << "G4LivermoreComptonModel: low energy limit increased from " <<
94 LowEnergyLimit()/eV << " eV to " << lowEnergyLimit << " eV" << G4endl;
95 SetLowEnergyLimit(lowEnergyLimit);
96 }
97
98 if (HighEnergyLimit() > highEnergyLimit)
99 {
100 G4cout << "G4LivermoreComptonModel: high energy limit decreased from " <<
101 HighEnergyLimit()/GeV << " GeV to " << highEnergyLimit << " GeV" << G4endl;
102 SetHighEnergyLimit(highEnergyLimit);
103 }
104
105 // Reading of data files - all materials are read
106
107 crossSectionHandler = new G4CrossSectionHandler;
108 crossSectionHandler->Clear();
109 G4String crossSectionFile = "comp/ce-cs-";
110 crossSectionHandler->LoadData(crossSectionFile);
111
112 G4VDataSetAlgorithm* scatterInterpolation = new G4LogLogInterpolation;
113 G4String scatterFile = "comp/ce-sf-";
114 scatterFunctionData = new G4CompositeEMDataSet(scatterInterpolation, 1., 1.);
115 scatterFunctionData->LoadData(scatterFile);
116
117 // For Doppler broadening
118 shellData.SetOccupancyData();
119 G4String file = "/doppler/shell-doppler";
120 shellData.LoadData(file);
121
122 meanFreePathTable = 0;
123 meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
124
125 if (verboseLevel > 2)
126 G4cout << "Loaded cross section files for Livermore Compton model" << G4endl;
127
128 InitialiseElementSelectors(particle,cuts);
129
130 G4cout << "Livermore Compton model is initialized " << G4endl
131 << "Energy range: "
132 << LowEnergyLimit() / keV << " keV - "
133 << HighEnergyLimit() / GeV << " GeV"
134 << G4endl;
135
136 //
137
138 if(isInitialised) return;
139
140 if(pParticleChange)
141 fParticleChange = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
142 else
143 fParticleChange = new G4ParticleChangeForGamma();
144
145 isInitialised = true;
146
147}
148
149//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
150
151G4double G4LivermoreComptonModel::ComputeCrossSectionPerAtom(
152 const G4ParticleDefinition*,
153 G4double GammaEnergy,
154 G4double Z, G4double,
155 G4double, G4double)
156{
157
158 if (verboseLevel > 3)
159 G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreComptonModel" << G4endl;
160
161 G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
162
163 return cs;
164
165}
166
167//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
168
169void G4LivermoreComptonModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
170 const G4MaterialCutsCouple* couple,
171 const G4DynamicParticle* aDynamicGamma,
172 G4double,
173 G4double)
174{
175
176 // The scattered gamma energy is sampled according to Klein - Nishina formula.
177 // then accepted or rejected depending on the Scattering Function multiplied
178 // by factor from Klein - Nishina formula.
179 // Expression of the angular distribution as Klein Nishina
180 // angular and energy distribution and Scattering fuctions is taken from
181 // D. E. Cullen "A simple model of photon transport" Nucl. Instr. Meth.
182 // Phys. Res. B 101 (1995). Method of sampling with form factors is different
183 // data are interpolated while in the article they are fitted.
184 // Reference to the article is from J. Stepanek New Photon, Positron
185 // and Electron Interaction Data for GEANT in Energy Range from 1 eV to 10
186 // TeV (draft).
187 // The random number techniques of Butcher & Messel are used
188 // (Nucl Phys 20(1960),15).
189
190 if (verboseLevel > 3)
191 G4cout << "Calling SampleSecondaries() of G4LivermoreComptonModel" << G4endl;
192
193 G4double photonEnergy0 = aDynamicGamma->GetKineticEnergy();
194
195 if (photonEnergy0 <= lowEnergyLimit)
196 {
197 fParticleChange->ProposeTrackStatus(fStopAndKill);
198 fParticleChange->SetProposedKineticEnergy(0.);
199 fParticleChange->ProposeLocalEnergyDeposit(photonEnergy0);
200 return ;
201 }
202
203 G4double e0m = photonEnergy0 / electron_mass_c2 ;
204 G4ParticleMomentum photonDirection0 = aDynamicGamma->GetMomentumDirection();
205
206 // Select randomly one element in the current material
207 G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0);
208
209 G4double epsilon0 = 1. / (1. + 2. * e0m);
210 G4double epsilon0Sq = epsilon0 * epsilon0;
211 G4double alpha1 = -std::log(epsilon0);
212 G4double alpha2 = 0.5 * (1. - epsilon0Sq);
213
214 G4double wlPhoton = h_Planck*c_light/photonEnergy0;
215
216 // Sample the energy of the scattered photon
217 G4double epsilon;
218 G4double epsilonSq;
219 G4double oneCosT;
220 G4double sinT2;
221 G4double gReject;
222
223 do
224 {
225 if ( alpha1/(alpha1+alpha2) > G4UniformRand())
226 {
227 epsilon = std::exp(-alpha1 * G4UniformRand()); // std::pow(epsilon0,G4UniformRand())
228 epsilonSq = epsilon * epsilon;
229 }
230 else
231 {
232 epsilonSq = epsilon0Sq + (1. - epsilon0Sq) * G4UniformRand();
233 epsilon = std::sqrt(epsilonSq);
234 }
235
236 oneCosT = (1. - epsilon) / ( epsilon * e0m);
237 sinT2 = oneCosT * (2. - oneCosT);
238 G4double x = std::sqrt(oneCosT/2.) / (wlPhoton/cm);
239 G4double scatteringFunction = scatterFunctionData->FindValue(x,Z-1);
240 gReject = (1. - epsilon * sinT2 / (1. + epsilonSq)) * scatteringFunction;
241
242 } while(gReject < G4UniformRand()*Z);
243
244 G4double cosTheta = 1. - oneCosT;
245 G4double sinTheta = std::sqrt (sinT2);
246 G4double phi = twopi * G4UniformRand() ;
247 G4double dirx = sinTheta * std::cos(phi);
248 G4double diry = sinTheta * std::sin(phi);
249 G4double dirz = cosTheta ;
250
251 // Doppler broadening - Method based on:
252 // Y. Namito, S. Ban and H. Hirayama,
253 // "Implementation of the Doppler Broadening of a Compton-Scattered Photon Into the EGS4 Code"
254 // NIM A 349, pp. 489-494, 1994
255
256 // Maximum number of sampling iterations
257 G4int maxDopplerIterations = 1000;
258 G4double bindingE = 0.;
259 G4double photonEoriginal = epsilon * photonEnergy0;
260 G4double photonE = -1.;
261 G4int iteration = 0;
262 G4double eMax = photonEnergy0;
263 do
264 {
265 iteration++;
266 // Select shell based on shell occupancy
267 G4int shell = shellData.SelectRandomShell(Z);
268 bindingE = shellData.BindingEnergy(Z,shell);
269
270 eMax = photonEnergy0 - bindingE;
271
272 // Randomly sample bound electron momentum (memento: the data set is in Atomic Units)
273 G4double pSample = profileData.RandomSelectMomentum(Z,shell);
274 // Rescale from atomic units
275 G4double pDoppler = pSample * fine_structure_const;
276 G4double pDoppler2 = pDoppler * pDoppler;
277 G4double var2 = 1. + oneCosT * e0m;
278 G4double var3 = var2*var2 - pDoppler2;
279 G4double var4 = var2 - pDoppler2 * cosTheta;
280 G4double var = var4*var4 - var3 + pDoppler2 * var3;
281 if (var > 0.)
282 {
283 G4double varSqrt = std::sqrt(var);
284 G4double scale = photonEnergy0 / var3;
285 // Random select either root
286 if (G4UniformRand() < 0.5) photonE = (var4 - varSqrt) * scale;
287 else photonE = (var4 + varSqrt) * scale;
288 }
289 else
290 {
291 photonE = -1.;
292 }
293 } while ( iteration <= maxDopplerIterations &&
294 (photonE < 0. || photonE > eMax || photonE < eMax*G4UniformRand()) );
295
296 // End of recalculation of photon energy with Doppler broadening
297 // Revert to original if maximum number of iterations threshold has been reached
298
299 if (iteration >= maxDopplerIterations)
300 {
301 photonE = photonEoriginal;
302 bindingE = 0.;
303 }
304
305 // Update G4VParticleChange for the scattered photon
306
307 G4ThreeVector photonDirection1(dirx,diry,dirz);
308 photonDirection1.rotateUz(photonDirection0);
309 fParticleChange->ProposeMomentumDirection(photonDirection1) ;
310
311 G4double photonEnergy1 = photonE;
312
313 if (photonEnergy1 > 0.)
314 {
315 fParticleChange->SetProposedKineticEnergy(photonEnergy1) ;
316 }
317 else
318 {
319 fParticleChange->SetProposedKineticEnergy(0.) ;
320 fParticleChange->ProposeTrackStatus(fStopAndKill);
321 }
322
323 // Kinematics of the scattered electron
324 G4double eKineticEnergy = photonEnergy0 - photonEnergy1 - bindingE;
325 G4double eTotalEnergy = eKineticEnergy + electron_mass_c2;
326
327 G4double electronE = photonEnergy0 * (1. - epsilon) + electron_mass_c2;
328 G4double electronP2 = electronE*electronE - electron_mass_c2*electron_mass_c2;
329 G4double sinThetaE = -1.;
330 G4double cosThetaE = 0.;
331 if (electronP2 > 0.)
332 {
333 cosThetaE = (eTotalEnergy + photonEnergy1 )* (1. - epsilon) / std::sqrt(electronP2);
334 sinThetaE = -1. * sqrt(1. - cosThetaE * cosThetaE);
335 }
336
337 G4double eDirX = sinThetaE * std::cos(phi);
338 G4double eDirY = sinThetaE * std::sin(phi);
339 G4double eDirZ = cosThetaE;
340
341 G4ThreeVector eDirection(eDirX,eDirY,eDirZ);
342 eDirection.rotateUz(photonDirection0);
343
344// SI - The range test has been removed wrt original G4LowEnergyCompton class
345
346 fParticleChange->ProposeLocalEnergyDeposit(bindingE);
347
348 G4DynamicParticle* dp = new G4DynamicParticle (G4Electron::Electron(),eDirection,eKineticEnergy) ;
349 fvect->push_back(dp);
350
351}
352
353//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
354
355G4double G4LivermoreComptonModel::GetMeanFreePath(const G4Track& track,
356 G4double, // previousStepSize
357 G4ForceCondition*)
358{
359 const G4DynamicParticle* photon = track.GetDynamicParticle();
360 G4double energy = photon->GetKineticEnergy();
361 const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
362 size_t materialIndex = couple->GetIndex();
363
364 G4double meanFreePath;
365 if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
366 else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
367 else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
368 return meanFreePath;
369}
370
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