source: trunk/source/processes/electromagnetic/lowenergy/src/G4LivermorePolarizedRayleighModel.cc@ 992

Last change on this file since 992 was 991, checked in by garnier, 17 years ago

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26// $Id: G4LivermorePolarizedRayleighModel.cc,v 1.1 2008/10/30 14:16:35 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-02 $
28//
29
30#include "G4LivermorePolarizedRayleighModel.hh"
31
32//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
33
34using namespace std;
35
36//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
37
38G4LivermorePolarizedRayleighModel::G4LivermorePolarizedRayleighModel(const G4ParticleDefinition*,
39 const G4String& nam)
40:G4VEmModel(nam),isInitialised(false)
41{
42 lowEnergyLimit = 250 * eV; // SI - Could be 10 eV ?
43 highEnergyLimit = 100 * GeV;
44
45 SetLowEnergyLimit(lowEnergyLimit);
46 SetHighEnergyLimit(highEnergyLimit);
47 //
48 verboseLevel= 0;
49 // Verbosity scale:
50 // 0 = nothing
51 // 1 = warning for energy non-conservation
52 // 2 = details of energy budget
53 // 3 = calculation of cross sections, file openings, sampling of atoms
54 // 4 = entering in methods
55
56 G4cout << "Livermore Polarized Rayleigh is constructed " << G4endl
57 << "Energy range: "
58 << lowEnergyLimit / keV << " keV - "
59 << highEnergyLimit / GeV << " GeV"
60 << G4endl;
61}
62
63//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
64
65G4LivermorePolarizedRayleighModel::~G4LivermorePolarizedRayleighModel()
66{
67 delete crossSectionHandler;
68 delete formFactorData;
69}
70
71//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
72
73void G4LivermorePolarizedRayleighModel::Initialise(const G4ParticleDefinition* particle,
74 const G4DataVector& cuts)
75{
76// Rayleigh process: The Quantum Theory of Radiation
77// W. Heitler, Oxford at the Clarendon Press, Oxford (1954)
78// Scattering function: A simple model of photon transport
79// D.E. Cullen, Nucl. Instr. Meth. in Phys. Res. B 101 (1995) 499-510
80// Polarization of the outcoming photon: Beam test of a prototype detector array for the PoGO astronomical hard X-ray/soft gamma-ray polarimeter
81// T. Mizuno et al., Nucl. Instr. Meth. in Phys. Res. A 540 (2005) 158-168
82
83 if (verboseLevel > 3)
84 G4cout << "Calling G4LivermorePolarizedRayleighModel::Initialise()" << G4endl;
85
86 InitialiseElementSelectors(particle,cuts);
87
88 // Energy limits
89
90 if (LowEnergyLimit() < lowEnergyLimit)
91 {
92 G4cout << "G4LivermorePolarizedRayleighModel: low energy limit increased from " <<
93 LowEnergyLimit()/eV << " eV to " << lowEnergyLimit << " eV" << G4endl;
94 SetLowEnergyLimit(lowEnergyLimit);
95 }
96 if (HighEnergyLimit() > highEnergyLimit)
97 {
98 G4cout << "G4LivermorePolarizedRayleighModel: high energy limit decreased from " <<
99 HighEnergyLimit()/GeV << " GeV to " << highEnergyLimit << " GeV" << G4endl;
100 SetHighEnergyLimit(highEnergyLimit);
101 }
102
103 // Read data files for all materials
104
105 crossSectionHandler = new G4CrossSectionHandler;
106 crossSectionHandler->Clear();
107 G4String crossSectionFile = "rayl/re-cs-";
108 crossSectionHandler->LoadData(crossSectionFile);
109
110 G4VDataSetAlgorithm* ffInterpolation = new G4LogLogInterpolation;
111 G4String formFactorFile = "rayl/re-ff-";
112 formFactorData = new G4CompositeEMDataSet(ffInterpolation,1.,1.);
113 formFactorData->LoadData(formFactorFile);
114
115 //
116 if (verboseLevel > 2)
117 G4cout << "Loaded cross section files for Livermore Polarized Rayleigh model" << G4endl;
118
119 G4cout << "Livermore Polarized Rayleigh model is initialized " << G4endl
120 << "Energy range: "
121 << LowEnergyLimit() / keV << " keV - "
122 << HighEnergyLimit() / GeV << " GeV"
123 << G4endl;
124
125 if(isInitialised) return;
126
127 if(pParticleChange)
128 fParticleChange = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
129 else
130 fParticleChange = new G4ParticleChangeForGamma();
131
132 isInitialised = true;
133}
134
135//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
136
137G4double G4LivermorePolarizedRayleighModel::ComputeCrossSectionPerAtom(
138 const G4ParticleDefinition*,
139 G4double GammaEnergy,
140 G4double Z, G4double,
141 G4double, G4double)
142{
143 if (verboseLevel > 3)
144 G4cout << "Calling CrossSectionPerAtom() of G4LivermorePolarizedRayleighModel" << G4endl;
145
146 G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
147 return cs;
148}
149
150//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
151
152void G4LivermorePolarizedRayleighModel::SampleSecondaries(std::vector<G4DynamicParticle*>* /*fvect*/,
153 const G4MaterialCutsCouple* couple,
154 const G4DynamicParticle* aDynamicGamma,
155 G4double,
156 G4double)
157{
158 if (verboseLevel > 3)
159 G4cout << "Calling SampleSecondaries() of G4LivermorePolarizedRayleighModel" << G4endl;
160
161 G4double photonEnergy0 = aDynamicGamma->GetKineticEnergy();
162
163 if (photonEnergy0 <= lowEnergyLimit)
164 {
165 fParticleChange->ProposeTrackStatus(fStopAndKill);
166 fParticleChange->SetProposedKineticEnergy(0.);
167 fParticleChange->ProposeLocalEnergyDeposit(photonEnergy0);
168 // SI - IS THE FOLLOWING RETURN NECESSARY ?
169 return ;
170 }
171
172 G4ParticleMomentum photonDirection0 = aDynamicGamma->GetMomentumDirection();
173
174 // Select randomly one element in the current material
175 G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0);
176
177 G4double outcomingPhotonCosTheta = GenerateCosTheta(photonEnergy0, Z);
178 G4double outcomingPhotonPhi = GeneratePhi(outcomingPhotonCosTheta);
179 G4double beta=GeneratePolarizationAngle();
180
181 // incomingPhoton reference frame:
182 // z = versor parallel to the incomingPhotonDirection
183 // x = versor parallel to the incomingPhotonPolarization
184 // y = defined as z^x
185
186 // outgoingPhoton reference frame:
187 // z' = versor parallel to the outgoingPhotonDirection
188 // x' = defined as x-x*z'z' normalized
189 // y' = defined as z'^x'
190
191 G4ThreeVector z(aDynamicGamma->GetMomentumDirection().unit());
192 G4ThreeVector x(GetPhotonPolarization(*aDynamicGamma));
193 G4ThreeVector y(z.cross(x));
194
195 // z' = std::cos(phi)*std::sin(theta) x + std::sin(phi)*std::sin(theta) y + std::cos(theta) z
196 G4double xDir;
197 G4double yDir;
198 G4double zDir;
199 zDir=outcomingPhotonCosTheta;
200 xDir=std::sqrt(1-outcomingPhotonCosTheta*outcomingPhotonCosTheta);
201 yDir=xDir;
202 xDir*=std::cos(outcomingPhotonPhi);
203 yDir*=std::sin(outcomingPhotonPhi);
204
205 G4ThreeVector zPrime((xDir*x + yDir*y + zDir*z).unit());
206 G4ThreeVector xPrime(x.perpPart(zPrime).unit());
207 G4ThreeVector yPrime(zPrime.cross(xPrime));
208
209 // outgoingPhotonPolarization is directed as x' std::cos(beta) + y' std::sin(beta)
210 G4ThreeVector outcomingPhotonPolarization(xPrime*std::cos(beta) + yPrime*std::sin(beta));
211
212 fParticleChange->ProposeMomentumDirection(zPrime);
213 fParticleChange->ProposePolarization(outcomingPhotonPolarization);
214 fParticleChange->SetProposedKineticEnergy(photonEnergy0);
215
216}
217
218//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
219
220G4double G4LivermorePolarizedRayleighModel::GenerateCosTheta(G4double incomingPhotonEnergy, G4int zAtom) const
221{
222 // d sigma k0
223 // --------- = r0^2 * pi * F^2(x, Z) * ( 2 - sin^2 theta) * std::sin (theta), x = ---- std::sin(theta/2)
224 // d theta hc
225
226 // d sigma k0 1 - y
227 // --------- = r0^2 * pi * F^2(x, Z) * ( 1 + y^2), x = ---- std::sqrt ( ------- ), y = std::cos(theta)
228 // d y hc 2
229
230 // Z
231 // F(x, Z) ~ --------
232 // a + bx
233 //
234 // The time to exit from the outer loop grows as ~ k0
235 // On pcgeant2 the time is ~ 1 s for k0 ~ 1 MeV on the oxygen element. A 100 GeV
236 // event will take ~ 10 hours.
237 //
238 // On the avarage the inner loop does 1.5 iterations before exiting
239
240 const G4double xFactor = (incomingPhotonEnergy*cm)/(h_Planck*c_light);
241 //const G4VEMDataSet * formFactorData = GetScatterFunctionData();
242
243 G4double cosTheta;
244 G4double fCosTheta;
245 G4double x;
246 G4double fValue;
247
248 do
249 {
250 do
251 {
252 cosTheta = 2.*G4UniformRand()-1.;
253 fCosTheta = (1.+cosTheta*cosTheta)/2.;
254 }
255 while (fCosTheta < G4UniformRand());
256
257 x = xFactor*std::sqrt((1.-cosTheta)/2.);
258
259 if (x > 1.e+005)
260 fValue = formFactorData->FindValue(x, zAtom-1);
261 else
262 fValue = formFactorData->FindValue(0., zAtom-1);
263
264 fValue/=zAtom;
265 fValue*=fValue;
266 }
267 while(fValue < G4UniformRand());
268
269 return cosTheta;
270}
271
272//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
273
274G4double G4LivermorePolarizedRayleighModel::GeneratePhi(G4double cosTheta) const
275{
276 // d sigma
277 // --------- = alpha * ( 1 - sin^2 (theta) * cos^2 (phi) )
278 // d phi
279
280 // On the average the loop takes no more than 2 iterations before exiting
281
282 G4double phi;
283 G4double cosPhi;
284 G4double phiProbability;
285 G4double sin2Theta;
286
287 sin2Theta=1.-cosTheta*cosTheta;
288
289 do
290 {
291 phi = twopi * G4UniformRand();
292 cosPhi = std::cos(phi);
293 phiProbability= 1. - sin2Theta*cosPhi*cosPhi;
294 }
295 while (phiProbability < G4UniformRand());
296
297 return phi;
298}
299
300//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
301
302G4double G4LivermorePolarizedRayleighModel::GeneratePolarizationAngle(void) const
303{
304 // Rayleigh polarization is always on the x' direction
305
306 return 0;
307}
308
309//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
310
311G4ThreeVector G4LivermorePolarizedRayleighModel::GetPhotonPolarization(const G4DynamicParticle& photon)
312{
313
314// SI - From G4VLowEnergyDiscretePhotonProcess.cc
315
316 G4ThreeVector photonMomentumDirection;
317 G4ThreeVector photonPolarization;
318
319 photonPolarization = photon.GetPolarization();
320 photonMomentumDirection = photon.GetMomentumDirection();
321
322 if ((!photonPolarization.isOrthogonal(photonMomentumDirection, 1e-6)) || photonPolarization.mag()==0.)
323 {
324 // if |photonPolarization|==0. or |photonPolarization * photonDirection0| > 1e-6 * |photonPolarization ^ photonDirection0|
325 // then polarization is choosen randomly.
326
327 G4ThreeVector e1(photonMomentumDirection.orthogonal().unit());
328 G4ThreeVector e2(photonMomentumDirection.cross(e1).unit());
329
330 G4double angle(G4UniformRand() * twopi);
331
332 e1*=std::cos(angle);
333 e2*=std::sin(angle);
334
335 photonPolarization=e1+e2;
336 }
337 else if (photonPolarization.howOrthogonal(photonMomentumDirection) != 0.)
338 {
339 // if |photonPolarization * photonDirection0| != 0.
340 // then polarization is made orthonormal;
341
342 photonPolarization=photonPolarization.perpPart(photonMomentumDirection);
343 }
344
345 return photonPolarization.unit();
346}
347
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