source: trunk/source/processes/electromagnetic/lowenergy/src/G4LivermorePolarizedRayleighModel.cc @ 1347

Last change on this file since 1347 was 1347, checked in by garnier, 13 years ago

geant4 tag 9.4
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26// $Id: G4LivermorePolarizedRayleighModel.cc,v 1.5 2009/05/02 15:20:53 sincerti Exp $
27// GEANT4 tag $Name: geant4-09-04-ref-00 $
28//
29// History:
30// --------
31// 02 May 2009   S Incerti as V. Ivanchenko proposed in G4LivermoreRayleighModel.cc
32//
33// Cleanup initialisation and generation of secondaries:
34//                  - apply internal high-energy limit only in constructor
35//                  - do not apply low-energy limit (default is 0)
36//                  - remove GetMeanFreePath method and table
37//                  - remove initialisation of element selector
38//                  - use G4ElementSelector
39
40#include "G4LivermorePolarizedRayleighModel.hh"
41
42//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
43
44using namespace std;
45
46//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
47
48G4LivermorePolarizedRayleighModel::G4LivermorePolarizedRayleighModel(const G4ParticleDefinition*,
49                                             const G4String& nam)
50:G4VEmModel(nam),isInitialised(false),crossSectionHandler(0),formFactorData(0)
51{
52  lowEnergyLimit = 250 * eV; 
53  highEnergyLimit = 100 * GeV;
54 
55  //SetLowEnergyLimit(lowEnergyLimit);
56  SetHighEnergyLimit(highEnergyLimit);
57  //
58  verboseLevel= 0;
59  // Verbosity scale:
60  // 0 = nothing
61  // 1 = warning for energy non-conservation
62  // 2 = details of energy budget
63  // 3 = calculation of cross sections, file openings, sampling of atoms
64  // 4 = entering in methods
65
66  if(verboseLevel > 0) {
67    G4cout << "Livermore Polarized Rayleigh is constructed " << G4endl
68         << "Energy range: "
69         << lowEnergyLimit / eV << " eV - "
70         << highEnergyLimit / GeV << " GeV"
71         << G4endl;
72  }
73}
74
75//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
76
77G4LivermorePolarizedRayleighModel::~G4LivermorePolarizedRayleighModel()
78{ 
79  if (crossSectionHandler) delete crossSectionHandler;
80  if (formFactorData) delete formFactorData;
81}
82
83//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
84
85void G4LivermorePolarizedRayleighModel::Initialise(const G4ParticleDefinition* particle,
86                                       const G4DataVector& cuts)
87{
88// Rayleigh process:                      The Quantum Theory of Radiation
89//                                        W. Heitler,       Oxford at the Clarendon Press, Oxford (1954)                                                 
90// Scattering function:                   A simple model of photon transport
91//                                        D.E. Cullen,      Nucl. Instr. Meth. in Phys. Res. B 101 (1995) 499-510                                       
92// Polarization of the outcoming photon:  Beam test of a prototype detector array for the PoGO astronomical hard X-ray/soft gamma-ray polarimeter
93//                                        T. Mizuno et al., Nucl. Instr. Meth. in Phys. Res. A 540 (2005) 158-168                                       
94
95  if (verboseLevel > 3)
96    G4cout << "Calling G4LivermorePolarizedRayleighModel::Initialise()" << G4endl;
97
98  if (crossSectionHandler)
99  {
100    crossSectionHandler->Clear();
101    delete crossSectionHandler;
102  }
103 
104  // Read data files for all materials
105
106  crossSectionHandler = new G4CrossSectionHandler;
107  crossSectionHandler->Clear();
108  G4String crossSectionFile = "rayl/re-cs-";
109  crossSectionHandler->LoadData(crossSectionFile);
110
111  G4VDataSetAlgorithm* ffInterpolation = new G4LogLogInterpolation;
112  G4String formFactorFile = "rayl/re-ff-";
113  formFactorData = new G4CompositeEMDataSet(ffInterpolation,1.,1.);
114  formFactorData->LoadData(formFactorFile);
115
116  InitialiseElementSelectors(particle,cuts);
117
118  //
119  if (verboseLevel > 2) 
120    G4cout << "Loaded cross section files for Livermore Polarized Rayleigh model" << G4endl;
121
122  InitialiseElementSelectors(particle,cuts);
123
124  if (verboseLevel > 0) { 
125    G4cout << "Livermore Polarized Rayleigh model is initialized " << G4endl
126         << "Energy range: "
127         << LowEnergyLimit() / eV << " eV - "
128         << HighEnergyLimit() / GeV << " GeV"
129         << G4endl;
130         }
131
132  if(isInitialised) return;
133  fParticleChange = GetParticleChangeForGamma();
134  isInitialised = true;
135}
136
137//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
138
139G4double G4LivermorePolarizedRayleighModel::ComputeCrossSectionPerAtom(
140                                       const G4ParticleDefinition*,
141                                             G4double GammaEnergy,
142                                             G4double Z, G4double,
143                                             G4double, G4double)
144{
145  if (verboseLevel > 3)
146    G4cout << "Calling CrossSectionPerAtom() of G4LivermorePolarizedRayleighModel" << G4endl;
147
148  if (GammaEnergy < lowEnergyLimit || GammaEnergy > highEnergyLimit) return 0.0;
149
150  G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
151  return cs;
152}
153
154//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
155
156void G4LivermorePolarizedRayleighModel::SampleSecondaries(std::vector<G4DynamicParticle*>* /*fvect*/,
157                                              const G4MaterialCutsCouple* couple,
158                                              const G4DynamicParticle* aDynamicGamma,
159                                              G4double,
160                                              G4double)
161{
162  if (verboseLevel > 3)
163    G4cout << "Calling SampleSecondaries() of G4LivermorePolarizedRayleighModel" << G4endl;
164
165  G4double photonEnergy0 = aDynamicGamma->GetKineticEnergy();
166 
167  if (photonEnergy0 <= lowEnergyLimit)
168  {
169      fParticleChange->ProposeTrackStatus(fStopAndKill);
170      fParticleChange->SetProposedKineticEnergy(0.);
171      fParticleChange->ProposeLocalEnergyDeposit(photonEnergy0);
172      return ;
173  }
174
175  G4ParticleMomentum photonDirection0 = aDynamicGamma->GetMomentumDirection();
176
177  // Select randomly one element in the current material
178  // G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0);
179  const G4ParticleDefinition* particle =  aDynamicGamma->GetDefinition();
180  const G4Element* elm = SelectRandomAtom(couple,particle,photonEnergy0);
181  G4int Z = (G4int)elm->GetZ();
182
183  G4double outcomingPhotonCosTheta = GenerateCosTheta(photonEnergy0, Z);
184  G4double outcomingPhotonPhi = GeneratePhi(outcomingPhotonCosTheta);
185  G4double beta=GeneratePolarizationAngle();
186 
187  // incomingPhoton reference frame:
188  // z = versor parallel to the incomingPhotonDirection
189  // x = versor parallel to the incomingPhotonPolarization
190  // y = defined as z^x
191 
192  // outgoingPhoton reference frame:
193  // z' = versor parallel to the outgoingPhotonDirection
194  // x' = defined as x-x*z'z' normalized
195  // y' = defined as z'^x'
196 
197  G4ThreeVector z(aDynamicGamma->GetMomentumDirection().unit()); 
198  G4ThreeVector x(GetPhotonPolarization(*aDynamicGamma));
199  G4ThreeVector y(z.cross(x));
200 
201  // z' = std::cos(phi)*std::sin(theta) x + std::sin(phi)*std::sin(theta) y + std::cos(theta) z
202  G4double xDir;
203  G4double yDir;
204  G4double zDir;
205  zDir=outcomingPhotonCosTheta;
206  xDir=std::sqrt(1-outcomingPhotonCosTheta*outcomingPhotonCosTheta);
207  yDir=xDir;
208  xDir*=std::cos(outcomingPhotonPhi);
209  yDir*=std::sin(outcomingPhotonPhi);
210 
211  G4ThreeVector zPrime((xDir*x + yDir*y + zDir*z).unit());
212  G4ThreeVector xPrime(x.perpPart(zPrime).unit());
213  G4ThreeVector yPrime(zPrime.cross(xPrime));
214 
215  // outgoingPhotonPolarization is directed as x' std::cos(beta) + y' std::sin(beta)
216  G4ThreeVector outcomingPhotonPolarization(xPrime*std::cos(beta) + yPrime*std::sin(beta));
217 
218  fParticleChange->ProposeMomentumDirection(zPrime);
219  fParticleChange->ProposePolarization(outcomingPhotonPolarization);
220  fParticleChange->SetProposedKineticEnergy(photonEnergy0); 
221
222}
223
224//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
225
226G4double G4LivermorePolarizedRayleighModel::GenerateCosTheta(G4double incomingPhotonEnergy, G4int zAtom) const
227{
228  //  d sigma                                                                    k0
229  // --------- =  r0^2 * pi * F^2(x, Z) * ( 2 - sin^2 theta) * std::sin (theta), x = ---- std::sin(theta/2)
230  //  d theta                                                                    hc
231 
232  //  d sigma                                             k0          1 - y
233  // --------- = r0^2 * pi * F^2(x, Z) * ( 1 + y^2), x = ---- std::sqrt ( ------- ), y = std::cos(theta)
234  //    d y                                               hc            2
235
236  //              Z
237  // F(x, Z) ~ --------
238  //            a + bx
239  //
240  // The time to exit from the outer loop grows as ~ k0
241  // On pcgeant2 the time is ~ 1 s for k0 ~ 1 MeV on the oxygen element. A 100 GeV
242  // event will take ~ 10 hours.
243  //
244  // On the avarage the inner loop does 1.5 iterations before exiting
245 
246  const G4double xFactor = (incomingPhotonEnergy*cm)/(h_Planck*c_light);
247  //const G4VEMDataSet * formFactorData = GetScatterFunctionData();
248
249  G4double cosTheta;
250  G4double fCosTheta;
251  G4double x;
252  G4double fValue;
253
254  do
255    {
256      do
257        {
258          cosTheta = 2.*G4UniformRand()-1.;
259          fCosTheta = (1.+cosTheta*cosTheta)/2.;
260        }
261      while (fCosTheta < G4UniformRand());
262 
263      x = xFactor*std::sqrt((1.-cosTheta)/2.);
264 
265      if (x > 1.e+005)
266        fValue = formFactorData->FindValue(x, zAtom-1);
267      else
268        fValue = formFactorData->FindValue(0., zAtom-1);
269   
270      fValue/=zAtom;
271      fValue*=fValue;
272    }
273  while(fValue < G4UniformRand());
274
275  return cosTheta;
276}
277
278//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
279
280G4double G4LivermorePolarizedRayleighModel::GeneratePhi(G4double cosTheta) const
281{
282  //  d sigma
283  // --------- = alpha * ( 1 - sin^2 (theta) * cos^2 (phi) )
284  //   d phi
285 
286  // On the average the loop takes no more than 2 iterations before exiting
287
288  G4double phi;
289  G4double cosPhi;
290  G4double phiProbability;
291  G4double sin2Theta;
292 
293  sin2Theta=1.-cosTheta*cosTheta;
294 
295  do
296    {
297      phi = twopi * G4UniformRand();
298      cosPhi = std::cos(phi);
299      phiProbability= 1. - sin2Theta*cosPhi*cosPhi;
300    }
301  while (phiProbability < G4UniformRand());
302 
303  return phi;
304}
305
306//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
307
308G4double G4LivermorePolarizedRayleighModel::GeneratePolarizationAngle(void) const
309{
310  // Rayleigh polarization is always on the x' direction
311
312  return 0;
313}
314
315//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
316
317G4ThreeVector G4LivermorePolarizedRayleighModel::GetPhotonPolarization(const G4DynamicParticle&  photon)
318{
319
320// SI - From G4VLowEnergyDiscretePhotonProcess.cc
321 
322  G4ThreeVector photonMomentumDirection;
323  G4ThreeVector photonPolarization;
324
325  photonPolarization = photon.GetPolarization(); 
326  photonMomentumDirection = photon.GetMomentumDirection();
327
328  if ((!photonPolarization.isOrthogonal(photonMomentumDirection, 1e-6)) || photonPolarization.mag()==0.)
329    {
330      // if |photonPolarization|==0. or |photonPolarization * photonDirection0| > 1e-6 * |photonPolarization ^ photonDirection0|
331      // then polarization is choosen randomly.
332 
333      G4ThreeVector e1(photonMomentumDirection.orthogonal().unit());
334      G4ThreeVector e2(photonMomentumDirection.cross(e1).unit());
335 
336      G4double angle(G4UniformRand() * twopi);
337 
338      e1*=std::cos(angle);
339      e2*=std::sin(angle);
340 
341      photonPolarization=e1+e2;
342    }
343  else if (photonPolarization.howOrthogonal(photonMomentumDirection) != 0.)
344    {
345      // if |photonPolarization * photonDirection0| != 0.
346      // then polarization is made orthonormal;
347 
348      photonPolarization=photonPolarization.perpPart(photonMomentumDirection);
349    }
350 
351  return photonPolarization.unit();
352}
353
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