source: trunk/source/processes/electromagnetic/lowenergy/src/G4LivermorePolarizedRayleighModel.cc @ 991

Last change on this file since 991 was 991, checked in by garnier, 15 years ago

update
File size: 12.6 KB
Line 
1//
2// ********************************************************************
3// * License and Disclaimer                                           *
4// *                                                                  *
5// * The  Geant4 software  is  copyright of the Copyright Holders  of *
6// * the Geant4 Collaboration.  It is provided  under  the terms  and *
7// * conditions of the Geant4 Software License,  included in the file *
8// * LICENSE and available at  http://cern.ch/geant4/license .  These *
9// * include a list of copyright holders.                             *
10// *                                                                  *
11// * Neither the authors of this software system, nor their employing *
12// * institutes,nor the agencies providing financial support for this *
13// * work  make  any representation or  warranty, express or implied, *
14// * regarding  this  software system or assume any liability for its *
15// * use.  Please see the license in the file  LICENSE  and URL above *
16// * for the full disclaimer and the limitation of liability.         *
17// *                                                                  *
18// * This  code  implementation is the result of  the  scientific and *
19// * technical work of the GEANT4 collaboration.                      *
20// * By using,  copying,  modifying or  distributing the software (or *
21// * any work based  on the software)  you  agree  to acknowledge its *
22// * use  in  resulting  scientific  publications,  and indicate your *
23// * acceptance of all terms of the Geant4 Software license.          *
24// ********************************************************************
25//
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
Note: See TracBrowser for help on using the repository browser.