source: trunk/source/processes/electromagnetic/polarisation/src/G4PolarizedComptonModel.cc

Last change on this file was 1337, checked in by garnier, 14 years ago

tag geant4.9.4 beta 1 + modifs locales
File size: 13.7 KB
Line 
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26//
27// $Id: G4PolarizedComptonModel.cc,v 1.4 2007/05/23 08:52:20 vnivanch Exp $
28// GEANT4 tag $Name: geant4-09-04-beta-01 $
29//
30// -------------------------------------------------------------------
31//
32// GEANT4 Class file
33//
34//
35// File name:     G4PolarizedComptonModel
36//
37// Author:        Andreas Schaelicke
38//
39// Creation date: 01.05.2005
40//
41// Modifications:
42// 18-07-06 use newly calculated cross sections (P. Starovoitov)
43// 21-08-05 update interface (A. Schaelicke)
44//
45// Class Description:
46//
47// -------------------------------------------------------------------
48//
49//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
50//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
51
52#include "G4PolarizedComptonModel.hh"
53#include "G4Electron.hh"
54#include "G4Gamma.hh"
55#include "Randomize.hh"
56#include "G4DataVector.hh"
57#include "G4ParticleChangeForGamma.hh"
58
59
60#include "G4StokesVector.hh"
61#include "G4PolarizationManager.hh"
62#include "G4PolarizationHelper.hh"
63#include "G4PolarizedComptonCrossSection.hh"
64
65//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
66
67G4PolarizedComptonModel::G4PolarizedComptonModel(const G4ParticleDefinition*,
68                                             const G4String& nam)
69  : G4KleinNishinaCompton(0,nam),
70    verboseLevel(0)
71{
72  crossSectionCalculator=new G4PolarizedComptonCrossSection();
73}
74
75//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
76
77G4PolarizedComptonModel::~G4PolarizedComptonModel()
78{
79  if (crossSectionCalculator) delete crossSectionCalculator;
80}
81
82
83
84G4double G4PolarizedComptonModel::ComputeAsymmetryPerAtom
85                       (G4double gammaEnergy, G4double /*Z*/)
86 
87{
88 G4double asymmetry = 0.0 ;
89
90 G4double k0 = gammaEnergy / electron_mass_c2 ;
91 G4double k1 = 1 + 2*k0 ;
92
93 asymmetry = -k0;
94 asymmetry *= (k0 + 1.)*sqr(k1)*std::log(k1) - 2.*k0*(5.*sqr(k0) + 4.*k0 + 1.);
95 asymmetry /= ((k0 - 2.)*k0  -2.)*sqr(k1)*std::log(k1) + 2.*k0*(k0*(k0 + 1.)*(k0 + 8.) + 2.);           
96
97 // G4cout<<"energy = "<<GammaEnergy<<"  asymmetry = "<<asymmetry<<"\t\t GAM = "<<k0<<G4endl;
98 if (asymmetry>1.) G4cout<<"ERROR in G4PolarizedComptonModel::ComputeAsymmetryPerAtom"<<G4endl;
99
100 return asymmetry;
101}
102
103
104G4double G4PolarizedComptonModel::ComputeCrossSectionPerAtom(
105                                const G4ParticleDefinition* pd,
106                                      G4double kinEnergy, 
107                                      G4double Z, 
108                                      G4double A, 
109                                      G4double cut,
110                                      G4double emax)
111{
112  double xs = 
113    G4KleinNishinaCompton::ComputeCrossSectionPerAtom(pd,kinEnergy,
114                                                      Z,A,cut,emax);
115  G4double polzz = theBeamPolarization.p3()*theTargetPolarization.z();
116  if (polzz!=0) {
117    G4double asym=ComputeAsymmetryPerAtom(kinEnergy, Z); 
118    xs*=(1.+polzz*asym);
119  }
120  return xs;
121}
122
123
124//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
125
126void G4PolarizedComptonModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
127                                                const G4MaterialCutsCouple*,
128                                                const G4DynamicParticle* aDynamicGamma,
129                                                G4double,
130                                                G4double)
131{
132  const G4Track * aTrack = fParticleChange->GetCurrentTrack();
133  G4VPhysicalVolume*  aPVolume  = aTrack->GetVolume();
134  G4LogicalVolume*    aLVolume  = aPVolume->GetLogicalVolume();
135
136  if (verboseLevel>=1) 
137    G4cout<<"G4PolarizedComptonModel::SampleSecondaries in "
138          <<  aLVolume->GetName() <<G4endl;
139
140  G4PolarizationManager * polarizationManager = G4PolarizationManager::GetInstance();
141
142  // obtain polarization of the beam
143  theBeamPolarization =  aDynamicGamma->GetPolarization();
144  theBeamPolarization.SetPhoton();
145
146  // obtain polarization of the media
147  const G4bool targetIsPolarized = polarizationManager->IsPolarized(aLVolume);
148  theTargetPolarization = polarizationManager->GetVolumePolarization(aLVolume);
149
150  // if beam is linear polarized or target is transversely polarized
151  // determine the angle to x-axis
152  // (assumes same PRF as in the polarization definition)
153
154  G4ThreeVector gamDirection0 = aDynamicGamma->GetMomentumDirection();
155
156  // transfere theTargetPolarization
157  // into the gamma frame (problem electron is at rest)
158  if (targetIsPolarized)
159    theTargetPolarization.rotateUz(gamDirection0);
160
161  // The scattered gamma energy is sampled according to Klein - Nishina formula.
162  // The random number techniques of Butcher & Messel are used
163  // (Nuc Phys 20(1960),15).
164  // Note : Effects due to binding of atomic electrons are negliged.
165 
166  G4double gamEnergy0 = aDynamicGamma->GetKineticEnergy();
167  G4double E0_m = gamEnergy0 / electron_mass_c2 ;
168
169
170  //
171  // sample the energy rate of the scattered gamma
172  //
173
174  G4double epsilon, epsilonsq, onecost, sint2, greject ;
175
176  G4double epsilon0   = 1./(1. + 2.*E0_m);
177  G4double epsilon0sq = epsilon0*epsilon0;
178  G4double alpha1     = - std::log(epsilon0);
179  G4double alpha2     = 0.5*(1.- epsilon0sq);
180
181  G4double polarization = theBeamPolarization.p3()*theTargetPolarization.p3();
182  do {
183    if ( alpha1/(alpha1+alpha2) > G4UniformRand() ) {
184      epsilon   = std::exp(-alpha1*G4UniformRand());   // epsilon0**r
185      epsilonsq = epsilon*epsilon; 
186
187    } else {
188      epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand();
189      epsilon   = std::sqrt(epsilonsq);
190    };
191
192    onecost = (1.- epsilon)/(epsilon*E0_m);
193    sint2   = onecost*(2.-onecost);
194
195
196    G4double gdiced = 2.*(1./epsilon+epsilon);
197    G4double gdist  = 1./epsilon + epsilon - sint2
198      - polarization*(1./epsilon-epsilon)*(1.-onecost);
199
200    greject = gdist/gdiced;
201
202    if (greject>1) G4cout<<"ERROR in PolarizedComptonScattering::PostStepDoIt\n"
203                         <<" costh rejection does not work properly: "<<greject<<G4endl;
204
205  } while (greject < G4UniformRand());
206 
207  //
208  // scattered gamma angles. ( Z - axis along the parent gamma)
209  //
210
211  G4double cosTeta = 1. - onecost; 
212  G4double sinTeta = std::sqrt (sint2);
213  G4double Phi;
214  do {
215    Phi     = twopi * G4UniformRand();
216     G4double gdiced = 1./epsilon + epsilon - sint2
217       + std::abs(theBeamPolarization.p3())*
218       ( std::abs((1./epsilon-epsilon)*cosTeta*theTargetPolarization.p3())
219        +(1.-epsilon)*sinTeta*(std::sqrt(sqr(theTargetPolarization.p1()) 
220                                    + sqr(theTargetPolarization.p2()))))
221       +sint2*(std::sqrt(sqr(theBeamPolarization.p1()) + sqr(theBeamPolarization.p2())));
222
223     G4double gdist = 1./epsilon + epsilon - sint2
224       + theBeamPolarization.p3()*
225       ((1./epsilon-epsilon)*cosTeta*theTargetPolarization.p3()
226        +(1.-epsilon)*sinTeta*(std::cos(Phi)*theTargetPolarization.p1()+
227                               std::sin(Phi)*theTargetPolarization.p2()))
228       -sint2*(std::cos(2.*Phi)*theBeamPolarization.p1()
229               +std::sin(2.*Phi)*theBeamPolarization.p2());
230     greject = gdist/gdiced;
231
232    if (greject>1.+1.e-10 || greject<0) G4cout<<"ERROR in PolarizedComptonScattering::PostStepDoIt\n"
233                                      <<" phi rejection does not work properly: "<<greject<<G4endl;
234
235    if (greject<1.e-3) {
236      G4cout<<"ERROR in PolarizedComptonScattering::PostStepDoIt\n"
237            <<" phi rejection does not work properly: "<<greject<<"\n";
238      G4cout<<" greject="<<greject<<"  phi="<<Phi<<"   cost="<<cosTeta<<"\n";
239      G4cout<<" gdiced="<<gdiced<<"   gdist="<<gdist<<"\n";
240      G4cout<<" eps="<<epsilon<<"    1/eps="<<1./epsilon<<"\n";
241    }
242     
243  } while (greject < G4UniformRand());
244  G4double dirx = sinTeta*std::cos(Phi), diry = sinTeta*std::sin(Phi), dirz = cosTeta;
245
246  //
247  // update G4VParticleChange for the scattered gamma
248  //
249   
250  G4ThreeVector gamDirection1 ( dirx,diry,dirz );
251  gamDirection1.rotateUz(gamDirection0);
252  G4double gamEnergy1 = epsilon*gamEnergy0;
253  fParticleChange->SetProposedKineticEnergy(gamEnergy1);
254
255
256  if(gamEnergy1 > lowestGammaEnergy) {
257    fParticleChange->ProposeMomentumDirection(gamDirection1);
258  } else { 
259    fParticleChange->ProposeTrackStatus(fStopAndKill);
260    gamEnergy1 += fParticleChange->GetLocalEnergyDeposit();
261    fParticleChange->ProposeLocalEnergyDeposit(gamEnergy1);
262  }
263 
264  //
265  // kinematic of the scattered electron
266  //
267
268  G4double eKinEnergy = gamEnergy0 - gamEnergy1;
269  G4ThreeVector eDirection = gamEnergy0*gamDirection0 - gamEnergy1*gamDirection1;
270  eDirection = eDirection.unit();
271
272  //
273  // calculate Stokesvector of final state photon and electron
274  //
275  G4ThreeVector  nInteractionFrame;
276  if((gamEnergy1 > lowestGammaEnergy) ||
277     (eKinEnergy > DBL_MIN)) {
278
279    // determine interaction plane
280//     nInteractionFrame =
281//       G4PolarizationHelper::GetFrame(gamDirection1,eDirection);
282    if (gamEnergy1 > lowestGammaEnergy) 
283      nInteractionFrame = G4PolarizationHelper::GetFrame(gamDirection1,gamDirection0);
284    else 
285      nInteractionFrame = G4PolarizationHelper::GetFrame(gamDirection0, eDirection);
286
287    // transfere theBeamPolarization and theTargetPolarization
288    // into the interaction frame (note electron is in gamma frame)
289    if (verboseLevel>=1) {
290      G4cout << "========================================\n";
291      G4cout << " nInteractionFrame = " <<nInteractionFrame<<"\n";
292      G4cout << " GammaDirection0 = " <<gamDirection0<<"\n";
293      G4cout << " gammaPolarization = " <<theBeamPolarization<<"\n";
294      G4cout << " electronPolarization = " <<theTargetPolarization<<"\n";
295    }
296
297    theBeamPolarization.InvRotateAz(nInteractionFrame,gamDirection0);
298    theTargetPolarization.InvRotateAz(nInteractionFrame,gamDirection0);
299
300    if (verboseLevel>=1) {
301      G4cout << "----------------------------------------\n";
302      G4cout << " gammaPolarization = " <<theBeamPolarization<<"\n";
303      G4cout << " electronPolarization = " <<theTargetPolarization<<"\n";
304      G4cout << "----------------------------------------\n";
305    }
306
307    // initialize the polarization transfer matrix
308    crossSectionCalculator->Initialize(epsilon,E0_m,0.,
309                                       theBeamPolarization,
310                                       theTargetPolarization,2);
311  }
312
313  //  if(eKinEnergy > DBL_MIN)
314  {
315    // in interaction frame
316    // calculate polarization transfer to the photon (in interaction plane)
317    finalGammaPolarization = crossSectionCalculator->GetPol2();
318    if (verboseLevel>=1) G4cout << " gammaPolarization1 = " <<finalGammaPolarization<<"\n";
319    finalGammaPolarization.SetPhoton();
320
321    // translate polarization into particle reference frame
322    finalGammaPolarization.RotateAz(nInteractionFrame,gamDirection1);
323    //store polarization vector
324    fParticleChange->ProposePolarization(finalGammaPolarization);
325    if (finalGammaPolarization.mag() > 1.+1.e-8){
326      G4cout<<"ERROR in Polarizaed Compton Scattering !"<<G4endl;
327      G4cout<<"Polarization of final photon more than 100%"<<G4endl;
328      G4cout<<finalGammaPolarization<<" mag = "<<finalGammaPolarization.mag()<<G4endl;
329    }
330    if (verboseLevel>=1) {
331      G4cout << " gammaPolarization1 = " <<finalGammaPolarization<<"\n";
332      G4cout << " GammaDirection1 = " <<gamDirection1<<"\n";
333    }
334  }
335
336  //    if (ElecKineEnergy > fminimalEnergy) {
337  {
338    finalElectronPolarization = crossSectionCalculator->GetPol3();
339    if (verboseLevel>=1) 
340      G4cout << " electronPolarization1 = " <<finalElectronPolarization<<"\n";
341
342    // transfer into particle reference frame
343    finalElectronPolarization.RotateAz(nInteractionFrame,eDirection);
344    if (verboseLevel>=1) {
345      G4cout << " electronPolarization1 = " <<finalElectronPolarization<<"\n";
346      G4cout << " ElecDirection = " <<eDirection<<"\n";
347    }
348  }
349  if (verboseLevel>=1)
350    G4cout << "========================================\n";
351       
352
353  if(eKinEnergy > DBL_MIN) {
354
355    // create G4DynamicParticle object for the electron.
356    G4DynamicParticle* aElectron = new G4DynamicParticle(theElectron,eDirection,eKinEnergy);
357    //store polarization vector
358    if (finalElectronPolarization.mag() > 1.+1.e-8){
359      G4cout<<"ERROR in Polarizaed Compton Scattering !"<<G4endl;
360      G4cout<<"Polarization of final electron more than 100%"<<G4endl;
361      G4cout<<finalElectronPolarization<<" mag = "<<finalElectronPolarization.mag()<<G4endl;
362    }
363    aElectron->SetPolarization(finalElectronPolarization.p1(),
364                               finalElectronPolarization.p2(),
365                               finalElectronPolarization.p3());
366    fvect->push_back(aElectron);
367  }
368}
369
370//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
371
372
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