G4PolarizedCompton.cc

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// $Id: G4PolarizedCompton.cc 109176 2018-04-03 06:53:39Z gcosmo $
// 
//
// File name:     G4PolarizedCompton
//
// Author:        Andreas Schaelicke
//                based on code by Michel Maire / Vladimir IVANTCHENKO
// Class description
//
// modified version respecting media and beam polarization
//     using the stokes formalism
//
// Creation date: 01.05.2005
//
// Modifications:
//
// 01-01-05, include polarization description (A.Stahl)
// 01-01-05, create asymmetry table and determine interactionlength (A.Stahl)
// 01-05-05, update handling of media polarization (A.Schalicke)
// 01-05-05, update polarized differential cross section (A.Schalicke)
// 20-05-05, added polarization transfer (A.Schalicke)
// 10-06-05, transformation between different reference frames (A.Schalicke)
// 17-10-05, correct reference frame dependence in GetMeanFreePath (A.Schalicke)
// 26-07-06, cross section recalculated (P.Starovoitov)
// 09-08-06, make it work under current geant4 release (A.Schalicke)
// 11-06-07, add PostStepGetPhysicalInteractionLength (A.Schalicke)
// -----------------------------------------------------------------------------


#include "G4PolarizedCompton.hh"
#include "G4SystemOfUnits.hh"
#include "G4Electron.hh"

#include "G4StokesVector.hh"
#include "G4PolarizationManager.hh"
#include "G4PolarizedComptonModel.hh"
#include "G4ProductionCutsTable.hh"
#include "G4PhysicsTableHelper.hh"
#include "G4KleinNishinaCompton.hh"
#include "G4PolarizedComptonModel.hh"
#include "G4EmParameters.hh"

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G4PhysicsTable* G4PolarizedCompton::theAsymmetryTable = nullptr;

G4PolarizedCompton::G4PolarizedCompton(const G4String& processName,
  G4ProcessType type):
  G4VEmProcess (processName, type),
  buildAsymmetryTable(true),
  useAsymmetryTable(true),
  isInitialised(false),
  mType(10),
  targetPolarization(0.0,0.0,0.0)
{
  SetStartFromNullFlag(true);
  SetBuildTableFlag(true);
  SetSecondaryParticle(G4Electron::Electron());
  SetProcessSubType(fComptonScattering);
  SetMinKinEnergyPrim(1*MeV);
  SetSplineFlag(true);
  emModel = nullptr;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
 
G4PolarizedCompton::~G4PolarizedCompton()
{
  CleanTable();
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
 
void G4PolarizedCompton::CleanTable()
{
  if( theAsymmetryTable) {
    theAsymmetryTable->clearAndDestroy();
    delete theAsymmetryTable;
    theAsymmetryTable = nullptr;
  }
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

G4bool G4PolarizedCompton::IsApplicable(const G4ParticleDefinition& p)
{
  return (&p == G4Gamma::Gamma());
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

void G4PolarizedCompton::InitialiseProcess(const G4ParticleDefinition*)
{
  if(!isInitialised) {
    isInitialised = true;
    if(0 == mType) {
      if(!EmModel(0)) { SetEmModel(new G4KleinNishinaCompton()); }
    } else {
      emModel = new G4PolarizedComptonModel();
      SetEmModel(emModel); 
    }
    G4EmParameters* param = G4EmParameters::Instance();
    EmModel(0)->SetLowEnergyLimit(param->MinKinEnergy());
    EmModel(0)->SetHighEnergyLimit(param->MaxKinEnergy());
    AddEmModel(1, EmModel(0));
  } 
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

void G4PolarizedCompton::PrintInfo()
{
  G4cout << " Total cross sections has a good parametrisation"
         << " from 10 KeV to (100/Z) GeV" 
         << "\n      Sampling according " <<  EmModel(0)->GetName() << " model" 
   << G4endl;
}         

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

void G4PolarizedCompton::SetModel(const G4String& ss)
{
  if(ss == "Klein-Nishina")     { mType = 0; }
  if(ss == "Polarized-Compton") { mType = 10; }
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

G4double G4PolarizedCompton::GetMeanFreePath(const G4Track& aTrack,
               G4double   previousStepSize,
               G4ForceCondition* condition)
{
  // *** get unploarised mean free path from lambda table ***
  G4double mfp = G4VEmProcess::GetMeanFreePath(aTrack, previousStepSize, condition);

  if (theAsymmetryTable && useAsymmetryTable && mfp < DBL_MAX) {
    mfp *= ComputeSaturationFactor(aTrack);
  }
  if (verboseLevel>=2) {
    G4cout << "G4PolarizedCompton::MeanFreePath:  " << mfp / mm << " mm " << G4endl;
  }
  return mfp;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

G4double G4PolarizedCompton::PostStepGetPhysicalInteractionLength(
           const G4Track& aTrack,
           G4double   previousStepSize,
           G4ForceCondition* condition)
{
  // save previous values
  G4double nLength = theNumberOfInteractionLengthLeft;
  G4double iLength = currentInteractionLength;

  // *** compute unpolarized step limit ***
  // this changes theNumberOfInteractionLengthLeft and currentInteractionLength
  G4double x = G4VEmProcess::PostStepGetPhysicalInteractionLength(aTrack, 
                  previousStepSize, 
                  condition);
  G4double x0 = x;
  G4double satFact = 1.0;
  
  // *** add corrections on polarisation ***
  if (theAsymmetryTable && useAsymmetryTable && x < DBL_MAX) {
    satFact = ComputeSaturationFactor(aTrack);
    G4double curLength = currentInteractionLength*satFact;
    G4double prvLength = iLength*satFact;
    if(nLength > 0.0) {
      theNumberOfInteractionLengthLeft = 
        std::max(nLength - previousStepSize/prvLength, 0.0);
    }
    x = theNumberOfInteractionLengthLeft * curLength;
  }
  if (verboseLevel>=2) {
    G4cout << "G4PolarizedCompton::PostStepGPIL: " 
           << std::setprecision(8) << x/mm  << " mm;" << G4endl 
           << "               unpolarized value: " 
           << std::setprecision(8) << x0/mm << " mm." << G4endl;
  }
  return x;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

G4double G4PolarizedCompton::ComputeSaturationFactor(const G4Track& aTrack)
{
  G4double factor = 1.0;

  // *** get asymmetry, if target is polarized ***
  const G4DynamicParticle* aDynamicGamma = aTrack.GetDynamicParticle();
  const G4double GammaEnergy = aDynamicGamma->GetKineticEnergy();
  const G4StokesVector GammaPolarization = aTrack.GetPolarization();
  const G4ParticleMomentum GammaDirection0 = aDynamicGamma->GetMomentumDirection();

  G4Material*         aMaterial = aTrack.GetMaterial();
  G4VPhysicalVolume*  aPVolume  = aTrack.GetVolume();
  G4LogicalVolume*    aLVolume  = aPVolume->GetLogicalVolume();

  //   G4Material* bMaterial = aLVolume->GetMaterial();
  G4PolarizationManager * polarizationManger = G4PolarizationManager::GetInstance();

  const G4bool VolumeIsPolarized = polarizationManger->IsPolarized(aLVolume);
  G4StokesVector ElectronPolarization = polarizationManger->GetVolumePolarization(aLVolume);

  if (VolumeIsPolarized) {
     
    if (verboseLevel>=2) {
      G4cout << "G4PolarizedCompton::ComputeSaturationFactor: " << G4endl;
      G4cout << " Mom " << GammaDirection0  << G4endl;
      G4cout << " Polarization " << GammaPolarization  << G4endl;
      G4cout << " MaterialPol. " << ElectronPolarization  << G4endl;
      G4cout << " Phys. Volume " << aPVolume->GetName() << G4endl;
      G4cout << " Log. Volume  " << aLVolume->GetName() << G4endl;
      G4cout << " Material     " << aMaterial          << G4endl;
    }

    size_t midx = CurrentMaterialCutsCoupleIndex();
    const G4PhysicsVector* aVector = nullptr;
    if(midx < theAsymmetryTable->size()) { 
      aVector = (*theAsymmetryTable)(midx);
    }
    if (aVector) {
      G4double asymmetry = aVector->Value(GammaEnergy);

      //  we have to determine angle between particle motion 
      //  and target polarisation here  
      //      circ pol * Vec(ElectronPol)*Vec(PhotonMomentum)
      //  both vectors in global reference frame
     
      G4double pol = ElectronPolarization*GammaDirection0;     
      G4double polProduct = GammaPolarization.p3() * pol;
      factor /= (1. + polProduct * asymmetry);
      if (verboseLevel>=2) {
  G4cout << " Asymmetry:     " << asymmetry      << G4endl;
  G4cout << " PolProduct:    " << polProduct     << G4endl;
  G4cout << " Factor:        " << factor         << G4endl;
      }   
    } else {
      G4ExceptionDescription ed;
      ed << "Problem with asymmetry table: material index " << midx 
   << " is out of range or the table is not filled";
      G4Exception("G4PolarizedComptonModel::ComputeSaturationFactor","em0048",
      JustWarning, ed, "");
    }
  }
  return factor;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

void G4PolarizedCompton::BuildPhysicsTable(const G4ParticleDefinition& part)
{
  // *** build (unpolarized) cross section tables (Lambda)
  G4VEmProcess::BuildPhysicsTable(part);
  if(buildAsymmetryTable && emModel) { 
    G4bool isMaster = true;
    const G4PolarizedCompton* masterProcess = 
      static_cast<const G4PolarizedCompton*>(GetMasterProcess());
    if(masterProcess && masterProcess != this) { isMaster = false; }
    if(isMaster) { BuildAsymmetryTable(part); }
  }
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

void G4PolarizedCompton::BuildAsymmetryTable(const G4ParticleDefinition& part)
{
  // cleanup old, initialise new table
  CleanTable();
  theAsymmetryTable = 
    G4PhysicsTableHelper::PreparePhysicsTable(theAsymmetryTable);

  // Access to materials
  const G4ProductionCutsTable* theCoupleTable=
        G4ProductionCutsTable::GetProductionCutsTable();
  size_t numOfCouples = theCoupleTable->GetTableSize();
  if(!theAsymmetryTable) { return; }
  G4int nbins = LambdaBinning();
  G4double emin = MinKinEnergy();
  G4double emax = MaxKinEnergy();
  G4PhysicsLogVector* aVector = nullptr;
  G4PhysicsLogVector* bVector = nullptr;

  for(size_t i=0; i<numOfCouples; ++i) {
    if (theAsymmetryTable->GetFlag(i)) {

      // create physics vector and fill it
      const G4MaterialCutsCouple* couple = theCoupleTable->GetMaterialCutsCouple(i);
      // use same parameters as for lambda
      if(!aVector) { 
  aVector = new G4PhysicsLogVector(emin, emax, nbins); 
        aVector->SetSpline(true);
        bVector = aVector;
      } else {
  bVector = new G4PhysicsLogVector(*aVector);
      }

      for (G4int j = 0; j <= nbins; ++j ) {
  G4double energy = bVector->Energy(j);
  G4double tasm=0.;
  G4double asym = ComputeAsymmetry(energy, couple, part, 0., tasm);
  bVector->PutValue(j,asym);
      }
      G4PhysicsTableHelper::SetPhysicsVector(theAsymmetryTable, i, bVector);
    }
  }
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

G4double G4PolarizedCompton::ComputeAsymmetry(G4double energy,
                const G4MaterialCutsCouple* couple,
                const G4ParticleDefinition& aParticle,
                G4double cut,
                G4double & tAsymmetry)
{
  G4double lAsymmetry = 0.0;
  tAsymmetry=0;

  //
  // calculate polarized cross section
  //
  G4ThreeVector thePolarization=G4ThreeVector(0.,0.,1.);
  emModel->SetTargetPolarization(thePolarization);
  emModel->SetBeamPolarization(thePolarization);
  G4double sigma2=emModel->CrossSection(couple,&aParticle,energy,cut,energy);

  //
  // calculate unpolarized cross section
  //
  thePolarization=G4ThreeVector();
  emModel->SetTargetPolarization(thePolarization);
  emModel->SetBeamPolarization(thePolarization);
  G4double sigma0=emModel->CrossSection(couple,&aParticle,energy,cut,energy);

  // determine assymmetries
  if (sigma0 > 0.) {
    lAsymmetry = sigma2/sigma0-1.;
  }
  return lAsymmetry;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....