Geant4 LXR

Cross-Referencing   Geant4
Geant4/processes/optical/src/G4OpMieHG.cc

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  ////////////////////////////////////////////////////////////////////////
  //
  // File G4OpMieHG.hh
  // Description: Discrete Process -- Mie Scattering of Optical Photons
  // Created: 2010-07-03
  // Author: Xin Qian
  // Based on work from Vlasios Vasileiou
  //
  // This subroutine will mimic the Mie scattering based on
  // Henyey-Greenstein phase function
  // Forward and backward angles are treated separately.
  //
  ////////////////////////////////////////////////////////////////////////
  
  #include "G4OpMieHG.hh"
  #include "G4PhysicalConstants.hh"
  #include "G4OpticalParameters.hh"
  #include "G4OpProcessSubType.hh"
  
  //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
  G4OpMieHG::G4OpMieHG(const G4String& processName, G4ProcessType type)
    : G4VDiscreteProcess(processName, type)
  {
    Initialise();
    if(verboseLevel > 0)
    {
      G4cout << GetProcessName() << " is created " << G4endl;
    }
    SetProcessSubType(fOpMieHG);
  }
  
  //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
  G4OpMieHG::~G4OpMieHG() = default;
  
  //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
  void G4OpMieHG::PreparePhysicsTable(const G4ParticleDefinition&)
  {
    Initialise();
  }
  
  //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
  void G4OpMieHG::Initialise()
  {
    SetVerboseLevel(G4OpticalParameters::Instance()->GetMieVerboseLevel());
  }
  
  //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
  G4VParticleChange* G4OpMieHG::PostStepDoIt(const G4Track& aTrack,
                                             const G4Step& aStep)
  {
    aParticleChange.Initialize(aTrack);
  
    const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
    const G4MaterialPropertiesTable* MPT =
      aTrack.GetMaterial()->GetMaterialPropertiesTable();
  
    G4double forwardRatio = MPT->GetConstProperty(kMIEHG_FORWARD_RATIO);
  
    if(verboseLevel > 1)
    {
      G4cout << "OpMie Scattering Photon!" << G4endl
             << " Old Momentum Direction: " << aParticle->GetMomentumDirection()
             << G4endl
             << " MIE Old Polarization: " << aParticle->GetPolarization()
             << G4endl;
    }
  
    G4double gg;
    G4int direction;
    if(G4UniformRand() <= forwardRatio)
    {
      gg        = MPT->GetConstProperty(kMIEHG_FORWARD);
      direction = 1;
   }
   else
   {
     gg        = MPT->GetConstProperty(kMIEHG_BACKWARD);
     direction = -1;
   }
 
   G4double r = G4UniformRand();
 
   // sample the direction
   G4double theta;
   if(gg != 0.)
   {
     theta = std::acos(2. * r * (1. + gg) * (1. + gg) * (1. - gg + gg * r) /
                         ((1. - gg + 2. * gg * r) * (1. - gg + 2. * gg * r)) -
                       1.);
   }
   else
   {
     theta = std::acos(2. * r - 1.);
   }
   G4double phi = G4UniformRand() * twopi;
 
   if(direction == -1)
     theta = pi - theta;  // backward scattering
 
   G4ThreeVector newMomDir, oldMomDir;
   G4ThreeVector newPol, oldPol;
 
   G4double sinth = std::sin(theta);
   newMomDir.set(sinth * std::cos(phi), sinth * std::sin(phi), std::cos(theta));
   oldMomDir = aParticle->GetMomentumDirection();
   newMomDir.rotateUz(oldMomDir);
   newMomDir = newMomDir.unit();
 
   oldPol = aParticle->GetPolarization();
   newPol = newMomDir - oldPol / newMomDir.dot(oldPol);
   newPol = newPol.unit();
 
   if(newPol.mag() == 0.)
   {
     r = G4UniformRand() * twopi;
     newPol.set(std::cos(r), std::sin(r), 0.);
     newPol.rotateUz(newMomDir);
   }
   else
   {
     // There are two directions perpendicular to new momentum direction
     if(G4UniformRand() < 0.5)
       newPol = -newPol;
   }
 
   aParticleChange.ProposePolarization(newPol);
   aParticleChange.ProposeMomentumDirection(newMomDir);
 
   if(verboseLevel > 1)
   {
     G4cout << "OpMie New Polarization: " << newPol << G4endl
            << " Polarization Change: " << *(aParticleChange.GetPolarization())
            << G4endl << " New Momentum Direction: " << newMomDir << G4endl
            << " Momentum Change: " << *(aParticleChange.GetMomentumDirection())
            << G4endl;
   }
 
   return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);
 }
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
 G4double G4OpMieHG::GetMeanFreePath(const G4Track& aTrack, G4double,
                                     G4ForceCondition*)
 {
   G4double attLength = DBL_MAX;
   G4MaterialPropertiesTable* MPT =
     aTrack.GetMaterial()->GetMaterialPropertiesTable();
   if(MPT)
   {
     G4MaterialPropertyVector* attVector = MPT->GetProperty(kMIEHG);
     if(attVector)
     {
       attLength = attVector->Value(
         aTrack.GetDynamicParticle()->GetTotalEnergy(), idx_mie);
     }
   }
   return attLength;
 }
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
 void G4OpMieHG::SetVerboseLevel(G4int verbose)
 {
   verboseLevel = verbose;
   G4OpticalParameters::Instance()->SetMieVerboseLevel(verboseLevel);
 }