G4OpWLS.cc

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// $Id$
//
// Optical Photon WaveLength Shifting (WLS) Class Implementation
//
// File:        G4OpWLS.cc
// Description: Discrete Process -- Wavelength Shifting of Optical Photons
// Version:     1.0
// Created:     2003-05-13
// Author:      John Paul Archambault
//              (Adaptation of G4Scintillation and G4OpAbsorption)
// Updated:     2005-07-28 - add G4ProcessType to constructor
//              2006-05-07 - add G4VWLSTimeGeneratorProfile
// mail:        gum@triumf.ca
//              jparcham@phys.ualberta.ca
//

#include "G4OpWLS.hh"

#include "G4ios.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4OpProcessSubType.hh"

#include "G4WLSTimeGeneratorProfileDelta.hh"
#include "G4WLSTimeGeneratorProfileExponential.hh"

// Class Implementation

// Constructors

G4OpWLS::G4OpWLS(const G4String& processName, G4ProcessType type)
  : G4VDiscreteProcess(processName, type)
{
  SetProcessSubType(fOpWLS);

  theIntegralTable = 0;
 
  if (verboseLevel>0) {
    G4cout << GetProcessName() << " is created " << G4endl;
  }

  WLSTimeGeneratorProfile = 
       new G4WLSTimeGeneratorProfileDelta("WLSTimeGeneratorProfileDelta");

  BuildThePhysicsTable();
}

// Destructors

G4OpWLS::~G4OpWLS()
{
  if (theIntegralTable != 0) {
    theIntegralTable->clearAndDestroy();
    delete theIntegralTable;
  }
  delete WLSTimeGeneratorProfile;
}

// Methods

// PostStepDoIt
// -------------
//
G4VParticleChange*
G4OpWLS::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep)
{
  aParticleChange.Initialize(aTrack);
  
  aParticleChange.ProposeTrackStatus(fStopAndKill);

  if (verboseLevel>0) {
    G4cout << "\n** Photon absorbed! **" << G4endl;
  }
  
  const G4Material* aMaterial = aTrack.GetMaterial();

  G4StepPoint* pPostStepPoint = aStep.GetPostStepPoint();
    
  G4MaterialPropertiesTable* aMaterialPropertiesTable =
    aMaterial->GetMaterialPropertiesTable();
  if (!aMaterialPropertiesTable)
    return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);

  const G4MaterialPropertyVector* WLS_Intensity = 
    aMaterialPropertiesTable->GetProperty("WLSCOMPONENT"); 

  if (!WLS_Intensity)
    return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);

  G4int NumPhotons = 1;

  if (aMaterialPropertiesTable->ConstPropertyExists("WLSMEANNUMBERPHOTONS")) {

     G4double MeanNumberOfPhotons = aMaterialPropertiesTable->
                                    GetConstProperty("WLSMEANNUMBERPHOTONS");

     NumPhotons = G4int(G4Poisson(MeanNumberOfPhotons));

     if (NumPhotons <= 0) {

        // return unchanged particle and no secondaries

        aParticleChange.SetNumberOfSecondaries(0);

        return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);

     }

  }

  aParticleChange.SetNumberOfSecondaries(NumPhotons);

  G4int materialIndex = aMaterial->GetIndex();

  // Retrieve the WLS Integral for this material
  // new G4PhysicsOrderedFreeVector allocated to hold CII's

  G4double WLSTime = 0.*ns;
  G4PhysicsOrderedFreeVector* WLSIntegral = 0;

  WLSTime   = aMaterialPropertiesTable->
    GetConstProperty("WLSTIMECONSTANT");
  WLSIntegral =
    (G4PhysicsOrderedFreeVector*)((*theIntegralTable)(materialIndex));
   
  // Max WLS Integral
  
  G4double CIImax = WLSIntegral->GetMaxValue();
  
  for (G4int i = 0; i < NumPhotons; i++) {
    
    // Determine photon energy
    
    G4double CIIvalue = G4UniformRand()*CIImax;
    G4double sampledEnergy = 
      WLSIntegral->GetEnergy(CIIvalue);
    
    if (verboseLevel>1) {
      G4cout << "sampledEnergy = " << sampledEnergy << G4endl;
      G4cout << "CIIvalue =        " << CIIvalue << G4endl;
    }
    
    // Generate random photon direction
    
    G4double cost = 1. - 2.*G4UniformRand();
    G4double sint = std::sqrt((1.-cost)*(1.+cost));

    G4double phi = twopi*G4UniformRand();
    G4double sinp = std::sin(phi);
    G4double cosp = std::cos(phi);
    
    G4double px = sint*cosp;
    G4double py = sint*sinp;
    G4double pz = cost;
    
    // Create photon momentum direction vector
    
    G4ParticleMomentum photonMomentum(px, py, pz);
    
    // Determine polarization of new photon
    
    G4double sx = cost*cosp;
    G4double sy = cost*sinp;
    G4double sz = -sint;
    
    G4ThreeVector photonPolarization(sx, sy, sz);
    
    G4ThreeVector perp = photonMomentum.cross(photonPolarization);
    
    phi = twopi*G4UniformRand();
    sinp = std::sin(phi);
    cosp = std::cos(phi);
    
    photonPolarization = cosp * photonPolarization + sinp * perp;
    
    photonPolarization = photonPolarization.unit();
    
    // Generate a new photon:
    
    G4DynamicParticle* aWLSPhoton =
      new G4DynamicParticle(G4OpticalPhoton::OpticalPhoton(),
                photonMomentum);
    aWLSPhoton->SetPolarization
      (photonPolarization.x(),
       photonPolarization.y(),
       photonPolarization.z());
    
    aWLSPhoton->SetKineticEnergy(sampledEnergy);
    
    // Generate new G4Track object:
    
    // Must give position of WLS optical photon

    G4double TimeDelay = WLSTimeGeneratorProfile->GenerateTime(WLSTime);
    G4double aSecondaryTime = (pPostStepPoint->GetGlobalTime()) + TimeDelay;

    G4ThreeVector aSecondaryPosition = pPostStepPoint->GetPosition();

    G4Track* aSecondaryTrack = 
      new G4Track(aWLSPhoton,aSecondaryTime,aSecondaryPosition);
   
    aSecondaryTrack->SetTouchableHandle(aTrack.GetTouchableHandle()); 
    // aSecondaryTrack->SetTouchableHandle((G4VTouchable*)0);
    
    aSecondaryTrack->SetParentID(aTrack.GetTrackID());
    
    aParticleChange.AddSecondary(aSecondaryTrack);
  }

  if (verboseLevel>0) {
    G4cout << "\n Exiting from G4OpWLS::DoIt -- NumberOfSecondaries = " 
       << aParticleChange.GetNumberOfSecondaries() << G4endl;  
  }
  
  return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);
}

// BuildThePhysicsTable for the wavelength shifting process
// --------------------------------------------------
//

void G4OpWLS::BuildThePhysicsTable()
{
  if (theIntegralTable) return;
  
  const G4MaterialTable* theMaterialTable = 
    G4Material::GetMaterialTable();
  G4int numOfMaterials = G4Material::GetNumberOfMaterials();
  
  // create new physics table
  
  if(!theIntegralTable)theIntegralTable = new G4PhysicsTable(numOfMaterials);
  
  // loop for materials
  
  for (G4int i=0 ; i < numOfMaterials; i++)
    {
      G4PhysicsOrderedFreeVector* aPhysicsOrderedFreeVector =
    new G4PhysicsOrderedFreeVector();
      
      // Retrieve vector of WLS wavelength intensity for
      // the material from the material's optical properties table.
      
      G4Material* aMaterial = (*theMaterialTable)[i];

      G4MaterialPropertiesTable* aMaterialPropertiesTable =
    aMaterial->GetMaterialPropertiesTable();

      if (aMaterialPropertiesTable) {

    G4MaterialPropertyVector* theWLSVector = 
      aMaterialPropertiesTable->GetProperty("WLSCOMPONENT");

    if (theWLSVector) {
      
      // Retrieve the first intensity point in vector
      // of (photon energy, intensity) pairs
      
      G4double currentIN = (*theWLSVector)[0];
      
      if (currentIN >= 0.0) {

        // Create first (photon energy) 
       
        G4double currentPM = theWLSVector->Energy(0);
        
        G4double currentCII = 0.0;
        
        aPhysicsOrderedFreeVector->
          InsertValues(currentPM , currentCII);
        
        // Set previous values to current ones prior to loop
        
        G4double prevPM  = currentPM;
        G4double prevCII = currentCII;
        G4double prevIN  = currentIN;
        
        // loop over all (photon energy, intensity)
        // pairs stored for this material

            for (size_t j = 1;
                 j < theWLSVector->GetVectorLength();
                 j++)       
          {
        currentPM = theWLSVector->Energy(j);
        currentIN = (*theWLSVector)[j];
        
        currentCII = 0.5 * (prevIN + currentIN);
        
        currentCII = prevCII +
          (currentPM - prevPM) * currentCII;
        
        aPhysicsOrderedFreeVector->
          InsertValues(currentPM, currentCII);
        
        prevPM  = currentPM;
        prevCII = currentCII;
        prevIN  = currentIN;
          }
      }
    }
      }
    // The WLS integral for a given material
    // will be inserted in the table according to the
    // position of the material in the material table.

    theIntegralTable->insertAt(i,aPhysicsOrderedFreeVector);
    }
}

// GetMeanFreePath
// ---------------
//
G4double G4OpWLS::GetMeanFreePath(const G4Track& aTrack,
                         G4double ,
                         G4ForceCondition* )
{
  const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
  const G4Material* aMaterial = aTrack.GetMaterial();

  G4double thePhotonEnergy = aParticle->GetTotalEnergy();

  G4MaterialPropertiesTable* aMaterialPropertyTable;
  G4MaterialPropertyVector* AttenuationLengthVector;
    
  G4double AttenuationLength = DBL_MAX;

  aMaterialPropertyTable = aMaterial->GetMaterialPropertiesTable();

  if ( aMaterialPropertyTable ) {
    AttenuationLengthVector = aMaterialPropertyTable->
      GetProperty("WLSABSLENGTH");
    if ( AttenuationLengthVector ){
      AttenuationLength = AttenuationLengthVector->
    Value(thePhotonEnergy);
    }
    else {
      //             G4cout << "No WLS absorption length specified" << G4endl;
    }
  }
  else {
    //           G4cout << "No WLS absortion length specified" << G4endl;
  }
  
  return AttenuationLength;
}

void G4OpWLS::UseTimeProfile(const G4String name)
{
  if (name == "delta")
    {
      delete WLSTimeGeneratorProfile;
      WLSTimeGeneratorProfile = 
             new G4WLSTimeGeneratorProfileDelta("delta");
    }
  else if (name == "exponential")
    {
      delete WLSTimeGeneratorProfile;
      WLSTimeGeneratorProfile =
             new G4WLSTimeGeneratorProfileExponential("exponential");
    }
  else
    {
      G4Exception("G4OpWLS::UseTimeProfile", "em0202",
                  FatalException,
                  "generator does not exist");
    }
}