G4Cerenkov.cc

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//
////////////////////////////////////////////////////////////////////////
// Cerenkov Radiation Class Implementation
////////////////////////////////////////////////////////////////////////
//
// File:        G4Cerenkov.cc
// Description: Discrete Process -- Generation of Cerenkov Photons
// Version:     2.1
// Created:     1996-02-21
// Author:      Juliet Armstrong
// Updated:     2007-09-30 by Peter Gumplinger
//              > change inheritance to G4VDiscreteProcess
//              GetContinuousStepLimit -> GetMeanFreePath (StronglyForced)
//              AlongStepDoIt -> PostStepDoIt
//              2005-08-17 by Peter Gumplinger
//              > change variable name MeanNumPhotons -> MeanNumberOfPhotons
//              2005-07-28 by Peter Gumplinger
//              > add G4ProcessType to constructor
//              2001-09-17, migration of Materials to pure STL (mma)
//              2000-11-12 by Peter Gumplinger
//              > add check on CerenkovAngleIntegrals->IsFilledVectorExist()
//              in method GetAverageNumberOfPhotons
//              > and a test for MeanNumberOfPhotons <= 0.0 in DoIt
//              2000-09-18 by Peter Gumplinger
//              > change: aSecondaryPosition=x0+rand*aStep.GetDeltaPosition();
//                        aSecondaryTrack->SetTouchable(0);
//              1999-10-29 by Peter Gumplinger
//              > change: == into <= in GetContinuousStepLimit
//              1997-08-08 by Peter Gumplinger
//              > add protection against /0
//              > G4MaterialPropertiesTable; new physics/tracking scheme
//
//
////////////////////////////////////////////////////////////////////////
 
#include "G4ios.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4Poisson.hh"
#include "G4EmProcessSubType.hh"
 
#include "G4LossTableManager.hh"
#include "G4MaterialCutsCouple.hh"
#include "G4ParticleDefinition.hh"
 
#include "G4OpticalParameters.hh"
#include "G4Cerenkov.hh"
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4Cerenkov::G4Cerenkov(const G4String& processName, G4ProcessType type)
  : G4VProcess(processName, type)
  , fNumPhotons(0)
{
  SetProcessSubType(fCerenkov);
 
  thePhysicsTable = nullptr;
 
  if(verboseLevel > 0)
  {
    G4cout << GetProcessName() << " is created." << G4endl;
  }
  Initialise();
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4Cerenkov::~G4Cerenkov()
{
  if(thePhysicsTable != nullptr)
  {
    thePhysicsTable->clearAndDestroy();
    delete thePhysicsTable;
  }
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4bool G4Cerenkov::IsApplicable(const G4ParticleDefinition& aParticleType)
{
  return (aParticleType.GetPDGCharge() != 0.0 &&
          aParticleType.GetPDGMass() != 0.0 &&
          aParticleType.GetParticleName() != "chargedgeantino" &&
          !aParticleType.IsShortLived())
           ? true
           : false;
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4Cerenkov::Initialise()
{
  G4OpticalParameters* params = G4OpticalParameters::Instance();
  SetMaxBetaChangePerStep(params->GetCerenkovMaxBetaChange());
  SetMaxNumPhotonsPerStep(params->GetCerenkovMaxPhotonsPerStep());
  SetTrackSecondariesFirst(params->GetCerenkovTrackSecondariesFirst());
  SetStackPhotons(params->GetCerenkovStackPhotons());
  SetVerboseLevel(params->GetCerenkovVerboseLevel());
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4Cerenkov::BuildPhysicsTable(const G4ParticleDefinition&)
{
  if(thePhysicsTable)
    return;
 
  const G4MaterialTable* theMaterialTable = G4Material::GetMaterialTable();
  G4int numOfMaterials                    = G4Material::GetNumberOfMaterials();
 
  thePhysicsTable = new G4PhysicsTable(numOfMaterials);
 
  // loop over materials
  for(G4int i = 0; i < numOfMaterials; ++i)
  {
    G4PhysicsOrderedFreeVector* aPhysicsOrderedFreeVector = 0;
 
    // Retrieve vector of refraction indices for the material
    // from the material's optical properties table
    G4Material* aMaterial = (*theMaterialTable)[i];
    G4MaterialPropertiesTable* aMaterialPropertiesTable =
      aMaterial->GetMaterialPropertiesTable();
 
    if(aMaterialPropertiesTable)
    {
      aPhysicsOrderedFreeVector = new G4PhysicsOrderedFreeVector();
      G4MaterialPropertyVector* theRefractionIndexVector =
        aMaterialPropertiesTable->GetProperty(kRINDEX);
 
      if(theRefractionIndexVector)
      {
        // Retrieve the first refraction index in vector
        // of (photon energy, refraction index) pairs
        G4double currentRI = (*theRefractionIndexVector)[0];
 
        if(currentRI > 1.0)
        {
          // Create first (photon energy, Cerenkov Integral) pair
          G4double currentPM  = theRefractionIndexVector->Energy(0);
          G4double currentCAI = 0.0;
 
          aPhysicsOrderedFreeVector->InsertValues(currentPM, currentCAI);
 
          // Set previous values to current ones prior to loop
          G4double prevPM  = currentPM;
          G4double prevCAI = currentCAI;
          G4double prevRI  = currentRI;
 
          // loop over all (photon energy, refraction index)
          // pairs stored for this material
          for(size_t ii = 1; ii < theRefractionIndexVector->GetVectorLength();
              ++ii)
          {
            currentRI  = (*theRefractionIndexVector)[ii];
            currentPM  = theRefractionIndexVector->Energy(ii);
            currentCAI = prevCAI + (currentPM - prevPM) * 0.5 *
                                     (1.0 / (prevRI * prevRI) +
                                      1.0 / (currentRI * currentRI));
 
            aPhysicsOrderedFreeVector->InsertValues(currentPM, currentCAI);
 
            prevPM  = currentPM;
            prevCAI = currentCAI;
            prevRI  = currentRI;
          }
        }
      }
    }
 
    // The Cerenkov integral for a given material will be inserted in
    // thePhysicsTable according to the position of the material in
    // the material table.
    thePhysicsTable->insertAt(i, aPhysicsOrderedFreeVector);
  }
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4VParticleChange* G4Cerenkov::PostStepDoIt(const G4Track& aTrack,
                                            const G4Step& aStep)
// This routine is called for each tracking Step of a charged particle
// in a radiator. A Poisson-distributed number of photons is generated
// according to the Cerenkov formula, distributed evenly along the track
// segment and uniformly azimuth w.r.t. the particle direction. The
// parameters are then transformed into the Master Reference System, and
// they are added to the particle change.
 
{
  ////////////////////////////////////////////////////
  // Should we ensure that the material is dispersive?
  ////////////////////////////////////////////////////
 
  aParticleChange.Initialize(aTrack);
 
  const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
  const G4Material* aMaterial        = aTrack.GetMaterial();
 
  G4StepPoint* pPreStepPoint  = aStep.GetPreStepPoint();
  G4StepPoint* pPostStepPoint = aStep.GetPostStepPoint();
 
  G4ThreeVector x0 = pPreStepPoint->GetPosition();
  G4ThreeVector p0 = aStep.GetDeltaPosition().unit();
  G4double t0      = pPreStepPoint->GetGlobalTime();
 
  G4MaterialPropertiesTable* MPT = aMaterial->GetMaterialPropertiesTable();
  if(!MPT)
    return pParticleChange;
 
  G4MaterialPropertyVector* Rindex = MPT->GetProperty(kRINDEX);
  if(!Rindex)
    return pParticleChange;
 
  G4double charge = aParticle->GetDefinition()->GetPDGCharge();
  G4double beta = (pPreStepPoint->GetBeta() + pPostStepPoint->GetBeta()) * 0.5;
 
  // fNumPhotons = 0;  // in PostStepGetPhysicalInteractionLength()
 
  G4double MeanNumberOfPhotons =
    GetAverageNumberOfPhotons(charge, beta, aMaterial, Rindex);
 
  if(MeanNumberOfPhotons <= 0.0)
  {
    // return unchanged particle and no secondaries
    aParticleChange.SetNumberOfSecondaries(0);
    return pParticleChange;
  }
 
  G4double step_length = aStep.GetStepLength();
  MeanNumberOfPhotons  = MeanNumberOfPhotons * step_length;
  fNumPhotons          = (G4int) G4Poisson(MeanNumberOfPhotons);
 
  if(fNumPhotons <= 0 || !fStackingFlag)
  {
    // return unchanged particle and no secondaries
    aParticleChange.SetNumberOfSecondaries(0);
    return pParticleChange;
  }
 
  ////////////////////////////////////////////////////////////////
  aParticleChange.SetNumberOfSecondaries(fNumPhotons);
 
  if(fTrackSecondariesFirst)
  {
    if(aTrack.GetTrackStatus() == fAlive)
      aParticleChange.ProposeTrackStatus(fSuspend);
  }
 
  ////////////////////////////////////////////////////////////////
  G4double Pmin = Rindex->GetMinLowEdgeEnergy();
  G4double Pmax = Rindex->GetMaxLowEdgeEnergy();
  G4double dp   = Pmax - Pmin;
 
  G4double nMax        = Rindex->GetMaxValue();
  G4double BetaInverse = 1. / beta;
 
  G4double maxCos  = BetaInverse / nMax;
  G4double maxSin2 = (1.0 - maxCos) * (1.0 + maxCos);
 
  G4double beta1 = pPreStepPoint->GetBeta();
  G4double beta2 = pPostStepPoint->GetBeta();
 
  G4double MeanNumberOfPhotons1 =
    GetAverageNumberOfPhotons(charge, beta1, aMaterial, Rindex);
  G4double MeanNumberOfPhotons2 =
    GetAverageNumberOfPhotons(charge, beta2, aMaterial, Rindex);
 
  for(G4int i = 0; i < fNumPhotons; ++i)
  {
    // Determine photon energy
    G4double rand;
    G4double sampledEnergy, sampledRI;
    G4double cosTheta, sin2Theta;
 
    // sample an energy
    do
    {
      rand          = G4UniformRand();
      sampledEnergy = Pmin + rand * dp;
      sampledRI     = Rindex->Value(sampledEnergy);
      cosTheta      = BetaInverse / sampledRI;
 
      sin2Theta = (1.0 - cosTheta) * (1.0 + cosTheta);
      rand      = G4UniformRand();
 
      // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
    } while(rand * maxSin2 > sin2Theta);
 
    // Create photon momentum direction vector. The momentum direction is still
    // with respect to the coordinate system where the primary particle
    // direction is aligned with the z axis
    rand              = G4UniformRand();
    G4double phi      = twopi * rand;
    G4double sinPhi   = std::sin(phi);
    G4double cosPhi   = std::cos(phi);
    G4double sinTheta = std::sqrt(sin2Theta);
    G4ParticleMomentum photonMomentum(sinTheta * cosPhi, sinTheta * sinPhi,
                                      cosTheta);
 
    // Rotate momentum direction back to global reference system
    photonMomentum.rotateUz(p0);
 
    // Determine polarization of new photon
    G4ThreeVector photonPolarization(cosTheta * cosPhi, cosTheta * sinPhi,
                                     -sinTheta);
 
    // Rotate back to original coord system
    photonPolarization.rotateUz(p0);
 
    // Generate a new photon:
    G4DynamicParticle* aCerenkovPhoton =
      new G4DynamicParticle(G4OpticalPhoton::OpticalPhoton(), photonMomentum);
 
    aCerenkovPhoton->SetPolarization(photonPolarization);
    aCerenkovPhoton->SetKineticEnergy(sampledEnergy);
 
    G4double NumberOfPhotons, N;
 
    do
    {
      rand            = G4UniformRand();
      NumberOfPhotons = MeanNumberOfPhotons1 -
                        rand * (MeanNumberOfPhotons1 - MeanNumberOfPhotons2);
      N =
        G4UniformRand() * std::max(MeanNumberOfPhotons1, MeanNumberOfPhotons2);
      // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
    } while(N > NumberOfPhotons);
 
    G4double delta = rand * aStep.GetStepLength();
    G4double deltaTime =
      delta /
      (pPreStepPoint->GetVelocity() +
       rand * (pPostStepPoint->GetVelocity() - pPreStepPoint->GetVelocity()) *
         0.5);
 
    G4double aSecondaryTime          = t0 + deltaTime;
    G4ThreeVector aSecondaryPosition = x0 + rand * aStep.GetDeltaPosition();
 
    // Generate new G4Track object:
    G4Track* aSecondaryTrack =
      new G4Track(aCerenkovPhoton, aSecondaryTime, aSecondaryPosition);
 
    aSecondaryTrack->SetTouchableHandle(
      aStep.GetPreStepPoint()->GetTouchableHandle());
    aSecondaryTrack->SetParentID(aTrack.GetTrackID());
    aParticleChange.AddSecondary(aSecondaryTrack);
  }
 
  if(verboseLevel > 1)
  {
    G4cout << "\n Exiting from G4Cerenkov::DoIt -- NumberOfSecondaries = "
           << aParticleChange.GetNumberOfSecondaries() << G4endl;
  }
 
  return pParticleChange;
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4Cerenkov::PreparePhysicsTable(const G4ParticleDefinition&)
{
  Initialise();
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4Cerenkov::GetMeanFreePath(const G4Track&, G4double,
                                     G4ForceCondition*)
{
  return 1.;
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4Cerenkov::PostStepGetPhysicalInteractionLength(
  const G4Track& aTrack, G4double, G4ForceCondition* condition)
{
  *condition         = NotForced;
  G4double StepLimit = DBL_MAX;
  fNumPhotons        = 0;
 
  const G4Material* aMaterial = aTrack.GetMaterial();
  G4int materialIndex         = aMaterial->GetIndex();
 
  // If Physics Vector is not defined no Cerenkov photons
  if(!(*thePhysicsTable)[materialIndex])
  {
    return StepLimit;
  }
 
  const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
  const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();
 
  G4double kineticEnergy                   = aParticle->GetKineticEnergy();
  const G4ParticleDefinition* particleType = aParticle->GetDefinition();
  G4double mass                            = particleType->GetPDGMass();
 
  G4double beta  = aParticle->GetTotalMomentum() / aParticle->GetTotalEnergy();
  G4double gamma = aParticle->GetTotalEnergy() / mass;
 
  G4MaterialPropertiesTable* aMaterialPropertiesTable =
    aMaterial->GetMaterialPropertiesTable();
 
  G4MaterialPropertyVector* Rindex = nullptr;
 
  if(aMaterialPropertiesTable)
    Rindex = aMaterialPropertiesTable->GetProperty(kRINDEX);
 
  G4double nMax;
  if(Rindex)
  {
    nMax = Rindex->GetMaxValue();
  }
  else
  {
    return StepLimit;
  }
 
  G4double BetaMin = 1. / nMax;
  if(BetaMin >= 1.)
    return StepLimit;
 
  G4double GammaMin = 1. / std::sqrt(1. - BetaMin * BetaMin);
  if(gamma < GammaMin)
    return StepLimit;
 
  G4double kinEmin = mass * (GammaMin - 1.);
  G4double RangeMin =
    G4LossTableManager::Instance()->GetRange(particleType, kinEmin, couple);
  G4double Range = G4LossTableManager::Instance()->GetRange(
    particleType, kineticEnergy, couple);
  G4double Step = Range - RangeMin;
 
  // If the step is smaller than 1e-16 mm, it may happen that the particle
  // does not move. See bug 1992.
  //  2019-03-11: change to 1e-15
  if(Step < 1.e-15 * mm)
    return StepLimit;
 
  if(Step < StepLimit)
    StepLimit = Step;
 
  // If user has defined an average maximum number of photons to be generated in
  // a Step, then calculate the Step length for that number of photons.
  if(fMaxPhotons > 0)
  {
    const G4double charge = aParticle->GetDefinition()->GetPDGCharge();
    G4double MeanNumberOfPhotons =
      GetAverageNumberOfPhotons(charge, beta, aMaterial, Rindex);
    Step = 0.;
    if(MeanNumberOfPhotons > 0.0)
      Step = fMaxPhotons / MeanNumberOfPhotons;
    if(Step > 0. && Step < StepLimit)
      StepLimit = Step;
  }
 
  // If user has defined an maximum allowed change in beta per step
  if(fMaxBetaChange > 0.)
  {
    G4double dedx = G4LossTableManager::Instance()->GetDEDX(
      particleType, kineticEnergy, couple);
    G4double deltaGamma =
      gamma - 1. / std::sqrt(1. - beta * beta * (1. - fMaxBetaChange) *
                                    (1. - fMaxBetaChange));
 
    Step = mass * deltaGamma / dedx;
    if(Step > 0. && Step < StepLimit)
      StepLimit = Step;
  }
 
  *condition = StronglyForced;
  return StepLimit;
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4Cerenkov::GetAverageNumberOfPhotons(
  const G4double charge, const G4double beta, const G4Material* aMaterial,
  G4MaterialPropertyVector* Rindex) const
// This routine computes the number of Cerenkov photons produced per
// GEANT4-unit (millimeter) in the current medium.
//              ^^^^^^^^^^
{
  const G4double Rfact = 369.81 / (eV * cm);
  if(beta <= 0.0)
    return 0.0;
  G4double BetaInverse = 1. / beta;
 
  // Vectors used in computation of Cerenkov Angle Integral:
  //    - Refraction Indices for the current material
  //    - new G4PhysicsOrderedFreeVector allocated to hold CAI's
  G4int materialIndex = aMaterial->GetIndex();
 
  // Retrieve the Cerenkov Angle Integrals for this material
  G4PhysicsOrderedFreeVector* CerenkovAngleIntegrals =
    (G4PhysicsOrderedFreeVector*) ((*thePhysicsTable)(materialIndex));
 
  if(!(CerenkovAngleIntegrals->IsFilledVectorExist()))
    return 0.0;
 
  // Min and Max photon energies
  G4double Pmin = Rindex->GetMinLowEdgeEnergy();
  G4double Pmax = Rindex->GetMaxLowEdgeEnergy();
 
  // Min and Max Refraction Indices
  G4double nMin = Rindex->GetMinValue();
  G4double nMax = Rindex->GetMaxValue();
 
  // Max Cerenkov Angle Integral
  G4double CAImax = CerenkovAngleIntegrals->GetMaxValue();
 
  G4double dp, ge;
  // If n(Pmax) < 1/Beta -- no photons generated
  if(nMax < BetaInverse)
  {
    dp = 0.0;
    ge = 0.0;
  }
  // otherwise if n(Pmin) >= 1/Beta -- photons generated
  else if(nMin > BetaInverse)
  {
    dp = Pmax - Pmin;
    ge = CAImax;
  }
  // If n(Pmin) < 1/Beta, and n(Pmax) >= 1/Beta, then we need to find a P such
  // that the value of n(P) == 1/Beta. Interpolation is performed by the
  // GetEnergy() and Value() methods of the G4MaterialPropertiesTable and
  // the Value() method of G4PhysicsVector.
  else
  {
    Pmin = Rindex->GetEnergy(BetaInverse);
    dp   = Pmax - Pmin;
 
    G4double CAImin = CerenkovAngleIntegrals->Value(Pmin);
    ge              = CAImax - CAImin;
 
    if(verboseLevel > 1)
    {
      G4cout << "CAImin = " << CAImin << G4endl << "ge = " << ge << G4endl;
    }
  }
 
  // Calculate number of photons
  G4double NumPhotons = Rfact * charge / eplus * charge / eplus *
                        (dp - ge * BetaInverse * BetaInverse);
 
  return NumPhotons;
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4Cerenkov::SetTrackSecondariesFirst(const G4bool state)
{
  fTrackSecondariesFirst = state;
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4Cerenkov::SetMaxBetaChangePerStep(const G4double value)
{
  fMaxBetaChange = value * CLHEP::perCent;
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4Cerenkov::SetMaxNumPhotonsPerStep(const G4int NumPhotons)
{
  fMaxPhotons = NumPhotons;
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4Cerenkov::DumpPhysicsTable() const
{
  G4PhysicsOrderedFreeVector* v;
  for(size_t i = 0; i < thePhysicsTable->entries(); ++i)
  {
    v = (G4PhysicsOrderedFreeVector*) (*thePhysicsTable)[i];
    v->DumpValues();
  }
}