G4PhononReflection.cc

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//
//
// This process handles the interaction of phonons with
// boundaries. Implementation of this class is highly 
// geometry dependent.Currently, phonons are killed when
// they reach a boundary. If the other side of the 
// boundary was Al, a hit is registered.
//  
//
// 20131115  Throw exception if track's polarization state is invalid.

#include "G4PhononReflection.hh"
#include "G4ExceptionSeverity.hh"
#include "G4GeometryTolerance.hh"
#include "G4LatticePhysical.hh"
#include "G4PhononLong.hh"
#include "G4PhononTransFast.hh"
#include "G4PhononTransSlow.hh"
#include "G4PhysicalConstants.hh"
#include "G4Step.hh"
#include "G4StepPoint.hh"
#include "G4SystemOfUnits.hh"
#include "G4VParticleChange.hh"


G4PhononReflection::G4PhononReflection(const G4String& aName)
  : G4VPhononProcess(aName),
    kCarTolerance(G4GeometryTolerance::GetInstance()->GetSurfaceTolerance()) {;}

G4PhononReflection::~G4PhononReflection() {;}

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// Always return DBL_MAX and Forced. This ensures that the process is
// called at the end of every step. In PostStepDoIt the process
// decides whether the step encountered a volume boundary and a
// reflection should be applied

G4double G4PhononReflection::GetMeanFreePath(const G4Track&, G4double,
               G4ForceCondition* condition) {
  *condition = Forced;
  return DBL_MAX;
}

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// This process handles the interaction of phonons with
// boundaries. Implementation of this class is highly geometry
// dependent.Currently, phonons are killed when they reach a
// boundary. If the other side of the boundary was Al, a hit is
// registered.
  
G4VParticleChange* G4PhononReflection::PostStepDoIt(const G4Track& aTrack,
                const G4Step& aStep) { 
  aParticleChange.Initialize(aTrack);
   
  //Check if current step is limited by a volume boundary
  G4StepPoint* postStepPoint = aStep.GetPostStepPoint();
  if (postStepPoint->GetStepStatus()!=fGeomBoundary) {
    //make sure that correct phonon velocity is used after the step
    int pol = GetPolarization(aTrack);
    if (pol < 0 || pol > 2) {
      G4Exception("G4PhononReflection::PostStepDoIt","Phonon001",
      EventMustBeAborted, "Track is not a phonon");
      return &aParticleChange;    // NOTE: Will never get here
    }

    // FIXME:  This should be using wave-vector, shouldn't it?
    G4double vg = theLattice->MapKtoV(pol, aTrack.GetMomentumDirection());
    
    //Since step was not a volume boundary, just set correct phonon velocity and return
    aParticleChange.ProposeVelocity(vg);
    return &aParticleChange;
  }
  
  // do nothing but return is the step is too short
  // This is to allow actual reflection where after
  // the first boundary crossing a second, infinitesimal
  // step occurs crossing back into the original volume
  if (aTrack.GetStepLength()<=kCarTolerance/2) { 
    return &aParticleChange;
  }
  
  G4double eKin = aTrack.GetKineticEnergy();     
  aParticleChange.ProposeNonIonizingEnergyDeposit(eKin);
  aParticleChange.ProposeTrackStatus(fStopAndKill);
  
  return &aParticleChange; 
}

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