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/// \file exoticphysics/phonon/src/XPhononStackingAction.cc
/// \brief Implementation of the XPhononStackingAction class
///     This stacking action is necessary to ensure that velocity and 
///     propagation direction are set properly for phonons created with
///     G4ParticleGun
//
// $Id$
//

#include "XPhononStackingAction.hh"
#include "G4LatticeManager.hh"
#include "G4PhononLong.hh"
#include "G4PhononPolarization.hh"
#include "G4PhononTrackMap.hh"
#include "G4PhononTransFast.hh"
#include "G4PhononTransSlow.hh"
#include "G4RandomDirection.hh"
#include "G4SystemOfUnits.hh"
#include "G4ThreeVector.hh"
#include "G4Track.hh"
#include "G4TrackStatus.hh"

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XPhononStackingAction::XPhononStackingAction() {;}

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XPhononStackingAction::~XPhononStackingAction() {;}

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G4ClassificationOfNewTrack 
XPhononStackingAction::ClassifyNewTrack(const G4Track* aTrack) {
  G4ClassificationOfNewTrack classification = fUrgent;

  if (aTrack->GetParentID() == 0) {
    //Obtain LatticeManager for phonon dynamics
    G4LatticeManager* LM = G4LatticeManager::GetLatticeManager();
    
    G4int pol = G4PhononPolarization::Get(aTrack->GetDefinition());
    
    //Compute random wave-vector (override whatever ParticleGun did)
    G4ThreeVector Ran = G4RandomDirection();
    
    //Store wave-vector as track information
    G4PhononTrackMap* theKmap = G4PhononTrackMap::GetPhononTrackMap();
    theKmap->SetK(aTrack, Ran);
    
    //Compute direction of propagation from wave vector
    G4ThreeVector momentumDir = LM->MapKtoVDir(aTrack->GetVolume(), pol, Ran);
    
    //Compute true velocity of propagation
    G4double velocity = LM->MapKtoV(aTrack->GetVolume(), pol, Ran);
    
    //cast to non-const pointer so we can set the velocity
    G4Track* theTrack = const_cast<G4Track*>(aTrack);

    theTrack->SetMomentumDirection(momentumDir);
    theTrack->SetVelocity(velocity);
    theTrack->UseGivenVelocity(true);
  }
  
  return classification; 
}

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