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//
/// \file PrimaryGeneratorAction.cc
/// \brief Implementation of the PrimaryGeneratorAction class
//
//
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#include "PrimaryGeneratorAction.hh"

#include "DetectorConstruction.hh"
#include "PrimaryGeneratorMessenger.hh"

#include "G4Event.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

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PrimaryGeneratorAction::PrimaryGeneratorAction(DetectorConstruction* det)
:G4VUserPrimaryGeneratorAction(),
 fDetector(det),fRndmBeam(0.), fGunMessenger(0)
{
  fParticleGun  = new G4ParticleGun(1);
  SetDefaultKinematic();
    
  //create a messenger for this class
  fGunMessenger = new PrimaryGeneratorMessenger(this);  
}

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PrimaryGeneratorAction::~PrimaryGeneratorAction()
{
  delete fParticleGun;
  delete fGunMessenger;  
}

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void PrimaryGeneratorAction::SetDefaultKinematic()
{
  G4ParticleDefinition* particle
           = G4ParticleTable::GetParticleTable()->FindParticle("e-");
  fParticleGun->SetParticleDefinition(particle);
  fParticleGun->SetParticleEnergy(500*keV);  
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(1.,0.,0.));
  G4double position = -0.45*(fDetector->GetWorldSizeX());
  fParticleGun->SetParticlePosition(G4ThreeVector(position,0.*cm,0.*cm));
}
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void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of event
    
  //randomize the beam, if requested.
  //
  if (fRndmBeam > 0.) 
    {
      G4ThreeVector oldPosition = fParticleGun->GetParticlePosition();
      if (fRndmBeam > fDetector->GetAbsorSizeYZ())
        fRndmBeam = fDetector->GetAbsorSizeYZ(); 
      G4double rbeam = 0.5*fRndmBeam;
      G4double x0 = oldPosition.x();
      G4double y0 = oldPosition.y() + (2*G4UniformRand()-1.)*rbeam;
      G4double z0 = oldPosition.z() + (2*G4UniformRand()-1.)*rbeam;
      fParticleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));
      fParticleGun->GeneratePrimaryVertex(anEvent);
      fParticleGun->SetParticlePosition(oldPosition);      
    }

  else fParticleGun->GeneratePrimaryVertex(anEvent);
}

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