// This code implementation is the intellectual property of
// the GEANT4 collaboration.
//
// By copying, distributing or modifying the Program (or any work
// based on the Program) you indicate your acceptance of this statement,
// and all its terms.
//
// $Id: ExN03PrimaryGeneratorAction.cc,v 1.3 2000/11/21 10:59:45 maire Exp $
// GEANT4 tag $Name: geant4-03-01 $
//
// 

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#include "ExN03PrimaryGeneratorAction.hh"

#include "ExN03DetectorConstruction.hh"
#include "ExN03PrimaryGeneratorMessenger.hh"

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

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ExN03PrimaryGeneratorAction::ExN03PrimaryGeneratorAction(
                                               ExN03DetectorConstruction* ExN03DC)
:ExN03Detector(ExN03DC),rndmFlag("off")
{
  G4int n_particle = 1;
  particleGun  = new G4ParticleGun(n_particle);
  
  //create a messenger for this class
  gunMessenger = new ExN03PrimaryGeneratorMessenger(this);

  // default particle kinematic

  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4String particleName;
  G4ParticleDefinition* particle
                    = particleTable->FindParticle(particleName="e-");
  particleGun->SetParticleDefinition(particle);
  particleGun->SetParticleMomentumDirection(G4ThreeVector(1.,0.,0.));
  particleGun->SetParticleEnergy(50.*MeV);
  G4double position = -0.5*(ExN03Detector->GetWorldSizeX());
  particleGun->SetParticlePosition(G4ThreeVector(position,0.*cm,0.*cm));

}

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ExN03PrimaryGeneratorAction::~ExN03PrimaryGeneratorAction()
{
  delete particleGun;
  delete gunMessenger;
}

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void ExN03PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of event
  // 
  G4double x0 = -0.5*(ExN03Detector->GetWorldSizeX());
  G4double y0 = 0.*cm, z0 = 0.*cm;
  if (rndmFlag == "on")
     {y0 = (ExN03Detector->GetCalorSizeYZ())*(G4UniformRand()-0.5);
      z0 = (ExN03Detector->GetCalorSizeYZ())*(G4UniformRand()-0.5);
     } 
  particleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));

  particleGun->GeneratePrimaryVertex(anEvent);
}

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