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// $Id: PrimaryGeneratorAction.cc,v 1.3 2006/06/29 16:57:14 gunter Exp $
// GEANT4 tag $Name: geant4-09-03-cand-01 $
//
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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 "Randomize.hh"

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PrimaryGeneratorAction::PrimaryGeneratorAction(
                                               DetectorConstruction* DC)
:Detector(DC)					       
{
  particleGun  = new G4ParticleGun(1);
  G4ParticleDefinition* particle
           = G4ParticleTable::GetParticleTable()->FindParticle("gamma");
  particleGun->SetParticleDefinition(particle);
  particleGun->SetParticleEnergy(100*TeV);  
  particleGun->SetParticleMomentumDirection(G4ThreeVector(1.,0.,0.));
    
  rndmBeam = 0.;
    
  //create a messenger for this class
  gunMessenger = new PrimaryGeneratorMessenger(this);  
}

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

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void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of event
  //
  G4double x0 = -0.5*(Detector->GetSize());
  G4double y0 = 0.*cm, z0 = 0.*cm;
    
  //randomize the beam, if requested.
  //
  if (rndmBeam > 0.) 
    {
      G4double rbeam = 0.5*(Detector->GetSize())*rndmBeam;
      y0 = (2*G4UniformRand()-1.)*rbeam;
      z0 = (2*G4UniformRand()-1.)*rbeam;
    }
  particleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));  
  particleGun->GeneratePrimaryVertex(anEvent); 
}

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