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/// \file electromagnetic/TestEm14/src/PrimaryGeneratorAction.cc
/// \brief Implementation of the PrimaryGeneratorAction class
//
// $Id: PrimaryGeneratorAction.cc 68313 2013-03-21 18:15:21Z maire $
// 
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#include "PrimaryGeneratorAction.hh"

#include "DetectorConstruction.hh"

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

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PrimaryGeneratorAction::PrimaryGeneratorAction(DetectorConstruction* det)
:G4VUserPrimaryGeneratorAction(),fParticleGun(0),fDetector(det)
{
  fParticleGun  = new G4ParticleGun(1);
  G4ParticleDefinition* particle
           = G4ParticleTable::GetParticleTable()->FindParticle("gamma");
  fParticleGun->SetParticleDefinition(particle);
  fParticleGun->SetParticleEnergy(1*MeV);    
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(1.,0.,0.));
}

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

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void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of event
  //
  G4double halfSize = 0.5*(fDetector->GetSize());
  G4double x0 = - halfSize;
  
  //randomize (y0,z0)
  //
  G4double beam = 0.8*halfSize; 
  G4double y0 = (2*G4UniformRand()-1.)*beam;
  G4double z0 = (2*G4UniformRand()-1.)*beam;
  
  fParticleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));
  fParticleGun->GeneratePrimaryVertex(anEvent);
}

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