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// $Id: PrimaryGeneratorAction.cc,v 1.2 2006/06/29 16:43:32 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* det)
:detector(det)					       
{
  particleGun  = new G4ParticleGun(1);
  G4ParticleDefinition* particle
           = G4ParticleTable::GetParticleTable()->FindParticle("e-");
  particleGun->SetParticleDefinition(particle);
  particleGun->SetParticleEnergy(4*MeV);  
  particleGun->SetParticlePosition(G4ThreeVector());
  particleGun->SetParticleMomentumDirection(G4ThreeVector(1,0,0));
          
  rndmBeam   = true;
    
  //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)
{    
  //randomize the beam, if requested.
  //
  if (rndmBeam) 
    {
     //distribution uniform in solid angle
     //
     G4double cosTheta = 2*G4UniformRand() - 1., phi = twopi*G4UniformRand();
     G4double sinTheta = std::sqrt(1. - cosTheta*cosTheta);
     G4double ux = sinTheta*std::cos(phi),
              uy = sinTheta*std::sin(phi),
              uz = cosTheta;
     particleGun->SetParticleMomentumDirection(G4ThreeVector(ux,uy,uz));    
    }

  particleGun->GeneratePrimaryVertex(anEvent);
}

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