examples/extended/medical/fanoCavity/src/PrimaryGeneratorAction.cc

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/// \file medical/fanoCavity/src/PrimaryGeneratorAction.cc
/// \brief Implementation of the PrimaryGeneratorAction class
//
// $Id: PrimaryGeneratorAction.cc 68459 2013-03-27 18:45:08Z maire $
//
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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 "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

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PrimaryGeneratorAction::PrimaryGeneratorAction(DetectorConstruction* det)
:fParticleGun(0), fDetector(det), fGunMessenger(0)                                              
{
  fParticleGun  = new G4ParticleGun(1);
  G4ParticleDefinition* particle
           = G4ParticleTable::GetParticleTable()->FindParticle("gamma");
  fParticleGun->SetParticleDefinition(particle);
  fParticleGun->SetParticleEnergy(1.25*MeV);  
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(0.,0.,1.));
    
  fRBeam   = 1.;
    
  //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::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of event
  //
  G4double z0 = -0.5*(fDetector->GetTotalThickness());
  G4double x0 = 0.*cm, y0 = 0.*cm;
    
  //beam width
  //
  if (fRBeam > 0.) 
    {
      G4double beam  = fRBeam*(fDetector->GetWallRadius());
      G4double r     = beam*std::sqrt(G4UniformRand());
      G4double theta = twopi*G4UniformRand();
        x0 = r*std::cos(theta);
        y0 = r*std::sin(theta);
    }
  fParticleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));  
  fParticleGun->GeneratePrimaryVertex(anEvent);
}

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