basic/B1/src/B1PrimaryGeneratorAction.cc

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// $Id: B1PrimaryGeneratorAction.cc 69565 2013-05-08 12:35:31Z gcosmo $
//
/// \file B1PrimaryGeneratorAction.cc
/// \brief Implementation of the B1PrimaryGeneratorAction class

#include "B1PrimaryGeneratorAction.hh"

#include "G4LogicalVolumeStore.hh"
#include "G4LogicalVolume.hh"
#include "G4Box.hh"
#include "G4RunManager.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

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B1PrimaryGeneratorAction::B1PrimaryGeneratorAction()
: G4VUserPrimaryGeneratorAction(),
  fParticleGun(0), 
  fEnvelopeBox(0)
{
  G4int n_particle = 1;
  fParticleGun  = new G4ParticleGun(n_particle);

  // default particle kinematic
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4String particleName;
  G4ParticleDefinition* particle
    = particleTable->FindParticle(particleName="gamma");
  fParticleGun->SetParticleDefinition(particle);
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(0.,0.,1.));
  fParticleGun->SetParticleEnergy(6.*MeV);
}

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B1PrimaryGeneratorAction::~B1PrimaryGeneratorAction()
{
  delete fParticleGun;
}

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void B1PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
  //this function is called at the begining of ecah event
  //

  // In order to avoid dependence of PrimaryGeneratorAction
  // on DetectorConstruction class we get Envelope volume
  // from G4LogicalVolumeStore.
  
  G4double envSizeXY = 0;
  G4double envSizeZ = 0;

  if (!fEnvelopeBox)
  {
    G4LogicalVolume* envLV
      = G4LogicalVolumeStore::GetInstance()->GetVolume("Envelope");
    if ( envLV ) fEnvelopeBox = dynamic_cast<G4Box*>(envLV->GetSolid());
  }

  if ( fEnvelopeBox ) {
    envSizeXY = fEnvelopeBox->GetXHalfLength()*2.;
    envSizeZ = fEnvelopeBox->GetZHalfLength()*2.;
  }  
  else  {
    G4ExceptionDescription msg;
    msg << "Envelope volume of box shape not found.\n"; 
    msg << "Perhaps you have changed geometry.\n";
    msg << "The gun will be place at the center.";
    G4Exception("B1PrimaryGeneratorAction::GeneratePrimaries()",
     "MyCode0002",JustWarning,msg);
  }

  G4double size = 0.8; 
  G4double x0 = size * envSizeXY * (G4UniformRand()-0.5);
  G4double y0 = size * envSizeXY * (G4UniformRand()-0.5);
  G4double z0 = -0.5 * envSizeZ;
  
  fParticleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));

  fParticleGun->GeneratePrimaryVertex(anEvent);
}

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