PrimaryGeneratorAction.cc

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#include "PrimaryGeneratorAction.hh"
 
#include "G4Box.hh"
#include "G4LogicalVolume.hh"
#include "G4LogicalVolumeStore.hh"
#include "G4ParticleGun.hh"
#include "G4ParticleTable.hh"
#include "G4SystemOfUnits.hh"
#include "globals.hh"
 
namespace B4 {
 
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PrimaryGeneratorAction::PrimaryGeneratorAction() {
  G4int nofParticles = 1;
  fParticleGun       = new G4ParticleGun(nofParticles);
 
  // default particle kinematic
  //
  auto particleDefinition = G4ParticleTable::GetParticleTable()->FindParticle("e-");
  fParticleGun->SetParticleDefinition(particleDefinition);
  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(0., 0., 1.));
  fParticleGun->SetParticleEnergy(300. * MeV);
}
 
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PrimaryGeneratorAction::~PrimaryGeneratorAction() { delete fParticleGun; }
 
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void PrimaryGeneratorAction::GeneratePrimaries(G4Event* event) {
  // This function is called at the beginning of event
 
  // In order to avoid dependence of PrimaryGeneratorAction
  // on DetectorConstruction class we get world volume
  // from G4LogicalVolumeStore
  //
  G4double worldZHalfLength = 0.;
  auto worldLV              = G4LogicalVolumeStore::GetInstance()->GetVolume("World");
 
  // Check that the world volume has box shape
  G4Box* worldBox = nullptr;
  if (worldLV) {
    worldBox = dynamic_cast<G4Box*>(worldLV->GetSolid());
  }
 
  if (worldBox) {
    worldZHalfLength = worldBox->GetZHalfLength();
  } else {
    G4ExceptionDescription msg;
    msg << "World volume of box shape not found." << G4endl;
    msg << "Perhaps you have changed geometry." << G4endl;
    msg << "The gun will be place in the center.";
    G4Exception("PrimaryGeneratorAction::GeneratePrimaries()", "MyCode0002", JustWarning, msg);
  }
 
  // Set gun position
  fParticleGun->SetParticlePosition(G4ThreeVector(0., 0., -worldZHalfLength));
 
  fParticleGun->GeneratePrimaryVertex(event);
}
 
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} // namespace B4