ucn/src/ExUCNPrimaryGeneratorAction.cc

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0025 //
0026 /// \file ExUCNPrimaryGeneratorAction.cc
0027 /// \brief Implementation of the ExUCNPrimaryGeneratorAction class
0028
0029 #include "ExUCNPrimaryGeneratorAction.hh"
0030
0031 #include "ExUCNDetectorConstruction.hh"
0032
0033 #include "G4Event.hh"
0034 #include "G4ParticleDefinition.hh"
0035 #include "G4ParticleGun.hh"
0036 #include "G4ParticleTable.hh"
0037 #include "G4PhysicalConstants.hh"
0038 #include "G4SystemOfUnits.hh"
0039 #include "Randomize.hh"
0040
0041 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0042
0043 ExUCNPrimaryGeneratorAction::ExUCNPrimaryGeneratorAction(void)
0044 {
0045   G4int n_particle = 1;
0046   fParticleGun = new G4ParticleGun(n_particle);
0047
0048   G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
0049
0050   G4ParticleDefinition* particle = particleTable->FindParticle("neutron");
0051   fParticleGun->SetParticleDefinition(particle);
0052 }
0053
0054 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0055
0056 ExUCNPrimaryGeneratorAction::~ExUCNPrimaryGeneratorAction()
0057 {
0058   delete fParticleGun;
0059 }
0060
0061 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0062
0063 void ExUCNPrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
0064 {
0065   // This function is called at the begining of event
0066
0067   fParticleGun->SetParticlePosition(G4ThreeVector(0.0, 0.0, 0.0));
0068   fParticleGun->SetParticlePolarization(G4ThreeVector(0, 1, 0));
0069
0070   G4double particleEnergy = 1e-9 * eV + G4UniformRand() * (1e-7 * eV - 1e-9 * eV);
0071   fParticleGun->SetParticleEnergy(particleEnergy);
0072
0073   G4double theta = 2 * pi * G4UniformRand();
0074   G4double phi = std::acos(1 - 2 * G4UniformRand());
0075   if (phi > pi / 2 && phi < pi) phi = pi - phi;
0076
0077   G4double z = std::sin(phi) * std::cos(theta);
0078   G4double x = std::sin(phi) * std::sin(theta);
0079   G4double y = std::cos(phi);
0080
0081   fParticleGun->SetParticleMomentumDirection(G4ThreeVector(x, y, z));
0082
0083   fParticleGun->GeneratePrimaryVertex(anEvent);
0084 }
0085
0086 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......