ucn/src/ExUCNPrimaryGeneratorAction.cc

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0027 /// \file exoticphysics/ucn/src/ExUCNPrimaryGeneratorAction.cc
0028 /// \brief Implementation of the ExUCNPrimaryGeneratorAction class
0029 //
0030
0031 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0032 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0033
0034 #include "ExUCNPrimaryGeneratorAction.hh"
0035
0036 #include "ExUCNDetectorConstruction.hh"
0037
0038 #include "G4Event.hh"
0039 #include "G4ParticleDefinition.hh"
0040 #include "G4ParticleGun.hh"
0041 #include "G4ParticleTable.hh"
0042 #include "G4PhysicalConstants.hh"
0043 #include "G4SystemOfUnits.hh"
0044 #include "Randomize.hh"
0045
0046 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0047
0048 ExUCNPrimaryGeneratorAction::ExUCNPrimaryGeneratorAction(void)
0049 {
0050   G4int n_particle = 1;
0051   fParticleGun = new G4ParticleGun(n_particle);
0052
0053   G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
0054
0055   G4ParticleDefinition* particle = particleTable->FindParticle("neutron");
0056   fParticleGun->SetParticleDefinition(particle);
0057 }
0058
0059 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0060
0061 ExUCNPrimaryGeneratorAction::~ExUCNPrimaryGeneratorAction()
0062 {
0063   delete fParticleGun;
0064 }
0065
0066 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0067
0068 void ExUCNPrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
0069 {
0070   // This function is called at the begining of event
0071
0072   fParticleGun->SetParticlePosition(G4ThreeVector(0.0, 0.0, 0.0));
0073   fParticleGun->SetParticlePolarization(G4ThreeVector(0, 1, 0));
0074
0075   G4double particleEnergy = 1e-9 * eV + G4UniformRand() * (1e-7 * eV - 1e-9 * eV);
0076   fParticleGun->SetParticleEnergy(particleEnergy);
0077
0078   G4double theta = 2 * pi * G4UniformRand();
0079   G4double phi = std::acos(1 - 2 * G4UniformRand());
0080   if (phi > pi / 2 && phi < pi) phi = pi - phi;
0081
0082   G4double z = std::sin(phi) * std::cos(theta);
0083   G4double x = std::sin(phi) * std::sin(theta);
0084   G4double y = std::cos(phi);
0085
0086   fParticleGun->SetParticleMomentumDirection(G4ThreeVector(x, y, z));
0087
0088   fParticleGun->GeneratePrimaryVertex(anEvent);
0089 }
0090
0091 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......