particleGun/src/PrimaryGeneratorAction3.cc

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0025 //
0026 /// \file PrimaryGeneratorAction3.cc
0027 /// \brief Implementation of the PrimaryGeneratorAction3 class
0028
0029 #include "PrimaryGeneratorAction3.hh"
0030
0031 #include "PrimaryGeneratorAction.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 PrimaryGeneratorAction3::PrimaryGeneratorAction3(G4ParticleGun* gun) : fParticleGun(gun)
0044 {
0045   // direction
0046   //
0047   G4double theta = 90 * deg, phi = 45 * deg;
0048   fNewUz = G4ThreeVector(std::sin(theta) * std::cos(phi), std::sin(theta) * std::sin(phi),
0049                          std::cos(theta));
0050
0051   fAlphaMax = 15 * deg;
0052 }
0053
0054 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0055
0056 void PrimaryGeneratorAction3::GeneratePrimaries(G4Event* anEvent)
0057 {
0058   // particle direction uniform around fNewUz axis
0059   //
0060   // 1- in World frame
0061   // cosAlpha uniform in [cos(0), cos(fAlphaMax)]
0062   G4double cosAlpha = 1. - G4UniformRand() * (1. - std::cos(fAlphaMax));
0063   G4double sinAlpha = std::sqrt(1. - cosAlpha * cosAlpha);
0064   G4double psi = twopi * G4UniformRand();  // psi uniform in [0, 2*pi]
0065   G4ThreeVector dir(sinAlpha * std::cos(psi), sinAlpha * std::sin(psi), cosAlpha);
0066
0067   // 2- rotate dir   (rotateUz transforms uz to fNewUz)
0068   dir.rotateUz(fNewUz);
0069
0070   fParticleGun->SetParticleMomentumDirection(dir);
0071
0072   // set energy
0073   //
0074   fParticleGun->SetParticleEnergy(1 * MeV);
0075
0076   // create vertex
0077   //
0078   fParticleGun->GeneratePrimaryVertex(anEvent);
0079 }
0080
0081 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......