particleGun/src/PrimaryGeneratorAction0.cc

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0025 //
0026 /// \file PrimaryGeneratorAction0.cc
0027 /// \brief Implementation of the PrimaryGeneratorAction0 class
0028
0029 #include "PrimaryGeneratorAction0.hh"
0030
0031 #include "PrimaryGeneratorAction.hh"
0032
0033 #include "G4Event.hh"
0034 #include "G4ParticleGun.hh"
0035 #include "G4SystemOfUnits.hh"
0036 #include "Randomize.hh"
0037
0038 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0039
0040 PrimaryGeneratorAction0::PrimaryGeneratorAction0(G4ParticleGun* gun) : fParticleGun(gun)
0041 {
0042   // solid angle
0043   //
0044   G4double alphaMin = 0 * deg;  // alpha in [0,pi]
0045   G4double alphaMax = 60 * deg;
0046   fCosAlphaMin = std::cos(alphaMin);
0047   fCosAlphaMax = std::cos(alphaMax);
0048
0049   fPsiMin = 0 * deg;  // psi in [0, 2*pi]
0050   fPsiMax = 360 * deg;
0051 }
0052
0053 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0054
0055 void PrimaryGeneratorAction0::GeneratePrimaries(G4Event* anEvent)
0056 {
0057   // vertex position fixed
0058   //
0059   G4double x0 = 0 * mm, y0 = 0 * mm, z0 = 0 * mm;
0060   fParticleGun->SetParticlePosition(G4ThreeVector(x0, y0, z0));
0061
0062   // direction uniform in solid angle
0063   //
0064   G4double cosAlpha = fCosAlphaMin - G4UniformRand() * (fCosAlphaMin - fCosAlphaMax);
0065   G4double sinAlpha = std::sqrt(1. - cosAlpha * cosAlpha);
0066   G4double psi = fPsiMin + G4UniformRand() * (fPsiMax - fPsiMin);
0067
0068   G4double ux = sinAlpha * std::cos(psi), uy = sinAlpha * std::sin(psi), uz = cosAlpha;
0069
0070   fParticleGun->SetParticleMomentumDirection(G4ThreeVector(ux, uy, uz));
0071
0072   fParticleGun->GeneratePrimaryVertex(anEvent);
0073 }
0074
0075 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......