Hello, experts!
How to specify pencil beam radius?
fParticleGun->SetParticleDefinition(G4Neutron::NeutronDefinition());
fParticleGun->SetParticleMomentumDirection(G4ParticleMomentum(cos(30.0deg),0.0,cos(60.0deg)));
void SimpleParticleSource::GeneratePrimaries(G4Event* anEvent)
{
G4double radius = 0.4*cm;
G4double phi = 360.*deg;
G4double rRan = radius*(G4UniformRand());
G4double phiRan = phi*(G4UniformRand());
G4double z0 = -6.8*cm;
fParticleGun->SetParticlePosition(G4ThreeVector(rRan*cos(phiRan)-9.18*cm,rRan*sin(phiRan),z0));
fParticleGun->GeneratePrimaryVertex(anEvent);
}
Best regards,