Line Source on generator particle gun

I have a detector to get the gamma spectrum from a Cs-137 (662 KeV) point source. But, now I have to change my point source into a line source (at least 2 cm long line source)?

I have attached my code, is it correct? does my code will simulate 20 Cs-137 with 2 mm separations?

fParticleGun = new G4ParticleGun(1);


delete fParticleGun;

void MyPrimaryGenerator::GeneratePrimaries(G4Event *anEvent)

G4int Z = 55;
G4int A = 137;    

    G4double charge   = 0.*eplus;
    G4double energy = 0.662*MeV;

G4ParticleDefinition* particle;
G4ParticleDefinition* ion = G4IonTable::GetIonTable()->GetIon(Z,A,energy);
G4double x0 = 0.0*mm;
G4double x1 = 2.0*mm;
G4double x = x0 + (x1-x0)*G4UniformRand()*20;

    G4ThreeVector pos(0., 0., x);
    G4ThreeVector mom(0., 0., 1.);




I’ve closed this as the question has already been asked here: Cs-137 Line Source