Simulation for transmission polarimetry

Hello G4 Forum members,

I am currently simulating the transmission of circular polarized gammas (3MeV) through a polarized iron block (15cm). Depending on the chirality of the photon polarization, or whether the polarization direction of the iron is parallel or antiparallel to the propagation direction of the photons, there should be an asymmetry.
But unfortunately I see only a small, statistical difference. When I simulate 1M incident photons I get a difference of some hundred photons, but there should be thousands

Usually I let the polarization of the gammas stay the same and flip the polarization direction of the iron block.

I am using the G4EmLivermorePolarizedPhysics Physics List.

Set the polarization of the iron block in the detector construction with
auto polvec=G4ThreeVector(0.,0.,1.0);
G4PolarizationManager * polMgr = G4PolarizationManager::GetInstance();
polMgr->SetVolumePolarization(magnetLV, polvec);

and the polarization of the gammas in the macro with
/gun/polarization 0. 0. 1. , or 0. 0. -1

Does anybody have an idea what I might have missed ? Or rather: Does anybody know what i need to do to simulate the passage of circularly polarized photons through a polarized iron block correctly?

Kind Regards,



please, have a look into $G4INSTALL/examples/extended/polarisation/Pol01

and into reference: Design and optimization of a polarized positron source for future linear collider using Geant4. S. Riemann, A. Schaelicke, A. Ushakov 2011, 5pp. Published in J. Phys: Conf. Ser. 295: 012154, 2011.