Dear all, I have a question about X-Ray considering in GATE. I defined a simple cubic phantom filled with Water with a 0.5 mm Pb in front of it(2 cm distance) and a sheet of gamma source at the 0.5 m of phantom. I simulate this combination for 140,364,511 kev in GATE with and without XRay . according to GATE user's manual I set the XRay physics as below: 1- considering xRay and deltaRay: # Activate X - R A Y S /gate/physics/setXRayCut 5 keV /gate/physics/setDeltaRayCut 5 keV 2- inactive XRay and deltaRay: # I N A C T I V E X - R A Y S /gate/physics/setXRayCut 1 GeV /gate/physics/setDeltaRayCut 1 GeV 3- active Delta Ray and inactive XRays: # I N A C T I V E X - R A Y S /gate/physics/setXRayCut 1 GeV /gate/physics/setDeltaRayCut 1 keV I simulate 1e8 Bq in 1second for dose calculation for each energy. But the output of three cases (for each energy) are exactly the same and the gaterun.dat file of three cases are also exactly the same. we know that in interaction of each of these gamma source with lead(Pb), considerable XRay photons should be produced. what is the reason? I think (with this changes in physics) GATE did not considered or tracked the X_Rays produced. is it true idea? regards. -- Ali Asghar Parach,Ph.D. student in Medical Physics,Tarbiat Modares University,Tehran,Iran