A discharge lamp comprising a discharge vessel, at least one electrode arranged within the discharge vessel, wherein at least parts of the electrode are provided with a particle composite coating made up of a matrix layer and particles embedded in the matrix layer, wherein the extinction coefficient k of the material for the matrix layer is less than 0. The interface structures may be rails, slots or elongated electrical connectors. The gating signal may thus be used as an indicator that an energy deposit in a nearby gamma-ray spectrometer is associated with a decay transitions in the radioactive isotope.