A discharge vessel with a ceramic wall is filled with inert gas and metal and is ignited and operated by an electronic circuit including a half bridge converter with an LC circuit which, when the lamp is not ignited, enters an oscillation state near a resonance frequency which lies near the third harmonic of the switching frequency of the half bridge converter. The vessel encloses a cylindrical discharge space of diameter D and length L, wherein L</=D</=1.2 L.
