Abstract: A ceramic plug (7) is sintered into an end of a tubular discharge vessel 6). The plug (7) has an opening with a cylindrical portion (12) and a conical portion (13). The conical opening faces the electrode (10, 11) and extends up to an electrode coil (11). The outer surface of the plug having the conical opening is formed with pockets (14) sseparated by radially extending ribs in which metallic fill can condense, electrically insulated and mechanically isolated from the current supply to the electrode. This ensures improved heat transition from the tubular discharge vessel (4, 6) to the plug (7), thereby increasing cold-spot temperature, so that the discharge vessel can be used with sodium high-pressure discharge lamps of improved color rendition indices, as well as for plug-in types and, further, have improved resistance against damage or disturbances caused by shock and vibration.