HIGH PRESSURE METAL-VAPOR DISCHARGE LAMP HAVING ALUMINA TUBE WITH THICKENED END PORTIONS SEALED BY ALUMINA DISKS

A high-pressure metal-vapor discharge tube having improved characteristics is disclosed. The tube has an alumina hollow discharge enclosure tube member, the ends of which are sealed by alumina end disks. The end disks have central apertures through which electrode lead in wires or rods extend into the discharge enclosure. The lead in wires or rods are made of a material which is resistant to the corrosive effects of metal halide. The hollow discharge enclosure tube member has walls which are thicker at the two ends than in the intermediate region of the tube member. Preferably, the ends are more than twice as thick as the central walls. This results in a stronger seal between the alumina end disks and the tube member, thus not only avoiding the risk of breakage when sealing the tube member and manufacturing defects such as a defective seal, but also ensuring longer life of the lamp.