Patent ID: 8390198

Claim:
A discharge lamp wherein an anode and a cathode are present in the interior of a discharge vessel, wherein said cathode is made up from a thoriated tungsten part with a tungsten filling ratio of at least 90 vol.-% and a main body part connected to said thoriated tungsten part and consisting of pure tungsten, wherein a ratio S T /S of a side surface area S T of said thoriated tungsten part and a side surface area S of said cathode is in a range of from 0.005 to 0.15, with the proviso that, in case the cathode has a length in the direction of the cathode axis which exceeds twice the maximum diameter of the cathode, a side surface area S is used for calculating the ratio S T /S which corresponds to the side surface area where the distance along the cathode axis from a tip end adjacent to the anode is twice the maximum diameter of the cathode.