Discharge lamp with a cathode, which is for a part made of pure tungsten and, on the other hand, of thoriated tungsten

摘要

Discharge lamp, in which an anode (4) and a cathode (5) in the interior of a discharge vessel (1) are provided, wherein the cathode (5) consists of a part (7) of thoriated tungsten with a tungsten content of at least 90 volume% -% and a main body portion (6) is formed with said part (7) of thoriated tungsten is connected and of pure tungsten, and wherein the ratio s_T/S of the side surface s_T of the part (7) of thoriated tungsten to the side surface s of the cathode (5) in a range from 0,005 to 0,15, the side surface s_T the lateral surface of the part (7) of thoriated tungsten and the circular surface of the cathode tip (51), and wherein the side surface s from the side surface s_T and the lateral surface of the part (7) of thoriated tungsten up to the rear end of the cathode (5), with the proviso that, when the cathode (5) a length (l) in the cathode according to the direction of more than twice the maximum cathodes by knife (d), the side surface s is limited to a maximum value, in that only the part of the side surface s is taken into account, which in the cathode according to the direction of a distance from the cathode tip (51), of the double the maximum diameter (d) of the cathode (5) does not exceed.