Abstract: To improve the arc stability of high-pressure discharge lamps, particularly f power ratings of up to about only 250 W, the cathode (4) is formed as an elongated, essentially cylindrical base body (8) having a tapering, conical region (9) terminating in a tip (10). The base body (8), only, is covered with a carbide coating along its length, except for an end portion for electrical connection; the carbide coating starts at the junction or transition between the cylindrical base body portion and the conical end portion. This cathode construction is easier and cheaper to make than prior art cathodes, by coating an essentially cylindrical cathode and then etching or grinding and polishing the tapering end region (9). The electrode is preferably made essentially of tungsten, doped with thorium oxide present up to about 0.6%, optionally also potassium, aluminum and silicon in tiny amounts. The electrode spacing is between 0.4 to 0.

Abstract: To permit high lamp currents to be applied to lamp electrodes (5, 6) of a discharge vessel (2) from which two elongated necks (3, 4) extend via current supply leads (23, 35), the discharge vessel is first made as a generally rotation-symmetrical element, to which tubular cylindrical neck tubes (17) are sealed. A cylindrical plug element (26, 40) is placed in the neck tube adjacent the discharge vessel. A subassembly is then made of a core element, which can be constructed as a single or a composite structure of quartz glass, for example by telescopically fitting quartz glass tubes over a central core, and melt-sealing the tubes and core together. Molybdenum disks (7, 8; 22) are placed against the end faces of the core element, and a plurality, for example four, molybdenum connecting foils (11-16, 27) are secured to the circumferences of the disks, to axially connect them together.