GB818505A - Gaseous discharge device - Google Patents

Abstract

818,505. Discharge lamps. GERMESHAUSEN, K. J. Nov. 22, 1956, No. 35718/56. Class 39(1). In a gaseous discharge device, particularly for use in flash illumination, a cup shaped screen, formed a least in part of mesh-like construction, is dispose( about the cathode with th opening toward the anod for trapping particles sput tered off the cathode during a discharge. As shown in Fig. 1 the mesh-like portio: of the trapping means 5, which may be of insulatin or conducting material, i in contact with the envelop at its open end and is secured to an insulating disc 9 at its lower end. Any sputtered particles which are not trapped by the mesh upon the expansion of the gas due to the initiation of a discharge pass through the mesh but are trapped by it on the subsequent return of the gas into the region between anode and cathode so that no particles are deposited upon the walls of the tube between the anode and cathode. If the discharge through the tube is oscillatory, trapping means may be disposed about both main electrodes. Trapping means for use with a cylindrical cathode may comprise an insulating sleeve surrounding the cathode and extending almost to the walls of the tube and a planar mesh stretched over the end of the sleeve remote from the anode. In a further embodiment the trapping means comprises an insulating cylinder 9, Fig. 4, a cylindrical mesh 5 and a metal disc 15 supported by the cathode lead 1. In this device substantially all the sputtered particles are trapped by the disc 15 upon the expansion of the gas. The cathode may be a cold cathode of a substance such as tungsten, molybdenum or tantalum, uniformly sintered and bound together into a unitary mass with an oxygen-containing compound of barium, strontium, calcium or the like and upon which a relatively small cold-cathode spot is formed. The discharge may be started with the aid of an external trigger electrode 13, Fig. 1.