ELECTRODE FOR DISCHARGE TUBE AND DISCHARGE TUBE USING IT

摘要

A discharge tube 10 is comprised of a glass bulb 12, a cathode 14, and an anode 16. The cathode 14 is provided with a cathode tip portion 22 and a lead rod 24. The lead rod 24 has a cylindrical shape and is made of molybdenum and a projection 24b of a cylindrical shape is formed on one end face 24a. The cathode tip portion 22 is made by impregnating porous tungsten with barium and has a conical cusp 22a on one end side to face the anode 16 and a cylindrical insert hole 22d to accommodate the projection 24b of the lead rod 24, in an end face 22c on the other end side. A clearance between the end face 24a of the lead rod 24 and the end face 22c of the cathode tip portion 22 is filled with a molybdenum-ruthenium brazing filler metal 26.