High-load and high-intensity discharge lamp

Abstract

The present high-load and high-intensity discharge lamp includes a cathode made of a material which does not (substantially) include thorium but can be used as a cathode material of high heat load, so that a long lifetime and high stability corresponding to those of thoriated-tungsten can be realized. Specifically, the cathode is made of a metal base having a high melting point which mainly consists of tungsten and includes a coexisting substance in which an oxide of at least one kind of metal selected from lanthanum, cerium, yttrium, scandium, and gadolinium and an oxide of at least one kind of metal selected from titanium, zirconium, hafnium, niobium, and tantalum are coexistent. The conversion grain size of the coexisting substance is 15 μm or greater, and the plurality of coexisting substances are present in the metal base with a high melting point.

Dependencies are inferred from the claim text.