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摘要

PROBLEM TO BE SOLVED: To provide a method of using an electron emitting cathode holding a reservoir so as not to easily drop by enduring repeated temperature rises and drops, and having a long life and high reliability. SOLUTION: In this method of using an electron emitting cathode, an electron emitting cathode having a metallic base, a coated layer to lower the work function of the metallic base by coating the surface of the metallic base, and a supply source to supply a substance to compose the coated layer, is operated at a lower temperature than the transformation temperature of the substance composing the supply source.