| 摘要 |
PROBLEM TO BE SOLVED: To prevent deterioration of an emitter caused by moisture and blowout of the emitter caused by dew condensation by specifying the component constituting the emitter of a cathode disc to a carbonate. SOLUTION: An emitter impregnated cathode disc is formed by impregnating an emitter comprising BaO, CaO, and Al2 O3 in a substrate made of porous tungsten. BaO and CaO in the emitter included in the cathode disc are converted into carbonates. Molten emitter (BaO:CaO:Al2 O3 =4:1:1) is impregnated in the cathode disc 14, excess emitter attached on the surface is removed, the cathode disc 14 is put into a vacuum bath, heated at 800 deg.C under the specified degree of vacuum, and held. In this state, a mixture gas of CO and CO2 is slowly introduced into the vacuum bath, the introduction pressure is kept at 400 Torr, and held for 20 minutes. By this operation, the emitter in the surface layer of the cathode disc is completely converted from the oxide into the carbonate. |
