| 摘要 |
<p>PURPOSE:To enhance the electron emission efficiency of the captioned cathode, by decreasing excessive Ba evaporating from the void holes of an electron emission surface and the wasteful evaporation of BaO in order to promote the effective utilization of an electron emission substance and also by increasing the number of electron emission point on the cathode substrate surface. CONSTITUTION:The captioned cathode is composed of an impregnated part made of porous substrate containing an electron emission substance, a material with is formed by being adhered closely to the electron emission surface side of said impregnated part and more active to BaO than the substance forming the above-mentioned porous substrate, and a permeable porous layer whose porosity is the same as or less than that of the above-mentioned porous substrate. The material of the porous substrate is selected from among W, Mo, Ta and Ni. The porosity of the porous substrate is desired to be 17-30% like a conventional one. Any material which has been used in the impregnated cathode up to the present may be used as an electron emission substance, it is generally a material mainly composed of oxides of alkaline earth metals, especially a mateial containing BaO; a substance whose constituents are BaO, CaO, Al2O3 is most generally used. A material forming the permeable layer is required to have higher activity than that of the material forming the impregnated part.</p> |
