| 摘要 |
<p>PURPOSE:To make it possible to feed enough quantity of Ba to an electron radiative monoatomic layer of the front side of a cathode for a long period of time, by filling an electron radiative material to the recessed portion of a cathode base and making it contain a plenty of Ba. CONSTITUTION:A cathode base 1 is a sintered body of tungsten with 29% of porousness, while an electron radiative material 2 is a tablet of powdered material mixing 4BaO.CaO.Al2O3, and W-Os (50/50wt%), and at the rear side of the base 1 (porous tungsten with 29% porousness), a recessed portion is formed to insert the tablet 2. Since such a plenty quantity of electron radiative material is covered by the cathode base 1 and the absolute amount of Ba is large, Ba can be fed sufficiently to the Ba monoatomic layer of the base surface for a long period of time even though the porousness of the base is high. Furthermore, since the electron radiative material covered by the base is a mixture with a reductive metal, a low temperature operation is possible compared with the conventional impregnated type cathode with cavity, resulting in a reduction of the evaporation of Ba.</p> |
