| 摘要 |
<p>PURPOSE:To reduce a first grid current as well as to lessen an aging reduction in thermionic emission characteristics, by installing a base body metal containing a reducing agent only at a region where a thermionic emission oxide is applied, of an oxide cathode having the small area of a thermionic emission part. CONSTITUTION:An oxide layer 1 is applied only to a base body metal 21 of almost the same form as that of this layer, and furthermore the base body metal 21 is made up of, for example, Ni, Mo or W, etc., or Ni-W, Ni-W-Mo alloys and set up on a metal cap 7 containing no reducing agent such as Mg, Si, etc. With this, the base body metal 21 is not exposed by directly opposing a first grid so that scattering of the reducing agent contained in the base body metal 21 is reduced whereby deterioration of thermionic emission characteristics in the oxide layer 1 can be lessened.</p> |
