| 摘要 |
<p>PURPOSE:To provide an electron gun having an impregnated cathode which can maintain stable electron emission over a long period without disturbing the electric field of an electronic-lens system and greatly varying the structure and the condition of an electron-emitting surface. CONSTITUTION:In an electron gun which has at least an impregnated cathode and a plurality of grids 17, 18, the impregnated cathode has a recess 20 provided in its part opposite an electron-beam passing hole 21 in the first grid 17 of an electron-emitting surface. The recess 20 is so formed as to be in rotation symmetry with respect to an axis normal to the electron emitting surface, and the electron emitting surface is configured to be similar in shape to the electron beam passing hole 21 of the first grid 17.</p> |
