| 摘要 |
<p>PROBLEM TO BE SOLVED: To obstruct vapor deposition of an emitter vaporized from a cathode base substance on an insulating support by tapering a cathode holding cylinder so that the tip is gradually widened outward approaching a cathode base substance, and forming a flare for shutting off the emitter vaporized from the cathode base substance to the surface of the insulating support. SOLUTION: A cathode structure 5 is mounted on the inside of a cathode holding cylinder 2 to constitute a cathode supporting structure B. A first grid 6 is made of metal in a cup shape whose lower surface is opened, and the cathode supporting structure B, to a supporting frame 1 is fit to the inside of the first grid 6 to constitute an electron gun structure B. A flare 31 formed in the cathode holding cylinder 2 is tapered so as to widened toward the outer circumference side, a line C connecting a point A and a point B can make an angleθon the inside small compared with a case where the flare 31 is horizontal, and a point E where the line C reaches is located in a position distant from a cathode base substance 8.</p> |
