| 摘要 |
<p>PURPOSE:To generate stably an electron beam of high current density while reducing an influence of emission non-uniformity inside the cathode surface by forming plural hollows on the electron emission part of the cathode opposed to the anode. CONSTITUTION:Slit-shaped hollows are digged on the cathode 13 so that minute openings 20 of the anode may fall on said slit part and its upper part. Accordingly, electron beams are to be focused on a position on the anode surface opposed to the slit end part 14, while the slit part forms a convex lens between the plate-shaped anode and itself so that the electron beams emitted from the slit inside are given a focusing action for having about the uniform current density. The width W of said slit part is set up to be about equal to or smaller than the gap (d) between the cathode 13 and the anode 2. Thereby, the electron beams of high emitting current density can be about uniformly generated by edge emission of the hollow part and the convex lens action.</p> |
