| 摘要 |
<p>PROBLEM TO BE SOLVED: To suppress generation of grid emissions and variations in a long range cut-off voltage by providing an electron emission surface of a porous metal sintered body so that the impregnation amount of an electron emission material in the region including an electron emission region or its neighborhood is set larger than that of the electron emission material in the region excluding the mentioned region. SOLUTION: In the process of manufacturing an impregnated cathode, an electron emission material 26 and a porous tungsten disk 27 are arranged in a housing hole 23 of a holder 22, and an impregnated negative electrode pellet 28 is formed through a vacuum heating treatment. At this time, a section of a lower face of the tungsten disk 27 contacts an upper face of a projecting part 24 of the holder 22. For this reason, the electron emission material 26, with which the surface of the electron emission region is impregnated, does not evaporate, and the tungsten disk 27 is fully impregnated with the electron emission material 26. The projecting part 24 does not contact the remaining surface, and the extra electron emission material 26, with which the surface except the electron emission region is impregnated, evaporates through an interstice 29.</p> |
