| 摘要 |
PURPOSE:To prevent the vibration of a filament cathode and stabilize the orbit of an electron beam by arranging a spacer between the filament cathode and a mating electrode and making the portion brought into contact with the filament cathode conductive. CONSTITUTION:A filament cathode 33 is arranged with one end fixed and the other end stretched by a spring. The distance between the filament cathode 33 and a vertical scanning electrode 32 is kept constant, the upper half surface on the side brought into contact with the filament cathode 33 made of a high- heat resistance insulating material of a spacer 34 to prevent the mechanical vibration of the filament cathode 33 is covered with a metal film 37 by deposition or the like. The surface of the spacer 34 is covered with the metal film 37 near this filament cathode 33 and is conductive. It is thereby stabilized at the potential equal to the potential applied to the filament cathode 33, thus no effect is given to the orbit of an electron beam, and an image with good quality can be obtained.
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