| 摘要 |
PURPOSE:To obtain a high assembling precision and fix a mechanically strong electrode, by providing a two-step concave part on the second grid electrode and a single-step concave part on the intermediate electrode, and by making the outside diameter of the second step of the concave part on the second grid electrode 2 smaller than the inside diameter of the concave part on the intermediate electrode. CONSTITUTION:An electron gun is constituted by the first grid electrode 1, an intermediate electrode 21, the second grid electrode 32 and an insulating rod 4. Said electrode 21 is subjected to shallow coining so as to possess one-step concave part and maintain mechanical strength. And also, a two-step concentric concave part is formed on said electrode 32 which is subjected to coining. Thus, the influence of pressure molding of said electrode 21 is indicated by the direction of dotted line, and when a spacer 5 is inserted/removed, a gap length S1 and an electrode length l1 can be set at a high precision without any trouble. Also, said electrode 32 can let said influence get away without any trouble with respect to a spacer 6 and also to a beam disc support 30; and a gap length S2, electrode lengths l2, l3 can be set precisely. Consequently, a highly precise and strong assembling can be achieved. |
