| 摘要 |
PURPOSE:To improve the breaking strength of cathode filament while to uniform the characteristics by supporting a cathode support by means of a spacer fitted to a magnetic pole. CONSTITUTION:Cathode supports 3, 4 are inserted through a spacer 21 made of insulation material which is fitted to a fitting section provided on a magnetic pole 12 while held by the magnetic pole 12 and sealing metal 20. Since the cathode supports 3, 4 are supported by a spacer 21, the distance between the cathode filament and supports, 3, 4 can be shortened to increase the resisting force of cathode supports 3, 4 against the external force thus to improve strength of cathode filament. While since the spacer 21 inserted with cathode supports 3, 4 is fitted coaxially with the magnetic pole 21, positional accuracy of cathode filament 7 is improved to uniform the characteristic. |
