| 摘要 |
PURPOSE:To simplify assembly and to make the positional relationship between an electrode and a filament highly precise by sticking pipes to two stem pins respectively, by suspending the coil-like filament across both pipes, and by covering a focusing electrode so that the filament is located in the focusing groove of the focusing electrode. CONSTITUTION:Stem pins 17, 18 are penetrated and planted through a stem 16 at a predetermined distance, and pipes 19, 20 are stuck to the stem pins respectively. A directly heated coil-like filament 21 is suspended across the pipes 19, 20. In addition, separate stem pins 22, 23 are penetrated and planted through the stem 16, and a cup-like focusing electrode 25 with focusing groove 24 is fixed to the stem pins 22, 23 so that the filament 21 is located at the inside space portion of the focusing groove 24. Accordingly, the relative position beween the focusing electrode and the filament can be made highly precise and the assembly can be simplified. |
