| 摘要 |
PURPOSE:To minimize the drift of beam current and stably hold it for a long period of time by securing a filament gun in the projection in a base through the conical support member with setscrews. CONSTITUTION:An electron emission filament is secured in the projection in a base through the conical support member 9 with the setscrews 3a and 3b. The filament bench 1 is fixed at the top of the support member 9 with the setscrews 10a and 10b. This support member 9 has the larger thermal expansion coefficient than the member which constitutes Wehnelt electrode 6. This compensates the thermal ex- pansion of the Wehnelt electrode 6 for that of the support member 9. As a result, the drift of beam current is minimized and be stably retained for a long period of time. |
