| 摘要 |
PURPOSE:To suppress a change of beam current, by supporting a Wehnelt electrode with a supporter consisting of materials with a small coefficient of thermal expansion. CONSTITUTION:Both ends of a filament 6 are fixed respectively to ends of stems 3a and 3b. While the other ends of the stems are engaged respectively with electrodes 7a, 7b connected to a filament heating power source. A Wehnelt electode 8 is supported by a supporter 10 consisting of materials with a small coefficient of thermal expansion. In this way, a change of distance between the Wehnelt electrode 8 and the filament 6 can be decreased when the filament 6 is heated, thus capable of suppressing a change of beam current. |
