| 摘要 |
PURPOSE:To obtain a small divergence angle of an electron beam even for a relatively large electron beam current, by arranging a movable prepositioned electron lens intermediately between an electron gun and main electron lens. CONSTITUTION:At almost the rotary shaft symmetrical position with respect to an axial line 11 of an electron beam that comes passing through the central hole of an anode 21 of an electron gun, a prepositioned electron lens 1 is provided. Said prepositioned electron lens 1 is shiftably supported to a certain distance. A current is fed to a coil 27 by a DC power source to reduce a divergence angle of the electron beam simultaneously perform a correction of the axial line 11 of the electron beam by a shifting means 28. |
