| 摘要 |
PURPOSE:To stabilize an electron beam, by performing control to symmetrically irradiate the electron beam around a blanking aperture except at the time of generation of an electron beam pulse to cause a contaminant to symmetrically cling. CONSTITUTION:An electron beam pulse gate is constructed so that a deflector 3 moves an electron beam 14 across the aperture 41 of a blanking aperture member 4 at a prescribed phase in every prescribed period to make an electron beam pulse 15. Deflection voltage generation means 5, 6, 7, which operate according to a clock signal 81 from a multiplier 8, are used to drive deflectors 1, 2 to rotate the electron beam 14 along a square around the aperture 41 except at the time of the generation of the electron beam pulse 15 to make the contamination of the aperture symmetric. This results in preventing the electron beam 14 from becoming unstable due to the electrostatic force of the electrified contamination.
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