| 摘要 |
PURPOSE:To form a crossover image at the center of a Wien type filter by adjusting the intensity of a focusing lens so as to provide a zero interval among plural crossover images of plural ion beams differing in their mass numbers. CONSTITUTION:An ion source 2 for generating plural ion beams each differing in mass numbers by heating an eutectic alloy, etc., a focusing lens 8, a Wien type filter 10, and an objective lens 16 are successively arranged to form a crossover image on a specimen 17. Generated secondary electrons are detected by a detector 20 and displayed on a display device 21, while a detected signal is supplied to a CPU23 via a measuring circuit 22 to control power sources 9, 11. Accordingly, by adjusting a power source 15 so as to provide a clear image on the display device 21 together with the adjustment of the power source 9 to allow images on the display device 21 to overlap with each other, the crossover image can be formed at the center of the filter 10 and energy dispersion therein can be reduced. |
