| 摘要 |
<p>A first pair of magnetic members (33A,33B) extends along the Z-axis in a convergence magnet (32) and are arranged oppositely on the X-axis to shield the three electron beams arranged in array against any external magnetic fields. A second pair of magnetic (60A,60B) members are arranged on the inner surface of a ring-shaped hexapole magnet plate symmetrically near the Y-axis. With the above arrangement, the effect of the magnetic force on the center beam can be reduced without reducing the effect of the magnetic force on the two side beams to minimize the undesired displacement of the center beam. <IMAGE></p> |
