| 摘要 |
<p>Particle-optical rotationally symmetrical lenses inevitably have chromatic aberration. This lens fault determines the limit of the resolution of known particle-optical apparatus at a comparatively low acceleration voltage (0.5 kV to 5 kV) of the particle beam. This lens fault cannot be eliminated by compensation by means of rotationally symmetrical fields. In order to enhance the resolution of the particle-optical apparatus nevertheless, it has already been proposed to mitigate said lens fault by means of a Wien type corrector. Such a known configuration is provided with a number of electrical and magnetic multipoles. In order to achieve easier adjustment of the various multipole fields, the pole faces (30-i) governing the multipole fields according to the invention have a specific length L = (2π2n2)/(K¿obj?2Cc,obj), in which Kobj is the strength of the focusing lens to be corrected and Cc,obj is the coefficient of chromatic aberration of this lens.</p> |
