| 摘要 |
Embodiments of the invention provide a particle beam generator apparatus comprising: a source member; a first electrode; and a second electrode, the generator being operable to extract particles from the source member by means of a potential difference applied between the source member and the first electrode, the first electrode being arranged to focus the particles toward a focal point a distance F1 from the first electrode, the second electrode being arranged to focus the particles to a point a distance F1' from the first electrode, distance F1' being greater than distance F1 thereby to increase an effective focal length of the first electrode. |
