| 摘要 |
An electrostatic multipole lens consisting of flat electrodes, a pair of rod-like electrodes, and means for applying potentials to these electrodes. Each of the flat electrodes takes the form of a flat plate. The flat electrodes are disposed along an equipotential plane in an electrostatic n-pole field in or near planes given by y=+/-(tan( pi /n))x, the planes intersecting each other at the Z axis. The flat electrodes are cut out in the vicinity of the Z axis. The rod-like electrodes have surfaces which approximate in shape to a second equipotential plane in the n-pole field. The rod-like electrodes are located on the X axis in a region which contains the Z axis and is located between the planes. The potentials applied to these two kinds of electrodes correspond to the equipotential planes associated with the electrodes. Since the lens essentially consists only of the flat electrodes and the rod-like electrodes, the structure is simple. The dimension of the lens taken along the Y axis can be shortened.
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