Electrostatic corrector for eliminating the chromatic aberration of particle lenses

摘要

An electrostatic corrector for eliminating the chromatic aberration of particle lenses, includes a corrector having a straight optical axis and an electrostatic quadrupole for allocating to the objective lens. Two corrector pieces are positioned behind the quadrupole, along the optical axis in the direction of radiation. Each corrector piece has three electrical quadrupole fields with an overlying circular lens field. The quadrupole fields, however, are rotated 90° about the optical axis in relation to each other. This arrangement is adjusted so that the astigmatic first image of one sectional view lies in one corrector piece and the astigmatic first image perpendicular thereto, of the other sectional view, lies in the other corrector piece, with another electrostatic quadrupole being located on the output side.