Patent ID: 8785880
Filing Date: 2014-07-22
Classification: H01J

Abstract:
1. A chromatic aberration corrector for use with an electron microscope, said chromatic aberration corrector comprising: a first multipole element for producing a first electromagnetic field; and a second multipole element for producing a second electromagnetic field, wherein said first multipole element has a first portion, a second portion, and a third portion arranged along an optical axis; wherein each of the first portion, second portion, and third portion has a thickness in the direction of travel of an electron beam and produces a quadrupole field in which an electric quadrupole field and a magnetic quadrupole field are superimposed; wherein in said first portion, the electric quadrupole field is set stronger than the magnetic quadrupole field; wherein in said second portion, the magnetic quadrupole field is set stronger than the electric quadrupole field; wherein in said third portion, the electric quadrupole field is set stronger than the magnetic quadrupole field; wherein said second portion produces a two-fold astigmatism component that is opposite in sign to two-fold astigmatism components produced by the first and third portions; and wherein said second electromagnetic field is angularly shifted by 90 degrees about the optical axis with respect to said first electromagnetic field.