ABERRATION CORRECTION OF HOMOGENEOUS MAGNETIC DEFLECTION SYSTEMS.

The eikonal method is used to derive relatively simple integral expressions for the coefficients of the second-order aberrations, first-order chromatic aberrations, and the dispersions of first and second degree of homogeneous magnetic bending systems. Relations are given that connect the multipole components of the magnetic scalar potential about the curved axis with the geometry of the pole faces. All second-order aberrations can be eliminated simultaneously by imposing symmetry conditions on the field and the paraxial rays and by incorporating actual six-pole magnets. As an example, an imaging magnetic energy filter is proposed that causes neither second-order aberrations nor dispersion and off-axial chromatic aberrations in the final image. In addition the aberrations in the energy selection plane are largely suppressed. This filtering process should not impair the field of view or the resolution of the final image.