Aberration correction in a low voltage SEM by a multipole corrector

We have set up a high resolution SEM dedicated for low beam energies with a quadrupole/octupole corrector for the correction of spherical and chromatic aberration. The correction of these aberrations allows theoretically for a resolution limit of 1 nm at beam energies between 0.5 and 1 keV. At the present state we were already able to reduce the resolution limit in low voltage SEM to below 2 nm at 1 keV.