A novel imaging energy filter for cathode lens electron microscopy

A double spherical deflector energy analyzer with individual deflections<π and total deflection 2π, called α-Spherical Deflector Analyzer (α-SDA), is reported. Its compact design and the “in-column” feature enables simple adaption to surface imaging systems using cathode lenses such as PEEM or LEEM and its contribution to chromatic- and geometrical aberration is negligible. It allows quasi-simultaneous observation of real and reciprocal images by quick switching one of the spherical deflectors on and off.