ACHROMATIC FOCUSING FOR PROBEFORMING OF HIGH-RESOLUTION MICROBEAMS

The possibility to use achromatic quadrupole lenses for probe forming of high resolution microbeams is reviewed. To measure the harmonic contamination in an achromatic lens the grid shadow method has to be utilized. The grid shadow pattern can also guide during the alignment of the lenses. Computer calculations show that the Lund achromatic triplet should be able to produce a 100 nm beam probe. Finally a computer controlled beam focussing system is described.