Superconducting lenses for high-voltage microscopy. Final report

A superconducting shielding lens was designed and its applicability as an objective lens in electron microscopy, in particular at high beam voltages, was tested. The following requirements had to be fulfilled: construction of a testing microscope for beam voltages in the 400 kV range, preparation of superconducting material with high shielding capability, orientation investigations outside of the electron microscope to determine image aberrations, and design of specific cryotechnic devices. The resolution test was carried out in a cryogenic lens system consisting of the shielding lens as an objective lens, the iron circuit intermediate lens with a superconducting coil, and superconducting correcting devices. A lattice resolution of 0.34 nm and a point resolution below 0.5 nm at a beam voltage of 350 kV could be proved. A second system, subsequently constructed and containing four superconducting lenses, was provided with a side entry stage