High Brightness Field Emission Electron Probe Forming Systems.

A field emission electron source with high angular current density and two high brightness electron probe forming systems were developed. The nitrogen processing technique for a tungsten field emitter provide a concentrated beam in the forward direction. A complete illumination system for a high resolution experimental electron microscope (HREM) was designed. Attention was paid to the optimization of an electrostatic pre-accelerator lens with minimum spherical and chromatic aberrations. The complete illumination system was experimentally evaluated using the HREM as the measuring system. A prototype probe forming system capable of producing an even higher brightness and beam current was designed and evaluated. A computer optimized magnetic preaccelerator lens was used instead of the electrostatic lens.