Focal properties and spherical aberration of a field emission electron gun.

The focal properties and spherical aberration of a simple model of a field emission electron gun are investigated theoretically. Results are presented graphically. For a fixed source position, spherical aberration decreases as the grid aperture increases, but for a fixed image position, spherical aberration decreases as the grid aperture decreases, down to 0<mid>1S, where S is the grid-anode distance. The results are almost independent of the anode aperture. [ABSTRACT FROM AUTHOR]