Hundreds of electron beams from a single source

Most electron sources are used to create a single beam. For high resolution instruments such as electron microscopes and electron lithography machines, most of the current that is emitted by the source is cut away by apertures. The typical emission current from a CRT (Cathode Ray Tube) impregnated tungsten source is hundreds of milli-amperes and from a Schottky source (field assisted emission from a ZrO covered tungsten tip) is tens of microamperes, while the typical beam currents in high resolution instruments are pico-amperes up to tens of nano-amperes. This means there is room to use these sources for creating hundreds of sub-beams, at the same brightness (A/m²srV) as the single beam.