Magnetic channel cathode for a flat panel display

An electron source, e.g. for a flat panel display, comprises a permanent magnet 102,104 having channels extending between opposite poles. The internal surfaces of the channels are conductive. A cathode (204, fig 2) is located at a first pole of the magnet, at one end of the channels. Each channel within the magnet has a plurality of perforations 106 located on a surface of the permanent magnet. A potential applied between the cathode and the conductive internal surfaces of the channels causes electrons to be received into the channels Each perforation 106 gives rise to a null field region where electrons collect. An electron beam for guidance towards a target can be extracted from the null field region 602 by applying an electric field over the perforation. A variety of kinds of cathode are described, including line filament cathodes and micromachined cathodes.