| 摘要 |
An electron source comprises a first permanent magnet having a first channel, extending between first and second poles of the magnet, the internal surfaces of the first channel being conductive. A cathode means is located in the first channel at a first pole of the magnet, a potential being applied between the cathode means and the conductive internal surfaces of the first channel causing electrons to be received into the first channel. A plurality of apertures is located on a wall of the first channel, the wall abutting a second permanent magnet having a plurality of second channels extending between first and second poles of the second magnet. The second pole of the second permanent magnet is adjacent to the aperture located on a wall of the first magnet such that electrons received into the first channel are distributed into the plurality of second channels.
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