| 摘要 |
An ion source comprises an arc chamber (11) having an extraction slit (17) for extraction of an ion beam (19) by extraction electrode (18). A primary ion producing discharge (15) is produced by a cathode (12), for example a heated coil cathode of the Penning/Bernas type, or a heated filament cathode of the Freeman type. At the base of the arc chamber (11) a container (25) contains a feed material (27) consisting of or containing an element from which ions are to be produced. The second electrode is formed either by the body of material (27), or by the container (25), and is held at a negative voltage more negative than the cathode (12). A feed gas such as a halide of the element may be fed through the material (27) in the container (25), or may be supplied close to the surface of the material (27). The second electrode produces an intense localised secondary discharge which produces transfer of the required element from the feed material (27) into the primary discharge (15). |
