| 摘要 |
PROBLEM TO BE SOLVED: To simplify a structure of a discharging vessel top plate, minimize a plasma loss and enhance an ion production efficiency. SOLUTION: A structure for insulating a discharging vessel top plate 2 from a discharging vessel 1 which is a discharging cathode by an insulating spacer 12, while removing a plasma closing magnet on a discharging vessel top plate 2 having been mounted as a conventional ion source, is provided. Thereby, the structure on the discharging vessel top plate 2 is simplified, a plasma loss on the discharging vessel top plate in the absence of the magnet is minimized and the reduction of an ion production efficiency can be prevented. Further, to set a potential of the discharging vessel top plate 2, a resistor 15 is disposed between the discharging vessel 1 and the discharging the vessel top plate 2 to connect them. Furthermore, according to the present invention, by enhancing the ion production efficiency, the life of a filament can be lengthened by a high current of an ion beam 9 and/or the reduction of a discharging power.
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