| 摘要 |
PURPOSE:To reduce cleaning time of an electrode by arranging an earthed plate so as to be able to be taken out or put in the position opposed to an outgoing electrode while opening a gas lead-in port for introducing inert gas between the outgoing electrode, on which negative voltage is to be impressed, and the plate. CONSTITUTION:A plate 2 is moved to the position opposed to an outgoing electrode 3 while impressing voltage between the plate 2 and the outgoing electrode 3 so that the side of the electrode may be negative and opening a valve 5 of a gas lead-in port 4 to introduce inert gas. Then, the plate 2 is taken out for generating plasma between the plate 2 and the outgoing electrode 3 while making the ions of positively ionized inert gas to collide with atoms of impurities on the electrode surface to exfoliate and remove impurities from the electrode surface with its impact. During ordinary working hours, a valve 5 provided at the gas lead-in port 4 is closed and the plate 2 is made to retreat to a position not impeding an ion beam coming flying from an ion source 1. Thereby, cleaning time of the electrode can be sharply reduced.
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