PURPOSE: To simplify the structure of a vacuum exhaust system by providing one or more pipes arranged along an electron beam orbit in an ion generating chamber and provided with multiple nozzles facing this electron beam.
CONSTITUTION: When the ionized gas with the pressure higher than the pressure in an ion generating chamber 1 is sprayed toward an electron beam 5 through the hole 3 or the nozzle of a pipe 2 arranged along the electron beam orbit, the pressure near the hole 3 or the nozzle can be locally made higher than the pressure in the ion generating chamber 1. The vacuum pressure necessary to obtain the ion beam current about the same as that when the whole ion generating chamber 1 is made low vacuum over the long distance along the pipe 2 can be attained only near the hole 3 or the nozzle of the pipe in which the electron beam passes, and the whole ion generating chamber 1 can be kept at high vacuum. A vacuum exhaust system can be thereby simplified without making the structure large-sized.
NAKAMURA TSUYOSHI
KAWASE YUTAKA
