title: Optical measurement of Cs distribution in the large negative ion source.
abstract: To investigate a Cs behavior, optical diagnostic tools have been installed in the large negative ion source, an arc discharge used at large helical device neutral beam injector. A large Cs sputtering is observed during beam extraction due to the backstreaming H(+) ions. Distribution of Cs(+) light is uniform in the case of a balanced arc discharge, but large increase of Cs(+) light during beam extraction is observed in a nonuniform arc discharge. Controlling of the discharge uniformity is effective to reduce the local heat loading from the backstreaming H(+) ions at the backplate of ion source.
authors.affiliation: National Institute for Fusion Science, Toki, Gifu, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ikeda
authors.forename: K
authors.initials: K
authors.lastname: Nagaoka
authors.forename: Y
authors.initials: Y
authors.lastname: Takeiri
authors.forename: U
authors.initials: U
authors.lastname: Fantz
authors.forename: O
authors.initials: O
authors.lastname: Kaneko
authors.forename: M
authors.initials: M
authors.lastname: Osakabe
authors.forename: Y
authors.initials: Y
authors.lastname: Oka
authors.forename: K
authors.initials: K
authors.lastname: Tsumori