title: Extraction of a strongly focusing He+ beam from three-stage concave electrodes for alpha particle measurement system in ITER.
abstract: A strongly focusing He(+) ion beam source equipped with concave multi-aperture electrodes was developed for production of He(-) through a charge exchange cell. The beam was extracted at a voltage less than 20 kV from 301 apertures distributed in an area of 100 mm φ, and focused at 750 mm distance. The beam current and the beam size of 2 A and 20 mm in diameter, respectively, were achieved with an arc power less than 10 kW. The optimum perveance was obtained at 0.02 A∕kV(1.5) at the beam energy less than 20 keV which is suitable for the conversion to He(-) in an alkali vapor cell.
authors.affiliation: National Institute for Fusion Science, Toki, Gifu 509-5292, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kobuchi
authors.forename: M
authors.initials: M
authors.lastname: Sasao
authors.forename: M
authors.initials: M
authors.lastname: Kisaki
authors.forename: K
authors.initials: K
authors.lastname: Tsumori
authors.forename: N
authors.initials: N
authors.lastname: Tanaka
authors.forename: A
authors.initials: A
authors.lastname: Okamoto
authors.forename: S
authors.initials: S
authors.lastname: Kitajima
authors.forename: O
authors.initials: O
authors.lastname: Kaneko
authors.forename: K
authors.initials: K
authors.lastname: Shinto
authors.forename: M
authors.initials: M
authors.lastname: Wada