title: Magnetic multipole line-cusp plasma generator for neutral beam injectors.
abstract: The magnetic multipole line-cusp device developed by MacKenzie and associates has been adapted for use as a neutral beam ion source. It has produced high-density, large volume, quiescent, uniform hydrogen plasmas, which makes it a potential candidate for use as a plasma generator for neutral beam injectors. The device is a water-cooled cylindrical copper discharge chamber (25 cm in diameter by 36 cm long) with one end enclosed by a set of extraction grids with a 15-cm-diam multi-aperture pattern. The chamber wall serves as an anode and is surrounded by an external system of rare-earth cobalt magnets arranged in a line-cusp geometry of 12 cusps; plasma is produced by electron emission from a hot cathode assembly. This source has achieved extracted beam currents of 12 A at 18.5 kV, radial plasma density uniformities of +/-5% over a 15-cm diameter, noise levels of less than +/-0.5%, and arc efficiencies (beam current/arc power) of 0.6 A/kW.
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830.
authors.forename: W L
authors.initials: WL
authors.lastname: Stirling
authors.forename: P M
authors.initials: PM
authors.lastname: Ryan
authors.forename: C C
authors.initials: CC
authors.lastname: Tsai
authors.forename: K N
authors.initials: KN
authors.lastname: Leung