title: Development of a radio frequency ion source with multi-helicon plasma injectors for neutral beam injection system of Versatile Experiment Spherical Torus.
abstract: Despite of high plasma density, helicon plasma has not yet been applied to a large area ion source such as a driver for neutral beam injection (NBI) system due to intrinsically poor plasma uniformity in the discharge region. In this study, a radio-frequency (RF) ion source with multi-helicon plasma injectors for high plasma density with good uniformity has been designed and constructed for the NBI system of Versatile Experiment Spherical Torus at Seoul National University. The ion source consists of a rectangular plasma expansion chamber (120 × 120 × 120 mm(3)), four helicon plasma injectors with annular permanent magnets and RF power system. Main feature of the source is downstream plasma confinement in the cusp magnetic field configuration which is generated by arranging polarities of permanent magnets in the helicon plasma injectors. In this paper, detailed design of the multi-helicon plasma injector and plasma characteristics of the ion source are presented.
authors.affiliation: Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea.
authors.forename: Kyumin
authors.initials: K
authors.lastname: Choe
authors.affiliation: Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea.
authors.forename: Bongki
authors.initials: B
authors.lastname: Jung
authors.affiliation: Center for Advance Research in Fusion Reactor Engineering, Seoul National University, Seoul 151-744, South Korea.
authors.forename: Kyoung-Jae
authors.initials: KJ
authors.lastname: Chung
authors.affiliation: Department of Nuclear Engineering, Seoul National University, Seoul 151-744, South Korea.
authors.forename: Y S
authors.initials: YS
authors.lastname: Hwang