title: Fast ion charge exchange spectroscopy measurement using a radially injected neutral beam on the large helical device.
abstract: An experimental technique to investigate fast ion confinement based on charge exchange spectroscopy of H(alpha)-light was applied to evaluate the confinement property of perpendicular fast ions in large helical device (LHD). Sensitivities of the H(alpha) spectra to the pitch angles of injected neutral beams (NBs) and these to the angle between the sight line of the measurement and NB injection path are examined. The energy dependence of the charge exchange cross section significantly affects the observed spectra since the driving NB is injected perpendicular to the magnetic field lines in the geometry of LHD. The measured spectra are compared to the spectra of GNET simulation results and the simulated spectra agreed well with the experimental measurement when we take into account the contribution of halo neutrals. Although it is difficult to obtain the fast ion distribution functions directly, this technique provides useful experimental data in benchmarking simulation codes.
authors.affiliation: National Institute for Fusion Science, Toki 509-5292, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Osakabe
authors.forename: Sadayoshi
authors.initials: S
authors.lastname: Murakami
authors.forename: Mikirou
authors.initials: M
authors.lastname: Yoshinuma
authors.forename: Katsumi
authors.initials: K
authors.lastname: Ida
authors.forename: Allan
authors.initials: A
authors.lastname: Whiteford
authors.forename: Motoshi
authors.initials: M
authors.lastname: Goto
authors.forename: Daiji
authors.initials: D
authors.lastname: Kato
authors.forename: Takako
authors.initials: T
authors.lastname: Kato
authors.forename: Kenichi
authors.initials: K
authors.lastname: Nagaoka
authors.forename: Tokihiko
authors.initials: T
authors.lastname: Tokuzawa
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Takeiri
authors.forename: Osamu
authors.initials: O
authors.lastname: Kaneko