title: Measurement of electrostatic potential fluctuation using heavy ion beam probe in large helical device.
abstract: Heavy ion beam probe (HIBP) for large helical device (LHD) has been improved to measure the potential fluctuation in high-temperature plasmas. The spatial resolution is improved to about 10 mm by controlling the focus of a probe beam. The HIBP is applied to measure the potential fluctuation in plasmas where the rotational transform is controlled by electron cyclotron current drive. The fluctuations whose frequencies change with the time constant of a few hundreds of milliseconds and that with a constant frequency are observed. The characteristics of the latter fluctuation are similar to those of the geodesic acoustic mode oscillation. The spatial profiles of the fluctuations are also obtained.
authors.affiliation: National Institute for Fusion Science, Gifu 509-5292, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ido
authors.forename: Akihiro
authors.initials: A
authors.lastname: Shimizu
authors.forename: Masaki
authors.initials: M
authors.lastname: Nishiura
authors.forename: Haruhisa
authors.initials: H
authors.lastname: Nakano
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Ohshima
authors.forename: Shinji
authors.initials: S
authors.lastname: Kato
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Hamada
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: Shin
authors.initials: S
authors.lastname: Kubo
authors.forename: Takashi
authors.initials: T
authors.lastname: Shimozuma
authors.forename: Hiroe
authors.initials: H
authors.lastname: Igami
authors.forename: Hiromi
authors.initials: H
authors.lastname: Takahashi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Toi
authors.forename: Fumitake
authors.initials: F
authors.lastname: Watanabe