title: Note: Multi-pass Thomson scattering measurement on the TST-2 spherical tokamak.
abstract: In multi-pass Thomson scattering (TS) scheme, a laser pulse makes multiple round trips through the plasma, and the effective laser energy is enhanced, and we can increase the signal-to-noise ratio as a result. We have developed a coaxial optical cavity in which a laser pulse is confined, and we performed TS measurements using the coaxial cavity in tokamak plasmas for the first time. In the optical cavity, the laser energy attenuation was approximately 30% in each round trip, and we achieved a photon number gain of about 3 compared with that obtained in the first round trip. In addition, the temperature measurement accuracy was improved by accumulating the first three round trip waveforms.
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Togashi
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ejiri
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Hiratsuka
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Takase
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Furui
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Imamura
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Inada
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kakuda
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Nakanishi
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Oosako
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Shinya
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Sonehara
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Tsuda
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Tsujii
authors.affiliation: The University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Wakatsuki
authors.affiliation: Kyushu University, Kasuga 816-8580, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: Kyushu University, Kasuga 816-8580, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nagashima
authors.affiliation: National Institute for Fusion Science, Toki 509-5292, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Narihara
authors.affiliation: National Institute for Fusion Science, Toki 509-5292, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Yamada
authors.affiliation: Japan Atomic Energy Agency, Naka 311-0193, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tojo