title: Fast visible imaging and edge turbulence analysis in QUEST.
abstract: A fast visible imaging system is installed on the spherical tokamak QUEST to study edge turbulence. The camera uses a complementary metal-oxide semiconductor detector with a maximum resolution of 1024 × 1024 at 7000 frames∕s (fps) and can achieve 775 kfps at a resolution of 128 × 24. In this paper, we present the salient features of the system and its application to study edge turbulence in 8.2 GHz ECRH driven slab plasma, without plasma current. Vertical magnetic field (B(z)) topology is varied with three sets of poloidal field (PF) coils and the variation in the edge turbulence is investigated as a function of the B(z) strength and curvature. Fluctuation amplitude was highest for the shallow PF well. Cross-correlation coefficient shows distinct coherent mode along z direction at the steep density gradient region and it grows with the PF mirror ratio.
authors.affiliation: IGSES, Kyushu University, Kasuga, Fukuoka 816-8580, Japan. santanu@triam.kyushu-u.ac.jp
authors.forename: Santanu
authors.initials: S
authors.lastname: Banerjee
authors.forename: H
authors.initials: H
authors.lastname: Zushi
authors.forename: N
authors.initials: N
authors.lastname: Nishino
authors.forename: Y
authors.initials: Y
authors.lastname: Nagashima
authors.forename: K
authors.initials: K
authors.lastname: Hanada
authors.forename: M
authors.initials: M
authors.lastname: Ishiguro
authors.forename: T
authors.initials: T
authors.lastname: Ryoukai
authors.forename: S
authors.initials: S
authors.lastname: Tashima
authors.forename: T
authors.initials: T
authors.lastname: Inoue
authors.forename: K
authors.initials: K
authors.lastname: Nakamura
authors.forename: H
authors.initials: H
authors.lastname: Idei
authors.forename: M
authors.initials: M
authors.lastname: Hasegawa
authors.forename: A
authors.initials: A
authors.lastname: Fujisawa
authors.forename: K
authors.initials: K
authors.lastname: Matsuoka