title: Initial results of the high resolution edge Thomson scattering upgrade at DIII-D.
abstract: Validation of models of pedestal structure is an important part of predicting pedestal height and performance in future tokamaks. The Thomson scattering diagnostic at DIII-D has been upgraded in support of validating these models. Spatial and temporal resolution, as well as signal to noise ratio, have all been specifically enhanced in the pedestal region. This region is now diagnosed by 20 view-chords with a spacing of 6 mm and a scattering length of just under 5 mm sampled at a nominal rate of 250 Hz. When mapped to the outboard midplane, this corresponds to ~3 mm spacing. These measurements are being used to test critical gradient models, in which pedestal gradients increase in time until a threshold is reached. This paper will describe the specifications of the upgrade and present initial results of the system.
authors.affiliation: University of California San Diego, La Jolla, California 92093-0354, USA. eldond@fusion.gat.com
authors.forename: D
authors.initials: D
authors.lastname: Eldon
authors.forename: B D
authors.initials: BD
authors.lastname: Bray
authors.forename: T M
authors.initials: TM
authors.lastname: Deterly
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.forename: M
authors.initials: M
authors.lastname: Watkins
authors.forename: R J
authors.initials: RJ
authors.lastname: Groebner
authors.forename: A W
authors.initials: AW
authors.lastname: Leonard
authors.forename: T H
authors.initials: TH
authors.lastname: Osborne
authors.forename: P B
authors.initials: PB
authors.lastname: Snyder
authors.forename: R L
authors.initials: RL
authors.lastname: Boivin
authors.forename: G R
authors.initials: GR
authors.lastname: Tynan