title: Boundary displacement measurements using multi-energy soft x-rays.
abstract: The Multi-Energy Soft X-ray (ME-SXR) system on NSTX provides radial profiles of soft X-ray emission, measured through a set of filters with varying thickness, which have been used to reconstruct the electron temperature on fast time scales (∼10 kHz). In addition to this functionality, here we show that the ME-SXR system can be used to measure the boundary displacement of the NSTX plasma with a few mm spatial resolution during magnetohydrodyamic (MHD) activity. Boundary displacement measurements can serve to inform theoretical predictions of neoclassical toroidal viscosity, and will be used to investigate other edge phenomena on NSTX-U. For example, boundary measurements using filtered SXR measurements can provide information on pedestal steepness and dynamic evolution leading up to and during edge localized modes (ELMs). Future applications include an assessment of a simplified, filtered SXR edge detection system as well as its suitability for real-time non-magnetic boundary feedback for ELMs, MHD, and equilibrium position control.
authors.affiliation: Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: K
authors.initials: K
authors.lastname: Tritz
authors.affiliation: Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA.
authors.forename: A
authors.initials: A
authors.lastname: Diallo
authors.affiliation: Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA.
authors.forename: B P
authors.initials: BP
authors.lastname: LeBlanc
authors.affiliation: Department of Applied Physics and Mathematics, Columbia University, New York City, New York 10027, USA.
authors.forename: S
authors.initials: S
authors.lastname: Sabbagh
authors.affiliation: Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: D
authors.initials: D
authors.lastname: Stutman