Soft x-ray measurements of resistive wall mode behavior in NSTX

L. Delgado-Aparicio*, D. Stutman, S. A. Sabbagh, R. E. Bell, J. W. Berkery, K. Tritz, S. P. Gerhardt, B. Leblanc, M. Finkenthal, J. P. Levesque, K. C. Lee, J. Menard, S. Paul, L. Roquemore

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

A multi-energy soft x-ray (ME-SXR) array is used for the characterization of resistive wall modes (RWMs) in the National Spherical Torus Experiment (NSTX). Modulations in the time history of the ME-SXR emissivity profiles indicate the existence of edge density and core temperature fluctuations in good agreement with the slow evolution of the n = 1 magnetic perturbation measured by the poloidal and radial RWM coils. The characteristic 20-25 Hz frequency in the SXR diagnostics is approximately that of the n = 1 stable RWM, which is also near the measured peak of the resonant field amplification (RFA) and inversely proportional to the wall time. Together with the magnetics, the ME-SXR measurements suggest that in NSTX the RWM is not restricted exclusively to the reactor wall and edge, and that acting with the stabilizing coils on its global structure may result in density and temperature fluctuations that can be taken into account when designing the feedback process.

Original languageEnglish
Article number035005
JournalPlasma Physics and Controlled Fusion
Volume53
Issue number3
DOIs
StatePublished - Mar 2011
Externally publishedYes

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