SPIRAL Field Mapping on NSTX for Comparison to Divertor RF Heaat Deposition
Authors: Joel Hosea, R. Perkins, M.A. Jaworski, G.J. Kramer, J.-W. Ahn, N. Bertelli, S. Gerhardt, T.K. Gray, B.P. LeBlanc, R. Maingi, C.K. Phillips, L. Roquemore, P.M. Ryan, S. Sabbagh, G. Taylor, K. Tritz, J.R. Wilson and NSTX Team
Abstract:
Field-aligned losses of HHFW power in the SOL of NSTX have been studied with IR cameras and probes, but
the interpretation of the data depends somewhat on the magnetic equilibrium reconstruction. Both EFIT02 and
LRDFIT04 magnetic equilibria have been used with the SPIRAL code to provide field mappings in the scrape off layer
(SOL) on NSTX from the midplane SOL in front of the HHFW antenna to the divertor regions, where the heat deposition
spirals are measured. The field-line mapping spiral produced at the divertor plate with LRDFIT04 matches the HHFWproduced
heat deposition best, in general. An independent method for comparing the field-line strike patterns on the
outer divertor for the two equilibria is provided by measuring Langmuir probe characteristics in the vicinity of the outer
vessel strike radius (OVSR) and observing the effect on floating potential, saturation current, and zero-probe-voltage
current (IV=0) with the crossing of the OVSR over the probe. Interestingly, these comparisons also reveal that LRDFIT04
gives the more accurate location of the predicted OVSR, and confirm that the RF power flow in the SOL is essentially
along the magnetic field lines. Also, the probe characteristics and IV=0 data indicate that current flows under the OVSR in
the divertor tiles in most cases studied.
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Presented at: 20th Topical Conference on Radio Frequency Power in Plasmas, Sorrento, Italy, June 25-28, 2013
Published: AIP Conf. Proc. 1580, 251 (2014); DOI: http://dx.doi.org/10.1063/1.4864535
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