Dependence of divertor heat flux widths on heating power, flux expansion, and plasma current in the NSTX

T. K. Gray, R. Maingi, V. A. Soukhanovskii, J. E. Surany, J. W. Ahn, A. G. McLean

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Abstract

We report the dependence of the lower divertor surface heat flux profiles, measured from infrared thermography and mapped magnetically to the mid-plane on loss power into the scrape-off layer (PLOSS), plasma current (I p), and magnetic flux expansion (fexp), as well as initial results with lithium wall conditioning in NSTX. Here we extend previous studies [R. Maingi et al., J. Nucl. Mater. 363-365 (2007) 196-200] to higher triangularity ∼0.7 and higher Ip ≤ 1.2 MA. First we note that the mid-plane heat flux width mapped to the mid-plane, λqmid, is largely independent of PLOSS for PLOSS ≥ 4 MW. λqmid is also found to be relatively independent of fexp; peak heat flux is strongly reduced as fexp is increased, as expected. Finally, λqmid is shown to strongly contract with increasing Ip such that λqmid∝Ip-1.6 with a peak divertor heat flux of q div, peak ∼ 15 MW/m2 when Ip = 1.2 MA and PLOSS ∼ 6 MW. These relationships are then used to predict the divertor heat flux for the planned NSTX-Upgrade, with heating power between 10 and 15 MW, Bt = 1.0 T and Ip = 2.0 MA for 5 s.

Original languageEnglish
Pages (from-to)S360-S364
JournalJournal of Nuclear Materials
Volume415
Issue number1 SUPPL
DOIs
StatePublished - Aug 1 2011

Funding

The authors are grateful to the NSTX research team for diagnostic and technical support. T.K. Gray is supported under an appointment to the US DOE. Fusion Energy Postdoctoral Research Program administered by the Oak Ridge Institute for Science and Education under Contract Number DE-AC05-06OR23100 between the US DOE and Oak Ridge Associated Universities. This research is sponsored by US DOE Contracts DE-AC05-00OR22725, DE-AC52-07NA27344, and DE-AC02-09CH11466.

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