Dependence of SOL widths on plasma current and density in NSTX H-mode plasmas

The dependence of various SOL widths on the line-averaged density ((n) over bar (e)) and plasma current (I-p) for the quiescent H-mode plasmas with Type-V ELMs in the National Spherical Torus Experiment (NSTX) was investigated. It is found that the heat flux SOL width (lambda(q)), measured by the IR camera, is virtually insensitive to (n) over bar (e) and has a strong negative dependence on I-p. This insensitivity of lambda(q) to (n) over bare is consistent with the scaling law from JET H-mode plasmas that shows a very weak dependence on the upstream density. The electron temperature, ion saturation current density, electron density, and electron pressure decay lengths (lambda(Te), lambda(jsat), lambda(ne), and lambda(pe), respectively) measured by the probe showed that lambda(Te) and lambda(jsat) have strong negative dependence on I-p, whereas lambda(ne) and lambda(pe) revealed only a little or no dependence. The dependence of lambda(Te) on I-p is consistent with the scaling law in the literature, while lambda(ne) and lambda(pe) dependence shows a different trend. (C) 2009 Elsevier B.V. All rights reserved.