Dependence of SOL widths on plasma parameters in NSTX

The dependence of various upstream Scrape-Off Layer (SOL) widths on the line-averaged density ($\overline n _e )$, plasma current ($I_{p})$, and power into the SOL ($P_{SOL})$ for H-mode plasmas was investigated, using the mid-plane fast reciprocating probe and Thomson scattering diagnostics, in the National Spherical Torus Experiment (NSTX). The heat flux width (\textit{$\lambda $}$_{q})$ at the divertor plate, measured by the IR camera, was also measured and compared with the upstream SOL widths. The edge density profile remains fixed during the H-mode, such that the separatrix density is constant even though $\overline n _e $ is ramping. Thus \textit{$\lambda $}$_{q}$, \textit{$\lambda $}$_{Te,}$ and \textit{$\lambda $}$_{ne}$ are insensitive to $\overline n _e $. \textit{$\lambda $}$_{Te}$ and \textit{$\lambda $}$_{jsat}$ have strong negative dependence on $I_{p}$, whereas there was only a very weak change in \textit{$\lambda $}$_{ne}$ when $I_{p}$ was varied. These empirical results have been compared with scaling laws in the literature. The \textit{$\lambda $}$_{Te}$ dependence on $I_{p}$ is consistent with an H-mode \textit{$\lambda $}$_{Te}$ scaling law, while the insensitivity of \textit{$\lambda $}$_{ne}$ to $\overline n _e $ is not consistent with the \textit{$\lambda $}$_{ne}$ scaling law. Dependence of decay lengths on plasma parameters in a wide range of plasma conditions will be presented. This work was supported by the US Department of Energy, contract numbers DE-FG02-03ER54731, DE-AC02-76CH03073, DE-AC05-00OR22725, and DE-AC52-07NA27344.