Characterization of small transport events triggered with n=3 fields below the ELM destabilization threshold in NSTX

ELMs can be reliably triggered in NSTX with the application of n=3 fields above a threshold level [1]. The destabilization threshold is a combination of the applied Amp-turns in the external coils, the length of the applied pulse, and the edge safety factor. Even for pulses below the threshold, however, a small perturbation in the divertor $\mbox{D}_\alpha $ emission is observed. We refer to this as a ``transport response,'' characterized by small perturbations in the soft X-ray emission, divertor fluxes, and other diagnostic signals. Unfortunately these events appear to be insufficient to reduce the impurity accumulation observed in lithium-enhanced ELM-free H-modes. A characterization of these events will be presented, for applied n=3 fields of various amplitudes, pulse lengths and periods. Work supported by DE-AC05-00OR22725, DE-AC02-09CH11466 and by the Magnetic Fusion Energy fellowship from ORISE.\\[4pt] [1] Canik, J.M., \textit{et al.}, Nucl. Fusion \textbf{50} (2010) 034012.