Observation of a High Performance Operating Regime with Small Edge-Localized Modes in the National Spherical Torus Experiment

Abstract

We report observation of a high performance scenario in the National Spherical Torus Experiment with very small edge-localized modes (ELMs). These ELMs have no measurable impact on stored energy and are consistent with high bootstrap current operation with line average density approaching Greenwald scaling. The ELM perturbation is observed to typically originate near the lower divertor region, as opposed to the outer midplane for ELMs described in the literature. If extrapolable, this scenario would provide an attractive operating regime for next step fusion experiments.2 Introduction -The desire for high performance operating regimes with few or no

Status and Plans for the National Spherical Torus Experimental Research Facility

“…Another fast visible camera viewing tangentially in the divertor region (42) has revealed a variety of interesting ELM behavior including new Type-V ELMs, which cause minimal plasma energy losses. (43) In the area of the edge power flow to plasma facing components (PFCs), three infrared (IR) cameras are monitoring the power flow to the divertor and wall surfaces. A faster IR camera will be installed to capture the transient energy flow during fast MHD events such as ELMs.…”