Abstract
The formation of the radial electric field at the boundary of high temperature plasmas can be induced by the radial “gyrocenter shift” during the charge exchange process with neutrals. The model of the gyrocenter shift to be discussed here is different from the conventional gyrocenter drift. Specifically, in this model, the induced electric field is a strong function of neutral density and its gradient in addition to the conventional E×B and diamagnetic terms. The preliminary calculation of the gyrocenter shift of the H-mode plasma on the National Spherical Torus Experiment (NSTX) demonstrates the sensitive dependence of the radial electric field on the neutral density profile. An assessment of diagnostics on NSTX is carried out for the measurement of neutral density. The required spatial and time resolutions for the measurements are 2mm and a few kilohertz, respectively. In this article, the predicted profile of the edge electric field on NSTX based on the gyrocenter shift model is discussed in conjunction with the in and out asymmetry of diverter D-alpha camera data and the measurement of the edge electron density by the far infrared tangential interferometer/polarimeter system.
Published Version
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