Abstract
The National Spherical Torus Experiment (NSTX) routinely studies overdense plasmas with ne of (1–5)×1019m−3 and total magnetic field of <0.6T, so that the first several electron cyclotron harmonics are overdense. The electrostatic electron Bernstein wave (EBW) can propagate in overdense plasmas, exhibits strong absorption, and is thermally emitted at electron cyclotron harmonics. These properties allow thermal EBW emission to be used for local Te measurement. A significant upgrade to the previous NSTX EBW emission diagnostic to measure thermal EBW emission via the oblique B-X-O mode conversion process has been completed. The new EBW diagnostic consists of two remotely steerable, quad-ridged horn antennas, each of which is coupled to a dual channel radiometer. Fundamental (8–18GHz) and second and third harmonic (18–40GHz) thermal EBW emission and polarization measurements can be obtained simultaneously.
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