167 research outputs found

    Current Drive by Electron Bernstein Waves in Spherical Tori

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    Current Drive by Electron Bernstein Waves in Spherical Tokamaks

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    Alternative optical concept for electron cyclotron emission imaging

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    The implementation of advanced electron cyclotron emission imaging (ECEI) systems on tokamak experiments has revolutionized the diagnosis of magnetohydrodynamic (MHD) activities and improved our understanding of instabilities, which lead to disruptions. It is therefore desirable to have an ECEI system on the ITER tokamak. However, the large size of optical components in presently used ECEI systems have, up to now, precluded the implementation of an ECEI system on ITER. This paper describes a new optical ECEI concept that employs a single spherical mirror as the only optical component and exploits the astigmatism of such a mirror to produce an image with one-dimensional spatial resolution on the detector. Since this alternative approach would only require a thin slit as the viewing port to the plasma, it would make the implementation of an ECEI system on ITER feasible. The results obtained from proof-of-principle experiments with a 125 GHz microwave system are presented.open0

    Te (R,t) Measurements using Electron Bernstein Wave Thermal Emission on NSTX

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    The National Spherical Torus Experiment (NSTX) routinely studies overdense plasmas with ne of (1–5) X 1019 m-3 and total magnetic field of <0.6 T, 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 (8–18 GHz) and second and third harmonic (18–40 GHz) thermal EBW emission and polarization measurements can be obtained simultaneously

    Status and Plans for the National Spherical Torus Experimental Research Facility

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    Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

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