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           measurements using electron Bernstein wave thermal emission on NSTX

Diem, S. J.; Taylor, G.; Efthimion, P. C.; LeBlanc, B.P.; Carter, M.; Caughman, J. B. O.; Wilgen, J. B.; Harvey, R. W.; Preinhaelter, J.; Urbán, J.

doi:10.1063/1.2235112

Cited by 10 publications

(6 citation statements)

References 12 publications

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“…EBE measurements presented in this Letter are acquired with a remotely steered quad-ridged microwave antenna measuring fundamental, second, and third harmonic (18-36 GHz) emission. The antenna is mounted outside of the vacuum vessel and coupled to an absolutely calibrated heterodyne radiometer system [23,24]. The antenna beam waist diameter is 13 cm at the LCFS, which is located 50 cm from the antenna.…”

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confidence: 99%

Collisional Damping of Electron Bernstein Waves and its Mitigation by Evaporated Lithium Conditioning in Spherical-Tokamak Plasmas

et al. 2009

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The first experimental verification of electron Bernstein wave (EBW) collisional damping, and its mitigation by evaporated Li conditioning, in an overdense spherical-tokamak plasma has been observed in the National Spherical Torus Experiment (NSTX). Initial measurements of EBW emission, coupled from NSTX plasmas via double-mode conversion to O-mode waves, exhibited <10% transmission efficiencies. Simulations show 80% of the EBW energy is dissipated by collisions in the edge plasma. Li conditioning reduced the edge collision frequency by a factor of 3 and increased the fundamental EBW transmission to 60%.

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confidence: 99%

Collisional Damping of Electron Bernstein Waves and its Mitigation by Evaporated Lithium Conditioning in Spherical-Tokamak Plasmas

et al. 2009

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“…The EBE diagnostic on NSTX consists of two remotely steered, quadridged microwave antennas [9,10]. The antennas are located outside the vacuum vessel, 50 cm from the plasma edge, and have an oblique view of the plasma so the diagnostic is optimized to measure the B-X-O emission.…”

Section: Experimental Setup and Ebe Simulationmentioning

confidence: 99%

A novel high-density embedded AND-type split gate flash memory

Shen

Wang

Pan

et al. 2014

Jpn. J. Appl. Phys.

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High-β spherical tokamak (ST) plasma conditions cut off propagation of electron cyclotron (EC) waves used for heating and current drive in conventional aspect ratio tokamaks. The electron Bernstein wave (EBW) has no density cutoff and is strongly absorbed and emitted at the EC harmonics, allowing EBWs to be used for heating and current drive in STs. However, this application requires efficient EBW coupling in the high-β, H-mode ST plasma regime. EBW emission (EBE) diagnostics and modelling have been employed on the National Spherical Torus Experiment (NSTX) to study oblique EBW to O-mode (B-X-O) coupling and propagation in H-mode plasmas. Efficient EBW coupling was measured before the L-H transition, but rapidly decayed thereafter. EBE simulations show that EBW collisional damping prior to mode conversion (MC) in the plasma scrape off reduces the coupling efficiency during the H-mode phase when the electron temperature is less than 30 eV inside the MC layer. Lithium evaporation during H-mode plasmas was successfully used to reduce this EBW collisional damping by reducing the electron density and increase the electron temperature in the plasma scrape off. Lithium conditioning increased the measured B-X-O coupling efficiency from less than 10% to 60%, consistent with EBE simulations.

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“…8 The antennas are mounted outside of the vacuum vessel, 50 cm from the plasma edge. The antenna ridges are oriented to measure emission polarization components perpendicular and parallel to the magnetic field at the MC layer.…”

Section: Ebe Diagnostic and Simulation Codementioning

confidence: 99%

Electron Bernstein wave emission based diagnostic on National Spherical Torus Experiment (invited)

Diem

Taylor

Caughman

et al. 2008

Review of Scientific Instruments

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National Spherical Torus Experiment (NSTX) is a spherical tokamak (ST) that operates with n(e) up to 10(20) m(-3) and B(T) less than 0.6 T, cutting off low harmonic electron cyclotron (EC) emission widely used for T(e) measurements on conventional aspect ratio tokamaks. The electron Bernstein wave (EBW) can propagate in ST plasmas and is emitted at EC harmonics. These properties suggest thermal EBW emission (EBE) may be used for local T(e) measurements in the ST. Practically, a robust T(e)(R,t) EBE diagnostic requires EBW transmission efficiencies of >90% for a wide range of plasma conditions. EBW emission and coupling physics were studied on NSTX with an obliquely viewing EBW to O-mode (B-X-O) diagnostic with two remotely steered antennas, coupled to absolutely calibrated radiometers. While T(e)(R,t) measurements with EBW emission on NSTX were possible, they were challenged by several issues. Rapid fluctuations in edge n(e) scale length resulted in >20% changes in the low harmonic B-X-O transmission efficiency. Also, B-X-O transmission efficiency during H modes was observed to decay by a factor of 5-10 to less than a few percent. The B-X-O transmission behavior during H modes was reproduced by EBE simulations that predict that EBW collisional damping can significantly reduce emission when T(e)<30 eV inside the B-X-O mode conversion (MC) layer. Initial edge lithium conditioning experiments during H modes have shown that evaporated lithium can increase T(e) inside the B-X-O MC layer, significantly increasing B-X-O transmission.

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T e ( R , t ) measurements using electron Bernstein wave thermal emission on NSTX

Cited by 10 publications

References 12 publications

Collisional Damping of Electron Bernstein Waves and its Mitigation by Evaporated Lithium Conditioning in Spherical-Tokamak Plasmas

Collisional Damping of Electron Bernstein Waves and its Mitigation by Evaporated Lithium Conditioning in Spherical-Tokamak Plasmas

A novel high-density embedded AND-type split gate flash memory

Electron Bernstein wave emission based diagnostic on National Spherical Torus Experiment (invited)

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