Quasi-coherent mode evolution in discharges with positive radial electric field at the T-10 tokamak

The effect of the high-power ECRH on the quasi-coherent (QC) mode in the plasma of the T-10 tokamak with the magnetic field Bt = 2.2 T, plasma current Ipl = 230 kA and chord-averaged electron density ≈ 1⋅1019 m-3 is discussed. The most pronounced changes appear in the core plasma region with r < 0.5a. For the ECRH power PECRH = 2.2 MW causing the appearance of the positive radial electric field ErEC=+20V/cm (in the OH stage, the occurring field is ErOH=−75V/cm ), the mean frequency of the QC-mode gradually decreases from fQCOH=80−100kHz (in the OH stage) to fQCEC=20kHz , and its frequency spread Δf QC decreases from ΔfQCOH=±50kHz to ΔfQCEC=±10kHz . For the ECRH power PECRH = 1.7 MW and weak negative radial electric field ( FrEC=−20V/cm ), the mean frequency decreases to fQCEC=40kHz , and the frequency spread becomes ΔfQCEC=±30kHz . After the ECRH-induced drop, the QC-mode mean frequency increases with increasing line-averaged density.

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