Radial structure of quasi-coherent mode in ohmic plasma of the T-10 tokamak

The paper presents the recent results from the quasi-coherent (QC) mode studies performed in the ohmic plasma of the T-10 tokamak (R = 1.5 m. a = 0.3 m, B₀ = 2.2 T, I_pl = 230 kA, and n_e ≈ 1⋅10¹⁹ m⁻³) using Heavy Ion Beam Probe diagnostics (HIBP). The radial distribution of the amplitude of the density perturbations caused by the QC-mode has two pronounced peaks (approximately 5 and 1.5 % at radii of 25–30 and 8–14 cm, respectively) with an intermediate zone of lower amplitude in between them (<1% at radii of 16–21 cm). The mean QC-mode frequency remains nearly constant within the studied region (75–80 kHz). For the edge plasma, the HIBP observations were confirmed by the Langmuir probe measurements.