Ion Temperature Fluctuations in ELMy H-mode of the X3 EC-heated Plasmas on TCV

This paper focuses on interpreting variations in the NPA measured energy distribution of neutral fluxes from the TCV high density H-mode plasma discharges with strong third harmonic electron cyclotron heating (P_{X3}>P_{\Omega}). Two quasi-stationary regimes: ELMy H-mode and ELM-free H-mode, routinely and reproducibly obtained in TCV, with a plasma density 5–10×10^{19} m^{−3}, electron temperature 2–3 keV and ion temperature of 0.7–1.0 keV. The ELMy X3-heated H-mode plasma on TCV is significantly perturbed by ELMs, sawteeth activity and modes. In X3-heated plasmas ELMs are characterised by increased amplitudes and lower frequencies than are typical in ohmic H-modes with strong sawteeth synchronised with ELM cycle. The energy losses per ELM can exceed the 15% of the total stored energy and the plasma density and electron temperature profiles were resolved during the ELM cycle. NPA measurements in the presence of ELMs and sawteeth cannot be explained with the classical theory of two-body Coulomb electron-ion collisions alone. Additional effects (such as a modification of the ion temperature radial profile and/or ion redistribution in the coordinate and velocity space due to plasma perturbations) must be considered.