Fluctuation signatures of rotation reversals and non-local transport events in KSTAR L-mode plasmas

TL;DR

This study investigates how electron cyclotron resonance heating influences non-local heat transport and intrinsic rotation in KSTAR tokamak plasmas, revealing that ECH can extend thresholds and alter turbulence characteristics.

Contribution

It demonstrates the impact of ECH on non-local heat transport, rotation reversal thresholds, and turbulence spectra, linking micro-fluctuations to macro plasma phenomena.

Findings

ECH extends the cut-off density for non-local heat transport.

Rotation reversal thresholds are significantly affected by ECH.

Core turbulence spectra are broader in ECH plasmas.

Abstract

Experiments of electron cyclotron resonance heating (ECH) power scan in KSTAR tokamak clearly demonstrate that both the cut-off density for non-local heat transport (NLT) and the threshold density for intrinsic rotation reversal can be determined by the collisionality. We demonstrate that NLT can be affected by ECH, and the intrinsic rotation direction follows the changes of NLT. The cut-off density of NLT and threshold density for rotation reversal can be significantly extended by ECH. The poloidal flow of turbulence in core plasma is in the electron and the ion diamagnetic direction in ECH plasmas and high density OH plasma, respectively. The auto-power spectra of density fluctuation are almost the same in the outer region for both ECH and OH plasmas. On the other hand, in the core region of ECH plasmas, the power spectra of the density fluctuations are broader than those of OH plasma. All these observations in macroscopic parameters and micro fluctuations suggest a possible link between the macro phenomena and the structural changes in micro-fluctuations.