Experimental investigation for cross-scale interaction between electron-scale and ion-scale turbulence in Large Helical Device (LHD)

Some simulation studies indicate that the cross-scale interaction between electron-scale and ion-scale turbulence has a large influence on the turbulent transport in certain T_e/T_i region[1]. To study such a cross-scale phenomenon, we observed electron-scale and ion-scale turbulence in combination with millimeter-wave backscattering system[2] and Doppler backscattering system. To obtain a significant change in T_e/T_i, we performed several ECH power scan experiments. As a result, we successfully observed electron-scale (ρ_ik_⊥ ~ 5) and ion-scale (ρ_ik_⊥ ~ 0.5) turbulence simultaneously at the same position with significant change in T_e and constant T_i. The electron-scale turbulence intensity is negatively correlated with the ion-scale turbulence intensity in certain T_e/T_i region, while it is positively correlated in the other region. We will discuss the results of more detailed correlation analysis at the conference.

[1] S. Maeyama et al 2022 Nat. Commun. 13:3166

[2] T. Tokuzawa et al 2021 Rev. Sci. Instrum. 92 043536