A turbulence transition induced by lower hybrid waves in an ELMy H-mode pedestal at EAST

We report a turbulence transition in an edge-localized-mode (ELMy) H-mode pedestal when modulating the injected power of lower hybrid wave (LHW) to investigate its impact on ELM behavior. Simultaneous measurements of lithium beam emission spectroscopy (measuring larger-scale electron density fluctuation with perpendicular wavenumber k⊥ below 3 cm−1) and Doppler backscattering system (measuring smaller-scale electron density fluctuation with k⊥ usually larger than 3 cm−1) show that the dominant electron density fluctuation in the pedestal region transits from the edge coherent mode (ECM) to a broadband fluctuation (BBF) with a more radially localized distribution as the LHW is switched on. Comparing edge profiles (including electron density, temperature, and pressure) with and without LHW suggests that the LHW-induced decrease in the edge electron collisionality seems to account for such a suppression of ECM with the nature of a dissipative trapped electron mode, and subsequently allowing for the generation of the BBF. This work may shed more light into the underlying physics behind LHW's influence on ELMs.