Impact of lower hybrid wave injection on edge localized modes in the HL-3 tokamak

Abstract Experiments of edge localized modes (ELMs) control with lower hybrid wave (LHW) injection were carried out in the newly operation HL-3 tokamak for the first time, and the experimental results demonstrated that ELMs could be effectively suppressed by LHW injection. During the process of ELMs control with LHW injection, the heat load on the divertor target plate was significantly reduced. Simultaneously, the plasma confinement performance was improved, accompanied by a decrease in both resistivity and collisionality. Moreover, the corresponding simulations of the Peeling-Ballooning mode with BOUT++ code revealed a substantial decrease in both the linear growth rate and the pedestal nonlinear energy loss rate. Further analysis of the LHW injection simulation by GENRAY code and the DBS measurements indicated that LHW injection did not directly affect the ELM behavior. Instead, it enhanced the particle transport within the pedestal region by intensifying edge electrostatic turbulences, leading to a wider and flatter pedestal pressure profile, ultimately suppressing ELMs. The experiments and simulations carried out in the HL-3 tokamak for the first time significantly contribute to a more profound and comprehensive understanding of the physical mechanisms of ELMs control with LHW injection.