The nonlinear density limit of driving plasma current by lower hybrid waves in tokamak plasmas

Self-consistent modeling and simulation of the nonlinear power deposition in the scrape-off layer (SOL) plasma during lower hybrid current drive (LHCD) are established by coupling the power transfer among waves through parametric decay instability (PDI) to the propagation of lower hybrid waves (LHWs). The anomalous power loss of LHCD in high-density plasma observed in multiple tokamaks is successfully reproduced through theory and simulation, and the simulation results are validated by the experimental findings among multiple tokamaks. Moreover, we obtained a theoretical scaling of the nonlinear density limit as nPDI∝ P₀-2/3Ly2/3Tₑω₀²B₀4/3, which is further validated by both simulation and experimental results. According to the scaling of the nonlinear density limit, the applicability of driving plasma current through lower hybrid waves is still guaranteed for future fusion reactors.