This paper mainly studies the effects of high magnetic field and quasi-linear effects on lower hybrid current drive (LHCD) in fusion reactor-level tokamak. The critical magnetic field Bc value for LHCD is 9.64 T. Below this value, high magnetic field effect do not need to be considered for LHCD on fusion reactor-level tokamaks such as ITER and China Fusion Engineering Test Reactor (CFETR). On the CFETR tokamak with toroidal magnetic field up to 6.5 T, a comparative study of low-field and high-field side (HFS) launch of LHCD was conducted using coupled ray-tracing equation and the Fokker–Planck equation. The spectrum N||0 of LHCD with three typical frequencies, which can effectively drive currents, is −1.7 to −1.6. The optimal poloidal launching angles are θ =145 ∼ 165° on HFS, and θ = −60° to −30° or 30°–50° on low-field side (LFS). At injection power of 1 MW, the current drive efficiency is 30–60 kA MW−1. The current profile is relatively localized, with its peak at a radial position where ρ > ∼0.50. Injection from HFS or LFS has a significant impact on LHCD. For high-power injection, the influence of quasi-linear effect needs to be considered. When injecting from HFS, the LHCD efficiency increases significantly with the increase of injection power, reaching ∼60 kA MW−1 at 30–40 MW. For injection from LFS, LHCD efficiency increases gradually with the increase of injection power, with a maximum not exceeding 50 kA MW−1 even at 100 MW. HFS injection should be prioritized for LHCD on fusion reactor level tokamaks, and the output power level of a single klystron needs to be higher for higher LHCD efficiency.
Effort of lower hybrid current drive experiments toward to H-mode in EAST