Improvement of confinement by lower hybrid waves

Quasi-steady-state H-mode has been achieved by combination of two lower hybrid waves in HT-6M tokamak. Plasma energy confinement time increases by two times, and the particle confinement time increases by a factor of three under a high plasma density condition. The wave diffusion and current radial diffusion code is used to simulate the experimental data on HT-6M. The calculated results show that the off-axis power deposition of lower hybrid wave is formed due to the low toroidal magnetic field and high plasma density. Reversed sheared(RS) configuration of the plasma current density is formed during H-mode phase. The RS configuration and internal transport barrier are attributed to the enhanced confinement improvement. The experimental data also gives the evidence for the reversed shear formation.