Study of current profile control and improved confinement with lower hybrid current drive in the HT-7 tokamak

The effectiveness of the plasma current profile control and confinement improvement with lower hybrid current drive (LHCD) in the HT-7 superconducting tokamak has been observed successfully. Numerical simulations and hard X-ray evolution spectra indicate that the power spectrum of lower hybrid wave, toroidal magnetic field and plasma density are the key factors for changing the plasma current profile. In the optimal LHCD condition, profiles of plasma density and temperatures have been changed as expected. And the internal transport barriers have appeared in the profiles of both electron and ion temperatures. Both the energy confinement time and the particle confinement time have been improved. (author)