Numerical study of the synergy effects of electron cyclotron wave and two lower-hybrid waves in the current drive process

In recent experiments on the experimental advanced superconducting tokamak, the electron cyclotron wave and the two lower-hybrid waves at different frequencies, i.e., 4.6 GHz and 2.45 GHz, are applied simultaneously to sustain and control the plasma current. To investigate the synergy effects of the three waves, the Fokker-Planck equation with the quasi-linear diffusions induced by the three waves is solved numerically with the CQL3D code [R. W. Harvey and M. G. McCoy, in Proceedings of IAEA Technical Committee Meeting on Advances in Simulation and Modeling of Thermonuclear Plasmas, Montreal, Canada (1992)]. It is found that there might be strong synergy effects between the three waves. The electrons in the low velocity region in the velocity space can be accelerated perpendicularly by the electron cyclotron wave, and their parallel velocities can be increased due to scattering and fall into the resonance regions of the lower-hybrid waves. Therefore, such processes may bring more electrons to resonate wit...