The combined current drive of the lower hybrid wave and the high harmonic fast wave under the influence of the radial transport of fast electrons

The combined current drive (CD) of the lower hybrid wave (LHW) and the high harmonic fast wave (HHFW) is investigated theoretically under the influence of the radial transport of fast electrons in DIII-D. The simulation results show that the combined CD of the LHW and the HHFW has a significant synergy effect even though the radial transport of fast electrons is considered. Positive or negative synergy effects occur in current driven by the combined LHW and HHFW when different frequencies and parallel refractive indices of the LHW and the HHFW are adopted. The relatively ideal total driven current is 375 kA with a synergy current of 150 kA, and the synergy factor for the driven current is 1.66. In addition, it is found that the synergy effect is not limited to the CD but also has a positive synergy effect on the power deposition. The additional deposition power not only accelerates more electrons in the parallel direction and forms a larger driven current, but it also plays a role in the acceleration of electrons in the vertical direction, which may also have a synergy effect on the heating of the plasma.