Modeling of Synergy Between 4th and 6th Harmonic Absorptions of Fast Waves on Injected Beams in DIII‐D Tokamak

In recent moderate to high harmonic fast wave heating and current drive experiments in DIII‐D, a synergy effect was observed when the 6th harmonic 90 MHz fast wave power is applied to the plasma preheated by neutral beams and the 4th harmonic 60 MHz fast wave. In this paper, we investigate how the synergy can occur using ORBIT‐RF coupled with AORSA. Preliminary simulations suggest that damping of 4th harmonic FW on beam ions accelerates them above the injection energy, which may allow significant damping of 6th harmonic FW on beam ion tails to produce synergy.