High harmonic fast wave propagation in the scrape-off layer of NSTX and NSTX-U*

We perform simulations using a 2D full-wave (FW2D) code for high harmonic fast wave (HHFW) in the scrape-off layer (SOL), the region of the plasma between the last closed flux surface (LCFS) and the tokamak vacuum vessel, of NSTX and NSTX-U. The SOL is important for HHFW heating because up to 60% of the coupled power can be lost in the SOL. In this presentation, we examine the collisional power losses in the SOL (P_abs) by adopting various values of the electron density in front of antenna (N_ant), the magnetic field strength (B₀) as well as the distance between the LCFS and the antenna (Δ). The results clearly show that P_abs increases with increasing N_ant, and/or weaker B_0, showing consistency with NSTX experiments. We also found that vessel shape strongly affects the power lost to the SOL, hence P_abs increases when Δ increases. We also examine the HHFW in the NSTX/NSTX-U using recently developed Petra-M code and compare with the results from FW2D.