Analysis of Parametric Decay Instabilities Driven by Helicon Waves in Tokamak Experiments

In this study, we analyse and compute the local growth rate of parametric decay instabilities of helicon waves under typical scrape-off layer conditions. Our findings are consistent with previous work [Porkolab et al., AIP Conference Proceedings 2984 , 070004 (2023)], confirming that the dominant decay channels are ion cyclotron quasi-modes and their harmonics. While the parametric instability can be excited at extremely low input power, it can be suppressed by a higher electron temperature. Conversely, higher plasma densities increase the local growth rate, suggesting that helicon waves may face challenges in high-density plasmas.