Local Gyrokinetic Study of Electrostatic Microinstabilities in a Field-Reversed Configuration

Field-reversed configuration (FRC) has been increasingly studied in recent years, such as the C-2U in Tri. Alpha Energy Co. and KMAX in USTC. The results on C-2U experiments and GTC simulations [1] showed that, under higher parameters, turbulence caused by electrostatic micro-instabilities have significant impact on transport in a FRC. However, the theoretical illustration on these micro-instabilities behavior in FRC under a wider range of parameters has not been reported up to now. Here, the electrostatic micro-instabilities in the core region and scrape-off-layer of an equilibrium FRC are investigated, based on the gyro-kinetic dispersion relationship and 1D particle-in-cell simulation. The effects of a wide range of parameters, such as temperature gradients, density gradients, vertical wave-vector, electron-to-ion temperature ratio and mass ratio, on the growth-rate and mode structure of the instabilities were given. This work provides more theoretical support for understanding turbulent transport in a FRC.
[1] Schmitz, L.; Fulton, D. P.; Ruskov, E.; and et. al., Suppressed ion-scale turbulence in a hot high-β plasma, Nat. Commun., 7, 13860(2016).