STABILITY OF ALFVEN GAP MODES IN BURNING PLASMAS

A stability analysis is carried out for energetic particle-Alfven gap modes. Three modes have been identified: the toroidicity, ellipticity, and noncircular triangularity induced Alfven eigenmodes (TAE, EAE, and NAE). In highly elongated plasma cross sections with kappa - 1 approximately 1, the EAE may be a more robust mode than the TAE and NAE. It is found that electron Landau damping in highly elongated plasmas has a strong stabilizing influence on the n = 1 EAE, while ion Landau damping stabilizes the n = 1 TAE in high-density regimes. Furthermore, the NAE turns out to be stable for all currently proposed ignition experiments. The stability analysis of a typical burning plasma device, Burning Plasma Experiment (BPX) [Phys. Scr. T16, 89 (1987)] shows that n > 1 gap modes can pose a serious threat to the achievement of ignition conditions.