Global Stability Issues for a Next Step Burning Plasma Experiment

We present analysis which supports the feasibility of a next-step burning plasma experiment. The FIRE design has R = 2 m, a = .525 m, κ_95 = 1.77, δ_95 = 0.4, B = 10(12) T, I = 6.44(7.7) MA, H = 1.2 (1.0) for the reference (high-field) discharge, with monotonic q-profile and sawtoothing ELMy H-mode operation. The primary issues for MHD are associated with (1) the q=1 surface, (2) energetic particle modes (3) edge currents due to the H-mode pedestal,(4) neoclassical tearing modes, and (5) error fields and locked modes. We find (1) the m=1, n=1 mode requires non-linear analysis including energetic-particle effects, (2) α-particle driven Alfven modes, RTAE and KTAE, are expected to be stable for β_α 0 < 0.5 %, (3) the predicted critical value for the onset of the NTM is very close to the operating point for the high-field option, and may be mediated by self or active control of seed island width or active island current drive, (4) the nominal self-consistent operating point is stable to external kink modes without a conducting wall and (5) error field requirements need to be revisited. Advanced operating modes with q > 2 everywhere and high-bootstrap fraction also hold promise but need to be further developed.