Beta limits for the BIG DEE

Equilibria for the BIG DEE (Doublet III upgrade) are obtained which are optimized with respect to both shape and current profile for stability to ideal-MHD modes. With a wall reasonably far from the plasma surface, it is inferred that the external kink constrains q s to be above 2.0, where q s is the plasma surface value of the safety factor, and the ballooning mode limits the value of beta. Then, stable BIG DEE equilibria with beta at least as large as 17% can be found. The wall position necessary to stabilize the n = 1 and n = 2 kink modes is outside the coils and the equilibrium is stable for n ≥ 3 with a wall at infinity. This equilibrium is not in a separated second stability region and thus there are no problems regarding accessibility.