Beta optimization for peaked pressure profile reversed magnetic shear equilibria with JET type parameters

The ideal MHD b limit of reversed shear equilibria, due to n = 1, n = 2 and ballooning modes, is investigated for peaked pressure profiles, consistent with those occurring when the internal transport barrier is established in JET optimized shear discharges. Higher bN can be reached with the control of the minimum q value, and a conducting wall can further improve the stable domain. The n = 2 mode plays an insignificant role, unless the conducting wall improves the n = 1 stability when the shear reversal is large. Increasing the amount of shear reversal generally improves MHD stability, and the effect is stronger for the n = 2 mode. b* ( = 2m0 ?P2 ?1/2/B02) increases with normalized current (Ip/aB0) but bN is only weakly affected.