Ideal MHD stability of a spherical tokamak power plant and a component test facility

We have investigated ideal MHD stability of two advanced spherical tokamak confinement concepts: the spherical tokamak power plant (STPP), a 3 GW concept fusion power plasma producing 1 GW of electric power, and the component test facility (CTF), a concept designed for in situ materials testing for ITER and beyond. Detailed stability studies for toroidal mode number n = 1, 2, 3 displacements are presented as a function of conformal wall radius R(w) and on-axis safety factor q(0). For the STPP marginal stability scans held the current profile fixed, but varied the total plasma current. For the CTF we have extended and parallelized earlier marginal stability scans to scan over both the plasma beta and q(0) by varying the current profile to preserve the total plasma current. These confirm that both concepts are stable provided that the wall is sufficiently close and q(0) sufficiently large (q(0) > 2.8 for the power plant and q(0) > 2.1 for the CTF). Both power plant and CTF configurations are found to be ballooning stable.