Pressure Limiting Instabilities in Tokamaks

The plasma pressure achievable in a tokamak fusion reactor may be limited by instabilities like the ideal ballooning mode, a pressure-driven instability that acts to degrade plasma confinement. Here we investigate the sensitivity of the shape of the magnetic flux surface to the ideal ballooning mode; in particular, we modify the parameters describing the shape of magnetic flux surfaces of the equilibrium and perform infinite-n ideal ballooning scans to assess how shaping affects proximity to marginal instability. We find that for the parameter space considered, increasing squareness and elongation could help stabilise the plasma against the ideal ballooning mode instability.