A quasi-isodynamic stellarator configuration towards a fusion power plant

This work demonstrates that magnetohydrodynamic (MHD) stable, quasi-isodynamic (QI) stellarator equilibria with reduced turbulence can be generated with an optimised coilset. We present one such equilibrium which, when being generated by coils, maintains the benefits of its excellent QI quality (low neoclassical transport at small particle collisionality net toroidal current and good fast-particle confinement) while demonstrating ideal-MHD stability and lower ion-temperature-gradient-driven turbulent heat flux than W7-X. As a consequence of its optimised rotational transform profile, this plasma equilibrium has nested flux surfaces and a chain of large islands at the plasma’s edge, for which we present an island divertor design. It additionally features an electron root – a large region in the plasma core in which the radial electric field points outwards, towards the plasma boundary – which provides a potential solution for preventing impurity accumulation in a fusion device.