Long citation – Alan Goodman

Quasi-isodynamic stellarator optimisation

With the success of Wendelstein 7-X (W7-X), it has become clear that stellarators offer a particularly promising route to fusion energy. A central physics question is how a magnetic field can be shaped in such a way that the performance is maximised. Dr. Goodman’s thesis is cumulative in nature and treats different topics of stellarator optimisation. It shows, for the first time, that a magnetic field of the type used in W7-X can be tailored to confine high-energy particles well enough for a fusion reactor whilst preserving or improving all other plasma properties of interest. It is possible that a magnetic field broadly similar to that of W7-X can be tailored in such a way that the level of plasma turbulence is significantly reduced. Dr. Goodman also demonstrated that the turbulence reduction can be combined with all the other main criteria traditionally used in stellarator optimisation. The thesis presents a first-of-its-kind approach to finding a stable, quasi-isodynamic design (SQuID) for a stellarator. The work details an efficient algorithm for achieving precise quasi-isodynamic (QI) fields for a stellarator and proposes a handful of simple target functions for optimising QI stellarator configurations with respect to macroscopic and microscopic plasma stability, turbulent transport, impurity accumulation and coil construction. The results have provided the motivation for several private fusion companies to choose the quasi-isodynamic stellarator as their path to commercial fusion energy. In conclusion, the thesis of Alan Goodman describes a very substantial amount of work of extraordinary quality.