Optimisation of stellarator equilibria with ROSE

It is well known that optimisation of the MHD equilibrium of stellarators can have great influence on the performance and hence have a significant effect on the potential of stellarators as potential power plants.

The ROSE code was written to carry out an optimisation based on an equilibrium evaluation using VMEC and several additional codes. This paper presents both a quasi-axially symmetric and a quasi-isodynamic equilibrium obtained with ROSE and demonstrates two important features that are new to stellarator optimisation. One allows the reduction of coil complexity by analysing a current sheet obtained with NESCOIL. The second is a new way of accounting for properties of the vacuum field while simultaneously optimising the finite beta equilibrium. (paper)