Fast recovery of the magnetic vacuum configurations of the WEGA stellarator with error field effects

With a background of having obtained positive results with function parametrization (FP) applied to stellarator configurations, the technique was used once again for recovering the vacuum magnetic field configurations of the WEGA stellarator including the main symmetry-breaking magnetic islands. A classical stellarator of type l = 2, WEGA has an inherent n = 1 (leading order) field perturbation responsible for these islands. The perturbation is assumed to be generated by a misalignment between the centres of the toroidal and helical field generating coil systems. These n = 1-periodic WEGA configurations, displaying no stellarator symmetry, were numerically generated around the experimental boundaries and analysed with FP. For the first time FP models with 4th order polynomials and non-linear regressions with rational functions were needed to parametrize the physical state of the configurations. Modelling of the widths of the magnetic islands was challenging, however. The FP-functions are in the process of being implemented to run with the WEGA control system.