On the estimate of near fields for the WEST ICRF travelling wave array launcher

This study focuses on the Ion Cyclotron Range of frequency (ICRF) Travelling Wave Array (TWA) launcher proposed for the WEST tokamak. This launcher aims to mitigate the detrimental effects associated with resonant ICRF launchers, currently used in most magnetic plasma confinement experiments. The WEST TWA launcher, characterized by reduced near fields and an optimized spatial spectrum, is compared to current WEST ICRF launchers. The parallel component of the electric field on the limiters is particularly investigated, which is a proxy for sheath rectification and impurity production. Full-wave modelling using ANSYS HFSS software, paired with an in-house Python library, was employed to simulate the near fields generated by the TWA and WEST ICRF launchers. The models use experimental equilibrium and plasma profiles from a WEST discharge, with perfect electric conductor boundaries and artificial loss added to the plasma dielectric tensor to damp wavefield amplitude away from the launcher. Results indicate that the TWA launcher present design significantly reduces the amplitude of the toroidal components of the electric field on the limiter surfaces by a factor of more than four compared to the WEST ICRF launchers, which is expected to reduce the impurity production.