The optimization of resonant magnetic perturbation spectra for the COMPASS tokamak

The COMPASS tokamak, recently transferred from UKAEA Culham to IPP Prague, is equipped with a set of saddle coils for producing controlled resonant magnetic perturbations (RMPs). In the future experimental programme of COMPASS we plan to focus on studies of RMPs, especially in view of their application as an ELM control mechanism and their considered use in ITER. In the present contribution we describe the preparatory calculations for the planned experiments. We computed the spectra of perturbations for several different equilibria predicted by MHD simulations and determined the positions and sizes of the resulting islands. It is shown how the saddle coils of COMPASS can be adapted to our equilibria to obtain good island overlap at the edge, which is believed to be a key component in the ELM mitigation effect. The techniques used for adapting the coils to achieve this result are described. Those are fairly general and could be used in the design of RMP coils on other machines.