Skin effect modifications of the Resistive Wall Mode dynamics in tokamaks

We present the first evidence of the skin-effect modification of the Resistive Wall Mode (RWM) dynamics in a tokamak. The computations are performed with the CarMa code, using its unique ability of treating volumetric 3D conducting structures. The results prove that conventional thin-wall models and codes, assuming the thin equivalent wall located on the inner side of a real (thick) wall, may fail to get accurate estimates of RWM growth rates, since the inclusion of the skin effect makes the growth rates always larger than otherwise. The difference is noticeable even for the conventional slow RWMs and becomes substantial for faster modes. Some possible equivalent thin-wall modeling approaches are also discussed. •We present evidence of the skin-effect modification of RWM dynamics in a tokamak.•Conventional thin-wall codes may fail to get accurate estimates of RWM growth rates.•The inclusion of the skin effect makes the growth rates always larger than otherwise.•Some possible equivalent thin-wall modeling approaches are also discussed.