MHD stability of the ITER pedestal and SOL plasma and its influence on the heat flux width

MHD stability of ITER plasmas has been analyzed for QDT = 10 edge and SOL plasma conditions, showing that the SOL plasma is MHD stable down to pressure gradient scale lengths of λp ∼ 1 mm, but that MHD pedestal plasma stability can limit λp to values of 5-8 mm just inside the separatrix. Modelling of the corresponding plasma conditions with the SOLPS code shows that heat flux widths λq ∼ 1.2-1.5 mm can be obtained which are compatible with λp ∼ 5-8 mm. This is due to the fact that the ITER divertor plasma enters the high recycling regime at low values of separatrix densities (∼4.0 × 1018 m−3), which leads to the appearance of a region with reversed flow near the separatrix, modifying plasma transport and leading to high SOL density gradient scale lengths and divertor plasma pressures near the separatrix.