Deduction of SOL transport coefficients using 2D modelling for hot-ion ELM-free H-modes in JET

Abstract

Profiles of T e and J sat measured by Langmuir probes at the target plates of the JET MkI divertor and the target plate power loading are modelled via the EDGE2D/NIMBUS codes. The low-density ( n e ∼ 1 × 10 19 m −3 ) OH plasma preceding high-power NBI, as well as the ELM-free high performance H ∗ and high performance rollover H RO phases are considered. Experimentally, the power splitting between ions ( P i ≥ 7 MW) and electrons ( P e < 1 MW) in conjunction with the H-mode transport barrier effects that T e and J sat change little from OH to H ∗ conditions, although P in ∼ 2 → 20 MW and n e can increase up to a factor of three as the H ∗-phase progresses. In modelling χ i is taken as 1 m 2/s. To match the divertor T e - profiles, χ e must be varied from the strike point outwards as ∼ 0.5 → 3 m 2/ s in all phases. Perpendicular particle transport is assumed to be purely diffusive or with a pinch. Duplication of J sat ( R) requires: D ⊥ ∼ 0.03 → 0.015 m 2/s (OH → H ∗) , or ν pinch D ⊥ ∼ 15 → 45 → 25 m −1 (OH → H ∗ → H RO) with D ⊥ = 0.1 m 2/ s. Sensitivity studies involving different recycling scenarios, deep and shallow computational grids, wall material and the thermal transport barrier are carried out to judge the possible influences on the deduced transport coefficients.