Empiricial scaling of inter-ELM power widths in ASDEX Upgrade and JET

The SOL power decay length (λ_q) deduced from analysis of fully attached divertor heat load profiles from two tokamaks, JET and ASDEX Upgrade with carbon plasma facing components, are presented. Interpretation of the target heat load profiles is performed by using a 1D-fit function which disentangles the upstream λ_q and an effective diffusion in the divertor (S), the latter essentially acting as a power spreading parameter in the divertor volume. It is shown that the so called integral decay length λ_int is approximately given by λ_int ≈ 1_q +1:64 × S. An empirical scaling reveals parametric dependency λ_q/mm ≃ 0:9 · B_T ^-0.7q_cy^1.2_lP⁰ _SOLR⁰_geo for type-I ELMy H-modes. Extrapolation to ITER gives λ_q ≃1 mm. Recent measurements in JET-ILW and from ASDEX Upgrade full-W confirm the results. It is shown that a regression for the divertor power spreading parameter S is not yet possible due to the large effect of different divertor geometries of JET and ASDEX Upgrade Divertor-I and Divertor-IIb.