A multi-machine database for the H-mode scrape-off layer power fall-off length, λq in JET, DIII-D, ASDEX Upgrade, C-Mod, NSTX and MAST has been assembled under the auspices of the International Tokamak Physics Activity. Regression inside the database finds that the most important scaling parameter is the poloidal magnetic field (or equivalently the plasma current), with λq decreasing linearly with increasing Bpol. For the conventional aspect ratio tokamaks, the regression finds , yielding λq,ITER ≅ 1 mm for the baseline inductive H-mode burning plasma scenario at Ip = 15 MA. The experimental divertor target heat flux profile data, from which λq is derived, also yield a divertor power spreading factor (S) which, together with λq, allows an integral power decay length on the target to be estimated. There are no differences in the λq scaling obtained from all-metal or carbon dominated machines and the inclusion of spherical tokamaks has no significant influence on the regression parameters. Comparison of the measured λq with the values expected from a recently published heuristic drift based model shows satisfactory agreement for all tokamaks.

Experimental measurements of the SOL power decay length (λq) estimated from analysis of fully attached divertor heat load profiles from two tokamaks, JET and ASDEX Upgrade, are presented. Data was measured by means of infrared thermography. An empirical scaling reveals parametric dependency λq/mm = 0.73 • B −0.78

Abstract. The installation of a new poloidal charge exchange recombination spectroscopy (CXRS) diagnostic at ASDEX Upgrade (AUG) has enabled the determination of the radial electric field, , using the radial force balance of impurity ions.has been derived from charge exchange (CX) spectra measured on different impurity species, such as He 2+ , B 5+ , C 6+ and Ne 10+ . The resulting profiles are found to be identical within the uncertainties regardless of the impurity species used, thus, demonstrating the validity of the diagnostic technique. The profile has been compared to the main ion pressure gradient term, which is found to be the dominant contribution at the plasma edge, thus, supporting that the well is created by the main ion species. The profile has been measured in different confinement regimes including L-, I-and H-mode. The depth of the well and the magnitude of the shear are correlated with the ion pressure at the pedestal top. The temporal evolution of the measured CX profiles and the resulting have been studied during an ELM cycle. At the ELM crash, the minimum is less deep resulting in a reduction of the E×B shear. Within 2 ms after the ELM crash, the edge kinetic profiles have nearly recovered and the well is observed to recover simultaneously. In high density type-I ELM mitigated H-mode plasmas, obtained via externally applied magnetic perturbations with toroidal mode number = 2, no clear effect on due to the magnetic perturbations has been observed.