Effect of neutrals on the power decay length at the divertor target

EDGE2D modelling of JET divertor plasmas with wide variation of main plasma parameters was aimed at identification of operational domains of the applicability of the 2/7×λ^Te scaling for predicting the power deposition profile width at the outer divertor target plate in high recycling conditions. Contrary to expectations, under no conditions, including lowest density plasmas just entering the conduction regime, was this scaling capable of correctly predicting the width and peak value of target power deposition profiles. Poorer ion parallel heat conduction, compared to the electron channel, in combination with reduced energy convection and volumetric power losses in divertor, of which charge exchange was found to play the dominant role, resulted in large deviations from the predictions of the 2/7×λ^Te scaling.