Assessment of the DIVIMP 'onion-skin' model in the JET mark I divertor

The DIVIMP-NIMBUS [1] 'Onion-Skin' model has been used to predict upstream plasma parameters using as input measurements by Langmuir probes in the divertor target tiles. Measurements of density and temperature (both T-i and T-e) across the SOL close to the stagnation point at the top of the torus have been made using a reciprocating probe carrying both Langmuir and retarding field analyzer (RFA) heads. In addition, a lithium beam diagnostic has been used to measure radial distributions of density upstream. Ohmic, L-mode and H-mode discharges have been studied, and good agreement with code predictions in the three cases has been found. The heat transport coefficient, chi(perpendicular to)(r), has been evaluated across the SOL, and is found to increase with increasing distance from the separatrix.