Assessment of the DIVIMP ‘onion-skin’ model in the JET Mark I divertor

Abstract 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, χ ⊥ ( r ), has been evaluated across the SOL, and is found to increase with increasing distance from the separatix.