Interpretive modelling of scrape-off plasmas on the MAST tokamak

Electrical currents in the scrape-off layer (SOL) of MAST are modelled using an interpretive Onion-Skin Model (OSM) constrained with experimental data from MAST diagnostics. The model was extended to include the effects of the magnetic mirror force, which has a strong influence on the particle and momentum balance in spherical tokamaks, such as MAST [1]. These modifications serve to more accurately model the parallel electric fields present in the MAST SOL, which can alter plasma dynamics via the E x B drift. Simulations show that the electrical current at the divertor targets is predominantly thermoelectric, whereas Pfirsch-Schluter currents have a greater contribution to the total current in the bulk of the SOL plasma. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved