Effect of the tokamak size in edge transport modelling and implications for DEMO

The edge plasma of four devices, AUG, JET, ITER and a prototypical DEMO near ignition, is modelled with B2-EIRENE with a linear neutral model, carbon impurity, and variable throughput and scrape-off layer power. The scaling from ITER to DEMO is quantified as a power law scaling in device size, and JET and AUG simulations are compared to this scaling. Compared to ITER at the same scrape-off layer power per unit device volume and the same operating point relative to the edge-based density limit, edge helium density and peak power per unit area is found to be similar, and helium influx lower, for DEMO with impurity seeding. With a full neutral model, helium parameters are improved by a factor 3. Results of core modelling show that ignited operation of DEMO is possible with the impurity seeding required to render peak power loads compatible with a helium-cooled divertor.