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Recent research in scrape-off layer (SOL) and divertor physics is reviewed; new and existing data from a variety of experiments have been used to make cross-experiment comparisons with implications for further research and ITER. Studies of the region near the separatrix have addressed the relationship of profiles to turbulence as well as the scaling of the parallel power flow. Enhanced low-field side radial transport is implicated as driving parallel flows to the inboard side. The medium-n nature of edge localized modes (ELMs) has been elucidated and new measurements have determined that they carry ~10?20% of the ELM energy to the far SOL with implications for ITER limiters and the upper divertor. The predicted divertor power loads for ITER disruptions are reduced while those to main chamber plasma facing components (PFCs) increase. Disruption mitigation through massive gas puffing is successful at reducing PFC heat loads. New estimates of ITER tritium retention have shown tile sides to play a significant role; tritium cleanup may be necessary every few days to weeks. ITER's use of mixed materials gives rise to a reduction of surface melting temperatures and chemical sputtering. Advances in modelling of the ITER divertor and flows have enhanced the capability to match experimental data and predict ITER performance.

The latest results of B2-Eirene modelling of ITER divertor operation are presented. The operational window is further explored with an improved model of the neutral transport, the effect of gas leaks between the divertor cassettes is assessed and the sensitivity of the results to the features of the divertor geometry and to the gas puffing arrangement is analysed. The presence of neutral–neutral collisions in the model makes the results rather insensitive to the detail of the divertor shape. The analysis shows that the effect of the gas leak on the divertor performance in ITER is weak and therefore inter-cassette sealing may be not critical.

The B2-EIRENE code has been compared with plasma edge measurements from Alcator C-MOD, DIII-D, JET, JT-60U in L-mode and H-mode regimes. Similarities in L-mode discharges between JET and JT-60U are well reproduced by the code as well as the sudden approach to detachment seen in JT-60U when a 1% chemical sputtering yield for carbon is assumed. Comparisons between similar L-mode regimes in JET, JT-60U and Alcator C-MOD reveal the larger importance of anomalous energy convection in Alcator C-MOD with regard to larger tokamaks. H-mode discharges of DIII-D and JET can be satisfactorily modelled with similar values of the transport coefficients (approximately an order magnitude smaller than in L-mode) when the power flow into the scrape-off layer (SOL) is dominated by the ion channel, as previous EDGE2D simulations for JET suggested.

Experimental results obtained on the Tokamak de Varennes during a series of reproducible ohmic discharges are presented. Profiles of basic plasma parameters are constructed and compared with theoretical predictions. In particular, the measured plasma resistivity agrees with the neoclassical scaling rather than with Spitzer resistivity. The study of electron-density fluctuations indicates a linear dispersion relation with a propagation velocity of 3.0 × 104 cm s−1. Particle transport investigations are initiated, giving experimental diffusion and convection coefficients across the plasma radius for electrons and impurity ions.

The effect of variation of the divertor geometry in ITER is re-evaluated with the recently developed non-linear model of the transport of the neutral particles, taking into account neutral–neutral and molecule-ion collisions. The importance of the ‘dome’ for the neutral gas compression in the divertor is confirmed. Unlike earlier studies with a linear model of neutral transport, the present results show only a weak sensitivity of the divertor performance to the details of the divertor shape.

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.

Results of a detailed study of the parameter space of the ITER divertor with the B2-Eirene code are presented. Relations between plasma parameters at the separatrix, the interface between the core and edge plasma, are parametrized to provide a set of boundary conditions for the core models. The reference ITER divertor geometry is compared with the straight target option, and the possibility of controlling the edge density by shifting the plasma equilibrium in ITER is explored.