The work of the ITPA SOL/divertor group is reviewed and implications for ITER discussed. Studies of near SOL gradients have revealed a connection to underlying turbulence models. Analysis of a multi-machine database shows that parallel conduction gradients near the separatrix scale as major radius. New SOL measurements have implicated low-field side transport as driving parallel flows to the inboard side. The high-n nature of 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. Analysis of ELM measurements imply that the ELM continuously loses energy as it travels across the SOL-larger gaps should reduce surface loads. The predicted divertor power loads for ITER disruptions has been reduced as a result of finding that the divertor footprint broadens during the thermal quench and that the plasma can lose up to 80% of its thermal energy before the thermal quench (not true for VDEs or ITBs). On the other hand predictions of power loading to surfaces outside the divertor have increased. Disruption mitigation through massive gas puffing has been successful at reducing divertor heat loads but estimates of the effect on the main chamber walls indicate 10s of kG of Be could be melted/mitigation. Estimates of ITER tritium retention have reduced the amount retained/discharge although the uncertainties are large and tritium cleanup may be necessary every few days to weeks. Long-pulse studies have shown that the fraction of injected gas that can be recovered after a discharge decreases with discharge length. The retention rate on the sides of tiles appears to ~ 1-3% of the ion flux to the front surface for C tiles and ~100x less for Mo tiles. T removal techniques are being developed based on surface heating and surface ablation although ITER mixed materials will make T removal more difficult. The use of mixed materials gives rise to a number of potential processes-e.g. reduction of surface melting temperatures (formation of alloys) and reduction of chemical sputtering. Advances in modelling of the ITER divertor and flows have enhanced the capability to match experimental data and predict ITER performance.

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Plasma periphery investigation performed in the T-10 tokamak has shown an essential increase of the perpendicular anomalous particle flux in the scrapeoff layer (SOL) with an average plasma density rise. The strengthening of the radial transport is found to occur at an average electron density above a threshold level, which depends on a plasma current I p . The value of the threshold level is about 0.3 times the Greenwald density. Langmuir probe measurements of SOL plasma parameters indicate that intermittent events can play a significant role in the cross-field transport. Intermittent behaviour of the plasma parameters is associated with formation and propagation of the plasma regions (or structures) with high density. The structures move in radial and poloidal directions. Radial movement is predominantly directed to the vacuum vessel wall in the SOL. The radial velocity of the high density plasma structures reduces from 1000 m s −1 near the last closed flux surface to 200 m s −1 at the wall of the vacuum chamber. The radial size of the structures also decreases with minor radius from 3 to 0.5 cm. The poloidal velocity is equal to 1000-1300 m s −1 and is directed towards an ion diamagnetic velocity; the poloidal size of the plasma structures is 2-3 cm. The observed plasma structures can be responsible for more than 50% of the total radial turbulent particle flux. T-10 results support the hypothesis that intermittent convection rather than diffusion can define the cross-field transport.

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Experimental investigation of the Scrape-Off Layer (SOL) turbulence and the perpendicular anomalous particle transport in the high density regime in the T-10 tokamak is presented. Comparison of the plasma parameters measured at the low-field side (LFS) and the high-field side (HFS) of the tokamak shows that the inboard turbulence essentially differs from the outboard one. Turbulence has an intermittent character but the fluctuation level of the inboard ion saturation current is about two times lower than at the LFS. The radial turbulent particle flux and the effective perpendicular diffusion coefficient measured at the LFS are about 3-5 times higher than those observed at the HFS. Enhanced perpendicular particle flux at the LFS is defined by the high density plasma structures formed in the vicinity of the last closed flux surface. The poloidal electric field inside the high density structures has different directions at the inboard and outboard sides of the plasma column. The radial electric drift induced by the poloidal electric field is directed towards the vacuum vessel at both the LFS and the HFS. These experiments support the hypothesis that SOL parallel flow might be caused by an additional mechanism such as 'ballooning' transport, which generates a larger flux of particles from the core into the SOL at the outer mid-plane.