Edge transport in fusion plasmas

Abstract

It has long been recognized that the plasma edge and the interaction of the plasma with material interfaces through the scrape-off layer (SOL) is crucial for the successful operation of future fusion machines, e.g. ITER. Tremendous progress has been achieved in the last decade in diagnosing, modelling and understanding this plasma region. Nonetheless, many important questions remain unanswered, e.g. the origin of parallel SOL flows, of ELM types or even of the L–H transition itself. While scientists often specialize and work either on the confined edge region or on the open magnetic field line region (SOL) it is obvious that the unsolved problems in the field can only be addressed by treating the pedestal and SOL regions in an integrated manner, thereby capturing their dynamical interaction.The present cluster issue is intended to provide an actual overview of the field of plasma edge and scrape-off layer both from the simulation/theory and the experimental side. The papers originate from contributions made to the IEA Large Tokamak IA Workshop on `Edge Transport in Fusion Plasmas' which was held in Krakow, Poland, 11–13 September 2006, in the cultural centre `Dom Polonii' (http://www.etfp2006.ifpilm.waw.pl). The workshop was attended by 30 participants from all over the world, many of whom are leading experts in their respective areas of work. The presentations focused on both experimental and theoretical aspects, from edge turbulence, edge localized modes (ELMs), to challenges in edge modelling using fluid and kinetic codes. It was a goal of the meeting, which was held in a convivial atmosphere of scientific debate, to bring together the progress made in diagnostics with the current state of the art in theory and code development.The nine papers in this cluster issue will provide an actual snapshot of this exciting and quickly evolving field. They cover a large number of themes, from edge turbulence measurements (Zweben) and simulation (Scott), via experimental (Kamiya) and numerical (Pankin) investigations of ELMs, towards developments of integrated transport codes (Kawashima) and a discussion of challenges facing edge modelling in the future (Schneider). The contributions also deal with topical themes of SOL flows (Zagorski), magnetic field ergodization (Jakubowski) and liquid lithium limiters (Pericoli). It is hoped that they provide compact access and a point of reference for the rapidly progressing work towards scientific understanding and finally control of the plasma edge and SOL region.