Stochasticity in fusion plasmas

Abstract

In recent years the importance of externally imposed resonant magnetic fields on plasmashas become more and more recognized. These fields act either at well defined plasma layers, e.g. byergodization or more globally by exciting large-size modes in the plasma. A majorachievement of research in recent years is the possibility to suppress large type 1 ELMS byresonant perturbation fields which modify the transport at the plasma edge. This option hasbeen studied extensively at DIII-D and recently progress has also been made at JET andTEXTOR. Several devices are preparing further experiments to study the important aim of avoidingtransient heat pulses and thus to substantially increase the lifetime of ITER. Other topics ofinterest for fusion reactors are the option of distributing the heat to a large area, optimizingmethods for heat and particle exhaust, and understanding the transport around tearingmode instabilities.Since October 2003, three SFP workshops have taken place. Important papers from the first twoworkshops have been published in previous special issues of Nuclear Fusion (stacks.iop.org/NF/44/i=6 and stacks.iop.org/NF/46/i=4)and the contents of this issue are based on presentations to the Third Workshop onStochasticity in Fusion Plasmas (SFP) held in Jülich, Germany, 5–7 March 2007.The SFP workshops have been stimulated by the installation of the Dynamic Ergodic Divertor(DED) in the TEXTOR tokamak. It has attracted colleagues working on various plasmaconfigurations such as tokamaks, stellarators or reversed field pinches. The workshop isdevoted to phenomena on the plasma edge and to transport questions over the whole plasmacross section. It is a meeting place for experimental and theoretical working groups. Thenext workshop is planned for February/March 2009 in Jülich. For details see www.fzjuelich.de/sfp/.We hope that the article series in Nuclear Fusion will stimulate interest in the fascinatingsubject of plasma physics.