Energetic particles in magnetic confinement systems

Abstract

Dominating α-particle heating will be the qualitatively new physics element of ITER. As it constitutes both a conceptually challenging as well as a practically highly relevant field, it has attracted the attention of a large and growing scientific community. Theoretical and diagnostic tools should be fully developed at the commencement of the thermonuclear operation of ITER. Fortunately effective methods exist to produce significant fractions of energetic ions already in present experiments. Although these populations differ qualitatively in their energy and pitch-angle spectra from those of fusion-alphas, they offer an excellent opportunity to test theoretical models and codes and to develop and benchmark diagnostic techniques. ITER itself will not mark the last stage in the development of fusion heating, and a comprehensive ab initio understanding of fast particle results on this device will be a necessary prerequisite for bridging the gap to DEMO. The study of the confinement properties of energetic particles, and in particular their interaction with the background plasma, is therefore a key element in the preparation for ITER and DEMO operation.The papers contained in this special section are based on invited presentations at the 10th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems held in Kloster Seeon, Germany, 8–10 October 2007, hosted by the Max-Planck-Institut für Plasmaphysik, Garching. The main topics of the presentations at this meeting were experimental observations and theoretical results on instabilities driven by energetic ions in tokamaks and stellarators, recent diagnostic developments, runaway electrons, heating and current drive.The papers presented here are devoted to the most challenging topics in energetic particle physics: the drive of instabilities via resonant interaction between energetic particles and plasma waves and the non-linear back-reaction on the confinement of the fast ions. Experimental observations in various magnetic confinement devices (tokamaks, spherical tokamaks, stellarators) are presented as well as theoretical investigations based on true ab initio physics models.