Special section containing papers from the 8th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems

Abstract

The 8th IAEA Technical Meeting on Energetic Particles in MagneticConfinement Systems was held in San Diego, California, USA on 6--8 October2003 and was hosted by General Atomics and the University ofCalifornia, Irvine. The purpose of the meeting was todiscuss the status of experimental andtheoretical work on suprathermal electrons and ions in a wide variety of magnetic confinement geometries. Topics included the formation and transport of energetic particles, the collective instabilities they drive, their effect on the plasma, and energetic particle diagnostics. The meetingwas attended by 59 scientists from 10 different countries. There were20 contributed poster presentations, 17 contributed oral presentations,16 invited talks, and 4 summary and discussion sessions. This specialissue contains 8 papers based on the invited talks.Many of the presentations focused on the various Alfvén eigenmodes (AE) thatare driven unstable by energetic ions. These instabilities, which havebeen investigated intensively in conventional tokamaks formore than a decade, are now the subject of detailed study in other toroidalconfigurations. Many properties of the toroidicity-induced AE (TAE) in theLarge Helical Device are similar to TAEs in conventional tokamaks but newinstabilities are observed as well, such as a helicity-induced AE(Toi et al). In spherical tokamaks, both AE with steady frequenciesand AE with rapidly changing frequencies (`chirping')are commonplace. As the plasmabeta increases in the START and MAST spherical tokamaks, a progressionfrom steady TAE activity to rapid frequency chirping to stable operationis often observed (Gryaznevich and Sharapov). The rapid frequencychirping in MAST can be understood by a theory that attributesthe phenomenon to `holes' and `clumps' in phasespace (Pinches et al). In conventional tokamaks, recent efforts havefocused on plasmas with reversed shear. Instabilities with gradualfrequency sweeping that are called an `Alfvén cascade' ora `reversed-shear AE' are observed in JT-60U (Shinohara et al).Projections for ITER and other burning plasma experiments appearedprominently in the meeting. Ferritic inserts in JFT-2M cause significantreductions inthe energetic particle losses associated with toroidal field rippleand provide the basis for accurate predictions of alpha-particle losses inITER (Shinohara et al). In an ITERplasma with a central current hole, calculations suggest that the combination of poor centralconfinement and edge ripple losses will result in an unacceptablelevel of alpha particle losses (Tobita et al). JET experimentsstudied the linear stability of AEs, with the particular aim of developingpotential control techniques for ITER. Some experiments exploredthe impact of relaxing the energetic-ion pressure gradient that drivesthe instability, while others altered the magnetic configuration toincrease the plasma damping that opposes instability (Testa et al).A theoretical study suggests that the nonlinear evolution ofAlfvén instabilities in reversed-shear plasmas in ITER will be strongly affected by convective radial transport of the alpha particles (Vlad et al). Finally, considerable progress has beenmade in neutron diagnostics for ITER but alpha-particle diagnosticsremain an outstanding challenge (Sasao et al).