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In preparation for next step burning plasma such as ITER, experimental studies of instabilities and confinement of energetic ions were performed on JET and on MAST, with innovative diagnostic techniques, in conventional and shear-reversed plasmas, exploring a wide range of effects for energetic ions. �Alpha tail� production using 3rd harmonic ICRH of 4He beam ions has been employed on JET for studying (4)He of the MeV energy range in a �neutron-free� environment. The evolution of ICRH-accelerated ions of 4He with E > 1.7 MeV and D with E>500 keV was assessed from nuclear gamma-ray emission born by the fast ions colliding with Be and C impurities. A simultaneous measurement of spatial profiles of fast (4)He and fast D ions relevant to ITER were performed and found to be in agreement with classical fast ion orbits in positive and strongly reversed magnetic shear discharges. Time-resolved gamma-ray diagnostics for ICRH-accelerated (3)He and H minority ions allowed changes in the fast ion distribution function to be assessed during sawteeth, TAEs, EAEs and Alfven Cascades (ACs). A significant decrease of gamma-ray intensity from H ions with E>5 MeV was detected caused by the �tornado� modes (TAEs inside the q=1 surface); this was interpreted as TAE-induced loss of fast ions with drift orbit widths Dela f/ ?a/2. Experiments performed in the opposite case, Delta f/ a << 1, for ICRH-accelerated (3)He ions with E>500 keV, have shown excitation of numerous TAEs, EAEs, and ACs without a notable degradation of the fast ion confinement. Instabilities excited by super-Alfvenic beam ions were investigated on the spherical tokamak MAST. Due to higher values of beta and a higher proportion of fast ions on MAST than on JET, a wider variety of modes and nonlinear regimes for the Alfven instabilities were observed. The MAST and START data showed that TAE and chirping modes decrease both in their mode amplitudes and in the number of unstable modes with increasing beta. Combining the J

Additional information

Authors: SHARAPOV S E et al, EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon (GB)
Bibliographic Reference: An oral paper given at: 20th IAEA Fusion Energy Conference Organised by: International Atomic Energy Agency Held at: Centrtro de Fusao Nuclear, Vilamoura (PT)
Availability: Available from Association EURATOM-CEA, Departement de Recherches sur la Fusion Controlee, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail:
Record Number: 200417814 / Last updated on: 2004-12-01
Original language: en
Available languages: en