Study of acceleration, confinement and sawtooth induced redistribution of fast resonant protons during ICRH in TFTR

A natural diamond detector (NDD), developed in the Russian Federation, has been used for the first time for fast charge exchange H0 atom spectrometry and flux evolution measurements during H+ minority ICRH experiments in deuterium plasmas in TFTR. The behaviour of deeply trapped RF driven H+ ions was studied in quiescent plasmas and under the influence of sawtooth oscillations during central and off-axis ICRH. H+ ion energy spectra measured by the NDD yielded data on the efficiency of H+ minority ion acceleration by ICRF waves and the H+ ion confinement at different ICRH powers and resonance layer positions. The evolution of the hydrogen charge exchange atom flux measured by the NDD was compared with fast proton losses measured by escaping charged particle detectors to demonstrate that fast H+ ions are redistributed from the plasma core to well beyond the q = 1 surface. The redistribution is sufficiently far from the plasma centre for fast ions to leave the plasma due to stochastic ripple diffusion. In contrast with non-deeply-trapped fast ions, Alfvén eigenmode (AE) activity does not significantly affect the spatial and energy distributions of deeply trapped fast ions.