TJ-II: Infuence of AEs on ExB transport: role of phase shift effects: Difference between revisions

In recent JET discharges, the 3-ion heating scheme <ref>Ongena, J. et al. Synergetic heating of D-NBI ions in the vicinity of the mode conversion layer in H-D plasmas in JET with the ITER like wall. In EPJ Web of Conferences, volume 157, page 02006. EDP Sciences, 2017.</ref> <ref>2] Kazakov, Y. O., et al. Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating. Nature Physics, 13(10):973–978, 2017.</ref> was used to produce a significant population of MeV ions leading to the excitation of intense TAE. Under these circumstances, a significant improvement of thermal transport was observed, likely due to the reduction of turbulent transport. Such discharges were modelled using the state-of-the-art gyro-kinetic code GENE [3] in its flux-tube approximation in order to shed light on the underlying mechanism for such improved confinement. It was observed that the presence of highly energetic ions and intense TAE activity was accompanied by a dramatic reduction of turbulent transport. Also, the generation of large amplitude zonal flows was observed, suggesting a mechanism where TAEs lead to an excitation of zonal flows and hence to a subsequent reduction of turbulence [4]. However, a concomitant effect might take place due to the modification of the phase shift between the density/temperature and electrostatic potential induced by the parallel dynamics of Alfvén eigenmodes. The modification of the phase shift during the suppression of turbulent transport is evidenced in the attached PowerPoint presentation.