Fishbone-induced zonal flows
2024 Research Campaign, Thrust: Fast Ions, Turbulence and Alfven Waves Interaction
Purpose of Experiment
In ITER and future fusion reactors, good confinement of fusion-born alpha particles and other energetic particles (EP) is essential to maintain a dominantly self-heated plasma. The presence of EP can also destabilize instabilities at different spatial scales, which may lead to their outward transport. Fishbone, a helicoidal EP-driven instability of the core plasma, is one of such instabilities that could drive large EP transport due to the global mode structure. Recent self-consistent simulations suggest that fishbone-induced EP redistribution can generate zonal flows, which in turn dominate the fishbone nonlinear saturation. In addition, it has been observed on multiple devices that there exists a strong correlation between fishbone and internal transport barrier (ITB) formation. One plausible explanation is that fishbone-induced zonal flows suppress turbulent transport and thus form ITB. This experiment seeks to experimentally measure and characterize fishbone-induced zonal flows and understand the causality between fishbones and ITB formation.