Award Description
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.
Experimental Approach:
The main experimental approach is to optimize the plasma scenario for zonal flow measurement, vary the safety factor (q) profile (especially q=1 location), and change the drive of fishbone and background turbulence level. The validation of fishbone-induced zonal flows and ITB formation models can be of great interest to the advanced scenario development of ITER and future fusion reactors. If fishbone oscillations may not cause significant EP redistribution and can form ion ITB, we can trigger fishbones on purpose, rather than avoiding them, by tailoring fast-ion distribution.
