TJ-II observations of nonlinear wave-wave coupling in play during Alfven-Eigenmode:Turbulence:Zonal-Flow interactions

TJ-II Flexible Heliac, a stellarator, has a major radius of 1.5 m, averaged minor radius 0.2 m, B field of 1 T, and a high degree of configuration flexibility (rotational transform spans 0.9 to 2.5). Time series of probe signals are presented from 11 TJ-II shots fueled by neutral-beam injection (NBI). Typical parameters for both electrons and ions are density = 10^19 m^-3 and core temperatures are Te = 300 eV and Ti = Te/2. Energetic ions, seeded by NBI, resonate at a given Alfven eigenmodes (AE) frequency and toroidal Alfven eigenmode (TAE) activity arises. One probe, from one Langmuir probe array, and 8 radially incremented probes, from a second array, measure floating potential at separate toroidal and poloidal positions. We observe, analyze (by the bispectrum), and confirm nonlinear, incommensurate-frequency, wave-wave coupling signatures and document the cross-bi-phase between AE (200kHz) and broadband turbulence (20kHz) on TJ-II in terms of the interaction's role in establishing Long-Range Correlations and in generating zonal flows in fusion-relevant plasma. No other fusion-relevant facility can simultaneously examine these issues. These results lead us to hypothesize that interactions between coexisting zonal flow and broadband turbulence may rely on AE dynamics.