EXPERIMENTAL-EVIDENCE OF 3-WAVE COUPLING ON PLASMA TURBULENCE

Experimental evidence of the nonlinear nature of the broadband edge fl uctuations has been obtained in edge turbulence in the Advanced Toroid al Facility torsatron. Whereas little nonlinear wave interaction is fo und in the scrape-off layer region, three-wave coupling is enhanced in the plasma edge region (r < a(shear)). The degree of three-wave coupl ing strongly depends on the plasma conditions; it decreases in the tem perature range (T(e) almost-equal-to 10 eV) where the ionization rates depend strongly on T(e) suggesting a link between ionization source a nd turbulence.