ELM-RELATED FLUCTUATIONS IN PBX-M H-MODES

Edge Localized Modes have been studied in PBX-M discharges with high d ata sampling rate magnetic diagnostics with good spatial coverage. Hig h frequency (greater-than-or-equal-to 250 kHz) activity appears prior to the increase in the D(alpha) emission. While this high frequency ac tivity is global, with high coherence for all coils both on the inside and outside midplane, there is no identifiable mode structure. A very intense outward ballooning feature appears simultaneously with the in crease in the D(alpha) emission, and lasts for about 5 msec. The toroi dal mode structure of this feature is clearly identifiable, consisting of a series of toroidal harmonics from n=3 to 8, at frequencies given by f(n)=f0+nDELTAf, where DELTAf=20-30 kHz and f0=30-50 kHz. This fea ture may be caused by the kinetic ballooning mode.