EDGE PLASMA FLUCTUATIONS AND TRANSPORT IN A REVERSED-FIELD PINCH

Edge plasma fluctuations are studied with inserted triple Langmuir probes and magnetic coils in the TPE-1RM20 reversed-field pinch [Y Yagi et al., in Plasma Physics and Controlled Nuclear Fusion Research 1992 (International Atomic Energy Agency, Vienna, 1993), Vol. 2, p. 611]. Two-point measurements show that density and potential fluctuations have relatively low mode numbers (m < 3, n < 40). High coherence (gamma = 0.5) with magnetic field fluctuations and similar mode spectra suggest that density and potential fluctuations are mainly caused by electromagnetic turbulence. Broadband magnetic fluctuations are dominated by m = 0, low-n modes and internally resonant m = 1 and m = 2 modes. A coherent (f = 20-30 kHz) m = 0, low-n mode is also observed. Particle flux driven by electrostatic electric field fluctuations is 50%-100% of total flux obtained from D(alpha) line intensity measurement. Low-frequency fluctuations (f < 100 kHz) give the main contribution to the total flux. Electrostatic fluctuation driven electron energy flux is only of the order of 10% of total nonradiative power loss.