SUPPRESSION OF RAYLEIGH-TAYLOR TYPE FLUCTUATIONS BY VELOCITY SHEAR

Experimental investigation of the curvature induced Rayleigh-Taylor (R -T) instability in the presence of a sheared electric field is reporte d in a low-beta toroidal plasma device, BETA (Basic Experiments in Tor oidal Assembly). Coherent low frequency fluctuations are excited at 20 0 gauss. The R-T instability arises from an unfavourable curvature in the magnetic field (simulating the effective gravity) with density gra dient (del n) antiparallel to it and the sheared electric field is inb uilt in the device. Results show that the R-T instability driven fluct uations are suppressed where the E(r) x B shear is above a critical va lue. This critical value of shear is found to be consistent with the t heoretical predictions. (C) 1997 Elsevier Science S.A.