BROAD-BAND DENSITY FLUCTUATION MEASUREMENTS USING A HEAVY-ION BEAM PROBE ON THE TEXAS EXPERIMENTAL TOKAMAK

Broad bandwidth (60 kHz less than or equal to f less than or equal to 500 kHz), long wavelength ((k) over bar(theta)less than or equal to 2 cm(-1)) density fluctuation measurements were made using a heavy ion b eam probe on the Texas Experimental Tokamak (TEXT) [K. W. Gentle, Nucl . Technol./Fusion 1, 479 (1981)]. Fluctuation amplitudes and correlati on length scalings do not correspond to linear or quasilinear drift wa ve theory. Power-weighted root-mean-square (rms) wave number estimates are much lower ([(k) over bar(theta)](rms)rho(s) less than or equal t o 0.1, rho(s)=[m(i)T(e)](1/2)/eB) than quasilinear theoretical expecta tions ((k) over bar(perpendicular to)rho(s) similar to 0.3). Core resu lts indicate strong turbulence with a wave number spread, Delta k simi lar to (k) over bar at fixed frequency f, consistent with strong turbu lence predictions, while edge results can be considered consistent wit h weak turbulence. In between the core and edge (0.6 less than or equa l to r/a less than or equal to 0.8) is a transition region. (C) 1995 A merican Institute of Physics.