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 beam probe on the Texas Experimental Tokamak (TEXT) [K. W. Gentle, Nucl. Technol./Fusion 1, 479 (1981)]. Fluctuation amplitudes and correlation length scalings do not correspond to linear or quasilinear drift wave theory. Power-weighted root-mean-square (rms) wave number estimates are much lower ([(k) over bar(theta)](rms)rho(s) less than or equal to 0.1, rho(s)=[m(i)T(e)](1/2)/eB) than quasilinear theoretical expectations ((k) over bar(perpendicular to)rho(s) similar to 0.3). Core results indicate strong turbulence with a wave number spread, Delta k similar to (k) over bar at fixed frequency f, consistent with strong turbulence predictions, while edge results can be considered consistent with weak turbulence. In between the core and edge (0.6 less than or equal to r/a less than or equal to 0.8) is a transition region. (C) 1995 American Institute of Physics.