Frequency scaling of the lower-hybrid-current-drive density limit in tokamak plasmas.
It is shown experimentally that the lower-hybrid-current-drive density limit is a function of the RF source frequency. While in previous 800-MHz experiments this limit occurred at n-bar/sub e/ = 6 x 10/sup 12/ cm/sup -3/, with a newly installed 2.45-GHz, 100-kW RF system on the Versator II tokamak, fully RF-driven discharges have been achieved at densities up to n-bar/sub e/ = 1.0 x 10/sup 13/ cm/sup -3/, without increasing the toroidal magnetic field (B 1). Incremental current increases in Ohmically heated discharges have been observed at densities exceeding n-bar/sub e/ = 2.0 x 10/sup 13/ cm/sup -3/.