Lower hybrid current drive efficiency in the JT-60 tokamak

Abstract
Lower hybrid current drive (LHCD) experiments on JT-60 have been carried out in parameter ;e = (0.6−1.6)×1019 m−3, Ip = 0.5−1.5 MA, BT = 2.7−4.5 T, PLH < 2.5 MW, f = 1.75 and 2.0 GHz, with and without NB heating (PNB < 6 MW), limiter and lower side single null divertor configurations, and narrow and wide spectra. The current drive efficiency increases with the volume averaged electron temperature Te and with decreasing Zeff and a high efficiency of ηCDeRPIRF/PLH ≤ 2.65 × 1019 m−2AW−1 was achieved by LHCD alone. The experimental data set has shown that the current drive efficiency is consistent with the scaling of ηCD ~ 12 Te/(5+Zeff)×l019 m−2AW−1. Low N1 waves with a narrow spectrum have a higher current drive efficiency than higher N1 waves with a wide spectrum insofar as launched waves satisfy the accessibility