Power dependence of density and current drive efficiency in full LHCD plasmas on TRIAM-1M

Full lower hybrid current drive (LHCD) plasmas on TRIAM-1M have been investigated in the wide ranges of line-averaged electron density, n-bare=0.1-4.7x1019m-3, plasma current, IP=15-100kA, and injected power, PLH=0.003-0.2MW. Strong gas-puff makes a termination of the discharge in high density region, where the density is still much lower than the limit predicted by wave propagation characteristics. The achieved en and the current drive efficiency, ηCD, have a significant relation to PLH, and their power dependences are close to the one predicted by a model derived from the balance between the energy confinement, τE, and ηCD of the LHCD scalings. This density limit depends on the injected PLH. This limit will appear in full CD discharges, including ECCD, NBCD, and bootstrap current and it wanes with the increase of the portion of the ohmic heating power. (author)