REGIME OF VERY HIGH CONFINEMENT IN THE BORONIZED DIII-D TOKAMAK

Following boronization, tokamak discharges in DIII-D have been obtained with confinement times up to a factor of 3.5 above the ITER89-P L-mode scaling and 1.8 times greater than the DIII-D/JET H-mode scaling relation. Very high confinement phases are characterized by relatively high central density with n(e) (0) almost-equal-to 1 x 10(20) m-3 , and central ion temperatures up to 13.6 keV at moderate plasma currents (1.6 MA) and heating powers (12.5-15.3 MW). These discharges exhibit a low fraction of radiated power, P less-than-or-equal-to 25%, Z(eff)(0) close to unity, and lower impurity influxes than comparable DIII-D discharges before boronization.