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 {ital L}-mode scaling and 1.8 times greater than the DIII-D/JET {ital H}-mode scaling relation. Very high confinement phases are characterized by relatively high central density with {ital n}{sub {ital e}}(0){approx}1{times}10{sup 20} m{sup {minus}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, {ital P}{le}25%, {ital Z}{sub {ital e}{ital f}{ital f}}(0) close to unity, and lower impurity influxes than comparable DIII-D discharges before boronization.