Achievement of reactor-relevant β in low-q divertor discharges in the doublet III-D Tokamak

A volume average toroidal ..beta.. of 6.2% has been obtained with 10 MW of hydrogen neutral beam injection into deuterium divertor discharges in DIII-D. High-..beta.. discharges were maintained quiescently for many energy confinement times in elongated, kappa = 2, divertor discharges where the safety factor at the 95% flux surface was near 2. The maximum ..beta.. calculated to be stable against ideal kinks and ideal ballooning modes is 8.5%--9.5%, confirming that these I/aBapprox. =2.5 MA/m T discharges are some distance below the stability limit.