The DIII-D tokamak and energy confinement at low q

A summary of DIII-D capabilities and recent improvements is given. The ability to produce highly shaped plasmas in DIII-D has been exploited to produce (beta)(sub T) values of 11 percent. Stability calculations indicate that the current and pressure profile details effect the maximum (beta)(sub T) that can be achieved. The linear increase of H-mode confinement with plasma current ceases for I(sub p)/B(sub T) larger than approx. 1 (MA/T). The most likely cause for the degradation is increased transport due to sawteeth. It has been determined, experimentally, that the saturation of confinement is not the result of a ceiling imposed by saturated Ohmic confinement, by the plasma reaching a (beta) limit, by enhanced plasma radiation, or by ELMs.