Confinement studies of auxiliary heated NSTX plasmas

Making use of newly installed kinetic profile diagnostics, core thermal confinement and particle transport during neutral beam and high-harmonic fast wave heating is investigated. Analysis suggests that the ion thermal transport may be exceptionally low in the core of neutral-beam-heated plasmas. This is highlighted by noting that the ion temperature often exceeds the electron temperature by a factor near two, which is inconsistent with classical NBI power deposition partition computed by TRANSP and suggests that classical slowing down might not be the sole energy transfer process. In both the NBI and HHFW heated cases, gyrokinetic analysis suggests that long-wavelength ITG modes, normally associated with ion thermal transport, are stable or are suppressed by ExB shear. Ion particle transport based on analysis of gas puffing is at neoclassical levels within the q=2 surface. The main thermal loss channel is through electrons in HHFW and NBI discharges. The dynamics of the H-mode operation, which has been achieved with NBI and HHFW auxiliary heating, is discussed. (author)