Confinement, Transport and Turbulence Properties of NSTX Plasmas

are predominantly heated by up to 7 MW of 90 keV D0 neutral beams, and thus NSTX is an excellent laboratory in which to study electron physics. This is underscored by the fact that in H-mode plasmas the ion transport is often close to neoclassical while the electron transport is anomalous. The data to be presented in this paper is taken from experimental campaigns during 2004 to 2007 in which R=0.83 to 0.89 m, a=0.57 to 0.66 m (R/a~1.3 to 1.45), Ip = 0.6 to 1.2 MA, BT = 0.3 to 0.55 T, elongation = 1.7 to 2.5, triangularity =0.4 to 0.85 and ne = 1.5 to 7.0 x 10 19 m -3. Results from dedicated Ip, BT and power scans will be presented that will include both global and local analysis. The data from the power scans are used to study the beta dependence of confinement. Furthermore, results from statistical studies of momentum diffusivity will be presented. BT and Ip Dependence of Confinement Dedicated parameter scans, one at fi xed plasma current and one at fixed toroidal field were used as a basis to determine the dependence of thermal and global confinement on BT and Ip respectively in NSTX (3). These scans were carried out at similar densities and fixed injected power (4 MW) in Lower Single Null deuterium H- mode discharges. The results of these scans are shown in Figs. 1 a and b for a toroidal field scan at I p=0.7 MA and a plasma current scan at B T=0.55 T respectively. The results show a much stronger toroidal field scaling than plasma current scaling for both the thermal and total (including fast ion contribution) confinement times. The results from these dedicated scans confirmed earlier results from statistical analysis (4). These dependences, with E ~ B T 0.9 Ip 0.4 are quite different than those at conventional aspect ratio, as typified by the ITER98pby,2 scaling (5) and given by E ~ BT 0.15 Ip 0.93 . A BT scan was performed also at Ip=0.9 MA, and this showed a weaker dependence, with E~BT 0.6 , indicating a possible non-linear dependence on q or Ip. Local transport analysis was carried out to determine the source of the underlying transport giving rise to these confinement trends. As was reported in (3,6),