L. Delgado-Aparicio, D. Stutman, K. Tritz, M. Finkenthal, S. Kaye, R. Bell, R. Kaita, B. LeBlanc, F. Levinton, J. Menard, S. Paul, D. Smith, H. Yuh
||Nuclear Fusion, 2009, Vol.49 (8), pp.085028 (10pp)
||Institute of Physics Journal
The first experimental assessment of low-Z impurity transport in a neutral beam heated, high-confinement H-mode plasma sustained in a low-field, low-aspect ratio spherical tokamak, was performed at the National Spherical Torus Experiment (NSTX). The injected impurities penetrate to the core on a hundred millisecond time scale, indicating a low core particle diffusivity ( 1 m2 s−1) in good agreement with the values predicted by neoclassical transport theory. In addition, a fixed q -profile magnetic field scan that showed reduced impurity penetration at high fields is also reported. This result suggests that anomalous ion particle transport associated with turbulent long-wavelength electrostatic instabilities must be largely suppressed in the NSTX core.