Session CO3 - NSTX and Other ST.
ORAL session, Monday afternoon, November 15
Room 204/205, SCC
The high harmonic fast wave heated plasmas in NSTX are ideal plasmas for studying electron confinement regimes. Energy confinement times twice that of the ITER-L97 confinement law are produced at high electron plasma pressure-to-magnetic pressure ratios. Peaked density and temperature L-mode type profiles showing good particle confinement with low eta-e values as well as electron ITB discharges in low or weakly reversed magnetic shear profiles are analyzed for transport using standard drift wave transport models. The ETG mode gives the best interpretation of the heat flux versus gradient relationship. Although the trapped electron fraction is high, the trapped electron modes are suppressed by the high plasma pressure and high MHD alpha-factor that produces favorable bounce averaged guiding center drifts among other stabilizing effects. We show nonlinear simulations with specified heating power and edge losses that explain the inverse cascade in the ETG spectrum and produce thermal diffusivity profiles similar to the TRANSP power balance profiles.
Work supported by the Department of Energy Basic Energy Sciences.