Investigation of transport in the DIII-D edge pedestal

A comparison of various heat conduction theories with data from several DIII-D [Luxon, Nucl. Fusion 42, 614 (2002)] shots indicates: (1) that neoclassical theory is in somewhat better agreement with experiment than is ion temperature gradient mode theory for the ion thermal conductivity in the edge pedestal, although both are in reasonable agreement with experiment for most discharges; and (2) that electron temperature gradient theory (k⊥cs⩽ωpe) is in much better agreement with experiment than is electron drift wave theory (k⊥cs⩽Ωi) for the electron thermal conductivity. New theoretical expressions derived from momentum balance are presented for: (1) a “diffusive-pinch” particle flux, (2) an experimental determination of the momentum transfer frequency, and (3) the density gradient scale length. Neither atomic physics nor convection can account for the measured momentum transfer frequencies, but neoclassical gyroviscosity predictions are of the correct magnitude.