(Georgia Institute of Technology, 2012)
Stacey, Weston M.; Groebner, Rich J.; Evans, T. E.
There are (at least) two classical mechanisms for non-diffusive transport in the edge plasma: i) particle “pinch” velocities due to forces such as VxB, and Er; and ii) outward drifts due to ion-orbit loss and X-transport. A theoretical development for the treatment of these non-diffusive transport mechanisms within the context of fluid theory is assembled and applied to several DIII-D discharges in order to investigate the importance of these non-diffusive transport mechanisms in the edge pedestal. Several interesting insights emerge from this investigation.
(Georgia Institute of Technology, 2010-08)
Stacey, Weston M.; Groebner, Rich J.
The evolution of edge pedestal parameters between edge-localized modes (ELMs) is analyzed for an H-mode DIII-D [J Luxon, Nucl. Fusion 42, 612 (2002)] discharge. Experimental data are averaged over the same sub-intervals between successive ELMs to develop data that characterize the evolution of density, temperature, rotation velocities, etc. over the interval between ELMs. These data are interpreted within the context of the constraints imposed by particle, momentum and energy balance, in particular in terms of the pinch-diffusion relation for radial particle flux that is required by momentum balance. It is found that in the edge pedestal there is an increase of both inward (pinch) electromagnetic and outward (diffusive) pressure gradient forces over the inter-ELM interval.
(Georgia Institute of Technology, 2006)
Stacey, Weston M.; Groebner, Rich J.
A new procedure for inferring χ[subscript i,e] in the plasma edge from experimental data and
integrated modeling code calculations has been developed which takes into account
atomic physics and radiation effects and convective as well as conductive heat flux
profiles. Application to DIII-D shots indicates that the sharp temperature gradient
pedestal region may be caused as much, if not more, by an increase (with radius) of the
conductive heat flux as by a decrease of the thermal transport coefficient. Inferred χ[subscript i,e][superscript exp] are compared with theoretical predictions.
(Georgia Institute of Technology, 2005-10)
Stacey, Weston M.; Groebner, Rich J.
A calculation based on the requirements of particle, momentum and energy conservation,
conductive heat transport and atomic physics resulting from a recycling and fueling neutral influx was
employed to investigate the experimental density, temperature, rotation velocities and radial electric field
profiles in the edge of three DIII-D [J. Luxon, Nucl. Fusion, 42, 614 (2002)] high-mode plasmas. The
calculation indicated that the cause of the pedestal structure in the density was a momentum balance
requirement for a steep negative pressure gradient to balance the forces associated with an edge peaking
in the inward pinch velocity (caused by the observed edge peaking in the radial electric field and rotation
velocity profiles) and, to a lesser extent, in the outward radial particle flux (caused by the ionization of
recycling neutrals). Thermal and angular momentum transport coefficients were inferred from
experiment and compared with theoretical predictions, indicating that thermal transport coefficients were
of the magnitude predicted by neoclassical and ion-temperature-gradient theories (ions) and electrontemperature-
gradient theory (electrons), but that neoclassical gyroviscous theory plus atomic physics
effects combined were not sufficient to explain the inferred angular momentum transfer rate throughout
the edge region.