May 1-3

Log in

Abstract Details

files Add files

status:file name:submitted:by:
approvedespinosa_sherwood17.pdf2017-03-08 15:14:44Silvia Espinosa
approvedespinosacatto_pop_apsdpp.pdf2017-03-08 14:27:27Silvia Espinosa

Abstracts

Author: Silvia Espinosa
Requested Type: Pre-Selected Invited
Submitted: 2017-03-08 14:37:59

Co-authors: P.J.Catto

Contact Info:
MIT Plasma Science and Fusion Center
77 Massachusetts Avenue, NW16-
Cambridge, MA   02139
USA

Abstract Text:
Recent measurements of pedestal impurity poloidal flow and in-out asymmetries in H and I mode Alcator C-Mod plasmas can be explained with a novel neoclassical pedestal model for impurity behavior. Having correctly verified this behavior, the model then establishes that impurity accumulation is avoided by I mode operation.

In order to keep impurity diamagnetic drifts as well as the ExB drift self-consistently, stronger radial gradients of the impurity density must be allowed. As a result, radial impurity flow effects need to be included. These effects substantially alter the parallel and poloidal impurity flows. The resulting modification in the impurity friction with the banana regime background ions then allows stronger poloidal variation. By using these measurements of the poloidal impurity flow and in-out impurity density asymmetry, the contributions to the radial flux of impurities can be determined.

In summary, we have developed the first self-consistent theoretical model retaining the impurity diamagnetic flow and the 2D features it implies due to its associated non-negligible radial flow. It successfully explains the experimental impurity density and temperature, and radial electric field, in-out asymmetries neoclassically. Moreover, it provides a means of calculating the neoclassical impurity radial flux from currently available measurements, providing insight on optimal tokamak operation to prevent impurity accumulation [1]. In particular, it predicts outward neoclassical impurity flux, and therefore inward fueling, occurs for I-mode operation in C-Mod.

[1] S. Espinosa and P. J. Catto, accepted by Phys. Plasmas (2017).

Comments: