On the formation of edge electric fields in negative triangularity plasmas

The Negative Triangularity (NT) plasma edge is studied with full orbit simulations and compared with similar simulations using a Positive Triangularity (PT) edge geometry. It is found that the thermal edge ions in NT are less well confined than in PT. The edge ion losses in NT set-up an electric field inside the plasma in the loss region. This electric field leads to counter-current edge plasma flows and are consistent with observations in NT plasmas. It could also explain the good edge confinement in NT discharges via the E × B flow shear turbulence suppression mechanism.. Authors: Kramer, Gerrit J. [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000151058139); Nelson, Andrew Oakleigh [Columbia Univ., New York, NY (United States)] (ORCID:0000000296121936); Thome, Kathreen E. [General Atomics, San Diego, CA (United States)] (ORCID:0000000248013922). DOE Contract: AC02-09CH11466; FC02-04ER54698; SC0022270. Subjects: electric fields; negative triangularity; plasma edge; positive triangularity; tokamak