On the formation of edge electric fields in negative triangularity plasmas

Abstract 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mstyle displaystyle="false" scriptlevel="0"> <mml:mtext> </mml:mtext> <mml:mrow> <mml:mrow> <mml:mi mathvariant="bold-italic">E</mml:mi> </mml:mrow> <mml:mo>×</mml:mo> <mml:mrow> <mml:mi mathvariant="bold-italic">B</mml:mi> </mml:mrow> </mml:mrow> </mml:mstyle> </mml:mrow> </mml:math> flow shear turbulence suppression mechanism.