Verifying Improved Particle Trapping in Negative Triangularity Plasmas

Negative triangularity plasmas offer improved core confinement, lower impurity retention, and inherent edge stability, making them a potentially attractive choice for a tokamak reactor solution. This study seeks to verify improved particle trapping in negative triangularity plasmas; namely, that negative triangularity plasmas have a higher fraction of particles bouncing in the good-curvature region, which improves core confinement. We also investigate the effect of elongation on the good-curvature trapped fraction. Both of these factors are studied using Bounce, a particle orbit code, to generate paths of individual particles with a variety of energies and initial velocities. The path data is passed through a sorting algorithm to determine whether the particle is passing or bouncing and if it bounces in the good or bad curvature region of the plasma. Negative triangularity plasmas are found to have a higher good-curvature trapped particle fraction than their positive triangularity counterparts, whereas elongation does not have a significant impact.