Changes in ion orbit loss, intrinsic rotation, and particle pinch across the L-H transition in DIII-D plasmas

Abstract

Some thermalized ions flowing slowly radially outward have sufficient energy to access loss orbits which allow them to free stream out of the confined plasma region and become ion orbit lost (IOL). Ions flowing in the counter-current (ctr-$I_{p}$) direction are more readily lost, exerting a net torque on the ions in the co-current direction. A particle-momentum-energy balance analysis, including the effects of IOL, was performed on three similar DIII-D discharges. After the L-H transition, the intrinsic rotation due to IOL decreases for a short time in the plasma edge near the separatrix. For 1 of the 3 discharges, there is a corresponding decrease in the measured carbon rotation in the edge. For all of the discharges, the electromagnetic pinch velocity went from weakly inward in L-mode to strongly inward in H-mode near the separatrix.