Improvements to an ion orbit loss calculation in the tokamak edge

Abstract

An existing model of collisionless particle, momentum, and energy ion orbit loss from the edge region of a diverted tokamak plasma has been extended. The extended ion orbit loss calculation now treats losses of both thermal ions and fast neutral beam injection ions and includes realistic flux surface and magnetic field representations, particles returning to the plasma from the scrape off layer, and treatment of x-transport and x-loss. More realistic flux surface geometry allows the intrinsic rotation calculation to predict a peaking in the profile closer to the separatrix, which is consistent with experiment; and particle tracking calculations reveal a new mechanism of "x-transport pumping," which predicts larger ion losses when coupling conventional ion orbit loss and x-loss mechanisms, though still dominated by conventional ion orbit loss. Sensitivity to these ion orbit loss model enhancements is illustrated by fluid predictions of neoclassical rotation velocities and radial electric field profiles, with and without the enhancements. Published by AIP Publishing.

Analysis of equilibrium and turbulent fluxes across the separatrix in a gyrokinetic simulation

“…The subject of neoclassical direct ion orbit losses and their contribution to the edge flows and electric fields has been treated substantially, both computationally and theoretically [43][44][45][46][47][48][49][50][51][52] . Here, we offer a new argument to support our claim that the potential structure at the LFS is due to the excursions of trapped ions on their banana orbits.…”

Experiment and simulation of ELM in NBI heated plasma on EAST tokamak

“…This can contribute to the increase of |E r | according to equation ( 4). Because the lack of detailed ion profiles on the edge in this shot, it is not clear whether the E r change in the edge is due to the influence of the toroidal rotation at the edge or the ion losses [25,26].…”

Extended fluid transport theory in the tokamak plasma edge

“…The calculation of the ion orbit loss fraction is discussed in [9][10][11][12][13], and this paper is concerned more with how to include these ion orbit loss fractions in a fluid model calculation. We have in mind low collisionality edge plasmas and did not include the additional ion orbit loss that would be associated with confined ions scattering into the loss cone.…”

“…There is also a similar loss of fast ions produced by neutral beam injection (nbi), which must be taken into account in calculating the source of thermalized ions [13] (and in calculating the alpha particles remaining in the plasma in future fusion plasmas).…”