Numerical studies of current generation by radio-frequency traveling waves

TLDR

Injecting radio‑frequency traveling waves into a tokamak can continuously generate toroidal electron currents. The authors numerically solve a two‑dimensional Fokker–Planck equation with a quasi‑linear term and compare the results to Fisch’s one‑dimensional analytic model, which predicts reduced plasma resistivity for high‑phase‑velocity waves. Two‑dimensional velocity‑space effects lower the power‑to‑current ratio by about 40%, enhancing the appeal of steady‑state tokamak reactors using this current‑generation technique.

Abstract

By injecting radio-frequency traveling waves into a tokamak, continuous toroidal electron currents may be generated. This process is studied by numerically solving the two-dimensional Fokker–Planck equation with an added quasi-linear term. The results are compared with the one-dimensional analytic treatment of Fisch, which predicted a reduced plasma resistivity when high-phase-velocity waves are employed. It is shown that two-dimensional velocity space effects, while retaining the predicted scaling, further reduce the ratio of power dissipated to current generated by about 40%. These effects enhance the attractiveness of steady-state tokamak reactors utilizing this method of current generation.