Review of current drive theory: selected topics

Two themes in current drive theory in tokamaks are reviewed, both relevant to the progression of tokamak experiments toward the reactor regime. The author reviews the understanding of the physics of tail electrons. These electrons are capable of carrying enormous RF-driven electric current, and, in the course of current-drive experiments worldwide not only has the current drive effect been demonstrated, but the underlying physical description of these tail electrons has been established. Anticipating the presence of the energetic alpha particles that result from D-T reactions in a reactor, the author examine's certain mechanisms through which these alpha particles can be used to facilitate current-drive.