Electron cyclotron resonance heating of weakly relativistic plasmas

Electron cyclotron resonance heating of magnetically confined plasmas is examined with a new formalism which allows convenient evaluation of wave energy deposition in electron energy and momentum spaces, as well as in real space. The formalism applies to wave propagation in general directions in a weakly relativistic plasma. The special case of wave perpendicular to the magnetic field is examined analytically and illustrated with numerical case studies. In that analysis, a general magnetic field profile is assumed. For the mirror-type devices, it is shown that, in contrast to tokamak heating, efficient wave absorption is obtainable at electron temperatures as low as a few eV. For the tandem mirror which operates at a very high temperature, it is shown that electron cyclotron resonance heating (ECRH) results in either edge heating or formation of suprathermal electrons in the center. In comparison, it is shown that in the linear magnetic field profile of the tokamak, high electron temperature would actually favor heating of thermal electrons provided the wave is injected from the low magnetic field side.