On the influence of α-particle cyclotron damping on the lower hybrid current drive

Preliminary results are reported of investigating the effect of the cyclotron harmonic damping of lower hybrid waves by alpha particles produced in thermonuclear reactions. The quasilinear change of the slope of the alpha particle distribution function is considered. The presented analytical estimates show that the power absorbed by alpha particles can reach a saturation level, provided that the wave energy density is sufficiently high. For the parameters of a hypothetical hybrid reactor, the saturated power was found to be much lower than that computed in the linear theory. Thus, the alpha particles need not represent a serious obstacle to the lower hybrid current drive in hybrid reactors. Some further aspects of the effect in question are discussed. (J.U.)