Influences of Charged Fusion Products on the Low-Frequency Gradient Instabilities in a Thermonuclear Plasma

Abstract

In spite of their small relative number, the high energy charged fusion products in a thermonuclear plasma, e.g. , the α-particles form D-T reactions, can have certain influences on the dispersion characteristics of the plasma. In this paper, low-frequency gradient modes (drift waves) in a uniform magnetic field is considered in the electrostatic approximation taking the relative number Δ= n α / n e (≪1) and the relative gradient ρ=∇ln n α /∇ln n e (| ρ|∼1) as parameters, where n α and n e are the density of α-particles and electrons, respectively. It is found that in the normal case with ρ> 0, the α-particles act to enhance/reduce the stability in the kinetic/hydrodynamic regime of density-gradient modes at small values of the perpendicular wavenumber; the contrary holds for the rather peculiar case of ρ< 0. The α-particles have no significant direct effects on the temperature-gradient modes.