Absorption of lower hybrid slow waves by fusion alpha particles

Abstract

The absorption of lower hybrid slow (LHS) waves in a thermonuclear plasma is investigated by accounting for both (self-consistent) quasi-linear electron Landau damping and (linear) absorption by fusion alpha particles. The full cold plasma wave dispersion properties are taken into account. A cylindrical geometry is adopted and it is assumed that the poloidal component of the wave vector can be disregarded. Analytical expressions for both absorption coefficients are presented, with emphasis on the case where the parallel refractive index of the LHS wave is near the accessibility value. In this case, electromagnetic effects are important. Numerical results for the profile of the radial power deposition on both electrons and alpha particles as well as the driven current density are given and discussed for parameters typical of a NET-like plasma. In particular, the fraction of the power absorbed by the alpha particles is evaluated. Conditions which ensure the absence of wave absorption by alpha particles are discussed.