Study of the absorption coefficient of alpha particles to lower hybrid waves in tokamak

Abstract

Part of the energy of the Lower Hybrid (LH) waves may be absorbed by the α particles via the so-called perpendicular landau damping mechanism, which depends on various parameters of fusion reactors and the LH waves. In this article, we calculate the absorption coefficient γα of LH waves due to α particles. Results show that, the γα increases with the parallel refraction index n∥ while deceases with increasing the frequency of LH waves ωLH over a wide range. Higher background plasma temperature and toroidal magnetic field will increase the absorption, and there is a peak value of γα when ne≈8×1019m−3 for ITER-like scenario. The thermal corrections to the cold plasma dispersion relation will change the damping rate to a certain extent under some specific conditions. We have also evaluated the fraction of LH power absorbed by the alpha particles, η ≈ 0.47% and 4.1% for an LH frequency of 5 GHz and 3.7 GHz respectively for ITER-like scenario. This work gives the effective reference for the choice of parameters of future fusion reactors.