  A novel channel for fuel ions heating in tokamak core plasma is proposed and
analyzed using nonlinear gyrokinetic theory. The channel is achieved via
spontaneous decay of reversed shear Alfven eigenmode (RSAE) into low frequency
Alfven modes (LFAM), which then heat fuel ions via collisionless ion Landau
damping. The conditions for RSAE spontaneous decay are investigated, and the
saturation level and the consequent fuel ion heating rate are also derived. The
channel is expected to be crucial for future reactors operating under reversed
shear configurations, where fusion alpha particles are generated in the tokamak
core where the magnetic shear is typically reversed, and there is a dense RSAE
spectrum due to the small alpha particle characteristic dimensionless orbits.
