A generalized condition is derived for the velocity-space distribution of suprathermal alpha-particles to be monotonically decreasing with energy – and hence stable to homogeneous plasma instabilities – during the heating phase of a tokamak reactor. This stability condition is easily satisfied for presently envisaged neutral-injection heating of reactors, but may be violated in strong heating of smaller plasmas or during fast compressional heating.
Tokamak Fusion Test Reactor D-T results