On excitation of a trapped ion mode in a tokamak with a group of fast particles

The possibility of exciting the mode on trapped ions in a tokamak with injection of fast neutral atoms and in a thermonuclear tokamak-reactor containing reaction product, i.e. α-particles, is considered. The destabilizing effect of a high-energy ion beam is due to resonance interaction of the wave with trapped beam particles in which the wave frequency in the drifting-banana reference system coincides with the harmonic of the oscillation frequency of a trapped ion. The instability increment is calculated. It is concluded that the mode on trapped ions in a tokamak with injection is stable and that it can be excited in a tokamak-reactor at the relative α-particle density exceeding 10-3