Neutral injection heating of a tokamak plasma. Theory and experiment

A powerful beam of neutral hydrogen is injected tangentially into the plasma produced in the Cleo-Tokamak apparatus. The effect on the macroscopic parameters of the plasma and on the equilibrium are found to be small. The energy spectrum of the resulting fast ions contained in the plasma is deduced from measurements of tangentially emitted charge-exchange neutrals. The results for injection parallel and anti-parallel to the plasma current are compared with a classical theoretical model, and good agreement is obtained. Measurements of the perpendicular energy spectrum of ''plasma ions'' show that the bulk of the ions are heated by about 10 %, and that the low-energy ion distribution has a 'tail', which is consistent with the spectrum of decelerated injected ions