A confined alpha particle diagnostic using pellet injection is proposed. The alpha particle density can be obtained from the number of decaying photons emitted from the radiative decay of He+* (n ≥ 2) ions produced through the one-electron transfer reaction of an alpha particle by a probing ion ablated from the pellet before it is fully ionized. The counting rate, estimated using theoretical cross-sections, and the calculated pellet ablation rate are sufficient for observation against the bremsstrahlung background. The alpha particle velocity distribution can also be obtained from the Doppler broadening of the emission lines.
Alpha particle physics experiments in the Tokamak Fusion Test Reactor