MEASUREMENTS OF FAST CONFINED ALPHAS ON TFTR

This Letter reports the first measurements of the fast confined alpha-particle energy distribution in a fusion plasma. The pellet charge exchange technique shows the fusion generated alpha's in the core of the Tokamak Fusion Test Reactor plasma slow down classically, and appear to be well confined. Preliminary indications are that stochastic ripple effects are responsible for steepening the energy distribution outside the plasma core (r/a greater than or similar to 0.35). Sawteeth mixing of fast alpha's is suggested in data during the post-beam-heating plasma decay.