New Techniques for Studying Some Effects of Suprathermal Alpha Particles

Phase-space grouping techniques have been applied to two distinct problems in fusion product physics: (a) slowing down drift motion of highly energetic alpha particles in a symmetric toroidal field, and (b) first wall loading by 3.52-MeV alpha particles resulting from magnetic ripple. In the former, a weighted energy-loss approximation method permits the evolving orbits to be determined for any representative phase-space group. This enables rapid computation of several important suprathermal effects in a tokamak plasma. For example, code SYMALF, which embodies this idea, is applied to plasma heating and alpha-particle thermalization source problems. In the ripple field case, a probabilistic density function is employed to determine drift losses associated with ripple-trapped, 3.52-MeV alpha particles. When used to determine 3.52-MeV alpha-particle wall loadings, code RIPALF, which is based on this probability function, predicts the position of local “hot spots” along the first wall.