SIMULATION OF ALPHA-PARTICLE REDISTRIBUTION DUE TO SAWTEETH ON THE TOKAMAK FUSION TEST REACTOR

In recent deuterium-tritium experiments on the Tokamak Fusion Test Rea ctor (TFTR), both the pellet charge exchange (PCX) [Phys. Rev. Lett. 7 5, 846 (1995); Nucl. Fusion 35, 1437 (1995)] and the alpha charge exch ange recombination spectroscopy (alpha-CHERS) [Phys. Rev. Lett. 75, 64 9 (1995)] diagnostics indicate that sav;tooth oscillations can cause s ignificant broadening of the fusion alpha radial density profile. Inve stigation of this sawtooth mixing phenomenon was performed by applying a Hamiltonian guiding center approach. A model of time evolution of t he Kadomtsev-type sawtooth [Sov. J. Plasma Phys. 1, 389 (1976)] is con structed. The presence of more than one mode in the nonlinear stage of the sawtooth crash is necessary to cause significant broadening of th e alpha density profile. Use of numerical equilibria allows us to perf orm detailed comparisons with TFTR experimental data. The simulation r esults are in reasonable agreement with alpha-CHERS and show a broaden ing of alpha particles similar to that seen in PCX measurements. (C) 1 997 American Institute of Physics.