Simulation of a-Particle Redistribution due to Sawteeth on TFTR
Authors: Yi Zhao, Roscoe B. White
In recent Deuterium-Tritium experiments on the Tokamak Fusion Test Reactor (TFTR), both the Pellet Charge Exchange (PCX) [Phys. Rev. Lett. 75 , 846 (1995)], [Nucl. Fusion 35 , 1437 (1995) ] and the alpha Charge Exchange Recombination Spectroscopy (a-CHERS) [Phys. Rev. Lett. 75 , 649 (1995)] diagnostics indicate that sawtooth oscillations can cause signicant broadening of the fusion alpha radial density profile. We investigate this sawtooth mixing phenomenon by applying a Hamiltonian guiding center approach. A model of time evolution of the Kadomtsev-type sawtooth [Sov. J. Plasma Phys. 1 , 389 (1976)] is constructed. The presence of more than one mode in the nonlinear stage of the sawtooth crash is necessary to cause signicant broadening of the alpha density profile. Use of numerical equilibria allows us to perform detailed comparisons with TFTR experimental data. Our results are in reasonable agreement with a-CHERS and show a broadening of alpha particles similar to that seen in PCX measurements.