Heat pulse propagation studies on DIII-D and the Tokamak Fusion Test Reactor

Sawtooth phenomena have been studied on DIII-D and the Tokamak Fusion Test Reactor (TFTR) [D. Meade and the TFTR Group, in Proceedings of the Internat ional Conference on Plasma Physics and Controlled Nuclear Fusion, Washingto n, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, pp. 9-24]. In the experiments the sawtooth characteristics were studied with f ast electron temperature (ECE) and soft x-ray diagnostics. For the first ti me, measurements of a strong ballistic electron heat pulse were made in a s haped tokamak (DIII-D) [J. Luxon and DIII-D Group, in Proceedings of the 11 th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Kyoto (International Atomic Energy Agency, Vienna, 1987), Vol. 1 , p. 159] and the "ballistic effect" was stronger than was previously repor ted on TFTR. Evidence is presented in this paper that the ballistic effect is related to the fast growth phase of the sawtooth precursor. Fast, 2 ms i nterval, measurements on DIII-D were made of the ion temperature evolution following sawteeth and partial sawteeth to document the ion heat pulse char acteristics. It is found that the ion heat pulse does not exhibit the very fast, "ballistic" behavior seen for the electrons. Further, for the first t ime it is shown that the electron heat pulses from partial sawtooth crashes (on DIII-D and TFTR) are seen to propagate at speeds close to those expect ed from the power balance calculations of the thermal diffusivities whereas heat pulses from fishbones propagate at rates more consistent with sawtoot h induced heat pulses. These results suggest that the fast propagation of s awtooth-induced heat pulses is not a feature of nonlinear transport models, but that magnetohydrodynamic events can have a strong effect on electron t hermal transport. (C) 2000 American Institute of Physics. [S1070-664X(00)02 012-7].