Use of a pattern recognition algorithm to obtain a parametrization of low-mode and high-mode plasma states

A pattern recognition algorithm has been used to identify a small set of plasma parameters which provide good discrimination between the low-mode (L-mode) and high-mode (H-mode) states in the DIII-D tokamak [J.L. Luxon, R. Anderson, F. Batty , in Proceedings of the 11th Conference on Plasma Physics and Controlled Fusion Research, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159]. The parameters studied were the electron temperature T-e, electron density n(e), electron pressure P-e and their gradients, evaluated in the region where the H-mode transport barrier forms, and the plasma current I-p and toroidal magnetic field B-T. The L-mode and H-mode states were found to separate well into a parameter space based on the temperature scale length T-e/delT(e) and the normalized temperature gradient delT(e)/I-p. These parameters provide a more reliable separation of the L- and H-states than do T-e and n(e). This parametrization provides constraints on theories and may provide insight into the physics of the L-H transition and of edge transport. (C) 2002 American Institute of Physics.