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 et al., 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 Te, electron density ne, electron pressure Pe and their gradients, evaluated in the region where the H-mode transport barrier forms, and the plasma current Ip and toroidal magnetic field BT. The L-mode and H-mode states were found to separate well into a parameter space based on the temperature scale length Te/∇Te and the normalized temperature gradient ∇Te/Ip. These parameters provide a more reliable separation of the L- and H-states than do Te and ne. This parametrization provides constraints on theories and may provide insight into the physics of the L–H transition and of edge transport.