Local variables affecting H-mode threshold on Alcator C-Mod

Abstract

An edge temperature threshold for the L-H transition is found on the Alcator C-Mod tokamak. The critical temperature depends weakly on density and increases with and with unfavourable drift direction. at the H-L transition can be greater than or equal to the L-H threshold. Magnetic fluctuations are observed at some H-L transitions. Measured parameters are compared with H-mode theories, including nonlinear drift-ballooning code simulations.