Further rotation reversal studies in C-Mod L-mode plasmas

Studies of core toroidal rotation reversal phenomenology in C-Mod deuterium L-mode plasmas have been expanded to include details the dependences on plasma current and magnetic field. Rotation occurs at a critical density, universal scaling indicates that product ncritq95R ∼ BT/2, with ncrit 1020/m3, R m, BT T. Measurements H He exhibit similar behavior, including connection linear Ohmic confinement/saturated confinement transition cutoff for non-diffusive heat transport. Electron density ion cyclotron range frequencies power modulation experiments suggest collisionality ν* is unifying parameter. Strong impurity puffing causes increase, indicating situation more complicated than only collisionality, perhaps involving effects dilution temperature gradient mode stability.