Pedestals and confinement in Alcator C-Mod H-modes

The study of H-mode regimes, pedestal conditions and confinement is a focus of research on the Alcator C-Mod tokamak. In addition to the usual ELM-free regime, a new regime has been observed on C-Mod which has good energy confinement but lower particle and impurity confinement, named the "Enhanced D-alpha (EDA) H-mode" for one of its signatures [1]. This mode can be steady-state and usually has no discrete ELMs, making it potentially attractive for a reactor. Since the main changes in H-mode are in the plasma edge region, measurements of the pedestal are critical to this study. New, high resolution diagnostics and profiles are described below.