Confinement and divertor studies in Alcator C - Mod

Early results from the Alcator C-Mod tokamak indicate that ohmic energy confinement does not obey the Neo-Alcator scaling. Instead 'Ohmic L-mode' confinement, close to ITER89-P, is obtained, which substantially exceeds Neo-Alcator under some circumstances. ICRF-heated plasmas follow the same scaling. H-modes are observed both in ohmic and ICRF heated plasmas, with confinement enhancements of about 2 for ELM-free conditions. Divertor operation into the closed chamber shows different regimes, depending on the density. Of particular interest is the progressive pressure detachment at moderate to high densities. Power to the divertor plates is generally low, reflecting the influence of strong radiation in the divertor. The scaling of parameters from Alcator's growing edge database is briefly summarized.