High-density discharges in the Alcator tokamak

Peak plasma densities in excess of 10/sup 15/ cm/sup -3/ have been obtained in the Alcator tokamak with 60 < or = B/sub T/ < 85 kG. The highest average density so far achieved is n-bar/sub e/ = 6 x 10/sup 14/ cm/sup -3/; the corresponding n/sub 0/tau/sub E/ = 2 x 10/sup 13/ cm/sup -3/ s. These ultrahigh-density discharges exhibit (i) nearly complete energy equilibration between electrons and ions, (ii) severe attenuation of energetic--neutral-particle fluxes ,(iii) a minor role of impurities, and (iv) energy-confinement properties consistent with neoclassical estimates.