High confinement dissipative divertor operation on Alcator C-Mod

Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] has o perated a High-confinement-mode (H-mode) plasma together with a dissipative divertor and low core Z(eff). The initially attached plasma is characteriz ed by steady-state enhancement factor, H-ITER89P [P. N. Yushmanov et al., N ucl. Fusion 30, 1999 (1990)], of 1.9, central Z(eff) of 1.1, and a radiativ e fraction of similar to 50%. Feedback control of a nitrogen gas puff is us ed to increase radiative losses in both the core/edge and divertor plasmas in almost equal amounts. Simultaneously, the core plasma maintains H-ITER89 P of 1.6 and Z(eff) of 1.4 in this nearly 100% radiative state. The power a nd particle flux to the divertor plates have been reduced to very low level s while the core plasma is relatively unchanged by the dissipative nature o f the divertor. (C) 1999 American Institute of Physics. [S1070-664X(99)9330 5-0].