Observations of cold, high density plasma in the private flux region of the Alcator C-Mod divertor

Significant plasma density has been observed in the private flux zone of th e Alcator C-Mod tokamak. The behavior of the D-gamma emission profiles is c onsistent with the source of the plasma being due to an (E) over right arro w x (B) over right arrow drift generated by a poloidal temperature gradient . The plasma flux due to this drift is derived and evaluated. A plasma flux into the private flux zone is inferred by measurements of volumetric recom bination using a tangentially viewing CCD camera and several spectroscopic views observing the high n-lines of the D-0 Balmer series. For the case of an attached divertor the inferred plasma flux to the PFZ has a linear scali ng with respect to plasma pressure, as is expected from the temperature-gra dient-induced, (E) over right arrow x (B) over right arrow drift. (C) 2001 Elsevier Science B.V. All rights reserved.