title: Self-acceleration of a tokamak plasma during ohmic H mode
abstract: Core plasma rotation is observed to change from counter direction to co-current direction during the transition from low (L) to high (H) confinement mode, in Alcator C-Mod plasmas that are heated purely Ohmically and, hence, have no momentum input. The changes of the toroidal velocities, deduced independently from impurity Doppler measurements and from magnetic perturbations associated with sawteeth, agree. The magnitude of the change is consistent with the previously documented scaling for rotation in ion cyclotron rf-heated H modes. The rotation in this Ohmic experiment is obviously not an rf effect but demonstrates unequivocally a transport effect accelerating the plasma.
authors.affiliation: Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts.
authors.initials: IH
authors.lastname: Hutchinson
authors.initials: JE
authors.lastname: Rice
authors.initials: RS
authors.lastname: Granetz
authors.initials: JA
authors.lastname: Snipes