title: Demonstration of effective control of fast-ion-stabilized sawteeth by electron-cyclotron current drive.
abstract: In a tokamak plasma, sawtooth oscillations in the central temperature, caused by a magnetohydrodynamic instability, can be partially stabilized by fast ions. The resulting less frequent sawtooth crashes can trigger unwanted magnetohydrodynamic activity. This Letter reports on experiments showing that modest electron-cyclotron current drive power, with the deposition positioned by feedback control of the injection angle, can reliably shorten the sawtooth period in the presence of ions with energies >or=0.5 MeV. Certain surprising elements of the results are evaluated qualitatively in terms of existing theory.
authors.affiliation: Association EURATOM-CEA, DSM/IRFM, CEA/Cadarache, 13108 St. Paul-lez-Durance, France.
authors.forename: M
authors.initials: M
authors.lastname: Lennholm
authors.forename: L-G
authors.initials: LG
authors.lastname: Eriksson
authors.forename: F
authors.initials: F
authors.lastname: Turco
authors.forename: F
authors.initials: F
authors.lastname: Bouquey
authors.forename: C
authors.initials: C
authors.lastname: Darbos
authors.forename: R
authors.initials: R
authors.lastname: Dumont
authors.forename: G
authors.initials: G
authors.lastname: Giruzzi
authors.forename: M
authors.initials: M
authors.lastname: Jung
authors.forename: R
authors.initials: R
authors.lastname: Lambert
authors.forename: R
authors.initials: R
authors.lastname: Magne
authors.forename: D
authors.initials: D
authors.lastname: Molina
authors.forename: P
authors.initials: P
authors.lastname: Moreau
authors.forename: F
authors.initials: F
authors.lastname: Rimini
authors.forename: J-L
authors.initials: JL
authors.lastname: Segui
authors.forename: S
authors.initials: S
authors.lastname: Song
authors.forename: E
authors.initials: E
authors.lastname: Traisnel