Demonstration of effective control of fast-ion-stabilized sawteeth by electron-cyclotron current drive.
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.
Lennholm
M
M
Association EURATOM-CEA, DSM/IRFM, CEA/Cadarache, 13108 St. Paul-lez-Durance, France.
Eriksson
L-G
LG
Turco
F
F
Bouquey
F
F
Darbos
C
C
Dumont
R
R
Giruzzi
G
G
Jung
M
M
Lambert
R
R
Magne
R
R
Molina
D
D
Moreau
P
P
Rimini
F
F
Segui
J-L
JL
Song
S
S
Traisnel
E
E