Stability and energy confinement of highly elongated plasmas in TCV
The operating space of the TCV tokamak has been extended to higher elongation, k = 2.8, and higher normalised current, IN = IP/aB = 3.6 MA/mT, than were previously attainable. This has been achieved by optimising the parameters of the vertical position control system and by optimising the plasma shape. Experimental current and beta limits were found to be consistent with ideal MHD stability calculations, using measured plasma shapes and profiles. The sawtooth period was measured as a function of elongation and sawtooth oscillations are found to disappear, at high elongation, when the internal inductance drops below li ~ 0.69. MHD events at high elongation have been analysed, using magnetic fluctuation measurements. The electron energy confinement time at high elongation, 2.2< k <2.7, shows a strong dependence on density and power flux through the plasma surface, but no statistically significant dependence on k. Finally, we have applied off-axis, second harmonic, X-mode electron cyclotron resonance heating (ECRH) in order to flatten the current profile and improve vertical stability. This gave access to previously inaccessible domains in k - IN space.
Bibliographic Reference: An article published in: Plasma Physics and Controlled Fusion 43 (December 2001) pp. A161-A173
Record Number: 200214426 / Last updated on: 2002-02-20
Original language: en
Available languages: en