Stability analysis of the ideal internal kink mode in a toroidally rotating tokamak plasma with ultra flat q profile
2004 (English)In: 12th International Congress on Plasma Physics, October 25 - 29 2004, Nice, France, 2004, P1-090 p.Conference paper (Refereed)
The ideal MHD stability of the m = n = 1 internal kink, or “quasi-interchange” mode in a toroidally rotating tokamak plasma with the safety factor q ≈ 1 within a wide area in the plasma core is analysed. It is shown that rigid, toroidal rotation stabilizes this mode if the rotation frequency (Omega) is larger than a critical frequency Omega-crit. Unless the plasma pressure and the radial extent of the region with ultra flat q both are rather large, rotation frequencies of the order of a few percent of the Alfvén frequency are found to be sufficient to stabilize the quasi-interchange mode. The stabilization is caused by the nonuniform plasma density and associated Brunt-Väisälä frequency created by the centrifugal force. When Omega exceeds Omega-crit, the quasi-interchange instability transforms into a stable oscillation with a frequency close to the lowest Brunt-Väisälä frequency in the region with ultra flat q. This stabilizing mechanism may be of interest for the interpretation of tokamak discharges in the “hybrid scenario”, and in discharges in the spherical tokamak NSTX where stabilization of the internal kink mode by toroidal rotation has been observed.
Place, publisher, year, edition, pages
2004. P1-090 p.
IdentifiersURN: urn:nbn:se:uu:diva-70685OAI: oai:DiVA.org:uu-70685DiVA: diva2:98596