"Excitation of flow-stabilized resistive wall mode in rotating tokamak plasmas"
Event details
| Date | 08.10.2014 |
| Hour | 10:30 › 11:30 |
| Speaker | Dr. Nobuyuki AIBA, Japan Atomic Energy Agency, J |
| Location |
PPB 019
|
| Category | Conferences - Seminars |
Magnetohydrodynamic (MHD) instability in rotating tokamak plasmas is found numerically for the first time. This instability is excited by the interplay between a resistive wall mode (RWM) and a stable MHD mode. When the plasma has a stable ideal MHD mode, a reversed shear Alfven eigenmode (RSAE) for example, this mode is Doppler-shifted by rotating the plasma. The MHD instability appears in the case that resistive wall surrounds the plasma and the Doppler-shifted mode frequency approaches to zero. After passing zero frequency, the unstable mode changes from RWM to a negative energy ideal MHD mode. This destabilization of MHD mode is basically the same as the coupling between unstable RWM and a stable ideal kink mode in a cylindrical plasma discussed by Lashmore-Davies etc.. In tokamaks, however, we found that not only an external kink mode but also many Alfven eigenmodes can become the counterparts of the coupling, and the excited mode can appear even when both RWM and ideal!
MHD mode are stable. The destabilization is also observed even when continuum damping and ion Landau damping effects affect the MHD stability. This result suggests that for steady state high beta tokamaks, like DEMO, it is necessary to shape the safety factor profile in such a way that no stable eigenmode exists in the band of rotation frequency.
MHD mode are stable. The destabilization is also observed even when continuum damping and ion Landau damping effects affect the MHD stability. This result suggests that for steady state high beta tokamaks, like DEMO, it is necessary to shape the safety factor profile in such a way that no stable eigenmode exists in the band of rotation frequency.
Practical information
- Informed public
- Free
Organizer
- Prof. P. Ricci
Contact
- Prof. P. Ricci