Abstract
Alfvénic activity has been observed in the TJ-II stellarator which resembles the frequency sweeping demonstrated by Alfvén cascade modes in tokamaks. A numerical validation study was conducted using a reduced magnetohydrodynamic (MHD) model to show that such modes could only have been observed in discharges where the rotational transform profile was non-monotonic. During experiments, coil current was varied which resulted in shifting of the minimum value of the rotational transform profile. To mimic this effect, we study the Alfvénic activity predicted by the reduced MHD model for a set of input rotational transform profiles with varying minima. A mode is found whose toroidal and poloidal mode numbers match those predicted in experiments which sweeps downward/upward in frequency as the minimum value of the rotational transform profile is increased/decreased. The results serve as a demonstration of the validity and utility of MHD spectroscopy.
| Original language | English |
|---|---|
| Article number | 036005 |
| Journal | Nuclear Fusion |
| Volume | 64 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 2024 |
Funding
We acknowledge financial support from the FusionCAT Project (001-P-001722) co-financed by the European Union Regional Development Fund within the framework of the ERDF Operation Program of Catalonia 2014–2020 with a grant of 50% of total cost eligible. We also acknowledge the collaboration and support of J.L. Depablos, A. Cappa, C. Hidalgo, K. McCarthy, F. Medina and the whole TJ-II team.
Keywords
- Alfvén cascades
- RSAE
- TJ-II
- reversed-shear Alfvén eigenmodes
