Abstract Details
Abstracts
Author: Xu Chu
Requested Type: Consider for Invited
Submitted: 2025-02-21 20:55:50
Co-authors: S.C.Cowley, N.Ferraro, F.I.Parra, Y.Zhou
Contact Info:
Princeton University/PPPL
100 Stellarator Rd.
Princeton, 08540
Mercer
Abstract Text:
Ballooning mode saturation is investigated in realistic stellarator configurations using the flux tube approach of Ham et. al.[1][2]. Numerical tools are implemented using the DESC[3] equilibrium solver. The lack of exact force balance in stellarator equilibrium solvers that assumes existence of nested flux surfaces poses difficulties in evaluating the nonlinear stability of the ballooning mode using the flux tube model. A variational approach for calculating flux tube energy is developed to overcome this force error problem in stellarator numerical equilibria. Saturated flux tube states that cross 10-20% of the plasma cross section are shown for linearly ballooning unstable profiles. Metastable saturated states are found in compact stellarator equilibrium close but below the marginal ballooning linear instability. This suggests that Edge-Localized-Mode-like explosive MHD behavior is possible in stellarators. A direct comparison of the flux tube structure in a full nonlinear MHD simulation of Wendelstein 7X [4] with the structure predicted by our model demonstrates good agreement. Saturated flux tube states may play an important role in the beta limits of stellarators.
[1] Ham C., Cowley S., Brochard G. and Wilson H. 2018 Plasma Physics and Controlled Fusion 60 075017
[2] Ham C., Cowley S., Brochard G. and Wilson H. 2016 Physical Review Letters 116 235001
[3] Panici D., Conlin R., Dudt D., Unalmis K. and Kolemen E. 2023 Journal of Plasma Physics 89 955890303
[4] Zhou Y., Aleynikova K., Liu C. and Ferraro N. 2024 Physical Review Letters 133 13510
This work was supported by US DOE Contract No. DE-AC02-09CH11466.
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