Abstract Details
Abstracts
Author: Sanket A. Patil
Requested Type: Poster
Submitted: 2024-04-12 22:57:49
Co-authors: Carl R. Sovinec
Contact Info:
University of Wisconsin-Madison
1500 Engineering Dr
Madison, WI 53706
United States
Abstract Text:
The recent success of stellarator optimization has generated possibilities for improved performance in stellarators. However, the feasibility of optimized plasma configurations is contingent on quiescent magnetohydrodynamic (MHD) behavior on transport scales. NIMSTELL [1] has been developed to address the need to model non-ideal MHD in stellarators computationally. Here, we present recent developments to improve computational efficiency for stellarator configurations with multiple field periods. NIMSTELL uses Fourier series in a generalized toroidal coordinate to represent the geometry, the equilibrium fields and the perturbed fields. Upon discretization of the poloidal plane using spectral elements, the linearized MHD equations form a large, sparse linear system for each Fourier component of the perturbed fields. These Fourier components are coupled due to the asymmetry of the equilibrium and the geometry. For faster convergence with an iterative solver, the linear system is preconditioned by solving directly the equations for subsets of Fourier components, called “bands.” Previously, each band could only include consecutive Fourier components. However, this is inefficient if a stellarator configuration has more than one field period, where the strongest coupling is not among consecutive harmonics. Thus, a new capability has been added where the Fourier components included in the preconditioning bands can be specified by the user based on periodicity-dependent coupling. Using this added capability, a tearing mode benchmark of NIMSTELL against JOREK and CASTOR3D has been completed for a set of W7-A configurations reported in [2]. The growth rates calculated by the three codes are in good agreement.
*Work supported by US DOE grants DE-SC0018642 and DE-FG02-99ER54546.
References:
[1] C. R. Sovinec and B. S. Cornille, BAPS 66(13), PP11.00092 (2021).
[2] N. Nikulsin, et al., Phys. Plasmas 29, 063901 (2022).
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