Abstract Details
Abstracts
Author: Jacob Halpern
Requested Type: Poster
Submitted: 2026-03-03 12:40:17
Co-authors: N. Logan, E. Paul, C. Paz-Soldan, M. Pharr, J. Cho, J. Lee, P. Lunia, D. Burgess, B. Lyons
Contact Info:
Columbia University
144 West 109th Street
New York, New York 10025
United States
Abstract Text:
A new open source code written entirely in Julia has been developed to calculate the vacuum energy response matrix associated with arbitrary perturbed displacements in both tokamak and stellarator equilibria. Previously, this calculation was only available in tokamaks or inflexibly within large closed source codes. In the tokamak framework, the code constructs this matrix via Green's second identity with a collocation discretization following the approach of Chance’s VACUUM code [Chance Phys. Plasmas 1997]. Our implementation reproduces the Chance fortran code’s 2D axisymmetric results while improving code modularity, numerical transparency, and runtime performance. We also extend this formulation to nonaxisymmetric geometries using a higher-order singular correction scheme [Malhotra et al. Plasma Phys. Control. Fusion 2019], enabling accurate evaluation of singular surface integrals on 3D boundaries. We present initial results of the axisymmetric energy calculations, benchmarking the results against the VACUUM code and showcasing our improvements. We further demonstrate error less than 0.1% between the axisymmetric vacuum response matrix and that of the 3D approach with an axisymmetric test case discretized as a 3D surface. Finally, we show convergence of the method with toroidal resolution for a representative 3D stellarator equilibrium. This code enables fast calculations of the perturbed vacuum energy for use in free boundary stability and perturbed equilibrium calculations.
Characterization: 1.0
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