Systematic analysis of magnetic equilibrium reconstruction with eddy currents on LTX-<i>β</i>

Abstract Magnetic equilibrium reconstruction in the Lithium Tokamak Experiment-Beta (LTX- β ) is complicated by strong eddy currents and toroidal asymmetries arising from its segmented, close-fitting conducting shell. In the earlier experiment LTX, these three-dimensional (3D) conductor effects significantly distorted diagnostic signals and challenged conventional axisymmetric reconstruction methods. In this work, we demonstrate that accurate plasma equilibria can be recovered on LTX- β by incorporating a small number of dominant eddy current modes derived from realistic conductor models. Using the open-source TokaMaker Grad–Shafranov solver, we reconstruct equilibria across a systematically selected set of LTX- β discharges and validate them against the legacy PSI-Tri hybrid 2D-3D code. Our results show that fully 2D TokaMaker reconstructions achieve significantly improved agreement with flux loop and Mirnov probe measurements, reducing total chi-squared fitting errors, especially during startup. Finally, we develop new hybrid 2D-3D TokaMaker reconstructions by integrating the ThinCurr 3D eddy current model, which we optimize for significant further reduction of chi-squared in most scenarios. These findings underscore the importance of realistic wall-current modeling in short-pulse tokamaks, and establish a physics-based reconstruction framework that is extensible to devices with complex passive structures and 3D wall interactions.