Basic Fusion’s Magnetized Goal Fusion strategy includes compressing a spherical tokamak plasma to realize fusion circumstances. This presentation will element how the COMSOL Multiphysics® software program was used within the LM26 fusion demonstration, which has been in operation since February 2025. Initially, COMSOL® was used to mannequin the magnetomechanical compression of small-scale lithium rings and cylinders. These 2D axisymmetric fashions, which coupled the nonlinear stable mechanics, magnetic discipline, and warmth switch modules, had been validated towards high-speed imagery and laser diagnostics from these experiments. The validated fashions had been then instrumental in defining the LM26 compressor design and working circumstances.
A central problem is that plasma equilibrium traits and lithium liner mannequin parameters have to be adjusted throughout a compression shot. Whereas some materials testing was carried out on lithium samples in stress and compression, the investigated vary was inadequate to cowl all of the experimental circumstances of LM26. To beat this, a Bayesian inference reconstruction course of was used to resolve an inverse downside. This course of started by recreating the lithium liner’s compression sequence utilizing a parametric sweep of COMSOL Multiphysics fashions, which had been constrained by experimental structured mild reconstruction (SLR) and photon doppler velocimetry (PDV) measurements in LM26. This technique enabled Basic Fusion to supply exact magnetic flux boundary circumstances to inside Grad–Shafranov magnetohydrodynamic (MHD) solvers. The MHD solvers, in flip, had been used to reconstruct the plasma equilibrium and decide the plasma density profiles wanted to calculate its temperature. This work is essential, as Basic Fusion goals to have LM26 attain a plasma temperature of 1 keV, with a future aim of 10 keV.
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