Harnessing Multiphysics Modeling for Fusion Energy: The General Fusion & COMSOL story
The pursuit of fusion energy – a clean, sustainable power source - is one of the defining scientific challenges of our time. General Fusion is tackling this challenge with a unique approach: Magnetized Target Fusion (MTF). This innovative method relies on compressing a spherical tokamak plasma to the extreme conditions necessary for fusion. But achieving controlled, efficient compression requires refined modeling and simulation. This is where COMSOL Multiphysics® comes into play, playing a pivotal role in General Fusion’s LM26 fusion demonstration project, operational since February 2025.
The Challenge of Magnetized Target Fusion
MTF differs from other fusion approaches, like tokamaks and stellarators, in its method of compression. Instead of solely relying on magnetic fields, MTF utilizes a physical liner – in General Fusion’s case, liquid lithium – to rapidly compress the plasma. This creates a high-density, high-temperature environment conducive to fusion reactions. However, modeling this complex interplay of physics presents important hurdles.
Specifically, accurately predicting the behavior of the lithium liner under immense pressure, coupled with the dynamic magnetic fields and heat transfer within the plasma, demands a powerful multiphysics simulation tool. Furthermore, real-world experiments introduce uncertainties in material properties and operating conditions that must be accounted for.
COMSOL Multiphysics: A Key enabler for LM26
General Fusion initially leveraged COMSOL® to model the magnetomechanical compression of small-scale lithium rings and cylinders. These 2D axisymmetric models integrated nonlinear solid mechanics, magnetic field interactions, and heat transfer. Crucially, these simulations weren’t conducted in isolation.
The team rigorously validated the COMSOL models against experimental data obtained through high-speed imagery and laser diagnostics. This validation process built confidence in the simulation results and allowed them to accurately define the design and operating parameters of the full-scale LM26 compressor.
Solving the Inverse Problem: Reconstructing Reality with Bayesian Inference
A central difficulty in MTF is the need to adjust plasma equilibrium characteristics and lithium liner model parameters during a compression shot. Traditional material testing provided a limited dataset, insufficient to cover the full range of conditions experienced within LM26. To overcome this limitation, General Fusion implemented a sophisticated Bayesian inference reconstruction process.
Here’s how it works:
- Parametric Sweep: A series of COMSOL Multiphysics models were run,systematically varying key parameters related to the lithium liner’s compression.
- Experimental Constraints: The simulation results were constrained by real-time experimental measurements from LM26, specifically structured light reconstruction (SLR) and photon Doppler velocimetry (PDV). these techniques provide precise data on the liner’s shape and velocity.
- Inverse Problem Solution: the Bayesian inference algorithm identified the model parameters that best matched the experimental observations, effectively ”reconstructing” the actual compression sequence.
- Magnetic Flux Boundary Conditions: This reconstruction process yielded precise magnetic flux boundary conditions, which were then fed into internal Grad-Shafranov magnetohydrodynamic (MHD) solvers.
- Plasma Equilibrium & Density Profiles: the MHD solvers, in turn, reconstructed the plasma equilibrium and persistent the plasma density profiles necessary for calculating its temperature.
this innovative approach allows General Fusion to refine their understanding of the complex physics at play and optimize the LM26 system for maximum performance.
The Path to 1 keV and Beyond
This work is not merely academic. General Fusion is actively working to achieve a plasma temperature of 1 keV within LM26,with an enterprising future goal of reaching 10 keV – the threshold for sustained fusion reactions. The accurate modeling capabilities provided by COMSOL Multiphysics are instrumental in achieving these milestones. By bridging the gap between simulation and experiment, General Fusion is accelerating the advancement of a viable fusion energy solution.
Frequently Asked Questions About COMSOL and Fusion Modeling
Q: What is COMSOL Multiphysics used for in fusion research?
A: COMSOL Multiphysics is used to model the complex interplay of physics involved in fusion, including magnetomechanics, heat transfer, and plasma behavior. It helps researchers design and optimize fusion devices like General Fusion’s LM26.
Q: How does General Fusion validate its COMSOL models?
A:
