Commonwealth Fusion Systems creates viable path to commercial fusion power with world’s strongest magnet
On Wednesday, Commonwealth Fusion Systems (CFS) and Massachusetts Institute of Technology (MIT) announced the successful test of the world’s strongest high-temperature superconducting (HTS) fusion magnet, saying that it will unlock the path to clean commercial fusion energy. So, what have they done and why does it matter?
What have they done?
They have constructed a large high-temperature superconducting electromagnet, which was ramped to a field strength of 20 tesla—a world record for a fusion magnet. The magnet weighs 10 tons and is in a D-shape as required for a tokamak magnet. It is representative of the size needed for their demonstration plant, SPARC.
Why is this result impressive?
Firstly, it's the highest field strength ever achieved for a high-temperature superconducting fusion magnet. Secondly, it is of a shape and scale relevant to the magnets that will be needed for CFS’s next tokamak fusion device. Private fusion company Tokamak Energy Ltd, also developing high-temperature superconducting magnet technology, announced a magnetic field of 24T from an HTS magnet in 2019. Also an impressive achievement, the Tokamak Energy magnet was at a smaller scale than this new CFS magnet and not in a D-shape.
Why is it important?
CFS/MIT say this advance paves the way for the creation of practical fusion power plants. Simulations suggest that the magnetic field of 20T is enough to enable CFS’s compact tokamak device SPARC to achieve net energy from fusion. Developing the new magnet was seen as the greatest technological hurdle to making that happen.
High-temperature superconductor (HTS) technology development is an important part of the fusion commercialisation pathway for magnetic confinement approaches. HTS magnets enable a much stronger magnetic field in a smaller space, which means that fusion machines could be made smaller (and therefore cheaper). A fusion device using HTS magnets could be 40 times smaller in volume than a machine using only conventional low-temperature superconducting magnets to achieve the same performance.
CFS CEO Bob Mumgaard: "What it does is allow us to build devices faster, smaller, and at less cost."
What’s next?
With the magnet technology now successfully demonstrated, CFS/MIT are on track to build the world's first fusion device (SPARC) that produces more energy than it consumes, targeted for completion in 2025. CFS has a site in Devens, Massachusetts, which will be the home of SPARC and a manufacturing facility for HTS magnets. They will start producing magnets next year. We look forward to hearing how they progress from this single magnet to the full set of tokamak, which could bring some further challenges due to the way that the magnetic fields interact and generate forces.
SPARC is a testbed to prove the CFS concept before construction of a full-size, fusion power-producing plant called ARC, which will be about twice the size of SPARC.