UK-based stealth-stage company developing compact reactor technology originally based on the patented Epicyclotron concept — pivoting toward neutron-source applications.
Crossfield Fusion is a UK-based fusion technology company founded in 2019 by James McKenzie and Chris Macdonald-Bradley, registered at 128 City Road, London. The company originally pursued a compact fusion reactor based on patented technology called the Epicyclotron, a closed-orbit system designed to confine ions at fusion-relevant energies using combined electric and magnetic fields in a compact geometry.[1]
The Epicyclotron was conceived as a velocity-resonant confinement system in which ions follow closed orbits within crossed electric and magnetic fields. The concept aimed to achieve fusion conditions in a device small enough to be factory-manufactured, roughly the size of a shipping container, targeting advanced fuel cycles that would minimize neutron production. A working device was built and tested in 2021.[1]
Following initial experimental testing and detailed modeling of loss mechanisms, Crossfield concluded that the Epicyclotron would not scale to deliver a net-gain fusion reactor as originally projected. The company has since redirected its technology toward near-term commercial applications as a high-output compact neutron source, with potential uses in radiotherapy, medical isotope production, and materials testing.[2]
The company's long-term vision still includes manufacturing compact fusion reactors with potential output of approximately 1 MWe or 2–3 MWth, though the path to net energy gain remains under development.[2]
Crossfield Fusion operates in stealth mode with limited public disclosure of its current technical direction, funding, or team size. The company is registered as active on UK Companies House. Its pivot from net-gain fusion to neutron-source applications represents a pattern seen in several early-stage fusion companies that find nearer-term commercial value in fusion-adjacent technologies.[3]