Hephaestus has emerged from stealth after raising $17.2 million to advance rare-earth-free high-temperature superconducting materials and develop a fusion reactor based on negative triangularity plasma geometry. The latest funding round was led by CiRi Ventures, with existing investors including Prescience Ventures, Teampact Ventures, Climate Capital, Unruly Capital, and CiRi Ventures.
Founded in London in 2019, Hephaestus is focused on reducing two significant cost and scalability challenges associated with fusion power: the high-temperature superconducting magnets used to confine plasma and edge-localized modes, or ELMs, that can increase the complexity and cost of conventional tokamak designs.
The company used an AI-based plasma solver to evaluate a broad range of tokamak design parameters and identified negative triangularity as a potentially lower-cost configuration. Negative triangularity reverses the conventional D-shaped plasma geometry used in many tokamaks.
Hephaestus said subsequent results from research facilities including DIII-D, JET, and SMART have demonstrated that negative triangularity can provide strong plasma performance without ELM instabilities.
The company moved into hardware development with Anvil 0, which it completed in 2024. Hephaestus describes the device as the world’s first tokamak designed specifically for negative triangularity from its inception.
Hephaestus is also developing high-temperature superconducting materials using its proprietary MaDi-AI materials discovery platform. The company said it has identified, manufactured, and characterized multiple novel HTS materials at laboratory scale, with validation from the U.K.’s National Physical Laboratory.
Most HTS magnets currently used in fusion rely on REBCO, or rare-earth barium copper oxide. Hephaestus is developing alternatives that do not use rare-earth materials, with the goal of making superconductors less expensive to manufacture, easier to scale, and less dependent on geographically concentrated supply chains.
The new funding will support the company’s next major milestones. Hephaestus plans to begin HTS manufacturing at a new 70,000-square-foot facility in New Jersey in 2027.
By 2030, the company is targeting a demonstration of the commercial potential of negative triangularity through a net-energy-gain reactor designed to achieve Q greater than 1.
Hephaestus has also begun early-access discussions with other fusion developers interested in sourcing its HTS technology. The company is expanding hiring across its New Jersey, London, and Rome locations as it builds both its materials manufacturing capabilities and fusion development program.
KEY QUOTES:
“Fusion has the potential of adding tens of GW’s per year of clean stable power to the grid, but that only happens if it becomes affordable and scalable. That’s why we chose negative triangularity, and why we’re manufacturing our own novel HTS magnets, to realise fusion’s full industrial potential.”
Jack Zamattio, CEO And Founder Of Hephaestus
