Hephaestus Exits Stealth Having Raised $17.2M to Supply Rare-Earth-Free HTS Superconductors and Build Low-Cost Fusion Power

Hephaestus today emerged from stealth with solutions that address two of the largest cost drivers in fusion power: the high temperature superconducting (HTS) magnets that confine the plasma, and the edge-localized modes (ELMs – major plasma instabilities) that drive up the cost and complexity of conventional reactor designs. The company also announced the close of a new funding round led by CiRi Ventures.

Hephaestus was founded in London in 2019 with a single mission – to help make fusion energy cheap enough to compete on the grid. Its AI plasma solver initially swept the full space of tokamak design parameters, unconstrained by the legacy designs and materials much of the industry is already committed to, and identified negative triangularity (NT), which inverts the D-shaped plasma used in most tokamaks, as the most likely configuration for low-cost fusion energy.

Subsequent results from facilities worldwide, including the DIII-D, JET, and SMART, have shown that NT can deliver strong performance without ELM instabilities.

In February 2021, Antoine Pochelon joined as co-founder and Head of the Experimental Campaign. Dr. Pochelon spent decades at EPFL, producing many of negative triangularity's foundational experimental results, and is among the field’s leading authorities on NT physics.

The company has already moved into hardware. Its first device, Anvil 0, the world's first tokamak designed for NT from inception, was completed in 2024.

Hephaestus has applied the same AI-first approach to fusion's largest capital cost and biggest bottleneck to scale: the HTS magnets that confine the plasma. Using its proprietary AI materials discovery platform, MaDi-AI, the company has identified, manufactured, and characterized at lab scale multiple novel HTS materials, validated by the UK's National Physical Laboratory.

Every HTS magnet in fusion today is made from REBCO (rare-earth barium copper oxide), a superconductor whose manufacture is slow, expensive to scale, and concentrated in regions of geopolitical risk. Hephaestus is developing rare-earth-free HTS materials that are more affordable, more scalable and far less exposed to geostrategic bottlenecks than REBCO, positioning the company as a foundational supplier to the wider fusion sector as well as a fusion energy provider in its own right.

The new funding will accelerate two critical milestones: HTS manufacturing at its new 70,000 ft² New Jersey facility starting in 2027 and, by 2030, a demonstration of NT's commercial advantages in a net gain demonstration reactor (Q>1). Existing investors include Prescience Ventures, Teampact Ventures, Climate Capital, Unruly Capital, and CiRi Ventures.

“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,” said Jack Zamattio, CEO and founder of Hephaestus. “That’s why we chose negative triangularity, and why we're manufacturing our own novel HTS magnets, to realise fusion’s full industrial potential.”

Hephaestus has already opened early-access discussions with fusion developers seeking HTS supply, and is actively hiring across its New Jersey, London, and Rome sites.

About Hephaestus

Hephaestus is commercializing fusion energy through HTS magnet manufacturing and negative triangularity plasmas. Founded in London in 2019, the company has offices in London, Rome and New York and a large production facility in New Jersey.

Website

www.hephaestus.energy

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