Hephaestus, a London-based fusion energy company founded in 2019, has emerged from stealth with a dual strategy to reduce the largest cost drivers in fusion power: high-temperature superconducting magnets and major plasma instabilities. The company also announced the close of a new funding round led by CiRi Ventures, bringing its total raised to US$17.2 million. The funding will support manufacturing and a net gain demonstration reactor planned for 2030.
A Dual Track Strategy for Lower Cost Fusion
Hephaestus was founded in London in 2019 with a mission to make fusion energy cheap enough to compete on the grid. The company applied an AI plasma solver to evaluate the full tokamak design space without legacy constraints. That process identified negative triangularity, which inverts the D-shaped plasma used in most tokamaks, as the most likely configuration for low-cost fusion energy.
Funding and Investor Support
The latest round was led by CiRi Ventures. Existing investors include Prescience Ventures, Teampact Ventures, Climate Capital, Unruly Capital, and CiRi Ventures. The new capital will help Hephaestus move toward two critical milestones: HTS magnet manufacturing in New Jersey from 2027 and a net gain demonstration reactor by 2030.
Scientific Validation for Negative Triangularity
Results from facilities worldwide, including DIII-D, JET, and SMART, have demonstrated that negative triangularity can deliver strong performance without edge localized modes, or ELMs. ELMs are major plasma instabilities that increase cost and complexity in conventional reactor designs. By avoiding them, the company believes its approach can simplify reactor engineering and reduce overall system cost.
Anvil 0 and Experimental Leadership
In February 2021, Antoine Pochelon joined as co-founder and Head of the Experimental Campaign. Dr. Pochelon spent decades at EPFL and produced many of negative triangularity's foundational experimental results. Hephaestus completed Anvil 0 in 2024, which it describes as the world's first tokamak designed for negative triangularity from inception.
Rare-Earth-Free HTS Superconductors
Hephaestus has also applied its AI-first approach to fusion's largest capital cost: the high temperature superconducting magnets that confine the plasma. The company used its proprietary MaDi-AI materials discovery platform to identify, manufacture, and characterize multiple novel HTS materials at lab scale. These materials were validated by the UK's National Physical Laboratory and are intended to replace rare-earth barium copper oxide, or REBCO.
Manufacturing and Supply Ambitions
Today's HTS magnets rely on REBCO, a superconductor that is slow and 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 less exposed to geostrategic bottlenecks. The company has opened early-access discussions with fusion developers seeking HTS supply and is actively hiring across its New Jersey, London, and Rome sites.
Next Milestones Toward Net Gain
The new funding will accelerate HTS manufacturing at a 70,000 square foot New Jersey facility starting in 2027. By 2030, the company plans to demonstrate the commercial advantages of negative triangularity in a net gain demonstration reactor with Q greater than 1. This timeline positions Hephaestus as both a potential fusion energy provider and a foundational supplier to the wider fusion sector.
Hephaestus is betting that negative triangularity and rare-earth-free superconducting magnets can remove two major obstacles to grid competitive fusion energy. With a new funding round led by CiRi Ventures, the company now has US$17.2 million in total funding to advance its manufacturing and demonstration goals. If successful, its approach could lower costs across the fusion industry while helping to deliver clean, stable power at scale.