$17.2m · Other round · Energy · London, UK
London-founded fusion company Hephaestus has raised $17.2m in funding in a round led by CiRi Ventures. According to the funding announcement, the capital will support rare-earth-free high-temperature superconducting magnet manufacturing at a new 70,000 sq ft New Jersey facility from 2027 and development of a negative-triangularity reactor intended to demonstrate net energy gain by 2030.
Turning a reactor bottleneck into a supplier business
Hephaestus is pursuing two connected products. Its MaDi-AI materials platform screens superconducting compounds computationally before lab work, and the company says it has manufactured and characterised several candidates at lab scale, with validation by the UK's National Physical Laboratory. In parallel, it is designing tokamaks around negative triangularity, an inverted plasma shape intended to avoid costly edge-localised instabilities. The company says its first device, Anvil 0, was completed in 2024 and successfully produced and shaped plasma, although it was an engineering pathfinder rather than an energy-producing reactor.
The commercial logic is to treat the magnet as a product, not only as a component of Hephaestus's own future power plant. The company says fusion developers are already in early-access discussions for HTS supply. If those discussions turn into qualified orders, magnet sales could create an earlier customer pathway than waiting for the full reactor programme, while giving Hephaestus manufacturing feedback from multiple designs. That strategy also makes the 2027 factory milestone important: lab-scale material performance must become repeatable production before the supplier model can generate revenue.
Two milestones, two execution tests
The funding therefore backs two different technical transitions. For the magnet business, Hephaestus must scale candidate materials beyond laboratory characterisation and produce them consistently enough for fusion customers to design around. For its reactor platform, it must progress from Anvil 0's shaped-plasma work to a machine capable of testing whether negative triangularity delivers the promised performance and cost advantages at a much more demanding scale.
Hephaestus says current fusion magnets rely on REBCO, a rare-earth barium copper oxide whose supply is costly and concentrated. A rare-earth-free alternative could reduce both material cost and supply-chain exposure, but the announced manufacturing start and 2030 net-gain target remain forward plans. The value of this round will be measured by whether the company can industrialise the material and validate the reactor architecture on those timelines.
