Build fusion plants small and modular enough (50-500 MW) to sit at a factory or data centre and supply heat and power on site, using a simple old fusion geometry made workable by new superconducting magnets.
ResearchStage 1 of 5
WHAM running at 17 T; CFS magnet deal signed; Madison R&D site; pilot plant mid-2030s.
Updated 15 Jul 2026·Checked 11 Oct·0 updates this week
Milestones
Next · Prototype mirror system operating
ARPA-E funds WHAM at UW-Madison, MIT and CFS ($10M)2020Complete.
Realta spins out of the WHAM project2022Complete.
Launches with $12M: Khosla-led seed plus DOE award31 May 2023Complete.
WHAM first plasma at a record 17 tesla15 Jul 2024Complete.
$36M Series A led by Future Ventures13 May 2025Complete.
CFS to supply HTS magnets for prototypes and plants2 Apr 2026Complete.
Direct energy conversion demonstratedJun 2026Complete.
Madison headquarters and R&D site chosen15 Jul 2026Complete.
Prototype mirror system operatingTarget 2028Current milestone.
Q4 2026Construction of Madison R&D facility begins (next)
2028Prototype mirror system operating
Current obstacles
Scale-up from WHAMWHAM proved the magnets; it has not shown fusion-relevant plasma performance. The prototype must show far better confinement.
CapitalVenture equity so far is about $45M; the CEO says the company still has significant capital needs for its prototype and pilot plant.
Physics limits
Open ends always leakParticles that collide and end up moving along the field lines slip through the ends; confinement depends on the end magnets and electric plugs, never on a closed loop.
Magnets near a hot plasmaSuperconducting magnets must stay at cryogenic temperatures metres from a plasma of tens of millions of degrees and its neutrons, which needs heavy shielding.
How it works
4 parts
Mirror
Fields that bounce particles back
Charged particles spiral along field lines; where the field squeezes tighter at each end, most are pushed back toward the middle.
Mirror ratio
Why magnet strength matters
The stronger the ends relative to the middle, the fewer particles escape. Ratios near 2 never reached breakeven; 10 or more might.
Heating
Microwaves and neutral beams
Microwaves heat the electrons; injected beams of fast neutral atoms supply hot ions that bounce between the ends.
Tandem mirror
Electric plugs at both ends
Hammir adds dense end cells whose electric potential pushes escaping ions back into a long central cell where fusion happens.
The team behind CoSMo mirror fusion (WHAM to Hammir)
RF
Realta Fusion
Magnetic mirror fusion, HTS magnets, industrial heat
Madison, Wisconsin spinout of the University of Wisconsin's WHAM experiment, developing compact magnetic-mirror fusion plants of 50-500 MW to supply heat and power on site to industry.
WHAM, its joint experiment with UW-Madison, held plasma at a record 17 tesla in 2024 using CFS magnets.
April 2026: CFS to build the superconducting magnets for its prototypes and plants, a deal it says could be worth billions.
About $45M in venture equity plus $9.5M debt; one of eight firms in DOE's Milestone-Based Fusion Development Program.
