Milestones
- First plasma2018Complete.
- 100 million °C ion temperature2022Complete.
- Upgrade programme with lithium-coated wallsNowCurrent milestone.
Most important updates
- 4 Dec 2024
- 2022
Current obstacles
- Little room to shield the centre postSpherical tokamaks have a thin centre post, leaving little room to shield a power plant's magnets from neutrons.
Physics limits
- Copper magnets burn their own powerCopper resists current, so coils heat up and shots last seconds. At power-plant scale, copper magnets would consume most of the plant's output.
- Plasma density hits a ceilingBeyond the Greenwald limit, set by plasma current and size, the plasma edge cools and the discharge collapses, capping fuel density and so fusion power.
- Pressure limits still applySpherical tokamaks can hold higher plasma pressure relative to the field than classic ones, but still hit instabilities that cap fusion power per tesla.
How it works
Shape
An apple-core tokamak
A spherical tokamak squeezes the doughnut until its hole is just a thin central post, which holds plasma pressure more efficiently.
Magnets
Pulsed copper coils
ST40 uses copper magnets pulsed for short shots, enough to study hot plasmas in this shape before superconducting versions.
Heating
Beams heat the fuel
Neutral-particle beams heat the plasma; in 2022 ST40 reached ion temperatures above 100 million °C, a first for a private tokamak.
Update log
Wed 4 Dec 2024
- Major: PressFunding
2022
- Major: PressTest
About Tokamak Energy
Tokamak Energy
Spherical tokamaks, HTS magnets, ST40
UK company combining spherical tokamaks (a compact, apple-core shape) with high-temperature superconducting magnets. Its ST40 reached 100-million-degree plasma in 2022, and it also sells its magnet tech to other industries.
- ST40 reached 100 million °C in 2022, a record for a privately funded spherical tokamak.
- Building Demo4, a full set of HTS magnets in tokamak shape, to test fusion-level fields.
- Part of the US DOE Milestone-Based Fusion Development Program.
tokamakenergy.com (opens tokamakenergy.com)Company profile →
- Founded
- 200917 yrs
- Headquarters
- United Kingdom
- Status
- Private
- Valuation
- private
- Works in
- EnergyFusion
- Coverage
- 2 programs · 8 updateslatest 14 Apr 2026checked 25 Sep