The machine · Halvard One

A star in amagnetic bottle.

A compact tokamak: sixteen superconducting magnets hold a ring of plasma hotter than the Sun's core, and a molten-salt blanket turns its neutrons into heat.

TypeCompact HTS tokamak

Plasma150 M °C

Field12 T on axis

Net output400 MWe

Halvard One · how it works

Anatomy of a shot

Seven systems, one job: keep a star-hot plasma in the middle of the room for long enough to make more energy than it takes. Scroll to take the machine apart.

01 · 18 T peak field

Central solenoid

Six stacked coils drive the plasma current, like the primary winding of a transformer.

02 · 1 kHz control loop

Shaping coils

Four rings squeeze and steer the plasma into its D shape, correcting it a thousand times a second.

03 · 12 T on axis

Toroidal field coils

Sixteen superconducting D-coils wrap the chamber in a magnetic bottle, cooled to −253 °C.

04 · 150,000,000 °C

The plasma

Hydrogen fuel heated ten times hotter than the Sun's core, held clear of every wall by field alone.

05 · 6,400 tiles

Vacuum vessel

A double steel wall lined with 6,400 tungsten tiles. The lithium blanket behind them breeds new fuel.

06 · 10 MW per m²

Divertor

The exhaust. It strips helium ash from the plasma edge and takes heat like a rocket nozzle.

07 · 1,900 t

Cryostat base

Carries the 1,900-tonne machine and keeps the cold parts cold inside a vacuum jacket.

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MachineHalvard OneTypeCompact HTS tokamakNet output400 MWe

Magnets

The coil isthe company.

Our magnets are wound from rare-earth superconducting tape, a hundredth of a millimetre thick, cooled to −253 °C. At that temperature the tape carries current with no resistance, so a coil the size of a bus makes a field 250,000 times stronger than the Earth's. Stronger field means a smaller machine: Halvard One is one fortieth the volume of the international research reactor.

12 T

field on the plasma axis

400 km

tape in each coil

11 weeks

to wind one coil

1/40

the volume of ITER

How a shot works

Four steps fromseawater to socket.

010.5 g of fuel per hour

Fuel in

Deuterium from seawater and tritium bred inside the machine are frozen into pellets smaller than a grain of rice and fired into the chamber, 20 times a second.

0212 tesla on axis

Magnets on

Sixteen superconducting coils make a field 250,000 times stronger than the Earth's. It holds the plasma in a ring, clear of every wall.

03650 °C blanket outlet

Heat out

Fusing nuclei throw off fast neutrons. They are stopped in a molten-salt blanket around the chamber, which heats up to 650 °C and breeds new fuel.

04400 MW net

Power out

The hot salt boils water, the steam turns a standard turbine, and the grid sees what it always sees: steady, synchronous power.

Safety

Why it cannotrun away.

Fusion is hard to start and easy to stop. There is no chain reaction and no fuel stockpile inside the machine, so the worst case is that the plasma goes out.

It stops by itself

If anything goes wrong the plasma cools and goes out in a fraction of a second. There is nothing to keep it burning.

Two grams of fuel

The chamber holds about two grams of fuel at any moment, enough for a few seconds of running.

No long-lived waste

Parts that get activated cool down within decades, not millennia, and are recycled on site.

Licensed like a hospital

Fusion is regulated in the UK like other radiation facilities, not like a fission power station.

Specification

Halvard One,in numbers.

Design values for the first commercial plant. Values marked design are confirmed on our H-0 test machine or in the magnet test hall.

Major radius2.1 m

Plasma volume34 m³

Toroidal field on axisdesign12 T

Plasma temperature150 M °C

Fusion power1,050 MW thermal

Blanket outletmolten FLiBe salt650 °C

Tritium breeding ratiodesign1.12

Net electrical output400 MWe

Availability target92 %

Shot lengthcontinuous, burn-controlled

Site area9 ha

Design life40 years

See it

Walk thecoil hall.

We run site visits at Culham every month for utilities, journalists and students. Bring questions, leave with a tape sample.

Talk to our team See the plant→