Fusion devices and the history of fusion research

Early concepts: The pinch device• Toroidal chamber

enclosing a hot plasma, with an electric current ‘pinching’ the plasma and keeping it away from the wall

• Developed by Peter Thonemann (Australia) and Sir George Thomson (UK)

R=25cm a=3cm

ZETA experiment at Harwell, UK (1950s). USA and USSR also built early pinch devices

Early concepts: The pinch device

The tokamak• Evolution of the pinch device,

but using two sets of magnetic field (toroidal and poloidal) to confine the plasma, allowing fusion reactions to take place

The tokamak• Pioneered in the

Soviet Union in the 1950s and 1960s

• Landmark T3 device at Kurchatov Institute, Moscow achieved breakthrough in fusion performance – 1968

• Joint European Torus (Culham, UK) now the largest tokamak operating (since 1983)

EAST – China

KSTAR – South Korea

Tokamaks past and present

JT-60U – Japan

JET – Europe

TFTR – U.S.

ASDEX – Germany

DIIID – U.S.

Tore Supra – France

START – U.K.

ITER – the future of tokamaks

• Global project sited in Cadarache, France

• Forecast to produce net energy gain of 10

• 500MW output power• Scheduled to operate

from early 2020s

Stellarator

Alternative magnetic fusion concept, dating from 1950s. Similar to tokamak but with helical magnetic

field generated by ‘figure of 8’ shaped coils

Stellarator

Difficult to engineer but has more stable plasma. W 7-X device being built by EU in Greifswald, Germany

Inertial confinement fusion (ICF)

Uses lasers to heat and compress pellets of fuel to induce fusion reactions. Either ‘direct drive’ (laser fired directly at pellet – a), or ‘indirect drive’ (laser

fired at a cylinder around the pellet – b)

Inertial confinement fusion (ICF)

National Ignition Facility (NIF, California, U.S.) – leading experiments in indirect drive ICF research

Cold fusion• In 1989, Fleischmann and

Pons claimed to have produced fusion neutrons at room temperature

• Research not peer-reviewed and has never been replicated by other scientists

• Not thought to have been nuclear fusion – and not enough heat produced for a useful source of energy