Power & energy

Tokamak fusion reactor

Fusion energy · Magnetic confinement

How do you hold something ten times hotter than the Sun’s core without it touching anything?

A tokamak is a doughnut-shaped machine that tries to make energy the way the Sun does, by fusing light hydrogen atoms into helium. The fuel is heated to about 150 million °C, so hot that it becomes a glowing gas called plasma. Giant magnets hold the plasma in mid-air, because no wall could survive touching it.

A tokamak confines a deuterium–tritium plasma at about 10–20 keV (over 100 million kelvin) in a doughnut-shaped magnetic cage made from a strong toroidal field plus the poloidal field of a current flowing in the plasma itself. Fusion becomes self-sustaining only when density, temperature and energy confinement time together satisfy the Lawson triple-product criterion, and every other system in the machine — magnets, blanket, divertor, heating, fuelling, diagnostics and cryostat — exists to reach or exploit that condition.

Key facts

D–T reaction energy

17.6 MeV (3.5 MeV α + 14.1 MeV neutron)

Optimum ion temperature

≈ 10–20 keV (≈ 120–230 million K)

Ignition triple product

n T τ_E ≳ 3 × 10²¹ keV s m⁻³

ITER major / minor radius

R ≈ 6.2 m, a ≈ 2.0 m, plasma volume ≈ 830 m³

ITER toroidal field / plasma current

5.3 T on axis / 15 MA

ITER goal

Q = 10: 500 MW fusion from 50 MW heating

Parts you can explore (15)

• Plasma (illustrative)
• Toroidal field coils
• Central solenoid
• Poloidal field coils
• Magnet supports and feeders
• Vacuum vessel
• Thermal shield
• Cryostat
• Blanket modules
• Divertor cassettes
• Neutral beam injector
• RF heating antennas
• Fuelling systems
• Diagnostics
• Cooling and vacuum pumping

In the 3D model

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