tokamak

American  

[toh-kuh-mak, tok-uh-] / ˈtoʊ kəˌmæk, ˈtɒk ə- /

noun

Physics.

1. a type of experimental nuclear fusion reactor in which a plasma of atoms circulates in a toroidal tube and is confined to a narrow beam by an electromagnetic field.

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tokamak British  

/ ˈtɒkəˌmæk /

noun

1. physics a toroidal reactor used in thermonuclear experiments, in which a strong helical magnetic field keeps the plasma from contacting the external walls. The magnetic field is produced partly by current-carrying coils and partly by a large inductively driven current through the plasma

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Etymology

Origin of tokamak

1960–65; < Russian tokamák, acronym from toroidálʾnaya kámera s aksiálʾnym magnítnym pólem toroidal chamber with an axial magnetic field

Example Sentences

When comparing the two systems, he says a tokamak is a "beast" while the stellarator is a "little cat".

From BBC • Apr. 20, 2026

A common approach to fusion is to build a tokamak.

From BBC • Apr. 20, 2026

These experimental results offer new physical insight into how the long-standing density barrier in tokamak operation might be broken in the pursuit of fusion ignition.

From Science Daily • Jan. 4, 2026

China has invested heavily in its own tokamak program, achieving record plasma temperatures and confinement times.

From The Wall Street Journal • Dec. 28, 2025

Such momentary, explosive ELMs need to be avoided because they can damage the inner components of a tokamak, draw impurities from the tokamak walls into the plasma and make the fusion reaction less efficient.

From Science Daily • May 14, 2024