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

TAE has focused on field-reversed-configuration fusion devices, which are relatively efficient and simpler than the tokamak fusion machines used by rivals and viewed as more stable.

From MarketWatch • May 18, 2026

A common approach to fusion is to build a tokamak.

From BBC • Apr. 20, 2026

Well, if the design works, the twists and turns of a stellarator make the burning hot plasma easier to control than in the rival tokamak design, says Sciortino.

From BBC • Apr. 20, 2026

Despite this advantage, tokamak experiments have long been constrained by an upper density limit.

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