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.

---

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

---

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

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

From The Wall Street Journal • Dec. 28, 2025

Previously, researchers led by Kolemen successfully deployed a separate AI controller to predict and avoid another type of plasma instability in real time at the DIII-D tokamak.

From Science Daily • Jun. 5, 2024

The difference in tokamak proportions impacts plasma and, as the model indicates, the pedestal.

From Science Daily • May 28, 2024

A 3D plasma model should enhance understanding of how different plasma configurations can impact heat fluxes or the movement patterns of heat in the tokamak.

From Science Daily • May 14, 2024

DIII-D is a tokamak, a device that uses magnetic fields to confine a fusion plasma in a donut shape.

From Science Daily • Apr. 16, 2024