The antimatter chamber (or antimatter confinement) was a component of the warp propulsion system aboard most starships that utilized a matter-antimatter reaction, such as Federation starships. The chamber was designed to generate and to spin reverse antiprotons. These antiprotons were used in the warp core to create a reaction with deuterium, in order to provide power to the nacelles. The chamber was connected to the antiproton injection subsystem, which injected antiprotons into the dilithium regulation chamber. Antiprotons were confined to the chamber by antiproton injection seals. Aboard Galaxy-class starships, this chamber was located on Deck 42. (TNG: "Contagion")