The dilithium crystal chamber is a component in a starship's warp core that contains the dilithium crystals. (TNG: "Galaxy's Child", "The Drumhead", "Cost of Living")

The dilithium crystal chamber for the USS Enterprise-D was designed at Outpost Seran T-1 on stardate 40052. (TNG: "Booby Trap")

On the USS Voyager, Crewman Hogan's main responsiblity was to keep the dilithium chamber filled. (VOY: "Alliances")

Background

There are four types of dilithium chamber that have been shown to date. One was that of the NX-class starship, though exactly which component of the reactor was the chamber itself was never disclosed.

The second was used on board the original configuration of the Constitution-class. It was a squat cylinder with a blunt domed top in the center of main engineering. The dilithium crystals were housed in a framework that rose out of one side of the chamber.

The next was the columnar "swirl" chamber, as shown in the Constitution-class refit and the Intrepid-class. Backstage information, including interviews with Rick Sternbach, indicate that in this model of chamber, the entirety of the column is the reaction chamber, which is lined with a layer of dilithium to moderate the reaction.

The last type is the familiar "ball" or "hub" chamber, shown throughout Star Trek: The Next Generation and Star Trek: Deep Space Nine.