Deuterium Cartridge
From Star Trek : Freedom's Wiki
The deuterium cartridges are components of a starship's warp drive system, presumably relating to the deuterium fuel source.
In 2370, Lieutenant Commander Geordi La Forge asked Ensign Tyler to help Farrell inspect the deuterium cartridges shortly before a new warp core was to be activated aboard the USS Enterprise-D. (TNG: "Phantasms")
