Radiometric converter

From Memory Alpha, the free Star Trek reference

A radiometric converter is a device aboard Federation starships such as the Intrepid-class, which absorbs the theta radiation from antimatter waste and recycles the energy to power other systems. The engineering principles of radiometric converters are the same as those of plasma manifolds.

In early 2375, the USS Voyager crew offered radiometric converter technology to Controller Emck of the Malon, but he wasn't interested. (VOY: "Night")