AAR

An AAR, an Antimatter Annihilation Reactor, is an energy source that produces enery by annihilating a particle with its antiparticle, which produces the pure energy of the mass of these particles (following E=mc^2). As the creation of antimatter particles also costs a lot of energy (they're created in very complex and advanced, black hole-simulating, machines) it is not used for commercial power production (He-3 fusion is) but more for storage of energy (creation of antimatter particles takes about 85-90% of the energy that both particles produce in the annihilation process).

Mostly large starships and orbital stations use AARs.