The plasma cannon was a typical weapon mounted on warships and other armed vessels.
The shots it fired were miniature thermonuclear explosions. The triggers were laser arrays aimed inward toward the pellet of tritium at the heart of each cannon. When tripped, the lasers compressed the tritium to fusion and directed its energy toward the one missing tile in the thermonuclear furnace which was aligned with the bore. The laser array directed the charge. The guns’ iridium barrels were necessary to reduce side-scatter caused by the inevitable atoms in the jet's path in even hard vacuum. That problem and the resulting bore erosion were much worse in an atmosphere; most battles took place in vacuum.9:21
The cannons were a relatively short-ranged weapon, typically used for defense. Their bolts of charged particles could deflect incoming missiles by vaporizing portions of the projectile and converting that mass into slewing thrust.2:1
There were much smaller, but still deadly versions, that could be carried for use on the surface.2:7