Plasma torpedo

Were you looking for the closely-named Plasma Cannon, the Covenant portable cannon?

The Plasma Turret is a Covenant starship weapon, placed on many of their ships even including Frigates. It fires a spear of Plasma and can strike at almost any range. Upon contact it causes severe damage to the target. The weapon can be used in conjunction with Plasma Torpedoes, and Energy Projectors to decimate an entire human fleet. The armament may be used against infantry as well.

The turret itself is antenna-like in appearance and is located along the sides of the ship. The beam is red and short with a ball-like head. The turrets, from afar, usually appear as short spikes on the sides, the upper sides, and the bow of the vessel.

Before the weapon fires, it first has to charge. When the weapon charges, a ball of superheated plasma forms in front of the turret, then after about 3 seconds, it fires outward at its target. Because of the sheer power of the weapon, Covenant fleets have usually won all encounters against the UNSC Navy. The closest weapon that the UNSC has that is anywhere near as powerful as the Plasma turret is the MAC gun.

Physics
Inside the turret, gas is superheated by the ship's reactor to produce the charge of plasma. Magnetic coils shape and guide the plasma, acting as a sophisticated focusing lens.

When the plasma charge impacts its target, it super heats the material which boils through shields and melts through armor.