A medium range energy cannon that delivers an electro-magnetic pulse (EMP) and can quickly disable enemy systems/engines.
The Ion Cannon's nonstandard gain medium projects highly ionized baryonic matter in a coherent bolt. When the ion bolt impacts the target it creates a localized magnetic field which plays havoc with all manner of electronics, including sensors, fuel igniters, targeting modules, computers, etc. The weapon also fuses certain circuits, and can mildly strain shield generators, thus it does negligible amount of permanent damage. Rarely the only weapon type fitted on ships.
The Ion Cannon is a small energy weapon that deals most of its damage as electromagnetic pulse (EMP) damage, which can disable surface systems of ships such as weapons and engines. It is notably very flux efficient, but its range is quite short and it is more expensive to equip than other small energy weapons.
When hitting hull or armor an EMP arc will form in addition to the Ion Cannon direct damage, potentially striking weapons or engines far from the impact point. This makes dropping shields against an Ion Cannon particularly risky.