It's the only one! And it's only in the Profundity Expansion Pack (and also the Super Star Destroyer).
Real quick though, let's look at what can take an Ion Cannon:
- CR90 Corvette B
- MC75 Armored Cruiser
- MC80 Liberty-Class
- MC80 Home One-Class
- Raider II-Class Corvette
- Victory II-Class Star Destroyer
- Interdictor-Class Cruiser
- Imperial I-Class Star Destroyer
- Imperial II-Class Star Destroyer
- Imperial Star Destroyer Kuat Refit
- Star Dreadnaughts (2x each for Assault Prototype / Executor II-Class)
Heavy Ion Emplacements - 9 points
Blue Critical: You may exhaust this card. If you do, the defending hull zone and each adjacent hull zone loses 1 shield.
This is a huge impact card in an expansion full of impact cards. Blue Critical rolls are now worth 4 unbraceable damage against full shield targets. SSD's practically have Damage Control Officer stapled to them because this card exists. It's turned Interdictors from a joke into something to fear. Disposable Capacitor VSD II's are equally terrifying.
Basically if you are bringing a ship that can take Ion Cannons, you're looking hard at this upgrade, then deciding whether you can reliably get and stick that critical. Another source of rerolls is almost necessary, or some way of guaranteeing the result (Screed for example). Otherwise, the Ion Cannon slot reverts back into a way of getting a rerolls via Leading Shots and smoothing out your damage.
It's also only really effective against targets with shields, but if your target already has shields stripped, you don't really need the extra damage that badly, do you?
In short, this is one of the better upgrades, and probably the best at the Ion Cannon slot. Just by existing it forces SSD's to use an officer slot for DCO, and it give Screed something to play with besides Ordnance. It makes Fire Control Team usable.
Maybe we'll get a good Red Critical at some point?