The Disintegrator is the signature weapon of the Orkulus Star Base, acquired via Level 1 Assault Systems upgrade. It appears to be purely nanite-based, as it release a purple cloud or stream that does not appear to be an energy or kinetic weapon.
It has limited range (shorter than the starbase's standard-issue Pulse Guns), but high damage against heavily-armored targets - like structures. Combined with Orkulus's mobility, the Assault Deployment upgrade or the Rebel's Starbase Mobilization research, this more than compensates for the Vasari's lack of an Anti-Structure Cruiser.