Does cancelling die results count as modifying them?
If Yes:
Accuracy Corrector is optional, but you use it before Ion Cannon kicks in. So you end up with two hits that can't be modified. Then Ion Cannon kicks in, but it isn't optional. It does its one damage + ion token, then it tries to cancel dice rolls. Except it can't, so three damage?
If No:
Then cool, and it acts just like any other Ion Cannon attack.