The Ion cannon card says that when you roll to hit deal 1 damage and assign a ion token.

Does the defender get a defense roll against your hits or is it automatic damage?

Thanks

"When this attack Hits" does not refer to rolling little solid explody-symbols.
It refers to a status after attack dice are canceled by defensive dice and tokens/abilities.

In other words, if you roll 2 [KABLAM]s and a [boom], and your opponent rolls 1 [squiggle] and two blanks, but has an Evade token, they cancel out a Hit and a Crit, but there is still one result left uncanceled. Your attack has now Hit.'

Therefore, when using an Ion Cannon, your opponent rolls their agility value and whatever modifiers they are afforded, as you asked.

for reference, the game's definition of "hit" can be found on page 12 of the rule book, in the "compare results" step.

An attack is only considered "hit" if there are uncancelled [boom] or [kablam] results after the "compare results" step. So yes, the defender gets to roll defense dice. Best not to refer to the explodey symbols as hits as that confuses the terminology. So if you roll 3 [boom] results and the defender rolls 1 evade the attack is considered a "hit". The ion cannon cancels the remaining results and deals the defender a damage and and ion token.

Edit: wow super ninja'd!

Thanks for the quick and easy to understand responses

In other words, if you roll 2 [KABLAM]s and a [boom], and your opponent rolls 1 [squiggle] and two blanks, but has an Evade token, they cancel out a Hit and a Crit, but there is still one result left uncanceled. Your attack has now Hit.'

If you can not cancel all hit/crit results, you are better of not spending any evade tokens as the ion cannon (and most, but not all ion weapons) will not do more then the one damage regardless of how many hit/crits are left uncanceled.

Better save the evade for future attacks.

In other words, if you roll 2 [KABLAM]s and a [boom], and your opponent rolls 1 [squiggle] and two blanks, but has an Evade token, they cancel out a Hit and a Crit, but there is still one result left uncanceled. Your attack has now Hit.'

If you can not cancel all hit/crit results, you are better of not spending any evade tokens as the ion cannon (and most, but not all ion weapons) will not do more then the one damage regardless of how many hit/crits are left uncanceled.

Better save the evade for future attacks.

I was using it as an example to show that it could be done, not that it was wise to do so. It makes my example more applicable to Assault Missiles, though.