Just how bad can an Ion burn be?

[Notimetolooz]

I did occur to me that the ions would be hitting the wall in a bent gun tube and since the ion trap magnet isn't strong enough to effect the ions much, they would never reach the screen. Even if the trap was mis-adjusted. I remember seeing a picture. maybe in that same book, of a gun element with a notch in the side of the aperture, produced by electron bombardment from a mis-adjusted trap.