[Ulzgoroth]

There is no fusion pion drive. An antimatter pion drive, as described, annihilates a matter-antimatter fuel in a 1:1 ratio and uses the charged particle (pion) byproducts of that annihilation as reaction mass, directed by magnetic fields.

Almost nothing in that process can be confined by material means. You'd probably have particle and anti-particle beams intersecting in a space largely surrounded by field generating hardware.

I imagine you wouldn't be able to see the antimatter pion rocket's exhaust, because while it's very energetic there's very little of it. The antimatter pion torch is a tad different in that respect of course...