Haven't been since 1958, when NASA was formed. Of course not. And everyone around the lab gets a laugh when they hear about that one. Oh yeah, let me just check on my neutron accelerator. You can't accelerate neutrons.
Particle accelerators work by moving charged particles in an electromagnetic field.
And neutrons have no charge. As in neutral particle. So you wouldn't get much acceleration there. You wouldn't get any. You can manipulate neutrons because they have a quadropole moment.