Calutron - one of the original machines proposed for refining Uranium 235 for the creation of an atomic bomb. It worked by creating a beam of uranium ions and accelerating them around a circular track. The heavier uranium 238 ions would move towards the outside and would be discarded; the lighter uranium 235 ions would stay nearer the center and could be collected.
It competed with the isotron, a more elegant approach that might have helped us develop the bomb a few months earlier, but due to politicking, it won sole funding. Eventually, it too was discarded in favor of a purely mechanical process involving miles of pipes and ultrafine filters.
See How to enrich uranium.