Stable levitation of a magnet over a pair of counter-rotating cylinders: The Alcon levitator

The Alcon levitator is an experimental setup that demonstrates the levitation of a bar magnet above two counter-rotating metal cylinders. Stable levitation is achieved only above a critical angular velocity—about 9000 rpm in our setup. The precise physical mechanism behind this stability remains under investigation. In this work, we combine theoretical analysis and numerical simulations to examine the mechanism, which originates from the interplay between lift and braking forces acting on the magnet and their dependence on the magnetic Reynolds number, i.e., the angular velocity of the cylinders.