On Mechanical Motion Damping of a Magnetically Trapped Diamagnetic Particle

We discuss eddy-current-induced limitations of the attenuation of mechanical motion of a diamagnetic particle trapped by an inhomogeneous magnetic eld in the Earth gravity potential. We show that the mechanical frequency of the particle oscillation is independent on the particle properties and is proportional to the free fall acceleration constant, similarly to the classical mechanical pendulum. The frequency can be used to measure the gravity eld. The eddy-current induced attenuation constant does not depend on the mass of the particle and reduces with the particle volume. The quality factor of the mechanical motion can be as high as 10^9 and is comparable withthe attenuation due to interaction of the particle with incompletely evacuated air.