Superconducting gyroscope - Drift data and mathematical model.

Drift data are presented for an experimental cryogenic gyroscope which consists of a spinning superconducting sphere levitated in a vacuum by a magnetic field. A Fourier analysis of the data has yielded estimates for the parameters in a relation r = A\ sina + A% sina COSQJ + A% sina (5 cos2a — 1) + A± sina (7 cos3a — 3 cosa), which expresses the dependence of torque on the angle a between the rotor spin axis and the vertical symmetry axis of the levitation field. These parameters can be related to rotor defects: mass-unbalance, nonsphericity, and trapped flux. Mass-unbalance is the main source of drift. The magnitude of drift due to nonsphericity is consistent with the measured variation in radius of the rotor (±7 juin.). Trapped flux is the least source of torque as a result of magnetic shielding during cool-down.