Superconductivity applied to gravimetry

A gravimeter was developed which uses the levitation of a superconducting sphere by the field of persistent current magnets. Instabilities in the field were reduced to the point where environmental noise on local gravity is greater than the instrument noise. At present, the persistent currents are decaying at a rate of 2 parts in 107/yr. Concurrent measurements of magnetic field and gravimeter signal allows for correction of this drift. The device is being applied to geophysical problems through measurements of: (1) secular variations in local gravity; (2) tides of the solid earth; (3) effects of oceans and atmosphere on local gravity; and (4) normal modes of the earth