Superconductivity applied to gravimetry

A gravimeter has been developed which uses the levitation of a superconducting sphere by the field of persistent current magnets. Instabilities in the field have been reduced to the point where environmental noise on local gravity is greater than the instrument noise. In present results the persistent currents are decaying at a rate of 2 parts in 10
⁷
/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: secular variations in local gravity, tides of the solid earth, effects of oceans and atmosphere on local gravity, and normal modes of the earth.