| 摘要 |
Apparatus for measuring gravitational fields comprising a superconducting string (1) fixed at both ends and forming part of a closed superconducting loop inductively coupled to two driving solenoids (L d1, L d2). Displacement of the string in response to a gravitational field is sensed by two magnetic flux transformers each comprising a signal coil and two pick-up coils (L p1, L p2). Pairs of pick-up coils lie in two perpendicular planes providing two independent channels of measurements. The two arms of each flux transformer are balanced to convert only the amplitudes of the string's antisymmetric natural modes into an output voltage. The output voltage of each channel is used to produce a feed-back current distribution (I y1, I y2 ) proximate and parallel to the string. By adjusting the feed-back current, the effectiv e relaxation time and resonant frequency of the first antisymmetric mode of the string ca n be adjusted, while leaving the symmetric modes unchanged, thus increasing the apparatus' sensitivity to gravity gradients.
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