Preliminary tests of a newly developed superconducting gravity gradiometer

We have recently completed a series of tests on a newly developed superconducting gravity gradiometer consisting of two 400 g niobium proof masses separated by a distance of 15 cm. The resonance frequency of the proof mass suspension systems is 25 Hz. The sensitivity of this gradiometer obtained during these tests was 1 to 2 Eötvös Hz
^-1/2
(1 Eötvös = 10
^-9
s
^-2
\equiv1
E) below 1Hz, and 0.2 E Hz
^-1/2
between 15 and 20 Hz. Using this gradiometer, a prototype experiment has been performed to demonstrate a new source-independent null test of the inverse square law of gravitation. The result, assuming a potential of the form
\phi(r) = -(GM/r) [1 + \alpha \exp(-\mur)]
, is α = + 0.024 ± 0.036 at μ
^-1
= 1m.