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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">≡1</tex> 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">φ(r) = -(GM/r) [1 + α exp(-)]</tex> , is α = + 0.024 ± 0.036 at μ -1 = 1m.