Dynamic Gravity Revisited in the Hz Regime, incl. Shielding

With many recent advances in multi-messenger astronomy, fully controlled transmitter receiver laboratory experiments on dynamic gravitational fields (DGFs) have become more important. This implies measuring their phase and amplitude and assessing any non-gravitational crosstalk. Very little is known about shielding of a DGF.

Dynamic gravity experiments consist of a periodically moving mass distribution (here two rotating tungsten bars). The detector system consists of a high Q (10⁴), 42 Hz resonant titanium bending beam. Its gravitationally induced motion is analyzed using three laser Doppler vibrometers and multichannel lock-in amplifiers. Following up on our Nature Physics paper, an analytical solution for the generated gravitational field is presented. Neutron tomography and cesium magnetometry proved that the transmitter bars can be well considered homogeneous and non-magnetic. Q factors of the detector are independently measured by ringdown experiments. We then present the latest theoretical and experimental results on precise determination of G and distance curves. Shielding of DGFs using different metal shields with dimensions of about 1.4 × 0.3 × 0.1 m and mass of up to ~500 kg placed in between transmitter and detector are also presented. At a frequency of more than four orders of magnitude higher than previous quasistatic shielding investigations and in a series of ceteris paribus experiments, the relative change of the amplitude and phase of the response signal is smaller than about 10^-2 and 0.5°, respectively, for both a 9 cm thick brass shield and a 10 cm thick lead shield.