Gravitational constant $\mathrm{G}$ measured with a superconducting gravimeter

We report in this paper the results of a measurement of the gravitational constant $G$ obtained in a laboratory at distances of about 1 m, using a superconducting gravimeter. The instrument measured the gravitational effect due to an annular mass of about 280 kg moving up and down around the gravimeter. The experiment yielded for the gravitational constant the value $G=(6.675\pm 0.007){10}^{-11}\mathrm{N}{\mathrm{m}}^2/\mathrm{k}{\mathrm{g}}^2$ which agrees, within its uncertainty, with the last CODATA value.

Figure 1

Experimental values of $G$ obtained in the last decades. The data are in chronological order; for references see the text.

Figure 2

The experimental apparatus. On the left the annular ring and the dewar containing the gravity sensor are visible. On the right is the electronics controlling the system.

Figure 3

Four days of tidal signal as acquired by the SCG at the Brasimone site during 2003. The overall intensity of the tide was sligtly less then $3$ volts, corresponding to about $2000\mathrm{n}\mathrm{m}{\mathrm{s}}^{-2}$. The spikes in the signal are due to seismic noise.

Figure 4

SCG signal due to tide and annular mass. The 16” oscillations due to the moving mass are superposed on the more slowly varying tide, here close to a minimum.

Figure 5

After subtracting the tide what is left is the effect of the moving mass, that is a gravity signal of about 0.108 volts or $69.7{\mathrm{n}\mathrm{m}\mathrm{s}}^{-2}$.

Figure 6

Linear fit of the experimental data as a function of simulated data. The slope of the fitting line provides the ratio $G/G_{\mathrm{c}\mathrm{o}\mathrm{d}}$