Absolute gravity acceleration measurement in atomic sensor laboratories

Abstract

Abstract. This paper reports the results from the accurate measurement of the acceleration of gravity g taken at two separate premises in the Polo Scientifico of the Florence University (Italy). In these laboratories, two separate experiments aiming at measuring the Newtonian constant and testing the measurement of forces with high spatial resolution are in progress. Both experiments require an independent knowledge on the local value of g. Gravity measurements were conducted using an FG5 absolute gravimeter, and accompanied by seismic recordings for evaluating the noise condition at the site. The absolute accelerations of gravity at the two laboratories are (980 492 160.6 ± 4.0)µGal and (980 492 048.3 ± 3.0)µGal for the European Laboratory for Non-Linear Spectroscopy (LENS) and Dipartimento di Fisica e Astronomia, respectively. Other than for the two referenced experiments, the data here presented will serve as a benchmark for any future study requiring an accurate knowledge of the absolute value of the acceleration of gravity in the study region.

Measuring the gravitational acceleration with matter-wave velocimetry

“…By linear interpolation, we determine the slope α 0 = k eff g for which ∆φ = 0 and we extract the gravitational acceleration as g = α 0 /k eff . After a 2-hour measurement run, we obtain g = 9.8049234(21) ms −2 , consistent within 2σ with the previous measurement performed in our laboratory with the FG5 mechanical gravimeter, g FG5 = 9.80492048(3) ms −2 [31].…”

Simultaneous measurement of gravity acceleration and gravity gradient with an atom interferometer

“…We estimate the effect of the Coriolis acceleration by measuring the average horizontal velocities of the two atomic clouds along the eastwest direction with a precision of $0:1 mm=s. 27 Finally, after correcting for the gravity gradient produced by the closest masses, 26 we obtain c ¼ ð3:1360:03Þ Â 10 À6 s À2 , in fair agreement with the standard free-air value of 3:09 Â 10 À6 s À2 . The uncertainty is dominated by the Coriolis shift, which, however, can be efficiently suppressed with the use of a tip-tilt mirror.…”

“…Using three ellipses with slightly different value of the interferometer time T, in order to determine the fringe order, we derive an absolute value for the gravity acceleration g ¼ 9:80497260:000079 m=s 2 , in good agreement with the value of 9:80492048 60:00000003 m=s 2 measured with a commercial FG5 gravimeter in the same location. 26 While reliable Gaussian fitting requires histograms with a large number of points, the temporal resolution can be improved by using a Bayesian estimator. Let us assume that the actual phase is normally distributed around the unknown value / 0 with variance r, and let us neglect the probability for / to fall outside the range ½À3p; þ3p, while experimental points / i are folded in the ½Àp; þp interval; to determine / 0 and its standard error we employ the Bayesian estimator…”

Measuring the Newtonian constant of gravitation G with an atomic interferometer

“…The value of g has been measured with an absolute gravimeter with an uncertainty of about 10 −8 m s −2 , more than adequate for our purposes. The result has been reported in [31]. Since we do not correct for tidal effects the uncertainty on g is actually of the order of 10 −6 m s −2 .…”