A mobile three-dimensional active vibration isolator and its application to cold atom interferometry

Abstract

Vibration noise has an influence on the sensitivity and stability for many precision instruments, especially for atom interferometers. In this paper, a mobile three-dimensional active vibration isolation system is established for portable atom interferometer that is effectively isolated from the ground vibration, thereby improving the sensitivity of the portable atom interferometer, and can be deployed and recovered to working state rapidly. With the home-developed integrated feedback algorithm, this system achieves a good vibration suppression in a wide frequency range in three directions. It suppresses the ground vibration by three orders of magnitude in the vertical direction, and one order of magnitude in the horizontal direction. In a frequency range less than 10 Hz which the atom interferometer is sensitive to, the vibration noise is suppressed to 4.8 × 10<sup>–9</sup> m/s<sup>2</sup>/Hz<sup>1/2</sup> in the vertical direction and to 2.7 × 10<sup>–7</sup> m/s<sup>2</sup>/Hz<sup>1/2</sup> in the horizontal direction. The influence of vibration noise on the sensitivity of the atom interferometer reaches to 2 μGal/Hz<sup>1/2</sup>, which is reduced by two orders of magnitude compared with the result without our system.

A portable atom gravimeter operating in noisy urban environments

“…Meanwhile, it can also fit inside a miniVan and be robust enough to be transported in the long range. Even after over 1300-km-long transportation from Shanghai to the comparison site at National Institute of Metrology of China in Changping, Beijing, our gravimeter still exhibit an 2σ uncertainty of 15.6 µGal and reach a degree of equivalence of -12.5 µGal compare with the reference value given by the FG5-type gravimeter NIM-3A [32,40].…”

“…The residual vibration noise is reduced by a factor of 2000 from 0.01 Hz to 10 Hz, as the residual noise to crosstalk between horizontal and vertical directions is further suppressed by extra horizontal feedback channels. The vibration noise is also reduced horizontally by a factor of 30 from 0.01 Hz to 10 Hz (not shown here) [32]. The longterm performance of the three-dimension active vibration isolator is presented in Fig.…”

“…The residual vibration noises go through an anolog-digital converter are transferred to a programmable digital feedback filter with a sampling rate of 1 kHz. By passing through a digital-analog converter and the VCCS, the output signal from the filter is turned into current to drive the voice coils that implement the feedback force in three dimensions [32].…”

Calibration of a compact absolute atomic gravimeter*

“…The residual noise in vertical direction can be reduced by three orders of magnitude. [27] All the lasers for operating the atomic gravimeter, including the cooling laser, repump laser, Raman lasers for interference, as well as the detection lasers are provided by the laser module that includes two diode lasers (DL-I and DL-II) and a tapered amplifier (TA). DL-I is locked on 87 Rb transition line by the magnetic enhanced modulation transfer spectroscopy, [28] providing repump laser and one of the Raman lasers.…”

“…The detection noise is caused by the signal to noise ratio of the detected fluorescence signal, contributing a noise of 17.4 µGal/ √ Hz. Benefiting from the extremely quiet environment in Changping Campus, NIM, as well as the 3D active vibration isolator, [27] the vibration noise of the ground is greatly suppressed and only contributes 1. 5…”