Vibration Rejection on Atomic Gravimeter Signal Using a Seismometer
We use atom interferometry to perform an absolute measurement of the gravitational acceleration g.
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Vibration Rejection on Atomic Gravimeter Signal Using a Seismometer S. Merlet, J. Le Gouët, Q. Bodart, A. Clairon, A. Landragin, F. Pereira Dos Santos, and P. Rouchon
Abstract We use atom interferometry to perform an absolute measurement of the gravitational acceleration g. The sensitivity of the interferometer is predominantly limited by vibration noise, even when drastically reduced by using a passive isolation platform. We present here an original correction scheme of the residual vibration induced interferometer phase fluctuations, based on the use of a low noise seismometer. In the best conditions, our instrument reaches an excellent sensitivity of 1.4 × 10−8 g at 1 s, despite operating in an urban environment. But the method presented here allows reaching good performances even when operating without any vibration isolation. The sensitivity of our instrument at night is then as low as 5.5 × 10−8 g at 1 s.
16.1 Introduction Over the last 15 years, atom interferometry techniques have been used to develop novel inertial sensors, which now compete with state of the art “classical” instruments (Niebauer et al., 1995). After the first demonstration experiments in the early 1990s (Kasevich and Chu, 1991; Riehle et al., 1991), the performance of this technology has been pushed and highly sensitive instruments have been realized. A key feature of these instruments is to provide an absolute measurement with improved long term stability compared to
S. Merlet () LNE-SYRTE, Observatoire de Paris, 77 avenue Denfert Rochereau, Paris 75014, France e-mail: [email protected]
other sensors, due to the stability of their intrinsic scale factor. Applications of this technology are growing, from the measurement of fundamental constants, such as the Newtonian gravitational constant G (Bertoldi et al., 2006; Fixler et al., 2007), to the development of transportable devices for navigation, gravity field mapping (Yu et al., 2006), detection of underground structures and finally for space missions, where ultimate performances can be met, because of the absence of gravity and a low vibration environment. At LNE-SYRTE, we are currently developing a cold atom gravimeter based on atom interferometry, within the frame of the watt balance project, conducted by the Laboratoire National de Métrologie et d’Essais (LNE) (Genevès et al., 2005; Merlet et al., 2008b). In this project an absolute measurement of gravity with a targeted relative accuracy of 10–9 is needed to link the unit of mass to electrical units with relative accuracy of a few parts in 108 (Steiner et al., 2007; Robinson and Kibble, 2007). In this article, we investigate the limits to the sensitivity of our atomic gravimeter, especially when operating without vibration isolation. We first describe our experimental setup and then introduce and compare two measurement schemes that allow operating the sensor in the presence of large vibration noise. In particular, we show how gravity measurements can be performed even though the interferometer phase noise amplitude excee
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