Typical atomic gravimeters have a heavy magnetic shielding to avoid the quadratic Zeeman effect, and also a complicated active vibration isolation system to suppress the vibration noise. Both of them make it difficult to build a mobile and compact gravimeter. In this paper, we present the implementation of an atomic gravimeter aiming at field applications. Our gravimeter uses improved magnetic coils instead of the expensive mu-metal for magnetic shielding. The quadratic Zeeman shift is evaluated with high accuracy. Moreover, a portable platform of relatively small size is applied for vibration isolation. The total interrogation time is optimized to 120 ms and the repetition rate is 2.2 Hz. A sensitivity of 1.0 × 10−7 g Hz−1/2 and a resolution of 5.7 × 10−9 g within 1000 s integration time are reached. A continuous g measurement over 128 h is carried out. Moreover, a whole seismic wave of about 1 h that occurred in Pakistan on 28 September 2013 is recorded by our atomic gravimeter. The results coincide with that recorded by a traditional seismic detector very well.

The quadratic Zeeman coefficient was previously measured by using the single pulse spectroscopy method, in which the experimental resolution is limited by the line width of the spectrum of the clock transition. In this paper, an accurate measurement of the quadratic Zeeman coefficient is presented by using the Ramsey atom interferometer. The line width of the central Ramsey fringe of the 87 Rb clock transition, which depends on the interrogation time, is much narrower than that of the single pulse spectroscopy method. The measurement uncertainty of less than 1 Hz G −2 is realized, which is much better than the other current existing results. The measured quadratic Zeeman coefficient of the 87 Rb clock transition is 575.33±0.36 Hz G −2 by the Raman Ramsey atom interferometer, and 575.48 ± 0.30 Hz G −2 by the microwave Ramsey atom interferometer, which coincides well with the theoretical result of 575.15 Hz G −2 calculated by the Breit-Rabi formula.

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Ellipse fitting is a useful tool to obtain the differential signal of two atom interference gravimeters. The quality standard of ellipse fitting should be the deviation between the true phase and the fitting phase of the interference fringe. In this paper, we present a new algorithm to fit the ellipse. The algorithm is to minimize the differential noise of two interference gravimeters and obtain a more accurate value of the gravity gradient. We have theoretically derived the expression of the differential-mode noise and implemented the ellipse fitting in the program. This new algorithm is also compared with the classical methods.

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