微伽级冷原子重力仪研究

A study of the μ-Gal-level cold atom gravimeter

在石油及矿产勘探和地质构造研究等领域,重力法是一种常用的重要方法,重力法的应用范围在很大程度上取决于重力测量设备—重力仪,高精度重力仪对重力法的应用和普及起着重要作用。因此提出研究有望用于物探领域的高精度小型化冷原子重力仪。首先,用改进的磁场线圈代替昂贵且笨重的坡莫合金来实现杂散磁场的屏蔽;其次,利用一个紧凑且小尺寸的被动隔振平台来实现地面振动的抑制。在探询时间为120 ms且重复率为2.2Hz的情况下,该冷原子重力仪的重力测量灵敏度达到1.0×10-7g/Hz1/2;1 000 s积分时间,重力测量分辨率为5.7×10-9g。为了验证冷原子重力仪设备的稳定性,不间断测量了128 h的潮汐信号。除此之外,发生在2013年9月28号巴基斯坦的一小时地震波信号被我们的高精度冷原子重力仪采集到,该信号与附近的传统地震仪测量到的地震波信号完全吻合。

In the field of oil prospecting,mineral exploration and geological structure research,the gravity method is a commonly used method. The application range of the gravity method mainly depends on the gravimeter. High-precision gravimeter plays an important role in the application and population of the gravity methods. In this paper,the authors present the investigation of a high- precision transportable cold atom gravimeter,which is expected to be used in the field applications. The improved magnetic coils are used in the gravimeter instead of the expensive mu- metal for magnetic shielding. Besides,a portable platform of relatively small size is applied to the vibration isolation. The total interrogation time is optimized to 120 ms and the repetition rate is 2. 2 Hz. A sensitivity of and a resolution of within 1000 s integration time have been reached. The continuous measurement of g over 128 hours is carried out. Moreover,a whole seismic wave of about 1 hour that occurred in Pakistan on September 28,2013 was recorded by the atomic gravimeter. The result coincides well with that recorded by a traditional seismic detector.