宽频带超导重力仪的研制进展

Progress in the development of a wide-band superconducting gravimeter

本文报道一种构建宽频带高分辨率超导重力仪(SG)的方法.与已商业化的GWR超导重力仪类似,新型超导重力仪同样使用磁悬浮超导检验质量来构建弹簧振子结构,不同的是弹簧振子的固有频率更高,可以有效覆盖地脉动频带.同时,利用基于超导量子干涉器件(SQUID)的位移传感技术,大幅提高了位移传感灵敏度,以保证仪器在测量带宽扩展之后仍具有与GWR仪器相当的测量分辨率,从而实现对时变重力信号与地球背景噪声信号的同时高分辨观测.宽频带超导重力仪核心部件垂向超导加速度计(VSA)的设计、组装和初步测试已经完成.结果表明,加速度计的噪声本底为8μGal/Hz1/2@0.1Hz,实现了对地脉动信号的高分辨率测量.而为了将仪器噪声本底降低到GWR仪器水平,加速度计的固有频率需要进一步减小,该部分参数优化工作正在进行.本文将对垂向超导加速度计的工作原理、结构和测试结果进行详细介绍.

In this paper,a method to construct superconducting gravimeter（SG）has been described.Similar to the commercial GWR superconducting gravimeter（SG）,a superconducting test mass is levitated to form the spring-oscillator.However,the spring-oscillator is designed to have higher natural frequency,so that the frequency band can cover the microseism signals.At the same time,more sensitive technology based on superconducting quantum interference devices（SQUID）is used to detect the displacement of the spring-oscillator.In this way,high sensitivity can be attained even if the instrument bandwidth has been broadened.Therefore,the constructed SG can record both the time-varying gravity signals and the earth ambient noise simultaneously.A prototype of vertical superconducting accelerometer（VSA）has been fabricated with a nature frequency of about 20 Hz.The accelerometer shows a noise floor of 8μGal/Hz1/2@0.1 Hz,and the microseism signals have been measured by the VSA with high sensitivity.In order to improve the instrumental noise level to be better than the GWR SG,the natural frequency of the VSA must be further reduced.The works to optimize the accelerometer parameters is on the way.The working principle,structure and test results of the superconducting accelerometer will be present in detail.