用于MT方法的超小型感应式磁场传感器

The ultra-small induction magnetometer for MT method

感应式磁场传感器广泛应用于地球物理电磁勘探仪器,受物理原理制约,该类磁传感器的噪声水平与其长度和体积约成正比,典型用于大地电磁测深方法(Magnetotellurics MT)的感应式磁场传感器长度约为1.0~1.4 m,重量在6~10kg.本文采用一种磁通聚集器技术,突破了传统感应式磁场传感器的设计瓶颈,能大幅度降低传感器的长度,本文设计的用于MT方法的超小型感应式磁场传感器长度<230 mm,直径<110 mm,重量<6 kg,长度约为传统MT磁场传感器的20%,工作频率范围为1 mHz^1 kHz,噪声水平0.1 Hz为5pT//Hz,1 Hz为0.5 pT/(Hz)^(1/2),10~100 Hz为0.1 pT/(Hz)^(1/2);野外实验表明:单轴可用于MT测量中垂直方向测量,可极大地提高施工效率;如将集成为三方向的矢量磁场传感器,总体积不超过23 cm×23 cm×23 cm,重量小于21 kg,可放置在标准17英寸的深海浮球内,实现海洋MT、CSEM方法测量,将有效降低整个海洋电磁仪器的体积和成本,具有广阔的应用前景.

The text of English The induction magnetometer （IM） is widely used in geophysical electromagnetic apparatus. Because of the physical principle, the length o{ traditional IM for the Magnetotellurics （MT） is about 1. 041.4 m, and the mass 6. 0- 10 kg. In this work, a compact and low noise IM with a flux concentrator was developed. The length is less than 230 mm, diameter 110 ram, and mass 6.0 kg. Its frequency bancl is from 10-3 Hz till 1000 Hz, the equivalent magnetic field noise level is 5 pT/Hz at 0. 1 Hz, 0. 5 pT/Hz at 1 Hz, 0. 1 pT/Hz at 10 - 100 Hz respectively. Field test show that the ultr-small IM can be used in land MT method, and bring with a huge convenience in field working. If the IM is integrated to the one of three axes, the whole mass is less than 21 kg and it could be put into a standard size （17 inches） Borosilicate glass sphere which is widely-used as the marine instrumentation housing. The improvement in volume and mass could efficiently decrease the cost of marine EM acquisition station, which shows a potential prospect in marine MT and CSEM method applications.