基于阶梯磁补偿的航空三分量超导磁力仪动态范围拓展方法研究

Compared with the traditional scalar magnetic survey, aeromagnetic vector survey can effectively reduce the multiple solutions of inversion, and improve the detecting resolution as well as positioning accuracy of the underground ore body. Superconducting magnetometer which can be used for vector magnetic measurement has the highest sensitivity, but its dynamic range is too small due to the limitation of working principle, so it easily loses locking as magnetic field exceeds the measurement range on mobile survey. One method of using flux quantum counting to improve the dynamic range reduces the measurement sensitivity. In this project, the traditional research method, i.e., thinking-way of improving dynamic range only from magnetometer is changed and the research from the angle of magnetic field under measurement is carried out. Taking advantage of large dynamic range of magnetic compensation as well as high sensitivity of flux-locked loop, the method of combining flux-lock with magnetic compensation is explored, so as to improve the dynamic range on the premise of high sensitivity. By researching the logical relationship between magnetic compensation loop and flux-locked loop, establishing the stepped magnetic compensation strategy, developing the three-axis orthogonal magnetic compensation coils and high-performance current source, as well as implementing stepped three-axis orthogonal compensation magnetic field, the magnetic measurement range of the three-component superconducting magnetometer can be extended from ±280nT to ±10000nT on the premise of sensitivity of 0.1pT/√Hz, which will solve one key problem of high-precision aeromagnetic vector survey, and provide the technical support for the deep resources prospecting and exploitation.

航空矢量磁测与传统的标量磁测方法相比可减少反演中的多解性，提高地下矿体探测分辨率和定位精度。超导磁力仪是目前灵敏度最高的矢量磁测仪器，但因工作原理限制，动态范围小，移动测量时易超出量程而失锁，而利用磁通量子计数方法提高其动态范围时损失了磁测灵敏度。本项目改变常规研究方法中仅从磁力仪本身来提高动态范围的思路，从被测磁场角度开展研究，利用磁补偿系统动态范围大和磁通锁定环灵敏度高的优势，探索磁通锁定和磁补偿两种模式结合并实现优势互补的方法，实现高灵敏度前提下的动态范围拓展。通过研究磁补偿回路与磁通锁定环之间的逻辑关系，建立阶梯磁补偿策略，研制三轴正交磁补偿线圈和高性能电流源，实现阶梯三轴正交补偿磁场，在保证三分量超导磁力仪灵敏度0.1pT/√Hz前提下，将其量程由原来的±280nT提高到±10000nT，解决高精度航空矢量磁测关键问题，为深地资源勘查开采提供技术支撑。

航空磁测是目前应用广泛的地球物理探测方法之一，其通过在航空器上搭载磁测系统来测量磁性矿产资源引起的磁异常变化，从而快速评估矿产资源及其分布概况。随着磁法勘探理论和方法的不断发展，航空磁测由原来的总场强度测量，后来的总场梯度测量，演化到现在的矢量（三分量或梯度张量）测量。可进行矢量磁测的磁通门磁力仪灵敏度约为10pT/√Hz，受工作原理的限制，其发展也已到了瓶颈期。为实现高精度的航空矢量磁测，还需引入或研制灵敏度更高的矢量磁测仪器。超导磁力仪采用工作于液氮或液氦中的超导量子干涉器SQUID为传感器，灵敏度优于 0.1pT/√Hz，是目前灵敏度最高的矢量磁测仪器，与磁通门磁力仪相比具有突出的优势，国际上多个国家正在尝试将其引用到航磁测量中。但因工作原理限制，超导磁力仪的动态范围小，移动测量时易超出量程而失锁，而利用磁通量子计数方法提高其动态范围时损失了磁测灵敏度。本项目改变常规研究方法中仅从磁力仪本身来提高动态范围的思路，从被测磁场角度开展研究，利用磁补偿系统动态范围大和磁通锁定环灵敏度高的优势，探索了磁通锁定和磁补偿两种模式结合并实现优势互补的方法，实现了高灵敏度前提下的动态范围拓展。主要研究内容包括分析磁补偿回路与磁通锁定环之间的逻辑关系，建立阶梯磁补偿策略，研制三轴正交磁补偿线圈和高性能电流源，实现阶梯三轴正交补偿磁场，在保证三分量超导磁力仪灵敏度0.1pT/√Hz，将其量程提高到了14000nT。研制的组合式三分量超导磁力仪在利用无磁小车搭载进行了地面移动式测量实验，结果表明该仪器系统在地磁场环境下能够稳定锁定工作，验证了其动态测量性能。本项目研究成果为开展高精度航空矢量磁测解决了核心关键问题，为深地资源勘查开采提供技术支撑。