超导重力梯度仪交叉耦合效应的实验研究

With the intrinsically low noise and high stability, superconducting gravity instrument (SGI) is considered as the most promise instruments in precision gravity measurements, and thus expected to become a more powerful air-borne tool in exploration survey. However，the low SGI intrinsic noise indicates nothing else but the physical limit to the sensitivity. In the practical dynamic environment, the extrinsic noise, which is resulted from the coupling of environmental noise into measurements, will be much larger than the intrinsic one. Thus, depression of extrinsic noise is essentially important for applicable SGI. Among them, the cross-coupling noise (CCN) from vibration in non-sensitive degrees of freedom is a key item. In this project, we will precisely and independently measure the cross-coupling functions for two basic cross-coupling mechanics in superconducting accelerometer, i.e., the coupling through the relative motion of the test mass with respect to the reference frame and that through magnetic interference. Based on the measurement results, we will be able to carry out the design of superconducting accelerometer with optimized CCN and test it experimentally. Furthermore, concerning the superconducting gravity gradiometer, we will investigate the cross-couplings between signal detection in sensitive degree of freedom and feedback controlling in non-sensitive degrees of freedom, and search for effective method to depress the CCN. The project aims at providing fundamental experimental data which is indispensable for the design of applicable superconducting gravity instruments.

超导重力梯度仪具有固有噪声低稳定性高的优点，在航空资源勘探等领域有广阔的应用前景，其研制是国际前沿研究课题。超导重力仪器的固有噪声只代表其分辨率的物理极限，在动态应用环境下，外部耦合噪声远高于固有噪声。因此，压制外部噪声是超导重力梯度仪实用化的核心任务。在外部噪声中，非敏感自由度的交叉耦合噪声是一个关键项。本项目通过实验手段，分别独立测量超导加速度计中相对运动与磁场串扰两种基本交叉耦合关系，并在实验测试基础上，最终完成超导加速度计结构与电磁参数设计优化。在此基础上，利用全自由度超导磁悬浮检验质量，开展超导重力梯度仪中敏感方向重力测量与非敏感自由度控制的交叉耦合效应研究，系统评估超导重力梯度仪中的交叉耦合效应，提出抑制动态环境下超导重力梯度仪交叉耦合噪声的有效技术方案。本项目的顺利实施将为超导重力仪器的工程化与实用化提供必不可少的基础实验数据，从基础层面支撑我国超导重力仪器的研制。

超导重力梯度仪具有固有噪声低稳定性高的优点，在航空资源勘探等领域有广阔的应用前景，其研制是国际前沿研究课题。超导重力仪器的固有噪声只代表其分辨率的物理极限，在动态应用环境下，外部耦合噪声远高于固有噪声。因此，压制外部噪声是超导重力梯度仪实用化的核心任务。在外部噪声中，非敏感自由度的交叉耦合噪声是一个关键项。本项目针对磁场串扰和几何误差两种交叉耦合效应进行实验测量与评估，并给出了相应的抑制方案。.首先针对磁场串扰机制，设计搭建了低温测量装置，通过磁场调制方法测量超导加速度计中磁场串扰交叉耦合关系。测量结果表明，非敏感自由度内侧壁类线圈的磁耦合系数为1E-9Wb/A量级，外侧壁类线圈为1E-10Wb/A量级，两类线圈中各线圈的耦合系数略有差异。同时利用低温纳米位移台，测定了各线圈有效电感对检验质量的位置的依赖关系曲线，并据此给出通过磁场耦合的悬浮检验质量运动交叉耦合系数，评估了在研超导重力梯度仪的磁场耦合交叉耦合效应。评估结果表明，在实验室环境下，该效应可以忽略；在航空环境下，该效应增大至5-10E/square root Hz，需要通过对检验质量非敏感自由度运动的反馈控制来抑制该效应。.针对梯度仪几何误差引入的交叉耦合效应，我们分析了在不同环境下敏感轴取向偏差对重力梯度测量噪声水平的影响，设计了测定敏感轴取向偏差测定的低温调制实验装置，评估了该装置的测量灵敏度，并制定了利用低温纳米位移执行机来调节减少敏感轴取向偏差的技术方案。目前，调制实验装置的搭建尚在进行中，取向调节实验将在调节实验装置完成后进行。