Design, Regulation, and Fast Measurement Method of Weak Magnetic Force Gradient Based on Superconducting Gravimeter

In this article, based on the magnetic levitation structure of superconducting gravity measurement, the design, adjustment, and fast measurement method of the weak magnetic force gradient are introduced. Based on the numerical simulation method of H-formulation, the weak magnetic force gradient of minimum -0.001 N·m is designed. The proposed 'semiopen-loop magnetic force gradient adjustment method' can achieve the magnetic force gradient adjustment of less than -0.01 N·m. Aiming at the defect that the conventional solid earth tide observation method requires several or even tens of hours of long-term observation when measuring the magnetic force gradient, the proposed 'closed-loop electromagnetic excitation method' can realize fast and accurate measurement in the process of force gradient adjustment, and evaluate the measurement accuracy of the gravity instrument at any time. The prototype is placed in the field observation station of the National Institute of Metrology where the environment is more stable to observe the solid earth tide signals. The force gradient of -0.00264 N·m was obtained using the method proposed in this article, and its correctness was verified by comparison with experimental results. This article is of great significance for improving the convenience of users, promoting the localization and commercialization of superconducting gravimeters, and promoting the in-depth research in the field of geodynamics.