Research On The Facility For Producing Uinform Magnetic Field Within Closed Ferromagnetic Boundaries

The nearly zero uniform magnetic field environment is a basic experimental environment for multidisciplinary frontier experiments such as aerospace,life sciences,and particle physics,so it has important scientific significance.Harbin Institute of Technology undertakes the construction of National Large Research Infrastructure "Space Magnetic Environment Simulation and Research System".which purpose is to realize a nearly zero magnetic environment similar to space.It is also called a zero magnetic facility and is an important part of the construction of weak magnetic facility in China.This paper addresses the unique design issues of uniform magnetic field coil systems(referred to as coils)in the zero magnetic facility.The study of the magnetic field analytical model,new design method of the coils under the ferromagnetic boundary,and the mapping between key indicators and design parameters are developed,which provides a theoretical basis for the design of geomagnetic compensation coils and weak magnetic field coils in the zero magnetic facility,and even the design of large uniform magnetic field generating facilities.The research work of this paper is mainly divided into four parts:Firstly,the analytical model of the magnetic field of the coils in the ferromagnetic shielding layer is a necessary for the coil design.Based on the image method,a three-dimensional image magnetic field analytical model is proposed.Computational program for calculation of space magnetic field is written.The accuracy of the analytical model is verified by comparing the calculated results from analytical method and the finite element method.Secondly,the principle of coils design is proposed which is maximizing the volume of the uniform magnetic field around the center.Based on the analytical model of magnetic field of the coils in the shield layer,a new design method for the coils in the shield layer is proposed.This method is based on the given uniformity index,with a goal of maximizing the volume around the center,the parameters of the coil are optimized.Compared with the conventional coils,the uniform volume of the coils designed according to the new method is greatly increased.Thirdly,starting with the application requirements of weak magnetic field coils,the influence of the coupling strength of the coils and ferromagnetic shield layer and the coil uniformity index on the coil design parameters is analyzed,and the coils design guidance is given.Based on the design method of coils in the shield layer,a design method of the bias coils is proposed.The relationship between the uniform volume and the center of the bias is analyzed,and the best location of the coils center is given.The design of the bias coils is verified by using the finite element method.Finally,experimental coils are designed and an experimental system is built.The performance of the coils is tested.For the proposed analytical model of magnetic field of coils in the cubic shield layer,the analytical results are compared with experimental results to verify the accuracy of the analytical model.For the proposed design method of coils in the cubic shield layer,the theoretical design value of the amplitude deviation rate is compared with the measured value to verify the rationality and effectiveness of the design method.