Research on the Design Method of Gradient Magnetic Field Coil Based on the Magnetic Shielding Room.

Standard gradient magnetic flux (GMF) is widely used in the research and development of biotechnology and the error calibration of magnetic detection systems and can directly support the development of life sciences, geological exploration, ocean exploration, space exploration, and other fields. Because a magnetic shielding room (MSR) can create a noise-free environment (within a static magnetic field less than 0.2 nT and magnetic noise less than 10 fT/ $\surd $ Hz), the construction of a standard magnetic gradient source in MSR will further promote the detection accuracy of related technologies. The existing gradient coil design methods cannot achieve the best uniformity in a certain uniform zone. In addition, when the gradient coils are placed in the MSR, the magnetic and conductive materials of the MSR will further deteriorate the uniformity. In this essay, the calculation model for the magnetic flux gradient value of the coil in the MSR is formulated first. On the basis of the calculation model, a design method for gradient coil with optimal uniformity in any uniform zone is proposed. The new method can realize the design of improving the uniformity index for any uniform zone and take advantage of the adverse factor of ferromagnetic boundary conditions introduced by MSR to make the gradient uniformity better. Meanwhile, in the research process of the design method, the coil volume utilization and efficiency are introduced into the design evaluation process through analysis, avoiding the singular result that the volume utilization and efficiency are less than 1/10 of the normal result, and the limitations of the design ability of the new method have been significantly improved. Finally, the core parameters of the new coil at different working conditions are summarized, which can be intended for leading the rapid gradient coils’ design. The validity and accuracy of the new approach are proved by finite element simulation and experiment, and the experiment shows that the uniformity of the new coil is improved from 44.79% of the traditional coil to 23.47% with $\Delta \text{G}$ decreasing by 47.6%.