Optimal Shimming Design And Magnetic Field Quality Research For Highly Homogeneous Superconducting Magnet Based On LPT

Highly homogeneous superconducting magnets are used in magnetic resonance imaging system,ion trap,particle spectrometer etc.;the imaging quality and the measurement precision of these devices depend on the magnetic field homogeneity.Therefore,the field quality analysis and a fast shimming design method with high accuracy and strong robustness play key roles in these projects.Based on the superconducting magnet being developed for Lanzhou Penning Trap(LPT)by Institute of Modern Physics(IMP),this thesis conducts researches on shimming system design and field quality analysis.First,in terms of active shimming design methodology research,Analytical based Particle Swarm Optimization(APSO)method has been put forward to design the shimming coils based on the comparison between analytical design method and Linear Programming(LP)method.Compared to analytical method,APSO method solves the off-centre region shimming problem and yields more feasible results.Meanwhile APSO method eliminates the error from current approximation and calculates faster than LP method.Combining professional electromagnetic field software and a comman platform,an automatic method for shimming coils design has been proposed,which is suitable for fast shimming design.A set of visual software for shimming coil design has been developed with C# language and Windows Form platform,which supplies two methods for comparing design.Then,a comprehensive analysis on main field quality has been completed for LPT magnet.The persistent current effect on field homogeneity and spherical coefficients has been firstly calculated with Bean model,from which the hysteresis of some harmonics has been found.The geometrical error and the magnetic residual effect have been analyzed by Monte Carlo method and FEM method repectively.In addition,the necessity of refining design on coils has been demonstrated and the Particle Swarm Optimization was introduced for the LPT coils refining design;PSO has been used effectively for designing several kinds of magnet coils.At last,the shimming design,analysis and test for LPT magnet have been conducted.The magnetic coupling between shimming pieces has been analyzed,which demonstrated that the coupling effect is negligible.The shimming effect affected by density of shimming pieces has been researched;the passive shimming system for LPT magnet has been designed,fabricated and tested.The shimming coils for LPT magnet have been designed by the developed software.In addition,the copper tapes shimming technology has been put forward and its field quality has been discussed.Shimming coils for LPT magnet has been wound and tested.