Design and construction of a dipolar Halbach array with a homogeneous field from identical bar magnets: NMR Mandhalas

Magnets of the Halbach layout are interesting for the use in mobile NMR/MRI devices. Therefore, the ideal Halbach magnet was iterated using identical bar magnets, which are positioned and oriented based on analytical equations. These configurations were simulated with two‐dimensional finite‐element methods. Performance factors were defined to relate field strength with homogeneity and mass. A geometry of 16 magnets provided a good compromise between performance and special requirements for the desired use to store hyperpolarized xenon. The construction of such a magnet required the design of dedicated support frames and procedures to mount them. The field strength and homogeneity in the finished magnet were measured by a Hall probe and agreed well with the simulations. The calculation and construction are described in detail and together with the tabled field values for n magnets with n ≤ 80 may prove helpful for building similar devices, which were named NMR Mandhalas ( M agnet A rrangements for N ovel D iscrete Ha lbach La yout).