Spherical harmonic decomposition of the magnetic field generated by a HTS bulk magnet

On the market of NMR spectroscopy, there is a growing interested in compact and high-resolution magnets. This can only achieve by using High Temperature Superconducting bulks magnets such as GdBaCuO. Moreover, bulk HTS magnets exhibit ultra-high stability and offer the possibility to use cryogen free cooling. A way to design NMR magnet is to exploit the magnetic field produced by two face-to-face HTS bulks. Since uniformity required by NMR systems is crucial, dedicated tools are required in order to improve the magnetization process of HTS bulks and also for designing the shim coils efficiently. In this paper, we address the problem of estimation of magnetic field uniformity produce by a HTS bulk magnet by means of spherical harmonics decomposition.