Speakers
Description
A 1.15 GHz nuclear magnetic resonance (NMR) spectrometer magnet has been under study at the Institute of Electrical Engineering of the Chinese Academy of Sciences. This NMR magnet requires spatial field homogeneity to reach 4 per million (ppm) in a sphere with a diameter of 40 millimeters. To achieve such a high magnetic field quality, each double pancake was wound with Bi-2223 tapes to reduce screening current. However, the actual parameters of the magnet are different from the designed parameters due to manufacturing errors, which still affect central magnetic field qualities. In this paper, the effects of different kinds of errors on the homogeneity of the central magnetic field and the feasibility of fabrication of joints between double pancakes with different outer diameters are analyzed. And then a scheme was proposed to optimize the position of the double cakes with different sizes in the magnet. The simulation and experimental results show that the quality of the central magnetic field is obviously improved and the influence of the manufacturing error on the magnetic field uniformity is reduced, which will create favorable conditions for the subsequent active shim coils and multi-layer ferromagnetic shims.
