This paper describes an analytical method to predict undesirable magnetic field inhomogeneity caused by manufacturing errors and evaluation of the permissible manufacturing tolerance for a high temperature superconductor (HTS) NMR magnet. Recently, HTS magnets have been actively studied for high-field nuclear magnetic resonance (NMR) (>1 GHz) magnet worldwide. Most high-field HTS magnet wound with REBCO tapes are composed of stacks of single or double pancake coils with hundreds of turns per each pancake. Even following ideally homogeneous magnet design, the magnetic field in a certain region of interest (ROI) of an initially manufactured REBCO NMR magnet must be inhomogeneous because of machining tolerance errors, the REBCO conductor’s dimensional variation of thickness and width, and human errors during winding and assembling. Also, if the manufacturing-error-induced inhomogeneity exceeds the maximum shim strength of ferromagnetic shim and/or shim coils, the magnet cannot be used for an NMR. In this paper, we present 1) a draft design of 400-MHz/54-mm REBCO NMR magnet; 2) a stochastic modeling and statistical analysis of the mangetic field homogeneity affected by manufacturing errors and 3) evaluation of the maximum manufacturing tolerance under the limit of ferromagnetic shim strength.
|Submitters Country||Republic of Korea|