Cylindrical Halbach magnet shimming coils

Abstract

The invention provides a target field method for design shimming coils for cylindrical Halbach magnet (commonly known as a magic ring magnet). All orders of shimming rings which are designed according to the invention are respectively fixed on all coaxial cylindrical surfaces on the inner side of the permanent magnet. Closed loops as shown in Drawings 3 to 10 are cut into 'open loops' at appropriate positions, and the close open loops are sequentially and serially connected and an order of shimming coil is formed. Every order of shimming coil is electrified and generate precise corresponding order of harmonic magnetic field in an interested area in the center of the magnet. When in design, the value of a stream function meets the condition that the magnetic fields of the coils do not exceed a target harmonic field for a certain threshold, the power consumption functions of the coils are minimum, and the projection of the isolines of the stream function realizes the distribution of leads. After being fed with appropriate reversing current, all orders of harmonic shimming coils designed according to the invention can precisely offset harmful harmonic components in the magnetic fields, so that the purpose of shimming horizontal magnetic fields Bx of the magic ring permanent magnet is achieved, and simultaneously, the cylindrical Halbach magnet shimming coils have the characteristics that the power consumption of the coils is low and the shimming efficiency is high.

Description

technical field [0001] The invention relates to a target field method for designing shim coils of cylindrical Halbach magnets (also known as magic ring magnets). The high-field permanent magnet is particularly suitable for use as a movable or portable nuclear magnetic resonance spectrometer magnet and a beam current deflection magnet for controlled moving arms in accelerator radiotherapy equipment. Background technique [0002] With the wide application of nuclear magnetic resonance spectrometers in the fields of chemistry, biology, medicine, quality control, etc., it has become an important research direction to develop magic ring cylindrical high-field permanent magnets as the main magnets of nuclear magnetic resonance spectrometers. Traditional cylindrical superconducting magnets, magic ring permanent magnets (Zu Donglin et al., Static magnetostatic boundary value problems and magic ball magic ring permanent magnets, University Physics, 18(3): 17-20, 2001) do not require ...

AI Technical Summary

Problems solved by technology

However, the general target field method is not used successfully in the design of the shim coil of the magic ring magnet. The shimming coil of the ring magnet is a cylindrical surface, and the main magnetic field is a transverse field perpendicular to the axis. The axisymmetric relationship is broken, and it is difficult to select an effective function set to represent the current distribution during design. Therefore, the magic ring cylindrical permanent The design of the shimming coil of the magnet mainly uses the positive method (Tang Xiaoying, Zhao Wei. Chinese patent: 200810176587.6, 2009-05-20), which has relatively large limitations, and the target field method is still blank

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