A high magnetic field and high homogeneity superconducting magnet system for nuclear magnetic resonance

Abstract

A high - magnetic - field and high - homogeneity superconducting magnet system for nuclear magnetic resonance, belonging to the technical field of nuclear magnetic resonance, solves the problem of how to design a superconducting magnet system with high magnetic field strength and high homogeneity; in the magnet of the present invention, the high - field region inside uses a coil made of niobium - tin superconducting wire, and the low - field region outside uses a coil made of niobium - titanium superconducting wire; the main coils work in series and operate at liquid helium temperature, and can generate an effective central magnetic field strength of 18.8 T; the designed homogeneity of the central magnetic field can be better than 0.01 ppm within a 1 - cm - diameter spherical range; the main magnetic field coils can shield more than 90% of the external electromagnetic interference; the shielding coils can effectively control the size of the stray field of the magnet system, and the 5 - Gs - line stray field can be limited within an ellipsoid with a radial dimension of 1.5 m and an axial dimension of 2.5 m respectively; the present invention is applicable to scenarios such as nuclear magnetic resonance spectrometers, animal imaging, and Fourier - transform ion cyclotron resonance.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear magnetic resonance, and relates to a high-field and high-homogeneity superconducting magnet system for nuclear magnetic resonance. Background Art

[0002] Nuclear magnetic resonance (NMR) spectroscopy is one of the most commonly used and direct means for identifying the structures of pure compounds and mixtures (liquid or solid) in the fields of chemistry, physics, biology, medicine, materials, etc. It is one of the few techniques capable of detecting three states of matter, and the structural analysis of almost all organic or biological molecules and many inorganic molecules begins with NMR spectroscopy.

[0003] NMR spectrometers come in various forms, but the basic components are the same, mainly including: a magnet that provides a high-homogeneity and high-stability main magnetic field, components that generate pulses and receive the generated NMR signals, a probe for placing samples, hardware for stabilizing the main magnetic field and optimizing signals, a computer for controlling the operation of the instrument and processing NMR signals, etc.

[0004] The magnet that provides the main magnetic field is the most critical and core component of the NMR system. The earliest NMR spectrometers used electromagnets and operated in continuous wave mode, with the characteristics of low sensitivity and poor stability. Modern desktop permanent magnet instruments have low costs and are simple to use and maintain, but their sensitivity is still very low. Currently, the vast majority of scientific research spectrometers use superconducting magnets and operate in pulsed Fourier transform mode. Compared with ordinary copper conductor materials, superconducting wires have a higher current density, and their current-carrying capacity is two to three orders of magnitude higher than that of traditional normal-conducting metal materials. Superconducting magnets developed based on superconducting wires have a higher magnetic field strength, a more compact magnet structure, and better magnetic field stability. At the same time, since the chemical shift and its difference increase with the increase of the field strength, the strong magnetic field of the superconducting magnet has a better effect on distinguishing nuclear magnetic signals.

[0005] High-homogeneity and high-field coils can be achieved by combining superconducting wires of different specifications. There are already domestic patented technologies (CN101552077B, CN112908609B) that can generate a high-homogeneity magnetic field, but the NMR superconducting coils they use are made of niobium-titanium (NbTi) conductors, so the magnetic field is only 9.4T (corresponding to a proton resonance frequency of 400 MHz). To generate a magnetic field above 9.4T, a combination of niobium-titanium and niobium-tin (Nb3Sn, Nb3(Ta)Sn, etc.) coils needs to be used. The patent document "A High-Field Superconducting Magnet System" (CN113889313B) gives a preliminary coil combination structure, but the magnetic field strength is 14T and it is applied in the field of nuclear magnetic resonance imaging (MRI), not the field of nuclear magnetic resonance spectroscopy (NMR). At the same time, this patent document does not consider the influence of electromagnetic force on brittle niobium-tin materials. Summary of the Invention

[0006] The technical solution of the present invention is used to solve the problem of how to design a superconducting magnet system with high magnetic field strength and high uniformity.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] A high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance, comprising: a main coil subsystem, a compensation coil subsystem, a shielding coil subsystem, and an anti-interference coil subsystem; the main coil subsystem includes: a first niobium-tin coil, a second niobium-tin coil, a third niobium-tin coil, a first niobium-titanium coil, and a second niobium-titanium coil; the first niobium-tin coil, the second niobium-tin coil, the third niobium-tin coil, the first niobium-titanium coil, and the second niobium-titanium coil are concentrically and coaxially nested in layers from the inside to the outside along the radial direction; at least one of the first niobium-tin coil, the second niobium-tin coil, and the third niobium-tin coil is provided with a binding layer on the outside; at least one of the first niobium-titanium coil and the second niobium-titanium coil is provided with a binding layer on the outside; the compensation coil subsystem includes: a first low-order magnetic field harmonic component compensation coil, a second low-order magnetic field harmonic component compensation coil, a first high-order magnetic field harmonic component elimination coil, a second high-order magnetic field harmonic component elimination coil, a first high-order magnetic field harmonic component compensation coil, and a second high-order magnetic field harmonic component compensation coil; the first low-order magnetic field harmonic component compensation coil, the first high-order magnetic field harmonic component elimination coil, the first high-order magnetic field harmonic component compensation coil, the second high-order magnetic field harmonic component compensation coil, the second high-order magnetic field harmonic component elimination coil, and the second low-order magnetic field harmonic component compensation coil are symmetrically and coaxially sleeved outside the main coil subsystem from top to bottom; the shielding coil subsystem is arranged on the outermost side of the magnet; the anti-interference coil is arranged inside the main coil subsystem; the main coil subsystem, the compensation coil subsystem, and the shielding coil subsystem work in series, with the same working current magnitude, and are excited by the same power supply; the function of the compensation coil subsystem is to compensate for the second-order, fourth-order, and sixth-order non-uniform magnetic fields of the long solenoid structure magnetic field of the main coil subsystem; the working current direction of the shielding coil subsystem is opposite to the working current directions of the main coil subsystem and the compensation coil subsystem; the anti-interference coil subsystem has no working current in the initial state, and the anti-interference coil subsystem is electromagnetically coupled with the main coil subsystem, the compensation coil subsystem, and the shielding coil subsystem.

[0009] Furthermore, for the multiple coils in the main coil subsystem, the axial length of the coil radially closer to the center is less than or equal to the outer coil adjacent to it radially, that is, the axial length of the first niobium-tin coil is less than or equal to the axial length of the second niobium-tin coil, the axial length of the second niobium-tin coil is less than or equal to the axial length of the third niobium-tin coil, the axial length of the third niobium-tin coil is less than or equal to the axial length of the first niobium-titanium coil, and the axial length of the first niobium-titanium coil is less than or equal to the axial length of the second niobium-titanium coil.

[0010] Further, the current-carrying capacity of the superconducting wire materials respectively used by multiple coils in the main coil subsystem is such that, in the same environment, the current-carrying capacity of the wire material radially closer to the center is greater than or equal to that of the superconducting wire material used by the outer coil adjacent to it radially.

[0011] Further, the main coil subsystem, the compensation coil subsystem, the shielding coil subsystem, and the anti-interference coil subsystem all use paraffin or epoxy impregnation.

[0012] Further, the shielding coil subsystem includes: a first shielding coil and a second shielding coil; the first shielding coil and the second shielding coil are two identical rings, and the first shielding coil and the second shielding coil are symmetric from top to bottom and coaxially sleeved outside the compensation coil subsystem.

[0013] Further, the anti-interference coil includes: an anti-interference main coil, a first anti-interference end compensation coil, and a second anti-interference end compensation coil; the anti-interference main coil is a cylindrical coil, and the first anti-interference end compensation coil and the second anti-interference end compensation coil are both rings, and the first anti-interference end compensation coil and the second anti-interference end compensation coil are symmetrically arranged above and below inside or outside the anti-interference main coil.

[0014] Further, the shielding coil subsystem adopts a reversed-field solenoid shielding coil.

[0015] Further, the steps for manufacturing the binding layer arranged outside the Nb₃Sn coil are: winding the Nb₃Sn coil on a skeleton, heat-treating the Nb₃Sn coil, performing epoxy vacuum impregnation on the Nb₃Sn coil, machining the space required for winding the binding layer on the outer surface of the impregnated Nb₃Sn coil, and winding the binding layer.

[0016] Further, the steps for manufacturing the binding layer arranged outside the NbTi coil are: winding the NbTi coil on a skeleton, performing epoxy vacuum impregnation on the NbTi coil, machining the space required for winding the binding layer on the outer surface of the impregnated NbTi coil, and winding the binding layer.

[0017] Further, the axial winding length of the binding layer is less than or equal to the axial length of the coil, but not less than 50% of the coil length; the material of the binding layer is pure metal wire or metal wire with an insulating layer.

[0018] The advantages of the present invention are:

[0019] The high magnetic field strength and high uniformity superconducting magnet system for nuclear magnetic resonance of the present invention is a magnet for an 800 MHz superconducting nuclear magnetic resonance spectrometer; the high-field region inside the magnet of the present invention is a coil using niobium-tin superconducting wire, and the coil in the outer low-field region uses niobium-titanium superconducting wire. All coils are nested and assembled coaxially inside and outside; the main coil, compensation coil, and shielding coil work in series and operate at liquid helium temperature, and can generate an effective central magnetic field strength of 18.8 T (corresponding to a proton resonance frequency of 800 MHz); through the optimized design of the main coil and each compensation coil, the designed uniformity of the central magnetic field can be better than 0.01 ppm within a 1 cm diameter spherical range; the anti-interference coil can shield more than 90% of the external electromagnetic interference without damaging the long-term stability of the main magnet magnetic field; introducing a shielding coil can effectively control the size of the stray field of the magnet system, and the 5 Gs line (5 gauss line) stray field can be limited within an ellipsoid of 1.5 m and 2.5 m in the radial and axial directions respectively; the present invention is suitable for high magnetic field strength and high uniformity magnets with a bore diameter of 50 - 200 mm, and is applied to scenarios such as nuclear magnetic resonance spectrometers (NMR), animal imaging (pre-clinic MRI), and Fourier transform ion cyclotron resonance (FT-ICR). BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural marking diagram of each subsystem in the axial half-sectional view of the high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance in the first embodiment of the present invention;

[0021] Figure 2 It is a structural marking diagram of each coil in the axial half-sectional view of the high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance in the first embodiment of the present invention;

[0022] Figure 3 It is a structural composition diagram of the anti-interference coil subsystem of the high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance in the first embodiment of the present invention;

[0023] Figure 4 It is a schematic diagram of a binding layer arranged outside the niobium-tin or niobium-titanium coil of the high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance in the first embodiment of the present invention;

[0024] Figure 5 It is a magnetic field uniformity distribution diagram on different sized spheres of the high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance in the first embodiment of the present invention;

[0025] Figure 6 It is a stray field distribution diagram of the superconducting magnet of the high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance in the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments:

[0028] Embodiment 1

[0029] As Figure 1 shown, a high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance includes: a main coil subsystem 10, a compensation coil subsystem 20, a shielding coil subsystem 30, and an anti-interference coil subsystem 40.

[0030] As Figure 2 shown, the main coil subsystem 10 includes: a first niobium tin coil 101, a second niobium tin coil 102, a third niobium tin coil 103, a first niobium titanium coil 104, and a second niobium titanium coil 105.

[0031] The first niobium tin coil 101, the second niobium tin coil 102, the third niobium tin coil 103, the first niobium titanium coil 104, and the second niobium titanium coil 105 are all cylindrical coils. The first niobium tin coil 101, the second niobium tin coil 102, the third niobium tin coil 103, the first niobium titanium coil 104, and the second niobium titanium coil 105 are concentrically and coaxially nested in layers from the inside to the outside in the radial direction, that is, the first niobium tin coil 101 is concentrically and coaxially nested inside the second niobium tin coil 102, the second niobium tin coil 102 is concentrically and coaxially nested inside the third niobium tin coil 103, the third niobium tin coil 103 is concentrically and coaxially nested inside the first niobium titanium coil 104, and the first niobium titanium coil 104 is concentrically and coaxially nested inside the second niobium titanium coil 105.

[0032] For the multiple coils in the main coil subsystem 10, the coil axially closer to the center in the radial direction has an axial length less than or equal to that of the adjacent outer coil in the radial direction, that is, the axial length of the first niobium tin coil 101 is less than or equal to the axial length of the second niobium tin coil 102, the axial length of the second niobium tin coil 102 is less than or equal to the axial length of the third niobium tin coil 103, the axial length of the third niobium tin coil 103 is less than or equal to the axial length of the first niobium titanium coil 104, and the axial length of the first niobium titanium coil 104 is less than or equal to the axial length of the second niobium titanium coil 105.

[0033] The current-carrying capacity of the superconducting wire used in each of the multiple coils within the main coil subsystem 10 is such that, in the same environment, the current-carrying capacity of the wire radially closer to the center is greater than or equal to that of the superconducting wire used in the outer coil adjacent to it radially. That is, the current-carrying capacity of the first niobium-tin coil 101 is greater than or equal to that of the second niobium-tin coil 102, the current-carrying capacity of the second niobium-tin coil 102 is greater than or equal to that of the third niobium-tin coil 103, the current-carrying capacity of the third niobium-tin coil 103 is greater than or equal to that of the first niobium-titanium coil 104, and the current-carrying capacity of the first niobium-titanium coil 104 is greater than or equal to that of the second niobium-titanium coil 105.

[0034] The main coil subsystem 10, the compensation coil subsystem 20, the shielding coil subsystem 30, and the anti-interference coil subsystem 40 are all impregnated with paraffin or epoxy to ensure structural rigidity.

[0035] The diameter of the first niobium-tin coil 101 is approximately 80 mm to produce a room-temperature aperture of 54 mm.

[0036] At least one of the first niobium-tin coil 101, the second niobium-tin coil 102, and the third niobium-tin coil 103 is externally provided with a binding layer, which is used to prevent the electromagnetic force from damaging the niobium-tin material coil.

[0037] Due to its low critical magnetic field, niobium-titanium superconducting wire is generally used to make magnets below 10 T. For magnets above 10 T, superconducting conductors with high critical magnetic fields such as niobium-tin are required. Niobium-tin superconducting conductors are composed of composite materials such as niobium-tin raw materials, bronze, and copper-based materials. Niobium-tin conductors need to undergo high-temperature heat treatment to form conductors with superconducting properties, and they have the disadvantages of poor mechanical properties and high brittleness. Therefore, for superconducting coils using niobium-tin materials, it is very important to have measures to maintain the strength of the coil and prevent the electromagnetic force from damaging the niobium-tin material. In the working state of a superconducting coil wound by superconducting materials, the interaction between the current and the magnetic field will form an outward-expanding electromagnetic force on the superconducting coil. This electromagnetic force must be well controlled so that the electromagnetic strain of the coil under the electromagnetic force meets the design requirements. The current-carrying performance of niobium-tin materials is related to their strain state. By controlling the strain of the coil, the decline in the current-carrying capacity of the superconducting material caused by the electromagnetic force can be controlled. Niobium-tin superconducting coils generally use vacuum impregnation (paraffin or epoxy) and external winding of a binding layer to control their strain state. Vacuum impregnation is used to fill the gaps between layers and turns of the superconducting coil, which can maintain the rigidity of the superconducting coil and resist the axial electromagnetic pressure of the coil. The binding layer is a way to control the influence of the radial force on the coil. Usually, non-magnetic high-strength materials such as 304, 316, 316L, and 316LN stainless steel are used to wind binding layers with different radial thicknesses on the outside of the superconducting coil wound by superconducting conductors according to the magnitude of the electromagnetic force. The structure of the binding layer is as Figure 4As shown (other components such as the coil former are hidden for clarity of structure). The axial winding length of the lashing layer is less than or equal to the axial length of the superconducting coil, but not less than 50% of the coil length. Therefore, there are gaps at the upper and lower ends of the lashing layer. The material of the lashing layer can be pure metal wire, or metal wire with insulation (such as glass cloth sleeve, etc.); it can be directly dry-wound outside the coil, or after winding, it can be vacuum-impregnated together with the coil; the winding of the lashing layer material can be completed before the heat treatment of the niobium-tin superconducting wire, or after the heat treatment of the niobium-tin superconducting wire.

[0038] The main steps for manufacturing the lashing layer provided outside the niobium-tin coil are as follows: winding the niobium-tin coil on the former, heat-treating the niobium-tin coil, epoxy vacuum-impregnating the niobium-tin coil, machining the space required for winding the lashing layer on the outer surface of the impregnated niobium-tin coil, and winding the lashing layer. When machining the space for the post-processed lashing layer, it is recommended that the overall axial length be less than the length of the coil, mainly to ensure that other components at the ends are not damaged during machining. In this manufacturing method, the winding of the lashing layer material is after the heat treatment, so the mechanical strength of the lashing layer material will not degrade due to high-temperature heat treatment. The method of the embodiment of the present invention can control the electromagnetic force with less lashing material, making the overall structure of the magnet more compact.

[0039] There is also a lashing layer provided outside the niobium-titanium coil. The main steps for manufacturing the lashing layer provided outside the niobium-titanium coil are as follows: winding the niobium-titanium coil on the former, epoxy vacuum-impregnating the niobium-titanium coil, machining the space required for winding the lashing layer on the outer surface of the impregnated niobium-titanium coil, and winding the lashing layer; the axial winding length of the lashing layer is less than or equal to the axial length of the niobium-titanium coil, but not less than 50% of the niobium-titanium coil length.

[0040] Such as Figure 2As shown in the figure, the compensation coil subsystem 20 includes: a first low-order magnetic field harmonic component compensation coil 201, a second low-order magnetic field harmonic component compensation coil 202, a first high-order magnetic field harmonic component cancellation coil 203, a second high-order magnetic field harmonic component cancellation coil 204, a first high-order magnetic field harmonic component compensation coil 205, and a second high-order magnetic field harmonic component compensation coil 206. The first low-order magnetic field harmonic component compensation coil 201 and the second low-order magnetic field harmonic component compensation coil 202 are two identical circular rings. The first high-order magnetic field harmonic component cancellation coil 203 and the second high-order magnetic field harmonic component cancellation coil 204 are two identical circular rings. The first high-order magnetic field harmonic component compensation coil 205 and the second high-order magnetic field harmonic component compensation coil 206 are two identical circular rings. The first low-order magnetic field harmonic component compensation coil 201, the first high-order magnetic field harmonic component cancellation coil 203, the first high-order magnetic field harmonic component compensation coil 205, the second high-order magnetic field harmonic component compensation coil 206, the second high-order magnetic field harmonic component cancellation coil 204, and the second low-order magnetic field harmonic component compensation coil 202 are symmetrically and coaxially sleeved outside the main coil subsystem 10 from top to bottom.

[0041] As Figure 2 shown in the figure, the shielding coil subsystem 30 is arranged on the outermost side of the magnet. The shielding coil subsystem 30 includes: a first shielding coil 301 and a second shielding coil 302. The first shielding coil 301 and the second shielding coil 302 are two identical circular rings. The first shielding coil 301 and the second shielding coil 302 are symmetric from top to bottom and coaxially sleeved outside the compensation coil subsystem 20. The number of shielding coils can be greater than 2.

[0042] As Figure 3 shown in the figure, the anti-interference coil subsystem 40 includes: an anti-interference main coil 401, a first anti-interference end compensation coil 402, and a second anti-interference end compensation coil 403. The anti-interference main coil 401 is a cylindrical coil. The first anti-interference end compensation coil 402 and the second anti-interference end compensation coil 403 are both circular rings. The first anti-interference end compensation coil 402 and the second anti-interference end compensation coil 403 are symmetrically arranged above and below inside or outside the anti-interference main coil 401. The anti-interference coil subsystem 40 is arranged inside the main coil subsystem 10. In this embodiment, the anti-interference coil subsystem 40 is sleeved outside the second niobium-tin coil 102. The anti-interference coil subsystem 40 can also be sleeved outside the first niobium-tin coil 101, the third niobium-tin coil 103, or the first niobium-titanium coil 104.

[0043] Working principle of the magnet:

[0044] The described main coil subsystem 10, compensation coil subsystem 20, and shielding coil subsystem 30 work in series, with the same working current magnitude and are excited by the same power supply.

[0045] The function of the described compensation coil subsystem 20 is to compensate for the second-order, fourth-order, sixth-order, etc. non-uniform magnetic fields of the long solenoid structure magnetic field of the main coil subsystem 10; using multiple groups of compensation coils can make each harmonic component of the axial magnetic field of the magnet system less than 0.01 ppm.

[0046] The working current direction of the described shielding coil subsystem 30 is opposite to that of the main coil subsystem 10 and the compensation coil subsystem 20, used to reduce the magnitude of the stray field of the magnet and reduce the installation area requirements of users.

[0047] The described shielding coil subsystem 30 uses a reverse-field solenoid shielding coil;

[0048] The described anti-interference coil subsystem 40 has no working current in the initial state; the anti-interference coil subsystem 40 is electromagnetically coupled with the main coil subsystem 10, compensation coil subsystem 20, and shielding coil subsystem 30 to cancel out the magnetic field changes generated by the external electromagnetic disturbance at the magnet center position by the main coil subsystem 10, compensation coil subsystem 20, and shielding coil subsystem 30 of the main magnet; this is because when there is an external electromagnetic disturbance, the main magnet has a magnetic field response to the disturbance. This response will affect (usually deteriorate) the magnetic field quality at the magnetic field center position; the anti-interference coil subsystem 40 can generate a response opposite to that of the main magnet through electromagnetic induction with the main magnet, thereby eliminating the external electromagnetic interference of the magnet. At the same time, due to the presence of the anti-interference coil subsystem 40, it will not exacerbate the magnetic field decay rate of the entire magnet. On the contrary, through electromagnetic coupling with the main magnet, the anti-interference coil subsystem 40 can reduce the magnetic field decay rate of the entire magnet and increase the magnetic field stability of the magnet; the first anti-interference end compensation coil 402 and the second anti-interference end compensation coil 403 of the anti-interference coil subsystem 40 ensure that the magnetic field response of the anti-interference coil subsystem 40 to the main magnet will not damage the magnetic field uniformity of the main magnet.

[0049] Figure 5 It is the magnetic field uniformity distribution diagram on different-sized spherical surfaces of the high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance of the present invention; as Figure 5 shown, the magnetic field uniformity distribution equipotential lines within a 2 cm spherical surface centered on the coil, the peak-to-peak magnetic field uniformity within the 2 cm sphere is better than 0.025 ppm, and the peak-to-peak magnetic field uniformity within the 1 cm sphere is better than 0.01 ppm.

[0050] Figure 6 It is the stray field distribution diagram of the superconducting magnet of the high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance of the present invention; asFigure 6 As shown, the stray field of the 5Gs line (5 gauss line) can be limited within the ellipsoids of 1.5 m and 2.5 m in the radial and axial directions respectively.

[0051] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high - magnetic - field and high - homogeneity superconducting magnet system for nuclear magnetic resonance, characterized in that, Using a magnet with a bore diameter of 50 - 200 mm, applied in the fields of nuclear magnetic resonance spectrometers, animal imaging, and Fourier transform ion cyclotron resonance, generating an effective central magnetic field strength of 18.8 T, and the designed uniformity of the central magnetic field is better than 0.01 ppm within a 1 cm diameter spherical range; the main coil subsystem includes: the first, second, and third niobium tin coils and the first and second niobium titanium coils, and the first, second, and third niobium tin coils and the first and second niobium titanium coils are concentrically and coaxially nested in layers from the inside to the outside along the radial direction; at least one of the first, second, and third niobium tin coils is externally provided with a lashing layer, and at least one of the first and second niobium titanium coils is externally provided with a lashing layer. The niobium tin or niobium titanium coils are subjected to epoxy vacuum impregnation, and after impregnation, the space required for winding the lashing layer is machined on the outer surface of the niobium tin or niobium titanium coils for winding the lashing layer; the compensation coil subsystem includes: the first and second low - order magnetic field harmonic component compensation coils, the first and second high - order magnetic field harmonic component cancellation coils, and the first and second high - order magnetic field harmonic component compensation coils; the first low - order magnetic field harmonic component compensation coil, the first high - order magnetic field harmonic component cancellation coil, the first high - order magnetic field harmonic component compensation coil, the second high - order magnetic field harmonic component compensation coil, the second high - order magnetic field harmonic component cancellation coil, and the second low - order magnetic field harmonic component compensation coil are symmetrically and coaxially sleeved outside the main coil subsystem from top to bottom; the shielding coil subsystem is arranged on the outermost side of the magnet; the anti - interference coil subsystem is arranged inside the main coil subsystem; the main coil subsystem, the compensation coil subsystem, and the shielding coil subsystem are connected in series with the same working current magnitude; the working current direction of the shielding coil subsystem is opposite to that of the main coil subsystem and the compensation coil subsystem; the anti - interference coil subsystem has no working current in the initial state and is electromagnetically coupled with the main coil subsystem, the compensation coil subsystem, and the shielding coil subsystem. The anti - interference coil subsystem includes: an anti - interference main coil, a first anti - interference end compensation coil, and a second anti - interference end compensation coil; the anti - interference main coil is a cylindrical coil, and both the first anti - interference end compensation coil and the second anti - interference end compensation coil are circular rings, and the first anti - interference end compensation coil and the second anti - interference end compensation coil are symmetrically arranged above and below inside or outside the anti - interference main coil.

2. The high magnetic field and high homogeneity superconducting magnet system for nuclear magnetic resonance according to claim 1, wherein For the multiple coils in the main coil subsystem, the axial length of the coil radially closer to the center is less than or equal to that of the radially adjacent outer coil, that is, the axial length of the first niobium tin coil is less than or equal to that of the second niobium tin coil, the axial length of the second niobium tin coil is less than or equal to that of the third niobium tin coil, the axial length of the third niobium tin coil is less than or equal to that of the first niobium titanium coil, and the axial length of the first niobium titanium coil is less than or equal to that of the second niobium titanium coil.

3. The high magnetic field and high homogeneity superconducting magnet system for nuclear magnetic resonance according to claim 1, wherein The current - carrying capacity of the superconducting wires used for the multiple coils in the main coil subsystem, under the same environment, the current - carrying capacity of the wire radially closer to the center is greater than or equal to that of the superconducting wire used for the radially adjacent outer coil.

4. The high magnetic field and high homogeneity superconducting magnet system for nuclear magnetic resonance according to claim 1, characterized in that, The main coil subsystem, the compensation coil subsystem, the shielding coil subsystem, and the anti - interference coil subsystem are all impregnated with paraffin or epoxy.

5. The high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance according to claim 1, characterized in that, The shielding coil subsystem includes: a first shielding coil and a second shielding coil; the first shielding coil and the second shielding coil are two identical rings, the first shielding coil and the second shielding coil are symmetric from top to bottom, and are coaxially sleeved outside the compensation coil subsystem.

6. The high magnetic field and high homogeneity superconducting magnet system for nuclear magnetic resonance according to claim 1, characterized in that, The shielding coil subsystem uses a reversed-field solenoid shielding coil.

7. The high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance according to claim 1, characterized in that, The steps for manufacturing the binding layer provided outside the niobium-tin coil are as follows: the niobium-tin coil is wound on a skeleton, the niobium-tin coil is heat-treated, the niobium-tin coil is epoxy vacuum-impregnated, a space required for winding the binding layer is machined on the outer surface of the impregnated niobium-tin coil, and the binding layer is wound.

8. The high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance according to claim 1, characterized in that, The steps for manufacturing the binding layer provided outside the niobium-titanium coil are as follows: the niobium-titanium coil is wound on a skeleton, the niobium-titanium coil is epoxy vacuum-impregnated, a space required for winding the binding layer is machined on the outer surface of the impregnated niobium-titanium coil, and the binding layer is wound.

9. The high magnetic field and high homogeneity superconducting magnet system for nuclear magnetic resonance according to claim 7 or 8, characterized in that, The axial winding length of the binding layer is less than or equal to the axial length of the coil, but not less than 50% of the coil length.

10. The high magnetic field and high uniformity superconducting magnet system for nuclear magnetic resonance according to claim 7 or 8, characterized in that, The material of the binding layer is pure metal wire or metal wire with an insulating layer.

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