Lightweight asymmetric magnet arrays with mixed-phase magnet rings
地域：
Ariel
摘要
A magnet array includes multiple magnet rings and a frame. The multiple magnet rings are positioned along a longitudinal axis and coaxially with the longitudinal axis, wherein at least two of the magnet rings include mixed-phase magnet rings that are phase-dissimilar. The multiple magnet rings are configured to jointly generate a magnetic field along a direction parallel to the longitudinal axis of at least a given level of uniformity inside a predefined inner volume. The frame is configured to fixedly hold the multiple magnet rings in place.
說明書
This application claims the benefit of U.S. Provisional Patent Application 62/772,638, filed Nov. 29, 2018, and U.S. Provisional Patent Application 62/780,272, filed Dec. 16, 2018, whose disclosures are incorporated herein by reference.
The present invention relates generally to magnet assemblies, and particularly to lightweight magnet assemblies comprising permanent magnets and design methods thereof.
Designs of permanent magnet arrays aiming at achieving a strong and uniform magnetic field have been previously reported in the patent literature. For example, U.S. Pat. No. 7,423,431 describes a permanent magnet assembly for an imaging apparatus having a permanent magnet body having a first surface and a stepped second surface which is adapted to face an imaging volume of the imaging apparatus, wherein the stepped second surface contains at least four steps.
權(quán)利要求
The invention claimed is:1. A magnet array, comprising:multiple magnet rings, which are positioned along a longitudinal axis and coaxially with the longitudinal axis, wherein at least two of the magnet rings comprise mixed-phase magnet rings that are phase-dissimilar, and wherein the magnet rings are arranged with reflectional asymmetry with respect to the longitudinal axis, the multiple magnet rings configured to jointly generate a magnetic field along a direction parallel to the longitudinal axis of at least a given level of uniformity inside a predefined inner volume; and a frame, which is configured to fixedly hold the multiple magnet rings in place. 2. The magnet array according to claim 1 , wherein two of the at least two mixed-phase magnet rings contain only a single permanent magnetic phase with a magnetization vector in a direction different by more than 45 degrees from one another. 3. The magnet array according to claim 1 , wherein each magnet ring has a rotational symmetry with respect to an in-plane rotation of the magnet ring around the longitudinal axis. 4. The magnet array according to claim 1 , wherein at least one of the magnet rings encircles the predefined inner volume, and wherein a minimal inner radius of the magnet rings positioned on one side of a center of the inner volume along the longitudinal axis is different from the minimal inner radius of the magnet rings positioned on the other side of the center of inner volume. 5. The magnet array according to claim 1 , wherein the inner volume is an ellipsoid of revolution around the longitudinal axis. 6. The magnet array according to claim 1 , wherein a given magnet ring is made of one of a single solid element and an assembly of discrete magnet segments. 7. The magnet array according to claim 6 , wherein the magnet ring is pre-magnetized with a respective magnetization direction that maximizes uniformity of the magnetic field inside the inner volume. 8. The magnet array according to claim 6 , wherein the magnet ring is pre-magnetized with a respective magnetization direction that minimizes a fringe field outside the magnet array. 9. The magnet array according to claim 6 , wherein the discrete magnet segments are electrically insulated from each other. 10. The magnet array according to claim 6 , wherein each of the discrete magnet segments has a shape that is one of a shape of sphere, a cylinder, an ellipsoid and a polygonal prism. 11. The magnet array according to claim 6 , wherein the discrete magnet segments are separated of each other by at least one non-magnetic element comprising a solid, gas or liquid. 12. The magnet array according to claim 1 , wherein each of the magnet rings has a shape comprising one of an ellipse, a circle and a polygon. 13. The magnet array according to claim 1 , wherein each of the mixed phase rings has a discrete rotational symmetry of at least an order eight. 14. The magnet array according to claim 1 , and comprising one or more additional arrays of magnet rings, wherein the magnet rings in the additional arrays are coaxial with respective longitudinal axes that are set at respective angles from the longitudinal axis. 15. A method for producing a magnet array, the method comprising:positioning multiple magnet rings along a longitudinal axis and coaxially with the longitudinal axis, wherein at least two of the magnet rings comprise mixed-phase magnet rings that are phase-dissimilar, and wherein the magnet rings are arranged with reflectional asymmetry with respect to the longitudinal axis, the multiple magnet rings configured to jointly generate a magnetic field along a direction parallel to the longitudinal axis of at least a given level of uniformity inside a predefined inner volume; and fixedly holding the multiple magnet rings in place using a frame. 16. The method according to claim 15 , wherein two of the at least two mixed-phase magnet rings contain only a single permanent magnetic phase with a magnetization vector in a direction different by more than 45 degrees from one another. 17. The method according to claim 15 , wherein each magnet ring has a rotational symmetry with respect to an in-plane rotation of the magnet ring around the longitudinal axis. 18. The method according to claim 15 , wherein at least one of the magnet rings encircles the predefined inner volume, and wherein a minimal inner radius of the magnet rings positioned on one side of a center of the inner volume along the longitudinal axis is different from the minimal inner radius of the magnet rings positioned on the other side of the center of inner volume. 19. The method according to claim 15 , wherein the inner volume is an ellipsoid of revolution around the longitudinal axis. 20. The method according to claim 15 , wherein a given magnet ring is made of one of a single solid element and an assembly of discrete magnet segments. 21. The method according to claim 20 , wherein the magnet ring is pre-magnetized with a respective magnetization direction that maximizes uniformity of the magnetic field inside the inner volume. 22. The method according to claim 20 , wherein the magnet ring is pre-magnetized with a respective magnetization direction that minimizes a fringe field outside the magnet array. 23. The method according to claim 20 , wherein the discrete magnet segments are electrically insulated from each other. 24. The method according to claim 22 , wherein each of the discrete magnet segments has a shape that is one of a shape of sphere, a cylinder, an ellipsoid and a polygonal prism. 25. The method according to claim 22 , wherein the discrete magnet segments are separated of each other by at least one non-magnetic element comprising a solid, gas or liquid. 26. The method according to claim 15 , wherein each of the magnet rings has a shape comprising one of an ellipse, a circle and a polygon. 27. The method according to claim 15 , wherein each of the mixed phase rings has a discrete rotational symmetry of at least an order eight. 28. The method according to claim 15 , and comprising positioning one or more additional arrays of magnet rings, wherein the magnet rings in the additional arrays are coaxial with respective longitudinal axes that are set at respective angles from the longitudinal axis.
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