Hybrid Halbach permanent and electro magnet array for harmonic gyrotrons

Abstract

A non-cryogenic electro-permanent magnet for use in a gyrotron comprises a plurality of toroidal-shaped sets of electromagnet coils and a plurality of toroidal-shaped permanent magnets, each permanent magnet comprising a plurality of arc segment blocks. Each set of the coils is separated from an adjacent set of the coils by one or more of the permanent magnets disposed between the adjacent sets of coils, such that the coils and the permanent magnets are arranged concentrically to form an open central bore. A combination of magnetic fields in the permanent magnets and magnetic fields in the coils generates a substantially uniform axial magnetic field in the bore.

Claims

1. A non-cryogenic electro-permanent magnet for use in a gyrotron comprising: a plurality of toroidal-shaped sets of electromagnet coils; a plurality of toroidal-shaped permanent magnets, each permanent magnet comprising a plurality of arc segment blocks; wherein each set of the coils is separated from an adjacent set of the coils by one or more of the permanent magnets disposed between adjacent sets of coils, such that the coils and the permanent magnets are arranged concentrically to form a bore.

2. The non-cryogenic electro-permanent magnet for use in a gyrotron according to claim 1, wherein a combination of first magnetic fields of the permanent magnets and second magnetic fields of the coils generate a substantially uniform axial magnetic field in the bore.

3. The non-cryogenic electro-permanent magnet for use in a gyrotron according to claim 1, wherein one of the permanent magnets surrounds the one or more permanent magnets between adjacent sets of the coils.

4. The non-cryogenic electro-permanent magnet for use in a gyrotron according to claim 1, wherein one of the permanent magnets surrounds a set of the coils.

5. The non-cryogenic electro-permanent magnet for use in a gyrotron according to claim 1, a ferromagnetic band surrounding the permanent magnets.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:

(2) FIG. 1 schematically illustrates a gyrotron usable with the disclosed magnet assembly.

(3) FIGS. 2-7 illustrate conventional gyrotron magnets according to the related art.

(4) FIG. 8 illustrates an exterior perspective view of an electro-permanent magnet according to a first example embodiment of the present invention.

(5) FIG. 9 illustrates an exterior bore view of the electro-permanent magnet according to the first example embodiment of the present invention.

(6) FIG. 10 illustrates a cross-sectional view of the electro-permanent magnet according to the first example embodiment of the present invention.

(7) FIG. 11 illustrates a magnetization vector map of the permanent magnet rings according to the first example embodiment of the present invention.

(8) FIG. 12 illustrates a cross-sectional view of electro-permanent magnet assembly according to a second example embodiment of the present invention.

(9) FIG. 13 illustrates a finite element analysis B field map according to the second example embodiment of the present invention.

(10) FIG. 14 illustrates a graph of the B field on the centerline of the bore region versus axial position for several different coil currents according to the second example embodiment of the present invention.

(11) FIG. 15 illustrates a cross-sectional view of the electro-permanent magnet assembly according to third and fourth example embodiments of the present invention.

(12) FIG. 16 illustrates a cross-sectional view of the electro-permanent magnet assembly according to fifth example embodiment of the present invention.

(13) FIG. 17 illustrates a finite element analysis B field map according to the fifth example embodiment of the present invention.

(14) FIG. 18 illustrates a graph of the B field on the centerline of the bore region versus axial position for according to the fifth example embodiment of the present invention.

(15) FIG. 19 illustrates a cross-sectional view of the electro-permanent magnet assembly according to the fifth example embodiment of the present invention.

(16) FIG. 20 illustrates a comparison of magnetic characteristics of the electro-permanent magnet assemblies of the first and fifth embodiments.

DETAILED DESCRIPTION OF THE INVENTION

(17) Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, like reference numbers will be used for like elements. It should be understood that the principles described herein are not limited in application to the details of construction or the arrangement of components set forth in the following description or illustrated in the drawings. The principles may be embodied in other embodiments and may be practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

(18) According to the embodiments of the invention, a non-cryogenic electro-permanent magnet for use in a gyrotron comprises a plurality of toroidal-shaped sets of electromagnet coils and a plurality of toroidal-shaped permanent magnets, each permanent magnet comprising a plurality of arc segment blocks. Each set of the coils is separated from an adjacent set of the coils by one or more of the permanent magnets disposed between the adjacent sets of coils, such that the coils and the permanent magnets are arranged concentrically to form an open central bore. A combination of magnetic fields in the permanent magnets and magnetic fields in the coils generates a substantially uniform axial magnetic field in the bore.

(19) In further embodiments, one of the permanent magnets surrounds a set of the coils, and one of the permanent magnets surrounds the one or more permanent magnets between adjacent sets of the coils. In other embodiments, a ferromagnetic band surrounds the surrounding permanent magnets. In still further embodiments, a ferromagnetic band surrounds one or more of the sets of the coils.

(20) The magnet assemblies described herein provides a uniform axial magnetic field in a cylindrical volume from the superposition of magnetic fields from a modified, permanent magnet Halbach array, and a plurality of coiled, current carrying, conductors. The bore diameter and volume, field magnitude and field uniformity are suitable for application in 2.sup.nd or other harmonic gyrotrons. The magnet assemblies described herein comprise an assembly of a plurality of similar permanent magnet segments into rings. Plural rings are assembled, each having various magnetization vector orientations suitably arranged to create a uniform, predominantly axial magnetic field in a cylindrical bore volume. Multi-turn coiled current carrying conductors are located inside and outside of the permanent magnet rings with appropriate current magnitude and direction to reinforce and shape a magnetic field strength and uniformity in the cylindrical volume.

(21) Active fluid cooling may be employed inside the conductors and/or external to the conductors to control the hybrid magnet temperature and electrical properties.

(22) The use of a modified cylindrical Halbach Array enables higher magnetic field levels than that obtained by the existing art, and enables the elimination of ferromagnetic materials in the magnet if desired.

(23) Also disclosed herein is a non-cryogenic gyrotron main magnet that uses an all-permanent-magnet structure (i.e., no ferromagnetic material) and a multi-coil configuration.

(24) FIG. 8 illustrates an exterior perspective view of an electro-permanent magnet (EPM) assembly 800 according to a first example embodiment of the present invention. FIG. 9 illustrates an exterior bore view of the EPM assembly 800 according to the first example embodiment of the present invention. FIG. 10 illustrates a cross-sectional view of the EPM assembly 800 according to the first example embodiment of the present invention.

(25) As illustrated in each of FIG. 8, FIG. 9, and FIG. 10, the EPM assembly 800 includes a plurality of coils 810.1, 810.2, 810.3, 810.4, 810.5, 810.6, 810.7, 810.8, the plurality of coils 810.1-810.8 being arranged in plural sets of coils 810A, 810B, and 810C. As further illustrated in FIG. 8, FIG. 9, and FIG. 10, the EPM assembly 800 comprises an array of permanent magnet (PM) rings 820.1, 820.2, 820.3, 820.4, 820.5, 820.6, 820.7.

(26) The plurality of coils 810.1-810.8 are electro-magnet coils (e.g., a toroid, loop, helix, or spiral) and may be composed of a copper coil or other conductive material (e.g., aluminum, silver, gold, etc.) and/or may be tape wound. In some instances, one or more cooling plates (not illustrated) may be disposed between the plurality of coils 810.1-810.8. In addition, and in an example configuration, each of the plurality of coils 810.1-810.8 may be configured at a 9 inch outer diameter, at a height of 0.26 inch, and assembled with 0.08 inch tall, interleaved, micro-channel, cooling plates (not illustrated) having the same 9 inch outer diameter.

(27) Each of the PM rings 820.1-820.7 may be constructed with a plurality of arc segment blocks. Permanent magnets may include high energy product, rare earth magnet materials such as Samarium Cobalt and/or Neodymium Iron Boron alloys. Each of the PM rings 820.1-820.7, or segments thereof, may be magnetized using known techniques.

(28) FIG. 9 illustrates the bore region 830 of the EPM assembly 800. EPM assembly 800 is configured to provide a maximum and uniform magnetic field within bore region 830. In an example configuration, the bore region 830 may have a diameter of approximately 2 inches or 50 mm. In this example configuration, and in connection with the 2 inch bore diameter, the outer diameter (OD) of the magnet ring is 8.3 inches, and the height is 1.5 inches.

(29) FIG. 10 illustrates a cross-section of the EPM assembly 800 which includes three (3) sets of coils 810A, 810B, and 810C (individual turns not illustrated), and an array of seven (7) PM magnet rings 820.1-820.7. This configuration is exemplary, and the embodiments of the invention are not so limited.

(30) In the first embodiment, there are three coil sub-assemblies illustrated; two outboard and one inboard of the PM assembly. In addition, the PM assembly includes seven (7) ring subassemblies, illustrated with 36 magnet segments per ring. Here, there are only three unique segment geometries used in the assembly. It should be noted that the first embodiment is exemplary, and the embodiments of the invention are not so limited.

(31) FIG. 11 illustrates a magnetization vector map 1100 of the PM rings 820.1-820.7 according to the first example embodiment of the present invention. As illustrated in FIG. 11, the magnetization vectors of the PM rings 820.1-820.7 vary in a counterclockwise direction (or alternatively, a clockwise direction depending on point of reference) beginning at PM ring 820.1 and proceeding through the remaining PM rings 820.2-820.7. Each of 820.1 and 820.7, the two rings adjacent to the EPM bore region 830, depict multiple vectors to illustrate that the angle of the magnetic field may be varied in the design process to optimize the bore field level and uniformity in conjunction with the fields produced by the current in the plurality of coils 810.1-810.8. Similarly, the angle of the magnetic field for each of PM rings 820.1-820.2 may be varied in the design process to optimize the bore field level and uniformity. The magnetic fields of the PM rings 820.1-820.7 superimpose to generate an axial B field in the bore region 830. Combined with the B fields produced by the coils, a large, uniform, axial magnetic field results in the bore region 830 with much lower current and power than may be obtained with only coils. In addition, the example configuration and magnetization of PM rings 820.1-820.7 and the plurality of coils 810.1-810.8 do not require use of ferromagnetic materials (e.g., ferromagnetic band 1250, as shown in FIG. 12) to function. However, configurations with ferromagnetic material may be configured to modify the magnetic fields and/or provide shielding of the external magnetic fields.

(32) FIG. 11 further illustrates the orientation of the magnetization vectors of the PM segments of the magnet assembly of FIGS. 8-10 to create a toroidal Halbach array. Each of the segments in a ring have the same magnetization orientation. The two, inner most, rings show 3 different vectors illustrating how deviation from the classic Halbach orientation (arrows pointing inboard) may be used to shape the bore region field.

(33) FIG. 12 illustrates a cross-sectional view of EPM assembly 1200 according to a second example embodiment of the present invention.

(34) As illustrated in each of FIG. 12, the EPM assembly 1200 includes a plurality of coils 1210.1-1210.8, the plurality of coils 1210.1-1210.8 being arranged in plural sets of coils 1210A, 1210B, and 1210C. As further illustrated in FIG. 12, the EPM assembly 1200 comprises an array of permanent magnet (PM) rings 1220.1-1220.7. PM rings 1220.3, 1220.4, and 1220.5 are disposed adjacent to casing 1250 (e.g., a ferromagnetic band on the outer diameter), which may be constructed of a ferromagnetic material to modify the magnetic fields and/or provide shielding of the external magnetic fields.

(35) The plurality of coils 1210.1-1210.8 are electro-magnet coils (e.g., a toroid, loop, helix, or spiral) and may be constructed of a copper coil or other conductive material (e.g., aluminum, silver, gold, etc.) and/or may be tape wound. In some instances, one or more cooling plates (not illustrated) may be disposed between the plurality of coils 1210.1-1210.8. In addition, and in an example configuration, the plurality of coils 1210.1-1210.8 may be configured at a 9 inch outer diameter, at a height of 0.26 inch, and assembled with 0.08 inch tall, interleaved, micro-channel, cooling plates (not illustrated) having the same 9 inch outer diameter.

(36) Each of the PM rings 1220.1-1220.7 may be constructed with a plurality of arc segment blocks. Permanent magnets may include high energy product, rare earth magnet materials such as Samarium Cobalt and/or Neodymium Iron Boron alloys. Each of the PM rings 1220.1-1220.7, or segments thereof, may be magnetized using known techniques.

(37) FIG. 13 illustrates a finite element analysis (FEA) B field map 1300 according to the second example embodiment of the present invention. FIG. 13 illustrates the resulting magnetic field distribution and magnitude for a set of PM properties, magnetization vectors, number of coils, turns and currents selected to yield a maximum magnitude and uniformity of the B field in the bore region 1230.

(38) FIG. 14 illustrates a graph of the B field on the centerline of the bore region versus axial position for several different coil currents according to the second example embodiment of the present invention. As shown, the B field is maximum and uniform in the bore region 1230, between 30 and 70 mm (i.e., a cavity or active region having a maximum and uniform magnetic field), at approximately 1.7 T using different current configurations in the plurality of coils.

(39) FIG. 15 illustrates a cross-sectional view of the EPM assembly 1500 according to third and fourth example embodiments of the present invention.

(40) As illustrated in each of FIGS. 15A and 15B, each of the EPM assemblies 1500A and 1500B includes a plurality of coils 1510.1-1510.10, the plurality of coils 1510.1-1510.10 being arranged in plural sets of coils 1510A, 1510B, and 1510C. As further illustrated in FIG. 15, each of the EPM assemblies 1500A and 1500B comprises an array of permanent magnet (PM) rings 1520.1-1520.7 (portions of 1520.4 being omitted in the configuration illustrated in FIG. 15B). PM Rings 1520.1-1520.7 and plurality of coils 1510.1-1510.10 being enclosed in casing 1570.

(41) The plurality of coils 1510.1-1510.10 are electro-magnet coils (e.g., a toroid, loop, helix, or spiral) and may be constructed of a copper coil or other conductive material (e.g., aluminum, silver, gold, etc.) and/or may be tape wound. One or more cooling plates (not illustrated) are disposed between the plurality of coils 1510.1-1510.10. Cooling liquid may be supplied to the cooling plates using one or more cooling manifolds. For example, cooling manifolds 1560.1, 1560.2, and 1560.3 may be functionally coupled to each set of coils 1510A, 1510B, 1510C, respectively.

(42) Each of the PM rings 1520.1-1520.7 may be constructed with a plurality of arc segment blocks. Permanent magnets may include high energy product, rare earth magnet materials such as Samarium Cobalt and/or Neodymium Iron Boron alloys. Each of the PM rings 1520.1-1520.7, or segments thereof, may be magnetized using known techniques.

(43) The structural material of casing 1570 may be non-ferromagnetic in this embodiment. Alternatively, a ferromagnetic casing or band on the outer diameter may be used to modify the magnetic fields and/or provide shielding of the external magnetic fields. Casing 1570 may be structurally enforced using a plurality connectors 1575 (e.g., bolts or screws).

(44) Each of FIGS. 15A and 15B illustrates cross-sections of EPM assembly 1500A and 1500B, respectively. In FIG. 15B, EPM assembly 1500B enables access to the center coil set 1510B to facilitate electrical connections, and the ingress and egress of coolant by leaving one or more magnet segments of 1520.4 out of the magnet array.

(45) FIG. 16 illustrates a cross-sectional view of the EPM 1600 according to fifth example embodiment of the present invention.

(46) As illustrated in each of FIG. 16, the EPM 1600 includes a plurality of coils 1610.1-1610.9, the plurality of coils 1610.1-1610.9 being arranged in plural sets of coils 1610A, 1610B, and 1610C. As further illustrated in FIG. 16, the EPM assembly 1600 comprises an array of permanent magnet (PM) rings 1620.1-1620.4.

(47) The plurality of coils 1610.1-1610.9 are electro-magnet coils (e.g., a toroid, loop, helix, or spiral) and may be constructed of a copper coil or other conductive material (e.g., aluminum, silver, gold, etc.) and/or may be tape wound. In some instances, one or more cooling plates (not illustrated) may be disposed between the plurality of coils 1610.1-1610.9.

(48) Each of the PM rings 1620.1-1620.4 may be constructed with a plurality of arc segment blocks. Permanent magnets may include high energy product, rare earth magnet materials such as Samarium Cobalt and/or Neodymium Iron Boron alloys. Each of the PM rings 1620.1-1620.4, or segments thereof, may be magnetized using known techniques.

(49) The plurality of coils 1610.1-1610.9 and the plurality of permanent magnet (PM) rings 1620.1-1620.4 may enclosed within casing 1650 (e.g., a ferromagnetic material or band on the outer surface or outer diameter), which may be constructed of a ferromagnetic material to modify the magnetic fields and/or provide shielding of the external magnetic fields.

(50) In this embodiment, EPM assembly 1600 uses a thick radial cross section ring of ferromagnetic material 1650 as a low reluctance return path for the magnetic field in place of the three outermost rings of permanent magnets. Two optional ferromagnetic end plates are included in this design, but one or both may be omitted.

(51) FIG. 17 illustrates a finite element analysis (FEA) B field map 1700 according to the fifth example embodiment of the present invention. FIG. 17 illustrates the resulting magnetic field distribution and magnitude for a set of PM properties, magnetization vectors, number of coils, turns and currents selected to yield a maximum magnitude and uniformity of the B field in the bore region 1630.

(52) FIG. 18 illustrates a graph of the B field on the centerline of the bore region 1630 versus axial position for according to the fifth example embodiment of the present invention. As shown, the B field is maximum and uniform in the bore region 1630, between 60 and 100 mm i.e., a cavity or active region having a maximum and uniform magnetic field), at approximately 1.8 T.

(53) FIG. 18 plots the axial magnetic field versus the bore center axial position. This configuration has a uniform field as the result of suitable selection of coil N*I (number of turns times current in amperes) and permanent magnet vector orientations. The magnet field vectors in the two concentric rings of magnets may have different radial and axial vector components. The top and bottom rings have complementary magnetizations that superimpose with the field from the top rings and the coil fields yielding a high magnitude, uniform bore field. Geometry, material and component temperature trades (e.g., magnet energy product, conductor density and conductivity, ferromagnetic permeability and density, coolant temperature, etc.) enable scaling of the size of the uniform bore field along with selection of the hardware weight and coil power.

(54) FIG. 19 illustrates a cross-sectional view of the EPM assembly 1900 according to the fifth example embodiment of the present invention.

(55) As illustrated in each of FIG. 19, the EPM assembly 1900 includes a plurality of coils 1910.1-1910.10, the plurality of coils 1910.1-1910.10 being arranged in plural sets of coils 1910A, 1910B, and 1910C. As further illustrated in FIG. 19, the EPM assembly 1900 comprises an array of permanent magnet (PM) rings 1920.1-1920.4. PM Rings 1920.1-1920.4 and plurality of coils 1910.1-1910.10 being enclosed in casing 1970.

(56) The plurality of coils 1910.1-1910.10 are electro-magnet coils (e.g., a toroid, loop, helix, or spiral) and may be constructed of a copper coil or other conductive material (e.g., aluminum, silver, gold, etc.) and/or may be tape wound. One or more cooling plates are disposed between the plurality of coils 1910.1-1910.10. Cooling liquid may be supplied to the cooling plates using one or more cooling manifolds. For example, cooling manifolds 1960.1, 1960.2, and 1960.3 may be coupled to each set of coils 1910A, 1910B, 1910C, respectively.

(57) Each of the PM rings 1920.1-1920.4 may be constructed with a plurality of arc segment blocks. Permanent magnets may include high energy product, rare earth magnet materials such as Samarium Cobalt and/or Neodymium Iron Boron alloys. Each of the PM rings 1920.1-1920.4, or segments thereof, may be magnetized using known techniques.

(58) The structural material of casing 1970 may be non-ferromagnetic in this embodiment. Alternatively, a ferromagnetic casing or band on the outer diameter may be used to modify the magnetic fields and/or provide shielding of the external magnetic fields. Casing 1970 may be structurally enforced using a plurality connectors 1975 (e.g., bolts or screws).

(59) FIG. 20 illustrates a comparison of magnetic characteristics of the electro-permanent magnet assemblies of the first and fifth embodiments. In particular, FIG. 20 illustrates a comparison axial bore field at the center versus axial position of the first embodiment shown in FIGS. 8-10 and the fifth embodiment shown in FIG. 16. Curve 2090 is for the multi coil, all permanent magnet array embodiment as illustrated by FIGS. 8-10, and curve 2080 is the multi coil and combined permanent magnet ring arrays with ferromagnetic return path as illustrated by FIG. 16.

(60) In the various embodiments described above, the electro-permanent magnets described herein provide a large, uniform, axial magnetic field in the bore region with much lower current and power than may be obtained with only coils. In addition, the example configurations and magnetization of PM rings and the plurality of coils do not require use of ferromagnetic materials. However, configurations with ferromagnetic material may be configured to modify the magnetic fields and/or provide shielding of the external magnetic fields.

(61) Ferromagnetic materials may include low Carbon Iron, Iron Cobalt alloys and/or Nickel Iron alloys. Permanent magnets may include high energy product, rare earth magnet materials such as Samarium Cobalt and/or Neodymium Iron Boron alloys. High conductivity conductor materials may include oxygen free copper, aluminum, silver and gold. Insulating material may include the use of polyimide films such as Kapton and/or polytetrafluoroethene (PTFE) (Teflon), rubber and/or fiberglass. Coolants may include water, glycol/water mixtures, mineral and synthetic oils, and/or dielectric fluids including Novec and Fluorinert

(62) The geometries and/or data presented in FIG. 8 through FIG. 20 are for 2 (50 mm) diameter. For the 2 bore diameter, the outer diameter (OD) of the magnet ring is 8.3 with a height of 1.5.

(63) The electro-magnet coils are presently designed at a 9 OD and height of 0.26 and assembled with 0.08 tall, interleaved, micro-channel, cold plates of the same OD.

(64) The overall assembly height is 7.2 inches, weight is estimated at 150 Lbs. and estimated operating power is between 25-40 KW, depending on operating temperature and duty cycle.

(65) It will be apparent to those skilled in the art that various modifications and variations may be made in the hybrid halbach permanent and electromagnet array for 2.sup.nd or other harmonic gyrotrons of the present invention without departing form the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.