Conductor on molded barrel magnet assembly and associated systems and methods

Abstract

A Conductor on Molded Barrel (COMB) magnet assembly optimized for High Temperature Superconducting (HTS) materials. The magnet assembly comprises a magnetic coil(s) carried by a conductor support structure and configured in cosine-theta geometry. Created using additive manufacturing, the conductor support structure features a continuous cable channel that fittedly carries and positions elongated straight portion(s) of the magnetic coil(s) parallel to a magnetic axis. The conductor support structure may be cylindrically shaped and longitudinally bored, with the continuous cable channel comprising an outer channel portion (distal on the cylinder) and an inner channel portion (proximal on the cylinder). A transition hole that joins the outer channel portion and the inner channel portion allows a single magnetic coil to be wound along both the outer and inner surfaces of the conductor support structure. The conductor support structure may be fabricated as longitudinally-symmetrical halves, and secured for operation using azimuthal and/or midplane shims.

Claims

1. A magnet assembly comprising: at least one magnetic coil characterized by cosine-theta geometry and comprising at least one conductive cable comprising a plurality of elongated straight portions; and a conductor support structure characterized by a substantially cylindrical shape defining a distally-positioned outer surface and by a longitudinal bore defining a proximally-positioned inner surface, and having a continuous cable channel comprising an outer channel portion incised in the distally-positioned outer surface, an inner channel portion incised in the proximally-positioned inner surface, and a transition hole configured to join the outer channel portion and the inner channel portion; wherein the outer channel portion, the inner channel portion, and the transition hole of the continuous cable channel are configured to fittedly receive the at least one magnetic coil and to position the plurality of elongated straight portions parallel to a magnetic axis of the at least one magnetic coil.

2. The magnet assembly according to claim 1 wherein the at least one magnetic coil is of a material type selected from the group consisting of High Temperature Superconducting (HTS), Low Temperature Superconducting (LTS), and purely resistant cable.

3. The magnet assembly according to claim 2 wherein the at least one magnetic coil is of the material type HTS and is selected from the group consisting of Rare Earth, Barium-Copper-Oxide (REBCO) and Bi.sub.2Sr.sub.2CaCu.sub.2O.sub.x (Bismuth 2212).

4. The magnet assembly according to claim 1 wherein the at least one magnetic coil is further characterized by a cable geometry selected from the group consisting of round, square, and rectangular.

5. The magnet assembly according to claim 1 wherein the at least one magnetic coil is further characterized by a poles type selected from the group consisting of dipole, quadrupole, sextupole, octupole and decapole.

6. The magnet assembly according to claim 1 wherein the conductor support structure further comprises a support material selected from the group consisting of Stainless Steel, Titanium, Copper, Bronze, Brass, Aluminum, plastic, and fiber-reinforced composite.

7. The magnet assembly according to claim 1 wherein the conductor support structure is further characterized by two longitudinally-symmetrical halves, defined as a first half and a second half.

8. The magnet assembly according to claim 7 further comprising an azimuthal shim positioned in mechanical communication with the outer surface of the first half of the conductor support structure, and a midplane shim positioned in mechanical communication with both the first half and the second half of the conductor support structure along a plane of symmetry between the first half and the second half.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, where like designations denote like elements, and in which:

(2) FIG. 1 is an assembled, perspective top view of an exemplary Rutherford type cable structure according to the prior art;

(3) FIG. 2 is a cutaway, perspective top view of an exemplary High Temperature Superconducting (HTS) tape according to the prior art;

(4) FIG. 3 is an assembled, perspective top view of a Conductor on Molded Barrel (COMB) magnet assembly according to an embodiment of the present invention;

(5) FIG. 4 is a perspective top view of the COMB magnet assembly illustrated in FIG. 1 exploded through line 1-1 of FIG. 1;

(6) FIG. 5 is a perspective top view of the COMB magnet assembly illustrated in FIG. 1 exploded through line 1-1 of FIG. 1 and cutaway through angle 2-3 of FIG. 4;

(7) FIG. 6A is a perspective top view of a magnetic coil of the COMB magnet assembly illustrated in FIG. 1;

(8) FIG. 6B is a perspective top view of a conductor support structure of the COMB magnet assembly illustrated in FIG. 1 exploded through line 1-1 of FIG. 1 and cutaway through angle 2-3 of FIG. 4;

(9) FIG. 6C is a perspective top view of azimuthal shims and midplane shims according to an embodiment of the present invention, and as deployed with the COMB magnet assembly illustrated in FIG. 1 exploded through line 1-1 of FIG. 1 and cutaway through angle 2-3 of FIG. 4;

(10) FIG. 7A is a schematic diagram illustrating magnetic performance as simulated for a first exemplary configuration of the COMB magnet assembly illustrated in FIG. 1 and taken through line 4-4 of FIG. 4;

(11) FIG. 7B is a schematic diagram illustrating magnetic performance as simulated for a second exemplary configuration of the COMB magnet assembly illustrated in FIG. 1 and taken through line 4-4 of FIG. 4;

(12) FIG. 8A is a schematic diagram illustrating magnetic performance as simulated for a third exemplary configuration of the COMB magnet assembly illustrated in FIG. 1 and taken through line 4-4 of FIG. 4;

(13) FIG. 8B is a schematic diagram illustrating magnetic performance as simulated for a fourth exemplary configuration of the COMB magnet assembly illustrated in FIG. 1 and taken through line 4-4 of FIG. 4;

(14) FIG. 9A is a table illustrating summary performance results using the simulated first and second exemplary configurations of FIGS. 7A and 7B:

(15) FIG. 9B is a table illustrating summary performance results using the simulated third and fourth exemplary configurations of FIGS. 8A and 8B;

(16) FIG. 10A is a schematic diagram illustrating von Mises stresses as simulated for a cool down condition illustrated in the table of FIG. 9A; and

(17) FIG. 10B is a schematic diagram illustrating von Mises stresses as simulated for a maximum condition illustrated in the table of FIG. 9A.

(18) Like reference numerals refer to like parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

(19) The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

(20) Although the following detailed description contains many specifics for the purposes of illustration, anyone of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the invention. Accordingly, the following embodiments of the invention are set forth without any loss of generality to, and without imposing limitations upon, the claimed invention.

(21) As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims.

(22) Furthermore, in this detailed description, a person skilled in the art should note that quantitative qualifying terms such as “generally,” “substantially,” “mostly,” and other terms are used, in general, to mean that the referred to object, characteristic, or quality constitutes a majority of the subject of the reference. The meaning of any of these terms is dependent upon the context within which it is used, and the meaning may be expressly modified.

(23) Referring initially to FIGS. 3-6, a Conductor on Molded Barrel (COMB) magnet assembly according to an embodiment of the present invention is now described in detail. Throughout this disclosure, the present invention may be referred to as a COMB assembly, a COMB magnet, a COMB device, an electromagnet assembly, a magnet assembly, a magnet, an assembly, a device, a system, a product, and/or a method for augmenting a particle accelerator design. Those skilled in the art will appreciate that this terminology is only illustrative and does not affect the scope of the invention. For instance, the present invention may just as easily relate to stand-alone electromagnet technology.

(24) Generally speaking, Conductor on Molded Barrel (COMB) magnet technology introduces individual conductor support to the traditional cosine-theta magnet technology used in superconducting magnets of every particle accelerator starting from Tevatron. This technology, as described hereinbelow, may allow magnet designers to work with unconventional (e.g. round) conductor geometries, as well as produce magnet designs that may reduce the mechanical stresses on the conductors, may improve the conductor positional tolerances and consequently the magnetic field quality, and may minimize the labor needed during coil fabrication. Although originally conceived for dipole coils made of High Temperature Superconducting (HTS) materials, COMB magnet technology may be adaptable to normal or skew magnets with any number of poles (e.g. quadrupoles, sextupoles, octupoles, decapoles, etc.) made of HTS, Low Temperature Superconducting (LTS) or purely resistive cables.

(25) Referring now to FIG. 3, in more detail, a Conductor on Molded Barrel (COMB) magnet assembly 300, according to an embodiment of the present invention, may include one or more magnetic coils (as illustrated, a top coil 320 and a bottom coil 340) each configured in a cosine-theta geometry and carried by a conductor support structure (as illustrated, comprising a top half structure 310 to carry the top coil 320, and a bottom half structure 330 to carry the bottom coil 340). The magnetic coil(s) 320, 340 of the magnet assembly 300 may be constructed of a conductive material of a High Temperature Superconducting (HTS) type to exploit the performance gains possible with HTS materials (although the present design may still be operable and provide advantages even when Low Temperature Superconducting (LTS) materials and/or purely resistant cable are employed). For example, and without limitation, an HTS coil may be made of Rare Earth, Barium-Copper-Oxide (REBCO), Bi.sub.2Sr.sub.2CaCu.sub.2O.sub.x (Bismuth 2212), MgB.sub.2 (Magnesium Diboride), and/or iron-based superconducting material.

(26) A person of skill in the art will immediately recognize that individual conductor support is inherent to Canted-Cosine-Theta (CCT) magnet design with the traditional cosine-theta coil geometry. The present invention may support such a simple, single-layer implementation (referred to herein as a “single-COMB design”), that may be similar in outcomes to the CCT geometry in terms of the canted angle approaching zero (i.e. conductors extending parallel to the magnet axis). That is, the single-COMB design is useful for applications that require single-layer coils with individual support of every turn. However, additional benefits of COMB magnet technology become more fully realized in the double-COMB design detailed herein.

(27) An exploded view of the magnet assembly 300 featuring a double-COMB design is shown in FIGS. 3 and 4. One solid conductor support structure (e.g., the top half structure 310) may be configured to fittedly carry two layers of cabling that may comprise a magnetic coil 320 (see also FIG. 5 for an illustration of exemplary cabling layers present in the coil 320). Such layering, created by “winding” of a single cable to present separate layers to be carried by opposite (e.g., inner and outer) surfaces of the top half structure 310, may advantageously eliminate the challenges present in legacy magnet designs (e.g., disconnected parts that must fit together with high precision, as well as a layer-to-layer interface that may be a source of magnet training). For example, the known 15 T dipole design described above has twenty-three (23) separate parts per half-coil (excluding the poles, which may be made as solid pieces), which makes required coil winding very labor intensive. Also, misaligned parts in that prior art design may cause local cable stress concentrations and degraded magnet performance.

(28) Referring again to FIGS. 4 and 5, similar to traditional cosine-theta coils, one or more elongated straight portions 510 of the magnetic coil/conductor 320 may be configured parallel to a magnet axis 420 of the magnet assembly 300 while opposite ends 530, 540 of the coil 320 may be wound comparatively compactly. Such geometry may serve to maximize the useful field region and the integral strength of the coil 320 (that is, 100% of the cable in the straight portions 510 generates the useful transverse field because the cables are positioned parallel to the magnet axis). Also, because the ends 530, 540 are very compact, the magnetic length may be maximized as a result.

(29) The exemplary double-COMB design 300 of FIGS. 3 and 4 may advantageously require no splice in between the respective layers of the exemplary coils 320 and 340, which may be especially important when employing HTS materials. Instead, as demonstrated in FIGS. 5 and 6A, the two-layer magnetic coil 320 may be wound from a single cable piece. Referring additionally to FIG. 6B, mating of this magnetic coil 320 with the conductor support structure 310 configured to fittedly carry that coil 320 may require pulling approximately half of the coil 320 through a transition hole 610 in the COMB structure 310 prior to coil winding into outer 620 and inner 630 continuous cable channels.

(30) Because each half of the double-COMB conductor support structure 310, 330 may feature a continuous cable channel of complicated topology spanning both inner 630 and outer 620 surfaces of the barrel 600, such a structure 600 may not be well suited for computer numerical control (CNC) machining. Instead, the complete “barrel” structure 600 may be readily produced by additive manufacturing (e.g., 3D printing) using Direct Metal Laser Sintering (DMLS) or another metal-friendly material deposition process—hence the word “molded” in the name COMB. In the case of a long magnet assembly 300 (e.g., such that the length of the assembly 300 may be much larger than the assembly's 300 transverse dimensions), the central (e.g. straight) part of the conductor support structure 600 may also be assembled from extruded blocks or stamped laminations to minimize fabrication time and cost, with only the ends of the structure 600 requiring 3D printing. Note also that COMB structures may be 3D printed from a variety of metals or also plastics for low field applications. Careful selection of printing materials may also yield cost savings (e.g., Aluminum rather than the significantly more expensive Stainless Steel or Titanium).

(31) Employing a substantially-cylindrical and longitudinally-bored full conductor support structure 600 (e.g., formed from joining the top half structure 310 and the bottom half structure 330), the COMB magnet 300 may be assembled from half-coils (for a dipole) that the conductor support structure 600 may carry and position for retrofit with complementary internal or external HTS or LTS coils. (A person of skill in the art will immediately recognize that “substantially-cylindrical” may include, but is not limited to, definition as circular cylinders, elliptical cylinders, or oval cylinders and still achieve the results and uses described herein).

(32) Referring now to FIG. 6C, a shimmed double-COMB magnet assembly 650 may include midplane 652 and azimuthal 654 shims configured to individually control the prestress in each half-coil. Such shims 652, 654 may be longitudinally coextensive with the conductor support structure 600 or, depending on the planned application and/or required performance of the magnet assembly, may comprise one or more shims that may be longitudinally coextensive with only a portion of the conductor support structure (see, for example, midplane 452 and azimuthal 454 shim pairs as illustrated in FIG. 4). Shimming as described herein may allow the number of magnet assembly layers (e.g., additional inner and/or outer coils) to be easily scalable to achieve a variety of desired fields. For example, and without limitation, the exemplary double-COMB magnet assembly 300 of FIG. 3 may be designed to fit into the bore of a legacy host 15 T dipole magnet as described above.

(33) To assess double-COMB magnet assembly 300 performance with HTS inserts, the magnetic analysis presented hereinbelow was performed for four configurations shown in FIGS. 7A, 7B, 8A, and 8B. The designs were based on the CORC® W5 cable with the average reported J.sub.e of 365 A/mm2 at 20 T and 4.2 K that was parameterized in a relevant range of fields and temperatures. In performance schematic 700 of FIG. 7A, the assembly “insert” 300 was designed to fit into the 60 mm bore of the Fermilab's 15 T dipole 704. In performance schematic 720 of FIG. 7B, the insert 300 was designed to fit into the 123 mm bore formed by the outer coils of that magnet 724.

(34) The larger coil 300 of FIG. 7B with 100 mm clear bore is envisioned as the first step in the technology demonstration based on the current generation of CORC® cables due to the large minimum cable bending diameter of 51 mm. The smaller insert coil 300 of FIG. 7A with 40 mm clear bore and the minimum bending diameter of 18 mm may be made when more flexible cables based on the next generation of thinner REBCO tapes become available or from the Bi-2212 conductor.

(35) Performances of the HTS coils 300 of FIGS. 7A and 7B are summarized in Table 900 of FIG. 9A at different conditions. The maximum bore fields approach 13-18 T at 1.9 K for the two HTS coils powered to 100% of the Short Sample Limit (SSL) independently of the LTS magnet (with an extra pair of current leads and a power supply). When powered in series, the maximum bore fields of 8.4-11.5 T at 1.9 K are limited by the HTS performance.

(36) While the bore fields are considerably smaller than in the case of independent powering, the forces on the HTS conductors are only 12% lower because of the increased current at lower fields, which makes this test just as useful for evaluating the COMB structure performance. It can be realized with a single pair of current leads and a power supply, but the quench protection of the HTS insert will require a careful consideration to avoid damaging it by the large energy stored in the LTS magnet.

(37) FIGS. 8A and 8B shows the field distribution in the stand-alone HTS coil 300 tests with and without the iron yoke. Performances of the HTS coils 300 of FIGS. 8A and 8B are summarized in Table 910 of FIG. 9B at different conditions. In the stand-alone tests, the HTS coils 300 can first be tested at the liquid nitrogen temperature to 0.5-0.8 T bore fields and then to 3-4.4 T bore fields at 1.9 K, depending on the presence of the iron yoke. While not revealing the full HTS performance, these may still be useful intermediate tests for demonstrating the COMB technology.

(38) The structural analysis was performed for the worst case in terms of the total forces and stresses in the HTS coil, which corresponds to independent powering of the HTS coil 300 of FIG. 7B at 1.9 K. The following assumptions were used: the gap in the iron yoke closes during the cool-down and remains closed under all conditions (i.e., the shell/clamp system is strong enough to make it happen); there is a free sliding contact between HTS-LTS coils, LTS coil and the iron yoke as well as between the cables and the pole blocks in that coil; the coils are prestresses by means of the radial and azimuthal shims during the assembly at the room temperature to the level that all conductors stay in contact with the adjacent parts up to the maximum load; the COMB structure is made of 316L stainless steel.

(39) The equivalent (von Mises) stresses in the coils 310, 320 and the support structure 600 are shown in FIG. 10A after the cool-down from room temperature to 1.9 K 1000 and at the maximum current 1020 quoted in Table 900 of FIG. 9A. After the cool-down 1000, the stress is relatively uniform and on a level of 90-100 MPa in the HTS and the LTS coils. At the maximum current 1020, the stress distribution changes with the bias towards the midplane and the peak stress reaches 160 MPa in the LTS coil (which is acceptable for Nb.sub.3Sn conductor). However, the peak stress in the HTS coil goes only slightly up to 110 MPa, which indicates the stress management (SM) benefits of the COMB structure. This level of stress is low enough even for the strain-sensitive Bi-2212, while the REBCO-based cables can tolerate stresses up to 170 MPa without the critical current degradation. The peak stress in the structure is only 143 MPa, which is approximately half of the yield stress for 316L stainless steel.

(40) For example, and without limitation, such COMB magnet technology may be practically applied not only to cylindrical or dipole geometries, but to any number of poles and odd coils that must depart from self-supporting Roman-arch geometry employed with LTS materials (e.g., quadrupoles for arcs and interaction regions: multipole correctors (e.g. dipole, quadrupole, sextupole, etc.), curved and/or twisted (i.e. helical magnets); gantry systems of proton/ion therapy facilities; polarized beam and muon cooling experiments and light sources; rotors/stators of motors and generators. The operating temperatures supported by the present invention may be in 1.9 K-77 K range, depending on the performance requirements (e.g., cooling by LHe, GHe or LN2; conduction cooling by cryocoolers, which may work especially well with aluminum structures).

(41) The system and method according to an embodiment of the present invention may advantageously boost magnetic performance of future hadron colliders (that is, achieve higher beam energies through increased magnetic field strength), as well as augment legacy LTS magnets (that is, used as inserts in niobium-tin magnets for boosting magnetic field). Fabrication advantages of 3D printing include production cost savings, production time savings, scalability, and compatibility.

(42) Some of the illustrative aspects of the present invention may be advantageous in solving the problems herein described and other problems not discussed which are discoverable by a skilled artisan.

(43) While the above description contains much specificity, these should not be construed as limitations on the scope of any embodiment, but as exemplifications of the presented embodiments thereof. Many other ramifications and variations are possible within the teachings of the various embodiments. While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

(44) Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, and not by the examples given.