US3193734A - Superconducting flux concentrator - Google Patents

Superconducting flux concentrator Download PDF

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Publication number
US3193734A
US3193734A US181762A US18176262A US3193734A US 3193734 A US3193734 A US 3193734A US 181762 A US181762 A US 181762A US 18176262 A US18176262 A US 18176262A US 3193734 A US3193734 A US 3193734A
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United States
Prior art keywords
coil
superconducting
flux
current
wire
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Expired - Lifetime
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US181762A
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English (en)
Inventor
Charles F Hempstead
Young B Kim
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AT&T Corp
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Bell Telephone Laboratories Inc
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Priority to US181762A priority Critical patent/US3193734A/en
Priority to GB9225/63A priority patent/GB1038554A/en
Priority to JP1335263A priority patent/JPS4022705B1/ja
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Publication of US3193734A publication Critical patent/US3193734A/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/02—Quenching; Protection arrangements during quenching
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/825—Apparatus per se, device per se, or process of making or operating same
    • Y10S505/88—Inductor

Definitions

  • This invention relates to magnetic circuits and more particularly to magnetic iiux concentrators utilizing superconducting coils.
  • the need for very high magnetic tields has increased greatly in the past several years as a result of the rapid progress in many areas of physical research.
  • these high magnetic fields have, until recent years, been achieved in one of twoways;
  • the rst the so-called brute torce method, provides sustained magnetic fields at the cost of large and elaborate electromagnets and correspondingly large power and cooling apparatus.
  • rlhe secondmethod provides short-duration pulsed 4magnetic fields with less elaborate magnetic coils but at the cost of shortened coil life.
  • the iirst method is generally undesirable due to the prohibitive cost of the equipment, whereas the second method may be undesirable due to the short time duration of the magnetic iield.
  • superconducting Wire is understood to refer to wire formed of a material displaying zero resistivity to a current owing therein at temperatures below a point referred to as the superconducting transition temperature.
  • Such magnets however, still require means for establishing the initial current and for regulating it once it is established.
  • this requirement has necessitated current conducting elements between the 10W temperature superconducting coil and the high temperature power supply.
  • heat is introduced into the low temperature environment surrounding the superconductingT magnet both by resistive heating of, and by heat conduction through, the current conductinff elements. This, in turn, necessitates additional refrigeration in order that the necessary low temperature be maintained.
  • lt is therefore an object of the present invention to provide sustained high magnetic fields with superconducting coils requiring no external current source.
  • the flux distribution can be varied. ln accordance with the principles oi the present invention, the conserved iiux is distributed throughout a smaller volume by utilizing certain Lcoil geometries so that a higher ux density is achieved.
  • FIG. l is aperspective view of one embodiment of the present invention utilizing two solenoidal superconducting Coils; t
  • FlG. 2 is a perspective view, partially broken away, of another embodiment of the present invention utilizing a single multilayer solenoidal coil
  • FlG. 3 is a graphical representation of the flux distribution in the embodiment of FIG. 2;
  • FIG. 4 is a view, partially in cross-section, of still another embodiment of the present invention utilizing a coil of pancake geometry; y f
  • FIG. 4A is a cross-sectional view of a superconducting wire having an outer coatingof normal conducting substance useful in practicing the present invention.
  • FIG. 5 is across-sectional view showing the pancake coil of FIG. 4 in a test setup.
  • FIG. l shows two single-layer solenoidal coils 1 and 2.
  • Coilk l has a length I1 and radius r1 and is wound of superconducting wire with nlturns per unit length.
  • Coil 2 has a length l2, radius r2, and is Wound of superconducting wire with n2 turns per unit length, rThe ends, 3-3 of the winding of coil 1 are connected to ends 4 4', respectively, of coil 2'also by means of superconducting wire.
  • Such wire can be formed of Nb-Zr, Nb3Sn or any of the other superconducting materials known in the art.
  • coils 1 and 2 and the connecting Wires are cooled-to a temperature below their superconducting transition point by suitable refrigerating means not shown.
  • the external magnetic iield H0 is ythen removed.
  • ViniW/zHo H 7 2 (Verwarm The flux concentration factor ,B is defined as the ratio of H2 to H0 and is equal to Vrnmz V17L12+V2n22 L* "a1 l@ a2 712 V1 "i From Equation 8, it is seen that as long as n2 is greater than n1, a flux concentration factor greater than unity can be achieved. For example, if r11/n2 equals 3A0 and V2/V1 equals lAOO, in the circuit of FIG. 1, the flux concentration factor equals five.
  • FIG. 2 y is a partially broken away perspective illustrat-ion of another embodiment of the present invention comprising a single multilayer solenoidal coil 20 wound of superconducting wire.
  • Coil 20 has an outer radius a2, an inner radius al, and a length b.
  • the two ends 21 and 21' of coil 20 are shorted together by means of a superconducting element 22 so that -when coil 20 is cooled below its superconducting transition temperature, it denes a single current loop whose resistance is zero.
  • the flux linkages with a turn at a distance r from th axis of coil 20 is given by Denning m as the number of turns per unit length along the axis of coil 20 and n as the number of layers of wire per unit length in the radial direction, the total ilux linktages through the coil is
  • the electromotive force induced in a closed loop is given by oa E.l ⁇ /l.F.--t-R
  • R O. Therefore,
  • the radius of coil 20 is plotted along the abscissa and the flux density along the ordinate.
  • the dashed curve 31 represents the initial uniform flux density H0 within coil 2t).
  • the solid curve 32 shows the approximate distribution of flux density resulting from the induced current z'. In practice, the sloping portion of curve 32 will depart from perfect linearity to the extent that the above-mentioned assumptions depart from reality.
  • Equation 12 The final flux density Hm as seen from curve 32 can be written as By utilizing the expressions of Equation 11 and integrating, the total flux Ar linking a single turn at an arbitrary radius r is Equation 12, when integrated once again over the entire coil, yields an expression for the total flux linkages )r1 due to current z'.
  • a solenoidal coil such as coil 2t) of FIG. 2 has a length b that is not long compared to its diameter, the flux concentration factor can be greater than the value calculated from Equation 14. This is due to the fact that the lines of magnetic flux diverge near the ends of the coil; and whereas this eifect can be neglected in the case of a long coil, it must be considered in a complete analysis of a shorter coil.
  • the magnitude of the flux density can be further increased by the subsequent reapplication of the uniform external field in a direction opposite to the first direction, while the coil is still in its superconducting state.
  • the additional current induced in the coil as a result of this reapplication of an external field establishes an additional magnetic field component tending to oppose the new change in iiux.
  • the additional magnetic field component thereby established is therefore in the same direction as the previously established field.
  • a new uniform external magnetic field Ho is applied along the axis of coil 20 as shown.
  • the total current i is caused to increase as a result, until the total linx linkages through coil 20 equals the original flux x0 plus the new iiux linkages.
  • the resulting iiux density is equal to H1 plus the new flux density I13H0 minus the external field flux density H.
  • the total iiux at point A, designated H1' is therefore given by the The same principle applies equaly well to the embodiment of FIG. 1.
  • the new external field H0 would be applied only to coil 1 in a direction opposite H0 and the new flux in coil 2 would become equal to ,BH0-
  • the wire having a diameter of approximately .025 inch, waswound on a stainless steel form 4i?. There were 39 layers of winding consisting of 191/2 turns per layer. Each layer was separated by a .001 inch wrapper of stainless steel. The inside diameter of the coil 41 was .25 inch, the outside diameter was 2.276 inches and the length was .5l inch. As in the case of the previous embodiment, the ends 42 and 43 of the coil were shorted together.
  • FIG. 5 is a simplified cross-sectional View of the coil of FIG. 4 installed in a typical test setup.
  • Coil 40 is shown suspended in the air gap of a magnet having a controllable magnetic field. For reasons of clarity the suspension means for coil 40 have not been shown. Likewise, only the pole pieces 50 and 51 of the magnet have been illustrated. Coil 40 is oriented near the center of the air gap with its axis perpendicular to the faces of pole pieces 50 and 51. Surrounding coil 40 is a Dewar liask 53. A uniform magnetic field of 6.8 kilogauss was established through coil 4) while it was in its normal conducting state.
  • the present invention can be practiced by utilizing any of the superconducting wire known in the art.
  • the operation of the invention is enhanced, however, by utilizing wire having a core of superconducting ma-terial and an outer layer of normal or nonsuperconducting material.
  • a cross-sectional view of such Wire is shown in FIG. 4A wherein the superconducting core is designated by numeral 44 andthe normal conducting outside coating is designated by numeral 45.
  • Typical of this type wire is the NbBSn Wire disclosed in the abovementioned copending application of E. Buehler and J. E. Kunzler and the metallically insulated wire disclosed in the copending application of T. H. Geballe, Serial No. 52,409, filed August 29, 1960, now United States Patent No. 3,109,963 issued November 5, 1963.
  • circuits represent only a limited number of embodiments of the present invention. Many other embodiments including those utilizing different coil geometries and core materials can be constructed by those skilled in the art without departing from the spirit and scope of the present invention.
  • a flux concentrator comprising, a lirst coil of superconducting wire having nl turns per unit length wound in the form of a cylinder having a volume V1, a second coil of superconducting wire having n2 turns per unit length Wound in the form of a cylinder having a volume V2, where n1 n2 and means for connecting the first and second ends of said first coil to the first and second ends of said second coil respectively, external means for establishing a constant magnetic yfield component along the axis of said first coil while said coil is in its normal conducting state, means for establishing a substantially uniform magnetic fieldv through said coil parallel to the axis thereof, said externally applied eld being established while said coil is in its knormal conducting state, means for changing said coil to its superconducting state, and means for subsequently removing said externally applied field.
  • the method of concentrating the ux of a magnetic eld comprising the steps of, applying an external uniform magnetic eld through a shorted multilayer coil Wound of superconducting Wire in a direction substantially parallel to the axis of said coil while said wire is in its normal conducting state, cooling said Wire to a temperature below its superconducting transition temperature,

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
  • Superconductor Devices And Manufacturing Methods Thereof (AREA)
US181762A 1962-03-22 1962-03-22 Superconducting flux concentrator Expired - Lifetime US3193734A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US181762A US3193734A (en) 1962-03-22 1962-03-22 Superconducting flux concentrator
GB9225/63A GB1038554A (en) 1962-03-22 1963-03-08 Apparatus for generating magnetic flux
JP1335263A JPS4022705B1 (cs) 1962-03-22 1963-03-20

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3283217A (en) * 1963-03-21 1966-11-01 Rca Corp Electromagnetics
US3818396A (en) * 1973-04-09 1974-06-18 Us Navy Super stable superconducting coil
US4851799A (en) * 1987-06-29 1989-07-25 General Dynamics/Space Systems Division Producing high uniformity magnetic field or magnetic shielding using passive compensating coils
US20070152788A1 (en) * 2005-09-29 2007-07-05 Oxford Instruments Superconductivity Limited Superconducting electromagnet
NL2000755C2 (nl) * 2007-07-16 2009-01-19 Easycup Internat Ltd Verpakking voor een fluïdum.
US10981209B2 (en) * 2014-09-04 2021-04-20 Temper Ip, Llc Forming process using magnetic fields
US11408706B2 (en) * 2020-03-18 2022-08-09 The Boeing Company Apparatuses and methods for a superconducting explosive

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2625047B1 (fr) * 1987-12-21 1990-05-18 Centre Nat Etd Spatiales Dispositif de stockage d'energie electrique dans un supraconducteur

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3088077A (en) * 1955-10-31 1963-04-30 Gen Electric Superconducting circuits

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3088077A (en) * 1955-10-31 1963-04-30 Gen Electric Superconducting circuits

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3283217A (en) * 1963-03-21 1966-11-01 Rca Corp Electromagnetics
US3818396A (en) * 1973-04-09 1974-06-18 Us Navy Super stable superconducting coil
US4851799A (en) * 1987-06-29 1989-07-25 General Dynamics/Space Systems Division Producing high uniformity magnetic field or magnetic shielding using passive compensating coils
US20070152788A1 (en) * 2005-09-29 2007-07-05 Oxford Instruments Superconductivity Limited Superconducting electromagnet
NL2000755C2 (nl) * 2007-07-16 2009-01-19 Easycup Internat Ltd Verpakking voor een fluïdum.
US10981209B2 (en) * 2014-09-04 2021-04-20 Temper Ip, Llc Forming process using magnetic fields
US11408706B2 (en) * 2020-03-18 2022-08-09 The Boeing Company Apparatuses and methods for a superconducting explosive

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Publication number Publication date
JPS4022705B1 (cs) 1965-10-07
GB1038554A (en) 1966-08-10

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