WO1992018992A1 - Duplicateur de champ magnetique et procede - Google Patents

Duplicateur de champ magnetique et procede Download PDF

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Publication number
WO1992018992A1
WO1992018992A1 PCT/US1991/001193 US9101193W WO9218992A1 WO 1992018992 A1 WO1992018992 A1 WO 1992018992A1 US 9101193 W US9101193 W US 9101193W WO 9218992 A1 WO9218992 A1 WO 9218992A1
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Prior art keywords
replicator
field
bulk
magnetic field
magnet
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PCT/US1991/001193
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English (en)
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Roy Weinstein
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Roy Weinstein
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Priority to PCT/US1991/001193 priority Critical patent/WO1992018992A1/fr
Publication of WO1992018992A1 publication Critical patent/WO1992018992A1/fr

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/20—Permanent superconducting devices

Definitions

  • This invention relates generally to a class of devices known as magnetic field replicators and to methods for their creation, operation and uses. Although it is not so limited, it is particularly useful for replicating complex fields with high precision, low weight and low cost, and in short real times. It may also replicate strong or very strong magnetic fields, and can produce magnets of large surface area. In addition, these replicators can also be used in much smaller devices such as for field magnets of generators.
  • Type II superconductors Superconducting materials for which the Meisner Effect is literally true - i.e., materials which completely expel all of their internal magnetic fields when the magnetic field strength is less than the critical field strength, Q - are known as Type I superconductors.
  • Superconducting materials for which the Meisner Effect is not literally true - i.e., those which demonstrate either the Incomplete Meisner Effect or the Very Incomplete Meisner Effect - are known as Type II superconductors.
  • the magnetic field is totally penetrating - i.e., completely contained within the body of the SC - when the strength of the magnetic field is greater than the critical field strength, Q , and the property of superconductivity is lost
  • the magnetic flux lines penetrate the body when the field strength is greater than a first critical level Hc_., but the superconductivity property is not lost until the field strength exceeds a second critical level, Hr2 « This "window", for the Incomplete or Very Incomplete Meissner effect, allows the theoretical possibility for retention of strong magnetic fields in bulk SC materials, which is fundamentally different from creation of such fields by currents through wires or ribbons.
  • liquid nitrogen Materials which become superconducting above the temperature of liquid nitrogen can use liquid nitrogen as a coolant. Since liquid nitrogen is much cheaper and easier to handle than liquid helium, it is convenient, from a practical standpoint, to take the dividing line between low T c and high T c superconductivity as the temperature of liquid nitrogen even though this temperature may not represent the actual demarcation line between these two classes of materials. In a historical sense, the high T c superconductors were the first to exhibit superconductivity above temperatures of about 30 Kelvin.
  • Rabinowitz 1 work, so far as is known to date, is limited to the class of superconductors known as metallic superconductors, which to date are further limited to tempera ⁇ tures within a very few degrees of absolute zero (30K or less).
  • This limitation requires the use of liquid helium as the coolant, which not only greatly increases the cost but which, due to extreme difficulties of handling, greatly limits the practical applications of such devices. According to "Dependence Of Maximum Trappable Field On Superconducting Nb3Sn Cylinder Wall Thickness", M. Rabinowitz et al..
  • U.S. Patent 4,176,291 "Stored Field Superconducting Electrical Machine And Method", to Rabinowitz, discloses the employment of a metallic superconductor known as "A-15, beta- tungsten structure" superconductor formed in the shape of cylinders. These cylinders are formed in concentric layers of superconducting materials and thermally and electrically conductive materials in order to insulate the magnetic field replicator from thermal and electromagnetic forces and from heat build up which might otherwise cause the extremely low T c of the Rabinowitz device to be exceeded, with resultant loss of superconductivity and the impressed magnetic field. Rabinowitz discloses the use of the "warm process" method to impress the desired field in his specialized cylinder, and states that with that process he has been able to store a magnetic field in the superconductor of up to about one-half
  • U.S. Patent 4,190,817 "Persistent Current Supercon ⁇ ducting Method And Apparatus", to Rabinowitz, discloses, for low T c , metallic superconductors, various means for varying the field, for creating complex and/or spatially large fields, and for miniaturizing fields, as well as means for increasing the fidelity, magnitude, and stability of the magnetic field stored in such low T c superconductors.
  • the field strength which decays with time logarithmically, does so initially at a precipitous rate, and then abruptly changes to a more moderate rate of decline.
  • the decay rate following this inflection point is referred to as "Creep", or flux creep, analogous to the dislocation line movement in crystalline materials.
  • Creep flux creep
  • some of the field strength is lost - i.e., some magnetic flux lines escape - within very short time periods (on the order of 10 seconds), but thereafter the field appears to stabilize and, within the time limits of the Rabinowitz experimenters, the loss appears to be virtually zero.
  • creep is minor, and the trapped field may persist for millenia.
  • the creep can reduce the trapped field by several per cent in one week and is referred to as "Giant Creep". While some applications are possible in high T c materials in spite of the Giant Creep phenomena, many more applications would be possible if the phenomena v/ere eliminated, significantly reduced, or otherwise overcome or controlled. Still another difficulty confronting the high tempera ⁇ ture superconductivity researcher is that the superconductivity property is not isotropic, i.e., is not uniform in all direc ⁇ tions. Typically, the SC property is manifested in only two directions, i.e., a plane, and is smaller, or non-existent in a direction perpendicular to this plane.
  • Magnets twice the strength of the largest present practical superconducting magnets, if not greater, may be produced by the principals of this invention. These devices are not ordinary permanent magnets, and are unlike previous superconducting magnets. They are far simpler and fundamentally different devices, and have great applicability because they do not require geometric or dimensional precision. Normally, superconducting magnets of the previously known types have relied upon precisely aligned current-carrying wires or ribbons to create desired field shapes. Permanent magnets also rely upon precise geometry of the magnetic materials to produce a given field design.
  • This new class of fundamentally different devices which may be called supercon ⁇ ducting magnet replicators, functions by trapping an external magnetic field which is maintained by large numbers of local ⁇ ized, persistent SC currents which may also be called micro- currents, by relatively larger currents which may circulate throughout the volume of the SC replicator, or by a combina ⁇ tion of these two types of currents.
  • SC currents which may also be called micro- currents
  • the repli ⁇ cators behave similarly to permanent magnets but do not re ⁇ quire precise geometry. For example, they may be transferred and used where needed without electrical leads or connections.
  • the geometric shape and accuracy of the body of the SC replicators have little effect upon the shape and accuracy of the magnetic field which may be repli ⁇ cated.
  • the proper number, size, and orientation of a multitude of persistent currents may be created, thereby producing a faith ⁇ ful copy of the magnetic field of almost any "parent" magnet that may be desired.
  • a high T c SC replicator formed in the shape of a hollow member such as a cylinder.
  • a convenient shape may be formed by packing and pressing high T c SC powders followed by sintering at high temperature.
  • "1,2,3" material has been found satisfactory for such powders, i.e., material of the class Ba2Cu3 07_ x , as have many other materials.
  • improved cylinders can be fabricated out of thin, small-area grains.
  • An improved cylinder may be processed by directional partial melting-soli ⁇ dification along the large axis to grow large and preferably- oriented superconducting crystals or grains, or, alternatively, the cylinder can be fabricated from smaller grains, separately produced in a simpler geometry. It is to be understood that the cylindrical shape, while convenient and useful, is not essential: for example, dipole and quadrapole fields may be replicated very well by square-pipe shaped replicas.
  • One satisfactory method of creating imperfections is to introduce silver to the "1,2,3" material while in the powdered form.
  • the introduction of silver increases the maximum field which may be trapped, and makes it easier to produce uniform materials.
  • the term "laminate” may be thought of as applying to any method of stacking such chips parallel to the direction of trapped field, while the term “mosaic” may be thought of as applying to any method of arranging such chips perpendicular to the direction of trapped field.
  • two or more such chips may be stacked or “laminated” together and then activated; if two such chips are so laminated and then activated, then the resultant field strength, B, will, except for geometric effects, be very nearly twice the field strength obtainable from one such chip.
  • the chips may be activated either before or after assembly, as desired.
  • a large number of chips with identical fields could be assembled "edge-to-edge" on a. surface to create a very strong, uniform field over a relatively large spatial distance, or, if desired, chips with different fields could be utilized to create a complex field. If the desired, spatially large and complex field already exists, a large number of un-activated chips may be simply arranged in a mosaic pattern and then activated to quickly and accurately capture and reproduce the complex field pattern.
  • a light, small surface area activating magnet can be used to activate mosaic components. These components may then be assembled to create a large surface area magnet.
  • a large area dipole replica may be con ⁇ structed although only a small area activator is present.
  • the power dissi ⁇ pation characteristic of conventional magnets is eliminated by the bulk replicators of the present invention.
  • a high T c SC replicator may be formed in virtually any desired shape by packing and pressing "1,2,3" powder and then sintering at high temperature.
  • hollow circular cylinders have been found particularly advantageous for many applications, while other hollow forms, such as squares or other polygons, and various solid forms have been found advan ⁇ tageous for still other applications.
  • the high T c SC replicator may be formed by melting-solidification methods, or by lamination and mosaic fabrication.
  • the repli ⁇ cator formed by any of these methods may be improved by pro ⁇ ton, neutron, or other heavy particle bombardment, or it may be improved by the admixture of impurities such as silver, or the Lanthanide group, or it may be formed by any method which allows high persistent currents at high magnetic fields. It may also be fabricated out of sections produced by any of these methods.
  • material of the class RBa2Cu3 ⁇ 7_ x where R is a lanthanide element other than lan ⁇ thanum, cerium, praseodymium, promethium or terbium, is also satisfactory, as are the superconductive bismuth-strontium- calcium-copper-oxygen compounds and the superconductive thal ⁇ lium-barium-calcium-copper-oxygen compounds.
  • Satisfactory re ⁇ sults may also be obtained with mixtures of YBa2Cu3 ⁇ 7_ x and RBa2Cu3 07_ x , where R may be any of the lanthanide elements, including those whose individual barium copper oxides are not satisfactory when formulated indivdually.
  • R may be any of the lanthanide elements, including those whose individual barium copper oxides are not satisfactory when formulated indivdually.
  • any of the lanthanide element oxides are also satisfactory when formulated as mixtures of at least two or more of such materials.
  • a warm SC cylinder is placed in a preexisting magnetic field perpendicular to the axis of the cylinder and then cooled through the transition temperature.
  • the SC cylinder is first cooled into its superconductivity state and then an external field is turned on to a magnitude exceeding H c ⁇ of the SC.
  • part of the field is retained, or “captured”, in the SC cylinder when the external field is turned off.
  • the SC repels all flux lines (or virtually all flux lines) from the interior of the body of the SC until some threshold level of external field is applied.
  • This threshold level, or B S hield' is the amount of magnetic field, B, that can be repelled or "shielded" from the SC.
  • the relationship may also be thought of as describing a saturation effect. From the examples, it may be seen that the first 40,000 Gauss of activating field, B 0 , will result in a trapped field of 17,293 Gauss, whereas an additional 40,000 Gauss would result in an increase of the trapped field of only 2,341 Gauss. If the activating field is to be pro ⁇ **d by an expensive magnet, then it may be highly preferable for economic reasons to construct the activating magnet to provide activating fields no greater than 30,000 or 40,000 Gauss. For some applications, cylindrical high T c SC's are preferred, while pipes of square or other cross section, or chips or disk-shaped high T c SC's are preferred for other applications. The following examples illustrate some results achieved from applying the techniques of the present invention to magnetize either individual chips or cylinders.
  • Example II illustrates the uniformity of field that may be obtained in a high T c SC replicator of 1,2,3 material with 15% Ag formed as a hollow cylinder or tube.
  • a highly preferred method of inducing highly homoge ⁇ neous imperfections is that of radiation bombardment.
  • gamma-ray bombardment is least preferred, neutron bombardment more preferred, and bombardment by any positively- charged ions such as protons most preferred.
  • High energy, heavy particle bombardment permits much greater control of both spacing and depth of induced imperfections.
  • a column of nuclei may be knocked out of the polycrystalline lattice with the resulting plurality of miniature dipoles all aligned. Any desired pattern may be created - i.e., one column out of ten, one column out of four, a "checkerboard" pattern, etc.
  • Such currents may also be reduced by employing multiple layers of thin mosaics separated by any material which is either insulating or at least non-superconductive at the tem ⁇ peratures of interest.
  • the Giant Creep effect is a diminution of retained B (B r ) at the rate of about seven to fourteen percent (7-14%) per week during the first week.
  • B r retained B
  • the rate of decay is proportional not to time but to a logarithmic function of time
  • Example IV utilizes a large grain sample about 1cm x 1cm x 1mm, for which the maximum trappable field, B ⁇ ( ax)' -- s 600 Gauss. If the field trapped, B , is near the maximum trappable B, then the Giant Creep effect will initially reduce the field at the rate of about 13% during the first week. However, if the field trapped is only a fraction of the maximum trappable B ( max) , say, on the order of 25%, then the initial field decrease is less than 1.0 % in the first week, which results in virtually no losses thereafter. As the maximum field which can be trapped in ⁇ creases, the field strength for which the Giant Creep effect is negligible also increases.
  • Example V which utilizes a two-grain mosaic disk, illustrates a mapping of the trapped field, for various levels of applied fields, as the probe traverses the sample.
  • a field less than the strength of the field re ⁇ taine d b etween the grain boundaries By applying a field less than the strength of the field re ⁇ taine d b etween the grain boundaries, a very uniform field strength may be obtained (bottom curve). For a sample of un ⁇ known characteristics, this may be obtained by first applying a relatively high field and mapping to determine the uniformity, and then, if insufficiently uniform, quenching and applying another field of strength less than the field retained between the boundaries and mapping the sample again. This "backing down" procedure may be repeated as necessary to obtain the degree of uniformity desired.
  • the ability to vary B is desire ⁇ able. This may be done in several ways.
  • long magnets are used.
  • a long cy ⁇ linder, activated as a dipole magnet, for example, may be com ⁇ prised of shorter cylinders.
  • the fields of all cylinders can be, for example, vertical. Field may then be decreased by rotating two cylinders by an angle, ⁇ , in opposite directions. These two cylinders behave as though their effective field is Bcos ⁇ . Since ⁇ may be continuously varied, the effective field may be continously varied.
  • Trim coils may be used in addition to the magnet replica to vary the field slightly, by conventional means.
  • a framework of superconducting wires may be used to provide a temporary (pulsed) field of the desired shape and magnitude.
  • the replica can then be warmed, and then cooled again and recharged whenever desired, by pulsing the activating magnet.
  • Fig. 1 is a plan view of a simplified schematic repre ⁇ sentation of a portion of a high T c SC magnetic sample whose lattice structure has been distorted by the addition of im ⁇ purities.
  • Fig. 2 is a simplified schematic representation of a portion of a sample which has undergone heavy particle bom ⁇ bardment.
  • Figs. 3A and 33 schematically represent, in vertical cross-section, a portion of a sample of a SC replicator com ⁇ prising a mis-aligned grain boundary, before and after bombard ⁇ ment, respectively.
  • Fig. 4 is a schematic representation of a macroscopic- sized portion of a sample replicator, arbitrarily shown of rectangular configuration.
  • Fig. 5 is a vertical cross-section of a cylindrically shaped SC sample subsequent to activation.
  • Fig. 6 is a perspective view of a pair of SC magnetic samples, in this instance shown as hollow cylinders, which have been rotated from an initial vertical alignment of the respective fields by an equal but opposite angle ⁇ .
  • Fig. 7 schematically represents an end view of a pair of other SC magnetic samples which have been rotated from a vertical alignment of the respective fields by an equal but opposite angle ⁇ .
  • Fig. 8 is a perspective view of a series of SC mag ⁇ netic replicas, again in this instance portrayed as cylindrical samples, stacked end-to-end.
  • Figs. 9A, 9B and 9C are perspective views illustrating one method of combining discrete SC magnetic replicas to obtain an increase in field strength.
  • Figs. 10A and 10B are perspective views illustrating another method of combining discrete SC magnetic replicas to obtain an increase in field strength.
  • Figs. 11A, 11B and 11C are schematic views of other methods of combining SC magnetic replicas, with the magnetic field vectors not shown for clarity.
  • Figs. 12A, 12B and 12C are schematic views of still other methods of combining SC magnetic replicas, with the magnetic field vectors not shown for clarity.
  • Fig. 12A de ⁇ picts a pair of samples from a direction parallel to the direction of greatest field strength.
  • Fig. 12B depicts the same samples rotated 90°, i.e., from a direction perpendicular to the direction of greatest field strength.
  • Fig. 12C depicts three samples from the same direction on that of Fig. 12B, i.e., an "edge" view.
  • Fig. 13 is a schematic view from an edge of an assembly which has been assembled using both laminate and mosaic tech- ni ⁇ ues.
  • Fig. 14 is a perspective view of a shaped structure, chosen for illustrative purposes as a cylinder, to which SC magnetic replicas have been applied in a mosaic manner.
  • Fig. 1 there may be seen in plan view a simplified schematic representation of one of the sim ⁇ plest of many possible forms of distortion of a high T c SC replicator.
  • the particular form illustrated is one layer only of a chemical/physical substitution of a few larger atoms or molecules for the smaller atoms of 'solvent' at the lattice points.
  • the imperfections shown schematically may in some in ⁇ stances represent regions of poor superconductivity, and in other instances may represent regions of good superconductivity that beome superconducting at temperatures different from ad ⁇ joining regions.
  • Persistent superconducting microcurrents may subsequently be induced in vortices around distorting positions such as 11 and 12, which such current vortices (and associated fields) may not cross, thus “trapping” or “pinning” such vortices and their resultant fields.
  • the 'solute' atoms or molecules could just as easily be smaller than the 'solvent' atoms, and they could be dis ⁇ persed at many locations other than at lattice points. They could also be imperfections which do not prevent superconduc ⁇ tivity: they could, for example, just locally modify T c .
  • Figure 2 is intended as a simplified schematic repre ⁇ sentation of a portion of a sample which has undergone heavy particle bombardment, such as by neutrons, protons or the like. It may be considered to represent a vertical cross- section of a SC replicator which has been bombarded from the vertical direction and from which at least a portion of a column of nuclei has been ejected or at least displaced.
  • the "holes" in the crystal are represented functionally by minia ⁇ ture bar magnets, since they will function as dipoles.
  • all the miniature dipoles (21 et seq.) will be perfectly aligned with the activating field. This feature, combined with the ability to create any pattern of distortions quite homogeneously, should allow the maximum field for any given material to be retained.
  • Figure 3A schematically represents, in vertical cross- section, a portion of a SC replicator comprising a misaligned grain boundary before bombardment;
  • Fig. 3B the portion after bombardment.
  • the 'dipoles' of the grain which was not aligned with the direction of bombard ⁇ ment e.g., those of column 32
  • the preferably-oriented dipoles of the grain which was so aligned i.e., column 31, and are thus able to make the maximum possible contribution to the desired magnetic field.
  • the elements 41 through 45 are schematic representations of per ⁇ sistent microcurrents, shown, for clarity, on a surface only.
  • per ⁇ sistent microcurrents are preferably distributed throughout the volume or bulk of the SC replicator as a whole, preferably as profusely as possible. The more uniform the distribution, the more accurately most magnetic fields can be replicated. Also, the more uniform the distribution, the higher the maximum field that can be trapped.
  • the overall resultant field strength is mainly proportional to the total aligned persistent microcurrent since, to the extent shielding can be neglected, no relatively large persistent current flows will be established in the bulk of the SC replicator by the cool method.
  • the overall resul ⁇ tant field strength may be thought of as comprising one or both of two components, one of which may be considered the resultant of the numerous persistent micro-currents.
  • the other component may be considered the resultant of one or more relatively large persistent currents which circulate either through the bulk of the SC replicator as a whole or through relatively large portions of the replicator.
  • Element 46 is a schematic representation of one such relatively large, bulk- circulating, persistent current.
  • Figure 5 portrays a vertical cross-section of a cylin- drically-shaped SC sample after activation.
  • the looping lines 52, 53 represent the magnetic lines of field external to the sample, while the vectors B represent the magnetic field internal to the sample.
  • Figure 6 is a perspective view of a pair of SC magnetic samples, chosen in this instance as cylinders, wherein the internal magnetic field lines are repre ⁇ sented schematically by vectors shown at the visible end of each such sample. It is to be understood that the internal magnetic fields extend the lengths of the cylinders, and that each cylindrical sample has an external magnetic field asso ⁇ ciated therewith, of the general nature of that shown in Figure 5, e.g., force lines 52, 53.
  • Figure 7- is a simple schematic representation of a pair of hollow polygonal SC magnetic samples. If the equal but opposite angle through which each has been rotated is ⁇ , and if B 0 represents the field strength of each such member in the vertical direction prior to rotation, then the horizontal component of the fields may be represented by Bsin ⁇ . In this manner, one may manipu ⁇ late the cylinders 61 and 62, or the members 71 and 72, so as to have a chosen component thereof, such as their horizontal components, diminish as desired, or cancel, and thus design the shape of the field.
  • Figure 8 illustrates one means of obtaining spatially larger magnets and stronger fields than one may have available to replicate.
  • Each of the individual samples 81, 82, etc. may be constructed by any of the means of this invention to replicate an original and then, while the temperature is main ⁇ tained below the critical level, be assembled in the end-to- end or 'stacked' arrangement depicted. In this manner, a SC magnetic replicator spatially many times larger than any single pre-existing magnet may be created.
  • the indivi ⁇ dual replicators may take any desired shape, and that as many individual replicators as desired may be so 'stacked'.
  • each individual replicator may be essentailly identical, if a highly uniform field is desired, or each or any combination thereof may have different fields if a complex field is desired.
  • Figure 9 illustrates another method of increasing the field strength.
  • each discrete sample is a rectangular, planar sample or chip, but such samples may be of any desired shape and may in fact be curvilinear if desired.
  • a first sample may be created and activated by any of the principles of this invention, creating an exter ⁇ nal field in association therewith represented schematically by the vector B ⁇ of Fig. 9A.
  • a second sample 92 may similarly be created; if the same original is used for each replica, B ⁇ will be very nearly the equal of B2 « Placing the two samples 91, 92 in close proximity to one another will result in the creation of a resultant field, B3, larger than either of Bi or B2 «
  • the method of Figure 10 is preferred.
  • the two discrete samples are joined or laminated prior to activation, as shown in Fig. 10A.
  • the field strength of an individually activated sample is B, then, upon activation of the laminated pair of samples.
  • the final field strength will be very closely equal to 2B at a point very near the center of the outer surface of joined element 102 (or at the same distance on the opposite side, i.e., near the center of the outer surface of joined element 101), provided that the resultant field strength is not limited by saturation effects.
  • the final field will be slightly less than 2B only because one sample is further away than the other.
  • Figure 11 depicts methods of obtaining still stronger fields.
  • two separate samples for example, each activated to produce a field strength of B (at a point removed from a major surface by a distance of roughly one-tenth the length of the sample), are brought into close proximity but spaced apart from each other, as shown.
  • the resultant field strength at the point P will be 2B, or twice the field strength at the point from only one of such samples.
  • a preferred method of increasing trapped field in this geometry is to assemble unactivated samples in the geometry shown, and then activate them.
  • two sets of two samples each may be first laminated and then activated, and then brought into close proximity; the resultant field strength at the point P will be nearly 4B, except for spacing effects, again providing no saturation.
  • the samples may be just laminated, then brought into close proximity, and then activated.
  • two sets of three laminae being shown in Fig. 11C, although the diminish ⁇ ing returns will as a matter of practicality normally limit such structures to a maximum thickness not more than a few times the distance from the point P to the surface of the first sample.
  • Figure 12 depicts an alternate method of combining SC magnetic replicas, designated the 'mosaic' method, in con ⁇ tradistinction to the 'laminate' designation applied to the preceding method.
  • the samples - which may also be of any desired shape, planar or curvilinear, etc. - are joined in an end-to-end arrangement, or edge-to-edge.
  • the discrete replicas of Fig. 12A may be activated either before or after assembly; in either event, the field strength at point P of such an assembly will be very nearly twice that of one such replica.
  • the procedure may be extended to three 'mosaics', as illustrated in Fig. 12C, for which the resultant field strength will be less than three times that of one replica, or to as many as desired.
  • a large mosaic may be assembled rapidly and cheaply and then activated quite expeditiousl .
  • each individual replicator may be activated before assembly to reproduce as large a field as is available, or to reproduce different fields for a complex overall field.
  • the mosaic and laminate methods may be combined, as is illustrated in Fig. 13. Again,, a stronger field may be obtained if each pair to be laminated is first laminated and then activated.
  • Figure 14 illustrates still another method of creating spatially large and strong or complex fields.
  • the substrate 141 shown is cylindrical, but may be of any desired shape.
  • only a portion of the surface of substrate 141 is shown covered with individual SC magnetic replicas.
  • the entire surface may be covered with single, powerful replicas, or such portions as may be desired. It should be appreciated that enormously powerful magnets may thus be created.
  • several layers (laminae) of replicas may be used, and the entire replica may be activated after fabrica ⁇ tion.
  • the field is shown parallel to the longitudinal axis, but may be of any desired direction.
  • Individual chips, disks, or grains replicating a single powerful field may be activated, maintained below the critical temperature, and assembled on the shaped substrate.
  • the substrate were the substrate to be a cylinder large enough to accomodate a per ⁇ son, say 1 meter diameter and 1 meter in length, it would have approximately 3.14 square meters of surface area.
  • this surface Were this surface to be covered with individual chips with current densities of 200,000 amps/cm 2 , a field strength on the order of 240,000 Gauss would be created.
  • Such cylinders could be extended as desired.
  • Complex fields may be created by applying individual chips, disks, or grains of different strengths over the sur ⁇ face area in such patterns as may be desired. They may also be created by activating the entirety after fabrication with the desired field.
  • the magnetic replicas of the present invention are particularly useful because of their low cost, low weight, zero power consumption (except for the coolant), and accurate reproduction of field shapes of any multipolarity.
  • the usual requirement is for precision machining and assembly.
  • the replica when the replica is fabricated (whether with components or as a whole) and is then activated, the replica itself may be a crude rather than precision-machined device.
  • the techniques of this invention will create the precise configuration of the persistent currents within the superconductor needed to copy the impressed field with preci ⁇ sion. Thus the requirement for precision has been removed from the exterior to the interior of the device, and the pro ⁇ cedure for obtaining such precision automated.
  • beam lines external to accelerators involve many expensive magnets which are usually dipoles and quadrupoles, and even sextuples.
  • One dipole will suffice as the parent for a series of dipole replicas, and one quadrupole as the parent for a series of quadrupole rep ⁇ licas.
  • the cost of a typical beam line which may have 5 dipole and 20 quadrupole replicas, will be dramatically re ⁇ pokerd by use of the replicas of the present invention, perhaps by as much as 90%. Any quench in any of the replicas can be quickly corrected by reinitializing the replica with the de ⁇ sired parent magnet.
  • the consumption of electrical energy is an important and often limiting factor.
  • accelerators are often limited in their operation by agree ⁇ ments with local utilities on maximum power usage, and are limited in the fraction of the year they can operate by the cost of the power, which often is several million dollars per year. Replicas operating with no power drain are thus very attractive.
  • Replicas can also be used as field magnets in generators, thus decreasing power loss. Similarly they can be used for motors. In sufficient size, they can be used for magnetic resonance imaging magnets, or for levitation or propulsion magnets in transportation, and literally in a myriad of other useful and beneficial applications.

Abstract

Nouvelle classe de dispositifs fondamentalement différents (61, 141) et leurs procédés de fabrication et d'utilisation. Ces duplicateurs non épitaxiés de champ magnétique n'exigent aucun usinage ou alignement de précision pour pouvoir dupliquer de manière précise les champs magnétiques (B), cela quelle que soit la complexité de ces derniers, tout comme ils n'exigent point de stabilité extrême de position pour maintenir leur supraconduction. Ces dispositifs non épitaxiés peuvent être constitués de matériaux supraconducteurs à température critique élevée ou non, mais sont adaptés tout particulièrement pour être constitués de matériaux à température critique élevée.
PCT/US1991/001193 1991-04-10 1991-04-10 Duplicateur de champ magnetique et procede WO1992018992A1 (fr)

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GB2339889A (en) * 1998-07-17 2000-02-09 Gec Marconi Aerospace Limited Magnetising a superconductor at cryogenic temperatures
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EP0797261A1 (fr) * 1996-03-22 1997-09-24 International Superconductivity Technology Center Matériau composé supraconducteur
US5920246A (en) * 1996-03-22 1999-07-06 International Superconductivity Technolgy Center Superconductive composite materials
GB2339889A (en) * 1998-07-17 2000-02-09 Gec Marconi Aerospace Limited Magnetising a superconductor at cryogenic temperatures
GB2339968A (en) * 1998-07-17 2000-02-09 Marconi Electronic Syst Ltd A magnetizing arrangement for a high temperature superconductor
US6281773B1 (en) 1998-07-17 2001-08-28 Picker International, Inc. Magnetizing magnet
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