JP4723936B2 - Persistent current superconducting coils and magnets - Google Patents

Description

  The present invention relates to a permanent current superconducting coil and magnet used for superconducting equipment in fields such as medical, semiconductor manufacturing, and space.

  In a magnetic resonance imaging apparatus (MRI apparatus) and a semiconductor crystal pulling apparatus, a permanent current superconducting coil or a magnet capable of obtaining a stable high magnetic field is used. FIG. 12 is a diagram showing a configuration of a conventional permanent current superconducting coil. As shown in the figure, when a permanent current superconducting coil is made using a superconducting wire, a connecting portion 2a for connecting the lead wires 1a and 1b is necessary. Moreover, when connecting the permanent current switch 3 for exciting the superconducting coil 1, the connection part 2b is required (refer patent document 1 below).

In order to obtain a good current maintaining performance, it is necessary to superconductingly connect the connecting portions 2a and 2b. However, a technology for superconducting connection of oxide superconductors other than specific superconductors has not yet been developed. A permanent current superconducting coil using a physical superconductor has not been realized. Since the oxide superconductor has a high critical temperature, the cooling equipment can be simplified, and a permanent current superconducting coil and magnet using the oxide superconductor are strongly desired.
JP 60-157208 A

  An object of the present invention is to provide a permanent current superconducting coil and a magnet that do not attenuate current caused by a connecting portion even when an oxide superconductor is used.

In order to solve the above problems, a permanent current superconducting coil according to the present invention, the persistent current superconducting coil formed by winding a closed circuit superconductor constituting a closed circuit without having been connected portion cut from superconductor thin plate The closed circuit superconducting conductor has a substrate layer, a superconductor layer formed on the substrate layer, and a stabilization layer formed on the superconductor layer, and the superconductor layer is the closed layer. The circuit superconducting conductor is arranged near the neutral axis of the strain in the thickness direction .
Furthermore, a permanent current superconducting magnet according to the present invention is characterized by comprising the above permanent current superconducting coil and a cooling means for cooling the permanent current superconducting coil.

  According to the present invention, it is possible to provide a permanent current superconducting coil and a magnet having no current attenuation caused by the connecting portion even when an oxide superconductor is used.

  Hereinafter, first to fourth embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment, In the range which does not change the summary, it can implement suitably.

(First embodiment)
In the present embodiment, a closed frame superconducting conductor 4 having a rectangular frame shape as shown in FIG. 1 cut out from a thin plate-shaped superconductor is used. By winding this closed circuit superconducting conductor 4 from the winding start portion 5 to the winding end portion 6, a permanent current superconducting coil composed of two coils of an element coil 7 and an element coil 8 is produced as shown in FIG. . In this configuration, in the permanent current superconducting coil, the direction 9 of the magnetic field of the element coils 7 and 8 is opposite. Therefore, the permanent current superconducting coil 1 having the same magnetic field direction 9 is constituted by reversing one coil, for example, reversing the direction of the element coil 8 as shown in FIG.

In addition, the permanent current superconducting coil which consists of more than two element coils can be comprised by making the shape of the closed circuit superconducting conductor 4 into a comb shape as shown in FIG. Further, like the winding start portion 5 and the winding end portion 6 shown in FIG. 1, the closed circuit superconducting conductor 4 can be easily wound or the element coil can be reversed by changing the shape of the closed circuit. Further, the critical current value can be adjusted by changing the width of the closed circuit superconducting conductor 4 according to the use conditions of temperature and magnetic field.
According to the present embodiment, by using the closed circuit superconducting conductor 4, it is possible to provide a permanent current superconducting coil having no connection portion and no current attenuation due to the connection resistance.

(Second Embodiment)
In the present embodiment, a closed circuit superconducting conductor 4 having a sectional configuration as shown in FIG. 5 is used. In general, a superconductor has a characteristic that a critical current deteriorates when a strain exceeding an allowable value is applied. In the present embodiment, the superconductor layer 10 is sandwiched between the substrate layer 11 made of Hastelloy or Ni—W alloy and the stabilization layer 12 made of copper or silver, and is disposed near the neutral axis of the strain. In the case where a large bending deformation is applied when a permanent current superconducting coil is formed, such as when the element coil 8 is reversed as shown in FIG. However, the closed circuit superconducting conductor 4 is less deteriorated. Moreover, as a material of the superconductor layer 10, YBCO (oxide superconductor mainly composed of yttrium, boron, carbon and oxygen) having a large critical current density can pass a sufficient current even in a thin layer. Therefore, the superconductor layer 10 can be disposed only in the vicinity of the neutral axis, which is particularly suitable for the present embodiment.

  According to the present embodiment, since the superconductor layer 10 is disposed in the vicinity of the neutral axis in the thickness direction, the closed circuit superconducting conductor 4 that is resistant to bending deformation is obtained, and the permanent current having a large critical current value and a high quality is obtained. A current superconducting coil can be provided.

(Third embodiment)
FIG. 6 shows the permanent current superconducting coil of the present embodiment. In other words, a part of the superconducting coil is provided with the switch mechanism 13 for controlling transition between the superconducting state and the normal conducting state, and the current source 14 is excited through both ends thereof. As a method for controlling the transition between the normal conducting state and the superconducting state, heating means 15 such as a heater is used. Since the switch mechanism 13 is more easily excited and demagnetized as the resistance at the normal conduction transition increases, a configuration in which the stabilization layer 12 is not provided on the closed circuit superconducting conductor 4 in the switch mechanism 13 as shown in FIG. To increase the resistance.

  According to the present embodiment, a part of the superconducting coil using the closed circuit superconducting conductor 4 is provided with the switch mechanism 13 and energized from the current source 14 through both ends thereof, so that the permanent current superconducting coil that is easily excited and demagnetized can be obtained. Can be offered. Further, by using a heating means as the switch mechanism 13 or removing the stabilization layer 12 corresponding to the switch mechanism 13 of the closed circuit superconducting conductor 4 to increase the resistance of the normal conducting state, excitation and demagnetization can be performed more easily. A permanent current superconducting coil can be provided.

(Fourth embodiment)
A permanent current superconducting magnet according to a fourth embodiment of the present invention is shown in FIG. That is, the permanent current superconducting magnet includes a permanent current superconducting coil 16 composed of the closed circuit superconducting conductor 4 and the switch mechanism 13, a radiation shield 19 surrounding the permanent current superconducting coil 16, and a vacuum vessel surrounding the radiation shield 19. 20, a refrigerator 17 attached to the vacuum vessel 20 and having a cooling end penetrating into the radiation shield 19, and a transmission made of a silver or copper block provided between the cooling end of the refrigerator 17 and the permanent current superconducting coil 16. The heat means 18 is comprised.

  The permanent current superconducting magnet of the present embodiment may be configured such that the permanent current superconducting coil 16 is installed in the refrigerant container 22 and cooled by the refrigerant 21 as shown in FIG. When a high-temperature superconductor such as YBCO is used as the material of the superconductor layer 10 constituting the closed circuit superconductor 4, practical critical current characteristics can be obtained even at a temperature of 30K to 80K. Therefore, a simple configuration using the single stage refrigerator 23 as shown in FIG. 10 is possible. Moreover, as shown in FIG. 11, it is good also as a structure using the liquid nitrogen 24 as a refrigerant | coolant.

  According to the present embodiment, by using the permanent current superconducting coil 16 using the closed circuit superconducting conductor 4, it is possible to provide a permanent current superconducting magnet having high current maintaining performance. By selecting a high-temperature superconductor such as YBCO as the material of the superconductor layer 10 to be configured, a permanent current superconducting magnet having a simple structure and high reliability can be provided.

The top view which shows the closed circuit superconducting conductor which comprises the permanent current superconducting coil of the 1st Embodiment of this invention. The perspective view which shows the state in the middle of manufacture of the permanent current superconducting coil of the 1st Embodiment of this invention. The perspective view which shows the permanent current superconducting coil of the 1st Embodiment of this invention. The top view which shows the other example of the closed circuit superconducting conductor which comprises the permanent current superconducting coil of the 1st Embodiment of this invention. Sectional drawing which shows the closed circuit superconducting conductor which comprises the permanent current superconducting coil of the 2nd Embodiment of this invention. The perspective view which shows the permanent current superconducting coil of the 3rd Embodiment of this invention. Sectional drawing which shows the closed circuit superconducting conductor which comprises the permanent current superconducting coil of the 3rd Embodiment of this invention. Sectional drawing which shows the permanent current superconducting magnet of the 4th Embodiment of this invention. Sectional drawing which shows the 1st modification of the permanent current superconducting magnet of the 4th Embodiment of this invention. Sectional drawing which shows the 2nd modification of the permanent current superconducting magnet of the 4th Embodiment of this invention. Sectional drawing which shows the 3rd modification of the permanent current superconducting magnet of the 4th Embodiment of this invention. The connection diagram which shows the structure of the permanent current superconducting coil of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Superconducting coil, 1a, 1b ... Lead wire, 2a, 2b ... Connection part, 3 ... Permanent current switch, 4 ... Closed-circuit superconducting conductor, 5 ... Winding start part, 6 ... Ending part of winding, 7, 8 ... Element Coil, 9 ... Magnetic direction, 10 ... Superconductor layer, 11 ... Substrate layer, 12 ... Stabilization layer, 13 ... Switch mechanism, 14 ... Current source, 15 ... Heating means, 16 ... Permanent current superconducting coil, 17 ... Refrigeration 18 ... Heat transfer means, 19 ... Radiation shield, 20 ... Vacuum container, 21 ... Refrigerant, 22 ... Refrigerant container, 23 ... Single stage refrigerator, 24 ... Liquid nitrogen.

Claims (9)

In a permanent current superconducting coil formed by winding a closed circuit superconducting conductor that is cut out from a thin plate-shaped superconductor and forms a closed circuit without having a connection part ,
The closed circuit superconductor has a substrate layer, a superconductor layer formed on the substrate layer, and a stabilization layer formed on the superconductor layer, and the superconductor layer is the closed circuit superconductor. A permanent current superconducting coil, wherein the coil is disposed near a neutral axis of strain in a thickness direction of a conductor .   2. The permanent current superconducting coil according to claim 1, wherein the width and shape of the closed circuit superconducting conductor are determined according to a required critical current value. 3. The permanent current superconducting coil according to claim 1, wherein the superconductor layer is made of YBCO. Comprising a switch mechanism for transition control the superconducting state and the normal conducting state to a portion of the closed circuit superconductor, one of claims 1 to 3, characterized in that as excited from the current source through both ends of the switch mechanism persistent current superconducting coil crab according. 5. The permanent current superconducting coil according to claim 4, wherein the switch mechanism has a heating means. 5. The permanent current superconducting coil according to claim 4 , wherein a normal conduction state resistance value per unit length of a portion corresponding to the switch mechanism of the closed circuit superconducting conductor is higher than a resistance value of other portions. A persistent current superconducting coil according to any one of claims 1 to 6, the permanent current superconducting magnet, characterized in that it comprises a cooling means for cooling the permanent current superconducting coil. The permanent current according to claim 7 , wherein the cooling means includes a refrigerator that cools the permanent current superconducting coil by heat conduction, and the permanent current superconducting coil is maintained at a temperature of 30K to 80K. Superconducting magnet. 8. The permanent current superconducting magnet according to claim 7 , wherein the cooling means is liquid nitrogen stored in a refrigerant container and dipping the permanent current superconducting coil.

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