JP2014192490A - Permanent current switch and superconducting device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent current switch capable of reducing a movement amount of heat generated by the electrification of a heater to a superconducting coil.SOLUTION: A permanent current switch includes: a spool 13 for winding a coil therearound; a heater wire 14 wound around the spool 13 in a coil shape; a superconducting wire wound around the spool 13 in the coil shape; and a lead wire connected to the superconducting wire and drawn from the spool 13. In the permanent current switch which disconnects a superconducting closed circuit, a switch part 11 around which the superconducting wire is wound so as to be overlapped on the heater wire 14, and a heat resistance part 12 which inhibits heat transfer from the switch part 11 to the lead wire by winding only the superconducting wire are provided in the spool 13.

Description

  The present invention relates to a permanent current switch that forms a closed circuit through which a permanent current caused by superconducting flows, and a superconducting device including the permanent current switch.

  For example, in an apparatus that needs to generate a static magnetic field, such as an MRI (magnetic resonance imaging) apparatus or an NMR (nuclear magnetic resonance) apparatus, a static magnetic field is generated by operating a superconducting magnet (superconducting magnet) in a permanent current mode. The permanent current mode means that the superconducting magnet is excited by the permanent current. In order to operate the superconducting magnet in the permanent current mode, the permanent current is passed through a closed circuit composed of superconducting wires and incorporating the superconducting magnet. Must-have.

  To pass a permanent current through a closed circuit incorporating a superconducting magnet, first supply current to the superconducting magnet from a power supply outside the closed circuit, and then close the closed circuit after the current value flowing through the superconducting magnet reaches the rating. And the supplied current is confined in a closed circuit composed of superconducting wires. This confined current flows through the closed circuit as a permanent current, and the disconnection and connection of the closed circuit are switched by a permanent current switch connected to the superconducting magnet in the closed circuit. This permanent current switch is a member necessary for constructing a closed circuit including a superconducting magnet. As the permanent current switch, methods such as a thermal type, a magnetic type, and a mechanical type have been devised, but easy to manufacture. Therefore, “thermal permanent current switches” are mainly used.

  Specifically, the thermal type permanent current switch controls the energization to the heater incorporated in the permanent current switch itself, so that the superconducting wire constituting the permanent current switch is in a superconducting state (switch ON state). Or it switches to a normal conduction state (switch OFF state). If the superconducting wire is brought into a superconducting state (switch ON state) by this switching, a closed circuit incorporating the superconducting magnet is formed. Therefore, the current supplied from an external power source is confined in the closed circuit, and the superconducting magnet is made a permanent current. Can be excited in mode. On the contrary, if the superconducting wire of the permanent current switch is set to the normal conduction state (switch OFF state), the closed circuit is disconnected, so that the permanent current mode is canceled.

Such a permanent current switch is already well known, but various devices as disclosed in Patent Documents 1 and 2 have been made for the configuration and operation thereof.
In the superconducting coil device disclosed in Patent Document 1, the permanent current switch of the superconducting coil is a “permanent current switch using a metallic superconductor as an operating material”, and an oxide high temperature is provided between the permanent current switch and the superconducting coil. It is characterized in that a current lead made of a superconductor is interposed.

  Moreover, the refrigerator-cooled superconducting magnet disclosed in Patent Document 2 includes a superconducting coil that generates a magnetic field, a permanent current mode that does not supply current from an external power source to the superconducting coil by using the superconducting critical temperature of the superconducting material, and current. A permanent current switch that switches between a current supply mode for supplying the superconducting coil, a first cryogenic refrigerator that cools the superconducting coil, another second cryogenic refrigerator that cools the permanent current switch, the superconducting coil, and the A refrigerator-cooled superconducting magnet comprising a permanent current switch and a vacuum vessel for internally storing the cooling stage of the first and second cryogenic refrigerators in a vacuum state, the superconducting coil and the permanent current switch comprising: A superconducting wire to be connected; and at least one superconducting bypass wire that is installed in parallel with the superconducting wire and is electrically coupled along the longitudinal direction. , Superconducting critical temperature of the superconducting bypass line is for being greater than the superconducting critical temperature of the permanent current switch.

Japanese Patent Laid-Open No. 2003-151821 JP 2010-283186 A

By the way, for example, in a superconducting magnet of the type that is conductively cooled by a refrigerator, it becomes a factor that increases the load on the refrigerator, so it is desirable to minimize the amount of heat generated from the heater of the permanent current switch.
Under such a background, in the superconducting coil device of Patent Document 1, in order to suppress the amount of heat transferred from the permanent current switch to the superconducting coil via the superconducting wire, an oxide high temperature superconducting wire is used between the permanent current switch and the superconducting coil. A current lead wire is added.

However, in the method disclosed in Patent Document 1, the metallic superconducting wire of the permanent current switch and the oxide superconducting wire are connected. However, since superconducting connections between superconducting wires are difficult, a connection resistance is generated between the metal-based superconducting wire and the oxide-based superconducting wire, and this connection resistance is a magnetic field attenuation when operated in the permanent current mode. May be a major factor.
Further, in the refrigerator-cooled superconducting magnet of Patent Document 2, a superconducting wire that connects a permanent current switch and a superconducting coil is combined with a superconducting wire (bypass wire) having a higher critical temperature, so that the permanent current switch is switched to the superconducting coil. The method of suppressing the transmitted heat is taken.

However, in reality, most of the heat generated by the heater of the permanent current switch passes through the copper stable member that constitutes the superconducting wire, so that the heat transmitted through the superconducting wire is connected by solder or the like. It cannot be expected to flow through the superconducting bypass line so much, and it seems that the effect obtained by adding the superconducting bypass line is very low.
Therefore, an object of the present invention is to provide a permanent current switch that can reduce the movement of heat generated by energization of a heater to a superconducting coil.

In order to achieve the above-described object, the present invention takes the following technical means.
A permanent current switch according to the present invention includes a winding frame for winding a coil, a heater wire wound in a coil shape on the winding frame, a superconducting wire wound in a coil shape on the winding frame, A permanent current switch for connecting and disconnecting the superconducting circuit, the winding frame being wound so that the superconducting wire overlaps the heater wire. It is characterized by having a turned switch part and a thermal resistance part for suppressing heat transfer from the switch part to the lead wire by winding only the superconducting wire.

Here, it is preferable that the switch part is constituted by the superconducting wire wound non-inductively, and the thermal resistance part is constituted by the superconducting wire wound non-inductively.
Moreover, it is good for the said winding frame to form the partition wall which partitions off the said switch part and the said heat resistance part thermally.
Furthermore, the superconducting wire wound around the switch part and the superconducting wire wound around the thermal resistance part may be electrically connected in series.

In addition, the innermost diameter of the superconducting wire wound around the thermal resistance portion may be larger than the innermost diameter of the superconducting wire or heater wire wound around the switch portion.
Here, the superconducting wire in the switch unit is wound so as to form a plurality of layers in the radial direction of the winding frame, and the superconducting wire in the thermal resistance unit is wound in the radial direction of the winding frame. The outermost diameter along the radial direction of the superconducting wire wound so as to form at least one layer and wound by the switch portion is the outer diameter of the innermost layer of the superconducting wire wound by the thermal resistance portion. It is good that it is substantially the same.

In addition, it is good for the superconducting wire wound by the said switch part and the said heat resistance part to be impregnated.
A superconducting device according to the present invention includes any one of the above-described permanent current switches, a superconducting coil wound with a superconducting wire, a storage container for storing the superconducting coil, and at least one of the superconducting coil and the storage container. A refrigerator that cools below point transfer, and the permanent current switch is thermally connected to the refrigerator in the storage container.

  In addition, a superconducting device according to the present invention includes any one of the permanent current switches described above, and the permanent current switch is immersed in a liquid refrigerant.

  The permanent current switch according to the present invention can reduce the movement of heat generated by energization of the heater to the superconducting coil.

It is a figure which shows schematic structure of the superconducting apparatus provided with the permanent current switch by embodiment of this invention. It is a figure which shows the cross section of the permanent current switch by this embodiment. It is a figure which shows the structure of a reel, (a) shows the whole reel, (b) shows the cross section when it cut | disconnects in the surface which passes along the axial center of a reel. It is a figure which shows the structure of the winding frame around which the heater wire was wound, (a) shows the whole winding frame, (b) shows the cross section when it cut | disconnects in the surface which passes along the axial center of a winding frame. It is a figure which shows the structure of the winding frame around which the switch part was wound, (a) shows the whole winding frame, (b) shows the cross section when it cut | disconnects in the surface which passes along the axial center of a winding frame. It is a figure which shows the structure of the permanent current switch by this embodiment by which the thermal resistance part was wound, (a) shows the whole permanent current switch, (b) cut | disconnected by the surface which passes along the axial center of a reel. A cross-section is shown. It is a figure which shows the whole permanent current switch by which the interlayer insulation material was inserted | pinched between the thermal resistance parts.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, embodiment described below is an example which actualized this invention, Comprising: The structure of this invention is not limited with the specific example. Therefore, the technical scope of the present invention is not limited to the contents disclosed in the present embodiment. Moreover, in each embodiment demonstrated below, suppose that the same code | symbol and the same name are attached | subjected to the same structural member. Therefore, the same description will not be repeated for the components having the same reference numerals and the same names.

A permanent current switch 10 according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of a superconducting apparatus 1 which is a magnetic field generating apparatus used in an MRI (magnetic resonance imaging) apparatus, an NMR (nuclear magnetic resonance) apparatus, or the like. The permanent current switch 10 according to the present embodiment is provided in a superconducting device 1 as shown in FIG.
First, the configuration of the superconducting device 1 in which the permanent current switch 10 is provided will be described with reference to FIG.

The superconducting device 1 includes a storage container 2, a superconducting coil 3 stored in the storage container 2, a vacuum container 4 that holds the storage container 2 inside so that the outer surface of the storage container 2 does not come into contact with the air at room temperature, And a cooling means 5 for cooling the superconducting coil 3 to a superconducting transition temperature or lower.
The storage container 2 is a hollow container formed of a material having excellent mechanical strength and corrosion resistance, such as thin stainless steel. The storage container 2 stores a superconducting coil 3 that will be described in detail later, and also stores a cooling means 5, whereby the superconducting coil 3 in the storage container 2 is cooled to a superconducting transition temperature or lower.

  The superconducting transition temperature is a cryogenic temperature of several K (Kelvin) as a thermodynamic temperature. Therefore, when the storage container 2 formed of a material having high thermal conductivity such as stainless steel is placed at room temperature, heat enters the storage container 2 from room temperature, so the inside of the storage container 2 is kept below the superconducting transition temperature. It is difficult. Therefore, the storage container 2 is held in a later-described vacuum container 4 whose inside is evacuated so that the outer surface does not come into contact with air at room temperature.

  The superconducting coil 3 is a coil obtained by winding a wire made of a superconductor (superconducting substance), and is accommodated in the storage container 2. When a current is supplied to the superconducting coil 3 at a temperature lower than the superconducting transition temperature, the supplied current continues to flow through the superconducting coil 3 whose electric resistance is substantially zero 0 as a so-called permanent current. The superconducting coil 3 generates a magnetic field by electromagnetic induction caused by this permanent current.

The superconducting coil 3 can be connected to a power supply unit (external power supply) that supplies current to the superconducting coil 3 and is used to form a closed circuit (superconducting circuit) through which a permanent current flows. A permanent current switch 10 to be described later is connected to the superconducting coil 3. By switching the permanent current switch 10 between ON (connection) and OFF (disconnection), it is possible to switch between the formation and cancellation of a closed circuit through which a permanent current flows (interconnection of the closed circuit), and the permanent current switch 10 is turned ON (connection). ) To form a closed circuit, and to OFF (disconnect) to cancel the closed circuit. At this time, the cable forming the closed circuit is formed of a superconductor in the same manner as the superconducting coil 3.

  The vacuum container 4 is a hollow container formed of a material having excellent mechanical strength and corrosion resistance, such as stainless steel, and holds the storage container 2 for storing the superconducting coil 3 in the same manner as the storage container 2. To do. The vacuum container 4 holds the storage container 2 inside a vacuum so that the outer surface of the storage container 2 whose inside is extremely low, such as a superconducting transition temperature or less, does not come into contact with the air at room temperature. In other words, the vacuum container 4 holds the storage container 2 across a vacuum space. That is, the storage container 2 and the vacuum container 4 form a so-called thermos structure, and the storage container 2 and the room temperature are insulated from each other with a vacuum space formed by the vacuum container 4 therebetween.

  The cooling means 5 is, for example, a cryogenic refrigerator such as a GM (Gifford McMahon) refrigerator. The refrigerator (hereinafter referred to as the refrigerator 5) serving as the cooling means 5 is rod-shaped and long, and is provided with a drive unit 50 including a compressor or the like on one end side, and further toward the other end from the drive unit 50. It has a first stage 51 for heat exchange in the middle, and a second stage having a second stage 52 on the other end. The first stage 51 is a heat exchanging part that can be cooled to about 30K, for example, and the second stage 52 is a heat exchanging part that can be cooled to about 4K.

  As shown in FIG. 1, the refrigerator 5 passes through the vacuum container 4 and the storage container 2 from the outside of the vacuum container 4, and holds the second stage 52 inside the storage container 2. The drive unit 50 of the refrigerator 5 is hermetically held around the through hole of the vacuum vessel 4, the first stage 51 is tightly connected to the storage container 2, and the second stage 52 is inside the storage container 2, It is connected to the superconducting coil 3 via a plate-like cooling member 6 (for example, a copper member) having a low thermal resistance. Thus, by connecting the superconducting coil 3 to the second stage 52, the superconducting coil 3 can be cooled to a superconducting transition temperature of 4K or lower, for example.

The superconducting device 1 having the above-described configuration further includes a permanent current switch 10. Hereinafter, the configuration of the permanent current switch 10 will be described with reference to FIGS.
First, the problems recognized by the inventors of the present application in conventional permanent current switches will be described.
Conventionally, it is well known that a CuNi / NbTi material using a CuNi material (CuNi stabilizing material) is used as a stabilizing member for a superconducting wire constituting a permanent current switch. This CuNi material has a thermal conductivity about two orders of magnitude smaller than that of the Cu material. Specifically, while the thermal conductivity of Cu stabilizing material (OFHC) under 4.2K is about 180 W / m · K, the thermal conductivity of CuNi stabilizing material (Cu-10wt% Ni). The rate is 1.2 W / m · K.

  If the superconducting wire (CuNi / NbTi wire) made of this CuNi / NbTi material is used as a lead wire between the superconducting coil and the permanent current switch, it becomes possible to suppress the flow of heat from the permanent current switch to the superconducting coil. . Here, the CuNi / NbTi wire exhibits an effect as a thermal resistance part in the switch OFF state (when the permanent current switch is cut off (OFF) by energizing the heater to bring the superconducting wire into the normal conduction state). The heat conduction from the permanent current switch to the superconducting coil can be suppressed.

  However, the CuNi / NbTi wire is less stable than the Cu-stabilized NbTi wire (Cu / NbTi wire), so the switch is turned on (the heater is de-energized and the superconducting wire is put into the superconducting state). When the permanent current switch is connected (ON), the risk of quenching the superconducting wire increases. In particular, an NMR or MRI magnet that requires a higher magnetic field or a smaller size requires a higher current density. This causes quenching by applying a very high electromagnetic force to a superconducting lead wire locally. May end up. Therefore, the inventor of the present application avoids the use of a CuNi / NbTi wire, which has a high risk of quenching, as a lead wire as much as possible, and a permanent current switch that can suppress conduction of heat generated by the heater wire to the superconducting coil. Invented and illustrated as a permanent current switch 10.

Therefore, as shown in FIG. 2, the permanent current switch 10 according to the present embodiment is different from the switch portion (PCS portion) 11 around which the superconducting wire (CuNi / NbTi wire) is wound. On the side, a thermal resistance portion 12 in which only a CuNi / NbTi wire having a low thermal conductivity was wound was provided.
The permanent current switch 10 is connected to the superconducting coil 3 by a conductive wire (cable) to form a closed circuit for flowing a permanent current, and includes a winding frame 13, a heater wire 14, a switch unit 11, and a thermal resistance. The unit 12 is configured. Hereinafter, it demonstrates in order.

  The configuration of the reel 13 will be described with reference to FIG. 3A and 3B are diagrams showing the reel 13, FIG. 3A is a diagram showing the entire reel 13, and FIG. 3B is a cross-sectional view taken along a plane passing through the axis of the reel 13. It is. The reel 13 has a cylindrical body portion 13A, a cylindrical body portion 13B having a larger diameter than the body portion 13A and adjacent to the body portion 13A, and a partition wall 13C provided between the body portion 13A and the body portion 13B. And a disc-shaped flat plate (flange) 13D provided at the end of the trunk portion 13A, and a disc-shaped flat plate (flange) 13E provided at the end of the trunk portion 13B. The body portions 13A and 13B, the partition walls 13C, and the flanges 13D and 13E constituting the winding frame 13 are made of, for example, GFRP (glass fiber reinforced plastic) or the like in order to suppress heat transfer of heat generated by the heater wire 14 to be described later. Consists of materials with high thermal resistance.

The body portion 13A is, for example, a cylindrical member having an outer diameter of about 30 mm, and the length (the height of the cylinder) along the axial direction of the cylindrical shape is orthogonal to the axial center, for example. It is formed to be several times the diameter (diameter of the cylinder).
The trunk portion 13B is a cylindrical member having an outer diameter of about 37 mm as in the trunk portion 13A. However, the trunk portion 13B has a length along the axial direction of the columnar shape (the height of the cylinder) with respect to the trunk portion 13A. Is short, and the diameter perpendicular to the axis (the diameter of the cylinder) is formed to be large.

The trunk portion 13A and the trunk portion 13B are disposed so that their respective ends are opposed to each other and the respective axial centers are arranged substantially in a straight line.
13 C of partition walls are the members formed in the disk shape which has predetermined | prescribed thickness, Comprising: The diameter larger than the diameter of trunk | drum 13A and trunk | drum 13B, The thickness is the trunk | drum 13A and trunk | drum 13B. It is formed to be shorter than the length along the axial direction. Further, the partition wall 13C is connected to the end portions of the body portion 13A and the body portion 13B facing each other so that the disc-shaped shaft center is substantially aligned with the shaft centers of the body portion 13A and the body portion 13B. The Further, the partition wall 13C is formed with a notch 13F in the outer peripheral portion for communicating the trunk portion 13A side and the trunk portion 13B side.

  The flanges 13D and 13E are members having substantially the same shape as the partition wall 13C, and are formed in a disk shape having a diameter substantially the same as that of the partition wall 13C and having a predetermined thickness. The flange 13D is provided at the end portion of the trunk portion 13A connected to the partition wall 13C so that the disc-shaped axis is continuous with the axial center of the trunk portion 13A. Further, the flange 13E is provided at the end of the trunk portion 13B connected to the partition wall 13C so that the disc-shaped axis is continuous with the axis of the trunk portion 13B.

  Further, both the flanges 13D and 13E are formed with groove-shaped notches 13G and 13H communicating the one end face and the other end face on the outer peripheral portion. In the flange 13D, two groove-shaped notches 13G are formed substantially in parallel, so that a protrusion 13I is formed between the two notches 13G. Also in the flange 13E, two groove-shaped notches 13H are formed substantially in parallel, so that a protrusion 13J is formed between the two notches 13H.

  As shown in FIG. 3, the notches 13G and 13H of the flanges 13D and 13E are located on the outer peripheral surface at positions corresponding to the positions of the notches 13F formed in the partition wall 13C, that is, the notches 13F of the partition wall 13C. Is formed at a position where the rotation angle with respect to is substantially zero 0 °. However, the notch 13H of the flange 13E may be formed at a position where the rotation angle with respect to the notch 13F of the partition wall 13C is 180 °. The reason for this will be described later.

The reel 13 is configured to have the body portions 13A and 13B, the partition wall 13C, and the flanges 13D and 13E configured as described above. However, the reel 13 is cut out from a single cylinder. Like the other members, the body portions 13A and 13B, the partition wall 13C, and the flanges 13D and 13E are integrally formed.
The heater wire 14 will be described with reference to FIG. 4A and 4B are views showing the reel 13 around which the heater wire 14 is wound. FIG. 4A shows the entire reel 13 and FIG. 4B passes through the axis of the reel 13. It is sectional drawing when cut | disconnecting by a surface.

The heater wire 14 is a conductive member that generates heat when energized, such as a constantan wire, and is wound around the body portion 13A having an outer diameter of 30 mm in a coil shape with a non-inductive winding length of about 200 mm and a length corresponding to 100Ω. . In FIG. 4, the heater wire is wound along the longitudinal direction of the trunk portion 13A so as not to overlap in the radial direction of the trunk portion 13A. The heater wire 14 is introduced and wound around the body 13A through the flange 13D, and is drawn from the body 13A through the flange 13D.

The switch unit 11 will be described with reference to FIG. 5A and 5B are diagrams illustrating the reel 13 around which the switch unit 11 is wound. FIG. 5A is a diagram illustrating the entire reel 13, and FIG. 5B passes through the axis of the reel 13. It is sectional drawing when cut | disconnecting by a surface.
The switch portion 11 is a superconducting wire wound in a coil shape in the trunk portion 13A, and is wound in a coil shape by non-inductive winding on the heater wire 14 wound in the trunk portion 13A. The superconducting wire wound as the switch unit 11 is, for example, a Cu10Ni / NbTi wire having a diameter Φ of 1.0 mm (for example, a Cu-10 wt% Ni / NbTi wire having a cross-sectional ratio of 1.3).

  The superconducting wire is folded into a U-shape to form a folded portion 11A, and two superconducting wires, one superconducting wire and the other superconducting wire sandwiching the formed folded portion 11A, are adjacent to each other to form a pair. In this way, when a direct current is passed from the superconducting wire on one side across the folded portion 11A to the superconducting wire on the other side, the direction of the current on the one side is always opposite to the direction of the current on the other side. The folded portion 11A of the superconducting wires bundled in this way is hooked on the protrusion 13I of the flange 13D, and the one side and the other side of the two superconducting wires paired in order from the superconducting wire close to the folded portion 11A It winds around 13 A of trunk | drums so that it may not overlap in the radial direction of 13 A of trunk | drums, but may line up along the longitudinal direction of 13 A of trunk | drums. Thereby, non-inductive winding of the switch unit 11 is realized.

  As shown in the cross-sectional view of FIG. 5B, in the present embodiment, for example, a superconducting wire having a length at which both-end resistance at room temperature is 60Ω is wound around a plurality of layers (for example, seven layers). . When winding on a plurality of layers, in each layer, either one of the two superconducting wires paired is wound only once, and the superconducting wire adjacent to the radial direction of the trunk portion 13A is wound. However, the superconducting wire is wound so that the direction of current flow is opposite.

With reference to FIG. 5B, by winding the superconducting wire as described above, the direction of the current flowing through the wound superconducting wire is opposite to the direction of the current flowing through the adjacent superconducting wire. The electromagnetic force generated by each superconducting wire is canceled (canceled) by canceling out the electromagnetic force in the opposite direction generated by the adjacent superconducting wire.
When the switch unit 11 wound with the superconducting wire is cooled below the superconducting transition point, the electrical resistance becomes almost zero 0, so that it is turned on (connected), and the heat generation of the heater wire 14 causes the superconducting transition point. If it exceeds, an electric resistance is generated, so that it is turned off (disconnected).

The thermal resistance unit 12 will be described with reference to FIG. 6A and 6B are diagrams showing the reel 13 around which the thermal resistance portion 12 is wound. FIG. 6A is a diagram showing the entire reel 13, and FIG. 6B is the axis of the reel 13. It is sectional drawing when cut | disconnecting in the surface which passes.
First, after the superconducting wire is wound around the trunk portion 13A to form the switch portion 11, the pair of superconducting wires wound as the switch portion 11 is stretched over the notch 13F of the partition wall 13C and pulled out to the trunk portion 13B side. .

  The thermal resistance portion 12 is obtained by winding the superconducting wire drawn out toward the body portion 13B on a plurality of layers (for example, 3 layers) with a winding width of about 80 mm around the body portion 13B having an outer diameter of 37 mm. The superconducting wire is configured to be drawn out as a lead wire (leading wire) from a notch (switch opening portion) 13H of the flange 13E. As described above, the thermal resistance portion 12 is continuously wound in a coil shape with the same superconducting wire as the switch portion 12 and is electrically connected in series with the switch portion 11.

The lead wire drawn out from the flange 13E is superconductively connected to a Cu-stabilized NbTi wire (Cu / NbTi wire) immediately after being drawn out, and is electrically connected to the superconducting coil 3.
At this time, the superconducting wire is wound by non-inductive winding in the body portion 13B in the same manner as the switch portion 11, and the electromagnetic force generated by each superconducting wire is the electromagnetic force in the opposite direction generated by the adjacent superconducting wire. Are canceled (cancelled) by canceling each other.

  As described above, the thermal resistance section 12 is provided to suppress heat transmitted from the permanent current switch 10 to the outside. Specifically, the thermal resistance section 12 prevents the heat generated in the heater wire 14 from being transmitted to the outside of the permanent current switch 10 through the lead wire (leading wire) drawn from the permanent current switch 10, that is, permanently. The object is to suppress the amount of heat transmitted to the outside of the current switch 10 to a minimum.

  For this purpose, as shown in FIGS. 2 and 6, the inner diameter (most inner diameter) of the superconducting wire wound around the thermal resistance portion 12 is wound around the switch portion 11. It is preferable that the superconducting wire or the heater wire 14 is larger than the inner diameter (the innermost diameter) closest to the trunk portion 13A. As an example, the superconducting wire wound around the thermal resistance portion 12 has an outer diameter (the outermost diameter along the radial direction of the superconducting wire) of the superconducting wire wound around the switch portion 11 that is farthest from the body 13A. The outer diameter of the layer (innermost layer) closest to the body portion 13B may be substantially the same.

  As a result, the distance from the position where the superconducting wire is pulled out from the trunk portion 13A to the position where the superconducting wire is pulled out from the trunk portion 13B (the position of the notch 13H) can be increased, so the amount of heat transmitted to the outside of the permanent current switch 10 can be reduced. Can be suppressed. In addition, when the notch 13H is formed at a position where the rotation angle of the partition wall 13C with respect to the notch 13F is 180 °, the distance from the position where the superconducting wire is drawn out from the trunk portion 13A to the position of the notch 13H is further increased. Therefore, the amount of heat transmitted to the outside of the permanent current switch 10 can be further suppressed.

By impregnating EPON (registered trademark), which is an epoxy resin, with the winding frame 13 in which the switch unit 11 and the thermal resistance unit 12 are formed as described above, the switching unit 11 and the thermal resistance unit 12 are placed on the winding frame 13. Is fixed, the permanent current switch 10 according to the present embodiment is obtained.
In the permanent current switch 10 according to the present embodiment, the superconducting wire is vibrated by subjecting the superconducting wire wound around the switch portion 11 and the thermal resistance portion 12 to impregnation with an epoxy resin and fixing. Quenching by doing can be suppressed.

  The characteristics of the permanent current switch 10 according to the present embodiment are summarized as follows. When the heater wire 14 generates heat by energization, the superconducting wire of the switch unit 11 undergoes normal conduction transition. However, the heat generated by the heater wire 14 is less transferred by the superconducting wire (CuNi / NbTi wire) of the heat resistance portion 12 having a high thermal resistance, which is transferred to the lead wire outside the permanent current switch 10.

  Next, after the energization of the heater wire 14 is stopped and the switch unit 11 is superconductively transferred, the rated operating current of the superconducting coil 3 is supplied to the switch unit 11 and the thermal resistance unit 12. The internal electromagnetic force almost cancels out due to the non-inductive winding in both of the thermal resistance portions 12. In addition, since both the switch part 11 and the thermal resistance part 12 are fixed by the impregnation treatment, the risk of quenching due to vibration of the superconducting wire is very small.

  Here, returning to FIG. 1, the arrangement of the permanent current switch 10 in the superconducting device 1 will be described. The permanent current switch 10 is supported by physically contacting a plate-like cooling member (for example, a copper member) 7 having a low thermal resistance at a position where the influence of the magnetic field generated by the superconducting coil 3 is small. Are physically connected to the second stage 52 of the refrigerator 5. In this way, the permanent current switch 10 is thermally connected to the second stage 52 of the refrigerator 5, so that it is cooled to around 4.2 K, which is the superconducting transition point of the switch unit 11.

When the superconducting coil 3 is cooled with a liquid refrigerant such as liquid helium in the superconducting device 1, the permanent current switch 11 is disposed so as to be immersed in the liquid refrigerant that cools the superconducting coil 3, and is cooled below the superconducting transition point. It doesn't matter.
The operation of the permanent current switch 10 arranged as described above will be described.
The permanent current switch 10 according to the present embodiment is installed in a 0.5T magnetic field environment in a refrigerator conduction cooling type 1.5T (Tesla) MRI magnet (superconducting coil 3) in the superconducting apparatus 1 as shown in FIG. An operation test was conducted.

First, a current of about 50 mW was applied to the heater wire 14 to generate heat, and the switch unit 11 was transferred to normal conduction. At this time, although the temperature of the switch part 11 rose to about 10K, the temperature of the switch outlet part 13H is around 4.2K, and the heat generation of the heater wire 14 is caused by the switch outlet part 13H.
It was not transmitted to the subsequent lead wires.
Next, the energization of the heater unit 14 was stopped to switch the switch unit 11 to the superconducting state, and the superconducting coil 3 was shifted to the operation in the permanent current mode. At this time, a current of about 400 A was flowing through the switch section 11 and the thermal resistance section 12, but the heater section 14 and the switch section 11 were not quenched, and the permanent current switch 10 operated stably.

Finally, a modification of the permanent current switch 10 according to the present embodiment will be described with reference to FIG. FIG. 7 is a diagram illustrating the entire permanent current switch 20 in which the interlayer insulating material 21 is inserted into the thermal resistance portion 12.
When the superconducting wire is wound on a plurality of layers in the thermal resistance portion 12, it is wound while sandwiching a heat insulating material (interlayer insulating material 21) between the layers (interlayer). Since heat transfer between the layers is suppressed by the interlayer insulating material 21, from the position where the superconducting wire is drawn out from the body portion 13A to the upper layer, that is, from the inner peripheral side to the outer peripheral side of the thermal resistance portion 12. The movement of heat can be suppressed, and the amount of heat transmitted to the outside of the permanent current switch 20 can be suppressed more reliably.

  By the way, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, such as operating conditions and measurement conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that is normally implemented by those skilled in the art. Instead, values that can be easily assumed by those skilled in the art are employed.

  In addition, the method of implement | achieving non-inductive winding in a switch part and a thermal resistance part is not restricted to the above-mentioned method. If the electromagnetic force in the switch part and the thermal resistance part can be eliminated (cancelled), non-inductive winding may be realized using a known method.

DESCRIPTION OF SYMBOLS 1 Superconducting device 2 Storage container 3 Superconducting coil 4 Vacuum container 5 Refrigerator 6,7 Cooling member 10,20 Permanent current switch 11 Switch part 11A Folding part 12 Heat resistance part 13 Winding frame 13A, 13B Trunk part 13C Partition wall 13D, 13E Flange 13F, 13G Notch 13H Notch (Switch outlet)
14 Heater wire 21 Interlayer insulation material

Claims (9)

A winding frame for winding a coil, a heater wire wound in a coil shape on the winding frame, a superconducting wire wound in a coil shape on the winding frame, and the superconducting wire connected to the winding A permanent current switch for interrupting the superconducting circuit, comprising a lead wire drawn out from the frame,
The reel is
A switch unit wound so that the superconducting wire overlaps the heater wire;
By winding only the superconducting wire, a heat resistance portion that suppresses heat transfer from the switch portion to the lead wire, and
A permanent current switch comprising: The switch part is constituted by the superconducting wire wound non-inductively,
2. The permanent current switch according to claim 1, wherein the thermal resistance portion is constituted by the superconducting wire wound in a non-inductive manner. In the reel,
The permanent current switch according to claim 1, wherein a partition wall that thermally partitions the switch portion and the thermal resistance portion is formed.   The superconducting wire wound by the said switch part and the superconducting wire wound by the said thermal resistance part are electrically connected in series, The permanent in any one of Claims 1-3 characterized by the above-mentioned. Current switch.   5. The inner diameter of a superconducting wire wound around the thermal resistance portion is larger than the innermost diameter of a superconducting wire or heater wire wound around the switch portion. Of permanent current switch. The superconducting wire in the switch portion is wound so as to form a plurality of layers in the radial direction of the reel, and the superconducting wire in the thermal resistance portion is at least one layer in the radial direction of the reel. Wound to form,
The outermost diameter along the radial direction of the superconducting wire wound by the switch part is substantially the same as the outer diameter of the innermost layer of the superconducting wire wound by the thermal resistance part. 5. The permanent current switch according to 5.   The permanent current switch according to any one of claims 1 to 6, wherein an impregnation treatment is applied to a superconducting wire wound around the switch section and the thermal resistance section. A permanent current switch according to any one of claims 1 to 7, a superconducting coil around which a superconducting wire is wound, a housing container for housing the superconducting coil, and at least one of the superconducting coil and the housing container is a superconducting point. A refrigerator that cools below the relocation,
The superconducting device, wherein the permanent current switch is thermally connected to the refrigerator in the storage container. The permanent current switch according to any one of claims 1 to 7,
The superconducting device, wherein the permanent current switch is immersed in a liquid refrigerant.

Images