JPH0412037B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a superconducting switch that utilizes the mutual transition between a superconducting state and a normal conducting state, so-called S/N transition, which is produced by controlling the temperature of a superconducting wire, and particularly relates to the structure of its connection portion. It is.

Conventional superconducting switches of this type include those shown in FIGS. 1 to 4. Figure 1,
Figure 2 is a front view and side view showing a partial cross section.
1 is a drum-shaped winding frame made of a heat insulating material such as FRP, and 2 is a base material 3 made of a material with high electrical resistance such as Cypronickel, as shown in the enlarged cross section of FIG. A superconducting wire constructed by embedding a superconducting wire 4 such as Ti, as shown in FIG. It consists of a winding fixed part 2a which is wound and fixed, and a connecting part 2b which is connected to this winding fixed part 2a and is used for connection with an end part 5 of an adjacent device. Reference numeral 6 denotes a heater wire that is electrically insulated from the superconducting wire 2 and wound and fixed on the winding frame 1 in close proximity to the superconducting wire 2, and when turned on and off from an external power source (not shown), the S/S of the superconducting wire 2 is removed. Controls N transition. The winding fixing portion 2a and the heater wire 6 are impregnated and fixed with synthetic resin such as epoxy. Reference numeral 7 denotes a cover made of a heat insulating material such as FRP, which is disposed to cover the outer periphery of the winding fixing part 2a and the heater wire 6, and has a through part 7a for pulling out the connecting part 2b and the end of the heater wire 6. are doing. The winding frame 1, the superconducting wire 2, and the heater wire 6 constitute a superconducting switch 8.

Next, the operation of the conventional superconducting switch constructed as described above will be explained with reference to FIG. FIG. 5 shows an example in which a conventional superconducting switch is applied to a general superconducting circuit. In the figure, 9 is a superconducting coil that is connected in parallel with superconducting switch 8 as an adjacent device and generates a magnetic field due to superconducting current.
The superconducting coil 9 is constructed by winding a so-called copper stabilized superconducting wire consisting of a superconducting wire such as Nb-Ti, and as shown in FIG. electrically connected by means.
10 is a protective resistor inserted in parallel to the superconducting switch 8 and superconducting coil 9; 11 is an excitation power source connected via a circuit breaker 12; The superconducting switch 8, the connecting portion 2b, and the superconducting coil 9 and the end portion 5 are housed in the cryostat chamber 13,
Operates in an atmosphere below the critical temperature. In such a superconducting circuit, first the superconducting switch 8 is opened. That is, when the heater wire 6 is energized from an external power source to raise the temperature of the superconducting wire 2 above the critical temperature and become normal conductive, both the base material 3 made of Cypronickel and the superconducting wire 4 made of Nb-Ti become superconducting. Since it exhibits a very high resistance value compared to the coil 9, the superconducting switch 8 assumes a substantially open state. Here, when the circuit breaker 12 is turned on and the excitation power source 11 is applied, a predetermined current flows through the superconducting coil 9. Next, the superconducting switch 8 is closed.

That is, when the power supply to the heater wire 6 is cut off, the temperature of the superconducting wire 2 is lowered below the critical temperature, the superconducting wire 2 is brought into a superconducting state again, the resistance value of the superconducting switch 8 is set to zero, and the current of the excitation power source 11 is decreased, and the superconducting coil 9 The current flows to the superconducting switch 8 side. After the current from the excitation power source 11 drops to zero, the circuit breaker 1
By opening 2, the superconducting coil 9 and the superconducting switch 8 constitute a so-called persistent current circuit, and the superconducting coil 9 can be operated with a persistent current.

Now, in a persistent current circuit, all of its components are operated in an atmosphere below the critical temperature, so ideally the resistance loss of the circuit is zero, and once a persistent current circuit state is established, the current will continue forever. There should be no attenuation. However, in reality, the connection between the connecting portion 2b and the end portion 5 is extremely difficult due to the structure of the superconducting wires, so as shown in Figure 4, the base material of each superconducting wire is Since the connection is made through the connection resistor, the current in the persistent current circuit gradually attenuates.

Now, the self-inductance of the persistent current circuit is L,
Assuming that the connection resistance is R, the current I in the persistent current circuit at time t is expressed by the following equation.

I=Ioe ^{-R/L tHere} , Io indicates the current value at time t=0. Therefore, if the self-inductance L is constant, the larger the connection resistance R, the faster the current will attenuate. This impairs the advantage of superconducting circuits, which is persistent current operation.
CT (Nuclear Magnetic Resonance Computer)
This becomes a serious problem in cases where magnetic field stability is strictly required, such as in cases where magnetic field stability is strictly required. In the case of a superconducting switch, as mentioned above, it is necessary to ensure the resistance value in the open state is above a certain value, and the specific resistance of the base material 3 is a metal material (10〓) with a sufficiently high electrical resistance such as Cypronickel. 1.4 × 10 ^-7 Ωm, copper is approximately 1.0 × 10 ^-10 Ωm), so in order to keep the connection resistance R below the allowable value, extremely requires longer dimensions.

However, in the conventional superconducting switch as described above, the superconducting switch 8 and the superconducting coil 9
All connections to the cryostat are made at the connection part 2b, and as a result, the length of the connection part 2b becomes very long, which increases the space for the connection and makes it difficult to store and fix it inside the cryostat. Part 2b
Compared to the winding fixing part 2a impregnated and fixed with synthetic resin such as epoxy, the mechanical strength is lower and the electrical resistance of the base material 3 is higher, so the stability of the superconductor is inferior, so the movement of the wire etc. The disadvantage is that the superconductor is easily destroyed by external disturbances, and the method of fixing the connecting portion 2b to prevent this is complicated.

This invention was made in order to eliminate such drawbacks of the conventional superconducting switch, and one end of the base material is attached to the superconducting wire at the winding fixing part. By using the other end of the new electrically connected superconducting wire as the connection part with adjacent equipment,
It is an object of the present invention to provide a superconducting switch in which the dimensions of the connection part are short and compact, so that it can be easily stored and fixed in a cryostat, and the method of fixing the connection part is simple.

Embodiments of the present invention will be described below with reference to the drawings.

6 to 10 show a superconducting switch according to an embodiment of the present invention, and the winding frame 1, heater wire 6, cover 7, through hole 7a, and end portion 5 of adjacent equipment are the same as in the conventional case. The explanation will be omitted. Figures 6 and 7 are front and side views showing a partial cross section, and 14 is an enlarged view of the cross section shown in Figure 8. The first superconducting wire is constructed by embedding the first superconducting wire 16 such as Nb-Ti inside the base material 15 of the It consists of a winding fixing part 14a that is wound and fixed to the winding frame 1 with an insulating material (not shown) interposed therebetween, and an extension part 14b that continues to this winding fixing part 14a. 17, as shown in the enlarged cross section of FIG.
The second superconducting wire is constructed by embedding a second superconducting strand 19, and as shown in FIG.
In addition, the connecting part 17b used for connecting with the end part 5 of the adjacent device on the other end side is attached to the extension part 14b by means such as soldering, and the first superconducting wire 1
It is electrically connected so that the connection resistance with 4 is less than or equal to a predetermined value.

The winding fixing portion 14a and the coupling portion 17a are impregnated and fixed together with the heater wire 6 with a synthetic resin such as epoxy. Then, the winding frame 1, both superconducting wires 14, 17
and the heater wire 6 constitute a superconducting switch 20.

The superconducting switch in one embodiment of the present invention constructed in this manner is housed in a cryostat together with adjacent equipment and operated in an atmosphere below the critical temperature, as in the conventional case. In this case, since the second superconducting wire 17 having the second base material 18 made of copper or the like and having a very low electrical resistance is used for the connecting portion 17b, the dimensions of the connecting portion 17b can be made very short and compact. This makes it easy to store and fix in the cryostat, and since the bonded portion of both superconducting wires 14 and 17 is wrapped and impregnated with synthetic resin such as epoxy, it is mechanically strong. Therefore, a stable superconducting state is ensured, and the connecting portion 17b can be fixed by a simple method.

FIG. 11 is an explanatory diagram showing a part of both superconducting wires 14 and 17 of a superconducting switch according to another embodiment of the present invention. Since it is wound and impregnated with synthetic resin and fixed, it has the advantage of ensuring a more stable superconducting state.

In each of the above embodiments, the winding fixing part 14a and the coupling part 17a are impregnated and fixed with a synthetic resin such as epoxy together with the heater wire 6, but other means such as mechanical tightening using a tightening band or the like may be used. The same effect can be obtained even if an attachment means or the like is adopted.

As explained above, the present invention includes a first superconducting wire wound and fixed on a winding frame composed of a first base material and a first superconducting strand, and a first superconducting wire having an electric resistance of the first base material. and a second superconducting wire, which is composed of a smaller second base material and a second superconducting wire, and one end of which is attached to and electrically connected to the first superconducting wire at the winding fixing part. As a result, the dimensions of the connection part with adjacent equipment are short and compact, making it easy to store and fix inside the cryostat, and the connection of both superconducting wires is performed at the mechanically strong winding fixing part. This has the advantage that the connection portion can be fixed in a simple manner.

[Brief explanation of drawings]

Figure 1 is a partially sectional front view of a conventional superconducting switch, Figure 2 is a side view thereof, Figure 3 is an enlarged cross-sectional view of the superconducting wire used in the superconducting switch in Figure 1, and Figure 4 is Fig. 1 is an explanatory diagram showing a part of the superconducting wire of the superconducting switch developed, Fig. 5 is a superconducting circuit diagram to which a conventional superconducting switch is applied, and Fig. 6 is an illustration of a superconducting switch according to an embodiment of the present invention. 7 is a side view thereof, and FIGS. 8 and 9 are enlarged cross-sectional views of the first superconducting wire and the second superconducting wire used in the superconducting switch in FIG. 6, respectively; FIG. 10 is an explanatory diagram showing a partially expanded view of both superconducting wires of the superconducting switch in FIG. FIG. In the figure,
1 is a winding frame, 6 is a heater wire, 14 is a first superconducting wire, 14a is a winding fixing part, 15 is a first base material, 1
6 is a first superconducting wire, 17 is a second superconducting wire,
Reference numeral 17a designates a joint portion as one end of the second superconducting wire, 18 a second base material, 19 a second superconducting strand, and 20 a superconducting switch. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A first superconducting wire composed of a first base material and a first superconducting wire embedded inside the first base material and wound and fixed on a winding frame; a heater wire that is electrically insulated from the first superconducting wire and arranged close to the first superconducting wire; a second base material having an electrical resistance smaller than that of the first base material; and the second base material. and a second superconducting wire buried inside, the second superconducting wire having one end attached to and electrically connected to the first superconducting wire at the winding fixing part. A superconducting switch. 2. The superconducting switch according to claim 1, wherein the first superconducting wire is extended from the winding fixing portion, and this extended portion is attached to and electrically connected to the second superconducting wire. 3. The superconducting switch according to claim 1 or 2, wherein the first superconducting strand is a Nb-Ti wire. 4. The superconducting switch according to claim 3, wherein the second superconducting strand is a Nb-Ti wire. 5. The superconducting switch according to claim 4, wherein the first base material is Capronnickel. 6. The superconducting switch according to claim 5, wherein the second base material is copper. 7. The superconducting switch according to any one of claims 1 to 6, wherein the winding fixing portion is impregnated and fixed with a synthetic resin such as epoxy.