JPS6260830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal persistent current switch in a superconducting device.

A general schematic diagram of a superconducting device is shown in FIG. As is clear from FIG. 1, the superconducting device houses a thermal persistent current switch body 7 consisting of a superconducting coil 3, a superconducting wire 8, and a heating wire 10 in a container 2 containing a refrigerant 1 such as liquid helium. The coil 3 is connected to an external power source 6 via superconducting lead wires 4 and 54 and a copper lead wire 5, while the superconducting wire 8 in the persistent current switch body 7 is connected to the superconducting lead wire 4 via superconducting lead wires 9 and 59. , 54, and the heating wire 10 is connected to the heater power source 12 via the lead wire 11.

In this configuration, when a voltage is applied from the switch power source 12 to the heating wire 10 in the thermal persistent current switch 7 to generate heat, the superconducting wire 8 is heated to a critical temperature or higher and becomes a normal conductive state, that is, When the superconducting coil 3 undergoes a normal conduction transition and a voltage is applied from the external power source 6 at this time, the resistance of the superconducting coil 3 is 0, so a current flows through the superconducting coil 3. After generating a desired magnetic field in the superconducting coil 3 through such operations, when the current in the heating wire 10 in the thermal persistent current switch body 7 is briefly cut off, the superconducting coil 3 and the lead wire 5
4. A closed circuit formed by the lead wire 59, the superconducting wire 8, the lead wire 9, the lead wire 4, and the superconducting coil 3 is created, and even if the external power supply 6 is temporarily cut off, a current flows in the superconducting coil 3 and remains permanently. Form a magnet and sustain it.

As mentioned above, the thermal persistent current switch transitions the superconducting wire 8 from a superconducting state to a normal conducting state or from a normal conducting state to a superconducting state by intermittent current flowing through the heating wire 10, and causes a large change in electrical resistance during this time. This is used to open and close persistent current circuits.

As shown in Fig. 2, the thermal persistent current switch described above includes a superconducting wire 8 in which the copper part of a copper matrix Nb-Ti-Zr alloy fine multi-wire is partially removed.
A gate wire 13 made of an insulated nichrome heating wire 10 wound spirally is non-inductively wound around a bobbin 14 made of synthetic resin, and the whole is fixed with synthetic resin 15.

Now, in general, the performance of a thermal persistent current switch is as follows.
The shorter the time from when the switch power source 12 is turned on until the superconducting wire 8 is turned off, that is, the heating time, the better, and the shorter the time from when the switch power source 12 is turned off until the superconducting wire 8 is turned on, that is, the cooling time is shorter. Moderately good. In this case, in order to improve the former property, it is conventional to improve the contact between the superconducting wire 8 and the heating wire 10, or to thicken the synthetic resin layer so that the liquid
There are methods such as reducing heat conduction to the He refrigerant, but such measures have the problem of worsening the latter's characteristics. On the other hand, if heat conduction is improved by providing a refrigerant passage or adding metal powder to the synthetic resin layer, the cooling time will be shortened and the latter properties will improve, but the former properties will deteriorate.

As described above, in the conventional thermal persistent current switch, improving one of the heating and cooling characteristics results in deterioration of the other, and it has been extremely difficult to obtain a switch that is excellent in both characteristics.

The present invention has been made in view of the above-mentioned points, and its object is to provide a thermal persistent current switch which has good heating characteristics and cooling characteristics and is excellent in quick response.

The present invention provides good thermal conductivity in which at least a part of the gate wire is in contact with a refrigerant in order to cool a gate wire that is inserted into a synthetic resin layer and is made up of a superconducting wire and a means for heating the superconducting wire to cause a normal conduction transition. The desired purpose is achieved by providing a body and a means for heating the good heat conductor to temporarily block its cooling effect.

That is, the heating properties can be improved by heating a good thermal conductor and blocking its cooling effect, while the cooling properties can be improved by bringing the good thermal conductor into contact with a refrigerant. be.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments. Incidentally, the same reference numerals are used for the same parts as in the past.

FIG. 3 shows an embodiment of the present invention. The thermal persistent current switch of this embodiment shown in the figure has bobbin 1.
4. The gate wire 13 and other parts are the same as those used in the conventional switch, but an aluminum plate 17 with a thickness of about 1 mm with a nichrome wire 16 embedded in it is placed inside the bobbin. Aluminum plate 1
7, and the whole is fixed with a synthetic resin 15.
The outer periphery of the thermal persistent current switch 7 is constructed to protrude from the synthetic resin 15 on the outer periphery of the main body of the thermal persistent current switch.

FIG. 4 shows a circuit configuration diagram of a circuit applied to the thermal persistent current switch shown in FIG. Good conductive metal plate,
That is, it is a switch that turns on and off the nichrome wire 16 inside the aluminum plate 17.

In this configuration, when it is desired to turn the superconducting wire 8 constituting the gate line from on to off, switches 18 and 19 are turned on at the same time. Then, the gate wire 13 is turned off due to the heat generated by the nichrome heating wire 10, but at the same time, the metal plate 17 is heated by the nichrome wire 16, so the time until the gate wire 13 is turned off is shorter than when the nichrome wire 16 is not used. can do. Once the gate line is turned off, the gate line 13 remains off even if the switch 19 is turned off.

Next, if the gate line 13 is to be turned on from off, it is sufficient to turn off the switch 18. In this case, the switch 19 is already off and the aluminum plate 17, which is a conductive metal, is in contact with liquid helium, so the time it takes for the gate line to turn on is shortened compared to the conventional one. I can do it.

Now, the conventional thermal persistent current switch shown in Fig. 2 and the thermal persistent current switch according to this embodiment were immersed in liquid helium and the switch response was measured. Fig. 5 shows the response speed of both. FIG. By the way, the fifth
In the figure, A is the characteristic of the thermal permanent switch of this example.
B corresponds to the characteristics of a conventional thermal persistent current switch.

As is clear from Fig. 5, switches 18, 1
The time from the time 9 are both turned on to start energizing the heating wire 10 until resistance is generated in the superconducting wire 8, that is, the heating time, is longer in the thermal permanent current switch of this embodiment than in the conventional thermal permanent current switch. Approximately 2 for current switch
It was less than one-fold.

In addition, the heating wire 10 is turned off, that is, the switch 18
Compared to conventional thermal persistent current switches, the thermal persistent current switch of this embodiment has a shorter time from turning off the current to the heating wire 10 until the gate wire 13 becomes superconducting, that is, the cooling time. The thermal persistent current switch of this embodiment has much better responsiveness than the conventional one.

As explained in the above embodiments, the thermal persistent current switch according to the present invention is a composite of a thermal persistent current switch using a non-magnetic conductive metal plate, such as an aluminum plate, in which a heating wire, such as a nichrome wire, is embedded. Since it has a resin layer, the heating wire heats the metal plate, shortening the heating time of the gate wire, and the conductive metal plate comes into contact with liquid helium outside the switch. As a result, the heat conduction of the switch as a whole is improved and the cooling time of the gate wire can be shortened, making it possible to obtain a thermal persistent current switch with excellent heating and cooling characteristics and excellent quick response. be.

In the above example, the heating wire is a nichrome wire, the superconducting wire is a Nb-Ti-Zr fine multi-wire,
Although aluminum is used as an example of a highly conductive metal plate, these materials are not limited to this, and manganin wire and Nb-
Similar effects can be obtained by using a Ti alloy wire, a Nb ₃ Sn compound wire, or the like. Further, various shapes and heating methods of the highly thermally conductive metal plate can be considered, and this does not impede the implementation of the present invention.

According to the thermal persistent current switch of the present invention described below, at least one of A good thermal conductor is provided, a part of which is in contact with the refrigerant, and a means is provided to heat the good thermal conductor and temporarily prevent its cooling effect.
Heating properties can be improved by heating a good heat conductor and blocking its cooling effect, while cooling properties can be improved by bringing a good heat conductor into contact with a refrigerant. ,
It is possible to obtain a thermal persistent current switch with excellent quick response and good heating and cooling characteristics.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a general superconducting device, FIG. 2 is a sectional view of a conventional thermal persistent current switch, and FIG. 3 is a sectional view of a thermal persistent current switch according to an embodiment of the present invention. Fig. 4 is a circuit configuration diagram of a circuit applied to the thermal persistent current switch shown in Fig. 3, and Fig. 5 is a response characteristic diagram of the thermal persistent current switch shown in Figs. 2 and 3. . 3...Superconducting coil, 8...Superconducting wire, 10...
...Heating wire, 13...Gate wire, 14...Bobbin,
15...Synthetic resin, 16...Nichrome wire, 17...
...aluminum plate.

Claims (1)

[Scope of Claims] 1. A gate line consisting of a superconducting wire, a means for heating the superconducting wire to cause a normal conduction transition, a bobbin around which the gate wire is non-inductively wound, and a bobbin having the gate wire wrapped around the bobbin. In a thermal persistent current switch formed by providing a switch body made of a synthetic resin layer for fixing a wire in a refrigerant, the switch is inserted into the synthetic resin layer,
and providing a good thermal conductor at least a part of which is in contact with the refrigerant in order to cool the gate line,
A thermal persistent current switch characterized by having means for heating the good thermal conductor and temporarily blocking its cooling effect. 2. The gate wire is composed of a superconducting wire and a heating wire wound around the superconducting wire, and is a metal plate in which a heating wire is embedded in a good thermal conductor that is inserted into a synthetic resin layer and at least a portion of which is in contact with the refrigerant. A thermal persistent current switch according to claim 1, characterized in that: