JPH0121564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to provide a forced cooling type superconducting wire with excellent thermal conductivity.

A conventional forced cooling type superconducting wire, as shown in FIG. Either supercritical helium is forcibly circulated in the gap 5, or as shown in FIG. 2, a plurality of superconductors 2 are built into the stabilizing metal 3, a conduction pipe 6 is provided in the center, and liquid helium is introduced into the pipe. At least it is cooled down.

If a normal conductive part is locally generated in a conductor, the problem is how to cool it and return it to a superconducting state. Methods for this include compounding large amounts of stabilizing metals, increasing the surface area of the conductor, or interposing an extremely thin thermal barrier material between the conductor and the refrigerant.

However, when using these methods, if heat generation occurs inside the conductor that cannot be predicted from the design stage, the refrigerant boils suddenly and the large current from the superconductor cannot be diverted to the normal conductor, causing damage to the entire superconductor or conductor. This could lead to a major accident in which the gas melts down.

The present invention has been made as a result of extensive research aimed at improving these drawbacks, and has resulted in the discovery of a superconducting wire made of a superconductor that improves the thermal conductivity between a forced cooling superconductor and a refrigerant and does not melt under any conditions. . That is, the present invention provides a forced cooling type superconducting wire in which a superconductor is embedded in oxide powder and at least one refrigerant communication pipe is provided.

The superconductor of the present invention will be explained with reference to the drawings. As shown in FIG. 3, a superconductor 2 has a plurality of wires 1 embedded in a stabilizing metal 3, which are housed in a pressure tube 4 such as a stainless steel tube, and further inside the pressure tube there is a fine wire that serves as a passage for a refrigerant 8. A porous conduction pipe 9 is provided and oxide powder 7 is filled.

The superconductor may be an alloy superconductor such as a NbTi alloy or a compound superconductor such as Nb ₃ Sn, V ₃ Ga.

Further, the stabilizing metal preferably has high conductivity, preferably Cu, Al, Ag, etc., and may be composited with an alloy material such as bronze or Cypronickel if necessary.

Note that in the present invention, it is not necessarily necessary to provide a large amount of stabilizing metal.

Further, the pressure pipe must be able to withstand the electromagnetic force in the magnet winding, withstand the refrigerant pressure (10 to 20 kg/cm ² ), and have excellent corrosion resistance against water and the atmosphere.

In addition, there are no restrictions on the material used for the conduction tube other than non-magnetic material, but there are many fine holes on the circumference.
It is designed to allow the refrigerant to seep out. This conduction tube normally conducts in the longitudinal direction of the superconducting wire, but it may conduct in the radial direction. Furthermore, the position does not need to be provided in the center of the conductor, and there is no limit to the number of conductors as long as there is one or more.

The oxide may be any of Al ₂ O ₃ , BeO, CuO, etc., and the thermal conductivity of the oxide depends on the density, temperature range,
Depending on impurity content, close connection with heat source, etc.
It changes by about 10 to 100 times.

Next, examples of the present invention will be described. 100,000 on the outside of oxygen-free copper through Nb Valise in the center
We obtained a 1.69mmφ composite wire made of bronze matrix with a built-in Nb core. This wire 57
Book and +100 mesh Al ₂ O ₃ powder and BeO powder 1:
1 mixed powder was housed in a SUS tube with a wall thickness of 0.8 mm and an outer diameter of 10 x 25 mm. In addition, in the center of the tube, there is a
Inner diameter 3mmφ with many micro holes equivalent to 150 mesh,
An annealed copper communication tube with an outer diameter of 3.5 mmφ was inserted.

After that, 700℃×100Hr in argon atmosphere.
The superconducting wire of the present invention was obtained by heating to form Nb ₃ Sn at the interface between Nb and bronze.

In addition, for comparison with the present invention, a comparative superconducting wire was obtained in the same manner except that no oxide powder was used.

For these superconducting wires, 1.8K supercritical helium was circulated as a pancake coil of 800 mmφ, and the critical current value was measured in an external magnetic field of 12 T.

In the present invention, the first energization is 35000A,
Even after the second test, it was possible to conduct electricity stably within the range of 35,000±100A. It was also an extremely stable conductor against fluctuations in the magnetic field.

On the other hand, in the comparative example, at the first energization
Although it was possible to energize up to 21,050A, the helium pressure showed an abnormality during the transition to the normal conduction state, and on the second energization, the temperature rose significantly above 5,000A, making it impossible to energize. Even after the third attempt, it was not possible to pass current of more than 5000A.

As detailed above, the present invention has the following effects.

(1) Efficiently transfer the heat generated during the transition from the superconducting state to the normal conducting state to the refrigerant.

(2) Since the amount of stabilizing metal around the superconducting wire can be reduced, the current density of the conductor can be increased.

(3) Electrical insulation between wires is improved.

(4) It is possible to prevent the joining and fusing of wires during high-temperature heating, and the cable becomes flexible.

(5) By making the oxide particles finer and using the physical properties of supercritical helium, it is possible to sufficiently infiltrate helium into the gaps between the particles.

[Brief explanation of drawings]

1 and 2 are schematic explanatory diagrams showing an example of a conventional superconducting wire, and FIG. 3 is a schematic explanatory diagram showing an example of the superconducting wire of the present invention. DESCRIPTION OF SYMBOLS 1...Element wire, 2...Superconductor, 3...Stabilizing metal, 4...Pressure tube, 5...Gap, 6...Conducting tube, 7...Oxide powder, 8...Refrigerant, 9 ...Microporous conduction tube.

Claims (1)

[Scope of Claims] 1. A forced cooling type superconducting wire, characterized in that a plurality of superconductors are embedded in oxide powder and at least one refrigerant communication pipe having a refrigerant seepage hole is provided. . 2. The superconducting wire according to claim 1, wherein the superconductor is embedded in oxide powder via a highly conductive metal. 3. The superconducting wire according to claim 1, wherein the oxide powder is made of aluminum oxide or beryllium oxide.