JPH05243043A - Current lead for superconducting apparatus - Google Patents

Abstract

PURPOSE:To enable execution of stable electrification by making it possible to reduce sharply the amount of invasion of heat into a first thermal source for cooling down the body of a superconducting apparatus and also to reduce invasion of heat into an intermediate cooling part at the time of nonelectrification and by preventing a sharp change of the internal pressure of a low-temperature vessel. CONSTITUTION:A body 4 of a superconducting apparatus is kept cooled by a first thermal source 3, an intermediate cooling part 7 is cooled by a second thermal source 8, a high-temperature superconductor 9 is provided between the body 4 of the superconducting apparatus and the intermediate cooling part 7, a part on the high-temperature side from the intermediate cooling part 7 is constructed of a metal member 10, and the high-temperature superconductor 9 and the metal member 10 are constructed removably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current lead for introducing a current into a superconducting device such as a superconducting magnet device or a superconducting power transmitting device.

[0002]

2. Description of the Related Art FIG. 5 shows, for example, JP-A-60-32374.
FIG. 7 is a cross-sectional view showing a conventional current lead for a superconducting device described in Japanese Patent Publication No. This current lead is applied to, for example, a superconducting magnet device as a superconducting device. In the figure, 1 is a vacuum container, 2 is a vacuum container 1, and a first cold heat source, for example, a low temperature container for storing liquid helium 3,
Reference numeral 4 denotes a superconducting magnet which is housed in the cryocontainer 2 and cooled by liquid helium 3. Reference numeral 5 denotes an energization attaching / detaching member which is connected to the superconducting magnet 4 and attached to the outer wall of the cryocontainer 6,
Is a detachable current lead made of copper that is detachably attached to the energizing detachable member 5 in a vacuum, and 7 is an intermediate portion of the detachable current lead 6.
This is an intermediate cooling unit that is cooled to a temperature higher than the liquid helium temperature by a cold heat source such as liquid nitrogen 8.

In the current lead for the superconducting device constructed as described above, the detachable current lead 6 is moved in the direction of arrow A when energized and connected to the energizing detachable member 5. When not energized, the current lead 6 is disconnected in a vacuum as shown in FIG. With this configuration, the amount of heat entering the liquid helium 3 cooling the superconducting magnet 4 can be reduced.

[0004]

In the conventional current lead for a superconducting device as described above, the current lead 6 is disconnected in a vacuum when it is not energized. Therefore, the current lead in the energizing attachment / detachment member 5 and the vacuum container 1 is cut off. Electrical extraction and vacuum resistance are required at the take-out portion, which complicates the structure. Further, since the current is supplied in a vacuum, the volume of the structural member of the current lead 6 is increased in order to prevent the burnout due to the heat generated during the supply of current. Further, the low temperature side of the current lead 6 is cooled at the temperature of the intermediate cooling section when not connected to the energization attaching / detaching member 5, and this temperature is higher than the liquid helium temperature. Therefore, when it is connected to the energization attaching / detaching member 5, heat is rapidly applied to the liquid helium 3 from the current lead 6. However, since liquid helium 3 has a very small latent heat of vaporization of about 20 J / g, it rapidly vaporizes. As a result, the internal pressure of the cryogenic container 2 rises, and there is a risk that the superconducting magnet 4 will be quenched when the superconducting magnet 4 is operating in the permanent current mode. Further, since the high temperature (room temperature) part and the intermediate cooling part 7 are thermally short-circuited by the current lead 6, there is a problem that heat enters the intermediate cooling part 7 even when the power is not supplied.

The present invention has been made to solve the above problems, and can greatly reduce the amount of heat entering a first cold heat source for cooling the body of a superconducting device such as a superconducting magnet, for example, liquid helium, Another object of the present invention is to obtain a current lead for a superconducting device, which can reduce heat intrusion into the intermediate cooling part when not energized, prevent the internal pressure of the cryogenic container from abruptly changing, and can stably energize.

[0006]

According to a first aspect of the present invention, there is provided a superconducting device current lead, the superconducting device main body being cooled and held by a first cold heat source, and an intermediate cooling section being cooled by a second cold heat source. In the current lead for a superconducting device which has a current flowing through the main body of the superconducting device, a high temperature superconductor is provided between the superconducting device body and the intermediate cooling part, and the high temperature side of the intermediate cooling part is made of a metal member, The metal member is detachably configured.

Further, in addition to the invention of claim 1, the current lead for a superconducting device according to the invention of claim 2 is a high temperature superconductor at a low temperature end and a high temperature end of a pair of high temperature superconductors corresponding to a reciprocating current. It is provided with a protective element.

[0008]

In the current lead for the superconducting device constructed as described above, the high temperature superconductor is used to reduce the amount of heat conduction to the first cold heat source and the amount of heat intrusion due to resistance heating. Also, since the high temperature superconductor and the metal member are detachable, the metal member is cut off at the intermediate cooling part of the current lead when not energized.
Since heat intrusion from the room temperature end in the intermediate cooling unit can be reduced and a current lead with a low heat intrusion amount can be realized in the cooling gas, the structure of the superconducting device is simplified. In addition, since the intermediate cooling unit does not attach / detach in the vicinity of the superconducting device main body, the transient heat does not flow into the first cold heat source when the current lead is attached, and the second cold heat source is Liquid nitrogen (77
When K) is used, the temperature is higher than that of liquid helium and the latent heat of vaporization is about 200 J / g, which is about 10 times larger, so there is no sudden vaporization and the effect on the second cold heat source is small.

Even if the high temperature superconductor is quenched, since the high temperature superconductor protection element is connected to the low temperature end, the energy stored in the main body of the superconducting device is absorbed by the protection element. Therefore, the high temperature superconductor does not burn out. Further, since the high-temperature superconductor protection element is also connected to the high-temperature end, even if the high-temperature superconductor is not turned off during quenching, the high-temperature superconductor can be prevented from burning.

[0010]

【Example】

Example 1. 1 and 2 are sectional views showing a current lead for a superconducting device according to an embodiment of the present invention. In the figure, 1 is a vacuum container, 2 is a low temperature container, 4 is a superconducting device main body housed in the low temperature container 2, for example, a superconducting magnet, in a liquid helium 3 having a temperature of 4.2K as a first cold heat source. It is cooled. Reference numeral 7 is an intermediate cooling portion of the current lead for the superconducting device, and 8 is liquid nitrogen having a temperature of 77K which is a second cold heat source, and cools the intermediate cooling portion 7. Reference numeral 9 is a high-temperature superconductor provided in a portion extending from the superconducting magnet 4 to the intermediate cooling section 7, and its high-temperature end 9a is connected to the intermediate cooling section 7. The other low temperature end 9b is further connected to the superconducting device body 4 via a metal member. Reference numeral 10 denotes a metal member connected to the high temperature side (room temperature) portion from the intermediate cooling unit 7,
For example, it is made of a metal rod such as copper or ceramic. Reference numeral 11 denotes an energization attaching / detaching member that detachably holds the high temperature superconductor 9 and the metal member 10, and a portion in contact with the metal member 10 is made of an insulator such as a thin plate of glass epoxy. FIG. 1 is a cross-sectional view showing a state in which the high-temperature superconductor 9 and the metal member 10 are energized in the current lead shown in Example 1, and FIG. 2 is a diagram showing the high-temperature superconductor 9 and the metal member 10 separated when de-energized. It is a sectional view showing the state where it was opened.

In the current lead for a superconducting device constructed as described above, for example, a Bi type high temperature superconducting bulk material is used for the high temperature superconductor 9, and the intermediate cooling section 7 is filled with liquid nitrogen (77).
In K), the high temperature superconductor 9 is cooled to the critical temperature (115 K) or less. Since the thermal conductivity of the Bi-based high-temperature superconductor 9 is stainless steel or less, the amount of heat entering the low-temperature portion 9b can be reduced to about 1/10 or less as compared with the case where only the conventional copper current lead is used.

FIG. 3 shows the results of measuring the amount of heat penetration of a conventional current lead made of, for example, copper and the current lead using the Bi-based superconductor having a length of 30 cm according to the first embodiment. (Cm), and the vertical axis represents the amount of heat penetration (W). In the figure, curve A is the amount of heat penetration of a current lead made of copper that is not cooled by evaporative gas (q = 0), and curve B is cooled by evaporative gas equivalent to 0.5 W (q = 0.5 W).
The amount of heat penetration of a current lead made of copper, curve C shows the amount of heat penetration of a current lead using a Bi-based superconductor that is not cooled by evaporative gas (q = 0), and curve D shows the background.

According to the measurement results of the amount of heat penetration in the gas when each current lead is not energized, the amount of heat penetration is about 0.55 W even when the current lead made of copper is cooled by the evaporative gas. On the other hand, a current lead using a Bi-based superconductor has a cross-sectional area of 5
The amount of heat penetration was about 0.03 W, which was about 1/20 of that of the current lead made of copper, although it was doubled and the gas was not cooled. By using a high temperature superconductor like this,
The amount of heat entering the liquid helium 3, which is the first cold heat source, can be greatly reduced.

Further, when the rated (500 A) current is applied, the current lead using the high temperature superconductor 9 only generates heat at the connecting portion, and the amount of heat penetration hardly increases. However, the current lead made of copper increases about twice even when it is gas cooled. As described above, when the high-temperature superconductor 9 is used as the current lead, the amount of heat entering the first cold heat source 3 can be made extremely small. You don't have to.

However, the high temperature side of the intermediate cooling unit 7 is connected by the metal member 10. For example, in the case of a current lead of 500 A class, the amount of heat penetration into the temperature fixed point is several tens to several hundreds W. Therefore, if the metal member 10 is cut off during non-energization, this amount of heat penetration is almost eliminated. Further, when the metal member 10 is attached at a temperature close to room temperature, the liquid nitrogen 8 has a latent heat of vaporization of about 10 times that of liquid helium, and therefore, no rapid vaporization occurs. Further, since the liquid nitrogen 8 is not directly involved in cooling the superconducting magnet 4, it has almost no effect on the superconducting magnet 4.

The operating current density of the high temperature superconductor is generally determined by the temperature of the intermediate cooling section 7 having a low critical current density Jc.
For example, when a Bi-based superconducting bulk material is used as the high-temperature superconductor and the intermediate cooling part is 77K, Jc is about 200.
A 0A / cm ² or so, in the vicinity of 77K is the specific heat of the structural material is 0.1 J / g · K or more. This is a value that is two or more orders of magnitude higher than that of 4.2K, and it is stable because the temperature does not easily rise and quenching does not occur easily.

As described above, according to the above-described embodiment, the amount of heat entering the first cold heat source for cooling the main body of the superconducting device such as the superconducting magnet 4, for example, liquid helium 3 can be greatly reduced, and at the time of non-energization. It is possible to obtain the current lead for the superconducting device which can reduce the heat intrusion into the intermediate cooling part 7 and prevent the internal pressure of the cryogenic container 2 from changing rapidly and can supply stable current.

Example 2. However, the high temperature superconductor 9 has a low thermal conductivity and is not provided with a metal coating. Therefore, if the high temperature superconductor 9 is quenched during energization for some reason,
Even if a part is quenched and heat is generated, the quench is hard to be transmitted to the entire superconductor. The high-temperature superconductor 9 has a normal conductivity of 0.
Since it is as high as about 1 μΩcm, for example, the superconducting magnet 4
If the high-temperature superconductor 9 is quenched during energization, the energy stored in the superconducting magnet 4 may be added to the resistance generating portion and burned even if the power is turned off.

The current lead for a superconductor device according to the second embodiment of the present invention is made to solve the problems caused by using the high temperature superconductor 9 as described above. Second Embodiment FIG. 4 is a circuit diagram showing a current lead for a superconducting device according to a second embodiment of the present invention. In the figure, 13, 14
Is a pair of high temperature superconductors corresponding to the round trip current, 12a,
Reference numeral 12b is a high-temperature superconductor protection element connected to the high-temperature ends 13a, 14a and the low-temperature ends 13b, 14b of the high-temperature superconductor 13 and the high-temperature superconductor 14, and is, for example, a protection diode.

In the current lead for the superconducting device constructed as described above, the high temperature superconductors 13 and 14 use a bulk material without coating such as metal in order to reduce heat penetration. When the high temperature superconductors 13 and 14 are quenched when the superconducting magnet 4 is energized, high resistance is generated and a voltage is generated to turn on the protection diode 12a. The current flowing through the superconducting magnet 4 hardly flows through the high temperature superconductors 13 and 14, but flows through the protective diode 12a and is gradually attenuated. Therefore, the high-temperature superconductors 13 and 14 do not generate heat and do not burn. Since the protection diode 12b is connected to the high temperature ends 13a and 14a according to the same principle, the high temperature superconductors 13 and 14 can be protected even when the high temperature superconductors 13 and 14 are quenched and the power cannot be turned off.

In this way, even if the high temperature superconductors 13 and 14 are quenched, for example, the diode 12 is used as a protection element.
Since a and 12b are connected, it is possible to prevent the high temperature superconductors 13 and 14 from being burnt out. Further, since the high-temperature superconductor protection diodes 12a and 12b are connected to both ends of the pair of high-temperature superconductors 13 and 14, the amount of heat entering the first cold heat source 3 does not increase.

Further, the above-mentioned high temperature superconductor protection element 12
The a and 12b are not limited to the diodes, and may be resistors having a value smaller than the resistance generated when the high temperature superconductors 13 and 14 are quenched, and have the same effect as above.
When the protection resistor is used as the high temperature superconductor protection element, a resistor having a resistance value lower than that of the high temperature superconductor resistance at the time of quench is connected, and like the diode, the current of the superconducting magnet 4 flows to the protection resistor at the time of quench. It is possible to prevent the high-temperature superconductor from burning.

In the above embodiment, the metal member 10 is made of a metal rod such as copper or ceramic. However, the metal member 10 may be made of a pipe so that gas can be removed from the inside.

[0024]

As described above, according to the first aspect of the invention, the superconducting device main body is cooled and held by the first cold heat source, and the intermediate cooling section is cooled by the second cold heat source. In the current lead for the superconducting device that energizes the superconducting device main body, a high temperature superconductor is provided between the superconducting device main body and the intermediate cooling part, and the high temperature side from the intermediate cooling part is made of a metal member, and the high temperature superconductor and the metal member are attached and detached. With the flexible structure, the amount of heat entering the first cold heat source for cooling the main body of the superconducting device can be greatly reduced, and the current lead for the superconducting device can be obtained which can be stably energized.

According to the invention of claim 2, claim 1
In addition to the invention described above, the high temperature superconductor protection element is provided at each of the low temperature end and the high temperature end of the pair of high temperature superconductors corresponding to the reciprocating current, so that even if the high temperature superconductor is quenched, it is prevented from burning. There is an effect that a current lead for a superconducting device can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state when a current lead for a superconducting device according to a first embodiment of the present invention is energized.

FIG. 2 is a sectional view showing a state in which the current lead for the superconducting device according to the first embodiment of the present invention is not energized.

FIG. 3 is a graph showing the results of measuring the amount of heat penetration of a current lead using the high-temperature superconductor according to Example 1 and a conventional copper current lead.

FIG. 4 is a circuit diagram showing a current lead for a superconducting device according to Embodiment 2 of the present invention.

FIG. 5 is a cross-sectional view showing a conventional current lead for a superconducting device.

[Explanation of symbols]

 3 First Cold Heat Source 4 Superconducting Device Main Body 7 Intermediate Cooling Section 8 Second Cold Heat Source 9 High-Temperature Superconductor 10 Metal Member 11 Detaching Member for Energization 12a High-Temperature Superconductor Protection Element 12b High-Temperature Superconductor Protection Element 13 High-Temperature Superconductor 14 High temperature superconductor

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[Procedure amendment]

[Submission date] April 8, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Example 2. However, the high temperature superconductor 9 has a low thermal conductivity and is not provided with a metal coating. Therefore, if the high temperature superconductor 9 is quenched during energization for some reason,
Even if a part is quenched and heat is generated, the quench is hard to be transmitted to the entire superconductor. The high-temperature superconductor 9 has a normal conductivity of 0.
Since 1 m [Omega] cm approximately as high, for example, superconducting magnet 4
If the high-temperature superconductor 9 is quenched during energization, the energy accumulated in the superconducting magnet 4 may be added to the resistance generating portion and burned even if the power is turned off.

Claims (2)

[Claims] 1. A current lead for a superconducting device, comprising: a superconducting device main body cooled and held by a first cold heat source; and an intermediate cooling section cooled by a second cold heat source, wherein the superconducting device current lead energizes the superconducting device main body. A high-temperature superconductor is provided between the superconducting device main body and the intermediate cooling unit, a high temperature side of the intermediate cooling unit is configured by a metal member, and the high temperature superconductor and the metal member are detachably configured. Current lead for superconducting device. 2. A current lead for a superconducting device according to claim 1, wherein a high temperature superconductor protection element is provided at each of a low temperature end and a high temperature end of a pair of high temperature superconductors corresponding to a reciprocating current. ..