JP2007017109A - Insulated demagnetized refrigerator and insulated demagnetized refrigerator unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow endurance against an acceleration by simple constitution, even when the acceleration is applied, in an insulated demagnetized refrigerator and an insulated demagnetized refrigerator unit for cooling a cooled object to an extremely low temperature, using a superconductive coil and a salt pill. <P>SOLUTION: In this insulated demagnetized refrigerator having the superconductive coils 28A, 28B and applied with the acceleration along an arrow-Z direction, the superconductive coils 28A, 28B are arranged to make the center lines MA2, MB2 of magnetic fields generated by the superconductive coils 28A, 28B orthogonal to the acceleration applied direction (Z direction), i.e. to make those laid laterally with respect to a precooling stage 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an adiabatic demagnetization refrigerator and an adiabatic demagnetization refrigerator unit, and more particularly to an adiabatic demagnetization refrigerator and an adiabatic demagnetization refrigerator unit that cools an object to be cooled to an ultra-low temperature using a superconducting coil and a salt pill.

  In one of the magnetic refrigerators, the entropy representing the degree of irregularity of the system of magnetic moments at a certain temperature is adiabatic based on the principle that when a magnetic field is applied, the magnetic moments are partially aligned and lowered. There is a degaussing refrigerator. This adiabatic demagnetization refrigerator cools an object to be cooled by utilizing the magnetic field dependence of the entropy of a magnetic material that is a thermal work substance (see, for example, Patent Document 1).

  FIG. 1 shows an adiabatic demagnetization cooling unit 1 (hereinafter simply referred to as a cooling unit 1) as an example of the prior art. The cooling unit 1 shown in FIG. 1 includes first and second adiabatic demagnetization refrigerators 2A and 2B (hereinafter simply referred to as refrigerators 2A and 2B), a preliminary cooling stage 3, and first and second heat switches 4A and 4B. , Cold stage 5 and the like. This cooling unit 1 is used, for example, to cool the X-ray detector 6.

  The first and second refrigerators 2A and 2B have first and second salt pills 7A and 7B and first and second superconducting coils 8A and 8B, respectively. Each of the salt pills 7A and 7B stores a working substance made of, for example, a paramagnetic salt. The salt pills 7A and 7B are provided so as to be positioned inside the superconducting coils 8A and 8B, and thus the magnetic field generated by the superconducting coils 8A and 8B is applied.

  The first and second superconducting coils 8 </ b> A and 8 </ b> B have a cylindrical shape and are fixed on the preliminary cooling stage 3 so as to be erected using the supporting members 10 </ b> A and 10 </ b> B. This precooling stage 3 is an auxiliary refrigerator (not shown) such as liquid helium, Gifford McMahon (GM) refrigerator, Stirling refrigerator, etc. for auxiliary cooling of each superconducting coil 8A, 8B and salt pills 7A, 7B. It is connected to the.

  A thermal link 9A is disposed between the preliminary cooling stage 3 and the salt pill 7A. A thermal link 9B is disposed between the salt pill 7A and the salt pill 7B. A second heat switch 4B for turning on / off the thermal state of the salt pill 7A and the salt pill 7B is provided in the middle of the thermal link 9B. Further, the right end portion of the thermal link 9B in the drawing extends upward from the salt pill 7B, and the cold stage 5 is provided at the end portion. The cold stage 5 is provided with the detector 6 described above.

  In this cooling unit 1, first, the preliminary cooling stage 3 is cooled by an auxiliary refrigerator, whereby the first and second heat switches 4A, 4B and the first heat switches 4A, 4B are connected to the first and second heat switches 4A, 4B via the thermal links 9A, 9B and the supporting members 10A, 10B. Then, the second superconducting coils 8A and 8B are cooled to about the liquid helium temperature.

  First, the first superconducting coil 8 </ b> A is excited for a predetermined time, and the first heat switch 4 </ b> A is turned on to discard the magnetization heat to the preliminary cooling stage 3. Next, the heat switch 4A is turned off, the salt pill 7A is thermally isolated, and the first superconducting coil 8A is demagnetized to obtain a cryogenic temperature of about 30 to 50 mK. At this time, the second heat switch 4B is in a thermally closed state, and the excitation of the second superconducting coil 8B is also stopped.

Next, the excitation of the first superconducting coil 8A is stopped, and the second superconducting coil 8B is excited for a predetermined time. Further, the second heat switch 4B is turned on, the salt pill 7A and the salt pill 7B are thermally connected, and the heat of magnetization generated in the salt pill 7B is discarded to the salt pill 7A. Next, the heat switch 4B is turned off, the salt pill 7B is thermally isolated, and the second superconducting coil 8B is demagnetized to obtain a cryogenic temperature of about 10 mK. This cold is transmitted to the detector 6 via the thermal link 9B and the cold stage 5, and the detector 6 is cooled to an extremely low temperature of about 10 mK.
JP 2003-240384 A

By the way, since the cooling unit 1 described above is easy to control the magnetic field, it may be mounted on an artificial satellite for space observation. In this case, a large acceleration is applied at the time of launch. Conventionally, as shown in FIG. 1, the first and second refrigerators 2A and 2B having a generally cylindrical shape as a whole are erected with respect to the preliminary cooling stage 3, that is, the first and second refrigerators. The central axes M _A1 and M _B1 of the magnetic field generated by the machines 2A and 2B are configured to extend in the vertical direction with respect to the preliminary cooling stage 3.

  However, in the conventional configuration, since the first and second refrigerators 2A and 2B are erected on the preliminary cooling stage 3, the center of gravity of each of the refrigerators 2A and 2B is high (separated) from the preliminary cooling stage 3. Therefore, the stability of each refrigerator 2A, 2B was poor. For this reason, when a large acceleration is applied to the cooling unit 1 at the time of launch, the support members 10A and 10B are strengthened so as to withstand the load and the superconducting coils 8A and 8B are firmly fixed, and the salt pills 7A and 7B are fixed. Need to be firmly fixed.

  When the load support is strengthened in this way, the support members 10A, 10B and the like for performing the load support inevitably increase in size, and heat intrusion into the salt pills 7A, 7B and the cold stage 5 from the support members 10A, 10B, etc. The amount will increase. For this reason, there has been a problem that the cooling efficiency is lowered and the detection accuracy by the detector 6 is lowered. In addition, when the salt pills 7A and 7B and the superconducting coils 8A and 8B are improved in performance to compensate for this, there is a problem that the cooling unit 1 is increased in size and the product cost is increased.

  On the other hand, as described above, in the cooling unit 1, the first and second superconducting coils 8A and 8B and the first and second heat switches 4A and 4B perform switching operations at predetermined timings, respectively, thereby efficiently. The detector 6 (cold stage 5) is cooled. However, the conventional cooling unit 1 has a configuration in which the first superconducting coil 8A and the second superconducting coil 8B are arranged in parallel.

  For this reason, when one superconducting coil (for example, the first superconducting coil 8A) generates a magnetic field, the leakage magnetic field from the first superconducting coil 8A is transferred to the other superconducting coil (second superconducting coil 8B). The eddy current due to the change of the magnetic field is generated in the second superconducting coil 8B. When the eddy current is generated in this way, the second superconducting coil 8B generates heat, and this heat is conducted to the salt pill 7B, and is also conducted to the cold stage 5 through the thermal link 9B. There was a problem that would decrease. On the contrary, when the second superconducting coil 8B generates a magnetic field, the first superconducting coil 8A similarly generates heat due to the eddy current, and the cooling efficiency decreases.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an adiabatic demagnetization refrigerator that can withstand a large amount of acceleration applied.

  Another object of the present invention is an adiabatic demagnetizing refrigerator that suppresses the generation of eddy currents caused by magnetic interference with each other even when a plurality of superconducting coils are arranged close to each other and prevents a decrease in cooling efficiency. To provide a unit.

  In order to solve the above-described problems, the present invention is characterized by the following measures.

The invention described in claim 1
In an adiabatic demagnetization refrigerator that has a superconducting coil and acceleration is applied,
The superconducting coil is arranged such that a center line of a magnetic field generated by the superconducting coil is orthogonal to the acceleration application direction.

The invention according to claim 2
In the adiabatic demagnetization refrigerator that is configured such that a plurality of superconducting coils are installed on the stage to be cooled and acceleration is applied,
The superconducting coil is installed horizontally with respect to the cooling stage.

  According to the first and second aspects of the invention, since the superconducting coil is disposed so that the center of gravity is at a low position, stability can be increased even when acceleration is applied, and the superconducting coil is supported. Simplification of the member can be achieved.

The invention according to claim 3
In an adiabatic demagnetization refrigerator unit having a cooling stage for cooling an object to be cooled and a plurality of adiabatic demagnetization refrigerators for cooling the cooling stage,
The superconducting coils are arranged such that the center lines of the magnetic fields generated by the respective superconducting coils provided in the plurality of adiabatic demagnetization refrigerators are not parallel to each other.

  According to the above invention, by arranging the superconducting coils so that the center lines of the magnetic fields generated by the plurality of superconducting coils are not parallel to each other, one of the plurality of superconducting coils generates a magnetic field (hereinafter, Even if the superconducting coil adjacent to this superconducting coil stops the generation of the magnetic field (hereinafter, this superconducting coil is called the stop coil), the magnetic field of the driving coil acts on the stop coil. Thus, eddy currents can be prevented from occurring in the stop coil. Thereby, it can prevent that the heat | fever by an eddy current generate | occur | produces in a stop coil, and can improve cooling efficiency.

The invention according to claim 4
In the adiabatic demagnetization refrigerator unit according to claim 3,
The plurality of adiabatic demagnetization refrigerators are disposed on a stage that cools the superconducting coil, and a center line of a magnetic field generated by the superconducting coil intersects the superconducting coil when the stage is viewed in plan. It is characterized by having comprised so.

  According to the above invention, the configuration is such that the center line of the magnetic field generated by the superconducting coil intersects when the stage is viewed in plan, so that the plurality of heat-insulating demagnetization refrigerators are stacked and the installation area is reduced. Can do.

  As described above, according to the present invention, since the center of gravity of the superconducting coil is at a low position, it is possible to maintain high stability even when acceleration is applied. In addition, it is possible to prevent unnecessary eddy currents from being generated in the superconducting coil, and to prevent a temperature rise due to the eddy currents, thereby improving the cooling efficiency for the superconducting coil.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 2 shows an adiabatic demagnetization cooling unit 20A (hereinafter simply referred to as a cooling unit 20A) using adiabatic demagnetization refrigerators 22A and 22B (hereinafter simply referred to as refrigerators 22A and 22B) according to an embodiment of the present invention. .

  The cooling unit 20A shown in FIG. 1 includes first and second adiabatic demagnetization refrigerators 22A and 22B (hereinafter simply referred to as refrigerators 22A and 22B), a preliminary cooling stage 23, and first and second heat switches 24A and 24B. , A cold stage 25, and the like. The cooling unit 20A is used for cooling the X-ray detector 26, for example. The cooling unit 20A is installed in a space station, for example. For this reason, a large acceleration (25G to 125G) is applied during launch.

  The first and second refrigerators 22A and 22B have first and second salt pills 27A and 27B and first and second superconducting coils 28A and 28B, respectively. Each of the salt pills 27A and 27B stores a working substance made of, for example, a paramagnetic salt. The salt pills 27A and 27B are provided so as to be positioned inside the superconducting coils 28A and 28B, and thus the magnetic field generated by the superconducting coils 28A and 28B is applied.

  The first and second superconducting coils 28 </ b> A and 28 </ b> B have a cylindrical shape and are disposed on the preliminary cooling stage 23. The precooling stage 23 is an auxiliary refrigerator (not shown) such as liquid helium, Gifford McMahon (GM) refrigerator, Stirling refrigerator, etc., for auxiliary cooling of the superconducting coils 28A, 28B and salt pills 27A, 27B. It is connected to the.

  A thermal link 29A is disposed between the precooling stage 23 and the salt pill 27A. A thermal link 29B is disposed between the salt pill 27A and the salt pill 27B. A second heat switch 24B for turning on / off the thermal state of the salt pill 27A and the salt pill 27B is provided in the middle of the thermal link 29B.

  Furthermore, the lower end of the thermal link 29C is thermally connected to the salt pill 27A. The thermal link 29C extends from the salt pill 27A to a position above the refrigerators 22A and 22B, and a cold stage 25 is thermally connected to an upper end portion of the thermal link 29C. The cold stage 25 is provided with a detector 26 that performs various detections in the artificial satellite.

  Here, attention is paid to the fixing structure of the first and second refrigerators 22A and 22B in the present embodiment. As described above, the first and second refrigerators 22 </ b> A and 22 </ b> B are fixed to the preliminary cooling stage 23. In addition, the cooling unit 20A on which the first and second refrigerators 22A and 22B are mounted is arranged such that the preliminary cooling stage 23 is orthogonal to the launch direction when the rocket is launched. Therefore, the acceleration applied to the cooling unit 1 at the time of launch is applied in the downward direction (arrow Z direction) in the figure. Therefore, at the time of launch, a load corresponding to the acceleration at launch and the mass of each component is applied to each component of the cooling unit 20A.

In the present embodiment, the center lines M _A2 and M _B2 (indicated by the alternate long and short dash line in the figure) of the magnetic fields generated by the superconducting coils 28A and 28B are orthogonal to the acceleration application direction (Z direction). Each superconducting coil 28A, 28B is arranged. In other words, this embodiment is characterized in that the superconducting coils 28A and 28B are installed horizontally with respect to the preliminary cooling stage 23. However, the center line M _A2 of the magnetic field of the first superconducting coil 28A, the center line M _B2 of the magnetic field of the second superconducting coil 28B is disposed so as to be parallel to each other.

Thus, the magnetic field center lines M _A2 and M _B2 of the superconducting coils 28A and 28B are orthogonal to the acceleration application direction (Z direction), and the superconducting coils 28A and 28B are connected to the precooling stage 23. By installing horizontally, the position of the center of gravity of each superconducting coil 28A, 28B is compared with the conventional configuration (see FIG. 1) in which the superconducting coils 8A, 8B are erected on the preliminary cooling stage 3. It can be in a low position. Thereby, stability of refrigerator 22A, 22B on the precooling stage 23 can be improved.

  Therefore, even when a large load is applied to the refrigerators 22A and 22B constituting the cooling unit 20A by applying a high acceleration at the time of launching the rocket, the superconducting coils 28A and 28B on the preliminary cooling stage 23 are highly stable. The superconducting coils 28A and 28B can be fixed on the precooling stage 23 with a simple support structure.

  Accordingly, it is possible to prevent heat from entering the salt pills 27A and 27B via the support members that support the superconducting coils 28A and 28B, and to improve the cooling efficiency of the refrigerators 22A and 22B. In addition, since the superconducting coils 28A and 28B can be securely fixed with a simple and downsized support member, the cost of the support member can be reduced and the cost of the cooling unit 20A can be reduced.

Further, in the cooling unit 20A according to the present embodiment, the cold stage 25 is arranged at a position spaced from the magnetic field center lines M _A2 and M _{B2 of the} superconducting coils 28A and 28B. On the magnetic field center lines M _A2 and M _{B2 of the} superconducting coils 28A and 28B, the magnetic field is the strongest part. By providing the cold stage 25 at a position separated from the magnetic field center lines M _A2 and M _B2 , the cold stage 25 It is possible to prevent a magnetic field from being applied to the detector 26 mounted on the. Thereby, it can prevent that the magnetic field of superconducting coil 28A, 28B affects the detector 26, and can improve the detection accuracy by the detector 26. FIG.

  Next, a cooling unit 20B according to an embodiment of the present invention will be described with reference to FIG. In FIG. 3, components corresponding to those shown in FIG.

  The cooling unit 20B according to the present embodiment also includes the first and second refrigerators 22A. The first and second superconducting coils 28 </ b> A and 28 </ b> B constituting 22 </ b> B are configured to be installed horizontally with respect to the preliminary cooling stage 23. Therefore, since the superconducting coils 28A and 28B can be fixed on the precooling stage 23 with a simple support structure, it is possible to prevent the heat intrusion into the salt pills 27A and 27B through the support member, thereby improving the cooling efficiency. In addition, the cost of the support member can be reduced.

Further, as shown in FIG. 3A, the cooling unit 20B according to the present embodiment includes a magnetic field generated by each of the superconducting coils 28A and 28B provided in a plurality of (two in this embodiment) refrigerators 22A and 22B. The superconducting coils 28A and 28B are arranged so that their centerlines M _A3 and M _B3 are not parallel to each other. In the present embodiment, the second refrigerator 22B is disposed above the first refrigerator 22A. Therefore, the first superconducting coil 28A constituting the first refrigerator 22A and the second superconducting coil 28B constituting the second refrigerator 22B are laminated.

  At this time, as shown in FIG. 3B, when the precooling stage 23 is viewed in plan (when the precooling stage 23 is viewed from the Z direction), the MA3 and the second superconductivity generated by the first superconducting coil 28A. MB3 generated by the coil 28B is configured to intersect on the superconducting coils 28A and 28B stacked.

  Next, the operation of the cooling unit 20B configured as described above will be described. First, the first superconducting coil 28 </ b> A is excited for a predetermined time, and the first heat switch 24 </ b> A is turned on to discard the magnetizing heat to the preliminary cooling stage 23. At this time, the second superconducting coil 28B is not excited. Therefore, it is conceivable that the magnetic field generated by the first superconducting coil 28A affects the second superconducting coil 28B.

However, in the cooling unit 20B according to the present embodiment, as described above, the superconducting coils 28A and 28B are arranged so that the center lines M _A3 and M _{B3 of} the magnetic fields generated by the superconducting coils 28A and 28B are not parallel to each other. Has been. For this reason, even if the first superconducting coil 28A generates a magnetic field, the magnetic field of the first superconducting coil 28A is inclined with respect to the second superconducting coil 28B that has stopped generating a magnetic field adjacent thereto. Since it is applied, it is possible to prevent an eddy current from being generated in the second superconducting coil 28B. Thereby, it can prevent that the heat | fever by an eddy current generate | occur | produces in the 2nd superconducting coil 28B, and can improve cooling efficiency.

  Next, the heat switch 24A is turned off to thermally isolate the salt pill 27A and demagnetize the first superconducting coil 28A. Thereby, a very low temperature of about 230 to 2250 mK can be obtained in the salt pill 27A.

  Next, the excitation of the first superconducting coil 28A is stopped, and the second superconducting coil 28B is excited for a predetermined time. Further, the second heat switch 24B is turned on, the salt pill 27A and the salt pill 27B are thermally connected, and the magnetization heat generated in the salt pill 27B is thrown away to the salt pill 27A.

Thus, even when the second superconducting coil 28B is excited and the first superconducting coil 28A is de-energized, the center of the magnetic field generated by each superconducting coil 28A, 28B as described above. Since the lines M _A3 and M _B3 are non-parallel to each other, it is possible to prevent the magnetic field of the excited second superconducting coil 28B from affecting the first superconducting coil 28A. The generation of current can be prevented. Thereby, it is possible to prevent the heat generated by the eddy current from being generated in the first superconducting coil 28A, and the cooling efficiency can be increased.

  Next, the heat switch 24B is turned off, the salt pill 227B is thermally isolated, and the second superconducting coil 28B is demagnetized. Thereby, an extremely low temperature of about 10 mK can be obtained. This cold is transmitted to the detector 26 via the thermal link 29C and the cold stage 225, and the detector 26 is cooled to an extremely low temperature of about 10 mK.

  In the above-described embodiment, the center lines MA3 and MB3 of the magnetic field generated by the superconducting coils 28A and 28B intersect with each other on the refrigerators 22A and 22B stacked when the preliminary cooling stage 23 is viewed in plan. Although miniaturization has been attempted, when miniaturization is not required, it is not always necessary to intersect the magnetic field center lines MA3 and MB3 on the refrigerators 22A and 22B, and the first refrigerator 22A and the second refrigerator There is no need to stack 22B.

FIG. 1 is a diagram for explaining a conventional refrigerator and refrigerator unit. FIG. 2 is a diagram for explaining the refrigerator unit according to the first embodiment of the present invention. FIG. 3 is a diagram for explaining a refrigerator unit according to a second embodiment of the present invention.

Explanation of symbols

20A, 20B Cooling units 22A, 22B First refrigerator 23 Precooling stages 24A, 24B First heat switch 24B Second heat switch 25 Cold stage 26 Detectors 27A, 227B Salt pills 28A, 28B First superconducting coil 29A ~ 29C Thermal Link

Claims (4)

In adiabatic demagnetization refrigerator that has a superconducting coil and acceleration is applied,
An adiabatic demagnetization refrigerator, wherein the superconducting coil is disposed so that a center line of a magnetic field generated by the superconducting coil is orthogonal to an acceleration application direction. In the adiabatic demagnetization refrigerator that is configured such that a plurality of superconducting coils are installed on the stage to be cooled and acceleration is applied,
An adiabatic demagnetizing refrigerator, wherein the superconducting coil is installed horizontally with respect to the cooling stage. In an adiabatic demagnetization refrigerator unit having a cooling stage for cooling an object to be cooled and a plurality of adiabatic demagnetization refrigerators for cooling the cooling stage,
An adiabatic demagnetizing chiller unit, wherein the superconducting coils are arranged such that the center lines of magnetic fields generated by the respective superconducting coils provided in the plurality of adiabatic demagnetizing chillers are not parallel to each other. In the adiabatic demagnetization refrigerator unit according to claim 3,
The plurality of adiabatic demagnetization refrigerators are disposed on a stage that cools the superconducting coil, and a center line of a magnetic field generated by the superconducting coil intersects the superconducting coil when the stage is viewed in plan. A heat-insulating demagnetizing refrigerator unit, characterized in that it is configured.

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