JPH08248001A - Apparatus for measuring physical properties under magnetic field - Google Patents

Abstract

PURPOSE: To obtain a small-sized apparatus for measuring physical properties under magnetic field in which installation and running cost is reduced while facilitating replacement of sample. CONSTITUTION: In the apparatus for measuring physical properties under field wherein a sample holder 14 is disposed under the field generated from a superconducting magnet 13, the superconducting magnet 13 and the sample holder 14 are thermally coupled, respectively, with first and second stages 17, 18 of a two-stage refrigerator 16. Since only one refrigerator 16 is required, the size can be reduced along with the installation and running cost while facilitating the replacement of sample. Furthermore, the sample can be replaced quickly when the space for disposing the sample holder 14 is sealed hermetically with respect to the space for disposing the superconducting magnet 13 and a vacuum container 11 and the sample holder 14 can be opened directly to the outside of the vacuum container 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring physical properties under a magnetic field which is small in size, inexpensive in equipment cost and running cost, and easy in sample exchange.

[0002]

2. Description of the Related Art An apparatus for measuring physical properties under low magnetic field for measuring low temperature physical properties of a sample using magnetic field and temperature as parameters is
A device as shown in FIG. 6 (a) is commercially available. This device is configured by inserting a sample accommodating portion of a cryostat 63 for controlling a sample cooling temperature into a room temperature bore 62 of a cryostat 61 for cooling a superconducting magnet for applying a magnetic field. The cryostat for cooling the superconducting magnet
Reference numeral 61 is a liquid helium immersion type cryostat, in which the superconducting magnet 13 is housed in a liquid helium storage container 50, and the liquid helium storage container 50 is designed to prevent external heat from entering.
It is surrounded by a heavy heat radiation shield 65. The heat radiation shield 65 is cooled by the refrigerator 16. Further, these are placed in a vacuum container 11 and vacuum-insulated. On the other hand, the sample cooling temperature control cryostat 63 is cooled by a refrigerator 66, and the sample 19 is surrounded by a heat shield plate (not shown) and a vacuum container 11.

Since the above-mentioned apparatus is large because it is composed of two cryostats 61 and 63 having a vacuum container, the room temperature bore 62 of the cryostat 61 for cooling the superconducting magnet should be vacuum-sealed to contain the sample therein. Has proposed a compact device that does not require the cryostat 63 for controlling the sample cooling temperature (Japanese Patent Laid-Open No. 5-291631). However, the trouble of handling a refrigerant such as liquid helium remains in this device. On the other hand, a conduction cooling type superconducting magnet device has been proposed in which the superconducting magnet is cooled by a refrigerator (Japanese Patent Laid-Open No. 6-132567).
issue). This apparatus uses a two-stage refrigerator 16 having two stages as shown in FIG.
The structure is such that the oxide (high temperature) superconducting current lead 26 is cooled in the stage 17, and the superconducting magnet 13 is cooled in the second stage 18. In this apparatus, the sample is cooled by another cryostat (not shown) and is housed in the space A on the center side of the superconducting magnet 13. This device does not require handling of a refrigerant such as liquid helium.

[0004]

However, the device shown in FIG. 6B has the following problems. Two cryostats, one for controlling the sample cooling temperature and one for cooling the superconducting magnet, are required, which increases the size of the entire apparatus. Since the cryostat for controlling the sample cooling temperature is pulled out from the cryostat for cooling the superconducting magnet at the time of exchanging the sample, labor is required for exchanging the sample. Equipment cost and running cost are high because two refrigerators are used. An object of the present invention is to provide a device for measuring physical properties under a magnetic field, which is small in size, has low equipment cost and running cost, and can easily exchange samples.

[0005]

SUMMARY OF THE INVENTION The present invention is a magnetic field physical property measuring apparatus in which a sample holder is arranged under a magnetic field generated by a superconducting magnet, and has a first stage and a second stage.
A superconducting magnet is thermally connected to a first stage of a multistage refrigerator, and a sample holder is thermally connected to a second stage of the multistage refrigerator.

In the present invention, the superconducting magnet contains Y ₁ Ba.
₂ Cu ₃ O _x , Bi ₂ St ₂ Ca ₂ Cu ₃ O _x , Bi ₂
St ₂ Ca ₁ Cu ₂ O _x , Tl ₂ Ba ₂ Cu ₂ Ca ₃ O
Any oxide superconductor such as _x , a metal-based or compound-based superconductor, or the like is applied. The refrigerator has a GM
(Gifford McMahon) Any refrigerator such as a refrigerator is used. When using a GM refrigerator, 35 in the first stage
K, it can be cooled to about 4K in the second stage.

In the apparatus of claim 2, a magnet bobbin is attached to the first stage of the multi-stage refrigerator, a superconducting magnet is attached to the magnet bobbin, and the magnet bobbin and the superconducting magnet are surrounded by a vacuum container. A sample holder arrangement space in which the second stage of the multistage refrigerator is arranged is provided inside the space in which the magnet bobbin and the superconducting magnet are arranged, and the sample holder arrangement space is the superconducting material in the vacuum container. The physical property measuring device under a magnetic field is characterized in that it is airtightly partitioned from a space in which a magnet is arranged and can be opened to the outside.

[0008]

According to the first aspect of the invention, in the physical property measuring apparatus under the magnetic field in which the sample holder is arranged under the magnetic field generated by the superconducting magnet, the superconducting magnet is provided in the first stage of the two-stage refrigerator, and the second stage is used.
Each sample holder is thermally connected to the stage. Therefore, the superconducting magnet and the sample can be cooled by one refrigerator, the device is small, the workability is good, and the equipment cost and the running cost are both low. According to the invention of claim 2, in the apparatus for measuring physical properties under magnetic field of the invention of claim 1, since the sample holder arrangement space is formed as described above, the temperature of the superconducting magnet is returned to room temperature or the vacuum of the vacuum container is reduced. The sample holder placement space can be opened outward without breaking. Therefore, sample exchange can be performed quickly.

[0009]

The present invention will be described below in detail with reference to examples. (Embodiment 1) FIG. 1 shows the first embodiment of the apparatus for measuring physical properties under a magnetic field of the present invention.
It is a side explanatory view showing an example of. A magnet bobbin 12 is arranged in a vacuum container 11, a superconducting magnet 13 is arranged on an inner side surface of the magnet bobbin 12, and a sample holder 14 is arranged in a space surrounded by these. Since the magnet bobbin 12 is inside the vacuum container 11 and its surroundings are in a high vacuum, the invasion of heat from the outside is suppressed. The sample holder 14 is surrounded by an inner heat radiation shield 15 to block radiant heat from the magnet bobbin 12 side. The sample holder 14 is attached with its heat transfer plate connected to the opening of the inner heat radiation shield 15.

A two-stage refrigerator 16 is provided below the vacuum container 11.
The first stage 17 of the refrigerator 16 is inserted from the bottom surface of the vacuum container 11 into the vacuum container 11, and the bottom surface of the magnet bobbin 12 is connected to the top of the first stage 17. Further, the inner heat radiation shield 15 is connected to the top of the second stage 18 protruding from the first stage. The inner heat radiation shield 15 cools the sample holder 14 and at the same time blocks the radiation heat from the magnet coil 12. The radiant heat shielding effect is enhanced as the inner heat radiation shield 15 is cooled to a lower temperature.

The upper part of the magnet bobbin 12 is an outer heat radiation shield.
It is closed by 28, blocking the entry of heat from the outside. The outer heat radiation shield 28 is cooled by the magnet bobbin 12 to enhance the radiation heat blocking effect. The magnet bobbin 12 is made of a material having good thermal conductivity such as aluminum. The sample holder 14 and the inner and outer heat radiation shields 15 and 28 are made of high-purity aluminum or copper having good heat conductivity. Outer heat radiation shield 28, magnet bobbin 12,
In addition, the inner heat radiation shield 15 has a radiant heat shielding effect enhanced by winding the outer periphery thereof in multiple layers with a polyester film (super insulation) on which aluminum is thinly vapor-deposited or by applying gold plating, if necessary.

The second stage 18 of the refrigerator 16 is controlled to a predetermined temperature by a heater 22 wound around it. The voltage of the heater 22 is automatically controlled by the heater controller 66 based on the signal of the temperature sensor 23 attached to the sample holder 14. The temperature sensor 23 is connected to the hermetic connector 21 through the lead wire 20. The sample holder 14 in the inner heat radiation shield 15 connected to the second stage is cooled by radiation conduction from the inner heat radiation shield 15. Further, the inside of the sample holder 14 can be evacuated or filled with helium gas or the like through the valved pipe 24. Helium gas is
Convection in the sample holder promotes uniform temperature of the sample 19. A sample 19 is held in the sample holder 14. A measurement lead 20 is attached to the sample 19, and the measurement lead 20 is connected to a hermetic connector 21 arranged on the upper surface of the vacuum container 11.

Current to the superconducting magnet 13 is supplied from a magnet power supply 25 via a current lead 26. This current lead 26
A metal-based current lead such as copper is used from the magnet power supply to the magnet coil, but the oxide superconducting current lead 26
Is used to suppress generation of Joule heat and heat intrusion from the outside as much as possible. The oxide superconducting current lead 26 is brought into contact with the magnet bobbin 12 to cool it. Oxide superconducting current lead
The same oxide superconductor as the superconducting magnet 13 can be used for the material of 26. In the figure, 27 is a mount.

Next, a method of mounting a sample on this apparatus will be described. At room temperature, the lid 29 of the vacuum container, the outer heat radiation shield 28, and the inner heat radiation shield 15 are sequentially removed, and then the inner heat radiation shield 15 and the sample holder 14 are taken out so that the second stage 18 of the refrigerator can be seen. . Next, the sample holder 14 is removed from the inner heat radiation shield 15, and the sample 19 is mounted in the sample holder 14. At the same time, the temperature sensor 23 and the measurement lead 20 are attached to the sample holder 14.
Next, this is fixed to the inner heat radiation shield 15, and this inner heat radiation shield 15 is connected to the second stage 18 of the refrigerator. Also, install the valved pipe 24. In connection with the inner heat radiation shield 15 and the second stage of the refrigerator, in consideration of thermal conductivity, grease or varnish having high thermal conductivity is applied to the connection interface, or an indium sheet is inserted.
If electrical insulation is required, insert thin insulation.
This technique also applies to other connections that require heat transfer.
Next, the upper opening of the magnet bobbin 12 is provided with an outer heat radiation shield.
28, the upper opening of the vacuum container 10 is closed by the lid 29.

The procedure for measuring the physical properties of the sample will be described below. First, the inside of the vacuum container 11 is evacuated. Vacuum container
11 When the inside reaches a predetermined vacuum degree, operate the refrigerator 16 and
The superconducting magnet 13 and the sample 19 are cooled. Superconducting magnet 1
3. If the mass of the sample 19, the sample holder 14, the inner heat radiation shield 15, the magnet bobbin 12, the outer heat radiation shield 28, etc. is large and their heat capacity is large, it may take several hours to several days for cooling. Heater for heating when cooled to some extent
22 is operated to control the sample 19 to a predetermined temperature. Helium gas is introduced from the valved pipe 24 to promote uniformization of the sample temperature. Then, a magnetic field is applied to measure the physical properties of the sample. The physical properties of the sample are recorded in a recorder (not shown) via the measurement lead and the hermetic connector 21.

When replacing the sample 19, the refrigerator 16 is stopped and the superconducting magnet 13 and the sample 19 are returned to room temperature. Even if the heater 22 for heating is used for heating, it takes some time to return to normal temperature. When the temperature returns to room temperature, the lid 29 of the vacuum container 11 is removed, and the sample 19 is removed in the reverse order of the sample mounting procedure. The procedure for mounting and arranging the sample is performed by the same method as described above.

Since this superconducting magnet is a refrigerator conduction type, troublesome handling of the refrigerant is unnecessary. The first stage of the refrigerator
When the oxide superconducting magnet is cooled to a predetermined temperature by 17 and becomes superconducting, a magnetic field is generated by supplying an electric current. The sample can be easily controlled to a predetermined temperature by cooling by the second stage 18 of the refrigerator and heating by the heater 22. In this way, one refrigerator can apply a magnetic field and control the cooling temperature of the sample, so the device is small,
Equipment costs and running costs are also low. Also, sample exchange is easy.

(Embodiment 2) FIG. 2 is a side view showing a second embodiment of the device for measuring physical properties under a magnetic field of the present invention. In this device, the side wall of the inner heat radiation shield 15 is extended upward as compared with that of the first embodiment (FIG. 1). The upper part of the extended side wall is flared outward in a brim shape. The flange 46 is in close contact with the inner peripheral edge of the upper surface of the magnet bobbin 12. A tubular body 40 is provided between the upper surface of the collar portion 46 and the lid 29 of the vacuum container 11. The inside of the vacuum container 11 and the inside of the tubular body 40 are hermetically shut off from each other. As a result, the sample holder placement space A is open to the outside without impairing the vacuum state in the vacuum container 11. The upper portion of the tubular body 40 is sealed by the flange portion 42 of the baffled flange 41. The flange portion 42 is connected to the lid 29 of the vacuum container 11.
As shown in the perspective view of FIG. 3, the baffled flange 41 is provided with a shaft rod 43 in the flange portion 42, and a plurality of baffles 44 are attached to the shaft rod 43 at predetermined intervals.
The baffle 44 reflects the radiant heat from the outside and prevents the heat from entering. For the flange 42 and the baffle 44, thin plates having conductivity such as copper and aluminum are used. The sample holder 14 is attached to the bottom of the inner heat radiation shield 15 as shown in FIG.
The second stage is arranged in the opposite direction to that of the case with the heat transfer plate 45 facing down and through the bottom portion of the inner heat radiation shield 15.
Cooled by 18. This sample holder placement space is
As in the case of the apparatus shown in FIG. 1, evacuation or helium gas replacement is performed by the valved pipe 24. In this example, the valved pipe 24 is connected to the baffled flange 41. The lead wire 20 attached to the sample 19 and the lead wire attached to the temperature controller 23 of the sample holder 14 are connected to the hermetic connector 21 arranged on the upper surface of the baffled flange 41.

This apparatus has a sample holder arrangement space A
However, the inner heat radiation shield 15 and the tubular body 40 are in a state where they are hermetically shielded from the superconducting magnet arrangement space C in the vacuum container and are directly opened to the outside. Therefore, the sample exchange can be performed, for example, as described below. First, at least the inner surface side of the inner heat radiation shield 15 is heated by a heater (not shown) to return it to room temperature, and then the baffled flange 41 is removed to replace the sample 19. Next, after the sample holding space A is closed again by the baffled flange 41, the heating of the inner surface of the inner heat radiation shield 15 is stopped, the temperature of the sample holding space A is lowered again, and a vacuum is drawn. First, remove the baffled flange 41 to remove sample 19
Is exchanged, and then the water adhering to the sample holding space A is evaporated and removed by a heating source (not shown). Then, the flange 41 with a baffle is attached to close the sample holding space A, and the space A is evacuated. And cooling. First, the heater 22 attached to the second stage 18 is put in, and the inside of the inner heat radiation shield 15 is returned to room temperature. Then, the flange 41 with the baffle is removed and the sample 19 is replaced. Thereafter, the flange 41 is closed, heating by the heater 22 is stopped, and the sample holding space A is evacuated and cooled. As described above, in the apparatus of this embodiment, the sample exchange can be limited to the vicinity of the portion where the sample 19 is installed in the portion for heating or opening to the atmosphere. Therefore, it is not necessary to bring the space C in the vacuum container in which the superconducting magnet 13 is installed to atmospheric pressure, and it is not necessary to return the superconducting magnet 13 to room temperature. Therefore, the sample exchange time is shortened. In addition, only by heating the vicinity of the portion where the sample 19 is installed, the portion where the superconducting magnet 13 having a large heat capacity is not returned to room temperature. This shortening of the sample exchange time is similarly exhibited even when applied to a low temperature physical property measuring device to which a magnetic field is not applied.

The collar portion on the top of the above-mentioned inner heat radiation shield 15
46 is connected to the opening of the magnet bobbin 12 and serves as a heat anchor. That is, a part of the amount of heat that flows in from the outside is absorbed by the magnet bobbin (heat sink) 12 via the collar (heat anchor) 46, and the flow of external heat into the sample holder 14 is reduced. The temperature around the opening of the magnet bobbin 12 when the magnet bobbin 12 is connected to the first stage of the refrigerator 16 is about 50K.

(Embodiment 3) FIG. 4 is a side view showing the third embodiment of the physical property measuring apparatus under the magnetic field of the present invention. In the apparatus of this embodiment, a thermal switch 70 is installed in an intermediate cooling section (thermal anchor section) consisting of the magnet bobbin 12 and the flange section 46 of the inner heat radiation shield 15. This thermal switch 70
Controls the amount of heat transfer between the magnet bobbin 12 and the inner heat radiation shield 15. The thermal switch 70 may be mechanical, but the structure is complicated. The thermal switch 70 shown in FIG. 4 has a structure in which the helium gas 72 is put into and taken out of the casing 71, and the structure is simple. This thermal switch 70
Then, when the sample is cooled, the casing 71 is filled with the helium gas 72, and the convection thereof causes the invasion heat from the inner heat radiation shield 15 to be rapidly absorbed by the magnet bobbin 12. When exchanging the sample, the inside of the casing is evacuated to insulate the space between the magnet bobbin 12 and the inner heat radiation shield 15 so that the sample returns to the normal temperature in a short time. If the connection between the inner heat radiation shield 15 and the magnet bobbin 12 is warmed, the time required for returning to room temperature is further shortened. If the return time is shortened, the temperature rise of the magnet bobbin 12 and the superconducting magnet 13 can be suppressed to the minimum. It should be noted that the material and dimensions of the casing must be determined in consideration of the fact that the casing itself becomes a heat medium.

FIG. 5 is an explanatory view of a method for reducing the inflowing heat quantity using a general heat anchor. Neck of liquid helium storage container 50
A metal piece (thermal anchor) 52 is connected to 51, and a liquid nitrogen storage container (heat sink) 53 is connected to the other end of the metal piece 52. Of the heat input Q ₁ from the outside, Q ₂ is a metal piece 52
After being absorbed by the heat sink 53, the remaining heat quantity Q ₃ flows into the liquid helium. Due to this heat sink 53, the heat quantity of Q ₁ that should originally flow into the liquid helium is (Q ₁ -Q
₂ ). In order to improve the thermal conductivity, the metal pieces 52 are connected by welding, soldering, or bolting via indium or the like.

[0023]

As described above, the apparatus for measuring physical properties under a magnetic field according to the present invention cools a superconducting magnet and a sample with a single refrigerator, is small in size, and has low equipment costs and running costs. Is. Also, sample exchange is easy. Further, the sample holder arrangement space is hermetically shielded from the superconducting magnet arrangement space in the vacuum container, and the sample holder arrangement space can be directly opened to the outside of the vacuum container, so that the sample can be quickly exchanged.

[Brief description of drawings]

FIG. 1 is a side view illustrating a first embodiment of a physical property measuring apparatus under a magnetic field of the present invention.

FIG. 2 is a side view showing a second embodiment of the device for measuring physical properties under a magnetic field of the present invention.

FIG. 3 is a perspective view of a flange with a baffle for blocking heat inflow from the outside.

FIG. 4 is a side view showing the third embodiment of the physical property measuring apparatus under the magnetic field of the present invention.

FIG. 5 is an explanatory diagram of a method of reducing an inflowing heat amount by using a thermal anchor.

FIG. 6 is a side view illustrating a conventional physical property measuring device under a magnetic field.

[Explanation of symbols]

 11,71 ─ Vacuum container 12 ── Magnet bobbin 13 ─── Superconducting magnet 14 ─── Sample holder 15 ─── Inner heat radiation shield 16,66 ─ Refrigerator 17 ─── First stage 18 ─── Second stage 19 ─── Sample 20 ─── Measuring lead 21 ─── Hermetic connector 22 ─── Heater 23 ─── Temperature sensor 24 ─── Pipe with valve 25 ─── Power supply for superconducting magnet 26 ─── Oxidation Superconducting conductive lead 27 ─── Frame 28 ─── Outside heat radiation shield 29 ─── Vacuum container lid 40 ─── Cylindrical body 41 ─── Baffled flange 42 ─── Flange 43 ─── Shaft rod 44 ─── Baffle 45 ─── Heating plate of sample holder 46 ─── Collar of inner heat radiation shield 50 ─── Liquid helium storage container 51 ─── Neck of liquid helium storage container 52 ─── Metal strip 53 ─── Liquid nitrogen storage container 61 ─── Cryostat for cooling superconducting magnets 62 ─── Room temperature bore 63 ─── Cryostat for controlling sample cooling temperature 65 ─── Heat radiation shield 66 ─── Heater controller 70 ─── Thermal switch 71 ─── Casing 72 ─── Helium gas

Claims (2)

[Claims] 1. A device for measuring physical properties under a magnetic field in which a sample holder is arranged under a magnetic field generated by a superconducting magnet, wherein a superconducting magnet is provided at a first stage of a multistage refrigerator having a first stage and a second stage. An apparatus for measuring physical properties under a magnetic field, wherein sample holders are thermally connected to a stage. 2. A magnet bobbin is attached to the first stage of the multi-stage refrigerator, a superconducting magnet is attached to the magnet bobbin, the magnet bobbin and the superconducting magnet are surrounded by a vacuum container, and the magnet bobbin and the superconducting magnet are attached. A sample holder arrangement space in which the second stage of the multistage refrigerator is arranged is provided inside the space in which the and are arranged, and the sample holder arrangement space is arranged with the superconducting magnet in the vacuum container. An apparatus for measuring physical properties under a magnetic field according to claim 1, wherein the apparatus is airtightly partitioned from the open space and can be opened to the outside.