JP6937610B2 - Cryogenic device - Google Patents

Description

The present invention relates to a cryogenic device for cooling a superconducting device to a cryogenic state using a cryogenic agent such as liquid helium, and more particularly to a cryogenic device having a built-in recondensing means for the cryogenic agent.

Conventionally, in a cryogenic device used by cooling a superconducting magnet for MRI or the like with a cold agent such as liquid helium, it is common to incorporate a small refrigerator for recondensing the vaporized cold agent. Examples of the cryogenic device having such a small refrigerator built-in include a structure in which a refrigerator head is fitted in an opening (neck tube) communicating with a container as shown in Patent Document 1 below, and the following. As shown in Patent Document 2, a structure in which a small refrigerator is housed in an independent chamber has been proposed.

JP-A-2009-162480 U.S. Patent US9234691B2 Gazette

By the way, in the structure shown in Patent Document 1, the neck tube for mounting a small refrigerator has a large diameter, and as the number of superconducting sensors increases, the number of conducting wires for connecting to the neck tube also increases. There is a tendency for the heat of penetration to increase through the conductors and the like that are wired inside. On the other hand, in the structure of Patent Document 2, although the diameter of the neck tube can be reduced, a space for installing the refrigerator is required separately, so that the entire device tends to be large.

Therefore, the present invention has been devised to solve these problems, and an object of the present invention is to provide a novel cryogenic device capable of suppressing intrusion heat while avoiding an increase in the size of the entire device. There is.

In order to solve the above problems, the first invention is a cryogenic device including an inner container for accommodating a body to be cooled together with a cryogen and an outer container for accommodating the inner container, from the inner container to the outer container. A neck tube is formed so as to penetrate the neck tube, a refrigerator is fitted in the neck tube, a partition cover is provided so as to surround the refrigerator in the neck tube, and the refrigerator is formed inside the partition cover. A gas supply port is connected to the first gap, a gas discharge port is formed in the second gap formed on the outside of the partition cover, and the gas discharge port and the gas supply port are connected by a gas circulation line. It is a cryogenic device characterized by this.

According to such a configuration, the gap around the refrigerator is divided into the inner first gap and the outer second gap by the partition cover, so that the gas in the gas circulation line is divided into the inner first gap from the gas supply port. After being directly cooled by the refrigerator and recondensed (liquefied), it is supplied to the inner container. On the other hand, the vaporized gas generated in the inner container passes through the second void on the outside of the partition cover, and a flow is generated in which the vaporized gas is exhausted from the gas discharge port to the gas circulation line. Then, since the sensible heat of the vaporized gas flowing through the second void can efficiently cool the neck tube, which is one of the invasion heat paths, the invasion heat into the inner container is suppressed to a low level while avoiding an increase in the size of the entire device. be able to.

The second invention is a cryogenic device including an inner container for accommodating a body to be cooled together with a cryogen and an outer container for accommodating the inner container, and forms a neck tube penetrating the outer container from the inner container. At the same time, the refrigerator is mounted in the neck tube so as to be fitted, a partition cover is provided so as to surround the refrigerator in the neck tube, and a communication hole is formed in the partition cover to form the partition cover. The first void formed on the inside and the second void formed on the outside of the partition cover are communicated with each other, and the open end of the partition cover is closed with a lid member having a liquid passage. It is a cryogenic device.

According to such a configuration, since the void around the refrigerator is divided into the inner first void and the outer second void by the partition cover, the gas in the inner first void is directly cooled by the refrigerator. After recondensing (liquefying), it flows down into the inner container. Then, since the pressure inside the first void inside the partition cover becomes negative, the vaporized gas generated in the inner container passes through the communication hole formed in the partition cover from the second void outside the partition cover and enters the first void. A continuous gas flow in one direction is generated from the second void to the first void. Then, since the sensible heat of the vaporized gas flowing through the second void can efficiently cool the neck tube, which is one of the invasion heat paths, the invasion heat into the inner container is suppressed to a low level while avoiding an increase in the size of the entire device. be able to.

A third invention is a cryogenic device according to the first or second invention, wherein a lead wire connected to the cooled body and a pipe for supplying the cryogen are arranged in the second void. .. According to such a configuration, not only the neck tube, which is one of the paths of invading heat due to the sensible heat of the vaporized gas flowing through the second void, but also the lead wire connected to the cooled body and the pipe for supplying the cryogen. It can be cooled efficiently.

According to the present invention, the sensible heat of the vaporized gas flowing through the second void can efficiently cool the neck tube, which is one of the paths of invading heat, the lead wire connected to the object to be cooled, and the tube for supplying the cryogen. , It is possible to significantly reduce the heat entering the inner container while avoiding the increase in size of the entire device.

It is sectional drawing which shows one Embodiment of the cryogenic device 100 which concerns on this invention. It is a partially enlarged view which shows the part A in FIG. It is sectional drawing which shows the other embodiment of the cryogenic device 100 which concerns on this invention. It is sectional drawing which shows the other embodiment of the cryogenic device 100 which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an embodiment of the cryogenic device 100 according to the present invention. As shown in the figure, the cryogenic device 100 has a cylindrical inner container 110 for accommodating the cooled body 10 together with the cryogen 11, and a cylindrical inner container 110 for accommodating the inner container 110 via a vacuum space 20 and a width radiation shield 130. It has a double structure with the outer container 120.

A circular opening 111 is formed in the center of the top plate of the inner container 110, and the opening 111 is provided with a tubular neck tube 140 extending vertically upward from the opening 111. The upper end of the neck tube 140 penetrates the top plate of the outer container 120, and the condenser 151 of the small refrigerator 150 is provided so as to fit inside the upper end opening of the neck tube 140.

The small refrigerator 150 is, for example, a low-vibration refrigerator called a pulse tube, and is composed of a condenser 151 located inside and a refrigerator head 152 exposed to the outside as described above. A compressor 154 is connected to the refrigerator head 152 via a plurality of gas pipes 153, and the compressor 154 compresses and circulates the refrigerant for the refrigerator to form a refrigeration cycle. The refrigerator currently on the market has a condensing capacity of about 1 W at a helium temperature.

The body to be cooled 10 housed in the inner container 110 is a superconducting magnetic sensor such as a SQUID (superconducting quantum interference element) that operates in a cryogenic state, and measures an extremely weak field generated from a living body. Can be done. As the cryogenic agent 11 that cools the body 10 to be cooled, a cryogenic liquid such as liquid helium having an atmospheric boiling point of 4.2 K is used, for example.

FIG. 2 is an enlarged view showing a part A in FIG. 1, showing a detailed structure in the vicinity of the neck tube 140 extending from the inner container 110 to the outer container 120. As shown in the figure, the neck tube 140 has a cylindrical shape with both upper and lower ends open, and is provided so as to connect between the opening 111 of the top plate of the inner container 110 and the top plate of the outer container 120. Further, a ring-shaped adapter 160 having a U-shaped cross section is provided on the upper end side of the neck tube 140, that is, on the top plate of the outer container 120 so as to surround the upper end opening of the neck tube 140. A donut disk-shaped refrigerator flange 161 is mounted on the 160.

Then, the condenser 151 side of the small refrigerator 150 is inserted through the opening of the refrigerator flange 161 and the refrigerator head 152 side is fixed on the refrigerator flange 161 so that the condenser 151 is formed as shown in the figure. It is installed so as to fit inside the neck tube 140.

Further, on the lower surface side of the refrigerator flange 161, a cylindrical partition cover 170 is provided so as to extend vertically downward from the lower surface side. The partition cover 170 has an open lower end and an inner diameter larger than the outer diameter of the condenser 151, and has a predetermined gap (first gap) having an annular shape with the surface of the condenser 151. It is provided so as to surround S1). Further, the outer diameter of the partition cover 170 is smaller than the inner diameter of the neck tube 140, and an annular gap (second gap S2) is formed between the partition cover 170 and the neck tube 140.

A gas supply port 162 is formed in the refrigerator flange 161 and communicates with the first void S1 inside the partition cover 170. On the other hand, a gas discharge port 163 is formed in the adapter 160 to which the refrigerator flange 161 is attached, and communicates with the second void S2 on the outside of the partition cover 170. A gas circulation line L is connected to the gas discharge port 163 and the gas supply port 162 as shown in FIG.

The gas circulation line L includes a circulation pump 30, a gas cylinder 31 having a valve 34, and a discharge pipe 32 having a valve 33. The circulation pump 30 allows the gas discharge port 163 to enter the second gap S2. The vaporized gas is extracted and circulated so as to be supplied into the first void S1 from the gas supply port 162. Then, in the process of this gas circulation, a part of the gas can be appropriately discharged from the discharge pipe 32 or the gas can be replenished from the gas cylinder 31.

Further, as shown in FIG. 2, the adapter 160 to which the refrigerator flange 161 is attached is provided with a liquid supply port 164 in addition to the gas discharge port 163. A liquid supply pipe (not shown) is connected to the liquid supply port 164 so that the cryogen 11 such as liquid helium can be directly supplied into the inner container 110. A transfer tube insertion tube 165 is connected to the inside of the liquid supply port 164, and the transfer tube insertion tube 165 is arranged so as to pass downward in the second gap S2.

Further, in the second void S2, a plurality of conducting wires C extending from a cooled body 10 or the like such as a superconducting magnetic sensor arranged in the inner container 110 are wired so as to pass upward. It extends outward from a drawer 180 having an airtight structure formed between the adapter 160 and the outer container 120 and is connected to an external device (not shown).

The adapter 160, the refrigerator flange 161 and the small refrigerator 150 can be attached to and detached from the outer container 120, respectively, and are sealed to the outside air by an O-ring or packing at the time of assembly. Further, the inner container 110, the outer container 120, the neck tube 140, the partition cover 170, and the like are formed of a low heat conductive material such as glass fiber reinforced plastic (FRP), and the amount of heat that penetrates through them is suppressed to a low level. ing.

Next, the operation of the cryogenic device 100 according to the present invention having such a configuration will be described. As shown in FIG. 1, the cooled body 10 such as a superconducting magnetic sensor arranged in the inner container 110 fully exerts its function by being cooled to a cryogenic state by a cryogenic agent 11 such as liquid helium. However, in the inner container 110 in that state, the liquid cryogenic agent 11 constantly evaporates due to invading heat from various routes and becomes vaporized gas to fill the inner container 110.

As shown in FIG. 2, the vaporized gas in the inner container 110 tends to go out from the opening 111 formed in the top plate of the inner container 110, and at this time, the first void S1 partitioned by the partition cover 170 Is high pressure due to the circulating gas that is sequentially supplied, so it flows to the second void S2 side, which is the low pressure outside, and passes through this so as to rise from the gas discharge port 163 to the gas circulation line L. It is discharged.

Then, the low-temperature vaporized gas generated in the inner container 110 continuously flows on the second gap S2 side, so that the lead wire C and the transfer tube insertion tube 165 arranged in the second gap S2 and the transfer tube insertion tube 165 Since the neck tube 140 is effectively cooled by its sensible heat, the amount of heat that conducts these and enters the inner container 110 side can be suppressed to a low level.

On the other hand, the gas discharged from the gas discharge port 163 to the gas circulation line L is again supplied from the gas supply port 162 into the first void S1 inside the partition cover 170 by the pump 30, and is supplied by the condenser 151 of the small refrigerator 150. Since it is forcibly cooled and recondensed (liquefied), becomes a liquid, drops (drops) into the inner container 110, and is reused as the cryogen 11, the cryogen 11 in the inner container 110 is not insufficient. ..

As described above, in the cryogenic device 100 according to the present invention, the gap around the condenser 151 of the small refrigerator 150 is divided into the first gap S1 and the second gap S2 by the partition cover 170, and the vaporization generated in the inner container 110 is performed. Since the gas is exhausted by passing through the outer second void S2, the neck tube 140 and the lead wire C, which are one of the invading heat paths, can be efficiently cooled by the sensible heat of the vaporized gas flowing through the gas. can. As a result, it is possible to significantly reduce the heat entering the inner container 110 while avoiding an increase in the size of the entire device.

Next, FIG. 3 shows another embodiment of the cryogenic device 100 according to the present invention. As shown in the figure, in the present embodiment, one or more communication holes 173 are formed on the upper end side of the partition cover 170 to communicate the first gap S1 and the second gap S2, and the open end of the partition cover 170. The portion is closed with a funnel-shaped lid member 171 having a liquid passage 172, and the gas discharge port 163 and the gas supply port 162 are closed.

With such a configuration, the vaporized gas generated in the inner container 110 cannot flow into the inside of the partition cover 170, that is, the first gap S1 because of the lid member 171. It flows to the S2 side, rises there, passes through the communication hole 173 on the upper end side thereof, and flows into the first gap S1. As a result, the conductor C, the transfer tube insertion tube 165, and the neck tube 140 arranged in the second gap S2 are effectively cooled by the sensible heat of the vaporized gas as in the above embodiment. The amount of heat that conducts and enters the inner container 110 side can be suppressed to a low level.

On the other hand, the vaporized gas that has flowed into the first void S1 is forcibly cooled by the condenser 151, recondensed (liquefied), becomes a liquid, and drops onto the lid member 171. Further, since the inside of the first void S1 becomes more negative pressure than the second void S2 by this recondensing step of the vaporized gas, the vaporized gas of the second void S2 smoothly and continuously flows into the first void S1. become. Then, the liquid dropped on the lid member 171 falls from the liquid passage 172 in the central portion into the inner container 110 and is reused as the cryogen 11.

Even if one or more communication holes 173 are formed on the upper end side of the partition cover 170 and the open end of the partition cover 170 is closed by the lid member 171 as described above, the same as in the above embodiment. The sensible heat of the vaporized gas can efficiently cool the neck tube 140, the lead wire C, etc., which are one of the intrusion heat paths. As a result, not only can the heat entering the inner container 110 be significantly suppressed while avoiding an increase in the size of the entire device, but also the gas circulation line L can be abolished, and the entire device can be simplified. can.

The liquid passage 172 formed in the lid member 171 has a small diameter (thin tube) as much as possible in order to maintain a state in which the inside is always filled (closed) with the liquid in order to prevent the invasion of vaporized gas. However, if it is too small, the liquid may freeze inside the liquid due to the inclusion of impurities and the like, and the liquid may be clogged. Therefore, as shown in the drawing, an electric heater 174 may be attached to the outside of the liquid passage 172, and the liquid passage 172 may be appropriately heated to prevent blockage due to freezing.

Further, the liquid supply port 164 formed in the adapter 160 is used only for supplying the cryogen 11 at the initial stage of operation and for replenishing the liquid in the event of a failure of the small refrigerator 150, and is not normally used, but the liquid supply port 164 is used. Since the transfer tube insertion tube 165 extending to the inner container 110 side is connected to the above, the heat entering through the liquid supply port 164 is not small. Therefore, as shown in FIG. 4, it is desirable to devise the structure of the liquid supply port 164 to further suppress the invading heat from this portion.

That is, the transfer tube insertion tube 165 has a double tube structure of an outer tube 201 and an inner tube 202, both ends thereof are closed, and a vacuum is maintained by a vacuum seal 203 between them. The room temperature portion 204 bent into an L shape from the transfer tube insertion tube 165 is inserted into the port 205 provided in the adapter 160 and kept airtight by the O-ring 206 and the restraint 207, and if necessary, is external. The transfer tube 208 is inserted into the inner tube 202 of the transfer tube insertion tube 165 via the connection adapter 209. The connection adapter 209 is provided with O-rings 210, 211 and restraints 212, 213 at both ends to maintain airtightness.

10 ... Cooling bath 11 ... Cooling bath 100 ... Cryogenic device 110 ... Inner container 120 ... Outer container 140 ... Neck tube 150 ... Small refrigerator 165 ... Transfer tube insertion tube 170 ... Partition cover 171 ... Lid member 172 ... Liquid passage 173 ... Communication hole 174 ... Electric heater C ... Lead wire S1 ... First gap S2 ... Second gap

Claims (2)

A cryogenic device including an inner container for accommodating a body to be cooled together with a cryogen and an outer container for accommodating the inner container.
A neck tube that penetrates the outer container from the inner container is formed, and the refrigerator is mounted so as to fit inside the neck tube.
A partition cover is provided so as to surround the refrigerator in the neck tube.
A gas supply port is connected to the first gap formed inside the partition cover, and a gas discharge port is formed in the second gap formed outside the partition cover.
A cryogenic device characterized in that the gas discharge port and the gas supply port are connected by a gas circulation line having a circulation pump. In the cryogenic device according to claim 1,
A cryogenic device characterized in that a conducting wire connected to the cooled body and a pipe for supplying the cryogen are arranged in the second void.

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