JP3996553B2 - High thermal efficiency dewar - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a medical diagnostic apparatus for measuring a magnetic field generated from a human body or a living body, a physical property measuring apparatus for measuring the magnetic permeability of a magnetoencephalograph material, and a communication for magnetic signal transmission interface. The present invention relates to a dewar suitable for storing a SQUID (Superconducting Quantum Interference Device) used for an apparatus or the like, and particularly relates to a high thermal efficiency dewar that can be used for a magnetoencephalograph.
[0002]
[Prior art]
Liquid helium is indispensable for extremely low temperature properties research and cooling of measuring instruments using superconducting elements. In addition, in a brain magnetic measurement system or the like that detects a magnetic field emitted from a human brain, a SQUID (superconducting quantum interferometer) that can measure brain activity noninvasively with high spatio-temporal resolution is used. For cooling this SQUID Liquid helium is also used.
[0003]
In most of the devices described above, currently liquid helium for cooling evaporates and is released into the atmosphere. Even in the conventional liquid helium tank used in the above system, The evaporated helium gas is almost open to the atmosphere. However, in this case, there is a problem in terms of economy and resources because a large amount of expensive helium, which costs about 1200 yen per liter, is wasted. Therefore, it is desired to recover the evaporated helium gas, liquefy it again, and reuse it. The requirements are very strong.
For this reason, recently, a recirculation system that collects all of the helium gas vaporized in the liquid helium storage tank, removes contaminants in the helium gas in the system, and then recondenses and liquefies (patents). Reference 1).
[0004]
[Patent Document 1]
Japanese Patent Application No. 2003-25525
[0005]
[Problems to be solved by the invention]
The helium circulation device in the above application uses the first stage refrigeration cycle having a large cooling capacity to cool most of the recovered helium gas to a low temperature gas of about 40K without using a 4KGM refrigerator. After that, it is supplied to the neck tube part of the Dewar and recovered as a high temperature gas again to exhibit the cooling capacity. The recovered part of the gas is then kept at 4K by using the entire refrigeration cycle to 4K liquid helium and injected into the dewar from another supply line. At the same time, a system is adopted in which the evaporated helium gas is recovered at the lowest possible temperature, immediately recondensed into liquid helium, and returned to the dewar again.
However, the above apparatus has a part to be improved in that it collects low-temperature helium gas generated in the dewar and efficiently recovers the heat entering and generating in the dewar.
[0006]
Accordingly, the present invention has been made to solve the above-described problems, and can efficiently recover low-temperature helium gas (about 4K) generated in the dewar and send it to the recondensing refrigerator. An object of the present invention is to provide a high thermal efficiency dewar that can efficiently recover the heat that has entered inside and the heat generated in the dewar using helium gas of about 40K, and can be discharged outside the dewar.
[0007]
[Means for Solving the Problems]
For this reason, the technical solution means adopted by the present invention is:
In the high thermal efficiency dewar in which the inner tank is disposed in the outer tank and a vacuum layer is formed between the two, and liquid helium is stored in the inner tank, there is a through hole for inserting a transfer tube in the upper part of the inner tank. A first vacuum part and a second vacuum part are disposed with a gap , a transfer tube is disposed in the through-hole, and high-temperature (about 40K) helium gas from the transfer tube is It is a high thermal efficiency dewar characterized in that it can be discharged into the gap of the second vacuum part.
Moreover, in the high thermal efficiency dewar which arrange | positions an inner tank in an outer tank and makes a vacuum layer between both, and also stores liquid helium in an inner tank, arrange | positions a heat-transfer material in the said vacuum layer, One end is connected to the inner tank wall as a thermal anchor, and the upper part in the inner tank is arranged with a first vacuum part and a second vacuum part having a through hole for inserting a transfer tube with a gap, A transfer tube is placed in the through hole, and high-temperature (about 40K) helium gas from the transfer tube is opened in the gap between the first vacuum part and the second vacuum part, so that the outer periphery of the first vacuum part can be cooled. It is a high thermal efficiency dewar characterized by
Moreover, in the high thermal efficiency dewar which arrange | positions an inner tank in an outer tank and makes a vacuum layer between both, and also stores liquid helium in an inner tank, arrange | positions a heat-transfer material in the said vacuum layer, One end thereof is connected to the inner tank wall to form a thermal anchor, and the inner tank is provided with a first vacuum part and a second vacuum part having a through hole for inserting a transfer tube, and the transfer tube is provided in the through hole. And a high-temperature (about 40K) helium gas from the transfer tube is opened between the first vacuum part and the second vacuum part so that the outer periphery of the first vacuum part can be cooled. High heat efficiency dewar.
The thermal anchor is a high thermal efficiency dewar characterized in that it is positioned higher than between the first vacuum part and the second vacuum part from which 40K helium is blown.
Each vacuum part is a high thermal efficiency dewar characterized in that it is arranged with a predetermined gap between it and the inner tank wall.
Moreover, it is a high thermal efficiency dewar characterized by comprising the lower surface of the said 2nd vacuum part as the cone shape which inclined upwards.
Further, the dewar is a high thermal efficiency dewar characterized in that another member having a conical shape inclined upward is attached to the lower surface of the second vacuum portion.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the dewar according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a magnetoencephalograph.
In the figure, the dewar 100 is supported by a support member (not shown), a SQUID sensor having a SQUID element, a substantially cylindrical inner tank 1 that can store liquid helium L as a cooling medium, and the inner tank. An outer tub 2 that surrounds the inner tub 1 and forms a heat insulating layer such as a vacuum layer 3 between the inner tub 1 and holds the inner tub 1 in a heat insulating state, and a closing member that closes the upper portions of the inner layer 1 and the outer tub 2 4 is provided. In the figure, reference numeral 5 denotes a support member for supporting the dewar 100.
[0009]
The outer tub 2 is made of a heat insulating material such as FRP, and the upper portion of the vacuum layer 3 between the outer tub 2 and the inner tub 1 is closed with a heat insulating material 6 in a sealed state. Further, the upper part of the outer tub 2 is closed by a closing member 4, and the closing member 4 has a line 7 for depriving heat by heat anchors 9 and 16 (described later) and sending helium gas heated to a recondensing refrigerator. It is connected. In the vacuum layer 3, a plurality of heat transfer materials 8a, 8b, and 8c formed so as to surround the inner tank 1 are arranged (three in this example). One end of the first heat transfer material 8a and the second heat transfer material 8b is a free end below the vacuum layer 3, and the other end is thermally connected to a predetermined position of the wall material forming the inner tank 1. A thermal anchor 9 is formed. In this example, the mounting position of the thermal anchor 9 is an intermediate portion of the first vacuum portion 10 described later (in other words, the thermal anchor is located between the first vacuum portion and the second vacuum portion where 40K helium is blown out. Is also located above).
. The third heat transfer material 8c is formed in a cylindrical shape covering the lower surface of the inner tank 1, and the inner tank wall at a position corresponding to the gap 12 between the first vacuum part 10 and the second vacuum part 11 described later. To form a thermal anchor 9.
[0010]
A first vacuum part 10 and a second vacuum part 11 are arranged vertically in the inner tank 1, and a transfer tube 13 is disposed through each of the vacuum parts 10 and 11. The transfer tube 13 has a structure in which 4K liquid helium flows in the center, 4K helium gas flows on the outer periphery, and 40K helium gas flows on the outer side.
The first vacuum unit 10 disposed in the upper part of the inner tank 1 allows high-temperature helium gas (about 40 K) released from a transfer tube (described later) to flow upward between the outer periphery and the inner tank 1. The flow path 14 for this is formed. Further, a plurality of heat transfer materials 15 (two in this example) are arranged in the first vacuum portion 10, and each is connected to the wall portion of the first vacuum portion to form a heat anchor 16. A transfer tube 13 penetratingly arranged at the center of the first vacuum unit 10 is disposed in close contact with the first vacuum unit 10, and 40 K helium gas cooled by a recondensing refrigerator (not shown) is supplied to the first vacuum unit 10. 10 is jetted into the inner tank 1 from the vicinity of the lower surface.
[0011]
A second vacuum part 11 is disposed below the first vacuum part 10 with a gap 12. The second vacuum part 11 is disposed so that a slight gap 17 is formed between the outer periphery of the second vacuum part 11 and the inner tank 1, and the lower surface 18 of the second vacuum part 11 is further upward from the outer periphery to the center part. It is formed with a conical surface inclined toward the. The conical surface can be formed by the second vacuum part itself, but the lower surface of the second vacuum part 11 is a flat surface, and another member having a conical surface inclined upward from the outer periphery to the central part on the flat surface. It is also possible to install and configure. As the material of the separate member, an appropriate material such as urethane can be used. At the center of the second vacuum part 11, a transfer tube 13 made of a tube through which the 4K liquid helium and the 4K low-temperature helium gas flow is disposed with a gap 19 therebetween. Below the second vacuum part 10, liquid helium L for cooling a SQUID sensor (not shown) is stored.
[0012]
In the dewar 100 configured as described above, liquid helium is supplied from the 4K liquid helium line at the center of the transfer tube 13 into the magnetoencephalograph dewar. In addition, most of the helium gas (about 4K) evaporated in the magnetoencephalograph dewar flows along the inclined portion of the lower surface 18 of the second vacuum portion 11 toward the upper central portion, and from the 4K helium gas line of the transfer tube 13. Suctioned and returned to the recondensing refrigerator. Part of the helium gas (about 4K) evaporated in the dewar 100 passes through the gap 19 between the transfer tube 13 and the second vacuum part 11 and enters the gap 12 between the first vacuum part 10 and the second vacuum part 11. Flowing. On the other hand, 40 K helium gas is supplied into the inner tank 1 from the recondensing refrigerator from the 40 K helium gas line of the transfer tube 13. The 40K helium gas supplied into the inner tank 1 is mixed with the 4K helium gas, passes through the gap 14 between the inner tank 1 and the first vacuum part 10, and cools the thermal anchors 9 and 16 to be transmitted. The heat materials 8 and 15 are deprived of heat and raised in temperature, and finally become high-temperature helium gas of about 300K and returned to the recondensing refrigerator.
[0013]
As described above, in the present invention, since the second vacuum part 11 is formed, the heat intrusion from the upper part of the dewar is reduced, the amount of liquid helium gas stored in the dewar can be reduced, and the evaporated low-temperature helium gas (About 4K) can be efficiently recovered, and the recondensing efficiency in the recondensing refrigerator increases. Further, the heat anchor can be efficiently cooled by 40K helium gas, and the heat that has entered the dewar and the heat generated in the dewar can be efficiently recovered.
[0014]
Although the embodiment of the present invention has been described, the position of the thermal anchor, the number of heat transfer materials, the shape, and the like can be appropriately selected in accordance with a dewar (for example, a dewar for a magnetoencephalograph). Further, the angle of the inclined surface of the second vacuum portion can be determined in accordance with each dewar at the time of design. As a matter of course, the high thermal efficiency dewar described above can be used as it is as a dewar for a magnetoencephalograph.
In addition, the present invention can be implemented in any other form without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner.
[0015]
【The invention's effect】
As described above, according to the dewar for high thermal efficiency of the present invention, the low-temperature helium gas (about 4K) generated in the dewar can be efficiently recovered and sent to the recondensing refrigerator, and has entered the dewar. The heat and the heat generated in the dewar can be efficiently recovered using about 40K of helium gas and discharged outside the dewar.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a high thermal efficiency dewar according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inner tank 2 Outer tank 3 Vacuum layer 4 Closure member 5 Support member 6 Heat insulating material 7 Line 8, 15 Heat-transfer material 9, 16 Heat anchor 10 1st vacuum part 11 2nd vacuum part 12, 14, 17, 19 19 Transfer tube 18 bottom

Claims (6)

In the high thermal efficiency dewar in which the inner tank is disposed in the outer tank and a vacuum layer is formed between the two, and liquid helium is stored in the inner tank, there is a through hole for inserting a transfer tube in the upper part of the inner tank. A first vacuum part and a second vacuum part are disposed with a gap , a transfer tube is disposed in the through-hole, and high-temperature (about 40K) helium gas from the transfer tube is A high thermal efficiency dewar characterized in that it can be discharged into the gap of the second vacuum part. In the high thermal efficiency dewar in which the inner tank is arranged in the outer tank and a vacuum layer is formed between the two, and liquid helium is stored in the inner tank, a heat transfer material is arranged in the vacuum layer, and one end thereof Is connected to the inner tank wall as a thermal anchor, and the first vacuum part having a through hole for inserting a transfer tube and the second vacuum part are arranged with a gap in the upper part in the inner tank, and the penetration A transfer tube was placed in the hole, and high-temperature (about 40K) helium gas from the transfer tube was opened in the gap between the first vacuum part and the second vacuum part, so that the upper periphery of the first vacuum part could be cooled. Dewar with high thermal efficiency. 3. The high thermal efficiency dewar according to claim 2, wherein the thermal anchor is provided at a position higher than between the first vacuum part and the second vacuum part from which 40 K helium is blown. The high heat efficiency dewar according to any one of claims 1 to 3, wherein each of the vacuum parts is arranged with a predetermined gap between the vacuum part and the inner tank wall. The high thermal efficiency dewar according to any one of claims 1 to 4, wherein the lower surface of the second vacuum part is configured as a conical shape inclined upward. 5. The high thermal efficiency dewar according to claim 1, wherein another member having a conical shape inclined upward is attached to a lower surface of the second vacuum portion.

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