JP2004116914A - Cooling pipe and cryogenic cryostat using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling pipe capable of reducing the helium consumption with a small-sized facility by removing the blocking and influence of magnetic noise by a cryogenic means which are observed in helium circulation, and a cryogenic cryostat using it. <P>SOLUTION: This cooling pipe has a cryogenic refrigerator mounted on the upper end of a cylindrical vacuum vessel, the cold generation part of the cryogenic refrigerator arranged within the vacuum vessel, and a heat transfer pipe of a prescribed length having one end connected to the cold generation part and the other end exposed from the lower end of the vacuum vessel to form a cold exposition part. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cryogenic cryostat for biomagnetism measurement using a cold material such as liquid helium, and provides a cold supply means for extending a low-temperature holding time and reducing a helium evaporation amount.
[0002]
The present invention is applicable not only to a cryogenic cryostat for biomagnetic measurement, but also to a cryostat that requires a refrigerant to maintain a low temperature, for example, an MRI (nuclear magnetic resonance imaging diagnostic device) using a superconducting magnet or a helium cryostat for studying physical properties. Is also applicable.
[0003]
[Prior art]
[0004]
[Non-patent document 1]
Kawakatsu et al. “Reconversion of helium for biomagnetic measurement system and circulation system
Development, Vol. 14 No. 1 2001,
p274-275, Transactions of the 16th Annual Meeting of the Japanese Society of Biomagnetism.
[Non-patent document 2]
S. Fujimoto et. al. "Cooling of SQUIDs using a Gifford-McMahorn cryocooler containing magnetic regenerative material to measure biomagnetism," Cryogenetics, 35, Crypogenics. 138-143. ]
[0005]
FIG. 13 shows a configuration diagram of a liquid helium circulation system, cited from the prior art described in Non-Patent Document 1. This is a method in which helium gas evaporating from the cryogenic cryostat 2 is temporarily stored in the gas bag 4, returned to liquid helium by the reliquefaction machine 8, and returned to the cryogenic cryostat, so that the cycle of replenishing liquid helium is extended. Things.
[0006]
In the figure, reference numeral 1 denotes a magnetic shield room for obtaining a quiet magnetic environment for measuring biomagnetism. Reference numeral 2 denotes a cryogenic cryostat that holds liquid helium as a refrigerant and cools a highly sensitive superconducting magnetic sensor (SQUID). The liquid helium stored in the cryogenic cryostat 2 evaporates little by little due to external heat. Usually, it is thrown away into the atmosphere, but is stored in the gas bag 4 through the exhaust pipe 3.
[0007]
The stored helium gas is pressurized by a circulation pump 5, and water and impurity gas mixed in the middle are removed through a water remover 6 and an impurity gas remover 7, and purified into high-purity helium gas. The liquid is cooled and condensed to the liquid helium temperature in the re-condenser 8 which cools down, and then temporarily stored in the helium container 9. After a certain amount of liquid helium has accumulated, it is transferred to the cryogenic cryostat 2 through the liquid helium transfer tube 10.
[0008]
In this method, the evaporated gas is reliquefied by a small liquefaction facility, but in facilities that consume large amounts, a recovery line is set up inside the facility, and the large liquefaction facility reconstitutes the gas and uses it in a helium container. The means of delivery to equipment is taken.
[0009]
On the other hand, in Non-Patent Document 2, a cryogenic refrigerator is directly connected to a cryostat to keep the internal gas in a cold state and reliquefy it for use in measurement. FIG. 14 is a simplified transcription of FIG. 5 described in Non-Patent Document 2.
[0010]
A refrigerator 106 is connected to an upper part of a cryostat 105 installed in the magnetically shielded room 104. A rotary valve 107 for supplying and discharging compressed gas is connected to the refrigerator 106, and a high-pressure / low-pressure gas pipe is connected by a compressor 108.
[0011]
The cold generation unit 109 of the refrigerator 106 is exposed to a helium gas tank 110 which is a separate room inside the cryostat 105, and cools the helium gas at an extremely low temperature to cool the entire helium gas tank 110. A SQUID sensor 112 is connected to a sensor mounting base 111 connected to a lower part of the helium gas tank 110, and the SQUID is cooled by heat conduction.
[0012]
Reference numeral 113 denotes a space vacuum layer surrounding the helium gas tank 110, which is provided for heat insulation. The vacuum layer contains a heat radiation shield foil not shown in the figure to reduce radiation heat transfer.
[0013]
[Problems to be solved by the invention]
A problem common to the cryogenic cryostat for biomagnetism measurement is that a vacuum heat insulating layer is narrow due to its structure, and sufficient heat shielding cannot be performed. This is due to the measurement purpose that a sufficient SN (signal-to-noise ratio) cannot be obtained unless a sensor placed at an extremely low temperature is brought as close as possible to a weak magnetic signal source for measurement.
[0014]
Therefore, liquid helium used as a cryogen evaporates rapidly, and the replenishment cycle is at most about one week. When the capacity of the cryogenic cryostat is increased, the structural strain is increased, the narrow vacuum heat insulating layer may be crushed, and a thermal short circuit may occur. In order to cover such problems, techniques such as Non-Patent Documents 1 and 2 have been proposed.
[0015]
A general problem of recirculation similar to Non-Patent Document 1 is the mixing of impurity gas.
The gas bag 4 is usually made of rubber, but easily permeates impurity gases such as water, air and carbon dioxide. The cryogenic cryostat itself also has the property of permeating gas because it uses a lot of resin, and if a resin pipe is used for piping, it will also enter from there.
[0016]
When the impurity gas is mixed, it solidifies in the cold part of the recondenser 8 and clogs the piping. Therefore, the impurity gas having a high boiling point and freezing point other than liquid helium to be liquefied is removed by the impurity gas remover 7 using a molecular sieve, activated carbon, a cryotrap or the like.
[0017]
However, the impurity gas remover 7 cannot completely remove the impurity gas, but clogs the re-condenser 8 and also clogs the impurity gas remover 7 itself. Playback operation must be performed. Therefore, even a small helium circulation system requires maintenance as well as large equipment.
[0018]
Further, the equipment scale for circulating helium includes a gas bag and the like, and even if the cryogenic cryostat is small, the equipment related to circulation becomes large, which is disadvantageous in terms of cost and space.
[0019]
Further, the loss during liquid helium transfer is large, and the exhaust must be released without being able to be recovered by a normal gas bag, and the recovery efficiency is reduced accordingly. To improve the recovery efficiency, a gas bag of an unrealistic size must be prepared.
[0020]
On the other hand, there is a method similar to Non-Patent Literature 2 in which direct cooling by a refrigerator is used instead of helium circulation, but it has not been put to practical use due to the following problem of magnetic noise.
(1) Generation of magnetic noise by magnetic regenerator:
In order to generate cold, the antiferromagnetic material and the superconducting material are held inside the expander. However, due to the vibration caused by the pulsation of the gas flowing through the inside, a weak magnetic field and a fluctuation of the magnetic gradient are brought around. This is several tens to several hundreds of pT (picotesla), which is an extremely large interference signal in weak measurements such as biomagnetism of several tens of fT (femtotesla) to several tens of pT.
[0021]
(2) The expander of the cryogenic refrigerator is made of stainless steel (SUS) having low heat conductivity, but has a small but magnetic property. Since vibration is generated by the fluctuation of the inflation gas pressure, the noise becomes magnetic noise as described above.
[0022]
(3) Since the cold part and the normal temperature part form a loop with different metals, a thermoelectromotive force is generated, and a current flows in the loop. This is close to a steady-state current if the temperature is constant, but when vibration is applied, it becomes fluctuating magnetic noise according to the amplitude and disturbs the external magnetic field.
[0023]
From the above, in the field of biomagnetic measurement, it is difficult to directly attach a cryogenic refrigerator to a cryogenic cryostat, and at present the helium circulation system has been proposed as the next best means. However, as described above, there are new problems such as an increase in equipment size and cost.
[0024]
The problems of the conventional technique are shown as representatives of the above two examples. In summary, the cryogenic cryostat for biomagnetism measurement has a large amount of evaporation, and the only countermeasure is to use a gas recovery / reliquefaction cycle or to provide a means for generating refrigeration directly connected to the cryogenic cryostat. However, the former has a large problem of equipment, and the latter has a large problem of noise generated from a refrigerator.
[0025]
However, the root cause is a large heat penetration into the cryogenic cryostat. The cryogenic cryostat uses the sensible heat of evaporation of helium gas to cool the thermal shield.
[0026]
However, the temperature of the thermal shield of the cryogenic cryostat for biomagnetism measurement is high due to a large amount of heat penetrating, which results in high evaporation. Therefore, the first solution to the problem is to provide a cryostat with a low-noise supply means to lower the temperature of the thermal shield.
[0027]
However, even if the temperature of the thermal shield is lowered, the helium gas that has evaporated once will be exhausted, so if cold is not supplied in the cryogenic cryostat and reliquefied, only the cold gas will be exhausted and the amount of evaporation will increase significantly. No significant reduction can be expected. Therefore, the second solution is to re-liquefy without discharging to an external system such as recirculation.
[0028]
A first object of the present invention is to provide a cooling pipe and a cryogenic cryostat using the same, which do not cause the problem of clogging observed in helium circulation.
[0029]
A second object of the present invention is to provide a cooling pipe which is not affected by magnetic noise by a small cooling means and a cryogenic cryostat using the same.
[0030]
A third object of the present invention is to provide a cooling pipe capable of reducing helium consumption with a small facility and a cryogenic cryostat using the same.
[0031]
[Means for Solving the Problems]
The configuration of the present invention for achieving such an object is as follows.
(1) a cryogenic refrigerator attached to an upper end of a cylindrical vacuum vessel, a cold generating part of the cryogenic refrigerator arranged in the vacuum vessel, and one end connected to the cold generating part; A heat transfer tube having a predetermined length, the end of which is exposed to the outside from the lower end of the vacuum vessel to form a cold exposed portion.
[0032]
(2) The cold generating section includes a first-stage cold generating section (high-temperature side) and a second-stage cold generating section (low-temperature side) connected to the cryogenic refrigerator. A heat radiation shield member is provided that is in thermal contact and surrounds at least the first stage and second stage cold generation units, and is coupled to the heat radiation shield member via a first stage cold generation unit and a first heat transfer tube, and A second heat transfer tube having a predetermined length, one end of which is connected to the second-stage cold generating portion inside the heat radiation shield member and the other end of which is exposed to the outside from the lower end of the vacuum vessel to form a cold exposed portion. Item 2. The cooling pipe according to Item 1.
[0033]
(3) The cooling tube according to claim 2, wherein nitrogen is sealed in the first heat transfer tube and helium is sealed in the second heat transfer tube.
[0034]
(4) One end is connected to the first stage cold generating section, and the other end is provided with a third heat transfer pipe extending concentrically around the second heat transfer pipe and extending below the vacuum vessel. The cooling pipe according to claim 1, wherein:
[0035]
(5) The cooling tube according to claim 4, wherein the other end of the third heat transfer tube is exposed to the outside in the middle of the vacuum vessel to form a cold exposed portion.
[0036]
(6) The cooling pipe according to any one of claims 1 to 5, wherein a strain absorbing member is provided at both ends or one end of the heat transfer pipe.
[0037]
(7) The heat transfer tube according to any one of claims 1 to 6, wherein both ends or one end of the heat transfer tube are formed of a high heat conductive material, and the other tube portions are formed of a material having low heat conductivity. Cooling pipe.
[0038]
(8) The cooling tube according to claim 7, wherein a vacuum heat insulating portion is formed around the tube portion made of a material having low thermal conductivity in the heat transfer tube.
[0039]
(9) One or more additional cryogenic refrigerators additionally provided at the upper end of the vacuum vessel to the cryogenic refrigerator, and additional refrigeration generated by coupling the additional cryogenic refrigerator to the inside of the vacuum vessel. The cooling pipe according to any one of claims 1 to 8, further comprising a cooling unit, wherein the additional cold generating unit is connected to the heat radiation shield member or the first cold generating unit.
[0040]
(10) The cooling pipe according to any one of claims 1 to 9 is connected to a vacuum part of a cryogenic cryostat, and the cold discharge part of the cooling pipe is connected to a heat radiation shield plate inside the cryogenic cryostat. A cryogenic cryostat characterized by being brought into contact with a high-temperature portion, or in a cooling pipe having a plurality of cold-exposed portions, with a plurality of heat shield plates corresponding to a plurality of temperatures of a cryogenic cryostat.
[0041]
(11) A heat radiation shield plate, wherein the cooling pipe according to any one of claims 1 to 9 is inserted into an opening of the cryogenic cryostat, and is connected to a vacuum layer near the opening of the cryogenic cryostat. A cryogenic cryostat characterized in that a cold exposed portion of the cooling pipe is arranged so as to be in contact with an isothermal surface generated near a base.
[0042]
(12) The coldest exposed portion of the plurality of cold exposed portions of the cooling pipe according to any one of claims 1 to 9 is in contact with the cryogenic gas phase portion above the liquid reservoir of the cryogenic cryostat. A cryogenic cryostat characterized by being located at
[0043]
(13) The cryogenic cryostat according to any one of claims 10 to 12, further comprising separate cooling pipes respectively inserted into the heat radiation shield plate of the vacuum layer and the upper gas phase of the liquid reservoir.
[0044]
(14) In the cooling pipe or the cryogenic cryostat, a magnetically shielded plate of a high magnetic permeability material is provided so as to surround the cryogenic refrigerator, and a vibration absorbing material is inserted into a weight holding portion of the cooling pipe. A cryogenic cryostat using the cooling pipe or the cooling pipe according to any one of claims 1 to 13.
[0045]
(15) In the cooling pipe or the cryogenic cryostat, the cryogenic refrigerator is taken out of the magnetic shield device having a through-hole, and the weight holding portion of the cooling pipe is installed with a vibration absorbing material provided outside. A cryogenic cryostat using the cooling pipe or the cooling pipe according to any one of claims 1 to 13.
[0046]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a basic structure of a cooling pipe to which the present invention is applied.
[0047]
A structural feature of the present invention is that a cryogenic refrigerator as a cold generating unit and a cold exposed unit requiring cold are separated by a vacuum insulated container, and a predetermined length provided with a heat radiation shield therebetween. To be connected by heat transfer tubes.
[0048]
For the sake of convenience in the following description, cold means absorbing heat, and is used in the opposite sense to heat dissipation and heat flow. Further, a high-pressure gas supply pipe and a gas compressor attached to the refrigerator are omitted.
[0049]
In FIG. 1, reference numeral 11 denotes an expander portion of a refrigerator, which is made of a non-magnetic metal having a low heat conductivity such as SUS, and is hermetically attached to an upper end portion of a SUS cylindrical vacuum vessel. The vacuum vessel comprises an upper vacuum vessel 12 to which the refrigerator is connected and a lower vacuum vessel 17 made of a SUS tube connected and extended below the upper vacuum vessel 12.
[0050]
Reference numeral 13 denotes a cold-generating part made of copper, which is arranged in a hollow part in the upper vacuum vessel 12. The cold generating section 13 is combined with the expander 12 of the refrigerator to form a part of the structure of the refrigerator, and generates an extremely low temperature at this portion.
[0051]
Reference numeral 14 denotes a multilayer heat radiation shield foil forming a heat radiation shield member. The structure is made of a heat radiation shielding foil made by depositing a metal with high heat reflection efficiency such as aluminum on a film of plastic such as mylar etc. with a thin plastic spacer with low thermal conductivity so as not to contact each other. It functions as a high-performance cold insulator that prevents radiant heat transfer from the outside of the foil.
[0052]
Reference numeral 15 denotes a heat transfer tube formed of a heat pipe or the like, one end of which is connected to the cold generating unit 13. The heat transfer tube is accommodated in the lower vacuum vessel 17, and the other end thereof is exposed to the outside from the lower end of the lower vacuum vessel 17 to form a cold exposed portion 18 for transmitting cold to the outside.
[0053]
The function of the heat transfer tube 15 is to transfer cold to the outside, and when the distance is short or the heat transport amount is small, a copper or aluminum block may be used. In the case of a heat pipe, the type of gas to be internally charged is changed according to the temperature of the cold generating unit 13. For example, in order to transmit a nitrogen temperature of 50K to 80K, nitrogen gas is sealed at an appropriate pressure, A gas that can have a liquid-gas phase under gas pressure is sealed.
[0054]
The heat radiation shield foil 14 is connected to the cold generating section 13 and is disposed so as to surround the cold generating section 13 in the upper vacuum vessel 12 and the heat transfer tube 15 in the lower vacuum vessel 17, and is provided from outside the foil. Prevent radiant heat transfer. Reference numeral 16 denotes a spacer made of resin or the like having a low thermal conductivity, which is inserted for the purpose of preventing the lower vacuum vessel 17 and the heat transfer tube 15 from being thermally short-circuited.
[0055]
19 is a vacuum sealing valve attached to the outer peripheral portion of the upper vacuum container 12. Its function is to use only when opening the valve by connecting it to the evacuation device when discharging the internal gas, and it is normally closed and airtight. Reference numeral 20 denotes a sealing plate, which is provided at the lower end of the lower vacuum vessel 17 and penetrates through the heat transfer tube 15 to ensure air-tight joining between the two.
[0056]
The lower vacuum vessel 17 made of a SUS tube is made thinner toward the tip, so that the conduction heat transfer from the cold exposed portion 18 to the upper direction of the lower vacuum vessel 17 is reduced. The sealing plate 20 is thin and has a spring property, and has a spring property for absorbing a distortion caused by a linear expansion difference due to a temperature difference between the lower vacuum vessel 17 and the heat transfer tube 15 and a temperature difference between the upper and lower portions of the lower vacuum vessel 17. Shall have.
[0057]
When a single-stage refrigerator such as a GM refrigerator, a Stirling refrigerator, or a pulse tube refrigerator is used as a refrigerator, the copper cold generator 13 of the refrigerator expander 11 generates about 40 to 80K of cold. Heat exchange with the outside takes place through this part. Helium gas as a working fluid fluctuates in pressure inside, and the piston of the GM refrigerator also moves. Therefore, the expander 11 of the SUS refrigerator generates magnetic noise due to vibration.
[0058]
This is because the SUS has a weak remanence and forms a magnetic noise field in the surrounding space at the vibration frequency. The inside is filled with a SUS mesh or an antiferromagnetic material and functions as a cold storage material, but the residual magnetism in this portion also contributes.
[0059]
On the other hand, during cooling, high-pressure gas flows to the low-pressure side to exchange heat, but since there is a temperature difference between the copper in the cold generating part of the refrigerator and the SUS pipe, a thermocouple is formed and the internal current is reduced. Reflux. Since the internal gas flow pulsates and the temperature also pulsates, electromagnetic noise is generated due to the temporal fluctuation of the gas flow.
[0060]
The above-described magnetic noise is emitted mainly from the upper vacuum container 12 that accommodates the expander 11 and the cold generating unit 13 of the refrigerator, but the magnetic noise has a large distance attenuation and is attenuated by the second to third power of the distance. Therefore, if the cold generating section 13 is extended by another means, it can be used for weak magnetic measurement such as biomagnetic measurement.
[0061]
The heat transfer tube 15 may be formed of a rod having high thermal conductivity such as copper or aluminum when the heat transfer amount to be transferred is small, but a heat transfer distance d (a predetermined length sufficient for attenuation of magnetic noise). In the case where the length of the heat pipe 15 and the interval of 13 to 18) are secured and the amount of heat transported is several watts or more, the temperature of the cold exposure part 18 rises. Used.
[0062]
Heat pipes transfer heat when the upper part is low temperature and the lower part is high temperature, and the fluid moves up and down while changing phase in the gas-liquid phase, and the mobility to move from the lower part to the upper part in the gas phase is particularly high. Therefore, efficient heat transport can be realized.
[0063]
Since the gas phase and the liquid phase must be mixed in the temperature range to be used, for example, in a refrigerator of about 50 K, efficient heat transport can be realized by enclosing nitrogen or the like as a working fluid.
[0064]
At this time, when the temperature is too high, for example, in a cooling process, a liquid phase is not formed, and efficient heat transport is not performed, so a gas having a higher boiling point is sealed or a gas species having a different boiling point is sealed. A plurality of heat pipes may be juxtaposed.
[0065]
If the juxtaposed heat pipes are thermally bonded inside, a heat transfer tube having a wide temperature range can be realized. On the other hand, the cold transfer to the cold exposed portion 18 is hindered by heat radiation or heat transfer from the surroundings of the heat transfer tube 15.
[0066]
For this reason, the periphery of the cold generating part 13 and the periphery of the heat transfer tube 15 are hermetically sealed by the upper vacuum container 12 and the lower vacuum container 17 and vacuum insulated, and the multilayer heat radiation shielding foil 14 prevents heat intrusion. Further, since the SUS tube forming the upper and lower vacuum containers has a low thermal conductivity, heat penetration due to conduction through the container is reduced. The tip of the SUS pipe is made thin to reduce the thermal conductivity.
[0067]
With the above-described cooling pipe structure, the cold can be transmitted to a distant place. Therefore, if it is brought into thermal contact with a cold required part such as a cryogenic cryostat for biomagnetism measurement, it is possible to prevent mixing of magnetic noise and to reduce the amount of refrigerant evaporation.
[0068]
FIG. 2A is a cross-sectional view showing a configuration of another embodiment in which the configuration of FIG. 1 is expanded, and FIG. 2B is a cross-sectional view taken along the line AA ′ of FIG. 1 shows a configuration for transporting the second stage of cold in FIG. 2 (a) and 2 (b), reference numeral 21 denotes a two-stage refrigerator, which is provided with a first-stage cold generating unit 24 connected to a lower part as a part thereof, and further provided with a second-stage cold generating unit 25 at a lower part thereof.
[0069]
Reference numeral 26 denotes a multilayer heat radiation shielding foil, which is in thermal contact with the first-stage cold generating unit 24 and surrounds the first-stage cold generating unit 24, the second-stage cold generating unit 25, and a second heat transfer tube 31 described later.
[0070]
Reference numeral 31 denotes a second heat transfer tube having a predetermined length. One end of the second heat transfer tube is connected to the second-stage cold generating section 25 inside the multilayer heat radiation shielding foil 26, and the other end is exposed to the outside from the lower end of the lower vacuum vessel 32 and is cooled. An exposed portion 34 is formed.
[0071]
Reference numeral 29 denotes a third heat transfer tube, one end of which is connected to the first-stage cold generating section 24 directly or via a heat radiation shield network 30 described later. The heat radiation shield net 30 extends concentrically around the second heat transfer tube 31 to the lower portion of the lower vacuum vessel 32.
[0072]
In such a two-stage configuration, a low temperature of, for example, 50K is achieved in the first-stage cold generation unit 24, and an extremely low temperature of 4K is achieved in the second-stage cold generation unit 25, but may be two or more stages. In general, when the temperature is extremely low at about 4K, the amount of heat emission is extremely small. Therefore, the radiation shield must be stricter than the cold transport of the single-stage refrigerator shown in FIG.
[0073]
In the first-stage cold generating section 24, the inside is thermally shielded by a heat radiation shield network 30 which is in thermal contact with and insulates and insulates a thin wire such as copper. Further, a first heat transfer tube 27 formed of a metal rod such as copper or a heat pipe is connected to transmit cold downward.
[0074]
Reference numeral 28 denotes a relay plate, which is a structure having a high thermal conductivity that transmits the cold of the first-stage cold generating section 24 to the third heat transfer pipe 29 below. This may be metal or ceramic, but it may be omitted and the first heat transfer tube 27 and the third heat transfer tube 29 may be integrated.
[0075]
The outer structures 27, 28, and 29 in these vacuum vessels are not in contact with each other because they need to be thermally separated from the inner structure 31. A second heat transfer tube 31 is connected to the second-stage cold generating section 25, and discharges cold at a cold exposing section 34 at a lower end portion.
[0076]
The heat radiation shield net 30 contacts the third heat transfer tube 29 and efficiently transports the intruding radiation heat to the first-stage cold generating unit 24, thereby preventing the radiation heat from entering the internal second heat transfer tube 31. I do.
[0077]
The internal working fluid of the second heat transfer tube 31 connected to the second-stage cold generating section 25 is a material in which a substance which generates a liquid-gas phase state at an extremely low temperature such as helium or hydrogen depending on the temperature is enclosed. I do.
[0078]
As described above, since the heat radiation shield net is connected to the first stage cold generating part 24 of the two-stage refrigerator and the heat radiation shield net 30 is provided at the lower part via the second heat transfer pipe 29, the efficiency is improved. Then, the temperature of the heat radiation shield net 30 is lowered.
[0079]
For this reason, heat intrusion into the internal space from the heat radiation shield net 30 is suppressed, and the temperature rise of the cryogenic part with a small amount of heat discharge can be prevented, and the heat connected to the second-stage cold generating part 25 can be prevented. For example, 4K of cold can be generated from the cold exposed portion 34 of the second heat transfer tube 31 such as a pipe.
[0080]
In a multi-stage refrigerator having two or more stages, a structure for further preventing heat intrusion may be provided by forming a multilayer structure of 30 heat radiation shield networks or the like. Further, here, the two-stage refrigerator has two heat transport sections connected to the respective cold generating sections, but a plurality of heat shield structures may be provided for each of the cold generating sections.
[0081]
This is the same for FIG. For example, in FIG. 1, a single heat-generating unit 13 is connected to a heat shield network (which has a small amount of heat transfer) without a heat transfer tube in order to lower the heat conductivity, and is provided for use as a heat shield. By adopting a structure in which the heat is transported in a cold manner by the heat transfer tube, loss on the way is reduced.
[0082]
FIG. 3 is a simplified cross-sectional view showing a configuration of an embodiment in which a heat transfer tube 37 and a heat radiation shield net 28 are directly connected to a cold generating section 36 connected to an expander 35 in the case of the single-stage refrigerator described in FIG. The vacuum vessel and the multilayer heat radiation shielding foil are omitted.
[0083]
In this embodiment, the configuration of the radiant heat shield network is characterized by a mesh metal such as copper having a relatively low thermal conductivity compared to a heat transfer tube such as a heat pipe, which is connected to the cold generating section. The heat shield can be configured without excessively applying a heat load to the heat transfer tube, and heat intrusion into the heat transfer tube can be reduced.
[0084]
In the embodiment shown in FIG. 4 (a), the heat shield of the cryogenic cold transmission unit from the second stage cold generation unit in the two-stage refrigerator is not the heat shield by the heat radiation shield network, but the first stage cold generation. It is realized by a hollow cylindrical heat pipe connected to the section, and this heat pipe combines cold conduction and heat shield.
[0085]
A first heat transfer tube 42 is connected to the first-stage cold generating section 40, and a heat radiation shield network 43 of 43 is attached so as to be in contact with and surround the first heat-transfer tube 42. Shielded in the cold. The heat radiation shield network 43 may be a cylindrical metal plate such as copper.
[0086]
FIG. 4B is a cross-sectional view taken along the line AA ′ of FIG. 4A, and includes a hollow cylindrical heat pipe surrounding the second heat transfer tube 44 connected to the second-stage cold generating section 41. Three heat transfer tubes 46 are in thermal contact with the relay plate 45. The heat pipe structure of the third heat transfer tube 46 includes a gas sealing portion 50 surrounded by an inner tube 49 and an outer tube 48 as shown in the cross-sectional view of FIG. ing.
[0087]
With such a configuration, the volume of the gas sealing portion 50 can be increased in the third heat transfer tube 46, so that the flow rate of the working gas increases and the amount of cold transport can be increased. Since the heat inflow due to external radiation is proportional to the square of the length of the pipe, it is effective when the length of the transport pipeline is long.
[0088]
If the heat transfer speed is low, the temperature of the shield rises toward the end, so that the temperature of the cold exposed part 47 eventually rises, but this is effective in preventing this. In addition, structural stability and rigidity are increased as compared with a mesh or the like, so that there is an advantage that accidents such as a thermal short can be prevented.
[0089]
5A and 5B show the heat transfer tube 15 shown in FIG. 1, the second heat transfer tube 31 shown in FIG. 2, the heat transfer tube 37 shown in FIG. 3, and the second heat transfer tube 44 shown in FIG. It is sectional drawing which shows the specific example of a structure.
FIG. 5 (a) is not a uniform hollow pipe but an end made of a different material. The heat transfer tube 51 is a thin hollow tube made of SUS having a low thermal conductivity, and both ends are sealed with metal caps 52a and 52b made of copper or the like having a high thermal conductivity. Etc. are sealed at an appropriate pressure.
[0090]
FIG. 5B shows an example in which the heat transfer tube 54 has a double structure of a thin SUS hollow pipe, and a vacuum heat insulating portion 57 is formed around the heat transfer tube. Both ends are sealed with metal caps 56a and 56b made of copper or the like having a high thermal conductivity, and a gas such as nitrogen or helium is sealed at an appropriate pressure in an internal gas sealing portion 55.
[0091]
In this case, the gas may be sealed with a tube having a high thermal conductivity such as a copper tube as the heat transfer tube. However, by forming a long portion with a material having a low thermal conductivity such as a SUS tube, the heat radiation shielding foil or the like can be formed. In addition to the above, when the contact of the refrigerator occurs, there is an effect of reducing conduction heat intrusion and preventing a backflow of cold when the refrigerator is turned off.
[0092]
Heat pipes generally transport heat or cold under conditions where the upper part is cold and the lower part is hot, but when the operation of the refrigerator is stopped, the upper part becomes hot and the movement of the working fluid of the heat pipe stops. .
[0093]
However, the heat transfer through the tube wall of the heat transfer tube (as opposed to the internal working fluid) is irrelevant to the direction, so the lower refrigeration will rise. As shown in FIG. 5A, a material having low thermal conductivity such as SUS is effective for the heat transfer tube 51 in order to reduce the conductive heat transfer.
[0094]
When the internal fluid is nitrogen or the like, resin or the like can be used. On the other hand, since the upper and lower ends absorb and dissipate cold, the mobility of heat conduction needs to be high, and the sealing of copper caps 52a and 52b having high heat conductivity such as copper is effective.
[0095]
In FIG. 5B, by providing the vacuum heat insulating portion 57 in the SUS tube portion of the heat transfer tube 54, it is possible to improve the performance of reducing the conductive heat penetration in the lateral direction, and at the same time, to increase the rigidity due to the double structure. .
[0096]
Also, the same effect can be obtained in reducing the thermal conductivity by replacing the vacuum heat insulating portion 57 with glass, resin, a heat insulating foam, or a metal spacer having a low thermal conductivity.
As described above, according to the configuration of FIG. 5, it is possible to reduce a loss due to heat intrusion from the middle of the conduction path.
[0097]
The embodiment of FIG. 6 shows another embodiment of the cooling pipe, and is a diagram for explaining means for connecting the heat transfer pipe by a leaf spring together with vibration insulation and electric insulation. FIG. 6 (a) explains the thermoelectromotive force generated in the cooling pipe placed at a very low temperature. The lower part has a very low temperature and the upper part has a room temperature.
[0098]
The upper vacuum vessel to which the expander 60 of the refrigerator is attached is made of SUS, the lower vacuum vessel 58 is also made of SUS, the cold generating section 59 and the cold exposed section 57 are made of copper. The thermoelectromotive force generation point 62 of the cold generation part 59 has substantially the same temperature.
[0099]
In addition, since dissimilar metals are connected in the directions of generating electromotive forces in opposite directions, they should in principle cancel each other out and no internal current should occur. However, since the respective structural members are not completely made of the same material, the unbalanced current 63 flows from the upper part to the lower part in the path indicated by the arrow. This is emitted as a magnetic field to the outside and becomes electromagnetic noise.
[0100]
FIG. 6B shows a structure in which an insulating material such as an insulating resin or insulating rubber is provided in the middle of an electric path for electric insulation. 64a is an insulating material provided at a connecting portion between the expander 60 of the refrigerator and the upper vacuum container, 64b is an insulating material provided at a connecting portion between the upper vacuum container and the lower vacuum container 58, and 64c is provided at the cold exposed portion 57. It is an insulating material. The insulating material may be provided at any one place, or a plurality of these different insertion positions may be used in combination.
[0101]
FIG. 6C shows another configuration of electrical insulation, in which a flange portion is formed in the middle of the lower vacuum vessel 58 and an insulating material (for example, rubber) 64d is sandwiched therebetween.
[0102]
As described above, according to the configuration of FIG. 6, the current path of the circulating current is cut off by the insulating material of the insulating resin or the insulating rubber, so that the time noise due to the thermoelectromotive force is not emitted to the outside.
[0103]
Also, by providing a leaf spring 65 inside or by providing a resilient insulating material 64 such as rubber, a spring property can be provided between the internal structure and the external structure. Can be prevented from being damaged at the time of cooling due to the difference in the coefficient of linear expansion.
[0104]
FIG. 7 is a cross-sectional view showing a configuration of another embodiment for providing a plurality of cold exposure portions in a cooling pipe. In this configuration, the heat is brought into thermal contact with the third heat transfer tube 66 described with reference to FIG. 2 and the cold is released to the outside from the cold exposed portion 67 formed of a high conductivity material such as copper. On the other hand, the cold having a lower temperature is led out from the cold exposed portion 68 of the second heat transfer tube.
[0105]
If the configuration of FIG. 7 is extended, since a plurality of heat transfer tubes can output cold at different temperatures, the method of using the cryostat in cold can be expanded. For example, as will be described later with reference to FIGS. 9 and 10, the cold-side exposed portion 67 on the high-temperature side is supplied to the radiation shield, the cold-side exposed portion 68 on the low-temperature side is connected to a lower-temperature radiation shield, or the gas phase temperature in the cryostat is reduced. It can be used for cooling or exposure to the gas phase to liquefy.
[0106]
FIG. 8 is a cross-sectional view showing a configuration of an embodiment in which two refrigerators as cold supply means are connected. In this configuration, the expander 70 of the single-stage refrigerator is installed on the expanded upper vacuum vessel 71 in addition to the expander 69 of the two-stage refrigerator. 72 is a vacuum sealing valve. The configuration of the two-stage refrigerator is the same as that of FIG. 2, and includes a first-stage cold generation unit 73, a second-stage cold generation unit 74, a third heat transfer tube 75, a cold exposure unit 76, and a heat radiation shield net 78.
[0107]
Numeral 79 denotes a cold generating unit connected to the expander 70 of the single-stage refrigerator, and is thermally connected to the third heat transfer tube 75 via the first heat transfer tube 80 and the relay plate 81. The relay plate 81 is formed of a high heat conductive material, and may be a metal such as copper or a heat pipe.
[0108]
In the vicinity of the lower end of the third heat transfer tube 75 connected to the first heat transfer tube 80, a cold exposure portion similar to the cold exposure portion 67 shown in FIG. 7 may be formed to take out the cold outside. Reference numeral 82 denotes a multilayer heat radiation shielding foil disposed around the cold generating section 79.
[0109]
In the configuration of FIG. 7, since the heat load of the first-stage cold generating section is used for heat shield and external cold supply, when the heat load is larger than the cold generating capacity, the temperature of the second-stage cold generating section increases. There is a problem.
[0110]
In the embodiment structure of FIG. 8, the third heat transfer tube 75 is not connected to the first-stage cold generating section 73 but is connected to the cold generating section 79, so that the first-stage cold generating section 73 of the two-stage refrigerator is provided. A large heat load is reduced, and the temperature of the second-stage cold generating section 74 does not rise.
[0111]
On the other hand, when cold is supplied outside the heat shield or the cold exposing portion 76, the cold source is the cold generating portion 79, so that the cold generating portion 79 does not affect the cold generating portion 73 of the two-stage refrigerator. A sufficient cooling function can be performed. In this embodiment, two refrigerators having different numbers of stages are shown. However, two refrigerators having the same number of stages may be used. If this configuration is extended, more than two refrigerators can be added. It is.
[0112]
FIG. 9 is a cross-sectional configuration diagram showing an embodiment of the cryogenic cryostat to which the cooling pipe of the present invention described in FIGS. 1 to 8 is connected, and also shows a driving unit of a refrigerator. To the expander 86 of the refrigerator, gas is switched by a valve motor 89 via a gas pipe 100 via a high-pressure pipe 91 and a low-pressure pipe 92 of a compressor 90. The upper vacuum vessel 87 is fixedly installed above the magnetically shielded room 83 via a vibration isolating pedestal 88.
[0113]
The lower vacuum vessel 93 penetrates the wall of the magnetically shielded room 83 and is further attached to the cryogenic cryostat 84 in the magnetically shielded room by penetrating the heat insulating foam 94 at the neck. The upper cold exposure part 95 is in thermal contact with an isothermal surface formed near the upper or lower part of the thermal anchor 98.
[0114]
The lower cold generating section 96 is connected to a cold diverging section 97 exposed to the liquid reservoir gas phase section having the liquid helium 83 at the bottom. The cold diverging part 97 is formed of a member that easily radiates cold, such as a copper mesh.
[0115]
In this embodiment, a method of cold exposure in the gas phase portion of the cryogenic cryostat has been described. However, the configuration for connecting the cold to the thermal anchor 88 may be one or more. Further, the configuration may be such that only the lower cold exposure portion 96 is provided without providing the upper cold exposure portion 95.
[0116]
Further, in this embodiment, the cold can be transmitted to the heat radiation shield net 99 by providing the upper cold exposing portion 95 near the thermal anchor 98. Therefore, the transfer of the radiant heat to the liquid tank in which the liquid helium 85 is stored is reduced, and the helium evaporation amount is reduced. Further, since the cooling is performed by the cold diverging unit 97, the temperature of the gas phase at the upper part of the liquid tank is lowered, so that the evaporation rate is reduced.
[0117]
When the cold diverging section 97 is sufficiently cooled, liquefaction starts in the liquid phase of the liquid reservoir of the cryostat, so that the amount of evaporation can be further reduced. On the other hand, since the expander 86 of the refrigerator is provided outside the magnetic shield room 83, acoustic vibration and magnetic noise do not adversely affect the inside of the magnetic shield room 83. In addition, since the vibration is installed on the vibration isolating pedestal 88, the influence of the propagation of the vibration into the inside of the magnetic shield room 83 is small.
[0118]
FIG. 10 is a sectional view showing still another embodiment of a cryogenic cryostat using the cooling pipe of the present invention.
The embodiment shown in FIG. 10 is a configuration example in which an expander 86 of a refrigerator is surrounded by a magnetic shield box 103 containing a soundproofing and vibration-proof material 102 and installed in a magnetic shield room 83. Here, a lower vacuum container 93 may be inserted into the neck of the cryogenic cryostat 84 as shown in FIG.
[0119]
That is, the cold exposing portion 101 below the lower vacuum vessel 93 is connected by a vacuum layer of the upper thermal anchor 98, and has a structure for efficiently transmitting the cold to the heat radiation shielding net 99.
[0120]
In this embodiment, since it is directly connected to the upper thermal anchor 98 in the vacuum layer, the thermal resistance is small and the efficiency is high as compared with the cold transport via the gas phase or the cryostat structural material. Therefore, the shield temperature can be lowered, and the helium evaporation amount can be reduced. Although an example of connection to the upper thermal anchor is shown here, the same effect can be obtained by connecting to the lower thermal anchor.
[0121]
Further, even if two cold-exposed portions having different temperatures are connected to two thermal anchors having different temperatures using a two-stage refrigerator or the like, the shield temperature can be lowered, and the helium evaporation amount is further reduced. be able to. On the other hand, since the connection is made using the magnetic shield box 103 in the magnetic shield room 83, the length of the lower vacuum vessel 93 can be short.
[0122]
In general, since heat penetration increases in proportion to the square of the length of the heat transfer tube, the amount of heat to be exhausted by the refrigerator can be reduced, and the temperature of the cold generation part decreases. As a result, it is effective in reducing the helium evaporation.
[0123]
In order to reduce the amount of cryogen (helium) evaporated in the cryogenic cryostat of the SQUID magnetometer for biomagnetism measurement, the auxiliary cooling and re-liquefaction means of the cryogenic cryostat, which has a relatively weak heat shield, is provided. The purpose was to provide it without the effects of magnetic noise. However, it is clear that the present invention is also useful for other applications in which the influence of vibration and refrigerator noise should be avoided, and the following development is expected.
[0124]
FIG. 11 is a configuration diagram showing an example in which the cooling pipe of the present invention is applied to a superconducting magnet for MRI, and is simplified and shown. Reference numeral 201 denotes an outer shell that houses a magnet and supports the whole, and is made of a non-magnetic material.
[0125]
The superconducting magnet 202 is wound around a gap in the outer shell, and the gap is filled with liquid helium. The periphery is surrounded by a vacuum heat insulating layer 200. A heat radiation shield 204 is incorporated in the vacuum heat insulating layer 200 to prevent heat from entering the superconducting magnet from the outside. 205 is a penetration part.
[0126]
In the case of radiation shielding with liquid nitrogen, a multi-layer structure is provided in which a vacuum layer is provided outside the superconducting magnet 202 filled with liquid helium, and a liquid nitrogen tank is further provided outside. Reference numeral 203 denotes the cooling pipe of the present invention, which is connected to the heat radiation shield 204, but may be connected to a liquid nitrogen tank. When connecting a cooling pipe having two or more cold exposure parts, it may be connected to a plurality of heat radiation shields, respectively, or one may be exposed to a liquid helium tank.
[0127]
According to such a configuration, since the cooling pipe 203 can keep a distance from the magnet main body, it is possible to take soundproofing measures for the noise generating unit. In addition to preventing the noise caused by the pressure vibration of the refrigerator, the evaporation amount can be reduced regardless of the model by simply inserting a cooling pipe into the helium injection port for magnets that do not have a structure to connect the existing refrigerator. There is an advantage that you can plan.
[0128]
Further, even in a device using liquid nitrogen as a shield, it is effective to reduce the amount of evaporation, similarly to a cryostat for biomagnetism measurement.
[0129]
FIG. 12 is a connection diagram showing an application example of the cooling pipe of the present invention to an electron beam exposure apparatus as an application example to a general vacuum apparatus, and is an example of use as a cryopump for obtaining a high vacuum. .
[0130]
Reference numeral 206 denotes an anti-vibration table for shutting off ambient vibration, 207 denotes a stepper for moving a point to be exposed, and 208 denotes an electron beam column having a built-in electron beam source for applying an electron beam to a target. The inside is hollow and in a vacuum state.
[0131]
Reference numeral 209 denotes a vacuum evacuation pipe for maintaining a vacuum inside the electron beam column, and the cold exposure part 210 of the cooling pipe 211 of the present invention is in contact with its cooling part. It is. Reference numeral 211 denotes a shield box, which has a built-in refrigerator and shields the magnetic noise of the refrigerator so as not to leak outside.
[0132]
An electron beam column such as an electron microscope and an electron beam exposure apparatus requires a high vacuum, but at the same time, extremely dislikes vibration and magnetic noise. These use the effect of enlarging and reducing the image by taking advantage of the straightness of electrons flying in a vacuum, but magnetic noise and vibration of equipment cause image blurring, which significantly impairs performance. .
[0133]
Cryogenic refrigerators are often used in high-vacuum equipment for semiconductors as cryopumps for freezing and adsorbing gas molecules. The structure that can be connected at a distance by the cooling pipe of the present invention has a distance attenuation effect of magnetic noise and vibration absorption / It works advantageously in terms of vibration isolation.
[0134]
【The invention's effect】
As is clear from the above description, according to the present invention, the following effects can be expected.
(1) It is possible to easily realize a cooling pipe and a cryogenic cryostat using the same without causing a blockage problem observed in helium circulation.
(2) It is possible to easily realize a cooling pipe and a cryogenic cryostat using the cooling pipe which are not affected by magnetic noise by a small cooling means.
(3) A cooling pipe capable of reducing helium consumption with a small facility and a cryogenic cryostat using the same can be easily realized.
[0135]
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram showing a basic configuration of a cooling pipe to which the present invention is applied.
FIG. 2 is a sectional view showing another embodiment of the present invention.
FIG. 3 is a cross-sectional configuration diagram of a main part showing still another embodiment of the present invention.
FIG. 4 is a sectional configuration view of a main part showing still another embodiment of the present invention.
FIG. 5 is a sectional view showing a configuration example of a heat transfer tube of the present invention.
FIG. 6 is a sectional configuration view of a main part showing still another embodiment of the present invention.
FIG. 7 is a cross-sectional configuration diagram showing still another embodiment of the present invention.
FIG. 8 is a sectional configuration view showing still another embodiment of the present invention.
FIG. 9 is a sectional configuration diagram showing an embodiment of a cryogenic cryostat using the cooling pipe of the present invention.
FIG. 10 is a cross-sectional configuration diagram showing still another embodiment of a cryogenic cryostat using the cooling pipe of the present invention.
FIG. 11 is a connection diagram showing an application example of the cooling pipe of the present invention to a superconducting magnet for MRI.
FIG. 12 is a connection diagram showing an application example of the cooling pipe of the present invention to an electron beam exposure apparatus.
FIG. 13 is a configuration diagram of a helium circulation system showing a conventional technique described in Non-Patent Document 1.
FIG. 14 is a cryostat connection configuration diagram of a cryogenic refrigerator showing a conventional technique described in Non-Patent Document 2.
[Explanation of symbols]
11 Expander
12 Upper vacuum container
13 Cold generating part
14 Multilayer heat radiation shielding foil
15 Heat transfer tubes
16 Spacer
17 Lower vacuum vessel
18 Cold exposure
19 Vacuum sealing valve
20 sealing plate

Claims (15)

A refrigerator attached to the upper end of the cylindrical vacuum vessel, a cold generating section of the refrigerator arranged in the vacuum vessel, one end connected to the cold generating section, and the other end connected to the lower end of the vacuum vessel A heat transfer tube having a predetermined length that is further exposed to the outside to form a cold exposed portion. The cold generating section includes a first-stage cold generating section (high-temperature side) and a second-stage cold generating section (low-temperature side) connected to the refrigerator, and is in thermal contact with the first-stage cold generating section and at least. A heat radiation shield member surrounding the first and second stage cold generating portions is provided. The heat radiation shield member is coupled to the first and second stage cold generating portion via a first heat transfer tube, and the inside of the heat radiation shield member is provided. 2. The cooling system according to claim 1, further comprising a second heat transfer tube having a predetermined length, one end of which is connected to the second-stage cold generating section and the other end of which is exposed to the outside from the lower end of the vacuum vessel to form a cold exposed section. tube. The cooling pipe according to claim 2, wherein nitrogen is sealed in the first heat transfer pipe, and helium is sealed in the second heat transfer pipe. 3. A third heat transfer pipe extending from the lower part of the vacuum vessel, one end of which is connected to the first stage cold generating part, and the other end of which concentrically surrounds the second heat transfer pipe. 4. The cooling pipe according to any one of 1 to 3. 5. The cooling pipe according to claim 4, wherein the other end of the third heat transfer pipe is exposed to the outside in the middle of the vacuum vessel to form a cold exposure part. The cooling pipe according to any one of claims 1 to 5, wherein a strain absorbing member is provided on both ends or one end of the heat transfer pipe. The cooling pipe according to any one of claims 1 to 6, wherein both ends or one end of the heat transfer pipe are made of a high heat conductive material, and the other pipes are made of a material having low heat conductivity. . 8. The cooling pipe according to claim 7, wherein a vacuum heat insulating section is formed around the pipe section made of a material having low thermal conductivity in the heat transfer pipe. An additional refrigeration unit additionally provided at the upper end of the vacuum vessel, which is additionally provided to the refrigerator; and an additional refrigeration generator coupled with the additional refrigeration unit in the vacuum vessel. The cooling pipe according to any one of claims 1 to 8, wherein a generator is connected to the heat radiation shield member or the first cold generator. The cooling pipe according to any one of claims 1 to 9 is connected to a vacuum part of a cryogenic cryostat, and the cold discharge part of the cooling pipe is connected to a high temperature part of a heat radiation shield plate inside the cryogenic cryostat. A cryogenic cryostat, wherein the cryogenic cryostat is brought into contact with, or in contact with, a plurality of heat shield plates at a plurality of temperatures corresponding to the cryogenic cryostat in a cooling pipe having a plurality of cold exposed portions. The cooling pipe according to any one of claims 1 to 9 is inserted into an opening of the cryogenic cryostat, and near a root of a heat radiation shield plate connected to a vacuum layer near the opening of the cryogenic cryostat. A cryogenic cryostat characterized in that the cold-exposed portion of the cooling pipe is arranged so as to be in contact with the generated isothermal surface. The coldest exposed part of the plurality of cold exposed parts of the cooling pipe according to any one of claims 1 to 9 is positioned so as to be in contact with the very low temperature gaseous phase part above the liquid reservoir of the cryogenic cryostat. A cryogenic cryostat characterized by the following. The cryogenic cryostat according to any one of claims 10 to 12, further comprising separate cooling pipes respectively inserted into the heat radiation shield plate and the upper gas phase of the liquid reservoir of the vacuum layer. 2. The cooling pipe or the cryogenic cryostat, wherein a magnetically shielded plate of a high magnetic permeability material is provided so as to surround the refrigerator, and a vibration absorbing material is inserted into a weight holding portion of the cooling pipe. 14. A cooling tube according to any one of claims 13 to 13 or a cryogenic cryostat using the same. In the cooling pipe or the cryogenic cryostat, the refrigerator is taken out from a magnetic shield device having a through-hole, and a weight holding portion of the cooling pipe is installed with a vibration absorbing material provided outside. A cryogenic cryostat using the cooling pipe according to any one of claims 1 to 13.

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