JP2003214764A - High performance helium gas refining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lengthen the operation time by solidifying impurities in helium gas and removing it, and simultaneously heating a solidified part to be liquefied, and quickly re-starting the refrigerating operation. <P>SOLUTION: Helium gas gasified in a liquid helium bath is introduced into a capillary 22 of the refining device 10, and cooled in the course of passing through an inner pipe 18, and circulated through a copper pipe 13 bypassing a fin 14. When impurities such as nitrogen and oxygen are mixed in the gasified helium gas, it is frozen in the course of meandering the fin 14. When the pipe is blocked by freezing, an upper pipe 11 is heated by a heater 16 to liquefy the gas. The liquid is transmitted through the fin 14 and a flange part 20 to drop in a liquid reservoir 21 and stored there. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance helium gas purifier for refrigerators, and more particularly to a helium gas purifier suitable for a reliquefaction device for liquid helium. More specifically, in a liquid helium storage tank for maintaining the magnetoencephalograph at a cryogenic temperature, it can be applied to a circulation type liquid helium reliquefaction device in which the helium gas vaporized from the tank can be recycled to the liquid helium storage tank. A high-performance helium gas purifier that can efficiently remove impurities mixed in helium gas.

[0002]

2. Description of the Related Art Development of a brain magnetic measurement system for detecting a magnetic field emitted from a human brain is in progress. This system uses SQUID (superconducting quantum interferometer) that can measure brain activity non-invasively with high spatio-temporal resolution, and this SQUID is immersed in liquid helium stored in a thermally insulated tank. , Used in a cooled state. In the conventional liquid helium tank used in the above system, the helium gas evaporated from the tank is open to the atmosphere in most cases. However, in this case, a large amount of expensive helium, which costs about 1200 yen per liter, is wastefully consumed, which is economically and resource problematic. For this reason, in a place where a large amount of helium is used, a system for collecting evaporative gas and liquefying it at a low temperature center is operating. In a small system, the gas is collected in a gas bag, transported to a liquefaction system, and then reliquefied. However, it is impossible to completely recover liquid helium, and impurities are mixed in the gas during gas recovery,
There is a problem that gas is polluted. In particular, it is inevitable that nitrogen and oxygen are mixed into the recovered helium gas as impurities for some reason, which is a major obstacle in promoting the reuse of the recovered helium gas.

Since all of these impurities have higher liquefaction and solidification temperatures than helium gas, when helium gas containing impurities is used, the impurities are liquefied in the low temperature portion of the process, and further frozen and solidified. The flow path is blocked, and during a long-term continuous operation, the flow of helium gas is stopped, which impedes the circulation of helium gas. For this reason, as a removal means for removing impurities mixed in the helium gas, conventionally, a helium gas purifier has been proposed as a type to be placed inside the freezing chamber and a type to be placed outside the chamber. The latter adopts a method of cooling helium gas with another refrigerator or liquid nitrogen, but in that case, preparing another refrigerator has major drawbacks such as price and size. . Also, the method of cooling with liquid nitrogen is inexpensive and simple,
Since liquid nitrogen has to be refilled, it is troublesome.

From the above background, recently, a recirculation system has been proposed in which the entire amount of helium gas vaporized in a liquid helium storage tank is recovered, impurities in the helium gas are removed in the system, and then recondensation is performed to liquefy. There is. An example of this liquid helium recirculation system will be described with reference to FIG.
In the figure, 101 is a liquid helium storage tank containing a magnetoencephalograph, 102 is a dry pump for recovering the helium gas vaporized in the storage tank 101, and 103 is a dryer for removing water mixed in the helium gas. 104 is a flow rate control valve, 105 is a purifier for removing impurities mixed in helium gas, 106 is an auxiliary refrigerator, 107 is a first heat exchanger of the auxiliary refrigerator 106, and 108 is a recondensing refrigerator. 1
Reference numeral 09 is a recondensing heat exchanger of the recondensing refrigerator 108. After vaporizing and raising the temperature in the liquid helium storage tank 101, about 300
The helium gas which has become K is sucked by the dry pump 102, dried by the drier 103, and further the impurities in the helium gas are removed by the purifier 105. The helium gas from which the impurities have been removed is cooled by the auxiliary refrigerator 106 to a cryogenic helium gas having a temperature of about 40 K, and the recondensing refrigerator 1 is further cooled.
The re-condensation heat exchanger 109 of No. 08 liquefies liquid helium at a temperature of 4K, and the liquid helium is supplied from here to the liquid helium storage tank via the transfer line 110.

Now, the structure of the conventional purifier 105 used in the liquid helium recirculation system will be described with reference to the drawings. FIG. 5 is a sectional view of the purifier. In the drawing, 120 is an outer wall, 121 is a wall of a freezing chamber, a space between both walls is formed as a vacuum layer B for maintaining heat insulation, and a freezing chamber R is an insulating chamber surrounded by the vacuum layer B. Has been formed.
A refining body 122 is arranged in the freezing chamber R, and the refining body 122 is configured as a double tubular body having a copper pipe 123 on the outer periphery and a stainless pipe 124 on the inner periphery. The 123 and the stainless steel pipe 124 are communicated with the vacuum layer B as shown in the drawing, and the copper pipe 123 and the stainless steel pipe 124 are thermally insulated. Also the main body 122
The lower part of the copper tube 123 forming the
It is mounted on one side in a sealed state. Stainless tube 12
The lower part of 4 is arranged so as to project into the vacuum layer B formed between the outer wall 120 and the wall 121 of the freezing chamber R, and a helium gas of about 300 K is placed at the lower end of the stainless tube 124.
The thin tube 126 to be introduced into the inside is connected, and this thin tube 1
As shown in FIG. 4, a dryer 103 is connected to 26. In addition, fins 125 for removing (solidifying) impurities in the helium gas are attached to the upper part of the stainless steel pipe 124 so as to project from the inner wall of the stainless steel pipe 124 into the flow path, and further, are mounted on the upper end of the stainless steel pipe 124. A pipe 127 for supplying helium gas to the auxiliary refrigerator 106 is connected. The pipe 127 and the copper pipe 123 are joined in a sealed state.

By the way, in the purifier shown in FIG.
When the helium gas of K flows into the stainless steel pipe 124 of the purifier body through the thin pipe 126, the stainless steel pipe 124
The same gas flows inside the stainless steel pipe 124 upward in the figure, and the gas temperature is lowered to about 40 K by the upper portion of the stainless steel pipe 124 cooled by the temperature of about 40 K in the freezing chamber. In this process, impurities that solidify at a temperature higher than about 40 K when the helium gas passes through the fin 125 are solidified and removed by the fin cooled to about 40 K. The helium gas from which impurities have been removed is supplied to the auxiliary refrigerator 106. In this refiner, the height of the refiner body (height of the stainless steel pipe 124) h is set to a certain level in order to reduce the thermal gradient, and the inner diameter 2r of the stainless steel pipe 124 is as small as possible. The diameter of the thin tube 126 is made small as much as possible. With this configuration, in this purifier, the heat of invasion from the 300 K helium gas into the freezing chamber R maintaining the temperature of about 40 K is suppressed as small as possible.

The process of purifying helium gas using the purifier S will be described. The helium gas having a temperature of about 300K vaporized in the liquid helium storage tank is placed in the freezing chamber R at a temperature of about 40K. It is introduced into the thin tube 126 of the purifier body 121. Then, the helium gas flowing from the thin tube 126 into the stainless steel tube 124 flows toward the upper portion of the stainless steel tube, which is cooled to about 40K by the cold air in the freezing chamber, and is cooled while meandering the fins 125 in this process. Then, when the helium gas passes through the fins 125, impurities such as nitrogen and oxygen mixed in the helium gas are removed. That is, since the impurities nitrogen and oxygen solidify (freeze) at temperatures of 63 and 54K, respectively, the impurities are solidified on the fins while the helium gas meanders between the fins 125 cooled to about 40K. Helium gas is purified.

[0008]

However, although the above-mentioned conventional purifier can be expected to have an extremely excellent effect as compared with the method of cooling with liquid nitrogen, it has the following problems. That is, since the inner diameter 2r of the stainless steel pipe 124 is made as small as possible in order to reduce the heat invasion, the volume of the impurity solidification portion composed of the fins 125 arranged on the upper part of the stainless steel pipe is inevitably small.
When the refining period is long, the solidified impurity substance accumulates on the fins 125 and further on the inlet portion of the pipe 127, which causes a problem that the flow path is blocked. Therefore, there is an inconvenience that the operation must be stopped while removing the solidified impurities. For this reason, it is extremely difficult to efficiently remove a large amount of contaminants with the helium gas purifier of the type described above, which is placed in the freezing chamber, while suppressing heat intrusion into the freezing chamber. However, the current situation is that only continuous operation for about two weeks is possible. In addition, no refiner with good performance can be found at present.

[0009]

Therefore, the present invention provides a helium gas purifier that can reliably and easily remove impurities in a gas without increasing heat intrusion from the helium gas purifier into the refrigeration chamber. By providing it, it aims at solving the said problem. In the present invention, the diameter of the impurity solidification portion of the purifier is made larger than the diameter of the stainless steel tube, thereby increasing the contact area between the fins arranged in the solidification portion and the helium gas, and promoting solidification of the impurities.
Further, by rapidly heating the impurities solidified in the impurity solidifying section, the solidified impurities can be liquefied and easily removed. By doing so, the solidified impurities can be removed in a short time, the refrigerating operation can be restarted promptly, and the operation time can be made 10 times longer than that of the conventional product.

[0010]

Therefore, the means for solving the problems adopted by the present invention is arranged in a refrigerating chamber of a liquid helium reliquefaction apparatus, and introduces a high temperature (about 300 K) helium gas and gradually introduces the same gas. A lower tube for cooling, nitrogen,
In a purifier consisting of an upper tube equipped with a solidification section that solidifies (freezes) impurities such as oxygen, the diameter of the upper tube connected to the lower tube is set to be larger than that of the lower tube, and the impurities are solidified inside. It is a high-performance helium gas purifier characterized in that fins forming parts are arranged so that the flow path becomes zigzag. A pipe serving as a helium gas discharge pipe is provided above the upper pipe, an impurity solidifying portion (freezing portion) made of an appropriate number of fins is provided on an inner wall of the upper pipe, and a lower portion of the upper pipe is further provided. It is a high performance helium gas purifier characterized by forming a liquid pool. Further, in the purifier arranged in the refrigeration chamber of the liquid helium reliquefaction device, the purifier comprises an upper pipe and a lower pipe having a diameter smaller than that of the upper pipe inserted and fixed in the upper pipe. , A hat-shaped shape consisting of a small diameter part and a large diameter part,
A high-performance helium characterized in that an impurity solidification portion consisting of an appropriate number of fins is formed inside the small diameter portion, and a liquid pool is formed in the large diameter portion between the inner wall of the large diameter portion and the periphery of the lower tube. It is a gas purifier. Further, the lower pipe is a high-performance helium gas purifier characterized in that a shape of a long flow path is adopted to make a temperature gradient gentle. Further, in the high-performance helium gas purifier, the fins are densely arranged on the upper side and coarsely arranged on the lower side so as to uniformly solidify impurities in the gas. Further, in the high performance helium gas purifier, a heater for liquefying impurities accumulated on the fins is arranged in the upper tube. Further, the heater operates by detecting a pressure increase in the pipe due to the blockage of the helium gas passage, and when the temperature in the upper pipe reaches a predetermined temperature, the heating by the heater is stopped and the operation of the purifier can be restarted. It is a high-performance helium gas purifier characterized by. Further, the heater operates when the gas flow velocity in the helium gas passage becomes a predetermined value or less, and when the flow velocity in the upper pipe reaches the predetermined flow velocity, the heating by the heater is stopped and the operation of the purifier is restarted. It is a high-performance helium gas purifier characterized by being able to do so. Further, the heater is operated by detecting an increase in pressure in the pipe due to blockage of the helium gas passage, and stops heating of the heater when the pressure in the pipe falls below a predetermined pressure. It is a purifier. Further, the heater is operated by detecting that the temperature of the helium gas passage is blocked by the solidified substance and is below a predetermined temperature, and stops the heating when the solidified substance is melted and reaches a predetermined temperature or more. It is a high-performance helium gas purifier. The freezing chamber is placed in a vacuum,
The lower pipe is a double pipe consisting of an inner pipe and an outer pipe, the inner pipe is made of stainless steel, and the outer pipe is made of copper, which is a high performance helium gas purifier.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A helium gas purifier according to the present invention will be described below with reference to the drawings. FIG. 1 shows that the entire amount of helium gas vaporized in a liquid helium storage tank according to the present invention is recovered and recondensed. It is sectional drawing of the refiner as 1st Embodiment used for the recirculation system which liquefyes and is liquefied.

In FIG. 1, the purifier 10 is placed in a freezing chamber R at a temperature of about 40K, similar to the liquid helium recirculation system described above. The periphery of the freezing chamber R is provided as a vacuum layer to enhance heat insulation. The purifier 10 comprises an upper pipe 11 made of copper and a double pipe 12 inserted and fixed at the lower end of the upper pipe 11. Upper pipe 11 with a diameter larger than double pipe 12
A copper pipe 13 serving as an exhaust pipe of helium gas cooled to a temperature of about 40 K by removing impurities is fixed to the upper part of the inner wall of the upper pipe 11, and a copper fin (impurity solidification part) 14 is formed on the inner wall of the upper pipe 11. Are provided in an appropriate number so that the flow paths are staggered alternately, and the fins 14 are arranged with a slight inclination toward the center. The lower part of the upper pipe 11 is closed by a bottom plate 15 made of copper, which is fixed to the lower end of the upper pipe 11 and the outer pipe 19 of the double pipe 12 by welding or the like, and a liquid pool 21 of impurities described later is formed in this portion. To do. A heater 16 for liquefying the impurities solidified in the solidifying section and a thermometer 17 as a sensor are provided on the outer circumference of the upper tube 11. It is also possible to arrange the fins 14 densely on the top and roughly on the bottom so that the thickness of the impurity deposition layer is uniform.

The double pipe 12 is an inner pipe 18 made of stainless steel.
And an outer tube 19 made of copper, and an inner tube 1 made of stainless steel
8 and the outer tube 19 made of copper are in communication with a vacuum layer formed around the freezing chamber. A flange portion 20 formed by processing a copper outer pipe 19 and a stainless steel inner pipe 18 is formed on the upper part of the double pipe 12 in the figure, and the flange portion is closely bonded to both. The collar portion 20 is inclined downward toward the inner peripheral wall of the upper pipe 11 to facilitate the flow of impurities, thereby improving the natural flow of liquefied impurities. Further, a gap S1 is provided between the collar portion 20 and the inner wall of the upper pipe 11 so that the liquefied impurities are stored in the liquid pool 2 described above.
It is designed to fall to 1. The lower end of the outer pipe 19 forming the double pipe 12 is fixed to the wall 121 of the freezing chamber R in a sealed state by an appropriate means, and the lower end of the inner pipe 18 is connected to a 300K helium gas introduction pipe. The thin tube 22 is fixed. The thin tube 22 is provided with a pressure gauge P that detects the pressure inside the tube 22 outside the outer wall 120, as shown in the figure.

The process of purifying helium gas by the purifier will be described below. The helium gas vaporized in the liquid helium storage tank is introduced into the narrow tube 22 of the purifier 10 in the state of 300K, passes through the inner tube 18 made of stainless steel, and is cooled to about 40K by the cold air in the freezing chamber. Tube 1
Reach 1. In the upper pipe 11, the helium gas is fin 1
While bypassing 4, it is cooled to about 40 K, sent from the copper tube 13 to a heat exchanger (not shown), and liquefied. At this time, if impurities such as nitrogen or oxygen are mixed in the helium gas, the impurities such as nitrogen or oxygen are finned while meandering through the fins 14 of the upper tube 11 cooled to a temperature of about 40K. It is solidified (freezing) on 14 and removed.

When the fins 14 are solidified and accumulated during the refining and the flow path is closed, the pressure of the pressure gauge P rises. For example, when the pressure in the thin tube 22 becomes about 200 mmAq, the circulation of the helium gas is once stopped, the heater 16 is turned on via a control device (not shown), and the heater 16 turns on the upper tube 11 and the fin 14. To heat. By this heating, impurities such as nitrogen and oxygen solidified in the fin 14 are liquefied,
The liquid travels along the slanted fins 14 and the collar portion 20 and drops into the liquid pool 21 for storage. The impurities accumulated in the liquid pool can be taken out to the outside by an appropriate means. In this way, the clogged state of the fin 14 portion, the copper tube 13, etc. due to the solidification is eliminated. Heater 1 for liquid impurities stored in liquid pool
If it is heated too much by 6, it will vaporize again and pollute the system gas. Therefore, monitor the temperature of the fin 14 with the thermometer 17, and when the fin temperature reaches around 77K, the heater 16
Is turned off, and the operation of the purifier is automatically restarted at a temperature slightly lower than the nitrogen vaporization temperature of 77K. When the flow path of the fin 14, the copper tube 13, etc. is clogged due to the solidification of impurities, the flow path pressure detection and the heater 16 ON / OFF operation may be performed either automatically or manually. Further, the heater is operated only when the pressure inside the pipe reaches a predetermined value due to the blockage of the helium gas passage, only when the temperature inside the pipe reaches a predetermined value, or only the gas flow velocity in the helium gas passage is detected. You may make it operate | move. After the heater is operated, the heater is stopped after detecting that a predetermined pressure, a predetermined temperature, and a predetermined time have elapsed.

Next, a second embodiment will be described with reference to FIG. FIG. 2 shows a second embodiment of the purifier according to the present invention, and the same reference numerals are used for the purifier 30 and members having the same structure as the purifier 10 of the first embodiment. Since the functions are the same, their explanations are omitted. by the way,
This purifier 30 is different from the purifier 10 of the first embodiment in that the portion in the vacuum below the thin tube 22 provided at the lower end of the inner tube 18 and serving as the high-temperature helium gas introduction tube is spiraled. That is, the path is formed in a long shape in the shape 22a or in the zigzag shape. By forming a part of the thin tube 22 in a spiral shape or a zigzag shape, the thermal gradient can be reduced, so that the height (length) H of the double tube 12 made of copper or stainless steel can be shortened. Can be miniaturized.
The process of removing impurities of the helium gas introduced into the inner pipe 18 is the same as in the first embodiment.

Next, a third embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a third embodiment of the purifier according to the present invention and a plan view of fins. In this embodiment, the outer shape of the impurity solidification portion is reduced when there is no space in the upper portion. Moreover, it is characterized in that the volume of the upper pipe is increased and a sufficient liquid pool is secured in the lower portion.

The purifier 40 includes an upper pipe 41 and an upper pipe 41.
It is composed of a double tube 42 inserted and fixed in. The upper pipe 41 has a hat-shaped shape including a small diameter portion 43 and a large diameter portion 44, and a copper pipe 45 serving as a discharge pipe of helium gas at a temperature of 40K from which impurities are removed is fixed to the upper portion of the small diameter portion 43. The fins 46 are alternately provided on the inner wall of the small diameter portion 43 in an appropriate number. The fins 46 are attached to the attachment rod 55 in a shape with a part of a circle omitted as shown in the drawing, and the fins 46 are arranged with a slight inclination toward the center. A large fin 53 made of copper is attached to the inner circumference of the large diameter portion 44. As shown in the drawing, the large fin 53 is provided with a hole 54 for liquid flow, if necessary.
The fins 46 and the large fins 53 are connected by a mounting rod 55 or the like.

A heater 47 and a thermometer 48 are provided on the outer circumference of the large-diameter portion 44. Further, in the large-diameter portion 44, an inner pipe 49 made of stainless steel and an outer pipe 50 made of copper are connected. The double pipe 42 is arranged, and the lower end of the large diameter portion 44 and the outer pipe 50 are fixed to the wall 121 of the freezing chamber in a hermetically sealed state. In addition, the inner wall portion of the large diameter portion 44 and the outer pipe 50 form a liquid pool 52.
Is configured. The inner tube 49 is provided with a thin tube 51 serving as a 300 K helium gas introduction tube, and a portion of the thin tube 51 arranged in a vacuum is formed to have a long path in a spiral shape 51a or a zigzag shape. This makes it possible to reduce the heat gradient and reduce the upper diameter of the purifier. Further, if the diameter of the upper portion is increased, the height of the entire purifier can be reduced. The outer tube 50, the large diameter portion 44, and the freezing chamber R may be fixed integrally.

Since the refiner 40 of this embodiment has the small diameter portion 43 above the upper pipe 41, it can be used even when the upper portion cannot be made large due to the storage space. With such a configuration, the helium gas vaporized in the liquid helium storage tank is introduced into the thin tube 22 of the purifier 40 and passes through the inner tube 49 made of stainless steel.
It is cooled while staying in the large diameter portion 44, further flows through the copper pipe 45 while bypassing the fins 46, and is liquefied by the heat exchanger. Although the impurities are removed by the fins 46 in this process, the process of solidifying and liquefying the impurities is the same as that in each of the above-described embodiments, and thus the description thereof is omitted.

Although the embodiment of the present invention has been described, the purifier according to the present invention is not limited to a cylindrical cross-section, and various triangles, squares, and other shapes can be adopted, and the shape of the upper pipe, As for the shape of the fin, various forms can be adopted as long as they can achieve the same function as described above. Furthermore, the fins may have irregularities on the surface to increase the surface area. Further, the closed state of the flow path can be detected not by the temperature or pressure but by the flow velocity or the like, and the operating temperature and operating time of the heater can be arbitrarily changed manually or automatically. In the case of automatic setting, it can be easily realized by using a personal computer or the like. Furthermore, the present invention may be embodied in any other form without departing from its spirit or main characteristics. Therefore, the above-described embodiments are merely examples in all respects and should not be limitedly interpreted.

[0022]

As described above, according to the present invention,
It is possible to provide an efficient purifier suitable for a recirculation system, in which the entire amount of helium gas vaporized in the liquid helium storage tank is recovered, recondensed and liquefied. Further, by enlarging the impurity solidification section in the purifier, it is possible to more efficiently and reliably remove impurities such as nitrogen and oxygen mixed in the helium gas circulation. By forming the helium gas inlet tube (thin tube) in a spiral or zigzag shape, the size of the purifier can be reduced while maintaining the thermal gradient of helium gas at the same level as the conventional method without increasing the amount of heat penetration. can do. Further, when impurities are accumulated in the solidified portion and the flow path is blocked, the solidified portion is rapidly heated to turn the solidified liquid into a liquid, and the blockage of the flow path can be eliminated. Further, by immediately restarting the refrigeration operation after liquefying and storing the liquefied gas in the storage portion without re-gasifying, the operable time can be extended ten times or more compared with the conventional product. Further, by making the upper tube into a hat shape or the thin tube into a spiral shape or a zigzag shape, the purifier can be installed even in a small space.

[Brief description of drawings]

FIG. 1 is a first embodiment of the refiner of the present invention.

FIG. 2 is a second embodiment of the purifier of the present invention.

FIG. 3 is a third embodiment of the purifier of the present invention.

FIG. 4 is a schematic diagram of a conventional liquid helium recirculation system.

FIG. 5 is a schematic view of a conventional refiner.

[Explanation of symbols]

10 Purifier 11 Upper tube 12 double pipe 13 Copper tube 14 fins 15 Bottom plate 16 Heater 17 Thermometer 18 inner tube 19 outer tube 20 Tsuba 21 liquid pool 22 Capillary 30 Purifier 40 Purifier 41 Upper tube 42 double tube 43 Small diameter part 44 Large diameter part 45 copper tube 46 fins 47 Heater 48 thermometer 49 inner tube 50 outer tube 51 thin tube 52 liquid pool R Freezing chamber

Claims (11)

[Claims] 1. A lower tube for arranging in a refrigerating chamber of a liquid helium reliquefaction apparatus, for introducing a high temperature (about 300 K) helium gas and gradually cooling the gas, and solidifying impurities such as nitrogen and oxygen ( In a purifier consisting of an upper tube with a solidifying portion that freezes), the diameter of the upper tube connected to the lower tube is set to be larger than that of the lower tube, and a fin that forms an impurity solidifying section is flowed inside the upper tube. A high performance helium gas purifier characterized by arranging the passage in a zigzag manner. 2. A pipe serving as a helium gas discharge pipe is provided above the upper pipe, and an impurity solidifying portion (freezing portion) made of an appropriate number of fins is provided on an inner wall of the upper pipe. The high-performance helium gas purifier according to claim 1, wherein a liquid pool is formed in the lower portion of the pipe. 3. A purifier arranged in a refrigeration chamber of a liquid helium reliquefaction apparatus, wherein the purifier has an upper tube,
It is composed of a lower tube having a diameter smaller than that of the upper tube inserted and fixed in the upper tube, and the upper tube has a hat-shaped shape including a small diameter portion and a large diameter portion, and an appropriate number of fins are provided inside the small diameter portion. A high-performance helium gas purifier, characterized in that an impurity solidification portion is formed, and a liquid pool is formed in the large diameter portion by the inner wall of the large diameter portion and the periphery of the lower tube. 4. The lower pipe has a long flow passage shape for easing a temperature gradient.
The high-performance helium gas purifier according to claim 3. 5. The fins are densely arranged on the upper side and coarsely arranged on the lower side so as to uniformly solidify the impurities in the gas. High performance helium gas purifier. 6. A heater for liquefying impurities deposited on the fins is arranged in the upper tube.
The high-performance helium gas purifier according to claim 5. 7. The heater operates by detecting a pressure increase in the pipe due to blockage of a helium gas passage, and stops heating by the heater when the temperature in the upper pipe reaches a predetermined temperature.
7. The operation of the purifier can be restarted.
High-performance helium gas purifier described in. 8. The heater operates when the gas flow velocity in the helium gas passage is below a predetermined value, and stops heating by the heater when the flow velocity in the upper pipe reaches a predetermined flow velocity,
7. The operation of the purifier can be restarted.
High-performance helium gas purifier described in. 9. The heater is operated by detecting an increase in pressure in the pipe due to blockage of a helium gas passage, and stops heating the heater when the pressure in the pipe becomes equal to or lower than a predetermined pressure. Item 7. A high performance helium gas purifier according to Item 6. 10. The heater operates when it detects that the helium gas passage is blocked by solidified matter and the temperature is below a predetermined temperature, and stops heating when the solidified matter melts and reaches a predetermined temperature or higher. The high performance helium gas purifier according to claim 6, which is characterized in that. 11. The freezing chamber is arranged in a vacuum, and the lower tube is a double tube consisting of an inner tube and an outer tube,
The high performance helium gas purifier according to any one of claims 1 to 8, wherein the inner tube is made of stainless steel and the outer tube is made of copper.