JP2005291628A - Helium re-liquefying device, purifier, valve mechanism, and condenser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly perform helium re-liquefying treatment for recovering a helium evaporated in a storage tank in which an extremely low temperature liquid helium is stored, re-liquefying, and returning to the storage tank. <P>SOLUTION: This helium re-liquefying device 20 comprises a purifier 30 having a porous arresting part 325 cooling, solidifying, and arresting impurities in a helium gas, an exhaust gas pump 25 connected to the fluid inlet of the purifier 30, a check valve 50 connected to the fluid outlet of the purifier 30, and a condenser 40 having a liquid reserving part 406 storing the impurities solidified in a condenser body 401 together with a liquid helium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to helium reliquefaction processing for recovering helium vaporized in a storage tank storing cryogenic liquid helium, reliquefying it, and returning it to the storage tank, and in particular, used for such helium reliquefaction processing. To purifiers, helium reliquefaction devices, valve mechanisms and condensers that can be made.

  Conventionally, cryogenic (approximately 4K) liquid helium has been used to cool measuring instruments such as biomagnetic measurement systems, magnetocardiographs, NMR apparatuses, and MRI apparatuses. Since such liquid helium is a scarce resource and relatively expensive, it is not preferable to release the helium gas vaporized in the cooling process to the atmosphere. For this reason, a helium re-liquefaction device that recovers helium vaporized in a storage tank storing cryogenic liquid helium, re-liquefies it, and returns it to the storage tank is known as a technology for enabling reuse of helium gas. (See, for example, Patent Document 1 and Patent Document 2.)

  The above-mentioned helium reliquefaction apparatus is recovered from a Gifford McMahon cycle refrigerator (hereinafter referred to as “GM refrigerator”) capable of cooling helium to approximately 4K, a condenser connected to the GM refrigerator, and a storage tank. A purifier that cools and solidifies the impurities in the helium gas. The low-temperature (approximately 4 to 10 K) helium gas generated in the storage tank is sent to the condenser and re-liquefied into cryogenic liquid helium. Further, the relatively high temperature (approximately 300 K) helium gas generated in the storage tank is collected by a circulation pump and introduced into a purifier, where impurities such as nitrogen and oxygen are removed from the helium gas. The helium gas that has passed through the purifier is cooled stepwise by the GM refrigerator and then sent to the condenser where it is reliquefied into cryogenic liquid helium.

JP-A-10-105072 US Pat. No. 6,442,948

  The purifier used for the helium reliquefaction process as described above must be capable of reliably capturing impurities in the helium gas and suppressing the outflow of impurities downstream. Further, when the purifier starts to be blocked by impurities, it is necessary to reliably remove impurities from the purifier while reliably suppressing the outflow of impurities to the downstream side. Furthermore, since impurities may flow from the purifier to the condenser, a valve mechanism that operates reliably in a low temperature environment is indispensable to prevent the impurities from flowing downstream.

  The present invention is directed to overcoming one or more of the problems as set forth above.

  The purifier of the present invention is used for a helium reliquefaction process in which helium vaporized in a storage tank storing cryogenic liquid helium is recovered, reliquefied, and returned to the storage tank. This purifier cools and solidifies the impurities in the helium gas collected from the storage tank, and includes a purifier body and porous trapping means. The trapping means is configured to allow the helium gas to flow and to be in sufficient contact with the helium gas, and is disposed on the outlet side (the most downstream side) of the purifier main body and, for example, cold heat such as a GM refrigerator. Connected to the source. According to this purifier, impurities such as nitrogen and oxygen in the helium gas recovered from the storage tank can be reliably captured by cooling and solidifying. In this case, the distance from the inlet of the purifier body to the inlet of the capturing means should be made as long as possible. Further, the purifier main body may include a meandering channel between the inlet and the inlet of the capturing means.

  Preferably, the capturing means includes a large number of microparticles gathered at a high density. In this case, the impurities in the helium gas are cooled and solidified by the cold heat from the cold heat source, and are reliably trapped in the minute gaps formed between the many minute particles. Further, the size of the micro granular material may be changed stepwise along the flow direction of the helium gas.

  Another purifier of the present invention is also used for the helium reliquefaction process in which helium vaporized in a storage tank storing cryogenic liquid helium is recovered, reliquefied, and returned to the storage tank. This purifier cools and solidifies the impurities in the helium gas collected from the storage tank and captures it, for example, a purifier main body connected to a cooling heat source such as a GM refrigerator, and the inside of the purifier main body. And a plurality of cooling chambers arranged side by side. Adjacent cooling chambers communicate with each other so that helium gas flows along the inner wall of one cooling chamber and then flows into the other cooling chamber, thereby forming a meandering channel through which helium gas flows. Is done. Moreover, the dimension of the cooling chamber in the axial direction of the purifier main body becomes smaller as it approaches the outlet of the purifier main body.

  In such a purifier, the flow path of the helium gas in the purifier main body can be further lengthened, and the establishment of contact between the wall surface of each cooling chamber and the helium gas can be enhanced. Further, by reducing the size of the cooling chamber in the axial direction of the purifier main body as it approaches the outlet of the purifier main body, it becomes possible to cool the helium gas uniformly and satisfactorily suppress clogging of the purifier. . In this case, it is preferable that a baffle plate is disposed inside each cooling chamber so as to change the course of the helium gas.

  The helium reliquefaction apparatus of the present invention collects helium vaporized in a storage tank storing cryogenic liquid helium, reliquefies it, and returns it to the storage tank. This helium reliquefaction device includes a purifier that cools and solidifies impurities in the helium gas recovered from the storage tank, a heater that heats the impurities captured by the purifier, and a fluid inlet of the purifier And a check valve connected to the fluid outlet of the purifier. The check valve is disposed inside the body having a valve inlet and a valve outlet, and moves so as to open or close the valve inlet depending on a pressure difference between the valve inlet and the valve outlet. And a valve body capable of

  In this helium reliquefaction apparatus, the heater and the suction means are operated when the purifier starts to block. When the heater is operated, the impurities captured by the purifier are heated and vaporized. When the suction means is operated, the valve inlet side of the check valve becomes lower in pressure than the valve outlet side, and the valve body moves so as to close the valve inlet. Thereby, the impurities vaporized in the purifier can be prevented from flowing out downstream of the check valve. The impurities vaporized in the purifier are sucked by the suction means and discharged to the outside. As a result, in this helium reliquefaction apparatus, it is possible to reliably remove impurities from the purifier while reliably suppressing the outflow of impurities to the downstream side.

  The valve mechanism according to the present invention is a valve mechanism used in a low temperature environment. The valve mechanism is disposed inside the main body having a valve inlet and a valve outlet, and moves so as to open or close the valve inlet depending on a pressure difference between the valve inlet and the valve outlet. And a valve body capable of

  In this valve mechanism, the valve inlet can be opened or closed only by creating a pressure difference between the valve inlet and the valve outlet. Therefore, this valve mechanism operates very reliably even in a low temperature environment of about 4 to 40K, for example.

  Preferably, the main body of the valve mechanism includes a tapered surface that receives the valve body and a restricting unit that restricts movement of the valve body to the valve outlet. The valve body may be a sphere or a cone.

  The condenser according to the present invention is used for helium reliquefaction processing in which helium vaporized in a storage tank storing cryogenic liquid helium is recovered, reliquefied, and returned to the storage tank. This condenser re-liquefies the helium gas collected from the storage tank into cryogenic liquid helium, and includes a condenser main body and a liquid reservoir provided in the condenser main body. The liquid reservoir stores the impurities solidified in the condenser body together with liquefied helium. Therefore, according to this condenser, impurities such as nitrogen and oxygen can be reliably captured.

  Preferably, the condenser includes a return pipe for returning liquid helium from the condenser main body to the storage tank, and a tilting means for tilting the condenser main body, and a connection portion between the condenser main body and the return pipe. Is disposed in association with a position of the liquid surface formed in the liquid reservoir not to be displaced even when the condenser body is inclined by the inclination means. Thereby, it becomes possible to suppress reliably that an impurity mixes in the liquefied helium returned to a storage tank.

  According to the present invention, helium reliquefaction processing for recovering helium vaporized in a storage tank storing cryogenic liquid helium, reliquefying it, and returning it to the storage tank can be performed very smoothly for a long time. It becomes.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a partial cross-sectional view showing a biomagnetic measurement system which is an example of a measurement system including a helium reliquefaction apparatus according to the present invention. The biomagnetic measurement system 1 includes a superconducting quantum interferometer (hereinafter referred to as “SQUID”) 2 capable of noninvasively measuring brain activity and the like with high spatio-temporal resolution, and a magnetic field generated from a human brain or the like. Can be detected. The SQUID 2 is contained in a dewar (storage tank) 3 that stores approximately 4K of liquid helium therein, and is cooled to approximately 4K, which is an operating temperature, by the liquid helium in the dewar 3.

  The SQUID 2 and the dewar 3 are arranged in a magnetic shield room SR defined by a nonmagnetic partition wall 4. As can be seen from FIG. 1, the dewar 3 is supported by a support member 5 so as to be rotatable around a horizontally extending shaft 6. Is done. Thereby, in the biomagnetic measurement system 1, the dewar 3 is rotated (tilted) around the axis 6 to generate a magnetic field generated from the subject's brain or the like lying on the seat or the subject lying on the bed. Can be measured.

  The biomagnetic measurement system 1 collects the helium vaporized in the dewar (liquid helium storage tank) 3 by cooling the SQUID 2 and re-liquefies it in order to effectively use helium, which is a scarce resource and is relatively expensive. It has a helium reliquefaction device 20 that returns to the dewar 3. The helium reliquefaction device 20 has a cold chamber 23 that houses a GM refrigerator, which will be described later, and a container 26 that houses various pipes. The helium reliquefaction device 20 is placed in a storage room AR placed next to the magnetic shield room SR. Yes. A magnetic shield material is adhered to the inner surface of the partition wall 7 that defines the storage chamber AR in order to suppress sound emitted from the helium reliquefaction device 20 and leakage of magnetism to the outside.

  A shaft 8 extending coaxially and horizontally with the shaft 6 in the magnetic shield chamber SR is fixed to the support mechanism for the cold chamber 23 and the container 26, and the shaft 8 is rotatably supported by the support block 9. A rotation handle 11 is connected to the shaft 8 via a speed reduction mechanism 10 such as a worm gear mechanism. By operating the rotation handle 11, the cold chamber 23 and the container 26 can be rotated around the shaft 8. it can. A counterweight W is attached to the lower part of the container 26.

  In addition, the biomagnetic measurement system 1 includes a drive shaft 12 that penetrates the partition wall 4 that defines the magnetic shield chamber SR and the partition wall 7 of the storage chamber AR that faces the partition wall 4. If the drive shaft 12 combined with the shaft 8 in the storage chamber AR is rotated, the cold chamber 23 and the container 26 in the storage chamber AR can be rotated (inclined) from the magnetic shield chamber SR. That is, in the biomagnetic measurement system 1, when the dewar 3 in the magnetic shield room SR is moved in accordance with the patient's posture, the helium reliquefaction device 20 in the storage chamber AR is moved in accordance with the posture of the dewar 3. be able to.

  As shown in FIG. 1, the dewar 3 and the cold chamber 23 of the helium reliquefaction device 20 are connected to each other via a transfer tube 14 having a multilayer structure. The transfer tube 14 is formed by integrating a later-described high-temperature recovery pipe L1, a second cooling pipe L5, a low-temperature recovery pipe L6, and a return pipe L7. The transfer tube 14 passes through an arcuate slot 4a formed in the partition 4 of the magnetic shield chamber SR and an arc-shaped slot 7a formed in the partition 7 of the storage chamber AR. The long holes 4a and 7a are formed around the rotation center (the shaft 6, the shaft 8, etc.) of the dewar 3 or the helium reliquefaction device 20. When the movement of the dewar 3, the helium reliquefaction device 20, and the transfer tube 14 is completed, the magnetic shield material 15 is loaded into the long holes 4a and 7a.

  FIG. 2 is a system diagram of the helium reliquefaction device 20. As shown in the figure, the helium reliquefaction device 20 mainly includes a circulation pump 21, two GM refrigerators 22, two purifiers 30, a condenser 40, a GM refrigerator 22, a purifier 30 and a condenser. A cold chamber 23 containing the vessel 40, and a high temperature recovery pipe L1 for recovering a relatively high temperature (approximately 300K) helium gas from the dewar 3. Each GM refrigerator 22 has a first freezer 22a for cooling helium gas to about 40K and a second freezer 22b for cooling helium gas to about 4K.

  The high temperature recovery pipe L1 is connected to the upper part of the dewar 3 and the suction port of the circulation pump 21, and has a valve V1, a mass flow meter MF3, and a solenoid valve EV1 (normally open) in the middle. One end of a gas pipe L2 is connected to the discharge port of the circulation pump 21, and the gas pipe L2 includes filters F1, F2 and F3, a constant flow rate control valve MFC1, a flow meter FM and a valve V2. The other end of the gas pipe L <b> 2 is connected to a fluid inlet of one purifier 30 in the cold chamber 23. One end of the first cooling pipe L3 is connected to the fluid outlet of the purifier 30 via a check valve 50. The first cooling pipe L3 includes a heat transfer pipe HP1 arranged in the first freezing section 22a of one GM refrigerator 22 and a heat transfer pipe HP2 arranged in the second freezing section 22b of the one GM refrigerator 22. Have. The other end of the first cooling pipe L3 is connected to the condenser 40.

  Further, the gas pipe L4 is branched from the gas pipe L2 between the filter F3 and the constant flow control valve MFC1. The gas pipe L4 has a constant flow control valve MFC2, a flow meter FM, and a valve V3 in the middle. The other end of the gas pipe L4 is connected to the fluid inlet of the other purifier 30 in the cold chamber 23. One end of the second cooling pipe L5 is connected to the fluid outlet of the purifier 30 via a check valve 50. The second cooling pipe L5 includes a heat transfer pipe HP3 that is disposed in the second refrigeration unit 22b of one GM refrigerator 22. The other end of the second cooling pipe L5 is connected to the upper part of the dewar 3. In addition, the 2nd cooling pipe L5 is provided in the outermost layer of the above-mentioned transfer tube 14, and plays the role which cools the helium which distribute | circulates the center.

  The relatively high temperature (about 300 K) helium gas evaporated from the dewar 3 is recovered from the dewar 3 by the circulation pump 21. Part of the recovered helium gas is sent to one of the purifiers 30 via the gas pipe L2, and impurities such as nitrogen and oxygen in the helium gas are removed by the purifier 30. While the helium gas flowing out of the purifier 30 flows through the first cooling pipe L3, the helium gas is stepped by the first freezing unit 22a of one GM freezer 22 and the second freezing unit 22b of the freezer 22. Then, it is sent to the condenser 40.

  The condenser 40 is connected to the second refrigeration units 22b of the two GM refrigerators 22, and the internal temperature of the condenser 40 is maintained at about 4K by each of the second refrigeration units 22b. A low temperature recovery pipe L6 and a return pipe L7 are connected to the condenser 40. The low-temperature (approximately 4 to 10 K) helium gas generated in the dewar 3 is sent to the condenser 40 via the low-temperature recovery pipe L6, and is reliquefied into extremely low-temperature (approximately 4 K) liquid helium by the condenser 40. . Similarly, the helium gas from the first cooling pipe L3 is also reliquefied into cryogenic liquid helium by the condenser 40. The reliquefied helium is returned from the condenser 40 to the dewar 3 through the return pipe L7. Further, the remainder of the relatively high temperature (approximately 300 K) helium gas recovered from the dewar 3 is sent to the other purifier 30 via the gas pipe L4, and the purifier 30 is used for nitrogen and oxygen in the helium gas. Impurities are removed. The helium gas flowing out of the purifier 30 is sent to the dewar 3 after being cooled to about 40K by the first freezing section 22a of one GM refrigerator 22 while flowing through the second cooling pipe L5.

  On the other hand, a helium cylinder 24 is connected between the circulation pump 21 of the gas pipe L2 and the filter F1 via a valve V4, a filter F4, a mass flow meter MF4, and an electromagnetic valve EV4. The helium cylinder 24 stores helium gas at room temperature (300K). Thereby, in the helium reliquefaction apparatus 20, the helium gas from the helium cylinder 24 is sent to the first cooling pipe L3 by opening the electromagnetic valve EV4 and the valve V2, and the condenser 40 converts the liquid helium to cryogenic liquid helium. It is possible to supply (replenish) the dewar 3 after reliquefaction.

  Further, as shown in FIG. 2, the mass flow meter MF5 is connected between the flow meter FM of the gas pipe L2 and the valve V2 via the electromagnetic valve EV3 (normally closed) via the electromagnetic valve EV2 (normally closed). The gas pipe L4 is connected between the flow meter FM and the valve V3. An exhaust pump (suction means) 25 is connected to the mass flow meter MF5 via a valve V5 and a vacuum port. The exhaust pump 25 is used when removing impurities from the purifier 30 as described later.

  In addition, the helium reliquefaction device 20 has pressure sensors P1, P2 and P3. The pressure sensor P1 detects the pressure of helium gas in the dewar 3. The pressure sensor P2 detects the pressure of helium gas at the inlet of the purifier 30 connected to the first cooling pipe L3, and the pressure sensor P3 detects helium gas at the inlet of the purifier 30 connected to the second cooling pipe L5. Detect the pressure. These pressure sensors P1 to P3 are connected to a controller (not shown) together with other sensors not shown. This controller controls the above-described circulation pump 21, exhaust pump 25, various valves and the like based on detection values of various sensors.

  Next, the refiner 30, the check valve 50, and the condenser 40 of the helium reliquefaction apparatus 20 will be described in detail.

(Purifier)
The purifier 30 cools and solidifies the impurities in the helium gas recovered from the dewar 3 and captures it in a generally cylindrical shape by a copper material having good thermal conductivity as shown in FIG. The purifier body 301 is formed. The purifier 30 is disposed in the cold chamber 23 described above, and the periphery of the purifier 30 is maintained in a vacuum atmosphere. The purifier main body 301 includes an upper portion 302 and a lower portion 303 having a larger thickness than the upper portion 302. An annular hole 303a is formed in the lower part 303, and a heater H is disposed in the hole 303a. The lower end of the purifier main body 301 (lower part 303) is connected to the first freezing part 22a of the GM refrigerator 22 via a connecting member 304. Thereby, during operation of the helium reliquefaction apparatus 20, the purifier main body 301 is cooled to approximately 40K by the GM refrigerator 22. An upper end portion of the purifier main body 301 (upper portion 302) is closed by a closing member 305.

  A cylindrical introduction tube 306 is disposed at the center of the purifier main body 301, and a cylindrical inner tube 307 is disposed coaxially with the introduction tube 306 around the introduction tube 306. The inner tube 307 is fixed to a support portion 303 b that extends inward from the inner wall surface of the lower portion 303. The upper end of the introduction pipe 306 is fixed to the upper end of the inner pipe 307 by a fixing member 308. A space is defined between the above-described closing member 305 and the upper end of the introduction pipe 306. The heat insulating space 309 is defined by the outer wall surface of the introduction pipe 306, the inner wall surface of the inner pipe 307, and the fixing member 308. The interior of the heat insulating space 309 is maintained in a vacuum atmosphere as is the case with the purifier body 301.

  Between the inner wall surface of the upper portion 302 of the purifier main body 301 and the outer wall surface of the inner tube 307, a plurality of flow path forming members 310 are disposed in the axial direction of the purifier main body 301. The flow path forming member 310 is formed of a copper material having good thermal conductivity, and has a ceiling portion 312 having a central hole portion into which the inner tube 307 is inserted and a generally fan-shaped opening 311, and a ceiling portion 312. And a cylindrical side wall 314 extending downward from the outer periphery (see FIGS. 3 and 4). The flow path forming members 310 adjacent to each other in the vertical direction are arranged so that the openings 311 do not overlap in the vertical direction, and a cooling chamber is provided between the flow path forming members 310 (ceiling portions 312) adjacent to each other in the vertical direction. 315 is defined. In addition, a partition plate 319 is disposed between the flow path forming members 310 (ceiling portions 312) adjacent in the vertical direction. The partition plate 319 has one side edge (for example, the lower side edge in FIG. 4) of the opening 311 located on the upper side and the other side edge (for example, FIG. 5) of the opening 311 located on the lower side. The basic flow direction of the fluid in the cooling chamber 315 is set to one direction.

  As a result, the cooling chambers 315 adjacent to each other in the vertical direction communicate with each other so that helium gas flows along the inner wall of the upper cooling chamber 315 and then flows into the lower cooling chamber 315. As a result, the helium gas flows. A meandering flow path is formed. In each cooling chamber 315, a plurality of baffle plates 320 are arranged so as to form a zigzag flow path in the cooling chamber 315 by changing the course of the helium gas. Furthermore, in the present embodiment, the flow path forming member 310 has a lower height as it is disposed on the lower side (downstream side) in the purifier body 301. Therefore, the height of the cooling chamber 315 (the size of the cooling chamber 315 in the axial direction of the purifier main body 310) decreases as it approaches the lower end (exit 324) in the purifier main body 301.

  Between the inner wall surface of the lower portion 303 of the purifier main body 301 and the outer wall surface of the inner tube 307, a porous plate (copper wire mesh) 321 is disposed so as to be located near the upper end of the lower portion 303. A perforated plate (copper wire mesh) 322 is disposed below the perforated plate 321 with a predetermined interval. A space 323 is defined between the perforated plate 322 and the support portion 303 b of the lower portion 303, and an outlet pipe (fluid outlet) 324 is connected to the space 323.

  The space between the porous plate 321 and the porous plate 322 is filled with a large number of microspheres (microparticles) at high density. As a result, a porous trap 325 is formed on the outlet side (the most downstream side) of the purifier main body 301 while allowing the fluid to flow and sufficiently contacting the fluid. In the present embodiment, a copper sphere having a diameter of 2 mm is filled in an approximately one third region above the porous capturing portion 325, and an approximately one third region in the center of the porous capturing portion 325 is provided. A copper sphere with a diameter of 1 mm is filled, and a copper sphere with a diameter of 0.5 mm is filled in a region of about one third of the lower side of the porous trap 325. That is, in the present embodiment, the size of the microsphere is changed stepwise along the fluid flow direction. Note that a folded mesh material may be disposed in the porous capturing portion 325 instead of the microsphere (microparticle).

  In the purifier 30 described above, approximately 300 K of helium gas recovered from the dewar 3 is introduced into the inlet (fluid inlet) 306 a of the introduction pipe 306. The helium gas rises inside the introduction pipe 306 and flows out from the upper end of the introduction pipe 306. The helium gas flowing out from the upper end of the introduction pipe 306 flows into a meandering flow path (each cooling chamber 315) defined around the introduction pipe 306 by a plurality of flow path forming members 310.

  The helium gas that has flowed into the uppermost cooling chamber 315 flows along the inner wall of the cooling chamber 315 (the inner peripheral surface of the side wall 314), and flows into the lower cooling chamber 315 through the opening 311. The helium gas then flows down to the cooling chamber 315 below. At this time, since each flow path forming member 310 is cooled to approximately 40K by the GM refrigerator 22 through the purifier main body 301, helium gas is supplied to the ceiling portion 312, the side wall 314, and the partition of the flow path forming member 310. It contacts the plate 319 and the baffle plate 320 and is cooled uniformly.

  As described above, in the purifier 30, the plurality of cooling chambers 315 described above are disposed in the purifier main body 301 as described above, so that the flow path of helium gas in the purifier main body 301 is further increased. The establishment of contact between the wall surfaces of the cooling chambers 315 and the helium gas can be enhanced. In addition, by reducing the height of the cooling chamber 315 as it approaches the outlet of the purifier main body 301, the helium gas can be uniformly cooled, and the blockage of the purifier 30 can be suppressed well.

  The helium gas that has flowed out of the cooling chamber 315 at the lowest stage flows into the porous trap 325 through the porous plate 321. As described above, the porous trap 325 includes a large number of copper microspheres assembled at a high density, and these microspheres are cooled to approximately 40 K by the GM refrigerator 22 through the purifier body 301. Has been. Therefore, when the helium gas passes through the minute gaps formed between the many microspheres of the porous trap 325, the impurities in the helium gas are cooled and solidified through the microspheres. It will surely be captured in a gap. As a result, according to the purifier 30, impurities such as nitrogen and oxygen in the helium gas recovered from the dewar 3 can be cooled and solidified and reliably captured.

  Further, as in this embodiment, by reducing the size of the microsphere stepwise along the flow direction of the helium gas, the impurities in the helium gas are reliably captured and the impurities are discharged from the purifier 30. Can be reliably suppressed. Furthermore, since the purifier main body 301 includes a meandering flow path from the inlet 306a to the inlet (porous plate 322) of the porous trap 325, the distance from the inlet 306a to the porous trap 325 is made as long as possible. be able to. This makes it possible to capture impurities as much as possible and reduce the temperature of the helium gas before the porous trap 325.

(Check valve)
The check valve 50 connected to the outlet pipe 324 of the purifier 30 described above can be used in a cryogenic environment of approximately 4 to 40 K, for example, where a conventional check valve cannot operate. As shown in FIG. 6, the check valve 50 includes a valve main body 501 and a valve body 502 movably accommodated inside the valve main body 501. The valve body 501 includes a lower half 503 and an upper half 504. Both the lower half 503 and the upper half 504 are formed in a generally cylindrical shape from a copper material having high thermal conductivity. In the present embodiment, the valve body 502 is formed in a spherical shape from a lightweight and highly rigid material such as ceramic.

  The lower half 503 includes a valve inlet 505 having an inner diameter smaller than the diameter of the valve body 502 on the lower end side, and a cavity 506 having an inner diameter larger than the valve inlet 505 (the diameter of the valve body 502) on the upper end side. including. A tapered surface 507 is formed in the lower half 503 between the valve inlet 505 and the cavity 506. The tapered surface 507 is expanded from the bottom to the top, and the valve body 502 is received by the tapered surface 507. The upper half 504 includes a valve outlet 508 on the upper end side and a protrusion 509 that restricts the movement of the valve body 502 to the valve outlet 508 on the lower end side. The protrusion 509 is formed with an opening 510 that allows the cavity 506 (the valve inlet 505) of the lower half 503 to communicate with the valve outlet 508 of the upper half 504.

  This check valve 50 is preferably used with the valve inlet 505 on the bottom and the valve outlet 508 on the top. When helium gas flows from the purifier 30 to the valve inlet 505, the lightweight valve body 502 is moved toward the valve outlet 508 by the helium gas, thereby opening the valve inlet 505. The helium gas that has flowed into the cavity 506 from the valve inlet 505 flows to the valve outlet 508 through the opening 510 of the protrusion 509. Further, the movement of the valve body 502 to the valve outlet 508 is regulated by the tip of the protrusion 509. On the other hand, when the supply of helium gas to the valve inlet 505 is stopped or the pressure at the valve inlet 505 is set smaller than the pressure at the valve outlet 508, the valve body 502 moves toward the valve inlet 505. The valve body 502 engages with the tapered surface 507 and closes the valve inlet 505.

  Thus, the valve body 502 moves so as to open or close the valve inlet 505 in accordance with the pressure difference between the valve inlet 505 and the valve outlet 508. Therefore, in the check valve 50, the valve inlet 505 can be opened or closed only by creating a pressure difference between the valve inlet 505 and the valve outlet 508. Since it has such a simple structure, the check valve 50 operates extremely reliably even in a low temperature environment of 4 to 40K. The valve body 502 may be formed as a cone engaging with the tapered surface 507 instead of being formed into a spherical shape.

(Removal of impurities from the purifier)
As the above-described helium reliquefaction device 20 is operated, the porous trap 325 and the like of the above-described purifier 30 may be clogged with solidified impurities such as nitrogen and oxygen. There is a possibility that the porous trap 325 and the like of the purifier 30 may be blocked. When the purifier 30 starts to block, the pressure of helium gas at the inlet of the purifier 30 detected by the pressure sensors P2 and P3 exceeds a predetermined threshold. For this reason, the controller of the helium reliquefaction apparatus 20 opens the electromagnetic valve EV2 and the valve V5 and activates the exhaust pump 25, for example, when the detection value of the pressure sensor P2 exceeds the threshold value. In addition, the controller stops the refrigerator 22 at an appropriate timing, and operates the heater H of the purifier 30 connected to the first cooling pipe L3.

  When the heater H of the purifier 30 is activated, the impurities trapped in the porous trap 325 and the meandering channel of the purifier 30 are heated and vaporized. When the exhaust pump 25 is operated, the valve inlet 505 of the check valve 50 becomes lower in pressure than the valve outlet 508, so that the valve body 502 moves so as to close the valve inlet 505. Thereby, the impurities vaporized in the purifier 30 can be prevented from flowing out downstream of the check valve 50. The impurities evaporated in the purifier 30 are sucked by the exhaust pump 25 and discharged to the outside. As a result, the helium reliquefaction device 20 can reliably remove impurities from the purifier 30 while reliably suppressing the outflow of impurities downstream.

  When removing impurities from the purifier 30 connected to the second cooling pipe L5, the electromagnetic valve EV3 and the valve V5 are opened, the exhaust pump 25 is operated, and the heater of the purifier 30 is further operated. What is necessary is just to operate H. Further, as shown in FIG. 2, a helium discharge pipe having a solenoid valve EV5 is connected to the high temperature recovery pipe L1 in the middle, and when removing impurities from the purifier 30, the solenoid valve EV5 is used. The helium gas vaporized in the dewar 3 is discharged into the atmosphere through a helium discharge pipe.

(Condenser)
As shown in FIG. 7, the condenser 40 includes a condenser body 401 having a chamber 402, a porous block 403 having a large number of holes 404 (see FIGS. 7 and 8), and a mounting plate 405. The condenser main body 401, the porous block 403, and the mounting plate 405 are all formed of a copper material having high thermal conductivity. The holes 404 of the porous block 403 are opened only downward, and the upper part of the porous block 403 is fixed to the center of the back surface of the mounting plate 405. Similarly, the upper end (open end) of the condenser body 401 is also fixed to the center of the back surface of the mounting plate 405, and the porous block 403 is accommodated in the chamber 402. At this time, a space is defined between the lower end surface of the porous block 403 and the bottom surface of the chamber 402. Further, a liquid reservoir portion 406 that is continuous with the chamber 402 is formed in the lower portion of the condenser main body 401 (below the chamber 402).

  Both ends of the mounting plate 405 are connected to the second freezing unit 22b of the GM refrigerator 22, respectively, so that the condenser body 401, the porous block 403, and the mounting plate 405 It is cooled to about 4K by the GM refrigerator 22. In addition, a low temperature recovery pipe L6 for recovering low temperature (approximately 4 to 10 K) helium gas from the dewar 3 is connected to the condenser body 401 so as to communicate with the upper portion of the chamber 402. Furthermore, the condenser body 401 is connected so that the first cooling pipe L <b> 3 communicates with the lower part of the chamber 402. The condenser body 401 is connected to a return pipe L7 for returning the reliquefied helium to the dewar 3.

  In the condenser 40 described above, low-temperature (approximately 4 to 10 K) helium gas is introduced into the chamber 402 of the condenser main body 401 through the first cooling pipe L3 and the low-temperature recovery pipe L6. The helium gas flows into the hole 404 of the porous block 403 in the chamber 402, and is liquefied again by exchanging heat with the porous block 403 or the like, and drops from the hole 404 to the bottom of the chamber 402. Then, the re-liquefied helium is returned to the dewar 3 by an appropriate amount via the return pipe L7, and excess helium is stored in the liquid reservoir 406. At this time, even if impurities such as nitrogen and oxygen remain in the helium gas, the impurities are cooled and solidified in the chamber 402 in the same manner as helium, and are collected at the bottom of the liquid reservoir 406 by gravity. It will be. Thereby, according to the condenser 40, impurities such as nitrogen and oxygen that could not be completely processed by the purifier 30 can be reliably captured.

  By the way, as described above, when the dewar 3 in the magnetic shield room SR is moved according to the posture of the patient, the cold chamber 23 and the container 26 in the storage room AR are also moved so as to match the posture of the dewar 3 ( Tilted). In the present embodiment, when the helium reliquefaction device 20 is moved (tilted), the condenser 40 in the container 26 is tilted in the direction of the arrow in FIG.

  For this reason, in this embodiment, as can be seen from FIG. 9, two condensers 40 (mounting plates 405) are tilted by a minute angle θ (for example, about 2 to 3 °) in the direction of the arrow in FIG. It is connected to the GM refrigerator 22. The liquid reservoir 406 that stores solidified impurities together with liquid helium is provided in the condenser main body 401 so as to be farthest from the rotation center (such as the shaft 8) of the condenser 40 (container 26). And the connection part of the condenser main body 401 and the return pipe L7 is a position in the liquid surface LL formed in the liquid reservoir 406 that is not displaced even when the condenser main body 401 is inclined (the liquid surface LL in FIG. 8). It is arranged on the extension line of (center). Thereby, even if the condenser main body 401 is tilted, it is possible to reliably suppress impurities from being mixed into the liquefied helium returned to the dewar 3.

  It should be noted that the present invention can be implemented in any other form without departing from the concept and main features thereof. For this reason, the above-described embodiment is merely an example in all respects and should not be construed in a limited manner.

It is a fragmentary sectional view which shows an example of the measurement system containing the helium reliquefaction apparatus by this invention. It is a systematic diagram of the helium reliquefaction apparatus by this invention. It is sectional drawing which shows the refiner | purifier contained in the helium reliquefaction apparatus of FIG. It is sectional drawing about the IV-IV line in FIG. It is sectional drawing about the VV line | wire in FIG. It is sectional drawing which shows the non-return valve contained in the helium reliquefaction apparatus of FIG. It is a front view of the condenser contained in the helium reliquefaction apparatus of FIG. It is sectional drawing about the VIII-VIII line in FIG. It is a side view of the condenser of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biomagnetic measurement system 20 Helium reliquefaction apparatus 22 GM refrigerator 30 Purifier 325 Porous trapping part 40 Condenser 50 Check valve

Claims (9)

Helium vaporized in a storage tank storing cryogenic liquid helium is recovered, re-liquefied and used for helium re-liquefaction treatment to return to the storage tank, and the impurities in the helium gas recovered from the storage tank are cooled. A purifier that solidifies and captures,
A purifier body,
A porous trapping means configured to allow the flow of the helium gas and to be in sufficient contact with the helium gas, disposed on the outlet side of the purifier body, and connected to a cold heat source; A purifier characterized by comprising.   The purifier according to claim 1, wherein the capturing unit includes a large number of fine particles aggregated at a high density. Helium vaporized in a storage tank storing cryogenic liquid helium is recovered, re-liquefied and used for helium re-liquefaction treatment to return to the storage tank, and the impurities in the helium gas recovered from the storage tank are cooled. A purifier that solidifies and captures,
A purifier body connected to a cold heat source;
A plurality of cooling chambers arranged in parallel inside the purifier body,
The cooling chambers adjacent to each other are communicated so that helium gas flows along the inner wall of one cooling chamber and then flows into the other cooling chamber, and the cooling chambers in the axial direction of the purifier main body are connected to each other. The size of the purifier decreases as it approaches the outlet of the purifier body.   The purifier according to claim 3, wherein a baffle plate is disposed in each cooling chamber so as to change a course of helium gas. A helium reliquefaction device that recovers helium vaporized in a storage tank storing cryogenic liquid helium, reliquefies it, and returns it to the storage tank,
A purifier that cools and solidifies impurities in the helium gas recovered from the storage tank;
A heater for heating impurities trapped by the purifier;
Suction means connected to the fluid inlet of the purifier;
A body connected to the fluid outlet of the purifier and having a valve inlet and a valve outlet; and disposed within the body, the valve depending on a pressure difference between the valve inlet and the valve outlet A helium reliquefaction device comprising a check valve including a valve body capable of moving to open or close the inlet. A valve mechanism used in a low temperature environment,
A body having a valve inlet and a valve outlet;
A valve mechanism that is disposed inside the main body and includes a valve body that can move to open or close the valve inlet according to a pressure difference between the valve inlet and the valve outlet.   The valve mechanism according to claim 6, wherein the main body includes a tapered surface that receives the valve body, and a restricting unit that restricts movement of the valve body to the valve outlet. The helium vaporized in a storage tank storing cryogenic liquid helium is collected, re-liquefied, and used for helium re-liquefaction processing to be returned to the storage tank. A vessel,
The condenser body,
A condenser provided in the condenser body, and comprising a liquid reservoir for storing impurities solidified in the condenser body together with liquefied helium. A return pipe for returning liquid helium from the condenser body to the storage tank; and a tilting means for tilting the condenser body;
The connecting portion between the condenser main body and the return pipe is disposed in association with a position where the condenser main body is not displaced even when the condenser main body is tilted by the tilting means on the liquid surface formed in the liquid reservoir. The condenser according to claim 8.

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