JP2018138896A - Cryostat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that since a sensor is arranged on the top surface of a container in a conventional manner, the sensor is arranged in a vacuum layer, and cooled by thermal conduction from liquid helium stored below the container, which makes it necessary to disassemble the container for performing access to the sensor, and difficult to perform maintenance of the sensor.SOLUTION: A cryostat comprises: a casing; an opening provided on at least a part of the casing, which discharges helium from the inside of the casing; a storage part provided above the opening in the casing, which stores the helium injected from the outside of the casing; and a magnetic sensor arranged so as to be brought into contact with a top surface of the casing in the casing, which is cooled by using the helium, therein the opening discharges the helium after the magnetic sensor is cooled.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a cryostat for a biomagnetic measurement apparatus.

  A magnetic field generated by a living body such as a human is weak. For this reason, the biomagnetic field is measured by using a sensor utilizing superconductivity in a magnetic shield room for blocking an external magnetic field. At this time, the sensor is cooled with liquid helium so that the sensor is in a superconducting state. Since helium is expensive, a technique for collecting and reusing helium after cooling is known (see Patent Document 1).

  Patent Document 2 discloses a technique in which a sensor is arranged on the upper surface of a cryostat in order to measure a magnetic field from the back side of a subject in a supine position in a cryostat that houses liquid helium that cools the sensor and the sensor. Yes.

JP 2004-215777 A US Pat. No. 5,494,033

  In the technique described in Patent Document 2, liquid helium is stored below the cryostat, and the sensor disposed in the vacuum heat insulating layer is cooled by conduction. Therefore, in order to perform maintenance of the sensor, it is necessary to disassemble the cryostat itself. There is a problem that maintenance is difficult.

  This invention is made | formed in view of such a subject, The objective is to provide the cryostat which can perform maintenance of a sensor easily.

  A cryostat according to an embodiment of the present invention is provided in a housing, at least a part of the housing, an opening for discharging helium from the housing, and provided in the housing above the opening. A storage part for storing the helium injected from outside the casing, and a magnetic sensor disposed in contact with the upper surface of the casing in the casing and cooled using the helium, The helium is discharged after cooling the magnetic sensor.

  In the cryostat according to an embodiment of the present invention, the storage portion is open on the upper side of the housing, and a bottom surface provided substantially parallel to the bottom surface of the housing; an outer side surface in contact with the housing; The helium may be stored in a region surrounded by an inner side surface provided corresponding to the outer side surface.

  The cryostat in one embodiment of the present invention may include a vacuum layer between the bottom surface of the housing and the bottom surface of the storage portion.

  In the cryostat according to the embodiment of the present invention, the inner side surface of the storage portion has a double structure including a first side surface on the helium side and a second side surface provided on the outer side of the first side surface. A vacuum layer may be included between the first side surface and the second side surface.

  In the cryostat according to one embodiment of the present invention, the opening is provided at the center of the bottom surface of the housing, and the magnetic sensor is the center of the top surface of the housing and corresponds to the opening. It is good also as arrange | positioning in a position.

  In the cryostat according to the embodiment of the present invention, the housing may have a double structure including an outer surface and an inner surface, and may include a vacuum layer between the outer surface and the inner surface.

  The cryostat according to the embodiment of the present invention may further include a heat radiation shield provided in the vacuum layer and capable of reducing the incidence of heat into the housing.

  In the cryostat according to an embodiment of the present invention, the helium stored in the storage unit evaporates, and the gaseous helium after cooling the magnetic sensor is exhausted to the outside of the housing through the opening. It may be characterized by further including an exhaust connection port.

  In the cryostat in one embodiment of the present invention, the cryostat further includes a cable connected to the magnetic sensor and extending to the outside of the opening through the reservoir, and the magnetic sensor is cooled by heat conduction of the cable. This may be a feature.

  The cryostat according to one embodiment of the present invention may further include a liquid injection connection port for injecting liquid helium into the reservoir through at least a part of the housing.

  In the cryostat according to the embodiment of the present invention, the injection port may inject liquid helium into the reservoir through the opening.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between a method, an apparatus, a system, etc. are also effective as an aspect of the present invention.

  According to the cryostat of the present invention, it is possible to easily perform sensor maintenance.

1 is a perspective view schematically showing an overall configuration of a biomagnetic measurement device according to an embodiment of the present invention. It is a figure which shows typically the functional structure of the biomagnetic measuring device which concerns on one Embodiment of this invention. It is a figure which shows typically the structural example of the cryostat which concerns on one Embodiment of this invention. It is a figure which shows typically the structural example of the cryostat which concerns on a 1st modification. It is a figure which shows typically the structural example of the cryostat which concerns on a 2nd modification. It is a figure which shows typically the structural example of the cryostat which concerns on a 3rd modification.

  An embodiment of the present invention will be described with reference to the drawings. Below, the biomagnetic measuring device 1 using the cryostat which concerns on one Embodiment of this invention is demonstrated first. Thereafter, a cryostat according to an embodiment of the present invention will be described.

  FIG. 1 is a diagram schematically showing an overall configuration of a biomagnetic measurement apparatus 1 according to an embodiment of the present invention. The biomagnetic measurement apparatus 1 according to an embodiment of the present invention includes a magnetic shield room 10, a cryogenic refrigerator 20, a cryostat 30, a transfer tube 40, a gantry 50, a gantry 60, and a connection unit 80. Here, the cryostat 30, the gantry 50, and the connection portion 80 are installed inside the magnetic shield room 10. The cryogenic refrigerator 20 and the gantry 60 are installed outside the magnetic shield room 10. The cryogenic refrigerator 20 can be realized by using, for example, a known 4K pulse tube refrigerator.

  The transfer tube 40 penetrates the magnetic shield room 10 and is connected to the cryogenic refrigerator 20 and the cryostat 30. More specifically, the transfer tube 40 is directly connected to the cryogenic refrigerator 20, and is connected to the cryostat 30 via the connection unit 80.

  Inside the magnetic shield room 10, a stand 90 for the subject 70 to lie down is also installed. As shown in FIG. 1, a part of the cryostat 30 extends to the position of the lumbar vertebra of the subject 70, and also functions as a table 90. Although not shown in FIG. 1, the cryostat 30 houses a magnetic sensor. Although not shown, a computer for analyzing data measured by the biomagnetic measurement apparatus 1 and controlling the operation of the magnetic sensor is also provided.

  In FIG. 1, a right-handed coordinate system 2 is set that includes a z-axis in the vertical direction in the drawing, an x-axis in the direction from left to right in the drawing, and a y-axis perpendicular to the x-axis and the z-axis. The right-handed coordinate system 2 shown in other figures referred to in this specification is the same as the right-handed coordinate system 2 shown in FIG.

  Here, as shown in FIG. 1, the connecting portion 80 is provided on the side of the cryostat 30 on the side of the cryogenic refrigerator 20 at a height that is about the same as the liquid helium outlet of the cryogenic refrigerator 20. Thereby, the biomagnetism measuring apparatus 1 shortens the moving radius of the cryostat 30 at the time of rotation. As a result, since the distance for moving the cryostat 30 which is a heavy object to move the magnetic sensor 32 is shortened, the convenience for the user can be improved.

  FIG. 2 is a diagram schematically illustrating a functional configuration of the biomagnetic measurement device 1 according to the embodiment of the present invention, and is a diagram for mainly explaining a measurement function in the biomagnetic measurement device 1. FIG. 2 is a view of the biomagnetic measurement device 1 shown in FIG. 1 as viewed from a direction perpendicular to the yz plane of the right-handed coordinate system 2.

  As described with reference to FIG. 1, the subject 70 lies on the table 90 inside the magnetic shield room 10. The magnetic sensor 32 is accommodated in the cryostat 30 so as to come to the position of the lumbar spine of the subject 70. The magnetic sensor 32 can be realized by using, for example, a known SQUID (Superconducting QUantum Interference Device).

  The information processing unit 12 comprehensively controls the measurement function in the biomagnetic measurement device 1. The information processing unit 12 also analyzes biomagnetic data measured by the biomagnetic measurement device 1. The information processing unit 12 can be realized using a computer such as a PC (Personal Computer) or a workstation. The magnetic sensor drive circuit 14 controls the operation of the magnetic sensor 32 under the control of the information processing unit 12. The amplifier / analog filter unit 16 amplifies biomagnetic data measured by the magnetic sensor 32 or removes noise. The data acquisition unit 18 converts the data processed by the amplifier / analog filter unit 16 into digital data. The data acquisition unit 18 can be realized using, for example, a known A / D converter. The data acquired by the data acquisition unit 18 is sent to the information processing unit 12, and various analyzes are executed.

  As described above, the biomagnetic measurement device 1 according to the embodiment of the present invention is a device for measuring a biomagnetic field generated in the body of the subject 70. Since the position where the magnetic sensor 32 should be arranged differs depending on the gender and physique of the subject 70, it is preferable that the position of the magnetic sensor 32 be changed to some extent. On the other hand, as described above, the magnetic sensor 32 is realized using, for example, a SQUID sensor. Since the SQUID sensor is a magnetic sensor using a superconductor, it needs to be cooled to an extremely low temperature (for example, 4K or less) in order to function as a sensor. For this reason, the magnetic sensor 32 is accommodated in a cryostat 30 that stores liquid helium. The magnetic sensor 32 is cooled by liquid helium stored in the cryostat 30.

  In addition, the biomagnetic measurement device 1 according to an embodiment of the present invention may be cooled by heat conduction of a cable disposed in the cryostat 30. FIG. 3 is a diagram illustrating a structure example of the cryostat 30 according to the embodiment of the present invention. As shown in FIG. 3, a cable 33 is connected to the magnetic sensor 32 in the cryostat 30, and the cable 33 extends outside the opening 301 through a liquid helium storage 302 in the cryostat 30. Yes. Here, the opening 301 is “plugged” by urethane foam or the like so as not to come into contact with the outside air. The cable 33 extends to the outside of the cryostat 30 through a gap between “plugs” provided in the opening 301. As shown in FIG. 3, since the cable 33 is immersed in liquid helium, the magnetic sensor 32 is cooled by the heat conduction of the cable 33. The “plug” provided in the opening 301 is not limited to urethane foam, and may be formed of any material.

  In order to change the position of the magnetic sensor 32, the cryostat 30 that houses the magnetic sensor 32 is moved. Therefore, the biomagnetic measurement device 1 according to an embodiment of the present invention is configured such that the cryostat 30 is rotatable with a plane parallel to the yz plane in FIG. 2 as a rotation plane. More specifically, the cryostat 30 is configured to be rotatable about the central axis in the longitudinal direction of the transfer tube 40 as the rotation center.

  FIG. 3 is a diagram illustrating a structure example of the cryostat 30 according to the embodiment of the present invention. As shown in FIG. 3, the cryostat 30 includes a housing 300, an opening 301, and a storage 302. Further, as shown in FIG. 3, a magnetic sensor 32 is provided in the housing 300 of the cryostat 30.

  The cryostat 30 includes a casing 300 having a predetermined shape. The predetermined shape may be any shape such as a cylinder or a rectangular parallelepiped. The material of the casing 300 is, for example, a glass fiber reinforced resin that does not interfere with the magnetic field measurement. A metal such as aluminum or stainless steel may be used partially or entirely. The material of the housing 300 is not limited to these resins and metals, and any material can be used as long as it can accommodate liquid helium.

  The magnetic sensor 32 is disposed in at least a part of the housing 300 of the cryostat 30. For example, the magnetic sensor 32 is disposed in contact with the upper surface 3000 in the housing 300. More specifically, the magnetic sensor 32 is disposed near the center of the upper surface 3000 in the housing 300. The position at which the magnetic sensor 32 is disposed is merely an example, and may be disposed at any position in the housing 300 as long as the magnetic sensor 32 can measure biomagnetic data. .

  For example, the opening 301 is provided in at least a part of the cryostat 30, and helium can be discharged from the inside of the housing 300 of the cryostat 30. The opening 301 can discharge gaseous helium after evaporation.

  As shown in FIG. 3, the opening 301 is provided at the center of the bottom surface 3001 of the housing 300, for example. The position where the opening 301 is provided on the bottom surface 3001 may be a position corresponding to the magnetic sensor 32 disposed on the top surface 3000 of the housing 300. Since the opening 301 is provided at a position corresponding to the magnetic sensor 32 on the bottom surface 3001 of the housing 300, the magnetic sensor 32 can be accessed from the opening 301, and maintenance of the magnetic sensor 32 is easily performed. It becomes possible.

  Note that the position at which the opening 301 is provided is not necessarily limited to the bottom surface of the housing 300, and any position in the housing 300 as long as the opening 301 is provided below the storage portion 302 for storing helium. May be provided.

  The shape of the opening 301 may be any shape such as a circle or a square.

  The storage unit 302 is provided above the opening 301 in the housing 300 and stores helium injected from outside the housing 300. As shown in FIG. 3, the storage unit 302 has an opening on the upper side (that is, the magnetic sensor 32 side) in the housing 300, and a bottom surface 3020 provided substantially parallel to the bottom surface 3000 of the housing 300, An outer side surface 3021 in contact with the housing 300 and an inner side surface 3022 provided corresponding to the outer side surface 3021 are included. The storage unit 302 stores liquid helium in a region surrounded by the bottom surface 3020, the outer side surface 3021, and the inner side surface 3022.

  Note that the bottom surface 3020 of the storage unit 302 does not necessarily need to be substantially parallel to the bottom surface 3001 of the housing 300. The bottom surface 3020 corresponds to the bottom surface 3000 when the storage unit 302 has a mortar shape, for example. It may be provided to have a predetermined inclination. Further, the bottom surface 3020 is not necessarily a flat surface, and may have any shape.

  In addition, the inner side surface 3022 does not necessarily have to be provided corresponding to the outer side surface 3021. When observed from the upper part of the storage portion 302, the inner side surface 3021 has a quadrangular shape, whereas the inner side surface 3021 has a rectangular shape. Any shape may be used, such as the shape of 3022 being circular.

  As shown in FIG. 3, the housing 300 has a double structure including an outer surface and an inner surface, and includes a vacuum layer between the outer surface and the inner surface. Since the housing 300 includes a vacuum layer between the outer surface and the inner surface, the incidence of heat from the outside on the housing 300 can be reduced.

  In addition, as illustrated in FIG. 3, a vacuum layer is included between the bottom surface 3001 of the housing 300 and the bottom surface 3020 of the storage unit 302. Since a vacuum layer is included between the bottom surface 3001 of the housing 300 and the bottom surface 3020 of the storage portion 302, incidence of heat from the outside to the storage portion 302 can be reduced.

  As shown in FIG. 3, the cryostat 30 according to an embodiment of the present invention includes a heat radiation shield 303 in the vacuum layer. The heat radiation shield can reduce the incidence of heat, and can reduce the incidence of heat from the outside to the inside of the housing 300. In addition, as shown in FIG. 3, the heat radiation shield 303 may be provided twice. The heat radiation shield is not limited to double, and may be a single layer or multiple layers.

  As shown in FIG. 3, the cryostat 30 according to an embodiment of the present invention is configured to store gaseous helium after evaporation of liquid helium stored in the storage unit 302 through the opening 301. An exhaust connection port 304 for exhausting air to the outside of the body 300 is included. The gaseous helium is discarded outside the housing 300 through the exhaust connection port 304.

  Here, one end of the transfer tube 40 is connected to the exhaust connection port 304. The evaporated gaseous helium is exhausted by the transfer tube 40 through the exhaust connection port 304. In addition, the transfer tube 40 for injection, which is different from the transfer tube for exhaust, is connected at one end to a liquid injection connection port 305 described below.

  Furthermore, as shown in FIG. 3, the cryostat 30 according to an embodiment of the present invention includes a liquid injection connection port 305 for injecting liquid helium into the reservoir 302. Liquid helium is supplied from the cryogenic refrigerator 20 into the cryostat 30 through the injection port 305. In this sense, the injection port 305 is a liquid helium channel formed between the cryogenic refrigerator 20 and the cryostat 30.

  The liquid injection connection port 305, for example, injects liquid helium into the reservoir 302 through the opening 301. The storage unit 302 may include a probe (not shown) that can measure the amount of liquid helium in the storage unit 302, and the injection port 305 includes the helium measured by the probe. Based on the amount, liquid helium is injected into the reservoir 302. For example, the injection port 305 injects a predetermined amount of liquid helium into the reservoir 302 when the amount of helium measured by the probe is less than or equal to a predetermined value.

  As described above, in the cryostat 30 according to the embodiment of the present invention, the storage unit 302 is provided below the magnetic sensor 32, the magnetic sensor 32 is not immersed in liquid helium, and the storage Since the portion 302 includes the inner side surface 3022, the magnetic sensor 32 can be accessed from the opening 301. Therefore, it is possible to easily perform maintenance of the magnetic sensor 32.

(First modification)
FIG. 4 is a diagram illustrating another structural example of the cryostat 30 according to an embodiment of the present invention.

  As shown in FIG. 4, in the cryostat 30, the inner side surface 3022 of the storage portion 302 includes a liquid-form first side surface 3023 on the helium side and a second side surface 3024 provided outside the first side surface 3023. And includes a vacuum layer between the first side surface 3023 and the second side surface 3024. Since a vacuum layer is included between the first side surface 3023 and the second side surface 3024, incidence of heat from the outside to the storage portion 302 can be reduced. In particular, as shown in FIG. 4, by including a vacuum layer between the first side surface 3023 and the second side surface 3024, it is possible to reduce the incidence of heat from the outside through the opening 301 to the storage unit 302. it can.

(Second modification)
FIG. 5 is a diagram illustrating a structure example of the cryostat 30 according to the embodiment of the present invention.

  As shown in FIG. 5, in the cryostat 30, the inner side surface 3022 of the storage unit 302 includes a first side surface 3023 on the liquid helium side, and a second side surface 3024 provided outside the first side surface 3023. And includes a vacuum layer between the first side surface 3023 and the second side surface 3024. A heat radiation shield 303 is included in the vacuum layer between the first side surface 3023 and the second side surface 3024. The heat radiation shield 303 can reduce the incidence of heat, and can reduce the incidence of heat from the outside into the storage portion 302. In particular, as shown in FIG. 5, by including a heat radiation shield in the vacuum layer between the first side surface 3023 and the second side surface 3024, it is possible to prevent heat from entering through the opening 301 to the storage portion 302. Can be reduced.

  In addition, as shown in FIG. 5, the heat radiation shield 303 may be provided twice. The heat radiation shield is not limited to double, and may be single or multiple.

(Third Modification)
FIG. 6 is a diagram illustrating a structure example of the cryostat 30 according to an embodiment of the present invention.

  As shown in FIG. 6, in the cryostat 30, a liquid injection connection port 305 for injecting liquid helium into the storage portion 302 may be provided on the side surface portion of the housing 300. By providing the injection port 305 in the side surface of the housing 300, it is possible to reduce the complexity of the structure of the opening 301. In addition, since the injection port 305 does not pass through the opening 301, it is not necessary to remove the injection port 305 from the reservoir 302 when accessing the magnetic sensor 32 from the opening 301. 32 can be more easily maintained.

  In the above, this invention was demonstrated based on one Embodiment of this invention. One embodiment of the present invention is an exemplification, and it is understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are within the scope of the present invention. It is a place.

DESCRIPTION OF SYMBOLS 1 Biomagnetism measuring device 2 Right hand coordinate system 10 Magnetic shield room 12 Information processing part 14 Magnetic sensor drive circuit 16 Amplifier / analog filter part 18 Data acquisition part 20 Cryogenic refrigerator 30 Cryostat 32 Magnetic sensor 40 Transfer tube 50 Gantry 60 Base 80 Connection unit 90 units 300 Case 301 Opening 302 Reservoir 303 Heat radiation shield 304 Exhaust connection port 305 Injection port

Claims (11)

A housing,
An opening that is provided in at least a portion of the housing and discharges helium from within the housing;
A storage unit that is provided above the opening in the housing and stores the helium injected from outside the housing;
A magnetic sensor disposed in contact with the upper surface of the casing in the casing and cooled using the helium;
The cryostat is characterized in that the opening discharges the helium after cooling the magnetic sensor.   The reservoir is open on the upper side of the housing, and is provided corresponding to the bottom surface provided substantially parallel to the bottom surface of the housing, the outer side surface in contact with the housing, and the outer side surface. The cryostat according to claim 1, wherein the helium is stored in a region surrounded by an inner side surface.   The cryostat according to claim 2, further comprising a vacuum layer between a bottom surface of the housing and a bottom surface of the storage portion.   The inner side surface of the storage portion has a double structure including a first side surface on the helium side and a second side surface provided outside the first side surface, and the first side surface and the second side surface. The cryostat according to claim 2, further comprising a vacuum layer. The opening is provided at the center of the bottom surface of the housing,
5. The cryostat according to claim 1, wherein the magnetic sensor is disposed at a position corresponding to the opening in a central portion of the upper surface of the housing.   The cryostat according to any one of claims 1 to 5, wherein the casing has a double structure including an outer surface and an inner surface, and includes a vacuum layer between the outer surface and the inner surface.   The cryostat according to claim 6, further comprising a heat radiation shield provided in the vacuum layer and capable of reducing the incidence of heat into the housing.   An exhaust connection port for exhausting the gaseous helium after the helium stored in the storage unit evaporates and cooling the magnetic sensor to the outside of the housing through the opening; The cryostat according to claim 1, wherein the cryostat is included. A cable connected to the magnetic sensor and extending outside the opening through the reservoir;
The cryostat according to claim 1, wherein the magnetic sensor is cooled by heat conduction of the cable.   The cryostat according to any one of claims 1 to 9, further comprising a liquid injection connection port for injecting liquid helium into the reservoir through at least a part of the casing. .   11. The cryostat according to claim 10, wherein the liquid injection connection port injects liquid helium into the reservoir through the opening.