JP2017126691A - Liquid nitrogen container and superconductor magnetic sensing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce degradation of sensitivity of a superconducting magnetic sensor caused from bubbles of nitrogen gas.SOLUTION: The liquid nitrogen container for a superconducting magnetic sensor which operates under liquid nitrogen temperature has a liquid nitrogen container. The liquid nitrogen container includes: a container body which has an internal space filled with liquid nitrogen and a superconducting magnetic sensor set therein; and a resin member which extends at least either one of downward and sideward of the superconducting magnetic sensor in the internal space.SELECTED DRAWING: Figure 5A

Description

  The present disclosure relates to a liquid nitrogen container and a superconductor magnetic sensing device.

  A SQUID (Superconducting Quantum Interference Device) having a structure with a Josephson junction as a loop is used as an ultrasensitive magnetic sensor. A Josephson junction refers to a configuration in which two superconductors are weakly coupled, for example, through a thin insulator or normal conductor barrier layer of several nanometers. Due to the Josephson junction, a superconducting electron pair tunnels through the barrier layer and a superconducting current flows between the two superconductors. When an external magnetic field is applied to the SQUID, the superconducting current changes in response to the magnetic field, and a voltage change occurs at both ends of the Josephson junction. By adding a circuit that cancels this voltage change, the SQUID can measure a weak magnetic field that cannot be measured by a conventional sensor. Application of SQUID to medical care, geomagnetic observation, etc. is expected.

  A metal-based superconductor is generally used for the Josephson junction. However, since an oxide-based superconductor can be used at a high temperature of 77 K, which is the boiling point of liquid nitrogen, an oxide-based superconductor is used. Development of the used Josephson junction is underway (see, for example, Patent Documents 1 and 2).

JP 07-321380 A Japanese Patent Laid-Open No. 2001-4652

  By the way, liquid nitrogen always evaporates and goes out of the liquid nitrogen container no matter what liquid nitrogen container is used. Accordingly, nitrogen gas bubbles are generated in the liquid nitrogen container. In the conventional liquid nitrogen container, it is difficult to reduce the deterioration of the sensitivity of the superconducting magnetic sensor due to such nitrogen gas bubbles.

  Therefore, in one aspect, an object of the present invention is to provide a liquid nitrogen container and a superconductor magnetic sensing device that can reduce deterioration in sensitivity of a superconducting magnetic sensor due to nitrogen gas bubbles.

According to one aspect, in a liquid nitrogen container for a superconducting magnetic sensor operating at liquid nitrogen temperature,
A container body having an internal space filled with liquid nitrogen, the superconducting magnetic sensor being set in the internal space;
There is provided a liquid nitrogen container including a resin member extending to at least one of a lower side and a side of the superconducting magnetic sensor in the inner space.

  A liquid nitrogen container and a superconductor magnetic sensing device that can reduce deterioration in sensitivity of the superconducting magnetic sensor due to nitrogen gas bubbles can be obtained.

It is a schematic diagram of the superconducting magnetic sensor of the embodiment. It is a top view which shows the structural example of the superconducting magnetic sensor as a magnetometer. It is a figure which shows the positional relationship of an input coil and a SQUID loop. It is a top view which shows the structural example of the superconducting magnetic sensor as a gradiometer. It is a figure which shows typically the state of the superconducting magnetic sensor in the liquid nitrogen container by Example 1. FIG. It is a figure which shows typically the state of the superconducting magnetic sensor in the liquid nitrogen container by a comparative example. It is a figure which shows typically the state of the superconducting magnetic sensor in the liquid nitrogen container by Example 2. FIG. It is a 3rd page figure which shows each example of a bubble guard and a spacer. It is a 3rd page figure which shows an example of a base part. It is a figure which shows typically the state of the superconducting magnetic sensor in the liquid nitrogen container by Example 3. It is a 3rd page figure which shows each example of a bubble guard and a spacer.

  Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram of a superconducting magnetic sensor 1 according to an embodiment. Superconducting magnetic sensor 1 includes a SQUID 10 using a Josephson junction 15, a pickup loop 11, and an input coil 12.

  SQUID 10 is a circuit formed of a superconductor. The pickup loop 11 and the input coil 12 are each formed of a conductor, a good conductor, a superconductor, or the like. The external magnetic field captured (detected) by the pickup loop 11 is input to the SQUID 10 by the input coil 12. The SQUID 10 has a Josephson junction 15 formed in a SQUID loop 13 of a superconductor, and converts a detected magnetic field into an electric signal. In the figure, the position of the Josephson junction 15 is indicated by a cross mark (x mark). In this example, SQUID 10 has two Josephson junctions.

  Four electrode pads 36 to 39 are connected to the SQUID 10. When a predetermined bias current is applied from the electrode pads 36 and 38 to the SQUID 10 and the magnetic flux passes through the SQUID loop 13, a superconducting current corresponding to this magnetic flux flows through the Josephson junction 15, and a voltage is applied across the SQUID 10. Occur. By extracting the generated voltage from the electrode pads 37 and 39, the magnetic field can be measured. The superconducting magnetic sensor 1 using the SQUID 10 can measure a minute magnetic field with high sensitivity.

  FIG. 2 is a top view showing a configuration example of the superconducting magnetic sensor 1 as a magnetometer. In FIG. 2, the pickup loop 11 and the SQUID 10 are formally hatched to improve visibility. A superconducting magnetic sensor 1 illustrated in FIG. 2 is a magnetometer using a single coil pickup loop 11. The SQUID 10 is disposed on the substrate 21. The SQUID 10 includes a washer 13W serving as a SQUID loop 13 and a superconducting pattern 31 in which a Josephson junction 15 is formed.

In this example, the substrate 21 is an oxide substrate such as MgO (magnesium oxide) or STO (strontium titanate), but a semiconductor substrate such as silicon may be used. The superconducting pattern 31 including the washer 13W and the Josephson junction 15 is formed of an oxide high temperature superconducting film such as YBa ₂ Cu ₃ O ₇ (YBCO) or Bi ₂ Sr ₂ Ca ₂ Cu ₃ O ₁₀ (BSCCO). Is done.

  When the oxide-based superconducting pattern 31 is used, a crystal grain boundary formed at the interface of the superconducting material can be used as the barrier layer of the Josephson junction 15. As a configuration for generating a crystal grain boundary, a bicrystal structure, a biepitaxial structure, a step edge structure, a ramp edge structure, or the like can be used.

  An input coil 12 is formed above the SQUID 10 via an insulating film 22. A pickup loop 11 is formed on the insulating film 22 together with the input coil 12. The input coil 12 and the pickup loop 11 are formed of an oxide high temperature superconducting thin film such as YBCO. The substrate 21 can be designed to an arbitrary size, and the diameter of the pickup loop 11 is also adjusted as appropriate. The substrate 21 may be cut out to a predetermined size after a large number of superconducting magnetic sensors 1 are formed on the wafer.

  FIG. 3 is a diagram showing an example of the positional relationship between the input coil 12 and the SQUID loop 13 (washer 13W). 2 and 3, the input coil 12 is arranged above the SQUID loop 13 when viewed from the surface of the substrate 21 in the vertical direction. However, the present invention is not limited to this arrangement example, and the input coil 12 may be arranged on the substrate surface, and the SQUID loop 13 may be arranged above the input coil 12.

  In the example shown in FIGS. 1 to 3, the superconducting magnetic sensor 1 using two Josephson junctions 15 has been described. However, one Josephson junction 15 can also be used. When a single Josephson junction 15 is used, for example, a coil (inductor) may be arranged in the vicinity of the SQUID 10 and a high frequency may be applied, and a voltage generated at both ends of the Josephson junction 15 due to magnetic field resonance may be taken out.

  FIG. 4 is a top view showing a configuration example of the superconducting magnetic sensor 2 as a gradiometer. In FIG. 4, the pickup loop 51 is hatched formally in order to improve the visibility.

  Superconducting magnetic sensor 2 as a gradiometer has pickup coils 51a and 51b of the same size wound in opposite phases. The pickup coils 51a and 51b are combined to form a pickup loop 51. The pickup loop 51 extracts the difference between the signals detected by the two pickup coils 51a and 51b, thereby canceling the external magnetic noise and extracting only the target magnetic signal. For example, when measuring a magnetic signal such as an α wave, the influence of the geomagnetism is canceled and the magnetic signal of the target is taken out.

  In the configuration example of FIG. 4, a pickup loop 51 is formed on the same plane as the SQUID 10 fabricated on the substrate 21, and the superconducting magnetic sensor 2 is a planar gradiometer. In the superconducting magnetic sensor 2, in addition to the four electrode pads 36 to 39 for current and voltage, electrode pads 53 and 54 for monitoring are arranged. A feedback coil 56 is disposed between the electrode pads 53 and 54.

  Next, a superconductor magnetic sensing device that can include both the superconducting magnetic sensor 1 and the superconducting magnetic sensor 2 described above will be described. In the following, an example of a superconductor magnetic sensing device including the superconducting magnetic sensor 1 will be described as a representative, but the same applies to a superconductor magnetic sensing device including the superconducting magnetic sensor 2.

[Example 1]
FIG. 5A is a diagram schematically illustrating the superconductor magnetic sensing device 100 according to the first embodiment. FIG. 5B is a diagram schematically showing the state of the superconducting magnetic sensor 1 in the liquid nitrogen container 60 ′ in the superconductor magnetic sensing device according to the comparative example. 5A and 5B show a longitudinal sectional view along a vertical plane passing through the center of the liquid nitrogen container 60. FIG.

  In the following description, the vertical direction is defined as the direction shown in FIG. 5A. Here, the upper side in the vertical direction is the side on which the bubbles rise. The vertical direction typically corresponds to the vertical direction of the vertical direction.

  In the first embodiment, the superconductor magnetic sensing device 100 includes the superconducting magnetic sensor 1 and the liquid nitrogen container 60.

  Since the above-described superconducting magnetic sensor 1 (the same applies to the superconducting magnetic sensor 2) can be used at 77K, the superconductor magnetic sensing device 100 is used by being cooled in a liquid nitrogen container 60 filled with liquid nitrogen. The That is, the superconducting magnetic sensor 1 operates by being immersed in liquid nitrogen in the liquid nitrogen container 60 and cooled.

  The liquid nitrogen container 60 includes a container body 62 and a bubble guard 70 (an example of a resin member). The container main body 62 is called a dewar and is made of, for example, quartz glass. The container body 62 includes a side wall 621 and a bottom wall 622 and forms an internal space 61. The internal space 61 is filled with liquid nitrogen and the superconducting magnetic sensor 1 is set. That is, the internal space 61 is filled with liquid nitrogen, and the superconducting magnetic sensor 1 is immersed in liquid nitrogen. Note that the side wall 621 and the bottom wall 622 may have various heat insulating structures including a double structure. Hereinafter, as an example, it is assumed that the container body 62 has a cylindrical shape.

  A lid 7 is provided on the upper portion of the container main body 62 in a manner that enhances the airtightness of the internal space 61 of the container main body 62. The lid 7 is provided with a conductor support portion 8 in such a manner as to penetrate the lid 7 up and down. The conducting wire support portion 8 supports the wiring for measurement electrically connected to the electrode pads 36 to 39 (see FIG. 1) by built-in or locking. The conducting wire support portion 8 is formed of a resin pipe, for example. In this case, the signal can be taken out through the wiring inside the pipe. The superconducting magnetic sensor 1 is fixed to the lower end of the conductor support 8.

  Here, as described above, since there is heat inflow from the surroundings in the container main body 62, the liquid nitrogen always evaporates and goes out of the container main body 62 regardless of the container main body 62 used. . For this reason, the generation of nitrogen gas bubbles is inevitable in the container body 62. In FIG. 5A (also in FIG. 5B), the bubble rising path is schematically shown by a picture of the bubble to which reference numeral B is attached. Nitrogen gas bubbles are mainly generated from the side wall 621 and the bottom wall 622 of the container body 62 and move upward (see arrow R1). The same applies to the comparative examples described later.

  As a physical guard, the bubble guard 70 has a guard function for reducing the upward movement of nitrogen gas bubbles from hitting the superconducting magnetic sensor 1. The bubble guard 70 extends to at least one of the side and the lower side of the superconducting magnetic sensor 1 as a configuration for expressing the guard function. When the bubble guard 70 extends to the side of the superconducting magnetic sensor 1, the side of the superconducting magnetic sensor 1 can be at least partially guarded from the bubbles. Further, when the bubble guard 70 extends below the superconducting magnetic sensor 1, the lower portion of the superconducting magnetic sensor 1 can be at least partially guarded from the bubbles. Here, in general, the bubbles move upward while drifting, but the bubbles that can collide with the superconducting magnetic sensor 1 are mainly near the bottom of the superconducting magnetic sensor 1 in the bottom wall 622 of the liquid nitrogen container 60. It occurred in the area. For this reason, when the bubble guard 70 extends below the superconducting magnetic sensor 1, the possibility that bubbles generated at the bottom wall 622 of the liquid nitrogen container 60 may hit the superconducting magnetic sensor 1 can be efficiently reduced.

  In the example shown in FIG. 5A, the bubble guard 70 has a cylindrical cylindrical portion 71 surrounding the side of the superconducting magnetic sensor 1, and extends downward from the cylindrical portion 71. And a bottom portion 72 extending to the bottom. That is, as shown in FIG. 5A, the bubble guard 70 forms a space 73 that is closed except at the top. Accordingly, in the example shown in FIG. 5A, the bubble guard 70 can at least partially guard the side and bottom of the superconducting magnetic sensor 1 from the bubbles. The cylindrical part 71 and the bottom part 72 may be integrally formed. Note that the bubble guard 70 does not contact the superconducting magnetic sensor 1 and the conductor support 8 as shown in FIG. 5A. That is, liquid nitrogen filled in the space 73 exists between the bubble guard 70 and the superconducting magnetic sensor 1 and the conductor support 8 as shown in FIG. 5A.

  The bubble guard 70 is made of resin (plastic) so that the thermal conductivity is low. The bubble guard 70 has a thermal conductivity of 0.5 W / m · K or less, for example. Thereby, generation | occurrence | production of the bubble from the surface of the bubble guard 70 resulting from the heat which can be transmitted from the container main body 62 can be reduced (the bubble generated from the liquid nitrogen in the space 73 can be reduced). As the resin, polyethylene terephthalate (PET) or the like can be used. In addition, when the container main body 62 is formed of quartz glass, the bubble guard 70 is not limited to the thermal conductivity (1.2 to 1.4 W / m · K) or less of the quartz glass. For example, it may include a resin to which a specific additive or the like is added.

  The support method of the bubble guard 70 is arbitrary. For example, the bubble guard 70 may be supported on at least one of the side wall 621 and the bottom wall 622 of the container body 62. For example, in the example shown in FIG. 5A, the bubble guard 70 is supported in such a manner that it contacts the bottom wall 622 of the container body 62. The bubble guard 70 may be bonded to the bottom wall 622 of the container body 62 with an adhesive or the like. Alternatively, the bubble guard 70 may be brought into contact with the bottom wall 622 of the container body 62 by the action of gravity by placing a weight or the like on the bottom 72.

  The liquid nitrogen container 60 ′ according to the comparative example is different from the liquid nitrogen container 60 according to the first embodiment in that the bubble guard 70 is not provided.

  In the case of the comparative example, as schematically shown in FIG. 5B, the bubbles collide with the superconducting magnetic sensor 1 in the liquid nitrogen and cause the superconducting magnetic sensor 1 to generate minute vibrations. When such a minute vibration is generated in the supersensitive magnetic sensor 1 with high sensitivity, noise is generated, and the sensitivity (signal-to-noise ratio) of the superconductive magnetic sensor 1 may be deteriorated.

  In this regard, in the first embodiment, a bubble guard 70 is provided as schematically shown in FIG. 5A. By providing the bubble guard 70, it is possible to reduce the nitrogen gas bubbles moving upward from hitting the superconducting magnetic sensor 1 as described above. Therefore, according to the first embodiment, it is possible to reduce deterioration of the sensitivity of the superconducting magnetic sensor 1 due to nitrogen gas bubbles.

  Further, according to the first embodiment, since the bubble guard 70 is provided apart from the superconducting magnetic sensor 1, the bubble guard 70 itself is smaller than when contacting the superconducting magnetic sensor 1. The possibility that vibration is transmitted to the superconducting magnetic sensor 1 can be reduced. For example, when the bubble guard 70 is in contact with the superconducting magnetic sensor 1, the superconducting magnetic sensor 1 can vibrate slightly due to the minute vibration of the bubble guard 70 caused by the collision of the bubble with the bubble guard 70. In this regard, according to the first embodiment, since the bubble guard 70 is substantially physically separated from the superconducting magnetic sensor 1, minute vibrations of the bubble guard 70 itself are directly applied to the superconducting magnetic sensor 1. Can be prevented from being transmitted to.

  Further, according to the first embodiment, since the bubble guard 70 is supported by the container main body 62, the bubble guard 70 is supported more than the case where it is supported by another member (for example, the conductor support 8 or the superconducting magnetic sensor 1 itself). The possibility that the minute vibration of the bubble guard 70 itself is transmitted to the superconducting magnetic sensor 1 can be reduced. For example, when the bubble guard 70 is supported by the conducting wire support portion 8, the conducting wire support portion 8 that holds the superconducting magnetic sensor 1 due to minute vibration of the bubble guard 70 due to the collision of the bubbles with the bubble guard 70. Can vibrate slightly. Therefore, in this case, there is a possibility that minute vibrations of the bubble guard 70 itself are transmitted to the superconducting magnetic sensor 1 through the conductor support 8. In this regard, according to the first embodiment, since it is supported by the container body 62 that is substantially physically separated from the superconducting magnetic sensor 1, minute vibrations of the bubble guard 70 itself are caused to pass through other members. Thus, transmission to the superconducting magnetic sensor 1 can be prevented.

  In the example shown in FIG. 5A, the bubble guard 70 is supported in a state of being in surface contact with the bottom wall 622 of the container body 62, but the bubble guard 70 is in contact with the bottom wall 622 of the container body 62 with dots or lines. May be supported in such a manner. Thereby, the area which contacts the bottom wall 622 of the container main body 62 can be made small. The smaller the area in contact with the bottom wall 622 of the container body 62, the smaller the heat transfer from the container body 62, so that the generation of bubbles from the surface of the bubble guard 70 can be reduced. For example, the bubble guard 70 may have a form that protrudes downward. More specifically, the bottom portion 72 of the bubble guard 70 may have a conical shape with a tip portion (head) cut away when the cylindrical portion 71 has a cylindrical shape. In this case, the bubble guard 70 can be supported in such a manner that it substantially makes point contact with the bottom wall 622 of the container body 62.

[Example 2]
FIG. 6 is a diagram showing the superconductor magnetic sensing device 100A according to the second embodiment, and schematically showing the state of the superconducting magnetic sensor 1 in the liquid nitrogen container 60A. Note that in FIG. 6, the bubble rising path is schematically shown by a bubble picture denoted by reference symbol B. FIG. 7 is a three-view diagram (top view and two-side view) showing an example of the bubble guard 70A and the spacer 80. FIG. FIG. 8 is a three-view diagram (top view and two-side view) showing an example of the base portion 90.

  In the second embodiment, the superconductor magnetic sensing device 100A includes the superconducting magnetic sensor 1 and a liquid nitrogen container 60A.

  The liquid nitrogen container 60A according to the second embodiment is different from the liquid nitrogen container 60 according to the first embodiment described above in that the bubble guard 70 is replaced with the bubble guard 70A, and the spacer 80 and the base portion 90 are added. . Components that may be the same as those of the liquid nitrogen container 60 according to the first embodiment described above are denoted by the same reference numerals in FIG.

  The bubble guard 70A includes a cylindrical cylindrical portion 71A that surrounds the side of the superconducting magnetic sensor 1, and a bottom portion 72A that extends downward from the cylindrical portion 71A and extends below the superconducting magnetic sensor 1. including. In the example shown in FIG. 6, the bottom 72A has a downwardly convex shape. More specifically, the cylindrical portion 71A and the bottom portion 72A have a form in which the cross-sectional area in the horizontal plane of the space 73 decreases as it goes downward. That is, the bubble guard 70A has a form in which the surface area per unit height decreases as it goes downward. Thereby, the surface area of the bubble guard 70A can be efficiently reduced while maintaining the above-described guard function, and bubbles that can be generated from the surface of the bubble guard 70A can be reduced.

  The bubble guard 70A is formed of a resin, similar to the bubble guard 70 according to the first embodiment described above.

  The bottom 72A of the bubble guard 70A has a through hole 74 that penetrates obliquely downward. By providing the through-hole 74, when the liquid nitrogen level rises beyond the through-hole 74 when liquid nitrogen is injected, the liquid nitrogen can be evenly distributed inside the space 73 and outside the space 73. . The position of the through hole 74 is arbitrary, but is preferably a position away from a region near the superconducting magnetic sensor 1. Thereby, a fall of the guard function of the bubble guard 70A resulting from the through hole 74 can be reduced.

  The spacer 80 is provided between the bubble guard 70 </ b> A and the side wall 621 of the container main body 62. The spacer 80 restrains the horizontal displacement of the bubble guard 70 </ b> A relative to the container body 62. That is, the spacer 80 is provided in such a manner as to abut against the side wall 621 of the container body 62 in the horizontal direction. Accordingly, the horizontal displacement of the bubble guard 70A with respect to the container body 62 is restricted, and minute vibrations that can occur in the bubble guard 70A itself due to the collision of the bubbles with the bubble guard 70A are reduced. Here, when a minute vibration is generated in the bubble guard 70A itself, the minute vibration can be transmitted to the supersensitive magnetic sensor 1 with high sensitivity via liquid nitrogen. Therefore, if the minute vibration that can be generated in the bubble guard 70A itself is reduced, the minute vibration that can be transmitted to the supersensitive superconducting magnetic sensor 1 via liquid nitrogen is reduced. 1 deterioration of sensitivity can be reduced.

  The spacer 80 is preferably formed of a resin so that the thermal conductivity is low, like the bubble guard 70A. The spacer 80 may be fixed to the bubble guard 70A by adhesion or the like, or may be fixed to the container body 62. When the spacer 80 is formed of the same material as the bubble guard 70A, the spacer 80 may be formed integrally with the bubble guard 70A.

  In the example shown in FIGS. 6 and 7, the spacer 80 includes a first spacer 810 provided on the outer periphery of the cylindrical portion 71 </ b> A and a second spacer 820 provided on the outer periphery of the bottom portion 72 </ b> A. The first spacer 810 and the second spacer 820 may be provided continuously over the entire circumference, but are preferably provided only in part with respect to the entire circumference of the bubble guard 70A. In the example shown in FIG. 7, a plurality of locations (4 locations) are provided separately. Thereby, the upward movement of the bubbles generated below the spacer 80 (the upward movement of the bubbles outside the cylindrical portion 71A) becomes possible. The side wall 621 of the container body 62 may be provided with a protrusion that supports the lower surfaces of the first spacer 810 and the second spacer 820.

  The base portion 90 is provided between the bubble guard 70 </ b> A and the bottom wall 622 of the container body 62. The base portion 90 supports the bubble guard 70 </ b> A with respect to the container body 62. By providing the base portion 90, direct contact between the bubble guard 70A and the bottom wall 622 of the container main body 62 is eliminated, so heat transfer from the bottom wall 622 of the container main body 62 to the bubble guard 70A can be reduced.

  The base portion 90 is preferably formed of a resin so as to have a low thermal conductivity, like the bubble guard 70A. The base portion 90 may be fixed to the bubble guard 70 </ b> A by adhesion or the like, or may be fixed to the bottom wall 622 of the container body 62. When the base part 90 is formed of the same material as the bubble guard 70A, the base part 90 may be formed integrally with the bubble guard 70A. When the base portion 90 is fixed to the bubble guard 70A, the base portion 90 integrated with the bubble guard 70A may be fixed to the bottom wall 622 of the container body 62 in a removable manner, or may be firmly fixed. Also good. When the base portion 90 is fixed to the bottom wall 622, the bubble guard 70A may be fixed to the base portion 90 in a removable manner.

  In the example shown in FIGS. 6 and 8, the base portion 90 includes a plate-like portion 910 and a cylindrical leg portion 920 coupled to the lower surface of the plate-like portion 910. The plate-like portion 910 has a circular shape with an outer diameter corresponding to the inner diameter of the container main body 62, and restrains the horizontal displacement of the bubble guard 70 </ b> A relative to the container main body 62, similar to the spacer 80. That is, the plate-like portion 910 is provided in a manner that it abuts against the side wall 621 of the container body 62 in the horizontal direction. Thereby, the horizontal displacement of the bubble guard 70A with respect to the container main body 62 is restrained, and minute vibrations that can occur in the bubble guard 70A itself are reduced. The plate-like portion 910 is provided with through holes 94 (four through holes 94 in the examples shown in FIGS. 6 and 8). Thereby, the upward movement of the bubbles generated below the plate-like portion 910 becomes possible. The leg 920 is supported in such a manner that the leg 920 contacts the bottom wall 622 of the container body 62 in a substantially line (circular line).

  In the example shown in FIGS. 6 and 8, the plate-like portion 910 of the base portion 90 has an outer diameter that is substantially the same as the inner diameter of the container body 62 so as to contact the side wall 621 of the container body 62 in the horizontal direction. However, it may have an outer diameter that is significantly smaller than the inner diameter of the container body 62. In this case, since the upward movement of the bubbles generated below the plate-like portion 910 is possible through the gap between the side wall of the container main body 62 and the plate-like portion 910, the plate-like portion 910 has a through hole. 94 may not be included.

[Example 3]
FIG. 9 is a diagram showing the superconductor magnetic sensing device 100B according to the third embodiment, and schematically showing the state of the superconducting magnetic sensor 1 in the liquid nitrogen container 60B. Note that, in FIG. 9, the bubble rising path is schematically shown by a bubble picture denoted by reference symbol B. FIG. 10 is a three-view diagram (top view and two-side view) showing an example of each of the bubble guard 70B and the spacer 80B.

  In the third embodiment, the superconductor magnetic sensing device 100B includes the superconducting magnetic sensor 1 and the liquid nitrogen container 60B.

  The liquid nitrogen container 60B according to the third embodiment is different from the liquid nitrogen container 60A according to the second embodiment described above in that the bubble guard 70 is replaced with the bubble guard 70B and the spacer 80 is replaced with the spacer 80B. Components that may be the same as those of the liquid nitrogen container 60A according to the second embodiment described above are denoted by the same reference numerals in FIG.

  The bubble guard 70B includes a cylindrical cylindrical portion 71B that surrounds the side of the superconducting magnetic sensor 1, and a cylindrical bottom portion 72B that extends downward from the cylindrical portion 71B and has a smaller diameter than the cylindrical portion 71B. including. In the example illustrated in FIG. 9, the cylindrical portion 71 </ b> B has a form in which the cross-sectional area in the horizontal plane of the space 73 decreases as it goes downward. The opening on the lower side of the bottom portion 72 </ b> B is closed by the base portion 90. Accordingly, the surface area of the bubble guard 70B can be efficiently reduced while maintaining the above-described guard function, and bubbles that can be generated from the surface of the bubble guard 70B can be reduced.

  The bubble guard 70B is preferably made of resin so that the thermal conductivity is low, like the bubble guard 70 according to the first embodiment described above.

  The bottom 72B of the bubble guard 70B has a through hole 74B that penetrates in a substantially horizontal direction. By providing the through holes 74B, liquid nitrogen can be evenly distributed inside the space 73 and outside the space 73 when the liquid nitrogen level rises beyond the through hole 74B when liquid nitrogen is injected. . Moreover, since the through-hole 74B faces to the side substantially perpendicular to the rising direction of the bubbles, it is possible to reduce the deterioration of the guard function of the bubble guard 70B caused by the through-hole 74B.

  The bottom part 72B of the bubble guard 70B may be fixed to the base part 90 by bonding or the like. When the base part 90 is formed of the same material as the bubble guard 70B, the base part 90 may be formed integrally with the bubble guard 70B.

  The spacer 80B is preferably formed of a resin so that the thermal conductivity is low, like the spacer 80 according to the second embodiment described above. The spacer 80 </ b> B is provided between the bubble guard 70 </ b> B and the side wall 621 of the container main body 62. The spacer 80 </ b> B restrains the horizontal displacement of the bubble guard 70 </ b> B with respect to the container body 62. That is, the spacer 80 </ b> B is provided in such a manner that the spacer 80 </ b> B contacts the side wall 621 of the container body 62 in the horizontal direction. Thereby, the horizontal displacement of the bubble guard 70B with respect to the container body 62 is restrained, and minute vibrations that can be generated in the bubble guard 70B itself are reduced. In the example shown in FIGS. 9 and 10, the spacers 80B are provided discretely at a plurality of locations (four locations) with respect to the entire circumference of the bubble guard 70B. Thereby, the upward movement of the bubbles generated below the spacer 80B becomes possible.

  Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes can be made within the scope described in the claims. It is also possible to combine all or a plurality of the components of the above-described embodiments.

In addition, the following additional remarks are disclosed regarding the above Example.
(Appendix 1)
In a liquid nitrogen container for a superconducting magnetic sensor operating at liquid nitrogen temperature,
A container body having an internal space filled with liquid nitrogen, the superconducting magnetic sensor being set in the internal space;
A liquid nitrogen container including a resin member extending to at least one of a lower side and a side of the superconducting magnetic sensor in the inner space.
(Appendix 2)
The resin member includes a cylindrical part surrounding a side of the superconducting magnetic sensor, and a bottom part extending between the bottom wall of the container body and the superconducting magnetic sensor. Liquid nitrogen container.
(Appendix 3)
The liquid nitrogen container according to appendix 2, wherein the bottom portion of the resin member has a form that protrudes downward.
(Appendix 4)
The liquid nitrogen container according to appendix 2 or 3, wherein a through hole is formed in the bottom portion of the resin member.
(Appendix 5)
The liquid nitrogen container according to any one of appendices 1 to 4, wherein the resin member is provided apart from the superconducting magnetic sensor.
(Appendix 6)
The liquid nitrogen container according to any one of appendices 1 to 5, wherein the resin member is supported by the container body.
(Appendix 7)
The liquid nitrogen container according to any one of appendices 1 to 6, further including a resin spacer provided between the resin member and a side wall of the container main body.
(Appendix 8)
The liquid nitrogen container according to appendix 7, wherein the spacer is fixed to the resin member and abuts against a side wall of the container body.
(Appendix 9)
The liquid nitrogen container according to appendix 8, wherein the spacer contacts the side wall of the container body at a part of the entire circumference of the side wall of the container body.
(Appendix 10)
The supplementary member according to any one of appendices 1 to 9, further including a resin base portion provided between the resin member and a bottom wall of the container body and supporting the resin member with respect to the container body. Liquid nitrogen container.
(Appendix 11)
The liquid nitrogen container according to appendix 10, wherein the base portion includes a plate-shaped portion that abuts against a side wall of the container main body, and a through-hole is formed in the plate-shaped portion.
(Appendix 12)
The liquid nitrogen container according to any one of appendices 1 to 11, wherein the resin member has a form in which a surface area per unit height decreases as going downward.
(Appendix 13)
The liquid nitrogen container according to any one of appendices 1 to 12, wherein the resin member has a thermal conductivity of 0.5 W / m · K or less.
(Appendix 14)
A container body having an internal space filled with liquid nitrogen, and a liquid nitrogen container comprising a resin member provided in the internal space;
A superconducting magnetic sensor disposed in the internal space and operating at a liquid nitrogen temperature,
The superconductor magnetic sensing device, wherein the resin member extends to at least one of a lower side and a side of the superconducting magnetic sensor.
(Appendix 15)
In a resin member for a liquid nitrogen container provided with a container body,
A resin member extending to at least one of a lower side and a side of the superconducting magnetic sensor in the container body filled with liquid nitrogen.

1, 2 Superconducting magnetic sensor 10 SQUID (superconducting circuit)
11 Pickup loop 12 Input coil 13 SQUID loop 15 Josephson junction 21 Substrate 31 Superconducting pattern
60, 60A, 60B Liquid nitrogen container
61 Internal space 62 Container body
621 Side wall 622 Bottom wall 70, 70A, 70B Bubble guard
71, 71A, 71B Cylindrical part 72, 72A, 72B Bottom part 74, 74B Through hole 80, 80B Spacer
90 base portion 910 plate-like portion 94 through hole 100, 100A, 100B superconductor magnetic sensing device

Claims (9)

In a liquid nitrogen container for a superconducting magnetic sensor operating at liquid nitrogen temperature,
A container body having an internal space filled with liquid nitrogen, the superconducting magnetic sensor being set in the internal space;
A liquid nitrogen container including a resin member extending to at least one of a lower side and a side of the superconducting magnetic sensor in the inner space.   The said resin member is a cylindrical part surrounding the side of the said superconducting magnetic sensor, The bottom part extended between the bottom wall of the said container main body and the said superconducting magnetic sensor is set forth in Claim 1. Liquid nitrogen container.   The liquid nitrogen container according to claim 2, wherein the bottom portion of the resin member has a form that protrudes downward.   The liquid nitrogen container according to claim 2, wherein a through hole is formed in the bottom portion of the resin member.   The liquid nitrogen container according to claim 1, wherein the resin member is provided apart from the superconducting magnetic sensor.   The liquid nitrogen container according to claim 1, wherein the resin member is supported by the container body.   The liquid nitrogen container according to claim 1, further comprising a resin spacer provided between the resin member and a side wall of the container main body.   The resin base part provided between the said resin member and the bottom wall of the said container main body, and further including the resin base part which supports the said resin member with respect to the said container main body is any one of Claims 1-7. Liquid nitrogen container. A container body having an internal space filled with liquid nitrogen, and a liquid nitrogen container comprising a resin member provided in the internal space;
A superconducting magnetic sensor disposed in the internal space and operating at a liquid nitrogen temperature,
The superconductor magnetic sensing device, wherein the resin member extends to at least one of a lower side and a side of the superconducting magnetic sensor.

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