JP2009291375A - Squid, biomagnetism measuring instrument, magnetoencephalograph, magnetocardiograph, squid magnetic searching equipment, squid microscope, and squid metal detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a SQUID for suppressing the filling amount of a cryogen for cooling a SQUID sensor, a biomagnetism measuring instrument, a magnetoencephalograph, a magnetocardiograph, SQUID magnetic searching equipment, a SQUID microscope, and a SQUID metal detector. <P>SOLUTION: The SQUID 1 includes: a pickup coil 31 which is constituted of a superconductive body so as to detect a magnetic field from an object; a SQUID element 33 which is connected to the pickup coil 31 via a superconductive wire 32, includes Josephson junction, and converts the magnetic field detected by the pickup coil 31 into a voltage; an immersing and cooling means which includes a Dewar 7 for containing liquid helium 5, immerses the SQUID element 33 in the liquid helium 5, and cools the element; and a conductive cooling means for cooling the pickup coil 31 arranged on the outside of the liquid helium 5 by thermal conduction from a cooling stage 11, etc. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a SQUID device, a biomagnetic measuring device, a magnetoencephalograph, a magnetocardiograph, a SQUID magnetic flaw detector, a SQUID microscope, and a SQUID metal detector.

Conventionally, as a technique in such a field, a biomagnetic measuring device described in Patent Document 1 below is known. This biomagnetic measurement apparatus measures and analyzes a magnetic field generated in a human brain, and includes a SQUID sensor that detects a weak magnetic field. Since this SQUID sensor needs to maintain a stable temperature at the superconducting transition temperature, the device is equipped with a dewar that contains a cryogenic liquid cryogen, and the SQUID sensor is the cryogen (here, It is immersed in liquid helium) and cooled.
JP 2005-291629 A

  In this type of apparatus, it is necessary to evacuate the interior of the dewar once every maintenance and refill the dewar again with the cryogen. For example, liquid helium, which is widely used as a cryogen, is very expensive. Therefore, the smaller the cryogen filling amount, the lower the maintenance cost of this type of apparatus. Also, the less cryogen that the device holds, the more safe the operation of the system. Thus, in an apparatus using a SQUID sensor, it is desired to reduce the filling amount of the cryogen.

  Therefore, the present invention provides a SQUID device, a biomagnetic measurement device, a magnetoencephalograph, a magnetocardiograph, a SQUID magnetic flaw detector, a SQUID microscope, and a SQUID metal detector that can suppress the amount of cryogen filling for cooling the SQUID sensor. For the purpose.

  The SQUID device of the present invention is a pickup coil that is made of a superconductor and detects a magnetic field from an object, and is connected to the pickup coil by a superconducting wire and has a Josephson junction to detect a magnetic field detected by the pickup coil. Heat conduction from a low heat source, including a SQUID element for converting to voltage, an immersion cooling means having a cryogen container for storing a liquid cryogen and immersing the SQUID element in the cryogen, and a pickup coil disposed outside the cryogen And a conductive cooling means for cooling by the above.

  The biomagnetic measurement device of the present invention is a biomagnetic measurement device that measures and analyzes a magnetic field generated in a living body, and is composed of a superconductor and detects a magnetic field generated in the living body, and a pickup coil. A SQUID element that has a Josephson junction and converts the magnetic field detected by the pickup coil into a voltage, and a cryogen container that contains a liquid cryogen, and immerses the SQUID element in the cryogen. And a cooling means for cooling the pick-up coil arranged outside the cryogen by heat conduction from a low heat source.

  The magnetoencephalograph of the present invention is a magnetoencephalograph that measures and analyzes the magnetic field generated in the subject's brain, and includes a pickup coil made of a superconductor for detecting the magnetic field generated in the subject's brain, A SQUID element that has a Josephson junction and converts the magnetic field detected by the pickup coil into a voltage and a cryogen container that contains a liquid cryogen and is immersed in the cryogen for cooling. And a cooling means for cooling the pick-up coil arranged outside the cryogen by heat conduction from a low heat source.

  The magnetocardiograph of the present invention is a magnetocardiograph that measures and analyzes the magnetic field generated in the subject's heart, and includes a pickup coil that is made of a superconductor and detects the magnetic field generated in the subject's heart, A SQUID element that has a Josephson junction and converts the magnetic field detected by the pickup coil into a voltage and a cryogen container that contains a liquid cryogen and is immersed in the cryogen for cooling. And a cooling means for cooling the pick-up coil arranged outside the cryogen by heat conduction from a low heat source.

  The SQUID magnetic flaw detection apparatus of the present invention is a SQUID magnetic flaw detection apparatus that performs flaw detection of an inspection object by measuring and analyzing the magnetic field from the inspection object. A pick-up coil for detecting the temperature, a SQUID element that is connected to the pick-up coil by a superconducting wire, has a Josephson junction, and converts a magnetic field detected by the pick-up coil into a voltage, and a cryogen container that contains a liquid cryogen It is characterized by comprising immersion cooling means for immersing and cooling the SQUID element in a cryogen, and conduction cooling means for cooling a pickup coil disposed outside the cryogen by heat conduction from a low heat source.

  The SQUID microscope of the present invention is a SQUID microscope that obtains a magnetic flux distribution image of an inspection object by measuring and analyzing the magnetic field from the inspection object, and is made of a superconductor and detects the magnetic field from the inspection object. A pickup coil, a superconducting wire connected to the pickup coil, a SQUID element having a Josephson junction and converting a magnetic field detected by the pickup coil into a voltage, and a cryogen container containing a liquid cryogen Immersion cooling means for immersing the SQUID element in a cryogen and cooling, and a conduction cooling means for cooling a pickup coil arranged outside the cryogen by heat conduction from a low heat source.

  The SQUID metal detector according to the present invention is a SQUID metal detector that detects a metal in an inspection object by measuring and analyzing a magnetic field from the inspection object. Pick-up coil for detecting the magnetic field, a SQUID element connected to the pick-up coil with a superconducting wire and having a Josephson junction for converting the magnetic field detected by the pick-up coil into a voltage, and a cryogen containing a liquid cryogen Immersion cooling means that has a container and cools the SQUID element by immersing it in a cryogen, and a conduction cooling means that cools a pickup coil arranged outside the cryogen by heat conduction from a low heat source. .

  In these devices, the SQUID element having a Josephson junction that dislikes temperature fluctuations is immersed in a liquid cryogen to suppress temperature fluctuations during cooling. On the other hand, the pick-up coil that allows some temperature fluctuation is arranged outside the cryogen and is cooled by heat conduction. Therefore, the cryogen container does not need to accommodate the pickup coil and can be reduced in size. As a result, it is possible to suppress the filling amount of the cryogen in these apparatuses.

  Further, in the above SQUID device, magnetoencephalograph, and magnetocardiograph, the conduction cooling means holds a pickup coil, and has a coil holding part that conducts low heat from a low heat source to the pickup coil. It is preferably supported by a low heat source so that the orientation relative to the cryogen container can be changed. The posture of a cryogen container that contains a liquid cryogen cannot be easily changed. However, by adopting the above configuration, the orientation of the pickup coil can be freely changed without changing the posture of the cryogen container. . Therefore, for example, even when it is difficult to change the posture of the inspection object, by changing the direction of the pickup coil, the magnetic field can be changed without changing both the posture of the inspection object and the posture of the cryogen container. Measurement is possible.

  According to the present invention, there are provided a SQUID device, a biomagnetic measuring device, a magnetoencephalograph, a magnetocardiograph, a SQUID magnetic flaw detector, a SQUID microscope, and a SQUID metal detector capable of suppressing the filling amount of the cryogen for cooling the SQUID sensor. be able to.

  Hereinafter, preferred embodiments of a SQUID apparatus according to the present invention will be described in detail with reference to the drawings.

  The SQUID apparatus 1 shown in FIG. 1 includes a magnetic field detection unit 1A, and the magnetic field detection unit 1A includes a plurality of SQUID sensors 3 that detect a magnetic field from the inspection object α. As shown in FIG. 2, the SQUID sensor 3 includes a pickup coil 31 that detects a magnetic field from the inspection object α in the vicinity of the surface of the inspection object α. The pickup coil 31 is an annular circuit formed on the chip. The SQUID device 1 further includes a SQUID element 33 connected to the pickup coil 31 by a superconducting wire 32. The SQUID element 33 includes an input coil 35 that is formed on a chip and receives a current from the superconducting wire 32, and a SQUID circuit 37 that is formed in an annular shape on the same chip so as to face the input coil 35. ing. The SQUID circuit 37 has two Josephson junctions 37a and converts a weak magnetic field input from the input coil 35 into a voltage and outputs the voltage.

  When a magnetic field from the inspection object α acts on the pickup coil 31, a current is generated in a closed loop circuit formed by the pickup coil 31, the superconducting wire 32, and the input coil 35. A magnetic field generated in the input coil 35 with this current is input from the input coil 35 to the SQUID circuit 37, converted into a voltage by the SQUID circuit 37, and output from the SQUID element 33 as an electrical signal. This electric signal is transmitted to the information processing unit 1C, and the electric signal is analyzed in the information processing unit 1C, whereby the magnetic field from the inspection object α is measured and analyzed, and used for information processing according to the purpose. Can do. For example, a personal computer is used as the information processing unit 1C.

  The pickup coil 31, the superconducting wire 32, the input coil 35, and the SQUID circuit 37 of the SQUID sensor 3 are all made of a superconductor, and when the SQUID device 1 is in operation, it is cooled so that the superconducting transition is performed and the operation is stable. Has been. Hereinafter, the SQUID apparatus 1 including the cooling means for the pickup coil 31 and the cooling means for the SQUID element 33 will be described with reference to FIG. 1 again. In FIG. 1, the vertical direction in the figure is shown as the vertical direction.

  As shown in FIG. 1, the SQUID apparatus 1 includes a dewar (a cryogen container) 7 that stores liquid helium (a cryogen) 5, and a coil holding unit 9 that holds a pickup coil 31. The SQUID element 33 of each SQUID sensor 3 is cooled to about 4K by being immersed in the liquid helium 5 of the dewar 7. Further, the pickup coils 31 of each SQUID sensor 3 are held by the coil holding unit 9 in a two-dimensional array. At the time of measurement by the SQUID apparatus 1, the plurality of pickup coils 31 are arranged along the surface of the inspection object α.

  The SQUID apparatus 1 further includes a cooling stage 11 as a low heat source, and a heat transfer plate 13 connected to the cooling stage 11 and extending downward. The coil holding portion 9 is supported by the heat transfer plate 13 via a hinge 15. The coil holding part 9 is rotatable with respect to the heat transfer plate 13 around the hinge 15. The cooling stage 11 is cooled to about 4K by the refrigerator 1 </ b> D, and the pickup coil 31 is cooled by heat conduction via the cooling stage 11, the heat transfer plate 13, and the coil holding unit 9. Thus, the pickup coil 31 is also cooled to about 4K by heat conduction. The heat transfer plate 13 and the coil holding part 9 are made of a material exhibiting high thermal conductivity such as copper or aluminum. For example, the superconducting wire 32 is provided with a heat transfer coating (not shown), and the heat transfer coating is thermally connected to the heat transfer plate 13 so that the superconducting wire 32 is cooled to about 4K. Is done.

  In the SQUID sensor 3, in the SQUID element 33 including the Josephson junction 37a (see FIG. 2), a temperature fluctuation of about 0.1K causes noise generation, and thus cooling is performed with the temperature fluctuation suppressed extremely low. There is a need to. On the other hand, in the pickup coil 31, some temperature fluctuation is allowed, and the pickup coil 31 can operate normally even under a temperature fluctuation of about 0.3K.

  Based on such knowledge, in the SQUID apparatus 1, the SQUID element 33 that dislikes temperature fluctuation is immersed and cooled in the liquid helium 5 as described above. By being immersed and cooled in the liquid helium 5, the temperature of the SQUID element 33 is stabilized at about 4K, and the temperature fluctuation can be suppressed to be extremely small. As a result, noise in the SQUID element 33 is suppressed, and a weak magnetic field can be detected by the SQUID sensor 3. On the other hand, the pickup coil 31 is disposed outside the dewar 7 as described above, and is cooled by heat conduction from the cooling stage 11. According to such conduction cooling, the pickup coil 31 may be subject to a temperature fluctuation of about 0.3K while being cooled to about 4K. However, since the pickup coil 31 operates normally while allowing such a temperature fluctuation, it is sufficient that the pickup coil 31 is cooled by heat conduction, and there is no inconvenience.

  Thus, the dewar 7 does not need to accommodate the pickup coil 31 and can be reduced in size. As a result, the filling amount of the liquid helium 5 in the SQUID apparatus 1 can be suppressed.

  In particular, considering the case where the SQUID device 1 is applied to a magnetoencephalograph, the number of SQUID sensors 3 and pickup coils 31 is several tens to several hundreds (64, 128, 256, etc.). These pickup coils 31 are arranged at a predetermined pitch over the width of the human head. Therefore, if all the pickup coils 31 are to be immersed in the liquid helium 5, it is necessary to secure the width of the dewar 7 to be equal to or larger than the width of the human head, and there is a limit to reducing the filling amount of the liquid helium 5. On the other hand, according to the SQUID apparatus 1, only the SQUID elements 33 that can be collected in one place and accommodated compactly are immersed in the liquid helium 5, and the pickup coil 31 to be arranged with a certain width is the liquid helium 5 It can be arranged outside. Therefore, according to the configuration of the SQUID apparatus 1, particularly in the case of a SQUID apparatus using a plurality of pickup coils 31 such as a magnetoencephalograph, the effect of suppressing the filling amount of the cryogen is great.

  Further, in the SQUID apparatus 1, the coil holding unit 9 is rotatable with respect to the heat transfer plate 13. Therefore, for example, by picking up the pickup coil 31 by turning the coil holding portion 9 and arranging the pickup coil 31 downward along the horizontal plane, or by turning the pickup coil 31 by 90 ° as shown in FIG. The coils 31 can be horizontally oriented and arranged along a vertical plane. The pickup coils 31 can be arranged along an inclined surface in an arbitrary direction.

  In such a SQUID apparatus 1, the dewar 7 containing the liquid helium 5 cannot be easily changed in posture in order to maintain the cooling efficiency, but the dewar 7 is inclined according to the above mechanism of the coil holding unit 9. The orientation of the arrangement surface of the pickup coil 31 can be changed. Accordingly, the magnetic field is measured from the side of the inspection object α, or the magnetic field is measured from above the inspection object α without changing both the attitude of the dewar 7 and the inspection object α. Easy to do. According to this configuration, even when it is difficult to change the orientation of the measurement target (subject), such as a magnetoencephalograph or magnetocardiograph, the magnetic field from the required direction can be changed without changing the posture of the subject. Since measurement is possible, the effect is particularly high.

  Specifically, such a SQUID apparatus 1 is used in a biomagnetic measurement apparatus for measuring and analyzing a magnetic field generated in a living body. As this biomagnetism measuring device, there are a magnetoencephalograph for measuring / analyzing a magnetic field generated in a subject's brain, and a magnetocardiograph for measuring / analyzing a magnetic field generated in the subject's heart. The SQUID apparatus 1 measures and analyzes the magnetic field from the inspection object α by measuring and analyzing the magnetic field from the inspection object α, and measures and analyzes the magnetic field from the inspection object α. It is used as a SQUID microscope that obtains a magnetic flux distribution image of the object α or a SQUID metal detector that detects a metal in the object α by measuring and analyzing a magnetic field from the object α.

  Next, a case where the SQUID device 1 is used as a magnetoencephalograph will be described with reference to FIG.

  A magnetoencephalograph (SQUID device, biomagnetic measurement device) 101 shown in FIG. 4 accommodates a subject P inside a cylindrical magnetic shield 11, and a weak magnetic field generated along with nerve activity of the brain of the subject P. Is a device that measures and analyzes the contactless. The magnetoencephalograph 1 includes a magnetic field detection unit 1A arranged inside the magnetic shield body 103, an information processing unit 1C arranged outside the magnetic shield body 103, and a refrigerator 1D. The configurations of the magnetic field detection unit 1A, the information processing unit 1C, and the refrigerator 1D are as described above.

  In this magnetoencephalograph 1, since it is necessary to detect a very weak magnetic field generated in the brain of the subject P, it is necessary to remove the influence of the external magnetic field from the vicinity of the pickup coil 31. For this reason, the magnetic shield body 103 has a structure in which a magnetic shield film made of a superconductor is formed on the entire inner wall surface of a cylindrical substrate made of nickel. This shield film is made of a bismuth oxide superconductor and has a film thickness sufficiently larger than the magnetic flux penetration length. Here, as the bismuth-based oxide superconductor used for the shield film 11b, for example, Bi2223 represented by the composition formula Bi2Sr2Ca2Cu3Ox or Bi2212 represented by the composition formula Bi2Sr2CaCu2Ox is suitably employed.

  Then, a cryogenic refrigerant (for example, helium in this case) sent from the refrigerator unit 1B of the magnetoencephalograph 1 is circulated through a refrigerant tube that circulates the refrigerant along the outer wall surface of the magnetic shield body 103, thereby magnetically. The shield film of the shield body 103 is cooled to the superconducting transition temperature and exhibits complete diamagnetism. Since the magnetic field detection unit 1A surrounded by the magnetic shield body 103 is shielded from the external magnetic field by the complete diamagnetism of the shield film, the SQUID sensor 3 has a weak magnetic field with almost no noise due to the external magnetic field. Measurement becomes possible.

  According to the magnetoencephalograph 101, when the posture of the subject P is sitting in the magnetic shield body 103 (the posture shown in FIG. 4), the coil holding unit 9 is oriented in the direction shown in FIG. The magnetic field can be measured from the top of the subject P. Further, even when the subject P is in a sleeping posture in the magnetic shield body 103, the subject can be rotated without changing the posture of the dewar 7 by rotating the coil holding portion 9 by 90 degrees to the orientation shown in FIG. It is possible to measure the magnetic field from the top of P.

It is sectional drawing which shows one Embodiment of the SQUID apparatus which concerns on this invention. It is a figure which shows the SQUID sensor of the SQUID apparatus of FIG. In the SQUID apparatus of FIG. 1, it is a figure which shows the state which rotated the coil holding | maintenance part. It is a block diagram which shows the state by which the SQUID apparatus of FIG. 1 was applied to the magnetoencephalograph.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... SQUID apparatus, biomagnetic measuring device, magnetoencephalograph, magnetocardiograph, SQUID magnetic flaw detector, SQUID microscope, SQUID metal detector, 1A ... magnetic field detection unit, 1D ... refrigerator (conduction cooling means, low heat source), 3 ... SQUID sensor, 5 ... Liquid helium (cold agent), 7 ... Dewar (immersion cooling means, cryogen container), 9 ... Coil holding part (conduction cooling means), 11 ... Cooling stage (conduction cooling means, low heat source), 13 ... Transmission Hot plate (conduction cooling means, low heat source), 31 ... pickup coil, 32 ... superconducting wire, 33 ... SQUID element, 37 ... SQUID circuit, 37a ... Josephson junction, 101 ... SQUID device, magnetoencephalograph, P ... subject, α: Inspection object.

Claims (10)

A pickup coil made of a superconductor and detecting a magnetic field from an object;
A SQUID element connected to the pickup coil by a superconducting wire, having a Josephson junction, and converting a magnetic field detected by the pickup coil into a voltage;
Immersion cooling means having a cryogen container for storing a liquid cryogen and immersing and cooling the SQUID element in the cryogen;
Conduction cooling means for cooling the pickup coil disposed outside the cryogen by heat conduction from a low heat source;
A SQUID device comprising: The conduction cooling means includes
Holding the pickup coil, and having a coil holding portion for conducting low heat from the low heat source to the pickup coil;
2. The SQUID apparatus according to claim 1, wherein the coil holding unit is supported by the low heat source so that a direction with respect to the cryogen container can be changed. A biomagnetic measuring device for measuring and analyzing a magnetic field generated in a living body,
A pickup coil made of a superconductor and detecting a magnetic field generated in the living body;
A SQUID element connected to the pickup coil by a superconducting wire, having a Josephson junction, and converting a magnetic field detected by the pickup coil into a voltage;
Immersion cooling means having a cryogen container for storing a liquid cryogen and immersing and cooling the SQUID element in the cryogen;
Conduction cooling means for cooling the pickup coil disposed outside the cryogen by heat conduction from a low heat source;
A biomagnetic measuring device comprising: A magnetoencephalograph that measures and analyzes the magnetic field generated in the subject's brain,
A pickup coil made of a superconductor and detecting a magnetic field generated in the subject's brain;
A SQUID element connected to the pickup coil by a superconducting wire, having a Josephson junction, and converting a magnetic field detected by the pickup coil into a voltage;
Immersion cooling means having a cryogen container for storing a liquid cryogen and immersing and cooling the SQUID element in the cryogen;
Conduction cooling means for cooling the pickup coil disposed outside the cryogen by heat conduction from a low heat source;
A magnetoencephalograph characterized by comprising: The conduction cooling means includes
Holding the pickup coil, and having a coil holding portion for conducting low heat from the low heat source to the pickup coil;
5. The magnetoencephalograph according to claim 4, wherein the coil holding part is supported by the low heat source so that a direction with respect to the cryogen container can be changed. A magnetocardiograph that measures and analyzes the magnetic field generated in the subject's heart,
A pickup coil made of a superconductor and detecting a magnetic field generated in the subject's heart;
A SQUID element connected to the pickup coil by a superconducting wire, having a Josephson junction, and converting a magnetic field detected by the pickup coil into a voltage;
Immersion cooling means having a cryogen container for storing a liquid cryogen and immersing and cooling the SQUID element in the cryogen;
Conduction cooling means for cooling the pickup coil disposed outside the cryogen by heat conduction from a low heat source;
A magnetocardiograph characterized by comprising: The conduction cooling means includes
Holding the pickup coil, and having a coil holding portion for conducting low heat from the low heat source to the pickup coil;
The magnetocardiograph according to claim 6, wherein the coil holding part is supported by the low heat source so as to be able to change a direction with respect to the cryogen container. A SQUID flaw detection apparatus that performs flaw detection on the inspection object by measuring and analyzing a magnetic field from the inspection object,
A pickup coil made of a superconductor and detecting a magnetic field from the inspection object;
A SQUID element connected to the pickup coil by a superconducting wire, having a Josephson junction, and converting a magnetic field detected by the pickup coil into a voltage;
Immersion cooling means for cooling the SQUID element by immersing the SQUID element in the cryogen having a cryogen container for storing a liquid cryogen;
Conduction cooling means for cooling the pickup coil disposed outside the cryogen by heat conduction from a low heat source;
A SQUID magnetic flaw detector characterized by comprising: A SQUID microscope that obtains a magnetic flux distribution image of the inspection object by measuring and analyzing a magnetic field from the inspection object,
A pickup coil made of a superconductor and detecting a magnetic field from the inspection object;
A SQUID element connected to the pickup coil by a superconducting wire, having a Josephson junction, and converting a magnetic field detected by the pickup coil into a voltage;
Immersion cooling means having a cryogen container for storing a liquid cryogen and immersing and cooling the SQUID element in the cryogen;
Conduction cooling means for cooling the pickup coil disposed outside the cryogen by heat conduction from a low heat source;
A SQUID microscope characterized by comprising: A SQUID metal detector for detecting a metal in the inspection object by measuring and analyzing a magnetic field from the inspection object,
A pickup coil made of a superconductor and detecting a magnetic field from the inspection object;
A SQUID element connected to the pickup coil by a superconducting wire, having a Josephson junction, and converting a magnetic field detected by the pickup coil into a voltage;
Immersion cooling means for cooling the SQUID element by immersing the SQUID element in the cryogen having a cryogen container for storing a liquid cryogen;
Conduction cooling means for cooling the pickup coil disposed outside the cryogen by heat conduction from a low heat source;
A SQUID metal detector comprising:

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