JP5492600B2 - Magnetic flux transformer and coaxial three-dimensional gradiometer - Google Patents

Description

The present invention relates to a magnetic flux transformer and a coaxial three-dimensional gradiometer, for example, a magnetic flux transformer and a coaxial three-dimensional gradiometer that detect a weak magnetic signal with high sensitivity and high accuracy.

Conventionally, SQUIDs having a superconductor Josephson junction as a loop have been used as ultra-sensitive magnetic sensors. This superconductor Josephson junction is made using a metal-based superconductor or an oxide-based superconductor, but the properties of the oxide-based Josephson junction are not sufficient, and the metal-based Josephson junction is mainly used. It has been.

However, while the metal-based Josephson junction operates near the liquid helium temperature, the oxide-based Josephson junction operates at 77 K, which is the liquid nitrogen temperature, and therefore, research to improve the characteristics continues. For example, a YBCO (YBa ₂ Cu ₃ O ₇ ) -based Josephson junction using an interface modification barrier has been proposed (see, for example, Non-Patent Document 1).

When configuring a magnetic sensor with such a SQUID, in order to eliminate the influence of geomagnetism and the like and to efficiently capture the external magnetic field to be detected, a pair of superconductor pickup loops symmetrical to the SQUID is used. Arranged gradiometers have been developed.

However, the size of this superconductor pickup loop is limited by the size of the oxide substrate such as MgO, and the structure is also limited to the structure of a planar gradiometer in which the SQUID loop and the pickup loop are arranged on the same plane. It was.

Under such circumstances, a tape wire is prepared by forming a thin film or a thick film of a high-temperature oxide superconductor on a nonmagnetic metal substrate such as a heat-resistant Ni-based alloy Hastelloy (registered trademark). Technology has been developed (see, for example, Patent Document 1 or Patent Document 2).

The tape wire can be elongated and has a feature that the degree of freedom of deformation is sufficiently larger than that of the oxide substrate. Therefore, a superconductor pickup loop that can efficiently capture an external magnetic field using such a tape wire, that is, a magnetic flux transformer has been proposed (for example, see Non-Patent Document 2).

By this proposal, a coaxial three-dimensional gradiometer in which a planar gradiometer made of an oxide high temperature superconductor and a pair of pickup loops and a magnetic flux transformer made of an oxide high temperature superconductor are bonded together, that is, a coaxial type Solid gradiometers have become widely used.

10A and 10B are configuration explanatory views of an example of a conventional flexible magnetic flux transformer, FIG. 10A is a schematic plan view, and FIG. 10B is a conceptual cross-sectional view of a position where a superconducting pickup loop exists. is there. Here, an example will be described in which a superconducting pickup loop is formed by patterning a superconducting tape wire on the surface by patterning an oxide superconductor layer on the surface using an ion milling method.

For example, as shown in FIG. 10B, a GdZrO buffer layer 12 having a Gd ₂ Zr ₂ O ₇ composition, a CeO ₂ buffer layer 13, and GdBa on a nonmagnetic metal substrate 11 made of Hastelloy (registered trademark). A tape wire in which GdBCO films 14 having a composition of ₂ Cu ₃ O ₇ are sequentially deposited is used. The GdZrO buffer layer 12 is deposited by ion beam assisted vapor deposition (IBAD).

The GdBCO film 14 is patterned on this tape wire, and a superconducting pickup loop comprising a pair of symmetrical pseudo ring portions 16 in the figure, a pseudo square portion 17 serving as a central magnetic transmission circuit, and a connecting portion 18 connecting them. 15 is formed as a magnetic flux transformer.

Japanese Patent Laid-Open No. 04-329867 Japanese Patent Laid-Open No. 04-331795

B. H. Moeckly et al., Appl. Phys. Lett. , Vol. 71, p. 2526, 1997 M.M. Bick et al. , Appl. Phys. Lett. , Vol. 84, p. 5347, 2004

However, when a nonmagnetic metal substrate is used as the base of the tape wire, an eddy current is generated in the nonmagnetic metal substrate by a magnetic field. Since the eddy current is generated so as to form a magnetic field that cancels the magnetic signal to be measured, the generation of the eddy current impairs the sensitivity of the SQUID.

Therefore, an object of the present invention is to improve the detection sensitivity of a magnetic field by suppressing the generation of eddy currents.

From one aspect disclosed, it comprises a nonmagnetic metal substrate and a superconducting loop made of an oxide superconductor having a plane symmetry with respect to the central axis in the minor axis direction formed on the nonmagnetic metal substrate. A magnetic flux transformer in which a cut portion that reaches the back surface of the nonmagnetic metal substrate in the superconducting loop is provided in plane symmetry with respect to the central axis in the short axis direction at the central portion of the superconducting loop. A transformer is provided.

  From another viewpoint to be disclosed, a bobbin provided with a hook-shaped portion, the above-described magnetic flux transformer arranged in a curved shape along the shape of the hook-shaped portion on the hook-shaped portion of the bobbin, and the hook There is provided a coaxial three-dimensional gradiometer having a planar gradiometer disposed on the magnetic flux transformer via an insulator film at the top of the shape portion.

  According to the disclosed magnetic flux transformer and coaxial three-dimensional gradiometer, since the cutting portion reaching the back surface of the nonmagnetic metal substrate is provided, the generation of eddy current can be suppressed, thereby increasing the detection sensitivity of the magnetic field. be able to.

It is a structure explanatory view of the flexible magnetic flux transformer of an embodiment of the invention. 1 is a configuration explanatory diagram of a flexible magnetic flux transformer according to a first embodiment of the present invention. FIG. It is a structure explanatory view of a plane type gradiometer. It is a notional block diagram of the coaxial solid-type gradiometer using the flexible magnetic flux transformer of Example 1 of this invention. It is explanatory drawing of the magnetic field sensitivity of the coaxial solid-type gradiometer of this invention. It is a notional top view of the modification of the flexible magnetic flux transformer of Example 1 of this invention. It is a notional top view of other modifications of the flexible magnetic flux transformer of Example 1 of the present invention. It is a structure explanatory drawing of the flexible magnetic flux transformer of Example 2 of this invention. It is explanatory drawing of the modification of the flexible magnetic flux transformer of Example 2 of this invention. It is structure explanatory drawing of the conventional flexible magnetic flux transformer.

  Here, with reference to FIG. 1, the flexible magnetic flux transformer of embodiment of this invention is demonstrated. FIG. 1 is an explanatory diagram of a configuration of a flexible magnetic flux transformer according to an embodiment of the present invention, FIG. 1 (a) is a schematic plan view, and FIG. 1 (b) is a conceptual diagram of a portion where a superconducting pickup loop exists. It is sectional drawing.

As shown in FIG. 1B, a tape wire in which an oxide superconductor 3 is deposited on a nonmagnetic metal substrate 1 with a buffer layer 2 interposed therebetween is prepared. As the nonmagnetic metal substrate 1, the composition is Hastelloy (54.5-66.5) Ni- (15-30) Mo-C-Fe (-Cr-W) based heat-resistant Ni-based alloy ( Registered trademark), Ni-based alloys, Cu-based alloys, or stainless steels of other compositions. The non-magnetic metal substrate 1 is a thin substrate that can be bent to form a coaxial three-dimensional gradiometer.

The material of the buffer layer 2 is arbitrary, but typically, a stacked structure of a GdZrO buffer layer having a Gd ₂ Zr ₂ O ₇ composition deposited by an IBAD method and a CeO ₂ layer serving as an interlayer insulating film is used. The material of the oxide superconductor 3 is not particularly limited, but typically, a so-called YBCO-based oxide high-temperature superconductor in which Y is made of a rare earth element such as GdBa ₂ Cu ₃ O ₇ is used. .

As shown in FIG. 1A, by patterning the oxide superconductor 3 by ion milling, a pair of symmetrical pseudo ring portions 5 and a pseudo square portion 6 serving as a central magnetic transmission circuit are connected. A superconducting loop 4 composed of the connecting portion 7 is formed to form a magnetic flux transformer. The formation of the superconducting loop 4 is arbitrary, and the pseudo ring portion 5 may be rectangular, circular, or elliptical in addition to the rectangular corner as shown in the figure. Further, the pseudo square portion 6 is not essential. Furthermore, as will be described later, a simple loop as shown in FIG. 9 may be used.

Next, as shown in FIG. 1A, a cutting portion 8 that penetrates the nonmagnetic metal substrate 1 is provided inside the superconducting loop 4 in order to suppress the generation of eddy current. The cut portion 8 may be formed by laser irradiation, or may be formed by punching by pressing. Further, the shape of the cutting portion 8 is arbitrary, but it is desirable that the cut portion 8 has a plane symmetric structure with respect to a plane perpendicular to the center of the central axis in the longitudinal direction of the superconducting pickup loop, that is, a symmetric structure in the drawing.

  In the magnetic flux transformer according to the embodiment of the present invention, since the cut portion 8 penetrating the nonmagnetic metal substrate 1 is provided inside the superconducting pickup loop, generation of eddy current that causes a decrease in magnetic field detection sensitivity is generated. Can be effectively suppressed.

  A coaxial three-dimensional gradiometer is formed by aligning the pickup loop formed on the SQUID chip with respect to the pseudo square portion 6 in a state where the magnetic ring transformer is curved and the pseudo ring portions 5 on both sides are opposed to each other. can get.

Based on the above, next, a flexible magnetic flux transformer according to a first embodiment of the present invention and a coaxial three-dimensional gradiometer using the same will be described with reference to FIGS. FIGS. 2A and 2B are configuration explanatory views of the flexible magnetic flux transformer according to the first embodiment of the present invention, FIG. 2A is a schematic plan view, and FIG. 2B is a conceptual view of a position where a superconducting pickup loop exists. It is sectional drawing.

As shown in FIG.2 (b), the tape wire which consists of a commercially available oxide superconductor is prepared. For example, this tape wire has a GdZrO buffer layer 12, a CeO ₂ buffer layer 13, and a GdBCO with a thickness of 1 μm on a tape-like nonmagnetic metal substrate 11 made of Hastelloy (registered trademark) with a thickness of 100 μm. A tape wire on which the film 14 is sequentially deposited is used. The GdZrO buffer layer 12 is deposited by an ion beam assisted vapor deposition method with a Gd ₂ Zr ₂ O ₇ composition. The GdBCO film 14 has a GdBa ₂ Cu ₃ O ₇ composition. Such a tape wire has a width of 10 mm and a length of several tens to several hundreds of meters. Here, the tape wire is cut into a length of about 90 mm.

Next, a resist is spin-coated on the GdBCO film 14, and the pattern of the superconducting pickup loop 15 including the pseudo ring portion 16, the pseudo square portion 17 serving as a central magnetic transmission circuit, and the connection portion 18 shown in FIG. Transfer with mask and contact aligner. Next, unnecessary portions are removed by ion milling with Ar ions using the resist pattern as a mask to form a superconducting pickup loop 15 having a line width of 0.5 to 1.0 mm. The superconducting pickup loop 15 has a plane-symmetric structure as viewed from the center of the pseudo square portion 17. The size of the central pseudo-square portion 17 is the same as the size of the pickup loop formed on the SQUID chip described later.

Next, the flexible magnetic flux transformer of Example 1 of the present invention is completed by forming a cutting groove 19 penetrating the nonmagnetic metal substrate 11 along the major axis direction of the superconducting pickup loop 15 by laser irradiation. In this case, a UV laser having a wavelength of 355 nm was used as the laser, the output was 4.5 W, the scan speed was 2 mm / second, the Q switch value was 10 kHz, the beam spot diameter was about 20 μm, and irradiation was performed in oxygen assist gas.

  Next, a planar gradiometer made of a SQUID chip will be described with reference to FIG. 3. The planar gradiometer itself has basically the same configuration as a conventionally used planar gradiometer. FIG. 3 is an explanatory diagram of the configuration of a planar gradiometer, FIG. 3 (a) is a schematic plan view, and FIG. 3 (b) is a schematic cross-sectional view of a surface-modified Josephson junction constituting the SQUID. is there.

First, for example, a BaZrO ₃ film 22 having a thickness of 10 nm, a ground plane layer 23 having a thickness of 200 nm are formed on an MgO substrate 21 having a thickness of 15 mm and a thickness of 0.5 mm using off-axis and magnetron sputtering. A SrSnO ₃ interlayer film 24 having a thickness of 200 nm is deposited. As the ground plane layer 23, for _example, using a _{Pr 1.4 Ga 0.4 Ba 1.6 Cu 2.6} O x.

Subsequently, the lower superconducting layer 25 made of SmBa ₂ Cu ₃ O _{7 having a} thickness of 200 nm to 250 nm and the SrSnO ₃ interlayer film 26 having a thickness of 200 nm are sequentially deposited using off-axis and magnetron sputtering.

Next, the lower superconducting layer 25 is processed by ion milling with Ar ions to form a mesa structure of a predetermined size having a ramp inclined surface. Next, Ar ions or Ar ions + O ₂ ions are irradiated at an acceleration voltage of 280 V to 500 V for 1 minute to 3 minutes to amorphize the surface of the ramp inclined surface to form the surface modified layer 27.

Next, using the laser pulse deposition method, the upper superconductivity made of La _0.2 Er _0.95 Ba _1.95 Cu ₃ O _x having a thickness of 200 nm on the entire surface with the substrate temperature set at, for example, 600 ° C. Layer 28 is deposited. Next, an Au thin film (not shown) having a thickness of 200 nm is deposited on the entire surface at room temperature by a sputtering method.

Next, two square pick-up loops 30 are formed by Ar ion milling using a resist pattern formed by a normal lithography method as a mask, and the upper electrode of the SQUID 29 shown in the enlarged view of FIG. Form. In this case, the pickup loop 30 has a 4.0 mm square outer shape and a 0.5 mm line width.
Further, the lower wiring 32 is connected from the lower electrode pad 31 to the lower electrode of the SQUID 29, and the upper wiring 34 is connected from the upper electrode 33 to the upper electrode. A feedback coil 36 connected to the pad 35 is provided outside the pickup loop 30.

  This SQUID chip is called a planar gradiometer 20 and efficiently captures a magnetic field by a square pickup loop 30, and by providing two pickup loops 30 of the same size, the SQUID chip is generated due to geomagnetism that causes noise. To cancel the current.

  FIG. 4 is a conceptual configuration diagram of a coaxial three-dimensional gradiometer using the flexible magnetic flux transformer according to the first embodiment of the present invention. FIG. 4A is a schematic perspective view of a bobbin constituting the skeleton of the coaxial three-dimensional gradiometer, and FIG. 4B is an assembly view of the coaxial three-dimensional gradiometer.

As shown in FIG. 4A, the bobbin 40 is made by processing a non-magnetic material, for example, bakelite, and has a hook-like portion 41 for bending and fixing a flexible magnetic flux transformer at the center upper portion.

  As shown in FIG. 4B, the flexible magnetic flux transformer 10 is arranged along the shape of the bowl-shaped portion 41 of the bobbin 40, and a holding plate 42 made of a non-magnetic material, for example, bakelite, is attached to the bobbin 40 by screws 43. Attached to the side, the flexible magnetic flux transformer 10 is fixed. At this time, the pair of pseudo ring portions 16 provided in the flexible magnetic flux transformer 10 are opposed to each other at the same horizontal position. Further, the pseudo-square portion 17 at the center is located at the center of the top of the bowl-shaped portion 41.

Next, a housing part 45 is provided in the central portion inside the lid member 44 made of a non-magnetic material, for example, bakelite, and the planar gradiometer 20 made of a SQUID chip is housed in the housing part 45. It fixes to the upper surface of the bobbin 40 with the screw 46. The fixing mechanism for the lid member 44 and the pressing plate 42 is not limited to the screws 43 and 46, and a fitting mechanism may be used.

At this time, as shown in the enlarged view on the right side of FIG. 4B, the thickness is, for example, 20 nm so that one of the pickup loops 30 and the pseudo square portion 17 formed in the superconducting pickup loop 15 are aligned. The insulating thin film 47 is laminated through, for example, medicine wrapping paper. Either pick-up loop 30 may be used in this case, but usually the pick-up loop 30 that does not obstruct the electrode wiring arranged on the upper side in FIG.

FIG. 5 is an explanatory diagram of the magnetic field sensitivity of the coaxial three-dimensional gradiometer of the present invention, FIG. 5 (a) is a magnetic field sensitivity characteristic of a conventional magnetic flux transformer without a cutting groove, and FIG. It is a magnetic field sensitivity characteristic of the magnetic flux transformer of this invention. Here, a solenoid was installed so as to contact one pseudo ring portion of the flexible magnetic flux transformer, and an alternating current was supplied to the solenoid to supply a magnetic field. Both used the same solenoid.

As shown in FIG. 5 (a), the magnetic field sensitivity of the conventional flux transformer, the solenoid current of 2.7mA is equivalent to one unit flux quantum phi _0. On the other hand, the magnetic field sensitivity of the flux transformer of the first embodiment of the present invention, the solenoid current of 0.32mA have to correspond to one unit flux quantum phi _0, that the magnetic field sensitivity was improved by about 8.4 times Recognize.

Thus, in the first embodiment of the present invention, since the cutting groove is provided inside the superconducting pickup loop constituting the flexible magnetic flux transformer, the generation of eddy current is suppressed, and as a result, the magnetic field sensitivity is improved.

Next, a modification of the flexible magnetic transformer according to the first embodiment of the present invention will be described with reference to FIGS. 6 and 7. The basic configuration is exactly the same as that of the first embodiment, and the structure of the cutting portion is different. Only the plan view is shown. As shown in FIG. 6A, the cutting portion may be constituted by a plurality of short long-axis direction cutting grooves 51, and in this case, the long-axis direction cutting grooves 51 are symmetrical with respect to the central pseudo-square portion 17. It is desirable to arrange in.

In addition, as shown in FIG. 6B, the cutting portion may be constituted by a plurality of short short-axis direction cutting grooves 52. In this case, the short-axis direction cutting grooves 52 are formed in the central pseudo-square portion 17. It is desirable to arrange them symmetrically.

Further, as shown in FIG. 6C, even when the cutting part is constituted by a plurality of short long-axis direction cutting grooves 51, a plurality of (here, three) are shown in the left and right pseudo ring parts 16 having a large area. ) Major axis direction cutting grooves 51 may be arranged in parallel.

Alternatively, as shown in FIG. 7D, a fence-like cutting groove 53 that is a combination of a long-axis direction cutting groove and a short-axis direction cutting groove may be arranged in the left and right pseudo-ring portions 16. Also in this case, it is desirable to arrange the fence-shaped cutting groove 53 symmetrically with respect to the central pseudo-square portion 17.

Moreover, such a cutting part is not limited to a slit-shaped cutting groove, and may be formed by punching a through hole having a predetermined area by pressing. For example, as shown in FIG. 7E, a rectangular through hole 54 of 5.0 mm × 10.0 mm may be provided in the left and right pseudo-ring portions 16. Alternatively, as shown in FIG. 7F, a circular through hole 55 having a diameter of 5.0 mm may be provided. In addition, although illustration is abbreviate | omitted, you may use an elliptical through-hole or a through-hole of the shape which rounded the corner | angular of the rectangle.

Next, with reference to FIG. 8, the flexible magnetic flux transformer of Example 2 of this invention is demonstrated. FIGS. 8A and 8B are explanatory diagrams of the configuration of the flexible magnetic flux transformer according to the second embodiment of the present invention. FIG. 8A is a schematic plan view, and FIG. 8B is a conceptual view of a position where a superconducting pickup loop exists. It is sectional drawing.

As shown in FIG. 8 (b), the configuration of the tape wire is exactly the same as in Example 1, and a tape wire made of a commercially available oxide superconductor is prepared. That is, this tape wire has, for example, a GdZrO buffer layer 12, a CeO ₂ buffer layer 13, and a thickness of 1 μm on a tape-like nonmagnetic metal substrate 11 made of Hastelloy (registered trademark) having a thickness of 100 μm. The GdBCO film 14 is sequentially deposited. A tape wire having a width of 10 mm is used after being cut to a length of about 90 mm.

Next, the superconducting pickup loop 61 is formed by processing in exactly the same manner as in the first embodiment, but in this second embodiment, a simple shape is formed by rounding the four corners of a long rectangle. Next, the laser beam spot is scanned and irradiated in the same manner as in the first embodiment to form the cutting groove 62, thereby completing the flexible magnetic flux transformer of the second embodiment of the present invention.

Also in the second embodiment of the present invention, since the cutting groove is provided inside the superconducting pickup loop, the generation of eddy current can be suppressed, thereby improving the magnetic field sensitivity.

As in the case of the above-described first embodiment, the cutting portion is not limited to a single slit-shaped cutting groove. Next, referring to FIG. 9, the flexible magnetic flux transformer according to the second embodiment of the present invention. A modified example will be described.

For example, as shown in FIG. 9A, the cutting portion may be formed by arranging a plurality of long slit-shaped cutting grooves 62 in parallel. Moreover, as shown in FIG.9 (b), it is good also as the fence-shaped cutting groove 63 which combined the long slit-shaped cutting groove and the short short axis direction cutting groove. Alternatively, as shown in FIG. 9C, a long through hole 64 or a plurality of circular through holes 65 as shown in FIG. 9D may be used.

Or although illustration is abbreviate | omitted, you may provide not the long slit-shaped cutting groove but the short long-axis direction cutting groove as shown to Fig.6 (a) symmetrically in the shape of a two-dimensional matrix. Or you may comprise a cutting part only by the short-axis direction cutting groove as shown in FIG.6 (b).

In addition, when the cut portion is constituted by the through-hole, the circular through-hole shown in FIG. 9 (d) is a rectangular through-hole, an elliptical through-hole, and further rounded the four corners of the rectangle. You may comprise by a through-hole of a shape.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations shown in the embodiments, and various modifications can be made. For example, the shape of the superconducting pickup loop may be a shape obtained by removing the central pseudo-square portion from the shape of the first embodiment. Or the shape of the intermediate state of Example 1 and Example 2 may be sufficient.

Further, the configuration of the cutting portion is not limited to the shape shown in each of the above-described embodiments and modifications thereof, and the disclosed cutting grooves or through holes may be used in combination.

Here, the following supplementary notes are disclosed regarding the embodiment of the present invention including Example 1 and Example 2.
(Supplementary Note 1) A magnetic flux transformer comprising a nonmagnetic metal base material and a superconducting loop formed of an oxide superconductor having a plane symmetry with respect to the central axis in the minor axis direction formed on the nonmagnetic metal base material. A magnetic flux transformer in which a cut portion that reaches the back surface of the nonmagnetic metal substrate in the superconducting loop is provided symmetrically with respect to the central axis in the minor axis direction at the central portion of the superconducting loop .
(Supplementary note 2 ) The magnetic flux transformer according to supplementary note 1 , wherein the cutting portion is provided in parallel to a central axis in a major axis direction of the superconducting loop.
(Supplementary note 3 ) The magnetic flux transformer according to supplementary note 1 , wherein the cutting portion includes a through hole whose planar shape is any of a rectangular shape, a circular shape, or an elliptical shape.
(Supplementary note 4 ) The magnetic flux transformer according to supplementary note 3 , wherein a plurality of the through holes are formed.
(Supplementary note 5 ) The magnetic flux transformer according to any one of supplementary notes 1 to 4 , wherein the nonmagnetic metal substrate is a Ni-based alloy in which at least Mo, C, and Fe are added to Ni.
(Supplementary note 6 ) The magnetic flux transformer according to any one of supplementary notes 1 to 5 , wherein a shape of both ends in a longitudinal direction of the superconducting loop is a ring shape.
(Supplementary note 7 ) The magnetic flux transformer according to any one of supplementary notes 1 to 6 , wherein a pseudo square portion serving as a magnetic transmission circuit is provided at a central portion of the superconducting loop.
(Supplementary note 8 ) The magnetic flux transformer according to any one of supplementary notes 1 to 7 , wherein the bobbin is provided with a bowl-shaped part, and the bowl-shaped part of the bobbin is curved along the shape of the bowl-shaped part. And a planar three-dimensional gradiometer having a flat gradiometer disposed on the magnetic flux transformer via an insulator film at the top of the bowl-shaped portion.

DESCRIPTION OF SYMBOLS 1 Nonmagnetic metal base material 2 Buffer layer 3 Oxide superconductor 4 Superconducting loop 5 Pseudo ring part 6 Pseudo square part 7 Connection part 8 Cutting part 10 Flexible magnetic flux transformer 11 Nonmagnetic metal base material 12 GdZrO buffer layer 13 CeO ₂ buffer layer 14 GdBCO film 15, 61 Superconducting pickup loop 16 Pseudo ring part 17 Pseudo square part 18 Connection part 19, 62 Cutting groove 20 Planar gradiometer 21 MgO substrate 22 BaZrO ₃ layer 23 Ground plane layer 24 SrSnO ₃ interlayer film 25 Lower superconducting layer 26 SrSnO ₃ interlayer film 27 Surface modification layer 28 Upper superconducting layer 29 SQUID
30 Pickup Loop 31 Lower Electrode Pad 32 Lower Wiring 33 Upper Electrode Pad 34 Upper Electrode 35 Pad 36 Feedback Coil 40 Bobbin 41 Gutter 42 Presser Plate 43 Screw 44 Lid Member 45 Housing 46 Screw 47 Insulating Thin Film 51 Longitudinal Cutting Groove 52 Short axis direction cutting grooves 53, 63 Fence-shaped cutting grooves 54, 55, 65 Through hole 64 Long through hole

Claims (4)

A magnetic flux transformer comprising: a nonmagnetic metal base material; and a superconducting loop made of an oxide superconductor having a plane symmetry with respect to the central axis in the minor axis direction formed on the nonmagnetic metal base material,
A magnetic flux transformer in which a cut portion that reaches the back surface of the nonmagnetic metal substrate in the superconducting loop is provided symmetrically with respect to a central axis in a short axis direction at a central portion of the superconducting loop . The magnetic flux transformer according to claim 1 , wherein the cutting portion is provided in parallel to a central axis in a major axis direction of the superconducting loop. 2. The magnetic flux transformer according to claim 1 , wherein the cut portion is a through-hole whose planar shape is any of a rectangular shape, a circular shape, or an elliptical shape. A bobbin with a hook-shaped part in the center;
The magnetic flux transformer according to any one of claims 1 to 3 , wherein the magnetic flux transformer is disposed on the bowl-shaped part of the bobbin so as to be curved along the shape of the bowl-shaped part.
A coaxial three-dimensional gradiometer having a planar gradiometer disposed on the magnetic flux transformer via an insulator film at the top of the bowl-shaped portion.

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