JP2020113631A - High frequency superconducting laminate - Google Patents

Abstract

To solve a problem in which a rare-earth superconducting wire developed for DC applications, which is currently in practical use, has no loss at DC, but the conductor loss does not become so small in a high frequency band, and therefore, a high Q value cannot be realized even when a coil is manufactured using the rare-earth superconducting wire.SOLUTION: A high frequency superconducting laminate according to the present invention includes at least one spiral superconductor coil, and at least two dielectric supports, and the spiral superconductor is sandwiched between the dielectric supports, and the dielectric loss of the dielectric supports is 7.0×10-5 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a superconductor, and particularly to a high frequency superconducting laminate including a spiral superconductor coil sandwiched between dielectric supports.

For the resonator used in the high frequency band (several KHz to several 100 MHz), the detection coil (resonator) for receiving the resonance signal of MRI and NMR equipment using nuclear magnetic resonance, and the nuclear quadrupole resonance (NQR) are used. There are explosives and detection coils (resonators) for illicit drug detection devices, and power transmission/reception coils (resonators) used for wireless power transmission (WPT), which has been attracting attention recently.

The most basic way to improve the performance (eg sensitivity and transmission efficiency) of these devices is to use high Q factor (low conductor loss) coils.

However, these coils are usually made of copper wire, and the conductor loss cannot be further reduced. Therefore, the high Q value cannot be realized, and the improvement in the performance of MRI, NMR, NQR, and WPT has reached the limit.

One of the ways to solve this problem is to use "superconductor".

Superconductors are lossless in the case of direct current, and can be expected to have conductor loss three or more orders of magnitude lower than that of copper in the high frequency band. Therefore, by using a superconductor for the coil, a dramatically high Q value can be realized, and improvement in the performance of various devices can be expected.

However, the rare earth-based superconducting wire developed for direct current applications that is currently in practical use has no loss in direct current, but the conductor loss does not become so small in the high frequency band. We could not achieve a high Q value. Further, the superconducting thin film substrate has a planar structure, and it is difficult to increase the area.

Therefore, the application of superconducting materials in the high frequency band was unexplored. Non-Patent Document 1 proposes a new structure of a superconducting wire (a high-frequency superconducting wire) to solve the above problem.

N. Sekiya, Y. Monjugawa, "A novel REBCO wire structure that improves coil quality factor in MHz range and its effect on wireless power transfer systems," IEEE Trans. Appl. Supercond. vol. 27, 6602005, 2017-6

However, in Non-Patent Document 1, high-frequency superconducting wires such as (1) a method for bonding the superconducting wires, (2) a structure for supporting the superconducting wires, and (3) a thin protective film. There were problems to be solved in order to realize.

The present inventors have attempted to solve the above problems by using a spiral superconductor coil manufactured from a superconducting bulk. However, since it is technically difficult to increase the diameter of the superconducting bulk, it is not easy to increase the number of turns of the spiral superconductor coil by simply increasing the diameter of the coil. Further, in order to reduce the resonance frequency of the spiral superconductor coil, it is preferable to increase the number of turns of the spiral superconductor coil, but it is difficult to increase the diameter of the spiral superconductor coil as described above. Therefore, we examined increasing the number of turns by narrowing the wire distance and wire width of the spiral superconductor coil, but it was found that the Q value decreases when the wire distance and wire width are narrowed. That is, there is a limit to lowering the resonance frequency of the spiral superconductor coil while maintaining a high Q value.

Therefore, as a result of earnest research, the present inventors have revealed that all of the above problems can be solved by using a superconducting laminate in which a spiral superconductor coil is sandwiched by dielectric supports.

The present invention is
At least one spiral superconductor coil;
At least two dielectric supports,
The spiral superconductor is sandwiched between the dielectric supports,
The dielectric loss of the dielectric support is 7.0×10 ⁻⁵ or less,
It is a superconducting laminate for high frequencies.

Such a superconducting laminated body does not require (1) the bonding of the superconducting wire, (2) does not need a structure for maintaining the coil shape, and (3) the superconducting wire is formed by the step of forming the protective film. Therefore, there is an advantage that the protective film can be easily thinned.

FIG. 1 shows a development view of a high-frequency superconducting laminated body having a structure in which two dielectric support members 20 sandwich one spiral superconducting coil. FIG. 2 is a perspective cross-sectional view of a high-frequency superconducting laminate in which two dielectric support members 20 sandwich one spiral superconducting coil. FIG. 3 shows a developed view of a high-frequency superconducting laminate including two spiral superconductor coils and three dielectric supports. FIG. 4 is a graph showing a simulation result of changes in the Q value depending on the line distance g and the line width w of the spiral superconductor coil in the high frequency superconducting laminate. FIG. 5 is a graph showing a simulation result of the relationship between the dielectric loss of the dielectric support and the Q value in the high frequency superconducting laminate. FIG. 6 is a graph showing simulation results of the relationship between the relative dielectric constant of the dielectric support and the resonance frequency in the high frequency superconducting laminate. FIG. 7 is a graph showing a simulation result of the relationship between the thickness of the dielectric support and the resonance frequency in the high frequency superconducting laminate. FIG. 8: is a graph which shows the simulation result of the Q value change by the line distance g of the 1st spiral superconductor coil and the 2nd spiral superconductor coil in the high frequency superconducting laminated body, and the line width w. ..

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

The numerical ranges and parameters given in the present invention are approximations, but the numerical values given in the specific examples are stated as accurately as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Also, the term "about" as used herein generally means within 10%, 5%, 1%, or 0.5% of a given value or range. Alternatively, the term “about” means within an acceptable standard error when considered by one of skill in the art.

First Embodiment A high frequency superconducting laminate according to the present embodiment includes one spiral superconductor coil and two dielectric supports, and the spiral superconductor is the dielectric support. It is sandwiched between the bodies, and the dielectric loss of the dielectric support is 7.0×10 ⁻⁵ or less.

High Frequency Superconducting Laminated Body FIG. 1 shows one spiral superconductor coil 10 according to the present embodiment with two dielectric supports 20 (first dielectric support 21 and second dielectric support 22). The development view of the high frequency superconducting laminated body 1 of the structure sandwiched between is shown. FIG. 2 shows a state in which one spiral superconductor coil 10 according to the present embodiment is sandwiched by two dielectric supports 20 (first dielectric support 21 and second dielectric support 22). The perspective sectional view of the superconducting laminated body 1 for high frequencies is shown. As shown in FIG. 2, when the high-frequency superconducting laminate 1 is used, the spiral superconductor coil 10 is sandwiched between the first dielectric support 20a and the second dielectric support 20b. That is, when the high-frequency superconducting laminate 1 is used, the first dielectric support 20a is in contact with one surface of the spiral superconductor coil 10 and the second dielectric support 20b is spiral. It is in contact with the other surface of the superconductor coil 10. The one surface and the other surface of the spiral superconductor coil 10 are surfaces on which the central axis of the spiral superconductor coil 10 passes vertically, and are in a front-back relationship with each other. The Q value of the spiral superconductor coil 10 in the high frequency superconducting laminate 1 is preferably 10000 or more, more preferably 18000 or more, and further preferably 20000 or more.

Spiral Superconductor Coil The spiral superconductor coil 10 is a superconductor coil having a spiral shape on a plane. The diameter of the spiral superconductor coil 10 is not particularly limited, but may be substantially the same as the diameter of the superconducting bulk used when manufacturing the spiral superconductor coil 10. The thickness of the spiral superconductor coil 10 may be determined based on the actual environment of implementation, for example, any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mm. The thickness may be in the range between the two points or may be more than 10 mm.

The superconducting material of the spiral superconductor coil 10 is selected from the group consisting of, but not limited to, an alloy material, a copper oxide superconductor material, and an iron superconductor material. The alloy-based material is selected from, but is not limited to, the group consisting of NbTi, Nb ₃ Sn, MgB ₂ and NbN. Copper oxide superconductor material _is selected from the group consisting of _{Bi 2 Sr 2 CaCu 2 O 8} , Bi 2 Sr 2 Ca 2 Cu 3 O 10, YBa 2 Cu 3 O 7 and REBa ₂ Cu ₃ O ₇ (However, RE (rare earth element) is selected from the group consisting of La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu).

The spiral superconductor coil 10 is, for example, a method of processing a superconducting bulk obtained by crystallizing a superconductor material into a coil shape (GF method), or a precursor composed of components of the superconductor material. Can be manufactured by a method (FG method) in which the is processed into a coil shape and then crystallized.

The superconducting bulk may be produced by a melt crystallization method in which a partially melted state is slowly cooled to grow crystals. The superconducting bulk is preferably single crystal. Here, the term "single crystal" may mean a perfect single crystal or a single crystal having a defect (such as a small tilt grain boundary) that does not interfere with practical use.

The spiral superconductor coil 10 can be manufactured by forming spiral grooves in the superconducting bulk. The manufacturing method includes, for example, (1) a step of slicing the superconducting bulk into a predetermined thickness and processing it into a disk shape, and (2) a step of forming a spiral groove in the sliced superconducting bulk. For the slicing process, a cutting process using a blade having diamond powder embedded therein is suitable. Swirl processing can be performed by small diamond point or sandblasting.

The line-to-line distance g of the spiral superconductor coil 10 is not particularly limited as long as it is possible to realize that the Q value of the spiral superconductor coil 10 is 10,000 or more, but 0.2 mm or more. Preferably, for example, 0.2, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 and It is within a range between any two points of 5.0 mm.

The line width w of the spiral superconductor coil 10 is not particularly limited as long as it is possible to realize that the Q value of the spiral superconductor coil 10 is 10000 or more, but 1.5, 1.6, It is preferably within a range between any two points of 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 and 2.5 mm.

If it is possible to realize that the Q value of the spiral superconductor coil 10 is 10000 or more, the spiral superconductor coil 10 may be provided with any protective layer or protective film. A protective layer or protective film is not essential. Preferably, the spiral superconductor coil 10 has no artificial layer or film forming process on its surface. If it is possible to realize that the Q value of the spiral superconductor coil 10 is 10,000 or more, the space between the spiral superconductor coils 10 may be filled with any substance, but No need to fill with material. The space between the spiral superconductor coils 10 is preferably filled with air, more preferably a vacuum. When the space between the spiral superconductor coils 10 is to be evacuated, the high frequency superconducting laminate 1 may have a sealed structure capable of forming a vacuum inside. It may be a closed structure capable of creating a vacuum inside the device that covers the laminate 1.

Dielectric Support The size of the dielectric support 20 is such that the spiral superconductor coil 10 is covered when the spiral superconductor coil 10 is sandwiched. The dielectric support 20 may have a disc shape or a rectangular plate shape. Further, it may have a shape in which a part of the spiral superconductor coil 10 is not covered, such as a cross shape. Regarding the dimensions of the first dielectric support 21, the dimensions of the second dielectric support 22 may be the same or different from each other.

The dielectric loss of the dielectric support 20 is not particularly limited as long as it can realize that the Q value of the spiral superconductor coil 10 is 10000 or more, but it is preferably 7.0×. It is 10 ⁻⁵ or less, more preferably 1.0×10 ⁻⁵ or less, and further preferably 1.0×10 ⁻⁶ or less. The derivative support may be made of MgO or Al ₂ O ₃ (sapphire), preferably Al ₂ O ₃ (sapphire). Since Al ₂ O ₃ (sapphire) has a high thermal conductivity, it is possible to cool the spiral superconducting coil by utilizing heat conduction from the cold head of the refrigerator when cooling the refrigerator. That is, the spiral superconductor coil 10 can be cooled while the Q value of the spiral superconductor coil 10 is maintained at a high value.

The thickness of the dielectric support 20 can be changed according to a desired resonance frequency, and is 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mm. May be in the range between any two points, and may be more than 10 mm based on the actual operating environment.

Second Embodiment FIG. 3 shows two spiral superconductor coils 100 (first spiral superconductor coil 101, second spiral superconductor coil 102) and three dielectrics according to the present embodiment. The development view of the high frequency superconducting laminated body 2 including the support body 200 (first dielectric support body 201, second dielectric support body 202, third dielectric support body 203) is shown. The first spiral superconductor coil 101 is sandwiched between a first dielectric support 201 and a second dielectric support 202. The second spiral superconductor coil 102 is sandwiched between the second dielectric support 202 and the third dielectric support 203. Various conditions and parameters of the spiral superconductor coil 10 and the dielectric support 20 in the high frequency superconducting laminate 1 are determined by the spiral superconductor coil 100 and the dielectric support in the high frequency superconducting laminate 2. The same applies to various conditions and parameters of the body 200.

The central axis of the first spiral superconductor coil 101 exists on the same straight line as the central axis of the second spiral superconductor coil 102. The spiral direction of the first spiral superconductor coil 101 is opposite to the spiral direction of the second spiral superconductor coil 102. It is important that the resonance frequencies of the two coils facing each other match. When the coils with the same resonance frequency are combined, the resonance frequency splits in two. By using the resonance frequency on the low frequency side, the resonance frequency can be lowered to the low frequency while using the coil of the same size as the case of one coil. Therefore, it is preferable to prepare two coils having the same shape, but even if the coils have different shapes, if the resonance frequencies of the two coils match, the two coils can be combined to reduce the frequency. That is, if the resonance frequencies are the same, the number of turns of the first spiral superconductor coil 101 may be the same as or different from the number of turns of the second spiral superconductor coil 102. .. The diameter of the first spiral superconductor coil 101 may be the same as or different from the diameter of the second spiral superconductor coil 102.

When the two coils facing each other have the same size and shape, the spiral direction of the first spiral superconductor coil 101 may be the same as the spiral direction of the second spiral superconductor coil 102. In this case, the resonance frequency of the combined coil does not decrease, but the thickness of the combined coil is the same as the sum of the thicknesses of the two facing coils. This is applicable when there are manufacturing restrictions, but it is desired to use thicker coils.

Simulation 1
FIG. 4 is a graph showing simulation results of changes in the Q value depending on the line distance (gap) g of the spiral superconductor coil 10 and the line width w in the high frequency superconducting laminate 1 according to the present embodiment. A three-dimensional electromagnetic field simulator (CST Studio Suite) was used for the simulation. The conductivity of the spiral superconductor coil 10 is 9×10 ¹¹ S/m, the diameter of the spiral superconductor coil 10 is 65 mm, the thickness of the spiral superconductor coil 10 is 1 mm, and the spiral superconductor coil 10 is When the line width w of 10 is between 1.5 mm, 2.0 mm and 2.5 mm, the Q value of 10,000 or more is realized by setting the line distance g of the spiral superconductor coil 10 from 0.2 mm to 5.0 mm. It became clear that it was possible.

FIG. 5 is a graph showing simulation results of the relationship between the dielectric loss (dielectric loss (loss tangent)) of the dielectric support and the Q value in the high-frequency superconducting laminate 1 according to the present embodiment. The conductivity of the spiral superconductor coil 10 is 9×10 ¹¹ S/m, the diameter of the spiral superconductor coil 10 is 65 mm, the thickness of the spiral superconductor coil 10 is 1 mm, and the spiral superconductor coil 10 is When the line width w of 10 is 1.5 mm, the line distance g of the spiral superconductor coil 10 is 0.95 mm, and the relative permittivity e of the dielectric support is 9.9, the dielectric loss is 7.0×10 ^-5 or less. It was revealed that a Q value of 10,000 or more can be realized by using a dielectric support having

FIG. 6 is a graph showing the simulation result of the relationship between the relative dielectric constant of the dielectric support and the resonance frequency [MHz] in the high frequency superconducting laminate 1 according to the present embodiment. is there. The conductivity of the spiral superconductor coil 10 is 9×10 ¹¹ S/m, the diameter of the spiral superconductor coil 10 is 65 mm, the thickness of the spiral superconductor coil 10 is 1 mm, and the spiral superconductor coil 10 is The line width w of 10 was 1.5 mm, the line distance g of the spiral superconductor coil 10 was 0.95 mm, and the dielectric loss of the dielectric support was 1.0×10 ⁻⁷ . As shown in FIG. 6, it became clear that the resonance frequency decreases as the relative permittivity of the dielectric support increases.

FIG. 7 is a graph showing a simulation result of the relationship between the thickness of the dielectric support and the resonance frequency in the high-frequency superconducting laminate 1 according to this embodiment. The conductivity of the spiral superconductor coil 10 is 9×10 ¹¹ S/m, the diameter of the spiral superconductor coil 10 is 65 mm, the thickness of the spiral superconductor coil 10 is 1 mm, and the spiral superconductor coil 10 is The line width w of 10 was 1.5 mm, the line distance g of the spiral superconductor coil 10 was 0.95 mm, and the dielectric support was a sapphire dielectric support. As shown in FIG. 7, it was revealed that the resonant frequency decreased as the thickness of the dielectric support increased.

From the above simulation results, by using a dielectric support with a dielectric loss of 7.0 × 10 ^-5 or less, the line width w can be 1.5 mm and 2.0 mm without changing the diameter of the spiral superconductor coil. And 2.5 mm, a high Q value can be realized by setting the line distance g of the spiral superconductor coil 10 from 0.2 mm to 5.0 mm. In addition, by increasing the relative permittivity or increasing the thickness of the dielectric support, it is possible to reduce the resonance frequency of the spiral superconductor coil while maintaining a high Q value.

Simulation 2
FIG. 8 shows Q according to the line distance (gap) g and the line width w of the first spiral superconductor coil 101 and the second spiral superconductor coil 102 in the high-frequency superconducting laminate 2 according to the present embodiment. It is a graph which shows the simulation result of a change of a value. When the conductivity, diameter, thickness and line width w of the first spiral superconductor coil 101 and the second spiral superconductor coil 102 are 9×10 ¹¹ S/m, 65 mm, 1 mm and 1.5 mm, respectively, It has been clarified that a Q value of 10,000 or more can be realized by setting the line distance g of the spiral superconductor coil 10 from 0.4 mm to 3.9 mm. Further, when the line width w is 2.0 mm, it is clear that the Q value of 10,000 or more can be realized by setting the line distance g of the spiral superconductor coil 10 from 0.3 mm to 3.5 mm. It was

Spiral superconductor coil 10 (single, no dielectric support), high frequency superconducting laminate 1 (single sand), first spiral superconductor coil 101 and second spiral superconductor coil 102 (double , No dielectric support) and the high frequency superconducting laminate 2 (double sand), and the Q value and the resonance frequency were determined. The results are shown in Table 1.

In Table 1, the resonance frequency of the single sand is lower than the resonance frequency of the single because the capacitance component of the LC resonance is increased by the dielectric. In Double and Double sand, the resonance frequency is lower than that of Single due to the coupling between the coils. The resonance frequency of the double sand is lower than that of the double because the capacitive coupling between the coils is strengthened by inserting the dielectric material and the capacitance component of the LC resonance is increased. Because it will increase.

As shown in Table 1, the resonance frequency decreases from single to double sand. That is, it has been clarified that the larger the number of spiral superconductor coils and the number of dielectric supports sandwiching the spiral superconductor coil, the lower the resonance frequency.

The following can be said from the results of the second embodiment and the simulation 2. That is, the resonance frequency can be shifted to a low frequency by connecting the two coils. Also, the resonance frequency is determined by the size of the coupling between the two coils. Therefore, the smaller the distance between the two coils is, the larger the coupling becomes, and the frequency shifts to the low frequency. Stray capacitance can be confined between the coils by facing the two coils. This reduces the effect of the dielectric approaching. In particular, the effect of confining stray capacitance is greater when the coil is sandwiched between dielectrics.

The high-frequency superconducting laminate according to the present invention can dramatically improve the transmission efficiency when used in a power transmission/reception coil for wireless power transmission. Further, by using the high-frequency superconducting laminate according to the present invention in a coil of various analyzers (NMR, MRI, NQR, etc.), the sensitivity of the analyzer can be dramatically improved. Furthermore, the high frequency superconducting laminate according to the present invention can be used for a high sensitivity high frequency antenna and a high frequency low loss filter.

DESCRIPTION OF SYMBOLS 1 High-frequency superconducting laminated body 2 High-frequency superconducting laminated body 10 Spiral superconductor coil 100 Spiral superconductor coil 101 First spiral superconductor coil 102 Second spiral superconductor coil 20 Dielectric support Body 200 Dielectric support 21 First dielectric support 22 Second dielectric support 201 First dielectric support 202 Second dielectric support 203 Third dielectric support g Spiral superconductor coil wire Distance w The line width of the spiral superconductor coil

Claims (7)

At least one spiral superconductor coil;
At least two dielectric supports,
The spiral superconductor is sandwiched between the dielectric supports,
The dielectric loss of the dielectric support is 7.0×10 ⁻⁵ or less,
High frequency superconducting laminate. The high frequency superconducting laminate according to claim 1, wherein a dielectric loss of the dielectric support is 1.0×10 ⁻⁵ or less. The high frequency superconducting laminate according to claim ₂ , wherein the derivative support is made of MgO or Al ₂ O ₃ . The high-frequency superconducting laminate according to claim 1, wherein the spiral superconductor coil is manufactured by forming a spiral groove in a superconducting bulk. When there are two or more spiral superconductor coils, the central axis of each spiral superconductor coil exists on the same line, and the superconducting laminate for high frequencies according to any one of claims 1 to 4. body. The high-frequency superconducting laminate according to claim 5, wherein the spiral superconducting coils that are adjacent to each other with the dielectric support interposed therebetween are in mutually opposite spiral directions. The high-frequency superconducting laminate according to any one of claims 1 to 6, wherein a line distance of the spiral superconductor coil is 0.2 mm to 5.0 mm.