High-sensitivity device and method for measuring high-temperature superconducting microwave surface resistance

Abstract

The invention discloses a high-sensitivity device and method for measuring high-temperature superconducting microwave surface resistance, and belongs to the technical field of electronics, the device comprises a test seat, a calibration seat, a calibration plate, a supporting plate and a sealing cavity, the test seat comprises a test cavity, a dielectric cylinder, an input coupling structure, an output coupling structure and a dielectric supporting device, the dielectric cylinder is a different-diameter coaxial cylinder and is divided into a supporting column and a resonance column, the supporting column is fixed to the testing cavity through a dielectric supporting device, the tail end face of the resonance column and the bottom end face of the testing cavity are located on the same plane, and the diameter of the supporting column is smaller than that of the resonance column. Therefore, the support column and the test cavity jointly form a cut-off waveguide relative to the required resonant frequency, so that the electromagnetic field is bound around the dielectric column, and the test sensitivity is improved. The invention further provides a double-sided cross test method capable of rapidly testing the microwave surface resistance of the front and back surfaces of the high-temperature superconductor sample to be tested, the system error can be remarkably reduced, and the accuracy and reliability of the test are ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronics, and particularly relates to a high-sensitivity device and method for measuring the microwave surface resistance of high-temperature superconductors. Background Art

[0002] High-temperature superconductors (HTS) have important application values in microwave technology. Their superconducting microwave surface resistance (Rs) is closely related to the energy loss characteristics of superconducting devices, thereby affecting the system efficiency and performance. For high-temperature superconductors, Rs is not only an important parameter for evaluating the superconducting state characteristics of materials, but also can reflect key information such as grain boundary defects or film uniformity in the microscopic structure of materials. By accurately measuring Rs of high-temperature superconducting materials, it not only helps to improve the performance levels of devices such as superconducting filters and resonators, but also provides important technical support for the research in frontier fields such as quantum communication and terahertz technology.

[0003] Currently, the dielectric resonator method is generally used at home and abroad to measure Rs of high-temperature superconducting thin films. Taking the national standard as an example, the double dielectric resonator method is adopted, and the structure is as Figure 1 shown. The resonator of this method is composed of a metal cavity wall and two dielectric columns with different heights. By placing two high-temperature superconducting thin film samples and measuring the quality factor of the formed resonator, through formula derivation, the microwave surface resistance value of the high-temperature superconducting thin film is obtained. However, the double dielectric resonator method generally requires at least two high-temperature superconducting thin film samples in use, and at least 2 temperature cycles are required for the test of a single high-temperature superconducting thin film sample, which affects the test efficiency. And the temperature conditions for the test need to meet both high-temperature superconducting thin film samples at the same time. When measuring Rs near the quench temperature of the high-temperature superconducting thin film sample, if one of the high-temperature superconducting thin film samples quenches, the test of the other high-temperature superconducting thin film sample cannot be carried out. If one of the two high-temperature superconducting thin film samples is replaced with a metal with a known surface resistance, single-sided testing can be achieved, but this change will cause the quality factor of the resonator to decrease, thereby reducing the test sensitivity. In addition, the double dielectric resonator method uses two sapphire dielectric columns with different heights and assumes that the loss tangent values of the materials of the two sapphire dielectric columns are the same during calculation. However, in the actual device, the existence of the coupling device and the difference in the loss tangent of the two sapphire dielectric columns both introduce systematic errors into the measurement.

[0004] The traditional mirror resonator method proposed in Appendix B of the national standard GB / T 22586—2018 achieves the effect of single-sided testing of high-temperature superconducting thin films. However, the systematic errors existing in this device will affect the accuracy of the test. Due to the tiny differences in the process, there is a certain degree of asymmetry between the calibration resonator and the test resonator (such as: the conductivity difference caused by inconsistent oxidation of the metal surface, or the difference in the loss tangent value of the sapphire dielectric column used), which also introduces a certain systematic error to the test. In addition, the traditional mirror resonator method uses a polytetrafluoroethylene clamping ring to directly contact and fix the sapphire dielectric column. Since the electromagnetic field of the resonant structure is mainly concentrated near the sapphire dielectric column, this fixing method will cause the loss of the electromagnetic field of the resonant structure, resulting in a decrease in the resonant quality factor of the resonator, thereby reducing the test sensitivity. Summary of the Invention

[0005] Aiming at the problems of low test sensitivity and low test accuracy existing in the traditional mirror resonator method, the present invention provides a high-sensitivity device and method for measuring the microwave surface resistance of high-temperature superconductors. By using a stepped coaxial cylindrical dielectric column, the loss introduced by the dielectric support structure is reduced, the test sensitivity is improved, and combined with the double-sided cross-test method, the systematic error is reduced to ensure the accuracy and reliability of the Rs test.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A high-sensitivity device for measuring the microwave surface resistance of high-temperature superconductors, comprising a test seat, a calibration seat, a calibration plate, a support plate and a sealing cavity;

[0008] The test seat includes a test cavity with an open bottom end, a dielectric column, an input coupling structure, an output coupling structure and a dielectric support device; wherein, the dielectric column is a stepped coaxial cylinder, located at the center inside the test cavity, and is divided into a support column and a resonant column. The support column is fixed to the test cavity through the dielectric support device. The end face of the resonant column is in the same plane as the bottom end face of the test cavity. The diameter of the support column is smaller than that of the resonant column, so that the support column and the test cavity together form a cut-off waveguide relative to the required resonant frequency;

[0009] The calibration seat has the same structure as the test seat and is detachably arranged at the bottom end faces of the dielectric column and the test cavity;

[0010] The calibration plate has a known microwave surface resistance and is detachably arranged at the bottom end faces of the dielectric column and the test cavity;

[0011] The high-temperature superconductor sample to be tested is placed at the bottom end faces of the dielectric column and the test cavity, and the high-temperature superconductor sample to be tested is fastened by a detachable support plate;

[0012] The sealing cavity is detachably arranged at the outer extension of the bottom end face of the test cavity.

[0013] Further, the method for determining the diameter of the support pillar is as follows: Assume that the dielectric pillar is a regular cylinder. According to the required resonance frequency, adjust the diameters of the dielectric pillar and the inner wall of the test cavity. Take the diameter of the adjusted dielectric pillar as the diameter of the resonance pillar, coaxially place a support pillar with an unknown diameter above the resonance pillar, and simulate the cut-off frequency of the waveguide jointly formed by the support pillar and the adjusted test cavity. By adjusting the diameter of the support pillar, make the cut-off frequency of the waveguide higher than the required resonance frequency, and then determine the diameter of the support pillar.

[0014] Further, the input coupling structure and the output coupling structure are symmetrically distributed on both sides of the test cavity, and the test cavity, the dielectric pillar, and the dielectric support device are coaxial.

[0015] Further, both the input coupling structure and the output coupling structure are coupling loop-to-coaxial structures.

[0016] Further, the test cavity is plated with silver using a hard metal material; the dielectric pillar is made of a high-Q material with low loss and high dielectric constant, including rutile, sapphire, beryllium oxide ceramics, etc.; the dielectric support device is made of a high dielectric constant material with low loss, including nylon, polytetrafluoroethylene, polyethylene foam, etc.

[0017] Further, the thickness of the superconductor coating of the high-temperature superconductor sample to be measured is greater than 200 nm, and its planar size is greater than the planar size of the bottom end face of the test cavity.

[0018] The present invention proposes a method for measuring the high-temperature superconducting microwave surface resistance, which specifically includes the following steps:

[0019] Step A1: Load the calibration seat onto the bottom end face of the test seat. The two are mirror-symmetrical about the bottom end face, and use a sealed cavity to seal the calibration seat. Keep the obtained test device at the working temperature of the high-temperature superconductor sample to be measured, and measure the quality factor Q1 at the resonance frequency.

[0020] Step A2: Load the calibration plate onto the bottom end face of the test seat, and use a sealed cavity to seal the calibration plate. Keep the obtained test device at the working temperature of the high-temperature superconductor sample to be measured, and measure the quality factor Q2 at the resonance frequency.

[0021] Step A3: Load the high-temperature superconductor sample to be measured onto the bottom end face of the test seat, and fix it with a support plate. Use a sealed cavity to seal the high-temperature superconductor sample to be measured and the support plate. Keep the obtained test device at the working temperature of the high-temperature superconductor sample to be measured, and measure the quality factor Q0 at the resonance frequency.

[0022] Step A4: According to the formula:

[0023]

[0024] The microwave surface resistance R of the high-temperature superconducting sample to be measured at the resonant frequency is calculated S , specifically the microwave surface resistance of the side of the high-temperature superconducting sample to be measured facing the test seat; where R SN is the microwave surface resistance of the calibration plate at the resonant frequency.

[0025] Furthermore, the working mode of the test device is the TE011 mode.

[0026] The present invention also proposes another method for measuring the microwave surface resistance of high-temperature superconductors, which can be used to quickly test the microwave surface resistance of both sides of the high-temperature superconducting sample to be measured, while greatly reducing the systematic error.

[0027] A method for measuring the microwave surface resistance of high-temperature superconductors, used to test the microwave surface resistance of both sides of the high-temperature superconducting sample to be measured, specifically includes the following steps:

[0028] Step B1: Load the calibration seat onto the bottom end face of the test seat, and the two are mirror-symmetrical about the bottom end face. Use a sealed cavity to seal the calibration seat, and keep the obtained test device at the working temperature of the high-temperature superconducting sample to be measured, and measure the quality factor Q1 at the resonant frequency;

[0029] Step B2: Load the calibration plate and the calibration seat onto the bottom end face of the test seat in sequence, and use a sealed cavity to seal the calibration plate and the calibration seat. Keep the obtained test device at the working temperature of the high-temperature superconducting sample to be measured, and measure the quality factor Q of the test seat 1T and the quality factor Q of the calibration seat 1C at the resonant frequency;

[0030] Step B3: Load the high-temperature superconducting sample to be measured and the calibration seat onto the bottom end face of the test seat in sequence, where the front side of the high-temperature superconducting sample to be measured faces the test seat side, and the back side faces the calibration seat side. Use a sealed cavity to seal the high-temperature superconducting sample to be measured and the calibration seat, and keep the obtained test device at the working temperature of the high-temperature superconducting sample to be measured, and measure the quality factor Q of the front side of the test seat 0T_X and the quality factor Q of the back side of the calibration seat 0C_Y at the resonant frequency;

[0031] Step B4: Turn over the high-temperature superconducting sample in Step B3, specifically with the back side facing the test seat side and the front side facing the calibration seat side, and continue to measure the quality factor Q of the back side of the test seat 0T_Y and the quality factor Q of the front side of the calibration seat 0C_X at the resonant frequency;

[0032] Step B5: According to the formula:

[0033]

[0034] The front - side microwave surface resistance \(R\) of the high - temperature superconductor sample to be measured at the resonant frequency is calculated S_X and the back - side microwave surface resistance \(R\). S_Y .

[0035] Furthermore, the working mode of the test device is the TE011 mode.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1. The present invention proposes a high - sensitivity device for measuring the microwave surface resistance of high - temperature superconductors. Using the TE011 mode as the working mode of the dielectric resonator and an anisodiametric coaxial cylindrical dielectric column, a section of cutoff waveguide is introduced between the dielectric support device and the resonant structure (composed of the resonant column and the corresponding part of the test cavity), effectively reducing the loss introduced by the dielectric support structure into the resonant cavity, confining the electromagnetic field around the dielectric column, reducing the cavity - wall loss, and thus improving the test sensitivity;

[0038] 2. Based on the above high - sensitivity device, the present invention proposes two methods for measuring the microwave surface resistance of high - temperature superconductors. Specifically, on the basis of the first traditional test method, a second double - sided cross - test method for quickly measuring the microwave surface resistances of the front and back sides of the high - temperature superconductor sample to be measured is innovatively proposed. The calibration seat is not only used to calibrate the test seat but also participates in the same test process as the test seat, thereby significantly reducing the systematic error of the device to ensure the accuracy and reliability of the \(R_s\) test. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0040] Figure 1 It is a sectional structure diagram of a device for measuring microwave surface resistance using the double - dielectric - resonator method;

[0041] Figure 2 It is a sectional structure diagram of the test seat in the high - sensitivity device for measuring the microwave surface resistance of high - temperature superconductors proposed in Embodiment 1 of the present invention;

[0042] Figure 3 It is a sectional structure diagram of the test device after the test seat is loaded with the calibration seat in Embodiment 1 of the present invention;

[0043] Figure 4 It is a sectional structure diagram of the test device after the test seat is loaded with the calibration plate in Embodiment 1 of the present invention;

[0044] Figure 5 This is the cross-sectional structure diagram of the test device after sequentially loading the high-temperature superconductor sample to be tested and the support plate in Embodiment 1 of the present invention;

[0045] Figure 6 This is a partial S-parameter test image of calibrating values A and B of the high-sensitivity device for measuring the high-temperature superconducting microwave surface resistance proposed in Embodiment 1 of the present invention; among them, (a) is for calibrating value A; (b) is for calibrating value B;

[0046] Figure 7 This is a partial S-parameter test image of the high-sensitivity device for measuring the high-temperature superconducting microwave surface resistance proposed in Embodiment 1 of the present invention when loading different high-temperature superconductor samples to be tested; among them, (a) is for loading the first high-temperature superconductor sample to be tested; (b) is for loading the second high-temperature superconductor sample to be tested; (c) is for loading the third high-temperature superconductor sample to be tested;

[0047] Figure 8 This is the cross-sectional structure diagram of the test device after sequentially loading the calibration plate and the calibration seat in Embodiment 2 of the present invention;

[0048] Figure 9 This is the cross-sectional structure diagram of the test device after sequentially loading the high-temperature superconductor sample to be tested and the calibration seat in Embodiment 2 of the present invention;

[0049] Figure 10 This is a partial S-parameter test image of calibrating values A and B of the high-sensitivity device for measuring the high-temperature superconducting microwave surface resistance proposed in Embodiment 2 of the present invention; among them, (a) is for calibrating value A; (b) is for calibrating value B T value; (c) is for calibrating value B C value;

[0050] Figure 11 This is a partial S-parameter test image of the test seat loading the high-temperature superconductor sample to be tested in Embodiment 2 of the present invention; among them, (a) is for loading the front side of the high-temperature superconductor sample to be tested; (b) is for loading the back side of the high-temperature superconductor sample to be tested;

[0051] Figure 12 This is a partial S-parameter test image of the calibration seat loading the high-temperature superconductor sample to be tested in Embodiment 2 of the present invention; among them, (a) is for loading the front side of the high-temperature superconductor sample to be tested; (b) is for loading the back side of the high-temperature superconductor sample to be tested;

[0052] Figure 13 This is the intrinsic simulation modeling and partial electric field simulation results of the stepped coaxial cylindrical dielectric column in Embodiment 3 of the present invention;

[0053] Figure 14 This is the intrinsic simulation modeling and partial electric field simulation results of the traditional regular cylindrical dielectric column in Comparative Example 1;

[0054] The descriptions of the marks in the attached drawings are as follows:

[0055] 1 - test socket; 2 - calibration socket; 3 - sealing cavity; 4 - support plate; 5 - test cavity; 6 - resonant cavity; 7 - input coupling structure; 8 - output coupling structure; 9 - dielectric support device; 10 - dielectric column; 11 - calibration plate; 12 - high-temperature superconductor sample to be tested. Specific embodiments

[0056] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0057] For all raw materials of the present invention, there is no particular limitation on their sources, and they can be purchased on the market or prepared by conventional methods well-known to those skilled in the art.

[0058] For all raw materials of the present invention, there is no particular limitation on their purity. The present invention preferably uses analytically pure or the conventional purity requirements in the field of atomic layer deposition.

[0059] For all raw materials and process procedures of the present invention, their trade names or abbreviations are all conventional trade names or abbreviations in the field. Each trade name or abbreviation is clear and definite in the field of its relevant uses. Those skilled in the art can purchase them from the market or prepare them by conventional methods according to the trade name, abbreviation and corresponding uses, or implement them using the corresponding equipment.

[0060] The present invention will be further described in detail below in conjunction with embodiments:

[0061] Example 1

[0062] This example proposes a high-sensitivity device for measuring the microwave surface resistance of high-temperature superconductors, including a test socket 1, a calibration socket 2, a calibration plate 11, a support plate 4, and a sealing cavity 3. The structure of the test socket 1 is as Figure 2 shown, including a test cavity 5 with an open bottom end, a dielectric column 10, an input coupling structure 7, an output coupling structure 8, and a dielectric support device 9.

[0063] The input coupling structure 7 and the output coupling structure 8 are symmetrically distributed on both sides of the test cavity 5, and both are coupling hole-to-coaxial structures, which can effectively avoid direct coupling and have high test accuracy.

[0064] The dielectric column 10 is a coaxial cylindrical column with different diameters, located at the center inside the test cavity 5, and is divided into two connected parts: a support column and a resonant column. The support column is fixed to the test cavity 5 through a dielectric support device 9. The end face of the resonant column is in the same plane as the bottom end face of the test cavity 5. The diameter of the support column is smaller than that of the resonant column, such that the support column and the test cavity together form a cutoff waveguide with respect to the required resonant frequency.

[0065] The test cavity 5, the dielectric column 10, and the dielectric support device 9 are coaxial.

[0066] The calibration seat 2 has the same structure as the test seat 1 and is detachably arranged on the bottom end faces of the dielectric column 10 and the test cavity 5, such that the calibration seat 2 and the test seat 1 are symmetric with respect to the bottom end face.

[0067] The microwave surface resistance of the calibration plate 11 is known, and it is detachably arranged on the bottom end faces of the dielectric column 10 and the test cavity 5.

[0068] A sample with a high-temperature superconductor film plated on one side of a 1-mm-thick lanthanum aluminate cylindrical wafer is used as the high-temperature superconductor sample 12 to be measured, and the nominal thickness of the film is 500 nm. The high-temperature superconductor sample 12 to be measured is placed on the bottom end faces of the dielectric column 10 and the test cavity 5 and is fastened by a detachable support plate 4.

[0069] The sealed cavity 3 is detachably arranged on the outer extension of the bottom end face of the test cavity 5.

[0070] In this embodiment, the test cavity 5 is made of silver-plated brass, with a diameter of about 40 mm and a height of 20 mm. The dielectric column 10 is made of a high-Q material with low loss and high dielectric constant, specifically sapphire. The diameter of the resonant column is about 11 mm, the height is about 5 mm, the diameter of the support column is about 2 mm, and the height is about 14 mm. The dielectric support device 9 is made of a high-dielectric-constant material with low loss, specifically polytetrafluoroethylene.

[0071] In this embodiment, the high-temperature superconductor sample 12 to be measured and the test seat 1 form a dielectric resonator with a TE011 mode of operation. The internal hollow region forms a resonant cavity 6. The quality factor Q0 of the dielectric resonator at a resonant frequency of 12 GHz and the microwave surface resistance R s of the high-temperature superconductor sample 12 to be measured satisfy the following relationship:

[0072] Q0 -1 = A + BR s Equation (1)

[0073] where A and B are both constants determined by the measurement method.

[0074] Based on the above high-sensitivity device, this embodiment proposes a method for measuring the microwave surface resistance of high-temperature superconductors, which specifically includes the following steps:

[0075] Step A1: Load the calibration seat 2 onto the bottom end face of the test seat 1. The two are mirror-symmetric with respect to the bottom end face, and use the sealed cavity 3 to seal the calibration seat 2. Keep the obtained test device as shown in Figure 3 Figure at the working temperature 77K of the high-temperature superconductor sample 12 to be measured, and measure the quality factor Q1 at the resonant frequency.

[0076] Step A2: Load the calibration plate 11 onto the bottom end face of the test seat 1, and use the sealed cavity 3 to seal the calibration plate 11. Keep the obtained test device as shown in Figure 4 Figure at the working temperature 77K of the high-temperature superconductor sample 12 to be measured, and measure the quality factor Q2 at the resonant frequency.

[0077] Step A3: Load the high-temperature superconductor sample 12 to be measured onto the bottom end face of the test seat 1. The side of the high-temperature superconductor sample 12 plated with the high-temperature superconductor film faces the test seat 1, and use the support plate 4 to fix it. Use the sealed cavity 3 to seal the high-temperature superconductor sample 12 to be measured and the support plate 4. Keep the obtained test device as shown in Figure 5 Figure at the working temperature 77K of the high-temperature superconductor sample 12 to be measured, and measure the quality factor Q0 at the resonant frequency.

[0078] Step A4: Substitute the quality factors Q1 and Q2 into Equation (1) to calculate A = 1 / Q1, B = (1 / Q2 - A) / R SN ;

[0079] Furthermore, obtain the microwave surface resistance R of the high-temperature superconductor sample 12 to be measured at the resonant frequency S The calculation formula is:

[0080]

[0081] The obtained microwave surface resistance R S Specifically, it is the microwave surface resistance of the high-temperature superconductor film; where R SN Is the microwave surface resistance of the calibration plate 11 at the resonant frequency.

[0082] In order to verify the test accuracy of the high-sensitivity device proposed in this embodiment, three different high-temperature superconductor samples 12 to be measured (the first high-temperature superconductor sample to be measured, the second high-temperature superconductor sample to be measured, and the third high-temperature superconductor sample to be measured) are loaded onto the high-sensitivity device for testing. Specifically, the quality factors Q1, Q2, and Q0 are measured under the conditions of a resonant frequency of about 12 GHz and a working temperature of 77K, and the microwave surface resistance R of the calibration plate 11 SNThe nominal value is 18.23 mΩ, and then the microwave surface resistance R of three samples 12 of high-temperature superconductors to be measured is calculated. S .

[0083] Figure 6 Figure (a) of Figure 6 is the test image of some S parameters for the calculated calibration A value and B value, where Figure 6 Figure (a) is the image of the calibration A value, Figure 6 Figure (b) of Figure 6 is the image of the calibration B value; Figure 7 Figure (a) of Figure 7 is the test image of some S parameters for the high-sensitivity device loaded with different samples 12 of high-temperature superconductors to be measured, where Figure 7 Figure (a) is the image when the first sample of high-temperature superconductor to be measured is loaded, Figure 7 Figure (b) of Figure 7 is the image when the second sample of high-temperature superconductor to be measured is loaded, Figure 7 Figure (c) of Figure 7 is the image when the third sample of high-temperature superconductor to be measured is loaded.

[0084] According to Figure 6 and Figure 7 the test results shown in Table 1 are obtained from the test images of some S parameters.

[0085]

[0086] In the actual test of this embodiment, three repeated tests were carried out on the above three different samples 12 of high-temperature superconductors to be measured, and the test samples were removed and reloaded each time. The test results of each sample 12 of high-temperature superconductor to be measured are relatively stable, and the relative standard deviation of the calculated value of R S is within 0.005 mΩ, indicating that the high-sensitivity device for measuring the microwave surface resistance of high-temperature superconductors proposed in this embodiment has very high test accuracy.

[0087] Taking the repeated test of the first sample of high-temperature superconductor as an example, the results of the repeated test are shown in Table 2.

[0088] Table 2

[0089]

[0090] The high-sensitivity device and method for measuring the microwave surface resistance of high-temperature superconductors proposed in this embodiment are compared with the improved image dielectric resonator method (Appendix B) recommended by the national standard GB / T 22586—2018. Specifically, the device described in the improved image dielectric resonator method is used, operating in the TE011 mode. The test method is the same as that of this embodiment. Two different high-temperature superconductor samples to be measured (the fourth and fifth high-temperature superconductor samples to be measured, with nominal values of 0.259 mΩ and 0.300 mΩ respectively) are loaded for testing. Specifically, the quality factors Q1, Q2, and Q0 are measured at a resonant frequency of about 12 GHz and a working temperature of 77 K, and then the microwave surface resistance R of the two high-temperature superconductor samples to be measured is calculated. S , and the results are shown in Table 3.

[0091] Table 3

[0092] Loading condition Quality factor Calibration base <![CDATA[Q1 = 2.60×10 5 > Calibration plate <![CDATA[Q2 = 40300]]> Fourth high-temperature superconductor sample to be measured <![CDATA[Q0 = 2.35×10 5 > Fifth high-temperature superconductor sample to be measured <![CDATA[Q0 = 2.31×10 5 >

[0093] By comparing Table 1 and Table 2, it can be seen that compared with the device described in the improved image dielectric resonator method, for the test device loaded with the calibration seat 2, the quality factor Q1 can be increased to 3 times, and for the test device loaded with the high-temperature superconductor sample 12 to be measured, the quality factor Q0 can be increased to 2 times.

[0094] If the test sensitivity of the device is defined as:

[0095]

[0096] It can be found that this test sensitivity is related to the test reference value. Generally, the smaller the test reference value of R S , the higher the test sensitivity. The value of S when R S tends to 0 is defined as the theoretical maximum sensitivity S0 of the device, then

[0097]

[0098] At this time, the value of S0 is 5.5734e+5 (mΩ) -1 . Compared with S0 = 78323 (mΩ) -1 of the device described in the improved image dielectric resonator method, the sensitivity of the high-sensitivity device described in this embodiment is increased to more than 7 times.

[0099] Example 2

[0100] Based on the high-sensitivity device for measuring the microwave surface resistance of high-temperature superconductors proposed in Example 1, this embodiment measures the microwave surface resistance of the high-temperature superconductor sample 12 with high-temperature superconductor films plated on both the front and back sides.

[0101] The high-temperature superconducting sample 12 to be measured used in this embodiment is specifically a sample with high-temperature superconducting films plated on both the front and back sides of a 1-mm-thick lanthanum aluminate cylindrical wafer, and the nominal thickness of the film is 500 nm.

[0102] In this embodiment, the high-temperature superconducting sample 12 to be measured and the test seat 1 and the calibration seat 2 both form dielectric resonators in the TE011 mode of operation. The quality factor Q of the high-temperature superconducting sample 12 to be measured is loaded on the bottom end face of the test seat 1 0T and the quality factor Q of the high-temperature superconducting sample 12 to be measured is loaded on the bottom end face of the calibration seat 2 0C and the microwave surface resistance R of the high-temperature superconducting sample 12 to be measured S The relational expression is:

[0103] Q 0T -1 +Q 0C -1 =2A+(B T +B C )R s Equation (2)

[0104] In the formula, A and B T and B C are both constants. A is determined by the test method of Embodiment 1, and B T is the B value obtained after loading the calibration plate 11 on the bottom end face of the test seat 1, and B C is the B value obtained after loading the calibration plate 11 on the bottom end face of the calibration seat 2.

[0105] Based on the high-sensitivity device described in Embodiment 1, the method for measuring the microwave surface resistance of high-temperature superconductors proposed in this embodiment specifically includes the following steps:

[0106] Step B1: Load the calibration seat 2 onto the bottom end face of the test seat 1, and the two are mirror-symmetrical about the bottom end face. Use the sealing cavity 3 to seal the calibration seat 2, and keep the obtained test device as shown Figure 3 at the working temperature of the high-temperature superconducting sample 12 to be measured, and measure the quality factor Q1 at the resonant frequency;

[0107] Step B2: Load the calibration plate 11 and the calibration seat 2 onto the bottom end face of the test seat 1 in sequence, and use the sealing cavity 3 to seal the calibration plate 11 and the calibration seat 2. Keep the obtained test device as shown Figure 8 at the working temperature of the high-temperature superconducting sample 12 to be measured, and measure the quality factor Q of the test seat 1T and the quality factor Q of the calibration seat 1C ;

[0108] Step B3: Sequentially load the high-temperature superconductor sample 12 to be tested and the calibration seat 2 on the bottom end face of the test seat 1, where the front of the high-temperature superconductor sample 12 to be tested faces the test seat 1 and the back faces the calibration seat 2, and use the sealed cavity 3 to seal the high-temperature superconductor sample 12 to be tested and the calibration seat 2, and keep the obtained test device as shown in Figure 9 at the operating temperature of the high-temperature superconductor sample 12 to be tested, and measure the quality factor Q of the front of the test seat at the resonant frequency 0T_X and the quality factor Q of the back of the calibration seat 0C_Y ;

[0109] Step B4: Turn over the high-temperature superconductor sample 12 in Step B3, specifically, the back faces the test seat 1 and the front faces the calibration seat 2, and continue to measure the quality factor Q of the back of the test seat at the resonant frequency 0T_Y and the quality factor Q of the front of the calibration seat 0C_X ;

[0110] Step B5: Substitute the quality factors Q1, Q 1T and Q 1C into Equation (2) to calculate A = 1 / Q1, B T = (1 / Q 1T - A) / R SN , B C = (1 / Q 1C - A) / R SN ;

[0111] Furthermore, obtain the calculation formulas for the front microwave surface resistance R S_X and the back microwave surface resistance R S_Y of the high-temperature superconductor sample 12 to be tested at the resonant frequency:

[0112]

[0113] The nominal value of the microwave surface resistance R SN of the calibration plate 11 is 18.23 mΩ. Measure the quality factors Q1, Q 1T and Q 1C at the resonant frequency of about 12 GHz and the operating temperature of 77 K, and obtain the partial S-parameter test images of the calibration A value and B value as shown in Figure 10 , where Figure 10 (a) is the calibration A value, Figure 10 (b) is the calibration B T value, Figure 10 (c) is the calibration B C value, and obtain the data results shown in Table 4.

[0114] Table 4

[0115]

[0116] Based on the method for measuring the microwave surface resistance of high-temperature superconductors proposed in Embodiment 1, the microwave surface resistance R of the front and back sides of the high-temperature superconductor sample 12 to be measured is respectively tested under the conditions of a resonance frequency of about 12 GHz and a working temperature of 77 K. S Specifically, the front and back sides of the high-temperature superconductor sample 12 to be measured are respectively oriented towards the test seat 1, and step A3 is respectively executed once to obtain the quality factor of the front side of the test seat and the quality factor of the back side of the test seat; the calibration seat 2 is used to replace the test seat 1, and the front and back sides of the high-temperature superconductor sample 12 to be measured are respectively oriented towards the calibration seat 2, and the quality factor of the front side of the calibration seat and the quality factor of the back side of the calibration seat are also obtained; then, the microwave surface resistance R corresponding to the quality factor of the front side of the test seat, the quality factor of the back side of the test seat, the quality factor of the front side of the calibration seat, and the quality factor of the back side of the calibration seat is calculated using the formula in step A4. S The obtained R S The microwave surface resistance normalized to 10 GHz is denoted as Rs@10 GHz (mΩ), and the data results are shown in Table 5.

[0117] Table 5

[0118]

[0119] Based on the method for measuring the microwave surface resistance of high-temperature superconductors proposed in this embodiment, the quality factors Q 0T_X , Q 0C_Y , Q 0T_Y , and Q 0C_X are obtained by testing under the conditions of a resonance frequency of about 12 GHz and a working temperature of 77 K. Then, the microwave surface resistance R of the front and back sides of the high-temperature superconductor sample 12 to be measured after symmetry correction is calculated according to the formula in step B5. S The obtained R S The microwave surface resistance normalized to 10 GHz is denoted as Rs@10 GHz (mΩ). Figure 11 This is a partial S-parameter test image of the test seat loaded with the high-temperature superconductor sample to be measured in this embodiment. Among them, Figure 11 (a) shows the front side of the test seat loaded with the high-temperature superconductor sample to be measured, Figure 11 (b) shows the back side of the test seat loaded with the high-temperature superconductor sample to be measured; Figure 12 This is a partial S-parameter test image of the calibration seat loaded with the high-temperature superconductor sample to be measured in this embodiment. Among them, Figure 12 (a) shows the front side of the calibration seat loaded with the high-temperature superconductor sample to be measured, Figure 12 (b) shows the back side of the calibration seat loaded with the high-temperature superconductor sample to be measured. According to Figure 11 and Figure 12 the partial S-parameter test images, the test results shown in Table 6 are obtained.

[0120] Table 6

[0121]

[0122] Comparing Table 4 and Table 5, for the case where the symmetry of the material physical property electrical parameters between the test seat 1 and the calibration seat 2 is poor, in this embodiment, by improving the test method and calculation formula, the test accuracy of the microwave surface resistance of the high-temperature superconductor sample 12 to be measured can be significantly improved.

[0123] Example 3

[0124] In this embodiment, a stepped coaxial cylindrical dielectric column model used in Example 1 is established in the simulation software. Specifically, a support column and a resonant column integrally formed of sapphire material are used. Since the support column is fixed to the test cavity 5 through the dielectric support device 9 made of polytetrafluoroethylene material, a polytetrafluoroethylene clamping structure is provided above the stepped coaxial cylindrical dielectric column model.

[0125] Comparative Example 1

[0126] In this comparative example, a traditional regular cylindrical dielectric column model is established in the simulation software. To ensure structural consistency, on the basis of Example 3, the sapphire material of the support column is replaced with polytetrafluoroethylene material in this comparative example, and thus only the resonant column is made of sapphire material. Since the materials of the resonant column and the support column are different, an inevitable polytetrafluoroethylene clamping ring is introduced and is integrally provided with the support column. The bottom surface boundary condition of the traditional regular cylindrical dielectric column model is the perfect electric conductor boundary (PEC).

[0127] To verify the function of the cutoff waveguide jointly formed by the support column and the test cavity, simulation tests are respectively carried out on the stepped coaxial cylindrical dielectric column model established in Example 3 and the traditional regular cylindrical dielectric column model established in Comparative Example 1, and the eigen simulation modeling and partial electric field simulation results as shown in Figure 13 and Figure 14 are obtained. Among them, the color represents the electric field strength, and the arrow direction represents the electric field direction. The eigen simulation data results are shown in Table 7.

[0128] Table 7

[0129] Resonant frequency (GHz) Quality factor Example 3 11.997 639478 Comparative example 1 11.621 391309

[0130] By comparing the simulation results of Example 3 and Comparative Example 1, it can be seen that compared with the traditional regular cylindrical dielectric column model, the unloaded quality factor of the resonant cavity of the stepped coaxial cylindrical dielectric column model is increased by 60%. Combining with as shown in Figure 13 and Figure 14For the electric field situation shown, it can also be found that in the traditional regular cylindrical dielectric column model, a part of the working mode electric field acts on the polytetrafluoroethylene clamping ring, while in the stepped coaxial cylindrical dielectric column model, the working mode electric field is confined within the sapphire resonant column due to the action of the cutoff waveguide, and the working mode electric field acts on the sapphire and the air. Since polytetrafluoroethylene is an organic polymer material and has a relatively large loss tangent compared to sapphire (nearly two orders of magnitude), the loss characteristics of air can be neglected. Therefore, compared with the stepped coaxial cylindrical dielectric column model, the traditional regular cylindrical dielectric column model will cause greater energy loss. Furthermore, it can be known that the energy consumption of the resonator by the traditional regular cylindrical dielectric column model is significantly higher than that of the stepped coaxial cylindrical dielectric column model, indicating that introducing a section of cutoff waveguide between the dielectric support device and the resonant structure (composed of the resonant column and the corresponding part of the test cavity) can effectively reduce the loss introduced by the dielectric support structure to the resonant cavity and improve the quality factor.

[0131] In this article, specific examples are used to elaborate on the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A highly sensitive device for measuring the microwave surface resistance of high-temperature superconductors, characterized in that, It includes a test base, a calibration base, a calibration plate, a support plate and a sealing cavity; The test base includes a test cavity with an open bottom end face, a dielectric column, an input coupling structure, an output coupling structure and a dielectric support device; wherein, the dielectric column is a stepped coaxial cylinder, located at the center inside the test cavity, and is divided into a support column and a resonant column. The support column is fixed to the test cavity through the dielectric support device. The end face of the resonant column is in the same plane as the bottom end face of the test cavity. The diameter of the support column is smaller than that of the resonant column, so that the support column and the test cavity together form a cut-off waveguide with respect to the required resonant frequency; The calibration base has the same structure as the test base and is detachably arranged at the bottom end faces of the dielectric column and the test cavity; The calibration plate has a known microwave surface resistance and is detachably arranged at the bottom end faces of the dielectric column and the test cavity; The high-temperature superconductor sample to be measured is placed at the bottom end faces of the dielectric column and the test cavity, and the high-temperature superconductor sample to be measured is fastened by a detachable support plate; The sealing cavity is detachably arranged at the outer extension of the bottom end face of the test cavity.

2. The high-sensitivity device for measuring the high-temperature superconducting microwave surface resistance according to claim 1, characterized in that, The method for determining the diameter of the support column is as follows: Assume that the dielectric column is a regular cylinder. According to the required resonant frequency, adjust the diameters of the dielectric column and the inner wall of the test cavity; Take the diameter of the adjusted dielectric column as the diameter of the resonant column, and coaxially place a support column with an unknown diameter above the resonant column, and simulate the cut-off frequency of the waveguide formed by the support column and the adjusted test cavity together; By adjusting the diameter of the support column, make the waveguide cut-off frequency higher than the required resonant frequency, and then determine the diameter of the support column.

3. The high-sensitivity device for measuring the high-temperature superconducting microwave surface resistance according to claim 1, wherein The input coupling structure and the output coupling structure are symmetrically distributed on both sides of the test cavity, and the test cavity, the dielectric column and the dielectric support device are coaxial.

4. The highly sensitive device for measuring the high-temperature superconducting microwave surface resistance according to claim 3, characterized in that, Both the input coupling structure and the output coupling structure are coupling loop coaxial structures.

5. The device for efficiently measuring the microwave surface impedance of a high-temperature superconducting thin film according to claim 1, characterized in that The test cavity is plated with silver using a hard metal material; the material of the dielectric column is rutile, sapphire or beryllium oxide ceramic; the material of the dielectric support device is nylon, polytetrafluoroethylene or polyethylene foam.

6. The device for efficiently measuring the microwave surface impedance of a high-temperature superconducting thin film according to claim 1, wherein The thickness of the superconducting film of the high-temperature superconductor sample to be measured is greater than 200 nm, and its planar size is greater than the planar size of the bottom end face of the test cavity.

7. A method for measuring the microwave surface resistance of high-temperature superconductors, characterized in that, Based on the device for efficiently measuring the microwave surface impedance of a high-temperature superconducting thin film according to any one of claims 1 to 6, it specifically includes the following steps: Step A1: Load the calibration base onto the bottom end face of the test base, and the two are mirror-symmetrical about the bottom end face. Use the sealing cavity to seal the calibration base, and keep the obtained test device at the working temperature of the high-temperature superconductor sample to be measured, and measure the quality factor Q1 at the resonant frequency; Step A2: Load the calibration plate onto the bottom end face of the test base, and use the sealing cavity to seal the calibration plate. Keep the obtained test device at the working temperature of the high-temperature superconductor sample to be measured, and measure the quality factor Q2 at the resonant frequency; Step A3: Load the high-temperature superconductor sample to be measured onto the bottom end face of the test base, and fix it with a support plate. Use the sealing cavity to seal the high-temperature superconductor sample to be measured and the support plate, and keep the obtained test device at the working temperature of the high-temperature superconductor sample to be measured, and measure the quality factor Q0 at the resonant frequency; Step A4: According to the formula: Calculate the microwave surface resistance \(R\) of the high-temperature superconductor sample to be measured at the resonant frequency S , specifically the microwave surface resistance of the side of the high-temperature superconductor sample to be measured facing the test seat; where \(R\) SN is the microwave surface resistance of the calibration plate at the resonant frequency; The working modes of the test devices in the described method are all in the TE011 mode.

8. A method for measuring the microwave surface resistance of high-temperature superconductors, characterized in that, It is implemented based on the device for efficiently measuring the microwave surface impedance of high-temperature superconducting thin films according to any one of claims 1 to 6, and specifically includes the following steps: Step B1: Load the calibration seat onto the bottom end face of the test seat, and the two are mirror-symmetrical about the bottom end face. Use a sealed cavity to seal the calibration seat, and maintain the obtained test device at the working temperature of the high-temperature superconductor sample to be measured, and measure the quality factor Q1 at the resonant frequency; Step B2: successively load a calibration plate and a calibration seat on the bottom end face of the test socket, seal the calibration plate and the calibration seat with a sealing cavity, maintain the obtained test device at the working temperature of the high-temperature superconductor sample to be measured, and measure the quality factor Q of the test socket at the resonance frequency 1T and the quality factor Q of the calibration seat 1C ; Step B3: Sequentially load the high-temperature superconductor sample under test and the calibration seat on the bottom end face of the test socket, where the front face of the high-temperature superconductor sample under test faces the test socket side and the back face faces the calibration seat side, and use a sealed cavity to seal the high-temperature superconductor sample under test and the calibration seat, keep the obtained test device at the operating temperature of the high-temperature superconductor sample under test, and measure the quality factor Q of the front face of the test socket at the resonant frequency 0T_X and the quality factor Q of the back face of the calibration seat 0C_Y ; Step B4: Turn over the high-temperature superconducting sample to be measured in Step B3, specifically with the reverse side facing the test seat and the front side facing the calibration seat, and continue to measure the quality factor Q of the reverse side of the test seat at the resonant frequency. 0T_Y and the quality factor Q of the front side of the calibration seat. 0C_X ; Step B5: According to the formula: Calculate the front microwave surface resistance R of the high-temperature superconducting sample to be measured at the resonant frequency S_X and the back microwave surface resistance R S_Y ; The working modes of the test devices in the described method are all in the TE011 mode.

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