A device and method for efficiently measuring microwave surface impedance of high temperature superconducting thin films

Abstract

The application discloses a kind of high-efficiency measurement high-temperature superconducting film microwave surface impedance device and method, belong to electronics technical field, device includes test probe, calibration probe, metal plate and sealed cavity, the open type bottom end surface of test probe is test plane, calibration probe and the structure of test probe are completely same, and the mirror image symmetry of two about test plane;The microwave surface resistance of metal plate is known;By with the calibration probe, metal plate or the detachable measured HTS film being placed in test plane, and being covered with sealed cavity, the working temperature of the measured HTS film is placed respectively under no-load quality factor and resonance frequency test, and the R S And X S Of the measured HTS film is obtained by calculation.The application can simultaneously measure the microwave surface impedance of the front and back of the measured HTS film, greatly improve the testing efficiency while ensuring the accuracy of the test results, suitable for mass industrial testing of HTS film, and suitable for widely used 2-inch and above size HTS film.

Description

Technical Field

[0001] This invention belongs to the field of electronics technology, specifically relating to an efficient device and method for measuring the microwave surface impedance of high-temperature superconducting thin films. Background Technology

[0002] Since the global surge in research on high-temperature superconductors (HTS), high-temperature superconducting thin films, as an application of high-temperature superconductors, have become a hot topic in the field of electronic materials research. HTS thin films possess extremely low microwave surface resistivity R0. S And the frequency-independent surface penetration depth λ, mainly used in the fabrication of microwave passive devices, such as resonators, filters, and antennas. Microwave surface reactance Z S As one of the most important parameters of HTS thin films, its value is closely related to the performance of high-temperature superconducting microwave passive devices. Therefore, it is particularly important to measure the microwave surface reactance Zs of HTS thin films.

[0003] Z S =R S +jXs,X S =ωμ0λ; where, R S X represents the microwave surface resistivity, characterizing the microwave loss of the HTS thin film and reflecting the density of quasiparticles; S The microwave surface reactance, proportional to the magnetic penetration depth λ, reflects the electron pair density. From its relationship with temperature, information about the superconducting band gap can be obtained. Therefore, accurate measurement of microwave surface impedance (including R0) is crucial. S and X S This is of great significance for understanding the physical and electronic properties of materials, developing new materials, and designing superconducting electronic components.

[0004] Currently, HTS films are used in R S The testing method in international testing standards is the dual-dielectric resonator method, which employs methods such as... Figure 1 The two resonator structures are shown. Each resonator consists of two HTS thin films and a sapphire dielectric pillar between them. The two sapphire dielectric pillars have the same dielectric constant ε, loss tangent tanδ, and diameter d, and their heights are h and 3h, respectively. Their resonant modes are TE and TE, respectively. 011 and TE 013 However, this method requires two separate temperature cycles for each of the two resonators, meaning two temperature cycles for the HTS film under test, in order to obtain the Ro of the HTS film under test. SThe testing process is relatively time-consuming. For example, during testing, the testing device needs to be immersed in liquid nitrogen to cool the HTS film under test. After the test, the testing device needs to be reheated to room temperature. This process is a temperature cycle and takes at least one hour. Moreover, the result of this method is the average of two HTS films under test. To obtain the R value of a single side of a single sample... S At least three superconducting samples are required, and six temperature cycles are needed, resulting in low testing efficiency.

[0005] Typically, the R of HTS films S and X S The measurement requires the use of the same resonant structure; therefore, for the X-ray of the HTS thin film... S The measurement method currently widely used internationally is the dielectric resonator method, such as... Figure 2 As shown. The X-ray diffraction (XRD) of the HTS thin film under test is obtained by measuring the relationship between the resonant frequency f0 of the entire resonant device and temperature. S .like Figure 2 As shown in (a), firstly, metal plates with good conductors are loaded at both ends of the sapphire dielectric pillar, and the relationship between the resonant frequency of the entire resonant device and temperature, f1(T), is measured; then, the metal plates are replaced with the HTS thin film to be tested, as shown in (a). Figure 2 As shown in (b), the relationship between the resonant frequency of the entire resonant device and temperature is measured as f2(T). Finally, the difference between f1(T) and f2(T) is used to calculate X. S However, this method introduces testing errors caused by the metal plate during the testing process, therefore, it is still necessary to separately test the microwave surface reactance X of the metal plate. S The relationship between temperature and X-rays indicates that three heating / cooling processes are required to measure the X-rays of the HTS film under test. S The testing efficiency is also relatively low.

[0006] However, the above method can only measure the microwave surface impedance of one side of the HTS film under test. At present, there is no method that can simultaneously measure the microwave surface impedance of both sides of the HTS film under test. Summary of the Invention

[0007] To address the problem of low efficiency in existing microwave surface impedance testing of HTS thin films, this invention provides an efficient device and method for measuring the microwave surface impedance of high-temperature superconducting thin films. It can simultaneously measure the microwave surface impedance of both sides of the HTS thin film under test, greatly improving testing efficiency while ensuring the accuracy of test results. It is suitable for large-scale industrial testing of HTS thin films and applicable to widely used HTS thin films of 2 inches and above.

[0008] The technical solution adopted in this invention is as follows:

[0009] The device for efficiently measuring microwave surface impedance of high-temperature superconducting thin film comprises a test probe, a calibration probe, a metal plate and a sealed cavity.

[0010] An open bottom end surface of the test probe is a test plane, the calibration probe is completely identical in structure to the test probe, and the two are mirror-symmetric about the test plane.

[0011] The microwave surface resistance of the metal plate is known.

[0012] The sealed cavity is used to cover the test plane.

[0013] By detachably placing the calibration probe, the metal plate or the HTS thin film to be measured on the test plane and covering them with the sealed cavity, the unloaded quality factor is tested at a temperature below the working temperature of the HTS thin film to be measured, and the microwave surface resistance R S and microwave surface reactance X S of the front and back surfaces of the HTS thin film to be measured are calculated.

[0014] Further, the test probe comprises a shielded cavity with an open bottom end surface, a dielectric column, a dielectric clamping ring, an input coupling structure and an output coupling structure; the dielectric column is located at the center inside the shielded cavity and is fixed to the shielded cavity through the dielectric clamping ring; the bottom end surface of the dielectric column and the bottom end surface of the shielded cavity are in the same plane and together constitute the test plane of the test probe; the input coupling structure and the output coupling structure are symmetrically distributed on both sides of the shielded cavity.

[0015] Further, the shielded cavity, the dielectric column and the dielectric clamping ring are coaxial.

[0016] Further, the input coupling structure and the output coupling structure both adopt a coupling ring structure, and the plane where the coupling ring is located is parallel to the test plane.

[0017] Further, the shielded cavity adopts brass as the processing material, and the surface treatment uses a silver plating process; the dielectric column adopts a high-Q value material with low loss and high dielectric constant, such as sapphire; and the dielectric clamping ring adopts a low-loss material with low dielectric constant, such as nylon, polytetrafluoroethylene, etc.

[0018] Further, the diameter of the HTS thin film to be measured is greater than 2 inches, and the film thickness is not less than 200 nm.

[0019] Further, the method for efficiently measuring the microwave surface resistance of high-temperature superconducting thin film specifically comprises the following steps:

[0020] Step A1, load the calibration probe onto the bottom end surface of the test probe, the two are mirror-symmetric about the test plane, and cover the calibration probe with the sealed cavity, introduce protective gas after sealing, and place the obtained test device below the working temperature of the HTS thin film to be measured to test the unloaded quality factor Q0H ;

[0021] Step A2, heating the test device obtained in step A1 to room temperature, and removing the calibration probe; then loading a metal plate with microwave surface resistance R SN on the bottom end surface of the test probe, and covering the metal plate with a sealed cavity, after sealing, introducing protective gas, and placing the obtained test device below the working temperature of the HTS film to be tested, the unloaded quality factor Q 0N is tested.

[0022] Step A3, heating the test device obtained in step A2 to room temperature, and removing the metal plate; then loading the front surface of the HTS film to be tested on the bottom end surface of the test probe, and loading the calibration probe on the back surface of the HTS film to be tested, the test probe and the calibration probe are mirror symmetric about the HTS film to be tested, and covering the calibration probe with a sealed cavity, after sealing, introducing protective gas, and placing the obtained test device below the working temperature of the HTS film to be tested, the unloaded quality factor Q 0T of the test probe and the unloaded quality factor Q 0C of the calibration probe are tested respectively.

[0023] Step A4, calculating the microwave surface resistance R S1 of the front surface of the HTS film to be tested according to the formula

[0024]

[0025] .

[0026] Step A5, calculating the microwave surface resistance R S2 of the back surface of the HTS film to be tested according to the formula

[0027]

[0028] .

[0029] Further, by performing only one temperature cycle on the HTS film to be tested, the microwave surface resistances of the front and back surfaces of the HTS film to be tested can be measured simultaneously; and for other HTS films to be tested, only steps A3-A5 need to be repeated, that is, one temperature cycle, and the microwave surface resistances of the front and back surfaces of the HTS film to be tested can be measured simultaneously.

[0030] Further, the method for efficiently measuring the microwave surface reactance of a high-temperature superconducting film specifically comprises the following steps:

[0031] Step B1, loading the calibration probe on the bottom end surface of the test probe, the two are mirror symmetric about the test plane, placing the obtained test device below the working temperature of the HTS film to be tested, and measuring the unloaded quality factor Q 0H vs. temperature T curve Q 0H(T), and the resonance frequency f 01 The curve Q(T) 01 (T), this step is called calibration process one;

[0032] Step B2, heating the test device obtained in step B1 to room temperature, and removing the calibration probe; then loading the metal plate to the bottom end surface of the test probe, and placing the obtained test device below the working temperature of the HTS film to be tested, and testing to obtain the unloaded quality factor Q 0N The curve Q(T) 0N (T), this step is called calibration process two;

[0033] Step B3, heating the test device obtained in step B2 to room temperature, and removing the metal plate; then loading the front surface of the HTS film to be tested to the bottom end surface of the test probe, and loading the calibration probe to the back surface of the HTS film to be tested, and the test probe and the calibration probe are mirror-symmetric about the HTS film to be tested, and placing the obtained test device below the working temperature of the HTS film to be tested, and testing to obtain the unloaded quality factor Q 0T The curve Q(T) 0T (T) of the test probe 0T The curve f(T) 0T (T) of the calibration probe 0C The curve Q(T) 0C (T) of the calibration probe 0C The curve f(T) 0C (T);

[0034] Step B4, calculating the front surface microwave surface resistance R c (T S1 ) of the HTS film to be tested at the quench temperature T c ;

[0035] According to the formula

[0036]

[0037] The relative value ΔX S1 (T) of the front surface microwave surface reactance of the HTS film to be tested with respect to temperature T is calculated;

[0038] In the formula, T min is the lowest test temperature; f 0T (T min ) is the resonance frequency f min of the test probe at T 0T ; f 01 (T min ) is the resonance frequency f min at T 01 ;

[0039] The absolute value X S1 (T) of the temperature variation of the microwave surface reactance of the front surface of the HTS film to be measured S1 (T) exists

[0040] ΔX S1 (T) = X S1 (T) - X S1 (T min ) (26)

[0041] And the HTS film to be measured satisfies

[0042] X S1 (T C ) = R S1 (T C ) (5)

[0043] The absolute value X S1 (T) of the temperature variation of the microwave surface reactance of the front surface of the HTS film to be measured is calculated

[0044] In the formula, X S1 (T min ) is the microwave surface reactance of the front surface of the HTS film to be measured at temperature T min ; X S1 (T c ) is the microwave surface reactance of the front surface of the HTS film to be measured at T c ;

[0045] Step B5, calculating the microwave surface resistance R c (T S2 ) of the back surface of the HTS film to be measured at T c ;

[0046] According to the formula

[0047]

[0048] The relative value ΔX S2 (T) of the temperature variation of the microwave surface reactance of the back surface of the HTS film to be measured is calculated

[0049] In the formula, f 0C (T min ) is the resonant frequency f min of the calibration probe at T 0C ;

[0050] The absolute value X S2 (T) of the temperature variation of the microwave surface reactance of the back surface of the HTS film to be measured S2 (T) exists

[0051] ΔX S2 (T) = XS2 (T)-X S2 (T min ) (27)

[0052] and the measured HTS thin film is in the superconducting state

[0053] X S2 (T C )=R S2 (T C ) (8)

[0054] X S2 (T) is calculated;

[0055] wherein X S2 (T min ) is the microwave surface reactance of the reverse side of the measured HTS thin film at temperature T min ; and X S2 (T c ) is the microwave surface reactance of the reverse side of the measured HTS thin film at temperature T c .

[0056] Further, through two calibration processes and only one temperature rising and falling process of the measured HTS thin film, the microwave surface reactance of the front and reverse sides of the measured HTS thin film can be measured simultaneously; and for other measured HTS thin films, only the steps B3-B5 are repeated, i.e. only one temperature rising and falling process is performed, so that the microwave surface reactance of the front and reverse sides of the measured HTS thin film can be measured simultaneously.

[0057] Further, the formula for calculating R S1 (T c ) in step B4 is:

[0058]

[0059] wherein R SN (T) is the microwave surface resistance of the metal plate varying with temperature T; Q 0T (T c ) is the unloaded quality factor Q c of the test probe at temperature T 0T ; Q 0H (T c ) is the unloaded quality factor Q c at temperature T 0H ; and Q 0N (T c ) is the unloaded quality factor Q c at temperature T 0N .

[0060] The formula for calculating R S2 (T c ) in step B5 is:

[0061]

[0062] In the formula, Q 0C (T c ) is T c The unloaded quality factor Q 0C .

[0063] Further, steps B1-B3 are completed by loading the corresponding test device into the refrigerator to complete the temperature test.

[0064] Compared with the prior art, the present application has the following advantages:

[0065] The present application provides a device and method for efficiently measuring the microwave surface impedance of high-temperature superconducting thin films, which is called an improved mirror dielectric resonator method. On the one hand, compared with the national standard test method-double dielectric resonator method, the present application only needs to perform one temperature cycle on the measured HTS thin film, and can simultaneously measure the microwave surface resistance of the front and back surfaces of the measured HTS thin film. The present application greatly improves the test efficiency while ensuring high test sensitivity and accuracy, avoids damage to the thin film caused by repeatedly placing the measured HTS thin film into liquid nitrogen for testing, and is especially suitable for widely used 2-inch and larger size HTS thin films, and is suitable for large-scale industrial testing. On the other hand, compared with the national standard test method-dielectric resonator method, the present application eliminates the influence of the frequency drift of the resonator caused by the change of the dielectric constant of the dielectric column due to temperature change through two calibration processes, reduces the test error, and ensures the accuracy of the test results. Thereafter, only one temperature rising / dropping process is needed for the measured HTS thin film, and the microwave surface impedance of the front and back surfaces of the measured HTS thin film can be simultaneously measured, greatly improving the test efficiency of the microwave surface impedance of the measured HTS thin film. BRIEF DESCRIPTION OF DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0067] Figure 1 Structure diagram for measuring microwave surface resistance by double dielectric resonator method;

[0068] Figure 2 Structure diagram for measuring microwave surface impedance by dielectric resonator method; (a) is a resonator structure loaded with a metal plate; (b) is a resonator structure loaded with a measured HTS thin film;

[0069] Figure 3A sectional structure diagram of a test probe in a device for efficiently measuring microwave surface impedance of a high-temperature superconducting thin film proposed in Embodiment 1 of the present application;

[0070] Figure 4 A sectional structure diagram of a test device after a test probe is loaded with a calibration probe in the device for efficiently measuring microwave surface impedance of a high-temperature superconducting thin film proposed in Embodiment 1 of the present application;

[0071] Figure 5 A sectional structure diagram of a test device after a test probe is loaded with a metal plate in the device for efficiently measuring microwave surface impedance of a high-temperature superconducting thin film proposed in Embodiment 1 of the present application;

[0072] Figure 6 A sectional structure diagram of a test device after a test probe is loaded with a calibration probe in the device for efficiently measuring microwave surface impedance of a high-temperature superconducting thin film proposed in Embodiment 1 of the present application;

[0073] Fig. 7 is a curve of resonant frequency of the test device in Embodiment 3 of the present application versus temperature, wherein the test probe is loaded with a calibration probe in sequence;

[0074] Figure 8 A curve of relative values of microwave surface reactance of the front and back surfaces of the measured HTS thin film versus temperature measured in Embodiment 3 of the present application;

[0075] Figure 9 A curve of absolute values of microwave surface resistance and microwave surface reactance of the front and back surfaces of the measured HTS thin film versus temperature measured in Embodiment 3 of the present application;

[0076] The following is a description of the reference numerals in the drawings:

[0077] 1-test probe; 2-shielding cavity; 3-dielectric clamping ring; 4-dielectric column; 5-input coupling structure; 6-output coupling structure; 7-metal plate; 8-sealing cavity; 9-calibration probe; 10-measured HTS thin film; 11-front surface of the measured HTS thin film; 12-back surface of the measured HTS thin film. DETAILED DESCRIPTION

[0078] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with the embodiments, but it should be understood that the descriptions are only for further illustrating the features and advantages of the present application, and are not limitations on the claims of the present application.

[0079] All raw materials of the present application are not particularly limited in source, and can be purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0080] The purity of all raw materials of the present application is not particularly limited, and the present application preferably uses analytical purity or the purity required in the field of atomic layer deposition.

[0081] The grade or abbreviation of all raw materials and processes of the present application all belong to the conventional grade or abbreviation in the field, and each grade or abbreviation is clear and explicit in the field of its related use. Those skilled in the art can purchase or prepare by conventional methods according to the grade, abbreviation and corresponding use, or use the corresponding equipment to realize it.

[0082] The present application will be further described in conjunction with the following examples:

[0083] Example 1

[0084] The present embodiment proposes a device for efficiently measuring the microwave surface impedance of high-temperature superconducting thin film, which comprises a test probe 1, a calibration probe 9, a sealed cavity 8 and a metal plate 7.

[0085] The structure of the test probe 1 is shown in Figure 3 The test probe 1 comprises a shielded cavity 2 with an open bottom end surface, a dielectric clamping ring 3, a dielectric column 4, an input coupling structure 5 and an output coupling structure 6. The dielectric column 4 is located inside the shielded cavity 2 and is fixed to the shielded cavity through the dielectric clamping ring 3. The bottom end surface of the dielectric column 4 and the bottom end surface of the shielded cavity 2 are in the same plane, together constituting the test plane of the test probe 1. The input coupling structure 5 and the output coupling structure 6 are symmetrically arranged on both sides of the shielded cavity 2, both adopting a coupling loop structure, and the plane of the coupling loop is parallel to the test plane of the test probe. The test probe 1, the dielectric column 4 and the dielectric clamping ring 3 have the same central axis.

[0086] The sealed cavity 8 is used to cover the test plane.

[0087] The calibration probe 9 has the same structure and size as the test probe 1. As shown in Figure 4 The calibration probe 9 can be loaded on the bottom end surface of the test probe 1, and the two are mirror-symmetric about the test plane. The sealed cavity 8 is detachably arranged on the extension of the bottom end surface of the test probe 1 to cover the calibration probe 9.

[0088] The microwave surface resistance R SN It is known that in order to ensure the stability of the microwave surface resistance of the metal plate 7, gold plating process is used for the surface treatment of the metal plate. As shown in Figure 5 The metal plate 7 can be loaded on the bottom end surface of the test probe 1, and the sealed cavity 8 is detachably arranged on the extension of the bottom end surface of the test probe 1 to cover the metal plate 7.

[0089] The diameter of the HTS thin film 10 to be measured is 2 inches or more, and the coating thickness d is 200 nm or more. As shown in Figure 6As shown, the front surface 11 of the HTS film to be measured is loaded on the bottom end surface of the test probe 1, the calibration probe 9 is loaded on the back surface 12 of the HTS film to be measured, and the sealed cavity 8 is detachably arranged outside the bottom end surface of the test probe 1 to cover the calibration probe 9 and the HTS film to be measured 10.

[0090] In this embodiment, the test probe 1 and the calibration probe 9 are both made of brass material, the surface is plated with silver, the main cavity is a cylindrical structure with a diameter of about 35 mm and a height of 10 mm; the dielectric column 4 is made of a high-Q value material with low loss and high dielectric constant, specifically sapphire, the surface must be polished, the diameter is about 8 mm, and the height is about 6 mm; the dielectric clamping ring 3 is made of a low-loss low-dielectric-constant material, specifically polytetrafluoroethylene.

[0091] In this embodiment, the HTS film to be measured 10 and the test probe 1 and the calibration probe 9 all constitute a dielectric resonator with a TE 011 mode working mode, the working frequency is 12 GHz, and the relationship between the unloaded quality factor Q0 of the dielectric resonator and the microwave surface resistance R S of the HTS film to be measured 10 is:

[0092]

[0093] In the formula, A and B are both geometric factors of the resonant cavity, and are independent of the microwave surface resistance R S of the HTS film to be measured 10, and are determined by the measurement method.

[0094] Embodiment 2

[0095] Based on the device for efficiently measuring the microwave surface impedance of the high-temperature superconducting film in Embodiment 1, this embodiment proposes a method for efficiently measuring the microwave surface resistance of the high-temperature superconducting film, comprising the following steps:

[0096] Step A1, load the calibration probe 9 on the bottom end surface of the test probe 1, the two are mirror-symmetric about the test plane, the resistance R S at the test plane (mirror surface) is 0; cover the calibration probe 9 with the sealed cavity 8, specifically cover the calibration probe 9 and the bottom end surface of the test probe 1, after sealing, introduce the protective gas, immerse the sealed cavity 8 of the obtained test device in liquid nitrogen, that is, below the working temperature (i.e. the superconducting temperature T c ) of the HTS film to be measured 10, connect the test instrument, and test to obtain the unloaded quality factor Q 0H .

[0097] According to the formula

[0098]

[0099] The A value of the improved mirror dielectric resonator can be obtained;

[0100] Step A2, the test device obtained in step A1 is heated to room temperature, and the calibration probe 9 is removed; then a metal plate 7 with a microwave surface resistance of R SN is loaded onto the bottom end surface of the test probe 1, and the metal plate 7 is covered with the sealed cavity 8, specifically the bottom end surface of the test probe 1 and the metal plate 7, after sealing, protective gas is introduced, and the sealed cavity 8 of the obtained test device is immersed in liquid nitrogen, that is, placed below the working temperature of the HTS film 10 to be tested, and the test instrument is connected, and the unloaded quality factor Q 0N of the test probe is tested.

[0101] According to the formula

[0102]

[0103] The B value of the improved mirror medium resonator can be obtained;

[0104] Step A3, the test device obtained in step A2 is heated to room temperature, and the metal plate 7 is removed; then the front surface 11 of the HTS film to be tested is loaded onto the bottom end surface of the test probe 1, and the calibration probe 9 is loaded onto the back surface 12 of the HTS film to be tested, the test probe 1 and the calibration probe 9 are mirror-symmetric about the HTS film 10 to be tested, and the calibration probe 9 is covered with the sealed cavity 8, specifically the bottom end surface of the test probe 1 and the calibration probe 9, after sealing, protective gas is introduced, and the sealed cavity 8 of the obtained test device is immersed in liquid nitrogen, that is, placed below the working temperature of the HTS film 10 to be tested, and the test instrument is connected, and the unloaded quality factor Q 0T of the test probe and the unloaded quality factor Q 0C of the calibration probe are tested respectively.

[0105] Step A4, the microwave surface resistance R c of the front surface 11 of the HTS film to be tested at the quenching temperature T S1 is calculated according to the formula

[0106]

[0107] c S1

[0108] Step A5, the microwave surface resistance R c of the back surface 12 of the HTS film to be tested at the quenching temperature T S2 is calculated according to the formula

[0109]

[0110] c S2

[0111] Furthermore, by performing only one temperature cycle on the HTS film 10 under test, the microwave surface resistance of both sides of the HTS film 10 under test can be measured simultaneously; and for other HTS films under test, only steps A3 to A5 need to be repeated, that is, one temperature cycle needs to be performed, and the microwave surface resistance of both sides of the HTS film under test can be measured simultaneously.

[0112] In step 1, if the loss tangent tanδ of the dielectric column 4 used in test probe 1 and calibration probe 9 is different, it will cause asymmetry between test probe 1 and calibration probe 9, resulting in R at the mirror surface. S ≠0. Mirror surface R S The fact that A = 0 is the theoretical basis for accurately calculating the value of A, and the calculation of the value of B is also based on the premise that A is an accurate value. Therefore, verifying R at the mirror surface... S Whether the value is 0 or not will verify whether the model and theoretical derivation of the method for efficiently measuring the microwave surface resistance of high-temperature superconducting thin films proposed in this embodiment are correct.

[0113] Furthermore, in order to verify the R at the mirror surface of the device used in this embodiment... S Whether it is 0 indicates the consistency of the loss tangent tanδ of the dielectric pillar 4 used by test probe 1 and calibration probe 9. Based on step A3, step A6 is given. Then, the microwave surface resistance of the HTS film 10 under test is calculated on both sides to compare the difference in test results of the same side of the HTS film 10 under test using test probe 1 and calibration probe 9 respectively. The specific operation is as follows:

[0114] Step A6: Flip the HTS film 10 to be tested from Step A3, i.e., load the reverse side 12 of the HTS film to be tested onto the bottom surface of the test probe 1, and then load the calibration probe 9 onto the front side 11 of the HTS film to be tested. The test probe 1 and the calibration probe 9 are mirror images of the HTS film 10 to be tested. The calibration probe 9 is covered by a sealed cavity 8. After sealing, a protective gas is introduced. The sealed cavity 8 of the resulting test device is immersed in liquid nitrogen, i.e., placed below the operating temperature of the HTS film 10 to be tested. The test instrument is connected, and the unloaded quality factor Q′ of the test probe is measured. 0T and the unloaded quality factor Q′ of the calibration probe 0C ;

[0115] Step A7: According to the formula

[0116]

[0117] The microwave surface resistance R on the front side of the HTS thin film under test was calculated. S ′1;

[0118] Step A8: According to the formula

[0119]

[0120] The microwave surface resistance R on the reverse side of the HTS thin film under test was calculated. S ′2.

[0121] Furthermore, based on the test value R S1 R S2 R S ′1 and R S 2. The actual microwave surface resistance values ​​of the HTS thin film 10 on both sides are calculated. The derivation process is as follows:

[0122] exist Figure 6 In the test, the HTS thin film 10, together with the test probe 1 and the calibration probe 9, forms two dielectric resonators, one above the other. The relationship between its unloaded quality factor Q0 and the corresponding internal loss of the dielectric resonator is as follows:

[0123]

[0124] In the formula, ω0 is the resonant angular frequency; P m This is the power consumed by shielded cavity 2; P d This is the power consumed by the corresponding dielectric pillar 4 in the upper and lower dielectric resonators; P sr This is the power consumed by the dielectric clamping ring 3; P s The microwave surface resistance R of the HTS thin film 10 to be tested is... S The power consumed; W is TE 011 The average energy stored in the resonant cavity during one resonant cycle of a mode.

[0125] According to formula (9), let

[0126]

[0127]

[0128] exist Figure 4 In the test, specifically for probe 1, its unloaded quality factor Q is... T Relationship with probe internal power loss

[0129]

[0130] Where P T =P m +P dT +P sr P dT The power consumed by the dielectric column 4 of probe 1 for testing.

[0131] exist Figure 4 In the context of calibration probe 9 alone, its unloaded quality factor Q is... CRelationship with probe internal power loss

[0132]

[0133] Where P C =P m +P dC +P sr P dC The power consumed by the dielectric column 4 for calibrating probe 9.

[0134] Because the loss tangents of the dielectric column 4 of test probe 1 and calibration probe 9 are different, their power consumption is also different. Therefore, P dT ≠P dC .

[0135] exist Figure 4 In the test setup, the unloaded quality factor Q is... 0H

[0136]

[0137] Therefore, from formulas (17) to (19), we can obtain formula (20).

[0138]

[0139] exist Figure 6 In the process of loading the HTS film 10 under test, the dielectric resonator formed by the front side 11 of the HTS film under test and the test probe 1 is viewed separately, and its unloaded quality factor Q is... 0T

[0140]

[0141] exist Figure 6 In the process, after flipping the HTS film 10 under test, the dielectric resonator formed by the front side 11 of the HTS film under test and the calibration probe 9 is viewed separately, and its unloaded quality factor Q′ is determined. 0C

[0142]

[0143] Therefore, the microwave surface resistance R of the front side of the HTS thin film to be tested can be calculated using formulas (1), (13) and (20) to (22). S The actual value is

[0144]

[0145] According to formulas (1) and (13), the microwave surface resistance R of the front side of the HTS thin film to be tested can be obtained. S Relationship between actual value and test value

[0146]

[0147] the actual value of the microwave surface resistance R of the front side 11 of the HTS film to be tested S is the average of the test values measured by the test probe 1 and the calibration probe 9 respectively.

[0148] Similarly, the actual value of the microwave surface resistance R of the back side 12 of the HTS film to be tested S and the test value

[0149]

[0150] Using the method for efficiently measuring the microwave surface resistance of the high-temperature superconducting film described in this embodiment, the test probe 1 and the calibration probe 9 are used to respectively measure the front side and the back side of the same piece of HTS film 10 in a liquid nitrogen environment for 6 times, and the R S test results are shown in Table 1.

[0151] For the front side and the back side of the HTS film 10 to be tested, the two sets of data with the largest difference in the test results obtained by using the test probe 1 and the calibration probe 9 respectively are compared, and the relative deviation of the average value (considered as the actual value) and the test value is compared using formulas (24) and (25), as shown in Table 2. S

[0152] For the same side of the HTS film 10 to be tested, the test probe 1 and the calibration probe 9 are used to test the 6 test results respectively, and the test error of the test value is measured by using the standard deviation (precision) in the national standard GB / T22586-2018, as shown in Table 3.

[0153] It can be found that for the same side of the same piece of HTS film 10 to be tested, whether the test results are verified by using the method for efficiently measuring the microwave surface resistance of the high-temperature superconducting film described in this embodiment or the test error is measured by using the standard deviation in the national standard GB / T22586-2018 (generally required to be not more than 20%), the relative deviation of the results of R S measured by using the test probe 1 and the calibration probe 9 is very small, both within 6%, indicating that the method for efficiently measuring the microwave surface resistance of the high-temperature superconducting film described in this embodiment has high test accuracy and repeatability.

[0154] Table 1

[0155]

[0156] Table 2

[0157]

[0158] ​

[0159] Table 3

[0160]

[0161] The method for efficiently measuring the microwave surface resistance of high-temperature superconducting thin films described in this embodiment has significant advantages over the testing methods in international standards. Specifically, the dual-dielectric resonator method requires two temperature cycles, and the test results are obtained from two HTS thin films under test. S To obtain the average value, the HTS film to be tested must be exchanged multiple times to obtain the R value of a single sample. S The testing is inefficient, and this testing method does not take into account TE (Test Components). 011 and TE 013 Errors are introduced by different radial radiation losses. The method for efficiently measuring the microwave surface resistance of high-temperature superconducting thin films described in this embodiment can measure the Rt of both sides of a single HTS thin film 10 during a single temperature cycle. S And provide a method to verify R S The test error between the test value and the actual value improves testing efficiency and ensures the accuracy of test results, making it suitable for large-scale industrial testing.

[0162] Example 3

[0163] Based on the efficient device for measuring the microwave surface impedance of high-temperature superconducting thin films in Example 1, this example proposes an efficient method for measuring the microwave surface reactance of high-temperature superconducting thin films. The method involves measuring the relative value ΔX of the resonant frequency f0 of the dielectric resonator formed by the HTS thin film 10 under test, the test probe 1, and the calibration probe 9, and the microwave surface reactance of the HTS thin film 10 under test. S The relationship with temperature T is as follows:

[0164]

[0165] In the formula, A S The distribution of the electromagnetic field inside the resonant cavity is determined and is independent of the HTS thin film 10 under test. In this embodiment, A S The value of is equal to B; Δf(T) is the frequency shift caused by the change of the frequency of the HTS film 10 under test with temperature T; f0 is the resonant frequency of the dielectric resonator when operating at the lowest test temperature.

[0166] The method for efficiently measuring the microwave surface reactance of high-temperature superconducting thin films proposed in this embodiment specifically includes the following steps:

[0167] Step Bl, load calibration probe 9 onto the bottom end face of test probe 1, which is mirror-symmetric about the test plane, load the resulting test setup into the cryostat, connect the test equipment, and use the cryostat to ramp down to below the operating temperature of the HTS film 10 under test, and measure the unloaded quality factor Q 0H Q as a function of temperature T 0H (T), and the resonant frequency f 01 f as a function of temperature T 01 (T), this step is called calibration process one;

[0168] Step B2, heat the test setup from step Bl to room temperature and remove the calibration probe 9, then load the metal plate 7 onto the bottom end face of test probe 1, load the resulting test setup into the cryostat, connect the test equipment, and use the cryostat to ramp down to below the operating temperature of the HTS film 10 under test, and measure the unloaded quality factor Q 0N Q as a function of temperature T 0N (T), this step is called calibration process two;

[0169] Step B3, heat the test setup from step B2 to room temperature and remove the metal plate 7, then load the front side 11 of the HTS film under test onto the bottom end face of test probe 1, and load the calibration probe 9 onto the back side 12 of the HTS film under test, the test probe 1 and the calibration probe 9 are mirror-symmetric about the HTS film 10 under test, load the resulting test setup into the cryostat, connect the test equipment, and use the cryostat to ramp down to below the operating temperature of the HTS film 10 under test, and measure the unloaded quality factor Q 0T Q as a function of temperature T 0T (T), the resonant frequency f 0T f as a function of temperature T 0T (T), the unloaded quality factor Q 0C Q as a function of temperature T 0C (T), and the resonant frequency f 0C f as a function of temperature T 0C (T);

[0170] Step B4, calculate the front side microwave surface resistance R c (T S1 ) of the HTS film 10 under test at the critical temperature T c , the formula is:

[0171]

[0172] where R SN (T C ) is the microwave surface resistance of the metal plate at T cthe microwave surface resistance of the front surface 11 of the HTS film 10 at temperature T 0T (T c ) is the unloaded quality factor Q of the test probe 1 at temperature T c 0T ; Q 0H (T c ) is the unloaded quality factor Q of the test probe 1 at temperature T c 0H ; Q 0N (T c ) is the unloaded quality factor Q of the test probe 1 at temperature T c 0N ;

[0173] The relative value ΔX

[0174]

[0175] of the microwave surface reactance of the front surface 11 of the HTS film 10 is calculated as a function of temperature T S1 (T) according to the formula

[0176] where T min is the lowest test temperature; f 0T (T min ) is the resonance frequency f min of the test probe 1 at temperature T 0T ; f 01 (T min ) is the resonance frequency f min of the test probe 1 at temperature T 01 ;

[0177] Since the absolute value X S1 (T) of the microwave surface reactance of the front surface 11 of the HTS film 10 as a function of temperature and ΔX S1 (T) exist

[0178] ΔX S1 (T) = X S1 (T) - X S1 (T min ) (26)

[0179] and the HTS film 10 under test satisfies

[0180] X S1 (T C ) = R S1 (T C ) (5)

[0181] X S1 (T) is calculated;

[0182] where X S1 (T min ) is the temperature T min ​​​the front surface 11 of the HTS film under test at T S1 (T c ) is T c the front surface 11 of the HTS film under test at T

[0183] Step B5, calculate the back surface microwave surface resistance R c of the HTS film under test 10 at T S2 (T c ), the formula is:

[0184]

[0185] where Q 0C (T c ) is the unloaded quality factor Q c of the test probe at T 0C ;

[0186] According to the formula

[0187]

[0188] the relative value ΔX S2 (T) of the back surface microwave surface reactance of the HTS film under test 12 with temperature T is calculated.

[0189] where f 0C (T min ) is the resonance frequency f 0C of the calibration probe 9 at T min ;

[0190] Since the absolute value X S2 (T) of the back surface microwave surface reactance of the HTS film under test 12 with temperature changes and ΔX S2 (T) exist

[0191] ΔX S2 (T) = X S2 (T) - X S2 (T min ) (27)

[0192] And the HTS film under test 10 loses superconductivity when it satisfies

[0193] X S2 (T C ) = R S2 (T C ) (8)

[0194] X S2 (T) is calculated.

[0195] where X S2 (T min) is the microwave surface reactance of the opposite side 12 of the HTS film 10 to be tested at temperature T min . S2 (T c ) is the microwave surface reactance of the opposite side 12 of the HTS film 10 to be tested at temperature T c .

[0196] Further, through the two calibration processes and only one temperature rising and falling process of the HTS film 10 to be tested, the microwave surface reactance of the opposite side 12 of the HTS film 10 to be tested can be measured simultaneously; and for other HTS films to be tested, only the steps B3-B5 are repeated, i.e. only one temperature rising and falling process is performed, so that the microwave surface reactance of the opposite side 12 of the HTS film 10 to be tested can be measured simultaneously.

[0197] In the embodiment, the interval of the test temperature is 1K, the lowest test temperature is 77K, and the highest test temperature is the critical temperature of the HTS film 10 to be tested, wherein the critical temperature of the front side 11 of the HTS film 10 to be tested is 106K, and the critical temperature of the opposite side 12 of the HTS film 10 to be tested is 102K.

[0198] Fig. 7 is a curve of the resonant frequency ΔF of the test device of the test probe 1 loaded with the calibration probe 9 alone and the test device of the test probe 1 loaded with the calibration probe 9 and the HTS film 10 to be tested together with the change of temperature, ΔF = f0(T) - f0(T min ). Further, Fig. 7(a) is the curve corresponding to the front side 11 of the HTS film 10 to be tested, wherein the curve ΔF of the test probe is ΔF 01 = f 01 (T) - f 01 (T min ), the curve ΔF of the front side of the HTS film to be tested is ΔF 0T = f 0T (T) - f 0T (T min ), and the difference between the two is ΔF = ΔF 0T - ΔF 01 . Fig. 7(b) is the curve corresponding to the opposite side 12 of the HTS film 10 to be tested, wherein the curve ΔF of the test probe is ΔF 01 = f 01 (T) - f 01 (T min ), the curve ΔF of the opposite side of the HTS film to be tested is ΔF 0C = f 0C (T) - f 0C (T min ), and the difference between the two is ΔF = ΔF 0C - ΔF 01 .

[0199] Figure 8 This is a curve showing the relationship between the relative values ​​of the microwave surface reactance of the HTS film 10 on both sides and the temperature, as measured in this embodiment. Figure 9 The curves show the absolute values ​​of microwave surface resistance and microwave surface reactance on both sides of the HTS film 10 under test as a function of temperature, as measured in this embodiment.

[0200] The curve ΔF corresponding to the front side 11 of the HTS film under test is shown in Figure 7(a). Using formula (4), the relative value ΔX of the microwave surface reactance of the front side 11 of the HTS film under test relative to the lowest test temperature can be obtained. S1 (T), such as Figure 8 As shown; similarly, the curve ΔF corresponding to the reverse side 12 of the HTS film under test is shown in Figure 7(b). The relative value ΔX of the microwave surface reactance of the reverse side 12 of the HTS film under test relative to the lowest test temperature is calculated using formula (7). S2 (T), such as Figure 8 As shown. Then, based on formulas (5) and (8) satisfied by the timeout condition of the HTS film 10 under test, the microwave surface reactance X on the front side 11 of the HTS film under test is calculated. S1 (T) and the microwave surface reactance X on the reverse side of the HTS film to be tested. S2 (T), such as Figure 9 As shown.

[0201] In summary, this embodiment, by performing two calibrations on the test probe 1 with the calibration probe 9 and the metal plate 7 respectively, can obtain the microwave surface reactance X of both sides of the HTS film 10 under test during a single heating / cooling process. S This greatly improves the testing efficiency of HTS thin film microwave surface reactance, making it suitable for large-scale industrial testing. In addition, the two calibration processes can eliminate the test error caused by the frequency drift of the resonator due to the change of the dielectric constant of the dielectric pillar with temperature, ensuring the accuracy of the test results.

[0202] The principles and implementations of the present application are described herein with specific examples, and the above description of the embodiments is only used to help understand the method of the present application and its core idea, including the best mode, and also enable any person skilled in the art to practice the present application, including manufacturing and using any device or system, and implementing any combined method. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application. The scope of patent protection of the present application is defined by the claims, and can 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 language expressions of the claims, or if they include equivalent structural elements that are not substantially different from the language expressions of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for efficiently measuring microwave surface impedance of high temperature superconducting thin films, characterized by, The measuring device comprises a test probe, a calibration probe, a metal plate and a sealed cavity; The open bottom end surface of the test probe is a test plane, the calibration probe is identical in structure to the test probe, and the two are mirror-symmetric about the test plane; The microwave surface resistance of the metal plate is known; The sealed cavity is used to cover the test plane; The unloaded quality factor and the resonant frequency are tested respectively by placing the calibration probe, the metal plate or the HTS film to be measured on the test plane and covering it with a sealed cavity below the working temperature of the HTS film to be measured, and the microwave surface resistance R S and the microwave surface reactance X S of the front and back surfaces of the HTS film to be measured are calculated. The specific process for efficiently measuring the microwave surface resistance of the high-temperature superconducting thin film is as follows: Step Al, load the calibration probe onto the bottom end face of the test probe, both mirror symmetric about the test plane, and enclose the calibration probe with a sealed cavity, after sealing, introduce a protective gas, and place the resulting test device below the operating temperature of the HTS film to be tested, and test to obtain the unloaded quality factor Q 0H ; Step A2, the test device obtained in step Al is heated to room temperature, and the calibration probe is removed; then a metal plate with a microwave surface resistance of is loaded onto the bottom end surface of the test probe, and the metal plate is covered with a sealed cavity. After sealing, protective gas is introduced, and the obtained test device is placed below the working temperature of the HTS film to be tested. The unloaded quality factor Q 0N is obtained by testing. Step A3, heating the test device obtained in step A2 to room temperature, removing the metal plate; then loading the front surface of the HTS film to be tested to the bottom end surface of the test probe, loading the calibration probe to the back surface of the HTS film to be tested, the test probe and the calibration probe being mirror-symmetric about the HTS film to be tested, and sealing the calibration probe with a sealed cavity, after sealing, introducing a protective gas, and placing the obtained test device below the working temperature of the HTS film to be tested, respectively testing to obtain the unloaded quality factor Q 0T of the test probe 0C and the unloaded quality factor Q 0C of the calibration probe Step A4, according to the formula ； The calculated front surface microwave surface resistance R of the HTS thin film under test S1 ; Step A5, according to the formula ； The measured HTS film surface resistance R is calculated S2 ; The specific process for efficiently measuring the microwave surface reactance of the high-temperature superconducting thin film is as follows: Step B1. Load the calibration probe onto the bottom end face of the test probe, both in mirror symmetry about the test plane, place the resulting test apparatus below the operating temperature of the HTS film under test, and measure the unloaded quality factor Q 0H Plot of Q as a function of temperature T 0H (T), and the resonant frequency f 01 Plot of f as a function of temperature T 01 (T); Step B2, the test device from step Bl is heated to room temperature and the calibration probe is removed; the metal plate is then loaded onto the bottom end face of the test probe and the resulting test device is placed below the operating temperature of the HTS film under test to obtain the unloaded quality factor Q 0N Q as a function of temperature T 0N (T); Step B3, the test device obtained in step B2 is heated to room temperature, and the metal plate is removed; then the front surface of the HTS film to be tested is loaded to the bottom end surface of the test probe, and the calibration probe is loaded to the back surface of the HTS film to be tested, the test probe and the calibration probe are mirror-symmetric about the HTS film to be tested, and the obtained test device is placed below the working temperature of the HTS film to be tested, to obtain the unloaded quality factor Q of the test probe 0T the curve of Q with temperature T 0T (T), the resonant frequency f of the test probe 0T the curve of f with temperature T 0T (T), the unloaded quality factor Q of the calibration probe 0C the curve of Q with temperature T 0C (T), and the resonant frequency f of the calibration probe 0C the curve of f with temperature T 0C (T); Step B4: Calculate the quench temperature of the HTS film under test. The front microwave surface resistance The specific formula is as follows: ； wherein is the microwave surface resistance of the metal plate as a function of temperature; is the unloaded quality factor Q of the test probe under 0T ; is the unloaded quality factor Q under 0H ; is the unloaded quality factor Q under 0N ;​​​ According to the formula ； The relative value of the front microwave surface reactance of the HTS thin film to be tested with respect to temperature T is calculated ; In the formula, This is the lowest test temperature; for The test probe resonant frequency f 0T ; for The resonant frequency f at the bottom 01 ; Due to the absolute value of the temperature dependence of the front microwave surface reactance of the HTS thin film to be measured with there is ； And when the measured HTS thin film loses superconductivity, it satisfies ； calculated ; wherein is the measured HTS film front-side microwave surface reactance at temperature is the measured HTS film front-side microwave surface reactance at temperature is the measured HTS film front-side microwave surface reactance at temperature​ Step B5, the backside microwave surface resistance of the HTS film under test is calculated , and the specific formula is:​ ； In the formula, is unloaded quality factor Q of the test probe 0C ; According to the formula ； The relative value of the microwave surface reactance of the reverse side of the HTS thin film to be tested with respect to temperature T is calculated ; In the formula, is the calibration probe resonance frequency f 0C ; Due to the absolute value of the temperature dependence of the microwave surface reactance of the opposite side of the HTS thin film to be measured with there is ； And when the measured HTS thin film loses superconductivity, it satisfies ； calculated ; wherein is the measured HTS film backside microwave surface reactance at temperature is the measured HTS film backside microwave surface reactance at temperature is the measured HTS film backside microwave surface reactance at temperature​ 2. The method of claim 1, wherein the high-temperature superconducting thin film microwave surface impedance is measured with high efficiency. The test probe comprises a shielded cavity with an open bottom end surface, a dielectric column, a dielectric clamping ring, an input coupling structure and an output coupling structure; the dielectric column is located at the center inside the shielded cavity and is fixed to the shielded cavity through the dielectric clamping ring; the bottom end surface of the dielectric column and the bottom end surface of the shielded cavity are in the same plane and together constitute a test plane of the test probe; the input coupling structure and the output coupling structure are symmetrically distributed on both sides of the shielded cavity.

3. The method of claim 2, wherein the high-temperature superconducting thin film microwave surface impedance is measured with high efficiency. The shielded cavity, the dielectric column and the dielectric clamping ring are coaxial.

4. The method of measuring the microwave surface impedance of a high temperature superconducting thin film with high efficiency according to claim 2, wherein The input coupling structure and the output coupling structure both adopt a coupling ring structure, and the plane on which the coupling ring is located is parallel to the test plane.

5. The method of measuring the microwave surface impedance of a high temperature superconducting thin film with high efficiency according to claim 2, wherein The shielded cavity adopts brass as the processing material, and the surface treatment uses a silver plating process; the material of the dielectric column is sapphire; and the material of the dielectric clamping ring is nylon or polytetrafluoroethylene.

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