A superconducting coaxial cable and a method for preparing the same

Abstract

The present invention relates to the technical field of coaxial cables, and in particular to a superconducting coaxial cable and a preparation method thereof, comprising: a superconducting coaxial cable is composed of an inner conductor, an insulating layer, a shielding layer and a protective layer from inside to outside; the inner conductor is made of a plurality of wires for transmitting signals; the insulating layer is coated on the outer periphery of the inner conductor for isolating current and reducing heat conduction, and the insulating layer is made of a flexible material; the shielding layer is longitudinally coated on the outer periphery of the insulating layer for shielding internal and external signal interference, and the thickness of the shielding layer is determined by the inner conductor diameter, the insulating layer thickness and the standard bending radius; the protective layer is coated on the outer periphery of the shielding layer for protecting the shielding layer, and the protective layer is made of a flexible material. The present invention can realize signal transmission in an ultra-low temperature superconducting state, and can reduce the heat conduction efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of coaxial cables, and in particular to a superconducting coaxial cable and a preparation method thereof. Background Art

[0002] With the improvement of communication technology, the application of coaxial cables is becoming more and more extensive, and its various requirements are becoming higher and higher, which puts forward higher requirements on the electrical performance, mechanical performance and environmental performance of RF coaxial cables. The signal loss of RF signals in coaxial cables is divided into two parts, one is the loss caused by the polarization of cable insulation, and the other is the loss caused by the resistance characteristics of the inner and outer conductors. In an ultra-low temperature environment, the resistance of superconductors is absolutely zero, that is, the resistance disappears completely. When the resistance disappears completely, the signal loss of RF signals passing through the cable on the outer surface of the inner conductor and the inner surface of the outer conductor is zero, which enhances the strength of the terminal signal.

[0003] At present, quantum communication technologies such as quantum radar, quantum antenna and quantum computer are still in the research stage, and they are all closely related to superconducting technology. Some important research results have been achieved, which show that quantum communication technology can greatly improve the performance and efficiency of communication and provide better technical support for future communication and radar. The design of quantum computers, quantum antennas and quantum communications must be based on the principles of quantum mechanics, taking into account the superposition and entanglement of quantum transmission and quantum states, and high-performance (ultra-low temperature, ultra-low loss) coaxial cables are essential for providing precise high-frequency microwave signals to quantum bits, changing their states and performing operations.

[0004] Due to the ultra-low temperature environment required by quantum chips, the coaxial cable used as a signal transmission line must also have extremely low thermal conductivity to prevent excessive heat from being transferred to the chip working environment through the cable. In physics, heat is transmitted through electrons and phonons, where the heat transfer by electrons is much greater than that by phonons. In ultra-low temperature environments, superconductors produce superconducting effects, and the electrons inside the superconductors form pairs that cannot move freely. Only phonons inside the superconductors conduct heat, while electrons in non-superconductors still have the function of transferring heat. Therefore, in ultra-low temperature environments, the thermal conductivity of superconductors that produce superconducting properties is much lower than that of non-superconductors. At present, there is an urgent need to design coaxial cables that can meet ultra-low temperature conditions and low thermal conductivity efficiency. Summary of the invention

[0005] To this end, the present invention provides a superconducting coaxial cable and a preparation method thereof, so as to overcome the problem in the prior art that the thermal conduction efficiency of the cable is relatively high under ultra-low temperature conditions.

[0006] To achieve the above object, the present invention provides a superconducting coaxial cable, which is composed of an inner conductor, an insulating layer, a shielding layer and a protective layer from inside to outside;

[0007] The inner conductor is composed of a plurality of wires and is used to transmit signals;

[0008] The insulating layer is coated on the outer periphery of the inner conductor to isolate the current and reduce heat conduction, and the insulating layer is made of a flexible material;

[0009] The shielding layer is longitudinally wrapped around the outer periphery of the insulating layer to shield internal and external signal interference, and the thickness of the shielding layer is determined by the inner conductor diameter, the insulating layer thickness and the standard bending radius;

[0010] The protective layer is coated on the outer periphery of the shielding layer to protect the shielding layer. The protective layer is made of flexible material.

[0011] Furthermore, the conductor is a niobium-titanium alloy round wire, the shielding layer is a niobium-titanium alloy film, and the insulating layer and the protective layer are both PTFE dielectrics.

[0012] Furthermore, the thickness of the shielding layer is 0.01 mm to 0.1 mm.

[0013] On the other hand, the present invention also provides a method for preparing a superconducting coaxial cable, comprising:

[0014] Step S1, performing a bending deformation test with a preset maximum bending radius of the inner conductor to obtain a conductor misalignment amount between adjacent wire bundles of the inner conductor;

[0015] Step S2, determining the thickness of the insulating layer according to the conductor misalignment amount, the elastic modulus of the insulating layer material and the first parameter;

[0016] Step S3, performing a bending deformation test on the semi-finished cable having an inner conductor coated with an insulating layer according to a standard bending radius of the superconducting coaxial cable to determine the displacement of the insulating layer;

[0017] Step S4, determining whether the thickness of the insulating layer is qualified based on the insulating layer misalignment amount and the conductor misalignment amount, and correcting the first parameter to re-determine the thickness of the insulating layer if it is unqualified;

[0018] Step S5, determining the longitudinal diameter of the shielding layer based on the thickness of the insulating layer and the diameter of the inner conductor;

[0019] Step S6, determining a stretching ratio of the shielding layer according to the longitudinal package diameter and the standard bending radius, and calculating a minimum thickness of the shielding layer based on the stretching ratio;

[0020] Step S7, preparing a superconducting coaxial cable using the determined insulation layer thickness, shielding layer thickness and longitudinal sheath diameter.

[0021] Furthermore, the bending deformation test step includes:

[0022] Marking a first point and a second point, as well as a midpoint between the first point and the second point, on a preset length of the measured object;

[0023] Taking the middle point as the bending axis, the measured object is bent with a set bending radius and maintained for a preset time;

[0024] Keeping the bending state, measuring a first length value and a first radial value in the length extension direction of the measured target body;

[0025] The misalignment amount is calculated according to the first length value, the first radial value and the original preset length, wherein the misalignment amount includes a radial misalignment amount and an axial misalignment amount.

[0026] Further, determining the thickness of the insulating layer includes:

[0027] A first comparison value is determined according to the conductor misalignment amount, and the first comparison value is compared with a preset comparison threshold value, and a method for determining the thickness of the insulating layer is determined based on the comparison result, wherein the determination method is determined according to the ratio of the elastic modulus of the insulating layer material to the first parameter or according to twice the ratio of the elastic modulus of the insulating layer material to the first parameter.

[0028] Furthermore, in the step S4, it includes:

[0029] Determine a second comparison value according to the insulation layer misalignment amount;

[0030] The first comparison value is compared with the second comparison value, and whether the thickness of the insulating layer is qualified is determined according to the comparison result.

[0031] Furthermore, in the step S4, it includes:

[0032] Under the unqualified condition, the correction range of the first parameter is determined according to the ratio of the first comparison value to the second comparison value.

[0033] Furthermore, in step S6, it includes:

[0034] Determining the stretching ratio of the shielding layer according to the ratio of the longitudinal package diameter to the standard bending radius;

[0035] The minimum thickness of the shielding layer is positively correlated with the stretching ratio.

[0036] Further, in the step S2, the first parameter is determined according to the ratio of the elastic modulus of the insulating layer material to the difference between the inner conductor wire diameter and the inner conductor diameter.

[0037] Compared with the prior art, the beneficial effect of the present invention is that the inner conductor and the shielding layer of the present invention are set as superconducting materials, which can realize signal transmission under ultra-low temperature conditions and reduce the efficiency of heat conduction. The shielding layer can also shield the interference of internal and external signals, reduce the attenuation of signals during transmission, and ensure the quality of high-frequency signal transmission; the insulating layer is set for insulation, which can isolate the current and reduce heat conduction, thereby reducing the efficiency of heat conduction; the protective layer is set to protect the shielding layer and the internal overall structure, which can ensure the structural integrity of the coaxial cable, increase the service life and ensure the performance of the coaxial cable.

[0038] Furthermore, the present invention determines the conductor misalignment by performing a bending deformation test on the inner conductor, thereby determining the thickness of the insulation layer, which can ensure the insulation effect of the insulation layer, and can isolate the current to the maximum extent and reduce heat conduction. By performing a bending deformation test on the semi-finished cable with the inner conductor coated with the insulation layer to determine whether the thickness of the insulation layer needs to be re-determined, the insulation effect of the insulation layer can be further improved. By determining the longitudinal diameter of the shielding layer based on the thickness of the insulation layer and the diameter of the inner conductor, the stretching ratio of the shielding layer is determined, and the minimum thickness of the shielding layer is calculated, the shielding effect of the shielding layer can be improved, and the quality of the shielding layer can be guaranteed, and the shielding layer can be prevented from being easily damaged due to bending.

[0039] Furthermore, the bending deformation testing method of the present invention can improve the accuracy and efficiency of the bending test. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the structure of a superconducting coaxial cable according to an embodiment of the present invention;

[0041] Figure 2 This is a schematic structural diagram of a cross section of a superconducting coaxial cable according to an embodiment of the present invention;

[0042] Figure 3 The present invention is a schematic diagram of a method for preparing a superconducting coaxial cable according to an embodiment of the present invention;

[0043] Figure 4 Schematic diagram of the process of the bending deformation testing method according to an embodiment of the present invention;

[0044] In the figure: 1. inner conductor; 2. insulation layer; 3. shielding layer; 4. protective layer. DETAILED DESCRIPTION

[0045] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0047] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0048] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] See also Figure 1 and Figure 2 As shown, Figure 1 is a schematic diagram of the structure of a superconducting coaxial cable according to an embodiment of the present invention, Figure 2 Schematic diagram of the cross section of a superconducting coaxial cable according to an embodiment of the present invention.

[0050] The embodiment of the present invention provides a superconducting coaxial cable, which is composed of an inner conductor 1, an insulating layer 2, a shielding layer 3 and a protective layer 4 from inside to outside;

[0051] The inner conductor 1 is composed of a plurality of conductors and is used to transmit signals. The inner conductor 1 is made of superconducting material;

[0052] In implementation, the inner conductor can be made of one wire or of multiple twisted wires. The actual implementer can set the number of inner conductor wires according to actual conditions or based on the performance of superconducting coaxial cables that have passed qualification tests in historical data. Preferably, the number of inner conductor wires is 1 to 5.

[0053] The insulating layer 2 is wrapped around the outer periphery of the inner conductor 1 to isolate current and reduce heat conduction;

[0054] The shielding layer 3 is longitudinally wrapped around the outer periphery of the insulating layer 2 to shield internal and external signal interference; the thickness of the shielding layer 3 is determined by the diameter of the inner conductor 1, the thickness of the insulating layer 2 and the standard bending radius, and the shielding layer 3 is a superconducting material;

[0055] The protective layer 4 is coated on the outer periphery of the shielding layer 3 to protect the shielding layer 3 . The protective layer is made of a flexible material.

[0056] It can be understood that the inner conductor and the shielding layer are both superconducting materials. Superconducting materials refer to materials that exhibit absolute zero resistance and complete anti-magnetic properties under certain low temperature conditions, such as niobium-titanium alloy, niobium-zirconium alloy, niobium-tin, and bismuth-based superconducting materials.

[0057] It is understandable that the insulating layer and the protective layer are made of flexible materials, which not only have extremely good dielectric properties and reduce losses, but also can improve the bending performance of the coaxial cable and reduce weight. Preferably, the insulating layer and the protective layer are made of PTFE (polytetrafluoroethylene) material.

[0058] Specifically, the conductor is a niobium-titanium alloy round wire, the shielding layer 3 is a niobium-titanium alloy film, the insulating layer 2 is a solid PTFE medium, and the protective layer 4 is a solid PTFE medium.

[0059] Specifically, the thickness of the shielding layer 3 is 0.01 mm to 0.1 mm. Preferably, the thickness of the shielding layer 3 is 0.03 mm.

[0060] The inner conductor and shielding layer of the present invention are set to superconducting materials, which can realize signal transmission under ultra-low temperature conditions and reduce the efficiency of heat conduction. The shielding layer can also shield the interference of internal and external signals, reduce the attenuation of signals during transmission, and ensure the quality of high-frequency signal transmission; the insulating layer is set for insulation, which can isolate the current and reduce heat conduction, thereby reducing the efficiency of heat conduction; the protective layer is set to protect the shielding layer and the internal overall structure, which can ensure the structural integrity of the coaxial cable, increase the service life and ensure the performance of the coaxial cable.

[0061] In a specific embodiment, a comparative coaxial cable is provided: the comparative inner conductor is a niobium-titanium alloy round wire, the comparative shielding layer is a seamless niobium-titanium alloy tube, and the comparative insulating layer in the middle is solid PTFE. In an ultra-low temperature environment, the comparative inner conductor and the comparative shielding layer of the cable are both in a superconducting state, and the heat conduction formula per unit length is as follows:

[0062] (1),

[0063] (2),

[0064] (3),

[0065] (4),

[0066] Where A0 is the heat conduction efficiency per unit length; λ1, λ2, and λ3 are the heat conduction coefficients of the inner conductor, the insulating layer, and the shielding layer respectively; S1, S2, and S3 are the cross-sectional areas of the inner conductor, the insulating layer, and the shielding layer respectively; D1, D2, and D3 are the diameter of the inner conductor, the outer diameter of the insulating layer, and the outer diameter of the shielding layer respectively; the inner conductor and the shielding layer are both made of niobium-titanium alloy, so λ1=λ3;

[0067] In the above formulas (1) to (4), D1 and D2 are constant values ​​due to the setting of cable impedance and size, and thus S1 and S2 are also constant values; λ1, λ2, and λ3 are also constant values ​​due to the material properties themselves, and the thermal conductivity coefficient of the insulating material is much lower than that of the alloy material, that is, λ1>>λ2, λ3>>λ2.

[0068] The structure material and diameter of the inner conductor of the superconducting coaxial cable of the present invention remain unchanged, and the material is a niobium-titanium alloy round wire with a diameter of D1; the structure material and diameter of the insulating layer remain unchanged, and the material is solid PTFE with a diameter of D2; the shielding layer is changed from the original seamless niobium-titanium alloy tube to a niobium-titanium alloy film longitudinal package, and the thickness of the niobium-titanium alloy film is 0.03 mm, then the outer diameter of the layer is D2+0.06, and the wall thickness of the original semi-rigid structure niobium-titanium alloy tube is not less than 0.10 mm, so D2+0.06<D2+0.1×2, that is, D2+0.06<D2+0.2; because the shielding layer is a thin film layer, it is easy to be damaged when bent, so a solid PTFE layer is extruded outside the film as a protective layer of the cable structure, and the diameter of the protective layer is D3; the inner conductor and the shielding layer are both made of niobium-titanium alloy material, so λ1=λ3; the insulating layer and the protective layer are both solid PTFE, so λ2=λ4; in an ultra-low temperature environment, the inner conductor and the outer conductor of the cable are both in a superconducting state, and the heat conduction formula per unit length is as follows:

[0069] (5),

[0070] (6),

[0071] (7),

[0072] (8),

[0073] (9),

[0074] Among them, A2 is the thermal conductivity efficiency per unit length of the superconducting coaxial cable of the present invention; λ1, λ2, λ3, and λ4 are respectively the thermal conductivity coefficients of the inner conductor, insulating layer, shielding layer, and protective layer of the superconducting coaxial cable of the present invention; S4, S5, S6, and S7 are respectively the cross-sectional areas of the inner conductor, insulating layer, shielding layer, and protective layer of the superconducting coaxial cable of the present invention; D1, D2, and D4 are respectively the inner conductor diameter, the outer diameter of the insulating layer, and the outer diameter of the protective layer of the superconducting coaxial cable of the present invention; the radio frequency signal is transmitted through the coaxial cable, and in an ultra-low temperature environment, the niobium-titanium inner conductor and the shielding layer are in a superconducting state, and the signal transmission characteristics are equivalent to those of the original ultra-low temperature semi-rigid cable, but its thermal conductivity efficiency is much lower than that of the original ultra-low temperature semi-rigid cable. Since λ1>>λ2, and characteristic D2>>0.00036, therefore,

[0075] (10),

[0076] The result of the above formula (10) is the reduction value of the thermal conductivity efficiency of the superconducting coaxial cable of the present invention compared with the coaxial cable of the comparative example.

[0077] It can be understood that the superconducting coaxial cable of the present invention can not only meet the requirements of signal conduction in the ultra-low temperature superconducting state, but also reduce the heat conduction efficiency.

[0078] See also Figure 3 As shown, it is a schematic diagram of the process of the method for preparing a superconducting coaxial cable according to an embodiment of the present invention; the embodiment of the present invention also provides a method for preparing a superconducting coaxial cable, comprising:

[0079] Step S1, performing a bending deformation test with a preset maximum bending radius of the inner conductor to obtain a conductor misalignment amount between adjacent wire bundles of the inner conductor;

[0080] In implementation, actual implementers can set the preset maximum bending radius based on the average of the maximum bending radius of the inner conductor corresponding to the superconducting coaxial cables that have passed the qualification test in historical data, or set the preset maximum bending radius based on the maximum bending radius after the inner conductor is bent several times. Preferably, the value range of the preset maximum bending radius is set to 15mm~25mm.

[0081] See also Figure 4 As shown, it is a schematic flow chart of a bending deformation test method according to an embodiment of the present invention; specifically, the bending deformation test method includes:

[0082] Step S001, marking a first point and a second point, as well as a midpoint between the first point and the second point, on a preset length of the measured object;

[0083] In implementation, the preset length can be set to 1 / 5 to 1 / 10 of the length of the target object to be measured.

[0084] Step S002, taking the middle point as the bending axis, bending the measured object with a set bending radius and keeping it for a preset time;

[0085] In actual application scenarios, the set bending radius is the preset maximum bending radius.

[0086] In implementation, actual implementers may set a preset time length based on the maximum bending time length corresponding to the bending deformation test of the superconducting coaxial cable that has passed the qualification inspection in historical data. Preferably, the preset time length is 30s to 60s.

[0087] Step S003, maintaining the bending state, measuring a first length value and a first radial value in the length extension direction of the measured target body;

[0088] Step S004: calculating the misalignment amount according to the first length value, the first radial value and the original preset length, wherein the misalignment amount includes a radial misalignment amount and an axial misalignment amount.

[0089] In implementation, the axial offset is determined according to the difference between the first length value and the preset length, and the radial offset is determined according to the difference between the first radial value and the diameter of the measured target at the midpoint.

[0090] The above-mentioned bending deformation test method is adopted in both step S1 and step S3 of the present invention, and the test method can effectively mark the deformation amount of the cable and improve the accuracy and efficiency of the bending test.

[0091] Step S2, determining the thickness of the insulating layer according to the conductor misalignment amount, the elastic modulus of the insulating layer material and the first parameter;

[0092] Specifically, determining the thickness of the insulating layer includes:

[0093] A first comparison value is determined according to the conductor misalignment amount, and the first comparison value is compared with a preset comparison threshold value, and a method for determining the thickness of the insulating layer is determined based on the comparison result, wherein the determination method is determined according to the ratio of the elastic modulus of the insulating layer material to the first parameter or according to twice the ratio of the elastic modulus of the insulating layer material to the first parameter.

[0094] In implementation, a first comparison value is determined based on the ratio of the radial misalignment and the axial misalignment of the conductor. If the first comparison value is greater than a preset comparison threshold, the thickness of the insulating layer is determined based on the ratio of the elastic modulus of the insulating layer material to the first parameter. If the first comparison value is less than or equal to the preset comparison threshold, the thickness of the insulating layer is determined based on twice the ratio of the elastic modulus of the insulating layer material to the first parameter.

[0095] It can be understood that actual implementers can determine the preset comparison threshold based on the preset comparison threshold and the average of the ratios of radial misalignment and axial misalignment of superconducting coaxial cables that have passed qualification tests in historical data. Preferably, the preset comparison threshold is set in the range of 2 to 5.

[0096] Specifically, in step S2, the first parameter is determined according to the ratio of the elastic modulus of the insulating layer material to the difference between the inner conductor wire diameter and the inner conductor diameter.

[0097] In a specific embodiment, the radial misalignment of the conductor is 1 mm, the axial misalignment is 5 mm, the preset comparison threshold is 2, the elastic modulus of the insulating layer material is 0.5 GPa, the inner conductor wire diameter is 1 mm, and the inner conductor diameter is 10 mm. The first comparison value is 1 / 5=0.2, the first parameter is 0.5 / (10-1)=1 / 18 GPa / mm, and the first comparison value is less than the preset comparison threshold. Then the thickness of the insulating layer is: 0.5 / (1 / 18)=9 mm.

[0098] Step S3, performing a bending deformation test on the semi-finished cable having an inner conductor coated with an insulating layer according to a standard bending radius of the superconducting coaxial cable to determine the displacement of the insulating layer;

[0099] It is understandable that actual implementers can set the standard bending radius according to actual conditions or based on the average of the maximum bending radius and the minimum bending radius of superconducting coaxial cables that have passed qualification inspection in historical data. Preferably, the value range of the standard bending radius is set to 10mm to 15mm.

[0100] Step S4, determining whether the thickness of the insulating layer is qualified based on the insulating layer misalignment amount and the conductor misalignment amount, and correcting the first parameter to re-determine the thickness of the insulating layer if it is unqualified;

[0101] Specifically, in step S4, it includes:

[0102] Determine a second comparison value according to the insulation layer misalignment amount;

[0103] The first comparison value is compared with the second comparison value, and whether the thickness of the insulating layer is qualified is determined according to the comparison result.

[0104] In implementation, the second comparison value is determined according to the ratio of the radial misalignment and the axial misalignment of the insulating layer. If the first comparison value is greater than 120% to 200% of the second comparison value, the thickness of the insulating layer is qualified; if the first comparison value is less than or equal to 120% to 200% of the second comparison value, the thickness of the insulating layer is unqualified.

[0105] Specifically, in step S4, it includes:

[0106] Under the unqualified condition, the correction range of the first parameter is determined according to the ratio of the first comparison value to the second comparison value.

[0107] In implementation, the correction ratio is determined according to the ratio of the first comparison value to the second comparison value, and the correction amplitude of the first parameter is determined according to the product of the correction ratio and the original first parameter; wherein, if the correction ratio is greater than 1, the first parameter is increased by the correction amplitude, and if the correction ratio is less than 1, the first parameter is decreased by the correction amplitude. For example: if the first comparison value is 0.2, the second comparison value is 0.1, the first parameter is 1 / 18GPa / mm, and the thickness of the insulating layer is unqualified, the correction ratio is 0.2 / 0.1=2, so the correction amplitude of the first parameter is: 2×(1 / 18)=1 / 9GPa / mm, that is, the original first parameter is increased to obtain the corrected first parameter: 1 / 18+1 / 9=1 / 6GPa / mm.

[0108] Step S5, determining the longitudinal diameter of the shielding layer based on the thickness of the insulating layer and the diameter of the inner conductor;

[0109] It can be understood that the sum of twice the thickness of the insulating layer and the diameter of the inner conductor is the longitudinal diameter of the shielding layer.

[0110] Step S6, determining a stretching ratio of the shielding layer according to the longitudinal package diameter and the standard bending radius, and calculating a minimum thickness of the shielding layer based on the stretching ratio;

[0111] Specifically, step S6 includes:

[0112] Determining the stretching ratio of the shielding layer according to the ratio of the longitudinal package diameter to the standard bending radius;

[0113] The minimum thickness of the shielding layer is positively correlated with the stretching ratio.

[0114] In implementation, the first coefficient may be determined according to a ratio of a minimum bending radius to a maximum bending radius of a semi-finished cable having an inner conductor coated with an insulating layer.

[0115] In a specific embodiment, the minimum bending radius and the maximum bending radius of the semi-finished cable with an inner conductor coated with an insulating layer can be determined after the semi-finished cable with an inner conductor coated with an insulating layer is bent several times. The actual implementer can determine the number of bending times based on the ratio of the maximum plastic deformation to the minimum plastic deformation of the semi-finished cable with an inner conductor coated with an insulating layer that meets the qualification test in historical data (the number of bending times is determined by rounding off the comparison value). For example: the longitudinal package diameter is 20mm, the minimum bending radius is 1mm, and the maximum bending radius is 20mm. The first coefficient is 1 / 20=0.05, the standard bending radius is 20mm, and the stretching ratio of the shielding layer is 20 / 20=1. The minimum thickness of the shielding layer is: 0.05×1=0.05mm.

[0116] It can be understood that the thickness of the shielding layer is preferably in the range of 0.01 mm to 0.1 mm, and the maximum thickness is no more than 1 mm.

[0117] Step S7, preparing a superconducting coaxial cable using the determined insulation layer thickness, shielding layer thickness and longitudinal sheath diameter.

[0118] Specifically, the thickness of the protective layer 4 is determined according to the diameter of the inner conductor 1 , the thickness of the insulating layer 2 , and the thickness of the shielding layer 3 .

[0119] It can be understood that the cross-sectional areas of the inner conductor 1, the thickness of the insulating layer 2, the thickness of the shielding layer 3 and the thickness of the protective layer 4 can be determined respectively, and the thermal conductivity efficiency per unit length of the coaxial cable can be determined according to the sum of the product of the thermal conductivity coefficient of each layer in the superconducting state and the cross-sectional area of ​​each layer. Therefore, based on the thermal conductivity efficiency requirements of the coaxial cable in actual applications, the thickness of the protective layer 4 can be determined.

[0120] The present invention determines the thickness of the protective layer according to the inner conductor diameter, the thickness of the insulating layer and the thickness of the shielding layer, which can protect the structural integrity of the coaxial cable, avoid damage to the internal structure when the cable is bent, and reduce the heat conduction efficiency.

[0121] The present invention determines the conductor misalignment by performing a bending deformation test on the inner conductor, thereby determining the thickness of the insulating layer, which can ensure the insulation effect of the insulating layer, and can isolate current to the maximum extent and reduce heat conduction. By performing a bending deformation test on a semi-finished cable with an inner conductor coated with an insulating layer to determine whether the thickness of the insulating layer needs to be re-determined, the insulation effect of the insulating layer can be further improved. By determining the longitudinal diameter of the shielding layer based on the thickness of the insulating layer and the diameter of the inner conductor, the stretching ratio of the shielding layer is determined, and the minimum thickness of the shielding layer is calculated, the shielding effect of the shielding layer can be improved, and the quality of the shielding layer can be guaranteed, and the shielding layer can be prevented from being easily damaged due to bending.

[0122] In a specific embodiment, an inner conductor that meets the size requirements is formed by a drawing or twisting process, a layer of solid PTFE is extruded on the outer periphery of the inner conductor as the insulating layer of the superconducting coaxial cable, and the shielding layer film is tightly wrapped on the outer periphery of the insulating layer by a longitudinal wrapping process, and finally a layer of solid PTFE is extruded on the outer periphery of the shielding layer as a protective layer of the superconducting coaxial cable.

[0123] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A superconducting coaxial cable, characterized in that: The superconducting coaxial cable is composed of an inner conductor, an insulating layer, a shielding layer and a protective layer from inside to outside; The inner conductor is composed of a plurality of wires and is used to transmit signals; The insulating layer is coated on the outer periphery of the inner conductor to isolate the current and reduce heat conduction, and the insulating layer is made of a flexible material; The shielding layer is longitudinally wrapped around the outer periphery of the insulating layer to shield internal and external signal interference, and the thickness of the shielding layer is determined by the inner conductor diameter, the insulating layer thickness and the standard bending radius; The protective layer is coated on the outer periphery of the shielding layer to protect the shielding layer, and the protective layer is made of a flexible material; Wherein, the inner conductor and the shielding layer are both superconducting materials; The method for preparing the superconducting coaxial cable comprises: Step S1, performing a bending deformation test with a preset maximum bending radius of the inner conductor to obtain a conductor misalignment amount between adjacent wire bundles of the inner conductor; Step S2, determining the thickness of the insulating layer according to the conductor misalignment amount, the elastic modulus of the insulating layer material and the first parameter; Step S3, performing a bending deformation test on the semi-finished cable having an inner conductor coated with an insulating layer according to a standard bending radius of the superconducting coaxial cable to determine the displacement of the insulating layer; Step S4, determining whether the thickness of the insulating layer is qualified based on the insulating layer misalignment amount and the conductor misalignment amount, and correcting the first parameter to re-determine the thickness of the insulating layer if it is unqualified; Step S5, determining the longitudinal diameter of the shielding layer based on the thickness of the insulating layer and the diameter of the inner conductor; Step S6, determining a stretching ratio of the shielding layer according to the longitudinal package diameter and the standard bending radius, and calculating a minimum thickness of the shielding layer based on the stretching ratio; Step S7, preparing a superconducting coaxial cable using the determined insulation layer thickness, shielding layer thickness and longitudinal package diameter; The steps of the bending deformation test include: Marking a first point and a second point, as well as a midpoint between the first point and the second point, on a preset length of the measured object; Taking the middle point as the bending axis, the measured object is bent with a set bending radius and maintained for a preset time; Keeping the bending state, measuring a first length value and a first radial value in the length extension direction of the measured target body; Calculate the offset according to the first length value, the first radial value and the original preset length, wherein the offset includes a radial offset and an axial offset; In the step S2, it includes: Determine a first comparison value according to the conductor misalignment amount; Wherein, the first comparison value is determined according to the ratio of the radial misalignment amount to the axial misalignment amount of the conductor; In the step S4, it includes: Determine a second comparison value according to the insulation layer misalignment amount; Comparing the first comparison value with the second comparison value, and determining whether the thickness of the insulating layer is qualified according to the comparison result; Wherein, the second comparison value is determined according to the ratio of the radial misalignment amount to the axial misalignment amount of the insulating layer; In the step S6, it includes: Determining the stretching ratio of the shielding layer according to the ratio of the longitudinal package diameter to the standard bending radius; The minimum thickness of the shielding layer is positively correlated with the stretching ratio; In the step S2, the first parameter is determined according to the ratio of the elastic modulus of the insulating layer material to the difference between the inner conductor wire diameter and the inner conductor diameter.

2. The superconducting coaxial cable according to claim 1, characterized in that: The conductor is a niobium-titanium alloy round wire, the shielding layer is a niobium-titanium alloy film, and the insulating layer and the protective layer are both PTFE dielectrics.

3. The superconducting coaxial cable according to claim 2, characterized in that: The thickness of the shielding layer is 0.01 mm to 0.1 mm.

4. The superconducting coaxial cable according to claim 3, characterized in that: In the step S2, determining the thickness of the insulating layer includes: The first comparison value is compared with a preset comparison threshold, and a method for determining the thickness of the insulating layer is determined based on the comparison result, wherein the determination method is determined according to the ratio of the elastic modulus of the insulating layer material to the first parameter or according to twice the ratio of the elastic modulus of the insulating layer material to the first parameter.

5. The superconducting coaxial cable according to claim 4, characterized in that: In the step S4, it includes: Under the unqualified condition, the correction range of the first parameter is determined according to the ratio of the first comparison value to the second comparison value.

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