Refrigeration type integrated superconducting low-temperature current comparison device and method

Abstract

The embodiment of the invention provides a refrigeration type integrated superconducting low-temperature current comparison device and method, and belongs to the field of electromagnetic metering, the refrigeration type integrated superconducting low-temperature current comparison device comprises a Dewar tank, a cold head, a compressor, a probe rod, a cabinet, a superconducting device box and a resistor switching box, the Dewar tank is provided with a refrigeration cavity, the refrigeration cavity is used for containing liquid helium, the tail end of the cold head extends into the refrigeration cavity, the compressor is connected with the cold head, and the superconducting device box is connected with the probe rod. The compressor drives a refrigerant, converts the refrigerant from a low-pressure state to a high-pressure state and then conveys the refrigerant to the cold head to absorb heat of the refrigeration cavity, the probe rod extends into the refrigeration cavity and is used for connecting the superconducting device box and the resistance switching box, the superconducting device box is immersed in liquid helium, and the resistance switching box is used for connecting a resistor to be tested. According to the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the invention, the refrigeration cavity is cooled through the cooperation of the compressor and the cold head, so that the volatilized helium is liquefied into liquid helium again and then flows into the bottom of the refrigeration cavity, the leakage of the helium in the operation process is reduced, and the supplementing period of the helium is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic metrology, and in particular to a refrigeration type integrated superconducting cryogenic current comparator and method. BACKGROUND

[0002] A superconducting cryogenic current comparator (CCC) is a core instrument for establishing quantum resistance and current reference in international national metrology institutes. The current superconducting cryogenic current comparator mainly relies on liquid helium for cooling, has poor cooling performance, and has helium leakage during operation, and needs to be supplemented with liquid helium regularly. SUMMARY

[0003] Embodiments of the present application provide a refrigeration type integrated superconducting cryogenic current comparator and method to solve the above technical problems.

[0004] In a first aspect, a refrigeration type integrated superconducting cryogenic current comparator is provided, comprising:

[0005] A Dewar flask having a refrigeration cavity for containing liquid helium;

[0006] A cold head having an end located in the refrigeration cavity, the cold head containing a refrigerant therein, the cold head being configured to absorb heat from the refrigeration cavity;

[0007] A compressor connected to the cold head, the compressor being configured to drive the refrigerant and convert the refrigerant from a low pressure state to a high pressure state and then deliver the refrigerant to the cold head;

[0008] A superconducting cryogenic current comparator assembly comprising a superconducting device box and a resistance adapter box, the superconducting device box being connected to the resistance adapter box, the superconducting device box being located in the liquid helium, the resistance adapter box being located outside the Dewar flask, the resistance adapter box being configured to connect to a resistance under test, the superconducting cryogenic current comparator assembly being configured to measure the resistance of the resistance under test in a superconducting cryogenic environment.

[0009] In combination with the first aspect, a water chiller is further included, the water chiller comprising a water pump, a water tank, a heat dissipation fin and a fan, the compressor comprising a water inlet and a water outlet;

[0010] The water pump is connected to the water tank, the heat dissipation fin, the water inlet and the water outlet in sequence through a corrugated pipe to form a water circulation path;

[0011] The water pump is configured to drive water in the water tank to dissipate heat from the compressor, and the fan is configured to dissipate heat from the heat dissipation fin.

[0012] In combination with the first aspect, the ultralow-temperature current comparison assembly further comprises a probe rod having a first end and a second end, the first end being located in the refrigeration cavity, the second end being located outside the dewar, the superconducting device box being connected to the first end, and the resistance adapter box being connected to the second end.

[0013] In combination with the first aspect, the ultralow-temperature current comparison assembly further comprises a temperature sensor arranged at the first end of the probe rod, the temperature sensor being configured to monitor the temperature of the liquid helium.

[0014] In combination with the first aspect, the ultralow-temperature current comparison assembly further comprises a fixing flange connected to the dewar, and the probe rod is connected to the fixing flange.

[0015] In combination with the first aspect, the ultralow-temperature current comparison assembly further comprises a magnetic flux locker connected to the second end of the probe rod, the magnetic flux locker being configured to obtain a magnetic flux and output an analog signal linearly related to the magnetic flux.

[0016] In combination with the first aspect, the superconducting device box is provided with a superconducting proportioner, the superconducting proportioner comprising a primary winding, a secondary winding, and a detection coil, the detection coil being coupled to the primary winding and the secondary winding.

[0017] The primary winding, the secondary winding, and the detection coil are all wound with superconducting wire.

[0018] In combination with the first aspect, the superconducting device box further comprises a superconducting quantum interference device, the superconducting quantum interference device comprising an input coil and a feedback coil, the input coil being connected to the detection coil and configured to convert a monitored magnetic communication signal into a voltage signal, and the superconducting proportioner further comprises a compensation coil configured to compensate for leakage magnetic flux of the superconducting device box.

[0019] In combination with the first aspect, the ultralow-temperature current comparison assembly further comprises a coil switching box connected to the second end of the probe rod.

[0020] The primary winding has a first tap, the secondary winding has a second tap, and the compensation coil has a third tap, the first tap, the second tap, and the third tap being connected to the coil switching box, and the coil switching box is configured to control the turns ratio between the primary winding, the secondary winding, and the compensation coil by adjusting the connection relationship of the first tap, the second tap, and the third tap.

[0021] In combination with the first aspect, the ultra-low temperature current comparison assembly further comprises a current source controller, the current source controller comprising a current source master module, a master current source and a slave current source, the master current source being connected with the primary winding and the standard resistance, the slave current source being connected with the secondary winding, the compensation coil and the resistance under test;

[0022] The current source master module is connected with and controls the master current source and the slave current source respectively.

[0023] In combination with the first aspect, the current source controller further comprises a zero pointer, the zero pointer being connected with the standard resistance, the resistance under test and the current source master module respectively, and the zero pointer being used to detect the balance state between the standard resistance and the resistance under test.

[0024] In combination with the first aspect, the current source controller further comprises a differential compensation module, the differential compensation module comprising a first resistance network and a second resistance network, the first resistance network being connected in series with the secondary winding, and the second resistance network being connected in series with the compensation coil, and the differential compensation module adjusting the current on the first resistance network and the second resistance network based on the unbalance state between the standard resistance and the resistance under test, so as to make the standard resistance and the resistance under test reach balance.

[0025] In combination with the first aspect, the cabinet is used to integrate the display and control cabinet, the resistance switching cabinet, the feedback control cabinet, the precision current source cabinet, the low temperature control cabinet and the power supply cabinet.

[0026] In the second aspect, the embodiments of the present application provide a refrigeration type integrated ultra-low temperature current comparison method, comprising:

[0027] The vacuum degree of the vacuum layer of the Dewar flask is reduced to vacuum;

[0028] The temperature of the refrigeration cavity of the Dewar flask is reduced to ultra-low temperature by the compressor and the water chiller;

[0029] The probe rod is placed into the liquid helium in the refrigeration cavity;

[0030] The standard resistance, the resistance under test and the ultra-low temperature current comparison instrument are connected in the form of a resistance bridge;

[0031] In the case of voltage balance of the zero pointer, the resistance value and the ratio value of the resistance under test are obtained based on the ultra-low temperature current comparison instrument.

[0032] One of the above technical solutions has the following advantages or beneficial effects:

[0033] The embodiment of the present application provides a refrigeration type integrated superconducting low-temperature current comparison device, which comprises: a Dewar flask, the Dewar flask has a refrigeration cavity, the refrigeration cavity is used for containing liquid helium; a cold head, the cold head is located in the refrigeration cavity, the cold head contains a refrigerant, and the cold head is used for absorbing heat of the refrigeration cavity; a compressor, the compressor is connected with the cold head, the compressor is used for driving the refrigerant, and the refrigerant is transported to the cold head after being converted from a low-pressure state to a high-pressure state; and a super-low-temperature current comparison assembly, the super-low-temperature current comparison assembly comprises a superconducting device box and a resistance adapter box, the superconducting device box is connected with the resistance adapter box, the superconducting device box is located in the liquid helium, the resistance adapter box is located outside the Dewar flask, the resistance adapter box is used for connecting a resistance to be measured, and the super-low-temperature current comparison assembly is used for measuring the resistance value of the resistance to be measured in a super-low-temperature environment. The refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application is cooled by the cooperation of the compressor and the cold head, so that the volatilized helium gas is liquefied into liquid helium again and flows into the bottom of the refrigeration cavity, thereby reducing the leakage of the helium gas in the running process and greatly prolonging the replenishment period of the helium gas. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0035] In order to more completely understand the present application and its beneficial effects, the following will be described in conjunction with the drawings, wherein the same reference numerals in the following description represent the same parts.

[0036] Figure 1 The structure diagram of the Dewar flask in the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application is shown in the figure.

[0037] Figure 2 The connection structure schematic diagram of the water chiller in the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application is shown in the figure.

[0038] Figure 3 The structure schematic diagram of the probe rod in the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application is shown in the figure.

[0039] Figure 4 The electrical connection schematic diagram in the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application is shown in the figure.

[0040] Figure 5 The structure schematic diagram of the cabinet of the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application is shown in the figure.

[0041] Figure 6 A modular connection schematic diagram of the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application;

[0042] Figure 7 A circuit structure schematic diagram of the differential compensation module in the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application;

[0043] Figure 8 A software flow schematic diagram of the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application;

[0044] Figure 9 A refrigeration type integrated superconducting low-temperature current comparison method flow schematic diagram provided by the embodiment of the present application.

[0045] Marked with reference numerals:

[0046] 100-dewar; 200-super low-temperature current comparison assembly; 210-coil switching box; 211-magnetic flux lock connector cable; 220-magnetic flux lock; 221-coil switching box connection cable; 230-wiring box; 240-probe rod; 250-mounting flange; 260-superconducting device box; 300-cold head; 310-compressor; 320-water chiller; 321-water tank; 322-fan; 323-radiator fin; 324-water pump; 400-cabinet; 410-display control case; 420-keyboard mouse; 430-resistance adapter case; 440-feedback control case; 450-precision current source case; 460-low-temperature control case; 470-power supply case; 500-dewar support foot. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0048] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0049] In the embodiments of the present application, at least one means one or more; and a plurality means two or more than two. In the description of the present application, the terms "first", "second", "third" and the like are used only to distinguish different objects described, and cannot be understood as indicating or implying relative importance, nor can be understood as indicating or implying order.

[0050] In the description of the present application, the reference "one embodiment" or "some embodiments" and the like means that the specific features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, in the present application, the terms "include", "contain", "have" and their variants mean "include but not limited to", unless otherwise specifically emphasized.

[0051] It should be noted that in the embodiments of the present application, the association relationship of the associated objects described by "and / or" means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character " / ", unless otherwise specified, generally represents a "or" relationship between the associated objects before and after.

[0052] It should be noted that in the embodiments of the present application, "connection" can be understood as electrical connection, and the connection between two electrical elements can be direct or indirect connection between the two electrical elements. For example, A and B are connected, which can be direct connection between A and B, or indirect connection between A and B through one or more other electrical elements.

[0053] The specific embodiments of the present application are described below through examples:

[0054] As Figure 1As shown, the embodiment of the present application provides a refrigeration type integrated superconducting low-temperature current comparison device, which comprises: a Dewar pot 100, the Dewar pot 100 has a refrigeration cavity, the refrigeration cavity is used for containing liquid helium; a cold head 300, the cold head 300 has an end in the refrigeration cavity, the cold head 300 contains a refrigerant, and the cold head 300 leads the refrigerant in a high-pressure state to the end to absorb the heat of the refrigeration cavity, so as to liquefy the volatilized helium gas into liquid helium; a compressor 310, the compressor 310 is connected with the cold head 300, the compressor 310 is used for driving the refrigerant, and the compressor 310 is used for converting the refrigerant from a low-pressure state to a high-pressure state and then conveying the refrigerant to the cold head 300; and a super-low-temperature current comparison assembly 200, the super-low-temperature current comparison assembly 200 comprises a superconducting device box 260, a resistance adapter box, a magnetic flux locker 220 and a coil switching box 210, the superconducting device box 260 is connected with the resistance adapter box, the superconducting device box 260 is located in the liquid helium, the resistance adapter box is located outside the Dewar pot 100, the resistance adapter box is used for connecting a to-be-measured resistance, and the super-low-temperature current comparison assembly 200 is used for measuring the resistance value of the to-be-measured resistance in a super-low-temperature environment. Specifically, the Dewar pot 100 is placed on a Dewar support foot 500, and the Dewar support foot 500 is used for providing stable support for the Dewar pot 100. The Dewar pot 100 comprises an outer shell and an inner shell, and a vacuum layer is formed between the outer shell and the inner shell, and the inner shell encloses the refrigeration cavity. Although the vacuum layer can isolate the heat of the external environment from being conducted to the refrigeration cavity, the liquid helium in the refrigeration cavity will still volatilize during the working process. The cooperation of the compressor 310 and the cold head 300 can continuously reduce the temperature in the refrigeration cavity. During the refrigeration process of the Dewar pot 100, the compressor 310 first pressurizes the helium gas to a high pressure, pre-cools the helium gas through the cold head 300, and then reduces the temperature to below 4K (K is an abbreviation of the international standard unit of thermodynamic temperature, Kelvin) after adiabatic expansion by pushing a piston, so that the helium gas at the top of the refrigeration cavity is liquefied into liquid helium, and the liquid helium flows back to the bottom of the refrigeration cavity. By liquefying the volatilized helium gas into liquid helium, a closed loop is formed between the helium gas and the liquid helium, so that it is not necessary to additionally supplement the helium gas or the liquid helium into the refrigeration cavity.

[0055] In the embodiment of the present application, when the temperature in the refrigeration cavity is maintained at a super-low temperature through the cooperation of the compressor 310 and the cold head 300, the super-low-temperature current comparison assembly 200 measures the to-be-measured resistance based on a standard resistance, so as to determine the resistance value of the to-be-measured resistance.

[0056] It can be understood that the cooperation of the compressor 310 and the cold head 300 is used for cooling the refrigeration cavity in the Dewar pot 100, so that the volatilized helium gas is liquefied into liquid helium and then flows into the bottom of the refrigeration cavity, thereby reducing the leakage of the helium gas during the operation and greatly prolonging the supplement period of the helium gas.

[0057] As Figure 2As shown in the embodiment of this application, a water chiller 320 is also included. The water chiller 320 includes a water pump 324, a water tank 321, heat dissipation fins 323, and a fan 322. The compressor 310 includes an inlet and an outlet. The water pump 324 is connected to the water tank 321, the heat dissipation fins 323, the inlet, and the outlet in sequence through a corrugated pipe to form a water circulation path. The water pump 324 is used to drive the water in the water tank 321 to dissipate heat from the compressor 310, and the fan 322 is used to dissipate heat from the heat dissipation fins 323. Specifically, the water pump 324 drives the cold water in the water tank 321 to flow through the inlet of the compressor 310 and into the water-cooling channel inside the compressor 310. The cold water comes into direct contact with the heat-generating components of the compressor 310, efficiently absorbing heat and preventing the compressor 310 from shutting down due to local overheating. After absorbing heat, the hot water first flows through the heat dissipation fins 323, which increase the contact area between the water and the air. Then, the fan 322 blows air through the water, quickly dissipating the heat from the water into the outside air, ensuring that the water entering the compressor 310 remains at a low temperature. The water circulation path connecting the water chiller 320 and the compressor 310 via a corrugated pipe extends the service life of the pipes, preventing low-temperature brittleness or high-temperature aging, and also isolates vibrations between the equipment, reducing vibration transmission.

[0058] It is understandable that by connecting a water chiller 320 to the compressor 310, the operating temperature of the compressor 310 can be controlled within a safe range, avoiding component aging or performance degradation caused by high temperature, and significantly extending the service life of the compressor 310.

[0059] like Figure 3 As shown in this embodiment, the cryogenic current comparison assembly 200 further includes a probe 240, which has a first end and a second end. The first end is located in the cooling chamber, and the second end is located outside the Dewar jar 100. A superconducting device box 260 is connected to the first end, and a resistor adapter box is connected to the second end. Specifically, the superconducting device box 260 contains a superconducting proportional device and a superconducting quantum interference device (SQUID). The main function of the probe 240 is to extend the superconducting device box 260 into the cooling chamber, thereby allowing the superconducting device box 260 to be completely immersed in liquid helium, so as to measure the resistance value of the resistor under test in a superconducting cryogenic environment. The resistor adapter box is used to connect the resistor under test and a standard resistor. The standard resistor is a resistor whose specific resistance value can be determined, while the resistor under test is a resistor whose resistance value cannot be accurately determined. The probe 240 has a corresponding circuit inside that connects the superconducting device box 260 to the resistor adapter box, thereby establishing signal transmission between the superconducting device box 260 and the resistor adapter box. This allows for confirmation of environmental information in the cooling chamber and the circuit status of the superconducting device box 260, enabling timely responses and adjustments.

[0060] It can be understood that the purpose of setting the probe rod 240 is to carry the superconducting device box 260 and the resistance switching box, so that the superconducting device box 260 can work in the liquid helium and in the ultra-low temperature environment, and the probe rod 240 can also establish electrical connection between the superconducting device box 260 and the superconducting quantum interference device and the coil switching box.

[0061] In the embodiment of the present application, a temperature sensor is further included, which is arranged at the first end of the probe rod 240 and is used to monitor the temperature of the liquid helium. Specifically, the temperature sensor is usually arranged at the first end of the probe rod 240, or can be arranged on the inner wall and the bottom of the refrigeration cavity. The temperature sensor can be in direct contact with the liquid helium, or can be arranged on the surface of the superconducting device box 260 to measure the temperature of the periphery of the superconducting device box 260.

[0062] In some embodiments, a temperature sensor is arranged at the low-temperature end of the cold head 300 to monitor the actual refrigeration effect of the cold head 300, so as to avoid the continuous increase of the temperature in the refrigeration cavity due to the failure of the cold head 300.

[0063] It is worth noting that in some embodiments, in order to determine the pressure condition in the Dewar 100, a pressure sensor is further arranged in the Dewar 100, which is usually arranged at the top of the Dewar 100 and connected in the shell of the Dewar 100, and the probe of the pressure sensor extends into the refrigeration cavity. Since the liquid helium is easy to vaporize during work, when too much liquid helium is vaporized into helium gas, the gas phase pressure in the refrigeration cavity will increase, and when the pressure exceeds the limit that the refrigeration cavity can bear, the Dewar 100 may be broken due to overpressure. Therefore, by arranging the pressure sensor in the refrigeration cavity, the pressure of the gas in the refrigeration cavity can be monitored in real time, and when the pressure exceeds a certain threshold, the pressure sensor triggers a corresponding alarm and cooperates with the safety valve to release pressure, so as to avoid the overpressure rupture of the Dewar 100.

[0064] In some embodiments, in order to determine the liquid level of the liquid helium in the refrigeration cavity, a liquid level sensor is further arranged in the refrigeration cavity, which is usually a rod type liquid level sensor vertically inserted into the refrigeration cavity from the top of the Dewar 100, and the probe part of the rod type liquid level sensor is immersed in the liquid helium and covers the main liquid depth range of the refrigeration cavity. It is mainly used to determine the liquid level of the liquid helium, so as to avoid the excessive vaporization of the liquid helium and the excessive decrease of the liquid level of the liquid helium, so that the superconducting device box 260 cannot be completely immersed in the liquid helium, thereby losing the ultra-low temperature protection.

[0065] In some embodiments, in order to determine the vacuum degree of the vacuum layer, a corresponding vacuum detection interface is reserved on the shell, and a vacuum gauge is in communication with the vacuum layer through the vacuum detection interface to directly measure the vacuum degree in the vacuum layer. The high vacuum of the vacuum layer usually needs to be maintained at 10 -4 ~10 -6Below Pa, the vacuum level is used to prevent external heat from being conducted into the cooling chamber. If the vacuum level of the vacuum layer decreases, outside air will enter the vacuum layer, causing external heat to rapidly intrude and simultaneously causing a sharp increase in the vaporization rate of liquid helium in the cooling chamber. Therefore, by setting up a vacuum gauge, the vacuum level can be monitored in real time, and an alarm can be issued in time when a decrease in the vacuum level is detected, reminding the user to replenish the vacuum.

[0066] In some embodiments, if it is necessary to control the pressure of liquid helium in the cooling chamber, a low-power heating wire, typically a nickel-chromium alloy wire, can be placed inside the cooling chamber of the Dewar 100 and wrapped with an insulating layer to prevent heat loss. When the heating wire is heated, its temperature rises, and the liquid helium in the cooling chamber vaporizes into helium gas, thereby increasing the pressure in the cooling chamber.

[0067] like Figure 3 As shown in the embodiment of this application, a fixed flange is also included, which is connected to the Dewar 100, and the probe 240 is connected to the fixed flange. Specifically, the outer shell of the Dewar 100 is provided with a flange mounting hole, which leads directly to the cooling chamber. The diameter of the flange mounting hole matches the outer diameter of the fixed flange, and a metal reinforcing ring is welded around the flange mounting hole to increase strength. The fixed flange is connected to the outer shell by bolts. It is worth noting that the fixed flange also needs to extend into the vacuum layer. The fixed flange located in the vacuum layer is designed as a long and thin metal neck, which is mostly made of stainless steel or oxygen-free copper. The length of the metal neck matches the thickness of the vacuum layer. The outer wall of the metal neck is sealed to the flange mounting hole of the outer shell by welding, such as argon arc welding. After welding, helium mass spectrometry leak detection is required to ensure that the leak rate is ≤1×10-10 Pa*m. 3 / s, thus preventing outside air from entering the vacuum layer through the gap between the fixed flange and the outer shell. The end of the fixed flange facing the inside of the refrigeration chamber must mate with the probe 240 to ensure that the probe 240 can be stably extended into the refrigeration chamber. The probe 240 is inserted into the mounting hole from the outside of the fixed flange and fixed to the fixed flange by locking nuts or clamps. There are sealing grooves on the mating surfaces of the fixed flange and the outer shell, as well as on the mating surfaces of the fixed flange and the probe 240. Metal sealing gaskets are placed in the sealing grooves to achieve a seal.

[0068] Understandably, by setting a fixed flange to connect the probe 240 to the cooling chamber of the Dewar 100, not only is a stable connection of the probe 240 achieved, ensuring that the probe 240 can extend into the cooling chamber, but the core requirements of the Dewar 100 for ultra-low temperature, high vacuum, and leak-free operation are also met.

[0069] like Figure 4As shown in this embodiment, the flux lock 220 is connected to the second end of the probe 240. The flux lock 220 is used to acquire magnetic flux and output an analog signal based on the magnetic flux. Specifically, the flux lock 220 includes a feedback coil, an integrator, an amplifier, and a feedback resistor. The feedback coil is coupled to the superconducting quantum interference device (SQU). One end of the feedback coil is grounded, and the other end is connected to the output of the integrator through the feedback resistor. The positive input of the amplifier is connected to the output of the SQU, the negative input of the amplifier is connected to the operating voltage, the output of the amplifier is connected to the input of the integrator, and the output of the integrator is connected to the feedback control circuit. The feedback control circuit outputs a current feedback control signal based on the input analog signal and converts the current feedback control signal into an optical signal, which is transmitted to the current source main control module via optical fiber. The current source main control module controls the current source to output a corresponding current value so that the magnetic flux reaches balance.

[0070] In this embodiment, since the original voltage signal output by the superconducting quantum interference device (SQU) is extremely weak, it is amplified by an amplifier and then sent to an integrator. The integrator integrates the amplified voltage signal, and its output generates a feedback magnetic flux through a feedback resistor and a feedback coil. This feedback magnetic flux is added to the external magnetic flux, ensuring that the voltage across the SQU remains constant. Therefore, the integrator's output is linearly related to the change in external magnetic flux, thus enabling precise measurement of the magnetic flux.

[0071] Understandably, the main function of the flux lock 220 is to generate a negative feedback flux equal to the change in the flux to be measured through the flux lock ring readout circuit, so that the superconducting ring of the superconducting quantum interference device is kept in a state of zero flux change.

[0072] like Figure 3 As shown in the embodiment of this application, the superconducting proportional controller includes a primary winding, a secondary winding, and a detection coil, with the detection coil coupled to both the primary and secondary windings. All three windings—primary, secondary, and detection—are wound with superconducting wire. Specifically, the primary, secondary, and detection windings, made of superconducting wire, do not experience current loss in cryogenic environments. Figure 4 As shown, the primary winding N1, the secondary winding N2, and the compensation coil N AThe primary winding N1 and the secondary winding N2 are wound by superconducting wire with different turns, the proportional coil adopts I type structure, and the proportional winding is wound in the hollow ring-shaped superconducting shield with the first and last overlaps. The superconducting shield for isolating the current comparator detection coil and the proportional coil, the superconducting proportioner and the superconducting quantum interference device work at liquid helium temperature close to absolute zero. Due to the complete anti-magnetic effect (i.e. Meissner effect) of the superconducting shield, the main current I1 applied to the primary winding N1 and the secondary current I2 applied to the secondary winding N2 have the following relationship: I1 / I2 = -N2 / N1, and the main current I1 and the secondary current I2 are output by the current source cabinet. When the ampere-turns are unbalanced, the unbalanced magnetic flux is coupled into the input coil of the superconducting quantum interference device by the detection coil, and the unbalanced voltage signal is output through the flux locker 220. The voltage signal is processed by the feedback control circuit in the feedback control cabinet 440, and the size of the secondary current is changed by the secondary current source of the current source cabinet, so as to form the feedback to keep the ampere-turns balanced. Since the turns ratio of the primary winding N1 and the secondary winding N2 is determined, the proportion is accurate. However, there may be a certain leakage magnetic flux in the circuit, and the compensation coil N A The magnetic flux is compensated. The compensation coil N A The differential compensation module connected to the precision current source cabinet 450 controls the differential compensation module to shunt the secondary current, so that the magnetic flux in the circuit is finally balanced.

[0073] As Figure 4As shown, in the embodiment of the present application, the superconducting quantum interference device includes an input coil and a feedback coil, the input coil is connected with the detection coil, and is used to convert the monitored magnetic flux signal into a voltage signal. Specifically, the superconducting quantum interference device is the highest sensitivity magnetic flux detector at present, and uses the Josephson effect and quantum interference phenomenon of superconductor to realize the component of ultra-high sensitivity detection of extremely weak magnetic signal, electric signal (such as magnetic flux, current, voltage). In the embodiment of the present application, a direct current superconducting quantum interference device (DC-SQUID, English: Direct Current Superconducting Quantum Interference Device) can be used, and the input coil and the feedback coil are integrated in the DC-SQUID chip. The detection coil is directly coupled with the superconducting proportioner, and is used to detect the magnetic flux of the superconducting proportioner. The detection coil is connected with the input coil of the DC-SQUID, the magnetic flux of the superconducting proportioner is transmitted to the DC-SQUID through the detection coil, and the magnetic flux signal is finally converted into a voltage signal by the DC-SQUID. Since the converted voltage signal is usually only microvolts and has a nonlinear relationship with the magnetic flux signal. Therefore, the magnetic flux locker 220 is designed as a direct readout type magnetic flux locker 220. The input of the direct readout type magnetic flux locker 220 is connected to the output of the DC-SQUID, and is fed back to the feedback coil through a feedback resistor to form a direct readout type magnetic flux locking ring, and an analog signal corresponding to the magnetic flux is output, which enters the SQUID adapter box in the feedback control cabinet 440.

[0074] It can be understood that by setting the superconducting quantum interference device, the monitored weak magnetic flux signal can be converted into a corresponding voltage signal, thereby helping to eliminate the interference of external magnetic flux in the circuit on the circuit and improving the measurement accuracy of the measured resistance.

[0075] As shown, Figure 4 As shown, in the embodiment of the present application, the coil switching box 210 is connected to the second end of the probe rod 240; the primary winding has a first tap, the secondary winding has a second tap, and the compensation coil has a third tap, the first tap, the second tap and the third tap are connected to the coil switching box 210, and the coil switching box 210 controls the turns ratio between the primary winding, the secondary winding and the compensation coil by adjusting the connection relationship of the first tap, the second tap and the third tap. Specifically, the taps of each coil are connected to the coil switching box 210, and the coil switching box 210 can freely combine the connection relationship of each coil to form a turns ratio of 1:1 to 1:4096. It is worth noting that if a relay or an analog switch or other remotely controllable switch is added to the coil switching box 210 to control the switching of each coil, it is possible to introduce leakage current and other noise to interfere with the circuit. Therefore, to avoid unnecessary interference, the coil switching can be manually switched.

[0076] It can be understood that the adjustment of the arbitrary turn ratio between the coils is realized by setting the coil switching box 210, and at the same time, the unnecessary interference is avoided by manually switching the coil switching switch, thereby improving the accuracy of the measured resistance measurement.

[0077] As shown in the prior art, Figure 4 In the embodiment of the present application, the ultra-low temperature current comparison assembly 200 further comprises a current source controller, the current source controller comprising a current source master control module, a main current source and a slave current source, the main current source being connected with the primary winding and the standard resistance, and the slave current source being connected with the secondary winding, the compensation coil and the measured resistance; the current source master control module is connected with and controls the main current source and the slave current source. Specifically, the main current source and the slave current source are both current output units, the main current source is used to provide a reference, and the slave current source provides follow-up compensation; the main current source and the slave current source are both controlled by the current source master control module, thereby realizing the accurate current driving of the primary winding and the secondary winding, and finally realizing the high-precision measurement of the measured resistance.

[0078] It can be understood that the accurate current control of the primary winding and the secondary winding is realized by setting the main current source, the slave current source and the current source master control module, the interference and element drift in the circuit are maximally offset, and the accurate measurement of the measured resistance is ensured.

[0079] As shown in the prior art, Figure 4 In the embodiment of the present application, the current source controller further comprises a zero pointer, the zero pointer being connected with the standard resistance, the measured resistance and the current source master control module, and the zero pointer being used to detect the balance state between the standard resistance and the measured resistance. Specifically, the resistance difference between the measured resistance and the standard resistance is usually small, and therefore the voltage difference between the two is very weak, far below the detection lower limit of a conventional voltmeter; the weak deviation signal can be detected by the zero pointer, and the deviation signal is converted into a standard electric signal and transmitted to the current source master control module. The current source master control module adjusts the output of the main current source or the slave current source according to the electric signal, thereby ensuring that the circuit is in a balanced state.

[0080] It can be understood that the small deviation between the measured resistance and the standard resistance can be captured by the zero pointer, and the small deviation is amplified and converted into an electric signal, thereby enabling the current source master control module to drive the corresponding current source to correct the deviation and maintain the balance and stability of the circuit.

[0081] As shown in the prior art, Figure 7 In the embodiment of the present application, the current source controller further comprises a differential compensation module, the differential compensation module comprising a first resistance network R L and a second resistance network R H , the first resistance network R L being connected in series with the secondary winding, and the second resistance network R HConnected in series with the compensation coil, the differential compensation module adjusts the first resistor network R based on the imbalance between the standard resistor and the resistor under test. L Second resistor network R H A current is applied to balance the standard resistor and the resistor under test. Specifically, the first resistor network R... L This network consists of n resistors and switches connected in parallel (n is a positive integer greater than 1). The resistors include a first resistor R11, a second resistor R12, ..., an nth resistor R1n; the switches include a first switch K11, a second switch K12, ..., an nth switch K1n. The first resistor R11 is connected in series with the first switch K11, the second resistor R12 is connected in series with the second switch K12, ..., the nth resistor R1n is connected in series with the nth switch K1n. The resistors and switches are connected in series and then in parallel. The second resistor network R... H The system includes m resistors (m is a positive integer greater than 1) and switches. The resistors include a first resistor R21, a second resistor R22, ..., an m-th resistor R2m. The switches include a first switch K21, a second switch K22, ..., an m-th switch K2m. The first resistor R21 is connected in series with the first switch K21, the second resistor R22 is connected in series with the second switch K22, ..., the m-th resistor is connected in series with the m-th switch. The resistors and switches are then connected in parallel. By controlling the on and off states of the switches, different proportional resistance values ​​can be created, thus realizing the first resistor network R. L Second resistor network R H Shunt control. For each different turns ratio, the first resistor network R... L Second resistor network R H The proportionality coefficient can be calibrated and stored in non-volatile memory, and then used as a correction value for the calibrated current ratio.

[0082] It is understandable that by adopting a shunt structure for the differential compensation module, and simultaneously compensating coil N... A It is connected in series with the secondary winding N2, and the first resistor network R is controlled. L Second resistor network R H The current shunting ratio is used to shun the current from I2 to form a compensation current I. A Compensation current I A Input to compensation coil N A The circuit is compensated.

[0083] like Figure 5 and Figure 6As shown, in the embodiment of the present application, a cabinet 400 is further included, which is used to integrate the display control cabinet 410, the resistance adapter cabinet 430, the feedback control cabinet 440, the precision current source cabinet 450, the low-temperature control cabinet 460 and the power supply cabinet 470. Specifically, the cabinet 400 is divided into six layers of cabinets, and the layout from top to bottom is the display control cabinet 410, the resistance adapter cabinet 430, the feedback control cabinet 440, the precision current source cabinet 450, the low-temperature control cabinet 460 and the power supply cabinet 470. Among them, the display control cabinet 410 is mainly composed of an industrial computer, a touch display screen with shielding, a multi-channel isolated RS485 / USB communication module, a keyboard and a mouse. The multi-channel isolated RS485 / USB communication module is connected to the communication interfaces of the low-temperature control cabinet 460, the current source cabinet and the differential compensation feedback cabinet, to realize the communication function. The industrial computer is built-in with superconducting low-temperature current comparator host computer software, which integrates the functions of low-temperature parameter (temperature, air pressure, liquid level) monitoring and control, current source parameter setting, resistance measurement, proportional measurement, system setting and the like in one software, and the current software flow is as follows Figure 8The software is divided into a front end (for a main thread) and a back end (for a sub-thread), and the front end is connected to the back end through a signal and a slot function. The front end is responsible for processing human-computer interaction and data display, and the back end is responsible for data acquisition, data processing, and the like. The front end includes a main window and a sub-window, wherein the main window includes data monitoring, system setting, and the like, and the sub-window includes real-time monitoring, a refrigeration system, parameter configuration, current source setting, and differential setting, and the like. The back end includes a serial port management module, a data processing thread, a data file management module, a configuration file management module, and the like. The serial port management module is responsible for managing serial port communication, including serial port self-connection and serial port sending, and also manages a serial port receiving module and a serial port data splicing module. Serial port sending is used for connecting with a data acquisition unit of a lower computer and sending signals to the lower computer. Serial port receiving is mainly used for connecting with a controller of the lower computer and receiving information sent by the lower computer. The data processing thread is responsible for transforming received original data and solving related statistical quantities. The data file management module is responsible for interacting with a file reading and writing class to complete file reading and writing. The configuration file management module is responsible for interacting with a configuration reading and writing class to complete configuration file reading and writing. Sub-module initialization mainly initializes sub-modules used for assisting the back end to complete various functions, including signal initialization, configuration management initialization, log saving initialization, file management initialization, serial port management initialization, data processing initialization, and the like, to ensure smoothness of the UI and real-time performance of data processing. The HDMI (High-Definition Multimedia Interface) port / USB port of the industrial personal computer is connected with a shielded touch display screen to realize display of the interface and touch input. The keyboard and the mouse adopt a one-piece structure with a handle, and the keyboard and the mouse can be pulled out for use when needed. The keyboard and the mouse are connected with the USB port of the industrial personal computer to realize input functions.

[0084] As shown in Figure 5 and Figure 6 In the embodiment of the present application, the resistance adapter case 430 realizes the adapter of the interface of the standard resistance and the resistance to be measured and the resistance of the current source case. Since the interface form of the standard resistance is various, the external interface of the resistance adapter case 430 has three kinds, and the internal connection is connected to the precise current source case 450.

[0085] As shown in Figure 5 and Figure 6As shown in this embodiment, the feedback control chassis 440 mainly consists of a SQUID adapter box, a feedback control circuit, and a battery. The battery powers the SQUID adapter box and the feedback control circuit. The SQUID adapter box is connected to the flux lock 220 interface, powers the flux lock 220, and simultaneously sets the parameters of the flux lock 220 via serial communication, and converts the output analog signal. This analog signal is input to the feedback control circuit, which outputs a current feedback control signal and converts it into an optical signal, which is then transmitted via optical fiber to the main control module of the precision current source chassis 450, thereby controlling the current value of the current source.

[0086] like Figure 5 and Figure 6 As shown, the precision current source chassis 450 mainly consists of a main current source, a slave current source, a null indicator, a differential compensation module, a current source main control module, and a battery. The main and slave current sources have identical structures, both employing a modified Howland topology. The current output range is -150mA to 150mA, and the current ratio between the main and slave current sources ranges from 1:1 to 4096:1. The main current is output to the primary winding, and the slave current is output to the secondary winding. In a resistance measurement system using a superconducting current comparator, the null indicator is used to indicate the unbalanced voltage of the resistance bridge. The coil switching box 210 forms the primary winding N1, the secondary winding N2, and the compensation coil N. A It is connected to the precision current source chassis 450 via an interface.

[0087] like Figure 5 and Figure 6 As shown, the cryogenic control chassis 460 mainly consists of a cryogenic control circuit board and a USB communication module. The interfaces of the cryogenic control chassis 460 include a power interface, a temperature sensor interface, a pressure sensor interface, a vacuum gauge interface, and a USB interface, which are respectively connected to the DC power supply of the power supply chassis 470, the temperature sensor, the pressure sensor, the vacuum gauge, and the USB interface of the display and control chassis 410. The cryogenic control circuit board achieves real-time monitoring of temperature, air pressure, liquid level, and vacuum level data by collecting the voltage / current values ​​of each sensor, and performs closed-loop control of air pressure by controlling the current of the heating wire.

[0088] like Figure 5 and Figure 6 As shown, the power supply chassis 470 mainly consists of an AC-DC (Alternating Current to Direct Current) power conversion module and a battery charger, which provides power to the display and control chassis 410 and the cryogenic control chassis 460, and charges the batteries in the precision current source chassis 450 and the feedback control chassis 440.

[0089] It is worth noting that, in terms of power supply and grounding, the compressor 310 and the water-cooled machine 320 are commonly used with 380VAC power supply, the power cabinet 470 is powered by 220VAC, and the display control cabinet 410 and the low-temperature control cabinet 460 are powered by the direct current power supply converted by the source cabinet. In order to meet the safety standards, the cabinet 400, the display control cabinet 410, the low-temperature control cabinet 460, and the power cabinet 470 are grounded. The resistance switching cabinet 430, the feedback control cabinet 440, and the precision current source cabinet 450 are powered by batteries. The ground is floating and connected to the Dewar 100 to avoid interference coupling through the power supply to the power grid or other components. In order to ensure that the resistance switching cabinet 430, the feedback control cabinet 440, and the precision current source cabinet are isolated from the cabinet 400, an insulating layer is designed on the metal layer and the inner wall. When the feedback control cabinet 440 or the precision current source cabinet 450 needs to be charged, the internal switch can disconnect the internal circuit from the battery, and after the charging is completed, the switch connects the battery to the circuit for work.

[0090] In summary, the refrigeration type integrated superconducting low-temperature current comparison device provided by the embodiment of the present application can convert the weak magnetic communication signal in the circuit into a corresponding voltage signal, thereby helping to eliminate the interference of external magnetic flux in the circuit on the circuit, generate a negative feedback magnetic flux equal to the measured magnetic flux change through the magnetic flux locking ring readout circuit, and maintain the superconducting ring of the superconducting quantum interference device in a zero magnetic flux change state. By setting the differential compensation module and adopting a shunt structure for the differential compensation module, the magnetic flux in the circuit can be completely balanced. By setting the compressor 310 and the cold head 300, the refrigeration cavity in the Dewar 100 is cooled, so that the volatilized helium gas is liquefied into liquid helium and then flows into the bottom of the refrigeration cavity, thereby reducing the leakage of helium gas during operation and prolonging the helium gas replenishment period.

[0091] As shown in Figure 9 The embodiment of the present application also provides a refrigeration type integrated superconducting low-temperature current comparison method, which comprises:

[0092] S1: The vacuum degree of the vacuum layer of the Dewar 100 is reduced to vacuum.

[0093] The specific steps include:

[0094] The vacuum pump is connected to the flange interface of the Dewar 100 to pump the vacuum layer of the Dewar 100, so that the vacuum degree reaches below 0.01 Pa, which is used to isolate heat.

[0095] S2: The temperature of the refrigeration cavity of the Dewar 100 is reduced to ultra-low temperature by the compressor 310 and the water-cooled machine 320.

[0096] The specific steps include:

[0097] Connect the helium cylinder, open the inlet pipeline, start the compressor 310 and the water chiller 320 to make it refrigerate; after pre-cooling, you can choose to fill liquid helium or wait for the compressor 310 and the cold head 300 to cool down to produce liquid helium;

[0098] During the cooling process, the vacuum degree of the vacuum layer continues to decrease, and when it decreases to 10 -6 orders of magnitude, the vacuum valve is closed, and the vacuum pump is closed.

[0099] S3: Place the probe rod 240 into the liquid helium in the refrigeration cavity.

[0100] The specific steps include:

[0101] Continue to observe the temperature, air pressure, liquid level and vacuum degree parameters, and when the parameters are normal and stable, start placing the probe rod 240. When placing the probe rod 240, wait for the air pressure to stabilize after placing each distance until it is placed in place.

[0102] S4: Connect the standard resistance, the resistance to be measured and the superconducting low-temperature current comparator into a resistance bridge form.

[0103] The specific steps include:

[0104] Continue to observe the temperature, air pressure, liquid level and vacuum degree parameters, and when the parameters are normal and stable, start placing the probe rod 240. When placing the probe rod 240, wait for the air pressure to stabilize after placing each distance until it is placed in place. Figure 4

[0105] Manually operate the coil switching box 210 to switch the superconducting proportioner to the required number of turns ratio. Connect the a end of the standard resistance and the resistance to be measured through the coil switching box 210 to the one end of the primary winding and the secondary winding coils respectively, and the b end of the resistance through the coil switching box 210 to the positive pole of the main current source and the slave current source respectively. The negative poles of the main current source and the slave current source are also connected to the other end of the primary winding and the secondary winding coils respectively through the coil switching box 210. Connect the zero pointer instrument between the a ends of the standard resistance and the resistance to be measured, and the output of the zero pointer instrument is connected to the main control circuit board inside the precision current source case 450.

[0106] S5: In the case of zero pointer instrument voltage balance, obtain the resistance value and ratio value of the resistance to be measured based on the superconducting low-temperature current comparator.

[0107] The specific steps include:

[0108] ​The main current source and the slave current source are turned on, the output of the SQUID and the direct readout flux locked 220 is fed back to the slave current source to form ampere-turn balance, and the output of the null instrument is fed back to the differential compensation system to form voltage balance. At this time, the group value and the ratio value of the tested resistance under test can be read from the superconducting cryogenic current comparator software.

[0109] Through testing, the superconducting cryogenic current comparator has a proportional adjustable range of 1:1-4096:1, and the best uncertainty reaches 10 -10 orders of magnitude.

[0110] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as the above preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make slight changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution range of the present application. Any modification, change and modification of the above embodiments, equivalent changes and modifications, which do not depart from the technical solution content of the present application, are still within the scope of the present application.

Claims

1. A refrigerated integrated superconducting cryogenic current comparator, characterized in that, include: A Dewar jar (100) having a cooling chamber for containing liquid helium; A cold head (300) has its end located in the refrigeration chamber. The cold head (300) contains refrigerant and is used to absorb heat from the refrigeration chamber. A compressor (310) is connected to the cold head (300). The compressor (310) is used to drive the refrigerant and deliver the refrigerant from a low-pressure state to a high-pressure state to the cold head (300). A cryogenic current comparator (200) includes a superconducting device box (260) and a resistance adapter box. The superconducting device box (260) is connected to the resistance adapter box. The superconducting device box (260) is located in liquid helium. The resistance adapter box is located outside the Dewar jar (100). The resistance adapter box is used to connect the resistor to be measured. The cryogenic current comparator (200) is used to measure the resistance value of the resistor to be measured in a cryogenic environment.

2. The integrated superconducting cryogenic current comparator of the cooling type according to claim 1, characterized in that, It also includes a water chiller (320), which includes a water pump (324), a water tank (321), heat dissipation fins (323) and a fan (322), and the compressor (310) includes an inlet and an outlet; The water pump (324) is connected to the water tank (321), the heat dissipation fins (323), the water inlet and the water outlet in sequence through a corrugated pipe to form a water circulation path; The water pump (324) is used to drive the water in the water tank (321) to dissipate heat from the compressor (310), and the fan (322) is used to dissipate heat from the heat dissipation fins (323).

3. The integrated superconducting cryogenic current comparator of the cooling type according to claim 1, characterized in that, The cryogenic current comparison assembly (200) also includes a probe (240), which has a first end and a second end. The first end is located in the cooling chamber, and the second end is located outside the Dewar jar (100). The superconducting device box (260) is connected to the first end, and the resistor adapter box is connected to the second end.

4. The integrated superconducting cryogenic current comparator of the cooling type according to claim 3, characterized in that, It also includes a temperature sensor disposed at the first end of the probe (240), the temperature sensor being used to monitor the temperature of the liquid helium.

5. The integrated superconducting cryogenic current comparator of the cooling type according to claim 3, characterized in that, It also includes a fixed flange, which is connected to the Dewar flask (100), and the probe (240) is connected to the fixed flange.

6. The refrigerated integrated superconducting cryogenic current comparator according to claim 5, characterized in that, The cryogenic current comparison component (200) further includes a flux lock (220), which is connected to the second end of the probe (240). The flux lock (220) is used to acquire the magnetic flux and output an analog signal that is linearly related to the magnetic flux based on the magnetic flux.

7. The integrated superconducting cryogenic current comparator of the cooling type according to claim 6, characterized in that, The superconducting device box (260) is provided with a superconducting proportional device, which includes a primary winding, a secondary winding and a detection coil, and the detection coil is coupled to the primary winding and the secondary winding. The primary winding, the secondary winding, and the detection coil are all wound with superconducting wire.

8. The integrated superconducting cryogenic current comparator of the cooling type according to claim 7, characterized in that, The superconducting device box (260) also includes a superconducting quantum interference device, which includes an input coil and a feedback coil. The input coil is connected to the detection coil and is used to convert the monitored magnetic flux signal into a voltage signal. The superconducting proportional device also includes a compensation coil, which is used to compensate for the leakage magnetic flux of the superconducting device box (260).

9. The integrated superconducting cryogenic current comparator of the cooling type according to claim 8, characterized in that, The cryogenic current comparison assembly (200) also includes a coil switching box (210), which is connected to the second end of the probe (240); The primary winding has a first tap, the secondary winding has a second tap, and the compensation coil has a third tap. The first tap, the second tap, and the third tap are connected to the coil switching box (210). The coil switching box (210) controls the turns ratio between the primary winding, the secondary winding, and the compensation coil by adjusting the connection relationship of the first tap, the second tap, and the third tap.

10. The refrigerated integrated superconducting cryogenic current comparator according to claim 8, characterized in that, The cryogenic current comparison component (200) further includes a current source controller, which includes a current source master control module, a main current source, and a slave current source. The main current source is connected to the primary winding and the standard resistor, and the slave current source is connected to the secondary winding, the compensation coil, and the resistor to be measured. The current source master control module is connected to and controls the main current source and the slave current source respectively.

11. The refrigerated integrated superconducting cryogenic current comparator according to claim 10, characterized in that, The current source controller also includes a null pointer, which is connected to the standard resistor, the resistor under test, and the current source main control module. The null pointer is used to detect the balance state between the standard resistor and the resistor under test.

12. The refrigerated integrated superconducting cryogenic current comparator according to claim 10, characterized in that, The current source controller further includes a differential compensation module, which includes a first resistor network and a second resistor network. The first resistor network is connected in series with the secondary winding, and the second resistor network is connected in series with the compensation coil. The differential compensation module adjusts the current on the first resistor network and the second resistor network based on the imbalance between the standard resistor and the resistor under test, so that the standard resistor and the resistor under test reach a balance.

13. The refrigerated integrated superconducting cryogenic current comparator according to claim 1, characterized in that, It also includes a cabinet (400) for integrating a display and control chassis (410), a resistor adapter chassis (430), a feedback control chassis (440), a precision current source chassis (450), a cryogenic control chassis (460), and a power supply chassis (470).

14. A cooling-type integrated superconducting cryogenic current comparison method, characterized in that, include: Reduce the vacuum level of the vacuum layer of the Dewar jar (100) to a vacuum; The temperature of the cooling chamber of the Dewar jar (100) is reduced to an ultra-low temperature by a compressor (310) and a water chiller (320); Place the probe (240) into the liquid helium in the cooling chamber; The standard resistor, the resistor to be measured, and the superconducting cryogenic current comparator are connected in the form of a resistance bridge. With the null indicator voltage balanced, the resistance and ratio of the resistor under test are obtained based on the superconducting cryogenic current comparator.

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