Temperature fixed point sensor

Abstract

The invention relates to the technical field of extremely low temperature measurement, and provides a temperature fixed point sensor. The temperature fixed point sensor comprises a base, a magnetoelectric sensing assembly and a magnetic shielding assembly. Wherein the base comprises a base and a sample fixing frame, and the base is used for establishing thermal connection with an external environment; the sample fixing frame is integrally formed and arranged at one end of the base, a sample containing cavity is formed in the sample fixing frame, and the sample containing cavity is used for containing and limiting a superconducting sample in a surface contact mode; the magnetoelectric sensing assembly is arranged on the periphery of the sample fixing frame and is used for applying an excitation magnetic field to the superconducting sample and sensing the magnetic flux change of the superconducting sample; the magnetic shielding assembly covers the periphery of the magnetoelectric sensing assembly and is used for shielding an external magnetic field. According to the invention, the defects of overlarge interface thermal resistance and slow thermal response caused by threaded connection in the prior art are overcome, rapid thermal response is realized, the thermal balance time is shortened, and the measurement efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of ultra-low temperature measurement technology, and in particular to a temperature fixed-point sensor. Background Technology

[0002] In ultra-low temperature (below 1 Kelvin) measurements, fixed-point temperature sensors are used to provide accurate and reproducible temperature reference values ​​to ensure the consistency and transfer of temperature measurements. These sensors, based on the phase transition properties of superconducting materials, provide a fixed point at a specific temperature, thereby aiding in temperature calibration and measurement.

[0003] A superconducting fixed-point sensor in the prior art includes a copper base and a copper cage, which are fixed by a threaded connection.

[0004] However, because the copper base and the copper cage are connected by threads, a large interfacial thermal resistance will be generated in extremely low temperature environments. This results in a slow thermal response of the sensor and an excessively long thermal equilibrium time, which affects the measurement efficiency and accuracy. Summary of the Invention

[0005] This invention provides a fixed-point temperature sensor to address the shortcomings of existing technologies, such as excessive interfacial thermal resistance and slow thermal response caused by threaded connections. It achieves rapid thermal response, shortens thermal equilibrium time, and improves measurement efficiency.

[0006] This invention provides a temperature fixed-point sensor, comprising: Base, the base comprising: The base is used to establish a thermal connection with the external environment; A sample holder is integrally formed and disposed at one end of the base. The sample holder has a sample receiving cavity inside, which is used to receive and limit the superconducting sample in a surface contact manner. A magnetoelectric sensing component is disposed on the outer periphery of the sample holder and is used to apply an excitation magnetic field to the superconducting sample and sense the change in magnetic flux of the superconducting sample. A magnetic shielding component is placed around the outer periphery of the magnetoelectric sensing component and connected to the base to shield external magnetic fields.

[0007] According to the present invention, a temperature fixed-point sensor is provided, wherein the magnetoelectric sensing component comprises: A primary coil is wound around the outer periphery of the sample holder. The primary coil is used to be electrically connected to an AC power supply to apply an excitation magnetic field to the superconducting sample. An electrostatic shielding layer is sleeved on the outer periphery of the primary coil, and the electrostatic shielding layer has circumferential gaps. A secondary coil is wound around the outer periphery of the electrostatic shielding layer. The secondary coil is used to be electrically connected to a lock-in amplifier to sense changes in the magnetic flux of the superconducting sample.

[0008] According to a temperature fixed-point sensor provided by the present invention, the secondary coil includes at least one sub-coil; When the number of sub-coils is greater than or equal to two, the sub-coils are connected in series and are arranged one-to-one on the outer periphery of the superconducting sample.

[0009] According to a temperature fixed-point sensor provided by the present invention, the magnetoelectric sensing assembly further includes a coil support; The coil support is sleeved on the outer periphery of the sample holder, and the primary coil is disposed on the outer periphery of the sample holder through the coil support.

[0010] According to a temperature fixed-point sensor provided by the present invention, the magnetic shielding assembly includes: A soft magnetic shield is detachably connected to the base. The soft magnetic shield has a through hole for the connection ends of the primary coil and the secondary coil to extend to the outside. A superconducting shield is disposed on the inner wall of the soft magnetic shield.

[0011] According to the present invention, a temperature fixed-point sensor is provided, wherein the soft magnetic shielding component has a cylindrical structure, and the end near the base is open, while the end away from the base is closed.

[0012] According to a temperature fixed-point sensor provided by the present invention, the magnetic shielding assembly further includes a connector; The connector has a limiting part on its outside, and the limiting part has an external thread. The soft magnetic shield is threadedly connected to the limiting part. The connector has a threaded hole inside, and the base passes through the threaded hole and is threadedly connected to the threaded hole.

[0013] According to the present invention, a temperature fixed-point sensor is provided, wherein the base comprises: A first threaded connection part is provided at one end of the sample holder, and the first threaded connection part is threadedly connected to the threaded hole; The base body is located at the end of the first threaded connection portion away from the sample holder, and the diameter of the base body is larger than the diameter of the first threaded connection portion.

[0014] According to a temperature fixed-point sensor provided by the present invention, a second threaded connection portion is provided at one end of the base body away from the first threaded connection portion, and the second threaded connection portion is used to fix the temperature fixed-point sensor. The side wall of the base body is provided with a threaded hole, which is used to assist in fixing the second threaded connection.

[0015] According to a temperature fixed-point sensor provided by the present invention, the side wall of the sample holder is provided with a plurality of through grooves at intervals, and the end of the sample holder away from the first threaded connection is provided with an opening.

[0016] The temperature fixed-point sensor provided by this invention eliminates the interfacial thermal resistance caused by threaded connections by adopting a base structure in which the base and sample holder are integrally formed. This allows the superconducting sample to achieve efficient heat conduction with the sample holder through surface contact, thereby significantly shortening the thermal equilibrium time and improving the response speed and efficiency of temperature measurement. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional view of the temperature fixed-point sensor provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the base of the temperature fixed-point sensor provided by the present invention.

[0020] Figure 3 This is a schematic diagram showing the positional relationship between the secondary coil of the temperature fixed-point sensor provided by the present invention and the superconducting sample.

[0021] Figure label: 100: Base; 110: Base; 111: Second threaded connection; 112: Base body; 113: First threaded connection; 114: Threaded hole; 120: Sample holder; 121: Through groove; 122: Sample receiving cavity; 200: Magnetoelectric sensing component; 210: Coil support; 220: Primary coil; 230: Electrostatic shielding layer; 240: Secondary coil; 241: Sub-coil; 300: Magnetic shielding component; 310: Soft magnetic shielding component; 311: Through hole; 320: Superconducting shielding component; 330: Connector; 400: Superconducting sample. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] The following is combined with Figures 1-3 Describe the structure and working principle of the present invention.

[0024] Reference Figure 1 and Figure 2 The present invention provides a temperature fixed-point sensor comprising a base 100, a magnetoelectric sensing component 200, and a magnetic shielding component 300. The base 100 includes a base 110 and a sample holder 120. The base 110 is used to establish a thermal connection with the external environment. The sample holder 120 is integrally formed at one end of the base 110 and has a sample receiving cavity 122 inside, which is used to receive and limit a superconducting sample 400 in surface contact. The magnetoelectric sensing component 200 is disposed on the outer periphery of the sample holder 120 and is used to apply an excitation magnetic field to the superconducting sample 400 and sense changes in the magnetic flux of the superconducting sample 400. The magnetic shielding component 300 covers the outer periphery of the magnetoelectric sensing component 200 and is connected to the base 110 to shield external magnetic fields.

[0025] Specifically, the base 100 is integrally formed from a solid bar of high-purity oxygen-free copper (99.9999% purity) through machining. The manufacturing process does not include welding, brazing, or assembly steps, resulting in a seamless monolithic structure. The superconducting sample 400 can be any high-purity metal single crystal or alloy exhibiting a defined superconducting phase transition, including aluminum, iridium, cadmium, tungsten, beryllium, gold-indium alloys, iridium-rhodium alloys, etc. Before assembling the superconducting sample 400 into the sample receiving cavity 122, aluminum points are first connected to both ends of the superconducting sample 400 to prevent overcooling.

[0026] It is understood that the sample receiving cavity 122 achieves the containment and restraint of the superconducting sample 400 by forming a 360-degree enveloping surface contact with the outer surface of the superconducting sample 400 through its inner wall surface. The geometry of the sample receiving cavity 122 matches the shape of the superconducting sample 400. When the superconducting sample 400 is placed into the sample receiving cavity 122, the sidewall of the sample receiving cavity 122, through a continuous contact surface formed by precision machining, clamps and fixes the superconducting sample 400 inside the cavity in an interference or tight fit manner. This structure ensures maximum fit between the outer surface of the superconducting sample 400 and the inner wall of the sample receiving cavity 122, thereby achieving stable surface contact in terms of both mechanical restraint and thermal conduction. Specifically, the sample receiving cavity 122 and the superconducting sample 400 can be cylindrical in shape, but their shapes are not limited to cylindrical and can be designed according to actual conditions.

[0027] In use, the base 110 of the base 100 establishes a thermal connection with the external cooling system, transferring the cold energy to the integrally formed sample holder 120. The sample receiving cavity 122 of the sample holder 120 forms omnidirectional surface contact with the superconducting sample 400 through its inner wall, achieving efficient heat transfer and enabling the superconducting sample 400 to quickly reach and stabilize at the target ultra-low temperature. The magnetoelectric sensing component 200 applies an excitation magnetic field to the superconducting sample 400 on the outer periphery of the sample holder 120 and senses the change in magnetic flux at this temperature. When the superconducting sample 400 undergoes a phase transition, its magnetization intensity changes abruptly, and the magnetoelectric sensing component 200 detects this characteristic signal. The magnetic shielding component 300 covers the outer periphery of the magnetoelectric sensing component 200, effectively shielding the interference of the external environmental magnetic field, ensuring that the magnetic flux change signal detected by the magnetoelectric sensing component 200 originates from the phase transition process of the superconducting sample 400, thereby accurately determining the temperature fixation point corresponding to the superconducting phase transition.

[0028] This invention eliminates the interfacial thermal resistance caused by threaded connections by using an integral structure where the base 100 is formed from the base 110 and the sample holder 120. This allows the superconducting sample 400 to achieve efficient heat conduction with the sample holder 120 through surface contact, significantly shortening the thermal equilibrium time and improving the response speed and efficiency of temperature measurement. The magnetoelectric sensing component 200 directly detects the magnetic flux transition of the superconducting sample 400, and combined with the isolation effect of the magnetic shielding component 300 against external interfering magnetic fields, it ensures the accuracy and reproducibility of phase transition signal detection.

[0029] Reference Figure 1In some embodiments of the present invention, the magnetoelectric sensing component 200 includes a primary coil 220, an electrostatic shielding layer 230, and a secondary coil 240. The primary coil 220 is wound around the outer periphery of the sample holder 120 and is electrically connected to an AC power source to apply an excitation magnetic field to the superconducting sample 400. The electrostatic shielding layer 230 is sleeved around the outer periphery of the primary coil 220 and has circumferential gaps. The secondary coil 240 is wound around the outer periphery of the electrostatic shielding layer 230 and is electrically connected to a lock-in amplifier to sense changes in the magnetic flux of the superconducting sample 400.

[0030] Specifically, the primary coil 220 can be made of niobium-titanium superconducting wire and is fixed to the sample holder 120 by epoxy resin adhesive or mechanical snap-fit. The two leads of the primary coil 220 are used for electrical connection to an external AC power supply. The electrostatic shielding layer 230 can be made of thin-walled copper tubing, which is sleeved and fixed to the outer periphery of the primary coil 220. The copper tubing has an insulating slit extending axially in the circumferential direction to prevent capacitive coupling. The secondary coil 240 can be made of high-purity copper wire and is tightly wound around the outer surface of the electrostatic shielding layer 230. Its winding method is similar to that of the primary coil 220, and it is fixed in a similar manner. The two leads of the secondary coil 240 are used for electrical connection to an external lock-in amplifier.

[0031] In operation, the primary coil 220 is first connected to an AC power supply, and the secondary coil 240 is connected to a lock-in amplifier. The AC power supply is then activated, generating an alternating current in the primary coil 220, which in turn excites an alternating magnetic field within the sample receiving cavity 122 of the sample holder 120. This alternating magnetic field acts on the superconducting sample 400. When the superconducting sample 400 undergoes a phase transition, its magnetization state changes, causing a change in the spatial magnetic flux distribution. The secondary coil 240 senses this change in magnetic flux and generates a corresponding induced electrical signal. The lock-in amplifier detects and analyzes this signal to determine the occurrence of the superconducting phase transition.

[0032] In this embodiment, the primary coil 220 is directly wound around the outer periphery of the sample holder 120, which can efficiently generate an excitation magnetic field at the superconducting sample 400. The electrostatic shielding layer 230 is disposed between the primary coil 220 and the secondary coil 240 and has a circumferential gap, which effectively eliminates the distributed capacitance coupling between the primary coil 220 and the secondary coil 240 and prevents the AC excitation signal from directly entering the signal detection terminal. The secondary coil 240 is wound around the outer periphery of the electrostatic shielding layer 230, which can sensitively sense the small magnetic field changes caused by the magnetic flux jump of the superconducting sample 400, thereby accurately detecting the phase transition point.

[0033] Reference Figure 3In some embodiments of the present invention, the secondary coil 240 includes at least one sub-coil 241; when the number of sub-coils 241 is greater than or equal to two, the sub-coils 241 are connected in series and are disposed on the outer periphery of the superconducting sample 400 in a one-to-one correspondence.

[0034] Specifically, when there are two or more sub-coils 241, these sub-coils 241 are arranged sequentially at intervals along the axial direction of the sample holder 120. Each sub-coil 241 is connected in series with a wire to form a complete detection circuit. Furthermore, the axial position of each sub-coil 241 corresponds one-to-one with the superconducting sample 400 contained in the corresponding position within the sample receiving cavity 122, enabling each sub-coil 241 to specifically sense the magnetic flux change of the superconducting sample 400 in its directly opposite region. The length of each sub-coil 241 is less than the length of the superconducting sample 400.

[0035] In use, the main lead of the series-connected secondary coil 240 is electrically connected to a lock-in amplifier. When the sensor is cooled, different superconducting samples 400 undergo superconducting phase transitions at their respective characteristic phase transition temperatures. Each phase transition event causes a sudden change in the local magnetic field of its corresponding region, which is induced by a specific sub-coil 241 directly above it. Since all sub-coils 241 are connected in series, these induced electrical signals are superimposed and transmitted to the lock-in amplifier. By analyzing the received composite signal, the lock-in amplifier can identify multiple phase transition steps, thereby determining multiple temperature fixes accordingly.

[0036] This embodiment achieves simultaneous detection of multiple superconducting phase transition signals by a single sensing component through the arrangement of multiple series-connected sub-coils 241 in the secondary coil 240, aligning them spatially with multiple superconducting samples 400. This structure utilizes a single measurement loop to simultaneously acquire signals from multiple preset temperature fixed points within a wide temperature range, significantly expanding the calibrable temperature range for a single measurement, meeting the requirements for wide-temperature-range calibration, reducing the tedious process of multiple sensor replacements or repeated measurements, and improving calibration efficiency.

[0037] In other possible embodiments, each sub-coil 241 may have an independent lead terminal and be electrically connected to a different input channel of a multi-channel lock-in amplifier. This embodiment achieves completely independent acquisition and parallel processing of the induced signal generated by each superconducting sample 400 by configuring an independent signal output path for each sub-coil 241.

[0038] Reference Figure 1In some embodiments of the present invention, the magnetoelectric sensing assembly 200 further includes a coil support 210; the coil support 210 is sleeved on the outer periphery of the sample holder 120, the primary coil 220 is disposed on the outer periphery of the sample holder 120 through the coil support 210, the electrostatic shielding layer 230 is sleeved on the outer periphery of the primary coil 220, and the secondary coil 240 is wound around the outer periphery of the electrostatic shielding layer 230. Specifically, the coil support 210 may be made of polyoxymethylene resin.

[0039] Specifically, the coil support 210 can be made of polyoxymethylene resin into a cylindrical structure, which is fitted onto the outer periphery of the sample holder 120 with a slight interference fit at room temperature. When the entire sensor is cooled to extremely low temperatures, taking advantage of the fact that the thermal shrinkage rate of polyoxymethylene resin at low temperatures is significantly greater than that of metallic copper, the coil support 210 will undergo more significant radial shrinkage than the sample holder 120, thereby generating a strong clamping force, which tightly hugs the outer peripheral surface of the sample holder 120, forming a stable mechanical connection and good thermal contact. The primary coil 220 is fixed by directly winding it and using low-temperature epoxy resin to adhere it to the outer peripheral surface of the coil support 210, thus indirectly being located on the outer periphery of the sample holder 120.

[0040] In this embodiment, the coil support 210 is made of polyoxymethylene resin, and the difference in thermal shrinkage between it and metallic copper is utilized to automatically achieve a tight fit with the sample holder 120 at low temperatures. This design provides stable and low thermal resistance mechanical support and a heat conduction path, ensuring the positional accuracy of the primary coil 220 relative to the superconducting sample 400, facilitating the dissipation of the small amount of heat generated during coil operation, preventing localized temperature rises from interfering with the temperature stability of the superconducting sample 400, and simplifying the installation process.

[0041] Reference Figure 1 In some embodiments of the present invention, the magnetic shielding assembly 300 includes a soft magnetic shield 310 and a superconducting shield 320. The soft magnetic shield 310 is detachably connected to the base 110, and the soft magnetic shield 310 is provided with a through hole 311 for the connection ends of the primary coil 220 and the secondary coil 240 to extend to the outside; the superconducting shield 320 is disposed on the inner wall of the soft magnetic shield 310.

[0042] Specifically, the soft magnetic shield 310 can be made into a cylindrical structure using a high-permeability soft magnetic alloy with a nickel content of approximately 85%. Its bottom end has an outwardly folded flange, which is detachably fixed to the base 110 by a set of screws, achieving both mechanical fixation and electrical contact. The upper part of the cylindrical wall of the soft magnetic shield 310 has one or more through holes 311, which allow the lead ends of the primary coil 220 and secondary coil 240 to pass through and extend to external equipment. The superconducting shield 320 can be made of superconducting niobium material, which is fixed to the entire inner wall surface of the soft magnetic shield 310 by low-temperature epoxy resin adhesive or mechanical pressing, forming a complete inner lining.

[0043] In use, the superconducting shield 320 is first installed and fixed to the inner wall of the soft magnetic shield 310. Then, the leads of the primary coil 220 and the secondary coil 240 are led out through the through hole 311. Subsequently, the soft magnetic shield 310 is fixed to the base 110 with screws, completing the assembly of the magnetic shielding assembly 300. When the sensor is cooled to its extremely low operating temperature, the superconducting shield 320 first enters the superconducting state, repelling external static magnetic fields and low-frequency magnetic fields through the Meissner effect; the soft magnetic shield 310, utilizing its high permeability, provides a magnetic path for shunting and shielding external magnetic fields. Both work together, with the through hole 311 providing a channel for the leads while its size is designed to be as small as possible to reduce magnetic field leakage.

[0044] This embodiment achieves effective shielding against external magnetic fields across a wide frequency range by employing a double-layer composite shielding structure consisting of a soft magnetic shield 310 and a superconducting shield 320. The soft magnetic shield 310 primarily provides effective shielding against mid-to-high frequency alternating magnetic fields, while the superconducting shield 320, after reaching its critical temperature, exhibits near-perfect shielding effectiveness against static and low-frequency magnetic fields. The two components complement each other functionally, jointly creating a near-zero magnetic environment for the internal superconducting sample 400, thus preventing interference from external magnetic fields on the superconducting transition temperature.

[0045] In other possible embodiments, the magnetic shielding assembly 300 may include a soft magnetic shield 310 and a superconducting shield 320. The superconducting shield 320 may be independently of the soft magnetic shield 310, fabricated as a cylindrical cover with one open end. This open end of the cover is directly connected to the base 110 via screws. The soft magnetic shield 310 serves as an outer cover, fitted and fixed to the outside of the superconducting shield 320. In this embodiment, by using the superconducting shield 320 as the inner main shield directly connected to the base 110, it can be cooled more directly by the base 100, facilitating a faster transition to the superconducting state and improving shielding stability. The soft magnetic shield 310 serves as an outer auxiliary shield, further attenuating residual magnetic field interference. This split structure also facilitates individual maintenance or replacement of each shield.

[0046] Reference Figure 1 In some embodiments of the present invention, the soft magnetic shield 310 has a cylindrical structure, and one end near the base 110 is open, and the open end is threaded to be threaded to the base 110. The other end away from the base 110 is closed, that is, the end of the soft magnetic shield 310 away from the base 110 is provided with a cover, and the through hole 311 passes through the cover.

[0047] Specifically, the corresponding outer peripheral surface of the base 110 is machined with matching external threads. The soft magnetic shield 310 is screwed to engage its internal threads with the external threads of the base 110, thereby achieving a detachable fixed connection. The end of the soft magnetic shield 310 away from the base 110 is a closed end cap integrally stamped or welded, which forms part of its cylindrical structure. Through holes 311 are provided on this end cap, and the number of through holes can be one or more, as long as all lines can be led out.

[0048] In this embodiment, the soft magnetic shielding component 310 is designed as an integral cylindrical structure with one open end and internal thread, and the other end closed. This allows it to be assembled and sealed with the base 110 through a simple screwing action, making the operation convenient and the connection reliable. The closed end cap structure and the cylindrical wall together form a nearly complete magnetic shielding cavity.

[0049] In other possible embodiments, the soft magnetic shield 310 can be designed as a split structure, with one end of its cylindrical portion open and threaded for connecting to the base 110, while the other end is closed by a separate cap. This cap is connected to the cylindrical portion by threads or snap-fit, and a through hole 311 passes through this separate cap. This embodiment, by employing a split end cap design, allows for the removal of only the end cap when replacing leads or maintaining the internal coil, without unscrewing the entire soft magnetic shield 310 from the base 110. This makes operation more flexible and convenient, and reduces the risk of interference to connected leads.

[0050] Reference Figure 1 In some embodiments of the present invention, the magnetic shielding assembly 300 further includes a connector 330; the connector 330 has a limiting portion on its exterior, the limiting portion having an external thread, and the soft magnetic shielding component 310 is threadedly connected to the limiting portion; the connector 330 has a threaded hole inside, the base 110 passes through the threaded hole and is threadedly connected to the threaded hole. Specifically, the connector 330 has a stepped structure, and the external thread is provided on the narrower area of ​​the step. When the soft magnetic shielding component 310 is connected to the connector 330, its outer surface is coplanar with the outer surface of the wider area of ​​the step.

[0051] Specifically, the connector 330 can be made of phenolic resin material into a stepped cylindrical structure with a raised limiting part on its exterior. This limiting part is located in the narrower area of ​​the stepped structure, and its outer cylindrical surface is machined with external threads. The open end of the soft magnetic shield 310 is machined with matching internal threads. By screwing, the internal threads of the soft magnetic shield 310 engage with the external threads of the limiting part of the connector 330, achieving a detachable connection between the two. The connector 330 has a through internal threaded hole machined along its axial direction. The corresponding end of the base 110 has external threads machined on its outer cylindrical surface. By screwing, the base 110 is screwed into the internal threaded hole of the connector 330 and tightened. When the soft magnetic shield 310 is fully tightened to the limiting part of the connector 330, the outer surface of the soft magnetic shield 310 is flush with and coplanar with the outer end face of the wider area of ​​the stepped structure of the connector 330.

[0052] In use, first align the internal threaded hole of connector 330 with the threaded end of base 110 and tighten it. Then, align the open end of soft magnetic shield 310 with the limiting part of connector 330, which is already fixed on base 110, and rotate soft magnetic shield 310 to engage with the external thread on connector 330 until the end face of soft magnetic shield 310 is completely coplanar with the stepped surface of connector 330 and tighten it. During this process, ensure that the leads of primary coil 220 and secondary coil 240 have passed through the through hole 311 on soft magnetic shield 310.

[0053] This embodiment achieves precise alignment and fixation of the soft magnetic shield 310 relative to the base 110 by using an independent stepped connector 330 that forms a threaded connection with both the base 110 and the soft magnetic shield 310. The stepped structure provides a clear axial positioning reference for the installation of the soft magnetic shield 310, ensuring that its outer surface is coplanar with the connector 330 after tightening, resulting in a flat appearance and a continuous shielding surface, which helps reduce discontinuities in the magnetic circuit and magnetic field leakage. This structure also facilitates the individual disassembly and maintenance of the soft magnetic shield 310.

[0054] In other possible embodiments, the magnetic shielding assembly 300 may further include a connector 330, which may be machined into a flange-like structure. Its external limiting portion may have a set of circumferentially distributed threaded holes, rather than external threads. The open end of the soft magnetic shielding component 310 is correspondingly provided with a set of through holes. A set of screws passes through these through holes and is screwed into the threaded holes of the connector 330, achieving a detachable connection between the soft magnetic shielding component 310 and the connector 330. The connection between the connector 330 and the base 110 can still be a threaded connection. This embodiment uses a screw connection to fix the soft magnetic shielding component 310, providing a wider range of connection preload selection and more intuitive confirmation of the tightening status, suitable for applications with more stringent vibration environment requirements. The flange-like structure also provides a larger contact area, helping to improve connection stability and the overall rigidity of the shield.

[0055] Reference Figure 2 In some embodiments of the present invention, the base 110 includes a base body 112 and a first threaded connection portion 113. The first threaded connection portion 113 is disposed at one end of the sample holder 120 and is threadedly connected to a threaded hole; the base body 112 is disposed at the end of the first threaded connection portion 113 away from the sample holder 120, and the diameter of the base body 112 is larger than the diameter of the first threaded connection portion 113.

[0056] Specifically, the base 110 is integrally formed from high-purity oxygen-free copper material through machining. The first threaded connection part 113 is a cylindrical rod-shaped structure, located at the end of the sample holder 120 away from the opening of the sample receiving cavity 122, and shares a common central axis with the sample holder 120. The outer circumferential surface of the first threaded connection part 113 is machined with external threads, which match the threaded hole inside the connector 330, achieving a threaded connection by tightening. The base body 112 is a larger diameter disc-shaped or flange-shaped structure, located at the end of the first threaded connection part 113 away from the sample holder 120, and integrally formed with the first threaded connection part 113. The diameter of the base body 112 is larger than the diameter of the first threaded connection part 113, forming a stepped transition.

[0057] In use, first align the first threaded connection 113 of the base 110 with the threaded hole inside the connector 330. Rotate the base 110 to gradually screw it into the threaded hole until the end face of the base body 112 is tightly fitted and tightened with the corresponding end face of the connector 330. During this process, ensure that the sample holder 120 and its components are in the correct orientation. The large diameter design of the base body 112 provides a better gripping surface during installation and increases the contact area with external cold sources. After installation, the soft magnetic shield 310, the wider area of ​​the connector 330, and the outer surface of the base body 112 are coplanar.

[0058] In this embodiment, the base 110 is designed as an integrated structure comprising a base body 112 of different diameters and a first threaded connection portion 113. The first threaded connection portion 113 provides an interface for connection with the connector 330, achieving reliable mechanical fixing and thermal connection. The large-diameter structure of the base body 112 not only increases the contact area with the external cooling system and improves heat conduction efficiency, but also provides a better operating foundation for the installation and disassembly process. This stepped structure ensures accurate installation positioning while maintaining the compactness and stability of the overall structure.

[0059] Reference Figure 2 In some embodiments of the present invention, a second threaded connection 111 is provided at one end of the base body 112 away from the first threaded connection 113, and the second threaded connection 111 is used to fix the temperature fixed point sensor; a threaded hole 114 is provided on the side wall of the base body 112, and the threaded hole 114 is used to assist in fixing the second threaded connection 111.

[0060] Specifically, the second threaded connection 111 is integrally formed with the base body 112, and its outer surface is machined with external threads for engaging with corresponding internal threads on an external cooling system or mounting bracket to achieve overall fixed installation of the temperature fixed point sensor. The side wall of the base body 112 is provided with one or more threaded holes 114 radially. The axes of these threaded holes 114 intersect perpendicularly with the axis of the second threaded connection 111. Each threaded hole 114 is used to screw in a set screw. After being tightened, the end of the set screw can abut against the external component connected to the second threaded connection 111, thereby providing additional anti-loosening fixation.

[0061] In use, first screw the second threaded connection 111 of the base 110 into the pre-set threaded interface on the external cooling system or mounting bracket until it is tightened in place, thus installing the main body of the sensor. Then, use a tool to screw the set screw into the threaded hole 114 on the side wall of the base body 112 until the screw tip is firmly pressed against the surface of the external interface, thereby preventing the sensor from accidentally loosening due to vibration or thermal cycling during use.

[0062] In this embodiment, a second threaded connection portion 111 is provided on the base body 112 as the main mounting interface, realizing a standard threaded connection between the sensor and the external system, ensuring the reliability of mechanical fixation and the tightness of thermal contact. The threaded hole 114 and set screw added to the side wall constitute an auxiliary anti-loosening mechanism. This mechanism provides additional radial locking force, effectively preventing the connection from loosening due to material shrinkage or external vibration in extremely low temperature environments, enhancing the stability of installation, and thus ensuring the long-term reliability of the thermal connection.

[0063] Reference Figure 2In some embodiments of the present invention, the sidewall of the sample holder 120 is provided with a plurality of through slots 121 at intervals, and the end of the sample holder 120 away from the first threaded connection portion 113 is provided with an opening. That is, the sample holder 120 is a cage-like structure with an opening at the top.

[0064] Specifically, the sample holder 120 is machined from oxygen-free copper material through integral turning and milling. Its sidewalls are machined with several through-slots 121 spaced axially, each through-wall thickness. The length of each through-slot 121 is greater than the length of the coil support 210. The coil support 210 is assembled outside the through-slots 121, that is, the coil support 210 is located between the two ends of the through-slots 121. The through-slots 121 are evenly distributed circumferentially, dividing the sidewalls of the sample holder 120 into multiple independent elastic arms. The end of the sample holder 120 furthest from the first threaded connection 113 is a completely open opening, making the sample holder 120 an overall cage-like structure with an open top. The sample receiving cavity 122 is located inside this cage-like structure, and its diameter is slightly smaller than the diameter of the superconducting sample 400.

[0065] In use, the superconducting sample 400 is axially inserted into the sample receiving cavity 122 through the opening at the top of the sample holder 120. Since the diameter of the sample receiving cavity 122 is slightly smaller than that of the superconducting sample 400, during insertion, the superconducting sample 400 slightly expands the elastic arms formed by the through slot 121, causing these elastic arms to deform elastically and generate a continuous radial clamping force on the superconducting sample 400. This ensures that the outer surface of the superconducting sample 400 forms a complete and tight surface contact with the inner wall of the sample receiving cavity 122. Subsequent coil installation and cooling measurements can then be performed.

[0066] In this embodiment, a flexible cage-like structure is formed by machining spaced through slots 121 on the sidewall of the sample holder 120 and making one end open. This structure allows the inner diameter of the sample holder 120 to undergo moderate elastic expansion when the superconducting sample 400 is inserted, thereby utilizing the material's own resilience to achieve a uniform and stable hold on the superconducting sample 400. This ensures efficient heat transfer while providing good mechanical restraint, preventing sample movement within the cavity.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A temperature fixed-point sensor, characterized in that, include: A copper base (100), the base (100) comprising: The base (110) is used to establish a thermal connection with the external environment; The sample holder (120) is integrally formed at one end of the base (110). The sample holder (120) has a sample receiving cavity (122) inside, which is used to receive and limit the superconducting sample (400) in a surface contact manner. A magnetoelectric sensing component (200) is disposed on the outer periphery of the sample holder (120) for applying an excitation magnetic field to the superconducting sample (400) and sensing the change in magnetic flux of the superconducting sample (400); A magnetic shielding component (300) is placed around the outer periphery of the magnetoelectric sensing component (200) and connected to the base (110) to shield external magnetic fields.

2. The temperature fixed-point sensor according to claim 1, characterized in that, The magnetoelectric sensing component (200) includes: A primary coil (220) is wound around the outer periphery of the sample holder (120). The primary coil (220) is used to be electrically connected to an AC power source to apply an excitation magnetic field to the superconducting sample (400). An electrostatic shielding layer (230) is sleeved on the outer periphery of the primary coil (220), and the electrostatic shielding layer (230) has circumferential gaps; A secondary coil (240) is wound around the outer periphery of the electrostatic shielding layer (230). The secondary coil (240) is used to be electrically connected to a lock-in amplifier to sense changes in the magnetic flux of the superconducting sample (400).

3. The temperature fixed-point sensor according to claim 2, characterized in that, The secondary coil (240) includes at least one sub-coil (241); When the number of sub-coils (241) is greater than or equal to two, the sub-coils (241) are connected in series and are arranged one-to-one on the outer periphery of the superconducting sample (400).

4. The temperature fixed-point sensor according to claim 2 or 3, characterized in that, The magnetoelectric sensing assembly (200) also includes a coil support (210); The coil support (210) is sleeved on the outer periphery of the sample holder (120), and the primary coil (220) is disposed on the outer periphery of the sample holder (120) through the coil support (210).

5. The temperature fixed-point sensor according to claim 2, characterized in that, The magnetic shielding assembly (300) includes: A soft magnetic shield (310) is detachably connected to the base (110). The soft magnetic shield (310) is provided with a through hole (311). The through hole (311) is used to allow the connection end of the primary coil (220) and the secondary coil (240) to extend to the outside. A superconducting shield (320) is disposed on the inner wall of the soft magnetic shield (310).

6. The temperature fixed-point sensor according to claim 5, characterized in that, The soft magnetic shield (310) has a cylindrical structure, with one end near the base (110) being open and the other end away from the base (110) being closed.

7. The temperature fixed-point sensor according to claim 6, characterized in that, The magnetic shielding assembly (300) also includes a connector (330); The connector (330) has a limiting part on its outside, the limiting part has an external thread, and the soft magnetic shield (310) is threadedly connected to the limiting part; The connector (330) has a threaded hole inside, and the base (110) passes through the threaded hole and is threadedly connected to the threaded hole.

8. The temperature fixed-point sensor according to claim 7, characterized in that, The base (110) includes: A first threaded connection part (113) is provided at one end of the sample holder (120), and the first threaded connection part (113) is threadedly connected to the threaded hole; The base body (112) is located at the end of the first threaded connection (113) away from the sample holder (120), and the diameter of the base body (112) is larger than the diameter of the first threaded connection (113).

9. The temperature fixed-point sensor according to claim 8, characterized in that, The base body (112) has a second threaded connection (111) at one end away from the first threaded connection (113), and the second threaded connection (111) is used to fix the temperature fixed point sensor. The base body (112) has a threaded hole (114) on its side wall, which is used to assist in fixing the second threaded connection (111).

10. The temperature fixed-point sensor according to claim 8, characterized in that, The sample holder (120) has several through slots (121) spaced apart on its side wall, and the sample holder (120) has an opening at one end away from the first threaded connection (113).

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