A small high-temperature superconducting device testing system

Abstract

The present application discloses a small high-temperature superconducting device testing system, which includes a refrigerator, a compressor, a controller and a sample holder fixed on a bottom plate; the refrigerator is connected to the compressor to achieve refrigeration of the testing system; the refrigerator is connected to the sample holder, and the provided cold source directly refrigerates the sample holder; a silicon lens is placed on the sample holder to introduce and focus terahertz waves and extract radiation; the controller controls the operation of the compressor. The testing system adopts a compact and integrated design, featuring miniaturization and portability, reducing the cost of the testing system, effectively reducing noise on the premise of meeting basic measurement requirements, and being convenient to carry. The entire system can be well compatible with existing measurement equipment, such as current sources and related electrical transport property measurement equipment, and can conduct relevant tests in the terahertz field, such as RT cooling tests, terahertz source radiation tests, terahertz mixing detection tests, etc., and has good practicability.

Description

Technical Field

[0001] The present invention belongs to the technical fields of superconducting physics and cryogenic measurement, and particularly relates to a small high-temperature superconducting device test system. Background Art

[0002] A superconductor, also known as a superconducting material, refers to a conductor with zero resistance at a certain temperature. In an experiment, if the measured value of the conductor resistance is lower than 10 -25 Ω, it can be considered that the resistance is zero.

[0003] The 1980s was the golden age of the exploration and research of superconductivity. In 1981, an organic superconductor was synthesized. In 1986, Müller and Bednorz discovered a ceramic metal oxide LaBaCuO composed of barium, lanthanum, copper, and oxygen, with a critical temperature of about 35K (-238°C). Since ceramic metal oxides are generally insulating substances, this discovery was of great significance, and they won the Nobel Prize in Physics in 1987.

[0004] In 1987, there was another new breakthrough in the exploration of superconducting materials. The group of physicist Paul Chu at the University of Houston in the United States and Zhao Zhongxian et al. from the Institute of Physics of the Chinese Academy of Sciences successively announced the fabrication of a superconducting material YBCO with a critical temperature of about 90K (-183°C).

[0005] In early 1988, Japan announced the fabrication of a Bi-Sr-Ca-Cu-O superconductor with a critical temperature of 110K. Thus, people finally realized the dream of a superconductor in the liquid nitrogen temperature range, achieving a major breakthrough in the history of science. Since the critical temperature of this type of superconductor is above the liquid nitrogen temperature of 77K (-196°C), it belongs to high-temperature superconductors.

[0006] Since the discovery of high-temperature superconducting materials, a wave of superconductivity fever has swept the globe. Scientists also found that the critical temperature of thallium-based compound superconducting materials can reach 125K (-148°C), and that of mercury-based compound superconducting materials can reach 135K (-138°C). If mercury is placed under high-pressure conditions, its critical temperature can reach an incredible 164K (-109°C). In 1997, researchers found that a gold-indium alloy is both a superconductor and a magnet near absolute zero. In 1999, scientists discovered that ruthenium copper compounds have superconductivity at 45K (-228°C). Due to the unique crystal structure of this compound, its application potential in computer data storage will be very great.

[0007] Josephson theoretically predicted the Josephson effect in 1962 and won the Nobel Prize in Physics in 1973. Due to the extraordinary sensitivity of its superconducting current to external electromagnetic fields, the Josephson junction can be used not only for the measurement of magnetocardiogram and magnetoencephalogram, but also for the detection of high-frequency electromagnetic field radiation.

[0008] At present, in the application field of high-temperature superconducting electronic devices, such as high-temperature superconducting terahertz radiation sources, high-sensitivity terahertz detectors, high-temperature superconducting SQIF, etc., all need to work in a low-temperature system. Therefore, various means of obtaining a low-temperature environment have become the basis of superconducting research and applications. The cryostat is an important carrier for studying superconducting devices. The cryostat is a low-temperature device that provides a constant-temperature system at a specified temperature through various refrigeration methods and can measure one or more physical quantities. Cryostats are widely used in research fields such as optics, thermology, electronics, material physics, and superconducting physics in low-temperature environments.

[0009] Since the superconducting transition temperature of high-temperature superconductors has been greatly increased compared with traditional superconductors, the working temperature of Josephson junction samples prepared with high-temperature superconducting materials is relatively much higher. The requirement for the refrigeration temperature of the refrigeration mechanism is not as strict as that of traditional superconductors. Therefore, the requirement for the portability of the refrigerator is relatively higher.

[0010] At present, relatively common refrigerator models such as the K535 Stirling refrigerator of Ricor Company can reach a temperature of about 35K, but it has disadvantages such as high power consumption, high noise, large volume, and inconvenient movement, and cannot meet our needs for the miniaturization of superconducting device characterization. Another example is the Montana S200 refrigerator, which can reach a temperature of 3.5K, but its cooling time is too long to meet the requirements of rapid measurement. For existing miniaturized refrigerators, such as the C376 type refrigerator, it is small in volume, but its functions are often relatively simple and crude, the relevant test interfaces are incomplete, and the installation is unstable and easy to damage, making it difficult to meet the daily test requirements. And the existing low-temperature test systems generally have a relatively high cost. For example, the Stirling is priced at 200,000, and the Montana is priced at 800,000 - 1,200,000. In summary, these refrigeration devices have excellent refrigeration performance and comprehensive functions, but their costs are relatively high, their volumes are large, their cooling times are long, and they lack portability, and cannot give full play to the advantage of the low working temperature of high-temperature superconducting materials. Summary of the Invention

[0011] Aiming at the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a small high-temperature superconducting device test system, which realizes the miniaturization and portability of the test system, reduces the cost of the test system, and on the premise of meeting the basic measurement requirements, minimizes noise as much as possible and is designed in a compact manner to meet the use requirements.

[0012] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0013] A small high-temperature superconducting device test system includes a refrigerator, a compressor, a controller, and a sample holder fixed on a bottom plate; the refrigerator is connected to the compressor to realize the refrigeration of the test system; the refrigerator is connected to the sample holder, and the provided cold source directly refrigerates the sample holder; a silicon lens is placed on the sample holder to introduce and focus terahertz waves and radiate them out; the controller controls the operation of the compressor.

[0014] The sample holder is divided into upper and lower parts for cooperative use. The upper part is a cylindrical hollow structure with downward pins, and the lower part is a circular ring structure with notches for cooperating with the pins. After the pins are inserted into the notches, the overall sample holder is nearly fully enclosed.

[0015] The sample holder is made of oxygen-free copper.

[0016] A silicon lens is placed in the middle of the hollow structure of the upper part of the sample holder.

[0017] The sample holder is fixed to the cold finger of the refrigerator through screws and a copper sheet at the bottom.

[0018] A transparent window is installed on the top of the sample holder.

[0019] The left half of the refrigerator is fixed to the bottom plate through two drilled parts, and the right half is fixed through a metal clamp. At the same time, two fans are pre-installed on the right for heat dissipation.

[0020] Beneficial effects: Compared with the prior art, the advantages of the present application are as follows:

[0021] 1) The test system adopts a compact and integrated design, featuring miniaturization and portability, reducing the cost of the test system, effectively reducing noise on the premise of meeting basic measurement requirements, and being convenient to carry.

[0022] 2) The entire system can be well compatible with existing measurement devices, such as current sources and related electrical transport property measurement devices, and can perform relevant tests in the terahertz field, such as RT cooling tests, terahertz source radiation tests, terahertz mixing detection tests, etc.

[0023] 3) The sample holder has a reasonable structure, can lead out and introduce terahertz wave radiation, and can introduce and couple the local oscillator signal in mixing, with good practicability. Description of the Drawings

[0024] Figure 1 is the design schematic diagram of a small high-temperature superconducting device test system;

[0025] Figure 2 It is a schematic structural diagram of a sample rack for placing samples;

[0026] Figure 3 It is a schematic diagram of the connection between the sample rack and the cold finger;

[0027] Figure 4 It is a schematic diagram of the connection between the sample rack, the cold finger of the refrigerator and the compressor

[0028] Figure 5 It is a schematic structural diagram of a small high-temperature superconducting device test system;

[0029] Figure 6 It is an RT curve graph of the sample;

[0030] Figure 7 It is a voltage-current curve graph and a cooling time graph of the sample;

[0031] Figure 8 It is a mixing result graph. Specific embodiments

[0032] The present invention will be further described below in conjunction with specific embodiments.

[0033] As Figure 1 shown, the main equipment of the small high-temperature superconducting device test system of the present application includes a refrigerator, a compressor, a controller and a sample rack; the refrigerator is connected to the compressor to realize the refrigeration of the test system; the cold source provided by the refrigerator directly cools the sample rack; a silicon lens is placed on the sample rack to introduce and focus terahertz waves and radiate them out; the controller controls the operation of the compressor and the entire test system. When the small high-temperature superconducting device test system is in use, only the test sample needs to be placed on the sample rack, irradiated by an external microwave source, and tested and detected in cooperation with a directional coupler, a filter, a frequency synthesizer, a spectrum analyzer, etc.

[0034] As Figure 2 shown, the sample rack 1 is divided into upper and lower parts for coordinated use. The upper part 11 is a cylindrical hollow structure and has downward pins. The lower part 12 is a circular ring structure and has notches for cooperating with the pins. After the pins are inserted into the notches, the whole sample rack 1 is almost completely enclosed, and this design can reduce the interference of external noise; in addition, the whole sample rack 1 is made of oxygen-free copper material, and the heat conduction performance is better. A silicon lens 4 is placed in the middle of the hollow structure of the upper part 11, and the silicon lens 4 is used to introduce and focus terahertz waves and radiate them out.

[0035] As Figure 3 shown, the sample rack 1 is fixed to the cold finger 3 of the refrigerator 5 through screws and a copper sheet 2 at the bottom, which is convenient for taking and placing the sample rack 1. As Figure 4As shown, the sample holder 1 is connected to the cold finger 3 of the refrigerator 5 and the compressor 6. As Figure 5 As shown, a transparent window 7 is used at the top of the sample holder 1 for external terahertz radiation detection and irradiation of various microwaves on the sample. At the same time, when the refrigerator 5 is working, the compressor 6 will generate vibrations. For a precise cryogenic measurement system, vibrations are likely to affect the accuracy of the test. Therefore, in this application, the entire refrigerator 5 is fixed on a bottom plate 8 to reduce vibrations. The left half of the refrigerator 5 is fixed to the bottom plate 8 through two drilled parts, and the right half is fixed through metal clamps. At the same time, two fans are pre-installed on the right for heat dissipation. The outer shell of the refrigerator 5 is in direct contact with the bottom plate, which can also play a part in assisting heat dissipation. The middle and lower part is the installation position of the controller.

[0036] The overall system of this small high-temperature superconducting device test system can adopt a double-layer structure. The first layer places the refrigerator and the controller, and the second layer places a 220V to 24V switching power supply to support the power supply requirements of the refrigerator. Therefore, only a power cord needs to be simply connected to achieve rapid cooling. Embodiment 1

[0037] Based on the small high-temperature superconducting device test system of this application, a micro-nano device prepared by a high-temperature superconductor BSCCO is used as a detector, which can perform mixing detection of terahertz signals. Due to the highly non-linear characteristics of Josephson junctions, BSCCO with a series structure of multiple Josephson junctions is very suitable for mixer detection. In this embodiment, a 110GHz microwave source is used to irradiate the detector sample on the sample holder, and a spectrum analyzer is used to analyze the intermediate frequency output, and the following results are obtained:

[0038] Figure 6 is the RT curve graph of the sample, Figure 7 is the voltage-current curve graph of the sample, Figure 8 is the mixing result. After calculation, it is 67 times of mixing. At the same time, the terahertz radiation source is also tested, and a terahertz wave of 371GHz is detected.

[0039] The results confirm that the system can test terahertz radiation and can also perform normal radiation mixing detection of terahertz waves. Therefore, this application can fully meet the relevant test requirements of high-temperature superconducting samples, and has the advantages of small size, portability, fast cooling time, low power consumption, and convenient testing.

Claims

1. A small high-temperature superconducting device testing system, characterized in that: It includes a refrigerator (5), a compressor (6), a controller, and a sample holder fixed on a bottom plate (8); the refrigerator (5) is connected to the compressor (6) to achieve refrigeration of the test system; the refrigerator (5) is connected to the sample holder (1), and the provided cold source directly refrigerates the sample holder (1); a silicon lens is placed on the sample holder (1) for introducing and focusing terahertz waves and radiating them out; the controller controls the operation of the compressor; the sample holder (1) is divided into upper and lower parts for cooperative use, the upper part (11) is a cylindrical hollow structure and has downward pins, the lower part (12) is an annular structure and has notches for cooperating with the pins, and after the pins are inserted into the notches, the whole sample holder (1) is nearly fully enclosed; the sample holder (1) is made of oxygen-free copper; a silicon lens (4) is placed in the middle of the hollow structure of the upper part (11) of the sample holder (1); the sample holder (1) is fixed to the cold finger (3) of the refrigerator (5) through a screw, a copper sheet (2) at the bottom; a transparent window piece (7) is installed at the top of the sample holder (1).

2. The small high-temperature superconducting device testing system according to claim 1, characterized in that: The left half of the refrigerator (5) is fixed to the bottom plate (8) through two drilled parts, and the right half is fixed through a metal clamp. At the same time, two fans are pre-installed on the right for heat dissipation.

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