A telescopic liquid helium dewar with a single-layer optical window

Abstract

The present invention discloses a telescopic liquid helium dewar with a single-layer optical window, comprising a first dewar assembly and a second dewar assembly, both of which are vacuum-sealed structures; the bottom of the first dewar assembly is connected to the second dewar assembly, and the bottom of the first dewar assembly is a sample chamber; the second dewar assembly comprises a telescopic tube assembly, a radiation protection assembly, and a single-layer optical window; the top of the telescopic tube assembly is connected to the bottom of the first dewar assembly, and the single-layer optical window is connected to the bottom of the telescopic tube assembly; the radiation protection assembly is located inside the telescopic tube assembly and is coaxially arranged; after the telescopic tube assembly is compressed, the top of the radiation protection assembly extends into the sample chamber. The present invention has the following beneficial effects: simple operation, improved testing efficiency, cost savings, and guaranteed sealing; the radiation protection assembly can achieve excellent heat conduction and temperature control, greatly reducing the loss rate of light during transmission; strong scalability, and can introduce optical measurement methods such as optical fiber.

Description

Technical Field

[0001] The present invention relates to the field of liquid helium dewar, in particular to a telescopic liquid helium dewar adopting a single-layer optical window. Background Art

[0002] Cryogenic measurements, particularly those made with liquid helium, are a crucial area of ​​modern physics testing. Liquid helium dewars are ideal containers and essential tools for storing cryogenic liquids and conducting cryogenic research. Liquid helium dewars are capable of achieving an effective, extremely low-temperature environment, and they possess an insulation system capable of maintaining this low-temperature environment for extended periods. Consequently, their application in cryogenic measurement is becoming increasingly widespread and their importance is growing.

[0003] Understanding the response of functional materials to electromagnetic waves across different spectra has long been a fundamental means of gaining a deeper understanding of new materials, new mechanisms, and novel properties, and is fundamental to research in materials science and materials science. The terahertz (THz) band is a crucial frequency range. With the increasing maturity of THz wave generation technology in recent years, interest in it has grown, and its applications have broadened. These applications have expanded to include THz communications, medical imaging, security testing, microelectronics testing, life sciences, and, of course, materials science and materials science. The THz band holds significant significance for research in materials science and materials science. As research on matter and materials deepens to the microscopic level and examines multiple parameters (phonons, charge, spin, momentum, etc.), interest in the interaction between matter and THz electromagnetic waves, particularly at the micro- and nanoscale, has intensified. This interaction holds numerous new effects and mechanisms with broad application prospects. Therefore, the development of advanced, high-resolution, high-sensitivity, and precise material property measurement techniques within the THz spectrum is crucial, particularly in the THz near-field. Terahertz near-field imaging has been developed based on relatively mature ideas and methods in visible light and other bands. It inherits the latter's function of high-resolution non-destructive scanning of sample surface morphology, and has the unique ability to image some embedded samples and obtain sub-surface information. It has considerable application value in the fields of carrier concentration measurement, micro-nanostructure microscopy, crystal property research, biomedical imaging diagnosis, etc.

[0004] As disclosed in publication number CN201811635596.7, an independent and detachable low-loss liquid helium dewar for a sample chamber in a confined space comprises five cylinders with increasing diameters, which are respectively called, from thick to thin, cylinder A (1), cylinder B (2), cylinder C (3), cylinder D (4), and cylinder E (5). They are coaxially sheathed together and arranged vertically to form an upper nested structure. The dewar also comprises five tubes with increasing diameters, which are respectively called, from thick to thin, cylinder A (21), cylinder B (22), cylinder C (23), cylinder D (24), and cylinder E (25). They are coaxially sheathed together to form a lower nested structure. The lower nested structure is located below the upper nested structure and is coaxial with it. The cylinder A (1 ) is sealed with the upper cover A (8), the lower end of the cylinder A (1) is sealed with the lower cover A (12), the lower end of the lower cover A (12) is connected to the upper end of the A tube (21) by means of flange sealing, the upper end of the cylinder B (2) is sealed with the upper cover B (9), the upper cover B (9) is fixedly installed with a liquid nitrogen infusion tube (17), the lower end of the cylinder B (2) is sealed with the lower cover B (13), the lower end of the lower cover B (13) is connected to the upper end of the B tube (22) by means of vacuum sealing, the upper end of the cylinder C (3) is sealed with the upper cover C (10), the lower end of the cylinder C (3) is sealed with the lower cover C (14) is sealed and connected, the lower end of the lower cover C (14) is connected to the upper end of the C tube (23) in a vacuum-sealed manner, the upper end of the cylinder D (4) is sealed and connected to the upper cover D (11), the upper cover D (11) is fixedly installed with a liquid helium infusion tube (16), the lower end of the cylinder D (4) is sealed and connected to the lower cover D (15), the lower end of the lower cover D (15) is connected to the upper end of the D tube (24) in a vacuum-sealed manner, the lower end of the cylinder E (5) is connected to the upper end of the E tube (25) in a vacuum-sealed manner, the top of the upper cover C (10) and the top of the upper cover B (9) are respectively connected to the H tube (6) The two ends of the tube are sealed and connected, the tube (6) is coaxially sleeved outside the tube (5), and further includes a cold cover tube (26) and a cold cover tube (27). The cold cover tube (26) is coaxially sleeved outside the cold cover tube (27) to form a double cold cover structure. The double cold cover structure is located below the lower nested structure and coaxial with it. The bottom of the sandwich formed by the tube (22) and the tube (23) is sealed and connected to the upper end of the cold cover tube (26) through a fastener. The bottom of the sandwich formed by the tube (24) and the tube (25) is sealed and vacuum-sealed to the upper end of the cold cover tube (27) through a metal ring sealing flange. This application can adapt to small spaces, but it is mostly a detachable mode. When replacing the sample, the bottom of the Dewar needs to be disassembled. The detachable form also has problems such as multiple disassembly affecting the sealing.

[0005] Furthermore, placing the terahertz near-field measurement in a low-temperature environment is a difficulty. When terahertz light enters a low-temperature environment, it needs to be insulated to prevent water condensation on the window surface, so it generally needs to pass through two layers of optical windows, which will greatly increase the loss of light during transmission. Furthermore, when conducting terahertz near-field tests, it is generally necessary to add external environmental regulation, such as magnetic fields. The magnetic field is provided by magnets, and the test space that magnets can provide is generally extremely limited. The magnet aperture is generally relatively small, and coupled with the volume of the measuring device itself, this places higher demands on the design of the Dewar. Therefore, how to make terahertz light, low temperature, and strong magnetic field compatible is a difficult problem.

[0006] The information disclosed in this background section is only intended to enhance understanding of the overall background of the invention and should not be considered as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to solve the current problems of cumbersome sample replacement, low efficiency and impact on sealing.

[0008] The present invention solves the above technical problems through the following technical means:

[0009] A telescopic liquid helium dewar with a single-layer optical window includes a first dewar assembly and a second dewar assembly, both of which are vacuum-sealed structures; the bottom of the first dewar assembly is connected to the second dewar assembly, and the bottom of the first dewar assembly is a sample chamber;

[0010] The second Dewar assembly includes a telescopic tube assembly, a radiation protection assembly, and a single-layer optical window; the top of the telescopic tube assembly is connected to the bottom of the first Dewar assembly, the single-layer optical window is connected to the bottom of the telescopic tube assembly, the radiation protection assembly is located inside the telescopic tube assembly and is coaxially arranged, and the top of the radiation protection assembly extends into the sample chamber after the telescopic tube assembly is compressed.

[0011] During use, the present invention places a sample on top of the radiation shielding assembly. By compressing the telescopic tube assembly, the radiation shielding assembly is pushed upward into the sample chamber of the second dewar assembly, and cryogenic liquid nitrogen or / and liquid helium is injected into the first dewar assembly, thereby conducting testing in a low-temperature environment. After the test is completed, the compression of the telescopic tube assembly is released, and the radiation shielding assembly is then pulled back into the telescopic tube assembly. After returning to room temperature, the sample or measuring device is removed from the radiation shielding assembly. The present invention adopts a telescopic structure, which allows the sample to enter the sample chamber after installation and be retracted after testing. This method has many advantages. First, only a small number of parts at the bottom of the second dewar assembly need to be disassembled, which is simpler than the current method that requires disassembly of multiple parts and improves testing efficiency. The first dewar assembly does not need to be disassembled, ensuring its sealing. Second, after the test is completed, the room temperature can be restored in the second dewar assembly, eliminating the need for a separate room temperature recovery device, thus saving costs. In addition, during use of the present invention, the radiation shielding assembly can achieve excellent heat conduction and temperature control. Therefore, a single optical window can meet the required test temperature, thereby reducing light loss.

[0012] Preferably, it also includes a window flange, the top of which is connected to the bottom of the telescopic tube assembly, the single-layer optical window is connected to the bottom of the window flange, and the bottom end support of the radiation protection assembly is connected to the inner end face of the window flange.

[0013] Preferably, the telescopic tube assembly includes a first flange, a second flange, a bellows, and a plurality of drive connecting rods. The first flange and the second flange are respectively connected to the two ends of the bellows. A plurality of drive connecting rods are arranged in a circular array on the outer circumference of the bellows. The top end of the drive connecting rod is connected to the first flange, and the second flange is connected to the drive connecting rod in a liftable manner.

[0014] The bellows is retractable. After the bellows are compressed, the radiation shielding assembly can be driven toward the sample cavity until the sample is placed in the sample cavity for testing.

[0015] Preferably, the radiation protection component includes at least one light path circular tube and multiple radiation protection screens. The multiple radiation protection screens are connected to the outside of the light path circular tube at intervals. The light path circular tube is coaxially arranged with the single-layer optical window, and the radiation protection screen is a cylindrical structure.

[0016] Preferably, the radiation protection assembly further comprises a radiation protection elastic cover capable of contacting the inner wall of the first Dewar, and the radiation protection elastic cover is connected to the middle portion of the optical path circular tube.

[0017] The present invention realizes heat conduction through the radiation-proof screen and the radiation-proof elastic cover, so as to better control the temperature.

[0018] Preferably, a valve capable of switching the first dewar assembly and the second dewar assembly is further included, and the bottom end of the first dewar assembly and the top end of the second dewar assembly are both connected to the sealing valve.

[0019] Preferably, the first Dewar assembly as a whole has a structure that is thick at the top and thin at the bottom, wherein the sample chamber is located at the thin part of the first Dewar assembly.

[0020] Preferably, the first Dewar assembly includes a first shell, a second shell, a third shell, and a fourth shell that are sequentially spaced and sleeved from the outside to the inside. The first shell, the second shell, the third shell, and the fourth shell are all structures that are thick at the top and thin at the bottom, and the bottom ends of the first shell, the second shell, the third shell, and the fourth shell are connected together.

[0021] Preferably, it also includes a fifth shell and an exchange gas port, one end of the exchange gas port is connected to the bottom end of the fourth shell, and the top end of the fifth shell is connected to the other end of the exchange gas port. The fifth shell is located inside the third shell, and the bottom of the fifth shell is connected to the third shell, and the fifth shell contains a sample chamber.

[0022] Preferably, a first vacuum layer is formed between the first shell and the second shell, a liquid nitrogen chamber is formed between the second shell and the third shell, a second vacuum layer is formed between the third shell and the fourth shell, a liquid helium chamber is formed in the fourth shell, the liquid helium chamber is communicated with the sample chamber, and the first vacuum layer is communicated with the second vacuum layer.

[0023] The present invention adopts a first Dewar assembly that is thick at the top and thin at the bottom. The interior of the thin part is the sample cavity. The sample cavity can be made as large as possible while meeting the low temperature requirements, which is convenient for use with microscopic imaging devices such as scanning probe microscopes. The entire structure is compact, and the Dewar is suitable for extreme conditions with limited space. For example, it can be placed within the diameter of a magnet. It has strong scalability and can introduce optical measurement methods such as optical fiber, solving the design difficulty of the compatibility of terahertz light, low temperature and strong magnetic field.

[0024] The advantages of the present invention are:

[0025] (1) When the present invention is used, the sample is placed on the top of the radiation protection component. By compressing the telescopic tube component, the radiation protection component is pushed upward into the sample cavity of the second Dewar assembly, and the first Dewar assembly is flushed with low-temperature liquid nitrogen or / and liquid helium, thereby performing testing in a low-temperature environment. After the test is completed, the compression state of the telescopic tube component is released, and the radiation protection component is then pulled back into the telescopic tube component. After the sample is restored to room temperature, the sample or measuring device is taken out from the radiation protection component. The present invention adopts a telescopic structure, and the sample is installed and then inserted into the sample cavity. After the test is completed, the sample is retracted, which has many advantages. First, only a small number of parts at the bottom of the second Dewar assembly need to be disassembled, which is simpler than the current method of disassembling multiple parts, thereby improving the test efficiency. The first Dewar assembly does not need to be disassembled, thereby ensuring its sealing. Furthermore, the room temperature can be restored in the second Dewar assembly after the test is completed, without the need to set up a room temperature recovery device separately, thereby saving costs. In addition, during the use of the present invention, the radiation protection component can achieve good heat conduction and temperature control. Therefore, a single-layer optical window can meet the temperature required for the test, thereby reducing light loss.

[0026] (2) The bellows is retractable. After the bellows are compressed, the radiation shielding assembly can be driven toward the sample cavity until the sample is placed in the cavity for testing.

[0027] (3) The present invention achieves heat conduction through the radiation shield and the radiation shield elastic cover to better control the temperature;

[0028] (4) The present invention adopts a first Dewar assembly that is thick at the top and thin at the bottom, with the thin part inside being the sample cavity. The sample cavity can be made as large as possible while meeting the low temperature requirement, which is convenient for use with microscopic imaging devices such as scanning probe microscopes. The entire structure is compact, and the Dewar is suitable for extreme conditions with limited space, such as being placed within the aperture of a magnet. It has strong scalability and can introduce optical measurement methods such as optical fiber, thus solving the design difficulty of compatibility of terahertz light, low temperature, and strong magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of a telescopic liquid helium dewar using a single-layer optical window according to an embodiment of the present invention;

[0030] Figure 2 This is an exploded view of a telescopic liquid helium dewar using a single-layer optical window according to an embodiment of the present invention;

[0031] Figure 3 1 is an exploded schematic diagram of the second dewar assembly according to an embodiment of the present invention;

[0032] Figure 4 1 is a schematic structural diagram of the second dewar assembly according to an embodiment of the present invention;

[0033] Figure 5This is a front view of the second dewar assembly according to an embodiment of the present invention;

[0034] Figure 6 yes Figure 5 Cross-sectional view at AA in the middle;

[0035] Figure 7 is a schematic structural diagram of a telescopic assembly according to an embodiment of the present invention;

[0036] Figure 8 is a schematic structural diagram of a telescopic assembly according to an embodiment of the present invention;

[0037] Figure 9 is a front view of a telescopic assembly according to an embodiment of the present invention;

[0038] Figure 10 yes Figure 9 Cross-sectional view at the middle BB;

[0039] Figure 11 is a three-dimensional diagram of the first dewar assembly according to an embodiment of the present invention;

[0040] Figure 12 This is a front view of the first dewar assembly according to an embodiment of the present invention;

[0041] Figure 13 yes Figure 12 Cross-sectional view at CC;

[0042] Figure 14 yes Figure 13 Enlarged view of point D in the middle;

[0043] Figure 15 yes Figure 13 Enlarged view of point E in the middle;

[0044] Figure 16 is a schematic diagram of a radiation protection component entering a sample chamber according to an embodiment of the present invention;

[0045] Figure 17 is a cross-sectional view of the radiation protection component entering the sample chamber according to an embodiment of the present invention;

[0046] Figure 18 yes Figure 17 Enlarged view of point F in the middle;

[0047] Numbers in the figure:

[0048] 1. First Dewar Assembly; 11. First Shell; 12. Second Shell; 13. Third Shell; 14. Fourth Shell; 15. Infusion Accessories; 16. Fifth Shell; 17. Exchange Gas Port; 18. Shell Flange; 19. Adapter Sleeve;

[0049] 2. Second Dewar assembly; 21. Telescopic tube assembly; 211. First flange; 212. Second flange; 213. Bellows; 214. Drive connecting rod; 22. Radiation protection assembly; 221. Optical path tube; 222. Radiation protection screen; 223. Radiation protection elastic cover; 224. Sample carrier; 225. Radiation protection support frame; 23. Single-layer optical window; 24. Window flange; 241. First window connecting flange; 242. First connecting tube; 243. Second window connecting flange; 25. Vacuum flange;

[0050] 3. Valve; 4. Vacuum port; 5. Circuit box; DETAILED DESCRIPTION

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0052] Example 1:

[0053] like Figure 1 、 Figure 2 As shown, a telescopic liquid helium dewar with a single-layer optical window includes a first dewar assembly 1, a second dewar assembly 2, and a valve 3, all of which are vacuum-sealed structures. The bottom of the first dewar assembly 1 is connected to the top of the second dewar assembly 2, and the first and second dewar assemblies 1 and 2 are connected and disconnected via the valve 3. The second dewar assembly 2 is also provided with a vacuum outlet 4 at one end near the valve 3, and the bottom of the second dewar assembly 2 is connected to a circuit box 5. The bottom of the first dewar assembly 1 is a sample chamber. The second dewar assembly 2 includes a telescopic tube assembly 21, a radiation shielding assembly 22, and a single-layer optical window 23. The top of the telescopic tube assembly 21 is connected to the bottom of the first dewar assembly 1, and the single-layer optical window 23 is connected to the bottom of the telescopic tube assembly 21. The radiation shielding assembly 22 is located inside the telescopic tube assembly 21 and is coaxially arranged. After the telescopic tube assembly 21 is compressed, the top of the radiation shielding assembly 22 extends into the sample chamber.

[0054] like Figure 1 、 Figure 3 As shown, the second Dewar assembly 2 further includes a window flange 24, the top end of which is connected to the bottom of the telescopic tube assembly 21, the single-layer optical window 23 is connected to the bottom end of the window flange 24, and the bottom end support of the radiation shielding assembly 22 is connected to the inner end surface of the window flange 24. The window flange 24 has a certain height and can be formed by combined assembly. Figure 6 As shown, the window flange 24 is formed by connecting the first window connecting flange 241, the first connecting tube 242, and the second window connecting flange 243 in sequence, wherein the interior of the second window connecting flange 243 has an axially upward protruding sleeve-like structure, and a supporting space is formed between the first connecting tube 242 and the second window connecting flange 243 for supporting the radiation protection component 22.

[0055] like Figure 3 、 Figure 4 As shown, the second dewar assembly 2 further includes a vacuum flange 25, which is used to connect to the vacuum port 4 for installation. The vacuum flange 25 is connected to the top of the telescopic tube assembly 21. The interiors of the vacuum flange 25, the telescopic tube assembly 21, and the window flange 24 are interconnected to form a cavity for accommodating the radiation shielding assembly 22, and the bottom of the radiation shielding assembly 22 is supported on the window flange 24. Of course, in this embodiment, each flange is a detachable structure. Although it is a detachable structure, not all flanges need to be removed during use. Please refer to the usage process for details.

[0056] like Figure 3 、 Figure 4 、 Figure 5 As shown, the telescopic tube assembly 21 includes a first flange 211, a second flange 212, a bellows 213, and a plurality of drive connecting rods 214. The first flange 211 and the second flange 212 are respectively connected to the two ends of the bellows 213. A plurality of drive connecting rods 214 are circumferentially arrayed on the outer circumference of the bellows 213. The top ends of the drive connecting rods 214 are connected to the first flange 211, and the second flange 212 is connected to the drive connecting rods 214 in a manner that allows them to be lifted or lowered. That is, one of the drive connecting rods 214 serves as a drive rod, the top end of which can be connected to the first flange 211 via a bearing. The shaft of the drive connecting rod 214 is threaded, and the shaft portion is threadedly connected to the second flange 212, so that the drive connecting rod 214 can be rotated. The remaining drive connecting rods 214 serve as guide rods, and the second flange 212 is slidably connected to the remaining drive connecting rods 214. When the drive rod rotates forward or reverse, the second flange 212 can move up and down in the vertical direction, remembering to compress or relax the bellows 213.

[0057] The bellows 213 is retractable. After the bellows 213 is compressed, the radiation protection component 22 can be driven toward the sample cavity until the sample is placed in the sample cavity for testing.

[0058] like Figure 7As shown, the radiation protection assembly 22 includes a light path circular tube 221 and multiple radiation shields 222. In this embodiment, there are two light path circular tubes 221, one with a larger diameter and one with a smaller diameter. The radiation shields 222 are cylindrical structures with one end being a circular plate welded to the outer wall of the light path circular tube 221 and the other end being open. The multiple radiation shields 222 are spaced apart and connected to the exterior of the light path circular tube 221. The light path circular tube 221 is coaxially arranged with the single-layer optical window 23. The inner surface of the light path circular tube 221 is polished for optical transmission.

[0059] In this embodiment, the radiation protection component 22 also includes a radiation protection elastic cover 223 that can contact the inner wall of the first Dewar after the sample enters the sample chamber. The radiation protection elastic cover 223 is connected to the middle part of the optical path tube 221; the diameter of the radiation protection screen 222' located at the upper part of the radiation protection elastic cover 223 is smaller than the diameter of the radiation protection screen 222" located at the lower part, mainly because the radiation protection screen 222 located at the upper part can enter the sample chamber, so it is smaller in size. The radiation protection elastic cover 223 has a strip-shaped cage structure. Specifically, one end of the radiation protection elastic cover 223 is plate-shaped and connected to the optical path tube 221, and the cover body is a plurality of strip structures with the middle part protruding outward. The middle part of the outwardly protruding strip structure can be in contact with the interior of the first Dewar assembly 1, achieving better heat conduction and facilitating temperature control.

[0060] The radiation protection component 22 also includes a sample loading platform 224 and a radiation protection support frame 225. The sample loading platform 224 is connected to the top end of the optical path circular tube 221. The sample loading platform 224 is in the shape of a circular plate and is provided with a plurality of placement holes for placing samples; the radiation protection support frame 225 is connected to the bottom end of the optical path circular tube 221. The radiation protection support frame 225 is a structure that is larger than the radiation protection screen 222 and has a similar shape to the radiation protection screen 222. The radiation protection support frame 225 supports the first connecting tube 242 and the second window connecting flange 243 to form a support space.

[0061] When this embodiment is used, the vacuum layer of the first Dewar assembly 1 and the sample chamber are first evacuated to a high vacuum state, and then liquid nitrogen is stored in the liquid nitrogen chamber of the first Dewar assembly 1 and liquid helium is stored in the liquid helium chamber.

[0062] Place the sample on the sample carrier 224, and connect the radiation protection support frame 225 to the window flange 24, then build the radiation protection component 22 into the bellows 213, and then connect the window flange 24 to the bellows 213 in a vacuum-tight manner, evacuate the bellows 213 to a high vacuum through the vacuum port 4, and then open the valve 3, and send the radiation protection component 22 into the sample chamber by compressing the bellows 213 upwards until the sample on the top of the radiation protection component 22 reaches the appropriate position, and the radiation protection elastic cover 223 can abut against the inner wall of the first Dewar assembly 1. If you choose to use exchange gas for cooling, you can use the vacuum port 4 and the exchange gas port 17 on the top to cool the sample or measuring device for testing. After the test is completed, the radiation protection component 22 is moved from the sample chamber into the bellows 213 by pulling the bellows 213 downward, then the valve 3 is closed, and helium at room temperature is introduced into the bellows 213 through the vacuum port 4. After the sample or measuring device returns to room temperature, the window flange 24 and the bellows 213 are disassembled and the sample or measuring device is taken out.

[0063] During use of this embodiment, the sample is installed and then placed in the sample chamber, and then retracted after testing, which produces many advantages. First, only a small number of parts such as the vacuum flange 25 need to be disassembled, which is simpler to operate than the current need to disassemble multiple parts, thereby improving test efficiency. Furthermore, after the test is completed, the first Dewar assembly 1 and the second Dewar assembly 2 can be disconnected through the valve 3, and room temperature recovery can be completed in the bellows 213 without the need to set up a room temperature recovery device separately, thereby saving costs. In addition, during use of this embodiment, the radiation protection component 22 can achieve good heat conduction and temperature control. Therefore, a single-layer optical window 23 can meet the temperature required for the test, greatly reducing the light loss rate during transmission. It has strong scalability and can introduce optical measurement methods such as optical fiber.

[0064] Example 2:

[0065] like Figure 11 、 Figure 12 、 Figure 13 As shown, in this embodiment, based on the first embodiment, the first Dewar assembly 1 has an overall structure of being thick at the top and thin at the bottom, wherein the sample chamber is located at the thin part of the first Dewar assembly 1 .

[0066] The first Dewar assembly 1 includes a first shell 11, a second shell 12, a third shell 13, and a fourth shell 14, which are sequentially spaced and sleeved from the outside to the inside. The first shell 11, the second shell 12, the third shell 13, and the fourth shell 14 are all thick at the top and thin at the bottom, and the bottom ends of the first shell 11, the second shell 12, the third shell 13, and the fourth shell 14 are connected together.

[0067] Specifically, a first vacuum layer is formed between the first shell 11 and the second shell 12, and a vacuum extraction tube is provided on the top of the first shell 11. The upper part of the first shell 11 is a thicker cylindrical structure, and the lower part is a thinner cylindrical structure, and the two are sealed and connected. The structure of the second shell 12 is similar to that of the first shell, but is smaller in size; a liquid nitrogen chamber is formed between the second shell 12 and the third shell 13, and the second shell 12 has a pipe for inputting liquid nitrogen, which passes through the first shell 11 to the outside; a second vacuum layer is formed between the third shell 13 and the fourth shell 14, and the first vacuum layer is connected to the second vacuum layer; a liquid helium chamber is formed in the fourth shell 14, and the liquid helium chamber is connected to the sample chamber. The first Dewar assembly 1 also includes an infusion accessory 15 for inputting liquid helium into the sample chamber. The infusion accessory 15 passes through the first shell 11, the second shell 12, the third shell 13 and the fourth shell 14 in sequence and extends into the interior of the fourth shell 14.

[0068] The first Dewar assembly 1 also includes a fifth shell 16 and an exchange gas port 17. One end of the exchange gas port 17 is connected to the bottom end of the fourth shell 14, and the top of the fifth shell 16 is connected to the other end of the exchange gas port 17. The fifth shell 16 is located inside the third shell 13, and the bottom of the fifth shell 16 is connected to the third shell 13. The fifth shell 16 contains a sample chamber.

[0069] The first Dewar assembly 1 also includes a shell flange 18, wherein the bottom ends of the first shell 11, the second shell 12, the third shell 13, and the fifth shell are directly or indirectly connected to the shell flange 18; because the inner diameters of the shells 11 are different, each shell can be directly connected to the shell flange 18, or connected to the shell flange 18 through a switching sleeve 19. For example, after the bottom ends of the second shell 12, the third shell 13, and the fifth sleeve 16 are connected to the connecting plate, a step-like structure is formed at the connecting plate, which is then connected to the switching sleeve 19, and the bottom of the switching sleeve 19 is then connected to the shell flange 18; in short, the bottoms of the first shell 11, the second shell 12, and the third shell 13 are closed ends, the fourth shell 14 and the fifth shell 16 are coaxially arranged up and down, and the two are connected through the exchange air port 17. The fifth shell 16 is used for the entry of the radiation protection component 22. The outer surface of the third shell 13 is fixedly installed with alternating multiple layers of aluminum film and vacuum insulation fiber paper. The inner surfaces of the first shell 11 and the third shell 13 are provided with activated carbon for adsorbing difficult-to-extract gases in a vacuum to facilitate vacuuming.

[0070] like Figure 16 、 Figure 17 、 Figure 18As shown, the bellows 213 is compressed to send the radiation protection component 22 into the sample cavity until the sample on the top of the radiation protection component 22 reaches the appropriate position, and the radiation protection elastic cover 223 can abut against the inner wall of the adapter sleeve 19. At this time, liquid nitrogen is introduced into the fourth shell 14 through the infusion accessory 15, and the temperature in the sample cavity is lowered through the exchange gas port 17.

[0071] This embodiment adopts a first Dewar assembly 1 that is thick at the top and thin at the bottom. The interior of the thin part is a sample cavity. The sample cavity can be made as large as possible while meeting the low temperature requirements, which is convenient for use in microscopic imaging devices such as scanning probe microscopes; and the entire structure is compact. The Dewar is suitable for extreme conditions with limited space, such as being placed within the aperture of a magnet. The advantage of this embodiment is that it can minimize the volume occupied by the Dewar itself and provide a large sample cavity volume in a smaller space; the sample cavity is large, such as in this embodiment, the sample cavity is large enough in a limited space, the sample cavity can be 120 mm, the size of a microscope is generally more than 20 mm in diameter, and together with other optical parts, it does not exceed 100 mm, which is convenient for use in microscopic imaging devices such as scanning probe microscopes.

[0072] When using this embodiment, the first vacuum layer, the second vacuum layer, and the sample chamber are first evacuated to a high vacuum state. Liquid nitrogen is then stored in the liquid nitrogen chamber, and liquid helium is stored in the liquid helium chamber. During use, a cooling method is optional. This embodiment can utilize both gas exchange and direct solid-state heat conduction cooling, providing wide practicality.

[0073] In actual use, it can also be changed for magnets of different calibers, but this embodiment can minimize the volume occupied by the Dewar itself and provide a large sample chamber volume in a smaller space.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A telescopic liquid helium dewar using a single-layer optical window, characterized in that: It includes a first Dewar assembly and a second Dewar assembly, both of which are vacuum sealed structures; the bottom of the first Dewar assembly is connected to the second Dewar assembly, and the bottom of the first Dewar assembly is a sample chamber; The second Dewar assembly includes a telescopic tube assembly, a radiation shielding assembly, and a single-layer optical window; the top of the telescopic tube assembly is connected to the bottom of the first Dewar assembly, the single-layer optical window is connected to the bottom of the telescopic tube assembly, the radiation shielding assembly is located inside the telescopic tube assembly and is coaxially arranged, and the top of the radiation shielding assembly extends into the sample chamber after the telescopic tube assembly is compressed; It also includes a window flange, the top of which is connected to the bottom of the telescopic tube assembly, the single-layer optical window is connected to the bottom of the window flange, and the bottom end support of the radiation protection assembly is connected to the inner end surface of the window flange; The radiation protection assembly includes at least one optical circular tube and a plurality of radiation protection screens, wherein the plurality of radiation protection screens are connected to the outside of the optical circular tube at intervals, and the optical circular tube is coaxially arranged with the single-layer optical window; It also includes a valve capable of realizing the on-off connection between the first dewar assembly and the second dewar assembly, wherein the bottom end of the first dewar assembly and the top end of the second dewar assembly are both connected to the sealing valve; The first Dewar assembly is generally in a structure of being thick at the top and thin at the bottom, wherein the sample chamber is located at the thin part of the first Dewar assembly.

2. The telescopic liquid helium dewar with a single-layer optical window according to claim 1, characterized in that: The telescopic tube assembly includes a first flange, a second flange, a bellows, and multiple drive connecting rods. The first flange and the second flange are respectively connected to the two ends of the bellows. Multiple drive connecting rods are arranged in a circular array on the outer circumference of the bellows. The top end of the drive connecting rod is connected to the first flange, and the second flange is connected to the drive connecting rod in a liftable manner.

3. The telescopic liquid helium dewar with a single-layer optical window according to claim 1, characterized in that: The radiation protection component also includes a radiation protection elastic cover capable of contacting the inner wall of the first Dewar, the radiation protection elastic cover is connected to the middle part of the optical path circular tube, and the radiation protection screen is a cylindrical structure.

4. The telescopic liquid helium dewar with a single-layer optical window according to claim 1, characterized in that: The first Dewar assembly includes a first shell, a second shell, a third shell, and a fourth shell that are sequentially spaced and sleeved from the outside to the inside. The first shell, the second shell, the third shell, and the fourth shell are all structures that are thick at the top and thin at the bottom, and the bottom ends of the first shell, the second shell, the third shell, and the fourth shell are connected together.

5. The telescopic liquid helium dewar with a single-layer optical window according to claim 4, characterized in that: It also includes a fifth shell and an exchange gas port, one end of the exchange gas port is connected to the bottom end of the fourth shell, the top of the fifth shell is connected to the other end of the exchange gas port, the fifth shell is located inside the third shell, and the bottom of the fifth shell is connected to the third shell, and the fifth shell contains a sample chamber.

6. The telescopic liquid helium dewar with a single-layer optical window according to claim 4, characterized in that: A first vacuum layer is formed between the first shell and the second shell, a liquid nitrogen chamber is formed between the second shell and the third shell, a second vacuum layer is formed between the third shell and the fourth shell, a liquid helium chamber is formed in the fourth shell, the liquid helium chamber is communicated with the sample chamber, and the first vacuum layer is communicated with the second vacuum layer.

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