Novel long-tail dewar and water-cooled magnet apparatus

Abstract

The application discloses a novel long-tail Dewar device and a water-cooled magnet device. The novel long-tail Dewar device comprises a Dewar shell, a low-temperature Dewar assembly and a sample rod assembly. The low-temperature Dewar assembly comprises an upper cooling and heat-insulating part and a lower cooling and heat-insulating part which are connected in series, and a sample rod sleeve which penetrates through the upper cooling and heat-insulating part and extends into the lower cooling and heat-insulating part. The upper cooling and heat-insulating part comprises a cover, a first upper heat-insulating sleeve, a second upper heat-insulating sleeve and a liquid helium switch structure. The lower cooling and heat-insulating part comprises a lower heat-insulating sleeve which is connected with the bottom of the first upper heat-insulating sleeve, and a flow guide pipe. The water-cooled magnet device comprises the novel long-tail Dewar device. The application has the advantages that the low temperature in the second upper heat-insulating sleeve and the lower heat-insulating sleeve is reduced from being transmitted outward, and the flow guide pipe is arranged to reduce the low temperature from being transmitted outward during the flow of the liquid helium, so that the cooling and temperature reduction precision of the sample end of the sample rod assembly is ensured, and the low-temperature requirement of the superconducting coil entering the superconducting state is met.

Description

Technical Field

[0001] This invention relates to the field of water-cooled magnet technology, specifically to a novel long-tailed Dewar device and a water-cooled magnet device. Background Technology

[0002] Liquid helium and liquid nitrogen have boiling points of 4.2K and 77K at atmospheric pressure, respectively. Using liquid helium and liquid nitrogen as cold sources and assisted by heat exchange with the gaseous working fluid, any temperature above their boiling points can be obtained. Traditional cryogenic Dewars can achieve variable-temperature isostatic control, but they cannot reduce or eliminate environmental current ripple and vibration in harsh experimental environments, such as those caused by water-cooled magnets and other experimental devices. This leads to distortion of scientific experimental data and the loss of some important scientific discoveries.

[0003] Chinese invention patent document CN121215385A discloses a water-cooled magnet magnetic field ripple shielding system and its usage method. The water-cooled magnet magnetic field ripple shielding system includes a thermostat and a superconducting block. The superconducting block is located in the thermostat cavity of the thermostat and is coaxial with the room temperature hollow cavity at the center of the thermostat. Liquid nitrogen is injected into the thermostat cavity. When the superconducting block enters the superconducting state, the sum of the change in magnetic flux induced by the water-cooled magnet power supply inside the annular cavity of the superconducting block and the change in magnetic flux generated by the induced current of the superconducting block itself is zero, and the magnetic flux in the room temperature hollow cavity is in a steady state.

[0004] Chinese utility model patent document with publication number CN204943012U discloses a cryogenic Dewar chamber. By designing a cryogenic Dewar chamber, using stainless steel materials and a double-layer insulation system, the problems of high vacuum leakage rate and poor insulation performance are solved, achieving low leakage rate, high efficiency insulation and low liquid helium consumption, reducing costs and extending liquid helium residence time.

[0005] The aforementioned patents all disclose the method of injecting liquid nitrogen to cool the superconducting block or superconducting magnet into a superconducting state. However, for the long-tailed cryogenic Dewar structure, the liquid nitrogen injection channel is relatively long, and its cooling capacity is easily absorbed by the external environment, which cannot meet the low-temperature requirements for the superconducting block to enter a superconducting state. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to meet the low-temperature requirements for superconducting coils to enter the superconducting state.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A novel long-tailed Dewar device includes a Dewar shell, a low-temperature Dewar assembly, and a sample rod assembly. The Dewar shell is a cylindrical structure that is thicker at the top and thinner at the bottom and open at the top. The low-temperature Dewar assembly is sealed inside the Dewar shell and corresponds to its shape. The sample end of the sample rod assembly extends into the bottom of the low-temperature Dewar assembly. The low-temperature Dewar assembly includes an upper cooling insulation section and a lower cooling insulation section that are connected vertically, as well as a sample rod sleeve that penetrates the upper cooling insulation section and extends into the lower cooling insulation section. The upper cooling insulation section is located inside the coarse structure of the Dewar shell, the lower cooling insulation section is located inside the thin structure of the Dewar shell, and the sample rod assembly is located inside the sample rod sleeve. The upper cooling insulation part includes a cover, a first upper insulation sleeve, a second upper insulation sleeve, and a liquid helium switch structure. The cover is a sealing cap located at the upper opening of the Dewar shell. The top of the first upper insulation sleeve is open and is located inside the robust structure of the Dewar shell, forming a first vacuum chamber with a gap between it and the Dewar shell. The second upper insulation sleeve is located inside the first upper insulation sleeve and forms a second vacuum chamber with a gap between it and the first upper insulation sleeve. The first vacuum chamber and the second vacuum chamber are connected. A liquid nitrogen chamber is provided on the wall of the first upper insulation sleeve. The inner cavity of the second upper insulation sleeve is a liquid helium chamber. One end of the liquid helium switch structure is located on the cover, and the other end is located inside the second upper insulation sleeve. The lower cooling insulation section includes a lower insulation sleeve and a guide tube connected to the bottom of the first upper insulation sleeve. The lower insulation sleeve is set inside the thin structure of the Dewar shell and forms a third vacuum chamber that communicates with the first vacuum chamber through a gap. One end of the sample rod sleeve passes through the second upper insulation sleeve and extends into the bottom of the lower insulation sleeve. One end of the guide tube set inside the sample rod sleeve is set at the bottom of the sample rod sleeve, and the other end is connected to the liquid helium switch structure.

[0009] This invention cools the sample rod assembly inside the sample rod sleeve using liquid nitrogen and liquid helium chambers. A first, second, and third vacuum chamber provide insulation for the second upper and lower insulating sleeves, reducing the outward leakage of low temperatures from these sleeves and ensuring precise cooling of the sample end of the sample rod assembly. Furthermore, a flow guide tube directs liquid helium from the liquid helium chamber to the bottom of the sample rod sleeve. This not only allows the liquid helium to flow rapidly into the superconducting coil position at the sample end of the sample rod assembly, reducing the outward leakage of low temperatures during flow, but also reduces the flow area of ​​the liquid helium, further minimizing the outward leakage of low temperatures. This ensures precise cooling of the sample end of the sample rod assembly, meeting the low-temperature requirements for the superconducting coil to enter the superconducting state.

[0010] Preferably, the liquid helium switch structure includes a needle valve and a valve seat. One end of the needle valve is located outside the cap, and the other end extends through the cap into the interior of the second upper insulation sleeve and cooperates with the valve seat located inside the second upper insulation sleeve. The valve seat is provided with a flow guiding channel and a needle valve hole that can seal the insertion of the needle valve. One end of the flow guiding channel communicates with the inner cavity of the second upper insulation sleeve through the needle valve hole, and the other end communicates with the flow guiding tube.

[0011] Preferably, the cover is provided with a first flange tube, the flange end of the first flange tube is located outside the cover, the end away from the flange passes through the cover and communicates with the second upper insulation sleeve, one end of the needle valve is detachably sealed to the flange end of the first flange tube, and the other end passes through the first flange tube and extends into the second upper insulation sleeve.

[0012] Preferably, the cap is provided with multiple second flanges that communicate with the liquid nitrogen chamber.

[0013] Preferably, the cover is provided with a third flange tube that communicates with the inner cavity of the Dewar shell.

[0014] Preferably, the outer walls of both the first and second upper insulating sleeves are provided with an insulating layer.

[0015] Preferably, the Dewar housing includes an upper housing and a lower housing connected together, the upper housing having a larger diameter than the lower housing, the upper cooling and heat insulation part being disposed inside the upper housing, the lower cooling and heat insulation part being disposed inside the lower housing, and the sealing cover being disposed at the top opening of the upper housing.

[0016] Preferably, the sample rod assembly includes a sample rod, an aviation plug, a sample stage, and a superconducting coil. The sample rod is sealed to the top of the sample rod sleeve via the aviation plug, and the other end extends into the bottom of the sample rod sleeve and is connected to the sample stage. The sample stage has a sample cavity inside, and a superconducting coil is disposed on the sample stage to enclose the sample cavity.

[0017] Preferably, an insulating sleeve is provided on the inner wall of the superconducting coil.

[0018] Preferably, the present invention also provides a water-cooled magnet device, including the novel long-tailed Dewar device described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are: The sample rod assembly inside the sample rod sleeve is cooled by liquid nitrogen and liquid helium chambers. The first, second, and third vacuum chambers provide insulation for the second upper and lower insulating sleeves, reducing the outward leakage of low temperatures from these sleeves and ensuring precise cooling of the sample end of the sample rod assembly. Furthermore, a flow guide tube directs liquid helium from the liquid helium chamber to the bottom of the sample rod sleeve. This not only allows the liquid helium to flow rapidly into the superconducting coil position at the sample end of the sample rod assembly, reducing the outward leakage of low temperatures during flow, but also reduces the flow area of ​​the liquid helium, further minimizing the outward leakage of low temperatures. This ensures precise cooling of the sample end of the sample rod assembly, meeting the low-temperature requirements for the superconducting coil to enter the superconducting state. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the novel long-tailed Dewar device according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the Dewar shell according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the low-temperature Dewar assembly according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the cooling and heat insulation part in an embodiment of the present invention; Figure 5 This is a schematic diagram of the valve seat structure according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the cooling and heat insulation section in an embodiment of the present invention; Figure 7 This is a schematic diagram of the sample rod assembly according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the structure of the water-cooled magnet device according to an embodiment of the present invention.

[0021] In the diagram: 1. Dewar outer shell; 11. Upper outer shell; 12. Lower outer shell; 2. Cryogenic Dewar assembly; 201. First vacuum chamber; 202. Second vacuum chamber; 203. Third vacuum chamber; 21. Upper cooling and insulation section; 211. Cover; 212. First upper insulation sleeve; 2121. Liquid nitrogen chamber; 213. Second upper insulation sleeve; 2131. Liquid helium chamber; 214. Liquid helium switch structure; 2141. Needle valve; 2142. Valve seat; 2 1421, Flow channel; 21422, Needle valve hole; 215, Second flange tube; 216, Third flange tube; 217, First flange tube; 218, Fourth flange tube; 22, Lower cooling insulation section; 221, Lower insulation sleeve; 222, Flow guide tube; 23, Sample rod sleeve; 3, Sample rod assembly; 31, Sample rod; 32, Aviation plug; 33, Sample stage; 331, Sample chamber; 34, Superconducting coil; 35, Insulating sleeve. Detailed Implementation

[0022] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with the accompanying drawings.

[0023] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] In this application, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise expressly and specifically limited.

[0025] See Figure 1 This embodiment discloses a novel long-tailed Dewar device, including a Dewar shell 1, a low-temperature Dewar assembly 2, and a sample rod assembly 3. The Dewar shell 1 is a cylindrical structure that is thicker at the top and thinner at the bottom and has an open top. The low-temperature Dewar assembly 2 is sealed inside the Dewar shell 1 and corresponds to its shape. The sample end of the sample rod assembly 3 extends into the bottom of the low-temperature Dewar assembly 2.

[0026] See Figure 2 The Dewar shell 1 includes an upper shell 11 and a lower shell 12 connected to each other. The diameter of the upper shell 11 is larger than the diameter of the lower shell 12, so that the Dewar shell 1 is formed into a cylindrical structure that is thicker at the top and thinner at the bottom and open at the top.

[0027] See Figure 3 The low-temperature Dewar assembly 2 includes an upper cooling and heat insulation part 21 and a lower cooling and heat insulation part 22 that are connected vertically, and a sample rod sleeve 23 that passes through the upper cooling and heat insulation part 21 and extends into the lower cooling and heat insulation part 22. The upper cooling and heat insulation part 21 is disposed inside the upper outer shell 11, the lower cooling and heat insulation part 22 is disposed inside the lower outer shell 12, and the sample rod assembly 3 is disposed inside the sample rod sleeve 23.

[0028] See Figure 4 The upper cooling and heat insulation part 21 includes a cover 211, a first upper heat insulation sleeve 212, a second upper heat insulation sleeve 213, and a liquid helium switch structure 214. The cover 211 is sealed at the upper opening of the upper outer shell 11 and is connected to the upper outer shell 11 by multiple screws. Two sets of sealing rings are provided at the upper opening of the upper outer shell 11 for sealing.

[0029] The top of the first upper insulating sleeve 212 is open and coaxially disposed inside the upper outer shell 11, forming a first vacuum chamber 201 with a gap between it and the inner wall of the upper outer shell 11. The second upper insulating sleeve 213 is coaxially disposed inside the first upper insulating sleeve 212, forming a second vacuum chamber 202 with a gap between it and the inner wall of the first upper insulating sleeve 212. The first vacuum chamber 201 and the second vacuum chamber 202 are connected. Similarly, the second upper insulating sleeve 213 is coaxially sleeved outside the sample rod sleeve 23. The cylinder wall of the first upper insulating sleeve 212 is provided with a sealed liquid nitrogen chamber 2121, and the inner cavity of the second upper insulating sleeve 213 is a liquid helium chamber 2131, which is used to cool down the sample rod assembly 3 inside the sample rod sleeve 23.

[0030] The cover 211 is provided with multiple second flange pipes 215 that communicate with the liquid nitrogen chamber 2121. Specifically, one end of the second flange pipe 215 is located outside the cover 211 and is used to connect with the external liquid nitrogen input system and liquid nitrogen output system to realize the input of liquid nitrogen and the discharge of nitrogen gas in the liquid nitrogen chamber 2121, thereby realizing the cooling of the internal structure of the first upper insulating sleeve 212. The other end of the second flange pipe 215 passes through the cover 211 and communicates with the liquid nitrogen chamber 2121.

[0031] The cover 211 is provided with a third flange pipe 216 that communicates with the inner cavity of the upper outer shell 11. It is used to evacuate the first vacuum chamber 201 and the second vacuum chamber 202 and monitor the vacuum level. It forms a vacuum zone with the second upper insulating sleeve 213 to isolate the outside world and thus achieve the heat insulation effect of the second upper insulating sleeve 213.

[0032] The cover 211 is also provided with a first flange pipe 217. The flange end of the first flange pipe 217 is located outside the cover 211, and the end away from the flange passes through the cover 211 and is connected to the second upper insulation sleeve 213.

[0033] Furthermore, the outer walls of both the first upper insulating sleeve 212 and the second upper insulating sleeve 213 are provided with an insulating layer for heat insulation, thereby reducing the outward transmission of low temperature from the second upper insulating sleeve 213.

[0034] Furthermore, both the second flange pipe 215 and the first flange pipe 217, which are located inside the upper outer shell 11, are corrugated pipes in order to increase the cryogenic transmission path of the liquid nitrogen chamber 2121 and the liquid helium chamber 2131 and reduce the transmission of cryogenic temperature to the outside.

[0035] See also Figure 4 The liquid helium switch structure 214 has one end located outside the cap 211 and the other end located inside the second upper insulating sleeve 213. The liquid helium switch structure 214 includes a needle valve 2141 and a valve seat 2142. One end of the needle valve 2141 is detachably and sealingly connected to the flange end of the first flange tube 217, and the other end extends through the first flange tube 217 into the interior of the second upper insulating sleeve 213 and cooperates with the valve seat 2142 fixed inside the second upper insulating sleeve 213. (See reference...) Figure 5 The valve seat 2142 is provided with a flow guide channel 21421 and a needle valve hole 21422. One end of the flow guide channel 21421 is connected to the inner cavity of the second upper insulation sleeve 213 through the needle valve hole 21422, and the other end is connected to the lower cooling insulation part 22. The needle valve 2141 can be inserted into the needle valve hole 21422 to seal the flow guide channel 21421, so that the flow guide channel 21421 is no longer connected to the inner cavity of the second upper insulation sleeve 213.

[0036] Furthermore, both the end of the needle valve 2141 and the needle valve hole 21422 are V-shaped.

[0037] See Figure 5 and Figure 6 The lower cooling insulation section 22 includes a lower insulation sleeve 221 connected to the bottom of the first upper insulation sleeve 212 and a guide pipe 222. The lower insulation sleeve 221 is disposed inside the lower outer shell 12 and forms a third vacuum chamber 203 with a gap between it and the inner wall of the lower outer shell 12, which communicates with the first vacuum chamber 201, thereby achieving the insulation effect inside the lower outer shell 12. One end of the sample rod sleeve 23 passes through the second upper insulation sleeve 213 and extends into the bottom of the lower insulation sleeve 221. One end of the guide pipe 222 disposed inside the sample rod sleeve 23 is disposed at the bottom of the sample rod sleeve 23, and the other end is connected to the guide channel 21421 on the valve seat 2142.

[0038] A fourth flange pipe 218 is also provided perpendicular to the sample rod sleeve 23 located outside the cover 211, which is used for evacuating the sample rod sleeve 23 in the early stage and venting helium in the later stage.

[0039] See Figure 7 The sample rod assembly 3 includes a sample rod 31, an aviation plug 32, a sample stage 33, and a superconducting coil 34. The sample rod 31 is sealed to the top of the sample rod sleeve 23 via the aviation plug 32, and the other end extends into the bottom of the sample rod sleeve 23 and is connected to the sample stage 33. The sample stage 33 has a sample cavity 331 for placing the sample. The superconducting coil 34 is arranged on the sample stage 33 to wrap the sample cavity. The superconducting coil 34 achieves a superconducting state to reduce or even eliminate the ripple signal of the external environment. The inner wall of the superconducting coil 34 is provided with an insulating sleeve 35, which not only provides electrical insulation between the sample stage 33 and the superconducting coil 34, but also limits the position of the superconducting coil.

[0040] Furthermore, the sample rod 31 and the sample stage 33 are respectively provided with a wiring cavity and a wiring hole. The wiring hole is connected to the wiring cavity and is used for the arrangement of scientific experimental wires, superconducting coil signal lines, temperature monitoring lines, etc., and is transmitted to scientific research equipment through the aviation plug 32.

[0041] Furthermore, an insulation layer is provided on the outer wall of the sample rod 31 to reduce radiant heat.

[0042] The working principle of this embodiment is as follows: When the V-shaped needle valve 2141 is fully engaged with the needle valve orifice 21422, the liquid helium in the liquid helium chamber 2131 no longer flows into the bottom of the sample rod sleeve 23 through the guide channel 21421. The sample rod assembly 3 inside the sample rod sleeve 23 can then be removed to replace the experimental sample. When the sample rod assembly 3 is installed and a scientific experiment is to be conducted, the sample rod sleeve 23 is evacuated through the fourth flange tube 218 to achieve the required vacuum level. The needle valve 2141 is then turned upwards with a wrench, disengaging the V-shaped tip of the needle valve 2141 from the needle valve orifice 21422. The liquid helium in the liquid helium chamber 2131 then flows sequentially through the needle valve orifice 21422, the guide channel 21421, and the guide tube 222 into the bottom of the sample rod sleeve 23. This ensures that the temperature at the sample stage 33 and the superconducting coil 34 inside the sample rod assembly 3 reaches the test temperature, thereby ensuring that the superconducting coil 34 reaches a superconducting state to reduce or even eliminate ripple signals from the external environment.

[0043] In this embodiment, the sample rod assembly 3 inside the sample rod sleeve 23 is cooled down through the liquid nitrogen chamber 2121 and the liquid helium chamber 2131. The first vacuum chamber 201, the second vacuum chamber 202, and the third vacuum chamber 203 provide insulation for the second upper insulating sleeve 213 and the lower insulating sleeve 221, reducing the outward leakage of low temperatures from the second upper insulating sleeve 213 and the lower insulating sleeve 221, thereby ensuring the accuracy of cooling the sample end of the sample rod assembly 3. Furthermore, since this Dewar device is a novel long-tailed Dewar device, the sample rod sleeve... The longer section 23 inside the lower insulating sleeve 221 guides the liquid helium in the liquid helium chamber 2131 to the bottom of the sample rod sleeve 23 through the guide tube 222. This not only allows the liquid helium to flow quickly into the sample stage 33 and the superconducting coil 34 within the sample rod assembly 3, reducing the outward transmission of low temperature during its flow, but also reduces the flow area of ​​the liquid helium by the guide tube 222, further reducing the outward transmission of low temperature during its flow. This ensures the accuracy of cooling the sample end of the sample rod assembly 3, meeting the low temperature requirements for the superconducting coil 34 to enter the superconducting state.

[0044] For further details, please refer to [link / reference]. Figure 8 This embodiment also provides a water-cooled magnet device, including the novel long-tailed Dewar device described above.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0046] The above embodiments are merely illustrative of implementation methods of the invention. The scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A novel long-tailed Dewar device, characterized in that: It includes a Dewar shell, a low-temperature Dewar assembly, and a sample rod assembly. The Dewar shell is a cylindrical structure that is thicker at the top and thinner at the bottom and open at the top. The low-temperature Dewar assembly is sealed inside the Dewar shell and corresponds to its shape. The sample end of the sample rod assembly extends into the bottom of the low-temperature Dewar assembly. The low-temperature Dewar assembly includes an upper cooling insulation section and a lower cooling insulation section that are connected vertically, as well as a sample rod sleeve that penetrates the upper cooling insulation section and extends into the lower cooling insulation section. The upper cooling insulation section is located inside the coarse structure of the Dewar shell, the lower cooling insulation section is located inside the thin structure of the Dewar shell, and the sample rod assembly is located inside the sample rod sleeve. The upper cooling insulation part includes a cover, a first upper insulation sleeve, a second upper insulation sleeve, and a liquid helium switch structure. The cover is a sealing cap located at the upper opening of the Dewar shell. The top of the first upper insulation sleeve is open and is located inside the robust structure of the Dewar shell, forming a first vacuum chamber with a gap between it and the Dewar shell. The second upper insulation sleeve is located inside the first upper insulation sleeve and forms a second vacuum chamber with a gap between it and the first upper insulation sleeve. The first vacuum chamber and the second vacuum chamber are connected. A liquid nitrogen chamber is provided on the wall of the first upper insulation sleeve. The inner cavity of the second upper insulation sleeve is a liquid helium chamber. One end of the liquid helium switch structure is located on the cover, and the other end is located inside the second upper insulation sleeve. The lower cooling insulation section includes a lower insulation sleeve and a guide tube connected to the bottom of the first upper insulation sleeve. The lower insulation sleeve is set inside the thin structure of the Dewar shell and forms a third vacuum chamber that communicates with the first vacuum chamber through a gap. One end of the sample rod sleeve passes through the second upper insulation sleeve and extends into the bottom of the lower insulation sleeve. One end of the guide tube set inside the sample rod sleeve is set at the bottom of the sample rod sleeve, and the other end is connected to the liquid helium switch structure.

2. A novel long-tailed Dewar device according to claim 1, characterized in that: The liquid helium switch structure includes a needle valve and a valve seat. One end of the needle valve is located outside the cap, and the other end extends through the cap into the interior of the second upper insulation sleeve and cooperates with the valve seat located inside the second upper insulation sleeve. The valve seat is provided with a flow channel and a needle valve hole that can seal the insertion of the needle valve. One end of the flow channel is connected to the inner cavity of the second upper insulation sleeve through the needle valve hole, and the other end is connected to the flow tube.

3. A novel long-tailed Dewar device according to claim 2, characterized in that: The cover is provided with a first flange tube. The flange end of the first flange tube is located outside the cover. The end away from the flange passes through the cover and communicates with the second upper insulation sleeve. One end of the needle valve is detachably sealed to the flange end of the first flange tube, and the other end passes through the first flange tube and extends into the second upper insulation sleeve.

4. A novel long-tailed Dewar device according to claim 1, characterized in that: The cover is equipped with multiple second flanges that communicate with the liquid nitrogen chamber.

5. A novel long-tailed Dewar device according to claim 1, characterized in that: The cover is equipped with a third flange that communicates with the inner cavity of the Dewar shell.

6. A novel long-tailed Dewar device according to claim 1, characterized in that: Both the outer walls of the first and second upper insulating sleeves are provided with insulating layers.

7. A novel long-tailed Dewar device according to claim 1, characterized in that: The Dewar housing includes an upper housing and a lower housing connected together. The diameter of the upper housing is larger than that of the lower housing. The upper cooling and heat insulation part is located inside the upper housing, and the lower cooling and heat insulation part is located inside the lower housing. The sealing cover is located at the top opening of the upper housing.

8. A novel long-tailed Dewar device according to claim 1, characterized in that: The sample rod assembly includes a sample rod, an aviation plug, a sample stage, and a superconducting coil. The sample rod is sealed to the top of the sample rod sleeve via the aviation plug, and the other end extends into the bottom of the sample rod sleeve and is connected to the sample stage. The sample stage has a sample cavity inside, and a superconducting coil is placed on the sample stage to enclose the sample cavity.

9. A novel long-tailed Dewar device according to claim 1, characterized in that: An insulating sleeve is provided on the inner wall of the superconducting coil.

10. A water-cooled magnet device, characterized in that: The novel long-tailed Dewar device includes any one of claims 1-9 above.

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