A small cryostat

Abstract

The application provides a small cryostat, which comprises a tube shell and a liquid inlet outer tube connected with the tube shell; the tube shell is internally provided with a sample cavity and a vacuum cavity; the top of the sample cavity is provided with a sample insertion opening, the lower portion of the sample cavity is provided with a heat exchanger and a heating element arranged on the surface of the heat exchanger, and the outlet of the heat exchanger is communicated with the sample cavity; the liquid inlet outer tube is internally provided with a liquid inlet inner tube, a liquid inlet conveying tube and a gas return tube, and the proximal end of the liquid inlet inner tube is provided with a sealing joint; the sealing joint is provided with a liquid inlet interface and a gas return interface, the liquid inlet interface is located at the central portion of the liquid inlet inner tube, the gas return interface is located at the position close to the side wall of the liquid inlet inner tube on the outer side of the liquid inlet interface, and the port of the liquid inlet interface at the inner side end of the liquid inlet inner tube is a plug interface; the liquid inlet interface is connected with the inlet of the heat exchanger through the liquid inlet conveying tube; and the gas return interface is communicated with the sample cavity through the gas return tube. The application has the advantages of compact structure, small size, convenient sample replacement, stable temperature control and wide temperature range.

Description

Technical Field

[0001] This invention relates to the field of cryogenic engineering technology, and specifically to a small cryogenic thermostat. Background Technology

[0002] Currently, in physical science research and medical testing, the measurement of physical properties and optical waveband testing at low temperatures are increasingly becoming research hotspots. Low temperature and vacuum environments are indispensable and crucial conditions in the testing process. Maintaining a low temperature environment relies on a reliable and temperature-stable cryostat. Cryostats can provide long-term low-temperature environments for various scientific and medical tests on samples at low temperatures. However, existing cryostats still have many shortcomings, such as: crude design, unstable temperature control, narrow temperature range, high liquid helium consumption, cumbersome sample replacement, long testing cycles, and high operational difficulty. Summary of the Invention

[0003] In order to solve the technical problems existing in the background art, the present invention proposes a small low-temperature thermostat.

[0004] The present invention proposes a small low-temperature thermostat, comprising: a vertically arranged shell and a horizontally arranged inlet outer tube connected to the shell;

[0005] The tube shell has a sample chamber and a vacuum chamber coaxially arranged outside the sample chamber; the top of the sample chamber is provided with a sample insertion port for sample insertion, and a heat exchanger and a heating element arranged on the surface of the heat exchanger are provided below the sample chamber and inside the vacuum chamber, and the outlet of the heat exchanger is connected to the sample chamber.

[0006] The outer inlet tube is equipped with an inner inlet tube, an inlet delivery tube, and a return gas tube. The distal end of the inner inlet tube extends to the outside of the outer inlet tube, and a sealing joint is installed at the proximal end of the inner inlet tube. The sealing joint is equipped with an inlet port and a return gas port. Both the inlet port and the return gas port are connected to the inside of the inner inlet tube. The inlet port is located at the center of the inner inlet tube, and the return gas port is located outside the inlet port near the side wall of the inner inlet tube. The port of the inner end of the inner inlet tube is configured as an insertion port for the liquid helium delivery tube to be inserted.

[0007] The liquid inlet is connected to the inlet of the heat exchanger via the liquid inlet delivery pipe; the gas return inlet is connected to the sample chamber via the gas return pipe.

[0008] Preferably, it further includes a vacuum system for maintaining and obtaining vacuum conditions. The vacuum system includes a first vacuum line and a second vacuum line, wherein the first vacuum line is connected to the sample chamber and the second vacuum line is connected to the vacuum chamber.

[0009] Preferably, a sample chamber safety valve and a shut-off valve are installed in the first vacuum line.

[0010] Preferably, the casing includes an inner tube and an outer tube; a headstock is installed at the top of the outer tube, the headstock has a chamber inside, the lower end of the chamber is open to communicate with the interior of the outer tube, the top of the chamber is provided with a through port, and the side wall of the chamber is provided with a first interface, a second interface and a third interface; the inner tube is coaxially disposed inside the outer tube, and its top extends through the through port to the upper end of the headstock to form a sample insertion port; the internal space of the inner tube constitutes a sample chamber, and the cavity between the inner tube and the outer tube constitutes a vacuum chamber; the liquid inlet outer tube is connected to and connected to the first interface, and a vacuum safety valve is installed on the liquid inlet outer tube; the first vacuum pumping line is connected to and connected to the inner tube through the second interface; the second vacuum pumping line is connected to and connected to the third interface.

[0011] Preferably, a cylindrical cold screen coaxial with both is provided between the outside of the sample chamber and the inside of the vacuum chamber. A heat sink made of thermally conductive metal material is installed at the top of the cold screen. The heat sink has an air inlet and an air outlet. An air passage connecting the air inlet and the air outlet is provided inside the heat sink. The air inlet of the heat sink is connected to the sample chamber. It has two air outlets, one of which is connected to the first vacuum line and the other is connected to the return air line.

[0012] Preferably, the heat exchanger is supported by a support plate mounted at its bottom to form a gap between the support plate and the cold shield, the support plate being made of a non-thermal conductive material.

[0013] Preferably, the heat exchanger is supported by a support plate mounted at its bottom, forming a gap between the support plate and the cold shield. The support plate is made of a non-thermal-conductive material. Preferably, the heat exchanger has a spiral channel inside, with one end of the spiral channel being an outlet communicating with the sample chamber and the other end being an inlet communicating with the liquid inlet delivery pipe. The heating element is disposed outside the spiral channel.

[0014] Preferably, the heat exchanger is equipped with a temperature sensor for monitoring the temperature at its outlet.

[0015] Preferably, the liquid inlet delivery pipe includes a transition pipe connected to the liquid inlet interface and a capillary tube connecting the transition pipe and the heat exchanger, wherein the capillary tube is a flexible metal tube with a diameter smaller than that of the transition pipe.

[0016] Preferably, the inner inlet tube and the outer inlet tube are coaxial and supported by an insulating support ring, with the outer ring surface of the insulating support ring in point contact with the inner wall of the outer inlet tube and the inner ring surface of the insulating support ring in point contact with the outer wall of the inner inlet tube.

[0017] Preferably, the outer surface of the sample cavity is mirror polished, and the middle section of the peripheral wall of the sample cavity is thinned so that the wall thickness of the middle section is less than the wall thickness of its two ends.

[0018] Preferably, a sample mounting flange is installed at the sample insertion port.

[0019] The vertically arranged sample chamber and the sample insertion port at the top of the sample chamber facilitate sample replacement. The heat exchanger located below the sample chamber and the heating element on the surface of the heat exchanger convert the liquid helium entering the heat exchanger into gaseous helium, which is then transported from below the sample chamber into the sample chamber, thus maintaining a low-temperature environment inside the sample chamber. This method effectively reduces the consumption of liquid helium, facilitates temperature control, makes temperature control more stable, and allows for a wider temperature range. The horizontally arranged outer inlet pipe and the inner inlet pipe inside the outer inlet pipe facilitate the connection of the liquid helium delivery pipe. A sealing joint is installed near the end of the inner inlet pipe, and the sealing joint is equipped with an inlet port, a return port, and a plug-in port on the inlet port. The liquid helium delivery pipe is then inserted into the plug-in port to connect with the liquid helium delivery pipe, thereby allowing the liquid helium to be delivered to the heat exchanger through the liquid helium delivery pipe. The helium gas discharged from the sample chamber flows back to the inner inlet pipe through the return port and is discharged from the cavity between the inner inlet pipe and the liquid helium delivery pipe. This structural design has the advantages of compact structure and small size. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a small low-temperature thermostat proposed in this invention;

[0021] Figure 2 This is a schematic diagram of the heat exchanger in a small low-temperature thermostat proposed in this invention.

[0022] Figure 3 This is a schematic diagram of the liquid inlet inner tube and liquid inlet outer tube in a small low-temperature thermostat proposed in this invention.

[0023] Figure 4 This is a front view of a small low-temperature thermostat proposed in this invention;

[0024] Figure 5 This is a top view of a small cryogenic thermostat proposed in this invention;

[0025] Figure 6 This is an isometric view of a small cryogenic thermostat proposed in this invention;

[0026] Figure 7 This is a schematic diagram of the internal structure of the headstock in a small low-temperature thermostat proposed in this invention;

[0027] Figure 8 This is a schematic diagram of the installation of the heat exchanger and the cold shield in a small low-temperature thermostat proposed in this invention.

[0028] Figure 9 This is a schematic diagram of the axial locking head in a small low-temperature thermostat proposed in this invention. Detailed Implementation

[0029] Reference Figure 1 The present invention proposes a small low-temperature thermostat, comprising: a vertically arranged shell 1 and a horizontally arranged inlet outer tube 2 connected to the shell 1.

[0030] The shell 1 contains a sample chamber and a vacuum chamber coaxially arranged outside the sample chamber. The top of the sample chamber has a sample insertion port for sample insertion and a sample mounting flange 20 installed at the insertion port for sample installation and fixation. The outer surface of the sample chamber is mirror-polished to improve surface smoothness and brightness, reduce the emissivity of the material, and decrease radiative heat leakage. The middle section of the sample chamber's peripheral wall is thinned so that its wall thickness is less than that at its ends; specifically, the wall thickness at the thinned section is 0.2 mm, and the thickness at the other ends is 0.5 mm.

[0031] Reference Figure 2 Below the sample chamber and inside the vacuum chamber, there is a heat exchanger 3, a heating element 4 on the surface of the heat exchanger 3, and a temperature sensor 5 at the output end of the heat exchanger 3. The heat exchanger 3 has a spiral channel inside, one end of which is the outlet and communicates with the sample chamber, and the other end is the inlet. The heating element 4 is a resistance heating wire with a resistance of 100 ohms.

[0032] Reference Figure 3 The outer inlet pipe 2 contains an inner inlet pipe 6, an inlet delivery pipe 7, and a return gas pipe 8. The inner inlet pipe 6 is coaxial with the outer inlet pipe 2 and is supported by an insulating support ring 9, which separates the inner inlet pipe 6 from the outer inlet pipe 2 to prevent them from contacting each other. The outer ring surface of the insulating support ring 9 makes point contact with the inner wall of the outer inlet pipe 2, and the inner ring surface of the insulating support ring 9 makes point contact with the outer wall of the inner inlet pipe 6 to reduce the contact area and lower heat leakage. Specifically, both the inner and outer ring surfaces of the insulating support ring 9 have at least two circumferentially distributed protrusions. The protrusions on the outer ring surface of the insulating support ring 9 contact the inner wall of the outer inlet pipe 2, and the protrusions on the inner ring surface of the insulating support ring 9 contact the outer wall of the inner inlet pipe 6.

[0033] The distal end of the inner inlet tube 6 extends to the outside of the outer inlet tube 2, and a sealing joint 10 is installed at the proximal end of the inner inlet tube 6. The sealing joint 10 is provided with an inlet port and a return port. Both the inlet port and the return port are connected to the inside of the inner inlet tube 6, with the inlet port located at the center of the inner inlet tube 6 and the return port located outside the inlet port near the side wall of the inner inlet tube 6. The port of the inlet port located at the inner end of the inner inlet tube 6 is configured as an insertion port 11 for inserting a liquid helium delivery tube. The inlet port is connected to the inlet of the heat exchanger 3 via the inlet delivery tube 7, and the return port is connected to the sample chamber via the return tube 8.

[0034] During operation, the sample is inserted into the sample chamber through the sample insertion port at the top of the tube shell 1. The output end of the liquid helium delivery tube extends into the liquid inlet tube 6 and is connected to the insertion port 11, so that liquid helium is input into the heat exchanger 3 through the liquid inlet delivery tube 7. After being heated by the heating element 4, it forms gaseous helium gas, which enters the sample chamber to purge the sample, thereby achieving the acquisition of various temperatures of the sample from low to high temperature. The temperature sensor 5 at the output end of the heat exchanger 3 can monitor the temperature of the helium output in real time.

[0035] Furthermore, in this embodiment, the liquid inlet delivery pipe 7 includes a transition pipe 701 connected to the liquid inlet interface and a capillary tube 702 connecting the transition pipe 701 and the heat exchanger 3. The capillary tube 702 is a flexible metal tube with a diameter smaller than that of the transition pipe 701. The design of the capillary tube 702 can reduce the fluctuation of liquid helium during delivery, ensure the continuity of the flow rate during liquid helium delivery, and the outer surface of the capillary tube 702 is wrapped with heat insulation material to reduce the radiative heat leakage of the atmospheric environment to the sample chamber, so that the sample chamber can obtain a lower temperature, while reducing the loss of liquid helium.

[0036] Reference Figure 4-5 The heat exchanger in the small low-temperature thermostat proposed in this invention further includes a vacuum system for maintaining and obtaining vacuum conditions. The vacuum system includes a first vacuum line 14 and a second vacuum line 21, wherein the first vacuum line 14 is connected to the sample chamber, and the second vacuum line 21 is connected to the vacuum chamber. A sample chamber safety valve 15 and a shut-off valve 16 are installed in the first vacuum line 14. During operation, the second vacuum line 21 ensures the vacuum environment inside the vacuum chamber. When a lower temperature is required in the sample chamber, the first vacuum line 14 is used to evacuate the sample chamber to achieve a lower temperature. When the medium pressure of the low-temperature thermostat exceeds a specified value, the medium is discharged through the sample chamber safety valve 15, thereby preventing the thermostat from bursting due to excessive medium pressure.

[0037] Reference Figure 6-7Furthermore, to improve the compactness of the structure, facilitate installation and disassembly of components, and make the overall thermostat smaller, the shell 1 in this embodiment adopts a structure design of inner tube 101 and outer tube 102. A headstock 22 is installed at the top of the outer tube 102. The headstock 22 has a chamber inside, with the lower end of the chamber open to communicate with the interior of the outer tube 102. The top of the chamber has a through port, and the side wall of the chamber has a first interface, a second interface, and a third interface. The inner tube 101 is coaxially arranged inside the outer tube 102, and its top extends through the through port to the upper end of the headstock 22 to form a sample insertion port. The internal space of the inner tube 101 constitutes a sample chamber, and the cavity between the inner tube 101 and the outer tube 102 constitutes a vacuum chamber. The liquid inlet outer tube 2 is connected to and conducts through the first interface. To prevent the medium from leaking into the vacuum chamber, a vacuum safety valve 23 is installed on the liquid inlet outer tube 2 to avoid the thermostat from bursting or causing personal injury due to the medium leaking into the vacuum interlayer. The first vacuum line 14 is connected to and conducts through the second interface to the inner tube 101. The second vacuum line 21 is connected to the third interface.

[0038] In this embodiment, a cold shield 17 is also provided between the outside of the sample chamber and the inside of the vacuum chamber. The cold shield 17 has a cylindrical structure, and its outer surface is covered with heat-insulating material. A heat sink 18 made of thermally conductive metal material is installed at the top of the cold shield 17. The heat sink 18 has an air inlet and an air outlet, and an air passage connecting its air inlet and outlet is provided inside the heat sink 18. The air inlet of the heat sink 18 is connected to the sample chamber, and it has two air outlets, one of which is connected to the first vacuum line 14, and the other is connected to the return gas line 8. During operation, the low-temperature return gas exchanges heat with the cold shield 17 through the heat sink 18 to cool the cold shield 17, thereby reducing radiative heat leakage from the sample chamber and allowing the sample area to obtain a lower temperature, thus reducing the loss of liquid helium.

[0039] Reference Figure 8 In order to prevent the heat exchanger 3 from contacting the cold screen 17, this embodiment installs a support plate 19 made of non-thermal conductive material at the bottom of the heat exchanger 3 to form a gap between the support plate 19 and the cold screen 17. Specifically, the material of the support plate 19 is G10. G10 is a plate-shaped insulating material made of alkali-free glass fiber cloth impregnated with epoxy resin and with the addition of corresponding flame retardants, adhesives and other additives, and processed by hot pressing.

[0040] Reference Figure 9The distal end of the liquid inlet tube 6 is provided with a transition joint 12 and an axial locking joint 13. One end of the transition joint 12 is connected to the liquid inlet tube 6, and the other end is a threaded connection end. The interior of the transition joint 12 has a channel communicating with the liquid inlet tube 6. The axial locking joint 13 has an inherent through channel inside. The axial locking joint 13 includes a push joint 1302 threadedly connected to the transition joint 12, an intermediate connecting head 1301 connected to the push joint 1302 and rotatable relative to the push joint 1302, a locking end head 1303 threadedly connected to the intermediate connecting head 1301, a locking ring 1304 located between the intermediate connecting head 1301 and the locking end head 1303, and a channel that sequentially passes through the push joint 1302, the intermediate connecting head 1301 and the locking end head 1303 and connects to the transition joint 12. The locking ring 1304 is an open ring with wedge-shaped bevels on both sides. The wedge-shaped bevels on both sides form beveled fits with the intermediate connecting head 1301 and the locking end head 1303, so that when the locking ring 1304 is squeezed by the locking end head 1303, the head and tail of the locking ring 1304 gradually approach each other to lock the inner pipe. The specific structure is as follows: the locking end 1303 includes a threaded cylinder and a retaining ring located inside one end port of the threaded cylinder; the threaded cylinder is sleeved on the end of the intermediate connector 1301 and threadedly engaged with it, and the retaining ring is opposite to the end face of the intermediate connector 1301; the inner surface of the retaining ring is inclined away from the intermediate connector 1301 to form a first inclined surface, the end face of the intermediate connector 1301 is inclined away from the retaining ring to form a second inclined surface, and a gap is reserved between the first inclined surface and the second inclined surface to form a V-shaped groove cavity with the groove opening facing inward; the locking ring 1304 is located in the V-shaped groove cavity, and the wedge-shaped inclined surfaces on both sides of it form inclined surface engagement with the first inclined surface and the second inclined surface, respectively. During operation, the locking end 1303 is loosened beforehand to allow the locking ring 1304 to relax. Then, the output end of the liquid helium delivery tube is inserted into the axial locking joint 1303 through the through-hole on the locking end 1303, and then through the axial locking joint 1303 and the transition joint 12 into the inlet inner tube 6 before being inserted into the insertion port 11. Subsequently, the locking end 1303 is tightened to compress the locking ring 1304, causing the locking ring 1304 to grip the liquid helium delivery tube tightly. Finally, the push joint 1302 is tightened to pull the liquid helium delivery tube towards the inlet inner tube 6, so that the output end of the liquid helium delivery tube is tightly inserted into the insertion port 11 to ensure the sealing of the insertion end and avoid liquid helium leakage.

[0041] As can be seen from the above, the vertically arranged sample chamber and the sample insertion port at the top of the sample chamber facilitate sample replacement. The heat exchanger 3 located below the sample chamber and the heating element 4 located on the surface of the heat exchanger 3 convert the liquid helium entering the heat exchanger 3 into gaseous helium, which is then transported from below the sample chamber to the sample chamber, so that the inside of the sample chamber is in a low-temperature environment. This method can effectively reduce the consumption of liquid helium, facilitate temperature control, make the temperature control more stable, and make the temperature range wider. The horizontally arranged outer inlet pipe 2 and the inner inlet pipe 6 inside the outer inlet pipe 2 facilitate the connection of the liquid helium delivery pipe. A sealing joint 10 is installed near the end of the inner inlet pipe 6. The sealing joint 10 is provided with an inlet port and a return port, as well as a plug port 11 on the inlet port, so that the liquid helium delivery pipe can be plugged into the plug port 11 to connect with the liquid inlet delivery pipe 7. Then, the liquid helium delivered by it is delivered to the heat exchanger 3 through the liquid inlet delivery pipe 7, while the helium gas discharged from the sample chamber flows back to the inner inlet pipe 6 through the return port 8, so as to be discharged from the cavity between the inner inlet pipe 6 and the liquid helium delivery pipe. This structural design has the advantages of compact structure and small size.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A small cryostat, characterized by, The utility model relates to a kind of liquid helium sample holder, including: Vertically arranged shell (1) and transversely arranged and connected with shell (1) liquid inlet outer tube (2); Shell (1) has sample chamber and coaxially arranged vacuum chamber outside sample chamber inside, the top of sample chamber is equipped with sample insertion port for sample insertion, the lower of sample chamber and inside vacuum chamber is equipped with heat exchanger (3) and heating element (4) arranged on the surface of heat exchanger (3), the outlet of heat exchanger (3) is communicated with sample chamber; Liquid inlet inner tube (6) is arranged inside liquid inlet outer tube (2), liquid inlet delivery tube (7) and back gas pipe (8), the distal end of liquid inlet inner tube (6) extends to the outside of liquid inlet outer tube (2), and the proximal end of liquid inlet inner tube (6) is equipped with sealing joint (10);Sealing joint (10) is equipped with liquid inlet interface and back gas interface, and liquid inlet interface and back gas interface are communicated with the inside of liquid inlet inner tube (6), and liquid inlet interface is located at the central part of liquid inlet inner tube (6), back gas interface is located at the position of liquid inlet inner tube (6) side wall outside liquid inlet interface, and the port of liquid inlet interface inside liquid inlet inner tube (6) is set as plug-in interface (11) for liquid helium delivery tube plug-in connection; Liquid inlet interface is connected with the inlet of heat exchanger (3) through liquid inlet delivery tube (7);Back gas interface is communicated with sample chamber through back gas pipe (8); The distal end of liquid inlet inner tube (6) is equipped with transition joint (12) and axial locking joint (13), one end of transition joint (12) is connected with liquid inlet inner tube (6), the other end is threaded connection end, and the inside of transition joint (12) has channel communicated with liquid inlet inner tube (6);Axial locking joint (13) has inherent through channel inside, and axial locking joint (13) includes push joint (1302) connected with transition joint (12) by screwing, middle adapter (1301) connected with push joint (1302) and rotatable relative to push joint (1302), locking end (1303) connected with middle adapter (1301) by screwing, locking ring (1304) between middle adapter (1301) and locking end (1303), and channel sequentially through push joint (1302), middle adapter (1301) and locking end (1303) and connected with transition joint (12);Locking end (1303) includes threaded cylinder and blocking ring inside the port of threaded cylinder one end, and the threaded cylinder is sleeved on the end of middle adapter (1301) and is matched with it by screwing, and the blocking ring is opposite to the end surface of middle adapter (1301);The inside of the blocking ring is inclined to form first inclined surface in the direction away from middle adapter (1301), and the end surface of middle adapter (1301) is inclined to form second inclined surface in the direction away from blocking ring, and the first inclined surface and the second inclined surface are reserved spacing to form V-shaped groove cavity with notch towards inside;Locking ring (1304) is open ring, and both sides of locking ring (1304) are wedge-shaped inclined surface, and locking ring (1304) is located in V-shaped groove cavity, and the wedge-shaped inclined surface of both sides of locking ring (1304) forms inclined surface cooperation with first inclined surface and second inclined surface respectively.

2. The small cryostat according to claim 1, characterized in that The vacuum system for maintaining and obtaining vacuum condition comprises a first vacuum pipeline (14) and a second vacuum pipeline (21), wherein the first vacuum pipeline (14) is connected to the sample chamber, and the second vacuum pipeline (21) is connected to the vacuum chamber.

3. The small cryostat according to claim 2, characterized in that The sample chamber safety valve (15) and the stop valve (16) are installed in the first vacuum pipeline (14).

4. The small cryostat according to claim 2, characterized in that The tube shell (1) comprises an inner tube (101) and an outer tube (102); the top end of the outer tube (102) is provided with a head seat (22), the inside of the head seat (22) has a chamber, the lower end of the chamber is open to communicate with the inside of the outer tube (102), the top end of the chamber is provided with a through opening, and the side wall of the chamber is provided with a first interface, a second interface and a third interface; the inner tube (101) is coaxially arranged in the inside of the outer tube (102), the top of the inner tube (101) extends to the upper end of the head seat (22) through the through opening to form a sample insertion port; the inside space of the inner tube (101) constitutes a sample chamber, and the clamping cavity between the inner tube (101) and the outer tube (102) constitutes a vacuum chamber; a liquid inlet outer tube (2) is connected and communicated with the first interface, and the vacuum safety valve (23) is installed on the liquid inlet outer tube (2); a first vacuum pipeline (14) is connected and communicated with the inner tube (101) through the second interface, and a second vacuum pipeline (21) is connected and communicated with the third interface.

5. The small cryostat according to claim 2, characterized in that A cylindrical cold shield (17) coaxial with the sample chamber and the vacuum chamber is arranged between the outside of the sample chamber and the inside of the vacuum chamber; the top end of the cold shield (17) is provided with a heat sink seat (18) made of heat-conducting metal material; the heat sink seat (18) has an air inlet and an air outlet; the inside of the heat sink seat (18) is provided with an air channel communicating the air inlet and the air outlet; the air inlet of the heat sink seat (18) is communicated with the sample chamber; the air outlet of the heat sink seat (18) has two outlets, one of which is connected with the first vacuum pipeline (14), and the other of which is connected with the gas return tube (8).

6. The small cryostat according to claim 5, characterized in that The heat exchanger (3) is supported by a support plate (19) installed at the bottom of the heat exchanger (3) to form a space between the support plate (19) and the cold shield (17); the support plate (19) is made of non-heat-conducting material.

7. The small cryostat according to claim 1, characterized in that The heat exchanger (3) has a spiral channel in the inside thereof; one end of the spiral channel is an outlet communicated with the sample chamber, and the other end of the spiral channel is an inlet connected with the liquid inlet delivery tube (7); and the heating element (4) is arranged outside the spiral channel.

8. The small cryostat according to claim 1, characterized in that The heat exchanger (3) is provided with a temperature sensor (5) for monitoring the temperature of the outlet end of the heat exchanger (3).

9. The small cryostat according to claim 1, characterized in that The liquid inlet delivery tube (7) comprises a transition tube (701) connected with the liquid inlet interface and a capillary tube (702) connecting the transition tube (701) with the heat exchanger (3); the capillary tube (702) is a metal hose with a smaller diameter than the transition tube (701).

10. The small cryostat according to claim 1, characterized in that The liquid inlet inner tube (6) is coaxial with the liquid inlet outer tube (2) and is supported by a heat-insulating support ring (9); the outer ring surface of the heat-insulating support ring (9) is in point contact with the inner wall of the liquid inlet outer tube (2), and the inner ring surface of the heat-insulating support ring (9) is in point contact with the outer wall of the liquid inlet inner tube (6).

11. The small cryostat according to any one of claims 1 to 10, characterized in that The outer surface of the sample chamber is mirror-polished; and the middle section of the peripheral wall of the sample chamber is thinned to make the wall thickness of the middle section smaller than the wall thickness of the two ends.

12. The small cryostat according to claim 10, characterized in that A sample mounting flange is installed at the sample insertion port.

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