Small cryostat

Abstract

The invention provides a small-sized cryostat. The small-sized cryostat comprises a tube shell and a liquid inlet outer tube connected with the tube shell, a sample cavity and a vacuum cavity are formed in the tube shell; a sample insertion opening is formed in the top of the sample cavity, a heat exchanger and a heating element arranged on the surface of the heat exchanger are arranged below the sample cavity, and an outlet of the heat exchanger is communicated with the sample cavity; a liquid inlet inner pipe, a liquid inlet conveying pipe and an air return pipe are arranged in the liquid inlet outer pipe, and a sealing connector is installed at the near end of the liquid inlet inner pipe. The sealing joint is provided with a liquid inlet port and an air return port, the liquid inlet port is located in the center of the liquid inlet inner pipe, the air return port is located at the position, close to the side wall of the liquid inlet inner pipe, of the outer side of the liquid inlet port, and a port, located at the inner side end of the liquid inlet inner pipe, of the liquid inlet port is an insertion port; the liquid inlet connector is connected with an inlet of the heat exchanger through a liquid inlet conveying pipe. The air return interface is communicated with the sample cavity through an air return pipe. The device is compact in structure, small in size, convenient in sample replacement, more stable in temperature control and wider in temperature zone.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-low temperature engineering, and in particular to a small low temperature thermostat. Background Art

[0002] At present, in physical science research and medical testing, physical property measurement and optical band testing at low temperatures are becoming increasingly hot research topics. Among them, low temperature environment and vacuum environment are indispensable and decisive conditions in the testing process. Maintaining a low temperature environment must rely on a low temperature thermostat with reliable performance and stable temperature control. The thermostat can provide a long-term low temperature environment for various scientific and medical tests on samples at low temperatures. Existing thermostats still have many shortcomings, such as: rough design, unstable temperature control, narrow temperature range, large consumption of liquid helium, cumbersome sample replacement, long test cycle, and difficult operation. Summary of the invention

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

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

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

[0006] The inner liquid inlet tube, the liquid inlet delivery tube and the gas return tube are arranged inside the liquid inlet outer tube, the distal end of the liquid inlet inner tube extends to the outside of the liquid inlet outer tube, and the proximal end of the liquid inlet inner tube is installed with a sealing joint; the sealing joint is provided with a liquid inlet interface and a gas return interface, both of which are communicated with the inside of the liquid inlet inner tube, and the liquid inlet interface is located at the center of the liquid inlet inner tube, the gas return interface is located outside the liquid inlet interface and close to the side wall of the liquid inlet inner tube, and the port of the liquid inlet interface located at the inner end of the liquid inlet inner tube is arranged as a plug-in interface for plugging in the liquid helium delivery tube;

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

[0008] Preferably, it also includes a vacuum pumping system for maintaining and obtaining vacuum conditions, and the vacuum pumping system includes two vacuum pumping pipelines, one of which is connected to the sample chamber, and the other is connected to the vacuum chamber.

[0009] Preferably, a sample chamber safety valve and a stop valve are installed in the vacuum line connected to the sample chamber.

[0010] Preferably, the tube shell includes an inner tube and an outer tube; a head seat is installed at the top of the outer tube, and the interior of the head seat has a chamber, 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 arranged inside the outer tube, and its top passes through the through port and extends to the upper end of the head seat to form a sample insertion port; the internal space of the inner tube constitutes a sample chamber, and the sandwiched cavity between the inner tube and the outer tube constitutes a vacuum chamber; the liquid inlet outer tube is connected and communicated with the first interface, and a vacuum safety valve is installed on the liquid inlet outer tube; the vacuum pumping pipeline connected to the sample chamber is connected and communicated with the inner tube through the second interface; the vacuum pumping pipeline connected to the vacuum chamber is connected and communicated with the third interface.

[0011] Preferably, a cylindrical cold screen coaxial with the outside of the sample chamber and the inside of the vacuum chamber is provided between the two, a heat sink seat made of a heat-conducting metal material is installed on the top of the cold screen, the heat sink seat has an air inlet and an air outlet, an air duct connecting the air inlet and the air outlet is provided inside the heat sink seat, the air inlet of the heat sink seat is connected to the sample chamber, and two air outlets are provided, one of which is connected to the vacuum pipeline connected to the sample chamber, and the other is connected to the return air pipe.

[0012] Preferably, the heat exchanger is supported by a support plate mounted on the bottom thereof so as to form a gap between the support plate and the cold shield, and the support plate is made of a non-heat-conductive material.

[0013] Preferably, the heat exchanger is supported by a support plate installed at the bottom thereof so as to form a gap between the support plate and the cold shield, and the support plate is made of a non-heat-conducting material. Preferably, a spiral channel is provided inside the heat exchanger, one end of the spiral channel is an outlet communicating with the sample chamber, and the other end is an inlet connected to the liquid inlet delivery pipe, and the heating element is arranged outside the spiral channel.

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

[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, and the capillary tube is a metal hose with a smaller diameter than the transition pipe.

[0016] Preferably, the inner liquid inlet tube is coaxial with the outer liquid inlet tube and supported by an insulating support ring, and the outer annular surface of the insulating support ring is in point contact with the inner wall of the outer liquid inlet tube, and the inner annular surface of the insulating support ring is in point contact with the outer wall of the inner liquid 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 smaller than the wall thickness at both ends.

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

[0019] The vertically arranged sample cavity and the sample insertion port arranged at the top of the sample cavity can facilitate the replacement of samples; the heat exchanger arranged below the sample cavity and the heating element arranged on the surface of the heat exchanger convert the liquid helium entering the heat exchanger into gaseous helium, which is then transported from the bottom of the sample cavity into the sample cavity, so that the interior of the sample cavity is in a low-temperature environment. This method can effectively reduce the consumption of liquid helium, is conducive to temperature control, makes the temperature control more stable, and makes the temperature range wider. The transversely arranged liquid inlet outer tube and the liquid inlet inner tube arranged inside the liquid inlet outer tube facilitate the access of the liquid helium delivery tube; a sealing joint is installed at the proximal end of the liquid inlet inner tube, a liquid inlet interface and a gas return interface are arranged on the sealing joint, and a plug interface is arranged on the liquid inlet interface, so that the liquid helium delivery tube is plugged into the plug interface to be connected with the liquid inlet delivery tube, and then the liquid helium delivered by it is delivered to the heat exchanger by the liquid inlet delivery tube, and the helium discharged from the sample cavity flows back to the liquid inlet inner tube through the gas return tube, so as to be discharged from the sandwich cavity between the liquid inlet inner tube and the liquid helium delivery tube. This structural design has the advantages of compact structure and small size. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a small cryostat proposed by the present invention;

[0021] Figure 2 This is a structural schematic diagram of the heat exchanger in a small cryostat proposed by the present invention;

[0022] Figure 3 This is a structural schematic diagram of the liquid inlet inner tube and the liquid inlet outer tube in a small-sized low-temperature thermostat proposed by the present invention;

[0023] Figure 4 A front view of a small cryostat proposed by the present invention;

[0024] Figure 5 A top view of a small cryostat proposed by the present invention;

[0025] Figure 6 An axonometric view of a small cryostat proposed by the present invention;

[0026] Figure 7 This is a schematic diagram of the internal structure of the head base in a small cryostat proposed by the present invention;

[0027] Figure 8 This is a schematic diagram of the installation of the heat exchanger and the cold shield in a small cryostat proposed by the present invention;

[0028] Fig. 9 This is a schematic structural diagram of the axial locking head in a small cryostat proposed by the present invention. DETAILED DESCRIPTION

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

[0030] The tube shell 1 has a sample cavity and a vacuum cavity coaxially arranged outside the sample cavity; the top of the sample cavity is provided with a sample insertion port for inserting the sample and a sample mounting flange 20 installed at the sample insertion port for mounting and fixing the sample. The outer surface of the sample cavity is mirror-polished to improve the surface finish and brightness, reduce the emissivity of the material itself, and reduce radiation heat leakage. 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 the two ends. Specifically, the wall thickness of the thinned part is 0.2 mm, and the other parts are 0.5 mm.

[0031] Reference Figure 2 A heat exchanger 3, a heating element 4 arranged on the surface of the heat exchanger 3, and a temperature sensor 5 arranged at the output end of the heat exchanger 3 are arranged below the sample cavity and inside the vacuum cavity. The heat exchanger 3 has a spiral channel inside, one end of the spiral channel is an outlet and connected to the sample cavity, and the other end is an inlet; the heating element 4 uses a resistance heating wire with a resistance of 100 ohms.

[0032] Reference Figure 3 , an inner liquid inlet tube 6, a liquid inlet delivery tube 7 and an air return tube 8 are arranged inside the outer liquid inlet tube 2. The inner liquid inlet tube 6 is coaxial with the outer liquid inlet tube 2, and is supported by an insulating support ring 9, so as to separate the inner liquid inlet tube 6 from the outer liquid inlet tube 2 through the insulating support ring 9 to avoid contact between the two. The outer annular surface of the insulating support ring 9 is in point contact with the inner wall of the outer liquid inlet tube 2, and the inner annular surface of the insulating support ring 9 is in point contact with the outer wall of the inner liquid inlet tube 6, so as to reduce the contact area and reduce heat leakage. Specifically: the inner annular surface and the outer annular surface of the insulating support ring 9 are both provided with at least two circumferentially distributed protrusions, and the protrusions on the outer annular surface of the insulating support ring 9 are in contact with the inner wall of the outer liquid inlet tube 2, and the protrusions on the inner annular surface of the insulating support ring 9 are in contact with the outer wall of the inner liquid inlet tube 6.

[0033] The distal end of the liquid inlet inner tube 6 extends to the outside of the liquid inlet outer tube 2, and a sealing joint 10 is installed at the proximal end of the liquid inlet inner tube 6; the sealing joint 10 is provided with a liquid inlet interface and a gas return interface, both of which are connected to the inside of the liquid inlet inner tube 6, and the liquid inlet interface is located at the center of the liquid inlet inner tube 6, and the gas return interface is located outside the liquid inlet interface near the side wall of the liquid inlet inner tube 6, and the port of the liquid inlet interface located at the inner end of the liquid inlet inner tube 6 is set as a plug-in interface 11 for plugging in a liquid helium delivery tube. The liquid inlet interface is connected to the inlet of the heat exchanger 3 via the liquid inlet delivery tube 7, and the gas return interface is connected to the sample chamber via the gas return tube 8.

[0034] During operation, the sample is inserted into the sample cavity through the sample insertion port at the top of the tube shell 1, and the output end of the liquid helium delivery tube extends into the liquid inlet inner tube 6 and plugs into the plug port 11, so that the liquid helium is input into the heat exchanger 3 through the liquid inlet delivery tube 7, and the gaseous helium is heated by the heating element 4 and enters the sample cavity to purge the sample, so as to obtain various temperatures of the sample from low temperature to high temperature. The temperature sensor 5 arranged at the output end of the heat exchanger 3 can monitor the temperature of the helium output in real time.

[0035] Furthermore, the liquid inlet delivery pipe 7 in this embodiment includes a transition pipe 71 connected to the liquid inlet interface and a capillary 72 connecting the transition pipe 71 and the heat exchanger 3. The capillary 72 is a metal hose with a smaller diameter than the transition pipe 71. The design of the capillary 72 can reduce the fluctuation of liquid helium during the transportation process and ensure the continuity of the flow rate during the liquid helium transportation process. The outer surface of the capillary 72 is wrapped with an insulating material to reduce the radiation heat leakage of the atmospheric environment to the sample cavity, so that the sample cavity can obtain a lower temperature and reduce the loss of liquid helium.

[0036] Reference Figure 4-5 The heat exchanger in the small low-temperature thermostat proposed by the present invention also includes a vacuum pumping system for maintaining and obtaining vacuum conditions. The vacuum pumping system includes two vacuum pumping lines 14 and 21, one of which is connected to the sample chamber, and the other is connected to the vacuum chamber by the vacuum pumping line 14. The sample chamber safety valve 15 and the stop valve 16 are installed in the vacuum pumping line 14 connected to the sample chamber. During operation, the vacuum environment inside the vacuum chamber is guaranteed by the vacuum pumping line 21, and when the sample chamber needs to obtain a lower temperature, the sample chamber is evacuated through the vacuum pumping line 14 to obtain a lower temperature inside the sample chamber. When the medium pressure of the low-temperature thermostat exceeds the specified value, the medium is discharged through the sample chamber safety valve 15, thereby preventing the danger of the thermostat bursting due to excessive medium pressure.

[0037] Reference Figure 6-7Furthermore, in order to improve the compactness of the structure, facilitate installation and disassembly of parts, and make the entire thermostat smaller, the tube shell 1 in this embodiment adopts the structural design of the inner tube 101 and the outer tube 102, and the head seat 22 is installed at the top of the outer tube 102. The head seat 22 has a chamber inside, the lower end of the chamber is open to communicate with the inside of the outer tube 102, the top of the chamber is provided with a through hole, 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 inside the outer tube 102, and its top passes through the through hole and extends to the upper end of the head seat 22 to form a sample insertion port; the internal space of the inner tube 101 constitutes a sample cavity, and the sandwich cavity between the inner tube 101 and the outer tube 102 constitutes a vacuum cavity. The liquid inlet outer tube 2 is connected and conducted with the first interface, and in order to prevent the medium from leaking into the vacuum cavity, a vacuum safety valve 23 is installed on the liquid inlet outer tube 2 to avoid the explosion of the thermostat or casualties caused by the leakage of the medium into the vacuum interlayer. The vacuum pumping line 14 connected to the sample chamber is connected to and communicated with the inner tube 101 through the second interface. The vacuum pumping line 21 connected to the vacuum chamber is connected to the third interface.

[0038] In this embodiment, a cold shield 17 is also provided between the outside of the sample cavity and the inside of the vacuum cavity. The cold shield 17 is a cylindrical structure. The outer surface of the cold shield 17 is coated with a heat insulating material. A heat sink seat 18 made of a heat conductive metal material is installed at the top of the cold shield 17. 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 passage connecting the air inlet and the air outlet. The air inlet of the heat sink seat 18 is connected to the sample cavity. There are two air outlets, one of which is connected to the vacuum pumping pipeline 14 connected to the sample cavity, and the other is connected to the return air pipe 8. During operation, the low-temperature return air exchanges heat with the cold shield 17 through the heat sink seat 18 to cool the cold shield 17, thereby reducing the radiation heat leakage of the sample cavity, so that the sample area can obtain a lower temperature to reduce the loss of liquid helium.

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

[0040] Reference Fig. 9A transition joint 12 and an axial locking joint 13 are provided at the distal end of the liquid inlet inner tube 6. One end of the transition joint 12 is connected to the liquid inlet inner tube 6, and the other end is a threaded connection end. The interior of the transition joint 12 has a channel connected to the liquid inlet inner tube 6. The axial locking joint 13 has an inherent through passage inside, and the axial locking joint 13 includes a push joint 1302 threadedly connected to the transition joint 12, an intermediate connector 1301 connected to the push joint 1302 and rotatable relative to the push joint 1302, a locking end 1303 threadedly connected to the intermediate connector 1301, a locking ring 1304 located between the intermediate connector 1301 and the locking end 1303, and a passage that passes through the push joint 1302, the intermediate connector 1301 and the locking end 1303 in sequence and connects with the transition joint 12; the locking ring 1304 is an open ring, and its side surfaces on both sides are wedge-shaped bevels, and the wedge-shaped bevels on both sides form bevels with the intermediate connector 1301 and the locking end 1303, so that when the locking ring 1304 is squeezed by the locking end 1303, the head end and the tail end of the locking ring 1304 gradually approach each other to achieve locking of the inner pipe. The specific structure is as follows: the locking end 1303 includes a threaded barrel and a retaining ring located on the inner side of one end of the threaded barrel; the threaded barrel is sleeved on the end of the intermediate connector 1301 and matched with its thread, and the retaining ring is opposite to the end face of the intermediate connector 1301; the inner side of the retaining ring is inclined in the direction away from the intermediate connector 1301 to form a first inclined surface, and the end face of the intermediate connector 1301 is inclined in the direction away from the retaining ring to form a second inclined surface, and a spacing is reserved between the first inclined surface and the second inclined surface to form a V-shaped groove cavity with the notch facing inward; the locking ring 1304 is located in the V-shaped groove cavity, and the wedge-shaped inclined surfaces on both sides thereof form inclined surfaces with the first inclined surface and the second inclined surface respectively. During operation, the locking end 1303 is loosened in advance to allow the locking ring 1304 to enter a relaxed state; then the output end of the liquid helium delivery tube is passed through the through hole on the locking end 1303 into the axial locking joint 1303, and passes through the axial locking joint 1303 and the transition joint 12 into the liquid inlet inner tube 6 and then inserted into the plug-in port 11; subsequently, the locking end 1303 is tightened to squeeze the locking ring 1304 so that the locking ring 1304 holds the liquid helium delivery tube tightly; finally, the pushing joint 1302 is tightened to pull the liquid helium delivery tube to move toward the liquid inlet inner tube 6 so that the output end of the liquid helium delivery tube is tightly inserted into the plug-in port 11 to ensure the sealing of the plug-in end and avoid the problem of liquid helium leakage.

[0041] As can be seen from the above, the vertically arranged sample chamber and the sample insertion port arranged at the top of the sample chamber of the present invention can facilitate the replacement of samples; the heat exchanger 3 arranged below the sample chamber and the heating element 4 arranged on the surface of the heat exchanger 3 convert the liquid helium entering the heat exchanger 3 into gaseous helium and then transport it from the bottom of the sample chamber to the sample chamber, so that the interior of the sample chamber is in a low-temperature environment. This method can effectively reduce the consumption of liquid helium, and is conducive to temperature control, making the temperature control more stable and making the temperature range wider. The transversely arranged liquid inlet outer tube 2 and the liquid inlet inner tube 6 arranged inside the liquid inlet outer tube 2 facilitate the access of the liquid helium delivery tube; a sealing joint 10 is installed at the proximal end of the liquid inlet inner tube 6, and a liquid inlet interface and a gas return interface are arranged on the sealing joint 10, and a plug-in interface 11 is arranged on the liquid inlet interface, so that the liquid helium delivery tube is plugged into the plug-in interface 11 to be connected with the liquid inlet delivery tube 7, and then the liquid helium delivered by it is delivered to the heat exchanger 3 by the liquid inlet delivery tube 7, and the helium discharged from the sample cavity is refluxed into the liquid inlet inner tube 6 through the gas return pipe 8, so as to be discharged from the sandwich cavity between the liquid inlet inner tube 6 and the liquid helium delivery tube. This structural design has the advantages of compact structure and small size.

[0042] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A small cryostat, characterized in that: include: A vertically arranged tube shell (1) and a transversely arranged liquid inlet outer tube (2) connected to the tube shell (1); The tube shell (1) has a sample cavity and a vacuum cavity coaxially arranged outside the sample cavity. The top of the sample cavity is provided with a sample insertion port for inserting the sample. A heat exchanger (3) and a heating element (4) arranged on the surface of the heat exchanger (3) are provided below the sample cavity and inside the vacuum cavity. The outlet of the heat exchanger (3) is connected to the sample cavity. The liquid inlet outer tube (2) is provided with a liquid inlet inner tube (6), a liquid inlet delivery tube (7) and a gas return tube (8); the distal end of the liquid inlet inner tube (6) extends to the outside of the liquid inlet outer tube (2); the proximal end of the liquid inlet inner tube (6) is provided with a sealing joint (10); the sealing joint (10) is provided with a liquid inlet interface and a gas return interface, both of which are communicated with the inside of the liquid inlet inner tube (6), and the liquid inlet interface is located at the center of the liquid inlet inner tube (6); the gas return interface is located at the outside of the liquid inlet interface and close to the side wall of the liquid inlet inner tube (6); the port of the liquid inlet interface located at the inner side end of the liquid inlet inner tube (6) is configured as an insertion interface (11) for plugging in a liquid helium delivery tube; The liquid inlet interface is connected to the inlet of the heat exchanger (3) via a liquid inlet delivery pipe (7); and the gas return interface is connected to the sample chamber via a gas return pipe (8).

2. The small cryostat according to claim 1, characterized in that Also included is a vacuum pumping system for maintaining and obtaining vacuum conditions, the vacuum pumping system comprising two vacuum pumping pipelines (14, 21), one of which is connected to the sample chamber, and the other is connected to the vacuum chamber. Preferably, a sample chamber safety valve (15) and a stop valve (16) are installed in the vacuum pumping pipeline (14) connected to the sample chamber.

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

4. The small cryostat according to claim 2, characterized in that A cylindrical cold shield (17) coaxial with the outside of the sample chamber and the inside of the vacuum chamber is provided between the two. A heat sink seat (18) made of a heat-conducting metal material is installed on the top of the cold shield (17). The heat sink seat (18) has an air inlet and an air outlet. An air duct connecting the air inlet and the air outlet is provided inside the heat sink seat (18). The air inlet of the heat sink seat (18) is connected to the sample chamber, and two air outlets are provided, one of which is connected to a vacuum line (14) connected to the sample chamber, and the other is connected to a return air pipe (8).

5. The small cryostat according to claim 4, characterized in that The heat exchanger (3) is supported by a support plate (19) installed at the bottom thereof so as to form a gap between the support plate (19) and the cold shield (17), and the support plate (19) is made of a non-heat-conductive material.

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

7. 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 at its outlet end.

8. The small cryostat according to claim 1, characterized in that The liquid inlet delivery pipe (7) comprises a transition pipe (71) connected to the liquid inlet interface and a capillary tube (72) connecting the transition pipe (71) and the heat exchanger (3); the capillary tube (72) is a metal hose with a smaller diameter than the transition pipe (71).

9. 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), wherein the outer annular 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 annular surface of the heat-insulating support ring (9) is in point contact with the outer wall of the liquid inlet inner tube (6).

10. The small cryostat according to any one of claims 1 to 9, characterized in that: The outer surface of the sample cavity is mirror-polished; the middle section of the peripheral wall of the sample cavity is thinned so that the wall thickness of the middle section is smaller than the wall thickness of both ends; preferably, a sample mounting flange is installed at the sample insertion port.

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