Super-long endurance sample transmission system for cryoelectron microscope

Abstract

The invention relates to the technical field of electron microscopes, aims at solving the problems that in an existing sample transfer support, the low-temperature holding time of a sample rod is short, liquid nitrogen in a Dewar tank is boiled, so that the sample rod vibrates, electron microscope imaging drifts are caused, and the inclination angle of the sample rod is limited, and provides an ultra-long endurance sample transmission system for a cryoelectron microscope, which comprises the Dewar tank and the sample rod, the Dewar tank comprises an outer tank and an inner tank, the inner tank is located in the outer tank, first low-temperature fluid is stored in the outer tank, second low-temperature fluid is stored in the inner tank, and the boiling point of the second low-temperature fluid is higher than that of the first low-temperature fluid; a cold guide plate is arranged in the inner tank, the sample rod comprises an outer rod and a cold guide rod, the cold guide rod is located in the outer rod, one end of the cold guide rod extends into the inner tank and is connected with the cold guide plate, and the other end of the cold guide rod extends out of the outer rod and is connected with the sample rack; the outer rod is connected with a first connecting assembly, the Dewar tank is connected with a second connecting assembly, and the first connecting assembly is detachably connected with the second connecting assembly. The low-temperature holding time is long, drifting is small, and the inclination angle of the sample rod is large.

Description

Technical Field

[0001] The present invention relates to the field of electron microscopy technology, and in particular to an ultra-long endurance sample transmission system for a cryo-electron microscope. Background Art

[0002] Cryo-electron microscopy preserves the natural state of samples by rapidly freezing them and then observing them at extremely low temperatures (≤-136°C). Cryo-electron microscopy can be used to study the ultrastructure of cells, such as protein complexes, organelles, and cell membranes. It provides scientists with tools to study many important issues in biology, such as cell differentiation, viral infection mechanisms, and cell signaling. When cryo-electron microscopy collects the microstructure of samples at low temperatures, it usually requires a liquid nitrogen-cooled frozen sample stage, and the data collection time is relatively long, generally requiring more than 10 hours.

[0003] At present, the low-temperature sample transfer bracket commonly used in the market has a vacuum liquid nitrogen tank with a capacity of about 200ml at the tail of the sample rod. The cold amount is transferred to the sample holder at the front end of the sample rod through the built-in cooling rod, and the sample is kept at a low temperature (≤-150℃). Then the sample rod is inserted into the electron microscope as a whole to complete the data collection. Due to the limited capacity of the vacuum liquid nitrogen tank of the sample rod, each time it is filled with liquid nitrogen, it can only maintain a low temperature (≤-150℃) for about 3 hours. When the liquid nitrogen is refilled, the vibration caused by the boiling of liquid nitrogen will cause the sample to drift and data cannot be collected. Therefore, data cannot be collected automatically for a long time.

[0004] In addition, liquid nitrogen needs to be added to the cryo-transfer sample rod before loading the sample to cool the cryo-transfer sample rod and keep it at a low temperature. When the sample rod is inserted into the cryo-electron microscope, the sample rod needs to be rotated 90° for insertion, and the mouth of the liquid nitrogen tank is changed from vertical to horizontal, and the liquid nitrogen in the tank will pour out. After the vacuum is evacuated in the cryo-electron microscope cavity, the sample rod is rotated back to the initial position (the mouth of the liquid nitrogen tank is facing up), and liquid nitrogen is manually added again. This step also has the risk of liquid nitrogen splashing and scalding the operator, and the boiling point of liquid nitrogen is low. The liquid nitrogen poured out of the tank will vaporize instantly, resulting in a waste of liquid nitrogen. If it is in a confined space, there is also a risk of suffocation.

[0005] In summary, the existing sample transfer bracket has the following problems:

[0006] 1. The sample rod has a short low temperature retention time of about 3 to 4 hours, which cannot meet the needs of long-term (more than 10 hours) automatic data collection;

[0007] 2. The bubbles of boiling liquid nitrogen in the Dewar tank will vibrate the sample rod, causing the electron microscope image to drift;

[0008] 3. The sample rod has a limited inclination angle. When the rotation angle is too large, liquid nitrogen will overflow. Due to the limited inclination angle, there is a blind spot in the imaging.

[0009] 4. The commonly used sample transfer stand (with a liquid nitrogen tank at the tail) has a small capacity and needs to be refilled with liquid nitrogen multiple times, which is troublesome to operate and has certain risks. Summary of the invention

[0010] The present invention aims to provide an ultra-long endurance sample transfer system for a cryo-electron microscope, so as to solve the problems of a short low-temperature holding time of a sample rod in an existing sample transfer bracket, bubbles boiling in liquid nitrogen in a dewar tank causing vibration of the sample rod resulting in electron microscope imaging drift, and a limited inclination angle of the sample rod.

[0011] The present invention is achieved by adopting the following technical solutions:

[0012] The present invention provides an ultra-long endurance sample transmission system for a cryo-electron microscope, comprising a dewar tank and a sample rod;

[0013] The Dewar tank comprises an outer tank and an inner tank, wherein the inner tank is located inside the outer tank, a cryogenic fluid 1 is stored in the outer tank, and a cryogenic fluid 2 is stored in the inner tank, wherein the boiling point of the cryogenic fluid 2 is higher than the boiling point of the cryogenic fluid 1;

[0014] A cooling plate is arranged in the inner tank, and the sample rod comprises an outer rod and a cooling rod, wherein the cooling rod is located inside the outer rod, one end of the cooling rod extends into the inner tank and is connected to the cooling plate, and the other end of the cooling rod extends out of the outer rod and is connected to the sample holder;

[0015] The outer rod is connected with a connecting component 1, and the Dewar tank is connected with a connecting component 2. The connecting component 1 and the connecting component 2 are detachably connected.

[0016] As the preferred technical solution:

[0017] A handle is provided on the other side of the Dewar jar.

[0018] As the preferred technical solution:

[0019] The first cryogenic fluid is liquid nitrogen, and the second cryogenic fluid is liquid oxygen;

[0020] Alternatively, the cryogenic fluid 1 and the cryogenic fluid 2 are both liquid nitrogen, and the gas pressure in the outer tank is lower than the gas pressure in the inner tank.

[0021] As the preferred technical solution:

[0022] The outer tank is a vacuum insulation structural component, comprising an outer shell and an inner liner, wherein the inner liner is located inside the outer shell, a vacuum layer is formed between the outer shell and the inner liner, and the inner tank is located inside the inner liner.

[0023] As the preferred technical solution:

[0024] The connecting component 2 includes a transition pipe 1, a transition pipe 2, a transition joint 1, a horn joint and a vacuum joint 1; one end of the transition pipe 1 is connected to one side of the inner tank, and the transition pipe 1 is communicated with the interior of the inner tank, and the other end of the transition pipe 1 is connected to the transition joint 1; one end of the horn joint is a large head end, and the other end is a small head end, the large head end of the horn joint is connected to one side of the outer tank, and the transition pipe 2 and the transition joint 1 are both located in the horn joint; one end of the transition pipe 2 is connected to the transition joint 1, and the other end of the transition pipe 2 is connected to the inner wall of the small head end of the horn joint; the outer wall of the small head end of the horn joint is connected to the vacuum joint 1.

[0025] Since the openings at both ends of the horn connector are of different sizes, one end has a larger opening and the other end has a smaller opening. Therefore, the above-mentioned large end refers to the end of the horn connector with a larger opening, and the small end refers to the end of the horn connector with a smaller opening.

[0026] As the preferred technical solution:

[0027] The outside of the cooling rod is connected with a transition joint 2, the transition joint 2 is connected with a transition pipe 3, and a sealing gasket is arranged between the transition joint 2 and the transition joint 1.

[0028] The transition joint 2, the transition pipe 3 and the sealing gasket cooperate to form a sealing structure, and the sealing gasket can prevent the fluid in the inner tank from flowing to the vacuum joint 1 during the movement of the system.

[0029] As the preferred technical solution:

[0030] A limit pin and a sealing ring are connected between the vacuum joint 1 and the horn joint.

[0031] As the preferred technical solution:

[0032] The connecting component 1 includes a vacuum connector 2, and the vacuum connector 2 is detachably connected to the vacuum connector 1.

[0033] As the preferred technical solution:

[0034] The second vacuum joint is connected to the vacuum joint via a clamp.

[0035] As the preferred technical solution:

[0036] A knob switch is provided on the outer rod, and the knob switch is connected to one side of the second vacuum joint; the knob switch is connected to the pull rod inside the cooling rod, and a sample cover is slidably provided on the sample rack, and one end of the pull rod extends out of the cooling rod and is connected to the sample cover.

[0037] As the preferred technical solution:

[0038] A filling device is provided between the outer tank and the inner tank, and the filling device includes a compensator 1 connected between the outer shell and the inner tank, a filling pipe is provided inside the compensator 1, a compensator 2 is connected to the top of the inner tank, and the filling pipe is connected to the compensator 2;

[0039] The top of the compensator 1 is connected with an outer cover, the outer cover is provided with an exhaust port, and an exhaust pipe is installed at the exhaust port.

[0040] As the preferred technical solution:

[0041] A compensator three is connected between the outer shell and the inner tank, a liquid level gauge is arranged inside the compensator three, and the liquid level gauge extends into the inner tank. An outer cover is connected to the top of the compensator three.

[0042] As the preferred technical solution:

[0043] The system also includes an adjustment platform, on which a slide rail is provided, on which a mounting platform is slidably connected, and the mounting platform can slide along the slide rail; the Dewar tank is mounted on the mounting platform; and the sample rod is mounted on the angle measuring platform of the electron microscope.

[0044] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0045] 1. When the sample transmission system of the present invention is in working state, the dewar tank is not in direct contact with the sample rod, and the weight of the dewar tank and the fluid inside it will not be transferred to the electron microscope, so that the loading capacity of the low-temperature fluid in the dewar tank is large, and an ultra-long endurance of more than 10 hours can be achieved, so that the sample rod can be kept at a low temperature for a long time, and the ultra-long endurance eliminates the hidden danger of operators being frostbitten by liquid nitrogen due to multiple fillings of liquid nitrogen;

[0046] 2. In the sample transmission system of the present invention, the cooling rod of the sample rod contacts the fluid in the inner tank through the cooling plate in the working state, and the fluid in the outer tank continuously transfers cold energy to the fluid in the inner tank, and then the sample on the sample rack is kept at a low temperature through the cooling plate and the cooling rod. Due to the heat exchange between the fluid in the outer tank and the fluid in the inner tank and the heat leakage of the system, the fluid in the outer tank will evaporate and boil, but because the boiling point of the fluid in the outer tank is lower than that of the fluid in the inner tank, the fluid in the inner tank will not boil, and the bubble vibration generated by the boiling of the fluid in the outer tank cannot be directly transmitted to the sample rod, so the present invention can achieve smaller imaging drift and higher resolution;

[0047] 3. When the sample transmission system of the present invention is in working state, the connection component 1 and the connection component 2 are disassembled and separated, the Dewar tank is not in direct contact with the sample rod, and the cold in the inner tank is transferred through the cold conduction plate. Therefore, the sample rod can be rotated 360° for observation, with a larger observation angle and no blind spots in imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is an external schematic diagram of the ultra-long endurance sample transmission system for cryo-electron microscopy described in the present invention.

[0049] Figure 2 This is a half-section diagram of the ultra-long endurance sample transmission system for cryo-electron microscopy described in the present invention.

[0050] Figure 3 Schematic diagram of the ultra-long endurance sample transport system for cryo-electron microscopy after the KF clamp is closed.

[0051] Figure 4 Schematic diagram of the ultra-long endurance sample transfer system for cryo-EM after the KF clamp is opened.

[0052] Figure 5 for Figure 3 Cross-section view along the AA direction.

[0053] Figure 6 for Figure 4 Cross-sectional view along the BB direction.

[0054] Figure 7 This is a schematic diagram of the sample transfer support of the present invention being installed on an adjustment platform.

[0055] Icons: 1-Dewar tank, 2-sample rod, 3-handle, 4-outer tank, 5-inner tank, 6-outer shell, 7-inner liner, 8-vacuum layer, 9-liquid nitrogen, 10-liquid oxygen, 11-cooling plate, 12-cooling rod, 13-outer rod, 14-transition tube 1, 15-transition joint 1, 16-transition tube 2, 17-transition joint 2, 18-sealing pad, 19-transition tube 3, 20-horn joint, 21-KF vacuum joint 1, 22-limit pin, 23- Sealing ring, 24-KF vacuum joint 2, 25-center frame, 26-KF clamp, 27-sample rack, 28-sample cover, 29-knob switch, 30-pull rod, 31-compensator 1, 32-filling pipe, 33-compensator 2, 34-outer cover, 35-exhaust pipe, 36-compensator 3, 37-liquid level gauge, 38-vacuum valve, 39-aviation plug connector, 40-adjustment platform, 41-slide rail, 42-installation platform, 43-sample transfer bracket. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Example 1

[0058] like Figure 1-Figure 7 As shown, this embodiment proposes an ultra-long endurance sample transmission system for a cryo-electron microscope, including a dewar 1 and a sample rod 2, one end of the sample rod 2 extends into the dewar 1 from one side of the dewar 1, and a handle 3 is provided on the other side of the dewar 1.

[0059] The Dewar tank 1 includes an outer tank 4 and an inner tank 5 , and the inner tank 5 is located inside the outer tank 4 .

[0060] The outer tank 4 is a vacuum insulation structural member, which can reduce heat transfer and reduce heat leakage of the system. Specifically, the outer tank 4 includes an outer shell 6 and an inner liner 7, the inner liner 7 is located inside the outer shell 6, a vacuum layer 8 is between the outer shell 6 and the inner liner 7, and the inner tank 5 is located inside the inner liner 7.

[0061] The outer tank 4 stores a cryogenic fluid 1. Specifically, the cryogenic fluid 1 is located in the inner tank 7. The inner tank 5 stores a cryogenic fluid 2. The boiling point of the cryogenic fluid 2 is higher than that of the cryogenic fluid 1. The temperatures of the cryogenic fluid 1 in the outer tank 4 and the cryogenic fluid 2 in the inner tank 5 can be transferred to each other. The coldness of the cryogenic fluid 1 can be transferred to the cryogenic fluid 2, so that the temperature of the cryogenic fluid 2 is reduced to the same temperature as that of the cryogenic fluid 1, while keeping the volume unchanged. The cryogenic fluid 1 will partially evaporate due to heat exchange with the cryogenic fluid 2. Since the boiling point of the cryogenic fluid 1 is lower, all the heat leakage of the system will first cause the cryogenic fluid 1 to boil and evaporate. The cryogenic fluid 2 will continue to remain in liquid state and will not evaporate because the boiling point has not been reached. Naturally, the volume of the cryogenic fluid 2 remains unchanged.

[0062] In this embodiment, the inner tank 5 is a metal thin-wall tank, which is beneficial to the temperature transfer between the fluid in the outer tank 4 and the inner tank 5 .

[0063] In this embodiment, the inner tank 7 stores liquid nitrogen 9, and the melting point of liquid nitrogen 9 is -210°C and the boiling point is -195.8°C under standard atmospheric pressure (absolute pressure 101.325kPa); the inner tank 5 stores liquid oxygen 10, and the melting point of liquid oxygen 10 is -218°C and the boiling point is -183°C under standard atmospheric pressure; liquid oxygen 10 is solid below the melting point, liquid between the melting point and the boiling point, and gaseous above the boiling point. Liquid nitrogen 9 and liquid oxygen 10 are both at -195.8°C after heat exchange through the wall of the inner tank 5. Since the boiling point of liquid oxygen 10 is higher than that of liquid nitrogen 9, liquid nitrogen 9 will evaporate due to heat exchange with liquid oxygen 10 and system heat leakage, but liquid oxygen 10 will continue to remain in liquid state and will not evaporate because its boiling point has not been reached, and its volume remains unchanged.

[0064] A cooling plate 11 is provided in the inner tank 5, and the sample rod 2 includes an outer rod 13 and a cooling rod 12. The cooling rod 12 is located inside the outer rod 13, and one end of the cooling rod 12 is connected to one side of the cooling plate 11. The cooling plate 11 is partially immersed in the low-temperature fluid 2, thereby transferring the cold energy to the sample rod 2.

[0065] A transition pipe 14 is connected to one side of the inner tank 5, and the transition pipe 14 is connected to the inside of the inner tank 5. One end of the transition pipe 14 is fixedly connected to the side of the inner tank 5, and the other end of the transition pipe 14 passes through the inner tank 7. The outer wall of the transition pipe 14 is connected and sealed to the contact part of the inner tank 7. The liquid level of the low-temperature fluid 2 in the inner tank 5 is lower than the bottom height of the transition pipe 14. The inner tank 7 is filled with the low-temperature fluid 1, and the low-temperature fluid 1 surrounds the inner tank 5 and the transition pipe 14.

[0066] One end of the transition pipe 14 extending out of the inner liner 7 is located in the vacuum layer 8, and this end of the transition pipe 14 is connected to a transition joint 15, one end of the transition joint 15 is inserted into the transition pipe 14 and fixedly connected to the transition pipe 14, and the other end of the transition joint 15 passes through the outer shell 6, and the outer wall of the transition joint 15 is connected and sealed to the contact part of the outer shell 6. One end of the transition joint 15 extending out of the outer shell 6 is connected to a transition pipe 2 16.

[0067] The outside of the cooling rod 12 is connected to a transition joint 2 17, which is located inside the transition joint 1 15, and a sealing gasket 18 is provided between the transition joint 2 17 and the transition joint 1 15. One end of the transition joint 2 17 is connected to a transition pipe 3 19, which is located inside the transition pipe 2 16.

[0068] A horn joint 20 is connected to the outer side of the housing 6. One end of the horn joint 20 has a larger opening and the other end has a smaller opening. The end of the horn joint 20 with a larger opening is fixed to the housing 6. The transition joint 15, the transition joint 2 17, the transition pipe 2 16 and the transition pipe 3 19 are all located in the horn joint 20. One end of the transition pipe 2 16 is connected to the transition joint 1 15, and the other end of the transition pipe 2 16 is connected to the inner wall of the end with a smaller opening of the horn joint 20, thereby fixing the transition pipe 2 16. A KF vacuum joint 1 21 is connected to the outer wall of the end with a smaller opening of the horn joint 20. The KF vacuum joint 1 21 can rotate 360° around the axis direction of the horn joint 20.

[0069] A limit pin 22 is connected between the KF vacuum joint 21 and the horn joint 20, and the KF vacuum joint 21 is limited to move axially by the limit pin 22. Two sealing rings 23 are arranged between the KF vacuum joint 21 and the horn joint 20 for sealing therebetween.

[0070] One end of the KF vacuum joint 1 21 is connected to the horn joint 20, and the other end of the KF vacuum joint 1 21 is connected to the KF vacuum joint 2 24. A center frame 25 is provided between the KF vacuum joint 1 21 and the KF vacuum joint 2 24, and the KF vacuum joint 1 21 and the KF vacuum joint 2 24 are positioned and sealed by the center frame 25, and the KF vacuum joint 1 21 and the KF vacuum joint 2 24 are connected and fixed by a KF clamp 26.

[0071] One end of the cooling rod 12 penetrates from the outer rod 13, and then passes through the KF vacuum joint 24, the KF vacuum joint 1 21, the transition pipe 3 19, the transition pipe 1 14 in sequence, and is connected to the center of the cooling plate 11. The cooling rod 12 is in a suspended state, and does not directly contact the Dewar tank 1, and only contacts the fluid in the inner tank 5 through the cooling plate 11. Since the cooling rod 12 does not directly contact the fluid in the outer tank 4, the vibration generated by the boiling of the fluid in the outer tank 4 cannot be directly transmitted to the sample rod 2. In this way, the drift caused by the electron microscope imaging will be smaller than the direct contact of the prior art, which is very beneficial to imaging. The other end of the cooling rod 12 extends out of the outer rod 13 and is connected to a sample rack 27. The sample rack 27 is provided with a sample slot, and the sample slot is used to place the sample. The cooling plate 11 transfers the cold in the inner tank 5 to the sample rack 27 by solid conduction, and keeps the sample in a low temperature state. A sample cover 28 is slidably disposed on the sample rack 27 , and the sample cover 28 can close the sample slot, thereby protecting the sample from contamination when transferring the sample.

[0072] The outer rod 13 is provided with a knob switch 29, and the knob switch 29 is connected to one side of the KF vacuum joint 24. The interior of the knob switch 29 is connected to the pull rod 30 inside the cooling rod 12, one end of the pull rod 30 is connected to the knob switch 29, and the other end extends out of the cooling rod 12 and is connected to the sample cover 28. By rotating the knob switch 29, the pull rod 30 moves forward and backward, thereby opening and closing the sample cover 28, and protecting the sample during the transfer of the sample to the cryo-electron microscope.

[0073] Furthermore, in order to realize filling of the inner tank 5 and the outer tank 4, a filling device is provided between the outer tank 4 and the inner tank 5, and the filling device includes a compensator 1 31 connected between the outer shell 6 and the inner tank 7, a filling pipe 32 is provided inside the compensator 1 31, and a compensator 2 33 is connected to the top of the inner tank 5, and the filling pipe 32 is connected to the compensator 2 33. The inner tank 5 is filled through the filling pipe 32, and the outer tank 4 is filled through the gap between the compensator 1 31 and the filling pipe 32. The top of the compensator 1 31 is threadedly connected with an outer cover 34, and an exhaust port is opened on the outer cover 34, and an exhaust pipe 35 is installed at the exhaust port.

[0074] Furthermore, a compensator 36 is connected between the outer shell 6 and the inner liner 7, and a liquid level gauge 37 is arranged inside the compensator 36, and the liquid level gauge 37 extends into the inner liner 7. The top of the compensator 36 is also connected to an outer cover 34.

[0075] Furthermore, the two sides of the KF vacuum connector 24 are respectively connected with a vacuum valve 38 and an aviation plug connector 39. Figure 3 shown.

[0076] In this embodiment, the KF vacuum joint 1 21 and the KF vacuum joint 2 24 adopt KF vacuum flanges.

[0077] like Figure 7 As shown, the system further includes an adjustment platform 40, on which a pair of slide rails 41 are disposed, and a mounting platform 42 is slidably connected to the slide rails 41, and the mounting platform 42 can slide along the slide rails 41. The Dewar tank 1 and the sample rod 2 form a sample transfer bracket 43, and the sample transfer bracket 43 can be fixedly mounted on the mounting platform 42, and move linearly along the front and rear edges together with the mounting platform 42.

[0078] In the working state, the dewar tank 1 is directly mounted on the mounting platform 42, and the sample rod 2 is mounted on the angle measuring platform of the electron microscope; since the dewar tank 1 is not in direct contact with the sample rod 2, the weight of the dewar tank 1 and the fluid therein will not be transferred to the sample rod 2 and the electron microscope, so that the fluid capacity in the dewar tank 1 can be made larger without causing damage to the angle measuring platform of the electron microscope, and more liquid nitrogen 9 can achieve ultra-long temperature endurance, which eliminates the risk of operators being frostbitten by liquid nitrogen due to multiple refillings. Moreover, since the dewar tank 1 is not in direct contact with the sample rod 2, the coldness of the inner tank 5 is transferred through the cold conduction plate 11, so the sample rod 2 can achieve 360° rotation observation, with a larger observation angle and no blind spots for imaging.

[0079] In the working state, the cold conduction plate 11 is only in contact with the fluid in the inner tank 5. Since the boiling point of the fluid in the outer tank 4 is higher than that of the fluid in the inner tank 5, the fluid in the inner tank 5 will not boil, and the bubble vibration generated by the boiling of the fluid in the outer tank 4 cannot be directly transmitted to the sample rod 2. Therefore, the present invention can achieve smaller imaging drift and higher resolution.

[0080] When in use, firstly, the KF vacuum joint 1 21 and the KF vacuum joint 2 24 are manually clamped and fixed by the KF clamp 26, so that the sample rod 2 is connected to the Dewar tank 1 as a whole. At the same time, since the transition joint 15 and the transition joint 2 17 are sealed by the sealing gasket 18, it can be prevented that the fluid in the inner tank 5 flows to the KF vacuum joint 1 21 during the movement of the system; then, the outer cover 34 on the top of the compensator 1 31 is unscrewed, and the compensator 1 is filled with vacuum from the gap between the compensator 1 31 and the filling pipe 32. The outer tank 4 is filled with fluid medium (such as liquid nitrogen 9). After the temperatures of various components are balanced, the outer tank 4 is replenished with liquid nitrogen 9 to its full liquid level, and the outer cover 34 is screwed on; then the inner tank 5 is quantitatively replenished with fluid (such as liquid oxygen 10), and the cold energy of the liquid oxygen 10 is transferred to the sample rack 27 at the front end through the cooling rod 12. The cold energy of the liquid nitrogen 9 in the outer tank 4 is continuously transferred to the liquid oxygen 10 through the thin-walled inner tank 5. The cold energy of the liquid nitrogen 9 in the outer tank 4 is actually consumed in this system; at this time, the sample can be loaded onto the sample rack 27 through the sample stage, and the sample cover 28 is closed. Move the entire system to the adjustment platform 40, rotate the sample rod 2, the KF vacuum joint 24, the KF clamp 26 and other components 90° along the axial direction of the horn joint 20. At this time, the outer tank 4 and the inner tank 5 remain stationary, and the cooling rod 12 and the cooling plate 11 rotate 90° synchronously. After the sample rod 2 is aligned with the electron microscope port, push the sample transfer bracket 43 and the installation platform 42 forward synchronously. After the electron microscope is evacuated, manually rotate the KF vacuum joint 24 and other components to rotate them back to their original positions, continue to push the sample transfer bracket 43 to the bottom, and then manually open the KF clamp 26, move the outer tank 4 as a whole backward by about 10 to 15 mm, and the system installation is complete. Figure 4 and Figure 6 As shown, at this time, the sample rod 2 and the Dewar tank 1 on the electron microscope are disconnected from the KF vacuum joint 24, without any rigid connection, and the cold continues to be transferred from the cooling rod 12 to the sample holder 27 at the front end. This system can completely avoid the vibration caused by the boiling of liquid nitrogen 9 and reduce the sample drift rate. And because the Dewar tank 1 is supported by the mounting platform 42 and is completely separated from the sample rod 2 on the electron microscope, the capacity of the Dewar tank 1 can be made larger, and more liquid nitrogen 9 can be added at a time, so the low temperature can be maintained for a longer time (more than 10 hours), extending the effective observation time of the sample.

[0081] Example 2

[0082] The difference between this embodiment and embodiment 1 is that:

[0083] The outer tank 4 and the inner tank 5 are both filled with liquid nitrogen 9. After the outer tank 4 is filled with liquid nitrogen 9, it is sealed by covering the outer cover 34, and the exhaust pipe 35 connected to the outer cover 34 is connected to the vacuum pump, and the vacuum pump is started to make the air pressure in the outer tank 4 lower than the standard atmospheric pressure, while the air pressure in the inner tank 5 remains unchanged. At this time, the temperature and phase change point of the liquid nitrogen 9 in the outer tank 4 will also decrease accordingly; it is only necessary to keep the temperature in the outer tank 4 in the range of -195.8 to -210°C, so that the liquid nitrogen 9 in the inner tank 5 can be kept in a liquid state without boiling; if the air pressure of the outer tank 4 is controlled at an absolute pressure of 45KPa, the temperature and boiling point of the liquid nitrogen 9 are -202°C. At this time, the liquid nitrogen 9 in the inner tank 5 and the liquid nitrogen 9 in the outer tank 4 are both at -202°C after heat exchange through the wall of the inner tank 5, and the boiling point of the liquid nitrogen 9 in the inner tank 5 is higher than the boiling point of the liquid nitrogen 9 in the outer tank 4. By changing the gas pressures of the outer tank 4 and the inner tank 5 , the gas pressure in the outer tank 4 is made lower than the gas pressure in the inner tank 5 , thereby changing the boiling points of the fluids in the two tanks.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultra-long-duration sample transport system for cryo-electron microscopy, Features: Includes Dewar and sample rod; The Dewar tank comprises an outer tank and an inner tank, wherein the inner tank is located inside the outer tank, a cryogenic fluid 1 is stored in the outer tank, and a cryogenic fluid 2 is stored in the inner tank, wherein the boiling point of the cryogenic fluid 2 is higher than the boiling point of the cryogenic fluid 1; A cooling plate is arranged in the inner tank, and the sample rod comprises an outer rod and a cooling rod, wherein the cooling rod is located inside the outer rod, one end of the cooling rod extends into the inner tank and is connected to the cooling plate, and the other end of the cooling rod extends out of the outer rod and is connected to the sample holder; The outer rod is connected with a connecting component 1, and the Dewar tank is connected with a connecting component 2. The connecting component 1 and the connecting component 2 are detachably connected.

2. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 1, Features: The first cryogenic fluid is liquid nitrogen, and the second cryogenic fluid is liquid oxygen; Alternatively, the cryogenic fluid 1 and the cryogenic fluid 2 are both liquid nitrogen, and the gas pressure in the outer tank is lower than the gas pressure in the inner tank.

3. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 1, Features: The outer tank is a vacuum insulation structural component, comprising an outer shell and an inner liner, wherein the inner liner is located inside the outer shell, a vacuum layer is formed between the outer shell and the inner liner, and the inner tank is located inside the inner liner.

4. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 1, Features: The connecting component 2 includes a transition pipe 1, a transition pipe 2, a transition joint 1, a horn joint and a vacuum joint 1; one end of the transition pipe 1 is connected to one side of the inner tank, and the transition pipe 1 is communicated with the interior of the inner tank, and the other end of the transition pipe 1 is connected to the transition joint 1; one end of the horn joint is a large head end, and the other end is a small head end, the large head end of the horn joint is connected to one side of the outer tank, and the transition pipe 2 and the transition joint 1 are both located in the horn joint; one end of the transition pipe 2 is connected to the transition joint 1, and the other end of the transition pipe 2 is connected to the inner wall of the small head end of the horn joint; the outer wall of the small head end of the horn joint is connected to the vacuum joint 1.

5. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 4, Features: The outside of the cooling rod is connected with a transition joint 2, the transition joint 2 is connected with a transition pipe 3, and a sealing gasket is arranged between the transition joint 2 and the transition joint 1.

6. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 4, Features: The connecting component 1 includes a vacuum connector 2, and the vacuum connector 2 is detachably connected to the vacuum connector 1.

7. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 6, Features: A knob switch is provided on the outer rod, and the knob switch is connected to one side of the second vacuum joint; the knob switch is connected to the pull rod inside the cooling rod, and a sample cover is slidably provided on the sample rack, and one end of the pull rod extends out of the cooling rod and is connected to the sample cover.

8. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 3, Features: A filling device is provided between the outer tank and the inner tank, and the filling device includes a compensator 1 connected between the outer shell and the inner tank, a filling pipe is provided inside the compensator 1, a compensator 2 is connected to the top of the inner tank, and the filling pipe is connected to the compensator 2; The top of the compensator 1 is connected with an outer cover, the outer cover is provided with an exhaust port, and an exhaust pipe is installed at the exhaust port.

9. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 3, Features: A compensator three is connected between the outer shell and the inner tank, a liquid level gauge is arranged inside the compensator three, and the liquid level gauge extends into the inner tank. An outer cover is connected to the top of the compensator three.

10. The ultra-long endurance sample transmission system for cryo-electron microscopy according to claim 1, Features: The system also includes an adjustment platform, on which a slide rail is provided, on which a mounting platform is slidably connected, and the mounting platform can slide along the slide rail; the Dewar tank is mounted on the mounting platform; and the sample rod is mounted on the angle measuring platform of the electron microscope.

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