Water vapor cryopump and method for testing water vapor pumping speed

Abstract

The application discloses a water-vapor low-temperature pump, which comprises a refrigerator, a shell, a baffle, a radiation cold shield, a low-temperature plate and a drainage assembly. The shell is connected with the refrigerator. The radiation cold shield is connected with a first-stage cooling table of the refrigerator. The low-temperature plate is connected with a second-stage cooling table of the refrigerator. The baffle is connected with the top of the radiation cold shield. The radiation cold shield is located in the interior of the shell. The radiation cold shield and the shell are coaxially arranged. The bottom of the shell and the radiation cold shield is an inclined surface. The shell and the inclined surface of the radiation cold shield are provided with a water outlet. The water outlet of the shell is connected with the drainage assembly. The application further discloses a water-vapor pumping speed test method. The application has the beneficial effects that the regeneration time of the low-temperature pump is shortened, the regeneration effect is improved, the adverse effect on the front-stage pump is avoided, the operation efficiency of the coating equipment is improved, the water-vapor test method of the low-temperature pump can optimize the theoretical calculation parameters and improve the calculation precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-temperature vacuum technology, and in particular to a water-vapor pumping low-temperature pump and a water-vapor pumping speed testing method. BACKGROUND

[0002] A low-temperature pump is an ultra-high vacuum pump that captures gas by using low-temperature condensation, low-temperature adsorption and low-temperature trapping mechanisms. The ultimate vacuum can reach 10 -11 Pa. The low-temperature pump has the advantages of high pumping speed, high ultimate vacuum, no moving parts and true cleanliness without oil, and is widely used in high-end manufacturing fields such as optical coating and integrated circuits.

[0003] With the continuous development of industrial level and vacuum technology, the types of substrate materials and coating materials for vacuum coating are increasing, and higher requirements are also put forward for coating equipment and coating processes. Sputtering coating is a common method in coating processes. It is a coating method that uses high-speed inert gas ions to bombard atoms, atomic groups or molecules on the surface of the target in a vacuum, and then deposits them on the substrate. Optical thin film is a common functional thin film, from glasses to mobile phones, computers, LCD displays to LED lighting, and is widely used in various aspects of our lives. This film layer requires a clean vacuum environment during preparation, and is particularly sensitive to water vapor in the vacuum system. The presence of water vapor not only affects the deposition quality of the film layer, but also affects the optical properties of the thin film. Therefore, optical coating equipment needs to be equipped with an ultra-high vacuum pump with high pumping speed for water vapor. Common ultra-high vacuum pumps include oil diffusion pumps, molecular pumps and low-temperature pumps. However, due to the risk of oil contamination, oil diffusion pumps need to be used with a cold trap. Molecular pumps have slow pumping speed and poor water vapor pumping effect in high vacuum, and low-temperature pumps have become the preferred ultra-high vacuum pump in optical coating equipment in recent years.

[0004] With the widespread use of low-temperature pumps in the field of optical coating, a large amount of water vapor is captured in the pump body during use. During the saturation and regeneration process of the low-temperature pump, the water vapor will be liquefied into water and remain in the pump body. Before restarting, a pre-pump is used to pre-pump the vacuum, but the pumping speed of the pre-pump for water vapor is relatively poor, and long-term pumping of water vapor will quickly degrade the performance of the pre-pump. For example, Chinese patent application CN113236530A discloses a low-temperature pump with water vapor regeneration, which uses a pre-pump to pump out the water vapor generated during the regeneration process. This method not only has slow pumping speed, but also affects the service life of the pre-pump.

[0005] According to the JB / T 11081-2011 industry standard of "Refrigerator Low Temperature Pump", the pumping speed test of the low temperature pump adopts two methods of flow method and flow guide method, both of which need high-purity test gas and high-precision flow meter to control the gas flow, and the two methods can accurately measure the second and third type gases such as N2, Ar and H2, but are not applicable to the first type gas H2O, and at present, the industry basically adopts the theoretical calculation method to determine the pumping speed of H2O, and lacks the actual test method of H2O.

[0006] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the general background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art that is already known in this field. SUMMARY

[0007] One of the technical problems to be solved by the application is how to solve the automatic drainage of the existing low temperature pump and solve the problem of slow pumping speed and short service life of the front stage pump caused by a large amount of water vapor during regeneration.

[0008] The second technical problem to be solved by the application is how to provide a pumping speed test method suitable for water vapor.

[0009] The application solves the above technical problems by the following technical means:

[0010] The water vapor low temperature pump comprises a refrigerator, a shell, a baffle, a radiation cold screen, a low temperature plate and a drainage assembly; the shell is connected with the refrigerator, the radiation cold screen is connected with a first stage cooling table of the refrigerator, the low temperature plate is connected with a second stage cooling table of the refrigerator, the baffle is connected with the top of the radiation cold screen, the radiation cold screen is located in the interior of the shell, the radiation cold screen and the shell are coaxially arranged, the bottom of the shell and the radiation cold screen is an inclined surface, the inclined surface of the shell and the radiation cold screen is provided with a water outlet, and the water outlet of the shell is connected with the drainage assembly.

[0011] The application is mainly applied to the coating equipment with high water vapor content, and the shell is connected with the coating machine through a flange during use, the low temperature pump is pre-pumped to the starting pressure value, the refrigerator is lowered to low temperature, and the vacuum chamber is pumped to the required vacuum degree through low temperature condensation and adsorption; the low temperature pump shell and the bottom of the radiation cold screen are designed into an arch bottom head shape, the liquid water during regeneration is directed to flow to the groove bottom of the arch bottom head of the pump body, the drainage assembly is installed at the lowest position of the arch bottom head, and the water generated during regeneration is quickly discharged from the pump body at normal temperature, so that the pre-pumping time of the front stage pump is greatly shortened, and the regeneration efficiency of the low temperature pump is improved.

[0012] Preferably, a heating block is further connected with the first stage cooling table and the second stage cooling table of the refrigerator.

[0013] The heating block is installed on the first cooling table and the second cooling table, and functions to heat the first cooling table and the second cooling table during regeneration, reduce the temperature recovery time, and ensure complete regeneration of the adsorbent material on the low-temperature plate.

[0014] Preferably, the shell comprises a pump flange, a cylinder, and a bottom seal, the cylinder is a cylindrical tube with open ends, the pump flange is connected to the outside of the top end of the cylinder, the bottom end of the cylinder is connected to the bottom seal, the bottom surface of the bottom seal is an inclined surface, the water outlet is located at the lowest point of the inclined surface, and the drainage assembly is connected to the bottom seal.

[0015] Preferably, the baffle comprises a plurality of annular plates and a plurality of connecting plates, one end of the plurality of connecting plates is connected, and the other end is connected to the inner wall of the radiation cold screen, the plurality of annular plates are connected to the connecting plates at equal intervals, and the diameter of one end of the annular plate close to the air inlet is smaller than that of the other end away from the air inlet.

[0016] Preferably, the low-temperature plate comprises a mounting cylinder and a plurality of low-temperature single plates, the plurality of low-temperature single plates are connected to the outside of the mounting cylinder in the height direction of the mounting cylinder, and the mounting cylinder is connected to the refrigerator.

[0017] Preferably, the drainage assembly comprises a filter device and a solenoid valve, the drainage port is connected to the filter device, and the filter device is connected to the solenoid valve.

[0018] The drainage assembly is composed of a filter device and a solenoid valve, and is installed at the lowest point of the pump body; when the intelligent controller identifies that the temperature and the pump body pressure meet the set conditions, the solenoid valve is automatically opened to discharge the liquid water in the pump body; the filter device is installed at the water inlet of the valve, mainly plays a role in filtering solid impurities in the water body, and guarantees the sealing property of the valve; and the valve is automatically closed after being opened for a certain period of time.

[0019] Preferably, the gas purging joint is further included, and the gas purging joint is connected to the shell and extends into the inside of the radiation cold screen.

[0020] The gas purging joint functions to purge high-purity N2 in the shell during regeneration, accelerates the regeneration time of the low-temperature pump, and simultaneously, part of the water vapor in the low-temperature pump is also discharged from the safety valve with the gas.

[0021] The application further provides a water vapor pumping speed test method, comprising the water vapor pumping low-temperature pump, a test sealing device, a heating device, a sealed measuring cylinder, and an evacuation device; the water vapor pumping low-temperature pump is connected to the test sealing device, the test sealing device comprises a vacuum gauge and an air inlet, the sealed measuring cylinder is connected to the test sealing device through a gas pipeline, and the sealed measuring cylinder is connected to the evacuation device through an evacuation pipeline.

[0022] The heating device heats the sealed cylinder while recording the water level scale, opens the evacuation device; when the water in the sealed cylinder starts to boil, the water vapor is introduced into the test sealing device to the vacuum value to be tested and the timing is started, the water vapor is kept for more than 10 minutes, the water vapor is closed, the water level scale value and the continuous water vapor time are recorded, the water vapor pumping speed of the water vapor cryogenic pump under the vacuum value to be tested is obtained through S=Q / P, the above operation is repeated for several times, the water vapor pumping speed under different vacuum values is obtained, and finally the water vapor pumping speed curve of the water vapor cryogenic pump is obtained.

[0023] Preferably, the heating device comprises a thermostat heater, a vessel, water in the vessel, the sealed cylinder is located in the vessel, and the vessel is located on the thermostat heater.

[0024] Preferably, a needle valve and a hand valve are further included, the needle valve is connected to the gas pipeline, and the hand valve is connected to the evacuation pipeline.

[0025] The application has the advantages that:

[0026] (1) The application is mainly applied to a coating equipment with high water vapor content, when used, the shell is connected with the coating machine, the cryogenic pump is pre-evacuated to the starting pressure value, the refrigerator is lowered to low temperature, and the vacuum chamber is pumped to the required vacuum degree through low-temperature adsorption; the shell and the bottom of the radiation cold screen of the cryogenic pump are designed in the shape of a bow bottom head, realizing directional flow of liquid water to the groove bottom of the bow bottom head of the pump body during regeneration, and the drain assembly is installed on the lowest position of the bow bottom head to quickly drain the water generated during regeneration at room temperature, greatly shortening the pre-evacuation time of the front-stage pump, improving the regeneration efficiency of the cryogenic pump, shortening the regeneration time of the cryogenic pump, improving the regeneration effect of the cryogenic pump, avoiding adverse effects on the front-stage pump, and improving the operation efficiency of the coating equipment.

[0027] (2) The heating block is installed on the first-stage cooling table and the second-stage cooling table, and functions to heat the first-stage cooling table and the second-stage cooling table during regeneration, reduce the temperature recovery time, and ensure complete regeneration of the adsorption material on the low-temperature plate.

[0028] (3) The drain assembly is composed of a filter device and an electromagnetic valve, and is installed at the lowest position of the pump body; when the temperature and the pump body pressure meet the set conditions, the intelligent controller automatically opens the electromagnetic valve to drain the liquid water in the pump body; the filter device is installed at the water inlet of the valve, mainly functions to filter solid impurities in the water body, ensure the sealing property of the valve, and automatically close the valve after being opened for a certain time.

[0029] (4) The gas purging connector functions to purge high-purity N2 in the shell during regeneration, accelerates the regeneration time of the cryogenic pump, and part of the water vapor in the cryogenic pump is also discharged from the safety valve with the gas; the methods of draining, purging and heating are adopted to ensure complete removal of the water vapor, reduce the regeneration time, and improve the regeneration effect of the cryogenic pump.

[0030] (5) The low-temperature pump water vapor test method provided by the application can obtain the measured data of the water vapor pumping speed of the low-temperature pump, and can also comprehensively compare the data with the theoretically calculated data, optimize the theoretical calculation parameters, and improve the calculation accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a structural schematic diagram of the water vapor pumping low-temperature pump in the embodiment one of the application;

[0032] Figure 2 is a sectional view of the water vapor pumping low-temperature pump in the embodiment one of the application;

[0033] Figure 3 is a rear schematic diagram of the hidden shell and the radiation cold screen in the embodiment one of the application;

[0034] Figure 4 is a schematic diagram of the low-temperature pump water vapor test system in the embodiment two of the application;

[0035] Markings in the figure:

[0036] 1, water vapor pumping low-temperature pump; 11, refrigerator; 12, shell; 121, pump port flange; 122, cylinder; 123, bottom sealing; 13, baffle; 131, annular plate; 132, connecting plate; 133, bending piece; 14, radiation cold screen; 15, low-temperature plate; 151, mounting cylinder; 152, low-temperature single plate; 16, drainage assembly; 161, filtering device; 162, electromagnetic valve; 17, heating block; 18, gas purging joint;

[0037] 2, test sealing device; 3, heating device; 31, constant-temperature heater; 32, vessel; 4, sealed cylinder; 5, evacuation device; 6, gas pipeline; 7, evacuation pipeline; DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the embodiments of the application more clear, the technical scheme in the embodiments of the application will be described clearly and completely below in combination with the embodiments of the application. Obviously, the described embodiments are some of the embodiments of the application, but not all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0039] Embodiment one:

[0040] As shown in Figure 1 , Figure 2 , the water vapor pumping low-temperature pump 1 comprises a refrigerator 11, a shell 12, a baffle 13, a radiation cold screen 14, a low-temperature plate 15, a drainage assembly 16, and a heating block 17.

[0041] In this embodiment, the refrigerator 11 is a G-M refrigerator, which is used as a low-temperature heat source of the cryogenic pump. The refrigerator has the advantages of simple structure and few low-temperature moving parts. The refrigerator uses bipolar refrigeration, and has a first cooling stage with a first cooling temperature and a second cooling stage with a second cooling temperature. The first cooling stage is cooled to 65-100K, and the second cooling stage is cooled to 10-15K.

[0042] The shell 12 comprises a pump flange 121, a cylinder body 122, and a bottom seal 123. The cylinder body 122 is a cylindrical barrel with open ends. The pump flange 121 is connected to the outside of the top end of the cylinder body 122. The bottom end of the cylinder body 122 is connected to the bottom seal 123. The bottom seal 123 has a disc-shaped structure with a raised middle part and a lower periphery. The top edge of the bottom seal 123 has the same outer contour as the cylinder body 122, ensuring reliable connection between the cylinder body 122 and the bottom seal 123. The bottom seal 123 has an inclined surface, and the water outlet is located at the lowest point of the inclined surface. The drain assembly 16 is connected to the water outlet of the bottom seal 123. During regeneration, liquid water collects at the water outlet along the inclined surface and is discharged by the drain assembly 16. The middle part of the bottom seal 123 is provided with a circular hole, and a transition cylinder is connected to the circular hole. The transition cylinder is located outside the refrigerator 11 and is connected to the refrigerator 11.

[0043] As shown in Figure 3 The baffle 13 comprises a plurality of annular plates 131, a plurality of connecting plates 132, and a plurality of bending pieces 133. The plurality of connecting plates 132 are arranged in a diverging manner, and one end of the plurality of connecting plates 132 is connected together, and the other end is connected to the inner wall of the radiation cold shield 14 through the L-shaped bending piece 133. In this embodiment, the connecting plate 132 and the bending piece 133 are both six and arranged in a circumferential array. The plurality of annular plates 131 are arranged at equal intervals, and each annular plate 131 is connected to the connecting plate 132. Specifically, the connecting plate 132 can be provided with a plurality of inclined grooves in the length direction, and the annular plate 131 is inserted into the inclined groove and welded. The sizes of the plurality of annular plates 131 gradually increase from the center axis of the cryogenic pump to the outward extension direction, and the annular plate 131 is inclined. The diameter of one end of the annular plate 131 close to the air inlet is smaller than the diameter of the other end away from the air inlet. The baffle 3 is installed in the air inlet of the cryogenic pump in a manner of facing the vacuum chamber, and is designed as a louver structure. The baffle 3 functions to remove water vapor in the vacuum chamber, pre-cools the second and third types of gas, and reduces thermal radiation to the internal structure.

[0044] As shown in Figure 2As shown, the radiation cold shield 14 is arranged between the shell 12 and the adsorption array and surrounds the cryopanel 15, the bottom of the radiation cold shield 14 is in thermal connection with the primary cooling stage of the refrigerator 11 through bolts, and the bottom head of the radiation cold shield 14 also adopts an arch bottom head structure, that is, has an inclined surface, the length of the inclined surface can match the size of the baffle 13 and the cryopanel 15, so as to ensure that the water melted from the baffle 13 flows to the bottom of the groove through the cryopanel 15. The radiation cold shield 14 is coaxially arranged with the shell 12. The radiation cold shield 14 is located inside the shell 12.

[0045] As shown in the drawings, Figure 2 The cryopanel 15 includes a mounting cylinder 151 and a plurality of cryopanels 152, the plurality of cryopanels 152 are connected to the outside of the mounting cylinder 151 in the height direction of the mounting cylinder 151, and the mounting cylinder 151 is connected to the refrigerator 11, specifically, the cryopanel 15 is connected to the secondary cooling stage of the refrigerator 11, and the cryopanel 152 is a circular plate structure as a whole, and the edge thereof is inclined downward to facilitate water flow downward.

[0046] As shown in the drawings, Figure 2 The drainage assembly 16 includes a filter device 161 and a solenoid valve 162, the drainage port is connected to the filter device 161, and the bottom of the filter device 161 is connected to the solenoid valve 162. The drainage assembly 16 is composed of the filter device 161 and the solenoid valve 162, and is installed at the lowest part of the pump body. When the intelligent controller identifies that the temperature and the pump body pressure meet the set conditions, the solenoid valve 162 is automatically opened to drain the liquid water in the pump body. The filter device 161 is installed at the water inlet of the valve, and mainly functions to filter solid impurities in the water body and ensure the sealing property of the valve. The valve is automatically closed after being opened for a certain period of time.

[0047] The heating block 17 is connected to the primary cooling stage and the secondary cooling stage of the refrigerator 11. The heating block 17 is installed on the primary cooling stage and the secondary cooling stage, and functions to heat the primary cooling stage and the secondary cooling stage during regeneration, reduce the rewarming time, and ensure complete regeneration of the adsorption material on the cryopanel.

[0048] The water vapor cryopump 1 further includes a gas purging connector 18 connected to the shell 12 and extending into the inside of the radiation cold shield 14. The gas purging connector 18 functions to purge high-purity N2 in the shell 12 during regeneration, accelerate the regeneration time of the cryopump, and simultaneously discharge part of the water vapor in the cryopump from the safety valve together with the gas.

[0049] The embodiment is mainly applied to the coating equipment with high water vapor content. When in use, the shell 12 is connected with the coating machine, the temperature pump is pre-extracted to the starting pressure value, the refrigerator 11 is lowered to low temperature, and the vacuum chamber is extracted to the required vacuum degree through low-temperature adsorption. In the embodiment, the low-temperature pump shell 12 and the bottom of the radiation cold screen 14 are designed into an arch bottom head shape, so that the liquid water generated during regeneration is directed to flow to the groove bottom of the arch bottom head of the pump body. The drainage assembly 16 is installed in the lowest position of the arch bottom head and is used for quickly draining the water generated during regeneration at room temperature. The pre-extraction time of the front-stage pump is greatly shortened, and the regeneration efficiency of the low-temperature pump is improved.

[0050] The low-temperature pump in the embodiment can shorten the regeneration time of the low-temperature pump, improve the regeneration effect of the low-temperature pump, avoid the adverse effect on the front-stage pump, and improve the operation efficiency of the coating equipment.

[0051] Embodiment two:

[0052] As shown in Figure 4 , the embodiment provides a water vapor extraction speed test method. The test system includes the water vapor extraction low-temperature pump 1, the test sealing device 2, the heating device 3, the sealed cylinder 4, the evacuation device 5, the gas pipeline 6, and the evacuation pipeline 7 in the above-mentioned embodiment one.

[0053] The water vapor extraction low-temperature pump 1 is mechanically connected with the test sealing device 2 through the pump flange. The test sealing device 2 includes a vacuum measuring gauge. The sealed cylinder 4 is connected with the test sealing device 2 through the gas pipeline 6. The sealed cylinder 4 is connected with the evacuation device 5 through the evacuation pipeline 7. A needle valve is connected on the gas pipeline 6, and a hand valve is connected on the evacuation pipeline 7.

[0054] The heating device 3 includes a constant-temperature heater 31 and a vessel 32. The vessel 32 contains water. The sealed cylinder 4 is located in the vessel 32. The vessel 32 is located on the constant-temperature heater 31. The water in the vessel 32 heats the water in the sealed cylinder 4. The vessel 32 is made of glass, so that the situation in the vessel 32 and the sealed cylinder 4 can be observed.

[0055] In the embodiment, the water vapor extraction low-temperature pump 1 adopts the DN550 caliber low-temperature pump commonly used in vacuum coating. The structure design is shown in Figure 1 、 Figure 2 . The water vapor extraction low-temperature pump 1 has the characteristics of high water vapor extraction speed and simple water drainage. The vacuum measuring gauge has a measuring range of 10 -7The vacuum range is ~1Pa. The vacuum value inside the water vapor cryogenic pump 1 is displayed in real time by the display instrument. The installation position is in accordance with the test standard. The needle valve can finely adjust the flow rate of water vapor entering the cryogenic pump and adjust the vacuum value of the water vapor cryogenic pump 1, thereby obtaining the pumping speed results of the water vapor cryogenic pump 1 under different vacuum values. The gas pipeline 6 is used to connect the entire test device and provide a channel for the evaporated water vapor to enter the water vapor cryogenic pump 1. The hand valve is used to control the evacuation device 5 to evacuate the test device. The evacuation device 5 is a dry pump. The dry pump is used to evacuate the test device, reduce the gas pressure of the test device, lower the boiling point of water, and obtain water vapor at a lower temperature. The sealed measuring cylinder 4, glass container 32 and constant temperature heater 31 are devices for obtaining water vapor. By heating the water, the evaporation rate of water can be accelerated to obtain a large amount of water vapor.

[0056] First, according to Figure 4 As shown, a test system was built and leak detection was performed on the system. Specifically, a helium mass spectrometer leak detector was used for leak detection, with a required leak rate of <5×10⁻⁶. -9 Pa.m 3 / s, ensure the device is sealed, turn on the constant temperature heater 31 to heat the water in the sealed measuring cylinder 4 to a certain temperature, and record the water level scale value at the same time. Turn on the evacuation device 5 and the hand valve. When the water in the sealed measuring cylinder 4 begins to boil and produce bubbles, slowly open the needle valve to adjust to the vacuum value to be measured and start timing. After ventilating for a period of time, more than 10 minutes, close the needle valve and the hand valve, and record the water level scale value and the continuous ventilation time again. The water vapor pumping speed of the cryogenic pump 1 under the vacuum value to be measured can be obtained by the formula S=Q / P. The above operation can be repeated many times to obtain the water vapor pumping speed under different vacuum values, and finally obtain the water vapor pumping speed curve of the cryogenic pump 1.

[0057] This embodiment can obtain measured data on the water vapor pumping speed of a cryogenic pump, and can also compare it with the data calculated theoretically to optimize the theoretical calculation parameters and improve the calculation accuracy.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for testing water vapor pumping speed, characterized in that, It includes a water vapor cryogenic pump, a test sealing device, a heating device, a sealing measuring cylinder, and a vacuum device; the water vapor cryogenic pump is located inside the test sealing device, the test sealing device includes a vacuum gauge, the sealing measuring cylinder is connected to the test sealing device through a gas pipeline, and the sealing measuring cylinder is connected to the vacuum device through a vacuum pipeline. The heating device heats the sealed measuring cylinder and records the water level scale. The evacuation device is then turned on. When the water in the sealed measuring cylinder begins to boil, steam is introduced into the test sealing device to the vacuum value to be tested and timing is started. The steam is kept for more than 10 minutes. The steam is then turned off, and the water level scale value and the continuous steam time are recorded. The steam pumping speed of the cryogenic pump under the true control value to be tested is obtained by S=Q / P. The above operation is repeated multiple times to obtain the steam pumping speed under different vacuum values. Finally, the steam pumping speed curve of the cryogenic pump is obtained. The heating device includes a constant temperature heater and a vessel containing water. A sealed measuring cylinder is located inside the vessel, and the vessel is located on the constant temperature heater. It also includes a needle valve and a hand valve, wherein the needle valve is connected to the gas pipeline and the hand valve is connected to the evacuation pipeline.

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