Magnetic suspension rotor vacuum gauge water vapor calibration device and method

Abstract

The invention relates to the technical field of vacuum measurement, in particular to a magnetic suspension rotor vacuum gauge water vapor calibration device and method.The device comprises an air inlet cavity, a pressure stabilizing cavity, an air exhaust cavity, a measuring cavity, flow limiting elements and a vacuum pump set, and the flow limiting elements comprise the first flow limiting element and the second flow limiting element; the air inlet cavity is respectively connected with the air exhaust cavity and the pressure stabilizing cavity through a high-vacuum angle valve; the pressure stabilizing cavity is connected with the measuring cavity through a high-vacuum angle valve and a first flow limiting element; the air exhaust cavity is connected with the measuring cavity through a high-vacuum angle valve; the vacuum pump sets comprise the first vacuum pump set and the second vacuum pump set. The calibration of the magnetic suspension rotor vacuum gauge to the water vapor can be realized based on the dynamic flow method, the conductance of the molecular flow to the water vapor by the small hole and the pumping speed of the molecular pump to the water vapor under different preceding stage pressures can be accurately measured and calculated, and the full-scale calibration of the water vapor is realized.

Description

Technical Field

[0001] The present application relates to the field of vacuum measurement technology, and in particular to a device and method for calibrating water vapor of a magnetically suspended rotor vacuum gauge. Background Art

[0002] When a vacuum system is exposed to the atmosphere, water vapor molecules in the atmosphere will be adsorbed on the walls of the vacuum chamber in a short period of time. During the process of pumping the vacuum system with a mechanical pump and a molecular pump, a large number of water vapor molecules will be desorbed and completely pumped out in a short period of time. The small amount of water vapor left is in a molecular flow state. The water vapor molecules in the chamber wall will gradually migrate and diffuse to the wall and then desorb. In the high vacuum range, the main gas component affecting the background of the vacuum system is water vapor.

[0003] In the fields of semiconductors, photolithography machines, aerospace, etc., halogen hydrides and water vapor are the main pollutants, which are related to the safe production operation of equipment and product quality control. A magnetic levitation rotor vacuum gauge is needed to accurately measure the water vapor pressure in the background of the high vacuum system. During ground calibration, the front unit of the mass spectrometer needs to be provided with a standard water vapor pressure. Unlike permanent and neutral gases, water vapor has a large viscosity coefficient and is easily adsorbed on the chamber and rotor surface, which can easily cause the tangential momentum transfer coefficient of the magnetic levitation rotor vacuum gauge to change nonlinearly.

[0004] Therefore, how to use a magnetically levitated rotor vacuum gauge to accurately measure water vapor pressure and how to determine when the water vapor molecules reach equilibrium in the chamber have become urgent problems to be solved. Summary of the Invention

[0005] The present application provides a water vapor calibration device and method for a magnetic levitation rotor vacuum gauge, which tests the water vapor pressure in a vacuum system based on a dynamic flow method, and can achieve accurate calibration of the tangential momentum transfer coefficient and time of the magnetic levitation rotor vacuum gauge for water vapor.

[0006] In order to achieve the above-mentioned objectives, the present application provides a water vapor calibration device for a magnetic levitation rotor vacuum gauge, comprising an air inlet chamber, a pressure stabilizing chamber, an air exhaust chamber, a measuring chamber, a current limiting element and a vacuum pump group, wherein: the current limiting element comprises a first current limiting element and a second current limiting element; the air inlet chamber is connected to the air exhaust chamber and the pressure stabilizing chamber respectively through a high vacuum angle valve; the pressure stabilizing chamber is connected to the measuring chamber through a high vacuum angle valve and the first current limiting element; the air exhaust chamber is connected to the measuring chamber through a high vacuum angle valve; the vacuum pump group comprises a first vacuum pump group and a second vacuum pump group, the first vacuum pump group is connected to the air exhaust chamber through a high vacuum angle valve, and the second vacuum pump group is connected to the measuring chamber through a high vacuum angle valve and the second current limiting element.

[0007] Further, it also includes a first capacitance diaphragm vacuum gauge, a second capacitance diaphragm vacuum gauge, a third capacitance diaphragm vacuum gauge, and a standard volume chamber, where: the measuring range of the first capacitance diaphragm vacuum gauge is 13 Pa, and it is connected to the intake chamber and the pressure stabilizing chamber respectively through high-vacuum angle valves; the measuring range of the second capacitance diaphragm vacuum gauge is 133 kPa, and it is connected to the intake chamber and the pressure stabilizing chamber respectively through high-vacuum angle valves; the measuring range of the third capacitance diaphragm vacuum gauge is 1.33 kPa, and it is connected to the measuring chamber through a high-vacuum angle valve; the volume of the standard volume chamber is 0.60787 L, and it is connected to the intake chamber and the pressure stabilizing chamber respectively through high-vacuum angle valves.

[0008] Further, it also includes an H2O sample chamber and a Kr gas cylinder, and both the H2O sample chamber and the Kr gas cylinder are connected to the intake chamber through high-vacuum angle valves and fine adjustment valves.

[0009] Further, a non-evaporable getter pump, a magnetically levitated rotor vacuum gauge, and a sputter ion pump are also connected to the measuring chamber, and the non-evaporable getter pump, the magnetically levitated rotor vacuum gauge, and the sputter ion pump are all connected to the measuring chamber through high-vacuum angle valves.

[0010] Further, the vacuum pump sets are all composed of a mechanical dry pump and a turbomolecular pump. Among them, the mechanical dry pump of the first vacuum pump set is also connected to the intake chamber through a high-vacuum angle valve.

[0011] Further, the background leak rate and outgassing rate of the intake chamber, the pumping chamber, and the measuring chamber are all ≤ 1×10 -11 Pa·m 3 / s.

[0012] Further, the flow area of the small hole of the current-limiting element is ≤ 0.01% of the inner surface area of the measuring chamber.

[0013] In addition, the present application also provides a method for calibrating water vapor using a magnetically levitated rotor vacuum gauge calibration device, including the following steps:

[0014] Step 1: Perform volume tests on the intake chamber, the pressure stabilizing chamber, the pumping chamber, and the measuring chamber;

[0015] Step 2: Pump air from the standard volume chamber, the intake chamber, the pressure stabilizing chamber, the pumping chamber, and the measuring chamber, and detect the gas pressures of each chamber through the first capacitance diaphragm vacuum gauge and the second capacitance diaphragm vacuum gauge;

[0016] Step 3: Open the Kr gas cylinder, fill krypton gas into the intake chamber, the pumping chamber, and the standard volume chamber, close the high-vacuum angle valve between the standard volume chamber and the pumping chamber, and pump air from the intake chamber and the pumping chamber using the first vacuum pump set;

[0017] Step 4: Expand the krypton gas in the standard volume chamber into the intake chamber, the pumping chamber, the pressure stabilizing chamber, and the measuring chamber in sequence, and calculate the expanded standard pressure;

[0018] Step 5: After repeating Step 4 for six groups of tests, calculate the average volumes of the intake chamber, the pumping chamber, the pressure stabilizing chamber, and the measurement chamber according to Boyle's equation.

[0019] Step 6: Repeat Step 2. Charge krypton gas into the intake chamber and the pressure stabilizing chamber. When the display value of the second capacitance diaphragm vacuum gauge reaches 3000 Pa, stop charging and record the display value of the second capacitance diaphragm vacuum gauge.

[0020] Step 7: After the krypton gas in the intake chamber and the pressure stabilizing chamber flows into the measurement chamber through the first flow limiting element, record the readings of the magnetic suspension rotor vacuum gauge every 30 s, and calculate the flow conductance of the first flow limiting element for krypton gas.

[0021] Step 8: Select at least 30 calibration points at 100 Pa - 3000 Pa, and at least 10 calibration points at 1 Pa - 10 Pa and 10 Pa - 100 Pa respectively. After obtaining the flow conductance of the first flow limiting element for krypton gas at different intake pressures, deduce the flow conductance of the first flow limiting element for water vapor at different intake pressures.

[0022] Step 13: After the measurement of the flow conductance of the first flow limiting element for krypton gas in Step 8 is completed, turn on the vacuum pump set to pump the measurement chamber, and deduce the flow conductance of the second flow limiting element for krypton gas by combining the readings of the third capacitance diaphragm vacuum gauge and the magnetic suspension rotor vacuum gauge.

[0023] Step 10: After deionized water is cryogenically frozen and impurity gases are pumped out, water vapor continuously sublimes and vaporizes to obtain experimental water vapor in the H2O sample chamber.

[0024] Step 11: Let the water vapor in the intake chamber, the H2O sample chamber, and the pressure stabilizing chamber enter the measurement chamber through the first flow limiting element. Obtain a balanced and stable water vapor pressure in the measurement chamber, and calculate the tangential momentum transfer coefficient of the magnetic suspension rotor vacuum gauge for water vapor.

[0025] A water vapor calibration device and method for a magnetic suspension rotor vacuum gauge provided by this application have the following

[0026] Beneficial effects:

[0027] Based on the dynamic flow method, this application can achieve the calibration of the magnetic suspension rotor vacuum gauge for water vapor, that is, the correlation characteristics between the tangential momentum transfer coefficient and the measured pressure of the magnetic suspension rotor vacuum gauge are characterized. It can accurately calculate the flow conductance of the small hole for water vapor under molecular flow and the pumping speed of the molecular pump for water vapor at different intake pressures, and can provide an accurate reference time for the calibration of the magnetic suspension rotor vacuum gauge for water vapor, realizing full-range calibration of water vapor. Description of the Drawings

[0028] The accompanying drawings, which form a part of this application, are used to provide a further understanding of this application, making other features, objectives, and advantages of this application more obvious. The schematic embodiments and their descriptions of this application are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0029] Figure 1 is a schematic diagram of a water vapor calibration device for a magnetic levitation rotor vacuum gauge according to an embodiment of this application;

[0030] In the figure: 1 - First capacitance diaphragm vacuum gauge, 2 - Second capacitance diaphragm vacuum gauge, 3 - Standard volume chamber, 4, 5, 6, 9, 10, 11, 12, 15, 16, 18, 19, 21, 22, 24, 28, 30, 32, 34, 36 - High vacuum angle valve, 7 - Intake cavity, 8 - Fine adjustment valve, 13 - Pressure stabilizing cavity, 14 - First current limiting element, 17 - Exhaust cavity, 20, 29 - Turbomolecular pump, 23, 31 - Mechanical dry pump, 25 - Non-evaporable getter pump, 26 - Measurement cavity, 27 - Second current limiting element, 33 - Magnetic levitation rotor vacuum gauge, 35 - Third capacitance diaphragm vacuum gauge, 37 - Sputtering ion pump. Detailed implementation manners

[0031] In order to enable those skilled in the art of this technology to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0032] It should be noted that the terms "first", "second", etc. in the specification and claims of this application and the above accompanying drawings are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances for the embodiments of this application described here. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily need to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0033] In this application, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated devices, elements, or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0034] Moreover, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0035] In addition, the meaning of the term "plural" should be two or more.

[0036] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will detail this application with reference to the drawings and in combination with the embodiments.

[0037] As Figure 1 shown, this application provides a water vapor calibration device for a magnetic levitation rotor vacuum gauge, including an intake cavity 7, a pressure stabilizing cavity 13, an evacuation cavity 17, a measurement cavity 26, a current limiting element, and a vacuum pump group, wherein: the current limiting element includes a first current limiting element 14 and a second current limiting element 27; the intake cavity 7 is respectively connected to the evacuation cavity 17 and the pressure stabilizing cavity 13 through high-vacuum angle valves (12, 16); the pressure stabilizing cavity 13 is connected to the measurement cavity 26 through a high-vacuum angle valve 15 and the first current limiting element 14; the evacuation cavity 17 is connected to the measurement cavity 26 through a high-vacuum angle valve 18; the vacuum pump group includes a first vacuum pump group and a second vacuum pump group, the first vacuum pump group is connected to the evacuation cavity 17 through a high-vacuum angle valve 19, and the second vacuum pump group is connected to the measurement cavity 26 through a high-vacuum angle valve 28 and the second current limiting element 27.

[0038] Furthermore, it further includes a first capacitance diaphragm vacuum gauge 1, a second capacitance diaphragm vacuum gauge 2, a third capacitance diaphragm vacuum gauge 35, and a standard volume chamber 3, wherein: the range of the first capacitance diaphragm vacuum gauge 1 is 13 Pa, and it is respectively connected to the intake cavity 7 and the pressure stabilizing cavity 13 through a high-vacuum angle valve 4; the range of the second capacitance diaphragm vacuum gauge 2 is 133 kPa, and it is respectively connected to the intake cavity 7 and the pressure stabilizing cavity 13 through a high-vacuum angle valve 5; the range of the third capacitance diaphragm vacuum gauge 35 is 1.33 kPa, and it is connected to the measurement cavity 26 through a high-vacuum angle valve 34; the volume of the standard volume chamber 3 is 0.60787 L, and it is respectively connected to the intake cavity 7 and the pressure stabilizing cavity 13 through a high-vacuum angle valve 6.

[0039] Further, it also includes an H2O sample chamber and a Kr gas cylinder, and both the H2O sample chamber and the Kr gas cylinder are connected to the intake chamber 7 through high-vacuum angle valves (9, 10) and a fine adjustment valve 8.

[0040] Further, a non-evaporable getter pump 25, a magnetically levitated rotor vacuum gauge 33, and a sputter ion pump 37 are also connected to the measurement chamber 26. The non-evaporable getter pump 25, the magnetically levitated rotor vacuum gauge 33, and the sputter ion pump 37 are all connected to the measurement chamber 26 through high-vacuum angle valves (24, 32, 36).

[0041] Specifically, the magnetically levitated rotor vacuum gauge water vapor calibration device provided in the embodiment of the present application is mainly used for the magnetically levitated rotor vacuum gauge 33 to accurately calibrate the tangential momentum transfer coefficient and time of water vapor. Based on the static expansion method, krypton gas at a certain pressure in the standard volume chamber 3 is expanded into the intake chamber 7, the pumping chamber 17, the pressure stabilizing chamber 13, and the measurement chamber 26 respectively to obtain the volume ratio between the chambers or the specific volume of the required chamber; based on the static pressure rise method, the krypton gas in the pressure stabilizing chamber 13 is transported into the measurement chamber 26 through the first flow limiting element 14, and the magnetically levitated rotor vacuum gauge 33 is used to measure the pressure change value of the measurement chamber 26 within a certain time, and then the conductance of the first flow limiting element 14 to water vapor is calculated therefrom; based on the dynamic flow method, the vacuum pump group connected to the second flow limiting element 27 is used to pump out the nitrogen gas transported into the measurement chamber 26 through the first flow limiting element 14, and the magnetically levitated rotor vacuum gauge 33 is used to measure the pressure in the measurement chamber 26, and then the conductance of the second flow limiting element 27 to water vapor is calculated therefrom; based on the dynamic flow method, the water vapor prepared in the water vapor sample chamber is transported into the intake chamber 7 and the pressure stabilizing chamber 13, and then transported into the measurement chamber 26 through the first flow limiting element 14. The water vapor in the measurement chamber 26 is pumped out by the turbomolecular pump in the second vacuum pump group, and the magnetically levitated rotor vacuum gauge 33 is used to measure the water vapor pressure in the measurement chamber 26. The standard water vapor pressure in the measurement chamber 26 is calculated based on the conductance of the measured first flow limiting element 14 and the second flow limiting element 27 to water vapor, and the calibration of water vapor is realized according to the functional relationship between the actual tangential momentum transfer coefficient and the pressure measured by the magnetically levitated rotor vacuum gauge 33.

[0042] More specifically, in the embodiments of the present application, the intake chamber 7 is used to introduce the gas used in the experiment; the pumping chamber 17 is used to connect to the first vacuum pump group and pump the fore-vacuum system; the pressure stabilizing chamber 13 is used to provide a balanced and stable fore-gas pressure for dynamic flow calibration; the first flow limiting element 14 is used to control the gas flow from the pressure stabilizing chamber 13 into the measurement chamber 26; the second flow limiting element 27 is used to control the pumping speed of the molecular pump to avoid gas backflow. The vacuum pump group is used to pump each chamber; the first capacitance diaphragm vacuum gauge 1 and the second capacitance diaphragm vacuum gauge 2 are used to monitor the gas pressure in the intake chamber 7, the pumping chamber 17, and the pressure stabilizing chamber 13; the third capacitance diaphragm vacuum gauge 35 is used to monitor the gas pressure in the measurement chamber 26; the standard volume chamber 3 is used to measure the volumes of the intake chamber 7, the measurement chamber 26, the pressure stabilizing chamber 13, and the measurement chamber 26; the sputter ion pump 37 is used to obtain a high-vacuum background pressure; the non-evaporable getter pump 25 is used to pump out gas molecules such as H2, N2, H2O, CO, CO2, etc. desorbed from the inner wall of the chamber during the measurement process; the Kr gas cylinder is used to provide krypton gas; the H2O sample chamber is used to provide water vapor; high-vacuum angle valves are arranged on each connecting pipeline, and by controlling the opening and closing of the high-vacuum angle valves, the control of the gas flow in the pipeline is realized.

[0043] Furthermore, the vacuum pump group is composed of mechanical dry pumps (23, 31) and turbo molecular pumps (20, 29). Among them, the mechanical dry pump 23 of the first vacuum pump group is also connected to the intake chamber 7 through high-vacuum angle valves (22, 11). The mechanical dry pump and the turbo molecular pump are used to continuously pump each chamber to ensure the required vacuum degree inside each chamber during the measurement process.

[0044] Furthermore, the background leak rate and outgassing rate of the intake chamber 7, the pumping chamber 17, and the measurement chamber 26 are all ≤ 1×10 -11 Pa·m 3 / s. When detecting leaks, the minimum leak rate of the helium mass spectrometer leak detector used is up to 1×10 -13 Pa·m 3 / s.

[0045] Furthermore, the flow area of the small hole of the flow limiting element is ≤ 0.01% of the inner surface area of the measurement chamber 2638.

[0046] In addition, the present application also provides a method for calibrating water vapor using a magnetic levitation rotor vacuum gauge device, which specifically includes the following steps:

[0047] Step 1: Perform volume tests on the intake chamber 7, the pressure stabilizing chamber 13, the pumping chamber 17, and the measurement chamber 26;

[0048] Step 1.1: Before the test, bake the device at 150 °C for 48 h and repeatedly clean the device three times with Kr; during the process of evacuating the Kr gas in the intake chamber 7 and the pumping chamber 17 with the mechanical dry pump 23 through the pipeline provided with the high-vacuum angle valves (11, 22) and the fine-tuning valve 8, it is necessary to close the high-vacuum angle valve 21 to prevent the gas from flowing back into the turbo molecular pump 20 and damaging it;

[0049] Step 1.2: Close all the angle valves except the high-vacuum angle valves (5, 6, 10), slowly open the fine-tuning valve 8, and introduce Kr into the standard volume chamber 3 and the intake chamber 7. After the reading of the second capacitance diaphragm vacuum gauge 2 reaches about 80 kPa and stabilizes, close the fine-tuning valve 8 and the high-vacuum angle valve 10 to stop the gas filling, and record the gas pressure at this time as p3;

[0050] Step 1.3: Close the high-vacuum angle valve 6, open the high-vacuum angle valve 11, and use the mechanical dry pump 23 to evacuate the intake chamber 7 and its attached pipelines; when the reading of the second capacitance diaphragm vacuum gauge 2 is less than 12 Pa, close the high-vacuum angle valve 11, open the high-vacuum angle valves (16, 19, 21), and use the turbo molecular pump 20 to evacuate the intake chamber 7, the pumping chamber 17 and their attached pipelines. When the reading of the first capacitance diaphragm vacuum gauge 1 is 0.000 Pa, close the fine-tuning valve 8 and the high-vacuum angle valve 16 to stop the evacuation, and close the high-vacuum angle valve 4 to stop the measurement of the first capacitance diaphragm vacuum gauge;

[0051] Step 1.4: Open the high-vacuum angle valve 6, expand the gas in the standard volume chamber 3 into the intake chamber 7, and record the gas pressure at this time as p7; open the high-vacuum angle valve 16, expand the gas in the standard volume chamber 3 and the intake chamber 7 into the pumping chamber 17, and record the gas pressure at this time as p 17 ; open the high-vacuum angle valve 18, expand the gas in the standard volume chamber 3, the intake chamber 7 and the pumping chamber 17 into the measurement chamber 26, open the high-vacuum angle valve 35, and record the gas pressure of the third capacitance diaphragm vacuum gauge 35 at this time as p 26 ;

[0052] Step 1.5: Calculate the volume of the intake chamber 7 according to formula (1), calculate the volume of the pumping chamber 17 according to formula (2), and calculate the volume of the measurement chamber 26 according to formula (3):

[0053]

[0054] In the above formulas, V7 is the volume of the intake chamber 7; V 17 is the volume of the pumping chamber 17; V 26 is the volume of the measurement chamber 26; repeatedly measure six groups of the volumes of the intake chamber 7, the pumping chamber 17, and the measurement chamber 26 and take the average value.

[0055] Step 2: Evacuate the standard volume chamber 3, the intake chamber 7, the pressure stabilizing chamber 13, the extraction chamber 17, and the measurement chamber 26, and detect the gas pressure in each chamber using the first capacitance diaphragm vacuum gauge 1 and the second capacitance diaphragm vacuum gauge 2;

[0056] Step 2.1: Close the high-vacuum angle valves (15, 18), open the high-vacuum angle valves (19, 28), and use the turbomolecular pumps (20, 29) to evacuate the intake chamber 7, the extraction chamber 17, and the measurement chamber 26 respectively. After the pressure measurement value of the magnetic levitation rotor vacuum gauge 33 is less than 1×10 -4 Pa, open the high-vacuum angle valves (24, 36) respectively, and use the non-evaporable getter pump 25 and the sputter ion pump 37 to evacuate the measurement chamber 26. After the pressure measurement value of the magnetic levitation rotor vacuum gauge 33 is less than 1×10 -5 Pa, close the high-vacuum angle valves (28, 36), and only open the non-evaporable getter pump 25 to adsorb gas molecules such as H2, N2, H2O, CO, and CO2 desorbed from the chamber wall to maintain a good background pressure during the measurement;

[0057] Step 2.2: When the display value of the second capacitance diaphragm vacuum gauge 2 is less than 13 Pa, open the high-vacuum angle valve 4 to enable the first capacitance diaphragm vacuum gauge 1 to detect the gas pressure in the intake chamber 7, the extraction chamber 17, and the pressure stabilizing chamber 13;

[0058] Step 2.3: After 12 h, close the high-vacuum angle valve 19, stop the evacuation of the turbomolecular pump 20, and zero the first capacitance diaphragm vacuum gauge 1.

[0059] Step 3: Open the Kr gas cylinder, fill Kr gas into the intake chamber 7, the extraction chamber 17, and the standard volume chamber 3, close the high-vacuum angle valve 6 between the standard volume chamber 3 and the extraction chamber 7, and use the first vacuum pump set to evacuate the intake chamber 7 and the extraction chamber 17.

[0060] Step 4: Expand the Kr gas in the standard volume chamber 3 into the intake chamber 7, the extraction chamber 17, the pressure stabilizing chamber 13, and the measurement chamber 26 in sequence, and calculate the expanded standard pressure.

[0061] Step 5: After repeating Step 4 for six groups, calculate the average values of the volumes of the intake chamber, the extraction chamber, the pressure stabilizing chamber, and the measurement chamber according to Boyle's law.

[0062] Step 6: Repeat Step 2, fill Kr gas into the intake chamber 7 and the pressure stabilizing chamber 13, and stop the gas filling when the display value of the second capacitance diaphragm vacuum gauge 2 is 3000 Pa, and record the display value of the second capacitance diaphragm vacuum gauge 2.

[0063] Step 7: After the Kr gas in the intake chamber 7 and the pressure stabilizing chamber 13 flows into the measurement chamber 26 through the first flow limiting element 14, record the reading of the magnetic levitation rotor vacuum gauge 33 every 30 s, and calculate the conductance of the first flow limiting element 14 to Kr gas.

[0064] Specifically, open the Kr gas cylinder, and fill krypton gas into the intake cavity 7 and the pressure stabilizing cavity 13, and record the reading of the second capacitance diaphragm vacuum gauge 2 at this time as p 13 ; Then, the krypton gas filled into the intake cavity 7 and the pumping cavity 17 is transported into the measurement cavity 26 through the first flow-limiting element 14. After that, record the measured pressure of the magnetic levitation rotor vacuum gauge 33 every 30 s, and calculate the flow conductance of the first flow-limiting element 14 for Kr through Equation (4):

[0065]

[0066] In the above formula, p SRG ′, p SRG correspond to the pressure measurement values of the magnetic levitation rotor vacuum gauge 33 at the start and end of the measurement respectively; Δt and Δp correspond to the time and pressure change amounts during the measurement process respectively.

[0067] Step 8: At least select 30 calibration points at 100 Pa - 3000 Pa, at least select 10 calibration points at 1 Pa - 10 Pa and 10 Pa - 100 Pa respectively. After obtaining the flow conductance of the first flow-limiting element 14 for krypton gas at different intake pressures, calculate the flow conductance of the first flow-limiting element 14 for water vapor at different intake pressures according to Equation (5):

[0068]

[0069] In the above formula, M kr is the molecular mass number of krypton gas; M H2O is the molecular mass number of water vapor.

[0070] Step 9: After the measurement of the flow conductance of the first flow-limiting element 14 for krypton gas in Step 8 is completed, turn on the vacuum pump set to pump the measurement cavity 26, and calculate the flow conductance of the second flow-limiting element 27 for krypton gas by combining the readings of the third capacitance diaphragm vacuum gauge 35 and the magnetic levitation rotor vacuum gauge 33;

[0071] Specifically, open the high-vacuum angle valve 27, and use the turbomolecular pump 29 to pump the measurement cavity 26. The effective pumping speed of the turbomolecular pump 29 for krypton gas can be calculated by Equation (6):

[0072]

[0073] In the above formula, C 27，Kr is the flow conductance of the second flow-limiting element 27 for krypton gas. Since the pumping speed of the molecular pump 29 for krypton gas is much greater than the flow conductance of the second flow-limiting element 27 for krypton gas, it is considered that the effective pumping speed of the turbomolecular pump 29 for krypton gas is equal to the flow conductance of the molecular pump flow-limiting element 27 for krypton gas;

[0074] The effective pumping speed of the turbomolecular pump 29 for water vapor can be calculated by Equation (7):

[0075]

[0076] Step 10: After deionized water is cryogenically frozen and impurity gases are evacuated, water vapor continuously sublimes and vaporizes, and experimental water vapor is obtained in the H2O sample chamber. Open the high-vacuum angle valves (5, 6, 9), and use the second capacitance diaphragm vacuum gauge 2 to measure the pressure value during the sublimation and vaporization of water vapor.

[0077] Step 11: Let the water vapor in the intake cavity 7, the H2O sample chamber, and the pressure stabilizing cavity 13 enter the measurement cavity via the first flow-limiting element 14, obtain a balanced and stable water vapor pressure in the measurement cavity 26, and calculate the tangential momentum transfer coefficient of the magnetically levitated rotor vacuum gauge 33 for water vapor;

[0078] Specifically, open the high-vacuum angle valve 28, evacuate the measurement cavity 26 with the turbomolecular pump 29, open the high-vacuum angle valve 15, let the water vapor in the H2O sample chamber, the intake cavity 7, and the pressure stabilizing cavity 13 enter the measurement cavity 26 via the first flow-limiting element 14, obtain a balanced and stable water vapor pressure in the measurement cavity 26, and calculate the tangential momentum transfer coefficient of the magnetically levitated rotor vacuum gauge 33 for water vapor by Equation (8):

[0079]

[0080] In the above formula, p ind is the measured pressure value of the magnetically levitated rotor vacuum gauge 33 for water vapor; p std is the calculated standard pressure; p b is the intake water vapor pressure (measured by the second capacitance diaphragm vacuum gauge 2);

[0081] Calculate the pressure-independent

[0082]

[0083] At the same time, determine the slope m and the correction coefficient f corr :

[0084]

[0085] According to Equations (9)-(11), the measured value of the calibrated magnetically levitated rotor vacuum gauge 33 for water vapor can be corrected by the following formula:

[0086]

[0087] Therefore, the water vapor calibration device for the magnetic levitation rotor vacuum gauge provided by the embodiments of the present application can realize the calibration of the magnetic levitation rotor vacuum gauge for water vapor based on the dynamic flow method, that is, the correlation characteristics between the tangential momentum transfer coefficient and the measured pressure of the magnetic levitation rotor vacuum gauge can accurately calculate the conductance of the small hole for water vapor under molecular flow and the pumping speed of the molecular pump for water vapor under different inlet pressures, and can provide an accurate reference time for the calibration of the magnetic levitation rotor vacuum gauge for water vapor, realizing full-range calibration of water vapor.

[0088] The foregoing are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A steam calibration device for a magnetic levitation rotor vacuum gauge, characterized in that, It includes an intake cavity, a pressure stabilizing cavity, a pumping cavity, a measurement cavity, a current limiting element, and a vacuum pump group, where: The current limiting element includes a first current limiting element and a second current limiting element; The intake cavity is connected to the pumping cavity and the pressure stabilizing cavity respectively through high vacuum angle valves; The pressure stabilizing cavity is connected to the measurement cavity through a high vacuum angle valve and the first current limiting element; The pumping cavity is connected to the measurement cavity through a high vacuum angle valve; The vacuum pump group includes a first vacuum pump group and a second vacuum pump group. The first vacuum pump group is connected to the pumping cavity through a high vacuum angle valve, and the second vacuum pump group is connected to the measurement cavity through a high vacuum angle valve and the second current limiting element.

2. The water vapor calibration device for the magnetic levitation rotor vacuum gauge according to claim 1, characterized in that, It also includes a first capacitance diaphragm vacuum gauge, a second capacitance diaphragm vacuum gauge, a third capacitance diaphragm vacuum gauge, and a standard volume chamber, where: The range of the first capacitance diaphragm vacuum gauge is 13 Pa, and it is connected to the intake cavity and the pressure stabilizing cavity respectively through high vacuum angle valves; The range of the second capacitance diaphragm vacuum gauge is 133 kPa, and it is connected to the intake cavity and the pressure stabilizing cavity respectively through high vacuum angle valves; The range of the third capacitance diaphragm vacuum gauge is 1.33 kPa, and it is connected to the measurement cavity through a high vacuum angle valve; The volume of the standard volume chamber is 0.60787 L, and it is connected to the intake cavity and the pressure stabilizing cavity respectively through high vacuum angle valves.

3. The vapor calibration device for the magnetic levitation rotor vacuum gauge according to claim 2, wherein, It also includes an H2O sample chamber and a Kr gas cylinder. Both the H2O sample chamber and the Kr gas cylinder are connected to the intake cavity through high vacuum angle valves and fine adjustment valves.

4. The vapor calibration device for a magnetic levitation rotor vacuum gauge according to claim 3, characterized in that, A non-evaporable getter pump, a magnetically levitated rotor vacuum gauge, and a sputter ion pump are also connected to the measurement cavity. The non-evaporable getter pump, the magnetically levitated rotor vacuum gauge, and the sputter ion pump are all connected to the measurement cavity through high vacuum angle valves.

5. The vapor calibration device for the magnetic levitation rotor vacuum gauge according to claim 4, wherein The vacuum pump group is composed of a mechanical dry pump and a turbomolecular pump. Among them, the mechanical dry pump of the first vacuum pump group is also connected to the intake cavity through a high vacuum angle valve.

6. The water vapor calibration device for the magnetic levitation rotor vacuum gauge according to claim 5, characterized in that, The background leak rate and outgassing rate of the intake cavity, the extraction cavity, and the measurement cavity are all ≤ 1×10 -11 Pa·m 3 / s.

7. The water vapor calibration device for the magnetic levitation rotor vacuum gauge according to claim 6, characterized in that, The flow area of the small hole of the current limiting element ≤ 0.01% of the inner surface area of the measurement cavity.

8. A method for calibrating water vapor using the magnetic levitation rotor vacuum gauge water vapor calibration device according to claim 7, characterized in that, It includes the following steps: Step 1: Conduct a volume test on the intake cavity, the pressure stabilizing cavity, the pumping cavity, and the measurement cavity; Step 2: Pump air from the standard volume chamber, the intake cavity, the pressure stabilizing cavity, the pumping cavity, and the measurement cavity, and detect the gas pressure of each chamber through the first capacitance diaphragm vacuum gauge and the second capacitance diaphragm vacuum gauge; Step 3: Open the Kr gas cylinder, fill krypton gas into the intake cavity, the pumping cavity, and the standard volume chamber, close the high vacuum angle valve between the standard volume chamber and the pumping cavity, and pump air from the intake cavity and the pumping cavity with the first vacuum pump group; Step 4: Expand the krypton gas in the standard volume chamber into the intake cavity, the pumping cavity, the pressure stabilizing cavity, and the measurement cavity in sequence, and calculate the expanded standard pressure; Step 5: After repeating Step 4 for six groups, calculate the average value of the volumes of the intake cavity, the pumping cavity, the pressure stabilizing cavity, and the measurement cavity according to Boyle's law; Step 6: Repeat Step 2, fill krypton gas into the intake cavity and the pressure stabilizing cavity, stop filling when the display value of the second capacitance diaphragm vacuum gauge is 3000 Pa, and record the display value of the second capacitance diaphragm vacuum gauge. Step 7: After the krypton gas in the intake chamber and the pressure stabilizing chamber flows into the measurement chamber through the first flow-limiting element, record the readings of the magnetically levitated rotor vacuum gauge every 30 s, and calculate the flow conductance of the first flow-limiting element for krypton gas. Step 8: At least 30 calibration points are selected in the range of 100 Pa - 3000 Pa, and at least 10 calibration points are respectively selected in the ranges of 1 Pa - 10 Pa and 10 Pa - 100 Pa. After obtaining the flow conductance of the first flow-limiting element for krypton gas at different intake pressures, extrapolate the flow conductance of the first flow-limiting element for water vapor at different intake pressures. Step 9: After the measurement of the flow conductance of the first flow-limiting element for krypton gas in Step 8 is completed, turn on the vacuum pump set to evacuate the measurement chamber, and combine the readings of the third capacitance diaphragm vacuum gauge and the magnetically levitated rotor vacuum gauge to extrapolate the flow conductance of the second flow-limiting element for krypton gas. Step 10: After the deionized water is cryogenically frozen and the impurity gases are removed, the water vapor continuously sublimes and vaporizes to obtain experimental water vapor in the H2O sample chamber. Step 11: Let the water vapor in the intake chamber, the H2O sample chamber and the pressure stabilizing chamber enter the measurement chamber through the first flow-limiting element, obtain a balanced and stable water vapor pressure in the measurement chamber, and calculate the tangential momentum transfer coefficient of the magnetically levitated rotor vacuum gauge for water vapor.

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