Vacuum measuring device and method based on background gas self-correction

Abstract

The application discloses a vacuum measuring device and method based on background gas self-correction. The device adopts three nanometer gratings, a pair of anti-Helmholtz coils and a vacuum chamber to realize the function of capturing cold atoms. The method adopts the device, and first, the loss rate G1 of the cold atoms in the three-dimensional magnetic optical trap with the trap depth W1 is measured; second, the three-dimensional magnetic trap with the trap depth W2 is switched to, and the loss rate G2 of the cold atoms is measured; third, the collision loss rate coefficients K of the cold atoms with hydrogen and other residual gases are respectively calculated according to the semi-classical theory loss (W1) 氢气 , K loss (W2) 氢气 , K loss (W1) 其他 and K loss (W2) 其他 ; fourth, the proportion of hydrogen and other residual gases in the ultra-high vacuum background is analyzed, the system loss rate coefficient K loss is corrected, and the vacuum pressure is calculated. The application realizes the self-correction of the composition of the background gas in the ultra-high vacuum based on the quantum characteristics of the cold atoms, solves the technical bottleneck that the existing vacuum gauge cannot accurately measure the ultra-high vacuum, and provides a new way of vacuum tracing.

Description

Technical Field

[0001] This invention relates to the field of cold atom and ultra-high vacuum pressure measurement technology, and in particular to a vacuum measurement method based on background gas self-correction. Background Technology

[0002] Over the past three decades, laser cooling and trapping technology for atoms has developed rapidly, giving rise to various interdisciplinary fields related to cold atoms. Among these, the study of the dynamic characteristics of cold atoms is a significant undertaking in experimental science. A novel method for accurately measuring ultra-high / extremely high vacuum using the loss rate from collisions between cold atoms and background gases is being researched extensively both domestically and internationally. Experiments show that the number of cold atoms in the trapped region decreases over time, closely related to gas composition, gas concentration, and potential well depth. Currently, the commonly used ionization vacuum gauge measures vacuum pressure by ionizing gas molecules and measuring the number of ions. However, in extremely high vacuum, the background residual gas is primarily hydrogen, making nitrogen-based ionization vacuum gauges less suitable. Furthermore, the gas released by the ionization gauge itself affects the measured vacuum level, failing to reflect the true vacuum pressure. Based on this, we have developed a vacuum measurement device and method based on background gas self-correction, starting from the collision characteristics of cold atoms with background gas molecules. This invention corrects the contribution of various gas components in the vacuum background to the cold atom loss rate, improving the measurement accuracy of extremely high vacuum and offering the advantage of non-destructive measurement. Summary of the Invention

[0003] The purpose of this invention is to provide a vacuum measurement device and method based on background gas self-correction, addressing the shortcomings of existing technologies. The device employs three nanoscale gratings, a pair of energized anti-Helmholtz coils, and a vacuum chamber to form a three-dimensional magneto-optical trap chamber and a three-dimensional magnetic trap chamber. A spherical lens, a photomultiplier tube, and a data acquisition card are configured outside the vacuum chambers to acquire cold atom fluorescence signals. See details... Figure 1 Schematic diagram of the apparatus. The method of this invention uses the above-described apparatus. The method comprises the following steps: First, under extremely high vacuum conditions, measuring the loss rate Γ1 of cold atoms in a three-dimensional magneto-optical trap with a depth of W1; Second, switching the three-dimensional magneto-optical trap to a three-dimensional magnetic trap, and measuring the loss rate Γ2 of cold atoms in a three-dimensional magnetic trap with a depth of W2; Third, calculating the collision loss rate coefficient K between cold atoms and hydrogen gas at different trap depths (W1 and W2) according to semi-classical theory. loss (W1) 氢气 K loss (W2) 氢气 And the average collision loss rate coefficient K between cold atoms and other residual gases loss (W1) 其他 and K loss (W2) 其他The fourth step is to analyze the ratio of hydrogen to other residual gases under the current ultra-high vacuum condition and correct the effective loss rate coefficient K. loss The system vacuum pressure P is calculated. Based on the quantum collision characteristics of cold atoms, this invention utilizes the fact that switching the magneto-optical trap to the magnetic trap does not affect the vacuum conditions inside the system, achieving self-correction of the background gas composition in extremely high vacuum. This solves the technical bottlenecks of existing vacuum gauges and other potential vacuum measurement methods, such as low measurement accuracy under extremely high vacuum conditions and the influence of gas outflow from the device itself on the measured vacuum pressure. It greatly improves the precision and accuracy of vacuum measurement and has the advantage of non-destructive measurement.

[0004] The specific technical solution for achieving the objective of this invention is as follows:

[0005] A vacuum measurement device based on background gas self-correction is characterized by comprising four subsystems: a vacuum system, an optical system, a magnetic field system, and a signal collection and processing system. The system components include an atomic evaporation furnace, a vacuum chamber, a laser, three nanoscale gratings, a pair of anti-Helmholtz coils, a composite getter pump, a spherical lens, a photomultiplier tube, and a data acquisition card.

[0006] The vacuum system consists of an atomic evaporation furnace, a vacuum chamber, and a composite getter pump. The atomic evaporation furnace is connected to the track of the vacuum chamber, and the composite getter pump is connected to the gas path of the vacuum chamber.

[0007] The optical system consists of a laser, three nanoscale gratings, a spherical lens, and a photomultiplier tube. The laser and the three nanoscale gratings are connected to the optical path of the vacuum chamber from the top and bottom sides, respectively, while the spherical lens and the photomultiplier tube are connected to the optical path of the vacuum chamber from the right side.

[0008] The magnetic field system consists of a pair of anti-Helmholtz coils and a vacuum chamber, and is an important part of the three-dimensional magneto-optical trap and the three-dimensional magnetic trap.

[0009] The signal collection and processing system consists of a photomultiplier tube and a data acquisition card, which are connected by a data cable.

[0010] A vacuum measurement method based on background gas self-correction, characterized by the following steps:

[0011] 1. Under extremely high vacuum conditions, measure the loss rate Г1 of cold atoms in a three-dimensional magneto-optical trap with a depth of W1;

[0012] 1.1 Start the composite getter pump to bring the vacuum chamber to an extremely high vacuum;

[0013] 1.2. Heat the atomic evaporation furnace to 350℃, start the laser, and set the output optical power and laser frequency. The laser beam is diffracted by three nanoscale gratings to form a light field in the vacuum chamber to trap cold atoms. At the same time, a suitable current value is input to a pair of anti-Helmholtz coils. With this light field, a three-dimensional magneto-optical trap with a depth of W1 is formed in the vacuum chamber to trap atoms emitted from the atomic evaporation furnace to form a three-dimensional cold atom cluster.

[0014] 1.3 After the cold atom clusters are loaded, the atomic evaporation furnace is turned off; the photomultiplier tube collects the fluorescence emitted by the three-dimensional cold atom clusters in real time through the focusing effect of the spherical lens and transmits it to the data acquisition card. Based on the cold atom fluorescence collected at different times, the loss curve of cold atom fluorescence decaying with time is plotted. Finally, the curve is fitted to obtain the cold atom loss rate Г1 in the three-dimensional magneto-optical trap.

[0015] 2. Switch the three-dimensional magneto-optical trap to a three-dimensional magnetic trap and measure the loss rate Г2 of cold atoms in the three-dimensional magnetic trap with a depth of W2;

[0016] 2.1. Turn off the laser, set the current of a pair of anti-Helmholtz coils to form a three-dimensional magnetic trap with a depth of W2 in the vacuum chamber, and load the cold atom clusters in the three-dimensional magneto-optical trap into the three-dimensional magnetic trap.

[0017] 2.2 Turn on the laser, use a photomultiplier tube to collect cold atom fluorescence, and record it through a data acquisition card; since the cold atom clusters in the three-dimensional magnetic trap will disappear after each fluorescence collection, it is necessary to change the residence time of the cold atom clusters in the three-dimensional magnetic trap, record the fluorescence signal multiple times, plot the loss curve of cold atoms point by point, and then fit it to obtain the cold atom loss rate Г2 in the three-dimensional magnetic trap.

[0018] 3. Calculate the collision loss rate coefficient K between cold atoms and hydrogen gas at different trap depths (W1 and W2) based on semiclassical theory. loss (W1) 氢气 K loss (W2) 氢气 And the average collision loss rate coefficient K between cold atoms and other residual gases loss (W1) 其他 and K loss (W2) 其他 ;

[0019] 3.1. Based on semiclassical theory, establish 7 A theoretical model of the collisions between lithium atoms and hydrogen molecules in the Li+H2 system was used to obtain the collision loss rate coefficient K between lithium atoms and hydrogen. loss氢气 The relationship between K and the pit depth is used to calculate K. loss (W1) 氢气 and K loss (W2) 氢气 ;

[0020] 3.2 Similarly, the collision loss rate coefficients of lithium atoms with other residual gases (N2, CO, CO2, H2O, etc.) are obtained, and the average value is taken to calculate K. loss (W1) 其他 and K loss (W2) 其他 ;

[0021] 4. Analyze the ratio of hydrogen to other residual gases under the current ultra-high vacuum background, and correct the effective loss rate coefficient K. loss Calculate the system vacuum pressure P;

[0022] 4.1 Compare the measurement results Г1 and Г2 from steps 1.3 and 2.2 above, analyze the proportion of hydrogen and other residual gases under the current ultra-high vacuum background, and correct the cold atom collision loss rate coefficient K for different trap depths. loss The system vacuum pressure P is obtained using the following formula:

[0023] P = (Г / K) loss修正 )×k B T.

[0024] This invention uses the aforementioned apparatus and method to analyze the residual gas composition inside the system under ultra-high vacuum by measuring the cold atom loss rate Γ at different trap depths. Considering the different effects of collisions between different gas molecules and cold atoms, the cold atom collision loss rate coefficient K is corrected. loss The vacuum pressure P of the current system is calculated.

[0025] The calculation process is as follows:

[0026] Collisions between background gas molecules and cold atoms in a vacuum cause the cold atoms to escape the confined space, and the decay of the cold atoms over time satisfies formula (1).

[0027] N(t) = N0 × e -Гt (1)

[0028] In equation (1), Γ represents the loss rate due to collisions between cold atoms and gas molecules, and N0 represents the total number of cold atoms captured at the initial moment. Ideally, the gas molecule number density n in a vacuum and the cold atom loss rate Γ satisfy the following condition:

[0029] n = Г / K loss (2)

[0030] In equation (2), K loss This is the cold atom collision loss rate coefficient. The ideal gas law in vacuum physics is...

[0031] P = nk B T (3)

[0032] In equation (3), k B is Boltzmann's constant, and T is the ambient temperature. Combining formulas (2) and (3), we can obtain the theoretical formulas for vacuum pressure P and cold atom loss rate Г.

[0033] P = (Г / K) loss )×k B T (4)

[0034] Under extremely high vacuum, the residual gas inside the system is mainly hydrogen, accounting for approximately 97%, with other remaining gases including nitrogen, carbon monoxide, carbon dioxide, and water molecules. Based on semi-classical theory, a system is established... 7 A theoretical model of the collision between lithium atoms and hydrogen molecules in the Li+H2 system was established, and a similar model of the collision between lithium atoms and other gas molecules (N2, CO, CO2, H2O, etc.) was established to obtain the relationship between the collision loss rate coefficient of lithium atoms with different gas molecules and the well depth. Substituting the known well depths W1 and W2, the cold atom collision loss rate coefficient K can be calculated. loss (W1) 氢气 and K loss (W2) 氢气 K loss (W1) 氮气 and K loss (W2) 氮气 K loss (W1) 一氧化碳 and K loss (W2) 一氧化碳 K loss (W1) 二氧化碳 and K loss (W2) 二氧化碳 K loss (W1) 水分子 and K loss (W2) 水分子 Since the proportions of the remaining gases other than hydrogen are not significantly different, K loss (W1 / W2) 其他 This can be approximated by averaging the collision loss rate coefficients corresponding to these gas molecules. Assuming that the proportion of hydrogen is a and the proportion of other remaining gases is (1-a), then the cold atom collision loss rate coefficients of the system at different trap depths can be expressed by the following equations (5) and (6).

[0035] K loss1 =a×K loss (W1) 氢气 +(1-a)×K loss (W1) 其他 (5)

[0036] K loss2=a×K loss (W2) 氢气 +(1-a)×K loss (W2) 其他 (6)

[0037] During the experimental measurement, when the three-dimensional magneto-optical trap is switched to a three-dimensional magnetic trap, the vacuum conditions of the entire system remain unchanged. Therefore, according to the above equation (4), equation (7) can be obtained.

[0038] Г1 / [a×K loss (W1) 氢气 +(1-a)×K loss (W1) 其他 ]=Г2 / [a×K loss (W2) 氢气 +(1-a)×K loss (W2) 其他 (7)

[0039] Solving equation (9) yields the equation coefficient a, thereby determining the proportion of hydrogen and other residual gases in the background gas under extremely high vacuum. Substituting these into equations (5) and (6) corrects the cold atom collision loss rate coefficient of the system. Substituting the cold atom loss rate and collision loss rate coefficient into equation (4) yields the actual vacuum pressure value P in the vacuum system.

[0040] Advantages of this invention:

[0041] ① This invention effectively solves the problem of accurately measuring vacuum pressure in the ultra-high vacuum range. Considering the differences in the collision loss rate coefficients of hydrogen and other gases on cold atoms, an algorithm for self-correcting the composition ratio of the ultra-high vacuum background gas is proposed, which greatly improves the measurement accuracy of ultra-high vacuum.

[0042] ② Compared with traditional vacuum measurement methods, this invention is based on the quantum properties of cold atoms colliding with other background gas molecules, realizing non-destructive measurement of the vacuum system under test, and accurately reflecting the true state of the ultra-high vacuum without introducing other influencing factors.

[0043] This invention utilizes the quantum properties of cold atoms to solve the technical bottlenecks of existing vacuum gauges, such as the inability to accurately analyze background gas composition under extremely high vacuum conditions, low measurement accuracy, and the impact of device outgassing on measurement. It achieves self-correction for cold atom collision losses caused by different background gas compositions, improves the measurement accuracy of extremely high vacuum, and has the advantage of non-destructive measurement. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0045] Figure 2 This is a schematic diagram showing the time decay of the number of cold atoms in a three-dimensional magneto-optical trap and a three-dimensional magnetic trap. Detailed Implementation

[0046] Implementation example:

[0047] See Figure 1 This invention relates to a vacuum measurement device based on background gas self-correction, which consists of four subsystems: a vacuum system, an optical system, a magnetic field system, and a signal collection and processing system. The system components include an atomic evaporation furnace 1, a vacuum chamber 2, a laser 3, three nanoscale gratings 4, a pair of anti-Helmholtz coils 5, a composite getter pump 7, a spherical lens 8, a photomultiplier tube 9, and a data acquisition card 10.

[0048] The vacuum system consists of an atomic evaporation furnace 1, a vacuum chamber 2, and a composite getter pump 7. The atomic evaporation furnace 1 is connected to the vacuum chamber 2 by rail, and the composite getter pump 7 is connected to the gas path of the vacuum chamber 2.

[0049] The optical system consists of a laser 3, three nanoscale gratings 4, a spherical lens 8, and a photomultiplier tube 9. The laser 3 and the three nanoscale gratings 4 are connected to the optical path of the vacuum chamber 2 from the upper and lower sides, respectively, while the spherical lens 8 and the photomultiplier tube 9 are connected to the optical path of the vacuum chamber 2 from the right side.

[0050] The magnetic field system consists of a pair of anti-Helmholtz coils 9 and a vacuum chamber 2, and is an important part of the three-dimensional magneto-optical trap and the three-dimensional magnetic trap.

[0051] The signal collection and processing system consists of a photomultiplier tube 9 and a data acquisition card 10, which are connected by a data cable.

[0052] See Figure 1 The vacuum measurement method based on background gas self-correction, implemented using the device of the present invention, comprises the following steps:

[0053] 1. Under extremely high vacuum conditions, measure the loss rate Г1 of cold atoms in a three-dimensional magneto-optical trap with a depth of W1;

[0054] 1.1 Start the composite getter pump 7 to bring the vacuum chamber 2 to an extremely high vacuum;

[0055] 1.2. Heat the atomic evaporation furnace 1 to 350°C, start the laser 3, set the output optical power and laser frequency, and the laser beam is diffracted by three nanoscale gratings 4 to form a light field that traps cold atoms in the vacuum chamber 2; at the same time, a suitable current value is input to a pair of anti-Helmholtz coils 5, which, together with this light field, form a three-dimensional magneto-optical trap with a depth of W1 in the vacuum chamber 2, trapping atoms emitted from the atomic evaporation furnace 1 to form a three-dimensional cold atom cluster 6;

[0056] 1.3 After the cold atom cluster 6 is loaded, the atomic evaporation furnace 1 is turned off; the photomultiplier tube 9 collects the fluorescence emitted by the three-dimensional cold atom cluster 6 in real time through the focusing effect of the spherical lens 8 and transmits it to the data acquisition card 10. Based on the cold atom fluorescence collected at different times, the loss curve of cold atom fluorescence decaying with time is plotted. Finally, the curve is fitted to obtain the cold atom loss rate Г1 in the three-dimensional magneto-optical trap.

[0057] 2. Switch the three-dimensional magneto-optical trap to a three-dimensional magnetic trap and measure the loss rate Г2 of cold atoms in the three-dimensional magnetic trap with a depth of W2;

[0058] 2.1. Turn off the laser 3, set the current of a pair of anti-Helmholtz coils 5 to form a three-dimensional magnetic trap with a depth of W2 in the vacuum chamber 2, and load the cold atom cluster 6 in the three-dimensional magneto-optical trap into the three-dimensional magnetic trap.

[0059] 2.2 Turn on the laser 3, use the photomultiplier tube 9 to collect cold atom fluorescence, and record it through the data acquisition card 10; since the cold atom cluster 6 in the three-dimensional magnetic trap will disappear after each fluorescence collection, it is necessary to change the residence time of the cold atom cluster 6 in the three-dimensional magnetic trap, record the fluorescence signal multiple times, plot the loss curve of cold atoms point by point, and then fit it to obtain the cold atom loss rate Г2 in the three-dimensional magnetic trap.

[0060] 3. Calculate the collision loss rate coefficient K between cold atoms and hydrogen gas at different trap depths (W1 and W2) based on semiclassical theory. loss (W1) 氢气 K loss (W2) 氢气 And the average collision loss rate coefficient K between cold atoms and other residual gases loss (W1) 其他 and K loss (W2) 其他 ;

[0061] 3.1. Based on semiclassical theory, establish 7 A theoretical model of the collisions between lithium atoms and hydrogen molecules in the Li+H2 system was used to obtain the collision loss rate coefficient K between lithium atoms and hydrogen. loss氢气 The relationship between K and the pit depth is used to calculate K. loss (W1) 氢气 and K loss (W2) 氢气 ;

[0062] 3.2 Similarly, the collision loss rate coefficients of lithium atoms with other residual gases (N2, CO, CO2, H2O, etc.) are obtained, and the average value is taken to calculate K. loss (W1) 其他 and K loss (W2) 其他 ;

[0063] 4. Analyze the proportion of hydrogen and other residual gases under the current ultra-high vacuum background, and correct the effective loss rate coefficient K. loss Calculate the system vacuum pressure P;

[0064] 4.1 Compare the measurement results Г1 and Г2 from steps 1.3 and 2.2 above, analyze the proportion of hydrogen and other residual gases under the current ultra-high vacuum background, and correct the cold atom collision loss rate coefficient K for different trap depths. loss The system vacuum pressure P is obtained using the following formula:

[0065] P = (Г / K) loss修正 )×k B T.

[0066] See Figure 2 , Figure 2 (a) is the fitting result of the cold atom loss rate Г1 in the three-dimensional magneto-optical trap. The vertical axis is the fluorescence voltage signal collected by the photomultiplier tube, and the horizontal axis is the measurement time of the photomultiplier tube. Figure 2 (b) is the fitting result of the cold atom loss rate Г2 in the three-dimensional magnetic trap. The vertical axis is the fluorescence voltage signal collected by the photomultiplier tube, and the horizontal axis is the residence time of the cold atom in the magnetic trap. Figure 2 The black data points in (a) and (b) are all fluorescence signals collected during the experiment, and the black curves are all fitting results based on the above calculation formula (1) combined with the data points.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A vacuum measuring device based on self-correction of background gas, characterized by: It consists of four subsystems, namely vacuum system, optical system, magnetic field system and signal collection and processing system, system components include atomic evaporation furnace (1), vacuum chamber (2), laser (3), three nanometer grating (4), a pair of anti-Helmholtz coil (5), composite getter pump (7), spherical lens (8), photomultiplier (9), data acquisition card (10); The vacuum system is composed of atomic evaporation furnace (1), vacuum chamber (2) and composite getter pump (7), wherein the atomic evaporation furnace (1) is connected with the vacuum chamber (2) track, and the composite getter pump (7) is connected with the vacuum chamber (2) gas path; The optical system is composed of laser (3), three nanometer grating (4), spherical lens (8), photomultiplier (9), wherein the laser (3) and three nanometer grating (4) are connected with the vacuum chamber (2) light path from the upper and lower sides respectively, and the spherical lens (8) and photomultiplier (9) are connected with the vacuum chamber (2) light path from the right side; The magnetic field system is composed of a pair of anti-Helmholtz coil (5) and vacuum chamber (2), which is an important part of three-dimensional magnetic optical trap and three-dimensional magnetic trap; The signal collection and processing system is composed of photomultiplier (9) and data acquisition card (10), which are connected by data line.

2. A vacuum measurement method based on background gas self-correction, characterized in that it comprises the following steps: 2.1, under the condition of ultra-high vacuum, the loss rate of cold atoms in the three-dimensional magnetic optical trap with trap depth W1 is measured; 2.1.1, start the composite getter pump (7), so that the vacuum chamber (2) is in ultra-high vacuum; 2.1.2, the atomic evaporation furnace (1) is heated to 350℃, the laser (3) is started, the output optical power and laser frequency are set, the laser beam is diffracted by three nanometer grating (4) to form an optical field in the vacuum chamber (2) to capture cold atoms; At the same time, a pair of anti-Helmholtz coil (5) is input with appropriate current value, which cooperates with the optical field to form a three-dimensional magnetic optical trap with trap depth W1 in the vacuum chamber (2), and captures the atoms emitted from the atomic evaporation furnace (1) to form a three-dimensional cold atom group (6); 2.1.3, after the cold atom group (6) is loaded, the atomic evaporation furnace (1) is closed; The photomultiplier (9) collects the fluorescence emitted by the three-dimensional cold atom group (6) in real time through the gathering effect of the spherical lens (8), and transmits it to the data acquisition card (10); According to the cold atom fluorescence collected at different time, the loss curve of cold atom fluorescence with time is drawn, and finally the loss rate of cold atoms in three-dimensional magnetic optical trap is obtained by fitting the curve; 2.2, switch the three-dimensional magnetic optical trap to three-dimensional magnetic trap, and measure the loss rate of cold atoms in the three-dimensional magnetic trap with trap depth W2; 2.2.1, close the laser (3), set the current of the pair of anti-Helmholtz coil (5), and form a three-dimensional magnetic trap with trap depth W2 in the vacuum chamber (2), and load the cold atom group (6) in the three-dimensional magnetic optical trap into the three-dimensional magnetic trap; 2.2.2, open the laser (3), using photomultiplier tube (9) to collect cold atom fluorescence, and record it through the data acquisition card (10); because after each collection of fluorescence, the cold atom group (6) in the three-dimensional magnetic trap will disappear, so it is necessary to change the residence time of the cold atom group (6) in the three-dimensional magnetic trap, record the fluorescence signal multiple times, draw the loss curve of the cold atom point by point, and then fit to obtain the cold atom loss rate in the three-dimensional magnetic trap Г2; 2.3, Calculate the collision loss rate coefficient K of cold atoms with hydrogen gas under different well depths W1 and W2 respectively according to semi-classical theory loss (W1) 氢气 , K loss (W2) 氢气 , and the average collision loss rate coefficient K of cold atoms with other residual gases loss (W1) 其他 and K loss (W2) 其他 ; 2.3.

1. According to the semi-classical theory, the relationship between the collision loss rate coefficient K and the well depth V0 is established 7 The theoretical model of the collision between lithium atom and hydrogen molecule in Li+H2 system is obtained, and the collision loss rate coefficient K of lithium atom and hydrogen is obtained loss氢气 The relationship between K and the well depth V0 is calculated loss (W1) 氢气 And K loss (W2) 氢气 ; 2.3.2、Similarly, the collision loss rate coefficients of lithium atoms with other residual gases N2, CO, CO2, H2O are obtained, averaged, and calculated to obtain K loss (W1) 其他 and K loss (W2) 其他 ; 2.4, analyze the proportion of hydrogen and other residual gas in the current ultra-high vacuum background, correct the effective loss rate coefficient K loss , calculate the system vacuum pressure P; 2.4.1, Compare the measurement results Г1 and Г2 in the above steps 2.1.3 and 2.2.2, analyze the proportion of hydrogen and other residual gases under the current ultra-high vacuum background, and correct the cold atom collision loss rate coefficient K at different trap depths loss , Obtain the system vacuum pressure P, the calculation formula is as follows: P = (Г / K loss修正 )×k B T.

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