Quadrupole mass spectrum leak detector integrating positive and negative pressure leak detection modes

Abstract

The invention provides a quadrupole mass spectrum leak detector integrating positive and negative pressure leak detection modes. The quadrupole mass spectrum leak detector comprises a mass spectrum analysis unit, a detection unit, an evacuation unit, a power supply unit and a control unit. According to the quadrupole mass spectrum leak detector, the mass spectrum analysis unit, the detection unit, the evacuation unit, the power supply unit and the control unit are modularly integrated, two working modes of positive pressure leak detection and negative pressure leak detection are realized in the same equipment, and leak rate detection of different types of detected parts can be completed without rebuilding an independent detection system; through gas path switching of the sample injection valve group and linkage control of the control unit, automatic introduction and detection of leakage indication gas in positive and negative pressure modes can be realized, the operation process is simplified, and the detection efficiency is improved; the device supports the detection of a plurality of leakage indicating gases, and can meet the high-precision detection requirement of tiny leakage; the leak detector is compatible with various leak detection modes such as a helium cover method, a leak detection box method, a pressurized vacuum method and a suction gun method, and has wide application value.

Description

Technical Field

[0001] This invention relates to the field of gas leak detection technology, and in particular to a quadrupole mass spectrometer leak detector that integrates positive and negative pressure leak detection modes. Background Technology

[0002] The research and application of quadrupole mass spectrometers for leak detection using various leak-indicating gases are quite widespread, especially in the leak detection of high-vacuum sealed structures such as spacecraft and spaceships, where there are numerous practical cases. For example, during the assembly and testing phases of aerospace systems, researchers typically build specific leak detection systems using quadrupole mass spectrometers based on the structural characteristics of the components under test. This enables the detection of various leak-indicating gases such as helium, neon, krypton, sulfur hexafluoride, hydrogen, or xenon. These systems generally consist of a quadrupole mass spectrometer, a vacuum pump, valve groups, connecting pipelines, and data acquisition devices, enabling mass analysis of multiple gases and leak rate assessment.

[0003] During helium mass spectrometry leak detection, after a leak signal is detected, the inspected part needs to be re-inspected in situ or relocated (after sealing and relocation for leak detection). Often, the helium background does not decrease for a long time, which seriously affects the efficiency of on-site work. Moreover, it is difficult to detect small leak signals at high background, which greatly complicates the accurate determination of the leak rate value of the inspected part.

[0004] To address this, a quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes is proposed. Summary of the Invention

[0005] In view of this, the present invention provides a quadrupole mass spectrometer leak detector that integrates positive and negative pressure leak detection modes, so as to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial alternative.

[0006] The technical solution of this invention is implemented as follows: a quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes, comprising:

[0007] The mass spectrometry analysis unit includes a quadrupole mass spectrometer, a mass spectrometry chamber, and a vacuum gauge. The mass spectrometry chamber is a bakeable structure and is connected to the quadrupole mass spectrometer, the sampling valve group, and the vacuum pump system via CF flange interfaces to achieve gas ionization and mass-to-charge ratio separation.

[0008] The mass spectrometry chamber is a cylindrical stainless steel vacuum cavity with internal dimensions of Φ38mm × 150mm, a volume of approximately 0.2L, and an internal surface area of ​​approximately 150cm². 2 The leakage rate of the cavity should not exceed 3×10 -10 Pa·m 3 / s;

[0009] The mass spectrometer chamber is equipped with three CF flange interfaces. Two CF35 interfaces are connected to the vacuum gauge and the sampling valve assembly, respectively, for real-time monitoring of chamber pressure and sampling gas introduction. The other CF63 interface is connected to the quadrupole mass spectrometer, realizing the connection between the ion source and the gas channel of the analyzer. This structure not only ensures the shortest path design of the gas path, but also reduces gas diffusion hysteresis and signal response delay. The mass spectrometer chamber is connected to the main pump through a DN35 short pipe, which maintains good airflow conduction while reducing pipeline conduction loss and improving the pumping speed utilization and detection sensitivity of the system.

[0010] A high-vacuum angle valve is installed between the mass spectrometer chamber and the main pump, with a single valve leakage rate not exceeding 1×10⁻⁶. -10 Pa·m 3 / s;

[0011] A fully metal miniature high-vacuum valve is installed between the mass spectrometry chamber and the sampling valve assembly, with an external leakage rate of no more than 5 × 10⁻⁶. - 11 Pa·m 3 / s;

[0012] The total leakage rate generated by the connecting valves is approximately 3.0 × 10⁻⁶. -10 Pa·m 3 / s;

[0013] The detection unit includes a leak detection chamber, a leak detection interface, a sample injection valve group, and a second vacuum gauge. The leak detection interface is used to connect to the test piece, and the sample injection valve group is used to switch the gas path between positive pressure leak detection mode and negative pressure leak detection mode, and is connected to the mass spectrometry analysis unit.

[0014] The injection valve assembly adopts a dual-channel high-vacuum switching structure, which can automatically switch between positive and negative pressure gas paths under the command of the control unit to achieve seamless switching;

[0015] When in positive pressure mode, the system collects escaping gas from outside the test piece; when in negative pressure mode, the system draws gas from inside the test piece to create negative pressure and introduces it into the analysis unit; the second vacuum gauge is used to monitor the real-time pressure changes in the leak detection chamber and pipeline, assisting in the control of airflow balance and injection rate, and ensuring the stability of gas flow and data repeatability in different modes.

[0016] The evacuation unit includes a main pump and a forepump. The main pump is a turbomolecular pump used to achieve vacuum in the mass spectrometry chamber and the leak detection chamber. The forepump is used to maintain the vacuum in front of the main pump and the pre-evacuation vacuum in the leak detection chamber.

[0017] The effective pumping speed of the fore-stage mechanical pump during the pre-pumping stage of the leak detection chamber is approximately 0.56 L / s, and it can reduce the pressure in the leak detection chamber from 1.0 × 10⁻⁶ L / s within no more than 14 seconds. 5 Pa decreased to 10 Pa;

[0018] The nominal pumping speed of the turbomolecular pump is approximately 80 L / s. After passing through a DN35 short tube for molecular flow conduction, the effective pumping speed to the mass spectrometry chamber is approximately 14 L / s, corresponding to a total leakage rate of approximately 1.6 × 10⁻⁶ for the mass spectrometry analysis unit. -9 Pa·m 3 / s, thus the theoretical ultimate pressure is approximately 1.1 × 10⁻⁶. -7 Pa·m 3 / s;

[0019] The power supply unit includes a 24V DC power supply and a power distributor, which are used to power the mass spectrometer, vacuum pump and control gas valves.

[0020] The control unit, including a control computer and a human-machine interface, is used to control the switching of gas circuit valves, the linkage start and stop of pumps and valves, the acquisition and processing of mass spectrometry signals, and to output the leak rate value.

[0021] The control unit is equipped with multiple leak gas quality selection windows and calibration curves, supports the selective detection of He, Ne, Kr, SF6, H2 and Xe gases, and can achieve automatic calibration based on standard leak signals;

[0022] in,

[0023] When the device is in positive pressure leak detection mode, the inside of the tested component is pre-filled with a certain concentration of leak indicator gas. At the tiny leak point, the gas escapes outward. At this time, the leak detection chamber collects the escaping gas through the sample injection valve group. After flow balancing, it is introduced into the mass spectrometry analysis unit for detection. Since the quadrupole mass spectrometer can distinguish the mass-to-charge ratio signals of multiple gases at the same time, the control unit can automatically match the mass channel according to the selected gas type to achieve accurate identification of the target leak indicator gas and leak rate calculation. This mode is particularly suitable for leak detection of internal pressurized seals such as vacuum containers and weld joints, and can achieve rapid detection without disrupting the internal gas environment.

[0024] In negative pressure leak detection mode, the leak detection interface is directly connected to the inside of the tested component. A negative pressure is created inside the tested component by the pre-pump of the evacuation unit, allowing external air or leak-indicating gas to enter the tested cavity through potential leak points. The leaking gas is then introduced into the mass spectrometry analysis unit via the sample injection valve assembly for detection, thereby confirming the leak location and leak rate. This mode is suitable for applications requiring internal evacuation for testing, such as large pipelines, valve bodies, and container shells.

[0025] This invention enables dual-mode leak detection (positive and negative pressure) and selective analysis of multiple leak-indicating gases on the same device. Through the dual-channel design of the injection valve group and the automatic logic switching of the control unit, the positive and negative pressure modes can be interchanged on the same device without disassembling or reconstructing the gas path, greatly improving operational efficiency and detection flexibility. The multi-gas identification function of the quadrupole mass spectrometer allows the invention to flexibly select the leak-indicating gas according to environmental conditions or on-site background, avoiding the problem of high background that is difficult to reduce in single helium detection, and realizing selective analysis and re-inspection of multiple gases.

[0026] Furthermore, under standard leak calibration conditions, this invention employs the "signal difference method between closed and open standard leaks" to determine the minimum detectable leak rate. By detecting the difference between the background signal when the standard leak is closed and the stable signal after it is opened, the sensitivity limit of the instrument is calculated, and its minimum detectable leak rate is approximately 1.0 × 10⁻⁶. 14 Pa·m 3 / s, capable of accurately identifying minute leakage signals and quickly recovering to a stable state.

[0027] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions:

[0028] This invention, a quadrupole mass spectrometer leak detector, modularly integrates a mass spectrometry analysis unit, a detection unit, a vacuum unit, a power supply unit, and a control unit. It achieves both positive and negative pressure leak detection modes within a single device, eliminating the need to rebuild an independent detection system to detect leak rates in different types of test components. Through the gas path switching of the sample injection valve assembly and the linkage control of the control unit, automatic introduction and detection of leak-indicating gases in both positive and negative pressure modes can be achieved, simplifying the operation process and improving detection efficiency. This invention supports the detection of multiple leak-indicating gases, exhibits high sensitivity, and can meet the high-precision detection requirements for minute leaks. The leak detector is compatible with various leak detection methods, including helium hood method, leak detection box method, pressurized vacuum method, and suction gun method, and can be directly connected to test components of different shapes, making it widely applicable.

[0029] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a model diagram of the quadrupole mass spectrometer leak detector of the present invention;

[0032] Figure 2 This is a schematic diagram illustrating the working principle of the quadrupole mass spectrometer leak detector of the present invention. Detailed Implementation

[0033] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0034] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0035] like Figure 1-2 As shown, this embodiment of the invention provides a quadrupole mass spectrometer leak detector with both positive and negative pressure leak detection modes, which mainly consists of a mass spectrometry analysis unit, a detection unit, a vacuum unit, a power supply unit, and a control unit.

[0036] The mass spectrometry analysis unit includes a quadrupole mass spectrometer, a mass spectrometry chamber, and a vacuum gauge. The mass spectrometry chamber is a cylindrical 304 stainless steel vacuum chamber with internal dimensions of Φ38 mm × 150 mm, a volume of approximately 0.2 L, and an internal surface area of ​​approximately 150 cm². 2 The inner wall of the mass spectrometer chamber was pretreated with hydrogen, and the material efflux rate (after 24 h of evacuation) was 2.0 × 10⁻⁶. -12 Pa·m 3 / s·cm 2 The total leakage rate of the inner surface is approximately 3×10. - 10 Pa·m 3 / s, the outer surface of the mass spectrometer is equipped with a baking heating structure, which can be baked at 250 ℃.

[0037] The mass spectrometer chamber is equipped with three CF flange interfaces. Two of them, CF35 interfaces, are connected to the vacuum gauge and the sampling valve assembly, respectively, for real-time monitoring of chamber pressure and sampling gas introduction. The other, CF63 interface, is connected to the quadrupole mass spectrometer, realizing the connection between the ion source and the analyzer's gas channel. This not only ensures the shortest path design of the gas path but also reduces gas diffusion hysteresis and signal response delay. The mass spectrometer chamber is connected to the main pump via a DN35 short pipe, which maintains good airflow conduction while reducing pipeline conduction loss and improving the system's pumping speed utilization and detection sensitivity.

[0038] The detection unit includes a leak detection chamber, a leak detection interface, a sample injection valve assembly, and a second vacuum gauge. It is mainly used to collect the leaked gas of the test piece and introduce it into the mass spectrometry analysis unit. The leak detection interface is used to connect to the test piece, and the sample injection valve assembly realizes the switching between positive and negative pressure gas paths.

[0039] The evacuation unit consists of a main pump and a backing pump. The main pump is a turbomolecular pump (Edwards NEXT 85, pumping speed 80 L / s); the backing pump is a dry mechanical pump (Edwards NXDS 6i, pumping speed 6 L / s), used to pre-evacuate the mass spectrometer chamber and leak detection chamber during system startup, and to provide a backing vacuum for the turbomolecular pump during detection. This ensures that the system maintains high vacuum purity while possessing good responsiveness, enabling rapid switching of detection modes and shortening evacuation time.

[0040] The power supply unit provides 24V DC power and a power distributor to power the vacuum pump and control gas valves. It has electrical isolation and overcurrent protection functions. The low-voltage DC design not only improves the safety and anti-interference ability of the whole machine, but also facilitates modular mobile use in the field.

[0041] The control unit consists of a control computer and a human-machine interface, enabling gas path switching, pump-valve linkage, signal acquisition, and leak rate display. The control logic adopts a graded start-stop mechanism: during the evacuation phase, the fore-pump and main pump are automatically started sequentially; during the detection phase, the injection valve group path is automatically switched according to the selected positive or negative pressure mode; during the calibration or shutdown phase, the relevant valves are automatically closed and the gas is vented. This control strategy reduces manual intervention and ensures the reliability and ease of operation of the system.

[0042] Regarding the airtight structure, this invention adopts a high-standard vacuum connection scheme. High-vacuum angle valves are used for the mass spectrometer chamber and the main pump, and the external leakage rate of a single valve is less than 1×10⁻⁶. -10 Pa·m 3 / s; An all-metal miniature high-vacuum valve is used between the mass spectrometer chamber and the sampling valve assembly, with an external leakage rate of less than 5×10. -11 Pa·m 3 / s, the total leakage rate generated by the connecting valve is approximately 3×10⁻⁶. -10 Pa·m 3 / s, this sealing level is superior to the system leakage performance of conventional helium mass spectrometer leak detectors (typically 10). -8 Pa·m 3 This ensures that the entire mass spectrometry analysis unit operates stably under high vacuum conditions for a long period of time ( / s), thereby ensuring that the entire mass spectrometry analysis unit operates stably under high vacuum conditions for a long period of time.

[0043] The total leakage rate of the mass spectrometry analysis unit is approximately 1.6 × 10⁻⁶. -9 Pa·m 3 / s.

[0044] (1) The main pump is mainly used to obtain vacuum in the mass spectrometer chamber and the leak detection chamber. Based on the previous design analysis, the total leakage rate of the mass spectrometer chamber is 1.6 × 10⁻⁶. -9 Pa·m 3 / s, the mass spectrometer chamber is connected to the turbomolecular pump via a DN35 valve. According to the molecular flow conductance calculation model of a short pipe with a circular cross-section, as shown in formula (1), with D=35mm and L=100mm, Uf=16L / s can be calculated.

[0045] (1)

[0046] Where: Uf—pipe conductance, m3 / s;

[0047] D—Pipe diameter, in meters;

[0048] L—Pipe length, in meters;

[0049] —Klausing coefficient, when L / d = 2.85, =0.305, when L / d=5.71, =0.181, when L / d=6.25, =0.168.

[0050] According to the molecular flow series model, as shown in formula (2), the effective pumping speed of the turbomolecular pump to the mass spectrometer chamber is calculated to be 14L.

[0051] (2)

[0052] Where: Se—effective pumping speed of the vacuum pump, m3 / s;

[0053] S—Nominal pumping speed of evacuation, m3 / s.

[0054] According to the calculation model of the ultimate pressure of the vacuum chamber, as shown in Equation (3), the theoretical ultimate pressure of the mass spectrometer chamber can be calculated to be 1.1×10-7 Pa.

[0055] (3)

[0056] Where: Ps—the ultimate pressure of the vacuum chamber, Pa;

[0057] QZ—Total leakage rate of the vacuum chamber, Pa·m3 / s;

[0058] Se—Effective pumping speed of the evacuation system, m³ / s.

[0059] (2) Backing pump

[0060] The backing pump is used to maintain the pre-vacuum during the operation of the main pump and to pre-evacuate the leak detection chamber when changing the test piece. Based on the previous analysis, the mass spectrometer tubing is approximately 0.3L. The pre-evacuation tubing diameter of the mass spectrometer is initially estimated to be D=16mm, L=300mm, which is a long circular cross-section pipe. According to formula (4), the conductance of the mass spectrometer is Un=2.9L / s. According to formula (2), the effective pumping speed of the backing pump for the dynamic leak detection chamber is Se=0.56L / s. According to formula (5), the evacuation time to pre-evacuate the dynamic leak detection chamber to 10Pa is 4s, and the evacuation time to pre-evacuate the cumulative leak detection chamber to 10Pa is 14s. This result indicates that the evacuation time of the selected backing pump for pre-evacuating the leak detection chamber is negligible, meeting the requirements for rapid detection.

[0061] (4)

[0062] Where: Un—pipe conductance, m3 / s;

[0063] —The average pressure in the pipeline is taken as 10 Pa.

[0064] (5)

[0065] Where: t—evacuation time, s;

[0066] Kq—Correction factor, which is related to the pressure when the equipment stops pumping air. Here, Kq=2 is taken.

[0067] pi—the pressure at which the pumping begins, taken as 1×10⁵ Pa;

[0068] p0—Pressure when pumping stops, taken as 10 Pa.

[0069] Table 1 Main Hardware Configuration

[0070] name Specifications / Model Performance indicators mass spectrometer Hiden Mass number 1–100 amu, 1–200 amu, 1–300 amu turbomolecular pump Edwards NEXT 85 80 L / s mechanical pump Edwards NXDS 6i 6 L / s Vacuum gauge Edwards BGP <![CDATA[10 5 –10 -1 Well]]> Vacuum gauge Edwards TPF <![CDATA[10 -1 –10 -8 Well]]> Sample injection valve module VAT Dual-channel structure

[0071] Performance testing:

[0072] The key performance indicators of a helium mass spectrometer leak detector are the minimum detectable leak rate and the reaction time. The performance of a quadrupole mass spectrometer leak detector is also verified by evaluating these two parameters to determine whether the instrument is performing well.

[0073] Minimum detectable leak rate test:

[0074] The test is conducted according to the definition of the minimum detectable leak rate of the instrument. The leak detector is preheated and adjusted to its optimal state. Using pure helium at one atmosphere as the leak indicator gas, the test measures the minimum leak rate that can be detected during dynamic leak detection. Generally, a standard leak hole Q0 is connected to the instrument's test port.

[0075] With the standard leak closed, according to noise I n The noise value is measured by definition; the leakage rate value when the instrument background is relatively stable is observed, which is the background I0; then, the standard leak hole is opened, and the leakage rate value after its signal stabilizes is the leakage hole's displayed value I1 on the instrument. The data processing method for the minimum detectable leakage rate of the instrument is according to formula (6);

[0076] (6)

[0077] This experiment used three standard leaks of different magnitudes for testing. The average of the three sets of experimental results was taken as the minimum detectable leak rate of the instrument, as shown in Table 2.

[0078] Table 2. Minimum Detectable Leakage Rate Detection Results

[0079] Minimum detectable leak rate Q (Pa·m³ / s) Noise In (Pa·m³ / s) <![CDATA[Background I0 (Pa·m³ / s)]]> <![CDATA[Reaction value I1 (Pa·m³ / s)]]> <![CDATA[Standard leak Q0 (Pa·m³ / s)]]> <![CDATA[1.0×10 -14 ]]> <![CDATA[1.0×10 -14 ]]> <![CDATA[1.9×10 -13 ]]> <![CDATA[1.1×10 -9 ]]> <![CDATA[1.1×10 -9 ]]> <![CDATA[1.0×10 -14 ]]> <![CDATA[1.0×10 -14 ]]> <![CDATA[2.0×10 -13 ]]> <![CDATA[1.1×10 -8 ]]> <![CDATA[1.2×10 -8 ]]> <![CDATA[1.0×10 -14 ]]> <![CDATA[1.0×10 -14 ]]> <![CDATA[1.8×10 -13 ]]> <![CDATA[1.5×10 -7 ]]> <![CDATA[1.5×10 -7 ]]> average value <![CDATA[1.0×10 -14 ]]> — — —

[0080] As shown in the table, the minimum detectable leak rate of the instrument is approximately 1.0 × 10⁻⁶. -14 Pa·m 3 / s.

[0081] Reaction time test:

[0082] The instrument's reaction time is another important performance indicator. To ensure leak detection efficiency and sensitivity, the instrument's reaction time is typically required to be no more than 3 seconds. The reaction time refers to the time required for the leak signal to reach 63% of its final stable value. It is usually tested using a standard leak orifice. However, during testing, the standard leak orifice may accumulate some helium source due to being closed, making direct reaction time measurement inaccurate. By definition, the instrument's reaction time is equal to the clearing time. The clearing time is relatively easy to measure. After the instrument has warmed up and stabilized, the standard leak orifice is opened. After the signal stabilizes, the standard leak orifice is closed. The time required for the signal to drop to 37% of its maximum value is the clearing time.

[0083] The reaction time of the instrument was determined to be 2.6 s using the above testing method, as shown in Table 3.

[0084] Table 3 Reaction Time Test Results

[0085] Time (s) for the leak-closing signal to drop to baseline Clearing time (s) Standard leak rate (Pa·m³ / s) 7.1 2.6 <![CDATA[1.5×10 -7 ]]>

[0086] Therefore, the instrument's reaction time is 2.6 seconds.

[0087] In summary, the quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes provided by this invention, based on the multi-gas mass analysis capability of the quadrupole mass spectrometer, achieves automatic switching between positive and negative pressure leak detection modes and sensitive detection of multiple leak-indicating gases through modular integration of mass spectrometry analysis unit, detection unit, evacuation unit, power supply unit, and control unit. Furthermore, its compact, integrated design eliminates the need for redundant external gas path systems, enabling rapid completion of the entire evacuation, detection, and venting process; and it achieves a minimum detectable leak rate of 1.0 × 10⁻⁶. -14 Pa·m 3 With a response time of approximately 2.6 seconds, this device meets the requirements for high sensitivity and rapid response in detection. It is applicable to various leak detection methods, including helium hood method, leak detection box method, pressurized vacuum method, and suction gun method. It can be widely used in aerospace manufacturing, vacuum equipment testing, and sealing component inspection, and has broad application value.

[0088] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes, characterized in that, include: The mass spectrometry analysis unit includes a quadrupole mass spectrometer, a mass spectrometry chamber, and a vacuum gauge. The mass spectrometry chamber is a bakeable structure and is connected to the quadrupole mass spectrometer, the sampling valve group, and the vacuum pump system via CF flange interfaces to achieve gas ionization and mass-to-charge ratio separation. The detection unit includes a leak detection chamber, a leak detection interface, a sample injection valve group, and a second vacuum gauge. The leak detection interface is used to connect to the test piece, and the sample injection valve group is used to switch the gas path between positive pressure leak detection mode and negative pressure leak detection mode, and is connected to the mass spectrometry analysis unit. The evacuation unit includes a main pump and a forepump. The main pump is a turbomolecular pump used to achieve vacuum in the mass spectrometry chamber and the leak detection chamber. The forepump is used to maintain the vacuum in front of the main pump and the pre-evacuation vacuum in the leak detection chamber. The control unit, including a control computer and a human-machine interface, is used to control the switching of gas circuit valves, the linkage start and stop of pumps and valves, the acquisition and processing of mass spectrometry signals, and to output the leak rate value. The power supply unit, including a 24V DC power supply and a power distributor, is used to supply power to the mass spectrometer, vacuum pump and control gas valves. It has electrical isolation and overcurrent protection functions. The low-voltage DC design not only improves the safety and anti-interference ability of the whole machine, but also facilitates modular mobile use in the field environment. in, When in positive pressure leak detection mode, the leak detection chamber collects the gas escaping from the test piece through the sample injection valve group and introduces it into the mass spectrometry analysis unit for detection; When in negative pressure leak detection mode, the leak detection interface draws in the gas inside the test piece to create negative pressure and introduces it into the mass spectrometry analysis unit for detection via the sample injection valve group; It enables dual-mode leak detection under both positive and negative pressure and selective analysis of multiple leak-indicating gases on the same device.

2. The quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 1, characterized in that: The mass spectrometry chamber is a cylindrical stainless steel vacuum cavity with internal dimensions of Φ38mm × 150mm, a volume of approximately 0.2L, and an internal surface area of ​​approximately 150cm². 2 The leakage rate of the cavity is no greater than 3×10 -10 Pa·m 3 / s.

3. The quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 1, characterized in that: The mass spectrometer chamber is equipped with three CF flange interfaces, two of which are CF35 interfaces connected to the vacuum gauge and the sampling valve assembly, respectively, and the other CF63 interface connected to the quadrupole mass spectrometer. The mass spectrometer chamber is connected to the main pump via a DN35 short pipe.

4. A quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 3, characterized in that: A high-vacuum angle valve is installed between the mass spectrometer chamber and the main pump, with a single valve leakage rate not exceeding 1×10⁻⁶. -10 Pa·m 3 / s.

5. A quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 4, characterized in that: A fully metal miniature high-vacuum valve is installed between the mass spectrometry chamber and the sampling valve assembly, with an external leakage rate of no more than 5 × 10⁻⁶. -11 Pa·m 3 / s, the total leakage rate generated by the connecting valve is approximately 3.0 × 10⁻⁶. -10 Pa·m 3 / s.

6. A quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 5, characterized in that: The nominal pumping speed of the turbomolecular pump is approximately 80 L / s. After passing through a DN35 short tube for molecular flow conduction, the effective pumping speed to the mass spectrometry chamber is approximately 14 L / s, corresponding to a total leakage rate of approximately 1.6 × 10⁻⁶ for the mass spectrometry analysis unit. -9 Pa·m 3 / s, thus the theoretical ultimate pressure is approximately 1.1 × 10⁻⁶. -7 Pa·m 3 / s.

7. A quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 6, characterized in that: The effective pumping speed of the fore-stage mechanical pump during the pre-pumping stage of the leak detection chamber is approximately 0.56 L / s, and it can reduce the pressure in the leak detection chamber from 1.0 × 10⁻⁶ L / s within no more than 14 seconds. 5 Pa decreased to 10 Pa.

8. A quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 7, characterized in that: The control unit is equipped with multiple leak gas quality selection windows and calibration curves.

9. A quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 8, characterized in that: The control unit is configured to support selective detection of He, Ne, Kr, SF6, H2 and Xe gases, and can perform automatic calibration based on standard leak signals.

10. A quadrupole mass spectrometer leak detector integrating positive and negative pressure leak detection modes according to claim 1, characterized in that: Under standard leak calibration conditions, the leak detector uses the signal difference method between closed and open standard leak holes to determine the minimum detectable leak rate, which is approximately 1.0 × 10⁻⁶. 14 Pa·m 3 / s.

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