Three-tube coaxial low-pressure auxiliary end face enhanced microwave plasma ion source

Abstract

The utility model provides a low-pressure auxiliary end face enhanced microwave plasma ion source with three coaxial pipes. The low-pressure auxiliary end face enhanced microwave plasma ion source is composed of an inner pipe, a middle pipe, a first vacuum sealing ring, a second vacuum sealing ring, an outer pipe, a microwave solid-state source, a microwave transmission line, a sealing gasket, a vacuum exhaust pipe, a vacuum pump, a third vacuum sealing ring, a microwave enhanced electrode and low-pressure microwave plasma. The ion source adopts a three-tube coaxial structure and a vacuum sealing design, so that the air pressure of a plasma generation area is effectively reduced, the signal background interference is reduced, and the plasma stability is greatly improved. The microwave enhancement electrode is adopted, the electric field intensity of the end face is further enhanced, and the excitation efficiency and stability of microwave plasma are improved. Compared with the prior art, the ion source has the advantages that the structural design is simplified, the working parameters of the ion source are optimized, the sensitivity and the accuracy of mass spectrometry are improved, and the efficient and stable analysis performance is realized. The device is reasonable in design, compact in structure and convenient to adjust.

Description

Technical Field

[0001] The utility model belongs to the technical field of mass spectrometry, and relates to a low-pressure assisted end-face enhanced microwave plasma ion source with a three-tube coaxial structure. Through a unique three-tube coaxial structure and vacuum sealing design, the ion source realizes the stable operation of microwave plasma under low pressure and reduces signal background interference. At the same time, the excitation efficiency and stability of microwave plasma are improved through an end-face enhanced electrode, the ionization efficiency of the ion source and the sensitivity of mass spectrometry detection are enhanced, and the detection data of samples are enriched. Background Technique

[0002] The ionization source is an important part of a mass spectrometer, mainly used for ionizing sample molecules. The ionization performance of the ionization source directly determines the sensitivity and detection range of the instrument. The microwave plasma torch is a common mass spectrometry ionization source, which mainly operates at atmospheric pressure and uses microwave energy to excite plasma to ionize sample molecules. However, the signal background interference is large at atmospheric pressure, and the excitation of helium and argon plasmas is relatively difficult. Summary of the Invention

[0003] In order to overcome the deficiencies in the prior art, the purpose of the present utility model is to provide a low-pressure assisted end-face enhanced microwave plasma ion source with three coaxial tubes, which consists of an inner tube, a middle tube, a first vacuum sealing ring, a second vacuum sealing ring, an outer tube, a microwave solid-state source, a microwave transmission line, a gasket, a vacuum extraction tube, a vacuum pump, a third vacuum sealing ring, a microwave enhancement electrode, and a low-pressure microwave plasma. The inner tube is located at the central position of the middle tube and is used to introduce helium or argon gas with a flow rate of 1 - 200 ml / min. The middle tube is located at the central position of the outer tube and is fabricated into an L shape by bending to facilitate the introduction of gas into the middle tube. It is used to introduce helium or argon gas with a flow rate of 1 - 200 ml / min. The first vacuum sealing ring is located between the inner tube and the middle tube and is used to fix the inner tube in the middle tube and seal the space between the two. The second vacuum sealing ring is located between the middle tube and the outer tube and is used to fix the middle tube in the outer tube and seal the space between the two. The outer tube is located outside the middle tube, and the ratio of the inner diameter of the outer tube to the outer diameter of the middle tube is between 2.3 - 2.6, forming a microwave resonant cavity. The microwave solid-state source is located above the microwave transmission line and is connected to the microwave transmission line, and is used to generate microwave energy with frequencies such as 915 MHz, 2450 MHz, or 5.8 GHz. The microwave transmission line is located between the middle tube and the microwave solid-state source and is used to enable microwaves to enter the space between the outer tube and the middle tube. The gasket is located between the microwave transmission line and the outer tube and is used to vacuum-seal the microwave transmission line and the outer tube. The vacuum extraction tube is located at the rear of the outer tube and is used to connect the outer tube to the vacuum pump. The vacuum pump is located below the ion source and is connected to the vacuum extraction tube and is used to extract the vacuum inside the outer tube and maintain the vacuum at 0.1 - 100 mbar. The third vacuum sealing ring is located between the outer tube and the microwave enhancement electrode and is used to vacuum-seal the outer tube and the microwave enhancement electrode. The microwave enhancement electrode is located at the rear end of the outer tube and the third vacuum sealing ring. The low-pressure microwave plasma is located at the rear end of the inner tube and is at the central position of the microwave enhancement electrode. After the microwave resonates in the microwave resonant cavity, the maximum electric field intensity is reached near the microwave enhancement electrode, and a low-pressure microwave plasma is excited in the microwave enhancement electrode.

[0004] The material of the inner tube is copper or other metal materials. It is located at the central position of the middle tube and is used to introduce helium or argon gas, and the flow rate of the introduced gas is 1 - 200 ml / min.

[0005] The material of the middle tube is copper or other metal materials. It is located at the central position of the outer tube and is fabricated into an L shape by bending. It is used to introduce helium or argon gas, and the flow rate of the introduced gas is 1 - 200 ml / min.

[0006] The material of the first vacuum sealing ring is a sealing material such as fluororubber. It is located between the inner tube and the middle tube and is used to fix the inner tube in the middle tube and seal the space between the two.

[0007] The material of the second vacuum sealing ring is a sealing material such as fluororubber. It is located between the middle tube and the outer tube, used to fix the middle tube inside the outer tube and seal the space between the two.

[0008] The material of the outer tube is copper or other metal materials. It is located outside the middle tube. The ratio of the inner diameter of the outer tube to the outer diameter of the middle tube is preferably 2.3, forming a microwave resonant cavity.

[0009] The microwave solid state source is a microwave generator. It is located above the microwave transmission line and connected to the microwave transmission line, used to generate microwave energy with frequencies such as 915 MHz, 2450 MHz or 5.8 GHz.

[0010] The microwave transmission line is located between the middle tube and the microwave solid state source, used to make the microwave enter the space between the outer tube and the middle tube.

[0011] The material of the gasket is an insulating material such as polytetrafluoroethylene. It is located between the microwave transmission line and the outer tube, used to vacuum seal the microwave transmission line and the outer tube.

[0012] The material of the vacuum evacuation tube is a metal material such as stainless steel. It is located at the rear of the outer tube, used to connect the outer tube to the vacuum pump.

[0013] The vacuum pump is a mechanical pump. It is located below the ion source and connected to the vacuum evacuation tube, used to evacuate the vacuum inside the outer tube and maintain the vacuum (working air pressure) at 0.1 - 100 mbar.

[0014] The material of the third vacuum sealing ring is a sealing material such as fluororubber. It is located between the outer tube and the microwave enhancement electrode, used to vacuum seal the outer tube and the microwave enhancement electrode.

[0015] The material of the microwave enhancement electrode is a metal material such as stainless steel. It is located at the rear end of the outer tube and the third vacuum sealing ring. After the microwave resonates in the microwave resonant cavity, the maximum electric field strength is reached near the microwave enhancement electrode, and a low-pressure microwave plasma is excited inside the microwave enhancement electrode.

[0016] The low-pressure microwave plasma is located at the rear end of the inner tube and at the center position of the microwave enhancement electrode, used for efficient ionization to provide more sample molecule information.

[0017] The utility model reduces signal background interference through a unique vacuum sealing design, while improving the ionization efficiency of the sample and the intensity of the mass spectrometry detection signal. Using the three-tube coaxial structure design is beneficial to the stable operation of the microwave plasma under low pressure. At the same time, by adding an end face enhancement electrode, the electric field strength of the end face is further enhanced, effectively improving the excitation efficiency and stability of the microwave plasma, thereby significantly improving the ionization performance of the ionization source, increasing the ionization efficiency of the sample, improving the sensitivity and accuracy of mass spectrometry analysis, and enriching the detection data of the sample.

[0018] The utility model has the following advantages:

[0019] (1) Introduce low-pressure assistance technology to reduce signal background interference under atmospheric pressure, and at the same time improve the ionization efficiency of samples and the intensity of mass spectrometry detection signals;

[0020] (2) Through the structure of three tubes coaxial, it is more conducive to the stable operation of the plasma, can provide a stable plasma environment, realize the efficient conduction of microwave energy, and thus improve the ionization efficiency of samples;

[0021] (3) Adopt end-face enhanced microwave design, add microwave enhancement electrodes, further enhance the electric field intensity of the end face, effectively enhance the concentration and stability of the microwave field, are more likely to excite and maintain microwave plasma, ensure the full utilization of microwave energy, and significantly improve the excitation efficiency and stability of microwave plasma;

[0022] (4) The device is reasonably designed, easy to operate, and the technical solution is mature, can significantly improve the sensitivity of instrument detection, and has high practicability and economic benefits in practical applications. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of an embodiment of the utility model, used to show a low-pressure assisted end-face enhanced microwave plasma ion source with three tubes coaxial.

[0024] Figure 2 It is a physical working photo of a low-pressure assisted end-face enhanced microwave plasma ion source with three tubes coaxial made according to the method provided by the utility model. The quartz glass and the red vacuum seal ring in the figure are used for separate plasma testing. During testing, they are used to seal the ports of the plasma device to ensure that the plasma ion source works under vacuum. It can be seen that under the action of the vacuum pump, after the quartz glass presses and seals the vacuum seal ring, microwave plasma can be stably generated.

[0025] Figure 3 It is the mass spectrometry data of the detection of harmful gases in the air after the low-pressure assisted end-face enhanced microwave plasma ion source with three tubes coaxial made according to the method provided by the utility model is combined with a mass spectrometer. The sample concentration is 10 ppb (that is, harmful substances with a concentration of one in a billion can be detected), and the detection limit can reach the ppt level, showing the excellent ionization performance of the ion source of the utility model. Detailed Embodiments

[0026] The technical solution of the present utility model will be further described below in conjunction with the accompanying drawings and through specific embodiments. Among them, the accompanying drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to this application; in order to better illustrate the embodiments of the present utility model, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0027] Embodiment 1

[0028] See Figure 1 , a low-pressure assisted end-face enhanced microwave plasma ion source with three coaxial tubes, which consists of an inner tube 1, a middle tube 2, a first vacuum sealing ring 3, a second vacuum sealing ring 4, an outer tube 5, a microwave solid-state source 6, a microwave transmission line 7, a gasket 8, a vacuum extraction tube 9, a vacuum pump 10, a third vacuum sealing ring 11, a microwave enhancement electrode 12, and a low-pressure microwave plasma 13. The inner tube 1 is located at the central position of the middle tube 2 and is used to introduce helium or argon gas, and the gas flow rate is 1 - 200 ml / min. The middle tube 2 is located at the central position of the outer tube 5 and is bent into an L shape for introducing helium or argon gas, and the gas flow rate is 1 - 200 ml / min. The first vacuum sealing ring 3 is located between the inner tube 1 and the middle tube 2 and is used to fix the inner tube 1 in the middle tube 2 and seal it. The second vacuum sealing ring 4 is located between the middle tube 2 and the outer tube 5 and is used to fix the middle tube 2 in the outer tube 5 and seal it. The outer tube 5 is located outside the middle tube 2, and the ratio of the inner diameter of the outer tube 5 to the outer diameter of the middle tube 2 is about 2.3, forming a microwave resonant cavity. The microwave solid-state source 6 is located above the microwave transmission line 7 and is connected to the microwave transmission line 7, and is used to generate microwave energy with frequencies such as 915 MHz, 2450 MHz, or 5.8 GHz. The microwave transmission line 7 is located between the middle tube 2 and the microwave solid-state source 6 and is used to make the microwave enter between the outer tube 5 and the middle tube 2. The gasket 8 is located between the microwave transmission line 7 and the outer tube 5 and is used to vacuum-seal the microwave transmission line 7 and the outer tube 5. The vacuum extraction tube 9 is located at the rear of the outer tube 5 and is used to connect the outer tube 5 to the vacuum pump 10. The vacuum pump 10 is connected to the vacuum extraction tube 9 and is used to extract the vacuum inside the outer tube 5 to maintain the vacuum at 0.1 - 100 mbar. The third vacuum sealing ring 11 is located between the outer tube 5 and the microwave enhancement electrode 12 and is used to vacuum-seal the outer tube 5 and the microwave enhancement electrode 12. The microwave enhancement electrode 12 is located at the rear of the outer tube 5 and the third vacuum sealing ring 11. After the microwave resonates in the microwave resonant cavity, the maximum electric field intensity is reached near the microwave enhancement electrode 12, and a low-pressure microwave plasma 13 is excited inside the microwave enhancement electrode 12. The low-pressure microwave plasma 13 is located at the rear end of the inner tube 1 and is inside the microwave enhancement electrode 12, and is used for efficient ionization to provide more sample molecule information.

[0029] Embodiment 2

[0030] As Figures 1-3 shown, using the device provided by the present utility model, the ion source is used according to the following steps:

[0031] 1. First, start the vacuum pump 10, extract the gas inside the outer tube 5 through the vacuum extraction pipe 9, and maintain the vacuum inside the device within the range of 0.1 - 100 mbar;

[0032] 2. Introduce helium or argon through the inner tube 1 and the middle tube 2, adjust the gas flow rate as needed, and control the gas flow rate to remain at 1 - 200 ml / min;

[0033] 3. Turn on the microwave solid - state source 6 to generate microwave energy with a frequency of 2450 MHz or 5.8 GHz, etc. The microwave energy is transmitted into the space between the outer tube 5 and the middle tube 2 through the microwave transmission line 7. After resonating in the microwave resonator cavity, the microwave energy reaches the maximum electric field strength at the microwave enhancement electrode 12, and a low - pressure microwave plasma 13 is excited inside the microwave enhancement electrode 12;

[0034] 4. Introduce the sample to be measured into the rear end of the inner tube 1, and perform efficient ionization through the low - pressure microwave plasma 13 to generate a large number of sample molecular ions.

[0035] The above is only a preferred specific embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present utility model, according to the technical solution and inventive concept of the present utility model, makes equivalent substitutions or changes, and should be covered within the protection scope of the present utility model.

[0036] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non - exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

Claims

1. A low-pressure assisted end-face enhanced microwave plasma ion source with three coaxial tubes, characterized in that, It consists of an inner tube (1), a middle tube (2), a first vacuum sealing ring (3), a second vacuum sealing ring (4), an outer tube (5), a microwave solid state source (6), a microwave transmission line (7), a gasket (8), a vacuum extraction pipe (9), a vacuum pump (10), a third vacuum sealing ring (11), a microwave enhancement electrode (12), and a low-pressure microwave plasma (13); among them, the inner tube (1) is located at the central position of the middle tube (2), the middle tube (2) is located at the central position of the outer tube (5), the first vacuum sealing ring (3) is located between the inner tube (1) and the middle tube (2), the second vacuum sealing ring (4) is located between the middle tube (2) and the outer tube (5), the outer tube (5) is located outside the middle tube (2), the microwave solid state source (6) is located above and connected to the microwave transmission line (7), the microwave transmission line (7) is located between the middle tube (2) and the microwave solid state source (6), the gasket (8) is located between the microwave transmission line (7) and the outer tube (5), the vacuum extraction pipe (9) is located at the rear of the outer tube (5), the vacuum pump (10) is connected to the vacuum extraction pipe (9), the third vacuum sealing ring (11) is located between the outer tube (5) and the microwave enhancement electrode (12), the microwave enhancement electrode (12) is located at the rear end of the outer tube (5) and the third vacuum sealing ring (11), and the low-pressure microwave plasma (13) is located at the rear end of the inner tube (1) and is inside the microwave enhancement electrode (12).

2. The low-pressure assisted end-face enhanced microwave plasma ion source with three coaxial tubes according to claim 1, characterized in that, The microwave plasma operates at low pressure, and the operating pressure ranges from 0.1 to 100 mbar.

3. A low-pressure assisted end-face enhanced microwave plasma ion source with three coaxial tubes according to claim 1, characterized in that, The ratio of the inner diameter of the outer tube (5) to the outer diameter of the middle tube (2) is between 2.3 and 2.6, forming a microwave resonator cavity, and the microwave frequency is 915 MHz, 2450 MHz, or 5.8 GHz.

4. A low-pressure assisted end-face enhanced microwave plasma ion source with three coaxial tubes, characterized in that, The working gas of the microwave plasma is helium or argon.

5. A low-pressure assisted end-face enhanced microwave plasma ion source with three coaxial tubes, characterized in that, The materials of the outer tube, middle tube, and inner tube are all copper.

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