A semi-open full dielectric barrier discharge low-temperature plasma ionization source device

Abstract

The application relates to the technical field of low-temperature plasma, in particular to a semi-open full dielectric barrier discharge low-temperature plasma ionization source device which comprises a sample tube, a jet tube and an ion region. One end of the sample tube is provided with a sample input end, and the other end is a closed end. The closed end is penetrated by the jet tube. One end of the jet tube located inside the cavity of the sample tube is provided with a receiving port, and the other end is connected with the ion region arranged outside the jet tube through an output port. An air inlet pipe is arranged on the wall of the side of the sample tube close to the jet tube. A first ring-shaped electrode is arranged on the outer wall of the end of the sample tube far from the jet tube. A second ring-shaped electrode is arranged outside the jet tube. A third ring-shaped electrode is arranged outside the air inlet pipe. The device combines the technical means of semi-open structure, low-temperature plasma filling the cavity, bidirectional jet and directional jet path, and is suitable for in-situ ionization of irregular, low-concentration and difficult-to-vaporize solids. The ionization efficiency, signal strength and detection sensitivity are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of low-temperature plasma technology, specifically a semi-open all-dielectric barrier discharge low-temperature plasma ionization source device. Background Technology

[0002] Ion mobility spectrometry (IMS) separates and detects different ions based on the difference in migration velocity of ions in a neutral gas under the influence of an electric field. IMS offers advantages such as millisecond-level single-spectrum analysis speed, suitability for developing portable instruments, and the ability to be coupled with highly efficient atmospheric pressure chemical ionization sources. Detection limits can be as low as pptv (10–12), making it widely used for rapid on-site detection of trace explosives and industrial hazardous chemicals. A crucial step in ion mobility spectrometry is converting the neutral molecules of the analyte into their ionic form. This can be achieved using various ionization methods. Depending on the ionization method, ion mobility spectrometry ionization sources include radioactive ionization sources, corona discharge ionization sources, photoionization sources, electrospray ionization sources, dielectric barrier discharge ionization sources, pressurized DC glow discharge ionization sources, flame ionization, and so on. The traditional dielectric barrier discharge ionization source (DBDI) is an open-environment ionization source used for solid detection. Currently, common dielectric barrier discharge ionization sources have two main structures: ring-ring discharge and needle-ring discharge. Closed-loop DBDIs are primarily used for detecting gases and liquids. For solid detection, traditional DBDIs typically use open-loop ionization sources. This type of ionization source design has some obvious drawbacks and limitations, mainly in the following aspects:

[0003] 1. Sample dissipation: The sample loss is large. An open ionization source means that sample molecules are easy to diffuse into the surrounding environment during the ionization process, resulting in a small amount of sample actually participating in ionization, which affects the ionization efficiency.

[0004] 2. Environmental background interference: (1) Interference from ambient air: Open ionization sources are easily interfered with by other components in the ambient air (such as water vapor, carbon dioxide, volatile organic compounds, etc.). These components may be mis-ionized or react chemically with the target sample, generating interfering ions and affecting the analysis results; (2) Unstable ionization environment: Since the ionization region is exposed to the air, changes in environmental conditions (such as temperature, humidity, airflow, etc.) will have an unstable effect on ionization efficiency and ion signal, resulting in poor repeatability of results;

[0005] 3. Low ion collection efficiency: (1) Difficulty in ion capture: Ions in open ion sources are easily dispersed under the action of electric field, making it difficult to be effectively captured and guided to ion mobility spectrometers or mass spectrometers, resulting in significant signal loss and reduced detection sensitivity; (2) Irregular ion paths: The flight paths of ions in open ion sources are easily affected by environmental factors and may deviate from the predetermined collection direction, causing signal noise and inaccurate detection results. Therefore, in view of the above situation, it is urgent to develop a semi-open all-dielectric barrier discharge low-temperature plasma ionization source device to overcome the shortcomings in current practical applications. Summary of the Invention

[0006] The purpose of this invention is to provide a semi-open all-dielectric barrier discharge low-temperature plasma ionization source device to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A semi-open all-dielectric barrier discharge low-temperature plasma ionization source device includes: a sample tube, a jet tube, an ion region, a first annular electrode, a second annular electrode, a third annular electrode, and an inlet pipe. One end of the sample tube has a sample input end, and the other end is a closed end, penetrated by the jet tube, forming a semi-open structure for sample introduction and ionization. The jet tube has a receiving port at one end and an output port at the other end, both connected to the inner cavity of the jet tube. The output port is also connected to the ion region located outside the jet tube. An inlet pipe is located on the side of the sample tube closest to the jet tube for inputting discharge gas. A first annular electrode is arranged around the outer wall of the sample tube furthest from the jet tube and connected to a grounding wire. A second annular electrode is arranged around the outer side of the jet tube, and a third annular electrode is arranged around the outer side of the inlet pipe. Both the second and third annular electrodes are connected to a high-voltage power supply.

[0009] As a further aspect of the present invention: the first ring electrode, the second ring electrode, and the third ring electrode are installed in the discharge region, and the electrodes are covered with dielectric material to achieve dielectric barrier discharge.

[0010] As a further aspect of the present invention, a closed structure is provided on the inner side of the sample tube cavity.

[0011] As a further aspect of the present invention, it also includes an ion gate and a migration region, wherein the ion gate is disposed at the end of the ion region away from the jet tube, and the ion gate is connected to the migration region.

[0012] As a further aspect of the present invention: the migration region further includes a Faraday disk and a shielding grid, wherein a shielding grid is provided on the inner side of the migration region away from the ion region, and a Faraday disk is also provided on the shielding grid.

[0013] As a further aspect of the present invention, the discharge gas is helium.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] During device operation, the sample is placed at the sample input end of the sample tube, and helium discharge gas is introduced through the gas inlet pipe. A voltage is applied between the first, second, and third annular electrodes by a high-voltage power supply. The electric field is uniformly distributed within the cavity through the annular electrodes, causing dielectric barrier discharge of the discharge gas. Due to the flow direction of the discharge gas and the design of the device structure, two plasma jets are simultaneously formed within the structure. These two jets exist simultaneously and act on different target areas. The resulting low-temperature plasma fills the entire cavity. Under the action of the first and third annular electrodes, an ionizing jet pointing towards the sample surface is formed in the sample tube cavity. High-energy particles can act concentratedly on the analyte, forming a highly efficient ionization effect. In this stage, the ionizing jet provides direct plasma contact to the analyte, causing the analyte molecules to ionize into charged ions and other active products. Simultaneously, under the action of the first and second annular electrodes, a transport jet pointing towards the ion region is formed in the jet tube cavity. The plasma jet propels ionization products from the discharge region to the ionization region, ensuring their smooth transfer. Compared to existing DBDI devices that often employ closed or completely open structures, this application addresses the limitations of closed structures on sample size and condition, which restrict in-situ detection, while open structures suffer from low ionization and transfer efficiency and are susceptible to environmental interference. By adopting a semi-open structure, the stability of the ionization region is ensured while allowing the plasma jet to directly act on the external sample, significantly improving detection convenience and efficiency. Furthermore, the semi-open design effectively isolates some external air impurities and humidity, contributing to improved ionization efficiency and detection sensitivity. This application also employs a three-electrode ring bidirectional jet structure, achieving bidirectional jetting within a single device. The ionization jet effectively ionizes the sample, while the transfer jet stably transports the ionization products. Under the combined action of the bidirectional jets, the low-temperature plasma fills the entire cavity, effectively preventing ion neutralization, reducing ion loss, and improving signal strength and detection sensitivity. This design is particularly suitable for detecting low-concentration or solid samples. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a semi-open, all-dielectric barrier discharge low-temperature plasma ionization source device.

[0017] Figure 2 A three-dimensional structural diagram of a semi-open all-dielectric barrier discharge low-temperature plasma ionization source device.

[0018] Figure 3 This is a schematic diagram of the DBDI structure.

[0019] Figure 4 This is a schematic diagram of the DBDI-IMS structure.

[0020] In the diagram: 1-Sample tube, 2-Jet tube, 3-Ion region, 4-High voltage power supply, 5-First annular electrode, 6-Second annular electrode, 7-Third annular electrode, 8-Closed end, 9-Inlet pipe, 10-Sample input end, 11-Receiver port, 12-Outlet port, 13-Sample tube cavity, 14-Jet tube cavity, 15-Grounding wire, 16-Ion gate, 17-Migration region, 18-Faraday disk, 19-Shielding grid. Detailed Implementation

[0021] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0022] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0023] Please see Figure 1 , Figure 2 and Figure 3 In one embodiment of the present invention, a semi-open all-dielectric barrier discharge low-temperature plasma ionization source device includes: a sample tube 1, a jet tube 2, an ion region 3, a first annular electrode 5, a second annular electrode 6, a third annular electrode 7, and an inlet pipe 9. One end of the sample tube 1 is provided with a sample input end 10, and the other end is a closed end 8, which is penetrated by the jet tube 2, thus forming a semi-open structure for sample introduction and ionization. One end of the jet tube 2 located inside the sample tube cavity 13 is provided with a receiving port 11, and the other end is provided with an output port 12. Both the output port 12 and the output port 12 are connected to the jet tube cavity 14 inside the jet tube 2. The output port 12 is also connected to the ion region 3 located outside the jet tube 2. An inlet pipe 9 is provided on the side wall of the sample tube 1 near the jet tube 2 to input the discharge gas. A first annular electrode 5 is arranged around the outer wall of the end of the sample tube 1 away from the jet tube 2. The first annular electrode 5 is connected to the grounding wire 15. A second annular electrode 6 is arranged around the outside of the jet tube 2. A third annular electrode 7 is arranged around the outside of the inlet pipe 9. Both the second annular electrode 6 and the third annular electrode 7 are connected to the high-voltage power supply 4.

[0024] In this embodiment, the first annular electrode 5 is tightly fitted onto the sample tube 1 and connected to the ground via a grounding wire 15. The second annular electrode 6 is tightly fitted onto the jet tube 2 and connected to a high-voltage power supply 4. The third annular electrode 7 is tightly fitted onto the inlet pipe 9 and connected to the high-voltage power supply 4. When the device is running, the sample is placed at the sample input end 10 of the sample tube, and helium discharge gas is introduced through the inlet pipe 9. A voltage is applied between the first annular electrode 5, the second annular electrode 6, and the third annular electrode 7 by the high-voltage power supply 4. The electric field is evenly distributed in the cavity through the annular electrodes, causing the discharge gas to undergo dielectric barrier discharge. Due to the design of the discharge gas flow direction and device structure, two plasma jets are simultaneously formed within the structure. These two jets exist concurrently and act on different target areas, generating low-temperature plasma that fills the entire cavity. Under the action of the first annular electrode 5 and the third annular electrode 7, an ionizing jet pointing towards the sample surface is formed in the sample tube cavity 13. High-energy particles can concentrate on the analyte, forming a highly efficient ionization effect. At this stage, the ionizing jet provides direct plasma contact to the analyte, causing the analyte molecules to ionize into charged ions and... Other active products, simultaneously, under the action of the first annular electrode 5 and the second annular electrode 6, a transport jet pointing towards the ion region 3 is formed in the jet tube cavity 14. This transport jet pushes the ionized products from the discharge region to the ion region 3. The ionized products are successfully transported to the ion region 3. Compared with the prior art, which mostly adopts a closed or completely open structure for DBDI devices, the closed structure has limitations on sample size and state and cannot detect in situ, while the open structure has low ionization and transport efficiency and is easily affected by environmental interference. By adopting a semi-open structure, the stability of the ionization region is ensured while allowing the plasma jet to... Directly acting on external samples significantly improves the convenience and efficiency of detection. At the same time, the semi-open design is effective in isolating some impurities and humidity from the outside air, which helps to improve ionization efficiency and detection sensitivity. This application also adopts a three-electrode ring bidirectional jet structure, realizing bidirectional jet in a single device. The ionization jet can effectively ionize the sample, while the transmission jet stably transmits the ionization products. Under the combined action of the bidirectional jet, the low-temperature plasma fills the entire cavity, effectively preventing ion neutralization, reducing ion loss, and improving signal strength and detection sensitivity. It is particularly suitable for the detection needs of low-concentration samples.

[0025] In one embodiment of the present invention, the first annular electrode 5, the second annular electrode 6, and the third annular electrode 7 are installed in the discharge region, and the electrodes are covered with dielectric material to achieve dielectric barrier discharge and ensure stable plasma generation.

[0026] In one embodiment of the present invention, the inner side of the sample tube cavity 13 is provided with a closed structure to isolate impurities and moisture in the outside air and avoid interfering with the ion generation process.

[0027] In one embodiment of the present invention, it further includes an ion gate 16 and a migration region 17, wherein the ion gate 16 is disposed at the end of the ion region 3 away from the jet tube 2, and the ion gate 3 is connected to the migration region 17.

[0028] In one embodiment of the present invention, the migration region 17 further includes a Faraday disk 18 and a shielding grid 19. The shielding grid 19 is disposed on the inner side of the migration region 17 away from the ion region 3, and the Faraday disk 18 is also disposed on the shielding grid 19. By setting the migration region 17, ionization products (including charged ions) are smoothly transported to the ion region 3 and then enter the migration region 17, and finally an electrical signal is formed on the Faraday disk 18 for analysis.

[0029] In one embodiment of the present invention, the discharge gas is helium.

[0030] In one embodiment of the present invention, the diameter, length and connection angle of the conduit are controlled by precision machining to achieve a bidirectional jet flow path and ensure the stability of the airflow direction and jet path.

[0031] This semi-open, all-dielectric barrier discharge cryogenic plasma ionization source device, through its semi-open structural design, effectively shields the ionization region from interference from humidity and impurities in the outside air, thereby reducing noise signal generation and significantly improving detection sensitivity and accuracy. The partially enclosed area isolates the ionization region from direct contact with the outside air, reducing the impact of water vapor and other volatile impurities on the ionization process, thus lowering the generation of interfering ions and improving signal clarity and detection reliability. The directional jet design makes the ion transport path more regular and the signal transmission more stable. Compared to a completely open structure, the semi-open directional jet significantly improves signal... The repeatability and stability of the DBDI are particularly outstanding in the detection of low-concentration samples. The design of the directional jet path reduces fluctuations in the signal transmission process, making ion transmission more concentrated and efficient, significantly improving the repeatability and sensitivity of the signal, and meeting the needs of high-precision analysis. Compared with a completely closed structure, the semi-open design allows the ionization source to act directly on the sample surface, eliminating the need for sample pretreatment or transfer required by traditional ionization sources. Traditional closed DBDIs cannot achieve in-situ detection of large or irregular samples because the sample needs to enter the ionization region. The semi-open DBDI can directly perform ionization and analysis on the sample site, improving the convenience and efficiency of detection.

[0032] This device employs a three-electrode ring bidirectional jet structure design, allowing the ionization jet to directly ionize the sample, while the transport jet rapidly transports the ionized products to the ion detection zone. By separating the ionization and transport paths, the bidirectional jet design significantly improves the efficiency of both processes. The unique structure of the bidirectional jet ensures that ionization and product transport are independent, avoiding instability in the jet direction and ensuring that ionized products enter the detection zone efficiently and stably, thereby improving detection accuracy and signal transmission stability. Under the action of the bidirectional jet, low-temperature plasma fills the entire cavity, forming an active ion environment that effectively prevents ions in the ionized products from undergoing neutralization reactions. This design reduces ion loss during transport, thus improving detection sensitivity and signal strength. The filling effect of the low-temperature plasma ensures that ions throughout the cavity remain active during transport, avoiding signal attenuation due to ion neutralization. This characteristic makes the device particularly effective for detecting low-concentration samples, ensuring high-quality signal transmission.

[0033] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A semi-open, all-dielectric barrier discharge low-temperature plasma ionization source device, characterized in that, include: The sample tube comprises a sample tube, a jet tube, an ionization region, a first annular electrode, a second annular electrode, a third annular electrode, and an inlet pipe. One end of the sample tube has a sample input end, and the other end is a closed end, penetrated by the jet tube. This closed end, together with the jet tube, forms a semi-open structure for sample introduction and ionization. The jet tube has a receiving port at one end and an output port at the other end, both connected to the inner cavity of the jet tube. The output port is also connected to the ionization region located outside the jet tube. An inlet pipe is located on the side of the sample tube closest to the jet tube for inputting discharge gas. A first annular electrode is arranged around the outer wall of the sample tube furthest from the jet tube and connected to a grounding wire. A second annular electrode is arranged around the outside of the jet tube, and a third annular electrode is arranged around the outside of the inlet pipe. Both the second and third annular electrodes are connected to a high-voltage power supply. The first annular electrode is tightly fitted onto the sample tube and connected to the ground via a grounding wire. The second annular electrode is tightly fitted onto the jet tube and connected to a high-voltage power supply. The third annular electrode is tightly fitted onto the inlet pipe and connected to a high-voltage power supply. A voltage is applied between the first, second, and third annular electrodes by the high-voltage power supply. Under the action of the first and third annular electrodes, an ionization jet pointing towards the sample surface is formed in the sample tube cavity. At the same time, under the action of the first and second annular electrodes, a transport jet pointing towards the ion region is formed in the jet tube cavity.

2. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 1, characterized in that, The first, second, and third annular electrodes are installed in the discharge region, and the electrodes are covered with dielectric material to achieve dielectric barrier discharge.

3. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 1, characterized in that, The sample tube cavity is provided with a closed structure on the inside.

4. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 1, characterized in that, Also includes: The ion gate is located at the end of the ion region furthest from the jet tube, and the ion gate is connected to the migration region.

5. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 4, characterized in that, The migration region further includes a Faraday disk and a shielding grid. A shielding grid is provided on the inner side of the migration region away from the ion region, and a Faraday disk is also provided on the shielding grid.

6. The semi-open all-dielectric barrier discharge cryogenic plasma ionization source device according to claim 1, characterized in that, The discharge gas is helium.

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