VUV lamp ionization source device with efficient heat dissipation capability

Abstract

The invention relates to the technical field of analysis instrument ionization sources, in particular to a VUV lamp ionization source device with efficient heat dissipation capacity. The device comprises a VUV lamp, a heat dissipation unit, a VUV lamp driving electrode, a driving circuit and an ion guide focusing unit. The heat dissipation unit carries out cooperative heat dissipation on the VUV lamp and the pulse transformer through a fan, and the problems of signal attenuation and device aging caused by temperature rise are solved. The driving electrode adopts a pairwise pairing structure of upper and lower and left and right electrode pairs to form an inclined electric field to prevent ions from bombarding the lamp wall and the light window; the drive circuit is a half-bridge or full-bridge topology, can adjust the pulse frequency and the power supply voltage, and achieves the switching between a high-voltage low-frequency mode and a low-voltage high-frequency mode. The ion guide focusing unit efficiently leads out and separates ions through cooperation of a conical focusing electric field and a conductive film forward electric field. Through four-dimensional innovation of heat dissipation, electrodes, driving and transmission, the stability, the service life and the detection sensitivity of the device are improved, and the device is suitable for analytical instruments such as ion mobility spectrometry and mass spectrometry.

Description

Technical Field

[0001] This invention relates to the field of ionization source technology for analytical instruments, and in particular to a VUV lamp ionization source device with high-efficiency heat dissipation capability. Background Technology

[0002] Ionization sources are one of the core components of analytical instruments such as ion mobility spectrometry and mass spectrometry, and their performance directly determines the sensitivity, stability, and lifespan of the instrument. Traditional radioactive ionization sources (such as 63Ni) are gradually being replaced by non-radioactive ionization sources due to issues such as safety regulations, environmental restrictions, and limited ion concentration. Among these, vacuum ultraviolet (VUV) photoionization sources have attracted widespread attention and become a current research hotspot due to their high selectivity, high sensitivity, and lack of radioactive pollution.

[0003] As a key component of photoionization sources, the performance optimization of VUV lamps is crucial. However, existing VUV lamp ionization sources still face a series of technical bottlenecks in practical applications: Performance degradation and lifespan issues: VUV lamps generate a significant amount of heat during operation, leading to an increase in lamp body temperature. This, in turn, reduces luminous efficiency and ionization capacity, causing signal output to decay over time. Simultaneously, the core electronic components driving the VUV lamp (such as the pulse transformer) also generate heat due to continuous operation, weakening the driving capability, further exacerbating signal instability, and significantly shortening the lifespan of the VUV lamp and its driving circuitry. Current technology lacks a systematic solution for coordinated and efficient heat dissipation of the lamp body and driver.

[0004] The limited driving methods and defects in electrode structure: VUV lamps are mainly driven by two methods: high-voltage low-frequency and low-frequency high-voltage. Conventional driving circuits (such as DC boost circuits) can usually only achieve one dominant mode, lacking flexibility and making it difficult to optimize performance for different application scenarios. Regarding electrode structure, the common top-bottom electrode design (CN105719937B) easily causes ions generated during discharge to vertically impact the lamp wall, forming a reverse electric field and weakening the discharge capability. Meanwhile, the left-right electrode design (CN111211036B and CN111211037B) easily causes ions to impact the optical window at the front end, leading to a decrease in window transmittance due to contamination or sputtering. Both of these structures can cause signal attenuation, affecting long-term stability.

[0005] Low ion transport efficiency: When a VUV lamp is directly applied to an ion migration tube, ions generated by ionization tend to accumulate in front of the lamp window, making it difficult to quickly and effectively introduce them into the subsequent ion migration reaction zone. The traditional repulsion electrode structure (funnel-shaped CN110828281B) has limited ability to guide and focus ions, resulting in low ion utilization, especially poor rapid and efficient separation and extraction of positive and negative ions, which limits further improvement in detection sensitivity.

[0006] In conclusion, developing a VUV lamp ionization source that can effectively dissipate heat, possess high-performance electrodes and flexible driving methods, and achieve efficient ion transport is of vital importance for promoting the industrialization of high-end analytical instruments. Summary of the Invention

[0007] In view of this, the present invention provides a VUV lamp ionization source device with high heat dissipation capability.

[0008] Therefore, the present invention provides the following technical solution: A VUV lamp ionization source device with high-efficiency heat dissipation capability includes a VUV lamp, a heat dissipation unit, a VUV lamp driving electrode, a driving circuit, and an ion guiding and focusing unit. The heat dissipation unit includes a fan and a fan bracket. The VUV lamp is fixedly installed in the receiving area of ​​the fan bracket, and the end of the fan corresponding to the VUV lamp away from the light window is installed on the fan bracket. The VUV lamp driving electrode includes an upper electrode, a lower electrode, a left electrode, and a right electrode. The upper and lower electrodes are arranged horizontally on the upper and lower sides of the VUV lamp, forming an upper and lower electrode pair. The left and right electrodes are arranged vertically on the left and right sides of the VUV lamp, forming a left and right electrode pair. The upper, lower, left, and right electrodes are electrically connected in pairs by wires to form an independent first electrode group and a second electrode group. The driving circuit includes a pulse transformer, a MOSFET, resistors, a pulse signal generating unit, and a DC power supply. The two output terminals of the secondary side of the pulse transformer are simultaneously electrically connected to one electrode in the first electrode group and one electrode in the second electrode group. One end of the primary side of the pulse transformer is electrically connected to the DC power supply, and the other end is electrically connected to the drain of the MOSFET. The source of the MOSFET is grounded, and the base is connected to two resistors. One resistor is pulled down to ground, and the other resistor is electrically connected to the signal output terminal of the pulse signal generating unit. The ion-guided focusing unit includes a repulsion electrode, an ionization region electrode, a conductive film, and an insulating layer. A fan bracket is fixedly mounted on the insulating layer. A hollow ionization region with an axial through-hole is provided in the center of the insulating layer. The repulsion electrode and the ionization region electrode are sequentially embedded inside the insulating layer in a direction away from the VUV lamp, and both are coaxially arranged with the ionization region. The inner wall of the ionization region electrode is exposed in the ionization region. The light window of the VUV lamp faces the ionization region, and the end face of the light window is located at the entrance end of the ionization region. The conductive film is fixed tightly against the outer surface of the light window of the VUV lamp, and the conductive film is electrically connected to the repulsion electrode. A sample inlet is provided on the insulating layer and the repulsion electrode in a radial direction perpendicular to the ionization region axis. This sample inlet is connected to the ionization region and is used to allow the sample gas path to extend into the ionization region.

[0009] Furthermore, the insulating layer, the repulsion electrode, and the ionization region electrode are all annular structures, and the inner diameter of the ionization region has a gradually expanding conical structure along the direction away from the VUV lamp.

[0010] Furthermore, the conductive film is an ultra-high transmittance film or a metal mesh; wherein, the thickness of the ultra-high transmittance film is less than 0.5 mm and the transmittance is not less than 95%; the wire diameter of the metal mesh is less than 0.1 mm and the mesh size is not less than 90%.

[0011] Furthermore, the frequency range of the pulse signal output by the pulse signal generating unit is 1kHz-500kHz and 1MHz-10MHz.

[0012] Furthermore, the topology of the driving circuit is a half-bridge or full-bridge configuration, wherein the input terminal of the half-bridge or full-bridge topology is electrically connected to a DC power supply, and the output terminal is electrically connected to the primary side of a pulse transformer.

[0013] Furthermore, the upper electrode, lower electrode, left electrode, and right electrode are structured as thin electrode sheets, electrode rings, or irregular structures with heat dissipation fins.

[0014] Furthermore, the pairing method is selected from one of the following two: The first method: the left electrode and the upper electrode are electrically connected to form the first electrode group, and the right electrode and the lower electrode are electrically connected to form the second electrode group; The second method: the left electrode and the right electrode are electrically connected to form the first electrode group, and the upper electrode and the lower electrode are electrically connected to form the second electrode group.

[0015] Advantages and positive effects of the present invention: An integrated, high-efficiency heat dissipation system significantly improves stability and lifespan. This invention designs a synergistic heat dissipation structure for VUV lamps and their pulse transformers. Active cooling by a fan efficiently dissipates heat from the VUV lamp and the core heat-generating components of the driver circuit. This solves the problems of signal attenuation and device aging caused by temperature rise, ensuring the stability of light intensity during long-term operation of the VUV lamp and the reliability of the driver's output power, and significantly extending the lifespan of the entire ionization source device.

[0016] Combined drive electrode design optimizes discharge performance and long-term reliability: This invention employs a combined driving electrode structure that combines upper and lower electrode pairs (upper and lower electrodes) with left and right electrode pairs (left and right electrodes). Each electrode is electrically connected in pairs via wires, causing the discharged ions in the VUV lamp to move obliquely. This prevents ions from concentrating and bombarding the lamp wall and light window, thus preventing the formation of a reverse electric field and protecting the light transmittance of the light window. From a physical structure perspective, this invention solves the key factors that lead to signal attenuation and maintains the continuous and stable strong discharge capability of the VUV lamp.

[0017] The controllable pulse drive circuit enables flexible adjustment of the drive mode. Based on the controllable pulse drive circuit design consisting of a pulse transformer, MOSFET, resistor, pulse signal generation unit and DC power supply, the drive circuit topology is in the form of half bridge or full bridge. It supports flexible adjustment of the frequency of the output signal of the pulse signal generation unit and the supply voltage of the DC power supply through programming or external setting. It can switch between multiple working modes such as high voltage low frequency and low voltage high frequency. Users can select the optimal drive parameters according to different sample ionization requirements or working conditions to improve the applicability and performance optimization potential of the device.

[0018] Built-in light window and conductive thin film enable efficient ion extraction and separation: The ions generated by ionization accumulate charge on the surface of the insulating layer. Combined with the geometry of the electrode, this forms a strong focusing electric field pointing inward into the ionization region, effectively guiding the ions accumulated in front of the lamp into the reaction zone, thus achieving efficient ion extraction.

[0019] A conductive film is placed close to the light window and electrically connected to the repulsion electrode. A high voltage is applied to generate a positive electric field toward the ionization region, which further accelerates ion extraction and promotes the separation of positive and negative ions. This provides a quenching site for the separated ions, reduces ion neutralization and quenching phenomena, and significantly improves ionization efficiency and detection sensitivity.

[0020] In summary, this invention provides a stable, long-lasting, highly efficient, and adaptable VUV lamp ionization source device through synergistic innovation in four dimensions: heat dissipation, electrodes, drive, and transmission. This has powerfully promoted the advancement and industrial application of non-radioactive ionization source technology. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a VUV lamp ionization source device with high-efficiency heat dissipation capability provided by the present invention.

[0023] In the diagram: 1. Fan; 2. Fan bracket; 3. VUV lamp; 4. Wire; 5. Left electrode; 6. Upper electrode; 7. Right electrode; 8. Light window; 9. Conductive film; 10. Repulsion electrode; 11. Insulating layer; 12. Ionization region electrode; 13. Ionization region; 14. Sample inlet; 15. Lower electrode; 16. Pulse transformer; 17. DC power supply; 18. Resistor; 19. MOSFET; 20. Pulse signal. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] This invention provides a VUV lamp ionization source device with high-efficiency heat dissipation capability, such as... Figure 1 As shown, it includes a VUV lamp 3, a heat dissipation unit, a VUV lamp driving electrode, a driving circuit, and an ion guiding focusing unit.

[0027] The heat dissipation unit includes a fan 1 and a fan bracket 2. The VUV lamp 3 is fixedly installed in the receiving area of ​​the fan bracket 2. The end of the fan 1 corresponding to the VUV lamp 3 away from the light window 8 is installed on the fan bracket 2.

[0028] The VUV lamp driving electrode includes an upper electrode 6, a lower electrode 15, a left electrode 5, and a right electrode 7. The upper electrode 6 and the lower electrode 15 are horizontally arranged on the upper and lower sides of the VUV lamp 3, forming an upper and lower electrode pair. The left electrode 5 and the right electrode 7 are vertically arranged on the left and right sides of the VUV lamp 3, forming a left and right electrode pair. The upper electrode 6, the lower electrode 15, the left electrode 5, and the right electrode 7 are electrically connected in pairs through wires 4 to form an independent first electrode group and a second electrode group.

[0029] The pairing method is selected from one of the following two: The first method: the left electrode 5 and the upper electrode 6 are electrically connected to form the first electrode group, and the right electrode 7 and the lower electrode 15 are electrically connected to form the second electrode group.

[0030] The second method: the left electrode 5 and the right electrode 7 are electrically connected to form the first electrode group, and the upper electrode 6 and the lower electrode 15 are electrically connected to form the second electrode group.

[0031] The upper electrode 6, lower electrode 15, left electrode 5, and right electrode 7 are structured as thin electrode sheets, electrode rings, or irregularly shaped structures with heat dissipation fins. This ensures both uniform electric field distribution and enhanced heat dissipation of the electrodes themselves.

[0032] The driving circuit includes a pulse transformer 16, a MOSFET 19, a resistor 18, a pulse signal generation unit 20, and a DC power supply 17. Each of the two output terminals on the secondary side of the pulse transformer 16 is simultaneously electrically connected to one electrode in the first electrode group and one electrode in the second electrode group. In the first configuration, one output terminal on the secondary side of the pulse transformer 16 is electrically connected to the left electrode 5 or the upper electrode 6 of the first electrode group and simultaneously to the right electrode 7 or the lower electrode 15 of the second electrode group; the other output terminal is electrically connected to the unconnected remaining electrode in the first electrode group and simultaneously to the unconnected remaining electrode in the second electrode group. In the second configuration, one output terminal on the secondary side of the pulse transformer 16 is electrically connected to the left electrode 5 or the right electrode 7 of the first electrode group and simultaneously to the upper electrode 6 or the lower electrode 15 of the second electrode group; the other output terminal is electrically connected to the unconnected remaining electrode in the first electrode group and simultaneously to the unconnected remaining electrode in the second electrode group. The driving circuit has a half-bridge or full-bridge topology. The input terminal of the half-bridge or full-bridge topology is electrically connected to the DC power supply 17, and the output terminal is electrically connected to the primary side of the pulse transformer 16. One end of the primary winding of pulse transformer 16 is electrically connected to DC power supply 17, and the other end is electrically connected to the drain of MOSFET 19. The source of MOSFET 19 is grounded, and its base is connected to two resistors 18. One resistor 18 is pulled down to ground, and the other resistor 18 is electrically connected to the signal output terminal of pulse signal generation unit 20. The pulse signal output by pulse signal generation unit 20 has a frequency range of 1kHz-500kHz and 1MHz-10MHz.

[0033] The ion-guided focusing unit includes a repulsion electrode 10, an ionization region electrode 12, a conductive film 9, and an insulating layer 11. A fan bracket 2 is fixedly mounted on the insulating layer 11. The insulating layer 11 has a hollow ionization region 13 that extends through the ionization region along the center. The repulsion electrode 10 and the ionization region electrode 12 are sequentially embedded inside the insulating layer 11 in a direction away from the VUV lamp 3, and both are coaxially arranged with the ionization region 13. The inner wall of the ionization region electrode 12 is exposed in the ionization region 13. The light window 8 of the VUV lamp 3 faces the ionization region 13, and the end face of the light window 8 is located at the entrance end of the ionization region 13. The conductive film 9 is fixed tightly against the outer surface of the light window 8 of the VUV lamp 3, and the conductive film 9 is electrically connected to the repulsion electrode 10. An inlet 14 is provided on the insulating layer 11 and the repulsion electrode 10 in a radial direction perpendicular to the axial direction of the ionization region 13. The inlet 14 is connected to the ionization region 13 and is used to allow the sample gas path to extend into the ionization region 13.

[0034] The insulating layer 11, the repulsion electrode 10, and the ionization region electrode 12 are all annular structures, and the inner diameter of the ionization region 13 is a gradually expanding conical structure along the direction away from the VUV lamp 3.

[0035] The conductive film 9 is an ultra-high light transmittance film or metal mesh; wherein, the thickness of the ultra-high light transmittance film is less than 0.5 mm and the light transmittance is not less than 95%; the wire diameter of the metal mesh is less than 0.1 mm and the mesh size is not less than 90%.

[0036] Working principle: After the device is started, the heat dissipation unit is the first to enter the working state. Fan 1 blows cooling airflow to the VUV lamp 3 and pulse transformer 16 housed in the bracket, continuously cooling the lamp body of VUV lamp 3 and the core heat-generating components of the drive circuit.

[0037] DC power supply 17 provides adjustable DC power supply, and pulse signal generation unit 20 outputs wideband pulse signals of 1kHz-500kHz or 1MHz-10MHz. The half-bridge or full-bridge topology of the drive circuit receives the above power supply and signal and completes the inverter processing, converting DC power into pulsed AC power and transmitting it to the primary side of pulse transformer 16. After the pulse transformer 16 boosts the pulse signal, it outputs high-voltage pulses to two sets of paired electrodes through the two output terminals of the secondary side. The first electrode group and the second electrode group form an oblique cross electric field through a preset pairing method, which guides the ions generated by the discharge inside the VUV lamp 3 to move obliquely, avoiding the ions from vertically bombarding the lamp wall and the light window 8.

[0038] The VUV lamp 3 discharges stably under the high voltage pulse of the two sets of paired electrodes, and the emitted vacuum ultraviolet light shines directly into the ionization region 13 through the light window 8; the sample gas path sends the sample molecules into the ionization region 13 through the sample inlet 14, and the sample molecules are ionized under the irradiation of vacuum ultraviolet light to form a mixture of positive and negative ions.

[0039] After the conductive film 9 is electrically connected to the repulsion electrode 10, it synergistically generates a strong focusing electric field. Combined with the guiding effect of the cone-shaped ionization region 13, it quickly pushes away the ions accumulated in front of the light window 8, avoiding ion neutralization quenching. At the same time, it accelerates the movement of positive and negative ions along the expansion direction of the ionization region 13, realizing efficient ion separation and extraction, and delivering a high-purity ion flow to the subsequent detection unit.

[0040] The driving circuit dynamically matches the output frequency of the pulse signal generation unit 20 with the supply voltage of the DC power supply 17, flexibly switching between high-voltage low-frequency and low-voltage high-frequency working modes to adapt to the ionization requirements of different samples. The heat dissipation unit continuously cools down key components such as the VUV lamp 3 and the pulse transformer 16, and works in conjunction with the lamp body protection mechanism of the oblique electric field and the ion efficient extraction mechanism of the focusing electric field to ensure long-term stable output and high detection sensitivity of the device.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A VUV lamp ionization source device with high-efficiency heat dissipation capability, characterized in that, Includes VUV lamp (3), heat dissipation unit, VUV lamp driving electrode, driving circuit and ion guiding focusing unit; The heat dissipation unit includes a fan (1) and a fan bracket (2). The VUV lamp (3) is fixedly installed in the accommodating area of ​​the fan bracket (2). The end of the fan (1) corresponding to the VUV lamp (3) away from the light window (8) is installed on the fan bracket (2). The VUV lamp driving electrode includes an upper electrode (6), a lower electrode (15), a left electrode (5), and a right electrode (7). The upper electrode (6) and the lower electrode (15) are arranged horizontally on the upper and lower sides of the VUV lamp (3) to form an upper and lower electrode pair. The left electrode (5) and the right electrode (7) are arranged vertically on the left and right sides of the VUV lamp (3) to form a left and right electrode pair. The upper electrode (6), the lower electrode (15), the left electrode (5), and the right electrode (7) are electrically connected in pairs through wires (4) to form an independent first electrode group and a second electrode group. The driving circuit includes a pulse transformer (16), a MOS transistor (19), resistors (18), a pulse signal generating unit (20), and a DC power supply (17). The two output terminals of the secondary side of the pulse transformer (16) are simultaneously electrically connected to one electrode in the first electrode group and one electrode in the second electrode group. One end of the primary side of the pulse transformer (16) is electrically connected to the DC power supply (17), and the other end is electrically connected to the drain of the MOS transistor (19). The source of the MOS transistor (19) is grounded, and the base is connected to two resistors (18). One resistor (18) is pulled down to ground, and the other resistor (18) is electrically connected to the signal output terminal of the pulse signal generating unit (20). The ion-guided focusing unit includes a repulsion electrode (10), an ionization region electrode (12), a conductive film (9), and an insulating layer (11). The fan bracket (2) is fixedly installed on the insulating layer (11). The center of the insulating layer (11) is provided with a hollow ionization region (13) that runs through the axial direction. The repulsion electrode (10) and the ionization region electrode (12) are sequentially embedded inside the solid of the insulating layer (11) in a direction away from the VUV lamp (3), and both are coaxially arranged with the ionization region (13). The inner wall of the ionization region electrode (12) is exposed outside the ionization region (11). 3) The light window (8) of the VUV lamp (3) is set facing the ionization region (13), and the end face of the light window (8) is located at the entrance end of the ionization region (13); the conductive film (9) is fixed in close contact with the outer surface of the light window (8) of the VUV lamp (3), and the conductive film (9) is electrically connected to the repulsion electrode (10); the insulating layer (11) and the repulsion electrode (10) are provided with a sample inlet (14) in a radial direction perpendicular to the axial direction of the ionization region (13), and the sample inlet (14) is connected to the ionization region (13) for the sample gas path to extend into the ionization region (13).

2. The VUV lamp ionization source device with high-efficiency heat dissipation capability according to claim 1, characterized in that, The insulating layer (11), the repulsion electrode (10), and the ionization region electrode (12) are all annular structures, and the inner diameter of the ionization region (13) is a gradually expanding conical structure along the direction away from the VUV lamp (3).

3. The VUV lamp ionization source device with high-efficiency heat dissipation capability according to claim 1, characterized in that, The conductive film (9) is an ultra-high transmittance film or a metal mesh; wherein, the thickness of the ultra-high transmittance film is less than 0.5 mm and the transmittance is not less than 95%; the wire diameter of the metal mesh is less than 0.1 mm and the mesh size is not less than 90%.

4. The VUV lamp ionization source device with high-efficiency heat dissipation capability according to claim 1, characterized in that, The pulse signal output by the pulse signal generating unit (20) has a frequency range of 1kHz-500kHz and 1MHz-10MHz.

5. The VUV lamp ionization source device with high-efficiency heat dissipation capability according to claim 1, characterized in that, The topology of the driving circuit is a half-bridge or full-bridge type. The input terminal of the half-bridge or full-bridge topology is electrically connected to the DC power supply (17), and the output terminal is electrically connected to the primary side of the pulse transformer (16).

6. The VUV lamp ionization source device with high-efficiency heat dissipation capability according to claim 1, characterized in that, The upper electrode (6), lower electrode (15), left electrode (5) and right electrode (7) are thin electrode sheets, electrode rings, or irregular structures with heat dissipation fins.

7. The VUV lamp ionization source device with high-efficiency heat dissipation capability according to claim 1, characterized in that, The pairing method is selected from one of the following two: The first method: the left electrode (5) and the upper electrode (6) are electrically connected to form the first electrode group, and the right electrode (7) and the lower electrode (15) are electrically connected to form the second electrode group; The second method: the left electrode (5) and the right electrode (7) are electrically connected to form the first electrode group, and the upper electrode (6) and the lower electrode (15) are electrically connected to form the second electrode group.

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