A four-way atmospheric pressure plasma jet array method based on a cascaded power division structure

Abstract

This invention discloses a method for a four-channel atmospheric pressure plasma jet array based on a cascaded power divider structure, belonging to the field of plasma jet technology. The method includes steps S1 (precision forming of the outer cavity), S2 (segmented machining of the inner conductor), S3 (annular ceramic preparation), S4 (LC parameter simulation pre-design), S5 (graded alignment assembly), and S6 (segmented debugging of the entire machine). This method for a four-channel atmospheric pressure plasma jet array based on a cascaded power divider structure produces products that can be widely used in large-area continuous industrial applications such as low-temperature sterilization of medical devices and surface activation of polymer sheets. It improves the yield rate by over 30%, reduces the ceramic scrap rate from the traditional 25% to less than 3%, has strong process reproducibility, eliminates the risk of localized heat accumulation and breakdown, and increases the continuous rated power of the equipment from the traditional 1.2kW to 3-5kW, meeting the needs of high-power continuous industrial production lines. It possesses outstanding innovation and industrialization value.

Description

Technical Field

[0001] This invention relates to the field of plasma jet technology, specifically to a method for a four-channel atmospheric pressure plasma jet array based on a cascaded power divider structure. Background Technology

[0002] Currently, the fabrication of industrial-scale four-channel coaxial microwave plasma jets both domestically and internationally falls into two main categories: unsupported suspended inner conductor technology and ceramic drilling and hollowing compensation technology. Both technologies suffer from inherent structural defects. The unsupported suspended inner conductor solution requires a pre-reserved conductor support structure, which leads to local field distortion within the cavity. Prolonged high-power operation can easily result in local breakdown, and assembly and positioning are difficult, resulting in a yield rate of less than 60%, making it difficult to meet the needs of mass production. On the other hand, the ceramic drilling and hollowing compensation technology requires machining coaxial through holes in the center of the ceramic dielectric, which demands extremely high ceramic machining precision. The scrap rate of the fine grinding and drilling process after sintering is as high as 25%, significantly increasing the manufacturing cost. Furthermore, the hollowed-out ceramic will encroach on the inner conductor space, limiting the continuous rated power of the equipment. The maximum power of traditional solutions is usually no more than 1.2kW, which cannot meet the high-power requirements of large-area continuous industrial processing.

[0003] Patent application CN118296994A discloses a simulation method and related apparatus for atmospheric pressure plasma jet arrays. The method involves constructing an atmospheric pressure plasma jet array model, setting relevant simulation parameters, and finally performing simulation calculations using the model to obtain simulation results. This invention accurately describes the generation and transmission process of plasma jet arrays. Based on the simulation results, the performance of the plasma jet array, such as uniformity, stability, and active particle yield, is analyzed. Through simulation technology, efficient optimization of the plasma jet array is achieved, reducing experimental and time costs. The simulation results are accurate and reliable.

[0004] Patent application publication number CN117336935A discloses a method and system for magnetically confined three-dimensional plasma jet array. The system generates a discharge high voltage through a high-voltage power supply unit and supplies it to the high and low voltage electrodes of the jet array. The system also supplies discharge reaction gas through a high-voltage gas supply unit to the adjustable three-dimensional jet array discharge chamber within the three-dimensional plasma jet array unit. The system confines the plasma generated in the discharge region through a magnetic confinement unit. The system measures electrical and optical parameters and allows for the adjustment of one or more jet units in the array structure as needed, thereby forming an adjustable three-dimensional jet array structure.

[0005] Patent application CN116390316B discloses an array-type plasma jet device. Each dielectric column has a positive high-voltage electrode inserted inside. The distance between the opening of each dielectric column and the tip of the inserted positive high-voltage electrode gradually increases along the direction from the center of the dielectric column array towards the two side edges. This reduces the suppression of the electric field of the central positive high-voltage electrode by the edge positive high-voltage electrode. Working gas enters each dielectric column and generates a plasma jet at the tip of the positive high-voltage electrode within each column, greatly reducing energy loss and improving the device's safety. This array-type plasma jet device can generate a plasma jet array with good uniformity, low energy consumption, and safe contact with the human body based on the synergistic effect of corona discharge and dielectric barrier discharge.

[0006] None of the aforementioned patents proposed a low-cost, high-yield preparation scheme for the cascaded power divider structure of four-way microwave plasma jets. They failed to address the core industry pain points of high scrap rate in traditional ceramic drilling processes and low power limit due to easy breakdown of traditional unsupported inner conductors. They also failed to disclose a process approach that replaces traditional ceramic drilling by necking the inner conductor and matching it with a complete circular ceramic ring. Therefore, they cannot meet the needs of high-power continuous industrial production.

[0007] To address the aforementioned issues, there is an urgent need for innovative designs based on existing methods. Summary of the Invention

[0008] The purpose of this invention is to provide a method for a four-channel atmospheric pressure plasma jet array based on a cascaded power divider structure, in order to solve the problems mentioned in the background art. The prior art methods do not offer a low-cost, high-yield preparation scheme for the cascaded power divider structure of four-channel microwave plasma jets, do not address the core industry pain points of high scrap rate in traditional ceramic drilling processes, easy breakdown of traditional unsupported inner conductors, and low power upper limit, and do not disclose the process idea of ​​replacing traditional ceramic drilling with inner conductor necking and matching with a complete circular ceramic ring, thus failing to meet the needs of high-power continuous industrial production.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for a four-channel atmospheric pressure plasma jet array based on a cascaded power divider structure, comprising the following steps: Step S1, Precision forming process of the outer cavity: The TU oxygen-free copper raw material is selected and the five-axis CNC integrated milling is used to form a tree-like cascaded 90° arc smooth outer cavity that is divided into two parts and then into four parts. The standard outer diameter of the outer cavity is 13mm and the inner diameter is 11mm. The bifurcation position adopts an arc transition without right angle. After forming, the inner hole is honed and stress-relief annealed at 280℃. Step S2, Inner conductor segmentation machining process: The inner conductor is divided into a standard section with an outer diameter of 4.8mm and a stepped necking section at the support point. The necking ratio k (k=dneck / dstd) is controlled between 0.21 and 0.64. The axial length of the necking section is set separately for Lneck. There are no transition chamfers at both ends of the necking section. The finished product is silver-plated as a whole. The end is machined into a discharge cone section with a cone angle of 8.31° and a height of 15mm. Step S3, Ring-shaped ceramic preparation process: High-purity alumina with a dielectric constant of 9.2-9.8 is selected for solid non-porous pressing. The inner and outer diameters of the ceramic are interference-fitted with the outer diameter of the neck and the inner diameter of the outer cavity, respectively. The axial thickness H of the ceramic is exactly equal to the corresponding neck length Lneck. The qualified thickness range is 8mm≤H≤12.5mm. It is sintered and finely ground at 1650℃. Step S4, LC parameter simulation pre-design process: Based on the resonant frequency formula The resonance formula uses 2.45GHz as the target frequency point, calculates the matching parameters of the compensation inductor and parasitic capacitance, and verifies them using HFSS simulation. Parameters exceeding the range of 0.21~0.64 and 8~12.5mm are deemed unqualified. Step S5, graded alignment and assembly process: Assembly is carried out step by step from the feed end to the end, ensuring that the axial installation area of ​​the ceramic is completely overlapped with the necking section. If the axial misalignment is greater than 0.5mm, rework is required. The ceramic is assembled with temperature difference interference. Three 1-to-2 modules are spliced ​​into a 1-to-4 cascaded power distribution structure. Step S6, Segmented debugging of the whole machine: The vector network analyzer is swept from 2.2 to 3.0 GHz, and S11 ≤ -35dB at 2.45 GHz indicates acceptable impedance; microwave power is tested in stages from 500W to 5kW under no-load temperature rise.

[0010] Preferably, in step S2, the necking ratio k=0.27, corresponding to a necked outer diameter of 1.3mm, and the matching ceramic preferably has a thickness H=11.1mm, with a ceramic dielectric constant... Under alumina conditions, the finished product has an input return loss of S11 = -41.14dB at 2.45GHz.

[0011] Preferably, when the ceramic dielectric constant is replaced with 9.2 in step S3, the corresponding optimization method is: the diameter reduction ratio is reduced to 0.23 or the ceramic thickness is increased to 11.7mm, and after optimization, S11 ≤ -40dB; when the baseline parameters of 0.27 and 11.1mm are maintained, the finished product S11 = -19.28dB, which still meets the usage standard.

[0012] Preferably, in step S1, the total width of the 1-to-2 single module is 71mm, the center distance between the two output ports is 45mm, and the total height of the entire 1-to-4 external cavity is 158.2mm.

[0013] Preferably, in the actual working conditions of step S6, the air intake flow rate for sterilization is 5-10 L / min, and the nozzle distance from the workpiece is 5-15 mm; the air intake flow rate for plate modification is 10-20 L / min, and the nozzle distance from the substrate is 10-20 mm.

[0014] Preferably, after completing the temperature rise and adjustment in step S6, process gas at a rate of 5-20 L / min is introduced to measure the four plasma jets. If the power error is <0.02 dB, the finished product is considered qualified. This method introduces a series inductance through necking to cancel the parasitic capacitance of the ceramic, realizes local LC resonance, stabilizes the coaxial impedance of the dielectric section at 50 Ω, eliminates the ceramic drilling process, and realizes the preparation of 3-5 kW high-power four-channel plasma jets.

[0015] Preferably, in step S1, the radius R of the transition arc at the bifurcation position of the outer cavity is 8mm, and the tangent of the arc is smoothly tangent to the coaxial center line of the main branch and the branch circuit, so as to avoid microwave reflection loss caused by the right angle structure.

[0016] Preferably, in step S2, the semi-cylindrical bonding surface at the bifurcation point of the inner conductor is milled to ensure complete conductor conductivity after adjacent modules are spliced. The thickness of the silver plating layer on the surface is controlled between 3μm and 5μm to improve the conductor's conductivity and reduce microwave transmission loss.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. Eliminating the entire ceramic drilling process significantly reduces mass production costs and improves yield. Traditional hollowing processes require three additional steps: blank drilling, hole inspection, and waste ceramic screening. This invention eliminates the need for drilling in solid ceramics, reducing the ceramic sintering scrap rate from 25% to less than 3% and increasing raw material utilization by 32%. The process of repeatedly changing ceramics for trial fitting is also eliminated, shortening the single-unit debugging cycle from 3-5 days to less than 4 hours, increasing the production line efficiency by more than 6 times, and reducing manufacturing costs by 28%.

[0018] 2. The all-solid ceramic retains high thermal conductivity and high mechanical properties, resulting in a leapfrog increase in equipment power capacity. The ceramic has no hollow sections, and 98% of the solid cross-section opens up radial heat conduction channels, allowing heat to be quickly discharged to the copper outer cavity under high power, eliminating the risk of localized heat accumulation and breakdown. The continuous rated power of the equipment has been increased from the traditional 1.2kW to 3-5kW, meeting the needs of high-power continuous industrial production lines. The mechanical strength of the ceramic has been greatly improved, the resistance to thermal stress cracking has been increased by 4 times, and the equipment maintenance cycle has been extended by more than 3 times.

[0019] 3. Furthermore, parameter standardization and product consistency fundamentally solve the pain point of power distribution imbalance in the four channels. This invention uses dual-parameter quantitative control of the diameter reduction ratio and ceramic thickness, and relies on the LC formula for precise matching. The S11 fluctuation of products in the same batch is controlled within ±2dB, and the power distribution error of the four channels is reduced from >20% to <0.02dB. The length and density of the four plasma jets are completely consistent, and there is no local leakage in large-area processing, which greatly improves the workpiece yield.

[0020] 4. Furthermore, it has strong frequency band adaptability, resists microwave source frequency drift, and improves operational stability. The LC local resonant structure maintains excellent impedance matching in a wide frequency range of 2.3 to 2.6 GHz. After microwave frequency drift caused by power grid fluctuations, there is no surge in standing waves or source-end protection shutdown problem. The stability of continuous production around the clock is significantly better than that of traditional hollow solutions.

[0021] 5. Furthermore, it has strong process compatibility, adapts to different dielectric ceramics, and offers flexible raw material selection. For the two mainstream alumina ceramics on the market, 9.2 and 9.8, precise compensation can be achieved by only slightly adjusting the diameter reduction or ceramic thickness. Raw material procurement is not limited by a single ceramic specification, making it more adaptable to industrialization. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall operation process of the method of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0024] Example 1: In a specific embodiment, the present invention provides the following technical solution: a method for a four-channel atmospheric pressure plasma jet array based on a cascaded power divider structure, such as... Figure 1 As shown, the preparation and implementation of the benchmark optimal parameters ( Alumina (core preferred process) is implemented in accordance with the six preparation steps of this invention. The detailed processing, assembly and debugging parameters are as follows; The entire fabrication process of this invention is divided into six standardized steps: S1 precision machining of the outer cavity, S2 segmented forming of the inner conductor, S3 fabrication of a solid ring ceramic, S4 LC parameter simulation pre-design, S5 graded precise alignment and assembly, and S6 overall impedance and plasma segmented debugging. The process parameters, operating procedures, and control thresholds for each step are as follows: Step S1: Precision CNC forming process of the outer cavity (outer conductor); The raw material is TU1 high-purity oxygen-free copper rod (containing ≥99.99% copper). The outer cavity of the power divider is formed by five-axis CNC integrated milling, which is a three-level tree-like cascaded power divider. The standard outer diameter of the cavity is 13mm and the nominal inner diameter of the inner hole is 11mm. All the branching and turning points of the one-to-two power dividers adopt a smooth transition structure with a 90° radius arc, completely eliminating right-angle inflection points and avoiding the risk of electric field distortion and breakdown at right angles. After the cavity is formed, the inner hole is honed and precision machined to a roughness Ra≤0.8μm, removing tool marks, burrs, and protrusions, and eliminating the concentration of electric field at microscopic tips. Annular positioning slots are reserved at the ceramic mounting positions corresponding to each level of power divider. The air inlet holes are uniformly machined according to the process hole diameter. After machining, the cavity is annealed at a constant temperature of 280℃ for 90 minutes to eliminate residual internal stress from machining and avoid thermal deformation during high-temperature service.

[0025] Step S2: Inner conductor segmentation and shaping process; The inner conductor is divided into two types of structures: standard equal-diameter section and stepped necked section, which are machined separately. The standard section has a uniform outer diameter d=4.8mm, with no abrupt change in diameter throughout, and naturally maintains a standard coaxial impedance of 50Ω in the air dielectric section. At each ceramic mounting point, a stepless neck is machined without transition, and there are no direct abrupt changes in size at either end without rounded chamfers. The necked outer diameter... The necking ratio k = dstd, and dneck is strictly limited to the acceptable process range of 0.21 to 0.64, with the optimal baseline k = 0.27 (corresponding to...). =1.3mm); axial length of the necking The thickness H of the matching ceramic is exactly the same; the inner conductor is silver-plated as a whole, with a plating thickness of ≥5μm to reduce microwave skin loss; the end discharge cone section is machined with a cone angle of 8.31° and a total axial length of 15mm, using the cone-shaped converging electric field to improve gas breakdown efficiency.

[0026] Step S3: Preparation of a solid ring-shaped ceramic green body; The raw material is selected from ceramics with high dielectric constant. High-purity alumina powder (optional) (Industrial alumina), eliminating the blank drilling process entirely, using ring-shaped solid pressing, with an interference fit between the ceramic inner hole and the necked outer diameter, and an 11mm interference fit between the outer circle and the inner diameter of the outer cavity; ceramic axial thickness H and matching necking. Equal length, with H=11.1mm as the preferred standard, and the acceptable thickness range for the process is 8mm≤H≤12.5mm. <8mm cannot meet the support stiffness, and >12.5mm cannot achieve precise LC matching; sintered at high temperature and normal pressure at 1650℃, and the inner and outer circles are finely ground after sintering, with dimensional tolerance controlled at ±0.03mm to ensure the coaxial accuracy of interference fit, and to completely preserve the ceramic solid structure and radial heat conduction channels.

[0027] Step S4: LC resonance parameter simulation pre-design process; Using 2.45GHz as the target resonant frequency, the required compensation inductance is calculated in reverse using the LC resonant formula, locking in the two major parameter boundaries: a diameter reduction ratio of 0.21–0.64 and a ceramic thickness of 8–12.5mm. The benchmark optimal parameters are k=0.27 and H=11.1mm. When the ceramic dielectric constant changes from 9.8 to 9.2, corresponding fine-tuning is performed: the diameter reduction ratio is lowered to 0.23 or the ceramic thickness is increased to 11.7mm, which still ensures S11≤-19dB, meeting industrial standards. HFSS electromagnetic simulation pre-verification is performed, and parameters exceeding the range (k<0.21 or k>0.64, H<8 or H>12.5) are judged as unqualified blanks and are prohibited from entering the assembly process, thus controlling the impedance consistency of the finished product from the source.

[0028] Step S5: Graded precision coaxial assembly process; Assembly sequence: Assembly proceeds step by step from the end of the cavity to the microwave feed end. First, the ceramic ring is positioned, then the segmented inner conductor is inserted, ensuring that the axial range of the ceramic is completely aligned with the necked section. An axial misalignment greater than 0.5mm is considered a rework, as misalignment will directly lead to L and C space mismatch and LC resonance failure. The ceramic is assembled using a temperature difference interference fit with low-temperature pre-cooling and slight heating of the cavity, without any knocking or bumping, to prevent ceramic assembly cracking. The three 1-to-2 modules are sequentially spliced ​​into an inverted Y-shaped 1-to-4 overall power divider architecture, and finally the RF connector and air inlet are assembled.

[0029] Step S6: Overall impedance and plasma operating condition segmented debugging process Impedance testing: A vector network analyzer was used to sweep the entire frequency band from 2.2GHz to 3.0GHz. An impedance of S11 ≤ -35dB at 2.45GHz was considered acceptable. The baseline finished product had an impedance of S11 = -41.14dB. If the impedance was unacceptable, the necking or ceramic thickness was slightly adjusted. No-load heating and debugging: The microwave power was gradually increased from 500W to 1.5kW to 3kW to 5kW, with each level held for 30 minutes. The ceramic was observed to have no abnormal temperature rise or arcing. Plasma measurement: The gas inlet was 5-20L / min, the nozzle distance from the substrate was 5-20mm, and the length and density of the four jets were consistent. A power error of <0.02dB was considered a qualified finished product.

[0030] The outer cavity is made of TU1 oxygen-free copper, milled in one piece, with an outer diameter of 13mm, an inner diameter of 11mm, and an overall length of 158.2mm. The width of each single module is 71mm (45+26mm). The distance between the graded support points and the feed port is 37.5mm and 86.1mm, respectively. All transitions are 90° rounded. The inner hole is honed to Ra0.7μm and annealed at 280℃ for 90min. The inner conductor has a standard section length of 4.8mm, with the support point stepped necking to 1.3mm. The k=0.27 necking axial length is 11.1mm, and there are no transition chamfers at both ends. The discharge cone angle at the end is 8.31°, and the cone height is 15mm. The entire piece is silver-plated to 5μm. The ceramic is made of ε=9.8 high-purity alumina, a solid, non-porous annular part with inner and outer diameters matching 1.3mm and 11mm, respectively. The axial thickness H=11.1mm is exactly equal to the necking length. It is sintered at 1650℃ with a dimensional tolerance of ±0.02mm.

[0031] Pre-simulation, HFSS input into LC formula for verification, L and C resonance matching at 2.45GHz, S11 theoretical value -41.5dB, assembly, low temperature pre-cooling of ceramic, micro-heating interference assembly of cavity, axial zero misalignment between ceramic and necking, three 1-to-2 modules assembled into an inverted Y 1-to-4 structure.

[0032] Overall debugging: The measured vector network frequency was 2.45 GHz, S11 = -41.14 dB, and the error of the four S-parameters was <0.02 dB; the power was stepped up to 5 kW and ignited continuously for 3 hours without temperature rise; the air intake flow rate was 12 L / min, the length of the four plasma jets was completely consistent, the measured electric field cloud showed that the electric field strength in the ceramic support area was extremely low (dark blue), the electric field distribution of the four nozzles was highly symmetrical, there were no local field singularities, and the single unit could stably operate continuously at 3-5 kW under air-cooling conditions for a long time.

[0033] Example 2: Optimized preparation of ceramic dielectric 9.2; Raw material replacement Commercial alumina, with other processing dimensions remaining unchanged, two optimized preparation schemes: Scheme 1: The diameter reduction ratio is reduced from 0.27 to 0.23 ( Scheme 1: With a diameter of ≈1.104mm and a ceramic thickness of 11.1mm, the simulated and measured S11 is -40.66dB, which meets the requirements. Scheme 2: With the diameter reduced to 0.27mm and the ceramic thickness increased to 11.7mm, the measured S11 is -42.73dB. If the original parameters of 0.27mm and 11.1mm are maintained, the finished product S11 is -19.28dB (< -10dB acceptable line), which can still be used normally in 3kW conditions.

[0034] Example 3: Comparative preparation for critical parameter verification (control group A: ceramic thickness variable); The processing parameters for all other components are the same as in Example 1, with only the ceramic thickness being changed: Control group A1: H=8mm (lower critical limit), finished product S11=-10.82dB, just meeting the standard, but the ceramic support stiffness is too weak, so it is not preferred for mass production; Control group A2: H=12.5mm (upper critical limit), finished product S11=-10.94dB, the reflection is too large, and it cannot operate at full power for a long time; Samples with H<8 or H>12.5mm have S11>-10dB and are judged to be scrapped, which confirms the rationality of the process boundary of 8~12.5mm thickness.

[0035] Example 4: Critical parameter verification and comparative preparation (control group B: diameter reduction ratio variable); With the baseline dimensions unchanged, only the k value is changed: B1: k=0.21 (d≈1.008mm), S11=-11.07dB, critically acceptable; B2: k=0.64 (d≈3.072mm), S11=-10.16dB, critically acceptable; k<0.21 or k>0.64 (e.g., 0.65), S11>-9.7dB, impedance mismatch is severe, and the process parameter range of 0.21~0.64 is verified by actual measurement.

[0036] Example 5: Three sets of invalid comparative examples (to verify the inventiveness of the present invention and the defects of existing solutions); Comparative Example 1: No necking, inner conductor all 4.8mm (traditional straight inner conductor plus all solid ceramic) Preparation: The stepped necking was eliminated, the inner conductor was 4.8mm in length throughout, and the dimensions of the rest of the ceramic and cavity were the same as in Example 1; the measured S1=-1.9dB, most of the microwaves were reflected, the electric field was highly concentrated at the bifurcation point, and the power could only be ≤600W, which made it impossible to achieve high-power four-way jet, proving that necking is an essential innovative process for inductor manufacturing.

[0037] Comparative Example 2: The neck and ceramic are axially misaligned by 3mm, the component dimensions remain unchanged, and the ceramic is offset by 3mm during assembly. The L and C spatial misalignment causes LC resonance failure; the measured S11=-4.73dB, the electric field distortion is severe, and normal degassing is impossible, verifying the necessity of the "ceramic and neck are of equal length and coincident" assembly process.

[0038] Comparative Example 3: The ceramic is removed, the necking is retained, there is no supporting ceramic, the inner conductor is suspended, although there is a necking inductor, there is no parasitic capacitance C and LC compensation cannot be formed, the whole machine is almost total reflection across the entire frequency band, S11 is close to 0dB, and the inner conductor is not centered and is very easy to be eccentric, proving that the ceramic and the necking are indispensable.

[0039] Comparative Example 4: Traditional perforated ceramic with no necking (current mainstream process), inner conductor 4.8mm unchanged, ceramic with large area hollowing, actual measured power deviation of four channels 21.7%, rated power upper limit 1.1kW, far inferior to the 3-5kW index of the present invention, intuitively demonstrating the creative advantages of the present invention.

[0040] In the above embodiments, the medical sterilization preparation prototype is produced according to the process of Example 1, with a microwave power of 100W, an air intake of 8L / min, a nozzle distance of 8mm from the culture dish, and plasma treatment at normal pressure and temperature for 15s, which completely inactivates E. coli and does not burn consumables with high temperature, making it suitable for batch sterilization production lines for medical consumables; the board modification prototype is powered by 400W, with an air intake of 15L / min, and a nozzle distance of 12mm from the PP board. After plasma activation, the bonding strength is increased by more than 3 times, replacing the base coat adhesive, enabling green mass production and increasing the overall creativity.

[0041] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A four-way atmospheric pressure plasma jet array method based on a cascaded power splitting structure, characterized by: Includes the following steps: Step S1, Precision forming process of the outer cavity: The TU oxygen-free copper raw material is selected and the five-axis CNC integrated milling is used to form a tree-like cascaded 90° arc smooth outer cavity that is divided into two parts and then into four parts. The standard outer diameter of the outer cavity is 13mm and the inner diameter is 11mm. The bifurcation position adopts an arc transition without right angle. After forming, the inner hole is honed and stress-relief annealed at 280℃. Step S2, Inner conductor segmentation machining process: The inner conductor is divided into a standard section with an outer diameter of 4.8mm and a stepped necking section at the support point. The necking ratio k (k=dneck / dstd) is controlled between 0.21 and 0.

64. The axial length of the necking section is set separately for Lneck. There are no transition chamfers at both ends of the necking section. The finished product is silver-plated as a whole. The end is machined into a discharge cone section with a cone angle of 8.31° and a height of 15mm. Step S3, Ring-shaped ceramic preparation process: High-purity alumina with a dielectric constant of 9.2-9.8 is selected for solid non-porous pressing. The inner and outer diameters of the ceramic are interference-fitted with the outer diameter of the neck and the inner diameter of the outer cavity, respectively. The axial thickness H of the ceramic is exactly equal to the corresponding neck length Lneck. The qualified thickness range is 8mm≤H≤12.5mm. It is sintered and finely ground at 1650℃. Step S4, LC parameter simulation pre-design process: Resonance frequency formula The resonance formula takes 2.45GHz as the target frequency point, and calculates the matching parameters of the compensation inductance and the parasitic capacitance. The HFSS simulation verification is carried out, and the parameters exceeding the range of 0.21-0.64, 8-12.5mm are determined as unqualified. Step S5, graded alignment and assembly process: Assembly is carried out step by step from the feed end to the end, ensuring that the axial installation area of ​​the ceramic is completely overlapped with the necking section. If the axial misalignment is greater than 0.5mm, rework is required. The ceramic is assembled with temperature difference interference. Three 1-to-2 modules are spliced ​​into a 1-to-4 cascaded power distribution structure. Step S6, Segmented debugging of the whole machine: The vector network analyzer is swept from 2.2 to 3.0 GHz, and S11 ≤ -35dB at 2.45 GHz indicates acceptable impedance; microwave power is tested in stages from 500W to 5kW under no-load temperature rise.

2. The method for fabricating a four-channel atmospheric pressure plasma jet array based on a cascaded power divider structure according to claim 1, characterized in that: In the step S2, the necking ratio k=0.27 is preferred, corresponding to the necked outer diameter 1.3 mm, and the ceramic thickness H=11.1 mm is preferred, with the ceramic dielectric constant The finished product has a 2.45 GHz input return loss S11=-41.14 dB under the working condition of aluminum oxide.

3. The method of claim 1, wherein the four-way atmospheric plasma jet array is prepared based on a cascaded power-division structure. When the ceramic dielectric constant is replaced with 9.2 in step S3, the corresponding optimization method is: reduce the diameter reduction ratio to 0.23 or increase the ceramic thickness to 11.7mm. After optimization, S11 ≤ -40dB; when the baseline parameters of 0.27 and 11.1mm are maintained, the finished product S11 = -19.28dB, which still meets the usage standard.

4. The method of claim 1, wherein the four-way atmospheric plasma jet array is prepared based on a cascaded power-division structure. In step S1, the total width of the 1-to-2 single module is 71mm, the center distance between the two output ports is 45mm, and the total height of the entire 1-to-4 external cavity is 158.2mm.

5. The method of claim 1, wherein the four-way atmospheric plasma jet array is prepared based on a cascaded power-division structure. In the actual test conditions of step S6, the air intake flow rate for sterilization is 5-10 L / min, and the nozzle distance from the workpiece is 5-15 mm; the air intake flow rate for plate modification is 10-20 L / min, and the nozzle distance from the substrate is 10-20 mm.

6. The method of claim 1, wherein the four-way atmospheric plasma jet array is prepared based on a cascaded power-division structure. After completing the temperature rise and adjustment in step S6, process gas at a rate of 5-20 L / min is introduced to measure the four plasma jets. If the power error is <0.02 dB, the finished product is considered qualified. This method introduces a series inductor through necking to cancel the parasitic capacitance of the ceramic, realizes local LC resonance, stabilizes the coaxial impedance of the dielectric section at 50 Ω, eliminates the ceramic drilling process, and realizes the preparation of 3-5 kW high-power four-channel plasma jets.

7. The method of claim 1, wherein the method further comprises: In step S1, the radius R of the transition arc at the bifurcation position of the outer cavity is 8mm, and the tangent of the arc is smoothly tangent to the coaxial center line of the main branch and the branch circuit to avoid microwave reflection loss caused by the right angle structure.

8. The method of claim 1, wherein the four-way atmospheric plasma jet array is prepared based on a cascaded power-division structure. In step S2, the semi-cylindrical bonding surface at the bifurcation point of the inner conductor is milled to ensure complete conductor conductivity after adjacent modules are spliced ​​together. The thickness of the silver plating layer on the surface is controlled between 3μm and 5μm to improve the conductor's conductivity and reduce microwave transmission loss.

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