A method and apparatus for ultrasonic assisted magnetron plasma polishing of hard and brittle elements

Abstract

The application belongs to the technical field of hard and brittle difficult-to-machine optical element machining, and particularly relates to a kind of hard and brittle element ultrasonic auxiliary magnetic control plasma polishing method and device, the method comprises: mixing working gas and compressed oxygen and steady voltage delivery to plasma conduit;By high pressure tungsten needle electrode ionization gas, generate plasma jet, and adjust discharge parameter;Utilize annular ultrasonic array to form high intensity ultrasonic field, suppress arc divergence, make jet focus orderly;Guiding jet into the region of conical rotating magnetic field, through rotating magnetic field secondary focusing and acceleration, improve energy concentration degree;Jet acts on optical element surface, realize physical etching or chemical reaction.The application restrains plasma by rotating magnetic field, accurately controls motion trajectory, improves machining precision, solves the problems of arc instability, low machining efficiency, high surface roughness, subsurface damage and poor material adaptability in the prior art.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hard and brittle optical element processing, and particularly relates to a hard and brittle element ultrasonic-assisted magnetic control plasma polishing method and device. BACKGROUND

[0002] In modern optical systems, optical elements, as the core component, play a key role in aerospace, national defense and high-end civilian fields (such as satellite observation, laser weapons, and lithography machines). The machining precision of these elements directly determines the imaging quality and stability of the optical system. However, optical materials (such as quartz and sapphire) usually have high hardness and brittleness, and traditional machining methods are difficult to meet the requirements of ultra-precision machining, which easily leads to surface cracks and subsurface damage, thereby affecting the performance of optical elements.

[0003] Currently, the machining methods of optical elements mainly include mechanical machining, chemical etching, and laser machining. Among them, mechanical machining (such as grinding and polishing) can improve the machining precision to a certain extent, but it is easy to produce micro-cracks and surface damage for hard and brittle materials, and the machining efficiency is relatively low; chemical etching method can remove large area uniformly, but its machining precision is relatively low, and the surface quality is difficult to strictly control; laser machining has high energy density and good machining precision, but it is easy to cause thermal damage and material melting in the process of machining hard and brittle materials, which affects the final surface quality. The limitations of these traditional machining methods make the precision manufacturing of optical elements face great challenges, limiting the further improvement of machining precision and quality.

[0004] In recent years, plasma jet machining technology, as a new optical element machining method, has shown unique advantages. Plasma jet has high temperature, high energy density and good directivity, which can realize efficient etching and surface modification of optical materials. In the machining process, the active particles in the plasma jet and the optical material surface have physical and chemical effects, thereby removing the material and regulating the surface topography. Compared with traditional machining methods, plasma jet machining has higher machining precision, better surface quality, and can also realize the machining of complex shapes, so it has broad application prospects in the field of ultra-precision optical element manufacturing.

[0005] However, there are still some key technical problems to be solved in current plasma jet machining technology. Among them, the focusing and acceleration of plasma jet are important factors affecting the effect of ultra-precision machining. Traditional plasma jet usually shows the characteristics of divergence and disorder, resulting in low energy density and difficult further improvement of machining precision. Therefore, researchers have proposed a series of methods for focusing and accelerating plasma jet, such as electromagnetic field constraint, gas dynamics regulation and optical constraint technology. However, these methods still have certain limitations in practical application, such as the precision of electromagnetic field constraint difficult to meet the demand of ultra-precision machining, the gas dynamics regulation easy to introduce additional fluid disturbance, and the optical constraint technology has problems such as energy loss and optical element damage.

[0006] Therefore, in view of the demand for ultra-precision machining of hard and brittle optical elements, it is urgent to develop a new type of plasma machining method with high efficiency and low damage to further improve the machining quality and precision and meet the demand of high-end optical manufacturing. SUMMARY

[0007] In view of the above problems, the present application provides a hard and brittle element ultrasonic assisted magnetron plasma polishing method and device, which solves the problems of instability of arc caused by factors such as gas flow and pressure fluctuation, low machining efficiency, high surface roughness of optical element material and subsurface damage, and poor adaptability to different materials. Through the effective constraint of rotating magnetic field on plasma, the motion trajectory of plasma is accurately controlled by Lorentz force, the jet beam width is reduced, and the energy concentration is improved, so that the machining process is more efficient and accurate.

[0008] In one aspect, the present application provides a hard and brittle element ultrasonic assisted magnetron plasma polishing method, which comprises:

[0009] Step 1: Mix the working gas with compressed oxygen according to a predetermined ratio, and adjust the pressure through a gas pressure reducing mixer to make the mixed gas flow stably into the inner cavity of the plasma conduit;

[0010] Step 2: Ionize the mixed gas under the action of high-frequency high-voltage through a high-voltage tungsten needle electrode to generate plasma jet, and adjust the discharge parameters through a frequency matching controller;

[0011] Step 3: Make the plasma jet pass through the annular ultrasonic array to form a high-intensity ultrasonic field under the driving of the annular ultrasonic array controller, use the ultrasonic field to suppress the arc from the disordered state to the concentrated ordered state, and regulate the motion trajectory of the plasma to pre-focus the plasma jet;

[0012] Step 4: Direct the plasma jet pre-focused by the ultrasonic field to the conical rotating magnetic field region, generate a conical rotating magnetic field by the conical rotating magnetic field generating device under the action of the conical coil core, and perform secondary focusing and acceleration on the pre-focused plasma jet.

[0013] Step 5: Apply the plasma jet beam secondarily focused and accelerated by the magnetic field to the surface of the optical element to be processed, and cause physical etching or chemical reaction between the high-energy active particles in the plasma and the surface of the optical element material.

[0014] In the preferred implementation, further, in step 3, the process of forming the ultrasonic field includes: the ultrasonic transducer array is arranged in a ring shape, and when the ultrasonic transducer receives the high-frequency electric signal generated by the driving power supply, it quickly converts the electric energy into mechanical vibration to generate high-frequency ultrasonic waves. The ultrasonic waves propagate in the air medium to form alternating compression waves and rarefaction waves, and a highly focused acoustic field structure is generated in the plasma jet region.

[0015] In the preferred implementation, further, in step 3, by adjusting the driving frequency and power of the ultrasonic transducer, the intensity and distribution of the ultrasonic field can be dynamically controlled, and the focusing degree and energy density of the plasma jet can be optimized.

[0016] In the preferred implementation, further, the secondary focusing and acceleration process of the conical rotating magnetic field includes: the magnetic force generated by the rotating magnetic field in its action region further focuses the already pre-focused plasma jet, reduces the divergence degree of the jet, and improves the density and energy concentration of the jet. The charged particles in the plasma move in a spiral trajectory under the action of the magnetic force, increasing their speed and kinetic energy in the jet.

[0017] In the preferred implementation, further, in step 5, physical etching is achieved by the impact and stripping effect of high-energy ions on the material surface; chemical reaction is achieved by the chemical reaction between reactive gas or free radicals in the plasma and the material, which converts part of the surface layer of the material into volatile substances or oxidation products.

[0018] In the preferred implementation, further, in step 5, physical etching is suitable for removing hard optical materials, and chemical reaction is suitable for fine control and cleaning of the material surface.

[0019] In the preferred implementation, further, in step 1, the working gas includes but is not limited to one or more of argon, carbon tetrafluoride, and sulfur hexafluoride.

[0020] In another aspect, the present application also provides an ultrasonic coupling electromagnetic controlled plasma hard and brittle component processing device, which is used to implement the hard and brittle component ultrasonic assisted magnetron plasma polishing method according to any one of the above aspects; the device comprises a plasma guide pipe, a plasma generating component, an ultrasonic focusing component and a conical rotating magnetic field generating component, wherein:

[0021] The plasma guide pipe has an inner cavity, a mixed gas inlet for compressed oxygen and working gas is arranged at the top of the inner cavity, and a gas outlet is arranged at the bottom of the inner cavity, below which the optical component material to be processed is placed, and the gas outlet is used to act the high-energy focused jet beam on the surface of the optical component material to be processed.

[0022] The plasma generating component comprises a high-voltage tungsten needle electrode arranged at the top of the inner cavity of the plasma guide pipe; the high-voltage tungsten needle electrode is used to discharge and ionize the mixed gas to form a plasma jet.

[0023] The ultrasonic focusing component comprises a ring-shaped ultrasonic array located below the high-voltage tungsten needle electrode, the ring-shaped ultrasonic array is composed of a plurality of ultrasonic emission units, each of which is uniformly distributed and embedded in the inner cavity wall of the plasma guide pipe; the ring-shaped ultrasonic array is used to generate an ultrasonic wave field and pre-focus the plasma jet.

[0024] The conical rotating magnetic field generating component comprises a conical coil and a conical coil core, the conical coil core is arranged in the inner cavity of the plasma guide pipe and located below the ring-shaped ultrasonic array, the conical opening of the conical coil core faces downward and communicates with the gas outlet of the plasma guide pipe, and a plurality of conical coils are uniformly arranged along the surface of the conical coil core; the conical coil is used to generate a conical rotating magnetic field when the focused plasma jet passes through, so that the plasma jet performs spiral contraction motion along the magnetic induction line track, obtains kinetic energy gain, and thus forms a high-energy focused jet beam.

[0025] In a preferred implementation, further, the plasma generating component further comprises a gas pressure reducing mixer and a variable frequency matching controller, the electrode tail of the high-voltage tungsten needle electrode is connected to the variable frequency matching controller, and the gas pressure reducing mixer is connected to the gas inlet of the plasma guide pipe through a pipeline.

[0026] The conical rotating magnetic field generating component further comprises an insulating sheet, which is installed outside each conical coil and covers the entire area of the conical coil.

[0027] In the preferred implementation, further, the plasma conduit is composed of a straight cylinder structure at the upper part and a tapered cylinder structure at the lower part, which are connected to each other and communicate with each other, and together form the inner cavity of the plasma conduit; the straight cylinder structure is located at the upper part of the plasma conduit, and the top thereof is provided with an air inlet; the tapered cylinder structure at the lower part is tapered and shrunk, with the taper angle downward, and the bottom end thereof is provided with an air outlet; the outer surface of the tapered coil core matches the inner surface of the tapered cylinder structure of the plasma conduit.

[0028] The beneficial effects of the present application are:

[0029] Firstly, the hard and brittle element ultrasonic-assisted magnetic control plasma polishing method of the present application realizes multi-stage focusing and trajectory accurate control of the plasma jet through the synergistic effect of the ultrasonic field and the tapered rotating magnetic field, improves the stability and precision of processing. The pre-focusing effect of the ultrasonic field effectively suppresses the arc divergence, changes the plasma jet from disorder to order, ensures the concentrated use of plasma energy, reduces the problem of processing precision decline caused by energy dispersion of traditional plasma jet, and the secondary focusing and acceleration of the tapered rotating magnetic field further enhances the energy density and directionality of the jet, improves the material removal rate, and effectively reduces the heat affected zone in the processing process, reduces the risk of material damage. Compared with traditional methods such as mechanical processing, chemical etching and laser processing, this method can effectively reduce the heat affected zone in the processing process, reduce material damage, and is particularly suitable for fine processing of high-precision optical elements, meeting the processing needs of complex topography and high surface quality in high-end manufacturing field.

[0030] Secondly, in the preferred implementation, step 3 of the present application forms a highly focused acoustic field structure in the plasma jet area through high-frequency mechanical vibration of the annular ultrasonic transducer array, realizing accurate regulation of the plasma. The compression wave and the sparse wave of the ultrasonic wave alternately act, effectively suppressing the divergence of the plasma jet, improving its stability and energy concentration. At the same time, by adjusting the driving frequency and power of the ultrasonic transducer, the intensity and distribution of the ultrasonic field can be dynamically optimized, so as to accurately control the focusing degree and energy density of the plasma jet, improve the uniformity and efficiency of processing, reduce material damage, and meet the needs of high-precision hard and brittle element processing.

[0031] Thirdly, in the preferred implementation, the method of the present application realizes secondary focusing and acceleration of the pre-focused plasma jet through the tapered rotating magnetic field, effectively reduces the divergence of the jet, and improves its density and energy concentration. Under the action of the rotating magnetic field, the charged particles in the plasma move along a spiral trajectory, so that their speed and kinetic energy in the jet are further enhanced, thereby improving the material etching efficiency and processing precision.

[0032] Fourth, in the preferred implementation, the method of the present application combines physical etching and chemical reaction processing mechanisms, enabling the plasma jet to adapt to different types of optical material processing needs. The impact and stripping effect of high-energy ions can efficiently remove hard optical materials, improving material removal rate, while reactive gases or radicals in the plasma can chemically react with the material, achieving fine control and cleaning of the material surface layer, and improving surface quality.

[0033] Fifth, the ultrasonic coupling electromagnetic control plasma hard brittle element processing device provided by the present application realizes precise control and efficient focusing of high-energy plasma jet through multi-stage regulation of plasma generation, ultrasonic focusing and conical rotating magnetic field. The plasma guide tube ensures stable supply of mixed gas and jet guidance, and the high-pressure tungsten needle electrode realizes efficient ionization and forms a stable plasma jet. The annular ultrasonic array regulates the plasma motion trajectory through high-frequency acoustic field, suppresses jet divergence, and improves the energy concentration of the jet. The conical rotating magnetic field further spirally contracts and accelerates the jet, significantly increasing its energy density and enhancing the etching and fine processing capability of the optical element material.

[0034] Sixth, in the preferred implementation, the device of the present application realizes stable adjustment of mixed gas supply and precise control of plasma discharge parameters by adding a gas pressure-reducing mixer and a variable frequency matching controller in the plasma generation component, ensuring the stability and uniformity of the plasma jet. At the same time, an insulating sheet is introduced in the conical rotating magnetic field generation component, effectively isolating the conical coil and preventing electromagnetic interference, improving the control precision of the magnetic field and the safety of the device operation.

[0035] Seventh, in the preferred implementation, the device of the present application adopts a plasma guide tube design combining an upper straight cylinder structure and a lower conical cylinder structure, enabling the plasma jet to be stabilized in the straight cylinder structure first and then limited to contract in the conical cylinder structure when passing through the guide tube, improving the directionality and energy density of the jet. The contraction effect of the conical cylinder structure enhances the focusing effect of the airflow and plasma, further reducing jet divergence and improving processing precision. At the same time, the outer surface of the conical coil core matches the inner surface of the conical cylinder structure, enabling the conical rotating magnetic field to act more efficiently on the plasma jet, achieving better spiral contraction and acceleration, improving plasma energy transfer efficiency, and ultimately improving the processing quality and efficiency of optical elements. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a flowchart of the hard brittle element ultrasonic assisted magnetic plasma polishing method of the embodiment of the present application;

[0037] Figure 2 is an effect diagram of the method of the prior art that does not use ultrasonic focusing and conical rotating magnetic field combination to process optical element materials;

[0038] Figure 3 The effect diagram of the optical element material processed by the brittle element ultrasonic-assisted magnetron plasma polishing method of the embodiment of the present application;

[0039] Figure 4 The structural schematic diagram of the ultrasonic coupling electromagnetic control plasma brittle element processing device of the embodiment of the present application;

[0040] Figure 5 The structural schematic diagram of the conical rotating magnetic field of the ultrasonic coupling electromagnetic control plasma brittle element processing device of the embodiment of the present application;

[0041] Figure 6 The structural schematic diagram of the ultrasonic emission unit of the ultrasonic coupling electromagnetic control plasma brittle element processing device of the embodiment of the present application;

[0042] Figure 7 The high-voltage arc change diagram under the action of the ultrasonic field of the embodiment of the present application;

[0043] Figure 8 The principle diagram of the plasma motion trajectory change under the action of the conical rotating magnetic field of the embodiment of the present application.

[0044] Wherein, 1-ring ultrasonic array controller, 2-conical rotating magnetic field generating device, 3-insulated high-voltage tungsten needle electrode base, 4-high-voltage tungsten needle electrode fastening screw, 5-high-voltage tungsten needle electrode, 6-conical coil, 7-optical element material, 8-mixed gas inlet, 9-ring ultrasonic array, 10-plasma conduit nozzle, 11-workbench, 12-gas pressure reducing mixer, 13-frequency conversion matching controller, 14-manual pressure reducing valve, 15-compressed oxygen, 16-working gas, 17-insulating sheet, 18-conical coil core, 19-ultrasonic emission unit, 20-high-voltage arc, 21-ion motion trajectory, 22-conical rotating magnetic field magnetic induction line distribution. DETAILED DESCRIPTION

[0045] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in combination with the drawings and embodiments.

[0046] The up, down, left, right, front and back orientation terms in the present application file are established based on the positional relationship shown in the drawings. If the drawings are different, the corresponding positional relationship may also change accordingly, so it cannot be understood as a limitation on the protection scope.

[0047] In the present application, the terms "mounting", "connecting", "connecting", "connecting", "fixing" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected, or it can be mechanically connected, or it can be electrically connected or can communicate with each other, or it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components, or it can be the interaction relationship of two components. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0048] The present application aims to provide a hard and brittle element ultrasonic assisted magnetic plasma polishing method and device, which combines the focusing and acceleration effects of ultrasonic field and conical magnetic field, and can realize non-damage ultraprecision machining of hard and brittle materials (such as silicon carbide, calcium fluoride, fused quartz, etc.). First, the acoustic force is used to stably focus the high-voltage arc, so that the arc changes from a divergent disordered state to a concentrated ordered state, and the radiation force of the high-frequency sound field greatly stabilizes the arc trajectory. Subsequently, the rotating magnetic field generated by the conical three-phase coil acts on the charged particles through the Lorentz force, constrains the motion trajectory of the particles, and accelerates the speed of the spiral plasma, thereby reducing the width of the plasma beam. The plasma generated by ionizing the working gas through high-frequency voltage physically and chemically reacts with the optical element to remove the material at the atomic scale. Through the synergistic effect of ultrasonic and magnetic field, the focused and accelerated plasma is significantly improved in speed, density, kinetic energy and beam width compared with single plasma jet, thereby improving the machining efficiency and precision.

[0049] Referring to the description attached Figure 1 The present application discloses a hard and brittle element ultrasonic assisted magnetic plasma polishing method, which first stably focuses the high-voltage arc through the acoustic force, so that the arc changes from a divergent disordered state to a concentrated ordered state, and the radiation force of the high-frequency sound field can greatly stabilize the arc trajectory. Then, the rotating magnetic field generated by the conical three-phase coil generates the Lorentz force on the charged particles, constrains the motion trajectory of the particles, and accelerates the motion speed of the spiral plasma, thereby reducing the width of the plasma beam. The plasma generated by ionizing the working gas through high-frequency voltage physically and chemically reacts with the optical element to remove the material at the atomic scale. The specific steps are as follows:

[0050] Step 1: Mix the working gas with compressed oxygen according to a predetermined ratio, and adjust the pressure through a gas pressure reducing mixer to make the mixed gas flow stably into the inner cavity of the plasma guide tube.

[0051] The purpose of step 1 is to optimize the generation conditions of the plasma jet, ensure the stability, uniformity and controllability of the plasma, improve the machining precision of subsequent ultrasonic focusing and magnetic field acceleration, and adapt to the machining requirements of different optical element materials.

[0052] Specifically, according to the material properties of the optical element to be processed, select the appropriate working gas (such as argon (Ar), carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), etc.), and mix with compressed oxygen (O2) at a predetermined ratio. For example: quartz glass (SiO2) uses argon (Ar) + oxygen (O2) as the working gas, and the recommended ratio is Ar:O2=80:20, to enhance discharge stability, improve removal rate, and reduce surface roughness. Sapphire (Al2O3) uses argon (Ar) + carbon tetrafluoride (CF4) + oxygen (O2) as the working gas, and the recommended ratio is Ar:CF4:O2=60:30:10, which improves plasma stability through argon, enhances chemical etching through CF4, and improves surface uniformity through O2. Calcium fluoride (CaF2) uses carbon tetrafluoride (CF4) + oxygen (O2) as the working gas, and the recommended ratio is CF4:O2=70:30, to enhance chemical reactivity, improve processing efficiency, and reduce subsurface damage. Silicon-based optical materials (Si, Si3N4, SiC) use sulfur hexafluoride (SF6) + argon (Ar) + oxygen (O2) as the working gas, and the recommended ratio is SF6:Ar:O2=50:30:20, which improves etching selectivity through SF6, improves plasma density through argon, and optimizes surface chemical stability through O2, suitable for high-precision microstructure processing.

[0053] Compressed oxygen and working gas are input from independent gas cylinders, and independent gas pressure reducing valves are used to adjust the inlet pressure of compressed oxygen and working gas respectively. The pressure of working gas (Ar, CF4, SF6) is set to 0.1-0.5 MPa, and the pressure of compressed oxygen (O2) is set to 0.05-0.3 MPa. After the gas enters the mixing chamber, the residence time is controlled to 0.2-1.0 seconds to ensure complete mixing before flowing into the plasma conduit.

[0054] Step 2: Ionize the mixed gas under the action of high-frequency high-voltage through a high-pressure tungsten needle electrode to generate a plasma jet, and adjust the discharge parameters through a frequency matching controller.

[0055] The purpose of step 2 is to optimize the stability, energy density, and uniformity of the plasma jet, providing a high-quality plasma source for subsequent ultrasonic focusing and magnetic field acceleration. Precise control of discharge parameters through a frequency matching controller ensures that the plasma has appropriate electron density, temperature, and ion energy to meet the processing needs of different optical elements. Reducing arc instability and overheating problems prevents material surface melting or micro-cracks, improving processing quality.

[0056] Specifically, a high-voltage tungsten needle electrode is used, with its tip pointing towards the inner cavity of the plasma conduit, ensuring stable generation of the plasma jet. The electrode is installed on an insulating high-voltage tungsten needle electrode base to avoid high-voltage leakage and is fixed by a high-voltage tungsten needle electrode tightening screw to ensure long-term stable operation. The tungsten needle electrode can be made of W-2%Th (2% thorium tungsten alloy), which has high heat resistance and low electron work function, improving discharge stability.

[0057] The frequency matching controller selects the appropriate discharge mode according to the processing requirements, including radio frequency (RF) discharge, microwave discharge, and pulsed direct current discharge. RF discharge is suitable for ultra-precision low-damage processing with high plasma uniformity. Microwave discharge is suitable for high-density plasma applications to improve etching rate. Pulsed direct current discharge is suitable for controlling the heat affected zone to improve material removal rate.

[0058] The discharge parameters of the frequency matching controller include voltage, frequency, and power. The voltage adjustment range is 10-30 kV. The frequency adjustment range is 13.56 MHz for RF discharge, 2.45 GHz for microwave discharge, and 1-10 kHz for pulsed direct current discharge. The power control range is low power (10-50 W) for ultra-precision surface modification, medium power (50-200 W) for uniform etching, and high power (200-500 W) for fast material removal.

[0059] The plasma excitation process includes: the excitation of plasma begins with the high-voltage tungsten needle electrode, which is connected to a high-frequency high-voltage power supply (10-30 kV) to form a strong electric field in the gas flow area. This electric field accelerates free electrons, allowing them to gain enough energy and collide with working gas molecules, causing electron collision ionization and forming plasma (including electrons, ions, and neutral particles). To ensure the uniformity and stability of the plasma, the discharge electric field strength is optimized to ≥10 5 V / m, effectively reducing local arc jitter, suppressing arc drift, and improving the consistency of the plasma jet.

[0060] Step 3: The plasma jet passes through the annular ultrasonic array, which forms a high-intensity ultrasonic field under the control of the annular ultrasonic array controller. The ultrasonic field suppresses the disordered state of the arc and transforms it into a concentrated ordered state, and regulates the motion trajectory of the plasma, pre-focusing the plasma jet.

[0061] The purpose of step 3 is to reduce arc drift and randomness by the action of the ultrasonic field, make the jet more directional, and enhance the uniformity of the flow field. Suppress the divergence characteristics of the plasma jet, reduce the angular spread of the plasma jet, make its energy more concentrated, and improve the processing precision. Through the focusing effect of ultrasonic waves, the plasma particles arrange more orderly under the action of sound waves, reduce random motion, and improve jet density. Provide more uniform and high-density plasma input for magnetic field control and acceleration, and improve overall processing performance and energy utilization.

[0062] Specifically, a ring-shaped ultrasonic transducer array is used to ensure uniform distribution of ultrasonic energy and form an axisymmetric ultrasonic field in the plasma jet area. The ultrasonic transducer is embedded in the inner wall of the plasma guide pipe to ensure that the jet is stably acoustically modulated when passing through the ultrasonic field.

[0063] The formation process of the ultrasonic field includes: the ultrasonic transducer array is arranged in a ring shape, when the ultrasonic transducer receives the high-frequency electric signal emitted by the driving power supply, it quickly converts the electric energy into mechanical vibration to generate high-frequency ultrasonic waves. Ultrasonic waves propagate in air medium, forming alternating compression and rarefaction waves, and generating a highly focused acoustic field structure in the plasma jet area.

[0064] The way the ultrasonic field acts on the plasma jet includes acoustic field modulation of arc shape, acoustic force acting on plasma particles, and ultrasonic wave guiding jet trajectory. The acoustic field modulation of arc shape is that the periodic pressure wave of the ultrasonic field affects the shape of the arc, making the high-voltage discharge change from disordered divergence state to concentrated ordered state. The acoustic force acting on the plasma particles is that the vibration energy of the ultrasonic wave acts on the electrons, ions and neutral particles in the plasma jet, under the pressure gradient of the sound wave, the particle motion direction is more orderly, and the uniformity and stability of the plasma jet are improved. The ultrasonic wave guides the jet trajectory, which is that the ultrasonic pressure makes the jet particles move in the set direction, reduces the irregular diffusion of the jet, and improves the energy density of the jet.

[0065] In addition, by accurately adjusting the driving frequency and power of the ultrasonic transducer in step 2, the intensity and distribution of the ultrasonic field can be dynamically controlled, and the focusing degree and energy density of the plasma jet can be optimized, ensuring the efficiency and stability of the subsequent processing process.

[0066] Step 4: Direct the plasma jet pre-focused by the ultrasonic field to the conical rotating magnetic field area, and use the conical rotating magnetic field generating device to generate a conical rotating magnetic field under the action of the conical coil core to perform secondary focusing and acceleration on the pre-focused plasma jet.

[0067] The purpose of Step 4 is to further accelerate the particles in the plasma jet through the action of the conical rotating magnetic field, enhance its kinetic energy, and provide higher processing efficiency and accuracy. The focusing effect of the plasma jet is enhanced, based on the pre-focusing in the ultrasonic field, through the focusing action of the magnetic field, the directionality and density of the jet are further improved, and the processing accuracy of the target area is improved. Through dynamic regulation of the magnetic field, the energy distribution of the plasma jet is accurately controlled, avoiding excessive concentration or loss of energy, and ensuring uniform and stable processing effect. By using the special design of the conical rotating magnetic field, the stability of the jet in the processing process is improved, and the influence of external interference on the jet trajectory is reduced.

[0068] Specifically, in the conical rotating magnetic field generating device, a conical coil core is used, which is precisely designed in shape and material to generate a uniform and high-strength rotating magnetic field. The magnetic field interacts with the plasma jet, causing the particles in the jet to gain additional acceleration kinetic energy. The rotation direction of the magnetic field matches the flow direction of the jet, causing the particles in the plasma to accelerate along the magnetic field lines, forming a tighter beam. By controlling the current intensity and frequency, the magnetic field strength can be adjusted to optimize the acceleration and focusing effect of the magnetic field on the plasma jet.

[0069] The secondary focusing and acceleration process of the conical rotating magnetic field includes: the magnetic force generated by the rotating magnetic field in its action area further focuses the already pre-focused plasma jet, reducing the divergence of the jet and improving the density and energy concentration of the jet. The rotating magnetic field causes the charged particles in the plasma to move in a spiral trajectory under the action of the magnetic force, increasing their speed and kinetic energy in the jet.

[0070] In Step 4, by adjusting the conical rotating magnetic field generating device, the strength and characteristics of the conical rotating magnetic field are accurately controlled, enabling secondary focusing and acceleration of the plasma jet, thereby improving the speed and accuracy of the jet. The main ways to adjust the conical rotating magnetic field include: adjustment of magnetic field strength, adjustment of frequency, local magnetic field adjustment, optimization of magnetic field direction and form.

[0071] The adjustment of the magnetic field strength is achieved by adjusting the current and voltage to change the strength of the conical rotating magnetic field. A strong magnetic field can accelerate the charged particles in the plasma jet, thereby increasing the speed and energy density of the jet.

[0072] The frequency adjustment is achieved by controlling the frequency of the magnetic field rotation, which can adjust the acceleration effect of the jet to adapt to different processing needs. For example, by adjusting the frequency, the efficiency of the acceleration stage can be optimized, and the acceleration speed of the jet can be controlled.

[0073] Local magnetic field adjustment is based on the needs of processing, and different regions of the magnetic field strength can be designed in the magnetic field generating device to achieve accurate regulation of the jet.

[0074] The optimization of the magnetic field direction and shape directly affects the focusing effect and motion trajectory of the plasma jet. By adjusting the angle or position of the magnetic field, the motion path of the jet can be optimized to ensure its concentration and stability during processing, and to achieve the required processing precision.

[0075] Through these adjustment means, the plasma jet can be ensured to act on the surface of the optical element to be processed at high speed, concentration and precision when passing through the area of the conical rotating magnetic field, thereby achieving super-precision and non-destructive processing effect.

[0076] Step 5: The plasma jet beam after secondary focusing and acceleration by the magnetic field is applied to the surface of the optical element to be processed, and physical etching or chemical reaction occurs between the high-energy active particles in the plasma and the surface of the optical element material.

[0077] The purpose of Step 5 is to achieve high-precision and non-destructive surface processing by applying the plasma jet beam after secondary focusing and acceleration by the magnetic field to the surface of the optical element to be processed. This step causes physical etching or chemical reaction between the high-energy active particles in the plasma and the surface of the optical element, thereby modifying or polishing the surface of the optical element, improving its surface quality and processing precision, and meeting the manufacturing requirements of super-precision optical elements.

[0078] Specifically, when the plasma jet beam after secondary focusing and acceleration is applied to the surface of the optical element to be processed, the high-energy electrons, ions, radicals and other active particles in the plasma interact with the surface of the optical element material. These active particles can remove surface materials through physical etching or chemical reaction mechanisms, or rearrange the surface atoms and molecules to improve the surface topography. Physical etching mainly removes hard optical materials through the impact and stripping action of high-energy ions. Chemical reaction is suitable for fine control and cleaning of the material surface by chemical reaction between reactive gas or radicals in the plasma and the material, which converts part of the surface layer of the material into volatile substances or oxidation products.

[0079] Further, by adjusting the density, energy and action time of the plasma jet beam, the action intensity and depth on the surface of the optical element can be controlled. By controlling these parameters, the surface quality, roughness and processing precision can be precisely controlled. By adjusting the flow rate and intensity of the plasma jet, the balance between surface etching rate and processing precision is ensured. Too fast processing may cause excessive etching, while too slow processing may affect production efficiency. By fine-tuning the focusing and energy distribution of the plasma jet, the uniformity and smoothness of the optical element surface after processing are ensured, and uneven surface damage or small cracks are avoided.

[0080] In addition to physical etching, plasma can also be used to modify the surface, for example, by chemical reaction to form a thin film or change the composition of surface elements, to enhance the wear resistance, corrosion resistance or optical properties of the material. By adjusting the plasma atmosphere and activation process, directional modification of the optical element surface can also be achieved, such as adding an anti-reflection coating or modifying the optical properties.

[0081] Example 1

[0082] Most existing plasma processing methods rely on a single physical force (such as arc, laser, etc.) to remove or surface treat the material. This embodiment demonstrates the advantages of the present invention by comparing the plasma processing methods of the present invention and the prior art.

[0083]

[0084]

[0085]

[0086] Example 2

[0087] Referring to the drawings accompanying the specification Figures 2-3 , Figure 2 Figure 1 is an effect diagram of processing optical element material using the method of the prior art without ultrasonic focusing and conical rotating magnetic field combination, Figure 3 Figure 2 is an effect diagram of processing optical element material using the method of the present invention. From Figure 2 It can be seen that the frequency of active ions reacting with the material is low, and the distribution of ions is relatively disordered, and many ions fail to effectively react with the surface atoms of the material. Due to the uneven distribution of ions, the surface flatness of the processed material is low and the surface roughness is high. From Figure 3 It can be seen that under the action of ultrasonic focusing and conical rotating magnetic field, ultrasonic focusing provides local high energy density, and active ions in a specific area obtain higher energy, thereby increasing the survival time of the ions, and the Lorentz force generated by the conical rotating magnetic field further guides the active ions to form stable rotational motion, improving the uniformity of material removal and processing efficiency. Ions are constrained by the Lorentz force generated by the conical rotating magnetic field, concentrated in a specific area and the motion path becomes more orderly, mainly concentrated along the direction of magnetic field contraction, forming a local high electron density processing reaction zone. Due to the high concentration of ions in the processing area, the material removal is more uniform and controllable, avoiding irregular etching of random removal.

[0088] Referring to the drawings accompanying the specification Figures 4-8 , the present invention also discloses an ultrasonic coupling electromagnetic controlled plasma hard and brittle element processing device, which comprises a plasma conduit, a plasma generating component, an ultrasonic focusing component, a conical rotating magnetic field generating component and an optical element material 7.

[0089] The plasma conduit is composed of an upper straight cylinder structure and a lower tapered cylinder structure, which are connected to each other and internally communicate, together forming the inner cavity of the plasma conduit. The inner cavity serves as the operating space for plasma generation and ultrasonic wave regulation of plasma self-organization, to ensure stable delivery and continuous flow of gas flow or plasma.

[0090] The straight cylinder structure is located at the upper part of the plasma conduit, and the top thereof is provided with a gas inlet for introducing the mixed gas of compressed oxygen 15 and working gas 16 into the inner cavity for reaction. The lower tapered cylinder structure is tapered and shrunk, with a downward taper angle, and the bottom end thereof is provided with a gas outlet for outputting the formed plasma. After stable flow and ultrasonic wave regulation in the inner cavity, the plasma is applied to the surface of the optical element material 7 below through the gas outlet. In this process, the plasma and the atoms on the surface of the material undergo physical and chemical reactions, realizing high-precision and non-damaging surface modification and processing, and ensuring high-quality processing effect of the material surface.

[0091] In addition, the structural design of the plasma conduit helps to optimize the stability and uniformity of the plasma, improve the controllability of the processing process, and is suitable for different types of optical material surface treatment needs.

[0092] In the implementation manner of the present application, the tapered barrel structure of the plasma conduit is a nozzle 10 as shown in the drawings. Figure 4 The nozzle 10 optimizes the gas flow distribution through precise design of the structure, to improve the stability and uniformity of the plasma jet. The nozzle 10 can adopt a specific inner wall curvature or multi-stage contraction and expansion structure to regulate the gas flow velocity and pressure distribution, to ensure the effect of the plasma on the target area. At the same time, the material of the nozzle 10 can be selected from high-temperature-resistant and plasma-erosion-resistant materials such as ceramics or high-temperature alloys, to improve the durability and reduce the interference with the jet characteristics.

[0093] The plasma generation component includes a high-voltage tungsten needle electrode 5, a gas pressure-reducing mixer 12 and a variable frequency matching controller 13. The high-voltage tungsten needle electrode 5 is fixedly installed on the inner side center of the top of the straight cylinder structure of the plasma conduit, with the tip thereof facing the inner cavity of the plasma conduit, to ensure stable discharge. The tail of the electrode is connected to the variable frequency matching controller 13 through an insulating high-voltage tungsten electrode base, and the variable frequency matching controller 13 can accurately adjust the discharge parameters such as voltage, frequency and power, to optimize the generation process of the plasma and improve the discharge stability and plasma activity.

[0094] The gas pressure-reducing mixer 12 is responsible for the proportional mixing and pressure regulation of the working gas to optimize the plasma environment. The gas pressure-reducing mixer 12 is connected to the gas inlet of the plasma guide through a pipeline, mixes the compressed oxygen 15 and the working gas 16 according to the preset ratio, and reduces the pressure of the mixed gas to make it flow stably into the inner cavity of the plasma guide within the set pressure range. Suitable gas flow rate and pressure not only improve the stability of the plasma, but also effectively control the physical parameters of the discharge area to adapt to different application requirements.

[0095] To enhance the structural stability and discharge reliability, the plasma generating component further includes an insulated high-voltage tungsten needle electrode base 3 and a high-voltage tungsten needle electrode fastening screw 4. The insulated high-voltage tungsten needle electrode base 3 is installed at the top of the straight cylinder structure of the plasma guide to provide electrical insulation and mechanical fixation. The gas inlet of the mixed gas of the compressed oxygen 15 and the working gas 16 is opened on the insulated high-voltage tungsten needle electrode base 3, as shown in the mixed gas inlet 8 in the description accompanying drawings. The high-voltage tungsten needle electrode 5 is locked in the center of the insulated high-voltage tungsten needle electrode base 3 through the high-voltage tungsten needle electrode fastening screw 4, ensuring its accurate positioning and long-term work without displacement or loosening. Figure 4

[0096] In the implementation of the present application, the working gas 16 can be selected according to the material properties of different optical elements, including but not limited to argon (Ar), carbon tetrafluoride (CF4) or sulfur hexafluoride (SF6), etc. These gases can be used alone or mixed in a certain proportion to meet the plasma processing needs of different materials. For example, argon can be used to improve discharge stability, while carbon tetrafluoride or sulfur hexafluoride is suitable for enhancing chemical reactivity to optimize the effect of plasma on the target material.

[0097] The plasma generating component also includes a manual pressure-reducing valve 14. The gas cylinders of the compressed oxygen 15 and the working gas 16 are connected to the gas pressure-reducing mixer 12 through independent pipelines, and a manual pressure-reducing valve 14 is provided on each pipeline to independently adjust and control the gas pressure, ensuring stable and controllable gas supply at the input end of the mixer 12.

[0098] The ultrasonic focusing component includes a ring-shaped ultrasonic array controller 1 and a ring-shaped ultrasonic array 9 located below the high-voltage tungsten needle electrode 5. The ring-shaped ultrasonic array 9 is composed of a plurality of ultrasonic emission units 19 which are uniformly distributed and embedded in the straight cylinder structure of the plasma guide. The ring-shaped ultrasonic array controller 1 realizes synchronous driving and phase control of the ultrasonic array 9 through precise signal regulation to form a specific ultrasonic focusing mode.

[0099] ​Specifically, the plurality of ultrasonic transmitting units 19 in the annular ultrasonic array 9 are uniformly arranged along the axial and radial directions of the plasma conduit at a preset interval, and can form a single-layer or multi-layer annular structure to optimize the distribution of ultrasonic energy in the plasma region. Each ultrasonic transmitting unit 19 is connected in series or parallel with adjacent units through flexible wires or integrated circuit flat cables, ensuring the stability and consistency of the entire array signal transmission. The series connection mode is suitable for low-voltage and high-current driving, which can reduce line loss and improve energy utilization. The parallel connection mode is suitable for high-voltage and low-current driving, which can improve the system redundancy, so that other units can still work normally even if part of the units fail. In actual design, the series and parallel connection modes can be combined to optimize the circuit characteristics and ensure the efficiency of ultrasonic wave coherent synthesis. The ultrasonic transmitting units 19 are made of piezoelectric ceramics or other ultrasonic transducer materials, and their resonant frequencies are matched with the working environment to ensure efficient propagation of ultrasonic waves and action on the plasma region.

[0100] The annular ultrasonic array controller 1 is connected to each ultrasonic transmitting unit 19 through independent signal driving lines, and provides high-frequency alternating current signals to drive the ultrasonic transducer to vibrate and generate ultrasonic waves. The annular ultrasonic array controller 1 is used to accurately regulate the working state of the annular ultrasonic array 9, and realizes focusing and energy optimization of ultrasonic waves through phase control, amplitude adjustment, frequency matching and mode switching. Phase control is used to adjust the phase of the excitation signal of each ultrasonic transmitting unit 19 to form a specific ultrasonic interference effect, and to focus ultrasonic energy in the target area through phased array technology, thereby enhancing the energy density of the plasma. The amplitude adjustment dynamically adjusts the driving voltage or power of each unit according to the real-time monitored data to optimize the action effect of ultrasonic waves. Frequency matching adjusts the driving signal frequency according to the plasma working environment and material characteristics, so that the ultrasonic wave is matched with the natural vibration frequency of the plasma, improves the coupling efficiency of ultrasonic energy, and enhances the stability of the plasma. In addition, the controller can switch modes to set different ultrasonic wave working modes, such as diffusion mode, focusing mode or sweep mode, to adapt to different working condition requirements. For example, the diffusion mode is used in the initial stage to improve the uniformity of the plasma, and the focusing mode is switched in the processing stage to improve the local energy density, thereby optimizing the action effect of the plasma.

[0101] The conical rotating magnetic field generating component is embedded in the nozzle 10, and its conical structure makes the plasma jet spiral accelerate and shrink from the large end to the small end of the magnetic field. The conical rotating magnetic field generating component includes a conical rotating magnetic field generating device 2, a conical coil 6, an insulating sheet 17 and a conical coil core 18.

[0102] The conical coil core 18 is made of high permeability material, and its outer surface precisely matches the inner surface of the plasma conduit conical cylinder structure, ensuring the uniformity of the magnetic field distribution. Its role is to focus and guide the magnetic field generated by the coil, improve the magnetic induction intensity, and enhance the stability and control accuracy of the rotating magnetic field. Multiple conical coils 6 are uniformly arranged along the surface of the conical coil core 18 and arranged at certain intervals. The conical coil 6 is a 12-pole three-phase coil. After these coils are energized, a rotating magnetic field is generated on the surface of the core. Through corresponding driving control, the direction, intensity, and rotation speed of the magnetic field can be adjusted to adapt to different plasma working conditions.

[0103] The insulating sheet 17 is installed on the outside of each conical coil 6, covering the entire area. The insulating sheet is made of high-heat-resistant and voltage-resistant material, which provides electrical isolation to prevent short circuits between coils and optimizes heat management to reduce heat accumulation in the coils due to long-term operation. The conical rotating magnetic field generating device 2, as the core driving control unit, is responsible for providing alternating current to the conical coil 6 to form an adjustable rotating magnetic field. The conical rotating magnetic field generating device 2 is used to accurately control the current parameters of the conical coil 6 to form a stable rotating magnetic field, improving the confinement ability and uniformity of the plasma. By phase control, the phase difference of the current of each coil is adjusted to make the magnetic field rotate in the set direction and optimize the spatial distribution of the magnetic field to ensure uniform magnetic field action. Through frequency control, the frequency of the alternating current is dynamically adjusted according to the working parameters of the plasma, so that the magnetic field matches the characteristics of the plasma, thereby enhancing the stable confinement effect of the magnetic field on the plasma. Through magnetic field intensity adjustment, the input current amplitude of the coil is adjusted according to the real-time working condition to accurately control the magnetic field intensity, further optimize the stability and uniformity of the plasma, and improve the working efficiency of the overall system.

[0104] In the implementation of the present application, the conical coil 6 and the conical coil core 18 adopt a close-fitting structure to ensure efficient magnetic field conduction and reduce magnetic flux loss. The insulating sheet 17 is installed between the conical coil 6 and the external environment to ensure electrical isolation between the coil units and prevent short circuits or damage caused by high-voltage breakdown. Each conical coil 6 is connected to the conical rotating magnetic field generating device 2 through independent wires and is uniformly powered and controlled by the device to realize the rotation control of the magnetic field. The driving current of the conical coil 6 adopts a multi-phase alternating method (such as three-phase or multi-phase alternating current) to form a stable rotating magnetic field and improve the magnetic confinement ability of the plasma. In different application scenarios, the arrangement interval of the conical coil 6 can be adjusted according to the magnetic field intensity requirement to adapt to different plasma working conditions.

[0105] To realize the reliable connection of the annular ultrasonic array 9 and the annular ultrasonic array controller 1, and the conical coil 6 and the conical rotating magnetic field generating device 2, a wire through hole needs to be opened at the corresponding position of the plasma conduit to ensure the stability of signal and power transmission, while avoiding affecting the working environment of the plasma. To ensure the air tightness and electrical insulation of the plasma conduit, the wire through hole needs to be sealed to prevent the external environment from affecting the stability of the plasma. Silicon rubber, high-temperature epoxy resin or ceramic sealing material can be used to fill the through hole to prevent high-temperature leakage or electrical breakdown. Or the through hole can use O-ring + high-temperature ceramic sleeve double-layer protection to improve the pressure resistance and air tightness. Or increase the surface of the wire with high-temperature polyimide coating to enhance the electrical insulation performance.

[0106] The ultrasonic coupling electromagnetic controlled plasma hard brittle component processing device of the present application utilizes the synergistic effect of ultrasonic field and magnetic field to realize high-density and high-energy plasma jet beam to meet the requirements of high efficiency, low damage and ultra-precision machining. The working principle is as follows:

[0107] First, the compressed oxygen 15 and the working gas 16 are mixed by the gas pressure reducing mixer 12 and input into the plasma conduit through the mixed gas inlet 8. The high-voltage tungsten needle electrode 5 generates a high-voltage arc under the precise control of the frequency converter controller 13, but the initial state of the arc is disordered and easily disturbed by the external environment. Then the high-voltage arc passes through the annular array 9. Under the action of the ultrasonic sound field, the ultrasonic pressure dynamically modulates the arc, making the arc shrink and stable in direction, forming a plasma jet 20 in the inner cavity of the plasma conduit. Then the stabilized plasma jet enters the conical rotating magnetic field 22, which is generated by the 12-pole conical three-phase coil 6 and precisely controlled by the conical rotating magnetic field generating device 2. The magnetic field exerts a Lorentz force on the charged particles in the plasma, making them spiral and shrink along the magnetic field line 21 trajectory. The plasma gains kinetic energy during the shrinkage from the large end to the small end of the magnetic field, and the density and energy are improved, forming a high-energy focused jet beam. Finally, the high-energy plasma jet is precisely injected through the nozzle 10 of the plasma conduit to the surface of the optical element material 7 placed on the workbench 11, and reacts with the material atoms to realize non-damage and high-precision surface modification and microstructure processing. To adapt to different optical materials, the device can adjust the type and proportion of the working gas 16, such as argon (Ar) for improving discharge stability, carbon tetrafluoride (CF4) or sulfur hexafluoride (SF6) for enhancing chemical reaction activity, to optimize the processing effect. Through the synergistic effect of ultrasonic field stabilized jet, magnetic field focusing and acceleration, and working gas optimization and control, the device greatly improves the density, directionality and processing precision of the plasma, ensuring the high-quality processing of optical elements and being suitable for ultra-precision manufacturing field.

[0108] The above description is merely that of the embodiments of the present application, and the common knowledge and characteristics in the art are not described in detail. It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all aspects as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and range of the equivalent elements of the claims are intended to be encompassed by the present application. Any reference signs in the claims should not be considered as limiting the involved claims.

Claims

1. A method of ultrasonic assisted magnetron plasma polishing of a hard and brittle element, characterized in that, The method comprises: Step 1: mixing the working gas with compressed oxygen in a preset ratio, and adjusting the pressure through a gas pressure reducing mixer to make the mixed gas flow stably into the inner cavity of the plasma conduit; Step 2: ionizing the mixed gas under the action of high-frequency high voltage through a high-pressure tungsten needle electrode to generate a plasma jet, and adjusting the discharge parameters through a variable frequency matching controller; Step 3: making the plasma jet pass through a ring-shaped ultrasonic array to form a high-intensity ultrasonic field under the driving of a ring-shaped ultrasonic array controller, using the ultrasonic field to suppress the arc divergence disorder state and make it change to a concentrated ordered state, and regulating the motion trajectory of the plasma to pre-focus the plasma jet; Step 4: guiding the plasma jet pre-focused by the ultrasonic field to a conical rotating magnetic field region, using a conical rotating magnetic field generating device to generate a conical rotating magnetic field under the action of a conical coil core to perform secondary focusing and acceleration on the plasma jet after pre-focusing; Step 5: making the plasma jet beam after secondary focusing and acceleration by the magnetic field act on the surface of the optical element to be processed to make the high-energy active particles in the plasma physically etch or chemically react with the surface of the optical element material.

2. The hard and brittle element ultrasonic-assisted magnetron plasma polishing method according to claim 1, characterized in that, In step 3, the formation process of the ultrasonic field includes: the ultrasonic transducer array is arranged in a ring shape, when the ultrasonic transducer receives the high-frequency electric signal generated by the driving power supply, it quickly converts the electric energy into mechanical vibration to generate high-frequency ultrasonic waves, the ultrasonic waves propagate in the air medium to form alternating compression waves and rarefaction waves, and a highly focused acoustic field structure is generated in the plasma jet region.

3. The hard and brittle element ultrasonic-assisted magnetron plasma polishing method according to claim 1, characterized in that, In step 3, by adjusting the driving frequency and power of the ultrasonic transducer, the intensity and distribution of the ultrasonic field can be dynamically controlled, and then the focusing degree and energy density of the plasma jet can be optimized.

4. The hard and brittle element ultrasonic-assisted magnetron plasma polishing method according to claim 1, characterized in that, The secondary focusing and acceleration process of the conical rotating magnetic field includes: the magnetic force generated by the rotating magnetic field in its action region further focuses the plasma jet that has been pre-focused, reduces the divergence degree of the jet, and improves the density and energy concentration of the jet; the charged particles in the plasma move in a spiral trajectory under the action of the magnetic force, increasing their speed and kinetic energy in the jet.

5. The hard and brittle element ultrasonic-assisted magnetron plasma polishing method according to claim 1, characterized in that, In step 5, physical etching is achieved by the impact and stripping effect of high-energy ions on the material surface; chemical reaction is achieved by the chemical reaction between reactive gas or free radicals in the plasma and the material to convert part of the surface layer of the material into volatile substances or oxidation products.

6. The hard and brittle element ultrasonic-assisted magnetron plasma polishing method according to claim 1, characterized in that, In step 5, physical etching is suitable for removing hard optical materials, and chemical reaction is suitable for fine regulation and cleaning of the material surface.

7. The hard and brittle element ultrasonic-assisted magnetron plasma polishing method according to claim 1, characterized in that, In step 1, the working gas includes one or more of argon, carbon tetrafluoride, and sulfur hexafluoride.

8. An ultrasonic coupling electromagnetic controlled plasma hard brittle component machining device, characterized by, The device is used to implement the hard and brittle element ultrasonic-assisted magnetic control plasma polishing method of any one of claims 1-7; the device comprises a plasma conduit (3), a plasma generating component, an ultrasonic focusing component, and a conical rotating magnetic field generating component, wherein: The plasma conduit (3) has an inner cavity, a top of which is provided with a mixed gas inlet for compressed oxygen and working gas, and a bottom of which is provided with a gas outlet, below which is placed an optical element material to be processed, and the gas outlet is used to act on the surface of the optical element material to be processed by a high-energy focused jet beam; The plasma generating component includes a high-voltage tungsten needle electrode (5) arranged at the top of the inner cavity of the plasma conduit (3), which is used for discharging and ionizing the mixed gas to form a plasma jet; The ultrasonic focusing component includes a ring-shaped ultrasonic array (9) below the high-voltage tungsten needle electrode (5), which is composed of a plurality of ultrasonic emission units (19) uniformly distributed and embedded in the inner cavity wall of the plasma conduit (3), and is used to generate an ultrasonic wave field and pre-focus the plasma jet; The tapered rotating magnetic field generating component includes a tapered coil (6) and a tapered coil core (18) arranged in the inner cavity of the plasma conduit (3) below the ring-shaped ultrasonic array (9), with its tapered opening downwardly communicating with the gas outlet of the plasma conduit (3), and a plurality of tapered coils (6) uniformly arranged along the surface of the tapered coil core (18), which is used to generate a tapered rotating magnetic field when the focused plasma jet passes through, so that the plasma jet performs spiral contraction motion along the magnetic induction line trajectory, obtains kinetic energy gain, and forms a high-energy focused jet beam.

9. The ultrasonic coupling electromagnetic controlled plasma hard brittle component machining device according to claim 8, characterized in that The plasma generating component further includes a gas pressure reducing mixer (12) and a variable frequency matching controller (13), the electrode tail of the high-voltage tungsten needle electrode (5) is connected to the variable frequency matching controller (13), and the gas pressure reducing mixer (12) is connected to the gas inlet of the plasma conduit through a pipeline; The tapered rotating magnetic field generating component further includes an insulating sheet (17) installed on the outside of each tapered coil (6) and covering the entire area of the tapered coil (6).

10. The ultrasonic coupling electromagnetic controlled plasma hard brittle component machining device according to claim 8, characterized in that, The plasma conduit is composed of a straight cylinder structure at the top and a tapered cylinder structure at the bottom, which are connected to each other and internally communicate to form the inner cavity of the plasma conduit; the straight cylinder structure is located at the top of the plasma conduit, and the top thereof is provided with a gas inlet; the tapered cylinder structure at the bottom is tapered and contracted, with a downward taper angle, and the bottom end thereof is provided with a gas outlet; the outer surface of the tapered coil core (18) matches the inner surface of the tapered cylinder structure of the plasma conduit.

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