Femtosecond laser processing system and method for emitter of electrospray thruster

Abstract

The invention relates to a femtosecond laser processing system and method for an emitter of an electrospray thruster. The femtosecond laser processing method comprises the steps that the femtosecond laser processing system is built; the precise three-axis displacement table is adjusted through the program control computer, so that the femtosecond pulse laser is focused to the surface of the porous ceramic processing sample through the focusing objective lens; rough machining of an emitter structure is carried out, and linkage scanning of femtosecond pulse laser on the surface of a porous ceramic machining sample is achieved by controlling a galvanometer and a precise three-axis displacement table through a program control computer; the emitter structure is subjected to finish machining, reciprocating scanning of femtosecond pulse laser on the surface of a porous ceramic machining sample is achieved through a galvanometer, a mechanical shutter is controlled in the scanning process, and ablation-free of a conical emitter structure area is achieved; rough machining and finish machining are repeated, and array expansion is carried out on the conical emitter structure; and performing ultrasonic cleaning. The problems that traditional machining precision is low, edge breakage exists on ceramic materials, and pores are blocked are solved, the service life of the electrospray thruster is prolonged, and the specific impulse of the electrospray thruster is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of femtosecond laser application, and relates to a femtosecond laser processing system and method for an emitter of an electrospray thruster. Background Art

[0002] In recent years, with the growth of space exploration and space operation needs, micro-nano satellites have developed rapidly and have become one of the main directions of satellite development. As an electrostatic electric thruster, ion thrusters have the characteristics of high specific impulse, small mass, compact structure and flexible control, and are one of the ideal alternative propulsion systems for micro-nano satellites.

[0003] The emitter is a key core component of the electrospray thruster. It directly or indirectly determines the performance and life of the thruster. The processing of high-performance emitters has always been a bottleneck problem restricting the development of electrospray thrusters. At present, the processing of the emitter mostly adopts the method of precision CNC machine tools, using micro milling cutters to process a triangular rib structure array with a structural size of about 300μm on the surface of porous borosilicate ceramic materials. However, this method is limited by the accuracy of the machine tool, and the processed structure has errors in shape and size, which affects the performance of the thruster. At the same time, for hard and brittle materials such as ceramics, mechanical processing methods are very prone to edge collapse. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to propose a femtosecond laser processing system and method for the emitter of an electrospray thruster, to overcome the low precision of traditional mechanical processing, the problems of edge collapse and pore clogging for hard and brittle materials such as ceramics, and to improve the working life and specific impulse of the electrospray thruster.

[0005] The technical solution of the present invention is: a femtosecond laser processing system for an electrospray thruster emitter, comprising a femtosecond laser, an aperture, a mechanical shutter, an ultrafast reflector, a galvanometer, a plano-convex lens, a CCD camera, a dichroic mirror A, a focusing objective lens, a precision three-axis translation stage, a broadband light source, a program-controlled computer and a dichroic mirror B;

[0006] The femtosecond pulse laser emitted by the femtosecond laser passes through the aperture and mechanical shutter, and then enters the galvanometer through the ultrafast reflector. The galvanometer realizes the translational scanning of the femtosecond pulse laser. After passing through the galvanometer, the femtosecond pulse laser is collimated by a plano-convex lens and then reflected by a dichroic mirror A, and then focused to the surface of the porous ceramic processing sample through a focusing objective lens. The visible light emitted by the broadband light source passes through a dichroic mirror B, a dichroic mirror A and a focusing objective lens and then irradiates the porous ceramic processing sample, providing background light for CCD camera imaging.

[0007] The program-controlled computer is connected to a CCD camera to realize real-time imaging of the surface of the porous ceramic processing sample; connected to a femtosecond laser, a mechanical shutter and a galvanometer to realize control of the femtosecond pulse laser; and connected to a precision three-axis translation stage to realize three-dimensional positioning of the porous ceramic processing sample.

[0008] Furthermore, the centers of the aperture, the mechanical shutter and the ultrafast reflector are located at the same height as the light exit hole of the femtosecond laser; the ultrafast reflector and the transmission direction of the femtosecond pulse laser form a preset angle to ensure that the femtosecond pulse laser enters the galvanometer.

[0009] A femtosecond laser processing method for an electrospray thruster emitter comprises the following steps:

[0010] Step 1: Build a femtosecond laser processing system;

[0011] Step 2: Adjust the precision three-axis translation stage through a program-controlled computer so that the femtosecond pulse laser is focused on the surface of the porous ceramic processing sample through a focusing objective lens;

[0012] Step 3: Perform rough processing of the emitter structure, and control the galvanometer and the precision three-axis translation stage through a programmable computer to achieve linkage scanning of the femtosecond pulse laser on the surface of the porous ceramic processing sample;

[0013] Step 4: Perform fine processing of the emitter structure, and use a galvanometer to scan the surface of the porous ceramic sample back and forth with a femtosecond pulse laser. During the scanning process, a mechanical shutter is controlled to avoid ablation of the conical emitter structure area.

[0014] Step 5, repeating steps 2 to 4, expanding the processed conical emitter structure into an array, and completing the processing of the complete emitter structure;

[0015] Step 6: Ultrasonic cleaning of the processed porous ceramic samples.

[0016] Furthermore, during the rough machining of the emitter structure, the repetition frequency of the femtosecond pulse laser is 50-200 KHz, the energy of a single pulse is 5-20 μJ, the theoretical inner diameter of the femtosecond pulse laser spot is d1=30 μm, and the bottom diameter is d2=120 μm.

[0017] Furthermore, during the rough machining of the emitter structure, the scanning speed of the galvanometer is 200-700 mm / s, the scanning interval is 100-300 μm, and the height of the porous ceramic processing sample is adjusted by 20-30 μm through the precision three-axis translation stage.

[0018] Furthermore, during the fine machining of the emitter structure, the repetition frequency of the femtosecond pulse laser is 50-200 KHz, the energy of a single pulse is 0.5-1.5 μJ, the theoretical inner diameter of the femtosecond pulse laser spot is d1=30 μm, and the bottom diameter is d2=120 μm.

[0019] Furthermore, during the fine machining of the emitter structure, the scanning speed of the galvanometer is 200-700 mm / s, the scanning interval is 10-30 μm, and the height of the porous ceramic processing sample is adjusted to a spacing of 2 to 3 μm.

[0020] The beneficial effects of the present invention compared with the prior art are:

[0021] (1) The femtosecond laser processing method of the electrospray thruster emitter of the present invention realizes the emitter structure processing on the porous ceramic surface through femtosecond laser direct writing scanning processing. Compared with traditional mechanical processing, the processing accuracy is significantly improved, and the edge collapse and pore clogging of traditional mechanical processing are avoided.

[0022] (2) The femtosecond laser processing system and method of the electrospray thruster emitter of the present invention are suitable for hard and brittle materials such as ceramics. Compared with traditional mechanical processing, the electrospray thruster emitter processed by the method of the present invention can effectively improve the service life and specific impulse of the electrospray thruster. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a femtosecond laser processing system for an emitter of an electrospray thruster according to the present invention;

[0024] Figure 2 (a) Schematic diagram of femtosecond laser rough machining process;

[0025] Figure 2 (b) Schematic diagram of femtosecond laser finishing process;

[0026] Figure 3 Schematic diagram of the layer-by-layer scanning process for fine machining;

[0027] Among them: 1- femtosecond laser, 2- aperture, 3- mechanical shutter, 4- ultrafast reflector, 5- galvanometer, 6- plano-convex lens, 7- CCD camera, 8- dichroic mirror A, 9- focusing objective lens, 10- porous ceramic processing sample, 11- precision three-axis translation stage, 12- broadband light source, 13- program-controlled computer, 14- dichroic mirror B. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0029] Example 1

[0030] like Figure 1As shown, a femtosecond laser processing system for an electrospray thruster emitter of the present embodiment includes a femtosecond laser 1, an aperture 2, a mechanical shutter 3, an ultrafast reflector 4, a galvanometer 5, a plano-convex lens 6, a CCD camera 7, a dichroic mirror A8, a focusing objective lens 9, a precision three-axis translation stage 11, a broadband light source 12, a programmable computer 13 and a dichroic mirror B14.

[0031] The centers of the aperture 2 , the mechanical shutter 3 and the ultrafast reflector 4 are located at the same height as the light exit hole of the femtosecond laser 1 ; the ultrafast reflector 4 forms a preset angle with the transmission direction of the femtosecond pulse laser to ensure that the femtosecond pulse laser enters the galvanometer 5 .

[0032] The working principle of the femtosecond laser processing system is as follows: the femtosecond pulse laser emitted by the femtosecond laser 1 passes through the aperture 2 and the mechanical shutter 3, and then enters the galvanometer 5 through the ultrafast reflector 4, and the galvanometer 5 realizes the translational scanning of the femtosecond pulse laser. After passing through the galvanometer 5, the femtosecond pulse laser is collimated by the plano-convex lens 6 and reflected by the dichroic mirror A8, and then focused to the surface of the porous ceramic processing sample 10 through the focusing objective lens 9. The visible light emitted by the broadband light source 12 passes through the dichroic mirror B14, the dichroic mirror A8 and the focusing objective lens 9 and irradiates the porous ceramic processing sample 10, providing background light for the CCD camera 7 imaging. The program-controlled computer 13 is connected to the CCD camera 7 to realize real-time imaging of the surface of the porous ceramic processing sample 10; the program-controlled computer 13 is connected to the femtosecond laser 1, the mechanical shutter 3 and the galvanometer 5 to realize the control of the femtosecond pulse laser; the program-controlled computer 13 is connected to the precision three-axis translation stage 11 to realize the three-dimensional positioning of the porous ceramic processing sample 10.

[0033] In this embodiment, the substrate of the porous ceramic processed sample 10 is corrosion-resistant porous borosilicate ceramic.

[0034] This embodiment provides a method for forming a periodic emitter structure on the surface of porous ceramics by scanning and ablating porous ceramics using a femtosecond laser, comprising the following steps:

[0035] Step 1: Build the femtosecond laser processing system, including a femtosecond laser 1, an aperture 2, a mechanical shutter 3, an ultrafast reflector 4, a galvanometer 5, a plano-convex lens 6, a CCD camera 7, a dichroic mirror A8, a focusing objective lens 9, a precision three-axis translation stage 11, a broadband light source 12, a programmable computer 13 and a dichroic mirror B14.

[0036] Step 2: The precise three-axis translation stage 11 is adjusted by the program-controlled computer 13 so that the femtosecond pulse laser is focused onto the surface of the porous ceramic processing sample 10 through the focusing objective lens 9 .

[0037] Step 3: Figure 2As shown in (a), the galvanometer 5 and the precision three-axis translation stage 11 are controlled by the program-controlled computer 13 to realize the linkage scanning of the surface of the porous ceramic processing sample 10 by the femtosecond pulse laser. The repetition frequency of the femtosecond pulse laser is 50-200KHz, the energy of a single pulse is 5-20μJ, the theoretical inner diameter of the femtosecond pulse laser spot is d1=30μm, and the bottom diameter is d2=120μm; the scanning speed of the galvanometer 5 is 200-700mm / s, and the scanning spacing is 100-300μm. Subsequently, the height of the porous ceramic processing sample 10 is adjusted by 20-30μm through the precision three-axis translation stage 11. Repeat step three 10 times to realize the rough processing of the emitter structure.

[0038] Step 4: Figure 2 As shown in (b), the femtosecond pulse laser is scanned back and forth on the surface of the porous ceramic processing sample 10 through the galvanometer 5. During the scanning process, the mechanical shutter 3 is controlled simultaneously to achieve ablation-free conical emitter structure area. The repetition frequency of the femtosecond pulse laser is 50-200KHz, the energy of a single pulse is 0.5-1.5μJ, the theoretical inner diameter of the femtosecond pulse laser spot is d1=30μm, and the bottom diameter is d2=120μm; the scanning speed of the galvanometer 5 is 200-700mm / s, and the scanning spacing is 10-30μm. Adjust the height of the porous ceramic processing sample 10, the spacing is 2-3μm, repeat the processing process of step four, and achieve fine processing of the emitter structure, as shown in FIG. Figure 3 shown.

[0039] Step 5: Repeat steps 2 to 4 to expand the processed conical emitter structure into an array to complete the processing of the complete emitter structure.

[0040] Step 6: Place the processed porous ceramic sample 10 in an alcohol solution for ultrasonic cleaning for half an hour.

[0041] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0042] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A femtosecond laser processing system for an electrospray thruster emitter, characterized in that: It includes a femtosecond laser (1), an aperture (2), a mechanical shutter (3), an ultrafast reflector (4), a galvanometer (5), a plano-convex lens (6), a CCD camera (7), a dichroic mirror A (8), a focusing objective lens (9), a precision three-axis translation stage (11), a broadband light source (12), a program-controlled computer (13) and a dichroic mirror B (14); The femtosecond pulse laser emitted by the femtosecond laser (1) passes through an aperture (2) and a mechanical shutter (3), and then passes through an ultrafast reflection mirror (4) to enter a galvanometer (5), and the galvanometer (5) realizes translational scanning of the femtosecond pulse laser; after passing through the galvanometer (5), the femtosecond pulse laser is collimated by a plano-convex lens (6), and then reflected by a dichroic mirror A (8), and then focused by a focusing objective lens (9) onto the surface of a porous ceramic processing sample (10); the visible light emitted by the broadband light source (12) passes through a dichroic mirror B (14), a dichroic mirror A (8), and a focusing objective lens (9), and then irradiates the porous ceramic processing sample (10), providing background light for CCD camera (7) imaging; The program-controlled computer (13) is connected to a CCD camera (7) to realize real-time imaging of the surface of a porous ceramic processing sample (10); connected to a femtosecond laser (1), a mechanical shutter (3) and a galvanometer (5) to realize control of a femtosecond pulse laser; and connected to a precision three-axis translation stage (11) to realize three-dimensional positioning of the porous ceramic processing sample (10).

2. A femtosecond laser processing system for an electrospray thruster emitter according to claim 1, characterized in that: The centers of the aperture (2), the mechanical shutter (3) and the ultrafast reflector (4) are located at the same height as the light exit hole of the femtosecond laser (1); the ultrafast reflector (4) forms a preset angle with the transmission direction of the femtosecond pulse laser to ensure that the femtosecond pulse laser is incident on the galvanometer (5).

3. A femtosecond laser processing method for an electrospray thruster emitter based on the system according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: Build a femtosecond laser processing system; Step 2: adjusting the precision three-axis translation stage (11) by means of a program-controlled computer (13) so that the femtosecond pulse laser is focused onto the surface of a porous ceramic processing sample (10) through a focusing objective lens (9); Step 3: rough machining of the emitter structure is performed by controlling the galvanometer (5) and the precision three-axis translation stage (11) through the program-controlled computer (13) to achieve linkage scanning of the surface of the porous ceramic processing sample (10) by the femtosecond pulse laser; Step 4: Perform fine processing of the emitter structure, use a galvanometer (5) to scan the surface of the porous ceramic processing sample (10) back and forth with a femtosecond pulse laser, and control a mechanical shutter (3) during the scanning process to avoid ablation of the conical emitter structure area; Step 5, repeating steps 2 to 4, expanding the processed conical emitter structure into an array, and completing the processing of the complete emitter structure; Step six: ultrasonically clean the processed porous ceramic sample (10).

4. The femtosecond laser processing method for an electrospray thruster emitter according to claim 3, characterized in that: During the rough machining of the emitter structure, the repetition frequency of the femtosecond pulse laser is 50-200 KHz, the single pulse energy is 5-20 μJ, the theoretical inner diameter of the femtosecond pulse laser spot is d1=30 μm, and the bottom diameter is d2=120 μm.

5. The femtosecond laser processing method for an electrospray thruster emitter according to claim 3, characterized in that: During the rough processing of the emitter structure, the scanning speed of the galvanometer (5) is 200-700 mm / s, the scanning interval is 100-300 μm, and the height of the porous ceramic processing sample (10) is adjusted by 20-30 μm through the precision three-axis displacement stage (11).

6. The femtosecond laser processing method for an electrospray thruster emitter according to claim 3, characterized in that: During the fine machining of the emitter structure, the repetition frequency of the femtosecond pulse laser is 50-200 KHz, the energy of a single pulse is 0.5-1.5 μJ, the theoretical inner diameter of the femtosecond pulse laser spot is d1=30 μm, and the bottom diameter is d2=120 μm.

7. The femtosecond laser processing method for an electrospray thruster emitter according to claim 3, characterized in that: During the fine processing of the emitter structure, the scanning speed of the galvanometer (5) is 200-700 mm / s, the scanning interval is 10-30 μm, and the height of the porous ceramic processing sample (10) is adjusted to an interval of 2-3 μm.

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