A method for measuring the wall erosion rate in different regions of a plasma thruster

Abstract

This invention discloses a method for measuring the wall erosion rate of different regions of a plasma thruster. The method includes preparing a calibration film sample, the steps of which are: placing a perforated mask on a quartz substrate, performing sputtering deposition on the quartz substrate using a magnetron sputtering device, removing the mask after deposition to obtain the calibration film sample, and measuring the thickness of the calibration film using a profilometer and a scanning electron microscope. The calibration film sample of this invention is deposited on a quartz substrate, and the mask is also made of quartz material, which will not cause significant interference or contamination to the plasma performance of the plasma thruster. Furthermore, calibration films of the same material can be deposited according to different plasma thruster wall material types.

Description

Technical Field

[0001] This invention relates to a method for measuring the wall erosion rate of different regions of a plasma thruster, belonging to the field of plasma reactive sputtering deposition. Background Technology

[0002] Over the past few decades, various types of space electric propulsion devices have been developed and successfully applied to various space missions, such as ion grid thrusters, Hall thrusters, and electrodeless magnetic nozzle thrusters based on radio frequency, helical wave, and microwave heating. The erosive effect of plasma on the walls of plasma thrusters is a key factor affecting their performance and lifespan. For example, during Hall thruster operation, plasma causes sputtering erosion of the ceramic wall material. Damage to the wall material ultimately exposes the magnetic circuit elements to plasma, ending the Hall thruster's lifespan. Even in electrodeless magnetic nozzle thrusters, the strong interaction between high-density plasma and the inner wall of the dielectric tube can damage the plasma source. To effectively assess thruster performance and lifespan, it is crucial to develop methods to measure and avoid erosion rates. While the wall is being eroded by plasma, it is simultaneously undergoing a redeposition process of sputtered material from other areas. Therefore, quantitative monitoring of net erosion rate, gross erosion rate, and net erosion velocity is essential for understanding the plasma-wall interaction process. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a method for measuring the wall erosion rate of different regions of a plasma thruster.

[0004] This invention is achieved through the following technical solution:

[0005] A method for measuring the wall erosion rate of different regions of a plasma thruster includes preparing a calibration film sample. The steps are as follows: placing a perforated mask on a quartz substrate, performing sputtering deposition on the quartz substrate using a magnetron sputtering device, removing the mask after deposition to obtain the calibration film sample, and measuring the thickness of the calibration film using a profilometer and a scanning electron microscope.

[0006] The method for measuring the wall erosion rate of different regions of a plasma thruster further includes the installation of a calibration film sample, the steps of which are: attaching the calibration film sample to the inner wall of the spiral wave plasma source tube of the spiral wave plasma device, and then turning on the spiral wave plasma device.

[0007] The method for measuring the wall erosion rate of different regions of a plasma thruster also includes a plasma sputtering process, the steps of which are: adjusting the magnetic field coil current, radio frequency input power and air intake flow parameters, and running the helical wave plasma source in a steady-state working state for 20-40 minutes.

[0008] The method for measuring the wall erosion rate of different regions of a plasma thruster employs a profilometer and a scanning electron microscope to measure the film thickness after sputtering. Based on the thickness difference of the calibration film before and after discharge and the running time, the gross erosion rate and net erosion rate of the wall material are calculated. Combined with the measurement of the calibration film at different wall positions, the overall sputtering and redeposition process of the inner wall of the helical wave plasma source dielectric tube is established.

[0009] The method for measuring the wall erosion rate of different regions of a plasma thruster, wherein the thickness of the calibration film is 0.8-1.2 μm.

[0010] The method for measuring the wall erosion rate of different regions of a plasma thruster, wherein the mask is a quartz plate with two holes of different diameters.

[0011] The method for measuring the wall erosion rate of different regions of a plasma thruster involves attaching a calibration film sample to the inner wall of a helical wave plasma source tube using high-temperature ceramic adhesive.

[0012] The method for measuring the wall erosion rate of different regions of a plasma thruster, wherein the plasma sputtering process is as follows: magnetic field coil current 100A, axial magnetic field strength of helical wave plasma source region 1300G, discharge gas is argon with a flow rate of 50sccm, radio frequency source frequency 13.56MHz, input power 1000W, and reflected power less than 50W.

[0013] The method for measuring the wall erosion rate of different regions of a plasma thruster includes a spiral wave plasma device comprising a vacuum chamber, a spiral wave plasma source tube disposed within the vacuum chamber, a radio frequency antenna disposed at the spiral wave plasma source tube, a DC magnetic field coil disposed outside the vacuum chamber, and an air inlet pipe connected to the vacuum chamber.

[0014] The method for measuring the wall erosion rate of different regions of a plasma thruster is described above, wherein a spiral wave plasma source shielding shell is provided outside the spiral wave plasma source tube.

[0015] The beneficial effects achieved by this invention are as follows:

[0016] 1. This invention enables a simple and rapid measurement of the erosion rate of space plasma thruster walls, which helps to deepen the understanding of the plasma-matter interaction process on the thruster walls and provides a solution for the efficient evaluation of the performance and lifespan of space plasma thrusters.

[0017] 2. The calibration film sample is deposited on a quartz substrate, and the mask is also made of quartz material, which will not cause too much interference or contamination to the plasma performance of the plasma thruster. In addition, calibration films of the same material can be deposited according to different plasma thruster wall material types.

[0018] 3. The invention can simultaneously measure multiple locations on the propeller wall, especially areas such as electrode gaps and the inner wall of the source tube that are difficult to reach by ordinary measurement methods, thus shortening the experimental cycle and significantly reducing experimental costs. Attached Figure Description

[0019] Figure 1 This is a flowchart of the preparation of calibration thin film samples according to the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of a spiral wave plasma device.

[0021] In the figure: 1. Vacuum chamber, 2. Calibration film sample, 3. Helical wave plasma source tube, 4. DC magnetic field, 5. Helical wave plasma source shielding shell, 6. Radio frequency antenna, 7. Coaxial transmission line, 8. Inlet pipe. Detailed Implementation

[0022] The present invention will now be further described. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0023] A method for measuring the erosion rate of a plasma thruster wall includes the following steps:

[0024] 1. For the alumina ceramic inner wall of the helical wave plasma source tube in the example, an alumina calibration thin film sample was prepared: First, using a mask and magnetron sputtering equipment, two calibration thin films (approximately 1 μm thick), one large (10 mm in diameter) and the other small (1 mm in diameter), were pre-deposited on a quartz substrate. After deposition, the mask was removed, and the thickness of the calibration thin film was measured using a profilometer and a scanning electron microscope. The preferred mask was a quartz sheet (0.2 mm thick, 20 mm in length and width, with holes of 10 mm diameter for the large hole and 1 mm diameter for the small hole). The preferred magnetron sputtering target was alumina (99.99% purity). The film thickness was calibrated using a profilometer or scanning electron microscope with an accuracy better than 1 μm.

[0025] 2. Calibration Film Sample Installation: Open vacuum test chamber 1, connect the gas path and circuit of the spiral wave plasma source, and simultaneously attach the calibration film sample 2 to the designated test area on the inner wall of the spiral wave plasma source tube 3 using high-temperature ceramic adhesive. After the ceramic adhesive has completely solidified, close the vacuum chamber and evacuate the system to background vacuum to simulate the space environment. SAUEREISEN Aluseal Adhesive Cement NO.2 PASTE is preferred as the ceramic adhesive, ensuring excellent thermal conductivity while maintaining high-temperature resistance, and ensuring a solidification time of more than 48 hours.

[0026] 3. Start-up of the spiral wave plasma source: Adjust the current of the magnetic field coil 4, the RF input power, and the inlet gas flow rate to ignite the high-density spiral wave plasma. Run the spiral wave plasma source in a steady-state operating condition for 30 minutes to ensure sufficient sputtering and erosion of the calibration film sample. A magnetic field coil current of 100A is preferred to ensure an axial magnetic field strength of 1300G in the spiral wave plasma source region. Argon is preferred as the discharge gas, with a flow rate of 50 sccm. The preferred RF source frequency is 13.56MHz, with an input power of 1000W and a reflected power below 50W.

[0027] 4. Sampling with the Helical Wave Plasma Source Off: Stop igniting the helical wave plasma source, open the vacuum chamber, and remove all calibration film samples attached to the wall. During sampling, a small amount of alcohol (preferably 50% alcohol concentration) can be injected into the area where the calibration film sample adheres to the wall to promote the dissolution of the ceramic adhesive. When removing the calibration film samples, care should be taken not to touch the film area to avoid damage, and contact with contaminated areas should also be avoided to ensure the film remains uncontaminated.

[0028] 5. Calibration Film Analysis: Using a profilometer and scanning electron microscope again, the film thickness after sputtering was measured. Based on the thickness difference of the calibration film before and after discharge and the running time, the gross erosion rate (for large-diameter calibration films) and net erosion rate (for small-diameter calibration films) of the wall material were calculated. Combined with measurements of calibration samples at different wall locations, the overall sputtering and redeposition process of the inner wall of the helical wave plasma source dielectric tube was established.

[0029] The specific applications and effects of this invention are as follows: It is mainly used for testing the wall life of helical waves and Hall thrusters. In addition, it can also be applied to the calibration of the sputtering rate of target plates in plasma sputtering deposition technology and the study of the erosion process of plasma-oriented materials in fusion devices.

[0030] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for measuring the wall erosion rate in different regions of a plasma thruster, characterized in that, The method includes preparing calibration film samples, the steps of which are as follows: placing a perforated mask on a quartz substrate, performing sputtering deposition on the quartz substrate using a magnetron sputtering device, removing the mask after deposition to obtain the calibration film sample, and measuring the thickness of the calibration film using a profilometer and a scanning electron microscope; the thickness of the calibration film is 0.8-1.2 μm; the mask is a quartz sheet with two holes of different diameters, characterized in that the smaller hole has a diameter of 1 mm and the larger hole has a diameter of 10 mm; It also includes the installation of calibration film samples, the steps of which are: attaching the calibration film sample to the inner wall of the spiral wave plasma source tube of the spiral wave plasma device, and then turning on the spiral wave plasma device; It also includes the plasma sputtering process, the steps of which are: adjusting the magnetic field coil current, radio frequency input power and air intake flow parameters, and running the spiral wave plasma source in a steady state for 20-40 minutes. The thickness of the film after sputtering was measured using a profilometer and a scanning electron microscope. Based on the thickness difference of the calibration film before and after discharge and the running time, the gross erosion rate of the wall material was calculated using a large-diameter calibration film, and the net erosion rate was calculated using a small-diameter calibration film. Combined with the measurement of calibration films at different wall positions, the overall sputtering and redeposition process of the inner wall of the helical wave plasma source dielectric tube was established.

2. The method for measuring the wall erosion rate of different regions of a plasma thruster according to claim 1, characterized in that, The calibration film sample was attached to the inner wall of the spiral wave plasma source tube using high-temperature ceramic adhesive.

3. The method for measuring the wall erosion rate of different regions of a plasma thruster according to claim 1, characterized in that, The plasma sputtering process is as follows: magnetic field coil current 100A, axial magnetic field strength in the helical wave plasma source region 1300G, discharge gas is argon with a flow rate of 50sccm, radio frequency source frequency 13.56MHz, input power 1000W, and reflected power less than 50W.

4. A method for measuring the wall erosion rate of different regions of a plasma thruster according to any one of claims 1-3, characterized in that, The spiral wave plasma device includes a vacuum chamber, in which the spiral wave plasma source tube is installed. A radio frequency antenna is installed at the spiral wave plasma source tube. A DC magnetic field coil is also installed outside the vacuum chamber. The vacuum chamber is connected to an air inlet pipe.

5. The method for measuring the wall erosion rate of different regions of a plasma thruster according to claim 4, characterized in that, The spiral wave plasma source tube is provided with a spiral wave plasma source shielding shell.

Images