A planar magnetic induction probe array for measuring arc rotation angular velocity of microcathode arc thruster

Abstract

This invention discloses a planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster. Specifically, it includes a quartz shell (11), a measuring coil (12), a polytetrafluoroethylene sleeve (13), a probe base (14), a solder pad (15), and a magnetic induction probe array structure (6) to measure the arc rotation angular velocity of the microcathode arc thruster. This invention targets the measurement of the arc rotation angular velocity of a single ignition discharge arc in a microcathode arc thruster, designing a magnetic induction probe array structure including a measuring coil and several magnetic induction probes. Based on Faraday's law of electromagnetic induction, the change in magnetic flux on the measuring coil is measured, and the instantaneous high-frequency magnetic field changes in time and space are accurately captured through a special magnetic induction probe arrangement, thereby realizing the measurement of the arc rotation angular velocity of the microcathode arc thruster.

Description

Technical Field

[0001] This invention relates to the field of electric propulsion plasma diagnostics, specifically to a planar magnetic induction probe array for measuring the rotational angular velocity of the discharge arc of a microcathode arc thruster using a non-contact measurement method. Background Technology

[0002] Microcathode arc thrusters are a type of advanced propulsion device that uses pulsed discharge to generate an electric arc that ablates a conductive thin film and a cathode to generate plasma. Charged particles are then accelerated and ejected through an electromagnetic field to obtain propulsion power. They have significant advantages such as high specific impulse, high efficiency, and high integration. They have broad application prospects in space missions such as orbit control of large spacecraft, deep space exploration, and interstellar travel. Currently, they are widely used in the main propulsion systems of satellites and deep space probes.

[0003] The discharge characteristics of microcathode arc thrusters, such as the magnetic field strength generated by the discharge and the rotational speed of the discharge arc, are crucial for evaluating engine life, optimizing engine design, and improving engine performance. Magnetic induction probes are a fundamental testing method for measuring plasma energy distribution. As a non-contact measurement method, they offer advantages such as high measurement accuracy and minimal disturbance to the plasma within the discharge channel. However, the magnetic field generated by the discharge arc exhibits problems such as rapid decay over time and changes in the direction of magnetic field lines. Traditional single magnetic induction probes can only measure the decaying magnetic field strength of a single peak over time, which fails to reflect the rotational characteristics of the discharge arc in microcathode arc thrusters. Currently, there is no specific method for measuring the rotational characteristics of the discharge arc in microcathode arc thrusters. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster. This solves the problem that the measurement results of a single magnetic induction probe currently in use cannot reflect the rotational characteristics of the discharge arc of the microcathode arc thruster, and enables the measurement of the arc rotation angular velocity of the microcathode arc thruster.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: a planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster, characterized in that it comprises a quartz shell, a measuring coil, a polytetrafluoroethylene sleeve, a probe base, solder pads, and a magnetic induction probe array structure.

[0008] The quartz shell is a hollow, semi-enclosed structure;

[0009] The measuring coil is located inside the quartz shell, and the axis of the measuring coil is parallel to the axis of the quartz shell;

[0010] The polytetrafluoroethylene sleeve is tightly fitted onto the outer periphery of the open end of the quartz shell and fixedly installed at one end of the probe base;

[0011] The probe base has a hollow structure;

[0012] The pad is located inside the probe base. The signal line from the measuring coil is soldered to the pad and an external circuit is led out through the pad and the other end of the probe base. The external circuit is connected to an RC integrator, which is used to integrate the induced current so that the induced electromotive force after integration has a linear proportional relationship with the magnetic field strength, thereby obtaining the time distribution of the magnetic field generated by the discharge arc during the first ignition of the microcathode arc thruster.

[0013] The magnetic induction probe array structure includes several measurement coils. The axes of all the measurement coils are located in the same two-dimensional plane, and the center of all the measurement coils is equidistant from the center of the magnetic induction probe array structure. That is, the center of all the measurement coils is located on a circle centered on the center of the magnetic induction probe array structure, and the axes of all the measurement coils coincide with the tangent direction of the circle. All the measurement coils are uniformly distributed on the circle so as to obtain the spatial distribution of the magnetic field generated by the discharge arc during the first ignition operation of the microcathode arc thruster through the measurement value of each measurement coil.

[0014] In some instances, the process of obtaining the temporal and spatial distribution of the magnetic field generated by the discharge arc during the first ignition operation of the microcathode arc thruster is as follows:

[0015] The current density j at the measurement position of the magnetic induction probe generates an induced magnetic field strength B on the measurement coil, which follows Ampere's circuital law. The current density and magnetic field strength generated by the discharge arc of the microcathode arc thruster are obtained according to the following formulas (1) and (2):

[0016]

[0017] Where μ0 is the vacuum permeability; ε is the curl of the magnetic field strength; ε is the induced electromotive force; A is the magnetic flux area of ​​the horizontal or vertical magnetic coil; N is the number of turns of the horizontal or vertical magnetic coil; Φ is the magnetic flux passing through the measuring coil.

[0018] In some instances, the outer diameter of the quartz shell is 4-5 mm.

[0019] In some instances, the measuring coil is located at the closed end of the quartz housing.

[0020] In some instances, the measuring coil is made of yarn-covered wire with a diameter of 0.05-0.1mm, consisting of 10-15 strands twisted together, with a coil skeleton diameter of 1-2mm and 350-400 turns.

[0021] In some instances, the signal lines and external circuitry of the measurement coil are twisted-pair structures.

[0022] In some instances, the RC integrator circuit is located outside the magnetic induction probe.

[0023] In some instances, the probe base is made of stainless steel.

[0024] In some instances, the magnetic induction probe array structure includes 3-6 of the measurement coils.

[0025] (III) Beneficial Effects

[0026] This invention provides a planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster, which has the following advantages:

[0027] 1) The measuring coil of the magnetic induction probe of the present invention is located inside the glass shell, so it can realize the measurement close to the position where the discharge arc is generated, and the temperature resistance can reach 1000K, and it can obtain the magnetic field strength parameters near the discharge arc.

[0028] 2) The external integration circuit of the present invention greatly reduces the volume of the probe body, making it easier to measure the discharge arc of the micro cathode arc thruster, and also facilitates the arrangement of the magnetic induction probe array.

[0029] 3) This invention uses a twisted-pair cable structure, which can effectively reduce the induction area other than the measuring coil, thereby effectively reducing electromagnetic interference and noise and increasing measurement accuracy;

[0030] 4) The magnetic induction probe array structure of the present invention can effectively obtain the spatial distribution and spatial variation of the magnetic field strength generated by the discharge arc during the discharge process of the micro cathode arc thruster;

[0031] 5) The magnetic induction probe array structure of the present invention, by using multiple uniformly arranged magnetic induction probes, can clearly distinguish the magnetic field strength generated by the high-speed discharge arc at different times through the waveform phase of each magnetic induction probe.

[0032] 6) The magnetic induction probe array structure of the present invention can accurately capture the transient changes in magnetic field strength generated during the rotation of the discharge arc by using multiple magnetic induction probes arranged in a ring. This is beneficial for measuring microcathode arc thrusters with different positions and arc rotation angles generated in each discharge. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a single magnetic induction probe in the magnetic induction probe array of the present invention.

[0034] Figure 2 This is a schematic diagram of the magnetic induction probe array structure of the present invention.

[0035] Figure 3 This is a schematic diagram of the external circuit of the present invention.

[0036] Figure 4 This is a schematic diagram of the measurement principle of the magnetic induction probe array structure of the present invention.

[0037] Figure 5 This is a schematic diagram of the measurement curve of the magnetic induction probe array structure of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described below are intended to facilitate the understanding of the present invention and are not intended to limit it in any way.

[0039] like Figure 1 As shown, the magnetic induction probe in the planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster of the present invention includes: a quartz shell 11, a measuring coil 12, a polytetrafluoroethylene (PTFE) sleeve 13, a probe base 14, and a solder pad 15. The quartz shell 11 is a hollow, semi-enclosed structure, i.e., closed at one end and open at the other; the probe base 14 is a hollow structure. The measuring coil 12 is located inside the quartz shell 11. Both ends of the probe base have openings, with the open end of the quartz shell placed inside one of the open ends of the probe base. The PTFE sleeve 13 is tightly fitted onto the outer periphery of the open end of the quartz shell 11 and fixedly installed at one end of the probe base 14. The outer diameter of the PTFE sleeve 13 is tightly fitted with the positioning step of the probe base 14, and together with the quartz shell 11, is fixedly connected to the probe base 14. Figure 1 As shown, the quartz shell 11 is preferably cylindrical, forming a coaxial channel with the probe base 14, which is also preferably cylindrical. Furthermore, the inner surface of the quartz shell 11 is flush with the inner surface of the probe base 14.

[0040] In this example, the measuring coil 12 is located at the closed end of the quartz housing 11. Two signal lines are led out from the side of the measuring coil 12 near the open end of the quartz housing 11 and soldered to pads 15 located inside the probe base 14. External circuitry is led out through the pads 15 and the other end of the probe base 14. There are two pads, each connected to one of the two signal lines. Similarly, two connecting wires are used for connecting to the external circuitry.

[0041] As a feasible implementation, the two leads of the coil 12 can be directly connected to the external circuit without the solder pads. Alternatively, insulating material can be provided on the outside of the solder pad 15, thereby fixing the solder pad 15 to a fixed component, such as the probe base 14.

[0042] Furthermore, those skilled in the art will understand that the materials described above are merely examples and not mandatory. For instance, other suitable materials can be chosen for the housing and sleeve.

[0043] like Figure 3 As shown, an RC integrator is connected to the external circuit. This RC integrator is used to integrate the induced current, so that the induced electromotive force after integration has a linear proportional relationship with the magnetic field strength, so as to obtain the time distribution of the magnetic field generated by the discharge arc during the first ignition of the microcathode arc thruster.

[0044] The induced magnetic field strength B generated by the current density j at the measurement position of the magnetic induction probe on the measuring coil 12 follows Ampere's circuital law. The current density and magnetic field strength generated by the discharge arc of the microcathode arc thruster are obtained according to the following formulas (1) and (2):

[0045]

[0046] Where μ0 is the vacuum permeability; ε is the curl of the magnetic field strength; ε is the induced electromotive force; A is the magnetic flux area of ​​the horizontal or vertical magnetic coil; N is the number of turns of the horizontal or vertical magnetic coil; Φ is the magnetic flux passing through the measuring coil 12. Therefore, the magnetic field strength B can be determined from the relationship between the voltage signal of the magnetic induction probe and dB / dt, enabling the measurement of the magnetic field distribution generated by the discharge arc of the micro-cathode arc thruster during the first ignition operation of the thruster.

[0047] like Figure 2 The diagram shows the magnetic induction probe array structure 6 of the present invention. The magnetic induction probe array structure 6 contains n magnetic induction probes. For simplicity, Figure 2Only the measuring coil 12 is shown. The axes of all measuring coils 12 are located in the same two-dimensional plane, and the center of all measuring coils 12 is equidistant from the center of the magnetic induction probe array structure 6. That is, the center of all measuring coils 12 is located on a circle centered on the center of the magnetic induction probe array structure 6, and the axes of all measuring coils 12 coincide with the tangent direction of the circle. All measuring coils 12 are evenly distributed on the circle so as to obtain the spatial distribution of the magnetic field generated by the discharge arc during the first ignition operation of the microcathode arc thruster through the measurement value of each measuring coil 12.

[0048] In this example, the detailed measurement principle of the magnetic induction probe array structure 6 is as follows: Figure 4 As shown, the magnetic induction probe array structure 6 is placed at the outlet of the microcathode arc thruster. The head structure of the microcathode arc thruster includes: a shell 21, a cathode 22, a conductive film 23, an anode 24, and an insulating substrate 25. When the thruster discharges, a discharge arc is generated between the cathode 22 and the anode 24. According to Ampere's circuital law, the magnetic field strength B generated by the current I of the discharge arc is obtained from formulas (3) and (4).

[0049] ∫ l Bdl=μ0I (3)

[0050]

[0051] Where μ0 is the vacuum permeability; r is the distance between the magnetic induction probe array structure 6 and the discharge arc. During the single ignition operation of the microcathode arc thruster, the discharge arc will continuously rotate, and the magnitude and direction of the magnetic field strength it generates will also change accordingly. Therefore, when the discharge arc sweeps across the location of each measuring coil 12, a maximum induced voltage peak will be generated in the swept measuring coil 12 at that moment, and the moment when the maximum induced voltage peak is generated by different measuring coils 12 is different.

[0052] like Figure 5 The figure shows the induced voltage waveforms generated when the discharge arc sweeps through the first to nth coils. Based on the induced voltage waveforms, the magnetic field strength generated when the discharge arc rotates to a certain measuring coil 12 can be determined by the peak value of the induced voltage; the time required for the discharge arc to rotate from one measuring coil 12 to the next can be obtained by the time difference between each two peak values, thus determining the average rotational speed of the discharge arc within that interval.

[0053] In particular, although the RC integrator is part of the circuit, it is located outside the magnetic induction probe, reducing the size of the probe body.

[0054] Specifically, the measuring coil 12 and its lead-out signal lines are made of yarn-covered wire, which enables the transmission of induced current signals.

[0055] Specifically, the signal lines and external circuit lines of the measuring coil 12 are stranded wires.

[0056] In some embodiments, the outer diameter of the quartz housing 11 is 5 mm.

[0057] In some embodiments, the coil skeleton of the measuring coil 12 has a diameter of 1.5 mm, and the yarn-covered wire used has a diameter of 0.07 mm, is 14 strands twisted together, and has 398 turns, with no ferromagnetic material inside.

[0058] In some embodiments, the probe base 14 may be made of stainless steel.

[0059] In some embodiments, the magnetic induction probe array structure 6 includes four magnetic induction probes.

[0060] For those skilled in the art, various modifications and improvements can be made to the embodiments of the present invention without departing from the inventive concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. A planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster, characterized in that, include: Multiple magnetic induction probes, each including a housing and a measuring coil (12); The outer shell is a hollow, semi-enclosed structure; the measuring coil (12) is located inside the outer shell, and the axis of the measuring coil (12) is parallel to the axis of the outer shell; The axes of all the measuring coils (12) are located in the same two-dimensional plane, and the center of all the measuring coils (12) is equidistant from the center of the magnetic induction probe array structure. That is, the center of all the measuring coils (12) is located on a circle centered on the center of the magnetic induction probe array structure, and the axes of all the measuring coils (12) coincide with the tangent direction of the circle. All the measuring coils (12) are evenly distributed on the circle so as to obtain the spatial distribution of the magnetic field generated by the discharge arc during the first ignition operation of the micro cathode arc thruster by measuring the value of each measuring coil (12). The outer casing is a quartz casing (11), and / or the outer diameter of the outer casing is 4-5 mm; and / or the measuring coil (12) is located at the closed end of the outer casing; It also includes a polytetrafluoroethylene sleeve (13) and a probe base (14). The polytetrafluoroethylene sleeve (13) is tightly fitted around the outer periphery of the opening end of the quartz shell (11) and fixedly installed at one end of the probe base (14). The probe base (14) has a hollow structure. The signal line led out from the measuring coil (12) is connected to an external circuit. The external circuit is connected to an RC integrator. The RC integrator is used to realize the integration of the induced current, so that the induced electromotive force after integration has a linear proportional relationship with the magnetic field strength, so as to obtain the time distribution of the magnetic field generated by the discharge arc during the first ignition of the micro cathode arc thruster.

2. The planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster according to claim 1, characterized in that, The process of obtaining the magnetic field distribution generated by the discharge arc of the microcathode arc thruster during its first ignition operation is as follows: The current density j at the magnetic induction probe measurement position generates an induced magnetic field strength B on the measurement coil (12) that follows Ampere's circuital law. The current density and magnetic field strength generated by the discharge arc of the microcathode arc thruster are obtained according to the following formulas (1) and (2): Where μ0 is the vacuum permeability; ε is the curl of the magnetic field strength; ε is the induced electromotive force; A is the magnetic flux area of ​​the horizontal or vertical magnetic coil; N is the number of turns of the horizontal or vertical magnetic coil; Φ is the magnetic flux passing through the measuring coil (12).

3. The planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster according to claim 1 or 2, characterized in that, The measuring coil (12) is made of yarn-covered wire with a diameter of 0.05-0.1mm and 10-15 strands twisted together. The coil skeleton diameter is 1-2mm and the winding is 350-400 turns. Alternatively, the measuring coil (12) is a twisted pair structure.

4. The planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster according to claim 1, characterized in that, The RC integrator is located outside the magnetic induction probe.

5. The planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster according to claim 1, characterized in that, The probe base (14) is made of stainless steel.

6. The planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster according to claim 1 or 2, characterized in that, The magnetic induction probe array structure contains 3-6 magnetic induction probes.

7. The planar magnetic induction probe array for measuring the arc rotation angular velocity of a microcathode arc thruster according to claim 1 or 2, characterized in that, All the measuring coils (12) are evenly distributed on the circle.

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