Planar magnetic induction probe array for measuring arc rotation angular velocity of micro-cathode arc thruster

Abstract

The invention discloses a planar magnetic induction probe array for measuring the arc rotation angular velocity of a micro-cathode arc thruster, which specifically comprises a quartz shell (11), a measuring coil (12), a polytetrafluoroethylene sleeve (13), a probe base (14), a bonding pad (15) and a magnetic induction probe array structure (6) so as to measure the arc rotation angular velocity of the micro-cathode arc thruster. The invention designs a magnetic induction probe comprising a measuring coil and a magnetic induction probe array structure comprising a plurality of magnetic induction probes for measuring the rotation angular velocity of a discharge arc of single ignition of a micro-cathode arc thruster. Based on the Faraday's law of electromagnetic induction, the change condition of the magnetic flux on the coil is measured, and the change of an instantaneous high-frequency magnetic field in time and space is accurately captured through a special magnetic induction probe arrangement mode, so that the measurement of the arc rotation angular velocity of the micro-cathode arc thruster is realized.

Description

Technical Field

[0001] The invention relates to the field of electric propulsion plasma diagnosis, and in particular to a planar magnetic induction probe array for measuring the rotational angular velocity of a discharge arc of a micro cathode arc thruster using a non-contact measurement method. Background Art

[0002] Micro cathode arc thruster is a kind of advanced propulsion device that uses pulse discharge to generate discharge arc to ablate conductive film and cathode to generate plasma, and accelerates and ejects charged particles through electromagnetic field to obtain propulsion power. It has significant advantages of high specific impulse, high efficiency and high integration. It has broad application prospects in space missions such as orbit control of large spacecraft, deep space exploration and interstellar navigation. It has been widely used in the main propulsion systems of satellites and deep space probes.

[0003] The discharge characteristics of the microcathode arc thruster, such as the magnetic field strength generated by the discharge and the rotation speed-related parameters of the discharge arc, are of great significance for evaluating the life of the engine, optimizing the engine design, and improving the engine performance. The magnetic induction probe is one of the basic test methods for measuring the energy distribution of the plasma. It is a non-contact measurement method with the advantages of high measurement accuracy and small disturbance to the plasma in the discharge channel. However, the magnetic field generated by the discharge arc has problems such as fast decay over time and the direction of the magnetic flux lines changing over time. The traditional single magnetic induction probe can only measure the decay of the magnetic field strength of a single peak over time for the decaying and direction-changing magnetic field, which results in the measurement results being unable to reflect the rotation characteristics of the discharge arc of the microcathode arc thruster. At present, there is no method specifically for measuring the rotation characteristics of the discharge arc of the microcathode arc thruster. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a planar magnetic induction probe array for measuring the angular velocity of arc rotation of a micro-cathode arc thruster, which solves the problem that the measurement results of a single magnetic induction probe currently used cannot reflect the rotation characteristics of the discharge arc of the micro-cathode arc thruster, and can realize the measurement of the angular velocity of arc rotation of the micro-cathode arc thruster.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented by the following technical scheme: a planar magnetic induction probe array for measuring the arc rotation angular velocity of a micro cathode arc thruster, characterized in that it includes a quartz housing, a measuring coil, a polytetrafluoroethylene sleeve, a probe base, a welding pad, 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 housing, and the axis of the measuring coil is parallel to the axis of the quartz housing;

[0010] The polytetrafluoroethylene sleeve is tightly fitted on the outer periphery of the opening end of the quartz housing and is fixedly mounted on one end of the probe base;

[0011] The probe base is a hollow structure;

[0012] The pad is located inside the probe base, and the signal wire led out of the measuring coil is welded on 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, and the RC integrator is used to realize the integration of the induced current, so that the induced electromotive force after integration has a linear positive proportional relationship with the magnetic field intensity, so as to obtain the time distribution of the magnetic field generated by the discharge arc during the primary ignition of the micro-cathode arc thruster;

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

[0014] In some examples, the process of obtaining the temporal and spatial distribution of the magnetic field generated by the discharge arc during the primary ignition operation of the micro-cathode arc thruster is as follows:

[0015] The induced magnetic field strength B generated by the current density j at the measuring position of the magnetic induction probe on the measuring coil follows the Ampere loop law. The current density and magnetic field strength generated by the discharge arc of the micro cathode arc thruster are obtained according to the following formulas (1) and (2):

[0016]

[0017]

[0018] Where μ0 is the magnetic permeability of vacuum; 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 induction coil (12).

[0019] In some examples, the outer diameter of the quartz housing is 4-5 mm.

[0020] In some examples, the measurement coil is located at a closed end of the quartz housing.

[0021] In some examples, the measuring coil is made of yarn-wrapped wire with a wire diameter of 0.05-0.1 mm and 10-15 strands twisted together, a coil skeleton diameter of 1-2 mm, and 350-400 turns of winding.

[0022] In some examples, the signal line of the measuring coil and the external circuit line are twisted pair structures.

[0023] In some examples, the RC integrator circuit is located outside the magnetic induction probe.

[0024] In some examples, the probe base is made of stainless steel.

[0025] In some examples, the magnetic induction probe array structure includes 3-6 measurement coils.

[0026] (III) Beneficial effects

[0027] The present invention provides a planar magnetic induction probe array for measuring the arc rotation angular velocity of a micro cathode arc thruster, which has the following beneficial effects:

[0028] 1) The measuring coil of the magnetic induction probe of the present invention is located inside the glass shell, so that the measurement can be achieved close to the position where the discharge arc is generated, the temperature resistance can reach 1000K, and the magnetic field intensity parameters near the discharge arc can be obtained;

[0029] 2) The external integration circuit of the present invention greatly reduces the volume of the probe body, is more convenient for measuring the discharge arc of the micro-cathode arc thruster, and is convenient for the arrangement of the magnetic induction probe array;

[0030] 3) The present invention adopts a twisted pair structure, which can effectively reduce the induction area other than the measuring coil, effectively reduce electromagnetic interference and noise, and increase the accuracy of measurement;

[0031] 4) The magnetic induction probe array structure of the present invention can effectively obtain the spatial distribution and spatial variation of the magnetic field intensity generated by the discharge arc during the discharge process of the micro cathode arc thruster;

[0032] 5) The magnetic induction probe array structure of the present invention, by using a plurality of evenly arranged magnetic induction probes, can clearly distinguish the magnetic field intensity generated by the high-speed discharge arc at different times through the waveform phase of each magnetic induction probe;

[0033] 6) The magnetic induction probe array structure of the present invention, by using multiple magnetic induction probes distributed in a ring, can accurately capture the transient changes in the magnetic field strength generated during the rotation of the discharge arc, which is beneficial for measuring micro-cathode arc thrusters with different discharge arc positions and arc rotation angles for each discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the structure of a single magnetic induction probe in the magnetic induction probe array of the present invention.

[0035] Figure 2 It is a schematic diagram of the structure of the magnetic induction probe array of the present invention.

[0036] Figure 3 It is a schematic diagram of the external circuit of the present invention.

[0037] Figure 4 It is a schematic diagram of the measurement principle of the magnetic induction probe array structure of the present invention.

[0038] Figure 5 It is a schematic diagram of the measurement curve of the magnetic induction probe array structure of the present invention. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with 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 do not have any limiting effect on the present invention.

[0040] 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 micro-cathode arc thruster of the present invention includes: a quartz shell 11, a measuring coil 12, a polytetrafluoroethylene sleeve 13, a probe base 14, and a welding pad 15. The quartz shell 11 is a hollow semi-closed structure, that is, one end is closed and the other end is open; 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, and the open end of the quartz shell is placed within an open end of the probe base, and the polytetrafluoroethylene sleeve 13 is tightly fitted on the outer periphery of the end of the opening of the quartz shell 11, and is fixedly installed on one end of the probe base 14. The outer diameter of the polytetrafluoroethylene sleeve 13 is tightly fitted with the positioning step of the probe base 14, and is fixedly connected to the probe base 14 together with the quartz shell 11. As shown Figure 1 As shown, the quartz housing 11 is preferably cylindrical, and integrally forms a coaxial channel with the probe base 14 which is also preferably cylindrical. Further, the inner surface of the quartz housing 11 is flush with the inner surface of the probe base 14.

[0041] In this example, the measuring coil 12 is located at the closed end of the quartz housing 11, and two signal lines are led out from the side of the measuring coil 12 close to the open end of the quartz housing 11, which are welded to the pad 15 located inside the probe base 14, and the external circuit is led out through the pad 15 and the other end of the probe base 14. There are two pads, which are respectively connected to the two signal lines. Similarly, there are two connecting lines for connecting to the external circuit.

[0042] As a feasible implementation, the two lead wires of the coil 12 may be directly connected to the external circuit without providing the pad. Alternatively, an insulating material may be provided outside the pad 15 so that the pad 15 can be fixed to a fixed component, such as the probe base 14.

[0043] In addition, those skilled in the art know that the above materials are only examples and are not required. For example, the housing and the sleeve may also be made of other suitable materials.

[0044] like Figure 3 As shown, an RC integrator is connected to the external circuit, and the RC integrator is used to realize the integration of the induced current, so that the induced electromotive force after integration has a linear positive 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 primary ignition of the micro-cathode arc thruster.

[0045] The induced magnetic field strength B generated by the current density j at the measuring position of the magnetic induction probe on the measuring coil 12 follows the Ampere loop law. The current density and magnetic field strength generated by the discharge arc of the micro cathode arc thruster are obtained according to the following formulas (1) and (2):

[0046]

[0047]

[0048] Where μ0 is the magnetic permeability of vacuum; is the curl of the magnetic field intensity; 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 induction coil 12. Therefore, from the relationship between the voltage signal of the magnetic induction probe and dB / dt, the magnetic field intensity B can be determined, and the magnetic field distribution generated by the discharge arc of the micro-cathode arc thruster can be measured during the thruster primary ignition operation.

[0049] like Figure 2 As shown, the magnetic induction probe array structure 6 of the present invention. The magnetic induction probe array structure 6 includes n magnetic induction probes. For the sake of simplicity, Figure 2Only the measuring coil 12 is shown in the figure, and the axes of all the measuring coils 12 are located in the same two-dimensional plane, and the centers of all the measuring coils 12 are equidistant from the center of the magnetic induction probe array structure 6, that is, the centers of all the measuring coils 12 are located on a circle centered on the center of the magnetic induction probe array structure 6, and the axes of all the measuring coils 12 coincide with the tangent direction of the circle, and 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 primary ignition of the micro-cathode arc thruster through the measurement value of each measuring coil 12.

[0050] 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 exit of the micro cathode arc thruster. The head structure of the micro cathode 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 circuit law, the magnetic field intensity B generated by the current I of the discharge arc is obtained by formula (3) and formula (4):

[0051] ∫ l Bdl=μ0I (3)

[0052]

[0053] Wherein, μ0 is the vacuum magnetic permeability; r is the distance between the magnetic induction probe array structure 6 and the discharge arc. During the ignition operation of the micro cathode arc thruster, the discharge arc will always rotate, and the magnitude and direction of the magnetic field intensity generated by it will also change accordingly. Therefore, when the discharge arc sweeps over the position of each measuring coil 12, a maximum induced voltage peak value will be generated in the swept measuring coil 12 at that moment, and the maximum induced voltage peak values ​​generated by different measuring coils 12 are generated at different moments.

[0054] like Figure 5 As shown, it is the induced voltage waveform diagram generated when the discharge arc sweeps through the 1st to nth coils. According to the induced voltage waveform diagram: the magnetic field strength generated when the discharge arc rotates to a certain measuring coil 12 can be determined by the induced voltage peak value; the time required for the discharge arc to rotate from one measuring coil 12 to the next measuring coil 12 can be obtained by the time difference between each two peak values, thereby determining the average rotation speed of the discharge arc in this interval.

[0055] In particular, although the RC integrator is part of the circuit, it is located outside the magnetic induction probe, which reduces the volume of the probe body.

[0056] In particular, the measuring coil 12 and the signal wire led out thereof are made of yarn-covered wire, which can realize the signal transmission of the induced current.

[0057] In particular, the signal line of the measuring coil 12 and the external circuit line are twisted wire structures.

[0058] In some embodiments, the outer diameter of the quartz housing 11 is 5 mm.

[0059] In some embodiments, the coil skeleton diameter of the measuring coil 12 is 1.5 mm, the yarn-wrapped wire used is 0.07 mm in diameter, 14 strands are twisted, 398 turns are wound, and there is no ferromagnetic material inside.

[0060] In some embodiments, the probe base 14 may be made of a stainless steel material.

[0061] In some embodiments, the magnetic induction probe array structure 6 includes four magnetic induction probes.

[0062] For those skilled in the art, several modifications and improvements can be made to the embodiments of the present invention without departing from the inventive concept of the present application, and all of these belong to the protection scope of the present application.

Claims

1. A planar magnetic induction probe array for measuring the arc rotation angular velocity of a micro cathode arc thruster, characterized in that: include: A plurality of magnetic induction probes, each of which comprises a housing and a measuring coil (12); The shell is a hollow semi-enclosed structure; the measuring coil (12) is located inside the shell, and the axis of the measuring coil (12) is parallel to the axis of the shell; The axes of all the measuring coils (12) are located in the same two-dimensional plane, and the centers of all the measuring coils (12) are equidistant from the center of the magnetic induction probe array structure, that is, the centers of all the measuring coils (12) are 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, and 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 primary ignition operation of the micro-cathode arc thruster through the measurement value of each measuring coil (12).

2. The planar magnetic induction probe array for measuring arc rotation angular velocity of a micro cathode arc thruster according to claim 1, characterized in that: The process of obtaining the magnetic field distribution generated by the discharge arc of the thruster during the primary ignition of the micro-cathode arc thruster is as follows: The induced magnetic field strength B generated by the current density j at the measuring position of the magnetic induction probe on the measuring coil (12) follows the Ampere loop law. The current density and magnetic field strength generated by the discharge arc of the micro cathode arc thruster are obtained according to the following formulas (1) and (2): Where μ0 is the magnetic permeability of vacuum; 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 induction coil (12).

3. The planar magnetic induction probe array for measuring arc rotation angular velocity of a micro cathode arc thruster according to claim 1 or 2, characterized in that: The housing is a quartz housing (11), and / or the outer diameter of the housing is 4-5 mm; and / or the measuring coil (12) is located at the closed end of the housing.

4. The planar magnetic induction probe array for measuring arc rotation angular velocity of a micro cathode arc thruster according to claim 1 or 2, characterized in that: It also comprises a polytetrafluoroethylene sleeve (13) and a probe base (14); the polytetrafluoroethylene sleeve (13) is tightly fitted on the outer periphery of the open end of the quartz housing (11) and is fixedly mounted on one end of the probe base (14); the probe base (14) is a hollow structure.

5. The planar magnetic induction probe array for measuring arc rotation angular velocity of a micro cathode arc thruster according to claim 4, characterized in that: The signal line led out of the measuring coil (12) is connected to an external circuit, and 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 positive proportional relationship with the magnetic field intensity, so as to obtain the time distribution of the magnetic field generated by the discharge arc during the primary ignition operation of the micro cathode arc thruster.

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

7. The planar magnetic induction probe array for measuring arc rotation angular velocity of a micro cathode arc thruster according to claim 5, characterized in that: The RC integration circuit is located outside the magnetic induction probe.

8. The planar magnetic induction probe array for measuring arc rotation angular velocity of a micro cathode arc thruster according to claim 4, characterized in that: The probe base (14) is made of stainless steel.

9. The planar magnetic induction probe array for measuring arc rotation angular velocity of a micro cathode arc thruster according to claim 1 or 2, characterized in that: The magnetic induction probe array structure comprises 3-6 magnetic induction probes.

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

Images