Method and apparatus for measuring the charge of particles in a plasma

Abstract

The application relates to the technical field of particle detection with points, and particularly relates to a method and device for measuring the charge of particles in plasma, which specifically comprises a Faraday cup device structure design with a storage bin and a controllable particle dropping device to solve the problem that the traditional measurement method is difficult to measure the charge of a single large particle. The Faraday cup device with a storage bin comprises a metal charge collector, a collector base, a base storage bin, a shielding shell, a shielding cover, a drift tube, an insulating base, an insulating top cover, a magnet and a magnet fixing device; the controllable particle dropping device comprises a main body back, a main body right, a main body left, a push-pull electromagnet and a screw. The application provides a method and device for measuring the charge of particles in plasma, solves the problems that the capacity of a Faraday cup collector is small, the charge of multiple particles cannot be measured, a large number of particles simultaneously enter the Faraday cup, and signals cannot be distinguished, etc.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of charged particle detection, and particularly relates to a method and device for measuring the charge of particles in plasma. BACKGROUND

[0002] Plasma environment is very common in the field of aerospace, and common plasma environments include but are not limited to the ionosphere of the earth, solar wind, thruster plume, etc. In various ground experimental systems, in order to simulate the cosmic environment, various plasma environments are also created, or a large amount of plasma is generated in the experimental environment when conducting thruster experiments. Objects in the plasma environment will be charged due to the influence of the plasma, and the charging of these objects may have various influences. The equipment and instruments in the plasma environment can eliminate the influence of charge accumulation through grounding, but small particles such as debris in the earth's orbit, dust and micro-meteors widely existing in the cosmic space, etc. are easy to be charged for a long time, and then bring greater harm to the objects they contact or collide with. Therefore, it is necessary to measure the charging of various particles in the plasma environment.

[0003] Faraday cup devices are commonly used to measure plasma beam current, and are a relatively common and general plasma diagnostic method. Faraday cups can be used in many analytical instruments that need to detect ions or electrons, such as mass spectrometers. Faraday cups are not as sensitive as other charged particle detectors such as electron multipliers and microchannel plates. However, Faraday cups can obtain accurate charge quantities through current and charge conversion. They are often used together, with Faraday cups used to detect strong signals and electron multipliers or microchannel plates used to detect small signals. In addition, Faraday cups can also be designed in the form of a retarding field analyzer (RFA) to measure the intensity and energy distribution of ion beams. However, due to the larger size of the particles and the discontinuous inflow, the traditional Faraday cup device cannot effectively measure the charging of the particles. In addition, the existing device is not easy to control the particles to enter the Faraday cup one by one, so it is difficult to measure the charging of individual particles, and it is difficult to analyze the relationship between the charging of the particles and the parameters of the plasma environment they are in, as well as their particle size and shape. At the same time, compared with continuous and large ion beam current, the charging of individual particles is smaller, and the signal processing method of the traditional Faraday cup cannot measure such small charge quantities. SUMMARY

[0004] To solve the above problems, the embodiment of the present application provides a method and device for measuring the charge of particles in plasma, which specifically comprises a Faraday cup device structure design with a storage bin and a controllable particle dropping device to solve the problem that it is difficult to measure the charge of a single large particle in the traditional measurement method.

[0005] The technical scheme of the present application is as follows:

[0006] A Faraday cup device with a storage bin comprises a metal charge collector, a collector base, a base storage bin, a shielding shell, a shielding cover, a drift tube, an insulating base, an insulating top cover, a magnet, and a magnet fixing device.

[0007] The metal charge collector is placed in the collector base and positioned by a positioner and a positioning hole. The collector base is coaxially placed on the base storage bin and fixedly connected to the base storage bin. The collector base and the base storage bin are placed in the shielding shell and the shielding cover. The shielding shell and the shielding cover form a complete shielding layer. The shielding cover is centrally provided with a through hole with a diameter of 2-3 times that of the measured particle (for example, a 4-6 mm diameter slot for a 2 mm diameter particle) to allow the particle to pass through. The shielding layer is placed in the insulating base and the insulating top cover. The insulating base and the insulating top cover form a complete insulating layer. The insulating top cover is centrally provided with a through hole with a diameter of 2-3 times that of the measured particle (for example, a 4-6 mm diameter slot for a 2 mm diameter particle) to allow the particle to pass through. The drift tube is coaxially placed in the through hole in the center of the insulating top cover. The magnet is fixed in the magnet fixing device. The magnet fixing device is fixed around the insulating top cover to generate a magnetic field to shield the plasma.

[0008] Further, the metal charge collector can be a conductive and non-magnetic metal such as red copper, brass, silver, etc. The lowest part is provided with a through hole with a diameter of 2-3 times that of the measured particle (for example, a 4-6 mm diameter slot for a 2 mm diameter particle) to allow the particle to pass through, and the bottom is slotted to weld a lead wire.

[0009] Further, the shielding shell and the shielding cover and the drift tube can be a conductive and non-magnetic metal such as red copper, brass, silver, etc.

[0010] Further, the collector base, the base storage bin, the insulating base, and the insulating top cover can be an insulating material with certain strength and high temperature resistance such as epoxy resin and polycarbonate.

[0011] Further, the magnet fixing device can be a conductive and non-magnetic metal such as red copper, brass, silver, etc., or an insulating material with certain strength and high temperature resistance such as epoxy resin and polycarbonate.

[0012] Further, the magnet can be a permanent magnet of various materials such as a neodymium iron boron magnet and an aluminum nickel cobalt magnet, or an electromagnet with appropriate number of turns.

[0013] A controllable particle falling device, comprising a main body back, a main body right, a main body left, a push-pull electromagnet, and a screw;

[0014] The main body back has a middle opening for fixing the screw, the main body right is fixed to the main body back by a screw, the surface of the main body right is grooved, the groove depth and width are matched with the particle size, for example, the groove diameter is 2.4 mm for a 2 mm diameter particle, the main body left is a polycarbonate transparent plate, which is fixed to the main body right by a screw, the rated voltage of the push-pull electromagnet is 12 V, and the screw is fixed to the front end of the push-pull electromagnet and has a vertical small hole in the front end for particle passing.

[0015] Further, the main body right and the main body back can use any material with certain strength and high temperature resistance;

[0016] Further, the main body left can use any transparent material with certain strength and high temperature resistance;

[0017] Further, the rated voltage of the push-pull electromagnet can be selected according to the output voltage range of the power supply;

[0018] Further, the thickness of the screw and the diameter of the small hole in the front end should correspond to the corresponding particle size;

[0019] The beneficial effects of the present application are:

[0020] (1) The design of the Faraday cup with a storage bin solves the problem of small capacity of the Faraday cup collector, which cannot measure the charge of multiple particles.

[0021] (2) The design of the magnet fixing device, the magnet and the drift tube can shield the plasma into the Faraday cup, solving the problem that the plasma beam will enter the Faraday cup and cannot capture the charge of the particles.

[0022] (3) The design of the drift tube can change the sheath structure in the channel by adding a bias voltage, solving the problem of change of the charge of the particles entering the sheath when passing through the channel.

[0023] (4) The controllable particle falling device can control the single falling of particles of different sizes, solving the problem that a large number of particles enter the Faraday cup at the same time and the signal cannot be distinguished.

[0024] (5) The controllable particle falling device can control the single falling of particles by the push-pull electromagnet, solving the problem that the device cannot be manually controlled in the laboratory.

[0025] (6) The design of using a charge-sensitive amplifier after the Faraday cup can measure small charges, solving the problem that the traditional Faraday cup cannot measure small charges. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Structure diagram of the Faraday cup device with storage for the embodiment of the present application;

[0027] Figure 2 Structure diagram of the controllable particle dropping device for the embodiment of the present application;

[0028] Figure 3 System diagram of the method and device for measuring the charged quantity of particles in plasma for the embodiment of the present application;

[0029] Figure 4 A typical signal curve diagram for the embodiment of the present application;

[0030] Figure 5 Diagram of the relationship between the charged quantity of particles and the particle size in a plasma environment for the embodiment of the present application;

[0031] 1 - metal charge collector, 2 - collector base, 3 - base storage, 4 - shield shell, 5 - shield cover, 6 - drift tube, 7 - insulating base, 8 - insulating top cover, 9 - magnet, 10 - magnet fixing device, 11 - main body back, 12 - particle track, 13 - main body right, 14 - screw, 15 push-pull electromagnet fixing hole, 16 - controllable particle dropping device, 17 - plasma source, 18 - Faraday cup device with storage DETAILED DESCRIPTION

[0032] In order for those skilled in the art to better understand the technical solutions in the patent application of the present application, the technical solutions in the present application will be clearly and completely described below in combination with the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0033] Embodiment 1:

[0034] Figure 1The structure diagram of the Faraday cup device with storage bin of the embodiment of the present application is shown in the figure. The bottom surface of the bowl-shaped metal charge collector 1 is inclined. The bottom corner is provided with a through hole slightly larger than the diameter of the measured particles for the particles to enter the storage bin. The bottom is provided with a slot for signal line welding. The collector base 2 and the base storage bin 3 are integrated structures for fixing and supporting the metal charge collector. The base storage bin 3 is used for collecting the entering particles. The shielding shell 4 and the shielding cover 5 form a complete shielding layer ground. The principle of Faraday cage is used to prevent the signal of the metal charge collector 1 from being disturbed by the outside world. The insulating base 7 and the insulating top cover 8 form a complete insulating support, which serves as the shell of the entire Faraday cup. The drift tube 6 is placed on the insulating top cover 8 and is used for plasma shielding and changing the thickness of the sheath to reduce the influence on the charging amount of the particles. The magnet 9 is installed in the magnet fixing device 10, which is fixed around the insulating top cover 8. The magnet 9 generates a magnetic field in the shielding tube to shield the plasma. The charged particles enter the Faraday cup through the drift tube, and the rest of the plasma is shielded to achieve the purpose of measuring the charging amount of the particles in the plasma environment.

[0035] Figure 2 The structure diagram of the controllable particle dropping device of the embodiment of the present application is shown in the figure. The main body back 11, the main body left and the main body right 13 form a complete main body. The main body right 13 is provided with a slot 12 for storing and passing particles and controlling the particle size. The front end of the screw 14 is provided with a vertical hole for controlling the passing of single particles. The rear end is provided with a horizontal threaded hole connected with the push-pull electromagnet. The push-pull electromagnet is fixed with the main body back 11 through the fixing hole 15. The on-off of the push-pull electromagnet can control the single and sequential dropping of the particles.

[0036] Embodiment 2:

[0037] Figure 3 The system diagram of the method and device for measuring the charging amount of particles in plasma of the embodiment of the present application is shown in the figure. The controllable particle dropping device 16 controls the single and sequential dropping of particles of different sizes through a plasma region. The plasma region is provided by different plasma sources 17, including but not limited to hot tungsten wire, hollow cathode, various ion sources and electric thruster, etc. After passing through the plasma region, the particles enter the Faraday cup device 18 with storage bin, are collected by the metal charge collector 1 and are transmitted to the subsequent signal processing circuit. The signal processing circuit mainly includes a charge sensitive amplifier and a filter. The main purpose is to amplify the charge of the order of C to a voltage signal of several tens of millivolts to several volts which is easy to measure and has a good signal-to-noise ratio, and to eliminate the 50 Hz power frequency interference generated by the electric appliance. -13

[0038] ​Moreover, the foregoing description of the implementations has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Many modifications and variations are possible in light of the disclosure. It is intended that the scope of the implementations be limited not by this detailed description, but rather by the claims appended hereto. Moreover, the described implementations can be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the implementations. The embodiments described herein have been chosen and described in order to explain the principles of the implementations and the practical application and to enable others skilled in the art to understand for various implementations with various modifications as are suited to the particular use contemplated. Accordingly, the description is not intended to limit the scope of the claims.

[0039] The foregoing description of the implementations has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Many modifications and variations are possible in light of the disclosure. It is intended that the scope of the disclosure be limited not by this detailed description, but rather by the claims appended hereto. Moreover, the described implementations can be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the implementations. The embodiments described herein have been chosen and described in order to explain the principles of the implementations and the practical application and to enable others skilled in the art to understand for various implementations with various modifications as are suited to the particular use contemplated. Accordingly, the description is not intended to limit the scope of the claims. The implementations described herein can be implemented in electronic hardware, computer software, or any combination thereof. Any feature described herein can be implemented in electronic hardware, computer software, or any combination thereof.

Claims

1. A method and apparatus for measuring the amount of charge on particles in a plasma, comprising a Faraday cup apparatus with a storage bin design and a controllable particle drop apparatus; wherein the Faraday cup apparatus with a storage bin design comprises: Metal charge collector (1), collector base (2), base storage (3), shield shell (4), shield cover (5), drift tube (6), insulating base (7), insulating top cover (8), magnet (9), magnet fixing device (10); A controllable particle falling device, including body back (11), body right (13), body left, push-pull electromagnet, screw (14); The metal charge collector (1) is placed in the collector base (2) and positioned by the positioner and the positioning hole. The collector base (2) is coaxially placed on the base storage (3) and adhesively fixed with the base storage (3). The collector base (2) and the base storage (3) are placed in the shield shell (4) and the shield cover (5). The shield shell (4) and the shield cover (5) form a complete shielding layer. The shield cover (5) is centrally provided with a through hole with a diameter of 2-3 times the diameter of the measured particles (for example, a 4-6 mm diameter slot for a 2 mm diameter particle) to allow the particles to pass through. The shielding layer is placed in the insulating base (7) and the insulating top cover (8). The insulating base (7) and the insulating top cover (8) form a complete insulating layer. The insulating top cover (8) is centrally provided with a through hole with a diameter of 2-3 times the diameter of the measured particles (for example, a 4-6 mm diameter slot for a 2 mm diameter particle) to allow the particles to pass through. The drift tube (6) is coaxially placed in the through hole in the center of the insulating top cover (8). The magnet (9) is fixed in the magnet fixing device (10). The magnet fixing device (10) is fixed around the insulating top cover (8) to generate a magnetic field to shield the plasma. The body back (11) is centrally provided with a screw hole as a fixed screw fixing point. The body right (13) and the body back are fixed with screws. The surface of the body right (13) is provided with a slot (12) with a depth and width suitable for the size of the particles passing through. For example, a 2.4 mm diameter slot for a 2 mm diameter particle. The body left is a transparent acrylic plate fixed with screws with the body right (13). The rated voltage of the push-pull electromagnet is 12V, which is fixed on the body back (11). The screw (14) is fixed at the front end of the push-pull electromagnet and the front end is provided with a vertical small hole for the particles to pass through.

2. A Faraday cup device structure design with a storage bin as claimed in claim 1, characterized in that, The metal charge collector can be easy to conduct electricity and non-magnetic metal such as red copper, brass, silver, etc. The lowest part is provided with a through hole slightly larger than the diameter of the measured particles for the particles to pass through, and the bottom is provided with a slot for welding a wire.

3. A Faraday cup device structure design with a storage bin as claimed in claim 1, characterized in that, The shield shell and the shield cover and the drift tube can be easy to conduct electricity and non-magnetic metal such as red copper, brass, silver, etc.

4. A Faraday cup device structure design with a storage bin as claimed in claim 1, characterized in that, The collector base, base storage, insulating base, and insulating top cover can be insulating materials with certain strength and high temperature resistance such as epoxy resin and acrylic.

5. A Faraday cup device structure design with a storage bin as claimed in claim 1, characterized in that, The magnet fixing device can be easy to conduct electricity and non-magnetic metal such as red copper, brass, silver, etc., or insulating materials with certain strength and high temperature resistance such as epoxy resin and acrylic.

6. A Faraday cup device structure design with a storage bin as claimed in claim 1, characterized in that, The magnet can be a permanent magnet of various materials such as neodymium iron boron magnet, aluminum nickel cobalt magnet, etc., or an electromagnet with appropriate number of turns.

7. A controllable particle drop device as claimed in claim 1, characterized in that The body right and the body back can use any material with certain strength and high temperature resistance.

8. A controllable particle drop device as claimed in claim 1, characterized in that The body left can use any transparent material with certain strength and high temperature resistance.

9. A controllable particle drop-off device as claimed in claim 1, characterized in that The rated voltage of the push-pull magnet can be selected according to the output voltage range of the power supply.

10. A controllable particle drop device as claimed in claim 1, characterized in that The screw thickness and the front-end small hole diameter should correspond to the corresponding particle diameter size.

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