A helicon plasma discharge device based on permanent magnets

Abstract

The application discloses a spiral wave plasma discharge device based on permanent magnet, which comprises a gas source, a radio frequency power supply system, a gas inlet pipeline, a flow regulating valve, a discharge tube, a spiral wave antenna, a permanent magnet, a ring-shaped permanent magnet support, a vacuum discharge chamber and a vacuum pump. The radio frequency power supply is connected with an impedance matching device; the impedance matching device is connected with the antenna; the spiral wave antenna passes through the discharge tube; the discharge tube passes through the ring-shaped permanent magnet support and is supported at the front end and connected with the gas inlet pipeline at the tail end; the permanent magnet is clamped by the specially designed ring-shaped permanent magnet support and generates an adjustable axial magnetic field. The permanent magnet has the advantages of no need of power and cooling system, small volume, low energy consumption and no heat production, effectively reduces the volume and cost of the equipment and is beneficial to the development of compact spiral wave plasma discharge device. The system selects the permanent magnet to generate a magnetic field and can realize the excitation of high-density spiral wave plasma.

Description

Technical Field

[0001] This invention belongs to the fields of material surface treatment, thermonuclear fusion and space electric propulsion, and specifically relates to a spiral wave plasma discharge device based on a permanent magnet. Background Technology

[0002] Helical waves are a type of bounded whistle wave that can generate high-density plasmas with low electron temperatures under a wide range of flexible external conditions. Compared to electron cyclotron resonance plasmas, helical wave plasmas have lower requirements for magnetic fields and show promising and broad application prospects in thin film deposition, etching, space particle acceleration, and plasma propulsion.

[0003] Generating helical wave plasma requires a magnetic field, which can be achieved using copper coil electromagnets, permanent magnets, or superconducting magnets. Currently, most helical wave devices employ electromagnets with copper coils, where the magnetic field can be controlled by adjusting the current. However, this generates significant heat, necessitating a cooling system and resulting in high design costs. Superconducting coils generate no heat, are small in size and lightweight, and produce high magnetic field strength, but require cryogenic facilities, making their implementation technically challenging. Permanent magnets, on the other hand, require no electricity or cooling system, are small in size, consume little energy, and generate no heat. Using permanent magnets to generate the magnetic field effectively reduces the size and cost of the equipment, facilitating the development of compact helical wave plasma discharge devices.

[0004] Permanent magnets have a large surface magnetic field and very strong magnetic force. During installation, it is crucial to consider how to securely fix the permanent magnet around the discharge tube to generate the magnetic field. Currently, there are no published works specifically addressing the installation of permanent magnets. This invention primarily focuses on helical wave plasma discharge devices, employing permanent magnets and designing a ring-shaped permanent magnet support for fixing them. This structure is beneficial for studying the influence of magnetic field configuration on the plasma parameters of helical wave plasma sources. Summary of the Invention

[0005] To overcome the limitation of generating magnetic fields using electromagnets in helical wave plasma discharge devices, this invention provides a helical wave plasma discharge device based on permanent magnets. The main design of this invention is a ring-shaped permanent magnet support for mounting the permanent magnet. Through a special design, the highly magnetic permanent magnet is firmly fixed, providing a magnetic field for the helical wave plasma source device. This support can generate different magnetic field configurations by increasing or decreasing the number of magnet bars according to experimental requirements, facilitating the study of the influence of different magnetic field configurations on plasma parameters.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A helical wave plasma discharge device based on a permanent magnet includes a gas source, a radio frequency power supply, an impedance matching device, an air inlet pipe, a flow regulating valve, a discharge tube, a helical wave antenna, a permanent magnet, a ring permanent magnet support, and a vacuum discharge chamber.

[0008] The radio frequency power supply is connected to an impedance matching device; the impedance matching device is connected to a spiral wave antenna; the spiral wave antenna passes through a discharge tube and then through a ring-shaped permanent magnet support; the discharge tube passes through the ring-shaped permanent magnet support, with its front end connected to an air inlet and its rear end connected to a vacuum discharge chamber; the permanent magnet is held in place by the ring-shaped permanent magnet support, generating an axial magnetic field; the gas source is connected to a flow regulating valve through an air inlet pipe; the flow regulating valve controls the air inlet flow rate, and the discharge working medium enters the discharge tube through the air inlet pipe, forming a high-density spiral wave plasma under the action of the magnetic field generated by the spiral wave antenna and the permanent magnet.

[0009] Furthermore, the spiral wave plasma discharge device relies on a radio frequency power supply to excite the plasma, and the frequency of the radio frequency power supply is 13.56 MHz.

[0010] Furthermore, it also includes a vacuum pump, which consists of a backstage mechanical pump and a backstage molecular pump.

[0011] Furthermore, the gas supplied by the gas source is air or an inert gas.

[0012] Furthermore, different magnetic field configurations can be generated by increasing or decreasing the number of permanent magnets.

[0013] Furthermore, the annular permanent magnet support is composed of four pieces of 316 stainless steel, connected by a threaded rod in the middle. Two pieces of 316 stainless steel are made into stainless steel rings with an inner diameter of 52 mm, an outer diameter of 182 mm, and a thickness of 15 mm. Rectangular grooves with a length of 30 mm, a width of 15 mm, and a depth of 38 mm are opened at both ends of the stainless steel rings to hold the permanent magnets. The remaining ungrooved areas have eight first M6 threaded holes with a radial depth of 15 mm. Four symmetrical 12.4 mm through holes are opened on the surface of the stainless steel rings. The surfaces of the other two 316 stainless steel rings have four symmetrical M8 threaded holes. Each stainless steel ring has an annular stainless steel component with an inner diameter of 182 mm, an outer diameter of 212 mm, and a thickness of 14 mm. The surface of the annular stainless steel component has 16 second M6 threaded holes, eight of which are used to clamp the permanent magnets, and eight are used to connect to the inner stainless steel rings. An insulating sleeve is fitted onto the threaded rod between the two middle stainless steel rings to prevent connection with the helical wave antenna.

[0014] Furthermore, the permanent magnet is surrounded by stainless steel to fix it in place, and the two permanent magnets are stacked one on top of the other; the N pole of one permanent magnet is placed outwards, and the S pole of the other permanent magnet is placed outwards.

[0015] Furthermore, the permanent magnet uses neodymium iron boron material.

[0016] Beneficial effects:

[0017] This invention employs a permanent magnet scheme to provide the magnetic field in helical wave discharge. The advantages of this scheme are: the structure can be easily modified by increasing or decreasing the number of magnets to generate different magnetic field configurations according to experimental requirements, which is beneficial for studying the influence of magnetic field configurations on the plasma parameters of helical wave plasma sources. Furthermore, using permanent magnets to provide the magnetic field eliminates the need for electricity and cooling systems, resulting in smaller size, lower energy consumption, and no heat generation. Using permanent magnets to generate the magnetic field effectively reduces the size and cost of the equipment, facilitating the development of compact helical wave plasma discharge devices. Since permanent magnets have a large surface magnetic field and very strong magnetic force, this paper focuses on designing a structure for fixing the permanent magnets. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a spiral wave plasma discharge device based on a permanent magnet according to the present invention.

[0019] Figure 2 This is a schematic diagram of the annular permanent magnet support structure of a helical wave plasma discharge device based on a permanent magnet according to the present invention.

[0020] Figure 1 In the middle: 1-RF power supply, 2-impedance matching device, 3-gas source, 4-flow regulating valve, 5-discharge tube, 6-helical wave antenna, 7-ring permanent magnet support, 8-permanent magnet, 9-vacuum discharge chamber.

[0021] Figure 2 In the middle: 8-permanent magnet, 10-cubic groove, 11-first M6 threaded hole, 12-through hole, 13-M8 threaded hole, 14-ring stainless steel component, 15-second M6 threaded hole, 16-threaded rod, 17-stainless steel ring. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] like Figure 1As shown, a helical wave plasma discharge device based on a permanent magnet according to the present invention includes a radio frequency power supply 1, an impedance matching device 2, a gas source 3, a flow regulating valve 4, a discharge tube 5, a helical wave antenna 6, a ring permanent magnet support 7, a permanent magnet 8, a vacuum discharge chamber 9, and a vacuum pump. The radio frequency power supply 1 is connected to the impedance matching device 2; the impedance matching device 2 is connected to the helical wave antenna 6; the helical wave antenna 6 passes through the discharge tube 5; the discharge tube 5 passes through the ring permanent magnet support 7, with its front end connected to the air inlet and its rear end connected to the vacuum discharge chamber 9; the permanent magnet 8 is held in place by the ring permanent magnet support 7, generating an axial magnetic field; the gas source 3 is connected to the flow regulating valve 4 through an air inlet pipe; the flow regulating valve 4 controls the air inlet flow rate, and the discharge working medium enters the discharge tube 5 through the air inlet pipe, forming a high-density helical wave plasma under the action of the magnetic field generated by the helical wave antenna 6 and the permanent magnet 8.

[0024] A radio frequency power supply 1 with a frequency of 13.56 MHz is connected to an impedance matching device 2. The impedance matching device is adjusted to make the reflected power 0, thereby coupling the radio frequency power into the plasma.

[0025] The spiral wave antenna 6 passes through the discharge tube 5 and then through the stainless steel annular permanent magnet support 7.

[0026] The front end of the discharge device is connected to a gas source to introduce inert gas and control the gas pressure at about 1 Pa. The rear end is connected to a vacuum discharge chamber 9.

[0027] A vacuum pump is a gas transfer pump used to improve, generate, and maintain a vacuum, and to maintain the pressure required in a sealed space. The vacuum pump evacuates the background gas pressure to... pa.

[0028] The permanent magnet 8 provides the magnetic field strength required for helical wave discharge.

[0029] like Figure 2As shown, the permanent magnet 8 is held in place by a ring-shaped permanent magnet bracket 7, generating an axial magnetic field. The ring-shaped permanent magnet bracket 7 can generate different magnetic field configurations by increasing or decreasing the number of permanent magnets according to experimental requirements, facilitating the study of the influence of different magnetic field configurations on plasma parameters. The ring-shaped permanent magnet bracket 7 consists of four pieces of 316 stainless steel connected by a threaded rod 16. Two of the 316 stainless steel pieces are made into stainless steel rings 17 with an inner diameter of 52 mm, an outer diameter of 182 mm, and a thickness of 15 mm. Each stainless steel ring 17 has a cuboid groove 10 with a length of 30 mm, a width of 15 mm, and a depth of 38 mm at both ends of its diameter for holding the permanent magnet 8. The remaining ungrooved areas have eight first M6 threaded holes 11 with a depth of 15 mm along the radial direction. The surface of the stainless steel rings 17 has four symmetrical 12.4 mm through holes 12. The other two 316 stainless steel rings differ from the aforementioned two only in that their surfaces have four symmetrical M8 threaded holes 13. Each stainless steel ring 17 has an outer ring stainless steel component 14 with an inner diameter of 182 mm, an outer diameter of 212 mm, and a thickness of 14 mm. The surface of the ring stainless steel component 14 has 16 second M6 threaded holes 15, 8 of which are used to clamp the permanent magnet 8, and 8 are used to connect to the inner stainless steel ring 17. An insulating sleeve is fitted onto the threaded rod 16 between the two middle stainless steel rings 17 to prevent contact with the helical wave antenna 6.

[0030] The discharge device uses permanent magnets 8 to provide the magnetic field, eliminating the need for electromagnets, making it easy to disassemble and change the configuration of the magnetic field. The specifications of each permanent magnet 8 are as follows: The magnetized surface is on the NS surface. The permanent magnet 8 is surrounded by stainless steel, and two permanent magnets 8 are stacked one on top of the other. The permanent magnet on one side of the discharge device has its N pole facing outward, and the permanent magnet on the other side has its S pole facing outward.

[0031] This invention uses permanent magnets to generate a magnetic field, thereby achieving the excitation of high-density spiral wave plasma.

[0032] The specific embodiments described above provide a further detailed explanation of the technical solution of the present invention. Any modifications or substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A permanent magnet based helicon plasma discharge device, characterized by, The spiral wave plasma discharge device comprises a gas source, a radio frequency power source, an impedance matcher, an air inlet pipeline, a flow regulating valve, a discharge tube, a spiral wave antenna, a permanent magnet, a ring-shaped permanent magnet support, and a vacuum discharge chamber. The radio frequency power source is connected with the impedance matcher, the impedance matcher is connected with the spiral wave antenna, the spiral wave antenna passes through the discharge tube and the ring-shaped permanent magnet support, the discharge tube passes through the ring-shaped permanent magnet support, the front end of the discharge tube is connected with the air inlet, and the tail end of the discharge tube is connected with the vacuum discharge chamber; the permanent magnet is clamped by the ring-shaped permanent magnet support to generate an axial magnetic field; the gas source is connected with the flow regulating valve through the air inlet pipeline; the flow regulating valve controls the air inlet flow, and the discharge medium enters the discharge tube through the air inlet pipeline to form high-density spiral wave plasma under the action of the magnetic field generated by the spiral wave antenna and the permanent magnet. The ring-shaped permanent magnet support is composed of four 316 stainless steel parts; two of the 316 stainless steel parts are used to manufacture a stainless steel ring with an inner diameter of 52 mm, an outer diameter of 182 mm, and a thickness of 15 mm, and a cuboid groove with a length of 30 mm, a width of 15 mm, and a depth of 38 mm is formed on the two ends of the diameter of the stainless steel ring to place the permanent magnet; the remaining part without the groove is provided with eight first M6 threaded holes with a depth of 15 mm along the radial direction; four through holes with a diameter of 12.4 mm are symmetrically formed on the surface of the stainless steel ring; the surfaces of the other two 316 stainless steel parts are provided with four symmetric M8 threaded holes; each of the stainless steel rings is provided with an annular stainless steel part with an inner diameter of 182 mm, an outer diameter of 212 mm, and a thickness of 14 mm; the surface of the annular stainless steel part is provided with 16 second M6 threaded holes, eight of which are used to press the permanent magnet, and the other eight are used to connect the inner stainless steel rings; the two middle stainless steel rings are connected by a threaded rod; the threaded rod between the two middle stainless steel rings is provided with an insulating sleeve to avoid being connected with the spiral wave antenna.

2. A permanent magnet based helicon plasma discharge apparatus as claimed in claim 1, characterized in that: The spiral wave plasma discharge device is excited by the radio frequency power source, and the frequency of the radio frequency power source is 13.56 MHz.

3. A permanent magnet based helicon plasma discharge apparatus as claimed in claim 1, wherein: The spiral wave plasma discharge device further comprises a vacuum pump composed of a front-stage mechanical pump and a rear-stage molecular pump.

4. A permanent magnet based helicon plasma discharge apparatus as claimed in claim 1, wherein: The gas source is connected with air or inert gas.

5. A permanent magnet based helicon plasma discharge apparatus as claimed in claim 1, wherein: Different magnetic field patterns are generated by increasing or decreasing the number of permanent magnets.

6. A permanent magnet based helicon plasma discharge apparatus as claimed in claim 1, wherein: The periphery of the permanent magnet is surrounded by stainless steel to fix the magnet, and the two permanent magnets are stacked from top to bottom; the magnetic pole N of the permanent magnet on one side is placed outward, and the magnetic pole S of the permanent magnet on the other side is placed outward.

7. A permanent magnet based helicon plasma discharge apparatus as claimed in claim 1, wherein: The permanent magnet is made of neodymium iron boron material.

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