CN115734448A - A Helicon Wave Plasma Discharge Device Based on Permanent Magnets - Google Patents

Abstract

The invention discloses a helical wave plasma discharge device based on a permanent magnet, which includes a gas source, a radio frequency power supply system, an air intake pipe, a flow regulating valve, a discharge tube, a helical wave antenna, a permanent magnet, an annular permanent magnet bracket, a vacuum discharge chamber, vacuum pump. The RF power supply is connected to the impedance matching device; the impedance matching device is connected to the antenna; the helical wave antenna passes through the discharge tube; the discharge tube is supported through the ring permanent magnet bracket, the front end is connected to the air inlet, and the tail end is connected to the vacuum discharge chamber; the permanent magnet is used The specially designed annular permanent magnet bracket is clamped to generate an adjustable axial magnetic field. Permanent magnets have the advantages of not requiring electricity and cooling systems, small size, low energy consumption, and no heat generation, which effectively reduces the volume and cost of equipment, and is conducive to the development of compact helicon wave plasma discharge devices. The system of the invention selects a permanent magnet to generate a magnetic field, which can realize the excitation of high-density helicon wave plasma.

Description

A Helicon Wave Plasma Discharge Device Based on Permanent Magnets

technical field

The invention belongs to the fields of material surface treatment, thermonuclear fusion and space electric propulsion, and in particular relates to a permanent magnet-based helical wave plasma discharge device.

Background technique

The helicon wave is a bounded whistler wave that can obtain plasmas with high density and low electron temperature under a wide range of flexible external conditions. Compared with electron cyclotron resonance plasma, helicon wave plasma requires less magnetic field, and has good and wide application prospects in the fields of thin film deposition, etching, space particle acceleration and plasma propulsion.

The generation of helicon wave plasma requires the participation of a magnetic field. Existing methods for generating a magnetic field include copper coil electromagnets, permanent magnets or superconducting magnets. At present, most helicon wave devices use copper coils of electromagnets to control the magnetic field through current regulation, but the heat generation is severe, and a cooling system is required, which results in high design costs. The superconducting coil scheme does not generate heat, is small in size, light in weight, and generates a high magnetic field strength, but requires low-temperature facilities, making it difficult to realize the technology. The permanent magnet scheme does not require electricity and cooling systems, has the advantages of small size, low energy consumption, and no heat generation. The use of permanent magnets to generate magnetic fields effectively reduces the size and cost of equipment, and is conducive to the development of compact helicon wave plasma discharge devices.

The surface magnetic field of the permanent magnet is relatively large and has a very strong magnetic force. When installing, it must be considered how to firmly fix the permanent magnet around the discharge tube to generate a magnetic field. At present, there are no specific published works on the installation of permanent magnets. The invention mainly aims at the helical wave plasma discharge device, adopts permanent magnets, and designs an annular permanent magnet bracket for fixing the permanent magnets. This structure is beneficial to study the influence of the magnetic field configuration on the plasma parameters of the helicon wave plasma source.

Contents of the invention

In order to solve the limitation of the magnetic field generated by the electromagnet in the helicon wave plasma discharge device, the present invention provides a helicon wave plasma discharge device based on a permanent magnet. The present invention mainly designs an annular permanent magnet support for permanent magnet installation. Through special design, the permanent magnet with strong magnetic field is firmly fixed to provide magnetic field for the helicon wave plasma source device. The support bracket can generate different magnetic field patterns by increasing or decreasing the number of magnets according to experimental requirements, which is convenient for studying the influence of different magnetic field patterns on plasma parameters.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A helicon wave plasma discharge device based on a permanent magnet, including a gas source, a radio frequency power supply, an impedance matching device, an air intake pipe, a flow regulating valve, a discharge tube, a helical wave antenna, a permanent magnet, an annular permanent magnet bracket, and a vacuum discharge chamber room;

The radio frequency power supply is connected to the impedance matching device; the impedance matching device is connected to the helical wave antenna; the helical wave antenna passes through the discharge tube, and then passes through the annular permanent magnet support; the discharge tube passes through the annular permanent magnet support, and the front end is connected to the air inlet, The tail end is connected to the vacuum discharge chamber; the permanent magnet is clamped by the ring-shaped permanent magnet bracket to generate an axial magnetic field; the gas source is connected to the flow regulating valve through the intake pipe; the flow regulating valve controls the intake flow, and the discharge working medium enters through the intake pipe In the discharge tube, a high-density helicon wave plasma is formed under the action of the magnetic field generated by the helical wave antenna and the permanent magnet.

Further, the helicon wave plasma discharge device excites the plasma by radio frequency power, and the frequency of the radio frequency power is 13.56MHz.

Further, a vacuum pump is also included, and the vacuum pump is composed of a front-stage mechanical pump and a rear-stage molecular pump.

Further, the gas fed into the gas source is air or inert gas.

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

Further, the ring-shaped permanent magnet bracket is composed of 4 pieces of 316 stainless steel, the middle of which is connected by a threaded rod; 2 pieces of 316 stainless steel are made of a stainless steel ring with an inner diameter of 52mm, an outer diameter of 182mm, and a thickness of 15mm. There is a cuboid groove with a length of 30mm, a width of 15mm, and a depth of 38mm in the direction position, which is used to place the permanent magnet; the remaining positions without the groove are provided with the first M6 threaded hole with a depth of 15mm along the radial direction, a total of 8; stainless steel ring The surface is symmetrically opened with 12.4mm through holes, a total of 4; the surface of the other two stainless steel rings made of 316 stainless steel is provided with 4 symmetrical M8 threaded holes; each stainless steel ring outer ring has a circular stainless steel part, The inner diameter is 182mm, the outer diameter is 212mm, and the thickness is 14mm; there are 16 second M6 threaded holes on the surface of the annular stainless steel part, 8 of which are used to press the permanent magnet, and 8 are used to connect the inner stainless steel ring; the middle two stainless steel rings The threaded rods between are covered with insulating sleeves to avoid connecting with the helical wave antenna.

Further, the periphery of the permanent magnet is surrounded by stainless steel, which acts as a fixed magnet, and two permanent magnets are stacked up and down; 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.

Further, the permanent magnet uses NdFeB material.

Beneficial effect:

The present invention adopts the permanent magnet scheme to provide the magnetic field in the helical wave discharge. The advantage of this scheme is that the structure can easily generate different magnetic field positions by increasing or decreasing the number of magnets according to the experimental requirements, which is beneficial to the study of the magnetic field position. Effects on plasma parameters of a helicon wave plasma source. In addition, permanent magnets are used in this paper to provide magnetic fields, which do not require electricity and cooling systems, and have the advantages of small size, low energy consumption, and no heat generation. The use of permanent magnets to generate magnetic fields can effectively reduce the volume and cost of equipment, and is conducive to the development of compact helicon wave plasmas. discharge device. However, the surface magnetic field of the permanent magnet is large and has a very strong magnetic force. This paper focuses on designing a structure for fixing the permanent magnet.

Description of drawings

Fig. 1 is the structural representation of a kind of helicon wave plasma discharge device based on permanent magnet of the present invention;

Fig. 2 is a kind of annular permanent magnet support structure schematic diagram of the helicon wave plasma discharge device based on permanent magnet of the present invention;

In Figure 1: 1-RF power supply, 2-impedance matching device, 3-air source, 4-flow regulating valve, 5-discharge tube, 6-helical wave antenna, 7-ring permanent magnet bracket, 8-permanent magnet, 9 - Vacuum discharge chamber.

In Figure 2: 8-permanent magnet, 10-cuboid groove, 11-first M6 threaded hole, 12-through hole, 13-M8 threaded hole, 14-ring stainless steel part, 15-second M6 threaded hole, 16- Threaded rod, 17-stainless steel ring.

Detailed ways:

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

As shown in Fig. 1, a kind of helicon wave plasma discharge device based on permanent magnet of the present invention comprises radio frequency power source 1, impedance matcher 2, gas source 3, flow control valve 4, discharge tube 5, helical wave antenna 6, ring Permanent magnet support 7, permanent magnet 8, vacuum discharge chamber 9, vacuum pump. The RF 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 annular permanent magnet bracket 7, and the front end is connected to the air inlet, The tail end is connected to the vacuum discharge chamber 9; the permanent magnet 8 is clamped by the annular permanent magnet bracket 7 to generate an axial magnetic field; the gas source 3 is connected to the flow regulating valve 4 through the intake pipe; the flow regulating valve 4 controls the intake flow, and the discharge worker The plasma enters the discharge tube 5 through the intake pipe, and forms high-density helicon wave plasma under the action of the magnetic field generated by the helical wave antenna 6 and the permanent magnet 8 .

The RF power supply 1 with a frequency of 13.56MHz is connected to the impedance matching device 2, and the impedance matching device is adjusted to make the reflected power 0, and the RF power is coupled into the plasma.

The helical wave antenna 6 passes through the discharge tube 5 , and then passes through the stainless steel annular permanent magnet support 7 .

The front end of the discharge device is connected to a gas source to feed inert gas to control the air pressure at about 1 Pa, and the tail end is connected to a vacuum discharge chamber 9 .

Vacuum pumps are gas transfer pumps used to improve, generate and maintain vacuum and maintain the pressure required for sealed spaces. The vacuum pump pumps the background pressure down to 10 ^-4 Pa.

The permanent magnet 8 provides the required magnetic field strength for the helicon wave discharge.

As shown in FIG. 2 , the permanent magnet 8 is clamped by the annular permanent magnet bracket 7 to generate an axial magnetic field. The ring-shaped permanent magnet support 7 can generate different magnetic field patterns by increasing or decreasing the number of permanent magnets according to experimental requirements, which is convenient for studying the influence of different magnetic field patterns on plasma parameters. The annular permanent magnet support 7 is made of 4 pieces of 316 stainless steel, which are connected by threaded rods 16 in the middle. Wherein 2 pieces of 316 stainless steel are made of inner diameter 52mm, outer diameter 182mm, stainless steel ring 17 of thickness 15mm, stainless steel ring 17 diameter two ends direction positions have length 30mm, width 15mm, deep 38mm cuboid groove 10, for placing permanent magnet 8. There are 8 first M6 threaded holes 11 with a depth of 15 mm in the remaining positions without grooves along the radial direction. There are 4 through holes 12 of 12.4 mm symmetrically on the surface of the stainless steel ring 17 . The other two 316 stainless steel rings differ from the aforementioned two pieces only in that the surface is 4 symmetrical M8 threaded holes 13 . The outer ring of every stainless steel ring 17 has an annular stainless steel part 14, internal diameter 182mm, external diameter 212mm, thickness 14mm. There are 16 second M6 threaded holes 15 on the surface of the annular stainless steel part 14, 8 of which are used to compress the permanent magnet 8, and 8 are used to connect the inner stainless steel ring 17. The threaded rod 16 between the two stainless steel rings 17 in the middle is put on an insulating sleeve to avoid connecting with the helical wave antenna 6.

The discharge device adopts the permanent magnet 8 to provide the magnetic field, without the participation of the electromagnet, it is convenient to disassemble and change the position of the magnetic field. The specification of each permanent magnet 8 is 50mm×25mm×15mm, and the magnetizing surface is on the N-S surface. The periphery of the permanent magnet 8 is surrounded by stainless steel, and two permanent magnets 8 are stacked up and down. The permanent magnet pole N on one side of the discharge device is placed outward, and the permanent magnet pole S on the other side is placed outward.

The invention uses a permanent magnet to generate a magnetic field to realize the excitation of high-density helicon wave plasma.

The specific embodiments described above have further described the technical solutions of the present invention in detail. Any modifications and replacements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. .

Claims (8)

1. A helicon wave plasma discharge device based on permanent magnets is characterized by comprising an air source, a radio frequency power supply, an impedance matcher, an air inlet pipeline, a flow regulating valve, a discharge tube, a helicon wave antenna, permanent magnets, an annular permanent magnet support and a vacuum discharge chamber;

the radio frequency power supply is connected with the impedance matcher; the impedance matcher is connected with the helical wave antenna; the helical wave antenna penetrates through the discharge tube and further penetrates through the annular permanent magnet support; the discharge tube penetrates through the annular 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 annular permanent magnet bracket to generate an axial magnetic field; the air source is connected with the flow regulating valve through an air inlet pipeline; the flow regulating valve controls the air inlet flow, the discharge working medium enters the discharge tube through the air inlet pipeline, and high-density helicon wave plasma is formed under the action of a magnetic field generated by the helicon wave antenna and the permanent magnet.

2. A permanent magnet based helicon wave plasma discharge apparatus according to claim 1, characterized in that: the helicon wave plasma discharge device excites plasma by means of a radio frequency power supply, and the frequency of the radio frequency power supply is 13.56MHz.

3. A helicon wave permanent magnet-based plasma discharge apparatus according to claim 1, wherein: the device also comprises a vacuum pump, wherein the vacuum pump consists of a front-stage mechanical pump and a rear-stage molecular pump.

4. A permanent magnet based helicon wave plasma discharge apparatus according to claim 1, characterized in that: the gas introduced by the gas source is air or inert gas.

5. A permanent magnet based helicon wave plasma discharge apparatus according to claim 1, characterized in that: different magnetic field patterns are generated by increasing or decreasing the number of the permanent magnets.

6. A permanent magnet based helicon wave plasma discharge apparatus according to claim 1, characterized in that: the annular permanent magnet bracket is composed of 4 pieces of 316 stainless steel, and the middle parts of the annular permanent magnet bracket are connected through a threaded rod; 2 stainless steel 316 is made into a stainless steel circular ring with the inner diameter of 52mm, the outer diameter of 182mm and the thickness of 15mm, and rectangular grooves with the length of 30mm, the width of 15mm and the depth of 38mm are arranged at the two ends of the diameter of the stainless steel circular ring and used for placing permanent magnets; the rest positions without grooves are radially provided with 8 first M6 threaded holes with the depth of 15 mm; the surface of the stainless steel circular ring is symmetrically provided with 4 through holes with the diameter of 12.4 mm; the surfaces of the other two stainless steel rings made of 316 stainless steel are provided with 4 symmetrical M8 threaded holes; the outer ring of each stainless steel circular ring is provided with an annular stainless steel part, the inner diameter is 182mm, the outer diameter is 212mm, and the thickness is 14mm; the surface of the annular stainless steel component is provided with 16 second M6 threaded holes, wherein 8 second M6 threaded holes are used for pressing the permanent magnets, and 8 second M6 threaded holes are used for connecting the inner stainless steel circular ring; the threaded rod between the two stainless steel rings in the middle is sleeved with an insulating sleeve to avoid being communicated with the helical wave antenna.

7. A helicon wave permanent magnet-based plasma discharge apparatus according to claim 1, wherein: the periphery of the permanent magnet is surrounded by stainless steel to play a role of fixing the magnet, and the two permanent magnets are stacked up and down; the magnetic pole N of the permanent magnet on one side is placed outwards, and the magnetic pole S of the permanent magnet on the other side is placed outwards.

8. A permanent magnet based helicon wave plasma discharge apparatus according to claim 1, characterized in that: the permanent magnet is made of neodymium iron boron materials.

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