CN111031652A

CN111031652A - Low-pressure long-pulse high-energy plasma electron beam generating device and method

Info

Publication number: CN111031652A
Application number: CN201911233874.0A
Authority: CN
Inventors: 高深; 蔡纪鹤
Original assignee: Changzhou Institute of Technology
Current assignee: Changzhou Institute of Technology
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2020-04-17

Abstract

The invention discloses a low-pressure long-pulse high-energy plasma electron beam generating device and a method. The device comprises a left permanent magnet, a left flat cathode, a left hole-shaped anode, a right flat cathode and a right permanent magnet, wherein the four-electrode structure is placed inside a vacuum tank, the permanent magnet is placed outside the vacuum tank, an extraction field anode is arranged above the double anodes, and an extraction field cathode is arranged below the double anodes; the upper end of the discharge cavity is connected with an accelerating field through a 90-degree arc solenoid structure, the tail end of the arc solenoid is an accelerating field cathode, the tail end of the accelerating field is an accelerating field anode, the accelerating field anode end is connected with an electron leading-out hole, and the electron leading-out hole penetrates through a collector of the leading-out hole. The device of the invention has small volume, and because the plasma electrons in the device of the invention are generated by the working medium gas and do not relate to the consumption of the structure of the electron beam generating device, the service life of the electron beam generating device can be infinitely prolonged theoretically.

Description

Low-pressure long-pulse high-energy plasma electron beam generating device and method

Technical Field

The invention relates to the technical field of electron beam processing and manufacturing, in particular to a low-pressure long-pulse high-energy plasma electron beam generating device and method.

Background

Microwave radiation is a product formed by interaction of a high-current particle beam and a corresponding microwave medium, and particularly in a plasma microwave radiation source, the current magnitude and the pulse width of an electron beam play an important role in the frequency and the radiation time of electromagnetic waves radiated by microwaves.

Conventional electron beams have two forms of generation, one being hot cathode emission and the other being field emission. The hot cathode is capable of generating a direct current electron beam, but the electron beam current is small, typically at several milliamps or tens of milliamps. In addition, the hot cathode material is easy to wear and has short service life. Field emission can produce a large current electron beam, the current of which can reach the kiloampere level, but the current pulse width of the electron beam is very short, usually tens of nanoseconds or hundreds of nanoseconds. Extracting the electron beam from the plasma can produce a large current and a long pulse width of the beam current. When the plasma is used as an electron beam source, the glow discharge structure is simple; the plasma has stable shape and is not easy to extinguish; the discharge temperature is low, cooling is not required to be considered, the loss of the counter cathode is small, and the service life of the cathode is long, so that glow discharge is a method used as a plasma electron beam source.

Generally, a plasma electron beam source mainly includes two parts: 1) a plasma generator based on a certain discharge; 2) an electron beam extraction system. The operating pressure of the glow discharge is typically 1-10pa, at which it is impossible to form a beam with a wide pulse and a large energy. Because the gas pressure of the acceleration field is higher at this moment, the molecular density of neutral gas is high, and electrons collide and ionize with neutral atoms in the acceleration field in the acceleration process to form a discharge breakdown phenomenon. Therefore, how to use low pressure (10)^-2pa) to generate glow plasma is a problem that needs to be solved at present. In addition, a large number of charged particles are generated during the gas discharge, which diffuse into the accelerating field due to space charge effects. At this time, the charged particles are accelerated by the electric field to obtain enough energy, and are easy to collide with neutral atoms in the acceleration field for ionization, so that the acceleration gap is closed, and the formation of high-energy electron beams is not facilitated. How to avoid the plasma from diffusing into the accelerating field is another key issue that needs to be addressed at present.

Disclosure of Invention

The invention aims to provide a low-pressure long-pulse high-energy devicePlasma electron beam generating apparatus and method, thereby solving the aforementioned problems in the prior art. The invention can be used under low pressure<5×10^-2pa), namely, the glow discharge starting pressure is reduced, the original accelerating field is divided into an extraction field and an accelerating field, and the plasma is inhibited from diffusing into the accelerating field by improving the related structure, so that the energy of the electron beam is ensured to meet the required requirement.

The technical scheme adopted by the invention is as follows:

the invention provides a generating device of a low-air-pressure long-pulse high-energy plasma electron beam, which comprises a left permanent magnet, a left flat cathode, a left hole-shaped anode, a right flat cathode, a right permanent magnet, and a four-electrode structure, wherein the four-electrode structure is placed in a vacuum tank; the upper end of the discharge cavity is connected with an accelerating field through a 90-degree arc solenoid structure, the tail end of the arc solenoid is an accelerating field cathode, the tail end of the accelerating field is an accelerating field anode, the accelerating field anode end is connected with an electron leading-out hole, and the electron leading-out hole penetrates through a collector of the leading-out hole.

Furthermore, the extraction field cathode and the extraction field anode are arranged in the discharge space of the double-anode structure, and the extraction field anode is of a hole-shaped aluminum plate structure.

Furthermore, the electron leading-out hole is an extraction field anode, a 90-degree arc solenoid device is arranged above the extraction field anode, and the solenoid is powered by a direct current power supply. The electrons are extracted from the extraction field and directly into the solenoid and change their direction of motion.

Further, the extraction cathode and anode are provided inside the discharge space.

Furthermore, the glow cathode and anode discharge power supply is a direct current power supply, the extraction field power supply is a high-voltage pulse power supply, the excitation power supply is a constant current source, and the acceleration field is a direct current constant voltage source. The cathode of the accelerating field voltage is grounded, and the rest power supplies adopt a suspension power supply to supply power.

Furthermore, the permanent magnets are arranged in a left and right mode, the size of the permanent magnets is equivalent to that of the cathode, and the permanent magnets are symmetrically distributed on the left and right outer sides of the vacuum tank.

Furthermore, the connection parts of all the structures of the device are respectively provided with a sealing groove, and rubber sealing rings are arranged in the sealing grooves.

Furthermore, the cathode, the anode, the extraction electrode and the acceleration electrode are all made of aluminum plates, and the vacuum tank is made of organic glass.

The invention also provides a method for generating electron beams by using the low-pressure long-pulse high-energy plasma electron beam generating device, which comprises the following steps:

s1, mounting the glow discharge cathode and anode plates, the cathode and anode outgoing lines, the extraction field cathode and anode plates, the extraction field outgoing lines and the vacuum tank together;

s2, vacuumizing the whole vacuum tank, the 90-degree arc solenoid and the acceleration field device to the required air pressure condition;

and S3, turning on the glow discharge power supply to generate glow plasma.

S4, opening the high-voltage pulse source of the extraction field, and extracting electrons in the plasma from the electron extraction hole to obtain an electron beam source;

s5, turning on an excitation current source to deflect the initial low-energy electron beam along the direction of the magnetic field generated by the excitation current and to make the electron beam source enter the accelerating field;

and S6, turning on an accelerating field constant voltage source to accelerate the electron beam to obtain a high-energy electron beam.

The invention has the advantages that:

1) the electron beam generating device with the structure has the characteristics of small volume, long service life, capability of bearing the reverse ion bombardment of a plasma filling device in a beam microwave medium and the like, and the electron beam source has the advantages of small volume and long service life.

2) Compared with the traditional plasma gas generating device, the low-pressure long-pulse high-energy plasma electron beam generating device and the method thereof provided by the invention have the advantage that the discharge pressure can be reduced to 5 multiplied by 10^-2pa or less, the glow starting condition of glow discharge is expanded. In the whole electron beam device, the probability of collision between electrons and neutral atoms in an acceleration field is reduced due to the reduction of the air pressure, so that the acceleration voltage of the electron beam is improved, and the kinetic energy of the electron beam is increased. In addition, by the improved four-electrode structure, the extraction electrode is placed in the glow discharge space, the aperture of the extraction anode is increased, and the electron density in the electron beam source is improved, namely, the electron beam current is increased.

3) Compared with the traditional plasma electron beam generating device, the low-pressure long-pulse high-energy plasma electron beam generating device and the method thereof provided by the invention theoretically have the acceleration field voltage of 100Kv on the basis that the pulse width of the electron beam reaches 10us-100 us. And according to the structural extraction characteristics of the electron beam of the device, the electron beam with single pulse can be further expanded to a high-energy electron beam device with repeatable frequency, and only a single high-voltage pulse source in an extraction field needs to be replaced by a high-voltage pulse source with repeatable frequency.

Drawings

FIG. 1 is a schematic diagram of a glow discharge cathode and anode configuration; wherein, a is a cathode plate structure, and b is a hole type anode plate structure;

FIG. 2 is a schematic view of glow discharge cathode and anode installation;

FIG. 3 is a vacuum canister seal groove structure (side view);

FIG. 4 is a vacuum tank seal groove structure (top view);

FIG. 5 is a side view of a bi-anode glow discharge structure;

FIG. 6 is a (top view) of a bi-anode glow discharge structure;

FIG. 7 is a diagram of the extraction field placement position and a 90 arc solenoid configuration;

FIG. 8 is a diagram of an accelerating field focusing apparatus;

FIG. 9 is a general block diagram of a low pressure long pulse high energy plasma electron beam configuration;

in the figure: 1. a wiring hole; 2. a permanent magnet; 3. a vacuum tank; 4. a hole-shaped anode; 5. a flat cathode; 6. a lower flange plate; 7. an upper flange plate; 8. an air extraction opening; 9. extracting a field anode port; 10. a 90-degree arc metal stainless steel pipe; 11. a solenoid coil; 12. extracting a field flat plate aluminum cathode; 13. extracting a field mesh anode; in fig. 4: 14. an accelerating field cathode; 15. an accelerating field anode; 16. an electron beam collector; 17. an arc-shaped metal electrode with holes; 18. a metal screw; 19. the vacuum device seals the groove.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

In general, the working pressure of glow discharge is required to be above 10Pa, hollow cathode glow discharge can reduce the discharge pressure to 1Pa, and if glow plasma is required to be generated at a lower pressure, a magnetic field or other conditions need to be introduced. The permanent magnets are arranged on the left side and the right side of the outside of the vacuum tank, magnetic lines of force in the vacuum tank are from an N pole to an S pole (note that the magnetic lines of force in the vacuum tank are not mutually exclusive of an NN pole or an SS pole), the magnetic lines of force penetrate through the cathode plate and the anode hole, and the cathode and the anode are made of aluminum materials. The introduction of the magnetic field leads the electrons to be constrained between the cathode and the anode to move back and forth, increases the moving path of the electrons, improves the collision probability of the electrons and neutral atoms, and reduces the starting pressure of glow discharge.

A conventional gas discharge is to generate a glow plasma between a cathode plate and an anode plate. The vacuum tank adopts a four-electrode structure inside, and the cathode plate, the anode hole and the cathode plate are sequentially arranged from left to right, so that electrons can penetrate through the anode hole under the action of a magnetic field to achieve the effect of reciprocating oscillation of the electrons between the anode and the cathode. In addition, the double-anode structure is adopted to facilitate the arrangement of the upper electrode and the lower electrode in the discharge space of the extraction field, and the density uniformity of the plasma in the double-anode area is improved.

Generally, the acceleration field and the extraction field of the electron beam are combined together, in this case, there is no difference for the electron beam of the hot cathode, but the current of the electron beam is not large due to the defect of low electron emission capability of the hot cathode, and the related requirements cannot be met, for the electron beam sources of the two forms of field emission and plasma extraction, the situation of plasma charged particle diffusion must be considered, after the electron extraction acceleration, the extraction field and the acceleration field are usually combined together, so the directions of the electric fields of the two fields are the same, the accelerated electrons are easy to be closed and broken down in the field gap, and the voltage of the acceleration field cannot be too large, so the energy obtained by the electron beam is low. The invention separates the extraction field and the acceleration field, the middle is connected by a 90-degree arc structure, the electron beam adopts 5-10Kv in the extraction process, the single pulse width is 10us-100us, the electron beam enters the acceleration field through the magnetic deflection drift inside the solenoid after extraction, and the plasma is not influenced by the magnetic field inside the solenoid due to the space charge effect, so the drift direction of the plasma can not be changed, and the plasma can bombard the inner wall of the solenoid and be lost. The plasma and the electron beam are further separated through the 90-degree arc structure, the plasma is prevented from diffusing into an accelerating field, and the accelerating voltage of the electron beam is improved.

As shown in FIG. 1, the cathode (shown as a in the figure) is a flat aluminum electrode with the thickness of 2mm, the length of 120mm and the width of 80 mm; the anode (shown as b in the figure) is a square hole type aluminum electrode, the thickness of the electrode is 2mm, the length of the outer edge is 120mm, the width of the electrode is 80mm, the length of the inner edge of the square hole is 100mm, and the width of the inner edge of the square hole is 60 mm; the size of the wiring hole is phi 6, a metal screw penetrates through the wiring hole, and two ends of each electrode wiring hole are fixed by nuts.

As shown in figure 2, the vacuum tank of the invention has a total of four electrodes, namely two cathodes and two anodes, which need to be installed and fixed in the vacuum tank, the vacuum tank is made of organic glass material and has the thickness of 20mm, the inner diameter of 160mm, the distance between the outer edges of the two cathodes is 70mm, the distance between the inner edges of the two anodes is 46mm, and the cathodes and the anodes are installed in bilateral symmetry; punching through holes (two through holes are respectively punched at the left side and the right side of the central line position of the cathode) at corresponding positions of the vacuum tank, penetrating the metal screw 18 out of the vacuum tank, fixing the inner wall and the outer wall of the vacuum tank by nuts, and sealing the inner drill hole and the outer drill hole of the vacuum tank by insulating resin to ensure the air extraction tightness of the vacuum tank.

As shown in fig. 3 and 4, a groove is formed between the inner radius and the outer radius of the vacuum tank, the groove depth is 3mm, the difference between the outer radius and the inner radius of the groove is 5mm, the groove is installed in a sealing groove 19 of a vacuum device by using a rubber ring with the thickness of 5mm, and the groove is directly pressed by a metal flat plate or a flat plate made of organic material at the upper part during air suction.

As shown in fig. 5 and 6, an upper flange 7 and a lower flange 6 are provided at both ends of the vacuum tank 3, the upper end of the vacuum tank 3 is an extraction field anode port 9, the lower end is an extraction port 8, two hole type anodes 4 are installed inside the vacuum tank 3, two flat cathodes 5 are installed outside, four electrodes are installed in bilateral symmetry, and screws for fixing the electrodes are not shown in the drawings. The left and right permanent magnets 2 are symmetrically arranged outside the vacuum tank, and magnetic lines of force generated by the two magnets in the vacuum tank are from an N pole to an S pole, but the N pole and the S pole of the N pole or the S pole of the S pole are mutually repelled, so that the installation mode plays an important role in generating glow plasma. The bottom of the vacuum tank is used as an air exhaust port, and a vacuum pump air exhaust device is arranged below the vacuum tank. The height of the vacuum tank is 170 mm. The upper part of the vacuum tank is provided with an electron beam source outlet which is connected with a 90-degree arc solenoid. The magnets may be mounted on an external insulating support (not shown).

As shown in fig. 7, the extraction field mesh anode 13 and the extraction field flat plate aluminum cathode 12 are located at two positions above and below the vacuum tank and fixed in the middle area of the double anode. The anode of the extraction field can be fixed with the upper flange plate through a screw rod, and the cathode can be fixed with the lower flange plate through a screw rod; the extraction field cathode adopts a flat aluminum electrode, and the extraction field anode is made of a reticular (grid 2mm x 2mm) or hole-shaped (aperture is not larger than the distance between the double anodes) metal plate. A90-degree arc solenoid coil 11 device is arranged above a vacuum tank, a 90-degree arc metal stainless steel pipe 10 can be in seamless sealing welding with a flange plate on the vacuum tank, and the connection mode does not influence the electric field distribution of an extraction field and the magnetic field distribution in the solenoid. On the basis of guaranteeing the vacuum pumping intensity, reduce arc tubular metal resonator wall thickness as far as possible, the purpose is to guarantee to be compacter when the arc pipe twines the coil.

As shown in fig. 8, in the structure diagram of the accelerating field focusing device, a flange is hermetically welded at the leading-out position of a 90-degree arc solenoid to serve as an electron beam accelerating field cathode 14, and the right side is externally connected with another vacuum tank which is also processed by organic glass. The flange of the accelerating field anode 15 is connected with an arc metal electrode 17 with holes, the middle of the accelerating field anode is provided with a hole, the diameter of the hole is 10mm, and the purpose is to accelerate and focus electron beams; the electrons exit the accelerating field anode focusing aperture and are incident on an electron beam collector 16. In practical applications, for example as a microwave radiation source, the collector shown above is not required, and the electron beam is passed out of the anode hole and directly enters the corresponding microwave medium for interaction.

The overall structure of the low-pressure long-pulse high-energy plasma electron beam generating device of the present invention is shown in fig. 9.

In summary, the present invention provides a device and a method for generating a low-pressure long-pulse high-energy plasma electron beam, and relates to the field of electron beam processing and manufacturing technology. The device is designed into a four-electrode structure by arranging a left permanent magnet and a right permanent magnet outside a vacuum chamber and designing the vacuum chamber, two flat plate cathodes are arranged on the outer side, two hole-shaped anodes are arranged on the inner side, and a 90-degree arc-shaped solenoid structure is designed between an extraction field and an acceleration field. The upper end of the discharge cavity is connected with an anode of an extraction field, and the anode of the extraction field adopts a hole-type structure; the lower end of the discharge cavity is connected with the cathode of the extraction field, and the cathode of the extraction field adopts a flat plate structure. The electron beam generating device with the structure has small volume and small occupied space, and simultaneously, because plasma electrons in the device are generated by working medium gas and do not relate to the consumption of the structure of the electron beam generating device, the service life of the electron beam generating device can be infinitely prolonged theoretically. In addition, the device can be 5 multiplied by 10^-2pa below, and by using a 90-degree arc structure, the device can be used for generating glow plasma at higher voltageSince the electron beam is accelerated and focused, it can generate an electron beam having a high energy, and is suitable for use in applications such as excitation of a plasma microwave radiation source.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements should also be considered within the scope of the present invention.

Claims

1. A low-pressure long-pulse high-energy plasma electron beam generating device is characterized by comprising a left permanent magnet, a left flat cathode, a left hole-shaped anode, a right flat cathode and a right permanent magnet, wherein the four-electrode structure is placed inside a vacuum tank; the upper end of the discharge cavity is connected with an accelerating field through a 90-degree arc solenoid structure, the tail end of the arc solenoid is an accelerating field cathode, the tail end of the accelerating field is an accelerating field anode, the accelerating field anode end is connected with an electron leading-out hole, and the electron leading-out hole penetrates through a collector of the leading-out hole.

2. The low-pressure long-pulse high-energy plasma electron beam generating device as claimed in claim 1, wherein the extraction field cathode and anode are disposed in the discharge space of the double anode structure, and the extraction field anode is made of a hole-type aluminum plate structure.

3. The low-pressure long-pulse high-energy plasma electron beam generating device as claimed in claim 1, wherein the electron exit hole is an extraction field anode, a 90 ° arc solenoid device is arranged above the extraction field anode, and the solenoid is powered by a dc power supply. The electrons are extracted from the extraction field and directly into the solenoid and change their direction of motion.

4. The low-pressure long-pulse high-energy plasma electron beam generating apparatus according to claim 1, wherein the extraction field cathode and anode are provided inside the discharge space.

5. The low-pressure long-pulse high-energy plasma electron beam generating device according to claim 1, wherein the glow cathode and anode discharge power supply is a direct-current power supply, the extraction field power supply is a high-voltage pulse power supply, the excitation power supply is a constant current source, and the acceleration field is a direct-current constant voltage source. The cathode of the accelerating field voltage is grounded, and the rest power supplies adopt a suspension power supply to supply power.

6. The low-pressure long-pulse high-energy plasma electron beam generating device according to claim 1, wherein the permanent magnets are disposed in two left and right directions, have a size corresponding to that of the cathode, and are symmetrically distributed on left and right outer sides of the vacuum tank.

7. The low-pressure long-pulse high-energy plasma electron beam generating device of claim 1, wherein a sealing groove is processed at the joint of each structure of the device, and a rubber sealing ring is arranged in each sealing groove.

8. The low-pressure long-pulse high-energy plasma electron beam generating device of claim 1, wherein the cathode, the anode, the extraction electrode and the acceleration electrode are all made of aluminum plates, and the vacuum tank is made of organic glass.

9. A method for generating an electron beam using the low-pressure long-pulse high-energy plasma electron beam generating apparatus according to any one of claims 1 to 8, comprising the steps of:

and S3, turning on the glow discharge power supply to generate glow plasma.