A device for exciting electromagnetic waves using plasma

Abstract

The application discloses a device for exciting electromagnetic wave by plasma, which comprises a waveguide in which plasma is formed, a sealed vacuum cavity in which electrons are generated and pass through an electron window to the waveguide, and the plasma in the waveguide is bombarded to generate uneven electron distribution, thereby causing electromagnetic wave oscillation, generating electromagnetic wave, and leading out the generated electromagnetic wave along the waveguide. In this way, the plasma is formed in the waveguide, and the GOL-3 device is replaced by the way that the electrons are generated in the sealed vacuum cavity and pass through the electron window to the waveguide, the electron-plasma interaction device is greatly reduced, the urgent needs of miniaturized electromagnetic wave radiation source are met, and diversified applications can be flexibly and widely met. In addition, compared with vacuum electron devices such as backward wave tube and magnetron, the device for exciting electromagnetic wave by plasma has the following advantages: 1) high output power, 2) simple structure, and 3) the interaction region does not need to be vacuum, and 4) the electromagnetic wave frequency can be simply adjusted by adjusting the plasma density.

Description

Technical Field

[0001] This invention belongs to the field of microwave device technology, and more specifically, relates to a device for generating electromagnetic waves using plasma. Background Technology

[0002] Vacuum electronic devices such as klystrons and traveling wave tubes utilize electron beams emitted from electron guns to form electron clusters. These clusters lose energy in a deceleration field, converting the electron kinetic energy into electromagnetic wave energy, thereby generating amplified or oscillating electromagnetic wave output.

[0003] Since their invention, vacuum electronic devices have been widely used as core components of microwave systems in military and civilian fields such as radar, electronic countermeasures, and communications. However, with the continuous increase in operating frequency, due to the "size co-transfer" effect, vacuum electronic devices also face the following major problems: 1) high loss and low coupling impedance; 2) low electron beam-electromagnetic wave interaction efficiency in slow-wave structures; 3) high current density requirements that cannot be achieved; and 4) the device structure is too small to be fabricated.

[0004] Plasma, also known as ionized plasma, is an ionized gaseous substance composed of positive and negative ions produced by the ionization of atoms and atomic groups after some electrons have been stripped away. It is the fourth state of matter and is electrically neutral overall. When an electron beam enters plasma, it generates electromagnetic radiation with a frequency higher than the plasma oscillation frequency. Thumm et al. reported an electron beam-plasma system experiment conducted on the GOL-3 facility in 2014. The experiment was performed at a density on the order of 10-1. 20 / m 3 In a strongly turbulent plasma, the conversion of electrostatic waves to electromagnetic waves was utilized to obtain a power density of 1 kW / cm² with a frequency of 0.23-0.30 THz. 3 The experiment observed electromagnetic radiation and second harmonics caused by nonlinear interactions. However, the experimental setup is large and expensive, thus limiting its flexibility in meeting diverse application needs. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing electron-plasma interaction devices, which are large and expensive and cannot flexibly and widely meet diverse application needs. The invention provides a device that uses plasma to excite electromagnetic waves, namely an electron-plasma electromagnetic wave generator, to meet the urgent need for miniaturized electromagnetic wave radiation sources.

[0006] To achieve the above-mentioned objective, the present invention provides a device for generating electromagnetic waves using plasma, characterized in that it comprises:

[0007] A waveguide in which plasma is formed;

[0008] An electron gun generates electrons in a sealed vacuum cavity, which then pass through an electron window formed by the vacuum and the electrons can easily penetrate the medium into a waveguide. The electrons bombard the plasma in the waveguide, causing non-uniform electron distribution, which in turn causes electromagnetic wave oscillation and generates electromagnetic waves. The generated electromagnetic waves are then led out through the waveguide.

[0009] Among these requirements, the plasma density needs to ensure that the frequency of the generated electromagnetic waves is higher than the waveguide cutoff frequency, i.e., the minimum operating frequency.

[0010] The objective of this invention is achieved as follows.

[0011] This invention utilizes a plasma-generated electromagnetic wave device. It employs a plasma-generated waveguide where electrons, generated in a sealed vacuum cavity, pass through an electron window into the waveguide, bombarding the plasma and causing electron non-uniformity. This induces electromagnetic wave oscillations, generating electromagnetic waves that are then carried out along the waveguide. This method of generating plasma in the waveguide and using electrons generated in a sealed vacuum cavity to pass through an electron window replaces the GOL-3 device, significantly reducing the size of the electron-plasma interaction device. This meets the urgent need for miniaturized electromagnetic wave radiation sources and can flexibly and widely satisfy diverse applications. Furthermore, compared to vacuum electronic devices such as retroreflectors and magnetrons, this plasma-generated electromagnetic wave device has the following advantages: 1) high output power; 2) simple structure, no vacuum required in the interaction region; 3) the electromagnetic wave frequency can be easily adjusted by regulating the plasma density (higher plasma density results in higher electromagnetic wave frequency, and vice versa). Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a specific embodiment of the device for generating electromagnetic waves using plasma according to the present invention;

[0013] Figure 2 This is a schematic diagram of another specific embodiment of the device for generating electromagnetic waves using plasma according to the present invention;

[0014] Figure 3 This is a simulation diagram of a typical signal output of the device for generating electromagnetic waves using plasma, as described in this invention. Detailed Implementation

[0015] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0016] Example 1

[0017] Figure 1This is a schematic diagram of a specific embodiment of the device for generating electromagnetic waves using plasma according to the present invention.

[0018] In this embodiment, as Figure 1 As shown, the device for generating electromagnetic waves using plasma according to the present invention includes a waveguide 1 and a sealed vacuum cavity 2. Plasma 3 is formed in the waveguide 1. An electron gun 4 generates electrons in the sealed vacuum cavity 2, and electrons exit through an electron window 201 formed by sealing the vacuum and allowing electrons to easily penetrate the medium into the waveguide 1, bombarding the plasma 3 in the waveguide 1, producing non-uniform electron distribution, which in turn causes electromagnetic wave oscillation, generating electromagnetic wave 5, which is led out with the waveguide 1. The density of plasma 3 needs to satisfy the requirement that the frequency of the generated electromagnetic wave 5 is higher than the cutoff frequency, i.e., the minimum operating frequency, of the waveguide 1.

[0019] In practical implementation, waveguide 1 can be a rectangular waveguide, an elliptical waveguide, or a circular waveguide. Waveguide 1 is made of metal, such as aluminum, gold, silver, copper, titanium, tungsten, rhenium, nickel, cobalt, iron, or their alloys. Since the cross-section of waveguide 1 determines the cutoff frequency of electromagnetic wave 5, i.e., the minimum operating frequency, the frequency at which electromagnetic wave 5 is generated must be higher than the cutoff frequency.

[0020] Electrons are generated by electron gun 4 to form electron beam 6. The intensity and voltage of the electron beam determine the power of the generated electromagnetic wave. The cross section of the injected electron beam 6 needs to be smaller than the side of the waveguide. The cross section of the electron beam 6 is generally a circular cross section, but there are also elliptical or rectangular cross sections. Therefore, it is necessary to design an electron gun with specific voltage, current and cross section to generate electron beam 6.

[0021] Plasma 3 is generated by various types of plasma generators, with typical structures being plasma torches and radio frequency plasmas.

[0022] Since electron guns typically generate electrons in a high vacuum environment, while plasma generation requires a pressure environment higher than 100 Pa, a medium is needed that can seal the vacuum and allow electrons to easily penetrate it. This medium can be diamond (relative permittivity of 5.68), quartz (relative permittivity of 2.5), boron nitride (relative permittivity of 4.0), ceramic (relative permittivity of 9), sapphire (relative permittivity of 9.4), or aluminum foil, etc.

[0023] To further explain, the electron beam 6 can generate electromagnetic waves simply by interacting with the plasma. Therefore, the electron beam 6 can be fed into the plasma 4 from any direction, according to the structural design requirements.

[0024] In this embodiment, as Figure 1 As shown, waveguide 1 is a circular waveguide, and plasma is generated using a plasma torch. In this embodiment, as... Figure 1As shown, the lower part of the circular waveguide 1 has an air inlet 101 through which the working gas 7 enters. A central conductor 102, which is an upward-facing cone with its tip pointing upwards, is located at the center of the air inlet 101. A voltage is applied between the central conductor 102 and the outer shell of the circular waveguide 1. This voltage ignites the working gas 7 at the tip of the central conductor 102, forming plasma 3 at the tip, which is structured as a plasma torch. The working gas 7 is then discharged from the exhaust window 103 on the upper side of the circular waveguide 1.

[0025] Electron gun 4 generates electrons in sealed vacuum cavity 2, forming electron beam 6, which passes through electron window 201 from the side into waveguide 1. By adjusting the power of plasma torch and gas flow rate, different plasma densities can be achieved. With the adjustment of plasma density, electromagnetic waves of different frequencies can be generated, and the generated electromagnetic waves are led out with the waveguide.

[0026] Example 2

[0027] Figure 2 This is a schematic diagram of another specific embodiment of the device for generating electromagnetic waves using plasma according to the present invention.

[0028] In this embodiment, as Figure 2 As shown, in the device for generating electromagnetic waves using plasma, waveguide 1 is a rectangular waveguide, and plasma is generated using an inductor coil: an inductor coil 8 is wound on the lower outer wall of the rectangular waveguide 1, and radio frequency oscillation is applied to the inductor coil 8. The bottom side of the rectangular waveguide 1 is an air inlet 101, and the working gas enters through the bottom side air inlet 101. Under the action of the radio frequency oscillation electromagnetic field, the working gas is ignited to form plasma 3. The sealed vacuum cavity 2 is located at the bottom of the rectangular waveguide 1. The electron gun 4 generates electrons in the sealed vacuum cavity 2, forming an electron beam 6, which passes through the electron window 201 from the bottom surface into the rectangular waveguide 1, bombarding the plasma 3 in the rectangular waveguide 1, producing non-uniform electron distribution, which in turn causes electromagnetic wave oscillation, generating electromagnetic wave 5. The generated electromagnetic wave 5 is led out with the rectangular waveguide 1, while the working gas is discharged from the exhaust window 103 on the upper side of the rectangular waveguide 1.

[0029] Figure 3 This is a simulation diagram of a typical signal output of the device for generating electromagnetic waves using plasma, as described in this invention.

[0030] In this embodiment, the simulation output is as follows: Figure 3 As shown. From Figure 3 It can be seen that a stable electromagnetic wave signal can be output after 40ns, which shows that the present invention is feasible and achieves the purpose of the invention, namely, to provide a device for generating electromagnetic waves using plasma, namely an electron-plasma electromagnetic wave generator, to meet the urgent need for miniaturized electromagnetic wave radiation sources.

[0031] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A device for generating electromagnetic waves using plasma, characterized in that, include: A waveguide in which plasma is formed; An electron gun generates electrons in a sealed vacuum cavity, which then pass through an electron window formed by the vacuum and the electrons can easily penetrate the medium into a waveguide. The electrons bombard the plasma in the waveguide, causing non-uniform electron distribution, which in turn causes electromagnetic wave oscillation and generates electromagnetic waves. The generated electromagnetic waves are then led out through the waveguide. Among these requirements, the plasma density needs to ensure that the frequency of the generated electromagnetic waves is higher than the waveguide cutoff frequency, i.e., the minimum operating frequency.

2. The device for generating electromagnetic waves using plasma according to claim 1, characterized in that, The waveguide is a circular waveguide with an air inlet at the bottom. The working gas enters through the air inlet and has a central conductor at the center. The central conductor is an upward-pointing cone with its tip pointing upward. A voltage is applied between the central conductor and the outer shell of the circular waveguide. The applied voltage ignites the working gas at the tip of the central conductor, forming a plasma at the tip. The structure is a plasma torch. The working gas is discharged from the exhaust window on the upper side of the circular waveguide.

3. The device for generating electromagnetic waves using plasma according to claim 1, characterized in that, The waveguide is rectangular, and plasma is generated using an inductor coil: an inductor coil is wound on the lower outer wall of the rectangular waveguide, and radio frequency oscillation is applied to the inductor coil. The bottom side of the rectangular waveguide is an air inlet, through which the working gas enters. Under the action of the radio frequency oscillation electromagnetic field, the working gas is ignited to form plasma. A sealed vacuum chamber is located at the bottom of the rectangular waveguide. An electron gun generates electrons in the sealed vacuum chamber, forming an electron beam. The electron beam passes through the electron window from the bottom surface into the rectangular waveguide, bombarding the plasma in the rectangular waveguide and producing non-uniform electron distribution, which in turn causes electromagnetic wave oscillation and generates electromagnetic waves. The generated electromagnetic waves are led out with the rectangular waveguide, while the working gas is discharged from the exhaust window on the upper side of the rectangular waveguide.

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