Gyrotron structure based on gradient output section and second harmonic electromagnetic wave generation method thereof

Abstract

The invention discloses a gyrotron structure based on a gradual change output section and a second harmonic electromagnetic wave generation method thereof. The gyrotron structure comprises an open type gyrotron resonator with a three-section cavity structure, the open type cyclotron resonator comprises a cut-off section cavity of an inclined annular open type metal structure, an interaction section cavity of an open type metal cylindrical waveguide structure and an output section cavity of an inclined gradual change annular open type metal structure. The cut-off section cavity, the interaction section cavity and the output section cavity are sequentially connected end to end from left to right. According to the invention, three cavity structures which are combined in sequence are adopted to form the open-type cyclotron resonator, so that high-power electromagnetic waves can be generated at 263 GHz, and the open-type cyclotron resonator has the characteristic of second harmonic operation; the open-type rotary resonance device with the three-section cavity structure is composed of an inclined annular open-type metal structure cut-off section, a cylindrical waveguide structure interaction section and an inclined gradual change annular open-type metal structure output section which are sequentially connected end to end from left to right. The gyrotron structure is simple in design and low in cost, and solves the problem of low output efficiency caused by the fact that second harmonic terahertz wave band electromagnetic waves generated by an existing gyrotron structure are difficult to be compatible with high beam-wave interaction efficiency and a suppression competition mode.

Description

Technical Field

[0001] This invention relates to the field of terahertz technology, and in particular to a gyrotron structure based on a gradually changing output segment and a method for generating second harmonic electromagnetic waves. Background Technology

[0002] Terahertz radiation sources based on vacuum electronics are an important class of terahertz radiation sources. In traditional vacuum electronic devices, electromagnetic radiation is generated by the interaction of free electrons with a periodic slow-wave structure. These devices exhibit a significant scale effect, meaning the size of the interaction structure is inversely proportional to the operating frequency; the higher the frequency, the smaller the interaction structure size. Simultaneously, due to factors such as space charge, the electron beam current density cannot be increased indefinitely, resulting in relatively low output power and beam-wave interaction efficiency in the terahertz band for traditional vacuum electronic devices. Cyclotrons (gyrotubes), based on the electron cyclotron stimulated emission mechanism, are fast-wave devices that overcome the scale effect. They do not require the slow-wave structure necessary for traditional vacuum electronic devices and can achieve watt-level or even megawatt-level power output in the terahertz band. Gyroscopes operate near the electron cyclotron frequency or its higher harmonics. Since the electron cyclotron frequency is proportional to the operating magnetic field, gyroscopes operating at the fundamental frequency in the terahertz band require a very strong longitudinal magnetic field. This results in high cost and large size. To achieve miniaturized and low-cost radiation source systems, harmonic operation is often used to reduce the required magnetic field strength. However, increasing the cyclotron harmonic order significantly reduces the efficiency of the beam-wave interaction and exacerbates mode competition. Therefore, it is necessary to select an appropriate harmonic order to balance the various effects. This invention proposes a gyroscope structure based on a gradually varying output segment and a method for generating second-harmonic electromagnetic waves to address the problems existing in the prior art. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to propose a gyrotron structure based on a gradient output section. This structure consists of a cutoff section cavity of an inclined annular open metal structure, an interaction section cavity of an open metal cylindrical waveguide structure, and an output section cavity of an inclined gradient annular open metal structure, connected end to end from left to right. The design is simple and low-cost, solving the problem that the terahertz beam generated by the existing second harmonic gyrotron structure is difficult to be compatible with high beam-wave interaction efficiency and the low output efficiency caused by suppressing competitive modes.

[0004] To achieve the objectives of this invention, the following technical solution is provided: a gyrotron structure based on a gradually changing output segment, comprising an open gyrotron resonator with a three-segment cavity structure. The open gyrotron resonator includes a cutoff segment cavity with a tilted annular open metal structure, an interaction segment cavity with an open metal cylindrical waveguide structure, and an output segment cavity with a tilted gradually changing annular open metal structure. The cutoff segment cavity, interaction segment cavity, and output segment cavity are arranged sequentially from left to right, connected end-to-end. The size of the cutoff segment cavity is used to ensure that the working mode does not disrupt the adiabatic compression process of electrons in the electron gun region or the gyrotron motion at the resonant cavity inlet. The cutoff cavity includes a circular metal waveguide with a certain angle. The dimensions of the interaction cavity are used to determine the intensity and frequency of energy exchange between the operating mode and the cyclotron. The interaction cavity includes a metal waveguide, and the cross-sectional dimensions of the interaction cavity's metal waveguide are consistent with the maximum cross-sectional dimensions of the cutoff cavity's metal waveguide. The dimensions of the output cavity are used to determine that the operating mode must be in a traveling wave state at the exit when transmitted through the interaction cavity. The output cavity includes a circular metal waveguide with a certain angle, and the minimum cross-sectional dimensions of the output cavity's metal waveguide are consistent with the cross-sectional dimensions of the interaction cavity's metal waveguide.

[0005] The further improvement lies in the following: the cut-off section cavity of the inclined annular open metal structure is rotationally symmetrical about the z-axis, the maximum cross-sectional radius of the cut-off section cavity of the inclined annular open metal structure is 2.053 mm, the length is 7.5 mm, the inclination angle is 5°, and the metal wall thickness is 6 mm.

[0006] The further improvement is that the interaction section cavity of the open metal cylindrical waveguide structure is rotationally symmetrical about the z-axis and the starting point is located at the end of the cutoff section cavity. The cross-sectional radius of the interaction section cavity of the open metal cylindrical waveguide structure is 2.053 mm, the length is 34 mm, and the metal wall thickness is 6 mm.

[0007] The further improvement lies in the following: the output section cavity of the inclined gradient annular open metal structure is rotationally symmetrical about the z-axis and the starting point is located at the end of the interaction section cavity. The minimum cross-sectional radius of the output section cavity of the inclined gradient annular open metal structure is 2.053 mm, the length is 10 mm, the tilt angle is 1.5°, and the metal wall thickness is 6 mm.

[0008] A further improvement is that the cutoff cavity of the inclined annular open metal structure, the interaction cavity of the open metal cylindrical waveguide structure, and the output cavity of the inclined gradient annular open metal structure are all made of oxygen-free copper.

[0009] A further improvement is that: the starting point of the output segment cavity of the inclined gradient annular open metal structure is located at the end of the interaction segment cavity; the cross-sectional dimension of the output segment cavity of the inclined gradient annular open metal structure is a distribution function of the cavity length; and the formula for calculating the distribution function of the cross-sectional dimension with respect to the cavity length is:

[0010]

[0011] In the formula, R(z) is the cross-sectional radius function, A, B and C are undetermined coefficients, and z is the axial distance from a certain point in the output cavity of the inclined gradient ring open metal structure to the end of the open metal cylindrical waveguide structure.

[0012] A gyrotron structure based on a gradually increasing output section and a method for generating second harmonic electromagnetic waves include the following steps: electrons emitted by an electron gun with applied voltage and current are adiabatically compressed by a magnetic field and rotate around the propagation axis. They then pass through a cutoff section cavity to an interaction section cavity, exciting electromagnetic waves in the working mode. The working mode electromagnetic waves radiate out along the output section cavity. Changing the electrical parameters, such as voltage, current, and magnetic field strength, can give the radiated electromagnetic waves a certain power and frequency.

[0013] The beneficial effects of this invention are as follows: This invention adopts a three-section cavity gyroscope structure with a tapered output section. This tapered output section gyroscope structure can generate electromagnetic waves in a high-efficiency operating mode at 263GHz, and has the characteristics of second harmonic operation. Moreover, the output section adopts a tapered cavity, which does not obstruct the emitted electromagnetic waves. The power and frequency of the output electromagnetic waves can be designed as needed to achieve flexible control. At the same time, the gyroscope structure with a tapered output section consists of a cutoff section cavity of an inclined annular open metal structure, an interaction section cavity of an open metal cylindrical waveguide structure, and an output section cavity of an inclined tapered annular open metal structure connected end to end from left to right. The design is simple and low-cost, which solves the problem that the terahertz beam generated by the existing second harmonic gyroscope structure is difficult to be compatible with high beam-wave interaction efficiency and the low output efficiency caused by suppressing competitive modes. It improves the working efficiency of the gyroscope and provides new possibilities for the application of terahertz beams in the field of enhanced nuclear magnetic resonance.

[0014] By using the distribution function of cross-sectional dimensions with cavity length as the basis for the radius of the tilted, gradually changing ring-shaped open metal structure, it is simple, easy to implement, and reduces the coupling between different modes, which is beneficial to the generation of high-output-efficiency terahertz beams. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the three-section cavity rotary tube structure of the gradual output section of the present invention;

[0017] Figure 2 This is a simulation result diagram of the oscillation current in Embodiment 2 of the present invention;

[0018] Figure 3 This is a graph showing the relationship between the beam-wave interaction efficiency and the operating frequency as a function of the operating magnetic field in Embodiment 2 of the present invention.

[0019] Figure 4 This is a graph showing the relationship between the injection-wave interaction efficiency and the operating frequency as a function of voltage in Embodiment 2 of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1

[0022] See Figure 1This embodiment provides a gyrotron structure based on a gradually changing output segment, including an open gyrotron resonator with a three-segment cavity structure. The open gyrotron resonator includes a cutoff segment cavity with a tilted annular open metal structure, an interaction segment cavity with an open metal cylindrical waveguide structure, and an output segment cavity with a tilted gradually changing annular open metal structure. The cutoff segment cavity, interaction segment cavity, and output segment cavity are arranged sequentially from left to right, end to end. The size of the cutoff segment cavity is used to ensure that the working mode does not disturb the adiabatic compression process of electrons in the electron gun region and the gyrotron motion at the resonant cavity entrance. The cavity contains a circular metal waveguide with a certain angle. The dimensions of the interaction section cavity are used to determine the intensity and frequency of energy exchange between the operating mode and the cyclotron. The interaction section cavity contains a metal waveguide, and the cross-sectional dimensions of the interaction section cavity metal waveguide are consistent with the maximum cross-sectional dimensions of the cutoff section cavity metal waveguide. The dimensions of the output section cavity are used to determine that the operating mode must be in a traveling wave state at the exit when propagating in the interaction section cavity. The output section cavity contains a circular metal waveguide with a certain angle, and the minimum cross-sectional dimensions of the output section cavity metal waveguide are consistent with the cross-sectional dimensions of the interaction section metal waveguide. The three-section cavity gyrotron structure with a tapered output section can generate electromagnetic waves in a high-efficiency operating mode at 263 GHz, exhibiting second-harmonic operation characteristics. Furthermore, the gyrotron structure with a tapered output section consists of, from left to right, a cutoff cavity of a tilted annular open metal structure, an interaction cavity of an open metal cylindrical waveguide structure, and an output cavity of a tilted tapered annular open metal structure. This simple and low-cost design solves the problem of existing second-harmonic gyrotron structures generating terahertz beams that are difficult to incompatible with high beam-wave interaction efficiency and have low output efficiency due to suppression of competing modes, thus improving the gyrotron's operating efficiency.

[0023] The cut-off section cavity of the inclined annular open metal structure is rotationally symmetrical about the z-axis, with a maximum cross-sectional radius of 2.53 mm, a length of 7.5 mm, an inclination angle of 5°, and a metal wall thickness of 6 mm.

[0024] The interaction section cavity of the open-type metallic cylindrical waveguide structure is rotationally symmetric about the z-axis and starts at the end of the cutoff section cavity. The cavity cross-sectional radius is 2.053 mm, the length is 34 mm, and the metal wall thickness is 6 mm.

[0025] The output section cavity of the inclined, gradually changing annular open metal structure is rotationally symmetrical about the z-axis and its starting point is located at the end of the interaction section cavity. The minimum cross-sectional radius of the cavity is 2.053 mm, the length is 10 mm, the tilt angle is 1.5°, and the metal wall thickness is 6 mm.

[0026] The cutoff cavity of the inclined annular open metal structure, the interaction cavity of the open metal cylindrical waveguide structure, and the output cavity of the inclined gradient annular open metal structure are all made of oxygen-free copper.

[0027] The starting point of the output section cavity of the inclined gradient annular open metal structure is located at the end of the interaction section cavity. The cross-sectional dimension of the output section cavity of the inclined gradient annular open metal structure is a distribution function of the cavity length. The formula for calculating the distribution function of the cross-sectional dimension with respect to the cavity length is:

[0028]

[0029] In the formula, R(z) is the cross-sectional radius function, A, B and C are undetermined coefficients, and z is the axial distance from a certain point in the output cavity of the inclined gradient ring open metal structure to the end of the open metal cylindrical waveguide structure. The main parameters are listed in Table 1 below.

[0030] Table 1

[0031]

[0032] By using the distribution function of cross-sectional dimensions with cavity length as the basis for the radius of the tilted, gradually changing ring-shaped open metal structure, it is simple, easy to implement, and reduces the coupling between different modes, which is beneficial to the generation of high-output-efficiency terahertz beams.

[0033] This embodiment also provides a gyrotron structure based on a gradually increasing output section and a method for generating second harmonic electromagnetic waves, including the following steps: electrons emitted by an electron gun with applied voltage and current are adiabatically compressed by a magnetic field and rotate around the propagation axis, and then excited to generate electromagnetic waves in the working mode through the cutoff section cavity to the interaction section cavity. The working mode electromagnetic waves are radiated out along the output section cavity. By changing the voltage, current and magnetic field magnitude of the electrical parameters, the radiated electromagnetic waves can have a certain power and frequency.

[0034] Example 2

[0035] See Figure 1 The beginning of the interaction section cavity of the open-type metallic cylindrical waveguide structure is connected to the end of the cutoff section cavity of the inclined annular open-type metallic structure. The length of the cutoff section cavity along the z-axis is L1, and it makes an angle θ1 with the z-axis. The radius of the end section is R1. The beginning of the output section cavity of the inclined gradient annular open-type metallic structure is connected to the end of the interaction section cavity of the open-type metallic cylindrical waveguide structure. The radius of the interaction section cavity is R1, and its length along the z-axis is L2. The length of the output section cavity along the z-axis is L3, and it makes an angle θ2 with the z-axis. The radius of the beginning section is R1.

[0036] See Figure 2To further investigate the potential mode competition within the cavity from a theoretical perspective, the starting current is used to study the potential mode competition within the cavity. Simultaneously, the magnetic field and electron beam current required for the excitation operating mode are analyzed. The starting current formula based on linear theory has the following form:

[0037]

[0038] Where, μ mn It is the nth root of the derivative of the m-th Bessel function, R g It is the radius of the electron beam guiding center, I start Q is the starting current, Q is the total quality factor of the cavity, Z0 and λ are the free space impedance and wavelength, m0 and e0 are the rest mass and charge of the electron, respectively, γ0 is the relativistic factor, f(z) is the normalized field amplitude, and k is the starting current. mn It is a transverse beam, where c is the speed of light in a vacuum, C mn It is the normalization constant, β ⊥0 and β z0 denoted as the transverse and longitudinal normalized velocities of electrons, respectively; L is the length of the interaction cavity; and s is the harmonic order.

[0039] See Figure 3 , Figure 4 To obtain the performance parameters of the gyrotron, such as its frequency and beam-wave interaction efficiency in operating mode, further analysis of the beam-wave interaction process is needed. Self-consistent nonlinear theory, combining the effect of the electromagnetic field on electrons and the excitation of the electromagnetic field by electrons, can accurately determine key parameters such as the gyrotron's resonant frequency and beam-wave interaction efficiency. The self-consistent nonlinear theory equations are as follows:

[0040]

[0041] Where: f(z) is the axial field distribution, e mn J is the transverse magnitude vector. ω The distribution represents the transverse current density, where ρ and I0 are the line charge density and DC electron injection current, respectively. t and v z These represent the transverse and longitudinal velocities of the electron, respectively.

[0042] The relationship between the start current and different magnetic fields in the operating mode is plotted on... Figure 2 From this, it can be seen that near an external magnetic field of 4.8T, TE 3,3 The starting current of the mode increases from 80mA to 250mA as the longitudinal exponent increases.

[0043] The operating frequency and beam-wave interaction efficiency of the operating mode are plotted against different magnetic fields. Figure 3 As can be seen, the operating frequency of the working mode changes from 263.71 GHz to 263.81 GHz with the increase of the operating magnetic field, and the beam-wave interaction efficiency increases from 2.45% to 23.7% with the increase of the operating magnetic field.

[0044] The operating frequency and beam-wave interaction efficiency of the operating mode are plotted against different voltages. Figure 4 As can be seen, the operating frequency of the working mode varies between 263.71 GHz and 263.72 GHz with the increase of the operating magnetic field, and the beam-wave interaction efficiency increases from 2.2% to 25.2% with the increase of the operating magnetic field.

[0045] Simulation experiments were conducted on the open cyclotron resonance structure with a three-segment cavity structure of the present invention, and the results are as follows: Figure 3 , Figure 4 As shown:

[0046] In the simulation, the starting current results showed that the electron transverse and longitudinal velocity ratio α = 1.5, and the guide center radius R... g =0.966mm;

[0047] In the simulation, the voltage was 10kV and the electron beam current I0 = 100mA.

[0048] In the simulation, the electron beam current I0 = 100mA and the magnetic field is 4.78T. The relationship between the electron beam-wave interaction efficiency and the operating frequency with the operating voltage is shown.

[0049] Figure 2 The curves showing the change of the starting current with the working magnetic field in the operating mode are shown.

[0050] Figure 3 The results show the relationship between injection-wave interaction efficiency and operating frequency as a function of the operating magnetic field.

[0051] Figure 4 The results show the relationship between injection-wave interaction efficiency and operating frequency as a function of operating voltage.

[0052] The performance and effects of the gyrotron structure with a gradually increasing output section were analyzed using linear and nonlinear calculations in Matlab. The results were presented graphically, which is quite convincing. It shows that the gyrotron structure with a gradually increasing output section can solve the problem of low output efficiency caused by the incompatibility of existing terahertz beams with high beam-wave interaction efficiency and suppression of competing modes. It proves that the gyrotron structure with a gradually increasing output section can be used for second harmonic operation and maintain good performance.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gyrotron structure based on a gradual output section, characterized by: The application relates to an open gyrotron resonator device comprising a three-section cavity structure, which comprises a cutoff section cavity of a tilted annular open metal structure, an interaction section cavity of an open metal cylindrical waveguide structure and an output section cavity of a tilted tapered annular open metal structure, which are sequentially connected in a head-to-tail mode from left to right, the cutoff section cavity is sized to determine that the working mode does not disturb the adiabatic compression process of the electrons in the electron gun region and the gyro motion at the entrance of the resonant cavity, the cutoff section cavity comprises a metal circular waveguide with a certain opening angle, the interaction section cavity is sized to determine the strength of the energy exchange between the working mode and the gyro electrons and the working frequency, the interaction section cavity comprises a metal waveguide, the cross-sectional dimension of the metal waveguide of the interaction section cavity is consistent with the maximum cross-sectional dimension of the metal waveguide of the cutoff section cavity, and the output section cavity is sized to determine that the working mode must be in a wave state at the outlet when transmitted in the interaction section cavity, the output section cavity comprises a metal circular waveguide with a certain opening angle, and the minimum cross-sectional dimension of the metal waveguide of the output section cavity is consistent with the cross-sectional dimension of the metal waveguide of the interaction section.

2. A gyrotron structure based on a tapered output section according to claim 1, characterized in that: The cutoff section cavity of the tilted annular open metal structure is rotationally symmetrical about the z-axis, the maximum cross-sectional radius of the cutoff section cavity of the tilted annular open metal structure is 2.053 mm, the length is 7.5 mm, the tilt angle is 5 DEG, and the metal wall thickness is 6 mm.

3. A gyrotron structure based on a tapered output section according to claim 1, characterized in that: The interaction section cavity of the open metal cylindrical waveguide structure is rotationally symmetrical about the z-axis and starts at the end of the cutoff section cavity, the cross-sectional radius of the interaction section cavity of the open metal cylindrical waveguide structure is 2.053 mm, the length is 34 mm, and the metal wall thickness is 6 mm.

4. A gyrotron structure based on a tapered output section according to claim 1, characterized in that: The output section cavity of the tilted tapered annular open metal structure is rotationally symmetrical about the z-axis and starts at the end of the interaction section cavity, the minimum cross-sectional radius of the output section cavity of the tilted tapered annular open metal structure is 2.053 mm, the length is 10 mm, the tilt angle is 1.5 DEG, and the metal wall thickness is 6 mm.

5. A gyrotron structure based on a tapered output section according to claim 1, characterized in that: The cutoff section cavity of the tilted annular open metal structure, the interaction section cavity of the open metal cylindrical waveguide structure and the output section cavity of the tilted tapered annular open metal structure are all made of oxygen-free copper.

6. The output section cavity of the tilted tapered annular open metal structure starts at the end of the interaction section cavity, the cross-sectional dimension of the output section cavity of the tilted tapered annular open metal structure is a distribution function of the cavity length, and the calculation formula of the cross-sectional dimension with the distribution function of the cavity length is as follows: In the formula, R(z) is a cross-sectional radius function, A, B and C are undetermined coefficients, and z is the axial distance from a certain position of the output section cavity of the tilted tapered annular open metal structure to the end of the open metal cylindrical waveguide structure.

7. A gyrotron structure based on a gradual output section and a method of generating a second harmonic electromagnetic wave thereof, characterized by, The application further relates to a method for manufacturing the open gyrotron resonator device. The electron emitted by the electron gun with applied voltage and current is adiabatically compressed by the magnetic field to make the axial gyration along the propagation axis, and then the working mode electromagnetic wave is excited by the cavity from the cutoff section to the interaction section, and the working mode electromagnetic wave is radiated along the output section, and the electric parameters changing the voltage, current and magnetic field size can make the radiated electromagnetic wave have certain power and frequency.

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