Cyclotron wave tube interaction system loaded with double-loss material composite and design method thereof

Abstract

The application discloses a gyrotron traveling wave tube interaction system loaded with double-loss material and a design method thereof. The application periodically loads a sheet-shaped mode selection attenuation waveguide in a nonlinear mode selection waveguide to suppress self-oscillation of a main competitive mode. In the case that the total length of the nonlinear mode selection waveguide is unchanged, the introduction of the sheet-shaped mode selection attenuation waveguide can increase the threshold of the starting current of the main competitive mode, so that higher working current can be stably worked, and high-power stable output of the gyrotron traveling wave tube is realized. In the case that the working current is unchanged, the mode selection attenuation waveguide realizes stable work in the case that the nonlinear mode selection waveguide is set, and the efficiency and gain of the beam-wave interaction of the gyrotron traveling wave tube are improved. The application has low sensitivity to the parameters of loss material and has application potential in the engineering implementation of the high average power gyrotron traveling wave tube. The application is simple and easy to implement in engineering, and exhibits excellent performance in the development of the gyrotron traveling wave tube.

Description

Technical Field

[0001] This invention relates to vacuum electronic devices—gyrotron technology, specifically to a gyrotron traveling wave tube interaction system with dual-loss material composite loading and its design method. Background Technology

[0002] Cyclotron amplifiers operate based on the relativistic principle of the electron cyclotron maser (ECM), capable of generating coherent electromagnetic wave radiation in the hundreds of kilowatts to megawatts range across millimeter-wave and submillimeter-wave frequency ranges. The gyrotron traveling-wave tube (Gyro-TWT) amplifier operates on the convective instability of the ECM. This device possesses both high power and wide bandwidth characteristics, making it the preferred high-power millimeter-wave transmitter for next-generation high-resolution imaging radar, outer space small target tracking, high-precision cloud imaging, and high-speed long-range communication electronic systems. Currently, gyrotron traveling-wave tubes in different frequency bands have been successfully developed. Despite the numerous advantages of gyrotron traveling-wave tubes, mode competition in their interaction systems remains a major bottleneck limiting their performance. Mode competition refers to the phenomenon where multiple electromagnetic modes (such as operating modes and competing modes) coexist and compete for energy during interaction. This phenomenon leads to unstable output power, spectrum pollution, and reduced efficiency; in severe cases, it can even cause self-oscillation of the device, resulting in equipment damage.

[0003] Currently, there are many methods for suppressing mode competition in gyrocopter interaction systems, such as lossy material loading techniques, confocal waveguide techniques, slotted waveguide techniques, grooved waveguide techniques, and graded waveguide techniques. However, most of these methods are applied to the linear segment of the gyrocopter interaction system. Under higher-order mode conditions, the attenuation capability of the structure is insufficient, limiting the high-power operation capability of the device. Furthermore, for the nonlinear segment where self-excited oscillations of competing modes are most likely to occur, the available methods are relatively limited, which greatly restricts the high-power performance of the gyrocopter. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a gyro traveling wave tube (GWT) interaction system with dual-loss material composite loading and its design method. Based on the fact that loss materials can suppress the self-excited oscillation in the GWT, by adding a weakly attenuated loss waveguide to the nonlinear interaction system of the GWT, the attenuation loss of the main competing modes is increased while ensuring minimal impact on the transmission characteristics of the operating mode. This improves the stability of the nonlinear segment, increases the operating current, and enables the GWT to operate stably at high power.

[0005] One object of the present invention is to provide a gyroscopic traveling wave tube interaction system with a composite loading of two lossy materials.

[0006] The gyroscopic traveling wave tube interaction system with dual-loss material composite loading of the present invention includes: a linear high-loss section waveguide, a nonlinear mode-selective waveguide, and a graded interaction waveguide; wherein, the linear high-loss section waveguide, the nonlinear mode-selective waveguide, and the graded interaction waveguide are connected into an integral tubular structure with a circular cross-section.

[0007] The linear high-loss waveguide consists of a uniform metallic circular waveguide and an attenuation loss waveguide. Multiple attenuation loss waveguides are arranged one-dimensionally and periodically along the axial direction. Adjacent attenuation loss waveguides are connected to each other as a whole by a uniform metallic circular waveguide. The inner diameter of the linear high-loss waveguide is consistent along the axial direction. The attenuation loss waveguide is made of a high-attenuation loss material. The linear high-loss waveguide enhances the loss of electromagnetic waves. It achieves a high transmission loss rate for electromagnetic waves through dense periodic attenuation loss waveguides, suppresses back-wave oscillations of all modes, and minimizes the entry of stray mode energy into the nonlinear mode-selective waveguide.

[0008] The nonlinear mode-selective waveguide comprises a graded-equal-metal circular waveguide and a mode-selective attenuation waveguide. Multiple sheet-like mode-selective attenuation waveguides are arranged one-dimensionally and periodically along the axial direction. The radial thickness and axial width of each sheet-like waveguide are consistent, while the inner diameter gradually increases along the axial direction. Adjacent sheet-like waveguides are connected as a single unit by the graded-equal-metal circular waveguide. The inner diameter of the nonlinear mode-selective waveguide gradually increases along the axial direction, with the inner diameter at the beginning of the nonlinear mode-selective waveguide equal to the inner diameter of the linear high-loss section waveguide. The loss material of the mode-selective attenuation waveguide is a weakly attenuating loss material, resulting in a transmission loss rate significantly higher than that of the metallic circular waveguide and lower... Attenuation loss waveguide in linear segment; Nonlinear mode selection waveguide for precise control of transmission loss capability of main competing modes; Based on the material of the sheet-like mode selection attenuation waveguide, the cutoff wavelength of the main competing modes, and the propagation constant and wavelength of the operating mode, the period, radial thickness, and axial width of the periodic sheet-like mode selection attenuation waveguide are determined. Thus, the periodic sheet-like mode selection attenuation waveguide introduced by the nonlinear mode selection waveguide suppresses the self-excited oscillation of the main competing modes, while ensuring that the transmission characteristics of the operating mode are not significantly affected, i.e., it has mode selectivity and low transmission loss of the operating mode, realizing a high-power cyclotron traveling wave tube;

[0009] The graded interaction waveguide is a graded metallic circular waveguide with an inner diameter that gradually increases along the axial direction. The inner diameter at the beginning of the graded interaction waveguide is equal to the inner diameter at the end of the nonlinear mode selection waveguide, and the operating mode is propagated through the graded interaction waveguide.

[0010] The three waveguide segments work synergistically: the linear high-loss waveguide and the nonlinear mode-selective waveguide work together. The linear segment reduces stray mode energy entering the nonlinear mode-selective waveguide through "pre-filtering," providing a stable environment for it. The nonlinear mode-selective waveguide, while suppressing the main competing modes through weak transmission loss, extends the interaction length, acting as a "pre-clustering" mechanism for the electron beam, which is beneficial for the amplification process of the subsequent gradient interaction segment. The combination of these three elements enables the gyrocopter interaction system to achieve high-power stable output, ultimately overcoming the power degradation and spectral pollution problems caused by mode competition in traditional schemes. This structure-function synergistic design retains the efficient interaction of the operating modes while dynamically balancing power and stability through a segmented transmission loss strategy, providing key technical support for the engineering of high-power gyrocopter systems.

[0011] The transmission loss range of the linear high-loss waveguide design is 10–50 dB / cm.

[0012] The periodic, sheet-like mode-selective attenuation waveguide introduced by the nonlinear mode-selective waveguide has a transmission loss of <5dB / cm for the operating mode. By increasing the radial thickness, its coverage of the strong field region of the main competing mode is extended, thereby enhancing the absorption efficiency of parasitic mode energy and significantly improving the oscillation current threshold of the main competing mode.

[0013] The tapered output waveguide is the primary site for interaction and energy exchange between the electron beam and the electromagnetic wave. After entering the tapered output interaction section, the electron beam's cyclotron motion gradually matches the phase velocity of the electromagnetic wave. The electron beam transfers energy to the electromagnetic wave through a synchronous resonance mechanism, thus achieving initial amplification. As the interaction between the electron beam and the electromagnetic wave continues, the energy transfer efficiency significantly improves, and the power of the electromagnetic wave increases rapidly. The tapered output interaction section is characterized by its high Q-factor and ultra-low loss characteristics, effectively suppressing energy dissipation and amplifying the electromagnetic wave. The use of a nonlinear mode-selective waveguide significantly increases the start-up current threshold of the main competing modes, ensuring that only the operating mode electromagnetic wave can be stably amplified within the tapered interaction section, guaranteeing that the cyclotron traveling wave tube can produce stable high-power output.

[0014] Based on the loss characteristics of the loss material applied to electromagnetic waves, the structural parameters of the attenuation loss waveguide in the linear high-loss section are set. These parameters include the permeability, dielectric constant, loss tangent, radial thickness, axial width, and period of the loss material. According to the electromagnetic wave transmission loss characteristics, the parameters of the attenuation loss waveguide in the linear high-loss section are adjusted. The higher the axial fill ratio of the attenuation loss waveguide within a single period, the stronger the equivalent loss of the periodic structure. Therefore, within one period, the axial width of the attenuation loss waveguide is 10 to 20 times that of the uniform metallic circular waveguide, and the duty cycle of the attenuation loss waveguide within a single period should be greater than 85%, depending on the type and frequency of the operating mode. The linear high-loss section waveguide enhances loss and suppresses back-wave oscillations of different modes without changing the existing main transmission characteristics, while maintaining the traveling wave dispersion characteristics of the waveguide, ensuring a high start-up threshold for the device, and improving the high-power operation capability of the system.

[0015] Traditional gyrotron traveling wave tube (TWT) interaction systems consist only of a linear high-loss waveguide and a graded-interaction waveguide. Generally, the longer the graded-interaction waveguide, the more complete the beam-wave interaction, which is more conducive to achieving high efficiency and high power. However, an excessively long graded-interaction waveguide will lower the threshold of the competing mode oscillation current, making it easy for the competing mode to oscillate and interfere with the amplification process of the operating mode. This will make the operation of the gyrotron TWT interaction system unstable, resulting in reduced output power and a cluttered output spectrum. This invention proposes a gyroscopic traveling wave tube (GWT) interaction system that incorporates a nonlinear mode-selective waveguide (MSCW). Within the MSCW, a periodic structure combining a sheet-like MSCW with a graded-scale metallic circular waveguide is employed. The sheet-like MSCW exhibits a significantly higher transmission loss rate than the metallic circular waveguide, but lower than that of conventional loss materials. The optimized duty cycle of the MSCW within a single cycle is 20%–40%, further suppressing self-oscillations of the dominant competing modes in the MSCW. Simultaneously, the driving power reaches 1kW–10kW in this segment, providing high-power drive for downstream high-power amplifiers and facilitating high-power output. The MSCW uses a weakly attenuated loss material, resulting in a transmission loss rate more than 1000 times higher than that of the metallic circular waveguide, depending on the operating frequency and the material parameters (dielectric constant and loss tangent).

[0016] Attenuation loss waveguides for linear high-loss waveguides and mode selection attenuation waveguides for nonlinear mode selection waveguides are typically made of composite ceramic materials, such as alumina-titanium oxide (Al2O3-TiO2), magnesium oxide-silicon oxide (MgO-SiO2), beryllium oxide-silicon oxide (BeO-SiO2), etc.

[0017] By adjusting the doping ratio, the dielectric constant (ε) and loss tangent (tanδ) can be precisely controlled, thereby precisely adjusting the transmission loss rate of the material for electromagnetic waves. The transmission loss rate is directly proportional to the loss tangent; the larger the loss tangent, the greater the transmission loss rate, and it is related to the dielectric constant and frequency.

[0018] Another objective of this invention is to propose a design method for a gyroscopic traveling wave tube interaction system with a composite loading of two lossy materials.

[0019] The design method of the gyroscopic traveling wave tube interaction system with dual-loss material composite loading of the present invention includes the following steps:

[0020] 1) Structural components of a gyroscopic traveling wave tube interaction system:

[0021] Multiple attenuation loss waveguides are arranged one-dimensionally and periodically along the axial direction. Adjacent attenuation loss waveguides are connected to each other by uniform metal circular waveguides to form a linear high-loss section waveguide. The inner diameter of the linear high-loss section waveguide is consistent along the axial direction. The attenuation loss waveguide is made of a high-attenuation loss material.

[0022] Multiple sheet-like mode-selective attenuation waveguides are arranged one-dimensionally and periodically along the axial direction. Adjacent sheet-like mode-selective attenuation waveguides are connected to form a nonlinear mode-selective waveguide by a graded-ratio metallic circular waveguide. The inner diameter of the nonlinear mode-selective waveguide gradually increases along the axial direction, and the inner diameter at the beginning of the nonlinear mode-selective waveguide is equal to the inner diameter of the linear high-loss section waveguide. The mode-selective attenuation waveguide is made of a low-attenuation loss material, and its transmission loss rate is much higher than that of the metallic circular waveguide but lower than that of the linear attenuation loss waveguide.

[0023] The graded interaction waveguide is a graded metallic circular waveguide with an inner diameter that gradually increases along the axial direction. The inner diameter at the beginning of the graded interaction waveguide is equal to the inner diameter at the end of the nonlinear mode selection waveguide.

[0024] A linear high-loss waveguide, a nonlinear mode-selective waveguide, and a graded-interaction waveguide are connected into a single tubular structure with a circular cross-section.

[0025] 2) Structural parameter settings for the attenuation loss waveguide of the linear high-loss section waveguide:

[0026] Based on the loss characteristics of the loss material on electromagnetic waves, the structural parameters of the attenuation loss waveguide of the linear high loss section waveguide are set. Within this period, the axial filling ratio is high, that is, the axial width of the attenuation loss waveguide is much larger than the width of the uniform metal circular waveguide.

[0027] 3) Setting the structural parameters of the mode-selective attenuation waveguide for nonlinear mode-selective waveguides:

[0028] A periodic mode-selective attenuation waveguide, introduced by a nonlinear mode-selective waveguide, suppresses the dominant competing modes. The structural parameters of the sheet-like mode-selective attenuation waveguide are set to satisfy the following conditions, based on the loss characteristics of the loss material on the electromagnetic wave:

[0029] a) Based on the phase velocity matching between the operating mode and the electron beam, the period of the plate-shaped mode selection attenuation waveguide is determined. By optimizing the period L, the dispersion distortion caused by the mismatch periodic loading of the operating mode is avoided, and the interaction gain is improved.

[0030] b) By increasing the radial thickness of the sheet-like mode selection attenuation waveguide, the start-up current of the main competing modes can be increased, so as to ensure that the sheet-like mode selection attenuation waveguide can effectively improve the start-up current of the main competing modes; the larger the ratio of radial thickness to waveguide radius, the more significant its disturbance to electromagnetic field distribution and the stronger the loss.

[0031] c) By reducing the axial width, the disturbance of the waveguide equivalent dispersion by the periodic sheet-like mode selection attenuation waveguide is reduced, while avoiding phase velocity mismatch or reflection caused by axial discontinuity of the operating mode.

[0032] In step 2), the loss characteristic α exerted by the loss material on the electromagnetic wave satisfies:

[0033]

[0034] Where ω is the angular frequency of the electromagnetic wave, μ is the permeability of the loss material, and ε₀ε₀ r t is the dielectric constant of the loss material, tanδ is the loss tangent of the loss material, and t r and t z Let denoted by , where is the radial thickness and axial width of the loss material, L is the period of the loss material, and a is the inner diameter of the waveguide. The larger the proportion of the radial thickness to the waveguide radius, the more significant its disturbance to the electromagnetic field distribution, resulting in enhanced loss. The higher the axial filling ratio within a single period, the stronger the equivalent loss of the periodic structure.

[0035] In step 3)a), the period L of the sheet-like mode selection attenuation waveguide satisfies:

[0036]

[0037] Where, β w λ is the propagation constant of the operating mode, and λ is the wavelength of the electromagnetic wave in the operating mode.

[0038] In step 3)b), to ensure that the sheet-like mode-selective attenuation waveguide can effectively improve the start-up current of the main competing modes, the radial thickness t of the sheet-like mode-selective attenuation waveguide is... r satisfy:

[0039]

[0040] Where, λ c ε is the cutoff wavelength for the main competing mode. r is the absolute dielectric constant of the lossy material.

[0041] In step 3)c), the loaded sheet-like mode selection attenuation waveguide also affects the operating mode. An excessively large axial width introduces significant dispersion, leading to bandwidth compression or spectral distortion in the operating mode. A smaller axial width, however, maintains the quasi-uniformity of the waveguide. The axial width t... z Should meet:

[0042]

[0043] In this case, the disturbance of waveguide equivalent dispersion by periodic loading structure can be reduced, and phase velocity mismatch or reflection caused by axial discontinuity in the operating mode can be avoided.

[0044] Advantages of this invention:

[0045] This invention employs a lossy material loading method. Based on the transmission characteristics of electromagnetic waves in a circular waveguide loaded with lossy material, it suppresses the self-excited oscillation of the main competing modes in a nonlinear interaction system by periodically loading a sheet-like mode selection attenuation waveguide onto the nonlinear mode selection waveguide of a gyroscopic traveling wave tube. Compared to the method of coating the walls of a metallic circular waveguide with a weak attenuation lossy material, this innovative design skips the development of the weak attenuation material, effectively avoiding the influence of the lossy material coating accuracy on the lateral dimensions of the interaction section. Compared to traditional smooth metallic circular waveguide nonlinear interaction systems, the sheet-like mode selection attenuation waveguide used in this invention has the following advantages: First, with the total length of the nonlinear mode selection waveguide remaining constant, the energy introduced by the sheet-like mode selection attenuation waveguide is significantly reduced. This invention improves the threshold of the oscillation current of the main competing modes, thereby enabling stable operation at higher operating currents and achieving high-power stable output of the gyrotron traveling wave tube. Secondly, with a constant operating current, the introduction of the mode-selective attenuation waveguide can achieve stable operation by appropriately increasing the length of the nonlinear mode-selective waveguide, thus improving the efficiency and gain of the beam-wave interaction of the gyrotron traveling wave tube. Finally, the plate-shaped mode-selective attenuation waveguide loading method used in this invention has low sensitivity to loss material parameters and can be extended to the linear section of the gyrotron, thus showing significant application potential in the engineering implementation of high-average-power gyrotron traveling wave tubes. This invention is simple and easy to implement in engineering, and is expected to demonstrate excellent performance in the development of gyrotron traveling wave tubes. Attached Figure Description

[0046] Figure 1This is an axial cross-sectional view of an embodiment of the gyroscopic traveling wave tube interaction system with dual-loss material composite loading according to the present invention.

[0047] Figure 2 The electric field distribution and dispersion curves of the operating mode under different parameter conditions are obtained for an embodiment of the gyro traveling wave tube interaction system with dual loss material composite loading according to the present invention.

[0048] Figure 3 The diagram shows a comparison between the gyratory traveling wave tube interaction system of the present invention with that of the prior art gyratory traveling wave tube, wherein (a) is a schematic diagram of the existing gyratory traveling wave tube and (b) is a schematic diagram of the gyratory traveling wave tube of the present invention.

[0049] Figure 4 The simulation results of the existing cyclotron traveling wave tube model are shown in the figure, where (a) is the output power diagram and (b) is the output spectrum diagram.

[0050] Figure 5 The following are simulation results of an embodiment of the gyrotron traveling wave tube interaction system with dual-loss material composite loading according to the present invention, wherein (a) is the output power diagram, (b) is the output spectrum diagram, and (c) is the correspondence diagram between output power and input power at different frequencies;

[0051] Figure 6 This is a comparison diagram of the interaction system of the gyro traveling wave tube with dual-loss material composite loading of the present invention and the gyro traveling wave tube of the prior art, wherein (a) is the TE 02 Comparison of start-up current threshold and axial field distribution of the mode, (b) is TE 22 Comparison of the starting current threshold and axial field distribution of the mode. Detailed Implementation

[0052] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0053] The design method of the gyroscopic traveling wave tube interaction system with dual-loss material composite loading in this embodiment includes the following steps:

[0054] 1) Structural components of a gyroscopic traveling wave tube interaction system:

[0055] Multiple attenuation loss waveguides are arranged one-dimensionally and periodically along the axial direction. Adjacent attenuation loss waveguides are connected to each other by uniform metal circular waveguides to form a linear high-loss section waveguide. The inner diameter of the linear high-loss section waveguide is consistent along the axial direction. The attenuation loss waveguide is made of a high-attenuation loss material.

[0056] Multiple sheet-like mode-selective attenuation waveguides are arranged one-dimensionally and periodically along the axial direction. Adjacent sheet-like mode-selective attenuation waveguides are connected to form a nonlinear mode-selective waveguide by a graded-ratio metallic circular waveguide. The inner diameter of the nonlinear mode-selective waveguide gradually increases along the axial direction, and the inner diameter at the beginning of the nonlinear mode-selective waveguide is equal to the inner diameter of the linear high-loss section waveguide. The mode-selective attenuation waveguide is made of a low-attenuation loss material, and its transmission loss rate is much higher than that of the metallic circular waveguide but lower than that of the linear attenuation loss waveguide.

[0057] The graded interaction waveguide is a graded metallic circular waveguide with an inner diameter that gradually increases along the axial direction. The inner diameter at the beginning of the graded interaction waveguide is equal to the inner diameter at the end of the nonlinear mode selection waveguide.

[0058] A linear high-loss waveguide, a nonlinear mode-selective waveguide, and a graded-interaction waveguide are connected into a single tubular structure with an internal vacuum and a circular cross-section perpendicular to the axis.

[0059] 2) Structural parameter settings for the attenuation loss waveguide of the linear high-loss section waveguide:

[0060] Based on the loss characteristics of the loss material on electromagnetic waves, the structural parameters of the attenuation loss waveguide of the linear high loss section waveguide are set. Within this period, the axial filling ratio is high, that is, the axial width of the attenuation loss waveguide is much larger than the width of the uniform metal circular waveguide.

[0061] The loss characteristic α of the lossy material to electromagnetic waves satisfies:

[0062]

[0063] Where ω is the angular frequency of the electromagnetic wave, μ is the permeability of the loss material, and ε₀ε₀ r ε is the dielectric constant of the loss material, ε0 is the vacuum dielectric constant, tanδ is the loss tangent of the loss material, and t r and t z Let L represent the radial thickness and axial width of the loss material, L be the period of the loss material, and a be the inner diameter of the waveguide. A larger proportion of radial thickness to waveguide radius results in more significant disturbance to the electromagnetic field distribution, increased loss, and a higher axial fill ratio within a single period, leading to stronger equivalent loss for the periodic structure. The uniform metallic circular waveguide material for the linear high-loss section is oxygen-free copper with a conductivity of 5.8 × 10⁻⁶. 7 The attenuation loss waveguide has an inner diameter of 3.62 mm, an outer diameter of 5.792 mm, an axial width of 8.69 mm, a period of 9.414 mm, and a duty cycle of 92.3% within a single period. The loss material is a beryllium oxide-silicon oxide (BeO-SiO2) doped composite ceramic material with a relative permittivity ε. rThe value is 13.4, and the loss tangent is 0.63;

[0064] 3) Setting the structural parameters of the mode-selective attenuation waveguide for nonlinear mode-selective waveguides:

[0065] The first mode selection attenuation waveguide of the nonlinear mode-selective waveguide has an inner diameter of 3.62 mm and an outer diameter of 9.774 mm. The loss material of the mode selection attenuation waveguide is a beryllium oxide-silicon oxide (BeO-SiO2) composite ceramic material with different doping ratios, a relative permittivity of 11.6, and a loss tangent of 0.42. To satisfy the loss characteristics of the loss material applied to the electromagnetic wave, the loss characteristics also change slightly due to the gradual increase in the inner diameter of the nonlinear mode selection waveguide. The periodic mode selection attenuation waveguide introduced by the nonlinear mode selection waveguide suppresses the main competing modes. The structural parameters of the sheet-like mode selection attenuation waveguide are set such that, while satisfying the loss characteristics of the loss material applied to the electromagnetic wave, the plane of the sheet-like mode selection attenuation waveguide is perpendicular to the axial direction, the radial thickness is increased, and the axial width is decreased. The axial width has a small duty cycle within one cycle, and the radial thickness is much larger than the axial width. The structural parameters satisfy the following conditions:

[0066] a) Based on the phase velocity matching between the operating mode and the electron beam, the period of the plate-shaped mode selection attenuation waveguide is determined. The optimized period L avoids dispersion distortion caused by mismatched periodic loading of the operating mode, while also improving the interaction gain. The period L of the plate-shaped mode selection attenuation waveguide satisfies:

[0067]

[0068] Where, β w λ is the propagation constant of the operating mode, and λ is the wavelength of the electromagnetic wave in the operating mode; the period of the plate-shaped mode selection attenuation waveguide is 3.04 mm, and the duty cycle of the mode selection attenuation waveguide in a single period is 28.6%.

[0069] b) By increasing the radial thickness of the sheet-like mode-selective attenuation waveguide, the start-up current of the main competing modes can be increased, ensuring that the sheet-like mode-selective attenuation waveguide can effectively enhance the start-up current of the main competing modes; the larger the proportion of radial thickness to waveguide radius, the more significant its disturbance to the electromagnetic field distribution, and the enhanced loss. The radial thickness t of the sheet-like mode-selective attenuation waveguide... r satisfy:

[0070]

[0071] Where, λ c ε is the cutoff wavelength for the main competing mode. r The absolute dielectric constant of the loss material;

[0072] c) The loaded sheet-like mode selection attenuation waveguide also affects the operating mode. An excessively wide axial width introduces significant dispersion, leading to bandwidth compression or spectral distortion in the operating mode. A smaller axial width, however, maintains the quasi-uniformity of the waveguide. The axial width t... z Should meet:

[0073]

[0074] In this case, the disturbance of waveguide equivalent dispersion by the periodically loaded structure can be reduced, and phase velocity mismatch or reflection caused by axial discontinuity in the working mode can be avoided; the axial width is 0.87 mm.

[0075] Figure 2 The diagram illustrates a gyroscopic traveling wave tube interaction system with a dual-loss material composite loading according to the present invention, for a selected attenuation ceramic sheet radial thickness in the W-band TE band. 02 Operating modes under different attenuation ceramic parameters (TE) 02 By comparing the electric field distribution and dispersion curves of the operating mode with simulation results under different attenuation ceramic parameters, a deeper understanding can be gained of the protection mechanism of this design for the operating mode and its robustness to changes in material parameters. It can be seen that the field distribution of the operating mode in the vacuum region differs from that in a smooth circular waveguide. 02 The field distributions of the modes are similar. Furthermore, it is known that the dispersion characteristics of the operating mode do not change significantly when the dielectric constant of the loss material changes by ±20% and the loss tangent changes by ±50% (loss material parameters: relative dielectric constant ε). r The loss tangent is 0.42 (11.6). The above analysis shows that the mode-selective attenuation waveguide of the nonlinear mode-selective waveguide used in this invention has minimal impact on the operating mode field distribution and exhibits high robustness and stability to changes in the parameters of the loss material. In the practical design of gyrotron interaction systems, the loss of the nonlinear interaction system is adjusted by changing the axial periodic structure. Increasing the period length enhances the attenuation effect on the main competing modes, while decreasing the period length optimizes the transmission efficiency of the operating mode. This flexible design method allows the scheme to adapt to the needs of different frequency bands and operating modes, providing reliable technical support for the development of high-performance gyrotron traveling wave tubes.

[0076] To verify the function and advantages of this invention, two gyroscopic traveling wave tubes were designed, such as... Figure 3 As shown, the total length of the cyclotron traveling wave tube is 106 mm. Figure 3 (a) is a traditional pure metal nonlinear interaction system, where the pure metal material with gradually changing output interaction section uses oxygen-free copper (conductivity 5.8 × 10⁻⁶). 7 The waveguide is made of (S / m), with a waveguide radius a = 3.62 mm and a gradient section length L. g=40mm, used for a smooth transition to the output port, with a gradient section end radius of 3.728mm. Figure 3 (b) is the cyclotron traveling wave tube proposed in this invention, wherein the mode-selective attenuation waveguide is composed of periodically loaded sheet-like magnesium oxide-beryllium oxide (BeO-SiO2) composite ceramic material (relative permittivity ε). r =11.6, loss tangent tanδ=0.42) constitutes the mode selection attenuation waveguide radial thickness t r = 6.154mm, axial width t z =0.87mm, the periodic length along the axial direction L = 3.04mm, the nonlinear mode selection attenuation waveguide is followed by a pure metallic graded output section, the length of the graded section L g =20mm. The linear segment structure and parameters of the two schemes are exactly the same, the difference lies only in the nonlinear segment. Figure 3 b is in Figure 3 This is based on the periodic loading of a weakly lossy ceramic sheet in the first half of the nonlinear segment.

[0077] Compared to the periodic loading method of attenuation ceramics in the linear segment of traditional gyroscopic traveling wave tubes (TWTs), the radial thickness and axial width of the attenuation ceramics loaded in the nonlinear segment are relatively large. This is done to increase attenuation of the main competing modes while minimizing the impact of the attenuation ceramic loading on the transmission characteristics of the nonlinear segment's operating modes. This is because, on the one hand, TE... 02 The electric field of the mode (angular electromagnetic field intensity E) θ ) and magnetic field (radial magnetic field strength H) r and axial magnetic field strength H z The main focus is on the waveguide center region, with mode selection attenuation waveguides and TE. 02 The coupling between modes is extremely weak; even with a large radial thickness of the ceramic sheet, the transmission loss to the operating mode is relatively small (<0.1dB / cm), while TE 22 The field energy of the mode is distributed in the middle and outer layers of the waveguide radius. The radial components of the electric and magnetic fields are significantly enhanced near the waveguide wall, and the axial distribution exhibits periodic variations. Increasing the radial thickness (t) r ) Scalable mode-selectable attenuation waveguide for TE 22 The coverage area of ​​the modulus field region enhances the energy absorption efficiency (attenuation constant α∝t). r / a, where a is the waveguide radius). On the other hand, TE 02 The phase velocity of the mode must be synchronized with the electron beam cyclotron velocity (v p ≈v e ), to ensure continuous energy exchange. Axial width (t) z An excessively large axial width t introduces periodic disturbances, leading to phase velocity mismatch and a decrease in gain. Maintaining a relatively small axial width t z(As shown in formula (4)) can reduce the disturbance of the periodic structure on the waveguide equivalent dispersion and maintain TE 02 The propagation constant β of the mode w Stability.

[0078] The two systems were simulated using the 3D particle simulation software CST, and the simulation results were compared. This embodiment designs the gyrotron interaction system based on the following parameters: W-band frequency and TE operating mode. 02 The operating mode is 70kV, the operating current is 13A, the horizontal-to-vertical velocity ratio is 1.2, and the electron beam velocity dispersion is 5%.

[0079] Figure 4 Based on Figure 3 (a) The simulation results of the model show that TE 02 The mode did not achieve stable high-power output. This is because the main competing mode, TE... 22 Self-excited oscillations occurred in the nonlinear segment, with a frequency of approximately 87 GHz. This severely affected the interaction effect of the operating mode in the system, disrupted the clustering state of the electron beam, and ultimately caused the output power to begin to decrease around 2.4 ns, eventually maintaining a low power level. Figure 5 Based on Figure 3 (b) shows the simulation results of the mode-selective attenuation waveguide. The simulation results show that, under the same operating voltage, cross-sectional velocity ratio, and velocity discretization conditions, this structure successfully suppresses the main competing mode TE. 22 The oscillation of the mode realizes TE 02 Stable output in this mode. The figure shows the amplification at a frequency of 92GHz, where the input power is 50W and the output power is approximately 360kW. Calculations show a gain of 38.5dB. Figure 5 (c) shows the relationship between input power and output power of a cyclotron traveling wave using a mode-selective attenuation waveguide at different frequencies. The maximum power is 360kW, and the bandwidth for 100kW and above is 10GHz.

[0080] Figure 6 For two configurations, TE 02 Pattern and TE 22 The start-up current threshold I and axial field distribution of the mode are represented by solid lines. Figure 3 (a) shows a traditional gyroscopic traveling wave tube structure, with the dashed line corresponding to... Figure 3 (b) shows a gyro traveling wave tube employing a mode-selective attenuation waveguide. It can be seen that in a traditional gyro traveling wave tube structure, the main competing mode is TE. 22The oscillation current threshold I of this mode is lower than the operating current (13A), therefore this mode will establish self-excited oscillation, thus affecting the amplification process of the operating mode, ultimately leading to a decrease in the output power of the gyrotron traveling wave tube and a cluttered output spectrum, such as... Figure 4 As shown. However, this invention employs a mode-selective attenuation waveguide in a gyroscopic traveling wave tube, where the main competing mode TE... 22 The oscillation current threshold I is increased to 15.4A, which is greater than the operating current, therefore TE will not occur. 22 The self-excited oscillation mode enables the cyclotron traveling wave amplifier to stably generate high power output, which further verifies the correctness of the invention.

[0081] As can be seen from the above comparison, the gyro traveling wave tube interaction system scheme with dual-loss material composite loading proposed in this invention can effectively suppress the self-excited oscillation of the main competing modes and realize the high-power stable operation of the gyro traveling wave tube.

[0082] This invention effectively suppresses self-excited oscillations of the main competing modes in an interaction system by adding a periodically loaded mode-selective attenuation waveguide to the nonlinear mode-selective waveguide, thus achieving high-power stable operation of the gyroscopic traveling wave tube (GWT). Furthermore, the improved interaction system of this invention is applicable to gyroscopic GWTs across various frequency bands. Finally, this invention is simple in design, easy to implement in engineering, and exhibits excellent performance, which can promote the research, application, and development of high-performance gyroscopic GWTs.

[0083] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.

Claims

1. A gyroscopic traveling wave tube interaction system with dual-loss material composite loading, characterized in that, The cyclotron traveling wave tube interaction system includes: a linear high-loss section waveguide, a nonlinear mode-selective waveguide, and a graded interaction waveguide; wherein, the linear high-loss section waveguide, the nonlinear mode-selective waveguide, and the graded interaction waveguide are connected into a whole tubular structure with a circular cross-section. The linear high-loss waveguide consists of a uniform metallic circular waveguide and an attenuation loss waveguide. Multiple attenuation loss waveguides are arranged one-dimensionally and periodically along the axial direction. Adjacent attenuation loss waveguides are connected to each other as a whole by a uniform metallic circular waveguide. The inner diameter of the linear high-loss waveguide is consistent along the axial direction. The attenuation loss waveguide is made of a high-attenuation loss material. The linear high-loss waveguide enhances the loss of electromagnetic waves. It achieves a high transmission loss rate for electromagnetic waves through dense periodic attenuation loss waveguides, suppresses back-wave oscillations of all modes, and minimizes the entry of stray mode energy into the nonlinear mode-selective waveguide. The nonlinear mode-selective waveguide comprises a graded-equal-metal circular waveguide and a mode-selective attenuation waveguide. Multiple sheet-like mode-selective attenuation waveguides are arranged one-dimensionally and periodically along the axial direction. The radial thickness and axial width of each sheet-like waveguide are consistent, while the inner diameter gradually increases along the axial direction. Adjacent sheet-like waveguides are connected as a single unit by the graded-equal-metal circular waveguide. The inner diameter of the nonlinear mode-selective waveguide gradually increases along the axial direction, with the inner diameter at the beginning of the nonlinear mode-selective waveguide equal to the inner diameter of the linear high-loss section waveguide. The loss material of the mode-selective attenuation waveguide is a weakly attenuating loss material, resulting in a transmission loss rate significantly higher than that of the metallic circular waveguide and lower... Attenuation loss waveguide in linear segment; Nonlinear mode selection waveguide for precise control of transmission loss capability of main competing modes; Based on the material of the sheet-like mode selection attenuation waveguide, the cutoff wavelength of the main competing modes, and the propagation constant and wavelength of the operating mode, the period, radial thickness, and axial width of the periodic sheet-like mode selection attenuation waveguide are determined. Thus, the periodic sheet-like mode selection attenuation waveguide introduced by the nonlinear mode selection waveguide suppresses the self-excited oscillation of the main competing modes, while ensuring that the transmission characteristics of the operating mode are not significantly affected, i.e., it has mode selectivity and low transmission loss of the operating mode, realizing a high-power cyclotron traveling wave tube; The graded interaction waveguide is a graded metallic circular waveguide with an inner diameter that gradually increases along the axial direction. The inner diameter at the beginning of the graded interaction waveguide is equal to the inner diameter at the end of the nonlinear mode selection waveguide, and the operating mode is propagated through the graded interaction waveguide.

2. The gyroscopic traveling wave tube interaction system as described in claim 1, characterized in that, The attenuation loss waveguide has a duty cycle greater than 85% in a single period.

3. The gyroscopic traveling wave tube interaction system as described in claim 1, characterized in that, The duty cycle of the mode-selective attenuation waveguide in a single period is 20% to 40%.

4. A design method for a gyroscopic traveling wave tube interaction system with dual-loss material composite loading as described in claim 1, characterized in that, The design method includes the following steps: 1) Structural components of a gyroscopic traveling wave tube interaction system: Multiple attenuation loss waveguides are arranged one-dimensionally and periodically along the axial direction. Adjacent attenuation loss waveguides are connected to each other by uniform metal circular waveguides to form a linear high-loss section waveguide. The inner diameter of the linear high-loss section waveguide is consistent along the axial direction. The attenuation loss waveguide is made of a high-attenuation loss material. Multiple sheet-like mode-selective attenuation waveguides are arranged one-dimensionally and periodically along the axial direction. Adjacent sheet-like mode-selective attenuation waveguides are connected to form a nonlinear mode-selective waveguide by a graded-ratio metallic circular waveguide. The inner diameter of the nonlinear mode-selective waveguide gradually increases along the axial direction, and the inner diameter at the beginning of the nonlinear mode-selective waveguide is equal to the inner diameter of the linear high-loss section waveguide. The mode-selective attenuation waveguide is made of a low-attenuation loss material, and its transmission loss rate is much higher than that of the metallic circular waveguide but lower than that of the linear attenuation loss waveguide. The graded interaction waveguide is a graded metallic circular waveguide with an inner diameter that gradually increases along the axial direction. The inner diameter at the beginning of the graded interaction waveguide is equal to the inner diameter at the end of the nonlinear mode selection waveguide. A linear high-loss waveguide, a nonlinear mode-selective waveguide, and a graded-interaction waveguide are connected into a single tubular structure with a circular cross-section. 2) Structural parameter settings for the attenuation loss waveguide of the linear high-loss section waveguide: Based on the loss characteristics of the loss material on electromagnetic waves, the structural parameters of the attenuation loss waveguide of the linear high loss section waveguide are set. Within this period, the axial filling ratio is high, that is, the axial width of the attenuation loss waveguide is much larger than the width of the uniform metal circular waveguide. 3) Setting the structural parameters of the mode-selective attenuation waveguide for nonlinear mode-selective waveguides: A periodic mode-selective attenuation waveguide, introduced by a nonlinear mode-selective waveguide, suppresses the dominant competing modes. The structural parameters of the sheet-like mode-selective attenuation waveguide are set to satisfy the following conditions, based on the loss characteristics of the loss material on the electromagnetic wave: a) Based on the phase velocity matching between the operating mode and the electron beam, determine the period of the plate-shaped mode selection attenuation waveguide. By optimizing the period L, avoid dispersion distortion caused by mismatched periodic loading of the operating mode, and at the same time improve the interaction gain. b) By increasing the radial thickness of the sheet-like mode selection attenuation waveguide, the start-up current of the main competing modes can be increased, so as to ensure that the sheet-like mode selection attenuation waveguide can effectively improve the start-up current of the main competing modes; the larger the ratio of radial thickness to waveguide radius, the more significant its disturbance to electromagnetic field distribution and the stronger the loss. c) By reducing the axial width, the disturbance of the waveguide equivalent dispersion by the periodic sheet-like mode selection attenuation waveguide is reduced, while avoiding phase velocity mismatch or reflection caused by axial discontinuity of the operating mode.

5. The design method as described in claim 4, characterized in that, In step 2), the loss characteristic α exerted by the loss material on the electromagnetic wave satisfies: in, The angular frequency of the electromagnetic wave. The permeability of the loss material, Let be the dielectric constant of the loss material. For the loss tangent of the loss material, t r and t z ε0 represents the radial thickness and axial width of the loss material, respectively; L represents the period of the loss material; a represents the inner diameter of the waveguide; and ε0 represents the vacuum permittivity.

6. The design method as described in claim 4, characterized in that, In step 3)a), the period L of the sheet-like mode selection attenuation waveguide satisfies: Where, β w λ is the propagation constant of the operating mode, and λ is the wavelength of the electromagnetic wave in the operating mode.

7. The design method as described in claim 4, characterized in that, In step 3)b), to ensure that the sheet-like mode-selective attenuation waveguide can effectively improve the start-up current of the competing modes, the radial thickness of the sheet-like mode-selective attenuation waveguide is... satisfy: Where, λ c ε is the cutoff wavelength for the main competing mode. r is the absolute dielectric constant of the loss material.

8. The design method as described in claim 4, characterized in that, In step 3)c), the loaded sheet-like mode selection attenuation waveguide affects the operating mode, and the axial width... satisfy: Where L is the period.

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