Terahertz folded waveguide traveling wave tube reliability analysis design method

Abstract

The invention relates to the technical field of vacuum electronics terahertz, and particularly discloses a terahertz folded waveguide traveling wave tube reliability analysis design method, which comprises an electron gun, a signal input window, a folded waveguide high-frequency structure, a signal output window, a collector, a high-frequency radiating fin and a radiating base, and is characterized in that the electron gun is used for emitting electron beams; the folded waveguide high-frequency structure generates terahertz radiation by reducing the interaction between the electromagnetic wave phase velocity and the electron beam; the signal input window and the signal output window are used for inputting and outputting signals; the collector is used for recovering and dissipating electron beam energy after beam-wave interaction; the high-frequency radiating fins and the radiating base are used for fixing the traveling wave tube; according to the simulation method provided by the invention, systematic reliability analysis is carried out on the whole traveling wave tube, different from analysis of all parts, structural defects can be found and solved easily, simulation analysis guidance is provided for actual machining and assembling, the success rate of engineering tube manufacturing is increased, the production cost is reduced, and the development period is shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of vacuum electronics terahertz, and in particular relates to a reliability analysis and design method for a terahertz folded waveguide traveling wave tube. Background Art

[0002] Terahertz (THz) waves refer to electromagnetic waves with a frequency between 0.1 and 10 THz and a wavelength range of 3 mm to 30 μm. Terahertz waves are located between the far infrared and submillimeter wave bands. They are a transitional field between electronics and photonics. They have unique electromagnetic wave properties, such as high transmittance, high resolution, low energy, coherence, and wide bandwidth. Terahertz technology is an innovative means to open up new scientific fields and has huge application potential in biomedicine, materials science, wireless communications, and other fields.

[0003] Terahertz radiation sources are key devices for the widespread application of terahertz technology. The generation methods mainly include radiation sources based on semiconductor electronics, radiation sources based on optics and photonics, and radiation sources based on vacuum electronics. Among them, the terahertz traveling wave tube is a vacuum electronics terahertz device that uses the interaction between electron beams and electromagnetic waves to amplify terahertz waves. It has the advantages of high power, high gain, and wide bandwidth. It is widely used in radar, communication, imaging, electronic countermeasures and other fields. The working environment of the terahertz traveling wave tube is complex and will be affected by vibration and shock, which has a great impact on the traveling wave tube. Reliability and stability pose challenges. As traveling wave tubes develop towards miniaturization, high power and high efficiency, the failure of traveling wave tubes caused by thermal management problems is becoming more and more serious. At present, the research on the reliability of terahertz traveling wave tubes at home and abroad is mostly focused on the thermal analysis and vibration analysis of electron guns, collectors, and slow-wave structure components, and there is a lack of systematic reliability research on the whole tube. Considering the complex process and expensive production cost of terahertz traveling wave tubes, a reliability analysis and design method for terahertz folded waveguide traveling wave tubes is proposed. Computer simulation technology should be used in the design stage to conduct a detailed reliability analysis of the whole tube to reduce the development risk.

[0004] The present invention provides a reliability analysis method for a 0.34THz folded waveguide traveling wave tube, which includes dynamic and static, high and low temperature thermal characteristics analysis and mechanical vibration analysis of the terahertz traveling wave tube. It guides the actual processing process, thereby reducing production costs, shortening cycles, and increasing the service life of the terahertz traveling wave tube. Summary of the invention

[0005] The purpose of the present invention is to provide a reliability analysis and design method for a terahertz folded waveguide traveling wave tube, so as to solve the problems that the existing terahertz traveling wave tube lacks a systematic reliability study on the whole tube, and lacks empirical formulas and simulation analysis guidance in the actual processing process, resulting in high traveling wave tube development cost, long cycle and low structural reliability.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A reliability analysis and design method for a terahertz folded waveguide traveling wave tube comprises an electron gun, a signal input window, a folded waveguide high-frequency structure, a signal output window, a collector, a high-frequency heat sink and a heat dissipation base.

[0008] Electron gun, used to emit electron beam;

[0009] Folded waveguide high-frequency structure generates terahertz radiation by reducing the phase velocity of electromagnetic waves and interacting with electron beams;

[0010] Signal input window and signal output window, used for signal input and output;

[0011] The collector is used to recover and dissipate the energy of the electron beam after the first wave of interaction;

[0012] The high-frequency heat sink and heat sink base are used to fix the traveling wave tube and provide conduction heat dissipation for the traveling wave tube.

[0013] Also includes:

[0014] Step 1: Establish a terahertz folded waveguide traveling wave assembly model;

[0015] Establish the original model according to the designed traveling wave tube structure dimensions, and set the material characteristic parameters of the corresponding components, including density, thermal conductivity, thermal expansion coefficient, Young's modulus, and Poisson's ratio;

[0016] Step 2: Analyze the dynamic and static, high and low temperature thermal characteristics of the terahertz traveling wave tube in ANSYS Workbench; import the established model into ANSYS Workbench, use the steady-state thermal analysis module to accurately divide the grid, apply heat loads to the electron gun, high-frequency structure, and collector according to the actual working environment and the thermal characteristics of the terahertz traveling wave tube under different working environments, set the convective ambient temperature and convective heat transfer coefficient on the surface of the traveling wave tube, analyze the temperature field distribution of the traveling wave tube under different temperatures and dynamic and static conditions, and understand the heat accumulation position of the traveling wave tube. If no heat accumulation occurs, it meets the requirements; if heat accumulation occurs and cannot be smoothly conducted, the thermal conductivity is enhanced by adding a heat dissipation structure; this analysis can guide the location of adding a heat dissipation structure;

[0017] At the same time, it is analyzed whether micro deformation will occur and affect the state of the electromagnetic field. If the micro deformation does not affect the state of the electromagnetic field, it is passed; if the micro deformation of a certain part affects the state of the electromagnetic field, the factors that can produce micro deformation are corrected. For example, the cathode will produce thermal expansion at high temperature, resulting in a decrease in the distance between the cathode and the bunching electrode and the high-frequency structure, thereby affecting the bunching and transmission of the electron beam, and thus the distance between the cathode, the bunching electrode, and the high-frequency structure is corrected;

[0018] Step 3: Perform thermal stress analysis of the terahertz traveling wave tube in ANSYS Workbench;

[0019] Using the steady-state thermal analysis and static structural coupling analysis modules, the steady-state thermal analysis results of step two (i.e., the results of the passing state) are used as the loads of the static structural analysis to simulate the thermal expansion deformation of the traveling wave tube. The base is set as a fixed support to obtain the thermal stress distribution results. The influence of the deformation structure caused by thermal stress on the output characteristics of the terahertz traveling wave tube is obtained. By judging the influence on the output characteristics, if the high-frequency signal output is stable, it meets the requirements; if the high-frequency signal output is unstable, it does not meet the requirements, and heat dissipation structure and heat conduction structure are added to reduce the influence and stabilize the high-frequency signal output.

[0020] Step 4: Perform modal analysis with temperature prestress in ANSYS Workbench;

[0021] Use the modal analysis module to use the thermal stress distribution results of step 3 as the load of modal analysis, solve the modal frequency and vibration mode of the traveling wave tube, and analyze the mechanical properties of the terahertz traveling wave tube under different thermal environments;

[0022] The natural frequency of the traveling wave tube obtained by analysis is compared with the vibration frequency in the working environment. If the deformation is small, the output is stable and meets the requirements; if the deformation is large and affects the stability of the output signal, the modal characteristics are modified.

[0023] Step 5: Perform terahertz traveling wave tube vibration analysis in ANSYS Workbench;

[0024] Use the random vibration analysis module, take the modal analysis results of step 4 as the load of vibration analysis, apply the acceleration power spectrum density, and solve the response of the traveling wave tube under random vibration excitation. Analyze the mechanical bearing capacity of key parts under random vibration conditions. According to the terahertz traveling wave tube design specifications (the design specifications can refer to the requirements of "Reliability Design of Spacecraft Electronic Products"), judge whether the mechanical bearing capacity of key parts is qualified. If qualified, it passes. If not, further reinforce to increase the bearing capacity to meet the design requirements, such as by adding stable brackets and reinforcing beams to increase the bearing capacity.

[0025] During operation, the traveling wave tube will be affected by mechanical environments such as vibration and shock, which may cause the performance of the traveling wave tube to degrade or fail. Therefore, it is very necessary to analyze the seismic performance of the traveling wave tube in the working state. By analyzing the dynamic characteristics of the structure, the structural design can be guided and improved to prevent the traveling wave tube from being damaged by resonance during operation. In addition, during the operation of the terahertz traveling wave tube, there is a multi-physical field coupling of "electromagnetic-thermal-mechanical", electromagnetic heat generation, heat causes changes in material properties, causes deformation, and then affects the vibration characteristics of the traveling wave tube. The vibration characteristics of the structure can be characterized by modal frequency and vibration mode, which can characterize the response degree and sensitivity of the structure to dynamic loads. At the same time, the response under different vibration excitations is also an important part of the dynamic characteristics, which can be used to evaluate the durability and safety of the structure. This section combines the thermal analysis results to perform modal analysis, and then performs random vibration analysis on the basis of modal analysis to study the response of the traveling wave tube under different vibration excitations.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The reliability analysis method of a terahertz folded waveguide traveling wave tube of the present invention has at least one of the following advantages over the prior art:

[0028] The simulation method proposed in the present invention performs a systematic reliability analysis on the entire traveling wave tube, which is different from the analysis of each component and is helpful to discover and solve structural defects, provide simulation analysis guidance for actual processing and assembly, improve the success rate of engineering tube manufacturing, reduce production costs, and shorten the development cycle.

[0029] The reliability analysis simulation method proposed in the present invention includes electromagnetic thermal effect analysis, dynamic and static high and low temperature thermal characteristics analysis, thermal deformation analysis, modal analysis, and random vibration analysis. The temperature field, structural stiffness, and vibration mode of the traveling wave tube are analyzed in detail. The components in the traveling wave tube that are prone to resonance and thermal deformation are analyzed in the design stage to prevent the failure of the terahertz traveling wave tube due to temperature control or vibration.

[0030] The present invention simulates the "electromagnetic-thermal-force-vibration" multi-physical field coupling process of the traveling wave tube in a working state, which is closer to the actual working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The original model of the traveling wave tube of the embodiment;

[0032] Figure 2 The reliability analysis process of the embodiment;

[0033] Figure 3 A meshing model for an embodiment;

[0034] Figure 4 The heat consumption power distribution of the embodiment;

[0035] Figure 5 It is a dynamic high temperature 55°C temperature field distribution cloud diagram of the embodiment;

[0036] Figure 6 It is a thermal stress cloud map of an embodiment;

[0037] Figure 7 It is a modal analysis vibration shape cloud diagram of the embodiment;

[0038] Figure 8 Stress cloud diagram of random vibration analysis of the embodiment.

[0039] In the figure: 1. Electron gun; 2. Signal input window; 3. Folded waveguide high-frequency structure; 4. Signal output window; 5. Collector; 6. High-frequency heat sink; 7. Heat sink base. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] A reliability analysis and design method for a terahertz folded waveguide traveling wave tube, comprising an electron gun 1, a signal input window 2, a folded waveguide high-frequency structure 3, a signal output window 4, a collector 5, a high-frequency heat sink 6 and a heat dissipation base 7. A reliability analysis and design method for a terahertz folded waveguide traveling wave tube, comprising an electron gun 1, a signal input window 2, a folded waveguide high-frequency structure 3, a signal output window 4, a collector 5, a high-frequency heat sink 6 and a heat dissipation base 7.

[0042] An electron gun 1, used for emitting electron beams;

[0043] Folded waveguide high-frequency structure 3, generating terahertz radiation by reducing the phase velocity of electromagnetic waves and interacting with electron beams;

[0044] Signal input window 2 and signal output window 4 are used for signal input and output;

[0045] The collecting electrode 5 is used to recover and dissipate the electron injection energy after the first wave of interaction;

[0046] The high-frequency heat sink 6 and the heat sink base 7 are used to fix the traveling wave tube and provide conduction heat dissipation for the traveling wave tube, and also include:

[0047] In this example, a 0.34THz folded waveguide traveling wave tube is selected as the model. The structure diagram is shown in the figure. Figure 1As shown in Figure 1, the materials involved include electric vacuum materials such as Kovar (4J33), oxygen-free copper (Tu1), 95 alumina insulating ceramics (A-95), pure iron (DT8), monel (Ni Cu40-2-1), samarium cobalt (Sm2Co17), molybdenum (Mo1) and tungsten (Wu), etc. Some material parameters are shown in Table 1.

[0048] Table 10. Material parameters of various components of 34THz traveling wave tube

[0049]

[0050]

[0051] The reliability analysis method of terahertz folded waveguide traveling wave tube is simulated using ANSYS Workbench. The whole simulation process is shown in Figure 2 . The process is divided into five steps.

[0052] Step 1: Establish a terahertz folded waveguide traveling wave assembly model;

[0053] According to the designed traveling wave tube structure size, the original model is established in the geometric structure module of ANSYS Workbench. Figure 1 The original model of the embodiment is established. Then, according to the material parameters in Table 1, material parameters are added in the engineering data module of ANSYS Workbench.

[0054] Step 2: Analyze the dynamic and static characteristics and high and low temperature thermal characteristics of the terahertz traveling wave tube in ANSYS Workbench;

[0055] Use ANSYS Workbench steady-state thermal analysis module to automatically mesh the model and encrypt the mesh of fine parts. Figure 3 The meshed traveling wave tube model is shown. According to the thermal characteristics of the 0.34THz traveling wave tube, the heat consumption of the electron gun part is 5W, the heat consumption of the high frequency part is 24W, and the heat consumption of the collector part is 55W. The heat consumption power distribution is shown in Figure 4 , the thermal power consumption distribution of the traveling wave tube is applied to the corresponding position of the traveling wave tube. According to the working environment requirements of the traveling wave tube, the storage temperature range is: -55℃~+70℃, and the working temperature range of the traveling wave tube is -40℃~+55℃. This article considers the maximum working temperature of the traveling wave tube at 55℃. The environment of the whole tube is natural air convection, and the convection heat transfer coefficient is set to 10W / (m 2 ·K). Set the ambient temperature on the surface of the traveling wave tube to 55°C and the convection heat transfer coefficient to 10W / (m 2 ·K), and applying the input signal at the same time, the dynamic high temperature 55℃ temperature field distribution of the traveling wave tube can be obtained; by changing the ambient temperature, the dynamic -40℃ temperature field distribution can be obtained. Figure 5The temperature field distribution of the whole traveling wave tube at a dynamic high temperature of 55℃ is shown. The highest temperature of the electron gun is 1492.5℃; the highest temperature of the folded waveguide high frequency is 199.6℃, with a temperature rise of 144.6℃, and the highest temperature is close to the high frequency output end; the highest temperature of the collector is 212℃, with a temperature rise of 157℃, and the highest temperature appears at the tail cone of the collector; the highest temperature of the installation base is 201.6℃, with a temperature rise of 146.6℃, and the highest temperature is at the installation of the collector. Based on the high-temperature working temperature distribution and raw material characteristics of the traveling wave tube, the temperature rise of the tube body caused by the heating of the traveling wave tube will not affect the tube body material and the performance of the whole tube, and the thermal control conditions of the platform can meet the long-term stable working requirements of the traveling wave tube.

[0056] Similarly, the static temperature field distribution of -55°C-70°C without applying a signal is obtained, which will not be described in detail.

[0057] At the same time, it is analyzed whether micro deformation will occur and affect the state of the electromagnetic field. If the micro deformation does not affect the state of the electromagnetic field, it is passed; if the micro deformation of a certain part affects the state of the electromagnetic field, the factors that can produce micro deformation are corrected. For example, the cathode will produce thermal expansion at high temperature, resulting in a decrease in the distance between the cathode and the bunching electrode and the high-frequency structure, thereby affecting the bunching and transmission of the electron beam, and thus the distance between the cathode, the bunching electrode, and the high-frequency structure is corrected;

[0058] Step 3: Perform thermal stress analysis of the terahertz traveling wave tube in ANSYS Workbench;

[0059] Using the ANSYS Workbench steady-state thermal analysis and static structural coupling analysis modules, the steady-state thermal analysis results of step 2 are used as the load for static structural analysis to simulate the thermal expansion deformation of the traveling wave tube. The base is set as a fixed support to obtain the thermal stress distribution results. Figure 6 The maximum thermal deformation occurs at the edge of the mounting base and will not affect the performance of the traveling wave tube.

[0060] Step 4: Perform modal analysis with temperature prestress in ANSYS Workbench;

[0061] Using the modal analysis module, the thermal stress distribution results of step 3 are used as the load of the modal analysis to solve the modal frequency and vibration mode of the traveling wave tube. In order to more clearly describe the vibration mode of the electron gun structure, the red potting glue wrapped on the outer surface of the electron gun is suppressed. The modal vibration mode cloud diagram is shown in Figure 7 , the modal frequencies are shown in Table 2. From the simulation results, the first-order natural frequency of the overall structure is 1729.6 Hz, which is a high-frequency vibration in nature. According to the actual application scenario, it can be considered that no resonance will occur during work.

[0062] Table 2 The first 6 modes of the traveling wave tube

[0063]

[0064]

[0065] Table 3 Random vibration test conditions

[0066]

[0067] It should be noted that PSD (power spectrum density) is power spectrum density; the identification level refers to more comprehensive and in-depth test indicators, while the acceptance level focuses more on verifying whether the basic functions and performance of the product are qualified; the power spectrum density is a trapezoid in the image.

[0068] Step 5: Perform terahertz traveling wave tube vibration analysis in ANSYS Workbench;

[0069] Using the random vibration analysis module, the modal analysis results of step 4 are used as the load for vibration analysis. Random vibration conditions are applied to the X, Y, and Z directions of the traveling wave tube. The applied power spectrum density is shown in Table 3. The response of the traveling wave tube under random vibration excitation is obtained, as shown in Table 3. Figure 8 According to the content of structural strength design in the basic design of aerospace electronic equipment in "Reliability Design of Spacecraft Electronic Products", the safety margin is calculated as follows:

[0070]

[0071] Where [σ] is the required stress. For brittle materials, the strength limit is σb; for other materials, the elastic limit is σ0.2. Generally, the safety factor for quasi-static loads is f≥1.5; the safety factor for vibration loads is f=1.2-1.35. Figure 8 It can be seen that the maximum 1σ stress of the THz traveling wave tube is 23.4Mpa, and its 3σ stress is 70.2MPa, which occurs at the sapphire window. The material is sapphire. The elastic limit is between 350-450MPa, and the structural strength safety margin is:

[0072]

[0073] Meet the design requirements of structural strength safety margin.

[0074] The traveling wave tube was designed to resist mechanical environment. Through structural mechanics analysis, it was shown that the fundamental frequency of the traveling wave tube met the requirements, the structural strength met the safety margin requirements, and the analysis results met the design requirements.

[0075] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A reliability analysis and design method for a terahertz folded waveguide traveling wave tube, comprising an electron gun (1), a signal input window (2), a folded waveguide high-frequency structure (3), a signal output window (4), a collector (5), a high-frequency heat sink (6) and a heat sink base (7). A reliability analysis and design method for a terahertz folded waveguide traveling wave tube, comprising an electron gun (1), a signal input window (2), a folded waveguide high-frequency structure (3), a signal output window (4), a collector (5), a high-frequency heat sink (6) and a heat sink base (7). An electron gun (1) for emitting an electron beam; Folded waveguide high-frequency structure (3) generates terahertz radiation by reducing the phase velocity of electromagnetic waves and interacting with electron beams; A signal input window (2) and a signal output window (4), used for input and output of signals; A collecting electrode (5) for recovering and dissipating the electron beam energy after the first wave of interaction; The high-frequency heat sink (6) and the heat sink base (7) are used to fix the traveling wave tube and provide conduction heat dissipation for the traveling wave tube, and also include: Step 1: Establish a terahertz folded waveguide traveling wave assembly model; Step 2: Analyze the dynamic and static characteristics and high and low temperature thermal characteristics of the terahertz traveling wave tube in ANSYS Workbench; Step 3: Perform thermal stress analysis of the terahertz traveling wave tube in ANSYS Workbench; Step 4: Perform modal analysis with temperature prestress in ANSYS Workbench; Step 5: Perform terahertz traveling wave tube vibration analysis in ANSYS Workbench.

2. According to the reliability analysis and design method of a terahertz folded waveguide traveling wave tube according to claim 1, the terahertz folded waveguide traveling wave assembly model is provided with material characteristic parameters of corresponding components, and the material characteristic parameters include density, thermal conductivity, thermal expansion coefficient, Young's modulus and Poisson's ratio.

3. According to the reliability analysis and design method of a terahertz folded waveguide traveling wave tube according to claim 1, the established terahertz folded waveguide traveling wave assembly model is imported into ANSYS Workbench, and the network is divided by a steady-state thermal analysis module.

4. According to the reliability analysis and design method of a terahertz folded waveguide traveling wave tube according to claim 1, the established terahertz folded waveguide traveling wave assembly model applies thermal load to the electron gun, high-frequency structure and collector part through different actual working environments.

5. According to the reliability analysis and design method of a terahertz folded waveguide traveling wave tube according to claim 1, a traveling wave tube is arranged on the established terahertz folded waveguide traveling wave assembly model, and the surface of the traveling wave tube is provided with a convective ambient temperature and a convective heat transfer coefficient.

6. According to the reliability analysis and design method of a terahertz folded waveguide traveling wave tube according to claim 1, the steady-state analysis result in step 2 is used as the load of static structural analysis through a steady-state thermal analysis and static structural coupling analysis module.

7. According to the reliability analysis and design method of a terahertz folded waveguide traveling wave tube according to claim 1, the thermal stress distribution result of step three is used as the load of modal analysis through module analysis.

8. According to the reliability analysis and design method of a terahertz folded waveguide traveling wave tube according to claim 1, the modal analysis result of step 4 is used as the load of vibration analysis through random vibration analysis.

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