A reliability analysis and design method for terahertz folded waveguide traveling wave tube

Abstract

The present application relates to the field of vacuum electronics terahertz technology, and specifically discloses a reliability analysis design method for a terahertz folded waveguide traveling wave tube, which 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, the electron gun is used for emitting an electron beam; 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 recycling and dissipating the energy of the electron beam after the interaction between the electron beam and the wave; and the high-frequency heat sink and the heat dissipation base are used for fixing the traveling wave tube; the simulation method provided by the present application performs a systematic reliability analysis on the whole traveling wave tube, which is different from the analysis of each component, and is helpful to find structural defects and solve problems, provides simulation analysis guidance for actual processing and assembly, improves the success rate of engineering tube production, reduces production cost and shortens the development cycle.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of vacuum electronics terahertz technology, and particularly relates to a reliability analysis design method of a terahertz folded waveguide traveling wave tube. BACKGROUND

[0002] Terahertz (THz) wave refers to electromagnetic wave with a frequency of 0.1-10 THz and a wavelength range of 3 mm-30 μm, and is located between the far infrared and submillimeter wave bands, is the transition field of electronics and photonics, and has unique electromagnetic wave properties such as high transmission, high resolution, small energy, coherence, and wide frequency band, and the terahertz technology is an innovative means for exploring new scientific fields, and has great application potential in biomedical science, material science, wireless communication and the like.

[0003] A terahertz radiation source is a key device for wide application of the terahertz technology, and the generation methods mainly include a terahertz wave radiation source based on semiconductor electronics, a terahertz wave radiation source based on optical and photonics methods, and a terahertz wave radiation source based on vacuum electronics methods, wherein the terahertz traveling wave tube is a vacuum electronics terahertz device for amplifying terahertz waves by utilizing the interaction between an electron beam and electromagnetic waves, has advantages of high power, high gain, wide frequency band and the like, and is widely applied in the fields of radar, communication, imaging, electronic countermeasure and the like, the working environment of the terahertz traveling wave tube is complex, and the terahertz traveling wave tube is affected by vibration impact, which poses challenges to the reliability and stability of the terahertz traveling wave tube, with the development of the terahertz traveling wave tube in the direction of miniaturization, high power and high efficiency, the failure of the terahertz traveling wave tube caused by thermal management problems is increasingly serious, at present, the research on the reliability of the terahertz traveling wave tube at home and abroad is mainly concentrated in the thermal analysis and vibration analysis of the electron gun, the collector and the slow wave structure components, and lacks systematic reliability research on the whole tube, considering the complex process and expensive production cost of the terahertz traveling wave tube, therefore, a reliability analysis design method of a terahertz folded waveguide traveling wave tube is provided, and the computer simulation technology is used for detailed reliability analysis of the whole tube in the design stage, so as to reduce the development risk.

[0004] The application provides a 0.34 THz folded waveguide traveling wave tube reliability analysis method, which contains terahertz traveling wave tube dynamic and static, high and low temperature thermal characteristic analysis and terahertz traveling wave tube anti-mechanical vibration analysis. SUMMARY

[0005] The present application aims to provide a reliability analysis design method of a terahertz folded waveguide traveling wave tube, so as to solve the problem of lack of systematic reliability research of the whole tube in the existing terahertz traveling wave tube, and the problem of high cost, long cycle and low structural reliability of the traveling wave tube caused by lack of empirical formula and simulation analysis guidance in the actual processing process.

[0006] To achieve the above object, the present application provides the following technical scheme:

[0007] A reliability analysis design method of a terahertz folded waveguide traveling wave tube, comprising 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] The electron gun is used for emitting an electron beam.

[0009] The folded waveguide high-frequency structure is used for generating terahertz radiation by reducing the interaction between electromagnetic wave phase velocity and the electron beam.

[0010] The signal input window and the signal output window are used for input and output of signals.

[0011] The collector is used for recycling and dissipating the energy of the electron beam after interaction with the wave.

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

[0013] Further comprising:

[0014] Step 1: Establish a terahertz folded waveguide assembly model.

[0015] According to the structure size of the designed traveling wave tube, an original model is established, and the material property parameters of the corresponding components are set, including density, thermal conductivity, thermal expansion coefficient, Young's modulus and Poisson's ratio.

[0016] Step 2: Perform dynamic and static, high and low temperature thermal property analysis of the terahertz traveling wave tube in ANSYS Workbench; import the established model into ANSYS Workbench, accurately divide the mesh using the steady-state thermal analysis module, set the environmental temperature and convective heat transfer coefficient of the convection on the surface of the traveling wave tube according to the actual working environment and the thermal properties of the terahertz traveling wave tube under different working environments, and apply thermal load at the electron gun, high-frequency structure and collector positions, so as to analyze the temperature field distribution of the traveling wave tube under different temperatures, dynamics and statics, so as to 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 successfully conducted, the heat dissipation structure is increased to enhance the heat dissipation performance; this analysis can guide the position of the added heat dissipation structure.

[0017] At the same time, whether micro-deformation is generated to affect the electromagnetic field state is analyzed. If the micro-deformation does not affect the electromagnetic field state, it is passed; if the micro-deformation of a part affects the electromagnetic field state, the factors that can generate the micro-deformation are modified, for example, the cathode generates thermal expansion at high temperature, which causes the distance between the cathode, the bunching electrode and the high-frequency structure to become smaller, 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 modified.

[0018] Step three, performing a terahertz traveling wave tube thermal stress analysis in ANSYS Workbench;

[0019] Using a steady-state thermal analysis and static structure coupling analysis module, the steady-state thermal analysis result (i.e. the result of passing the state) of step two is taken as the load of the static structure analysis, the thermal expansion deformation of the traveling wave tube is simulated, the base is set as a fixed support, the thermal stress distribution result is obtained, the influence of the deformation structure caused by the thermal stress on the output characteristics of the terahertz traveling wave tube is obtained, and the influence on the output characteristics is judged. 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 a heat dissipation structure and a heat conduction structure are added to reduce the influence and stabilize the high-frequency signal output.

[0020] Step four, performing a modal analysis with temperature pre-stress in ANSYS Workbench;

[0021] Using a modal analysis module, the thermal stress distribution result of step three is taken as the load of the modal analysis, the modal frequency and mode shape of the traveling wave tube are solved, and the mechanical properties of the terahertz traveling wave tube under different thermal environments are analyzed;

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

[0023] Step five, performing a terahertz traveling wave tube vibration analysis in ANSYS Workbench;

[0024] Using a random vibration analysis module, the modal analysis result of step four is taken as the load of the vibration analysis, the acceleration power spectral density is applied, the response of the traveling wave tube under random vibration excitation is solved, the mechanical bearing capacity of the key parts under random vibration conditions is analyzed, and whether the mechanical bearing capacity of the key parts is qualified is judged according to the terahertz traveling wave tube design specification (the design specification can refer to the requirements of Spacecraft Electronic Products Reliability Design). If it is qualified, it is passed; if it is not qualified, it is further reinforced to increase the bearing capacity to meet the design requirements, for example, by increasing a stable support and reinforcing a beam to increase the bearing capacity.

[0025] The traveling wave tube will be affected by vibration, impact and other mechanical environment in the working process, which may cause the performance of the traveling wave tube to decline or fail. Therefore, it is necessary to analyze the anti-vibration performance of the traveling wave tube in the working state. Through the analysis of the dynamic characteristics of the structure, the design of the structure is guided and improved to prevent the traveling wave tube from being damaged due to resonance when working. In addition, during the working process of the terahertz traveling wave tube, there is a multi-physical field coupling of 'electromagnetic-thermal-force', electromagnetic heat generation, heat leading to material property change, causing deformation, and then affecting the vibration characteristics of the traveling wave tube. The vibration characteristics of the structure can be characterized by modal frequency and mode shape, which can represent the degree and sensitivity of the structure to dynamic load. 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. In this section, the modal analysis is carried out combined with the thermal analysis results, and the random vibration analysis is carried out on the basis of the modal analysis, and the response of the traveling wave tube under different vibration excitations is studied.

[0026] Compared with the prior art, the beneficial effects of the present application are:

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

[0028] The simulation method proposed in the present application performs a systematic reliability analysis on the whole traveling wave tube, which is different from the analysis of each component, and is helpful to find structural defects and solve them, providing simulation analysis guidance for actual machining and assembly, improving the success rate of engineering tube production, reducing production cost and shortening development cycle.

[0029] The reliability analysis simulation method proposed in the present application includes electromagnetic thermal effect analysis, dynamic and static high and low temperature thermal characteristic analysis, thermal deformation analysis, modal analysis and random vibration analysis, which has detailed analysis on the temperature field, structural stiffness and mode shape of the traveling wave tube. In the design stage, the components prone to resonance and thermal deformation in the traveling wave tube are analyzed, which can prevent the failure of the terahertz traveling wave tube caused by temperature control or vibration.

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

[0031] Figure 1 The traveling wave tube is an example of a model;

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

[0033] Figure 3 The meshing model of the embodiment;

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

[0035] Figure 5 Dynamic high temperature 55℃ temperature field distribution cloud map for example;

[0036] Figure 6 Thermal stress cloud map for example;

[0037] Figure 7 Modal analysis mode shape cloud map for example;

[0038] Figure 8 Random vibration analysis stress cloud map for example.

[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 dissipation base. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0041] A terahertz folded waveguide reliability analysis design method for a 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 terahertz folded waveguide reliability analysis design method for a 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] The electron gun 1 is used for emitting an electron beam;

[0043] The folded waveguide high frequency structure 3 generates terahertz radiation by reducing the interaction of electromagnetic wave phase velocity and electron beam;

[0044] The signal input window 2 and the signal output window 4 are used for input and output of signals;

[0045] The collector 5 is used for recycling and dissipating the energy of the electron beam after the interaction of the electron beam and the wave;

[0046] The high frequency heat sink 6 and the heat dissipation base 7 are used for fixing the traveling wave tube and providing conduction heat dissipation for the traveling wave tube, and further comprising:

[0047] In this example, a 0.34THz folded waveguide traveling wave tube is selected as a model, and the structural diagram is as follows Figure 1The materials involved are shown in Table 1, including electrical vacuum materials such as Kovar (4J33), oxygen-free copper (Tu1), 95 alumina insulating ceramic (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 each component of the 0.34 THz traveling wave tube

[0049]

[0050]

[0051] The reliability analysis method of the terahertz folded waveguide traveling wave tube uses ANSYS Workbench for simulation, and the entire simulation process is shown in Figure 2 . The process is divided into five steps.

[0052] Step one, establish the terahertz folded waveguide traveling wave assembly model;

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

[0054] Step two, perform dynamic and static, high and low temperature thermal characteristic analysis of the terahertz traveling wave tube in ANSYS Workbench;

[0055] Use the steady-state thermal analysis module of ANSYS Workbench. Automatically mesh the model, and mesh the fine parts, Figure 3 shows the traveling wave tube model after meshing. According to the thermal characteristics of the 0.34 THz 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 heat 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℃ to +70℃, and the working temperature range of the traveling wave tube is -40℃ to +55℃. In this paper, the highest working temperature of the traveling wave tube is considered to be 55℃. The environment in which the whole tube is placed is natural air convection, and the convection heat transfer coefficient is set to 10W / (m 2 ·K). The environmental temperature of 55℃ and the convection heat transfer coefficient of 10W / (m 2 ·K) are set on the surface of the traveling wave tube, and at the same time, the input signal is applied, to obtain the dynamic high temperature field distribution of the traveling wave tube at 55℃; by changing the environmental temperature, the dynamic-40℃ temperature field distribution can be obtained. Figure 5The temperature field distribution of the whole tube at dynamic high temperature 55℃ is shown, the maximum temperature of the electron gun is 1492.5℃; the maximum temperature of the folded waveguide is 199.6℃, the temperature rise is 144.6℃, and the maximum temperature is close to the high-frequency output end; the maximum temperature of the collector is 212℃, the temperature rise is 157℃, and the maximum temperature appears at the tail cone of the collector; the maximum temperature of the mounting plate is 201.6℃, the temperature rise is 146.6℃, and the maximum temperature is at the mounting position of the collector. According to the high-temperature working temperature distribution of the traveling wave tube and the characteristics of the raw materials, the temperature rise of the traveling wave tube caused by heat will not affect the tube 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 temperature field distribution at static-55℃-70℃ without applying a signal is obtained, which is not described here.

[0057] At the same time, whether micro-deformation will occur and affect the electromagnetic field state is analyzed, if the micro-deformation does not affect the electromagnetic field state, it is passed; if the micro-deformation of a certain part affects the electromagnetic field state, the factors that can cause micro-deformation are modified, for example, the cathode will produce thermal expansion at high temperature, which will cause the distance between the cathode, the bunching electrode and the high-frequency structure to become smaller, 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 modified.

[0058] Step three, thermal stress analysis of the terahertz traveling wave tube in ANSYS Workbench;

[0059] Using the steady-state thermal analysis and static structure coupling analysis module of ANSYS Workbench, the steady-state thermal analysis results of step two are used as the load of static structure analysis, the thermal expansion deformation of the traveling wave tube is simulated, the base is set as a fixed support, and the thermal stress distribution results are obtained, as shown in Figure 6 The maximum thermal deformation occurs at the edge of the mounting base, which will not affect the performance of the traveling wave tube.

[0060] Step four, modal analysis with temperature pre-stress in ANSYS Workbench;

[0061] Using the modal analysis module, the thermal stress distribution results of step three are used as the load of modal analysis, and the modal frequency and mode shape of the traveling wave tube are solved, in order to more clearly describe the mode shape of the electron gun structure, the red sealing glue wrapped on the outer surface of the electron gun is suppressed, the modal shape cloud map is shown in Figure 7 , and the modal frequency is shown in Table 2. From the simulation results, the first-order natural frequency of the overall structure is 1729.6Hz, which belongs to high-frequency vibration in nature, and according to the actual application scene, it can be considered that resonance will not occur in working.

[0062] Table 2 First 6 orders of traveling wave tube modal

[0063]

[0064]

[0065] Table 3 Random vibration test conditions

[0066]

[0067] Note: PSD (power spectrum density) is the power spectrum density; the qualification level refers to more comprehensive and in-depth test indicators, while the acceptance level is more focused on verifying whether the basic functions and performance of the product are qualified; the power spectrum density is trapezoidal on the image.

[0068] Step five, THz traveling wave tube vibration analysis in ANSYS Workbench;

[0069] Using the random vibration analysis module, the modal analysis results of step four are used as the load of vibration analysis, and random vibration conditions are applied in the X, Y and Z directions of the traveling wave tube. The power spectrum density applied is shown in Table 3. The response of the traveling wave tube under random vibration excitation is solved, as shown in Figure 8 According to the content of structural strength design in Spacecraft Electronic Product Reliability Design and the basis of space electronic equipment structure design, the safety margin calculation is as follows:

[0070]

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

[0072]

[0073] The safety margin design requirement of the structural strength is met.

[0074] The traveling wave tube is subjected to anti-mechanical environment design, and through structural mechanics analysis, it is shown that the fundamental frequency of the traveling wave tube meets the requirements, the structural strength meets the safety margin requirements, and the analysis results meet the design requirements.

[0075] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1.A reliability analysis design method of a terahertz folded waveguide traveling wave tube, comprising: Step 1, establishing a terahertz folded waveguide assembly model, establishing a raw model of the traveling wave tube according to the structure size of the designed traveling wave tube in the geometric structure module of ANSYS Workbench, setting the material property parameters of the corresponding components, establishing an assembly model of the terahertz folded waveguide, the raw model of the 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); the electron gun (1) is used for emitting an electron beam; the folded waveguide high-frequency structure (3) is used for generating terahertz radiation by reducing the interaction between the electromagnetic wave phase velocity and the electron beam; the signal input window (2) and the signal output window (4) are used for input and output of signals; the collector (5) is used for recycling and dissipating the energy of the electron beam after interaction with the wave; the high-frequency heat sink (6) and the heat dissipation base (7) are used for fixing the traveling wave tube and providing conduction heat dissipation for the traveling wave tube; the material property parameters include density, thermal conductivity, thermal expansion coefficient, Young's modulus, and Poisson's ratio; Step 2, performing dynamic and static, high and low temperature thermal property analysis of the terahertz traveling wave tube in ANSYS Workbench, importing the established terahertz folded waveguide assembly model into ANSYS Workbench, performing meshing through the steady-state thermal analysis module, and applying thermal load to the electron gun (1), the folded waveguide high-frequency structure, and the collector part through different actual working environments; Step 3, performing thermal stress analysis of the terahertz traveling wave tube in ANSYS Workbench, using the steady-state thermal analysis and static structure coupling analysis module, taking the steady-state thermal analysis result of step 2 as the load of the static structure analysis, simulating the thermal expansion deformation of the traveling wave tube, setting the base as a fixed support, and obtaining the thermal stress distribution result; Step 4, performing modal analysis with temperature pre-stress in ANSYS Workbench, using the modal analysis module, taking the thermal stress distribution result of step 3 as the load of the modal analysis, solving to obtain the modal frequency and mode shape of the traveling wave tube, and analyzing the mechanical properties of the terahertz traveling wave tube under different thermal environments; Step 5, performing vibration analysis of the terahertz traveling wave tube in ANSYS Workbench, using the random vibration analysis module, taking the modal analysis result of step 4 as the load of the vibration analysis, applying the acceleration power spectral density, solving to obtain the response of the traveling wave tube under random vibration excitation, and analyzing the mechanical bearing capacity of the key parts under random vibration conditions. 2.The reliability analysis design method of a terahertz folded waveguide traveling wave tube according to claim 1, wherein the established terahertz folded waveguide assembly model is provided with a traveling wave tube, and the surface of the traveling wave tube is provided with an environmental temperature and a convective heat transfer coefficient.

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