Microscopic Study And Materials In High Power Traveling Wave Tube

With the characteristics of high power, high efficiency and large bandwidth, traveling wave tube (TWT), as one of the different types of microwave vacuum electronic devices, has been widely used in microwave communication systems, radar and electron counter measurement as the source of high-power emission. Compared with developed countries, the gap of TWT mainly embodies in quality and reliability in our country. Currently, the research on the TWT is usually based on the theory, design and others, however, the quality and reliability of TWT are mainly determined by the microstructure of the materials in some way. By using scanning electron microscopy and electron microprobe spectrometer combined with TWT process and using, the research on the gas proof materials, the comparative analysis of raw material composition and structure, microstructure analysis and evaluation are carried out. The main contents and results are summarized as follows.(1) The research on the influence of conductivity the samples for EDS analysis results. As a representative, brass of good conductivity and alumina ceramic of poor conductivity were selected to be analyzed by EDS. Inaccurate EDS analysis result of alumina ceramic was focus on and the impact mechanisms were discussed. Then, Methods for minimize measurement errors were proposed, for example, taking spraying carbon or gold film, reducing the voltage, fast and low multiples analysis, when a poor conductivity sample was analyzed.(2) Aim at the problem of a gas leakage occurring on a new group of pole pieces adopted, the normal and leaking pole pieces were selected to be analyzed, the failure causes were determined that deeper turning processing mark and the impure contents in the pole pieces significantly affected the properties of the welding, and finally causing the leakage failure. Research on the micro-leakage of gas proof material of nickel-copper alloy, The results showed that too high manganese existing in the nickel-copper alloy, then migration and oxidation of manganese happened on the surface of alloy in the process of hydrogen firing process, and manganese oxide precipitating in grain boundary would weaken the inter-granular cohesion obviously, and this brought about the inter-granular fracture in nickel-copper alloy. Thus, its gas proof property also became poor. Different micro-areas of the surface of the first metallizing of ceramic to metal seal were analyzed and compared, the failure causes were determined, which were because the non-standard operation in the paste-coating process, leading to surface of metalized ceramics polluted and finally affecting the sealing quality and gas proof property.(3) The microscopic analysis of the cathode and materials used for TWT. Aiming at the selection demand of tungsten powder, four batches of tungsten powder were analyzed and selected, finally, particles of small size and a wide range of size distribution were filtered and some suitable batches of tungsten powder were selected for the cathode production. Micro structure of the good cathode emission properties were analyzed, the results showed that, uniform porosity sponge tungsten before impregnated salts and fully impregnated emission materials after impregnated salts were obtained, which provided the criterion of the microstructure of qualified cathode. Comparative analysis of the microstructure of normal and poisoning cathode, combined with technological process, the failure cause was that leakage of TWT led the moist air into the tube, and ultimately affected the microstructure and emission properties of the cathode.(4) Aiming at the phenomenon of a batch of beryllia ceramic rod easily brittle fracture in the tubing, normal and brittle of ceramic rod were analyzed by micro micro-analysis methods, the results showed that, abnormal growth grains, larger pores and white ZrO2precipitate between the grain boundary existed on the surface of defective sample, which ultimately affected the mechanical properties of beryllia ceramic.(5) By micro-analysis methods, two kinds of defectively molybdenum sheets were analyzed combined with manufacturing process. The results showed that the piebald surface on molybdenum sheet was generated for the serious volatile in the rolling process, when heating temperature was too high or long in the protective atmosphere, and cracking was because of the inadequate density of original molybdenum billet.These results had provided microscopic evidences in the choice of the materials, process optimization, failure analysis and so on, that effectively promote the development and production of TWT and materials, which would also provide effective support for the performance improvements of the products and reliability assurance of TWT.