The Research Of Key Technology For The Gyro-TWT With Helical Waveguide

Gyrotron travelling wave tube(gyro-TWT) was an important high power microwave source which based on the principle of electron cyclotron maser(ECM). It has aroused great attention both at home and abroad due to its attractive potential application such as high resolution radar, millimeter communication, plasma diagnostics and medical imaging.With the development of gyro-TWT, many professional scholars try to improve its output power, broaden its bandwidth,make it less sensitive to velocity spread. It was found that helical waveguide can satisfy the requirements; it uses helical rippled structure instead of smooth structure waveguide. The use of helically corrugated waveguides radically change the dispersion of the operating eigenwave at zero axial wavenumber, the special structure of the helical waveguide couples TE11 and TE21 mode in the angular direction, so TE21-likely eigenmode occurred. The group velocity of operating eigenwave is almost constant positive in a wide range of frequency, which is favorable for beam-wave interaction, it makes the gyro-TWT with helical waveguide has advantages of high-power, broad band and insensitivity to velocity spread.Furthermore, the output window is one of the key components of the gyro traveling wave tube. On the one hand, it plays the role of isolating inside vacuum from outside atmosphere, on the other hand, it should assure that the enlarged microwave transmit without reflection as far as possible.This paper mainly studies the gyro-TWT with helical waveguide and output window. The main tasks of this thesis are as follows:1. Studies the operational principle of ECM, the development history and design concept of gyro-TWT, also development direction in the future.2. The coupling wave equations and dispersion formulae were derived by using perturbation theory and coupling wave method, coupling coefficient and angular selectivity expression were also obtained.3. Analyzed the dispersion characteristic of helical waveguide by Matlab code, mainly study the coupling characteristic, dispersion characteristic, field distribution and mode competition, then the helical waveguide was simulated by electromagnetic simulation software, observed the field distribution, analyzed the dispersion curve of operating mode and a comparative authentication is also carried out. Preliminary study on the application of pulse compression and the dispersion characteristics of the five fold helical waveguide spurious mode, it can lays a foundation for further work.4. Program was compiled through 3D PIC software, a gyro-TWT with helical waveguide was designed, also the beam-wave interaction process of gyro-TWT is studied. Furthermore, mainly analyzed how the changes of some critical parameters affect its output characteristics.5. According to the field matching theory, a cascade matrix was established. A single and a double x-band window was designed through numerical calculation and simulated optimization by using high frequency software HFSS.