TWT Research 0.14THz Confocal Waveguide Maneuver

As a new-born subject, because of its wide application prospect, after its birth terahertz technology has been paid general attention and develops rapidly. As the terahertz technology development’s base, terahertz source is always viewed as emphasis and difficult point in terahertz technology development. The gyro-twt is a kind of vacuum electron devices based on electron cyclotron maser, because of its high-power, wide-band and high-efficient output character in millimeter and even terahertz frequency range, gyro-twt has become research hot spot at home and abroad in these years.When devices work in high frequency, to solve the wavelength-size-matching effect and power capacity problem, the high order mode is usually used as operating mode, but this brings mode competition problem in. In terahertz band, because devices’ structure size is usually very small, it is more difficult to solve mode competition problem. So, it is urgent to find an interaction structure with mode selection character which is suitable for terahertz band. Confocal waveguide is a structure with lateral opening, which has mode selection character because of diffraction loss, this character can be used to solve the mode competition problem.The theme of this dissertation is terahertz gyro-twt with confocal waveguide structure. The studied details include:The derivation of field expression in confocal waveguide is presented, the field distribution is analysed, the diffraction loss of different mode is calculated, at last, the rule of mode selection is presented.The basic theory of electron cyclotron maser is discussed, the single particle theory of gyro-twt is derived detailedly. The theoretical calculation of confocal waveguide gyro-twt has been done using single particle theory for the first time domestically. The saturation effect and launching loss of0.14THz confocal wavguide gyro-TWT has been studied, kinds of operation parameter’s effects on output power is analysed, the electron velocity spread and waveguide loss’s effects on beam-wave interatction has been studied. The absolute instability induced parasitic oscilaation is analysed. At last, the output character of multiple section interaction structuture confocal waveguide gyro-twt calculated.The key components of0.14THz confocal waveguide gyro-twt is designed and simulated using3D software, including magnetic coil, beam-wave interaction structure, double anode MIG, input and output s structure. The result of beam-wave interaction PIC simulation reveals that, the output power achieves4.25kW, the Gain achieves36dB,3dB bandwidth achieves4.5GHz, the device can work stable without parasitic oscillation. The single particle theory is used to calculated the beam-wave interaction in PIC model, the calculation result is consistent with simulation result, so the theory can be verified.0.14THz confocal waveguide gyro-twt is designed and developed, this amplifier experiment is conducted for the first time domestically, the amplified terahertz signal is observed in this experiment, this device is verified working stably.The theory and design process of quasi-optical input structure basing on Gauss optics is presented in detail, take the quasi-optical input structure working in0.4THz for example, this structure is studied for the first time domestically. The simulation result reveals that, the maximum input efficiency exceeds64%, the bandwidth input efficiency beyond50%exeeds15GHz, the3dB bandwidth exceeds30%, compares to the normal input working in this band, this design resolves the input structure induced bandwidth narrowing problem.