| Summary: | 博士 === 國立臺灣大學 === 物理學研究所 === 106 === Vircator is a pulsed high power microwave source device with the advantages of simple structure, high peak power, low e-beam quality necessary and no external magnetic field, etc. However, short pulse width, frequency drift, output power instability and low beam-wave interaction is the main disadvantage of Vircator. We base on previous study [59] and use the MAGIC (PIC simulation software) for physical properties analysis and optimization of three-dimensional asymmetric coaxial structure to achieve TE11 output mode. In this thesis, we study the competition mechanism between TE11 and TM01 mode and increase the efficiency of beam-wave interaction to 7.6%, which the output frequency of 7.2GHz and the peak power of 2.78GW.
In this thesis, we use numerical simulation to illustrate mode excitation mechanism which is few noticed and discussed in literatures [21-68]. We find that in the same design structure, due to the adjustment of the gap between cathode and anode and variation of the virtual cathode will affect excitation mode. It is corresponding to self-oscillation of the virtual cathode and forth-and-back motion of e-beam in diode region.
Compared with literature [61], we optimize the enhanced coaxial vircator structure to improve the efficiency from 4% to 7.6%.
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