高效率TE11模式虛陰極振盪器研究

虛陰極振盪器(Vircator)為一產生脈衝式高功率微波源之裝置，具有結構簡單、高峰值功率、電子束品質要求低且無須外加磁場等優點，然其脈寬窄、頻率飄移、輸出功率不穩定與電子束-微波轉換效率低乃是虛陰極振盪器之主要缺點，本文使用具有PIC模擬功能的MAGIC程式進行物理特性分析與三維結構參數優化，設計結構相對於原有之優化同軸結構[59]，進一步採用非對稱的同軸設計結構，實現TE11模式輸出模式之虛陰極振盪器結構設計，並且研究其中TE11與TM01模式之間的競爭機制，並提高其設計結構電子轉換效率至7.6%、輸出頻率為7.2GHz、峰值功率2.78GW。相較於國內外文獻[21-68]，本文藉由三維數值模擬的方法，發現在相同設計結構中，因為陰陽極間隙的調整與虛陰極位置變動，對應到的虛陰極自身振盪與電子束來回反射兩者輻射機制所產生的模式激發競爭是前人較少注意到與討論的現象，另外相對於文獻[61]同樣是增強同軸式TE11模式激發，本文也將波-束轉換效率由4%提升至7.6%，大大提高效能。

關鍵字

MAGIC ； TE11模式；虛陰極振盪器

並列摘要

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%.