開口式共振腔之衍射品質因子之解析研究

開口式共振腔是磁旋管的作用結構，它為毫米、次毫米和太赫兹波段，提供了新的同調電磁波源。共振腔的一個開口端，是用來快速提取由高能電子束所產生的輻射能，在大多數的情況下，來自開口端的衍射損耗遠大於管壁的歐姆損耗，並且導致了低品質因子Q。在較早的研究中，對於微變截面的波導已求出了衍射Q 的解析公式，不過在這裡，另一個適用於更一般波導的公式被求出。在低階軸向模態的最低階近似下，它可化簡成先前的結果。至於較高階的軸向模態，它給出了更精準的Q，且由數個不同橫向模態的數值結果所驗證。

關鍵字

開口式共振腔；磁旋管；品質因子；縮尺法則；黎卡提方程

並列摘要

Open cavities are the interaction structures for a new generation of coherent millimeter, sub-millimeter, and terahertz radiation sources called the gyrotron. One of the open ends of the cavity is intended for rapid extraction of the radiation generated by a powerful electron beam. In the majority of cases, the diffraction loss from this open end dominates over the Ohmic losses on the walls and it results in a low quality factor Q. In earlier studies, an analytical expression of the diffraction Q was derived for weakly irregular waveguide. However, here another expression valid for a more general waveguide is derived. It reduces to previous one in the lowest order expansion of low-order axial mode. And for higher-order axial mode, it gives more precise Q, verified by numerical examples for various transverse modes.

並列關鍵字

open cavities ； gyrotrons ； quality factor ； scaling law ； Riccati equation

參考文獻

[1] Applications of High Power Microwaves, edited by A. V. Gaponov-Grekhov and V. L.

[3] Q. F. Li and K. R. Chu, “Analysis of Open Resonators,” Int. J. Infrared Millimeter Waves,

[5] R. J. Temkin, “Analytic theory of a tapered gyrotron resonator,” Int. J. Infrared Millimeter

waveguides as open resonators,” Radiophys. and Quantum Electron. 12, no. 8, 972 (1969).

[7] S. H. Kao, C. C. Chiu, and K. R. Chu , “A study of sub-terahertz and terahertz gyrotron

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開口式共振腔之衍射品質因子之解析研究

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