臺灣博碩士論文加值系統

磁旋返波振盪器可以藉由改變操作條件，如磁場或電壓，來調變其操作頻率，具有可連續調變頻率的特性。同軸波導結構具模式選擇特性，外導體與中心導體的電阻損耗對不同的振盪模式具有不同的衰減效果。然而，尚很少有磁旋返波振盪器的文獻採用同軸波導結構，在過去同軸波導磁旋返波振盪器研究中，採用軸向均勻磁場且半徑均勻之波導結構，並以分佈損耗抑制競爭模式的起振，僅達137 kW、效率9.1 %， 連續可調頻寬1.32 GHz（4.2 %）之性能。本論文擬採用漸變波導法，以突破同軸波導磁旋返波振盪器之效率與頻寬限制。計算程式是採用穩定態的粒子追蹤方法，軸向場分佈可由電子束與電磁波構成的一組非線性自洽方程式解出，能夠廣泛應用於小訊號與大訊號的問題。研究結果顯示，單級斜波導結構僅提昇磁旋返波振盪器之功率，但無法有效增加頻寬；兩級斜波導結構則可提昇磁旋返波振盪器之功率達316 kW（效率為27 %，此時頻寬為2.3 %），為均勻波導結構之2.3倍，頻寬達8.4 %（此時功率129 kW，效率8.6 %），為均勻波導結構之2.1倍。因此，藉由調整兩級斜波導結構之參數，可達到提昇功率及頻寬之需求。

The oscillation frequency of a gyrotron backward-wave oscillator (gyro-BWO) can be continuously tuned by changing the beam voltage or the magnetic field, so the gyro-BWO is characterized mainly by its superior frequency tunability. The coaxial waveguide has mode selective properties. The wall losses on the inner cylinder and the outer cylinder of a coaxial waveguide can attenuate different oscillation modes. However, little research has been done on the gyro-BWO with a coaxial interaction structure. In a recent study, the coaxial gyro-BWO, which used an axial uniform magnetic field and a uniform cross-section waveguide with distributed losses for suppressing oscillations, achieved an output power of 137 kW with an efficiency of 9.1 % and a 3dB continuously tunable bandwidth 1.32 GHz (4.2%). This paper intends to adopt a waveguide tapering method to remove the limit of the gyro–BWO efficiency and bandwidth. A steady-state, particle tracking code, which can be applied to the problem of small and large signals, is used to analyze the beam-wave interaction. The axial field distribution can be solved by a set of nonlinear self-consistent equations for the electron beam and electromagnetic waves. Simulation results show that single-stage tapered structure only enhance the power of the gyro-BWO, but can not effectively increase the bandwidth. The gyro-BWO with a two-stage tapered structure can achieve an output power of 316 kW with an efficiency 27% and a bandwidth of 2.3% (2.3 times the uniform structure), or a bandwidth of 8.4% (2.1 times the uniform structure) with an output power of 129 kW and an efficiency of 8.6%. Thus, the output power and the bandwidth of a coaxial gyro-BWO can be greatly enhanced by optimize the circuit parameters of the two-stage tapered structure.

摘要 ii
英文摘要 iii
誌謝 iv
目次 v
圖目錄 vii

第一章 緒論 1
1.1 磁旋管的發展 1
1.2 電子磁旋脈射( ECM )的輻射原理 2
1.3 磁旋管的基本類型 3
1.3.1 磁旋單腔振盪器 6
1.3.2 磁旋速調放大器 6
1.3.3 磁旋行波放大器 6
1.3.4 磁旋返波振盪器 7
1.4 磁旋返波振盪器之原理與發展 7
1.5 研究目的 15

第二章 研究方法 17
2.1 電磁場方程式 17
2.2 電子運動方程式 20
2.3 邊界條件 22

第三章 斜波導結構之效率與頻寬分析 24
3.1 均勻結構 24
3.2 單級結構 28
3.3 兩級結構 31

第四章 斜波導結構之穩定性分析 37
4.1 起振電流與漸變角度之關係 38
4.2 起振電流與磁場之關係 40

第五章 結論 41
參考文獻 42

[1]R. O. Twiss, “Radiation transfer and the possibility of negative absorption in radio astronomy,” Aust. J. Phys., vol. 11, pp. 567–579, 1958.
[2]朱國瑞、張存續、陳仕宏 “電子迴旋脈射 - 原理及應用” 物理雙月刊（廿八卷二期）2006年4月。
[3]A. V. Gapanov-Grekhov and V. L. Granatstein, Editors, Applications of High Power Microwaves, Norwood, MA: Artech House, 1994.
[4]V. L. Granatstein, and I. Alexeff, High-power Microwave Source, ARTECH HOUSE, 1985.
[5]G. S. Nusinovich, and O. Dumbrajs, “Theory of gyro-backward wave oscillator with tapered magnetic field and waveguide cross section,” IEEE Trans. Plasma Sci., vol. 24, no. 3, pp. 620-629, 1996.
[6]A. K. Ganguly, and S. Ahn, “Nonlinear analysis of the gyro-BWO in three dimensions,” Int. J. Electron., vol. 67, no 2, pp. 261-276, 1989.
[7]S. Y. Park, R. H. Kyser, C. M. Armstorng, R. K. Paker, and V. L. Granatstein, “Experimental study of a Ka-band gyrotron backward-wave oscillator,” IEEE Trans. Plasma Sci., vol. 18, no. 3, pp. 321-325, 1990.
[8]A. T. Lin, “Mechanisms of efficiency enhancement in gyrotron backward oscillator with tapered magnetic fields,” Phys. Rev. A, vol. 46, no 8, pp. R4516-R4519, 1992.
[9]C. S. Kou, S. H. Chen, L. R. Barnett, H. Y. Chen, and K. R. Chu, “Experimental study of an injection-locked gyrotron backward-wave oscillator,” Phys. Rev. Lett., vol. 70, no. 7, pp. 924-927, 1993.
[10]M. T. Walter, R. M. Gilgenbach, P. R. Menge, and T. A. Spencer, “Effects of tapered tubes on long-pulse microwave emission from intense e-beam gyrotron- backward- wave-ocillators,” IEEE Trans. Plasma Sci., vol. 22, no. 5, pp. 578-584, 1994.
[11]M. T. Walter, R. M. Gilgenbach, J. W. Luginsland, J. M. Hochman, I. Rintamaki, R. L. Jaynes, Y. Y. Lau, and T. A. Spencer, “Effects of tapering on gyrotron backward-wave oscillator,” IEEE Trans. Plasma Sci., vol. 24, pp. 636-647, 1996.
[12]C. S. Kou, C. H. Chen, and T. J. Wu, “Mechanisms of efficiency enhancement by a tapered waveguide in gyrotron backward wave oscillators,” Phys. Rev. E, vol. 57, no 6, pp. 7162-7168, 1998.
[13]S. H. Chen, T. H. Chang, K. F. Pao, C. T. Fan, and K. R. Chu, “Linear and time-dependent behavior of the gyrotron backward-wave oscillator,” Phys. Rev. Lett., vol. 89, no. 26, pp. 268303-1-268303-4, 2002.
[14]S. H. Chen, R. H. Chu, and T. H. Chang, “Saturated behavior of the gyrotron backward-wave oscillator,” Phys. Rev. Lett., vol. 85, no. 12, pp. 2633-2636, 2000.
[15]Y. S. Yeh, T. H. Chang, and T. S. Wu, “Comparative analysis of gyrotron backward-wave oscillators operating at different cyclotron harmonics,” Phys. Plasmas, vol. 11, no. 10, pp.4547-4553, 2004.
[16]K. F. Pao, T. H. Chang, C. T. Fang, S. H. Chen, C. F. Yu, and K. R. Chu, “Dynamics of mode competition in the gyrotron backward-wave oscillator,” Phys. Rev. Lett., vol. 95, 185101, 2005.
[17]T. H. Chang, C. T. Fang, K. F. Pao, and K. R. Chu, “Stability and tunability of the gyrotron backward-wave oscillator,” Appl. Phys. Lett. vol. 90, 191501, 2007.
[18]K. F. Pao, C. T. Fang, T. H. Chang, C. C. Chiu, and K. R. Chu, “Selective suppression of high order axial modes of the gyrotron backward-wave oscillator”, Phys. Plasmas, vol. 14, 093301, 2007.
[19]T. H. Chang, C. F. Yu, C. L. Hung, Y. S. Yeh, M. C. Hsiao, and Y. Y. Shin, “W-band TE01 gyrotron backward-wave oscillator with distributed loss”, Phys. of plasmas, vol. 15, 073105, 2008.
[20]N. C. Chen, T. H. Chang, C. P. Yuan, T. Idehara, and I. Ogawa, “Theoretical investigation of a high efficiency and broadband subterahertz gyrotron”, Appl. Phys. Lett. Vol. 96, 161501, 2010.
[21]C. L. Hung and Y. S. Yeh, “Stability analysis of a coaxial-waveguide gyrotron traveling-wave amplifier,” Phys. Plasmas, vol. 12, 103102, 2005.
[22]C. L. Hung, “Linear analysis of a coaxial-waveguide gyrotron traveling-wave amplifier,” Phys. Plasmas, vol. 13, 033109, 2006.
[23]C. L. Hung, “Geometrical effects on the performance of coaxial-waveguide gyrotron traveling-wave amplifiers,” Int. J. Infrared and Millimeter Waves, vol. 27, no. 7, pp.913-921, 2006.
[24]C. L. Hung, “Linear and saturated characteristics of a coaxial-waveguide gyrotron backward-wave oscillator,” Phys. Plasmas, vol. 16, 083101, 2009.
[25]C. L. Hung, “Stable coaxial-waveguide gyrotron backward wave oscillator with distributed losses”, Phys. Plasmas, vol. 17, 103102, 2010.
[26]C. L. Hung, T. H. Chang, and Y. S. Yeh, “Effects of tapering structures on the characteristics of a coaxial-waveguide gyrotron backward-wave oscillator”, Phys. Plasmas, vol. 18, 103113, 2011
[27]高功率同軸波導磁旋返波振盪器研究，NSC95-2221-E-346-002、NSC 96-2221-E-346-001，行政院國科會，主持人：洪健倫。
[28]高效率同軸波導磁旋返波振盪器研究，NSC99-2221-E-346-003、NSC 100-2221-E-346-010，行政院國科會，主持人：洪健倫。
[29]C. L. Hung and Y. S. Yeh, “Spectral domain analysis of coaxial cavities”, Int. J. Infrared and Millimeter Waves, vol.24, no.12, pp.2025-2041, 2003.
[30]K. R. Chu, H. Y. Chen, C. L. Hung, T. H. Chang, L. R. Barnett, S. H. Chen, T. T. Yang, and D. J. Dialetis, “Theory and experiment of ultrahigh-gain gyrotron traveling wave amplifier,” IEEE Trans. Plasma Sci., vol. 27, pp. 391-404, 1999.