磁旋行波放大器之穩定性分析

Gyro-TWT是所謂的磁旋行波放大器，其目的在於放大輸入波功率。Gyro-TWT操作原理是藉由電子在外部的固定磁場下，因勞倫茲力產生的磁旋現象，使電子攜帶有自身旋轉頻率，而在電子頻率和外部輸入電磁波頻率接近時，電子和電磁波會開始產生交互作用，並開始有能量的交換，使原本在電子裡的能量轉移到電磁波中，產生功率放大的效果。而其中對流不穩定和絕對不穩定會造成Gyro-TWT是否能穩定操作的關鍵。為了探討這兩種不穩定對系統造成的影響，本論文將針對[1]論文的放大效率及結果重現、並探討調變各種參數對於起振電流的變化。本系統為TE01模式(mode)並固定操作頻率在93.5GHz、第一次及第二次諧振模之分佈式損耗磁旋行波放大器進行理論上的分析。本系統採用分佈式損耗作用段，藉由改變壁上損耗段ρ、Velocity Ratio α、操作電場B0、速率分佈，目的在抑制這些可能產生的不穩定模式。而在本論文中，同時也展示了當磁旋管微縮時，導致電磁波看到的損耗量(Attenuation)放大的效應。並藉由損耗段和非損耗段組成的線路中呈現的場形，可以解釋不同模式的起振電流對於調變電子和結構參數的變化。

關鍵字

磁旋行波放大器；電子迴旋脈射；磁旋管

並列摘要

Gyrotron traveling-wave amplifier (gyro-TWT) is a millimeter wave amplifier, the basic mechanism is followed by ECM (electron cyclotron maser). The absolute and convective instabilities will cause oscillation of mode in waveguide, and the oscillation makes the gyro-TWT unstable. To discuss the different oscillation, this thesis reproduces saturated power and gain in [1]. By changing the different parameters in waveguide, electron and magnetic field, we can get a variation of start-oscillation current (Ist)[2] to analyze stability of gyro-TWT. The simulation system in this paper is operating in the TE01 mode at the fundamental cyclotron harmonic. In this thesis we also show that scaling down the size of waveguide has the effect of magnifying wall loss (attenuation of mode), and it makes start-oscillation current (Ist) be larger.

並列關鍵字

Gyro-TWT ； electron cyclotron maser ； scaling down effect

參考文獻

[1] Ran Yan, Yong Tang, and Yong Luo, “Design and Experimental Study of a High-Gain W-Band Gyro-TWT With Nonuniform Periodic Dielectric Loaded Waveguide,” IEEE Trans. Electron Devices, vol. 61, no. 12, pp. 2564–2569, July. 2014.

[2] K. R. Chu, H. Y. Chen, C. L. Hung, T. H. Chang, L. R. Barnett, S. H. Chen, T. T. Yang, and D. Dialetis, “Theory and experiment of ultrahigh-gain gyrotron traveling-wave amplifier,” IEEE Trans. Plasma. Sci., vol. 27, pp. 391–404, Apr. 1999.

[4] K. R. Chu, “ Overview of research on the gyrotron traveling-wave amplifier ” IEEE Trans. Plasma Sci., vol. 30, pp. 903–908, June 2002.

[5] V. L. Granatstein, B. Levush, B. G. Danly, and R. K. Parker, “A quarter century of gyrotron research and development,” IEEE Trans. Plasma Sci., vol. 25, pp. 1322–1335, Dec. 1997.

[7] J. L. Seftor, V. L. Granatstein, K. R. Chu, P. Sprangle, and M. E. Read, “The electron cyclotron maser as a high power traveling-wave amplifier of millimeter waves,” IEEE J. Quantum Electron., vol. QE-15, pp. 848–853, 1979.

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磁旋行波放大器之穩定性分析

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