高效率寬頻磁旋反波振盪器理論和實驗之研究

磁旋管是利用電子迴旋脈射機制 (electron cyclotron maser)，而產生同調電磁波源涵蓋了毫米波-太赫茲的電磁波段，具有高功率和寬頻等特性。本篇論文主要是在研究磁旋反波振盪器(gyro-BWO)的實驗和模擬。磁旋反波振盪器是唯一一種在磁旋管四大家族裡可以做調頻的，模擬顯示，在未加傾斜磁場的時候，最佳效率可達30%，然而在傾斜磁場的情況下，對不同電流、磁場優化所有參數，3dB的頻寬可高達35%以上，這表示在不同的頻率調變下，不同電流都可達幾乎一樣高的效率，深具應用和研究價值。磁旋反波振盪器不像磁旋單腔管(gyromonotron)有共振腔結構，而是基本上只有波導管的結構，所以存在的場型完全由電子和波的交互作用決定。在線性區間，有不同的軸向振盪模式，各自都具有固定的電子傳輸角(transit angle)；而在非線性區間，由於內部回饋線路的收縮，使得場形向電子入口處集中，造成效率對電流及長度產生飽和現象。由於場形可藉電子與電磁波的交互作用調變，而外加磁場又主導交互作用，故不僅可用磁場強度調變頻率，尚可用磁場斜率優化效率，使之在不同電流下，均能達到高效率。最後，以實驗佐證，加了傾斜磁場頻寬增加。

關鍵字

磁旋反波振盪器；電子槍；高效率；寬頻

並列摘要

The gyrotron is a coherent radiation source based on the electron cyclotron maser (ECM) instability and capable of generating unprecedented power levels in the millimeter to terahertz (THz) region of the electromagnetic spectrum. The focus of the present study in my paper is gyrotron backward-wave oscillator (gyro-BWO) simulation and experiment. Gyro-BWO is the only version of four basic embodiments of gyrotron with continuous frequency tunability The simulation has provided the highest efficiency about 30% without taper magnetic field. After optimized the efficiency by taper magnetic field, the 3dB bandwidth can achieve up to 35% which implied frequency tuning in different currents almost reach the highest efficiency, while it is also the least exploited version although many applications require frequency tunable broadband sources. The gyro-BWO employs a nonresonant interaction structure (basically a waveguide section). This makes the interaction dynamics fundamentally different from that of the cavity-based gyro-monotron. The existence of gyro-BWO oscillating modes and their field profiles must then depend entirely upon the beam-wave interaction. As it turns out, the field profiles of different axial modes are asymmetric in different ways, which in turn determines their competitive advantages. Moreover we can do the continuous frequency operation by tuning the magnetic field so optimized efficiency can be achieved through magnetic field and taper magnetic field in different current. In practical, we can also reach higher efficiency and bandwidth from low current to high current. A single-mode, stationary code and a multimode, time-dependent, particle-in-cell code are employed for electron dynamics and wave stability studies.

並列關鍵字

gyro-BWO ； E-gun ； high efficiency ； broadband

參考文獻

[39] T. H. Chang, L. R. Barnett, K.R. Chu, F. Tai and C.L. Hsu, Rev. of Sci. Instruments, 70, 1530 (1999).

[23] T. H. Chang, S. H. Chen, L. R. Barnett and K. R. Chu, Phys. Rev. Lett. 87, 064802 (2001).

[13] K. R. Chu, H. Y. Chen, C. L. Hung, T. H. Chang, L. R. Barnett, S. H. Chen, T. T. Yang and Demostehenes J. Dialetis, IEEE Trans. Plasma Sci. 27, 391 (1999).

[32] K. F. Pao, C. T. Fan, T. H. Chang, C. C. Chiu, and K. R. Chu, Phys. Plasmas 14, 093301 (2007).

[38] L.R. Barnett, L.H. Chang, H.Y. Chen, K.R. Chu, W.K. Lau, and C.C. Tu, Phys. Rev. Lett. 63, 1062 (1989).

國際替代計量

高效率寬頻磁旋反波振盪器理論和實驗之研究

全文下載

主題瀏覽