本論文之主要目的為設計出一支速度比(α≈1.5)及較低的速度發散(Δvz/vz < 8%)之溫度限流低電壓(< 30 kV)繞軸式電子槍提供給100 GHz TM11 mode磁旋反波振盪器圓柱形波導管使用。
本實驗室前期的研究顯示，TM模在返波振盪器的操作條件下，可以接近TE模態的轉換效率[1]，且TM11模隨著電壓的降低有更好的效率，此效率隨著電壓從100 kV降低而逐漸變大，至30 kV以下時效率大約達到飽和[2]。這與一般傳統概念相違背，根據電子迴旋脈射機制，越高電壓的電子γ值越大，理論上應該更有利於電子的群聚效應，增加轉換效率。故本論文設計出30 kV及20 kV的電子槍，以利將來提供給磁旋反波振盪器做實驗驗證。
但TM11模與TE01模有相同色散關係，彼此之間易有模式競爭。對於此問題，我們可利用繞軸式電子壓制TE01，讓電子只跟TM11產生耦合。此外，若需要提高磁旋管頻率或是降低磁場需求，而將磁旋管操作在高次諧波時，我們也可用繞軸式電子來避免高次諧波間的競爭[3][4]。
在不需要求超大功率(>100000 W)的前提下，低電壓所提供的功率已足夠提供給一般使用，且利於大幅縮減設備價錢及尺寸，降低能源成本，將來也可朝桌上型裝置發展[5]。

In this paper, we present a low voltage axis-encircling electron gun with pitch factor of 1.5 and axial velocity spread less than 8%, which is suitable for 100 GHz TM11 mode gyro-BWO operation.
According to previous studies of gyrotrons in our lab, the TM mode may be as effective as TE mode for the gyro-BWO interaction. Furthermore, the converting efficiency of TM11 mode become larger when we lower the beam voltage from 100 kV to 30 kV. The result is strange to us since the relativistic factor is typically considered to be a key factor of bunching mechanism. Therefore, a suitable electron gun for future experimental verification is needed.
However, there will be mode competition between TM11 and TE01 due to the same dispersion relation. The axis-encircling beam can suppress TE01 because of the mode selectivity property of the beam. Also, axis-encircling beam provide a great solution to the intense mode competition when gyrotron is operating at high-harmonic modes.
If the above can be realized, lowering the voltage while maintaining a good efficiency can result in a reduction of the cost of energy and the size of the equipment , that make portable gyrotron possible.

目錄
摘要 2
Abstract 3
第一章、緒論 5
1.1、兆赫波簡介 5
1.2、ECM與磁旋管簡介 6
1.3、電子槍簡介 9
第二章、理論探討與設計方法 14
2.1、電子運動方程 15
2.2、電子軌跡之理論探討 16
2.3、限制條件 19
2.4、電子槍特性分析與設計方法 24
2.5、磁鐵參數與設計 27
2.6、程式概論 28

第三章、模擬結果與分析 31
3.1、檢查模擬結果 31
3.2、操作範圍與敏感度測試 35
第四章、結論 39
參考資料 40
附錄 45

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