我們的團隊藉由電子蒸鍍的概念開發了一種利用磁控電子束轟擊金屬靶材的離子推進器—Metal Ion Thruster using Magnetron E-beam Bombardment (MIT-MEB)，此論文是透過實驗與模擬電子軌跡來研究此推進器中電子的行為。此推進器分為三個部分：金屬離子產生器、離子加速器和中和器。利用加速電壓V_{{
m acc}}提供的電場加速電子槍(E-gun)中熱燈絲產生的自由電子轟擊鋅製成的金屬靶材，使靶材被加熱蒸發。在靶材後方有放置磁鐵，因此電子會沿著磁力線轟擊靶材中心。一部分的金屬蒸氣被熱燈絲發射出的電子碰撞而游離，這些離子再經由電場加速排出產生推力，並帶走中和器提供的電子來保持推進的電中性。因此，電子的運行軌跡在此推進器中扮演很重要的角色。我們分別使用V_{{
m acc}}等於500、750和1000 V的加速電壓進行了一系列的實驗。從實驗結果我們發現，在使用較低的V_{{
m acc}}時，抵達靶材的電子會少於使用較高的V_{{
m acc}}。我們認為電子會被電場力加速往靶材移動，但磁鏡力會將它反彈回電子槍的燈絲，造成電子無法抵達靶材。因此，當V_{{
m acc}}較低時，較多的電子會被磁鏡力反彈。所以，我們利用模擬來探討電子軌跡。然而，在模擬中一旦V_{{
m acc}}大於1 V，電子就不會被磁鏡力反彈。透過簡單的模型中，只要V_{{
m acc}}geqq0.13 V就足以加速電子克服磁鏡效應，這符合模擬的結果。所以，我們排除了MIT-MEB中的磁鏡效應對電子軌跡的影響。然而，若我們將燈絲放置於偏心的位置，使得電場力中平行於磁鏡力方向的分量變小，便有機會利用磁鏡效應將電子侷限於燈絲與靶材之間。未來我們需要使用其他可模擬熱電子發射的模擬方式來探討MIT-MEB中電子的行為並更改推進器的設計。

The Metal Ion Thruster using Magnetron E-beam Bombardment (MIT-MEB), which uses the principle of electron-beam (E-beam) evaporation, was developed in our group. In this thesis, we studied electron behaviors in both experiments and simulations. There are three parts in the MIT-MEB: a metal evaporator, an ion accelerator, and a neutralizer. Electrons emitted by the heated filament of the E-gun are accelerated toward the target made of Zinc by the electric field provided by an accelerating voltage V_{{
m acc}}. A magnet is placed behind the target so that electrons follow the magnetic field lines and reach the center of the target. The target is heated and evaporated when electrons bombard on it. When the metal vapor is impacted by electrons emitted from the thermal filament, part of the vapor is ionized. Ions are then accelerated by the applied electric field providing thrusts. Electrons from the neutralizer would leave the thruster with ions and keep the thruster in neutral. Therefore, electron trajectories play an important role in MIT-MEB. We did a series of experiments with V_{{
m acc}} equal to 500, 750, and 1000 V. We found that fewer electrons reach the target in lower V_{{
m acc}} than that in higher V_{{
m acc}} in experiments. We suspected that the electric force would accelerate electrons toward the target while the magnetic-mirror force would reflect electrons back to the filament of the E-gun preventing them to reach the target. More electrons might be returned in lower V_{{
m acc}} than that in higher V_{{
m acc}}. Therefore, we studied electron trajectories in simulations. However, in simulations, no electrons were reflected by the magnetic mirror force once there was an electric force from V_{{
m acc}} greater than 1 V. It coincided with a simple analytic model where V_{{
m acc}}geqq0.13 V was sufficient to accelerate electrons overcoming the magnetic-mirror effect. So, we have rolled out the magnetic-mirror effect in the MIT-MEB. Nevertheless, we can move the filament of the E-gun sideway. In this case, the component of the electric field parallel to the magnetic-mirror force much smaller than the magnetic-mirror force will potentially reduce. Thus, electrons may be reflected by the magnetic-mirror force. Therefore, using other simulations which could simulate the thermionic electron emission, and changing the design of the MIT-MEB need to be conducted as future work.

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