Suppression of secondary electron multipactor on dielectric surface in TM mode

Abstract

To suppress the secondary electron multipactor on dielectric surfaces of a dielectric load accelerator under an electromagnetic field in TM mode, the method of adopting both groove structure and external axial magnetic field is introduced. As the electric field distribution of the TM mode is composed of both normal and tangential components, it is different from that under the condition of dielectric window in HPM. Thus, theoretical analysis and numerical simulation are employed to study the movement of electrons under different conditions: such as dielectric surface shapes, electric field strength, and magnetic field strength etc. Based on the particle-in-cell (PIC) simulation, the collision energy and transmit-duration of secondary electrons in different groove structures and axial magnetic fields are compared with one another. Results show that the magnetic field is useful for suppressing the development of secondary electron on dielectric surface, while it is not very efficient under high electric field strength. The method of introducing groove structure and certain axial magnetic field on dielectric surface at the same time is capable of affecting the movement of electrons in electric field of different strength. So it is great helpful in improving the ability of multipactor suppression, which is significant for improving the threshold of breakdown on dielectric surface and the power of cavity. However, a too high or too low magnetic field is not very useful for the suppression of multipactor. Furthermore, employing only one of the two parts of the method is also less effective in suppressing the multipactor.

Electromagnetic particle simulation of secondary electron multipactor characteristics in inner surface of 110 GHz microwave output window

“…蔡利兵和王建国对1 GHz微波斜入射到介质表面时的次级电 子倍增过程进行了静电粒子/蒙特卡洛碰撞模拟分析, 并比较了斜入射与正入射时的倍增参数(如平均电子 能量)之间的差异 [9] . 在微波频率为11.42 GHz下, 李爽等人对包含刻槽结构的介质表面的电子碰撞能量进 行了理论推导, 发现外加磁场并结合刻槽结构能够加强次级电子倍增的抑制效果 [10] . 左春彦等通过静电粒 子/蒙特卡洛碰撞模型描述高功率微波介质表面击穿过程, 重点分析了背景气体压强, 微波电场振幅和频率 对介质表面击穿特性的影响 [11] .…”