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Title: Asymmetric modes decomposition in an overmoded relativistic backward wave oscillator

Abstract

Most of the investigated overmoded relativistic backward wave oscillators (RBWOs) are azimuthally symmetric; thus, they are designed through two dimensional (2-D) particle-in-cell (PIC) simulations. However, 2-D PIC simulations cannot reveal the effect of asymmetric modes on beam-wave interaction. In order to investigate whether asymmetric mode competition needs to be considered in the design of overmoded RBWOs, a numerical method of determining the composition of both symmetric and asymmetric modes in three dimensional (3-D) PIC simulations is introduced in this paper. The 2-D and 3-D PIC simulation results of an X-band overmoded RBWO are analyzed. Our analysis indicates that the 2-D and 3-D PIC simulation results of our device are quite different due to asymmetric mode competition. In fact, asymmetric surface waves, especially EH{sub 11} mode, can lead to serious mode competition when electron beam propagates near the surface of slow wave structures (SWSs). Therefore, additional method of suppressing asymmetric mode competition, such as adjusting the reflections at both ends of SWSs to decrease the Q-factor of asymmetric modes, needs to be utilized in the design of overmoded RBWOs. Besides, 3-D PIC simulation and modes decomposition are essential for designing overmoded RBWOs.

Authors:
; ; ; ;  [1]
  1. College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)
Publication Date:
OSTI Identifier:
22303651
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 9; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ASYMMETRY; DESIGN; ELECTRON BEAMS; OSCILLATORS; PLASMA SIMULATION; WAVE PROPAGATION

Citation Formats

Zhang, Dian, Zhang, Jun, Zhong, Huihuang, Jin, Zhenxing, and Ju, Jinchuan. Asymmetric modes decomposition in an overmoded relativistic backward wave oscillator. United States: N. p., 2014. Web. doi:10.1063/1.4894480.
Zhang, Dian, Zhang, Jun, Zhong, Huihuang, Jin, Zhenxing, & Ju, Jinchuan. Asymmetric modes decomposition in an overmoded relativistic backward wave oscillator. United States. https://doi.org/10.1063/1.4894480
Zhang, Dian, Zhang, Jun, Zhong, Huihuang, Jin, Zhenxing, and Ju, Jinchuan. 2014. "Asymmetric modes decomposition in an overmoded relativistic backward wave oscillator". United States. https://doi.org/10.1063/1.4894480.
@article{osti_22303651,
title = {Asymmetric modes decomposition in an overmoded relativistic backward wave oscillator},
author = {Zhang, Dian and Zhang, Jun and Zhong, Huihuang and Jin, Zhenxing and Ju, Jinchuan},
abstractNote = {Most of the investigated overmoded relativistic backward wave oscillators (RBWOs) are azimuthally symmetric; thus, they are designed through two dimensional (2-D) particle-in-cell (PIC) simulations. However, 2-D PIC simulations cannot reveal the effect of asymmetric modes on beam-wave interaction. In order to investigate whether asymmetric mode competition needs to be considered in the design of overmoded RBWOs, a numerical method of determining the composition of both symmetric and asymmetric modes in three dimensional (3-D) PIC simulations is introduced in this paper. The 2-D and 3-D PIC simulation results of an X-band overmoded RBWO are analyzed. Our analysis indicates that the 2-D and 3-D PIC simulation results of our device are quite different due to asymmetric mode competition. In fact, asymmetric surface waves, especially EH{sub 11} mode, can lead to serious mode competition when electron beam propagates near the surface of slow wave structures (SWSs). Therefore, additional method of suppressing asymmetric mode competition, such as adjusting the reflections at both ends of SWSs to decrease the Q-factor of asymmetric modes, needs to be utilized in the design of overmoded RBWOs. Besides, 3-D PIC simulation and modes decomposition are essential for designing overmoded RBWOs.},
doi = {10.1063/1.4894480},
url = {https://www.osti.gov/biblio/22303651}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 9,
volume = 21,
place = {United States},
year = {Mon Sep 15 00:00:00 EDT 2014},
month = {Mon Sep 15 00:00:00 EDT 2014}
}