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Title: Sideband instability analysis based on a one-dimensional high-gain free electron laser model

Abstract

When an untapered high-gain free electron laser (FEL) reaches saturation, the exponential growth ceases and the radiation power starts to oscillate about an equilibrium. The FEL radiation power or efficiency can be increased by undulator tapering. For a high-gain tapered FEL, although the power is enhanced after the first saturation, it is known that there is a so-called second saturation where the FEL power growth stops even with a tapered undulator system. The sideband instability is one of the primary reasons leading to this second saturation. In this paper, we provide a quantitative analysis on how the gradient of undulator tapering can mitigate the sideband growth. The study is carried out semianalytically and compared with one-dimensional numerical simulations. The physical parameters are taken from Linac Coherent Light Source-like electron bunch and undulator systems. The sideband field gain and the evolution of the radiation spectra for different gradients of undulator tapering are examined. It is found that a strong undulator tapering (~10 % ) provides effective suppression of the sideband instability in the postsaturation regime.

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1416368
Grant/Contract Number:
AC02-76SF00515; FWP-2013-SLAC-100164
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Volume: 20; Journal Issue: 12; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Tsai, Cheng-Ying, Wu, Juhao, Yang, Chuan, Yoon, Moohyun, and Zhou, Guanqun. Sideband instability analysis based on a one-dimensional high-gain free electron laser model. United States: N. p., 2017. Web. doi:10.1103/physrevaccelbeams.20.120702.
Tsai, Cheng-Ying, Wu, Juhao, Yang, Chuan, Yoon, Moohyun, & Zhou, Guanqun. Sideband instability analysis based on a one-dimensional high-gain free electron laser model. United States. doi:10.1103/physrevaccelbeams.20.120702.
Tsai, Cheng-Ying, Wu, Juhao, Yang, Chuan, Yoon, Moohyun, and Zhou, Guanqun. Mon . "Sideband instability analysis based on a one-dimensional high-gain free electron laser model". United States. doi:10.1103/physrevaccelbeams.20.120702. https://www.osti.gov/servlets/purl/1416368.
@article{osti_1416368,
title = {Sideband instability analysis based on a one-dimensional high-gain free electron laser model},
author = {Tsai, Cheng-Ying and Wu, Juhao and Yang, Chuan and Yoon, Moohyun and Zhou, Guanqun},
abstractNote = {When an untapered high-gain free electron laser (FEL) reaches saturation, the exponential growth ceases and the radiation power starts to oscillate about an equilibrium. The FEL radiation power or efficiency can be increased by undulator tapering. For a high-gain tapered FEL, although the power is enhanced after the first saturation, it is known that there is a so-called second saturation where the FEL power growth stops even with a tapered undulator system. The sideband instability is one of the primary reasons leading to this second saturation. In this paper, we provide a quantitative analysis on how the gradient of undulator tapering can mitigate the sideband growth. The study is carried out semianalytically and compared with one-dimensional numerical simulations. The physical parameters are taken from Linac Coherent Light Source-like electron bunch and undulator systems. The sideband field gain and the evolution of the radiation spectra for different gradients of undulator tapering are examined. It is found that a strong undulator tapering (~10 % ) provides effective suppression of the sideband instability in the postsaturation regime.},
doi = {10.1103/physrevaccelbeams.20.120702},
journal = {Physical Review Accelerators and Beams},
number = 12,
volume = 20,
place = {United States},
year = {Mon Dec 18 00:00:00 EST 2017},
month = {Mon Dec 18 00:00:00 EST 2017}
}

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