Sideband instability analysis based on a onedimensional highgain free electron laser model
Abstract
When an untapered highgain 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 highgain tapered FEL, although the power is enhanced after the first saturation, it is known that there is a socalled 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 onedimensional numerical simulations. The physical parameters are taken from Linac Coherent Light Sourcelike 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:
 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:
 AC0276SF00515; FWP2013SLAC100164
 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 24699888
 Publisher:
 American Physical Society (APS)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 43 PARTICLE ACCELERATORS
Citation Formats
Tsai, ChengYing, Wu, Juhao, Yang, Chuan, Yoon, Moohyun, and Zhou, Guanqun. Sideband instability analysis based on a onedimensional highgain free electron laser model. United States: N. p., 2017.
Web. doi:10.1103/physrevaccelbeams.20.120702.
Tsai, ChengYing, Wu, Juhao, Yang, Chuan, Yoon, Moohyun, & Zhou, Guanqun. Sideband instability analysis based on a onedimensional highgain free electron laser model. United States. doi:10.1103/physrevaccelbeams.20.120702.
Tsai, ChengYing, Wu, Juhao, Yang, Chuan, Yoon, Moohyun, and Zhou, Guanqun. 2017.
"Sideband instability analysis based on a onedimensional highgain 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 onedimensional highgain free electron laser model},
author = {Tsai, ChengYing and Wu, Juhao and Yang, Chuan and Yoon, Moohyun and Zhou, Guanqun},
abstractNote = {When an untapered highgain 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 highgain tapered FEL, although the power is enhanced after the first saturation, it is known that there is a socalled 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 onedimensional numerical simulations. The physical parameters are taken from Linac Coherent Light Sourcelike 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 = 2017,
month =
}

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