Author: Li, P.
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TUPH09 Spontaneous Radiation of High-order Magnetic Field Undulator 146
 
  • T. Wei
    CAEP/IFP, Mainyang, Sichuan, People's Republic of China
  • P. Li
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  • Y. Li, J. Pflüger
    XFEL. EU, Schenefeld, Germany
  
  Based on the purpose of concision, nearly all the undulator radiation formulas have maken an assumption that the guiding magnetic field is a sinusoid wave. The assumption is consistent with the truth if the ratio of undulator gap to period length is large enough. However, high-order magnetic field exists widely in most undulators, especially those with long period length and short gap. This paper will derive the radiation output equations of high-order magnetic field undulator, what's more, the formulas are validated through numerical simulation with code SPECTRA.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SAP2017-TUPH09  
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TUPH21 Magnetic Measurement of the Undulator U38 for THz-FEL 156
 
  • L.G. Yan, D.R. Deng, M. Li, P. Li, J. Wang, X. Yang, H. Zhang
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  
  Funding: The work was supported by Ministry of Science and Technology under the project of the national large-scale instrument development (No. 2011YQ130018) and China NSAF Fund under grant of 11505174.
The high average power terahertz free electronic laser facility (THz-FEL) has one undulator named U38. As one of the most important components, U38 has a significant effect on entire facility. So, we measure the magnetic field of U38 to confirm its field qualities using magnetic field measurement bench before installation. The measurement gaps include 19 mm, 21 mm, 24 mm, 25.6 mm and 28 mm, and the longitudinal distribution of magnetic field on five lines at transverse positions of -6 mm, -3 mm, 0 mm, 3 mm and 6 mm are scanned. Electronic trajectory, peak field vs gap curve and peak-to-peak error are calculated based on the longitudinal distribution of magnetic field. We also measure the transverse distribution of magnetic field to test the good field region. In this proceeding, the measurement method is described and the results are presented and discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SAP2017-TUPH21  
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WEBH4 Beam Optimization and Measurment of CAEP FEL-THz Injector 179
 
  • D. Wu, C.L. Lao, M. Li, P. Li, S.F. Lin, X. Luo, Q. Pan, L.J. Shan, H. Wang, J. Wang, D.X. Xiao, X. Yang, K. Zhou
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  • X. Li
    TUB, Beijing, People's Republic of China
  
  Funding: Work supported by the National Natural Science Foundation of China with grant (11475159, 11505173, 11576254 and 11605190)
The FEL-THz facility in Chinese Academy of Engineering Physics (CAEP) requires high brightness high repetition electron beam, which needs optimization of multi-parameter and multi-objective, such as emittance, energy spread, bunch length, etc. In this paper, some studies of beam optimization based on differential evolution (DE) algorithm and Astra code are shown. Dozens of the DC-SRF-injector parameters have been considered in the optimization. Some measurements of the electron beam are also introduced, including emittance measurement with the three-profile method, energy spread measurement with analyzing magnet and beam length diagnostics with zero-phasing method. These studies indicate that the injector beam quality satisfies the requirement of the FEL-THz facility. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SAP2017-WEBH4  
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