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Popov, V.

Paper Title Page
MOPEA080 Electron Beam Polarization Measurement using Touschek Lifetime Technique 262
 
  • C. Sun, J.Y. Li, S.F. Mikhailov, V. Popov, W. Wu, Y.K. Wu
    FEL/Duke University, Durham, North Carolina
  • A. Chao
    SLAC, Menlo Park, California
  • H. Xu, J. Zhang
    USTC/NSRL, Hefei, Anhui
  
 

Touschek lifetime of an electron beam in a storage ring depends on the beam polarization through the intrabeam scattering effect. Consequently, the electron beam polarization can be determined by comparing the measured Touschek lifetime of a polarized beam and an unpolarized beam. In this paper, we report a systematic experimental procedure to study the radiative polarization of a stored electron beam. Based upon this technique, we have successfully observed the polarization build-up of a 1.15 GeV electron beam in the Duke storage ring. Using the Touchek lifetime data, we are able to determine the equilibrium degree of the electron beam polarization and the time constant for the polarization build-up process.

  
TUPE060 Study of FEL Mirror Degradation at the Duke FEL and HIGS Facility 2275
 
  • S.F. Mikhailov, J.Y. Li, V. Popov, Y.K. Wu
    FEL/Duke University, Durham, North Carolina
  
 

The Duke FEL and High Intensity Gamma-ray Source (HIγS) are operated with a wide range of electron beam energies (0.24 - 1.2 GeV) and photon beam wavelengths (190 - 1060 nm). Currently, the HIγS provides users with the gamma beams in the energy range from 1 to about 65 MeV, with a near future extension to about 100 MeV. The maximum total gamma-flux produced at the HIγS facility is up to 1010 gammas per second. Production of high level gamma-ray flux, requiring a very high average FEL intra-cavity power and high electron beam current, can cause significant degradation of the FEL mirrors. To ensure the predictability and stability of the HIγS operation for user research program, we have developed a comprehensive program to continuously monitor the performance of the FEL mirrors. This program has enabled us to use a particular set of FEL mirrors for a few hundreds hours of high gamma-flux operation with predictable performance. In this work, we discuss sources and consequences of the mirror degradation for a variety of wavelengths and present our estimates of the mirror life time as a function of the FEL wavelength, gamma-ray polarization, and total gamma-flux.