Soft orbit bump for duke storage ring VUV FEL operation
The Duke FEL and High Intensity Gamma-ray Source (HIS) facility is operated with anelectron beam from 0.24 to 1.2 GeV and an FEL photon beam from 190 to 1060 nm. The energyrange of the gamma-ray beam is from 1 MeV to about 100 MeV, with the maximum totalgamma-flux of more then 1010 gammas per second around 10 MeV. Production of thehigh-intensity, high energy gamma-beams of 60-158 MeV using UV-VUV mirrors of 250 - 150 nmrequires high current and high energy electron beams (0.9-1.20 GeV). Radiation damage tothe downstream FEL mirror becomes more severe for VUV FEL operation at 190 nm and below. Atthese VUV wavelengths with GeV electrons, the radiation from the end-of-arc (EOA) bendingmagnets, instead of the radiation from helical FEL wigglers, is the dominant cause of arapid degradation of the downstream mirror. In this work, we propose a concept of a"soft" orbit bump using designated orbit correctors to significantly reduce theradiation from the EOA dipole toward the FEL mirror. The strength of magnetic field ofthese correctors is limited to produce a radiation with a critical wavelength close orbelow the FEL wavelength. Copyright © 2012 by IEEE.
