On using a superconducting linac to drive a short wavelength FEL

In order to determine the suitability of using a superconducting radio frequency linac to generate XUV radiation, the beam dynamics in such a linac have been simulated using a vectorized two-dimensional beam breakup code, TDBBU. The energy spread and emittance of the accelerated beam are determined as a function of current for a linac like CEBAF (Continuous Electron Beam Accelerator Facility) and for a linac optimized for high peak currents. The results indicate that significant improvements in transverse emittance growth are possible by going to lower RF frequencies and by utilizing BNS phasing in the accelerating cavities. The transverse and longitudinal wakes typical in superconducting cavities are discussed. The results of the simulations are given, followed by a comparison of a linac-driven FEL (fee-electron laser) and a typical storage-ring-driven FEL. It is concluded that the former scheme looks promising because higher average power is possible.<
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