The TESLA X-FEL injector

The high-brightness beams demanded to drive future short-wavelength SASE FEL-based light sources result in stringent demands on the electron beam source. In the foreseen TESLA X-FEL, a slice emittance (over the cooperation length) of less than 1.6 mm-mrd and a rms bunch length of /spl sim/25 /spl mu/m (corresponding to a peak current of 5 kA) are required at the undulator entrance. In this paper, we present the conceptual design of the photoinjector system for the TESLA X-FEL including Beam Dynamics studies performed with the codes ASTRA and HOMDYN. The proposed injector can generate 1 nC bunches with mm-mrd transverse emittances and longitudinal emittance of 60 keV-mm at an energy of 140 MeV.