DESIGN OF A SOFT X-RAY FEL IN THE SLAC A-LINE

LCLS capabilities can be significantly extended with a second undulator aiming at the soft X-ray spectrum (1- 5 nm). To allow for simultaneous hard and soft X-ray operations, 13.6 GeV beams at the end of the LCLS accelerator can be intermittently switched into the SLAC A-line (the beam transport line to End Station A) where a second undulator may be located. Recently, a new optics has been designed to transport the LCLS beam through the A-Line while preserving the beam brightness. In this paper, we discuss the A-Line soft X-ray FEL design — parameter selection and performance expectations with an energy-chirped LCLS beam as required by the A-Line optics. Start-to-end simulations using realistic LCLS beams show that it is possible to generate 70 GW FEL power with a pulse duration as short as 2 fs at 20 pC charge.