Lattice optimization of 3 GeV linac and studies on the beam dynamics for X-ray FEL at PAL are presented. Investigation of microbunching instability due to coherent synchrotron radiation and wake fields in the PAL linac is also given.

We report on the design study of the low-emittance injector for the SASE-XFEL that is being considered as a possible choice for the next-generation light sources at the Pohang Accelerator Laboratory, POSTECH. Using the PARMELA code, beam dynamics simulations were performed aiming to achieve the invariant-envelope matching at booster entrance, and to insure beam emittance < 1 mm.mrad (at 1-nC bunch charge) at the injector end. We also utilized the MAGIC code for analyzing beam dynamics inside the RF-gun cavities and to confirm the part of PARMELA simulations. Hardware design was done with possible implementation of high-Q.E. photocathode, which could reduce burdens imposed on laser system, thus improving overall system stability and reliability.

A free-electron laser (FEL) based on self-amplified spontaneous emission has been designed. This FEL is utilizing the existing 2.5 GeV electron linear accelerator at Pohang Accelerator Laboratory (PAL). The radiation wavelength was chosen to be in the water-window region 3-4 nm which can be used for biological imaging. In this paper, it is shown that the PAL is particularly suited for this wavelength if the existing linear accelerator is employed without having major modification. For 4 nm wavelength, the saturated power is shown to be 12 GW with a saturation length of about 25 m.