Start-to-End Simulations of the LCLS Accelerator and FEL Performance at Very Low Charge

The Linac Coherent Light Source (LCLS) is an x-ray Free-electron Laser (FEL) being commissioned at SLAC. Recent beam measurements have shown that, using the LCLS injector-linac-compressors, the beam emittance is very small at 20 pC. In this paper we perform start-to-end simulations of the entire accelerator including the FEL undulator and study the FEL performance versus the bunch charge. At 20 pC charge, these calculations associated with the measured beam parameters suggest the possibility of generating a longitudinally coherent single x-ray spike with 2-femtosecond (fs) duration at a wavelength of 1.5 nm. At 100 pC charge level, our simulations show an x-ray pulse with 10 femtosecond duration and up to 10 photons at a wavelength of 1.5 Å. These results open exciting possibilities for ultrafast science and single shot molecular imaging. Presented at PAC09 conference, May 04-08, 2009, Vancouver, Canada. ∗Work supported by Department of Energy contract DE–AC02–76SF00515. Start-to-End Simulations of the LCLS Accelerator and FEL Performance at Very Low Charge∗ Y. Ding† , A. Brachmann, F.-J. Decker, D. Dowell, P. Emma, J. Frisch, S. Gilevich, G. Hays, Ph. Hering, Z. Huang, R. Iverson, H. Loos, A. Miahnahri, H.-D. Nuhn, D. Ratner, J. Turner, J. Welch, W. White, J. Wu SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA C. Pellegrini Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095