Issues and R&D critical to the LCLS

The Linac Coherent Light Source (LCLS) [1] is a high brightness X-ray free-electron laser project based on the SLAC linac. A new photocathode rf gun serves as injector for the last kilometer of the linac, which is fitted with two-stages of bunch compression. Acceleration to 15-GeV produces intense 1.5-Å coherent radiation by self-amplified spontaneous emission in a long undulator. A multi-laboratory project collaboration is addressing the most challenging issues, including: (1) feasibility of a stable injector with normalized emittance of 1 μm at 1 nC; (2) emittance control in the linac including effects of coherent synchrotron radiation in the bunch compressors; (3) stability of the final electron beam in the presence of charge, timing, and energy variations; (4) design, construction and alignment of a long planar undulator with 3-cm period and discrete periodic focusing lattice; (5) understanding and control of wakefields due to wall surface roughness in the undulator vacuum chamber; (6) radiation-matter interactions in the strong field regime with mirror and crystal optics for filtering and deflecting. These issues, and a project update, are presented