TUOANO03
SLAC, Menlo Park, California, USA
DESY, Hamburg, Germany
For the generation of ultrashort x-ray FEL pulses, a similarly short, high-brightness electron beam is needed with compression tuned to the extent that a narrow energy spread can still be preserved. Further reduction of the nominal LCLS bunch length by lowering the bunch charge or employing an upstream, emittance-spoiling foil promises to reduce the pulse duration to the level of only a few femtoseconds, presenting a challenge to the temporal resolution of existing longitudinal diagnostics. In answer to this, we have recently commissioned a single-shot, middle-infrared spectrometer for the LCLS. Developed as a robust and cost-effective alternative to other femtosecond-scale beam diagnostics, coherent mid-IR beam radiation measurements and analysis are then employed to probe the LCLS beam just prior to the undulator. Results resolving beam structure to the few-fs level for 20 - 150 pC beams will be presented. Practical design challenges and diagnostic limitations will also be discussed.
