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Femtosecond-scale x-ray FEL diagnostics with the LCLS X-band transverse deflector

Analysis of single-shot, lasing-induced changes of the longitudinal electron bunch properties has proven invaluable for fs-scale reconstruction of otherwise difficult to measure x-ray FEL pulse profiles. In this talk, we report on measurements following the recent installation of an X-band transverse deflecting mode cavity at the LCLS. Limitations of the FEL pulse profiling technique employed are discussed. An unprecedented 1 to 3 fs RMS time resolution of x-ray and electron bunch profiles is demonstrated. Phenomena impacting x-ray FEL performance are also observed. The new tool is proven as a powerful diagnostic in support of user experiments and machine improvement studies.