COMMISSIONING OF THE X-BAND TRANSVERSE DEFLECTOR FOR FEMTOSECOND ELECTRON/X-RAY PULSE LENGTH MEASUREMENTS AT LCLS

X-ray free-electron lasers provide ultrashort x-ray pulses from several to a few hundred femtoseconds for multidisciplinary users. However, tremendous challenges remain in the measurement and control of these ultrashort pulses with femtosecond precision, for both the electron bunch and the x-ray pulse. A new diagnostic scheme adding a transverse radio-frequency deflector at the end of the linac coherent light source (LCLS) undulator beamline has been proposed earlier. Two 1-m long deflecting structures have been installed at LCLS during the summer of 2012. Installation of the high power RF components including the klystron, waveguide, RF controls etc. has finished and commissioning has started since the spring of 2013. We report the latest progress of the commissioning of the deflector at LCLS.