Speaker
Description
At SwissFEL we employ photocathode temporal shaping to produce sub-femtosecond X-ray FEL pulses. Two optical laser pulses arrive on the photocathode with a time delay of few picoseconds, resulting in a notch at the center of the generated electron current profile. Longitudinal space charge and coherent synchrotron radiation effects that occur during beam transport and bunch compression then transform this notch into a large current spike. With this scheme (previously demonstrated at LCLS), we achieved peak currents tunable up to 12 kA after the second bunch compressor. The bunches then emitted FEL pulses, some of which contained only one spectrum spike. The photon energy was 6 keV at the hard X-ray beamline Aramis, or 535 eV at the soft X-ray beamline Athos. To our knowledge, this is the first demonstration of the method in the hard X-ray regime. Ongoing machine development is aimed at compatibility with SwissFEL's double bunch operation mode.
