Full Temporal Reconstruction Using an Advanced Longitudinal Diagnostic at the SPARC FEL.

The production of ultra-short (sub 100 fs) single-spike radiation possessing full longitudinal coherence from a free-electron laser (FEL) has been the subject of intense study. The diagnosis of said pulses has proven to be challenging. A Frequency-Resolved Optical Gating (FROG) diagnostic has been developed and tested at UCLA, which has the capability of providing a longitudinal reconstruction of these ultra-fast pulses. This paper reports the results of the application of the diagnostic at the SPARC FEL facility.