Аннотация:Free-Electron Lasers (FELs), which can generate radiation in extreme ultraviolet and Xray
range along with unprecedented intensities, opened up opportunities for investigation of
the valence and core electron dynamics. The temporal coherence and the high intensities
have made possible the single-shot diffraction [1] imaging of non-crystalline samples.
However, until recently the longitudinal coherence was not demonstrated which is essential
for coherent control experiments [2]. In this work, we present the first demonstration of
generation and characterisation of Attosecond Pulse Trains (APTs) at the seeded FEL
FERMI exploiting the ability to produce multiple phase locked harmonics. We also
demonstrate the ability to manipulate the amplitude and phase of the generated APTs
independently.