M. E. Couprie[a, b], G. De Ninno[a, b], D. Nutarelli[b], M. Hirsch[a, b], D. Garzella[a, b], E. Renault[a, b], L. Nahon[a, b], R. Roux[c]
a) CEA/SPAM b) LURE c) Sincrotrone Trieste
Systematic studies on the FEL line and micropulse have been performed on the Super-ACO storage ring FEL with a monochromator and a double sweep streak camera. The improvements of the longitudinal feedback system allow the FEL to be operated very close to the Fourier limit. Such an equilibrium state can only be maintained in absence of perturbations. In addition, the data show that the micropulse sometimes present some internal structure. The temporal evolution of these internal micropulses is characterized, with and without longitudinal feedback system. Such a phenomenon could be interpreted in terms of local modification of the electron bunch shape, as confirmed by simultaneous measurements of the electron bunch distribution and the FEL pulse in the Q-switched mode.
