The super-ACO free electron laser source in the UV and its applications

Free electron lasers (FELs) are new sources of tuneable coherent radiation, based on the interaction of a relativistic electron beam with a permanent magnetic field. The Super-ACO FEL operates in the UV (down to 300 nm) at 80 0 MeV, the nominal energy of the electron beam, with a high repetition rate (8 MHz). It presents a high average extracted power (up to 300 mW), short pulses (15-50 ps FWHM) and small bandwidth (3 x 10(-2) nm). Taking advantag e of these characteristics, we demonstrated for the first time the possibil ity of using a storage ring FEL as a coherent source of radiation for scien tific applications. In particular, the tuneable Super-ACO FEL source, combi ned with synchrotron radiation covering the X-ray to infra-red range, is a unique tool for the time-dependent studies of excited states. Such analysis benefits from the natural synchronisation of both sources at a high repeti tion rate, their mutual tunability, high intensity and coherence. Several e xperimental set-ups are now under operation. (C) 2001 Elsevier Science Ltd. All rights reserved.