Operation and extension to far-infrared of the CLIO FEL facility

Abstract

The CLIO infrared FEL is working as an open user facility. About 150 days of beam are attributed to various users by a program committee on the basis of scientific merit. Several experimental setup are available for users: • SFG (study of molecules adsorbed on surfaces and interfaces by resonant surface harmonic generation) • Photon echo and pump-probe experiments (with sensitivity of @ 0.1% in transmission variations) • Near-field infrared microscope • FT- ICR – Mass Spectrometer. Some recent examples of applications in Physics and Chemistry are given. The CLIO spectral domain has been extended recently and spans now from 3 to 90 µm. This has been obtained by (i) manufacturing an undulator with a larger gap and a longer period (ii) implementing an RF attenuator allowing to lower the electron energy in the accelerator without lowering it in the buncher i.e. without loosing peak current. It is planned to extend again the maximum wavelength by reducing further the diffraction losses by (i) manufacturing larger dipoles accommodating larger vacuum chamber, (ii) using the undulator vacuum chamber as a wave guide in the vertical direction. In this case, toroidal cavity mirrors will be used as the optical mode will be free-space in the horizontal direction and partially guided in the vertical. Calculations indicate that a maximum wavelength of approximately 150 µm should be reached.