The infrared free-electron laser offers a large tunability since the FEL gain remains high throughout the infrared spectral range, and the reflectivity of metal mirrors remains also close to 1. The main limitation comes from the diffraction of the optical beam due to the finite size of the vacuum chamber of the undulator. At CLIO, we had obtained previously an FEL tunable from 3 to 150 µm by operating the accelerator between 50 and 14 MeV. However, we found that a phenomenon of “power gaps” is observed in farinfrared: the laser power falls down to zero at some particular wavelengths, whatever the beam adjustments are. We showed that this effect is related to to the waveguiding effect of the vacuum chamber leading to different losses and power outcoupling at different wavelengths. To alleviate this effect we have designed a new undulator allowing to use a larger vacuum chamber without reducing the spectral tunability and agility of the FEL. From simulations, a large increase of available power is expected in farinfrared. The new undulator has been installed and its performances and first FEL measurement in far-infrared are presented.

Conference Title

International Particle Accelerator Conference (IPAC 2012)

Conference Country

United States of America

Conference Date

May 20, 2012 - May 25, 2012

Conference Sponsor

Convention center

Additional Info

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