FAR-IR/THz radiation from the Jefferson Laboratory, energy recovered linac, free electron laser

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Abstract
The free electron laser at Jefferson Laboratory is the first of a new generation of light sources based on a photoinjected energy recovered linac. The present machine has a 40 MeV electron beam and an average current of 5 mA. The electron bunches are extremely short with full width at half maximum values that are in the few hundred femtosecond regime. These electron bunches pass a chicane around the optical cavity, and therefore, emit synchrotron radiation. In the far-IR region, the wavelength of the light being emitted approaches that of the electron bunch length, giving rise to multiparticle coherent enhancement. The result is a broadband spectrum whose average brightness is more than five orders of magnitude higher than can be obtained from conventional incoherent synchrotron IR sources. We will discuss preliminary measurements of this radiation, and applications to spectroscopy and imaging.