Status of the UK free electron laser project

Abstract The aim of the UK project is to study the characteristics of a single-pass FEL over a wide operating range, using a four-section 5 m wiggler yielding a maximum K of 2.7. The laser is driven by the 165 MeV Kelvin Laboratory linac fitted with a modified electron gun incorporating a subharmonic buncher and an energy compression system to reduce the energy spread to 0.1%. The design wavelength operating range is 2–20 μm, although higher harmonics are also under investigation. Recent progress is reported, with emphasis on electron beam transport and diagnostics. Measurements have been made with the high-resolution electron spectrometer, and emittance measurements have been performed under different linac operating conditions. Details are given of the multichannel spectrum/profile monitors common to these measurements.