Status of the UK free electron laser project

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. © 1986.