INDUSTRIAL MICROWAVE FEL DEVICES

At the University of Liverpool we are developing prototype FELs which operate at energies of less than a few hundred keV and will lead to relatively compact, powerful and efficient designs for industrial use. Hence, we define the characteristics of an industrial FEL (IFEL). Our initial device operates in the X band (8 to 10 GHz) of the microwave region and employs a 85 keV electron beam and a wiggler period of 3.8 cm. The resonant structure consists of a dielectric loaded waveguide which reduces the beam energy required for the beam-wave interaction. This compact design incorporates a low current (1 - 10 mA) thermionic electron source with moderate electrostatic acceleration, allowing safe operation in a laboratory environment. Beam deceleration beyond the wiggler allows for efficient energy recovery and reduces X-ray emission. For low current operation the gain must be enhanced using a pre-bunching scheme. The prototype design and constructional progress are reported here.