A novel Smith-Purcell free electron laser

An experiment on a novel Smith-Purcell free electron laser (FEL) is describ ed in this paper. The FEL is driven by a relativistic sheet electron beam o f middle energy. The high frequency system of the device is a quasi-optical resonator composed of a diffraction grating and a three-mirror reflector. Coherent radiation with a peak power of tens of kW at the 3 mm waveband is sucessfully detected from an experimental facility. The main experimental p arameters are: sheet beam energy from 400 kV to 500 kV: pulse length of vol tage 70 ns; pulse beam current 0.2 kA; synchronous guide magnetic field up to 1.2 T with 10 ms pulse length; and grating period 2.2 mm.