Broadband Free Electron Laser by the Use of Prebunched Electron Beam

Abstract

Using prebunched electrons of 35 MeV from a linear accelerator, we have constructed a new type of free electron laser (FEL) which has a quasicontinuous spectrum in the millimeter wave region. The FEL consists of an open resonator and a bending magnet. Wave packets of coherent radiation from electron bunches are stored in the resonator to stimulate the radiation from the following bunches. The accumulated radiation is composed of overtones of the radio frequency of the accelerator and is quasicontinuously distributed over a wide region. By tuning the resonator, either all overtones or a part of them are amplified.