Free-electron maser based on two-dimensional distributed feedback

Abstract

The study of a co-axial free-electron maser (FEM) based on 2D and ID distributed feedback and driven by a large diameter (70 mm), annular electron beam is presented. It has been demonstrated that 2D distributed feedback in the input mirror allowed 8 mm radiation emitted from different parts of the oversized electron beam to be synchronized. The FEM operating in the (35.9 GHz to 38.9 GHz.) frequency region generated 60 MW, 150 ns duration millimetre wave pulses which contained ~9 J of energy in the pulse. Good agreement between theoretical predictions and experimental data is demonstrated.