Free-electron maser based on a cavity with two- and one-dimensional distributed feedback

The study of a coaxial free-electron maser (FEM) based on two-dimensional (2D) and one-dimensional (1D) distributed feedback, driven by a 70 mm diameter, annular electron beam is presented. A new cavity formed with 2D and 1D periodic lattices, positioned at the input and output of the interaction region, respectively, was used. It has been demonstrated that 2D distributed feedback in the input mirror allowed 8 mm radiation emitted from different parts of the electron beam to be synchronized. The FEM operating in the 35.9-38.9 GHz frequency region generated 65 MW, 150 ns duration millimeter wave pulses which contained ∼10 J of energy in the pulse. © 2008 American Institute of Physics.