Optimal design of free electron laser with coaxial static magnetic undulator at W band

A free electron laser based on a coaxial static magnetic undulator utilizes annular electron beam interacting with TE mode to coherently generate electromagnetic radiation, which is an important millimeter wave radiation source. The influencing laws of the coaxial inner and outer radii, the operation mode, the beam voltage and the period of the undulator on the radiation frequency are analyzed. The main principles to choose the electron average radius and the designing method of beam wave interaction cavity are studied. Based on theoretical analysis, a coaxial static magnetic free electron laser at W band is designed and simulated by PIC simulation. The radiation wave at 107 GHz and 35 MW power are acquired. The beam wave power conversation efficiency is 4.9%. The length of the undulator is shorter than 200 mm, and the magnetic field of the undulator is 0.34 T.