Potential for increasing the power of free electron masers using novel 2D Bragg coaxial structures

In this work the first successful measurements of a 2D Bragg coaxial mirror are presented. The results of experimental study of 2D Bragg structures as well as the results obtained from numerical calculations show that two dimensional distributed feedback can be used to obtain single mode excitation in a large diameter coaxial cavity. A joint experiment at the University of Strathclyde currently under progress aims to achieve single mode operation in a 37 GHz free electron maser (FEM) when driven by an oversized electron beam of diameter in excess of 10 wavelengths.