University of Strathclyde Viz Royal College of Science and Technology Glasgow United Kingdom
Two dimensional 2D periodic surface lattices PSLs constructed on the inner surface of a cylindrical, highly overmoded interaction region have been shown to provide a route to achieving an eigenmode that can be excited with an electron beam, resulting in a microwave source with a cavity diameter to wavelength ratio much larger than unity. The project combined analytical theory,numerical modelling, component design, construction and operation of an experiment. Two different methods were used to manufacture the two different types of 2D PSL. The first used electrochemical deposition of copper on an aluminum former with the aluminum subsequently removed by dissolving in strong alkali solution and the second used a 3D printing additive manufacturing technique. A water-cooled 1.8 T electromagnet solenoid provided the guide field for the electron beam. In the initial experiments 134 kW of mm-wave output was measured in W-band. The 2D PSL principle employed is independent of frequency and has the capability of higher output powers, as a consequence of achieving mode selectivity and control in large, highly-overmoded structures.