Experimental results from a coaxial vircator

Summary form only given. A coaxial vircator system has been developed at the High-Power Microwave Facility at Texas Tech University and the initial testing is complete. This paper details the experimental results for several different configurations of the coaxial vircator. The coaxial vircator generates microwave radiation by injecting a radial electron beam into a cylinder such that the space-charge limit of the region is exceeded. A virtual cathode forms and oscillates in radial position and amplitude, generating microwaves which are extracted through an attached waveguide with a circular cross-section. The cathode material is a cold field-emitter applied to the inside of a grounded cylinder. The anode is a semi-transparent cylinder located inside of, and concentric to, the cathode cylinder. The anode cylinder is pulsed positively. Extensive use of particle-in-cell simulations were employed to develop an experimental prototype, which was tested in eight different configurations. Most of the design for the coaxial vircator was done with the aid of the 2.5 dimensional, particle-in-cell code, MAGIC. Simulation geometries matching the experimental system as closely as possible were developed to allow for comparison to experimental results. However, direct comparisons are not accurate because of azimuthal variations in the electron beam and microwave radiation which turned up in the experimental system.