<title>Investigation of lower-order mode suppression in a high-current high-voltage gyro-BWO experiment</title>

Abstract

The Air Force Phillips Laboratory Gyro-BWO experiment is utilizing the RAMBO pulser, with electron beam parameters of: D= 300-800 kV; 1D=15°p ulselength = 1-3 p.s. An annular electron beam of 1-3 kA is produced by an annular aluminum cathode. The interaction cavity is designed to radiate in the frequency range of 4.2 -5.5 GHz in a TE01 mode. The interaction cavity has a radius of 4.37 cm and a length of 15 cm. Diode and interaction magnetic fields are used together to provide a magnetic compression of the electron beam. C-Band bevel-cut antennas located at the diode end of the experiment are used to extract the backward wave. Experiments have shown evidence of mode competition existing as two different frequency values appearing at the same time. A helical slotted cavity has been designed, in an effort to suppress the TEn1 modes, n 0. Analysis and numerical simulations from the 3-D code HFSS will be presented, as well as the latest experimental results.