Experiments on folded waveguide gyro-TWT amplifier

Summary form only given, as follows. Experiments on a folded waveguide gyro-TWT amplifier are underway to demonstrate high power (>50 kW), broadband (BW>15%), Ka-band radiation amplification. The interaction circuit is a periodic, H-plane bend, transverse folded waveguide employed with a high power axis-encircling electron beam. The electron beam with a large transverse momentum is produced by an advanced triple-pole-piece center-post electron gun designed by Litton for NRL millimeter wave gyro-amplifier experiments. For a proof-of-principle experiment, a low gain 12 period circuit is built and tested. A mode coalescing of the first stop-band predicted by an equivalent circuit model and a 3-D electromagnetic code is verified from experimental measurements. Measurements show a return loss of <-15 dB over the frequency bandwidth of >20%. Experimental data are presented and compared with slow-time scale non-linear code simulations.