Research progresses on Cherenkov and transit-time high-power microwave sources at NUDT

Research progresses on Cherenkov and transit-time high-power microwave (HPM) sources in National University of Defense Technology (NUDT) of China are presented. The research issues are focused on the following aspects. The pulse-shortening phenomenon in O-type Cerenkov HPM devices is suppressed. The compact coaxial relativistic backward-wave oscillators (RBWOs) at low bands are developed. The power efficiency in M-Type HPM tubes without guiding magnetic field increased. The power capacities and power efficiencies in the triaxial klystron amplifier (TKA) and relativistic transit-time oscillator (TTO) at higher frequencies increased. In experiments, some exciting results were obtained. The X-band source generated 2 GW microwave power with a pulse duration of 110 ns in 30 Hz repetition mode. Both L- and P-band compact RBWOs generated over 2 GW microwave power with a power efficiency of over 30%. There is approximately a 75% decline of the volume compared with that of conventional RBWO under the same power capacity conditions. A 1.755 GHz MILO produced 3.1 GW microwave power with power efficiency of 10.4%. A 9.37 GHz TKA produced the 240 MW microwave power with the gain of 34 dB. A 14.3 GHz TTO produced 1 GW microwave power with power efficiency of 20%.