Research activities on high-power microwave sources in National University of Defense Technology of China

Research activities on High-power microwave (HPM) sources in National University of Defense Technology (NUDT) of China are presented. The research issues are focused on following aspects. (1) Suppression of pulse-shortening phenomenon in O-type Cerenkov HPM devices. (2) Enhancement of the power efficiency in M-Type HPM tubes without guiding magnetic field. (3) Enhancement of the power efficiency in Space-charge device with multi-cavity. (4) Development of the compact coaxial relativistic backward-wave oscillator (RBWO) at low bands. (5) Enhancement of the power capacity and power efficiency in triaxial klystron amplifier (TKA) at higher frequencies. (6) Enhancement of the power capacity and power efficiency in relativistic transit-time oscillator (TTO) at higher frequencies. In experiments, some exciting results were obtained. The X-band source generated 2GW microwave power with pulse duration of 110ns in 30Hz repetition mode. A 1.755GHz MILO produced 3.1GW microwave power with power efficiency of 10.4%. Furthermore, the experimental waveforms for a 10 pulse, 2Hz shot series are obtained. A 4.1GHz multi-cavity VCO produced 1GW microwave power with power efficiency of 6.6%. Both L- and P-band compact RBWOs generated over 2GW microwave power with power efficiency of over 30%. There is approximately a 75% decline of the volume compared with that of conventional RBWO under the same power level. A 9.37GHz RKA produced the 240MW microwave power with the gain of 34dB. A 14.3GHz TTO produced 1GW microwave power with power efficiency of 20%.