Investigation Of A Self-coherent High Power Microwave Source

Generally,high power microwave(HPM)sources with high beam-wave conversion efficiency have a higher impedance.To improve the single-tube output power of HPM sources,simply reducing the impedance of the device and increase the power capacity is not enough,but ensuring that the operating current is less than the space limiting current at the same time.Based on the above consideration,an X-band self-coherent high power microwave source is proposed in this paper and the relative investigation is carried out,which has the ability to output two phase-locked high-power microwaves in one microwave source simultaneously.A dual-concentric annular cathode is applied in this microwave source,which is capable of emitting two concentric annular electron beams and driving the internal and external sub-source simultaneously.The advantage of this device are reducing the impedance and improving the injection electric power.Besides,it can make each sub-source operate in high impedance state,which ensures the current operating within the space current limitations.As a result,the beam-wave conversion efficiency will be improved.Considering the fact that the microwave source consists of two sub-sources,the power capacity will be greatly improved.In summary,the X-band self-coherent HPM source is expected to achieve higher output power in a single tube.X-band Self-coherent high power microwave source comprises a multi-wave Cerenkov oscillator(MWCG)which serves as the inner sub-source and a triaxial klystron amplifier(TKA)which serves as the outer sub-source.The operating process is as follows: First,part of microwave generated by the inner sub-source leaks out into the diode region.Then,this part of wave is injected into outer sub-source as the injection signal.Finally,two phase locked high power microwaves are generated by two sub-sources,and the two microwaves will be combined by the power combiner.Because of the two-way coherent microwaves are actually generated in one microwave source,the novel microwave device is called self-coherent high power microwave source.The main contents and conclusions are as follows:First,the design and analysis of the inner sub-source and the outer sub-source are carried out respectively.And the Particle in cell(PIC)simulation results show that when the MWCG diode voltage is 687 kV,the average output microwave power is 1.15 GW,the frequency is 9.68 GHz,and the power efficiency is 22.8%;when the TKA diode voltage is 650 kV,the average output power is 1.58 GW,the frequency is 9.68 GHz,the power efficiency is 21%,and the gain is 22.4 dB.Secondly,the inner sub-source and the outer sub-source are combined,and the PIC simulation of the combined self-coherent high power microwave source is carried out.The simulation results show that when the diode voltage is 687 kV,the average output power of the inner sub-source and the outer sub-source are 1.20 GW and 2.58 GW respectively,the frequencies are both 9.72 GHz,and the power efficiency are 28% and 30% respectively,the impedance of the device is 36 ?.Besides,the phase lock between the inner sub-source and the outer sub-source can be obtained within 30 ns,and the frequency difference fluctuation is less than ±6 MHz,the phase difference fluctuation is less than ±5 °,phase-locking continued for more than 70 ns.Finally,the investigation of coherent power combination is carried out.The combined average output power is 3.59 GW,the output frequency is 9.72 GHz,and the power conversion efficiency is 28%.