An Improved Ku-band MILO With Tapered Choke Cavity and Enlarged First Interaction Cavity

In order to further enhance the power capacity, and speed up the microwave start-up and saturation, an improved Ku-band magnetically insulated transmission line oscillator (MILO) with tapered choke cavity and enlarged first interaction cavity is proposed and investigated in this paper. The simplified plate model of MILO is analyzed to investigate the movement of individual electron. According to the theoretical analysis, the Ku-band MILO is optimized designed. In order to make the electrons emitted from the launch point of the cathode closer to the slow wave structure (SWS), especially the surface of the first interaction cavity, help to speed up the microwave start-up and saturation, the launch point of the cathode is optimized and designed 1.5 cm in front of the second choke vane. A tapered choke cavity is used to replace traditional uniform choke cavity, which helps further speed up the microwave start-up and saturation. An enlarged first interaction cavity with increased cavity gap is introduced to enhance the power capacity. Typical particle simulation results show that the improved Ku-band MILO can generate a microwave with a power of 1.65 GW and a frequency of 12.3 GHz under the diode voltage of 474 kV and the beam current of 42 kA. Compared with the traditional Ku-band MILO, the microwave start-up and saturation of the improved one are 2.5 and 5.5 ns faster, respectively. The power capacity of the improved Ku-band MILO is enhanced greatly due to that the RF electric field is decreased much from 1.3 to 1 MV/cm. At last, the experimental investigation of the improved Ku-band MILO is conducted. The device achieves a microwave output with a power of 1.2 GW, a frequency of 12.36 GHz, and a pulsewidth of 35 ns in the experiment. Both the power and the pulsewidth are enhanced significantly.