Experimental research on a gigawatt-class Ku-band coaxial transit-time oscillator with low guiding magnetic field

A Ku-band relativistic transit-time oscillator with a three-cavity extractor and a distance-tunable reflector was proposed in our previous work [Ling et al., Phys. Plasmas 24(1), 013103 (2017)]. Recently, a new experiment was carried out on this device with an intense relativistic electron beam generator that produces electron beams with a duration of 55 ns and voltage of 0.4-1 MV. In preliminary experiments, mode competition was found with three main frequencies of which the reasons are analyzed theoretically and experimentally. The results show that plasmas generated from the collector's surface are most likely to cause this problem. To solve this problem, the collector structure is extended axially. With an input voltage of 600 kV and a current of 11.7 kA, a microwave output power 1.9 GW with pulse width 26 ns and frequency 12.42 GHz is obtained under a 0.7 T guiding magnetic field. These experimental results effectively confirm the potential of high power capacity of this proposed Ku band transit-time oscillator. Published under an exclusive license by AIP Publishing.