Preliminary research on overmoded high-power millimeter-wave Cerenkov generator with dual-cavity reflector in low guiding magnetic field

Abstract

This paper presents preliminary research on a V-band overmoded Cerenkov generator with dual-cavity reflector operating in a low guiding magnetic field. It is found that the fluctuation of the electron envelope in the low guiding magnetic field can be predicted using an equivalent coaxial model of a foilless diode, and a dual-cavity reflector based on the model matching method can provide strong reflection at the front end of the overmoded structures so that any microwave power that leaks into the diode region can be effectively suppressed. Numerical simulations indicate that the control of the beam envelope and the use of the dual-cavity reflector ease generator operation in the low guiding magnetic field. In the experimental research, the fluctuation of the annular electron beam with the outer radius of 7.5 mm measures approximately 0.7 mm, which is in good agreement with the theoretical results. The disturbance caused by power leaking from the overmoded slow wave structure is eliminated by the dual-cavity reflector. With accurate fabrication and assembly processes, an operating frequency of 61.6 GHz is attained by the fifth harmonic heterodyne method, and the output power is measured to be approximately 123 MW by the far-field measurement method at a diode voltage of 445 kV, a beam current of 4.45 kA, and under a guiding magnetic field of 1.45 T. The output mode is measured using an array of neon flash bulbs, and the pulse shortening phenomenon is both observed and analyzed.

Research on TEM mode feedback and distributed reflection for high-power output of a V-band transit-time oscillator under a low guiding magnetic field

“…5 In 2015, Ye et al developed an overmode relativistic backward wave oscillator that generates 123 MW of V-band microwaves in a 1.45 T magnetic field with a conversion efficiency of 6.2%. 6 Then, in 2022, Chen et al built a V-band overmode relativistic Cherenkov oscillator with a microwave output of 226 MW and a conversion efficiency of 23% in a 2.0 T magnetic field. 7 The same year, Deng et al manufactured a V-band relativistic coaxial transit time oscillator (RCTTO) to generate microwaves with a power of up to 258 MW at a relatively low magnetic field of 1.0 T. However, the conversion efficiency is only about 12.3%.…”