Power Capacity Improvement of Subterahertz Coaxial Cherenkov Generator by External Quality Factor Regulating Mechanism

A novel subterahertz relativistic coaxial Cherenkov oscillator with an external quality factor regulation mechanism is proposed. This device achieves high output efficiency and power capacity simultaneously. To enhance output efficiency, a coaxial segmented slow wave structure (SWS) is employed. To improve power capacity, first, utilize an optimized SWS with a lower external quality factor ( ${Q}_{\text {e}}$ ). Then, as both quasi-transverse electromagnetic (TEM) and TM01 modes coexist in the device, a new approach is introduced by incorporating an additional middle cavity, tail cavity, and waveguide ring to further increase power capacity. These structures enable relatively independent regulation of the external quality factors for both quasi-TEM and TM01 modes through modifying the transmission and reflection characteristics of the terahertz wave. Particle-in-cell simulations show that at a diode voltage of 298 kV and beam current of 1.2 kA, a subterahertz wave at approximately 339 GHz with an output power of 105 MW is generated, corresponding to an output efficiency of 29.4%. Compared to the recent study on subterahertz multiwave Cherenkov generator (MWCG), the power capacity is higher, and the output power increases by nearly 50%.