Cherenkov-transition radiation in a waveguide partly filled with a resonance dispersion medium

We analyze the electromagnetic field of a charged particle that uniformly moves in a circular waveguide and crosses a boundary between a dielectric medium, which possesses frequency dispersion of a resonant type, and a vacuum area. The investigation of the waveguide mode components is analytically and numerically performed. It is shown that Cherenkov radiation (CR) can penetrate through the boundary, and Cherenkov-transition radiation (CTR) can be excited in the vacuum region. The conditions for this effect are obtained. It is shown that the CTR can be composed of a single mode (compared with the CTR in a nondispersive dielectric, which is multimode). The amplitude of the CTR is comparable to the amplitude of CR in an extensive range of parameters. The considered effect can be used to generate intense quasimonochromatic radiation.