An axial electron beam passing through a dielectric slow-wave structure can producecoherent Cherenkov radiation whose phase velocity is slightly slower than the velocity of the beam. This phenomenon is the basis of all traveling wave tubes.

• 轴向电子注通过介质慢波系统，当波的相速略低于电子注的速度时就可产生相干的切伦可夫辐射，这一现象是一切行波管的基础。