Spontaneous Coherent Cyclotron THz Super-Radiation from a Dense Electron Bunch

Short dense electron bunches produced by modern photo-injectors are attractive from the viewpoint of realization of powerful and effective sources of THz radiation based on spontaneous coherent radiation from bunches. This type of emission is realized, if the effective phase bunch size with respect to the wave is small enough. Therefore, the duration of the radiation process is limited due to the increase in the bunch size under effect of the Coulomb repulsion. In this work we show that this problem can be solved by using the cyclotron mechanism of the spontaneous radiation due to the compensation of the Coulomb repulsion in the cyclotron phase space.