Eects of emittance and energy spread in an electronbunch on THz radiation generated by a super-radiantsource

In this report we summarize our results on simulation of a super-radiant source operating at the THz spectral range. We consider an open-type undulator comprising plane magnets but without any guiding structure for generated THz field. The undulator is assumed to be driven by electron bunches of femtosecond duration which are produced by an rf Linac. Using a numerical model developed, we analyze effects of the bunch parameters on output performance of the super-radiant source and reveal some surprising results. Specifically, we show that degradation in bunch spatial quality (increase in the bunch emittance) should lead to decrease in angular divergence and spectral narrowing of the THz radiation. We also demonstrate that electron energy spread which commonly leads to bunch broadening and radiative energy drop can be eventually suppressed under appropriate conditions.