THz undulator radiation of dense electron bunches stabilized in the negative mass regime

The use of the “negative mass” regime can provide stabilization of longitudinal size of dense short photo-injector electron bunches at long distances as well as compression of the longer bunches. This allows one to increase significantly the power capabilities of a terahertz source based on coherent spontaneous undulator emission from a short bunch. The required configuration of the magnetic field can be achieved in a specially designed undulator.