Amplification of a surface electromagnetic wave by running over plasma   surface ultrarelativistic electron bunch as a new scheme for generation of   Teraherz radiation
  The amplification of a surface electromagnetic wave by means of ultrarelativistic monoenergetic electron bunch running over the flat plasma surface in absence of a magnetic field is studied theoretically. It is shown that when the ratio of electron bunch number density to plasma electron number density multiplied by a powered to 5 relativity factor is much higher than 1, i.e $\gamma^5 n_b/n_p>> 1$, the saturation field of the surface electromagnetic wave induced by trapping of bunch electrons gains the magnitude: $E_x=B_y\approx 0.16 \frac{\omega_p m c}{e} (\frac{2n_b}{\gamma^2 n_p})^{1/7}$ and does not approache the surface electromagnetic wave front breakdown threshold in plasma. The surface electromagnetic wave saturation energy density in plasma can exceed the electron bunch energy density. Here, we discuss the possibility of generation of superpower Teraherz radiation on a basis of such scheme. 
S. P. Sadykova, A. A. Rukhadze, T. G. Samkharadze and K. V.   Khishchenko
physics.plasm-ph