Relativistic formula of laser scattering from a plasma are derived and from which Spectra of the scattered light are calculated as parameters of electron temperature and scattering angle. The relativistic effect must be taken into account in the temperature estimation at the temperature higher than a few hundred eV, otherwise the temperature is overestimated in blue side of the spectrum. A few methods are presented for determining a correct temperature in relativistic Plasmas.
A new type of plasma, back-diffusion type plasma, is studied, where the energy distribution of the ion beam is controlled experimentally in the temperature as well as the beam velocity. The dependence of the beam energy and the temperature of ions on grid potentials and anode potentials is described. To interprete the mechanism of controlling the energy distribution function, a smiple model is proposed and compared with experimental results.