Radiation patterns of "plasma" electron beam on structures of metal grooves

It was previously reported about the possibility of existence of the effect of splitting of the far-field pattern of diffraction radiation caused by excitation of the plasma waves of space charge in the electron flow. It has been specified that the angle of splitting does not exceed one degree there. Therefore it is difficult to observe this phenomenon. Subsequent experimental works contain reports about observation of the fine structure of diffraction radiation with larger angles of splitting of the far-field pattern of the modulated electron flow. The previous article concerns the diffraction radiation oscillator as a modulator, and the work deals with the klystron modulator. However the theory of excitation of diffraction radiation on periodic unlimited gratings hasn´t allowed substantiating the phenomena observed. The two-dimensional theory of excitation of diffraction radiation with plasma electron flow moving close to diffraction grating of finite length is presented.