Experimental observation of the diffraction-radiation effect in the millimeter-wave range

Experimental results are presented concerning millimeter-wave diffraction radiation excited by a modulated electron beam moving near a diffraction grating. Directivity and polarization diagrams are obtained for the excitation of a linear H-polarized wave at a wavelength of 4.284; and results are presented on the splitting of the directivity diagram during variations of beam current and the focusing magnetic field for a wavelength of 5.725 mm. Characteristics of diffraction radiation are observed which are connected with the effect of the focusing magnetic field and with electron-wave processes in the electron beam. The propagation of electron waves in the beam can lead to the splitting of the directivity diagram and a change in the polarization characteristics of the diffraction radiation.