ELECTRON BEAM SPACE CHARGE WAVES ON DIF'FWCTION-CERENKOV RADIATION BY TIB METAL-DIELECTRIC PERIODIC STRUCTURES

One of the problems in the field of physics and engineering of and submillimeter wave ranges is the creation of highefficient sources of electromagnetic oscillations and element base of radiosystems. The theoretical end experimental research indicates an opportunity of using Cerenkov radiation (CR) or a combination of diffraction and Cerenkov radiation in some schemes of EHF [ 1, 21. Periodic metal-dielectric structures (MDS) of the dielectric layer (resonator) - band diffraction grating @G)-type are user in such devices for converting EB surface waves into volume waves. In a general case the energy characteristic of excited radiation is represented by the energy density determined by average value of Pointing vector stream: c Sn=- [E x H'l, 8& where n - number of radiation space harmonic, c - speed of light, E -relative dielectric permeability of the medium; E and H - vectors of electromagnetic wave excited by a monochromatic current of the space charge. It is possible to separate various regimes of radiation excitation which are realized by changing o fthe such parameters of system as E, I (period of DG), and p =V/c (relative velocity of EB). The numerical modeling carried out has provides for the investigation of the radiation properties in a wide interval of changing MDS and EB parameters wed practically (E = 2t100; p = 0.1;O.g). The dependencies SoE / S, on E and p for various values of DG filling factor U = coslrdll (d - width of DG bands) were obtained and analysed. As the analysis has shown one of the main factors influencing the density of CR energy is the screening influence of DG deposited on the dielectric surface along which EB is moving. The MCD experimental model investigated is presented in Figure 1. In this case monochromatic EB is