DENSE ELECTRON-BEAM RADIATION IN A DIELECTRIC MEDIUM

We have studied both the spectral intensity and the energy of radiatio n produced by an electron beam in dielectric medium. Since the device starts up from a photon vacuum the investigation is based on a quantum electrodynamics approach. We have assumed that the electron beam long itudinal size is indefinite and its energy spread is of Gaussian form. In such a case the radiation process has a cutoff with respect to the electron density rho(0). If the electron density is lower than some c haracteristic density rho(ch) then the radiation will be mainly sponta neous and its emission line will have Gaussian shape. If the electron beam is dense, rho(0)>rho(ch). then a drastic change of line form take s place. Namely, one observes a high and narrow peak (or superradiatio n effect) on its right-hand side and radiation energy saturation on it s left-hand side. Both of these phenomena are due to the stimulated pr ocesses of photon absorption and emission. We have evaluated the level of radiation fluctuations in the peak vicinity. Numerical estimations of both obtained effects are presented.