X-ray emission by a high-energy electron with a nonequilibrium field in an ultrathin crystal

Abstract

The process of coherent x-ray emission by an ultrarelativistic electron crossing a system of two targets, thick amorphous upstream and ultrathin crystalline downstream, is considered. It is shown that transformation of the electromagnetic field around the particle after its emission from the upstream target influences upon characteristics of radiation produced by the electron in the downstream target. The considered radiation is an interfering sum of parametric x-ray radiation and diffracted transition radiation. It is demonstrated that in the present case the properties of the x-ray pulse differ both from the ones typical for thick and ultrathin crystals and depend on the distance between the targets. At multi-GeV electron energies, such dependence is observable within macroscopically large values of this distance. Special attention is drawn to the study of the influence of the downstream target finiteness on radiation characteristics. It is shown that it results in the dependence of radiation yield on separation between the targets for macroscopically large values of such separation even at sub-GeV electron energies.