Non-dipolarity of channeling radiation at GeV beam energies

At electron-beam energies higher than about 1 GeV, the dipole approximation for channeling radiation (CR) loses its validity. The reason of non-dipolarity consists in the coupling of the longitudinal and transverse motions of the channeled particle, while, at lower energies, its transverse motion is assumed to be independent from the longitudinal one and is governed by the continuous potential only. The non-dipolarity of CR appears in a change of its energy spectrum and intensity. This effect cannot be ignored, e.g., at simulation of positron production by means of pair creation in the non-conventional scheme of a hybrid positron source. We present a classical method for calculation of the CR spectrum in the non-dipole case.