  The process of radiation of 120-GeV positrons moving in a channeling regime
in (011) plane of a single crystal was considered. At the beginning on the
basis of the theory of nonlinear oscillations the trajectory of moving
positrons at different initial conditions were derived. Then taking into
account the nonlinearity of motion the distribution function over oscillation
amplitudes of channeling particles was found. After this the intensity of
radiation at different initial conditions was calculated with the help of two
various methods. These results may be useful for comparison with experimental
data at positron energies from 100 and more GeV.
