1 INTENSIVE QUASI-MONOCHROMATIC, DIRECTED X-RAY RADIATION OF PLANAR CHANNELED POSITRON BUNCH.

The radiation of a positron in a planar channel of a crystal is studied, considering the dependence of the medium polarization on the transverse coordinate. The expression for the spectral distribution of the number of radiated photons is obtained for a single positron. It is shown that because of the medium polarization in the soft and hard regions not all positrons make a contribution to the radiation. The analytic formula for the total spectral distribution of the number of photons is obtained for the whole radiation frequency range. The theory is compared with experimental results at the hard frequency region. At the soft radiation region the number of radiated photons is of the same order as it is on the hard radiation frequency region