Spatial distribution of channeling long-wavelength X rays at the output of polycapillary structures

The distribution of the intensity of long-wavelength X rays at the output of microchannel plates at the glancing incidence of monochromatic radiation on the walls of microcapillaries has been studied experimentally and theoretically. The angular distribution of the radiation transmitted through microchannels has been analyzed for energies corresponding to the Si $L_{2,3}$ and O $K$ absorption edges. The conditions under which the primary radiation excites X-ray fluorescence propagating inside and beyond hollow microchannels have been revealed.