During an experiment on synchrotron radiation focusing with a capillar
y lens, an interference structure was observed at the focal spot of th
e lens, despite the fact that the lens capillary diameter is about a m
illion times greater than the wavelength of the X-ray photons (600 mu
m and 8 Angstrom, respectively). The width of the central peak is clos
e to the capillary diameter. At the same time the synchrotron radiatio
n concentration increased by more than one hundred times. Analysis sho
ws that the capillary lens acts in many respects as a macroscopic crys
tal. The observed effect is accounted for by wave theory. This phenome
non may have important practical effects in many fields.