Technological difficulties related to maintenance of regularity in the structure arise in micrometric measurements of
the channel. A violation in regularity significantly reduces the transfer functions of the given structures and, consequently,
decreases the sensitivity and precision of the technique. Therefore, it is necessary to use tested, calibrated capillary structures
that satisfy stringent requirements as regards the uniformity of transmission across the inlet area.
Such a property of Kumakhov optics systems as selectivity in terms of energy  also imposes certain constraints.
As a consequence of a decrease in the critical angle with increasing radiation energy there occurs a cut-off in the high-energy
part of the spectrum by the capillary structures. Such a cut-off also occurs as a result of the lesser efficiency of the scintillator
at high energies and, consequently, this error, which is introduced by the capillary structures, is not very substantial.