  Theoretical background and data on the ways of practical realization are
presented, related to the problem of detection of dangerous organic objects
(explosives, drugs, etc.) in the presence of other organic substances with
atomic number differing by no more than 20-30%. For this purpose, multi-energy
X-ray introscopy is used. It has been shown that the "weakest link" in the
existing multi-energy introscopes used for safety inspection and medicine are
detectors of ionizing radiation. In particular, critical is the type of
scintillator used in the low-energy detection subsystem. Data are presented on
design principles and properties of combined detectors based on a new type of
semiconductor scintillators (SCS) -- $ZnSe(Te,O)$, with conversion efficiency
of 19-22%, afterglow level less then $0.05 %$ after $10 ms$, and radiation
stability up to $500 Mrad$. Results are given on the practical use of
experimental samples of the low-energy detector subsystem based on the new SCS
material in two-energy introscopes of the 4th and 5th generation.
