Characteristic γ-radiation forming due to inelastic scattering reaction (A(n,n'γ)A), is registered by means of scintillation detectors based on BGO crystals.

γ-quanta detectors have the following properties:
• Good energy resolution in 1-12 MeV (8-2.5)% γ-quanta energy range, that is very important for correct determination of 12С, 14N and 16О characteristic γ-radiation line intensity;
• High efficiency of γ-quanta registration in the specified energy range, that allows getting required statistics for identifying hidden substances within short periods of time (~5-10 minutes);
• Low sensitivity in relation to background neutron radiation registration.

Gamma-detector consists of 8-dynode photomultiplier Hamamatsu R6233 with photocathode diameter of 76mm and BGO crystal. BGO deexcitation time is 300 ns, density – 7.13 g/cm³, and refraction factor – 2.15.

γ-detector energy resolution in line Еγ = 4.43 MeV is GE = (3.9 ± 0.1)%. Time resolution of characteristic γ-radiation registration system in coincidence with signals from α-detectors is 2.9 ns.